Wafer regrind method and chamfering device

Abstract

To provide a wafer re-grinding method that makes it possible to easily change the wafer of interest in a semiconductor manufacturing line from a wafer with an orientation flat to a wafer with a notch, or from a wafer with a notch to a wafer with an orientation flat, without altering the existing semiconductor manufacturing line.SOLUTION: The method includes the step of measuring the center position O of a wafer WOLD with a notch or with an orientation flat OF at a position AOF where the notch or the orientation flat is not formed. Next, the method includes the step of measuring the position of the notch formed part or the orientation flat formed part of the wafer with the notch or with the orientation flat, and storing in memory the center of the wafer and the position of the notch or orientation flat formed part of the wafer. A new grinding center O1 for re-grinding edges of the wafer is calculated and set on the basis of the stored center position of the wafer and position of the notch or orientation flat formed part of the wafer.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for re-grinding a notch or oriental flat (hereinafter referred to as an orientation flat) formed on the edge of a wafer, and more particularly to a wafer re-grinding method for re-grinding a notch formed on a single crystal wafer into an orientation flat or an orientation flat into a notch. [Background technology]

[0002] In particular, in the case of single crystal wafers, in order to clarify the crystal orientation of the wafer, a recessed notch or a circular plate with a straight cut is formed in the wafer material cut into a circular shape. In order to form a circuit on the wafer surface, the wafer with the notch or orientation flat undergoes various processing processes and is transported multiple times. For this reason, in semiconductor manufacturing, a transport container and a wafer holding means suitable for the orientation flat or notch are provided. These transport containers and holding means may be used for both orientation flat and notched wafers, or may be dedicated to orientation flat or notched wafers. In the latter case, if the wafer before circuit formation is a notched wafer, a processing machine or transport container for orientation flat wafers cannot be used, and if the wafer is an orientation flat wafer, a processing machine or transport container for notched wafers cannot be used. In some cases, the only single crystal wafers suitable for the intended use are notched or orientation flat wafers, and in such cases, the edges of the incompatible wafers must be reprocessed (regrinded).

[0003] To eliminate such inconveniences, Patent Document 1 describes a device that can align both the wafer notch and the orientation flat using the same device, and that includes a first rotating roller that can be stopped at an intermediate position and moves up and down, and a second rotating roller that rotates freely by entering the notch of the first wafer in accordance with the size of the notch.

[0004] Also, in Patent Document 2, in order to hold a wafer with an orientation flat and a wafer with a notch in accurate positions without replacing the mechanism, a wafer holding mechanism has a table on which the wafer is placed, first and second orientation flat contact rollers provided on the table and capable of contacting multiple points on the orientation flat formed on the wafer, and a contact roller provided on the table and capable of contacting the circumferential surface of the wafer. The wafer holding device further has a first pressing pin provided on the table and pressing the circumferential surface of the wafer against the first and second orientation flat contact rollers, and a second pressing roller provided on the table and pressing the circumferential surface of the wafer against the contact rollers, the first pressing pin being engageable with the notch formed in the wafer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-87475 [Patent Document 2] JP 2000-294618 A [Patent Document 3] JP 2017-183503 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, in semiconductor manufacturing, the semiconductors to be manufactured are mass-produced products, so the shape of the wafers to be used is set in advance, and processing machines and transport containers corresponding to that shape are installed or prepared. Therefore, if the wafers to be used do not fit the manufacturing line, the wafers themselves must be reprocessed to fit the manufacturing line. For example, when a wafer with an orientation flat is used in a wafer manufacturing line with a notch, the wafer with the orientation flat is first ground down to a circular wafer, and a notch is then formed on a circular wafer with a smaller diameter than the original wafer. In this case, the wafer was ground down to the orientation flat position by aligning the wafer center position with the processing center using the center position data of the original wafer, which reduces the yield of semiconductor manufacturing.

[0007] On the other hand, in the system described in Patent Document 1, a new mechanism is added to enable use with both wafers with orientation flats and wafers with notches, but since many processing steps are involved in forming circuits on a wafer, many devices are used, and adding new mechanisms for all of them is difficult or requires a great deal of expense. Also, depending on the processing step, there is no room to install such mechanisms. Furthermore, dedicated transport containers are used to transport wafers between processing steps to prevent the adhesion of dust, etc., but the necessity to change these depending on the wafer being processed could cause a stagnation in the series of wafer processing.

[0008] Furthermore, in Patent Document 2, a new mechanism is provided that makes it possible to hold both wafers with orientation flats and wafers with notches. However, even the system described in this publication has the disadvantage that installing such a device in every processing step would require significant changes to the production line, which would be difficult both economically and time-wise, and that, depending on the processing step, it may be impossible to secure the physical space to add such a new mechanism.

[0009] The present invention has been made in consideration of the above-mentioned problems of the conventional technology, and has an object to make it possible to easily change the target wafer in a semiconductor manufacturing line from a wafer with an orientation flat to a wafer with a notch without modifying the existing semiconductor manufacturing line. In addition to the above object, another object of the present invention is to minimize the amount of wafer grinding during this change. [Means for solving the problem]

[0010] The features of the present invention that achieve the above object are as follows. [1] A method for regrinding a wafer, comprising: detecting a center position of a wafer having a mark selected from the group consisting of a notch and an orientation flat and the position of the mark; and calculating a grinding center for grinding the outer periphery of the wafer to a circular shape without the mark based on the center position and the position of the mark. [2] A method for regrinding a wafer as described in [1], comprising: using the grinding center to grind the outer periphery to obtain a circular reground wafer without the mark; and forming another mark different from the one mark on the outer periphery of the reground wafer. [3] The method for regrinding a wafer according to [2], wherein the reground wafer has a smaller diameter than the wafer. [4] A wafer chamfering apparatus comprising a pre-alignment unit and a control device, wherein the pre-alignment unit detects a center position of a wafer having a mark selected from the group consisting of a notch and an orientation flat and the position of the mark, and the control device calculates a grinding center for grinding the outer periphery of the wafer to form a circle without the mark based on the center position and the position of the mark. [5] A wafer chamfering apparatus as described in [4], further comprising a processing unit that uses the grinding center to grind the outer periphery to obtain a circular reground wafer without the mark, and forms another mark different from the one mark on the outer periphery of the reground wafer. [6] A wafer chamfering apparatus comprising a pre-alignment unit and a control unit, the pre-alignment unit having a laser sensor, the pre-alignment unit measures the center position of a wafer with an orientation flat or a notched wafer at a position where no notch or orientation flat is formed, and measures the position of the notch forming portion or orientation flat forming portion of the notched or orientation flat wafer using the laser sensor, and the control unit stores the center position of the wafer and the position of the notch forming portion or orientation flat forming portion, and calculates and stores a new grinding center for re-grinding the edge portion of the wafer based on the stored center position of the wafer and the position of the notch forming portion or orientation flat forming portion.

[0011] Other features of the present invention that achieve the above object are as follows. A method for regrinding a notched or orientation flat wafer includes measuring the center position of the notched or orientation flat wafer at a position where no notch or orientation flat is formed, measuring the position of the notch or orientation flat forming part of the notched or orientation flat wafer, storing these wafer center positions and the positions of the notch or orientation flat forming part, and calculating and storing a new grinding center for regrinding the edge portion of the wafer based on the stored wafer center position and position of the notch or orientation flat forming part. The new grinding center is preferably a position displaced from the wafer center position to the anti-notch or anti-orientation flat side.

[0012] In the above-mentioned feature, if the wafer before grinding has an orientation flat, when the orientation flat length of the wafer is 2L and the radius of the wafer is R, the eccentricity δ of the grinding center from the wafer center is 0<δ≦(R-SQRT(R 2 -L 2 )) / 2, and if the wafer before grinding is a notched wafer, it is preferable that the eccentricity δ of the grinding center from the wafer center satisfies 0<δ≦d / 2, where d is the notch depth of the wafer and R is the radius of the wafer.

[0013] In the above-mentioned features, it is further preferable to determine a maximum inscribed circle centered on the new grinding center of the wafer calculated above, and to vary the grinding speed during grinding in accordance with the circumferential position of the wafer based on the distance between the determined inscribed circle and the outer peripheral surface of the wafer. If the wafer before regrinding has an orientation flat, it is preferable that the grinding start position of the wafer be one end of the orientation flat, and that the grinding speed be slow at both ends of the orientation flat and fastest on the opposite side of the wafer. Effect of the Invention

[0014] According to the present invention, by re-grinding the edge of a wafer with an orientation flat formed thereon, with a processing center different from the center of the original wafer, it is possible to form a new notched wafer that makes maximum use of the original wafer, while allowing the use of existing semiconductor manufacturing lines as is. It also improves wafer yields in semiconductor manufacturing. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a top view of one embodiment of a wafer chamfering apparatus embodying the present invention. [Diagram 2] 2 is a front view of a main part of the wafer chamfering device shown in FIG. [Diagram 3] 10A to 10C are diagrams for explaining a method for determining the grinding center of a wafer before regrinding. [Figure 4] FIG. 13 is a diagram showing the relationship between the regrinding speed and the circumferential position of the wafer. [Diagram 5] FIG. 2 is a schematic diagram showing the relationship between a grindstone and a wafer during grinding. [Figure 6] FIG. 6 is an enlarged schematic view of part A in FIG. 5. [Figure 7] 1 is a flowchart showing a regrinding procedure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The regrinding of the edge (periphery) of the wafer W according to the present invention will be described below with reference to the drawings. In the regrinding of the edge of the wafer W, for example, a chamfering device for the wafer W described in Patent Document 3 can be used. That is, the chamfering device 10 for the wafer W, the top view of which is shown in FIG. 1 and the front view of which is shown in FIG. 2, includes a supply and recovery section 12, a pre-alignment section 14, processing sections 16, 16, an orientation flat (hereinafter referred to as "orifura") polishing section 18, a cleaning section 20, a post-measurement section 22, a transport section 24, an operation panel 17, a control device 15, etc. In the following description, a case where a wafer W with an orientation flat is ground into a circle will be described as an example, but the same applies to a case where a wafer W with a notch is ground into a circle.

[0017] The supply / recovery section 12 includes a cassette table 32 and a supply / recovery robot 34, and supplies wafers with orientation flats (also referred to as old wafers) W to be reground from a wafer cassette 30 to the processing side 19. At the same time, it recovers the reground wafers W from the processing side 19 to the wafer cassette 30. The supply / recovery robot 34 takes out the wafers W one by one from each wafer cassette 30 set on the cassette table 32 and supplies them to the pre-alignment section 14. The supply / recovery robot 34 recovers the reground wafers W (new wafers W) from the processing side 19. NEW Also, it is used when storing the wafer (also referred to as "wafer cassette") from the post-measurement section 22 into the wafer cassette 30.

[0018] The pre-alignment unit 14 is a pre-alignment unit for aligning an old wafer W (old wafer W OLD The position and center of the orientation flat OF of the old wafer W is detected, and the grinding center O1 is determined by a procedure described below, thereby performing pre-alignment. Pre-alignment unit 14 is equipped with measuring table 50, thickness sensor 52, and orientation flat detection sensor 54. Measuring table 50 performs alignment of wafer W. Orientation flat detection sensor 54 is a laser sensor, and detects the position of the orientation flat OF of the old wafer W.

[0019] The processing units 16, 16 are arranged in parallel on the front portion of the wafer chamfering apparatus 10, and each is capable of performing all processing of the old wafer W, i.e., from rough processing to finish processing, and includes a wafer feed device 60, a peripheral grinding device 62, an orientation flat polishing unit 18, etc. The cleaning unit 20 cleans the new wafer W after regrinding, and includes a spin cleaning device 80 that sprays a cleaning liquid onto the surface of the wafer W while rotating the wafer W held on a cleaning table 82, thereby peeling off and removing dirt adhering to the surface of the wafer W. The post-measurement unit 22 measures and detects the diameter, cracks, etc. of the new wafer W, and includes a diameter measuring device 84 that measures the diameter of the wafer W, and a measurement table 86 that holds the wafer W and rotates and moves it up and down.

[0020] The transport unit 24 transports the wafer W to each unit of the wafer chamfering apparatus 10, and includes a grinding transfer unit 100, a cleaning transfer unit 104, a storage transfer unit 106, etc. The grinding transfer unit 100 transports the wafer W after alignment to the grinding table 134, and includes a transfer arm 114. A suction pad 116 is attached to the tip of the transfer arm 114. The transfer arm 114 can move horizontally and up and down while holding the wafer W.

[0021] The two processing units 16 each include a wafer feed device 60 and a peripheral grinding device 62. As shown in Fig. 2, the wafer feed device 60 has an X-axis base 121 mounted on a main body base 141, two X-axis guide rails 122, four X-axis linear guides 123, and an X-table 124 that is moved in the X direction in Fig. 2 by an X-axis driving means 125. The X-table 124 incorporates two Y-axis guide rails 126, four Y-axis linear guides 127, and a Y-table 128 that is moved in the Y direction in Fig. 2 by a Y-axis driving means.

[0022] A Z-table 131 is mounted on the upper part of the Y-table 128, and is guided by two Z-axis guide rails 129 and a Z-axis linear guide, and is moved in the Z direction in the figure by a Z-axis driving means 130. A θ-axis motor 132 and a θ-spindle 133 are mounted on the Z-table 131. A grinding table 134 for suction-mounting a wafer W is attached to the θ-spindle 133. The grinding table 134 rotates in the θ direction in FIG. 2 about its rotation axis CW. The transfer arm 114 shown in FIG. 1 is disposed on the upper surface of the grinding table 134, and a suction pad 116 is attached to the tip of the transfer arm 114 facing downward. The outer peripheral grinding device 62 is equipped with an outer peripheral grinding wheel spindle 151 to which a grinding wheel 152 is attached and which is rotated about an axis CH by an outer peripheral grinding wheel motor (not shown). The peripheral grinding device 62 is also provided with a notch grindstone 155 used for performing notch processing.

[0023] A method for regrinding a wafer W using the thus configured chamfering device for a wafer W will be described with reference to FIG. 3 and subsequent figures. In FIG. 3, the outer shape of a wafer W before grinding is OLD The outer shape of the wafer after grinding is W NEW 3 is a top view of the wafer W. The wafer center O is measured by the pre-alignment unit 14 and stored in the control device 15. OLD The grinding center O1 is the center position of the old wafer W before regrinding, which is used in the regrinding method according to the present invention, and is offset by δ from the center O toward the AOF on the opposite side of the orientation flat. The amount of eccentricity δ is obtained as follows:

[0024] That is, the old wafer W with the orientation flat OF detected by the orientation flat detection sensor 54 OLD From the angles α1 and α2 of the end points with respect to the center O, the orientation flat length L OF But, L OF = Rsin{(α1 + α2) / 2}, and δ = [R-Rcos{(α1 + α2) / 2}] / 2 is obtained. Here, R is the old wafer W OLD The radius of the old wafer W is a value that has already been measured by the pre-alignment unit 14. OLD At the point where the circumferential position is (α1 + α2) / 2, the grinding center O1 is set on a line perpendicular to the orientation flat OF, eccentric by δ from the center O to the AOF on the opposite side of the orientation flat, and the old wafer W OLD The amount of grinding at each circumferential position θ of the wafer W depends on the removal amount ΔR. If the removal amount ΔR is only ground, a new wafer W with a perfect circle of radius R1 centered on the grinding center O1 will be produced. NEW is obtained.

[0025] In addition, the orientation flat length L OF Old wafer W OLD The above formula is obtained by relating the circumferential angle of the orientation flat length L OF In this case, the eccentricity δ is ideally expressed as δ=[R−{R 2 -(L OF / 2) 2} 1 / 2 ] / 2, and at least 0<δ≦[R―{R2 -(L OF / 2) 2} 1 / 2 ] / 2. Old wafer W OLD The grinding center O1 is set on a straight line that passes through a point equidistant from both ends of the orientation flat OF and is perpendicular to the orientation flat OF, and is offset by δ from the center O to the AOF on the opposite side of the orientation flat. OLD Grind.

[0026] By the way, if the wafer W before grinding is a notched wafer, setting the eccentricity δ becomes easier. In other words, when the notch depth of the wafer W is d and the radius of the wafer W is r, the deviation (eccentricity) δ of the grinding center O1 from the wafer center O is ideally half the notch depth, d / 2, and at least 0<δ≦d / 2. The grinding center O1 moves by d / 2 from the wafer center O to the opposite side to the notch on the line connecting the bottom of the notch and the grinding center O1.

[0027] In the pre-alignment section 14, the old wafer W OLD The above relational expression is used to pre-align the grinding center O1 of the wafer W so that it coincides with the center of the grinding table 134 of the processing unit 16, and the processing unit 16 controls the X-table 124 and Y-table 128 of the wafer feed device 60 based on the pre-alignment. The grinding center O1 of the wafer W is positioned at the rotation center of the grinding table 134, and the X-table 124 and Y-table 128 are moved to a position where they come into contact with the grinding wheel 152. Once the wafer W comes into contact with the grinding wheel 152, the X-table 124 and Y-table 128 are not moved, and the grinding table 134 is rotated only in the θ direction to perform grinding. The Z-table 131 is positioned at the height of the grinding wheel 152 before grinding.

[0028] Next, the grinding state when the grinding wheel 152 is brought close to the wafer W and actually grinds it will be described with reference to Figs. 4 to 6. Fig. 4 is a table showing the grinding speed of the grinding wheel 152 with respect to the circumferential angle of the wafer W, and Fig. 5 is a diagram showing the relationship between the wafer W and the grinding wheel 152. Fig. 6 is an enlarged view of part A in Fig. 5, and is a diagram for explaining the grinding pass. The line connecting the midpoint of the orientation flat OF and the grinding center O1 of the orientation flat is set as the angular reference position of the wafer W. In order to suppress the amount of grinding of the wafer W per unit time to a predetermined amount or less, the edge portion of the wafer W is ground multiple times (multiple passes). Therefore, in the first pass (first pass), the grinding wheel 152 abuts against the wafer W at a position with an angle larger than θ=0°. The abutting point at which the wafer W first abuts in each grinding pass is called the starting point S. 5, X0 indicates the X-axis, which is a straight line passing through the center of the wafer W when no orientation flat OF is formed, and the orientation flat OF is formed parallel to this X0-axis. X1 indicates the X-axis position to which the grinding center O1 of the wafer W moves due to eccentricity after the orientation flat is formed.

[0029] S0 and E0 are the end points of the orientation flat OF. In the example described below, the angle θ of the start point S1 of the first pass is θ = approximately 18°. Similarly, the angle of the end point E1 of the first pass is different from 360°. In the example described below, it is θ = approximately 342°, which is symmetrical to the start point S1.

[0030] As is clear from FIG. 5, the old wafer W OLD The machining allowance ΔR in the regrinding varies in the circumferential direction of the wafer W. Therefore, in consideration of the grinding resistance, the grinding speed of the grinding wheel 152 is slowed down in the portion where the machining allowance ΔR is large, and the grinding speed V is fast in the portion where the machining allowance ΔR is small. This improves the efficiency of the grinding process and improves the throughput of the grinding process. In addition, since the grinding speed V is slowed down in the portion where the machining allowance ΔR is large, the occurrence of chipping due to grinding can also be reduced.

[0031] Maximum removal allowance ΔR MAX exceeds the capacity of the wafer chamfering device 10 or the maximum chamfering allowance ΔR MAXIf the grinding load on the wafer W becomes excessive when grinding the wafer W in one go, the maximum grinding allowance ΔR MAX is divided into multiple portions to determine the removal allowance ΔR in one grinding pass. This is called a grinding pass. In one grinding pass, the grinding wheel 152 is rotated once around the wafer W. Generally, the removal allowance ΔR in one grinding pass is at most about 500 μm, so the maximum removal allowance ΔR MAX If the thickness exceeds 500 μm, multiple grinding passes are required.

[0032] Figure 6 is a schematic diagram showing the start points S1, S2, ... of each grinding pass and the machining allowance ΔR1 for each pass when multiple grinding passes are required. The machining allowance ΔR1 is programmed to be equal for each pass P1, P2, .... As the number of grinding passes increases, the start points S1, S2, ... move toward the center of the orientation flat OF (toward the Y-axis). Even in this case, although not shown in the figure, the machining allowance ΔR at the start points S1, S2, ... is larger than at other positions, for example, the AOF on the opposite side of the orientation flat, so the grinding speed V is faster than at other positions. With the AOF on the opposite side of the orientation flat, the machining allowance ΔR is theoretically 0 in every grinding pass.

[0033] The above results are summarized in Figure 4. At the AOF on the anti-orientation flat side, the grinding amount is zero, so the wafer W is rotated at the fastest possible speed. On the other hand, at the start point S, the removal amount ΔR is large, and due to the influence of the orientation flat OF, the grinding wheel 152, which has not been in contact with the wafer W since the end point E, suddenly comes into contact with the wafer W, causing an impact force to act on the wafer W. Therefore, the rotational speed of the wafer W or that of the grinding wheel 152 is reduced, thereby reducing the grinding speed.

[0034] A specific example of the above procedure will be described with reference to the flowchart in Fig. 7. In this example, a case is shown where a wafer W with an orientation flat and an outer diameter of 150 mm, commonly known as a 6-inch wafer, is re-grinded. When the process of grinding the outer periphery of the wafer W is started to convert the wafer W with orientation flat into a wafer W with a notch, a measuring arm provided on the supply / recovery robot 34 takes out one wafer W from the wafer cassette 30 and carries the wafer W to measuring table 50 (step S710).

[0035] Pre-alignment is performed on the measurement table. More specifically, the outer diameter of the wafer W is first measured and stored at a position where no orientation flat OF is formed after the wafer W is transferred to measurement table 50. The stored outer diameter is used to determine the center position, and then orientation flat detection sensor 54 detects and measures the circumferential position of the orientation flat OF and / or the length of the orientation flat OF (step S720). Now that the length of the orientation flat OF or the circumferential position of the orientation flat OF has been obtained, the amount of eccentricity δ is calculated from the above-mentioned relational expression (step S730).

[0036] The outer diameter of the 6-inch wafer is 150 mm, so the radius R is 75 mm. OF When the measured value is 46 mm, the eccentricity δ is δ = {R - SQRT(R 2 -L OF 2 )} / 2=1.805 mm. Since the eccentricity δ is obtained, the grinding center O1 is moved by δ from the center O of the wafer W, and the maximum circle inscribed in the wafer W with the grinding center O1 as the center (new wafer W NEW Determine the external shape of.

[0037] The removal allowance ΔR is between the maximum inscribed circle and the wafer W. The removal allowance ΔR changes in the circumferential direction of the wafer W. The maximum removal allowance Δ RMAX If there was no orientation flat OF, it would occur on the circumference extending from a line passing through the midpoint of the orientation flat OF and the center of the wafer W. The removal allowance ΔR decreases as the circumferential angle to the AOF on the anti-orientation flat side changes.

[0038] Therefore, when the orientation flat OF is formed, the maximum removal allowance ΔR MAX occurs at the end of the orientation flat OF. In this example, the maximum removal allowance ΔR MAX occurs at the ends S and E of the orientation flat OF, and ΔR MAXis 3.529 mm. Since the maximum value of the removal allowance ΔR1 in one pass is about 500 μm, the number of passes is 8, and the average removal allowance ΔR1 per pass is about 440 μm. These values ​​are stored in the control device 15. The control device 15 also stores processing parameters for edge processing of the wafer W. The processing parameters include the material of the wafer W, the thickness of the wafer W, the material and grinding speed of the grinding wheel 152, the maximum removal allowance ΔR1 in one grinding, etc.

[0039] For comparison, in the conventional method of regrinding to the position of the orientation flat OF without decentering the processing center, the maximum removal allowance ΔR MAX The length is 3.613 mm, the number of passes is the same as before, 8 passes, and the average removal allowance ΔR1 is about 450 μm. OLD The total grinding area of ​​the new wafer W NEW The larger the diameter, the less

[0040] According to the method of the present invention, the total grinding area is about 841 mm per wafer. 2 By contrast, the conventional method was 1662 mm. 2 Therefore, the amount of grinding is about half of that in the past, and the time required for grinding can be reduced by changing the grinding speed according to the removal rate ΔR. For example, by controlling the grinding speed so that the grinding area per unit time is constant, that is, by controlling the moving speed of the wafer table 134 in the θ direction, the time required for grinding can be reduced by almost half.

[0041] Since the data on the grinding parameters and the wafer W have been obtained, the pre-alignment using the measurement table 50 is completed. After the pre-alignment, the wafer W is transferred to the wafer table 134 by using the transfer arm 114 of the grinding transfer unit 100 (step S740).

[0042] When the wafer W is transferred to the wafer table 134, the center O of the wafer W is offset by the above-mentioned eccentricity amount δ from the center position of the wafer table 134. Then, the grinding center O1 is aligned with the center position of the wafer table 134.

[0043] When the grinding center O1 and the rotation center of the wafer table 134 are aligned, the X-table 124 and the Y-table 128 are driven to move the wafer table 134 to a position where it abuts the grinding wheel 152 (step S750). The outer periphery of the wafer W is ground in multiple passes using the grinding parameters acquired by pre-alignment and stored in the control device 15 (step S760). At this time, the positions of the X-, Y-, and Z-tables 124, 128, and 131 are held fixed, and the wafer table 134 is rotated only in the θ direction for grinding. When the orientation flat OF has completely disappeared, grinding is completed.

[0044] If the wafer W is a single crystal wafer, it is convenient to mark the crystal orientation in the following steps. Therefore, in step S780, it is determined whether a notch is necessary as a mark of the crystal orientation. If a notch is necessary, the positions of the X-table 124 and the Y-table 128 are controlled and a notch is machined using the notch grindstone 155 while the θ-direction rotation of the Z-table 131 and the wafer table 134 is fixed (step S790). After the notch machining, the wafer W is cleaned in the cleaning section and then sent to the post-measuring section for inspection. Then, the wafer W is stored in the wafer cassette 30 by the storage transfer section 106 and awaits transport to the next process.

[0045] As explained above, in the method of this embodiment for regrinding the edge of the wafer W to convert a wafer with an orientation flat into a wafer with a notch, the grinding area near the edge of the wafer can be reduced by almost half compared to the conventional method, and the yield rate when manufacturing a large number of semiconductors from a single wafer is significantly improved. For example, by regrinding using this method, the ratio of the wafer area available for semiconductor production to the original wafer W can be increased to about 98%. [Explanation of symbols]

[0046] 10...wafer chamfering device, 12...supply and recovery section, 14...pre-alignment section, 15...control device, 16...processing section, 17...operation panel, 18...orientation flat polishing section, 20...cleaning section, 22...post-measurement section, 24...transport section, 30...wafer cassette, 32...cassette table, 34...supply and recovery robot, 50...measuring table, 52...thickness sensor, 54...orientation flat detection sensor, 60...wafer feed device, 62...periphery grinding device, 80...spin cleaning device, 82...cleaning table, 84...diameter measuring device, 86...measuring table, 100...grinding transfer section, 104...cleaning transfer section, 106...storage transfer section, 114 ...Transfer arm, 116...Suction pad, 121...X-axis base, 122...X-axis guide rail, 123...X-axis linear guide, 124...X table, 125...X-axis drive means, 126...Y-axis guide rail, 127...Y-axis linear guide, 128...Y table, 129...Z-axis guide rail, 130...Z-axis drive means, 131...Z table, 132...θ-axis motor, 133...θ spindle, 134...wafer table (grinding table), 141...main body base, 151...periphery grinding wheel spindle, 152...grinding wheel, 155...notch grinding wheel, AOF...opposite orientation flat side, CH...axis center, CW...wafer table rotation axis, L OF …Orientation flat length, O…(wafer) center, O1…grinding center, OF…Orientation flat (part), R…wafer radius, V…grinding speed, W…wafer, W NEW …New wafer, W OLD ...Old wafer, α1, α2...Circumferential angle, δ...Eccentricity, ΔR...Removal allowance, θ...Circumferential angle

Claims

1. Detecting a center position of a wafer having a mark selected from the group consisting of a notch and an orientation flat, and a position of the mark; calculating a grinding center for grinding the outer periphery of the wafer to a circular shape without the mark based on the center position and the position of the mark; using the grinding center to grind the outer periphery to obtain a circular reground wafer free of the mark; forming another mark different from the one mark on the outer periphery of the reground wafer.

2. 2. The method of claim 1, wherein the reground wafer is smaller in diameter than the wafer.

3. A wafer chamfering apparatus, comprising: A pre-alignment unit and a control device are provided, the pre-alignment unit detects a center position of a wafer having one mark selected from a group consisting of a notch and an orientation flat, and a position of the mark; the control device calculates a grinding center for grinding the outer periphery of the wafer so as to form a circular shape without the mark, based on the center position and the position of the mark; Further comprising a processing unit, The processing unit uses the grinding center to grind the outer periphery to obtain a circular reground wafer without the mark, and forms another mark different from the one mark on the outer periphery of the reground wafer.

4. A wafer chamfering apparatus, comprising: A pre-alignment unit and a control device are provided, the pre-alignment unit includes a laser sensor; the pre-alignment unit measures a center position of a wafer having one mark selected from the group consisting of a notch and an orientation flat at a position where the mark is not formed, and measures the position of a notch forming portion or an orientation flat forming portion of the wafer having the mark by the laser sensor; the control device stores a center position of the wafer and a position of the notch forming portion or the orientation flat forming portion, calculates and stores a new grinding center for re-grinding the edge portion of the wafer based on the stored center position of the wafer and the position of the notch forming portion or the orientation flat forming portion, Further comprising a processing unit, The processing unit uses the grinding center to grind the outer periphery of the wafer to obtain a circular reground wafer without the mark, and forms another mark different from the one mark on the outer periphery of the reground wafer.

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