JPH02201913A - Aligner - Google Patents

Abstract

PURPOSE:To enable fast positioning without transmitting vibration produced during driving of an XY-stage to an entire of a device by providing an air bearing between a state base and surface plate of the XY-stage and by floating and restricting the stage base. CONSTITUTION:In an exposure device of step and repeat system, XY-stages 3, 4 to mount a water chuck to fix a substrate are made to float slightly in direction of Z-axis from a surface plate 6. An air bearing is arranged through a fine clearance in direction of X-axis and Y-axis, that is, in a vertical direction to an optical axis of a projection lens to limit movement of a stage base 5. Thereby, various kinds of vibrations develop due to a fast movement of XY- stages 3, 4; however, since the stage base 5 floats from the surface plate 6 through air pats 8-1, 8-2, the vibrations are shielded and not transmitted to an entire of the device or a projection lens 1. Fast positioning can be realized in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure apparatus used in a semiconductor element manufacturing process, and more particularly to a support structure for a stage on which an exposed object such as a sea urchin is mounted.

(Prior Art) Conventionally, a device called a stepper is known as an exposure device used for manufacturing semiconductor devices.
While a substrate, such as a semiconductor wafer, is moved step by step under a projection lens, the pattern image formed on the original plate, i.e., a reticle (or mask), is reduced by the projection lens and exposed sequentially to multiple locations on one wafer. It is something.

In terms of performance in terms of resolution and overlay accuracy, steppers are
Currently, it is the mainstream of aligners (exposure devices).

FIG. 8 shows an example of the configuration of a conventional stepper, and FIG. 9 shows a portion of the stepper shown in FIG. 8 where the XY stage is mounted. In the figure, 1
is a projection lens that projects the image of the reticle onto the wafer, 2 is a top stage on which the surface is placed, 3 is a Y stage, and 4 is a
indicates the X stage, 5 indicates the stage base, 6 indicates the surface plate, and 7 indicates the servo mount.

Regarding semiconductor wafers processed by such an aligner, there is a tendency to use semiconductor wafers with a large diameter size in order to reduce the cost of semiconductor elements. Currently, the mainstream wafer size is φ6' (φ150mm), but 19
Around 1989, φ8'~φ10' (φ200mm~φ2
It is expected to be 50mm).

On the other hand, semiconductor devices (particularly DRAM) have become highly integrated from the IM (mega) bit era to the 4M (mega) era, and line widths have also become smaller, such as high-NA projection lenses, high-precision alignment, and high-precision XY stages. is desperately needed.

[Problem to be solved by the invention]

However, the conventional exposure equipment for φ3' to φ6' can be replaced by simply
’ to φ10’, and the XY stage to the 9th
The following problems arise with the conventional method of directly fixing to the surface plate 6 and the conventional XY stage 3.4 shown in the figure.

That is, by increasing the stroke of the XY stage 3.4, it is necessary to increase the guide rigidity in order to guarantee the same accuracy as before the stroke. Furthermore, due to the requirement for the high-precision stage, the stage weight increases even more than the weight increase due to simply increasing the stroke. As a result, vibration problems arise due to an increase in excitation force due to the acceleration of stage movement and a decrease in the relative rigidity of structures such as those that hold the lens due to an increase in the weight of the projection lens. - Productivity decrease due to reduction in XY stage movement speed; - Problems such as productivity decrease due to increase in vibration damping time due to increase in vibration occur.

Further, as the positioning of the XY stage is required to be highly accurate, vibrations generated from moving parts such as a wafer transport mechanism (not shown) attached to the surface plate 6 in FIG. 9 become a problem. In other words, since these vibrations become an obstacle to high-precision positioning, it becomes necessary to provide another vibration removal means, and
When aligning the stage, it is necessary to take measures such as stopping the wafer transport section.

In view of the problems of the conventional type described above, the present invention realizes vibration prevention of the device with a compact structure, and at the same time uses only an air bearing or a combination of an air bearing and a piezo element for the stationary restriction guide. The purpose of this invention is to form a fine movement mechanism on the side of a fixed surface plate rather than on the side of the stage's vertical movement part, thereby reducing the cost and weight of the stage.

(Means and effects for solving the problems) According to the present invention, the vibration of the apparatus is suppressed by raising the XY stage base above the surface plate using an air bearing.

In other words, a substrate having a photosensitive thin film is mounted on an XY stage and moved step by step under a projection lens, reducing the image formed on the original plate (reticle) with the projection lens and sequentially exposing multiple locations on the substrate. In step-and-repeat type exposure equipment, an XY stage equipped with a wafer chuck that fixes a substrate is lifted a small amount from a surface plate in the Z-axis direction, and then moved in the X-axis and Y-axis directions, that is, the optical axis of the projection lens. The air bearings are arranged with a small gap in the direction perpendicular to the stage base to restrict movement of the stage base.

Furthermore, the air pad of the air bearing is made capable of eight minute shifts using a piezo element, thereby performing minute attitude control and position control of the XY stage. Note that the posture control referred to here refers to the control of the rotation direction of the projection lens with respect to the optical axis and the angle between the optical axis and the XY plane.

(Embodiment) FIG. 1 shows a first embodiment of the present invention, in which 1 is a projection lens that projects a reticle image onto a wafer, 2 is a top stage on which the wafer is placed, 3 is a Y stage, and 4 is a In the X stage, 5 is a stage base, 6 is a surface plate, 7 is a servo mount, 8-1 and 8-2 are air bats, and 9 is a support portion for the air bat 8. The top stage 2 is supported on an XY stage 3° 4 and is movable in the XY force directions relative to the projection lens 1, and rotates in the optical axis direction (Z direction) of the projection lens 1, which is an exposure optical system, and in the horizontal plane. Direction (θ
direction). The surface plate 6 supports the stage base 5 and the projection lens 1. In order to regulate the XY force direction of the stage base 5, two air bats 8-1 are attached to each of the four sides of the stage base 5 in the X and Y directions, for a total of eight air bats 8-1.

Air butts 8-2 are attached at four locations on the upper surface of the surface plate 6 in order to air-float the stage base 5 in two directions. Second
The figure is a schematic diagram of a measurement system for yawing of an XY stage and a top stage. 11 is a laser head that is a light source, and 12 is the top (θ, Z) stage 2 in Fig. 1.
13-1 is an interferometer that measures the X direction, 13-2 is an interferometer that measures the Y direction, and 13-1 is an interferometer that measures the Y direction.
-3 is an interferometer that measures the yawing of the XY stage, that is, the θ direction with respect to the optical axis of the projection lens, 14-1.14-
2.14-3 is a receiver that converts interference fringes into electrical signals; 14-1 is for the X direction, 14-2 is for the direction, and 14-3 is for the θ direction.

First, a wafer (not shown) to be exposed is placed on the top stage 2, and a microcomputer (not shown) drives the XY stage 3.4 to transport the wafer to a predetermined position below the projection lens 1. . Then, the operation of moving to a step position with a large exposure diameter and exposing is repeated. At this time, the XY stage 3.4 moves at high speed eight times, thereby generating various vibrations. In this embodiment, this vibration is blocked and not transmitted to the entire apparatus or the projection lens 1 because the stage base 5 floats from the surface plate 6 via the air butts 8-1, 8-2 and is supported by air. However, although low frequency vibrations of several Hz or less cannot be blocked, vibrations of several Hz or less, that is, minute movements, can be dealt with by making minute movements of the XY stage.

3, 4, and 5 show a second embodiment of the present invention.

FIG. 3 is a side view of the stage portion of the exposure apparatus, and FIG. 4 is a top view. 21 is a sensor that measures the position of the stage base 5 in the Z direction; 22-1 is a sensor that measures the position of the stage base 5 in the X direction; and 22-2 is a sensor that measures the position of the stage base 5 in the Y direction. FIG. 5 is a block diagram of the control system of this embodiment. In the figure, numeral 51 is the X, Y, and yaw laser measurement system shown in FIG. 2, which measures the position of the top stage 2. 52 is a system for measuring the position of the stage base 5, which uses sensors 21 and 22. 53 is X
This is a microcomputer that issues optimal operation commands regarding the movement amount and speed of the Y stage, the movement of the XY stage, and the movement of the stage base, and feedback controls the means of movement and movement speed of the top stage at each moment.

56 is a servo motor that moves the XY stage 8 times 54
57 is a unit that changes the pressure of air supplied to the air vat, and 55 is a driver that drives the pressure control unit 57 according to instructions from the microcomputer 53. Next, the operation of this embodiment will be explained with reference to FIGS. 2, 3, 4, and 5. First, the shot layout of the wafer to be exposed and the amount of movement in the X and Y directions are manually entered into the microcomputer 53 in advance. Microcomputer-53
issues a drive command to the XY stage servo driver 54 based on these data. Next, based on the moving speed data and stage position measurement data manually inputted in real time from the laser measurement system 51 and the stage base position measurement system 52, the microcomputer 5
3 drives and controls the XY stage servo driver 54 and pressure control driver 55 in real time so as to perform positioning at the target stop position in the shortest possible time.

FIG. 6 is a diagram showing a structure in which a fine movement mechanism is added to the air bat 8-1, 8-2. A piezo actuator 61-1 is attached to the support member 9, and constitutes a mechanism for slightly moving the air butt 8-1. 61-2 is a piezo actuator attached to the surface plate 6, which constitutes a mechanism for slightly moving the air butt 8-2. FIG. 7 is a block diagram of FIG. 5 with a piezo actuator of 58 piezo drivers 59 added. That is, compared to the second embodiment, the drive control of the stage base 5 is performed more actively and with high precision by slightly moving the knee butts 8-1, 8-2. By using the piezo actuator 59, stage base drive control can be performed without relying on pressure control.
．． The pressure applied to 8-2 may be fixed constant. Also,
The fine movement mechanism of the top stage and the XY stage may be abolished, and the fine movement mechanism may be configured only by the piezo actuator 59.

〔Effect of the invention〕

As explained above, according to the present invention, by interposing an air bearing between the stage base of the XY stage and the surface plate to levitate and restrain the stage base, the vibrations generated when the XY stage is driven are suppressed throughout the apparatus. High-speed positioning is possible without transmission. Further, the influence of external vibrations on the XY stage can be suppressed, making it possible to make the entire apparatus more compact and reduce costs. Furthermore, by eliminating the fine movement mechanism of the stage and performing fine movement control using a piezo actuator, the stage can be simplified, which greatly contributes to making the entire device more compact and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a side view of an embodiment of the exposure apparatus according to the present invention, FIG. 2 is a schematic diagram of a laser measurement system for XY yaw of the exposure apparatus according to the present invention, and FIG. 3 is a side view of another embodiment of the exposure apparatus according to the present invention. 4 is a top view of the wafer mounting stage shown in FIG. 3; FIG. 5 is a control system block diagram of the exposure apparatus according to the present invention; and FIG. 6 is a further diagram of the wafer mounting stage according to the present invention. 7 is a control block diagram of the embodiment of FIG. 6, FIG. 8 is a side view of a conventional exposure apparatus, and FIG. 9 is a diagram of the stage portion of the exposure apparatus of FIG. 8. It is a schematic diagram. 1...Throwing 13 lenses, 2...Top stage, 3...
...Y stage, 4...X stage, 5...stage base, 6...surface plate, 8-1.8-2...air butt, 61-1.61-2...piezo actuator .

Claims (6)

[Claims] (1) An exposure optical system, a stage on which the object to be exposed is mounted, a moving means for moving the stage with respect to the exposure optical system, a base supporting the moving means, and the exposure optical system. An exposure apparatus comprising: a surface plate that supports a system and a base; and air support means interposed between the base and the surface plate. (2) The air support means is provided at a position that supports the base with respect to the surface plate in the optical axis direction of the optical system and restrains the substrate with respect to the surface plate in a direction perpendicular to the optical axis. An exposure apparatus according to claim 1, characterized in that: (3) the optical axis direction is a vertical up-down direction;
3. The exposure apparatus according to claim 2, wherein the air support means is arranged at a position that restrains the base in each direction of Y. (4) The stage is configured to be able to move slightly in the X direction, Y direction, rotation direction (θ direction), and optical axis direction (Z direction) by controlling the air pressure of the air support means. Exposure apparatus according to item 3. (5) The air support means is mounted so as to be finely movable, and the stage is configured to be finely movable in the X direction, Y direction, rotational direction (θ direction), and optical axis direction (Z direction) by fine movement control of the air support means. An exposure apparatus according to claim 3, characterized in that: (6) The exposure apparatus according to claim 5, wherein the air support means is configured to be finely movable by a piezo element.