JPH0157286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a straightness correction device for a straight traveling table, and in particular, a straightness correction device for a straight traveling table that requires highly accurate straightness, such as a traveling table for a reflective projection mask aligner. Regarding.

FIGS. 1 to 3 show an example of a reflective projection type mask aligner having a traveling table, which is the object of the present invention.

In the reflective projection mask aligner shown in these figures, a wafer 1 and a mask 2 are moved onto a traveling table 3.
put on top.

The traveling table 3 is formed into a saddle shape, and has a stone surface plate 4.
It is installed so that it straddles the . The traveling table 3 also has first and second upper air bearings 5a and 5b at one end in the traveling direction (hereinafter referred to as the X direction).
and first and second side air bearings 6a, 6b, and third and fourth upper air bearings 5 at the other end.
c, 5d and third and fourth side air bearings 6c, 6d
It has First to fourth upper surface bearings 5a, 5
d serves as a guide in the vertical direction (hereinafter referred to as Z direction) of the traveling table 3 with respect to the stone surface plate 4, and
The fourth side air bearings 6a to 6d serve as guides of the traveling table 3 relative to the stone surface plate 4 in a side direction (hereinafter referred to as the Y direction) orthogonal to the X direction.

Further, the traveling table 3 is connected to a drive system having a motor 7, a pulley 8, and a belt 9 connected to the traveling table 3 at both ends and passed around the pulley 8 in the middle. By rotating in the opposite direction, reciprocating scanning is performed via the pulley 8 and belt 9.

A reflection projection optical system 10 is mounted above the traveling table 3 with its feet placed on a stone surface plate 4.

And the first to fourth upper surface air bearings 5a to 5d.
By supplying air to the first to fourth side air bearings 6a to 6d, a small amount of air is applied to these air bearing surfaces and the stone surface plate surface.
Create an air layer of about 20μm. When the motor 7 is driven in this state, the traveling table 3 reciprocates in the X direction.

Below the mask 2, there is an exposure light source and an exposure optical system (not shown), which are fixed to a stone surface plate 4.

A light beam 11 from the light source passes through the mask 2 and passes through the reflection projection optical system 10 to form an image of the mask pattern on the surface of the wafer 1.

The reflection projection optical system 10 is composed of a concave mirror, a convex mirror, and a mirror (not shown), and reduces aberrations by 1:1.
An arc-shaped slit is used to form an image.

Therefore, in order to print a mask pattern over the entire area of the wafer 1, it is necessary to scan the traveling table 3, and the straightness of the traveling table 3 during printing of this mask pattern becomes a problem.

Now, considering the Z direction and Y direction of the traveling table 3, the Z direction is related to the depth of focus of mask pattern imaging. The flatness of the stone surface plate 4 is about 1 μm, whereas the depth of focus of the reflective projection mask aligner is ±5 μm, so the straightness of travel in the Z direction is a negligible value. The problem here is the movement in the Y direction that occurs when the traveling table 3 is scanned in the X direction. For example, to print a 2 μm pattern, the traveling straightness of the traveling table 3 is required to be about 0.2 μm, but as the pattern width becomes smaller, the straightness must also be kept smaller. However, since the finishing accuracy of the side surface of the stone surface plate 4 is about 1 μm, the traveling table 3 causes undulations while traveling. This causes a problem in that it causes transfer distortion during pattern printing, which has an adverse effect.

An object of the present invention is to provide a straightness correction device that can accurately and easily correct the straightness of a traveling table in the Y direction, which requires high-precision straightness as described above.

A feature of the present invention is that the surface plate is guided by side hydrostatic fluid bearings provided on both sides and below the plurality of locations set at least at intervals in the running direction, and the surface plate is driven by the power from the drive source. In a straightness correction device for a traveling table that travels straight on the traveling table, the traveling table is arranged close to each side hydrostatic fluid bearing at a predetermined interval in correspondence with the side hydrostatic fluid bearings at a plurality of locations in the traveling direction; Measurement reference blocks are installed at multiple positions on the side of the traveling table in a direction perpendicular to the traveling direction of the table, and a plurality of capacitance type A non-contact minute displacement meter is fixedly installed on a surface plate, and a fluid pressure servo valve that supplies fluid to a hydrostatic fluid bearing on each side is connected, and a set value corresponding to a preset reference displacement amount and each of the non-contact A comparator that determines a control amount by comparing the measured value of a minute displacement meter, a compensation circuit that removes fluctuation errors in the output signal of the comparator, and a servo amplifier that amplifies the output signal of the compensation circuit. providing a servo circuit for outputting, connecting each servo circuit to the fluid pressure servo valve on the non-contact minute displacement meter side, and supplying fluid pressure to the side hydrostatic fluid bearing through the fluid servo valve based on the control signal; The present invention is constructed so that the straightness of the straight table can be corrected so that the amount of displacement at a plurality of locations on the travel table matches each of the set values, and with this configuration, the above object can be reliably achieved. It was made.

Hereinafter, the present invention will be explained based on the drawings.

FIGS. 4 and 5 show an embodiment of the present invention.

In FIG. 4, parts that are the same as or have the same functions as those shown in FIG. 1 are designated by the same reference numerals, and further explanation thereof will be omitted.

In FIGS. 4 and 5, the traveling table 3
First and second measurement reference blocks 12 are arranged at one side in the Y direction perpendicular to the X direction of the block, with an interval in the X direction.
a, 12b are attached.

Further, a first side air bearing 6a of the pair of first and second side air bearings 6a and 6b is located corresponding to the first measurement reference block 12a.
A displacement meter 13a is installed, and a second displacement meter 13a is installed at a position corresponding to the second measurement reference block 12b and close to the third side air bearing 6c of the set of third and fourth side air bearings 6c and 6d. A displacement meter 13b is installed. The first and second displacement gauges 13a, 13b
For example, a capacitive type non-contact minute displacement meter is used, and such a capacitive type detects minute displacement of an object as a change in capacitance, converts it into an electrical quantity, and calculates the amount of displacement. 0.1μm
The following minute displacement measurements are possible.

The first to fourth side air bearings 6a to 6d are provided with first to fourth air servo valves 14a to 14a, respectively.
14d is connected, and the first to fourth air servo valves 14a to 14d are connected to the accumulator 15.

On the other hand, first and second servo circuits 16a and 16b are provided corresponding to the first and second displacement meters 13a and 13b. First and second servo circuits 16
As shown in FIG. 5, a and 16b are configured to include a comparator 17, a compensation circuit 18, and a servo amplifier 19. The set value and the measured value of the displacement amount of the traveling table 3 in the Y direction from the first and second displacement meters 13a and 13b are sent to the comparators 17 of the first and second servo circuits 16a and 16b. . A controlled amount is determined by each comparator 17 by comparing the set value and the measured value of the displacement amount, and the controlled amount is sent to the compensation circuit 18, where fluctuation errors and the like are removed. The signal is then amplified by a servo amplifier 19, and a control signal is output from the servo amplifier 19.

The first servo circuit 16a includes first and second servo circuits.
pneumatic servo valves 14a and 14b are connected to the second servo circuit 16b, and third and fourth pneumatic servo valves 14c and 14d are connected to the second servo circuit 16b,
The control signal output from the first servo circuit 16a is input to the first and second pneumatic servo valves 14a and 14b, and the control signal output from the second servo circuit 16a is input to the third and fourth pneumatic servo valves. valve 14
c, 14d.

In FIG. 5, the first to fourth servo valves are denoted by 14, the first to fourth side air bearings are denoted by 6, and the first and second displacement meters are denoted by 13.
These are shown as representative examples.

The straightness correction device of the above embodiment operates as follows.

That is, the amount of displacement in the Y direction of one end of the traveling table 3 in the X direction is measured by the first measurement reference block 12a and the first displacement meter 13a,
The measured value is sent to the comparator 17 of the first servo circuit 16a.

At the same time, the second measurement reference block 12a
and the second displacement meter 13a measure the amount of displacement in the Y direction of the other end of the traveling table 3 in the X direction, and the measured value is sent to the comparator 17 of the second servo circuit 16b.

Next, in the first servo circuit 16a, a comparator 17 compares the set value with the measured value sent from the first displacement meter 13a to determine a controlled amount, and the controlled amount is transmitted to the compensation circuit 18 and the servo amplification circuit. Vessel 1
9 and output as a control signal, and the control signal is transmitted to the first and second pneumatic servo valves 14a and 14.
b.

On the other hand, in the second servo circuit 16b, the set value is compared by the comparator 17 with the measured value sent from the second displacement meter 13b to determine a controlled amount, and the controlled amount is transmitted to the compensation circuit 18 and the servo amplification circuit. Vessel 1
9 and output as a control signal, and the control signal is sent to the third and fourth air servo valves 14c and 1.
4d.

Thus, the first and second pneumatic servo valves 14
a, 14d are controlled by a control signal outputted in accordance with the amount of displacement of the corresponding position of the traveling table 3 actually measured by the first displacement meter 13a, and are outputted from the accumulator 15 to the first and second pneumatic servos. Valve 1
4a, 14b to the first and second side air bearings 6
Air pressure corresponding to the amount of displacement of the traveling table 3 is inserted into a and 6b, and one end of the traveling table 3 in the X direction is pressed and adjusted to the left or right in the Y direction according to the displacement direction. , the amount of displacement at this position is corrected to match the set value.

Further, the third and fourth pneumatic servo valves 14
c and 14d are controlled by a control signal that is output corresponding to the amount of displacement of this position of the traveling table 3 actually measured by the second displacement meter 13b. Pneumatic pressure corresponding to the amount of displacement of the traveling table 3 is inserted into the third and fourth side air bearings 6c and 6d through the pneumatic servo valves 14c and 14d, so that the other end of the traveling table 3 in the X direction is in the displacement direction. Accordingly, it is pressed and moved to either the left or right in the Y direction, and the amount of displacement at this position is corrected to match the set value.

As a result, the amount of displacement of the traveling table 3 in the Y direction is accurately corrected within the set range, and the waviness of the traveling table 3 while traveling is eliminated.

The above-described correction of the traveling table 3 is performed both when the traveling table 3 is displaced in parallel to the Y direction and when the traveling table 3 is rotated and twisted in a horizontal plane.

In addition, in the present invention, the bearing that is the guide of the traveling table 3 is not limited to the air bearing shown in the figure, but a general hydrostatic fluid bearing can be used, and the displacement meter may be the capacitance type non-contact minute displacement meter described above. Although it is more effective than the above example, the servo circuit is not limited to this, and the servo circuit is not limited to the configuration shown in the drawings, as long as it can perform the intended function. Further, although the present invention exhibits a preferable effect when applied to the traveling table 3 of a reflection projection mask aligner, it is not limited thereto, and can of course be applied to any traveling table in general that requires highly accurate straightness.

The present invention has the configuration and operation described above,
The amount of displacement of the traveling table is measured at one side in the Y direction at multiple locations in the X direction of the traveling table, the measured value and the set value are compared to determine the control amount, and the fluid pressure is The servo valve is controlled to adjust the fluid pressure supplied to the side hydrostatic fluid bearings installed on both sides of the traveling table at multiple locations in the Since the amount of displacement is made to match, there is an effect that the traveling table can be easily corrected to highly accurate straightness. That is, when a hydrostatic fluid bearing is used as in the traveling table of the present invention, the machining accuracy of the straightness and flatness of the stationary side surface and the movable side surface greatly influences the traveling accuracy of the table.

Ideally, if the precision of the fixed side table and the machining accuracy of the moving table are perfect,
The present invention becomes unnecessary.

However, in reality, when the spacing between the fluid bearings supporting the table is large, as in the case of the stationary surface plate of the present invention, the machining accuracy (straightness) has an influence.

Furthermore, when the distance between the hydrodynamic bearings supporting the table is large as in the traveling table of the present invention, the accuracy of lateral parallel deviation, yawing, etc. will be affected.

Therefore, the relative machining accuracy (straightness) between the surface plate and the table is limited to a few μm/1000 mm, and it is impossible to achieve submicron precision with the method of driving the stage using the surface plate alone. It is possible.

Therefore, the present invention installs a plurality of measurement reference blocks that are positioned in advance in parallel to the running direction of the table at positions close to the hydrostatic fluid bearings on the side surface of the table, and A plurality of capacitance-type non-contact micro-displacement meters were installed at positions approaching the measurement reference block to measure the amount of displacement with respect to the measurement reference block.

Therefore, even if the processing accuracy of the surface plate and table is at the current level, the present invention enables measurement on the order of 0.01 μm using a capacitive non-contact micro-displacement meter at the location corresponding to each fluid bearing. By combining this displacement meter and the fluid pressure control of the fluid bearing, it is possible to correct the table straightness at a submicron level, and when applied to the traveling table of a reflective projection mask aligner, it is possible to eliminate pattern burn-in distortion. There is a small effect that can be achieved.

[Brief explanation of drawings]

FIG. 1 is a plan view of a reflective projection mask aligner equipped with a traveling table, which is the object of the present invention, FIG. 2 is a front view of the same, and FIG. 3 is a longitudinal sectional side view of a portion of the traveling table. 4 and 5 show one embodiment of the present invention, FIG. 4 is a plan view corresponding to FIG. 1, and FIG. 5 is a displacement meter, a servo circuit, an air servo valve, and a side view. FIG. 3 is a block diagram showing the relationship with an air bearing. 3... Traveling table, 4... Stone surface plate, 5a~5
d...First to fourth upper surface air bearings, 6a to 6d...
...first to fourth side air bearings which are side hydrostatic pressure fluid bearings, 7...motor for driving the traveling table, 8...
...Same pulley, 9...Same belt, 12a, 12b...
...first and second measurement standard blocks, 13a, 13
b...First and second displacement gauges, 14a to 14d...
First to fourth pneumatic servo valves, which are fluid pressure servo valves, 15...accumulator, 16a, 16b
...Servo circuit.

Claims (1)

[Claims] 1. Guided by side hydrostatic fluid bearings installed on both sides and below multiple locations at least spaced apart in the running direction, the vehicle travels straight on a surface plate using power from a drive source. In the straightness correction device for a traveling table, the device is arranged close to each side hydrostatic fluid bearing at a predetermined interval in correspondence with the plurality of side hydrostatic fluid bearings in the traveling direction, and is perpendicular to the traveling direction of the traveling table. Measurement reference blocks are installed at multiple positions on the side of a traveling table in the direction of movement, and a plurality of capacitance type non-contact minute displacement meters measure the amount of displacement with respect to the measurement reference blocks in correspondence with the measurement reference blocks. is fixedly installed on a surface plate, a fluid pressure servo valve that supplies fluid to each side hydrostatic fluid bearing is connected, and a set value corresponding to a preset reference displacement amount is measured by each of the non-contact micro displacement meters. A servo circuit that outputs a control signal, comprising a comparator that determines a control amount by comparing the values, a compensation circuit that removes fluctuation errors in the output signal of the comparator, and a servo amplifier that amplifies the output signal of the compensation circuit. and connect each servo circuit to the fluid pressure servo valve on the non-contact minute displacement meter side, and supply fluid pressure to the side hydrostatic fluid bearing through the fluid servo valve based on the control signal, and 1. A straightness correction device for a straight-travel table, characterized in that the straightness of the straight-travel table can be corrected so that the amount of displacement at a location matches each of the set values.