TW592890B - Copper process chemical mechanical polishing method - Google Patents

Abstract

The present invention relates to a method for planarizing a semiconductor wafer by chemical mechanical polishing (CMP). The semiconductor wafer has copper lines formed in a dielectric layer, and the dielectric layer comprises an excessive copper layer where the surface of the copper layer includes a layer of copper oxide. The invented method comprises: using a chemical etching solution containing citric acid to remove copper oxide; and performing a CMP by using a slurry containing abrasive particles and a chemical etching solution containing citric acid to remove excessive copper layer on the dielectric layer using the dielectric layer as a stop layer for exposing the copper lines. The citric acid can react with the copper oxide on the surface of the copper layer for removing copper oxide. The slurry contains abrasive particles with a low volume ratio and the abrasive particles can be used for repetitive mechanical polishing to remove excessive copper layer on the dielectric layer.

Description

592890 V. Description of the invention (1) Field of the invention: This is about a kind of chemical mechanical polishing method. More specifically, this chemical machine is based on a modified chemical mechanical polishing method made of copper. The Γ grinding method can make the processed copper surface of the wafer background of the invention open. In the manufacture of body components, 'metal wires are used in component circuit internals, and connected.' In other words, metal wires are used to connect discrete Yuan Yahun formed an integrated circuit. Insulation layers are used to insulate the metal wires from the inner wiring layers, and some holes are used between the two inner wiring conductive layers to provide a path for electrical conduction. In this winding process, the non-f ^ ancient ancient smooth insulation layer, because it is difficult to make images and pictures 荦-solid on the rough insulation layer. The method of ::::: will lead to poor step coverage of the subsequent deposited layer and the step coverage of the layer passing through the step, (V〇1d) structure. No, the hole structure between the topographical characteristics caused by the sedimentary layer will cause the reliability of the white ladder coverage and the topographical characteristics to decrease. When the semiconductor circuit ^ ^ is reduced, and the windings of the integrated circuit require multiple levels of winding to obtain an increase in the winding density within the element ^, the flattening of the charge quality in the semiconductor ": connection layer, so the level In the second two steps, it becomes a very important step. Page 5 592890 V. Description of the invention (2) step. With the progress of the process, the chemical secret m 1 1 [

Mechanical Polish · · CMP) made of bamboo > α ^ ^ ^ T ,, _ 1 ^ 衣 # 王 will occupy an increasingly important position in the wafer surface planarization process. In addition, in large-scale applications, the gold in the gate is generated by the RC time constant, which makes the subsequent high-temperature process required, and the element density becomes more and more stringent, so it is widely used. However, the development of the dry mechanical grinding method of the steel process could not be developed, and it was widely used in the super large-volume but the traditional copper appearance flatness and high-quality flatness, the traditional copper surface. Because in the general circle grinding, the surface is formed, and a layer of ^ is formed, and the formation is uneven, so it is not widely used during grinding, so that the requirements can be gradually gradual because of the small requirements. As chemistry gradually became more widespread, the time delay of the connection was reduced. However, the higher the metal layer and the RC time-delayed copper as the metal conducting copper, the more difficult it is to overcome the lack of engraving methods. This lack of body circuit (ULSI). High-temperature metal ore increasingly has a low resistance value and a high melting point. The line width is getting more and more ti me delay. The copper process of the line material forms high volatile matter points. With the copper point, the copper process is being made. Private chemical mechanical grinding method can not keep good. At the same time, the chemical mechanical polishing of the metal surface after the etchback cannot form a flat chemical mechanical polishing method. The metal copper of the semiconductor crystal plane has already naturally naturally bonded with oxygen copper oxide (Cu0). Its hardness is much higher than the thickness of metal copper and it is not controlled under control, so its thickness will cause uneven removal rate of metal copper.

Page 6 592890 V. Description of the invention (3) As a result, the surface resistance of the metal produced by grinding] 哽 chen will have uneven surface resistance, which also affects the characteristics and even the component failure . The more important thing is that after the copper wafers are removed from the semiconductor wafer, the remaining copper oxide fragments down to 1 ^ may also cause damage to the surface.

Injury, resulting in reduced rate. In the past, when the line width was wide, these defects still had a large impact. 'But as the component density becomes larger, the line width becomes smaller 1: = copper oxide residual debris problem' and the wafer surface jitter. The question becomes particularly important. The traditional chemical mechanical grinding method is used to grind the deposited gold layer. When grinding, Siurry is added as a chemical assistant. For example, the research and polymerization used for CMP etchback of metallic copper, + is used as a component of chemical removal (Chemical Rem oval), 32, _. It is specially composed of an oxidant (Oxidant) and an organic solvent (〇 mixed with rganic agents), and it involves extremely complex chemical reaction mechanisms, & with ° @ Mechanics (KmeUcs) problems, major semiconductor manufacturers are studying, still in the exploration stage, still Not thoroughly understood. Therefore, which kind of chemical mechanical polishing process is suitable for polishing wafers of various processes is still under development. In general, after the CMP etchback, the wafer surface is cleaned by a method of cleaning and polishing after the general CMP process, that is, = brush clearing, spray cleaning, and ultrasonic cleaning ( Ultrasonic cleaning). But now the general CMP process

592890 V. Description of the invention (4) _ When it is used in the interconnect process, it is still a key technology. The process with a line width far below 0.5_ is even more important. Leading manufacturers' must take the barrel of CMP technology = f = technology. In particular, although the CMP process can obtain better quality: the whole 1: because the requirements of the general surface polishing research and removal are relatively high; basic: after the second washing day, there will still be residual debris on the wafer surface and 7 :: 个 』程. When the line width is greater than 0, the effect is smaller: = The line width has already reached. .13 microns modern, these two problems are beyond the general stratified terrain. After the formation of different objects on the surface, the metal forms a flat metal process, including grasping chemistry, temperature, and surface rotation for chemical reactions to contain solid particles. In addition to this, the shell should be used in the manufacturing process, and then easily mechanically and chemically. In addition to grinding, it can provide smooth insulation-: ί Grinding can also be used to remove the combination of semiconductor wafer methods, producing π2 During the process, a very flat grinding plane was machined

Page 8. For example, the hole structure 11 11 on the insulating material layer is grown, and then chemical mechanical polishing is used to produce = ff and § In addition, a traditional chemical mechanical polishing method is a thin, flat semiconductor wafer. Under controlled conditions, P is removed by a wet grinding with the chemical etching solution in the slurry and the surface to be treated. Research: m: 1 such as Ming or Shi Xitu, is used to grind, water, and combine specific chemicals, and these chemistry ::: research workers say that the surface of different materials on the circle is chemically reacted 592890

592890 V. Description of the invention (6) Purpose and summary of the invention

One of the objectives of the present invention is to provide an improved chemical mechanical polishing method for a copper layer on a copper wafer semiconductor wafer, so that the uniformity of the film on the surface of the copper layer processed can be greatly improved. Another object of the present invention is to provide an improved chemical mechanical grinding method for a copper layer on a semiconductor wafer of a copper process so that the surface of the processed copper layer has no particles remaining thereon, so as to avoid affecting the process yield. Secondly, the present invention has another object, which is to improve the chemical mechanical polishing method of the copper layer on the copper wafer semiconductor wafer, so that the copper wire layer on the surface of the semiconductor wafer to be processed has a relatively uniform surface resistance, which means that The surface resistance change range is small, so the formed electronic component has better electrical properties.

Based on the above reasons, the present invention proposes a method for applying chemical mechanical polishing to planarize a copper wire layer of a semiconductor wafer. The above semiconductor wafer has copper wires formed in a dielectric layer, and the dielectric layer contains excess copper. Layer, the surface of this copper layer contains a layer of copper oxide. The method may include the following steps: firstly removing copper oxide with a chemical etching solution, then performing chemical mechanical polishing with a slurry containing the chemical etching solution, and removing the excess copper layer on the dielectric layer with the dielectric layer as a stop layer To expose the copper wire. The chemical etching solution containing citric acid can chemically interact with the copper oxide on the surface of the copper layer to remove copper oxide, and the composition of the slurry contains abrasive particles with a low abrasive particle volume ratio and citric acid-containing abrasive particles. Chemical etching

Page 10 592890 V. Description of the invention (7) Liquid, using the mismatch between the slurry and the steel that is easier to grind = 4 ticks to dissociate copper into copper ions and then form a mechanical grind to remove $ 'while using Grind the abrasive particles to perform a chemical etching solution on the copper layer = steel complex. Then, the abrasive particles of the slurry are repeatedly used to form a copper complex on the mechanical surface, and then the copper layer of the slurry is ground. Grinding to gradually remove the excess invention on the dielectric layer. Detailed description of the chemical mechanical polishing method of the semiconductor wafer surface. The new method of flattening is to prevent the mechanical processing of semiconductors. Good method. Bulk wafer surface electricity: two residual particles, and; = Lv, the present invention can solve the problem of ancient unevenness. Turn 9 w. The households that are being processed are very special W Λ Λ a, especially for copper p furnaces and avoiding them. The copper is made of semi-conductor semiconductors, and the cover is changed to π, ^ mechanical grinding. ^ Improved uniformity of the yen and yen After the invention: the grinding mechanism produces: Ί The goodness of the circle! The average problem, the copper process semiconductor processed 4 > J ', eight middle noteworthy ^^ θ Raise the copper hafnium semiconductor | Λ a The semi-conductor of the steel manufacturing process is called Yan Yanshi, 本, the present invention ^^ ^ body ^ Ning ^ ^ Conductor ® ® For the treatment of the bombardment, the preferred embodiment of the y month is not as good as the treatment. The semi-conductor of the copper process but the invention / as long as the chemical mechanical grinding :::: is limited to the processing of the metal :: two! : Fa: The chemical worm in the proposed chemistry x Fan Fan, the formula, the face, and the method of the present invention are all described in detail. : The following preferred embodiments 页 page 11 592890

^, Mao Ming ’s preferred embodiment of a chemical and mechanical grinding system for performing a chemical mechanical polishing process, as shown in the first figure, includes a polishing pad 5, a grinding head, and a grinding water supply device (for A slurry 8 is provided on the polishing pad 5). First = Fix the semiconductor wafer to be processed. With reference to the first figure, fix it on the polishing head 6 of the chemical and mechanical polishing device, and rotate the polishing head 6, so the semiconductor crystal 1 1 〇 also rotates with it, and then The slurry 8 provided in a preferred embodiment of the present invention is continuously and uniformly applied on the surface of the polishing pad 5. Then, using the polishing head and a controlled pressure, the entire semiconductor wafer is pressed against the polishing pad 5, and the polishing head 6 (or the polishing pad 5) can be rotated. The semiconductor wafer 10, as shown in the second figure, has copper wires 22 formed in the wire trenches of the dielectric layer 20, and the dielectric layer contains an excess copper layer 22a. Generally, the dielectric layer 20 and copper The conductive line 22 and a barrier layer 25 are provided between the dielectric layer 20 and the copper layer 22a. The surface of the copper layer 22a contains a layer of oxidized steel 24. In the slurry 8 proposed in the embodiment of the present invention, the composition includes solid particles 28 and a chemical etching solution, and the chemical etching solution further contains #citric acid. According to the embodiment of the present invention, In the proposed chemical mechanical polishing process, the aforementioned semiconductor wafer 10 is firstly subjected to a chemical solution containing a lemon and a chemical surname, so that the chemical etching solution can chemically interact with the oxide steel 24 on the surface of the copper layer 2 2 a. To remove the copper oxide 2 4.

Page 12 592890 V. Description of the invention (9) Chemical-mechanical polishing is performed with a slurry containing abrasive particles 28 and a chemical etching solution containing citric acid. Wherein, the chemical etching solution of the slurry is used to dissociate copper into copper ions and further form a complex of copper that is easier to be ground. At this time, a copper complex is formed on the surface of the copper layer 22a. The abrasive particles 28 in the slurry composition are then used for mechanical grinding to remove the copper complex. The results are shown in the third figure. ^ Then, the steps shown in the third figure above are repeatedly performed, and again, the research and development of the second chemical: engraving liquid to form a copper complex on the surface of the copper layer 223, and then research; r research: Π8 people for machinery Abrasion is performed to gradually remove the copper layer 22a. After the removal, the dielectric layer 20 is used as a termination layer to remove the copper layer 22a and the barrier layer 25 of the dielectric layer for exposing the substrate as shown in the fourth figure. 】 Duochen ". As a result, the chemical etching solution used in the present invention should be treated as necessary to conduct mechanical research, so that the copper oxide on the surface has been chemically separated from citric acid. The table uses the chemical etching solution of the slurry to dissociate the copper into copper ions == removed. The re-milled copper complex, so that it can be directly polished by mechanical grinding after the formation of easier conductor wafers. Grinding slurry with a ratio of abrasive particles to semi-abrasive particles. The low-grinding of copper layers caused the use of low-abrasive copper oxide. Among them, there is no grinding volume ratio.

P.13 592890 V. Description of the invention (10) "-0 This matter shows that the uniformity of the thin film on the circle can be greatly improved because of the above characteristics. According to the experimental results, it is confirmed that the invention The surface uniformity of the semiconductor wafer processed by the proposed improved chemical mechanical polishing method can reach between about 5% and 10%. However, the semiconductor wafer processed according to the conventional chemical mechanical polishing method has a surface uniformity of only about 20% to 35%. It can be seen that the slurry proposed by the chemical mechanical polishing method of the present invention can consistently improve Thin film uniformity of the processed wafer. In addition, because of the proposed slurry composition of the present invention, there is no residual particle on the surface of the semiconductor wafer processed by the improved chemical mechanical polishing method proposed by the present invention. In addition, the semiconductor wafer processed by the improved chemical mechanical polishing method proposed in the present invention has a uniformity (variation range) of the surface resistance (Rs) of the metal layer on the surface of the semiconductor wafer. Therefore, according to the present invention, A semiconductor element made of a wafer processed by the proposed method will have a better electronic characteristic curve, that is, its electrical property is better. The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of patent application for the present invention; any other equivalent changes or modifications made without departing from the spirit disclosed by the present invention, such as using different chemistry Mechanical polishing machine, or applying the present invention to different processes, as long as the main components and methods of the slurry proposed by the present invention are used to remove the metal layer on the surface of the semiconductor wafer in the chemical mechanical polishing process Those who flatten the metal surface are included in the spirit and scope of the present invention, so they should all be included in the scope of patent application described below.

Page 592890 Brief description of the diagram The first diagram shows the side view of the copper wafer semiconductor wafer and the chemical mechanical grinding device when the copper wafer is placed in the chemical mechanical polishing device. The second diagram shows the structure of the semiconductor wafer. Three figures show a schematic diagram of chemical mechanical polishing using a slurry to remove the copper layer; and the fourth figure shows a chemical mechanical polishing semiconductor wafer with a dielectric layer as a termination layer to remove the excess copper layer on the dielectric layer and Schematic diagram of the structure of the barrier layer.

Drawing number description Polishing head-6 slurry-8 dielectric layer-20 copper layer-22a barrier layer-2 5 polishing pad-5 slurry supply device-7 semiconductor wafer-10 copper wire-2 2 copper oxide-2 4 Abrasive particles-2 8

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Claims (1)

592890 VI. Application Patent Scope 1. A method for applying chemical mechanical polishing to planarize a semiconductor wafer. The semiconductor wafer has copper wires formed in a dielectric layer, and the dielectric layer contains an excess copper layer. The surface of the copper layer contains a layer of copper oxide. The method includes at least the following steps: removing the copper oxide with a chemical etching solution containing citric acid; and performing chemical mechanical polishing with a slurry containing abrasive particles and a chemical etching solution containing citric acid to The excess copper layer is removed, and the dielectric layer is used as a termination layer to expose the copper wire. 2. The method according to item 1 of the scope of the patent application, wherein the chemical etchant and the abrasive particles can be mechanically polished repeatedly to remove the copper layer. 3. The method according to item 1 of the scope of patent application, wherein the slurry is a volume ratio with low abrasive particles. 4. A method of applying chemical mechanical polishing to planarize the surface of a sloppy copper layer, the surface of the copper layer having a layer of copper oxide, the method comprising at least the following steps: removing the oxidation with a chemical etchant containing citric acid Copper; and chemical mechanical polishing with a slurry containing abrasive particles and a chemical etchant containing citric acid until the copper layer is flattened. 5. The method according to item 4 of the scope of patent application, wherein the chemical etchant Page 16 592890 Page 17