Manufacturing method of wafer

Abstract

To provide a manufacturing method of a wafer capable of providing a wafer not warped and having a uniform thickness, by appropriately setting a ratio of a grinding amount of one surface and the other surface.SOLUTION: A manufacturing method of a wafer W is for manufacturing the wafer W having a predetermined thickness by: a ratio setting step of setting a ratio of a grinding amount Δt1 of a first surface W1 and a grinding amount Δt2 of a second surface of an unfinished wafer W; a grinding amount calculation step of calculating the first grinding amount Δt1 of the first surface W1 and the second grinding amount Δt2 of the second surface W2 of the wafer W on the basis of the ratio set in the ratio setting step and a total grinding amount (t-t0) obtained by subtracting a preset finishing thickness t0 after grinding from a thickness t of the wafer W; a first grinding step of grinding the first surface W1 of the wafer W held in a chuck table by the first grinding amount Δt1; and a second grinding step of holding the first surface W1 ground in the first grinding step of the wafer W in the chuck table and grinding the second surface W2 of the wafer W by the second grinding amount Δt2.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a wafer manufacturing method for manufacturing wafers having a predetermined thickness by grinding sliced ​​wafers (unfinished wafers) sliced ​​from an ingot. [Background technology]

[0002] Sliced ​​wafers obtained by slicing an ingot have warpage and waviness. In order to remove this warpage and waviness, a processing method has been proposed in which a protective member such as an ultraviolet-curable resin is formed on one side of the sliced ​​wafer to flatten that side, the other side of the sliced ​​wafer is ground to flatten the other side while the flat surface of the protective member is held by the holding surface of a chuck table, the protective member is then peeled off and removed from the sliced ​​wafer, and one side of the sliced ​​wafer is ground to flatten the other side while the flat other side is held by the holding surface of a chuck table (see, for example, Patent Document 1).

[0003] However, when both sides of a sliced ​​wafer are ground by the above-mentioned processing method, if the grinding amount differs on both sides, the outer periphery of the sliced ​​wafer after grinding may become warped. Therefore, Patent Document 2 proposes grinding both sides of a sliced ​​wafer by the same amount. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-058925 [Patent Document 2] Japanese Patent Application Publication No. 2024-011097 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in reality, the roughness of one side of a sliced ​​wafer may differ from the roughness of the other side depending on the ingot. In such a case, if both sides of the sliced ​​wafer are ground by the same amount, the sliced ​​wafer will warp, making it impossible to produce wafers of uniform thickness.

[0006] Furthermore, when grinding silicon carbide (SiC) wafers, which have different crystal orientations on one side and the other side, the grinding conditions are different on one side and the other side, and the amount of grinding also differs on one side and the other side.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wafer manufacturing method that can obtain a wafer of uniform thickness without warping by appropriately setting the ratio of the amount of grinding between one surface and the other surface. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention is a wafer manufacturing method for manufacturing wafers of a predetermined thickness by grinding both sides, and is characterized in that wafers of a predetermined thickness are manufactured through the following steps: a ratio setting process for setting the ratio of the grinding amount of one side of an unfinished wafer to the grinding amount of the other side; a grinding amount calculation process for calculating a first grinding amount of one side of the unfinished wafer and a second grinding amount of the other side based on the total grinding amount obtained by subtracting a predetermined finishing thickness after grinding from the thickness of the unfinished wafer and the ratio set in the ratio setting process; a first grinding process for grinding one side of the unfinished wafer held on a chuck table by the first grinding amount; and a second grinding process for holding the one side of the unfinished wafer ground in the first grinding process on the chuck table and grinding the other side of the unfinished wafer by the second grinding amount. [Effects of the Invention]

[0009] According to the present invention, the grinding amount ratio is set to different values ​​between one side and the other side of the wafer, specifically, the grinding amount ratio is set according to the difference in roughness and crystal orientation on both sides due to the ingot, so that it is possible to produce wafers of uniform thickness without warping, regardless of the difference in roughness and crystal orientation on both sides. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a grinding apparatus for carrying out a wafer manufacturing method according to the present invention; [Figure 2] FIG. 2 is a perspective view of a peeling device provided in the grinding device shown in FIG. [Figure 3] 1 is a block diagram showing each step of a wafer manufacturing method according to the present invention. [Figure 4] 5(a) to 5(c) are longitudinal cross-sectional views showing the protective member forming steps in the order in which they are performed in the wafer manufacturing method of the present invention. [Figure 5] 4 is a vertical cross-sectional view showing a thickness measurement step in the wafer manufacturing method according to the present invention. FIG. [Figure 6] 10A and 10B are longitudinal cross-sectional views of an unfinished wafer illustrating a grinding amount calculation step in the wafer manufacturing method according to the present invention. [Figure 7] 3 is a vertical cross-sectional view showing a first grinding step in the wafer manufacturing method according to the present invention. FIG. [Figure 8] 4 is a vertical cross-sectional view showing a protective member removing step in the wafer manufacturing method according to the present invention. FIG. [Figure 9] 4 is a vertical cross-sectional view showing a second grinding step in the wafer manufacturing method according to the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0012] [Grinding equipment configuration] First, the overall configuration of a grinding apparatus for carrying out a wafer manufacturing method according to the present invention will be described with reference to Fig. 1. In the following description, the directions of the arrows shown in Fig. 1 are the X-axis (left-right direction), the Y-axis (front-back direction), and the Z-axis (up-down direction), respectively.

[0013] The grinding apparatus 1 shown in FIG. 1 grinds both sides of sliced ​​wafers (hereinafter referred to as "unfinished wafers" or simply "wafers") that have been sliced ​​from an ingot using a wire saw or laser device. Specifically, it grinds one side in a first grinding process and the other side in a second grinding process, as described below, and is equipped with the following components: That is, the grinding apparatus 1 is equipped with a transfer robot 10, a temporary placement stage 20, a chuck table 30, a grinding unit 40, a thickness measuring device 60, a spinner cleaning unit 70, a peeling device 80, a transfer mechanism 90, a control unit 100, and the like as its main components.

[0014] In this embodiment, the wafer W is made of a single-crystal silicon base material, but may be made of polycrystalline silicon. In addition to silicon (Si), the wafer W may be made of silicon carbide (SiC), glass, ceramics, sapphire (Al2O3), gallium arsenide (GaAs), or the like.

[0015] Next, the main components of the grinding device 1, namely the transport robot 10, temporary placement stage 20, chuck table 30, grinding unit 40, thickness measuring device 60, spinner cleaning unit 70, peeling device 80, transport mechanism 90 and control unit 100, will be described.

[0016] (Transport robot) Two cassette stages 2 and 3 that can be raised and lowered are arranged side by side in the left-right direction (X-axis direction) at the front (end in the -Y-axis direction) of the base 200 of the grinding apparatus 1, and a first cassette 4 and a second cassette 5 are placed on each of the cassette stages 2 and 3. A transfer robot 10 is disposed near the first cassette 4 and the second cassette 5. The first cassette 4 contains a plurality of wafers W before grinding, and the second cassette 5 contains a plurality of wafers W after grinding that have been cleaned by the spinner cleaning unit 70. The wafers W contained in the first cassette 4 have a protective member P (see FIG. 5) described below formed on the entire second surface W2 thereof.

[0017] Here, the transfer robot 10 is an articulated robot and includes a robot hand 11 and an articulated arm 12, and the robot hand 11 is capable of suction-holding the wafer W. The articulated arm 12 can raise and lower the robot hand 11 in the Z-axis direction, and can also rotate and move the robot hand 11 linearly within a horizontal plane (XY plane).

[0018] The transport robot 10 thus performs the function of holding and removing the wafer W stored in the first cassette 4 with the robot hand 11, transporting the removed wafer W to the temporary placement stage 20, and holding the wafer W after grinding that has been cleaned in the spinner cleaning unit 70 with the robot hand 11 and storing it in the second cassette 5.

[0019] (Temporary stage) A temporary placement stage 20 is disposed near the transfer robot 10 on the base 200, and the temporary placement stage 20 is provided with a disk-shaped temporary placement table 21, a thickness measuring device 22 that optically measures the thickness of the wafer W temporarily placed on the temporary placement table 21 in a non-contact manner, and a circumference detector 23 that detects the center position of the wafer W. The temporary placement table 21 can be rotated about a vertical central axis by a motor 24 that is a rotation drive source disposed below the table 21. The upper surface of the table 21 is a suction surface that is connected to a suction source 26 and that suction-holds the wafer W.

[0020] The thickness measuring device 22 irradiates the wafer W with measurement light and measures the thickness of the wafer W from the optical path difference between the light reflected by the upper surface and the lower surface of the wafer W. The outer periphery detector 23 captures images of, for example, three points on the outer periphery of the wafer W using a camera (not shown) while rotating the wafer W temporarily placed on the temporary placement table 21 at a low speed, and accurately detects the center position of the wafer W based on the captured images and geometrical calculation processing of the edge coordinates of the three points on the outer periphery of the wafer W. The thickness measuring device 22 and the outer periphery detector 23 are electrically connected to the control unit 100, and detection signals output from the thickness measuring device 22 and the outer periphery detector 23 are transmitted to the control unit 100.

[0021] (Chuck table) The chuck table 30 is a disk-shaped member that holds the unfinished wafer W, and its upper holding surface is selectively connected to a suction source 35 such as a vacuum pump shown in Fig. 7. In this embodiment, two chuck tables 30 are arranged at equal angular pitches (180° pitches) in the circumferential direction on a disk-shaped turntable 32, and each chuck table 30 has a rotation shaft 33 (see Fig. 7) extending vertically below it that is rotated at a predetermined speed around a vertical axis by a rotation mechanism (not shown), and revolves together with the turntable 32 around the central axis of the turntable 32.

[0022] (Grinding unit) 1, the grinding unit 40 includes a holder 41 that is open at the top, a spindle motor 42 that is a rotational drive source fixed to the holder 41 in a vertically installed state, a spindle 43 that is driven to rotate by the spindle motor 42, a disk-shaped mount 44 attached to the lower end of the spindle 43, and a grinding wheel 45 that is detachably attached to the underside of the mount 44. Here, the grinding wheel 45 is composed of a disk-shaped base 45a and a plurality of grinding stones 45b attached in an annular shape to the underside of the base 45a. The spindle motor 42 is electrically connected to a control unit 100, and its drive is controlled by the control unit 100.

[0023] The grinding unit 40 can be raised and lowered in the Z-axis direction (up and down direction) by a vertical movement mechanism 50, and this vertical movement mechanism 50 is disposed on the −Y-axis direction end face (front face) of a rectangular box-shaped column 201 that is erected vertically on the +Y-axis direction end face (rear end face) of the upper surface of the base 200, as shown in FIG. 1 . The vertical movement mechanism 50 raises and lowers a rectangular plate-shaped lift plate 51 attached to the back face of the holder 41, along the Z-axis direction, together with the holder 41 and the spindle motor 42, grinding wheel 45, etc. held by the holder 41, along a pair of left and right guide rails 52. The pair of left and right guide rails 52 are disposed perpendicular to the front face of the column 201 and parallel to each other.

[0024] A rotatable ball screw 53 is provided vertically along the Z-axis direction (up-down direction) between the pair of left and right guide rails 52, and the upper end of the ball screw 53 is connected to a motor 54, which serves as a drive source and can rotate forward and backward. The motor 54 is attached in a vertical position via a rectangular plate-shaped bracket 55 attached to the upper surface of the column 201. The lower end of the ball screw 53 is rotatably supported by the column 201, and a nut member (not shown) that protrudes horizontally from the back surface of the lifting plate 51 toward the rear (+Y-axis direction) is threadedly engaged with the ball screw 53.

[0025] Therefore, when the motor 54 is started to rotate the ball screw 53 forward or backward, the lifting plate 51, to which a nut member (not shown) that screws onto the ball screw 53 is attached, moves up and down along the Z-axis direction together with the grinding unit 40. The motor 54 is electrically connected to the control unit 100, and its driving is controlled by the control unit 100.

[0026] (Thickness measuring instrument) The thickness measuring device 60 is a height gauge that measures the thickness of the wafer W held on the chuck table 30 during grinding, and includes a first probe 61 that contacts the top surface of the wafer W and a second probe 62 that contacts the top surface of the chuck table 30. The first probe 61 measures the height of the top surface of the wafer W during grinding, and the thickness of the wafer W (including a protective member P, which will be described later, in this embodiment) is determined from the difference between the height of the top surface of the wafer W measured by the first probe 61 and the height of the top surface of the chuck table 30 measured by the second probe 62. The first probe 61 and the second probe 62 are electrically connected to the control unit 100, and their respective detection signals are sent to the control unit 100.

[0027] (Spinner cleaning unit) The spinner cleaning unit 70 is a unit that cleans the surface of the wafer W after grinding, and includes a spinner table 71 that holds and rotates the wafer W after grinding, and a cleaning nozzle 72 that sprays cleaning water toward the surface (ground surface) of the wafer W. Note that pure water is preferably used as the cleaning water.

[0028] (peeling device) The peeling device 80 is an apparatus that peels and removes the protective member P (see FIG. 5) formed on one side (second side) W2 of the wafer W in the protective member forming process described below, from the wafer W as shown in FIG. 8, and the details of its configuration are shown in FIG. 2.

[0029] 2 includes a holding means 81 that holds and transports a wafer W, and a peeling means 82 that peels off the protective material P from the wafer W, with the peeling means 82 being disposed below the holding means 81. The holding means 81 includes a disk-shaped transport pad 83 that suction-holds the wafer W, and the transport pad 83 is suspended from the tip of an arm 84. The transport pad 83 can be raised and lowered in the Z-axis direction by an elevating means 85, and can be moved horizontally in the Y-axis direction by a horizontal moving means 86. The elevating means 85 and the horizontal moving means 86 are configured using known ball screw mechanisms.

[0030] The peeling means 82 is composed of an outer periphery peeling means 82A that peels the outer periphery of the protective member P from the wafer W, and an entire peeling means 82B that peels the entire protective member P from the wafer W. Here, the outer periphery peeling means 82A is composed of a cylindrical limiting ring 82b arranged on the upper surface of a base 82a and seven gripping means 82c arranged around the limiting ring 82b. Furthermore, the entire peeling means 82B is composed of a gripping portion 82d that grips a portion of the outer periphery of the protective member P, a moving means 82e that horizontally moves the gripping portion 82d in the Y-axis direction, and a guide roller 82f that guides the peeling of the protective member P. Here, the moving means 82e is composed of a known ball screw mechanism.

[0031] A trash can 87 for collecting the protective material P peeled off from the wafer W is disposed below the peeling means 82, and a pair of guide bars 88 are erected obliquely on the top of this trash can 87 to guide the protective material P peeled off from the wafer W into the trash can 87.

[0032] (Transport mechanism) 1 is a mechanism for transporting a wafer W between the temporary placement table 21 of the temporary placement stage 20 and the chuck table 30, and between the chuck table 30 and the spinner cleaning unit 70, and is provided with a disk-shaped transport pad 91 that suction-holds the wafer W. The transport mechanism 90 is also provided with a rotating means (not shown) that rotates the transport pad 91 in a horizontal plane about a vertical rotation shaft 92, an elevating means 93 that raises and lowers the transport pad 91 in the Z-axis direction, and a horizontal moving means 94 that moves the transport pad 91 horizontally along the Y-axis direction.

[0033] (Control unit) The control unit 100 includes a CPU (Central Processing Unit) that performs arithmetic processing according to a control program, and storage units such as a ROM (Read Only Memory) and a RAM (Random Access Memory). In particular, in this embodiment, the control unit 100 sets a ratio between the grinding amount of one surface (first surface) of the wafer W and the grinding amount of the other surface (second surface), and calculates a total grinding amount obtained by subtracting a preset finishing thickness after grinding from the thickness of the unfinished wafer W, and a first grinding amount of one surface (first surface) of the unfinished wafer W and a second grinding amount of the other surface (second surface) based on the set ratio, which will be described in detail later.

[0034] [Function of grinding equipment] Next, the operation of the grinding apparatus 1 configured as above will be explained, while the method for manufacturing the wafer W according to the present invention will be explained.

[0035] The method for manufacturing a wafer W according to the present invention, which is carried out by the grinding apparatus 1 according to the present embodiment, is a method for manufacturing a wafer W having a predetermined thickness by grinding both surfaces of a sliced ​​wafer (unfinished wafer) cut from an ingot, and as shown in FIG. 1) Protective member forming process 2) Ratio setting process 3) Thickness measurement process 4) Grinding amount calculation process 5) First grinding process 6) Protective material removal process 7) Second grinding process By carrying out the above steps in this order, a wafer W having a uniform thickness and no warpage can be obtained. Each step will be explained below.

[0036] 1) Protective member forming process: The protective member forming step is a step of forming a protective member P (see FIG. 4(c)) on the second surface W2 of the wafer W through the steps shown in FIGS. 4(a) to 4(c). In this protective member forming step, as shown in FIG. 4(a), a thin, transparent sheet S having light-transmitting properties is placed on the upper surface of a case 6. Here, the case 6 is configured such that the upper surface of a cylindrical side wall 6A is covered with an extension table 7 made of light-transmitting, transparent glass, and the lower surface of the side wall 6A is covered with a bottom plate 6B, forming a space within which are housed a plurality of (eight in the illustrated example) UV lamps 8 that emit ultraviolet (UV) rays upward.

[0037] A disk-shaped holding table 13 is disposed above the case 6. This holding table 13 can be raised and lowered by a lifting mechanism 14, and a porous member 13A is incorporated in the center of its lower portion. The porous member 13A is connected to a suction source 16 by a pipe 15, and an on-off valve V1 is provided in the pipe 15. Therefore, when the on-off valve V1 is opened to connect the porous member 13A to the suction source 16, a negative pressure is generated in the porous member 13A, and the wafer W is attracted by this negative pressure and held on the underside of the holding table 13.

[0038] 4(a), liquid resin r is dropped from a nozzle (not shown) toward the center of the sheet S, and a small amount of liquid resin r is supplied from a nozzle (not shown) to the center of the second surface (the lower surface in FIG. 4(a)) W2 of the wafer W held by suction on the lower surface of the holding table 13. In this embodiment, an ultraviolet curable resin is used as the liquid resin r, but other liquid resins such as a thermosetting resin may also be used.

[0039] 4(b), the holding table 13 is lowered by the lifting mechanism 14, and the wafer W held by suction on the lower surface of the holding table 13 is pressed against the liquid resin r on the sheet S, spreading the liquid resin r to a uniform thickness. In this case, the liquid resin r that was dropped onto the center of the sheet S and left a depression in the center is replenished by a small amount of liquid resin r that is supplied to and adheres to the center of the wafer W.

[0040] As described above, when the liquid resin r is spread over the entire second surface W2 of the wafer W (the lower surface in Figure 4(b)), as shown in Figure 4(c), the on-off valve V1 is closed to cut off the connection between the porous member 13A and the suction source 16, releasing the suction holding force of the wafer W by the holding table 13, and the lifting mechanism 14 raises the holding table 13 away from the wafer W.

[0041] From the above state, as shown in Fig. 4(c), when the multiple UV lamps 8 inside the case 6 are turned on, ultraviolet (UV) rays emitted upward from each UV lamp 8 pass through the transparent extension table 7 and sheet S and are irradiated onto the liquid resin r, causing the liquid resin r to harden. As the liquid resin r hardens in this way, a protective member P is formed from the hardened resin R and sheet S on the second surface (the bottom surface in Fig. 4(c)) of the wafer W. Note that the surface (the bottom surface in Fig. 4(c)) of the protective member P made up of the hardened resin R and sheet S is a flat surface that fits along the flat upper surface of the extension table 7 of the case 6, because any warpage or undulations on the second surface W2 of the wafer W are transferred to the resin R.

[0042] In this embodiment, the wafers W having the protective members P formed on their second surfaces W2 in the protective member forming process are stored in the first cassette 4 shown in Fig. 1. That is, a plurality of wafers W having the protective members P formed thereon are stored by being placed on a plurality of shelves arranged vertically in the first cassette 4.

[0043] 2) Ratio setting process: The ratio setting process is a process of setting the ratio of the grinding amount of the first surface W1, which is one surface of the wafer W, to the second surface W2, which is the other surface. This ratio is set depending on the differences in roughness and crystal orientation between the first surface W1 and the second surface W2, but in this embodiment, as described below, the grinding amount of the first surface W1 (first grinding amount):grinding amount of the second surface W2 (second grinding amount) is set to 6:4.

[0044] In the ratio setting step, sliced ​​wafers are ground in advance on a trial basis at various ratios to find and set the optimum ratio. Alternatively, the ratio setting step may be performed by image processing a first image captured by a camera of one side of the wafer W and a second image captured by a camera of the other side of the wafer W. For example, the ratio can be set by comparing the first and second images after edge processing.

[0045] 3) Thickness measurement process: The thickness measurement process is a process of measuring the thickness of the wafer W excluding the protective member P. In this embodiment, when the wafer W stored in the first cassette 4 shown in FIG. 1 is removed by the transfer robot 10 and placed on the temporary placement table 21 of the temporary placement stage 20, the thickness t of the wafer W is optically measured in a non-contact manner by the thickness measuring device 22, as shown in FIG. 5. That is, when a measuring light is emitted toward the wafer W from a light-emitting unit (not shown) of the thickness measuring device 22, the measuring light is reflected by the front surface (first surface W1) of the wafer W and the protective member P, and each reflected light is received by a light-receiving unit (not shown) of the thickness measuring device 22. The thickness measuring device 22 then measures the thickness t of the wafer W based on the optical path difference of these reflected lights. Specifically, a signal (voltage signal) of the reflected light received by the light-receiving unit of the thickness measuring device 22 is transmitted to the control unit 100, and the control unit 100 calculates the thickness t of the wafer W based on this signal.

[0046] The upper surface of the temporary placement table 21 forms a holding surface, which is connected to a suction source 26 such as a vacuum pump via a suction path 21a formed at the axis of the temporary placement table 21 and a pipe 25. When an opening / closing valve V2 provided on the pipe 25 is opened to connect the holding surface to the suction source 26, a negative pressure is generated on the holding surface, and the wafer W is attracted by this negative pressure and held on the holding surface of the temporary placement table 21 by suction.

[0047] 4) Grinding amount calculation process: The grinding amount calculation step calculates the first grinding amount of the first surface W1 of the wafer W and the second grinding amount of the other surface W2 of the wafer W based on the ratio set in the ratio setting step. In the ratio setting step, the ratio is set according to the differences in roughness and crystal orientation between the first surface W1 and the second surface W2, as described above. In this embodiment, the grinding amount of the first surface W1 (first grinding amount):the grinding amount of the second surface W2 (second grinding amount) is set to 6:4. Specifically, as shown in FIG. 6, when the thickness t of the wafer W measured in the thickness measurement step is t = 795 μm, the first grinding amount Δt1 is set to Δt1 = 12 μm, and the second grinding amount Δt2 is set to Δt2 = 8 μm. Therefore, the finished thickness t0 of the wafer W is set to t0 = 795 - (12 + 8) = 775 μm. That is, the total grinding amount (t-t0) obtained by subtracting the finishing thickness t0 from the measured thickness t of the wafer W is divided at a ratio of 6:4 to calculate the first grinding amount Δt1 and the second grinding amount Δt2.

[0048] 5) First grinding process: The first grinding process is a process of grinding the first surface W1 of the wafer W (the surface on which the protective member P is not formed). In this first grinding process, the thickness of the wafer W held on the temporary placement table 21 of the temporary placement stage 20 shown in FIG. 1 is optically measured non-contact by a thickness measuring device 22, and when the center of the wafer W is detected by an outer periphery detector 23, the wafer W is suction-held by a transport pad 91 of a transport mechanism 90 and transported to the chuck table 30.

[0049] 7, a porous, disk-shaped porous member 30A is mounted in the upper center of the chuck table 30, and this porous member 30A is connected to a suction source 35 such as a vacuum pump via a suction passage 33a formed in the center of the chuck table 30 and a rotary shaft 33 that rotatably supports the chuck table 30, and via a pipe 34. An on-off valve V3 is provided in the pipe 34, and when the on-off valve V3 is opened to connect the porous member 30A to the suction source 35 via the suction passage 33a and the pipe 34, a negative pressure is generated in the porous member 30A, and the wafer W is attracted by this negative pressure and held by suction on the holding surface of the chuck table 30 with the protective member P facing downward.

[0050] As described above, when the wafer W transported to the chuck table 30 is held on the holding surface of the chuck table 30 with the protective member P facing downward, the turntable 32 shown in FIG. 1 rotates, and the chuck table 30, together with the wafer W held thereon, moves below the grinding wheel 45 of the grinding unit 40.

[0051] Then, the chuck table 30 and the wafer W held thereon are rotated at a predetermined speed around a vertical central axis, and the spindle motor 42 of the grinding unit 40 is started to rotate the spindle 43 and the grinding wheel 45 at a predetermined speed. At this time, the grinding wheel 45 is rotated at a predetermined speed by the spindle motor 42 in a state where it is positioned so that the circumscribed circle of the grinding stone 45b passes through the center of the wafer W.

[0052] From the above state, when the grinding wheel 45 is lowered by a predetermined amount by the vertical movement mechanism 50 shown in FIG. 1, the first surface W1 (upper surface in FIG. 7) of the wafer W, on which the protective member P is not formed, is ground by the grinding wheel 45b by a first grinding amount Δt1 (=12 μm). As a result, any warpage or waviness remaining on the first surface W1 of the wafer W is removed, and the first surface W1 of the wafer W is made flat. During grinding of the wafer W, grinding water (pure water) from the grinding water supply source 110 shown in FIG. 1 is supplied to the contact point (processing point) between the wafer W and the grinding wheel 45b through a plurality of injection holes 45a1 and injection nozzles 46 formed in the base 45a of the grinding wheel 45. The grinding water removes frictional heat generated at the processing point, suppressing a temperature rise at the processing point, and also washes away grinding debris generated during grinding.

[0053] In the first grinding process, the difference h1 between the top surface height of the wafer W measured by the first probe 61 of the thickness measuring device 60 and the top surface height of the chuck table 30 measured by the second probe 62, and the difference h1' between the top surface height of the wafer W measured by the first probe 61 and the top surface height of the chuck table 30 measured by the second probe 62 after the first surface W1 has been ground by the first grinding amount Δt1 (h1-h1') are calculated as the first grinding amount Δt1 (Δt1=h1-h1').

[0054] Thus, the wafer W, whose first surface (surface on which the protective member P is not formed) P1 has been ground flat in the first grinding step, is held by suction on the transfer pad 91 of the transfer mechanism 90 and transported to the spinner cleaning unit 70. The wafer W transported to the spinner cleaning unit 70 is then held by suction on the upper surface of the spinner table 71 with the second surface W2 on which the protective member P is formed facing downward, and is washed with cleaning water sprayed from the cleaning nozzle 72 while rotating together with the spinner table 71 at a predetermined speed, and grinding debris generated by the first grinding and adhering to the first surface W1 of the wafer W is washed away and removed by the grinding water.

[0055] 6) Protective material removal process: In the protective member removal process, the first surface W1 of the wafer W (the surface on which the protective member P is not formed) is ground to a flat surface in the previous first grinding process, and the protective member P formed on the second surface W2 of the wafer W cleaned by the spinner cleaning unit 70 is peeled off and removed from the wafer W.

[0056] In this protective member removal step, the wafer W held on the spinner table 71 of the spinner cleaning unit 70 is suction-held with the protective member P facing downward by a transfer pad 83 provided on a holding means 81 of a peeling device 80 shown in Fig. 2. Then, in the peeling device 80, the outer periphery of the protective member P formed on the second surface W2 of the wafer W is peeled off by an outer periphery peeling means 82A (see Fig. 2) of the peeling means 82, leaving a portion, and the portion remaining on the outer periphery is peeled off and removed from the wafer W by a total peeling means 82B (see Fig. 2) of the peeling means 82.

[0057] That is, when a portion of the protective material P remaining on the outer periphery is gripped by gripping portion 82d of total peeling means 82B and gripping portion 82d is moved in the direction of the arrow in Fig. 8 by moving means 82e, the protective material P is peeled off from the second surface W2 of the wafer W starting from guide roller 82f, and the peeled protective material P falls and is introduced into a waste box 87 along a pair of guide bars 88 and is collected in the waste box 87. Note that warping and undulation still remain on the second surface W2 of the wafer W from which the protective material P has been peeled off.

[0058] As described above, the wafer W from which the protective member P has been peeled off and removed from the second surface W2 is transferred from the transfer pad 83 of the separation device 80 to the spinner table 71 of the spinner cleaning unit 70, and, if necessary, is cleaned by the spinner cleaning unit 70. The wafer W is then held by the robot hand 11 of the transfer robot 10 shown in FIG. 1 and transferred upside down to the temporary placement table 21 of the temporary placement stage 20 with the second surface W2 facing up.

[0059] In the temporary placement stage 20, when the center of the wafer W held on the temporary placement table 21 is detected by the outer periphery detector 23, the wafer W is suction-held by the transfer pad 91 of the transfer mechanism 90 and transferred to the chuck table 30. Then, the wafer W is suction-held on the holding surface of the chuck table 30, and the chuck table 30 and the wafer W held thereon are moved to a position below the grinding wheel 45 of the grinding unit 40 as the turntable 32 makes a half rotation, and the second surface W2 of the wafer W (the surface from which the protective member P has been removed) is ground in the next second grinding step.

[0060] 7) Second grinding process: The second grinding step is a step of grinding the second surface W2 (the surface on which the protective member P was formed) of the wafer W from which the protective member P has been removed in the preceding protective member removal step. In this second grinding step, as shown in FIG. 9, the wafer W is suction-held on the holding surface of the chuck table 30 with the first surface W1 (the flat surface ground in the first grinding step) facing downward. The wafer W held on the chuck table 30 in this manner is held on the holding surface of the chuck table 30 with the flat first surface W1 ground in the first grinding step in close contact with the holding surface of the chuck table 30 (the upper surface of the porous member 30A). Note that warpage and waviness remain on the second surface W2 of the wafer W (the upper surface in FIG. 9 from which the protective member P has been removed).

[0061] 9, in the second grinding step, the second surface W2 (upper surface in FIG. 9) of the wafer W is ground by the grinding wheel 45 in the same manner as in the first grinding step. That is, the chuck table 30 is rotated together with the wafer W at a predetermined speed around the rotation axis by a rotation mechanism (not shown), and the grinding wheel 45 is positioned so that the circumscribed circle of the grinding stone 45b passes through the center of the wafer W, and the grinding wheel 45 is rotated at a predetermined speed around the rotation axis by the spindle motor 42.

[0062] From the above state, when the grinding wheel 45 is lowered by the vertical movement mechanism 50 by a predetermined amount of grinding, the second surface W2 (upper surface in FIG. 9 ) of the wafer W, on which the protective member P was formed, is ground by the grinding wheel 45b by a second grinding amount Δt2 (=8 μm). As a result, any warpage or waviness remaining on the second surface W2 of the wafer W is removed, and the second surface W2 of the wafer W is made flat. During grinding of the wafer W, grinding water (pure water) from the grinding water supply source 110 shown in FIG. 1 is supplied to the contact point (processing point) between the wafer W and the grinding wheel 45b through multiple injection holes 45a1 and injection nozzles 46 formed on the base 45a of the grinding wheel 45. The grinding water removes frictional heat generated at the processing point, suppressing a temperature rise at the processing point, and also washes away grinding debris generated during grinding.

[0063] In the second grinding process, the difference h2 between the top surface height of the wafer W measured by the first probe 61 of the thickness measuring device 60 and the top surface height of the chuck table 30 measured by the second probe 62 is calculated as the second grinding amount Δt2 (Δt2=h2-h2'), and the difference h2' between the top surface height of the wafer W measured by the first probe 61 and the top surface height of the chuck table 30 measured by the second probe 62 after the second surface W2 has been ground by the second grinding amount Δt2.

[0064] As described above, in the first grinding step, the first surface W1 (the surface on which the protective member P is not formed) is ground by a predetermined first grinding amount Δt1 (=12 μm), and in the second grinding step, the second surface W2 (the surface on which the protective member P was formed) is ground by a predetermined second grinding amount Δt2 (=8 μm). This produces a wafer W with a predetermined finished thickness t0 (=775 μm) in which both surfaces W1 and W2 are ground flat. In this embodiment, the grinding amount is set to different values ​​for the first surface W1 and the second surface W2 of the wafer W; specifically, the ratio of the first grinding amount Δt1 to the second grinding amount Δt2 is set to 6:4 in accordance with the difference in roughness and crystal orientation of the first surface W1 and the second surface W2 due to the ingot. This results in the effect that wafers W with a uniform thickness t0 = 775 μm without warping can be manufactured even if the difference in roughness and crystal orientation of the first surface W1 and the second surface W2 is different.

[0065] Thus, the wafer W whose second surface (the surface on which the protective member P was formed) W2 has been ground flat in the second grinding step is held by suction on the transfer pad 91 of the transfer mechanism 90 and transferred to the spinner cleaning unit 70. The wafer W transferred to the spinner cleaning unit 70 is then held by suction on the upper surface of the spinner table 71 with its first surface W1 facing downward, and is washed with cleaning water sprayed from the cleaning nozzle 72 while rotating together with the spinner table 71 at a predetermined speed, and grinding debris generated in the second grinding step and adhering to the second surface W2 of the wafer W is washed away and removed by the cleaning water.

[0066] As described above, the wafer W whose second surface W2 has been cleaned by the spinner cleaning unit 70 is suction-held by the robot hand 11 of the transport robot 10 and transported to the second cassette 5, and is then stored in the second cassette 5, thereby completing the series of grinding processes on the wafer W and producing a wafer W with flat surfaces, no warping, and a uniform thickness.

[0067] In the above embodiment, an example has been described in which the ratio of the first grinding amount Δt1 to the second grinding amount Δt2 of the wafer W is set to 6:4, but this ratio is merely an example and is not limited to 6:4, and can be set to an optimal value depending on the roughness and crystal orientation of both surfaces of the wafer W.

[0068] Furthermore, the present invention is not limited to the application of the above-described embodiments, and it goes without saying that various modifications are possible within the scope of the claims and the technical ideas described in the specification and drawings. [Explanation of symbols]

[0069] 1: grinding device, 2, 3: cassette stage, 4: first cassette, 5: second cassette, 6: Case, 6A: Side wall of the case, 6B: Bottom plate of the case, 7: Extension table, 8: UV lamp, 10: Transport robot, 11: Robot hand, 12: Articulated arm, 13: holding table, 13A: porous member, 14: lifting mechanism, 15: piping, 16: suction source, 20: temporary placement stage, 21: temporary placement table, 21a: suction path, 22: Thickness measuring device, 23: Outer circumference detector, 24: Motor, 30: Chuck table, 32: turntable, 33: rotating shaft, 33a: suction path, 34: piping, 35: suction source, 41: holder, 42: spindle motor, 43: spindle, 44: mount, 45: grinding wheel, 45a: base, 45a1: injection hole, 46: injection nozzle, 50: vertical movement mechanism, 51: lifting plate, 52: guide rail, 53: ball screw, 54: Motor, 55: Bracket, 60: Thickness measuring device, 61: First probe, 62: second probe, 70: spinner cleaning unit, 71: spinner table, 72: cleaning nozzle, 80: peeling device, 81: holding means, 82: peeling means, 82A: outer peripheral peeling means, 82B: whole peeling means, 82a: base, 82b: limiting ring, 82c: Gripping means, 82d: Gripping section, 82e: Moving means, 82f: Guide roller, 83: Transport pad, 84: Arm, 85: Lifting means, 86: Horizontal movement means, 87: Trash can, 88: guide bar, 90: transport mechanism, 91: transport pad, 92: swivel shaft, 83: lifting means, 84: horizontal movement means, 100: control unit, 110: grinding water supply source, 200: base, 201: column, P: protective member, r: liquid resin, R: hardened resin, S: sheet, t: wafer thickness, t0: finishing thickness, Δt1: first grinding amount, Δt2: second grinding amount, V1 to V3: on-off valves, W: wafer, W1: first surface (one side) of wafer, W2: Second side of the wafer (other side)

Claims

1. A wafer manufacturing method for manufacturing a wafer having a predetermined thickness by grinding both surfaces, a ratio setting step of setting a ratio between the amount of grinding on one side of the unfinished wafer and the amount of grinding on the other side of the unfinished wafer; a grinding amount calculation step of calculating a first grinding amount on one side of the unfinished wafer and a second grinding amount on the other side of the unfinished wafer based on a total grinding amount obtained by subtracting a preset finishing thickness after grinding from the thickness of the unfinished wafer and the ratio set in the ratio setting step; a first grinding step of grinding one surface of the unfinished wafer held on a chuck table by the first grinding amount; a second grinding step of holding the one surface of the unfinished wafer ground in the first grinding step on the chuck table and grinding the other surface of the unfinished wafer by the second grinding amount; A wafer manufacturing method comprising the steps of: manufacturing a wafer of a predetermined thickness through the steps of:

2. 2. The method for manufacturing a wafer according to claim 1, further comprising the step of measuring the thickness of the unfinished wafer by a thickness measuring device before the step of calculating the amount of grinding.

3. a protective member forming step of forming a protective member by spreading and hardening a liquid resin over the entire other surface of the unfinished wafer at least before the first grinding step; a protective member removing step of removing the protective member is performed after the first grinding step and before the second grinding step; 2. The method for manufacturing a wafer according to claim 1, wherein in the first grinding step, one surface of the unfinished wafer is ground while the unfinished wafer is held on the chuck table via the protective member.

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