JP2008068390A - Crystal material polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal material polishing method capable of obtaining sufficient polishing efficiency and polishing performance in polishing with a CMP method even in the case of polishing a material hard to be machined such as a single-crystal substrate composed of silicon carbide SiC and gallium nitride GaN. <P>SOLUTION: In polishing using the CMP method, the surface of a material hard to be machined such as a single-crystal substrate composed of silicon carbide SiC and gallium nitride GaN is polished by using a polishing pad including abrasive grains under the existence of oxidative polishing liquid, and high polishing efficiency can be thereby properly obtained, keeping low surface roughness. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing body suitably used for, for example, polishing processing of a semiconductor wafer by a CMP method and a manufacturing method thereof.

  Electronic devices such as semiconductor integrated circuits are often built on a silicon single crystal substrate, but for power devices that require a relatively large power control function, silicon carbide SiC or gallium nitride with even better electrical characteristics It is expected that a single crystal substrate made of GaN is used in place of the silicon single crystal substrate. A power device using such a single crystal substrate made of silicon carbide SiC or gallium nitride GaN is suitably used for a hybrid vehicle, a fuel cell vehicle, or the like as a control element for controlling the rotational speed and torque of a motor or generator. .

  In general, in the manufacture of VLSI, a manufacturing method is employed in which a large number of chips are formed on a semiconductor wafer and cut into each chip size in the final process. Recently, with the improvement of VLSI manufacturing technology, the degree of integration has dramatically improved, and the number of layers of wiring has increased. In the process of forming each layer, the entire semiconductor wafer has been flattened (global planarization). Required. One method for realizing the planarization of the entire semiconductor wafer is a polishing method called a CMP (Chemical Mechanical Polishing) method. This CMP method means that a wafer is pressed against a polishing pad such as a non-woven fabric or foam pad affixed on a surface plate and forcibly rotated, and a slurry containing fine abrasive particles (free abrasive grains) A thick suspension) dispersed in a liquid such as an alkaline aqueous solution is poured to perform polishing. According to the CMP method, relatively high-precision polishing is performed by a synergistic effect of chemical polishing using a liquid component and mechanical polishing using free abrasive grains.

  However, in such a conventional CMP method, polishing is performed while constantly supplying the slurry to the polishing pad, and the consumption of the slurry is increased. Since the used slurry is required to be treated as an industrial waste, it is not preferable from the viewpoint of environmental protection, in addition to a cost that cannot be ignored. In addition, the most cost in the polishing process by the CMP method is the abrasive particles contained in the slurry. Furthermore, not all of the abrasive particles contained in the slurry are necessarily involved in the polishing process. Was wasted and was uneconomical.

In order to solve such a problem, a solid polishing body has been devised for performing polishing by a CMP method without using a slurry. For example, the abrasive | polishing body described in patent document 1 and patent document 2 is it.
JP 2001-214154 A JP 2004-25415 A

  The abrasive body of Patent Document 1 is an abrasive body containing abrasive particles such as cerium oxide and a water-soluble substance such as dextrin in a water-insoluble substance such as a thermoplastic polymer. The purpose is to self-supply the free abrasive grains involved in the polishing process by releasing the abrasive particles from the abrasive body. However, in order to verify the effect, when the present inventor prototyped such a polishing body and used it for polishing processing, the polishing efficiency was inferior to polishing processing by the conventional CMP method using slurry. In addition, the result was that sufficient polishing performance was not obtained except those using abrasive particles having relatively excellent polishing performance such as cerium oxide or manganese dioxide.

On the other hand, the polishing body of Patent Document 2 performs a polishing process on the object to be polished by pressing the abrasive grains between the polishing object and the object to be polished and moving them relative to each other. In this method, attention is paid to the fact that necessary and sufficient abrasive particles need to be supplied by the abrasive body, and the critical surface tension of the matrix resin is used in order to make the abrasive particles easily separated from the matrix resin. Is within the range of 1.6 × 10 ^{−2 to} 4.0 × 10 ⁻² (N / m), and a polishing body capable of suitably self-supplying free abrasive grains is obtained. According to this, since the base material resin and the abrasive particles are fixed to each other with a necessary and sufficient bonding force, the abrasive particles are easily released from the base material resin during the polishing process by the CMP method. Since free abrasive grains can be suitably self-supplied between the substrate and the object to be polished, a relatively good polishing performance can be obtained for a silicon Si single crystal substrate, but it is made of silicon carbide SiC or gallium nitride GaN. Since the single crystal substrate has a high hardness and is difficult to process, it is difficult to obtain sufficient polishing efficiency and performance for polishing. For this reason, it is difficult to mass-produce at a low price, which has been a bottleneck for practical use.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to sufficiently polish even difficult-to-process materials such as single crystal substrates made of silicon carbide SiC or gallium nitride GaN in the CMP method. An object of the present invention is to provide a polishing method capable of obtaining high polishing efficiency and polishing performance.

  As a result of continual research to develop a polishing method for difficult-to-process materials by the CMP method, the present inventors have smoothly polished the surface of a crystal material using an abrasive-containing polishing pad in the presence of a polishing liquid. In the polishing method using the CMP method, it has been found that when an oxidizing agent is dissolved in the polishing solution to impart oxidizability, polishing efficiency and polishing performance are remarkably improved even for the difficult-to-process materials. . The present invention has been made based on this finding.

  That is, the gist of the present invention is a polishing method by a CMP method for smoothly polishing the surface of a crystal material using an abrasive-encapsulated polishing pad in the presence of a polishing liquid, and the polishing liquid is It is an oxidizing polishing liquid.

  In this way, in the polishing process by the CMP method, the surface of the crystal material is polished using the abrasive-encapsulated polishing pad in the presence of an oxidizing polishing liquid, so that high polishing is achieved while obtaining low surface roughness. Efficiency is suitably obtained.

  Here, the oxidizing polishing liquid is preferably one in which potassium permanganate or potassium thiosulfate is added as a redox potential regulator. In this way, an oxidizing polishing liquid can be easily obtained.

  The polishing liquid is an acidic polishing liquid. Preferably, the acidic polishing liquid has a pH of less than 7 by adding a pH adjuster. In this way, a higher polishing efficiency can be suitably obtained.

  The polishing pad is an abrasive-encapsulated polishing pad including a base material resin in which continuous air holes are formed and abrasive particles provided in the continuous air holes. In this way, higher polishing efficiency and lower surface roughness can be obtained.

  Further, the base resin of the abrasive-encapsulated polishing pad is composed of polyethersulfone (PES) resin. In this way, higher polishing efficiency can be obtained. However, for example, among fluorine-based synthetic resins such as polyvinyl fluoride, vinyl fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, vinylidene fluoride / hexafluoropropylene copolymer, polyethylene resin, and polymethyl methacrylate Even a synthetic resin containing at least one is preferably used.

  The abrasive particles include at least one of silica, ceria, alumina, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, and iron oxide. In this way, there is an advantage that it is possible to use abrasive particles having hardness corresponding to the object to be polished, which can obtain good surface roughness. The above-mentioned abrasive particles preferably have an average particle diameter in the range of 0.005 to 10 (μm). For example, as silica, for example, fumed silica (smoke silica: silicon tetrachloride, chlorosilane, etc., hydrogen and Silica fine particles obtained by high-temperature combustion in the presence of oxygen are preferably used. Preferably, the volume ratio of the abrasive particles to the polishing body is in the range of 20 to 50 (%), and the weight ratio is in the range of 51 to 90 (%).

The amount of the polishing liquid is extremely small, and is 0.1 to 200 ml / min / m ² per area of the polishing surface plate. In this way, higher polishing efficiency can be obtained and the surface roughness becomes finer.

  The crystal material is a single crystal of SiC or GaN. In this way, high polishing efficiency and low surface roughness can be obtained even with difficult-to-process materials such as SiC or GaN single crystals.

  Hereinafter, one application example of the present invention will be described with reference to the drawings.

  FIG. 1 conceptually shows a main part of a polishing apparatus 10 for performing polishing by a CMP (Chemical Mechanical Polishing) method to which an example of the present invention is applied, with a frame removed. Yes. In FIG. 1, the polishing apparatus 10 is provided with a polishing surface plate 12 rotatably supported around a vertical axis C <b> 1, and the polishing surface plate 12 includes a surface plate driving motor 13. Thus, it is driven to rotate in one rotation direction indicated by an arrow in the figure. The polishing pad (abrasive-encapsulated polishing pad) 14 of this embodiment is attached to the upper surface of the polishing surface plate 12, that is, the surface to which the object to be polished (crystal material) 16 is pressed. On the other hand, at a position deviated from the axis C1 on the polishing surface plate 12, a work holding member (carrier) 18 for holding the object 16 to be polished such as a SiC wafer on the lower surface by suction or using a holding frame or the like. The workpiece holding member 18 is arranged so as to be rotatable around the center C2 and movable in the direction of the axis C2. The workpiece holding member 18 is provided by a workpiece driving motor (not shown) or by a rotational moment received from the polishing surface plate 12. It can be rotated in one rotation direction indicated by an arrow in FIG. The workpiece 16 is held on the lower surface of the work holding member 18, that is, the surface facing the polishing pad 14, and the workpiece 16 is pressed against the polishing pad 14 with a predetermined load. Further, a dripping nozzle 22 and / or a spray nozzle 24 are provided in the vicinity of the work holding member 18 of the polishing apparatus 10, and a polishing liquid (lubricant) 20, which is an oxidizing aqueous solution sent from a tank (not shown), is provided. It is supplied on the polishing surface plate 12.

  The polishing apparatus 10 is disposed so as to be rotatable around an axis C3 parallel to the axis C1 of the polishing surface plate 12, and to be movable in the direction of the axis C3 and the radial direction of the polishing surface plate 12. An adjustment tool holding member (not shown) and a polishing body adjustment tool (conditioner) such as a diamond wheel (not shown) attached to the lower surface of the adjustment tool holding member, that is, the surface facing the polishing pad 14 are provided as necessary. The adjusting tool holding member and the polishing body adjusting tool attached to the adjusting tool holding member are pressed against the polishing pad 14 while being rotated by an adjusting tool driving motor (not shown), and in the radial direction of the polishing surface plate 12. By reciprocating, the polishing surface of the polishing pad 14 is adjusted, and the surface state of the polishing pad 14 is suitable for polishing. It is adapted to be maintained at all times to the state.

  When polishing by the CMP method by the polishing apparatus 10, the polishing surface plate 12, the polishing pad 14 attached thereto, the workpiece holding member 18, and the object 16 to be polished held on the lower surface of the polishing table 12 are fixed. While the polishing liquid 20 is being supplied from the dropping nozzle 22 and / or the spray nozzle 24 onto the surface of the polishing pad 14 while being rotated around the respective axis centers by the panel driving motor 13 and the workpiece driving motor, The object to be polished 16 held by the holding member 18 is pressed against the polishing pad 14. By doing so, the surface to be polished of the object to be polished 16, that is, the surface facing the polishing pad 14, is chemically polished by the polishing liquid 20 and contained in the polishing pad 14, and is removed from the polishing pad 14. The surface is polished flat by the mechanical polishing action by the self-supplied abrasive particles 26. For example, silica having an average particle size of about 80 nm is used for the abrasive particles 26.

  As shown in FIG. 2, the polishing pad 14 attached on the polishing surface plate 12 includes a base material resin 32 having continuous air holes 30 and a large number of the base air resin 30 filled in the continuous air holes 30. The abrasive particles 26 are formed in a disk shape, and have a size of about 300 (mmφ) × 5 (mm), for example. This polishing pad 14 is made of fumed silica having an average particle size of about 80 nm as polishing particles 26 and polyether-sulfone (PES) resin and N, N-dimethylformamide (N, N-dimethylformamide). : DMF) Mixed in a solvent, cast into a predetermined mold, and the DMF solvent is evaporated and cured to form a sheet having a size of 500 × 500 × 2 mm and used as a polishing pad 14 Cut to size. The polishing pad 14 is composed of, for example, about 26% by volume of abrasive particles 26, about 28% by volume of a base resin 32, and a continuous vent 30 that occupies the remaining volume. FIG. 2 is an enlarged view showing the structure of the polishing pad 14 by a scanning electron microscope. The continuous air holes 30 of the base material resin 32 formed in a sponge shape or a stitch shape are equal to or larger than the polishing particles 26. A large number of abrasive particles 26 are held in the continuous vent hole 30. The base material resin 32 and the abrasive particles 26 are fixed to each other with a necessary and sufficient bonding force. The polishing pad 14 of the present embodiment enables polishing by a CMP method by supplying a polishing liquid 20 that does not contain loose abrasive grains, without using a slurry containing, for example, colloidal silica.

  As shown in FIG. 2, the base resin 32 has a fiber shape with an average cross-sectional diameter of about 0.05 (μm), for example, and an average particle diameter is formed in the gap between the fibrous base resin 32. The abrasive particles 26 having a thickness of about 80 nm are present in a state where they are partly fixed to the base resin 32 or separated from the base resin 32 in the gaps. That is, the average cross-sectional area of the fibrous base material resin 32 is, for example, about 1/10 to 1/3 of the average particle diameter of the abrasive particles 26. Considering such a gap between the fibrous base material resins 32 as a plurality of continuous air holes 30, it can be said that the abrasive particles 26 are provided in the continuous air holes 30. The volume ratio of the continuous air holes 30 to the abrasive particles 26 is, for example, about 15 to 60 (%).

  When polishing is performed in the polishing apparatus 10 configured as described above, the polishing surface plate 12, the polishing pad 14 attached thereto, the work holding member 18 and the object 16 held on the lower surface thereof are provided. In addition, an oxidizing polishing liquid 20 such as a potassium permanganate aqueous solution is supplied from the dropping nozzle 22 to the polishing pad in a state where the platen driving motor 13 and a work driving motor (not shown) are driven to rotate around the respective axis centers. The object to be polished 16 held by the work holding member 18 is pressed against the surface of the polishing pad 14 while being supplied onto the surface of the polishing pad 14. By doing so, the surface to be polished of the object to be polished 16, that is, the surface facing the polishing pad 14, is caused by the chemical polishing action by the polishing liquid 20 and the abrasive particles 26 supplied by the polishing pad 14. It is polished flat by a mechanical polishing action.

[Experimental Example 1]
Hereinafter, Experimental Example 1 conducted by the present inventors will be described. First, a polishing test was performed using an apparatus configured similarly to the polishing apparatus 10 shown in FIG. 1 under the polishing conditions shown in Table 1 and six combinations of polishing pads and polishing liquids shown in Table 2. It was. The polishing pad IC-1000 used for test numbers No. 1 to No. 2 is a pad made of foamed polyurethane manufactured by Nitta Haas, and the polishing pad LHA pad used for test numbers No. 3 to No. 6 is Polyvinylidene fluoride (PVDF) resin and spherical silica with an average particle size of 250 nm are mixed in a DMF solvent and placed in a mold, and the DMF solvent is evaporated and cured to form a sheet of 500 × 500 × 2 mm. , Cut into a circle of 300 mmφ. Table 3 shows the polishing solution oxidation-reduction potential Eh (hydrogen electrode reference potential) and hydrogen ion concentration pH of the polishing solution used for each test number, the polishing rate PR and the surface roughness Ra as the polishing result. . This LHA pad contains 24.5 vol% spherical silica as abrasive particles. In this experimental example 1, the minute amount spraying of the polishing liquid is, for example, an amount of about 0.1 to 200 ml / min / m ² .

[Table 1]
Polishing equipment: Lapping Master LP-15 type polishing pad: 300 mmφ
Polishing pad rotation speed: 1 / sec
Object to be polished: SiC single crystal plate 6H (0001)
Shape of object to be polished: 3 plates of 10 mm x 10 mm x 0.26 mm Number of objects to be polished: 1 / sec
Polishing load (pressure): 24.6 kPa
Polishing liquid supply amount: 0.167 cm ³ / sec for IC-1000
0.0067cm ³ / sec (dry mist) on the LHA pad
Polishing time: 120 min
Conditioner: SD # 325 (Electroplated diamond wheel)

[Table 2]
Test number Polishing pad Polishing liquid
No.1 IC-1000 slurry (H ₂ O + silica 12.5Wt%)
No.2 IC-1000 slurry (H ₂ O + silica 12.5 Wt% + KMnO ₄ 0.1 mol / cm ³ )
No.3 LHA pad polishing liquid (H ₂ O)
No.4 LHA pad polishing liquid (H ₂ O + KMnO ₄ 0.1 mol / cm ³ )
No.5 LHA pad Polishing liquid (H ₂ O) Dry mist (trace spray)
No.6 LHA pad Polishing liquid (H ₂ O + KMnO ₄ 0.1 mol / cm ³ ) Dry mist

[Table 3]
Test number Redox potential Eh Hydrogen ion concentration pH Polishing rate Surface roughness Ra
No.1 560 mV 4.49 117 nm / h 1.43 nm
No.2 1016 mV 5.38 250 nm / h 0.54 nm
No.3 565 mV 4.99 67 nm / h 0.61 nm
No.4 1012 mV 5.69 133 nm / h 0.50 nm
No.5 565 mV 4.99 216 nm / h 0.63 nm
No.6 1012mV 5.69 366 nm / h 0.32 nm

As a result of the polishing test, the polishing rates PR (nm / h) of the test numbers No. 1 to No. 6 are shown in FIG. 3, and the surface roughness Ra (nm) is shown in FIG. Comparing each polishing rate, polishing particles (silica) and potassium permanganate KMnO are more than test numbers No.1, No.3, and No.5 using a polishing liquid that is a combination of abrasive particles (silica) and water. ₄ which is a combination polishing solution test No. No.2 using, No.4, high polishing rate towards the No.6. In addition, as shown in FIG. 5, even when looking at the relationship between the oxidation-reduction potential Eh (mV) and the polishing rate PR, No. 2, No. 4, and No. 6 with the higher oxidation-reduction potential Eh have higher polishing rates. PR is high. It is considered that the potassium permanganate KMnO ₄ in the polishing liquid caused an oxidizing action on SiC, and the SiO ₂ or Si formed on the surface was removed by the abrasive particles. In No. 3 and No. 4 where the same amount of polishing liquid was supplied to the LHA pad as in the case of free abrasive polishing of test numbers No. 1 and No. 2, the polishing rate PR was lower than that of free abrasive polishing. However, in No. 5 and No. 6 supplied in a small amount by dry mist, the polishing rate PR is higher than that of free abrasive polishing. This is considered to be because in No. 3 and No. 4, the supply amount was too large for the LHA pad, and SiC floated from the LHA pad, and the number of abrasive particles that acted substantially decreased. Furthermore, when comparing the roughness, the abrasive particles (silica) and potassium permanganate were compared to the test numbers No.1, No.3 and No.5 using the polishing liquid which is a combination of abrasive particles (silica) and water. KMnO which is a combination polishing solution test No. No.2 using the _4, No.4, found the following No.6, was scarcely observed streaks on the surface of the SiC single crystal plate is polished body, chemistry It looked like a polished surface with a. This also suggests the existence of chemical action of potassium permanganate KMnO ₄ contained in the polishing liquid.

[Experiment 2]
Hereinafter, Experimental Example 2 conducted by the present inventors will be described. First, a polishing test was performed using six types of combinations of the polishing pad and the polishing liquid shown in Table 4 under the polishing conditions shown in Table 1, using an apparatus configured similarly to the polishing apparatus 10 shown in FIG. It was. The polishing pad IC-1000 used for test numbers No. 1 to No. 9 is a pad made of foamed polyurethane manufactured by Nitta Haas, and the LHA pad used for test numbers No. 10 to No. 18 is abrasive particles. 26, fumed silica having an average particle size of about 80 nm and polyether-sulfone (PES) resin are mixed in a DMF solvent, cast into a predetermined mold, and the DMF solvent is evaporated. By curing, a sheet having a size of 500 × 500 × 2 mm is formed and cut into a circle of 300 mmφ. This LHA pad contains 24.5 vol% spherical silica as abrasive particles. In this experimental example 2, the minute amount of the polishing liquid is, for example, about 0.1 to 200 ml / min / m ² .

[Table 4]
Test number Polishing pad Polishing liquid
No.1 IC-1000 slurry (silica _{12.5Wt% + K 2 S 2 O} 3 0.1mol / l solution
+ HCl solution 0.1mol / l)
No.2 IC-1000 slurry (silica _{12.5Wt% + K 2 S 2 O} 3 0.1mol / l solution)
No.3 IC-1000 slurry (silica _{12.5Wt% + K 2 S 2 O} 3 0.1mol / l solution
+ KOH 0.1mol / l solution)
No.4 IC-1000 slurry (silica 12.5Wt% + HCl 0.1mol / l solution)
No.5 IC-1000 slurry (silica 12.5Wt% + H ₂ O)
No.6 IC-1000 slurry (silica 12.5Wt% + KOH solution 0.1mol / l)
No.7 IC-1000 Slurry (Silica 12.5Wt% + KMnO ₄ solution 0.1mol / l
+ HCl solution 0.1mol / l)
No.8 IC-1000 slurry (silica 12.5Wt% + KMnO ₄ solution 0.1mol / l)
No.9 IC-1000 Slurry (Silica 12.5Wt% + KMnO ₄ 0.1mol / l solution
+ KOH 0.1mol / l solution)
No.10 LHA pad K ₂ S ₂ O ₃ 0.1mol / l + HCl 0.1mol / l
No.11 LHA pad K ₂ S ₂ O ₃ 0.1mol / l solution drop
No.12 LHA pad K ₂ S ₂ O ₃ 0.1mol / l + KOH 0.1mol / l
No.13 LHA pad HCl 0.1mol / l in small amount
No.14 A small amount of LHA pad H ₂ O was dropped.
No.15 LHA pad KOH 0.1mol / l solution is dripped
No.16 LHA pad KMnO ₄ 0.1mol / l + HCl 0.1mol / l solution in small amount
No.17 LHA pad KMnO ₄ 0.1mol / l solution is added in a small amount
No.18 LHA pad KMnO ₄ 0.1mol / l + KOH 0.1mol / l solution in small amount

The values of the oxidation-reduction potential Eh (mV) of the polishing liquids of test numbers No. 1 to No. 18 in Experimental Example 2 function as potassium thiosulfate K ₂ S ₂ O ₃ that functions as a reducing agent and as an oxidizing agent. It is adjusted as shown in Table 4 by using a peroxide potassium manganese KMnO _4. Further, the hydrogen ion concentration pH values of the polishing liquids of test numbers No. 1 to No. 18 in Experimental Example 2 were adjusted as shown in Table 5 using hydrochloric acid HCl and potassium hydroxide KOH, and Table 5 shows the polishing rate PR and the surface roughness Ra measured in each test. FIG. 6 shows the relationship between the oxidation-reduction potential Eh and the hydrogen ion concentration pH in each of the test numbers No. 1 to No. 18.

[Table 5]
Test number Redox potential Eh Hydrogen ion concentration pH Polishing rate Surface roughness Ra
No.1 148 mV 2.0 28 nm / h 0.71 nm
No.2 266 mV 5.2 183 nm / h 0.62 nm
No.3 137 mV 12.4 35 nm / h 0.53 nm
No.4 755 mV 1.4 232 nm / h 0.53 nm
No.5 560 mV 4.5 117 nm / h 1.43 nm
No.6 241 mV 11.5 167 nm / h 1.57 nm
No.7 1359 mV 1.3 308 nm / h 0.24 nm
No.8 1016 mV 5.4 250 nm / h 0.53 nm
No.9 683 mV 11.5 162 nm / h 0.24 nm
No.10 137 mV 1.5 34 nm / h 0.44 nm
No.11 361 mV 6.2 67 nm / h 0.48 nm
No.12 40 mV 13.0 50 nm / h 1.07 nm
No.13 648 mV 1.3 150 nm / h 1.06 nm
No.14 565 mV 5.0 217 nm / h 0.63 nm
No.15 166 mV 12.8 200 nm / h 1.35 nm
No.16 1382 mV 1.2 400 nm / h 0.59 nm
No.17 1012 mV 5.7 450 nm / h 0.35 nm
No.18 735 mV 13.3 100 nm / h 0.83 nm

  FIG. 7 shows three-dimensional coordinates obtained by adding a polishing rate PR indicated by contour lines to the two-dimensional coordinates of redox potential Eh and hydrogen ion concentration pH, and surface roughness indicated by contour lines on two-dimensional coordinates of redox potential Eh and hydrogen ion concentration pH. FIG. 8 showing three-dimensional coordinates to which the degree Ra is added shows the values of test numbers No. 1 to No. 9 obtained by polishing with loose abrasive grains (silica). Further, the polishing rate PR and the surface roughness Ra value of test numbers No. 10 to No. 18 polished with the LHA pad are shown in FIGS. 9 and 10, respectively, in which the same three-dimensional display is performed.

  Both experiment numbers No. 8 and No. 17 contain an oxidizer, but the polishing rate (removal rate) of polishing with IC-1000 of experiment number No. 8 is higher than the LHA according to experiment number No. 17. The polishing rate PR of polishing with the pad shows a high value. The polishing rate PR of polishing with the LHA pad according to Experiment No. 17 is 1.8 times higher than that with the IC-1000 of Experiment No. 8. The slurry of Experiment No. 6 has the same oxidation-reduction potential Eh and hydrogen ion concentration pH as those of a commercially available known slurry for silicon wafers. The polishing rate PR for polishing with the LHA pad according to the experiment number No. 17 is about 2.7 times higher than the polishing rate PR of the experiment number No. 6. This indicates that the polishing rate PR is greatly improved by the polishing liquid made oxidizing by the addition of an oxidizing agent, and the polishing rate PR is also greatly increased by using an LHA pad. Has been shown to be improved. 7 to 10, the broken line indicates the boundary between the oxidizing region and the reducing region. 7 and 9, it is shown that the higher the redox potential Eh, the higher the hydrogen ion concentration pH and the lower the redox potential Eh. As a result, the oxidation-reduction potential Eh has a great influence on the polishing of the SiC single crystal with silica, and it is considered that an oxidation reaction has occurred.

Regarding the surface roughness Ra, the surface roughness Ra of the polishing with the IC-1000 of the experiment number No. 8 shows a good low value, and the surface roughness Ra of the polishing with the LHA pad according to the experiment number No. 17 is also a good low value Is shown. These experiment numbers No. 8 and No. 17 both have a high polishing rate PR. On the other hand, the surface roughness Ra of the polishing with the LHA pads of Experiment No. 6 and No. 15 is also large. These polishing liquids are strongly alkaline regions and do not have any oxidizing action or wear action. 8 and 10, the surface roughness Ra is improved in the acidic region, but it is considered that the surface roughness Ra is increased in the non-oxidized region and the strong alkali region. From these data, it is considered that the carbon atom C is oxidized to become carbon dioxide CO ₂ and can be easily detached from the SiC single crystal. If the polishing of the SiC single crystal with silica promotes the oxidation reaction, the polishing rate PR of the SiC single crystal is greatly improved. Also, compared to polishing with loose abrasive grains, the movement of the abrasive particles is retained by the LHA pad in the polishing by the LHA pad, so it is considered that the mechanical force of the LHA pad works strongly. Furthermore, the removal rate by the LHA pad is improved due to the effect of oxidation.

[Experiment 3]
Hereinafter, Experimental Example 3 performed by the present inventors will be described. First, a polishing test was performed using five types of combinations of the polishing pad and the polishing liquid shown in Table 6 under the polishing conditions shown in Table 1, using an apparatus configured similarly to the polishing apparatus 10 shown in FIG. It was. The LHA pads used in test numbers No. 1 to No. 5 are fumed silica having an average particle size of about 80 nm as abrasive particles 26, polyvinyl fluoride, vinyl fluoride / hexafluoropropylene copolymer, and polyvinylidene fluoride. , By mixing a fluororesin such as vinylidene fluoride / hexafluoropropylene copolymer in a DMF solvent, casting into a predetermined mold, and evaporating the DMF solvent to cure, the dimensions are 500 × 500 A sheet of × 2 mm is formed and cut into a 300 mmφ circle. Table 7 shows the polishing solution oxidation-reduction potential Eh and hydrogen ion concentration pH of the polishing solution used for each test number, the polishing rate PR and the surface roughness Ra, which are polishing results. This LHA pad contains 24.5 vol% spherical silica as abrasive particles. In this experimental example 3, the minute amount of the polishing liquid is, for example, about 0.1 to 200 ml / min / m ² .

[Table 6]
Test number Polishing pad Polishing liquid
No.1 LHA pad HCl 0.1mol / l in small amount
No.2 LHA pad K ₂ S ₂ O ₃ 0.1mol / l solution is added in a small amount
No.3 A small amount of LHA pad H ₂ O was dropped.
No.4 LHA pad KMnO ₄ 0.1mol / l solution is dripped in a small amount
No.5 LHA pad KOH 1mol / l solution is dripped in a small amount

[Table 7]
Test number Redox potential Eh Hydrogen ion concentration pH Polishing rate Surface roughness Ra
No.1 648 mV 1.32 317 nm / h 1.06 nm
No.2 361 mV 6.20 233 nm / h 1.16 nm
No.3 565 mV 4.99 217 nm / h 0.63 nm
No.4 1012 mV 5.69 367 nm / h 0.33 nm
No.5 166 mV 12.81 300 nm / h 2.35 nm

  FIG. 11 shows three-dimensional coordinates obtained by adding a polishing rate PR indicated by contour lines to the two-dimensional coordinates of redox potential Eh and hydrogen ion concentration pH, and surface roughness indicated by contour lines in two-dimensional coordinates of redox potential Eh and hydrogen ion concentration pH. FIG. 12 showing the three-dimensional coordinates to which the degree Ra is added shows the values of test numbers No. 1 to No. 5 polished with the LHA pad.

  In Experimental Example 3, the polishing rate PR increases as the oxidation-reduction potential Eh increases according to the polishing liquid rendered oxidizing by the addition of the oxidizing agent even by using an LHA pad having a fluororesin as a base material. It is shown that the surface roughness Ra is improved as the polishing liquid becomes more acidic, but the surface roughness Ra is increased in the non-oxidized region and the strong alkali region.

  Although not exemplified one by one, the present invention is used with various modifications within the scope not departing from the gist thereof.

It is a perspective view which shows notionally the structure of the grinding | polishing processing apparatus which implements the grinding | polishing processing method of one application example of this invention. It is a figure explaining a mode that the surface structure of the polishing pad shown in FIG. 1 was expanded with the scanning electron microscope. In Experimental example 1, it is a graph which respectively shows the value of polishing rate PR (nm / h) obtained in the grinding | polishing shown by six test numbers. In Experimental example 1, it is a graph which respectively shows the value of surface roughness Ra (nm) obtained in the grinding | polishing shown by six test numbers. In Experimental example 1, it is a figure which shows the relationship between the oxidation reduction potential Eh (mV) each obtained in the grinding | polishing shown by six test numbers, and polishing rate PR. In Experimental Example 2, the relationship between the oxidation-reduction potential Eh and the hydrogen ion concentration pH obtained in the polishing of each test number No. 1 to No. 18 is shown. In the three-dimensional coordinates obtained by adding the polishing rate PR indicated by the contour lines to the two-dimensional coordinates of the oxidation-reduction potential Eh and the hydrogen ion concentration pH, the free abrasive slurry of each test number No. 1 to No. 9 in Experimental Example 2 was used. It is a figure which shows the magnitude | size of polishing rate PR each obtained in grinding | polishing using a contour line. In the three-dimensional coordinates obtained by adding the surface roughness Ra indicated by the contour lines to the two-dimensional coordinates of the oxidation-reduction potential Eh and the hydrogen ion concentration pH, the free abrasive slurry of each test number No. 1 to No. 9 in Experimental Example 2 is used. It is a figure which shows the magnitude | size of surface roughness Ra each obtained in the grinding | polishing which used it using a contour line. In the three-dimensional coordinates obtained by adding the polishing rate PR indicated by contour lines to the two-dimensional coordinates of the oxidation-reduction potential Eh and the hydrogen ion concentration pH, in polishing using the LHA pads of test numbers No. 10 to No. 18 in Experimental Example 2. It is a figure which shows the magnitude | size of each obtained polishing rate PR using a contour line. Polishing using LHA pads of test numbers No. 10 to No. 18 in Experimental Example 2 in three-dimensional coordinates obtained by adding surface roughness Ra indicated by contour lines to two-dimensional coordinates of oxidation-reduction potential Eh and hydrogen ion concentration pH It is a figure which shows the magnitude | size of surface roughness Ra obtained in each using a contour line. In the three-dimensional coordinates obtained by adding the polishing rate PR indicated by contour lines to the two-dimensional coordinates of the oxidation-reduction potential Eh and the hydrogen ion concentration pH, in polishing using the LHA pads of test numbers No. 1 to No. 5 in Experimental Example 3. It is a figure which shows the magnitude | size of each obtained polishing rate PR using a contour line. Polishing using LHA pads of test numbers No. 1 to No. 5 in Experimental Example 3 in three-dimensional coordinates obtained by adding surface roughness Ra indicated by contour lines to two-dimensional coordinates of oxidation-reduction potential Eh and hydrogen ion concentration pH It is a figure which shows the magnitude | size of surface roughness Ra obtained in each using a contour line.

Explanation of symbols

10: Polishing processing device 12: Polishing surface plate 14: Polishing pad (polishing pad with abrasive grains)
16: Object to be polished (crystal material)
20: Polishing liquid 26: Polishing particle 30: Continuous vent 32: Base material resin

Claims (9)

A polishing method by a CMP method for smoothly polishing the surface of a crystal material using an abrasive-encapsulated polishing pad in the presence of a polishing liquid,
The polishing method, wherein the polishing liquid is an oxidizing polishing liquid. 2. The polishing method according to claim 1, wherein the oxidizing polishing liquid is added with potassium permanganate or potassium thiosulfate as a redox potential regulator. The polishing method according to claim 1 or 2, wherein the polishing liquid is an acidic polishing liquid. The polishing method according to claim 3, wherein the acidic polishing liquid has a pH of less than 7 by adding a pH adjuster. The polishing method according to any one of claims 1 to 4, wherein the abrasive-encapsulated polishing pad includes a base resin in which continuous air holes are formed and abrasive particles provided in the continuous air holes. 6. The polishing method according to claim 5, wherein the base resin of the abrasive-encapsulated polishing pad is composed of a polyethersulfone (PES) resin. The polishing method according to claim 5, wherein the abrasive particles contain at least one of silica, ceria, alumina, zirconia, titania, manganese oxide, barium carbonate, chromium oxide, and iron oxide. The polishing method according to claim 1, wherein the amount of the polishing liquid is 0.1 to 200 ml / min / m ² per area of the polishing platen. The polishing method according to claim 1, wherein the crystal material is a single crystal of SiC or GaN.

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