JPH02252228A - Exposure device - Google Patents

Abstract

PURPOSE:To improve exposure precision by a method wherein, when exposure amount reaches a specified value after exposure is started in an adjacent or close contact aligner, a shutter begins to be shut and a discharge lamp is turned OFF. CONSTITUTION:When an exposure starting signal 39 is input to a control circuit 31, a shutter operating signal 32 is turned ON; a shutter 40 begins to open: a mask 21 and a photo detector 10 begin to be irradiated with light. Until the shutter 40 turns to a wholly opened state, the light quantity for the mask 21 and the detector 10 increases, and the output of a shutter close position sensor 41 is inverted from 1 to 0. The output of the detector 10 is converted into a frequency proportional to the luminous intensity by a V/F 15, and delivered to a counter 17. When the count value becomes equal to the set value of an exposure amount setting switch 37, a comparator output 20 turns to 1; the signal 32 turns to a closed state; the shutter 40 begins to close. The comparator output 20 is simultaneously input to a discharge lamp operating apparatus 32, and the discharge lamp 6 is turned OFF. Since the lamp is turned OFF during the closing operation of the shutter 20, the exposure precision is not deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exposure apparatus used in a photolithography process in the manufacturing process of semiconductor devices such as ICs and LSIs. More specifically, an apparatus that uses a projection optical system to project and expose a pattern on an original plate (mask) onto a substrate to be exposed (wafer), or a pattern on the original plate after placing the original plate and the substrate to be exposed in close proximity. This is a device that performs close exposure or contact exposure on the substrate to be exposed, and improves the accuracy of the exposure amount by starting to close the shutter when the specified exposure amount is reached after the start of exposure, and turning off the discharge lamp. Related to exposure equipment.

[Prior Art] Currently, most integrated circuits such as VLSIs, LSIs, and ICs, which are typified by 4-megabit dynamic RAM, are manufactured using reduction projection exposure equipment called steppers. Many of the small-scale semiconductors having the above are manufactured by exposing and transferring a pattern of about 0.8 μm to 1 μm using an exposure device that performs both close exposure and close exposure in close exposure mode.

In these exposure apparatuses, exposure is started by continuously lighting an electric lamp during exposure, guiding the light into an illumination system, and opening a shutter provided within the illumination system. Next, at the same time as the exposure starts, a timer for limiting the exposure time or a light amount integrator called an integrating exposure meter starts integrating the light amount. The prescribed exposure is deemed to have ended when the output value of the light amount integrator reaches the integral value corresponding to the prescribed exposure amount. Then, from the end of exposure, the shutter began to close, and one exposure was completed.

FIG. 3 is a graph for explaining an exposure amount control method of a conventional cumulative exposure method exposure apparatus.

Figure A is a graph showing the mask surface illuminance ■ and shutter opening/closing timing over time, and Figure B is a graph showing the brightness L of the discharge lamp. Here, the discharge lamp is continuously lit at a constant brightness.

In Figure A, one exposure is defined as the time required for the ivy to go from the closed state to the fully open state, 1. , a time t2 during which exposure is continued at a constant mask surface illuminance, and a time t from when the shutter is fully open until it is completely closed.

In a conventional cumulative exposure type exposure apparatus, a signal instructing to open the shutter is output from the apparatus during times t and t2, and a signal instructing to close the shutter is output while time t continues.

[Problem to be solved by the invention] By the way, the integrating exposure meter is operating at times t1 and t.
This is the second period. Even if there is variation in the time from when the shutter closes to when the shutter opens at time t1, the exposure accuracy is not adversely affected because the integrating exposure meter is working. Furthermore, even if the brightness of the discharge lamp changes at times t and t2, the exposure accuracy is not adversely affected because the integrating exposure meter is working in the same way.

However, when the output of the light amount integrator of the integrating exposure meter at the end of time t2 reaches a value corresponding to the specified exposure amount, the device issues a timing signal to close the shutter, and the integrating exposure meter does not operate at the subsequent time t3. , Therefore, time t,
The problem is that if there is variation in the time from opening to closing of the shutter during the continuous process, or if the brightness of the discharge lamp changes and the illuminance I on the mask surface changes, the exposure accuracy will be adversely affected. There was a flash.

Therefore, based on the idea that the time ts is constant at any exposure time and the brightness L of the discharge lamp is constant during the time t3, the exposure amount J4 occurring during the time t3 is
Subtract its (i is mask surface illuminance) from the original exposure amount to determine the exposure amount command value that determines the shutter opening time, or determine the exposure amount at time t and the exposure at time t when the shutter is opened. Assuming that the amounts are equal, a method has been adopted in which the exposure amount %1t3=%it1 is subtracted from the original exposure amount to determine the exposure amount command value that determines the shutter opening time.

However, the time of t varies, and t is jlm or t
If it becomes 3b, the exposure accuracy will still be adversely affected. In particular, time 1. Since and t are considered to be approximately the same time, one exposure amount (t2+t,)i
The ratio t3/ of time t3 and time t2+t3 constituting
The larger (t2 +tl) is, the more it adversely affects exposure accuracy.

In the case of reduction projection exposure equipment called steppers used when manufacturing 4-megabit dynamometers, short-time exposures of about 80 m5ec are often performed in order to improve the throughput of divided exposure. Coupled with the line width of about 0.8 μm, if the fluctuation rate of the exposure amount exceeds 1.5%, many defective products will be produced, and there is a desire to improve the exposure accuracy.

Similarly, in the case of ultra-high frequency transistors manufactured using the contact exposure method, a similar fine pattern is exposed, and therefore, it is desired to improve the exposure accuracy.

In view of the above-mentioned problems with the conventional type, the present invention aims to accurately expose a fine pattern without deteriorating the exposure accuracy even if there are fluctuations in the closing time of the shutter or fluctuations in the brightness of the discharge lamp. The purpose is to provide an exposure apparatus that can perform

[Means and operations for solving the problem] In order to achieve the above object, the present invention turns off the discharge lamp at the same time as the shutter starts to close after the end of exposure, and closes the shutter and closes the original (
The device is equipped with a control means for relighting the discharge lamp after the surface illuminance of the mask becomes zero.

As a result, whether the timer detects the elapse of a predetermined time and ends the exposure, or the integrating exposure meter detects the specified exposure amount and ends the exposure, the surface of the original (mask) is Since the illuminance becomes zero, the exposure accuracy will not deteriorate due to subsequent fluctuations in the closing time of the shutter or fluctuations in the brightness of the discharge lamp.

In addition, by relighting the discharge lamp within the time (approximately 10 m5ec) when the discharge lamp can maintain a quasi-excited state, that is, a state where the temperature at the pole of the discharge lamp is high and the number of cations and electrons in the plasma near the pole is large. It is possible to continue exposure with high precision without causing the poles to wear out.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of an exposure apparatus according to an embodiment of the present invention. FIG. 2A is a graph showing the mask surface illuminance I and shutter opening/closing timing over time in the exposure apparatus of this embodiment, and FIG. 3A is a graph of the conventional example.
corresponds to FIG. 2B is a graph showing the brightness L of the discharge lamp, and corresponds to FIG. 3B. Here, the brightness goes back and forth between zero and a predetermined value, and continues at a constant brightness L except when it is zero.

First, with reference to FIG. 2, the features of the exposure apparatus of this embodiment will be explained.

In FIG. 2A, one exposure consists of a time T for the shutter to go from a closed state to a fully open state, and a time T2 for controlling the exposure at a constant mask surface illuminance.

These times T I and T 2 are as shown in FIG. 3 A, which shows the conventional example.
This corresponds to times tl and t2 in , respectively.

In this embodiment, during time TI+T2, the exposure device outputs a signal instructing to open the shutter, which is different from 1. in the conventional example. This is the same as when the exposure device outputs a signal instructing to open the shutter during +12. Then, the integrating exposure meter is opened for a time T, 72t. Therefore, time T
Even if there is variation in the time from closing to opening of the shutter in I, the exposure accuracy will not be adversely affected because the integrating exposure meter is working. Further, even if the brightness of the discharge lamp changes at times T and T2, exposure accuracy is similarly not adversely affected.

In this embodiment, unlike the conventional example, a command value that determines the shutter open time (TI+72) corresponding to the original exposure amount is given as is. Then, at the end of time T2, when the output of the light amount integrator of the integrating exposure meter reaches a value corresponding to the prescribed exposure amount, a shutter closing timing signal is issued and the shutter starts to close. At the same time, the output of the lighting device that lights the discharge lamp becomes zero, causing the discharge lamp to go out. Therefore, time T corresponds to time t in the conventional example.

However, in the apparatus of the disclosed embodiment at time T, the discharge lamp is off, and the mask surface illuminance is zero.

Next, with reference to FIG. 1, a schematic configuration of the exposure apparatus of this embodiment will be explained. The exposure apparatus of this embodiment is an exposure apparatus that performs both close exposure and contact exposure.

In the figure, 1 represents an illumination system. The light emitted from the discharge lamp 6 is focused by an elliptical mirror 2, reflected by a cold mirror 3, and further passes through a concave lens 4 and a fly's eye lens 5 to reach a mirror 7. The light is then reflected by the mirror 7, passes through the collimator lens 8, and is imaged onto the mask 21. A shutter 4o is provided between the concave lens 4 and the fly's eye lens 5.
is arranged to open and close the light irradiated onto the mask 21 surface.

A portion of the light incident on the mirror 7 passes through the mirror 7 and reaches the photodetector 10 via the integrated exposure optical system 9.

The light incident on this photodetector 10 is
It opens and closes in the same way as the light irradiated onto the mask surface.

The mask 21 is supported and fixed by a mask stage 23, and the wafer 22 is supported and fixed by a wafer chuck 25. The wafer chuck 25 passes through the mechanism 24 to the wafer stage 26
Fixed.

The wafers 21 and 22 are placed close to each other or in close contact with each other and exposed. In the case of a projection exposure type exposure apparatus, it can be considered that one new projection lens is inserted between the mask 21 and the wafer 22.

Next, the operation of the exposure apparatus of this embodiment will be explained along the exposure sequence.

First, the discharge lamp 6 is lit in advance by the discharge lamp lighting device 33 and continues to be lit continuously. 34 and 35 are a negative cord and a positive cord, respectively, which supply power to the discharge lamp 6.

Before starting exposure, the shutter 40 is controlled by the shutter control circuit 3.
Closed based on instructions from 1. Therefore, no light enters the photodetector 10, the output 12 of the preamplifier 11 that amplifies the photocurrent of the photodetector 10 is zero, and the output 14 of the subsequent amplifier 13 is also zero.

Therefore, the output 16 of the VF converter 15 is zero, and since the reset signal 38 has been inputted to the counter 17 from the shutter control circuit 31 in advance, the counter 1
The output 18 of 7 continues to be at zero.

The counter output 18 and the setting value 36 (≠0) of the exposure amount setting switch 37 are input to the comparator 19, and the comparison output 20 with the counter output 18 is in a zero state. Since the shutter 40 is closed, the output 42 of the shutter closed position sensor 41 continues to be in the state "1".

The shutter control circuit 31 that receives the comparator output 20 continues to close the shutter 40, and the discharge lamp lighting device 33
keeps the discharge lamp 6 lit.

Next, when an exposure start signal 39 is inputted to the shutter control circuit 31 from a control computer (not shown) of the exposure apparatus, the shutter opening/closing signal 32 becomes open and the shutter 40
begins to open, and light begins to hit the mask 21 and photodetector 10. The amount of light hitting the mask 21 and photodetector 10 increases until the shutter 40 is fully open, and eventually the output 42 of the shutter closed position sensor 41 is reversed from 1' to ON.

When light hits the photodetector 10, the photocurrent is amplified by a preamplifier 11 and further amplified by an amplifier 13.

Output 14 of amplifier 13 is input to VF converter 15. The output 14 is subjected to voltage-frequency conversion by a VF converter 15, and the frequency of the output 16 becomes proportional to the illuminance of the mask 21 and is input to the counter 17. and,
Counter output 18 and exposure setting switch 37 setting value 3
The shutter 40- remains open until the values of 6 become equal. A photodetector 10, a preamplifier 111, an amplifier 13, a V-F:7 amplifier 15, a counter 17, a comparator 19, and an exposure amount setting switch 37 constitute an integrating exposure meter.

Counter output 18 and exposure setting switch 37 setting value 3
6 match, the comparator output 20 is inverted and becomes “1”
The shutter opening/closing signal 32 of the shutter control circuit 31 is
is reversed to the closed state, and the shutter 40 starts to close from the fully open state.

At this time, the comparator output 20 simultaneously outputs the discharge lamp lighting device 3.
Since the comparator output 20 is inverted, the discharge lamp lighting device 33 stops supplying power to the minus cord 34 and the plus cord 35, turns off the discharge lamp 6, and completes one exposure. Next, when the shutter 40 returns to the closed state, the output 42 of the shutter closed position sensor 41 is reversed from 0'' to 1'', and the output signal 42 is transmitted to the discharge lamp lighting device 3.
3 will be done manually. The discharge lamp lighting device 33 outputs the negative code 34 and the positive code 35 at the timing of the reversal.
During this time, a high voltage for triggering is applied, and the discharge lamp 6 is lit again.

The time from turning off the discharge lamp to turning it on again is equal to the time from opening to closing of the shutter 40, and this time is 7 to 10 m5ec, so the high voltage for the trigger at the time of relighting is normally applied when the discharge lamp is cold. The value applied when it is 3000v~
A value of one to several tenths of 20,000v is sufficient. Therefore, even if the lamp is repeatedly turned off and turned on again, the wear on the poles of the discharge lamp is much less than when the discharge lamp is turned on during cooling.

This is because when the lamp is turned off for an extremely short time of 7 to 10 m5ec, the temperature at the pole of the discharge lamp 6 can maintain almost the same high temperature as when it is continuously lit, and the plasma near the pole remains in a state where there are many positive ions and electrons. , because the discharge lamp 6 is in a quasi-excited state.

The output 42 of the shutter closed position sensor 41 is also input to the shutter control circuit 31, and when the shutter 40 returns to the closed position,
A reset signal 38 is output to the counter 17, and the count output 18 is returned to its initial value, that is, zero.

[Other Embodiments] In the above embodiments, the time from when the lights go out to when the lights turn on again is determined using the output signal of the integrating exposure meter, but the time required for the shutter 40 to completely close from the fully open state is determined. If the time period during which the discharge lamp 40 remains in the quasi-excited state after being turned off is sufficiently long, the shutter closed position sensor 41 is omitted and the discharge lamp lighting device 33 supplies the voltage to the negative cord 34 and the positive cord 35. The same effect can be obtained by adopting a configuration in which the discharge lamp lighting device automatically lights the discharge lamp again after a certain time delay after the power is turned off.

[Effects of the Invention] As explained above, according to the present invention, since the discharge lamp is turned off at the same time as the shutter starts to close, it is possible to prevent the discharge lamp from being emitted when the shutter movement time varies or when the shutter starts to close. Even when the brightness of the electric light changes, the symptoms of deterioration in exposure accuracy that occur conventionally do not occur. Therefore, ultra-LSIs that require submicron resolution line widths
This has the effect of allowing the exposure of patterns such as ultra-high frequency transistors and ultra-high frequency transistors to be performed in a short time and with high precision. Furthermore, by re-lighting the discharge lamp after exposure is completed within a short period of time while the discharge lamp remains in a quasi-excited state, the trigger voltage at the time of re-lighting can be kept low, making it possible to repeatedly turn off and re-light the lamp. It also has the effect of maintaining the life of the discharge lamp, which is close to that of continuous lighting, and is excellent in economical efficiency.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of an exposure apparatus for both close exposure and contact exposure according to an embodiment of the present invention, and FIG. 2 shows mask surface illuminance and shutter opening/closing timing over time in the above embodiment. FIG. 3 is a graph showing mask surface illuminance, shutter opening/closing timing, and discharge lamp brightness over time in a conventional example. 1: Lighting system, 6: Discharge lamp, 11: Buliamp, ! 3: amplifier, 15: V-F converter, 17: counter, 19: comparator, 21: mask, 22: wafer, 23: mask stage, 24: wafer stage, 31: shutter control circuit, 33: discharge lamp lighting device, 37: Exposure amount setting switch, 40: Shutter, 41: Shutter close position sensor.

Claims (2)

[Claims] (1) A discharge lamp that generates light for exposure, an illumination system that guides the light of the discharge lamp onto the original plate on which the pattern to be exposed and transferred is drawn, and a shutter that opens and closes the illumination light output from the illumination system. , a shutter opening/closing means for opening and closing the shutter, a shutter opening time setting means, a shutter closing time determining means, a shutter open/close state detection means for detecting the open/close state of the shutter, and supporting the original plate. an exposure apparatus for exposing and transferring a pattern on the original plate onto the exposure target substrate, the exposure apparatus comprising a stage for supporting the substrate to be exposed, a stage for supporting the substrate to be exposed, and a lighting device for the discharge lamp; After starting exposure, the shutter starts to close based on a signal from the shutter opening time determining means and the discharge lamp is turned off, and further, the shutter opening/closing state detecting means detects that the shutter is in the closed state. An exposure apparatus characterized by comprising a control means for immediately re-lighting the discharge lamp. (2) The time it takes to turn on the discharge lamp again after turning it off;
2. The exposure apparatus according to claim 1, wherein the discharge lamp remains in a quasi-excited state for a period of time after being turned off.