JPS63303409A - Pressure controller - Google Patents

Abstract

PURPOSE:To control the pressure inside a chamber with high accuracy, by providing a proportional solenoid valve which changes its opening for adjusting the flow rate in accordance with control values. CONSTITUTION:The objective system 2a of a microscope system 2 is put into a helium chamber 1 and moves forward and backward when the observing position is changed. Therefore, the airtight bellows coupling the chamber 1 with the microscope 2 contract and expand and the pressure inside the chamber 1 changes. The change in pressure is detected by a pressure sensor 14 and compared with a reference values by means of a comparator 16. When the pressure is lower than the reference value, a comparison signal is sent to a helium gas supplying proportional solenoid valve driver 18 from the comparator 16 and a proportional solenoid valve supplies an operating helium gas to the chamber 1 with an opening proportional to the pressure difference. When the internal pressure is higher than the reference value, a comparison signal is sent to a vacuum supplying proportional solenoid valve driver 17 and a proportional solenoid valve 9 operates with an opening proportional to the pressure difference so as to extract the helium gas and correct the pressure.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a device for controlling the pressure within a sealed chamber to a nearly constant level, and in particular to a helium chamber used in an X-ray exposure device, etc. This relates to pressure control within.

[Conventional technology]

Conventionally, as an apparatus to which this type of apparatus is applied, an X-ray exposure apparatus as disclosed in, for example, Japanese Unexamined Patent Application Publication No. 126632/1984 has been known. As is well known, X-rays (soft X-rays are usually used in the field of semiconductor device manufacturing) are poorly attenuated in vacuum or in some types of inert gas. When irradiating a wafer with X-rays from a high vacuum (high vacuum) through a mask, there is a mechanical separation between the X-ray source and the mask (approximately 20 to 50 cm), so a chamber filled with helium gas is inserted between the X-ray source and the mask. This suppresses the attenuation of X-rays. The X-ray extraction window of this chamber is placed in close proximity to the mask, or so that the mask itself serves as the extraction core, so a microscope for mask and wafer alignment generally enters the chamber. Since the alignment microscope is installed so that it can move forward and backward within the chamber by penetrating the outer wall of the chamber, the internal volume of the chamber changes between the time of exposure and the time of alignment. This causes the X-ray extraction window and mask to be deformed, causing problems in exposure and alignment.

Therefore, with conventional devices, there are methods to reduce the change in internal pressure by causing a slight flow of helium gas in the chamber, methods to change the internal volume of the chamber so that the pressure in the chamber is almost constant, or methods to detect the internal pressure in the chamber. A method using a fluid circuit that automatically supplies and exhaust helium has been considered. In particular, the method using a fluid circuit installs a solenoid valve in the helium flow path and employs feedback control that opens and closes the solenoid valve in response to changes in chamber internal pressure, so it can respond to relatively small pressure fluctuations. There are advantages such as Therefore, the X-ray extraction window (made of polyimide or the like) having a thickness of 1 to several microns, the membrane of the mask, and the like are prevented from being bent due to the differential pressure between the chamber internal pressure and the atmospheric pressure.

[Problem that the invention seeks to solve]

In the conventional technology described above, the effective cross-sectional area of the solenoid valve is constant, so whether the pressure change inside the chamber is large or small, if the source pressure is stable, only a constant flow rate of gas can be taken in and taken out. Become.

Therefore, if the effective cross-sectional area of the solenoid valve is determined assuming a case where the pressure change is large, if the pressure change is small, the flow rate will be too large (too much and the correction will be applied too much, and conversely, assuming a case where the pressure change is small) If the effective cross-sectional area of the solenoid valve is determined in advance, there is a problem in that it takes time to correct when the pressure change is large.

Further, pressure correction based on volume change has the problem of being structurally complicated.

The present invention has been made in view of these conventional problems, and an object of the present invention is to provide a device that performs highly accurate pressure control regardless of the magnitude of pressure change within a chamber.

[Means for solving problems]

In order to solve the above problems, the present invention uses an IIT magnetic valve, a so-called proportional solenoid valve, which can adjust the flow rate according to a control value, and changes the opening degree of the solenoid valve according to the amount of pressure change in the chamber. The pressure change inside the chamber was stabilized within a certain value.

Furthermore, if there is a change in the source pressure, the gas flow rate will change even if the opening degree of the proportional solenoid valve is constant, making it difficult to set the gain that determines the opening degree of the proportional solenoid valve in response to changes in internal pressure. Therefore, in the present invention, this problem is solved by providing a preparatory chamber (preparatory pressure chamber) whose pressure is controlled to some extent before the proportional solenoid valve.

[For production]

In the present invention, a proportional solenoid valve is used, and the gas flow rate is made constant depending on the opening degree of the proportional solenoid valve, so the gas flow rate can be controlled depending on the magnitude of the pressure change in the chamber, and the gas flow rate can be quickly controlled. The pressure inside the chamber can be kept within a certain range.

〔Example〕

The figure is a block diagram of an embodiment of the present invention, in which a helium (He) chamber 1 includes a microscope system 20, an objective system 2,
A is holding his head, and microscope system 2 is holding objective system 2.
In order to change the observation position along with a, it moves back and forth as shown by arrow A in the figure. Therefore, the airtight bellows 3 connecting He chamber 1 and microscope 2 expands and contracts, and as a result, the pressure in He chamber 1 changes. do. Pressure changes are monitored by pressure sensor 14 and compared with a reference value by comparator 16. If the internal pressure is lower than the reference value, comparator 16
The comparison signal is sent to the He supply proportional solenoid valve driver 18, which operates the proportional solenoid valve 4 at an opening proportional to the pressure difference to supply He gas to the He chamber 1. If the internal pressure is higher than the reference value, the comparison signal from the comparator 16 is sent to the vacuum supply proportional solenoid valve driver 17, which operates the proportional solenoid valve 9 with an opening proportional to the pressure difference, removes He,
Correct pressure.

A preliminary chamber 6.11 and a regulator 7.1 are provided before each of the proportional solenoid valves 4.9 (on the supply source and vacuum source sides, respectively).
2 are connected as a pair to suppress the influence on the gain setting for flow rate control caused by fluctuations in He and vacuum supply pressure (original pressure).

The pressure inside the preliminary chamber 6.11 is also measured by the pressure sensor 5.11.
10, respectively, to enable monitoring in case the pressure in the preliminary chamber 6.11 becomes uncontrollable by the regulator 7.12.

Furthermore, as a safety measure in the event that the pressure within the He chamber 1 cannot be fully controlled by the proportional solenoid valve 4.9 and rises or falls below a certain specified value, the configuration is such that the detection signal from the pressure sensor 14 is always sent to the comparator 15. I'll keep it. When the chamber pressure detected here is larger or smaller than the specified value, the valve 13 is opened and the He in the He chamber 1 is removed.
It has a mechanism that releases gas to prevent pressure abnormalities.

Furthermore, in the middle of vacuum piping (between chamber 1 and solenoid valve 9)
Attach the oxygen sensor 8 to the chamber 1 to remove air from the inside of the chamber 1.
This allows the degree of Hefi in the He chamber 1 to be estimated by taking into account air leakage from the outer wall of the chamber or when replacing with e-gas. Oxygen sensor 8 in this position
If there is, even a type of sensor that generates heat can be used for measurement without affecting the microscope system 2 or the like. However, in this position, the oxygen concentration can only be measured when the vacuum side is activated, so an offset is placed on each driver 17 and 18 so that the vacuum system is always activated (from chamber l to He
This problem can be solved by performing an operation to exhaust the gas, and then opening the solenoid valve 4 to correct the pressure in the He supply system.

Next, the overall operation of this embodiment will be explained.

Positive pressure He gas from a He gas supply source (not shown) flows into the preliminary chamber 6 via the regulator 7 . The preparatory chamber 6 stores He gas while maintaining it at a certain pressure, and its volume is determined so that the maximum pressure change that can occur in the He chamber 1 can be corrected with sufficient accuracy. Negative pressure from a vacuum source (not shown) is also applied to the preliminary chamber 11.
is supplied to the pre-chamber 1 by the regulator 12.
The negative pressure inside 1 is controlled to be approximately constant.

In the figure, the He chamber 1 is a plan view seen from the X-ray source side of the apparatus, and the rectangular area PA is the circuit pattern area on the mask. The objective system 2a of the microscope system 2 is extended to a space above the circuit pattern area PA in the He chamber 1, and alignment between the mask and the wafer is performed here. During this time, in order to activate the oxygen sensor 8, as explained earlier, an offset is given in the feedback loop by the driver 17.1, and a slight H
E gas flows into the He chamber 1 via the solenoid valve 4,
Furthermore, the air is exhausted through the solenoid valve 9. Now,
When the alignment is completed, the objective system 2a of the microscope system 2 is retracted so as not to block the space above the circuit pattern area PA from X-rays. At this time, the pressure inside the He chamber 1 changes (depressurizes), but the amount of change is detected by the pressure sensor 14 and immediately compared with a reference value by the comparator 16, and the driver 18 causes the solenoid valve 4 to increase the opening angle. Outputs the control value. As a result, the pressure within the He chamber I is corrected to its original value. Of course, as the pressure approaches the original value, the opening degree of the solenoid valve 4 also decreases. Then, when the pressure within the He chamber 1 becomes stable, X-ray exposure is performed. Since X-ray exposure takes several times longer than normal light exposure, the pressure servo system operates constantly during this time to maintain the pressure in the He chamber 1 at a constant value.

In order for such a servo system to work stably and accurately, it is necessary that the pressure of He gas passing through the proportional solenoid valve 4 and the negative pressure drawn from the proportional solenoid valve 9 be approximately stable and at a constant value. In one embodiment, these conditions are achieved by means of a preliminary chamber 6.11 and a regulator 7.12.

Now, when the exposure is completed and the next area on the wafer is to be exposed in a step-and-repeat manner, the microscope 2 is moved out again. At this time, the pressure inside the He chamber 1 increases, so servo control is performed mainly to increase the opening degree of the proportional solenoid valve 9, and the pressure is corrected to the original pressure.

As described above, according to the present embodiment, even if the movement amount and movement speed of the microscope system 2 change, the pressure in the He chamber 1 can be adjusted with good responsiveness, and the proportional solenoid valve 4.9 can be adjusted to the preliminary chamber 6.11. When used in combination, precise pressure control is possible within an extremely large range.

〔Effect of the invention〕

As described above, according to the present invention, it becomes possible to extremely precisely servo control the pressure inside the chamber, which can change.

Furthermore, the present invention can be widely used in equipment that requires internal pressure control. For example, in a projection exposure apparatus, the projection magnification and focal plane can be controlled by controlling the pressure in the sealed air space within the projection lens. A similar effect can be obtained even when only a minute amount of correction is to be made.

[Brief explanation of the drawing]

The figure is a block diagram of a pressure control device according to an embodiment of the present invention. [Explanation of symbols of main parts] 1...He chamber, 2...Microscope system, 3
...Bellows, 4...Proportional solenoid valve, 5...Pressure sensor, 6...Preliminary chamber, 7...Regulator, 8...Oxygen sensor, 9...Proportional solenoid valve, 10. ...Pressure sensor, 11...Preliminary chamber, 12...Vacuum regulator, 13...
・Leak valve, 14...pressure sensor, 15...
・Comparator, 16... Comparator

Claims (2)

[Claims] (1) In a device that detects the pressure in a chamber whose internal pressure can change and performs feedback control so that the pressure becomes a predetermined value, there is a device between the chamber and the pressure source in order to take in and out the gas in the chamber. a solenoid valve unit that is provided to control the flow rate of the gas; and a solenoid valve unit that is provided between the solenoid valve unit and the pressure source, and that adjusts the flow rate of the gas according to a control value to the solenoid valve unit. A pressure control device characterized by comprising a preliminary pressure chamber for preliminary pressure adjustment. (2) The pressure source includes a pressurized gas supply source that supplies the gas to the chamber, and a negative pressure source that discharges the gas from the chamber, and the electromagnetic valve unit supplies the pressurized gas. a first proportional solenoid valve that is provided between the source and the chamber and controls the flow rate in accordance with the controlled amount; and a first proportional solenoid valve that is provided between the negative pressure source and the chamber and controls the flow rate in proportion to the controlled amount. a second proportional solenoid valve that controls the pressure, and the preliminary pressure chamber includes a first preliminary chamber provided between the pressurized gas supply source and the first proportional solenoid valve, and a second proportional solenoid valve that controls the negative pressure source. 2. The device according to claim 1, further comprising a second preliminary chamber provided between the second proportional electrode valve and the second proportional electrode valve.