Structure for fixing together chuck base and chuck table in grinding device

Abstract

A grinding device is provided with: a chuck base 50 that is provided to the distal end of a spindle 62; and a chuck table 52 that has a suction surface 58 for a wafer W and is placed on the upper surface of the chuck base 50. A structure for fixing together the chuck base 50 and the chuck table 52 comprises: a support member 54 for supporting the outer peripheral edge portion of the chuck table 52; and an elastic mechanism 80 for applying biasing force to the support member 54 so as to press the chuck table 52 toward the chuck base 50 through elastic deformation of an elastic member 86.

Description

Fixing Structure between Chuck Base and Chuck Table in Grinding Device

[0001] The present invention relates to a fixing structure between a chuck base provided at the tip of a spindle and a chuck table for supporting a wafer in a grinding device.

[0002] In the pre-process of semiconductor manufacturing, a wafer on which a large number of devices are formed is divided into a plurality of chips for each device in the dicing process. Prior to the dicing process, back grinding (thinning grinding) is performed to reduce the thickness of the entire wafer by a grinding device. The grinding device has a chuck base at the tip of the spindle, and a chuck table for supporting the wafer is fixed to the upper surface of the chuck base. When shifting to the back grinding process, the wafer is adsorbed and held by the chuck table with its surface (device formation surface), and the back surface is ground by a grinding wheel.

[0003] By the way, in recent years, the accuracy required for wafer thinning grinding has been increasing, and in some cases, accuracy on the order of sub-microns is required in terms of flatness. For this reason, the shape accuracy of the upper surface of the chuck table assembled to the chuck base has reached a level that affects the thinning grinding. Conventionally, after assembling the chuck table to the chuck base, self-grinding for obtaining the shape accuracy of the upper surface of the chuck table has been performed. However, due to the distortion during the assembly of the chuck base and the chuck table, minute displacements occur in the shape of the upper surface of the chuck table after self-grinding.

[0004] The chuck table is generally fastened to the chuck base with screws. Specifically, a plurality of screws are attached at equal intervals along the outer peripheral edge of the annular chuck table. On the other hand, a plurality of screw holes are arranged annularly on the upper surface of the chuck base so as to correspond to these screws. By screwing each screw into each screw hole, the chuck table is fastened to the chuck base (see, for example, Patent Document 1). At that time, by sequentially tightening a pair of screws that are symmetric with respect to the central axis of the chuck table, the distortion that affects the shape of the upper surface of the chuck table is evenly dispersed, and it is easy to maintain the shape accuracy.

[0005] Special Publication No. 2005-522336

[0006] However, at a microscopic level, the localized stress (stress concentration) generated when fastening screws can easily cause slight distortion around each screw on the chuck table or chuck base. If the amount of distortion differs at multiple fastening locations, it can affect the shape accuracy of the chuck table surface. In particular, when sub-micron order accuracy is required, it has been difficult to ensure that accuracy.

[0007] This invention has been made in view of these circumstances, and one of its objectives is to provide a fixing structure that can maintain high assembly accuracy between the chuck base and the chuck table.

[0008] One aspect of the present invention is a fixing structure for a chuck base and a chuck table in a grinding apparatus comprising a chuck base provided at the tip of a spindle and a chuck table having a wafer adsorption surface and placed on the upper surface of the chuck base. This fixing structure includes a support member that supports the outer peripheral edge of the chuck table and an elastic mechanism that applies a biasing force to the support member by elastic deformation of an elastic member to press the chuck table toward the chuck base.

[0009] Another aspect of the present invention is a fixing structure between a chuck base and a chuck table in a grinding apparatus comprising a chuck base provided at the tip of a spindle and a chuck table having a wafer adsorption surface and placed on the upper surface of the chuck base. This fixing structure includes a support member that supports the outer peripheral edge of the chuck table from above, a pressure receiving member that connects the support member and the chuck base while forming a sealed space between it and the lower surface of the chuck base, and a pressure supply unit that supplies fluid pressure to the sealed space in order to apply a biasing force to the support member so as to press the chuck table toward the chuck base.

[0010] According to the fixing structure of the present invention, the assembly accuracy between the chuck base and the chuck table can be maintained at a high level.

[0011] This is a diagram showing the configuration of a grinding apparatus according to the first embodiment. This is a diagram showing the configuration of a grinding apparatus according to the first embodiment. This is a diagram showing the configuration of a grinding apparatus according to the first embodiment. This is a diagram showing the configuration of a grinding apparatus according to the first embodiment. This is a perspective view showing the configuration of a chuck unit. This is a schematic cross-sectional view showing the configuration of a chuck unit and its drive unit. This is a perspective view showing the assembly structure of a chuck base and a chuck table. This is a plan view showing the structure of a chuck base. This is a diagram showing the fixing structure of a chuck base and a chuck table. This is a diagram showing the fixing structure of a chuck base and a chuck table. This is a diagram showing the fixing method of a chuck table and a chuck base. This is a diagram showing the principle of generating elastic force of an elastic member. This is a cross-sectional view showing the configuration of a chuck unit according to modification 1. This is a cross-sectional view showing the configuration of a chuck unit according to modification 2. This is a cross-sectional view showing the configuration of a chuck unit according to modification 3. This is a cross-sectional view showing the configuration of a chuck unit according to the second embodiment. This is an enlarged view of section L in Figure 16.

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiment and its modified examples, substantially identical components are denoted by the same reference numerals, and their descriptions are omitted as appropriate.

[0013] In this embodiment of the grinding apparatus, a support member is provided to support the outer edge of the chuck table, which is mounted on the chuck base, from above, and an elastic member is provided to apply a downward biasing force to the support member. By utilizing the appropriate elastic force provided by the elastic member to fix the chuck base and the chuck table, it is possible to suppress the generation of local stress between the two and, consequently, local distortion at the fixing point between them. As a result, a high level of assembly accuracy can be maintained between the two. The details will be described below.

[0014] [First Embodiment] (Overall Configuration of Grinding Apparatus) Figures 1 to 4 are diagrams showing the configuration of a grinding apparatus according to the first embodiment. Figure 1 is a perspective view, and Figure 2 is a plan view. Figure 3 is a cross-sectional view taken along the line A-A in Figure 2, and Figure 4 is a cross-sectional view taken along the line B-B in Figure 3 (same direction as Figure 2). For the sake of explanation, the left-right direction, front-back direction, and up-down direction, as viewed from the front of the apparatus, will be described as the X direction, Y direction, and Z direction, respectively.

[0015] As shown in Figure 1, the grinding apparatus 1 is a processing apparatus that thins the wafer by grinding the back surface of the wafer in stages so that the entire wafer reaches a predetermined thickness. In this embodiment, three grinding units 10a to 10c are provided to perform thinning grinding in three stages: rough grinding, medium grinding, and fine grinding. The grinding accuracy is highest in the order of fine grinding > medium grinding > rough grinding.

[0016] Rough grinding is performed by grinding unit 10a, intermediate grinding by grinding unit 10b, and fine grinding by grinding unit 10c. Each grinding unit has the same configuration except for the difference in the coarseness of the grinding wheel attached to its tip (lower end). Therefore, unless specifically distinguished, they are simply referred to as "grinding unit 10".

[0017] The grinding apparatus 1 comprises a rectangular base 2 in plan view, an index table 4 located in the center of the base 2, and grinding units 10a to 10c located above the index table 4. The index table 4 is equipped with a plurality of chuck units 12 for supporting the wafer W to be ground.

[0018] Multiple semiconductor devices (also simply called "devices") are formed on the surface of wafer W. In this embodiment, wafer W is a disc-shaped silicon wafer, but is not limited to this.

[0019] The chuck unit 12 includes a chuck base 50 provided at the tip of a spindle (described later) and a chuck table 52 placed on the upper surface of the chuck base 50. The chuck table 52 has a wafer adsorption surface on its upper surface. The wafer W is placed on the chuck table 52 in an inverted state so that its surface is in contact with the adsorption surface, and is vacuum-adsorbed to the adsorption surface (details described later).

[0020] The index table 4 is a turntable that has a circular shape in plan view and a rotation axis along its axis. By rotating the index table 4, each chuck unit 12 can be moved in the direction of its rotation. Inside the base 2, a drive mechanism and a control unit 6 for rotating the chuck units 12 are provided.

[0021] The control unit 6 consists of a general-purpose computer and includes a CPU for executing various calculation processes, memory or storage for storing control programs, memory used as a work area for data storage and program execution, input / output interfaces, etc. The control unit 6 controls each functional part (mechanism and device) of the grinding apparatus 1 according to the control program.

[0022] An arch-shaped column 8 is erected on the base 2 so as to straddle the index table 4. Grinding units 10a and 10b are arranged side by side on the front side of column 8, and grinding unit 10c is provided on the rear side of column 8 (the rear side of grinding unit 10b).

[0023] As shown in Figure 2, the column 8 has a rectangular shape in plan view, and has two rows of storage recesses 14 on its front side and two rows of storage recesses 14 on its back side. Grinding units 10a to 10c are housed in three of these four storage recesses 14. Each grinding unit 10 is located directly above each chuck unit 12.

[0024] As shown in Figure 3, the grinding unit 10 includes a wheel 18 on which grinding wheels 16 are arranged in an annular shape, a spindle 20 that coaxially supports the wheel 18, a base 22 that rotatably supports the spindle 20, and a moving mechanism 24 that moves the base 22 in the vertical direction. The grinding wheels 16 are detachable from the wheel 18. In this embodiment, a grinding wheel 16 for rough grinding is attached to the grinding unit 10a, a grinding wheel 16 for medium grinding is attached to the grinding unit 10b, and a grinding wheel 16 for fine grinding is attached to the grinding unit 10c, but these are interchangeable. By replacing the grinding wheels 16, the arrangement of each grinding area in the grinding device 1 can be changed.

[0025] Guide rails 15 extending in the Z direction are provided at the center of the bottom surface and on the left and right sides of the open end surface of each receiving recess 14 (see Figure 2). The base 22 is supported so as to be movable in the Z direction by the three guide rails 15 while holding the spindle 20. In this embodiment, the moving mechanism 24 is realized by a screw feed mechanism 26 and a motor 28 (servo motor) that drives it, but it may also be realized by a linear motor. The control unit 6 controls the driving of the moving mechanism 24.

[0026] As shown in Figure 1, each receiving recess 14 is provided with a pair of left and right constant-pressure cylinders 29 to restrict tilting as the spindle 20 rises. The constant-pressure cylinders 29 are known air cylinders including cylinders, pistons, compressors, etc. (not shown), but their explanation is omitted (see, for example, Japanese Patent Application Publication No. 2023-141577).

[0027] As shown in Figure 4, the space on the base 2 where the index table 4 is placed is divided into four areas (areas separated by dashed lines) to demarcate the front, back, left, and right sides. Specifically, the loading / unloading area S1, the rough grinding area S2, the medium grinding area S3, and the fine grinding area S4 are set in the rotational direction around the axis L of the index table 4.

[0028] The loading / unloading area S1 is the area for loading or unloading the wafer W into or out of the chuck table 52. The rough grinding area S2 is the area for rough grinding the wafer W. The intermediate grinding area S3 is the area for intermediate grinding the wafer W. The fine grinding area S4 is the area for fine grinding (finish grinding) the wafer W.

[0029] The index table 4 is a disc-shaped table that has a rotation axis 30 extending in the Z direction and is rotatable around its axis L. The index table 4 is divided into four regions by four partition walls 32 provided on its upper surface, and a chuck unit 12 is arranged in each region. That is, chuck tables 52 are arranged on the index table 4 at equal intervals of 90 degrees around the axis L. By providing partition walls 32 between each chuck table 52, the scattering of cutting fluid (cooling water) etc. between regions during the grinding process is suppressed.

[0030] The four chuck tables 52 move through four regions S1 to S4 while supporting the wafer W by the rotation of the index table 4. The wafer W is loaded into the loading / unloading region S1 and attached to the chuck table 52, and moves sequentially through the rough grinding region S2, the medium grinding region S3, and the fine grinding region S4, where grinding is performed at each stage. After finish grinding is performed in the fine grinding region S4, the wafer W moves back to the loading / unloading region S1 and is unloaded to the outside. In this embodiment, since grinding is performed in stages in this manner, the loading / unloading of the wafer W and the grinding at each stage can be performed in parallel.

[0031] (Chuck Unit Configuration) Figure 5 is a perspective view showing the configuration of the chuck unit 12. Figure 6 is a schematic cross-sectional view showing the configuration of the chuck unit 12 and its drive unit, corresponding to the section taken along the line C-C in Figure 4. Figure 7 is a perspective view showing the assembly structure of the chuck base 50 and the chuck table 52, showing the chuck table 52 partially cut out. Figure 8 is a plan view showing the structure of the chuck base 50.

[0032] As shown in Figure 5, the chuck unit 12 is constructed by coaxially fixing a chuck base 50 and a chuck table 52 via an annular support member 54. The chuck table 52 is placed on the chuck base 50, and the support member 54 is assembled so as to abut the outer peripheral edge of the chuck table 52 from above. The support member 54 is fixed to the chuck base 50 via an elastic mechanism, which will be described later. The support member 54 and the elastic mechanism are fixed together by a plurality of screws 56 arranged at equal intervals along the shape of the support member 54. An adsorption surface 58 for adsorbing wafers W is formed on the upper surface of the chuck table 52.

[0033] As shown in Figure 6, a drive mechanism 60 for rotationally driving the chuck unit 12 is provided inside the index table 4. The drive mechanism 60 includes a spindle 62 provided coaxially with the chuck unit 12, a motor 64 as a drive source, and a pulley 66 connecting the output shaft of the motor 64 to the spindle 62. In this embodiment, a pulley 66 is provided as a reduction mechanism, but the spindle 62 and the motor may be directly connected.

[0034] The chuck base 50 is provided at the tip of the spindle 62 so as to be integrally displaceable. The chuck base 50 is a disc-shaped member made of a metal such as stainless steel (hereinafter referred to as "SUS"). The chuck base 50 is assembled coaxially to the spindle 62.

[0035] The chuck table 52 includes a stepped disc-shaped table body 68 and a disc-shaped holding plate 70 assembled on the upper part of the table body 68. A circular recess 72 is provided on the upper surface of the table body 68 in plan view, and the holding plate 70 is fitted into and fixed to this recess 72. The table body 68 is made of a ceramic material such as alumina (aluminum oxide). The holding plate 70 is a porous member made of ceramics or the like, and its upper surface is an adsorption surface 58 that attracts and holds the wafer W. The height of the adsorption surface 58 is approximately equal to the height of the upper surface of the table body 68. A flange portion 74 that protrudes radially outward is provided on the outer peripheral edge (lower half) of the table body 68. The flange portion 74 is provided at a lower position than the adsorption surface 58 in the chuck table 52.

[0036] The support member 54 is a bottomed, annular resin member with an L-shaped cross-section. The support member 54 has a support portion 76 parallel to the upper surface of the chuck base 50 and a shielding portion 78 perpendicular to the upper surface of the chuck base 50. The shielding portion 78 functions as a "wall" that surrounds the elastic mechanism 80 from the outside. The lower surface of the shielding portion 78 is separated from the upper surface of the chuck base 50.

[0037] As shown in the figure, the lower surface of the support portion 76 abuts against the upper surface of the flange portion 74 of the chuck table 52. That is, the support member 54 is assembled to the chuck table 52 so as to support the flange portion 74 from above. The upper surface of the support member 54 is lower than the suction surface 58 of the chuck table 52. Therefore, when surface grinding (self-grinding) is performed to ensure the flatness of the suction surface 58 after the chuck table 52 has been assembled to the chuck base 50, interference between the grinding wheel and the support member 54 can be prevented. A radial storage space S is formed between the support member 54 and the chuck table 52, and the elastic mechanism 80 is arranged in this storage space S.

[0038] The elastic mechanism 80 is constructed by assembling an annular first member 82 and an annular second member 84 in the vertical direction. An annular elastic member 86 is interposed between the first member 82 and the second member 84. The elastic member 86 is made of an annular leaf spring and has an inner diameter larger than the outer diameter of the chuck table 52. Each member is fixed by a plurality of screws, the details of which will be described later. By forming a housing space S surrounded by the support portion 76 and shielding portion 78 of the support member 54, the intrusion of foreign matter into the space in which the elastic mechanism 80 is arranged can be suppressed, and the elastic member 86 and the like can be protected.

[0039] A constant temperature control unit 90 is provided between the chuck base 50 and the chuck table 52 to maintain a constant temperature for both. The chuck base 50 and the chuck table 52 are provided with suction passages 92 for evacuating the wafer W attached to the suction surface 58. The chuck base 50 is further provided with a fluid passage 94 for circulating a fluid (hereinafter also referred to as "temperature control fluid") for adjusting the temperature of the chuck table 52.

[0040] The suction passage 92 opens at one end into a recess 72 in the chuck table 52, and the other end is connected to the vacuum source 98 via a pipe 96. By driving the vacuum source 98, a vacuum is created, and the resulting suction force is applied to the wafer W through the porous structure of the holding plate 70. The wafer W is then attracted to the suction surface 58 by the negative pressure generated at this time. The control unit 6 controls the driving of the vacuum source 98.

[0041] The constant temperature control unit 90 is composed of a passage groove formed on the upper surface of the chuck base 50 and a fluid passage 100 formed between the lower surface of the chuck table 52. One end of the fluid passage 94 is connected to the fluid passage 100, and the other end is connected to the temperature-controlled fluid supply source 104 via piping 102. The temperature-controlled fluid supply source 104 supplies constant temperature chiller water as the temperature-controlled fluid, adjusted to a temperature of approximately 30°C, for example. This allows the temperature of the entire chuck table 52 to be adjusted to approximately 30°C. The control unit 6 controls the supply of constant temperature chiller water.

[0042] As shown in Figure 7, the elastic mechanism 80 is fixed to the chuck base 50 by fastening the first member 82 to the chuck base 50 with multiple screws. Multiple screw holes 110 corresponding to the multiple screws are arranged in an annular pattern on the upper surface of the chuck base 50. The elastic mechanism 80 is also fixed to the support member 54 by fastening the second member 84 to the support member 54 with multiple screws 56.

[0043] An embossed convex fitting portion 112 is provided in the center of the upper surface of the chuck base 50, surrounding the suction passage 92. On the other hand, a circular groove-shaped concave fitting portion 114 is provided in the center of the lower surface of the chuck table 52, surrounding the suction passage 92. The fitting of the convex fitting portion 112 and the concave fitting portion 114 allows the chuck base 50 and the chuck table 52 to be assembled coaxially, separating the inner suction passage 92 from the outer fluid passage 100. The opening of the fluid passage 94 is located outside the convex fitting portion 112. Therefore, the constant-temperature chiller water flowing through the fluid passage 100 is not drawn into the suction passage 92.

[0044] As shown in FIG. 8, the suction passage 92 is provided along the axis L1 of the chuck base 50. On the upper surface of the chuck base 50, a plurality of fluid passages 94 open on a virtual circle centered on the axis L1. On the upper surface of the chuck base 50, a plurality of passage grooves constituting the fluid passage 100 are also formed. That is, a plurality of annular grooves 120a to 120d provided concentrically around the axis L1, a plurality of connection grooves 122a to 122c that connect the annular grooves in the radial direction centered on the axis L1, and a plurality of discharge grooves 124 that open the annular groove 120d outward in the radial direction are formed.

[0045] A fluid passage 100 is formed between these passage grooves on the upper surface of the chuck base 50 and the lower surface of the chuck table 52. The thermostatic chiller water introduced from the fluid passage 94 into the fluid passage 100 is discharged to the outside through the discharge grooves 124 after sequentially passing through the annular grooves 120a to 120d. The thermostatic chiller water exchanges heat with the chuck base 50 and the chuck table 52 in the process, and keeps the temperatures of both at the set temperature.

[0046] FIGS. 9 and 10 are views showing the fixing structure between the chuck base 50 and the chuck table 52. FIG. 9(A) is an enlarged view of part D in FIG. 7. FIG. 9(B) is an exploded perspective view corresponding to FIG. 9(A). FIG. 10(A) is a cross-sectional view taken along the E-E arrow in FIG. 9(A), and FIG. 10(B) is a cross-sectional view taken along the F-F arrow. FIG. 10(C) is a cross-sectional view taken along the arrow corresponding to the G-G cross-section in FIG. 9(B).

[0047] As shown in FIGS. 9(A) and (B), the first member 82 is, for example, an annular member made of SUS and having a predetermined height. The first member 82 is fixed to the chuck base 50 by a plurality of screws 130 arranged along its shape. The screws 130 are screwed into the screw holes 110 described above (see FIG. 7). A plurality of mounting holes 132 for attaching the screws 130 are formed in the first member 82.

[0048] The second member 84 is, for example, a ring-shaped member made of SUS and having a predetermined height. The second member 84 has a plurality of screw holes 134 arranged along its shape. By screwing the above-described screw 56 into the screw hole 134, the support member 54 and the second member 84 can be fixed.

[0049] The elastic member 86 is, for example, composed of two annular leaf springs stacked. The elastic member 86 is fixed to the first member 82 by a plurality of screws 136 (functioning as "first screws") arranged along its shape. The first member 82 is provided with a plurality of screw holes 138 for screwing the screws 136. The second member 84 is provided with a plurality of through holes 140 (functioning as "second accommodating portions") for accommodating the heads of the screws 136. Note that the elastic member 86 may have a configuration other than the above-described configuration. For example, it may be composed of three or more leaf springs stacked, or may be composed of one leaf spring.

[0050] The elastic member 86 is also fixed to the second member 84 by a plurality of screws 142 arranged along its shape. The second member 84 is provided with a plurality of screw holes 144 for screwing the screws 142. The first member 82 is provided with a plurality of through holes 146 (functioning as "first accommodating portions") for accommodating the heads of the screws 142.

[0051] As shown in FIG. 10(A), the screw �6 and the screw 130 are coaxially arranged. The support member 54 is provided with a mounting hole 150 for attaching the screw 56. A counter bore 152 is formed in the support member 54 to accommodate the head of the screw 56. The first member 82 is fastened to the chuck base 50 by the screw 130, and the second member 84 is fastened to the support member 54 by the screw 56. Since the head of the screw 130 is accommodated in the mounting hole 132, it does not interfere with the upper elastic member 86.

[0052] As shown in Figure 10(B), the elastic member 86 is fastened to the first member 82 by a screw 136. The elastic member 86 is provided with a through hole 137 for inserting the male threaded portion of the screw 136. The head of the screw 136 is housed in the through hole 140 and does not interfere with the upper support member 54. Also, as shown in Figure 10(C), the elastic member 86 is fixed to the second member 84 by a screw 142 (which functions as a "second screw"). The elastic member 86 is provided with a through hole 143 for inserting the male threaded portion of the screw 142. The head of the screw 142 is housed in the through hole 146 and does not interfere with the lower chuck base 50.

[0053] In this configuration, the height h from the upper surface of the chuck base 50, against which the first member 82 abuts, to the upper surface of the flange portion 74, against which the support portion 76 abuts, is greater than the sum of the height of the second member 84, the thickness of the elastic member 86, and the height of the first member 82. Therefore, when the support member 54 is assembled to the chuck table 52, a gap S0 is formed between the members of the elastic mechanism 80. The leaf spring of the elastic member 86 deforms by the height of this gap S0, thereby exerting an elastic force F1.

[0054] This elastic force F1 becomes a biasing force that pulls the support member 54 downward and is transmitted to the chuck table 52 as a pressing force F2. That is, the elastic mechanism 80 applies a biasing force to the support member 54 by the elastic deformation of the elastic member 86, causing the chuck table 52 to press toward the chuck base 50. The support portion 76 of the support member 54 supports the outer peripheral edge of the chuck table 52 by pressing it from above. At this time, the chuck table 52 is uniformly pressed by the lower surface (annular surface) of the support portion 76.

[0055] Figure 11 shows the method of fixing the chuck table 52 to the chuck base 50. Figures 11(A) to (F) show the fixing procedure. When fixing the chuck table 52 to the chuck base 50, first, the first member 82 is fitted onto the chuck table 52 and placed on the upper surface of the chuck base 50. Then, the first member 82 is fixed to the chuck base 50 with multiple screws 130 (Figure 11(A)).

[0056] Next, the elastic member 86 is coaxially fixed to the second member 84 using multiple screws 142, and then placed on the upper surface of the first member 82 while being externally fitted onto the chuck table 52 (Figure 11(B)). At this time, the heads of the screws 142 are inserted into the through holes 146 of the first member 82 (Figure 11(C)). Then, the elastic member 86 is coaxially fixed to the first member 82 using multiple screws 136 (Figure 11(D)). As a result, the first member 82, the elastic member 86, and the second member 84 are fixed, and the elastic mechanism 80 is formed. At this time, each member constituting the elastic mechanism 80 is stacked vertically without any gaps (Figures 11(C), (D)).

[0057] Next, the support member 54 is placed on the upper surface of the chuck base 50 while being externally fitted onto the chuck table 52 (Figure 11(E)). At this time, the support portion 76 abuts against the upper surface of the flange portion 74. The elastic mechanism 80 is housed in the housing space S inside the shielding portion 78. A gap S0 is formed between the upper surface of the second member 84 and the lower surface of the support portion 76. In this state, the elastic mechanism 80 is in an unloaded state where no external force is acting on it and therefore does not generate elastic force, and no biasing force acts on the support member 54.

[0058] Then, the elastic member 86 is fastened to the second member 84 using multiple screws 56 (Figure 11(F)). At this time, the screwing in of the screws 56 applies an upward pulling load to the elastic member 86. As the screws 56 are screwed in, the leaf spring deforms (extends) in the height direction, and the load pulling the support member 54 toward the chuck table 52 increases. In other words, a pressing force F2 due to the elastic force F1 is applied. Since the upper surface of the second member 84 abuts against the lower surface of the support part 76, a gap S0 is formed between at least one of the first member 82 and the second member 84 and the elastic member 86.

[0059] Figure 12 is a diagram illustrating the principle of elastic force generation in the elastic member 86. Figure 12(A) is a schematic cross-sectional view showing the deformation mechanism of the elastic member 86. Figure 12(B) shows the deformation mode of the elastic member 86 in a slightly exaggerated manner. As shown in Figure 12(A), the first member 82 is fixed to the chuck base 50 and the second member 84 is fixed to the support member 54, but both have high rigidity and do not deform in the height direction. In contrast, the elastic member 86 has less rigidity than the first member 82 and the second member 84 because it is thinner. Therefore, as shown in the figure, it bends as the fastening position by the screws shifts in the height direction. That is, as shown in Figure 12(B), it deforms from an overall flat state (see dashed line) into a wave shape, thereby exhibiting the elastic force of a leaf spring. As described above, this elastic force is applied to the support member 54 as a biasing force, pressing the chuck table 52 against the chuck base 50.

[0060] As described above, the grinding apparatus 1 of this embodiment is provided with a support member 54 that supports the outer peripheral edge of the chuck table 52 from above, and an elastic mechanism 80 that applies a downward biasing force to the support member 54. The elastic force of the elastic mechanism 80 becomes the biasing force of the support member 54, pressing the chuck table 52 toward the chuck base 50. In other words, by using elastic force to fix the chuck base 50 and the chuck table 52, the increase in stress acting between them can be mitigated. The biasing force of the support member 54 that presses the chuck table 52 toward the chuck base 50 can be adjusted by the elastic deformation of the elastic member 86. As a result, the occurrence of localized stress (stress concentration) between them can be suppressed. For this reason, localized distortion is less likely to occur at the fixing point between the chuck base 50 and the chuck table 52, and the assembly accuracy of the two can be maintained at a high level.

[0061] Furthermore, by using an annular member as the support member 54 and continuously contacting the outer edge of the chuck table 52 from above in an annular manner (by pressing with the annular surface), the chuck table 52 can be biased uniformly. This synergistically enhances the effect of suppressing stress concentration.

[0062] Furthermore, by adopting a configuration in which an elastic mechanism 80 is interposed between the support member 54 and the chuck base 50, the height of the elastic mechanism 80 can be secured by providing the first member 82 and the second member 84 above and below the elastic member 86. Therefore, there is no need to increase the thickness of the leaf spring as the elastic member 86, and the amount of deformation of the leaf spring does not become excessive. As a result, the elastic force of the elastic member 86 can be set to an appropriate size, and the stress relaxation effect can be maintained.

[0063] [Modifications] (Modification 1) Figure 13 is a cross-sectional view showing the configuration of the chuck unit according to Modification 1. Figure 13(A) shows the fixing structure between the chuck base and the chuck table. Figure 13(B) is an enlarged view of part H in Figure 13(A), and Figure 13(C) is an enlarged view of part I in Figure 13(A).

[0064] As shown in Figure 13(A), the chuck unit 212 of this modified example is constructed by fixing the chuck base 250 and the chuck table 52 via an annular support member 254. An elastic mechanism 280 is disposed between the support member 254 and the chuck base 250. The elastic mechanism 280 consists only of an annular elastic member 286. That is, the elastic member 286 of this modified example has a configuration similar to the elastic mechanism 80 of the above embodiment, but with the first member 82 and the second member 84 omitted.

[0065] As shown in Figures 13(B) and (C), the elastic member 286 is constructed by stacking three annular leaf springs. The elastic member 286 is fixed to the lower surface of the support member 254 by a plurality of screws 142 (which function as "second screws") arranged at equal intervals along its shape (Figure 13(C)). The lower surface of the support member 254 is provided with a plurality of screw holes 144 for screwing in the plurality of screws 142. On the other hand, the upper surface of the chuck base 50 is provided with a plurality of housing holes 246 for accommodating the heads of the plurality of screws 142.

[0066] Furthermore, the elastic member 286 is fixed to the upper surface of the chuck base 250 by a plurality of screws 136 (which function as "first screws") arranged at equal intervals along its shape (Figure 13(B)). The support member 254 is provided with a plurality of through holes 244 for inserting the heads of the plurality of screws 136. On the other hand, the upper surface of the chuck base 250 is provided with a plurality of screw holes 110 for screwing in the plurality of screws 136.

[0067] In this modified example, the elastic force of the elastic mechanism 280 becomes the biasing force of the support member 254, pressing the chuck table 52 toward the chuck base 250. In other words, by using elastic force to fix the chuck base 250 and the chuck table 52 together, the increase in stress acting between them can be mitigated. The biasing force of the support member 254 that presses the chuck table 52 toward the chuck base 250 can be adjusted by the elastic deformation of the elastic member 286. Furthermore, since the elastic mechanism 280 is composed only of a leaf spring, the number of parts can be reduced, making it simple and low-cost to implement.

[0068] (Modification 2) Figure 14 is a cross-sectional view showing the configuration of the chuck unit according to Modification 2. Figure 14(A) shows the fixing structure between the chuck base and the chuck table. Figure 14(B) is an enlarged view of section J in Figure 14(A).

[0069] As shown in Figure 14(A), the chuck unit 312 of this modified example is constructed by fixing the chuck base 50 and the chuck table 52 via an annular support member 354. An elastic mechanism 380 is disposed between the support member 354 and the chuck table 52. The elastic mechanism 380 consists only of an annular elastic member 386 made of rubber.

[0070] As shown in Figure 14(B), the elastic member 386 is interposed between the flange portion 74 of the chuck table 52 and the support portion 76 of the support member 354. The support member 354 is fixed to the chuck base 50 by a plurality of screws 56 arranged at equal intervals along its shape. The support member 354 is provided with a plurality of mounting holes 150 for attaching the plurality of screws 56. On the other hand, the upper surface of the chuck base 50 is provided with a plurality of screw holes 110 for screwing in the plurality of screws 56.

[0071] As the screw 56 is screwed in, the rubber of the elastic member 386 is compressed in the height direction, exerting an elastic force F1 that presses the upper surface of the flange portion 74 downward. This elastic force F1 is transmitted to the chuck table 52 as a pressing force F2. In other words, the elastic mechanism 380 adjusts the biasing force of the support member 354 that presses the chuck table 52 toward the chuck base 50 by the elastic deformation of the elastic member 386.

[0072] In this modified example, the elastic force of the elastic mechanism 380 adjusts the biasing force of the support member 254, pressing the chuck table 52 toward the chuck base 50. In other words, by using elastic force to fix the chuck base 50 and the chuck table 52, the increase in stress acting between them can be mitigated. Localized distortion is less likely to occur at the fixing points of the two, and the assembly accuracy of the two can be maintained at a high level.

[0073] (Modification 3) Figure 15 is a cross-sectional view showing the configuration of the chuck unit according to Modification 3. Figure 15(A) shows the fixing structure between the chuck base and the chuck table. Figure 15(B) is an enlarged view of part K in Figure 15(A).

[0074] As shown in Figure 15(A), the chuck unit 412 of this modified example is constructed by fixing a chuck base 450 and a chuck table 52 via an annular support member 453. The support member 453 is constructed by assembling a first support member 454 and a second support member 456 vertically. The first support member 454 is annular, and the second support member 456 is a bottomed annular. An elastic mechanism 480 is disposed between the chuck base 450 and the second support member 456. The elastic mechanism 480 includes a plurality of elastic members 486 arranged in an annular shape. The elastic members 486 are compression coil springs.

[0075] As shown in Figure 15(B), the second support member 456 has a support portion 476 parallel to the lower surface of the chuck base 450 and a shielding portion 478 perpendicular to the lower surface of the chuck base 450. The upper end surface of the shielding portion 478 is fixed to the lower surface near the outer edge of the first support member 454. The shielding portion 432 surrounds the chuck table 52 and the chuck base 450.

[0076] Multiple mounting holes 432 for attaching multiple screws 430 are provided near the outer edge of the first support member 454, following its shape. Screw holes 434 are provided on the upper surface of the second support member 456 (the upper end surface of the shielding portion 478) at positions corresponding to each mounting hole 432. The first support member 454 and the second support member 456 are fixed together by multiple screws 430 arranged at equal intervals. The first support member 454 has a support portion 76 that supports the flange portion 74 of the chuck table 52 from above.

[0077] Multiple circular groove-shaped housing portions 440 are provided on the lower surface near the outer edge of the chuck base 450. The housing portions 440 are arranged in an annular shape at equal intervals along the shape of the chuck base 450. On the other hand, circular groove-shaped housing portions 442 are provided at equal intervals on the second support member 456 at positions opposite to the housing portions 440 on the support portion 476. The elastic member 486 is then placed in the housing space S formed by the housing portions 440 and 442.

[0078] A gap S0 is formed between the lower surface of the chuck base 450 and the upper surface of the support portion 476. As the screw 430 is screwed in, the compression coil spring of the elastic member 486 is compressed, exerting an elastic force F1 that pushes the support member 453 downward. This elastic force F1 is transmitted to the chuck table 52 as a pressing force F2. That is, a biasing force is applied to the support member 453 so that the chuck table 52 is pressed towards the chuck base 450. This biasing force is adjusted by the amount the screw 430 is screwed in.

[0079] In this modified example, the elastic force of the elastic mechanism 480 adjusts the biasing force of the support member 453, pressing the chuck table 52 toward the chuck base 450. In other words, by using elastic force to fix the chuck base 450 and the chuck table 52 together, the increase in stress acting between them can be mitigated. The biasing force of the support member 453 that presses the chuck table 52 toward the chuck base 450 can be adjusted by the elastic deformation of the elastic member 486.

[0080] [Second Embodiment] Figure 16 is a cross-sectional view showing the configuration of the chuck unit according to the second embodiment. Figure 17 is an enlarged view of section L in Figure 16. In this embodiment, the chuck table and the chuck base are fixed by applying fluid pressure.

[0081] As shown in Figure 16, the chuck unit 512 includes a chuck base 550, a chuck table 52, a support member 554, and a pressure-receiving member 556. The support member 554 is annular in shape, and the pressure-receiving member 556 is a bottomed annular shape. The pressure-receiving member 556 connects the support member 554 and the chuck base 550. The pressure-receiving member 556 has a pressure-receiving portion 576 parallel to the lower surface of the chuck base 550 and a shielding portion 578 perpendicular to the lower surface of the chuck base 550. The upper end surface of the shielding portion 578 is fixed to the lower surface near the outer edge of the support member 554. The shielding portion 578 surrounds the chuck table 52 and the chuck base 550.

[0082] The chuck base 550 is provided with a fluid passage 520 for supplying a pressing fluid toward the pressure-receiving member 556. One end of the fluid passage 520 opens toward the surface facing the pressure-receiving part 576, and the other end is connected to a fluid pressure supply source 524 via a pipe 522. In this embodiment, the fluid pressure supply source 524 is a gas supply source that supplies pressurized gas (air) as the fluid. Between the chuck base 550 and the fluid pressure supply source 524, a flow rate adjustment unit 526 is provided, which includes a control valve for adjusting the flow rate of the pressurized gas supplied from the fluid pressure supply source 524 toward the chuck base 550. The control unit 6 controls the flow rate adjustment unit 526.

[0083] As shown in Figure 17, the support member 554 has multiple mounting holes 532 near its outer edge, which are provided along its shape for attaching multiple screws 530. The upper surface of the pressure-receiving member 556 (the upper end surface of the shielding portion 578) has screw holes 534 at positions corresponding to each mounting hole 532. The support member 554 and the pressure-receiving member 556 are fixed together by multiple screws 530 arranged at equal intervals. The support member 554 has a support portion 76 that supports the flange portion 74 of the chuck table 52 from above.

[0084] The pressure-receiving member 556 is assembled to fit into a stepped portion 551 formed on the lower surface near the outer edge of the chuck base 550. The stepped portion 551 has a pressure-receiving surface 553 that faces the upper surface of the pressure-receiving portion 576. One end of the fluid passage 520 opens into the pressure-receiving surface 553. A seal ring 540 (annular seal member) is interposed between the upper part of the outer surface of the chuck base 550 and the inner surface of the shielding portion 578, and a seal ring 542 (annular seal member) is interposed between the lower part of the outer surface of the chuck base 550 and the inner surface of the pressure-receiving portion 576. As a result, a sealed space S5 is formed between the pressure-receiving member 556 and the lower surface (pressure-receiving surface 553) of the chuck base 550.

[0085] When fixing the chuck table 52 and the chuck base 550, pressurized gas is supplied from the fluid pressure supply source 524 towards the sealed space S5. The flow rate adjustment unit 526 and the fluid passage 520 function as a "pressure supply unit" that supplies fluid pressure using pressurized gas. When pressurized gas is supplied to the sealed space S5, a pressing force F1 is generated that pushes the pressure receiving member 556 downward. This pressing force F1 is transmitted to the chuck table 52 via the support member 554. That is, a biasing force is applied to the support member 554 that pushes the chuck table 52 toward the chuck base 550.

[0086] According to this embodiment, by using fluid pressure to fix the chuck base 550 and the chuck table 52, the increase in stress acting between them can be mitigated. Localized distortion is less likely to occur at the fixing points of the two, and high assembly accuracy can be maintained between the two.

[0087] When the chuck base 550 and the chuck table 52 are made of different materials, their thermal expansion coefficients will differ. In this case, the chuck base 550 and the chuck table 52 are kept at a constant temperature by the supply of temperature-controlled fluid, and the difference in thermal expansion coefficients does not generate stress. However, if the temperature setting is changed or the supply of temperature-controlled fluid is stopped, stress will be generated in the chuck table 52 and the chuck base 550 due to the difference in thermal expansion coefficients. In such cases, the control unit 6 stops the gas supply and releases the biasing force of the support member 554. This allows the chuck table 52 and the chuck base 550 to slide, thereby releasing the stress.

[0088] During the transient state of temperature changes in the chuck base 550 and chuck table 52, the biasing force of the support member 554 may be reduced by controlling (releasing) the pressure of the supplied pressurized gas, thereby releasing the fixing force between the chuck base 550 and the chuck table 52. Then, after the temperature stabilizes, the pressure of the pressurized gas may be increased to exert the biasing force of the support member 554 and fix the chuck base 550 and the chuck table 52. This can suppress the generation of stress due to differences in thermal expansion coefficients.

[0089] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these specific embodiments, and various modifications are possible within the scope of the technical concept of the present invention.

[0090] [Other Modifications] In the first embodiment described above, an example was shown in which the elastic mechanism 80 is configured such that a first member 82 (lower member) is placed below the elastic member 86 and a second member 84 (upper member) is placed above the elastic member 86. In the modifications, either the upper member or the lower member may be omitted, and the height of the other may be increased. If the lower member is omitted, the elastic member will be directly fixed to the chuck base. Even with this configuration, the leaf spring can be deformed in response to the screw that fastens the support member and the upper member, and the elastic force of the elastic member can be ensured. If the upper member is omitted, the elastic member will be directly fixed to the support member. Even with this configuration, the leaf spring can be deformed in response to the screw that fastens the elastic member and the lower member, and the elastic force of the elastic member can be ensured.

[0091] In the above embodiment, a disc-shaped structure is shown for the chuck base and chuck table, and an annular structure is shown for the support member. In modified examples, a chuck base with a rectangular or other shape in plan view may be used. The chuck table can also be any shape as long as it can be placed on and attached to the chuck base. The support member can also be any shape, such as an annular shape to match the shape of the outer edge of the chuck table. Furthermore, in the above embodiment, a single continuous annular structure was used as the support member, but a configuration in which multiple divided support members are arranged in an annular shape may also be used. In that case, the elastic mechanism of the first embodiment and its modified examples can be applied to each support member. Alternatively, the pressure-receiving member of the second embodiment may be applied to each support member, and the pressure supply unit may supply fluid pressure to impart biasing force to each support member. In that case, the sealed space may also be divided.

[0092] It should be noted that the present invention is not limited to the embodiments and modifications described above, and the components can be modified and implemented without departing from the spirit of the invention. Various inventions may be formed by appropriately combining the multiple components disclosed in the embodiments and modifications described above. In addition, some components may be deleted from all the components shown in the embodiments and modifications described above.

Claims

1. A fixing structure for a grinding apparatus comprising a chuck base provided at the tip of a spindle and a chuck table having a wafer adsorption surface and placed on the upper surface of the chuck base, the fixing structure comprising: a support member that supports the outer peripheral edge of the chuck table; and an elastic mechanism that applies a biasing force to the support member by elastic deformation of an elastic member to press the chuck table toward the chuck base.

2. The fixing structure according to claim 1, wherein the support member abuts the outer peripheral edge of the chuck table from above in an annular manner, and the elastic member includes an annular leaf spring having an inner diameter larger than the outer diameter of the chuck table.

3. The fixing structure according to claim 2, wherein the elastic mechanism is interposed between the support member and the chuck base, fixed to both the chuck base and the support member, and generates a load that pulls the support member toward the chuck table by the deformation of the leaf spring in the height direction.

4. The fixing structure according to claim 3, wherein the elastic mechanism includes an annular first member fixed to the chuck base and an annular second member fixed to the support member, the leaf spring is interposed between the first member and the second member and fixed to each of the first member and the second member, the support member is fixed to the second member via a screw, and the load pulling the support member toward the chuck table increases as the leaf spring extends in the height direction in response to the screw being screwed in.

5. The fixing structure according to claim 4, wherein the leaf spring is fixed to the first member by a plurality of first screws arranged in an annular manner, and fixed to the second member by a plurality of second screws arranged in an annular manner, the first member having a first housing portion for housing the heads of the second screws, and the second member having a second housing portion for housing the heads of the first screws.

6. The fixing structure according to claim 3, wherein the leaf spring is fixed to the upper surface of the chuck base by a plurality of first screws arranged in an annular manner, and fixed to the lower surface of the support member by a plurality of second screws arranged in an annular manner, and the heads of the first screws are inserted through holes that penetrate the support member vertically.

7. The fixing structure according to claim 1, wherein the chuck base has a suction passage for vacuuming a wafer to be attached to the chuck table and a fluid passage for circulating a fluid for adjusting the temperature of the chuck table.

8. The fixing structure according to claim 1, wherein the chuck table has a flange portion on its outer peripheral edge that is lower than the suction surface, the support member is assembled to the chuck table so as to support the flange portion, and the upper surface of the support member is lower than the suction surface of the chuck table.

9. A fixing structure for a grinding apparatus comprising a chuck base provided at the tip of a spindle and a chuck table having a wafer adsorption surface and placed on the upper surface of the chuck base, the fixing structure comprising: a support member that supports the outer peripheral edge of the chuck table from above; a pressure receiving member that connects the support member and the chuck base and forms a sealed space between itself and the lower surface of the chuck base; and a pressure supply unit that supplies fluid pressure to the sealed space in order to apply a biasing force to the support member so as to press the chuck table toward the chuck base.

10. The fixing structure according to claim 9, wherein the pressure-receiving member is an annular pressure-receiving member surrounding the chuck base, and an annular sealing member is provided between the chuck table and the pressure-receiving member to form the sealed space.

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