JPS62211236A - Holding material for plate-like member - Google Patents

Abstract

PURPOSE:To make it possible to contactlessly hold a plate-like material with a strong holding force, by providing a holding member for forming an averaged clearance between itself and a plate-like material, and further by providing a fluid jetting section for applying a pressure higher than the atmospheric pressure to the plate opposing the holding surface of the holding member and a fluid sucking section for applying a pressure lower than the atmospheric pressure. CONSTITUTION:In the case of a suction force is set to be balanced with the weight of the plate-like material 1 when the space (h) of a gap 3 is a designated gap space hc that is, a plate-like material 1 is located as shown by the broken line, if the plate-like material 1 is shifted to a position as indicated by the solid line so that the space (h) of the gap 3 increases to a value hb exceeding the space hc, the suction force becomes larger than the weight of the plate-like material 1. Accordingly, the plate-like material 1 located at the position indicated by the solid line is exerted with the a recovery force in the direction in which the plate-like material is returned to the position having the designed space hc. Similarly, even if the space (h) of the gap 3 becomes a value ha which is smaller than the space hc, the plate-like material 1 is exerted with a recovery force in the direction in which the plate-like material 1 is returned to the position having the space hc. With this arrangement, the plate-like material 1 is stably held being floated in a non-contact condition with the gap 3 having the space hc between the holding surface 2A of the holding member 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a holding device for a plate-shaped body, and in particular, the present invention relates to a holding device for a plate-shaped body, and in particular, it applies suction force and ejection force of fluid to the surface of the plate-shaped body to hold the plate-shaped body. The present invention relates to a device for holding a device in a non-contact state.

[Conventional technology]

Conventionally, as a device for holding a plate-shaped body by suction force of fluid, as shown in Japanese Unexamined Patent Publication No. 58-141536, for example, there is a device that jets fluid from the center of the plate-shaped body to be held toward the outer circumference. There is a device that adsorbs plate-like objects without contact using Bernoulli's principle.

As another measure, as shown in Japanese Patent Publication No. 40343, a suction pipe and a discharge pipe provided around the suction pipe are combined to drain fluid from the suction pipe and the discharge pipe. There is one that holds the plate-like body between the tips of the suction pipe and the discharge pipe without contact by flowing in and out.

[Problem that the invention seeks to solve]

In recent years, with the miniaturization of semiconductor manufacturing, it has become necessary to transport plate-shaped objects such as semiconductor wafers in a non-contact manner. In response to this requirement, the former device described above adsorbs plate-like objects using Bernoulli's principle, so it is necessary to create a wide gap between the plate-like object and its supporting surface and to flow a large amount of fluid into this gap. When , the fluid within this gap is an inviscid flow. Therefore, if some external force acts on the held plate-like body, the plate-like body may separate from the support surface and fall. In addition, in the latter device, the area where fluid force acts on the plate is limited to the inlet of the suction pipe and the outlet of the discharge pipe, and the flow rate in the discharge pipe changes with respect to the displacement in the direction perpendicular to the surface of the plate, which is held in a non-contact manner. Since the change is small, the holding force against the plate-like body, especially the holding restoring force, is small, so there is a problem that holding stability is lacking.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plate-shaped object holding device that can hold a plate-shaped object with a strong holding force and without contact.

[Means for solving problems]

The above-mentioned object of the present invention is to provide a device for holding a plate-shaped body in a non-contact manner by fluid force, and to provide a holder having a holding surface for forming a planar gap between the plate-shaped body and the holder. a fluid ejecting part that is provided on the holding surface of the holding body and generates pressure equal to or higher than atmospheric pressure against the plate-shaped body facing the holding surface; This is achieved by providing a fluid suction section provided with a constriction that generates a pressure equal to or lower than atmospheric pressure against the plate-shaped body.

[Effect]

The fluid suction section located around the fluid ejection section reduces the average pressure within the gap between the holding surface and the plate-like body to below atmospheric pressure by suctioning the fluid. This negative pressure supports the weight of the plate-shaped body. On the other hand, the fluid jet section supplies pressurized fluid to the gap between the holding surface and the plate-like body through the throttle. As a result, the pressure within the gap in this area decreases as the gap distance increases, and increases as the gap distance decreases. For this reason,
Due to the interaction with the negative pressure obtained by the fluid suction section, the plate-shaped body is supported without contact with the holding surface while maintaining a constant minute gap. In addition, in the gap between the holding surface and the plate-shaped body, a viscous flow occurs in the gap between the plate-shaped body and the non-viscous flow that occurs in a holding device using the Bernoulli principle. Generates strong holding force.

〔Example〕 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the apparatus of the present invention, and in these figures, numeral 1 indicates a plate-shaped object, such as a semiconductor wafer, which is to be held in a non-contact manner. 2 is plate-shaped body 1
It is a holding body. The plate-shaped body 1 is held in a non-contact state with respect to the holding surface 2A of the holding body 2 through a gap 3 having a distance of . 4. This opening 4 has a diaphragm 5.
It communicates with the pressurized fluid supply hole 6 through the pressurized fluid supply hole 6 . The pressurized fluid supply hole 6 is connected to a pressurized fluid supply source 8 through a pressurized fluid supply conduit 7 . An annular groove 9 is provided in the holding surface 2A of the holding body 2 so as to surround the opening 4. This annular groove 9 is connected to a fluid suction source 12 through a fluid suction hole 10 and a conduit 11. A blocking member 13 is provided around the holding body 2 to prevent movement of the held plate-like body 1 in the plane direction. In FIG. 1, arrow 14 indicates the direction in which gravity acts.

Next, the operation of one embodiment of the above-mentioned apparatus of the present invention will be described.

In FIG. 1, when the fluid suction source 12 is activated, fluid is suctioned from the annular groove 9 through the conduit 11 and the fluid suction hole [0, and the pressure in the annular groove 9 is reduced to below atmospheric pressure. . On the other hand, the pressurized fluid supply source 8, which is maintained at a high pressure by the pressure within the annular groove 9, supplies pressurized fluid to the pipe line 7.
．． Pressurized fluid is supplied from the pressurized fluid supply hole 6 to the gap 3 through the throttle 5, and a pressure higher than atmospheric pressure is applied to this portion. At this time, the pressure within the gap 3 and the force acting on the plate-like body 1 calculated from this pressure are theoretically as follows.

Now, it can be assumed that the flow within the gap 3 is an isothermal seven-layer flow when the gap between the gaps 3 is set sufficiently small, and the flow is dominated by viscous force compared to inertial force. At this time, the following equation and boundary conditions hold for the flow within the gap 3 using the coordinate system and symbols shown in FIG.

For the clearance r, h≦r≦ro, P=Pc at r= rl, P=Pv at
r= ro − (2) For the gap of t'a≦r≦f'b.

P=Pv at r=ra, P=Pa at r
= rb - (3) where, r: Seat shelf h measured from the center of the holder 2 in the direction in which the gap 3 widens; Distance of the gap 3 P: Pressure inside the gap 3 rL: Radius of the opening 4 ro: li The outer radius of the holding surface 2A surrounded by the annular groove 9, the inner radius ra of the annular groove 9: the outer radius of the Ii-shaped ff19) r b-: f4 m (4' 2 (7) m).

. □Pc: Pressure in the opening part 4 Pv: Pressure in the annular s9 Pa: Atmospheric pressure For the equation of the flow (pressure) in this gap 3, the pressure passes through the throttle 5 provided in the pressurized fluid supply hole 6 The gas mass flow rate mR is as follows: 0 port: orifice throttle flow coefficient (CD20, 85 for air) R: gas constant T: absolute temperature of gas Ps: supplied to pressurized fluid supply hole 6 Gas pressure K:
The specific heat ratio of the gas Also, the gas mass flow rate m1 flowing within the gap 3 where r1≦r≦ro is expressed as follows: where μ: viscosity coefficient of the gas, and these gas mass flow rates mtt, m).

The following continuity conditions are imposed.

m R” m h
(6) Equations (1) to (6) above are basic equations for the flow within the gap 3, and by solving these, the pressure within the gap 3 can be found. Based on the determined pressure within the gap 3, the suction force F (positive upward) acting on the plate-like body 1 is expressed as follows.

F=-f (P-Pa)2πrdr = -πrt" (Pc-Pa) / (P-Pa) 2πrd r -tc (r, z ro") (Pv-Pa)b -/ (P-Pa)2grdr -(7)t
'a Here, the solution of equations (1) to (3) for pressure P is, however, Pc is unknown, and this Pc is calculated using equations (4) to (6).
More determined.

Figure 4 shows the results of calculating the suction force F acting on the plate-like body 1 by changing the spacing of the gap 3 from the above equations (1) to (7).
Further, an explanatory diagram of the operation is shown in FIG.

The operation of one embodiment of the apparatus of the present invention described above will be explained as follows with reference to these figures.

Now, the spacing of gap 3 is the design gap spacing he.

That is, it is assumed that the setting is such that the suction force and the weight of the plate-like body 1 are balanced when the plate-like body 1 is at the position shown by the broken line in FIG. At this time.

The plate-like body 1 moves to the position shown by the solid line in FIG.
When the distance between the gaps 3 exceeds the set gap distance hc and increases to h5, the suction force becomes larger than the weight of the plate-shaped body 1, as shown in FIG. Therefore, the plate-shaped body 1 is located at the position shown by the solid line in FIG.

A restoring force acts in the direction of returning to the position of the clearance interval he, which is the design point. Similarly, when the gap 3 becomes h&, which is smaller than the design point gap he,
A restoring force acts on the plate-shaped body 1 in the direction of returning its position to the position of the designed clearance interval hc.

As a result, the plate-shaped body 1 is stably supported floating in a non-contact manner across the gap he between the holding surface 2A of the holding body 2 and the gap 3.

Also, at this time, since the annular groove 9 that is maintained at negative pressure is provided in an annular shape so as to surround the opening 4, all the fluid that has flowed into the gap 3 from the opening 4 is sucked and collected into the annular groove 9. On the contrary, outside air flows into the annular groove 9 from the outer periphery of the holder 2, but the negative pressure inside the annular groove 9 is about 200 to 300 m water column, and there is no gap. Unlike the conventional holding device using the Bernoulli principle, the gap 3 can be set small, so the flow rate of the fluid flowing into the gap may be small.

In the above-described embodiment, positive pressure is generated at the center of the plate-like body 1 in the gap between the holding surface 2A of the holding body 2 and the plate-like body 1, and negative pressure is generated around the central part of the plate-like body 1. can be reliably held in a non-contact state with respect to the holder 2. Therefore, as shown in FIG. The plate-like body 1 can be held in a non-contact manner no matter how the posture of the body 2 is changed.

As described above, in one embodiment of the present invention, the plate-shaped body 1 can be held without contact, so it is effective when used, for example, for handling semiconductor wafers where the processing surface should not be contaminated or scratched. . Furthermore, since no fluid is ejected outward from the apparatus, there is no possibility that surrounding dust will be stirred up to contaminate the wafers or displace wafers placed around the apparatus.

Here, the functions of the apparatus of the present invention will be described below in comparison with the conventional technology described in the prior art section.

First, a holding device using the Bernoulli principle blows compressed air into the gap between the holding surface of the holding body and the upper surface of the plate-like body to form a high-speed fluid flow within the gap. When the flow in the gap can be regarded as an inviscid flow, the following Bernoulli equation holds true for that flow.

P+−pv”=Po (const)
・= (8) Here, P: Pressure ρ: Density: Flow velocity Po: Total pressure If the flow velocity V is large, the pressure P in the gap becomes negative pressure, and due to the pressure difference between this negative pressure and the outside pressure, the plate-shaped object suction support without contact. On the other hand, in the present invention, the flow within the gap is a completely viscous flow dominated by viscous force, whereas in the holding device that uses the Bernoulli principle described above, the flow within the gap is a completely viscous flow with the exception of the wall boundary layer. This means that the flow needs to be inviscid. In the device of the present invention, in which the flow within the gap is a viscous flow, it is possible to reduce the gap between the gaps to about several μm, and in this case, the holding rigidity d F / d h for the plate-shaped body is increases with decreasing gap spacing, and fluid flow rate decreases with decreasing gap spacing. On the other hand, in a holding device using the Bernoulli principle, it is necessary to form an inviscid high-speed flow of fluid within the gap, so it is impossible to set the gap between the gaps as small as in the present invention. Further, as can be seen from equation (8), a flow rate of about 13 m/sec is required to generate a negative pressure of 1, for example, a submerged water 1011I11.

For these reasons, the device of the present invention only requires a smaller amount of fluid to be ejected than a holding device using the Bernoulli principle. Also,
Since the gap can be reduced, the holding force and the holding rigidity dF/dh can be increased.

Furthermore, in the present invention, a planar gap with a small gap is formed between the upper surface of the plate-shaped body 1 and the holding surface 2A of the holding body 2, whereas the conventional combination of a suction pipe and a discharge pipe The thing is that it doesn't exist.

In other words, in order to stably hold the plate-shaped body, when the plate-shaped body is displaced, the restoring force acting on the plate-shaped body, strictly defined, the holding rigidity d F / d h must be large. ,
It will be explained below that the above-mentioned planar clearance is necessary in order to obtain a large holding rigidity.

In the present invention, as can be seen from Equations 1 (7) and (8), dF/dh increases as apc/dh increases. That is, the larger the change in the outlet pressure Pc of the throttle 5 with respect to the change in the gap 3, the larger the holding rigidity d F/d h becomes. Similarly, in the above-mentioned prior art, the suction force F' acting on the plate-shaped body is:

F'=-(Pc-Pa) Aout (PV P
a) Ain - (0) where, Pc: Pressure in the pipe downstream of the restriction of the discharge pipe Aout:
Discharge pipe outlet area Pv : Suction pipe inlet pressure Ain : Suction pipe inlet area In this case as well, as in the case of the present invention, the change dpe in the output pressure Pc of the throttling mechanism with respect to the change in the clearance h
The larger /dh is, the larger the holding rigidity dF'/dh is. Furthermore, the reason why the throttle outlet pressure Pc changes with a change in the clearance h is that the gas mass flow rate ``mR'' passing through the throttle changes due to a change in the clearance h, and in the case of the conventional technology, equation (4) is also expressed. This is because the value of the throttle outlet pressure Pc changes in order to satisfy the expressed relationship. therefore.

Mass flow rate of gas passing through the throttling mechanism m8 with respect to change in clearance h
The larger the change in d my+/d h, the more dPc/dh
, dF/dh will be large.

Now, when dmR/dh is compared between the case of the present invention and the case of the prior art, the value of dmR/dh is larger in the case of the present invention. In the present invention, the mechanism in which the gas mass flow rate changes due to a change in the gap is expressed by equation (5). That is,
When the gap between the holding surface 2A of the holding body 2 and the top surface of the plate-like body 1 changes, as expressed by equation (5),
The flow rate flowing through the gap changes approximately in proportion to the width of the gap h. On the other hand, in the conventional technology, the mechanism that expresses the change in flow rate due to the change in the gap h is expressed by the following equation.

2πrouth mh = Go pcφ(P a/P
c) -(10) 1-1 Here, rout: Discharge pipe radius, that is, expressed by the equation of the drawing material end where the cylindrical gap between the outlet end of the discharge pipe and the top surface of the plate-shaped body is defined as the drawing clearance. be done. As can be seen from equation (10), in the prior art, the flow rate flowing through the gap changes approximately in proportion to the gap h. This shows that the change in flow rate with respect to the change in gap h is greater in the case of the present invention.

In this way, the present invention and the prior art are essentially different in the mechanism by which the gas mass flow rate passing through the aperture apple changes in response to a change in the gap h, and the mechanism by which the holding rigidity changes. For this purpose, it is effective to form a planar gap between the holding surface of the holding body and the upper surface of the plate-like body as in the present invention. Furthermore, not only does a planar gap cause a large change in flow rate, but in reality, as shown in the second term of equation (7), in the device of the present invention, the pressure distribution within the gap greatly contributes to the holding force. , this allows a large holding rigidity to be obtained. Furthermore, because of the planar gap, the present invention can operate with a smaller flow rate of gas for the same gap spacing.

FIG. 6 shows another embodiment of the apparatus of the present invention, in which the same reference numerals as in FIG. 1 represent the same or corresponding parts. In this embodiment, a plurality of holding bodies 2 shown in FIG. 1 are provided facing a plate-like body 1. These plurality of holders 2 are installed in the device frame 15. Further, the pressurized fluid supply hole 6 and the fluid suction hole 10 of each holder 2 are communicated with a common pressurized fluid supply source 8 and a common fluid suction source 12 through conduits 7 and 11, respectively.

According to this embodiment, the plate-like body 1 is held by the plurality of holders 2 in a non-contact manner, so even if the plate-like body 1 is displaced so as to be inclined with respect to the holding surface 2A of the holders 2. , it is possible to give a large restoring force to the plate-shaped body 1.

71st! 1 and 8 show still other embodiments of the apparatus of the present invention, and in these figures, the same reference numerals as in FIG. 1 indicate the same or corresponding parts. In this embodiment, the tube 17 and the pressurized fluid supply source 8 in the embodiment of the device of the present invention shown in FIG. The fluid intake hole 16 is configured to communicate with the fluid suction hole 16 which is open to the atmosphere through the hole.

Next, '!' of the present invention described above! The operation of yet another embodiment of AI will be described.

When the fluid suction source 12 is activated and fluid is sucked, the ninth
As shown in the figure, fluid is sucked from the annular groove 9 surrounding the opening 4 at the center of the holding surface 2A, and the pressure within the annular groove 9 is reduced to below atmospheric pressure, resulting in negative pressure. On the other hand, the fluid of the outside air flows into the opening 4 through the fluid suction hole 16 and the throttle 5 due to the suction of the fluid by the annular groove 9, so that the pressure in this portion becomes positive pressure. Due to this pressure generation.

irI! on the upper surface of the plate-like body 1 in the direction of gravity action 14! The weight of the plate-like body 1 is supported by this suction force, but the suction force acting on this plate-like body 1 is
As shown in Figure 0, if the gap 3 exceeds the set gap interval hc and increases to hb, it increases, and if it decreases to ha, it decreases.

That is, when the interval between the gaps 3 increases to ha as shown in FIG. 9, the resistance to the flow within the gaps 3 decreases, and the flow rate of gas passing through the throttle 5 increases. As a result, the amount of pressure drop in the throttle 5 increases, and since the pressure in the fluid suction hole 16 on the upstream side of the throttle 5 is constant at atmospheric pressure, the pressure in the pocket-shaped opening 4 on the downstream side of the throttle 5 increases. decreases.

As a result, the pressure in the gap 3 decreases, the difference between the pressure in the gap 3 and the atmospheric pressure increases, and the suction force acting on the plate-shaped body 1 increases, causing the plate-shaped body 1 to reach the set gap interval hc. Settling.

According to this embodiment, the plate-shaped body 1 can be reliably held in a non-contact manner, and a pressurized fluid supply source is not required, similarly to the embodiments described above, and the equipment is simplified. Furthermore, since it is of the type that sucks fluid, it can prevent dust from being thrown up and movement of adjacent wafers, especially when used for handling semiconductor wafers.

FIG. 11 shows another embodiment of the apparatus of the present invention, and in this figure, the same reference numerals as in FIG. 7 are the same parts.

In this embodiment, a plurality of holding bodies 2 shown in FIG. 7 are provided facing the plate-like body 1.

These plurality of holders 2 are installed in the device frame 15.

Further, the fluid suction holes 10 of each holding body 2 are connected to a common fluid suction source 12 through a conduit 11.

According to this embodiment, "the plate-shaped body 1 can be held by the plurality of holders 2 without contact, so that the holding surface 2A
A large restoring force can be applied to the tilting operation of the plate-shaped body 1 relative to the plate-shaped body 1, and its retention performance can be improved.

In addition, in the above-mentioned embodiment, the holding surface 2A of the holding body 2
A pocket-shaped opening 4 was provided approximately in the center of the
As shown in FIG. 2 and 13th, an opening consisting of an annular groove 4A and a cross-shaped groove 4B communicating with the annular groove 4A may be provided within the annular groove 4A. According to this opening, since the volume on the downstream side of the throttle 5 is small, it is possible to suppress the generation of automatic vibrations that occur in the plate-like body due to the compressibility of gas.

Further, in the above embodiment, an orifice-type aperture is used as the aperture 5, but a multi-hole aperture 1, a capillary aperture, a self-diameter 2 aperture L6, a surface aperture, or the like may be used.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to reliably hold a plate-like object without contact, and therefore, it is possible to improve the drying/grinding performance of a plate-like object that does not like dirt during holding. can.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of one embodiment of the device of the present invention. Fig. 2 is a bottom view thereof, Fig. 3 is an explanatory diagram showing the functions of the holding body constituting the device of the present invention, and Fig. 4 is the clearance and suction force in one embodiment of the device of the present invention shown in Fig. 1. FIG. 5 is an explanatory diagram showing the operation of the device of the present invention shown in FIG. 1, FIG. 6 is a longitudinal sectional view showing another embodiment of the device of the present invention, and FIG. 8 is a bottom view of FIG. 7, FIG. 9 is an explanatory diagram of the operation of the device of the present invention shown in FIG. 7, and FIG. Fig. 9 is a characteristic diagram showing the relationship between clearance and suction force in an embodiment of the device of the present invention, Fig. 11 is a longitudinal sectional front view showing another embodiment of the device of the present invention, and Fig. 12 is a characteristic diagram showing the relationship between the gap and suction force in an embodiment of the device of the present invention. FIG. 1 is a vertical front view showing another embodiment of the holding body used in the device of
Figure 3 is its bottom view. DESCRIPTION OF SYMBOLS 1... Plate-shaped body, 2... Holding body, 2A... Holding surface,
3...height 3 Fig. ■ 5 Fig. 6 Fig. 7 Fig.￥J g Fig.

Claims (1)

[Claims] 1. A device for holding a plate-like object in a non-contact manner using fluid force, comprising: a holding body having a holding surface for forming a planar gap between the holding body and the plate-like object; A fluid ejecting part is provided on the holding surface of the holding body and generates pressure equal to or higher than atmospheric pressure against the plate-shaped body facing the holding surface, and a holding part of the holding body is provided around the fluid ejecting part. 1. A holding device for a plate-shaped object, comprising: a fluid suction section provided on a surface and provided with a constriction that generates a pressure equal to or lower than atmospheric pressure to the plate-shaped object. 2. The device for holding a plate-shaped body according to claim 1, wherein the fluid suction section is connected to the fluid suction device, and the fluid jetting section is open to the atmosphere. Device. 3. The plate-shaped body holding device according to claim 1, wherein the fluid suction section is connected to a fluid suction device, and the fluid jetting section is connected to a fluid pressurization supply device. holding device. 4. In the device for holding a plate-like object as set forth in claim 2 or 3, the fluid ejection section is constituted by a fluid ejection hole having a diaphragm opening in the holding surface, and the fluid suction section is constituted by a fluid ejection hole provided with a diaphragm opening in the holding surface. 1. A holding device for a plate-shaped body, characterized in that it is composed of a surrounding fluid suction groove. 5. The device for holding a plate-like body according to claim 4, wherein the fluid ejection hole has a pocket-shaped opening in the holding surface. 6. In the holding device for a plate-shaped body as set forth in claim 4, the fluid jet hole has an opening in the holding surface consisting of an annular groove and a cross-shaped groove communicating with the annular groove. A holding device for a plate-shaped object, characterized in that: 7. The plate-shaped body holding device according to claim 5 or 6, wherein the fluid suction groove is one continuous groove. 8. The plate-shaped body holding device according to claim 5 or 6, wherein the fluid suction groove is a plurality of discontinuous grooves. 9. In the device for holding a plate-shaped body according to any one of claims 1 to 8, a plurality of holders each having a fluid ejection part and a fluid suction part are arranged with respect to the plate-shaped body. A holding device for a plate-shaped body, characterized in that: