Grinding device

Abstract

To prevent grinding chips from lying between an upper surface of a sensor unit and a lower surface of a grinding stone in a setup.SOLUTION: A grinding device (1) includes: a chuck table (12) to hold a wafer (W) with a holding surface (16); a grinding unit (30) for grinding the wafer (W) held on the holding surface with an annular grinding stone (37); a grinding water supply part (40) for supplying grinding water (L) to the grinding stone; a lifting unit (20) for lifting and lowering the grinding unit; a sensor unit (70) interposed between the holding surface and the lower surface of the grinding stone, and detecting a height at which the lower surface of the grinding stone comes into contact with the holding surface; and a control section (90). The control section controls forming of a slight clearance between the upper surface of the sensor unit and the lower surface of the grinding stone, and supply of grinding water from the grinding water supply part while rotating a spindle and dispersing of grinding water from the center of the grinding stone outward with a centrifugal force generated by the rotation of the spindle.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a grinding apparatus in which setup is performed.

Background Art

[0002] Patent Document 1 discloses a grinding apparatus that grinds a wafer with a grinding wheel. In such a grinding apparatus, the position where the holding surface of a chuck table that holds the wafer and the tip of the grinding wheel come into contact is defined as the origin position, and the grinding amount (finish thickness) of the wafer is controlled. Therefore, when grinding a wafer with the grinding apparatus, the tip of the grinding wheel is brought into contact with the holding surface of the chuck table, and a setup is performed to store the height of the grinding wheel at the time of this contact.

[0003] Patent Document 1 adopts a configuration equipped with a sensor unit in order to perform setup. For setup, for example, after an operator replaces a grinding wheel having a grinding stone, a detection unit of the sensor unit is disposed between the grinding wheel and the holding table. Then, the grinding wheel is lowered toward the holding surface, and the height position of the grinding wheel when the upper end of the detection unit in the sensor unit comes into contact with the grinding stone and the lower end of the detection unit comes into contact with the holding surface of the chuck table is stored. After the setup, grinding can be continued, reducing the labor of the operator and improving productivity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, if grinding chips adhere to the upper end of the detection unit in the sensor unit, the setup is completed with the grinding chips intervening between the upper end and the grinding wheel. Therefore, when the setup is performed based on the stored height of the grinding wheel, the vertical length of the grinding wheel is stored as being longer than the actual length by the amount of the intervening grinding chips. As a result, in the subsequent grinding process, when the grinding wheel is fed in the vertical direction, the time until the grinding wheel contacts the wafer becomes longer, resulting in a problem of reduced productivity.

[0006] In view of this point, the present invention is made, and one of the objects is to provide a grinding apparatus capable of preventing grinding chips from intervening between the upper surface of the sensor unit and the lower surface of the grinding wheel during setup.

Means for Solving the Problems

[0007] A wafer grinding apparatus according to an aspect of the present invention includes a chuck table that holds a wafer by a holding surface, a grinding unit that grinds the wafer held on the holding surface with an annular grinding wheel disposed at the tip of a spindle, a grinding water supply unit that passes through the inside of the spindle and supplies grinding water to the grinding wheel, a lifting unit that raises and lowers the grinding unit, a sensor unit that intervenes between the holding surface and the lower surface of the grinding wheel and detects the height at which the lower surface of the grinding wheel contacts the holding surface, and a control unit. The control unit forms a slight gap between the upper surface of the sensor unit and the lower surface of the grinding wheel, and controls the supply of grinding water from the grinding water supply unit while rotating the spindle to scatter the grinding water in a direction from the center to the outside of the grinding wheel by the centrifugal force generated by the rotation of the spindle.

Effects of the Invention

[0008] According to the present invention, even if grinding debris adheres to the upper surface of the sensor unit, the control unit can control so that the grinding water scattered into the gap passes through the gap while forming the above-described gap. Therefore, even if grinding debris intervenes between the upper surface of the sensor unit and the lower surface of the grinding wheel at the time of setup, it can be cleaned to remove the grinding debris, and the intervention of the grinding debris can be prevented.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Hereinafter, a grinding apparatus according to an embodiment will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a grinding apparatus according to an embodiment.

[0011] In the grinding apparatus 1, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are substantially horizontal directions, and the Z-axis direction is the vertical direction (up and down direction). Of the double-headed arrows indicating the X-axis direction, the +X side is the front and the -X side is the rear. Of the double-headed arrows indicating the Z-axis direction, the +Z side is the upper side and the -Z side is the lower side.

[0012] As shown in FIG. 1, a rectangular opening extending in the X-axis direction is formed on the upper surface of the base 10 in the grinding apparatus 1. This opening is covered with a moving plate 13 and a bellows-shaped waterproof cover 14 that are movable in the X-axis direction together with the chuck table 12.

[0013] The chuck table 12 includes a disk-shaped porous plate 15. The porous plate 15 is made of a porous material such as ceramics, and fine pores are formed throughout. The upper surface of the porous plate 15 constitutes a holding surface 16. The holding surface 16 sucks and holds the wafer W by a suction source (not shown).

[0014] In the present embodiment, the wafer W is formed in a substantially disk shape. Note that the wafer W may be any plate-shaped workpiece to be ground, such as a semiconductor substrate such as silicon or gallium arsenide, an inorganic material substrate such as ceramics, glass, or sapphire, or even a package substrate of a semiconductor product.

[0015] In the grinding process, the lower surface W2 of the wafer W is used as the surface to be held and adsorbed by the holding surface 16 of the chuck table 12, and the upper surface W1 of the wafer W is used as the surface to be ground. A protective tape may be attached to the lower surface W2 of the wafer W.

[0016] The chuck table 12 is rotationally driven about a central axis parallel to the Z-axis direction by a table rotation mechanism 60 (see FIG. 2, not shown in FIG. 1) provided below the moving plate 13. At a position where the chuck table 12 passes on the base 10, a thickness measuring device 17 for measuring the thickness of the wafer W held by the chuck table 12 and a sensor unit 70 are installed. The sensor unit 70 will be described later.

[0017] The thickness measuring device 17 includes a first height gauge for measuring the height position of the upper surface W1 of the wafer W held on the holding surface 16 of the chuck table 12 and a second height gauge for measuring the height position of the upper surface of the chuck table 12. The thickness of the wafer W is measured by the thickness measuring device 17 based on the difference between the measured value of the first height gauge and the measured value of the second height gauge.

[0018] The grinding device 1 further includes a lifting unit 20 and a grinding unit 30. The lifting unit 20 is provided on a column 19 erected at the rear of the base 10, and moves the grinding unit 30 up and down in the Z-axis direction.

[0019] The lifting unit 20 includes a pair of guide rails 21 arranged on the front side of the column 19 and extending in the Z-axis direction, a lifting table 22 installed movably in the Z-axis direction with respect to the pair of guide rails 21, and a ball screw 23 extending in the Z-axis direction and screwing into a screwing portion (not shown) of the lifting table 22.

[0020] One end of the ball screw 23 is connected to a motor 24. In the lifting unit 20, the ball screw 23 is rotated by the driving force of the motor 24, so that the lifting table 22 and the grinding unit 30 move up and down in the Z-axis direction. An encoder 26 for detecting the rotation speed (pulse number) is arranged on the motor 24, and the movement amount of the lifting table 22 and the grinding unit 30 can be acquired by a pulse signal output from the encoder 26.

[0021] The grinding unit 30 is attached to the front surface of the lifting table 22 via a holder 31, and rotatably supports a spindle 33 with respect to a spindle housing 32 supported by the holder 31. The spindle 33 rotates about an axis in the Z-axis direction by the driving force of a spindle motor 34.

[0022] A mount 35 is connected to the tip (lower end) of the spindle 33, and a grinding wheel 36 is mounted on the mount 35. A plurality of grinding wheels 37 are provided annularly on the lower surface of the grinding wheel 36. Therefore, an annular grinding wheel 37 is arranged at the tip of the spindle 33. The grinding unit 30 grinds the upper surface W1 of the wafer W sucked and held on the holding surface 16 of the chuck table 12 with the annular grinding wheel 37.

[0023] FIG. 2 is a schematic view showing a partial longitudinal cross-section of the grinding apparatus according to the embodiment. As shown in FIG. 2, the grinding unit 30 is provided with a grinding water supply unit 40 for supplying grinding water L (see FIG. 5B) to the grinding wheel 37. The grinding water supply unit 40 includes a grinding water discharge port 41 formed on the inner circumference of the grinding wheel 36, and a flow path 42 passing through the inside of the spindle housing 32, the spindle 33, the mount 35, and the grinding wheel 36. Further, the grinding water supply unit 40 includes a grinding water source 44 communicating with the upstream side of the flow path 42, and the grinding water L supplied from the grinding water source 44 can be discharged from the grinding water discharge port 41 through the flow path 42.

[0024] The base 10 is provided with a table moving mechanism 50 for moving the chuck table 12 in the X-axis direction and a table rotating mechanism 60 for rotationally driving the chuck table 12 about the Z-axis. The table moving mechanism 50 and the table rotating mechanism 60 are disposed below a waterproof cover 14 (see FIG. 1, not shown in FIG. 2).

[0025] The table moving mechanism 50 includes a guide rail 51 and a ball screw 52 extending in the X-axis direction, and the moving table 53 is supported so as to be movable along the guide rail 51. The ball screw 52 is screwed into a screwed portion 54 of the moving table 53. When the ball screw 52 is rotated by the operation of the motor 56, the moving table 53 and the chuck table 12 move in the X-axis direction. An encoder 57 for detecting the number of revolutions (number of pulses) is disposed on the motor 56, and the amount of movement of the moving table 53 and the chuck table 12 can be acquired by a pulse signal output from the encoder 57. The moving table 53 supports the moving plate 13 and the chuck table 12 via a support frame 58 provided on the upper surface. The table rotating mechanism 60 is disposed inside the support frame 58.

[0026] When grinding the wafer W held on the chuck table 12, the chuck table 12 and the wafer W are moved and positioned below the grinding unit 30 via the table moving mechanism 50. In this state, while rotating the grinding wheel 36 in the grinding unit 30, it is lowered at a predetermined speed for machining feed, and the upper surface W1 of the wafer W is ground by the grinding stone 37. During such grinding, the chuck table 12 is rotated, for example, in the same direction as the grinding wheel 36, and the wafer W rotates. The outer diameter of the grinding outer periphery by the grinding stone 37 is larger than the radius of the holding surface 16, and by passing through the center of the wafer W, the entire surface of the wafer W is uniformly ground by the grinding stone 37.

[0027] The grinding apparatus 1 further includes a sensor unit 70 that is installed on the base 10 and can be disposed so as to be interposed between the holding surface 16 of the chuck table 12 and the lower surface of the grinding stone 37 in the grinding unit 30. The sensor unit 70 is supported via a support column 71 provided on the base 10.

[0028] FIG. 3 is a schematic perspective view of the sensor unit. As shown in FIGS. 2 and 3, the sensor unit 70 includes a turning shaft 72 extending in the Z-axis direction, a turning motor 74 provided at the lower end of the turning shaft 72, and an arm 75 having a base connected to the upper end of the turning shaft 72 and extending in the horizontal direction. In the sensor unit 70, the turning shaft 72 is rotatably supported about a central axis parallel to the Z-axis direction with respect to the support column 71 (not shown in FIG. 3). The turning shaft 72 is rotatable by the drive of the turning motor 74, and the tip side of the arm 75 is rotationally displaced by this rotation. More specifically, due to the rotation of the turning shaft 72, as shown in FIGS. 1 and 2, the tip side of the arm 75 can be switched between a position interposed between the holding surface 16 of the chuck table 12 and the lower surface of the grinding stone 37 and a position retracted from between them.

[0029] Figure 4 is a schematic cross-sectional view of the tip side of the sensor unit and its surroundings. As shown in Figure 4, the sensor unit 70 includes a contact portion 77 and a detection portion 78 provided on the tip side of the arm 75. The contact portion 77 is disposed in a housing hole 79 formed to penetrate vertically on the tip side of the arm 75. The housing hole 79 is formed by a stepped hole, and an upper hole 791 having a round hole shape is formed with a larger diameter than a lower hole 792.

[0030] The contact portion 77 includes a columnar stage 81 formed to have the same or slightly smaller diameter as the upper hole 791 of the housing hole 79, and a round shaft-shaped probe 82 protruding downward from the lower surface of the stage 81. A spring member 83 is provided between the bottom of the upper hole 791 and the lower surface of the stage 81, and the spring member 83 is constituted by a compression coil spring. The contact portion 77 is supported from below via the spring member 83, the upper end side of the stage 81 protrudes upward from the upper opening of the housing hole 79, and the lower half of the probe 82 protrudes downward from the lower opening of the housing hole 79. The upper surface of the stage 81 forms the uppermost surface of the sensor unit 70, and the lower end of the probe 82 is formed in a hemispherical shape.

[0031] The contact portion 77 is provided so as to be relatively movable up and down with respect to the housing hole 79. Specifically, when a pressing force is applied downward by the lower surface of the grinding wheel 37 to the contact portion 77, the contact portion 77 relatively descends with respect to the housing hole 79 against the elastic force of the spring member 83. When such a pressing force is released, the contact portion 77 relatively ascends with respect to the housing hole 79 by the elastic force of the spring member 83 and returns to the vertical position of the initial position.

[0032] The detection unit 78 detects that the contact unit 77 has descended and the lower end of the probe 82 has contacted the holding surface 16 of the chuck table 12, and outputs the detection signal to a control unit 90 described later. In other words, the positions of the detection unit 78 and the contact unit 77 in the Z-axis direction are set so that the detection of the detection unit 78 can be switched at the timing when the lower end of the probe 82 contacts the holding surface 16. The height at which the lower surface of the grinding wheel 37 contacts the holding surface 16 is detected based on the detection signal from the detection unit 78 and the pulse signal from the encoder 26 of the lifting unit 20 described above.

[0033] The operations of the respective parts of the grinding apparatus 1 are controlled by a control unit 90 (see FIG. 1). The control unit 90 includes, in addition to a processor that executes various processes, a storage unit (memory) 91 that stores various parameters, programs, and the like. In the storage unit 91 of the control unit 90, programs for controlling the operations of, for example, the lifting unit 20, the grinding unit 30, the grinding water supply unit 40, the sensor unit 70, etc. are stored as a part of the control program. Further, the control unit 90 includes a gap formation control unit 92 and a grinding water supply control unit 93. For the operations of the respective parts of the grinding apparatus 1 described below, if the subject of control is not specified, it is assumed that the operations are controlled by control signals sent from the control unit 90.

[0034] Subsequently, before explaining the setup method of the present embodiment, the setup method of the comparative example will be explained. In the comparative example, when the same configuration as that of the above embodiment can be used, the same reference numerals as those of the above embodiment will be given to the configuration and will be described below.

[0035] Note that the setup is performed as needed, such as when the apparatus is started up, after self-grinding is performed, when the grinding wheel 37 is worn, or when the chuck table 12 is replaced. Self-grinding is an operation of making the holding surface 16 of the chuck table 12 and the lower surface of the grinding wheel 37 parallel by grinding the holding surface 16 with the grinding wheel 37.

[0036] When setting up the comparative example, the arm 75 is rotated by driving the turning motor 74 of the sensor unit 70, and a contact portion 77 is interposed between the holding surface 16 of the chuck table 12 and the lower surface of the grinding wheel 37. Then, the grinding unit 30 is lowered by the elevating unit 20, and the lower surface of the grinding wheel 37 is brought into contact with the upper surface of the stage 81 at the contact portion 77 to push down the detection unit 78. Then, the lower end of the probe 82 at the contact portion 77 comes into contact with the holding surface 16 of the chuck table 12 (see Fig. 5C), and the detection unit 78 detects this contact and outputs a detection signal to the control unit 90. The origin position is calculated and set up from the output from the encoder 26 (see Fig. 2) at the height position of the grinding wheel 37 at this time and the vertical width of the contact portion 77 recognized in advance.

[0037] Figs. 5A to 5C are explanatory diagrams showing the flow of setup when grinding debris adheres to the sensor unit in the embodiment. When setting up, as shown in Fig. 5A, grinding debris D may adhere to the upper surface of the stage 81 (sensor unit 70). In this case, when performing the setup of the comparative example, grinding debris D is interposed between the upper surface of the stage 81 and the lower surface of the grinding wheel 37, and the height position of the grinding unit 30 detected from the output of the encoder 26 is shifted upward. Therefore, the setup is performed assuming that the vertical length of the grinding wheel 37 is longer than the actual value by the amount of the interposed grinding debris D, and in the subsequent grinding process, the machining feed length of the grinding unit 30 until the grinding wheel 37 contacts the wafer W becomes long.

[0038] To avoid such a state, in this embodiment, the setup is performed as follows. First, as shown in Fig. 5A, with grinding debris D adhering to the upper surface of the stage 81, the setup is started in the same manner as in the comparative example. In the comparative example, the origin position was calculated, but such calculation is not performed at this point. Instead, the height of the grinding wheel 37 is detected from the output of the encoder 26 (see Fig. 2) of the elevating unit 20, and the detection result is stored in the storage unit 91 of the control unit 90.

[0039] After that, the gap formation control unit 92 of the control unit 90 controls the motor 24 of the lifting unit 20 to lift and retract the grinding unit 30. As a result, the lower surface of the grinding wheel 37 is separated upward from the contact portion 77, and the contact portion 77 is lifted by the elastic force of the spring member 83 and returns to the vertical position of the initial position. At this time, the lifting amount of the grinding unit 30 is calculated and adjusted by the gap formation control unit 92 based on the height of the grinding wheel 37 stored in the storage unit 91 and the upper surface height of the stage 81 at the contact portion 77 serving as the initial position. By such adjustment, as shown in FIG. 5B, a slight gap S is formed between the upper surface of the stage 81 and the lower surface of the grinding wheel 37. Although the vertical width of the gap S is changed according to various conditions, it can be exemplified as about 1 to 2 mm.

[0040] After the formation of the gap S shown in FIG. 5B, the grinding water supply control unit 93 of the control unit 90 controls the grinding water source 44 (see FIG. 2) of the grinding water supply unit 40, and discharges the grinding water L from the grinding water discharge port 41 (grinding water supply unit 40) to supply the grinding water L to the grinding wheel 37 side. While supplying the grinding water L in this way, the control unit 90 controls the spindle motor 34 of the grinding unit 30, and rotates the spindle 33, the grinding wheel 36, and the grinding wheel 37 at, for example, 2000 to 3000 min -1 in rotation. Due to the centrifugal force generated by such rotation, the grinding water L is scattered in the direction outward in the radial direction of the grinding wheel 36 (the direction from right to left in FIG. 5B). That is, the grinding water L receiving the centrifugal force flows through the gap S between the lower surface of the grinding wheel 37 and the upper surface of the stage 81 in the thickness direction of the grinding wheel 37. As a result, the grinding water L flows while having a predetermined pressure in the gap S, and the grinding debris D attached to the upper surface of the stage 81 is removed and cleaned.

[0041] After the upper surface of the stage 81 is cleaned with the grinding water L, as shown in FIG. 5C, the origin position is calculated by the same setup as in the comparative example, and the setup is completed.

[0042] According to the above embodiment, even if grinding debris D adheres to the upper surface of the stage 81 in the sensor unit 70, the control unit 90 can control to form a slight gap S between the upper surface of the stage 81 and the lower surface of the grinding wheel 37 and allow the grinding water L scattered into the gap S to pass through. Therefore, even when the grinding debris D is interposed as shown in FIG. 5B, it can be cleaned so that the grinding water L passing through the gap S removes the grinding debris D, and it is possible to prevent the grinding debris D from being interposed between the upper surface of the stage 81 and the lower surface of the grinding wheel 37.

[0043] As a result, it is possible to suppress the occurrence of an error in which the vertical length of the grinding wheel 37 becomes longer than the actual value due to the interposition of the grinding debris D during setup. As a result, in the subsequent grinding process, it is possible to avoid an increase in the machining feed time until the grinding wheel 37 contacts the wafer W, and it is possible to achieve energy saving and productivity improvement.

[0044] In addition, since the vertical width of the gap S through which the grinding water L passes is set to a slight width, the pressure of the grinding water L passing through the gap S can be increased to strengthen the flow momentum, and the cleaning effect can be enhanced.

[0045] Note that the present invention is not limited to the above embodiment, and various modifications can be made and implemented. In each of the above embodiments, the sizes, shapes, etc. illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, various modifications can be made and implemented as long as the scope of the object of the present invention is not deviated from. For example, in the above embodiment, the grinding water L passing through the gap S is supplied from the upper part of the spindle 33 by the grinding water supply unit 40. However, as disclosed in JP-A-2011-025380 and JP-A-2022-012800, the grinding water L may be supplied from a nozzle inside the grinding wheel 36 (mount 35) so as to receive the centrifugal force generated by the rotation of the grinding wheel 37. As another example, a grinding water ejection hole for ejecting grinding water L from the upper surface of the stage 81 may be provided on the upper surface of the stage 81, and the lower surface of the rotating grinding wheel 37 may receive the friction of the ejected grinding water L to remove grinding chips together with the grinding water L.

[0046] The configuration of the sensor unit 70 described above is merely an example, and as long as it exhibits the same functions as the above-described embodiment, for example, the shape of the contact portion 77 or the like may be changed.

Industrial Applicability

[0047] As described above, the present invention has an effect that it can be cleaned to remove grinding chips even if grinding chips are interposed between the upper surface of the sensor unit and the lower surface of the grinding wheel at the time of setup.

Explanation of Reference Numerals

[0048] 1: Grinding apparatus 12: Chuck table 16: Holding surface 20: Lifting unit 30: Grinding unit 33: Spindle 37: Grinding wheel 40: Grinding water supply unit 70: Sensor unit 90: Control unit L: Grinding water S: Gap W: Wafer

Claims

【Claim 1】 A grinding apparatus comprising: a chuck table for holding a wafer by a holding surface; a grinding unit for grinding the wafer held on the holding surface with an annular grinding wheel disposed at the tip of a spindle; a grinding water supply unit for passing through the inside of the spindle and supplying grinding water to the grinding wheel; a lifting unit for lifting and lowering the grinding unit; a sensor unit for detecting a height at which the lower surface of the grinding wheel contacts the holding surface and interposed between the holding surface and the lower surface of the grinding wheel; and a control unit, wherein the control unit, controls to form a slight gap between the upper surface of the sensor unit and the lower surface of the grinding wheel, and to supply grinding water from the grinding water supply unit while rotating the spindle to scatter the grinding water in a direction from the center of the grinding wheel toward the outside by the centrifugal force generated by the rotation of the spindle.

Images