JP2004235395A - Adhesive film for grinding rear surface of semiconductor wafer and method for grinding rear surface of semiconductor wafer using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive film for grounding the rear surface of a semiconductor wafer having excellent adhesive properties to and low contaminable characteristic of the front surface of the wafer. <P>SOLUTION: An adhesive layer is formed of the adhesive which contains an acrylic adhesive polymer prepared by emulsion polymerization and containing an alkyl (meth)acrylic ester main monomer unit (A) of 50-98 wt%, a monomer unit (B) having a functional group capable of being reacted with a crosslinking agent of 1-40 wt% and an acrylic acid derivative carboxylic acid monomer unit (C) of 1-20 wt%, and the crosslinking agent having two or more functional groups in one molecule of 0.1-15 pts.wt. to the adhesive polymer of 100 pts.wt. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００１４】
（一般式（１）中、Ｒは水素原子またはアルキル基を表わし、Ｘはエステル基および／またはエーテル基を含む炭素数４〜９の２価の炭化水素基を表わす）
及び、該アクリル系ポリマー１００重量部に対し、１分子中に官能基を２個以上有する架橋剤０．１〜３０重量部を含む粘着剤からなり、該粘着剤層の０〜２００℃における貯蔵弾性率が１×１０^３Ｐａ以上、１×１０^５Ｐａ以下、厚みが３〜１００μｍであることを特徴とする半導体ウェハ表面保護用粘着フィルム。
（２） 前記（メタ）アクリル酸アルキルエステル系モノマー（Ａ）が、炭素数１〜１２のアルキル基を有する（メタ）アクリル酸アルキルエステルであることを特徴とする（１）記載の半導体ウェハ裏面研削用粘着フィルム。
（３） 前記官能基を有するモノマー単位（Ｂ）が、アクリル酸、メタクリル酸、アクリル酸−２−ヒドロキシエチル、メタクリル酸−２−ヒドロキシエチル、アクリルアミド、及びメタクリルアミドから選ばれた少なくとも１種のモノマーであることを特徴とする（１）又は（２）に記載の半導体ウェハ裏面研削用粘着フィルム。
（４） アクリル系ポリマーが前記（Ａ）を８５重量％以上９９重量％以下、前記（Ｂ）を１重量％以上１０重量％以下、前記（Ｃ）を２重量％以上１０重量％以下含有したモノマー組成物を乳化重合により調整したアクリル系ポリマーであることを特徴とする（１）〜（３）いずれかに記載の半導体ウェハ裏面研削用粘着フィルム。
（５） 基材フィルムの厚みが１０〜５００μｍである（１）〜（４）いずれかに記載の半導体ウェハ裏面研削用粘着フィルム。
（６） （１）〜（５）のいずれか１項に記載の半導体ウェハ裏面研削用粘着フィルムを用いる半導体ウェハ裏面研削方法であって、半導体ウェハの回路形成表面に前記半導体ウェハ裏面研削用粘着フィルムを貼着して、半導体ウェハの裏面を研削し、研削終了後に該粘着フィルムを剥離することを特徴とする半導体ウェハ裏面研削方法。
に関する。
本発明に係る半導体ウェハ裏面研削用粘着フィルムの第１の特徴は、上記一般式（１）で表されるアクリル酸誘導体カルボン酸をモノマーとして特定量含有させたアクリル系ポリマーを用いる点、及び該ポリマーが乳化共重合で調製されたものである点、にある。また、第２の特徴は、粘着剤層の０〜２００℃における貯蔵弾性率が１×１０^３Ｐａ以上、１×１０^５Ｐａ以下の範囲内にある点にある。
【００１５】
かかる特徴を有する半導体ウェハ裏面研削用粘着テープは、半導体ウェハの裏面を研削するに際し、ウェハ表面と粘着剤層との密着性が向上し、裏面研削工程において水及び研削屑が浸入することに起因するウェハの破損及びウェハ表面の汚染が起こらない。また、適度の粘着力を有するので、ウェハ裏面の研削には剥離せず、粘着フィルムをウェハから剥離する際にはウェハの破損が起こらない。さらに、粘着フィルムをウェハから剥離した後に糊残り等による汚染が生じないので、半導体ウェハの表面を汚染することがない。
【００１６】
尚、本発明における粘着剤層の０〜２００℃における貯蔵弾性率は、後述の実施例に記載した方法により測定した値を意味する。
【００１７】
【発明の実施の形態】
以下、本発明について詳細に説明する。本発明は、基材フィルムの片表面に特定の組成の粘着剤により粘着剤層が形成された半導体ウェハ裏面研削用粘着フィルム、及び該粘着フィルムを使用する半導体ウェハ裏面研削方法である。
【００１８】
本発明の半導体ウェハ裏面研削用粘着フィルムは、基材フィルムまたは剥離フィルムの片表面に、アクリル系粘着剤ポリマー、架橋剤、その他必要に応じて他の添加剤を含む溶液またはエマルション液（以下、これらを総称して粘着剤塗布液という）を塗布、乾燥して粘着剤層を形成することにより製造される。
【００１９】
粘着剤塗布液を基材フィルムの片表面に塗布して粘着剤層を形成する場合は、環境に起因する汚染等から保護するために、塗布した粘着剤層の表面に剥離フィルムを貼着することが好ましい。他方、剥離フィルムの片表面に粘着剤塗布液を塗布して粘着剤層を形成する場合は、該粘着剤層を基材フィルムへ転写する方法が採られる。基材フィルム及び剥離フィルムのいずれの片表面に粘着剤塗布液を塗布するかは、基材フィルム及び剥離フィルムの耐熱性、半導体ウェハ表面の汚染性を考慮して決める。例えば、剥離フィルムの耐熱性が基材フィルムのそれより優れている場合は、剥離フィルムの表面に粘着剤層を設けた後、基材フィルムへ転写することが好ましい。耐熱性が同等または基材フィルムが優れている場合は、基材フィルムの表面に粘着剤層を設け、その表面に剥離フィルムを貼着することが好ましい。
【００２０】
しかし、半導体ウェハの裏面研削用粘着フィルムは、剥離フィルムを剥離した時に露出する粘着剤層の表面を介して半導体ウェハ表面に貼着されることを考慮し、粘着剤層による半導体ウェハ表面の汚染防止を図るためには、耐熱性の良好な剥離フィルムを使用し、その表面に粘着剤塗布液を塗布、乾燥して粘着剤層を形成し、これを基材フィルムへ転写する方法の方が好ましい。本発明の半導体ウェハ裏面研削用粘着フィルムは、通常、粘着剤層の表面に剥離フィルムを貼着した状態で保存され、使用の際にそれを剥離する。
【００２１】
本発明に用いる基材フィルムとしては、合成樹脂をフィルム状に成型加工したフィルムを用いる。基材フィルムは単層体であっても、また、積層体であってもよい。基材フィルムの厚みは１０〜５００μｍが好ましい。より好ましくは７０〜５００μｍである。基材フィルムの原料樹脂としては、ポリエチレン、ポリプロピレン、エチレン−酢酸ビニル共重合体、エチレン−エチルアクリレート共重合体、エチレン−プロピレン共重合体、ポリ塩化ビニル、ポリアミド、ポリエチレンテレフタレート等の合成樹脂が挙げられる。
【００２２】
これらの中で、裏面研削中のウェハの保護性能を考慮すれば、ＡＳＴＭ−Ｄ−２２４０−８６、またはＪＩＳ Ｋー７２１５−１９８６に規定されるショアーＤ型硬度が４０以下である原料樹脂が特に好ましい。これらの樹脂をフィルム状に成型加工する際には、必要に応じて、安定剤、滑剤、酸化防止剤、顔料、ブロッキング防止剤、可塑剤等を添加してもよい。基材フィルムを成型加工する際に安定剤等の各種添加剤を添加した場合、添加剤が粘着剤層に移行して、粘着剤の特性を変化させたり、ウェハ表面を汚染することがある。このような場合には、基材フィルムと粘着剤層の間にバリヤー層を設けることが好ましい。
【００２３】
また、半導体ウェハの裏面を研削した後に施されるエッチング液によるエッチング処理の際にも引き続き半導体ウェハの裏面研削用粘着フィルムを用いて半導体ウェハの表面を保護する場合には、耐薬品性に優れた基材フィルムを使用することが好ましい。例えば、基材フィルムの粘着剤層を設ける側と反対側の面にポリプロピレン等の耐薬品性フィルムを積層する等である。基材フィルムと粘着剤層との接着力を向上させるため、基材フィルムの粘着剤層を設ける面には、予め、コロナ放電処理または化学処理を施すことが好ましい。また、基材フィルムと粘着剤層の間に下塗剤を用いてもよい。本発明に使用する基材フィルムは、カレンダー法、Ｔダイ押出法、インフレーション法等、公知の技術により製造されるものの中から、生産性及び得られるフィルムの厚み精度等を考慮して選択することができる。
【００２４】
本発明に使用する剥離フィルムとしては、ポリプロピレン、ポリエチレンテレフタレート等の合成樹脂フィルムが挙げられる。必要に応じてその表面にシリコーン処理等が施されたものが好ましい。剥離フィルムの厚みは、通常１０〜２００μｍである。好ましくは３０〜１００μｍである。
【００２５】
本発明に用いる粘着剤塗布液は、（メタ）アクリル酸アルキルエステルモノマー単位（Ａ）、架橋剤と反応し得る官能基を有するモノマー単位（Ｂ）、及び上記一般式（１）で表されるカルボン酸（Ｃ）をそれぞれ特定量含むモノマー組成物を乳化重合して得られる共重合体のアクリル系粘着剤ポリマー、並びに、凝集力を上げたり粘着力を調整するための、官能基を１分子中に２個以上有する架橋剤を含有してなる溶液またはエマルション液からなる。溶液で使用する場合は、乳化重合で得られたエマルション液からアクリル系粘着剤ポリマーを塩析等で分離してから溶剤等で再溶解して使用するが、本発明に用いるアクリル系粘着剤ポリマーは分子量が充分に大きく、溶剤への溶解性が低く、若しくは溶解しない場合が多く、コスト的な観点から鑑みても、エマルション液のまま使用することが好ましい。
【００２６】
本発明に用いるアクリル系粘着剤ポリマーは、アクリル酸アルキルエステル、メタクリル酸アルキルエステル、又はこれらの混合物を主モノマー〔以下、モノマー（Ａ）〕と官能基を有するモノマー（Ｂ）と架橋剤と反応し得る（メタ）アクリル酸誘導体カルボン酸（Ｃ）を含有するモノマー組成物を共重合して得られる。
【００２７】
モノマー（Ａ）としては、炭素数１〜１２程度のアルキル基を有するアクリル酸アルキルエステル又はメタアクリル酸アルキルエステル〔以下、これらの総称して（メタ）アクリル酸アルキルエステルという〕が挙げられる。好ましくは、炭素数１〜８のアルキル基を有する（メタ）アクリル酸アルキルエステルである。具体的には、アクリル酸メチル、メタクリル酸メチル、アクリル酸エチル、メタクリル酸エチル、アクリル酸ブチル、メタクリル酸ブチル、アクリル酸−２−エチルヘキシルが挙げられる。これらは単独で使用しても、また、２種以上を混合して使用してもよい。モノマー（Ａ）の使用量は粘着剤ポリマーの原料である重合性モノマーの総量中、通常、１０〜９８重量％の範囲で含ませることが好ましい。更に好ましくは８５〜９５重量％である。モノマー（Ａ）の使用量をかかる範囲とすることにより、（メタ）アクリル酸アルキルエステルモノマー単位（Ａ）を１０〜９８重量％、好ましくは８５〜９５重量％含むポリマーが得られる。
【００２８】
架橋剤と反応し得る官能基を有するモノマー単位（Ｂ）としては、アクリル酸、メタクリル酸、イタコン酸、メサコン酸、シトラコン酸、フマル酸、マレイン酸、イタコン酸モノアルキルエステル、メサコン酸モノアルキルエステル、シトラコン酸モノアルキルエステル、フマル酸モノアルキルエステル、マレイン酸モノアルキルエステル、アクリル酸−２−ヒドロキシエチル、メタクリル酸−２−ヒドロキシエチル、アクリルアミド、メタクリルアミド、ターシャル−ブチルアミノエチルアクリレート、ターシャル−ブチルアミノエチルメタクリレート等が挙げられる。好ましくは、アクリル酸、メタクリル酸、アクリル酸−２−ヒドロキシエチル、メタクリル酸−２−ヒドロキシエチル、アクリルアミド、メタクリルアミド等が挙げられる。これらの一種を上記主モノマー（Ａ）と共重合させてもよいし、また２種以上を共重合させてもよい。架橋剤と反応し得る官能基を有するモノマー（Ｂ）の使用量は、粘着剤ポリマーの原料である重合性モノマー総量中に、通常、１〜４０重量％の範囲で含まれていることが好ましい。更に好ましくは１〜１０重量％である。而して、モノマー組成とほぼ等しい組成の構成単位（Ｂ）を有するポリマーが得られる。
【００２９】
本発明においては、高い凝集力と密着性を発現させる方策として、重合後生成するポリマー表面の架橋基点に着目し、重合溶液中に（メタ）アクリル酸誘導体カルボン酸を投入し、架橋点をポリマー表面に突出させることにより、官能基を１分子中に２個以上有する架橋剤と反応させる能力を付与する。これにより高い凝集力を発現し、且つ投入したカルボン酸により貯蔵弾性率を調整し、高い密着性を発現させることができる。反応性、着色及び入手のし易さ等の観点から、上記一般式（１）で表されるカルボン酸（Ｃ）が本発明の目的に適している。
【００３０】
アクリル系粘着剤ポリマーに特定のカルボン酸（Ｃ）を共重合することによって、粘着剤層とウェハ表面との密着性が向上し、ウェハ裏面を研削する際のウェハ表面と粘着剤層の間への水浸入を防止する（以下、耐水性）効果があり、しかも、粘着フィルムをウェハ表面から剥離する際のウェハの破損も起こらず、粘着剤層に起因するウェハ表面（特にハイバンプ電極を有するウェハの場合には該ハイバンプ電極の周辺）への汚染も生じない粘着剤が得られる。
一般式（１）で表されるカルボン酸（Ｃ）の使用量は、乳化重合の際の安定性、及び弾性率に影響を及ぼし、使用量が多すぎると重合安定性が低下し、且つ弾性率が増大する傾向にある。
かかる観点から、一般式（１）で表されるカルボン酸の使用量は、モノマー原料中に１重量％以上２０重量％以下、好ましくは２重量％以上１０重量％以下である。
【００３１】
一般式（１）中、Ｒは水素またはアルキル基であり、アルキル基としてメチル基等が挙げられる。Ｘは、エステル基および／またはエーテル基を含有してなる炭素数４〜９の２価の炭化水素である。 このようなカルボン酸を例示すると２―メタクロイルオキシエチルサクシネート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−）、２―アクロイルオキシエチルサクシネート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−）、３―メタクロイルオキシプロピルサクシネート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ２−）、３―アクロイルオキシプロピルサクシネート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−）、２―メタクロイルオキシエチルマレート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ＝ＣＨ−）、２―アクロイルオキシエチルマレート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ＝ＣＨ−）、３―メタクロイルオキシプロピルマレート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ＝ＣＨ−）、３―アクロイルオキシプロピルマレート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ＝ＣＨ−）、２―メタクロイルオキシエチルフタレート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−Ｃ_６Ｈ_４−）、２―アクロイルオキシエチルフタレート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−Ｃ_６Ｈ_４−）、３―メタクロイルオキシプロピルフタレート（Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−Ｃ_６Ｈ_４−）、２―アクロイルオキシプロピルフタレート（Ｒ＝Ｈ、Ｘ＝−ＣＨ_２ＣＨ_２ＣＨ_２−ＯＯＣ−Ｃ_６Ｈ_４−）等が挙げられ、これらは単独で使用しても良いし、または２種以上を併用してもよい。
【００３２】
本発明においては、その他に界面活性剤としての性質を有する特定のコモノマー（以下、重合性界面活性剤と称する）を共重合してもよい。重合性界面活性剤は、主モノマー及びコモノマーと共重合する性質を有すると共に、乳化重合する場合には乳化剤としての作用を有する。重合性界面活性剤を用いて乳化重合したアクリル系粘着剤ポリマーを用いた場合には、通常界面活性剤によるウェハ表面に対する汚染が生じない。また、粘着剤層に起因する僅かな汚染が生じた場合においても、ウェハ表面を水洗することにより容易に除去することが可能となる。
【００３３】
このような重合性界面活性剤の例としては、例えば、ポリオキシエチレンノニルフェニルエーテルのベンゼン環に重合性の１−プロペニル基を導入したもの〔第一工業製薬（株）製；商品名：アクアロンＲＮ−１０、同ＲＮ−２０、同ＲＮ−３０、同ＲＮ−５０等〕、ポリオキシエチレンノニルフェニルエーテルの硫酸エステルのアンモニウム塩のベンゼン環に重合性の１−プロペニル基を導入したもの〔第一工業製薬（株）製；商品名：アクアロンＨＳ−１０、同ＨＳ−２０等〕、及び分子内に重合性二重結合を持つ、スルホコハク酸ジエステル系〔花王（株）製；商品名：ラテムルＳ−１２０Ａ、同Ｓ−１８０Ａ等〕等が挙げられる。
更に必要に応じて、酢酸ビニル、アクリロニトリル、スチレン等の重合性２重結合を有するモノマーを共重合してもよい。界面活性剤の使用量は、モノマー原料１００重量部に対し、０．１重量部以上５重量部以下、好ましくは０．２重量部以上２重量部以下である。
【００３４】
アクリル系粘着剤ポリマーの重合反応機構としては、ラジカル重合、アニオン重合、カチオン重合等が挙げられる。粘着剤の製造コスト、モノマーの官能基の影響及び半導体ウェハ表面へのイオンの影響等を等慮すればラジカル重合によって重合することが好ましい。ラジカル重合反応によって重合する際、ラジカル重合開始剤として、ベンゾイルパーオキサイド、アセチルパーオキサイド、イソブチリルパーオキサイド、オクタノイルパーオキサイド、ジ−ターシャル−ブチルパーオキサイド、ジ−ターシャル−アミルパーオキサイド等の有機過酸化物、過硫酸アンモニウム、過硫酸カリウム、過硫酸ナトリウム等の無機過酸化物、２，２’−アゾビスイソブチロニトリル、２，２’−アゾビス−２−メチルブチロニトリル、４，４’−アゾビス−４−シアノバレリックアシッド等のアゾ化合物が挙げられる。
【００３５】
アクリル系粘着剤ポリマーは乳化重合法により重合されるので、これらのラジカル重合開始剤の中で、水溶性の過硫酸アンモニウム、過硫酸カリウム、過硫酸ナトリウム等の無機過酸化物、同じく水溶性の４，４’−アゾビス−４−シアノバレリックアシッド等の分子内にカルボキシル基を持ったアゾ化合物が好ましい。半導体ウェハ表面へのイオンの影響を考慮すれば、過硫酸アンモニウム、４，４’−アゾビス−４−シアノバレリックアシッド等の分子内にカルボキシル基を有するアゾ化合物が更に好ましい。４，４’−アゾビス−４−シアノバレリックアシッド等の分子内にカルボキシル基を有するアゾ化合物が特に好ましい。
【００３６】
本発明に用いる架橋性の官能基を１分子中に２個以上有する架橋剤は、アクリル系粘着剤ポリマーが有する官能基と反応させ、粘着力及び凝集力を調整するために用いる。架橋剤としては、ソルビトールポリグリシジルエーテル、ポリグリセロールポリグリシジルエーテル、ペンタエリスリトールポリグリシジルエーテル、ジグリセロールポリグリシジルエーテル、グリセロールポリグリシジルエーテル、ネオペンチルグリコールジグリシジルエーテル、レソルシンジグリシジルエーテル等のエポキシ系化合物、テトラメチレンジイソシアネート、ヘキサメチレンジイソシアネート、トリメチロールプロパンのトルエンジイソシアネート３付加物、ポリイソシアネート等のイソシアネート系化合物、トリメチロールプロパン−トリ−β−アジリジニルプロピオネート、テトラメチロールメタン−トリ−β−アジリジニルプロピオネート、Ｎ，Ｎ’−ジフェニルメタン−４，４’−ビス（１−アジリジンカルボキシアミド）、Ｎ，Ｎ’−ヘキサメチレン−１，６−ビス（１−アジリジンカルボキシアミド）、Ｎ，Ｎ’−トルエン−２，４−ビス（１−アジリジンカルボキシアミド）、トリメチロールプロパン−トリ−β−（２−メチルアジリジン）プロピオネート等のアジリジン系化合物、及びヘキサメトキシメチロールメラミン等のメラミン系化合物が挙げられる。これらは単独で使用してもよいし、２種以上に対して併用してもよい。
【００３７】
架橋剤の含有量は、通常架橋剤中の官能基数がアクリル系粘着剤ポリマー中の官能基数よりも多くならない程度の範囲で含有する。しかし、架橋反応で新たに官能基が生じる場合や、架橋反応が遅い場合等、必要に応じて過剰に含有してもよい。好ましい含有量は、アクリル系粘着剤ポリマー１００重量部に対し、架橋剤０．１〜３０重量部、更に好ましくは０．１〜１５重量部である。含有量が少ない場合、粘着剤層の凝集力が不十分となり、ウェハ表面（特にハイバンプ電極を有するウェハの場合には、該ハイバンプ電極の周辺）に粘着剤層に起因する糊残りを生じ易くなったり、粘着力が本発明の範囲を外れて高くなり、粘着フィルムをウェハ表面から剥離する際に自動剥がし機で剥離トラブルが発生したり、ウェハを完全に破損したりする場合がある。含有量が多い場合、粘着剤層とウェハ表面との密着力が弱くなり、研削中に水や研削屑が浸入してウェハを破損したり、研削屑によるウェハ表面の汚染が生じたりすることがある。
【００３８】
本発明に用いる粘着剤塗布液には、上記の特定の２官能モノマーを共重合したアクリル系粘着剤ポリマー、架橋剤の他に粘着特性を調整するためにロジン系、テルペン樹脂系等のタッキファイヤー、各種界面活性剤等を、本発明の目的に影響しない程度に適宜含有してもよい。また、塗布液がエマルション液である場合は、ジエチレングリコールモノアルキルエーテル等の造膜助剤を本発明の目的に影響しない程度に適宜添加してよい。造膜助剤として使用されるジエチレングリコールモノアルキルエーテル及びその誘導体は、粘着剤層中に多量に含有した場合、洗浄が不可能となる程度のウェハ表面の汚染を招くことがあることを考慮すれば、粘着剤塗工後の乾燥時の温度で揮発するものを使用し、粘着剤層中への残存量を低くすることが好ましい。
粘着剤層の厚みは３〜１００μｍが好ましい。より好ましい厚みは５〜８０μｍである。粘着剤層の厚みが薄くなると、耐水性が劣り、裏面研削中にウェハ表面と粘着剤層との間に水が浸入して、ウェハを破損したり、ウェハ表面に研削屑による汚染が生じたりする傾向にある。粘着剤層の厚みが厚くなると、粘着フィルムの作成が困難となったり、生産性に影響を与え、製造コストの増加につながることがある。
【００３９】
本発明における貯蔵弾性率は、制御された温度下にある対象物に、外部から引張り、曲げ、ねじり等の周期的な変形（歪み）を与え、生じた応答（応力）を、動的粘弾性測定装置を用いて測定されるものである。対象物に周期的な変形を与える方法としては、例えば、対象物を２枚の平行円盤で挟さんで該円盤を回転させる方法、対象物中に測定針を挿入して測定針を振動させる方法などが挙げられる。動的粘弾性測定装置としては、例えば、レオメトリックス社製、形式：ＲＭＳ−８００、オリエンテック社製、形式：Ｒｈｅｏｖｉｂｒｏｎ、ＤＤＶ−ＩＩ−ＥＰ、セイコーインスツルメンツ社製、形式：ＥＸＳＴＡＲ６０００、ＴＭＡ／ＳＳなどが挙げられる。
【００４０】
上記粘着剤ポリマー１００重量部、及び、１分子中に２個以上の架橋反応性官能基を有する架橋剤０．１〜３０重量部を含む粘着剤層の０〜２００℃における貯蔵弾性率を１×１０^３Ｐａ以上、１×１０^５Ｐａ以下の範囲になるように架橋剤を調整することが好ましい。
粘着剤層の貯蔵弾性率が低くなると、粘着フィルムを剥離した後のウエハ表面に汚染を生じることがある。粘着剤層の貯蔵弾性率が高くなると、ウエハ表面に対する密着性が低下し、研削水や薬液が浸入することがある。
本発明における半導体ウェハの裏面研削用粘着フィルムの粘着力は、ウェハ表面の研削条件、ウェハの直径、研削後のウェハの厚み等を勘案して適宜調整できるが、粘着力が低すぎるとウェハ表面への粘着フィルムの貼着が困難となったり、裏面研削中にウェハ表面と粘着剤層との間に水が浸入し、ウェハが破損したり、ウェハ表面に研削屑等による汚染が生じたりする傾向にある。また、粘着力が高すぎると、裏面研削後に粘着フィルムをウェハ表面から剥離する際に、自動剥がし機で剥離トラブルが発生する等、剥離作業性が低下したり、ウェハを破損したりすることがある。通常、ＳＵＳ３０４−ＢＡ板に対する粘着力に換算して５〜５００ｇ／２５ｍｍ、好ましくは１０〜２００ｇ／２５ｍｍである。
【００４１】
基材フィルムまたは剥離フィルムの片表面に粘着剤塗布液を塗布する方法としては、従来公知の塗布方法、例えばロールコーター法、リバースロールコーター法、グラビアロール法、バーコート法、コンマコーター法、ダイコーター法等が採用できる。塗布された粘着剤の乾燥条件には特に制限はないが、一般的には、８０〜２００℃の温度範囲において１０秒〜１０分間乾燥することが好ましい。更に好ましくは、８０〜１７０℃において１５秒〜５分間乾燥する。
架橋剤と粘着剤ポリマーとの架橋反応を十分に促進させるために、粘着剤塗布液の乾燥が終了した後に、半導体ウェハの裏面研削用粘着フィルムを４０〜８０℃において５〜３００時間程度加熱してもよい。
本発明における半導体ウェハの裏面研削用粘着フィルムの製造方法は、上記の通りであるが、半導体ウェハ表面の汚染防止の観点から、基材フィルム、剥離フィルム、粘着剤主剤等全ての原料資材の製造環境、粘着剤塗布液の調製、保存、塗布及び乾燥環境は、米国連邦規格２０９ｂに規定されるクラス１，０００以下のクリーン度に維持されていることが好ましい。
【００４２】
次に、本発明の半導体ウェハの裏面研削方法について説明する。本発明の半導体ウェハの裏面研削方法は、半導体ウェハの裏面を研削する際に、上記方法により製造された半導体ウェハの裏面研削用粘着フィルムを用いることに特徴がある。
【００４３】
その詳細は、先ず半導体ウェハの裏面研削用粘着フィルムの粘着剤層から剥離フィルムを剥離し、粘着剤層表面を露出させ、その粘着剤層を介して、半導体ウェハの集積回路が組み込まれた側の面（表面）に貼着する。次いで、研削機のチャックテーブル等に粘着フィルムの基材フィルム層を介して半導体ウェハを固定し、半導体ウェハの裏面（集積回路非形成面）を研削する。研削が終了した後、粘着フィルムは剥離される。ウェハの裏面の研削が完了した後、粘着フィルムを剥離する前にケミカルエッチング工程を経ることもある。また、必要に応じて粘着フィルム剥離後に、半導体ウェハ表面に対して、水洗、プラズマ洗浄等の処理が施される。
【００４４】
この様な裏面研削操作において、半導体ウェハは、研削前の厚みが、通常５００〜１０００μｍであるのに対して、半導体チップの種類等に応じ、通常１００〜６００μｍ程度まで研削される。必要に応じて、１００μｍより薄く削ることもある。研削する前の半導体ウェハの厚みは、半導体ウェハの直径、種類等により適宜決められ、研削後のウェハの厚みは、得られるチップのサイズ、回路の種類等により適宜決められる。
【００４５】
粘着フィルムを半導体ウェハに貼着する操作は、人手により行われる場合もあるが、一般に、ロール状の粘着フィルムを取り付けた自動貼り機と称される装置によって行われる。このような自動貼り機として、例えばタカトリ（株）製、形式：ＡＴＭ−１０００Ｂ、同ＡＴＭ−１１００、帝国精機（株）製、形式：ＳＴＬシリーズ等がある。
【００４６】
裏面研削方式としては、スルーフィード方式、インフィード方式等の公知の研削方式が採用される。それぞれ研削は、水を半導体ウェハと砥石にかけて冷却しながら行われる。裏面研削終了後、必要に応じてケミカルエッチングが行われる。ケミカルエッチングは、弗化水素酸、硝酸、硫酸、酢酸等の単独若しくは混合液からなる酸性水溶液、水酸化カリウム水溶液、水酸化ナトリウム水溶液等のアルカリ性水溶液からなる群から選ばれたエッチング液に、粘着フィルムを貼着した状態で半導体ウェハを浸漬する等の方法により行われる。該エッチングは、半導体ウェハ裏面に生じた歪の除去、ウェハのさらなる薄層化、酸化膜等の除去、電極を裏面に形成する際の前処理等を目的として行われる。エッチング液は、上記の目的に応じて適宜選択される。
裏面研削、ケミカルエッチング終了後、粘着フィルムはウェハ表面から剥離される。この一連の操作は、人手により行われる場合もあるが、一般には自動剥がし機と称される装置により行われる。このような自動剥がし機としては、タカトリ（株）製、形式：ＡＴＲＭ−２０００Ｂ、同ＡＴＲＭ−２１００、帝国精機（株）製、形式：ＳＴＰシリーズ等がある。
【００４７】
粘着フィルムを剥離した後のウェハ表面は、必要に応じて洗浄される。洗浄方法としては、水洗浄、溶剤洗浄等の湿式洗浄、プラズマ洗浄等の乾式洗浄等が挙げられる。湿式洗浄の場合、超音波洗浄を併用してもよい。これらの洗浄方法は、ウェハ表面の汚染状況により適宜選択される。
本発明の半導体ウェハ裏面研削用粘着フィルム及びそれを用いる半導体ウェハの裏面研削方法が適用できる半導体ウェハとして、シリコンウェハに限らず、ゲルマニウム、ガリウム−ヒ素、ガリウム−リン、ガリウム−ヒ素−アルミニウム等のウェハが挙げられる。
【００４８】
【実施例】
以下、実施例を示して本発明についてさらに詳細に説明する。以下に示す全ての実施例及び比較例において、米国連邦規格２０９ｂに規定されるクラス１，０００以下のクリーン度に維持された環境において粘着剤塗布液の調製及び塗布、並びに半導体シリコンウェハの裏面研削等を実施した。本発明はこれら実施例に限定されるものではない。尚、実施例に示した各種特性値は下記の方法で測定した。
（１）粘着力（ｇ／２５ｍｍ）
下記に規定した条件以外は、全てＪＩＳ Ｚ−０２３７−１９９１に準じて測定する。２３℃の雰囲気下において、実施例または比較例で得られた粘着フィルムをその粘着剤層を介して、５ｃｍ×２０ｃｍのＳＵＳ３０４−ＢＡ板（ＪＩＳＧ−４３０５−１９９１規定）の表面に貼着し、６０分放置する。試料の一端を挟持し、剥離角度１８０度、剥離速度３００ｍｍ／ｍｉｎ．でＳＵＳ３０４−ＢＡ板の表面から試料を剥離する際の応力を測定し、ｇ／２５ｍｍの粘着力に換算する。
（２）貯蔵弾性率（Ｐａ）
半導体ウェハ表面保護用粘着フィルムの粘着剤層の部分を厚さ１ｍｍになるように積層し、直径８ｍｍの粘弾性測定用試料を作製する。動的粘弾性測定装置（レオメトリックス社製：形式：ＲＭＳ−８００）を用いて、１５０℃及び２００℃において貯蔵弾性率を測定する。測定周波数は１Ｈｚとし、歪みは０．１〜３％とする。
（３）半導体ウェハの破損（枚数）
半導体ウェハ裏面研削工程、ダイボンディング用接着フィルム貼着工程、及び表面保護用粘着フィルム剥離工程における半導体ウェハの破損枚数を示す。
（４）汚染性評価
半導体シリコンウェハ（直径：８インチ、厚み：６００μｍ、スクライブラインの深さ：８μｍ、スクライブラインの幅：１００μｍ）の表面に試料用の表面保護用粘着フィルムをその粘着剤層を介して、半導体シリコンウェハの全表面に貼着し、半導体ウェハの裏面加工工程、ダイボンディング用接着フィルム貼着工程を経た後、粘着フィルムを剥離（日東精機（株）製、型式：ＨＲ８５００ＩＩ）した後の半導体ウェハの表面をレーザーフォーカス顕微鏡（ＫＥＹＥＮＣＥ製、形式：ＶＦ−７５１０、ＶＦ−７５００、ＶＰ−ＥＤ１００）を用いて２５０倍率で観察する。評価基準は、次の通り。○：糊残り無し。×：糊残り発生。
（５） 密着性（％）
集積回路が組み込まれた半導体シリコンウェハ（直径：６インチ、厚み：６００μｍ、スクライブラインの深さ：８μｍ、スクライブラインの幅：１００μｍ）の表面に試料用の粘着フィルムをその粘着剤層を介して、半導体シリコンウェハの全表面に貼着した状態で、レーザーフォーカス顕微鏡（ＫＥＹＥＮＣＥ製、形式：ＶＦ−７５１０、ＶＦ−７５００、ＶＰ−ＥＤ１００）を用いて２５０倍率で観察し、写真撮影する。密着性評価として、粘着剤のスクライブラインへの貼着面積とスクライブラインの全面積との比率をもって密着性の指標とし、粘着剤のスクライブラインへの貼着割合が７０％以上を高密着性とする。
【００４９】
実施例１
＜基材フィルムの作製＞
ショアーＤ型硬度が３５のエチレン−酢酸ビニル共重合体樹脂をＴ−ダイ押出機を用いて、厚み２００μｍのフィルムに成形した。この際、粘着剤層を塗布する側にコロナ処理を施した。得られたフィルムの厚みバラツキは±１．５％以内であった。
＜粘着剤主剤の重合＞
重合反応機に脱イオン水１５０重量部、重合開始剤として４，４’−アゾビス−４−シアノバレリックアシッド〔大塚化学（株）製、商品名：ＡＣＶＡ〕を０．６２５重量部、モノマー（Ａ）としてアクリル酸−２−エチルヘキシル９４重量部、モノマー（Ｂ）としてメタクリル酸−２−ヒドロキシエチル３重量部、及びアクリルアミド１重量部、モノマー（Ｃ）として２―メタクロイルオキシエチルサクシネート〔Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−〕２重量部、水溶性コモノマーとしてポリオキシエチレンノニルフェニルエーテル（エチレンオキサイドの付加モル数の平均値：約２０）の硫酸エステルのアンモニウム塩のベンゼン環に重合性の１−プロペニル基を導入したもの〔第一工業製薬（株）製、商品名：アクアロンＨＳ−１０〕０．７５重量部を装入し、攪拌下で７０〜７２℃において８時間乳化重合を実施し、アクリル系樹脂エマルションを得た。これを９重量％アンモニア水で中和（ｐＨ＝７．０）し、固形分４２．５重量％のアクリル系粘着剤ポリマー（粘着剤主剤）とした。
＜粘着剤塗布液の調製＞
得られた粘着剤主剤１００重量部（固形分）を採取し、さらに９重量％アンモニア水を加えてｐＨ９．５に調整した。次いで、エポキシ系架橋剤〔ナガセ化成工業（株）製、商品名：デナコールＥｘ−６１４〕０．５重量部を添加して粘着剤塗布液を得た。
＜粘着フィルムの作製＞
ロールコーターを用いて、上記粘着剤塗布液をポリプロピレンフィルム（剥離フィルム、厚み：５０μｍ）に塗布し、１２０℃で２分間乾燥して厚み４０μｍの粘着剤層を設けた。これに前述のエチレン−酢酸ビニル共重合体フィルム（基材フィルム）のコロナ処理面を貼り合わせ押圧して、粘着剤層を転写させた。転写後、６０℃において４８時間加熱した後、室温まで冷却することにより半導体ウェハ裏面研削用粘着フィルムを製造した。貯蔵弾性率の測定結果を〔表１〕に示す。また、汚染性評価結果等を表１にまとめた。
【００５０】
実施例２
実施例１の粘着剤主剤の重合において、モノマー（Ａ）の内アクリル酸−２−エチルヘキシルを８６重量部とし、モノマー（Ｃ）として２―メタクロイルオキシエチルサクシネート〔Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−〕を１０重量部とした以外は、コモノマー類と開始剤などの重合条件は全て実施例１と同一にて粘着剤主剤の重合を行った後、実施例１と同様の方法において粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの各種特性及び得られたチップ表面の汚染状況等を実施例１と同様にして評価した。測定結果を〔表１〕に示す。
【００５１】
実施例３
実施例１の粘着剤主剤の重合において、モノマー（Ｃ）として２―アクロイルオキシエチルサクシネート〔Ｒ＝ＣＨ_３、Ｘ＝−ＣＨ_２ＣＨ_２−ＯＯＣ−ＣＨ_２ＣＨ_２−〕を２重量部とした以外は、コモノマー類と開始剤などの重合条件は全て実施例１と同一にて粘着剤主剤の重合を行った後、実施例１と同様の方法において粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの各種特性及び得られたチップ表面の汚染状況等を実施例１と同様にして評価した。測定結果を〔表１〕に示す。
【００５２】
実施例４
実施例１の粘着剤主剤の重合において、モノマー（Ａ）をアクリル酸−２−エチルヘキシル６４重量部、アクリル酸−ｎ−ブチル１８重量部、及びメタクリル酸メチル１２重量部、モノマー（Ｂ）としてメタクリル酸−２−ヒドロキシエチル３重量部、及びアクリルアミド１重量部とした以外は、コモノマー類と開始剤などの重合条件は全て実施例１と同一にて粘着剤主剤の重合を行った後、実施例１と同様の方法において粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの各種特性及び得られたチップ表面の汚染状況等を実施例１と同様にして評価した。測定および評価結果を〔表１〕に示す。
【００５３】
実施例５
実施例１と同一の粘着剤主剤に対して、アジリジン系架橋剤〔日本触媒化学工業（株）製、商品名：ケミタイトＰｚ−３３〕０．８重量部添加して粘着剤塗布液を得た。その後、実施例１と同一の方法にて粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの各種特性及び得られたチップ表面の汚染状況等を実施例１と同様にして評価した。測定および評価結果を〔表１〕に示す。
【００５４】
【表１】

【００５５】
比較例１
実施例１において、モノマー（Ａ）をアクリル酸−２−エチルヘキシル９６重量部とし、モノマー（Ｃ）を使用しなかった以外は、実施例１と同一の方法にて粘着剤主剤の重合を行った後、実施例１と同様の方法において粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの粘着特性及びチップ表面の汚染状況等を実施例１と同様の手法を用いて評価した。測定および評価結果を〔表２〕に示す。
【００５６】
比較例２
実施例１と同一の粘着剤主剤に対して、架橋剤を使用しなかった以外は、実施例１と同一の方法にて粘着剤層の膜厚４０μｍの半導体ウェハ裏面研削用粘着フィルムを作製した。得られた粘着フィルムの各種特性及び得られたチップ表面の汚染状況等を実施例１と同様にして評価した。測定および評価結果を〔表２〕に示す。
【００５７】
比較例３
トルエン５０重量部及び酢酸エチル６５重量部の混合溶媒中、重合開始剤〔日本油脂（株）製 、ベンゾイルパーオキサイド系ナイパーＢＭＴ−Ｋ４０〕０．７重量部の存在下において、実施例１と同一の混合モノマーを用いて溶液重合を行ったところ、反応中にゲル化してしまい粘着剤主剤を得ることはできなかった。結果を〔表２〕に示す。
【００５８】
【表２】

【００５９】
【発明の効果】
本発明によれば、半導体ウェハの裏面を研削するに際し、裏面の研削応力に起因する研削中のウェハ破損が起こらないばかりでなく、ウェハ表面と粘着剤層との間に水及び研削屑が浸入することに起因するウェハの破損及びウェハ表面の汚染も起こらない。粘着フィルムをウェハから剥離する際のウェハの破損が起こらず、光照射装置等の設備を新たに導入する必要もない。さらに、粘着フィルムをウェハから剥離した後に糊残りがないので、半導体ウェハの表面を汚染することがない。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an adhesive film for grinding a back surface of a semiconductor wafer (hereinafter, adhesive film) and a method of grinding a back surface of a semiconductor wafer using the same. More specifically, the adhesive film is attached to a surface of a semiconductor wafer such as a silicon wafer on which the integrated circuit is incorporated (hereinafter, wafer surface), and another surface of the wafer (hereinafter, wafer back surface) is ground. The present invention relates to a method for grinding a back surface of a semiconductor wafer useful for preventing damage to a semiconductor wafer, and an adhesive film for grinding a back surface of a semiconductor wafer used in the method.
[0002]
[Prior art]
Normally, a semiconductor integrated circuit is formed by slicing a high-purity silicon single crystal or the like into a wafer, incorporating the integrated circuit by ion implantation, etching, etc., and further grinding the back surface of the wafer by grinding, polishing, lapping, etc. It is manufactured by a method in which the thickness is reduced to about 100 to 600 μm and then diced into chips. In these steps, an adhesive film for grinding the back surface of the semiconductor wafer is attached to the wafer surface via the adhesive layer to prevent breakage of the semiconductor wafer when grinding the back surface of the wafer and to facilitate the grinding process. Protection methods are used. Specifically, an adhesive film for grinding the back surface of a semiconductor wafer is directly adhered to the wafer surface via the adhesive layer to protect the wafer surface, and then the back surface of the wafer is ground. After the grinding is completed, the adhesive film is peeled off from the wafer surface.
[0003]
When using a conventional adhesive film for grinding the back surface of a semiconductor wafer when grinding the back surface of a semiconductor wafer in which an integrated circuit is incorporated up to the peripheral portion of the wafer, that is, a scribe line reaches the outermost periphery of the wafer. In some cases, water may enter between the wafer surface and the adhesive layer through the concave portion based on the scribe line, causing damage to the wafer or grinding debris entering with the water to contaminate the wafer surface. Was. In order to prevent these problems, measures have been taken to increase the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film and improve the adhesion between the concave portion on the wafer surface and the pressure-sensitive adhesive layer. However, when this method is used, the adhesive strength of the adhesive film to the wafer surface becomes greater than the strength of the wafer, and depending on various conditions such as the thickness and surface shape of the wafer, the adhesive film may be removed from the wafer surface after grinding the back surface. When peeling off from the wafer, a peeling trouble may occur in the automatic peeling machine or the wafer may be broken.
[0004]
As means for solving such a problem, for example, in Japanese Patent Application Laid-Open No. 60-189938, when grinding the back surface of a semiconductor wafer, a pressure-sensitive adhesive film is attached to the wafer surface, and after grinding, the adhesive film is removed. In the method for protecting a semiconductor wafer to be peeled, the above-mentioned pressure-sensitive adhesive film has a light-transmitting support and a pressure-sensitive adhesive layer having a property of being cured by light irradiation provided on the support to form a three-dimensional network. A method for protecting a semiconductor wafer, comprising irradiating the adhesive film with light after grinding and before peeling the adhesive film, is disclosed.
[0005]
The method for protecting a semiconductor wafer disclosed in the above invention can reduce the adhesive force of the adhesive film to the wafer surface by irradiating light before peeling, so that the problem of peeling workability and wafer breakage is not considered. In addition, the adhesion to the wafer surface during the back surface grinding can be sufficiently increased, and the problem of the intrusion of water and grinding debris between the wafer surface and the adhesive layer can be solved.
[0006]
However, when using this adhesive film, it is necessary to irradiate the light before the adhesive film is peeled off from the wafer surface after the back surface grinding, so it is necessary to introduce light irradiation equipment during the process, There has been a problem that the apparatus becomes larger and more complicated, and that the process becomes more complicated and the workability is reduced. It has also been pointed out that the working environment is deteriorated by ozone generated by light irradiation. Further, depending on various conditions such as the surface shape of the wafer, the light irradiation intensity, and the time, a problem of adhesive residue may occur on the wafer surface after peeling due to poor curing of the adhesive layer. In order to prevent the problem, it is necessary to fill the inside of the light irradiation device with an inert gas such as nitrogen, which raises the manufacturing cost and causes a further increase in the size and complexity of the process. .
[0007]
In order to solve these problems, the present inventors have disclosed in Japanese Patent Application Laid-Open No. H11-315259 a semiconductor having a pressure-sensitive adhesive layer containing a specific alkylene glycol-based polymer as an essential component. A protective adhesive film for wafer was proposed. The protective adhesive film of the semiconductor wafer, when grinding the back surface of the semiconductor wafer, suppresses damage to the wafer and contamination of the wafer surface due to water and grinding debris entering between the wafer surface and the adhesive layer. Can be. In other words, since the adhesive force is within an appropriate range, the wafer does not break when the adhesive film is peeled off from the wafer, and there is no need to newly introduce equipment such as a light irradiation device into the process. Since there is no adhesive residue after peeling, there is a feature that the surface of the semiconductor wafer is not contaminated.
[0008]
However, in recent years, with the demand for technological innovation and cost reduction in the semiconductor industry, semiconductor wafers tend to become larger and thinner year by year. In particular, as the demand for thinner semiconductor chips, such as thinner packaging and smart card applications, is increasing, the thickness of semiconductor wafers after back grinding is becoming thinner. is there. Since the time required for the back surface grinding increases with the area of the wafer, the problem of breakage and contamination of the wafer due to the intrusion of water and grinding dust during the grinding is considered to occur more easily as the size of the wafer increases. Furthermore, considering that the strength of the wafer itself decreases as the thickness of the wafer becomes thinner, the problem of the wafer being damaged at the time of peeling described above will become more serious with the thinner wafer. is expected.
[0009]
In addition, with the recent miniaturization and weight reduction of semiconductor devices, the diversification of the semiconductor wafer surface is rapidly progressing, and the surface shape of the adhesive for CPUs, flash memories, smart cards, etc. tends to remain. Wafers are increasing. For example, as a wafer having a chip suitable for smart card use, a wafer having a protruding high bump electrode having a height of 5 to 300 μm has been produced. When grinding the back surface of a semiconductor wafer having a protruding high bump electrode on the surface as described above, a part of the adhesive remains on the surface of the wafer when the adhesive film is peeled from the ground wafer, The surface could be contaminated. Contamination due to the adhesive residue often occurs particularly around the high bump electrodes. In such a case, it is difficult to remove the contamination even by post-processing such as cleaning, which may be a particularly serious problem.
[0010]
Under such circumstances, conventionally, the adhesive film for grinding the back surface of the semiconductor wafer adheres well to the concave portion of the wafer surface when grinding the back surface, and water infiltrates between the wafer surface and the pressure-sensitive adhesive layer. There are demands for performance such as not causing breakage or polishing debris to enter and causing contamination of the wafer surface, being capable of peeling with an appropriate adhesive force during peeling, and not contaminating the wafer surface after peeling. However, their required levels have become increasingly severe in recent years and are expected to become even more severe in the future. Therefore, there is a demand for an adhesive film for grinding the back surface of a semiconductor wafer that can meet the above-mentioned requirements at a higher level.
[0011]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to have an appropriate adhesive force that withstands the stress when grinding the back surface of the wafer and does not damage the wafer when peeling, and has excellent adhesion to the wafer surface and low contamination. An object of the present invention is to provide an adhesive film for grinding a back surface of a semiconductor wafer having the same, and a method for grinding a back surface of a semiconductor wafer using the same.
[0012]
[Means for Solving the Problems]
The present inventors consider the problem of contamination, and in order to express high cohesion, project a carboxylic acid serving as a crosslinking base point on the surface of the acrylic pressure-sensitive adhesive polymer, whereby the crosslinking reaction proceeds efficiently. As a result of intensive investigations, a specific amount of (meth) acrylic acid alkyl ester-based monomer unit (A), a monomer having a functional group capable of reacting with a cross-linking agent, when polymerizing an acrylic pressure-sensitive adhesive polymer by emulsion polymerization The inventors have found that the above problem can be solved by including the unit (B) and the (meth) acrylic acid derivative carboxylic acid (C) having a specific structure as a monomer, and have reached the present invention.
That is, the present invention
(1) A pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer in which a pressure-sensitive adhesive layer is provided on one surface of a substrate film, wherein the pressure-sensitive adhesive layer contains (A) an alkyl ester (meth) acrylate monomer in the total amount of monomers. 10% by weight or more and 98% by weight or less, and 1% by weight or more and 40% by weight or less of the monomer (B) having a functional group can react with the crosslinking agent represented by the general formula (1) An acrylic polymer prepared by emulsion polymerization of a monomer composition containing 1% by weight or more and 20% by weight or less of an acrylic acid derivative carboxylic acid (C);
[0013]
Embedded image

[0014]
(In the general formula (1), R represents a hydrogen atom or an alkyl group, and X represents a divalent hydrocarbon group having 4 to 9 carbon atoms including an ester group and / or an ether group.)
And a pressure-sensitive adhesive containing 0.1 to 30 parts by weight of a crosslinking agent having two or more functional groups in one molecule per 100 parts by weight of the acrylic polymer, and storing the pressure-sensitive adhesive layer at 0 to 200 ° C. Elastic modulus is 1 × 10 ³ Pa or more, 1 × 10 ⁵ An adhesive film for protecting a surface of a semiconductor wafer, wherein the pressure-sensitive adhesive film has a thickness of 3 to 100 μm or less.
(2) The back surface of the semiconductor wafer according to (1), wherein the (meth) acrylic acid alkyl ester-based monomer (A) is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms. Adhesive film for grinding.
(3) The monomer unit (B) having a functional group is at least one kind selected from acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, and methacrylamide. The adhesive film for grinding a back surface of a semiconductor wafer according to (1) or (2), which is a monomer.
(4) The acrylic polymer contained the above (A) in an amount of 85 to 99% by weight, the above (B) in an amount of 1 to 10% by weight, and the above (C) in an amount of 2 to 10% by weight. The adhesive film for grinding the back surface of a semiconductor wafer according to any one of (1) to (3), wherein the adhesive film is an acrylic polymer prepared by emulsion polymerization of a monomer composition.
(5) The pressure-sensitive adhesive film for grinding the back surface of a semiconductor wafer according to any one of (1) to (4), wherein the thickness of the base film is 10 to 500 μm.
(6) A method for grinding the back surface of a semiconductor wafer using the adhesive film for grinding the back surface of a semiconductor wafer according to any one of (1) to (5), wherein the adhesive for grinding the back surface of the semiconductor wafer is attached to a circuit forming surface of the semiconductor wafer. A method of grinding a back surface of a semiconductor wafer, comprising attaching a film, grinding the back surface of the semiconductor wafer, and peeling off the adhesive film after finishing the grinding.
About.
The first feature of the adhesive film for grinding a back surface of a semiconductor wafer according to the present invention is that an acrylic polymer containing a specific amount of an acrylic acid derivative carboxylic acid represented by the general formula (1) as a monomer is used. In that the polymer is prepared by emulsion copolymerization. The second characteristic is that the pressure-sensitive adhesive layer has a storage elastic modulus of 1 × 10 at 0 to 200 ° C. ³ Pa or more, 1 × 10 ⁵ The point lies in the range of Pa or less.
[0015]
The adhesive tape for grinding the backside of a semiconductor wafer having such characteristics improves the adhesion between the wafer surface and the adhesive layer when grinding the backside of the semiconductor wafer, and causes water and grinding chips to enter in the backside grinding process. Wafer damage and contamination of the wafer surface do not occur. Further, since the adhesive film has an appropriate adhesive strength, it does not peel off when grinding the back surface of the wafer, and does not break when the adhesive film is peeled off from the wafer. Further, since contamination due to adhesive residue or the like does not occur after the adhesive film is separated from the wafer, the surface of the semiconductor wafer is not contaminated.
[0016]
In addition, the storage elastic modulus at 0 to 200 ° C. of the pressure-sensitive adhesive layer in the present invention means a value measured by a method described in Examples described later.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail. The present invention relates to an adhesive film for grinding the back surface of a semiconductor wafer in which an adhesive layer having a specific composition is formed on one surface of a base film, and a method for grinding the back surface of a semiconductor wafer using the adhesive film.
[0018]
The adhesive film for grinding the back surface of a semiconductor wafer of the present invention is a solution or an emulsion solution containing an acrylic adhesive polymer, a cross-linking agent, and other additives as necessary, on one surface of a base film or a release film (hereinafter, referred to as an “adhesive film”). These are collectively referred to as a pressure-sensitive adhesive coating solution) and dried to form a pressure-sensitive adhesive layer.
[0019]
When the pressure-sensitive adhesive coating solution is applied to one surface of the base film to form a pressure-sensitive adhesive layer, a release film is adhered to the surface of the applied pressure-sensitive adhesive layer in order to protect it from contamination due to the environment. Is preferred. On the other hand, when an adhesive coating solution is applied to one surface of a release film to form an adhesive layer, a method of transferring the adhesive layer to a base film is employed. Which surface of the base film or the release film is coated with the pressure-sensitive adhesive coating solution is determined in consideration of the heat resistance of the base film and the release film and the contamination of the surface of the semiconductor wafer. For example, when the heat resistance of the release film is superior to that of the base film, it is preferable to provide an adhesive layer on the surface of the release film and then transfer the film to the base film. When the heat resistance is the same or the base film is excellent, it is preferable to provide an adhesive layer on the surface of the base film, and attach a release film to the surface.
[0020]
However, in consideration of the fact that the adhesive film for grinding the back surface of the semiconductor wafer is attached to the surface of the semiconductor wafer through the surface of the adhesive layer that is exposed when the release film is peeled, contamination of the surface of the semiconductor wafer with the adhesive layer is considered. In order to prevent this, it is better to use a release film with good heat resistance, apply an adhesive coating solution on the surface, dry it to form an adhesive layer, and transfer this to the base film. preferable. The pressure-sensitive adhesive film for grinding the back surface of a semiconductor wafer of the present invention is usually stored in a state where a release film is adhered to the surface of the pressure-sensitive adhesive layer, and is peeled off when used.
[0021]
As the base film used in the present invention, a film obtained by molding a synthetic resin into a film shape is used. The base film may be a single layer or a laminate. The thickness of the base film is preferably from 10 to 500 μm. More preferably, it is 70 to 500 μm. Examples of the raw material resin of the base film include synthetic resins such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, polyvinyl chloride, polyamide, and polyethylene terephthalate. Can be
[0022]
Among these, in consideration of the protection performance of the wafer during backside grinding, a raw material resin having a Shore D-type hardness of 40 or less specified in ASTM-D-2240-86 or JIS K-7215-1986 is particularly preferable. preferable. When these resins are formed into a film, a stabilizer, a lubricant, an antioxidant, a pigment, an antiblocking agent, a plasticizer, and the like may be added as necessary. When various additives such as a stabilizer are added during the molding process of the base film, the additives may transfer to the pressure-sensitive adhesive layer, change the properties of the pressure-sensitive adhesive, or contaminate the wafer surface. In such a case, it is preferable to provide a barrier layer between the base film and the pressure-sensitive adhesive layer.
[0023]
In addition, when the surface of the semiconductor wafer is protected by using the adhesive film for grinding the back surface of the semiconductor wafer during the etching process using the etchant applied after the grinding of the back surface of the semiconductor wafer, the chemical resistance is excellent. It is preferable to use a base film that has been used. For example, a chemical-resistant film such as polypropylene is laminated on the surface of the base film opposite to the side on which the pressure-sensitive adhesive layer is provided. In order to improve the adhesive strength between the base film and the pressure-sensitive adhesive layer, it is preferable that the surface of the base film on which the pressure-sensitive adhesive layer is provided is subjected to corona discharge treatment or chemical treatment in advance. Further, a primer may be used between the base film and the pressure-sensitive adhesive layer. The base film used in the present invention is selected from those manufactured by a known technique such as a calendar method, a T-die extrusion method, an inflation method, etc., in consideration of productivity, thickness accuracy of the obtained film, and the like. Can be.
[0024]
Examples of the release film used in the present invention include synthetic resin films such as polypropylene and polyethylene terephthalate. It is preferable that the surface thereof is subjected to a silicone treatment or the like as necessary. The thickness of the release film is usually from 10 to 200 μm. Preferably it is 30 to 100 μm.
[0025]
The pressure-sensitive adhesive coating liquid used in the present invention is represented by a (meth) acrylic acid alkyl ester monomer unit (A), a monomer unit (B) having a functional group capable of reacting with a crosslinking agent, and the general formula (1). Acrylic pressure-sensitive adhesive polymer of a copolymer obtained by emulsion polymerization of a monomer composition containing a specific amount of carboxylic acid (C), and one molecule of a functional group for increasing cohesive strength or adjusting adhesive strength It is composed of a solution or an emulsion liquid containing a crosslinking agent having two or more crosslinking agents. When used in a solution, the acrylic pressure-sensitive adhesive polymer used in the present invention is used after separating the acrylic pressure-sensitive adhesive polymer from the emulsion liquid obtained by emulsion polymerization by salting out and then re-dissolving with a solvent or the like. Has a sufficiently large molecular weight, often has low solubility in a solvent, or does not dissolve in many cases. From the viewpoint of cost, it is preferable to use the emulsion as it is.
[0026]
The acrylic pressure-sensitive adhesive polymer used in the present invention is obtained by reacting an alkyl acrylate, an alkyl methacrylate, or a mixture thereof with a main monomer (hereinafter, monomer (A)), a monomer (B) having a functional group, and a crosslinking agent. A (meth) acrylic acid derivative is obtained by copolymerizing a monomer composition containing a carboxylic acid (C).
[0027]
Examples of the monomer (A) include alkyl acrylates or alkyl methacrylates having an alkyl group having about 1 to 12 carbon atoms (hereinafter, these are collectively referred to as alkyl (meth) acrylates). Preferably, it is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate. These may be used alone or as a mixture of two or more. It is preferable that the amount of the monomer (A) used is usually in the range of 10 to 98% by weight based on the total amount of the polymerizable monomer which is a raw material of the pressure-sensitive adhesive polymer. More preferably, it is 85 to 95% by weight. By setting the amount of the monomer (A) to be in such a range, a polymer containing 10 to 98% by weight, preferably 85 to 95% by weight of the alkyl (meth) acrylate monomer unit (A) can be obtained.
[0028]
Examples of the monomer unit (B) having a functional group capable of reacting with a crosslinking agent include acrylic acid, methacrylic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, maleic acid, monoalkyl itaconate, and monoalkyl mesaconic ester Monoalkyl citraconic acid, monoalkyl fumarate, monoalkyl maleate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, tert-butylaminoethyl acrylate, tert-butyl Aminoethyl methacrylate and the like can be mentioned. Preferably, acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide and the like are mentioned. One of these may be copolymerized with the main monomer (A), or two or more thereof may be copolymerized. It is preferable that the amount of the monomer (B) having a functional group capable of reacting with the crosslinking agent is usually contained in the range of 1 to 40% by weight in the total amount of the polymerizable monomers which are the raw materials of the pressure-sensitive adhesive polymer. . More preferably, it is 1 to 10% by weight. Thus, a polymer having a constitutional unit (B) having a composition substantially equal to the monomer composition is obtained.
[0029]
In the present invention, as a measure for expressing high cohesive force and adhesion, attention is paid to the cross-linking base point of the polymer surface formed after polymerization, and a (meth) acrylic acid derivative carboxylic acid is put into the polymerization solution to change the cross-linking point of the polymer. Protruding the surface gives the ability to react with a crosslinking agent having two or more functional groups in one molecule. Thereby, a high cohesive force can be exhibited, and the storage elastic modulus can be adjusted by the added carboxylic acid, so that a high adhesion can be exhibited. The carboxylic acid (C) represented by the general formula (1) is suitable for the purpose of the present invention from the viewpoints of reactivity, coloring, availability, and the like.
[0030]
By copolymerizing a specific carboxylic acid (C) with the acrylic pressure-sensitive adhesive polymer, the adhesiveness between the pressure-sensitive adhesive layer and the wafer surface is improved, and between the wafer surface and the pressure-sensitive adhesive layer when grinding the back surface of the wafer. Has the effect of preventing water from entering the wafer (hereinafter referred to as "water resistance"), does not cause breakage of the wafer when the adhesive film is peeled off from the wafer surface, and has a wafer surface (particularly a wafer having a high bump electrode) caused by the adhesive layer. In this case, a pressure-sensitive adhesive that does not cause contamination of the high bump electrode) can be obtained.
The amount of the carboxylic acid (C) represented by the general formula (1) affects the stability and the elastic modulus during the emulsion polymerization, and if the amount is too large, the polymerization stability decreases and the elasticity is reduced. Rates tend to increase.
From such a viewpoint, the amount of the carboxylic acid represented by the general formula (1) is 1% by weight or more and 20% by weight or less, preferably 2% by weight or more and 10% by weight or less in the monomer raw material.
[0031]
In the general formula (1), R is hydrogen or an alkyl group, and examples of the alkyl group include a methyl group. X is a divalent hydrocarbon having 4 to 9 carbon atoms containing an ester group and / or an ether group. An example of such a carboxylic acid is 2-methacryloyloxyethyl succinate (R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -), 2-Acroyloxyethyl succinate (R = H, X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -), 3-methacryloyloxypropyl succinate (R = CH ₃ , X = -CH ₂ CH ₂ CH ₂ -OOC-CH ₂ CH2-), 3-Acroyloxypropyl succinate (R = H, X = -CH ₂ CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -), 2-methacryloyloxyethyl malate (R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH = CH-), 2-Acroyloxyethyl malate (R = H, X = -CH ₂ CH ₂ -OOC-CH = CH-), 3-methacryloyloxypropyl malate (R = CH ₃ , X = -CH ₂ CH ₂ CH ₂ -OOC-CH = CH-), 3-Acroyloxypropyl malate (R = H, X = -CH ₂ CH ₂ CH ₂ -OOC-CH = CH-), 2-methacryloyloxyethyl phthalate (R = CH ₃ , X = -CH ₂ CH ₂ -OOC-C ₆ H ₄ -), 2-Acroyloxyethyl phthalate (R = H, X = -CH ₂ CH ₂ -OOC-C ₆ H ₄ -), 3-methacryloyloxypropyl phthalate (R = CH ₃ , X = -CH ₂ CH ₂ CH ₂ -OOC-C ₆ H ₄ -), 2-Acroyloxypropyl phthalate (R = H, X = -CH ₂ CH ₂ CH ₂ -OOC-C ₆ H ₄ -) And the like, and these may be used alone or in combination of two or more.
[0032]
In the present invention, a specific comonomer having properties as a surfactant (hereinafter, referred to as a polymerizable surfactant) may be copolymerized. The polymerizable surfactant has a property of copolymerizing with the main monomer and the comonomer, and has an action as an emulsifier when emulsion polymerization is performed. When an acrylic pressure-sensitive adhesive polymer emulsion-polymerized using a polymerizable surfactant is used, the surface of the wafer is not normally contaminated by the surfactant. In addition, even when slight contamination caused by the pressure-sensitive adhesive layer occurs, it can be easily removed by washing the wafer surface with water.
[0033]
Examples of such a polymerizable surfactant include those obtained by introducing a polymerizable 1-propenyl group into a benzene ring of polyoxyethylene nonyl phenyl ether [manufactured by Daiichi Kogyo Seiyaku Co., Ltd .; trade name: Aqualon RN-10, RN-20, RN-30, RN-50, etc.), and those in which a polymerizable 1-propenyl group is introduced into the benzene ring of an ammonium salt of a sulfate of polyoxyethylene nonylphenyl ether [No. Manufactured by Ichi Kogyo Seiyaku Co., Ltd .; trade name: Aqualon HS-10, HS-20, etc.) and sulfosuccinic acid diester having a polymerizable double bond in the molecule [manufactured by Kao Corporation; trade name: Latemul S-120A, S-180A etc.].
Further, if necessary, a monomer having a polymerizable double bond such as vinyl acetate, acrylonitrile, and styrene may be copolymerized. The amount of the surfactant to be used is 0.1 to 5 parts by weight, preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the monomer material.
[0034]
Examples of the polymerization reaction mechanism of the acrylic pressure-sensitive adhesive polymer include radical polymerization, anionic polymerization, and cationic polymerization. In consideration of the production cost of the pressure-sensitive adhesive, the influence of the functional group of the monomer, the influence of ions on the surface of the semiconductor wafer, and the like, it is preferable to perform polymerization by radical polymerization. When polymerizing by radical polymerization reaction, organic radicals such as benzoyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, di-tert-butyl peroxide, di-tert-amyl peroxide are used as radical polymerization initiators. Inorganic peroxides such as peroxides, ammonium persulfate, potassium persulfate, and sodium persulfate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 4,4 And azo compounds such as' -azobis-4-cyanovaleric acid.
[0035]
Since the acrylic pressure-sensitive adhesive polymer is polymerized by an emulsion polymerization method, among these radical polymerization initiators, inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate; And azo compounds having a carboxyl group in the molecule, such as 4,4'-azobis-4-cyanovaleric acid. Considering the influence of ions on the surface of the semiconductor wafer, azo compounds having a carboxyl group in the molecule, such as ammonium persulfate and 4,4′-azobis-4-cyanovaleric acid, are more preferable. An azo compound having a carboxyl group in the molecule such as 4,4'-azobis-4-cyanovaleric acid is particularly preferred.
[0036]
The crosslinking agent having two or more crosslinkable functional groups in one molecule used in the present invention is used to react with the functional group of the acrylic pressure-sensitive adhesive polymer to adjust the adhesive strength and cohesive strength. Examples of the crosslinking agent include epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, and resorcin diglycidyl ether. , Tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate 3 adduct of trimethylolpropane, isocyanate compounds such as polyisocyanate, trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β- Aziridinyl propionate, N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxyamido ), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N'-toluene-2,4-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β Aziridine compounds such as-(2-methylaziridine) propionate; and melamine compounds such as hexamethoxymethylolmelamine. These may be used alone or in combination of two or more.
[0037]
The content of the cross-linking agent is usually within a range where the number of functional groups in the cross-linking agent does not become larger than the number of functional groups in the acrylic pressure-sensitive adhesive polymer. However, when a new functional group is generated by a crosslinking reaction, or when a crosslinking reaction is slow, an excessive amount may be contained as necessary. The preferred content is 0.1 to 30 parts by weight, more preferably 0.1 to 15 parts by weight, of the crosslinking agent based on 100 parts by weight of the acrylic pressure-sensitive adhesive polymer. When the content is small, the cohesive force of the pressure-sensitive adhesive layer becomes insufficient, and adhesive residue due to the pressure-sensitive adhesive layer easily occurs on the wafer surface (especially, in the case of a wafer having a high bump electrode, around the high bump electrode). Also, the adhesive strength may be increased outside the range of the present invention, and when the adhesive film is peeled off from the wafer surface, a peeling trouble may occur in an automatic peeling machine or the wafer may be completely damaged. If the content is high, the adhesion between the pressure-sensitive adhesive layer and the wafer surface will be weak, and water or grinding chips may enter during grinding, damaging the wafer, or causing contamination of the wafer surface by the grinding chips. is there.
[0038]
The pressure-sensitive adhesive coating solution used in the present invention includes, in addition to an acrylic pressure-sensitive adhesive polymer obtained by copolymerizing the above-mentioned specific bifunctional monomer, a cross-linking agent, a rosin-based or terpene resin-based tackifier for adjusting the adhesive properties. And various surfactants and the like may be appropriately contained to such an extent that the purpose of the present invention is not affected. When the coating liquid is an emulsion liquid, a film-forming auxiliary such as diethylene glycol monoalkyl ether may be appropriately added to such an extent that the purpose of the present invention is not affected. Considering that diethylene glycol monoalkyl ether and its derivatives used as a film-forming aid may cause contamination of the wafer surface to such an extent that cleaning becomes impossible when contained in a large amount in the pressure-sensitive adhesive layer. It is preferable to use a substance which volatilizes at the temperature at the time of drying after the application of the pressure-sensitive adhesive, so as to reduce the amount remaining in the pressure-sensitive adhesive layer.
The thickness of the pressure-sensitive adhesive layer is preferably from 3 to 100 μm. A more preferred thickness is 5 to 80 μm. When the thickness of the pressure-sensitive adhesive layer is reduced, the water resistance is poor, and water enters between the surface of the wafer and the pressure-sensitive adhesive layer during back surface grinding, which may damage the wafer or cause contamination of the wafer surface by grinding debris. Tend to. When the thickness of the pressure-sensitive adhesive layer is increased, it may be difficult to prepare a pressure-sensitive adhesive film, or may affect productivity, leading to an increase in manufacturing cost.
[0039]
The storage elastic modulus in the present invention is obtained by applying a periodic deformation (strain) such as tension, bending, torsion, etc. to an object under a controlled temperature from the outside, and generating a response (stress) by dynamic viscoelasticity. It is measured using a measuring device. As a method of giving a periodic deformation to an object, for example, a method of sandwiching the object between two parallel disks and rotating the disk, a method of inserting a measurement needle into the object and vibrating the measurement needle And the like. As a dynamic viscoelasticity measuring device, for example, Rheometrics, model: RMS-800, Orientec, model: Rheovibron, DDV-II-EP, Seiko Instruments, model: EXSTAR6000, TMA / SS, etc. Is mentioned.
[0040]
The storage elastic modulus at 0 to 200 ° C. of a pressure-sensitive adhesive layer containing 100 parts by weight of the pressure-sensitive adhesive polymer and 0.1 to 30 parts by weight of a cross-linking agent having two or more cross-linking reactive functional groups in one molecule is 1 × 10 ³ Pa or more, 1 × 10 ⁵ It is preferable to adjust the crosslinking agent so as to be in the range of Pa or less.
If the storage elastic modulus of the pressure-sensitive adhesive layer is low, the wafer surface after the release of the pressure-sensitive adhesive film may become contaminated. When the storage elastic modulus of the pressure-sensitive adhesive layer increases, the adhesion to the wafer surface decreases, and grinding water or a chemical solution may enter.
The adhesive force of the adhesive film for grinding the back surface of a semiconductor wafer in the present invention can be appropriately adjusted in consideration of the grinding conditions of the wafer surface, the diameter of the wafer, the thickness of the wafer after grinding, and the like. Adhesion of the adhesive film to the wafer becomes difficult, water infiltrates between the wafer surface and the adhesive layer during the back surface grinding, and the wafer is damaged or the wafer surface is contaminated by grinding debris or the like. There is a tendency. Also, if the adhesive force is too high, when peeling the adhesive film from the wafer surface after grinding the back surface, peeling trouble may occur in an automatic peeling machine, and peeling workability may be reduced or the wafer may be damaged. is there. Usually, it is 5 to 500 g / 25 mm, preferably 10 to 200 g / 25 mm in terms of the adhesive strength to the SUS304-BA plate.
[0041]
As a method of applying the pressure-sensitive adhesive coating solution to one surface of the base film or the release film, conventionally known coating methods, for example, a roll coater method, a reverse roll coater method, a gravure roll method, a bar coat method, a comma coater method, a die coater Method can be adopted. There are no particular restrictions on the drying conditions of the applied pressure-sensitive adhesive, but it is generally preferable to dry the adhesive in a temperature range of 80 to 200 ° C. for 10 seconds to 10 minutes. More preferably, drying is performed at 80 to 170 ° C. for 15 seconds to 5 minutes.
In order to sufficiently promote the crosslinking reaction between the crosslinking agent and the adhesive polymer, after the drying of the adhesive coating solution is completed, the adhesive film for grinding the back surface of the semiconductor wafer is heated at 40 to 80 ° C. for about 5 to 300 hours. May be.
The method for producing an adhesive film for grinding a back surface of a semiconductor wafer in the present invention is as described above, but from the viewpoint of preventing contamination of the semiconductor wafer surface, production of all raw materials such as a base film, a release film, and an adhesive base material. It is preferable that the environment, the preparation, storage, application and drying environment of the adhesive coating solution be maintained at a cleanliness of class 1,000 or less specified in US Federal Standard 209b.
[0042]
Next, a method for grinding the back surface of a semiconductor wafer according to the present invention will be described. The method of grinding the back surface of a semiconductor wafer according to the present invention is characterized in that when grinding the back surface of the semiconductor wafer, an adhesive film for grinding the back surface of the semiconductor wafer manufactured by the above method is used.
[0043]
Specifically, first, the release film is peeled off from the adhesive layer of the adhesive film for grinding the back surface of the semiconductor wafer, the surface of the adhesive layer is exposed, and the integrated circuit of the semiconductor wafer is integrated through the adhesive layer. Adhere to the surface (surface). Next, the semiconductor wafer is fixed to a chuck table or the like of a grinding machine via the base film layer of the adhesive film, and the back surface (the surface on which the integrated circuit is not formed) of the semiconductor wafer is ground. After the grinding is completed, the adhesive film is peeled off. After the grinding of the back surface of the wafer is completed, a chemical etching process may be performed before the adhesive film is peeled off. If necessary, after peeling off the adhesive film, the surface of the semiconductor wafer is subjected to processing such as water washing and plasma washing.
[0044]
In such a back surface grinding operation, the thickness of the semiconductor wafer before grinding is usually 500 to 1000 μm, but is typically ground to about 100 to 600 μm depending on the type of semiconductor chip and the like. If necessary, the thickness may be reduced to less than 100 μm. The thickness of the semiconductor wafer before grinding is appropriately determined according to the diameter and type of the semiconductor wafer, and the thickness of the wafer after grinding is appropriately determined according to the size of the obtained chip, the type of circuit, and the like.
[0045]
The operation of attaching the adhesive film to the semiconductor wafer may be performed manually, but is generally performed by an apparatus called an automatic attaching machine to which a roll-shaped adhesive film is attached. As such an automatic pasting machine, there are, for example, a model: ATM-1000B and ATM-1100, manufactured by Takatori Co., Ltd., a model: STL series, manufactured by Teikoku Seiki Co., Ltd.
[0046]
As the back surface grinding method, a known grinding method such as a through-feed method and an in-feed method is employed. Each grinding is performed while cooling the semiconductor wafer and the grinding wheel with water. After the back surface grinding, chemical etching is performed as necessary. Chemical etching adheres to an etching solution selected from the group consisting of an acidic aqueous solution composed of a single or mixed solution of hydrofluoric acid, nitric acid, sulfuric acid, and acetic acid, and an alkaline aqueous solution such as a potassium hydroxide aqueous solution and a sodium hydroxide aqueous solution. This is performed by a method such as immersing the semiconductor wafer with the film adhered. The etching is performed for the purpose of removing distortion generated on the back surface of the semiconductor wafer, further reducing the thickness of the wafer, removing an oxide film and the like, and performing pretreatment before forming electrodes on the back surface. The etching solution is appropriately selected according to the above purpose.
After the back surface grinding and the chemical etching are completed, the adhesive film is peeled off from the wafer surface. This series of operations may be performed manually, but is generally performed by a device called an automatic peeling machine. Examples of such an automatic peeling machine include Takatori Co., Ltd., Model: ATRM-2000B and ATRM-2100, Teikoku Seiki Co., Ltd., Model: STP series.
[0047]
The wafer surface from which the adhesive film has been peeled off is cleaned as necessary. Examples of the cleaning method include wet cleaning such as water cleaning and solvent cleaning, and dry cleaning such as plasma cleaning. In the case of wet cleaning, ultrasonic cleaning may be used together. These cleaning methods are appropriately selected depending on the state of contamination on the wafer surface.
The semiconductor wafer to which the adhesive film for grinding the backside of a semiconductor wafer of the present invention and the method for grinding the backside of a semiconductor wafer using the same are not limited to a silicon wafer, but include germanium, gallium-arsenic, gallium-phosphorus, gallium-arsenic-aluminum and the like. Wafer.
[0048]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In all of the following examples and comparative examples, preparation and application of an adhesive coating solution, and backside grinding of a semiconductor silicon wafer in an environment maintained at a cleanliness level of 1,000 or less specified in US Federal Standard 209b. And so on. The present invention is not limited to these examples. The various characteristic values shown in the examples were measured by the following methods.
(1) Adhesive strength (g / 25mm)
Except for the conditions specified below, all measurements are performed according to JIS Z-0237-1991. Under an atmosphere of 23 ° C., the pressure-sensitive adhesive film obtained in the example or the comparative example was adhered to the surface of a 5 cm × 20 cm SUS304-BA plate (JISG-4305-1991) through the pressure-sensitive adhesive layer, Leave for 60 minutes. One end of the sample was sandwiched, and a peeling angle of 180 ° and a peeling speed of 300 mm / min. Is used to measure the stress when the sample is peeled off from the surface of the SUS304-BA plate, and is converted to an adhesive force of g / 25 mm.
(2) Storage modulus (Pa)
The pressure-sensitive adhesive layer portion of the pressure-sensitive adhesive film for protecting a semiconductor wafer surface is laminated so as to have a thickness of 1 mm, thereby producing a viscoelasticity measurement sample having a diameter of 8 mm. The storage elastic modulus is measured at 150 ° C. and 200 ° C. using a dynamic viscoelasticity measuring device (manufactured by Rheometrics, model: RMS-800). The measurement frequency is 1 Hz, and the distortion is 0.1 to 3%.
(3) Breakage of semiconductor wafer (number)
The figure shows the number of damaged semiconductor wafers in a semiconductor wafer back surface grinding step, a die bonding adhesive film sticking step, and a surface protection adhesive film peeling step.
(4) Contamination evaluation
An adhesive film for protecting the surface of a sample is placed on the surface of a semiconductor silicon wafer (diameter: 8 inches, thickness: 600 μm, scribe line depth: 8 μm, scribe line width: 100 μm) via the adhesive layer. After sticking to the entire surface of the wafer, passing through a back surface processing step of the semiconductor wafer, and an adhesive film attaching step for die bonding, the adhesive film is peeled off (manufactured by Nitto Seiki Co., Ltd., model: HR8500II). The surface is observed at 250 magnification using a laser focus microscope (manufactured by KEYENCE, type: VF-7510, VF-7500, VP-ED100). The evaluation criteria are as follows. ：: No adhesive residue. ×: Glue residue occurred.
(5) Adhesion (%)
An adhesive film for a sample is placed on the surface of a semiconductor silicon wafer (diameter: 6 inches, thickness: 600 μm, scribe line depth: 8 μm, scribe line width: 100 μm) into which an integrated circuit is incorporated via the adhesive layer. Then, in a state of being attached to the entire surface of the semiconductor silicon wafer, observation and photography are performed at 250 magnifications using a laser focus microscope (manufactured by KEYENCE, model: VF-7510, VF-7500, VP-ED100). As the evaluation of adhesion, the ratio of the area of the adhesive to the scribe line and the total area of the scribe line is used as an index of adhesion. I do.
[0049]
Example 1
<Preparation of base film>
An ethylene-vinyl acetate copolymer resin having a Shore D-type hardness of 35 was formed into a film having a thickness of 200 μm using a T-die extruder. At this time, the side on which the pressure-sensitive adhesive layer was applied was subjected to corona treatment. The thickness variation of the obtained film was within ± 1.5%.
<Polymerization of adhesive base agent>
In a polymerization reactor, 150 parts by weight of deionized water, 0.64 part by weight of 4,4′-azobis-4-cyanovaleric acid [manufactured by Otsuka Chemical Co., Ltd., trade name: ACVA] as a polymerization initiator, and a monomer ( 94 parts by weight of 2-ethylhexyl acrylate as A), 3 parts by weight of 2-hydroxyethyl methacrylate and 1 part by weight of acrylamide as monomer (B), and 2-methacryloyloxyethyl succinate [R] as monomer (C) = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -] 2 parts by weight, as a water-soluble comonomer, a polymerizable 1-propenyl group was introduced into the benzene ring of the ammonium salt of a sulfate of polyoxyethylene nonyl phenyl ether (average number of moles of ethylene oxide added: about 20). 0.75 parts by weight of a product [manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: AQUALON HS-10] was charged, and emulsion polymerization was carried out at 70 to 72 ° C. for 8 hours with stirring to obtain an acrylic resin emulsion. Obtained. This was neutralized (pH = 7.0) with 9% by weight of aqueous ammonia to obtain an acrylic pressure-sensitive adhesive polymer (pressure-sensitive adhesive base) having a solid content of 42.5% by weight.
<Preparation of adhesive coating liquid>
100 parts by weight (solid content) of the obtained pressure-sensitive adhesive main agent was collected, and further adjusted to pH 9.5 by adding 9% by weight aqueous ammonia. Subsequently, 0.5 part by weight of an epoxy-based crosslinking agent [trade name: Denacol Ex-614, manufactured by Nagase Kasei Kogyo Co., Ltd.] was added to obtain an adhesive coating solution.
<Preparation of adhesive film>
The pressure-sensitive adhesive coating solution was applied to a polypropylene film (peeling film, thickness: 50 μm) using a roll coater and dried at 120 ° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 40 μm. The corona-treated surface of the above-mentioned ethylene-vinyl acetate copolymer film (substrate film) was bonded thereto and pressed to transfer the pressure-sensitive adhesive layer. After the transfer, the film was heated at 60 ° C. for 48 hours, and then cooled to room temperature to produce an adhesive film for grinding the back surface of a semiconductor wafer. Table 1 shows the measurement results of the storage elastic modulus. Table 1 summarizes the results of the evaluation of contamination.
[0050]
Example 2
In the polymerization of the pressure-sensitive adhesive base material of Example 1, 2-ethylhexyl acrylate of the monomer (A) was used at 86 parts by weight, and 2-methacryloyloxyethyl succinate [R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -] Was changed to 10 parts by weight, and the polymerization conditions of the comonomer and the initiator were all the same as in Example 1. After the polymerization of the main adhesive was carried out, the pressure-sensitive adhesive layer was produced in the same manner as in Example 1. The adhesive film for grinding the back surface of a semiconductor wafer having a thickness of 40 μm was prepared. Various properties of the obtained pressure-sensitive adhesive film and the contamination status of the obtained chip surface were evaluated in the same manner as in Example 1. The measurement results are shown in [Table 1].
[0051]
Example 3
In the polymerization of the main adhesive in Example 1, 2-acryloyloxyethyl succinate [R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -] Was changed to 2 parts by weight, and the polymerization conditions of the comonomer and the initiator were all the same as in Example 1. After the polymerization of the main adhesive was carried out, the pressure-sensitive adhesive layer was produced in the same manner as in Example 1. The adhesive film for grinding the back surface of a semiconductor wafer having a thickness of 40 μm was prepared. Various properties of the obtained pressure-sensitive adhesive film and the contamination status of the obtained chip surface were evaluated in the same manner as in Example 1. The measurement results are shown in [Table 1].
[0052]
Example 4
In the polymerization of the pressure-sensitive adhesive base material in Example 1, monomer (A) was converted to 2-ethylhexyl acrylate (64 parts by weight), n-butyl acrylate (18 parts by weight), methyl methacrylate (12 parts by weight), and methacrylic monomer (B). Except that the acid-2-hydroxyethyl 3 parts by weight and the acrylamide 1 part by weight were used, the polymerization conditions of the comonomer and the initiator were all the same as in Example 1, and after the polymerization of the main adhesive was carried out, In the same manner as in Example 1, an adhesive film for grinding the back surface of a semiconductor wafer having a thickness of the adhesive layer of 40 μm was prepared. Various properties of the obtained pressure-sensitive adhesive film and the contamination status of the obtained chip surface were evaluated in the same manner as in Example 1. The measurement and evaluation results are shown in [Table 1].
[0053]
Example 5
0.8 parts by weight of an aziridine-based cross-linking agent [manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd., trade name: Chemitite Pz-33] was added to the same adhesive main agent as in Example 1 to obtain an adhesive coating solution. . Thereafter, a pressure-sensitive adhesive film for grinding the back surface of a semiconductor wafer having a pressure-sensitive adhesive layer thickness of 40 μm was prepared in the same manner as in Example 1. Various properties of the obtained pressure-sensitive adhesive film and the contamination status of the obtained chip surface were evaluated in the same manner as in Example 1. The measurement and evaluation results are shown in [Table 1].
[0054]
[Table 1]

[0055]
Comparative Example 1
In Example 1, the main component of the pressure-sensitive adhesive was polymerized in the same manner as in Example 1 except that the monomer (A) was changed to 96 parts by weight of 2-ethylhexyl acrylate and the monomer (C) was not used. Thereafter, a pressure-sensitive adhesive film for grinding the back surface of a semiconductor wafer having a pressure-sensitive adhesive layer thickness of 40 μm was prepared in the same manner as in Example 1. The adhesive properties of the obtained adhesive film and the state of contamination on the chip surface were evaluated using the same method as in Example 1. The measurement and evaluation results are shown in [Table 2].
[0056]
Comparative Example 2
A pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer having a pressure-sensitive adhesive layer thickness of 40 μm was produced in the same manner as in Example 1, except that the crosslinking agent was not used for the same pressure-sensitive adhesive base material as in Example 1. . Various properties of the obtained pressure-sensitive adhesive film and the contamination status of the obtained chip surface were evaluated in the same manner as in Example 1. The measurement and evaluation results are shown in [Table 2].
[0057]
Comparative Example 3
Same as Example 1 in a mixed solvent of 50 parts by weight of toluene and 65 parts by weight of ethyl acetate in the presence of 0.7 parts by weight of a polymerization initiator [benzoyl peroxide nipper BMT-K40, manufactured by NOF Corporation] When solution polymerization was carried out using the mixed monomer of (1), gelation occurred during the reaction, and it was not possible to obtain an adhesive main agent. The results are shown in [Table 2].
[0058]
[Table 2]

[0059]
【The invention's effect】
According to the present invention, when grinding the back surface of the semiconductor wafer, not only does the wafer break during grinding caused by the grinding stress on the back surface, but also water and grinding debris enter between the wafer surface and the adhesive layer. Also, there is no damage to the wafer and no contamination of the wafer surface due to this. There is no breakage of the wafer when the adhesive film is peeled from the wafer, and there is no need to newly introduce equipment such as a light irradiation device. Further, since there is no adhesive residue after the adhesive film is peeled off from the wafer, the surface of the semiconductor wafer is not contaminated.

Claims (6)

A pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer having a pressure-sensitive adhesive layer provided on one surface of a base film, wherein the pressure-sensitive adhesive layer contains 10% by weight of (meth) alkyl acrylate-based monomer units (A) in the total amount of monomers. % To 98% by weight, and 1% to 40% by weight of the monomer unit (B) having a functional group, which can react with the crosslinking agent represented by the general formula (1) [Chemical Formula 1]. An acrylic pressure-sensitive adhesive polymer prepared by emulsion polymerization of a monomer composition containing 1% to 20% by weight of an acrylic acid derivative carboxylic acid (C);

(In the general formula (1), R represents a hydrogen atom or an alkyl group, and X represents a divalent hydrocarbon group having 4 to 9 carbon atoms including an ester group and / or an ether group.)
And a pressure-sensitive adhesive containing 0.1 to 30 parts by weight of a crosslinking agent having two or more functional groups in one molecule with respect to 100 parts by weight of the acrylic pressure-sensitive adhesive polymer. Wherein the storage elastic modulus is 1 × 10 ³ Pa or more and 1 × 10 ⁵ Pa or less, and the thickness is 3 to 100 μm. 2. The backside grinding of a semiconductor wafer according to claim 1, wherein the (meth) acrylic acid alkyl ester-based monomer unit (A) is a (meth) acrylic acid alkyl ester unit having an alkyl group having 1 to 12 carbon atoms. Adhesive film. The monomer unit (B) having a functional group is at least one monomer unit selected from acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, and methacrylamide. The pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer according to claim 1 or 2, wherein The acrylic pressure-sensitive adhesive polymer contains 85% to 98% by weight of (A), 1% to 10% by weight of (B), and 2% to 10% by weight of (C) in the total amount of monomers. The pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive film is an acrylic pressure-sensitive adhesive polymer prepared by emulsion polymerization of a monomer composition contained below. The pressure-sensitive adhesive film for grinding a back surface of a semiconductor wafer according to any one of claims 1 to 4, wherein the base film has a thickness of 10 to 500 µm. A method for grinding a back surface of a semiconductor wafer using the adhesive film for grinding a back surface of a semiconductor wafer according to any one of claims 1 to 5, wherein the adhesive film for grinding a back surface of the semiconductor wafer is attached to a circuit forming surface of the semiconductor wafer. Grinding the back surface of the semiconductor wafer and peeling the adhesive film after the grinding is completed.