Wafer processing method and chip manufacturing method

Abstract

To provide a wafer processing method which can prevent a device from being damaged due to an etching liquid to be used when applying wet etching to a rear surface side of a device wafer included in a bonded wafer.SOLUTION: Provided is a wafer in which an inclined plane is formed in an outer peripheral region. Further, when liquid (for example, an etching liquid to be used for wet etching) is supplied to the outer peripheral region, the liquid flows on the inclined plane to easily flow to the outside of the wafer. Therefore, in a bonded wafer in which the wafer has been applied as a support wafer, a device is prevented from being damaged due to an etching liquid to be used when applying wet etching to a rear surface side of a device wafer.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a wafer processing method and a wafer. [Background technology]

[0002] Chips for devices such as integrated circuits (ICs) are essential components in various electronic devices such as mobile phones and personal computers. These chips are manufactured, for example, by forming multiple devices on the front surface of a wafer made of semiconductor material and then dividing the wafer into regions containing individual devices.

[0003] Wafers are prone to cracking in their peripheral regions. Therefore, in the chip manufacturing process, the peripheral region of the wafer is generally chamfered prior to various processes. Furthermore, in the chip manufacturing process, the backside of the wafer is often ground prior to dividing the wafer in order to miniaturize the chips to be manufactured.

[0004] However, when the backside of a wafer with a chamfered peripheral region is ground, the backside of the peripheral region takes on a knife-edge shape. Stress tends to concentrate in this area, making it prone to cracks. Therefore, in the chip manufacturing process, after a process (edge ​​trimming) is performed to remove a portion of the front side of the peripheral region of the wafer and form a step, the backside of the wafer is sometimes ground to remove the remaining portion of the peripheral region (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-173961 Summary of the Invention [Problem to be solved by the invention]

[0006] A wafer (device wafer) having a plurality of devices formed on its front surface may be bonded to a wafer (support wafer) having the same diameter as the device wafer for the purpose of increasing the integration of the chips to be manufactured. In this way, the back surface of the device wafer may be ground.

[0007] However, grinding the back surface of the device wafer may damage the back surface of the device wafer, and therefore, in such a case, wet etching may be performed on the back surface of the device wafer after grinding the back surface of the device wafer.

[0008] If the etching solution used in this wet etching penetrates into the interface between the device wafer and the support wafer, there is a risk of damaging the devices formed on the front surface side of the device wafer. Therefore, in such cases, edge trimming may be performed to form a step on the front surface side of the peripheral region of the support wafer prior to bonding the front surface side of the device wafer and the front surface side of the support wafer.

[0009] However, if such a step is formed on the surface side of the peripheral region of the support wafer, the etching solution may remain below the step, which may etch the surface side of the support wafer and damage devices formed on the surface side of the device wafer.

[0010] In view of this, an object of the present invention is to provide a wafer processing method and a wafer that can suppress damage to devices caused by an etching solution used during wet etching of the backside of a device wafer included in a bonded wafer. [Means for solving the problem]

[0012] Original ClearlyAccording to the method, the method includes a holding step of holding a disk-shaped wafer on a holding surface of a chuck table that is rotatable around a rotation axis that is perpendicular to the holding surface and passes through the center of the holding surface, and after the holding step, a first cutting blade is attached to the tip of a first spindle that is rotatable around a rotation axis that is parallel to the holding surface, and while rotating the first spindle, the first cutting blade cuts into the outer peripheral region of the wafer, and the chuck table is rotated, thereby forming a flat surface at a constant distance from the holding surface in the outer peripheral region. and a second processing step, after the first processing step, of cutting the second cutting blade into the outer peripheral region where the flat surface is formed while rotating a second spindle, the second spindle being rotatable about a rotation axis that is a straight line non-parallel to the holding surface, and rotating the chuck table to form an inclined surface in the outer peripheral region of the wafer that slopes so that the distance from the holding surface decreases as the wafer approaches the outer peripheral edge. Note that this wafer processing method may further include, after the second processing step, a wet etching step in which an etching solution flows down from the wafer along the inclined surface. Also, in the wet etching step, the etching solution that has spread outward from the surface of the wafer on which the etching solution was dropped may flow down from the wafer along the inclined surface. The inclined surface may be inclined such that the distance from the front surface of the wafer in the thickness direction of the wafer increases toward the outer periphery of the wafer, and in the wet etching step, edge trimming of the front surface side of the device wafer, bonding the front surface side of the device wafer and the front surface side of the device wafer to form a bonded wafer, and grinding the back surface side of the device wafer may be performed in this order, so that the back surface side of the device wafer from which the chamfered outer periphery has been removed is subjected to wet etching. Furthermore, the present invention may be a chip manufacturing method in which, after performing this wafer processing method, the bonded wafer is divided along planned division lines of the device wafer to manufacture chips. [Effects of the Invention]

[0014] According to the present invention, a wafer is provided having an inclined surface formed in the peripheral region, and when a liquid (e.g., an etching liquid used in wet etching) is supplied to this peripheral region, the liquid flows on the inclined surface and easily flows out to the outside of the wafer.

[0015] Therefore, in a bonded wafer in which this wafer is used as a support wafer, damage to the device due to the etching solution used in wet etching the back surface side of the device wafer can be suppressed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1(A) is a top view that schematically shows an example of a wafer, and FIG. 1(B) is a cross-sectional view that schematically shows an example of a wafer. [Figure 2] FIG. 2 is a front view schematically showing an example of a cutting device. [Figure 3] FIG. 3 is a flowchart schematically illustrating an example of a wafer processing method. [Figure 4] 4(A), 4(B), and 4(C) are each a partial cross-sectional front view schematically showing the first processing step included in the wafer processing method shown in FIG. [Figure 5] FIG. 5(A) is a top view schematically showing an example of a wafer after the first processing step, and FIG. 5(B) is a cross-sectional view schematically showing an example of a wafer after the first processing step. [Figure 6] 6(A), 6(B), and 6(C) are partial cross-sectional front views each showing a schematic view of the second processing step included in the wafer processing method shown in FIG. [Figure 7] FIG. 7(A) is a top view schematically showing an example of a wafer after the second processing step, and FIG. 7(B) is a cross-sectional view schematically showing an example of a wafer after the second processing step. [Figure 8]FIG. 8(A) is a top view that schematically shows an example of a device wafer, and FIG. 8(B) is a cross-sectional view that schematically shows an example of a device wafer. [Figure 9] FIG. 9 is a flow chart schematically showing an example of a method for manufacturing a chip. [Figure 10] Figure 10(A) is a cross-sectional view schematically showing a device wafer that has been edge trimmed, Figure 10(B) is a cross-sectional view schematically showing an example of a bonded wafer, Figure 10(C) is a cross-sectional view schematically showing an example of a bonded wafer in which the back side of the device wafer has been ground, and Figure 10(D) is a cross-sectional view schematically showing wet etching being performed on the back side of the device wafer. DETAILED DESCRIPTION OF THE INVENTION

[0017] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1(A) is a top view schematically showing an example of a wafer, and Fig. 1(B) is a cross-sectional view schematically showing an example of the wafer. The wafer 11 shown in Figs. 1(A) and 1(B) is made of a semiconductor material such as silicon (Si). The wafer 11 has a disk-like shape including a front surface 11a and a back surface 11b that are generally parallel to each other.

[0018] The outer peripheral region of the wafer 11 is chamfered. That is, the side surface 11c of the wafer 11 is curved so as to be convex outward. Furthermore, the outer peripheral region of the wafer 11 is formed with a notch 11d that indicates a specific crystal orientation of the semiconductor material that constitutes the wafer 11.

[0019] There are no limitations on the material, shape, structure, size, etc. of the wafer 11. The wafer 11 may be made of, for example, a semiconductor material other than silicon (e.g., silicon carbide (SiC) or gallium nitride (GaN)). Also, an orientation flat may be formed in the outer peripheral region of the wafer 11 instead of the notch 11d.

[0020] Fig. 2 is a front view schematically showing an example of a cutting device capable of processing the wafer 11. Note that the X-axis direction (front-back direction) and the Y-axis direction (left-right direction) shown in Fig. 2 are directions that are perpendicular to each other on a horizontal plane, and the Z-axis direction (up-down direction) is a direction (vertical direction) that is perpendicular to the X-axis and Y-axis directions.

[0021] 2 has a cylindrical table base 4. A disk-shaped chuck table 6 on which a wafer 11 is placed is provided on top of the table base 4. The chuck table 6 has a frame 6a made of stainless steel or the like.

[0022] The frame 6a has a disk-shaped bottom wall and an annular side wall extending upward from the periphery of the bottom wall, so that a recess defined by the bottom wall and the side wall exists at the top of the frame 6a.

[0023] A circular porous plate (not shown) made of porous ceramics and having a diameter roughly the same as the inner diameter of the recess is fixed in the recess. The porous plate has an upper surface roughly parallel to the X-axis and Y-axis directions, and is connected to a suction source (not shown) such as a vacuum pump via a flow path formed in the frame 6a.

[0024] When the suction source is operated, a negative pressure is created in the space near the upper surface of the porous plate (the holding surface of the chuck table 6). Therefore, when the suction source is operated with the wafer 11 placed on the holding surface of the chuck table 6, the wafer 11 is held by suction on the chuck table 6.

[0025] Furthermore, a rotary drive source (not shown), such as a motor, connected to the chuck table 6 is provided inside the table base 4. When this rotary drive source is operated, the chuck table 6 rotates around a rotation axis that is perpendicular to the holding surface of the chuck table 6 and passes through the center of this holding surface.

[0026] The table base 4 is also connected to an X-axis direction movement mechanism (not shown). This X-axis direction movement mechanism includes, for example, a ball screw. When this X-axis direction movement mechanism is operated, the table base 4 and the chuck table 6 move along the X-axis direction.

[0027] A pair of cutting units 8a, 8b are provided opposite each other in the Y-axis direction above the chuck table 6. The cutting unit 8a has a cylindrical spindle (first spindle) 10a extending in a direction parallel to the Y-axis direction.

[0028] A cutting blade (first cutting blade) 12a having an annular cutting edge is attached to the tip end of the spindle 10a (the end on the cutting unit 8b side). This cutting blade 12a is a hub-type cutting blade that is integrally formed with an annular base made of, for example, metal or the like and an annular cutting edge that follows the outer periphery of the base.

[0029] The cutting edge of the hub-type cutting blade is made of an electroformed grinding stone in which abrasive grains made of diamond or cubic boron nitride (cBN) or the like are fixed with a binder such as nickel.

[0030] Alternatively, the cutting blade 12a may be a washer-type cutting blade having an annular cutting edge to which abrasive grains are fixed by a binder made of metal, ceramic, resin, etc. Further, a nozzle (not shown) is provided near the cutting blade 12a to supply cutting fluid (e.g., water) to the area of ​​the wafer 11 to be cut.

[0031] The other end (base end) of the spindle 10a is connected to a rotary drive source (not shown) such as a motor. When this rotary drive source operates, the cutting blade 12a rotates together with the spindle 10a. That is, when this rotary drive source operates, the cutting blade 12a rotates around a straight line along the Y-axis direction as its rotation axis.

[0032] Furthermore, the cutting unit 8a is connected to a Y-axis direction moving mechanism (not shown) and a Z-axis direction moving mechanism (not shown). Each of the X-axis direction moving mechanism and the Z-axis direction moving mechanism includes, for example, a ball screw. When the Y-axis direction moving mechanism is operated, the cutting unit 8a moves along the Y-axis direction. When the Z-axis direction moving mechanism is operated, the cutting unit 8a moves along the Z-axis direction.

[0033] Furthermore, cutting unit 8b has a cylindrical spindle (second spindle) 10b extending in a direction non-parallel to the holding surface of chuck table 6. This spindle 10b extends in a direction that overlaps with the Y-axis direction in a plan view and forms an angle θ with respect to the Y-axis direction that is greater than 0° and not greater than 5° in a front view, for example.

[0034] A cutting blade (second cutting blade) 12b having an annular cutting edge is attached to the tip end (the end on the cutting unit 8a side) of the spindle 10b. This cutting blade 12b is a hub-type or washer-type cutting blade. Furthermore, a nozzle (not shown) is provided near the cutting blade 12b to supply cutting fluid (e.g., water) to the area of ​​the wafer 11 to be cut.

[0035] The other end (base end) of the spindle 10b is connected to a rotary drive source (not shown) such as a motor. When this rotary drive source operates, the cutting blade 12b rotates together with the spindle 10b. That is, when this rotary drive source operates, the cutting blade 12b rotates around a rotation axis that is a straight line along the direction in which the spindle 10b extends.

[0036] Furthermore, the cutting unit 8b is connected to a Y-axis direction moving mechanism (not shown) and a Z-axis direction moving mechanism (not shown). Each of the X-axis direction moving mechanism and the Z-axis direction moving mechanism includes, for example, a ball screw. When the Y-axis direction moving mechanism is operated, the cutting unit 8b moves along the Y-axis direction. When the Z-axis direction moving mechanism is operated, the cutting unit 8b moves along the Z-axis direction.

[0037] 3 is a flow chart that schematically shows an example of a wafer processing method for processing the wafer 11 in the cutting device 2. Specifically, this method is an example of a method for edge trimming the wafer 11.

[0038] 3, first, a disk-shaped wafer 11 is held on the holding surface of the chuck table 6 (holding step: S1). Specifically, in this holding step (S1), the wafer 11 is loaded onto the holding surface of the chuck table 6 with the front surface 11a facing upward and the center of the back surface 11b aligned with the center of the holding surface of the chuck table 6. Then, a suction source communicating with the porous plate of the chuck table 6 is operated.

[0039] Next, a flat surface at a constant distance from the holding surface of the chuck table 6 is formed in the outer peripheral region of the wafer 11 (first processing step: S2). Figures 4(A), 4(B), and 4(C) are partial cross-sectional front views each showing a schematic view of the first processing step (S2).

[0040] In this first processing step (S2), first, the position of the chuck table 6 in the X-axis direction and / or the position of the cutting unit 8a in the Y-axis direction are adjusted so that the cutting blade 12a is positioned directly above the outer peripheral region of the wafer 11 (see Figure 4(A)).

[0041] Next, while rotating the spindle 10a, the cutting unit 8a is lowered until the lower end of the cutting blade 12a reaches a position lower than the surface 11a of the wafer 11 and higher than the holding surface of the chuck table 6 (see FIG. 4(B)). Next, while keeping the spindle 10a rotating, the chuck table 6 is rotated at least once (see FIG. 4(C)).

[0042] 5(A) is a top view schematically showing the wafer 11 after the first processing step (S2), and FIG. 5(B) is a cross-sectional view schematically showing the wafer 11 after the processing step (S2). In the peripheral region of the wafer 11 after the first processing step (S2), a portion of the front surface 11a side is removed to form a step 13.

[0043] The step 13 includes an upright surface 13a extending downward from the outer periphery of the surface 11a of the wafer 11 in a direction perpendicular to the surface 11a, and a flat surface 13b extending from the lower end of the upright surface 13a to the outer periphery of the wafer 11. The flat surface 13b is at a constant distance from the holding surface of the chuck table 6.

[0044] Next, an inclined surface is formed in the outer peripheral region of the wafer 11 so that the distance from the holding surface decreases as the wafer approaches the outer peripheral edge (second processing step: S3). Figures 6(A), 6(B), and 6(C) are partial cross-sectional front views each showing a schematic view of the second processing step (S3).

[0045] In this second processing step (S3), first, the position of the chuck table 6 in the X-axis direction and / or the position of the cutting unit 8b in the Y-axis direction are adjusted so that the lower end of the cutting blade 12b is positioned directly above the outer peripheral region of the wafer 11 and outside the upright surface 13a of the step 13 formed in this outer peripheral region (see Figure 6(A)).

[0046] Next, while rotating the spindle 10b, the cutting unit 8b is lowered until the lower end of the cutting blade 12b reaches a position lower than the flat surface 13b of the step 13 formed in the outer peripheral region of the wafer 11 and higher than the holding surface of the chuck table 6 (see FIG. 6(B)). Next, while keeping the spindle 10b rotating, the chuck table 6 is rotated at least once (see FIG. 6(C)).

[0047] 7(A) is a top view schematically showing the wafer 11 after the second processing step (S3), and FIG. 7(B) is a cross-sectional view schematically showing the wafer 11 after the second processing step (S3). In this second processing step (S3), the step 13 in the outer peripheral region of the wafer 11 is further ground to form an inclined surface 13c.

[0048] For example, in this second processing step (S3), a step 13 is formed that includes an upright surface 13a extending downward from the outer periphery of the surface 11a of the wafer 11 and an inclined surface 13c extending from the lower end of the upright surface 13a to the outer periphery of the wafer 11. Note that this inclined surface 13c is inclined so that the distance from the surface 11a of the wafer 11 in the thickness direction of the wafer 11 increases as it approaches the outer periphery of the wafer 11.

[0049] FIG. 8(A) is a top view schematically showing an example of a device wafer to be bonded to wafer 11, and FIG. 8(B) is a cross-sectional view schematically showing an example of a device wafer to be bonded to wafer 11.

[0050] 8(A) and 8(B) is made of a semiconductor material such as silicon (Si), and has a disk-like shape with the same diameter as the wafer 11, including a front surface 21a and a back surface 21b that are generally parallel to each other.

[0051] The peripheral region of the device wafer 21 is chamfered. That is, the side surface 21c of the device wafer 21 is curved so as to be convex outward. Furthermore, a notch 21d indicating a specific crystal orientation of the semiconductor material constituting the device wafer 21 is formed in the peripheral region of the device wafer 21.

[0052] Furthermore, the device wafer 21 is divided into a plurality of regions by a plurality of planned division lines that intersect with each other, and devices 23 such as ICs, LSIs, semiconductor memories, or CMOS (Complementary Metal Oxide Semiconductor) image sensors are formed on the surface 21a side of each region.

[0053] The device wafer 21 may also have openings (through holes extending from the front surface 21a to the back surface 21b) or grooves in which wiring such as through-silicon vias (TSVs) is provided.

[0054] There are no limitations on the material, shape, structure, size, etc. of the device wafer 21. The device wafer 21 may be made of, for example, a semiconductor material other than silicon (e.g., silicon carbide (SiC) or gallium nitride (GaN)). Also, an orientation flat may be formed in the outer peripheral region of the device wafer 21 instead of the notch 21d.

[0055] 9 is a flow chart schematically showing an example of a method for manufacturing chips from a wafer 11 used as a support wafer and a device wafer 21. In this method, first, edge trimming is performed on the device wafer 21 (S11).

[0056] 10(A) is a cross-sectional view schematically showing an edge-trimmed device wafer 21. The edge trimming of the device wafer 21 may be performed in the same manner as the edge trimming of the wafer 11 described above, or may be performed by any other known method.

[0057] Next, the device wafer 21 and the wafer (support wafer) 11 are bonded together to form a bonded wafer (S12). Fig. 10(B) is a cross-sectional view schematically showing an example of a bonded wafer. The bonded wafer 31 shown in Fig. 10(B) is formed by bonding the front surface 21a of the device wafer 21 to the front surface 11a of the wafer 11, for example, via an adhesive.

[0058] Next, the back surface 21b side of the device wafer 21 is ground until the chamfered outer peripheral region remaining on the back surface 21b side of the device wafer 21 is removed (S13). Fig. 10(C) is a cross-sectional view schematically showing the bonded wafer 31 after the back surface 21b side of the device wafer 21 has been ground. This grinding is performed using a known grinding apparatus.

[0059] Next, wet etching is performed on the back surface 21b side of the device wafer 21 (S14). Fig. 10(D) is a cross-sectional view that schematically shows how wet etching is performed on the back surface 21b side of the device wafer 21. This wet etching is performed, for example, by rotating the bonded wafer 31 in the circumferential direction of the bonded wafer 31 while dropping a known etching solution L onto the back surface 21b of the device wafer 21.

[0060] As a result, centrifugal force acts on the etching liquid L, causing the etching liquid L to spread so as to cover the back surface 21b of the device wafer 21. In addition, the etching liquid L that has spread outward from the back surface 21b of the device wafer 21 flows down from the wafer 11 via the step 13.

[0061] Next, the bonded wafer 31 is divided along the division lines of the device wafer 21 to manufacture chips (S15). This division is performed, for example, by a known cutting device.

[0062] In the above-described chip manufacturing method, the wafer 11 having the step 13 including the inclined surface 13c formed in the outer peripheral region is used as the support wafer. In this chip manufacturing method, when wet etching is performed on the back surface 21b side of the device wafer 21, the etching liquid L supplied to the back surface 21b of the device wafer 21 flows down from the wafer 11 via the step 13.

[0063] Here, the inclined surface 13c is inclined so that the distance from the front surface 11a of the wafer 11 in the thickness direction of the wafer 11 increases as the inclined surface 13c approaches the outer periphery of the wafer 11. Therefore, the etching liquid L supplied to the step 13 easily flows over the inclined surface 13c to the outside of the wafer 11. As a result, in the above-described chip manufacturing method, damage to the devices 23 formed on the front surface 21a side of the device wafer 21 by the etching liquid L can be suppressed.

[0064] The above-described content is one aspect of the present invention, and the content of the present invention is not limited to the above-described content. For example, in the present invention, edge trimming of the wafer 11 may be performed in a cutting device including a spindle extending in a direction parallel to the horizontal plane and a chuck table having a holding surface that is not parallel to the horizontal plane.

[0065] In other words, in the present invention, it is sufficient that the cutting blade attached to the tip of the spindle extending in a direction non-parallel to the holding surface of the chuck table can cut into the wafer 11 held on this holding surface, and there are no restrictions on the structure of the cutting device that performs this.

[0066] In the present invention, the inclined surface 13c may be formed without forming the upright surface 13a in the peripheral region of the wafer 11. That is, the present invention also includes a wafer processing method in which the first processing step (S2) is omitted from the wafer processing method shown in FIG.

[0067] 3 without the first processing step (S2) is preferable in that it reduces the number of steps required for edge trimming of the wafer 11. On the other hand, the wafer processing method shown in Fig. 3 is preferable in that it can form, in the outer peripheral region of the wafer 11, a step 13 including an upstanding surface 13a extending downward from the outer peripheral edge of the surface 11a along a direction perpendicular to the surface 11a of the wafer 11.

[0068] In addition, the structures and methods according to the above-described embodiments can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0069] 2:Cutting device 4: Table base 6: Chuck table (6a: frame) 8a: Cutting unit 8b: Cutting unit 10a: Spindle (first spindle) 10b: Spindle (second spindle) 11: Wafer (11a: front surface, 11b: back surface, 11c: side surface, 11d: notch) 12a: Cutting blade (first cutting blade) 12b: Cutting blade (second cutting blade) 13: Step (13a: standing surface, 13b: flat surface, 13c: sloped surface) 21: Device wafer (21a: front surface, 21b: back surface, 21c: side surface, 21d: notch) 23: Device 31: Bonded wafer

Claims

1. a holding step of holding a disk-shaped wafer on a holding surface of a chuck table that is rotatable about a rotation axis that is perpendicular to the holding surface and passes through the center of the holding surface; a first processing step in which, after the holding step, a first cutting blade is attached to the tip of a first spindle that can rotate around a rotation axis that is a straight line parallel to the holding surface, and the first spindle is rotated while the first cutting blade cuts into the outer peripheral region of the wafer, and the chuck table is rotated, thereby forming a flat surface at a constant distance from the holding surface in the outer peripheral region; a second processing step in which, after the first processing step, a second cutting blade is attached to the tip of a second spindle that can rotate around a rotation axis that is a straight line along a direction non-parallel to the holding surface, and the second spindle is rotated while the second cutting blade cuts into the outer peripheral region where the flat surface is formed, and the chuck table is rotated, thereby forming an inclined surface in the outer peripheral region that is inclined so that the distance from the holding surface becomes shorter as it approaches the outer peripheral edge of the wafer; A wafer processing method comprising:

2. 2. The wafer processing method according to claim 1, further comprising a wet etching step after the second processing step, in which an etching solution flows down from the wafer through the inclined surface.

3. 3. The wafer processing method according to claim 2, wherein in the wet etching step, the etching liquid that has spread outward from the surface of the wafer onto which the etching liquid has been dropped flows down from the wafer via the inclined surface.

4. the inclined surface is inclined so that the distance from the surface of the wafer in the thickness direction of the wafer increases as the inclined surface approaches the outer circumferential edge of the wafer; 4. The wafer processing method according to claim 2 or 3, wherein in the wet etching step, edge trimming of the front side of the device wafer, bonding the front side of the device wafer and the front side of the wafer to form a bonded wafer, and grinding the back side of the device wafer are carried out in that order, so that the back side of the device wafer from which the chamfered outer peripheral region has been removed is subjected to wet etching.

5. 5. A method for manufacturing chips, comprising the steps of: carrying out the wafer processing method according to claim 4; and then dividing the bonded wafer along the division lines of the device wafer to manufacture chips.

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