JPH10242040A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable controlling substrate carrying speed and prealignment pin driving speed, by detecting the substrate thickness, on the basis of a least one out of outputs of a means measuring the distance between a sensitized substrate and a mask in the optical axis direction, and a means moving the sensitized substrate to an image position. SOLUTION: In the state that a sensitized substrate 6 is not held, the distance in the optical axis direction of a projection optical system 7 between the surface of a substrate stage 4 and a mask 5 is measured with autofocus sensors 10A-10D. When the sensitized substrate 6 is mounted on the substrate stage 4, the distance in the optical axis direction of the projection optical system 7 between the surface of the sensitized substrate 6 and the mask 5 is again measured with the autofocus sensors 10A-10D. In a plate carrying speed control part 21 and a prealignment pin speed control part 22, a distance as the difference between the interval corresponding to the stored distance between the substrate stage and the mask and the interval corresponding to the distance between the sensitized substrate and the mask is obtained, and the thickness of the sensitized substrate 6 is obtained on the basis of the obtained distance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for manufacturing a semiconductor device or a liquid crystal display, and more particularly to a projection exposure apparatus having an automatic focus adjusting function.

[0002]

2. Description of the Related Art A projection exposure apparatus irradiates illumination light onto a mask while holding the mask and a photosensitive substrate so as to face each other via a projection optical system, and projects a pattern image of the mask by the illumination light passing through the mask. An image is projected on a photosensitive substrate via an optical system to expose the photosensitive substrate.

Normally, this type of projection exposure apparatus detects the positions of the mask and the photosensitive surface of the photosensitive substrate individually in the optical axis direction (focal direction) of the projection optical system, and based on the detection results, detects the position of the photosensitive substrate. A function of performing a predetermined correction operation (automatic focus adjustment function) is provided so that the photosensitive surface is located at the focal position of the projection optical system, whereby stable imaging performance can be obtained. .

[0004]

A glass substrate used in a liquid crystal display device is an example of a photosensitive substrate on which a pattern image of a mask is exposed by such a projection exposure apparatus.
In recent years, liquid crystal display panels have become larger and thinner, and accordingly, glass substrates exposed by a projection exposure apparatus have also become larger and thinner.
It has a substrate area of about 00 mm and a substrate thickness of 1.1 mm
Thickness or 0.7 mm thick is often used.
In order to transport a glass substrate whose thickness is extremely thin compared to the substrate area and place the glass substrate on the substrate mounting surface and perform a predetermined exposure operation with stable exposure accuracy, the thickness of the glass substrate is required. It is necessary to control the projection exposure apparatus accordingly.

For example, it is necessary to make the substrate transfer speed and the pre-alignment pin drive speed different between a thin substrate and a thick substrate. If the substrate transfer speed or the pre-alignment pin drive speed is too high for a thin substrate, the impact on the substrate may increase or vibration may occur, resulting in inability to obtain stable exposure accuracy. is there.
Therefore, conventionally, when a glass substrate having a different substrate thickness is transported and pre-aligned, a parameter for changing the substrate transport speed or the pre-alignment pin driving speed must be changed for each substrate thickness. It took time and effort.

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus capable of detecting the thickness of a substrate and controlling the speed of the substrate transfer speed and the pre-alignment / pin driving speed.

[0007]

FIG. 1 shows an embodiment of the present invention.
The object is to provide a mask stage (3) that moves while holding a mask (5) on which a pattern is drawn, and a projection optical system (7) that projects an image of the pattern onto a photosensitive substrate (6). And a substrate stage (4) holding the photosensitive substrate (6) and moving in synchronization with the mask stage (3)
Measuring means (10A to 10D) for measuring the distance between the photosensitive substrate (6) and the mask (5) in the optical axis direction of the projection optical system (7); the mask stage (3) and the substrate stage (4) And a moving means (20) for moving at least one of them in the optical axis direction of the projection optical system (7) to move the photosensitive substrate (6) to the image forming position of the projection optical system (7). In the device (1), the measuring means (10A ~
10D) and detecting means (21, 2) for detecting the thickness of the substrate based on the output of at least one of the moving means (20).
This is attained by a projection exposure apparatus characterized by having the above 2).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection exposure apparatus according to one embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a projection exposure apparatus 1 according to the present embodiment. In FIG. 1, a mask stage 3 is disposed inside a first side wall 2A of a carriage 2 having a U-shaped cross section, and a substrate having a leveling stage configuration is provided inside a second side wall 2B of the carriage 2. A stage 4 is provided, and the mask stage 3 and the substrate stage 4 hold the mask 5 and the photosensitive substrate 6 so as to face each other with the projection optical system 7 interposed therebetween.

An opening (not shown) formed in the first side wall 2A, an opening (not shown) of the mask stage 3, and a mask 5 are provided outside the first side wall 2A of the carriage 2. An illumination optical system 8 is provided so as to face the projection optical system 7 in order, and illuminates the mask 5 with illumination light emitted from the illumination optical system 8, and a mask obtained by illumination light passing through the mask 5. The pattern image No. 5 is formed and projected on a photosensitive surface 6A of a photosensitive substrate 6 via a projection optical system 7. The projection optical system 7 of the scanning exposure apparatus 1 according to the present embodiment projects the pattern image of the mask 5 on the photosensitive surface 6A of the photosensitive substrate 6 at the same magnification of the erect image. The carriage 2 can be moved in the longitudinal direction of the carriage 2 indicated by an arrow a with respect to the projection optical system 7 and the illumination optical system 8 by a drive mechanism (not shown).

The scanning exposure apparatus 1 according to the present embodiment
During operation, the mask 5 and the photosensitive substrate 6 move integrally in the direction of the arrow a via the carriage 2 so that the pattern image of the mask 5 is formed and projected on the photosensitive surface 6A of the photosensitive substrate 6 sequentially and partially. Thus, the photosensitive surface 6 of the photosensitive substrate 6
The entire surface of A can be exposed according to the pattern of the mask 5.

The scanning operation of the carriage 2 of the scanning type exposure apparatus 1 requires high accuracy. In order to maintain high scanning accuracy, it is essential that the inclination (tilt) of the photosensitive substrate 6 with respect to the photosensitive surface 6A in the scanning range is always a very small amount. Therefore, in the scanning exposure apparatus 1 according to the present embodiment, Four sets of focus sensors 10A to 10D are provided in the projection optical system 7 so that the state of the photosensitive surface 6A of the photosensitive substrate 6 can be detected from various angles.

In this case, each of the focus sensors 10A-1A
2D, as shown in FIG. 2, respectively, first and second light beams L1A and L1B emitted from first and second light sources (eg, LEDs) 11A and 11B through slits (not shown), respectively. To form a predetermined beam width, which is focused on the mask 5 or the photosensitive surface 6A of the photosensitive substrate 6, and the first reflected light L2A obtained by reflecting the first light beam L1A on the mask 5. And the second light beam L
1B is reflected by the photosensitive surface 6A of the photosensitive substrate 6 and the second reflected light L2B is parallel to the light receiving surface 13A of the detector 13 via the corresponding reflecting surfaces 12A and 12B of the prism 12, respectively. It is designed to be introduced and imaged.

As the detector 13, a CCD (Charg) is used.
e Coupled Device) image sensor and MOS (Metal Oxide Semiconductor)
ctor) A light position detector such as a linear image sensor is used, and as described later, the incident positions P1 and P2 of the first and second reflected lights L2A and L2B on the light receiving surface 13A of the detector 13 are determined. , Without being affected by the inclination of the mask 5 and the photosensitive substrate 6.

A first peak PA10 generated from the first reflected light L2A as shown in FIG.
And a second peak PA1 generated in the second reflected light L2B
1 is supplied to the focus control unit 20 shown in FIG.

The focus control unit 20 performs first processing by software processing based on the sensor signal S1 supplied from each of the autofocus sensors 10A to 10D.
And the center C of the first and second peaks PA10 and PA11 from the intersection of the edge of the second peak PA10 and PA11 (FIG. 3) with the slice level SL10 (FIG. 3).
10 and C11, respectively, and based on the calculation result, the distance K between the first and second peaks PA10 and PA11 (corresponding to the distance between the first and second reflected lights L2A and L2B on the detection surface of the detector 13). ) Is detected.

Further, the focus control unit 20 determines the first and second peaks PA10 and PA1 based on the detection result.
Control signal S2 so that the interval K between the two is always at a predetermined value.
(FIG. 1) are sequentially generated and sent to a drive mechanism (not shown) of the substrate stage 4 to move the photosensitive substrate 6 in the optical axis direction of the projection optical system 7 as necessary.

As a result, in the scanning exposure apparatus 1,
At the time of projection exposure, the distance between the mask 5 and the photosensitive surface 6A of the photosensitive substrate 6 can always be kept constant with respect to the mask 5, and the photosensitive surface 6A of the photosensitive substrate 6 is always positioned at the focal position of the projection optical system 7. It can be located at.

As described above, the method of positioning the photosensitive surface of the photosensitive substrate at the focal position of the projection optical system in the projection exposure apparatus according to the present embodiment uses the first and second light beams on the photosensitive surfaces of the mask and the photosensitive substrate, respectively. Irradiating the first and second light beams on the light-receiving surface of the light-receiving element in parallel with the first or second reflected light on the light-receiving surface of the light-receiving element. The distance between the first and second reflected lights is detected based on the output of the light receiving element, and the photosensitive substrate is moved in the optical axis direction of the projection optical system so that the distance always becomes a predetermined value. In this case, the distance between the first and second reflected lights on the light receiving surface of the light receiving element is determined by the distance between the center of the first peak corresponding to the first reflected light output from the optical axis element and the second reflected light. It is calculated as the distance between the center of the corresponding second peak.

Also, as shown in FIG.
0 is connected to a plate transport speed control unit 21 and a pre-alignment / pin speed control unit 22. The focus controller 20 controls the plate transport speed controller 21 and the pre-alignment / pin speed controller 22 as first and second control information for controlling the speeds thereof.
The interval K between the peaks PA10 and PA11 (hereinafter, interval K
). The sensor signal S1 is directly input from the autofocus sensors 10A to 10D to the plate transport speed control unit 21 and the pre-alignment / pin speed control unit 22 without passing through the focus control unit 20, and these speed control units 21 , 22 may be used to calculate the interval K.

The plate transport speed controller 21 and the pre-alignment / pin speed controller 22 detect the thickness of the substrate based on the input interval K, and based on the obtained thickness of the substrate, the substrate transport speed is controlled. Speed and pre-alignment
Control the speed of the pin. The operations of the plate transport speed control unit 21 and the pre-alignment / pin speed control unit 22 will be described with reference to FIGS.

First, the distance between the surface of the substrate stage 4 and the mask 5 in the direction of the optical axis of the projection optical system 7 between the surface of the substrate stage 4 and the mask 5 without holding the photosensitive substrate 6 is determined by the auto-focus sensors 10A to 10D. Measured by The distance between the substrate stage and the mask in a state in which the photosensitive substrate 6 is not held is such that the substrate stage 4 is lowered in preparation for the next photosensitive substrate to be transported and placed on the substrate stage 4. It is longer than the distance between masks.

That is, the auto focus sensors 10A-
The interval K between the first and second peaks PA10 and PA11 in 10D is wider than a predetermined value at the time of exposure. In this state, the paths L1B and L2B of the second light beams emitted from the second light sources 11B of the autofocus sensors 10A to 10D are shown by solid lines in FIG. Second light source 11
The second light beam emitted from B is reflected by two reflecting mirrors 16
a, reflected at 16b and reflected at the surface of the substrate stage 4,
The reflected light is reflected by the reflecting mirror 16c, further reflected by the reflecting surface 12B of the prism 12, and enters the detector 13.

On the other hand, the first light beam emitted from the first light source 11A is reflected by the two reflecting mirrors 17a and 17b and reflected by the surface of the mask 5, and the reflected light is reflected by the reflecting mirror 17c.
The light is further reflected by the reflecting surface 12A of the prism 12 and enters the detector 13. In this state, the interval K obtained based on the sensor signal S1 from each of the autofocus sensors 10A to 10D is the focus control unit 2
0 to the plate transport speed control unit 21 and the pre-alignment / pin speed control unit 22 and stored.

Next, when the photosensitive substrate 6 is conveyed and placed on the substrate stage 4, the surface of the photosensitive substrate 6 and the mask 5
And the distance between the photosensitive substrate and the mask, which is the distance in the optical axis direction of the projection optical system 7 between the autofocus sensors 10A to 10A.
Measure according to D. In this state, the second light emitted from the second light source 11B of the autofocus sensors 10A to 10D
The light beam paths L1B and L2B are indicated by two-dot chain lines in FIG. The second light beam emitted from the second light source 11B is reflected by the two reflecting mirrors 16a and 16b and enters the surface of the photosensitive substrate 6, and the reflected light is
The reflected light path is shifted by the thickness of the photosensitive substrate 6 as compared with the case where there is no light.

This reflected light is reflected by the reflecting mirror 16c and further reflected by the reflecting surface 12B of the prism 12, and
3 is incident. The position of the light beam from the second light source at the detector 13 is different from the position of the light source
Is shifted by the thickness of the substrate. In FIG. 2, the shift width of this position is indicated by a distance 15. On the other hand, the position of the first light beam emitted from the first light source 11A on the detector 13 does not change. In this state, the autofocus sensor 10A-
The interval K ′ based on the sensor signal S1 from each of the 10Ds is input to the plate transport speed control unit 21 and the pre-alignment / pin speed control unit 22 via the focus control unit 20 and stored.

The plate transport speed controller 21 and the pre-alignment / pin speed controller 22 determine the distance K corresponding to the stored distance between the substrate stage and the mask and the distance K ′ corresponding to the distance between the photosensitive substrate and the mask. Distance 1 which is the difference
5 is calculated, and the substrate thickness of the photosensitive substrate 6 is obtained based on the calculated value.

The above is the operation common to the plate transport speed control unit 21 and the pre-alignment / pin speed control unit 22. Next, the flow of each process will be described with reference to FIGS. First, the flow of processing of the plate transport speed control unit 21 will be described with reference to FIG. First, in step S1, the thickness of the substrate is calculated from the two intervals K and K 'output from the focus control unit 20 based on the two sensor signals S1 from the detector 13 (focus sensing).

Next, it is determined whether or not the obtained substrate thickness is within a predetermined range (step S2). If the obtained substrate thickness exceeds the predetermined range, an error process is performed and the process ends (step S3). If the substrate thickness is within the predetermined range, it is determined whether the substrate thickness is, for example, 0.7 mm or 1.1 mm (step S4).
In the case of (1), the process proceeds to step S5, and an instruction is made to increase the speed of plate conveyance. If the substrate thickness is 0.7 mm, the process proceeds to step S6, and an instruction is issued to reduce the speed of plate conveyance.

As described above, according to the plate transfer speed control unit 21 according to the present embodiment, during plate transfer, the transfer speed is increased for a thick plate and reduced for a thin plate, so that the plate can be safely transferred. The substrate can be stably transported. For example, in the processing of a substrate in units of one lot, the first substrate whose thickness is not known is transported at a low speed, and the plate transport speed control unit 21 finishes measuring the thickness of the first substrate. Then, the second and subsequent substrates can be transported at an appropriate transport speed.

In particular, by transporting a thin substrate at a low speed, the vibration of the substrate can be suppressed and the substrate can be transported stably. The speed control in step S4 and step S5 in FIG.
The value of the A-converter) may be switched by software, or two-stage (or multi-stage) speed settings may be prepared in advance, and the switch may be switched by software.

Next, the processing flow of the pre-alignment / pin drive speed control unit 22 will be described with reference to FIG. First, in step S10, the thickness of the substrate is calculated from the two intervals K and K 'output from the focus control unit 20 based on the two sensor signals S1 from the detector 13 (focus sensing). Next, it is determined whether or not the obtained substrate thickness is within a predetermined range (step S1).
1). If the obtained substrate thickness exceeds the predetermined range, error processing is performed and the processing is terminated (step S1).
2).

If the substrate thickness is within the predetermined range, it is determined whether the substrate thickness is, for example, 0.7 mm or 1.1 mm (step S13). If the substrate thickness is 1.1 mm, the process proceeds to step S14. Then, a drive command for increasing the drive speed of the pre-alignment pin is issued. If the substrate thickness is 0.7 mm, the process proceeds to step S15, where the pre-alignment
A drive command for lowering the drive speed of the pin is issued.

As described above, according to the pre-alignment pin driving speed control unit 22 according to the present embodiment, the pre-alignment pin pressing speed at the time of pre-alignment is
By increasing the speed for thick substrates and slowing for thin substrates, pre-alignment can be performed reliably and safely without impacting the substrate more than necessary. . Step S1 in FIG.
The speed control in step 4 and step S15 can be performed in the same manner as the control in the plate transport speed control unit 21.

The plate transport speed control unit 21 described above
When the operation of the pre-alignment / pin drive speed control unit 22 is completed, the focus control unit 20 outputs the control signal S
2 and the substrate stage 4 is moved in the optical axis direction of the projection optical system 7 so that the distance between the photosensitive substrate and the mask is a predetermined value (that is, the distance K between the first and second peaks PA10 and PA11 is always constant). (Predetermined value), and preparation for starting exposure is completed.

As described above, according to the projection exposure apparatus of the present embodiment, the sensor signal from the auto-focus sensors 10A to 10D for keeping the distance between the mask 5 and the photosensitive substrate 6 constant is used. The thickness can be measured. Using the measured substrate thickness information, the substrate transport speed can be controlled according to the thickness of the photosensitive substrate being transported, and the speed of the pre-alignment pins can be controlled. , And stable exposure accuracy can be obtained.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above-described embodiment, as means for positioning the photosensitive surface 6A of the photosensitive substrate 6 at the focal position of the projection optical system 7, the substrate stage 4 on which the photosensitive substrate 6 is mounted is moved in the optical axis direction of the projection optical system 7. However, the present invention is not limited to this, and the mask stage 3 on which the mask 5 is placed is moved in the optical axis direction of the projection optical system 7 or the mask 5 and the photosensitive substrate 6 are moved. Of course, it is also possible to move the projection optical system 7 in the optical axis direction.

In the above-described embodiment, the present invention is applied to the control of the substrate transfer speed and the control of the driving speed of the pre-alignment pins. However, the present invention is not limited to this. The present invention can be applied to set the suction force at the time of vacuum suction to an appropriate value according to the thickness of the substrate. In this case, if a thin substrate is suctioned with a high suction force, the suction area is bent,
The problem that the exposure accuracy is reduced can be solved.

[0038]

As described above, according to the present invention, it is possible to realize a projection exposure apparatus capable of judging the substrate thickness and controlling the substrate transfer speed and the pre-alignment / pin drive speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a focus sensor used in the projection exposure apparatus according to one embodiment of the present invention.

FIG. 3 is a diagram showing a waveform of a sensor signal output from a detector.

FIG. 4 is a diagram showing a processing flow in a plate transport speed control unit in the projection exposure apparatus according to one embodiment of the present invention.

FIG. 5 is a diagram showing a flow of processing in a pre-alignment / pin speed control unit in the projection exposure apparatus according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanning exposure apparatus 2 Carriage 3 Mask stage 4 Substrate stage 5 Mask 6 Photosensitive substrate 6A Photosensitive surface 7 Projection optical system 8 Illumination optical system 10A-10D Focus sensor 11A, 11B Light source 13 Detector 13A Light receiving surface 20 Control part C10, C11 Center K distance L1A, L1B Light beam L2A, L2B Reflected light PA11 Peak S1 Sensor signal S2 Control signal W10, W11 Peak width SL10 Slice level SLB Base level

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masamitsu Yanagihara Nikon Corporation 3-2-2 Marunouchi, Chiyoda-ku, Tokyo

Claims (2)

[Claims] 1. A mask stage that moves while holding a mask on which a pattern is drawn, a projection optical system that projects an image of the pattern onto a photosensitive substrate, and a mask stage that holds the photosensitive substrate and synchronizes with the mask stage. A moving substrate stage, measuring means for measuring a distance between the photosensitive substrate and the mask in an optical axis direction of the projection optical system, and at least one of the mask stage and the substrate stage is connected to the projection optical system. In a projection exposure apparatus having a moving unit that moves in the optical axis direction and moves the photosensitive substrate to an image forming position of the projection optical system, based on at least one output of the measuring unit and the moving unit, A projection exposure apparatus comprising a detection unit for detecting the thickness of the substrate. 2. The projection exposure apparatus according to claim 1, wherein the projection optical system is an optical system for erecting an equal-magnification image.