Chamfer grinding method and chamfer grinding device

Abstract

Even in the notch groove grinding process, good surface roughness is achieved, reducing the burden of the subsequent polishing process and improving the final surface roughness and shape accuracy. [Solution] A chamfer grinding method for grinding the end face of a plate-shaped workpiece W with a grinding wheel 72. The grinding wheel 72 has a groove portion 72-4 parallel to the axial direction as a processing groove 72-1, and inclined surfaces 72-2, 72-3 formed above and below the groove portion. The grinding wheel 72 is rotated and ultrasonic vibrations are applied in the axial direction, and the processing groove 72-1 is pressed against and abutted against the end face of the workpiece W from a vertical direction to grind it.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for high-precision chamfer grinding of the end faces of various materials such as silicon, sapphire, compounds, and glass, particularly plate-shaped workpieces such as semiconductor wafers and glass panels. [Background technology]

[0002] In recent years, there has been a strong demand for improved wafer quality, and the processing condition of the wafer edge (edge ​​portion) is becoming increasingly important. Semiconductor wafers such as silicon wafers are used to manufacture semiconductor devices, and to prevent chipping during handling, the edges are ground and chamfered. In addition, a subsequent process of polishing to achieve a mirror-like chamfer is performed. In the semiconductor manufacturing process, from wafer manufacturing to device manufacturing, improving the quality of edge characteristics is an essential process.

[0003] Silicon and other materials are hard and brittle, and if the edge of the wafer remains sharp during slicing, it can easily crack or chip during handling in subsequent processing steps, such as transport and alignment, and the fragments can scratch or contaminate the wafer surface. To prevent this, the edge of the sliced ​​wafer is chamfered using a diamond-coated chamfering wheel. During this process, it is necessary to match the outer diameter, which varies, and the width and length of the orientation flat (OF), as well as the dimensions of the tiny notch.

[0004] Furthermore, glass substrates used in smartphones and tablets, which are designed to be thinner and lighter, undergo mask printing, the formation of sensor electrodes, and then cutting. The quality of the chamfering, the roughness of the processed surface, and the occurrence of microcracks all have a direct impact on the edge strength of the glass substrate.

[0005] Furthermore, 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 stone, but in this case, scratches due to grinding in the circumferential direction are likely to occur in the chamfered portion. Therefore, it is known to perform so-called helical grinding, in which the chamfered portion of the wafer is ground by tilting, for example, the resin grinding stone relative to the wafer.

[0006] Helical grinding not only reduces processing distortion in the chamfered portion compared to normal grinding, but also increases the contact area between the chamfered portion of the wafer and the grinding stone, thereby improving the surface roughness of the chamfered portion.

[0007] In particular, in the manufacturing process of semiconductor devices, it is essential to form a notch groove by cutting out a portion of the peripheral edge of the wafer in an approximately V-shape or arc shape to facilitate alignment of the crystal orientation of the semiconductor wafer. The approximately V-shaped notch groove is widely adopted due to its advantages of being able to efficiently utilize the limited area of ​​the wafer and having excellent positioning accuracy.

[0008] A notch groove is a small cutout on the periphery of a wafer, and there are two main types of notch shapes: U-shaped or V-shaped. In recent years, V-shaped notch grooves, which result in less loss of wafer surface area, have been increasingly used to increase product yields. The notch groove is made by grinding the outer surface of a silicon single crystal block to a specified diameter using a cylindrical grinder, and then using an ingot cutting machine to form the V-shaped notch groove, which indicates the crystal orientation. The block is then ground and mirror-polished in a post-process.

[0009] Typically, the inclined and end faces of the notch groove are mirror-polished using a dedicated notch polishing device because the notch groove has a shape that is significantly different from the outer periphery. Mirror polishing of the notch groove is performed by pressing a polishing member, such as a disk- or ring-shaped polishing cloth with a peripheral portion that matches the shape of the notch groove, against the notch groove of the wafer while rotating it, as described in Patent Document 1, for example.

[0010] Before mirror-polishing the notch groove, it is common to perform a grinding process on the notch groove for chamfering, and it is required to process the notch groove to accurate dimensions. Therefore, in order to obtain a highly accurate V-shaped slope in the chamfering of the notch groove, it is known to provide a feed mechanism that moves a grinding wheel relatively along one V-shaped slope of the notch groove provided in the semiconductor wafer, and a feed mechanism that moves the grinding wheel relatively along the direction of the other V-shaped slope of the notch groove, and this is described in Patent Document 2. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-108968 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-28840 Summary of the Invention [Problem to be solved by the invention]

[0012] In the above-mentioned conventional techniques, mirror polishing is essential, but polishing is performed while the polishing member is pressed against the notch polishing area. As shown in Patent Document 1, the polishing member is pressed against the notch groove of the wafer while rotating, which requires frequent replacement of the polishing member, resulting in poor work efficiency.

[0013] Furthermore, even if high precision is achieved by moving the grinding wheel along the V-shaped slope of the notch groove as shown in Patent Document 2, if the roughness after grinding is too high, the subsequent polishing process will be costly and the shape will be distorted.

[0014] Furthermore, notch chamfering grinding, which simply involves rotating a metal grinding wheel, leaves marks from the abrasive grains in the grinding wheel on the grinding surface, resulting in a poor surface finish. Furthermore, similar to the above, the post-process notch polishing is costly and results in an inaccurate shape. Therefore, it would be desirable to perform helical grinding on the notch groove as well, but this is extremely difficult due to the shape of the notch, unlike other peripheral areas.

[0015] Furthermore, it is possible to use a grinding wheel with a resin bond instead of a metal grinding wheel, but even if the surface roughness is improved, this is not practical because it causes deformation of the groove shape and a decrease in sharpness.

[0016] The object of the present invention is to solve the problems of the prior art, particularly by suppressing the generation of scratches during the notch groove grinding process, achieving a surface roughness comparable to that achieved by helical grinding, and by reducing the burden of the subsequent polishing process, thereby maintaining the shape at the time of grinding even after polishing, thereby forming an accurate shape. [Means for solving the problem]

[0017] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0018] [1] A chamfer grinding method for grinding the end face of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, wherein the grinding wheel is a formed grinding wheel having a groove portion that is a machining groove parallel to the axial direction of the rotation axis and slopes formed above and below the groove portion, wherein the grinding wheel is rotated and ultrasonic vibrations are applied in the axial direction, and the end face of the workpiece is ground by pressing the machining groove against it from a vertical direction, and the width of the machining groove is made larger than the thickness of the workpiece by at least the amplitude of the ultrasonic vibration. [2] A chamfer grinding method according to [1], characterized in that a chamfered notch groove is formed by pressing the processed groove vertically against the end face of a sliced ​​V-shaped cross-section groove formed on the outer peripheral surface of the workpiece. [3] A chamfer grinding method according to claim 1 or 2, characterized in that the width dimension of the machining groove is the sum of the thickness dimension of the workpiece and the width dimension of the amplitude of the ultrasonic vibration. [4] A chamfer grinding method according to any one of [1] to [3], characterized in that the grinding wheel is replaceably attached to a grinding spindle provided with a vibration part that rotates the grinding wheel and applies the ultrasonic vibration to the grinding wheel, and the diameter of the grinding wheel is made smaller than the diameter of the vibration part. [5] A chamfer grinding method according to any one of [1] to [4], wherein the formed grinding wheel further has curved surfaces connecting the grooves and each of the inclined surfaces, and the surfaces of the curved surfaces are positioned on the workpiece side, based on the intersection of an imaginary line extending the grooves and an imaginary line extending the inclined surfaces, in a cross-sectional view of the grinding wheel, and are convex in the direction from the workpiece toward the grinding wheel. [6] A chamfer grinding device for grinding the end face of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, comprising a grinding spindle that rotates the grinding wheel and applies ultrasonic vibrations in the axial direction of the rotation axis, the grinding wheel being a formed grinding wheel having a groove portion parallel to the axial direction as a machining groove and slopes formed above and below the groove portion, the width of the machining groove being larger than the thickness of the workpiece by at least the amplitude of the ultrasonic vibration, and the chamfer grinding device characterized in that the machining groove is pressed against the end face of the workpiece from a vertical direction to grind. [7] The chamfer grinding device according to [6], characterized in that the grinding device presses the processed groove vertically against a sliced ​​V-shaped cross-sectional groove formed on the outer peripheral surface of the workpiece to form a chamfered notch groove. [8] The chamfer grinding device according to [6] or [7], characterized in that the width dimension of the processing groove is the sum of the thickness dimension of the workpiece and the width dimension of the amplitude of the ultrasonic vibration. [9] A chamfer grinding device according to any one of [6] to [8], characterized in that the grinding wheel is replaceably attached to the grinding spindle provided with a vibration unit that applies the ultrasonic vibration, and the diameter of the grinding wheel is smaller than the diameter of the vibration unit.

[10] A chamfer grinding device described in any of [6] to [9], wherein the formed grinding wheel further has curved portions connecting the groove portions and each of the inclined surfaces, and the surface of the curved portions is positioned on the workpiece side based on the intersection of an imaginary line extending the groove portions and an imaginary line extending the inclined surfaces in a cross-sectional view of the grinding wheel, and is convex in the direction from the workpiece toward the grinding wheel.

[0019] Another aspect of the present invention is a chamfer grinding method for grinding the end face of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, wherein the grinding wheel has a groove portion that is a machining groove parallel to the axial direction of the rotation axis and slopes formed above and below the groove portion, and the grinding wheel is rotated while ultrasonic vibrations are applied in the axial direction, and the end face of the workpiece is ground by pressing the machining groove against it in a vertical direction.

[0020] In addition, in the above, it is preferable to form a chamfered notch groove by pressing the processed groove vertically against the end face of a sliced ​​V-shaped cross-section groove formed on the outer peripheral surface of the workpiece.

[0021] Furthermore, in the above, it is preferable that the width of the processed groove is made larger than the thickness of the workpiece by at least the amplitude of the ultrasonic vibration.

[0022] Furthermore, in the above, it is preferable that the width of the machined groove is the sum of the thickness of the workpiece and the width of the amplitude of the ultrasonic vibration.

[0023] Furthermore, in the above, it is preferable that the grinding wheel is replaceably attached to a grinding spindle provided with a vibration part that rotates the grinding wheel and applies the ultrasonic vibration to the grinding wheel, and that the diameter of the grinding wheel is smaller than the diameter of the vibration part.

[0024] The present invention also provides a chamfer grinding device for grinding the end face of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, the device comprising a grinding spindle that rotates the grinding wheel and applies ultrasonic vibrations in the axial direction of the rotation axis, the grinding wheel having a groove portion parallel to the axial direction as a machining groove, and slopes formed above and below the groove portion, and the end face of the workpiece is ground by pressing the groove vertically against it.

[0025] Furthermore, in the above, it is preferable that the grinding device presses the processed groove vertically against a sliced ​​V-shaped cross-sectional groove formed on the outer peripheral surface of the workpiece to form a chamfered notch groove.

[0026] Furthermore, in the above, it is preferable that the width of the groove is made larger than the thickness of the workpiece by at least the amplitude of the ultrasonic vibration.

[0027] Furthermore, in the above, it is preferable that the thickness dimension of the workpiece is equal to the sum of the width dimension of the amplitude of the ultrasonic vibration.

[0028] Furthermore, in the above, it is preferable that the grinding wheel is replaceably attached to the grinding spindle provided with a vibration part that applies the ultrasonic vibration, and that the diameter of the grinding wheel is smaller than the diameter of the vibration part. [Effects of the Invention]

[0029] According to the present invention, a grinding wheel having a groove parallel to the axial direction as a processed groove and slopes formed above and below the groove is rotated and ultrasonic vibration is applied in the axial direction to grind, so that even in the grinding process of a notch groove, the generation of streaks can be suppressed and good surface roughness can be achieved. Therefore, the burden of the subsequent polishing process can be reduced and the final surface roughness and shape accuracy can be improved. [Brief explanation of the drawings]

[0030] [Figure 1]FIG. 1 is a plan view showing a main part of a notch grinding device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a plan view showing a configuration of a processing unit in one embodiment. [Figure 3] 10A and 10B are diagrams illustrating a process of forming a notch groove in one embodiment. [Figure 4] 10A and 10B are diagrams illustrating a detailed process for forming a notch groove in one embodiment; [Figure 5] FIG. 1 is a perspective view of a grinding spindle according to an embodiment; [Figure 6] FIG. 1 is a perspective view showing a tool holder according to an embodiment; [Figure 7] FIG. 1 is an external view showing a notch grinding wheel according to an embodiment; [Figure 8] FIG. 10 is a perspective view showing a tool holder according to another embodiment. [Figure 9] 1 is a cross-sectional view showing processing and the shape of a wafer W in one embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing details of a processed groove in one embodiment. [Figure 11] FIG. 10 is a diagram showing the improvement effect in one embodiment (surface roughness of the inclined surface portion); [Figure 12] FIG. 10 is a diagram showing an improvement effect in one embodiment (surface roughness of an end face portion). DETAILED DESCRIPTION OF THE INVENTION

[0031] Machining the notch groove to precise dimensions shortens the alignment time in the subsequent micromachining process, so high-precision grinding is required. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The invention is not limited to these embodiments, and the components in the embodiments include those that can be easily imagined by a person skilled in the art, or those that are substantially the same.

[0032] 1 is a plan view showing the main components of a chamfering device having a notch grinding device according to one embodiment of the present invention. The chamfering device mainly comprises a supply and recovery section 20 and a processing section 10, and also includes a pre-alignment section, a cleaning section, a post-measurement section, a transport section, etc., which are not shown.

[0033] The wafer processing process is carried out in the following order: slicing → chamfering → lapping → etching → donor killer → fine chamfering, with various cleaning procedures used between processes to remove dirt. Materials such as silicon are hard and brittle, and if the edge of the wafer remains sharp after slicing, it can easily crack or chip during handling in subsequent processing steps such as transport and alignment, and the fragments can scratch or contaminate the wafer surface. To prevent this, in the chamfering process, the edge of the cut wafer is chamfered with a diamond-coated chamfering grinding wheel.

[0034] The chamfering process is sometimes performed after the lapping process. At this time, variations in the outer diameter are adjusted, the width and length of the orientation flat (OF) are adjusted, and the dimensions of the minute notch called the notch are also adjusted.

[0035] The supplying and recovering section 20 supplies wafers W to be chamfered from a wafer cassette 30 to the processing section 10, and recovers the chamfered wafers into the wafer cassette 30. This operation is performed by a supplying and recovering robot 40. The wafer cassette 30 is set on a cassette table 31 and stores a large number of wafers W to be chamfered. The supplying and recovering robot 40 takes out wafers W one by one from the wafer cassette 30 and stores the chamfered wafers into the wafer cassette 30.

[0036] The supply and recovery robot 40 is equipped with a three-axis rotation type transfer arm 50, and the transfer arm 50 is equipped with a suction pad (not shown) on its upper surface. The transfer arm 50 holds the wafer W by vacuum-sucking the backside of the wafer W with the suction pad. That is, the transfer arm 50 of this supply and recovery robot 40 can move back and forth, up and down, and rotate while holding the wafer W, and the wafer W is transferred by combining these movements.

[0037] The processing unit 10 is disposed at the front of the wafer chamfering device and performs all processes for chamfering the outer periphery of the wafer W, from rough processing to finish processing. This processing unit 10 is composed of a wafer feed device 60, an outer periphery grinding device 62, a transfer arm 63 for transporting the wafer W, and a notch grinding device 61. The wafer feed device 60 has a chuck table (wafer table) 66 for holding the wafer W by suction.

[0038] FIG. 2 is a plan view showing the details of the processing unit 10. The chuck table 66 is driven by a driving means (not shown) to move in the front-to-back direction (Y-axis direction), left-to-right direction (X-axis direction), and up-to-down direction (Z-axis direction), and is also driven by a chuck table drive motor (not shown) to rotate around the central axis (θ-axis).

[0039] The outer periphery grinding device 62 is disposed at a position a predetermined distance in the Y-axis direction from the chuck table 66. This outer periphery grinding device 62 has an outer periphery spindle 68 that is driven to rotate by an outer periphery rough grinding motor (not shown). The outer periphery spindle 68 is configured to be movable in both the front-to-back direction (Y-axis direction) and the up-and-down direction (Z-axis direction) by being driven by a driving means (not shown).

[0040] An outer periphery grinding wheel 69 that grinds the outer periphery of the wafer W is attached to the outer periphery spindle 68, which serves as its rotation axis. The outer periphery grinding wheel 69 has a plurality of outer periphery grinding grooves formed on its outer periphery surface (form grinding wheel), and the outer periphery of the wafer W is ground by pressing the outer periphery of the wafer W against these grooves.

[0041] The notch grinding device 61 is disposed at a position spaced a predetermined distance in the X-axis direction from the chuck table 66. The notch grinding device 61 has a grinding spindle 71 that is driven to rotate by a notch grinding motor (not shown). The grinding spindle 71 is configured to be movable in both the left-right direction (X-axis direction) and the up-down direction (Z-axis direction) by being driven by a driving means (not shown). A notch grinding wheel 72 that chamfers a V-shaped notch groove formed in the wafer W is attached to the grinding spindle 71. Here, in FIG. 2, the notch grinding wheel 72 and the grinding spindle 71 are drawn large for ease of understanding, but their actual size is small enough to grind the inside of the notch groove 1.

[0042] The notch grinding wheel 72 has a notch grinding groove formed on its outer circumferential surface (form grinding wheel), and the notch groove formed by cutting is pressed against it to chamfer and grind the notch groove. At this time, the notch grinding wheel 72 is rotated by the grinding spindle 71, and ultrasonic vibrations are applied in the axial direction to grind the V-shaped notch groove into a predetermined shape.

[0043] By performing grinding while applying ultrasonic vibrations, the direction of movement of the abrasive grains intersects with the direction of movement of the outer periphery of the wafer W, just like in helical grinding. This increases the contact area, increases the number of abrasive grains in action, and prevents chips from falling onto the processed surface, thereby suppressing grinding stone wear and reducing deformation of the outer periphery.

[0044] Furthermore, since no chip marks or scratches are left on the machined surface, the roughness of the machined surface (ground surface) is better than with normal grinding. Therefore, if ultrasonic vibrations are applied to the outer peripheral grinding wheel 69 in the axial direction during grinding, in addition to grinding the notch groove, the same effect can be obtained.

[0045] Next, we will explain the details of the process from forming the notch groove to finishing. Figure 3 shows the process of forming the notch groove 1. The outer surface of the single crystal block 11 is ground to a predetermined crystal diameter using a cylindrical grinder, and a V-shaped cross-section groove 12 that will become the notch groove 1 indicating the crystal orientation or a flat surface 13 for an orientation flat 14 is formed to obtain a single crystal block.

[0046] Next, the single crystal block is sliced ​​into thin wafers about 1 mm thick in the slicing process, which then moves to the lapping process to smooth out any irregularities on the wafer surface, and chamfering is performed to remove the corners and edges of the wafer to prevent cracks or chips and to make the wafer even.

[0047] Next, the wafer is chemically treated with chemical etching (chemical polishing) to remove any processing strain that may have occurred on the wafer surface during slicing and lapping. After chemical etching, the wafer undergoes a heat treatment process to stabilize the wafer's resistance, and then the surface of the silicon single crystal wafer is polished to a mirror-like finish using mechanical and chemical polishing (polishing) to produce the final silicon single crystal wafer.

[0048] As described above, when single crystal block 11 is machined into wafer W, notch groove 1 indicating the crystal orientation can be formed in the crystal principal axis direction at a predetermined crystal orientation position in the circumferential direction of single crystal block 11. Furthermore, if the wafer W specification requires the addition of an orientation flat, a portion of the circumferential section of the outer circumferential surface of single crystal block 11, including V-shaped cross-section groove 12, can be machined to form a flat surface until the groove shape disappears, and the formed flat surface can be used as orientation flat 14.

[0049] 4 is a diagram showing in detail the process of forming the notch groove 1 from before notch grinding to after notch polishing. Before notch grinding, when the V-shaped cross-section groove 12 is sliced ​​and cut, the shape of the notch groove 1 remains sharp at the edge as shown in the upper left diagram, and it can easily crack or chip during handling such as transport and alignment in subsequent processing steps, with the fragments damaging or contaminating the wafer surface.

[0050] The upper right image shows the state after the end face of the notch groove 1 has been chamfered, with the top and bottom ends being chamfered and the V-shaped portion being ground to create an R. The lower image shows the state after polishing after grinding. The ground end is then mirror-polished to create a rounded shape.

[0051] Like the outer periphery of the wafer W, the edges of the notch groove 1 must be smooth, high-quality, and not sharp, to prevent chipping. At the same time, because they serve as a reference for aligning the crystal orientation of the semiconductor wafer, they must have precise dimensions and no deformation of the groove shape to ensure positional accuracy. In contrast, as shown in Figure 4, grinding can accurately shape the notch groove 1 and even produce a highly accurate V-shaped slope, but it is difficult to achieve a satisfactory surface finish.

[0052] Furthermore, while polishing can improve surface finishes such as surface roughness, a large amount of processing and processing load can significantly deform the groove shape, resulting in poor accuracy. Furthermore, the polishing material can be damaged, scratching the surface and requiring frequent replacement. Therefore, the notch groove 1 requires a grinding process to improve the surface finish.

[0053] If notch chamfer grinding is simply performed by rotating a metal bonded grinding wheel with diamond abrasive grains, the scratches from the abrasive grains contained in the grinding wheel will be transferred to the grinding surface, resulting in a poor surface finish, increased costs for notch polishing in the post-process, and ultimately an inaccurate shape for the notch groove 1. Therefore, in order to improve shape accuracy while eliminating scratches and improving surface roughness in the grinding process for the notch groove 1, we will achieve the same effect as helical grinding by not only rotating the wheel but also applying vibration in the thrust direction of the notch groove 1.

[0054] 5 to 7, a specific example of grinding by applying vibration in the thrust direction to the notch groove 1 will be described. Fig. 5 shows a grinding spindle 71 to which a notch grinding wheel 72 is attached, Fig. 6 shows a tool holder 73, and Fig. 7 shows the appearance of the notch grinding wheel 72. The notch grinding wheel 72 is attached to the tip of the grinding spindle 71 via the tool holder 73.

[0055] The grinding spindle 71 is provided with a bearing portion 74 and a vibration portion 75, and the vibration portion 75 is rotatably supported by the bearing portion 74. The tool holder 73 is attached to the tip of the vibration portion 75 in a replaceable manner. The vibration portion 75 has an ultrasonic vibrator (not shown) built in and generates ultrasonic vibrations in the axial direction. Therefore, the notch grinding wheel 72 rotates and is given ultrasonic vibrations in the axial direction. The axial direction corresponds to the thickness direction of the wafer W.

[0056] Furthermore, since the vibration part 75 is provided on the grinding spindle 71, ultrasonic vibration can be effectively applied with less power during processing. In particular, the ultrasonic vibration can be made to contribute to processing more efficiently than when ultrasonic vibration is applied to the wafer W side, which is the workpiece.

[0057] Furthermore, since the wafer W is fixed in the same manner as in the conventional method, the ultrasonic vibrations do not elastically deform the workpiece. Also, when the wafer W side is ultrasonically vibrated, the vibrations of the outer periphery of the wafer W are reduced, and the wafer W is not subjected to the shock. Therefore, damage such as scratches is not given to the processed surface, and the shape accuracy can be improved.

[0058] The machining groove 72-1 of the notch grinding wheel 72 is formed by electrical discharge machining. The machining groove 72-1 has three stages of the same shape, and the groove portion 72-4 is formed parallel to the axial direction of the rotation shaft of the notch grinding wheel 72 and along the rotation direction of the rotation shaft (FIGS. 6 and 7). Sloped surfaces 72-2 and 72-3 for chamfering in the thickness direction of the wafer W are formed above and below the groove portion 72-4 (FIGS. 6 and 7). The notch grinding wheel 72 has a diameter of about 4 mm and a length of about 12 mm, which is smaller than the diameter D of the vibration part 75. The groove 72-4 grinds the end surface of the workpiece by being pressed against the end surface from a vertical direction.

[0059] Furthermore, a metal bonded grinding wheel made by mixing diamond abrasive grains with metal powders such as Fe, Cr, and Cu as the main component is used as the notch grinding wheel 72. Metal bonded grinding wheels have a strong abrasive grain retention force, which allows the abrasive grains to protrude to a large extent, allowing for a larger cutting depth per abrasive grain and reducing the burden of the subsequent polishing process.

[0060] The diameter d of the tool holder 73 is made smaller than the diameter D of the vibrating part 75, and the position of the step is set to be the antinode of the standing wave at the vibration frequency of the vibrating part 75. The amplitude at the position of the notch grinding wheel 72 increases in accordance with the diameter ratio D / d, and the vibration energy of the vibrating part 75 is efficiently transmitted to the tip of the notch grinding wheel 72. The tool holder 73 is a stepped horn type vibrator horn that resonates with the basic vertical vibration of the ultrasonic vibrator built into the vibrating part 75 and amplifies the amplitude.

[0061] Figure 8 shows another embodiment of the tool holder 73, with the upper figure showing a conical horn and the lower figure showing an exponential horn. Taking into consideration the amplitude amplification rate, stress concentration factor, and cost, as well as the material of the notch grinding wheel 72, the amount of grinding, and the processing precision, the appropriate tool holder should be selected. The step horn type shown in Figure 5 has the highest amplitude amplification rate, followed by the exponential horn and then the conical horn, with the stress concentration factor decreasing in the opposite direction.

[0062] 9 shows the shape of the groove 72-1 of the notch grinding wheel 72 and the cross section of the wafer W to be chamfered. The groove 72-1 is composed of a groove portion 72-4 in the center and inclined surfaces 72-2 and 72-3 formed above and below the groove portion 72-4. The inclined surfaces 72-2 and 72-3 are formed at the same angle as the angle at which the edge of the wafer W is chamfered to prevent it from becoming sharp. The groove portion 72-4 is formed vertically.

[0063] The angle of the inclined surfaces 72-2 and 72-3 is 3 to 55°, preferably 5 to 45°. An inclined angle that is too large is undesirable in terms of increased grinding resistance and chipping or scratches at the upper and lower corners of the end face. Furthermore, the width T of the groove 72-1 is larger than the thickness of the wafer W by at least the amplitude of the ultrasonic vibration. In Figure 9, the arrows indicate that ultrasonic vibration is applied in the axial direction. If the amplitude of the ultrasonic vibration is ±3 μm, the width T of the groove 72-1 is 6 μm larger than the thickness t of the wafer W.

[0064] 10 shows the details of the groove 72-1. The notch grinding wheel 72 rotates at approximately 3,000 to 30,000 rpm while ultrasonically vibrating in the direction of the arrow at 30 to 50 kHz. Therefore, the vertical groove 72-4 contacts the wafer W at the edge of the wafer W, and grinding proceeds by combining the tangential force on the wafer W due to the rotation of the notch grinding wheel 72 with the force in the vibration direction indicated by the arrow. This results in fine notches due to the ultrasonic vibration. Furthermore, the number of working abrasive grains increases due to an effect similar to that of helical grinding, eliminating the scratches that would otherwise occur on the grinding surface when grinding by rotation alone.

[0065] On the other hand, at the chamfered portion of the wafer W, the inclined surfaces 72-2 and 72-3 also abut against the wafer W, but the width T of the processed groove 72-1 is larger than the thickness of the wafer W, resulting in intermittent grinding. Therefore, the grit size of the inclined surfaces 72-2 and 72-3 is set to #3000 to #6000, and the grit size of the groove portion 72-4 is set to #1500 to #3000. Furthermore, the grit size of the inclined surfaces 72-2 and 72-3 is set to be larger than the grit size of the groove portion 72-4, so that the abrasive grains are finer. The grinding of the upper and lower surfaces, which is intermittent grinding, is performed by using a notch grinding wheel 72 with a higher grit size than that of the center surface, thereby achieving uniformity.

[0066] Furthermore, it is desirable to use the notch grinding wheel 72 by impregnating a chamfering wheel material with a porous surface with a saturated fatty acid solution and a lubricant, drying the surface, and then water-cooling this lubricant-impregnated wheel during grinding. This ensures that the lubricant is supplied to the cutting point of the wheel, keeping the cutting point temperature below a predetermined temperature.

[0067] To widen the width of the processed groove 72-1, the groove is machined wide in advance by electrical discharge machining.

[0068] As described above, by applying ultrasonic vibrations while rotating the notch grinding wheel 72 relative to the wafer W, the direction of movement of the abrasive grains intersects with the direction of movement of the wafer W, and by making the width of the processing groove 72-1 wider than the workpiece, it is possible to obtain the same effect as applying helical grinding to chamfering. This reduces the surface roughness and processing distortion of the end face, and makes it possible to use a high-grit grinding wheel for a long time.

[0069] An example of the improvement effect when this embodiment is applied is shown in Figures 11 and 12. Figure 11 is a micrograph showing the surface roughness of the chamfered slope portion, and Figure 12 is a micrograph showing the surface roughness of the end face portion, with the right image showing grinding processing performed by simply rotating the notch grinding wheel 72, which is conventional technology, and the left image showing grinding processing performed by applying ultrasonic vibrations.

[0070] 11, ultrasonic vibrations cause the chamfered surface of the wafer W to be intermittently ground in the vertical direction, generating small chips. Furthermore, the lubrication condition at the interface between the notch grinding wheel 72 and the wafer W is improved, reducing friction, cleaning the grinding surface, and promoting the discharge of grinding chips. This increases the original cutting ability and the vibration acceleration motion of the abrasive grains, reducing cutting resistance and improving grinding performance.

[0071] In Figure 11, the grit size of the notch grinding wheel 72 is #3000. Grinding by rotation alone produced a surface roughness of 1.1 μm, while grinding with ultrasonic vibrations produced a surface roughness of 0.5 μm, achieving an improvement of more than 50%.

[0072] In the end face portion of Figure 12, ultrasonic vibration grinds parallel to the surface being machined, increasing the mobility of the abrasive grains and causing cavitation on the parallel surface, resulting in low-damage machining. As a result, in the right figure, which shows grinding performed by simply rotating the notch grinding wheel 72, scratches caused by the abrasive grains contained in the notch grinding wheel 72 are visible on the ground surface, but in the left figure, which shows grinding performed with ultrasonic vibration, the movement of the abrasive grains forms a crosshatch trajectory and the scratches are flattened.

[0073] In Figure 12, the grit size of the notch grinding wheel 72 is #3000. Grinding by rotation alone produced a surface roughness of 1.6 μm, while grinding with ultrasonic vibrations produced a surface roughness of 0.4 μm, achieving an improvement of more than 70%.

[0074] As described above, in the notch groove grinding process using ultrasonic vibration, the notch grinding wheel 72 rotates while ultrasonic vibration is applied in the axial direction, thereby suppressing the occurrence of scratches and achieving good surface roughness. This also reduces the burden of the subsequent polishing process, allowing the shape at the time of grinding to be maintained even after polishing, resulting in the formation of an accurate shape. Furthermore, improved processing efficiency, prevention of clogging, and processing performance also improve shape accuracy and grinding wheel life. It also promotes cleaning of the grinding surface and removal of grinding debris, thereby maintaining grinding performance and maintaining the precision of the grinding wheel shape.

[0075] Furthermore, even without chemical strengthening, the end face can have a good machined surface roughness and the occurrence of microcracks can be suppressed, resulting in a significant improvement in production efficiency and a practically sufficient end face strength.

[0076] Furthermore, not only the surface roughness but also the number of pieces that can be continuously machined before the grinding ability decreases and the specified outer peripheral surface width, outer peripheral angle, and outer peripheral shape are no longer satisfied after one grinding groove correction (tooling) can be increased.

[0077] While the above has been described as a grinding process in which ultrasonic vibrations are applied to the notch groove using the notch grinding wheel 72, it may also be applied to orientation flats, chamfering the outer periphery of a wafer, and edge processing of workpieces having a non-circular straight portion at the end of a flat shape. In addition, the present invention is effective not only for semiconductor wafers such as silicon wafers used in the manufacture of semiconductor devices, but also for high-precision chamfering of the edge of various materials such as silicon, sapphire, compounds, and glass, as well as plate-shaped workpieces such as glass panels. [Explanation of symbols]

[0078] 1...notch groove, 10...processing section, 11...single crystal block, 12...V-shaped cross-section groove, 13...flat surface, 14...orientation flat, 20...supply and recovery section, 30...wafer cassette, 31...cassette table, 40...supply and recovery robot, W...wafer, 50...transfer arm, 60...wafer feeder, 61...notch grinding device, 62...periphery grinding device, 63...transfer arm, 66...chuck table, 68...periphery spindle, 69...periphery grinding wheel, 71...grinding spindle, 72...notch grinding wheel, 72-1...processing groove, 72-2, 72-3...inclined surface, 72-4...groove section, 73...tool holder, 74...bearing section, 75...vibration section

Claims

1. A chamfer grinding method for grinding an end surface of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, comprising: The grinding wheel is a formed grinding wheel having a processing groove formed by a groove portion parallel to the axial direction of the rotation shaft and inclined surfaces formed above and below the groove portion, Rotating the grinding wheel and applying ultrasonic vibrations in the axial direction, Grinding is performed by pressing the processing groove against the end surface of the workpiece from a vertical direction and bringing it into contact with the end surface, The width of the processed groove is made larger than the width of the amplitude of the ultrasonic vibration relative to the thickness of the workpiece, The formed grinding wheel further has curved surface portions connecting the groove portions and each of the inclined surfaces, The surface of the curved surface portion, in a cross-sectional view of the grinding wheel, a chamfer grinding method in which the groove portion is positioned on the workpiece side based on the intersection of a virtual line extending the groove portion and a virtual line extending the inclined surface, and is convex in a direction from the workpiece toward the grinding wheel.

2. 2. The chamfer grinding method according to claim 1, A chamfer grinding method characterized by forming a chamfered notch groove by pressing the processed groove vertically against the end face of a sliced ​​V-shaped cross-section groove formed on the outer peripheral surface of the workpiece.

3. 3. The chamfer grinding method according to claim 1, wherein the width of the groove is the sum of the thickness of the workpiece and the width of the amplitude of the ultrasonic vibration.

4. 4. The chamfer grinding method according to claim 1, the grinding wheel is replaceably attached to a grinding spindle provided with a vibration unit that rotates the grinding wheel and applies the ultrasonic vibration to the grinding wheel; A chamfer grinding method, characterized in that the diameter of the grinding wheel is smaller than the diameter of the vibration part.

5. In a chamfer grinding device that grinds the end face of a plate-shaped workpiece with a grinding wheel that rotates around a rotation axis, a grinding spindle that rotates the grinding wheel and applies ultrasonic vibration in the axial direction of the rotation shaft; The grinding wheel is a formed grinding wheel having a processing groove formed therein, the processing groove being composed of a groove portion parallel to the axial direction and an inclined surface formed above and below the groove portion, The width of the processed groove is made larger than the width of the amplitude of the ultrasonic vibration relative to the thickness of the workpiece, The groove is pressed against the end face of the workpiece from a vertical direction to grind the workpiece. The formed grinding wheel further has curved surface portions connecting the groove portions and each of the inclined surfaces, The surface of the curved surface portion, in a cross-sectional view of the grinding wheel, A chamfer grinding device that is positioned on the workpiece side based on the intersection of an imaginary line extending the groove portion and an imaginary line extending the inclined surface, and is convex in the direction from the workpiece toward the grinding wheel.

6. 6. The chamfer grinding apparatus according to claim 5, A chamfer grinding device characterized in that the processed groove is pressed vertically against a sliced ​​V-shaped cross-sectional groove formed on the outer peripheral surface of the workpiece to form a chamfered notch groove.

7. 7. The chamfer grinding device according to claim 5, wherein the width of the groove is the sum of the thickness of the workpiece and the width of the amplitude of the ultrasonic vibration.

8. The chamfer grinding apparatus according to any one of claims 5 to 7, The grinding wheel is replaceably attached to the grinding spindle, which is provided with a vibration unit that applies the ultrasonic vibration, and the diameter of the grinding wheel is smaller than the diameter of the vibration unit.

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