JP2007078126A - Non-contact support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a non-contact support device which can improve support stiffness of an object to be supported with respect to a base. <P>SOLUTION: A static-pressure gas thrust bearing 10 supports a movable table 14 against a stationary guide 12 in a non-contact state by supplying air to the space between the stationary guide 12 and the movable table 14. The static-pressure gas thrust bearing 10 is provided with a gas-dispersion member 26, a gas passage 16, a means of supplying gas, and an orifice 30. The gas-dispersion member 26 provided to the movable table 14 disperses and exhausts the air, which is supplied from a long groove 26A, to the surface opposite to the stationary guide 12. Then the gas passage 16, one end of which is opened toward the long groove 26A of the gas-dispersion member 26, is provided to the stationary guide 12, and the means of supplying gas supplies air to the long groove 26A of the gas-dispersion member 26 through the gas passage 16. Then the orifice 30 is provided to the gas passage 16. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-contact support device for supporting a supported body in a non-contact manner with respect to a base.

For example, in a semiconductor exposure process, it is known to use a static pressure gas bearing to obtain high wafer positioning accuracy. In such a static pressure gas bearing, a gas dispersion portion made of a porous body and having a long groove for supplying air is provided on the moving table, and the gas supplied from the long groove is dispersed through the porous body on the surface facing the fixed guide body. A deep-grooved porous static pressure gas thrust bearing that is discharged and supported by the pressure of the gas so as to be movable in the longitudinal direction of the long groove without contacting the fixed guide body is considered (for example, Non-Patent Document 1). reference).
Miyatake, Yoshimoto, Yagi, "Study on Deep Hydrostatic Gas Thrust Bearings with Deep Grooves", Transactions of the Japan Society of Mechanical Engineers (C), 71, 702, February 2005

  However, in the conventional deep groove porous hydrostatic gas thrust bearing as described above, the supporting rigidity of the moving table with respect to the fixed guide body is low, and sufficient restoration is possible when the bearing gap between the moving table and the fixed guide body changes. There is a risk that the force cannot be obtained and the displacement of the movable table with respect to the fixed guide body cannot be eliminated.

  In view of the above fact, an object of the present invention is to obtain a non-contact support device capable of increasing the support rigidity of the supported body with respect to the base.

  In order to achieve the above object, a non-contact support device according to the first aspect of the present invention supports the supported body in a non-contact manner with respect to the base by supplying a gas between the base and the supported body. A non-contact support device that is provided on the supported body, disperses the gas supplied from the air supply port on a surface facing the base, and discharges the gas, and one end of the gas dispersion unit. A gas supply means for supplying gas to an air supply port of the gas dispersion unit through a gas flow channel provided in the base part and opened toward the air supply port; and a gas flow channel of the base part or the gas supply And a throttle means for providing fluid resistance provided in the gas flow path of the means.

  In the non-contact support device according to claim 1, when the gas from the gas supply means is supplied to the air supply port of the gas dispersion portion provided in the support through the gas flow path of the base portion, the gas is dispersed in the gas dispersion portion. Thus, the gas is dispersed and discharged between the gas dispersion portion (supported body) and the base, and the support is supported in a non-contact manner with respect to the base by the gas pressure.

  Here, since the throttle means is provided in the gas flow path of the base or the gas supply means, when the gap between the base and the supported body (between the opposed surfaces to which the gas is supplied) becomes large, the gap is small. Compared with, the internal pressure of the gap decreases. That is, by providing the throttle means, the change width of the gap internal pressure corresponding to the amount of change in the gap size between the base and the supported body is increased. Thereby, the support rigidity which supports a to-be-supported body with a predetermined clearance with respect to a base becomes high.

  Thus, in the non-contact support device according to the first aspect, the support rigidity of the supported body with respect to the base can be increased.

  A non-contact support device according to a second aspect of the invention is the non-contact support device according to the first aspect, wherein the base supports the supported body in a non-contact manner so as to be movable in a predetermined direction with respect to the base. The gas dispersion portion has a shape in which the air supply port is formed longitudinally along the predetermined direction.

  In the non-contact support device according to claim 2, since the air supply port of the gas dispersion portion is elongated in the direction in which the base portion guides the supported body, the non-contact state of the supported body with respect to the base portion is maintained. The supported body can be moved in a predetermined direction with respect to the base.

  A non-contact support device according to a third aspect of the present invention is the non-contact support device according to the second aspect, wherein the supported body is formed in a cylindrical shape through which the base is inserted, and the gas dispersion portion is provided on the inner surface side. Is provided.

  In the non-contact support device according to claim 3, the supported body formed in a cylindrical shape is movable in the axial direction while being guided by the base portion inserted through the inside.

  A non-contact support device according to a fourth aspect of the present invention is the non-contact support device according to the third aspect, wherein the supported body is provided with a plurality of the gas dispersion portions along a circumferential direction, The gas flow path of the base portion is branched so as to open toward the air supply ports of the plurality of gas dispersion portions, and the throttling means is provided at each branch downstream of the branch portion of the gas flow passage. Each is disposed in the flow path.

  In the non-contact support device according to the fourth aspect, the plurality of gas dispersion portions divided in the circumferential direction discharge the gas supplied from the respective air supply ports toward the respective opposing surfaces in the base portion. And since the throttle means is each arrange | positioned at the branch path for supplying air to each gas dispersion | distribution part, the internal pressure between each gas dispersion | distribution part and a base can be changed according to a clearance gap. Thereby, this non-contact support apparatus is corresponded to the structure which a to-be-supported body supports with a gas spring parallel with respect to a base, and can further improve the support rigidity of the to-be-supported body with respect to a base.

  The non-contact support device according to a fifth aspect of the present invention is the non-contact support device according to any one of the first to fourth aspects, wherein the gas dispersion portion communicates with the air supply port in a porous body. A surface other than the surface and the surface facing the base is sealed.

  In the non-contact support device according to the fifth aspect, since the porous body is used as the gas dispersion portion, the formation (processing) of the gas dispersion flow path is unnecessary, and the structure is simplified and the manufacture is facilitated.

  As described above, the non-contact support device according to the present invention has an excellent effect that the support rigidity of the supported body with respect to the multiple base portions can be increased.

  A static pressure gas thrust bearing 10 as a non-contact support device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

  FIG. 3 is a perspective view showing a schematic overall configuration of the static pressure gas thrust bearing 10. 1A shows a cross section along line 1A-1A in FIG. 3, and FIG. 1B shows a partially enlarged view of FIG. 1A. Further, FIG. 2 shows a cross-sectional view taken along line 2-2 of FIG. As shown in these drawings, the static pressure gas thrust bearing 10 includes a fixed guide body 12 as a base portion and a movable table 14 as a supported portion.

  The fixed guide body 12 is formed in a substantially rectangular parallelepiped block shape which is elongated in a predetermined direction indicated by an arrow A in FIG. A gas flow path 16 is formed in the fixed guide body 12, and an air supply port 16 </ b> A of the gas flow path 16 is connected to a discharge portion 22 </ b> A of the compressor 22 via a tube 18 and a regulator 20. The tube 18, the regulator 20, and the compressor 22 correspond to gas supply means in the present invention, and supply gas (air) having a predetermined pressure to the gas flow path 16 of the fixed guide body 12.

  As shown in FIGS. 1A and 2, the gas flow path 16 of the fixed guide body 12 includes a header flow path 16 </ b> B passing through an axial center portion on one end side in the longitudinal direction of the fixed guide body 12 and a header flow path 16 </ b> B. And four branch flow paths 16C branched from the end of the fixed guide body 12 in the radial direction. The end of each branch channel 16C is an exhaust port 16D that opens at the center in the longitudinal direction and width (vertical) direction of the corresponding peripheral surface 12A of the fixed guide body 12.

  As shown in FIG. 1A, the movable table 14 is formed in a rectangular cylinder shape, and the fixed guide body 12 is inserted through the movable table 14. More specifically, as shown in FIG. 1A, the movable table 14 includes a table main body 24 formed in a substantially square frame shape in a sectional view, and four flat inner peripheral surfaces of the table main body 24, respectively. The four gas dispersion members 26 are fixed to each other. The table body 24 is configured to place or hold a workpiece such as a semiconductor wafer (not shown).

  Each gas dispersion member 26 is formed of a porous body in a substantially rectangular parallelepiped shape. As the porous body constituting the gas dispersion member 26, ceramic, sintered metal, or the like can be used. In this embodiment, the gas dispersion member 26 is made of graphite. Each gas dispersion member 26 is fixed to a corresponding inner peripheral surface of the table main body 24 by adhesion or the like, and each end surface is sealed with an edge seal member 28. Thereby, the gas dispersion member 26 made of a porous body is configured to be able to discharge the gas supplied only from the inward surface facing the corresponding peripheral surface 12A of the fixed guide body 12 inserted through the movable table 14. ing.

  As shown in FIG. 4, a long groove (slit) 26 </ b> A that is elongated along the longitudinal direction of the fixed guide body 12 inserted through the movable table 14 is formed at the center in the width direction of each gas dispersion member 26. ing. In this embodiment, as shown in FIGS. 1 and 2, the long groove 26A is formed so as to penetrate the gas dispersion member 26 in the thickness direction, and the inner peripheral surface of the table body 24 forms the groove bottom. .

  As shown in FIG. 1A, each long groove 26 </ b> A is positioned facing a different exhaust port 16 </ b> D in the gas flow path 16. Therefore, the air discharged from the compressor 22 is supplied to each long groove 26 </ b> A as an air supply port of each gas dispersion member 26 through the regulator 20, the tube 18, and the gas flow path 16. As shown in FIG. 1B, each gas dispersion member 26, which is a porous body constituting the movable table 14, blows air supplied from each long groove 26A toward the opposing surface of the fixed guide body 12. It is. The white arrow in FIG. 1B conceptually shows the flow of air.

  With this gas pressure, a bearing gap C is formed between each gas dispersion member 26 and the corresponding peripheral surface 12A of the fixed guide body 12, and the movable table 14 is supported in a non-contact manner with respect to the fixed guide body 12. is there. Further, since each long groove 26 </ b> A that is an air supply port of the movable table 14 is elongated in the longitudinal direction of the fixed guide body 12, the movable table 14 is supported in a non-contact manner with respect to the fixed guide body 12. The guide body 12 is movable in the longitudinal direction. In this embodiment, the design value of the interval h0 of each bearing gap C is set to approximately 4 to 6 μm (maximum 8 to 12 μm) on one side.

  The static pressure gas thrust bearing 10 includes an orifice 30 as a throttle means disposed between the discharge portion 22A of the compressor 22 and each exhaust port 16D of the gas flow path 16. In this embodiment, the orifice 30 is configured by fitting an orifice member 32 having an orifice hole 32A penetrating the axial center portion and formed in a cylindrical shape into each branch channel 16C. In this embodiment, the orifice hole 32A is a cylindrical space having a circular cross section and having a substantially constant diameter over its entire length, and its diameter d0 is set to 0.15 mm or less.

  Next, the operation of this embodiment will be described.

  In the static pressure gas thrust bearing 10 having the above-described configuration, when the compressor 22 is operated, the air adjusted to a constant pressure by the regulator 20 passes through the tube 18 and the gas flow path 16 to each gas dispersion member 26 of the movable table 14 to each long groove. 26A. The air is dispersed through the inside of the gas dispersion member 26 which is a porous body, and is blown out substantially uniformly toward the corresponding peripheral surface 12A of the fixed guide body 12. Thereby, the movable table 14 is supported in a non-contact manner with respect to the fixed guide body 12.

  Here, in the static pressure gas thrust bearing 10, the orifice 30 is provided in the gas flow path 16. Therefore, when the gap h 0 of the bearing gap C between the fixed guide body 12 and the movable table 14 becomes large, the gap h 0 of the bearing gap C is increased. Compared with the case where it is small, the internal pressure of the bearing gap C is greatly reduced. That is, by providing the orifice 30, the change width of the internal pressure of the bearing gap C corresponding to the interval h0 of the bearing gap C between the fixed guide body 12 and the movable table 14 is increased. Thereby, the support rigidity which tends to support the movable table 14 with respect to the fixed guide body 12 at a predetermined interval is increased.

  The effect of improving the support rigidity due to the installation of the orifice 30 will be further described with reference to the numerical analysis results and the experimental results shown in FIGS.

  FIG. 5A shows the width direction of the gas dispersion member 26 when only one gas dispersion member 26 constituting the static pressure gas thrust bearing 10 is used to support a supported body corresponding to the movable table 14 (see FIG. The numerical analysis result of the pressure distribution of the bearing gap C along the short direction of the long groove 26A) is shown. On the other hand, FIG. 5B shows a numerical analysis result under the same conditions in a configuration without the orifice 30 as a comparative example.

  In these drawings, the horizontal axis representing the position in the width direction of the bearing gap C is shown by a schematic diagram of the analysis model. The sign of this analysis model coincides with the sign of the corresponding part and part of the static pressure gas thrust bearing 10. The pressures shown in these figures are obtained by dividing the absolute pressure by the atmospheric pressure to make it dimensionless, and the memory “1” represents the internal pressure (gauge pressure) 0. Furthermore, in the analysis of FIG. 5A, the diameter d0 of the orifice 30 is 0.2 mm.

  5A, in the configuration including the orifice 30 (hydrostatic gas thrust bearing 10), the pressure Psl in the long groove 26A is supplied by the regulator 20 when the interval h0 of the bearing gap C is extremely small (1 μm or less). When the pressure h of the bearing gap C is increased by exceeding 1 μm, the pressure in the bearing gap C (downstream of the orifice 30) is increased as the gap h0 increases. It can be seen that Psl decreases (see arrow B).

  On the other hand, from FIG. 5 (B), in the configuration without the orifice 30, when the interval h0 of the bearing gap C is very small (1 μm or less), the pressure distribution is the same as the configuration with the orifice 30; When the C interval h0 exceeds 1 μm, it can be seen that the change in the pressure Ps in the bearing gap C is small with respect to the change in the interval h0 of the bearing gap C.

  This is because in the configuration without the orifice 30, the inside of the long groove 26A is maintained at the supply pressure Ps0 regardless of the interval h0 of the bearing gap C (the air flow rate increases), whereas in the configuration with the orifice 30, the orifice 30 Since the increase in the amount of air supplied to the long groove 26A is suppressed by the squeezing effect (pressure loss), the pressure Psl in the long groove 26A decreases as the interval h0 of the bearing gap C increases, and as a result, the bearing gap C This is because the internal pressure Ps decreases.

  FIG. 6A shows experimental values (plots) of the air flow rate (supply air amount) Q to the long groove 26A and the pressure Psl in the long groove 26A with respect to the interval h0 of the bearing gap C in the same model as FIG. And the calculation results (diagrams) are shown superimposed. From this figure, it can be seen that in the configuration without the orifice 30, the air flow rate Q increases exponentially as the interval h0 of the bearing gap C increases. For this reason, the pressure Psl in the long groove 26A is maintained at the supply pressure Ps0.

  On the other hand, in the configuration including the orifice 30 (static pressure gas thrust bearing 10), it can be seen that the air flow rate Q gradually approaches a predetermined amount corresponding to the diameter d0 of the orifice 30 and the increase is suppressed. Accordingly, it can be seen that in the configuration including the orifice 30, the pressure Psl in the long groove 26A decreases as the interval h0 of the bearing gap C increases.

  From the above, it was experimentally confirmed that a pressure distribution as shown in FIG. 5 was obtained. Further, FIG. 6 (A) shows that the smaller the diameter d0 of the orifice 30, the smaller the air flow rate Q is, and the greater the decrease in the pressure Psl.

  Further, FIG. 6B shows experimental values (plots) and calculation results of the dimensionless load capacity W and the dimensionless static stiffness Ks with respect to the gap h0 of the bearing gap C in the same model as FIG. Diagram) is shown superimposed. The load capacity W is experimentally obtained by dividing the load (mass) supported at the interval h0 by the reference load to make it dimensionless, and can be obtained by measuring the sensation h0 using a known mass. it can. In numerical analysis, it is calculated as a function of the pressure Ps in the bearing gap C. The static stiffness Ks is experimentally calculated as ΔW / Δh0 obtained by dividing the minute change amount ΔW of the load capacity W (known mass) by the change amount Δh0 of the interval h0 associated with the minute change. W is differentiated by the interval h0.

  From FIG. 6B, it can be seen that in the configuration without the orifice 30, the load capacity decreases as the interval h0 increases in the region where the interval h0 of the bearing gap C is small (approximately 5 μm or less). It can be seen that the maximum value of the static stiffness is obtained when the interval h0 is approximately 2 μm. And in this comparative example model, it turns out that practical static rigidity is not obtained in the area | region of practical space | interval h0 = 5 micrometer from a viewpoint of the processing precision of each component, and an assembly | attachment precision.

  On the other hand, in the configuration including the orifice 30 (static pressure gas thrust bearing 10), it can be seen that the load capacity W decreases as the interval h0 increases in a wider region. In the configuration including the orifice 30, it can be seen that the maximum value of the static rigidity due to the porous restriction of the gas dispersion member 26 and the maximum value of the static rigidity due to the restriction of the orifice 30 appear. When the diameter d0 is reduced, the maximum value of the static stiffness due to the restriction of the orifice 30 approaches the maximum value of the static rigidity due to the porous restriction, and in this model, d0 = 0.15 mm or less, so It was confirmed that the squeezing action almost overlapped.

  As a result, high static rigidity can be obtained in a region around the interval h0 = 5 μm of the bearing gap C. Further, as shown in FIG. 6A, the air flow rate Q is kept small in the region around the interval h0 = 5 μm, and the air consumption does not increase in order to obtain the high static rigidity as described above.

  As described above, in the static pressure gas thrust bearing 10 provided with the orifice 30, the support force of the movable table 14 with respect to the fixed guide body 12 is increased when the interval h 0 of the bearing gap C is increased as compared with the configuration without the orifice 30. The restoring action is greatly reduced, and the restoring force that tries to return to a state in which the supporting force is balanced with the load, that is, the state in which the interval h0 is small is strongly exerted. That is, in the static pressure gas thrust bearing 10, the support rigidity (static rigidity Ks) for holding the movable table 14 at a predetermined interval with respect to the fixed guide body 12 is improved, thereby improving the positioning accuracy.

  In particular, in the static pressure gas thrust bearing 10, since the two pairs of gas dispersion members 26 facing each other constitute the movable table 14, in other words, the movable table 14 is in the vertical direction and the width direction with respect to the fixed guide body 12. Since both are supported by a pair of parallel springs, the support rigidity in each direction is further increased, and the positioning accuracy is further improved.

  Further, in the static pressure gas thrust bearing 10, since the gas dispersion member 26 having the long groove 26A is provided in the movable table 14, air is not supplied to the movable table 14 which is a movable side member, and in the movable direction of the movable table 14. A configuration in which the movable table 14 is moved relative to the fixed guide body 12 without increasing the air consumption by providing the long gas dispersion member 26 on the fixed guide body 12 is realized.

  Furthermore, since the movable table 14 is formed in a cylindrical shape through which the fixed guide body 12 is inserted, as described above, a plurality of gas dispersion members 26 (which constitute air springs independently of each other) are arranged in the circumferential direction to provide support rigidity. While improving, the structure which guides the movable table 14 only to one direction with respect to the fixed guide body 12 was implement | achieved. In particular, since the cross sections perpendicular to the axes of the fixed guide body 12 and the movable table 14 are non-circular, that is, non-rotating, it is not necessary to separately provide a detent guide.

  Further, in the static pressure gas thrust bearing 10, since the gas dispersion member 26 is formed of a porous body, it is not necessary to provide an air dispersion groove or the like, and the air supplied with a simple structure with a small number of processing steps. Was substantially uniformly dispersed and ejected into the bearing gap C.

  In the above-described embodiment, an example in which the gas dispersion member 26 made of a porous body is provided has been described. However, the present invention is not limited to this, and for example, a surface (bearing surface) facing the peripheral surface 12A of the fixed guide body 12 In other words, a gas dispersion member configured by communicating a large number of dispersion grooves (shallow grooves) opening toward the bearing gap C with an air supply groove corresponding to the long groove 26A can be used in place of the gas dispersion member 26. .

It is a figure which shows the static pressure gas thrust bearing which concerns on embodiment of this invention, Comprising: (A) is sectional drawing which follows the 1A-1A line | wire of FIG. 3, (B) is FIG. 1 (A) which shows the flow of air. It is a partial enlarged view. It is sectional drawing which follows the 2-2 line of FIG. 3 which shows the static pressure gas thrust bearing which concerns on embodiment of this invention. 1 is a perspective view showing a schematic overall configuration of a static pressure gas thrust bearing according to an embodiment of the present invention. It is a perspective view of a gas dispersion member which constitutes a static pressure gas thrust bearing concerning an embodiment of the present invention. (A) is a diagram showing the pressure distribution of the bearing gap in the hydrostatic gas thrust bearing according to the embodiment of the present invention, (B) is a diagram showing the pressure distribution of the bearing gap in a comparative example with the embodiment of the present invention. It is. (A) is a diagram showing the relationship between the bearing gap interval and the air flow rate, and the long groove pressure, and (B) is a diagram showing the relationship between the bearing gap interval and the load capacity and static stiffness of the static pressure gas thrust bearing. It is.

Explanation of symbols

10 Static pressure gas thrust bearing 12 Fixed guide body (base)
14 Movable table (supported body)
16 Gas flow path (base gas flow path)
16C branch channel 18 tube (gas channel of gas supply means)
22 Compressor (gas supply means)
26 Gas dispersion member (gas dispersion part)
26A long groove (air supply port)
30 Orifice (throttle means)

Claims (5)

A non-contact support device for supporting the supported body in a non-contact manner with respect to the base by supplying a gas between the base and the supported body,
A gas dispersion part that is provided on the supported body and that disperses and discharges the gas supplied from the air supply port on a surface facing the base part;
A gas supply means for opening one end toward the air supply port of the gas dispersion unit and supplying gas to the air supply port of the gas dispersion unit through a gas flow path provided in the base part;
A throttling means to be a fluid resistance provided in the gas flow path of the base or the gas flow path of the gas supply means;
A non-contact support device. The base has a guide shape capable of guiding in a predetermined direction while supporting the supported body in a non-contact manner,
The non-contact support device according to claim 1, wherein the gas distribution part has the air supply port formed longitudinally along the predetermined direction.   The non-contact support device according to claim 2, wherein the supported body is formed in a cylindrical shape through which the base portion is inserted, and the gas dispersion portion is provided on an inner surface side. The supported body is provided with a plurality of gas dispersion portions along a circumferential direction,
The gas flow path of the base portion is branched so as to open toward the air supply ports of the plurality of gas dispersion portions,
The non-contact support device according to claim 3, wherein the constricting means is disposed in each branch flow channel downstream of the branch portion of the gas flow channel.   The said gas dispersion | distribution part is comprised by sealing surfaces other than the communicating surface with the said air supply port in a porous body, and the surface facing the said base part. Contact support device.

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