Double-sided grinding apparatus, double-sided grinding method for semiconductor silicon wafers, and manufacturing method for double-sided ground silicon wafers.

Abstract

The double-sided polishing apparatus of the present invention comprises: upper and lower platforms, each individually fitted with polishing cloth; a slurry supply mechanism for supplying slurry between the upper and lower platforms; and a carrier for the double-sided polishing apparatus disposed between the upper and lower platforms and having a retaining hole for retaining a semiconductor silicon wafer clamped between the upper and lower platforms during polishing; wherein the carrier for the double-sided polishing apparatus is a metal carrier having a contact angle of 50° or more with pure water on the surface and back side in contact with the polishing cloth; and the polishing cloth having a contact angle of 100° or more with pure water and a compression ratio of 5.0% or more. This provides a double-sided polished silicon wafer with a high-quality surface characterized by fewer surface defects and lower haze levels, and a double-sided polishing apparatus capable of manufacturing such a double-sided polished silicon wafer.

Description

Technical Field

[0001] This invention relates to a double-sided polishing apparatus, a double-sided polishing method for semiconductor silicon wafers, a manufacturing method for double-sided polished silicon wafers, and semiconductor silicon wafers. Prior Technology

[0002] When simultaneously polishing both sides of a semiconductor silicon wafer (hereinafter, also simply referred to as "silicon wafer" or "wafer"), a carrier for a double-sided polishing apparatus (hereinafter, also simply referred to as "carrier") is used to hold the wafer. The carrier for the double-sided polishing apparatus is formed to be thinner than the wafer and has holding holes for holding the wafer. The wafer is inserted into these holding holes for holding, and the carrier is positioned at a predetermined position between the upper and lower platforms of the double-sided polishing apparatus. Abrasive cloth is attached to the upper and lower platforms, and the upper and lower surfaces of the wafer are clamped between them. Double-sided polishing is performed while abrasive paste (slurry) is supplied between the upper and lower platforms (Patent Document 1).

[0003] [Previous Technical Documents] (Patent Documents) Patent Document 1: Japanese Patent Application Publication No. 2015-123553 Patent Document 2: Japanese Patent Application Publication No. 2015-009315 Patent Document 3: International Publication No. 2018 / 105306 Patent Document 4: Japanese Patent Application Publication No. 2006-045757 Summary of the Invention

[0004] [The problem the invention aims to solve] In current double-sided grinding practices, the surface quality of the wafer is sacrificed to ensure grinding removal rate and wafer margin, making it difficult to produce wafers with high-quality surfaces. To address this issue, various attempts have been made to adjust the grinding components and grinding conditions. Current reports focus on various effects of adjusting the wettability of the grinding components during the double-sided grinding process to suppress increases in grinding removal rate and component wear (Patent Documents 2, 3, etc.). Among these, there are reports, such as those in Patent Document 4, of setting the contact angle of the grinding cloth surface to 60° or more but less than 130° to reduce scratches during grinding.

[0005] In double-sided wafer polishing, not only is high-precision planarization, a long-standing challenge, required, but in recent years, high-quality surfaces have also been demanded to improve semiconductor device yield. Examples of surface quality evaluation criteria include surface defects and haze. Surface defects are primarily processing-induced deterioration layers caused by abrasive particles during polishing; haze refers to the degree of blurring on the wafer surface. To improve these qualities, effective component and condition selection is crucial, making the selection of the most suitable components and conditions a critical issue.

[0006] The present invention is made to solve the above-mentioned problems, and aims to provide a double-sided polished silicon wafer with a high-quality surface having fewer surface defects and lower haze level, and a double-sided polishing apparatus for obtaining such a double-sided polished silicon wafer.

[0007] [Technical means to solve the problem] The present invention was made to achieve the above-mentioned objective, and provides a double-sided polishing apparatus comprising: upper and lower platforms, each individually having an polishing cloth attached thereto; a slurry supply mechanism for supplying slurry between the upper and lower platforms; and a carrier for the double-sided polishing apparatus disposed between the upper and lower platforms and having a retaining hole formed therein to retain a semiconductor silicon wafer clamped between the upper and lower platforms during polishing; wherein the carrier for the double-sided polishing apparatus is a metal carrier having a contact angle of 50° or more with pure water on the surface and the back side in contact with the polishing cloth; and the polishing cloth having a contact angle of 100° or more with pure water and a compression ratio of 5.0% or more.

[0008] Based on this double-sided grinding device, it is possible to obtain double-sided ground silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels.

[0009] At this time, the aforementioned abrasive cloth can be set as a foamed urethane or non-woven abrasive cloth with a Shore hardness A of 70 or higher.

[0010] This enables the production of stable, high-quality double-sided polished silicon wafers.

[0011] At this time, a double-sided polishing method for semiconductor silicon wafers can be configured, in which a double-sided polishing apparatus carrier is disposed between upper and lower platforms on which polishing cloths are individually attached; the aforementioned semiconductor silicon wafer is held in a holding hole formed in the double-sided polishing apparatus carrier, and double-sided polishing is performed while slurry is supplied between the aforementioned upper and lower platforms; wherein, the double-sided polishing method uses the aforementioned double-sided polishing apparatus.

[0012] Based on this double-sided grinding method for semiconductor silicon wafers, it is possible to obtain double-sided ground silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels.

[0013] At this point, a method for manufacturing a double-sided polished silicon wafer can be established, which uses the aforementioned double-sided polishing method for semiconductor silicon wafers to manufacture a double-sided polished silicon wafer.

[0014] This enables the manufacture of double-sided polished silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels.

[0015] The present invention also provides a double-sided polished silicon wafer, which, when converted to a wafer with a diameter of 300 mm, has fewer than 10 surface defects above 90 nm detected by a light scattering particle counter and a haze of less than 1.0 ppm.

[0016] This double-sided polished silicon wafer has fewer surface defects and lower haze levels, resulting in a high-quality surface and improving the yield of semiconductor devices.

[0017] [The effects of the invention] As described above, the double-sided polishing apparatus according to the present invention can obtain double-sided polished silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels. The double-sided polishing method for semiconductor silicon wafers according to the present invention can also obtain double-sided polished silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels. Furthermore, the double-sided polished silicon wafers of the present invention have high-quality surfaces due to their fewer surface defects and lower haze levels, which is beneficial for improving the yield of semiconductor devices. Simple Explanation of the Diagram

[0018] Figure 1 is a longitudinal cross-sectional view showing an example of the double-sided grinding apparatus of the present invention. Figure 2 is an internal structure diagram of an example of a double-sided grinding device viewed from above. Figure 3 shows the results of comparing the number of surface defects for Comparative Examples 1 and 2. Figure 4 shows the results of comparing the haze levels for Comparative Examples 1 and 2. Figure 5 shows the results of contact angle measurements of the vehicles used in Example 2 and Comparative Examples 3-5. Figure 6 shows the results of the contact angle measurement of the abrasive cloth used in Example 2 and Comparative Examples 3-5. Figure 7 shows the results of comparing the number of surface defects for Examples 1, 2 and Comparative Examples 3-5. Figure 8 shows the results of comparing the haze levels for Examples 1, 2 and Comparative Examples 3-5. Implementation

[0019] The present invention will now be described in detail, but the present invention is not limited to these embodiments.

[0020] As mentioned above, the aim is to obtain a double-sided polished silicon wafer with a high-quality surface characterized by fewer surface defects and lower haze levels, and a double-sided polishing apparatus capable of manufacturing such a double-sided polished silicon wafer.

[0021] The inventors have repeatedly and creatively examined the aforementioned problems and discovered a double-sided polishing apparatus comprising: upper and lower platforms, each individually affixed with polishing cloth; a slurry supply mechanism that supplies slurry between the upper and lower platforms; and a carrier for the double-sided polishing apparatus disposed between the upper and lower platforms and having a retaining hole formed therein to retain a semiconductor silicon wafer sandwiched between the upper and lower platforms during polishing; wherein the carrier for the double-sided polishing apparatus is a metal carrier having a contact angle of 50° or more with pure water on the surface and back side in contact with the polishing cloth; the polishing cloth has a contact angle of 100° or more with pure water and a compression ratio of 5.0% or more; thereby, a double-sided polishing apparatus can be used to obtain a high-quality double-sided polished silicon wafer with fewer surface defects and lower haze levels, thus completing the present invention.

[0022] The inventors have discovered a double-sided polished silicon wafer that, when converted to a 300mm diameter wafer, has fewer than 10 surface defects larger than 90nm detected by a light scattering particle counter and a haze of less than 1.0ppm; thereby improving the yield of semiconductor devices, etc., thus completing the present invention.

[0023] The following explanation is based on the diagram.

[0024] [Double-sided grinding device] First, the double-sided polishing apparatus of the present invention will be described. Figure 1 is a longitudinal sectional view of an example of the double-sided polishing apparatus of the present invention; Figure 2 is a top view of the internal structure of the double-sided polishing apparatus. As shown in Figures 1 and 2, the double-sided polishing apparatus 2 of the present invention includes a lower platform 3 and an upper platform 4 arranged opposite each other, and polishing cloth 5 is individually attached to the opposite side of each platform 3, 4. Furthermore, a slurry supply mechanism 6 (nozzle 7 and through hole 8 of the upper platform 4) is provided on the upper part of the upper platform 4 to supply slurry between the upper platform 4 and the lower platform 3. As the slurry, for example, an inorganic alkaline aqueous solution containing colloidal silicon oxide can be used.

[0025] The embodiments shown in Figures 1 and 2 are of a 4-way double-sided grinding device, in which a sun gear 9 is provided at the center between the upper platform 4 and the lower platform 3, and an internal gear 10 is provided at the periphery. However, the double-sided grinding device of the present invention is not limited to this planetary gear type; it can also be a rocking type grinding device.

[0026] A semiconductor silicon wafer W is held in the holding hole 11 of a carrier 1 for a double-sided polishing apparatus, and is sandwiched between an upper platform 4 and a lower platform 3. This carrier 1 for the double-sided polishing apparatus is made of metal, and the contact angle (hereinafter referred to as "contact angle") between the surface and the back side of the polishing cloth 5 that is in contact with pure water is 50° or more. When the contact angle is less than 50°, the number of surface defects increases. Furthermore, there is no particular upper limit to the contact angle; a larger contact angle, i.e., higher water repellency, is better, but it can be set to 80° or less, for example. Also, the carrier can be made of metal; examples of metals include SUS and titanium. Using a metal carrier can improve the polishing removal rate. In addition, the contact angle between the surface and the back side of the carrier can be adjusted according to the metal base material. A preferred contact angle is 60 ± 5°.

[0027] The abrasive cloth 5 used has a contact angle of 100° or more with pure water and a compression rate of 5.0% or more. When the contact angle is less than 100°, a sufficient reduction in haze level cannot be expected. Furthermore, when the compression rate is less than 5.0%, the number of surface defects increases.

[0028] There is no specific upper limit to the contact angle of the abrasive cloth; a larger contact angle, i.e., higher water repellency, is better, but it can be set to, for example, below 150°. The contact angle of the abrasive cloth can be adjusted by adding materials during the manufacturing process. An optimal contact angle is 120 ± 10°.

[0029] Furthermore, there is no specific upper limit to the compression rate of the abrasive cloth; a higher compression rate is generally better, but it can be set to, for example, below 15%. The compression rate of the abrasive cloth can be adjusted by additives used during its manufacturing process. A better compression rate is 5.0% or higher and 10.0% or lower. Additionally, the compression rate of the abrasive cloth is specified by JIS L 1096.

[0030] Furthermore, as the abrasive cloth 5, for example, a foamed polyurethane-based or non-woven abrasive cloth can be used, preferably an abrasive cloth with a Shore hardness A of 70 or higher. This is because it can obtain stable double-sided abrasive silicon wafers with high-quality surfaces. There is no particular upper limit to the Shore hardness A, but for example, an abrasive cloth with a Shore hardness A of 90 or lower can be used.

[0031] Furthermore, the contact angle of the carrier and abrasive cloth can be measured, for example, using the PCA-11 from Kyowa Interface Science Co., Ltd. The measurement can be performed, for example, by dropping a 2.0 μL drop of pure water onto the evaluation surface and obtaining the contact angle from image resolution. However, the method for measuring the contact angle is not limited to this and can be appropriately determined.

[0032] Furthermore, as shown in Figures 1 and 2, the outer peripheral teeth of the carrier 1 mesh with the teeth of the sun gear 9 and the internal gear 10. With the rotation of the upper platform 4 and the lower platform 3 generated by a drive source (not shown), the carrier 1 rotates on its own axis while revolving around the sun gear 9. At this time, the semiconductor silicon wafer W is held by the holding hole 11 of the carrier 1, and double-sided polishing is performed simultaneously by the upper and lower polishing cloths 5. Additionally, during polishing, slurry is supplied from the nozzle 7 through the through hole 8.

[0033] This double-sided grinding apparatus can produce double-sided ground silicon wafers with high-quality surfaces, characterized by fewer surface defects and lower haze levels.

[0034] [Double-sided grinding method and manufacturing method of double-sided ground silicon wafers] The double-sided polishing method for semiconductor silicon wafers of the present invention is a method implemented using the double-sided polishing apparatus of the present invention described above. That is, using the double-sided polishing apparatus of the present invention, a carrier for the double-sided polishing apparatus is disposed between upper and lower platforms on which polishing cloths are individually attached, the semiconductor silicon wafer is held in a holding hole formed in the carrier for the double-sided polishing apparatus, and double-sided polishing is performed while slurry is supplied between the upper and lower platforms.

[0035] Specifically, as shown in Figures 1 and 2, a carrier 1 for holding a semiconductor silicon wafer W is inserted between the upper and lower platforms 3 and 4 of the double-sided polishing apparatus 2. Next, the semiconductor silicon wafer W is held within the holding hole 11 of the carrier 1. Furthermore, while slurry is supplied to the polishing surface by the slurry supply mechanism 6, the upper and lower platforms 3 and 4 are rotated, and the carrier 1 rotates on its own axis and revolves around the center. This causes both sides of the semiconductor silicon wafer W to slide into contact with the polishing cloth 5, thereby enabling double-sided polishing of the semiconductor silicon wafer W.

[0036] If the double-sided grinding method of the semiconductor silicon wafer of the present invention is used, a double-sided ground silicon wafer with a high-quality surface, having fewer surface defects and a low haze level, can be manufactured.

[0037] [Double-sided ground silicon wafer] As described above, the double-sided polishing method for semiconductor silicon wafers implemented using the double-sided polishing apparatus of the present invention can obtain double-sided polished silicon wafers with high-quality surfaces. Specifically, based on a 300mm diameter wafer, the double-sided polished silicon wafer has fewer than 10 surface defects larger than 90nm detected by a light scattering particle counter and a haze level of less than 1.0ppm. This type of double-sided polished silicon wafer has a high-quality surface with few surface defects and low haze levels, which is beneficial for improving the yield of semiconductor devices. Furthermore, there are no particular limitations on the diameter, conductivity type, or surface orientation of the main surfaces of the silicon wafer.

[0038] [Example] The present invention is illustrated below with examples, but the present invention is not limited to these examples.

[0039] (Common experimental conditions) As a double-sided grinding device, a DSP-20B manufactured by Nachi-Fujikoshi Machinery Co., Ltd., a 4-way double-sided grinding device, was used. The grinding cloth was a foamed polyurethane pad with a Shore A hardness of 78; the slurry was a KOH-based slurry containing silicon oxide abrasive particles with an average particle size of 35 nm, a particle concentration of 1.0 wt%, pH 10.5. The double-sided grinding process was performed on P-type silicon wafers with a main surface area of ​​(100) and a diameter of 300 mm, and a total of 5 wafers were subjected to double-sided grinding. The processed wafers were then cleaned using SC-1 with a NH4OH:H2O2:H2O ratio of 1:1:15.

[0040] The contact angle between the carrier and the abrasive cloth was measured using a portable contact angle meter manufactured by Kyowa Interface Science Co., Ltd. The surface quality of the double-sided polished silicon wafer, including surface defects and haze, was measured using a KLA SP5 laser scattering particle counter. Measurement conditions were referenced to the haze measured in the DW-2 channel.

[0041] (Compare Examples 1 and 2) First, as described below, only change the compression rate of the abrasive cloth, and set all other conditions to be the same. Comparative Example 1: The compression rate of the abrasive cloth was set to 2.0%. Comparative Example 2: The compression rate of the abrasive cloth was set to 9.0%. To investigate the impact of variations in the compression rate of the abrasive cloth on the surface quality of double-sided polished silicon wafers, components such as the carrier and slurry, which affect surface quality other than the compression rate of the abrasive cloth, were standardized. Furthermore, the contact angle conditions of the carrier and the abrasive cloth were set to 30° for the carrier and 50° for the abrasive cloth.

[0042] Figure 3 shows the results of comparing the number of surface defects. Figure 4 shows the results of comparing the haze level. As shown in Figures 3 and 4, it can be seen that the wafer polished by the polishing cloth with a compression ratio of 9.0% in Comparative Example 2 has lower surface defects and haze, and is more suitable than the polishing cloth with a lower compression ratio in Comparative Example 1.

[0043] (Example 1) A SUS-made metal substrate with a contact angle of 50° (water-repellent) on both the front and back sides was used as the substrate. A polishing cloth with a contact angle of 100° (water-repellent) and a compression ratio of 5.0% or higher was used as the polishing cloth. Double-sided polishing of the silicon wafer was performed, and the surface quality was investigated. The results showed that the maximum number of surface defects was 16, with an average of 9.8. Furthermore, the maximum haze level was 0.88 ppm, with an average of 0.71 ppm. These results indicate good performance with low surface defects and haze.

[0044] (Comparative Examples 3-5, Example 2) Based on the results of Comparative Examples 1 and 2 above, an abrasive cloth with a compression rate of 9.0% was used in Examples 2 and 3-5. For the contact angles of the carrier and the abrasive cloth, carriers with a contact angle of less than 50° (hydrophilic) and carriers with a contact angle of 50° or more (water-repellent) were prepared; abrasive cloths with a contact angle of less than 100° (hydrophilic) and abrasive cloths with a contact angle of 100° or more (water-repellent) were prepared. Figure 5 shows the measurement results of the contact angles of the two types of carriers prepared; Figure 6 shows the measurement results of the contact angles of the two types of abrasive cloths prepared.

[0045] The prepared carrier and abrasive cloth are combined as follows to perform double-sided abrasive polishing of silicon wafers and investigate surface quality. Comparative Example 3: The contact angle of the vehicle is less than 50° (hydrophilic) + the contact angle of the abrasive cloth is less than 100° (hydrophilic). Comparative Example 4: The contact angle of the vehicle is less than 50° (hydrophilic) + the contact angle of the abrasive cloth is more than 100° (water-repellent). Comparative Example 5: The contact angle of the vehicle is 50° or more (water-repellent) + the contact angle of the abrasive cloth is less than 100° (hydrophilic). Example 2: The contact angle of the carrier is 50° or higher (water-repellent) + the contact angle of the abrasive cloth is 100° or higher (water-repellent).

[0046] Figure 7 shows the results of comparing the number of surface defects. Figure 8 shows the results of comparing the haze level. As shown in Figures 7 and 8, it can be seen that the wafer of Example 2 has the highest surface quality. Regarding the number of surface defects, even the maximum value of the wafer of Example 2 is less than 10 (the average is 4.8), and the deviation is small. Also, regarding the haze level, even the maximum value of the wafer of Example 2 is less than 1.0 ppm (the average is 0.64 ppm), which is a low level.

[0047] In the grinding conditions of Examples 1 and 2, both the carrier and the grinding cloth are set to have high water repellency. Therefore, to improve the surface quality of double-sided ground wafers, it can be determined that water-repellent components (contact angle of the carrier is 50° or more, and contact angle of the grinding cloth is 100° or more) and grinding cloth with high compressibility are the most suitable.

[0048] Furthermore, the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiment that has substantially the same structure and performs the same effect as the technical concept covered in the claims of the present invention is included in the technical scope of the present invention.

[0049] 1: Carrier (carrier for double-sided grinding device) 2: Double-sided grinding device 3: Lower Platform 4: Go to the platform 5: Abrasive cloth 6: Slurry supply mechanism 7: Nozzle 8: Through hole 9: Sun Gear 10: Internal gears 11: Retaining Hole W: Silicon wafer (semiconductor silicon wafer)

[0050] Domestic storage information (please note in order of storage institution, date, and number) none

[0051] Overseas storage information (please note in the order of storage country, institution, date, and number) none

Claims

1. A double-sided polishing apparatus comprising: upper and lower platforms, each individually affixed with polishing cloth; a slurry supply mechanism for supplying slurry between the upper and lower platforms; and a carrier for the double-sided polishing apparatus disposed between the upper and lower platforms and having a retaining hole for retaining a semiconductor silicon wafer clamped between the upper and lower platforms during polishing; characterized in that the carrier for the double-sided polishing apparatus is a metal carrier having a contact angle of 50° or more and 80° or less with pure water on the surface and back side in contact with the polishing cloth; and the polishing cloth having a contact angle of 100° or more and 150° or less with pure water and a compression ratio of 5.0% or more and 15% or less.

2. The double-sided grinding apparatus as described in claim 1, wherein, The aforementioned abrasive cloth is a foamed polyurethane or nonwoven abrasive cloth with a Shore hardness A of 70 or higher.

3. A method for double-sided polishing of a semiconductor silicon wafer, comprising: arranging a double-sided polishing apparatus carrier between upper and lower platforms on which polishing cloths are individually attached; holding the semiconductor silicon wafer in a holding hole formed in the double-sided polishing apparatus carrier, and performing double-sided polishing while supplying slurry between the upper and lower platforms; characterized in that the double-sided polishing apparatus described in claim 1 or 2 is used.

4. A method for manufacturing a double-sided polished silicon wafer, characterized in that the double-sided polished silicon wafer is manufactured by the double-sided polishing method of the semiconductor silicon wafer described in claim 3.

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