JPH11283903A - Projection optical system inspection device and projection aligner provided with the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately recognize the cleaning timing for a projection optical system and to prevent the incomplete cleaning of the projection optical system. SOLUTION: In this projection aligner, among irradiation lights irradiated from a light-emitting part 18 at a fixed interval timing, the irradiation light transmitted through a branching mirror 19 is reflected on the surface of a projection lens 9 and then received by a first light-receiving part 20, and the irradiation light branched by the branching mirror 19 is received by a second light-receiving part 21. Then, in a measurement control system 22, an arithmetic part 23 obtains a difference ΔR, between a prescribed reflectivity R0 read from a storage part 24 and the actual reflectivity Rr of the surface of the projection lens 9, based on photoelectric signals from both light receiving parts 20 and 21. Then, when the numerical value of a contamination degree based on the difference ΔR lies outside of an allowable range, the irradiation light from a light source 16 for irradiation in an optical cleaning device 17 is transmitted through a window material 11, the entire surface of the projection lens 9 is irradiated, and optical cleaning based on a Schumann-Runge absorption effect is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection apparatus for a projection optical system for projecting and exposing a pattern on a mask onto a substrate based on irradiation of exposure light in a photolithography step in a process of manufacturing a semiconductor integrated circuit and the like. The present invention relates to a projection exposure apparatus having the inspection apparatus.

[0002]

2. Description of the Related Art In a projection exposure apparatus used in a photolithography process for manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, or the like, a fine circuit pattern having a fine line width formed on a mask such as a reticle. Projection exposure is performed on a photosensitive substrate such as a wafer coated with a resist layer (hereinafter, described by taking a “wafer” as an example) via a high-resolution projection optical system. That is, after the wafer stage is moved up and down along the optical axis of the projection optical system and the wafer surface on the wafer stage is aligned with the focal position of the projection optical system, the wafer stage is orthogonal to the optical axis of the projection optical system. It is two-dimensionally moved in a predetermined direction in a plane. For example, in a step-and-repeat type projection exposure apparatus, the wafer stage is positioned at a position where the center (optical axis) of the exposure field of the projection optical system and the center of each shot area on the wafer coincide with the two-dimensional movement. Is stopped, and the exposure operation is performed at that position.

On the other hand, a photosensitive resin (for example, novolak resin) is generally used as a resist layer applied on the wafer in the projection exposure process. Therefore, at the time of the projection exposure, volatile substances and the like generated from the photosensitive resin may adhere to the surface of the optical member located closest to the wafer side of the projection optical system and contaminate the surface of the optical member. there were. Therefore, conventionally, in the projection exposure apparatus, an operation of wiping the surface of the optical member of the projection optical system by an operator, that is, a cleaning operation has been an essential operation.

[0004]

However, the cleaning operation is performed at a time when the operator visually confirms the contamination state, or periodically at a predetermined periodic timing. Was being done.

[0005] Therefore, in the case of a cleaning operation based on the visual inspection of each worker, if there is variation in the judgment criteria of each operator, the execution timing of the cleaning operation is overtaken despite the necessity of the cleaning operation. There was a risk. Therefore, in such a case, since the contamination state of the optical member surface is left as it is, the optical characteristics of the projection optical system are changed, and there is a possibility that exposure failure may be caused.

On the other hand, in the case of a regular cleaning operation, the cleaning operation is performed uniformly at a predetermined time without confirming the contamination state, so that unnecessary cleaning operation is performed from the viewpoint of maintenance. There were things. Therefore, in that case, the atmosphere in the clean room unnecessarily comes into contact with the projection optical system for the cleaning operation, which is not always preferable from the viewpoint of maintaining good exposure conditions.

Further, the degree of removal of the contaminated state by the cleaning operation depends on the skill of the cleaning operation of each operator. Therefore, even if the operator performs the cleaning operation, the contamination state of the optical member surface can be sufficiently reduced. Could not be removed. Furthermore,
In the case of a cleaning operation by an inexperienced operator, the contamination of the surface of the optical member may be worsened, and the optical characteristics of the projection optical system may be deteriorated more than before the operation.

The present invention has been made in view of the above circumstances, and an object of the present invention is to be able to accurately grasp the cleaning timing of a projection optical system in a projection exposure apparatus. or,
Another object is to be able to prevent incomplete cleaning of the projection optics.

[0009]

In order to achieve each of the above objects, the present invention relates to a projection optical system inspection apparatus, wherein the optical member closest to the photosensitive substrate W of the projection optical system 1 in the projection exposure apparatus is provided. 9 Measuring means 22 for measuring the degree of surface contamination
The gist is that it is provided. Therefore, according to the first aspect of the present invention, the degree of contamination on the surface of the optical member 9 closest to the photosensitive substrate W of the projection optical system 1 is measured by the measuring means 22,
Before the cleaning, the necessity of the cleaning operation is determined based on the measurement result, and after the cleaning, the quality of the dirt removal by the cleaning operation is determined.

[0010] Further, the invention of claim 2 of the present application is the above-mentioned claim 1.
In the invention described in the above, the measuring means 22 measures the reflectance of the reflected light reflected on the surface of the optical member 9 or the transmittance of the transmitted light transmitted through the surface of the optical member 9, and based on the measurement result, the optical The gist is to measure the degree of contamination on the surface of the member 9. Therefore, in the invention of claim 2, in addition to the operation of the invention of claim 1, the measurement of the degree of contamination is performed by obtaining the reflectance or transmittance of the surface of the optical member 9 to be measured. Will be

Further, the invention of claim 3 of the present application is the above-mentioned claim 2.
In the invention described in (1), the measuring means 22 is configured to determine the surface of the optical member 9 based on a comparison result between a preset predetermined reflectance R _O or predetermined transmittance and an actually measured actual reflectance R _r or actual transmittance. The gist is to measure the degree of pollution of the soil. Therefore, in the invention according to claim 3, in addition to the effect of the invention according to claim 2, the reflectance or transmittance of the surface of the optical member 9 to be measured is measured in advance, and the measurement is performed. The result is defined as a predetermined reflectance R _O or a predetermined transmittance, and then the actual reflectance R _r or the actual transmittance obtained by actually measuring is compared with the predetermined reflectance R _O or a difference obtained by comparing with the predetermined transmittance. The degree of contamination is measured.

Further, the invention of claim 4 of the present application is the above-mentioned claim 3.
In the invention described in the above, the measuring unit 22 receives light after the irradiation light is reflected by the surface of the optical member 9 or transmitted through the surface of the optical member 9 based on the irradiation light irradiated at a predetermined timing. The gist is that the actual reflectance _Rr or the actual transmittance is measured based on a comparison result between the photoelectric signal thus received and the photoelectric signal received without the irradiation light passing through the surface of the optical member 9. Therefore,
According to the fourth aspect of the invention, in addition to the operation of the third aspect of the invention, when the irradiation light is irradiated with the irradiation timing shifted a plurality of times during the execution of the cleaning operation, the change in the progress of the cleaning condition is caused. It is reflected on the actual reflectance _Rr or the actual transmittance measured based on the irradiation light of each time.

According to a fifth aspect of the present invention relating to a projection exposure apparatus, the projection optical system inspection apparatus 25 according to any one of the first to fourth aspects and the surface of the optical member 9 are provided. And a light cleaning device 17 for irradiating predetermined irradiation light having a light cleaning effect. Therefore, in the invention of claim 5, the projection optical system inspection apparatus 2
If it is determined that the cleaning operation is necessary based on the measurement result of 5, the optical cleaning device 17 irradiates predetermined irradiation light, and the surface of the optical member 9 is optically cleaned based on the irradiation.

[0014] The invention of claim 6 of the present application is directed to claim 5
In the invention described in (1), the gist is that the optical cleaning device 17 includes a gas supply unit 27 that supplies an oxidation promoting gas near the surface of the optical member 9. Therefore,
According to the sixth aspect of the invention, in addition to the operation of the fifth aspect of the present invention, an oxidation promoting gas is supplied to the vicinity of the surface of the optical member 9 at the time of the cleaning operation by the optical cleaning device 17, so that the cleaning effect is improved. improves.

[0015] The invention of claim 7 of the present application is the invention of claim 6.
In the invention described in (1), the gist is that the light cleaning device 17 includes a shielding unit 32 for shielding the atmosphere near the surface of the optical member 9 from the outside, including the optical path of the irradiation light. Therefore, in the invention of claim 7, in addition to the effect of the invention of claim 6, the gas supply means 2
When the oxidation promoting gas is supplied from the optical member 9,
The atmosphere near the surface is shielded from outside by the shielding means 32 so as to include the optical path of the irradiation light. Therefore, the cleaning is further promoted by the oxidation promoting gas.

Further, the invention of claim 8 of the present application is the invention of claim 5
The invention according to any one of claims 7 to 7,
The gist of the light cleaning device 17 is to irradiate the irradiation light to the optical member 9 through a replaceable window material 11. Therefore, in the invention of claim 8, in addition to the operation of the invention described in any one of claims 5 to 7, the light cleaning device 1 is provided by the window material 11.
7 is protected, and the window material 11 is replaced when the window material 11 becomes dirty, so that the light cleaning effect is favorably maintained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which the present invention is embodied in a step-and-repeat type projection exposure apparatus will be described below with reference to FIGS. As shown in FIG. 1, in the present embodiment, the Z axis is set in a direction parallel to the optical axis AX of the projection optical system 1, and FIG.
The X axis is taken in a direction parallel to the paper surface of FIG. 1, and the Y axis is taken in a direction perpendicular to the paper surface of FIG.

FIG. 1 shows a schematic configuration of the entire projection exposure apparatus. In FIG. 1, illumination light IL emitted from an exposure light source 2 has an illuminance comprising a collimator lens, a fly-eye lens, a reticle blind, and the like. The illuminance distribution is converted into a substantially uniform light beam by the uniformized illumination system 3 and is incident on the dichroic mirror 4. The illumination light IL bent vertically downward by the dichroic mirror 4 irradiates the reticle R, so that an image of the circuit pattern drawn on the reticle R with a line width of 1 μm is transmitted through the projection optical system 1. Projection exposure is performed on a wafer W as a photosensitive substrate.

The light source 2 according to the present embodiment has a laser beam (ultraviolet light) having a wavelength of 193 nm.
An rF excimer laser is used. Further, the projection exposure apparatus of the present embodiment performs stepping movement in the X-axis direction and the Y-axis direction at the time of exposure to project and expose a circuit pattern on each shot area on the wafer W. FIG. In this figure, the wafer W is not located at the exposure position in order to show a state at the time of measuring the degree of contamination of the optical system 1.

Below the dichroic mirror 4,
A reticle stage 6 movable by a drive system (not shown) including a motor and the like is provided. On the reticle stage 6, the reticle R is fixed and held by vacuum suction. On the reticle R, in addition to the circuit pattern described above, various alignment reticle patterns are formed so as to be located around the circuit pattern. Have been.

On the other hand, below the reticle stage 6, a wafer stage 7 is movably provided so as to sandwich the projection optical system 1 with the reticle stage 6. That is, the wafer stage 7 is capable of two-dimensional movement in the XY plane and minute rotation about the Z axis. Also,
A Z stage 8 movable in the Z-axis direction is provided on the wafer stage 7, and these wafer stage 7 and Z stage 8 can be moved by a drive system (not shown) including a motor and the like. Then, the wafer W coated with novolak resin, which is a kind of photosensitive resin, is held on the Z stage 8 by vacuum suction. By moving the Z stage 8 in the Z axis direction, the surface of the wafer W and the projection optical system are moved. 1 can be made to coincide with the imaging plane. In this embodiment, a projection lens 9 is provided as an optical member located closest to the wafer stage 7 in the projection optical system 1, and the surface of the lens 9 on the wafer stage 7 side is close to the surface of the wafer W during projection exposure. It has become.

Next, the light cleaning apparatus according to the present embodiment will be described. As shown in FIGS. 1 and 2, a housing 10 is provided on the wafer stage 7 near the Z stage 8.
Are buried and fixed so that the upper part thereof is slightly exposed. A window material 11 made of synthetic quartz or the like, which is capable of transmitting ultraviolet light efficiently, is removably fitted to an upper portion of the housing 10, and a mirror 12 is disposed in the housing 10 at an angle. A beam expander optical system 13 is provided on the side wall of the housing 10, and an emission end of an optical fiber 14 introduced from outside the wafer stage 7 is arranged near the optical system 13. A condensing lens 15 is provided outside the wafer stage 7 at the entrance end of the optical fiber 14.
Irradiation light source 16 made of ArF excimer laser different from
Irradiates ultraviolet light. That is, in the present embodiment, the light cleaning device 17 is constituted by the mirror 12, the optical fiber 14, the irradiation light source 16, and the like.

Next, a projection optical system inspection apparatus according to this embodiment will be described. As shown in FIGS. 1 and 2, a light emitting unit 18 is provided on the wafer stage 7 in the vicinity of an exposed portion of the housing 10. The light emitting section 18 emits predetermined irradiation light to the surface of the projection lens 9 from obliquely below, and a branch mirror 19 is disposed on an optical path connecting the surface of the lens 9 and the light emitting section 18. . A first light receiving unit 20 for receiving reflected light from the surface of the lens 9 based on irradiation from the light emitting unit 18 is disposed on the wafer stage 7, and a first light receiving unit 20 is disposed above the wafer stage 7. A second light receiving unit 21 for receiving the split light from the split mirror 19 based on the irradiation from the light emitting unit 18 is disposed in the second light receiving unit 21. The outputs of the first and second light receiving units 20 and 21 are supplied as photoelectric signals to a measurement control system 22 constituting a measuring unit.

As shown in FIG. 2, the measurement control system 22 is provided with a calculation unit 23 and a storage unit 24. The calculation unit 23 calculates the light reflectance of the surface of the projection lens 9 as the real reflectance based on the photoelectric signals output from the light receiving units 20 and 21, and stores the calculated real reflectance and the storage unit 24. The degree of contamination on the surface of the projection lens 9 is measured based on a result of comparison with a predetermined reflectance. In addition, the storage unit 24 sets the light reflectance of the surface of the projection lens 9 measured at the time of completion of the present apparatus, which is assumed to be not contaminated to such an extent that the surface of the projection lens 9 affects the optical characteristics, as the predetermined reflectance. It is stored in advance. In the present embodiment, the light emitting section 18 and the first and second light receiving sections 2
The projection optical system inspection device 25 is constituted by the measurement control systems 22 and 0 and 21. The projection optical system inspection device 2
The measurement result of the degree of surface contamination by 5 is displayed on display means 26, and the degree of contamination of the surface of the projection lens 9 in the projection optical system 1 can be objectively grasped from the display contents.

Next, the operation of the projection exposure apparatus according to this embodiment configured as described above will be described. First,
The wafer stage 7 is controlled by driving control of a main control system (not shown).
Is moved to the contamination degree measurement position in FIG. Then, the projection lens 9 located at the lowermost end in the projection optical system 1
The window material 20 on the upper part of the housing 10 is located directly below.
Then, in this state, the main control system
Is controlled at regular intervals.
The light emitting unit 1 is controlled based on the light emission control of the main control system.
When a predetermined irradiation light is emitted from the light source 8, the irradiation light transmitted through the branch mirror 19 of the irradiation light reaches the surface of the projection lens 9 and is reflected by the same, and the reflected light is transmitted to the first light receiving unit 20. Is received by the On the other hand, the irradiation light (branch light) branched by the branch mirror 19 is received by the second light receiving unit 21 without reaching the surface of the projection lens 9. Then, the photoelectric signals photoelectrically converted by the two light receiving units 20 and 21 are input to the measurement control system 22, respectively.

Then, the arithmetic unit 23 of the measurement control system 22 compares the photoelectric signal from the first light receiving unit 20 with the second light receiving unit 2
The reflectance of the surface of the projection lens 9 is calculated on the basis of the photoelectric signal from No. 1. That is, generally, when light is incident on the boundary surface between two media at a certain incident angle, its reflectance R
R = I _r / I ₀ where I ₀ is the energy intensity of the incident light beam and I _r is the energy intensity of the reflected light beam.
It is represented by Therefore, the computing unit 23 calculates the intensity of the energy based on the photoelectric signal from the first light receiving unit 20 as Ir _.
Assuming that the intensity of the energy based on the photoelectric signal from the second light receiving unit 21 is I ₀ , the actual reflectance R _r of the surface of the projection lens 9 is obtained.

Next, in the measurement control system 22, the arithmetic unit 2
3 reads the predetermined reflectance R ₀ from the storage unit 24, and calculates a difference ΔR (= R ₀ −R) between the predetermined reflectance R ₀ and the actual reflectance R _r.
r ) is calculated. Then, the obtained two reflectances R ₀ , R
_A display signal based on the difference ΔR of _r is output to the display means 26. Then, the display means 26 numerically displays the degree of contamination on the surface of the projection lens 9 based on the display signal.

On the other hand, the display signal based on the difference ΔR between the two reflectances R ₀ and R _r is also output to the main control system, and the main control system sets the contamination level based on the display signal to a predetermined tolerance. It is determined whether it is within the range. When it is determined that the numerical value is outside the allowable range, the irradiation light source 16 is caused to emit light. Then, irradiation light from the light source 16 is guided into the housing 10 via the condenser lens 15, the optical fiber 14, and the beam expander optical system 13. The direction of the irradiation light guided into the housing 10 is changed by the mirror 12, passes through the window material 11, and irradiates the entire surface of the projection lens 9.

Then, based on the irradiation, near the surface of the projection lens 9, oxygen in the air absorbs the irradiation light (ultraviolet light) to be in an excited state, and chemically changes to ozone having increased oxidizing power. That is, the absorption of the irradiation light (ultraviolet light) by oxygen is known as Schumann-Runge absorption. In this case, a light source that emits light having a wavelength of 200 nm or less, which is largely absorbed by oxygen, is used as the irradiation light source.
In the present embodiment, since the ArF excimer laser emitting ultraviolet light having a wavelength of 193 nm is used as the irradiation light source 16, the above-described Schumann-Runge absorption occurs. Accordingly, the surface of the projection lens 9 which is contaminated by the attachment of the volatile substance from the photosensitive resin (novolak resin) applied on the wafer W under an atmosphere in which the oxidizing power is enhanced based on the Schumann-Runge absorption. Then, the attached matter is oxidatively decomposed by the irradiation light. In this embodiment,
Thus, the surface of the projection lens 9 in the projection optical system 1 is optically cleaned.

As described above, when the light emission of the light emitting section 18 is repeatedly controlled by the main control system at regular intervals, the measurement control system 22 sets the predetermined reflectance R _{0 in} the same procedure as described above. The difference ΔR from the actual reflectance R _r is newly calculated each time, and a new display signal based on the calculation result is output to the display means 26. Then, the display means 26 numerically displays the degree of contamination on the surface of the projection lens 9 based on the new display signal.

Further, the main control system determines whether or not the numerical value of the contamination degree based on the new display signal is within a preset allowable range. When it is determined that the numerical value is still outside the allowable range, the light source 16 for irradiation is caused to emit light repeatedly. Accordingly, the surface of the projection lens 9 is light-cleaned based on the irradiation of the irradiation light from the irradiation light source 16 as described above. Then, after the light emission control of the light emitting section 18 by the main control system is repeated, when the main control system determines that the numerical value of the contamination degree based on the display signal is within a preset allowable range, The light cleaning operation of the surface of the projection lens 9 based on the irradiation light from the irradiation light source 16 is completed.

In the present embodiment, the following effects can be obtained by configuring the projection exposure apparatus as described above. (1) In the present embodiment, a projection optical system inspection device 25 for measuring the degree of surface contamination of the projection lens 9 in the projection optical system 1 is provided. That is, the projection lens 9 based on the measurement result output from the measurement control system 22 of the projection optical system inspection device 25.
The configuration is such that the degree of contamination on the surface is grasped and the necessity of cleaning work is determined.

Therefore, despite the necessity of the cleaning operation, the situation in which the surface contamination of the projection lens 9 is overlooked and the timing of performing the cleaning operation is not overlooked can be prevented. It is possible to reliably prevent the occurrence of exposure failure caused by leaving the apparatus unexposed.

Further, based on the measurement result output from the measurement control system 22, there is no possibility that unnecessary cleaning work is performed in maintenance. Therefore, for example, even in the case of performing manual wiping cleaning or the like without using the light cleaning device 17, the chance that the projection optical system 1 comes into contact with the outside air is minimized by temporarily opening the inside of the device case. And the possibility that the exposure conditions are deteriorated can be reduced. (2) In the present embodiment, the light reflectance of the surface of the projection lens 9 measured at the time of completion of the present apparatus, which is assumed to be not contaminated so as to affect the optical characteristics, is determined by the predetermined reflection. a rate R _0, a configuration in which numerical degree of contamination based on the difference ΔR between the actual reflectance R _r that actually measured with the predetermined reflectance R ₀ is cleaning work only if outside a predetermined tolerance range is carried out ing.

Accordingly, since the criteria for judging the necessity of the cleaning operation are clear and objective, the reliability of the measured numerical value of the degree of contamination can be improved. In addition, since it is possible to avoid the possibility that the execution timing of the cleaning operation varies, the cleaning operation of the surface of the projection lens 9 can be effectively performed only when necessary. Further, since the degree of contamination is measured based on the light reflectance of the surface of the projection lens 9, the presence or absence of a contamination state that may change the optical characteristics of the projection optical system 1 can be easily grasped. (3) In the present embodiment, the irradiation light source 16 has a wavelength of 1
An ArF excimer laser that emits 93-nm ultraviolet light is used, and the surface of the projection lens 9 is removed from the surface of the projection lens 9 by light cleaning using the Schumann-Lunge absorption function by the irradiation light from the light source 16. Therefore, in the atmosphere where the oxidizing power is enhanced by the absorption of Schumann Runge, it is possible to oxidize and decompose the deposits forming the surface contamination state, and it is possible to carry out the cleaning work efficiently, and what is the case of manual wiping cleaning On the contrary, there is no possibility that the cleaning operation may deteriorate the optical characteristics of the projection optical system 1. (4) In the present embodiment, the light emission unit 18 of the projection optical system inspection device 25 is repeatedly controlled to emit light at regular intervals by the main control system. Is repeated to measure the degree of surface contamination of the projection lens 9. Therefore, the cleaning operation by the optical cleaning device 17 does not end while the surface contamination state of the surface of the projection lens 9 is still incompletely removed.
The surface contamination state can be reliably removed. (5) In the present embodiment, the result of the contamination degree measurement by the projection optical system inspection device 25 is displayed by the display means 26. Therefore, the worker in charge of the cleaning operation can also accurately grasp the degree of surface contamination of the projection lens 9 each time. Therefore, even in a configuration in which light emission of the irradiation light source 16 is controlled by the main control system, a configuration in which a cleaning operation is performed manually by an operator or the like,
The cleaning operation can be accurately performed according to the display contents of the display means 26. (6) In the present embodiment, since the window material 11 fitted to the upper part of the housing 10 in the optical cleaning device 17 is detachable and replaceable with respect to the housing 10, the window material 11 may be damaged. In the case of equality, it can be easily replaced with a new window material, and the light cleaning action can be maintained satisfactorily.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, a gas supply unit 27 is added to the optical cleaning device 17 in the first embodiment, and the other configuration is the same as that of the first embodiment. That is, FIG. 3 does not show the projection optical system inspection device 25 including the light emitting unit 18 and the like, but the projection optical system inspection device 25 is also provided in the present embodiment. Therefore, only the gas supply means 27 will be described below, and the same reference numerals will be given to the components common to the first embodiment on the drawings, and redundant description will be omitted.

As shown in FIG. 3, in this embodiment, a gas supply means 27 is provided near the projection lens 9 in the projection optical system 1. This gas supply means 27
Is composed of a gas supply pipe 28 extending from an ozone gas generator (not shown), and a gas outlet 29 connected to the pipe 28 and arranged so as to surround the projection lens 9. Is controlled.

That is, the main control system controls light emission of the irradiation light source 16 and starts gas supply by the gas supply means 27 when the light cleaning device 17 cleans the surface of the projection lens 9 with light. Then, the ozone gas is blown out from the gas outlet 29 toward the surface of the projection lens 9, and the atmosphere near the surface of the lens 9 is filled with the ozone gas. In this state, when irradiation light is irradiated from the irradiation light source 16 toward the surface of the projection lens 9, Schumann
In an atmosphere in which the oxidizing power based on Runge absorption is enhanced, organic substances and the like adhering to the surface of the projection lens 9 are irradiated with the irradiation light source 1.
It is oxidatively decomposed by the irradiation light from 6.

Therefore, in this embodiment, the gas supply means 2
Since the vicinity of the surface of the projection lens 9 can be made into an ozone gas atmosphere with increased oxidizing power by the ozone gas supplied from 7,
The light cleaning action of the light cleaning device 17 can be promoted. Note that there are various methods of generating ozone gas, such as a discharge method and an ultraviolet method, and any method can be applied to the present embodiment. Also, gas supply means 27
May be any oxidizing gas suitable for accelerating the oxidative decomposition of organic substances and the like attached to the surface of the projection lens 9, and is not particularly limited to ozone gas.

Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, a gas supply unit 27 and a gas recovery unit 30 are added to the optical cleaning device 17 in the first embodiment, and the other points are the same as those in the first embodiment. . Accordingly, hereinafter, only the gas supply unit 27 and the gas recovery unit 30 will be described, and redundant description of other common components will be omitted.

As shown in FIG. 4, in the gas supply means 27 of this embodiment, a gas supply pipe 28 extending from an ozone gas generator (not shown) is embedded in the wafer stage 7. The gas outlet 29 connected to the gas supply pipe 28 is
Is disposed on the wafer stage 7 in the vicinity of, and blows out ozone gas toward the surface of the projection lens 9. A gas collecting means 30 together with a gas collecting pipe (not shown) is provided on the wafer stage 7 at a position opposite to the gas outlet 29 with the housing 10 interposed therebetween.
Is arranged.

Therefore, in this embodiment, when the ozone gas is blown out from the gas outlet 29, the ozone gas comes into contact with the entire surface of the projection lens 9 as a laminar flow, and is then sucked from the gas inlet 31. After that, it is recovered through a gas recovery pipe. Then, in an atmosphere in which ozone gas is supplied to the vicinity of the surface of the projection lens 9, a light cleaning operation based on irradiation light from the irradiation light source 16 is performed. Therefore, in the present embodiment, in addition to the effect of promoting the light cleaning under the ozone gas atmosphere similar to the case of the second embodiment, the ozone gas comes into contact with the entire surface of the projection lens 9 as a laminar flow. Organic substances and the like attached to all parts of the surface can be oxidized and decomposed uniformly. Further, since the gas supply pipe 28 is buried in the wafer stage 7, there is no possibility that the pipe 28 will interfere with other members when the stage is moved.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, a gas supply unit 27, a gas recovery unit 30, and a shielding unit 32 are added to the optical cleaning device 17 in the first embodiment, and the other configurations are the same as those of the first embodiment. It has become. Therefore, the gas supply means 27 and the gas recovery means 30 will be described below.
Only the shielding means 32 will be described.

As shown in FIG. 5, in this embodiment, when the light cleaning device 17 cleans the projection lens 9 by light, the shielding means 32 for shielding the atmosphere near the surface of the lens 9 from the outside is provided by the projection optical system 1. And the wafer stage 7. That is, the shielding means 32 is composed of a pair of partition walls 33 and 34 which form a half-split shape. The gas supply pipe 28 penetrates one partition wall 33 and the gas recovery pipe 35 penetrates the other partition wall 34. . And one partition 3
The tip opening of the gas supply pipe 28 facing the inner peripheral surface side of 3 is a gas outlet 29, and the leading opening of the gas recovery pipe 35 facing the inner peripheral surface of the other partition wall 34 is the gas inlet 31. .

Therefore, in this embodiment, when the ozone gas is blown out from the gas outlet 29 on the partition wall 33 side, the ozone gas fills the interior space 36 shielded from the outside by the partition walls 33 and 34. Then, in that state, the surface of the projection lens 9 is optically cleaned based on the irradiation light from the irradiation light source 16. During the light cleaning operation, the ozone gas blowout from the gas outlet 29 is appropriately performed, while the ozone gas filling the internal space 36 via the gas suction port 31 is appropriately collected. Therefore, in the present embodiment, in addition to the effect of promoting light cleaning under an ozone gas atmosphere similar to those of the second and third embodiments,
Since the ozone gas atmosphere can be reliably formed near the surface of the projection lens 9, the light cleaning effect can be further promoted.

Next, a fifth embodiment of the present invention will be described with reference to FIG. The fifth embodiment is also the same as the first embodiment except that a gas supply unit 27, a gas recovery unit 30, and a shielding unit 32 are added to the optical cleaning device 17, and the other configurations are the same as those of the first embodiment. It has become. Therefore, the gas supply means 27 and the gas recovery means 30 will be described below.
Only the shielding means 32 will be described.

As shown in FIG. 6, in the present embodiment, the gas supply pipe 28 of the gas supply means 27 and the gas recovery pipe 35 of the gas recovery means 30 are provided in the wafer stage 7.
Is buried. The opening at the tip of the gas supply pipe 28 is exposed on the wafer stage 7 near the housing 10 as a gas outlet 29, and the gas is recovered at a position opposite to the gas outlet 29 with the housing 10 interposed therebetween. Pipe 35
Is exposed as a gas inlet 31. Between the projection optical system 1 and the wafer stage 7, there is provided a shielding means 32 which is located outside the gas outlet 29 and the gas inlet 31 and shields the atmosphere near the surface of the projection lens 9 from the outside. Have been. Note that also in the present embodiment, the shielding means 32 is formed of a pair of partition walls 33, 3 which form a half-split shape.
4.

Therefore, also in this embodiment, the same effects as those of the fourth embodiment can be exerted, and the gas supply pipe 28 and the gas recovery pipe 35 are buried in the wafer stage 7, so that the stage can be moved. In some cases, it is possible to eliminate the possibility that the pipes 28 and 35 may interfere with other members.

The above embodiments may be embodied with the following modifications. In the above embodiments, the irradiation area of the irradiation light from the irradiation light source 16 at the time of light cleaning is the entire surface of the projection lens 9 on the wafer stage 7 side, but this is only the irradiation area of the exposure light at the time of projection exposure. Is also good. In this case,
Since the size of the housing 10 embedded on the wafer stage 7 can be reduced, the space on the wafer stage 7 where alignment marks and the like are formed can be given a margin.

In each of the above embodiments, the wafer stage 7 is stopped at a position corresponding to the window member 11 of the housing 10 immediately below the projection lens 9 of the projection optical system 1, and the surface of the projection lens 9 is stopped in the stopped state. Is cleaned, but the wafer stage 7 may be moved relative to the projection optical system 1 during light cleaning by the light cleaning device 17. In this case, the irradiation light source 1 at the time of the light cleaning is used.
Since the irradiation area of the irradiation light from 6 can be further narrowed, the space on the wafer stage 7 can be given more latitude.

In each of the above embodiments, the projection optical system inspection device 25 is configured to repeatedly measure the degree of contamination at regular intervals during the light cleaning operation by the light cleaning device 17 based on the control of the main control system. The measurement of the degree of contamination by the optical system inspection device 25 may be performed only once before performing the cleaning operation. In this case, it is impossible to judge whether or not the degree of removal of the contaminated state by the cleaning is good, but the control contents of the projection optical system inspection device 25 by the main control system can be simplified.

In the above embodiments, the light cleaning device 17
An ArF excimer laser was used as the irradiation light source 16 for the irradiation, but a wavelength of 200 n causing Schumann-Runge absorption was used.
m or less, for example, a wavelength of 17
Xenon lamp emitting 2nm light, 157nm wavelength
Or an EUVL such as a soft X-ray that emits light of the following type. That is, in this way, the degree of freedom in device design is expanded.

In the above embodiments, the light cleaning device 17
Although the irradiation light source 16 is provided at a different position from the wafer stage 7, the irradiation light source 16 may be installed in the housing 10 on the wafer stage 7, as shown in FIG. In this case, since a light guide member such as an optical fiber is not required, the apparatus configuration can be simplified accordingly, and the cost can be reduced.

In the above embodiments, the light reflectance of the surface of the projection lens 9 measured at the time of completion of the apparatus is used as the predetermined reflectance R ₀ to be compared with the actual reflectance R _r. The light reflectance according to the standard of the projection lens 9 alone may be set as the predetermined reflectance _R0 . In other words, if the surface of the projection lens 9 is a light reflectance in a state where it is assumed that the surface is not contaminated so as to affect its optical characteristics, it can be used as the predetermined reflectance _R0 .

In the above embodiments, the light cleaning device 17 is used.
Although the surface of the projection lens 9 of the projection optical system 1 is optically cleaned using the irradiation light emitted from the irradiation light source 16, an operator manually cleans the surface of the lens 9 by wiping and cleaning. May be implemented. Further, in the fourth and fifth embodiments, the partitions 33, 3 constituting the shielding means 32 are provided.
4 may be assembled and installed by an operator every time the optical cleaning operation is performed, and may be configured to be protruded and retracted from the inside of the lens barrel of the projection optical system 1 or the inside of the wafer stage 7 by driving a driving unit (not shown). Is also good.

In each of the above embodiments, the irradiation light source 16 of the light cleaning device 17 is provided separately from the exposure light source 2, but the exposure light source 2 emits ultraviolet light having a wavelength of 200 nm or less which causes Schumann-Runge absorption. If it emits,
This may be used also as an irradiation light source used for light cleaning. That is, the illumination light IL from the exposure light source 2 is guided to the inside of the housing 10 on the wafer stage 7 by a light guide member such as an optical fiber, and the mirror 12 controls the projection lens 9 by the mirror 12 as in the above-described embodiments. What is necessary is just to comprise so that it may irradiate to a surface. In this case, since the number of light sources provided as the whole projection exposure apparatus can be saved, the cost of the apparatus can be reduced accordingly.

When the exposure light source 2 is also used as an irradiation light source for light cleaning, a reflection mirror 37 is mounted and fixed on the wafer stage 7 as shown in FIG. Irradiation may be performed via the projection optical system 1 by irradiation light from the exposure light source 2. That is, the reflection mirror 3
The wafer stage 7 is moved so that 7 is located immediately below the projection lens 9 in the projection optical system 1, and the exposure light source 2 emits light in that state. Then, the surface of the projection lens 9 is exposed to the exposure light source 2 transmitted through the projection optical system 1.
The light is washed by both the illumination light IL from the light source and the light reflected from the reflection mirror 37.

Accordingly, in this case, not only the direct irradiation light but also the indirect reflection light is used, so that the efficiency of the light cleaning can be further improved. In addition, it is only necessary to mount and fix the reflecting mirror 37 on the wafer stage 7, and the member configuration such as the housing 10 can be omitted, so that the apparatus cost can be further reduced.

The illumination light IL from the exposure light source 2
May be guided to the light emitting portion 18 using a light guide member such as an optical fiber, and the light reflectance may be obtained based on the illumination light IL reflected by the surface of the projection lens 9. By doing so, the number of light sources provided as the whole projection exposure apparatus can be further reduced, and the cost of the apparatus can be reduced accordingly.

In each of the above embodiments, the irradiation light from the light emitting unit 18 of the projection optical system inspection device 25 is irradiated toward the surface of the projection lens 9 and the actual reflectance R _r obtained based on the reflected light is used. Although the degree of contamination on the surface of the lens 9 is measured, the degree of contamination may be measured based on light transmitted through the lens 9. That is, in this case, the light emitting unit 18
Is arranged such that the irradiation light thereof is transmitted through the projection lens 9, and the first light receiving unit 20 is arranged at a position where the transmitted light transmitted through the lens 9 is received. The light emitting unit 18
A split mirror 19 is disposed between the light source and the projection lens 9 on the optical path of the light emitted from the light emitting unit 18.
The second light receiving section 21 is located at a position where the branched light from the light receiving section 9 is received.
Place. Then, the light transmittance of the projection lens 9 is calculated as the actual transmittance by the arithmetic unit 23 of the measurement control system 22 based on the photoelectric signals output from the light receiving units 20 and 21, and the actual transmittance is stored in advance in the storage unit. 24, the degree of contamination is measured from the result of comparison with the predetermined transmittance stored. Even in this case, the same effects as those of the above embodiments can be obtained.

In each of the above embodiments, the step and repeat type projection exposure apparatus in which the pattern of the mask is exposed while the mask and the substrate are stationary and the substrate is sequentially moved is embodied. The present invention is also applicable to a scanning projection exposure apparatus that exposes a mask pattern by synchronously moving a mask and a substrate. Further, the type of the exposure apparatus is not limited to an exposure apparatus for manufacturing a semiconductor, and for example, an exposure apparatus for a liquid crystal that exposes a liquid crystal display element pattern to a square glass plate or a thin film magnetic head is manufactured. Is also applicable to an exposure apparatus for the purpose. In addition,
The projection optical system inspection apparatus and the projection exposure apparatus according to the present invention are constituted by the respective components already described in the respective embodiments, and these components are electrically or so as to achieve the respective functions described above. It is assembled by mechanically and optically connecting.

Next, technical ideas other than those described in the claims which can be grasped from the above embodiments will be described below together with their effects. (1) A gas supply means for supplying an oxidation promoting gas is disposed near the surface of the optical member, and a predetermined irradiation light having a light cleaning effect is provided in an atmosphere filled with the oxidation promotion gas supplied from the gas supply means. An optical cleaning device configured to irradiate the optical member surface. That is, this technical idea (1)
In the method, the vicinity of the surface of the optical member can be made into an atmosphere having increased oxidizing power by the action of the oxidation promoting gas, so that the light cleaning effect can be promoted.

(2) An optical cleaning apparatus according to the above technical idea (1), further comprising a shielding means for shielding an atmosphere near the surface of the optical member from the outside, including an optical path of the irradiation light. That is, in the technical idea (2), an atmosphere having increased oxidizing power can be reliably formed in the vicinity of the optical member surface by the action of the oxidation promoting gas, so that the light cleaning effect can be further promoted. .

(3) In the projection optical system inspection apparatus according to the third aspect, the measuring means reflects the reflection of the optical member surface in a predetermined state on the assumption that the degree of contamination of the optical member surface is within an allowable range. A projection optical system inspection device for setting a transmittance or a transmittance as the predetermined reflectance or the predetermined transmittance in advance. That is, in the technical idea (3), in addition to the effect of the invention described in claim 3, the reflectance or the transmission in a predetermined state where the degree of contamination is within a certain allowable range and there is no need for cleaning. The reflectance is defined as the predetermined reflectance R _O or the predetermined transmittance, and such a predetermined reflectance R _O or the predetermined transmittance is compared with the actual reflectance R _r or the actual transmittance to determine the necessity of cleaning or the like. . Therefore, in addition to the effect of the invention of claim 3,
Since it is possible to avoid a possibility that the judgment content based on the measurement result of the measuring means varies, the cleaning operation can be accurately performed when the cleaning operation is required based on the measurement result.

[0065]

According to the first aspect of the present invention, before the cleaning, the cleaning timing of the projection optical system can be grasped based on the measurement result of the measuring means.
By grasping the degree of dirt removal based on the cleaning, incomplete cleaning can be prevented.

According to the second aspect of the invention, in addition to the effect of the first aspect, the degree of contamination is measured based on the light reflectance or light transmittance of the optical member surface. The presence or absence of a contamination state that may change the optical characteristics of the projection optical system can be easily grasped.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, the criterion for measuring the degree of contamination is clear and objective, so that the reliability of the measurement result can be improved. it can.

According to the fourth aspect of the present invention, in addition to the effect of the third aspect of the present invention, for example, by repeatedly performing the contamination degree measurement while performing the cleaning operation of the optical member surface, the cleaning operation can be performed based on the cleaning operation. It is possible to grasp the progress change of the degree of dirt removal.

According to the fifth aspect of the present invention, the first to fifth aspects are described.
In addition to the effect of the invention described in any one of the fourth aspects, it is possible to avoid the possibility that the cleaning content varies.
According to the invention of claim 6, in addition to the effect of the invention of claim 5, light cleaning of the optical member surface can be performed in an atmosphere filled with an oxidation promoting gas, so that the light cleaning action can be promoted. it can.

According to the seventh aspect of the present invention, in addition to the effect of the sixth aspect of the present invention, an atmosphere of an oxidation promoting gas can be reliably formed in the vicinity of the surface of the optical member. Can be promoted.

According to the eighth aspect of the present invention, the fifth to fifth aspects are provided.
In addition to the effect of the invention of any one of claims 7, the light cleaning device can be protected by the window material,
When the window material becomes defective, the window material can be easily replaced, so that the light cleaning effect can be maintained satisfactorily.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an entire projection exposure apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a main part of the first embodiment.

FIG. 3 is a schematic diagram of a main part of a second embodiment.

FIG. 4 is a schematic diagram of a main part of a third embodiment.

FIG. 5 is a schematic view of a main part of a fourth embodiment.

FIG. 6 is a schematic diagram of a main part of a fifth embodiment.

FIG. 7 is a schematic view of a main part of another embodiment.

FIG. 8 is a schematic diagram of a main part of another embodiment.

[Explanation of symbols]

1: Projection optical system 9: Projection lens (optical member 11)
... window material 17 ... light cleaning device 22 ... measurement control system (measurement means) 2
5 Projection optical system inspection device 27 Gas supply means 32 Shielding means W Wafer (photosensitive substrate)

Claims (8)

[Claims] 1. An apparatus for inspecting a projection optical system comprising a measuring means for measuring the degree of contamination of the surface of an optical member closest to a photosensitive substrate in a projection optical system in a projection exposure apparatus. 2. The method according to claim 1, wherein the measuring unit measures a reflectance of the light reflected on the surface of the optical member or a transmittance of the light transmitted through the surface of the optical member, and contaminates the surface of the optical member based on the measurement result. The projection optical system inspection device according to claim 1, wherein the degree is measured. 3. The method according to claim 1, wherein the measuring unit measures a degree of contamination of the surface of the optical member based on a result of comparison between a preset predetermined reflectance or predetermined transmittance and an actually measured actual reflectance or actual transmittance. The projection optical system inspection device according to claim 2, wherein 4. The method according to claim 1, wherein the measuring unit is configured to determine, based on the irradiation light irradiated at a predetermined timing, a photoelectric signal received after the irradiation light is reflected by the optical member surface or transmitted through the optical member surface. 4. The projection optical system inspection device according to claim 3, wherein the actual reflectance or the actual transmittance is measured from a result of comparison with a photoelectric signal received without the irradiation light passing through the optical member surface. 5. A projection optical system inspection apparatus according to claim 1, wherein said optical member surface is irradiated with a predetermined irradiation light having a light cleaning effect on a surface of said optical member. And a projection exposure apparatus. 6. The projection exposure apparatus according to claim 5, wherein the optical cleaning device includes a gas supply unit that supplies an oxidation promoting gas near the optical member surface. 7. The projection exposure apparatus according to claim 6, wherein the light cleaning apparatus includes a shielding unit that shields an atmosphere near a surface of the optical member from outside including an optical path of the irradiation light. 8. The projection exposure according to claim 5, wherein the light cleaning device irradiates the irradiation light to the optical member through a replaceable window material. apparatus.