Holding table

Abstract

The present invention provides a holding table that can reduce the likelihood of damage to a workpiece when it is rotated while being held in place. [Solution] The holding table includes a holding base having a first surface that faces the workpiece when the workpiece is held and has an annular first groove and an annular second groove surrounding the first groove formed thereon. The holding base has a first connecting passage for connecting the space near the intermediate region located between the first groove and the second groove on the first surface to a suction source, and a second connecting passage for connecting the space near the central region located inside the first groove on the first surface to the space near the outer periphery surface. The second connecting passage includes a central portion that opens in the central region and extends along the thickness direction of the holding base, and a first branch portion and a second branch portion that each open on the outer periphery surface and extend from the central portion, the second branch portion being closer to the first surface than the first branch portion.

Description

Technical Field

[0001] The present invention relates to a holding table used when rotating a workpiece while holding it by applying an attractive force.

Background Art

[0002] Chips of semiconductor devices such as ICs (Integrated Circuits), which are essential components in various electronic devices such as mobile phones and personal computers, are manufactured through a semiconductor manufacturing process. This semiconductor manufacturing process includes a pre-process of forming a plurality of semiconductor devices each including a large number of circuit elements on a wafer, and a post-process of manufacturing a plurality of chips by processing the wafer as a workpiece.

[0003] In the post-process, the processing of the workpiece is performed while supplying a processing fluid such as water to the processing point in order to suppress overheating of the workpiece and remove processing chips generated during processing. Further, in the post-process, the workpiece is often washed each time processing is performed in order to remove the processing chips attached to the workpiece.

[0004] This washing is generally performed by supplying a cleaning liquid such as water to the workpiece while rotating the holding table while the workpiece is held by applying an attractive force to the workpiece through the holding table. However, when holding a workpiece that has been subjected to some processing, processing chips that remain attached to the workpiece without being removed by the processing fluid may be sandwiched between the workpiece and the holding table.

[0005] Then, when an attractive force is applied to the workpiece in a state where processing chips are sandwiched between the workpiece and the holding table, a locally strong force is applied to the portion of the workpiece to which the processing chips are attached, and the workpiece may be damaged. In view of this point, Patent Document 1 proposes a holding table capable of reducing the probability of the workpiece being damaged.

[0006] This holding table comprises a holding base having a surface that faces the workpiece when the workpiece is held and has a pair of concentric grooves formed thereon, and a pair of O-rings provided in the pair of grooves so as to protrude from the surface when the workpiece is not held. Furthermore, the holding base has a communication passage (suction hole) formed therein to connect the space near the intermediate region located between the pair of grooves on its surface with a suction source.

[0007] When using this holding table to hold a workpiece, an attractive force acts on the portion of the workpiece that overlaps with the intermediate area of ​​the surface of the holding base, while the workpiece is supported by a pair of O-rings. In this case, the likelihood of the workpiece being damaged can be reduced compared to when the attractive force acts on the entire workpiece and / or when the workpiece is supported by a rigid member. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2007-294588 [Overview of the project] [Problems that the invention aims to solve]

[0009] The aforementioned holding table also has a connecting passage (atmospheric vent) formed therein to maintain atmospheric pressure in the space near the central region located inside a pair of grooves on its surface. Specifically, this connecting passage includes a central portion that opens on the surface of the holding table and extends along the thickness direction, and branched portions that open on the outer circumferential surface of the holding table and extend from the central portion in a direction perpendicular to the thickness direction.

[0010] Incidentally, workpieces subjected to cleaning often have not only machining debris but also liquid (for example, machining fluid) adhering to them. And, as mentioned above, when cleaning workpieces, this liquid can flow into the center of the passage and accumulate at the bottom. Furthermore, when the holding table is rotated to clean the workpiece, centrifugal force acts on this liquid, causing it to flow from the center to the branching section.

[0011] When liquid flows into the branching section in this way, it forms a liquid film that seals the branching section, and this liquid film may move within the branching section away from the center of the connecting passage. In this case, the pressure in the central part of the connecting passage and the space near the central area of ​​the surface of the holding table may drop significantly. As a result, a strong suction force may act on the part of the workpiece that overlaps with the central area, potentially causing damage to the workpiece.

[0012] In view of this, the present invention provides a holding table that can reduce the likelihood of damage to a workpiece when it is rotated while being held. [Means for solving the problem]

[0013] According to the present invention, a holding table used when rotating a workpiece while holding it by applying suction force, comprising: a holding base having a first surface facing the workpiece when the workpiece is held and having an annular first groove and an annular second groove surrounding the first groove, a second surface located on the opposite side of the first surface, and an outer peripheral surface located between the outer circumference of the first surface and the outer circumference of the second surface; an annular first elastic body provided in the first groove so as to protrude from the first surface when the workpiece is not held; and a second elastic body provided in the second groove so as to protrude from the first surface when the workpiece is not held. The retaining base comprises an annular second elastic body, the retaining base having a first communication passage for connecting a space near an intermediate region located between the first groove and the second groove on the first surface with a suction source, and a second communication passage for connecting a space near a central region located inside the first groove on the first surface with a space near the outer circumferential surface, the second communication passage including a central portion that opens in the central region and extends along the thickness direction of the retaining base, and a first branch portion and a second branch portion that each open on the outer circumferential surface and extend from the central portion, the retaining table provided having the second branch portion closer to the first surface than the first branch portion.

[0014] Preferably, the central portion has a shape such that its cross-sectional area increases as it approaches the first branch from the first surface, and / or has a shape such that its cross-sectional area decreases as it approaches the second surface from the first branch. [Effects of the Invention]

[0015] In the holding base of the holding table of the present invention, a second communication passage for connecting the space near the central region of the first surface facing the workpiece and the space near the outer peripheral surface when the workpiece is held includes a central portion that opens in the central region, and a first branch portion and a second branch portion that open in the outer peripheral surface and are connected to the central portion, wherein the second branch portion is closer to the first surface than the first branch portion.

[0016] Furthermore, when the workpiece is rotated while being held using this holding table, if any liquid adhering to the workpiece flows into the second connecting passage, most of this liquid will pass through the first branching point and be discharged from the outer surface without passing through the second branching point. In this case, it becomes easier to maintain a state in which the space near the central region is in communication with the space near the outer surface via the central part of the second connecting passage and the second branching point.

[0017] In other words, in this case, the pressure in the space near the central region is maintained at approximately atmospheric pressure without a significant decrease. Therefore, by using the holding table of the present invention as a holding table used when rotating a workpiece while holding it in place by applying suction force, it becomes possible to reduce the likelihood of the workpiece being damaged due to a strong suction force acting on the part of the workpiece that overlaps with the central region. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic plan view showing an example of a holding table used to rotate a workpiece while holding it in place by applying suction force. [Figure 2] Figure 2(A) shows a cross-section of the holding table shown in Figure 1 along the line 2A-2A, and Figure 2(B) shows a cross-section of the holding table shown in Figure 1 along the line 2B-2B. [Figure 3] Figures 3(A), 3(B), and 3(C) are schematic cross-sectional views illustrating another example of a retaining base provided by a retaining table. [Figure 4] Figure 4 is a schematic plan view showing yet another example of a retaining base provided by a retaining table. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view schematically showing an example of a holding table used when rotating a workpiece such as a wafer while holding it by applying a suction force. FIG. 2(A) is a diagram schematically showing a cross section and the like at line 2A-2A of the holding table shown in FIG. 1, and FIG. 2(B) is a diagram schematically showing a cross section and the like at line 2B-2B of the holding table shown in FIG. 1. In each of FIG. 2(A) and FIG. 2(B), the components connected to this holding table are also shown as blocks.

[0020] The holding table 2 shown in FIG. 1 and FIGS. 2(A) and 2(B) includes a disk-shaped holding base 4. This holding base 4 has a first surface 4a facing the workpiece in a state of holding the workpiece, a second surface 4b located on the opposite side of the first surface, and an outer peripheral surface 4c located between the outer periphery of the first surface and the outer periphery of the second surface.

[0021] And on the first surface 4a, an annular first groove 4d and an annular second groove 4e surrounding the first groove 4d are formed such that the centers in their respective plan views coincide with the center of the first surface 4a. Note that the shapes of the first groove 4d and the second groove 4e in a cross section parallel to each of the thickness direction and the radial direction of the holding base 4 are trapezoidal shapes.

[0022] In the first groove 4d, an annular first elastic body 6a that protrudes from the first surface 4a and contacts the bottom surface and the upper ends of both side surfaces of the first groove 4d in a state of not holding the workpiece is provided. Similarly, in the second groove 4e, an annular second elastic body 6b that protrudes from the first surface 4a and contacts the bottom surface and the upper ends of both side surfaces of the second groove 4e in a state of not holding the workpiece is provided. Note that each of the first elastic body 6a and the second elastic body 6b is, for example, an O-ring.

[0023] Furthermore, the retaining base 4 has a first communication passage 8 formed therein for selectively connecting the space near the intermediate region 4f located between the first groove 4d and the second groove 4e on the first surface 4a to a suction source 12a or an air supply source 12b, which will be described later. Specifically, the first communication passage 8 includes a plurality (for example, four) of cylindrical first vertical sections 8a, each of which opens in the intermediate region 4f and extends along the thickness direction of the retaining base 4. The plurality of first vertical sections 8a are formed at approximately equal angular intervals (90° intervals if there are four first vertical sections 8a) with respect to the center of the first surface 4a in a plan view.

[0024] The outer end of a cylindrical horizontal section 8b, which extends radially along the base 4, is connected to the lower end of each first vertical section 8a. A disc-shaped intermediate section 8c is connected to the inner end of each horizontal section 8b. The upper end of a cylindrical second vertical section 8d, which opens in the center of the second surface 4b and extends along the thickness direction of the base 4, is connected to the center of the intermediate section 8c.

[0025] The second vertical section 8d communicates with a suction source 12a via a valve 10a and with an air supply source 12b via a valve 10b. The suction source 12a includes, for example, an ejector. The air supply source 12b includes, for example, a tank for storing high-pressure air, a filter for removing foreign matter mixed in with the air supplied from the tank, and a regulator for adjusting the pressure of the air supplied from the tank.

[0026] The suction source 12a is used to create negative pressure in the first communication passage 8, and the air supply source 12b is used to return the first communication passage 8 from negative pressure to normal pressure. Therefore, the second vertical section 8d may not be connected to the air supply source 12b via the valve 10b, but rather may be connected to the space around the holding table 2 via the valve 10b. In other words, the valve 10b may be used as a negative pressure release valve to return the second vertical section 8d, which has become negative pressure, to normal pressure.

[0027] Furthermore, the retaining base 4 has a second connecting passage 14 formed therein to connect the space near the central region 4g, which is located inside the first groove 4d on the first surface 4a, with the space near the outer circumferential surface 4c. Specifically, the second connecting passage 14 includes a cylindrical central portion 14a that opens in the central region 4g and extends along the thickness direction of the retaining base 4.

[0028] Near the bottom surface of this central portion 14a, the inner ends of a plurality (for example, four) of cylindrical first branch portions 14b are connected, each opening on the outer circumferential surface 4c and extending along the radial direction of the retaining base 4. The plurality of first branch portions 14b are positioned at the same location relative to each other in the thickness direction of the retaining base 4, and are formed at approximately equal angular intervals (90° intervals if there are four first branch portions 14b) with respect to the center of the first surface 4a in a plan view.

[0029] Furthermore, the inner ends of a plurality of cylindrical second branch portions 14c, each opening on the outer surface 4c and extending along the radial direction of the retaining base 4, are connected to the middle of the side surface of the central portion 14a. Each second branch portion 14c is closer to the first surface 4a than the plurality of first branch portions 14b and overlaps with one of the plurality of first branch portions 14b in the thickness direction of the retaining base 4.

[0030] In addition, the retaining base 4 is connected to the motor 16 via, for example, a pulley (not shown) and a belt (not shown) wrapped around the pulley. When the motor 16 is operated, the retaining table 2 rotates, for example, counterclockwise in a plan view (along the direction indicated by arrow A in Figure 1), with a rotation axis that passes through the center of the first surface 4a and is aligned with the thickness direction of the retaining base 4.

[0031] Then, when rotating the workpiece while holding it in place by applying suction force using the holding table 2, first, the workpiece is placed on the holding table 2 so that the intermediate region 4f of the first surface 4a is covered and it is supported by the first elastic body 6a and the second elastic body 6b. Next, the valve 10b is closed, then the valve 10a is opened and the suction source 12a is activated.

[0032] As a result, the space near the intermediate region 4f of the first connecting passage 8 and the first surface 4a becomes negatively pressurized, and an attractive force acts on the portion of the workpiece that overlaps with the intermediate region 4f. At this time, the first elastic body 6a and the second elastic body 6b that support the workpiece are pressed and elastically deform, for example, until the workpiece comes into contact with the first surface 4a of the holding base 4. As a result, the workpiece is held on a generally flat plane.

[0033] Next, the motor 16 is operated to rotate the holding table 2. This makes it possible to perform desired processing (e.g., cleaning) on ​​the workpiece that rotates with the holding table 2.

[0034] Once this process is complete, valve 10a is closed and the operation of suction source 12a is stopped, then valve 10b is opened and the air supply source 12b is activated. As a result, the space near the intermediate region 4f of the first communication passage 8 and the first surface 4a becomes atmospheric pressure, and the suction force acting on the part of the workpiece that overlaps with the intermediate region 4f is eliminated. Consequently, it becomes easier to separate the workpiece from the holding table 2.

[0035] As described above, in the holding base 4 of the holding table 2, the second communication passage 14 for connecting the space near the central region 4g of the first surface 4a facing the workpiece when the workpiece is held and the space near the outer surface 4c includes a central portion 14a that opens in the central region 4g, and a first branch portion 14b and a second branch portion 14c, which open in the outer surface 4c and are connected to the central portion 14a, respectively, and the second branch portion 14c is closer to the first surface 4a than the first branch portion 14b.

[0036] Furthermore, when the workpiece is rotated while being held using the holding table 2, if liquid adhering to the workpiece flows into the second communication passage 14, most of this liquid will pass through the first branching section 14b without passing through the second branching section 14c and will be discharged from the outer peripheral surface 4c. In this case, it becomes easier to maintain a state in which the space near the central region 4g is in communication with the space near the outer peripheral surface 4c via the central part 14a and the second branching section 14c of the second communication passage 14.

[0037] In other words, in this case, the pressure in the space near the central region 4g is maintained at approximately atmospheric pressure without a significant decrease. Therefore, by using the holding table 2 as a holding table used when rotating the workpiece while holding it in place by applying suction force, it becomes possible to reduce the likelihood of the workpiece being damaged due to a strong suction force acting on the part of the workpiece that overlaps with the central region 4g.

[0038] The above description represents one aspect of the present invention, and the present invention is not limited to the above description. For example, the holding table of the present invention may have a shape that is different in part or in whole from that of the holding table 2.

[0039] Specifically, the holding table of the present invention may include a rectangular plate-shaped holding base. Alternatively, the holding table of the present invention may include a holding base, each having a first and second annular groove formed on its first surface in a plan view, and a first and second elastic body, each having a first annular shape in a plan view. Furthermore, the first and second connecting passages formed in the holding base of the holding table of the present invention may be partially or entirely prismatic in shape.

[0040] Furthermore, the holding table of the present invention may be equipped with a holding base shown in Figure 3(A), Figure 3(B), Figure 3(C), or Figure 4 instead of the holding base 4. Note that each of the holding bases shown in Figure 3(A), Figure 3(B), Figure 3(C), and Figure 4 has the same shape as the holding base 4, except that the shape of its second connecting passage differs from the second connecting passage 14 shown in Figures 1, 2(A), and 2(B).

[0041] Specifically, the second connecting passage 20 formed in the retaining base 18 shown in Figure 3(A) includes a frustoconical or truncated pyramidal central portion 20a and a first branch portion 20b and a second branch portion 20c having the same shape as the first branch portion 14b and second branch portion 14c shown in Figure 2(B), etc. That is, the central portion 20a has a shape such that its cross-sectional area increases as it approaches the first branch portion 20b from the first surface 18a.

[0042] Furthermore, when the workpiece is rotated while being held using the holding table equipped with this holding base 18, if the liquid adhering to the workpiece flows into the second connecting passage 20, the centrifugal force acts on the liquid adhering to the side surface of the central part 20a, thereby promoting the flow of the liquid into the first branching part 20b. In this case, the probability of the workpiece being damaged can be further reduced.

[0043] Furthermore, the second connecting passage 24 formed in the retaining base 22 shown in Figure 3(B) includes a central portion 24a having an upper side with a shape similar to the central portion 20a shown in Figure 3(A) and an inverted truncated cone or inverted frustoconical lower side, and a first branch portion 24b and a second branch portion 24c, each connected to the upper side of the central portion 24a and having a shape similar to the first branch portion 14b and second branch portion 14c shown in Figure 2(B), etc. That is, the central portion 24a has a shape such that its cross-sectional area increases as it approaches the first branch portion 24b from the first surface 22a, and decreases as it approaches the second surface 22b from the first branch portion 24b.

[0044] Furthermore, when a workpiece is rotated while being held using the holding table equipped with the holding base 22, if liquid adhering to the workpiece flows into the second connecting passage 24, even if the amount of liquid is large, the flow of liquid into the second branch section 24c is suppressed, and the centrifugal force acts on the liquid accumulated below the central section 24a, promoting the flow of the liquid into the first branch section 24b. Therefore, in this case, the probability of the workpiece being damaged can be further reduced.

[0045] Furthermore, the second connecting passage 28 formed in the retaining base 26 shown in Figure 3(C) includes a central portion 28a having the same shape as the central portion 14a shown in Figure 2(B), etc., and a first branch portion 28b and a second branch portion 28c that are inclined so as they move from the inner end towards the outer end, they move away from the first surface 26a and approach the second surface 26b.

[0046] Furthermore, when the workpiece is rotated while being held using the holding table equipped with the holding base 26, if liquid adhering to the workpiece flows into the second connecting passage 28, the flow of the liquid into the first branching section 28b is promoted. Therefore, in this case, the probability of the workpiece being damaged can be further reduced.

[0047] Furthermore, the second connecting passage 32 formed in the retaining base 30 shown in Figure 4 includes a central portion 32a having a shape similar to the central portion 14a shown in Figure 1, etc., a plurality (for example, 4) of cylindrical or prismatic first branch portions 32b, each opening on the outer peripheral surface 30c and having an inner end IE1 connected near the bottom surface of the central portion 32a, and a plurality (for example, 4) of cylindrical or prismatic second branch portions 32c, each opening on the outer peripheral surface 30c and having an inner end IE2 connected around the middle of the side surface of the central portion 32a.

[0048] Furthermore, the multiple first branch portions 32b are positioned at the same location relative to each other in the thickness direction of the retaining base 30. In addition, the multiple second branch portions 32c are closer to the first surface 30a than the multiple first branch portions 32b and are positioned at the same location relative to each other in the thickness direction of the retaining base 30. Furthermore, the second branch portions 32c do not overlap with any of the multiple first branch portions 32b in the thickness direction of the retaining base 30.

[0049] Specifically, each first branch 32b is formed such that, in a plan view, its inner end IE1 is located in the direction of rotation of the holding table equipped with the holding base 30 (indicated by arrow A in Figure 4), as viewed from a virtual line L1 connecting its outer end OE1 and the center C of the first surface 30a. Furthermore, each second branch 32c is formed such that, in a plan view, its inner end IE2 is located in the direction opposite to the direction of rotation of the holding table equipped with the holding base 30, as viewed from a virtual line L2 connecting its outer end OE2 and the center C of the first surface 30a.

[0050] Furthermore, when a workpiece is rotated while being held using the holding table equipped with the holding base 30, if liquid adhering to the workpiece flows into the second connecting passage 32, the flow of the liquid into the first branch 32b is promoted while the flow into the second branch 32c is suppressed. Therefore, in this case, the probability of the workpiece being damaged can be further reduced.

[0051] Furthermore, the structures and methods of the embodiments described above can be modified as appropriate without departing from the scope of the present invention. [Explanation of symbols]

[0052] 2: Holding Table 4: Holding base (4a: 1st surface, 4b: 2nd surface, 4c: outer peripheral surface, 4d: 1st groove) (4e: 2nd groove, 4f: middle area, 4g: central area) 6a: First elastic body 6b: Second elastic body 8: First connecting passageway (8a: First vertical section, 8b: Horizontal section) (8c: middle part, 8d: second vertical part) 10a: Valve 10b: Valve 12a: Suction source 12b: Air supply source 14: Second connecting passage (14a: central section, 14b: first branching section, 14c: second branching section) 16: Motor 18: Holding base (18a: 1st side) 20: Second connecting passage (20a: central section, 20b: first branching section, 20c: second branching section) 22: Holding base (22a: 1st surface, 22b: 2nd surface) 24: Second connecting passage (24a: central section, 24b: first branching section, 24c: second branching section) 26: Holding base (26a: 1st side) 28: Second connecting passage (28a: central section, 28b: first branching section, 28c: second branching section) 30: Holding base (30a: 1st surface, 30c: outer peripheral surface) 32: Second connecting passage (32a: central section, 32b: first branching section, 32c: second branching section)

Claims

1. A holding table used to rotate a workpiece while holding it in place by applying suction force, A holding base having a first surface facing the workpiece while the workpiece is held, and having an annular first groove and an annular second groove surrounding the first groove, a second surface located on the opposite side of the first surface, and an outer peripheral surface located between the outer circumference of the first surface and the outer circumference of the second surface, An annular first elastic body provided in the first groove so as to protrude from the first surface when the workpiece is not being held, The device comprises an annular second elastic body provided in the second groove so as to protrude from the first surface when the workpiece is not being held, The retaining base is formed with a first communication passage for connecting the space near the intermediate region located between the first groove and the second groove on the first surface with the suction source, and a second communication passage for connecting the space near the central region located inside the first groove on the first surface with the space near the outer periphery surface. The second connecting passage includes a central portion that opens in the central region and extends along the thickness direction of the retaining base, and a first branch portion and a second branch portion that each open on the outer circumferential surface and extend from the central portion, The second branch is a holding table that is closer to the first surface than the first branch.

2. The holding table according to claim 1, wherein the central portion has a shape such that the cross-sectional area increases as it approaches the first branch portion from the first surface.

3. The holding table according to claim 1 or 2, wherein the central portion has a shape such that its cross-sectional area decreases as it approaches the second surface from the first branching portion.

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