Processing equipment and workpiece processing method

Abstract

This reduces power consumption when processing a workpiece by pressing the processing tool against it, while also avoiding the need for larger processing equipment. [Solution] The Z-axis ball screw 52 is rotated by the downward pressing force applied to the polishing mechanism 70 from the counterbalance 60 and the weight of the polishing mechanism 70, thereby lowering the polishing mechanism 70 and polishing the wafer 100. Therefore, the force (pressing force) that the polishing pad 77 presses against the wafer 100 can be easily increased. As a result, power consumption for lowering the polishing mechanism 70 can be reduced. In addition, since no upward force from the counterbalance 60 is applied to the Z-axis ball screw 52 during polishing, there is no need to use a thick ball screw that can withstand strong forces as the Z-axis ball screw 52. Therefore, it is possible to avoid increasing the size of the polishing device 1.

Description

Technical Field

[0001] The present invention relates to a processing apparatus and a method for processing a workpiece.

Background Art

[0002] As disclosed in Patent Documents 1 to 3, in a grinding apparatus, a spindle unit (processing unit) equipped with a grinding wheel is lowered, and the grinding wheel is pressed against a wafer to grind the wafer to a predetermined thickness.

[0003] For the raising and lowering of this spindle unit, the grinding apparatus includes a lifting mechanism and a counterbalance. The lifting mechanism rotates a ball screw extending in the vertical direction by a motor connected to the ball screw to raise and lower the spindle unit. The counterbalance applies an upward force to the spindle unit when lowering the spindle unit. As a result, the spindle unit can be lowered while maintaining a state where the backlash of the ball screw is eliminated, so that the lowering amount of the spindle unit can be accurately controlled.

[0004] Also, in the technique disclosed in Patent Document 4 regarding the grinding of wafers, a grinding wheel is pressed against a wafer with a predetermined pressing force.

[0005] In addition, the above counterbalance is also used in a polishing apparatus having a spindle unit equipped with a polishing pad instead of a grinding wheel, and pressing the polishing pad against a wafer to polish the wafer. In the technique disclosed in Patent Document 5 regarding the polishing of wafers, a polishing pad is pressed against a wafer with a predetermined pressing force.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] In the polishing apparatus equipped with the counterbalance described above, the force that lowers the spindle unit by the ball screw is greater than the upward force exerted by the counterbalance, and the ball screw is counteracting this upward force. Therefore, if it is desired to increase the force with which the polishing pad is pressed against the wafer in the polishing apparatus, it is necessary to supply a large amount of power to the motor and to use a thick ball screw that can withstand the strong force.

[0008] Therefore, the object of the present invention is to reduce power consumption when processing a workpiece by pressing a processing tool against it, and to avoid increasing the size of the processing equipment used to perform such processing. [Means for solving the problem]

[0009] The present invention (this processing apparatus) is a processing apparatus comprising a chuck table for holding a workpiece, a processing unit for processing the workpiece held on the chuck table with a processing tool, and a lifting mechanism for raising and lowering the processing unit in the vertical direction, wherein the lifting mechanism comprises a ball screw extending vertically while screwed into a threaded member connected to the processing unit, a motor for rotating the ball screw, a guide rail arranged parallel to the ball screw and guiding the vertical movement of the processing unit, and a counterbalance for canceling the weight of the processing unit, The counterbalance further comprises a control unit which includes a cylinder, a piston connected to the machining unit and sliding vertically within the cylinder, an upper biasing unit which biases the piston and the machining unit upward, and a lower biasing unit which biases the piston and the machining unit downward, and by biasing the machining unit downward with the lower biasing unit, the downward force caused by this bias and the weight of the machining unit rotate the ball screw to lower the machining unit, press the machining tool against the workpiece held in the chuck table, and machine the workpiece.

[0010] The processing apparatus may further include a contact detection unit that detects when the processing tool comes into contact with the workpiece. The control unit may lower the processing unit by rotating the ball screw while biasing the processing unit upward with the upward biasing unit until the contact detection unit detects contact between the workpiece and the processing tool. Once the contact detection unit detects contact between the workpiece and the processing tool, the control unit may bias the processing unit downward with the downward biasing unit, thereby rotating the ball screw and lowering the processing unit using the downward force from this biasing and the weight of the processing unit itself, pressing the processing tool against the workpiece held in the chuck table to process the workpiece.

[0011] A first machining method of the present invention is a method of machining a workpiece using the machining apparatus, comprising: biasing a machining unit, which is positioned above a workpiece held on the chuck table and equipped with a machining tool, downward by the downward biasing unit; thereby rotating the ball screw due to the downward force caused by this biasing and the weight of the machining unit itself, lowering the machining unit, pressing the machining tool against the workpiece, and machining the workpiece.

[0012] A second processing method of the present invention is a method for processing a workpiece using the processing apparatus, comprising: biasing the processing unit, which is positioned above a workpiece held on the chuck table and equipped with the processing tool, downward by the downward biasing unit, thereby rotating the ball screw and lowering the processing unit due to the downward force caused by this biasing and the weight of the processing unit; and applying an upward force to the processing unit by rotating the ball screw with the motor, thereby pressing the processing tool against the workpiece and processing the workpiece so that the load applied from the processing tool to the chuck table falls within a predetermined range. [Effects of the Invention]

[0013] In this invention, the processing unit is lowered and the workpiece is processed by rotating a ball screw using a downward force (pressing force) applied to the processing unit from the counterbalance and the weight of the processing unit itself.

[0014] Therefore, compared to a configuration where the processing unit is lifted by a counterbalance and lowered by a lifting mechanism to press the processing tool against the workpiece, the force with which the processing tool presses against the workpiece (pressing force) can be easily increased. As a result, the processing time for the workpiece can be shortened and productivity can be improved. In addition, power consumption for lowering the processing unit can be reduced.

[0015] In addition, since an upward force from the counterbalance is not applied to the ball screw during machining, there is no need to use a thick ball screw that can withstand a strong force. Therefore, it is possible to avoid increasing the size of the machining apparatus.

Brief Description of the Drawings

[0016] [Figure 1] It is a cross-sectional view showing the configuration of the polishing apparatus. [Figure 2] FIG. 2(a) is a graph showing the change over time of the height of the polishing pad, and FIG. 2(b) is a diagram showing an enlarged view of the range A in FIG. 2(a). [Figure 3] It is a cross-sectional view showing the Z-axis ball screw and nut. [Figure 4] FIG. 4(a) is a graph showing the change over time of the height of the polishing pad, and FIG. 4(b) is a diagram showing an enlarged view of the range B in FIG. 4(a).

Embodiments for Carrying Out the Invention

[0017] As shown in FIG. 1, the polishing apparatus 1 according to the present embodiment is an apparatus for polishing a wafer 100 as an example of a workpiece.

[0018] The wafer 100 is, for example, a circular semiconductor wafer and includes a front surface 101 and a back surface 102. In FIG. 1, the front surface 101 of the wafer 100 facing downward holds, for example, a plurality of devices and is protected by attaching a protective tape 103. The back surface 102 of the wafer 100 becomes the surface to be polished that is polished.

[0019] The polishing apparatus 1 has a control unit 7 that comprehensively controls the entire apparatus, and a wafer holding mechanism 30 including a chuck table 20.

[0020] The wafer holding mechanism 30 includes a chuck table 20 for holding wafers 100, a chuck table base 25 for supporting the chuck table 20, a rotation mechanism 26 for rotating the chuck table 20 and the chuck table base 25, and a plurality of support columns 28 for supporting the chuck table base 25. The support columns 28 are equipped with load sensors 281 for detecting the load applied to the chuck table 20 (and the wafers 100 held on the chuck table 20).

[0021] The chuck table 20 has a roughly disc-shaped base (frame) 23, and a holding part 21 made of a porous material such as porous ceramics is located in a recess provided on the upper part of the base 23. The upper surface of the holding part 21 is a holding surface 22 that holds the wafer 100 by suction. In the chuck table 20, the holding part 21 is connected to a suction source (not shown), so that the wafer 100 can be held by suction through the holding surface 22.

[0022] The rotation mechanism 26 rotates the chuck table 20 and the chuck table base 25 about a central axis that extends in the Z-axis direction passing through the center of the holding surface 22.

[0023] Furthermore, a horizontal movement mechanism 40 is provided below the wafer holding mechanism 30. The horizontal movement mechanism 40 moves the chuck table 20 and the polishing mechanism 70 relative to each other in the Y-axis direction, which is parallel to the holding surface 22. In this embodiment, the horizontal movement mechanism 40 is configured to move the wafer holding mechanism 30, including the chuck table 20, in the Y-axis direction relative to the polishing mechanism 70.

[0024] The horizontal movement mechanism 40 includes a pair of Y-axis guide rails 42 parallel to the Y-axis direction, a Y-axis movement table 45 that slides on the Y-axis guide rails 42, a Y-axis ball screw 43 parallel to the Y-axis guide rails 42, a Y-axis motor 44 connected to the Y-axis ball screw 43, a Y-axis encoder 46 for detecting the amount of rotation of the Y-axis ball screw 43, and a holder 41 for holding these together.

[0025] The Y-axis moving table 45 is slidably mounted on the Y-axis guide rail 42 via a sliding member 451. A nut 401 is provided on the underside of the Y-axis moving table 45. A Y-axis ball screw 43 is screwed onto this nut 401. The Y-axis motor 44 is connected to one end of the Y-axis ball screw 43.

[0026] In the horizontal movement mechanism 40, the Y-axis motor 44 rotates the Y-axis ball screw 43, causing the Y-axis movement table 45 to move in the Y-axis direction along the Y-axis guide rail 42. The wafer holding mechanism 30 is installed on the Y-axis movement table 45. Therefore, as the Y-axis movement table 45 moves in the Y-axis direction, the wafer holding mechanism 30, including the chuck table 20, also moves in the Y-axis direction.

[0027] In this embodiment, the chuck table 20 is moved along the Y-axis direction by a horizontal movement mechanism 40 between a wafer placement area on the -Y direction side for placing the wafer 100 on the holding surface 22 and a polishing area on the +Y direction side where the wafer 100 is polished.

[0028] Furthermore, the Y-axis encoder 46 of the horizontal movement mechanism 40 is rotated by the Y-axis motor 44 rotating the Y-axis ball screw 43, and can recognize the amount of rotation of the Y-axis ball screw 43 (number of rotations and rotation angle). In this embodiment, the control unit 7 can detect the position of the chuck table 20 in the Y-axis direction based on the amount of rotation of the Y-axis ball screw 43 recognized by the Y-axis encoder 46.

[0029] Furthermore, a column 3 is erected on the +Y direction side of the wafer holding mechanism 30. A polishing mechanism 70 for polishing the wafer 100 and a lifting mechanism 50 are provided on the front surface of the column 3.

[0030] The lifting mechanism 50 raises and lowers the polishing mechanism 70 in the vertical direction (Z-axis direction). The lifting mechanism 50 moves the chuck table 20 and the polishing mechanism 70 relative to each other in the Z-axis direction (polishing feed direction), which is perpendicular to the holding surface 22. In this embodiment, the lifting mechanism 50 is configured to move the polishing mechanism 70 up and down in the Z-axis direction relative to the wafer holding mechanism 30, which includes the chuck table 20.

[0031] The lifting mechanism 50 includes a pair of Z-axis guide rails 51 parallel to the Z-axis direction, a Z-axis moving table 53 that slides on the Z-axis guide rails 51, a Z-axis ball screw 52 parallel to the Z-axis guide rails 51, a Z-axis motor 54 which is a motor that rotates the Z-axis ball screw 52, ​​a Z-axis encoder 55 for detecting the amount of rotation of the Z-axis ball screw 52, ​​and a holder 56 attached to the Z-axis moving table 53. The holder 56 holds the polishing mechanism 70.

[0032] The Z-axis moving table 53 is slidably mounted on the Z-axis guide rail 51 via a sliding member 531. The Z-axis moving table 53 is provided with a nut 57. That is, the nut 57 is connected to the polishing mechanism 70 via the Z-axis moving table 53 and a holder 56. A Z-axis ball screw 52 extending in the Z-axis direction is screwed onto this nut 57. Therefore, the Z-axis ball screw 52 extends in the Z-axis direction (vertical direction) while screwed onto the nut 57 connected to the polishing mechanism 70. Furthermore, the Z-axis motor 54 is connected to one end of the Z-axis ball screw 52.

[0033] In the lifting mechanism 50, the Z-axis motor 54 rotates the Z-axis ball screw 52, ​​causing the Z-axis moving table 53 to move in the Z-axis direction along the Z-axis guide rail 51. As a result, the holder 56 attached to the Z-axis moving table 53, and the polishing mechanism 70 held in the holder 56, move together with the Z-axis moving table 53 along the Z-axis guide rail 51 in the Z-axis direction. Thus, the Z-axis guide rail 51 is positioned parallel to the Z-axis moving table 53 and guides the movement of the polishing mechanism 70 in the Z-axis direction (vertical direction).

[0034] Furthermore, the Z-axis encoder 55 of the lifting mechanism 50 is rotated by the Z-axis motor 54 rotating the Z-axis ball screw 52, ​​and can recognize the amount of rotation of the Z-axis ball screw 52 (number of rotations and rotation angle). In this embodiment, the control unit 7 can detect the height (height position) of the polishing mechanism 70 that is moved in the Z-axis direction based on the amount of rotation of the Z-axis ball screw 52 recognized by the Z-axis encoder 55. The height position of the polishing mechanism 70 is, for example, the height position of the lower surface of the polishing pad 77.

[0035] The polishing mechanism 70 is an example of a processing unit that processes a wafer 100 held on a chuck table 20 using a processing tool. The polishing mechanism 70 polishes the wafer 100, which is held by suction on the holding surface 22, with a polishing pad 77. The polishing mechanism 70 includes a spindle housing 71 fixed to a holder 56, a spindle 72 rotatably held in the spindle housing 71, a spindle motor 73 that rotationally drives the spindle 72, a wheel mount 74 attached to the lower end of the spindle 72, and a polishing wheel 75 supported by the wheel mount 74.

[0036] The spindle housing 71 is held in the holder 56 so as to extend in the Z-axis direction. The spindle 72 extends in the Z-axis direction so as to be perpendicular to the holding surface 22 of the chuck table 20 and is rotatably supported in the spindle housing 71.

[0037] The spindle motor 73 is connected to the upper end of the spindle 72 inside the spindle housing 71. This spindle motor 73 causes the spindle 72 to rotate around a rotation axis that extends in the Z-axis direction.

[0038] The wheel mount 74 is formed in a disc shape and is fixed to the lower end (tip) of the spindle 72. The wheel mount 74 supports the polishing wheel 75.

[0039] The polishing wheel 75 is formed to have an outer diameter approximately the same as the outer diameter of the wheel mount 74. The polishing wheel 75 includes a wheel base 76 formed from a metal material.

[0040] A polishing pad 77 is provided on the lower surface of the wheel base 76. The polishing pad 77 is an example of a processing tool for processing the wafer 100. The polishing pad 77 is made of a nonwoven fabric such as felt. The lower surface of the polishing pad 77 becomes the polishing surface for polishing the back surface 102 of the wafer 100. The polishing pad 77 is rotated by the spindle motor 73 together with the spindle 72 around its center axis, and polishes the back surface 102 of the wafer 100 held in the chuck table 20.

[0041] The polishing in the polishing apparatus 1 may be CMP polishing using a polishing liquid. In this case, the polishing mechanism 70 has a polishing liquid supply mechanism (not shown) for supplying polishing liquid to the polishing pad 77. When polishing is performed by the polishing pad 77, the polishing liquid supply mechanism supplies polishing liquid from a polishing liquid supply source, for example, through a polishing liquid supply passage (not shown) in the spindle 72, to the back surface 102 of the wafer 100, which is the surface to be polished, and the lower surface of the polishing pad 77.

[0042] Furthermore, the outer diameters of the polishing wheel 75 and the polishing pad 77 are designed to be larger than the outer diameter of the wafer 100. For this reason, the polishing fluid supply mechanism may be configured to spray polishing fluid onto the portion of the underside of the polishing pad 77 that extends beyond the wafer 100 when the wafer 100 is polished by the polishing pad 77. Furthermore, polishing in the polishing apparatus 1 may be dry polishing without the use of polishing fluid. In this case, the polishing mechanism 70 does not need to have a polishing fluid supply mechanism.

[0043] Furthermore, the lifting mechanism 50 is equipped with a pair of counterbalances 60 that cancel out the weight of the polishing mechanism 70.

[0044] The counterbalance 60 supports the outer surfaces of the holder 56 that holds the polishing mechanism 70 on the +X and -X sides, and counteracts the weight of the polishing mechanism 70 by lifting it with a force corresponding to its own weight. Note that the number of counterbalances 60 is not limited to one pair (two), but may be one or three or more.

[0045] In this embodiment, the counterbalance 60 is an air cylinder, and as shown in Figure 1, it comprises a cylindrical cylinder (cylinder case) 61, a piston 62 disposed inside the cylinder 61 and sliding vertically within the cylinder 61, and a piston rod 63 inserted into the cylinder 61 with its upper end attached to the piston 62. The lower end of the piston rod 63 is connected to a holder 56 that supports the polishing mechanism 70. Therefore, the piston 62 is connected to the polishing mechanism 70 via the piston rod 63 and the holder 56.

[0046] The upper end of the cylinder 61 is connected to a crane-shaped support arm 59 erected on the upper surface of the column 3. A first supply port 64 is formed in the cylinder 61 at a position below the sliding range of the piston 62. A second supply port 65 is formed in the cylinder 61 at a position above the sliding range of the piston 62.

[0047] The first supply port 64 is connected to the air supply source 201 via the first air passage 641 and the air valve 66. The second supply port 65 is connected to the air supply source 201 via the second air passage 651 and the air valve 66.

[0048] The air valve 66 is configured to allow compressed air or other air to be supplied from the air supply source 201 to either the first supply port 64 or the second supply port 65 by connecting either the first supply port 64 or the second supply port 65 to the air supply source 201.

[0049] The air supplied to the first supply port 64 via the air valve 66 is introduced into the space below the piston 62 inside the cylinder 61, biasing the piston 62, which is connected to the polishing mechanism 70, upward. Thus, the first supply port 64 and the air valve 66 function as an upward biasing unit that biases the piston 62 and the polishing mechanism 70 upward.

[0050] Furthermore, the air supplied to the second supply port 65 via the air valve 66 is introduced into the space above the piston 62 inside the cylinder 61, biasing the piston 62 connected to the polishing mechanism 70 downward. Thus, the second supply port 65 and the air valve 66 function as downward biasing units that bias the piston 62 and the polishing mechanism 70 downward.

[0051] Furthermore, a pressure sensor 67 is provided in the first air passage 641 between the air valve 66 and the first supply port 64. This pressure sensor 67 is for measuring the pressure of the air supplied from the first supply port 64 to the space below the piston 62 inside the cylinder 61. Furthermore, a pressure sensor 68 is provided in the second air passage 651 between the air valve 66 and the second supply port 65. This pressure sensor 68 is for measuring the pressure of the air supplied from the second supply port 65 to the space above the piston 62 inside the cylinder 61.

[0052] Furthermore, an electro-pneumatic regulator 69 is provided in the air supply path between the air supply source 201 and the air valve 66. The electro-pneumatic regulator 69, pressure sensor 68, and pressure sensor 67 are connected to the control unit 7. The control unit 7 controls the electro-pneumatic regulator 69 so that the pressure value of pressure sensor 68 or pressure sensor 67 becomes a predetermined pressure value, thereby adjusting the pressure of the air supplied from the air supply source 201 to the cylinder 61. The predetermined pressure value is set, for example, by an operator using a setting unit (not shown) of the polishing device 1.

[0053] For example, in this embodiment, the control unit 7 uses an electro-pneumatic regulator 69 to adjust the pressure of the air supplied from the air supply source 201 to the cylinder 61 via the air valve 66 and the first supply port 64, so that the pressure value detected by the pressure sensor 67 remains constant, thereby maintaining a constant force for the counterbalance 60 to lift the polishing mechanism 70.

[0054] Furthermore, the control unit 7 of the polishing apparatus 1 is equipped with a CPU that performs calculations according to a control program, and a storage medium such as memory. The control unit 7 controls each of the above-mentioned components of the polishing apparatus 1 to perform polishing on the wafer 100.

[0055] The polishing method for wafer 100 performed in polishing apparatus 1 is described below.

[0056] [Holding process] First, a holding process is performed. In this process, the control unit 7 moves the wafer holding mechanism 30, including the chuck table 20, to the wafer placement area on the -Y direction side. Then, the wafer 100 is placed on the holding surface 22 of the chuck table 20 so that the back surface 102, which is the surface to be polished, is facing upwards. The control unit 7 then connects the holding surface 22 to a suction source, and the wafer 100 is held in place by suction from the holding surface 22.

[0057] [Polishing preparation process] After the holding process, a polishing preparation process is carried out. In this process, the control unit 7 first moves the wafer holding mechanism 30, which includes the chuck table 20 holding the wafer 100, to the polishing area on the +Y side using the horizontal movement mechanism 40, and places it under the polishing mechanism 70. After that, the control unit 7 aligns the polishing pad 77 of the polishing mechanism 70 with the wafer 100.

[0058] Subsequently, the control unit 7 moves the polishing mechanism 70 in the Z-axis direction by rotating the Z-axis ball screw 52 with the Z-axis motor 54 of the lifting mechanism 50, thereby positioning the polishing pad 77 at the origin height position. This origin height position is above the rotation center of the wafer 100 held on the holding surface 22 of the chuck table 20, and is a height position where the lower surface of the polishing pad 77 does not come into contact with the wafer 100.

[0059] Furthermore, the control unit 7 rotates the spindle 72 and polishing pad 77 (polishing wheel 75) using the spindle motor 73, and rotates the chuck table 20 using the rotation mechanism 26.

[0060] Next, the control unit 7 rotates the Z-axis ball screw 52 with the Z-axis motor 54 of the lifting mechanism 50, thereby moving the polishing pad 77 of the polishing mechanism 70, which is at the origin height position, downward (-Z direction) and bringing it closer to the wafer 100 held on the chuck table 20.

[0061] Figure 2(a) shows the relationship between the height (height of the bottom surface) H of the polishing pad 77 and time t. As shown in this figure, the control unit 7 first lowers the polishing mechanism 70 at a relatively high initial speed V1 so that it approaches the chuck table 20 until the height of the polishing pad 77 reaches a predetermined air cut start height h1 (time t0~t1). The control unit 7 can detect the height of the polishing pad 77, for example, using a Z-axis encoder 55 provided on the lifting mechanism 50.

[0062] Then, after the lower surface of the polishing pad 77 reaches a predetermined air cut start height h1, the control unit 7 sets the lowering speed of the polishing mechanism 70 by the lifting mechanism 50 to an air cut speed V2 that is slower than the initial speed V1. Then, the control unit 7 uses the lifting mechanism 50 to move the polishing mechanism 70 closer to the chuck table 20 at the air cut speed V2 (time t1~t2).

[0063] Furthermore, between times t0 and t2, the control unit 7 rotates the Z-axis ball screw 52 with the Z-axis motor 54 to move the polishing mechanism 70 downwards, and at the same time applies an upward force to the polishing mechanism 70 in the +Z direction using the counterbalance 60.

[0064] Specifically, the control unit 7 controls the air valve 66 shown in Figure 1 to supply air from the air supply source 201 to the space below the piston 62 in the cylinder 61 via the first supply port 64. As a result, the piston 62 is biased upward in the +Z direction by the air, and a lifting force (lifting force) is applied to the polishing mechanism 70 in the +Z direction. At this time, the control unit 7 adjusts the air supply pressure using the electro-pneumatic regulator 69 based on the measurement value measured by the pressure sensor 67, thereby generating a lifting force sufficient to counteract the weight of the polishing mechanism 70. This eliminates the backlash of the Z-axis ball screw 52.

[0065] Here, we will explain how the backlash of the Z-axis ball screw 52 is eliminated by the counterbalance 60. Figure 3 shows the state in which the Z-axis ball screw 52 and the nut 57 are screwed together when the polishing mechanism 70 is being fed downwards for polishing. As shown in this figure, a single screw groove 521 is formed helically along the entire length of the outer surface of the Z-axis ball screw 52, ​​which extends in the Z-axis direction.

[0066] The nut 57 is attached to the outer circumference of the Z-axis ball screw 52, ​​and a single screw groove 571 corresponding to the screw groove 521 is formed on its inner surface.

[0067] Multiple balls 58 are arranged in a spiral pattern between the inner surface of the nut 57 and the outer surface of the Z-axis ball screw 52, ​​so as to be in close contact with each other in sequence. In other words, the space between the screw groove 571 of the nut 57 and the opposing screw groove 521 of the Z-axis ball screw 52 forms a ball passage, and the balls 58 roll along this ball passage.

[0068] Furthermore, a ball returner 573 is formed inside the nut 57 for circulating the balls 58. One end of the ball returner 573 opens to the inner circumferential surface of the nut 57.

[0069] When the polishing mechanism 70 is fed downward for polishing, the Z-axis motor 54 (see Figure 1) rotates the Z-axis ball screw 52 in the direction of arrow 301, causing the nut 57 to descend in the -Z direction relative to the Z-axis ball screw 52 together with the polishing mechanism 70.

[0070] In this process, the counterbalance 60 applies an upward force to the polishing mechanism 70, which in turn applies an upward force to the nut 57 as it moves in the -Z direction. As a result, the upper surface 522 of the screw groove 521 of the Z-axis ball screw 52 and the lower surface 572 of the screw groove 571 of the nut 57 come into contact via the ball 58, thereby eliminating the backlash BL in the Z-axis ball screw 52. Therefore, backlash is eliminated whether the polishing mechanism 70 is being lowered or raised.

[0071] When the air cut-off is completed and the rotating polishing pad 77 comes into contact with the wafer 100, the pressure value of the air supplied into the cylinder 61, as measured by the pressure sensor 67 shown in Figure 1, temporarily decreases. Therefore, the control unit 7 can detect that the polishing pad 77 has come into contact with the wafer 100 based on this decrease in pressure value. In this way, the pressure sensor 67 functions as a contact detection unit that detects when the polishing pad 77 (the lower surface of the polishing pad 77), which is a processing tool, comes into contact with the wafer 100.

[0072] Then, until the pressure sensor 67 detects contact between the wafer 100 and the polishing pad 77 (until time t2), the control unit 7 biases the piston 62 and the polishing mechanism 70 upward using the air valve 66 and the first supply port 64 as upward biasing units, thereby applying a lifting force to the polishing mechanism 70, while simultaneously lowering the polishing mechanism 70 by rotating the Z-axis ball screw 52 in the lifting mechanism 50.

[0073] [Polishing process] After the polishing preparation process, the polishing process is carried out. Specifically, when the control unit 7 detects contact between the wafer 100 and the polishing pad 77 by the pressure sensor 67 (time t2 in Figure 2(a)), it biases the polishing mechanism 70, which is mounted on the polishing pad 77 positioned above the wafer 100 held on the chuck table 20, downward using the air valve 66 and the second supply port 65 as downward biasing parts. This downward force (pressing force) and the weight of the polishing mechanism 70 rotate the Z-axis ball screw 52, ​​causing the polishing mechanism 70 to descend, pressing the polishing pad 77 against the wafer 100 and polishing the wafer 100.

[0074] Specifically, when the pressure sensor 67 detects contact between the wafer 100 and the polishing pad 77, the control unit 7 stops the rotation of the Z-axis ball screw 52 by the Z-axis motor 54 in the lifting mechanism 50, thereby enabling the Z-axis ball screw 52 to be rotated in response to an external force.

[0075] Subsequently, the control unit 7 uses the counterbalance 60 to apply a force to the polishing mechanism 70 that presses it against the wafer 100 in the -Z direction. Specifically, the control unit 7 controls the air valve 66 to supply air from the air supply source 201 to the space above the piston 62 in the cylinder 61 via the second supply port 65. As a result, the piston 62 is biased in the -Z direction by the air, and a force (pressing force) is applied to the polishing mechanism 70 that presses it in the -Z direction.

[0076] As a result, this pressing force and the downward force due to the weight of the polishing mechanism 70 are applied to the Z-axis ball screw 52 via the nut 57, causing the Z-axis ball screw 52 to rotate so as to move the polishing mechanism 70 downward. This causes the polishing mechanism 70 to descend, and the rotating polishing pad 77 is pressed against the back surface 102 of the rotating wafer 100, polishing the back surface 102 of the wafer 100 (times t2 to t3 in Figure 2(a)).

[0077] Furthermore, in this process, the control unit 7 can change the pressing force applied from the counterbalance 60 to the polishing mechanism 70 by controlling the air valve 66 and adjusting the pressure of the air supplied from the air supply source 201 to the cylinder 61 via the second supply port 65 using the electro-pneumatic regulator 69. Specifically, the control unit 7 monitors the pressure value of the pressure sensor 68 provided in the second air passage 651 and controls the electro-pneumatic regulator 69 so that the pressure value of the pressure sensor 68 becomes a predetermined pressure value. This allows the control unit 7 to adjust the pressing force applied to the polishing pad 77 against the wafer 100. Consequently, the control unit 7 can keep the load applied from the polishing pad 77 to the wafer 100 within a predetermined range. The control unit 7 may also use a load sensor 281 (see Figure 1) to detect the load applied to the wafer 100 during the polishing process, and adjust the pressing force (downward speed) of the polishing pad 77 so that this load falls within a predetermined range.

[0078] During polishing, the control unit 7 measures the thickness of the wafer 100 being polished using a thickness measuring instrument (not shown), and performs the polishing process until, for example, the thickness of the wafer 100 reaches a target thickness (finished thickness).

[0079] The Z-axis ball screw 52 and nut 57 shown in Figure 3 may be configured to form a large backlash BL. In this case, the control unit 7 may polish the wafer 100 in the polishing process by moving the polishing mechanism 70 up and down within the backlash BL using the counterbalance 60, without rotating the Z-axis ball screw 52. Furthermore, in configurations where a large backlash BL is formed, the counterbalance 60 can be used to retract the polishing pad 77 from the wafer 100.

[0080] [Evacuation process] Once the polishing process is complete (time t3 in Figure 2(a)), the retraction process is performed. In this process, the control unit 7 first stops the descent of the polishing mechanism 70 and maintains the height of the polishing pad 77 for a predetermined time. Then (time t4), the control unit 7 uses the lifting mechanism 50 to retract the polishing mechanism 70 to the origin height position at a relatively high retraction speed V5.

[0081] As described above, in this embodiment, during the polishing process, the control unit 7 rotates the Z-axis ball screw 52 by the downward pressing force applied to the polishing mechanism 70 from the counterbalance 60 and the weight of the polishing mechanism 70, thereby lowering the polishing mechanism 70 and polishing the wafer 100.

[0082] Therefore, compared to a configuration in which the polishing mechanism 70 is lifted by the counterbalance 60 and lowered by the lifting mechanism 50 to press the polishing pad 77 against the wafer 100, the force (pressing force) that the polishing pad 77 applies to the wafer 100 can be easily increased. As a result, the processing time for the wafer 100 can be shortened and productivity can be improved. In addition, power consumption for lowering the polishing mechanism 70 can be reduced.

[0083] Furthermore, since no upward force from the counterbalance 60 is applied to the Z-axis ball screw 52 during the polishing process, there is no need to use a thick ball screw capable of withstanding strong forces as the Z-axis ball screw 52. Therefore, it is possible to avoid increasing the size of the polishing device 1.

[0084] Furthermore, in this embodiment, the pressing force applied by the polishing pad 77 to the wafer 100 can be reduced simply by reducing the pressing force applied from the counterbalance 60 to the polishing mechanism 70. Therefore, since the pressing force can be quickly reduced, it is easy to prevent the polishing pad 77 from being pressed too hard against the wafer 100.

[0085] In this embodiment, when contact between the wafer 100 and the polishing pad 77 is detected, the control unit 7 stops the rotational drive of the Z-axis ball screw 52 by the Z-axis motor 54, and rotates the Z-axis ball screw 52 using the pressing force applied to the polishing mechanism 70 from the counterbalance 60 and the weight of the polishing mechanism 70 to lower the polishing mechanism 70 and polish the wafer 100. In this regard, the control unit 7 may stop the rotational drive of the Z-axis ball screw 52 before (for example, immediately before) contact between the wafer 100 and the polishing pad 77 is detected, and rotate the Z-axis ball screw 52 using the pressing force applied to the polishing mechanism 70 from the counterbalance 60 and the weight of the polishing mechanism 70 to lower the polishing mechanism 70 and polish the wafer 100.

[0086] Furthermore, in this embodiment, when the control unit 7 applies a pressing force in the -Z direction to the polishing mechanism 70 using the counterbalance 60, it stops the rotation of the Z-axis ball screw 52 by the Z-axis motor 54, leaving the Z-axis ball screw 52 in a state where it can be rotated in response to the external force. In this regard, when the control unit 7 applies a pressing force to the polishing mechanism 70, it may also use the Z-axis motor 54 to rotate the Z-axis ball screw 52, ​​for example with a gentle force, in a direction that lowers the polishing mechanism 70.

[0087] Furthermore, in this embodiment, as shown in Figure 4(a), in the polishing process, when the pressure sensor 67 detects contact between the wafer 100 and the polishing pad 77 (time t2), the control unit 7 biases the polishing mechanism 70, which is equipped with the polishing pad 77 positioned above the wafer 100 held on the chuck table 20, downward using the air valve 66 and the second supply port 65 as downward biasing units. This bias causes a downward force (pressing force) and the weight of the polishing mechanism 70 to rotate the Z-axis ball screw 52, ​​causing the polishing mechanism 70 to descend. Additionally, the Z-axis motor 54 rotates the Z-axis ball screw 52, ​​applying an upward force to the polishing mechanism 70. This allows the polishing pad 77 to be pressed against the wafer 100 and the wafer 100 to be processed, so that the load from the polishing pad 77 to the chuck table 20 falls within a predetermined range.

[0088] Specifically, when the pressure sensor 67 detects contact between the wafer 100 and the polishing pad 77 (time t2), the control unit 7 stops the rotation of the Z-axis ball screw 52 by the Z-axis motor 54 in the lifting mechanism 50, as described above, and puts the Z-axis ball screw 52 into a state where it can be rotated in response to an external force.

[0089] Subsequently, as described above, the control unit 7 uses the counterbalance 60 to apply a force to the polishing mechanism 70 in the -Z direction, pressing it against the wafer 100. As a result, a downward force is applied to the Z-axis ball screw 52 via the nut 57, causing the Z-axis ball screw 52 to rotate so that the polishing mechanism 70 moves downward. As a result, as shown in Figures 4(a) and (b), the polishing mechanism 70 descends at speed V6, and the polishing pad 77 is pressed against the wafer 100, causing the wafer 100 to be polished (time t2~t3).

[0090] Furthermore, during this polishing process, the control unit 7 detects the load applied to the wafer 100 using the load sensor 281 (see Figure 1). When the load applied to the wafer 100 approaches (or reaches) the upper limit of a predetermined range, the control unit 7 rotates the Z-axis ball screw 52 with the Z-axis motor 54, thereby applying an upward force to the polishing mechanism 70. As a result, as shown in Figures 4(a) and (b), the polishing mechanism 70 rises at speed V7, and the load applied from the polishing pad 77 to the wafer 100 (chuck table 20) weakens. At this time, the control unit 7 may interrupt the application of the pressing force from the counterbalance 60 to the polishing mechanism 70, or reduce the pressing force.

[0091] Subsequently, when the load on the wafer 100 approaches (or reaches) the lower limit of a predetermined range, the control unit 7 stops the rotation of the Z-axis ball screw 52 by the Z-axis motor 54, and lowers the polishing mechanism 70 at speed V6 using the pressing force from the counterbalance 60 onto the polishing mechanism 70 and the weight of the polishing mechanism 70 itself.

[0092] In this configuration, when the control unit 7 polishes the wafer 100 with the polishing pad 77, it repeatedly lowers and raises the polishing mechanism 70, thereby adjusting the load applied from the polishing pad 77 to the wafer 100 to be within a predetermined range, and polishing the wafer 100 with the polishing pad 77. Therefore, it is possible to effectively suppress the polishing pad 77 from being pressed too hard against the wafer 100.

[0093] Furthermore, in this embodiment, the counterbalance 60 supports the holder 56 that holds the polishing mechanism 70. In this regard, the counterbalance 60 may directly support the polishing mechanism 70. In this case, the lower end of the piston rod 63 may be connected to the spindle housing 71 of the polishing mechanism 70 held by the holder 56.

[0094] Furthermore, in this embodiment, a pressure sensor 67 is used as a contact detection unit to detect when the polishing pad 77 (the lower surface of the polishing pad 77 (the tip of the polishing tool)) which is a processing tool, comes into contact with the wafer 100.

[0095] In this regard, a load sensor 281 that detects the load applied to the chuck table 20 may be used as the contact detection unit. The load value detected by the load sensor 281 increases when the polishing pad 77 comes into contact with the wafer 100. Therefore, the control unit 7 can detect that the polishing pad 77 has come into contact with the wafer 100 based on the increase in the load detected by the load sensor 281.

[0096] Furthermore, a current value sensor (not shown) that detects the load current value of the spindle motor 73 in the polishing mechanism 70, or the load current value of the rotation mechanism 26 that rotates the chuck table 20, may be used as the contact detection unit. The load current value detected by the current value sensor increases when the polishing pad 77 comes into contact with the wafer 100. Therefore, the control unit 7 can detect that the polishing pad 77 has come into contact with the wafer 100 based on the increase in the load current value detected by the current value sensor.

[0097] Furthermore, in this embodiment, a polishing device 1 is shown as an example of a processing device. In this regard, the processing device according to this embodiment may be a processing device other than a polishing device, as long as it is a processing device that applies a load, such as a grinding device equipped with a grinding mechanism including a grinding wheel as a processing unit, or a cutting device equipped with a cutting mechanism including a cutting blade as a processing unit.

[0098] In this embodiment, a Z-axis ball screw 52 is screwed into a nut 57 connected to the polishing mechanism 70. In this regard, a screwed-in member such as a nut 57 only needs to be capable of having the Z-axis ball screw 52 screwed into it, be connected to the polishing mechanism 70 (processing unit), and be configured to move in the Z-axis direction together with the polishing mechanism 70 in accordance with the rotation of the Z-axis ball screw 52. The screwed-in member may be indirectly connected to the processing unit, as in the case of a nut 57, or it may be part of the processing unit. [Explanation of symbols]

[0099] 1: Polishing device, 3: Column, 7: Control unit, 20: Chuck table, 21: Holding unit, 22: Holding surface, 23: Base, 25: Chuck table base, 26: Rotation mechanism, 28: Support column, 30: Wafer holding mechanism, 40: Horizontal movement mechanism, 41: Holding base, 42: Y-axis guide rail, 43: Y-axis ball screw, 44: Y-axis motor, 45: Y-axis moving table, 46: Y-axis encoder, 50: Lifting mechanism, 51: Z-axis guide rail, 52: Z-axis ball screw, 53: Z-axis moving table, 54: Z-axis motor, 55: Z-axis encoder, 56: Holder, 57: Nut, 58: Ball, 59: Support arm 60: Counterbalance, 61: Cylinder, 62: Piston, 63: Piston rod, 64: First supply port, 65: Second supply port, 66: Air valve, 67: Pressure sensor, 68: Pressure sensor, 69: Electro-pneumatic regulator 70: Polishing mechanism, 71: Spindle housing, 72: Spindle, 73: Spindle motor, 74: Wheel mount, 75: Polishing wheel, 76: Wheel base, 77: Polishing pad, 100: Wafer, 101: Front surface, 102: Back surface, 103: Protective tape 201: Air supply source, 281: Load sensor, 401: Nut, 451: Sliding member, 521: Screw groove, 522: Top surface, 531: Sliding member, 571: Screw groove, 572: Bottom surface, 573: Ball returner, 641: First air passage, 651: Second air passage

Claims

1. A machining apparatus comprising a chuck table for holding a workpiece, a machining unit for machining the workpiece held on the chuck table with a machining tool, and a lifting mechanism for raising and lowering the machining unit in the vertical direction, The lifting mechanism is, A ball screw extending vertically while screwed into a workpiece connected to the processing unit, A motor that rotates the ball screw, A guide rail is positioned parallel to the ball screw and guides the vertical movement of the machining unit, It is equipped with a counterbalance that cancels out the weight of the processing unit, The counterbalance is, Cylinder and A piston connected to the processing unit slides vertically within the cylinder, An upward biasing unit that biases the piston and the machining unit upward, It comprises a piston and a downward biasing part that biases the processing unit downward, The control unit further comprises a downward biasing unit that biases the processing unit downward, thereby rotating the ball screw due to the downward force and the weight of the processing unit, lowering the processing unit, and pressing the processing tool against the workpiece held on the chuck table to process the workpiece. Processing equipment.

2. The tool further comprises a contact detection unit that detects when the tool comes into contact with the workpiece. The control unit is The upper biasing unit biases the machining unit upward while the rotation of the ball screw lowers the machining unit until contact between the workpiece and the machining tool is detected by the contact detection unit. When the contact detection unit detects contact between the workpiece and the machining tool, the downward biasing unit biases the machining unit downward. This downward force, along with the weight of the machining unit, rotates the ball screw, causing the machining unit to descend. The machining tool is then pressed against the workpiece held on the chuck table, and the workpiece is machined. The processing apparatus according to claim 1.

3. A method for processing a workpiece using the processing apparatus described in claim 1 or 2, The process involves biasing the machining unit, which is positioned above the workpiece held on the chuck table and equipped with the machining tool, downward by the downward biasing unit, thereby rotating the ball screw due to the downward force from this biasing and the weight of the machining unit itself, lowering the machining unit, pressing the machining tool against the workpiece, and machining the workpiece. Method for machining the workpiece.

4. A method for processing a workpiece using the processing apparatus described in claim 1 or 2, The process includes: biasing the processing unit, which is mounted with the processing tool positioned above the workpiece held on the chuck table, downward by the downward biasing unit, thereby rotating the ball screw due to the downward force caused by this biasing and the weight of the processing unit itself, and applying an upward force to the processing unit by rotating the ball screw with the motor, thereby pressing the processing tool against the workpiece and processing the workpiece so that the load from the processing tool to the chuck table is within a predetermined range; Method for machining the workpiece.

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