JP2019004017A - Vacuum chuck - Google Patents

Abstract

To provide a vacuum chuck which can secure good flatness of a substrate even when sucking and holding a substrate such as a wafer having large warp or the like.SOLUTION: An annularly recessed annular recessed part 10 is formed in a position surrounding an opening of a communication path 102 in the upper surface of a substrate 1, and a lower element 21 of a seal member 2 made of an annular elastic material is arranged in the annular recessed part 10, and an upper element 22 of the seal member 2 protrudes from the upper surface of the substrate 1. The upper element 22 includes a first part 22a extending upward toward an annular inward direction and a second part 22b extending upward toward an annular outward direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vacuum chuck that holds a substrate such as a wafer on the surface of a substrate by suction.

  Conventionally, a vacuum chuck that holds a substrate on the surface of the substrate by adsorbing the substrate such as a wafer by a negative pressure formed through a communication path formed on the substrate while supporting the substrate by a sealing member attached to the substrate. It has been known.

  For example, Patent Document 1 describes a vacuum chuck in which a skirt-like seal member made of an elastic material (for example, rubber) is formed on an outer edge of a base so as to gradually spread outward from the bottom to the top. Has been. Patent Document 2 describes a vacuum chuck having a configuration in which a seal member is fixed to a plate-like member and a plurality of the plate-like members are detachably fixed to a base.

  According to these vacuum chucks described in Patent Documents 1 and 2, even when the wafer is warped, wavy or stepped, the upper end of the seal member is brought into contact with the wafer over its entire circumference, A sealed region is formed in the gap. For this reason, the influence of the gap inherently formed between the substrate and the substrate due to the warp of the wafer is eliminated, and the wafer is reliably sucked and held by using the sealed region as a negative pressure.

Japanese Patent Laid-Open No. 07-308856 JP 2010-153419 A

  In recent years, the thickness of the substrate has been reduced, and there are cases where the substrate has large warpage, undulations, and steps. In order to adsorb such a substrate, it is necessary that the seal member be elastically deformed so as to largely fall down. When the sealing members described in Patent Documents 1 and 2 are configured in this way, when the sealing member collapses, the upper end portion in contact with the wafer greatly expands radially outward. Therefore, since the contact point between the substrate and the seal member moves greatly during the adsorption process, the substrate cannot be adsorbed while being stably supported, and the flatness of the substrate may not be ensured satisfactorily.

  Accordingly, an object of the present invention is to provide a vacuum chuck capable of ensuring good flatness of a substrate even when a substrate such as a wafer having a large warp is sucked and held.

  The present invention includes a base on which a communication path is formed, and an opening portion of the communication path that opens to the upper surface of the base, and is disposed on the upper surface of the base and the upper surface of the base through the communication path. The present invention relates to a vacuum chuck that sucks and holds the substrate on the upper surface side of the base body by forming a negative pressure region between the substrate and the substrate.

  In the vacuum chuck of the present invention, an annular recess that is annularly depressed is formed at a position surrounding the opening of the communication path on the upper surface of the base, and at least a lower portion of a seal member made of an annular elastic material is disposed in the annular recess. On the other hand, the upper portion of the seal member protrudes from the upper surface of the base, and the upper portion of the seal member extends upward while facing the inner side of the ring, and the outer side of the ring And a second portion extending upward while facing the direction.

  According to the vacuum chuck of the present invention, when the substrate is placed on the surface side of the base, even if a part of the seal member is elastically deformed and the substrate is warped or swelled, the part is entirely surrounded. Or it can be made to contact | abut with respect to a board | substrate over the perimeter.

  In addition, as a curvature aspect of a board | substrate, the aspect which the said board | substrate has deform | transformed into the bowl shape (or potato chips type) or the dome shape is mention | raise | lifted. In addition to the deformation of the middle convex shape in which the central portion of the substrate is above the peripheral portion, the deformation of the concave shape in which the central portion is below the peripheral portion is also included.

  Furthermore, since the upper element of the seal member has the first part and the second part in which the extending directions are different, the upper element described in Patent Documents 1 and 2 having only a part extending in one direction. Compared with the vacuum chuck, when the upper element falls down and elastically deforms, the upper end surface of the upper element that contacts the substrate does not move horizontally in the left direction, so that the flatness of the substrate can be stably secured. .

  In the vacuum chuck of one embodiment of the present invention, the upper portion of the first portion and the second portion has a portion that is thinner than the lower portion.

  According to the vacuum chuck having such a configuration, the thin portion falls first in a period when the vacuum suction force at the initial stage of vacuum suction is small, so that the substrate can be sucked while flexibly absorbing the peristalsis of the substrate. Become. Furthermore, when the vacuum suction force is increased thereafter, the thick part also falls down, so that the substrate can be firmly sucked and fixed.

  The vacuum chuck of one embodiment of the present invention is characterized in that a through hole or a notch is formed in at least one of the first portion and the second portion.

  According to the vacuum chuck having the above configuration, in the stage where the substrate and the seal member are not sufficiently in close contact with each other at the initial stage of vacuum adsorption, it is possible to suppress the gas flow generated by the vacuum evacuation from becoming too fast and The substrate can be sucked while being absorbed flexibly. Furthermore, when the vacuum suction force increases and the upper element falls down, the through hole is closed and the inflow of gas from the through hole is suppressed, so that the substrate can be firmly sucked and fixed.

The top view of the vacuum chuck as one embodiment of the present invention. II-II sectional view taken on the line of FIG. Explanatory drawing regarding the function of the vacuum chuck as one Embodiment of this invention. Explanatory drawing regarding other embodiment of a sealing member. Explanatory drawing regarding the other embodiment example of a sealing member. Explanatory drawing regarding the other embodiment example of a sealing member. Explanatory drawing regarding the comparative example of a sealing member.

(Constitution)
The vacuum chuck as an embodiment of the present invention shown in FIGS. 1 and 2 includes a base 1 made of a substantially disc-shaped ceramic sintered body. The substrate 1 is produced by firing a raw material powder molded body mainly made of ceramic powder such as silicon carbide, aluminum nitride, alumina or silicon nitride and performing necessary processing.

  A wafer W (substrate) is disposed on the surface (upper surface) side of the substrate 1. In addition to the communication path 102 (through hole) opened on the surface, the base 1 is formed with a lift pin through hole 104 through which a lift pin (not shown) for raising and lowering the wafer W is inserted.

  An annular recess 10 (for example, a depth of 1 to 10 [mm] and a width of 1 to 10 [mm]) is formed on the surface of the base 1 and is recessed in an annular shape surrounding the opening 102 a of the communication path 102. An annular seal member 2 is disposed in the annular recess 10.

  Furthermore, an annular convex portion 12 (for example, a height of 10 to 500 [μm]) protruding in an annular shape surrounding the annular concave portion 10 is formed on the surface of the base 1. The upper end portion of the annular convex portion 12 constitutes the “contact portion with the wafer W” in the base 1. In addition, a plurality of substantially cylindrical, hemispherical, or substantially truncated cone-shaped pins (not shown (for example, a height of 10 to 500 [μm])) protruding from the surface are formed on the surface of the base body 1 in a triangular lattice shape. Further, they may be regularly arranged such as a square lattice shape or a concentric circle shape. The upper end portions of the plurality of pins constitute a “contact portion with the wafer W” in the base 1 and define an adsorption plane. The suction plane is a set of discrete surfaces constituted by the upper end surface of the annular convex portion 12 and the upper end surface of each pin.

  The seal member 2 is made of an elastic material such as urethane, silicone resin, nitrile rubber, EPDM (ethylene propylene diene rubber), HNBR (hydrogenated nitrile rubber), butadiene rubber, or fluorine rubber.

  The seal member 2 is disposed in the annular recess 10 and has an annular lower element 21 that constitutes at least a lower part, and at least a part of the seal member 2 that protrudes upward from a position where the annular recess 10 contacts the wafer W on the surface of the substrate 1. The upper element 22 is provided (see FIG. 2). In this way, the seal member 2 includes two elements, that is, the upper element 22 and the lower element 21. The upper element 22 is an element positioned above, and the lower element 21 is an element positioned below.

  The upper element 22 is configured to be elastically tiltable up to the same height as the contact point (suction plane) with the wafer W on the surface of the substrate 1 so as to narrow the gap between the upper element 22 and the lower element 21 (see FIG. 3).

  The upper element 22 has a first part 22a extending upward while facing the annular inner direction, and a second part 22b extending upward while facing the annular outer direction, and the sealing member The upper part of 2 is comprised.

  Here, the first portion 22a extends linearly obliquely upward from the annular outer upper surface of the lower element 21 toward the inner direction (center direction). The second portion 22b extends linearly obliquely upward from the annular upper surface of the first portion 22a in the outward direction. Thereby, as for the upper element 22, the side part cross section is a dogleg shape (inclined L-shape).

  A connecting portion between the first portion 22 a and the second portion 22 b is located on the inner upper side of the outer peripheral end portion of the lower element 21. The upper end portion of the second portion 22 b is located above the upper end surface of the lower element 21.

  When the upper element 22 changes from a loaded state to a released state, the seal member 2 is required to have elasticity so that it returns to its original posture. In consideration of this point, the elastic modulus of the material constituting the seal member 2 and the thickness of the bent portion or the base end of the upper element 22 are designed. Here, the thickness of the first portion 22a and the second portion 22b is the same, but these thicknesses may be different.

(function)
According to the vacuum chuck having the above-described configuration, when the wafer W is placed on the surface side of the substrate 1, the upper element 22 which is a part of the seal member 2 may be warped, swelled, stepped, or the like. It can be brought into contact with the wafer W over the entire circumference or substantially the entire circumference. Then, the space (inner space) surrounded by the wafer W, the base 1 and the seal member 2 is vacuumed through the communication path 102.

  As a result, a negative pressure region is formed in the inner space, and the sealing member 2 is elastically deformed so that the upper element 22 is elastically crushed and becomes the same height as the suction plane of the base 1 (see FIG. 3). As a result, the wafer W can be brought into contact with the suction plane of the substrate 1 as a whole, and further, the area of the wafer W where the flatness is ensured can be expanded.

  Furthermore, when the upper element 22 has a portion extending in one direction upward from the upper surface of the lower element 21, the upper end surface of the portion in contact with the wafer W moves greatly when the portion collapses and elastically deforms. Therefore, the wafer W may not be supported well. In particular, when the wafer W is thin and warps, undulates and has a large step, it is necessary to ensure a sufficient amount of collapse of the portion, and it is difficult to support the wafer W with high flatness.

  On the other hand, when the upper element 22 has the first portion 22a and the second portion 22b, the upper end surface of the second portion 22b in contact with the wafer W is left when the portions 22a and 22b fall and elastically deform. Since it does not move in the horizontal direction, the flatness of the wafer W can be secured satisfactorily. Even when the thickness of the wafer W is thin and warping is large, it is possible to secure a sufficient amount of collapse of the upper element 22 and it is difficult to support the wafer W with high flatness.

(Other embodiments of the present invention)
The shapes of the seal member 2 and the annular recess 10 may be variously changed.

  For example, like the seal member 2A shown in FIG. 4, the upper element 22A has a first portion 22Aa and a second portion 22Ab, and the second portion 22Ab is an annular shape of the lower element 21A. The first portion 22Aa linearly extends obliquely upward from the inner upper surface toward the outer direction, and linearly extends obliquely upward from the annular upper surface of the second portion 22Ab toward the inner direction. May be.

  In this case, the connection portion between the first portion 22 </ b> Aa and the second portion 22 </ b> Ab is located on the outer upper side than the inner peripheral end portion of the lower element 21. The upper end portion of the first portion 22Aa is located above the upper end surface of the lower element 21.

  When the upper element 22A transitions from a state in which a load is applied to a state in which the upper element 22A is released from the load, the seal member 2A is required to have elasticity so as to return to the original posture. Considering this point, the elastic modulus of the material constituting the seal member 2A and the thickness of the bent portion or the base end of the upper element 22A are designed. Here, the first portion 22Aa and the second portion 22Ab have the same thickness, but these thicknesses may be different.

  The thus configured vacuum chuck has the same effect as the vacuum chuck shown in FIG.

  Further, for example, like the seal member 2B shown in FIG. 5, the upper element 22B has a first portion 22Ba and a second portion 22Bb, and the second portion 22Bb corresponds to the lower element 21B. The first portion 22Ba extends linearly obliquely upward from the annular inner upper surface toward the outer direction, and linearly extends obliquely upward from the annular upper surface of the second portion 22Bb toward the inner direction. You may do it.

  In this case, the connection portion between the first portion 22Ba and the second portion 22Bb is located above the upper end surface of the lower element 21B. The upper end portion of the first portion 22Ba is located on the inner upper side than the outer peripheral end portion of the lower element 21B.

  The thickness of the first portion 22Ba is thinner than the thickness of the second portion 22Bb.

  The thus configured vacuum chuck has the same effect as the vacuum chuck shown in FIG. Further, in the vacuum chuck configured as described above, only the first portion 22Ba having a small thickness collapses in a period in which the vacuum suction force at the initial stage of vacuum suction is small, so that the wafer W can be flexibly absorbed. The wafer W can be sucked. Further, when the vacuum suction force is increased thereafter, the thick second portion 22Bb also falls, so that the wafer W can be firmly sucked and fixed.

  Further, for example, a through hole 23 may be formed in the first portion 22Ca corresponding to the first portion 22Ba shown in FIG. 5 like the sealing member 2C shown in FIG. Instead of the through hole, a notch may be formed on the tip surface of the first portion 22Ca that is a contact portion with the wafer W. It is preferable that a plurality of through holes 23 or notches are formed in a distributed manner on the circumference. The shape of the through hole 23 or the cutout is, for example, a circle, an ellipse, a triangle, a rectangle, or the like, but is not limited thereto.

  The thus configured vacuum chuck has the same effect as the vacuum chuck shown in FIG. Further, in the vacuum chuck configured as described above, it is possible to prevent the gas flow generated by the evacuation from becoming too fast at the stage where the wafer W and the seal member 2C are not sufficiently in close contact at the initial stage of vacuum suction. Thus, the wafer W can be sucked while flexibly absorbing the swing of the wafer W. Furthermore, when the vacuum suction force increases and the upper element 22C falls down, the inflow of gas from the through hole is suppressed, so that the wafer W can be firmly sucked and fixed.

  In addition, the vacuum chuck of this invention is not limited to the thing of embodiment mentioned above, For example, the thing which abbreviate | omitted the annular convex part 12 may be used.

  For example, in the above embodiment, the upper element 22A has been described as having two parts, the first part 22Aa and the second part 22Ab. However, the upper element only needs to have a first portion extending upward while facing the annular inner direction and a second portion extending upward while facing the annular outer direction. For example, it may be provided with one or a plurality of portions extending vertically upward, or further extending upward while facing inward or outward of another annular shape.

  Further, the first portion 22Aa and the second portion 22Ab may not extend linearly, may extend in a curved shape or a shape combining a straight line and a curved line, and the first portion 22Aa. The length along the extending direction of the second portion 22Ab may be longer in the first portion 22Aa than in the second portion 22Ab, and the first portion 22Aa and the second portion 22Ab may be It may be the same.

  Furthermore, a groove extending in the circumferential direction may be formed on at least one of the inner peripheral surface and the outer peripheral surface of the first portion 22Aa and the second portion 22Ab that constitutes a contact portion with the wafer. Good. The ease of falling of the seal member 2 can also be adjusted by changing the depth, width, and density of the groove.

Example 1
A substrate 1 made of silicon carbide (SiC) and having an outer diameter of 300 mm and a thickness of 7 mm was prepared. An annular recess 10 having a width of 5 mm and a depth of 3.5 mm and a communication path 102 having a diameter of 2 mm were formed on the base 1.

  A seal member 2 made of fluororubber and shown in FIG. 2 was prepared. In the sealing member 2, the lower element 21 had an inner diameter of 274 mm, an outer diameter of 284 mm, a thickness of 2.5 mm, and the upper element 22 had a thickness of 0.5 mm. The first portion 22a of the upper element 22 was inclined inward from the upper end surface of the lower element 21 at an angle of 30 degrees, and the height was 12 mm. The second portion 22b of the upper element 22 was inclined outward at an angle of 30 degrees from the upper end surface of the first portion 22a, and the height was 6 mm.

  Then, the lower element 21 of the seal member 2 was inserted into the annular recess 10 of the base 1.

  As the wafer W, a silicon wafer having an outer diameter of 300 mm and a thickness of 0.7 mm and 0.3 mm was prepared. Here, the warpage of the wafer W having a thickness of 0.7 mm was 3 mm, and the warpage of the wafer W having a thickness of 0.3 mm was 7 mm.

  A wafer W having a thickness of 0.7 mm was placed on the upper end of the seal member 2 and sucked. The flatness of the wafer W held by suction was 0.8 μm, which was good. Further, the movement of the wafer W was not visually confirmed during suction.

  A wafer W having a thickness of 0.3 mm was placed on the upper end of the seal member 2 and sucked. The flatness of the wafer W held by suction was 1.0 μm, which was good. However, the movement of the wafer W was visually confirmed during suction.

(Example 2)
A seal member 2A made of urethane and shown in FIG. 4 was prepared. The lower element 21 of the seal member 2A had the same shape as the lower element 21 of the seal member 2A of Example 1. The thickness of the upper element 22A was 0.5 mm. The second portion 22Ab of the upper element 22A was inclined outward from the upper end surface of the lower element 21 at an angle of 30 degrees, and the height was 12 mm. The first portion 22Aa of the upper element 22A was inclined inward at an angle of 30 degrees from the upper end surface of the second portion 22Ab, and the height was 6 mm.

  A wafer W having a thickness of 0.7 mm was placed on the upper end of the seal member 2A and sucked. The flatness of the wafer W held by suction was 0.8 μm, which was good. Further, the movement of the wafer W was not visually confirmed during suction.

  A wafer W having a thickness of 0.3 mm was placed on the upper end of the seal member 2A and sucked. The flatness of the wafer W held by suction was 1.0 μm, which was good. However, the movement of the wafer W was visually confirmed during suction.

Example 3
A sealing member 2B made of urethane and shown in FIG. 5 was prepared. The lower element 21 of the seal member 2B has the same shape as the lower element 21 of the seal member 2A of Example 1. The second portion 22Bb of the upper element 22B was inclined outward at an angle of 30 degrees from the upper end surface of the lower element 21, and the height was 6 mm and the thickness was 0.8 mm. The first portion 22Ba of the upper element 22B is inclined inwardly at an angle of 30 degrees from the upper end surface of the second portion 22Bb, and has a height of 12 mm and a thickness of 0.5 mm.

  A wafer W having a thickness of 0.7 mm was placed on the upper end of the seal member 2B and sucked. The flatness of the wafer W held by suction was 0.7 μm, which was good. Further, the movement of the wafer W was not visually confirmed during suction.

  A wafer W having a thickness of 0.3 mm was placed on the upper end of the seal member 2B and sucked. The flatness of the wafer W held by suction was 0.9 μm, which was good. However, the movement of the wafer W was visually confirmed during suction.

(Example 4)
A seal member 2C shown in FIG. 6 was prepared. The seal member 2C was formed by forming 60 through holes 23 having a hole diameter of 2 mm at equal intervals along the circumferential direction with respect to the seal member 2B of Example 3.

  A wafer W having a thickness of 0.7 mm was placed on the upper end of the seal member 2C and sucked. The flatness of the wafer W held by suction was 0.8 μm, which was good. Further, the movement of the wafer W was not visually confirmed during suction.

  A wafer W having a thickness of 0.3 mm was placed on the upper end of the seal member 2C and sucked. The flatness of the wafer W held by suction was 1.0 μm, which was good. Further, the movement of the wafer W was not visually confirmed during suction.

(Comparative example)
A sealing member 2D made of urethane and shown in FIG. 7 was prepared. The lower element 21D of the seal member 2D has the same shape as the lower element 21 of the seal member 2A of Example 1. The thickness of the upper element 22D was 0.5 mm. The upper element 22D was inclined outward at an angle of 60 degrees from the upper end surface of the lower element 21, and the height was 12 mm.

  A wafer W having a thickness of 0.7 mm was placed on the upper end of the seal member 2D and sucked. The flatness of the wafer W held by suction was 1.0 μm, which was good. However, the movement of the wafer W was visually confirmed during suction.

  A wafer W having a thickness of 0.3 mm was placed on the upper end of the seal member 2D and sucked. The flatness of the wafer W held by suction was 2.0 μm, which was not good. Further, the movement of the wafer W and the displacement of the wafer W held by suction during the suction were visually confirmed.

DESCRIPTION OF SYMBOLS 1 ... Base | substrate, 2, 2A, 2B, 2C ... Sealing member 10 ... Annular recessed part 12 ... Annular convex part 22a, 22Aa, 22Ba ... 1st part, 22b, 22Ab, 22Bb ... 2nd part, 21 ... Lower element, 22 ... Upper element, 23 ... Through hole, 102 ... Communication path, 102a ... Opening, 104 ... Through hole for lift pin, W ... Wafer (substrate).

Claims (3)

A base on which a communication path is formed; and an opening portion of the communication path that opens to the upper surface of the base; between the upper surface of the base and the substrate disposed on the upper surface side of the base through the communication path A vacuum chuck for adsorbing and holding the substrate on the upper surface side of the base body by forming a negative pressure region on the substrate,
An annular recess that is annularly depressed is formed at a position surrounding the opening of the communication path on the upper surface of the base, and at least a lower part of a seal member made of an annular elastic material is disposed in the annular recess, The upper part protrudes from the upper surface of the substrate,
The upper part of the seal member has a first part extending upward while facing the inner side of the ring, and a second part extending upward while facing the outer side of the ring. A featured vacuum chuck.   2. The vacuum chuck according to claim 1, wherein the upper portion of the first portion and the second portion has a portion that is thinner than the lower portion.   The vacuum chuck according to claim 1, wherein a through hole or a notch is formed in at least one of the first part and the second part.