Polishing pad and wafer polishing method

Abstract

A polishing pad and a wafer polishing method are provided, which can suppress scratches on the polished wafer and achieve high precision and improved workability. In a double-sided polishing wafer polishing apparatus (10), the polishing pad can serve as a first polishing pad (7) and a second polishing pad (9). The wafer (W) is formed of SiC, with one of its first side (W1) and second side (W2) being a Si side and the other side being a C side. The polishing pad comprises: a base material (19) containing a bonding resin and having multiple pores (21, 23); and polishing particles (25a, 25b) retained within the base material (19) or within the pores (21, 23). The bonding resin is a sulfonic acid resin, and the polishing particles (25a, 25b) are composed of silicon dioxide with a Durometer hardness (D) of 30 to 52 and a density of 0.60 to 0.90 g / cm³. 3 .

Description

Technical Field

[0001] This invention relates to polishing pads and wafer polishing methods. Background Technology

[0002] A method for simultaneously polishing both sides of a SiC wafer is disclosed in Patent Document 1. This wafer polishing method is used in a double-sided polishing wafer polishing apparatus. In this apparatus, under a specified contact pressure, the first side of the wafer is moved relative to a first polishing pad to polish the first side with the first polishing pad, and the back side of the first side, i.e., the second side, is moved relative to a second polishing pad to polish the second side with the first polishing pad. At this time, an polishing slurry containing no abrasive particles is placed between the first side of the wafer and the first polishing pad, and between the second side of the wafer and the second polishing pad.

[0003] The wafer polishing apparatus, more specifically, includes a first polishing pad, a second polishing pad, and a carrier. The first polishing pad has a first polishing pad extending in a direction orthogonal to its axis, and rotates about its axis. The second polishing pad has a second polishing pad extending in a direction orthogonal to its axis and opposite to the first polishing pad, and rotates about its axis. The carrier has a fixing portion extending in a direction orthogonal to its axis and opposite to both the first and second polishing pads, and rotates relative to the first and second polishing pads.

[0004] The first and second abrasive pads are abrasive-embedded abrasive pads that include: a base material containing a bonding resin and forming multiple pores; and abrasive particles retained within the base material or pores. They are also known as LHA (Loosely Held Abrasive) pads.

[0005] In this wafer polishing method, when the first side of the wafer is a Si surface and the second side is a C surface, the polishing rate of the first polishing pad is lower than that of the second polishing pad because the polishing susceptibility of the second side is greater than that of the first side. This suppresses scratches on the polished wafer and achieves high workability and precision.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 7433170 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, in the existing wafer polishing methods described above, a first polishing pad and a second polishing pad with different polishing rates must be used, which results in insufficient workability.

[0011] In view of the above-mentioned existing situation, the present invention aims to solve the problem of providing a polishing pad and a wafer polishing method that can suppress scratches on the polished wafer and achieve high precision and higher workability.

[0012] Problem-solving methods

[0013] The polishing pad of the present invention is characterized in that it is used in a double-sided polishing wafer polishing apparatus to polish the first surface of a wafer by moving the first surface of the wafer relative to the first polishing pad under a specified contact pressure, and to polish the second surface of the wafer by moving the back side of the first surface of the wafer, i.e., the second surface, relative to the second polishing pad. It can serve as a polishing pad for both the first and second polishing pads.

[0014] The wafer grinding apparatus includes:

[0015] A first fixed plate having a first grinding pad extending in a direction orthogonal to the axis and rotating about the axis;

[0016] The second plate has a second abrasive pad extending in a direction orthogonal to the axis and opposite to the first abrasive pad, and rotates about the axis;

[0017] A carrier having a fixed portion extending along a direction orthogonal to the axis and opposite to the first grinding pad and the second grinding pad, and rotating relative to the first and second fixed plates.

[0018] The wafer is fixed in the fixing portion such that the first surface faces the first polishing pad and the second surface faces the second polishing pad.

[0019] The wafer is formed of SiC, with one of the first and second faces being a Si face and the other being a C face.

[0020] The abrasive pad comprises: a base material containing a bonding resin and having multiple pores; and abrasive particles retained within the base material or within the pores.

[0021] The adhesive resin is a sulfonic acid resin.

[0022] The abrasive particles are formed of silicon dioxide.

[0023] The Durometer hardness (D) ranges from 30 to 52.

[0024] Its density is 0.60–0.90 g / cm³. 3 .

[0025] Furthermore, the wafer polishing method of the present invention is characterized by using a wafer polishing apparatus equipped with the following:

[0026] A first fixed plate has a first grinding pad extending in a direction orthogonal to the axis and rotating about the axis;

[0027] The second plate has a second grinding pad extending in a direction orthogonal to the axis and opposite to the first grinding pad, and rotates about the axis;

[0028] A carrier having a fixed portion extending along a direction orthogonal to the axis and opposite to the first grinding pad and the second grinding pad, and rotating relative to the first and second fixed plates.

[0029] The wafer is fixed in the fixing part such that the first surface faces the first polishing pad, and the back surface of the first surface, i.e., the second surface, faces the second polishing pad.

[0030] Under a specified contact pressure, the first surface is ground by moving relative to the first abrasive pad, and the second surface is ground by moving relative to the second abrasive pad.

[0031] The wafer is formed of SiC, with one of the first and second faces being a Si face and the other being a C face.

[0032] The first and second abrasive pads are the same type of abrasive pad, comprising: a base material containing a binding resin and having multiple pores; and abrasive particles retained within the base material or the pores.

[0033] The adhesive resin is a sulfonic acid resin.

[0034] The abrasive particles are formed of silicon dioxide.

[0035] The Durometer hardness (D) ranges from 30 to 52.

[0036] Its density is 0.60–0.90 g / cm³. 3 .

[0037] According to the inventors' experimental results, if the first and second polishing pads use the aforementioned polishing pads, scratches on the polished wafer can be suppressed, and high precision can be achieved. Therefore, the wafer polishing method of the present invention, using the polishing pads of the present invention, eliminates the need for using first and second polishing pads with different polishing rates, and also achieves higher workability.

[0038] The effects of the invention

[0039] The polishing pad and wafer polishing method of the present invention can suppress scratches on the polished wafer and achieve high precision and higher workability. Attached Figure Description

[0040] Figure 1 This is a schematic cross-sectional view of the wafer grinding apparatus in an embodiment.

[0041] Figure 2 This is a 500x SEM image of the abrasive pad from Example 1.

[0042] Figure 3 This is a 2000x SEM image of the first region in the polishing pad of Example 1.

[0043] Figure 4 This is a 400x SEM image of the second region in the polishing pad of Example 1.

[0044] Figure 5 This is a 2000x SEM image of the second region in the polishing pad of Example 1.

[0045] Figure 6 These are schematic enlarged cross-sectional views of the abrasive pads in Examples 1 to 7. Detailed Implementation

[0046] Sulfonic acid resin is used as the bonding resin. For LHA pads, in addition to polyether, rigid polyurethane foam, epoxy resin, and polyethersulfone resin, fluorinated synthetic resins such as polyvinylidene fluoride, vinyl fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and vinyl fluoride-hexafluoropropylene copolymer, or polyethylene resin and polymethyl methacrylate, can also be used as the bonding resin. However, based on the inventors' experimental results, sulfonic acid resin is preferred for use as the first and second abrasive pads due to its excellent chemical resistance and wear resistance.

[0047] As a sulfonic acid resin, polyethersulfone (PES), polysulfone (PSU), polyphenylsulfone (PPSU), etc., can be used. The inventors confirmed the effects of the present invention using PES.

[0048] Silica is used as the abrasive particle. LHA pads can use silica, diamond, cubic boron nitride, boron carbide, silicon carbide, alumina, zirconium oxide, titanium dioxide, cerium oxide, manganese oxide, barium carbonate, chromium oxide, iron oxide, etc., as abrasive particles. However, based on the inventors' experimental results, silica is preferred as the abrasive pad used for both the first and second abrasive pads because its low Knoop hardness makes it difficult to scratch. This is based on its superior abrasive properties.

[0049] Based on the inventors' test results, the preferred abrasive pads used as the first and second abrasive pads have a Durometer hardness (D) of 30 to 52 and a density of 0.60 to 0.90 g / cm³. 3 .

[0050] According to the inventors' test results, the preferred composition is 17.6 to 26.2% by volume of bonding resin, 16.3 to 24.6% by volume of abrasive particles, and 49.2 to 66.1% by volume of pores.

[0051] The preferred pores include: micropores forming a three-dimensional network structure, and large pores with a volume larger than the micropores and connected to numerous micropores. In this case, the polishing surface of the polishing pad will have a first region without large pores and a second region with large pores. In the first region, the bonding resin forms a network structure, and abrasive particles are embedded within the pores. Furthermore, in the first region, the bonding resin and abrasive particles are densely present. Therefore, high-efficiency polishing can be expected in the first region. On the other hand, in the second region, a large number of micropores exist on the surface of the large pores, and abrasive particles are discharged from each micropore. In addition, polishing fluid is accumulated in the large pores. The abrasive particles discharged from the micropores into the large pores maintain their freedom of movement while polishing within the large pores. Furthermore, the large pores suppress the processing resistance of the wafer during double-sided polishing, resulting in a high-quality wafer after polishing and reducing wafer breakage during double-sided polishing.

[0052] Based on the inventors' experimental results, the preferred pore size is 44.1–51.6% of the volume, and the preferred pore size is 2.7–15.7% of the volume.

[0053] In traditional wafer polishing methods, the polishing slurry is placed between the wafer and a first polishing pad and between the wafer and a second polishing pad. However, in the wafer polishing method of this invention, a polishing slurry without polishing particles can be used. This improves the cleanability of the polished wafer and is also expected to reduce waste liquid costs.

[0054] (Examples and Comparative Examples)

[0055] First, prepare Figure 1 The wafer polishing apparatus 10 shown is a double-sided polishing type (9B double-sided polisher). This wafer polishing apparatus 10 has a first platen 1, a second platen 3, and a carrier 5. The wafer polishing apparatus 10 can simultaneously polish the first side W1 and the second side W2 of a wafer W.

[0056] The first fixed disk 1 is annular, with an annular first polishing pad 7 on its lower surface. The second fixed disk 3 is also annular, matching the first fixed disk 1, and has an annular second polishing pad 9 on its upper surface. A first rotating shaft (not shown) is provided on the first fixed disk 1, and a second rotating shaft (not shown) is provided on the second fixed disk 3. They extend along the axis X1 and rotate around the axis X1 at a predetermined speed under the drive of the drive device 11. Furthermore, the first fixed disk 1 and the second fixed disk 3 can be brought close together or separated. The first polishing pad 7 and the second polishing pad 9 extend horizontally in a direction orthogonal to X1 and are opposite each other.

[0057] The carrier 5 is positioned between the first grinding pad 7 and the second grinding pad 9. The carrier 5 is equipped with a driving force transmission mechanism (not shown), which causes the first fixed plate 1 and the second fixed plate 3 to rotate relative to each other at a predetermined speed around an axis X2 that is parallel to the axis X1.

[0058] The fixing part 5a of the carrier 5 extends horizontally along a direction orthogonal to the axis X2, and is opposite to the first polishing pad 7 and the second polishing pad 9. A wafer W is fixed on the fixing part 5a. The carrier 5 has multiple fixing parts 5a, and can load multiple wafers W.

[0059] Each wafer W is formed of SiC. The Si surface of SiC is the first surface W1, and the C surface of SiC is the second surface W2. The first surface W1 of wafer W is opposite to the first polishing pad 7, and the second surface W2 is opposite to the second polishing pad 9.

[0060] An annular tray 13 is disposed on the first fixed plate 1. The tray 13 can also rotate with the first fixed plate 1 around an axis X1. A plurality of nozzles 15 are provided facing the tray 13, and each nozzle 15 is connected to a storage tank (not shown). Therefore, the grinding fluid 17 in the storage tank is supplied to the tray 13 from each nozzle 15. A plurality of supply holes 13a are formed on the tray 13, and each supply hole 13a is connected to a tube 19 extending to the first fixed plate 1. A connecting hole 1a and an opening 7a are provided through the first fixed plate 1 and the first grinding pad 7, and the grinding fluid 17 in the tray 13 can be supplied to the space between the first grinding pad 7 and the second grinding pad 9 through each supply hole 13a, each tube 19, each connecting hole 1a and each opening 7a.

[0061] If the wafer W is fixed to the fixing part 5a and the wafer polishing apparatus 10 is activated, the first fixed disk 1 and the second fixed disk 3 approach each other. Each wafer W fixed to the fixing part 5a of the carrier 5 is pressurized with the first and second polishing pads 7 and 9 at a predetermined contact pressure. Simultaneously, the drive device 11 drives the first fixed disk 1, the second fixed disk 3, and the carrier 5 to rotate. Thus, the first surface W1 of the wafer W moves relative to the first polishing pad 7 at a predetermined speed to polish the first surface W1, and the second surface W2 of the wafer W moves relative to the second polishing pad 9 at a predetermined speed to polish the second surface W2. After a predetermined time, the polishing of the first surface W1 and the second surface W2 can be completed simultaneously.

[0062] On the other hand, prepare the following bonding resin, abrasive particles, solvent, pore-forming agent and additives.

[0063] (Adhesive resin)

[0064] Polyethersulfone (PES)

[0065] (Grinding particles)

[0066] Silica (SiO2) (Average particle size: 200nm)

[0067] (solvent)

[0068] N-methyl-2-pyrrolidone (NMP)

[0069] (Pore forming agent)

[0070] Granulated sugar (average particle size 200μm)

[0071] (additive)

[0072] glycerin

[0073] According to the proportions (volume %) in Table 1, mix the above-mentioned binder resin, abrasive particles, solvent, pore-forming agent, and additives to obtain a paste. Using the obtained pastes, form sheet-like molded articles using a T-die. Remove the solvent from each molded article and allow the binder resin to cure.

[0074] Table 1

[0075]

[0076] The resulting intermediate was finished to produce the polishing pads for Examples 1-7 and Comparative Example 1. A 500x SEM image of the polishing pad from Example 1 is shown. Figure 2 In the middle. By Figure 2It is known that the abrasive pads of Examples 1-7 include: a base material containing a binding resin and having multiple pores; and abrasive particles retained within the base material or within the pores. Furthermore, it is known that the pores include: fine pores with a three-dimensional network structure, and large pores with a volume larger than the fine pores and communicating with them. The fine pores are formed by a solvent, and the large pores are formed by granular sugar. Glycerin is used to adjust the solubility of the binding resin in the solvent.

[0077] As physical property values ​​of the abrasive pads of Examples 1-7 and Comparative Example 1, the Durometer hardness (D) and density (g / cm³) were measured. 3 The contents of the bonding resin (volume %), the abrasive particles (volume %), and the pores (volume %) were calculated. The results are shown in Table 2.

[0078] Table 2

[0079]

[0080] In addition, details of the pore content were also measured, namely the content of micropores (volume %) and the content of macropores (volume %). The results are shown in Table 3.

[0081] Table 3

[0082]

[0083] Additionally, in the polishing pad of Example 1, a 2000x SEM image of the first region, where there are no large pores, is shown. Figure 3 In addition, the additive density (volume %) of the bonding resin in the first region of the abrasive pads of Examples 1 to 7 and the additive density (volume %) of the abrasive particles are shown in Table 4.

[0084] Table 4

[0085]

[0086] Depend on Figure 3 It can be seen that in the first region, the bonding resin forms a network structure, and the abrasive particles are embedded within these pores. Furthermore, as shown in Table 4, the volume fraction of bonding resin and abrasive particles in large pores with a diameter of approximately 200 μm is densely distributed.

[0087] On the other hand, the 400x SEM images of the second region show... Figure 4 In the middle, the SEM image of the second region, magnified 2000 times, is shown Figure 5 In the middle. By Figure 4 and Figure 5 It can be seen that large atmospheric pores are formed in the second region, and a large number of fine pores with a diameter of about 4μm exist on the surface of the atmospheric pores, from which abrasive particles are discharged.

[0088] (test)

[0089] As the first polishing pad 7 and the second polishing pad 9 of the wafer polishing apparatus 10 described above, polishing tests were conducted under the following conditions using polishing pads from Examples 1 to 7 or Comparative Example 1.

[0090] Abrasive pad dimensions: 660mm diameter (with a 200mm diameter hole punched from the center) ring

[0091] Wafer W: SiC (4-inch diameter)

[0092] Grinding slurry: Permanganate aqueous solution (without grinding particles)

[0093] The grinding rate (μm / h), the surface roughness Ra (nm) of the Si surface, the surface roughness Ra (nm) of the C surface, the processing resistance (A) converted from current value, and TTV (μm) were measured. Furthermore, TTV is an indicator of the thickness deviation of the wafer W. A high TTV indicates a large thickness deviation, while a low TTV indicates a small thickness deviation. A low TTV is superior.

[0094] In addition, the cleanability is determined by observation with an electron microscope. Within an area of ​​5μm×5μm, 0 particles are marked with ◎, 5 or fewer particles are marked with ○, 5 or more but less than 10 particles are marked with △, and more than 10 particles are marked with ×.

[0095] The comprehensive evaluation is conducted according to the following standards: A grinding rate of 1.5 μm / h or higher, a surface roughness Ra of 0.15 nm or less on the Si surface, a surface roughness Ra of 0.25 nm or less on the C surface, a processing resistance of 0.40 A or less, a TTV of 1.0 μm or less, and a cleanability rating of ◎ are all considered a good rating. A grinding rate of 1.0 μm / h or higher, a surface roughness Ra of 0.20 nm or less on the Si surface, a surface roughness Ra of 0.30 nm or less on the C surface, a processing resistance of 0.40 A or less, a TTV of 1.5 μm or less, and a cleanability rating of ◎ or ○ are all considered a good rating. A grinding rate of 1.0 μm / h or less, a surface roughness Ra of 0.20 nm or more on the Si surface, a surface roughness Ra of 0.30 nm or more on the C surface, a processing resistance of 0.40 A or more, a TTV of 1.5 μm or more, and a cleanability rating of ○ or △ are all considered a good rating. When the grinding rate is below 1.0 μm / h, the surface roughness Ra of the Si surface is above 0.20 nm, the surface roughness Ra of the C surface is above 0.30 nm, the processing resistance is above 0.40 A, the TTV is above 2.0 μm, and the cleanability is △ or ×, the evaluation is ×. The results are shown in Table 5.

[0096] Table 5

[0097]

[0098] As shown in Table 5, if the first polishing pad 7 and the second polishing pad 9 are polishing pads of Examples 1 to 7, even if the first surface W1 is a Si surface and the second surface W2 is a C surface, the occurrence of scratches on the polished wafer W can be suppressed, and high precision can be achieved. Therefore, it can also be seen that the wafer polishing methods of Examples 1 to 7 using polishing pads of Examples 1 to 7 can eliminate the trouble of using first and second polishing pads with different polishing rates, and achieve higher workability.

[0099] In grinding tests, such as Figure 6 As shown, the first surface W1 or the second surface W2 of the wafer W moves relative to each other while being pressed against the first polishing pad 7 or the second polishing pad 9 by a predetermined force F in the presence of polishing slurry 17. During this process, the inventors speculate that because the polishing pads in Examples 1-6 consist of fine pores 21 and large pores 23, the following effect occurs.

[0100] That is, the base material 19 forms a three-dimensional mesh structure with fine pores 21, and abrasive particles 25a that do not aid in grinding are embedded inside the fine pores 21. The volume of the large pores 23 is larger than that of the fine pores 21, and they are connected to the numerous fine pores 21. The polishing fluid 17 is stored in the large pores 23. The abrasive particles 25a that do not aid in grinding are discharged from each of the numerous fine pores 21 into the large pores 23. The abrasive particles 25b discharged into the large pores 23 maintain their degrees of freedom while aiding in the grinding of the wafer W on the grinding surface 20. In addition, in the first region of the grinding surface 20, bonding resin and abrasive particles are densely present. In this way, high-precision and high-efficiency grinding can be performed.

[0101] The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Of course, appropriate changes can be made without departing from its spirit.

[0102] For example, in the wafer polishing apparatus 10 described above, the first axis X1 of the first and second fixed disks 1 and 3 is parallel to the second axis X2 of the carrier 5. However, in the wafer polishing apparatus used for the polishing pad and wafer polishing method of the present invention, the axes of the first and second fixed disks 1 and 3 may be aligned with the axis of the carrier 5.

[0103] Industrial availability

[0104] This invention can be applied to semiconductor device manufacturing apparatus, etc.

[0105] Explanation of reference numerals in the attached figures

[0106] W… wafer

[0107] W1…First Page

[0108] 7…First Grinding Pad

[0109] W2…Second side

[0110] 9…Second grinding pad

[0111] 10…Wafer Grinding Equipment

[0112] X1, X2... axis (X1... first axis, X2... second axis)

[0113] 1…First Settlement

[0114] 3…Second Fixing

[0115] 5a…Fixed part

[0116] 5…vehicles

[0117] 19…base material

[0118] 21, 23… pores (21… micropores, 23… macropores)

[0119] 25a, 25b... Grinding particles

Claims

1. An abrasive pad, characterized in that, This is a double-sided wafer polishing apparatus used to polish the first surface of a wafer by moving it relative to a first polishing pad under a specified contact pressure, and to polish the second surface of the wafer by moving it relative to a second polishing pad. It can also serve as a polishing pad for both the first and second polishing pads. The wafer grinding apparatus includes: A first fixed plate having a first grinding pad extending in a direction orthogonal to the axis and rotating about the axis; The second plate has a second abrasive pad extending in a direction orthogonal to the axis and opposite to the first abrasive pad, and rotates about the axis; A carrier having a fixed portion extending along a direction orthogonal to the axis and opposite to the first grinding pad and the second grinding pad, and rotating relative to the first and second fixed plates. The wafer is fixed in the fixing portion such that the first surface faces the first polishing pad and the second surface faces the second polishing pad. The wafer is formed of SiC, with one of the first and second faces being a Si face and the other being a C face. The abrasive pad comprises: a base material containing a bonding resin and having multiple pores; and abrasive particles retained within the base material or within the pores. The adhesive resin is a sulfonic acid resin. The abrasive particles are formed of silicon dioxide. The Durometer hardness D is 30–52. Its density is 0.60–0.90 g / cm³. 3 .

2. The abrasive pad according to claim 1, wherein, The adhesive resin is polyethersulfone.

3. The abrasive pad according to claim 2, wherein, The adhesive resin is 17.6–26.2% by volume. The abrasive particles comprise 16.3–24.6% by volume. The pores have a volume of 49.2 to 66.

1.

4. The abrasive pad according to any one of claims 1 to 3, wherein, The pores include: fine pores forming a three-dimensional network structure; and large pores with a larger volume than the fine pores and communicating with numerous fine pores.

5. The abrasive pad according to claim 4, wherein, The pores have a volume percentage of 44.1–51.6%. The atmospheric pores have a volume of 2.7 to 15.

7.

6. A wafer grinding method, characterized in that, Use a wafer grinding apparatus equipped with the following features: A first fixed plate has a first grinding pad extending in a direction orthogonal to the axis and rotating about the axis; The second plate has a second grinding pad extending in a direction orthogonal to the axis and opposite to the first grinding pad, and rotates about the axis; A carrier having a fixed portion extending along a direction orthogonal to the axis and opposite to the first grinding pad and the second grinding pad, and rotating relative to the first and second fixed plates. The wafer is fixed in the fixing part such that the first surface faces the first polishing pad, and the back surface of the first surface, i.e., the second surface, faces the second polishing pad. Under a specified contact pressure, the first surface is ground by moving relative to the first abrasive pad, and the second surface is ground by moving relative to the second abrasive pad, wherein... The wafer is formed of SiC, with one of the first and second faces being a Si face and the other being a C face. The first and second abrasive pads are the same type of abrasive pad, comprising: a base material containing a bonding resin and having multiple pores; and abrasive particles retained within the base material or the pores. The adhesive resin is a sulfonic acid resin. The abrasive particles are formed of silicon dioxide. The Durometer hardness D is 30–52. Its density is 0.60–0.90 g / cm³. 3 .

7. The wafer grinding method according to claim 6, wherein, The polishing slurry is positioned between the wafer and the first polishing pad and between the wafer and the second polishing pad. The grinding fluid does not contain grinding particles.

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