Grinding device

Abstract

The present invention provides a polishing device that shortens polishing time and makes in-plane thickness of a wafer uniform. A polishing device (1) has a chuck table (50) that holds a wafer (90) with a holding surface (502), a slider (59) that moves the chuck table to a position where the held wafer can be polished, and a control unit (19), and has a first polishing unit (30) that arranges a first polishing pad (306) having a lower surface that covers at least an area of an upper surface of the wafer at a lower end of a first spindle, and a second polishing unit (32) that arranges a second polishing pad (326) having a lower surface with a diameter smaller than a diameter of the wafer at a lower end of a second spindle. The control unit controls polishing of the wafer held by the holding surface with the first polishing pad and polishing of a prescribed portion of a radius region of the wafer polished with the first polishing pad with the second polishing pad.

Description

Technical Field

[0001] This invention relates to a grinding apparatus for grinding workpieces such as semiconductor wafers. Background Technology

[0002] For example, the polishing apparatus disclosed in Patent Document 1, which uses a polishing pad to polish a wafer, has a polishing pad covering the area of ​​the upper surface of the wafer held by the chuck stage mounted on the spindle. The spindle is rotated, which in turn rotates the chuck stage holding the wafer, pressing the polishing pad against the wafer to polish it.

[0003] Sometimes, uneven thickness, resembling ripples, occurs on wafers ground in this way, forming concentric circles centered on the wafer's center. Therefore, as disclosed in Patent Document 2, for example, by performing the grinding process while reciprocating between the chuck stage and the grinding pad in a horizontal direction parallel to the holding surface, uneven thickness is prevented from forming on the wafer, thus reducing the thickness difference of the ground wafer.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2003-305643

[0005] Patent Document 2: Japanese Patent Application Publication No. 2007-318041

[0006] However, even when polishing is performed by reciprocating the polishing pad and the wafer held by the chuck stage in a horizontal direction, a slight thickness difference remains on the polished wafer. Additionally, the horizontal reciprocating motion of the polishing pad in contact with the wafer results in a longer polishing time.

[0007] Therefore, there are several challenges to be addressed in polishing apparatuses for polishing wafers: reducing polishing time and ensuring uniform in-plane thickness of the polished wafers. Summary of the Invention

[0008] The present invention for solving the above-mentioned problems is a polishing apparatus comprising: a chuck stage for holding a wafer using a holding surface; a polishing unit for placing a polishing pad for polishing the wafer at the lower end of a spindle and polishing the wafer using the lower surface of the polishing pad; a slider for moving the chuck stage to a polishing position where the polishing unit can polish the wafer held by the holding surface; and a control unit, wherein the polishing unit comprises: a first polishing unit for placing a first polishing pad having a lower surface having an area covering at least the upper surface of the wafer at the lower end of a first spindle; and a second polishing unit for placing a second polishing pad having a lower surface having a diameter smaller than the diameter of the wafer at the lower end of a second spindle, and the control unit performing the following control: moving the chuck stage below the first polishing pad and polishing the wafer held by the holding surface using the first polishing pad; and polishing a predetermined portion of the radius region of the wafer polished by the first polishing pad using the second polishing pad.

[0009] The polishing apparatus of the present invention preferably includes: a horizontal moving unit that moves the second polishing unit in a horizontal direction; and a thickness measuring device that measures the thickness of a wafer that has been polished with the first polishing pad and held on the holding surface, wherein the specified location is the location with the largest thickness value among a plurality of thickness values ​​of the wafer measured by the thickness measuring device, and the horizontal moving unit can be used to position the second polishing pad of the second polishing unit at the specified location.

[0010] The polishing apparatus of the present invention preferably includes a conveying unit that moves a wafer into or out of the holding surface. A slider positions the chuck stage at a first polishing position, a second polishing position, or a move-in / move-out position. At the first polishing position, the wafer held by the holding surface is polished using the first polishing pad. At the second polishing position, the wafer held by the holding surface is polished using the second polishing pad. At the move-in / move-out position, the wafer is moved into or out of the holding surface by the conveying unit. The control unit performs the following control: polishing the wafer held by the holding surface using the first polishing pad; moving the wafer polished using the first polishing pad to the move-in / move-out position and measuring its thickness using the thickness measuring device; and polishing the portion with the largest thickness value among the multiple thickness values ​​measured by the thickness measuring device as the predetermined portion using the second polishing pad.

[0011] The polishing apparatus of the present invention preferably has a third polishing unit, which has a third polishing pad, which is made of a diameter smaller than the radius of the wafer and capable of surrounding the size of the second polishing pad, disposed at the lower end of the third spindle.

[0012] The grinding apparatus of the present invention preferably has two or more of the second grinding units.

[0013] The polishing apparatus of the present invention comprises: a first polishing unit which arranges a first polishing pad having a lower surface having an area covering at least the upper surface of a wafer at the lower end of a first spindle; and a second polishing unit which arranges a second polishing pad having a lower surface having a diameter smaller than the diameter of the wafer at the lower end of a second spindle, thereby controlling the following by a control unit: moving a chuck stage below the first polishing pad to polish the wafer held on a holding surface using the first polishing pad; and polishing a predetermined portion of the radius region of the wafer polished using the first polishing pad, i.e., a portion with a thickness difference compared to other portions of the wafer caused by polishing the wafer using the first polishing pad, using the second polishing pad. This reduces the total polishing time compared to a case where a single-axis polishing unit that contacts the wafer moves horizontally while polishing the wafer, and also ensures uniform in-plane thickness of the wafer polished using the second polishing pad.

[0014] The polishing apparatus of the present invention includes: a horizontal moving unit that moves a second polishing unit in the horizontal direction; and a thickness measuring device that measures the thickness of a wafer that has been polished with a first polishing pad and held on the holding surface of a chuck stage. The specified location is the location with the largest thickness value among multiple thickness values ​​of the wafer measured by the thickness measuring device. The horizontal moving unit can position the second polishing pad of the second polishing unit at the specified location. As a result, compared with the case where the polishing of the wafer is performed while the single-axis polishing unit that contacts the wafer in the horizontal direction is moved, the total polishing time can be shortened and the in-plane thickness of the wafer after polishing with the second polishing pad can be made uniform.

[0015] The polishing apparatus of the present invention includes a conveying unit that conveys a wafer into or out of a holding surface. A slider can position the chuck stage in a first polishing position, a second polishing position, or a conveying-in / conveying position. In the first polishing position, the wafer held on the holding surface is polished using a first polishing pad. In the second polishing position, the wafer held on the holding surface is polished using a second polishing pad. In the conveying-in / conveying position, the wafer is conveyed into or out of the holding surface by the conveying unit. The control unit can perform the following control: polishing the wafer held on the holding surface using the first polishing pad; moving the wafer polished using the first polishing pad to the conveying-in / conveying position and measuring the thickness using a thickness measuring device; and using the second polishing pad to polish the portion with the largest thickness value among the multiple thickness values ​​of the wafer measured by the thickness measuring device as a predetermined portion. As a result, compared with the case where the wafer is polished while the single-axis polishing unit is moved horizontally, the polishing time can be shortened and the in-plane thickness of the wafer polished using the second polishing pad can be made uniform.

[0016] The polishing apparatus of the present invention has a third polishing unit. The third polishing unit has a third polishing pad, which is made of a diameter smaller than the radius of the wafer and can surround the size of the second polishing pad, disposed at the lower end of the third spindle. The third polishing pad is used to polish a predetermined area of ​​the wafer with an in-plane thickness difference in a tracing manner for a short time. Then, the second polishing pad is used to polish the predetermined area of ​​the wafer with an in-plane thickness difference, thereby making the in-plane thickness of the polished wafer more uniform.

[0017] The grinding apparatus of the present invention, by having two or more second grinding units, can increase the production volume of wafer grinding processes. Attached Figure Description

[0018] Figure 1 This is a perspective view showing the grinding apparatus of Embodiment 1.

[0019] Figure 2 (A) is a top view showing the upper surface of a wafer that has been polished using the first polishing unit. Figure 2 (B) is a cross-sectional view of the wafer that has been polished using the first polishing unit.

[0020] Figure 3 This is a perspective view showing the grinding apparatus of Embodiment 2.

[0021] Figure 4 This is a perspective view showing the grinding apparatus of Embodiment 3.

[0022] Label Explanation

[0023] 90: Wafer; 902: Upper surface; 901: Lower surface; 1: Grinding apparatus of Embodiment 1; 10: First apparatus base; 11: Second apparatus base; 115: Processing area; 102: Wafer preparation area; 114: Loading / unloading position; 12: First pillar; 13: Second pillar; 150: First box holder; 1500: First box; 151: Second box holder; 1510: Second box; 155: Robot; 4: Transfer unit; 40 153: Loading arm; 154: Unloading arm; 155: Alignment unit; 156: Temporary storage area; 157: Cleaning unit; 158: Chuck table; 159: Perforated plate; 1502: Holding surface; 151: Frame; 152: Slider; 153: Lifting cylinder; 154: Rod; 155: Arm component; 16: Thickness measuring device; 17: First grinding feed unit; 18: Ball screw; 19: Pair of guide rails; 10: Motor; 11: Lifting plate; 12: 30: 31: Loading arm; 152: Unloading arm; 153: Alignment unit; 154: Temporary storage area; 155: Cleaning unit; 156: Cleaning unit; 157: Chuck table; 158: Perforated plate; 159: Perforated plate; 150: Holding surface; 151: Unloading arm; 152: Unloading arm; 153: Alignment unit; 154: Temporary storage area; 155: Cleaning unit; 156: Cleaning unit; 157: Chuck table; 158: Perforated plate; 159: Perforated plate; 150: Unloading arm; 151: Unloading arm; 152: Unloading arm; 153: Unloading arm; 154: Unloading arm; 155: Unloading arm; 156: Unloading arm; 157: Unloading arm; 158: Unloading arm; 159: Unloading arm; 150: Unloading arm; 151: Unloading arm; 152: Unloading arm; 153: Unloading arm; 154: Unloading arm; 155: Unloading arm; 156: Unloading arm; 300: First grinding unit; 301: Housing; 302: Motor; 303: Mounting base; 306: First grinding pad; 22: Second grinding feed unit; 220: Ball screw; 221: Pair of guide rails; 222: Motor; 223: Lifting plate; 32: Second grinding unit; 320: Second spindle; 321: Housing; 322: Motor; 323: Mounting base; 326: Second grinding pad; 23: Horizontal movement unit; 230: Ball screw; 231: A pair of guide rails; 232: Motor; 233: Movable plate; 19: Control unit; 191: Grinding part identification unit; 18: Grinding device of embodiment 2; 110: Portal column; 36: Second grinding unit; 360: Second spindle; 364: Second grinding pad; 17: Grinding device of embodiment 3; 38: X-axis movement unit; 37: Third grinding unit; 372: Third spindle; 375: Third grinding pad. Detailed Implementation

[0024] (Implementation Method 1)

[0025] Figure 1 The polishing apparatus 1 shown (hereinafter referred to as the polishing apparatus 1 of Embodiment 1) is, for example, an apparatus having a first polishing unit 30 and a second polishing unit 32 and polishing a wafer 90 held on any chuck stage 50 by means of the first polishing unit 30 and the second polishing unit 32.

[0026] The polishing apparatus 1 is configured, for example, to have a second apparatus base 11 connected to the rear (+Y direction side) of the first apparatus base 10. The first apparatus base 10 serves as a wafer preparation area 102 for loading and unloading, centering, and cleaning of the wafer 90 relative to the cassette, and the second apparatus base 11 serves as a processing area 115 for processing the wafer 90 held by the chuck stage 50 by the first polishing unit 30 or the second polishing unit 32. A portion of the processing area 115 is provided with a loading and unloading position 114 for loading the wafer 90 into or out of the chuck stage 50 by the transfer unit 4.

[0027] Figure 1 The wafer 90 shown is, for example, a circular plate-shaped semiconductor wafer formed from a silicon substrate, etc. Figure 1 Multiple devices are formed on the lower surface 901 of the wafer 90 facing downwards, and are protected by a protective strip (not shown). The upper surface 902 of the wafer 90 facing upwards becomes the surface to be processed by grinding.

[0028] A first box placement section 150 and a second box placement section 151 are provided on the front side (-Y direction side) of the first device base 10. The first box placement section 150 holds a first box 1500 for storing the wafer 90 before processing, and the second box placement section 151 holds a second box 1510 for storing the wafer 90 after processing.

[0029] A robot 155 is installed behind the opening of the first box 1500. The robot 155 takes out the unprocessed wafer 90 from the first box 1500 and moves the processed wafer 90 into the second box 1510. Figure 1 The robot 155 shown is capable of rotating and moving its arm in the horizontal plane (X-axis and Y-axis planes) via a multi-joint arm.

[0030] A temporary placement area 152 is provided adjacent to the robot 155, and an alignment unit 153 is provided in the temporary placement area 152. The alignment unit 153 uses a reduced-diameter alignment pin to align (center) the wafer 90 that is taken out from the first box 1500 and placed in the temporary placement area 152 to a predetermined position, thereby determining the center position of the wafer 90.

[0031] exist Figure 1In the example shown, a loading arm 40, which rotates while holding a wafer 90, is positioned adjacent to the alignment unit 153. The loading arm 40 holds and transports the wafer 90, which has been aligned in the alignment unit 153, to the chuck stage 50 located at the loading / unloading position 114. An unloading arm 41, which rotates while holding the processed wafer 90, is provided next to the loading arm 40. Furthermore, in this embodiment, the loading arm 40 and the unloading arm 41 constitute a transport unit 4 for loading the wafer 90 into the holding surface 502 of the chuck stage 50 or removing the wafer 90 from the holding surface 502.

[0032] Within the movable range of the unloading arm 41, a monolithic cleaning unit 156 is configured to clean the processed wafer 90 transported by the unloading arm 41. The wafer 90 cleaned by the cleaning unit 156 is then transferred to the second box 1510 by the robot 155.

[0033] like Figure 1 As shown, a slider 59 is provided on the second device base 11 to move the chuck stage 50 to various grinding positions where the first grinding unit 30 or the second grinding unit 32 can grind the wafer 90 held by the holding surface 502 of the chuck stage 50. In this embodiment 1, the slider 59 is a rotary table that is circular in plan view. A plurality of (e.g., three) chuck stages 50 are provided on the upper surface of the slider 59. These chuck stages 50 are arranged at equal intervals (e.g., 120-degree intervals) around the center of the slider 59 in the circumferential direction of the slider 59, and have a holding surface 502 for holding the wafer 90.

[0034] Alternatively, the slider can be a linear slider capable of mounting the chuck table 50 on the upper surface and moving linearly in the Y-axis direction.

[0035] A rotating shaft (not shown) for rotating the slider 59 is connected to the center of the slider 59. This rotating shaft, with its axis in the Z-axis direction, can be rotated by a motor (not shown). Furthermore, by rotating the slider 59 around its center, the multiple chuck stages 50 holding the wafer 90 can revolve, thereby positioning the chuck stages 50 sequentially from near the temporary placement area 152 below the first polishing unit 30, below the second polishing unit 32, and at the loading / unloading position 114. For example, the slider 59 can be lifted by air jets onto the upper and lower surfaces of the second device base 11, achieving the rotatable state described above.

[0036] like Figure 1As shown, the chuck stage 50 includes, for example, a perforated plate 500, which is circular in top view and has a holding surface 502 for holding the wafer 90; and a frame 501 that exposes the holding surface 502 and has a recess for accommodating the perforated plate 500. Furthermore, an attraction source (not shown) is connected to the holding surface 502 and transmits the attraction force generated by the attraction source.

[0037] The polishing apparatus 1 of Embodiment 1 has a first polishing unit 30 and a second polishing unit 32 as polishing units that place a polishing pad for polishing a wafer 90 at the lower end of a spindle and polish the wafer 90 using the lower surface of the polishing pad. The first polishing unit 30 places a first polishing pad 306 having a lower surface having an area that covers at least the upper surface 902 of the wafer 90 at the lower end of a first spindle 300. The second polishing unit 32 places a second polishing pad 326 having a lower surface having a diameter smaller than the diameter of the wafer 90 at the lower end of a second spindle 320.

[0038] like Figure 1 As shown, a first column 12 is erected at the rear of the second device base 11, and a first grinding feed unit 20 is mounted on the front surface of the first column 12. The first grinding feed unit 20 includes: a ball screw 200 having a vertical axis (Z-axis direction); a pair of guide rails 201 arranged parallel to the ball screw 200; a motor 202 connected to the ball screw 200 to rotate the ball screw 200; and a lifting plate 203, the nut inside of which is screwed into the ball screw 200. The side of the lifting plate 203 slides in contact with the guide rails 201. When the motor 202 rotates the ball screw 200, the lifting plate 203 is guided by the guide rails 201 to reciprocate in the Z-axis direction, and the first grinding unit 30 mounted on the lifting plate 203 also reciprocates in the Z-axis direction.

[0039] The first polishing unit 30 includes, for example,: a first spindle 300 with its axis in the Z-axis direction; a housing 301 that supports the first spindle 300 for rotation; a motor 302 that drives the first spindle 300 to rotate; a circular plate-shaped mounting base 303 fixed to the lower end of the first spindle 300; and a circular first polishing pad 306 that is detachably mounted on the lower surface of the mounting base 303 by means of a platen (not shown). The first polishing pad 306 is formed, for example, from a non-woven fabric such as felt. The diameter of the first polishing pad 306 is the same as the diameter of the mounting base 303, and is larger than the diameter of the wafer 90.

[0040] Furthermore, the first abrasive pad 306 can be bonded with an adhesive to hold abrasive grains. It can be an abrasive pad for dry grinding or a CMP (chemical mechanical polishing) abrasive pad using a polishing fluid. In the case of CMP grinding, a grid-like groove can be formed on the lower surface of the first abrasive pad 306 to allow the slurry to spread across the entire surface.

[0041] The first polishing unit 30 may be configured to perform CMP polishing by supplying slurry to the contact area between the wafer 90 and the first polishing pad 306 via the first spindle 300, or by directly supplying slurry sprayed from an external nozzle (not shown) to the contact area between the wafer 90 and the first polishing pad 306, or it may be configured to perform dry polishing on the wafer 90 without supplying slurry.

[0042] like Figure 1 As shown, a second column 13 is erected parallel to the first column 12 in the X-axis direction at the rear of the second device base 11. A second grinding feed unit 22 is mounted on the front surface of the second column 13. The second grinding feed unit 22 includes: a ball screw 220 having a vertical axis (Z-axis direction); a pair of guide rails 221 arranged parallel to the ball screw 220; a motor 222 connected to the ball screw 220 to rotate the ball screw 220; and a lifting plate 223, the nut inside of which is screwed into the ball screw 220. The side of the lifting plate 223 slides in contact with the guide rails 221. When the motor 222 rotates the ball screw 220, the lifting plate 223 is guided by the guide rails 221 to reciprocate in the Z-axis direction. The second grinding unit 32 mounted on the lifting plate 223 also reciprocates in the Z-axis direction.

[0043] The second polishing unit 32 includes, for example, a second spindle 320 with its axis in the Z-axis direction; a housing 321 that supports the second spindle 320 for rotation; a motor 322 that drives the second spindle 320 to rotate; a circular plate-shaped mounting base 323 fixed to the lower end of the second spindle 320; and a circular second polishing pad 326 that is detachably mounted on the lower surface of the mounting base 323 by means of a pressure plate (not shown). The second polishing pad 326 is formed, for example, from a non-woven fabric such as felt. The diameter of the second polishing pad 326 is smaller than the radius of the wafer 90, for example, set to about 1 / 3 to 1 / 4 of the diameter of the wafer 90, but is not limited thereto.

[0044] Furthermore, the second abrasive pad 326 can be bonded with an adhesive to hold abrasive grains. It can be an abrasive pad for dry grinding or an abrasive pad for CMP (chemical mechanical polishing) using a polishing fluid. In the case of CMP grinding, for example, a grid-like groove for spreading the slurry can be formed on the lower surface of the second abrasive pad 326.

[0045] For example, the polishing apparatus 1 of Embodiment 1 may have two or more second polishing units 32. In this case, for example, a column is erected on the side (+X direction side) of the second apparatus base 11, and a second second polishing unit 32 is disposed on the side of the column by means of a second second polishing feed unit. In this case, the production rate of the polishing process of the wafer 90 can be increased.

[0046] The second polishing unit 32 can be configured to perform CMP polishing by supplying slurry to the contact area between the wafer 90 and the second polishing pad 326 via the second spindle 320, or by directly supplying slurry sprayed from an external nozzle (not shown) to the contact area between the wafer 90 and the second polishing pad 326, or it can be configured to perform dry polishing on the wafer 90 without supplying slurry.

[0047] The grinding apparatus 1 in this embodiment includes, for example, a horizontal moving unit 23 that moves the second grinding unit 32 in the horizontal direction (X-axis direction). The horizontal moving unit 23, disposed on the front surface of the second column 13, includes: a ball screw 230 having an axis in the X-axis direction; a pair of guide rails 231 disposed parallel to the ball screw 230; a motor 232 connected to the ball screw 230 to rotate the ball screw 230; and a movable plate 233, the nut inside of which is screwed into the ball screw 230. The side of the movable plate 233 slides in contact with the guide rails 231. When the motor 232 rotates the ball screw 230, the movable plate 233 is guided by the guide rails 231 to move in the X-axis direction, and the second grinding unit 32 disposed on the movable plate 233 by means of the second grinding feed unit 22 also moves in the X-axis direction.

[0048] For example, a lifting cylinder 590 is disposed at the center of the upper surface of the slider 59 to raise and lower the rod 591 in the Z-axis direction. Furthermore, an arm member 592 extending horizontally is disposed at the upper end of the rod 591, and a thickness measuring device 57 is disposed at the front end of the arm member 592. This thickness measuring device 57 can be positioned above the chuck stage 50 to measure the thickness of the wafer 90. For example, since the lifting cylinder 590 can rotate about the Z-axis, the thickness measuring device 57 disposed at the front end of the arm member 592 can also rotate and move in the horizontal plane.

[0049] The thickness measuring device 57 is, for example, a reflective photoelectric sensor having a light-emitting part and a light-receiving part, capable of measuring the thickness of the wafer 90 in a non-contact manner. The thickness measuring device 57 illuminates the wafer 90, which is positioned below it, with measuring light (infrared light). Furthermore, by resolving the interference light between the reflected light reflected from the upper surface 902 of the wafer 90 and the reflected light reflected from the lower surface 901 of the wafer 90 after passing through the wafer 90, the thickness of the wafer 90 is measured based on the optical path difference of each reflected light.

[0050] For example, you can use the "SI-F80R series" spectroscopic interferometric wafer thickness gauge provided by KEYENCE Co., Ltd.

[0051] The thickness measuring device 57 can be, for example, a contact measuring instrument that measures the height of the upper surface 902 of the wafer 90. In this case, the thickness measuring device 57 measures and holds the height position of the holding surface 502 of the chuck stage 50 beforehand using a contact measuring instrument, and therefore has a calculation unit that calculates the thickness of the wafer 90 by subtracting the height of the holding surface 502 of the chuck stage 50 from the height position of the upper surface 902 of the wafer 90 before grinding held by the holding surface 502. Therefore, the thickness measuring device 57 measures the amount removed by grinding (removal amount) of the wafer 90 based on the difference between the height position of the upper surface 902 of the wafer 90 before grinding held by the holding surface 502 and the height position of the upper surface 902 of the wafer 90 after grinding. Based on the difference with the pre-measured height position of the holding surface 502 of the chuck stage 50, the thickness of the wafer 90 can be measured.

[0052] Alternatively, the measuring instrument can be a non-contact type. For example, it may have a light-projecting section and a light-receiving section, and based on the principle of triangulation, it can measure the height position of the upper surface 902 of the wafer 90 or the height position of the holding surface 502 of the chuck stage 50. It may be a type with an oscillating section that emits ultrasonic waves and a receiving section that receives the reflected ultrasonic vibrations. In the case of such a non-contact type measuring instrument, the thickness measuring device 57 may not be configured to be movable.

[0053] The polishing apparatus 1 includes a control unit 19 capable of controlling each component of the polishing apparatus 1 as described above. The control unit 19, composed of a CPU and storage elements such as a memory, is electrically connected to, for example, the first polishing feed unit 20, the first polishing unit 30, the slider 59, and the thickness measuring device 57. Under the control of the control unit 19, it controls the polishing feed operation of the first polishing unit 30 based on the first polishing feed unit 20, the rotation operation of the first polishing pad 306 in the first polishing unit 30, and the positioning operation of the chuck stage 50 based on the slider 59 relative to the second polishing unit 32. Furthermore, it sends information, such as the in-plane thickness of the wafer 90 after the first polishing, measured by the thickness measuring device 57, to the control unit 19.

[0054] For example, as a control unit 19 controls the first grinding feed unit 20 Figure 1The motor 202 shown is, for example, a servo motor. A rotary encoder (not shown) of the motor 202 is connected to a control unit 19, which also functions as a servo amplifier. An operation signal is provided to the motor 202 from the output interface of the control unit 19, causing the ball screw 200 to rotate. The rotational speed detected by the rotary encoder (not shown) is output as an encoder signal to the input interface of the control unit 19. Furthermore, the control unit 19, having received the encoder signal, can successively identify the height of the first grinding unit 30, which is being ground by the first grinding feed unit 20, and can provide feedback control over the grinding feed speed of the first grinding unit 30.

[0055] For example, the control unit 19 controls the rotation of the slider 59 by controlling the electric motor that rotates the rotating shaft connected to the slider 59.

[0056] The following is about the use Figure 1 The following describes the use of the polishing apparatus 1 to polish the wafer 90.

[0057] First, the slider 59 is controlled by the control unit 19. Figure 1 The slide 59 is rotated, and the chuck stage 50, which is not loaded with wafer 90, rotates clockwise when viewed from the +Z direction side, for example, and moves to the vicinity of the loading arm 40. That is, the chuck stage 50 is positioned at the loading / unloading position 114. Then, the robot 155 pulls a wafer 90 from the first tray 1500 and moves the wafer 90 to the temporary storage area 152.

[0058] After the center position of the wafer 90 is detected in the temporary placement area 152 by the alignment unit 153, the loading arm 40 transports the wafer 90 to the chuck stage 50, placing the wafer 90 on the holding surface 502 of the chuck stage 50 such that the center of the wafer 90 is approximately aligned with the holding surface 502 of the chuck stage 50. Then, a suction source (not shown) is activated, and the chuck stage 50 attracts and holds the wafer 90 on the holding surface 502 with the upper surface 902 exposed.

[0059] After the chuck stage 50 attracts and holds the wafer 90, Figure 1 The slider 59 is rotated to position the chuck stage 50, which holds the wafer 90, below the first polishing unit 30. This positioning is always performed during the polishing process in such a way that the first polishing pad 306 abuts against the entire upper surface 902 of the wafer 90, that is, in such a way that the first polishing pad 306 covers the upper surface 902 of the wafer 90 held by the chuck stage 50.

[0060] Next, under the control of the control unit 19 on the first grinding feed unit 20, the first grinding unit 30 descends via the first grinding feed unit 20, and the first grinding pad 306, rotating at a predetermined speed, comes into contact with the entire upper surface 902 of the wafer 90, thereby performing, for example, dry grinding in this embodiment. Furthermore, after the chuck stage 50 rotates and grinds the entire upper surface 902 of the wafer 90 for a predetermined time, the first grinding unit 30 is raised via the first grinding feed unit 20, causing the first grinding pad 306 to leave the wafer 90. In addition, compared to the conventional method where grinding is performed while the grinding pad in contact with the upper surface 902 of the wafer 90 is moved back and forth in the horizontal direction, the grinding time of the first grinding unit 30 on the wafer 90 is shorter.

[0061] Next, for example Figure 1 The arm component 592 shown rotates to position the thickness measuring device 57 at a location that allows it to pass through the center of the upper surface 902 of the wafer 90, which has been polished using the first polishing pad 306. Furthermore, the non-contact thickness measuring device 57, for example, is positioned above the wafer 90, between the center and the outer periphery of the wafer 90. Figure 2 The arc-shaped radius region R1 shown in (A) is rotated and moved in a manner that passes through once or multiple times, while measurement light is irradiated by the projection unit toward the wafer 90 below. Furthermore, by performing beam splitting interference to resolve the interference light between the reflected light reflected from the upper surface 902 of the wafer 90 and the reflected light reflected from the lower surface 901 of the wafer 90 after passing through the wafer 90, the measurement is performed based on the optical path difference of each reflected light. Figure 2 (A) shows multiple thicknesses within the radius region R1 of wafer 90. Measurement information regarding these thicknesses is sent to... Figure 1 The control unit 19 shown.

[0062] For example, the control unit 19 has a grinding part identification unit 191, which calculates the average value of multiple thickness values ​​in the radius region R1 of the wafer 90 sent from the thickness measuring device 57 and the differences relative to the average value, thereby being able to identify the X-axis and Y-axis coordinate positions of the parts with thickness differences in the radius region R1 of the wafer 90.

[0063] In addition, the grinding part identification unit 191 can identify either the X-axis coordinate position or the Y-axis coordinate position of the part with thickness.

[0064] On the wafer 90 that has been polished by the first polishing unit 30, sometimes as Figure 2 (A) Figure 2As shown in (B), there are regions with thickness differences (e.g., regions with a thickness difference of several μm compared to other regions) that exhibit concentric circular ripples centered on the center of wafer 90, i.e., regions with greater thickness in a top-view annular shape that are difficult to grind. Furthermore, through... Figure 1 The polishing location identification unit 191 shown identifies the coordinate position of the location 905, which has a thickness compared to other areas in the radius region R1 of the wafer 90. This location 905 is identified as a designated location 905 to be polished using the second polishing pad 326. Furthermore, in this embodiment, the designated location 905 identified within the radius region R1 of the wafer 90 polished with the first polishing pad 306 as the location to be polished next using the second polishing pad 326 is the location with the largest thickness value among multiple thickness values ​​of the wafer 90 measured by the thickness measuring device 57. Additionally, regarding the identification of the designated location to be polished next using the second polishing pad 326, for example, if there are multiple locations within the radius region R1 where the thickness difference exceeds the allowable difference relative to the average value, the polishing location identification unit 191 can also identify these multiple locations as locations to be polished using the second polishing pad 326.

[0065] In addition, the difference between adjacent thickness values ​​among multiple thickness values ​​can be calculated. If the calculated difference exceeds a preset allowable value, it is determined that the part should be polished using the second polishing pad 326.

[0066] Next, through Figure 1 The control unit 19 shown controls the slider 59 and the horizontal movement unit 23. Figure 1 The slider 59 shown rotates clockwise when viewed from the +Z direction side, and the second polishing unit 32 is moved in the X-axis direction by the horizontal moving unit 23. The wafer 90 held by the chuck stage 50 is aligned with the second polishing pad 326 in such a way that the second polishing pad 326 of the second polishing unit 32 covers the specified part 905 to be polished within the radius region R1 of the wafer 90 held by the chuck stage 50.

[0067] Under the control of the control unit 19 on the second polishing feed unit 22, the second polishing unit 32 descends via the second polishing feed unit 22, and the second polishing pad 326, rotating at a predetermined rotational speed, comes into contact with a predetermined portion 905 of the radius region R1 of the wafer 90 that has been polished by the first polishing pad 306, thereby performing, for example, dry polishing in this embodiment. Furthermore, the chuck stage 50 is rotated, thereby polishing the entire circumference of the thicker annular portion 905 of the wafer 90 from a top view using the second polishing pad 326. The thickness difference between the predetermined portion 905 and other portions of the wafer 90 is as small as a few μm, therefore the polishing time of the second polishing pad 326 is significantly reduced compared to the polishing time of the first polishing pad 306.

[0068] After grinding the entire circumference of the specified portion 905 of the radius region R1 (around the center of the holding surface 502) for a specified time to further improve the flatness of the wafer 90, the second grinding unit 32 is raised by the second grinding feed unit 22, causing the second grinding pad 326 to leave the wafer 90. Next, the unloading arm 41 attracts and holds the upper surface 902 of the wafer 90, which is positioned at the loading / unloading position 114, and transfers it from the chuck table 50 to the cleaning unit 156. After the wafer 90 is cleaned and dried in the cleaning unit 156, the robot 155 removes the wafer 90 from the cleaning unit 156 and stores it in the second box 1510.

[0069] As described above, the polishing apparatus 1 of the present invention includes: a first polishing unit 30, which arranges a first polishing pad 306 having a lower surface having an area covering at least the upper surface 902 of the wafer 90 at the lower end of a first spindle 300; and a second polishing unit 32, which arranges a second polishing pad 326 having a lower surface having a diameter smaller than the diameter of the wafer 90 at the lower end of a second spindle 320, thereby controlling the following by the control unit 19: moving the chuck stage 50 below the first polishing pad 306 to polish the wafer 90 held by the holding surface 502 using the first polishing pad 306; and using The second polishing pad 326 is used to polish a predetermined portion 905 of the radius region R1 of the wafer 90 that has been polished with the first polishing pad 306. This portion 905, which has a thickness difference compared to other portions of the wafer 90 due to the polishing of the wafer 90 with the first polishing pad 306, is for example, a portion 905 whose center is aligned with the center of the wafer 90 and is circular in plan view. Compared with the conventional case where the polishing unit of a single axis that contacts the wafer moves in the horizontal direction while polishing the wafer 90, the total polishing time can be shortened and the in-plane thickness of the polished wafer 90 can be made uniform.

[0070] The polishing apparatus 1 of the present invention includes: a horizontal moving unit 23 that moves a second polishing unit 32 in the horizontal direction; and a thickness measuring device 57 that measures the thickness of a wafer 90 that has been polished with a first polishing pad 306 and is held on the holding surface 502 of a chuck stage 50. The specified location to be polished with the second polishing pad 326 is the location 905 with the largest thickness value among the multiple thickness values ​​of the wafer 90 measured by the thickness measuring device 57. The second polishing pad 326 of the second polishing unit 32 can be positioned at the specified location by the horizontal moving unit 23. As a result, compared with the case where the polishing of the wafer 90 is performed while the single-axis polishing unit that contacts the wafer in the horizontal direction is moved, the total polishing time can be shortened and the in-plane thickness of the polished wafer 90 can be made uniform.

[0071] (Implementation Method 2)

[0072] Figure 3 The grinding apparatus 18 shown (hereinafter referred to as the grinding apparatus 18 of Embodiment 2) is used for... Figure 1 Part of the structure of the grinding apparatus 1 in Embodiment 1 has been modified. The same structural reference numerals are shown as those for the grinding apparatus 1, and the description is omitted. For example, the structure on the first device base 10 of the grinding apparatus 18 in Embodiment 2 is the same as that of the grinding apparatus 1 in Embodiment 1.

[0073] Hereinafter, the grinding apparatus 18 of Embodiment 2 and Figure 1 Different structures of the grinding apparatus 1 in Embodiment 1 will be described.

[0074] For example, Figure 3 As shown, the first device base 10 is provided with a holding surface 502 for moving the wafer 90 into the chuck stage 50 or a conveying unit 4 for moving the wafer 90 out of the holding surface 502. Only a first column 12 is erected at the rear of the second device base 11. A first grinding unit 30 is provided on the front surface of the first column 12 by means of the first grinding feed unit 20.

[0075] For example, two chuck stages 50 are provided on the upper surface of the slider 59. These two chuck stages 50 are arranged at equal intervals around the center of the slider 59 in the circumferential direction and have a holding surface 502 for holding the wafer 90. Furthermore, the slider 59 can position the chuck stages 50 in the following positions: a first grinding position where the wafer 90 held by the holding surface 502 is ground using the first grinding pad 306, i.e., below the first grinding unit 30; or a second grinding position where the wafer 90 held by the holding surface 502 is ground using the second grinding pad 364, i.e., below the second grinding unit 36; or a loading / unloading position 114 where the wafer 90 is loaded into or removed from the holding surface 502 by the transport unit 4.

[0076] In the grinding apparatus 18 of Embodiment 2, a portal column 110 is erected on the second apparatus base 11 in a manner that spans approximately the center of the slider 59. A horizontal moving unit 23 capable of moving the second grinding unit 36 ​​in the X-axis direction is provided on the front surface of the portal column 110.

[0077] A second grinding feed unit, such as an electric slider (not shown), is provided on the movable plate 233 of the horizontal moving unit 23 to move the second grinding unit 36 ​​up and down in the Z-axis direction.

[0078] The second grinding unit 36, which can move in the X-axis direction via the horizontal moving unit 23 and can move up and down in the Z-axis direction via the second grinding feed unit (not shown), supports the second spindle 362 in a non-contact manner via a housing 361 containing an air bearing or the like. A second grinding pad 364 is mounted on the lower end of the second spindle 362 via a mounting base 363 and a pressure plate (not shown). The raw material, diameter, and other properties of the second grinding pad 364 are described. Figure 1 The second abrasive pad 326 shown is the same.

[0079] For example, a support block 235, which is roughly L-shaped when viewed from the side, is provided on the movable plate 233 of the horizontal moving unit 23. The thickness measuring instrument 57 is positioned at the lower loading and unloading position 114 by the support block 235 so that it can be supported in a way that it is opposite to the wafer 90 held by the holding surface 502 of the chuck stage 50 in the Z-axis direction.

[0080] The following is about the use Figure 3 The case of the polishing apparatus 18 of Embodiment 2 polishing the wafer 90 will be described.

[0081] From the holding of the wafers 90 by the chuck stage 50 to the grinding of the wafers 90 by the first grinding unit 30, according to... Figure 1 The grinding apparatus 1 of Embodiment 1 shown is also performed in the grinding apparatus 18 in the same manner.

[0082] Next, for example, under the control of the slider 59 by the control unit 19, the slider 59 rotates clockwise when viewed from the +Z direction side, positioning the chuck stage 50 holding the wafer 90, which has been polished by the first polishing unit 30, at the loading / unloading position 114. Furthermore, the thickness measuring device 57 is moved in the X-axis direction by the horizontal movement unit 23, positioning it so that it can pass through the center of the upper surface 902 of the wafer 90 held by the chuck stage 50 at the loading / unloading position 114. Additionally, for example, the non-contact thickness measuring device 57 moves horizontally in the X-axis direction, passing through the radial region (in this embodiment, the radial region is a straight line, i.e., the radius) above the wafer 90 once or multiple times, while irradiating the wafer 90 downwards with measuring light from the light-projecting unit. Multiple thicknesses within the radial region of the wafer 90 are measured. Each measurement of this thickness is sent to the control unit 19.

[0083] Furthermore, the grinding part identification unit 191 identifies the areas of the wafer 90 that are thicker than other areas within the radius region. Figure 2 (A) Figure 2 The coordinate position of part 905 shown in (B). Furthermore, in this embodiment, part 905 is the part with the largest thickness value among the multiple thickness values ​​of the wafer 90 measured using the thickness measuring device 57. Next, by... Figure 2 The control unit 19 shown controls the slider 59 or the horizontal movement unit 23 to align the wafer 90 with the second polishing pad 364 in such a way that the second polishing pad 364 of the second polishing unit 36 ​​covers the specified part 905 of the wafer 90 held by the chuck stage 50 to be polished.

[0084] Furthermore, the second polishing unit 36 ​​is lowered, bringing the second polishing pad 364, which rotates at a predetermined speed, into contact with a predetermined portion 905 of the radius region of the wafer 90. This allows for, for example, dry polishing in this embodiment. Additionally, the chuck stage 50 rotates, thereby polishing the entire circumference of the thicker, annular portion 905 of the wafer 90 from a top view using the second polishing pad 364. Since the thickness difference between the predetermined portion 905 and other portions of the wafer 90 is only a few μm, the polishing time of the second polishing pad 364 is significantly reduced compared to the polishing time of the first polishing pad 306. After polishing the entire circumference of the predetermined portion 905 of the radius region for a predetermined time, further improving the flatness of the wafer 90, the second polishing pad 364 is removed from the wafer 90, ending the polishing process.

[0085] As described above, the polishing apparatus 18 of the present invention includes a conveying unit 4, which conveys the wafer 90 into or out of the holding surface 502 of the chuck stage 50. A slider 59 can position the chuck stage 50 in a first polishing position, a second polishing position, or a conveying-in / conveying position 114. In the first polishing position, the wafer 90 held by the holding surface 502 is polished using a first polishing pad 306. In the second polishing position, the wafer 90 held by the holding surface 502 is polished using a second polishing pad 364. In the conveying-in / conveying position 114, the wafer 90 is conveyed into or out of the holding surface 502 by the conveying unit 4. The control unit 19... The following control can be performed: the wafer 90 held on the holding surface 502 is polished using the first polishing pad 306; the wafer 90 polished using the first polishing pad 306 is moved to the loading / unloading position 114 and the thickness is measured using the thickness measuring device 57; and the portion 905 with the largest thickness value among the multiple thickness values ​​of the wafer 90 measured by the thickness measuring device 57 is designated as the portion 905 and polished using the second polishing pad 364. As a result, compared with the conventional case where the single-axis polishing unit that contacts the wafer 90 moves in the horizontal direction while polishing the wafer 90, the polishing time can be shortened and the in-plane thickness of the polished wafer 90 can be made uniform.

[0086] (Implementation Method 3)

[0087] Figure 4 The grinding apparatus 17 shown (hereinafter referred to as the grinding apparatus 17 of Embodiment 3) is used for... Figure 1 The structure of the grinding apparatus 1 in Embodiment 1 shown has been modified. For the same structure, it is shown with the same reference numerals as the grinding apparatus 1, and the description is omitted.

[0088] Hereinafter, the structure of the grinding apparatus 17 of Embodiment 3, which differs from that of the grinding apparatus 1 of Embodiment 1, will be described.

[0089] The grinding apparatus 17 of Embodiment 3 has a gate-shaped column 110 described in the grinding apparatus 18 of Embodiment 2, and an X-axis moving unit 38 that can move the third grinding unit 37 in the X-axis direction is provided on the front surface of the gate-shaped column 110.

[0090] The X-axis moving unit 38 includes: a ball screw 380 having an axis in the X-axis direction; a pair of guide rails 381 arranged parallel to the ball screw 380; a motor 382 connected to the ball screw 380 to rotate the ball screw 380; and a movable plate 383, the nut inside of which is screwed into the ball screw 380. The side of the movable plate 383 is in sliding contact with the guide rails 381. When the motor 382 rotates the ball screw 380, the movable plate 383 is guided by the guide rails 381 to move in the X-axis direction. A third grinding unit 37, which is arranged on the movable plate 383 by means of a third grinding feed unit (not shown), also moves in the X-axis direction.

[0091] A third grinding feed unit, such as an electric slider (not shown), is provided on the movable plate 383 of the X-axis moving unit 38 to move the third grinding unit 37 up and down in the Z-axis direction.

[0092] The third grinding unit 37, which can move in the X-axis direction via the X-axis moving unit 38 and can move up and down in the Z-axis direction via the third grinding feed unit (not shown), supports the third spindle 372 via a housing 371 containing an air bearing or the like, and a third grinding pad 375 is mounted on the lower end of the third spindle 372 via a mounting base 373 and a pressure plate (not shown).

[0093] The third abrasive pad 375, for example, is made of... Figure 1 The first polishing pad 306 or the second polishing pad 326 shown are formed from the same raw materials and are set to have a diameter smaller than the radius of the wafer 90 and capable of surrounding the size of the second polishing pad 326.

[0094] In addition, the X-axis moving unit 38 and the third grinding unit 37 can be disposed on the back of the portal column 110, and the disposal positions of the third grinding unit 37 and the second grinding unit 32 can be interchanged.

[0095] exist Figure 4 In the example shown, a thickness measuring device 57 that can be rotated and moved by the arm component 592 is provided on the slider 59, and a thickness measuring device 57 that can be moved along the X-axis by the X-axis moving unit 38 together with the third grinding unit 37 is provided on the front surface of the portal column 110, but it is sufficient to provide at least one of the thickness measuring devices 57.

[0096] The following is about the use Figure 4 The case of the polishing apparatus 17 of Embodiment 3 polishing the wafer 90 will be described.

[0097] The chuck stage 50 holds the wafer 90, the first grinding unit 30 grinds the wafer 90, and the thickness measuring device 57 on the slide 59, for example, holds the wafer 90. Figure 2 (A) Figure 2In the thickness measurement within the radius region R1 shown in (B) and the identification of the grinding part 905 of the wafer 90 by the grinding part identification unit 191, according to the... Figure 1 The grinding apparatus 1 of Embodiment 1 shown is also performed in the grinding apparatus 17 in the same manner.

[0098] Next, the slider 59 and the X-axis movement unit 38 are controlled by the control unit 19. Figure 4 The slider 59 shown rotates, and the third polishing unit 37 is moved in the X-axis direction by the X-axis moving unit 38, so as to polish the wafer 90 held by the chuck stage 50 by the third polishing pad 375 of the third polishing unit 37. Figure 2 (A) Figure 2 Position the chuck table 50 in the manner specified in part 905 as shown in (B).

[0099] Furthermore, the third polishing unit 37 descends, and the third polishing pad 375, rotating at a predetermined speed, comes into contact with the wafer 90. Figure 2 (A) Figure 2 The specified portion 905 of the radius region R1 shown in (B) abuts against the wafer, thereby performing dry polishing, for example, in this embodiment. In addition, the chuck stage 50 rotates, thereby polishing the entire circumference of the thicker annular portion 905 of the wafer 90 in a tracing manner for a short time by the third polishing pad 375, and then removing the third polishing pad 375 from the wafer 90.

[0100] Next, the slider 59 is rotated by the control unit 19, and the second polishing unit 32 is moved in the X-axis direction by the horizontal moving unit 23. The chuck stage 50, which holds the wafer 90, is positioned such that the second polishing pad 326 of the second polishing unit 32 covers the designated portion 905 of the wafer 90 held by the chuck stage 50 and polished by the third polishing pad 375 in a tracing manner. Afterward, the wafer 90 is polished using the same process as in the polishing apparatus 1 of Embodiment 1 described above, with the second polishing pad 326 polishing the portion 905 of the wafer 90 that has a thickness difference compared to other portions, and a flat wafer 90 can be produced.

[0101] As described above, the polishing apparatus 17 of Embodiment 3 has a third polishing unit 37. The third polishing unit 37 has a third polishing pad 375, which is made of a diameter smaller than that of the wafer 90 and can surround the size of the second polishing pad 326, disposed at the lower end of the third spindle. The third polishing pad 375 is used to polish a predetermined portion 905 of the wafer 90 that has been polished with the first polishing pad 306 in a tracing manner for a short time. Then, the second polishing pad 326 is used to polish the predetermined portion 905 of the wafer 90 that has an in-plane thickness difference, thereby making the in-plane thickness of the polished wafer 90 more uniform.

[0102] Furthermore, the grinding apparatus of the present invention is not limited to the grinding apparatus 1 of Embodiment 1, the grinding apparatus 18 of Embodiment 2, and the grinding apparatus 17 of Embodiment 3, and can be appropriately modified within the scope of being able to exert the effects of the present invention.

Claims

1. A grinding apparatus, comprising: Chuck The worktable utilizes a holding surface to hold the wafer; A table rotation unit that rotates the chuck table; The polishing unit has a polishing pad for polishing the wafer positioned at the lower end of the spindle and uses the lower surface of the polishing pad to polish the wafer. A slider that rotates the chuck stage about a vertical axis of rotation or moves it in a straight line in the horizontal direction to a grinding position where the grinding unit can grind the wafer held by the holding surface. as well as Control unit in, The grinding unit has: The first polishing unit has a first polishing pad having a lower surface having an area that covers at least the entire upper surface of the wafer disposed at the lower end of the first spindle. The second polishing unit has a second polishing pad with a lower surface having a diameter smaller than that of the wafer disposed at the lower end of the second spindle; A horizontal moving unit that moves the second grinding unit in the horizontal direction; The third polishing unit has a third polishing pad, which is made of a diameter smaller than the radius of the wafer and capable of surrounding the size of the second polishing pad, disposed at the lower end of the third spindle. The X-axis moving unit moves the third grinding unit in the horizontal direction; and A thickness measuring device that measures the thickness of a wafer that has been polished using the first polishing pad and held on the holding surface. The control unit performs the following control functions: The chuck stage is moved to a position below the first polishing pad, and the wafer held on the holding surface is polished using the first polishing pad. This thickness measuring instrument is used to measure multiple thickness values ​​of the wafer in an arc-shaped or straight radial region from the center of the wafer to its outer perimeter; Polishing is performed by tracing using a third polishing pad, which is positioned by the X-axis movement unit on a ring-shaped area centered on the wafer and having a thickness difference compared to other areas, based on multiple thickness values ​​of the wafer measured by the thickness gauge; and Fine polishing is performed using the second polishing pad, which is positioned by the horizontal moving unit on a top-view annular portion of the wafer that has a thickness difference from other portions and is based on multiple thickness values ​​of the wafer measured by the thickness measuring device.

2. The grinding apparatus according to claim 1, wherein, The grinding device has two or more of the second grinding units.

Images