JP2001176770A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner, in which negative variation of optical characteristics is suppressed and further positive control for the optical characteristics is performed easily, using a simple constitution. SOLUTION: In this aligner, provided with a lens unit 61 that has a pressure control chamber R2 for positively controlling the optical characteristics by varying pressure of gas, a first gas supply device that supplies a first gas (He), and a second gas supply device that supplies a second gas (N2) whose rate of change of the optical characteristics to pressure change is larger than that of the first gas, are provided. The first gas is supplied to a part R1 of the lens unit 61, excluding the pressure control chamber R2, and the second gas or mixed gas of the first and second gases is supplied to the pressure control chamber R2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for transferring a mask pattern onto a substrate in a lithography process for manufacturing, for example, a semiconductor device, a liquid crystal display device, or a thin film magnetic head.

[0002]

2. Description of the Related Art For example, in an exposure apparatus such as a stepper used for manufacturing a semiconductor device, in order to cope with an increase in the degree of integration and the degree of fineness of the semiconductor device, it is particularly required to increase the resolution. Since the resolving power is almost proportional to the wavelength of the illumination light, the exposure wavelength has been gradually shortened conventionally. That is, the illumination light ranges from the visible g-line (wavelength 436 nm) of the mercury lamp to the ultraviolet region i.
In recent years, KrF excimer laser light (wavelength 248 nm) and ArF excimer laser light (wavelength 193 nm) have been used instead of the line (wavelength 365 nm). Further, a shorter wavelength of _{F 2} laser beam (wavelength: 157
nm) are also being considered.

[0003] However, in a wavelength region of about the ArF excimer laser beam or less, that is, in a vacuum ultraviolet region (VUV) of about 200 nm or less, absorption by oxygen in the air occurs to generate ozone, and the transmittance is reduced. . Therefore, for example, in an exposure apparatus that uses ArF excimer laser light, a so-called nitrogen purge is performed in which most of the gas in the optical path of the illumination light is replaced with nitrogen. Furthermore, a wavelength range shorter than the wavelength of ArF excimer laser (more than about 190 nm), an absorption at nitrogen, especially F ₂ laser about a wavelength range. In this case, if the region passing through nitrogen is a very narrow region, the amount of absorption is small and there is little hindrance to exposure. However, in a long optical path, the amount of light decreases and an appropriate exposure amount cannot be obtained. Therefore, when using light in a wavelength range of about 190 nm or less, most of the optical path of the light is replaced with helium gas (He) that is inert and has high transmittance.

[0004] In addition, 190 such as ArF excimer laser is used.
Even in an exposure apparatus using light in a wavelength range longer than nm,
Helium gas is sometimes used as a purge gas because the change in optical characteristics with respect to pressure fluctuations due to atmospheric pressure fluctuations is small.

[0005] In some cases, an illumination optical system or a projection optical system provided in an exposure apparatus uses an optical characteristic adjusting apparatus utilizing the pressure dependence of the refractive index of gas. This optical characteristic adjusting device defines an airtight pressure control chamber between optical elements and adjusts the pressure of gas in the pressure control chamber, thereby moving optical elements such as lenses without moving optical elements such as lenses. It is a device that actively adjusts the characteristics, and in an optical system that replaces the optical path of the optical system with helium gas as described above, helium gas is also used as a gas used in such an optical characteristic adjustment device. Used.

[0006]

However, since the above-described optical characteristic adjusting device adjusts the optical characteristics by utilizing the pressure dependence of the refractive index of the gas, the change of the refractive index with respect to the pressure change. A gas with a higher rate may be more desirable.

That is, as described above, helium gas is used as a purge gas for an optical system because it has good characteristics such as high transmittance with respect to illumination light particularly in a short wavelength range. The characteristic that the pressure dependency with respect to the change in the refractive index is small is an advantage as a purge gas.However, in an optical characteristic adjusting device that adjusts the optical characteristic by positively changing the refractive index by changing the pressure. On the contrary, in order to perform sufficient adjustment of the optical properties,
It is necessary to make a large pressure change, and for that purpose, it is necessary to employ a pressure-resistant structure, a high-pressure supply device, and the like, which complicates the device configuration and has a problem that pressure control is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an exposure apparatus capable of suppressing negative fluctuations in optical characteristics and easily performing positive adjustment of optical characteristics with a simple configuration. The purpose is to do.

[0009]

Means for Solving the Problems In the following description, in order to facilitate understanding, each constituent element of the present invention will be described with reference numerals shown in the drawings of the embodiments. The constituent elements of the invention are not limited by these reference numerals.

An exposure apparatus according to the present invention is an exposure apparatus having an optical system (61) having a pressure control section (R2) for positively adjusting optical characteristics by changing the pressure of a gas. A first gas supply device (46) for supplying He), and a second gas supply device (84) for supplying a second gas (N ₂ ) having a rate of change in optical characteristics with respect to pressure change greater than the first gas. Wherein the first gas is applied to at least a part (R1) of the optical system excluding the pressure control unit, and the second gas or the mixture of the first gas and the second gas is applied to the pressure control unit. It is characterized by supplying gas.

According to the present invention, at least a part (all or part) of the optical system excluding the pressure control unit includes the first unit.
A gas is supplied, and as a first gas, for example, a helium gas is used, which has a characteristic that the pressure dependency of a change in refractive index is low, so that a negative change in pressure due to a change in atmospheric pressure (unintentional change) ) Can reduce fluctuations in optical characteristics, and it is possible to realize good optical characteristics. In addition, by using a gas having a characteristic of high transmittance (less loss) even for illumination light in a short wavelength range, such as helium gas, as the first gas, it is possible to cope with a short wavelength of illumination light. There is an advantage that can be.

On the other hand, a second gas or a mixed gas of the first gas and the second gas is supplied to the pressure control unit of the optical system, and the second gas is a rate of change in optical characteristics with respect to pressure change. Is larger than the first gas, the optical characteristics can be largely changed by applying a small pressure change as compared with the case where only the first gas is supplied. Therefore, it is not necessary to employ a device capable of supplying a high pressure, and positive adjustment of optical characteristics can be easily performed with a simple configuration.

As described above, two kinds of gas, the first gas and the second gas, can be supplied, and a gas having a large pressure dependence of optical characteristics is supplied to the pressure control unit of the optical system by the other parts of the optical system. At least a part of the gas is supplied with a gas having a small pressure dependency of the optical characteristics, so that the positive adjustment of the optical characteristics can be easily performed with a simple configuration, and the negative fluctuation of the optical characteristics can be reduced. Can be achieved in a compatible manner.

When helium gas is used as the first gas, a rare gas or nitrogen gas other than helium gas can be used as the second gas. When this nitrogen gas is used, nitrogen gas is slightly inferior to helium gas in terms of transmittance of illumination light in a short wavelength range, but the pressure adjustment unit occupies only a small part of the optical path of the illumination light. Therefore, the optical characteristics of the optical system as a whole are not degraded so much and the optical system is sufficiently practicable.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of a projection exposure apparatus according to an embodiment of the present invention, and FIG.

First, reference is made to FIG. A projection exposure apparatus is installed in a clean room on a floor F1 on a floor where a semiconductor manufacturing plant is located, and helium gas and nitrogen gas are supplied to the projection exposure apparatus on the floor in a so-called machine room (utility space) on the floor F2 below the floor. A gas circulating device is installed to supply and further collect and purify. By installing a device that easily generates dust and easily becomes a vibration source on a floor different from the floor where the projection exposure apparatus is installed, the cleanliness in the clean room where the projection exposure apparatus is installed is improved. It can be set extremely high and the influence of vibration on the projection exposure apparatus can be reduced. Also, an F ₂ laser light source 3 is placed on the floor F2, to reduce the area occupied by the bed F1 by the apparatus main body (footprint), and may reduce the vibration of the apparatus main body. However, such a gas circulation device may be placed on the floor where the projection exposure apparatus is installed. In the gas circulation device, the supply device may be arranged on the floor F2, and the recovery device may be arranged on the floor F1 or on the floor.

[0017] In a clean room on the floor F1, vibration isolation 2A, is provided a box-shaped case 1 through 2B, _{F 2} laser light source 3 as an illumination light source in the casing 1 (oscillation wavelength 157 nm), the exposure main body A beam matching unit (BMU) 4 that includes a movable mirror and the like for positionally matching an optical path between the unit and a light-shielding pipe 5 through which illumination light passes. Further, a box-shaped environment chamber 7 having good airtightness is installed next to the case 1, and is set on the floor F1 in the environment chamber 7 via vibration isolating tables 25A and 25B for attenuating vibration from the floor. A board 24 is provided, and an exposure main body 26 is provided on the surface board 24. A sub-chamber 6 with good airtightness extends from the pipe 5 protruding from inside the case 1 to the inside of the environmental chamber 7.
The sub-chamber 6 houses most of the illumination optical system.

[0018] During exposure, ultraviolet pulse light IL having a wavelength 157nm as illumination light emitted from the _{F 2} laser light source 3 in the casing 1 leads to subchamber 6 through the interior of BMU4 and pipe 5. In the sub-chamber 6, the ultraviolet pulse light IL enters the fly-eye lens 11 via a variable dimmer 8 as an optical attenuator and a beam shaping optical system including lens systems 9A and 9B. An aperture stop system 12 of an illumination system for changing illumination conditions in various ways is arranged on the exit surface of the fly-eye lens 11.

The ultraviolet pulse light IL emitted from the fly-eye lens 11 and having passed through a predetermined aperture stop in the aperture stop system 12 is reflected by a reflection mirror 13 and a condenser lens system 14.
, Fixed illumination field stop (fixed blind) 15 having a slit-shaped opening in reticle blind mechanism 16
A is incident on A. Further, in the reticle blind mechanism 16, a movable blind 15B for changing the width of the illumination visual field in the scanning direction is provided separately from the fixed blind 15A.

The ultraviolet pulse light IL shaped like a slit by the fixed blind 15A of the reticle blind mechanism 16
Irradiates a slit-shaped illumination area on the circuit pattern area of the reticle R with a uniform intensity distribution via an imaging lens system 17, a reflection mirror 18, and a main condenser lens system 19. In this embodiment, the exit surface of the light shielding pipe 5 to the main condenser lens system 19 is housed in the sub-chamber 6, it is also sealed further space from the interior of the pipe 5 to the exit surface of the F ₂ laser light source 3 , Sub-chamber 6. The space in the sub-chamber 6 is provided with a branch pipe 31 of the pipe 31 from the gas circulating device downstairs.
Helium gas (He) whose temperature is controlled to a predetermined purity or more is supplied at two points via a and a branch pipe 31b.

The pipe 31 is provided with an opening / closing valve V11. By controlling the opening / closing of the opening / closing valve V11 by the control system 45, the supply of helium gas to the projection exposure apparatus and the stop thereof can be switched. it can. Further, the branch pipe 31a of the pipe 31 is provided with an opening / closing valve V13, the branch pipe 31b is provided with an opening / closing valve V14 between itself and the projection optical system PL, and the opening / closing valve V15 between the illumination optical system (sub-chamber 6). Is provided. In addition, piping 31
Through the branch pipe 31c and the opening / closing valve V12,
Helium gas whose temperature is controlled at a predetermined purity or higher is supplied into the case 1 in which the _two laser light sources 3 and the BMU 4 and the like are stored. Therefore, the helium gas is supplied to at least one of the case 1, the sub-chamber 6 (illumination optical system), and the projection optical system PL by independently opening and closing the open / close valves V12 to V15 by the control system 45. It has become possible. However, since helium has a small molecular weight and easily leaks, part of the helium leaked naturally from the sub-chamber 6 rises and accumulates in the space 7 a near the ceiling of the environmental chamber 7.

Under the ultraviolet pulse light IL, the image of the circuit pattern in the illumination area of the reticle R is transferred to the slit-like exposure area of the resist layer on the wafer W via the projection optical system PL. The exposure area is located on one of the plurality of shot areas on the wafer. The projection optical system PL of the present embodiment is a dioptric system (refractive system). However, since the glass material that can transmit such short-wavelength ultraviolet light is limited, the projection optical system PL is formed of a catadioptric system ( As a catadioptric system) or a reflective system, the transmittance of the ultraviolet pulse light IL in the projection optical system PL may be increased. In the following description, the Z axis is taken parallel to the optical axis AX of the projection optical system PL, the X axis is taken parallel to the plane of FIG. 1 and the Y axis is taken perpendicular to the plane of FIG. 1 in a plane perpendicular to the Z axis. I do.

At this time, the reticle R is sucked and held on the reticle stage 20, and the reticle stage 20 can move on the reticle base 21 at a constant speed in the X direction (scanning direction), and can move in the X, Y, and rotation directions. It is mounted so that it can be moved slightly. The two-dimensional position and rotation angle of the reticle stage 20 (reticle R) are controlled by a drive control unit (not shown) equipped with a laser interferometer.

On the other hand, the wafer W is held by suction on a wafer holder 22, the wafer holder 22 is fixed on a wafer stage 23, and the wafer stage 23 is mounted on a surface plate 24. The wafer stage 23 controls the focus position (position in the Z direction) and the tilt angle of the wafer W by an autofocus method so that the surface of the wafer W is aligned with the image plane of the projection optical system PL, and the wafer stage 23 is moved in the X direction. , And stepping in the X and Y directions. The two-dimensional position and rotation angle of the wafer stage 23 (wafer W) are also controlled by a drive control unit (not shown) provided with a laser interferometer. At the time of scanning exposure, the reticle R is scanned via the reticle stage 20 via the wafer stage 23 in synchronization with the reticle R being scanned in the + X direction (or -X direction) at the speed Vr with respect to the illumination area of the ultraviolet pulse light IL. The wafer W is scanned in the −X direction (or + X direction) at a speed β · Vr (β is a projection magnification from the reticle R to the wafer W) with respect to the exposure area.

In the present embodiment, a gas circulating device downstairs (nitrogen circulating devices 38 to 40, 82 to
88, 95, etc.), the nitrogen content (N ₂ ) is controlled while the oxygen content is kept extremely low. The nitrogen gas circulated in the environment chamber 7 is returned to the nitrogen circulating device via, for example, an exhaust hole on the bottom surface side of the environment chamber 7, a pipe 95 connected to a side surface thereof, and an opening / closing valve V19.

The projection optical system PL has, for example, a projection lens unit 61 as shown in FIG. Three lenses 63, 64, 65 are provided at predetermined intervals in a lens barrel 62 of the projection lens unit 61, and are fixed by a holding ring 66. 67 is a lens 64
And a lens separating ring for maintaining a predetermined distance between the lens and the lens 65. Actually, the projection lens unit 61 has many lenses, but FIG. 2 shows only three of them for simplification of the description. Between the lenses 63 and 64 and between the lenses 64 and 65, these lenses and the lens barrel 62
Define lens chambers R1 and R2.

The lens chamber R1 has a gas supply port G1 having a quick coupler Q1 attached thereto and a quick coupler Q2.
Is provided with a gas outlet G2 to which a quick coupler Q3 is attached and a gas outlet G4 to which a quick coupler Q4 is attached in the lens chamber R2. Is provided.

Projection lens unit 61 of projection optical system PL
As in the sub-chamber 6, the temperature of the lens chamber R1 is controlled at a predetermined concentration or higher by a gas circulation device (helium circulation device) downstairs via a branch pipe 31b of a pipe 31 and an opening / closing valve V14. Helium gas is supplied. The helium gas in the lens chamber R1 is appropriately exchanged for a new gas by being discharged through the pipe 94 and the opening / closing valve V18. Helium gas leaking from the lens barrel of the projection optical system PL rises and accumulates in a space 7a near the ceiling of the environmental chamber 7.

The lens chamber R2 of the projection lens unit 61
Is the optical characteristic (magnification, focal position, etc.) of the projection optical system PL
It is a pressure control chamber which constitutes a part of the optical characteristic adjusting device for adjusting the pressure. This optical characteristic adjusting device utilizes the pressure dependency of the refractive index of gas, and includes a lens 64,
An apparatus that positively adjusts optical characteristics such as magnification and focal position without moving optical elements such as lenses by adjusting the pressure of gas in the pressure control chamber R2 defined between 65 and 65. It is.

That is, as shown in FIGS. 1 and 2, a branch pipe 31d is connected to a pipe 31 for supplying helium gas, and a branch pipe 31d is connected to a pipe 88 for supplying nitrogen gas. A pipe 88c is connected, and these branch pipes 31d and 88c are connected to a gas supply port of the pressure adjusting device 96. A pipe 97 is connected to a gas outlet of the pressure adjusting device 96. The other end of the pipe 97 is connected to the pressure control chamber R2 of the projection lens unit 61 of the projection optical system PL via the valve V26. I have.

The pressure adjusting device 96 mixes helium gas and nitrogen gas at an arbitrary mixing ratio based on control by a characteristic control device 99 managed by a main control system (not shown) for overall managing the projection exposure apparatus. This is a device that mixes and supplies the mixture to the pressure control chamber R2 at an arbitrary pressure. The characteristic control device 99
Determine the mixture ratio of helium gas and nitrogen gas,
The pressure in the pressure control chamber R2 required to realize the optimal optical characteristics is calculated in relation to the determined mixing ratio, and based on these, the pressure adjusting device 96 and the opening / closing valves (control valves) V26 and V27 are calculated. Control the opening and closing of

[0032] As described above, the optical path of the pulsed ultraviolet light IL from the exit surface of the F ₂ laser light source 3 to the main condenser lens system 19, and ultraviolet pulse light IL in the projection optical system PL
A helium gas having a high transmittance even for light of about 190 nm or less is supplied to the optical path (excluding the pressure control chamber R2). In addition, from the main condenser lens system 19 to the entrance surface of the projection optical system PL, from the exit surface of the projection optical system PL to the surface of the wafer W, and in the pressure control chamber R2, helium is used for light of about 190 nm or less. Although nitrogen gas having a transmittance lower than that of the gas is supplied, an optical path passing through the nitrogen gas is extremely short, so that the absorption amount by the nitrogen gas is small. Thus, ultraviolet pulse light IL emitted from the F ₂ laser light source 3, since the high transmittance as a whole (efficiency) reaches the surface of the wafer W, can reduce the exposure time (scanning exposure time), the throughput of the exposure step Is improved.

Since the helium gas has a thermal conductivity approximately six times better than that of the nitrogen gas, the helium gas is accumulated in the optical element in the illumination optical system and the optical element in the projection optical system PL by irradiation with the ultraviolet pulse light IL. The generated thermal energy is efficiently transmitted to the cover of the sub-chamber 6 and the lens barrel of the projection optical system PL through helium. Further, the thermal energy of the cover of the sub-chamber 6 and the lens barrel of the projection optical system PL is controlled by temperature-controlled air in a clean room,
Alternatively, the waste heat is efficiently discharged to the outside such as downstairs by the temperature-controlled nitrogen gas in the environment chamber 7. Therefore, the temperature rise of the illumination optical system and the optical element of the projection optical system PL is extremely low, and the deterioration of the imaging performance is minimized. Further, since the amount of change in the refractive index of the helium gas with respect to the pressure change is extremely small, for example, the refractive index in the projection optical system PL is extremely unlikely to change due to external factors. Image performance is maintained.

In addition, the pressure control chamber R2 of the projection optical system PL
Is supplied with a mixed gas of helium gas and nitrogen gas.Since the rate of change of optical characteristics with respect to pressure change of nitrogen gas is considerably larger than that of helium gas, it is compared with the case where only helium gas is supplied. Thus, it is possible to greatly change the optical characteristics by applying a small pressure change. Therefore, it is not necessary to employ a pipe 97, an open / close valve V26, or the like having a high pressure resistance, or a pressure regulator 96 or the like capable of supplying a high pressure. Can be done.

As described above, two types of helium gas and nitrogen gas can be supplied, and the pressure control chamber R2 of the projection optical system PL is provided with a mixed gas of helium gas and nitrogen gas having a large pressure-dependent optical characteristic. Is supplied to the other part of the projection optical system PL with a helium gas having a small pressure dependence of the optical characteristics. Therefore, the positive adjustment of the optical characteristics can be easily performed with a simple configuration, and the optical characteristics can be easily adjusted. It is possible to achieve both the reduction of the passive fluctuation (fluctuation caused by an external factor).

The reason that the mixed gas is supplied to the pressure control chamber R2 of the projection optical system PL is that the rate of change of the optical characteristics with respect to the rate of change of the pressure can be adjusted by adjusting the mixture ratio. This is because fine adjustment of optical characteristics can be performed. However, the pressure control chamber R2
May be supplied only with nitrogen gas. In this case, the piping 31d and the like can be omitted, the configuration is simplified, and the optical characteristics can be largely adjusted by slightly changing the pressure. It is. In FIG. 2, a nitrogen cylinder 84 as a nitrogen supply device (second gas supply device) and a helium cylinder 46 as a helium supply device (first gas supply device) are representatively shown. It is assumed that a nitrogen circulation device and a helium circulation device are also included.

Next, referring to FIG. 1 again, the gas circulation device of the present embodiment will be described in detail. Environmental chamber 7
Inside, the helium leaked from the sub-chamber 6 and the helium leaked from the projection optical system PL are lighter than nitrogen and rise and accumulate in the space 7a near the ceiling. However, the gas in the space 7a is a mixed gas containing nitrogen and air entering from outside the environment chamber 7 in addition to helium.

In this embodiment, a pipe 33 is connected to the space 7a from the outside of the environmental chamber 7, and the pipe 33 passes through an opening provided in the floor F1 and communicates with a gas circulation device downstairs. Further, the case 1 is connected to the pipe 33 by a pipe 92, and the pipe 92 has an on-off valve V16
Is provided. The illumination optical system (sub-chamber 6) and the projection optical system PL are also connected to the pipe 33 by pipes 93 and 94, respectively, and the pipes 93 and 94 are provided with open / close valves V17 and V18, respectively. Therefore,
The control system 45 independently opens and closes the opening / closing valves V16 to V18, so that at least one of the case 1, the illumination optical system (sub-chamber 6), and the projection optical system PL contains organic substances and dust. Helium gas can be recovered. The pressure control chamber R2 of the projection optical system PL (lens unit 61) is connected to the pipe 33 via a pipe 98, and the pipe 98 is provided with an open / close valve V27. However, the tip of the pipe 98 does not need to be connected to the pipe 33, and may be open to the environment chamber 7.

A suction pump (or fan) 34 is arranged in the middle of the pipe 33 on the bottom side of the floor F1.
3, and the mixed gas sucked from the space 7a or the like by the pump 34 goes to the gas circulation device downstairs. Then, the mixed gas that has passed through the pump 34 is discharged to the dust collecting and draining device 35.
, Where fine dust and moisture are removed to avoid clogging of the later adiabatic compression cooling passages.

The mixed gas that has passed through the dust collecting and draining device 35 is
It reaches a refrigeration unit 37 via a pipe 36, where it is subjected to adiabatic compression cooling.
Cooling to liquid nitrogen temperature. By this
Therefore, nitrogen and air components liquefy, so the liquefied nitrogen
Easily converts elemental air components and gaseous helium
Can be separated. Mainly nitrogen liquefied in the refrigerator 37
(N₂ The air component consisting of
To the cylinder 40 via the suction pump 39 arranged at
Collected.

On the other hand, the helium which remains as a gas in the refrigerating device 37 passes through a pipe 41 and a suction pump (or fan) 42 disposed in the middle thereof, and flows through a first flow of a mixing temperature adjusting device 43. Head to the entrance.

It is to be noted that helium gas is converted into impurities such as air, nitrogen,
A purification device that removes and separates other contaminants is configured.However, even with these devices, contaminants that may remain without being separated and removed can be further separated and removed to produce high-purity helium gas. In order to regenerate, a chemical filter suitable for separating and removing contaminants contained in the helium gas, other filtration devices, a separation device utilizing the difference in chemical properties between helium and contaminants, etc. It is desirable to provide the above or a combination thereof in the former stage (piping 36) or the latter stage (piping 41) of the refrigerating device 37.

In this embodiment, a removing device 80 for removing impurities contained in the mixed gas is provided between the dust collecting and draining device 35 and the refrigerating device 37. This removing device 80
Is an activated carbon filter (for example, Gigasorb manufactured by Nitta Corporation), a zeolite filter, or a combination thereof, and a siloxane (Si) existing inside the environmental chamber 7, the illumination optical system, and the projection optical system PL. -O-chain-based material) or silazane (Si-
A silicon-based organic substance such as a substance whose axis is the N chain) is removed.

Here, one of the siloxanes, Si-
A substance called "cyclic siloxane" in which O chains are looped,
It is contained in silicon-based adhesives, sealing agents, paints, and the like used in projection exposure apparatuses, and these are generated as degassing due to aging. Cyclic siloxane easily adheres to the surface of a photosensitive substrate or an optical element (such as a lens), and when exposed to ultraviolet light, is oxidized to become a SiO ₂ -based cloudy substance on the optical element surface.

As the silazane, there is HMDS (hexamethyldisilazane) used as a pretreatment agent in a resist coating step. HMDS reacts with water to change (hydrolyze) into a substance called silanol. Silanol easily adheres to the surface of photosensitive substrates and optical elements, etc.
When further irradiated with ultraviolet light, it is oxidized and becomes a SiO ₂ -based cloudy substance on the surface of the optical element. Silazane generates ammonia by the above-mentioned hydrolysis, and when this ammonia coexists with siloxane, the surface of the optical element is further easily clouded.

By the way, an organic substance (hydrocarbon) adhering to the surface of the optical element of the illumination optical system or the projection optical system, etc.
Is separated by light cleaning and mixed into the helium gas. In this embodiment, the hydrocarbon is also removed by the removing device 80. Further, in addition to the aforementioned silicon-based organic substances, plasticizers (such as phthalsan ester) and flame retardants (phosphoric acid, chlorine-based substances) are also generated as degassed wiring and plastics in the environmental chamber 7.
These plasticizers and flame retardants are also removed by the removal device 80. Even if ammonium ions, sulfate ions, and the like floating in the clean room enter the environment chamber 7, these ions are also removed by the removing device 80.

High-purity helium gas is supplied from a cylinder 46 filled with high-purity helium gas at a high pressure to a second inlet of the mixing temperature controller 43 via a pipe 47 and an opening / closing valve 48. I have. The liquefied helium may be stored in the cylinder 46. Further, a pipe 4 through which the purified helium passes through a refrigerating device 37 or the like.
In FIG. 1, a helium concentration meter 44 for measuring the concentration (or purity) of helium is installed near the inlet to the mixing temperature controller 43, and the measurement data is supplied to a control system 45. When the concentration of the collected helium measured by the helium concentration meter 44 does not reach the predetermined allowable value, the control system 45 opens the opening / closing valve 48 and sends the high-purity helium from the cylinder 46 into the mixing temperature controller 43. Add helium. When the helium concentration measured by the helium concentration meter 44 is equal to or more than the allowable value, the control system 45 closes the on-off valve 48. Further, the opening and closing valve 48 is closed even during the period in which the exposure operation is not performed. Note that an oxygen concentration meter may be used instead of the helium concentration meter 44.

Further, the mixing temperature controller 43 mixes the purified helium and the helium from the cylinder 46 within a predetermined pressure range to control the temperature to a predetermined temperature, and connects the temperature-controlled and pressure-controlled helium to a pipe. 31. The components from the dust collecting and draining device 35 to the mixing temperature adjusting device 43 constitute a helium circulating device. The pipe 31 passes through an opening provided on the floor F1 on the upper floor and reaches the clean room on the upper floor, and a pump for blowing air (or on the bottom side of the floor F1 in the middle of the pipe 31). Fan 32 is provided.
The helium gas having a concentration equal to or higher than a predetermined value within a predetermined atmospheric pressure range by the mixing temperature adjusting device 43 and controlled to a predetermined temperature is supplied to the pipe 31 and then supplied to the pipe 32 while being blown by the pump 32. 31 branch pipes 31a,
It is supplied to the inside of the case 1 of the projection exposure apparatus on the floor F1, the inside of the sub-chamber 6, and the inside of the projection optical system PL via 31b and 31c.

Here, in this embodiment, the control system 45 closes the on-off valve V11 of the pipe 31 and sets the pipes 92 to
With the open / close valves V16 to V18 of 94 opened, the pump 34 sucks gas (such as helium gas) in the case 1, the sub-chamber 6, and the projection optical system PL. At this time, it is desirable to close an open / close valve (not shown) provided near the inlet of the pipe 33 so that the gas mixture in the upper space 7 a of the environmental chamber 7 does not flow into the pipe 33. Thereafter, the opening / closing valves V16 to V18 are closed, and the opening / closing valve V11 is opened to supply helium to the case 1, the sub-chamber 6, and the projection optical system PL, respectively, and the helium concentration in the inside reaches a predetermined value. The opening / closing valves V12 to V15 are closed in order from the first, and after all the opening / closing valves V12 to V15 are closed, the opening / closing valve V11 is closed. Although not shown, a helium densitometer or an oximeter is provided in each of the case 1, the sub-chamber 6, and the projection optical system PL, and the control system 45 controls the open / close valve based on the output of the densitometer. V12 ~
Controls opening and closing of V15. One of the case 1, the sub-chamber 6, and the projection optical system PL, for example, the projection optical system P
When the helium concentration at L becomes lower than a predetermined value,
Helium is supplied by opening the on-off valves V11 and V14. At this time, a main control system (not shown) for overall control of the entire projection exposure apparatus checks the operation of the apparatus main body. For example, when the exposure processing of the wafer is in the middle, the supply of helium is started until the exposure processing is completed. The main control system sends a command to the control system 45 so as to wait.

As described above, in the present embodiment, most of the helium gas supplied so as to flow through most of the optical path of the illumination light (ultraviolet pulse light IL) of the projection exposure apparatus is supplied from the upper part of the environmental chamber 7 to the pipe 33. The helium is recovered in the helium circulation device downstairs, so that the amount of expensive helium used can be reduced. Therefore, the operating cost of the projection exposure apparatus can be reduced while increasing the transmittance to the illumination light and increasing the cooling efficiency of the optical element.

In the above embodiment, a cylinder (for example, the same as the above-described nitrogen cylinder 40) for storing the collected helium is provided between the freezing device 37 and the mixing temperature adjusting device 43 in FIG. Further, it may be provided. in this case,
In order to be able to store a large amount, it is desirable that helium be compressed to about 100 to 200 atmospheres by a compressor and stored in the cylinder. This reduces the volume by approximately 1/100 to 1/200. Further, helium may be liquefied and stored by a liquefier using a turbine or the like. The volume of helium is almost 1/7 due to liquefaction
00. When the highly compressed or liquefied helium is reused as described above, for example, when it is returned to a state of about 1 atm, the temperature decreases due to expansion, so that it is necessary to control the heating temperature with a heater or the like. It is desirable to provide a buffer space for keeping the pressure constant.

Further, an opening / closing valve is provided in front of (upstream of) the mixing temperature control device 43 to adjust the amount of helium taken in from a cylinder (not shown) for storing the collected helium, or to adjust the amount of helium taken in the flow passage (pipe 41). ) May be controlled. By using this open / close valve and the open / close valve 48 of the pipe 47 together, the helium concentration sent to the pipe 31 can be more easily adjusted.

In the above embodiment, the helium gas is supplied so as to circulate most of the optical path of the illumination light. However, the helium gas further covers the entire optical path, and the helium gas is supplied to the reticle stage 20 and the wafer stage 23. Helium gas may be supplied to the entire inside of the environmental chamber 7 in order to increase the cooling efficiency. However, even in this case, nitrogen gas or a mixed gas of nitrogen gas and helium gas is supplied to the pressure control chamber R2 of the projection optical system PL.

In the above embodiment, the helium purified by the mixing temperature controller 43 and the high-purity helium are mixed, but the concentration (purity) of the purified helium is adjusted.
Is low, there is a possibility that the concentration of helium supplied to the projection exposure apparatus cannot be rapidly increased to an allowable range by simply mixing. In such a case, the purified helium is stored in another cylinder, and the purity is further increased in another recycling factory, and the high-purity helium in the cylinder 46 is supplied to the projection exposure apparatus. It may be.

In the above-described projection exposure apparatus, the case 1, the sub-chamber 6, and the projection optical system PL (excluding the pressure control chamber R2) are filled (filled) with helium using the open / close valves V11 to V18. However, since a helium circulation device is provided, for example, the on-off valve V16
V18 may be closed, the helium may be supplied at all times while adjusting the flow rate of helium in accordance with the amount of helium leaking from the case 1, the sub-chamber 6, and the projection optical system PL. V11-V18
Helium may always be supplied at a predetermined flow rate while the helium is opened. In the latter case, in particular, the open / close valves V11 to V18
May not be provided.

Further, pipes 92 to connecting each of the case 1, the sub-chamber 6, and the projection optical system PL to the pipe 33 are provided.
94 (and the opening / closing valves V16 to V18) may not be provided. At this time, the opening / closing valves V11 to V15 may not be further provided. In this case, case 1, sub-chamber 6,
Since helium leaks from the projection optical system PL, helium may be replenished, that is, helium may be supplied constantly or as needed (periodically) so that the helium concentration is maintained at or above an allowable value.

Further, in this embodiment, F₂Laser light source
3 and the BMU 4 are housed in the case 1.
₂BMU4 etc. are stored in the housing separately from the laser light source 3
Then F ₂Helium gas is attached to the laser light source 3 and the housing, respectively.
May be supplied. At this time, F₂Leh
The light source 3 and the housing are mechanically connected to form a partition plate for both.
F₂Just provide a glass plate through which the laser can pass
No.

Next, the nitrogen circulating apparatus of this embodiment will be described in detail. In the environmental chamber 7 through the pipe 88,
And supplying nitrogen gas to the pressure adjusting device 96,
Nitrogen is recovered from the chamber 7 through the pipes 95, 98, 33, purified, and circulated. When the nitrogen concentration in the environmental chamber 7 reaches a predetermined value, the supply of the nitrogen gas is stopped, and the pipe 88 (or its branch paths 88a, 88a) is stopped.
b) and the pipe 95 are closed by the on-off valves V23 (or V24, V25) and V19, respectively, and when the nitrogen concentration in the environmental chamber 7 becomes lower than a predetermined value, the on-off valves V23 (and V24, V25) may be opened to supply nitrogen.

The nitrogen separated from the helium or the like in the refrigerating device 37 is collected by a pump 39 through a pipe 38 into a cylinder 40. Further, the nitrogen in the cylinder 40 is passed through a pipe 81 by a pump 83 to a temperature controller 86.
Sent to The pipe 81 is provided with an opening / closing valve V21 and a nitrogen concentration meter (or oxygen concentration meter) 82 for measuring the concentration of nitrogen sent to the temperature control device 86. The measured value of the concentration meter 82 is controlled. It is supplied to the system 45. When the nitrogen concentration measured by the concentration meter 82 has not reached the predetermined value, the control system 45 opens the on-off valve V22 of the pipe 85 connecting the nitrogen cylinder 84 and the temperature control device 86, and Supplies high-purity nitrogen to the temperature controller 86. On the other hand, when the nitrogen concentration is equal to or higher than the predetermined value, the control system 45 closes the on-off valve V22.
When the nitrogen concentration measured by the concentration meter 82 is extremely low, the on-off valve V21 may be closed and only nitrogen from the cylinder 84 may be sent to the temperature control device 86. And
When the nitrogen concentration measured by the densitometer 82 reaches an allowable value (a value smaller than the aforementioned predetermined value), the on-off valve V21 is opened.

Further, the temperature control device 86 mixes the recovered and purified nitrogen with the nitrogen from the cylinder 84 to a predetermined temperature,
The pressure is controlled, and the temperature-controlled and pressure-controlled nitrogen is supplied to the pipe 88. In the middle of the pipe 88, a pump (or fan) 87 for blowing air is provided on the bottom side of the floor F1. By this pump 87, nitrogen is supplied into the environmental chamber 7 through the branch pipes 88a and 88b of the pipe 88. Is done.

In the present embodiment, the discharge port of the branch pipe 88a is provided between the projection optical system PL and the wafer W so that nitrogen flows between the projection optical system PL and the wafer W.
On the other hand, the branch tube 88b is branched into two, one outlet is provided between the condenser lens 19 and the reticle R, and the other outlet is provided between the reticle R and the projection optical system PL. . As described above, high-purity nitrogen can be preferentially supplied between the illumination optical system (condenser lens 19) and the projection optical system PL, and between the projection optical system PL and the wafer W. The supply amount of nitrogen can be reduced as compared with the case where nitrogen is filled into 7 and its concentration is maintained at a predetermined value or more.

In this embodiment, the environment chamber 7 is set to a nitrogen atmosphere. However, for example, air from which impurities have been removed is supplied to the environment chamber 7, and the space between the illumination optical system and the projection optical system PL is supplied as described above. It is also possible to simply supply nitrogen between the projection optical system PL and the wafer W and to make both spaces have a nitrogen atmosphere. At this time, helium may be supplied instead of nitrogen. Further, as the air to be supplied to the environment chamber 7, chemically clean dry air (for example, having a humidity of about 5% or less) from which the above-described organic substances have been removed may be used. However, even in these cases, the projection optical system P
The L pressure control chamber R2 is supplied with a nitrogen gas or a mixed gas of a nitrogen gas and a helium gas.

The recovered nitrogen may be compressed to about 100 to 200 atm by a compressor, or may be liquefied by a liquefier using a turbine or the like and stored in the cylinder 40. The branch pipes 88a, 88b
The opening / closing valves V24 and V25 respectively provided for supplying nitrogen to only one between the illumination optical system and the projection optical system PL and between the projection optical system PL and the wafer W. When nitrogen is simultaneously supplied to the nozzles, the opening and closing valves V24 and V25 may not be provided.

Further, in the present embodiment, nitrogen is caused to flow between the illumination optical system and the projection optical system PL, and between the projection optical system PL and the wafer W, respectively.
The pipe 88 may be simply connected to the environmental chamber 7 without providing the 88b, and the opening / closing valve V23 may be closed when the nitrogen concentration in the environmental chamber 7 becomes a predetermined value or more. Also, regardless of the presence or absence of the branch pipes 88a and 88b,
Nitrogen may be supplied at a predetermined flow rate while the opening and closing valves V23 and V19 are open to circulate the nitrogen in the environment chamber 7. In this case, in particular, the open / close valves V23 and V19
May not be provided.

In this embodiment, nitrogen (or helium) or the like is supplied into the environment chamber 7. However, depending on the wavelength range of the exposure illumination light, the environment chamber 7 is chemically clean and temperature-dependent. It is only necessary to supply controlled air. For example, if the exposure wavelength is about 190 nm or more, the inside of the environment chamber 7 may be an air atmosphere.

Further, in this embodiment, most of the illumination optical system is housed in the sub-chamber 6 and a part of the sub-chamber 6 is installed in the environment chamber 7. It may be installed in. in this case,
The recovery rate of helium leaking from the sub-chamber 6 can be improved. Further, in order to collect helium leaking from a part of the sub-chamber 6 installed outside the environmental chamber 7, the sub-chamber 6 outside the environmental chamber 7 is covered with a housing, and a pipe 33 is connected to an upper part of the housing. You may.

The circulating apparatus (helium circulating apparatus, nitrogen circulating apparatus) as described above does not need to be provided for each of a plurality of exposure apparatuses. Alternatively, a smaller number of circulation devices than the number of exposure devices can be provided. By doing so, purification costs are reduced.

Further, for example, the supply of helium gas to the lens chamber R1 of the projection lens unit 61 and the supply of a mixed gas of helium gas and nitrogen gas to the lens chamber (pressure control chamber) R2 of the projection lens unit 61 shown in FIG. It is desirable to replace it with a new one. In particular, when the lens unit is used for the first time after assembly is completed, contaminants such as adhesives, fillers, paints, and cleaning agents aggregate and adhere to the lens surface, resulting in overall light transmittance. It is preferable that the replacement process be performed relatively frequently because the replacement process is highly likely to be partially or partially reduced. In addition, since such a phenomenon tends to gradually decrease with the elapse of the operation time,
The frequency of replacement may be reduced according to the operation time, and after a certain amount of operation time has elapsed, the purification process may be performed relatively diffusely and periodically. This exchange is measured by measuring the transmittance of the lens unit,
This may be performed when the transmittance becomes low.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, the pressure control chamber R2 of the projection optical system PL
The gas supplied to the gas need not necessarily be a mixed gas of nitrogen gas and helium gas, but only a nitrogen gas, a rare gas (such as neon) excluding helium gas, or a rare gas (such as neon) excluding helium gas. A mixed gas of helium gas or the like may be used.

Further, in the above embodiment, the gas (nitrogen gas and helium gas) used for pressure control of the optical property adjusting device is supplied from the nitrogen circulating device and the helium circulating device. It is not necessary to employ a system, and a gas for pressure adjustment may be supplied from a nitrogen cylinder or a helium cylinder. Further, a lens unit 6 having a pressure control chamber R2 constituting an optical characteristic adjusting device
A lens unit such as 1 can be provided in the illumination optical system.

[0072] In the embodiment described above, has been described employing an exposure apparatus which emits F ₂ excimer laser beam (wavelength 157 nm) as the light source, Kr
F excimer laser beam (wavelength 248 nm), ArF excimer laser beam (wavelength 193 nm), which was adopted which emits Ar ₂ laser beam (wavelength 126 nm), in addition, a so-called extreme ultraviolet (EUV, or XUV) region most The present invention can also be applied to an exposure apparatus that employs a light source that emits light having a wavelength of 13 nm or 7 nm close to X-rays, or X-rays having a wavelength of 1 nm.

In the above embodiment, the step
Although the description has been given of the reduction projection scanning exposure apparatus (scanning stepper) of the AND scan method, for example, the entire surface of the reticle pattern is irradiated with exposure illumination light while the reticle and the wafer are stationary, and the reticle is exposed. A step-up / repeat type reduction projection type exposure apparatus (stepper) for collectively exposing one section area (shot area) on a wafer to which a pattern is to be transferred, and an exposure apparatus such as a mirror projection type or a proximity type. The present invention can be applied to the same manner. Further, the projection optical system is not limited to a system in which all optical elements are refractive elements (lenses), and may be an optical system including only reflective elements (mirrors, etc.), or a refractive element and a reflective element (concave mirror). , A mirror, etc.). Further, the projection optical system is not limited to the reduction optical system, but may be an equal-magnification optical system or an enlargement optical system.

Further, a single-wavelength laser in the infrared or visible range oscillated from a DFB semiconductor laser or a fiber laser is used as exposure illumination light, for example, a fiber amplifier doped with erbium (or both erbium and yttrium). May be used, and a harmonic that is wavelength-converted to ultraviolet light using a nonlinear optical crystal may be used.

For example, the oscillation wavelength of a single wavelength laser is set to 1.
When the wavelength is in the range of 51 to 1.59 μm, the generated wavelength is 18
An eighth harmonic having a wavelength in the range of 9 to 199 nm or a tenth harmonic having a generation wavelength in the range of 151 to 159 nm is output. Especially the oscillation wavelength is 1.544 to 1.553 μm
m, 8 in the range of 193 to 194 nm.
A harmonic wave, that is, ultraviolet light having substantially the same wavelength as the ArF excimer laser is obtained, and the oscillation wavelength is set to 1.57 to 1.58 μm.
m, 1 in the range of 157 to 158 nm.
0 harmonic, i.e., ultraviolet light having almost the same wavelength as the F ₂ laser is obtained.

The oscillation wavelength is set to 1.03 to 1.12 μm
, A 7th harmonic whose output wavelength is in the range of 147 to 160 nm is output.
Assuming that the wavelength is in the range of 099 to 1.106 μm, the generated harmonic is the seventh harmonic in the range of 157 to 158 μm, that is, F _2.
Ultraviolet light having substantially the same wavelength as the laser is obtained. In addition,
As a single-wavelength oscillation laser, ytterbium-doped
A fiber laser is used.

Further, a semiconductor device, a liquid crystal display,
Not only projection exposure equipment used for manufacturing thin-film magnetic heads and imaging devices (such as CCDs), but also projection exposure equipment that transfers circuit patterns to glass substrates or silicon wafers to manufacture reticles or masks The present invention can also be applied. Here, DUV (far ultraviolet) light or VUV
In an exposure apparatus using (vacuum ultraviolet) light or the like, a transmissive reticle is generally used, and as a reticle substrate, quartz glass, quartz glass doped with fluorine, fluorite, magnesium fluoride, quartz, or the like is used. EUV
In an exposure apparatus, a reflection type mask is used. In a proximity type X-ray exposure apparatus or a mask projection type electron beam exposure apparatus, a transmission type mask (stencil mask, membrane mask) is used, and a silicon wafer is used as a mask substrate. Are used.

By the way, an illumination optical system composed of a plurality of lenses and a projection optical system are incorporated in the main body of the exposure apparatus for optical adjustment, and a reticle stage and a wafer stage composed of many mechanical parts are mounted on the main body of the exposure apparatus. The case 1, the illumination optical system (sub-chamber 6), the projection optical system PL (projection lens unit 61), and the environment chamber 7 are connected to a helium circulation device, a nitrogen circulation device, and the like, respectively. Further, the exposure apparatus of the above embodiment can be manufactured by performing overall adjustment (electrical adjustment, operation confirmation, and the like). It is desirable that the manufacture of the exposure apparatus be performed in a clean room in which the temperature, cleanliness, and the like are controlled.

In the semiconductor device, a step of designing the function and performance of the device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, and a step of manufacturing a reticle by the exposure apparatus of the above-described embodiment. It is manufactured through a step of exposing and transferring a pattern onto a wafer, a device assembling step (including a dicing step, a bonding step, and a package step), an inspection step, and the like.

[0080]

According to the present invention, as described in detail above, two types of gases, a first gas and a second gas, can be supplied. To
At least a part of the other parts of the optical system is supplied with a gas having a small pressure dependence of the optical characteristics, so that the positive adjustment of the optical characteristics can be easily performed with a simple configuration, and the depolarization of the optical characteristics. There is an effect that reduction of the target fluctuation can be achieved at the same time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a projection exposure apparatus according to an embodiment of the present invention, with a part thereof being in section.

FIG. 2 is a diagram illustrating a main configuration of a projection exposure apparatus according to an embodiment of the present invention.

[Explanation of symbols]

F1, F2 bed 3 F ₂ laser light source 6 sub-chamber 7 environmental chamber R reticle PL projection optical system W wafer 20 the reticle stage 23 wafer stage 26 exposure main 31,33,88 pipe 35 dust collecting drainage device 37 refrigeration system for 40 Nitrogen 43 Mixing temperature controller 46 Helium cylinder 61 Lens unit 62 Lens barrel 63-65 Lens R1, R2 (pressure control chamber) Lens chamber 84 Nitrogen cylinder 96 Pressure regulator 31d, 88c, 97, 98 Piping 99 Characteristic controller V26 , V27 opening and closing valve

Claims (4)

[Claims] 1. An exposure apparatus having an optical system having a pressure control unit for positively adjusting optical characteristics by changing a pressure of a gas, comprising: a first gas supply device for supplying a first gas; And a second gas supply device that supplies a second gas having a change rate of optical characteristics larger than the first gas to the first gas, wherein the first gas is provided in at least a part of the optical system excluding the pressure control unit. And supplying the second gas to the pressure control unit. 2. An exposure apparatus having an optical system having a pressure control unit for positively adjusting optical characteristics by changing a pressure of a gas, comprising: a first gas supply device for supplying a first gas; And a second gas supply device that supplies a second gas having a change rate of optical characteristics larger than the first gas to the first gas, wherein the first gas is provided in at least a part of the optical system excluding the pressure control unit. An exposure apparatus for supplying a mixed gas of the first gas and the second gas to the pressure control unit. 3. The exposure apparatus according to claim 1, wherein the first gas is a helium gas. 4. The exposure apparatus according to claim 3, wherein the second gas is a rare gas other than a helium gas or a nitrogen gas.