JP7685576B2 - Chamfering device with blast unit and chamfering method - Google Patents

Description

The present invention relates to a high-precision chamfering device and method for chamfering the edge of various materials such as silicon, sapphire, compounds, and glass, particularly plate-shaped workpieces such as semiconductor wafers and glass panels.

To prevent chipping during handling, semiconductor wafers such as silicon wafers used in the production of semiconductor devices are chamfered by grinding the edges, and then polished to a mirror finish. In other words, in the semiconductor manufacturing process, from wafer production to device manufacturing, quality improvement of edge characteristics is an essential process.

Currently, silicon is the mainstream material for wafers, but in recent years, production of wafers with various properties such as sapphire, glass, SiC, and GaN has also increased, and conventional processing methods optimized for processing silicon wafers are not sufficient. In particular, in the case of wafers made of high-hardness materials such as SiC, the grinding wheels quickly wear out and their lifespan becomes shorter, which is a direct cause of increased wafer manufacturing costs. In addition, in the case of wafers made of brittle materials such as GaN, the wafers cannot withstand the processing load and break, resulting in reduced yields. Furthermore, when a wafer breaks and the fragments collide with the grinding wheel, it can lead to damage or failure of the grinding wheel and the device itself.

For both the hard and brittle materials mentioned above, the processing (feed) speed must be slowed down to prevent wear on the grinding wheel and damage to the wafer, resulting in reduced throughput. Meanwhile, in recent years, the demands for quality on the edge of semiconductor wafers have been increasing, and conventional technology is unable to fully meet these demands.

In normal grinding, the chamfered portion is ground with the main surface of the wafer W perpendicular to the rotation axis of the resin grinding wheel, but in this case, grinding marks in the circumferential direction are likely to occur on the chamfered portion. For this reason, it is known to perform so-called helical grinding, in which, for example, a resin-bonded grinding wheel (resin grinding wheel) is tilted relative to the wafer to grind the chamfered portion of the wafer. For example, Patent Document 1 describes how helical grinding reduces processing distortion in the chamfered portion compared to normal grinding and improves the surface roughness of the chamfered portion.

In addition, in order to prevent chipping and cracking and polish the sides of a hard brittle material substrate, a method is known in which an elastic abrasive is sprayed from a spray nozzle along with compressed gas toward the side of a workpiece made of a hard brittle material substrate, colliding with the workpiece to polish the side of the workpiece, in which the elastic abrasive is sprayed toward the processing area at a processing point on the side of the workpiece in a spray direction that forms a predetermined inclination angle with respect to a contact line perpendicular to the width direction line of the side, and is described in Patent Document 2.

JP 2016-190284 A JP 2013-22684 A

In the above-mentioned conventional technology, the one described in Patent Document 1 leaves scratches from the diamond abrasive grains in the grinding wheel, called streaks, on the processed part as a damaged layer, which manifests itself in the form of a worsening of surface roughness. The appearance of these streaks cannot be avoided even with a finishing grinding wheel. In addition, since the grinding wheel continues to rotate around its axis, the abrasive grains inside it each move repeatedly along the same trajectory. Therefore, if even a part of the grinding wheel has a defect such as chipping or dulling, the damage (surface roughness) of the edge of the wafer worsens, abnormal streaks or scratches continue to appear intermittently, or it causes the wafer to break.

Furthermore, even if the grinding wheels were used under normal conditions, they would gradually wear down and the shape of the grooves would collapse, causing the edge shape of the wafer to become non-conforming after processing. In particular, the resin-bonded grinding wheels used for finishing were prone to wear and had a short lifespan.

In the method described in Patent Document 2, elastic abrasive material is sprayed onto the side from the direction of the contact line perpendicular to the width direction line, and the edge is chamfered and polished after chamfering. Therefore, it was not possible to sufficiently improve the shape precision of the edge and reduce streaks. In particular, when machining the chamfered slope of the edge on the side of the workpiece, the trajectory of the elastic abrasive material is obstructed and it can even bounce back, making it difficult to improve the surface roughness and flatness of the machined surface.

The object of the present invention is to provide a chamfering device with a blast unit that solves the problems of the conventional technology described above, improves the shape accuracy of the edge of the wafer W, which is a plate-shaped workpiece, improves surface roughness, eliminates waviness, and reduces streaks.

The configuration of the present invention to achieve the above objective is as follows:

[1] A chamfering device with a blast unit, comprising: a processing unit that performs chamfering by grinding the chamfered slopes of the edge portion of the wafer so that they become upper and lower slopes with a predetermined chamfer angle; and a blast unit that sprays the elastic abrasive onto each of the upper and lower slopes of the rotating wafer using a spray nozzle fixed in a direction that intersects with the scratches formed on the upper and lower slopes, respectively, at an angle other than 90 degrees and that is smaller than the chamfer angle so as to follow each of the upper and lower slopes, in order to suppress jumping of the elastic abrasive containing abrasive grains for polishing into an elastic base material due to scratches including streaks and undulations, thereby adjusting the amount of cutting by the elastic abrasive.
[2] When the elastic abrasive is sprayed onto an orientation flat on the wafer, the rotation of the wafer is stopped, and the spray nozzle is moved back and forth linearly in the direction of the orientation flat of the wafer to spray the elastic abrasive onto the orientation flat at an angle that intersects with the scratches formed on the upper and lower slopes, respectively, other than perpendicularly. This is the chamfering device with a blast unit described in [1].
[3] The chamfering device with a blast unit described in [1], in which, when the elastic abrasive is sprayed into a notch provided in the wafer, the rotation of the wafer is stopped and the spray nozzle is oscillated at a predetermined speed so that the center of rotation of the spray nozzle is the center point of curvature at the apex of the notch of the wafer, and the elastic abrasive is sprayed into the notch.
[4] A chamfering device with a blast unit as described in [1], comprising an upper holding plate and a lower holding plate which sandwich the wafer from above and below when the elastic abrasive is sprayed by the blast unit, the upper holding plate and the lower holding plate being shaped like a truncated cone, the angle of the truncated cone being equal to or less than the chamfering angle of the wafer, and the size of the bottom of the truncated cone being large enough to cover the portion of the wafer to be machined.
[5] A chamfering method comprising: performing chamfering processing by grinding so that the chamfered slopes of an edge portion of a wafer become upper and lower slopes with a predetermined chamfer angle; and spraying the elastic abrasive material onto each of the upper and lower slopes of the rotating wafer in a direction that intersects with the scratches formed on the upper and lower slopes at an angle other than 90 degrees and that is smaller than the chamfer angle so as to run along each of the upper and lower slopes, in order to suppress jumping of the elastic abrasive material containing abrasive grains for polishing into an elastic base material caused by scratches including streaks and undulations and adjust the amount of cutting by the elastic abrasive material.

Another aspect of the present invention is a chamfering device with a blast unit that chamfers the edge of a wafer, and includes a processing section that grinds the chamfered slopes of the edge so that they become upper and lower slopes with a predetermined chamfering angle (V), and a blast unit that sprays an elastic abrasive material, which is an elastic base material with dispersed abrasive grains, using a spray nozzle. The blast unit sprays the elastic abrasive material onto the upper and lower slopes in a predetermined spray direction (D) after grinding and shaping the upper and lower slopes.

In the above, it is preferable that the blast unit is equipped with a spray nozzle having two or more elastic abrasive nozzles and has a mechanism for spraying in any direction from the nozzles.

Furthermore, in the above, it is preferable that the injection nozzles have one facing the upper slope and one facing the lower slope, and each is set to have a predetermined injection direction and position.

Furthermore, in the above, it is preferable that the injection nozzle facing the upper slope and the injection nozzle facing the lower slope are provided on independent nozzle tables, and are fixed so that the injection direction is at a predetermined position.

Furthermore, in the above, it is preferable that the blast unit has an upper holding plate and a lower holding plate that sandwich the wafer from above and below when spraying the elastic abrasive material, the upper holding plate and the lower holding plate are shaped like a truncated cone, the angle of the truncated cone is equal to or less than the chamfer angle of the wafer, and the bottom surface is the same size as the processed portion of the wafer.

Furthermore, in the above, it is preferable that the elastic abrasive material is composed of the abrasive grains and a base material with particles of 2 mm or less, the base material being gelatin or rubber, the abrasive grains being dispersed in the base material or held on the surface, and the grain size of the abrasive grains being 0.1 to 20 μm.

Furthermore, in the above, assuming a contact line passing through the processing point of the chamfer slope, it is preferable that the spraying direction of the elastic abrasive is set so that the angle θ with respect to the contact line or the scratches on the chamfer slope is 5° or more and 80° or less with respect to the rotation direction of the wafer, and the angle r corresponding to the chamfer angle is (V-30°) or more and (V-10°) or less, where V is the chamfer angle.
However, for the angle θ, see FIGS. 9 and 11, and for the angle r, see FIGS.

Furthermore, in the above, it is preferable that the angle θ is 8°±2°.

Furthermore, in the above, it is preferable that the relative humidity be 60 to 80% when spraying the elastic abrasive material.

Furthermore, in the above, it is preferable that the blast unit is provided in the processing section or in a cleaning section that cleans the wafer after the chamfering process.

Furthermore, in the above, if the wafer has an orientation flat shape, when spraying the elastic abrasive onto the orientation flat, it is preferable to stop the rotation of the wafer and move the spray nozzle back and forth linearly in the direction of the orientation flat.

Furthermore, in the above, if the wafer has a notch shape, it is preferable to perform polishing of the notch by stopping the rotation of the wafer and oscillating the injection nozzle at a predetermined speed so that the center of rotation of the injection nozzle is the center point of the curvature at the apex of the notch.

The present invention also provides a method for chamfering the edge of a wafer, in which the edge of the wafer is ground so that the chamfered slopes of the edge become upper and lower slopes with a predetermined chamfering angle, and after the upper and lower slopes are ground and shaped, an elastic abrasive is sprayed onto the upper and lower slopes in a predetermined spray direction.

According to the present invention, after grinding the edge of the wafer so that the chamfered slopes become upper and lower slopes, elastic abrasive is sprayed onto the upper and lower slopes in a specified spray direction, which improves the shape precision of the edge of the wafer, improves surface roughness, eliminates waviness, and reduces streaks, enabling a highly smooth mirror polish. As a result, the quality of the edge can be improved even with high-hardness and brittle materials.

1 is a plan view showing an overall configuration of a chamfering device according to an embodiment of the present invention; FIG. 2 is a perspective view showing the configuration of processing units 16A and 16B in one embodiment. FIG. 4 is an explanatory diagram showing a state in which the end surface of the wafer W has been ground. FIG. 2 is a plan view showing the positional relationship between the blast unit 21 and the wafer W. 13 is a side view showing how the upper inclined surface Wu is polished. FIG. FIG. 13 is a side view showing a state in which the lower slope Wd is polished. 1 is a diagram showing the relationship between the jet direction and the processed surface of a wafer W in conventional polishing. 4 is a diagram showing the relationship between the spray direction and the processing surface of a wafer W according to an embodiment; FIG. 4 is a perspective view showing details of the ejection direction of the elastic abrasive material according to the embodiment. FIG. 1 is a perspective view showing the ejection direction of an elastic abrasive according to the prior art (Patent Document 2). FIG. 13 is an explanatory diagram showing the relationship between the streaks Ws on the chamfered slope and the ejection direction of the elastic abrasive. FIG. 11 is a side view showing the relationship between the chamfer angle V and the ejection direction of the elastic abrasive. FIG. 4 is an explanatory diagram showing polishing of an orientation flat portion. FIG. 4 is an explanatory diagram showing polishing of a notch portion. Polishing conditions in one embodiment. Optical microscope photograph of the workpiece surface after grinding. An optical microscope photograph of the surface polished at an angle θ=0° and r=30°. An optical microscope photograph of the surface polished at an angle θ=90°. An optical microscope photograph of the surface polished at an angle θ = 45°. An optical microscope photograph of the processed surface polished at an angle θ = 8°. Optical microscope photograph of the workpiece surface polished at low humidity. Optical microscope photograph of the workpiece surface polished under high humidity conditions.

Figure 1 is a plan view showing the overall configuration of a chamfering device with a blast unit 10 according to one embodiment of the present invention. As shown in the figure, the chamfering device with a blast unit 10 is composed of a supply and recovery section 12, a pre-alignment section 14, processing sections 16A and 16B, a notch polishing section 18, a cleaning section 20, a post-measurement section 22, and a transport section 24. The chamfering device with a blast unit 10 also includes an operation panel, a control device, etc., which are not shown.

The supply and recovery section 12 supplies the wafers W to be chamfered from the wafer cassette 30 and recovers the chamfered wafers W to the wafer cassette 30. As shown in FIG. 1, the supply and recovery section 12 has four cassette tables 32, 32, ... and one supply and recovery robot 34.

Wafer cassettes 30, 30, ... are set on four cassette tables 32, 32, .... The wafer cassettes 30, 30, ... store a large number of wafers W to be chamfered. The supply/recovery robot 34 takes out one wafer W from each wafer cassette 30 set on the cassette tables 32, 32, ... and supplies it to the pre-alignment section 14. The supply/recovery robot 34 then stores the chamfered wafers W from the post-measurement section 22 into the wafer cassette 30.

The supply and recovery robot 34 is equipped with a three-axis rotating transport arm 36, which is equipped with a suction pad (not shown) on its upper surface. The transport arm 36 holds the wafer W by vacuum adsorbing the back surface of the wafer W with this suction pad. The transport arm 36 is also mounted on a slide block 40 that is movable along a guide rail 38, and the slide block 40 is driven to move in the front-to-back direction (Y-axis direction). The transport arm 36 can move forward and backward, up and down, and rotate while holding the wafer W, and the wafer W is transported by combining these movements.

The pre-alignment unit 14 measures the thickness of the wafer W to be chamfered and performs pre-alignment. This pre-alignment unit 14 is composed of a measurement table 50, a sensor 52, and a notch detection sensor 54. The measurement table 50 is configured to be rotatable and move up and down freely, and suction-holds the back surface of the wafer W and rotates the wafer W around its central axis. The sensor 52 is composed of a pair of capacitance sensors, one above the other, and measures the distance to the front and back surfaces of the wafer W. The notch detection sensor 54 is composed of a laser sensor, and detects the position of the notch or orientation flat of the wafer W held and rotated on the measurement table 50.

The processing units 16A and 16B are arranged in parallel on the front of the chamfering device with blast unit 10, and each performs chamfering of the wafer W. The processing units 16A and 16B have the same configuration, and each is composed of a wafer feed device 60 and a grinding device 62.

The notch polishing section 18 performs finish processing on the notch portion of the wafer W. The notch polishing section 18 is composed of a wafer feed device 70 and a notch polishing unit 72. The wafer feed device 70 has a chuck table 74 that suction-holds the wafer W. The notch polishing unit 72 has a notch polishing head 76.

The cleaning unit 20 cleans the wafer W after chamfering. The cleaning unit 20 is equipped with a spin cleaning device 80. The spin cleaning device 80 rotates the wafer W held on the cleaning table 82 and sprays a cleaning liquid onto the surface of the wafer W, thereby peeling off and removing dirt adhering to the surface of the wafer W.

The post-measurement section 22 measures the diameter of the chamfered wafer W. The post-measurement section 22 is composed of a diameter measuring device 84 that measures the diameter of the wafer W and a measurement table 86 that holds the wafer W and rotates and moves it up and down, and measures the diameter of the wafer W using the diameter measuring device 84.

The transport section 24 transports the wafers W to each section of the chamfering device with blast unit 10. The transport section 24 is composed of a grinding transfer section 100, a notch transfer section 102, a cleaning transfer section 104, and a storage transfer section 106.

The grinding transfer unit 100 transports the wafer W that has been prealigned in the prealignment unit 14 to each processing unit 16A, 16B. The grinding transfer unit 100 is composed of a horizontal guide 110, a slide block 112 (not shown) that slides along the horizontal guide 110, and a transfer arm 114 that is mounted on the slide block.

The slide block 112 slides along the horizontal guide 110. A suction pad 116 is provided at the tip of the transfer arm 114. The transfer arm 114 moves horizontally and up and down while holding the wafer W to transport the wafer W.

The notch transfer unit 102 transports the wafers W that have been chamfered in each processing unit 16A, 16B to the notch polishing unit 18. The notch transfer unit 102 is composed of a horizontal guide 120, a slide block 122 that slides along the horizontal guide 120, and a transfer arm 124 that is provided on the slide block 122.

The slide block 122 slides along the horizontal guide 120. A suction pad 126 is provided at the tip of the transfer arm 124. The transfer arm 124 can move horizontally, vertically, and rotate while holding the wafer W, and transports the wafer W by combining these movements. As a result, the wafer W that has been chamfered in each processing section 16A, 16B is transported to the notch polishing section 18 while being held by the transfer arm 124.

The cleaning transfer section 104 transports the wafer W whose notch has been finished in the notch polishing section 18 to the cleaning section 20. The cleaning transfer section 104 is composed of a horizontal guide 130, a slide block 132 that slides along the horizontal guide 130, and a transfer arm 134 provided on the slide block 132.

The slide block 132 slides along the horizontal guide 130. A suction pad 136 is provided at the tip of the transfer arm 134. The transfer arm 134 transports the wafer W while holding the wafer W. The wafer W, whose notch has been finished in the notch polishing section 18, is transported to the cleaning section 20 while being held by the transfer arm 134.

The storage transfer section 106 transports the wafers W cleaned in the cleaning section 20 to the post-measurement section 22. The storage transfer section 106 is composed of a horizontal guide 120 shared with the notch transfer section 102, a slide block 142 that slides along the horizontal guide 120, and a transfer arm 144 provided on the slide block 142.

The slide block 142 slides along the horizontal guide 120. A suction pad 146 is provided at the tip of the transfer arm 144. The transfer arm 144 transports the wafer W while holding the wafer W. As a result, the wafer W cleaned in the cleaning section 20 is transported to the post-measurement section 22 while being held by the transfer arm 144.

Next, the configuration of the processing units 16A and 16B will be described with reference to FIG. 2. FIG. 2 is a perspective view showing the configuration of the processing units 16A and 16B. The processing units 16A and 16B include a wafer feed device 60 and a grinding device 62.

The wafer feed device 60 has a chuck table (wafer table) 150 that holds the wafer W by suction. The chuck table 150 is driven by a driving means (not shown) to move in each of the forward/backward direction (Y-axis direction), left/right direction (X-axis direction), and up/down direction (Z-axis direction). The chuck table 150 is driven by a chuck table drive motor 152 to rotate around its central axis.

The grinding device 62 is disposed at a predetermined distance in the Y-axis direction from the chuck table 150 of the wafer feed device 60. The grinding device 62 has a rough grinding spindle 156 that is driven to rotate by a rough grinding motor 154. The rough grinding spindle 156 is configured to be movable in both the forward and backward directions (Y-axis direction) and the up and down directions (Z-axis direction). A peripheral rough grinding wheel 158 that roughly processes (roughly grinds) the end face of the wafer W is attached to the rough grinding spindle 156. The peripheral rough grinding wheel 158 has multiple peripheral rough grinding grooves formed on its outer periphery, and the end face of the wafer W is roughly ground by pressing the outer periphery of the wafer W against these grooves.

The outer periphery rough grinding wheel 158 is made of a material mainly composed of metal powder such as Fe, Cr, Cu, etc., mixed with diamond abrasive grains. The material of the tool is one that can be processed by the outer periphery rough grinding wheel 158.

Figure 3 is an explanatory diagram showing the state in which the edge of the wafer W has been shaped by grinding, where (a) is the cross-sectional shape of the chamfered portion of the wafer W, and of the chamfered slopes, Wu is the upper slope of the edge, Wd is the lower slope of the edge, and Wc is the side. (b) shows an example of the surface roughness Wr of the upper slope Wu. Similarly, (c) shows the streaks Ws on the upper slope Wu, where scratches from the diamond abrasive grains in the grinding wheel remain as a damaged layer. In addition, since the abrasive grains in the grinding wheel each move repeatedly along the same trajectory, if there is a defect such as a chip or dullness in even a part of the grinding wheel, abnormal streaks Ws or scratches will continue to appear intermittently, or may cause damage to the wafer W.

In particular, resin-bonded grinding wheels used in finishing processes in conventional technology are prone to wear, and the grinding wheels gradually wear down, causing the shape of the grooves to collapse. As a result, after processing, the shape of the edge of the wafer W becomes incongruent, and the lifespan is short. In addition to the streaks Ws, there are cases where "waviness," which is a large wavy irregularity that appears on the processed surface, occurs.

Furthermore, in the case of wafers W made of brittle materials such as GaN, the wafers W cannot withstand the processing load and break, resulting in a decrease in yield. In addition, when the wafers W break, if the broken pieces collide with the grinding wheel, this can lead to damage or breakdown of the grinding wheel and the device itself. In addition, with both high-hardness and brittle materials, the processing (feed) speed must be slowed down to prevent wear on the grinding wheel and damage to the wafers W, resulting in a decrease in throughput.

Therefore, the chamfering device with blast unit 10 is equipped with a blast unit 21 that injects and collides an abrasive material into either the processing section 16A, 16B or the cleaning section 20. FIG. 4 is a plan view showing the positional relationship between the blast unit 21 and the wafer W, FIG. 5 is a side view showing the state of polishing the upper slope Wu, and FIG. 6 is a side view showing the state of polishing the lower slope Wd. The blast unit 21 injects an elastic abrasive material 300, which is an elastic base material with abrasive grains dispersed therein, or an elastic abrasive material 300, which is an elastic base material with abrasive grains attached to its surface, together with compressed gas toward the chamfered slope of the wafer W, and collides with the elastic abrasive material 300 to polish the chamfered slope of the edge portion. In other words, the chamfering device with blast unit 10 grinds and shapes the upper slope Wu and lower slope Wd, which are the chamfered slopes, at a predetermined chamfering angle V, and then injects the elastic abrasive material 300 into the upper slope Wu and lower slope Wd in a predetermined injection direction.

The blast unit 21 is installed on the nozzle table 222 and positioned at a predetermined distance in the radial direction from the wafer W. The blast unit 21 is equipped with injection nozzles 223, 224 that have two or more injection ports for the elastic abrasive 300 so that the upper slope Wu and the lower slope Wd can be polished. The abrasive has a mechanism for injecting the elastic abrasive 300 in any direction from each injection port of the injection nozzles 223, 224 by compressed gas or centrifugal force.

The nozzle table 222 can move in the XY directions as shown by the arrows in FIG. 4. The injection nozzles 223 and 224 have their injection directions three-dimensionally variable in the Z direction in FIG. 5 by the height of the injection nozzle and the rotation axis 229. The injection nozzle 223 is set to a predetermined injection direction and position toward the upper slope Wu, and the injection nozzle 224 is set to a predetermined injection direction and position toward the lower slope Wd. The nozzle table 222 moves each time the upper slope Wu and the lower slope Wd are polished.

In the embodiment described above, the injection nozzles 223 and 224 are provided on one nozzle table 222. However, two independent nozzle tables 222 may be provided, and the injection nozzles 223 and 224 may be separated from each other. In this case, there is no need to move the nozzle table 222, and each nozzle may be fixed so that its injection direction is in a predetermined position.

The wafer W is held on the holding table 226 by being sandwiched from above and below by an upper holding plate 227 and a lower holding plate 228. The holding table 226 is rotated by being driven by a holding motor 225. The holding unit 230 is configured to be movable in both the forward and backward directions (Y-axis direction) and the upward and downward directions (Z-axis direction).

The upper holding plate 227 and the lower holding plate 228 are frustoconical, and sandwich the wafer W with their bottom surfaces, which are the same size as the non-edge portion (the portion to be processed) of the wafer W. The angle of the frustoconical shape is equal to or less than the chamfer angle V. This prevents the elastic abrasive 300 from colliding with the non-edge portion. Furthermore, the trajectory of the elastic abrasive 300 is not impeded, and the elastic abrasive 300 abrasive sliding along the edge portion does not collide with the upper holding plate 227 and the lower holding plate 228 and bounce back toward the edge portion again. Furthermore, it is preferable that the surfaces of the upper holding plate 227 and the lower holding plate 228 are ceramic-coated.

The direction of injection of the elastic abrasive 300 and its action will be explained. The elastic abrasive 300 is composed of abrasive grains and a base material with particles of 2 mm or less. The base material is gelatin or rubber, etc., which is mainly composed of elastic protein, and the elastic abrasive 300 is used with abrasive grains dispersed in the base material or held on the surface. The abrasive grains are diamond, CBN, GC, etc., with a grain size equivalent to #3000 to 1200 and a grain size of 0.1 to 20 μm. Figure 7 is a diagram showing the relationship between the injection direction and the processed surface (surface roughness Wr) of the wafer W in conventional polishing, and Figure 8 is a diagram showing the relationship between the injection direction and the processed surface (surface roughness Wr) of the wafer W according to one embodiment.

In conventional polishing, the spray direction is approximately perpendicular to the machined surface as shown by arrow 301 in Figure 7. In this method, the elastic abrasive 300 strongly impacts the machined surface to exert a cutting force. However, the elastic abrasive 300 jumps as shown by arrow 302 on the machined surface, especially in areas with large surface roughness as streaks Ws. Patent Document 2 utilizes this effect to cut and chamfer the edge, or to polish a surface that has already been chamfered. For this reason, it has been difficult to improve the surface roughness of the chamfered slope of the edge and the flatness of the machined surface.

In one embodiment, as shown in FIG. 8, the elastic abrasive 300 is sprayed at a low angle along the processing surface as indicated by arrow 303. Therefore, the elastic abrasive 300 sprayed from the spray nozzles 223, 224 disperses stress and begins to deform quickly after arriving at the processing surface, and jumping is suppressed as it slides over a long distance on the processing surface as indicated by arrow 304. In other words, the elastic abrasive 300 deforms when it collides with the workpiece (wafer W), and slides over the workpiece surface to apply the abrasive grains. This prevents the abrasive grains from cutting too deeply into the workpiece, making it difficult for deep streaks Ws to remain on the workpiece, and enables highly smooth mirror polishing.

The chamfering device with blast unit 10 mainly processes semiconductor wafers. The workpiece is a substrate made of a material that is hard and brittle, and is suitable for substrates made of a material that is prone to chipping and cracking during grinding. The material of the workpiece is suitable for semiconductor materials including single crystal silicon, polycrystalline silicon, SiC, Ga2O3, sapphire, GaN, and GaAs. Other suitable materials include GaSb, InP, LT, LN, Ge, glass, ceramics, MgO, ZnO, quartz, LBO, BBO, BGO, CaF2, MgF2, LiF, BaF2, CeF3, KBr, GGG, YAG, ZnSe, ZnTe, ZnS, STO, YSL, LoB, etc. The wafer W shape types available are circle, notch, orientation flat, SOI, and the edge shape can be terrace, boat-shaped, etc.

Figure 9 is a perspective view showing details of the spray direction D of the elastic abrasive 300 according to one embodiment, and Figure 10 is a perspective view showing the spray direction D of the elastic abrasive 300 according to the prior art (Patent Document 2). Comparing Figures 9 and 10, the features of the processing method using the chamfering device 10 with a blast unit will be explained. The processing method is characterized in that the elastic abrasive 300 is sprayed in a spray direction D that forms a predetermined angle θ and angle r with respect to the processing points on the chamfering slopes of the edge portion of the wafer W, i.e., the upper slope Wu and the lower slope Wd (see Figure 3).

Figure 9 shows polishing of the upper slope Wu, where the processing point is a point on the upper slope Wu, and the contact line τ is assumed to pass through the processing point. The spray direction D of the elastic abrasive 300 is set so that the angle θ with respect to the contact line τ, or the streak Ws on the upper slope Wu, is 5° to 80°, preferably 8°±2°, with respect to the rotation direction φ of the wafer W. Furthermore, the spray nozzle 223 (see Figure 4) is set so that the spray direction D is such that the angle r corresponding to the chamfer angle V of the upper slope Wu is (V-30°) to (V-10°). The same applies to polishing of the lower slope Wd.

Then, to polish the entire circumference, the wafer W is rotated in the rotation direction φ at a predetermined speed. Since the injection direction D is fixed, this action moves the processing point of the wafer W. The lower slope Wd is polished in the same manner as the upper slope Wu, by moving the nozzle table 222 in the XY directions (see Figure 3). Note that a relative humidity of 60 to 80% during polishing is desirable in order to allow the elastic abrasive 300 to slide efficiently on the processing surface.

Figure 10 is a similar diagram to Figure 9, showing the injection direction D according to the conventional technology (Patent Document 2). Unlike Figure 9, in which the processing point is a point on the upper slope Wu, in this case the side surface Wc of the workpiece (wafer W) is the processing point. Also, Figure 10 assumes a width direction line H passing through the processing point on the side surface Wc, and a contact line T that is perpendicular to the width direction line H and in contact with the processing point. The injection direction D of the elastic abrasive 300 intersects with the width direction line H at the processing point, and a predetermined inclination angle ξ with respect to the contact line T is set to an angle of 2 to 60° in consideration of a decrease in cutting performance. Note that in this example, the injection direction D and the direction of the streaks Ws coincide with each other.

Figure 11 is an explanatory diagram showing the relationship between the streaks Ws on the beveled slope and the spray direction D of the elastic abrasive 300. (a) shows the case where the direction of the streaks Ws and the spray direction D of the elastic abrasive 300 coincide with the rotation direction φ at angle θ = 0°, (b) shows the angle θ = 90°, and (c) shows the angle θ = 45° (for spray direction D and angle θ, see Figure 9). In the case of (a), the streaks Ws are relatively large and deep scratches on the processed surface, so even the elastic abrasive 300 cannot polish away the streaks Ws.

In (b), the injection direction D is in a direction that erases the streaks Ws, but the sliding distance of the elastic abrasive 300 becomes short, and the cut of the abrasive grains must be made larger. In the case of (c), the sliding distance of the elastic abrasive 300 is increased, and it is possible to prevent the elastic abrasive 300 from jumping due to the streaks Ws.

Therefore, by making the angle θ relatively small relative to the direction of the streaks Ws, as in (c), the streaks Ws are less likely to remain, making it possible to polish to a highly smooth mirror surface. However, if θ is made too small, the state of (a) will result, and it will be difficult to remove the streaks Ws. As a result of repeated experiments through trial and error, it was found that an angle θ of 5° to 80° is practical, and that an angle of approximately 8°, or 8°±2°, is suitable for obtaining a highly smooth mirror surface.

Figure 12 is a side view showing the relationship between the chamfer angle V and the spray direction D of the elastic abrasive 300. As explained in Figure 8, it is desirable to spray the elastic abrasive 300 at a low angle so as to follow the machining surface. However, since the chamfer slope forms an angle V with the horizontal plane of the wafer W, if the spray direction D is set so that the angle r between the spray direction D and the horizontal plane of the wafer W is equal to the angle V, the amount of cutting by the elastic abrasive 300 becomes too small. Therefore, the spray direction D needs to balance the cutting force of the elastic abrasive 300 and the action due to the sliding of the abrasive grains. Therefore, it is desirable to set the angle r with respect to the chamfer angle V to be greater than (V-30°) and less than (V-10°).

As described above, after grinding the chamfered slope on the edge of the wafer W, the chamfered slope is blast-polished using an elastic abrasive 300, which reduces the scratches Ws that occur during grinding and improves surface roughness. In addition, the processed surface is polished flat and waviness is eliminated. Therefore, even with a wafer W made of brittle material, the shape precision of the edge can be improved and chipping due to handling, etc. can be prevented, improving quality.

In addition, blast polishing does not have the problems that are unique to processing with precision diamond grinding wheels, so it is possible to prevent wear on the grinding wheels and damage to the wafers W and improve yields. Furthermore, if the finishing process is replaced from precision diamond grinding wheels to blast polishing, the processing time can be shortened and high-rate processing can be performed.

Figure 13 is an explanatory diagram showing polishing of the orientation flat OF portion of an orientation flat shaped wafer W. Polishing is performed by stopping the rotation of the wafer W. Since the orientation flat OF portion is linear, the elastic abrasive 300 is sprayed by moving the spray nozzle 223 or 224 linearly back and forth in the X direction, that is, in the direction of the orientation flat OF. The spray direction D of the elastic abrasive 300 is at an angle θ with respect to the direction of the circular portion of the wafer W, the streak Ws, as in Figure 11.

Figure 14 is an explanatory diagram showing the polishing of a notch portion of a notched wafer W in which a notch WN is provided instead of an orientation flat OF. Polishing is performed by stopping the rotation of the wafer W and setting the angle θ of the spray direction D with respect to the contact line τ or streak Ws to 90°. For example, the spray nozzle 223 or 224 is swung at a predetermined speed to polish the apex of the notch WN, which is the center point Ot of its curvature. The movement of the processing point during polishing is faster than when polishing the circular portion of the wafer W, and the processing point is moved back and forth to repeat polishing.

The following describes an example in which the chamfered edge of a wafer W is processed using the chamfering device 10 with a blast unit of the present invention.

The workpiece was a semiconductor wafer made of SiC (silicon carbide). Figure 15 shows the detailed polishing conditions. The shaping process by grinding the chamfered portion was performed using a diamond wheel (grindstone). The surface roughness after grinding for shaping was 0.137 μm in arithmetic mean roughness Ra and 0.703 μm in maximum height Rz. Figure 16 is an optical microscope photograph of the workpiece surface after grinding. The arrow in the figure indicates the processing direction, and numerous streaks Ws can be seen.

Figure 17 is an optical microscope photograph of the surface to be polished with a jet direction D of θ = 0°, r = 30° (see Figure 9). The polishing conditions were that the base material of the elastic abrasive 300 had an average particle size of 300 μm and was made of gelatin. The abrasive grains were diamond with a grain size of #3000, and were dispersed in the base material or attached to the surface. The jet speed was 2000 m/min, and the humidity was 60%. After polishing, the arithmetic mean roughness Ra was 0.059 μm and the maximum height Rz was 0.234 μm, which is an improvement, but the striations Ws (see Figure 3) are still visible in the optical microscope photograph of Figure 17.

Figure 18 shows the same conditions but with θ = 90°. After polishing, the arithmetic mean roughness Ra is 0.045 μm, the maximum height Rz is 0.192 μm, and the streaks Ws are smoother at both the top and bottom than in Figure 17 when the injection direction D is θ = 0°, but the center part still remains.

Figure 19 shows the same conditions but with θ = 45°. After polishing, the arithmetic mean roughness Ra is 0.032 μm and the maximum height Rz is 0.185 μm, which shows the effect of the elastic abrasive 300 having a longer sliding distance, and is in a practical state.

Figure 20 shows the same conditions but with θ = 8°. After polishing, the arithmetic mean roughness Ra is 0.023 μm, the maximum height Rz is 0.156 μm, and the central streaks Ws that were partially present in Figure 19 have largely disappeared. This state is optimal in terms of reducing streaks Ws, improving surface roughness, eliminating waviness, and improving shape precision, and a highly smooth mirror surface has been obtained.

Figures 21 and 22 show the effect of humidity. The optical microscope photograph in Figure 21 shows the results of polishing at a low humidity of about 30%, while Figure 22 shows the results of polishing at a high humidity of about 60%. It was confirmed that a high humidity level is advantageous in terms of surface roughness.

From the above results, when performing blast polishing with elastic abrasive 300 after shaping the chamfered slope by grinding, it is practical to set the angle θ (see Figure 9) of the spray direction D of the elastic abrasive 300 to 5° or more and 80° or less. It was also confirmed that an angle θ of approximately 8°, or 8°±2°, is suitable for obtaining a highly smooth mirror surface. The angle θ is the angle (see Figure 9) of the contact line τ, or the angle of the rotation direction φ of the wafer W relative to the streaks Ws on the upper slope Wu. It was also confirmed that it is good to set the spray direction D so that the angle r corresponding to the chamfer angle V of the chamfered slope is (V-30°) or more and (V-10°) or less.

LIST OF SYMBOLS 10: Chamfering device with blast unit, 12: Supply and recovery section, 14: Pre-alignment section, 16A, 16B: Processing section, 18: Notch polishing section, 20: Cleaning section, 21: Blast unit, 22: Post-measurement section, 24: Transport section, 30: Wafer cassette, 32: Cassette table, 34: Supply and recovery robot, 36: Transport arm, 38: Guide rail, 40: Slide block, 50: Measurement table, 52: Sensor, 54: Notch detection sensor, 60: Wafer feed device, 62: Grinding device, 70: Wafer feed device, 72: Notch polishing unit, 74: Chuck table, 76: Notch polishing head, 80: Spin cleaning device, 82: Cleaning table, 84: Diameter measuring device, 86: Measurement table, 100: Grinding transfer section, 102 : notch transfer unit, 104 : cleaning transfer unit, 106 : storage transfer unit, 110 : horizontal guide, 112 : slide block, 114 : transfer arm, 116 : suction pad, 120 : horizontal guide, 122 : slide block, 124 : transfer arm, 126 : suction pad, 130 : horizontal guide, 132 : slide block, 134 : transfer arm, 136 : suction pad, 142 : slide block, 144 : transfer arm, 146 : suction pad, 150 : chuck table, 152 : chuck table drive motor, 154 : rough grinding motor, 156 : rough grinding spindle, 158 : outer periphery rough grinding wheel, 222 : nozzle table, 223, 224 : injection nozzle, 225 : holding motor, 226 : holding table, 227 : upper holding plate, 228: lower holding plate, 229: rotating shaft, 300: elastic abrasive material, 301, 302, 303, 304: arrows, D: jetting direction, H: width direction line, Ot: center point, Rz: maximum height,
T: contact line, W: wafer, WN: notch, OF: orientation flat, Wc: side, Wu: upper slope, Wd: lower slope, Ws: streak, V: chamfer angle, r: angle (angle corresponding to chamfer angle V), θ: angle (contact line τ, or angle of upper slope Wu relative to streak Ws), ξ: inclination angle, τ: contact line (contact line passing through the processing point of the chamfer slope), φ: rotation direction

Claims (5)

a processing unit that performs chamfering by grinding the edge of the wafer so that the chamfered slopes are upper and lower slopes having a predetermined chamfer angle;
a blast unit that sprays the elastic abrasive material onto each of the upper and lower slopes of the rotating wafer using a spray nozzle fixed in a direction that passes through a processing point of the scratch on the chamfer slope, at an angle other than 90 degrees to a contact line along the processing direction of processing at the processing point, and at an angle smaller than the chamfer angle so as to run along each of the upper and lower slopes, in order to suppress jumping of the elastic abrasive material containing abrasive grains for polishing into the elastic base material due to scratches including streaks and ripples formed on the chamfer slope by grinding with the processing part during the chamfering processing, and to adjust the amount of cutting by the elastic abrasive material. The chamfering device with a blast unit according to claim 1, in which, when the elastic abrasive is sprayed onto the orientation flat of the wafer, the rotation of the wafer is stopped, and the spray nozzle is moved back and forth linearly in the direction of the orientation flat of the wafer, spraying the elastic abrasive onto the orientation flat at an angle that intersects the contact line at an angle other than perpendicular to the chamfered slope of the orientation flat. The chamfering device with a blast unit according to claim 1, wherein when the elastic abrasive is sprayed onto a notch provided on the wafer, the rotation of the wafer is stopped, and the spray nozzle is oscillated at a predetermined speed so that the center of rotation of the spray nozzle is the center point of the curvature at the apex of the notch of the wafer, and the elastic abrasive is sprayed onto the notch. an upper holding plate and a lower holding plate which sandwich the wafer from above and below when the elastic abrasive is sprayed by the blast unit;
The upper support plate and the lower support plate are frustoconical,
the angle of the frustum is less than or equal to the chamfer angle of the wafer;
2. The chamfering device with a blast unit according to claim 1, wherein the size of the bottom surface of the truncated cone is large enough to cover the portion of the wafer to be machined. chamfering is performed by grinding the chamfered slopes of the edge of the wafer so that the upper and lower slopes have a predetermined chamfer angle;
A chamfering method, in which the elastic abrasive, which contains abrasive grains for polishing, is sprayed onto each of the upper and lower slopes of the rotating wafer in a direction that passes through the processing point of the scratch on the chamfer slope, at an angle other than 90 degrees to a contact line along the processing direction of processing at the processing point, and at an angle smaller than the chamfer angle so as to run along each of the upper and lower slopes, in order to suppress jumping of the elastic abrasive, which contains abrasive grains for polishing, into the elastic base material due to scratches, including streaks and ripples, formed on the chamfer slope by grinding at a processing section during the chamfering processing, and to adjust the amount of cutting by the elastic abrasive.