JP6894772B2 - Vacuum chuck - Google Patents

Description

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

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

According to the vacuum chucks described in Patent Documents 1 and 2, even if the wafer is warped, wavy or stepped, the upper end portion of the sealing member is brought into contact with the wafer over the entire circumference, and the wafer and the suction surface are brought into contact with each other. A closed region is formed in the gap between the two. Therefore, the influence of the gap originally generated between the wafer and the substrate due to the warp of the wafer is eliminated, and the wafer is reliably adsorbed and held with the sealed region as a negative pressure.

Japanese Unexamined Patent Publication No. 07-308856 JP-A-2010-153419

In recent years, the thickness of the substrate has become thin, and the substrate may have large warpage, waviness, or step. In order to attract such a substrate, it is necessary to configure the sealing member so that it is elastically deformed and greatly collapses. When the sealing member described in Patent Documents 1 and 2 is configured in this way, when the sealing member collapses, the upper end portion in contact with the wafer greatly expands outward in the radial direction. Therefore, since the contact point between the substrate and the sealing member moves significantly in the adsorption process, the substrate cannot be adsorbed while being stably supported, and the flatness of the substrate may not be ensured satisfactorily.

Therefore, 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 adsorbed and held.

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

In the vacuum chuck of the present invention, an annular recess formed in an annular shape at a position surrounding the opening of the communication path on the upper surface of the substrate, and at least the lower portion of a sealing member made of an annular elastic material is arranged in the annular recess. On the other hand, the upper part of the sealing member protrudes from the upper surface of the substrate, and the upper part of the sealing member has a first portion extending upward while facing the inner direction of the annular shape and the outer side of the annular shape. It is characterized by having a second portion extending upward while facing in the direction.

According to the vacuum chuck of the present invention, when the substrate is placed on the surface side of the substrate, even if a part of the sealing member is elastically deformed and the substrate is warped or wavy, the entire circumference of the part is covered. Alternatively, it can be brought into contact with the substrate over almost the entire circumference.

Examples of the warped mode of the substrate include a mode in which the substrate is deformed into a saddle shape (or potato chips type) or a dome shape. In addition to the deformation of the mid-convex mode in which the central portion of the substrate is above the peripheral portion, the deformation of the mid-concave mode in which the central portion is below the peripheral portion is also included.

Further, since the upper element of the seal member has a first portion and a second portion having different extending directions, the above-mentioned Patent Documents 1 and 2 have only a portion in which the upper element extends in one direction. Compared to the vacuum chuck, when the upper element is tilted and elastically deformed, the upper end surface of the upper element in contact with the substrate does not move horizontally to the left, so that the flatness of the substrate can be stably secured. ..

In the vacuum chuck of one aspect of the present invention, the portion of the first portion and the second portion located above has a portion thinner than the portion located below.

According to the vacuum chuck having this configuration, the thin portion collapses first during the period when the vacuum suction force at the initial stage of vacuum suction is small, so that it is possible to suck the substrate while flexibly absorbing the vibration of the substrate. Become. Further, after that, when the vacuum suction force is increased, the thick portion also collapses, so that the substrate can be firmly sucked and fixed.

Vacuum chuck of the present invention, at least one portion of the first portion and the second portion, wherein the through-holes or notches are formed.

According to the vacuum chuck having this configuration, when the substrate and the sealing member are not sufficiently adhered at the initial stage of vacuum suction, the gas flow generated by the vacuum exhaust is suppressed from becoming too fast, and the substrate is swayed. It becomes possible to suck the substrate while absorbing it flexibly. Further, after that, when the vacuum suction force becomes large and the upper element collapses, 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.

Top view of a vacuum chuck as an embodiment of the present invention. FIG. 1 is a sectional view taken along line II-II of FIG. The explanatory view about the function of the vacuum chuck as one Embodiment of this invention. Explanatory drawing about another embodiment of a sealing member. Explanatory drawing about another embodiment of a seal member. Explanatory drawing about another embodiment of a seal member. Explanatory drawing about a comparative example of a seal member.

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

The wafer W (substrate) is arranged on the surface (upper surface) side of the substrate 1. In addition to the communication path 102 (through hole) that opens on the surface, the substrate 1 is formed with a through hole 104 for a lift pin 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 substrate 1 so as to surround the opening 102a of the communication path 102. An annular seal member 2 is arranged in the annular recess 10.

Further, on the surface of the substrate 1, an annular convex portion 12 (for example, a height of 10 to 500 [μm]) is formed so as to surround the annular recess 10 and project in an annular shape. The upper end of the annular convex portion 12 constitutes the “contact point with the wafer W” on the substrate 1. In addition, on the surface of the substrate 1, a plurality of substantially cylindrical, substantially hemispherical, or substantially truncated cone-shaped pins (not shown (for example, height 10 to 500 [μm])) protruding from the surface are arranged in a triangular lattice shape. , Square grids, concentric circles, etc. may be regularly arranged and formed. The upper ends of the plurality of pins form the "contact point with the wafer W" on the substrate 1, and define the suction plane. The suction plane is a set of discrete surfaces composed of the upper end surface of the annular convex portion 12 and the upper end surface of each pin.

The sealing 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 sealing member 2 is arranged in the annular recess 10, and at least an annular lower element 21 constituting the lower portion and at least a part of the annular recess 10 project upward from the annular recess 10 on the surface of the substrate 1 so as to come into contact with the wafer W. (See FIG. 2). In this way, the seal member 2 includes two elements, an upper element 22 and a lower element 21, the upper element 22 is an element located above, and the lower element 21 is an element located below.

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

The upper element 22 has a first portion 22a that extends upward while facing the inner side of the ring, and a second portion 22b that extends upward while facing the outer side of the ring, and is a sealing member. It constitutes the upper part of 2.

Here, the first portion 22a extends in a straight line diagonally upward from the outer upper surface of the ring of the lower element 21 toward the inside (center direction). The second portion 22b extends in a straight line diagonally upward from the upper surface of the ring of the first portion 22a toward the outside. As a result, the upper element 22 has a dogleg-shaped (tilted L-shaped) side cross section.

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

The seal member 2 is required to have elasticity so that the upper element 22 returns to its original posture when the load is released from the load. Taking this point into consideration, the elastic modulus of the material constituting the seal member 2 and the thickness of the bending portion or the base end of the upper element 22 are designed. Here, the thicknesses of the first portion 22a and the second portion 22b are the same, but these thicknesses may be different.

(function)
According to the vacuum chuck having the above 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 sealing member 2 may be warped, wavy, stepped or the like on the wafer W. 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 substrate 1, and the sealing member 2 is vacuum-sucked 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 so that the sealing member 2 has the same height as the suction plane of the substrate 1 (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 the region where the flatness is guaranteed in the wafer W can be expanded.

Further, when the upper element 22 has a portion extending upward from the upper surface of the lower element 21 in one direction, when this portion falls and elastically deforms, the upper end surface of the portion in contact with the wafer W moves significantly. Therefore, the wafer W may not be supported satisfactorily. In particular, when the thickness of the wafer W is thin and the warp, waviness, and step are large, it is necessary to secure a sufficient amount of collapse of the portion, and it is difficult to support the wafer W with a high flatness.

On the other hand, when the upper element 22 has the first portion 22a and the second portion 22b, when these portions 22a and 22b are tilted and elastically deformed, the upper end surface of the second portion 22b in contact with the wafer W is on the left. Since it does not move in the horizontal direction as much, it is possible to secure good flatness of the wafer W. Even when the thickness of the wafer W is thin and the warp 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 a high flatness.

(Other Embodiments of the present invention)
The shapes of the seal member 2 and the annular recess 10 may be changed in various ways.

For example, as in the sealing 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 extends diagonally upward from the inner upper surface in an obliquely upward direction, and the first portion 22Aa extends diagonally upward inward from the annular upper surface of the second portion 22Ab. You may.

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

The seal member 2A is required to have elasticity so that the upper element 22A returns to its original posture when the load is released from the load. Taking this point into consideration, the elastic modulus of the material constituting the seal member 2A and the thickness of the bending portion or the base end of the upper element 22A are designed. Here, the thicknesses of the first portion 22Aa and the second portion 22Ab are the same, but these thicknesses may be different.

The vacuum chuck configured in this way has the same effect as the vacuum chuck shown in FIG. 3 above.

Further, for example, as in the sealing 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 is a lower element 21B. The first portion 22Ba extends diagonally upward from the inner upper surface of the ring in the outward direction, and the first portion 22Ba extends diagonally upward inward from the upper surface of the ring of the second portion 22Bb. You may be doing it.

In this case, the connecting 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 inwardly and upwardly with respect to 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 vacuum chuck configured in this way has the same effect as the vacuum chuck shown in FIG. 3 above. Further, in the vacuum chuck configured in this way, only the thin first portion 22Ba collapses during the period when the vacuum suction force at the initial stage of vacuum suction is small, so that the vibration of the wafer W can be flexibly absorbed. The wafer W can be sucked. Further, after that, when the vacuum suction force is increased, the thick second portion 22Bb also collapses, so that the wafer W can be firmly sucked and fixed.

Further, for example, as in the seal member 2C shown in FIG. 6, a through hole 23 may be formed in the first portion 22Ca corresponding to the first portion 22Ba shown in FIG. Instead of the through hole, a notch may be formed in the tip surface of the first portion 22Ca which is a contact point with the wafer W. It is preferable that a plurality of through holes 23 or notches are dispersed and formed on the periphery. The shape of the through hole 23 or the notch is, for example, circular, elliptical, triangular, rectangular, and the like, but is not limited thereto.

The vacuum chuck configured in this way has the same effect as the vacuum chuck shown in FIG. 5 above. Further, in the vacuum chuck configured in this way, it is possible to prevent the gas flow generated by the vacuum exhaust from becoming too fast at the stage where the wafer W and the sealing member 2C at the initial stage of vacuum suction are not sufficiently adhered to each other. Then, it becomes possible to suck the wafer W while flexibly absorbing the vibration of the wafer W. Further, after that, when the vacuum suction force is increased and the upper element 22C collapses, the inflow of gas from the through hole is suppressed, so that the wafer W can be firmly sucked and fixed.

The vacuum chuck of the present invention is not limited to the one of the above-described embodiment, and for example, the annular convex portion 12 may be omitted.

For example, in the above embodiment, the upper element 22A is described as having two parts, a first part 22Aa and a second part 22Ab. However, the upper element only needs to have a first portion that extends upward while facing the inside of the ring and a second portion that extends upward while facing the outside of the ring. For example, it may include one or a plurality of portions extending vertically upward, or another portion extending upward while facing inward or outward of another ring.

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

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

(Example 1)
A substrate 1 made of silicon carbide (SiC) having an outer diameter of 300 mm and a thickness of 7 mm was prepared. Then, 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 substrate 1.

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

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

Wafers W made of silicon wafers having an outer diameter of 300 mm and thicknesses of 0.7 mm and 0.3 mm were prepared. Here, the warp of the wafer W having a thickness of 0.7 mm was 3 mm, and the warp 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 sealing member 2 and sucked. The flatness of the adsorption-held wafer W was 0.8 μm, which was good. In addition, the vibration 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 sealing member 2 and sucked. The flatness of the adsorption-held wafer W was 1.0 μm, which was good. However, the vibration of the wafer W was visually confirmed during suction.

(Example 2)
The 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 the first embodiment. 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 had a height of 12 mm. The first portion 22Aa of the upper element 22A was inclined inward from the upper end surface of the second portion 22Ab at an angle of 30 degrees and had a height of 6 mm.

A wafer W having a thickness of 0.7 mm was placed on the upper end of the sealing member 2A and sucked. The flatness of the adsorption-held wafer W was 0.8 μm, which was good. In addition, the vibration 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 sealing member 2A and sucked. The flatness of the adsorption-held wafer W was 1.0 μm, which was good. However, the vibration of the wafer W was visually confirmed during suction.

(Example 3)
The seal member 2B made of urethane and shown in FIG. 5 was prepared. The lower element 21 of the seal member 2B had the same shape as the lower element 21 of the seal member 2A of the first embodiment. 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 had a height of 6 mm and a thickness of 0.8 mm. The first portion 22Ba of the upper element 22B was inclined inward at an angle of 30 degrees from the upper end surface of the second portion 22Bb, and had 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 sealing member 2B and sucked. The flatness of the adsorption-held wafer W was 0.7 μm, which was good. In addition, the vibration 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 sealing member 2B and sucked. The flatness of the adsorption-held wafer W was 0.9 μm, which was good. However, the vibration of the wafer W was visually confirmed during suction.

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

A wafer W having a thickness of 0.7 mm was placed on the upper end of the sealing member 2C and sucked. The flatness of the adsorption-held wafer W was 0.8 μm, which was good. In addition, the vibration 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 sealing member 2C and sucked. The flatness of the adsorption-held wafer W was 1.0 μm, which was good. In addition, the vibration of the wafer W was not visually confirmed during suction.

(Comparison example)
The seal member 2D made of urethane and shown in FIG. 7 was prepared. The lower element 21D of the seal member 2D had the same shape as the lower element 21 of the seal member 2A of the first embodiment. 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 had a height of 12 mm.

A wafer W having a thickness of 0.7 mm was placed on the upper end of the sealing member 2D and sucked. The flatness of the adsorption-held wafer W was 1.0 μm, which was good. However, the vibration 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 sealing member 2D and sucked. The flatness of the adsorption-held wafer W was 2.0 μm, which was not good. In addition, the vibration of the wafer W during suction and the misalignment of the wafer W held by suction were visually confirmed.

1 ... Base, 2,2A, 2B, 2C ... Seal member, 10 ... Annular recess, 12 ... Annular convex, 22a, 22Aa, 22Ba ... First part, 22b, 22Ab, 22Bb ... Second part, 21 ... Lower element, 22 ... Upper element, 23 ... Through hole, 102 ... Communication path, 102a ... Opening, 104 ... Through hole for lift pin, W ... Wafer (base).

Claims (2)

A substrate on which a communication path is formed and an opening of the communication path that opens on the upper surface of the substrate are provided, and between the upper surface of the substrate and the substrate arranged on the upper surface side of the substrate through the communication path. A vacuum chuck that attracts and holds the substrate on the upper surface side of the substrate by forming a negative pressure region.
An annular recess is formed on the upper surface of the substrate so as to surround the opening of the communication path, and at least the lower portion of the sealing member made of an annular elastic material is arranged in the annular recess, while the sealing member of the sealing member. The upper part protrudes from the upper surface of the substrate,
Upper portion of the sealing member is closed and the first portion extending upward while facing inwardly of said annular and a second portion extending upwardly while facing outwardly of said annular,
A vacuum chuck characterized in that a through hole or a notch is formed in at least one portion of the first portion and the second portion. The vacuum chuck according to claim 1, wherein a portion of the first portion and the second portion located above has a portion thinner than a portion located below.

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