Workpiece processing method

Abstract

To obtain a thinned workpiece having a uniform thickness.SOLUTION: In a method of processing a workpiece, a chuck table, a grinding unit including a grinding wheel for grinding a processed surface of the workpiece, a polishing unit including a polishing pad for polishing the processed surface, and a measuring unit for measuring a thickness of the workpiece are used to process the workpiece. The method includes: a grinding step in which the workpiece is ground from the processed surface with the grinding unit; a measuring step in which thicknesses of the workpiece at a plurality of measurement sites are measured with the measuring unit to obtain information regarding a thickness distribution of the workpiece after the griding step, and a polishing step in which the workpiece is polished from the processed surface with the polishing unit. In the polishing step, polishing conditions are determined based on the information regarding the thickness distribution of the workpiece obtained in the measuring step to polish the workpiece.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for processing a workpiece, in which a plate-shaped workpiece is thinned to a predetermined thickness by grinding and polishing. [Background technology]

[0002] In electronic devices such as mobile phones and personal computers, device chips equipped with devices such as electronic circuits are essential components. Device chips are obtained, for example, by dividing a wafer made of a semiconductor material such as silicon into a plurality of regions along planned dividing lines (streets), forming devices in each region, and then dividing the wafer along the planned dividing lines. If the wafer is thinned before being divided, thin device chips can be finally manufactured.

[0003] Plate-shaped workpieces such as wafers are thinned using an annular grinding wheel to which a grinding stone containing abrasive grains is fixed (see Patent Document 1). In general, when a workpiece is ground, minute irregularities such as processing marks and processing distortions are left on the processed surface. Therefore, in order to remove the irregularities from the processed surface, the workpiece is subjected to a polishing process such as CMP (Chemical Mechanical Polishing) after grinding (see Patent Document 2).

[0004] A grinding and polishing device equipped with a grinding unit and a polishing unit is used in this series of workpiece processing (see Patent Document 3). The grinding and polishing device grinds the workpiece while monitoring the thickness in a specific area of ​​the workpiece, and stops grinding the workpiece when it is confirmed that the workpiece has reached a predetermined thickness. The ground workpiece is then polished under predetermined conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-288881 A [Patent Document 2] Japanese Patent Application Publication No. 8-99265 [Patent Document 3] JP 2002-283243 A Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a remarkable trend toward miniaturization and high functionality in electronic devices equipped with chips, and as a result, importance is being placed on the stability of the quality of mass-produced chips. For example, to stabilize the quality of chips, high thickness uniformity (TTV: Total Thickness Variation) across the entire wafer is required for thinned wafers.

[0007] However, when a workpiece is ground under specified conditions using a grinding and polishing device, the ground surface of the workpiece may not be flat due to the variation in thickness of the workpiece itself and the state of the grinding and polishing device. That is, the height of the workpiece may vary from place to place on the surface of the workpiece. If a workpiece with an uneven surface height is simply polished under specified conditions, the height of the polished surface will also be uneven.

[0008] Therefore, a method for processing workpieces that can make the thickness of the workpieces uniform is required. However, the variation in height of the processed surface of each workpiece is not uniform, and even when the same type of workpiece is processed under the same processing conditions with the same grinding and polishing device, different variations occur in each workpiece. Therefore, it is not easy to process the workpieces so that the thickness is uniform.

[0009] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a method for processing a workpiece, which processes the workpiece to obtain a thinned workpiece having a uniform thickness. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a method for processing a workpiece using a chuck table, a grinding unit having a grinding wheel that grinds the workpiece surface of the workpiece held on the chuck table, a polishing unit having a polishing pad that polishes the workpiece surface held on the chuck table after grinding, and a measuring unit that measures the thickness of the workpiece held on the chuck table, the method including: a grinding step of grinding the workpiece from the workpiece surface with the grinding unit; a measuring step of measuring, after the grinding step, the thickness of the workpiece at a plurality of measurement points with the measuring unit to obtain information regarding the thickness distribution of the workpiece; and a polishing step of polishing the workpiece from the workpiece surface with the polishing unit, wherein in the polishing step, polishing conditions are determined based on the information regarding the thickness distribution of the workpiece obtained in the measuring step, and the workpiece is polished.

[0011] Preferably, the polishing unit further includes a controller having a memory section in which a plurality of types of polishing conditions are registered and controlling the polishing unit, and in the polishing step, the controller reads out the polishing conditions that are advantageous for uniforming the thickness of the workpiece from among the plurality of types of polishing conditions registered in the memory section based on information regarding the thickness distribution of the workpiece obtained in the measurement step, and proceeds with polishing of the workpiece in accordance with the read-out polishing conditions.

[0012] More preferably, the polishing pad of the polishing unit has an outer diameter larger than the outer diameter of the workpiece, and in the polishing step, the chuck table holding the workpiece and the polishing pad are subjected to relative oscillation along a direction parallel to the workpiece surface, while the polishing pad polishes the workpiece, and in the polishing step, the amount of oscillation and the center position of the oscillation are determined by the polishing conditions read out from the memory unit.

[0013] More preferably, the polishing conditions registered in the memory unit include the distance between the reference position, where the relative position of the polishing pad and the workpiece when the outer periphery of the workpiece is inscribed within the outer periphery of the polishing pad on the workpiece surface, and the center position of the oscillation, as well as the amount of the oscillation. Effect of the Invention

[0014] In a method for processing a workpiece according to one aspect of the present invention, the workpiece is ground from the surface to be processed, the thickness of the workpiece is measured to obtain information on the thickness distribution of the workpiece, and the workpiece is polished from the surface to be processed. When polishing the workpiece, polishing conditions are selected based on the information on the thickness distribution of the workpiece, and polishing of the workpiece is performed.

[0015] In this case, the thickness distribution of each ground workpiece is evaluated individually, and each workpiece can be polished by selecting the optimal polishing conditions individually corresponding to the shape of the workpiece after grinding. Therefore, unlike when each workpiece is polished under the same polishing conditions, each workpiece can be polished in response to the variation in thickness of each workpiece.

[0016] Therefore, according to one aspect of the present invention, there is provided a method for processing a workpiece, for processing the workpiece to obtain a thinned workpiece having a uniform thickness. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view showing a grinding and polishing apparatus (processing apparatus). [Diagram 2] FIG. 2 is a plan view illustrating a turntable, a grinding unit, and a polishing unit. [Diagram 3] FIG. 13 is a perspective view showing a schematic diagram of a grinding step being performed; [Figure 4] FIG. 2 is a cross-sectional view showing a schematic view of a workpiece immediately after the start of grinding. [Diagram 5] FIG. 2 is a cross-sectional view illustrating a workpiece that has been thinned by grinding. [Figure 6]10 is a plan view showing a schematic positional relationship between a measuring device and a workpiece in a measuring step; FIG. [Figure 7] 2 is a cross-sectional view illustrating a workpiece whose thickness is measured by a measuring unit. FIG. [Figure 8] FIG. 8(A) is a cross-sectional view showing a workpiece whose surface has been ground so that the center of the surface is lower than the surrounding area, resulting in a concave shape, and FIG. 8(B) is a cross-sectional view showing a workpiece whose surface has been ground so that the center of the surface is higher than the surrounding area, resulting in a convex shape. [Figure 9] FIG. 1 is a cross-sectional view showing a schematic diagram of a polishing step; [Figure 10] Figure 10(A) is a plan view showing a schematic example of the positional relationship between the polishing pad and the workpiece when the outer periphery of the workpiece is inscribed within the outer periphery of the polishing pad on the workpiece's processing surface, and Figure 10(B) is a plan view showing a schematic example of the positional relationship between the polishing pad and the workpiece when the outer periphery of the workpiece is not inscribed within the outer periphery of the polishing pad on the workpiece's processing surface. [Figure 11] 13 is a graph showing experimental results. [Figure 12] 3 is a flowchart showing the flow of each step of the method for machining a workpiece according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 3 includes a perspective view showing a workpiece 1 to be processed by the method for processing a workpiece according to the present embodiment. The workpiece 1 is, for example, a disk-shaped wafer formed using a semiconductor. More specifically, the material of the workpiece 1 is Si (silicon), SiC (silicon carbide), sapphire, or the like.

[0019] A workpiece 1, the surface 1a of which is partitioned into a plurality of small regions by a plurality of mutually intersecting division lines (streets), and in which a device such as an IC (Integrated Circuit) is formed in each small region, may be processed by the method for processing a workpiece according to this embodiment. The back surface 1b of this workpiece 1 is processed as the processed surface. A film-like protective member 3 (see FIG. 3, etc.) for protecting the device is attached to the surface 1a of the workpiece 1.

[0020] The protective member 3 includes a circular base material and an adhesive layer (glue layer) provided on the base material. The base material is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate, and the adhesive layer is made of an epoxy-, acrylic-, or rubber-based adhesive. The adhesive layer may also be made of an ultraviolet-curable resin that is cured by exposure to ultraviolet light.

[0021] However, there are no limitations on the material, shape, structure, size, etc. of the workpiece 1. For example, the workpiece 1 may be a substrate formed using materials such as other semiconductors, ceramics, resins, metals, etc. Similarly, there are no limitations on the type, number, shape, structure, size, arrangement, etc. of devices. The workpiece 1 may not have a device formed thereon. In that case, the protective member 3 may not be attached to the front surface 1a side of the workpiece 1.

[0022] Next, a grinding / polishing apparatus 2, which is a processing apparatus for carrying out the workpiece processing method according to this embodiment, will be described with reference to Fig. 1 etc. The grinding / polishing apparatus (processing apparatus) 2 performs grinding and polishing on the workpiece 1. The front-rear direction (X-axis direction), left-right direction (Y-axis direction), and vertical direction (Z-axis direction) used in the following description are perpendicular to one another.

[0023] The grinding / polishing apparatus (processing apparatus) 2 includes a base 4 that supports each of the components that make up the grinding / polishing apparatus 2. An opening 4a is formed in the upper surface of the front end side of the base 4, and a transport unit (transport mechanism) 6 is provided inside this opening 4a. In addition, in the area further forward of the opening 4a, a cassette mounting table 4b on which a cassette 8 is placed, and a cassette mounting table 4c on which a cassette 10 is placed are provided.

[0024] The cassettes 8, 10 house a plurality of workpieces 1 to which protective members 3 are attached in advance. In the grinding / polishing device 2, the workpieces 1 housed in the cassettes 8, 10 are drawn out one by one, processed, and returned to the cassettes 8, 10.

[0025] An alignment mechanism 12 is provided diagonally behind the opening 4a of the grinding / polishing device 2. The workpiece 1 accommodated in the cassettes 8, 10 is transported to the alignment mechanism 12 by the transport unit 6. Then, the alignment mechanism 12 aligns and positions the workpiece 1 at a predetermined position.

[0026] A transport unit (transport mechanism, loading arm) 14 that holds and rotates the workpiece 1 is provided at a position adjacent to the alignment mechanism 12. The transport unit 14 has a suction pad that adsorbs the top surface (rear surface 1b) of the workpiece 1, and transports the workpiece 1 aligned by the alignment mechanism 12 backward while adsorbing and holding it with the suction pad.

[0027] A disk-shaped turntable 16 is provided behind the transport unit 14. The turntable 16 is connected to a rotary drive source (not shown) such as a motor, and rotates around a rotation axis that is approximately parallel to the Z-axis direction (vertical direction, up-down direction). In addition, on the turntable 16, a plurality of chuck tables (holding tables) 18 (four in FIG. 1, etc.) that hold the workpiece 1 are arranged at approximately equal intervals along the circumferential direction of the turntable 16.

[0028] 2 includes a plan view showing the four chuck tables 18 mounted on the turntable 16. The upper surface of the chuck table 18 constitutes a holding surface 18a that holds the workpiece 1. The holding surface 18a is formed to have the same planar shape and approximately the same size as the workpiece 1. The holding surface 18a is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed inside the chuck table 18.

[0029] There is no limitation on the type or structure of the chuck table that holds the workpiece 1. For example, instead of the chuck table 18, a chuck table that holds the workpiece 1 by a mechanical method, an electrical method, or the like may be used.

[0030] Each of the chuck tables 18 is connected to a rotary drive source (not shown) such as a motor, and rotates around a rotation axis that is approximately parallel to the Z-axis direction. The turntable 16 rotates counterclockwise (in the direction indicated by the arrow α) in a plan view, and positions each of the chuck tables 18 in the following order: transfer position A, rough grinding position B, finish grinding position C, polishing position D, and transfer position A. The transfer unit 14 transfers the workpiece 1, the position of which has been adjusted by the positioning mechanism 12, onto the chuck table 18 positioned at the transfer position A.

[0031] A columnar support structure 20 is disposed behind the rough grinding position B and behind the finish grinding position C (behind the turntable 16). A Z-axis movement mechanism 22 is provided on the front side of the support structure 20. The Z-axis movement mechanism 22 includes a pair of Z-axis guide rails 24 disposed approximately parallel to the Z-axis direction, and a plate-shaped Z-axis movement plate 26 is attached to the pair of Z-axis guide rails 24 in a state that it can slide along the Z-axis guide rails 24.

[0032] A nut portion (not shown) is provided on the rear surface side (back surface side) of the Z-axis moving plate 26, and a Z-axis ball screw 28 arranged generally parallel to the Z-axis guide rail 24 is screwed into this nut portion. In addition, a Z-axis pulse motor 30 is connected to one end of the Z-axis ball screw 28. When the Z-axis pulse motor 30 rotates the Z-axis ball screw 28, the Z-axis moving plate 26 moves in the Z-axis direction along the Z-axis guide rail 24.

[0033] Grinding unit 32a that performs rough grinding of workpiece 1 is attached to the front side (surface side) of Z-axis moving plate 26 arranged above rough grinding position B. Meanwhile, grinding unit 32b that performs finish grinding of workpiece 1 is attached to the front side (surface side) of Z-axis moving plate 26 arranged above finish grinding position C. Movement of grinding units 32a and 32b in the Z-axis direction is controlled by Z-axis moving mechanism 22.

[0034] Each of the grinding units 32a, 32b includes a cylindrical housing 34 attached to the Z-axis moving plate 26. A cylindrical spindle 36 constituting a rotation shaft is rotatably accommodated in the housing 34, and the lower end (tip) of the spindle 36 protrudes from the lower end of the housing 34. As shown in Fig. 3, a wheel mount 37 to which grinding wheels 38a, 38b, which will be described next, are fixed is disposed at the lower end of the spindle 36.

[0035] A grinding wheel 38a for performing rough grinding of the workpiece 1 is attached to the lower end of the spindle 36 provided in the grinding unit 32a. A grinding wheel 38b for performing finish grinding of the workpiece 1 is attached to the lower end of the spindle 36 provided in the grinding unit 32b.

[0036] The grinding wheels 38a, 38b attached to the grinding units 32a, 32b include annular bases 39a, 39b made of metal such as stainless steel, aluminum, etc. A plurality of grinding stones 40a, 40b for grinding the workpiece 1 are arranged in an annular shape at approximately equal intervals on the lower surface side of the bases 39a, 39b.

[0037] For example, the grinding wheels 40a, 40b are formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), or the like, with a bonding material such as metal bond, resin bond, or vitrified bond. However, there are no limitations on the material, shape, structure, size, etc. of the grinding wheels 40a, 40b. In addition, the number of grinding wheels 40a, 40b provided on the grinding wheels 38a, 38b can be set arbitrarily.

[0038] A rotary drive source (not shown) such as a motor is connected to the upper end (base end) of the spindle 36, and the grinding wheels 38a, 38b rotate about a rotation axis roughly parallel to the Z-axis direction by a rotational force transmitted from the rotary drive source via the spindle 36. In addition, a grinding fluid supply path (not shown) for supplying a grinding fluid such as pure water is provided inside the grinding units 32a, 32b. The grinding fluid is supplied toward the workpiece and the grinding wheels 40a, 40b when the workpiece is ground.

[0039] Grinding unit 32a grinds workpiece 1 held by chuck table 18 positioned at rough grinding position B with grinding wheel 40a. This performs rough grinding of workpiece 1. Grinding unit 32b grinds workpiece 1 held by chuck table 18 positioned at finish grinding position C with grinding wheel 40b. This performs finish grinding of workpiece 1.

[0040] Note that measuring units 72 (see FIG. 3) for measuring the thickness of the workpiece 1 held by the chuck table 18 are disposed near the rough grinding position B and the finish grinding position C. The measuring unit 72 is, for example, a non-contact measuring unit that irradiates the upper surface of the workpiece 1 with a laser beam or light and detects the reflected light to measure the height of the upper surface of the workpiece 1 and measure the thickness of the workpiece 1. However, the measuring unit 72 is not limited to this, and may be a contact measuring unit that brings a probe into contact with the upper surface of the workpiece 1.

[0041] The non-contact measuring unit 72 includes, for example, a shaft 74 erected from the base 4 outside the turntable 16 along the Z-axis direction, and an arm 76 extending horizontally (in a direction parallel to the XY plane) from the upper end of the shaft 74. A measuring device 78 for measuring the height of the workpiece 1 is fixed to the tip of the arm 76. The measuring device 78 includes, for example, an illuminator for illuminating the upper surface (rear surface 1b) of the workpiece 1 with light or the like, and a sensor for receiving the light or the like reflected from the workpiece 1.

[0042] The measuring device 78 can be moved by rotating the shaft portion 74. By moving the measuring device 78, the location at which the measuring unit 72 measures the thickness on the upper surface (rear surface 1b) of the workpiece 1 can be changed.

[0043] A columnar support structure 41 is disposed to the side of the polishing position D (to the side of the turntable 16). An XZ-axis movement mechanism 42 is provided on the front surface side (the turntable 16 side) of the support structure 41. The XZ-axis movement mechanism 42 includes a pair of first guide rails 44 disposed generally parallel to the X-axis direction (front-rear direction), and a plate-shaped first movement plate 46 is attached to the pair of first guide rails 44 in a state capable of sliding along the first guide rails 44.

[0044] A nut portion (not shown) is provided on the rear surface side of the first moving plate 46, and a first ball screw 48 disposed generally parallel to the first guide rail 44 is screwed into this nut portion. A first pulse motor 50 is connected to one end of the first ball screw 48. When the first pulse motor 50 rotates the first ball screw 48, the first moving plate 46 moves in the X-axis direction along the first guide rail 44.

[0045] A pair of second guide rails 52 arranged generally parallel to the Z-axis direction are provided on the front surface side (turntable 16 side) of the first moving plate 46. A plate-shaped second moving plate 54 is attached to the pair of second guide rails 52 in a state in which it can slide along the second guide rails 52. A nut portion (not shown) is provided on the back surface side of the second moving plate 54, and a second ball screw 56 arranged generally parallel to the second guide rails 52 is screwed into this nut portion.

[0046] A second pulse motor 58 is connected to one end of the second ball screw 56. When the second pulse motor 58 rotates the second ball screw 56, the second moving plate 54 moves in the Z-axis direction along the second guide rail 52. A polishing unit 60 that polishes the workpiece 1 is attached to the front surface side (turntable 16 side) of the second moving plate 54. The XZ-axis movement mechanism 42 controls the movement of the polishing unit 60 in the X-axis and Z-axis directions.

[0047] The polishing unit 60 includes a cylindrical housing 62 attached to the second moving plate 54. A cylindrical spindle 64 constituting a rotation shaft is rotatably accommodated in the housing 62, and the lower end of the spindle 64 protrudes from the lower end of the housing 62. Fig. 9 includes a cross-sectional view showing a schematic view of the polishing unit 60. A mount 80 to which a polishing pad 66, which will be described next, is fixed is provided at the lower end of the spindle 64.

[0048] A disk-shaped polishing pad 66 for polishing the workpiece 1 is attached to the lower end of the spindle 64. The polishing pad 66 of the polishing unit 60 has, for example, an outer diameter larger than the outer diameter of the workpiece 1. A rotation drive source (not shown) such as a motor is connected to the upper end side (base end side) of the spindle 64. The polishing pad 66 rotates around a rotation axis approximately parallel to the Z-axis direction by the rotation force transmitted from the rotation drive source via the spindle 64.

[0049] The polishing pad 66 attached to the polishing unit 60 includes a disk-shaped base 82 made of a metal material such as stainless steel or aluminum. A polishing layer 84 for polishing the workpiece 1 is fixed to the lower surface side of the base 82. For example, the polishing layer 84 is formed in a disk shape having roughly the same diameter as the base 82, and is attached to the lower surface side of the base 82 by an adhesive or the like. The lower surface of this polishing layer 84 constitutes a polishing surface for polishing the workpiece 1.

[0050] The polishing layer 84 is formed by incorporating abrasive grains such as silicon dioxide (SiO2), green carborundum (GC), white alundum (WA) or the like into a base member such as nonwoven fabric or urethane foam. The abrasive grains contained in the polishing layer 84 may have an average grain size of, for example, 0.1 μm or more and 10 μm or less. However, the material of the polishing layer 84 and the grain size and material of the abrasive grains can be appropriately changed depending on the material of the workpiece 1 and the like.

[0051] For example, when the workpiece 1 is polished, no liquid (polishing liquid) such as a chemical solution (slurry) or pure water is supplied to the workpiece 1 and the polishing pad 66. In this case, the workpiece 1 is processed by dry polishing using the polishing pad 66 whose polishing layer 84 contains abrasive grains.

[0052] However, the workpiece 1 may be processed by wet polishing. In this case, when polishing the workpiece 1, a polishing liquid that does not contain abrasive grains is supplied to the workpiece 1 and the polishing pad 66. As the polishing liquid, for example, a chemical liquid such as an acidic polishing liquid or an alkaline polishing liquid, or pure water can be used. As the acidic polishing liquid, an acidic solution in which permanganate or the like is dissolved is used, and as the alkaline polishing liquid, an alkaline solution in which sodium hydroxide or potassium hydroxide is dissolved is used.

[0053] In addition, in wet polishing, a chemical solution (slurry) containing abrasive grains may be supplied to the workpiece 1 and the polishing pad 66. The chemical solution (slurry) contains abrasive grains made of, for example, silicon oxide (SiO2), alumina (Al2O3), etc. as free abrasive grains. In this case, the polishing pad 66 does not contain abrasive grains.

[0054] The polishing unit 60 may include a supply passage 86 passing through the spindle 64 along the Z-axis direction, and the chemical liquid (slurry) may be supplied to the workpiece 1 and the polishing pad 66 through this supply passage 86.

[0055] The polishing unit 60 polishes the workpiece 1 held by the chuck table 18 positioned at the polishing position D, with the polishing pad 66. In this way, the workpiece 1 is polished.

[0056] A transport unit (transport mechanism, unloading arm) 68 that holds and rotates the workpiece 1 is provided at a position adjacent to the transport unit 14. The transport unit 68 has a suction pad that suctions the upper surface (rear surface 1b) of the workpiece 1, and transports the workpiece 1 placed on the chuck table 18 arranged at the transport position A forward by suctioning and holding it with the suction pad. In addition, a cleaning unit (cleaning mechanism) 70 that cleans the workpiece 1 after processing with a cleaning liquid such as pure water is provided at the front side of the transport unit 68.

[0057] The workpiece 1 cleaned by the cleaning unit 70 is transported by the transport unit 6 and stored in the cassette 10. That is, the cassette 10 stores a plurality of workpieces 1 that have been processed by the grinding units 32a and 32b and the polishing unit 60.

[0058] The grinding / polishing apparatus 2 includes a controller (control unit) 88 that controls each of the components. The controller 88 is connected to each of the components described above. The controller 88 controls the operation of each of the components so that the workpiece 1 can be appropriately processed. The controller 88 is typically configured by a computer including a processing device such as a CPU (Central Processing Unit) and a storage device such as a flash memory. The functions of the controller 88 are realized by operating the processing device and the like in accordance with software stored in the storage device.

[0059] The controller 88 includes, for example, a storage unit 90 that stores various information, and a processing control unit 92 that controls the grinding units 32a, 32b and the polishing unit 60. A plurality of processing conditions to be performed on various types of workpieces 1 are registered in the storage unit 90. The processing conditions include various parameters for operating each component of the grinding and polishing device 2. The processing control unit 92 reads out processing conditions suitable for the type and state of the workpiece 1, the planned processing result, etc. from the storage unit 90, and controls the various components according to the processing conditions.

[0060] Next, a description will be given of the operation of the grinding and polishing apparatus 2 when the workpiece 1 is ground and polished by the grinding and polishing apparatus 2. When the workpiece 1 is processed, first, a plurality of unprocessed workpieces 1 are stored in cassettes 8 and 10, and the cassettes 8 and 10 are placed on the cassette placement tables 4b and 4c.

[0061] Next, one workpiece 1 accommodated in cassette 8, 10 is transported by transport unit 6 to alignment mechanism 12, which aligns workpiece 1. Then, after alignment, workpiece 1 is transported by transport unit 14 onto chuck table 18 arranged at transport position A.

[0062] The workpiece 1 is placed on the chuck table 18 so that the lower surface (front surface 1a) faces the holding surface 18a and the upper surface (rear surface 1b) is exposed upward. In this state, the workpiece 1 is sucked and held by the chuck table 18 via the protective member 3 by applying negative pressure from a suction source to the workpiece 1 through the holding surface 18a.

[0063] Next, the turntable 16 rotates, and the chuck table 18 holding the workpiece 1 is disposed at the rough grinding position B. Then, the workpiece 1 held by the chuck table 18 positioned at the rough grinding position B is ground by the grinding wheel 40a of the grinding unit 32a.

[0064] More specifically, while the chuck table 18 and the grinding wheel 38a are rotated in a predetermined direction at a predetermined rotation speed, the grinding wheel 38a is lowered toward the chuck table 18 by the Z-axis movement mechanism 22. The lowering speed of the grinding wheel 38a at this time is adjusted so that the multiple grinding stones 40a are pressed against the workpiece 1 with an appropriate force.

[0065] When the lower surfaces of the rotating grinding wheels 40a come into contact with the workpiece 1, the workpiece 1 is ground away. This causes the workpiece 1 to be ground, thinning it. When the workpiece 1 is thinned to a predetermined thickness, rough grinding of the workpiece 1 is complete.

[0066] When the workpiece 1 is ground by the grinding wheels 40a, a grinding fluid such as pure water is supplied to the workpiece 1 and the grinding wheels 40a. The grinding fluid cools the workpiece 1 and the grinding wheels 40a, and washes away chips (grinding chips) generated by grinding the workpiece 1.

[0067] Next, the turntable 16 rotates, and the chuck table 18 holding the workpiece 1 is disposed at the finish grinding position C. Then, the workpiece 1 held by the chuck table 18 positioned at the finish grinding position C is ground by the grinding wheel 40b of the grinding unit 32b.

[0068] The configuration and operation of the grinding unit 32b are the same as those of the grinding unit 32a. However, the average grain size of the abrasive grains of the grinding stones 40b included in the grinding wheel 38b is smaller than the average grain size of the abrasive grains of the grinding stones 40a included in the grinding wheel 38a. The lower surfaces of the grinding stones 40b included in the grinding wheel 38b come into contact with the workpiece 1, thereby grinding the workpiece 1. Then, when the workpiece 1 is thinned to a predetermined thickness, the finish grinding of the workpiece 1 is completed.

[0069] Here, the thickness of the workpiece 1 is monitored when the workpiece 1 is ground. The grinding and polishing device 2 is equipped with a measuring unit 72 that measures the thickness of the workpiece 1 held by the chuck table 18. The measuring unit 72 measures the height of the upper surface (rear surface 1b) of the workpiece 1 held by the chuck table 18 from the holding surface 18a, and measures the thickness of the workpiece 1. The measuring unit 72 confirms that the workpiece 1 has reached a predetermined thickness.

[0070] Next, the turntable 16 rotates, and the chuck table 18 holding the workpiece 1 is positioned at the polishing position D. Then, the workpiece 1 held by the chuck table 18 positioned at the polishing position D is polished by the polishing unit 60. When the chuck table 18 is positioned at the polishing position D, the workpiece 1 is positioned below the polishing unit 60.

[0071] When polishing the workpiece 1, for example, the polishing pad 66 is positioned so that the polishing layer 84 overlaps the entire workpiece 1 as shown in Fig. 9. Then, while the chuck table 18 and the polishing pad 66 are rotated in a predetermined direction at a predetermined rotation speed, the polishing pad 66 is lowered toward the chuck table 18 by the XZ axis moving mechanism 42. The lowering speed of the polishing pad 66 at this time is adjusted so that the polishing layer is pressed against the workpiece with an appropriate force.

[0072] The workpiece 1 is polished by pressing the polishing pad 66 against the workpiece 1 while rotating. When a predetermined amount of polishing has been performed, the polishing of the workpiece 1 is completed. This polishing removes the processing marks (cutting marks) and crushed layers formed on the workpiece 1 when the workpiece 1 was ground by the grinding units 32a and 32b, and flattens the upper surface of the polished workpiece 1.

[0073] When polishing the workpiece 1, a liquid (polishing liquid) such as a chemical liquid (slurry) or pure water may be supplied to the workpiece 1 and the polishing pad 66. In this case, the chemical liquid (slurry) is supplied to the workpiece 1 and the polishing pad 66 through the supply path 86.

[0074] Next, the turntable 16 rotates, and the chuck table 18 holding the workpiece 1 is disposed at the transfer position A. Then, the workpiece 1 that has been subjected to the grinding and polishing processes is transferred by the transfer unit 68 from the chuck table 18 positioned at the transfer position A to the cleaning unit 70. Then, the processed workpiece 1 is cleaned by the cleaning unit 70.

[0075] The workpieces 1 cleaned by the cleaning unit 70 are stored in the cassettes 8, 10 by the transport unit 6. In the grinding / polishing apparatus 2, the multiple workpieces 1 thus stored in the cassettes 8, 10 are processed one after another and returned to the cassettes 8, 10. Then, all of the workpieces 1 stored in the cassettes 8, 10 are pulled out, and when the processing of all of the workpieces 1 is completed and they are returned to the cassettes 8, 10, the cassettes 8, 10 are carried out from the grinding / polishing apparatus 2.

[0076] A workpiece 1 such as a semiconductor wafer is thinned to a predetermined thickness by a grinding and polishing device 2 and then divided into individual chips. The manufactured chips are mounted on electronic devices such as smartphones and PCs. In recent years, there has been a remarkable trend toward smaller electronic devices and higher functionality, and as a result, importance is being placed on the stability of the quality of mass-produced chips. For example, to stabilize the quality of chips, high total thickness uniformity (TTV) is required for the thinned workpiece 1.

[0077] However, when the workpiece 1 is ground under predetermined conditions by the grinding units 32a and 32b in the grinding and polishing apparatus 2, the ground surface (rear surface 1b) of the workpiece 1 may not be flat due to the influence of the variation in thickness of the workpiece 1 itself and the state of the grinding and polishing apparatus 2. For example, the ground surface may be convex in shape with the center higher than the surrounding area, or concave in shape with the center lower than the surrounding area.

[0078] Fig. 8(A) is a cross-sectional view showing a workpiece 5 whose surface (rear surface 5b) has been ground, so that the center 5c of the surface is lower than the surrounding area and has a concave shape. Fig. 8(B) is a cross-sectional view showing a workpiece 7 whose surface (rear surface 7b) has been ground, so that the center 7c of the surface is higher than the surrounding area and has a convex shape. Note that Figs. 8(A) and 8(B) show a case where the cross-sectional shape of the surface is linear from the centers 5c, 7c to the outer periphery, but the cross-sectional shape of the surface is not necessarily linear.

[0079] In the workpieces 5 and 7 in this state, the height of the work surface (reverse side 5b and 7b) is not uniform, and the distance between the front side 5a and 7a and the reverse side 5b and 7b, i.e., the thickness, is not uniform. If the workpiece 1 with an uneven work surface height is simply polished under general conditions with the polishing unit 60, the height of the polished work surface will also be uneven and not flat. Therefore, a processing method that can make the thickness of the workpiece 1 uniform is required.

[0080] However, since the variation in height of the processed surface of each workpiece 1 is not uniform, if the same type of workpiece 1 is processed under the same processing conditions, the processed surface of each workpiece 1 cannot be made flat. Therefore, in the method for processing a workpiece according to this embodiment, polishing conditions are selected according to the individual state of the workpiece 1 after grinding, and the workpiece 1 is polished. The method for processing a workpiece according to this embodiment will be described in detail below.

[0081] In the method for processing a workpiece according to this embodiment, the workpiece 1 is processed using the chuck table 18, grinding units 32a, 32b, polishing unit 60, and measuring unit 72. The method for processing a workpiece according to this embodiment is carried out, for example, by a grinding and polishing apparatus (processing apparatus) 2. Below, an example will be described in which the workpiece 1 is processed by the grinding and polishing apparatus (processing apparatus) 2. However, the method for processing a workpiece according to this embodiment does not have to be carried out by the grinding and polishing apparatus 2. FIG. 12 is a flowchart showing the flow of each step of the method for processing a workpiece according to this embodiment.

[0082] In the method for processing a workpiece according to this embodiment, first, a grinding step S10 is performed. Fig. 3 is a perspective view showing the grinding step S10, Fig. 4 is a cross-sectional view showing the workpiece 1 immediately after the start of grinding, and Fig. 5 is a cross-sectional view showing the workpiece 1 thinned by grinding.

[0083] In the grinding step S10, the workpiece 1 is ground from the surface to be processed (rear surface 1b) by the grinding units 32a and 32b. By carrying out the grinding step S10, the workpiece 1 is thinned to a predetermined thickness. When the grinding step S10 is carried out in two stages, that is, rough grinding and finish grinding of the workpiece 1, the grinding unit 32a carries out rough grinding of the workpiece 1, and then the grinding unit 32b carries out finish grinding of the workpiece 1.

[0084] The grinding step S10 will be described in detail. First, in the grinding / polishing device 2, the workpiece 1 is pulled out from the cassettes 8, 10 and placed on the holding surface 18a of the chuck table 18 positioned at the transfer position A. In this process, the back surface 1b of the workpiece 1, which is the surface to be processed, is directed upward, the position of the workpiece 1 is adjusted by the positioning mechanism 12, and the transfer unit 14 is caused to carry out the transfer operation of the workpiece 1 as specified. Then, the center of the workpiece 1 and the center of the holding surface 18a of the chuck table 18 overlap with each other.

[0085] Then, the workpiece 1 is sucked and held on the chuck table 18 via the protective member 3. Then, the turntable 16 is rotated counterclockwise when viewed from above, and the chuck table 18, which sucks and holds the workpiece 1, is positioned at the rough grinding position B. In other words, the chuck table 18 is moved below the grinding unit 32a.

[0086] Thereafter, while supplying grinding water such as pure water to the workpiece 1 and the grinding wheel 38a, the chuck table 18 and the grinding wheel 38a are rotated relative to each other to bring the grinding stone 40a of the grinding wheel 38a into contact with the back surface 1b of the workpiece 1. This performs rough grinding of the workpiece 1.

[0087] Next, the turntable 16 is rotated to move the chuck table 18, which suction-holds the workpiece 1, to the finish grinding position C. That is, the chuck table 18 is moved to below the grinding unit 32b.

[0088] Then, while supplying grinding water such as pure water to the workpiece 1 and the grinding wheel 38b, the chuck table 18 and the grinding wheel 38b are rotated relative to each other to bring the grinding stone 40b of the grinding wheel 38b into contact with the back surface 1b side (upper surface side) of the workpiece 1. This performs finish grinding of the workpiece 1.

[0089] When grinding the workpiece 1 in two stages, rough grinding is performed in grinding unit 32a to grind the workpiece 1 at high speed, and finish grinding is performed in grinding unit 32b to grind the workpiece 1 with high precision. At each stage of the grinding step S10, the thickness of the workpiece 1 is monitored by measuring unit 72, and grinding of the workpiece 1 is preferably terminated when the workpiece 1 reaches a predetermined thickness.

[0090] When the workpiece 1 is thinned to a predetermined finishing thickness by the grinding / polishing device 2, the rough grinding performed by the grinding unit 32a removes most of the total grinding amount planned for the workpiece 1. Furthermore, the finish grinding performed by the grinding unit 32b removes the damaged layer generated in the workpiece 1 during the rough grinding while thinning the workpiece 1 to the predetermined finishing thickness.

[0091] In the grinding step S10, the measurement of the thickness of the workpiece 1 using the measuring unit 72 is performed in an annular region at a constant distance from the center of the back surface 1b of the workpiece 1. That is, the height of the back surface 1b of the workpiece 1 is measured in the region overlapping with the measuring device 78 of the measuring unit 72, and the thickness of the workpiece 1 in that region is measured.

[0092] Conversely, in the grinding step S10, the measuring unit 72 does not measure the thickness of the workpiece 1 over the entire area of ​​the workpiece 1. In particular, since the grinding wheels 40a, 40b continue to contact the vicinity of the center of the processed surface (back surface) of the workpiece 1 while grinding is in progress, the measuring device 78 cannot move to overlap with the vicinity of the center of the processed surface. In other words, the measuring unit 72 cannot measure the thickness near the center of the workpiece 1 while grinding is in progress.

[0093] When the grinding step S10 is completed, the back surface 1b of the workpiece 1 is not necessarily flat. In other words, the thickness of the workpiece 1 is not necessarily uniform throughout. Therefore, it is possible to correct the shape of the processed surface in the polishing step S30 that is performed after the grinding. However, the shape of the processed surface of the workpiece 1 after grinding changes depending on the quality accuracy of the workpiece 1, the state of the grinding and polishing device (processing device) 2, etc., and is not a constant shape.

[0094] Therefore, after the grinding step S10 is completed, the measuring step S20 described below is performed. In the measuring step S20, the thickness of the workpiece 1 at a plurality of measurement points is measured by the measuring unit 72 to obtain information on the thickness distribution of the workpiece 1. Fig. 6 is a plan view showing a schematic positional relationship between the measuring device 78 and the workpiece 1 in the measuring step S20. Fig. 7 is a cross-sectional view showing a schematic positional relationship of the workpiece 1 whose thickness is measured by the measuring unit 72.

[0095] When measuring the height of the processing surface (rear surface 1b) of the workpiece 1 using the measuring unit 72, it is not possible to simultaneously perform measurement over the entire processing surface of the workpiece 1. In the first place, there is no need to measure the height over the entire processing surface to obtain information about the thickness distribution of the workpiece 1. By measuring the thickness of the workpiece 1 at multiple measurement points on the processing surface of the workpiece 1 and obtaining the thickness of the workpiece 1 at each measurement point, it is possible to infer the shape of the processing surface of the workpiece 1 and also obtain sufficient information about the thickness distribution of the workpiece 1.

[0096] 6 and 7, for example, the measuring device 78 is positioned so as to overlap with the processed surface (rear surface 1b) of the workpiece 1. When measuring the thickness of the workpiece 1 using the measuring unit 72 at the finish grinding position C, the grinding wheel 38b of the grinding unit 32b is retracted in advance from above the workpiece 1 so that the measuring device 78 can be positioned so as to overlap with the center of the processed surface of the workpiece 1.

[0097] Then, the measuring device 78 is operated to measure the height of the processed surface of the workpiece 1 near the center of the processed surface (rear surface 1b) of the workpiece 1. For example, the thickness of the workpiece 1 is obtained by subtracting the height of the holding surface 18a of the chuck table 18 from the height of the processed surface of the workpiece 1. In other words, measuring the height of the processed surface near the center of the workpiece 1 is synonymous with measuring the thickness of the workpiece 1 in that region.

[0098] Next, the measuring device 78 of the measuring unit 72 is moved. For example, as shown by the two-dot chain line in Fig. 6, the measuring device 78 is moved so as to overlap the region between the center and the outer periphery of the processing surface (rear surface 1b) of the workpiece 1. Then, the measuring device 78 is operated to measure the height of the processing surface of the workpiece 1 in that region. In other words, the thickness of the workpiece 1 in that region is measured.

[0099] Thereafter, the measuring device 78 of the measuring unit 72 is further moved. For example, as shown by another two-dot chain line in Fig. 6, the measuring device 78 is moved so as to overlap with the outer peripheral region of the processing surface (rear surface 1b) of the workpiece 1. Then, the measuring device 78 is operated to measure the height of the processing surface of the workpiece 1 in that region. In other words, the thickness of the workpiece 1 in that region is measured.

[0100] Thus, in the measurement step S20, the thickness at a plurality of measurement points of the workpiece 1 is measured by the measurement unit 72 to obtain information regarding the thickness distribution of the workpiece 1. Note that in the measurement step S20, the measuring device 78 may be moved above another region to measure the thickness of the workpiece 1 in that region.

[0101] Furthermore, during measurement of the thickness of the workpiece 1 in the measurement step S20, the chuck table 18 may rotate about an axis perpendicular to the holding surface 18a. For example, in the measurement step S20, the chuck table 18 may rotate at a rotation speed of about 60 to 750 revolutions per minute.

[0102] Due to the nature of the grinding process performed on the workpiece 1 in the grinding step S10, the height of the processed surface (rear surface 1b) of the workpiece 1 tends to be similar in each region that is equidistant from the center of the processed surface (rear surface 1b). Therefore, it is advisable to perform measurement by the measuring device 78 multiple times while rotating the chuck table 18, and to average the obtained measured values.

[0103] In this case, a value that more accurately reflects the actual height of the work surface of the workpiece 1 in an area a certain distance away from the center of the work surface (reverse surface 1b) is obtained. In other words, a value in which the effects of variations and the like are reduced is obtained. However, in the measurement step S20, the chuck table 18 does not need to rotate.

[0104] By carrying out the measuring step S20, it becomes clear whether the shape of the workpiece 1 after grinding is a concave shape in which the center of the back surface 1b is lower than the surroundings, or a convex shape in which it is higher. It also becomes clear how much the height of the center of the back surface 1b of the workpiece 1 after grinding is lower or higher than the surroundings. In this way, by carrying out the measuring step S20, information on the thickness distribution of the workpiece 1 is obtained.

[0105] However, the form of the information on the thickness distribution of the workpiece 1 is not limited to this. For example, the thickness distribution of the workpiece 1 may be a collection of the positions of a plurality of measurement points on the back surface 1b of the workpiece 1 and the height of the back surface 1b at each measurement point. Furthermore, the information on the thickness distribution of the workpiece 1 may be in another form.

[0106] In either case, information on the thickness distribution of the workpiece 1 obtained by carrying out the measurement step S20 may be registered in a memory unit 90 of a controller (control unit) 88 of the grinding / polishing apparatus (processing apparatus) 2. In the method for processing a workpiece according to this embodiment, the information on the thickness distribution of the workpiece 1 is utilized in the polishing step S30 described next.

[0107] In the method for processing a workpiece according to this embodiment, after the measuring step S20, a polishing step S30 is performed. In the polishing step S30, the workpiece 1 is polished by a polishing unit 60 from the surface to be processed (rear surface 1b).

[0108] Polishing of the ground workpiece 1 may be performed for the purpose of removing minute irregularities formed on the surface of the workpiece 1 by grinding, flattening the surface, and finishing the surface to a mirror finish. In the method for processing a workpiece according to this embodiment, a relatively thick portion of the workpiece 1 is polished with high intensity, and at the same time, a relatively thin portion is polished with low intensity, thereby making the thickness of the workpiece 1 closer to uniform.

[0109] 9 is a cross-sectional view showing a polishing step S30. In the polishing step S30, the turntable 16 is rotated to move the chuck table 18 that suction-holds the workpiece 1 to the polishing position D. That is, the workpiece 1 is sent to below the polishing unit 60.

[0110] Next, the chuck table 18 and the polishing pad 66 are rotated relative to each other, and the lower surface of the polishing pad 66 is brought into contact with the surface to be processed (rear surface 1b) of the workpiece 1 exposed upward. As a result, the workpiece 1 is polished by the polishing pad 66. At this time, a polishing liquid containing abrasive grains may be supplied to the workpiece 1 and the polishing pad 66 through a supply path 86. Alternatively, when the workpiece 1 is polished, a polishing liquid containing abrasive grains does not have to be supplied to the workpiece 1 and the polishing pad 66.

[0111] Furthermore, in the method for processing a workpiece according to this embodiment, in the polishing step S30, the XZ axis movement mechanism 42 may be operated to continue moving the polishing pad 66 along a direction approximately parallel to the vertical direction. That is, the polishing pad 66 may be periodically oscillated with respect to the workpiece 1. The oscillation of the polishing pad 66 is performed, for example, by reciprocating the rotation axis of the polishing pad 66 from one end to the other end of a predetermined movement range along the radial direction of the workpiece 1.

[0112] In particular, in the polishing step S30 in the method for processing a workpiece according to this embodiment, polishing conditions are determined based on information regarding the thickness distribution of the workpiece 1 obtained in the measuring step S20, and the workpiece 1 is polished. For example, the controller 88 reads out polishing conditions advantageous for uniforming the thickness of the workpiece 1 from among a plurality of types of polishing conditions registered in the memory unit 90 based on information regarding the thickness distribution of the workpiece 1 obtained in the measuring step S20. Then, polishing of the workpiece 1 proceeds according to the read polishing conditions.

[0113] More specifically, various examples of the thickness distribution of the workpiece 1 and polishing conditions advantageous for uniforming the thickness of the workpiece 1 having the thickness distribution associated with each example are registered in the memory unit 90. The controller 88 then compares the thickness distribution associated with the information obtained in the measurement step S20 with the various examples of thickness distribution stored in the memory unit 90. Then, from the various polishing conditions stored in the memory unit 90, the controller 88 selects polishing conditions advantageous for uniforming the thickness of the workpiece 1 having the thickness distribution associated with the information.

[0114] For example, the controller 88 determines the rotation speed of the polishing pad, the rotation speed of the chuck table 18, the supply amount of polishing liquid, the descending speed of the polishing unit 60, and the like, in accordance with the polishing conditions read out from the memory unit 90. Then, the processing control unit 92 of the controller 88 controls each component in accordance with these selected parameters, and causes the polishing of the workpiece 1 to proceed.

[0115] In the method for processing a workpiece according to the present embodiment, the surface to be processed (rear surface 1b) of each workpiece 1 can be polished so as to make the thickness of the workpiece 1 uniform, depending on the state of the surface to be processed (rear surface 1b) of each workpiece 1. As a result, a workpiece 1 with a uniform thickness can be obtained.

[0116] In the polishing step S30, when the workpiece 1 is polished with the polishing pad 66 while the chuck table 18 holding the workpiece 1 and the polishing pad 66 are oscillated relative to each other along a direction parallel to the workpiece surface (rear surface 1b) of the workpiece 1, the oscillation conditions are also set.

[0117] For example, the polishing conditions stored in the memory unit 90 include the amount of oscillation, the center position of the oscillation, and the like. The amount of oscillation and the center position of the oscillation are determined based on the polishing conditions read from the memory unit 90. In the polishing step S30, the processing control unit 92 oscillates the polishing pad 66 according to the determined amount of oscillation and center position of the oscillation. This allows the thickness of the workpiece 1 to be more uniform during the polishing process.

[0118] The polishing conditions do not necessarily have to include values ​​directly indicating the amount of oscillation and the central position of the oscillation. The polishing conditions including the amount of oscillation and the central position of the oscillation refer to polishing conditions that are indicated in a form that allows the amount of oscillation and the central position of the oscillation to be derived.

[0119] For example, the polishing conditions may include the positions of one end and the other end of the movement range of the polishing pad 66 (spindle 64) etc. due to the oscillation. The movement range of the polishing pad 66 etc. during the oscillation is determined by the positions of one end and the other end, and the amount of oscillation (movement amount) and the center position of the oscillation are also determined. In other words, the amount of oscillation and the center position of the oscillation may be registered in the storage unit 90 in the form of the positions of one end and the other end of the movement range of the polishing pad 66 etc. due to the oscillation.

[0120] Furthermore, the center position of the oscillation may be represented by the distance between a reference position as described below and the center position of the oscillation, and the center position of the oscillation may be stored in the storage unit 90 based on this distance. Here, the reference position is, for example, the relative position of the polishing pad 66 and the workpiece 1 when the outer periphery of the workpiece 1 is inscribed in the outer periphery of the polishing pad 66 on the processing surface (rear surface 1b) of the workpiece 1.

[0121] Fig. 10(A) is a plan view showing a schematic example of the positional relationship between the polishing pad 66 and the workpiece 1 when the outer periphery 1d of the workpiece 1 is inscribed in the outer periphery 66d of the polishing pad 66 on the processing surface (rear surface 1b) of the workpiece 1. In the example shown in Fig. 10(A), the diameter of the workpiece 1 is half the diameter of the polishing pad 66, and when viewed from the vertical direction (Z-axis direction), the outer periphery 1d of the workpiece 1 is inscribed in the outer periphery 66d of the polishing pad 66 and overlaps with the center 66c of the polishing pad 66.

[0122] For example, the positional relationship between the workpiece 1 and the polishing pad 66 as shown in Fig. 10(A) is set as the reference position. The center of oscillation of the polishing pad 66, etc. is expressed by the amount of deviation (distance) from this reference position. In the storage unit 90, the distance between the reference position and the center position of oscillation is registered as a value indicating the center position of oscillation, together with the amount of oscillation. However, the method for processing the workpiece according to this embodiment is not limited to this, and the center position of oscillation may be stored in the storage unit 90 in another format.

[0123] Here, the relationship between the relative oscillation between the polishing pad 66 and the chuck table 18 during polishing and the polishing result will be described in detail. That is, it will be described in detail how the polishing result of the workpiece 1 changes depending on the oscillation mode of the polishing pad 66. Here, an experiment in which the workpiece 1 was polished while oscillating the polishing pad 66 etc. under various conditions will be described.

[0124] In this experiment, multiple disk-shaped semiconductor wafers with a diameter of 150 mm were prepared as the workpieces 1, and these were polished with a polishing pad 66 with a diameter of 300 mm. The thickness of each part of the workpiece 1 after polishing was subtracted from the thickness of each part of the workpiece 1 before polishing (the height of the surface to be polished) to calculate the amount of polishing at each part. The amount of polishing was evaluated when the workpiece 1 was polished while the polishing pad 66, etc. was oscillated, and when the workpiece 1 was polished without oscillating the polishing pad 66, etc.

[0125] FIG. 11 is a graph showing the experimental results. In the graph shown in FIG. 11, the horizontal axis represents the position on the disk-shaped workpiece 1. More specifically, the horizontal axis represents the coordinates of each measurement point when the position of the center 1c on a line passing through the center 1c of the workpiece surface (rear surface 1b) of the workpiece 1 is set to zero, and one side of this line is set to the positive direction and the other side is set to the negative direction. That is, 75 mm (+75 mm) on the horizontal axis of the graph represents one outer periphery 1d of the workpiece 1 on this line. Also, -75 mm on the horizontal axis of the graph represents the other outer periphery 1d of the workpiece 1 on this line.

[0126] In the graph shown in Fig. 11, the vertical axis represents the amount of polishing performed. For example, when the vertical axis is 4.5 µm at a certain measurement point, it means that the workpiece 1 was removed by a thickness of 4.5 µm at that measurement point. In other words, it means that the height of the workpiece surface (rear surface 1b) of the workpiece 1 before and after polishing at that measurement point was reduced by 4.5 µm. The larger the vertical axis, the greater the amount of workpiece 1 removed by polishing, and the smaller the vertical axis, the smaller the amount of workpiece 1 removed by polishing.

[0127] First, a case where the workpiece 1 is polished by the polishing pad 66 without oscillating the polishing pad 66 etc. will be described. In particular, a polishing result will be described for a case where the outer periphery 1d of the workpiece 1 is inscribed in the outer periphery 66d of the polishing pad 66 in a plan view as shown in Fig. 10(A). In this case, the direction from the center 1c of the workpiece 1 toward the center 66c of the polishing pad 66 is defined as the positive direction, and the position of the center 1c of the workpiece 1 when the center 66c of the polishing pad 66 is defined as 0 mm is -75 mm. In other words, the distance 94 between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is 75 mm.

[0128] The measurement results in this case are represented by black triangles in the graph shown in Figure 11. In this case, it can be seen from the graph that the amount of polishing is relatively large near the center 1c of the workpiece 1, and the amount of polishing decreases as it approaches the outer periphery 1d of the workpiece 1.

[0129] Next, the polishing result will be described in the case where the center 1c of the workpiece 1 moves away from the center 66c of the polishing pad 66, resulting in a portion of the outer periphery 1d of the workpiece 1 not being covered by the polishing pad 66 as shown in Fig. 10(B). For example, when the center 66c of the polishing pad 66 is set to 0 mm, the position of the center 1c of the workpiece 1 is -100 mm. In other words, the distance 96 between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is 100 mm. In this case, the polishing pad 66 and the like are not oscillated.

[0130] The measurement results in this case are represented by black squares in the graph shown in Fig. 11. In this case, it can be seen from the graph that the amount of polishing is relatively small near the center 1c of the workpiece 1, and the amount of polishing increases as it approaches the outer periphery 1d of the workpiece 1.

[0131] From these results, it can be seen that even when the polishing pad 66 etc. is not oscillated, the polishing results can be completely reversed depending on the positional relationship between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66. Furthermore, since the polishing results tend to change significantly when the positional relationship between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is changed, it is not easy to adjust these positional relationships in order to obtain the desired polishing results.

[0132] Next, a case where the polishing pad 66 and the like are oscillated will be described. First, a case where the polishing pad 66 is oscillated so that the position of the center 1c of the workpiece 1 is in the range of -75 mm to -95 mm when the center 66c of the polishing pad 66 is set to 0 mm will be described. In this case, the polishing pad 66 is oscillated so that the distance between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is in the range of 75 mm to 95 mm.

[0133] In the graph shown in Fig. 11, the measurement results in this case are represented by a minus sign (-). In this case, it can be seen from the graph that the amount of polishing is relatively large near the center 1c of the workpiece 1, and decreases as the distance approaches the outer periphery 1d of the workpiece 1. However, the amount of polishing tends to be smaller overall than when the distance 94 between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is 75 mm and no oscillation occurs, and the difference in the amount of polishing between the location with the largest amount of polishing and the location with the smallest amount of polishing is also relatively small.

[0134] Next, a case will be described in which the polishing pad 66 oscillates so that the position of the center 1c of the workpiece 1 is in the range of -75 mm to -100 mm when the center 66c of the polishing pad 66 is set to 0 mm. In this case, the polishing pad 66 oscillates so that the distance between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is in the range of 75 mm to 100 mm.

[0135] In the graph shown in Fig. 11, the measurement results in this case are represented by diamond symbols. In this case as well, it can be seen from the graph that the amount of polishing is relatively large near the center 1c of the workpiece 1, and decreases as the amount of polishing approaches the outer periphery 1d of the workpiece 1. However, there is a tendency for the amount of polishing to decrease overall, and the difference in the amount of polishing between the location with the largest amount of polishing and the location with the smallest amount of polishing also becomes smaller.

[0136] Next, a case will be described in which the polishing pad 66 oscillates so that the position of the center 1c of the workpiece 1 is in the range of -75 mm to -105 mm when the center 66c of the polishing pad 66 is set to 0 mm. In this case, the polishing pad 66 oscillates so that the distance between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is in the range of 75 mm to 105 mm.

[0137] In the graph shown in Figure 11, the measurement results in this case are represented by a plus sign (+). In this case, it can be seen from the graph that there is no significant difference in the amount of polishing across the entire grinding surface of the workpiece 1. If anything, the amount of polishing is slightly greater near the center 1c of the workpiece 1 than around it.

[0138] Next, a case will be described in which the polishing pad 66 oscillates so that the position of the center 1c of the workpiece 1 is in the range of -75 mm to -110 mm when the center 66c of the polishing pad 66 is set to 0 mm. In this case, the polishing pad 66 oscillates so that the distance between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is in the range of 75 mm to 110 mm.

[0139] In the graph shown in Figure 11, the measurement results in this case are represented by a cross (x) symbol. In this case, too, it can be seen from the graph that there is no significant difference in the amount of polishing across the entire grinding surface of the workpiece 1. If anything, the amount of polishing is slightly less near the center 1c of the workpiece 1 than around it.

[0140] Next, a case will be described in which the polishing pad 66 oscillates so that the position of the center 1c of the workpiece 1 is in the range of -75 mm to -115 mm when the center 66c of the polishing pad 66 is set to 0 mm. In this case, the polishing pad 66 oscillates so that the distance between the center 1c of the workpiece 1 and the center 66c of the polishing pad 66 is in the range of 75 mm to 115 mm.

[0141] The measurement results in this case are represented by white circles in the graph shown in Fig. 11. In this case, it can be seen from the graph that the amount of polishing is relatively small near the center 1c of the workpiece 1, and the amount of polishing increases as it approaches the outer periphery 1d of the workpiece 1.

[0142] As described above, changing the conditions for oscillating the polishing pad 66 etc. changes the amount of polishing at each point on the processed surface (rear surface 1b) of the workpiece 1. Therefore, even if the thickness of the workpiece 1 is not uniform after the grinding step S10, the shape of the processed surface of the workpiece 1 can be corrected by selecting the polishing conditions in the polishing step S30 in accordance with the shape of the processed surface of the workpiece 1.

[0143] For example, when the information on the thickness distribution of the workpiece 1 obtained by carrying out the measuring step S20 indicates that the vicinity of the center 1c of the workpiece 1 is thicker than the periphery, it is preferable to make the range of oscillation of the polishing pad 66, etc., in the polishing step S30 relatively narrow. Also, when the information on the thickness distribution of the workpiece 1 obtained by carrying out the measuring step S20 indicates that the vicinity of the center 1c of the workpiece 1 is thinner than the periphery, it is preferable to make the range of oscillation of the polishing pad 66, etc., in the polishing step S30 relatively wide. The range of oscillation is preferably selected according to the difference in height between the highest and lowest parts of the workpiece surface of the workpiece 1.

[0144] In the above-described experiments, one end of the oscillation range was the same in all cases, and only the other end of the oscillation range was under different conditions. However, it is not necessary to fix the position of one end of the oscillation range. By changing both ends of the oscillation range, various polishing results can be obtained. In other words, by oscillating the polishing pad 66 etc. in the polishing step S30, the polishing amount at each point of the workpiece 1 can be adjusted more finely, and the shape of the workpiece surface of the workpiece 1 after grinding can be modified in more detail.

[0145] The above-described experiment is an example, and the polishing results obtained vary depending on the material, size, and thickness of the workpiece 1, the material, size, and thickness of the polishing pad 66 (polishing layer 84), the rotation speed of the chuck table 18, the rotation speed of the polishing pad 66, the temperature of the processing chamber, etc. Therefore, for example, in the grinding and polishing device (processing device) 2, it is preferable to test process the workpiece 1 while changing the polishing conditions in various ways, evaluate the polishing results, and register them in the memory unit 90.

[0146] The test processing may be carried out in advance by the manufacturer of the grinding / polishing device (processing device) 2, and the polishing results may be registered in the storage unit 90. Alternatively, the test processing may be carried out periodically by a user of the grinding / polishing device (processing device) 2, and the polishing results may be registered in the storage unit 90. In either case, when the polishing results of various test processing are registered in the storage unit 90 together with the polishing conditions under which the test processing was carried out, the polishing conditions can be selected so as to obtain polishing results that are closer to the desired polishing results.

[0147] As described above, in the method for processing a workpiece according to this embodiment, the polishing conditions are determined based on the thickness distribution of each workpiece 1 after grinding (the distribution of heights of the workpiece surfaces), and the workpiece 1 can be polished so as to have a uniform thickness.

[0148] By polishing the workpiece 1, the thickness of the workpiece 1 can be made uniform, and the unevenness of the workpiece surface (rear surface 1b) of the workpiece 1 is removed, resulting in a mirror finish of the workpiece surface. Thereafter, the turntable 16 is rotated to move the chuck table 18 to a position where the transport unit 68 can access the workpiece 1. Then, the suction hold of the workpiece 1 by the chuck table 18 is released, and the transport unit 68 transports the workpiece 1 to the cleaning unit 70, where the workpiece 1 is cleaned. Thereafter, the transport unit 6 stores the workpiece 1 in the cassettes 8, 10.

[0149] In this way, when the workpieces 1 contained in the cassettes 8, 10 are processed one after another using the workpiece processing method of this embodiment, the workpieces 1 are polished to correspond to the shapes of each workpiece 1 after grinding, so that the thickness of each workpiece 1 becomes extremely uniform.

[0150] The present invention is not limited to the above-described embodiment, and can be modified in various ways. For example, in the above-described embodiment, the workpiece 1 is test-processed (polished) in advance, the polishing result is registered in the storage unit 90, and the polishing result is used to select polishing conditions in the polishing step S30. However, the method for processing the workpiece according to one aspect of the present invention is not limited to this.

[0151] That is, test processing does not have to be performed in the grinding / polishing apparatus 2. For example, when a large number of workpieces 1 are processed by the grinding / polishing apparatus 2, the measurement step S20 is performed before and after the polishing step S30 to obtain information on the thickness distribution of the workpieces 1. This allows information on the change in the thickness distribution of the workpieces 1 before and after the polishing step S30 to be accumulated in the storage unit 90.

[0152] In other words, by storing the results of this processing together with the processing conditions (polishing conditions) in the memory unit 90, rather than test processing of the workpiece 1, this information can be utilized to select appropriate polishing conditions for subsequent polishing processing of the workpiece 1.

[0153] In the above embodiment, the method for processing a workpiece is performed by a processing device (grinding / polishing device 2) that is equipped with both the grinding units 32a and 32b and the polishing unit 60 at the same time, but the method for processing a workpiece according to one aspect of the present invention is not limited to this. For example, the method for processing a workpiece according to one aspect of the present invention may be performed by using both a grinding device equipped with the grinding units 32a and 32b and a polishing device equipped with the polishing unit 60.

[0154] In this case, for example, after the grinding step S10 and the measuring step S20 are performed in the grinding apparatus, the polishing step S30 is performed in the polishing apparatus. That is, the workpiece 1 is ground in the grinding apparatus, information on the thickness distribution of the workpiece 1 is acquired, and then the workpiece 1 is transferred to the polishing apparatus, where the workpiece 1 is polished. Then, the information acquired in the grinding apparatus is transmitted from the grinding apparatus to the polishing apparatus via, for example, a wired or wireless communication line, a storage medium such as a non-volatile memory, or the like. In the polishing apparatus, the workpiece 1 is polished under the polishing conditions determined based on the information.

[0155] In this case, the grinding device and the polishing device, each having its own component in a separate housing, function as one processing device (processing system) that performs a predetermined processing of the workpiece, thereby implementing one aspect of the present invention. Note that the grinding device and the polishing device may be installed in factories or the like built on different sites, or may be installed in a single factory or the like.

[0156] Furthermore, when the grinding device and the polishing device function as one processing device, the controller 88 including the memory unit 90 and the like may be provided in the grinding device, the polishing device, or both. The controller 88 may not be provided in both the grinding device and the polishing device, but may be provided in a management device or the like connected to each device belonging to a factory or the like that has the grinding device and the polishing device. In this case, the grinding device, the polishing device, and the management device function as one processing device (processing system) used in the method for processing a workpiece according to one aspect of the present invention.

[0157] In addition, the structures, methods, and the like according to the above-described embodiments and modifications can be implemented without departing from the scope of the present invention. [Explanation of symbols]

[0158] 1,5,7 Workpiece 1a,5a,7a surface 1b,5b,7b Back side 1c,5c,7c center 1d Circumference 3 Protective materials 2 Grinding and polishing equipment 4 Foundation 4a aperture 4b, 4c Cassette placement table 6 Transport unit 8,10 Cassette 12 Alignment mechanism 14 Transport unit 16 Turntable 18 Chuck table 18a Holding surface 20 Support structure 22 Z-axis movement mechanism 24 Z-axis guide rail 26 Z-axis moving plate 28 Z-axis ball screw 30 Z-axis pulse motor 32a, 32b Grinding unit 34 Housing 36 Spindle 37 Wheel mount 38a, 38b Grinding wheels 39a,39b base 40a, 40b Grinding wheel 41 Support structure 42 XZ axis movement mechanism 44 First guide rail 46 First moving plate 48 First ball screw 50 First pulse motor 52 Second guide rail 54 Second moving plate 56 Second ball screw 58 Second pulse motor 60 Polishing Unit 62 Housing 64 Spindle 66 Polishing Pad 66c center 66d Circumference 68 Transport Unit 70 Cleaning Unit 72 Measurement Units 74 Shaft 76 Arm 78 Measuring instruments 80 Mount 82 Foundation 84 Polishing layer 86 Supply route 88 Controller 90 Memory section 92 Processing control section 94,96 distance

Claims

1. A method for processing a workpiece using a chuck table, a grinding unit having a grinding wheel for grinding a surface of the workpiece held by the chuck table, a polishing unit having a polishing pad for polishing the surface of the workpiece held by the chuck table after grinding, and a measuring unit for measuring a thickness of the workpiece held by the chuck table, comprising: a grinding step of grinding the workpiece from the work surface by the grinding unit; a measuring step of measuring thicknesses of the workpiece at a plurality of measurement points using the measuring unit after the grinding step to obtain information regarding a thickness distribution of the workpiece; a polishing step of polishing the workpiece from the work surface with the polishing unit; The method for processing a workpiece, wherein in the polishing step, polishing of the workpiece is carried out by determining polishing conditions based on information regarding the thickness distribution of the workpiece obtained in the measuring step.

2. 2. The method for processing a workpiece according to claim 1, further comprising: processing the workpiece using a controller that controls the polishing unit and has a memory unit in which a plurality of types of polishing conditions are registered, the controller further comprising: In the polishing step, the controller reads out the polishing conditions advantageous for uniforming the thickness of the workpiece from among a plurality of types of polishing conditions registered in the memory unit based on information regarding the thickness distribution of the workpiece obtained in the measurement step, and proceeds with polishing of the workpiece in accordance with the read-out polishing conditions.

3. the polishing pad of the polishing unit has an outer diameter larger than an outer diameter of the workpiece; In the polishing step, the workpiece is polished with the polishing pad while the chuck table holding the workpiece and the polishing pad are oscillated relative to each other along a direction parallel to the work surface of the workpiece; 3. The method for processing a workpiece according to claim 2, wherein in the polishing step, the amount of oscillation and the center position of the oscillation are determined based on the polishing conditions read out from the memory unit.

4. The method for processing a workpiece as described in claim 3, characterized in that the polishing conditions registered in the memory unit include the distance between the reference position, when the relative position of the polishing pad and the workpiece when the outer periphery of the workpiece is inscribed in the outer periphery of the polishing pad on the processed surface of the workpiece is taken as the reference position, and the center position of the oscillation, as well as the amount of the oscillation.

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