JP2022047538A - Chamfer grinding method and chamfer grinding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide preferable surface roughness even when it is a process of grinding a notch groove, to reduce load of polishing process that is post-process, thereby improving final surface roughness and shape accuracy.

SOLUTION: In a chamfer grinding method for grinding an end face of a plate-like material W to be processed with a grinding abrasive wheel 72, the grinding abrasive wheel 72 includes: a groove part 72-4 parallel to an axial direction, as a processing groove 72-1; and slopes 72-2, 72-3 formed in an upper and a lower of the groove part. The chamfer grinding method includes: rotating the grinding abrasive wheel 72 and providing supersonic vibration in an axial direction to the grinding abrasive wheel; and pressing the processing groove 72-1 at the end face of the material W to be processed from a vertical direction so that they abut on each other to grind the object.

SELECTED DRAWING: Figure 9

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a highly accurate chamfering grinding method and chamfering grinding apparatus on end faces of various materials such as silicon, sapphire, compounds and glass, particularly plate-shaped workpieces such as semiconductor wafers and glass panels.

In recent years, there has been a strong demand for improving the quality of wafers, and the processing state of the end face (edge portion) of the wafer is regarded as important. Semiconductor wafers such as silicon wafers are used for manufacturing semiconductor devices and the like, but chamfering is performed by grinding the edges in order to prevent chipping due to handling. Further, as a subsequent process, mirror chamfering by polishing is performed. In the semiconductor manufacturing process, quality improvement of edge characteristics is an indispensable process from wafer manufacturing to device manufacturing.

Silicone is hard and brittle, and if the end face of the wafer remains sharp during slicing, it will easily crack or chip during handling such as transportation and alignment in the subsequent processing process, and the fragments will damage or contaminate the wafer surface. Or something. To prevent this, the end face of the cut wafer is chamfered with a diamond-coated chamfering wheel. At this time, it is also necessary to match the diameters of the outer circumferences with variations, to match the width of the orientation flat (OF), and to match the dimensions of a minute notch called a notch.

In addition, the glass substrate used for smartphones and tablets, which has been pursued to be thinner and lighter, is subjected to masking printing, sensor electrode formation, and then cutting. The generation of microcracks directly affects the end face strength of the glass substrate.

Further, in normal grinding, the chamfered portion is ground in a state where the main surface of the wafer W is perpendicular to the rotation axis of the resin grindstone, but in this case, the chamfered portion has streaks due to grinding in the circumferential direction. easy. Therefore, it is known to perform so-called helical grinding in which, for example, a resin grindstone is tilted with respect to the wafer to grind the chamfered portion of the wafer.

When helical grinding is performed, not only the processing distortion of the chamfered portion is reduced as compared with normal grinding, but also the contact region between the chamfered portion of the wafer and the grindstone is increased, and the surface roughness of the chamfered portion is improved.

In particular, in the process of manufacturing a semiconductor device, it is essential to form a notch groove formed by notching a part of the peripheral edge of the wafer in a substantially V-shape or an arc shape in order to facilitate the alignment of the crystal orientation of the semiconductor wafer. The substantially V-shaped notch groove is widely adopted because it can efficiently utilize the limited area of the wafer and has excellent positioning accuracy.

The notch groove is a small notch portion provided in the peripheral portion of the wafer, and there are two main notch shapes, a U-shape and a V-shape. Particularly in recent years, in order to increase the yield of products, V-shaped notch grooves with less loss of wafer surface area have been frequently used. The notch groove is formed by cutting the outer peripheral surface of the silicon single crystal block to a predetermined diameter with a cylindrical grinder and using an ingot cutting machine to form a V-shaped notch groove indicating the crystal orientation. Then, it is ground and mirror-polished as a post-process.

Normally, the inclined surface and the end surface of the notch groove are mirror-polished using a notch polishing device dedicated to the notch because the notch groove has a shape significantly different from the outer circumference. The mirror surface processing of the notch groove is performed by pressing and contacting the notch groove of the wafer while rotating a polishing member composed of a disk-shaped or ring-shaped polishing cloth having a peripheral portion matching the shape of the notch groove. For example, it is described in Patent Document 1.

Before mirror polishing the notch groove, it is common to grind the notch groove for chamfering, and it is required to process the notch groove to an accurate dimension. Therefore, in order to obtain a highly accurate V slope in the chamfering of the notch groove, a feed mechanism for relatively moving the grindstone along one V slope of the notch groove provided in the semiconductor wafer and a feed mechanism for moving the grindstone relative to the other V of the notch groove. It is known to provide a feed mechanism for relative movement along a slope direction, which is described in Patent Document 2.

Japanese Unexamined Patent Publication No. 2010-108968 Japanese Unexamined Patent Publication No. 2002-28840

In the above-mentioned prior art, mirror polishing is indispensable, but at the time of polishing, the polishing member is polished while being pressed against the notch polishing region. As shown in Patent Document 1, since the polishing member is pressed into the notch groove of the wafer while rotating, it is necessary to frequently replace the polishing member, resulting in poor work efficiency.

Further, even if the grinding wheel is moved along the V slope of the notch groove to improve the accuracy as shown in Patent Document 2, if the roughness after grinding is rough, the cost for polishing in the subsequent process is high. The shape of the hook was supposed to collapse.

Further, in the notch chamfering grinding in which the metal grindstone is simply rotated, the streaks of the abrasive grains contained in the grindstone are transferred to the surface to be ground, and the surface finish is poor. Further, similarly to the above, the notch polishing in the post-process is costly and the shape becomes inaccurate. Therefore, it is desirable to perform helical grinding on the notch groove as well, but unlike other outer peripheral portions, it is extremely difficult due to the shape of the notch.

Further, it is conceivable to use a grindstone using a resin-based resin bond for the metal grindstone, but even if the surface roughness is improved, it is not practical due to the deformation of the groove shape and the deterioration of the sharpness.

An object of the present invention is to solve the above-mentioned problems of the prior art, particularly to suppress the generation of streaks in the notch groove grinding process, and to realize a good surface roughness comparable to that of helical grinding. Then, the burden of polishing, which is a post-process, is reduced, the shape at the time of grinding is maintained even after polishing, and an accurate shape is formed.

As a result of diligent studies to solve the above problems, the present inventors have found that the above problems can be solved by the following configurations.

[1] A chamfering grinding method in which an end surface of a plate-shaped workpiece is ground with a grinding wheel that rotates about a rotation axis, and the grinding wheel is a machined groove parallel to the axial direction of the rotation axis. It is a total-shaped grindstone having a groove portion and slopes formed above and below the groove portion, and the grinding wheel is rotated and ultrasonic vibration is applied in the axial direction to form the machining groove on the end surface of the workpiece. A chamfering grinding method characterized in that the width of the machined groove is made larger than the amplitude of the ultrasonic vibration with respect to the thickness of the work material by pressing the grindstone from the vertical direction and contacting the grindstone.
[2] In the chamfering grinding method according to [1], the machined groove is pressed from the vertical direction against the end surface of the sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the material to be machined. A chamfer grinding method characterized by forming a chamfered notch groove.
[3] The chamfer grinding according to claim 1 or 2, wherein the width dimension of the machined groove is the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration. Method.
[4] The chamfering grinding method according to any one of [1] to [3], wherein the grinding wheel is provided with a vibrating portion that rotates the grinding wheel and gives the grinding wheel ultrasonic vibration. A chamfering method characterized in that the diameter of the grinding wheel is smaller than the diameter of the vibrating portion, which is replaceably attached to the grinding spindle.
[5] The total-shaped grindstone further has a curved surface portion connecting the groove portion and each of the slopes, and the surface of the curved surface portion is a virtual extension of the groove portion in the cross-sectional view of the grinding wheel. [1] to [4], which are arranged on the work material side with reference to the intersection of the line and the virtual line extending the slope, and are convex in the direction from the work material to the grinding wheel. The chamfer grinding method according to any one.
[6] In a chamfering grindstone that grinds the end face of a plate-shaped workpiece with a grindstone that rotates around a rotation axis, the grinding wheel is rotated and ultrasonic vibration is performed with respect to the axial direction of the rotation axis. The grinding wheel is a total-shaped grindstone having a groove portion parallel to the axial direction as a machining groove and slopes formed above and below the groove portion, and the width of the machined groove is the width of the machined groove. A chamfering grinding device characterized in that the amplitude of the ultrasonic vibration is increased with respect to the thickness of the material, and the machined groove is pressed against the end face of the material to be machined from the vertical direction to grind.
[7] In the chamfering grinding device according to [6], the grinding device presses the machined groove vertically into the sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the material to be machined to chamfer. A chamfering grinder characterized by forming a notched groove.
[8] The dimension of the width of the machined groove is the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration, according to [6] or [7]. Chamfer grinding device.
[9] In the chamfering grindstone according to any one of [6] to [8], the grinding wheel is replaceably attached to the grinding spindle provided with a vibrating portion that gives ultrasonic vibration, and the grinding wheel is interchangeably attached. A chamfer grinding device characterized in that the diameter of the grinding wheel is smaller than the diameter of the vibrating portion.
[10] The total-shaped grindstone further has a curved surface portion connecting the groove portion and each of the slopes, and the surface of the curved surface portion is a virtual extension of the groove portion in a cross-sectional view of the grinding wheel. [6] to [9], which are arranged on the work material side with reference to the intersection of the line and the virtual line extending the slope, and are convex in the direction from the work material to the grinding wheel. The chamfer grinding device according to any one.

Another embodiment of the present invention is a chamfering grinding method in which an end surface of a plate-shaped workpiece is ground with a grinding wheel that rotates about a rotation axis, and the grinding wheel is parallel to the axial direction of the rotation axis. It has a groove portion that is a smooth processing groove and slopes formed above and below the groove portion, and the grinding wheel is rotated and ultrasonic vibration is applied in the axial direction, and the processing groove is formed on the end surface of the work material. Is pressed from the vertical direction and abutted against each other to grind.

Further, in the above, the chamfered notch groove is formed by pressing the machined groove from the vertical direction and abutting against the end face of the sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the material to be machined. Is preferable.

Further, in the above, it is preferable that the width of the machined groove is made larger than the amplitude of the ultrasonic vibration with respect to the thickness of the work material.

Further, in the above, it is preferable that the width dimension of the machined groove is the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration.

Further, in the above, the grinding wheel is replaceably attached to a grinding spindle provided with a vibrating portion that rotates the grinding wheel and applies the ultrasonic vibration to the grinding wheel, and the diameter of the grinding wheel is the same as described above. It is preferable that the diameter is smaller than the diameter of the vibrating portion.

Further, according to the present invention, in a chamfering grindstone that grinds the end face of a plate-shaped workpiece with a grinding wheel that rotates about a rotation axis, the grinding wheel is rotated and the grinding wheel is rotated with respect to the axial direction of the rotation axis. The grinding wheel is provided with a grinding spindle that applies ultrasonic vibration, and the grinding wheel has a groove portion parallel to the axial direction as a machining groove and slopes formed above and below the groove portion, and the machining groove is formed on an end surface of the workpiece. Is provided for grinding by pressing from the vertical direction.

Further, in the above, the grinding device forms a chamfered notch groove by pressing the machined groove from the vertical direction into the sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the work material. Is preferable.

Further, in the above, it is preferable that the width of the machined groove is made larger than the amplitude of the ultrasonic vibration with respect to the thickness of the work material.

Further, in the above, it is preferable that the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration is set.

Further, in the above, the grinding wheel is interchangeably attached to the grinding spindle provided with a vibrating portion that gives ultrasonic vibration, and the diameter of the grinding wheel is made smaller than the diameter of the vibrating portion. Is preferable.

According to the present invention, a grinding wheel having a groove portion parallel to the axial direction as a machined groove and slopes formed above and below the groove portion is rotated, and ultrasonic vibration is applied in the axial direction for grinding. Even in the notch groove grinding process, it is possible to suppress the generation of streaks and achieve good surface roughness. Therefore, the burden of polishing, which is a post-process, can be reduced, and the final surface roughness and shape accuracy can be improved.

Top view showing the main part of the notch grinding apparatus which concerns on one Embodiment of this invention. Top view showing the structure of the machined part in one Embodiment The figure which shows the formation process of the notch groove in one Embodiment The figure which shows the detailed formation process of the notch groove in one Embodiment A perspective view showing a grinding spindle in one embodiment. A perspective view showing a tool holder in one embodiment. External view showing the notch grinding wheel in one embodiment. Perspective view showing the tool holder in another embodiment Cross-sectional view showing the processing and the shape of the wafer W in one embodiment. Sectional drawing which shows the detail of the machined groove in one Embodiment The figure which shows the improvement effect in one Embodiment (surface roughness of a slope part) The figure which shows the improvement effect in one Embodiment (surface roughness of an end face part)

Machining the notch groove to an accurate dimension can shorten the alignment time at the time of micromachining in the next process, so that 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 this embodiment, and the components in the embodiment include those easily conceivable by those skilled in the art or substantially the same.

FIG. 1 is a plan view showing a main part of a chamfering device having a notch grinding device according to an embodiment of the present invention. The chamfering device mainly has a supply / recovery unit 20 and a processing unit 10, and is further composed of a pre-alignment unit, a cleaning unit, a post-measurement unit, a transport unit, and the like, although not shown.

The wafer processing process is performed in the order of slicing → chamfering → wrapping → etching → donor killer → fine chamfering, and various cleanings are used to remove stains between the processes. Silicone is hard and brittle, and if the end face of the wafer remains sharp during slicing, it will easily crack or chip during handling such as transportation and alignment in the subsequent processing process, and the fragments will damage or contaminate the wafer surface. Or something. In order to prevent this, in the chamfering process, the end face of the cut wafer is chamfered with a chamfering grindstone coated with diamond.

The chamfering process may be performed after the wrapping process. At this time, the diameters of the outer circumferences having variations are matched, the width of the orientation flat (OF) is matched, and the dimensions of a minute notch called a notch are matched.

The supply / recovery unit 20 supplies the wafer W to be chamfered from the wafer cassette 30 to the processing unit 10, and collects the chamfered wafer to the wafer cassette 30. This operation is performed by the supply / recovery robot 40. The wafer cassette 30 is set on the cassette table 31 and contains a large number of wafers W to be chamfered. The supply / recovery robot 40 takes out wafers W one by one from the wafer cassette 30, and stores the chamfered wafers in the wafer cassette 30.

The supply / recovery robot 40 is provided with a 3-axis rotary type transfer arm 50, and the transfer arm 50 is provided with a suction pad (not shown) on the upper surface thereof. The transfer arm 50 holds the wafer W by vacuum suctioning the back surface of the wafer W with a suction pad. That is, the transfer arm 50 of the supply / recovery robot 40 can move back and forth, move up and down, and turn while holding the wafer W, and by combining these operations, the wafer W is transferred.

The processing portion 10 is arranged on the front portion of the wafer chamfering device, and performs all processing of the outer peripheral chamfering of the wafer W, that is, from rough processing to finishing processing. The processing section 10 includes a wafer feed device 60, an outer peripheral 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 that attracts and holds the wafer W.

FIG. 2 is a plan view showing the details of the machined portion 10, and the chuck table 66 is driven by a driving means (not shown) to be driven in the front-rear direction (Y-axis direction), the left-right direction (X-axis direction), and up and down. It moves in each direction (Z-axis direction) and rotates around the central axis (θ-axis) by being driven by a chuck table drive motor (not shown).

The peripheral grinding device 62 is arranged at a position separated from the chuck table 66 by a predetermined distance in the Y-axis direction. The outer peripheral grinding device 62 has an outer peripheral spindle 68 that is driven by an outer peripheral rough grinding motor (not shown) and rotates. The outer peripheral spindle 68 is configured to be movable in each of the front-rear direction (Y-axis direction) and the up-down direction (Z-axis direction) by being driven by a drive means (not shown).

An outer peripheral grinding wheel 69 for grinding the outer periphery of the wafer W is mounted on the outer peripheral spindle 68 and serves as a rotation axis thereof. The outer peripheral grinding wheel 69 has a plurality of outer peripheral grinding grooves formed on the outer peripheral surface thereof (total shape grindstone), and the outer periphery of the wafer W is ground by pressing the outer periphery of the wafer W against the grooves.

The notch grinding device 61 is arranged at a position separated from the chuck table 66 by a predetermined distance in the X-axis direction. The notch grinding device 61 has a grinding spindle 71 driven by a notch grinding motor (not shown) to rotate. The grinding spindle 71 is configured to be movable in each of 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 for chamfering a V-shaped notch groove formed in the wafer W is mounted on the grinding spindle 71. Here, in FIG. 2, the notch grinding wheel 72 and the grinding spindle 71 are drawn large for the sake of clarity, but the actual size is small enough to grind the inside of the notch groove 1.

The notch grinding wheel 72 has a notch grinding groove formed on its outer peripheral surface (total shape grindstone), and the notch groove is chamfered and ground by pressing the notch groove formed by cutting. At this time, the notch grinding wheel 72 is rotated by the grinding spindle 71, and ultrasonic vibration is applied in the axial direction to grind the V-shaped notch groove into a predetermined shape.

By grinding while applying ultrasonic vibration, the moving direction of the abrasive grains intersects with the moving direction of the outer periphery of the wafer W, as in the helical grinding. As a result, the contact area increases, the number of abrasive grains acting on the grindstone increases, and the grindstone does not fall on the machined surface due to grinding. ..

Further, since no scratches or streaks due to scratches are generated on the machined surface, the roughness of the machined surface (ground surface) is better than that of normal grinding. Therefore, the same effect can be obtained by not only grinding the notch groove but also grinding the outer peripheral grinding wheel 69 by applying ultrasonic vibration in the axial direction.

Next, the details from the formation of the notch groove to the finishing process will be described. FIG. 3 is a diagram showing a process of forming the notch groove 1. The outer peripheral surface of the single crystal block 11 is ground to a predetermined crystal diameter by a cylindrical grinder to form a V-shaped cross-section groove 12 or a flat surface 13 for an orientation flat 14 which is a notch groove 1 indicating a crystal orientation to form a single crystal mass. do.

Next, the single crystal mass is sliced into a thin wafer having a thickness of about 1 mm in the slicing step. After that, it is moved to a wrapping process for smoothing the unevenness of the surface of the wafer, and chamfering is performed to scrape the corners and the outer circumference of the outer peripheral portion of the wafer in order to prevent cracking and chipping or to adjust the size.

Next, in order to remove the processing strain generated on the surface layer of the wafer by slicing or wrapping, chemical etching (chemical polishing) for chemically treating the wafer is performed. After the chemical etching, the surface of the silicon single crystal wafer is polished like a mirror by mechanical chemical polishing (polishing) through a heat treatment process for the purpose of stabilizing the wafer resistance value, and the final silicon single crystal wafer is obtained. It becomes.

As described above, at the predetermined crystal orientation position in the circumferential direction of the single crystal block 11, when the single crystal block 11 is processed into a wafer W, a notch groove 1 indicating the crystal orientation is formed in the crystal main axis direction. be able to. Further, when the W standard of the wafer requires the addition of an orientation flat, the groove shape is formed on a part of the peripheral surface of the single crystal block 11 in the circumferential direction including the V-shaped cross-sectional groove 12. A flat surface is processed until it disappears, and the formed flat surface can be used as the orientation flat 14.

FIG. 4 is a diagram showing in detail the process of forming the notch groove 1 from before the notch grinding process to after the notch polishing process. The shape of the notch groove 1 when the V-shaped cross-section groove 12 is sliced and cut before the notch grinding process has the end portion remaining sharp at the time of slicing as shown in the upper left figure, and is conveyed in the subsequent processing process. It is easily cracked or chipped during handling such as alignment and alignment, and the fragments damage or contaminate the wafer surface.

The upper right figure shows a state in which the end surface of the notch groove 1 is chamfered, and the upper and lower end portions are chamfered and the V-shaped portion is ground so as to have an R. The figure below shows the state of polishing after grinding. The ground end is mirror-polished to give it a rounded shape.

Similar to the outer peripheral portion of the wafer W, the edge portion of the notch groove 1 needs to be smooth and of high quality without being sharp in order to prevent chipping. At the same time, since it serves as a reference for aligning the crystal orientation of the semiconductor wafer, it is required that the groove shape is not deformed with accurate dimensions so that position accuracy can be obtained. On the other hand, as shown in FIG. 4, in the grinding process, the shape of the notch groove 1 can be made accurate and the V slope can be made highly accurate, but it is difficult to make the surface finish sufficiently. Is.

Further, in the polishing process, the surface finish such as surface roughness can be improved, but if the processing amount and the processing load are large, the groove shape is greatly deformed and the accuracy is deteriorated. Furthermore, it was necessary to scratch the surface of the polishing member due to damage or to replace the polishing member frequently. Therefore, the notch groove 1 is required to have a better surface finish by grinding.

If the notch chamfering is performed by simply rotating the metal bond grindstone of diamond abrasive grains, the traces of the abrasive grains contained in the grindstone are transferred to the surface to be ground, and the surface finish is poor. Notch polishing is costly, and as a result, the shape of the notch groove 1 becomes inaccurate. Therefore, in the grinding process of the notch groove 1, in order to improve the shape accuracy, eliminate the generation of streaks and improve the surface roughness, not only the rotation but also the vibration in the thrust direction in the notch groove 1 is applied to perform helical grinding. The same effect will be obtained.

A specific example of grinding by applying vibration in the thrust direction to the notch groove 1 will be described with reference to FIGS. 5 to 7. FIG. 5 shows the grinding spindle 71 to which the notch grinding wheel 72 is attached, FIG. 6 shows the 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.

The grinding spindle 71 is provided with a bearing portion 74 and a vibrating portion 75, and the vibrating portion 75 is rotationally supported by the bearing portion 74. The tool holder 73 is replaceably attached to the tip of the vibrating portion 75. An ultrasonic vibrator (not shown) is built in the vibrating unit 75 and ultrasonically vibrates in the axial direction. Therefore, the notch grinding wheel 72 is rotated and ultrasonic vibration is applied in the axial direction. The axial direction corresponds to the thickness direction of the wafer W.

Further, since the grinding spindle 71 is provided with the vibrating portion 75, ultrasonic vibration can be effectively applied with a small amount of electric power during processing. In particular, ultrasonic vibration can be efficiently contributed to processing as compared with a material that ultrasonically vibrates the wafer W side of the material to be processed.

Further, since the fixing of the wafer W is the same as in the conventional case, the ultrasonic vibration does not elastically deform the workpiece. Further, when the wafer W side is ultrasonically vibrated, the vibration of the outer peripheral portion of the wafer W is reduced and the impact is not received. Therefore, the shape accuracy can be improved without damaging the machined surface such as scratches.

The machined grooves 72-1 of the notch grinding wheel 72 are formed by electric discharge machining. Further, the machined grooves 72-1 are provided in three stages having the same shape, and the groove portions 72-4 are parallel to the axial direction of the rotation axis of the notch grinding wheel 72 and along the rotation direction of the rotation axis. It is formed (FIGS. 6 and 7), and chamfering slopes 72-2 and 72-3 with respect to the thickness direction of the wafer W are formed at the upper and lower portions of 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 vibrating portion 75.
The groove portion 72-4 is pressed against the end face of the work material from the vertical direction and comes into contact with the end face to grind the end face.

Further, as the notch grinding wheel 72, for example, a metal bond grindstone formed by mixing metal powders such as Fe, Cr, and Cu with diamond abrasive grains as a main component is used. Since the metal bond grindstone has a strong holding force of the abrasive grains, the amount of protrusion of the abrasive grains is large, the amount of cut per abrasive grain can be increased, and the burden of the polishing process in the subsequent process can be reduced.

The diameter d of the tool holder 73 is made smaller than the diameter D of the vibrating portion 75, and the position of the step is set to a position that becomes an antinode of the standing wave at the frequency of the vibrating portion 75. The amplitude at the position of the notch grinding wheel 72 increases according to the diameter ratio D / d, and the vibration energy of the vibrating portion 75 is efficiently transmitted to the notch grinding wheel 72 at the tip. The tool holder 73 is a step horn type vibrator horn that resonates with the fundamental vibration in the vertical direction of the ultrasonic vibrator built in the vibration unit 75 and expands the amplitude.

FIG. 8 shows another embodiment of the tool holder 73, in which the upper figure is a conical horn and the lower figure is an exponential horn. In consideration of the amplitude expansion rate, the stress concentration coefficient, and the cost, the notch grinding wheel 72 is appropriately selected and used according to the material, the grinding amount, and the processing accuracy. The amplitude expansion rate is highest in the step horn type in FIG. 5, followed by the exponential type horn and the conical type horn, and the stress concentration coefficient is vice versa.

FIG. 9 shows the shape of the machined groove 72-1 of the notch grinding wheel 72 and the cross section of the wafer W to be chamfered. The machined groove 72-1 is composed of a groove portion 72-4 in the central portion and slopes 72-2 and 72-3 formed above and below the groove portion 72-4. The groove portions 72-4 are formed vertically so that the slopes 72-2 and 72-3 have the same angle as the chamfering angle of the end portion of the wafer W so as not to be sharp.

The angles of the slopes 72-2 and 72-3 are 3 to 55 °, preferably 5 to 45 °, and if the inclination angle is too large, the grinding resistance increases, the upper and lower corners on the end face are chipped, and scratches occur. Is not preferable. Further, the width T of the machined groove 72-1 is larger than the amplitude of the ultrasonic vibration with respect to the thickness of the wafer W. In FIG. 9, the arrow indicates that the ultrasonic vibration was applied in the axial direction, and when the amplitude of the ultrasonic vibration is ± 3 μm, the width T of the machined groove 72-1 is 6 μm larger than the thickness t of the wafer W. It has become.

FIG. 10 shows the details of the machined groove 72-1, and the notch grinding wheel 72 rotates at about 3000 to 30000 rpm while ultrasonically vibrating at 30 to 50 kHz in the arrow direction. Therefore, at the end surface of the waha W, the vertical groove portion 72-4 abuts on the waha W, and the tangential force with respect to the waha W due to the rotation of the notch grinding wheel 72 and the force in the vibration direction of the arrow are combined to proceed with the grinding. This results in a fine cut due to ultrasonic vibration. In addition, the number of working abrasive grains is increased by the same effect as helical grinding, and it is possible to eliminate the streaks generated on the surface to be ground, which cannot be avoided by grinding only by rotation.

On the other hand, in the chamfered portion of the wafer W, the slopes 72-2 and 72-3 similarly contact the wafer W, but the width T of the machined groove 72-1 is larger than the thickness of the wafer W, so that the slopes are intermittent. Grinding. Therefore, the particle size of the slopes 72-2 and 72-3 is # 3000 to # 6000, and the particle size of the groove 72-4 is # 1500 to # 3000. Further, the particle size of the slopes 72-2 and 72-3 is made larger than the particle size of the groove portion 72-4 so that the abrasive grains become finer. The upper and lower surface grinding, which is intermittent grinding, is made uniform by making the number of the notch grinding wheel 72 higher than the number of the central surface grinding.

Further, in the notch grinding wheel 72, a chamfering wheel material having a porous surface is impregnated with a lubricant together with a saturated fatty acid solution, and the surface is dried to obtain a lubricant-impregnated grindstone, and the grindstone containing this lubricant is water-cooled at the time of grinding. It is desirable to use it. As a result, the lubricant is reliably supplied to the cutting point of the grindstone, and the cutting point temperature can be set to a predetermined temperature or lower.

Further, in order to widen the width of the machined groove 72-1, it is machined widely by electric discharge machining in advance.

As described above, by rotating the notch grinding wheel 72 with respect to the wayha W and applying ultrasonic vibration, the moving direction of the abrasive grains intersects with the moving direction of the wayha W, and the machined groove 72-1 is formed. By making the width wider than the material to be machined, the same effect of applying helical grinding to chamfering can be obtained. As a result, the surface roughness and processing distortion of the end face are reduced, and even a high-count grindstone can be used for a long time.

11 and 12 show an example of the improvement effect when the present embodiment is applied. FIG. 11 is a photomicrograph showing the surface roughness of the chamfered slope portion, and FIG. 12 is a photomicrograph showing the surface roughness of the end face portion. The left figure is the grinding process with ultrasonic vibration added.

In the slope portion in FIG. 11, ultrasonic vibration causes intermittent grinding in the vertical direction with respect to the machined surface of the chamfered portion of the wafer W, and chips are generated in small steps. Further, the lubrication state is improved at the interface where the notch grinding wheel 72 and the wafer W are in contact with each other, and the friction reducing effect, the cleaning of the grinding surface, and the discharge of grinding debris are promoted. As a result, the original cutting ability and the vibration acceleration motion of the abrasive grains are added, the cutting resistance is reduced, and the grinding performance is improved.

In FIG. 11, the count of the notch grinding wheel 72 is set to # 3000, but the surface roughness is 0 in the grinding process in which ultrasonic vibration is applied to the surface roughness of 1.1 μm due to the grinding process just by rotating. The thickness was 5 μm, and an improvement effect of 50% or more was obtained.

At the end face portion in FIG. 12, the ultrasonic vibration results in grinding parallel to the machined surface, resulting in low damage processing in which the mobility of the abrasive grains is increased and cavitation is caused on the parallel surface. As a result, in the figure on the right, which is the grinding process only by rotating the notch grinding wheel 72, streaks due to the abrasive grains contained in the notch grinding wheel 72 are observed on the surface to be ground, but the grinding process with ultrasonic vibration is applied. In the figure on the left, the movement of the grindstone becomes a crosshatch locus, and the streaks are flattened.

In FIG. 12, the count of the notch grinding wheel 72 is set to # 3000, but the surface roughness is 0 in the grinding process in which ultrasonic vibration is applied to the surface roughness of 1.6 μm due to the grinding process just by rotating. The thickness was 4 μm, and an improvement effect of 70% or more was obtained.

As described above, in the notch groove grinding process to which ultrasonic vibration is applied, the notch grinding wheel 72 is rotated and ultrasonic vibration is applied in the axial direction, so that the generation of streaks is suppressed and the surface roughness is good. Can be realized. Then, the burden of polishing, which is a post-process, can be reduced, the shape at the time of grinding can be maintained even after polishing, and an accurate shape can be formed. In addition, the shape accuracy and the life of the grindstone can be improved by improving the processing efficiency, clogging prevention and processing performance. Cleaning of the ground surface and discharge of grinding debris can be promoted, and grinding performance can be maintained or the accuracy of the grindstone shape can be maintained.

Further, good processed surface roughness can be obtained even when the end face is not chemically strengthened, and the occurrence of microcracks can be suppressed. As a result, the production efficiency is extremely improved, and a practically sufficient end face strength can be obtained.

Furthermore, not only the surface roughness, but also the number of sheets that can be continuously machined after the grinding groove is corrected (tooling) once, until the grinding ability is reduced, the predetermined outer peripheral surface width, outer peripheral angle, and outer peripheral shape are not satisfied. Can be increased.

The above description describes the grinding process by applying ultrasonic vibration of the notch groove using the notch grinding wheel 72, but the orientation flat, the chamfering process on the outer peripheral portion of the wafer, and the cover having a straight portion other than a circle at the end of the planar shape. It may be applied to the end face processing of the processed material. In addition, not only semiconductor wafers such as silicon wafers used for manufacturing semiconductor devices, but also various materials such as silicon, sapphire, compounds, and glass, and high-precision chamfering on the end faces of plate-shaped workpieces such as glass panels. It is also effective for processing.

1 ... Notch groove, 10 ... Machined part, 11 ... Single crystal block, 12 ... V-shaped cross section groove, 13 ... Flat surface, 14 ... Orientation flat, 20 ... Supply and recovery part, 30 ... Wafer cassette, 31 ... Cassette table, 40 ... Supply and recovery robot, W ... Wafer, 50 ... Transfer arm, 60 ... Wafer feed device, 61 ... Notch grinding device, 62 ... Outer peripheral grinding device, 63 ... Transfer arm, 66 ... Chuck table, 68 ... Outer peripheral spindle, 69 ... Outer circumference Grinding wheel, 71 ... Grinding spindle, 72 ... Notch grinding wheel, 72-1 ... Machined groove, 72-2, 72-3 ... Slope, 72-4 ... Groove, 73 ... Tool holder, 74 ... Bearing, 75 ... Vibration Department

Claims (10)

A chamfer grinding method in which the end face of a plate-shaped workpiece is ground with a grinding wheel that rotates around a rotation axis.
The grinding wheel is a total-shaped grindstone having a groove portion that is a machined groove parallel to the axial direction of the rotation axis and slopes formed above and below the groove portion.
The grinding wheel is rotated and ultrasonic vibration is applied in the axial direction.
Grinding is performed by pressing the machined groove from the vertical direction against the end face of the material to be machined and abutting the groove.
A chamfering grinding method characterized in that the width of the machined groove is made larger than the amplitude of the ultrasonic vibration with respect to the thickness of the material to be machined. The chamfer grinding method according to claim 1.
Chamfering is characterized in that a chamfered notch groove is formed by pressing the machined groove from the vertical direction into contact with the end surface of the sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the material to be machined. Grinding method. The chamfer grinding method according to claim 1 or 2, wherein the width dimension of the machined groove is the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration. The chamfer grinding method according to any one of claims 1 to 3.
The grinding wheel is replaceably attached to a grinding spindle provided with a vibrating portion that rotates the grinding wheel and imparts ultrasonic vibration to the grinding wheel.
A chamfering grinding method characterized in that the diameter of the grinding wheel is made smaller than the diameter of the vibrating portion. The total-shaped grindstone further has a curved surface portion connecting the groove portion and each of the slope portions.
The surface of the curved surface portion is a cross-sectional view of the grinding wheel.
The claim that the imaginary line extending the groove portion and the imaginary line extending the slope are arranged on the work material side with reference to the intersection, and are convex in the direction from the work material toward the grinding wheel. The chamfer grinding method according to any one of 1 to 4. 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 to the axial direction of the rotating shaft is provided.
The grinding wheel is a total-shaped grindstone having a groove portion parallel to the axial direction as a machined groove and slopes formed above and below the groove portion.
The width of the machined groove is increased by the amplitude of the ultrasonic vibration or more with respect to the thickness of the work material.
A chamfer grinding apparatus characterized in that the machined groove is pressed against the end surface of the material to be machined from a vertical direction to grind. In the chamfer grinding apparatus according to claim 6,
A chamfering grinding apparatus characterized in that a chamfered notch groove is formed by pressing the machined groove from a vertical direction onto a sliced V-shaped cross-sectional groove formed on the outer peripheral surface of the material to be machined. The chamfer grinding apparatus according to claim 6 or 7, wherein the width dimension of the machined groove is the sum of the thickness dimension of the work material and the width dimension of the amplitude of the ultrasonic vibration. In the chamfer grinding apparatus according to any one of claims 6 to 8.
The grinding wheel is interchangeably attached to the grinding spindle provided with a vibrating portion that gives ultrasonic vibration, and the diameter of the grinding wheel is smaller than the diameter of the vibrating portion. .. The total-shaped grindstone further has a curved surface portion connecting the groove portion and each of the slope portions.
The surface of the curved surface portion is a cross-sectional view of the grinding wheel.
The claim that the imaginary line extending the groove portion and the imaginary line extending the slope are arranged on the work material side with reference to the intersection, and are convex in the direction from the work material toward the grinding wheel. The chamfer grinding apparatus according to any one of 6 to 9.

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