JP7589508B2 - Method for manufacturing plate-shaped body - Google Patents

Description

The present invention relates to a method for manufacturing a plate-shaped body, which includes a lapping process in which a difficult-to-cut plate-shaped body is processed to a desired thickness, and a surface grinding process in which the surface of the plate-shaped body after the lapping process is ground to a high degree of flatness and smoothness, and in particular, to a method for manufacturing a plate-shaped body that can reduce wear on the grinding wheel used in the surface grinding process.

Compared to silicon (Si), silicon carbide (SiC) has a band gap three times larger (4H-SiC: 3.8 eV, 6H-SiC: 3.1 eV, silicon: 1.1 eV) and a high thermal conductivity (5 W/cm K, silicon: 1.5 W/cm K). In recent years, SiC single crystals have begun to be used as a substrate material for power devices. For example, compared to conventional Si power devices, SiC power devices have a withstand voltage 5 to 10 times larger and an operating temperature several hundred degrees higher. Furthermore, they can reduce the power loss of the element to about one-tenth, so they have been put to practical use in inverters for railway vehicles, etc.

SiC single crystals used as substrate materials are usually produced by a gas phase method called sublimation recrystallization (modified Lely process) (see, for example, Non-Patent Document 1), and are processed to the desired diameter and thickness.

The modified Lely process is a method for growing bulk SiC single crystals by heating and subliming solid SiC raw material (usually powder) at high temperatures (2,400°C or higher), and transporting the sublimated Si and carbon atoms as vapor at 2,400°C through an inert gas atmosphere by diffusion, where they become supersaturated and recrystallize on a seed crystal placed at a lower temperature than the raw material.

However, because the process temperature in the modified Lely process is extremely high at over 2,400°C, it is extremely difficult to control the temperature and convection during crystal growth, and to control crystal defects. SiC single crystal substrates produced by this method contain numerous crystal defects called micropipes and other crystal defects (stacking faults, etc.), making it extremely difficult to manufacture high-quality SiC single crystal substrates that can withstand electronic device use with a high yield. As a result, high-quality SiC single crystal substrates with few crystal defects that can be used for electronic devices are very expensive, and devices using such SiC single crystal substrates are also expensive, which has hindered the widespread use of SiC single crystal substrates.

In response to this, in recent years, a method has been proposed in which a SiC substrate is manufactured by preparing a SiC single crystal substrate and a SiC polycrystalline substrate, bonding the SiC single crystal substrate and the SiC polycrystalline substrate together, and then thinning the SiC single crystal substrate to produce a SiC substrate in which a thin SiC single crystal layer is formed on the SiC polycrystalline substrate (see, for example, Non-Patent Document 2).

This method for manufacturing SiC substrates allows the thickness of SiC single crystal substrates to be reduced by several times to several hundred times compared to conventional methods. This allows the cost of SiC substrates to be significantly reduced compared to conventional methods in which the entire substrate is made of expensive, high-quality SiC single crystals. In addition, because elements such as power devices can be formed on a high-quality SiC single crystal layer with few crystal defects, device performance and manufacturing yields can be significantly improved.

In the process of bonding such a SiC single crystal substrate and a SiC polycrystalline substrate, the SiC polycrystalline substrate is required to be dense and highly pure, as well as highly flat. For this reason, chemical vapor deposition (hereinafter sometimes referred to as "CVD") is used to manufacture the SiC polycrystalline substrate, and a method for manufacturing a SiC polycrystalline substrate using the CVD method is described in Patent Document 1. The method for manufacturing a SiC polycrystalline substrate described in Patent Document 1 will be described below.

First, a growth furnace in which a carbonaceous support substrate (e.g., a graphite support substrate) 1 shown in Fig. 3(A) is placed is set to an environment of 1300°C or higher, and Si-based raw material gas such as _SiH4 , C-based raw material gas such as _CH4 , nitrogen gas as an impurity gas, and hydrogen gas as a carrier gas are introduced into the furnace, and a SiC polycrystalline film 2 shown in Fig. 3(B) is deposited by thermal reaction on the front and back surfaces and the outer peripheral end surface of the carbonaceous support substrate 1. Then, the carbonaceous support substrate 1 on which the SiC polycrystalline film 2 has been deposited is taken out of the growth furnace, and the carbonaceous support substrate 1 is beveled to expose the end surface of the carbonaceous support substrate 1 as shown in Fig. 3(C), and then only the carbonaceous support substrate 1 is burned using an electric furnace or the like, and two SiC polycrystalline substrates 3 made of the SiC polycrystalline film 2 formed on the front and back surfaces of the carbonaceous support substrate 1 as shown in Fig. 3(D) are obtained.

However, in this manufacturing method using the CVD method, the thickness of the formed SiC polycrystalline film 2 tends to be large near the outer edge (outer peripheral portion) of the carbonaceous support substrate 1 as shown in Figure 3 (B), and therefore the peripheral portion of the obtained SiC polycrystalline substrate 3 tends to be thicker than the central portion as shown in Figure 3 (D). Therefore, after burning and removing the carbonaceous support substrate 1, the following process was required to adjust the thickness and flatness of the SiC polycrystalline substrate 3 by grinding and polishing.

In other words, as shown in Figures 4(A)-(B), a cutting process is performed to cut out the peripheral portion of the SiC polycrystalline substrate 3, as shown in Figure 4(C) a lapping process is performed to process the SiC polycrystalline substrate 3 to approximately the desired thickness, as shown in Figure 4(C) a beveling process is performed to process the SiC polycrystalline substrate 3 to the desired diameter and then chamfer the end faces of the SiC polycrystalline substrate 3, a surface grinding process is performed to surface grind the surface of the SiC polycrystalline substrate 3 obtained in the lapping process to process it into a highly flat and smooth surface as shown in Figure 4(D), and a polishing process is performed to remove linear processing marks (not shown) generated in the surface grinding process by chemical mechanical polishing (mechanochemical polishing) and to make the surface of the SiC polycrystalline substrate 3 into a mirror surface as shown in Figure 4(E). Through these processes, the SiC polycrystalline substrate to be used in the manufacture of SiC substrates will be in the desired state.

Japanese Patent Application Publication No. 08-026714 JP 2018-051646 A

Yu. M. Tairov and V. F. Tsvetkov: J. of Cryst. Growth 43 (1978) 209 Journal of the Japan Society for Precision Engineering, 2017, Vol. 83, No. 9, pp. 833-836

Although silicon carbide (SiC) is a material that is extremely hard and difficult to cut, it is possible to reduce the processing time and cost of SiC polycrystalline substrates by low-pressure double-sided lapping using boron carbide ( _B4C ) abrasive grains with a grit size of approximately 100 (ISO 8486 designation) to 300 (ISO 8486 designation), for example, 280 (ISO 8486 designation). However, on the other hand, since steep irregularities are formed on the surface of the SiC polycrystalline substrate after the lapping process, when the SiC polycrystalline substrate is subjected to surface grinding using a vitrified grinding wheel containing diamond abrasive grains with a grit size of about 6000 (ISO 8486 designation) to 8000 (ISO 8486 designation), for example, 7000 (ISO 8486 designation), there is a problem that the wear rate of the grinding wheel [(wear amount of grinding wheel/machined amount of workpiece)×100%] becomes high after the beveling process. Specifically, when one surface of a SiC polycrystalline substrate is surface ground by 10 μm in a first surface grinding step, and the other surface of the SiC polycrystalline substrate is surface ground by 20 μm in a second surface grinding step, the wear rate of the grinding wheel is high, at 700% to 350%, and at 200% to 250%, in the first step, which poses a major problem because vitrified grinding wheels containing diamond abrasive grains are expensive.

The present invention was made with a focus on these problems, and its objective is to provide a method for manufacturing a plate-shaped body that has a lapping process and a surface grinding process, and that can reduce the wear rate of the vitrified grinding wheel (a grinding wheel containing diamond abrasive grains and a vitrified binder) used in the surface grinding process.

In order to solve the above problems, the inventors conducted repeated experiments while changing the processing conditions of the grinding device (see, for example, Patent Document 2) used in the surface grinding process, specifically, the "rotation speed of the spindle" to which the vitrified grinding wheel is attached, the "rotation speed of the chuck table" that holds the plate-shaped body, and the "processing feed speed" that moves the grinding wheel and the plate-shaped body relatively in the processing feed direction. As a result, they found the appropriate conditions that reduce the wear rate of the grinding wheel.

That is, the appropriate conditions for surface grinding the lapped surface (hereinafter sometimes referred to as the "#280 surface") of a plate-shaped body after the lapping process using #280 (ISO 8486) boron carbide ( _B4C ) abrasive grains, by a grinding device using a vitrified grinding wheel containing #7000 (ISO 8486) diamond abrasive grains, are as follows:
a) The "spindle rotation speed" is set to 1800 rpm,
b) The "chuck table rotation speed" is set to +151 to -251 rpm.
c) The "processing feed rate" is 0.05 μm/s,
It was found that, when the "#280 surface" was surface ground under the above conditions, the wear rate of the vitrified grinding wheel could be reduced.

Note that if the rotation direction of the chuck table is the same as the rotation direction of the spindle, a "+" is indicated, and if it is opposite to the rotation direction of the spindle, a "-" is indicated.

The steep unevenness formed after the lapping process is flattened by grinding the "#280 surface" a few μm with a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation). Since the wear rate of the grinding wheel after grinding 3 to 10 μm is almost constant, when further surface grinding the ground surface of the plate-shaped body flattened with a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation) (hereinafter sometimes referred to as the "#7000 surface"), the wear rate of the grinding wheel can be reduced by changing the grinding conditions from the "#280 surface" conditions to those suitable for the "#7000 surface".

The appropriate conditions for surface grinding the "#7000 surface" using a grinding device that uses a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation) are as follows:
a) The "spindle rotation speed" is 3500 rpm,
b) The "chuck table rotation speed" is set to +51 to -251 rpm.
c) The "processing feed rate" is 0.1 μm/s,
It was found that, when the "#7000 surface" was surface ground under the above conditions, the wear rate of the vitrified grinding wheel could be further reduced.

The present invention was made possible through these technical discoveries.

That is, the first invention according to the present invention is,
A method for manufacturing a plate-shaped body, comprising a lapping step in which a difficult-to-cut plate-shaped body is processed to a thickness close to a desired thickness, and a surface grinding step in which the plate-shaped body surface after the lapping step is surface ground to a highly flat and smooth surface, wherein the lapping step uses _B4C abrasive grains of No. 100 to No. 300 (ISO 8486 designation) and the surface grinding step uses a vitrified grinding wheel having diamond abrasive grains of No. 6000 to No. 8000 (ISO 8486 designation),
The hard-to-cut plate-shaped body is made of any material selected from silicon carbide, boron carbide, titanium carbide, alumina, and boron nitride, and
The surface grinding process is composed of a first grinding process in the front stage and a second grinding process in the rear stage,
The conditions of the first surface grinding in the first grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is attached is 1800 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +151 to -251 rpm;
c) the grinding wheel and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.05 μm/s;
The plate surface is ground to a thickness of 3 μm to 10 μm.
The conditions of the second surface grinding in the second grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is mounted is 3,500 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +51 to -251 rpm;
c) the grinding wheel and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.1 μm/s;
and surface-grinding the plate-shaped body surface to a desired thickness.

Next, the second invention according to the present invention is
In the method for producing a plate-like molded product according to the first aspect of the present invention,
In the first grinding step, one surface of the plate-shaped body is surface ground to 3 μm to 10 μm under the first surface grinding conditions, and then the other surface of the plate-shaped body is surface ground to 3 μm to 10 μm under the first surface grinding conditions;
a second processing step in which one surface of the plate-like body surface-ground under the first surface grinding conditions in the second grinding step is surface-ground under second surface grinding conditions, and then the other surface of the plate-like body surface-ground under the first surface grinding conditions is surface-ground under the second surface grinding conditions;
The method is characterized in that a plate-shaped molded body is produced by
The third invention is
In the method for producing a plate-like molded product according to the second aspect of the present invention,
The second processing step is characterized in that the thickness β to which one surface of the plate-shaped body is surface ground under the second surface grinding conditions is set to be larger than the thickness α to which one surface of the plate-shaped body is surface ground under the second surface grinding conditions (α < β).

According to the method for producing a plate-shaped molded product according to the first aspect of the present invention,
Regarding the conditions for surface grinding of the plate-shaped body surface after the lapping process using _B4C abrasive grains of No. 100 to No. 300 (ISO 8486 designation) with a vitrified grinding wheel containing diamond abrasive grains of No. 6000 to No. 8000 (ISO 8486 designation),
The method is composed of a first grinding step in the front stage and a second grinding step in the rear stage,
The conditions of the first surface grinding in the first grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is attached is 1800 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +151 to -251 rpm;
c) the grinding wheel and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.05 μm/s;
The plate surface is surface ground to a depth of 3 μm to 10 μm under the appropriate conditions.
The conditions of the second surface grinding in the second grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is mounted is 3,500 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +51 to -251 rpm;
c) The grindstone and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.1 μm/s
Because the appropriate conditions are set as follows,
It is possible to reduce the wear rate of the vitrified grinding wheel.

This is a graph showing the relationship between the polishing conditions of a SiC substrate and the grindstone wear rate %, and on the horizontal axis, "#280REF" (1st) is the grindstone wear rate % when the B (Back) surface, which is the lapped surface (#280 surface) of the SiC substrate, is ground to 5 μm under the comparison conditions [spindle rotation speed: 1800 rpm, CT (chuck table) rotation speed: +151 rpm, processing feed rate: 0.2 μm/s], and "#280REF" (2nd) is the grindstone wear rate % when the F (Front) surface, which is the lapped surface (#280 surface) of the SiC substrate, is ground to 5 μm under the comparison conditions [spindle rotation speed: 1800 rpm, CT (chuck table) rotation speed: +151 rpm, processing feed rate: 0.2 μm/s]. The table shows the wheel wear rate % when 5 μm surface grinding was performed under the conditions shown in FIG. 1. Also, “#280 Optimal” (1st) shows the wheel wear rate % when the B (Back) surface, which is the lapped surface (#280 surface) of the SiC substrate, was subjected to 5 μm surface grinding under the optimal conditions [spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, processing feed rate: 0.05 μm/s], and “#280 Optimal” (2nd) shows the wheel wear rate % when the F (Front) surface, which is the lapped surface (#280 surface) of the SiC substrate, was subjected to 5 μm surface grinding under the above optimal conditions. The wear rate % is shown, and "#7000REF" (1st) is the grindstone wear rate % when the B (Back) surface, which is the ground surface (#7000 surface) of the SiC substrate, is surface ground to 5 μm under the comparative conditions [spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, processing feed rate: 0.2 μm/s], and "#7000REF" (2nd) is the grindstone wear rate % when the F (Front) surface, which is the ground surface (#7000 surface) of the SiC substrate, is surface ground to 15 μm under the above comparative conditions. "#7000 Optimal" (1st) indicates the grinding wheel wear rate % when the B (Back) surface, which is the ground surface (#7000 surface) of the SiC substrate, is surface ground at 5 μm under optimal conditions [spindle rotation speed: 3500 rpm, CT rotation speed: -51 rpm, processing feed rate: 0.10 μm/s], "#7000 Optimal" (2nd) indicates the grinding wheel wear rate % when the F (Front) surface, which is the ground surface (#7000 surface) of the SiC substrate, is surface ground at 15 μm under the above optimal conditions, and "AVE" indicates the average value of the 1st and 2nd. This is a graph showing the relationship between the polishing conditions for SiC substrates and the grindstone wear rate %, and on the horizontal axis, "total REF" (1st) is the average value obtained by adding up the grindstone wear rate % of the above "#280REF" (1st) and "#7000REF" (1st), and "total REF" (2nd) is the average value obtained by adding up the grindstone wear rate % of the above "#280REF" (2nd) and "#7000REF" (2nd). "Overall optimum" (1st) indicates the average value obtained by adding up the grindstone wear rate % of the "#280 optimum" (1st) and the grindstone wear rate % of the "#7000 optimum" (1st), "overall optimum" (2nd) indicates the average value obtained by adding up the grindstone wear rate % of the "#280 optimum" (2nd) and the grindstone wear rate % of the "#7000 optimum" (2nd), and "AVE" indicates the average value of the 1st and 2nd. 1A to 1C are process diagrams illustrating a method for manufacturing a SiC polycrystalline substrate using a chemical vapor deposition method (CVD method). FIG. 4 is a process explanatory diagram showing a method for producing a plate-shaped body having a lapping step and a surface grinding step. 5(A) and (B) are explanatory diagrams of the configuration of a lapping device used in the lapping process.

The following describes an embodiment of the present invention.

The inventors conducted repeated experiments while changing the processing conditions of the grinding machine (DFG8340 manufactured by DISCO) used for surface grinding, i.e., the "spindle rotation speed" to which the vitrified grinding wheel is attached, the "chuck table rotation speed" to hold the plate-shaped body, and the "processing feed rate" to move the grinding wheel and the plate-shaped body relatively in the processing feed direction, and found the appropriate conditions to reduce the wear rate of the grinding wheel as described above.

Below, we will explain the experiments conducted by the inventor and explain the "spindle rotation speed," "CT (chuck table) rotation speed," and "processing feed rate" that reduce the wear rate of vitrified grinding wheels.

In addition, the lapped surface of a plate-shaped body (SiC polycrystalline substrate) lapped using No. 280 (ISO 8486 designation) boron carbide ( _B4C ) abrasive grains is abbreviated as the "#280 surface," and the ground surface of a plate-shaped body (SiC polycrystalline substrate) flat ground with a vitrified grinding wheel containing No. 7000 (ISO 8486 designation) diamond abrasive grains is abbreviated as the "#7000 surface."

1. Surface grinding conditions for lapped surface (#280 surface) (1) Test method (1-1) Equipment conditions Precision surface grinding machine: DISCO DFG8340
Grindstone: Vitrified grindstone containing diamond abrasive grains #7000 (ISO 8486) Grinding fluid: Pure water

(1-2) Equipment fixing conditions:
"Spindle speed": 1800 rpm
"CT (chuck table) rotation speed": +151 rpm

(2) Board used (#280 side):
A SiC polycrystalline substrate that has been subjected to low-pressure double-sided lapping using boron carbide (B ₄ C) abrasive grains of #280 (ISO 8486 designation) [SiC substrate (#280 surface)]
(2-1) "Machining feed speed" conditions (2-1-1) "♯280REF"
"Processing feed rate": Under the condition of 0.2 μm/s, the B (Back) surface of the SiC substrate (#280 surface) was surface ground (1st) by 5 μm, and then the F (Front) surface of the SiC substrate (#280 surface) was surface ground (2nd). The 1st and 2nd "grindstone wear rates" (average values) were measured by surface grinding four SiC substrates (#280 surfaces) and surface grinding the 1st and 2nd SiC substrates.

The results are shown in Figure 1 for "#280REF" (1st) (2nd). When the spindle rotation speed was set to 1800 rpm, the CT rotation speed to +151 rpm, and the processing feed rate to 0.2 μm/s in surface grinding of a SiC substrate (#280 surface), it was confirmed that the "grindstone wear rate" (average value) was extremely high, at approximately 890% for the 1st, approximately 490% for the 2nd, and approximately 690% for the average value of the 1st and 2nd.

(2-1-2) "#280 Optimal"
"Processing feed rate": Under the condition of 0.05 μm/s, the B (Back) surface of the SiC substrate (#280 surface) was surface ground to 5 μm (1st), and then the F (Front) surface of the SiC substrate (#280 surface) was surface ground to 5 μm (2nd). At the same time, four SiC substrates (#280 surfaces) were surface ground to measure the "grindstone wear rate" (average value) of the 1st and 2nd.

The results are shown in Figure 1, "Optimal #280" (1st) (2nd). When the spindle rotation speed was set to 1800 rpm, the CT rotation speed to +151 rpm, and the processing feed rate to 0.05 μm/s in surface grinding of a SiC substrate (#280 surface), it was confirmed that the "grindstone wear rate" (average value) improved to about 290% in the 1st, about 210% in the 2nd, and about 250% in the average value of the 1st and 2nd.

2. Surface grinding conditions for the ground surface (#7000 surface) (1) Test method (1-1) Equipment conditions Precision surface grinding machine: DISCO DFG8340
Grindstone: Vitrified grindstone containing diamond abrasive grains #7000 (ISO 8486) Grinding fluid: Pure water

(2) Board used (#7000 side):
A vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation) was used, and the B (Back) and F (Front) surfaces of a SiC polycrystalline substrate [SiC substrate (#280 surface)] were polished under the above-mentioned "#280REF" conditions. A SiC polycrystalline substrate [SiC substrate (#7000 surface)] in which the surface was surface ground, and a SiC polycrystalline substrate [SiC substrate (#280 surface)] in which the B (Back) A polycrystalline SiC substrate with the F (Front) surface ground [SiC substrate (#7000 surface)]

(2-1) Surface grinding conditions (2-1-1) "#7000REF"
The B (Back) surface of the SiC polycrystalline substrate [SiC substrate (#7000 surface)] surface ground under the above-mentioned "#280REF" conditions was subjected to 5 μm surface grinding (1st) under conditions of spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, and processing feed rate: 0.2 μm/s. Subsequently, the F (Front) surface of the above-mentioned SiC substrate (#7000 surface) was surface ground 15 μm (2nd), and four SiC substrates (#7000 surfaces) were also surface ground to measure the "grinding wheel wear rate" (average value) of the 1st and 2nd.

The results are shown in Figure 1 for "#7000REF" (1st) (2nd). When the spindle rotation speed was set to 1800 rpm, the CT rotation speed to +151 rpm, and the processing feed rate to 0.2 μm/s in surface grinding of a SiC substrate (#7000 surface), it was confirmed that the "grindstone wear rate" (average value) was high, at approximately 190% for the 1st, approximately 120% for the 2nd, and approximately 155% for the average value of the 1st and 2nd.

(2-1-2) "#7000 Optimal"
The B (Back) surface of the SiC polycrystalline substrate [SiC substrate (#7000 surface)] that had been surface ground under the above-mentioned "#280 optimum" conditions was surface ground 5 μm (1st) under conditions of spindle rotation speed: 3500 rpm, CT rotation speed: -51 rpm, and processing feed rate: 0.10 μm/s. Subsequently, the F (Front) surface of the above-mentioned SiC substrate (#7000 surface) was surface ground 15 μm (2nd), and four SiC substrates (#7000 surfaces) were also surface ground to measure the "grindstone wear rate" (average value) of the 1st and 2nd.

The results are shown in Figure 1, "Optimal #7000" (1st) (2nd). When the spindle rotation speed was set to 3500 rpm, the CT rotation speed to -51 rpm, and the processing feed rate to 0.10 μm/s in surface grinding of a SiC substrate (#7000 surface), it was confirmed that the "grindstone wear rate" (average value) was significantly improved to about 80% in the 1st, about 20% in the 2nd, and about 50% in the average value of the 1st and 2nd.

Meanwhile, the grinding amount of the B (Back) surface of the SiC substrate (#7000 surface) is 5 μm, while the grinding amount of the F (Front) surface is set to a large amount of 15 μm. The reason for this is that when the surface-ground SiC substrate is used as a SiC polycrystalline substrate to be bonded to a SiC single crystal substrate, the F (Front) surface, which has a larger amount of grinding, is made flatter, resulting in better bonding to the SiC single crystal substrate.

3. Overall evaluation of the lapped surface (#280 surface) and ground surface (#7000 surface) (1) The "overall REF" (1st) in Figure 2 is the average value (about 540%) obtained by adding up the grindstone wear rate of the above "#280REF" (1st) (about 890%) and the grindstone wear rate of the "#7000REF" (1st) (about 190%), and the "overall REF" (2nd) is the average value (about 305%) obtained by adding up the grindstone wear rate of the above "#280REF" (2nd) (about 490%) and the grindstone wear rate of the "#7000REF" (2nd) (about 120%), and the average value of the "overall REF" obtained by adding up the average values of the 1st and 2nd was about 420%.

In other words, when the B (Back) and F (Front) surfaces of a SiC substrate (#280 surface) are surface ground under the above comparative conditions [spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, and processing feed rate: 0.2 μm/s], and the B (Back) and F (Front) surfaces of a SiC substrate (#7000 surface) are also surface ground under the above comparative conditions [spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, and processing feed rate: 0.2 μm/s], it is confirmed that the overall grinding wheel wear rate is high, at approximately 420%.

(2) On the other hand, the "overall optimum" (1st) in Figure 2 is the average value (approximately 180%) obtained by adding up the grindstone wear rate of the above "#280 optimum" (1st) (approximately 290%) and the grindstone wear rate of the "#7000 optimum" (1st) (approximately 80%), and the "overall optimum" (2nd) is the average value (approximately 120%) obtained by adding up the grindstone wear rate of the above "#280 optimum" (2nd) (approximately 210%) and the grindstone wear rate of the "#7000 optimum" (2nd) (approximately 20%), and the average value of the "overall optimum" obtained by adding up the average values of the 1st and 2nd was approximately 150%.

In other words, when the B (Back) and F (Front) surfaces of a SiC substrate (#280 surface) are surface ground under the above-mentioned optimal conditions [spindle rotation speed: 1800 rpm, CT rotation speed: +151 rpm, and processing feed rate: 0.05 μm/s], and the B (Back) and F (Front) surfaces of a SiC substrate (#7000 surface) are surface ground under the above-mentioned optimal conditions [spindle rotation speed: 3500 rpm, CT rotation speed: -51 rpm, and processing feed rate: 0.10 μm/s], it is confirmed that the overall grinding wheel wear rate is significantly improved by approximately 150%.

(3) Reason why the wear rate of the grindstone is significantly different between the 1st and 2nd As can be seen from a comparison of the wear rate of the grindstone of "#280REF" (1st) (approximately 890%) and the wear rate of the grindstone of "#280REF" (2nd) (approximately 490%) shown in FIG. 1, the wear rate of the grindstone is significantly different between the 1st and 2nd.

The inventors speculate that the reason for this is as follows.

Before surface grinding, both the B (back) and F (front) surfaces of the SiC substrate (#280 surface) have steeply uneven surfaces. When the F (front) surface of the SiC substrate is attached to the CT (chuck table) and the B (back) surface of the SiC substrate (#280 surface) is ground (1st stage), the adhesion of the SiC substrate (#280 surface) to the CT (chuck table) is weak due to the steeply uneven surface (#280 surface), and this makes the holding of the SiC substrate (#280 surface) unstable, resulting in a high wear rate of the grinding wheel in the 1st stage.

On the other hand, when grinding (2nd) the F (Front) surface of a SiC substrate (#280 surface), the B (Back) surface of the SiC substrate has been surface ground to a flat surface (#7000 surface), so the adhesion force of the SiC substrate (#7000 surface) to the CT (chuck table) becomes stronger, and it is presumed that the SiC substrate (#7000 surface) is held more stably and the wear rate of the 2nd grinding wheel is lower.

4. Optimal conditions for surface grinding to reduce the wear rate of the grinding wheel From the above experimental results, the following optimal conditions are found.

That is,
(1) The appropriate conditions for surface grinding the lapped surface (#280 surface) of a plate-shaped body after the lapping process using boron carbide ( _B4C ) grains #280 (ISO 8486 designation) by a grinding device using a vitrified grinding wheel containing diamond grains #7000 (ISO 8486 designation) are as follows:
a) The rotation speed of the spindle equipped with the grinding wheel is 1800 rpm;
b) The rotation speed of the chuck table that holds the plate-like body is +151 to -251 rpm;
c) The processing feed speed for moving the grinding wheel and the plate-shaped body relatively in the processing feed direction is 0.05 μm/s;
and
(2) The appropriate conditions for surface grinding of a ground surface (#7000 surface) of a plate-shaped body flattened with a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation) by a grinding device using a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation) are as follows:
a) The rotation speed of the spindle on which the grinding wheel is attached is 3500 rpm;
b) The rotation speed of the chuck table that holds the plate-like body is +51 to -251 rpm;
c) The processing feed speed for moving the grinding wheel and the plate-shaped body relatively in the processing feed direction is 0.1 μm/s;
It is found that:

Examples of materials constituting the difficult-to-cut plate-shaped body include boron carbide, titanium carbide, alumina, and boron nitride in addition to silicon carbide (SiC).

The following is a detailed explanation of the present invention, including comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
A SiC polycrystalline substrate (wafer) was placed between the upper and lower plates of the lapping device shown in Figures 5 (A) and (B), and low-pressure double-sided lapping was performed while supplying a polishing liquid containing boron carbide ( _B4C ) abrasive grains No. 280 (ISO 8486 designation) between the upper and lower plates.

Next, the B (back) surface of the wafer (#280 surface) was surface ground to 5 μm (1st) using a grinding machine (DISCO Corp. DFG8340) with a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation), and then the F (front) surface of the wafer (#280 surface) was surface ground to 5 μm (2nd) using a grinding machine (DISCO Corp. DFG8340) with a vitrified grinding wheel containing diamond abrasive grains of #7000 (ISO 8486 designation).

The grinding conditions for the above wafer (#280 surface) are as follows:
a) The rotation speed of the spindle equipped with the grinding wheel is 1800 rpm;
b) The rotation speed of the chuck table holding the wafer is +151 rpm;
c) the processing feed speed for relatively moving the grindstone and the wafer in the processing feed direction is 0.05 μm/s;
was set to.

The wear rate of the grindstone when grinding a wafer (#280 surface) was examined and found to be approximately 290% in the 1st process [see "#280 Optimal" (1st) in Figure 1] and approximately 210% in the 2nd process [see "#280 Optimal" (2nd) in Figure 1].

Next, the B (Back) surface of the surface-ground wafer (#7000 surface) was surface-ground to 5 μm (1st) using the above-mentioned grinding device (DFG8340 manufactured by DISCO) with a vitrified grinding wheel containing #7000 (ISO 8486) diamond abrasive grains, and the F (Front) surface of the wafer (#7000 surface) was also surface-ground to 15 μm (2nd) using a grinding device (DFG8340 manufactured by DISCO) with a vitrified grinding wheel containing #7000 (ISO 8486) diamond abrasive grains to produce the plate-shaped molded body according to Example 1.

The grinding conditions for the above wafer (#7000 surface) are as follows:
a) The rotation speed of the spindle on which the grinding wheel is attached is 3500 rpm;
b) The rotation speed of the chuck table holding the wafer is −51 rpm;
c) the processing feed speed for relatively moving the grindstone and the wafer in the processing feed direction is 0.10 μm/s;
was set to.

Similarly, when the grinding wheel wear rate was examined when grinding a wafer (#7000 surface), it was about 80% in the 1st process [see "#7000 Optimal" (1st) in Figure 1] and about 20% in the 2nd process [see "#7000 Optimal" (2nd) in Figure 1].

[Comparative Example 1]
The grinding conditions for the above wafer (#280 surface) are as follows:
a) The rotation speed of the spindle equipped with the grinding wheel is 1800 rpm;
b) The rotation speed of the chuck table holding the wafer is +151 rpm;
c) the processing feed speed for relatively moving the grindstone and the wafer in the processing feed direction is 0.20 μm/s;
and
The grinding conditions for the above wafer (#7000 surface) are as follows:
a) The rotation speed of the spindle equipped with the grinding wheel is 1800 rpm;
b) The rotation speed of the chuck table holding the wafer is +151 rpm;
c) the processing feed speed for relatively moving the grindstone and the wafer in the processing feed direction is 0.20 μm/s;
A plate-like molded product according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the temperature was set to 100° C.

The wear rate of the grindstone when grinding a wafer (#280 surface) was examined and found to be approximately 890% in the 1st process [see "#280REF" (1st) in Figure 1] and approximately 490% in the 2nd process [see "#280REF" (2nd) in Figure 1].

Similarly, when the grinding wheel wear rate was examined when grinding a wafer (#7000 surface), it was about 190% in the 1st process [see "#7000REF" (1st) in Figure 1] and about 120% in the 2nd process [see "#7000REF" (2nd) in Figure 1].

[comprehensive evaluation]
(1) Example 1
The average value of the grinding wheel wear rate (1st) calculated by adding up the grinding wheel wear rate of the "#280 surface" (1st) (approximately 290%) and the grinding wheel wear rate of the "#7000 surface" (1st) (approximately 80%) was approximately 180%, and the average value of the grinding wheel wear rate (2nd) calculated by adding up the grinding wheel wear rate of the "#280 surface" (2nd) (approximately 210%) and the grinding wheel wear rate of the "#7000 surface" (2nd) (approximately 20%) was approximately 120%, so the average value of the grinding wheel wear rate in all processes (1st and 2nd) was approximately 150%.

(2) Comparative Example 1
The average value of the grinding wheel wear rate (1st) calculated by adding up the grinding wheel wear rate of the "#280 surface" (1st) (approximately 890%) and the grinding wheel wear rate of the "#7000 surface" (1st) (approximately 190%) was approximately 540%, and the average value of the grinding wheel wear rate (2nd) calculated by adding up the grinding wheel wear rate of the "#280 surface" (2nd) (approximately 490%) and the grinding wheel wear rate of the "#7000 surface" (2nd) (approximately 120%) was approximately 305%, so the average value of the grinding wheel wear rate for the entire process (1st and 2nd) was approximately 420%.

(3) The average wear rate of the grinding wheel in all processes (1st and 2nd) was approximately 150% in Example 1 and approximately 420% in Comparative Example 1, confirming that the wear of the grinding wheel can be significantly reduced by adopting the grinding conditions of Example 1.

The method of the present invention can reduce the wear rate of the grinding wheels used in the surface grinding process, and therefore has industrial applicability for use in the manufacture of silicon carbide (SiC) polycrystalline substrates.

1 Carbonaceous support substrate (graphite support substrate)
2 SiC polycrystalline film 3 SiC polycrystalline substrate

Claims (3)

A method for manufacturing a plate-shaped body, comprising a lapping step in which a difficult-to-cut plate-shaped body is processed to a thickness close to a desired thickness, and a surface grinding step in which the plate-shaped body surface after the lapping step is surface ground to a highly flat and smooth surface, wherein the lapping step uses _B4C abrasive grains of No. 100 to No. 300 (ISO 8486 designation) and the surface grinding step uses a vitrified grinding wheel having diamond abrasive grains of No. 6000 to No. 8000 (ISO 8486 designation),
The hard-to-cut plate-shaped body is made of any material selected from silicon carbide, boron carbide, titanium carbide, alumina, and boron nitride, and
The surface grinding process is composed of a first grinding process in the front stage and a second grinding process in the rear stage,
The conditions of the first surface grinding in the first grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is attached is 1800 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +151 to -251 rpm;
c) the grinding wheel and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.05 μm/s;
The plate surface is ground to a thickness of 3 μm to 10 μm.
The conditions of the second surface grinding in the second grinding step are as follows:
a) The rotation speed of the spindle on which the grinding wheel is mounted is 3,500 rpm;
b) the rotation speed of the chuck table holding the plate-like body is +51 to -251 rpm;
c) the grinding wheel and the plate-like body are moved relatively in the processing feed direction at a processing feed speed of 0.1 μm/s;
and surface-grinding the plate-shaped body surface to a desired thickness. In the first grinding step, one surface of the plate-shaped body is surface ground to 3 μm to 10 μm under the first surface grinding conditions, and then the other surface of the plate-shaped body is surface ground to 3 μm to 10 μm under the first surface grinding conditions;
a second processing step in which one surface of the plate-like body surface-ground under the first surface grinding conditions in the second grinding step is surface-ground under second surface grinding conditions, and then the other surface of the plate-like body surface-ground under the first surface grinding conditions is surface-ground under the second surface grinding conditions;
2. The method for producing a plate-like molded product according to claim 1, further comprising the steps of: The method for manufacturing a plate-shaped molded body according to claim 2, characterized in that in the second processing step, the thickness β to which one surface of the plate-shaped body is surface ground under the second surface grinding conditions is set to be larger than the thickness α to which one surface of the plate-shaped body is surface ground under the second surface grinding conditions (α < β).

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