Processing device, chuck shape correction method, and processing method

Abstract

To prevent a recess from forming in a wafer central part.SOLUTION: A processing device according to a first embodiment of the invention is a processing device 100 for grinding a wafer 102, and includes a chuck 103 which has a porous structure and suctions and holds the wafer 102, and a correction mechanism 101 which corrects a shape of the chuck 103. The correction mechanism 101 includes a grind stone 101b which grinds a chuck central part 103a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a processing apparatus, a chuck shape correction method, and a processing method. [Background technology]

[0002] In order to realize small and lightweight device chips, there are increasing opportunities to thin a wafer (hereinafter, referred to as "wafer") on the front side of which a device such as an integrated circuit is provided. For example, there is a back-grinding process in which a grinding wheel is pressed against the rear side of the wafer to grind and thin the wafer. In this back-grinding process, the front side of the wafer is held by the holding surface of a chuck, and a grinding wheel to which a grinding wheel containing abrasive grains is fixed and the chuck are rotated in opposite directions to press the grinding wheel against the rear side of the wafer while supplying a liquid (grinding fluid) such as pure water. Here, in this back-grinding process, it is required to grind the wafer to a thickness that is difficult to handle by itself. For this reason, the wafer is fixed on a support wafer via an adhesive.

[0003] In the back-grinding process described above, a process called self-grinding is performed to grind the holding surface of the chuck, which is the surface that comes into contact with the wafer (see, for example, Patent Document 1). In the back-grinding process, the wafer is fixed to the chuck by being sucked through a conduit that passes through the inside of the chuck and extends to the surface. On the other hand, grinding debris is generated during the grinding of the wafer, which clogs the conduit that extends to the chuck surface, making it difficult to fix the wafer. Here, by performing self-grinding on the chuck, the holding surface of the chuck is ground by a grinding wheel fixed to a grinding wheel in the same manner as the wafer, and clogging can be eliminated. The self-grinding is performed, for example, when replacing the chuck. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-91897 A Summary of the Invention [Problem to be solved by the invention]

[0005] On the other hand, in the processing of wafers, as the support member for supporting the wafer has been changed from a tape with a large TTV (total thickness variation, the difference between the maximum and minimum thickness values ​​in the flatness application area of ​​the wafer) to a support wafer with a small TTV, importance has been attached to slight thickness variations that were not observed before. Specifically, it has become necessary to make the TTV about 0.1 μm after the wafer processing. For example, when the wafer is ground by adsorbing it to a chuck, a recess of about 0.3 μm may be formed in the center of the wafer. The formation of the recess increases the TTV, and there is concern that the accuracy of the wafer manufacturing may decrease. Furthermore, when wafers are stacked three-dimensionally, there is concern that the accuracy of the stacked wafers may decrease because the thickness variation of each wafer due to the formation of the recess affects the thickness of the stacked wafers. Thus, the uniformity of the wafer thickness has been attached importance in recent years.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a processing apparatus, a chuck shape correction method, and a processing method that can prevent the formation of a recess in the center of a wafer. [Means for solving the problem]

[0007] Although the cause of the formation of the recess is unclear, one of the causes is that a protrusion of about 0.3 μm in height is formed in the center of the chuck in the self-grinding process described above. Therefore, in order to prevent the formation of a recess in the center of the wafer, it is important to prevent the formation of a protrusion in the center of the chuck. The gist of the present invention, which was made based on such findings, is as follows.

[0008] The processing apparatus according to the first embodiment of the present invention is a processing apparatus for grinding a wafer, and has a porous structure, a chuck for adsorbing and holding the wafer, and a correction mechanism for correcting the shape of the chuck, and the correction mechanism is equipped with a grinding wheel for grinding the center of the chuck.

[0009] The processing apparatus may further include a rough grinding stage for performing rough grinding, a fine grinding stage for performing fine grinding, and an alignment stage, in which the chuck adsorbs the wafer and the correction mechanism is disposed on the alignment stage.

[0010] A chuck shape correction method according to a second embodiment of the present invention is a method for correcting the shape of a chuck having a porous structure that adsorbs and holds a wafer, and includes a first grinding step of grinding the chuck by self-grinding, and a second grinding step of further grinding the central portion of the chuck after the first grinding step.

[0011] A processing method according to a third embodiment of the present invention is a processing method for grinding a wafer, and includes a first grinding step in which a chuck having a porous structure and which suction-holds the wafer is ground by self-grinding, and a second grinding step in which the center of the chuck is ground after the first grinding step. Effect of the Invention

[0012] According to the processing apparatus and the chuck shape correction method of the present invention, it is possible to prevent the formation of a recess in the central portion of the wafer. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram showing a processing device according to a first embodiment of the present invention. [Diagram 2] FIG. 13 is a cross-sectional view showing a schematic diagram of a correction mechanism for grinding the central portion of the chuck. [Diagram 3] FIG. 4 is a plan view showing the positional relationship between the chuck, the swing type thickness sensor, and the tilt mechanism. [Figure 4]FIG. 4 is a schematic diagram showing the installation position of a fixed thickness sensor. [Diagram 5] 1 is a schematic diagram showing the positional relationship of measurement points of a fixed thickness sensor on a wafer. FIG. [Figure 6] 10 is a flowchart showing a correction procedure of a chuck shape correcting method according to a second embodiment of the present invention. [Figure 7] 13 is a flowchart showing a second grinding step (step S2) of grinding the central portion of the chuck. [Figure 8] 11 is a schematic diagram showing how a correction mechanism flattens a protrusion formed in the center of the chuck. FIG. [Figure 9] 13 is a diagram showing a state in which a wafer is attracted to a chuck on which a convex portion is formed, and a concave portion is formed on the wafer. FIG. [Figure 10] FIG. 13 is a diagram showing thickness results of the central portion of the chuck before and after grinding of the central portion of the chuck in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a processing device according to a first embodiment of the present invention will be described with reference to the drawings.

[0015] First, a processing device according to a first embodiment of the present invention will be described. As shown in Fig. 1, the processing device 100 includes a frame 100a, a correction mechanism 101, a chuck 103 having a porous structure and suction-holding a wafer 102, a base 104 holding the chuck 103, a bearing (not shown) for rotating the chuck 103 and the base 104, a swing type thickness sensor 112, and a fixed type thickness sensor 113. The processing device 100 is applicable not only to the grinding process of the wafer 102 but also to the grinding process of the chuck 103, i.e., a self-grinding process. The swing type thickness sensor 112 and the fixed type thickness sensor 113 may be non-contact thickness measuring devices.

[0016] 1, the processing apparatus 100 is provided with four stages, namely, an alignment stage ST1 on which an alignment target is placed, a rough grinding stage ST2, a medium grinding stage ST3, and a fine grinding stage ST4. The processing apparatus 100 performs a plurality of grinding processes successively on a wafer 102 or a chuck 103. Note that the number of stages that sequentially process the chuck 103 upstream of the fine grinding stage ST4 is not limited to two, the rough grinding stage ST2 and the medium grinding stage ST3, and may be one or three or more.

[0017] The processing apparatus 100 includes an index table 105 that can rotate around a rotation axis 105a, and chucks 103 that are arranged on each of four stages at equal intervals on a concentric circle centered on the rotation axis 105a of the index table 105. By rotating the index table 105, the chuck 103 can move in the order of the alignment stage ST1, the rough grinding stage ST2, the medium grinding stage ST3, and the fine grinding stage ST4. Hereinafter, the direction of movement of the chuck 103 (ST1→ST2→ST3→ST4) is referred to as the forward direction, and the direction of movement of the chuck 103 opposite to the forward direction is referred to as the reverse direction.

[0018] FIG. 2 is a cross-sectional view showing a schematic diagram of the correction mechanism 101 for grinding the chuck central portion 103a. As shown in FIG. 2, the chuck 103 is divided into the chuck central portion 103a and a chuck peripheral portion 103b excluding the chuck central portion 103a. The chuck central portion 103a is a region corresponding to a cone-shaped or cylindrical portion having a certain diameter from the center of the chuck 103. The chuck peripheral portion 103b is a region of the chuck 103 excluding the region of the chuck central portion 103a. In addition, the diameter of the chuck central portion 103a is about 20 mm to 30 mm when the diameter of the chuck 103 is 300 mm, but may be 20 mm or less or 30 mm or more. The chuck 103 is made of ceramic.

[0019] Furthermore, the chuck 103 is uniformly formed by self-grinding performed before processing the wafer 102. The chuck 103 has a conduit (not shown) that passes through the inside and extends to the surface. The conduit is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint (not shown). When the vacuum source is activated, the wafer 102 placed on the chuck 103 is attracted and held by the chuck 103. When the compressed air source or the water supply source is activated, the attraction between the wafer 102 and the chuck 103 is released.

[0020] The base 104 holds the chuck 103. The base 104 is connected to a bearing (not shown). The bearing is configured to be rotatable about a rotation axis perpendicular to the base 104. The chuck 103 rotates or stops as the bearing connected to the base 104 is rotatably driven.

[0021] 3, the chuck 103 and the base 104 are supported by a tilt mechanism 106 capable of tilting a chuck rotation axis 103c (a vertical axis passing through the center of the chuck 103). The tilt mechanism 106 includes a tilt table 106a, a fixed support portion 106b, a first movable support portion 106c, and a second movable support portion 106d.

[0022] The tilt table 106a is formed in a substantially triangular shape in a plan view and is interposed between the index table 105 and the chuck 103, and supports the base 104.

[0023] The fixed support portion 106b, the first movable support portion 106c, and the second movable support portion 106d are arranged on the tilt table 106a at equal intervals on a concentric circle centered on the chuck rotation shaft 103c. The fixed support portion 106b is a bolt that connects the index table 105 and the tilt table 106a.

[0024] The first movable support part 106c is disposed upstream of the fixed support part 106b in the rotation direction D of the chuck 103. The second movable support part 106d is disposed downstream of the fixed support part 106b in the rotation direction D of the chuck 103. The first movable support part 106c and the second movable support part 106d are each configured to independently raise and lower the tilt table 106a relative to the index table 105 by rotating a ball screw (not shown) disposed vertically between the index table 105 and the tilt table 106a with a motor (not shown).

[0025] The correction mechanism 101 corrects the shape of the chuck 103, particularly the shape of the central portion 103a. The correction mechanism 101 also includes a grinding wheel 101b for grinding the chuck central portion 103a, and a mount 101a for mounting the grinding wheel 101b. The number of grinding wheels 101b mounted on the mount 101a may be multiple or may be one. For example, a red grinding wheel or a white grinding wheel may be used as the grinding wheel 101b. As shown in FIG. 2, the correction mechanism 101 may include a grinding wheel 101c that rotates the grinding wheel 101b, and the chuck 103 may be ground in a state in which the grinding wheel 101c rotates the grinding wheel 101b.

[0026] If a convex portion is formed in the chuck central portion 103a, the grinding wheel 101b grinds the convex portion, thereby flattening the chuck central portion 103a. As a result, when the wafer 102 is ground, the chuck 103 is attracted and held in a flattened state, so that the formation of a concave portion in the wafer central portion 102a can be prevented. Furthermore, by preventing the formation of the concave portion, the TTV value can be reduced.

[0027] The wafer 102 is held by suction by the chuck 103. The wafer 102 includes a wafer central portion 102a and a wafer peripheral portion 102b excluding the wafer central portion 102a. The wafer central portion 102a is a region on the surface of the wafer that corresponds to a conical or cylindrical portion having a certain diameter from the center of the wafer 102. The wafer peripheral portion 102b is a region on the surface of the wafer 102 excluding the region of the wafer central portion 102a. The diameter of the wafer central portion 102a of the wafer 102 is the same as the diameter of the chuck central portion 103a. In other words, the wafer central portion 102a is a region corresponding to the chuck central portion 103a, and the wafer peripheral portion 102b is a region corresponding to the chuck peripheral portion 103b.

[0028] The configuration of each of the four stages (ST1 to ST4) will be described below. In the alignment stage ST1, the first arm 107a takes out the wafer 102 from the first rack 107b (see FIG. 1) in which the unprocessed wafer 102 is accommodated, and transports it to the chuck 103 located in the alignment stage ST1. The wafer 102 is previously aligned so that its orientation coincides with a predetermined direction. In addition, the second arm 108a (see FIG. 1) receives the processed wafer 102 from the chuck 103 located in the alignment stage ST1, and transports it to the second rack 108b (see FIG. 1) in which the processed wafer 102 is accommodated. In addition, the alignment stage ST1 is provided with a correction mechanism 101. In addition, as shown in FIG. 1, the alignment stage ST1 is adjacent to the precision grinding stage ST4 in the rotation direction of the index table 105.

[0029] 1, the rough grinding stage ST2 is provided with a rough grinding device 109. The rough grinding device 109 includes a rough grinding wheel (not shown), a first spindle 109a having the rough grinding wheel attached to its lower end and rotatably supporting the rough grinding wheel, and a first spindle feed mechanism 109b for vertically raising and lowering the first spindle 109a. The rough grinding device 109 is also provided with a thickness sensor (not shown) for measuring the thickness of the wafer 102 during rough grinding.

[0030] The medium grinding stage ST3 is provided with a medium grinding device 110. The medium grinding device 110 includes a medium grinding wheel (not shown), a second spindle 110a having the medium grinding wheel attached to its lower end and rotatably supporting the medium grinding wheel, and a second spindle feed mechanism 110b for vertically raising and lowering the second spindle 110a. The medium grinding device 110 is also provided with a thickness sensor (not shown) for measuring the thickness of the wafer 102 during medium grinding.

[0031] The precision grinding stage ST4 is provided with a precision grinding device 111. The precision grinding device 111 includes a precision grinding wheel (not shown), a third spindle 111a having the precision grinding wheel attached to its lower end and supporting the precision grinding wheel rotatably about a rotation axis set along the vertical direction, and a third spindle feed mechanism (not shown) that raises and lowers the third spindle 111a in the vertical direction. The precision grinding device 111 is also provided with a thickness sensor (not shown) that measures the thickness of the wafer 102 during precision grinding.

[0032] The precision grinding stage ST4 is provided with a swing type thickness sensor 112. The swing type thickness sensor 112 measures the thickness (film thickness) of the wafer 102 before precision grinding and measures its shape. The swing type thickness sensor 112 is an optical sensor capable of detecting film thickness without contact, and as shown in FIG. 3, a sensor head 112b is attached to the tip of an arm 112a, and a base end of the arm 112a is connected to a drive shaft 112c outside the index table 105. The arm 112a can swing along a horizontal plane with the drive shaft 112c as a fulcrum, and the sensor head 112b can move from an outer periphery position P1 of the wafer 102 to a position overlapping with the center O of the wafer 102.

[0033] The processing apparatus 100 is provided with a fixed thickness sensor 113. The fixed thickness sensor 113 measures the thickness (film thickness) of the wafer 102 after precision grinding in a non-contact manner to measure the shape of the wafer. The fixed thickness sensor 113 is, for example, a spectroscopic interference type film thickness measuring device. The fixed thickness sensor 113 is provided on each of the upstream side and downstream side of the alignment stage ST1 in the rotation direction of the index table 105. Here, when the processed wafer 102 is transported from the precision grinding stage ST4 to the alignment stage ST1, the index table 105 may rotate in the forward direction or the reverse direction due to the relationship of the rotation mechanism of the index table 105. Therefore, it is necessary to provide a fixed thickness sensor 113 corresponding to each rotation direction of the index table 105. Therefore, one fixed thickness sensor 113 is provided on each of the upstream side and downstream side of the alignment stage ST1.

[0034] As shown in Fig. 4, the fixed thickness sensor 113 is fixed to a frame 100a installed in the processing apparatus 100, and is installed above the index table 105. The measurement point at which the fixed thickness sensor 113 measures the thickness of the wafer 102 is set on a rotational orbit R of the center O of the wafer 102 when viewed from above. Note that Fig. 4 illustrates only the fixed thickness sensor 113 provided between the alignment stage ST1 and the fine grinding stage ST4, and omits the fixed thickness sensor 113 provided between the alignment stage ST1 and the rough grinding stage ST2.

[0035] 5 is a schematic diagram showing the positional relationship of the measurement points of the fixed thickness sensor 113 on the wafer 102. FIG. 5 illustrates the positional relationship of the measurement points of the fixed thickness sensor 113 when the rotation speed of the index table 105 is set to 20 deg / sec, the rotation speed of the chuck 103 is set to 400 rpm, and the sampling period of the fixed thickness sensor 113 is set to 4 milliseconds. Since the wafer 102 passes directly below the fixed thickness sensor 113 while rotating, the trajectory of the measurement points of the fixed thickness sensor 113 includes the center O of the wafer 102 and spreads over the entire surface of the wafer 102. The trajectory of the measurement points of the fixed thickness sensor 113 can be appropriately changed depending on the rotation speed of the index table 105, the rotation speed of the chuck 103, and the sampling period of the fixed thickness sensor 113.

[0036] In addition, the fixed thickness sensor 113 is not limited to being placed on the upstream and downstream sides of the alignment stage ST1, so long as it is capable of measuring the thickness of the processed wafer 102 while it is being transported from the precision grinding stage ST4 to the alignment stage ST1.

[0037] The control device 114 controls the operation of the processing device 100. In detail, the control device 114 controls each of the components constituting the processing device 100. The control device 114 is composed of, for example, a CPU, a memory, and the like. Note that the functions of the control device 114 may be realized by control using software, or may be realized by operation using hardware.

[0038] The control device 114 drives the tilt mechanism 106 based on the thickness of the wafer 102 before precision grinding measured by the oscillating thickness sensor 112 so that the wafer 102 after precision grinding will approximately match the desired shape. Then, the tilt mechanism 106 tilts the chuck rotation axis 103c with respect to the rotation axis of the precision grinding wheel. Hereinafter, the angle of the chuck rotation axis 103c with respect to the rotation axis of the precision grinding wheel will be referred to as the "tilt angle."

[0039] Specifically, the control device 114 calculates the amount of grinding of the wafer 102 during precision grinding that matches the difference between the shape of the wafer 102 before precision grinding measured by the oscillating thickness sensor 112 and the target shape of the wafer 102 after grinding, and the tilt angle that realizes that amount of grinding. Furthermore, the control device 114 calculates the amount of lifting of the first movable support unit 106c and the second movable support unit 106d according to the tilt angle, and raises and lowers the first movable support unit 106c and the second movable support unit 106d, respectively. As a result, the tilt table 106a tilts the chuck rotation axis 103c with respect to the rotation axis of the precision grinding wheel, using the fixed support unit 106b as a reference.

[0040] Meanwhile, the control device 114 compares the shape of the wafer 102 after precision grinding measured by the fixed thickness sensor 113 with the desired target shape. If the shape of the wafer 102 after precision grinding does not match the desired target shape, a correction angle to be added to the tilt angle during precision grinding is stored so that the shape of the wafer 102 after precision grinding matches the difference between the shape of the wafer 102 after precision grinding and the desired target shape. Note that the control device 114 previously stores the relationship between the difference between the shape of the wafer 102 after precision grinding and the desired target shape, which has been obtained through experiments or the like, and the correction angle that alleviates the difference, as well as the lift amounts (correction lift amounts) of the first movable support unit 106c and the second movable support unit 106d that realize the correction angle of the tilt mechanism 106.

[0041] Next, a chuck shape correction method according to a second embodiment of the present invention will be described. Fig. 6 is a flowchart showing a correction procedure of the chuck shape correction method according to this embodiment. The chuck shape correction method according to this embodiment is a method for correcting the shape of a chuck 103 having a porous structure and adsorbing and holding a wafer 102, and includes a first grinding step (step S1) of grinding the chuck 103 by self-grinding, and a second grinding step (step S2) of further grinding a chuck central portion 103a after the first grinding step.

[0042] The first grinding step will be described below. As described above, in the back grinding process, a process called self grinding is performed to grind the holding surface of the chuck 103, which is the surface that contacts the wafer 102. The procedure of the self grinding process will be described in detail below. First, the chuck 103 is placed on the alignment stage ST1, and then the index table 105 rotates, and the chuck 103 moves toward the rough grinding stage ST2. Then, the rough grinding process is performed on the chuck 103. In the rough grinding process, the grinding surface of the rough grinding wheel is pressed against the chuck 103 while the rough grinding wheel and the chuck 103 are rotated, and the chuck 103 is roughly ground. After the chuck 103 is ground to an extent that clogging of the pipes extending to the surface of the chuck 103 can be eliminated, the rough grinding device 109 stops the rotation of the rough grinding wheel and the chuck 103, and retracts the rough grinding wheel upward to end the rough grinding.

[0043] Next, the index table 105 rotates, and the chuck 103 moves toward the medium grinding stage ST3. At the medium grinding stage ST3, medium grinding is performed on the chuck 103. In the medium grinding, the grinding surface of the medium grinding wheel is pressed against the chuck 103 while the medium grinding wheel and the chuck 103 are rotating, and medium grinding of the chuck 103 is performed. Thereafter, the medium grinding device 110 stops the rotation of the medium grinding wheel and the chuck 103, and retracts the medium grinding wheel upward, completing the medium grinding.

[0044] Next, the index table 105 rotates, and the chuck 103 moves toward the precision grinding stage ST4. Then, the arm 112a swings about the drive shaft 112c, and the sensor head 112b scans from the outer periphery position P1 of the wafer 102 to a position where it overlaps with the center of the chuck 103. This measures the shape of the wafer 102 before precision grinding.

[0045] Next, precision grinding is performed on the chuck 103. Specifically, in the precision grinding, the grinding surface of the precision grinding wheel is pressed against the chuck 103 while the precision grinding wheel and the chuck 103 are rotated, to perform precision grinding of the chuck 103. Thereafter, the precision grinding device 111 stops the rotation of the precision grinding wheel and the chuck 103, and retracts the precision grinding wheel upward, thereby completing the precision grinding.

[0046] Next, the index table 105 rotates, and the chuck 103 moves toward the alignment stage ST1. In the self-grinding process described above, the chuck 103 is subjected to rough grinding, medium grinding, and fine grinding, but only the rough grinding may be performed, or only the medium grinding and / or at least one of the fine grinding may be performed.

[0047] The self-grinding may be performed on a stage immediately adjacent to the stage where the success or failure of the shape correction of the chuck 103 is confirmed, i.e., the surface shape of the wafer 102 is measured. For example, when the surface shape of the wafer 102 is measured on the alignment stage ST1, the self-grinding may be performed on the precision grinding stage ST4. In this way, by performing the self-grinding on the precision grinding stage ST4, which is the stage immediately adjacent to the stage where the surface shape of the wafer 102 is measured, the success or failure of the shape correction of the chuck 103, which will be described later, can be quickly confirmed. Furthermore, since the precision grinding stage ST4 is the stage where the final processing of the wafer 102 is performed, the self-grinding of the chuck 103 can be performed in a state close to the state in which the wafer 102 is finally processed. Therefore, the in-plane thickness uniformity of the wafer 102 can be improved.

[0048] Next, the second grinding step will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a flowchart showing the procedure of the second grinding step in the chuck shape correction method according to this embodiment. Fig. 8 is a schematic diagram showing how the correction mechanism flattens a convex portion formed in the center of the chuck. However, the correction procedure shown in Fig. 7 and Fig. 8 is merely an example, and the procedure for correcting the shape of the chuck 103 is not limited to this correction procedure.

[0049] After the above-described self-grinding process, the correction mechanism 101 grinds the chuck central portion 103a in the following procedure. The procedure for correcting the shape of the chuck 103 is performed in accordance with steps S21 and S22 as shown in Fig. 7(a). First, the correction mechanism 101 is aligned (step S21, see Figs. 7(a) and 8(a)). That is, the grinding wheel 101b is aligned so as to be located directly above the chuck central portion 103a. However, when starting self-grinding, the chuck 103 is aligned to the center of the base 104 and is placed on the base 104. Therefore, the correction mechanism 101 does not need to acquire new position information of the chuck central portion 103a when grinding the chuck central portion 103a. Next, the grinding wheel 101b grinds the chuck central portion 103a (step S22, see Fig. 7(a) and Fig. 8(b)). In detail, while the chuck 103 is rotating by the bearings, the grinding wheel 101b aligned with the chuck central portion 103a descends vertically toward the chuck central portion 103a to grind the chuck central portion 103a. Next, after the grinding wheel 101b is withdrawn upward, or at the same time as the grinding wheel 101b is withdrawn upward, the rotation of the chuck 103 by the bearing is stopped. Then, grinding of the chuck 103 is completed (see FIG. 8(c)).

[0050] The procedure for correcting the shape of the chuck 103 may be performed in accordance with steps S21, S22, S24, and S23 as shown in Fig. 7(b). Fig. 7(b) shows a flowchart in the case where the second grinding step includes step S23 of measuring the surface shape of the wafer 102 and step S24 of grinding the wafer 102. 7(b), the correction procedure may include a procedure (step S23) of measuring the surface shape of the wafer 102 after the wafer 102 is attracted to the chuck 103 whose central portion 103a has been ground. By obtaining the surface shape of the wafer 102 in step S23, it is possible to observe the change in the surface shape of the wafer 102 before and after the shape correction of the chuck 103. Therefore, it is possible to confirm whether the shape correction of the chuck 103 has been successful. Furthermore, between steps S22 and S23, a procedure (step S24) of grinding the surface of the wafer 102 by the processing device 100 may be performed.

[0051] Here, for example, as shown in Fig. 9, if the wafer 102 is ground while being adsorbed to a chuck 103 having a convex portion formed in the chuck central portion 103a, a concave portion will be formed in the wafer central portion 102a. On the other hand, as shown in Fig. 8, if the convex portion in the chuck central portion 103a can be removed by the procedure after self-grinding, no concave portion will be formed in the wafer central portion 102a. This makes it possible to prevent the TTV of the wafer from becoming large.

[0052] Next, a processing method according to a third embodiment of the present invention will be described. The processing method according to this embodiment is a processing method for grinding the surface of the wafer 102, and includes a first grinding step of grinding the chuck 103, which has a porous structure and holds the wafer 102 by suction, by self-grinding, and a second grinding step of grinding the chuck central portion 103a after the first grinding step. The first grinding step may be performed according to the procedure of the self-grinding process described above. Furthermore, the second grinding step may be performed according to steps S21 and S22 in the shape correction method for the chuck 103 described above. Furthermore, the processing method according to this embodiment may include a third grinding step of grinding the surface of the wafer 102. The third grinding step may be performed according to step S24 in the shape correction method for the chuck 103 described above.

[0053] According to the processing method of this embodiment, even if the chuck central portion 103a is not sufficiently ground after self-grinding in the process of grinding the surface of the wafer 102 and a convex portion is formed in the chuck central portion 103a, the convex portion can be ground to flatten the chuck central portion 103a. Therefore, it is possible to prevent the formation of a concave portion in the wafer central portion 102a and reduce the TTV value.

[0054] The processing apparatus according to the first embodiment of the present invention is a processing apparatus for grinding a wafer, and has a porous structure, a chuck for adsorbing and holding the wafer, and a correction mechanism for correcting the shape of the chuck, and the correction mechanism is equipped with a grinding wheel for grinding the center of the chuck.

[0055] According to the processing apparatus of the first embodiment of the present invention, the grinding wheel grinds the convex portion at the center of the chuck, thereby flattening the chuck. As a result, when the wafer is ground, the chuck suction-holds the wafer in a flattened state, so that the formation of a concave portion at the center of the wafer can be prevented. Furthermore, by preventing the formation of the concave portion, the TTV value can be reduced.

[0056] According to the above processing apparatus, the correction mechanism may be disposed on the alignment stage, thereby making it possible to make the processing apparatus more compact.

[0057] According to the chuck shape correction method according to the second embodiment of the present invention, after the chuck is ground by self-grinding, the central portion of the chuck can be further ground and flattened. As a result, even if the central portion of the chuck is not sufficiently ground by self-grinding and a convex portion is formed in the central portion, the convex portion can be ground to flatten the central portion of the chuck.

[0058] A processing method according to a third embodiment of the present invention is a processing method for grinding a wafer, and includes a first grinding step in which a chuck having a porous structure and which suction-holds the wafer is ground by self-grinding, and a second grinding step in which the center of the chuck is ground after the first grinding step.

[0059] According to the above processing method, the processing method for grinding the wafer includes a first grinding step of grinding by self-grinding, and a second grinding step of grinding the center of the chuck after the first grinding step. Therefore, even if the center of the chuck is not sufficiently ground after self-grinding and a convex portion is formed in the center, the convex portion can be ground to flatten the center of the chuck. Therefore, since the wafer held by the flattened chuck is ground, it is possible to prevent the formation of a concave portion in the wafer. Therefore, the TTV value can be reduced.

[0060] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. EXAMPLES

[0061] The effects of the examples will be described in more detail. However, the conditions in the examples are merely examples of conditions adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples of conditions. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0062] A first grinding step of grinding the chuck by self-grinding, and a second grinding step of grinding the center of the chuck after the first grinding step were carried out. With the chuck rotating (by a bearing), a grinding wheel was applied to the center of the chuck, which had a diameter of about φ20 mm, and the chuck was ground with the grinding wheel. A mirror wafer with a diameter of 300 mm and an average thickness of 200.0 μm was used as the wafer. The shape correction of the chuck by the correction mechanism was carried out after the fine grinding finish of the self-grinding. The roughness of the grinding wheel may be the same as that of the grinding wheel used for the above-mentioned medium grinding and fine grinding. The success or failure of the chuck shape correction was judged by measuring the thickness of the wafer held by the chuck after the shape correction was performed, using a non-contact thickness measuring device. FIG. 10 shows the thickness results near the center of the wafer before and after grinding the center of the chuck.

[0063] From FIG. 10, it can be seen that when the center of the chuck was not ground by the correction mechanism, the thickness of the center of the wafer, i.e., the part about 20 mm away from the center of the wafer surface, was reduced by about 0.3 μm. In other words, it is believed that a convex part was formed in the center of the chuck because the shape of the chuck was not corrected by the correction mechanism after self-grinding. As a result, it is believed that a concave part was formed in the center of the wafer of the wafer adsorbed to the chuck. On the other hand, the thickness of the center of the wafer after the center of the chuck was ground by the correction mechanism was not reduced compared to the thickness of the wafer periphery. This is believed to be because when the shape of the chuck was corrected by the correction mechanism after self-grinding, the convex part formed in the center of the chuck was ground, and therefore no concave part was formed in the center of the wafer adsorbed to the chuck. [Explanation of symbols]

[0064] 100 Processing equipment 100a frame 101 Correction mechanism 101a Mount 101b Grinding wheel 101c Grinding Wheel 102 Wafer 102a Center of wafer 102b Wafer periphery 103 Chuck 103a Center of chuck 103b Chuck periphery 103c Chuck rotation axis 104 Base 105 Index Table 105a Rotating shaft 106 Tilt mechanism 106a Tilt table 106b Fixed support 106c first movable support 106d Second movable support 107a First Arm 107b First Rack 108a Second Arm 108b Second Rack 109 Rough grinding equipment 109a First Spindle 109b first spindle feed mechanism 110 Medium grinding equipment 110a Second spindle 110b Second spindle feed mechanism 111 Precision grinding equipment 111a Third Spindle 112 Swing type thickness sensor 112a Arm 112b Sensor head 112c Drive shaft 113 Fixed thickness sensor 114 Control device D Rotation direction O center P1 outer circumference position R (wafer center) rotation orbit ST1 Alignment Stage ST2 Rough grinding stage ST3 Medium grinding stage ST4 Precision grinding stage

Claims

1. A processing apparatus for grinding a wafer, comprising: a chuck having a porous structure and adapted to suction-hold the wafer; A correction mechanism for correcting the shape of the chuck, The correction mechanism is provided with a grinding wheel that grinds the center of the chuck.

2. The grinding apparatus further includes a rough grinding stage for performing rough grinding, a fine grinding stage for performing fine grinding, and an alignment stage. In the alignment stage, the chuck adsorbs the wafer, The processing apparatus according to claim 1 , wherein the correction mechanism is disposed on the alignment stage.

3. A method for correcting the shape of a chuck having a porous structure and adapted to suction-hold a wafer, comprising: a first grinding step of grinding the chuck by self-grinding; a second grinding step of further grinding a central portion of the chuck after the first grinding step; The chuck shape correction method includes:

4. A method for grinding a wafer, comprising the steps of: a first grinding step of grinding a chuck having a porous structure and adapted to suction-hold the wafer by self-grinding; a second grinding step of grinding a central portion of the chuck after the first grinding step; A processing method comprising:

Images