Polishing pad and processing method of workpiece

Abstract

To provide a polishing pad capable of suppressing remaining metal in a workpiece.SOLUTION: Provided is a polishing pad used in polishing a workpiece. The polishing pad has a disk-like base, and a polishing layer that is fixed to the base and contacts the workpiece to polish the workpiece. The polishing layer contains a metal absorbing particle that absorbs metal.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a polishing pad used for polishing a workpiece, and to a method for polishing a workpiece using the polishing pad. [Background technology]

[0002] The device chip manufacturing process uses a wafer in which semiconductor devices are formed in multiple regions defined by multiple streets (planned dividing lines) arranged in a grid pattern. By dividing this wafer along the streets, device chips equipped with semiconductor devices are obtained. The device chips are incorporated into various electronic devices such as mobile phones and personal computers.

[0003] Before semiconductor devices are formed on a wafer, the surface of the wafer on which the devices are to be formed (device surface) is sometimes polished to flatten the device surface. For example, in the process of forming power devices on a single crystal SiC wafer, chemical mechanical polishing (CMP) is performed, in which the device surface of the single crystal SiC wafer is polished with a polishing pad while a polishing liquid is supplied to the single crystal SiC wafer (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-92246 Summary of the Invention [Problem to be solved by the invention]

[0005] When a workpiece such as a wafer is polished with a polishing pad while a polishing liquid is being supplied to the workpiece, metals derived from the components of the polishing liquid may remain on the polished surface (polished surface) of the workpiece. For example, if the polishing liquid contains permanganate, which functions as an oxidizing agent, manganese will adhere to the polished surface during the polishing process. The manganese adhering to the polished surface of the workpiece will then oxidize, and manganese oxide particles will remain on the workpiece after polishing.

[0006] As described above, metals remaining on a workpiece adversely affect the quality of the workpiece. For example, on single-crystal SiC wafers, crystalline thin films (epitaxial layers) that constitute semiconductor devices are formed by epitaxial growth. However, if the above-mentioned metals remain on the device surface of a single-crystal SiC wafer, epitaxial growth is inhibited, making it difficult to form a high-quality epitaxial layer. Furthermore, the remaining metals may contaminate semiconductor devices, reducing their reliability and causing malfunctions.

[0007] The present invention has been made in view of the above problems, and has an object to provide a polishing pad and a method for processing a workpiece that can suppress the metal remaining on the workpiece. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a polishing pad for use in polishing a workpiece, the polishing pad having a disk-shaped base and a polishing layer fixed to the base and contacting the workpiece to polish it, the polishing layer containing metal-adsorbing particles that adsorb metal.

[0009] Preferably, the metal-adsorbing particles are silica particles having functional groups capable of adsorbing the metal. Preferably, the average particle size of the metal-adsorbing particles is 25 μm or more and 150 μm or less. Preferably, the metal-adsorbing particles adsorb the metal contained in the polishing liquid supplied when the workpiece is polished with the polishing layer. Preferably, the polishing layer contains abrasive grains.

[0010] According to another aspect of the present invention, there is provided a method for processing a workpiece by polishing the workpiece using a polishing pad, the polishing pad having a disk-shaped base and a polishing layer fixed to the base and contacting the workpiece to polish it, the method including a holding step of holding the workpiece on a chuck table, and a polishing step of bringing the polishing layer into contact with the workpiece while supplying a polishing liquid containing a metal to the workpiece, thereby polishing the workpiece, and the polishing layer contains metal-adsorbing particles that adsorb the metal.

[0011] Preferably, the polishing layer contains abrasive grains, but the polishing liquid does not contain abrasive grains. [Effects of the Invention]

[0012] A polishing pad according to one embodiment of the present invention includes a polishing layer containing metal-adsorbing particles. When a workpiece is polished using this polishing pad, the metal adhering to the workpiece during polishing is adsorbed and captured by the metal-adsorbing particles and removed from the workpiece. This reduces the amount of metal remaining on the workpiece. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. [Figure 2] FIG. 2(A) is a perspective view showing a grinding wheel for rough grinding, and FIG. 2(B) is a perspective view showing a grinding wheel for finish grinding. [Figure 3] FIG. 2 is a perspective view showing a polishing unit. [Figure 4] 1 is a flowchart showing a method for processing a workpiece. [Figure 5] FIG. 10 is a side view showing the processing device in a holding step. [Figure 6] FIG. 10 is a side view showing the processing device in the grinding process. [Figure 7] FIG. 10 is a partial cross-sectional side view showing the processing device in a polishing step. [Figure 8]FIG. 2 is a cross-sectional view showing a portion of the workpiece and the abrasive layer. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment according to one aspect of the present invention will be described below with reference to the accompanying drawings. First, a configuration example of a processing apparatus that polishes a workpiece using a polishing pad according to this embodiment will be described. FIG. 1 is a perspective view showing a processing apparatus (grinding / polishing apparatus) 2 that can perform grinding and polishing on a workpiece 11. In FIG. 1, the X-axis direction (first horizontal direction, left-right direction) and the Y-axis direction (second horizontal direction, front-rear direction) are perpendicular to each other. Furthermore, the Z-axis direction (up-down direction, height direction, vertical direction) is perpendicular to the X-axis direction and the Y-axis direction.

[0015] The processing device 2 includes a base 4 that supports or houses each of the components of the processing device 2. A rectangular opening 4a is provided on the upper surface side of the front end of the base 4. A transport unit 6 that transports the workpiece 11 is provided inside the opening 4a. For example, a transport robot equipped with a robot hand (end effector) that can hold the workpiece 11 is used as the transport unit 6.

[0016] Cassette support stands 8A and 8B are provided in front of the opening 4a. Box-shaped cassettes 10A and 10B are placed on the cassette support stands 8A and 8B, respectively. The cassettes 10A and 10B are containers that can accommodate a plurality of workpieces 11, which are objects to be processed by the processing device 2. When processing the workpieces 11 with the processing device 2, the cassettes 10A and 10B accommodating the plurality of workpieces 11 are set on the cassette support stands 8A and 8B.

[0017] The workpiece 11 is a disk-shaped wafer made of a semiconductor material such as single crystal SiC, and has a first surface 11a and a second surface 11b that are generally parallel to each other. However, there are no limitations on the type, material, shape, size, structure, etc. of the workpiece 11. For example, the workpiece 11 may be a substrate (wafer) made of a semiconductor other than SiC (Si, GaAs, InP, GaN, etc.), glass, ceramics, resin, metal, etc.

[0018] For example, the processing device 2 performs grinding and polishing on the first surface 11a of the workpiece 11. As a result, the workpiece 11 is thinned and the first surface 11a of the workpiece 11 is flattened. Then, a plurality of devices such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and MEMS (Micro Electro Mechanical Systems) devices are formed on the first surface 11a of the workpiece 11. Thereafter, the workpiece 11 is divided by a processing device such as a cutting device or a laser processing device, thereby manufacturing a plurality of device chips each including a device.

[0019] However, the processing device 2 can also process the workpiece 11 on which devices are already formed. For example, if a plurality of devices are formed on the first surface 11a of the workpiece 11, the processing device 2 may perform grinding and polishing on the second surface 11b of the workpiece 11.

[0020] An alignment mechanism (positioning mechanism) 12 is provided diagonally behind the opening 4a to align the workpiece 11. The alignment mechanism 12 includes a temporary placement table 14 on which the workpiece 11 is temporarily placed. The alignment mechanism 12 also includes, for example, a plurality of pins that come into contact with the outer periphery of the workpiece 11 and clamp the workpiece 11.

[0021] The workpieces 11 housed in the cassettes 10A and 10B are transported onto the temporary placement table 14 by the transport unit 6. Then, the alignment mechanism 12 holds the workpieces 11 on the temporary placement table 14 and clamps them with multiple pins, thereby placing the workpieces 11 in a predetermined position.

[0022] A gate-shaped support structure 16 is installed on the side of the base 4 so as to straddle the alignment mechanism 12. A transport unit 18 that transports the workpiece 11 is attached to the support structure 16. For example, the support structure 16 is provided with a ball screw type movement mechanism (not shown) that moves the transport unit 18 along the X-axis, Y-axis, and Z-axis directions, and the transport unit 18 is connected to the movement mechanism. The transport unit 18 also includes one or more suction pads (not shown) that suction-hold the top surface of the workpiece 11.

[0023] A rectangular opening 4b is provided behind the alignment mechanism 12. A disk-shaped turntable 20 is provided inside the opening 4b. A rotation drive source (not shown), such as a motor, is connected to the turntable 20 to rotate the turntable 20 around a rotation axis that is approximately parallel to the Z-axis direction.

[0024] A plurality of chuck tables (holding tables) 22 for holding the workpieces 11 are provided on the turntable 20. For example, four chuck tables 22 are arranged at approximately equal intervals (90° intervals) around the circumferential direction of the turntable 20. The turntable 20 rotates clockwise (in the direction indicated by the arrow R) in a plan view, and positions each chuck table 22 in the transfer area A, grinding area B (first grinding area, rough grinding area), grinding area C (second grinding area, finish grinding area), polishing area D, and transfer area A, in that order.

[0025] The upper surface of the chuck table 22 constitutes a holding surface 22a that holds the workpiece 11. The holding surface 22a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like formed inside the chuck table 22. In addition, the chuck table 22 is connected to a rotation drive source (not shown) such as a motor that rotates the chuck table 22 around a rotation axis that is approximately parallel to the Z-axis direction.

[0026] The workpiece 11, which has been aligned by the alignment mechanism 12, is transported by the transport unit 18 to the chuck table 22 positioned in the transport area A. Then, with the workpiece 11 placed on the holding surface 22a of the chuck table 22, when the suction force (negative pressure) of the suction source is applied to the holding surface 22a, the workpiece 11 is sucked and held by the chuck table 22.

[0027] A rectangular parallelepiped support structure 24 protruding upward from the upper surface of the base 4 is provided at the rear end of the base 4 (rear of the turntable 20 and chuck table 22). The surface (front surface) of the support structure 24 is disposed approximately parallel to the XZ plane. Movement mechanisms 26A and 26B for moving grinding units 38A and 38B, which will be described later, are provided on the surface side of the support structure 24.

[0028] Each of the movement mechanisms 26A, 26B includes a pair of guide rails 28 arranged along the Z-axis direction on the front surface side of the support structure 24. A flat movement plate 30 is attached to the pair of guide rails 28 so as to be slidable along the guide rails 28. A nut portion (not shown) is provided on the back surface side (rear surface side) of the movement plate 30. A ball screw 32 arranged along the Z-axis direction between the pair of guide rails 28 is threadedly engaged with this nut portion. A pulse motor 34 that rotates the ball screw 32 is connected to the end of the ball screw 32. When the pulse motor 34 rotates the ball screw 32, the movement plate 30 moves along the guide rails 28 in the Z-axis direction.

[0029] A support member 36 is fixed to the surface side (front side) of the moving plate 30. The support member 36 fixed to the moving plate 30 of the moving mechanism 26A supports a grinding unit 38A for rough grinding that performs rough grinding on the workpiece 11. On the other hand, the support member 36 fixed to the moving plate 30 of the moving mechanism 26B supports a grinding unit 38B for finish grinding that performs finish grinding on the workpiece 11. The grinding unit 38A is positioned above the grinding area B, and the grinding unit 38B is positioned above the grinding area C.

[0030] Each of the grinding units 38A, 38B includes a cylindrical housing 40. The housing 40 accommodates a columnar spindle 42 arranged along the Z-axis direction. The tip (lower end) of the spindle 42 is exposed from the housing 40, and a disk-shaped wheel mount 44 made of metal or the like is fixed to the tip of the spindle 42. A rotational drive source such as a motor that rotates the spindle 42 is connected to the base end (upper end) of the spindle 42.

[0031] A grinding wheel 46A for rough grinding is attached to the lower surface of the wheel mount 44 provided in the grinding unit 38A. On the other hand, a grinding wheel 46B for finish grinding is attached to the lower surface of the wheel mount 44 provided in the grinding unit 38B.

[0032] 2(A) is a perspective view showing a grinding wheel 46A mounted on a grinding unit 38A. The grinding wheel 46A includes an annular wheel base 48A made of a metal such as an aluminum alloy, and a plurality of grinding stones 50A fixed to the underside of the wheel base 48A. The grinding stones 50A are formed by fixing abrasive grains made of diamond, cBN (cubic boron nitride), or the like, with a bonding material such as a metal bond, a resin bond, or a vitrified bond. For example, a plurality of grinding stones 50A formed in a rectangular parallelepiped shape are arranged annularly at approximately equal intervals along the outer periphery of the wheel base.

[0033] 2(B) is a perspective view showing a grinding wheel 46B attached to the grinding unit 38B. The grinding wheel 46B includes an annular wheel base 48B and a plurality of grinding stones 50B fixed to the underside of the wheel base 48B. The wheel base 48B and the grinding stones 50B are similar in shape, material, configuration, function, etc. to the wheel base 48A and the grinding stone 50A, respectively. However, the average particle size of the abrasive grains contained in the grinding stones 50B is smaller than the average particle size of the abrasive grains contained in the grinding stone 50A.

[0034] The grinding wheels 46A, 46B each rotate around a rotation axis that is roughly parallel to the Z-axis direction by power transmitted from a rotation drive source via the spindle 42 and the wheel mount 44. This causes the multiple grinding wheels 50A and the multiple grinding wheels 50B to each revolve along an annular revolving path (rotation path) that is roughly parallel to the horizontal plane (XY plane).

[0035] The chuck table 22 holding the workpiece 11 is placed in the grinding area B (see FIG. 1), and the grinding stone 50A is brought into contact with the workpiece 11 while rotating the chuck table 22 and grinding wheel 46A, thereby subjecting the workpiece 11 to rough grinding. Thereafter, the chuck table 22 holding the workpiece 11 is placed in the grinding area C (see FIG. 1), and the chuck table 22 and grinding wheel 46B are rotated while bringing the grinding stone 50B into contact with the workpiece 11, thereby subjecting the workpiece 11 to finish grinding.

[0036] 1, polishing area D is provided with polishing unit 52 that polishes workpiece 11. After grinding of workpiece 11 by grinding units 38A and 38B is completed, chuck table 22 holding workpiece 11 is positioned in polishing area D, and workpiece 11 is polished by polishing unit 52.

[0037] 3 is a perspective view showing the polishing unit 52. The polishing unit 52 is supported by a rectangular parallelepiped support structure 54 provided in or near the polishing area D (see FIG. 1). The surface of the support structure 54 is disposed approximately parallel to the XZ plane. An X-axis movement mechanism 56 that moves the polishing unit 52 along the X-axis direction is provided on the surface side of the support structure 54.

[0038] The X-axis movement mechanism 56 includes a pair of X-axis guide rails 58 arranged along the X-axis direction on the front surface side of the support structure 54. A rectangular parallelepiped X-axis movement block 60 is attached to the pair of X-axis guide rails 58 so as to be slidable along the X-axis guide rails 58.

[0039] A nut portion (not shown) is provided on the back side of the X-axis moving block 60. An X-axis ball screw (not shown) is threadedly engaged with this nut portion, and is disposed along the X-axis direction between a pair of X-axis guide rails 58. An X-axis pulse motor 62 that rotates the X-axis ball screw is connected to the end of the X-axis ball screw. When the X-axis pulse motor 62 rotates the X-axis ball screw, the X-axis moving block 60 moves in the X-axis direction along the X-axis guide rails 58.

[0040] A Z-axis movement mechanism 64 that moves the polishing unit 52 along the Z-axis direction is provided on the surface side of the X-axis movement block 60. The Z-axis movement mechanism 64 includes a pair of Z-axis guide rails 66 that are arranged along the Z-axis direction on the surface side of the X-axis movement block 60. A rectangular parallelepiped Z-axis movement block 68 is attached to the pair of Z-axis guide rails 66 so as to be slidable along the Z-axis guide rails 66.

[0041] A nut portion (not shown) is provided on the back side of the Z-axis moving block 68. A Z-axis ball screw (not shown) is threadedly engaged with this nut portion, and is disposed along the Z-axis direction between a pair of Z-axis guide rails 66. A Z-axis pulse motor 70 that rotates the Z-axis ball screw is connected to the end of the Z-axis ball screw. When the Z-axis pulse motor 70 rotates the Z-axis ball screw, the Z-axis moving block 68 moves in the Z-axis direction along the Z-axis guide rails 66.

[0042] The polishing unit 52 is attached to the surface side of the Z-axis moving block 68. The polishing unit 52 includes a cylindrical housing 72 fixed to the Z-axis moving block 68. The housing 72 accommodates a columnar spindle 74 arranged along the Z-axis direction. The tip (lower end) of the spindle 74 is exposed from the housing 72, and a disk-shaped mount 76 made of metal or the like is fixed to the tip of the spindle 74. A rotational drive source such as a motor that rotates the spindle 74 is connected to the base end (upper end) of the spindle 74.

[0043] A polishing pad 78 used to polish the workpiece 11 is attached to the lower surface side of the mount 76. For example, the polishing pad 78 is detachably fixed to the mount 76 by a fixing device such as a bolt.

[0044] The polishing pad 78 includes a disk-shaped base 80 and a polishing layer 82 that is fixed to the base 80 and comes into contact with the workpiece 11 to polish the workpiece 11. The base 80 is made of a metal such as an aluminum alloy and has approximately the same diameter as the mount 76. The polishing layer 82 is formed, for example, in a disk shape having approximately the same diameter as the base 80 and is fixed to the underside of the base 80 with an adhesive or the like. However, multiple polishing layers 82 may be fixed to the underside of the base 80 while being separated from one another. The underside of the polishing layer 82 forms a polishing surface 82a that comes into contact with the workpiece 11 to polish the workpiece 11. The structure and function of the polishing layer 82 will be described in detail later (see FIG. 8).

[0045] The polishing pad 78 rotates around a rotation axis that is roughly parallel to the Z-axis direction by power transmitted from a rotation drive source via the spindle 74 and the mount 76. The chuck table 22 holding the workpiece 11 is placed in the polishing area D (see FIG. 1), and the polishing surface 82a of the polishing layer 82 is brought into contact with the workpiece 11 while the chuck table 22 and the polishing pad 78 are rotated, thereby polishing the workpiece 11.

[0046] 1, a cleaning unit 84 for cleaning the workpiece 11 is provided in front of the alignment mechanism 12. For example, the cleaning unit 84 includes a spinner table 86 that holds and rotates the workpiece 11, and a nozzle 88 that supplies a cleaning fluid.

[0047] The upper surface of the spinner table 86 constitutes a holding surface that holds the workpiece 11. The holding surface is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like formed inside the spinner table 86. In addition, the spinner table 86 is connected to a rotation drive source (not shown) such as a motor that rotates the spinner table 86 around a rotation axis that is approximately parallel to the Z-axis direction.

[0048] The tip of the nozzle 88 is disposed above the spinner table 86. A fluid supply source (not shown) that supplies a cleaning fluid to the nozzle 88 is connected to the nozzle 88. As the cleaning fluid, a liquid such as pure water or a mixed fluid obtained by mixing a liquid such as pure water with a gas such as air can be used.

[0049] When polishing of the workpiece 11 is completed, the turntable 20 rotates, and the chuck table 22 holding the workpiece 11 is again placed in the transfer area A. Then, the workpiece 11 is transferred from the chuck table 22 by the transfer unit 18 to the cleaning unit 84, where it is cleaned.

[0050] When cleaning the workpiece 11 in the cleaning unit 84, the workpiece 11 is held by the spinner table 86, and the tip of the nozzle 88 is positioned so as to overlap the workpiece 11. Then, the spinner table 86 rotates, and cleaning fluid is supplied from the nozzle 88 to the workpiece 11. This washes away foreign matter such as particles adhering to the workpiece 11. Thereafter, the workpiece 11 is placed in the cassette 10A or the cassette 10B by the transport unit 6.

[0051] The processing apparatus 2 also includes a controller (control unit, control section, control device) 90 that controls the processing apparatus 2. The controller 90 is connected to each component of the processing apparatus 2 (transport unit 6, alignment mechanism 12, transport unit 18, turntable 20, chuck table 22, moving mechanisms 26A, 26B, grinding units 38A, 38B, polishing unit 52, cleaning unit 84, etc.). The controller 90 controls the operation of the processing apparatus 2 by outputting control signals to each component of the processing apparatus 2.

[0052] For example, the controller 90 is configured by a computer and includes a processing unit that performs processing such as calculations necessary for the operation of the processing device 2, and a storage unit that stores various information (data, programs, etc.) used for the operation of the processing device 2. The processing unit includes a processor such as a CPU (Central Processing Unit), and the storage unit includes memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0053] Next, a specific example of a method for processing a workpiece 11 using the processing device 2 will be described. Fig. 4 is a flowchart showing the method for processing a workpiece. In the method for processing a workpiece according to this embodiment, after a holding step S1 in which the workpiece 11 is held by the chuck table 22 is performed, a grinding step S2 in which the workpiece 11 is ground with grinding wheels 46A, 46B, and a polishing step S3 in which the workpiece 11 is polished with a polishing pad 78 are performed.

[0054] In this embodiment, as an example, a case will be described in which the first surface 11a of the workpiece 11 shown in FIG. 1 is a surface to be ground and polished (a surface to be ground or polished). When processing the first surface 11a of the workpiece 11, a protective member may be fixed to the second surface 11b of the workpiece 11. For example, a film-like protective sheet made of resin or the like is attached to the second surface 11b of the workpiece 11 as the protective member. This protects the second surface 11b of the workpiece 11. Then, a cassette 10A or a cassette 10B containing a plurality of workpieces 11 is placed on the cassette support table 8A or the cassette support table 8B.

[0055] When the processing device 2 starts operating, first, the workpiece 11 stored in the cassette 10A or the cassette 10B is transported by the transport unit 6 to the alignment mechanism 12. Then, after the alignment mechanism 12 aligns the workpiece 11, the workpiece 11 is held by the transport unit 18 and transported to the chuck table 22 arranged in the transport area A.

[0056] 5 is a side view showing the processing device 2 in the holding step S1. The workpiece 11 is placed on the chuck table 22 so that the first surface 11a (the surface to be processed) is exposed upward and the second surface 11b faces the holding surface 22a. In this state, when the suction force of the suction source is applied to the holding surface 22a, the workpiece 11 is suction-held by the chuck table 22.

[0057] Next, the turntable 20 (see FIG. 1) rotates, and the chuck table 22 holding the workpiece 11 is positioned in the grinding area B. This positions the workpiece 11 below the grinding wheel 46A. Then, the workpiece 11 is ground by the grinding unit 38A, and the workpiece 11 is subjected to rough grinding.

[0058] FIG. 6 is a side view showing the processing device 2 in the grinding step S2. The chuck table 22 is positioned so that the center of the workpiece 11 and the rotation path of the grinding wheel 50A overlap in the Z-axis direction. In this state, while the chuck table 22 and the grinding wheel 46A are rotated, the grinding wheel 46A is lowered by the moving mechanism 26A (see FIG. 1) so that the grinding wheel 50A contacts the first surface 11a of the workpiece 11. As a result, the first surface 11a of the workpiece 11 is ground away by the grinding wheel 50A, and the workpiece 11 is roughly ground. Then, when the workpiece 11 is thinned to a predetermined thickness, the lowering of the grinding wheel 46A is stopped, and the rough grinding of the workpiece 11 is completed.

[0059] Next, the turntable 20 (see FIG. 1) rotates, and the chuck table 22 holding the workpiece 11 is positioned in the grinding area C. This positions the workpiece 11 below the grinding wheel 46B. The workpiece 11 is then ground by the grinding unit 38B, and finish grinding is performed on the workpiece 11. The procedure for grinding the workpiece 11 by the grinding unit 38B is the same as the procedure for grinding the workpiece 11 by the grinding unit 38A (see FIG. 6).

[0060] Specifically, the chuck table 22 is positioned so that the center of the workpiece 11 and the rotation path of the grinding wheel 50B (see FIG. 2(B)) overlap in the Z-axis direction. In this state, while the chuck table 22 and the grinding wheel 46B are rotated, the grinding wheel 46B is lowered by the moving mechanism 26B (see FIG. 1) and the grinding wheel 50B is brought into contact with the first surface 11a of the workpiece 11. As a result, the first surface 11a of the workpiece 11 is removed by the grinding wheel 50B, and the workpiece 11 is finish-ground. Then, when the workpiece 11 is thinned to a predetermined thickness, the lowering of the grinding wheel 46B is stopped, and the finish-grinding of the workpiece 11 is completed.

[0061] Nozzles (not shown) for supplying liquid (grinding fluid) such as pure water are provided inside or near the grinding units 38A, 38B, respectively. Grinding fluid is continuously supplied to the workpiece 11 and the grinding wheels 50A, 50B while the workpiece 11 is being ground. This cools the workpiece 11 and the grinding wheels 50A, 50B, and also washes away chips (grinding chips) generated by grinding the workpiece 11.

[0062] As described above, in the grinding step S2, the workpiece 11 is ground by the grinding wheels 46A, 46B, thereby performing rough grinding and finish grinding on the workpiece 11. When the first surface 11a of the workpiece 11 is ground by the grinding wheels 50A, 50B, arc-shaped grinding marks (saw marks) formed along the revolution paths of the grinding wheels 50A, 50B may remain on the first surface 11a of the workpiece 11.

[0063] Next, the turntable 20 (see FIG. 1) rotates, and the chuck table 22 holding the workpiece 11 is placed in the polishing area D. This positions the workpiece 11 below the polishing pad 78. Then, the workpiece 11 is polished by the polishing unit 52.

[0064] 7 is a partial cross-sectional side view showing the processing apparatus 2 in the polishing step S3. A polishing liquid supply path 92 is provided in the center of the polishing unit 52 so as to penetrate the polishing unit 52 along the Z-axis direction.

[0065] Specifically, a flow path 74a is provided in the center of the spindle 74, penetrating the spindle 74 in the height direction (Z-axis direction). A flow path 76a is provided in the center of the mount 76, penetrating the mount 76 in the thickness direction (Z-axis direction). A flow path 78a is provided in the center of the polishing pad 78, penetrating the polishing pad 78 in the thickness direction (Z-axis direction). The flow paths 74a, 76a, and 78a are connected to form a polishing liquid supply path 92. The tip (lower end) of the polishing liquid supply path 92 opens at the center of the polishing surface 82a. A polishing liquid supply source 94 that supplies the polishing liquid is connected to the base end (upper end) of the polishing liquid supply path 92.

[0066] When polishing the workpiece 11, a polishing liquid 96 is supplied from a polishing liquid supply source 94 to a polishing liquid supply path 92. For example, the polishing liquid 96 corresponds to a liquid (chemical liquid) that performs a chemical surface treatment on the workpiece 11. The polishing liquid 96 supplied to the polishing liquid supply path 92 flows inside the polishing layer 82 or flows out from the lower end of the polishing liquid supply path 92. In this way, the polishing liquid 96 is supplied to the workpiece 11 and the polishing layer 82.

[0067] In the polishing step S3, first, the positional relationship between the workpiece 11 and the polishing pad 78 is adjusted. Specifically, the position of the polishing pad 78 is adjusted by the X-axis movement mechanism 56 (see FIG. 3) so that the entire first surface 11a (surface to be processed) of the workpiece 11 is located inside the outer periphery of the polishing layer 82 of the polishing pad 78 in a plan view. As a result, the polishing layer 82 is positioned so as to overlap the entire workpiece 11.

[0068] Thereafter, while rotating the chuck table 22 and the polishing pad 78, the polishing pad 78 is lowered by the Z-axis movement mechanism 64 (see FIG. 3) to bring the workpiece 11 and the polishing pad 78 closer to each other (processing feed). Furthermore, a polishing liquid 96 is supplied from a polishing liquid supply source 94 to the workpiece 11 and the polishing layer 82 via a polishing liquid supply path 92. Then, when the polishing surface 82a of the polishing layer 82 comes into contact with the first surface 11a of the workpiece 11, the first surface 11a of the workpiece 11 is wet-polished.

[0069] As described above, when the first surface 11a of the workpiece 11 is polished, the first surface 11a is flattened. This improves the crystallinity of the first surface 11a of the workpiece 11. Furthermore, if grinding marks are formed on the first surface 11a of the workpiece 11 after the grinding step S2, the grinding marks are removed by polishing. Then, after polishing continues until the workpiece 11 reaches a predetermined thickness, the processing feed is stopped and polishing of the workpiece 11 is completed.

[0070] The material of the polishing liquid 96 supplied to the workpiece 11 and the polishing layer 82 is appropriately selected depending on the material of the workpiece 11, the purpose of polishing, the processing conditions, etc. Examples of the polishing liquid 96 include an acidic solution in which permanganate is dissolved, and an alkaline solution in which sodium hydroxide or potassium hydroxide is dissolved. The following describes, as an example, a case in which the polishing liquid 96 is an acidic solution.

[0071] For example, the polishing solution 96 may be an aqueous solution in which an oxidizing agent and a pH adjuster are dissolved in a solvent such as pure water. The oxidizing agent may be a permanganate such as sodium permanganate or potassium permanganate. The pH adjuster may be lanthanum nitrate or cerium nitrate. Adjusting the polishing solution 96 to a strong acidity (e.g., a pH value of less than 3) using a pH adjuster allows the oxidizing ability of the oxidizing agent (permanganate) to be fully exerted. This allows the polishing amount (polishing rate) of the workpiece 11 polished by the polishing layer 82 per unit time to be improved.

[0072] However, the pH adjuster can be appropriately selected depending on the material of the workpiece 11, the material of the oxidizing agent, etc. For example, the pH adjuster can be a water-soluble nitric acid compound (lanthanum nitrate, cerium nitrate, yttrium nitrate, zirconyl nitrate, etc.), a water-soluble hydrochloric acid compound (lanthanum chloride, cerium chloride, yttrium chloride, zirconyl chloride, etc.), a water-soluble sulfuric acid compound (lanthanum sulfate, cerium sulfate, yttrium sulfate, zirconyl sulfate, etc.), etc.

[0073] When the polishing liquid 96 is supplied to the contact area between the workpiece 11 and the polishing surface 82a of the polishing layer 82, the polishing liquid 96 acts on the first surface 11a side of the workpiece 11, repeatedly forming and removing an oxide layer on the first surface 11a side of the workpiece 11. In this way, the first surface 11a side of the workpiece 11 is subjected to CMP.

[0074] For example, if the workpiece 11 is a single-crystal SiC wafer, a polishing solution 96 containing permanganate as an oxidizing agent can be used. When the polishing solution 96 is supplied to the workpiece 11, Si atoms are oxidized by the oxidizing action of permanganate on the SiC crystal plane exposed on the first surface 11a of the workpiece 11, forming a silicon oxide layer. This silicon oxide layer is more brittle than SiC crystals and is easily removed by contact with the polishing layer 82. As a result, a new SiC crystal plane is exposed on the first surface 11a of the workpiece 11. Thereafter, the formation and removal of the silicon oxide layer is repeated in the same manner, thereby polishing the first surface 11a of the workpiece 11.

[0075] The C atoms contained in the single crystal SiC wafer are converted into carboxyl groups, carbon dioxide, etc. The carboxyl groups are converted into metal ions (La 3+ , Ce 3+ The carbon dioxide is extracted from the single crystal SiC wafer by coordinating with the abrasive grains contained in the polishing layer 82 and the like, or the like. The carbon dioxide is dissolved in the polishing solution 96 as carbonate ions, or is discharged from the polishing solution 96 as a gas.

[0076] Here, when the workpiece 11 is polished with the polishing pad 78 while the polishing liquid 96 is being supplied to the workpiece 11, metal derived from components contained in the polishing liquid 96 may remain on the first surface 11a of the workpiece 11. For example, if the polishing liquid 96 contains permanganate, manganese adheres to the first surface 11a of the workpiece 11 during polishing. This manganese then oxidizes, and manganese oxides (MnO2, MnO3, etc.) remain as particles on the workpiece 11 after polishing.

[0077] As described above, metal remaining in the workpiece 11 adversely affects the quality of the workpiece 11. For example, if the workpiece 11 is a single-crystal SiC wafer, a crystalline thin film (epitaxial layer) constituting a semiconductor device may be formed on the single-crystal SiC wafer by epitaxial growth. However, if metal remains in the single-crystal SiC wafer, epitaxial growth is inhibited, making it difficult to form a high-quality epitaxial layer. Furthermore, the remaining metal may contaminate the semiconductor device, causing a decrease in reliability or malfunction of the semiconductor device.

[0078] Therefore, in this embodiment, metal-adsorbing particles that adsorb metal are contained in the polishing layer 82 of the polishing pad 78 that polishes the workpiece 11. As a result, metal that adheres to the workpiece 11 during polishing is adsorbed and captured by the metal-adsorbing particles, and the metal remaining on the workpiece 11 is suppressed.

[0079] 8 is a cross-sectional view showing a portion of the workpiece 11 and the polishing layer 82. The polishing layer 82 includes a substrate (base material) 100 made of a resin such as polyurethane or a nonwoven fabric such as felt. The substrate 100 contains a plurality of abrasive grains 102 and a plurality of metal adsorption particles 104.

[0080] The abrasive grains 102 are held inside the substrate 100 and correspond to fixed abrasive grains that contribute to polishing the workpiece 11. For example, silica particles or alumina particles with an average particle size of 0.2 μm or more and 0.5 μm or less are used as the abrasive grains 102. However, the material and particle size of the abrasive grains 102 can be selected appropriately depending on the material of the workpiece 11, etc.

[0081] When the substrate 100 contains abrasive grains 102, the polishing liquid 96 (see FIG. 7) does not contain abrasive grains. However, the substrate 100 does not have to contain abrasive grains 102. In this case, the polishing liquid 96 contains abrasive grains (loose abrasive grains), and the loose abrasive grains are supplied to the contact area between the workpiece 11 and the polishing layer 82 together with the polishing liquid 96.

[0082] The metal-adsorbing particles 104 are particles (metal scavengers) capable of adsorbing a predetermined metal, and are dispersed generally uniformly within the substrate 100. For example, the metal-adsorbing particles 104 are silica particles having functional groups that adsorb the predetermined metal. The average particle size of the metal-adsorbing particles 104 is, for example, 25 μm or more and 150 μm or less (typically, 30 μm, 60 μm, 100 μm, etc.), which is larger than the average particle size of the abrasive grains 102. However, the material and particle size of the metal-adsorbing particles 104 can be appropriately selected depending on the material and amount of the metal to be adsorbed, etc. Examples of commercially available silica particles that can be used as the metal-adsorbing particles 104 include SCAVENGER / metal-removing silica (SH SILICA, SO3H SILICA, Diamine SILICA, NH SILICA, etc.) manufactured by Fuji Silysia Chemical Ltd.

[0083] The size relationship between the average particle size of the abrasive grains 102 and the average particle size of the metal-adsorbing particles 104 can be confirmed by measuring both using the same measurement method and comparing the measurement results. In addition, the specific values of the average particle sizes of the abrasive grains 102 and the metal-adsorbing particles 104 correspond to the particle size at 50% cumulative of the particle size distribution (median diameter, d50, 50% diameter) measured by, for example, a laser diffraction / scattering method.

[0084] The metal-adsorbent particles 104 are preferably spherical particles. In this case, the metal-adsorbent particles 104 have a shape that is a perfect sphere or similar to a perfect sphere. For example, the circularity of the metal-adsorbent particles 104 is 0.95 or more, preferably 0.96 or more, and more preferably 0.97 or more. Furthermore, for example, the perimeter envelopment of the metal-adsorbent particles 104 is 0.97 or more, preferably 0.98 or more, and more preferably 0.99 or more, and the area envelopment of the metal-adsorbent particles 104 is 0.94 or more, preferably 0.95 or more, and more preferably 0.96 or more.

[0085] If the metal-adsorbing particles 104 are spherical, even if the metal-adsorbing particles 104 are exposed on the polishing surface 82a when the workpiece 11 is polished by the polishing layer 82, only the smooth surface (curved surface) of the metal-adsorbing particles 104 comes into contact with the workpiece 11. Therefore, the contact between the workpiece 11 and the metal-adsorbing particles 104 is soft, and the contact between the workpiece 11 and the abrasive grains 102 predominantly contributes to the polishing of the workpiece 11. This prevents the metal-adsorbing particles 104 from interfering with the polishing of the workpiece 11.

[0086] When polishing the first surface 11a of the workpiece 11, the polishing surface 82a of the polishing layer 82 comes into contact with the first surface 11a of the workpiece 11, with the polishing liquid 96 (see FIG. 7) being supplied to the workpiece 11 and the polishing layer 82. At this time, the metal 106 contained in the polishing liquid 96 adheres to the first surface 11a of the workpiece 11.

[0087] The metal-adsorbing particles 104 adsorb and capture the metal 106 adhering to the first surface 11a of the workpiece 11, thereby removing it from the workpiece 11. For example, when the polishing liquid 96 contains permanganate, manganese is likely to adhere to the first surface 11a of the workpiece 11. Therefore, the base material 100 contains metal-adsorbing particles 104 having functional groups that adsorb manganese. Specifically, SO3H SILICA (manufactured by Fuji Silysia Chemical Ltd.), which is silica particles having a sulfo group, or the like can be used as the metal-adsorbing particles 104.

[0088] The permanganate contained in the polishing liquid 96 is ionized in the polishing liquid 96 to become permanganate ions, which adhere to the first surface 11a of the workpiece 11. Then, when the workpiece 11 comes into contact with the polishing layer 82, the polishing liquid 96 contributes to the polishing of the workpiece 11 by the polishing layer 82, and then the manganese ions are adsorbed to the metal-adsorbing particles 104 through bonding between the manganese ions and the sulfo groups of the metal-adsorbing particles 104. This removes manganese from the first surface 11a of the workpiece 11, making it difficult for particles (manganese oxides) to remain on the workpiece 11 after polishing.

[0089] However, the specific material of the metal-adsorbing particles 104 is appropriately selected depending on the material of the metal 106 that can be adhered to the workpiece 11. Furthermore, the substrate 100 may contain two or more types of metal-adsorbing particles 104 made of different materials.

[0090] The amount of metal-adsorbent particles 104 contained in polishing layer 82 is set appropriately so as to fully exert the effect of removing metal 106. For example, the content of metal-adsorbent particles 104 in polishing layer 82 is set to 0.1 vol% or more and 50 vol% or less, and preferably 10 vol% or more and 30 vol% or less. This content corresponds to the ratio of the total volume of metal-adsorbent particles 104 (the sum of the volumes of the plurality of metal-adsorbent particles 104) to the volume of polishing layer 82 (the sum of the volumes of substrate 100, abrasive grains 102, and metal-adsorbent particles 104).

[0091] As described above, in the polishing step S3, the workpiece 11 is polished by the polishing pad 78 having the metal adsorbent particles 104 contained in the polishing layer 82. This prevents the metal 106 adhering to the workpiece 11 from remaining.

[0092] In the polishing step S3, after the workpiece 11 has been polished to a predetermined thickness and the processing feed (relative movement between the chuck table 22 and the polishing pad 78) and the supply of the polishing liquid 96 have been stopped, the rotation of the chuck table 22 and the polishing pad 78 may be maintained for a certain period of time while the workpiece 11 and the polishing layer 82 are in contact with each other. For example, the rotation of the chuck table 22 and the polishing pad 78 may be maintained for 5 seconds or more, preferably 10 seconds or more. This allows the metal 106 adhering to the workpiece 11 to be more reliably adsorbed by the metal-adsorbent particles 104.

[0093] When the polishing step S3 is completed, the chuck table 22 is placed in the transfer area A (see FIG. 1) as described above. Then, the workpiece 11 is transferred from the chuck table 22 by the transfer unit 18 to the cleaning unit 84, and the cleaning unit 84 carries out a cleaning step of cleaning the workpiece 11.

[0094] In the cleaning process, the workpiece 11 is held on the holding surface of the spinner table 86 (see FIG. 1) so that the first surface 11a is exposed upward. Then, while the spinner table 86 is being rotated, a cleaning fluid is supplied from a nozzle 88 (see FIG. 1) to the first surface 11a of the workpiece 11. This washes away foreign matter such as particles adhering to the first surface 11a of the workpiece 11.

[0095] As described above, the polishing pad 78 according to this embodiment includes a polishing layer 82 containing metal-adsorbing particles 104 that adsorb metal 106. When this polishing pad 78 is used to polish the workpiece 11, the metal 106 that adheres to the workpiece 11 during the polishing process is adsorbed and captured by the metal-adsorbing particles 104, and is removed from the workpiece 11. This prevents the metal 106 from remaining on the workpiece 11.

[0096] In this embodiment, the case where the workpiece 11 is subjected to grinding and polishing by the processing device 2 has been described. However, when only polishing is performed on the workpiece 11, a processing device (polishing device) equipped with a polishing unit but not a grinding unit may be used. In this case, the grinding step S2 (see FIG. 6) is omitted.

[0097] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0098] 11 Workpiece 11a 1st page 11b Side 2 2 Processing equipment (grinding and polishing equipment) 4 Foundation 4a,4b opening 6 Transport unit 8A, 8B Cassette support stand 10A, 10B cassette 12 Alignment mechanism (positioning mechanism) 14 Temporary table 16 Support structure 18 Transport unit 20 Turntable 22 Chuck table (holding table) 22a Holding surface 24 Support structure 26A,26B Moving mechanism 28 Guide rail 30 Moving Plate 32 Ball screw 34 Pulse motor 36 Support member 38A, 38B Grinding Unit 40 Housing 42 Spindle 44 Wheel mount 46A, 46B Grinding Wheel 48A, 48B Wheel base 50A, 50B grinding wheels 52 Polishing unit 54 Support structure 56 X-axis movement mechanism 58 X-axis guide rail 60 X-axis moving block 62 X-axis pulse motor 64 Z-axis movement mechanism 66 Z-axis guide rail 68 Z-axis moving block 70 Z-axis pulse motor 72 Housing 74 Spindle 74a Channel 76 Mount 76a Channel 78 Polishing Pad 78a Channel 80 foundations 82 Polishing layer 82a Polished surface 84 Cleaning Unit 86 Spinner Table 88 nozzles 90 Controller (control unit, control section, control device) 92 Polishing liquid supply path 94 Polishing fluid supply source 96 Polishing liquid 100 Base material (base material) 102 Abrasive grain 104 Metal adsorption particles 106 Metal

Claims

1. A polishing pad used for polishing a workpiece, a polishing layer fixed to the base and in contact with the workpiece to polish the workpiece; The polishing pad is characterized in that the polishing layer contains metal-adsorbing particles that adsorb metals.

2. 2. The polishing pad according to claim 1, wherein the metal-adsorbing particles are silica particles having functional groups that adsorb the metal.

3. 3. The polishing pad according to claim 1, wherein the metal-adsorbing particles have an average particle size of 25 [mu]m or more and 150 [mu]m or less.

4. 3. The polishing pad according to claim 1, wherein the metal-adsorbing particles adsorb the metal contained in the polishing liquid supplied when the workpiece is polished with the polishing layer.

5. 3. The polishing pad according to claim 1, wherein the polishing layer contains abrasive grains.

6. A method for polishing a workpiece using a polishing pad, comprising: The polishing pad has a disk-shaped base and a polishing layer fixed to the base and in contact with the workpiece to polish the workpiece, a holding step of holding the workpiece on a chuck table; a polishing step of bringing the polishing layer into contact with the workpiece while supplying a polishing liquid containing a metal to the workpiece, thereby polishing the workpiece; The method for processing a workpiece is characterized in that the abrasive layer contains metal-adsorbing particles that adsorb the metal.

7. The polishing layer contains abrasive grains, 7. The method for processing a workpiece according to claim 6, wherein the polishing liquid does not contain abrasive grains.

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