US20230415293A1

US20230415293A1 - Method of forming truer

Info

Publication number: US20230415293A1
Application number: US18/324,151
Authority: US
Inventors: Shinichi KISHISHITA; Masaki Ishii
Original assignee: Tokyo Seimitsu Co Ltd
Current assignee: Tokyo Seimitsu Co Ltd
Priority date: 2022-06-22
Filing date: 2023-05-26
Publication date: 2023-12-28
Also published as: JP2024001517A; KR20230175103A

Abstract

A method of forming a truer in a truing where a groove of a grinding wheel used for grinding a chamfer portion of a wafer is formed by a truer having a disc-shape, wherein the method comprising: a process A for adjusting a diameter and a rough shape of the truer by a master grinding wheel for forming the truer; and a process B for forming an edge of the truer into a target shape, wherein the process A and the process B are performed by a plurality of master grooves having different shapes from each other, the plurality of master grooves being provided with the master grinding wheel or the process A and the process B are performed by a plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent specification is based on Japanese patent application, No. 2022-100214 filed on Jun. 22, 2022 in the Japan Patent Office, the entire contents of which are incorporated by reference herein.

PRIOR ART

[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-153085
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 2018-167331
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 2021-181151

BACKGROUND OF THE INVENTION

The present invention relates to a truing of a chamfering device for precisely chamfering an end surface of a plate shaped workpiece made of various materials such as silicon, sapphire, compound and glass (in particular, a semiconductor wafer and a glass panel) and relates to a method of forming a truer used in a truing for forming working grooves of a grinding wheel which grinds and chamfers a plate-shaped workpiece.
Conventionally, when the plate-shaped workpiece such as the semiconductor wafer is chamfered by grinding, the processing is performed by pressing the grinding wheel on an outer peripheral portion of the workpiece. In general, the outer peripheral portion of the grinding wheel is provided with the groove having the shape and dimension corresponding to the target shape of the plate-shaped workpiece. The grinding of the outer peripheral portion of the workpiece is performed by an inner peripheral surface of the groove by inserting the outer peripheral portion of the plate-shaped workpiece into the groove. The shape and the dimension of the groove are changed and the inner peripheral surface of the groove is worn or damaged after the chamfering processing is repeated. Thus, the accuracy of the processing deteriorates.
The chamfering processing is performed over a long period, it is necessary to replace the grinding wheel or form the shape of the grinding wheel again. Therefore, the grinding wheel is processed by a truing grinding wheel (truer). Namely, the truing is performed. In the truing, the truing grinding wheel is ground in a state that the truing grinding wheel is in contact with an inner peripheral surface of a total form groove of a master grinding wheel, the total form groove having the target shape of the workpiece. The total form groove having the same shape as the master grinding wheel is formed on the grinding wheel used for the actual chamfering processing by abutting the outer peripheral portion of the truing grinding wheel on the grinding wheel. The truing grinding wheel is made of the material (e.g., GC wheel) which is harder than the material (e.g., resin bond grinding wheel) of the grinding wheel used for the actual chamfering processing. The master grinding wheel is made of the material (e.g., metal bond grinding wheel) which is harder than the material of the truing grinding wheel.
As a method for truing the shape of the groove of a chamfering wheel used for a chamfering device for a plate-shaped workpiece into a desired shape easily, the method of transferring the groove shape of the master grinding wheel to the outer periphery of the truing grinding wheel and transferring the outer peripheral shape of the truing grinding wheel to the chamfering wheel to form the groove on the chamfering wheel is conventionally known. For example, the above described method is disclosed in Patent Document 1.
In a normal grinding, a chamfer portion is ground in a state that a main surface of the wafer is perpendicular to a rotation axis of a resin grinding wheel. In this case, grinding marks easily appear in a circumferential direction of the chamfer portion. A so-called helical grinding is known for grinding the chamfer portion of the wafer in a state that a resin bond grinding wheel is inclined with respect to the wafer.
In the helical grinding, when the formation or the correction (truing) of the groove is performed on the resin grinding wheel by using the truer having the end portion which is formed symmetrically in the vertical direction, a twist occurs in the truer since the resin grinding wheel is inclined. Thus, the groove of the resin grinding wheel is asymmetrically formed in the vertical direction. Patent Document 2 discloses the method of processing the upper part or the lower part in the expected position of the groove by the truer having the thickness smaller than the width of the groove of the grinding wheel for grinding the chamfer portion of the wafer and then relatively lowering or raising the truer in the thickness direction with respect to the grinding wheel. Thus, the transfer rate and the workability are improved in the truing and the accuracy of the groove formed by the truer is improved.
Patent Document 3 discloses the method of relatively moving the grinding wheel with respect to the workpiece so that the contact portion between the workpiece and the protruded grinding portion located at the outer peripheral portion of the grinding wheel is moved in accordance with the movement conditions calculated based on the curvature radius of an arc-shaped portion of the grinding wheel for performing the chamfering processing easily, efficiently and precisely with a simple structure for supporting and driving the workpiece and the grinding wheel and forming the shape of the grinding wheel easily.

SUMMARY OF THE INVENTION

In the above described conventional technology, Patent Document 1 uses the method where the shape of the groove of the master grinding wheel, which is the grinding wheel for forming the truer, is transferred to the edge of the truer as it is by cutting the truer with the groove of the master grinding wheel. Thus, only one kind of shape can be formed by one groove of the master grinding wheel. Accordingly, it is difficult to change the shape of the truer. It is impossible to change the shape when the processing conditions of the chamfering device (e.g., settings of rotation axis of grinding wheel) are changed.
In the methods described in Patent Documents 2 and 3, although the shape of the truer can be changed, the shape cannot be corrected precisely to obtain a desired processing shape and the accuracy of the edge shape of the truer cannot be further improved.
The present invention reduces time and cost for forming the truer and achieves quality uniformity. Furthermore, the present invention improves the transfer rate and the workability in the truing and improves the accuracy of the groove formed on the truer. In particular, the present invention improves the precision of an edge shape of the truer. Thus, the present invention further improves the dimensional accuracy of the groove shape and the angle of the groove of the outer periphery grinding wheel to which the shape of the truer is transferred. In addition, the present invention prevents the corner of the end portion from being rounded. Accordingly, the accuracy of the finally chamfered shape is improved.
The configurations of the present invention for achieving the above described purposes are as follows.
[1] A method of forming a truer in a truing where a groove of a grinding wheel used for grinding a chamfer portion of a wafer is formed by a truer having a disc-shape, wherein the method comprising: a process A for adjusting a diameter and a rough shape of the truer by a master grinding wheel for forming the truer; and a process B for forming an edge of the truer into a target shape, wherein the process A and the process B are performed by a plurality of master grooves having different shapes from each other, the plurality of master grooves being provided with the master grinding wheel or the process A and the process B are performed by a plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel.
[2] The method of forming the truer of [1], wherein the process A and the process B are performed by a first groove and a second groove which are the plurality of master grooves having different shapes from each other, the first groove and the second groove being provided with the master grinding wheel.
[3] The method of forming the truer of [2], wherein an edge processing is performed by using an end portion of the second groove after the truer is processed by the first groove.
[4] The method of forming the truer of [2], wherein a radius of an arc-shaped portion of an end portion of the second groove is larger than a radius of an arc-shaped portion of an end portion of the first groove.
[5] The method of forming the truer of any one of [2] to [4], wherein a chamfering processing of the truer is performed by at least one of the plurality of master grooves by moving the truer in a direction of separating from at least one of the plurality of master grooves.
[6] The method of forming the truer of [3], wherein a corner R processing of the truer is performed by using the end portion of the second groove for adjusting a shape, a radius and a roundness of the corner of the truer while reducing a moving distance of the truer.
[7] The method of forming the truer of [6], wherein the corner R processing of a lower surface of the truer is performed after the corner R processing of an upper surface of the truer is performed.
[8] The method of forming the truer of [7], wherein parameters of a movement start position, a machining speed, an escape position, an escape speed, a rotation speed of the truer, a machining start point and a machining end point are determined by using the value of the corner R processing of the upper surface and the value of the corner R processing of the lower surface, the movement start position including an entering point and an entering speed.
[9] The method of forming the truer of [8], wherein an amplitude, the machining speed, a spark-out time and the number of times of reciprocating motion are specified as a traverse motion independently for the corner R processing of the upper surface and the corner R processing of the lower surface.
[10] The method of forming the truer of [1], wherein the process A and the process B are performed by using the plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel, and the process B is performed by using an end portion of at least one of the plurality of master grooves.
[11] The method of forming the truer of [10], wherein the process A is performed by using a bottom portion of at least one of the plurality of master grooves.
[12] A master grinding wheel of forming a truer for forming a groove of a grinding wheel used for grinding a chamfer portion of a wafer, the master grinding wheel comprising: a first groove for adjusting a diameter and a rough shape of the truer; and a second groove for forming an edge of the truer into a target shape, the second groove being different from the first groove.
[13] A master grinding wheel of forming a truer for forming a groove of a grinding wheel used for grinding a chamfer portion of a wafer, wherein at least one master groove of the master grinding wheel comprising: a first portion for adjusting a diameter and a rough shape of the truer; and a second portion for forming an edge of the truer into a target shape, the second portion being different from the first portion.
The present invention reduces time and cost for forming the truer and achieves quality uniformity. Furthermore, the present invention improves the transfer rate and the workability in the truing and improves the accuracy of the groove formed on the truer. In particular, the present invention further improves the precision of the edge shape of the truer. Thus, the present invention improves the dimensional accuracy of the groove shape and the angle of the groove of the outer periphery grinding wheel to which the shape of the truer is transferred. In addition, the present invention prevents the corner of the end portion from being rounded. Accordingly, the accuracy of the finally chamfered shape is improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a main part of a chamfering device concerning an embodiment of the present invention.

FIG. 2 is a side view showing a truing process in an embodiment of the present invention.

FIGS. 3A and 3B are side views showing a state that a wafer W is processed by a grinding wheel 55 formed in a recessed groove in an embodiment of the present invention.

FIGS. 4A and 4B are side views showing a method of forming a truer 41 in an embodiment of the present invention.

FIGS. 5A to 5C are side views showing a precise machining performed by a second groove 62 in an embodiment of the present invention.

FIG. 6 is a flowchart showing procedures of a forming processing of the truer 41 in an embodiment of the present invention.

FIG. 7 is a flowchart showing procedures of an edge processing shown in FIG. 6 in an embodiment of the present invention.

FIGS. 8A to 8G are explanation drawings showing procedures of a forming processing of the truer 41 in an embodiment (second embodiment) of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Hereafter, an embodiment (first embodiment) of the present invention will be explained in detail referring to the drawings. FIG. 1 is a front view showing a main part of a wafer chamfering device concerning an embodiment of the present invention. A wafer chamfering device 10 comprises a wafer feeding unit 20, a grinding wheel rotating unit 50, a not-illustrated wafer supplying/housing portion, a not-illustrated wafer cleaning/drying portion, a not-illustrated wafer transferring unit and a controller for controlling the operations of the components of the wafer chamfering device, for example.
The wafer feeding unit 20 includes an X-axis base 21 placed on a body base 11, two X-axis guide rails 22, four X-axis linear guides 23 and an X table 24 which is moved in the X-direction shown in the figure by an X-axis driving mechanism 25 comprised of a ball screw and a stepping motor.
The X table 24 incorporates two Y-axis guide rails 26, four Y-axis linear guides 27 and a Y table 28 a which is moved in the Y-direction shown in the figure by a not-illustrated Y-axis driving mechanism comprised of a ball screw and a stepping motor.
The Y table 28 incorporates two Z-axis guide rails 29 and a Z table 31 which is moved in the Z-direction in the figure by a Z-axis driving mechanism 30 guided by not-illustrated four Z-axis linear guides and comprised of a ball screw and a stepping motor.
The Z table 31 a θ-axis motor 32 and a θ spindle 33. A wafer table 34 on which the wafer W (plate-shaped workpiece) is placed and sucked is attached to the θ spindle 33. The wafer table 34 is rotated in the θ direction shown in the figure around the rotation axis CW of the wafer table.
The wafer W and a truer 41 are rotated in the θ direction and moved in the X, Y and Z directions shown in the figure by the wafer feeding unit 20.
The grinding wheel rotating unit 50 includes a circumferential grinding spindle 51 on which a circumferential rough grinding wheel 52 is installed, a circumferential fine grinding spindle 54 and a circumferential fine grinding motor 56 which are installed on a turntable 53 arranged on an upper part. The circumferential grinding spindle 51 is driven by a not-illustrated circumferential grinding wheel motor to rotate around an axial center.
A grinding wheel 55, which is a chamfering wheel for performing finish-grinding on an outer periphery of the wafer W, is installed on the circumferential fine grinding spindle 54. The circumferential fine grinding spindle 54 performs the finish processing for chamfering the outer periphery of the wafer W in a state that the rotation axis of the circumferential fine grinding spindle 54 is inclined 3 to 15°, preferably 6 to 10° with respect to the rotation axis of the wafer W. The helical grinding is performed as described above. Although slight grinding marks are generated on the chamfer portion of the wafer W in an oblique direction, the effect of improving the surface roughness of the chamfer portion can be obtained compared to the normal grinding.
The wafer processing is performed in the order of slicing, chamfering, lapping, etching, donor killer and precise chamfering. Various cleanings are performed between the above described steps to remove the cut waste. The material such as silicon is hard and brittle. If the end surface of the wafer remains sharp after the slicing, the wafer is easily cracked or chipped when transferring or positioning the wafer in the subsequent processing. The pieces of the cracked or chipped wafer may damage or stain the surface of the wafer. In order to prevent the above described problem, the chamfering processing is performed for chamfering the end surface of the sliced wafer by the chamfering wheel coated with diamond.
The grinding wheel 55 used here is made of metal powder such as Fe, Cr and Cu as a main component of abrasive grain and is formed by mixing diamond abrasive grain, for example. The binder of the grinding wheel 55 is made of phenol resin, epoxy resin, polyimide resin, polystyrene resin or polyethylene resin as a main component and is preferably formed by mixing diamond abrasive grain or cubic boron nitride abrasive grain, for example.
In addition, the grinding wheel 55 used here is the resin bond grinding wheel using the diamond abrasive grain having the diameter of 50 mm and the grain size of #3000. The circumferential fine grinding spindle 54 is the spindle driven by a built-in motor using air bearing and is rotated at the rotation speed of 35000 rpm.
FIG. 2 is a side view showing the truing process. The working groove for the chamfering processing is formed on the grinding wheel 55 by the truer 41. The truer 41 having a disc-shape is installed on a lower portion of the wafer table 34 so that the truer 41 is coaxially with a rotation axis of the wafer table. Thus, the truer is rotated by the wafer table 34. The outer peripheral portion of the truer 41 is preliminarily chamfered by the master grinding wheel (shown in FIGS. 3A and 3B). Namely, the working groove for the chamfering processing is formed on the grinding wheel 55 by using the truer 41 in a state that the cross-sectional shape of the master grinding wheel (shown in FIGS. 3A and 3B) is transferred to the outer peripheral portion of the truer 41.
The truer 41 is preferably formed by combining abrasive grain made of silicon carbide by using the phenol resin while adding a filler if required and forming the combined material into the truer 41 having a disc-shape, for example. In addition, the truer 41 has the outer diameter equal to or smaller than the size of the wafer W, has the same thickness as the thickness of the wafer W and has a disc-shape. The truer 41 can be a GC (Green silicon carbide) wheel or WA (White fused alumina) wheel. It is preferable that the grain side of the grinding wheel is approximately #320.
FIGS. 3A and 3B are side views showing a state that the wafer W is processed by the grinding wheel 55 formed in a recessed groove. If the linear portion is processed by the protruded grinding wheel shown in Patent Document 3, the processing is performed by a point contact. Thus, uneven abrasion is generated on the grinding wheel and the machining locus appears as the streak. Accordingly, the surface roughness deteriorates and the processing time becomes long. In addition, if the processing is performed by the point contact of the protruded grinding wheel, the processing time becomes long and the processing stress escapes. Thus, it is difficult to form the target shape.
On the other hand, as shown in FIG. 3A, when a rough shape is formed by the recessed groove (recessed grinding wheel), the processing stress hardly escapes by cancelling the stresses of the upper inclined surface and the lower inclined surface. Thus, the shape hardly becomes bad even when forming the linear portion. In addition, the line contact is possible also at the linear portion when processed by the recessed groove. Accordingly, the processing time is short, the streak does not appear, the surface roughness is improved, the processing load is reduced and the wheel life is improved remarkably.
FIG. 3B shows the state that an arbitrary finished shape is formed by using an end portion shown by the arrow mark A which does not contribute to the processing of the diameter and the rough shape in the grinding wheel 55. Although the portion of the arrow mark A is shown by a straight line in the figure, this portion can also include a curved line (surface). Because of this, the shape, the radius, the roundness and the like of the corner portion can be formed more accurately. At this time, as shown by the arrow mark B, when the wafer W is moved in a pulling direction which is the direction of separating from the grinding wheel 55, the contact area between the wafer W and the grinding wheel 55 becomes larger. Thus, the processing load is reduced and the wheel life becomes long. In addition, if the difference between the shape before the processing and the target shape is large, the grinding amount ground by the end portion increases and the abrasion of the grinding wheel 55 b increases. Thus, it is preferable to preliminarily make the groove shape of the grinding wheel 55 close to the target shape.
FIG. 4A is a side view showing a method of forming the truer 41. A master grinding wheel 60 for forming the truer 41 includes a plurality of grooves (first groove 61, second groove 62) as the master grooves. The first groove 61 is used for adjusting the diameter and the rough shape of the truer 41. The first groove 61 can be the total form groove. In addition, the adjustment of the diameter and the rough shape adjusted by the first groove 61 can be the transferring of the grove shape of the first groove 61 to the truer 41. On the other hand, the second groove 62 is used for adjusting the edge of the truer 41 into a target shape (arbitrary and desired cross-sectional shape). The second groove 62 includes the arc-shaped (round-shaped, R-shaped) portion having a larger radius at the end portion (opening portion). Namely, the shapes of the first groove 61 and the second groove 62 are different from each other. When the arc-shaped portion of the second groove is used, the truer 41 having an arbitrary cross-sectional shape can be obtained although the arbitrary cross-sectional shape cannot be obtained merely by transferring the groove shape.
FIG. 4B is an enlarged view of the second groove 62. The second groove 62 includes a linear portion 81 which is approximately parallel to the thickness direction (Z-direction) of the master grinding wheel 60, upper and lower inclined portions 82 which are extended from the end portion of the linear portion 81, and upper and lower arc-shaped portions 83 having a curved line extended from the end portion of each of the inclined portions 82 to the opening portion. Although the second groove 62 shown in FIG. 4B includes the linear portion 81, the inclined portions 82 and the arc-shaped portions 83, the second groove 62 is not limited to the configuration shown in FIG. 4B. It is enough if the second groove 62 includes the linear portion 81 and the arc-shaped portions 83. Although the linear portion 81 and the inclined portions 82 are shown by straight lines (in the cross-sectional shape), the linear portion 81 and the inclined portions 82 can include curved lines (curved surfaces).
The master grinding wheel 60 is rotated at the rotation speed of 8000 rpm, for example. In this state, the Z table 31 is moved by the Z-axis driving mechanism 30 so that the height of the truer 41 is aligned with the height of each of the grooves of the master grinding wheel 60.
Then, the Y table 28 is moved toward the master grinding wheel 60. When the Y table 28 is moved in the Y-direction, the outer peripheral portion of the truer 41 is cut in the master groove of the master grinding wheel 60 and the wafer table 34 is slowly rotated by the θ-axis motor 32 for one revolution. Thus, the outer peripheral portion of the truer 41 is chamfered and the shape of the master groove is transferred to the outer peripheral portion of the truer 41. Then, the truer 41 is moved in the direction of separating from the master grinding wheel 60. Thus, the transfer from the cross-sectional shape of the master groove to the cross-sectional shape of the outer peripheral portion of the truer 41 is finished.
The transferring method from the master groove to the truer 41 (i.e., the forming processing of the truer 41) is as follows. First, as described above, the outer peripheral portion of the truer 41 is cut in the first groove 61 as shown in the arrow mark D for adjusting the diameter and the rough shape of the truer 41. Then, the edge processing including the adjustment to an accurate and arbitrary cross-sectional shape is performed by mainly using the arc-shaped portions 83 of the second groove 62.
FIGS. 5A to 5C are side views showing a precise machining performed by the second groove 62. FIG. 6 is a flowchart showing procedures of the forming processing of the truer 41. FIG. 7 is a flowchart showing detailed procedures of the edge processing in FIG. 6 (Step 4 in FIG. 6 ). The outline of the forming processing of the truer 41 shown in FIG. 6 is (1) input of various conditions (Step 1), (2) calculation of the processing conditions (machining start point, machining end point) of the chamfering device based on the various input conditions (Step 2), (3) forming processing of the truer 41, mainly diameter processing (Step 3) and (4) edge processing (Step 4).

Steps

1, 2

The various conditions to be inputted as parameters are a diameter, a chamfering angle, an end shape (straight line length m, surface width n, size of the corner R of the end portion), a movement start position (entering point, entering speed), a chamfering speed, a machining speed of the roundness of the corner, an escape position, an escape speed, a rotation speed of the truer 41 and a rotational speed of the master grinding wheel 60, for example.
The chamfering method using the chamfering device includes the transfer of the shape of the master groove shown in Step 3 below and the adjustment to an arbitrary shape shown in Step 4 below using the arc-shaped portion of the master groove (second groove). Therefore, an example of the conditions inputted in this step can be the data of an arbitrary and desired cross-sectional shape. The desired cross-sectional shape can be the total form groove. It is preferred that the desired cross-sectional shape is smaller than the cross-sectional shape after being ground by the first groove 61. The desired cross-sectional shape can be an arbitrary shape without depending on the groove shapes of the first groove 61 and the second groove 62. Note that the processing conditions calculated by the chamfering device are mainly the machining start point and the machining end point.

Step 3: Process A

Step 3 is the process of adjusting the diameter and the rough shape of the truer (process A). This step is performed by using the first groove 61. In this step, the master grinding wheel 60 is rotated at the rotation speed of 8000 rpm, for example. The height of the truer 41 is aligned with the height of the master groove (first groove 61) of the master grinding wheel 60 and the processing is started. The truer 41 is moved toward the master grinding wheel 60 as shown in the arrow mark D, and the outer peripheral portion of the truer 41 is cut in the master groove (first groove 61) of the master grinding wheel 60. Thus, the end surface of the outer peripheral portion of the truer 41 is mainly chamfered. In the diameter processing, the parameters of the processing conditions are determined by using two types of values: one is the value of the corner R processing (upper surface) and the other is the value of the corner R processing (lower surface). As one embodiment, the corner R processing of the lower surface is performed after the corner R processing of the upper surface is performed.
As described above, the adjustment of the diameter and the rough shape is performed by using the recessed groove in this method. Thus, the point contact between the master grinding wheel and the truer is avoided and the processing stress hardly escapes. As a result, the grinding process can be performed efficiently.

Step 4: Steps 401 to 407 in Detail: Process B

Step 4 is the process of forming the edge of the truer into a target shape (process B). The processing of this step is performed by using the second groove 62 having different (cross-sectional) shape from the shape of the first groove 61. “The second groove 62 having different shape from the shape of the first groove 61” means a state that the arc-shaped portion is provided at the end portion (near the opening portion) of the second groove 62 as one embodiment. The other shapes than the arc-shaped portion can be also used as long as the shape is different from the shape used in the process A. In the flowchart, specifically, after the diameter and the rough shape are formed by the first groove 61, the truer 41 is moved to the movement start position where the height of the truer 41 is aligned with the height of the second groove 62 as shown in FIG. 5A (Step 401).
The chamfering device specifies the parameters of the processing conditions based on the various conditions (e.g., data of desired cross-sectional shape) inputted beforehand (Step 402). Then, the truer 41 moves to the entering point at a predetermined entering speed (Step 403). The rotation of the truer 41 is started (Step 404) and the portion shown by the bold line in FIG. 5B is chamfered at a predetermined chamfering angle (Step 405). At this time, since the second groove 62 is the recessed groove, the processing is performed in the line contact state. Accordingly, the processing time is short, the streak does not appear, the surface roughness is improved and the processing load is reduced. In addition, it is preferred that the chamfering processing is performed in the direction of pulling the truer 41 (direction of separating from the groove) as shown in the arrow mark B in FIG. 5C for reducing the processing load.
After the chamfering processing, the corner R processing is performed for processing the more detailed portions while reducing the moving distance (i.e., machining feed amount) of the truer 41 (Step 406). Specifically, the corner R processing for forming the shape, the radius, the roundness and the like of the corner portion is performed. The corner R processing (upper surface) is performed by using the end portion of the second groove 62 having the arc-shaped portion shown by the arrow mark A which does not contribute to the processing of the diameter. The radius of the arc-shaped portion of the end portion of the second groove 62 is larger than the radius of the arc-shaped portion of the end portion of the first groove 61. Accordingly, the shape, the radius and the roundness of the corner portion of the truer 41 can be processed more accurately, the streak does not appear and the surface roughness is improved.
After the corner R processing (upper surface) is finished, the truer 41 is moved to the movement start position for performing the corner R processing (lower surface) in Step 401. Then, Step 401 to Step 405 are repeated similarly. In addition, the parameters such as the movement start position (entering point, entering speed), the escape position, the machining speed, the escape speed, the rotation speed of the truer 41, the machining start point, the machining end point are determined by using two types of values: one is the values of the corner R processing (upper surface) and the other is the corner R processing (lower surface).
It is preferred that the amplitude, the machining speed, the spark-out time, the number of times of reciprocating motion are specified as a traverse motion independently for each process for improving the surface roughness. Note that the spark-out means the operation of continuing the grinding without cutting at the end of the grinding operation. The processing is advanced by a minute amount.
When a predetermined width of the circumferential surface, a predetermined circumferential angle or a predetermined circumferential shape are not satisfied due to the reduction of the grinding ability, the correction (truing) of the groove of the grinding wheel 55 is appropriately performed by using the truer 41. At this time, when the truing of the present invention is performed, the number of the wafers capable of being processed by one truing increases and life becomes long even if the resin grinding wheel is used. The number of wafers capable of being processed by one resin grinding wheel increases. Accordingly, it is also possible to reduce the cost for manufacturing the semiconductor wafer.
In the present embodiment, it is not required to use another grinding wheel (groove) for forming the truer even when the grinding wheel 55 is changed to the other shape. Accordingly, the present embodiment can improve the accuracy of the grinding wheel 55 and eliminate the replacement operation or new creation of the grinding wheel. Thus, the cost can be reduced and the time from the order to the manufacturer of the grinding wheel to the delivery of the grinding wheel can be shorten compared to the case where the grinding wheel is newly manufactured.

Second Embodiment

Hereafter, the second embodiment of forming the diameter and the rough shape and adjusting to an arbitrary shape (edge processing) by using the second groove 62 will be explained. Note that the explanation of the wafer chamfering device and the like to be used is omitted since they are same as the first embodiment. Hereafter, the difference from the first embodiment will be mainly explained.
FIGS. 8A to 8G are explanation drawings showing the procedures of the forming processing of the truer 41 performed by using the second groove 62 in the present embodiment. First, FIG. 8A shows the state before the truer 41 is processed. In the following processes, the diameter and the rough shape of the truer 41 are adjusted to a cross-sectional shape 84.
Note that the drawings are schematically shown. The shapes are exaggeratingly shown for clearly explaining the difference before and after the truer 41 is processed. Although the object to be processed (ground) is the truer 41 in FIGS. 8A to 8G, this method can be also applied to the grinding of the wafer and the like without being limited to the truer 41.
FIG. 8B shows the state that the truer is cut in the rotating master grinding wheel 60 for adjusting the diameter and the rough shape of the truer 41 into the cross-sectional shape 84 (process A). At this time, the end portion of the truer 41 is contacted with the linear portion 81 and the inclined portion 82, which are the bottom portion of the second groove 62 of the master grinding wheel, and the truer 41 is ground. In other words, the process A is performed by using the linear portion 81 and the inclined portion 82 which are the bottom portion of the second groove 62 in the present embodiment. The linear portion 81 and the inclined portion 82 have the similar function as the already explained recessed groove such as the first groove 61. It is possible to adjust the diameter and the rough shape of the truer 41 in almost the line contact state so that stress does not escape.
After the rough shape is adjusted and the cross-sectional shape of the truer 41 becomes the state shown as 84, the edge processing is performed by the arc-shaped portions 83 (process B). The process B is performed by using the portion which is different from the portion used for the process A and this portion has the different shape from the shape of the portion used for the process A. Specifically, the process B is performed by using the arc-shaped portions 83 located at the end portion (end portion in the opening direction) of the second groove 62.
The linear portion 81 and the inclined portion 82 used in the process A have the function of the recessed groove as described above. The recessed groove can form the rough shape efficiently by contacting with the truer 41 in the line contact state so that stress does not escape. In other words, the groove shape can be easily transferred to the truer 41.
On the other hand, the arc-shaped portions 83 used in the process B have a convex shape protruded toward the inside of the groove. Thus, the shape is different from the linear portion 81 and the inclined portion 82 which are linearly formed. When the truer 41 is in contact with the arc-shaped portions 83, an arbitrary shape can be formed in accordance with the position of the truer and the manner of the contact.
The explanation of the steps will be restarted here. After, the diameter and the rough shape are adjusted, the truer 41 is moved in the Z (−) direction along the arc-shaped portions 83 located in the Z (−) direction of the second groove 62 while separating from the linear portion 81 and the inclined portion 82 (for changing the position to be used). The arrow mark shown in FIG. 8B shows the moving direction of the truer 41.
The edge processing of the truer 41 is performed while moving along the arc-shaped portions 83. FIG. 8C and 8D show the state of the edge processing processed by the arc-shaped portions 83. In this process, the edge shape and the like are adjusted by moving (reciprocating if required) the truer 41 along the arc-shaped portions 83 based on the data of the desired cross-sectional shape received in the Step 1 of FIG. 6 as described above. Typically, the arc-shaped portions 83 are preferably not in contact with the truer 41 in the process (process A) of adjusting the diameter and the rough shape. Since the arc-shaped portions 83 have a curved shape, it is easy to adjust the cross-sectional shape arbitrarily in accordance with the manner of abutting the truer 41 (i.e., manner of moving the truer 41 in Y-axis and Z-axis directions) (process B).
Then, similarly, as shown in FIG. 8E and FIG. 8F, the shape of (mainly) the upper end side of the truer 41 is adjusted by moving the truer 41 along the arc-shaped portion 83 located at the upper (Z (+)) side of the second groove 62. Although the lower surface of the truer 41 is processed in advance in the present embodiment, it is also possible to process the upper surface of the truer 41 in advance as already explained.
FIG. 8G shows the truer 41 after the edge processing is finished. A cross-sectional shape 85 of the truer 41 after the above described adjustment can have the different shape from 84 whose diameter and rough shape are adjusted by the linear portion 81 and the inclined portion 82. In other words, this method enables to adjust the diameter and the rough shape and further enables the processing to obtain an arbitrary cross-sectional shape by using the second groove 62.
In the conventional method of forming the truer using the master grinding wheel, the shape of the master groove is transferred to the truer and thus the shape of individual master groove corresponds to the cross-sectional shape of the individual truer. Therefore, when adjusting the shape of a plurality of truers into a different cross-sectional shape, a plurality of master grinding wheels is prepared and replaced to transfer the shape of each master grinding wheel or a master grinding wheel having a plurality of master grooves is used to transfer the shape of each master groove.
However, by using the method of the present invention, even when a plurality of master grinding wheels or a plurality of master grooves is not used, the cross-sectional shape of the truer can be arbitrarily adjusted by using the master groove having the arc-shaped portion at the opening portion.

DESCRIPTION OF THE REFERENCE NUMERALS

10: wafer chamfering device, 11: body base, 20: wafer feeding unit, 21: X-axis base, 22: X-axis guide rail, 23: X-axis linear guide, 24: X table, 25: X-axis driving mechanism, 26: Y-axis guide rail, 27: Y-axis linear guide, 28: Y table, 29: Z-axis guide rail, 30: Z-axis driving mechanism, 31: Z table, 32: θ-axis motor, 33: θ spindle, 34: wafer table, 41: truer, 50: grinding wheel rotating unit, 51: circumferential grinding spindle, 52: circumferential rough grinding wheel, 53: turntable, 54: circumferential fine grinding spindle, 55: grinding wheel, 56: circumferential fine grinding motor, 60: master grinding wheel, 61: first groove, 62: second groove, 81: linear portion, 82: inclined portion, 83: arc-shaped portion, 84: cross-sectional shape, 85: cross-sectional shape, CW: rotation axis of wafer table, GC: disc-shape, W: wafer, n: surface width

Claims

1. A method of forming a truer in a truing where a groove of a grinding wheel used for grinding a chamfer portion of a wafer is formed by a truer having a disc-shape, wherein

the method comprising:

a process A for adjusting a diameter and a rough shape of the truer by a master grinding wheel for forming the truer; and

a process B for forming an edge of the truer into a target shape, wherein

the process A and the process B are performed by a plurality of master grooves having different shapes from each other, the plurality of master grooves being provided with the master grinding wheel or the process A and the process B are performed by a plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel.

2. The method of forming the truer according to claim 1, wherein

the process A and the process B are performed by a first groove and a second groove which are the plurality of master grooves having different shapes from each other, the first groove and the second groove being provided with the master grinding wheel.

3. The method of forming the truer according to claim 2, wherein

an edge processing is performed by using an end portion of the second groove after the truer is processed by the first groove.

4. The method of forming the truer according to claim 2, wherein

a radius of an arc-shaped portion of an end portion of the second groove is larger than a radius of an arc-shaped portion of an end portion of the first groove.

5. The method of forming the truer according to claim 2, wherein

a chamfering processing of the truer is performed by at least one of the plurality of master grooves by moving the truer in a direction of separating from at least one of the plurality of master grooves.

6. The method of forming the truer according to claim 3, wherein

a corner R processing of the truer is performed by using the end portion of the second groove for adjusting a shape, a radius and a roundness of the corner of the truer while reducing a moving distance of the truer.

7. The method of forming the truer according to claim 6, wherein

the corner R processing of a lower surface of the truer is performed after the corner R processing of an upper surface of the truer is performed.

8. The method of forming the truer according to claim 7, wherein

parameters of a movement start position, a machining speed, an escape position, an escape speed, a rotation speed of the truer, a machining start point and a machining end point are determined by using the value of the corner R processing of the upper surface and the value of the corner R processing of the lower surface, the movement start position including an entering point and an entering speed.

9. The method of forming the truer according to claim 8, wherein

an amplitude, the machining speed, a spark-out time and the number of times of reciprocating motion are specified as a traverse motion independently for the corner R processing of the upper surface and the corner R processing of the lower surface.

10. The method of forming the truer according to claim 1, wherein

the process A and the process B are performed by using the plurality of portions having different shapes from each other in at least one of the plurality of master grooves provided with the master grinding wheel, and

the process B is performed by using an end portion of at least one of the plurality of master grooves.

11. The method of forming the truer according to claim 10, wherein

the process A is performed by using a bottom portion of at least one of the plurality of master grooves.

12. A master grinding wheel of forming a truer for forming a groove of a grinding wheel used for grinding a chamfer portion of a wafer, the master grinding wheel comprising:

a first groove for adjusting a diameter and a rough shape of the truer; and

a second groove for forming an edge of the truer into a target shape, the second groove being different from the first groove.

13. A master grinding wheel of forming a truer for forming a groove of a grinding wheel used for grinding a chamfer portion of a wafer, wherein

at least one master groove of the master grinding wheel comprising:

a first portion for adjusting a diameter and a rough shape of the truer; and

a second portion for forming an edge of the truer into a target shape, the second portion being different from the first portion.