TWI905030B - Method for manufacturing semiconductor crystal wafer - Google Patents

Abstract

The present invention provides a method for manufacturing semiconductor crystal wafer that is capable of easily and reliably manufacturing high-quality semiconductor crystal wafer.The method for manufacturing SiC wafer which is semiconductor crystal wafer 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).

Description

Methods for manufacturing semiconductor wafers

This invention relates to a method for manufacturing a semiconductor wafer by slicing a semiconductor ingot (ingot) that has been ground into a cylindrical shape.

Conventionally, as a method for manufacturing SiC wafers, which belong to this type of semiconductor crystalline wafer, as shown in Patent Document 1 below, there is a known method for manufacturing SiC wafers, wherein the wafer shape forming step includes: a wafer forming step, which processes a bulk monocrystalline SiC grown crystallize into a cylindrical wafer; a crystal orientation forming step, which forms a cut on a portion of the outer periphery to serve as a marker indicating the crystal orientation of the wafer; and a slicing step, which slices the monocrystalline SiC wafer to process it into a thin, round SiC wafer. The process includes: a wafer planarization step, which uses abrasive grains that do not reach the modified Mohs hardness to planarize the SiC wafer; an etch formation step, which forms an etch; and a chamfering step, which chamfers the outer periphery; next, a work-modified layer removal step, which removes the work-modified layer introduced into the SiC wafer in the previous steps; and finally, a mirror polishing step, which includes a chemical mechanical polishing (CMP) step that uses both the mechanical action of the polishing pad and the chemical action of the slurry for polishing. [Prior Art Documents][Patent Documents]

Patent Document 1: Japanese Patent Application Publication No. 2020-15646

[Problem to be solved by the invention] However, in this conventional SiC wafer manufacturing method, the manufacturing steps are numerous and complex, which leads to problems such as complex device configuration and increased manufacturing costs.

On the other hand, simplifying the manufacturing process makes it difficult to consistently achieve the quality required for SiC wafers.

Therefore, the purpose of this invention is to provide a method for manufacturing semiconductor wafers that can easily and reliably produce high-quality semiconductor wafers. [Means used to solve the problem]

The method for manufacturing a semiconductor wafer of the first invention involves separating a wafer from a semiconductor ingot that has been ground into a cylindrical shape by slicing. The method comprises: a lead wire forming step, in which a focal point formed by focusing laser light of a wavelength with penetrability to the semiconductor ingot is scanned on a predetermined cutting surface to form a slicing lead wire; and a separation step, in which a slicing lead wire is formed along the aforementioned lead wire. The wafer is separated from the aforementioned semiconductor crystalline ingot in a slice-like manner by cutting the lead wire formed in the lead wire forming step; wherein, by means of the aforementioned lead wire forming step, the first modified portion is formed adjacent to each other with a spacing where the first cracks extending from the first modified portion do not overlap, wherein the first modified portion is formed by a focusing point formed by focusing the aforementioned laser light; by means of the aforementioned lead wire forming step, in the adjacent first modified portions The second modified portion is formed such that a second crack extending from the second modified portion overlaps with the adjacent first crack, wherein the second modified portion is formed by a focusing point formed by focusing the aforementioned laser light; in the case where the aforementioned semiconductor crystal ingot has a crystal orientation that is tilted at an offset angle relative to its end face, in a cross-section in which the aforementioned first crack and the aforementioned second crack extend in a direction perpendicular to the aforementioned end face: the aforementioned first... The direction in which the first crack and the second crack extend is parallel to the crystal orientation. The second crack and the adjacent first crack overlap when viewed in projection of the end face. The second modified part is formed by the guide wire forming step, so that the ends of the adjacent first crack and the second crack form a continuous crack with a gap that is only regularly left between them, which is equivalent to the shortest distance of the height amplitude.

Previously, cracks extending from the modified portion could randomly connect or not connect with each other. Therefore, even if the wafer was separated by cracks, it was difficult to guarantee the smoothness of its surface. However, according to the semiconductor wafer manufacturing method of the first invention, the first modified portion is formed by firstly forming the first modified portion with a gap where the first cracks extending from the first modified portion do not overlap with each other, and then forming the second modified portion by overlapping the second crack extending from the second modified portion with the adjacent first crack at the position in between. This makes it easy and reliable to make the cracks extending from the modified portion regularly overlap.

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

Thus, according to the semiconductor wafer manufacturing method of the first invention, semiconductor wafers can be separated into slices with good precision, and high-quality semiconductor wafers can be manufactured easily and reliably.

Furthermore, when the semiconductor wafer has a crystal orientation that is tilted at an offset angle relative to its end face, the crack becomes parallel to the crystal orientation. Therefore, the cracks will be parallel to each other and will not overlap in a connected manner. However, according to the semiconductor wafer manufacturing method of the first invention, by forming a second modified part in such a way that the two ends of the second crack overlap with the adjacent first crack when viewed in projection of the end face, a continuous crack can be formed that only leaves a gap between the shortest distance of the first crack and the second crack in a regular manner.

Therefore, by simply using an external force that disrupts the regular shortest distance gap, wafers can be easily separated by overlapping cracks, and the smoothness of the wafer surface can be dramatically improved.

Thus, according to the semiconductor wafer manufacturing method of the first invention, even in the case of a crystal orientation that is tilted at an offset angle relative to the end face of the ingot, the semiconductor ingot can be separated into slices with good precision, and high-quality semiconductor wafers can be manufactured easily and reliably.

The method for manufacturing a semiconductor wafer of the second invention is based on the first invention. The separation step includes: a first external force application step, in which a first external force is applied in a direction perpendicular to the scanning direction, such that the semiconductor wafer is separated at the predetermined cutting surface; and a second external force application step, in which a second external force is applied in a horizontal direction penetrating the first modified portion and the second modified portion, after the first external force has been applied by the first external force application step.

According to the semiconductor wafer manufacturing method of the second invention, a plurality of first and second cracks extending parallel to each other form a continuous crack with only a regular gap between them. Therefore, in order to efficiently destroy this gap, an external force is applied parallel to the crack.

To generate this external force parallel to the crack, a first external force is applied in a direction perpendicular to the scanning direction. While the first external force is applied, a second external force is applied that penetrates the first and second modified portions connected by the continuous crack in a horizontal direction. This causes the first and second external forces to become shear stresses, allowing the gap to be easily sheared along the continuous crack. In this way, the gap can be destroyed, and the wafer can be easily separated by the overlapping cracks, resulting in a significant improvement in the smoothness of the wafer surface.

Thus, according to the semiconductor wafer manufacturing method of the second invention, even when the crystal orientation has an offset angle relative to the end face of the ingot, the semiconductor ingot can be separated into slices with good precision, and high-quality semiconductor wafers can be manufactured easily and reliably.

As shown in Figure 1, in this embodiment, the method for manufacturing a SiC wafer, which is a semiconductor crystalline wafer, is a method for obtaining a SiC wafer cut out in a slice shape from a SiC ingot that has been ground into a cylindrical shape. The method includes: a lead wire formation step (STEP100/Figure 1), a separation step (STEP110/Figure 1), a first surface processing step (STEP120/Figure 1), and a second surface processing step (STEP130/Figure 1).

The details of each step and the SiC wafer fabrication apparatus of this embodiment will be explained with reference to Figures 2 to 5. First, as shown in Figure 2, cut leads are formed on the cut predetermined surface by the lead forming step (STEP100/Figure 1).

Apart from the case where the predetermined cutting surface is parallel to the end face of the SiC ingot, when the SiC ingot has a crystal orientation tilted at an off angle relative to its end face, the surface parallel to the tilted crystal orientation (c-plane) becomes the predetermined cutting surface. That is, the c-plane is tilted at an off angle relative to the end face of the SiC ingot.

Furthermore, Figures 2 and 3 below illustrate the case where a SiC ingot has a crystal orientation that is tilted at an offset angle relative to its end face.

The lead wire formation step (STEP100/Fig. 1) involves scanning along the scanning line of the predetermined cutting surface from the end face of the SiC ingot to a focal point formed by focusing a laser beam with a penetrating wavelength onto the SiC ingot, thereby forming a cut lead wire. Alternatively, as a means of forming the cut lead wire, a laser oscillator that oscillates the aforementioned laser beam, or a concentrator (lens) that focuses the laser beam inside the SiC ingot, can be used.

Specifically, in the lead wire formation step, firstly, as shown in FIG2 (FIG2(A) is a structural view centered on a cross-section including a modified portion parallel to the end face, and FIG2(B) is a cross-sectional view including a crack in a direction perpendicular to the end face), a first modified portion 11 is formed by focusing a laser beam to form a focal point, and a first crack 12 is formed extending from the first modified portion 11 in a manner parallel to the crystal orientation.

At this time, the first crack 12 is formed such that the first crack 12 does not overlap with each other, as shown by the arrow in Figure 2(A), by making the first modified part 11 adjacent to each other at equal intervals, and as shown by the arrow in Figure 2(B), the first crack 12 have approximately the same height range.

In this state, as shown in Figure 3 (Figure 3(A) is a structural diagram centered on a cross-section containing the modified portion parallel to the end face, and Figure 3(B) is a cross-sectional view containing the crack in a direction perpendicular to the end face), a second modified portion 21 is formed between adjacent first modified portions 11, 11 by a focusing point formed by focusing laser light, and a second crack 22 is formed extending from the second modified portion 21 in a manner parallel to the crystal orientation.

At this time, as shown by the arrow in Figure 3(A), the second modified part 21 is formed at equal intervals so that the second crack 22 overlaps with the adjacent first crack 12, and as shown by the arrow in Figure 3(B), the second crack 22 has approximately the same height.

Furthermore, at this time, as shown by the arrow in Figure 3(A), the first modified part 11 and the second modified part 21 are arranged in a neat and evenly spaced manner, and as shown by the arrow in Figure 3(B), the first crack 12 and the second crack 22 are arranged in a neat and evenly spaced manner with approximately the same height.

That is, the SiC ingot is a continuous crack formed by the ends of the first crack 12 and the second crack 22 adjacent to each other, which are separated by a gap of approximately the shortest distance of the height amplitude.

The next separation step (STEP110/Fig. 1) involves separating the wafer from the SiC ingot in a slice shape along the cut leads formed by the lead forming step (STEP100/Fig. 1).

Specifically, since the ends of the first crack 12 and the second crack 22 adjacent to each other form a continuous crack with only a gap of approximately the shortest distance equivalent to the height amplitude, the SiC wafer can be easily separated by the overlapping cracks simply by breaking the regular shortest distance gap. As shown in Figure 4, the SiC wafer can be efficiently separated by applying an external force in an appropriate direction.

Specifically, as shown in Figure 4, in the predetermined cutting surface, a first external force F is applied in a direction away from the direction perpendicular to the laser scanning direction (first external force application step), and while this first external force F1 has been applied, a second external force F2 is applied in the transverse direction through the first modified part 11 and the second modified part 21 connected by the continuous crack (second external force application step), so that the first external force F1 and the second external force F2 become shear stresses, and the gap is simply cut along the continuous crack.

The first external force is formed, for example, by means of an auxiliary tool, which fixes the SiC ingot and has a lifting surface that is pulled up by an adhesive (double-sided tape) on the end face of the SiC ingot where the first external force is applied.

In addition, although the second external force can also be applied to the SiC ingot that is fixed and subjected to the first external force by using an actuator to form a rod that can move freely, it can also be easily applied by a hammer or the like.

In this way, by applying the first external force F1 and the second external force F2, the gaps can be easily broken by shear stress, and the SiC wafer can be easily separated by the overlapping cracks. Furthermore, the smoothness of the SiC wafer surface can be dramatically improved by the neatly arranged first and second cracks, as well as the continuous cracks with consistent spacing.

Next, as shown in Figure 5, for the separated wafer 30, one side 31 of the separation surface is used as a support surface by the first surface processing step (STEP120), and the remaining other side 32 is mechanically polished (high-precision grinding process).

Specifically, in the first surface processing step (STEP120), grinding is performed by a mechanical polishing device 50 (ultra-high precision grinding device) that applies mechanical polishing.

The mechanical polishing device 50 has a spindle 51 and a diamond polishing stone 53 on a platen 52 that serves as a platform.

First, one side 31 of the wafer 30 is used as the upper surface and supported by a vacuum porous chuck 54 that is adsorbed onto the spindle 51 as an adsorption plate. The other side 32 is used as the lower surface and is ground by a diamond grinding stone 53.

At this time, the spindle 51 and the diamond grinding stone 53 are rotated by a drive device not shown, and the spindle 51 is pressed against the diamond grinding stone 53 by a compressor not shown, thereby performing grinding on the other side 32.

In addition, after grinding, the diamond grinding stone 53 can be dressed using a dresser or similar tool.

In addition, the mechanical polishing device 50 may also have functional water supply piping as needed, so that multiple types of functional water can be used during processing.

Next, in the second surface processing step (STEP130), the other side 32 of the wafer 30, which has already undergone high-precision grinding in the first surface processing step, is used as the upper surface, and the same high-precision grinding process as in the first surface processing step is applied to one side 31.

That is, the other side 32 is used as the upper surface, which is adsorbed onto the vacuum porous suction cup 54 of the spindle 51 as the adsorption plate, and the other side 31 is used as the lower surface, which is ground by the diamond grinding stone 53.

In this case, the dressing tool or similar device can be pressed against the diamond polishing stone 53 as needed to apply the dressing.

The mechanical polishing (high-precision grinding) process of the first surface processing step (STEP120) and the second surface processing step (STEP130) uses either of the highly flat separation surfaces obtained by the separation step as the support surface (adsorption surface), and mechanical polishing (high-precision grinding) is applied to the remaining surfaces in sequence. This prevents the so-called transfer and obtains high-quality SiC wafers. It also greatly simplifies the complex manufacturing steps of the previous free grinding stone processing, which is one to four times of fine grinding (lapping).

More specifically, there is no need to replace the grinding stone for rough grinding and multiple finishing grinding. For example, a grinding stone of ♯30000 or higher can be used to directly perform finishing in one grinding process. Therefore, it is not only simple, but also has the advantage of greatly ensuring the availability of intrinsic semiconductor layers from wafer 30.

In addition, in the high-precision grinding process of the first surface processing step (STEP120) and the second surface processing step (STEP130), the size of the SiC wafer 30 is currently up to 8 inches, and the wafers of each diameter are set according to the area of the head (up to 12 inches) to perform high-precision grinding process.

The above details the manufacturing method of SiC wafers according to this embodiment. As explained in detail above, SiC ingots can be separated into sliced SiC wafers with good precision, and high-quality SiC wafers can be manufactured easily and reliably.

In addition, in the SiC wafer manufacturing method of this embodiment, a chemical mechanical polishing (CMP) step or a wafer cleaning step may be performed as needed after one of the above-mentioned series of processes.

Furthermore, although this embodiment has described a method for manufacturing SiC wafers from SiC ingots as semiconductor crystalline wafers, the semiconductor crystalline wafer is not limited to SiC, and may also be gallium arsenide, indium phosphide, silicon, or other compound semiconductors.

11: First Modified Section 12: First Crack 21: Second Modified Section 22: Second Crack 30: SiC Wafer (Wafer) 31: One Side 32: The Other Side 50: Mechanical Polishing Device (Ultra-High Precision Grinding Device) 51: Mandrel 52: Table 53: Diamond Grinding Stone 54: Vacuum Porous Chuck (Adsorption Plate) F1: First External Force F2: Second External Force STEP 100: Guide Wire Forming Step STEP 110: Separation Step STEP 120: First Side Machining Step STEP 130: Second Side Machining Step

Figure 1 is a flowchart showing the overall steps of the manufacturing method of SiC wafer (semiconductor wafer) of this embodiment.

Figure 2 is an explanatory diagram showing the lead wire formation step in the SiC wafer fabrication method of Figure 1. Figure 3 is an explanatory diagram showing the guide line formation step in the SiC wafer fabrication method of Figure 1. Figure 4 is an explanatory diagram showing the separation step in the SiC wafer fabrication method of Figure 1. Figure 5 is an explanatory diagram showing the surface processing step in the SiC wafer fabrication method of Figure 1.

STEP 100: Guide wire forming step STEP 110: Separation step STEP 120: First surface machining step STEP 130: Second surface machining step

Claims (2)

A method for manufacturing a semiconductor wafer involves separating a wafer from a semiconductor ingot that has been ground into a cylindrical shape using a slicing method. The method comprises: a lead wire formation step, in which a focal point formed by focusing laser light of a wavelength penetrating the semiconductor ingot is scanned across a predetermined slicing surface to form a slicing lead wire; and a separation step, in which the wafer is separated along the shape of the aforementioned lead wire. The wafer is separated from the aforementioned semiconductor crystalline ingot in a slice-like manner by cutting the leads formed in the aforementioned lead-forming step; wherein, by means of the aforementioned lead-forming step, the first modified portions are formed adjacent to each other with a spacing where the first cracks extending from the first modified portions do not overlap, wherein the first modified portions are formed by focusing the aforementioned laser light; and by means of the aforementioned lead-forming step, in the adjacent first modified portions The second modified portion is formed such that a second crack extending from the second modified portion overlaps with the adjacent first crack, wherein the second modified portion is formed by a focusing point formed by focusing the aforementioned laser light; in the case where the aforementioned semiconductor crystal ingot has a crystal orientation tilted at an offset angle relative to its end face, in a cross-section in which the aforementioned first crack and the aforementioned second crack extend in a direction perpendicular to the aforementioned end face, the aforementioned first... The direction in which the first crack and the second crack extend is parallel to the crystal orientation. The second crack and the adjacent first crack overlap when viewed in projection of the end face. The second modified part is formed by the guide wire forming step, so that the ends of the adjacent first crack and the second crack form a continuous crack with a gap that is only regularly left between them, which is equivalent to the shortest distance of the height amplitude. The method for manufacturing a semiconductor wafer as described in claim 1, wherein the separation step comprises: a first external force application step, wherein a first external force is applied in a direction perpendicular to the scanning direction, such that the semiconductor wafer is separated at the predetermined cutting surface; and a second external force application step, wherein a second external force is applied in a horizontal direction penetrating the first modified portion and the second modified portion, after the first external force has been applied by the first external force application step.