Method of manufacturing semiconductor crystal wafer

Abstract

To provide a method of manufacturing a semiconductor crystal wafer in which the semiconductor crystal wafer of high quality can be easily and securely manufactured.SOLUTION: A method of manufacturing an SiC wafer which is a semiconductor crystal wafer comprises a guideline forming process (STEP100 / Fig.1), a separation process (STEP110 / Fig.1), a first surface processing process (STEP120 / Fig.1), and a second surface processing process (STEP130 / Fig.1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing semiconductor crystal wafers by cutting wafers into slices from a semiconductor crystal ingot that has been ground into a cylindrical shape. [Background technology]

[0002] Conventionally, as a method for manufacturing a SiC wafer, which is this type of semiconductor crystal wafer, as shown in Patent Document 1 below, a method for manufacturing a SiC wafer is known, which includes, as a wafer shape formation process, an ingot formation process in which a mass of crystal-grown single crystal SiC is processed into a cylindrical ingot, a crystal orientation shaping process in which a notch is formed in part of the outer periphery to serve as a mark indicating the crystal orientation of the ingot, a slicing process in which the single crystal SiC ingot is sliced ​​and processed into thin, disk-shaped SiC wafers, a planarization process in which the SiC wafer is planarized using abrasive grains having a hardness less than the modified Mohs hardness, an imprint formation process in which an imprint is formed, and a chamfering process in which the outer periphery is chamfered, as well as a process-damaged layer removal process in which a process-damaged layer introduced into the SiC wafer in the preceding process is removed, and finally, as a mirror polishing process, a chemical mechanical polishing (CMP) process in which polishing is performed using a combination of the mechanical action of a polishing pad and the chemical action of a slurry. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-15646 Summary of the Invention [Problem to be solved by the invention]

[0004] However, such conventional SiC wafer manufacturing methods have the problem that they involve many complicated manufacturing steps, and the apparatus configuration is complicated, resulting in high manufacturing costs.

[0005] On the other hand, if the manufacturing process is simplified, it becomes difficult to consistently obtain the quality required for SiC wafers.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for manufacturing semiconductor crystal wafers that can easily and reliably produce high-quality semiconductor crystal wafers. [Means for solving the problem]

[0007] The method for producing a semiconductor crystal wafer of the first invention is a method for producing a semiconductor crystal wafer in which wafers are separated into slices from a semiconductor crystal ingot that has been ground into a cylindrical shape, a guideline forming step of forming cutting guidelines by scanning a focused point of a laser beam having a wavelength that is transparent to the semiconductor crystal ingot on a surface to be cut; a separating step of separating wafers into slices from the semiconductor crystal ingot along the cutting guide lines formed in the guide line forming step; Equipped with By the guideline forming process, The first modified regions are formed adjacent to each other at intervals where first cracks extending from the first modified regions formed by the focusing points of the laser beam do not overlap each other, and The second modified portion is formed between adjacent first modified portions so that a second crack extending from the second modified portion formed by the focal point where the laser beam is focused overlaps with the adjacent first crack.

[0008] According to the method for manufacturing a semiconductor crystal wafer of the first invention, conventionally, cracks extending from modified regions have connected or not connected randomly, making it difficult to ensure the smoothness of the surface even when the wafer is separated using the cracks as a means of separating the wafer. However, by forming first modified regions at intervals where the first cracks extending from the first modified regions do not overlap, and by forming second modified regions in the positions between them so that second cracks extending from the second modified regions overlap adjacent first cracks, it is possible to make the cracks extending from the modified regions overlap regularly, simply, and reliably.

[0009] Therefore, by separating the wafer using the regularly overlapping cracks, the smoothness of the wafer surface can be dramatically improved.

[0010] Thus, according to the method for producing a semiconductor crystal wafer of the first invention, the semiconductor crystal ingot can be separated into slices with high precision, and high-quality semiconductor crystal wafers can be produced simply and reliably.

[0011] The method for producing a semiconductor crystal wafer of the second invention is the method for producing a semiconductor crystal wafer of the first invention, When the semiconductor crystal ingot has a crystal orientation inclined at an off-angle with respect to the end face, in a cross section in which the first crack and the second crack extend in a direction perpendicular to the end face, the first cracks and the second cracks extend in a direction parallel to the crystal orientation; The second modified portion is formed in the guideline forming step so that the second crack overlaps with the adjacent first crack when projected onto the end face.

[0012] According to the method for manufacturing a semiconductor crystal wafer of the second invention, when a semiconductor crystal ingot has a crystal orientation that is inclined at an off-angle relative to its end face, the cracks are parallel to the crystal orientation, and therefore the cracks are parallel to each other and do not overlap in a connected form. However, by forming the second modified region so that both ends of the second crack overlap with the adjacent first crack in an end face projection view, it is possible to form continuous cracks that regularly leave only the shortest gap between the first crack and the second crack.

[0013] Therefore, the wafer can be easily separated by relying on the overlapping cracks, simply by applying an external force that destroys the regular gaps with the shortest distance, and the smoothness of the wafer surface can be dramatically improved.

[0014] Thus, according to the semiconductor crystal wafer manufacturing method of the second invention, even when the semiconductor crystal ingot has a crystal orientation that is inclined at an off-angle relative to the ingot end facets, the semiconductor crystal ingot can be separated into slices with high precision, and high-quality semiconductor crystal wafers can be manufactured simply and reliably.

[0015] The method for producing a semiconductor crystal wafer of the third invention is the method for producing a semiconductor crystal wafer of the second invention, The separating step includes a first external force applying step of applying a first external force in a direction perpendicular to the scanning direction so as to separate the semiconductor crystal ingot at the planned cutting surface; a second external force applying step of applying a second external force in a horizontal direction penetrating the first modified region 11 and the second modified region 21 while a first external force has been applied in the first external force applying step; The present invention is characterized by having the following.

[0016] According to the method for manufacturing a semiconductor crystal wafer of the third invention, the multiple first and second cracks running parallel to one another form a continuous crack that leaves only gaps of the shortest distance in a regular pattern, and therefore, in order to efficiently destroy such gaps, an external force is applied parallel to the cracks.

[0017] To generate an external force parallel to the crack, a first external force is applied in a direction perpendicular to the scanning direction, away from the wafer, and a second external force is applied laterally (horizontally) through the first modified area and the second modified area bounded by the continuous crack while the first external force is being applied. This causes the first and second external forces to act as shear stresses, allowing the wafer to slide easily along the continuous crack. In this way, the gap can be broken and the wafer can be easily separated using the overlapping cracks, dramatically improving the smoothness of the wafer surface.

[0018] Thus, according to the semiconductor crystal wafer manufacturing method of the third invention, even when the semiconductor crystal ingot has a crystal orientation that is inclined at an off-angle relative to the ingot end facets, the semiconductor crystal ingot can be separated into slices with high precision, and high-quality semiconductor crystal wafers can be manufactured simply and reliably. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a flowchart showing all steps of a method for manufacturing a SiC wafer (semiconductor crystal wafer) according to the present embodiment. [Figure 2] 2 is an explanatory diagram showing the guideline formation step in the SiC wafer manufacturing method of FIG. 1. [Figure 3] 2 is an explanatory diagram showing the guideline formation step in the SiC wafer manufacturing method of FIG. 1. [Figure 4] 2 is an explanatory diagram showing the details of a separation step in the method for producing the SiC wafer of FIG. 1. [Figure 5] 2 is an explanatory diagram showing the details of a surface processing step in the manufacturing method of the SiC wafer of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] As shown in FIG. 1, in this embodiment, the method for manufacturing a SiC wafer, which is a semiconductor crystal wafer, is a method for obtaining SiC wafers sliced ​​from a SiC ingot that has been ground into a cylindrical shape, and includes a guideline formation step (STEP 100 / FIG. 1), a separation step (STEP 110 / FIG. 1), a first surface processing step (STEP 120 / FIG. 1), and a second surface processing step (STEP 130 / FIG. 1).

[0021] The details of each step and the SiC wafer manufacturing apparatus of this embodiment will be described with reference to FIGS. First, as shown in FIG. 2, in the guideline formation step (STEP 110 / FIG. 1), cutting guidelines are formed on the surface to be cut.

[0022] The planned cutting surface may be parallel to the end face of the SiC ingot, or, if the SiC ingot has a crystal orientation tilted at an off-angle relative to the end face, a plane (c-plane) parallel to the off-angle tilted crystal orientation becomes the planned cutting surface. In other words, the c-plane is tilted at an off-angle relative to the end face of the SiC ingot.

[0023] 2 and 3 below, a case will be described in which the SiC ingot has a crystal orientation tilted at an off-angle relative to its end face.

[0024] In the guideline formation step (STEP 110 / FIG. 1), a cutting guideline is formed by scanning a laser beam having a wavelength that is transparent to the SiC ingot from its end face side along a scanning line on the intended cutting surface with the focused point. Note that the guideline means for forming the cutting guideline is made up of a laser oscillator that oscillates the laser beam and a condenser (lens) that condenses the laser beam inside the SiC ingot.

[0025] Specifically, in the guideline formation process, first, as shown in Figure 2 (Figure 2(A) is a skeleton diagram centered on a cross section including a modified portion parallel to the end face, and Figure 2(B) is a cross section including a crack in a direction perpendicular to the end face), a first modified portion 11 is formed by converging a laser beam to a focal point, and a first crack 12 extending from the first modified portion 11 parallel to the crystal orientation is formed.

[0026] At this time, the first cracks 12 are formed adjacent to each other at equal intervals as shown by the arrows in Figure 2(A) so that the first cracks 12 do not overlap each other, and the first cracks 12 have approximately the same height and width as shown by the arrows in Figure 2(B).

[0027] In this state, as shown in Figure 3 (Figure 3(A) is a skeleton diagram centered on a cross section including a modified area parallel to the end face, and Figure 3(B) is a cross section including a crack in a direction perpendicular to the end face), a second modified area 21 is formed between adjacent first modified areas 11, 11 by the focal point where the laser beam is focused, and a second crack 22 extending from the second modified area 21 parallel to the crystal orientation is formed.

[0028] At this time, second cracks 22 are formed at equal intervals as shown by the arrows in Figure 3(A) so that they overlap with adjacent first cracks 12, and the second cracks 22 have approximately the same height and width as shown by the arrows in Figure 3(B).

[0029] At this time, as shown by the arrows in Figure 3(A), the first modified areas 12 and the second modified areas 21 are aligned at equal intervals, and as shown by the arrows in Figure 3(B), the first cracks 12 and the second cracks 22 are aligned with approximately the same height and width.

[0030] That is, in the SiC ingot, the ends of adjacent first cracks 12 and second cracks 22 form continuous cracks in which only gap portions of approximately the shortest distance corresponding to the height width are left regularly.

[0031] In the subsequent separation step (STEP 110 / FIG. 1), wafers are separated from the SiC ingot in slices along the cutting guidelines formed in the guideline formation step (STEP 100 / FIG. 1).

[0032] Specifically, in an SiC ingot, the ends of adjacent first cracks 12 and second cracks 22 form a continuous crack that leaves only a regular gap of approximately the shortest distance corresponding to the height and width. Therefore, the SiC wafers can be easily separated by relying on the overlapping cracks with only an external force that destroys the regular gap of the shortest distance. However, the SiC wafers can be separated more efficiently by applying an external force in the appropriate direction, as shown in Figure 4.

[0033] Specifically, as shown in Figure 4, a first external force F is applied to the intended cutting surface in a direction away from the laser scanning direction (first external force application process), and while this first external force F1 is being applied, a lateral external force F2 is applied that penetrates the first modified area 11 and the second modified area 21 that are grouped together by the continuous crack (second external force application process), whereby the first external force F1 and the second external force F2 become shear stresses and the gap easily slides along the continuous crack.

[0034] The first external force is, for example, constituted by a jig or the like that fixes the SiC ingot and has a lifting surface that is lifted up via adhesive (double-sided tape) on the acting surface that applies the first external force to the end surface of the SiC ingot.

[0035] In addition, the second external force may be applied to the fixed SiC ingot to which the first external force is applied by a rod or the like that can be moved back and forth by an actuator, or simply by a hammer or the like.

[0036] In this way, by applying the first external force F1 and the second external force F2, the gap can be easily broken by shear stress, and the SiC wafer can be easily separated using the overlapping cracks. At the same time, the aligned first and second cracks, as well as the uniformly spaced continuous cracks, can dramatically improve the smoothness of the surface of the SiC wafer.

[0037] Next, as shown in FIG. 5, in the first surface processing step (STEP 120), the separated wafer 30 is subjected to mechanical polishing (high-precision grinding) on ​​the other surface 32 using one surface 31 of the separated surfaces as a support surface.

[0038] Specifically, in the first surface processing step (STEP 120), grinding is performed by a mechanical polishing device 50 (ultra-high synthesis, high precision grinding device) that performs mechanical polishing.

[0039] The mechanical polishing device 50 includes a spindle 51 and a diamond grinding wheel 53 on a platen 52 serving as a surface plate.

[0040] First, one surface 31 of the wafer 30 is supported by adsorption on a vacuum porous chuck 54, which is an adsorption plate of a spindle 51, with the other surface 32 being the lower surface, and the other surface 32 is ground with a diamond grindstone 53.

[0041] At this time, the spindle 51 and the diamond grinding wheel 53 are rotated by a drive device (not shown), and the spindle 51 is pressed against the diamond grinding wheel 53 by a compressor (not shown) or the like, thereby grinding the other surface 32.

[0042] After the grinding process, the diamond grindstone 53 may be dressed using a dresser or the like.

[0043] Furthermore, the mechanical polishing device 50 may have a functional water supply pipe so that multiple types of functional water can be used during processing, if necessary.

[0044] Next, in the second surface processing step (STEP 130), the other surface 32 of the wafer 30 that has been subjected to high-precision grinding in the first surface processing step is set as the upper surface, and the one surface 31 is subjected to high-precision grinding similar to that in the first surface processing step.

[0045] That is, the other surface 32 is attached to a vacuum porous chuck 54, which is an attachment plate of a spindle 51, with the other surface 32 serving as the upper surface, and the first surface 31 is ground with a diamond grindstone 53 with the first surface 31 serving as the lower surface.

[0046] In this case, too, dressing may be performed by pressing a dresser or the like against the diamond grinding wheel 53, if necessary.

[0047] According to the mechanical polishing (high-precision grinding) process in the first surface processing step (STEP 120) and the second surface processing step (STEP 130), one of the highly flat separated surfaces obtained in the separation step is used as a support surface (adsorption surface), and mechanical polishing (high-precision grinding) is sequentially performed on the remaining surfaces. This prevents so-called transfer and allows high-quality SiC wafers to be obtained, while also significantly simplifying the complicated manufacturing process that involves conventional free grinding stone processing, i.e., multiple lapping steps from the first to fourth stages.

[0048] More specifically, there is no need to change grinding stones to perform rough grinding or multiple finish grinding operations. For example, finishing can be performed directly in one grinding operation using a grinding stone of #30000 or higher. This is not only simple, but also has the advantage of being able to secure a large intrinsic semiconductor layer that can be used from the SiC wafer 30.

[0049] In the high-precision grinding process of the first surface processing step (STEP 120) and the second surface processing step (STEP 130), the size of the SiC wafer 30 is currently up to 8 inches, and wafers of each diameter are set according to the area of ​​the head (up to 12 inches are possible) and high-precision grinding process is performed.

[0050] The above is the details of the method for manufacturing a SiC wafer according to this embodiment. As explained in detail above, it is possible to precisely separate a SiC ingot into sliced ​​SiC wafers, and to easily and reliably manufacture high-quality SiC wafers.

[0051] In the method for manufacturing a SiC wafer according to this embodiment, after the series of processes described above, a chemical mechanical polishing (CMP) step and a wafer cleaning step may be carried out as necessary.

[0052] Furthermore, in this embodiment, a method for manufacturing a semiconductor crystal wafer has been described in which a SiC wafer is manufactured from a SiC ingot, but the semiconductor crystal is not limited to SiC, and may be gallium phosphate, indium phosphide, silicon, or other compound semiconductors. [Explanation of symbols]

[0053] 11...first modified portion, 12...first crack, 21...second modified portion, 22...second crack, 30...SiC wafer, 31...one side, 32...other side, 50...mechanical polishing device (ultra-high synthesis high precision grinding device), 51...spindle, 52...platen, 53...diamond grinding wheel, 54...vacuum porous chuck (suction plate), F1...first external force, F2...second external force.

Claims

1. A method for manufacturing a semiconductor crystal wafer, which comprises separating wafers into slices from a semiconductor crystal ingot that has been ground into a cylindrical shape, a guideline forming step of forming cutting guidelines by scanning a focused point of a laser beam having a wavelength that is transparent to the semiconductor crystal ingot on a surface to be cut; a separating step of separating wafers into slices from the semiconductor crystal ingot along the cutting guide lines formed in the guide line forming step; Equipped with By the guideline forming process, The first modified regions are formed adjacent to each other at intervals where first cracks extending from the first modified regions formed by the focusing points of the laser beam do not overlap each other, and A method for manufacturing a semiconductor crystal wafer, characterized in that a second modified portion is formed between adjacent first modified portions so that a second crack extending from the second modified portion formed by the focusing point of the laser beam overlaps with an adjacent first crack.

2. 2. The method for producing a semiconductor crystal wafer according to claim 1, When the semiconductor crystal ingot has a crystal orientation inclined at an off-angle with respect to the end face, in a cross section in which the first crack and the second crack extend in a direction perpendicular to the end face, the first crack and the second crack extend in a direction parallel to the crystal orientation; a guideline forming step of forming the second modified portion such that the second crack overlaps with the adjacent first crack when projected onto the end face;

3. 3. The method for producing a semiconductor crystal wafer according to claim 2, the separating step includes a first external force applying step of applying a first external force in a direction perpendicular to the scanning direction so as to separate the semiconductor crystal ingot at the planned cutting surface; a second external force applying step of applying a second external force in a horizontal direction penetrating the first modified region 11 and the second modified region 21 while a first external force has been applied in the first external force applying step; 1. A method for producing a semiconductor crystal wafer, comprising:

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