JPS63284813A - Projection aligner - Google Patents

Abstract

PURPOSE:To protect a controlled space from application of a pressure exceeding an allowable range by a method wherein a 1st maintaining means which maintains the pressure at about a certain value within a predetermined range when the pressure is judged to exceed the predetermined value and a 2nd maintaining means which maintains the pressure nearly equal to the atmospheric pressure when the operation of a control means is interrupted are provided. CONSTITUTION:A control means which controls the pressure of an enclosed space 3 provided in a light path between a mask R and a photosensitive substrate W in accordance with conditions of application of a lighting beam to a projection optical system or environmental conditions, a 1st maintaining means which maintains the pressure at about a certain value within a predetermined range when the pressure is judged to exceed the predetermined value while the operation of the control means is normal and a 2nd maintaining means which maintains the pressure nearly equal to the atmospheric pressure when the normal operation of the control means is interrupted are provided. With this constitution, a pressure exceeding the allowable range is not applied to the enclosed space and damages of lens elements and so forth constituting the enclosed space can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection optical device such as an exposure device used, for example, in the manufacture of integrated circuits, and particularly to a device for controlling its imaging characteristics.

[Prior Art] As an exposure apparatus used in the manufacturing process of integrated circuits, a large number of reduction projection exposure apparatuses that can obtain high alignment accuracy and overlay accuracy have come into use.

Such a reduction projection exposure apparatus uses a projection lens to reduce and project an image of a circuit pattern drawn on a reticle or mask onto a photosensitive substrate such as a semiconductor square coated with photoresist at a constant magnification.

However, when using the above-mentioned apparatus, the magnification and focal position (position of the imaging plane in the optical axis direction) of the projection lens may vary due to changes in the temperature and pressure (atmospheric pressure) of the outside air.

Fluctuations in optical characteristics due to such causes can be suppressed to a negligible level by placing the entire exposure apparatus in a constant temperature, constant pressure chamber or the like.

Furthermore, optical characteristics may vary due to causes other than those mentioned above. In other words, illumination light for exposure (hereinafter "exposure light")
When the exposure light enters the projection lens, the optical elements (lens elements) that make up the projection lens absorb a portion of the exposure light, and the interior of the lens changes thermally, causing optical characteristics to fluctuate. It is something.

Therefore, recently, projection exposure apparatuses that can correct magnification fluctuations and focal point fluctuations due to causes such as atmospheric pressure fluctuations and absorption of exposure light by a projection lens, and can always maintain predetermined optical characteristics have been attracting attention.

Such a projection exposure apparatus uses a space partitioned by a plurality of lens elements constituting the projection lens as an airtight space inside the lens barrel that is cut off from the outside air, and reduces the pressure of the gas (air, nitrogen gas, etc.) in this space. By controlling the refractive index in the space, the magnification and focal position of the projection lens are corrected. In this case, the pressure control of the space is performed by calculating, as a target value, a pressure value necessary for correcting fluctuations in the imaging characteristics of the projection optical system using an arithmetic device;
This is performed by adjusting the pressure in the space using a pressure adjusting means so that the pressure in the space becomes the calculated target pressure value.

[Problems to be Solved by the Invention] In the conventional projection exposure apparatus as described above, the calculation device that calculates the target pressure value in the space may be unable to perform normal calculations due to runaway of the processor, etc. In this case, there is a possibility that the calculation device outputs an abnormal target pressure value that exceeds the allowable range as a set value. In this case, the pressure regulating means operates based on the set value, and a pressure exceeding an allowable range is applied to the space. As a result, excessive force is applied to the lens elements that make up the space and the metal fittings that press the lens elements, resulting in permanent deformation that does not return to its original state even after the pressure is removed, or even destruction. There was a problem that there was a risk.

Further, even when normal control is performed, abnormal fluctuations in atmospheric pressure or surrounding pressure may occur. Even in such a case, in order to correct such pressure changes, a pressure value exceeding the allowable range will be set and applied to the space, and there is a problem that the same destruction as described above may occur. Ta.

The present invention has been made to solve such problems, and an object of the present invention is to provide a projection exposure apparatus that can prevent pressure exceeding an allowable range from being applied to a controlled space.

[Means for Solving the Problems] The projection exposure apparatus according to the present invention provides a projection exposure apparatus that is provided in the optical path between the mask and the photosensitive substrate based on the incident conditions of illumination light to the projection optical system or the environmental conditions. A control means for controlling the pressure in the sealed space; and when the control means is operating normally and it is determined that the pressure in the sealed space may exceed a predetermined range, the pressure in the sealed space is controlled to be within a predetermined range. The above problem is solved by providing a first holding means that holds the pressure at a substantially constant value; and a second holding means that holds the pressure in the sealed space substantially equal to the outside air when the control means does not operate normally. This solves the problem.

[Function] In the present invention, when it is determined that the pressure in the sealed space may exceed a predetermined range when the control means is operating normally, the pressure in the sealed space is adjusted to an acceptable level by the first holding means. The pressure is maintained at a substantially constant pressure within a range, and if the control means malfunctions, the pressure is maintained at substantially the same pressure as the outside air, so that pressure exceeding the allowable range will not be applied to the sealed space.

[Example] FIG. 1 is a configuration diagram showing an example of the present invention. The present embodiment will be described below with reference to the drawings.

First, the configuration of this embodiment will be explained.

In the figure, R is a mask or a reticle (hereinafter referred to as "reticle"), and a circuit pattern etc. to be transferred to a photosensitive substrate such as a semiconductor square is drawn on the reticle R. Illumination light emitted from above in the figure passes through the reticle R1 projection lens 1, and forms an image of the pattern drawn on the reticle R on the wafer W on the stage 2.

Next, 3 is an air chamber provided inside the projection lens 1. The air chamber 3 corresponds to the sealed space of the present invention, and may be one of a plurality of spaces partitioned by a plurality of lens elements constituting the projection lens 1, or one of the plurality of spaces. Two or more of them may be connected. Note that the spaces other than the air chamber 3 are open to the outside air.

The air chamber 3 is normally sealed from the outside air, and the internal pressure of the air chamber 3 is detected by a pressure sensor 14. The pressure sensor 14 detects the pressure inside the air chamber 3 as an absolute pressure, and outputs a detection signal 14a corresponding to the constantly detected pressure in units of mmHg, for example.

The air chamber 3 further communicates with the bellows pump 4 via vibrators 10 and 11, a solenoid valve 8, and vibrators 17 and 12. By opening and closing the solenoid valve 8, communication between the vibrator 11 and the vibrator 17, that is, the air chamber 3 and the bellows pump 4 is established.
communicate with or prevent such communication. The vibrator 17 is exposed to the outside air via a solenoid valve 9 on the side opposite to the solenoid valve 8. Further, the solenoid valve 9 communicates with the outside air and the vibrator 17 or blocks the communication by opening and closing the solenoid valve 9.

Next, 13 is a differential pressure sensor, and the differential pressure sensor 13
The vibrators 10 and 12 are connected to each other with no gas flowing therebetween. The differential pressure sensor 13 detects the pressure PI in the air chamber 3 and the pressure P in the bellows pump 4.
A detection signal 13a corresponding to the difference from 2 is constantly output.

Next, 16 is a position reading sensor composed of, for example, a linear encoder or the like, which detects the expansion/contraction position of the bellows pump 4 and outputs a detection signal 16a corresponding to the position.

Next, 15 is a pressure sensor, which is the pressure of outside air (atmospheric pressure) P
3 as an absolute value (unit: a+mHg) and outputs a detection signal 15a corresponding to the detected outside air pressure, and is the same as the pressure sensor 14. Note that if the exposure apparatus is equipped with a laser interferometer for measuring the position of the stage 2, this pressure sensor 15 also serves as a pressure sensor for detecting atmospheric pressure in order to stabilize the wavelength of the laser beam. You can also do that.

Next, 5 is a pressure control circuit, which includes a processor such as a microcomputer, and 13a.

Based on the human power of each detection signal of 14a, 15a, 16a,
The air chamber 3 is driven by the bellows pump 4 and the solenoid valves 8 and 9.
Adjust the pressure to the specified value.

Next, 18 is a measuring instrument that monitors changes in factors that change the imaging characteristics (for example, atmospheric pressure, illumination light energy, temperature, etc.) and sends an output signal 18a to the main controller 6. Note that among the quantities monitored by the measuring device 18, the pressure of outside air can be used also as the pressure census 5.

Next, 6 is the main control device, and the signal 1 from the measuring instrument 18 is
Air chamber 3 for taking in 8a and keeping imaging characteristics constant
The target pressure is calculated, and the calculated value is output to the pressure control circuit 5 as a signal 6a.

Next, a description will be given of the pressure adjustment operation performed by the above mechanism in a normal operating state when the target pressure has been calculated.

Basically, when the solenoid valve 9 is closed and the solenoid valve 8 is open; that is, when the communication between the bellows pump 4 and the outside air is blocked and the bellows pump 4 and the air chamber 3 are in communication. The bellows pump 4 always maintains a predetermined target pressure.
to be servo controlled.

When the extension of the bellows pump 4 reaches the up range or down range, that is, when the limit of depressurization or the limit of pressurization of the air chamber 3 is reached, and when further depressurization or pressurization is to be performed, a pumping operation is performed. .

Next, the pumping operation will be briefly explained.

For example, considering the case where the up range is reached, the pressure control circuit 5 first closes the solenoid valve 8 to prevent communication between the air chamber 3 and the bellows pump 4, and then opens the solenoid valve 9 to pump the bellows pump. 4 is communicated (leaked) to the outside air.

Next, the magnitude relationship between the detection signal 14a of the pressure sensor 14 and the detection signal 15a of the pressure sensor 15 is examined. 14a
When <15a, that is, when P<23, the bellows pump 4 is compressed to the midpoint or near the down range. This operation is performed while reading the detection signal 16a of the position reading sensor 16. Furthermore, when 14a>15a, that is, when Pl>P3, the bellows pump 4 is not driven.

On the other hand, when the extension of the bellows pump 4 reaches the down range, conversely, when 14a<15a, the bellows pump 4
is not driven, and when 14a>15a, the bellows pump 4 is extended to the intermediate point or near the up range.

Next, the solenoid valve 9 is closed to prevent communication between the bellows pump 4 and the outside air.

Next, while monitoring the detection signal 13a of the differential pressure sensor 13, the bellows pump 4 is compressed or expanded so that the detection signal 13a becomes the differential pressure O. When the differential pressure becomes 0, the solenoid valve 8 is opened and the bellows pump 4 and the air chamber 3 are communicated with each other.

By performing the above operations, the bellows pump 4 can be compressed or expanded again, so that the air chamber 3 can be further depressurized or pressurized.

Next, a method for calculating the target pressure in a normal operating state will be explained.

Here, magnification fluctuations are considered as the imaging state to be corrected. Note that the focus fluctuations are also substantially the same. Furthermore, as mentioned above, atmospheric pressure, temperature, and energy absorption of illumination light by the projection optical system are considered as fluctuation factors.

First, a method of calculating a target pressure corresponding to fluctuations in atmospheric pressure and temperature will be explained.

It has been experimentally confirmed that the magnification change changes linearly with atmospheric pressure and temperature. Therefore, the proportionality constant determined experimentally is stored in the main controller 6 in advance. The main controller 6 then reads the atmospheric pressure and temperature detection signals 18a from the measuring device 18, and calculates the amount of variation in the magnification from both.

Next, the main controller 6 calculates a pressure that cancels the amount of variation in the magnification, that is, a target pressure, from the variation characteristics of the magnification with respect to pressure changes in the air chamber 3.

In the manner described above, the target pressure corresponding to fluctuations in atmospheric pressure and temperature can be determined.

Next, a method of calculating a target pressure corresponding to energy absorption of illumination light will be explained.

The magnification variation characteristic with respect to the energy absorption of illumination light is due to the accumulation of incident energy. FIG. 2 is a diagram showing its characteristics. In the figure, the horizontal axis represents time t, and the vertical axis represents the magnification M of the projection lens 1.

Time t. If illumination light starts to enter at , the magnification is the initial value M. The magnification changes with time from then on, and at time 1, the magnification is saturated at m, and does not change even if it is further incident. When the incidence of illumination light is interrupted at time t2, the magnification gradually returns to its original value and stabilizes to the initial value M at time t3. Note that during the fluctuation characteristics, time t. - rise characteristics of tl and t2~
The falling characteristic of t3 shows an exponential change.

Further, the saturation value m changes depending on the energy incident on the projection lens 1.

Taking into consideration the fluctuation characteristics described above, the time constants of the rising and falling characteristics are experimentally determined, and the time constants for which the shutter is open and The ratio of the closed time and the energy incident on the projection lens 1 are repeatedly detected for each unit time. Alternatively, high-speed sampling of several milliseconds is used to sequentially detect the energy incident on or stored in the projection lens 1 at each sampling point.

The main controller 6 reads this detection signal and sets the initial value M of the magnification. The amount of magnification variation is calculated by integrating from the state of . From this result, the target pressure is calculated in the same way as in the case of atmospheric pressure and temperature.

As described above, the target pressure for each factor can be calculated. Actually, the main controller 6 outputs these algebraic sums to the pressure control circuit 5 as target pressures.

Next, the operation when normal pressure control as described above becomes impossible for some reason will be explained.

As an example where normal pressure control is impossible, the main control device 6
There may be cases where the main controller 6 is unable to perform normal calculations or the pressure in the air chamber 3 reaches the allowable pressure. 2) When the operator notices an abnormality in the main controller 6 (such as CPU runaway) and stops the control 3) When the pressure in the air chamber 3 reaches the limit value. think of.

In each case, a case where the air chamber 3 is opened to the outside air and a case where the pressure is maintained at a constant level will be explained.

Engineering) When the main controller 6 is unable to perform normal calculations and the device itself detects the abnormality, the main controller 6
If normal calculation cannot be performed, the main controller 6 first outputs an error signal to the pressure control circuit 5 upon determining this state. In this case, the pressure control circuit 5
The pressure control circuit 5 is equipped with a function to determine abnormality.
may also perform the determination.

When the pressure control circuit 5 detects an abnormality as described above, the pressure control circuit 5 notifies the operator of the abnormality using a buzzer or the like, and also opens the solenoid valve 9 to direct the air chamber 3 and bellows pump 4 to outside air (high pressure). open to atmospheric pressure). Note that the solenoid valve 8 is already in an open state. After this, the pressure control circuit 5 does not drive the bellows pump 4 until the return operation begins.

By the above-described operation, the magnification control is interrupted and the air chamber 3 is opened to the outside air, so that it is possible to prevent excessive force from being applied to the lens elements and the like constituting the air chamber 3 due to the pressure difference.

Next, the operation of restoring the control system will be explained.

As explained in the normal operation example above, the main controller 6 calculates the accumulation of incident energy of illumination light. When an abnormality occurs, is the calculation operation interrupted?
Even if the above calculation is performed, it is estimated that the calculated value within the main controller 6 is not a correct value. Therefore, it is necessary to repeat the energy integration from the beginning (from the initial value M).

Therefore, until the projection lens 1 is sufficiently cooled, ie M in FIG. Until it is determined that the state has returned to (
(t2 t+ )), and then performs the return operation after calculating the energy integration.

First, the main control device 6 clears the previous energy integration amount (the predicted value of the magnification change determined at that time) and newly calculates the target pressure.

On the other hand, the pressure control circuit 5 reads the calculated target pressure P and the signal 15a of the outside air pressure P3, and determines the expansion/contraction position of the bellows pump 4 based on the difference between the two.

When P4<P3, the bellows pump 4 is put into an expanded state, and when P4>P3, the bellows pump 4 is put into a compressed state. Furthermore, when P3 and P4 are approximately equal, the bellows pump 4 is compressed to approximately the midpoint. Thereafter, the electric valve 9 is closed and normal pressure control is performed so that the air chamber 3 reaches the target pressure. in this case,
If the target pressure is not reached by one expansion/contraction, the above-mentioned pumping operation is performed.

In the example described above, it is necessary to wait for the lens to cool down when performing the return operation, but by having means for monitoring energy accumulation and interruption time immediately before an abnormality occurs, the main controller 6 can It is also possible to perform a return operation by immediately clearing the previous value and calculating the integrated energy amount anew from the data on the energy accumulation and interruption time.

Next, the operation of a method for maintaining the air chamber 3 at a constant pressure, which is the same as the pressure at the time of abnormality occurrence, will be explained.

If the pressure control circuit 5 receives an error signal, from now on,
The pressure control circuit 5 ignores the signal from the main control circuit 6,
The pressure is adjusted so that the pressure in the air chamber 3 becomes the pressure at the time of occurrence of the abnormality. As a result, the control is interrupted, and as in the case where the air chamber 3 is opened to the outside air, damage to the lens elements and the like constituting the air chamber 3 can be prevented.

According to this example, compared to the case where the air chamber 3 is opened to the outside air, there is an advantage that there is no need to operate the electromagnetic valve both when an abnormality occurs and when returning.

In addition, in this example, even during interruption of pressure control,
A force due to the pressure difference between the outside air pressure and the internal pressure of the air chamber 3 is always applied to the lenses and the like that constitute the air chamber 3. Therefore, the pressure control circuit 5 always reads the detection signals 14a and 15a of the pressure sensors 14 and 15 to monitor the pressure in the air chamber 3 and the differential pressure with the external pressure, and if the differential pressure exceeds the allowable differential pressure, the differential pressure It is necessary to adjust the pressure in the air chamber 3 so that the pressure difference is within the allowable differential pressure.

In the method of keeping the air chamber 3 at a constant pressure, which is the same as the pressure at the time of abnormality occurrence, as explained above, the other operations are the same as when opening the air chamber 3 to the outside air, except that the solenoid valve is not opened/closed. be.

By the way, as a method for keeping the pressure in the air chamber 3 constant, in addition to the above example, a method using only the operation of a solenoid valve may be used. That is, if the solenoid valve 9 is opened after the solenoid valve 8 is closed, the air chamber 3 will be kept at a constant pressure unless there is a leak in the piping or the like.

2) When the operator notices an abnormality in the main control device 6 (such as CPU runaway) and stops the control In the embodiment shown in l), the device itself determines the abnormality and performs the operation; There may be cases in which it is not possible to determine the amount of pressure, and in this case, the operator will notice from the pressure display or the like and take action. In this case, the reset switch 7 can be used to forcibly start the same operation as in case 1).

In this example, when the reset switch 7 is turned on, a signal 7a from the reset switch 7 notifies the pressure control circuit 5 of the reset. The pressure control circuit 5 is l)
The air chamber 3 is released to the outside air or maintained at a constant pressure in the same way as in the above case. Further, the same applies to the return operation.

3) When the pressure in the air chamber 3 reaches the limit value As described above, the force applied to the lens elements and the like constituting the air chamber 3 is the pressure difference between the outside air pressure and the pressure in the air chamber 3. That is, the limit value of the internal pressure of the air chamber 3 is expressed in this case by a differential pressure. Therefore, when calculating the target pressure, the main controller 6 checks whether the target pressure is within the limit value, and when the target pressure reaches the limit value, outputs a signal to the pressure control circuit 5 notifying the limit value. The pressure control circuit 5 notifies the operator of this, and also opens the air chamber 3 to the outside air in the same manner as in case 1).

In this example, since the energy integration calculation is executed even during the interruption of pressure control, the return operation can be performed immediately when the target pressure falls within the limit value.

Also, to check the limit value, as in the example shown in 1),
This can also be done by comparing the outputs of pressure sensors 14 and 15.

Furthermore, if the limit value is exceeded due to an artificial cause such as energy absorption of illumination light, a method such as stopping exposure may be considered.

Next, an example of operation will be shown in which the pressure in the air chamber 3 is kept constant at the limit pressure.

When the calculated target pressure exceeds the limit value, the main controller 6 does not output the calculated target pressure as is, but outputs the limit pressure as the target pressure and notifies the operator. After that, the limit pressure continues to be output as the target pressure until the calculated target pressure falls within the limit value, and when the calculated target pressure falls within the limit value, the calculated target pressure is output again instead of the limit pressure. start and notify the operator that it has returned.

In this example, compared to the case where the air chamber 3 is opened to the outside air, there is an advantage that the operation can be performed immediately without operating a solenoid valve. Furthermore, if high precision in magnification is not required, it is possible to continue the exposure to a certain extent.

As mentioned above, the method of keeping the air chamber 3 at the limit pressure has various advantages, but if pressure control becomes impossible due to a power outage, the outside air pressure will fluctuate during the power outage and the differential pressure will rise to the limit value. Therefore, it is desirable to open the air chamber 3 to the outside air. In this case, the signal 7b of the reset switch 7
Although this will directly open the solenoid valve 9, it is preferable to use a normal oven type solenoid valve in case of a power outage.

Note that it is also possible to store the integrated amount of energy using a backup system and start control immediately after the power is restored.

Further, even when the apparatus is to be stopped for a long period of time other than during a power outage, it is desirable to open the air chamber 3 to the outside air for the same reason as mentioned above.

In each of the cases described above, the space inside the projection lens 1 other than the air chamber 3 was open to the outside air, but this may be controlled to a constant pressure. In this case, in order to control the pressure to a constant pressure, another set of the bellows unit system shown in FIG. 1 is provided, and the space other than the air chamber 3 is controlled by this bellows unit system.

In the above configuration, the force applied to the lens element, etc. that constitutes the air chamber 3 is not due to the pressure difference between the outside pressure and the pressure in the air chamber 3, but is due to the pressure difference between the pressure in the air chamber 3 and the space other than the air chamber 3. This is the difference between the pressure and the pressure. Therefore, in this case, the operation corresponding to the aforementioned operation of opening to the outside air is an operation of making the pressure in the air chamber 3 equal to the pressure in the space other than the air chamber 3.

This operation may be controlled by the pressure control circuit 5 so that the differential pressure is zero, or the air chamber 3 and a space other than the air chamber 3 may be directly communicated with each other.

In the embodiments of the present invention described above, the pressure inside the projection lens is controlled, but two parallel plane glasses are provided between the projection lens and the photosensitive substrate, and the pressure inside the projection lens is controlled. A method in which the pressure is controlled using the space between the glasses as a sealed space and the single magnification correction is performed by bending the parallel plane glass due to the pressure cannot be implemented in the same manner.

[Effects of the Invention] As explained above, the present invention includes a control means for controlling the pressure in a sealed space based on the incident conditions of illumination light to the projection optical system or environmental conditions; a first holding means for maintaining the pressure in the sealed space at a substantially constant value within a predetermined range when it is determined that the pressure in the sealed space may exceed a predetermined range; the control means operates normally; and a second holding means that maintains the pressure in the sealed space equal to that of outside air when the control means is operating normally. When it is determined that the pressure of Since the pressure is maintained, pressure exceeding the allowable range is not applied to the sealed space, and damage to the lens elements and the like that constitute the sealed space can be prevented.

In addition, during normal operation, that is, under controllable conditions, the internal pressure is maintained at a constant value, so even if excessive pressure is applied due to external factors, the projection optical The system is protected, and there is also the effect that normal pressure control can be continued immediately when the external factor disappears.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of the present invention, and FIG. 2 is a diagram showing magnification variation characteristics due to energy absorption of illumination light by a projection lens. [Description of symbols of main parts] 1. Projection lens, 3.. Air chamber 54.. Bellows pump, 5.. Pressure control circuit, 6.. Main controller, 7.
...Reset switch, 8.9...Solenoid valve, 13...
・Differential pressure sensor, 14.15...Pressure sensor, 18
···Measuring instrument.

Claims (3)

[Claims] (1) An illumination means that illuminates a mask on which a predetermined pattern is formed, a projection optical system that projects an image of the pattern onto a photosensitive substrate, and a projection optical system that is provided in an optical path between the mask and the photosensitive substrate and comprising a sealed space made of a sealed optical member and a pressure adjustment means for adjusting the pressure in the sealed space,
When projecting onto the photosensitive substrate with predetermined imaging characteristics via the projection optical system and the sealed space, the image forming characteristics can be corrected by adjusting the pressure in the sealed space using the pressure adjusting means. In the projection exposure apparatus, a control means for controlling the pressure in the sealed space based on conditions of incidence of illumination light on the projection optical system or environmental conditions; when the control means is operating normally, the pressure in the sealed space is controlled; a first holding means that maintains the pressure in the sealed space at a substantially constant value within a predetermined range when it is determined that the pressure may exceed a predetermined range; 1. A projection exposure apparatus comprising: second holding means for keeping the pressure in the sealed space substantially equal to the pressure in the outside air. (2) The control means sequentially calculates the amount of temporal change in the imaging characteristic based on the incident state and non-incident state of the illumination light to the projection optical system,
a calculation means for calculating a pressure value to be controlled in the sealed space in response to the amount of change; and a pressure adjustment means for controlling the pressure by sending gas to the sealed space in response to the calculated pressure value. and the first holding means includes: when the pressure value calculated by the calculation means exceeds the predetermined range, the first holding means sets the pressure value to approximately the limit value of the predetermined range and controls the pressure adjustment means. 2. A projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is a means for limiting the number of pixels. (3) The second holding means is provided in a gas flow path that communicates the sealed space and the pressure adjustment means, and comprises a member that opens the gas flow path to the outside air. A projection exposure apparatus according to scope 2.