JPH09243324A - Laser interferometer type x-y positioning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase positioning accuracy by restraining the temperature of a gas on a length-measuring optical path in an X-Y positioning device from becoming uneven for reduction of length measurement errors. SOLUTION: This laser interferometer type X-Y positioning device, which has laser interferometers 2, 5 for measuring positions along mutually perpendicular X- and Y-axes and an X-Y stage 1 movable along both the X- and Y-axes, and in which an X-axis moving mirror 4 and a Y-axis moving mirror 7 are fixed on the X-Y stage in such a way that their reflecting surfaces are perpendicular to the length-measuring optical paths 3, 6 of the laser interferometers, is provided with an airflow temperature regulating means 8 by which airflow 9 controlled to a certain temperature is blown from the side of the X-Y stage 1 toward the reflecting surface of the X-axis moving mirror 4 and that of the Y-axis moving mirror 7 at almost equal angles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an XY positioning apparatus, and more particularly to a high precision laser interferometer type XY positioning apparatus used in a semiconductor exposure apparatus, a reticle coordinate measuring apparatus and the like.

[0002]

2. Description of the Related Art In recent years, as the integration density of semiconductor integrated circuits has increased, the demand for forming ultra-fine patterns has increased, and the demand for alignment accuracy between a reticle and a wafer has also become more stringent. For this reason, an XY positioning device for mounting and positioning a wafer is also required to have an accuracy of 0.01 μm or less, and a laser interferometer is used for position measurement.

In the length measurement by a laser interferometer, a change in the refractive index of air on the length measurement optical path causes an error. The refractive index of air changes with temperature, the rate of change being about -1 ppm / ° C. In order to set the length measurement distance to 300 mm and to reduce the length measurement error due to temperature to 0.01 μm or less, it is necessary to reduce the air temperature fluctuation to 0.1 μm.
It must be kept below 03 ° C. For this reason, this type of XY positioning device has conventionally been provided with an air-conditioning means, and the upper surface (Z
The downflow from the direction) or the sideflow from the side surface (the X or Y direction) has been used to reduce the temperature fluctuation of the air on the length-measuring optical path.

The down-flow method is one ideal type, but in a semiconductor exposure apparatus, a reticle coordinate measuring apparatus, etc., a projection lens, a microscope, a focus detector, etc. are arranged close to the top table of an XY positioning apparatus. Therefore, it is difficult to realize by design. Therefore, the side flow method is often used.

FIG. 4 shows a plan view of a conventional example of a side-flow type XY positioning apparatus. In FIG. 4, 1 is an XY stage, 2 is an X direction laser interferometer, 3 is an X direction measuring optical path, 4 is an X direction moving mirror, 5 is a Y direction laser interferometer, 6 is a Y direction measuring optical path, and 7 is Y direction moving mirror, 10 is an air conditioner,
Reference numeral 11 is an airflow. In the above configuration, the temperature of the device is stabilized and the air temperatures of the length-measuring optical paths 3 and 6 are stabilized by the air flow 11 whose temperature is controlled by the air conditioner 10. The direction of the air flow is not particularly conscious, and according to the natural arrangement of the device as shown in Fig. 4,
Usually oriented in the X or Y direction.

[0006]

However, in such an XY positioning device, a heat source such as a motor for XY driving is provided, and the device temperature becomes higher than the air flow. Therefore, temperature irregularity occurs in the air flow (Japanese Patent Laid-Open No. 3-12)
9720, Ishida: O plus E October 1995 issue, pp. 84-89).

FIG. 3 shows the results of the temperature unevenness of the air flow obtained by simulation. In FIG. 3, the moving mirror is integrated with the XY stage 1 for simplification of calculation,
Reference numeral 4a is an X-direction moving mirror surface, and 7a is a Y-direction moving mirror surface.
The calculation conditions are a flow velocity of the blown air flow 11 of 0.5 m / s, a temperature of 0 ° C., and a temperature of the XY stage 1 of 1 ° C. As a result, the isotherms of 0.1 ° C and 0.3 ° C are shown.

As can be seen from FIG. 3, the X-direction moving mirror surface 4
The isotherm of the air flow in the vicinity of a is close to and parallel to the surface 4a, but the isotherm of the air flow in the vicinity of the Y-direction moving mirror surface 7a moves away from the surface 7a and becomes uneven as it goes downstream. That is, the temperature boundary layer for the surface 4a is thin and uniform, but the temperature boundary layer for the surface 7a is thick and non-uniform. This is because the X-direction moving mirror surface 4a is always hit by an airflow of a constant temperature, but becomes a parallel flow to the Y-direction moving mirror surface 7a, and a low-speed velocity boundary layer is formed in which the thickness grows toward the downstream side. This is because.

When the temperature of the air flow is uneven, a measurement error occurs. In the case of FIG. 3, since the temperature of the airflow in the vicinity of the Y-direction moving mirror surface 7a is non-uniform, the temperature distribution on the Y-direction length measuring optical path 6 changes depending on the position of the XY stage 1 in the X-direction. Measurement error occurs.

In view of the problems of the above-mentioned conventional example, an object of the present invention is to suppress the temperature unevenness of the gas on the length measuring optical path, reduce the length measuring error, and improve the positioning accuracy in the laser interferometer type XY positioning apparatus. Is to raise.

[0011]

In order to achieve the above-mentioned object, the present invention provides an air flow controlled to a constant temperature to a reflecting surface of an X-direction moving mirror and a reflecting surface of a Y-direction moving mirror. It is characterized in that it is provided with airflow temperature control means for blowing air from the side of the XY stage at equal angles.

[0012]

According to the present invention, an airflow of a constant temperature is constantly applied to the movable mirror surface in both the XY directions, the temperature boundary layer becomes thin and uniform, and the temperature unevenness of the airflow on the length-measuring optical path is suppressed. The long error is reduced and the positioning accuracy is improved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of an XY positioning device according to an embodiment of the present invention. In FIG. 1, 1 is an XY stage movable in the XY directions, 2 is an X-direction laser interferometer for measuring the position in the X-direction, 3 is an X-direction measuring optical path, and 4 is an X-direction fixed to the XY stage 1. A movable mirror, 5 is a Y-direction laser interferometer for measuring the position in the Y-direction, 6 is a Y-direction length measuring optical path, and 7 is an X-axis.
The Y-direction moving mirror 8 fixed to the Y-stage 1 is arranged so that the airflow controlled to a constant temperature is at substantially the same angle with respect to the reflecting surface of the X-direction moving mirror 4 and the reflecting surface of the Y-direction moving mirror 7. The airflow temperature adjusting means 9 to be blown in is an airflow blown out from the airflow temperature adjusting means 8.

In the apparatus shown in FIG. 1, light emitted from a laser interferometer light source (not shown) is introduced into the X-direction laser interferometer 2 and the Y-direction laser interferometer 5. The light introduced into the X-direction laser interferometer 2 is reflected by the laser interferometer 2 by a beam splitter (not shown) in the laser interferometer 2.
It is divided into light directed to a fixed mirror (not shown) inside and light directed to the X-direction moving mirror 4. The light directed to the X-direction moving mirror 4 is
The light passes through the X-direction length measuring optical path 3 and is incident on the X-direction moving mirror 4 fixed to the XY stage 1. The light reflected here returns again to the beam splitter in the laser interferometer 2 through the X-direction length measurement optical path 3, and is superimposed on the light reflected by the fixed mirror. By detecting the change in the interference of light at this time, X
Measure the distance traveled in the direction. The movement distance in the Y direction is also measured in the same manner as in the X direction. The moving distance information measured in this way is fed back to an XY driving device (not shown) to control the positioning of the XY stage.

By the way, in the above-mentioned structure, the airflow temperature controlled by the airflow temperature adjusting means 8 makes the airflow controlled at a constant temperature substantially equal to the reflecting surface of the X-direction moving mirror 4 and the reflecting surface of the Y-direction moving mirror 7. Then, it is blown in. FIG. 2 shows the result of the temperature distribution of the airflow obtained by simulation. In FIG. 2, the moving mirror is XY for simplification of calculation.
It is integrated with the stage 1, 4a is a moving mirror surface in the X direction,
Reference numeral 7a is a Y-direction moving mirror surface. The calculation conditions are a flow velocity of the blowing airflow 9 of 0.5 m / s, a temperature of 0 ° C., and a temperature of the XY stage 1 of 1 ° C. As a result, the isotherms of 0.1 ° C and 0.3 ° C are shown.

As can be seen from FIG. 2, the X-direction moving mirror surface 4
Both the airflow near a and the airflow near the Y-direction moving mirror surface 7a have a thin and uniform temperature boundary layer. This is because both the X-direction moving mirror surface 4a and the Y-direction moving mirror surface 7a are constantly exposed to the airflow having a constant temperature. As a result, the temperature unevenness of the airflow on the length-measuring optical path is suppressed for both XY, the length-measuring error is reduced regardless of the position of the XY stage, and the positioning accuracy is improved.

In this embodiment, as shown in FIG.
The airflow 9 is blown out in parallel to the XY plane, but it is not always necessary to be in parallel, and the airflow temperature adjusting means 8 is inclined, or the louver or partition plate has a Z component to make it slightly downflow. It is also possible. This method is effective when the heat source is located below. The blowing angle (depression angle) with respect to the XY stage 1 in the case of downflow is such that the airflow 9 having the constant temperature is always supplied to the entire length measurement optical paths 3 and 6 without being blocked by the projection lens or the microscope. It can be arbitrarily set within the range.

[0018]

As described above, according to the present invention,
The airflow controlled to a constant temperature is applied to the reflecting surface of the X-direction moving mirror and the reflecting surface of the Y-direction moving mirror at substantially the same angle X
By providing the airflow temperature control means that blows in from the side of the Y stage, the airflow of a constant temperature is constantly applied to the moving mirror surfaces in both XY directions, the temperature boundary layer becomes thin and uniform, and both XY of the airflow on the length measurement optical path. Temperature unevenness can be suppressed. Therefore, the length measurement error can be reduced regardless of the position of the XY stage, and the positioning accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of an XY positioning device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a result of air temperature distribution simulation in the apparatus of FIG.

FIG. 3 is a diagram showing an air temperature distribution simulation result for the conventional example of FIG.

FIG. 4 is a plan view of a conventional XY positioning device.

[Explanation of symbols]

1: XY stage, 2: X direction laser interferometer, 3: X direction measuring optical path, 4: X direction moving mirror, 5: Y direction laser interferometer, 6: Y direction measuring optical path, 7: Y direction moving mirror , 8: airflow temperature control means, 9: blown airflow.

Claims (2)

[Claims] 1. A laser interferometer for measuring positions in an X direction and a Y direction which are perpendicular to each other, and an X movable in the X and Y directions.
A laser interferometer having a Y stage, the X direction moving mirror and the Y direction moving mirror being fixedly mounted on the XY stage such that their reflection surfaces are perpendicular to the length measurement optical path of the laser interferometer. A XY positioning device of a system, wherein an air flow controlled to a constant temperature is applied to the side of the XY stage at substantially the same angle with respect to the reflecting surface of the X-direction moving mirror and the reflecting surface of the Y-direction moving mirror. An XY positioning device of a laser interferometer system, characterized in that it is provided with an air flow temperature adjusting means for blowing from the air. 2. The XY positioning device according to claim 1, wherein the airflow temperature adjusting means blows the airflow slightly downward on a moving surface of the XY stage.