JP4309671B2 - Adhesive film for semiconductor wafer back surface grinding and semiconductor wafer back surface grinding method using the same - Google Patents

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１×１０³Ｐａ以上、１×１０⁵Ｐａ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１×１０³Ｐａ以上、１×１０⁵Ｐａ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１×１０³Ｐａ以上、１×１０⁵Ｐａ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]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive film for semiconductor wafer back grinding (hereinafter referred to as an adhesive film) and a semiconductor wafer back grinding method using the same. Specifically, the adhesive film is attached to a surface (hereinafter referred to as a wafer surface) on which an integrated circuit of a semiconductor wafer such as a silicon wafer is incorporated, and the other surface of the wafer (hereinafter referred to as a wafer back surface) is ground. The present invention relates to a semiconductor wafer back surface grinding method useful for preventing breakage of a semiconductor wafer and the like, and a semiconductor wafer back surface grinding adhesive film used in the method.
[0002]
[Prior art]
Usually, a semiconductor integrated circuit is obtained by slicing a high-purity silicon single crystal or the like into a wafer, then incorporating the integrated circuit by ion implantation, etching, etc., and grinding the back surface of the wafer by grinding, polishing, lapping, etc. It is manufactured by a method of dicing into chips after reducing the thickness to about 100 to 600 μm. In these processes, to prevent damage to the semiconductor wafer during grinding of the backside of the wafer and to facilitate the grinding process, an adhesive film for grinding the backside of the semiconductor wafer is attached to the wafer surface via the adhesive layer. The protection method is used. Specifically, a semiconductor wafer back grinding adhesive film is directly attached to the wafer surface via the adhesive layer to protect the wafer surface, and then the wafer back surface is ground. After grinding is completed, the adhesive film is peeled off from the wafer surface.
[0003]
When a conventional semiconductor wafer backside grinding adhesive film is used to grind the backside of a semiconductor wafer in which an integrated circuit is built up to the periphery of the wafer, that is, the scribe line reaches the outermost periphery of the wafer In some cases, water enters between the wafer surface and the pressure-sensitive adhesive layer through a recess based on the scribe line, resulting in damage to the wafer, or grinding debris with water and contaminating the wafer surface. It was. In order to prevent these problems, measures are taken to increase the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film and improve the adhesion between the recesses on the wafer surface and the pressure-sensitive adhesive layer. However, when this method is used, the adhesive force of the adhesive film to the wafer surface is greater than the strength of the wafer, and depending on various conditions such as the thickness and surface shape of the wafer, When peeling from the wafer, peeling trouble may occur with the automatic peeling machine or the wafer may be destroyed.
[0004]
As a means for solving such a problem, for example, in JP-A-60-189938, when grinding the back surface of a semiconductor wafer, a pressure-sensitive adhesive film is attached to the wafer surface, and this adhesive film is applied after grinding. In the method for protecting a semiconductor wafer to be peeled off, the pressure-sensitive adhesive film described above is 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 is disclosed, wherein the adhesive film is irradiated with light before being peeled off after grinding.
[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 with light before peeling, and therefore does not consider the problem of peeling workability and wafer breakage. In addition, the adhesion to the wafer surface during back grinding can be sufficiently increased, and the above-described problem of water and grinding dust intrusion between the wafer surface and the adhesive layer can be solved.
[0006]
However, when this adhesive film is used, it is necessary to irradiate light before peeling the adhesive film from the wafer surface after back grinding, so it is necessary to introduce light irradiation equipment during the process, There is a problem that the apparatus becomes larger and complicated, or the process becomes complicated and workability is lowered. In addition, the problem that the working environment is deteriorated by ozone generated by light irradiation has been pointed out. Furthermore, depending on various conditions such as the surface shape of the wafer, light irradiation intensity, and time, a problem of adhesive residue may occur on the wafer surface after peeling due to poor curing of the pressure-sensitive adhesive layer. In order to prevent this problem, it is necessary to fill the inside of the light irradiation device with an inert gas such as nitrogen, resulting in an increase in manufacturing cost and a further increase in 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. 11-315259, a semiconductor having a pressure-sensitive adhesive layer containing a specific alkylene glycol polymer as an essential component. A protective adhesive film for the wafer was proposed. The protective adhesive film of the semiconductor wafer suppresses wafer breakage and contamination of the wafer surface caused by water and grinding debris entering between the wafer surface and the adhesive layer when grinding the back surface of the semiconductor wafer. Can do. In other words, since the adhesive strength is in an appropriate range, the wafer is not damaged when the adhesive film is peeled from the wafer, and there is no need to newly introduce equipment such as a light irradiation device into the process. Since no adhesive residue is produced after peeling, 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 be larger and thinner year by year. In particular, with the increasing demand for semiconductor chips that are required to be thin, such as thin packaging and smart card applications, the thickness of semiconductor wafers after back grinding tends to become thinner and thinner. is there. Since the time required for the back surface grinding increases with the area of the wafer, it is considered that the problem of wafer breakage / contamination due to the ingress of water and grinding debris described above is more likely to occur as the wafer becomes larger. Furthermore, considering the fact that the strength of the wafer itself decreases as the thickness of the wafer decreases, the above-mentioned problem of damage to the wafer at the time of peeling will become increasingly serious as the wafer becomes thinner. is expected.
[0009]
In addition, as semiconductor devices have become smaller and lighter in recent years, the surface of semiconductor wafers has rapidly diversified, and the surface shape of some adhesives for CPU, flash memory, smart cards, etc. is likely to remain. The number of wafers is increasing. For example, as a wafer having a chip suitable for a smart card application, 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 as described above, when the adhesive film is peeled off from the ground wafer, a part of the adhesive remains on the wafer surface. It sometimes contaminated the surface. Contamination due to the adhesive residue often occurs around the high bump electrode. In this case, it is difficult to remove the contamination even by post-treatment such as cleaning, which may be a particularly serious problem.
[0010]
Under such circumstances, conventionally, the adhesive film for semiconductor wafer backside grinding adheres well to the concave portion of the wafer surface during backside grinding, and water penetrates between the wafer surface and the adhesive layer. There are demands for performance such as breakage and intrusion of polishing debris to prevent contamination of the wafer surface, separation with an appropriate adhesive force at the time of peeling, and contamination of the wafer surface after peeling. However, these demand 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 a pressure-sensitive adhesive film for semiconductor wafer back grinding that can meet the above requirements at a higher level.
[0011]
[Problems to be solved by the invention]
In view of the above problems, the object of the present invention is to have an appropriate adhesive force that can withstand the stress during grinding of the wafer back surface and does not damage the wafer during peeling, and has excellent adhesion to the wafer surface and low contamination. It is an object of the present invention to provide a semiconductor wafer backside grinding adhesive film and a semiconductor wafer backside grinding method using the same.
[0012]
[Means for Solving the Problems]
In order to develop a high cohesive force in consideration of the problem of contamination, the present inventors make the crosslinking reaction proceed efficiently by protruding a carboxylic acid serving as a crosslinking base point on the surface of the acrylic pressure-sensitive adhesive polymer. As a result of diligent study, the monomer having a specific amount of a (meth) acrylic acid alkyl ester monomer unit (A) and a functional group capable of reacting with a crosslinking agent in the polymerization of an acrylic pressure-sensitive adhesive polymer by emulsion polymerization It has been found that the above problems can be solved by containing the unit (B) and the (meth) acrylic acid derivative carboxylic acid (C) having a specific structure as a monomer, and the present invention has been achieved.
That is, the present invention
(1) A pressure-sensitive adhesive film for grinding a semiconductor wafer back surface provided with a pressure-sensitive adhesive layer on one surface of a base film, wherein the pressure-sensitive adhesive layer contains a (meth) acrylic acid alkyl ester monomer (A) in the total amount of monomers. 10% by weight or more and 98% by weight or less, 1% by weight or more and 40% by weight or less of the monomer (B) having a functional group, and a 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 acrylic acid derivative carboxylic acid (C);
[0013]
[Chemical formula 2]

[0014]
(In general formula (1), R represents a hydrogen atom or an alkyl group, and X represents a C 4-9 divalent hydrocarbon group containing 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 polymer, and storing the pressure-sensitive adhesive layer at 0 to 200 ° C. Elastic modulus is 1 × 10 ^Three Pa or more, 1 × 10 ^Five A pressure-sensitive adhesive film for protecting a semiconductor wafer surface, having a Pa or less and a thickness of 3 to 100 μm.
(2) The back surface of a semiconductor wafer according to (1), wherein the (meth) acrylic acid alkyl ester 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 the functional group is at least one selected from acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, and methacrylamide. The pressure-sensitive adhesive film for grinding a semiconductor wafer back surface according to (1) or (2), which is a monomer.
(4) The acrylic polymer contained (A) in the range of 85 wt% to 99 wt%, (B) in the range of 1 wt% to 10 wt%, and (C) in the range of 2 wt% to 10 wt%. The adhesive film for grinding a semiconductor wafer back surface according to any one of (1) to (3), wherein the monomer composition is an acrylic polymer prepared by emulsion polymerization.
(5) The adhesive film for semiconductor wafer back grinding according to any one of (1) to (4), wherein the base film has a thickness of 10 to 500 μm.
(6) A semiconductor wafer back grinding method using the adhesive film for semiconductor wafer back grinding according to any one of (1) to (5), wherein the adhesive for semiconductor wafer back grinding is applied to a circuit forming surface of the semiconductor wafer. A semiconductor wafer back surface grinding method comprising attaching a film, grinding a back surface of a semiconductor wafer, and peeling the adhesive film after the grinding is completed.
About.
The first feature of the adhesive film for semiconductor wafer back grinding 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, and The polymer is prepared by emulsion copolymerization. In addition, the second feature is that the storage elastic modulus of the pressure-sensitive adhesive layer at 0 to 200 ° C. is 1 × 10. ^Three Pa or more, 1 × 10 ^Five It exists in the point which exists in the range below Pa.
[0015]
The adhesive tape for semiconductor wafer backside grinding having such characteristics is due to the improved adhesion between the wafer surface and the adhesive layer when the backside of the semiconductor wafer is ground, and the penetration of water and grinding debris in the backside grinding process. No wafer breakage or wafer surface contamination occurs. Further, since it has an appropriate adhesive force, it is not peeled off when grinding the back surface of the wafer, and the wafer is not damaged when the adhesive film is peeled off from the wafer. Further, since the contamination due to adhesive residue or the like does not occur after the adhesive film is peeled from the wafer, the surface of the semiconductor wafer is not contaminated.
[0016]
In addition, the storage elastic modulus in 0-200 degreeC of the adhesive layer in this invention means the value measured by the method described in the below-mentioned Example.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. The present invention is a pressure-sensitive adhesive film for grinding a semiconductor wafer back surface in which a pressure-sensitive adhesive layer is formed on one surface of a base film with a pressure-sensitive adhesive having a specific composition, and a semiconductor wafer back surface grinding method using the pressure-sensitive adhesive film.
[0018]
The pressure-sensitive adhesive film for semiconductor wafer backside grinding of the present invention is a solution or emulsion liquid (hereinafter, referred to as “an acrylic pressure-sensitive adhesive polymer”, “crosslinking agent”, and other additives as required) on one surface of a base film or a release film. These are collectively referred to as a pressure-sensitive adhesive coating solution) and dried to form a pressure-sensitive adhesive layer.
[0019]
When forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive coating solution to one surface of a base film, a release film is stuck on the surface of the applied pressure-sensitive adhesive layer in order to protect it from contamination caused by the environment. It is preferable. On the other hand, when an adhesive coating liquid is applied to one surface of a release film to form an adhesive layer, a method of transferring the adhesive layer to a substrate film is employed. Which one surface of the base film and the release film is to be coated with the adhesive coating liquid is determined in consideration of the heat resistance of the base film and the release film and the contamination of the semiconductor wafer surface. For example, when the heat resistance of the release film is superior to that of the base film, it is preferable to transfer to the base film after providing an adhesive layer on the surface of the release film. When the heat resistance is equivalent or the base film is excellent, it is preferable to provide a pressure-sensitive adhesive layer on the surface of the base film and attach a release film to the surface.
[0020]
However, 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 exposed when the release film is peeled off, and the semiconductor wafer surface is contaminated by the adhesive layer. In order to prevent this, the method of using a release film with good heat resistance, applying an adhesive coating solution on the surface, drying to form an adhesive layer, and transferring this to a base film is better. preferable. The pressure-sensitive adhesive film for semiconductor wafer back grinding according to 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 during use.
[0021]
As the base film used in the present invention, a film obtained by molding a synthetic resin into a film is used. The base film may be a single layer or a laminate. As for the thickness of a base film, 10-500 micrometers is preferable. More preferably, it is 70-500 micrometers. Examples of the raw material resin for the base film include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene copolymer, polyvinyl chloride, polyamide, and polyethylene terephthalate. It is done.
[0022]
Among these, in consideration of the protection performance of the wafer during back grinding, a raw material resin having a Shore D hardness of 40 or less as defined in ASTM-D-2240-86 or JIS K-7215-1986 is particularly preferable. preferable. When these resins are molded into a film, stabilizers, lubricants, antioxidants, pigments, antiblocking agents, plasticizers, and the like may be added as necessary. When various additives such as a stabilizer are added at the time of molding the base film, the additive may move to the pressure-sensitive adhesive layer to change the characteristics 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 protecting the surface of a semiconductor wafer using an adhesive film for grinding the back surface of a semiconductor wafer even during an etching process with an etching solution applied after grinding the back surface of the semiconductor wafer, the chemical resistance is excellent. It is preferred to use a substrate film. 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 force 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 previously subjected to corona discharge treatment or chemical treatment. Moreover, you may use undercoat between a base film and an adhesive layer. The base film used in the present invention should be selected from those produced by known techniques such as a calendar method, a T-die extrusion method, and an inflation method in consideration of productivity and the thickness accuracy of the obtained film. Can do.
[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 is subjected to silicone treatment or the like as necessary. The thickness of the release film is usually 10 to 200 μm. Preferably it is 30-100 micrometers.
[0025]
The pressure-sensitive adhesive coating solution 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). Copolymer acrylic pressure-sensitive adhesive polymer obtained by emulsion polymerization of monomer compositions each containing a specific amount of carboxylic acid (C), and one molecule of functional group for increasing cohesion and adjusting adhesive strength It consists of the solution or emulsion liquid containing the crosslinking agent which has 2 or more in it. When used in a solution, the acrylic pressure-sensitive adhesive polymer is separated from the emulsion liquid obtained by emulsion polymerization by salting out and then re-dissolved in a solvent, etc., but the acrylic pressure-sensitive adhesive polymer used in the present invention Is sufficiently large in molecular weight, low in solubility in solvents, or insoluble in many cases, and is preferably used as an emulsion liquid from the viewpoint of cost.
[0026]
The acrylic pressure-sensitive adhesive polymer used in the present invention reacts with a main monomer [hereinafter referred to as monomer (A)], a monomer (B) having a functional group, and a crosslinking agent. It can be obtained by copolymerizing a monomer composition containing a (meth) acrylic acid derivative carboxylic acid (C).
[0027]
Examples of the monomer (A) include acrylic acid alkyl esters or methacrylic acid alkyl esters having an alkyl group having about 1 to 12 carbon atoms (hereinafter collectively referred to as (meth) acrylic acid alkyl esters). 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 in combination of two or more. The amount of the monomer (A) used is usually preferably in the range of 10 to 98% by weight in the total amount of the polymerizable monomer that is the raw material of the pressure-sensitive adhesive polymer. More preferably, it is 85-95 weight%. By making the usage-amount of a monomer (A) into this range, the polymer which contains 10-98 weight% of (meth) acrylic-acid alkylester monomer units (A), Preferably 85-95 weight% is 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, itaconic acid monoalkyl ester, and mesaconic acid monoalkyl ester. , Citraconic acid monoalkyl ester, fumaric acid monoalkyl ester, maleic acid monoalkyl ester, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, tert-butylaminoethyl acrylate, tert-butyl Examples include aminoethyl methacrylate. Preferably, acrylic acid, methacrylic acid, acrylic acid-2-hydroxyethyl, methacrylic acid-2-hydroxyethyl, acrylamide, methacrylamide, etc. are mentioned. One of these may be copolymerized with the main monomer (A), or two or more may be copolymerized. The amount of the monomer (B) having a functional group capable of reacting with the crosslinking agent is preferably contained in the range of 1 to 40% by weight in the total amount of the polymerizable monomer that is the raw material of the pressure-sensitive adhesive polymer. . More preferably, it is 1 to 10% by weight. Thus, a polymer having the structural unit (B) having a composition almost equal to the monomer composition is obtained.
[0029]
In the present invention, as a measure for developing a high cohesive force and adhesion, paying attention to the crosslinking base point of the polymer surface produced after polymerization, the (meth) acrylic acid derivative carboxylic acid is introduced into the polymerization solution, and the crosslinking point is polymerized. Protruding to 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 expressed, and the storage elastic modulus can be adjusted by the carboxylic acid added, and high adhesion can be expressed. From the viewpoints of reactivity, coloring, and availability, the carboxylic acid (C) represented by the general formula (1) is suitable for the purpose of the present invention.
[0030]
By copolymerizing a specific carboxylic acid (C) with an acrylic pressure-sensitive adhesive polymer, the adhesion between the pressure-sensitive adhesive layer and the wafer surface is improved, and between the wafer surface and the pressure-sensitive adhesive layer when the wafer back surface is ground. The wafer surface (especially a wafer having a high bump electrode) caused by the pressure-sensitive adhesive layer does not cause damage to the wafer when the pressure-sensitive adhesive film is peeled off from the wafer surface. In this case, an adhesive that does not contaminate the periphery of the high bump electrode is obtained.
The amount of the carboxylic acid (C) represented by the general formula (1) affects the stability at the time of emulsion polymerization and the elastic modulus. If the amount is too large, the polymerization stability is lowered and the elasticity is increased. The rate tends to increase.
From this 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 general formula (1), R is hydrogen or an alkyl group, and examples of the alkyl group include a methyl group. X is a C 4-9 divalent hydrocarbon 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-acryloyloxyethyl 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-acryloyloxypropyl 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-acryloyloxyethyl maleate (R = H, X = -CH ₂ CH ₂ -OOC-CH = CH-), 3-methacryloyloxypropyl maleate (R = CH ₃ , X = -CH ₂ CH ₂ CH ₂ -OOC-CH = CH-), 3-acryloyloxypropyl maleate (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-acryloyloxyethyl 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-acryloyloxypropyl phthalate (R = H, X = -CH) ₂ CH ₂ CH ₂ -OOC-C ₆ H ₄ -) Etc. are mentioned, These may be used independently or may use 2 or more types together.
[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 a main monomer and a comonomer, and also 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 usually not contaminated by the surfactant. Even when slight contamination due to the pressure-sensitive adhesive layer occurs, it can be easily removed by washing the wafer surface with water.
[0033]
Examples of such polymerizable surfactants include, for example, those obtained by introducing a polymerizable 1-propenyl group into the benzene ring of polyoxyethylene nonylphenyl ether [Daiichi Kogyo Seiyaku Co., Ltd .; trade name: Aqualon RN-10, RN-20, RN-30, RN-50, etc.], a polyoxyethylene nonylphenyl ether sulfate ester ammonium salt introduced with a polymerizable 1-propenyl group in the benzene ring Manufactured by Ichi Kogyo Seiyaku Co., Ltd .; trade names: Aqualon HS-10, HS-20, etc.], and sulfosuccinic acid diester type 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, or styrene may be copolymerized. The amount of the surfactant 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 raw material.
[0034]
Examples of the polymerization reaction mechanism of the acrylic pressure-sensitive adhesive polymer include radical polymerization, anionic polymerization, and cationic polymerization. Polymerization by radical polymerization is preferable 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. When polymerizing by radical polymerization reaction, as radical polymerization initiator, organic compounds such as benzoyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, di-tertiary-butyl peroxide, di-tertiary-amyl peroxide, etc. Inorganic peroxides such as peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 4,4 Examples include 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 water-soluble 4 An azo compound having a carboxyl group in the molecule such as 4,4'-azobis-4-cyanovaleric acid is preferred. Considering the influence of ions on the semiconductor wafer surface, 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 preferable.
[0036]
The cross-linking agent having two or more cross-linkable functional groups used in the present invention is used to adjust the adhesive force and cohesive force by reacting with the functional group of the acrylic pressure-sensitive adhesive polymer. As crosslinking agents, epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, resorcin diglycidyl ether, etc. , Tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane toluene diisocyanate triadduct, isocyanate compounds such as polyisocyanate, trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β- Aziridinyl propionate, N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxyamino ), N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide), N, N′-toluene-2,4-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β Examples include aziridin compounds such as-(2-methylaziridine) propionate and melamine compounds such as hexamethoxymethylol melamine. These may be used alone or in combination of two or more.
[0037]
The content of the crosslinking agent is usually within a range in which the number of functional groups in the crosslinking agent does not exceed the number of functional groups in the acrylic pressure-sensitive adhesive polymer. However, when a functional group is newly generated by the crosslinking reaction, or when the crosslinking reaction is slow, it may be contained excessively as necessary. A preferable content is 0.1 to 30 parts by weight, more preferably 0.1 to 15 parts by weight with respect to 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 is likely to occur on the wafer surface (especially in the case of a wafer having a high bump electrode). When the adhesive film is peeled off the surface of the wafer, the adhesive strength may be increased and an automatic peeling machine may cause a peeling trouble or the wafer may be completely damaged. If the content is high, the adhesive force between the adhesive layer and the wafer surface will be weak, and water and grinding debris may enter during grinding and damage the wafer, or the wafer surface may be contaminated by grinding debris. is there.
[0038]
The pressure-sensitive adhesive coating solution used in the present invention includes an acrylic pressure-sensitive adhesive polymer copolymerized with the above-mentioned specific bifunctional monomer, a tackifier such as a rosin type or a terpene resin type in order to adjust the pressure-sensitive adhesive property in addition to the crosslinking agent. Various surfactants and the like may be appropriately contained so as not to affect the object of the present invention. When the coating solution is an emulsion solution, a film-forming aid such as diethylene glycol monoalkyl ether may be added as appropriate so as not to affect the purpose of the present invention. Considering that diethylene glycol monoalkyl ether and its derivatives used as film-forming aids may cause contamination of the wafer surface to the extent that cleaning is impossible when contained in a large amount in the pressure-sensitive adhesive layer. It is preferable to use a material that volatilizes at the drying temperature after the pressure-sensitive adhesive coating, and to reduce the residual amount in the pressure-sensitive adhesive layer.
The thickness of the pressure-sensitive adhesive layer is preferably 3 to 100 μm. A more preferred thickness is 5 to 80 μm. If the thickness of the pressure-sensitive adhesive layer is reduced, the water resistance will be inferior, and water may enter between the wafer surface and the pressure-sensitive adhesive layer during backside grinding, causing damage to the wafer or 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 produce a pressure-sensitive adhesive film, or the productivity may be affected, leading to an increase in manufacturing cost.
[0039]
In the present invention, the storage elastic modulus is obtained by subjecting an object under a controlled temperature to periodic deformation (strain) such as pulling, bending, and twisting from the outside, and the resulting response (stress) is converted into dynamic viscoelasticity. It is measured using a measuring device. Examples of a method of periodically deforming an object include, for example, a method of rotating the disk by sandwiching the object between two parallel disks, and a method of inserting a measuring needle into the object and vibrating the measuring needle Etc. As a dynamic viscoelasticity measuring device, for example, manufactured by Rheometrics, model: RMS-800, manufactured by Orientec, model: Rheobibron, DDV-II-EP, manufactured by Seiko Instruments Inc., model: EXSTAR6000, TMA / SS, etc. Is mentioned.
[0040]
The storage elastic modulus at 0 to 200 ° C. of the 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 crosslinking agent having two or more crosslinking reactive functional groups in one molecule is 1 × 10 ^Three Pa or more, 1 × 10 ^Five It is preferable to adjust the crosslinking agent so as to be in the range of Pa or less.
When the storage elastic modulus of the pressure-sensitive adhesive layer becomes low, contamination may occur on the wafer surface after the pressure-sensitive adhesive film is peeled off. When the storage elastic modulus of the pressure-sensitive adhesive layer is increased, the adhesion to the wafer surface is lowered, and grinding water or chemicals may enter.
The adhesive strength of the adhesive film for backside grinding of a semiconductor wafer in the present invention can be adjusted as appropriate in consideration of the grinding conditions of the wafer surface, the diameter of the wafer, the thickness of the wafer after grinding, etc. If the adhesive strength is too low, It may be difficult to attach the adhesive film to the surface, water may enter between the wafer surface and the adhesive layer during backside grinding, the wafer may be damaged, or the wafer surface may be contaminated with grinding debris, etc. There is a tendency. Also, if the adhesive strength is too high, when the adhesive film is peeled from the wafer surface after backside grinding, the peeling workability may be degraded, such as an automatic peeling machine, and 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 adhesive strength to a SUS304-BA plate.
[0041]
As a method for applying the adhesive coating solution to one surface of the base film or the release film, conventionally known coating methods such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coat method, a comma coater method, a die coater, etc. Can be adopted. Although there is no restriction | limiting in particular in the drying conditions of the apply | coated adhesive, Generally, it is preferable to dry for 10 second-10 minutes in the temperature range of 80-200 degreeC. More preferably, it is dried at 80 to 170 ° C. for 15 seconds to 5 minutes.
In order to sufficiently promote the cross-linking reaction between the cross-linking agent and the pressure-sensitive adhesive polymer, after drying of the pressure-sensitive adhesive coating solution is completed, the pressure-sensitive adhesive film for back grinding of a semiconductor wafer is heated at 40 to 80 ° C. for about 5 to 300 hours. May be.
The manufacturing method of the adhesive film for back grinding of a semiconductor wafer in the present invention is as described above. From the viewpoint of preventing contamination of the semiconductor wafer surface, manufacturing of all raw materials such as a base film, a release film, an adhesive main agent, etc. The environment, the preparation, storage, application and drying environment of the adhesive coating solution are preferably maintained at a cleanness of class 1,000 or less as defined in the US Federal Standard 209b.
[0042]
Next, the back surface grinding method of the semiconductor wafer of this invention is demonstrated. The method for grinding a back surface of a semiconductor wafer according to the present invention is characterized in that an adhesive film for grinding a back surface of a semiconductor wafer manufactured by the above method is used when grinding the back surface of a semiconductor wafer.
[0043]
The details are as follows. 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 semiconductor wafer integrated circuit is incorporated through the adhesive layer. Adhere to the surface. Next, the semiconductor wafer is fixed to the chuck table or the like of the grinding machine via the base film layer of the adhesive film, and the back surface (the surface where the integrated circuit is not formed) of the semiconductor wafer is ground. After the grinding is finished, the adhesive film is peeled off. After grinding the back surface of the wafer, a chemical etching process may be performed before the adhesive film is peeled off. In addition, after peeling the adhesive film as necessary, the surface of the semiconductor wafer is subjected to treatment 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, whereas it is usually ground to about 100 to 600 μm depending on the type of semiconductor chip. If necessary, it may be cut thinner than 100 μm. The thickness of the semiconductor wafer before grinding is appropriately determined depending on the diameter and type of the semiconductor wafer, and the thickness of the wafer after grinding is appropriately determined depending on the size of the chip to be obtained, the type of circuit, and the like.
[0045]
The operation of sticking the adhesive film to the semiconductor wafer may be performed manually, but is generally performed by an apparatus called an automatic pasting machine to which a roll-shaped adhesive film is attached. As such an automatic pasting machine, there are, for example, Takatori Co., Ltd., model: ATM-1000B, ATM-1100, Teikoku Seiki Co., Ltd., model: STL series.
[0046]
As the back surface grinding method, a known grinding method such as a through-feed method or an in-feed method is employed. Grinding is performed while cooling water over a semiconductor wafer and a grindstone. After the back grinding, chemical etching is performed as necessary. Chemical etching adheres to an etching solution selected from the group consisting of acidic aqueous solutions made of hydrofluoric acid, nitric acid, sulfuric acid, acetic acid and the like alone or in a mixed solution, alkaline aqueous solutions such as potassium hydroxide aqueous solution and sodium hydroxide aqueous solution. This is performed by a method such as immersing a semiconductor wafer with the film attached. The etching is performed for the purpose of removing strain generated on the back surface of the semiconductor wafer, further thinning the wafer, removing an oxide film, etc., pretreatment when forming an electrode on the back surface. The etching solution is appropriately selected according to the above purpose.
After completion of back grinding and chemical etching, the adhesive film is peeled off from the wafer surface. This series of operations may be performed manually, but is generally performed by an apparatus called an automatic peeling machine. Examples of such an automatic peeling machine include Takatori Co., Ltd., model: ATRM-2000B, ATRM-2100, Teikoku Seiki Co., Ltd., model: STP series.
[0047]
The wafer surface after peeling the adhesive film 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 in combination. These cleaning methods are appropriately selected depending on the contamination state of the wafer surface.
The semiconductor wafer to which the adhesive film for semiconductor wafer back grinding and the semiconductor wafer back grinding method using the semiconductor wafer of the present invention can be applied is not limited to a silicon wafer, but includes germanium, gallium arsenide, gallium phosphorus, gallium arsenide aluminum, and the like. A wafer is mentioned.
[0048]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In all the examples and comparative examples shown below, the preparation and application of an adhesive coating solution and the backside grinding of a semiconductor silicon wafer in an environment maintained at a cleanness of class 1,000 or less as defined in US Federal Standard 209b Etc. were carried out. The present invention is not limited to these examples. 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 made in accordance with JIS Z-0237-1991. In an atmosphere of 23 ° C., the adhesive film obtained in Example or Comparative Example was attached to the surface of a 5 cm × 20 cm SUS304-BA plate (JISG-4305-1991 regulation) through the adhesive layer, Leave for 60 minutes. One end of the sample was clamped, the peeling angle was 180 degrees, and the peeling speed was 300 mm / min. Then, the stress at the time of peeling the sample from the surface of the SUS304-BA plate is measured and converted to an adhesive force of g / 25 mm.
(2) Storage elastic modulus (Pa)
The adhesive layer portion of the adhesive film for protecting a semiconductor wafer surface is laminated so as to have a thickness of 1 mm, and a viscoelasticity measurement sample having a diameter of 8 mm is prepared. The storage elastic modulus is measured at 150 ° C. and 200 ° C. using a dynamic viscoelasticity measuring device (Rheometrics: model: RMS-800). The measurement frequency is 1 Hz and the distortion is 0.1 to 3%.
(3) Semiconductor wafer breakage (number)
The number of damaged semiconductor wafers in the semiconductor wafer back grinding process, the die bonding adhesive film attaching process, and the surface protecting adhesive film peeling process is shown.
(4) Pollution assessment
A semiconductor silicon wafer (diameter: 8 inches, thickness: 600 μm, scribe line depth: 8 μm, scribe line width: 100 μm) is coated with a surface protective adhesive film for the sample through the adhesive layer. After bonding to the entire surface of the wafer, passing through the backside processing process of the semiconductor wafer and the bonding process for bonding the adhesive film for die bonding, the adhesive film is peeled off (manufactured by Nitto Seiki Co., Ltd., model: HR8500II). The surface is observed at 250 magnifications using a laser focus microscope (manufactured by KEYENCE, model: VF-7510, VF-7500, VP-ED100). The evaluation criteria are as follows. ○: No adhesive residue. X: Adhesive residue generated.
(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) with an integrated circuit through the adhesive layer. In a state of being attached to the entire surface of the semiconductor silicon wafer, the laser focus microscope (manufactured by KEYENCE, model: VF-7510, VF-7500, VP-ED100) is used to observe at 250 magnifications and photograph. For the adhesion evaluation, the ratio of the adhesive area to the scribe line and the total area of the scribe line is used as an index of adhesion, and the adhesive ratio to the scribe line is 70% or more. To 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 corona treatment was applied to the side on which the pressure-sensitive adhesive layer was applied. The thickness variation of the obtained film was within ± 1.5%.
<Polymerization of adhesive main agent>
In a polymerization reactor, 150 parts by weight of deionized water, 0.625 parts by weight of 4,4′-azobis-4-cyanovaleric acid [manufactured by Otsuka Chemical Co., Ltd., trade name: ACVA] as a polymerization initiator, monomer ( A) 94 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of 2-hydroxyethyl methacrylate and 1 part by weight of acrylamide as monomer (B), 2-methacryloyloxyethyl succinate as monomer (C) [R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ -] 2 parts by weight, a polymerizable 1-propenyl group was introduced into the benzene ring of the ammonium ester salt of polyoxyethylene nonylphenyl ether (average number of moles of ethylene oxide added: about 20) as a water-soluble comonomer [Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon HS-10] was charged with 0.75 parts by weight, and the 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 with 9% by weight aqueous ammonia (pH = 7.0) to obtain an acrylic pressure-sensitive adhesive polymer (pressure-sensitive adhesive main agent) having a solid content of 42.5% by weight.
<Preparation of adhesive coating solution>
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. Next, 0.5 parts by weight of an epoxy crosslinking agent [manufactured by Nagase Kasei Kogyo Co., Ltd., trade name: Denacol Ex-614] was added to obtain a pressure-sensitive adhesive coating solution.
<Preparation of adhesive film>
The pressure-sensitive adhesive coating solution was applied to a polypropylene film (release film, thickness: 50 μm) using a roll coater, and dried at 120 ° C. for 2 minutes to provide a pressure-sensitive adhesive layer having a thickness of 40 μm. The corona-treated surface of the above-mentioned ethylene-vinyl acetate copolymer film (base film) was bonded to this 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 semiconductor wafer back grinding. The measurement results of the storage elastic modulus are shown in [Table 1]. In addition, Table 1 summarizes the results of contamination assessment.
[0050]
Example 2
In the polymerization of the pressure-sensitive adhesive main agent of Example 1, 86 parts by weight of 2-ethylhexyl acrylate in monomer (A) and 2-methacryloyloxyethyl succinate as monomer (C) [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, and after the polymerization of the pressure-sensitive adhesive main agent, the pressure-sensitive adhesive layer was prepared in the same manner as in Example 1. A pressure-sensitive adhesive film for grinding a semiconductor wafer back surface having a film thickness of 40 μm was prepared. Various characteristics of the obtained adhesive film and the state of contamination 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 adhesive main component of Example 1, 2-acryloyloxyethyl succinate [R = CH ₃ , X = -CH ₂ CH ₂ -OOC-CH ₂ CH ₂ The polymerization conditions for the comonomer and the initiator were all the same as in Example 1 except that the amount of-] was changed to 2 parts by weight, and the pressure-sensitive adhesive layer was polymerized in the same manner as in Example 1 after polymerization. A pressure-sensitive adhesive film for grinding a semiconductor wafer back surface having a film thickness of 40 μm was prepared. Various characteristics of the obtained adhesive film and the state of contamination 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 adhesive main agent of Example 1, monomer (A) was methacrylic acid as a monomer (B) of 64 parts by weight of acrylic acid-2-ethylhexyl, 18 parts by weight of acrylic acid-n-butyl, and 12 parts by weight of methyl methacrylate. Polymerization of the adhesive main agent was carried out under the same conditions as in Example 1 except that 3 parts by weight of acid-2-hydroxyethyl and 1 part by weight of acrylamide were used. In the same manner as in No. 1, a pressure-sensitive adhesive film for grinding a semiconductor wafer back surface having a pressure-sensitive adhesive layer thickness of 40 μm was prepared. Various characteristics of the obtained adhesive film and the state of contamination 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 crosslinking agent [manufactured by Nippon Shokubai Chemical Industry Co., Ltd., trade name: Chemitite Pz-33] was added to the same pressure-sensitive adhesive main agent as in Example 1 to obtain a pressure-sensitive adhesive coating solution. . Then, the adhesive film for semiconductor wafer back surface grinding with the film thickness of 40 micrometers of an adhesive layer was produced by the same method as Example 1. FIG. Various characteristics of the obtained adhesive film and the state of contamination 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 adhesive was polymerized by the same method as in Example 1 except that the monomer (A) was 96 parts by weight of 2-ethylhexyl acrylate and the monomer (C) was not used. Thereafter, a pressure-sensitive adhesive film for grinding a semiconductor wafer back surface having a pressure-sensitive adhesive layer thickness of 40 μm was produced in the same manner as in Example 1. The pressure-sensitive adhesive properties of the obtained pressure-sensitive 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 semiconductor wafer backside grinding with a pressure-sensitive adhesive layer thickness of 40 μm was prepared in the same manner as in Example 1 except that no crosslinking agent was used for the same pressure-sensitive adhesive main agent as in Example 1. . Various characteristics of the obtained adhesive film and the state of contamination 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 the presence of 0.7 parts by weight of a polymerization initiator (Nippon Yushi Co., Ltd., benzoyl peroxide-based Nyper BMT-K40) in a mixed solvent of 50 parts by weight of toluene and 65 parts by weight of ethyl acetate. When solution polymerization was carried out using the mixed monomer, gelation occurred during the reaction, and the pressure-sensitive adhesive main agent could not be obtained. 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 due to the grinding stress on the back surface, but also water and grinding debris enter between the wafer surface and the adhesive layer. The wafer is not damaged and the wafer surface is not contaminated. The wafer is not damaged when the adhesive film is peeled from the wafer, and it is not necessary to newly introduce equipment such as a light irradiation device. Furthermore, since there is no adhesive residue after peeling off the adhesive film from the wafer, the surface of the semiconductor wafer is not contaminated.

Claims (6)

A pressure-sensitive adhesive film for grinding a semiconductor wafer back surface provided with a pressure-sensitive adhesive layer on one surface of a base film,
The pressure-sensitive adhesive layer contains an acrylic pressure-sensitive adhesive polymer and 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. Consisting of agent,
The acrylic pressure-sensitive adhesive polymer comprises 10% by weight to 98% by weight of the (meth) acrylic acid alkyl ester monomer unit (A) in the total amount of monomers and a monomer unit having a functional group capable of reacting with the crosslinking agent ( 1% by weight or more of the (meth) acrylic acid derivative carboxylic acid (C) represented by the general formula (1) [Chemical Formula 1] that can react with the crosslinking agent at 1% by weight to 40% by weight of B) A monomer composition containing 20% by weight or less is prepared by emulsion polymerization.

(In the general formula (1), R represents a hydrogen atom or an alkyl group, and X represents a C 4-9 divalent hydrocarbon group containing an ester group and / or an ether group ),
A pressure-sensitive adhesive film for protecting a semiconductor wafer, wherein the pressure-sensitive adhesive layer has a storage elastic modulus at 0 to 200 ° C. of 1 × 10 ³ Pa to 1 × 10 ⁵ Pa and a thickness of 3 to 100 μm. 2. The semiconductor wafer back surface grinding according to claim 1, wherein the (meth) acrylic acid alkyl ester 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 capable of reacting with the cross-linking agent is at least selected from acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, and methacrylamide. The pressure-sensitive adhesive film for grinding a semiconductor wafer back surface according to claim 1, wherein the pressure-sensitive adhesive film is a single monomer unit. The acrylic pressure-sensitive adhesive polymer is 85% by weight or more and 98% by weight or less, (B) is 1% by weight or more and 10% by weight or less, and (C) is 2% by weight or more and 10% by weight or less in the total amount of monomers. The pressure-sensitive adhesive film for semiconductor wafer back grinding according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive polymer is an acrylic pressure-sensitive adhesive polymer prepared by emulsion polymerization. The thickness of a base film is 10-500 micrometers, The adhesive film for semiconductor wafer back surface grinding in any one of Claims 1-4. It is a semiconductor wafer back surface grinding method using the adhesive film for semiconductor wafer back surface grinding of any one of Claims 1-5, Comprising: The said adhesive film for semiconductor wafer back surface grinding is stuck on the circuit formation surface of a semiconductor wafer. Then, the back surface of the semiconductor wafer is ground, and the adhesive film is peeled off after the grinding is finished.