JP2001281374A - Stage mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and small-sized stage mechanism improved in reproducing precision of straight guide. SOLUTION: This stage mechanism comprises a fixed frame and movable part arranged axially symmetrically to a central axis, an elastic fulcrum double parallel link mechanism for guiding the movable part, a nut guide part, and a double parallel spring mechanism for guiding the nut guide part, a ball screw connected to a motor through a coupling is supported on the central axis of the fixed frame. A ball screw nut is fixed to the nut guide part, and the nut guide part is connected to the movable part through a connecting bar with circularly cutout elastic hinge arranged on the central axis to transmit only the axial displacement of the ball screw nut. The influence of an axial slippage is suppressed by the double parallel plate spring and further almost eliminated by the connecting bar with circularly cutout elastic hinge, thereby, high straight guide precision is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal substrate, a mask,
The present invention relates to an improvement of a fine movement stage mechanism such as a fine movement Z-axis for automatic focusing of a dimension measuring machine in which a measured object has a long dimension and a measured point is minute, particularly a magnetic head. For liquid crystal substrates, masks for liquid crystal substrates, thin film magnetic head baked wafers, etc.
It is required to measure the baked pattern over a length of about several tens mm to about 1000 mm with a measurement reproducibility of, for example, 0.2 μm or less. For such measurement, the object to be measured or the microscope is positioned on an XYZ stage, the object to be measured is imaged with a television microscope, the position of the point to be measured in the imaging field of view, and the position of the XY stage read by a laser interferometer or the like. 2. Description of the Related Art A two-dimensional measuring machine that measures a distance between measured points from a position is used. Focus control is performed in order to optimize the focus state when the object to be measured positioned on the XY stage is imaged by the television microscope in the two-dimensional measuring machine, but the point to be measured or the objective lens is moved along the optical axis of the microscope during the focus control. It is moved to the (Z) direction and positioned at the optimum focus point. If there is a reproduction error of the straight movement during the movement in the Z direction at the time of autofocus, an error in the measurement position occurs when the range to be measured is wide (or long). That is, if there is a reproduction error of the straight movement at the time of movement in the Z direction, each time the focus adjustment is performed, the focus cannot be accurately adjusted at the position of the XY coordinate designated to be measured. For this reason, a Z stage having a wide (or long) measurement object and high straightness movement accuracy is required.

As an example, the conventional Z-axis for auto-focusing has a movement amount of several hundred μm on the Z-axis for focusing.
m, positioning accuracy in the moving direction is about 0.1 μm over several 100 μm, and reproducibility of straight guide of the movement is 0.05
Stage mechanisms of the order of μm have been used. As a method of realizing such a movement accuracy, using a parallel leaf spring guide and a ball screw drive as shown in Japanese Patent Application No. Hei 10-186211, the effect of shaft runout due to the screw drive is reduced by a thrust ball bearing using a ball and a flat plate. Further, there has been a stage mechanism which reduces the influence by a connecting rod having a circumferential notch. In this method, the reproduction accuracy of the straight guide is about 0.05 μm. This was sufficient for a measurement reproducibility of about 0.5 μm over a length of several hundred mm which was conventionally required. However, recently, it is difficult to realize reproducibility of about 0.2 μm over a length of 1000 mm, for example. Further, in order to obtain a measurement reproducibility of about 0.1 μm over 1000 mm, which will be required in the future, it is desirable that the reproduction accuracy of the straight guide of the stage mechanism be about 0.01 μm.

[0003]

However, the conventional method has a problem that it is difficult to obtain a recently desired straight guide reproduction accuracy of about 0.01 μm. An object of the present invention is to provide a new mechanism for improving the reproduction accuracy of the straight guide of the stage mechanism to about 0.01 μm in order to solve this problem.

[0004]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides an accurate straight guide ball instead of a thrust ball bearing for transmitting the displacement of a ball screw, which has deteriorated the straight guide accuracy in the conventional device. By transmitting only the axial displacement of the ball screw with a double parallel spring mechanism that transmits only the axial displacement of the screw, this is transmitted to the movable part by a connecting rod with an arc notch,
The straight guide accuracy is improved.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are plan views,
The symbol A indicates two parts. FIG. 3 is a sectional view taken along the center line in FIGS. The stage section includes a movable section 1 for mounting a microscope (not shown), an outer frame 2 mounted on a moving stage (not shown), a double parallel link mechanism 3 for connecting the movable section 1 and the outer frame 2, a screw drive section 4 with a ball screw 41, A nut guide mechanism 5 for guiding the ball screw nut 42, a connecting portion 6 for transmitting the movement of the ball screw nut 42 to the movable portion 1
And has an axially symmetric structure with respect to the center line 100.

The double parallel link mechanism 3 is provided with four sets of two parallel links 31 of the same size. The adjacent parallel links 31 have one end connected to the rigid body 32 and the other end connected to the movable portion 1 and the outer frame 2. The two ends of the parallel link 31 are arc notches 3
3 are provided to form an elastic hinge 34. The screw drive unit 4 is provided with a bearing 43 that rotatably supports the ball screw 41 at a fixed position in the axial direction, and the bearing 43 is fixed to the outer frame 2 via a bearing bracket 44. Also,
The ball screw 41 is connected to a motor 46 via a coupling 45.
Are combined. Further, a ball screw nut 42 is screwed into the ball screw 41, and is vertically displaced with the rotation of the ball screw 41.

[0007] The nut guide mechanism 5 includes two parallel leaf springs 5.
One set of four parallel leaf springs 1 has one end connected to the rigid member 52 and the other end connected to the nut guide 53 or the outer frame 2. The connecting portion 6 is disposed on the central axis 100,
Circular notch 6 provided by two at the top and bottom that intersect at 90 °
A connecting rod 64 having an elastic hinge 63 formed by the members 1 and 62 has an upper end fixed to the nut guide section 53 and a lower end fixed to the movable section 1.

Hereinafter, this operation will be described. A pulse train is applied to a microstep motor driver (not shown) based on a focus signal from a control unit (not shown), and a pulse train is given to the motor 46 from the microstep motor driver. The motor 46 rotates according to the pulse train, and the ball screw 41
To rotate. When the ball screw 41 rotates, the ball screw nut 42 moves up and down. At this time, the nut guide mechanism 5 composed of a double parallel leaf spring (reference numeral 51) mechanism symmetrically arranged is used to precisely move the nut screw up and down. The ball screw nut 42 is guided and held down until the whirling of the ball screw nut 42 caused by the shaft runout accompanying the rotation of the ball screw 41 is almost eliminated.

Further, the remaining whirling is transmitted to the movable part 1 by the connecting rod 6 with high rigidity in the axial direction and very low rigidity in the direction perpendicular to the axis. Since the guide is strictly guided straight by the double parallel link mechanism 3, the movable part 1 moves straight along the center line. In this embodiment, the straight guide accuracy is 0.02 μm over the vertical movement amount of 500 μm, and the reproducibility of the straight guide is 0.01 μm.
was gotten. As a result, according to the present invention, the liquid crystal substrate, the mask, the magnetic head, and the like, particularly, the object to be measured has a long dimension, and the point to be measured is optimal for the fine movement Z-axis for autofocus of a fine dimension measuring machine. A fine movement stage mechanism can be provided. According to the present invention, it is possible to accurately move to a coordinate position designated to be measured when performing focus adjustment with a small reproduction error of the straight movement when moving in the Z direction. Therefore, it is most suitable as a Z stage when the measurement target is wide (or long).

[0010]

According to the embodiment of the present invention, the double parallel link mechanism is used for guiding the movable portion, but a double parallel leaf spring may be used as the guide mechanism. In this case, the stress applied to the leaf spring portion is reduced and a large displacement can be obtained, but the rigidity is reduced and the guiding accuracy is slightly deteriorated.

Although a double parallel leaf spring is used for guiding the ball screw nut, a double parallel link mechanism may be used as this guide mechanism. In this case, the displacement is small, but the guiding accuracy is improved. Although a ball screw is used to convert the rotation of the motor into a linear displacement, another type of screw may be used as long as there is no backlash and there is little friction.

As described above, according to the present invention, a guide portion is formed by a double parallel link mechanism and a double parallel spring mechanism integrally formed by cutting out from a thick plate, and a ball screw, a ball screw bearing, a bearing bracket, and a connection. The stage mechanism can be composed of several points such as rods, so that it is inexpensive, small, high-precision, and has no friction in the guide portion, so that a highly reliable stage mechanism can be composed.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a front view showing one embodiment of the present invention.

FIG. 3 is a sectional view showing one embodiment of the present invention.

[Explanation of symbols]

1: movable part, 2: outer frame, 3: double parallel link mechanism, 4:
Ball screw, 5: double parallel leaf spring mechanism, 6: connecting rod.

Claims (4)

[Claims] 1. A double parallel spring mechanism for transmitting only a displacement of a ball screw for moving a stage in an axial direction thereof, a connecting rod having an arc-shaped notch for transmitting only an axial displacement of the ball screw, and the connection. A stage mechanism having a movable part fixed to a rod. 2. A stage mechanism for driving a movable part by screw feed, comprising: a screw for transmitting rotation of a motor; a nut for changing the rotation of the screw in a moving direction of the stage; and one end fixed to the nut.
An elastic fulcrum parallel link guide having the other end fixed to the outer frame, and a connecting mechanism having a structure in which one end is fixed to the nut side and the other end is fixed to the stage, rigid in the axial direction and low in the direction perpendicular to the axis. A stage mechanism having an elastic fulcrum parallel link guide connecting the stage connected to the coupling mechanism and the outer frame. 3. A stage mechanism for driving a movable section by screw feed, wherein a fixed section, a movable section, and a guide mechanism have an integral structure formed of a thick plate, and are parallel to the moving direction of the movable section and the movable section. A pair of rigid bodies disposed on both sides outside the movable section symmetrically with a center line passing through the center of the movable section, and an outer frame formed by surrounding the pair of rigid bodies and the movable section, The pair of rigid bodies extend from both sides at right angles to the center line and in the direction of the center line to be connected to the outer frame, and have elastic hinge portions at both ends, and are arranged symmetrically with respect to the center line. A pair of parallel links of the same dimensions, and two sets of the same dimensions which are disposed adjacent to the inside of each of the parallel links and parallel to the parallel links, and extend from the pair of rigid bodies and are coupled to the movable portion. A double parallel link mechanism constituted by parallel links of A screw shaft rotatably fixed on the center line, a nut screwed into the screw shaft, a nut guide to which the nut is attached, and a symmetrical and parallel to the center line outside the nut guide. A pair of rigid members provided, and extend from both sides of the pair of rigid members at right angles to the center line and in the direction of the center line to be coupled to the outer frame, and are disposed symmetrically with respect to the center line. Two sets of parallel leaf springs having the same dimensions, and two sets of parallel leaf springs disposed adjacent to the inside of the parallel leaf springs in parallel with the leaf springs and extending from the pair of rigid members and coupled to the movable portion. A double parallel leaf spring mechanism constituted by four parallel leaf springs of the same direction, a connecting rod with an elastic hinge disposed on the center line and connecting the movable portion and the nut movable portion, and the screw A stage mechanism having a motor for rotating a shaft 4. The stage mechanism according to claim 3, wherein the screw shaft and the nut are constituted by a preload applying ball screw.