Grinding apparatus and wafer grinding method

Abstract

To minimize in-plane thickness differences and grind the wafer to a uniform thickness across its entire surface. [Solution] The method for grinding a wafer W includes a holding step of holding the wafer W on a chuck table 10, and a grinding step of grinding the wafer W to a predetermined finish thickness while measuring the temperature of multiple locations on the wafer W with a temperature measuring device 50 while grinding the wafer W with a grinding wheel 25b, and, based on the multiple temperature data measured by the temperature measuring device 50, spraying hot water from the spray nozzle 60 to locations where the temperature is lower than a set temperature range before spraying hot water or cold water from the spray nozzle 60, and spraying cold water from the spray nozzle 60 to locations where the temperature is higher than the set temperature range. Here, the grinding step includes a temperature measurement step, a calculation step, a spray nozzle positioning step, and a chuck table deformation step.

Description

[Technical Field]

[0001] The present invention relates to a grinding apparatus and a wafer grinding method for grinding a wafer held on the holding surface of a chuck table using a grinding wheel. [Background technology]

[0002] In a grinding apparatus for grinding wafers, a chuck table is used that has a conical holding surface that is slightly inclined downward along the outer circumference with the center as the apex. The wafer is held on the holding surface of this chuck table, and the lower surface of an annular grinding wheel is brought into contact with the radial portion of the wafer to grind the entire back surface of the wafer (see, for example, Patent Documents 1 to 3). In such a grinding method, the wafer is ground to have a uniform in-plane thickness by adjusting the inclination of the chuck table so that the holding surface of the chuck table is parallel to the grinding surface of the grinding wheel. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-264913 [Patent Document 2] Japanese Patent Publication No. 2013-119123 [Patent Document 3] Japanese Patent Publication No. 2014-226749 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, simply adjusting the inclination between the rotation axis of the chuck table and the rotation axis of the grinding wheel is insufficient to meet the recent requirement of keeping the in-plane thickness difference of wafers below 0.1 μm.

[0005] Furthermore, in a grinding method in which a bonded wafer, formed by bonding a support wafer and a device wafer, is held on a chuck table with the support wafer facing downwards, and the back surface (top surface) of the device wafer of the bonded wafer is ground, the surface of the device wafer may have ring-shaped irregularities due to the adhesive used to bond the surface of the device wafer (the bottom surface which is the bonding surface to the support wafer) to the support wafer. In such cases, there is a problem that the thickness of the ground device wafer will not be uniform.

[0006] The present invention has been made in view of the above circumstances, and its purpose is to provide a grinding apparatus and a wafer grinding method that can grind a wafer to a uniform thickness over its entire surface while minimizing the difference in in-plane thickness. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a grinding machine comprising: a chuck table having a conical holding surface with its apex at its center connected to a suction source to hold a wafer with the holding surface; a table rotation mechanism for rotating the chuck table around a table rotation axis passing through the apex of the porous member; a grinding unit for rotating an annular grinding wheel around a grinding wheel rotation axis passing through its center to grind the upper surface of the wafer with the lower surface of the grinding wheel; a lifting mechanism for raising and lowering the grinding unit; and a grinding water supply means for supplying grinding water to the point where the lower surface of the grinding wheel contacts the upper surface of the wafer. The device is characterized by comprising: a spray nozzle that sprays cold water or hot water from above the holding surface onto at least a portion of the radial portion of the holding surface; a temperature measuring device that measures the temperature of multiple locations on the radial portion of the wafer held on the holding surface; and a control unit that, based on the multiple temperature data measured by the temperature measuring device, sprays hot water from the spray nozzle at locations where the temperature is lower than a set temperature range before spraying hot or cold water from the spray nozzle, and sprays cold water from the spray nozzle at locations where the temperature is higher than the set temperature range, thereby expanding or contracting the chuck table to change the height of the holding surface.

[0008] The present invention also relates to a wafer grinding method implemented using the above grinding device, including: a holding step of holding the wafer on the chuck table; and a grinding step of grinding the wafer with the grinding wheel while measuring the temperatures of multiple locations on the wafer with a temperature measuring device, and among the multiple temperature data measured by the temperature measuring device, injecting warm water from the injection nozzle at locations lower than a preset temperature range before injecting warm water or cold water from the injection nozzle, and injecting cold water from the injection nozzle at locations higher than the preset temperature range, while grinding the wafer to a preset finish thickness.

Advantages of the Invention

[0009] According to the wafer grinding method of the present invention implemented using the grinding device of the present invention, while measuring the temperatures of multiple locations on the wafer with a temperature measuring device while grinding the wafer with a grinding wheel, among the multiple temperature data measured by the temperature measuring device, warm water is injected onto the wafer from the injection nozzle at locations where the temperature is lower than a preset temperature range, and a part of the holding surface of the chuck table corresponding to the part where warm water is injected is heated and expanded through the wafer, and cold water is injected from the injection nozzle at locations where the temperature is higher than a predetermined temperature range, and a part of the holding surface of the chuck table corresponding to the part where cold water is injected is cooled and contracted through the wafer. Therefore, the height of the holding surface is corrected. For this reason, the wafer held and ground on the holding surface of the chuck table in the grinding process has a small in-plane thickness difference and is uniformly ground to a preset finish thickness over the entire surface.

Brief Description of the Drawings

[0010] [Figure 1] It is a perspective view showing a part of the grinding device according to the present invention broken away. [Figure 2] It is a block diagram showing each step of the wafer grinding method according to the present invention. [Figure 3] (a) is a side cross-sectional view of the main part of the grinding device showing the grinding step and the temperature measurement step in the wafer grinding method according to the present invention, and (b) is a diagram showing the temperature distribution in the radial direction of the wafer. [Figure 4] This is a side cross-sectional view of the main part of a grinding apparatus showing the injection nozzle positioning step and the chuck table deformation step in the wafer grinding method according to the invention. [Figure 5] This flowchart shows the procedure for the wafer grinding method according to the present invention. [Figure 6] This figure is similar to Figure 4, which shows another embodiment of the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0012] [Configuration of the grinding machine] First, the configuration of the grinding apparatus according to the present invention will be described. In the following description, the arrow directions shown in Figure 1 will be the X-axis direction (left-right direction), the Y-axis direction (front-back direction), and the Z-axis direction (up-down direction), respectively.

[0013] The grinding apparatus 1 shown in Figure 1 is used to grind a thin, disc-shaped wafer W (including a first wafer, a second wafer, and a bonded wafer), which is the workpiece, and comprises the following components.

[0014] In other words, the grinding apparatus 1 includes a chuck table 10 that holds and rotates the wafer W, a table rotation mechanism 12 (see Figure 3) that rotates the chuck table 10, a grinding unit 20 that grinds the wafer W held on the chuck table 10, a lifting mechanism 30 that moves the grinding unit 20 up and down in a direction perpendicular to the holding surface 10a (see Figure 3) of the chuck table 10 (in the Z-axis direction), a grinding water supply means 40 that supplies grinding water toward the inside of the annular grinding wheel 25b (see Figure 3) during the grinding of the wafer W, and the holding surface 1 of the chuck table 10 The main components include a temperature measuring instrument 50 that measures the temperature of multiple locations on the wafer W held on the chuck table 10a, a spray nozzle 60 that sprays cold or hot water towards at least a portion of the radial portion of the wafer W held on the holding surface 10a of the chuck table 10, and a control unit 70 that sprays hot or cold water from the spray nozzle 60 onto the wafer W based on multiple temperature data of the wafer W measured by the temperature measuring instrument 50 to expand or contract the chuck table 10 and partially (ring-shaped) change the height of the holding surface 10a of the chuck table 10.

[0015] Here, the wafer W is made of, for example, a single-crystal silicon matrix, and in the state shown in Figure 1, a plurality of devices (not shown) are formed on the downward-facing surface, and these devices are protected by a protective tape (not shown) attached to the surface of the wafer W. The wafer W is held in place by suction on its surface (bottom surface in Figure 1) to the holding surface 10a of the chuck table 10 via the protective tape (not shown), and its back surface (top surface in Figure 1) is ground by the grinding wheel 25b of the grinding unit 20 while receiving grinding water from the grinding water supply means 40.

[0016] Next, the configurations of the main components of the grinding apparatus 1, namely the chuck table 10, the table rotation mechanism 12, the grinding unit 20, the lifting mechanism 30, the grinding water supply means 40, the temperature measuring instrument 50, the spray nozzle 60, and the control unit 70, will be described.

[0017] (Chuck table and table rotation mechanism) The chuck table 10 is a disc-shaped member, and as shown in Figure 3, a disc-shaped porous member 11 is incorporated in its center, with the upper surface of this porous member 11 forming a holding surface 10a for holding the wafer W. The porous member 11 is made of porous ceramic or the like and is selectively connected to a suction source (not shown), such as a vacuum pump.

[0018] Here, the upper surface of the chuck table 10 (porous member 11) is configured as a conical holding surface 10a, which slopes downward toward the outer circumference with the center as the apex, as shown in Figure 3. The surface of the wafer W (the bottom surface in Figure 3) is held on this holding surface 10a with a protective tape (not shown) facing downwards. Note that in Figure 3, the slope of the conical holding surface 10a of the chuck table 10 is exaggerated, but in reality, this slope is so slight that it cannot be seen with the naked eye.

[0019] The chuck table 10 is rotated counterclockwise in the direction of the arrow by the table rotation mechanism 12 shown in Figure 3, with respect to the table rotation axis CL1 which passes through the apex of the holding surface 10a. That is, the chuck table 10 has a table rotation axis (not shown) that extends vertically downward from its center, and this table rotation axis is rotated at a predetermined speed around the table rotation axis CL1 by the table rotation mechanism 12. Here, the table rotation mechanism 12 is composed of a servo motor (not shown) which is the drive source, and an encoder (not shown) which detects the rotation speed, rotation direction, rotation angle, etc. of the servo motor.

[0020] As shown in Figure 1, the grinding apparatus 1 according to this embodiment is equipped with a rectangular box-shaped base 100 that is long in the Y-axis direction (front-to-back direction), and a chuck table 10 faces a rectangular opening 100a that is long in the Y-axis direction and opens into the base 100. The area around the chuck table 10 in the opening 100a is covered by a rectangular plate-shaped cover 2, and the front and rear portions of the cover 2 in the opening 100a (-Y direction and +Y direction) are covered by bellows-shaped expandable covers 3 and 4 that move and expand together with the cover 2. Therefore, no matter what position the chuck table 10 is at on the Y-axis, the opening 100a is always closed by the cover 2 and the expandable covers 3 and 4, preventing foreign matter from entering the base 100 from the opening 100a.

[0021] Furthermore, the tilt of the chuck table 10 can be adjusted by a tilt adjustment mechanism (not shown). That is, the table rotation axis CL1 of the chuck table 10 can be tilted by an angle α shown with respect to the vertical line, thereby adjusting the tilt of the holding surface 10a of the chuck table 10 with respect to the horizontal plane.

[0022] Furthermore, the chuck table 10 is movable horizontally (in the Y-axis direction) by a horizontal movement mechanism 13 (see Figure 3) housed within the base 100. Since the horizontal movement mechanism 13 is composed of a known ball screw mechanism, a detailed explanation of it will be omitted.

[0023] (Grinding unit) As shown in Figure 1, the grinding unit 20 includes a spindle motor 22, which is a rotational drive source housed in a holder 21; a vertical spindle 23 that is rotationally driven by the spindle motor 22; a disc-shaped mount 24 attached to the lower end of the spindle 23; and a grinding wheel 25 that is detachably mounted on the lower surface of the mount 24. Here, the grinding wheel 25 is composed of a disc-shaped base 25a and a plurality of grinding wheels 25b, which are processing tools that are mounted in an annular shape on the lower surface of the base 25a. Here, the grinding wheels 25b are rectangular block-shaped processing tools for grinding wafers W, and their lower surfaces constitute a grinding surface that contacts the upper surface (workpiece surface) of the wafer W.

[0024] The spindle 23 of the grinding unit 20 rotates together with the mount 24 and the grinding wheel 25 around the grinding wheel rotation axis CL2. However, in the grinding apparatus 1 according to this embodiment, the grinding wheel rotation axis CL2 is positioned vertically and cannot be tilted. In contrast, the table rotation axis CL1 of the chuck table 10 can be tilted by a predetermined angle α relative to the vertical grinding wheel rotation axis CL2 by a tilt adjustment mechanism (not shown), for example as shown in Figure 3. This tilts the holding surface 10a of the chuck table 10 by an angle α with respect to the horizontal plane.

[0025] (Lifting mechanism) The lifting mechanism 30 is a mechanism that moves the grinding unit 20 closer to and further away from the holding surface 10a of the chuck table 10. As shown in Figure 1, it is positioned on the -Y-axis end face (front) of a rectangular box-shaped column 101 that is erected vertically on the +Y-axis end (rear end) of the upper surface of the base 100. This lifting mechanism 30 raises and lowers a rectangular plate-shaped lifting plate 31, which is attached to the back of the holder 21 of the grinding unit 20, along a pair of left and right guide rails 32 in the Z-axis direction, together with the holder 21 and the spindle 23 and grinding wheel 25 held in the holder 21. Here, the pair of left and right guide rails 32 are arranged perpendicularly and parallel to each other on the front surface of the column 101.

[0026] Furthermore, a rotatable ball screw 33 is erected vertically along the Z-axis direction (up and down direction) between a pair of left and right guide rails 32, and the upper end of the ball screw 33 is connected to a reversible servo motor 34, which is the drive source. Here, the servo motor 34 is mounted vertically on the column 101 via a rectangular plate-shaped bracket 35 attached to the upper surface of the column 101. The lower end of the ball screw 33 is rotatably supported on the column 101, and a nut member (not shown) that protrudes horizontally toward the rear (+Y-axis direction) from the back of the lifting plate 31 is screwed onto the ball screw 33. The servo motor 34 is equipped with an encoder 36 that detects the rotation direction and rotation speed of the servo motor 34, and the detection signal from this encoder 36 is transmitted to the control unit 70, and the control unit that receives this detection signal drives and controls the servo motor 34 based on the detection signal.

[0027] Therefore, by starting the servo motor 34 and rotating the ball screw 33 in the forward and reverse directions, the lifting plate 31, to which a nut member (not shown) that screws onto the ball screw 33 is attached, moves up and down along the pair of guide rails 32 together with the grinding unit 20, causing the grinding unit 20 to move up and down and setting the amount of grinding (grinding allowance) of the grinding wheel 26b on the wafer W.

[0028] (Means for supplying grinding water) The grinding water supply means 40 supplies grinding water, such as pure water, to the grinding region, which is the contact area between the grinding wheel 25b and the wafer W during grinding, and ejects the grinding water from the inside of the annular grinding wheel 25b that rotates during grinding. More specifically, as shown in Figure 1, the grinding water supply means 40 is equipped with a grinding water supply source 41 such as a water pump, and a pipe 42 extending from this grinding water supply source 41 is connected to a supply passage (not shown) formed perpendicular to the axis of the spindle motor 22. The supply passage (not shown) formed in the spindle motor 22 is connected to a supply passage 23a formed perpendicular to the axis of the spindle 23 shown in Figure 3, and the supply passage 23a is connected to a plurality of supply passages 24a that extend radially outward from the center of the mount 24. In addition, a plurality of nozzles 25c are formed on the base 25a of the grinding wheel 25, extending vertically downward from each supply passage 24a formed in the mount 24.

[0029] Therefore, the grinding water supplied from the grinding water supply source 41 to the spindle motor 22 via the piping 42 is sprayed from multiple nozzles 25c formed on the base 25a of the grinding wheel 25 toward the upper surface of the wafer W through a supply passage 23a formed in the spindle 23 and multiple supply passages 24a formed in the mount 24 as shown in Figure 3.

[0030] (temperature measuring device) The temperature measuring device 50 measures the temperature at multiple points on the surface of a wafer W held on the holding surface 10a of the chuck table 10 while the wafer W is being ground with a grinding wheel 25b. As shown in Figure 1, it includes a temperature sensor 53 attached to the tip of an arm 52 that extends horizontally from the upper end of a support shaft 51 that is rotatably erected vertically near the chuck table 10 on the base 100. A non-contact thermometer such as a radiation thermometer (infrared thermometer) is used as the temperature sensor 53. Note that the temperature sensor 53 may also be a thermal camera.

[0031] Here, the support shaft 51 incorporates a motor 54, which is a drive source for rotating the support shaft 51, and an encoder 55 that detects the rotation angle and direction of the motor 54. The motor 54 and encoder 55 are electrically connected to the control unit 70, and when a detection signal is transmitted from the encoder 55 to the control unit 70, the control unit 70 drives the motor 54 based on the received detection signal. In other words, the control unit 70 recognizes the position of the measurement point measured by the temperature sensor 53 in the radial direction of the wafer W based on the detection signal from the encoder 55.

[0032] Therefore, by starting the motor 54 to rotate the support shaft 51, and as the support shaft 51 rotates, the arm 52 is swung above the holding surface 10a of the chuck table 10, thereby causing the temperature sensor 53 attached to the tip of the arm 52 to reciprocate in the radial direction of the wafer W being held on the holding surface 10a of the rotating chuck table 10 and being ground by the grinding wheel 25b, the temperature of multiple locations in the radial portion of the surface of the wafer W being ground can be measured.

[0033] If the temperature sensor 53 is a radiation thermometer, the measurement range is pinpoint, so as described above, the radiation thermometer is moved horizontally along the radius of the wafer W to measure the surface temperature of the wafer W at multiple locations. In other words, the multiple measurement locations are multiple circles on the surface of the wafer W in a spiral or concentric pattern. In contrast, if the temperature sensor 53 is a thermal camera, the measurement range can be set to a wide area, so it is installed to measure the radius of the wafer W outside the grinding wheel 25b.

[0034] (Spray nozzle) The injection nozzle 60 injects cold water or hot water (hot water in this embodiment) from a cold water supply source 61 or a hot water supply source 62 shown in Figure 1 to at least one location (see Figure 5) on the holding surface 10a of the chuck table 10. The nozzle is attached to the tip of an arm 64 that extends horizontally from the upper end of a support shaft 63 which is rotatably erected vertically near the chuck table 10 on the base 100. The support shaft 63 incorporates a motor 65, which is a drive source for rotating the support shaft 63, and an encoder 66 that detects the rotation angle and direction of the motor 65. The motor 65 constitutes a horizontal movement mechanism that moves (horizontally rotates) the injection nozzle 60 horizontally above the holding surface 10a of the chuck table 10. The motor 65 and the encoder 66 are electrically connected to the control unit 70. When a detection signal from the encoder 66 is transmitted to the control unit 70, the control unit 70 drives and controls the motor 65 based on the received detection signal.

[0035] As shown in Figure 1, the pipes 67 and 68 extending from the chilled water supply source 61 and the hot water supply source 62, respectively, merge into a single pipe 69, which is connected to the injection nozzle 60. Each of the pipes 67 and 68 is provided with on-off valves V1 and V2, respectively, which are electrically connected to the control unit 70, and their opening and closing operations are controlled by the control unit 70.

[0036] Therefore, by activating the motor 65 that constitutes the horizontal movement mechanism and causing the arm 64 to swing around the pivot shaft 63, the spray nozzle 60 attached to the tip of the arm 64 can be moved horizontally in the radial direction of the holding surface 10a above the holding surface 10a of the chuck table 10, thereby spraying cold water or hot water at a predetermined location in the radial portion of the holding surface 10a (see Figure 5).

[0037] The injection nozzle 60 may consist of two or more nozzles, such as a hot water nozzle for injecting hot water and a cold water nozzle for injecting cold water. In addition to moving the injection nozzle 60 in the radial direction of the wafer W as described above, multiple injection nozzles 60 may be arranged in the radial portion of the holding surface 10a.

[0038] (Control Unit) The control unit 70 shown in Figure 1 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and a storage unit such as ROM (Read Only Memory) and RAM (Random Access Memory). In particular, in this embodiment, the control unit 70 includes a calculation unit 71 that calculates the median or average value of temperature data at multiple locations on the holding surface 10a of the chuck table 10 measured by the temperature sensor 53 of the wafer W during grinding. The control unit 70 also includes an tolerance value setting unit 72 that sets an allowable range for the temperature range of the wafer W. This tolerance value setting unit 72 sets the allowable range based on the median or average value calculated by the calculation unit 71. The control unit 70 then performs the function of causing at least a portion of the holding surface 10a to expand or contract via the wafer W, by horizontally moving the spray nozzle 60 above the location where the temperature difference exceeds a predetermined tolerance range if the difference between the measured temperature at each location on the surface of the wafer W during grinding is greater than or equal to the median or average value, and spraying cold water or hot water from the spray nozzle 60 toward the wafer W held on the holding surface 10a of the chuck table 10, which will be described in more detail later.

[0039] [Wafer grinding method] Next, an embodiment of the wafer grinding method according to the present invention, which is carried out using the grinding apparatus 1 configured as described above, will be described below with reference to Figures 3 to 5.

[0040] The method for grinding the wafer W according to this embodiment is as shown in Figure 2, 1) Holding process: 2) Grinding process: The following steps are performed in this order to grind the wafer W, and 2) the grinding process includes the following steps. 2-1) Temperature measurement process: 2-2) Calculation process: 2-3) Injection nozzle positioning process: 2-4) Chuck table deformation process: 2-5) Repeated process: The following explains each step in order.

[0041] 1) Holding process: The holding step is a step in which the chuck table 10 holds the wafer W. As shown in Figure 3, the chuck table 10 is tilted by a tilt adjustment mechanism (not shown) such that its table rotation axis CL1 is tilted by an angle α shown with respect to the vertical, and the wafer W is placed on the holding surface 10a of the chuck table 10. The porous member 11 of the chuck table 10 is connected to a suction source (not shown). As a result, the porous member 11 is evacuated by the suction source (not shown), generating negative pressure in the porous member 11. The wafer W is then attracted and held on the conical holding surface 10a of the chuck table 10 by this negative pressure (step S1 in Figure 5). In this case, the wafer W deforms into an umbrella shape with its center as the apex, following the shape of the holding surface 10a of the chuck table 10.

[0042] 2) Grinding process: The grinding process, as shown in Figure 3, involves grinding the upper surface (back surface) of the wafer W held on the holding surface 10a of the chuck table 10 with a grinding wheel 25b. In this grinding process, the horizontal movement mechanism 13 moves the wafer W held on the chuck table 10 horizontally in the +Y axis direction (to the right in Figure 3), and the chuck table 10 is positioned so that the circumscribed circle of the annular grinding wheel 25b of the grinding wheel 25 passes through the center of the wafer W. The inclination angle α of the chuck table 10 is set to a value such that the radial portion of the holding surface 10a of the chuck table 10 (the right half in Figure 3) is parallel to the horizontal lower surface (grinding surface) of the grinding wheel 25.

[0043] In the above state, the chuck table 10 and the wafer W held therein are driven to rotate at a predetermined speed in the direction of the arrow (counterclockwise) around the table rotation axis CL1 by the table rotation mechanism 12, and the grinding wheel 25 is driven to rotate at a predetermined speed in the same direction as the rotation direction of the chuck table 10 (counterclockwise) around the grinding wheel rotation axis CL2 by the spindle motor 22 of the grinding unit 20 shown in Figure 1. Then, the grinding unit 20 is lowered by the lifting mechanism 30, and when the grinding wheel 25b of the grinding wheel 25 contacts the radial portion of the upper surface of the wafer W, the entire surface of the wafer W is ground by the grinding wheel 25b (step S2 in Figure 5). At this time, the thickness of the wafer W is measured by a thickness measuring instrument (not shown) (step S3 in Figure 5). Furthermore, grinding water is supplied from the grinding water supply source 41 of the grinding water supply means 40 through piping 42 (see Figure 1), a supply passage (not shown) formed on the axis of the spindle motor 22, a supply passage 23a formed on the axis of the spindle 23 shown in Figure 3, and a plurality of supply passages 24a formed on the mount 24, and is sprayed toward the upper surface of the wafer W from a plurality of nozzles 25c formed perpendicularly on the base 25a of the grinding wheel 25. As a result, grinding debris generated by grinding the wafer W is removed by the grinding water, and the frictional heat generated at the contact point between the grinding wheel 25b and the wafer W is removed by the grinding water, cooling the contact point.

[0044] 2-1) Temperature measurement process: In the temperature measurement process, the chuck table 10 is rotated, and the temperature of multiple points on the radial portion of the grinding surface of the wafer W held on the holding surface 10a is measured by the temperature sensor 53 to determine the temperature distribution across the entire upper surface (grinding surface) of the wafer W (step S4 in Figure 5). In other words, in this temperature measurement process, when the support shaft 51 of the temperature measuring device 50 shown in Figure 1 is rotated by the motor 54 within a predetermined angular range, the arm 52 attached to the upper end of the support shaft 51 rotates horizontally around the support shaft 51. As a result, the temperature sensor 53 attached to the tip of the arm 52 moves from the center to the outer edge and from the outer edge to the center above the wafer W held on the holding surface 10a of the chuck table 10 outside the grinding wheel 25b, as shown in Figure 3(a). In this embodiment, the temperature of the wafer W is measured by the temperature sensor 53 at five points: the center point A, the outer edge point B, the midpoint between the two points C, the measurement point D between the center point A and the midpoint C, and the measurement point E between the midpoint C and the outer edge point B. However, the measurement points on the wafer W are not limited to five points. For example, the temperature of the wafer W may be measured by setting a sampling time (e.g., 10 msec) for which the temperature is measured by the temperature sensor 53 and the movement speed of the temperature sensor 53 (rotation speed of the pivot shaft 51).

[0045] As described above, Figure 3(b) shows the results of temperature measurements taken by the temperature sensor 53 at the center point A, measurement point D, intermediate point C, measurement point E, and outer edge point B of the wafer W. In this embodiment, the temperature at measurement point E of the wafer W is T E The temperature T was highest at the central point A, measurement point D, midpoint C, and outer point B, respectively. A , T D , T C , T B These show the same value T.

[0046] In this embodiment, as the temperature measuring device 50, one configured by attaching a temperature sensor 53 to the tip of an arm 52 that horizontally rotates around a support shaft 51 is used. However, one in which temperature sensors 53 are attached at five points on a horizontal arm 52 that does not rotate may also be used. Further, an encoder for recognizing the rotation angle of the chuck table 10 may be provided, and when the temperature sensor 53 measures the temperature, the rotation angle of the chuck table 10 may be simultaneously memorized.

[0047] 2-2) Calculation step: In the calculation step, the temperature data of the wafer W, in this embodiment, the temperatures T at the center point A, measurement point D, intermediate point C, measurement point E, and outer peripheral point B of the wafer W are calculated by a calculation unit 71 (refer to FIG. 1) provided in the control unit 70. A , T D , T C , T E , T B The average value Tmean is calculated by the following formula (step S5 in FIG. 5). Tmean = (T A + T B + T C + T D + T E ) / 5 …(1) Here, in this embodiment, the average value Tmean obtained by the formula (1) is indicated by a chain line in FIG. 3(b). In this embodiment, the average value Tmean obtained by the formula (1) is calculated. However, when the number of measurement data is large, the median value of the measured temperatures may be obtained.

[0048] [[ID=^33]] Thus, in this embodiment, the allowable value setting unit 72 of the control unit 70 shown in FIG. 1 sets the allowable temperature range ΔT O [[ID=^36]]of the wafer W as follows before injecting cold water or warm water from the injection nozzle 60 toward the wafer W as described later (step S6 in FIG. 5).

[0049] That is, the allowable temperature range ΔT O is set to a temperature range of ±2°C with respect to the average value Tmean calculated by the formula (1) as a reference value. That is, ΔT O =Tmean±2℃ This is set to ±2°C relative to the average value Tmean (reference value). Note that the allowable temperature of ±2°C is just an example, and the allowable temperature is not limited to ±2°C. In addition, the reference value may be set to the median, or a predetermined constant value may be set in advance.

[0050] 2-3) Injection nozzle positioning process: In the injection nozzle positioning process, as shown in Figure 3(b), the temperatures T at the center point A, measurement point D, intermediate point C, measurement point E, and outer edge point B of the wafer W, which were measured in the temperature measurement process, are measured. A , T D , T C , T E ,T B The absolute value of the difference ΔT between and the mean value Tmean calculated by equation (1), that is, |ΔT|, A -T mean |, |T B -T mean |, |T C -T mean |, |T D -T mean |, |T E -Tmean| is the absolute value of the allowable temperature range for the temperature difference |ΔT|. O Whether or not it exceeds (see Figure 3(b)) (|ΔT|>|ΔT) O The control unit 70 determines whether |?) is correct (step S7 in Figure 5).

[0051] In this embodiment, as shown in Figure 3(b), the absolute value of the temperature difference at measurement point E on the wafer W, |ΔT| = |T - Tmean|, is equal to the absolute value of the allowable temperature range |ΔT O Since it exceeds |, the judgment result in step S7 in Figure 5 is Yes, and the injection nozzle 60 is positioned (step S8 in Figure 5).

[0052] In other words, as shown in Figure 4, the absolute value of the temperature difference |ΔT| = |T - Tmean| is equal to the absolute value of the allowable temperature range |ΔT OThe injection nozzle 60 is positioned directly above the measurement point E of the wafer W, which exceeds |. Specifically, when the motor 65 shown in Figure 1 is started and the support shaft 63 is rotated by a predetermined angle, the arm 64 attached to the upper end of the support shaft 63 rotates horizontally, so that the injection nozzle 60 attached to the tip of the arm 64 moves horizontally above the wafer W, and as shown in Figure 4, the injection nozzle 60 is positioned directly above the circumference passing through the measurement point E of the holding surface 10a. Note that the absolute value of the temperature difference between each measurement point A to E on the wafer W, |ΔT|=|T-Tmean|, is equal to the absolute value of the allowable temperature range, |ΔT O If the value is less than | (Step S7: No in Figure 5), the injection nozzle 60 is not positioned.

[0053] 2-4) Chuck table deformation process: In the preceding step, the injection nozzle positioning step, when the injection nozzle 60 is positioned directly above the circumference passing through the measurement point E of the wafer W (step S8 in Figure 5), it is determined whether ΔT > 0 or not (step S9 in Figure 5). In this embodiment, as shown in Figure 3(b), ΔT = T E Since -Tmean>0 (Step S9: Yes), as shown in Figure 4, cold water is sprayed from the spray nozzle 60 toward the measurement point E of the wafer W, and the holding surface 10a of the chuck table 10 corresponding to the ring-shaped portion passing through the measurement point E of the wafer W is cooled by the cold water (Step S10 in Figure 5). In this way, by spraying cold water toward the measurement point E of the wafer W, the holding surface 10a of the chuck table 10 directly below the measurement point E can be cooled and contracted via the wafer W.

[0054] Specifically, as shown in Figure 4, the control unit 70 opens one on-off valve V1 and closes the other on-off valve V2. Then, chilled water is supplied from the chilled water supply source 61 through pipes 67 and 69 to the injection nozzle 60, and chilled water is injected from the injection nozzle 60 toward the measurement point E of the wafer W, and the ring-shaped portion of the wafer W passing through the measurement point E is cooled by the chilled water. Note that the absolute value of the temperature difference |ΔT|=|T-Tmean| is equal to the absolute value of the allowable temperature range |ΔT OIf there are multiple measurement points that exceed the | limit, the nozzle positioning process and the chuck table deformation process are repeated for each of those measurement points.

[0055] Conversely, for example, the measurement temperature T at measurement point E on wafer W. E Since ΔT = T is less than the mean Tmean E If -Tmean<0 (Step S9: No), the control unit 70 closes one of the on-off valves V1 shown in Figure 4 and opens the other on-off valve V2. Then, hot water is supplied from the hot water supply source 62 through the pipes 68 and 69 to the injection nozzle 60, and hot water is injected from the injection nozzle 60 toward the measurement point E of the wafer W (Step S11 in Figure 5). As a result, the holding surface 10a of the chuck table 10 corresponding to the ring-shaped portion passing through the measurement point E of the wafer W is heated by the hot water via the wafer W, and the ring-shaped portion of the holding surface 10a expands. Alternatively, during the temperature measurement process, the rotation angle of the chuck table 10 stored along with the temperature may be used to control the injection of cold water or hot water from the injection nozzle 60 within a predetermined angle range, thereby thermally deforming the holding surface 10a of the chuck table 10 into a fan shape.

[0056] 2-5) Repeated process: The control unit 70 repeats the temperature measurement step, the injection nozzle positioning step, and the chuck table deformation step until the wafer W is ground to a predetermined thickness. That is, it is determined whether the thickness of the wafer W measured by a thickness measuring instrument (not shown) is the predetermined thickness (step S12 in Figure 5), and if the thickness of the wafer W is ground to the predetermined thickness (step S12 in Figure 5: Yes), the series of grinding operations on the wafer W is completed (step S13 in Figure 5).

[0057] On the other hand, if the wafer W has not been ground to a predetermined thickness (step S12: No), the above steps of temperature measurement, calculation, injection nozzle positioning, and chuck table deformation are repeated until the wafer W reaches the predetermined thickness (steps S2 to S12 in Figure 5). This repeated operation is performed, for example, when the grinding unit 20 has descended a preset distance.

[0058] As described above, in this embodiment, while grinding the wafer W with the grinding wheel 25b, the temperature of multiple locations on the wafer W is measured with the temperature measuring instrument 50, and among the multiple temperature data measured by the temperature measuring instrument 50, a preset allowable temperature range ΔT is selected. O In lower areas, hot water is sprayed onto the wafer W from the spray nozzle 60, warming and expanding a portion of the holding surface 10a of the chuck table 10 corresponding to the area where the hot water was sprayed, thereby reaching a predetermined allowable temperature range ΔT. O In higher areas, cold water is sprayed from the spray nozzle 60, cooling and shrinking a portion of the holding surface 10a of the chuck table 10 corresponding to the area where the cold water is sprayed, thereby correcting the height of the holding surface 10a. As a result, the wafer W held and ground on the holding surface 10a of the chuck table 10 during the grinding process has a small difference in in-plane thickness and is uniformly ground to a predetermined finish thickness across its entire surface.

[0059] In the above embodiments, cold water was sprayed from the spray nozzle 60 toward the wafer W during the chuck table deformation process. However, hot water may be sprayed toward the wafer W held on the holding surface 10a to heat the holding surface 10a through the wafer W and cause that portion to expand.

[0060] Furthermore, the present invention can also be similarly applied to grinding a thin, disc-shaped bonded wafer W shown in Figure 6. Here, the bonded wafer W consists of a support wafer W1 and a device wafer W2 bonded on top of the support wafer W1, and multiple devices (not shown) are formed on the bonding surface (bottom surface in Figure 6) of the device wafer W2 to the support wafer W1. When grinding such a bonded wafer W, in the holding step the bonded wafer W is held by suction on the holding surface 10a of the chuck table 10 with the support wafer W1 facing downwards, and in the grinding step the top surface of the device wafer W2 is ground by a grinding wheel 25b. Note that in Figure 6, the same elements as those shown in Figure 4 are denoted by the same reference numerals.

[0061] In addition, in the bonded wafer W, the height of the holding surface 10a may be corrected to accommodate the difference in thickness of the bonded members.

[0062] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Explanation of symbols]

[0063] 1: Grinding device, 2: Cover, 3,4: Expandable cover, 10: Chuck table, 10a: Holding surface, 11: Porous member, 12: Table rotation mechanism, 13: Horizontal movement mechanism, 20: Grinding unit, 21: Holder, 22: Spindle motor, 23: Spindle, 24: Mount, 25: Grinding wheel, 25a: Base, 25b: Grinding wheel, 25c: Nozzle, 30: Lifting mechanism, 31: Lifting plate, 32: Guide rail, 33: Ball screw, 34: Servo motor, 35: Bracket, 36: Encoder, 40: Grinding water supply means, 41: Grinding water supply source, 42: Piping, 50: Temperature measuring instrument, 51: Support shaft, 52: Arm, 53: Temperature sensor, 54: Motor, 55: Encoder, 60: Injection nozzle, 61: Cold water supply source, 62: Hot water supply source, 63: Support shaft, 64: Arm, 65: Motor, 66: Encoder, 67-69: Piping, 70: Control unit, 71: Calculation unit, 72: Tolerance setting section, 100: Base, 100a: Opening of the base, 101: Column, CL1: Table rotation axis, CL2: Grinding wheel rotation axis, V1, V2: On / off valves, W: Wafer (bonded wafer), W1: Support wafer, W2: Device wafer, α: Chuck table tilt angle

Claims

1. A chuck table comprising a porous member having a conical holding surface with its apex at the center, which is connected to a suction source to hold a wafer with the holding surface, A table rotation mechanism that rotates the chuck table around a table rotation axis passing through the vertex of the porous member, A grinding unit that rotates a grinding wheel around a rotation axis passing through the center of an annular grinding wheel to grind the upper surface of a wafer with the lower surface of the grinding wheel, A lifting mechanism for raising and lowering the grinding unit, A grinding water supply means for supplying grinding water to the location where the lower surface of the grinding wheel contacts the upper surface of the wafer, A grinding device equipped with, A spray nozzle that sprays cold water or hot water from above the holding surface onto at least a portion of the radial portion of the holding surface, A temperature measuring device for measuring the temperature at multiple locations on the radial portion of the wafer held on the holding surface, A control unit that, among multiple temperature data measured by the temperature measuring instrument, sprays hot water from the spray nozzle where the temperature is lower than a set range before spraying hot or cold water from the spray nozzle, and sprays cold water from the spray nozzle where the temperature is higher than the set range, thereby expanding or contracting the chuck table and changing the height of the holding surface, A grinding device equipped with the following features.

2. A method for grinding a wafer using the grinding apparatus described in claim 1, A holding step of holding the wafer in the chuck table, A grinding step in which, while grinding the wafer with the grinding wheel, the temperature of multiple locations on the wafer is measured with the temperature measuring instrument, and among the multiple temperature data measured with the temperature measuring instrument, hot water is sprayed from the spray nozzle to locations where the temperature is lower than a set temperature range before spraying hot or cold water from the spray nozzle, and cold water is sprayed from the spray nozzle to locations where the temperature is higher than the set temperature range, while grinding the wafer to a predetermined finish thickness, A method for grinding wafers, including [a specific component].

3. The wafer is a bonded wafer comprising a support wafer and a device wafer having a device formed on the bonding surface to be bonded to the support wafer, The holding step involves using the chuck table to hold the support wafer by suction, The grinding step involves grinding the device wafer. The wafer grinding method according to claim 2.

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