Spindle unit and grinding device

Abstract

To grind a wafer whose thickness is uniform over the entire surface.SOLUTION: A grinding device 1 includes a chuck table 10, a grinding mechanism 20 for grinding a wafer 100, a rotation angle detection part 40 for detecting a rotation angle of a spindle 31, a non-contact thickness measurement device 50 for measuring a thickness of the wafer 100 in a non-contact manner, an inclination adjustment mechanism 70 for relatively adjusting an inclination of a holding surface 11 to a lower surface of a grinding wheel 242, and a control part 90, wherein the control part 90 includes a first storage part 91 for measuring the thickness of the wafer 100 by the non-contact thickness measurement device 50, and storing the thickness in association with the rotation angle of the spindle 31 detected by the rotation angle detection part 40, and an inclination control part 92 for controlling the inclination adjustment mechanism 70 so that the wafer 100 has a prescribed thickness radial direction distribution on the basis of thickness radial direction distribution data of the wafer 100 in which the rotation angle of the spindle 31 stored in the first storage part 91 is associated with the thickness of the wafer 100.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spindle unit and a wafer grinding apparatus including the same. [Background Art]

[0002] A grinding apparatus that grinds a wafer grinds the upper surface of the wafer held on a holding surface of a chuck table by bringing a rotating grinding wheel into contact with the upper surface of the wafer. Therefore, in order to make the thickness of the wafer uniform in the radial direction, the holding surface of the chuck table and the grinding surface (lower surface) of the grinding wheel need to be parallel to each other. is.

[0003] Accordingly, for example, Patent Document 1 proposes a grinding apparatus configured to stop grinding before the wafer reaches a predetermined finished thickness, measure the thickness of the wafer with a thickness measuring means, correct the inclination of the chuck table so that the thickness becomes uniform in the radial direction of the wafer, and then grind the wafer again until the wafer reaches the predetermined finished thickness.

[0004] Further, Patent Documents 2 and 3 propose a grinding apparatus configured to adjust the inclination of the chuck table without stopping the grinding of the wafer. According to this grinding apparatus, grinding does not need to be temporarily stopped for adjusting the inclination of the chuck table, so the grinding time for the wafer can be shortened. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-119123 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2014-172131 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2014-226749 [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] However, in the grinding apparatus proposed in Patent Documents 1 to 3, the thickness of the wafer is measured after grinding with the grinding wheel. That is, the thickness of the wafer is measured when no load (vertical load) is applied from the grinding wheel to the holding surface of the chuck table, and the tilt of the chuck table is adjusted before grinding. As a result, the vertical load applied to the grinding wheel and the chuck table is different when measuring the wafer thickness and when grinding is being performed. Therefore, the tilt of the chuck table is adjusted taking into account the amount of tilt of the chuck table due to the load, but even then, the thickness of the wafer may not be uniform.

[0007] Therefore, in a grinding apparatus for grinding wafers, there is a challenge in grinding the wafer to a uniform thickness across its entire surface by measuring the thickness of the wafer at the point where the grinding wheel is in contact with the wafer during the grinding process, and adjusting the inclination of the chuck table relative to the grinding wheel based on the measurement result. [Means for solving the problem]

[0008] The present invention relates to a processing apparatus that processes wafers held on a chuck table while measuring their thickness with a non-contact thickness measuring instrument, and comprises a mount on which a processing tool is attached. Rotatable A spindle unit connected to the tip of a spindle, the non-contact thickness measuring instrument comprises: a light-emitting unit disposed on the upper part of the spindle unit that emits measuring light downwards; a light-receiving unit that receives a first reflected light reflected from a first measuring surface and a second reflected light reflected from a second measuring surface at the upper part of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the first reflected light and the second reflected light received by the light-receiving unit. The spindle and the mount connected to the spindle It includes an optical path unit inside that allows the measurement light, the first reflected light, and the second reflected light to pass through. The optical path unit has an opening on the mounting surface on which the workpiece is attached, in a circle centered on the rotation center of the mount, and the light passing through the opening The thickness of the wafer is measured through an optical path that penetrates the processing tool. The optical path unit may include a first optical path extending axially downward from the upper end of the spindle's axis to the mount, a second optical path with one end connected to the lower end of the first optical path and extending perpendicularly to the first optical path toward the outer circumference of the mount, a first mirror connecting the first optical path and the second optical path, a third optical path connected to the other end of the second optical path and extending perpendicularly to the second optical path toward downward, and a second mirror connecting the second optical path and the third optical path. The present invention relates to a grinding apparatus for grinding a wafer equipped with the above-described spindle unit, comprising: a chuck table that holds the wafer on a holding surface and rotates around the center of the wafer as an axis; a grinding mechanism for grinding the wafer held on the holding surface, wherein a grinding wheel having grinding wheels arranged in an annular pattern on a base is mounted on the mount of the spindle unit; a rotation angle detection unit for detecting the rotation angle of the spindle; a non-contact thickness measuring instrument for measuring the thickness of the wafer non-contact using the optical path unit inside the spindle unit; a tilt adjustment mechanism for relatively adjusting the tilt of the holding surface with respect to the lower surface of the grinding wheel; and a control unit, wherein the non-contact thickness measuring instrument includes a light projection unit that projects measurement light downward from the top of the spindle unit through the optical path unit, and the upper surface of the wafer The control unit includes a light receiving unit that receives upper surface reflected light and lower surface reflected light from the lower surface of the wafer through the optical path unit at the top of the spindle unit, and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the upper surface reflected light and the lower surface reflected light received by the light receiving unit, and a first storage unit that stores the radial thickness of the wafer calculated by the thickness calculation unit in association with the angle detected by the rotation angle detection unit when measuring the thickness, and a tilt control unit that controls the tilt adjustment mechanism based on the radial thickness data of the wafer, which associates the rotation angle of the spindle stored in the first storage unit with the thickness of the wafer, so that the radial thickness trend of the wafer ground to a predetermined thickness becomes a preset radial thickness trend. The present invention relates to a grinding apparatus for grinding a wafer equipped with the above-described spindle unit, comprising: a chuck table that holds the wafer on a holding surface and rotates around the center of the wafer as an axis; a grinding mechanism for grinding the wafer held on the holding surface, wherein a grinding wheel having grinding wheels arranged in an annular manner on a base is mounted on the mount of the spindle unit; a rotation angle detection unit for detecting the rotation angle of the spindle; a non-contact thickness measuring instrument for measuring the thickness of the wafer non-contact using the optical path unit inside the spindle unit; a tilt adjustment mechanism for relatively adjusting the tilt of the holding surface with respect to the lower surface of the grinding wheel; and a control unit, wherein the non-contact thickness measuring instrument includes a light projection unit that projects measurement light downward from the top of the spindle unit through the optical path unit, and the wafer reflecting the measurement light from the upper surface of the wafer. The control unit includes a light receiving unit that receives light from the top surface reflected light and light from the holding surface reflected from the top surface outside the wafer at the same height as the holding surface, through the optical path unit at the top of the spindle unit, and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the light from the holding surface reflected light and the light from the top surface of the wafer received by the light receiving unit, and the control unit includes a first storage unit that stores the radial thickness of the wafer calculated by the thickness calculation unit in association with the angle detected by the rotation angle detection unit when measuring the thickness, and a tilt control unit that controls the tilt adjustment mechanism based on the radial thickness data of the wafer, which associates the rotation angle of the spindle stored in the first storage unit with the thickness of the wafer, so that the radial thickness trend of the wafer ground to a predetermined thickness becomes a preset radial thickness trend. The present invention relates to a grinding apparatus for grinding wafers equipped with the above-described spindle unit, comprising: a chuck table that holds the wafer on a holding surface and does not rotate; a grinding mechanism for grinding the wafer held on the holding surface, wherein a grinding wheel having grinding wheels arranged in an annular manner on a base is mounted on the mount of the spindle unit; a rotation angle detection unit for detecting the rotation angle of the spindle; a non-contact thickness measuring instrument for measuring the thickness of the wafer non-contact using the optical path unit inside the spindle unit; a horizontal movement mechanism for moving the chuck table and the grinding mechanism in a direction horizontal to the holding surface; and a control unit, wherein the non-contact thickness measuring instrument comprises a light projection unit that projects measuring light downward from the top of the spindle unit through the optical path unit. The control unit comprises: a light receiving unit that receives the upper surface reflected light from the upper surface of the wafer and the lower surface reflected light from the lower surface of the wafer through the optical path unit at the top of the spindle unit; a thickness calculation unit that receives the light from the light receiving unit and calculates the thickness of the wafer based on the optical path difference between the upper surface reflected light and the lower surface reflected light; a second storage unit that stores thickness data relating the thickness of the wafer calculated by the thickness calculation unit, the angle detected by the rotation angle detection unit during the measurement of the thickness, and the position of the chuck table that moves horizontally by the horizontal movement mechanism; and a vertical control unit that controls the vertical movement mechanism so that the wafer becomes a preset thickness based on the thickness data stored in the second storage unit. The present invention relates to a grinding apparatus for grinding wafers equipped with the above-described spindle unit, comprising: a chuck table that holds the wafer on a holding surface and does not rotate; a grinding mechanism for grinding the wafer held on the holding surface, wherein a grinding wheel having grinding wheels arranged in an annular manner on a base is mounted on the mount of the spindle unit; a rotation angle detection unit for detecting the rotation angle of the spindle; a non-contact thickness measuring instrument for measuring the thickness of the wafer non-contact using the optical path unit inside the spindle unit; a horizontal movement mechanism for moving the chuck table and the grinding mechanism in a direction horizontal to the holding surface; and a control unit, wherein the non-contact thickness measuring instrument includes a light projection unit that projects measuring light downward from the top of the spindle unit through the optical path unit, and the measurement on the upper surface of the wafer The control unit includes a holding surface light receiving unit that receives reflected light from the top surface of the wafer and reflected light from the holding surface, which is reflected from the upper surface of the wafer outside the wafer at the same height as the holding surface, through the optical path unit at the top of the spindle unit; a thickness calculation unit that receives the light from the light receiving unit and calculates the thickness of the wafer based on the optical path difference between the reflected light from the top surface of the wafer and the reflected light from the holding surface; a second storage unit that stores thickness data relating the thickness of the wafer calculated by the thickness calculation unit, the angle detected by the rotation angle detection unit during the measurement of the thickness, and the position of the chuck table that moves horizontally by the horizontal movement mechanism; and a vertical control unit that controls the vertical movement mechanism to make the wafer a preset thickness based on the thickness data stored in the second storage unit. [Effects of the Invention]

[0009] According to the spindle unit of the present invention, the thickness of the wafer is calculated by passing a measurement light, a first reflected light, and a second reflected light through an optical path that penetrates the workpiece. Therefore, the thickness of the wafer can be measured at the portion where the workpiece contacts the wafer during processing such as grinding and polishing of the wafer. Furthermore, according to the grinding apparatus of the present invention, the radial distribution of wafer thickness measured by a non-contact thickness measuring instrument is associated with the rotation angle of the spindle, and based on the associated data of the spindle rotation angle and the radial distribution of wafer thickness, the tilt adjustment mechanism is controlled to adjust the tilt of the chuck table so that the radial distribution of wafer thickness becomes a preset radial distribution, thereby enabling the wafer to be ground to a uniform thickness across its entire surface. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partially broken perspective view showing an example of a grinding apparatus according to the present invention. [Figure 2] This is a longitudinal cross-sectional view showing an example of a spindle unit according to the present invention. [Figure 3] This is a schematic cross-sectional view showing the positional relationship between the grinding wheel, the chuck table, and the wafer in a grinding apparatus. [Figure 4] This is a plan view showing the positional relationship between the wafer, the grinding wheel, and the wafer thickness measurement point during grinding. [Figure 5] This is a cross-sectional view taken along line II in Figure 4. [Figure 6] This is a plan view showing another example of the positional relationship between the wafer, the grinding wheel, and the wafer thickness measurement point during grinding. [Figure 7] This is a schematic cross-sectional view showing the measurement of the thickness of a wafer at a location where the grinding wheel does not make contact. [Figure 8] This is a cross-sectional view showing the state in which measuring light that has passed through the grinding wheel is reflected off the upper surface of the frame of the chuck table. [Figure 9] This is a longitudinal cross-sectional view showing another example of the spindle unit according to the present invention. [Figure 10] This is a longitudinal cross-sectional view showing the spindle unit according to the present invention with a polishing wheel attached. [Figure 11] This is a cross-sectional view showing the state in which the polishing pad is in contact with the upper surface of the wafer and polishing is performed with the polishing pad extending beyond the periphery of the wafer. [Figure 12]It is a cross-sectional view showing a state where measurement light is projected onto the upper surface of a wafer in contact with a polishing pad. [Figure 13] It is a cross-sectional view showing a state where measurement light that has passed through a polishing wheel is reflected on the upper surface of the frame body of a chuck table. Mode for Carrying Out the Invention

[0011] The grinding apparatus 1 shown in FIG. 1 is an apparatus for grinding a disk-shaped wafer 100 as a workpiece, and includes a rotating chuck table 10, a grinding mechanism 20 for grinding the wafer 100 suction-held on the chuck table 10, a vertical moving mechanism 60 for moving the grinding mechanism 20 up and down in a direction (Z-axis direction) perpendicular to the holding surface 11 of the chuck table 10, a tilt adjustment mechanism 70 for adjusting the tilt of the chuck table 10, a horizontal moving mechanism 80 for moving the chuck table 10 in a direction (Y-axis direction) horizontal with respect to the holding surface 11, and a control unit 90. Note that the horizontal moving mechanism 80 may be a turntable provided with a plurality of chuck tables 10.

[0012] Here, the wafer 100 is formed of a single-crystal silicon base material, a plurality of devices (not shown) are formed on the surface facing downward in the state shown in FIG. 1, and these devices are protected by a protective tape (not shown) attached to the surface of the wafer 100. Then, the surface (the lower surface in FIG. 1) of the wafer 100 is suction-held on the holding surface 11 of the chuck table 10, and the back surface (the upper surface in FIG. 1) is ground by the grinding mechanism 20.

[0013] The chuck table 10 comprises a disc-shaped porous member 13 supported by a frame 12 having a recess in the center, and the upper surface of the porous member 13 constitutes a holding surface 11 that sucks and holds a disc-shaped wafer 100. The holding surface 11 and the upper surface 120 of the frame 12 are formed flush. The porous member 13 is connected to a suction source (not shown), such as a vacuum pump. The chuck table 10 is driven by a motor (not shown) and is rotatable around the center of the wafer 100 held on the holding surface 11. The motor that serves as the rotational drive source for the chuck table 10 is electrically connected to a control unit 90 shown in Figure 1, and its drive is controlled by the control unit 90.

[0014] Here, as shown in Figure 1, the grinding device 1 is equipped with a rectangular box-shaped base 2 that is long in the Y-axis direction (front-to-back direction), and a chuck table 10 is housed in a rectangular opening 3 that is long in the Y-axis direction and opens at the top of the base 2. The area around the chuck table 10 in the opening 3 is covered by a rectangular plate-shaped cover 4, and the front and rear (-Y direction and +Y direction) of the cover 4 in the opening 3 are covered by bellows-shaped expandable covers 5 and 6 that move and expand together with the cover 4.

[0015] The grinding mechanism 20 comprises a spindle housing 22 fixed to a holder 21, a spindle unit 30 housed in the spindle housing 22, a mount 23 attached to the lower end of the rotatable spindle 31 of the spindle unit 30, and a grinding wheel 24 detachably mounted on the lower surface of the mount 23. Here, the grinding wheel 24 is composed of a ring-shaped base 241 and a plurality of grinding wheels 242, which are processing tools, mounted in an annular shape on the lower surface of the base 241. The lower surface of the grinding wheels 242 constitutes a grinding surface that contacts the wafer 100.

[0016] The vertical movement mechanism 60 moves the grinding mechanism 20 up and down in a direction perpendicular to the holding surface 11 of the chuck table 10 (Z-axis direction), and is positioned on the -Y direction end face (front face) of a rectangular box-shaped column 61 erected at the +Y direction end (rear end) of the upper surface of the base 2. This vertical movement mechanism 60 moves a rectangular plate-shaped lifting plate 62 attached to the back of the holder 21 up and down in the Z-axis direction along a pair of left and right guide rails 63, together with the holder 21, the spindle housing 22 held by the holder 21, and the grinding wheel 24. The pair of left and right guide rails 63 are arranged perpendicularly and parallel to each other on the front surface of the column 61.

[0017] Between a pair of left and right guide rails 63, a rotatable ball screw shaft 64 is erected along the Z-axis direction (vertical direction), and the upper end of the ball screw shaft 64 is connected to a reversible motor 65, which is the drive source. The motor 65 is mounted vertically via a rectangular plate-shaped bracket 66 attached to the upper surface of the column 61. The lower end of the ball screw shaft 64 is rotatably supported by the column 61, and a nut member (not shown), which protrudes horizontally toward the rear (+Y direction) from the back of the lifting plate 62, is screwed onto this ball screw shaft 64.

[0018] Therefore, when the motor 65 is driven to rotate the ball screw shaft 64 in forward and reverse directions, the lifting plate 62, to which a nut member (not shown) that screws onto the ball screw shaft 64 is attached, moves up and down along the Z axis together with the grinding mechanism 20. The motor 65 is electrically connected to the control unit 90, and its drive is controlled by the control unit 90.

[0019] The horizontal movement mechanism 80 is a mechanism for moving the chuck table 10 in a direction horizontal to the holding surface 11 (in the Y-axis direction), and as shown in Figure 1, it is disposed on a rectangular block-shaped internal base 81 housed inside the base 2. This workpiece horizontal movement mechanism 80 is equipped with a block-shaped slider 82, which is slidable in the Y-axis direction along a pair of left and right guide rails 83 that are arranged parallel to each other along the Y-axis direction (front-rear direction). Therefore, the chuck table 10 supported by the slider 82 and a drive source such as a motor (not shown) can slide together with the slider 82 along the Y-axis direction.

[0020] A rotatable ball screw shaft 84 extending in the Y-axis direction is positioned between a pair of left and right guide rails 83 on the internal base 81. One end of the ball screw shaft 84 in the Y-axis direction (the left end in Figure 1) is connected to a reversible motor 85, which is the drive source. The other end of the ball screw shaft 84 in the Y-axis direction (the right end in Figure 1) is rotatably supported by a bearing 86 erected on the internal base 81. A nut member (not shown), projecting downward from the slider 82, is screwed onto this ball screw shaft 84.

[0021] Therefore, when the motor 85 is rotated in both forward and reverse directions, causing the ball screw shaft 84 to rotate in both forward and reverse directions, a nut member (not shown) that is screwed onto the ball screw shaft 84 slides along the ball screw shaft 84 in the Y-axis direction together with the slider 82. As a result, the chuck table 10 also moves integrally along the Y-axis direction together with the slider 82. Consequently, the wafer 100, which is held by attraction on the holding surface 11 of the chuck table 10, also moves along the Y-axis direction. The motor 85 is electrically connected to the control unit 90, and its drive is controlled by the control unit 90.

[0022] As shown in Figure 2, the spindle unit 30 includes a spindle 31 rotatably housed inside a spindle housing 22 that opens downwards. The spindle 31 is rotatably supported by the spindle housing 22 by an axial bearing 32. The vertical thrust force acting on the spindle 31 is received by the spindle housing 22 via a thrust bearing 33. Compressed air is injected into the axial bearing 32 and the thrust bearing 33 from an air supply source 34, such as an air compressor, via an air pipe 7 and a plurality of air passages 8 formed in the spindle housing 22. A check valve 9 is provided in the middle of the air passage 8 to prevent backflow of compressed air towards the air supply source 34.

[0023] Furthermore, a spindle motor 35 for rotationally driving the spindle 31 is housed in the upper part of the spindle housing 22. Here, the spindle motor 35 comprises a rotor 351 attached to the upper end of the spindle 31 and a stator 352 fixed to the spindle housing 22 so as to surround the rotor 351. A cooling water jacket 36 is provided on the outer circumference of the stator 352 for circulating cooling water to cool the heat-generating coil (not shown) of the stator 352.

[0024] As shown in Figure 2, the spindle unit 30 includes a rotation angle detection unit 40 for detecting the rotation angle of the spindle 31, and a non-contact thickness measuring instrument 50 for non-contact measurement of the thickness of the wafer 100 held on the holding surface 11 of the chuck table 10.

[0025] As shown in Figure 2, the rotation angle detection unit 40 is composed of an encoder that optically detects the rotation angle of the spindle 31. It is a transmissive optical rotary encoder composed of a disc-shaped slotted disc 41 attached to the upper end of the spindle 31, and a light-emitting unit 42 and a light-receiving unit 43 arranged facing each other on the upper and lower surfaces of the slotted disc 41. This rotation angle detection unit 40 is electrically connected to the control unit 90 shown in Figure 1, and its detection signal (rotation angle signal) is transmitted to the control unit 90. The rotation angle detection unit 40 may be a reflective optical rotary encoder, or a magnetic one.

[0026] The non-contact thickness measuring instrument 50 measures the thickness of the portion of the wafer 100 held on the chuck table 10 that is in contact with the grinding wheel 242 in a non-contact optical manner. As shown in Figure 2, a measuring light L is projected onto the wafer 100 from above, and the thickness of the wafer 100 is measured by spectral interference of two reflected lights reflected from the upper surface 100a of the wafer 100, which is the first measuring surface, and the lower surface 100b of the wafer 100, which is the second measuring surface.

[0027] Specifically, as shown in Figure 2, the non-contact thickness measuring instrument 50 consists of a light-emitting unit 52 housed in a case 51 positioned on top of the spindle housing 22, a beam splitter 53, a diffraction grating 54, a light-receiving unit 55, a thickness calculation unit 56 positioned outside the case 51, an optical path unit U composed of a first optical path U1, a second optical path U2, and a third optical path U3, and a first mirror 57 and a second mirror 58 positioned in the second optical path U2. The first optical path U1 is composed of, for example, an optical fiber. On the other hand, the second optical path U2 and the third optical path U3 are composed of tubular spaces.

[0028] The light-emitting unit 52, housed in case 51, emits measurement light L, such as infrared light, in a horizontal direction. A beam splitter 53 is positioned in the optical path of this measurement light L at a 45° angle to the horizontal. Inside case 51, a diffraction grating 54 is positioned on the opposite side (upper side) from the reflection direction of the measurement light L, relative to the beam splitter 53, and a light-receiving unit 55 is positioned in the direction in which the light is reflected by the diffraction grating 54.

[0029] Here, the first optical path U1 constituting the optical path unit U extends in the Z-axis direction from the upper end of the axis of the spindle 31 downwards toward the mount 23, and the second optical path U2 extends within the mount 23 from the lower end of the first optical path U1 radially outward (to the left in Figure 2) perpendicular to the first optical path U1 toward the radial outer end of the mount 23. Furthermore, from the radial outer end of the mount 23 of the second optical path U2, a third optical path U3 extends downward perpendicular to the second optical path U2, passing through the base 241 of the grinding wheel 24 and the grinding wheel 242, and opening on the lower surface (grinding surface) of the grinding wheel 242. In this embodiment, the third optical path U3 is formed by creating a hole 242a in the grinding wheel 242, allowing the grinding wheel 24 to penetrate in a direction parallel to the axis of the spindle 31. However, the third optical path U3 may also be opened between two circumferentially adjacent grinding wheels 242 (on the lower surface of the base 241). In this case, the third optical path U3 penetrates the base 241 but not the grinding wheels 242.

[0030] A first mirror 57 is positioned at the radially inner end of the second optical path U2 (the axial center of the mount 23) to connect the first optical path U1 and the second optical path U2, and a second mirror 58 is positioned at the radially outer end (the left end in Figure 2) to connect the second optical path U2 and the third optical path U3. The first mirror 57 and the second mirror 58 are positioned rotated 45° counterclockwise from the horizontal direction (XY plane).

[0031] The tilt adjustment mechanism 70 shown in Figure 1 is a mechanism for adjusting the tilt of the chuck table 10, and is located at two locations in the circumferential direction below the chuck table 10. Here, two tilt adjustment mechanisms 70 and one pivot section 71 (see Figure 3) are arranged at equal angular pitches (120° pitches) in the circumferential direction at three locations in the circumferential direction below the chuck table 10.

[0032] Each tilt adjustment mechanism 70 adjusts the tilt of the chuck table 10 relative to the horizontal plane by tilting the chuck table 10 with respect to the pivot portion 71 by moving the actuator 72 up and down. These tilt adjustment mechanisms 70 are equipped with a vertical load measuring device 73, such as a load cell, for measuring the vertical load acting perpendicularly from the grinding wheel 242 to the wafer 100. The vertical load measuring device 73 is electrically connected to the control unit 90 shown in Figure 1, and the output signal from this vertical load measuring device 73 is transmitted to the control unit 90. In addition, the actuator 72 of each tilt adjustment mechanism 70 is electrically connected to the control unit 90, and its operation is controlled by the control unit 90.

[0033] The control unit 90 includes a CPU (Central Processing Unit) that performs calculations according to a control program, and memory such as ROM (Read Only Memory) and RAM (Random Access Memory). This control unit 90 drives and controls the spindle motor 35, which is the drive source for the grinding mechanism 20, and the motor 65 of the vertical movement mechanism 60 to control the rotational speed of the grinding wheel 242 and the movement speed of the vertical movement mechanism 60. In addition, it controls the drive of other drive sources not shown, such as the motor of the chuck table 10, and the actuator 72 (see Figure 3) of the tilt adjustment mechanism 70.

[0034] The control unit 90 includes a first storage unit 91 and a second storage unit 93 that receive signals transmitted from the thickness calculation unit 56 (see Figure 2) and the vertical load measuring instrument 73 (see Figure 3) of the non-contact thickness measuring instrument 50 and store various data, a tilt control unit 92 that controls the tilt adjustment mechanism 70, and a vertical control unit 94 that controls the vertical movement mechanism 60.

[0035] When grinding the wafer 100, the wafer 100 is placed face down on the holding surface 11 of the chuck table 10. Then, a suction source (not shown) connected to the porous member 13 of the chuck table 10 is driven to create a vacuum in the porous member 13. This generates negative pressure in the porous member 13, and the wafer 100, which is placed on the upper surface (holding surface 11) of the porous member 13, is attracted and held on the holding surface 11 by the negative pressure.

[0036] Here, as shown in Figure 3, the holding surface 11 of the chuck table 10 (the upper surface of the porous member 13) is formed as a conical surface with the rotational axis as its apex, that is, a slope that inclines downward radially outward from the rotational axis. Therefore, the wafer 100 held by the holding surface 11 of the chuck table 10 also forms a conical surface with the rotational axis as its apex, similar to the holding surface 11. Note that in Figure 3, the inclination of the conical surfaces of the holding surface 11 and the wafer 100 is exaggerated for ease of understanding, but in reality, this inclination of the conical surface is so minute that it cannot be perceived with the naked eye.

[0037] In this embodiment, the tilt adjustment mechanism 70 adjusts the tilt so that the holding surface 11 of the chuck table 10 is tilted by an angle α shown in the figure with respect to the horizontal plane (by an angle α shown with respect to the vertical rotation axis of the chuck table 10) so that the lower surface (grinding surface) of the grinding wheel 242, which rotates around a vertical central axis, is parallel to the holding surface 11 of the chuck table 10 and the upper surface (workpiece surface) of the wafer 100.

[0038] From the above state, the horizontal movement mechanism 80 is driven to move the chuck table 10 in the +Y direction (rearward), positioning the wafer 100, which is held by suction on the chuck table 10, below the grinding wheel 24 of the grinding mechanism 20. That is, when the motor 85 is started and the ball screw shaft 84 rotates, a slider 82, to which a nut member (not shown) is attached and screwed onto the ball screw shaft 84, slides along a pair of left and right guide rails 83 in the +Y direction together with the chuck table 10, etc., so that the wafer 100 held on the holding surface 11 of the chuck table 10 is positioned below the grinding wheel 24 of the grinding mechanism 20. At this time, the horizontal positional relationship between the two is adjusted so that the lower surface (machining surface) of the grinding wheel 242 passes through the center of the wafer 100.

[0039] Furthermore, a rotational drive mechanism such as a motor (not shown) is driven to rotate the chuck table 10, causing the wafer 100 held on the holding surface 11 of the chuck table 10 to rotate at a predetermined rotational speed (for example, 300 rpm), while the spindle motor 35 is driven to rotate the grinding wheel 24 at a predetermined rotational speed (for example, 2000 rpm).

[0040] As described above, with the wafer 100 and the grinding wheel 24 rotating, the vertical movement mechanism 60 is driven to lower the grinding wheel 24 in the -Z direction. That is, when the motor 65 is driven and the ball screw shaft 64 rotates, the lifting plate 62, which is provided with a nut member (not shown) that is screwed onto the ball screw shaft 64, descends in the -Z direction together with the spindle unit 30 and the grinding wheel 24. Then, the lower surface (machining surface) of the grinding wheel 242 of the grinding wheel 24 comes into contact with the upper surface (back surface) of the wafer 100. In this state, when the grinding wheel 24 is lowered further by a predetermined amount in the -Z direction from the state in which the lower surface of the grinding wheel 242 is in contact with the upper surface of the wafer 100, the upper surface of the wafer 100 is ground by the grinding wheel 242 by a predetermined amount.

[0041] During the grinding of the wafer 100, the thickness at three points A, B, and C in the circumferential direction of the portion being ground by the grinding wheel 242 (grinding area R shown in Figure 4) is measured by the non-contact thickness measuring instrument 50 as follows.

[0042] Specifically, the measurement light L emitted from the light-emitting unit 52 of the non-contact thickness measuring instrument 50 shown in Figure 2 is reflected by the beam splitter 53 and travels downward along the first optical path U1 of the optical path unit U. Then, it is reflected by the first mirror 57 provided in the second optical path U2, changing its direction of travel by 90° and traveling horizontally along the second optical path U2 towards the second mirror 58. This measurement light L is then reflected by the second mirror 58, changing its direction of travel by 90° and traveling downward along the third optical path U3, and is irradiated onto the wafer 100 from an opening on the lower surface of one grinding wheel 242. Then, as shown in Figure 5, it is reflected by the upper surface 100a and the lower surface 100b of the wafer 100, respectively.

[0043] The top-reflected light L1, reflected from the top surface 100a of the wafer 100, and the bottom-reflected light L2, reflected from the bottom surface 100b of the wafer 100, travel through the third optical path U3 towards the second mirror 58. At the second mirror 58, their direction of travel is changed by 90°, and they travel horizontally along the second optical path U2 towards the first mirror 57. Then, the direction of travel of these top-reflected light L1 and bottom-reflected light L2 is changed by 90° by the first mirror 57, and they travel upward along the first optical path U1, passing through the beam splitter 53 towards the diffraction grating 54. The top-reflected light L1 and bottom-reflected light L2 are spectrally separated by the diffraction grating 54, and after their direction of travel is changed by 90° by the diffraction grating 54, they are received by the light receiving unit 55. The thickness calculation unit 56 then calculates the thickness of the wafer 100 at the location irradiated by the measurement light L, based on the optical path difference between the upper surface reflected light L1 and the lower surface reflected light L2 received by the light receiving unit 55. For example, the thickness of the wafer 100 is calculated by analyzing the waveform of the interference light between the upper surface reflected light L1 and the lower surface reflected light L2.

[0044] In this embodiment, the thickness at three measurement points A, B, and C in the circumferential direction of the grinding area R of the wafer 100 shown in Figure 4 is measured. In this case, the measurement of the thickness at measurement points A, B, and C of the wafer 100 (the outer periphery, the radial middle, and the center of the wafer 100) is performed at the timing when a single grinding wheel 242, through which the third optical path U3 opens, passes through measurement points A, B, and C. This timing is determined by the rotation angle detection unit 40 detecting the rotation angle of the grinding wheel 242 (spindle 31). The first storage unit 91 of the control unit 90 stores in memory the thickness at measurement points A, B, and C of the wafer 100 measured by the non-contact thickness measuring instrument 50, i.e., the radial distribution of the thickness in the grinding area R of the wafer 100, and the rotation angle of the grinding wheel 242 (spindle 31) detected by the rotation angle detection unit 40, in association with each other.

[0045] Next, the tilt control unit 92 of the control unit 90 adjusts the tilt of the chuck table 10 by controlling the tilt adjustment mechanism 70 so that the radial distribution of the thickness of the wafer 100 becomes a preset radial distribution (for example, a uniform thickness), based on the rotation angle of the grinding wheel 242 (spindle 31) and the radial distribution data of the thickness of the wafer 100, which are associated and stored by the first storage unit 91. For example, if the thickness at measurement point A is the thickest, followed by the thickness at measurement point B, and the thickness at measurement point C is the thinnest, and the difference between the thickness at measurement point A and the thickness at measurement point C is 5 μm, and the preset radial distribution is a uniform value, the tilt adjustment mechanism 70 adjusts the inclination of the holding surface 11 of the chuck table 10 so that the portion of the holding surface 11 that holds measurement point A is 5 μm higher. Then, after adjusting the tilt of the chuck table 10, the tilt control unit 92 continues grinding the wafer 100 while measuring the thickness of measurement points A, B, and C on the wafer 100 as shown in Figure 4 using the non-contact thickness measuring instrument 50. If the radial distribution of the thickness of the wafer 100 does not match a preset radial distribution, the thickness measurement of the wafer 100 and the adjustment of the tilt of the chuck table 10 are repeated until the radial distribution of the thickness of the wafer 100 matches the preset radial distribution.

[0046] Furthermore, when the load control unit 99 controls the tilt adjustment mechanism 70 to change the tilt of the chuck table 10 (the tilt of the holding surface 11 relative to the grinding surface of the grinding wheel 242), it controls the vertical movement mechanism 60 to adjust the vertical load acting from the grinding wheel 242 to the wafer 100 so that the vertical load measured by the vertical load measuring instrument 73 maintains a preset value.

[0047] As described above, the spindle unit 30 is equipped with a first optical path U1, a second optical path U2, and a third optical path U3, and the third optical path U3 penetrates at least the mount 23 and the base 241 of the grinding wheel 24 (in the example of Figure 2, it also penetrates the grinding wheel 242), so that the thickness of the wafer 100 in the grinding area R can be measured during grinding. Therefore, the radial distribution of the thickness of the wafer 100 in the grinding area R measured by the non-contact thickness measuring instrument 50 is associated with the rotation angle of the grinding wheel 242 (spindle 31), and the tilt adjustment mechanism 70 is controlled based on the associated radial distribution data to adjust the tilt of the chuck table 10 so that the radial distribution of the thickness of the wafer 100 becomes a preset radial distribution. Then, by repeating the measurement of the wafer 100's thickness and the adjustment of the chuck table 10's tilt until the radial distribution of the wafer 100's thickness matches a preset radial distribution, the wafer 100 can be ground to a uniform thickness across its entire surface.

[0048] Furthermore, when the tilt of the chuck table 10 is changed by the tilt adjustment mechanism 70, the control unit 90 controls the vertical movement mechanism 60 to adjust the vertical load acting from the grinding wheel 242 to the wafer 100 so that the vertical load measured by the vertical load measuring instrument 73 maintains a preset value. This reduces the change in the vertical load acting on the grinding wheel 242 and the chuck table 10 due to the adjustment of the tilt of the chuck table 10, and makes it possible to make the thickness of the wafer 100 flat across its entire surface.

[0049] In the above embodiment, as shown in Figure 4, the thickness of the wafer 100 was measured at measurement points A, B, and C in the grinding area R to determine the radial distribution of the wafer 100's thickness. However, when measuring the thickness at three points, as shown in Figure 6, the thickness may be measured at one or two points in the grinding area R of the wafer 100, for example, only at measurement point F, and the thickness of the other two points or one point, for example, at measurement points D and E in the non-grinding area S, may be measured to determine the radial distribution of the wafer 100's thickness. Note that measurement point C and measurement point F are in the same location.

[0050] In this case, since measurement point F is in the same position as measurement point C in Figure 4, measurement light is projected from 52 through the optical path unit U, similar to measurement point C, and the reflected light from the upper surface 100a and lower surface 100b of the wafer 100 is received by the light receiving unit 43, and the thickness calculation unit 56 can determine the thickness of the wafer 100 based on the optical path difference. On the other hand, for measurement points D and E, the thickness of the wafer 100 is measured using a thickness measuring instrument 50a separate from the non-contact thickness measuring instrument 50, as shown in Figure 7, for example. This thickness measuring instrument 50a may be either a contact type or a non-contact type. This thickness measuring instrument 50a is driven by a horizontal movement mechanism 50b and is movable in the horizontal direction.

[0051] If the thickness measuring instrument 50a is a contact type, it is equipped with two gauges, one gauge is brought into contact with the upper surface 100a of the wafer 100, and the other gauge is brought into contact with the upper surface 120 of the frame 12, and the thickness of the wafer 100 is determined by calculating the difference in height between these two gauges. On the other hand, if it is a non-contact type, similar to the non-contact thickness measuring instrument 50, measuring light is projected onto the wafer 100, and the thickness of the wafer 100 is calculated based on the optical path difference between the reflected light from the upper surface 100a and the reflected light from the lower surface 100b of the wafer 100.

[0052] As shown in Figure 5, if a device protection tape T is attached to the lower surface 100b of the wafer 100, it is possible to determine the total thickness including the tape T (the sum of the thickness of the wafer 100 and the thickness of the tape T), not just the thickness of the wafer 100. In that case, for example, as shown in Figure 4, measurement light L is projected at three measurement points A, B, and C in the grinding area R, and as shown in Figure 8, measurement light L is projected onto the upper surface 120 of the frame 12 that is flush with the holding surface 11, in the area of ​​the upper surface of the chuck table 10 that does not hold the wafer 100. For example, measurement light L is projected towards measurement point G shown in Figure 4. Then, the wafer top surface reflected light reflected from the upper surface 100a of the wafer 100 at measurement points A, B, and C, and the holding surface reflected light L3 reflected from the upper surface 120 of the frame 12 at measurement point G are received by the thickness calculation unit 56. Here, the timing for projecting the measurement light L onto the upper surface of the frame 12 is determined based on the rotation angle detection result of the rotation angle detection unit 40 for the spindle 31.

[0053] The thickness calculation unit 56 is, for example, a triangulation displacement meter, and based on the received reflected light, it calculates the sum of the thickness of the wafer 100 and the thickness of the tape T at measurement points A, B, and C in relation to the height of the upper surface 120 of the frame 12 measured at measurement point G, using a triangulation method. In addition, when calculating the sum of the thickness of the wafer 100 and the thickness of the tape T, the thickness of the tape T can also be considered as part of the thickness of the wafer 100.

[0054] A white confocal displacement meter can also be used as the thickness calculation unit 56. In this case, white light is used as the measurement light L, and white light of different wavelengths is projected from the light projection unit 52 to each of the measurement points A, B, and C in the grinding area R shown in Figure 4, and white light of different wavelengths is projected onto the upper surface 120 of the frame 12 as shown in Figure 8. Then, by receiving the reflected light of the wavelength that is focused at the reflection position in the thickness calculation unit 56, the distances from the measurement points A, B, and C to the thickness calculation unit 56 and the distance from the upper surface 120 of the frame 12 to the thickness calculation unit 56 are determined. Then, by subtracting the distance from the upper surface 120 of the frame 12 to the thickness calculation unit 56 from the distances from the measurement points A, B, and C to the thickness calculation unit 56, the sum of the thickness of the wafer 100 and the thickness of the tape T at the measurement points A, B, and C is calculated.

[0055] As described above, the sum of the thickness of the wafer 100 and the thickness of the tape T at measurement points A, B, and C, calculated using a triangulation-type displacement meter or a white confocal displacement meter constituting the thickness calculation unit 56, is stored in the first storage unit 91 in association with the rotation angle of the spindle 31 detected by the rotation angle detection unit 40. Then, the tilt control unit 92 controls the tilt adjustment mechanism 70 to control the tilt of the holding surface 11 of the chuck table 10, based on the data associated with the rotation angle of the spindle 31 and the sum of the thickness of the wafer 100 and the thickness of the tape T at measurement points A, B, and C, so that the thickness trend of the wafer 100 ground to a predetermined thickness becomes a preset thickness trend. Here, the thickness trend refers to the overall thickness distribution of the wafer 100, which is determined by the thickness values ​​at specific locations within the wafer 100.

[0056] Furthermore, when the tilt of the chuck table 10 is changed by the tilt adjustment mechanism 70, the control unit 90 controls the vertical movement mechanism 60 to adjust the vertical load acting from the grinding wheel 242 to the wafer 100 so that the vertical load measured by the vertical load measuring instrument 73 maintains a preset value. This makes it possible to minimize the change in the vertical load acting on the grinding wheel 242 and the chuck table 10 after adjusting the tilt of the chuck table 10, and to make the thickness of the wafer 100 flat across its entire surface.

[0057] As shown in Figure 9, the first optical path U1, the second optical path U2, and the third optical path U3 constituting the optical path unit U can all be made of optical fibers. In this case, by curving the connection portion between the first optical path U1 and the second optical path U2, and the second connection portion between the second optical path U2 and the third optical path U3, the connection between the first optical path U1 and the second optical path U2, and between the second optical path U2 and the third optical path U3 can be made, thereby eliminating the need to provide components equivalent to the first mirror 57 and the second mirror 58 shown in Figure 2.

[0058] The grinding examples shown in Figures 4 and 6 are for infeed grinding, but the present invention can also be applied to creep-feed grinding. Creep-feed grinding is a method in which the lower surface of the grinding wheel 242 is positioned lower than the upper surface 100a of the wafer 100 held on the holding surface 11 of the chuck table 10, and the grinding wheel 242 is rotated while the chuck table 10 is not rotated, and the chuck table 10 and the grinding mechanism 20 are moved relative to each other in the (horizontal) Y-axis direction to grind the upper surface 100a of the wafer 100.

[0059] In creep feed grinding, when calculating the thickness of only the wafer 100, a spectroscopic interference displacement meter is used in the thickness calculation unit 56. As shown in Figure 5, measurement light L is projected from the light projection unit 52, and the thickness of the wafer 100 is determined in the thickness calculation unit 56, for example, by the spectroscopic interference displacement method, based on the optical path difference between the upper surface reflected light L1 at the upper surface 100a of the wafer 100 and the lower surface reflected light L2 at the lower surface 100b. In this case, the control unit 90 includes a second storage unit 93 that stores radial distribution data of the wafer thickness, which associates the radial distribution of the wafer thickness measured by the non-contact thickness measuring instrument 50 with the rotation angle of the grinding wheel 242 (spindle 31) detected by the rotation angle detection unit 40 and the position of the chuck table 10 that moves horizontally by the horizontal movement mechanism 80 shown in Figure 1, and a vertical control unit 94 that controls the vertical movement mechanism 60 so that the wafer 100 becomes a preset thickness based on the radial thickness distribution data stored in the second storage unit 93.

[0060] On the other hand, when calculating the sum of the thickness of the wafer 100 and the thickness of the tape T, a triangulation-type displacement meter or a white confocal displacement meter is used in the thickness calculation unit 56. In this case, the control unit 90 includes a second storage unit 93 that stores thickness data relating the sum of the thickness of the wafer 100 and the thickness of the tape T calculated by the thickness calculation unit 56, the angle detected by the rotation angle detection unit 40 during thickness measurement, and the position of the chuck table 10 that moves horizontally by the horizontal movement mechanism 80, and a vertical control unit 94 that controls the vertical movement mechanism 60 so that the wafer 100 becomes a preset thickness based on the thickness data stored in the second storage unit 93.

[0061] The method for measuring the thickness of the wafer 100 in creep-feed grinding and detecting the rotation angle of the grinding wheel 242 during thickness measurement is the same as in in-feed grinding. On the other hand, when storing the position of the chuck table 10, which is moved horizontally by the horizontal movement mechanism 80, in the second storage unit 93, for example, the rotation angle information detected by the encoder of the motor 85 shown in Figure 1 is used. Alternatively, a scale may be provided along the Y-axis direction of the grinding device 1, and the reading of the scale may be used as the horizontal position of the chuck table 10.

[0062] The above example shows a configuration in which the spindle unit 30 is applied to the grinding device 1, but the spindle unit 30 can also be used in any other processing device such as a polishing device or a cutting device. The polishing device shown in Figure 10 comprises a chuck table 10 and a spindle unit 30, and a polishing wheel 24a is attached to the lower end of the spindle 31 via a mount 23. The polishing wheel 24a consists of a base 241 mounted on the mount 23 and a polishing pad 243 fixed to the lower surface of the base 241. A hole 243a is formed in the polishing pad 243 that penetrates in the thickness direction, and a third optical path U3 is formed in communication with a hole 241a that penetrates in the thickness direction of the base 241. Here, in Figure 10, the same elements as those shown in Figure 2 are denoted by the same reference numerals, and their explanations are omitted. In addition, although not shown, the polishing device is equipped with a vertical movement mechanism 60, a tilt adjustment mechanism 70, and a horizontal movement mechanism 80 similar to those in Figure 1.

[0063] As shown in Figure 10, when polishing the upper surface 100a of the wafer 100 using the polishing pad 243, the lower surface 100b of the wafer 100 is held by the holding surface 11 of the chuck table 10, and the chuck table 10 is rotated. The spindle motor 35 is driven to rotate the polishing wheel 24a, and the vertical movement mechanism 60 lowers the spindle unit 30 in the -Z direction. Then, the lower surface (processing surface) of the grinding pad 243 comes into contact with the upper surface 100a of the wafer 100. From the state in which the lower surface of the polishing pad 243 is in contact with the upper surface of the wafer 100, if the polishing wheel 24a is lowered by a predetermined amount further in the -Z direction, the upper surface of the wafer 100 is polished by the polishing pad 243. The polishing pad 243 is formed to have a larger diameter than the wafer 100. When polishing the upper surface 100a of the wafer 100, as shown in Figure 11, the lower surface of the polishing pad 243 is in contact with the entire upper surface 100a of the wafer 100, and a portion of the polishing pad 243 extends beyond the periphery of the wafer 100.

[0064] If the thickness calculation unit 56 is a spectroscopic interference displacement meter, as shown in Figure 12, the measurement light L emitted from the light emission unit 52 is reflected from the upper surface 100a and lower surface 100b of the wafer 100 through the first optical path U1, the second optical path U2, and the third optical path U3, and the upper surface reflected light L4 from the upper surface 100a and the lower surface reflected light L5 from the lower surface 100b are received by the thickness calculation unit 56. The thickness calculation unit 56 calculates the thickness of the wafer 100 by analyzing the interference light of the upper surface reflected light L4 and the lower surface reflected light L5. Since the entire upper surface 100a of the wafer 100 is in contact with the lower surface of the polishing pad 243, the thickness calculation unit 56 calculates the thickness of the wafer 100 at regular time intervals and stores it in association with the rotation angle of the spindle 31.

[0065] If the thickness calculation unit 56 is a triangulation-type displacement meter or a white confocal displacement meter, the thickness is calculated by adding the thickness of the wafer 100 and the thickness of the tape T. Since the polishing pad 243 has a larger diameter than the wafer 100, there are times when the wafer 100 is not below the holes 243a formed near the periphery of the polishing pad 243. For example, each time the polishing pad 243 rotates, there are times when the wafer 100 is not below the holes 243a formed in the polishing pad 243, and only the frame 12 is positioned below. Therefore, when the measurement light L is projected at that time, as shown in Figure 13, the thickness calculation unit 56 receives the holding surface reflected light L6 reflected from the upper surface 120 of the frame 12 which is flush with the holding surface 11. If the thickness calculation unit 56 is a triangulation-type displacement meter, the thickness is calculated by adding the thickness of the wafer 100 and the thickness of the tape T using the triangulation method. If the thickness calculation unit 56 is a white confocal displacement meter, white light is used as the measurement light L, and the reflected light of the wavelength focused at the reflection position is received by the thickness calculation unit 56 to determine the distance from the top surface of the wafer 100 to the thickness calculation unit 56 at each measurement point, and the distance from the top surface 120 of the frame 12 to the thickness calculation unit 56. Then, by subtracting the distance from the top surface 120 of the frame 12 to the thickness calculation unit 56 from the distance from the top surface 100a of the wafer 100 to the thickness calculation unit 56, the total thickness of the wafer 100 and the tape T at each measurement point is calculated.

[0066] The sum of the thickness of the wafer 100 and the thickness of the tape T at each measurement point is stored in the first storage unit 91 in association with the rotation angle of the spindle 31 detected by the rotation angle detection unit 40. Then, the tilt control unit 92 controls the tilt adjustment mechanism 70 to control the tilt of the holding surface 11 of the chuck table 10, based on the data which is the sum of the thickness of the wafer 100 and the thickness of the tape T at each measurement point and the rotation angle of the spindle 31. The tilt control unit controls the tilt of the holding surface 11 of the chuck table 10 so that the thickness trend of the wafer 100 polished to a predetermined thickness matches a preset thickness trend.

[0067] Furthermore, when the tilt of the chuck table 10 is changed by the tilt adjustment mechanism 70, the vertical movement mechanism 60 is controlled to adjust the vertical load acting from the polishing pad 243 to the wafer 100 so that the vertical load measured by the vertical load measuring instrument 73 maintains a preset value. As a result, the change in the vertical load acting on the polishing pad 243 and the chuck table 10 after adjusting the tilt of the chuck table 10 can be reduced, and the thickness of the wafer 100 can be made flat across its entire surface.

[0068] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the technical idea described in the claims, specification, and drawings. [Explanation of symbols]

[0069] 1: Grinding device, 2: Base, 3: Opening, 4: Cover, 5, 6: Expandable cover, 7: Air piping, 8: Air passage, 9: Check valve, 10: Chuck table, 11: Holding surface, 12: Frame, 120: Top surface of the frame, 13: Porous member, 20: Grinding mechanism, 21: Holder, 22: Spindle housing, 23: Mount, 24: Grinding wheel, 241: Base, 242: Grinding wheel, 242a: Hole 24a: Polishing wheel, 243: Polishing pad, 243a: Hole 30: Spindle unit, 31: Spindle, 32: Axial bearing, 33: Thrust bearing, 34: Air supply source, 35: Spindle motor, 351: Rotor, 352: Stator, 36: Cooling water jacket, 40: Rotation angle detection unit, 41: Slit disc, 42: Light-emitting unit, 43: Light-receiving unit, 50: Non-contact thickness measuring instrument, 50a: Thickness measuring instrument, 50b: Horizontal movement mechanism 51: Case, 52: Light-emitting section, 53: Beam splitter, 54: Diffraction grating, 55: Light receiving unit, 56: Thickness calculation unit, 57: First mirror, 58: Second mirror, 60: Vertical movement mechanism, 61: Column, 62: Lifting plate, 63: Guide rail, 64: Ball screw shaft, 65: Motor, 66: Bracket, 70: Tilt adjustment mechanism, 71: Pivot section, 72: Actuator, 73: Vertical load measuring device, 80: Horizontal movement mechanism, 81: Internal base, 82: Slider, 83: Guide rail, 84: Ball screw shaft, 85: Motor, 86: Bearing 90: Control unit, 91: First memory unit, 92: Tilt control unit, 93: Second memory unit, 94: Vertical control unit, 100: Wafer, 100a: Top surface, 100b: Bottom surface A~G: Measuring point, L: Measuring light, L1: Top reflected light, L2: Bottom reflected light, L3: Holding surface reflected light, L4: Top surface reflected light, L5: Bottom surface reflected light R: Grinding area, S: Non-grinding area, U: Optical path unit, U1: First optical path, U2: Second optical path, U3: Third optical path, α: Tilt angle of the chuck table

Claims

1. A spindle unit is placed in a processing apparatus that processes wafers held on a chuck table while measuring their thickness with a non-contact thickness measuring instrument, and has a mount on which a processing tool is attached connected to the tip of a rotatable spindle, The non-contact thickness measuring instrument comprises: a light-emitting unit disposed on the upper part of the spindle unit that emits measuring light downwards; a light-receiving unit that receives a first reflected light reflected from a first measuring surface and a second reflected light reflected from a second measuring surface at the upper part of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the first reflected light and the second reflected light received by the light-receiving unit. The spindle and the mount connected to the spindle are equipped with an optical path unit that allows the measurement light, the first reflected light, and the second reflected light to pass through. The optical path unit has an opening on the mounting surface on which the workpiece is attached, in a circle centered on the rotation center of the mount, A spindle unit that measures the thickness of a wafer via an optical path that penetrates the processing tool using light passing through the aperture.

2. The spindle unit according to claim 1, comprising: a first optical path extending axially downward from the upper end of the axis of the spindle to the mount; a second optical path having one end connected to the lower end of the first optical path and extending perpendicularly to the first optical path toward the outer circumference of the mount; a first mirror connecting the first optical path and the second optical path; a third optical path having the other end connected to the second optical path and extending perpendicularly to the second optical path toward downward; and a second mirror connecting the second optical path and the third optical path.

3. A grinding apparatus for grinding wafers, comprising the spindle unit described in claim 1, The spindle unit comprises a chuck table that holds a wafer on a holding surface and rotates around the center of the wafer as an axis, a grinding mechanism in which a grinding wheel with grinding wheels arranged in an annular pattern on a base is mounted on the mount of the spindle unit and grinds the wafer held on the holding surface, a rotation angle detection unit that detects the rotation angle of the spindle, a non-contact thickness measuring instrument that measures the thickness of the wafer non-contact using an optical path unit inside the spindle unit, a tilt adjustment mechanism that relatively adjusts the inclination of the holding surface with respect to the lower surface of the grinding wheel, and a control unit. The non-contact thickness measuring instrument comprises: a light-emitting unit that emits measurement light downward from the top of the spindle unit through the optical path unit; a light-receiving unit that receives the upper surface reflected light from the upper surface of the wafer and the lower surface reflected light from the lower surface of the wafer through the optical path unit at the top of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the upper surface reflected light and the lower surface reflected light received by the light-receiving unit. The control unit includes a first storage unit that stores the radial thickness of the wafer calculated by the thickness calculation unit and the angle detected by the rotation angle detection unit during the measurement of the thickness in association with each other, and a first storage unit that stores the radial thickness data of the wafer, which is obtained by associating the rotation angle of the spindle stored in the first storage unit with the thickness of the wafer, A grinding apparatus comprising: a tilt control unit that controls the tilt adjustment mechanism so that the radial thickness trend of a wafer ground to a certain thickness conforms to a preset radial thickness trend.

4. A grinding apparatus for grinding wafers, comprising the spindle unit described in claim 1, The spindle unit comprises a chuck table that holds a wafer on a holding surface and rotates around the center of the wafer as an axis, a grinding mechanism in which a grinding wheel with grinding wheels arranged in an annular pattern on a base is mounted on the mount of the spindle unit and grinds the wafer held on the holding surface, a rotation angle detection unit that detects the rotation angle of the spindle, a non-contact thickness measuring instrument that measures the thickness of the wafer non-contact using an optical path unit inside the spindle unit, a tilt adjustment mechanism that relatively adjusts the inclination of the holding surface with respect to the lower surface of the grinding wheel, and a control unit. The non-contact thickness measuring instrument comprises: a light-emitting unit that emits measurement light downward from the top of the spindle unit through the optical path unit; a light-receiving unit that receives the wafer top surface reflected light, which is the measurement light reflected from the top surface of the wafer, and the holding surface reflected light, which is the measurement light reflected from the top surface outside the wafer at the same height as the holding surface, through the optical path unit at the top of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the holding surface reflected light and the wafer top surface reflected light received by the light-receiving unit. The grinding apparatus comprises: a first storage unit that stores the radial thickness of the wafer calculated by the thickness calculation unit and the angle detected by the rotation angle detection unit at the time of thickness measurement in association with each other; and a tilt control unit that controls the tilt adjustment mechanism based on the radial thickness data of the wafer, which is obtained by associating the rotation angle of the spindle stored in the first storage unit with the thickness of the wafer, so that the radial thickness trend of the wafer ground to a predetermined thickness becomes a pre-set radial thickness trend.

5. A grinding apparatus for grinding wafers, comprising the spindle unit described in claim 1, The device comprises a chuck table that holds a wafer on a holding surface and does not rotate, a grinding mechanism in which a grinding wheel with a grinding wheel arranged in an annular shape on a base is mounted on the mount of the spindle unit and grinds the wafer held on the holding surface, a rotation angle detection unit that detects the rotation angle of the spindle, a non-contact thickness measuring instrument that measures the thickness of the wafer non-contact using the optical path unit inside the spindle unit, a horizontal movement mechanism that moves the chuck table and the grinding mechanism in a direction horizontal to the holding surface, and a control unit. The non-contact thickness measuring instrument comprises: a light-emitting unit that emits measurement light downward from the top of the spindle unit through the optical path unit; a light-receiving unit that receives the upper surface reflected light from the upper surface of the wafer and the lower surface reflected light from the lower surface of the wafer through the optical path unit at the top of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the upper surface reflected light and the lower surface reflected light received by the light-receiving unit. Grinding apparatus comprising: a control unit, a second storage unit that stores thickness data relating the thickness of the wafer calculated by the thickness calculation unit, the angle detected by the rotation angle detection unit during the measurement of the thickness, and the position of the chuck table moved horizontally by the horizontal movement mechanism; and a vertical control unit that controls the vertical movement mechanism based on the thickness data stored in the second storage unit so that the wafer reaches a preset thickness.

6. A grinding apparatus for grinding wafers, comprising the spindle unit described in claim 1, The device comprises a chuck table that holds a wafer on a holding surface and does not rotate, a grinding mechanism in which a grinding wheel with a grinding wheel arranged in an annular shape on a base is mounted on the mount of the spindle unit and grinds the wafer held on the holding surface, a rotation angle detection unit that detects the rotation angle of the spindle, a non-contact thickness measuring instrument that measures the thickness of the wafer non-contact using the optical path unit inside the spindle unit, a horizontal movement mechanism that moves the chuck table and the grinding mechanism in a direction horizontal to the holding surface, and a control unit. The non-contact thickness measuring instrument comprises: a light-emitting unit that emits measurement light downward from the top of the spindle unit through the optical path unit; a holding surface light-receiving unit that receives the wafer top surface reflected light, which is the measurement light reflected from the upper surface of the wafer, and the holding surface reflected light, which is the measurement light reflected from the upper surface outside the wafer at the same height as the holding surface, through the optical path unit at the top of the spindle unit; and a thickness calculation unit that calculates the thickness of the wafer based on the optical path difference between the wafer top surface reflected light and the holding surface reflected light received by the light-receiving unit. Grinding apparatus comprising: a control unit, a second storage unit that stores thickness data relating the thickness of the wafer calculated by the thickness calculation unit, the angle detected by the rotation angle detection unit during the measurement of the thickness, and the position of the chuck table moved horizontally by the horizontal movement mechanism; and a vertical control unit that controls the vertical movement mechanism to move the wafer to a preset thickness based on the thickness data stored in the second storage unit.

Images