JP7649841B2 - Wafer regrind method and chamfering device - Google Patents

Description

The present invention relates to a method for regrinding a notch or oriental flat (hereinafter referred to as an orientation flat) formed on the edge of a wafer, and in particular to a method for regrinding a wafer in which a notch formed on a single crystal wafer is regrinded into an orientation flat or an orientation flat is regrinded into a notch.

In particular, in the case of single crystal wafers, in order to clarify the crystal orientation of the wafer, a notch or a disk with a straight cut is formed in the wafer material cut into a circle. In order to form circuits on the wafer surface, the wafer with the notch or orientation flat undergoes various processing and multiple transports. For this reason, in semiconductor manufacturing, transport containers and wafer holding means suitable for the orientation flat or notch are provided. These transport containers and holding means may be used for both wafers with orientation flats and notched wafers, but may also be used exclusively for wafers with orientation flats or notched wafers. In the latter case, if the wafer before circuit formation is a notched wafer, processing machines and transport containers for wafers with orientation flats cannot be used, and if the wafer is an orientation flat wafer, processing machines and transport containers for wafers with notches 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).

To eliminate this inconvenience, Patent Document 1 describes a device that uses the same device to align both the wafer notch and the orientation flat, and 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 according to the size of the notch.

In addition, in Patent Document 2, in order to hold a wafer with an orientation flat and a wafer with a notch in an accurate position without changing the mechanism, a wafer holding mechanism has a table on which the wafer is placed, first and second orientation flat contact rollers that are provided on the table and can contact multiple points on the orientation flat formed on the wafer, and a contact roller that is provided on the table and can be contacted by the circumferential surface of the wafer. The wafer holding device further has a first pressing pin that is provided on the table and presses the circumferential surface of the wafer against the first and second orientation flat contact rollers, and a second pressing roller that is provided on the table and presses the circumferential surface of the wafer against the contact rollers, and the first pressing pin is capable of engaging with the notch formed on the wafer.

Japanese Patent Application Publication No. 11-87475 JP 2000-294618 A JP 2017-183503 A

As mentioned above, in semiconductor manufacturing, because the semiconductors manufactured are mass-produced products, the wafer shape to be used is set in advance, and processing machines and transport containers corresponding to that shape are installed or prepared. Therefore, if the wafer to be used does not fit the manufacturing line, the wafer itself 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. At that time, 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, resulting in a decrease in the yield of semiconductor manufacturing.

Meanwhile, in the system described in Patent Document 1, a new mechanism is added so that it can be used for both wafers with orientation flats and wafers with notches. However, forming circuits on a wafer involves many processing steps, which requires a large amount of equipment, and adding new mechanisms for all of them is difficult or extremely expensive. Also, depending on the processing step, there is no room to install such mechanisms. Furthermore, special transport containers are used to transport wafers between processing steps to prevent the adhesion of dirt, but having to change these depending on the wafer being processed could cause a stagnation in the entire wafer processing process.

In addition, in Patent Document 2, a new mechanism is provided to enable the holding of both wafers with orientation flats and wafers with notches, but 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 for some processing steps, the physical space to add such a new mechanism cannot be secured.

The present invention was developed in consideration of the above-mentioned problems with the conventional technology, and its purpose is 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-mentioned object, another purpose of the present invention is to minimize the amount of wafer grinding during this change.

The features of the present invention that achieve the above object are as follows.
[1] A method for regrinding a wafer, the method comprising: 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; and calculating a grinding center for grinding an 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 according to [1], comprising: using the grinding center to grind the outer periphery to obtain a circular reground wafer having no 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 a position of the mark, and the control device calculates 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.
[5] The wafer chamfering apparatus 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] An apparatus for chamfering a wafer 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 with the laser sensor, 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.

Other features of the present invention that achieve the above object are as follows.
A method for regrinding a notched wafer or a notched 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.

In the above features, if the wafer before grinding is a wafer with an orientation flat, then it is preferable that, 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 satisfies 0<δ≦(R-SQRT( ^R2 - ^L2 ))/2; and if the wafer before grinding is a notched wafer, then it is preferable that, when the notch depth of the wafer is d and the radius of the wafer is R, the eccentricity δ of the grinding center from the wafer center satisfies 0<δ≦d/2.

Furthermore, in the above-mentioned features, it is preferable to determine the maximum inscribed circle centered on the new grinding center of the wafer calculated above, and to vary the grinding speed during grinding according to 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 to set the grinding start position of the wafer at one end of the orientation flat, and set the grinding speed slow at both ends of the orientation flat and fastest on the opposite side of the wafer.

According to the present invention, by regrinding the edge of a wafer on which an orientation flat has been formed, using a center position different from the center position of the original wafer as the processing center, a new notched wafer can be formed that makes maximum use of the original wafer, and existing semiconductor manufacturing lines can be used as is. In addition, wafer yields can be improved in semiconductor manufacturing.

FIG. 1 is a top view of one embodiment of a wafer chamfering apparatus embodying the present invention. FIG. 2 is a front view of a main part of the wafer chamfering apparatus shown in FIG. 1 . 10A to 10C are diagrams for explaining a method for determining the grinding center of a wafer before regrinding. FIG. 13 is a diagram showing the relationship between the regrinding speed and the circumferential position of the wafer. FIG. 2 is a schematic diagram showing the relationship between a grindstone and a wafer during grinding. FIG. 6 is an enlarged schematic view of part A in FIG. 5 . 1 is a flowchart showing a regrinding procedure.

The following describes the regrinding of the edge (periphery) of a wafer W according to the present invention, with reference to the drawings. For regrinding the edge of a wafer W, for example, a chamfering device for a wafer W described in Patent Document 3 can be used. That is, a chamfering device for a wafer W 10, 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, an example is taken of grinding a wafer W with an orientation flat into a circle, but the same applies to regrinding a wafer W with a notch into a circle.

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 is also used when storing the reground wafers W (also referred to as new wafers W _NEW ) from the post-measurement section 22 into the wafer cassette 30.

The pre-alignment unit 14 detects the position and center position of the orientation flat OF of the old wafer W (old wafer W _OLD ), locates the grinding center _O1 by a procedure described below, and performs pre-alignment. The pre-alignment unit 14 includes a measurement table 50, a thickness sensor 52, and an orientation flat detection sensor 54. The measurement table 50 performs alignment of the wafer W. The orientation flat detection sensor 54 is a laser sensor, and detects the position of the orientation flat OF of the old wafer W.

The processing units 16, 16 are arranged in parallel on the front of the wafer chamfering device 10, and each is capable of performing all processing of the old wafer W, i.e., from rough processing to finish processing, and is equipped with 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 re-grinding, and is equipped with 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 and cracks of the new wafer W, and is equipped with 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.

The transport unit 24 transports the wafer W to each part of the wafer chamfering device 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.

The two processing sections 16 are equipped with 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 the 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.

A Z table 131 is mounted on the upper part of the Y table 128, which 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 suctioning and placing 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 around the axis CH by an outer peripheral grinding wheel motor (not shown). The peripheral grinding device 62 is also equipped with a notch grindstone 155 used to perform notch processing.

A method of 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 the wafer before grinding is indicated as W _OLD , and the outer shape of the wafer after grinding is indicated as W _NEW . Fig. 3 is a top view of the wafer W. The wafer center O is the central position of the old wafer W _OLD to be ground before regrinding, which is measured by the pre-alignment unit 14 and stored in the control device 15. The grinding center _O1 is the central position of the regrinding of the old wafer W used in the regrinding method according to the present invention, and is eccentric from the center O by δ toward the anti-orientation flat side AOF. The amount of eccentricity δ is obtained as follows:

That is, from angles _α1 and _α2 of the end points of the orientation flat OF relative to the center O of the old wafer W _OLD detected by the orientation flat detection sensor 54, the orientation flat length L _OF is expressed as L _OF =Rsin{(α ₁ +α ₂ )/2}, and δ=[R-Rcos{(α ₁ +α ₂ )/2}]/2 is obtained. Here, R is the radius of the old wafer W _OLD , and is a value that has already been measured by the pre-alignment unit 14. At a point on the old wafer W _OLD where the circumferential position is (α ₁ +α ₂ )/2, a grinding center O ₁ is set on a line perpendicular to the orientation flat OF, eccentric by δ from the center O toward the anti-orientation flat AOF, and the old wafer W _OLD is ground. The grinding amount at each circumferential position θ of the wafer W at this time depends on the removal amount ΔR. By grinding the wafer by the removal allowance ΔR, a new wafer W _NEW that is a perfect circle having a radius R ₁ and centered on the grinding center O ₁ can be obtained.

Although the above formula is obtained by relating the orientation flat length L _OF to the circumferential angle of the old wafer W _OLD , the orientation flat length L _OF may also be measured directly. In that case, the eccentricity δ is ideally δ=[R-{R ² -(L _OF /2) ² } ^1/2 ]/2, and at least 0<δ≦[R-{R ² -(L _OF /2) ² } ^1/2 ]/2. The old wafer W OLD is ground by setting the grinding center _O1 on a straight line that passes through points equidistant from both end points of the orientation flat OF of the old wafer W _OLD and is perpendicular to the orientation flat OF, eccentric by δ from the center O to the _AOF on the anti-orientation flat side.

Incidentally, if the wafer W before grinding is a notched wafer, the setting of the eccentricity δ becomes easier. That is, 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 is at least 0<δ≦d/2. The grinding center _O1 moves by d/2 from the wafer center O to the opposite notch side on the line connecting the bottom of the notch and the grinding center _O1 .

In the pre-alignment section 14, the grinding center _O1 of the old wafer W _OLD is pre-aligned using the above relational expression so as to coincide with the center of the grinding table 134 of the processing section 16, and the processing section 16 controls the X-table 124 and the 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 the 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 the 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.

Next, the grinding state when the grinding wheel 152 is brought close to the wafer W and actually grinds the wafer W 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 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 grinding wheel 152 first abuts against the wafer W 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. Also, _X1 indicates the X-axis position to which the grinding center _O1 of the wafer W has moved due to eccentricity after the orientation flat is formed.

_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 symmetrical to the start point _S1 , and is θ = approximately 342°.

As is clear from Fig. 5, the machining allowance ΔR in regrinding the old wafer W _OLD 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. 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.

When the maximum allowance ΔR _MAX exceeds the capacity of the present wafer chamfering apparatus 10 or when grinding the maximum allowance ΔR _MAX in one pass would result in an excessive grinding load on the wafer W, the maximum allowance ΔR _MAX is divided into multiple portions to determine the allowance ΔR for 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 allowance ΔR for one grinding pass is at most about 500 μm, so when the maximum allowance ΔR _MAX exceeds 500 μm, multiple grinding passes are required.

6 is a schematic diagram showing the start points S ₁ , S ₂ , ... of each grinding pass and the machining allowance ΔR ₁ for one pass when multiple grinding passes are required. The machining allowance ΔR ₁ is programmed to be equal for each pass P ₁ , P ₂ , .... As the number of grinding passes increases, the start points S ₁ , S ₂ , ... move toward the center of the orientation flat OF (the Y-axis side). Even in this case, although not shown, the machining allowance ΔR at the start points S ₁ , S ₂ , ... is larger than that 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 any grinding pass.

The above results are summarized in Figure 4. At the AOF on the opposite side to the orientation flat, the amount of grinding is zero, so the wafer W is rotated as fast as possible. On the other hand, at the starting 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 the grinding wheel 152 is slowed down, thereby slowing down the grinding speed.

A specific example of the above procedure will be described using the flowchart in Figure 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 an orientation flat into a wafer W with a notch, the measurement arm of the supply/recovery robot 34 removes one wafer W from the wafer cassette 30 and transports the wafer W to the measurement table 50 (step S710).

Pre-alignment is performed on the measurement table. More specifically, the outer diameter of the wafer W transferred to measurement table 50 is first measured and stored at a position where no orientation flat OF is formed. 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).
Since 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).

The outer diameter of the 6-inch wafer mentioned above is 150 mm, so the radius R = 75 mm. When the orientation flat length L _OF is measured as 46 mm, the eccentricity δ is δ = {R - SQRT (R ² - L _OF ² )} / 2 = 1.805 mm. Now that 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 (the outer shape of the new wafer W _NEW ) that is inscribed in the wafer W and has the grinding center _O1 as its center is found.

The space between the maximum inscribed circle and the wafer W is the removal allowance ΔR. The removal allowance ΔR changes in the circumferential direction of the wafer W. If there was no orientation flat OF, the maximum removal allowance _ΔRMAX would occur on the circumference of a circle 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 of the AOF on the opposite side of the orientation flat changes.

Therefore, when the orientation flat OF is formed, the maximum removal allowance ΔR _MAX occurs at the end points of the orientation flat OF. In this example, the maximum removal allowance ΔR _MAX occurs at the end points S and E of the orientation flat OF, and ΔR _MAX is 3.529 mm. Since the maximum value of the removal allowance ΔR ₁ in one pass is about 500 μm, the number of passes is 8, and the average removal allowance ΔR ₁ 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 ΔR ₁ in one grinding, etc.

For comparison, in the conventional method of regrinding to the position of the orientation flat OF without decentering the processing center, the maximum removal amount ΔR _MAX occurs at all positions except the orientation flat OF, its length is 3.613 mm, the number of passes is also the same 8 passes, and the average removal amount ΔR1 is about 450 μm. There is no significant change in the number of passes from the conventional method, but the total ground area of the old wafer W _OLD becomes smaller as the diameter of the new wafer W _NEW becomes larger.

According to the method of the present invention, the total grinding area per wafer is about 841 ^mm2 , whereas it is 1662 ^mm2 with the conventional method. Therefore, the amount of grinding is about half that of the conventional method, and the time required for grinding can be reduced by changing the grinding speed according to the removal amount ΔR. For example, by controlling the grinding speed so that the grinding area per unit time is constant, that is, by controlling the movement speed of the wafer table 134 in the θ direction, the time required for grinding can be reduced by almost half.

Now that the grinding parameters and data regarding the wafer W have been obtained, pre-alignment using the measurement table 50 is completed. After pre-alignment, the wafer W is transferred to the wafer table 134 using the transfer arm 114 of the grinding transfer unit 100 (step S740).

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.

When the grinding center _O1 and the center of rotation 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 contacts 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 X-, Y-, and Z-tables 124, 128, and 131 are held in fixed positions, 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.

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 for the crystal orientation. If a notch is necessary, the X-table 124 and Y-table 128 are position-controlled and the notch is machined using the notch grindstone 155 while the θ-direction rotation of the Z-table 131 and 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. It is then stored in the wafer cassette 30 using the storage transfer section 106, and awaits transport to the next process.

As explained above, 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 can reduce the grinding area near the edge of the wafer by almost half compared to conventional methods, significantly improving the yield when manufacturing a large number of semiconductors from a single wafer. For example, by using this method for regrinding, the ratio of the wafer area available for semiconductor production to the original wafer W can be increased to approximately 98%.

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, O ₁ : grinding center, OF: orientation flat (part), R: wafer radius, V: grinding speed, W: wafer, W _NEW : new wafer, W _OLD : old wafer, α ₁ , α ₂ : circumferential angle, δ: eccentricity, ΔR: machining allowance, θ: circumferential angle

Claims (4)

Detecting a center position of a wafer having one of 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 indicia;
forming another mark different from the one mark on the outer periphery of the reground wafer. The method for regrinding a wafer according to claim 1, wherein the regrind wafer has a smaller diameter than the wafer. 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. 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.