JP2001102290A - Exposure method and apparatus - Google Patents

Abstract

(57) [Problem] To control the concentration of an absorbing material of an exposure beam at a low cost on an exposure beam optical path. SOLUTION: An illumination optical system 5, a reticle operation unit 6, a projection optical system PL, and a wafer operation unit 7 are respectively placed inside a box-shaped illumination system chamber 1, a reticle chamber 2, a lens barrel 3, and a wafer chamber 4. Store in a sealed state, isolated from the outside air.
The dew points (equivalent to humidity) of the gas in the illumination system chamber 1 to the wafer chamber 4 are measured by the dew point meters 29A to 29D, respectively. From this measurement result, the concentration (contamination ratio) of the light absorbing substance of the exposure beam in the illumination system chamber 1 to the wafer chamber 4 is estimated. Based on the estimation result, the gas exhaust from the illumination system chamber 1 to the wafer chamber 4 by the exhaust device 36 and the gas through which the exposure beam is transmitted to the illumination system chamber 1 to the wafer chamber 4 by the gas supply device 26 ( (Purge gas).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of projecting a mask pattern in a lithography process for manufacturing a device such as a semiconductor device, an image pickup device (CCD or the like), a liquid crystal display device, a plasma display device, or a thin film magnetic head. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and an exposure apparatus for transferring an image onto a substrate via an optical system.
This is suitable when using UV light (Vacuum Ultraviolet light).

[0002]

2. Description of the Related Art In recent years, a projection exposure apparatus used for transferring a reticle pattern as a mask onto a wafer (or a glass plate or the like) coated with a photosensitive material as a substrate via a projection optical system has been used. As the integrated circuit becomes finer and higher in density, further improvement in the resolution of the projection optical system is required. Since the resolution of the projection optical system increases as the wavelength (exposure wavelength) of the exposure light used as the exposure beam becomes shorter, the wavelength of the exposure light used in the projection exposure apparatus has been shortened year by year. Recently, KrF excimer laser light (wavelength: 248 nm) is mainly used as exposure light. However, a projection exposure apparatus using ArF excimer laser light (wavelength: 193 nm) in a vacuum ultraviolet region is being put into practical use. F ₂ laser beam having a wavelength (wavelength 157
nm) has also been attempted.

However, in addition to an optical member (such as a lens), a substance which absorbs the exposure light and greatly reduces the amount of the exposure light (hereinafter, referred to as an optical member (such as a lens)).
"Absorptive substances"). The light-absorbing substance varies depending on the wavelength of the exposure light.
For the above light, ozone or the like becomes a light-absorbing substance, and the wavelength 2
For light in the vacuum ultraviolet region of about 00 nm or less, oxygen, water vapor, carbon dioxide, and the like contained in the air also become light absorbing substances. In addition, a trace amount of organic substances and the like in the atmosphere around the optical member in the projection exposure apparatus may cause a photochemical reaction by vacuum ultraviolet light to generate a cloudy substance. The decrease in the amount of light becomes greater.

[0004] For this reason, conventionally, in a projection exposure apparatus, the light path of exposure light is covered with a highly airtight cover to isolate it from the outside air, and the gas inside the cover is replaced with a gas through which the exposure light passes. As a result, the above-mentioned light-absorbing substances and the like are removed or reduced from the optical path of the exposure light. Then, for example, an oxygen concentration meter is installed inside the cover or the like to measure the oxygen concentration as the concentration of the light absorbing material, thereby managing the light absorbing material on the optical path of the exposure light. There are various types of the oxygen concentration meter, and a galvanic cell type is generally used as the projection exposure apparatus in terms of size, cost, and the like.

[0005]

As described above, in the conventional projection exposure apparatus, the light path of the exposure light is covered with a highly airtight cover in order to suppress a decrease in the amount of light due to the light absorbing substance in the atmosphere of the light path of the exposure light. Was replaced with a gas through which exposure light was transmitted. By installing an oxygen concentration meter inside the cover, the light absorbing material on the optical path of the exposure light is managed.

However, the oxygen concentration meter is expensive and the optical path of the exposure light is divided into a plurality of spaces for each mechanism such as an illumination optical system and a projection optical system to be isolated from the outside air. It is necessary to install an oxygen concentration meter in each of the spaces, and there has been a problem that the manufacturing cost of the apparatus is increased. In addition, the oxygen concentration meter has a disadvantage that the life of the detecting unit is short and the parts of the detecting unit need to be periodically replaced, so that the maintenance cost is increased. Furthermore, the oximeter needs to calibrate the measured values relatively frequently, which has the disadvantage of increasing the time required for maintenance.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to provide an exposure method capable of controlling the concentration of a light absorbing substance in an atmosphere of an optical path of an exposure beam at low cost. Still another object of the present invention is to provide an exposure apparatus capable of performing such an exposure method.

[0008]

According to a first exposure method of the present invention, a first object (R) is illuminated with an exposure beam, and a second object (W) is exposed with an exposure beam passing through the pattern of the first object. In the exposure method of exposing, the humidity inside the hermetic chambers (1 to 4) provided on the optical path of the exposure beam is measured, and the mixing ratio of impurities inside the hermetic chamber is estimated from the measurement result. Based on the estimation result, at least one of gas exhaust from the hermetic chamber and gas supply to the hermetic chamber through the exposure beam is controlled. In the present invention, an impurity refers to a substance having a low transmittance to the exposure beam, and the type of the impurity varies depending on the wavelength of the exposure beam.

In the present invention, the gas transmitted by the exposure beam is a dry gas, and the impurities mixed into the airtight chamber are such that outside air (air or the like) having a certain humidity gradually enters the airtight chamber. In many cases, they are mixed together when they leak, and the concentration of the impurities has a certain correlation with the humidity in the airtight room. Furthermore, since the water vapor itself measured by humidity is also an impurity, it is estimated that when the humidity in the airtight room is high, the mixing ratio (or concentration) of the impurity is high, and when the humidity is low, the mixing ratio of the impurity is low. Therefore, when it is estimated that the humidity becomes high and the mixing ratio of impurities exceeds a predetermined allowable range, the gas in the hermetic chamber may be evacuated to supply (purge) the gas through which the exposure beam passes.

For the measurement of the humidity, for example, an inexpensive dew point meter can be used, and the impurity concentration in the optical path of the exposure beam can be measured without using a conventional expensive oxygen concentration meter for impurity management. It can be managed at low cost. Also, compared with the case of using an oximeter, parts replacement and calibration of the humidity detector (dew point meter, etc.)
Is performed less frequently, and the cost and time required for maintenance are reduced.

Next, in a second exposure method according to the present invention, an exposure beam illuminates a first object (R) with an exposure beam and exposes a second object (W) with an exposure beam having passed through the pattern of the first object. In the method, the pressure inside the hermetic chambers (1 to 4) provided on the optical path of the exposure beam is measured, and based on the measurement result, the mixing ratio of impurities inside the hermetic chamber is estimated. Based on the control, at least one of exhaust of gas from the hermetic chamber and supply of gas permeating the exposure beam to the hermetic chamber is controlled.

According to the present invention, when gas inside the hermetic chamber leaks or gas containing impurities enters from outside the hermetic chamber, the pressure inside the hermetic chamber changes. Therefore, the ratio (or concentration) of impurities in the hermetic chamber is estimated by using this. Since the pressure in the hermetic chamber, that is, the atmospheric pressure, can be measured by, for example, an inexpensive barometer, the mixing ratio of impurities inside the hermetic chamber can be estimated without using an expensive oxygen concentration meter, and the exposure beam The impurity concentration in the atmosphere of the optical path can be managed at low cost.

A first exposure apparatus according to the present invention illuminates a first object (R) with an exposure beam and transfers an image of a pattern of the first object onto a second object (W). , An airtight chamber (1) provided on the optical path of the exposure beam.
An exhaust mechanism (36) for exhausting the gas inside of (4),
An air supply mechanism (26) for supplying a gas through which the exposure beam permeates into the hermetic chamber, a humidity measuring device (29A to 29D) for measuring the humidity inside the hermetic chamber, and a humidity measuring device And a controller (25) for controlling the exhaust mechanism and the air supply mechanism based on the measurement result to replace the gas inside the airtight chamber. According to the present invention, the first exposure method of the present invention can be performed.

The second exposure apparatus according to the present invention illuminates a first object (R) with an exposure beam and transfers an image of a pattern of the first object onto a second object (W). , An airtight chamber (1) provided on the optical path of the exposure beam.
An exhaust mechanism (36) for exhausting the gas inside of (4),
An air supply mechanism (26) for supplying a gas through which the exposure beam passes into the hermetic chamber, a pressure measuring device (50A to 50D) for measuring a pressure inside the hermetic chamber, and the pressure measuring device And a controller (25) for controlling the exhaust mechanism and the air supply mechanism based on the measurement result to replace the gas inside the airtight chamber. According to the present invention, the second exposure method of the present invention can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a projection exposure apparatus of a step-and-scan method using vacuum ultraviolet light as an exposure beam. FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus of the present embodiment. In FIG. 1, the mechanism of the projection exposure apparatus of the present embodiment includes an illumination optical system unit 5, a reticle operation unit 6, a projection optical system PL, and a wafer. It is largely divided into an operation unit 7, which further comprises a box-shaped illumination system chamber 1, a reticle chamber 2, a lens barrel 3,
In addition, it is housed inside the wafer chamber 4 in a strictly sealed state isolated from the outside air. The illumination system chamber 1, reticle chamber 2, lens barrel 3, and wafer chamber 4 of the present example correspond to the hermetic chamber of the present invention. Further, the projection exposure apparatus of the present embodiment is housed in one large chamber in which the temperature of an internal gas (for example, purified air) is controlled within a predetermined range.

First, in the illumination optical system section 5, the emission end of the exposure light source 11 is inserted into the lower side surface of the illumination system chamber 1, and exposure light (exposure illumination light) IL from the exposure light source 11 as an exposure beam. Is injected into the illumination system chamber 1. Exposure light IL is F as vacuum ultraviolet light.
₂ Laser light (wavelength 157 nm), ArF (wavelength 193n)
m) and the like, and Kr ₂ laser light (wavelength 14
6 nm), Ar ₂ laser light (wavelength 126 nm), or Y
A harmonic of an AG laser or the like is used. Exposure light IL emitted from the exposure light source 11 is reflected by a mirror 12, and an automatic tracking unit (not shown) for adjusting an optical axis shift due to vibration or the like, and a beam for shaping the cross-sectional shape of the illumination system and controlling the light amount. The light enters a fly-eye lens (or a rod lens can be used) 14 as an optical integrator (homogenizer) via a shaping optical system 13. An aperture stop (not shown) is disposed on the exit surface of the fly-eye lens 14. Exposure light IL emitted from the fly-eye lens 14 and passing through the aperture stop is reflected in a substantially horizontal direction by a mirror 15 and relayed. The light reaches a field stop (reticle blind) 17 via a lens 16.

The arrangement surface of the field stop 17 is substantially conjugate with the pattern surface of the reticle R to be exposed.
It has a fixed blind that defines the shape of an elongated rectangular illumination area on the pattern surface, and a movable blind that closes the illumination area at the start and end of scanning exposure to prevent exposure to unnecessary parts. . The exposure light IL that has passed through the field stop 17 is transmitted to the relay lens 18 and the mirror 1
9, a rectangular (slit-shaped) illumination area on the pattern surface of the reticle R is illuminated with a uniform illuminance distribution via a condenser lens system 20 fixed to the tip of the illumination system chamber 1. The illumination optical system unit 5 is constituted by the exposure light source 11 to the condenser lens system 20, and the exposure light I in the illumination optical system unit 5 is formed.
L from the exposure light source 11 to the condenser lens system 2
The light path up to 0 is sealed by the illumination system chamber 1.

Under the exposure light IL, the image of the pattern in the illumination area of the reticle R is projected through the projection optical system PL at a projection magnification β (β is, for example, ４ ，, ５, etc.), and Is projected onto the wafer W coated with a photoresist as a mask. The wafer W is a disk-shaped substrate such as a semiconductor (silicon or the like) or SOI (silicon on insulator). The reticle R and the wafer W of the present example correspond to the first object and the second object of the present invention, respectively. The exposure light I
When L is light having a shorter wavelength even in the vacuum ultraviolet region such as F ₂ laser light (wavelength 157 nm), an optical glass material having a good transmittance is doped with fluorite (a crystal of CaF ₂ ), fluorine, or the like. Since it is limited to quartz glass, magnesium fluoride (MgF ₂ ), lithium fluoride (LiF), etc., it is difficult to obtain a desired imaging characteristic (such as chromatic aberration characteristic) by configuring the projection optical system only with a refractive optical member. Have difficulty. Therefore, as the projection optical system PL, it is desirable to use a catadioptric system in which a refractive optical member and a reflecting mirror are combined. Hereinafter, the Z axis is taken in parallel with the optical axis AX of the projection optical system PL, and the X axis is taken in a plane perpendicular to the Z axis (horizontal plane in this example) parallel to the plane of FIG. 1 and perpendicular to the plane of FIG. A description will be given taking the Y axis. The illumination area on the reticle R in this example is a rectangular shape elongated in the X direction, and the scanning direction of the reticle R and the wafer W during exposure is in the Y direction.

At this time, the reticle R is held on the reticle stage 21. The reticle stage 21 continuously moves the reticle R in the Y direction on a reticle base (not shown), and synchronizes in the X, Y, and rotation directions. The reticle R is minutely driven so as to reduce the error. The position of the reticle stage 21 is measured with high precision by a laser interferometer (not shown), and the reticle stage 21 is driven based on the measured values and control information from a main control system 25 composed of a computer that controls the overall operation of the apparatus. Is done. The reticle operating section 6 is composed of a reticle R, a reticle stage 21, and a reticle base and a reticle loader (not shown). The optical path of the exposure light IL in the reticle operating section 6, that is, from the condenser lens system 20 to the projection optical system PL. The optical path is closed by the reticle chamber 2.

On the other hand, the wafer W is held on the wafer stage 23 via the wafer
Numeral 3 continuously moves the wafer W in the Y direction on the wafer base 24 and stepwise moves the wafer W in the X and Y directions. In addition, the wafer stage 23 projects the surface of the wafer W by an autofocus method based on information on the position (focus position) in the optical axis AX direction of the surface of the wafer W measured by the autofocus sensors 8a and 8b. Focus on the image plane of PL. The position of the wafer stage 23 is measured with high accuracy by a laser interferometer (not shown),
The wafer stage 23 is driven based on the measured values and the control information from the main control system 25. The wafer operation unit 7 includes the wafer W, the wafer holder 22, the wafer stage 23, the auto focus sensors 8a and 8b, the wafer base 24, and a wafer loader (not shown). The optical path of the exposure light IL in the wafer operation unit 7, that is, projection. The optical path from the optical system PL to the wafer W is closed by the wafer chamber 4.
The projection optical system PL is housed in the lens barrel 3 in a sealed state, and the optical path from the optical member on the reticle side of the projection optical system PL to the optical member on the wafer side is sealed in the lens barrel 3.

At the time of exposure, the shot area to be exposed on the wafer W is moved stepwise before the exposure area of the projection optical system PL, and the reticle R is moved through the reticle stage 21 to the illumination area of the exposure light IL. The operation of scanning the wafer W in the Y direction at a constant speed β · VR (β is the projection magnification of the projection optical system PL) via the wafer stage 23 in synchronization with scanning at a constant speed VR in the Y direction.・
The reduced image of the pattern of the reticle R is sequentially transferred to each shot area on the wafer W by repeating the AND scan method.

When vacuum ultraviolet light such as F ₂ laser light is used as the exposure beam, the vacuum ultraviolet light
Oxygen (O ₂ ), carbon dioxide (CO
₂ ), since it is largely absorbed by light-absorbing substances such as water vapor (H ₂ O), organic substances, and halides, the concentration of the light-absorbing substance corresponding to these impurities of the present invention is required to prevent the attenuation of the exposure beam. Must be suppressed to about 10 ppm or less. Therefore, in this example, the gas in the atmosphere on the optical path of the exposure beam (the gas in the illumination system chamber 1 to the wafer chamber 4) is passed through the gas through which the exposure beam passes, ie, nitrogen (N
₂ ) Gas or helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (X
e) or high transmittance and chemically stable to an exposure beam such as a rare gas made of radon (Rn), and
The light-absorbing substance is replaced with a highly-removed gas (hereinafter referred to as "purge gas"). The nitrogen gas and the rare gas are collectively referred to as an inert gas.

The nitrogen gas can be used as a gas (purge gas) through which the exposure beam is transmitted up to a wavelength of about 150 nm even in a vacuum ultraviolet region.
The light substantially acts as a light-absorbing substance with respect to light of about nm or less. Therefore, it is desirable to use a rare gas as a purge gas for an exposure beam having a wavelength of about 150 nm or less. Also, among rare gases, it is desirable to use helium from the viewpoint of stability of refractive index and high thermal conductivity, but helium is expensive. May be used.
Further, as the purge gas, not only a single kind of gas may be supplied, but also a mixed gas such as a gas obtained by mixing nitrogen and helium at a predetermined ratio may be supplied.

As described above, the projection exposure apparatus of this embodiment is provided with a supply / exhaust mechanism for replacing the gas in the illumination system chamber 1 to the wafer chamber 4 with a purge gas. FIG. 2 shows a supply / exhaust mechanism of the present embodiment. In FIG. 2 in which parts corresponding to those in FIG. 1 are denoted by the same reference numerals, an exhaust unit 36 including a vacuum pump ~ Wafer chamber 4
It comprises an air supply device 26 for supplying a purge gas into the inside, a storage device 26a for storing a high-purity purge gas, and the like. The illumination system chamber 1 to the wafer chamber 4 each have a pipe 3
Connected to the exhaust device 36 through 2A to 32D,
Each of the pipes 32A to 32D has an electromagnetic open / close valve 3
3A to 33D are provided. Valves 33A to 33D
Is controlled by the main control system 25. Exhaust device 3
6 sucks a gas in an arbitrary space of the illumination system chamber 1 to the wafer chamber 4 until a predetermined pressure is reached according to control information from the main control system 25, separates a purge gas from the sucked gas, and temporarily To accumulate. The exhaust device 36 is connected to the air supply device 26 via a pipe 37 with a valve 38, and supplies the accumulated purge gas to the air supply device 26 as needed. In the storage device 26a, a high-purity purge gas is stored in a state of being squeezed or liquefied at a high pressure, and the storage device 26a is connected to the air supply device 26 through a pipe 40 with a valve 39, A purge gas is supplied to the air supply device 26 as needed. Air supply device 26
Adjusts the temperature of the purge gas from the storage device 26a or the exhaust device 36, and adjusts the HEPA filter (High Efficiency Parity).
The light-absorbing substances and the like are removed from the purge gas by a dust filter such as a ticulate air-filter) or a chemical filter for removing the light-absorbing substances and the like containing a trace amount of organic substances.

Materials removed by these filters include those that float in the optical path of the exposure beam and change the transmittance (illuminance) or illuminance distribution of the illumination optical system or projection optical system PL, or a projection exposure apparatus. And a substance which adheres to the optical member and causes fogging or a substance which adheres to the surface of the wafer W (resist) and deforms the pattern image after the development processing. Here, an activated carbon filter (for example, Gigasorb (trade name) manufactured by Nitta Co., Ltd.), a zeolite filter, or a combination thereof can be used as the filter. As a result, silicon-based organic substances such as siloxane (a substance having an Si-O chain as an axis) or silazane (a substance having an Si-N chain as an axis) are removed.

The air supply device 26 is provided in the illumination system chamber 1.
To the wafer chamber 4 via pipes 27A to 27D, respectively, and the pipes 27A to 27D are provided with valves 28A to 28D of an electromagnetic opening and closing type, respectively. Then, the air supply device 26 supplies a purge gas to the illumination system chamber 1 to the wafer chamber 4 according to control information from the main control system 25. By supplying the purge gas from the air supply device 26 and selectively opening and closing the valves 28A to 28D by the main control system 25, the purge gas is supplied at a desired flow rate to any space of the illumination system chamber 1 to the wafer chamber 4. It is configured to be able to.

An oxygen concentration meter 34 for detecting oxygen as a light-absorbing substance is connected to the air supply device 26 via a pipe 35, and the gas in the air supply device 26, that is, the illumination system chamber 1 is The oxygen concentration of the purge gas supplied into the wafer chamber 4 is measured, and the measured value is supplied to the main control system 25. In this case, when the oxygen concentration measured by the oxygen concentration meter 34, that is, the concentration of the representative impurity exceeds a predetermined allowable value, as an example, the main control system 25
Control information is issued such that the usage ratio of the purge gas collected from the exhaust device 36 is reduced and the usage ratio of the extremely high-purity purge gas supplied from the storage device 26a is increased with respect to 6.

The illumination system chamber 1 to the wafer chamber 4 are connected to the dew point meter 29A via pipes 31A to 31D, respectively.
To 29D are connected, the dew points of the gas in the illumination system chamber 1 to the wafer chamber 4 are measured at a predetermined sampling rate by the dew point meters 29A to 29D, and these measured values are supplied to the main control system 25. . Dew point meter 29A-29D
Corresponds to the humidity measuring device of the present invention.

The dew point refers to the temperature [° C.] of the surface when the surface starts to dew when an object is cooled in a gas, and when the surface starts to frost. Temperature (frost point) may be used. At a temperature at which dew begins to form on the surface of the object, the gas in contact with the object is saturated, so the partial pressure of the water vapor of the gas is equal to the saturated water vapor pressure at the dew point. In addition, the temperature of each part of the exposure apparatus and the temperature of the gas are controlled to approximately a predetermined temperature T1. Therefore, by measuring the dew point T2, the humidity of the gas, that is, the steam pressure at the temperature T1 (= the saturated steam pressure at the dew point T2) ph2 with respect to the saturated steam pressure ph1 at the temperature T1 (which is known) here. Of the ratio (= ph2 / ph1) in% (relative humidity). For example, a mirror surface of a metal can be cooled, and the dew point can be detected from the temperature when the surface is condensed and fogged. In this example, a semiconductor type sensor that is inexpensive and easy to maintain is used as a dew point meter. Further, the dew point [° C.] may be converted into the humidity [%], but the value of the dew point itself may be used as a value substantially representing the humidity.

For example, a gas whose moisture content (humidity or dew point) is controlled to be particularly low, such as nitrogen gas vaporized from liquid nitrogen, is used as a purge gas as a purge gas.
When the air is supplied to the inside of the wafer chamber 4), the outside air having a normal humidity gradually enters each airtight chamber, and the light absorbing substance is mixed into the airtight chamber. ) Increases, the dew point (humidity) increases as shown in FIG.

In FIG. 3, the horizontal axis represents the concentration C of the light absorbing substance in each hermetic chamber, and the vertical axis represents the dew point D (equivalent to humidity here) in the hermetic chamber. As shown in FIG. The dew point D changes substantially in proportion to the concentration C (substantially in inverse proportion to the concentration of the purge gas). Accordingly, the relationship between the dew point D and the concentration C of the light absorbing substance is determined in advance, and the dew points in the illumination system chamber 1 to the wafer chamber 4 are respectively measured, so that the main control system 25 can perform the illumination system chamber 1 to the wafer chamber 4, the concentration of the light absorbing substance in the atmosphere of the optical path of the exposure light can be detected. In this example, the relationship between the dew point D and the concentration C of the light-absorbing substance shown in FIG. 3 is obtained for each airtight chamber in the form of, for example, a linear function, and the allowable concentration C1 of the light-absorbing substance is also determined. The allowable concentration C1 is stored in the storage unit in the main control system 25 from the input device 25a in FIG. Since outside air is likely to be mixed in the reticle chamber 2 and the wafer chamber 4, for example, the allowable concentration C1 in the reticle chamber 2 and the wafer chamber 4 may be set higher than that in the illumination system chamber 1 and the lens barrel 3. Further, the main control system 25 is also connected with an alarm device 25b including, for example, a display device for displaying alarm information and the like.

When the exposure operation is started, in FIG. 1, the main control system 25 operates the exhaust device 36 to exhaust the gas in the illumination system chamber 1 to the wafer chamber 4, and then supplies the gas. The apparatus 26 is operated to fill the illumination system chamber 1 to the wafer chamber 4 with a temperature-controlled purge gas to a predetermined pressure (usually about 1 atm substantially equal to the outside pressure).
Until the dew points D in the illumination system chamber 1 to the wafer chamber 4 measured by the dew point meters 29A to 29D become smaller than the allowable value D1 corresponding to the allowable concentration C1 in FIG. 3, respectively.
The main control system 25 repeats the above-described exhausting and charging with the purge gas. For example, when it is difficult to make the structures of the reticle chamber 2 and the wafer chamber 4 into a structure having a large pressure resistance,
The gas in the corresponding airtight chamber may be replaced with a purge gas by gas flow control in which the exhaust by the exhaust device 36 and the air supply by the air supply device 26 are simultaneously performed at a predetermined flow rate. In this way, after the concentration C of the light-absorbing substance becomes lower than the allowable concentration C1 in each of the hermetic chambers, the valve 3
Exposure is started by closing 3A-33D and 28A-28D.

During the exposure, the main control system 25 monitors the value of the dew point D measured by the dew point meters 29A to 29D, and measures the measured value of the dew point D in a certain airtight room (for example, the illumination system chamber 1). Is greater than the allowable value D1 in FIG. 3, the exposure operation is stopped, the corresponding valve 33A is opened, and the exhaust device 3 is opened.
After performing the exhaust by 6, the valve 33A is closed and the valve 28A is opened to supply the purge gas from the air supply device 26 to the airtight chamber to the above-described predetermined pressure. This operation is repeated until the measured value of the dew point D becomes smaller than D1, then the valves 33A and 28A are closed and exposure is started again.

Thus, in each of the hermetic chambers of the present embodiment, the exposure is performed in a state where the concentration of the light absorbing substance is lower than the allowable concentration C1, so that the illuminance of the exposure light IL is maintained at a high level, and the throughput is good and good. Exposure can be performed with excellent imaging characteristics. In this example, the illumination system chamber 1
Since inexpensive dew point meters 29A to 29D are used for measuring (managing) the concentration of the light absorbing substance in the wafer chamber 4 instead of the expensive oxygen concentration meter as in the conventional example, the manufacture of the exposure apparatus The cost can be reduced, and the operating cost of the exposure apparatus can be reduced.

The dew point meters 29A to 29D also have the advantage of reducing the cost and time required for maintenance because the frequency of performing replacement and calibration (calibration) of parts such as the detection unit is reduced as compared with the oxygen concentration meter. is there. If the measured value of the dew point D in the predetermined hermetic chamber does not become smaller than the allowable value D1 even after exhausting the gas in each hermetic chamber and supplying the purge gas, the main control system 25 stops the exposure operation. To the operator through the alarm device 25b. In response to this, the operator may manually exhaust the gas in the airtight chamber and supply the purge gas, for example.

The rise in the concentration of the light-absorbing substance due to the incorporation of outside air into the illumination system chamber 1 to the wafer chamber 4 can be detected with high precision by the dew point meters 29A to 29D. For example, even if the light-absorbing substance is mixed in the air supply device 26 and the light-absorbing substance flows into the illumination system chamber 1 to the wafer chamber 4, the light absorbing substance is mixed with the dew point meter 29.
A to 29D may not be easily detected. Therefore, in this example, an oxygen concentration meter 34 is connected to a portion near the air supply port of the air supply device 26 to measure the oxygen concentration of the purge gas supplied to the illumination system chamber 1 to the wafer chamber 4. When the pressure rises, for example, the usage ratio of the extremely high-purity purge gas from the storage device 26a is increased. This makes it possible to prevent the supply of oxygen gas on the optical path of exposure light while minimizing the use of an expensive oxygen concentration meter.

The gas in the air supply device 26 is as follows.
It is desirable to measure the concentration of not only oxygen but also other light absorbing substances such as carbon dioxide. However, in the air supply device 26, the concentration of the purge gas may be measured instead of the concentration of the light absorbing substance. In addition, only when the projection exposure apparatus is installed,
For confirmation, the concentration of the light absorbing substance or the concentration of the purge gas in the gas in the air supply device 26 may be measured.

In the above embodiment, the dew point meters 29A to 29D are used to substantially measure the humidity in each airtight room.
Is used to measure the humidity of the water vapor pressure in order to measure substantially, or a normal hygrometer (dry-humidity meter, absorption hygrometer to detect the amount of water vapor absorption, electric resistance to detect the electrical resistance value) A hygrometer and an infrared absorption hygrometer for detecting the transmittance of infrared rays may be used.

Next, another example of the embodiment of the present invention will be described with reference to FIG. Also in this example, a projection exposure apparatus similar to that of FIG. 1 is used, but corresponding airtight chambers (illumination system chamber 1 to wafer chamber 4) are used instead of the dew point meters 29A to 29D.
Barometer 50A-50 that measures the pressure (atmospheric pressure) of the gas inside
The difference is that D is used. In this case, the main control system 25 controls the gas exhaust from each airtight chamber and the supply of the purge gas based on the air pressure in each airtight chamber measured by the barometers 50A to 50D. As the barometers 50A to 50D, a semiconductor type sensor which is cheaper and easier to maintain than an oxygen concentration meter, an aneroid barometer which expands and detects the amount of elastic deformation of a metal, a mercury barometer, or the like is used. As the barometers 50A to 50D of the present embodiment, microbarometers that detect only minute pressure fluctuations near the atmospheric pressure (approximately 1 atm) may be used.

In this embodiment, the concentration of the light-absorbing substance in each hermetic chamber, that is, the mixing ratio, is estimated from the measured value of the atmospheric pressure in each hermetic chamber (illumination system chamber 1 to wafer chamber 4). That is, when the purge gas leaks from each airtight chamber or outside air containing a light-absorbing substance is mixed in, the air pressure inside the airtight chamber changes, so that, for example, each airtight chamber is lower than the outside air (atmospheric pressure) P1 in advance. A purge gas is charged at an atmospheric pressure P2 (P1> P2). By reducing the atmospheric pressure, the amount of exposure light absorbed is reduced. And, as an example, the air pressure P1
And P2, an allowable value P3 (P1>P3> P2) is set, and when the air pressure in each airtight chamber exceeds the allowable value P3, the concentration of the light absorbing substance in the airtight chamber exceeds the allowable range. Then, the gas in the airtight chamber is exhausted and the purge gas is supplied. By measuring the atmospheric pressure in this way, as in the case of measuring the humidity (dew point),
Use of an expensive oxygen concentration meter can be minimized, and the concentration of the light-absorbing substance in the atmosphere in the optical path of the exposure light can be managed at low cost.

In the above embodiment, when the gas in each airtight chamber is replaced (purged) by the purge gas, the purge gas having a flow rate substantially equal to the flow rate of the gas to be exhausted is used instead of the suction method with the reduced pressure. May be used. When purging is performed by the gas flow control method, the higher the concentration of the light-absorbing substance in the hermetic chamber, the longer the time required for purging.
It is desirable to control the flow rate of the purge gas in accordance with the humidity (dew point) and pressure measured in A to 50D. That is, when the change amount of the humidity and the atmospheric pressure is large and the inflow amount of the light absorbing substance is large, it is desirable to increase the flow rate of the purge gas,
Thereby, the concentration of the light absorbing substance can be reduced in a short time.

As can be seen from FIG. 1, the optical path length of the exposure light in the optical path (hereinafter, referred to as "partial optical path") in the illumination system chamber 1, the reticle chamber 2, the lens barrel 3, and the wafer chamber 4 is apparent. The optical path lengths in the illumination system chamber 1 are the longest, and the optical path lengths in the lens barrel 3 are the next. The amount of the light-absorbing substance through which the exposure light passes is proportional to the optical path length when the concentration of the light-absorbing substance is constant. Therefore, the amount of decrease in illuminance is different between the four partial optical paths. It is desirable that the amount of the substance be small. Therefore, the allowable absorption rate (exposure rate) of the exposure light in each partial optical path
It is desirable to set the allowable concentration of the light-absorbing substance in each of the partial optical paths so that is constant. In this case, reticle chamber 2
Also, in the partial light path in the wafer chamber 4, the allowable concentration of the light absorbing substance is set higher than the allowable concentration in the other partial light paths, but the contribution to the reduction in the illuminance of the exposure beam as a whole is the same. Becomes

Further, for example, in a portion where the optical path length is short (the volume of the space where the concentration of the light absorbing material including the optical path is controlled is small), purging is performed with a cheaper gas (such as nitrogen gas), and the optical path length is long ( In a portion where the volume of the light-absorbing substance concentration including the optical path is controlled (the volume is large), management may be performed such as purging with helium gas or the like even if it is somewhat expensive. As a result, for example, the stability of the temperature control characteristics and the imaging characteristics can be improved without significantly increasing the operation cost. Further, an expensive gas (such as helium gas) is supplied to a portion having a high degree of sealing (air density), and an inexpensive gas (such as a nitrogen gas) is supplied to a portion having a low degree of sealing (a light absorbing substance is easily mixed). Even so, the operating cost can be reduced.

The housing (a cylindrical body or the like) constituting the illumination system chamber 1 to the wafer chamber 4 and the piping for supplying nitrogen, helium and the like are made of a material with little impurity gas (degassing), for example, stainless steel. Steel, ethylene tetrafluoride, tetrafluoroethylene-terfluoro (alkyl vinyl ether),
Alternatively, it is desirable to form from various polymers such as a tetrafluoroethylene-hexafluoropropene copolymer.
Further, it is also desirable that a cable for supplying electric power to a drive mechanism (reticle blind, each stage, etc.) in each housing or the like is similarly covered with the above-described material with a small amount of impurity gas (degas).

Further, even in an exposure apparatus using dry air as a purge gas, the concentration of the light-absorbing substance in the atmosphere of the optical path of the exposure light can be reduced by using a dew point meter or a barometer as in the above embodiment. Management can be performed at low cost. The present invention is not limited to a scanning exposure type projection exposure apparatus, but also a batch exposure type (stepper type) projection exposure apparatus.
Obviously, the present invention can be applied to a proximity type exposure apparatus, a contact type exposure apparatus, and the like.

The projection exposure apparatus of the above embodiment adjusts the illumination optical system and the projection optical system, and connects each component electrically, mechanically or optically to a predetermined state. Can be assembled. The work in this case is desirably performed in a clean room where the temperature is controlled. Then, the wafer W exposed as described above undergoes a developing process, a pattern forming process, a bonding process, and the like, whereby devices such as semiconductor elements are manufactured.

The present invention is not limited to the above-described embodiment, but may take various configurations without departing from the spirit of the present invention.

[0048]

According to the first and second exposure methods according to the present invention, the mixing ratio of impurities inside the hermetic chamber can be reduced without using an expensive oxygen concentration meter conventionally used for controlling impurities. Can be estimated, and the impurity concentration in the atmosphere of the optical path of the exposure beam can be managed at low cost. In addition, replacement of parts such as the detection unit and calibration (calibration)
And the cost and time required for maintenance are also reduced.

According to the first and second exposure apparatuses of the present invention, the first and second exposure methods of the present invention can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus used in an embodiment of the present invention in a partial cross section.

FIG. 2 is a configuration diagram showing a supply / exhaust mechanism of the projection exposure apparatus of FIG.

FIG. 3 is a diagram showing an example of a relationship between a dew point in each hermetic chamber of the projection exposure apparatus of FIG. 1 and a concentration of a light absorbing substance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Illumination system chamber, 2 ... Reticle room, 3 ... Lens barrel, 4 ...
Wafer chamber, 5: illumination optical system unit, 6: reticle operation unit, 7
... Wafer operation unit, 11 ... Exposure light source, R ... Reticle, PL
... Projection optical system, W ... Wafer, 25 ... Main control system, 26 ... Air supply device, 29A-29D ... Dew point meter, 34 ... Oxygen concentration meter,
36 ... exhaust device, 50A, 50D ... barometer

Claims (9)

[Claims] Illuminating a first object with an exposure beam;
In an exposure method for exposing a second object with an exposure beam having passed through a pattern of an object, a humidity inside an airtight chamber provided on an optical path of the exposure beam is measured, and impurities in the airtight chamber are measured based on the measurement result. Estimating a mixing ratio, and controlling at least one of exhaust of gas from the hermetic chamber and supply of gas permeating the exposure beam to the hermetic chamber based on the estimation result. Method. 2. The exposure method according to claim 1, wherein the humidity inside the airtight chamber is obtained from a measurement result of a dew point inside the airtight chamber. 3. A method for measuring at least one of a concentration of a predetermined gas absorbing the exposure beam and a concentration of a gas transmitted by the exposure beam inside the hermetic chamber, and obtaining the measurement result and the humidity measurement result. 3. The exposure method according to claim 1, wherein the mixing ratio of the impurities is estimated. Illuminating a first object with an exposure beam;
In an exposure method for exposing a second object with an exposure beam having passed through a pattern of an object, a pressure inside an airtight chamber provided on an optical path of the exposure beam is measured, and impurities in the airtight chamber are measured based on the measurement result. Estimating a mixing ratio, and controlling at least one of exhaust of gas from the hermetic chamber and supply of gas permeating the exposure beam to the hermetic chamber based on the estimation result. Method. 5. A method for measuring at least one of a concentration of a predetermined gas that absorbs the exposure beam and a concentration of a gas that the exposure beam transmits inside the hermetic chamber, based on the measurement result and the pressure measurement result. The exposure method according to claim 4, wherein the mixing ratio of the impurity is estimated. 6. The exposure method according to claim 1, wherein a flow rate of a gas transmitted through the exposure beam supplied to the airtight chamber is controlled. 7. illuminating a first object with an exposure beam;
An exposure apparatus for transferring an image of a pattern of an object onto a second object, comprising: an exhaust mechanism that exhausts gas inside an airtight chamber provided on an optical path of the exposure beam; An air supply mechanism for supplying gas passing therethrough, a humidity measurement device for measuring the humidity inside the airtight chamber, and controlling the exhaust mechanism and the air supply mechanism based on the measurement result of the humidity measurement device. An exposure apparatus, comprising: a controller that replaces gas inside the airtight chamber. 8. An exposure apparatus according to claim 7, wherein said humidity measuring device includes a dew point meter. 9. illuminating a first object with an exposure beam;
An exposure apparatus for transferring an image of a pattern of an object onto a second object, comprising: an exhaust mechanism that exhausts gas inside an airtight chamber provided on an optical path of the exposure beam; An air supply mechanism for supplying gas passing therethrough, a pressure measurement device for measuring the pressure inside the airtight chamber, and controlling the exhaust mechanism and the air supply mechanism based on the measurement result of the pressure measurement device. An exposure apparatus, comprising: a controller that replaces gas inside the airtight chamber.