JP2006093666A - Method for grinding silicon carbide crystal substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for grinding a silicon carbide crystal substrate with a high-precision and stable surface without processing stain and lack. <P>SOLUTION: This method has been devised to grind a silicon carbide crystal substrate. It contains a process where the grinding liquid (7) with the abrasive particles made of boron carbide is used to grind the silicon carbide crystal substrate (2) with a surface roughness Rz of 50 μm or less. In this way, the diamond used so far as an abrasive particle is replaced with the boron carbide so that damage to the materials to be polished such as the silicon carbide crystal and grind stool can be reduced and the surface can be ground with precision. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique related to polishing of silicon carbide crystals, and more particularly to a crystal polishing technique related to rough polishing.

  Power devices that handle electrical energy with low loss are widely used because they can greatly reduce power consumption. Current power devices are fabricated from silicon substrates, but there are limits to further performance enhancement due to the inherent characteristics of silicon. In particular, since silicon cannot be used at high temperatures, materials that replace silicon have become necessary.

  For this reason, in recent years, silicon carbide (SiC) has attracted attention. Since the forbidden band width of silicon carbide is three times the forbidden band width of silicon, it can be used under higher temperature conditions than silicon. In addition, since the breakdown electric field is about 10 times that of silicon, the size can be reduced. 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 silicon carbide has excellent characteristics as described above, the silicon carbide substrate is very promising as a power device substrate instead of a silicon substrate.

By the way, in order to fabricate a power device from a silicon carbide substrate, it is necessary to finally polish the surface as smoothly as possible. At present, a silicon carbide ingot purified by crystal growth is first sliced with a wire saw, blade saw, etc., and then ground to remove irregularities present on the substrate, and rough polishing using a hard polishing surface plate, a soft polishing pad Processing is carried out through a precision (mirror surface) polishing process using. Of these, precision polishing is the most important process, and as a known method, a polishing method using a suspension containing diamond abrasive grains and SiO ₂ (colloidal silica) as in Patent Document 1 is currently generally used. Yes. In addition, rough polishing, which is a pretreatment process for the final processed surface, is an important process as well as precision polishing. If the state after rough polishing is good, the processing time of the final process can be shortened.
Special table 2001-508597 gazette

  However, since the technique of Patent Document 1 uses diamond as the abrasive grains, the time required for polishing (processing rate) is short, but damage to the workpiece is large. That is, during polishing, the silicon carbide crystal is greatly damaged, and the silicon carbide crystal is easily damaged by aggregates formed from the diamond abrasive grains. Further, since a hard polishing surface plate is used in the rough polishing step, the damage to the polishing surface plate is large, and the surface of the polishing surface plate needs to be corrected in the next polishing. In rough polishing using a hard polishing surface plate, the shape of the polishing surface plate is transferred to the silicon carbide substrate, which is the material to be polished. This may cause deterioration of the processed surface state of the silicon substrate. Therefore, when polishing silicon carbide crystals, it is necessary to reduce damage to the polishing surface plate.

  The present invention solves the above-described conventional problems, and when obtaining a final pre-processed surface of a silicon carbide substrate, suppresses damage to the silicon carbide crystal and the hard polishing surface plate, and precisely polishes the surface. A silicon carbide crystal substrate polishing method that can be performed is provided.

  The silicon carbide crystal substrate polishing method of the present invention is a method for polishing a silicon carbide crystal substrate, wherein a silicon carbide crystal substrate having a surface roughness Rz of 50 μm or less using a polishing liquid containing abrasive grains made of boron carbide. And a polishing step of polishing the substrate.

  According to the present invention, by changing the abrasive grains from conventionally used diamond to boron carbide, it is possible to reduce damage to the silicon carbide crystal as the material to be polished and the surface of the polishing platen, and polishing the surface Can be performed precisely.

  The present invention is used when roughly polishing a silicon carbide crystal substrate. Here, the rough polishing means that the surface roughness Rz of the silicon carbide crystal substrate is more than 1 μm and not more than 50 μm, and after polishing is made 1 μm or less.

  Here, the “surface roughness Rz” is a value defined by JIS standard B0601, and is defined as the sum of the maximum value of the peak height of the contour curve and the maximum value of the valley depth in the reference length. In the present invention, the measurement is performed using a product name “Newview 5032” manufactured by Zygo Corporation of an optical interference type surface roughness measuring instrument.

  As the polishing liquid, a polishing liquid containing polishing abrasive grains made of boron carbide is used. The average particle diameter of boron carbide is preferably in the range of 100 μm or less. More specifically, in the present invention, since several processing steps are assumed in rough polishing, for example, boron carbide having an average particle diameter of 60 to 100 μm is suitable for a SiC substrate with Rz = 50 μm, For SiC substrates in the vicinity of Rz = 1 μm, boron carbide of 10 μm or less is suitable. The boron carbide particles are amorphous.

  Here, the average particle diameter is measured by a natural centrifugal sedimentation method, and the measuring apparatus measures the product name “CAPA-300” manufactured by Horiba, Ltd. The sample liquid containing about 1% by weight of the abrasive component is centrifuged in a measuring apparatus, and the average particle size is measured by the speed of the precipitated abrasive component.

  As this polishing liquid, for example, a dispersion obtained by dispersing boron carbide in a proportion of 0.1 wt% or more and 5 wt% or less as abrasive grains in pure water can be preferably used. Here, pure water is ion-exchanged water.

  The polishing method of the present invention can be used from rough polishing to finish polishing.

  In the method of the present invention, a polishing container containing a polishing liquid is placed on a polishing surface plate for polishing a silicon carbide crystal substrate, and the polishing liquid inside the polishing container is stirred in the polishing container so as not to precipitate. It is preferable to perform polishing while dropping the polishing liquid onto the polishing surface plate. In this way, since a polishing liquid having a uniform composition can be supplied to the surface of the silicon carbide crystal substrate, the polishing surface can be made uniform.

  In the polishing step of the present invention, it is preferable to include a plurality of polishing steps in which the average particle size of the polishing abrasive grains is different. If it does in this way, polish can be advanced in steps.

  In the above polishing step, the average particle size of the abrasive grains used in the first polishing step is larger than the average particle size of the polishing abrasive particles used in the last polishing step, and the average particle size is sequentially increased as the polishing step proceeds. It is preferable to reduce the diameter. If it does in this way, it can advance to precision polishing in steps from rough polishing.

  Furthermore, in the silicon carbide crystal substrate polishing method of the present invention, the average grain size of the abrasive grains used in the first polishing process is 60 μm or more and 100 μm or less, and the average grain diameter of the abrasive grains used in the last polishing process is 10 μm or less. Preferably there is. This is because the purpose of polishing is to increase the processing rate in the first polishing step, and the purpose is to improve the surface roughness in the final polishing step. In the final polishing step, smaller abrasive grains are used. The average grain size of the abrasive grains used in the last step is generally 1 μm as the minimum average grain size of commercially available boron carbide. For example, classification is performed to obtain an average grain size of 0.8 μm or an average grain size of 0 μm. Polishing may be performed with a thickness of 6 μm.

  Furthermore, the number of rotations of the polishing platen used in the method of the present invention is preferably 5 rpm or more and 40 rpm or less, and the dropping rate of the polishing liquid onto the polishing platen is preferably 5 cc / min or more. In this way, efficient polishing can be performed. The conditions here are conditions for preventing the polishing platen from drying, and there are no lower limit of rotation speed and no upper limit of dropping speed. Practically, the number of revolutions is preferably 5 rpm or more, and in terms of dropping speed, there is no upper limit in practical use because the polishing surface plate may be immersed in the polishing liquid.

  Furthermore, when the polishing liquid used in the method of the present invention uses pure water as a solvent and there is no dispersant for dispersing the abrasive grains in the solvent, the ratio of the abrasive grains to the polishing solution is 0.1% by weight. The content is preferably 5% by weight or less. This is because when the weight ratio of the abrasive grains is large, precipitation of the abrasive grains occurs in the polishing liquid, and conversely, when the weight ratio of the abrasive grains is small, the processing efficiency is deteriorated. .

  Furthermore, it is preferable that the entire upper surface of the polishing platen in the polishing step of the present invention is always covered with the polishing liquid. This is because the dry polishing surface plate and the wet polishing surface plate have different frictional resistances at the contact portions between the abrasive grains, the polishing surface plate, and the silicon carbide substrate. This is because it causes a large processing flaw on the surface of the substrate.

Further, in the polishing step of the present invention, it is preferable to perform polishing by applying a surface pressure of 100 gf / cm ² or more and 200 gf / cm ² or less to the silicon carbide crystal substrate. This is because a practical processing rate cannot be obtained at a surface pressure of less than 100 gf / cm ² , and conversely, a silicon carbide substrate may be damaged at a surface pressure of over 200 gf / cm ² .

  According to the present invention, by changing the abrasive grains from conventionally used diamond to boron carbide, it is possible to reduce damage to the silicon carbide crystal as the material to be polished and the surface of the polishing platen, and polishing the surface Can be performed precisely.

  An example of the method for polishing a silicon carbide substrate of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following Example.

  1A is a plan view of a polishing apparatus according to an embodiment of the present invention, FIG. 1B is a side view thereof, FIG. 1C is an enlarged view of a weight 12 and a work guide assembly 12 in FIG. 1B, and FIG. FIG. As shown in FIG. 1A to FIG. 1D, an affixing jig 3 in which a silicon carbide substrate 2 is affixed to a polishing surface plate 1 and an appropriate amount of weight 4 for applying pressure are placed. Then, the work guide 5 is attached to the outside of the silicon carbide substrate 2, the attaching jig 3, and the weight 4, and the polishing table 1 is rotated in the direction of arrow P so that the silicon carbide substrate 2 is attached in a form supported by the arm 6. The jig 3, the weight 4, and the work guide 5 rotate on the polishing surface plate 1 in the arrow Q direction. Then, a polishing liquid 7 containing abrasive grains made of boron carbide is periodically polished through a silicon tube 9 using a tubing pump 8 (for example, a cassette tubing pump SMP-21 manufactured by Tokyo Science Instrument Co., Ltd.). The polishing process proceeds by dripping onto the top. Here, as the polishing liquid 7, for example, a commercially available stirrer 10 containing a magnet is put in a container of the polishing liquid 7, and stirred by a commercially available stirrer 11 from the bottom of the container, and boron carbide in the polishing liquid 7 is added. So that the abrasive grains consisting of Here, as the stirrer 10 and the stirrer 11, for example, a magnetic stirrer and a stirrer manufactured by Tokyo Science Instruments Co., Ltd. may be used.

  At this time, the silicon carbide substrate 2, the bonding jig 3, the weight 4, and the work guide 5 can be rotated without attaching a motor to the arm 6. This is preferable because the silicon carbide substrate 2, the bonding jig 3, the weight 4, and the work guide 5 rotate at a more stable rotational speed. Further, the rotation direction of the polishing surface plate 1 and the arm 6 at this time may be the same direction or the reverse direction. Further, a swing mechanism may be attached to the arm 6.

  The composition of the polishing liquid 7 is composed of an abrasive grain component made of pure water and boron carbide, and the weight ratio between the abrasive grain made of boron carbide and pure water is preferably 0.1% or more and 5% or less. . When the weight ratio of the abrasive grains made of boron carbide in the polishing liquid 7 exceeds 5%, the abrasive grains of boron carbide precipitate in the polishing liquid 7 during the polishing process, resulting in abrasive grains that are not suitable for the polishing process. As a result, the processing efficiency deteriorates. Further, since the abrasive grains made of precipitated boron carbide aggregate and the shape of the abrasive grains is distorted, the polishing surface plate 1 and the silicon carbide substrate 2 are scratched during polishing. Further, since the concentration distribution is generated in the polishing liquid 7, the processing quality is uneven. If the weight ratio of boron carbide in the polishing liquid 7 is small (if it is not 0%), the processing efficiency is lowered, but the surface roughness of the silicon carbide substrate 2 after the polishing is improved.

  During the polishing process, it is preferable to supply the polishing liquid 7 onto the polishing surface plate 1 while constantly stirring the polishing liquid 7. This is because, even with the polishing liquid 7 in which the weight ratio of boron carbide is 2 to 3%, some precipitation occurs during long-time polishing. Further, for example, a dispersant such as ethylenediaminetetraacetic acid, which is an amine material, may be added to the polishing liquid 7 to increase the dispersibility.

  In addition, it is effective to perform the polishing step a plurality of times by changing the abrasive grains. That is, since the surface roughness of the silicon carbide substrate 2 before polishing is rough, the average particle size of boron carbide contained in the polishing liquid 7 in the first polishing is large, and as the polishing process proceeds, Sequentially, the average grain size of the abrasive grains should be reduced. In general, if the surface pressure applied to the substrate to be polished is the same, the processing rate increases (the polishing time decreases) and the surface roughness after polishing increases as the average particle size of the abrasive grains increases. Conversely, the smaller the average grain size of the abrasive grains, the smaller the processing rate and the smaller the surface roughness after polishing.

In Table 1, as an example of the practice of the present invention, the average particle size and carbonization of boron carbide contained in the polishing liquid 7 when the silicon carbide substrate 2 having a surface roughness of 50 μm (Rz: maximum height) is polished. The relationship between the surface pressure applied to the silicon crystal substrate 2 and the processing rate is shown. In Table 1, the average particle diameter of boron carbide contained in the polishing liquid 7 is 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, and 120 μm, and the surface pressure applied to the silicon carbide substrate 2 is 0 gf / cm ² (self weight only), 50 gf / cm ² , 100 gf / cm ² , 150 gf / cm ² , 200 gf / cm ² , and 250 gf / cm ² were set. Further, the processing rate was compared with the values calculated from the weight difference of the silicon carbide substrate 2 before and after processing measured by an electronic balance in each combination of the average particle size of boron carbide and the surface pressure applied to the silicon carbide substrate 2. If the processing rate is 30 μm / h or higher, the processing rate is A. If the processing rate is about 10 μm / h, the processing rate is B. If not, the processing rate is C. When the silicon carbide substrate 2 was damaged, D was used.

As shown in Table 1, when the surface pressure was 250 gf / cm ² or more, the substrate was damaged under all conditions, but under the surface pressure conditions of 200 gf / cm ² or less, the substrate was not damaged. Therefore, the surface pressure is preferably 200 gf / cm ² or less regardless of the average particle diameter of the abrasive grains. Further, boron carbide having an average particle size of 120 μm cannot be sufficiently agitated in the polishing liquid 7, so that precipitation and aggregation of abrasive grains occur, and effective polishing cannot be performed. Therefore, the average particle size of abrasive grains using boron carbide is preferably 100 μm or less.

Further, when the average particle size of boron carbide, which is an abrasive grain, is large, the relationship between the processing rate and the surface pressure is remarkable. That is, when the average particle size of boron carbide is 60 to 100 μm, the surface pressure at which the optimum processing rate is obtained is 100 to 200 gf / cm ² .

Therefore, the present invention uses polishing abrasive grains made of boron carbide having a large average particle diameter of about 60 μm to 100 μm in the initial polishing, and polishing is performed under the condition that the surface pressure applied to the silicon carbide substrate 2 is 100 to 200 gf / cm ^2. After performing the rough correction of the surface of the silicon carbide substrate 2, it is preferable to perform final polishing to obtain a desired polishing surface using polishing grains made of boron carbide having a small average particle diameter.

  In the final polishing, the surface roughness and surface state after polishing are more important than the processing rate compared to the initial polishing. Table 2 shows the surface roughness of the silicon carbide substrate 2 when polishing is performed under the conditions that the average particle size of boron carbide abrasive grains contained in the polishing liquid 7 is 1 μm, 5 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, and 100 μm. This is a summary.

  The surface roughness is measured by the Rz value after completion of polishing with the Zygo Corporation brand name “Newview 5032” apparatus. If the Rz value is 1.0 μm or less, A and the Rz value slightly exceed 1.0 μm. Then B, and C if the Rz value is clearly 1 μm or more. Here, it is preferable that the surface roughness of the silicon carbide substrate 2 after the final polishing in which polishing is performed using boron carbide is Rz = 1 μm or less, and therefore the average particle diameter of boron carbide contained in the polishing liquid 7 in the final polishing. Is preferably 10 μm or less.

The material of the polishing surface plate 1 is not a special one, and may be one used for rough polishing with normal diamond such as cast iron. As shown in Table 1, the surface pressure at which the silicon carbide substrate 2 is pressed against the polishing surface plate 1 is preferably 100 gf / cm ^{2 to} 200 gf / cm ² . When the surface pressure is higher than 200 gf / cm ^{2, the} silicon carbide substrate 2 is easily cracked as shown in Table 1.

  The rotation speed of the silicon carbide substrate 2 provided by the polishing surface plate 1 and the arm 6 is determined by the polishing surface plate 1, the size of the silicon carbide substrate 2, the material of the polishing surface plate 1, the combination of the groove shape and the silicon carbide substrate 2, and the polishing. Depending on the concentration of the liquid 7, the temperature during processing, the humidity, and the shape of the polishing apparatus, the polishing surface plate 1 made of cast iron has a diameter of 200 mm, the silicon carbide substrate 2 has 5.08 cm (2 inches), and the polishing made of boron carbide. When 5 cc of polishing liquid 7 having a concentration of abrasive grains of 5 wt% is dropped per minute, the maximum is 40 rpm. When the other polishing processing conditions are the same, the processing efficiency is deteriorated when the rotational speed is small, but the damage to the surface of the silicon carbide substrate 2 is small, which is particularly effective in the final stage of the present embodiment. On the contrary, when the rotational speed is large, the polishing liquid 7 on the polishing surface plate 1 is likely to be scattered, and the polishing surface plate 1 is more easily dried. Drying of the polishing platen 1 must be avoided because it leads to the aggregation of abrasive grains on the polishing platen 1 and causes scratches. In general, it is preferable that the number of rotations of the polishing surface plate 1 and the silicon carbide substrate 2 be reduced as the size of the polishing object corresponding to the polishing surface plate 1 and the silicon carbide substrate 2 in this embodiment increases. When the size of the polishing surface plate 1 and the material to be polished is large, the amount of the polishing liquid 7 required to keep the surface of the polishing surface plate 1 from being dried is larger than when the polishing surface plate 1 and the material to be polished are small. For this reason, the efficiency becomes worse unless machining is performed at a lower speed. Further, when the polishing surface plate 1 is large, the peripheral speed itself of the part that is actually processed increases, so that the processing efficiency is reduced even if the number of rotations is reduced as compared with the case where the size of the polishing surface plate 1 is small. Hateful. The same applies to the size of the silicon carbide substrate 2. As described above, these actual processing conditions are the size of the polishing surface plate 1, the silicon carbide substrate 2, the material of the polishing surface plate 1, the combination of the groove shape and the silicon carbide substrate 2, the concentration of the polishing liquid 7, and the temperature during processing. The influence of humidity, the shape of the polishing apparatus is also great. Further, the polishing surface plate 1 does not need to be circular, and it is not necessary to perform polishing while rotating, and may be linear motion or unsteady motion.

  Hereinafter, the effect of the polishing method of the present invention will be described in more detail with examples.

Example 1
A polishing liquid 7 consisting of abrasive grains made of boron carbide made by Denki Kagaku Kogyo Co., Ltd. and two kinds of average particle diameters (60 μm and 1 μm) and pure water was used. The ratio of the abrasive grains to the polishing solution was 5% by weight. An abrasive having an average grain size of 60 μm was used as the first step (initial polishing step), and an abrasive grain having an average particle size of 1 μm was used as the second step (finish polishing step). In each polishing process, the polishing liquid 7 was stirred with a stirrer so as not to cause precipitation of abrasive grains. The polished surface plate 1 was cast iron. The silicon carbide substrate 2 was a SiC single crystal substrate manufactured by CREE, INC. Electron wax made by Nikka Seiko Co., Ltd. was used for attaching the silicon carbide substrate 2 to the attaching jig 3.

5 cc of the polishing liquid 7 is dropped on the polishing platen 1 per minute, the rotation speed of the polishing platen 1 and the arm 6 is set to 40 rpm in the same direction, and the weight 4 is applied to the silicon carbide substrate 2 at a surface pressure of 200 gf / cm ^2. Pressure was applied. The initial state of the surface of the silicon carbide substrate 2 to be polished was Rz = 50 μm, and the processing time was 15 minutes for the first step and 60 minutes for the second step.

(Comparative Example 1)
A diamond slurry manufactured by FRT Japan Ltd. was used for the polishing liquid 7. The abrasive grains made of diamond in the diamond slurry had an average particle diameter of 1 μm. The weight 4 applied 150 gf / cm ² to the silicon carbide substrate 2 in terms of surface pressure. The processing was performed in only one processing step as in Example 1 except that the polishing liquid 7 used was diamond slurry and the surface pressure applied to the silicon carbide substrate 2 by the weight 4 was 150 gf / cm ² . The processing time was 45 minutes.

  Table 3 shows the processing rates under the respective processing conditions and the silicon carbide substrate 2 in Example 1 and Comparative Example 1 among the first and second steps of Example 1 and the polishing results of Comparative Example 1. The state of the final processing surface and the state of the polishing surface plate 1 are shown. The processing rate was calculated by measuring the weight of the silicon carbide substrate 2 before and after the polishing process in the first step, the second step, and the comparative example 1 in Example 1 with an electronic balance, and setting the specific gravity of the silicon carbide substrate 2 to 3.2. The amount of processing removal is shown by the amount per hour. Further, the final machined surface state of the silicon carbide substrate 2 was measured for surface roughness (Rz value) using a product name “New view 5032” manufactured by Zygo Corporation. Furthermore, the depth of the processing flaw on the surface of the silicon carbide substrate was measured with a laser microscope VK8500 manufactured by Keyence Corporation. The surface condition of the polishing surface plate 1 was confirmed by visual observation. If the surface condition was almost the same as that before processing, A was determined, and if a processing flaw was confirmed, it was determined as B.

  As shown in Table 3, when the average particle size of boron carbide is 1 μm (second step) and diamond (Comparative Example 1), the processing rate of the diamond of Comparative Example 1 is better. That is, in the case of processing equivalent to that of Comparative Example 1 only in the second step, the polishing time is 7.2 times longer than the result of the processing rate. However, by dividing the polishing process into two steps and using boron carbide with an average particle size of 60 μm in the first step, the polishing time can be shortened to about 1.7 times and the surface roughness after polishing is the same. I can do it. In addition, when comparing the second step and the depth of the processing flaw after the processing and polishing of Comparative Example 1, it is possible to reduce the processing flaw by 2.5 times when the polishing processing is performed in the second step. When the processing scratches on the surface of the silicon carbide substrate 2 after the rough polishing are shallow, there is an effect that the processing time in precision polishing, which is a subsequent process, can be greatly shortened. Here, since the precision polishing process requires several hours to several tens of hours of processing time, when the polishing processing of Example 1 is performed, it is considered that the total processing time is significantly shortened. Further, in Comparative Example 1, the processing scratches on the polished surface plate 1 after processing are significant, but no processing scratches are seen in the first step and the second step of the example. Therefore, if boron carbide is used for the abrasive grains, it is not necessary to correct the polishing surface plate even if the polishing process is performed a plurality of times compared to the conventional diamond abrasive grains, and the carbonized surface has a good quality crystal surface. A silicon substrate can be obtained.

  In addition, as shown in Example 1, in addition to the construction method using the first process having an average grain size of 60 μm as the first step and the second process having an average grain size of the abrasive grain of 1 μm, In the first step, the abrasive grains having an average particle size of 60 μm, in the second step, the abrasive grains having an average particle size of 10 μm, and in the third step, the abrasive grains having an average particle size of 1 μm are used. In the construction method, the first step has an average abrasive grain size of 80 μm, the second step has an average abrasive grain size of 10 μm, and the third step has an average abrasive grain size of 1 μm There is no problem even if the construction method using is used.

  According to the present invention, by using boron carbide for the abrasive grains, a silicon carbide substrate that suppresses damage to the silicon carbide substrate and the polishing surface plate as compared with rough polishing with normal diamond abrasive grains is provided. It can be provided and is useful as a method for polishing a silicon carbide substrate.

FIG. 1A is a plan view of a polishing apparatus in one embodiment of the present invention, and FIG. 1B is a side view thereof. 1C is an enlarged view of a portion 12 in FIG. 1B, and FIG. 1D is an assembly view of FIG. 1C.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing surface plate 2 Silicon carbide substrate 3 Sticking jig 4 Weight 5 Work guide 6 Arm 7 Polishing liquid 8 Tubing pump 9 Silicon tube 10 Stirrer 11 Stirrer 12 Weight and work guide assembly

Claims (10)

A method for polishing a silicon carbide crystal substrate, comprising:
A method for polishing a silicon carbide crystal substrate, comprising a polishing step of polishing a silicon carbide crystal substrate having a surface roughness Rz of 50 μm or less using a polishing liquid containing abrasive grains made of boron carbide.   The silicon carbide crystal substrate polishing method according to claim 1, wherein the polishing step includes a plurality of polishing steps in which the average particle size of the polishing abrasive grains is different.   In the polishing step, the average particle size of the polishing abrasive grains used in the first polishing step is larger than the average particle size of the polishing abrasive particles used in the last polishing step, and the average is sequentially increased as the polishing step proceeds. The silicon carbide crystal substrate method according to claim 2, wherein the grain size is reduced.   4. The silicon carbide crystal according to claim 3, wherein the average grain size of the abrasive grains used in the first polishing step is 60 μm or more and 100 μm or less, and the average grain diameter of the abrasive grains used in the last polishing step is 10 μm or less. Substrate polishing method.   In the polishing step, a polishing container in which the polishing liquid is placed on a polishing surface plate for polishing the silicon carbide crystal substrate is disposed, and the polishing particles in the polishing liquid inside the polishing container are not precipitated. The method for polishing a silicon carbide crystal substrate according to claim 3, wherein a polishing liquid is dropped onto the polishing platen while stirring.   The silicon carbide crystal substrate polishing method according to claim 5, wherein the polishing platen has a rotation speed of 40 rpm or less.   The silicon carbide crystal substrate polishing method according to claim 5, wherein a dropping rate of the polishing liquid onto the polishing platen is 5 cc / min or more.   The polishing liquid uses pure water as a solvent, and when there is no dispersant for dispersing the polishing abrasive grains in the solvent, the ratio of the polishing abrasive grains to the polishing solution is 5% by weight or less. 2. The method for polishing a silicon carbide crystal substrate according to 1.   The silicon carbide crystal substrate polishing method according to claim 1, wherein the entire upper surface of the polishing platen in the polishing step is always covered with the polishing liquid. The silicon carbide crystal substrate polishing method according to claim 1, wherein in the polishing step, polishing is performed by applying a surface pressure of 100 gf / cm ² or more to 200 gf / cm ² or less to the silicon carbide crystal substrate.

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