Workpiece holding device

Abstract

[Topic] The present application provides a workpiece holding device capable of processing a workpiece with high precision. [Solution] The holding portion (3) of the processing device (1) is a workpiece holding device, which holds a workpiece (W) processed by a grinding wheel (21) in a rotatable manner, and the workpiece holding device comprises: a base (34); a chuck (33), the chuck (33) being made of a material having a lower thermal expansion coefficient than the base (34), being placed on the base (34), and being capable of adsorbing and holding the workpiece (W); and a clamping member (40), the clamping member (40) being mounted on the base (34) in a radial direction (D) of the base (34) with a gap (G1, G2) between the chuck (33) and the chuck (33), and pressing a flange (36a) of the chuck (33) toward the base (34).

Description

Technical Field

[0001] The present invention relates to a workpiece holding device that rotatably holds a workpiece to be machined by a grinding wheel. Background Art

[0002] In the field of semiconductor manufacturing, a device for processing semiconductor wafers such as silicon wafers (hereinafter referred to as "workpieces") presses a grinding wheel against the workpiece held by suction on a chuck table to grind the surface of the workpiece flat.

[0003] As such processing devices, for example, Figure 6 As shown in (a), it comprises: a chuck table 100, which has an adsorption body 101 for holding a workpiece W and a frame 102 for fixing the adsorption body 101; a base 104, which carries the chuck table 100 and is integrated with the chuck table 100 by bolts 103, and by supplying constant temperature cooling water 105 to the adsorption body 101 and the frame 102, thereby maintaining the temperature of the chuck table 100 at a roughly equal level during processing (for example, see patent document 1).

[0004] Prior art documents

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-69429 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, if Figure 6 As shown in (b), in the processing device described in Patent Document 1, the amount of thermal expansion due to processing heat differs between the stainless steel base 104 and the alumina chuck table 100. The base 104 expands radially more than the frame 102. Furthermore, the bolts 103 cause the chuck table 100 to follow the expansion of the base 104, potentially causing concave warpage on the upper surface (the suction surface) of the chuck table 100. Furthermore, if this warpage occurs, the chuck table 100 may experience a problem in that the thickness of the workpiece W after processing may become uneven.

[0009] Therefore, in order to process a workpiece with high precision, a technical problem that needs to be solved arises, and the present invention aims to solve this problem.

[0010] Technical solutions to problems

[0011] In order to achieve the above-mentioned purpose, the workpiece holding device of the present invention holds the workpiece processed by the grinding wheel in a rotatable manner, and is characterized in that the workpiece holding device comprises: a base; a chuck, which is placed on the above-mentioned base and can adsorb and hold the above-mentioned workpiece; and a clamping component, which is installed on the above-mentioned base with a gap between it and the above-mentioned chuck in the radial direction of the above-mentioned base, and presses the peripheral edge of the above-mentioned chuck toward the above-mentioned base, and the above-mentioned clamping component comprises: a main body, which is fastened to the above-mentioned base by bolts; and a stop-rotation protrusion, which is offset relative to the above-mentioned bolt in the radial direction of the above-mentioned base and is supported on the above-mentioned main body, and the stop-rotation protrusion is embedded in the recess of the above-mentioned chuck to limit the circumferential rotation of the above-mentioned chuck relative to the above-mentioned base.

[0012] According to this configuration, the clamping part provided on the base maintains a state of pressing the periphery of the chuck toward the base while the base and the chuck can independently expand thermally. Therefore, even when the base expands significantly relative to the chuck due to processing heat associated with processing the workpiece, the workpiece can be processed with high precision without causing warping on the adsorption surface of the chuck.

[0013] Effects of the Invention

[0014] According to the present invention, even when the base greatly thermally expands relative to the chuck due to machining heat associated with machining the workpiece, the workpiece can be machined with high precision without causing warping on the suction surface of the chuck. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] [ Figure 1 ] is a schematic diagram of a processing device, which is applicable to a workpiece holding device related to an embodiment of the present invention.

[0016] [ Figure 2 ] is a top view of the workpiece holding device.

[0017] [ Figure 3 ] is to indicate Figure 2 Cross-sectional view and partial enlarged view along line AA.

[0018] [ Figure 4 ] is a diagram showing the structure of the clamping member, Figure 4 (a) is a top view, Figure 4 (b) is the main view, Figure 4 (c) is a side view.

[0019] [ Figure 5 ] is a three-dimensional diagram showing the installation position of the clamping component on the chuck table.

[0020] [ Figure 6 ] is a diagram showing an existing chuck table and base. Figure 6 (a) is a longitudinal cross-section, Figure 6 (b) is a schematic diagram showing a state in which warping occurs on the chuck table due to thermal expansion of the base. DETAILED DESCRIPTION

[0021] The embodiments of the present invention will be described with reference to the accompanying drawings. In the following, when reference is made to the number, value, amount, range, etc. of constituent elements, unless otherwise specified or clearly limited to a specific number in principle, the reference is not limited to that specific number and may be greater than or less than the specific number.

[0022] Furthermore, when referring to the shapes and positional relationships of components, except for cases where it is specifically stated otherwise or cases where it is obvious that this is not the case in principle, the shapes and positional relationships include cases where they are substantially similar or similar to the shapes and positions.

[0023] In addition, the drawings may sometimes be exaggerated to make features easier to understand, and the dimensional ratios of the components may not necessarily be the same as the actual ones. In addition, in the cross-sectional views, hatching of some components may be omitted to make the cross-sectional structure of the components easier to understand.

[0024] In addition, in this embodiment, the expressions indicating directions such as up and down and left and right are not absolute. They are appropriate when each component is in the posture depicted in the drawings, but when the posture changes, they should be interpreted in a modified manner according to the change in posture.

[0025] The processing device 1 performs grinding processing on the workpiece W. Figure 1 As shown, the machining device 1 includes a machining part 2 and a holding part 3 as a workpiece holding device.

[0026] The processing unit 2 includes a grinding wheel 21 , a grinding wheel spindle 22 , and a feeding mechanism 23 .

[0027] The grinding wheel 21 is, for example, a cup-shaped grinding wheel, and is mounted on the lower end of a grinding wheel spindle 22 .

[0028] The grinding wheel spindle 22 is configured to be rotatable around the rotation axis 2 a , and the grinding wheel 21 and the grinding wheel spindle 22 are rotatable integrally.

[0029] The feed mechanism 23 vertically raises and lowers the grinding wheel spindle 22. The feed mechanism 23 is a known structure, and is comprised of, for example, multiple linear guides that guide the movement of the grinding wheel spindle 22 and a ball screw slide mechanism that raises and lowers the grinding wheel spindle 22. The feed mechanism 23 is interposed between the grinding wheel spindle 22 and the column 24.

[0030] The holding portion 3 includes a chuck table 31 and a chuck spindle 32 .

[0031] like Figure 2 and Figure 3 As shown, the chuck table 31 has a chuck 33 and a base 34 .

[0032] The chuck 33 includes an adsorption body 35 and a frame 36. The adsorption body 35 is formed into a shape corresponding to the workpiece W in a plan view. The adsorption body 35 is made of a porous material of alumina.

[0033] The chuck table 31 has a pipeline (not shown) that extends through the interior and reaches the surface. The pipeline is connected to a vacuum pump P and a compressed air source or water supply (not shown) via a rotary joint (not shown). When the vacuum pump P is started, a negative pressure is generated between the workpiece W placed on the adsorption body 35 and the upper surface (adsorption surface 35a) of the adsorption body 35, and the workpiece W is adsorbed and held on the adsorption surface 35a. In addition, when the compressed air source or water supply source is started, the adsorption between the workpiece W and the adsorption body 35 is released.

[0034] The frame 36 is made of a dense body of alumina, and the adsorbent 35 is buried substantially in the center thereof. A flange 36 a is formed on the outer periphery of the frame 36 .

[0035] As mentioned above, the adsorbent 35 and the frame 36 generally use alumina, but any material having a lower thermal expansion coefficient than the base 34 can be used. It can also be silicon carbide which is lightweight and has excellent corrosion resistance and heat resistance, or aluminum nitride which has good thermal conductivity.

[0036] The base 34 is connected to the chuck spindle 32. A convex portion 34a provided at the center of the upper surface of the base 34 is tightly fitted into a central concave portion 36b provided at the center of the lower surface of the frame 36, thereby aligning the center of the frame 36 with the center of the base 34.

[0037] The base 34 is made of a material exhibiting a higher thermal expansion coefficient than the adsorber 35 and the frame 36, for example, stainless steel. The thermal expansion coefficient of alumina is 7.2x10 -6 / ℃, the thermal expansion coefficient of stainless steel (SUS304) is 17.3x10 -6 / ℃.

[0038] In addition, if Figure 4 As shown, the chuck table 31 has a clamping member 40. The clamping member 40 has a main body portion 41 and a protruding portion 42. The clamping member 40 is made of, for example, stainless steel.

[0039] The main body 41 is formed in a substantially fan-shaped shape in a plan view and is fastened to the base 34 by bolts B inserted through bolt holes 41 a.

[0040] The extension portion 42 is erected on the inner side surface 41b of the main body 41. A rotation-stopping protrusion 42a is provided below the extension portion 42. Figure 5As shown, the anti-rotation protrusion 42a is configured to be engageable with the outer peripheral groove 36c formed on the surface of the flange 36a.

[0041] As the tightening force of bolt B is applied, the anti-rotation protrusion 42a presses the flange 36a toward the base 34. Specifically, the clamped surface 36d facing the extension 42 of the flange 36a is pressed toward the base 34 via the clamping surface 42b of the anti-rotation protrusion 42a facing the flange 36a. Furthermore, the anti-rotation protrusion 42a is offset relative to the bolt B and cantilevered on the main body 41, thereby preventing excessive clamping force from acting on the flange 36a due to the tightening force of bolt B. Furthermore, because the anti-rotation protrusion 42a moves relative to the chuck 33 due to thermal expansion of the base 34 (described later), it is dimensioned to allow contact with the flange 36a before and after movement.

[0042] Preferably, at least one of the lower surface 36e of the frame 36 or the upper surface 34b of the base 34 is coated with a low-friction, slippery layer (not shown). Examples of this slippery layer include graphite, molybdenum disulfide, or DLC (diamond-like carbon). Alternatively, at least one of the frame 36 or the base 34 is preferably made of a material such as graphite, molybdenum disulfide, or DLC in which a solid lubricant is dispersed to exhibit low friction.

[0043] Furthermore, at least one of the clamped surface 36d or the clamping surface 42b is preferably coated with a low-friction, slippery layer (not shown). Examples of the slippery layer include graphite, molybdenum disulfide, or DLC. Alternatively, at least one of the frame 36 or the clamping member 40 is preferably made of a low-friction, slippery layer such as graphite, molybdenum disulfide, or DLC in which a solid lubricant is dispersed.

[0044] Gaps G1 and G2 are respectively maintained between the inner side surface 41b of the main body 41, the inner peripheral surface 42c of the extension 42, and the outer surface 36f of the frame 36. Gaps G1 and G2 are set so that the clamping member 40 does not contact the frame 36 in the radial direction D in the initial state before the base 34 expands in the radial direction D due to processing heat.

[0045] The chuck spindle 32 is configured to be capable of rotating and driving the chuck table 31 around the rotation axis 3a. The driving source of the chuck spindle 32 may be, for example, a servo motor or the like.

[0046] The operation of the processing device 1 is controlled by a control unit (not shown). The control unit controls each of the components of the processing device 1. The control unit is composed of, for example, a CPU and memory. The functions of the control unit can be implemented through software control or hardware operation.

[0047] Next, the operation of the processing device 1 will be described.

[0048] First, the workpiece W is placed on the chuck 33 by a transport robot (not shown), and negative pressure is generated between the workpiece W and the suction surface 35 a by a vacuum pump P. As a result, the workpiece W is sucked and held by the suction body 35 .

[0049] Next, the grinding wheel 21 is moved above the workpiece W via the slide of the feed mechanism 23. Then, while the grinding wheel 21 and chuck 33 are rotated, the grinding surface 21a of the grinding wheel 21 is pressed against the workpiece W, thereby grinding the workpiece W. For example, the rotation speeds of the grinding wheel 21 and the workpiece W are set to 2000 rpm and 300 rpm, respectively. Furthermore, the anti-rotation protrusion 42a engages with the outer peripheral recess 36c to limit the rotation of the chuck 33 in the radial direction D, thereby transmitting the rotational drive of the chuck spindle 32 to the chuck 33.

[0050] As machining by the grinding wheel 21 progresses, machining heat due to friction causes the base 34 and the chuck 33 to thermally expand and deform, expanding in the radial direction D. Furthermore, since the base 34 and the chuck 33 experience different thermal expansions, the base 34 expands relatively more than the chuck 33, causing the upper surface 34 b of the base 34 to slide relative to the lower surface 36 e of the frame 36.

[0051] At this time, if at least one of the lower surface 36e of the frame 36 or the upper surface 34b of the base 34 is coated with a slippery layer, or if at least one of the frame 36 or the base 34 is made of a material exhibiting low friction, the base 34 is easily thermally expanded to a relatively large extent relative to the chuck 33.

[0052] Again, such as Figure 3 As shown by the dotted line in the figure, even if the clamping part 40 moves outward in the radial direction D so that the clamping surface 42b slides laterally on the clamped surface 36d as the base 34 expands thermally, the anti-rotation protrusion 42a continues to press the flange 36a onto the base 34.

[0053] In other words, the clamping member 40 leaves the gaps G1 and G2 to press the chuck 33 toward the base 34 , thereby preventing the chuck 33 and the clamping member 40 from interfering with each other when the chuck 33 and the base 34 expand due to heat.

[0054] At this time, if at least one of the clamped surface 36d or the clamping surface 42b is coated with a slippery layer, or if at least one of the frame 36 or the clamping member 40 is made of a material exhibiting low friction, the clamping member 40 can be easily moved relative to the chuck 33.

[0055] When the workpiece W is ground to a desired thickness using a film thickness sensor (not shown), the rotation of the grinding wheel 21 and the chuck 33 is stopped, and the slide of the feed mechanism 23 is activated, thereby removing the grinding wheel 21 from the workpiece W. The chuck 33 then releases its suction and retention of the workpiece W, completing the grinding process of the workpiece W by the processing apparatus 1.

[0056] The structure is as follows: the holding portion 3 of this embodiment is a workpiece holding device that holds the workpiece W processed by the grinding wheel 21 in a rotatable manner, and is characterized in that the workpiece holding device has: a base 34; a chuck 33, which is made of a material having a lower thermal expansion coefficient than the base 34, is placed on the base 34, and can adsorb and hold the workpiece W; and a clamping component 40, which is installed on the base 34 with gaps G1 and G2 between it and the chuck 33 in the radial direction of the base 34, and presses the flange 36a of the chuck 33 toward the base 34.

[0057] According to this structure, the clamping part 40 provided on the base 34 maintains the state of pressing the flange 36a toward the base 34, while the base 34 and the chuck 33 can independently expand thermally. Therefore, even if the base 34 expands significantly relative to the chuck 33 due to the processing heat associated with the processing of the workpiece W, the workpiece W can be processed with high precision without causing warping on the adsorption surface 35a of the chuck 33.

[0058] Furthermore, the holding portion 3 of this embodiment is configured such that the clamping member 40 has the anti-rotation protrusion 42 a that fits into the outer peripheral recess 36 c of the chuck 33 to restrict the circumferential rotation of the chuck 33 relative to the base 34 .

[0059] According to this configuration, the anti-rotation protrusion 42 a fits into the outer peripheral recess 36 c , thereby restricting the circumferential rotation of the chuck 33 . Therefore, the workpiece W held by the chuck 33 can be ground with high precision.

[0060] Furthermore, the present invention can be modified in various ways without departing from the spirit of the present invention, and the present invention naturally extends to the modified aspects.

[0061] In this embodiment, eight clamping members 40 are provided at equal intervals around the outer periphery of the frame 36. However, the number of clamping members 40 provided may be seven or fewer or nine or more. Furthermore, the shape of the clamping members 40 is not limited to that described above, and for example, may be formed in an annular shape so as to surround the frame 36.

[0062] Furthermore, when the rotation speed of the chuck 33 is slow and the chuck 33 does not need to be stopped in the circumferential direction, the clamping part 40 can omit the stopping protrusion 42a and stop the chuck 33 in the circumferential direction only by the static friction force of the force pressing the chuck 33 toward 34.

[0063] In the present embodiment, description has been given of a case where the chuck 33 is made of a material exhibiting a lower thermal expansion coefficient than the base 34 , but the material of the chuck 33 is not limited thereto.

[0064] For example, if the chuck 33 is made of a material exhibiting a higher coefficient of thermal expansion than the base 34, the chuck 33 may thermally expand significantly relative to the base 34 due to the processing heat associated with processing the workpiece W. Even in such a case, according to the configuration of the present invention, the base 34 and the chuck 33 can thermally expand independently while the clamping member 40 provided on the base 34 maintains the state of pressing the flange 36a against the base 34. Therefore, the workpiece W can be processed with high precision without causing warping on the suction surface 35a of the chuck 33.

[0065] Furthermore, when the chuck 33 and the base 34 are made of materials exhibiting substantially equal coefficients of thermal expansion, the processing heat associated with machining the workpiece W is transferred to the chuck 33 more than to the base 34, and the chuck 33 thermally expands significantly relative to the base 43. Even in this case, according to the configuration of the present invention, the base 34 and the chuck 33 can thermally expand independently while the clamping member 40 provided on the base 34 maintains the state of pressing the flange 36a toward the base 34. Therefore, the workpiece W can be machined with high precision without causing warping on the suction surface 35a of the chuck 33.

[0066] Explanation of symbols

[0067] 1: Processing equipment

[0068] 2: Processing Department

[0069] 21: Grinding wheel

[0070] 21a: Grinding surface

[0071] 22: Grinding wheel spindle

[0072] 23: Feeding mechanism

[0073] 24: Pillar

[0074] 3: Maintaining part

[0075] 31: Chuck workbench

[0076] 32: Chuck spindle

[0077] 33: Chuck

[0078] 34: Base

[0079] 34a: flange

[0080] 34b: Upper surface (of the base)

[0081] 35: Adsorbent

[0082] 35a: Adsorption surface

[0083] 36: Frame

[0084] 36a: flange

[0085] 36b: Central fovea

[0086] 36c: Peripheral concave part

[0087] 36d: clamped surface

[0088] 36e: lower surface (of the frame)

[0089] 36f: Outer surface (of the frame)

[0090] 40: Clamping parts

[0091] 41: Main body

[0092] 41a: Bolt hole

[0093] 41b: Inner side (of the main body)

[0094] 42: Extension

[0095] 42a: Anti-rotation protrusion

[0096] 42b: Clamping surface

[0097] 42c: Inner circumference (of the extension)

[0098] G1, G2: Gap

[0099] W: workpiece.

Claims

1. A workpiece holding device for rotatably holding a workpiece to be machined by a grinding wheel, characterized in that: The workpiece holding device has: base; a chuck placed on the base and capable of sucking and holding the workpiece; and A clamping member is mounted on the base with a gap between the clamping member and the chuck in the radial direction of the base, and presses the peripheral edge of the chuck toward the base. The clamping member has: a main body portion, the main body portion being fastened to the base by bolts; and A rotation-stopping protrusion is offset relative to the bolt in the radial direction of the base and supported on the main body, and the rotation-stopping protrusion is engaged in the recess of the chuck to limit the circumferential rotation of the chuck relative to the base.

2. The workpiece holding device according to claim 1, wherein: At least one of the surface of the base facing the chuck or the surface of the chuck facing the base is coated with a slippery layer that facilitates the base to slide laterally relative to the chuck.

3. The workpiece holding device according to claim 1, wherein: At least one of the base or the chuck is made of a material that facilitates lateral sliding of the base relative to the chuck.

4. The workpiece holding device according to claim 1, wherein: At least one of a clamped surface of the chuck facing the clamping member or a clamping surface of the clamping member facing the chuck is coated with a slippery layer that facilitates lateral sliding of the clamping member relative to the chuck.

5. The workpiece holding device according to claim 1, wherein At least one of the chuck or the clamping member is made of a material that facilitates lateral sliding of the clamping member relative to the chuck.

Images