JP2007067166A - Chemomechanical polishing method of sic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient polishing method for obtaining a predetermined flatness by a chemomechanical polishing method in which an SiC substrate is polished using colloidal silica as abrasive grain. <P>SOLUTION: The chemomechanical polishing method uses colloidal silica as abrasive grain, drops an abrasive agent to a rotating polishing pad, and polishes the SiC substrate by depressing the SiC substrate under polish to the polishing pad with a predetermined pressure. The polishing is carried out using a mixed polishing agent of colloidal silica grain having a first abrasive grain distribution and a disperse catalyst containing pH adjuster, subsequently, the polishing is carried out using the mixed polishing agent of colloidal silica grain having a second abrasive grain distribution sharper than the first abrasive grain distribution and a disperse catalyst containing pH adjuster. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for polishing an SiC substrate, and more particularly to a method for polishing a SiC substrate using SiO ₂ (colloidal silica) as abrasive grains.

Power devices with low electrical energy loss and high performance directly contribute to a significant reduction in power consumption, and are used in many fields. Currently, a power device using a silicon wafer is used. However, due to material characteristics of silicon, there is a limit to further improving the performance of the power device by performing fine processing on silicon. In particular, since silicon cannot be used under conditions such as high temperatures, materials that replace silicon have become necessary.
For example, SiC (silicon carbide) is an alternative material for silicon, but the band gap of SiC is three times the band gap of silicon, so that it can be used under higher temperature conditions than silicon. In addition, since the electric breakdown field is about 10 times that of silicon, it can be downsized. Furthermore, the thermal conductivity is about three times that of silicon, and there is an advantage that it is excellent in heat dissipation and is easily cooled.

Since SiC has excellent characteristics as described above, the SiC substrate is attracting attention as a semiconductor substrate for power devices that replaces the silicon substrate. By the way, in order to use a SiC substrate as a power device, it is necessary to polish the surface. As the final polishing method, a polishing method using a polishing with diamond abrasive grains or a suspension containing SiO ₂ (colloidal silica) is currently generally used. (For example, refer to Patent Documents 1 and 2).
JP 2004-299018 A JP 7-288243 A (2nd page, right column)

When diamond abrasive grains are used as an abrasive, the polishing rate is high, but there is a problem that cracks due to processing scratches and chipping occur. When a suspension containing SiO ₂ (colloidal silica) is used, the above-mentioned processing scratches and cracks do not occur, and a high-quality surface is polished, but polishing with a smaller surface roughness (for example, 0.3 nm or less) Attempts to improve machining efficiency have been desired since machining cannot be performed in a short time.

The SiC substrate chemomechanical polishing method of the present invention uses colloidal silica as abrasive grains, drops a polishing agent on a rotating polishing pad, and presses the SiC substrate as a polishing target against the polishing pad with a predetermined pressure. In the chemomechanical polishing method for polishing the surface, polishing with an abrasive mixed with a dispersion catalyst containing colloidal silica abrasive grains having a first abrasive grain distribution and a pH adjuster,
Next, polishing is carried out with an abrasive mixed with a dispersion catalyst containing colloidal silica abrasive grains having a second abrasive grain distribution sharper than the first abrasive grain distribution and a pH adjuster. Is.
Also, the method of chemomechanical polishing of a SiC substrate of the present invention comprises colloidal silica as abrasive grains, dripping an abrasive onto a rotating polishing pad, and pressing the SiC substrate of the material to be polished against the polishing pad with a predetermined pressure. In a chemomechanical polishing method for polishing a SiC substrate, a first polishing step in which polishing is performed with an abrasive mixed with a dispersion catalyst containing abrasive grains of colloidal silica having a first abrasive grain distribution and a pH adjuster, A cleaning step of discharging the abrasive 40 used in the polishing step 1, and then a dispersion containing colloidal silica abrasive grains having a second abrasive grain distribution sharper than the first abrasive grain distribution and a pH adjuster And a second polishing step of polishing with an abrasive mixed with a catalyst.

  In the present invention, colloidal silica and a dispersion medium dispersed in colloidal silica are used. First, high-efficiency processing is performed using an abrasive having a broad abrasive grain distribution and an average particle diameter of 40 nm, and then the abrasive grain distribution is sharp. By polishing with an abrasive having an average particle diameter of 80 nm, the processing speed (processing efficiency) can be improved and the SiC substrate can be polished to a predetermined surface roughness or less.

A highly efficient SiC chemomechanical polishing method having a high polishing rate (polishing efficiency) and a small surface roughness will be described in detail with reference to the drawings.

  FIG. 1A is a view for explaining a polishing apparatus for polishing the SiC substrate 1, and FIG. 1B conceptually shows the abrasive 6.

  As shown in FIG. 1A, the pad 3 a is fixed to the rotary table (lower board) 2. The plate-like SiC material 1 is fixed to the weight 5, and the SiC material 1 is pressed against the pad 3 a by the load of the weight 5. In other words, the method for manufacturing the SiC substrate shown in FIG. 1A employs a method of performing polishing with a weight load. The shape of the SiC material 1 is, for example, a disk shape. The weight 5 is provided with a guide 4 for holding the SiC material 1 in a predetermined position. When the polishing table 6 is intermittently dropped on the pad 3a and the rotary table 2 is rotated in the direction of the arrow about the rotating shaft 7, the polishing pad 3 applied to the pad 3a, the SiC material 1, and Will be in contact. At the same time, when the weight 5 is rotated about the rotation shaft 9 in the direction of the arrow, the polishing of the SiC material 1 by the polishing pad 3 is started. In the example shown in FIG. 1A, the rotation direction of the rotary table 2 and the weight 5 is the same. However, if the polishing pad 3 moves relative to the SiC material 1, the rotary table 2 and the weight 5 are weighted. 5 may be rotated in the opposite direction, or only one of the rotary table 2 and the weight 5 may be rotated.

  As shown in FIG.1 (b), the abrasive | polishing agent 6 contains the colloidal silica 6a and the dispersion medium 6b in which the colloidal silica 6a was disperse | distributed. The abrasive 6 desirably contains colloidal silica 6a in a proportion of 5 to 40% by weight (Patent Document 1). If the content of the colloidal silica 6a in the polishing agent 6 is too large, the polishing agent 6 becomes unstable, for example, the polishing agent 6 gels during polishing of the surface of the SiC material 1, and if it is too low, the polishing efficiency is increased. This is because it gets worse. For example, when the rotary table 2 is rotated at a rotation speed of 40 rpm and the diameter of the rotary table 2 is 200 mm, a pad of 10 cc or more of abrasive 6 per minute at room temperature (about 23 ° C.) Add dropwise to 3a.

  In addition, for example, when the turntable 2 is rotated at a rotation speed of 40 rpm and the diameter is 300 mm, 10 cc or more of the abrasive 6 is dropped at room temperature (about 23 ° C.) for 30 seconds. In this way, the surface of the pad 3a can always be covered with the abrasive 6 without drying the surface of the pad 3a. If the diameter of the rotary table 2 is 300 mm or less, the rotational speed of the rotary table 2 is preferably 10 rpm to 100 rpm in consideration of the polishing speed and the consumption of the abrasive 6.

  It is preferable that the pad 3a used in the method for manufacturing the SiC substrate of the present embodiment includes a porous body. For example, the diameter of the fibers constituting the pad 3a is preferably 100 μm or less, and the fibers are non-woven on the pad 3a and are solidified with a thermoplastic resin or the like to form a porous film. Between the holes, the holes are connected by a thin column, but the diameter usually ranges from about 10 nm to about 1 mm.

  When the abrasive 6 is dropped and applied to the porous body, the colloidal silica 6a enters the pores of the porous body. The colloidal silica 6a that has entered the pores is fixed to the porous body by a hydration layer surrounding the colloidal silica 6a. Therefore, the colloidal silica 6a dropped on the pad 3a is as if it were a fixed abrasive. For example, the pad 3a preferably includes a porous body including at least one material selected from the group consisting of synthetic fibers, glass fibers, natural fibers, and resins. This is because the damage given to the SiC material 1 can be controlled by using the pad 3a containing such a soft material.

  Moreover, the surface state waviness of the substrate used in the method for producing a SiC substrate of the present invention is preferably 3 μm or less. For example, it is preferable to polish using a flat SiC substrate having a good surface state as shown in FIG. In addition, when polishing using a SiC substrate having a rough surface state having a waviness of about 10 microns as shown in FIG. 3, a difference occurs between the processing pressure at the convex portion of the surface profile and the processing pressure at the concave portion. It is conceivable that uniform processing on the entire surface is difficult. That is, the polishing method of the present invention improves the overall processing efficiency by performing a precision polishing finish polishing in which the surface state of the SiC substrate is polished to a predetermined flatness in the pretreatment stage of the SiC substrate. is there.

  Although there is no restriction | limiting in particular about the average particle diameter of the colloidal silica 6a, It is preferable that it is 200 nm or less. If the average particle size is too large, it becomes difficult to disperse the colloidal silica 6a in the dispersion medium 6b in a stable state, and problems such as a change in the average particle size occur during polishing. Further, if the average particle diameter is too large, the colloidal silica 6a is difficult to be fixed in the hole of the pad 3a, so that the polishing accuracy is lowered (the surface roughness of the SiC substrate is increased). . Therefore, the abrasive 6 containing colloidal silica 6a having an average particle diameter exceeding 200 nm is not particularly suitable for the final polishing step that requires a smaller surface roughness. As the dispersion medium 6b contained in the abrasive 6, for example, a solution obtained by adding a pH adjuster such as ammonia, citric acid, potassium hydroxide to pure water or the like can be used. In order to polish the SiC material 1 at a practically sufficient speed while reducing the load on the pad 3a and the like of the polishing apparatus and the environment, the pH of the abrasive 6 is required to be 4 to 10, but the abrasive 6 The pH of is preferably 7-10. This is because an ultra-smooth surface can be formed from (Patent Document 1).

The pressure for pressing the SiC material 1 against the polishing pad 3 is preferably 850 g / cm 2 or less. In the example shown in FIG. 1A, the SiC material 1 is pressed against the polishing pad 3 by the weight of the weight 5, so the pressure is a pressure applied to the SiC material 1 by the weight 5. When the pressure is large, the polishing rate increases, but the surface roughness of the SiC substrate increases. The reason why the SiC substrate with a small surface roughness cannot be obtained when the SiC material 1 is pressed against the polishing pad 3 by the weight of the weight 5 and the pressure pressing the SiC material 1 against the polishing pad 3 is too large will be described below. To do. In order to increase the pressure for pressing the SiC material 1 against the polishing pad 3, the weight 5 must be increased. However, when the weight 5 increases, the balance of the weight 5 is lost during rotation, and the weight 5 causes the SiC material 1 to be unbalanced. Cannot be processed smoothly with good uniformity. For example, to obtain a surface pressure of 850 g / cm ² for a 2-inch wafer, a weight of about 17 kg is required. Simply, when a 17 kg weight is created on a 2-inch wafer area with mild steel, a weight of 110 mm is required, making it difficult to balance the pressure on the workpiece, which is practically impossible.
Thus, the higher the pressure for pressing the SiC material 1 against the polishing pad 3, the higher the weight 5 becomes. When the height of the weight 5 is increased, the weight 5 is greatly shaken during the polishing of the SiC material 1, and the pressure applied to the SiC material 1 becomes uneven. As a result, the surface roughness of the polished SiC material 1 (SiC substrate) increases.

However, when the pressure for pressing the SiC material 1 against the polishing pad 3 is 850 g / cm 2 or less, a SiC substrate having a surface roughness as small as 0.3 nm or less can be obtained. The smaller the pressure with which the SiC material 1 is pressed against the polishing pad 3, the smaller the surface roughness of the polished SiC material 1 (SiC substrate), but the slower the polishing rate (polishing efficiency) In fact, the pressure for pressing the SiC material 1 against the polishing pad 3 is preferably 500 g / cm ² or more and 850 g / cm ² or less.

Further, the pressure may be changed according to the state of the polished surface of SiC material 1. For example, the process of polishing the surface of the SiC material 1 is performed in a plurality of steps, and the SiC material is applied at a pressure of 850 g / cm ² or less only in the final time of polishing so that the surface roughness becomes smaller among a plurality of times. The SiC material 1 may be polished while pressing the surface of 1 against the polishing pad 3.

  Further, for example, the step of polishing the surface of the SiC material 1 may be performed in a plurality of steps, and the SiC material 1 may be polished using a slurry containing diamond abrasive grains for the first time out of a plurality of times.

  For example, it is preferable to use a slurry containing diamond abrasive grains (average particle size: 125 nm) 0.2% weight and water 99.8%. Moreover, you may change the average particle diameter and abrasive grain distribution of the colloidal silica 6a each time.

  In the example shown in FIG. 1A, the SiC material 1 is pressed against the polishing pad 3 by the load of the weight 5, but the method of pressing the SiC material 1 against the polishing pad 3 is not limited to this. For example, the SiC material 1 may be pressed against the polishing pad 3 using a pressurizing apparatus as shown in FIG. The pressure device includes, for example, a pressure head 15 and a pressure mechanism. The pressure head 15 is used by being disposed on the opposite side of the polishing pad 3 of the SiC material 1, and the pressure mechanism can push the pressure head 15 in a direction in which the SiC material 1 is pressed against the polishing pad 3. For example, the pressure mechanism can push the pressure head 15 with at least one pressure selected from the group consisting of spring elastic pressure, hydraulic pressure, and air pressure.

  The pressurizing apparatus shown in FIG. 4 has a mechanism for pressing the surface of the SiC material 1 against the polishing pad 3 by air pressure. 4 includes a drive motor 11, an air supply path 12, a rotating shaft 13, an air bag 14, a pressure head 15, a head holding stand 16, and the like. The rotating shaft 13 rotates around the shaft 10 as the drive motor 11 rotates. The pressurizing mechanism of the pressurizing apparatus shown in FIG. 4 includes an air supply path 12 and an air bag 14. The airbag 14 has a structure in which the inside is covered with a soft material such as rubber. A pressure head 15 is directly attached to the bottom surface of the airbag 14. Therefore, when pressure is applied to the inside of the airbag 14, the pressure head 15 in contact with the bottom surface of the airbag 14 is pushed downward. Since the inside of the airbag 14 is pressurized by air, the same pressure is applied to the entire inner surface of the airbag 14. If the contact area between the air bag 14 and the pressure head 15 is made equal to or larger than the area of the SiC material 1 on the pressure head 15 side, the pressure applied to the SiC material 1 can be made uniform.

  In addition, since the pressurizing apparatus includes the head holding stand 16, the entire pressurizing apparatus is prevented from moving when the SiC material 1 is pressed against the polishing pad 3, and the SiC material 1 is processed smoothly with good uniformity. be able to.

When the SiC material 1 is pressed against the polishing pad 3 by pressing the pressure head 15 against the SiC material 1 by air pressure or the like as in the case of using the pressing device shown in FIG. As in the example, even if polishing is performed at a pressure (for example, 850 g / cm ² or more) higher than when the SiC material 1 is pressed against the polishing pad 3 by the load of the weight 5, the SiC material 1 is pressed with good uniformity. be able to. Therefore, it is possible to obtain a SiC substrate having a lower surface roughness at a higher speed. Even when the SiC material 1 is pressed against the polishing pad 3 by the pressurizing apparatus as shown in FIG. 4, the pressure for pressing the SiC material 1 against the polishing pad 3 is preferably 500 g / cm ² or more.

Further, the pressure for pressing the SiC material 1 against the polishing pad 3 using a pressurizing apparatus as shown in FIG. 4 may be changed according to the state of the surface to be polished of the SiC material 1. For example, the process of polishing the surface of the SiC material 1 is performed in a plurality of steps, and the SiC material is applied at a pressure of 850 g / cm ² or less only in the final time of polishing so that the surface roughness becomes smaller among a plurality of times. The SiC material 1 may be polished while pressing the surface of 1 against the polishing pad 3.

  Further, for example, the step of polishing the surface of the SiC material 1 may be performed in a plurality of steps, and the SiC material 1 may be polished using a slurry containing diamond abrasive grains for the first time out of a plurality of times. Moreover, you may change the average particle diameter and abrasive grain distribution of the colloidal silica 6a each time.

  In the example shown in FIG. 1A and FIG. 4, the SiC material 1 is polished by rotating the rotary table (lower board 2) and the SiC material 1 in the respective arrow directions. As shown in FIG. 5, the polishing pad 3 may be moved relative to the SiC material 1 by reciprocating the lower board 2 in the arrow direction. The diameter of the obtained substrate is usually 2 inches to 3 inches (50 mm to 70 mm).

  Below, an example of the SiC substrate manufacturing method of this invention is demonstrated still in detail. In addition, the average particle diameter of colloidal silica was calculated | required in conversion from the value of the surface area of colloidal silica measured with the surface area measuring device (the Yuasa Ionics company make, multisorb). The surface state of the SiC substrate was measured with an optical interference type surface roughness measuring instrument (manufactured by Zygo, New View 5032). The surface roughness of the SiC substrate was measured as follows. The surface roughness is measured using an optical interference type surface roughness measuring instrument (Zygo, NewView 5032), with respect to the center of the SiC substrate and four points (90-degree intervals) in a region within 5 mm from the outer periphery of the SiC substrate. The arithmetic average roughness was measured, and the average value (surface roughness) of these five points was determined. In addition, it means that the to-be-polished surface of the SiC material 1 is grind | polished uniformly and smoothly, so that the surface roughness calculated in this way is small. The measurement of the processing efficiency was performed by measuring the mass difference between the SiC substrate before and after polishing using an electronic balance (manufactured by Nippon Shibel Hegner, AG204, minimum resolution 0.1 mg), and the processing amount = mass difference / SiC specific gravity / Calculated by the substrate area / polishing time.

  Below, an example of the grinding | polishing method of the SiC substrate of this invention is demonstrated in detail. The average particle size was 40 nm, and the abrasive grain distribution used was an abrasive 40 in which broad colloidal silica 40% by weight and 60% by weight of a dispersion medium containing pure water and a pH adjuster were mixed. More specifically, the broad distribution of abrasive grains means that, as shown in FIG. 6, a large and small abrasive grain size of 1 nm to 150 nm has a wide distribution state around a particle diameter of 40 nm, and a particle diameter of 90 nm to 150 nm. Contains about 20% abrasive grains. The center particle size is 40 nm, but 40 nm ± 10 nm is a preferred range.

  Next, while the abrasive 40 is dropped intermittently on the pad 3a at room temperature (23 ° C.) using the pressurizing apparatus shown in FIG. 4, an arrow is centered on the rotary shaft 7 of the rotary table 2 (diameter 600 mm). Polished by rotating in the direction. The abrasive 40 was dropped onto the pad 3a so that 10 cc was applied to the pad 3a per minute. A commercially available polyurethane porous body (Nitta Haas Co., Ltd., SUBA400) was used for the pad 3a. The rotation speed of the turntable 2 was 40 rpm. The rotational speed of the SiC material 1 was 40 rpm. The pressure for pressing the SiC material 1 against the polishing pad 3 by the pressure head 15 biased by air pressure was 850 g / cm 2. The SiC substrate used was 3 inches.

  FIG. 7 shows the results of measuring changes in surface roughness every 2 hours from the start of polishing. When the polishing time exceeded 6 hours, almost no change in surface roughness was observed, and the surface roughness remained between 0.4 nm and 0.35 nm.

  The reason why the surface roughness does not decrease is that, as shown in FIG. 8, the waviness of the surface to be polished cannot be removed, and the surface cannot be flattened with good uniformity. Further, when the processing efficiency from the start of polishing to 6 hours of polishing was calculated, a SiC substrate having a processing amount of 90 nm polished in about 1 hour could be obtained. It can be seen that the processing amount of 90 nm / 1 hour is polished at a processing speed (processing efficiency) of about twice or more compared with the case where the abrasive 50 described in Example 2 is used. In addition, the abrasive 40 cannot remove the waviness of 0.4 nm to 0.35 nm on the polished surface, while the polishing with a high processing speed (processing efficiency) can be obtained. The purpose of the polishing method of the present invention is to achieve a high-quality SiC substrate with a high-efficiency polishing method. In order to realize a high-quality SiC substrate, the first broad abrasive is used. First, rough polishing using the abrasive 40 having a grain distribution is performed, and then finish polishing is performed with the abrasive having the second sharp abrasive grain distribution described in Example 2 to obtain a high-quality SiC substrate. Can be realized. Examples thereof will be described below.

  The polishing agent 50 used for the finish polishing has a sharp abrasive grain distribution shown in FIG. 9, and has a central particle diameter of 80 nm and a colloidal silica content of 40% by weight that occupies most of 70% with a particle diameter of 70 nm to 90 nm, This is an abrasive in which pure water and 60% by weight of a dispersion medium containing a pH adjuster are mixed. The central particle size is preferably in the range of 70 nm ± 10 nm.

  As in Example 1, the rotating shaft 7 of the rotary table 2 (diameter 600 mm) was used while intermittently dropping the abrasive 50 onto the pad 3a at room temperature (23 ° C.) using the pressurizing apparatus shown in FIG. Rotated in the direction of the arrow around the center and polished. The abrasive 50 was dropped onto the pad 3a so that 10 cc was applied to the pad 3a per minute. A commercially available polyurethane porous body (Nitta Haas Co., Ltd., SUBA400) was used for the pad 3a. The rotation speed of the turntable 2 was 40 rpm. The rotational speed of the SiC material 1 was 40 rpm. The pressure for pressing the SiC material 1 against the polishing pad 3 by the pressure head 15 biased by the air pressure was 850 g / cm 2. The SiC substrate used was 3 inches.

  FIG. 10 shows the result of measuring the change in surface roughness every 2 hours from the start of polishing. When the polishing time exceeded 14 hours, it was confirmed that the surface roughness value was reduced to 0.3 nm or less. When the processing efficiency from the start of polishing to the polishing for 14 hours was calculated, a SiC substrate with a processing amount of 40 nm polished in about 1 hour could be obtained. In view of the results of Examples 1 and 2 above, the abrasive 40 having a broad abrasive distribution with a central particle diameter of 40 nm is approximately equal to the abrasive 50 having a central particle diameter of 80 nm and a sharp abrasive distribution. A SiC substrate having a polishing rate (polishing efficiency) improved by 2 times or more could be obtained. Further, as shown in FIG. 11, when polishing was performed using a polishing agent 50 having a central particle diameter of 80 nm and a sharp abrasive grain distribution, a smooth and smooth SiC substrate could be obtained on the surface to be polished. .

  Next, by using FIGS. 12A and 12B, the polishing agent 40 used in Example 1 and the polishing method of the SiC substrate of the present invention for polishing by changing the polishing agent 50 during the polishing is performed. The process outline showing an example will be described.

In FIG. 12A, the abrasive 40 having a center particle diameter of 40 nm and a broad abrasive distribution is intermittently dropped onto the pad 3a at room temperature (23 ° C.) using the pressurization apparatus shown in FIG. However, the rotating table 2 (diameter 600 mm) was rotated around the rotating shaft 7 in the direction of the arrow and polished. The abrasive 40 was dropped onto the pad 3a so that 10 cc was applied to the pad 3a per minute. A commercially available polyurethane porous body (Nitta Haas Co., Ltd., SUBA400) was used for the pad 3a. The rotation speed of the turntable 2 was 40 rpm. The rotational speed of the SiC material 1 was 40 rpm. The pressure for pressing the SiC material 1 against the polishing pad 3 by the pressure head 15 biased by the air pressure was 850 g / cm ² . The SiC substrate used was 3 inches.

  After 6 hours have elapsed from the start of polishing of the SiC material 1 by the polishing agent 40, the dropping of the polishing agent 40 is stopped, and then, as shown in FIG. 12 (b), the cleaning head 30 descends and contacts the polishing pad 3. . The cleaning head 30 includes a brush 21, a brushing head 22, a rotating shaft 23, and a drive motor 24.

  The rotating shaft 23 rotates about the shaft 25 as the drive motor 24 rotates. That is, it is a mechanism that can be driven to rotate in the same direction as the rotation direction of the rotary table 2 (lower board). At the same time as the cleaning head 30 comes into contact with the polishing pad 3 and starts to rotate, the pure water 20 is poured and the cleaning of the polishing pad 3 is started. By this operation, the abrasive 40 adhering to the inside and the surface of the porous body of the pad 3 a is washed away and discharged from the polishing pad 3. That is, by discharging the abrasive 40 from the pad 3a, the polishing of the surface to be polished having a high polishing rate (polishing efficiency) is completed. For example, after the abrasive 40 is discharged from the pad 3a for 10 minutes or more, the brush 21 stops rotating, and the cleaning head 30 is lifted away from the polishing pad 3 as shown in FIG. The supply of water 20 stops and the cleaning operation is completed.

  Then, a polishing agent 50 having a center particle diameter of 80 nm and a sharp abrasive grain distribution is intermittently dropped onto the pad 3a, and polishing of the SiC material 1 by the polishing agent 50 is started again. That is, the abrasive 50 adheres to the inside and the surface of the porous body of the pad 3a, and finish polishing of the surface to be polished is started. When 2 hours have elapsed from the start of polishing with the polishing agent 50 (that is, polishing with the polishing agent 40 takes 6 hours, polishing with the polishing agent 50 takes 2 hours and polishing for a total of 8 hours) As a result of measurement, it was possible to obtain a SiC substrate capable of smoothly and smoothly polishing the surface to be polished with a surface roughness of 0.3 nm or less.

  A first polishing step with a polishing agent 40 having a first broad abrasive distribution, a cleaning step for discharging the abrasive 40 used in the first polishing step, and a second sharp abrasive distribution By performing the second polishing step, which is a finishing step with the abrasive 50 having the above, it is possible to polish the SiC substrate with a flatness with a surface roughness of 0.3 nm or less with high efficiency. Note that the first and second abrasive grain distributions are only examples, and the polishing times of the first and second polishing steps can be changed by changing the abrasive grain distribution of the abrasive. Can be changed.

  According to the present invention, by changing the average particle size and the particle size distribution during polishing, it is possible to consistently realize a process from a high polishing rate (polishing efficiency) to a finishing process to reduce the surface roughness. Therefore, the chemical mechanical polishing method for an SiC substrate of the present invention is useful as a method for producing a high-quality SiC substrate.

(A) is a figure which shows the grinding | polishing apparatus which implement | achieves the grinding | polishing method of the SiC substrate of this invention, (b) is a figure for demonstrating a polishing agent notionally The figure for demonstrating the surface state of a SiC substrate The figure for demonstrating the other surface state of a SiC substrate The figure which shows the other grinding | polishing apparatus for implement | achieving the grinding | polishing method of the SiC substrate of this invention The figure which shows the further another polishing apparatus for implement | achieving the grinding | polishing method of the SiC substrate of this invention. The figure which shows the abrasive grain distribution of the abrasive | polishing agent which has a broad distribution with the center particle diameter of 40 nm in this invention Example 1. The figure which shows the surface roughness change at the time of grind | polishing using the abrasive | polishing agent which has a broad abrasive grain distribution in Example 1 of this invention. The figure which shows the to-be-polished surface three-dimensionally when grind | polishing with the abrasive | polishing agent which has a broad abrasive grain distribution in Example 1 of this invention. The figure which shows the abrasive grain distribution of the abrasive | polishing agent which has a sharp distribution with the center particle diameter of 80 nm in Example 2 of this invention. The figure which shows the surface roughness change at the time of grind | polishing using the abrasive | polishing agent which has sharp abrasive grain distribution in Example 2 of this invention. The figure which shows the to-be-polished surface three-dimensionally when grind | polishing with the abrasive | polishing agent which has the sharp abrasive grain distribution in Example 2 of this invention. The figure which shows the grinding | polishing apparatus which implement | achieves the grinding | polishing method of the SiC substrate in Example 2 of this invention.

Explanation of symbols

1 SiC material 2 Rotary table (bottom)
DESCRIPTION OF SYMBOLS 3 Polishing pad 3a Pad 4 Guide 5 Weight 6 Polishing agent 6a Colloidal silica 6b Dispersion medium 7 Rotating shaft 9 Rotating shaft 10 Axis 11 Drive motor 12 Air supply path 13 Rotating shaft 14 Air bag 15 Pressure head 16 Head holding stand 20 Pure water 21 Brush 22 Brushing Head 23 Rotating Shaft 24 Drive Motor 25 Shaft 30 Cleaning Head 40 Abrasive Agent 50 Abrasive Agent

Claims (5)

In a chemomechanical polishing method in which colloidal silica is used as abrasive grains, an abrasive is dropped onto a rotating polishing pad, and the SiC substrate is polished by pressing the SiC substrate of the material to be polished against the polishing pad with a predetermined pressure.
Polishing with an abrasive mixed with a dispersion catalyst containing colloidal silica abrasive grains having a first abrasive grain distribution and a pH adjuster,
Next, polishing is performed with an abrasive mixed with a dispersion catalyst containing colloidal silica abrasive grains having a second abrasive grain distribution sharper than the first abrasive grain distribution and a pH adjuster. Chemomechanical polishing method. The first abrasive grain distribution has a center grain size of 40 nm ± 10 nm, an abrasive grain size distribution of 1 nm to 150 nm, and a content of abrasive grains of 90 nm to 150 nm is about 20%. The chemomechanical polishing method according to claim 1. The second abrasive grain distribution has a center particle diameter of 80 nm ± 10 nm and a sharper distribution than the first abrasive grain distribution, which occupies about 70% with a particle diameter of 10 nm before and after the center particle diameter. The chemomechanical polishing method according to claim 1. ^{2. The} chemomechanical polishing method according to claim 1, wherein the predetermined pressure for pressing the SiC substrate against the polishing pad is a pressure of 500 g / cm ² or more and 850 g / cm ² or less. In a chemomechanical polishing method in which colloidal silica is used as abrasive grains, an abrasive is dropped onto a rotating polishing pad, and the SiC substrate is polished by pressing the SiC substrate of the material to be polished against the polishing pad with a predetermined pressure.
A first polishing step of polishing with an abrasive mixed with a dispersion catalyst containing abrasive grains of colloidal silica having a first abrasive grain distribution and a pH adjuster;
A cleaning step of discharging the abrasive 40 used in the first polishing step;
Next, a second polishing step of polishing with an abrasive mixed with a dispersion catalyst containing colloidal silica abrasive grains having a second abrasive grain distribution sharper than the first abrasive grain distribution and a pH adjuster. When,
A chemomechanical polishing method comprising:

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