SiC substrate manufacturing method and lapping slurry

Abstract

To provide a method for manufacturing an SiC substrate, which can facilitate management of particle diameters of abrasives, realize cost reduction, reduce an environmental load, and suppress the occurrence of cracks, and a slurry for wrapping processing.SOLUTION: The method for manufacturing the SiC substrate comprises a processing step of wrapping one or both surfaces of the SiC substrate by using a slurry containing boron carbide abrasives and an additive for dispersing the boron carbide abrasives. In the processing step, a ratio of an average particle diameter of the boron carbide abrasives after processing to an average particle diameter of the boron carbide abrasives before processing is 0.91-1.2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a SiC substrate and a slurry for lapping. [Background technology]

[0002] Silicon carbide substrates are formed by slicing single-crystal SiC ingots. It is generally known that the sliced ​​SiC substrates have warpage and waviness. To improve the growth yield of SiC epitaxial films on SiC substrates, it is necessary to remove the warpage and waviness. To eliminate the waviness and warpage of the substrates, lapping is performed using a double-sided machine.

[0003] Lapping uses a slurry containing abrasive grains. For example, a slurry containing diamond abrasive grains is used as the abrasive grains. In recent years, a method has been proposed in which a slurry containing boron carbide as the abrasive grains is used to polish a SiC substrate with loose abrasive grains (Patent Document 1 and Patent Document 2). The method of Patent Document 1 discloses that the high brittleness of boron carbide abrasive grains is utilized to break the boron carbide abrasive grains while lapping the SiC substrate, thereby improving the processing speed.

[0004] Also, a method has been proposed in which a dispersant such as naphthalenesulfonic acid formalin condensate and / or its salt is mixed with abrasive grains of about 3 μm in diameter, such as iron or copper, in order to adjust the dispersibility of chips and abrasive grains in a slurry used when lapping a substrate (Patent Document 3).Patent Document 3 discloses the use of diamond as an abrasive grain for lapping.

[0005] Additionally, a method has been proposed in which, when lapping a substrate, a slurry containing a water-soluble glycol is used and abrasive grains are dispersed in the slurry (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-15643 [Patent Document 2] Patent No. 6670587 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-135840 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-502455 Summary of the Invention [Problem to be solved by the invention]

[0007] When lapping a SiC substrate using a slurry containing boron carbide as abrasive grains, as in Patent Documents 1 and 2, the particle size of the abrasive grains may be significantly reduced or the abrasive grains may be worn away during the lapping process. In lapping, the polishing of the SiC substrate is typically performed repeatedly under certain conditions. Therefore, if the particle size of the abrasive grains in the slurry is significantly reduced or worn away, the lapping speed changes, making it difficult to reuse the abrasive grains. Furthermore, if abrasive grains with reduced particle size are used as they are, the processing rate drops significantly, resulting in insufficient lapping.

[0008] When diamond, which has a high modified Mohs hardness, is used as the abrasive grains as in Patent Document 3, cracks may occur in the SiC substrate, making it impossible to flatten the SiC substrate with sufficient precision. Also, when boron carbide, which is highly brittle, is used as the abrasive grains as in Patent Document 4, the grain size of the abrasive grains decreases or the abrasive grains are worn away, resulting in the same problems as above.

[0009] As described above, with the methods disclosed in Patent Documents 1, 2, and 4, it is difficult to repeatedly perform lapping under the same conditions using a slurry containing abrasive grains that has already been used in lapping. Therefore, in order to perform lapping under the same conditions, it is necessary to replace the abrasive grains, and managing the grain size of the abrasive grains is complicated. Furthermore, the cost of replacing the abrasive grains increases, and in addition, a large amount of used slurry must be disposed of as waste liquid, which places a heavy burden on the environment. Furthermore, with Patent Document 3, there is a concern about the occurrence of cracks during lapping. [Means for solving the problem]

[0010] The present invention has been made in consideration of the above circumstances, and aims to provide a method for manufacturing a SiC substrate and a slurry for lapping processing that can facilitate control of the particle size of abrasive grains, reduce costs, reduce environmental impact, and suppress the occurrence of cracks.

[0011] (1) A method for manufacturing a SiC substrate according to a first aspect of the present invention includes a processing step of lapping one or both sides of a SiC substrate using a slurry containing boron carbide abrasive grains and an additive for dispersing the boron carbide abrasive grains, wherein in the processing step, the ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing is 0.91 or more and 1.2 or less.

[0012] (2) In the method for manufacturing a SiC substrate according to the above aspect, in the processing step, the average particle size of the boron carbide abrasive grains before processing may be 15 μm or more and 40 μm or less, and the average particle size of the boron carbide abrasive grains after processing may be 14 μm or more and 48 μm or less.

[0013] (3) In the method for manufacturing a SiC substrate according to the above aspect, the surface of the SiC substrate may be polished at a polishing rate of 14 μm / h or more and 45 μm / h or less.

[0014] (4) In the method for manufacturing a SiC substrate according to the above aspect, the processing step may use the slurry containing water as a main component.

[0015] (5) In the method for manufacturing a SiC substrate according to the above aspect, the processing step may use the slurry in which the proportion of the additive is 3% by volume or more and 20% by volume or less.

[0016] (6) In the method for manufacturing a SiC substrate according to the above aspect, the slurry may be used in the processing step, in which the proportion of the boron carbide abrasive grains is 15% by mass or more and 45% by mass or less.

[0017] (7) In the method for manufacturing a SiC substrate according to the above aspect, in the processing step, one or more additives selected from the group consisting of glycerin, 1-vinylimidazole, coconut oil fatty acid methyl taurate sodium, lauric acid amide ether sulfate sodium salt, myristate amide ether sulfate sodium salt, polyacrylic acid, and acrylic acid-maleic acid copolymer may be used.

[0018] (8) A second aspect of the present invention provides a lapping slurry used for processing the surface of a SiC substrate, the slurry comprising boron carbide abrasive grains and an additive, wherein the ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing the surface of the SiC substrate may be 0.91 or more and 1.2 or less.

[0019] (9) In the lapping slurry according to the above aspect, the average particle size of the boron carbide abrasive grains before processing may be 15 μm or more and 40 μm or less, and the average particle size of the boron carbide abrasive grains after processing may be 14 μm or more and 48 μm or less.

[0020] (10) The lapping slurry according to the above embodiment may further contain water, and may be composed mainly of water.

[0021] (11) In the lapping slurry according to the above aspect, the content of the additive may be 3% by volume or more and 20% by volume or less.

[0022] (12) In the lapping slurry according to the above aspect, the proportion of the boron carbide abrasive grains may be 15% by mass or more and 45% by mass or less.

[0023] (13) The lapping slurry according to the above embodiment may contain, as the additive, one or more selected from the group consisting of glycerin, 1-vinylimidazole, coconut oil fatty acid methyl taurate sodium, lauric acid amide ether sulfate sodium salt, myristate acid amide ether sulfate sodium salt, polyacrylic acid, and acrylic acid-maleic acid copolymer. [Effects of the Invention]

[0024] According to the present invention, it is possible to easily control the particle size of abrasive grains, reduce costs, reduce the environmental load, and suppress the occurrence of cracks. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view showing a state in which a processing step is performed on a SiC substrate using a polishing device in a method for manufacturing a SiC substrate according to the present invention. FIG. [Figure 2] FIG. 2 is a perspective view illustrating a modified example of the polishing apparatus of FIG. [Figure 3] FIG. 1 is an image diagram for explaining a method for measuring the thickness of a SiC substrate. [Figure 4] 1 is a graph showing the particle size distribution of boron carbide abrasive grains after lapping in Example 1 and Comparative Example 1. [Figure 5] 1 is a graph summarizing the results of the machining speed versus the machining time in Example 1. [Figure 6] 1 is a graph showing the processing speed of the lapping process in Comparative Example 1 and Example 1. [Figure 7] 1 is a graph showing the in-plane variation in substrate thickness of SiC substrates of Example 1 and Comparative Example 1. [Figure 8] 1 is a graph showing the particle size distribution of the boron carbide abrasive grains used in Comparative Example 1 after machining. [Figure 9] 1 is a graph summarizing the processing numbers of the SiC substrates used in Production Examples 1 to 3 and Example 1 and the processing speeds in the lapping process. [Figure 10] 1 is a graph showing the particle size distribution of the boron carbide abrasive grains used in Examples 1 and 2 before and after processing. [Figure 11] 10 is a graph summarizing the processing numbers of the SiC substrates used in Production Examples 7 and 8 and the processing speeds in the lapping process. [Figure 12] 10 is a graph showing a summary of the processing numbers of the SiC substrates used in Production Examples 9 to 11 and the processing speeds in the lapping process. [Figure 13] 1 is a graph showing changes in dispersity in slurries of Production Examples 12 to 19 and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0026] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand. Therefore, the dimensional ratios of each component may differ from the actual ones.

[0027] [SiC substrate manufacturing method] The method for manufacturing a SiC substrate according to this embodiment includes a processing step of lapping one or both sides of a SiC substrate using a slurry containing boron carbide abrasive grains and an additive for dispersing the boron carbide abrasive grains, and in the processing step, the ratio of the average grain size of the boron carbide abrasive grains after processing to the average grain size of the boron carbide abrasive grains before processing is 0.91 or more and 1.2 or less.

[0028] (Processing process) The processing step is a step that follows the slicing step in which, for example, a SiC ingot is sliced ​​to form a SiC substrate. The processing step serves to remove waviness and processing strain generated in the slicing step and flatten one or both sides of the SiC substrate.

[0029] The processing step can be performed, for example, by a loose abrasive method, and can be performed using a polishing apparatus 100 as shown in Fig. 1. The polishing apparatus 100 includes an upper surface plate 21 whose lower surface is a polishing surface and which is supported above so as to be freely movable up and down, a lower surface plate 22 disposed opposite the upper surface plate 21 and whose upper surface is also a polishing surface, a support shaft 20 provided at the axial center of the upper surface plate 21 and integral with the upper surface plate 21, a slurry tube 23 that supplies slurry between the upper surface plate 21 and the lower surface plate 22, and a carrier plate 24 for placing the SiC substrate 1 between the upper surface plate 21 and the lower surface plate 22.

[0030] The upper surface plate 21 is rotatable about the support shaft 20 by a drive device (not shown), and is rotated in the opposite direction to the lower surface plate 22. The upper surface plate 21 is provided with a plurality of slurry supply holes 21b which are through holes.

[0031] The lower surface plate 22 is rotatable about the support shaft 20 by a drive device (not shown), and is rotated in the opposite direction to the upper surface plate 21. The lower surface plate 22 is supported by, for example, a ring-shaped bearing (not shown).

[0032] A carrier plate 24 having a plurality of circular holes 24a for accommodating, for example, SiC substrates 1, which are the workpieces to be polished, is disposed between the upper surface plate 21 and the lower surface plate 22. The carrier plate 24 is configured to rotate and revolve around its axis by planetary motion using an inner pin gear (central gear) (not shown) and an outer pin gear (internal gear) (not shown) having a known mechanism, which are disposed in the center hole of the lower surface plate 22. In FIG. 1, only one carrier plate 24 is shown as a representative of the plurality of carrier plates disposed between the upper surface plate 21 and the lower surface plate 22.

[0033] When performing a processing step, polishing apparatus 100 supplies a lapping slurry S between upper surface plate 21 and lower surface plate 22, for example, via a slurry tube 23 provided through a plurality of slurry supply holes 21b provided in upper surface plate 21, and then applies a processing pressure to upper surface plate 21 and lower surface plate 22 in a direction perpendicular to the surface of SiC substrate 1, while rotating upper surface plate 21 and lower surface plate 22 in opposite directions. In Fig. 1, examples of the direction of the processing pressure and the direction of rotation of upper surface plate 21 and lower surface plate 22 are indicated by arrows labeled F and R, respectively.

[0034] The processing pressure is, for example, 53 g / cm 2 More than 300g / cm 2 Less than or equal to 130 g / cm 2 More than 160g / cm 2 Preferably, it is less than 0 rpm. The magnitude of the processing pressure significantly affects the processing speed of the SiC substrate, as will be described in detail later. The rotation speed of the upper surface plate 21 is, for example, 0 rpm to 40 rpm, and preferably 0 rpm to 9 rpm. The rotation speed of the lower surface plate 22 is, for example, 0 rpm to 70 rpm, and preferably 15 rpm to 20 rpm. The rotation speed of the central gear is, for example, 0 rpm to 35 rpm, and preferably 2 rpm to 20 rpm. The rotation speed of the internal gear is, for example, 0 rpm to 28 rpm, and preferably 0 rpm to 11 rpm. Here, a rotation speed of 0 rpm for the internal gear means that it is not rotating. In other words, the internal gear does not need to be rotated. The processing time is appropriately set depending on the degree of waviness and processing strain of the SiC substrate 1 before processing. When the waviness of the SiC substrate 1 before processing is 5 to 25 μm, the processing time is preferably 15 to 75 minutes. The supply rate of the slurry for lapping is selected arbitrarily depending on the number and size of the SiC substrates 1, but is, for example, 5 L / min to 30 L / min, preferably 12 L / min to 20 L / min. The slurry is used, for example, by circulating it. The supply rate and exhaust rate of the slurry are, for example, constant and the same.

[0035] Polishing pads for polishing the surface of the SiC substrate 1 may be attached to the lower surface of the upper surface plate 21 and the upper surface of the lower surface plate 22, respectively. While FIG. 1 illustrates an example in which the SiC substrate 1 is mounted on the carrier plate 24, the SiC substrate 1 may be directly mounted between the upper surface plate 21 and the lower surface plate 22 without the carrier plate 24. While the carrier plate 24 according to the above embodiment is configured to be capable of planetary motion, i.e., capable of rotation and revolution, this embodiment is not limited to a configuration including a carrier plate 24 capable of planetary motion. This embodiment is not limited to this example, and the processing step may be performed using a polishing apparatus according to a modification of FIG. 1 , as shown in FIG. 2. The polishing apparatus 100A illustrated in FIG. 2 includes a carrier plate 24A. The outer shape of the carrier plate 24A is similar to the shape of the lower surface plate 22 in a plan view, for example. The carrier plate 24A has a plurality of circular holes 24a formed therein, which are equally spaced about the support shaft 20, for example.

[0036] Next, the lapping slurry that can be used in this embodiment will be described in detail. In the loose abrasive processing step, a slurry S containing, for example, water, boron carbide abrasive grains, and an additive for dispersing the boron carbide abrasive grains is poured between the upper and lower plates 21 and 22, while pressure is applied to the SiC substrate 1 by the upper and lower plates 21 and 22, to flatten the surface of the SiC substrate 1. The slurry S used in the processing step is, for example, a slurry containing water as its main component. Using a slurry containing water as its main component improves the dispersibility of the boron carbide abrasive grains and reduces the occurrence of secondary aggregation during the processing step. Furthermore, when using a slurry containing water as its main component, the surface of the SiC substrate 1 facing the upper platen 21, which has the slurry supply holes 21b, is cleaned by directly supplying water, while the surface facing the lower platen 22, which does not have the slurry supply holes 21b, is cleaned by water supplied through the gap between the SiC substrate 1 and the carrier plate 24. The slurry used in the lapping process is collected in a tank (not shown) and supplied again from the tank.

[0037] The modified Mohs hardness (14) of boron carbide abrasive grains is slightly greater than the modified Mohs hardness (13) of a SiC substrate (a non-polished object), but less than the modified Mohs hardness (15) of diamond. Therefore, by using such a slurry, it is possible to relatively increase the processing speed while suppressing the occurrence of cracks in the SiC substrate, which has a modified Mohs hardness (13), and also to suppress a decrease in the particle size of the boron carbide abrasive grains.

[0038] The proportion of boron carbide abrasive grains in the slurry is, for example, 15% by mass or more and 45% by mass or less, preferably 20% by mass or more and 40% by mass or less, and more preferably 25% by mass or more and 35% by mass or less. By making the proportion of boron carbide abrasive grains in the slurry 15% by mass or more, the content of boron carbide abrasive grains in the slurry can be increased, thereby increasing the processing speed of the lapping process. Furthermore, by making the proportion of boron carbide abrasive grains in the slurry 45% by mass or less, the frequency and area of ​​contact between boron carbide abrasive grains can be reduced, making it easier to suppress the reduction in the particle size of the boron carbide abrasive grains and the wear of the boron carbide abrasive grains.

[0039] The boron carbide abrasive grains in the slurry used in the processing step have, for example, an average particle size of 15 μm to 40 μm, preferably 25 μm to 35 μm. Using boron carbide abrasive grains with an average particle size of 15 μm or more facilitates increased lapping speed of the surface of the SiC substrate 1 and allows sufficient adhesion of the additives described below to the surface, leading to improved dispersibility and reduced particle size reduction. Furthermore, setting the average particle size to 40 μm or less facilitates the suppression of cracking and breakage of the SiC substrate. Furthermore, excessive adhesion of the additives described below to the surface is suppressed, thereby preventing a decrease in processing speed due to a reduced contact area with the SiC substrate (the workpiece). Furthermore, using such boron carbide abrasive grains facilitates the suppression of changes in particle size before and after lapping. Here, the average particle size of the boron carbide abrasive grains is the average particle size of the boron carbide abrasive grains before processing, and the average particle size of the boron carbide abrasive grains after processing is, for example, 14 μm or more and 48 μm or less, and preferably 23 μm or more and 42 μm or less, since the ratio of the average particle sizes of the boron carbide abrasive grains before and after processing is 0.91 or more and 1.2 or less.

[0040] Here, the average particle size of the boron carbide abrasive grains is measured based on the particle size distribution measured by laser scattered light measurement using a particle size distribution measuring device, Mastersizer Hydro 2000MU (Spectris Co., Ltd.) or MT3000II (Microtrac Bell Co., Ltd.).

[0041] The additive may be a polyhydric alcohol, an ester and its salt, a homopolymer and its salt, a copolymer, etc. Specific examples include one or more selected from the group consisting of glycerin, 1-vinylimidazole, coconut oil fatty acid methyl taurate sodium, lauric acid amide ether sulfate sodium salt, myristate amide ether sulfate sodium salt, polyacrylic acid, and acrylic acid-maleic acid copolymer.

[0042] It is believed that these additives can improve the dispersibility of the boron carbide abrasive grains in the slurry.

[0043] The additive adheres to the surface of the boron carbide abrasive grains and prevents direct contact between the boron carbide abrasive grains, thereby improving the dispersibility of the boron carbide abrasive grains in the slurry and preventing particle size reduction of the abrasive grains during the processing step.

[0044] The proportion of additives in the slurry is, for example, 3% by volume or more and 20% by volume or less, preferably 5% by volume or more and 15% by volume or less, and more preferably 10% by volume or more and 15% by volume or less. Here, the proportion of additives in the slurry refers to the ratio obtained by dividing the volume of additives (additive components) such as glycerin by the volume of the slurry. When the additives in the slurry are within the above range, they adhere sufficiently to the surface of the boron carbide in the slurry, achieving a desirable degree of dispersion of the boron carbide abrasive grains in the slurry and making it easier to prevent the particle size of the boron carbide abrasive grains from decreasing during the processing step.

[0045] In the manufacturing method of a SiC substrate according to this embodiment, the processing speed for processing the surface of the SiC substrate in the processing step is, for example, 14 μm / h to 45 μm / h, preferably 16 μm / h to 40 μm / h, and more preferably 18 μm / h to 25 μm / h. The processing speed depends on the processing pressure and the average particle size of the boron carbide abrasive grains, as described above. Setting the processing speed to 45 μm / h or less is likely to suppress the reduction in particle size of the boron carbide abrasive grains and the wear of the boron carbide abrasive grains. Setting the processing speed to 14 μm / h or more increases throughput. When lapping is performed in multiple steps, the processing speed calculated by dividing the total change in thickness of the SiC substrate by the total processing time should be within the above range, and it is preferable that the processing speed at each timing be within the above range. In other words, when lapping is performed in multiple steps, it is preferable that the processing speed calculated for each step be within the above range.

[0046] Here, the processing speed is calculated from the difference in thickness of the SiC substrate 1 before and after lapping and the processing time. Specifically, the processing speed is calculated as follows. FIG. 3 is an illustration for explaining a method for measuring the thickness of the SiC substrate 1. The measurement positions for the thickness of the SiC substrate 1 are: position 1c, which corresponds to the center of the SiC substrate 1 before the orientation flat OF is formed on the SiC substrate 1; position 1a, which is 5 to 10 mm away from the midpoint of the orientation flat OF toward position 1c; position 1b, which is on the same line c as positions 1a and 1c and 5 to 10 mm away from the outer periphery of the SiC substrate 1 toward position 1a; and positions 1d and 1e, which are on a line perpendicular to line c and 5 to 10 mm away from the outer periphery of the SiC substrate 1 toward position 1a. The thicknesses of the SiC substrate 1 at these five positions 1a to 1e are measured using an indicator (ID-C150XB, manufactured by Mitutoyo), and the obtained thicknesses are treated as the thickness of the SiC substrate 1. The processing speed is calculated by dividing the difference in thickness (μm) of the SiC substrate 1 before and after processing thus obtained by the processing time (h).

[0047] According to the method for manufacturing a SiC substrate of this embodiment, an additive is attached to the surface of the boron carbide abrasive grains in the slurry used in the processing step, thereby improving the dispersibility of the boron carbide abrasive grains and suppressing contact between the boron carbide abrasive grains, thereby suppressing a decrease in the particle size of the boron carbide abrasive grains. Specifically, the change in particle size of the boron carbide abrasive grains can be suppressed to the extent that the ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing is 0.91 or more and 1.2 or less. Here, the reason why this ratio includes a value greater than 1 is that secondary aggregation of the boron carbide abrasive grains may occur during the processing step, causing the particle size of some of the boron carbide abrasive grains to become larger than before processing.

[0048] In conventional methods, the particle size of the boron carbide abrasive grains in the slurry is significantly reduced by the lapping process, so when lapping is performed again, it is necessary to add abrasive grains to the slurry each time, and each time, it is necessary to perform complicated management such as determining the particle size distribution of the abrasive grains in the slurry, which depends on the number of times the slurry has been used for lapping. As described above, in the manufacturing method of a SiC substrate according to this embodiment, it is possible to suppress changes in the boron carbide abrasive grains, so it is possible to perform lapping repeatedly using the same slurry. In this way, the method for manufacturing a SiC substrate according to this embodiment makes it easier to control the particle size of the boron carbide abrasive grains, reduces costs, reduces the environmental load, and suppresses the occurrence of cracks.

[0049] Furthermore, in the method for manufacturing a SiC substrate according to this embodiment, the particle size of the boron carbide abrasive grains does not change much, so changes in the processing speed during lapping are suppressed, and lapping can be continued under the same conditions. The method for manufacturing a SiC substrate according to this embodiment is particularly effective when using boron carbide as abrasive grains, which has a slightly higher modified Mohs hardness than silicon carbide as the non-polished object. Because the method for manufacturing a SiC substrate according to this embodiment uses such abrasive grains and substrate, it is also possible to suppress cracks that frequently occur when diamond is used as abrasive grains and a SiC substrate is used as the polished object.

[0050] Furthermore, in the method for manufacturing a SiC substrate according to this embodiment, reduction in the particle size of the boron carbide abrasive grains and wear can be suppressed, thereby reducing the variation in particle size of the boron carbide abrasive grains in the slurry during lapping. While the processing speed of lapping depends on the particle size of the abrasive grains used, in the method for manufacturing a SiC substrate according to this embodiment, variation in particle size of the abrasive grains can be suppressed, so the entire surface of the SiC substrate is processed with abrasive grains of roughly uniform particle size, reducing the in-plane variation of the processed SiC substrate.

[0051] In the above embodiment, an example in which both sides of a SiC substrate are lapped using the polishing apparatus 100, 100A shown in FIGS. 1 and 2 has been described. However, this embodiment may use other polishing apparatuses, or may lap only one side of a SiC substrate.

[0052] The method for manufacturing a SiC substrate according to this embodiment may include, before the processing step, a step of forming a SiC ingot, a step of slicing the SiC ingot, etc., and may include, after the processing step, a step of chamfering, a step of removing a processing-affected layer, etc. [Example]

[0053] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0054] [Example 1] First, 15 6-inch SiC substrates were prepared as processing targets. Next, for each of the 15 SiC substrates, the thickness of the SiC substrate was measured at five positions as shown in Figure 3. The measurement positions were: position 1c corresponding to the center of the SiC substrate; position 1a, 5 to 10 mm away from the midpoint of the orientation flat OF toward position 1c; position 1b, which was on the same line c as positions 1a and 1c and 5 to 10 mm away from the outer periphery of SiC substrate 1 in the direction toward position 1a; and positions 1d and 1e, which were on a line perpendicular to line c, were on the same line as position 1c, and 5 to 10 mm away from the outer periphery of SiC substrate 1 in the direction toward position 1c. The thickness of the SiC substrate 1 at these five positions 1a to 1e was measured using an indicator (ID-C150XB, manufactured by Mitutoyo), and the average was used as the thickness of the SiC substrate.

[0055] Next, a lapping slurry was prepared. The lapping slurry was obtained by adding a predetermined amount of boron carbide abrasive grains and AD8 (10% by volume) as an additive to water and dispersing them. The boron carbide abrasive grains used had a grain size of F320 (JIS R6001). Here, the proportion of glycerin (manufactured by Aichi Techno Co., Ltd.) as an additive in the slurry was 6% by volume.

[0056] The resulting slurry contained water, boron carbide abrasive grains, and additives, with water being the primary component. The particle size distribution of the boron carbide abrasive grains and the average particle size of the boron carbide abrasive grains were measured for this slurry. The particle size distribution of the boron carbide abrasive grains in the slurry was measured by laser scattering using a particle size distribution analyzer MT3000II (Microtrac-Bell Corporation). The particle size of the boron carbide abrasive grains in at least 5 mL of slurry was measured using the particle size distribution analyzer, and the cumulative particle size of the smallest 50% of the particle size distribution on a volume basis was used as the average particle size. The particle size distribution measurement results indicated that the average particle size of the boron carbide abrasive grains in the slurry was 38.0 μm.

[0057] Next, the 15 SiC substrates whose thicknesses had been measured were placed on a carrier plate of a polishing device as shown in FIG. 2 and subjected to lapping.

[0058] The lapping was carried out using a loose abrasive method, supplying a lapping slurry at a rate of 16 L / min. The lapping slurry was circulated and used.

[0059] The driving conditions of the polishing device in the lapping process are a processing pressure of 160 g / cm 2 The rotation speed of the lower surface plate was 16 rpm, the rotation speed of the upper surface plate was 5.5 rpm, the rotation speed of the central gear was 2.8 rpm, the rotation speed of the internal gear was 6.0 rpm, and the processing time was 40 minutes.

[0060] After lapping, the particle size distribution of the boron carbide abrasive grains in the slurry was measured for each of the 15 SiC substrates in the same manner as before lapping, and the thickness of the substrates was also measured in the same manner as before lapping, and the processing speed was also calculated. In this lapping process, the average processing speed for the 15 SiC substrates was 18 μm / h.

[0061] After the measurement, the slurry used in the previous lapping process was supplied and a second lapping process and measurement were performed while circulating the slurry. In Example 1, this process was repeated for a total of eight lapping processes and measurements.

[0062] [Comparative Example 1] As Comparative Example 1, lapping and measurement were carried out in the same manner as in Example 1, except that additive AD8 was not dispersed in the lapping slurry.

[0063] Figure 4 shows the particle size distribution of the abrasive grains after lapping in Example 1 and Comparative Example 1. In Figure 4, the horizontal axis represents the particle size (μm) of the boron carbide abrasive grains, and the vertical axis represents the SS concentration (suspended solids concentration) (g / L).

[0064] 4, in Example 1, the particle size of many of the boron carbide abrasive grains remained unchanged, whereas in Comparative Example 1, the particle size of most of the boron carbide abrasive grains decreased, and the degree of particle size reduction varied depending on the abrasive grain. Therefore, the particle size distribution in Comparative Example 1 is broader than that of Example 1.

[0065] In Example 1 and Comparative Example 1, the average particle size of the boron carbide abrasive grains before lapping was 38 μm. Similarly, the average particle size of the boron carbide abrasive grains after lapping in Example 1 was 34.8 μm. Similarly, the average particle size of the boron carbide abrasive grains after lapping in Comparative Example 1 was 10 μm. In Example 1, the ratio of the average particle size of the boron carbide abrasive grains after lapping to the average particle size of the boron carbide abrasive grains before lapping was approximately 0.92, a number within the range of 0.91 to 1.2. In Comparative Example 1, the ratio of the average particle size of the boron carbide abrasive grains after lapping to the average particle size of the boron carbide abrasive grains before lapping was 0.26, a number outside the range of 0.91 to 1.2. Measurement of the particle size distribution of the boron carbide abrasive grains before and after lapping confirmed that the particle size of the boron carbide abrasive grains in Example 1 was almost unchanged by the lapping.

[0066] Figure 5 shows a graph summarizing the results of the processing speed versus processing time in Example 1. The eight points in the graph in Figure 5 are the points at which the processing speed was calculated, and these points represent the processing speeds for lapping times of 0 to 40 minutes, 40 to 80 minutes, 80 to 120 minutes, 120 to 160 minutes, 160 to 200 minutes, 200 to 240 minutes, 240 to 280 minutes, and 280 to 320 minutes, respectively. Figure 5 confirms that the processing speed at all timings at which the processing speed was calculated was 15 μm / h or more and 45 μm / h or less, and that the processing speed in all lapping processes except the fifth lapping process was 15 μm / h or more and 30 μm / h or less.

[0067] As described above, in Example 1, since the processing conditions for the first to eighth lapping processes were constant and there was no significant change in the average particle size of the boron carbide abrasive grains before the first lapping process and after the eighth lapping process, it is inferred that there was no significant change in the particle size of the boron carbide abrasive grains throughout the entire process from the first lapping process to the eighth lapping process.

[0068] Figure 6 shows the lapping processing speeds for Comparative Example 1 and Example 1. The processing speeds shown in Figure 6 are the average processing speeds for 15 SiC substrates that were simultaneously lapped. Figure 6 confirms that Example 1, which used a slurry containing additive AD8, had an improved lapping processing speed compared to Comparative Example 1, which did not use additive AD8. This is presumably because the use of a slurry containing additive AD8 and boron carbide abrasive grains allowed the additive to adhere to the surface of the boron carbide abrasive grains, improving dispersibility while simultaneously preventing direct contact between the boron carbide abrasive grains and the workpiece, thereby preventing a decrease in the particle size of the boron carbide abrasive grains and wear of the abrasive grains.

[0069] FIG. 7 shows the in-plane variation in substrate thickness of 15 SiC substrates simultaneously lapped in Example 1 and Comparative Example 1. In FIG. 7, the horizontal axis represents the processing number of the SiC substrate, and the vertical axis represents the in-plane variation in substrate thickness. Here, the in-plane variation in substrate thickness is the difference between the maximum and minimum values ​​at the five measurement points 1a to 1e shown in FIG. 3. It was confirmed that the in-plane variation in substrate thickness was smaller in Example 1 than in Comparative Example 1. This is presumably because the addition of additive AD8 improved the dispersibility of the boron carbide abrasive grains and suppressed the reduction in the grain size of the boron carbide abrasive grains, thereby suppressing localized excessive polishing.

[0070] Figure 8 shows the particle size distribution of the boron carbide abrasive grains used in Comparative Example 1 after machining. Figure 8 shows that in Comparative Example 1, because a slurry containing no additive AD8 was used, the surfaces of the boron carbide abrasive grains were exposed, the abrasive grains could not be protected, and grains with a particle size of less than 1 μm were observed, resulting in a reduction in the particle size of the abrasive grains and wear of the abrasive grains. In Comparative Example 1, it was confirmed that the particle size distribution of the abrasive grains became broad due to the reduction in particle size of the abrasive grains and wear of the abrasive grains.

[0071] [Manufacturing Example 1] The lapping of the SiC substrate and measurements of the SiC substrate and the slurry were carried out in the same manner as in Example 1, except that the proportion of boron carbide abrasive grains in the slurry was changed to 25 mass %.

[0072] [Manufacturing Example 2] The lapping of the SiC substrate and measurements of the SiC substrate and the slurry were carried out in the same manner as in Example 1, except that the proportion of boron carbide abrasive grains in the slurry was changed to 30 mass %.

[0073] [Manufacturing Example 3] The lapping of the SiC substrate and measurements of the SiC substrate and the slurry were carried out in the same manner as in Example 1, except that the proportion of boron carbide abrasive grains in the slurry was changed to 35 mass %.

[0074] [Manufacturing Example 4] The lapping process of the SiC substrate and measurements of the SiC substrate and slurry were carried out in the same manner as in Example 1, except that the average particle size of the boron carbide abrasive grains contained in the slurry was changed to 16.1 μm and the proportion of the boron carbide abrasive grains was changed to 25 mass %.

[0075] [Manufacturing Example 5] The lapping process of the SiC substrate and measurements of the SiC substrate and slurry were carried out in the same manner as in Example 1, except that the average particle size of the boron carbide abrasive grains contained in the slurry was changed to 16.1 μm and the proportion of the boron carbide abrasive grains was changed to 30 mass %.

[0076] [Manufacturing Example 6] The lapping process of the SiC substrate and measurements of the SiC substrate and slurry were carried out in the same manner as in Example 1, except that the average particle size of the boron carbide abrasive grains contained in the slurry was changed to 16.1 μm and the proportion of the boron carbide abrasive grains was changed to 35 mass %.

[0077] [Example 2] Except for changing the average particle size of the boron carbide abrasive grains contained in the slurry to 26.6 μm and changing the additive contained in the slurry to Polity (registered trademark) A-550 (Lion Corporation), lapping of SiC substrates and measurements of the SiC substrates and slurry were carried out in the same manner as in Example 1. Polity (registered trademark) A-550 (Lion Corporation) contains a polyacrylic polymer as an additive component.

[0078] The average particle size of the boron carbide abrasive grains after lapping was not measured in Production Examples 1 to 6. However, the processing speed for lapping the SiC substrate was generally the same as in Example 1, and although not shown in the figures, there was little change in the processing speed in the lapping of the SiC substrate at each stage of 40-minute lapping. Therefore, in these Production Examples as well, it is estimated that the ratio of the average particle size of the boron carbide abrasive grains after lapping to the average particle size of the boron carbide abrasive grains before lapping was 0.91 or more and 1.2 or less.

[0079] The boron carbide abrasive grains and additives contained in the slurries used in Example 1 and Production Examples 1 to 7, and the processing speeds for the entire lapping process are summarized in Table 1. The processing speeds in Table 1 are the average processing speeds for 15 SiC substrates that were simultaneously subjected to lapping.

[0080] [Table 1] (※1: Not measured, ※2: Unknown due to confidentiality)

[0081] Fig. 9 is a graph summarizing the processing numbers and lapping speeds of the 15 SiC substrates used in each of Production Examples 1 to 3 and Example 1. Fig. 9 confirms that in each Example (Production Example), there was no variation in the processing speed for the SiC substrates with processing numbers 1 to 15 that were simultaneously subjected to lapping, and that the lapping could be performed stably.

[0082] Figure 10 shows the particle size distribution of the boron carbide abrasive grains used in Examples 1 and 2 before and after processing. In Example 1, the average particle size of the boron carbide abrasive grains before and after processing was 38 μm and 34.8 μm, respectively, as described above. The ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing was 0.916. Meanwhile, the average particle size of the boron carbide abrasive grains used in Example 2 before and after processing was measured using the same method as in Example 1. The average particle size before processing was 26.6 μm, and the average particle size after processing was 31.5 μm. That is, the ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing was 1.18. Thus, it was confirmed that the particle size of the boron carbide abrasive grains did not change significantly due to the lapping process in Examples 1 and 2.

[0083] [Manufacturing Example 7] The lapping and measurements were performed in the same manner as in Example 1, except that the number of SiC substrates to be simultaneously lapped was changed to 10, boron carbide with a grain size of F500 was used as the abrasive grains, and the proportion of boron carbide abrasive grains in the slurry was changed to 15 mass%.

[0084] [Manufacturing Example 8] The lapping and measurements were performed in the same manner as in Example 1, except that the number of SiC substrates to be simultaneously lapped was changed to 10, boron carbide with a grain size of F500 was used as the abrasive grains, and the proportion of boron carbide abrasive grains in the slurry was changed to 20 mass%.

[0085] [Manufacturing Example 9] The lapping and measurements were performed in the same manner as in Example 1, except that the number of SiC substrates lapping simultaneously was changed to 10, boron carbide with a grain size of F500 was used as the abrasive grains, and the proportion of boron carbide abrasive grains in the slurry was changed to 25 mass%.

[0086] [Manufacturing Example 10] The lapping and measurements were performed in the same manner as in Example 1, except that the number of SiC substrates to be simultaneously lapped was changed to 10, boron carbide with a grain size of F500 was used as the abrasive grains, and the proportion of boron carbide abrasive grains in the slurry was changed to 30 mass%.

[0087] [Manufacturing Example 11] The lapping and measurements were performed in the same manner as in Example 1, except that the number of SiC substrates to be simultaneously lapped was changed to 10, boron carbide with a grain size of F500 was used as the abrasive grains, and the proportion of boron carbide abrasive grains in the slurry was changed to 35 mass%.

[0088] The average particle size (volume average particle size) of the boron carbide abrasive grains of Production Examples 7 to 11 before lapping was determined in the same manner as in Example 1, and was found to be 16.1 μm.

[0089] Fig. 11 is a graph summarizing the processing numbers and lapping speeds of the 10 SiC substrates used in each of Production Examples 7 and 8. Fig. 11 confirms that in each Example (Production Example), there was no variation in the processing speed for the SiC substrates with processing numbers 1 to 10 that were simultaneously subjected to lapping, and that the lapping could be performed stably.

[0090] Fig. 12 is a graph summarizing the processing numbers and lapping speeds of the 10 SiC substrates used in each of Production Examples 9 to 11. Fig. 12 confirms that in each Example (Production Example), there was no variation in the processing speed for the SiC substrates with processing numbers 1 to 10 that were simultaneously subjected to lapping, and that the lapping could be performed stably.

[0091] In Production Examples 7 to 11, the processing speed of the 10 SiC substrates using the boron carbide abrasive grains for lapping was in the range of 15 μm / h to 30 μm / h inclusive. In addition, in Production Examples 7 to 11, the average processing speed of the 10 SiC substrates was in the range of 18 μm / h to 27 μm / h inclusive.

[0092] The average particle size of the boron carbide abrasive grains after lapping was not measured in Production Examples 7 to 11. However, the processing speed for lapping the SiC substrate was generally the same as in Example 1, and although not shown in the figures, there was little change in the processing speed in the lapping of the SiC substrate at each stage of 40-minute lapping. Therefore, in these Production Examples as well, it is estimated that the ratio of the average particle size of the boron carbide abrasive grains after lapping to the average particle size of the boron carbide abrasive grains before lapping was 0.91 or more and 1.2 or less.

[0093] [Manufacturing Example 12] A slurry containing water as the main component, boron carbide abrasive grains, and additive AD8 was prepared. The proportion of boron carbide abrasive grains in the slurry was 40% by mass, and the proportion of glycerin as an additive was 3% by volume. The slurry was dispersed by stirring and shaking, and then placed in a measuring cylinder.

[0094] [Manufacturing Example 13] The slurry was dispersed in the same manner as in Production Example 12, except that the proportion of glycerin as an additive in the slurry was changed to 5% by mass, and then placed in a measuring cylinder.

[0095] [Manufacturing Example 14] The slurry was dispersed in the same manner as in Production Example 12, except that the proportion of glycerin as an additive in the slurry was changed to 10% by mass, and then placed in a measuring cylinder.

[0096] [Manufacturing Example 15] The slurry was dispersed in the same manner as in Production Example 12, except that the proportion of glycerin as an additive in the slurry was changed to 15% by mass, and then placed in a measuring cylinder.

[0097] [Manufacturing Example 16] The additive to be contained in the slurry is lauric acid amide ether sulfate sodium salt (R=C 12 ) and myristate amide ether sulfate sodium salt (R=C 14 ) and its mixture (C 12 :C 14 The mixture was dispersed in the same manner as in Production Example 12, except that the water-diluted solution (water ratio = 7:3) was changed to Sanamide (registered trademark) CF-10 (NOF Corporation) and the proportion of the additive was changed to 10 mass %, and the mixture was placed in a measuring cylinder.

[0098] [Manufacturing Example 17] The additive (dispersant) contained in the slurry was changed to SET-002 (Sanyo Chemical Industries, Ltd.), and the proportion of the additive was changed to 10% by mass. Except for this, the slurry was dispersed in the same manner as in Production Example 12 and placed in a measuring cylinder.

[0099] [Manufacturing Example 18] The slurry was dispersed in the same manner as in Production Example 12, except that the additive contained in the slurry was changed to 1-vinylimidazole and the proportion of the additive was changed to 10% by mass, and then placed in a measuring cylinder.

[0100] [Manufacturing Example 19] The additive contained in the slurry was changed to Diapon (registered trademark) K-SF (NOF Corporation), a base mainly composed of coconut oil fatty acid methyl taurate sodium, and the slurry was dispersed in the same manner as in Production Example 12, except that the proportion of the additive was changed to 10 mass %. The slurry was then placed in a measuring cylinder.

[0101] Comparative Example 2 The slurry was dispersed in the same manner as in Production Example 12, except that no additives were added, and placed in a measuring cylinder.

[0102] Each slurries from Production Examples 12 to 19 and Comparative Example 2 was placed in a 20 mL measuring cylinder, dispersed by stirring and shaking, and allowed to stand for 5 minutes. For each slurry, the mL scale position of the top of the precipitate closest to the opening was checked every minute, and the mL scale position was divided by 20 mL and multiplied by 100 to measure the degree of dispersion (%). For example, if the top of the precipitate was located at the 18 mL scale after 1 minute, the degree of dispersion was calculated as 18 / 20 × 100 = 90%. Figure 13 shows the change in the degree of dispersion of boron carbide abrasive grains in the slurries from Production Examples 12 to 19 and Comparative Example 2. Figure 13 confirms that slurries containing 3% to 15% by volume of an additive selected from the group consisting of glycerin, fatty acid amide ether sulfate ester sodium salt, 1-vinylimidazole, and sodium cocoyl methyl taurate exhibited higher dispersibility even after a long period of time compared to slurries without any additives. The settling rate of the boron carbide abrasive grains in the slurries of Production Examples 12 to 19 calculated from the data in Figure 13 was approximately 10 to 15%, and the settling rate of the boron carbide abrasive grains in the slurry of Comparative Example 2 was approximately 33%. [Explanation of symbols]

[0103] 1: SiC substrate, 20: support shaft, 21: upper surface plate, 21b: slurry supply hole, 22: lower surface plate, 23: slurry tube, 24, 24A: carrier plate, 24a: circular hole, 100, 100A: polishing device

Claims

1. The method includes a processing step of lapping one or both surfaces of a SiC substrate by using a slurry containing boron carbide abrasive grains and an additive for dispersing the boron carbide abrasive grains, by a method using a polishing machine having an upper surface plate and a lower surface plate, The processing step is a step of processing the boron carbide abrasive grains so that the ratio of the average particle size of the boron carbide abrasive grains after processing to the average particle size of the boron carbide abrasive grains before processing is 0.91 or more and 1.2 or less, The slurry used in the processing step contains 15% by mass or more and 45% by mass or less of the boron carbide abrasive grains, 3% by volume or more and 20% by volume or less of the additive, and water, The average particle size of the boron carbide abrasive grains before processing is 15 μm or more and 40 μm or less, The rotation speed of the upper platen in the processing step is 0 rpm or more and 40 rpm or less, and the rotation speed of the lower platen is 0 rpm or more and 70 rpm or less, a processing pressure of the SiC substrate in the processing step is 53 g / cm 2 or more and 300 g / cm 2 or less; In the processing step, the slurry is circulated at a supply rate of 5 L / min or more and 30 L / min or less, The method for manufacturing a SiC substrate, wherein the processing step lasts for 15 minutes or more and 75 minutes or less.

2. A method for manufacturing a SiC substrate as described in claim 1, wherein the average particle size of the boron carbide abrasive grains after processing is 14 μm or more and 48 μm or less.

3. The method for manufacturing a SiC substrate according to claim 1 or 2, wherein the surface of the SiC substrate is polished at a processing speed of 14 μm / h or more and 45 μm / h or less.

4. 4. The method for manufacturing a SiC substrate according to claim 1, wherein the processing step uses the slurry containing water as a main component.

5. 5. The method for manufacturing a SiC substrate according to claim 1, wherein, in the processing step, one or more additives selected from the group consisting of glycerin, 1-vinylimidazole, coconut oil fatty acid methyl taurate sodium, lauric acid amide ether sulfate sodium salt, myristate amide ether sulfate sodium salt, polyacrylic acid, and an acrylic acid-maleic acid copolymer are used.

6. The grinding device further comprises a central gear and an internal gear; 6. The method for manufacturing a SiC substrate according to claim 5, wherein a rotation speed of the central gear in the processing step is 0 rpm or more and 35 rpm or less, and a rotation speed of the internal gear is 0 rpm or more and 28 rpm or less.

7. A slurry used when processing a surface of a SiC substrate, The boron carbide abrasive grains have an average particle size of 15 μm or more and 38 μm or less, and an additive for dispersing the boron carbide abrasive grains, The proportion of the additive in the slurry is 10% by volume or more and 15% by volume or less, When a processing step is performed under the following processing conditions, a ratio of an average particle size of the boron carbide abrasive grains after processing to an average particle size of the boron carbide abrasive grains before processing a surface of a SiC substrate is 0.91 or more and 1.2 or less, The processing conditions for the processing step were as follows: for a 6-inch SiC substrate, a polishing machine equipped with an upper surface plate, a lower surface plate, a central gear, and an internal gear was used, and the polishing machine was operated with a processing pressure of 160 g / cm using a free abrasive method while supplying slurry at a rate of 16 L / min. ２ The conditions are as follows: lower surface plate rotation speed 16 rpm, upper surface plate rotation speed 5.5 rpm, central gear rotation speed 2.8 rpm, internal gear rotation speed 6.0 rpm, processing time 40 minutes, average processing speed 14 μm / h or more and 18 μm / h or less, and the slurry is circulated to perform eight lapping processes; The abrasive includes 15% by mass or more and 45% by mass or less of boron carbide abrasive grains, and 10% by volume or more and 15% by volume or less of an additive, The average particle size of the boron carbide abrasive grains before processing is 15 μm or more and 38 μm or less.

8. The lapping slurry according to claim 7, further comprising water as a main component.

9. 9. The slurry for lapping according to claim 7, wherein the additive comprises one or more selected from the group consisting of glycerin, 1-vinylimidazole, coconut oil fatty acid methyl taurate sodium, lauric acid amide ether sulfate sodium salt, myristate acid amide ether sulfate sodium salt, polyacrylic acid, and acrylic acid-maleic acid copolymer.

10. The lapping slurry according to claim 9 , wherein the additive comprises glycerin or a polyacrylic polymer.

11. The average particle size of the boron carbide abrasive grains is 25 μm or more and 38 μm or less, The lapping slurry according to any one of claims 7 to 10, wherein the ratio of the boron carbide abrasive grains is 25% by mass or more and 35% by mass or less.

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