Manufacturing method of semiconductor crystal wafer

Abstract

The present invention provides a method for producing a semiconductor crystal wafer, which can easily and reliably produce a high-quality semiconductor crystal wafer. [Solution] A manufacturing method for a SiC wafer, which is a semiconductor crystal wafer, includes a guideline formation step (STEP 100 / Figure 1), a separation step (STEP 110 / Figure 1), a first surface processing step (STEP 120 / Figure 1), and a second surface processing step (STEP 130 / Figure 1).

Description

[Technical field]

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

[0002] Conventionally, as a manufacturing method for a SiC wafer, which is this type of semiconductor crystal wafer, as shown in Patent Document 1 below, a manufacturing method for a SiC wafer is known that includes, as a wafer shape forming step, an ingot forming step in which a lump of crystal-grown single crystal SiC is processed into a cylindrical ingot, a crystal orientation forming step in which a notch is formed in a part of the outer periphery to serve as a mark indicating the crystal orientation of the ingot, a slicing step in which the single crystal SiC ingot is sliced ​​and processed into a thin disk-shaped SiC wafer, a planarizing step in which the SiC wafer is planarized using abrasive grains having a hardness less than the modified Mohs hardness, an imprint forming step in which an imprint is formed, and a chamfering step in which the outer periphery is chamfered, next, as a process-affected layer removing step, a process-affected layer removing step in which the process-affected layer introduced into the SiC wafer in the preceding step is removed, and finally, as a mirror polishing step, a chemical mechanical polishing (CMP) step 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] JP 2020-15646 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, such conventional methods for manufacturing SiC wafers have problems in that the manufacturing steps are complicated 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 stably obtain the quality required for SiC wafers.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a method for manufacturing a semiconductor crystal wafer, which is capable of easily and reliably manufacturing a high-quality semiconductor crystal wafer. [Means for solving the problem]

[0007] The method for producing a semiconductor crystal wafer according to the first aspect of the present invention is a method for producing a semiconductor crystal wafer, which comprises separating wafers in slices from a semiconductor crystal ingot that has been ground into a cylindrical shape, and a guideline forming step of forming a cutting guideline 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 from the semiconductor crystal ingot in slices along the cutting guide lines formed by the guide line forming step; Equipped with By the guideline formation process, The first modified regions are formed adjacent to each other at intervals where first cracks extending from the first modified regions by the focusing points of the laser beam are not overlapped, and Between the adjacent first modified portions, a second crack extending from the second modified portion formed by the focusing point of the laser beam is overlapped with the adjacent first crack, and the second modified portion is formed. 、 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; The second modified portion is formed by the guideline forming step so that the second crack overlaps with the adjacent first crack when projected onto the end face, so that ends of the adjacent first crack and second crack form a continuous crack in which only a gap portion of the shortest distance corresponding to a height width is regularly left between the ends of the adjacent first crack and second crack. .

[0008] According to the method for manufacturing a semiconductor crystal wafer of the first invention, conventionally, cracks extending from the modified portion would sometimes connect randomly and sometimes not connect, making it difficult to ensure the smoothness of the surface even if the wafer was separated using the cracks as a remedy. However, by forming a first modified portion at a distance such that the first cracks extending from the first modified portion do not overlap, and forming a second modified portion in the position between them such that a second crack extending from the second modified portion overlaps an adjacent first crack, it is possible to make the cracks extending from the modified portion overlap in a regular, simple and reliable manner.

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

[0010] In this way, according to the method for producing a semiconductor crystal wafer of the first aspect of the 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.

[0012] Also, No. 1 According to the method for manufacturing a semiconductor crystal wafer of the 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 when projected onto the end face, it is possible to form a continuous crack that regularly leaves only a gap of the shortest distance between the first crack and the second crack.

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

[0014] Thus, the 1According to the method for producing a semiconductor crystal wafer of the present invention, even when the semiconductor crystal ingot has a crystal orientation that is inclined at an off-angle relative to the end facets of the ingot, the semiconductor crystal ingot can be separated into slices with high precision, and high-quality semiconductor crystal wafers can be produced simply and reliably.

[0015] No. 2 The method for producing a semiconductor crystal wafer of the present invention is as follows: 1 In the invention, The separation step includes a first external force application 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 intended 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 is applied in the first external force applying step; The present invention is characterized by having the following.

[0016] No. 2 According to the method for manufacturing a semiconductor crystal wafer of the invention, the multiple first and second cracks running parallel to one another form a continuous crack that regularly leaves only gaps of the shortest distance, and therefore, in order to efficiently destroy such gaps, an external force is applied parallel to the cracks.

[0017] In order to generate an external force parallel to the crack, a first external force is applied in a direction perpendicular to the scanning direction, and a second external force is applied in a lateral (horizontal) direction that penetrates the first modified area and the second modified area that are grouped together by the continuous crack while the first external force is being applied, so that the first external force and the second external force become shear stresses and the gap slides easily along the continuous crack. In this way, the gap can be broken and the wafer can be easily separated by relying on the overlapping cracks, and the smoothness of the wafer surface can be dramatically improved.

[0018] In this way, 2According to the method for producing a semiconductor crystal wafer of the present invention, even when the semiconductor crystal ingot has a crystal orientation that is inclined at an off-angle relative to the end face of the ingot, the semiconductor crystal ingot can be separated into slices with high precision, and high-quality semiconductor crystal wafers can be produced simply and reliably. [Brief description of the drawings]

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

[0020] As shown in FIG. 1, in this embodiment, the manufacturing method for a SiC wafer, which is a semiconductor crystal wafer, is a method for obtaining SiC wafers sliced ​​from a SiC ingot 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 manufacturing apparatus for the SiC wafer 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 a surface to be cut.

[0022] The intended cutting surface may be parallel to the end face of the SiC ingot, or when the SiC ingot has a crystal orientation tilted at an off angle with respect to the end face, the intended cutting surface may be a plane (c-plane) parallel to the off-angled crystal orientation. In other words, the c-plane is tilted at an off angle with respect 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 inclined 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 from the end face side of the SiC ingot along a scanning line on the intended cutting surface with a focused point. Note that a laser oscillator that oscillates the laser beam and a condenser (lens) that condenses the laser beam inside the SiC ingot are used as guideline means for forming the cutting guideline.

[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 concentrating the laser beam at a focusing point, and a first crack 12 extending parallel to the crystal orientation from the first modified portion 11 is formed.

[0026] At this time, the first modified regions 11 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 by the focusing point of the laser beam between adjacent first modified areas 11, 11, and a second crack 22 extending parallel to the crystal orientation is formed from the second modified area 21.

[0028] At this time, second modified areas 21 are formed at equal intervals as shown by the arrows in Figure 3(A) so that the second cracks 22 overlap with the 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, the first modified areas 12 and the second modified areas 21 are aligned at equal intervals, as shown by the arrows in Figure 3(A), and the first cracks 12 and the second cracks 22 are aligned with approximately the same height and width, as shown by the arrows in Figure 3(B).

[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 regularly left.

[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 a SiC ingot, the ends of adjacent first cracks 12 and second cracks 22 form a continuous crack that leaves only a regular gap portion of approximately the shortest distance corresponding to the height 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 an 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 perpendicular to 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 penetrating 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 that fixes the SiC ingot and has a lifting surface that is lifted up via an adhesive (double-sided tape) on an 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 configured to be freely moved forward and backward by an actuator, or may be applied 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 the shear stress, and the SiC wafer can be easily separated using the overlapping cracks. At the same time, the smoothness of the surface of the SiC wafer can be dramatically improved due to the aligned first and second cracks as well as the uniformly spaced continuous cracks.

[0037] Next, as shown in FIG. 5, in a first surface processing step (STEP 120), the separated wafer 30 is subjected to mechanical polishing (high-precision grinding) on ​​the remaining other surface 32 while one surface 31 of the separated surfaces is used 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 being adsorbed to a vacuum porous chuck 54 which is an adsorption plate of a spindle 51, and the other surface 32 is ground by a diamond grindstone 53.

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

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

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

[0044] Next, in a second-side processing step (STEP 130), the other side 32 of the wafer 30 that has been subjected to high-precision grinding in the first-side processing step is set as the upper surface, and the first side 31 is subjected to high-precision grinding similar to that in the first-side 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 an upper surface, and the one surface 31 is ground with a diamond grindstone 53 with the one surface 31 serving as a lower surface.

[0046] In this case as well, dressing may be performed by pressing a dresser or the like against the diamond grindstone 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 separated surfaces having high flatness 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, thereby preventing so-called transfer and obtaining high-quality SiC wafers, and also significantly simplifying the complicated manufacturing process such as the conventional free grinding stone processing, i.e., multiple lapping 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 process using a grinding stone of #30,000 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 undergo high-precision grinding processing.

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

[0051] In the method for producing a SiC wafer according to the present 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] In addition, 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. However, 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, comprising the steps of: separating wafers into slices from a semiconductor crystal ingot that has been ground into a cylindrical shape; a guideline forming step of forming a cutting guideline 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 from the semiconductor crystal ingot in slices along the cutting guide lines formed by the guide line forming step; Equipped with By the guideline formation process, The first modified regions are formed adjacent to each other at intervals where first cracks extending from the first modified regions by the focusing points of the laser beam are not overlapped, and The second modified portion is formed between adjacent first modified portions such that a second crack extending from the second modified portion formed by a focusing point at which the laser beam is focused overlaps with the adjacent first crack, 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 formation step of forming the second modified portion such that the second crack overlaps with the adjacent first crack when projected onto the end face, thereby forming a continuous crack between the ends of the adjacent first crack and second crack, the continuous crack regularly leaving only a gap portion of the shortest distance corresponding to a height width.

2. 2. A method for producing a semiconductor crystal wafer according to claim 1, comprising the steps of: The separation step includes a first external force application 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 intended 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 is applied in the first external force applying step; 2. A method for producing a semiconductor crystal wafer comprising the steps of:

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