JPH06260393A - Positioning device - Google Patents

Abstract

PURPOSE:To simultaneously use an optical focal point detector to control the height and the amount of inclination with high precision, by performing the length measuring of the height with a laser length measuring machine from the vertical direction of a substrate to be processed. CONSTITUTION:A top table 10 provided with a wafer 2 and a plane mirror 9 is moved upward and downward by a coarse Z-stage 13. The absolute height in the Z-direction is measured in a Z laser length measuring system 17 using the plane mirror 9. An optical focal position detector first causes a measuring light 21 to be reflected on the plane mirror 9, and calculates a reference phase by an interference fringe signal 25. Then, the measuring light 21 is reflected by a wafer 2 to perform a control for correcting the height in the Z-direction and the target value by the phase difference between the reference phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an electron beam drawing apparatus used in a lithographic process for manufacturing a semiconductor element, and particularly to placing a substrate such as a wafer and moving it two-dimensionally. The present invention relates to a positioning device having a mechanism for inclining with respect to a predetermined plane and requiring particularly high positioning accuracy.

[0002]

2. Description of the Related Art Reduction projection exposure apparatuses, so-called steppers, are currently the mainstream in the photography process of semiconductor integrated circuits. This device exposes a pattern formed on a reticle, which is an original plate of a photomask, onto a photoresist layer on a wafer through a projection lens,
Since a single exposure field is smaller than the wafer size, the stage on which the wafer is placed is moved two-dimensionally and exposure is performed by the step-and-repeat method. Conventionally, in this type of apparatus, an autofocus mechanism that detects focus at the exposure position of the wafer and controls the Z position (vertical direction) in the optical axis direction of the projection optical system is essential.
In recent years, the depth of focus has become shallow due to the high resolution of the projection lens, and resolution and line width uniformity within the exposure area due to unevenness and inclination of the wafer surface have become a problem. Therefore, a mechanism (leveling mechanism) for detecting and controlling the horizontal position of the wafer for each exposure region has been proposed. However, conventionally, as described in Japanese Patent Application No. 2-14818, not only an optical focus position detector but also an air micrometer type gab detector is used together.

[0003]

The optical focus position detector according to the conventional example described above has a short stroke capable of detecting height of 10 .mu.m and cannot absorb the unevenness of the wafer thickness of 50 .mu.m. Therefore, the wafer is moved to the positive focus of the lens on the Z stage with the air micrometer type detector, and from there the optical focus position detector is used.
Height and slope were measured. The air-micrometer type detector has a function to detect the wafer inclination, so that a gas with a constant pressure is jetted from at least three minute nozzles onto the wafer surface, and the back pressure is detected to detect the back pressure between each nozzle and the wafer surface. Since the height of the wafer surface is detected by averaging the intervals, the gap between the lower surface of the nozzle and the wafer surface can be set to only 60 μm, and if a large foreign matter is mixed in, the wafer surface may be damaged. Furthermore, the work area is small and maintenance is difficult, and the air-micrometer type detector has a large system, which occupies a large area and requires a long adjustment time. Further, the height position detection error occurred due to the fluctuation of the air source pressure. It is an object of the present invention to provide a positioning device that can downsize the system and detect and position the wafer surface height and inclination with high accuracy.

[0004]

In order to achieve the above object, in the present invention, the air micrometer type detector is abolished, and the Z laser length measuring device measures the normal focus height while moving the Z stage. In addition, the horizontal position of the wafer is detected and controlled by the optical focus detector in the exposure area.

[0005]

After the wafer is fixed to the wafer chuck, the normal focus height is detected by the laser length measuring device while moving the Z stage, and then the height is positioned. Next, the reference surface detected by the laser length measuring device is measured by the optical focus detector, and the result is used as the height reference. Next, the wafer surface is detected by an optical focus detector, the difference from the reference surface is added to the height measurement value, and feedback control is performed to detect the wafer surface height and tilt with high accuracy. , Can be positioned.

[0006]

EXAMPLES Examples of the present invention will be described below with reference to FIGS.
It will be explained based on.

FIG. 1 is a schematic diagram showing an example of the configuration of a projection exposure apparatus which is a countermeasure for applying the present invention. In the projection exposure apparatus shown in FIG. 1, the exposure light emitted from the exposure illumination system 6 is projected onto the fixed wafer on the stage 1 through the pattern of the reticle 5 and the reduction lens 7 to transfer the pattern. When performing this pattern transfer, the stage 1
Is measured by the laser measuring system 4 with an accuracy of 0.008 μm, repeated at a certain pitch, moved by the stage drive mechanism 3 such as a servomotor, and positioned with an accuracy of ± 0.02 μm.

FIG. 2 is a conceptual diagram showing an embodiment. Wafer chuck 8 for fixing the wafer 2 by vacuum suction
And the top table 10 provided with the plane mirror 9 adjusted to have the same height and inclination as the wafer 2 includes the rough X stage 1
A coarse Z stage 13 composed of a 1/50 taper M hook between the 1 and the fine movement frame 12 is rotated up and down by rotating the DC motor 14 and moving it with the feed screw 15. This coarse Z stage 13 has a height direction accuracy of ± 0.0
An origin sensor 16 such as a magnet sensor having a precision of 2 μm is installed to serve as an origin in the Z direction. The absolute height in the Z direction is
The measurement is performed by a Z laser length measuring system 17 installed beside the reduction lens 7, and control is performed through a coarse Z controller 18. In the optical focus detector, the laser emitted from the laser 18 is split into a reference light 20 and a measurement light 21 by a prism 19, reflected by two mirrors 22, and then condensed by a lens 23 to be collected by the CCD 2
Put in 4. The CCD 24 outputs the interference fringe signal 25,
The maximum position 27 of the spectrum is detected by the FFT 26, and the inclination and height calculation 28 is performed. As for the target value of the inclination, the fine Z controller 29 drives three fine Z piezos 30 installed on the fine movement frame 12, the movement amount is measured by the MGS (magnet sensor) 31, and the inclination is controlled. .

FIG. 3 is a control block diagram of the height control method. With respect to the target value 32 of the height, the distance from the Z laser length measuring system 17 to the plane mirror 9 becomes the Z laser current value 35, and the measurement light 21 of the optical focus detector based on this value 35.
Is reflected by the plane mirror 9, and the interference fringe signal 25 at that time is reflected.
The reference phase is calculated from this. Next, the measurement light 21 of the optical focus detector is reflected on the wafer 2, the phase difference 38 from the reference phase is put in the DAC 33, the DC motor 14 is rotated through the PID control 34, and the coarse Z stage is set by the feed screw 15. By moving 12 and repeating it until the height target value 32 is reached, highly accurate wafer surface height positioning can be performed.

[0010]

According to the present invention, the air-micrometer type detector can be eliminated, errors due to fluctuations in the original pressure of the air can be eliminated, and the wafer surface height and tilt can be accurately positioned. There is. In addition, the work area on the wafer surface is expanded and maintenance becomes easier.
Further, by eliminating the air-micrometer unit, the area occupied by the device can be reduced, and the adjustment time of the device can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a configuration example of a projection exposure apparatus to which the present invention is applied.

FIG. 2 is a conceptual diagram showing an embodiment of the present invention.

FIG. 3 is a control block diagram of the present invention.

[Explanation of symbols]

1 ... Stage, 2 ... Wafer, 3 ... Servo motor (stage drive mechanism), 4 ... Laser length measurement system, 5 ... Reticle,
6 ... Exposure illumination system, 7 ... Reduction lens, 8 ... Wafer chuck, 9 ... Planar mirror, 10 ... Top table, 11 ... Coarse X stage, 12 ... Fine movement frame, 13 ... Coarse Z stage, 14
... DC motor, 15 ... Feed screw, 16 ... Origin sensor, 1
7 ... Z laser length measuring system, 18 ... Coarse Z controller, 19 ...
Prism, 20 ... Reference light, 21 ... Measuring light, 22 ... Mirror, 23 ... Lens, 24 ... CCD, 25 ... Interference fringe signal,
26 ... FFT, 27 ... Spectrum maximum position detection, 28
... Tilt, height calculation, 29 ... Fine Z controller, 30 ... Fine Z piezo, 31 ... Magnet sensor, 32 ... Height target value, 3
3 ... DAC, 34 ... PID control, 35 ... Z laser present value, 36 ... Reference phase calculation on plane mirror, 37 ... Phase difference calculation on wafer, 38 ... Phase difference.

Claims (2)

[Claims] 1. An X, Y stage for holding a substrate to be processed and moving the substrate two-dimensionally within a predetermined reference plane, and the X, Y stage.
A Z stage movable in a direction substantially perpendicular to the reference plane, and the Z stage
In a device provided with a stage, which is capable of inclining the substrate in an arbitrary direction with respect to the reference plane, and a device for detecting an amount of inclination of the substrate, a laser measurement is performed from a vertical direction of the substrate to be processed. A positioning device characterized by measuring the height with a length gauge. 2. The Z-stage according to claim 1, wherein
Provide a plane mirror with the same height and inclination as the substrate to be processed,
In a tilt amount detecting device, a positioning device comprising means for comparing and controlling the flat mirror and a substrate to be processed.