Silicon wafer polishing method

Abstract

The invention discloses a silicon wafer polishing method, and belongs to the field of chemical mechanical polishing. The polishing method comprises a rough polishing stage and a fine polishing stage, a first polishing solution is used for polishing treatment in the rough polishing stage, and a second polishing solution is used for polishing treatment in the fine polishing stage; both the first polishing solution and the second polishing solution comprise a rate accelerator and a water-soluble polymer, wherein the rate accelerator A1 in the first polishing solution and the rate accelerator A2 in the second polishing solution meet the following content relation: ConA1 is greater than ConA2; the water-soluble polymer P1 in the first polishing solution and the water-soluble polymer P2 in the second polishing solution meet the following content relation: ConP1 is less than ConP2. By means of the polishing method, the silicon wafer with the low defect and the high-quality surface can be obtained, meanwhile, the removal rate is greatly increased, the machining time is effectively shortened, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of chemical mechanical polishing, and in particular to a silicon wafer polishing method. Background Art

[0002] With the development of the integrated circuit industry, advanced process technology has put forward higher requirements for the surface flatness of silicon wafers. Chemical mechanical polishing (CMP) and double-sided chemical mechanical polishing (DSP) and other technologies can achieve high flatness of silicon wafers. CMP technology is a technology that combines chemical and mechanical effects, and has the advantages of fast processing speed, high grinding quality, and reliable processing results. However, the processing process of CMP is complicated and is affected by many factors such as the type of material on the surface of the workpiece, the composition of the polishing liquid, and the pressure of the polishing head. The existing chemical mechanical polishing liquid on the market currently has a poor flattening effect on the overall silicon wafer, and it is difficult to obtain a high-quality mirror surface with low defects. At the same time, the existing polishing liquid has a low silicon surface material removal rate, resulting in a long polishing time and high processing cost for silicon carbide wafers. Therefore, it is urgent to develop a silicon wafer polishing method that can improve the surface material removal rate and overall flatness of the silicon wafer to obtain a low-defect high-quality mirror surface. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a silicon wafer polishing method, which can not only obtain silicon wafers with low defects and high quality surfaces, but also greatly improve the removal rate, effectively shorten the processing time and reduce production costs.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0005] A silicon wafer polishing method, comprising a rough polishing stage and a fine polishing stage, or comprising a rough polishing stage, a medium polishing stage and a fine polishing stage;

[0006] The rough polishing stage includes 2 to 3 rough polishing steps, the medium polishing stage includes 0 to 1 medium polishing step, and the fine polishing stage includes 2 fine polishing steps;

[0007] The first polishing liquid is used for polishing in both the rough polishing stage and the intermediate polishing stage, and the second polishing liquid is used for polishing in the fine polishing stage;

[0008] The first polishing liquid and the second polishing liquid both contain a rate accelerator and a water-soluble polymer, wherein:

[0009] The rate accelerator A1 contained in the first polishing liquid and the rate accelerator A2 contained in the second polishing liquid satisfy the following content relationship: ConA1>ConA2;

[0010] The water-soluble polymer P1 contained in the first polishing liquid and the water-soluble polymer P2 contained in the second polishing liquid satisfy the following content relationship: ConP1<ConP2.

[0011] As a preferred embodiment of the present invention, the first polishing liquid has the following composition: 20-30wt% abrasive, >0.5wt% rate accelerator, <0.05wt% water-soluble polymer, and the balance is water.

[0012] As a preferred embodiment of the present invention, the second polishing liquid has the following composition: 4-10wt% abrasive, <3wt% rate accelerator, >0.05wt% water-soluble polymer, and the balance is water.

[0013] As a preferred embodiment of the present invention, the polishing method comprises the following steps in sequence: in the 1st, 2nd and 3rd steps, a white rough polishing pad and the first polishing liquid are used to polish the silicon wafer; in the 1st and 2nd steps, a black velvet pad and the second polishing liquid are used to polish the silicon wafer.

[0014] As another preferred embodiment of the present invention, the polishing method includes steps in the following order: in the first and second steps, rough polishing uses a white rough polishing pad and the first polishing liquid to polish the silicon wafer; in the first step, intermediate polishing uses a black velvet pad and the first polishing liquid to polish the silicon wafer, or in the first step, intermediate polishing uses a white rough polishing pad and the second polishing liquid to polish the silicon wafer; in the first and second steps, fine polishing uses a black velvet pad and the second polishing liquid to polish the silicon wafer.

[0015] Preferably, the content of the rate accelerator A1 contained in the first polishing liquid is ConA1>0.5wt%, preferably more than 1wt%; the content of the rate accelerator A2 contained in the second polishing liquid is ConA2<1wt%.

[0016] Further preferably, the content of the rate accelerator A1 contained in the first polishing liquid is ConA1>3wt%; the content of the rate accelerator A2 contained in the second polishing liquid is ConA2<0.6wt%.

[0017] Preferably, the rate accelerator is selected from one or more of potassium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ethylenediamine, hydroxyethylethylenediamine, piperazine, imidazole, monoethanolamine, triethanolamine, and diglycolamine, preferably potassium hydroxide (KOH), ammonium hydroxide (NH3·H2O) and tetramethylammonium hydroxide (TMAH).

[0018] Preferably, the content of the water-soluble polymer P1 contained in the first polishing liquid is ConP1<0.05wt%, preferably less than 0.03wt%; the content of the water-soluble polymer P2 contained in the second polishing liquid is ConP2>0.1wt%.

[0019] More preferably, the content of the water-soluble polymer P1 contained in the first polishing liquid is ConP1<0.005wt%; the content of the water-soluble polymer P2 contained in the second polishing liquid is ConP2>0.2wt%.

[0020] Preferably, the water-soluble polymer is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, starch, carboxymethyl starch, pullulan, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide-polypropylene oxide, polyacrylic acid, ammonium polyacrylate, polyacrylamide, and polyglycerol, preferably hydroxyethyl cellulose (HEC), polyvinyl pyrrolidone (PVP), and polyethylene oxide-polypropylene oxide (PEO-PPO).

[0021] Preferably, when the water-soluble polymer is hydroxyethyl cellulose, the weight average molecular weight Mw of the hydroxyethyl cellulose is 100,000 to 500,000, preferably 250,000.

[0022] Preferably, when the water-soluble polymer is polyvinyl pyrrolidone, the weight average molecular weight of the polyvinyl pyrrolidone is 1.6 million or less, and more preferably 70,000 or less.

[0023] Preferably, when the water-soluble polymer is polyethylene oxide-polypropylene oxide, the weight average molecular weight of the polyethylene oxide-polypropylene oxide is 1000-4000, and more preferably 1000-3000.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention balances the chemical corrosion produced by the rate accelerator, the chemical inhibition produced by the high molecular polymer, and the mechanical effect of the abrasive, and is matched with a polishing pad of corresponding material to obtain a silicon wafer with high flatness under a certain pressure and rotation speed; the present invention controls the concentration range and molecular weight of the high molecular polymer to obtain a high-quality mirror silicon wafer with low defects;

[0026] 2. The silicon wafer polishing method provided by the present invention can greatly improve the material removal rate while obtaining a high-quality surface, effectively shortening the processing time and reducing the production cost. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific implementation modes.

[0028] A silicon wafer polishing method provided by the present invention includes a rough polishing stage and a fine polishing stage, and specifically includes the steps in the following order: in the 1st, 2nd and 3rd steps of rough polishing, a white rough polishing pad and a first polishing liquid are used to polish the silicon wafer; in the 1st and 2nd steps of fine polishing, a black velvet pad and the second polishing liquid are used to polish the silicon wafer.

[0029] The present invention also provides another silicon wafer polishing method, which includes a rough polishing stage, an intermediate polishing stage and a fine polishing stage, and specifically includes the steps in the following order: in the first and second steps of rough polishing, a white rough polishing pad and a first polishing liquid are used to polish the silicon wafer; in the first step of intermediate polishing, a black velvet pad and a first polishing liquid are used to polish the silicon wafer, or in the first step of intermediate polishing, a white rough polishing pad and the second polishing liquid are used to polish the silicon wafer; in the first and second steps of fine polishing, a black velvet pad and the second polishing liquid are used to polish the silicon wafer.

[0030] In the above method, the first polishing liquid and the second polishing liquid both contain a rate accelerator and a water-soluble polymer, wherein the rate accelerator A1 contained in the first polishing liquid and the rate accelerator A2 contained in the second polishing liquid satisfy the following content relationship: ConA1>ConA2; the water-soluble polymer P1 contained in the first polishing liquid and the water-soluble polymer P2 contained in the second polishing liquid satisfy the following content relationship: ConP1<ConP2.

[0031] Wherein, the rate accelerator is selected from one or more of potassium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ethylenediamine, hydroxyethylethylenediamine, piperazine, imidazole, monoethanolamine, triethanolamine, diglycolamine, preferably potassium hydroxide (KOH), ammonium hydroxide (NH3·H2O) and tetramethylammonium hydroxide (TMAH). The water-soluble polymer is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, starch, carboxymethyl starch, pullulan, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide-polypropylene oxide, polyacrylic acid, ammonium polyacrylate, polyacrylamide, polyglycerol, preferably hydroxyethyl cellulose (HEC), polyvinyl pyrrolidone (PVP), polyethylene oxide-polypropylene oxide (PEO-PPO) or polyglycerol (PGL).

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. The technology and method known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and method should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values.

[0034] The experimental methods in the following examples without specifying specific conditions are usually measured in accordance with national standards; if there is no corresponding national standard, the method is carried out in accordance with the general standard requirements or general methods.

[0035] Examples 1 to 10 and Comparative Examples 1 to 10

[0036] The average particle size and content of abrasives, the type and content of rate accelerators, and the type and content of water-soluble polymers in the polishing liquids used in Examples 1 to 10 and Comparative Examples 1 to 10 are specifically shown in Table 1. The pH of each polishing liquid is controlled at 10 to 12, and the polishing liquid AL is diluted 20 times before use, and the polishing liquid MQ is diluted 30 times before use.

[0037] Table 1 Ratio of each group of polishing liquid

[0038]

[0039]

[0040] The balance of the above polishing liquid is water, and the sum of the weight percentages of the abrasive, the rate accelerator, the water-soluble polymer and water is 100wt%.

[0041] The polishing steps of Examples 1 to 10 and Comparative Examples 1 to 10 are as follows:

[0042] S1, Step 1-2 Rough polishing:

[0043] Polishing machine: Shanghai Zhiling polishing machine (CP-1280B / DP)

[0044] Polishing pressure: 257Kg

[0045] Blasting head speed: 30rpm

[0046] Throwing plate speed: 30rpm

[0047] Polishing pad: SUBA 800PAD 1280MMD PJ

[0048] Polished wafer: thickness 725μm, P type (100), resistivity 0.5-100Ω

[0049] Polishing temperature: 28℃-32℃

[0050] S2, step 3, middle throw:

[0051] Polishing machine: Shanghai Zhiling polishing machine (CP-1280B / DP)

[0052] Polishing pressure: 257Kg

[0053] Blasting head speed: 30rpm

[0054] Throwing plate speed: 30rpm

[0055] Polishing pad: SUBA 800PAD 1280MMD PJ or 7355-000FE

[0056] Polished wafer: thickness 725μm, P type (100), resistivity 0.5-100Ω

[0057] Polishing temperature: 28℃-32℃

[0058] S3, Step 4-5 Fine Polishing:

[0059] Polishing machine: Shanghai Zhiling polishing machine (CP-1280B / DP)

[0060] Polishing pressure: 125Kg

[0061] Blasting head speed: 30rpm

[0062] Throwing speed: 29rpm

[0063] Polishing pad: 7355-000FE

[0064] Polished wafer: thickness 725μm, P type (100), resistivity 0.5-100Ω

[0065] Polishing temperature: 25℃-31℃

[0066] S4. Cleaning: unload the polished silicon wafer, and clean the silicon wafer with a cleaning solution of ammonia water (mass concentration is 29%): hydrogen peroxide (mass concentration is 30%): DIW = 1L: 3L: 30L.

[0067] Silicon Wafer Quality Evaluation

[0068] The quality of the silicon wafers prepared in Examples 1 to 10 and Comparative Examples 1 to 10 was evaluated, and the polishing method of the present invention was evaluated in combination with the polishing time.

[0069] Silicon wafer quality evaluation includes the number of particle defects and flatness. The specific evaluation methods are as follows:

[0070] 1. Evaluation of the number of particle defects

[0071] The entire surface of the silicon wafer is inspected using the "SURFSCAN SP2 XP" to count the number of particle defects larger than 0.12μm. The resulting defect counts are rated according to the following four levels: Level 4: 10 or less, Level 3: 10 to 20, Level 2: 20 to 50, and Level 1: 50 or more.

[0072] 2. Flatness (GBIR)

[0073] GBIR (2 mm area outside the edge) was evaluated according to the SEMI standard, and the measured values ​​were rated according to the following three levels: Level 3: 200 nm or less, Level 2: 200 nm to 300 nm, and Level 1: more than 300 nm.

[0074] Table 2 Polishing process and quality evaluation results of Example 1-2 and Comparative Example 1-2

[0075]

[0076]

[0077] Comparative Examples 1-2 and Example 1-2 respectively use four first polishing liquids containing different concentrations of rate accelerators for the rough polishing process. Comparative Example 1-2 has a lower chemical corrosion effect, resulting in a longer polishing time, and the surface flatness and particle defects of the silicon wafer obtained after CMP are poor; Example 1-2 balances the chemical corrosion effect of the rate accelerator, the chemical inhibition effect of the water-soluble polymer and the mechanical effect of the abrasive / polishing pad, which can effectively improve the surface flatness of the silicon wafer after CMP, reduce surface particle defects, shorten the polishing time, and improve the polishing efficiency.

[0078] Table 3 Polishing process and quality evaluation results of Examples 3-4 and Comparative Example 4

[0079]

[0080] Examples 3-4 and Comparative Example 3 respectively use first polishing liquids containing different concentrations of water-soluble polymers for the rough polishing process. Increasing the concentration of the water-soluble polymer will inhibit chemical corrosion, reduce the polishing rate, and extend the polishing time, thereby causing the flatness and particle defects to tend to deteriorate.

[0081] Table 4 Polishing process and quality evaluation results of Examples 3, 5 and Comparative Example 4

[0082]

[0083] Example 3, Example 5 and Comparative Example 4 respectively use first polishing liquids containing water-soluble polymers of different molecular weights for rough polishing. Increasing the molecular weight of the water-soluble polymer will increase the chemical inhibition, reduce the polishing rate, extend the polishing time, and tend to deteriorate the flatness.

[0084] Table 5 Polishing process and quality evaluation results of Examples 3, 6 and Comparative Example 5

[0085]

[0086] Example 3, Example 6 and Comparative Example 5 respectively use the second polishing liquid containing different concentrations of rate accelerator for the fine polishing process. Increasing the concentration of ammonia water is beneficial to reducing particle defects, but when the total rate accelerator concentration is higher than 1wt%, the surface flatness will tend to deteriorate.

[0087] Table 6 Polishing process and quality evaluation results of Examples 3, 7-8 and Comparative Example 6

[0088]

[0089] In Example 3, Example 7, Example 8 and Comparative Example 6, the second polishing liquid containing different concentrations of water-soluble polymers is used for the fine polishing process. Reducing the concentration of the water-soluble polymer HEC will make the surface particle defects tend to deteriorate. When the HEC concentration is lower than 0.1wt%, the flatness will also tend to deteriorate. In addition, increasing the concentration of the water-soluble polymer PVP will make the wafer surface particle defects tend to deteriorate.

[0090] Table 7 Polishing process and quality evaluation results of Example 3 and Comparative Example 7

[0091]

[0092] Example 3 and Comparative Example 7 respectively use the second polishing liquid containing water-soluble polymer PVP with different molecular weights for the fine polishing process. Increasing the molecular weight of the water-soluble polymer PVP will make the surface particle defects tend to become worse.

[0093] Table 8 Polishing process and quality evaluation results of Example 3 and Comparative Examples 8-9

[0094]

[0095] Example 3 and Comparative Examples 8-9 respectively use the second polishing liquid containing water-soluble polymer HEC of different molecular weights for the fine polishing process. When the molecular weight of HEC is too low, the surface defects of the silicon wafer will tend to deteriorate. When the molecular weight of HEC is too high, the chemical corrosion of the silicon surface will be greatly inhibited, the polishing rate will be reduced, and the polishing time will be prolonged.

[0096] Table 9 Polishing process and quality evaluation results of Examples 9-10 and Comparative Example 10

[0097]

[0098] Examples 9-10 and Comparative Example 10 are polished by 2-step rough polishing, 1-step medium polishing, and 2-step fine polishing. The medium polishing can use a SUBA800 rough polishing pad with a second polishing liquid, or a 7355 fine polishing pad with a first polishing liquid as the medium polishing step; compared with Comparative Example 10 without a medium polishing step, the medium polishing step can obtain better surface flatness and lower particle defects. Comparative Example 10 without a medium polishing step will require a longer polishing time, and the flatness and particle defects are poor.

[0099] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A method for polishing a silicon wafer, characterized in that: The method comprises a rough polishing stage and a fine polishing stage, wherein the rough polishing stage uses a first polishing liquid for polishing, and the fine polishing stage uses a second polishing liquid for polishing; the first polishing liquid and the second polishing liquid both contain a rate accelerator and a water-soluble polymer, wherein: The rate accelerator A1 contained in the first polishing liquid and the rate accelerator A2 contained in the second polishing liquid satisfy the following content relationship: ConA1>ConA2; The water-soluble polymer P1 contained in the first polishing liquid and the water-soluble polymer P2 contained in the second polishing liquid satisfy the following content relationship: ConP1<ConP2.

2. The silicon wafer polishing method according to claim 1, characterized in that: The polishing method comprises the following steps in order: in the first, second and third steps of rough polishing, a white rough polishing pad and the first polishing liquid are used to polish the silicon wafer; in the first and second steps of fine polishing, a black fluff pad and the second polishing liquid are used to polish the silicon wafer.

3. The silicon wafer polishing method according to claim 1, characterized in that: The polishing method also includes an intermediate polishing stage, which specifically includes the following steps in order: in the first and second steps, the rough polishing uses a white rough polishing pad and the first polishing liquid to polish the silicon wafer; in the first step, the intermediate polishing uses a black velvet pad and the first polishing liquid to polish the silicon wafer, or in the first step, the intermediate polishing uses a white rough polishing pad and the second polishing liquid to polish the silicon wafer; in the first and second steps, the fine polishing uses a black velvet pad and the second polishing liquid to polish the silicon wafer.

4. The silicon wafer polishing method according to claim 2 or 3, characterized in that: The content of the rate accelerator A1 contained in the first polishing liquid is ConA1>0.5wt%; the content of the rate accelerator A2 contained in the second polishing liquid is ConA2<1wt%.

5. The silicon wafer polishing method according to claim 4, characterized in that: The content of the rate accelerator A1 contained in the first polishing liquid is ConA1>3wt%; the content of the rate accelerator A2 contained in the second polishing liquid is ConA2<0.6wt%.

6. The silicon wafer polishing method according to claim 4, characterized in that: The rate accelerator is selected from one or more of potassium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ethylenediamine, hydroxyethylethylenediamine, piperazine, imidazole, monoethanolamine, triethanolamine, and diglycolamine, preferably potassium hydroxide, ammonium hydroxide, or tetramethylammonium hydroxide.

7. The silicon wafer polishing method according to claim 2 or 3, characterized in that: The content of the water-soluble polymer P1 contained in the first polishing liquid is ConP1<0.03wt%; the content of the water-soluble polymer P2 contained in the second polishing liquid is ConP2>0.1wt%.

8. The silicon wafer polishing method according to claim 7, characterized in that: The content of the water-soluble polymer P1 contained in the first polishing liquid is ConP1<0.01wt%; the content of the water-soluble polymer P2 contained in the second polishing liquid is ConP2>0.2wt%.

9. The silicon wafer polishing method according to claim 7, characterized in that: The water-soluble polymer is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, starch, carboxymethyl starch, pullulan, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide-polypropylene oxide, polyacrylic acid, ammonium polyacrylate, polyacrylamide, and polyglycerol, preferably hydroxyethyl cellulose, polyvinyl pyrrolidone, and polyethylene oxide-polypropylene oxide.

10. The silicon wafer polishing method according to claim 9, characterized in that: When the water-soluble polymer is hydroxyethyl cellulose, the weight average molecular weight of the hydroxyethyl cellulose is 100,000 to 500,000; when the water-soluble polymer is polyvinyl pyrrolidone, the weight average molecular weight of the polyvinyl pyrrolidone is less than 1.6 million; when the water-soluble polymer is polyethylene oxide-polypropylene oxide, the weight average molecular weight of the polyethylene oxide-polypropylene oxide is 1000 to 4000.

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