Method and apparatus for manufacturing silicon carbide single crystal substrates

Abstract

The objective is to provide a method and apparatus for manufacturing silicon carbide single crystal substrates with high flatness. [Solution] The method for manufacturing a silicon carbide single crystal substrate is characterized by measuring the first thickness of the central part of the silicon carbide single crystal substrate and the second thickness of the outer peripheral part located on the outer peripheral side of the central part, measuring the first pressure applied to the central part of the silicon carbide single crystal substrate and the second pressure applied to the outer peripheral part of the silicon carbide single crystal substrate, and determining the relationship between the first index obtained from the first pressure and the second pressure and the second index obtained from the first thickness and the second thickness.

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for manufacturing a silicon carbide single crystal substrate. [Background technology]

[0002] One type of silicon carbide substrate used in power devices and the like is a bonded silicon carbide substrate, which is made by bonding a silicon carbide single crystal substrate to a silicon carbide polycrystalline substrate. Patent Document 1 discloses a technique for planarizing a silicon carbide single crystal substrate used in such a bonded silicon carbide substrate by the CMP (Chemical Mechanical Polishing) method.

[0003] Furthermore, Patent Document 2 discloses a technique for flattening semiconductor wafers by individually controlling the pressure applied to the central and peripheral parts of the substrate, in order to prevent "sagging," where the amount of polishing at the periphery of the wafer is greater than that at the center of the wafer. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-15401 [Patent Document 2] Japanese Patent Publication No. 2010-253579 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In the manufacturing method of bonded silicon carbide substrates, a silicon carbide single crystal substrate bonded to a silicon carbide polycrystalline substrate is peeled off from the silicon carbide single crystal substrate. In the subsequent process, the peeled surface of the silicon carbide single crystal substrate is polished and planarized in order to reuse the silicon carbide single crystal substrate after peeling. The peeled silicon carbide single crystal substrate (the substrate to be polished) has a concave shape with a residual layer remaining on the outer periphery of the peeled surface. In the planarization process, polishing defects occur, such as insufficient polishing near the edges of the outer periphery due to pressure imbalances caused by the shape, or conversely, excessive polishing of the entire substrate. Thus, in the polishing process for reuse of a peeled silicon carbide single crystal substrate with a concave shape and a residual layer remaining on the outer periphery, it has been difficult to determine and set appropriate control values ​​to satisfy the necessary and sufficient amount of polishing and flatness.

[0006] The present invention aims to provide a method and apparatus for manufacturing a silicon carbide single crystal substrate with high flatness in order to solve the above problems. [Means for solving the problem]

[0007] A method for manufacturing a silicon carbide single crystal substrate according to one embodiment of the present invention includes a calibration step of determining the relationship between a first index obtained from a first pressure and a second pressure and a second index obtained from a first thickness and a second thickness, wherein the first pressure is the pressure applied to the central part of the substrate to be polished, the second pressure is the pressure applied to the outer periphery of the substrate to be polished, the first thickness is the thickness of the central part of the substrate to be polished, and the second thickness is the thickness of the outer periphery of the substrate to be polished that is located on the outer periphery side of the central part.

[0008] Furthermore, a silicon carbide single crystal substrate manufacturing apparatus according to one embodiment of the present invention comprises: a polishing head that applies a first load to the center of the head and a second load to the outer circumference of the head surrounding the center of the head; a polishing pad positioned opposite the polishing head so as to be able to sandwich the silicon carbide single crystal substrate and polishing the surface of the silicon carbide single crystal substrate to be polished by receiving the first load and the second load; and a pressure control unit that adjusts at least one of the first load and the second load based on the first pressure acting on the polishing pad due to the first load, the second pressure acting on the polishing pad due to the second load, and the target polishing thickness of the silicon carbide single crystal substrate. [Effects of the Invention]

[0009] According to the method and apparatus for manufacturing a silicon carbide single crystal substrate of the present invention, the flatness of the silicon carbide single crystal substrate can be improved. [Brief explanation of the drawing]

[0010] [Figure 1] Diagram illustrating a silicon carbide single crystal substrate with a residual layer. [Figure 2] A schematic diagram of the manufacturing apparatus for silicon carbide single crystal substrates according to an embodiment. [Figure 3] A top view of the sheet-shaped pressure distribution measurement sensor according to the embodiment. [Figure 4] A schematic diagram showing the relationship between a silicon carbide single crystal substrate and a distributed load according to an embodiment. [Figure 5] A flowchart showing the manufacturing process of a silicon carbide single crystal substrate according to an embodiment. [Figure 6] A flowchart showing the determination procedure in the calibration process of the silicon carbide single crystal substrate manufacturing method according to the embodiment. [Modes for carrying out the invention]

[0011] The following describes embodiments of a method for manufacturing a silicon carbide single crystal substrate and a manufacturing apparatus with reference to the drawings.

[0012] [Silicon carbide single crystal substrate] First, the structure of the silicon carbide single crystal substrate manufactured using the manufacturing apparatus according to the embodiment will be described. Figure 1 is an explanatory diagram of the silicon carbide single crystal substrate 1 (substrate to be polished) having a residual layer to be polished in the manufacturing apparatus according to the embodiment. Figure 1(a) is a schematic perspective view of the silicon carbide single crystal substrate 1, which is the substrate to be polished, Figure 1(b) is a schematic plan view of the silicon carbide single crystal substrate 1, and Figure 1(c) is a schematic cross-sectional view of the silicon carbide single crystal substrate 1. As shown in Figure 1, the silicon carbide single crystal substrate 1, which is the substrate to be polished, has a disc shape with an adsorption surface 2, a surface to be polished 3, and a side surface 4. The adsorption surface 2 of the silicon carbide single crystal substrate 1 has a smooth surface so that it can be adsorbed onto the pressure plate 27, which will be described later. The surface to be polished 3, located on the opposite side of the adsorption surface 2 of the silicon carbide single crystal substrate 1, has a concave shape with a fine residual layer 5 of silicon carbide single crystalline material on its outer circumference 7.

[0013] The central portion 6, located on the inner side of the outer peripheral portion 7, is formed by, for example, implanting hydrogen ions into the surface of a smoothly polished silicon carbide single crystal substrate, then bonding it to a silicon carbide polycrystalline substrate, and finally removing it due to the ablation of the implanted hydrogen atoms. In other words, the thickness of the silicon carbide single crystal substrate 1 before polishing is usually such that the outer peripheral portion 7 is thicker than the central portion 6, resulting in a concave shape.

[0014] code W A The thickness indicated is the target thickness for polishing the outer periphery, which is set as the amount of polishing required to smooth the outer periphery 7 of the silicon carbide single crystal substrate 1 in Figure 1 using the manufacturing apparatus according to this embodiment. The residual layer 5 is distributed continuously or discontinuously in the circumferential and radial directions of the outer periphery 7, and the thickness of the residual layer 5 is generally not uniform, but the outer periphery 7 is set to the target thickness W of the outer periphery polishing. A By polishing by that amount, the surface along the central part 6 can be made smooth.

[0015] Also, code W BThe thickness shown by is the overall polishing target thickness for polishing the central portion 6 of the silicon carbide single crystal substrate 1 in Fig. 1 by the manufacturing apparatus according to the present embodiment. Regarding the surface of the central portion 6, since it has minute irregularities (not shown) that occur when peeled off by ablation of hydrogen atoms, by polishing the central portion 6 by the amount of the overall polishing target thickness W B shown in , these minute irregularities can be smoothed.

[0016] The outer peripheral portion polishing target thickness W A for smoothing the residual layer 5 in the outer peripheral portion 7 is determined, for example, by the height difference between the maximum value and the minimum value in the uneven region. The overall polishing target thickness W B for smoothing the central portion 6 is determined, for example, according to the thickness of the damage layer generated in the ion implantation process performed prior to the thickness measurement step S101 shown in the flow of Fig. 5.

[0017] The ion implantation process is one of the manufacturing processes of the bonded silicon carbide substrate. In the ion implantation process, hydrogen ions are implanted at a high concentration into a region with a depth of about 0.5 μm from the surface of the single crystal substrate to form a damage layer. At this time, high-concentration phosphorus ions are implanted into the outermost surface of the single crystal substrate in order to reduce the interface resistance. It becomes possible to cleave and divide the single crystal with the damage layer provided in this ion implantation process.

[0018] Since the thickness of the damage layer remaining on the surface after cleavage and division is usually about several nm, the overall polishing target thickness W B is a thickness that can sufficiently remove the damage layer and can be determined, for example, to be a thickness of several nm so as not to remove it excessively. The outer peripheral portion polishing target thickness W A is also influenced by the thickness of the residual layer 5, but usually has a thickness of about several hundred nm.

[0019] The outer peripheral portion 7 is usually the outer peripheral portion polishing target thickness W AAs a result, the polished surface 3 of the silicon carbide single crystal substrate 1 has a downward-facing concave cross-sectional shape because it is thicker than the central part 6. Since the central part 6 also has a minute uneven layer, polishing and removal of the silicon carbide single crystal substrate 1 is performed not only on the outer periphery 7 but also on the central part 6, and the thickness of the side surface 4 is the overall target polishing thickness W, which is the area to be removed by polishing. B It includes.

[0020] [Manufacturing equipment for silicon carbide single crystal substrates] Figure 2 is a schematic diagram of a silicon carbide single crystal substrate manufacturing apparatus according to an embodiment. The silicon carbide single crystal substrate manufacturing apparatus 100 according to this embodiment includes a polishing apparatus 200 and a processing unit 300. The polishing apparatus 200 and the processing unit 300 are connected, for example, electrically.

[0021] <Polishing equipment> The polishing apparatus 200 comprises a polishing platen 21, a polishing head 22, and a sheet-shaped pressure distribution measurement sensor 23. Note that Figure 2 shows the polishing apparatus 200 as a vertical cross-sectional view.

[0022] The polishing platen 21 has a disc-shaped outer form that is aligned horizontally with respect to the platen rotation axis R0. The material of the polishing platen 21 is, for example, stainless steel or ceramic. A platen shaft 24 is fixed to the lower surface of the polishing platen 21 coaxially with the platen rotation axis R0. The platen shaft 24 is solid. The upper surface of the polishing platen 21 is flat. A polishing pad 25 is placed on the upper surface of the polishing platen 21. The material of the polishing pad 25 is generally urethane or suede.

[0023] The polishing head 22 has a cylindrical shape centered on the head rotation axis R1. In this embodiment, the polishing head 22 is made of stainless steel, but the material is not particularly limited as long as it is suitable for the application. The head rotation axis R1 is set parallel to the platen rotation axis R0 and at a different position from the platen rotation axis R0. A polishing head shaft 26 is fixed to the upper part of the polishing head 22 so as to be rotatable coaxially with the head rotation axis R1.

[0024] The polishing head 22 has a pressure plate 27 at the end opposite to the side to which the polishing head shaft 26 is fixed, with its lower surface being a pressure surface 27a. The cylindrical interior 22a formed inside the polishing head 22 by the cylindrical polishing head 22 and the pressure plate 27 is provided with an outer peripheral pressure mechanism 28 and a central pressure mechanism 29.

[0025] The central pressing mechanism 29 is located at the center of the cylindrical interior 22a of the polishing head 22 (i.e., on the side of the head rotation axis R1), and the outer peripheral pressing mechanism 28 is located on the outer circumference of the central pressing mechanism 29, surrounding it. Both the outer peripheral pressing mechanism 28 and the central pressing mechanism 29 are positioned to contact the upper surface 27b of the pressure plate 27. The outer peripheral pressing mechanism 28 and the central pressing mechanism 29 are each provided with actuators (not shown) that apply a load to the pressure plate 27.

[0026] The pressure surface 27a, which is the lower surface of the pressure plate 27, is spaced apart from and opposite to the upper surface 25a of the polishing pad 25. The pressure surface 27a of the pressure plate 27 is a flat surface perpendicular to the head rotation axis R1. The pressure surface 27a of the pressure plate 27 is provided with an adsorption mechanism (chuck plate) (not shown) for adsorbing and fixing the silicon carbide single crystal substrate 1. In this way, the polishing head 22 applies a first load P to the central part 6 of the silicon carbide single crystal substrate 1 via the pressure plate 27 by the central part pressure mechanism 29. A In addition to applying the pressure plate 27, a second load P is applied to the outer periphery 7 of the silicon carbide single crystal substrate 1. B It is configured to apply the effect.

[0027] The polishing apparatus 200 includes a relative position adjustment mechanism (not shown) that allows the relative distance between the pressure surface 27a of the pressure plate 27 and the upper surface 25a of the polishing pad 25 to be adjusted. The relative position adjustment mechanism may be, for example, a mechanism that moves the entire polishing head 22 and polishing head shaft 26 along the head rotation axis R1, or a mechanism that moves the polishing platen 21 and platen shaft 24 together with the polishing pad 25 along the platen rotation axis R0. By adjusting the position of the relative position adjustment mechanism, the silicon carbide single crystal substrate 1 can be sandwiched between the pressure surface 27a of the pressure plate 27 and the upper surface 25a of the polishing pad 25.

[0028] <Sheet-type pressure distribution measurement sensor> Figure 3 is a top view of a sheet-shaped pressure distribution measurement sensor 23 according to an embodiment. As shown in Figures 2 and 3(a), the sheet-shaped pressure distribution measurement sensor 23 has a sheet shape that can be positioned opposite the silicon carbide single crystal substrate 1 fixedly held on the upper surface 25a of the polishing pad 25 and the pressure surface 27a of the pressure plate 27, and is positioned on the upper surface 25a of the polishing pad 25 below the silicon carbide single crystal substrate 1 fixedly held on the pressure plate 27. The sheet-shaped pressure distribution measurement sensor 23 is equipped with a plurality of pressure detection elements 30 arranged in a matrix on its surface. The sheet-shaped pressure distribution measurement sensor 23 is electrically connected to the processing unit 300 via a circuit.

[0029] In Figure 3, components corresponding to the constituent elements in Figures 1 to 3 are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

[0030] As shown in Figure 3, the sheet-shaped pressure distribution measurement sensor 23 according to this embodiment has a square sheet shape in which the length of each side is greater than the diameter of the silicon carbide single crystal substrate 1. The sheet-shaped pressure distribution measurement sensor 23 measures the first load P during loading. A and second load P B It has a pressure detection element 30 that can read the pressure.

[0031] In Figure 3, the fine mesh-like matrix represents the cells 23a of the sheet-type pressure distribution measurement sensor 23. In this embodiment, the dimensions of one cell 23a of the sheet-type pressure distribution measurement sensor 23 used on the target 6-8 inch silicon carbide single crystal substrate 1 are approximately 5 mm square, and each cell 23a contains a pressure detection element 30 for detecting pressure.

[0032] In this embodiment, as shown in Figure 3, each cell 23a has either a load indicator A applied to each cell 23a in the outer perimeter 7, a load indicator B applied to each cell 23a in the central part 6, or a blank display. The load indicator A applied to each cell 23a in the outer perimeter 7 is located between the outer edge of the outer perimeter 7 and the outer edge of the central part 6, while the load indicator B applied to each cell 23a in the central part 6 is located within the outer edge of the central part 6. When the boundary line between the outer edge of the central part 6 and the outer edge of the outer perimeter 7, which is roughly an arc, crosses a cell 23a, a blank display is set in that cell 23a instead of the load indicator A applied to each cell 23a in the outer perimeter or the load indicator B applied to each cell 23a in the central part. The display can be set, for example, by a program via a computer, or by manual input.

[0033] Figure 3 shows that the system is equipped with 529 pressure detection elements 30 (a matrix of 23 cells x 23 cells). Each pressure detection element 30 is electrically connected to the sheet-shaped pressure distribution measurement sensor 23 via a circuit in order to transmit information linking its position information on the matrix, pressure value, and display information (load display A applied to each cell in the outer periphery 7, load display B applied to each cell in the central part 6, or a blank display) to the sheet-shaped pressure distribution measurement sensor 23.

[0034] Figure 3 shows an example equipped with a 23x23 cell pressure sensing element 30, but accuracy may be improved by changing the number of cells in the vertical and horizontal directions or the dimensions of cell 23a. Each pressure sensing element 30 is a capacitive or resistive element that reads the decrease in the gap between electrode metal films or the change in impedance in response to local pressure changes.

[0035] <Processing> The processing unit 300 includes a pressure control unit 31, a pressure measuring unit 32, and an index determination unit 33. The processing unit 300 is, for example, a computer having an arithmetic unit. The processing unit 300 may realize the functions of the pressure control unit 31, the pressure measuring unit 32, and the index determination unit 33 by the computer's arithmetic unit executing a predetermined program.

[0036] The manufacturing apparatus 100 has a circuit that electrically connects the polishing apparatus 200 and the processing unit 300, for example. Specifically, the pressure control unit 31 is electrically connected to actuators (not shown) of the outer peripheral pressurizing mechanism 28 and the central pressurizing mechanism 29. The pressure measuring unit 32 is electrically connected to the sheet-shaped pressure distribution measuring sensor 23, for example. Within the processing unit 300, the index determination unit 33 is electrically connected to the pressure control unit 31 and the pressure measuring unit 32, for example. The index determination unit 33 has an outer peripheral polishing target thickness W A and overall polishing target thickness W B It is equipped with a line that receives input.

[0037] [Operation of manufacturing equipment, polishing methods] Next, the operation of the silicon carbide single crystal substrate manufacturing apparatus and the method for polishing the silicon carbide single crystal substrate according to an embodiment having such a configuration will be described with reference to the drawings.

[0038] Figure 5 is a flowchart showing the manufacturing process of a silicon carbide single crystal substrate according to this embodiment. As shown in Figure 5, the manufacturing method of a silicon carbide single crystal substrate according to this embodiment includes a thickness measurement step S101, a removal target thickness setting step S102, an arrangement step S103, a test loading step S104, a calibration step S105, and an appropriate loading step S106. The details of steps S101 to S106 will be described below with further reference to the figure.

[0039] <Thickness measurement process> Thickness measurement step S101 is a step in which the thickness of the silicon carbide single crystal substrate 1 is optically measured using a measuring device (not shown). In this thickness measurement of the silicon carbide single crystal substrate 1, the silicon carbide single crystal substrate 1 is moved to a measuring device (not shown) outside the polishing apparatus 200, and the first thickness (average thickness of the central part 6) and the second thickness (average thickness of the side surface 4 including the residual layer 5) are measured. The difference between the first thickness and the second thickness is the target thickness W of the outer periphery polishing. A Therefore, the overall polishing target thickness W B This will be determined separately in the next step.

[0040] The thickness measuring device (not shown) measures the total thickness from the adsorption surface 2, which serves as the thickness reference surface, to the polished surface 3 using a non-contact measurement method such as spectral interference. In this case, it is preferable to acquire the unique thickness data at one point near the center of the central portion 6 and at several measurement points, for example, 4 to 8 points, set at predetermined radial positions from the center at regular intervals in the circumferential direction. Furthermore, the thickness data of the residual layer 5 is acquired at multiple locations along the circumferential direction. While it is common to acquire unique data at around 4 to 8 measurement points, the measurement accuracy can be improved by further increasing the number of measurement points.

[0041] The first and second thicknesses are calculated from the thicknesses of the side surface 4 and central section 6, including the residual layer 5, obtained at each measurement point. The first thickness is obtained by calculating the average or median value from the unique data of the central section 6. The second thickness is obtained by calculating the average or median value from the unique data of the side surface 4, including the residual layer 5. The target thickness W of the outer perimeter is calculated from the difference between the first and second thicknesses. A We determine the residual layer 5 or the target thickness W of the outer periphery. A The thickness is, for example, 1.0 μm to 1.5 μm. The measuring device and the processing unit 300 (not shown) are electrically connected, for example, to the target thickness W of the outer periphery polishing. A This is input to the indicator determination unit 33, which will be described later.

[0042] <Process for setting the target thickness of the material to be removed> The removal target thickness setting step S102 involves setting the first thickness obtained in the thickness measurement step S101 and the outer peripheral polishing target thickness W. AAccordingly, the overall target polishing thickness W is the thickness up to the flat surface obtained by polishing the polished surface 3 of the silicon carbide single crystal substrate 1. B This is the process of setting it up.

[0043] Overall polishing target thickness W B The target outer edge polishing thickness W obtained in the thickness measurement process S101 is shown. A The target thickness of the damage layer generated during the ion implantation process is set accordingly (e.g., several hundred nm). B This information is input to the indicator determination unit 33, which will be described later, for example, via a computer.

[0044] Overall polishing target thickness W B This is a desired amount that depends on the total thickness of the silicon carbide single crystal substrate 1, the crystal orientation, physical properties such as hardness and brittleness, the state of the damaged layer, and the polishing capacity of the polishing device 200. Furthermore, if the target thickness W of the outer periphery is due to some reason after polishing, A (For example, a few tens of nanometers) will not remain, so the overall polishing target thickness W B It is desirable to set it to have a margin of several hundred nanometers, for example.

[0045] <Installation Process> The assembly process S103 is a process of preparing and arranging the silicon carbide single crystal substrate 1, the polishing head 22, and the measuring instrument. The silicon carbide single crystal substrate 1 is set on a chuck plate (not shown) provided on the pressure surface of the pressure plate 27 of the polishing head 22, and is adsorbed and fixed in place.

[0046] When setting the silicon carbide single crystal substrate 1 on the chuck plate, a relative position adjustment mechanism (not shown) is used to adjust the vertical relative distance between the pressure surface 27a of the pressure plate 27 and the upper surface 25a of the polishing pad 25, for example by pulling the polishing head 22 vertically upward. After the silicon carbide single crystal substrate 1 is adsorbed and fixed, a sheet-shaped pressure distribution measuring sensor 23 is placed on the upper surface 25a of the polishing pad 25 at the point where the polished surface 3 of the silicon carbide single crystal substrate 1 will come into contact. After placing the sheet-shaped pressure distribution measuring sensor 23 on the upper surface 25a of the polishing pad 25, a relative position adjustment mechanism (not shown) is used to press the polished surface 3 of the silicon carbide single crystal substrate 1 against the upper surface of the sheet-shaped pressure distribution measuring sensor 23, for example by pushing the polishing head 22 vertically downward. In this way, the silicon carbide single crystal substrate 1 is sandwiched between the pressure plate 27 and the sheet-shaped pressure distribution measuring sensor 23.

[0047] Furthermore, when installing the sheet-shaped pressure distribution measurement sensor 23 on the polishing pad 25, if it is necessary to change the configuration due to wiring considerations such as the sensor cable, the sheet-shaped pressure distribution measurement sensor 23 may be installed on the polishing platen 21. In addition, to accurately display the pressure distribution between the silicon carbide single crystal substrate 1 and the sheet-shaped pressure distribution measurement sensor 23, alignment marks may be made on the sheet-shaped pressure distribution measurement sensor 23 in advance, or the center point of the silicon carbide single crystal substrate 1 may be estimated by superimposing the shape of the silicon carbide single crystal substrate 1 onto the obtained pressure distribution data.

[0048] <Test Loading Process> In the test loading process S104, the polishing head 22 is lowered to obtain a pressure reading Pr, and a load is applied to the silicon carbide single crystal substrate 1, which is located between the pressure plate 27 and the polishing pad 25. The pressure plate 27 is subjected to independent loading forces from a second load from the outer peripheral pressure mechanism 28 and a first load from the central pressure mechanism 29.

[0049] Figure 4 shows the distributed load when the silicon carbide single crystal substrate 1 is subjected to a load via the pressure plate 27 by the outer peripheral pressure mechanism 28 and the central pressure mechanism 29, after the relative position adjustment mechanism (not shown) is driven and the silicon carbide single crystal substrate 1 comes into contact with the pressure plate 27. The central part 6 is mainly subjected to the first load P by the central pressure mechanism 29. A The outer periphery 7 is subjected to a distributed load, and the outer periphery 7 is subjected to a second load P mainly by the outer periphery pressurizing mechanism 28. B It has a distributed load due to the first load P. In Figure 4, the first load P A and second load P B This is expressed as a concentrated or distributed load occurring at at least one point, but it can also be a uniformly distributed load or a uniformly variable distributed load.

[0050] The test loading process S104 involves measuring the pressure generated by this loading action. The pressure measurement uses a sheet-shaped pressure distribution measurement sensor 23 to measure the first pressure P applied to the central part 6 of the polished surface 3 by the loading. in and the second pressure P applied to the outer periphery 7 of the outer periphery of the central part 6 out Each of these is measured. The pressure reading Pr, which has the information read in this measurement (position on the matrix, pressure value, and display (load display A on each cell in the outer periphery, load display B on each cell in the center, or blank display)), is used by the pressure measuring unit 32 to calculate the pressure Ps (first pressure P, described later). in and second pressure P out It is converted to ) and transmitted to the indicator determination unit 33.

[0051] The pressure readings Pr, which are raw data of the pressure distribution obtained from the pressure detection elements 30 of each cell 23a, are input to the pressure measurement unit 32. The pressure measurement unit 32 may record the pressure readings Pr of each cell's pressure detection element 30 as pressure readings Pr(x,y), corresponding to the position (x coordinate, y coordinate) of each cell.

[0052] By mapping the cells 23a of the sheet-shaped pressure distribution measurement sensor 23 from which pressure readings Pr(x,y) are obtained, it is possible to determine which part of the sheet-shaped pressure distribution measurement sensor 23 is being loaded onto the polished surface 3 of the silicon carbide single crystal substrate 1. Based on this information, the positions of the cell 23a at the center of the silicon carbide single crystal substrate 1 and the cells 23a at the outer edge of the silicon carbide single crystal substrate 1 can be estimated. Furthermore, the pressure measurement unit 32 uses data obtained within a predetermined range from the cell 23a at the center of the sheet-shaped pressure distribution sensor 23a from which pressure readings Pr(x,y) are obtained to display the pressure P acting on the central part 6. Bi Group (P B1 , P B2 , P B3、 ..., P Bn ) and the data obtained from the cells on the outer periphery is used to represent the pressure P acting on the outer periphery 7. Ai Group (P A1 , P A2 , P A3、 ..., P Am Label it as ).

[0053] The pressure measuring unit 32 receives the pressure measurement value P labeled in this manner. B1 , P B2 , P B3、 ..., P Bn and P A1 , P A2 , P A3、 ..., P Am The values ​​are averaged to obtain the pressure calculation value Ps. In other words, the first pressure is the pressure display P Bi This is the average value for the group, and the second pressure is indicated by pressure P. Ai This is the average value for the group. The calculated pressure Ps is the first pressure P in and the second pressure P out The boundary line between the central portion 6 and the outer peripheral portion 7 can be determined, for example, by the ratio of the outer diameter of the silicon carbide single crystal substrate 1 to the outer diameter of the portion to be peeled off by hydrogen atom ablation.

[0054] In this way, the pressure reading Pr is converted to a calculated pressure value Ps and transmitted from the pressure measurement unit 32 to the index determination unit 33.

[0055] In this embodiment, the central region 6 is defined as the area where the diameter from the center is up to 80% of the outer diameter. Furthermore, if it is determined that the reliability of the pressure reading Pr(x,y) data of a cell is compromised because, for example, each cell crosses the boundary line between the central region 6 and the outer periphery 7, processing such as excluding the pressure data acquired by that cell (e.g., displaying a blank space) may be performed.

[0056] <Calibration process> In calibration step S105, the index determination unit 33 of the processing unit 300 determines the first pressure P in and second pressure P out Based on this, the first index C1 is determined, and the target thickness W of the outer perimeter polishing is determined. A and overall polishing target thickness W B The relationship with the second index C2, which is determined based on this, is judged, and the judgment command value Ci is set and output to the pressure control unit 31.

[0057] In this embodiment, the determination command value Ci is the second load P B This is a command to optimize the second load P. The second load P is determined by the judgment command value Ci. B The value may increase, decrease, or remain constant. The judgment command value Ci is set by determining its relationship with the first indicator C1 and the second indicator C2, which are described below.

[0058] The first index C1 is an index expressed by the following formula relating to the pressure acting on the polished surface 3.

[0059] [Mathematics 1] C1=P out / P in ×100(%)……(1)

[0060] As shown in equation (1), the first index C1 is equal to the second pressure P out The first pressure P in This shows the proportion of the total to the total, expressed as a percentage.

[0061] The second index C2 is an index related to the uneven shape of the surface to be polished 3, expressed by the following formula.

[0062] [Math 2] C2=(W A +W B ) / W B ×100(%)……(2)

[0063] As shown in equation (2), the target thickness W of the outer periphery is determined. A and overall polishing target thickness W B The sum of the total polishing target thickness W B This shows the proportion of the result as a percentage. In this embodiment, both equations (1) and (2) are shown using percentages, but the first index C1 and the second index C2 may be determined without using percentages.

[0064] The determination flow of the index determination unit 33 regarding the relationship between the first index C1 and the second index C2 in the calibration process S105 will be further explained.

[0065] Figure 6 is a flowchart showing the determination procedure in the calibration process of the manufacturing method of the silicon carbide single crystal substrate 1 according to the embodiment. The first index C1 and the second index C2 obtained in the test loading process S104 are first used by the pressure recording determination operator 33a to determine whether the absolute value of the difference between the first index C1 and the second index C2 is less than or equal to a predetermined threshold. If the value exceeds the predetermined threshold (for example, 10%) and the first index C1 is low, it is presumed that the residual layer 5 on the outer periphery 7 cannot be efficiently polished off, that is, the overall flatness of the silicon carbide single crystal substrate 1 is likely to deteriorate, and therefore the second load P is applied via the outer periphery pressurizing mechanism 28. B Set the judgment command value Ci to raise it.

[0066] Conversely, when the absolute value of the difference between the first index C1 and the second index C2 exceeds a predetermined threshold and the first index C1 is higher than the second index C2, it is presumed that the load on the outer periphery 7 is excessive, that is, the edges of the silicon carbide single crystal substrate 1 are prone to collapse. Therefore, the second load P on the outer periphery 7 is applied. BSet the determination command value Ci so as to decrease it. In the present embodiment, the predetermined threshold value is 10%, but this threshold value is a standard for ensuring flatness and can be appropriately set according to the required specifications.

[0067] When the pressure recording determination operator 33a does not satisfy the standard for ensuring flatness, the second pressure P out is regarded as inappropriate and the process proceeds to the pressure command determination operator 33b. The pressure command determination operator 33b determines whether the second index C2 is greater than the first index C1. When the second index C2 is greater than the first index C1 in the pressure command determination operator 33b, the second load P out is increased so as to increase the second pressure P B Set the determination command value Ci for increasing.

[0068] Conversely, when the second index C2 is smaller than the first index C1, the second load P out is decreased so as to decrease the second pressure P <00​​​​​​​​​​​​​​​​​​​​​​Regarding the adjustment, in addition to adjusting the load itself applied by each actuator of the central pressure mechanism 29 or the outer peripheral pressure mechanism 28, when using a hydraulic actuator or the like, it may also be possible to adjust the pressure of the hydraulic oil to each actuator.

[0070] When the flatness guarantee criterion is satisfied by the pressure recording determination operator 33a, the second pressure P out is recorded as an appropriate value and the process proceeds to the appropriate load step S106. Further, in addition to this appropriate second pressure P out , the first pressure P in , the outer peripheral polishing target thickness W A , the overall polishing target thickness W B , the first load P A and the second load P B and other performance data are recorded. When taking values close to the performance data in the test load step S104 newly performed for another silicon carbide single crystal substrate 1, the number of steps to reach the appropriate load step S106 may be shortened by using these as learned input data.

[0071] <Appropriate Load Step> After the determination of the appropriate second pressure P out is completed in this way, the sheet-like pressure distribution measurement sensor 23 is removed from above the polishing pad 25 of the polishing apparatus 200. Then, in the appropriate load step S106, the appropriate second load P B determined by the pressure recording determination operator 33a is loaded onto the silicon carbide single crystal substrate 1. After the loading is completed, polishing removal is performed.

[0072] Rotational power is applied to the polishing head shaft 26 by a head drive mechanism not shown in the figure, and it rotates about the head rotation axis R1 together with the polishing head 22 and the pressure plate 27.

[0073] On the silicon carbide single crystal substrate 1 adsorbed and fixedly held on the pressure surface of the pressure plate 27, the outer peripheral pressure mechanism 28 and the central pressure mechanism 29 apply the second load P B and the first load P by an actuator not shown in the figure that has received a command from the pressure control unit 31.A The first load P is applied and placed on the upper surface of the polishing pad 25. A and second load P B Following this, the polished surface 3 of the silicon carbide single crystal substrate 1 is polished (the polished surface 3 of the silicon carbide single crystal substrate 1 and the upper surface of the polishing pad 25 are rubbed against each other in the presence of polishing liquid and polished), thereby flattening the polished surface 3 of the silicon carbide single crystal substrate 1.

[0074] The polishing plate shaft 24 is powered by a rotational drive mechanism (not shown) and rotates together with the polishing platen 21 and polishing pad 25 around the polishing platen rotation axis R0. While the rotation direction of the polishing platen 21 and polishing pad 25 is usually limited to one direction, they may also be controlled to rotate in the opposite direction.

[0075] The polishing of the silicon carbide single crystal substrate 1 is carried out specifically as follows. During polishing, the silicon carbide single crystal substrate 1, which is fixedly held by an adsorption mechanism (not shown) on the pressure surface of the pressure plate 27, is pressed against the polishing pad 25, and the polishing platen 21 and polishing head 22 rotate respectively, while polishing agent is supplied from a polishing agent supply unit (not shown) to the center of the polishing pad 25 to polish the surface 3 of the silicon carbide single crystal substrate 1 and flatten the surface.

[0076] According to the method described above, by measuring the pressure distribution between the silicon carbide single crystal substrate and the polishing pad, as well as the thickness of the silicon carbide single crystal substrate, as a pre-process before polishing, and calculating the first and second indicators, it becomes possible to control the load and pressure applied to the residual layer during the polishing process with high precision and to determine appropriate values, thereby enabling quality control. This prevents edge rounding and over-polishing of the silicon carbide single crystal substrate, and allows for a polishing process that contributes to flattening within the allowable amount of polishing.

[0077] The embodiments described above can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in at least one of the scope and spirit of the present invention and the claims and their equivalents. [Explanation of symbols]

[0078] 1…Silicon carbide single crystal substrate, 2…Adsorption surface, 3…Surface to be polished, 4…Side, 5…Residual layer, 6…Center, 7…Outer periphery, 21…Polishing platen, 22…Polishing head, 22a…Inside of cylinder, 23…Sheet-shaped pressure distribution measurement sensor, 23a…Cell, 24…Platen shaft, 25…Polishing pad, 25a…Top surface, 26…Polishing head shaft, 27…Pressure plate, 27a…Pressure surface, 27b…Top surface, 28…Outer periphery pressurizing mechanism, 29…Center pressurizing mechanism, 30…Pressure detection element, 31…Pressure control unit, 32…Pressure measurement unit, 33…Indicator determination unit, 33a…Pressure record determination operator, 33b…Pressure command determination operator, 100…Manufacturing equipment, 200…Polishing equipment, 300…Processing unit, A…Load display on each cell in the outer periphery, B…Load display on each cell in the center, C1…First indicator, C2…Second indicator, P A ...first load, P B ...Second load, Pr...Pressure reading, Ps...Calculated pressure, R0...Surface plate rotation axis, R1...Head rotation axis, S101...Thickness measurement process, S102...Removal target thickness setting process, S103...Installation process, S104...Test loading process, S105...Calibration process, S106...Appropriate loading process, W A ...Target thickness for polishing the outer circumference, W B ...Target overall polishing thickness.

Claims

1. This includes a calibration process that determines the relationship between a first index obtained from a first pressure and a second pressure, and a second index obtained from a first thickness and a second thickness. The first pressure is the pressure applied to the central part of the substrate to be polished. The second pressure is the pressure applied to the outer periphery of the substrate to be polished. The first thickness is the thickness of the central part of the substrate to be polished. The second thickness is the thickness of the outer periphery of the substrate to be polished, which is located on the outer periphery side of the central part. A method for manufacturing a silicon carbide single crystal substrate.

2. In accordance with the aforementioned relationship, adjust at least one of the first load on the central part and the second load on the outer periphery. A method for manufacturing a silicon carbide single crystal substrate according to claim 1.

3. The second indicator is the overall target polishing thickness W Ｂ The target thickness for polishing the outer circumference is W Ａ When this is the case, the relation (W Ａ +W Ｂ ) / W Ｂ Determined by, A method for manufacturing a silicon carbide single crystal substrate according to claim 1.

4. The aforementioned relationship is the difference between the first indicator and the second indicator. Adjust at least one of the first load and the second load so that the difference is less than or equal to a predetermined value. A method for manufacturing a silicon carbide single crystal substrate according to claim 2.

5. The process includes measuring the first thickness of the central portion of the substrate to be polished and the second thickness of the outer periphery of the substrate to be polished, which is located on the outer periphery side of the central portion. A method for manufacturing a silicon carbide single crystal substrate according to claim 1.

6. The process includes a test loading step of measuring the first pressure applied to the central part of the substrate to be polished and the second pressure applied to the outer periphery of the substrate to be polished, respectively. A method for manufacturing a silicon carbide single crystal substrate according to claim 1.

7. A polishing head that applies a first load to the center of the head and a second load to the outer circumference of the head surrounding the center of the head, A polishing pad is positioned opposite the polishing head so as to be able to sandwich a silicon carbide single crystal substrate, and receives the first load and the second load to polish the surface of the silicon carbide single crystal substrate, A pressure control unit that adjusts at least one of the first load and the second load based on the first pressure acting on the polishing pad due to the first load, the second pressure acting on the polishing pad due to the second load, and the target polishing thickness of the silicon carbide single crystal substrate, A manufacturing apparatus for silicon carbide single crystal substrates, equipped with [specific features / equipment].

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