JPH10206714A - Lens moving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an inclinable angle large, to make bearing rigidity high in a radial direction, and to prolong stroke in an optical axis direction so as to improve positioning accuracy by supporting the guide surface of a lens holding board by means of a static pressure bearing means in a non-contact state, and respectively and individually supporting driving means by means of a base board. SOLUTION: The inside peripheral surface of a fixing member 2 and the outside peripheral surface being the guide surface of the lens holding board 3 are supported in the non-contact state each other by the static pressure or pressure fluid jetted from a porous pad 7 being an annular porous drawing type static pressure bearing means held by the inside peripheral surface, and a lens 4 can freely reciprocate along the axis (Z axis) of the member 2 and the guiding member 3. By making the size of the pad 7 in the Z-axis direction small, the allowable value of the inclination angle to the Z axis can be made large. A Z linear motor is provided with rotors 51a to 51c and stators 52a to 52c, and disposed outside the member 2 in a peripheral direction at an equal interval; and the rotors 51a to 51c are driven in the Z axis direction in accordance with supplied current amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for semiconductor lithography, a lens moving apparatus for positioning a lens in various precision processing machines or various precision measuring instruments, and the like.

[0002]

2. Description of the Related Art A mechanism in which a lens moving device is incorporated in a lens barrel as a means for correcting the magnification of a projection lens of a semiconductor exposure apparatus is described in Japanese Patent Publication No. 62-032613. The lens moving device described here includes a static pressure air bearing as a drive guide, a static pressure air bearing as a drive actuator that controls supply air pressure, an electrostrictive element and a magnetostrictive element, a diaphragm, and the like. .

[0003] Japanese Patent Application Laid-Open No. 06-226570 discloses that
A displacement reduction mechanism using a wedge-shaped input piece supported by a hydrostatic bearing is described.

[0004]

However, in the above-mentioned conventional example, the conventional lens moving device described in Japanese Patent Publication No. 62-032613 has a problem in that the lens is inclined between the diametrical ends of the lens in order to incline the lens from the optical axis. When a drive stroke difference of about 1 mm is required, there are drawbacks that it cannot be performed in principle and that the rigidity becomes very weak. In the lens moving device described in Japanese Patent Application Laid-Open No. 06-226570, when a driving stroke of about several mm is required in the lens optical axis direction, the positioning resolution of the lens becomes coarse or the mechanism itself becomes large. I will. Furthermore, there is a disadvantage that the shape and dimensions of each component must be maintained with high accuracy in order to match the direction in which the lens is moved with the lens optical axis direction.

The present invention has been made in view of the above-mentioned problems in the prior art, and has a relatively large tiltable angle, high radial bearing rigidity, and a long stroke in the optical axis direction. It is an object of the present invention to provide a highly accurate lens moving device.

[0006]

In order to achieve the above object, according to the present invention, there is provided a base plate having an opening so as not to block the optical path of a lens, a supporting means provided upright on the base plate, A lens holding plate having a guide surface facing the support surface of the support means, a hydrostatic bearing means for supporting the support surface and the guide surface in a non-contact manner with each other, and an axis parallel to the support surface. , And the driving means is individually supported by the lens base.

In the above arrangement, the positioning of the lens in the optical axis direction is performed by the driving means. The guide surface of the lens holding plate is supported in a non-contact manner by static pressure bearing means,
Further, since the driving means are individually supported by the base plate, the driving amount can be increased. Since an elastic member such as a leaf spring is not required, there is no possibility that the guide surface or the lens holding plate is deformed even if the driving amount is large, and the lens positioning accuracy is reduced. There is no fear of lens deformation. Further, if the driving means has at least three driving devices respectively connected to different portions of the lens holding plate in the circumferential direction, by changing the driving amount of each driving device, the center of the lens holding plate and the lens can be adjusted. The angle of inclination with respect to the vertical plane can be adjusted.

[0008]

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

FIGS. 1 and 2 show the structure of a lens moving device according to an embodiment of the present invention. FIG. 2 is a plan view, and FIG. 1 is a sectional view taken along a line AB in FIG.

The lens moving apparatus shown in FIG. 1 has an annular base 1 for supporting the entire apparatus, a fixing member 2 which is a cylindrical supporting means provided integrally therewith, and an inner peripheral surface which is a supporting surface thereof. A cylindrical lens holding board 3 that fits on a surface, a lens 4 held by the lens holding board 3, and a Z linear motor as three driving means for moving the lens 4 toward and away from the base 1. 5a to 5c and second support means (the mounting plate 15a, the porous pad 17, etc.) for restricting the rotation of the lens 4 with respect to the base 1. The inner peripheral surface of the fixed member 2 and the outer peripheral surface which is the guide surface of the lens holding plate 3 are formed from a porous pad 7 which is an annular porous diaphragm type hydrostatic bearing means held on the inner peripheral surface of the fixed member 2. The lenses 4 are supported in non-contact with each other by the static pressure of the jetted pressurized fluid, and therefore, the lens 4
, And can reciprocate along a central axis (hereinafter, referred to as “Z axis”) of the guide member 3. Further, the porous pad 7 can be inclined with respect to the Z-axis within a range allowed by the bearing gap, and by reducing the dimension of the porous pad 7 in the Z-axis direction, the allowable value of the inclination angle with respect to the Z-axis can be reduced. Can be bigger. Further, most of the weight of the lens holding plate 3 and the lens 4 is caused by bellows cylinders 8a to 8c serving as urging means provided between the base plate 1 and the linear motor movers 51a to 51c.
Is supported by the pressure of the pressurized fluid to the The fixing member 2 has an internal flow path (not shown) for supplying a pressurized fluid to the porous pad 7, and the base 1 has bellows cylinders 8a to 8c.
Has an internal flow path (not shown) for supplying a pressurized fluid to the fluid. Note that the distance between the porous pad 7 and the lens holding plate 3 is about 7 μm.

The Z linear motors 5a to 5c are mounted on the mounting plate 1.
The movers 51a to 51c fixed to the lens holding board 3 and the stators 52a to 52 fixed to the base plate 1 via 5a to 15c.
52c are provided outside the fixing member 2 at equal intervals in the circumferential direction. The movers 51a to 51c are attached to the mounting plate 15.
The coils are fixed to supports 16a to 16c integral with a to 15c, are connected to a predetermined drive circuit by wiring (not shown), and are driven in the Z-axis direction according to the amount of current supplied from the drive circuit. You. Each Z linear motor 5a-5
The stators 52a to 52c of c are cylindrical frames having a permanent magnet on the inner surface. If the amount of current supplied to each of the Z linear motors 5a to 5c is the same, the lens 4 moves in the Z-axis direction, and the amount of current supplied to each of the Z linear motors 5a to 5c is individually changed. 4 with respect to the Z axis can be changed.

As shown in FIG. 2, the mounting plates 15a to 15a
5c fits into the notches 18a to 18c of the fixing member 2. On the side surface of the cutout portion 18a of the fixing member 2 facing the side surface of the mounting plate 15a, a porous pad 17 which is a porous throttle type static pressure bearing means is provided. The mounting plate 15a has a side surface serving as a guide surface, and is supported in a non-contact manner by a pair of opposed porous pads 17. Therefore, the rotation of the lens 4 about the Z axis is restricted.

The base 1 has first non-contact type displacement sensors 9a to 9c adjacent to the Z linear motors 5a to 5c, respectively.
Each of the displacement sensors 9a to 9c has a detection end facing the illustrated lower surface of the mounting plates 15a to 15c, and detects a change in the position of the lens 4 in the Z-axis direction. By feeding back the outputs of the displacement sensors 9a to 9c to the drive circuit described above, the fine movement positioning of the lens 4 can be performed automatically.

In this embodiment, the Z linear motors 5a to 5c are individually supported on the base 1, and the lens holder 3 and the base 1 are not in contact with each other. There is no possibility that large vibrations occur during the movement. Further, since most of the weight of the lens holding plate 3 and the held lens 4 is supported by the bellows cylinders 8a to 8c, the driving force of the Z linear motors 5a to 5c can be small.

When the inclination angle of the lens 4 with respect to the Z axis is changed to adjust the initial mounting state of the lens, the dimension of the bearing gap of the porous pad 7 and the Z linear motor Although the gap size between the permanent magnet and the coil of each of 5a to 5c changes, such a small amount of inclination causes the contact between the porous pad 7 and the lens holding plate 3 or the driving amount of the linear motor. There is no danger of significant restrictions. That is, usually, the minimum gap of the linear motor is about 1 to 2 mm. For example, as shown in FIG. 3, the diameter of the bearing surface of the porous pad 7 is d, the dimension in the Z-axis direction is w, and the gap of the bearing gap is w. Assuming that the dimension at the center is h0 and the dimensions h1 and h2 at both ends of the bearing gap, d = 200 m
m, w = 20mm, if fine adjustment of the inclination angle of the lens 4 alpha is a 3x10 ^over 4 rad, the fluctuation amount of the size of the bearing gap (h1-h2) / 2 is about 3 [mu] m (amount of variation of h0 is However, as described above, since the initial setting values of the gap dimensions h1 and h2 of the porous pad 7 are set to about 7 μm, the above trouble does not occur. The movable stroke of each linear motor can be up to about 5 mm.

FIG. 4 shows a second embodiment. In this embodiment, a plurality of porous bearing pads 27 each having a flat guide surface are used in place of the annular porous bearing 7 of the first embodiment. This is a configuration provided to face each other. Therefore, without adding other support means such as the porous bearing pad 17 of FIG.
The rotation of the lens 4 about the Z axis is restricted.

It is to be noted that a combination of a piezoelectric element or a rotary motor and a screw or an elastic hinge can be used instead of the Z linear motor of the first and second embodiments.

[0018]

According to the lens moving device of the present invention, the bearing rigidity in the radial direction can be improved without sacrificing the stroke of the lens holding plate (static pressure bearing) in the direction of the inclination angle, so that the resistance to disturbance is improved. Therefore, even if the driving amount is large (a long stroke is possible), there is no possibility that the positioning accuracy of the lens is reduced. In addition, since the lens is stably supported and the degree of cleanness is high, there is no danger of contaminating the lens. Further, since the direction of movement of the lens can be adjusted to the direction of the lens optical axis by adjusting the tilt angle of the lens optical axis, the shape and dimensions of each component and the assembling accuracy can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a lens moving device according to one embodiment of the present invention.

FIG. 2 is a schematic plan view of the device of FIG.

FIG. 3 is an enlarged partial sectional view showing a part of the apparatus of FIG. 1 in an enlarged manner.

FIG. 4 is a schematic plan view of a lens moving device according to another embodiment of the present invention.

[Description of Signs] 1: Base board, 2: Fixing member, 3: Lens holding board,
4: Lens, 5a to 5c: Z linear motor, 7, 1
7, 27: porous pad, 8a to 8c: bellows, 9
a to 9c: displacement sensors.

Claims (5)

[Claims] A pedestal having an opening so as not to block a lens optical path; support means erected on the pedestal; a lens holding disk having a guide surface facing a support surface of the support means; Hydrostatic bearing means for supporting the support surface and the guide surface in non-contact with each other, and drive means for moving the lens holding plate along an axis parallel to the support surface, wherein the drive means is provided on the base. A lens moving device comprising a plurality of driving devices individually supported on a board. 2. The method according to claim 1, wherein the guide surface is an inner circumferential surface or an outer circumferential surface of a cylindrical guide member integrated with the lens holding plate, and the rotation around an axis parallel to the support surface of the lens holding plate is not contacted. 2. The lens moving device according to claim 1, further comprising a second hydrostatic bearing means for restricting the lens movement. 3. The lens moving device according to claim 1, wherein said hydrostatic bearing means is a porous diaphragm type. 4. The apparatus according to claim 1, wherein said driving means has at least three driving devices respectively connected to different circumferential portions of the lens holding plate. Lens moving device. 5. The lens moving device according to claim 1, wherein said driving means includes a linear motor.