JPH07273005A - Projection aligner - Google Patents

Abstract

PURPOSE:To conduct an exposing operation in the state wherein image formation characteristics are maintained in the desired state at all times even when a pupil filter is taken into a projection optical system or taken out therefrom, or the pupil filter is changed. CONSTITUTION:The illumination light, which passed through the aperture stop in a turret plate 4, illuminates a reticle R through a condensing lense 11B and the like, and the pattern of the reticle R is exposed on a wafer W through a projection optical system PL. A pupil filter 30A is provided in the vicinity of the pupil surface of the projection optical system PL corresponding to the type and the like of the reticle R to be exposed. Corresponding to the aperture stop of the illumination optical system and the pupil filter 30A, the amount of deviation of image formation characteristics is computed by switching a parameter in the main control system 6, and the image formation characteristics are corrected by slightly moving the reticle R by auxiliary control system 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus used for forming a fine pattern such as a semiconductor integrated circuit and a liquid crystal display, and more particularly to a mechanism for maintaining the image forming performance of a projection optical system. The present invention relates to a projection exposure apparatus having the same.

[0002]

2. Description of the Related Art In a photolithography process for forming a circuit pattern of a semiconductor element or the like, a substrate (semiconductor wafer or glass) on which a pattern formed on a reticle (mask) is coated with a photoresist through a projection optical system. A projection exposure apparatus (for example, a stepper) that transfers images onto a plate or the like is used.

In such a projection exposure apparatus, with the recent increase in the degree of integration of VLSIs and the like, the illumination conditions are optimized or the exposure method is devised in order to transfer a finer pattern. ing. For example, the coherence factor (σ value: ratio of the numerical aperture of the illumination optical system to the numerical aperture of the projection optical system) and the numerical aperture (NA. ) Is selected and the optimum combination is selected for each pattern line width to improve the resolution and the depth of focus.

Further, a so-called super-resolution technique such as an annular illumination method, a modified light source method, or a phase shift method has been proposed. Among them, the annular illumination method defines the light quantity distribution of the illumination light flux in the pupil plane of the illumination optical system or in the vicinity thereof as an annular zone, as disclosed in Japanese Patent Laid-Open No. 61-91662. This is a method of illuminating a reticle pattern, which is a modified light source method (S
HRINC method or tilted illumination method) is disclosed in
As disclosed in Japanese Unexamined Patent Application Publication No. 101148 or Japanese Unexamined Patent Application Publication No. 4-408096, a light amount distribution of an illumination light flux on a pupil plane of an illumination optical system or a plane in the vicinity thereof is determined by a predetermined amount from an optical axis of the illumination optical system. This is a method of irradiating the reticle pattern with the illumination light beam being inclined at a predetermined angle with a maximum at at least one position eccentric.

The phase shift method is disclosed in Japanese Examined Patent Publication No. 62-50.
As disclosed in Japanese Patent Publication No. 811 and the like, the phase of the transmitted light from a specific portion of the transmitted portion of the circuit pattern of the reticle is π [rad] with respect to the transmitted light from other transmitting portions.
This is a method of using a phase shift reticle provided with a phase shifter (dielectric thin film or the like), which is shifted only. The use of the phase shift reticle has the effect of improving the resolution as compared with the case of using a normal reticle (conventional reticle composed only of a light transmitting portion and a light shielding portion) for a predetermined pattern. Typical phase shift reticles are a spatial frequency modulation type (Japanese Patent Publication No. 62-50811), a halftone type (Japanese Patent Application Laid-Open No. 4-162039), a shifter shading type, and an edge enhancement type. .

However, in any of the above methods, it is not effective for all reticle patterns, that is, all line widths and shapes, and the optimum illumination method and conditions are selected for each reticle or its pattern. It is necessary for the projection exposure apparatus to have a structure in which the illumination conditions (σ value, etc.) in the illumination optical system are variable. For example, when the phase shift method is used, the σ value of the illumination optical system needs to be optimized.

By the way, in recent years, projection exposure apparatuses are required to maintain the image forming characteristics (projection magnification, focus position, etc.) of the projection optical system with high accuracy and at constant values. Therefore, various methods of correcting the imaging characteristics have been proposed and put to practical use. Among them, in order to correct the fluctuation of the image forming characteristics due to the absorption of the exposure light of the projection optical system, for example, in JP-A-60-78454,
The amount of energy (heat amount) accumulated in the projection optical system due to the incidence of exposure light (i-line, KrF excimer laser, etc.) on the projection optical system is sequentially calculated, and the amount of change in imaging characteristics due to this accumulated energy amount is calculated. There has been proposed a method of obtaining and finely adjusting the imaging characteristic by a predetermined correction mechanism. As a correction mechanism for this purpose, for example, there is a method of sealing a space sandwiched by two lens elements of a plurality of lens elements forming a projection optical system and adjusting the pressure of gas in the sealed space.

When changing the illumination condition of the illumination optical system as described above, when changing the reticle, or when changing the pattern to be exposed in the reticle by driving the reticle blind (illumination field stop). In the lens element near the pupil plane (Fourier transform surface with respect to the reticle pattern forming surface) of the projection optical system, the distribution of the amount of transmitted light may change due to the above change. Since the illumination light originally concentrates and passes in the vicinity of the pupil plane, a change in the light amount distribution here has a great influence on the variation of the imaging characteristics due to the illumination light absorption of the projection optical system. Therefore, as disclosed in, for example, Japanese Patent Laid-Open No. 62-229838, the calculation parameter used for calculating the change amount of the image forming characteristic of the projection optical system due to the absorption of the illumination light is corrected (changed) for each illumination condition. However, it has been considered that the corrected parameter (that is, the optimum calculation parameter for the changed illumination condition) is used to accurately obtain the change in the imaging characteristic due to the change of the illumination condition and the correction is performed. . Further, even when the projection optical system is not affected by the absorption of the illumination light, the imaging characteristics may change due to the delicate aberration condition of the projection optical system due to the difference in the light beam passage position. For this reason, there has been considered a method of applying a fixed amount of offset to the correction amount of the imaging characteristic according to the change of the illumination condition.

The above-mentioned conventional high resolution technique can effectively obtain advantages such as an improvement in resolution and an increase in depth of focus when the transferred circuit pattern is a periodic pattern having a relatively high density. , For discrete (isolated) patterns called contact hole patterns,
The current situation is that almost no effect is obtained. However, for example, the edge enhancement type phase shift reticle may improve the resolution and depth of focus for an isolated pattern.

Further, as another exposure method for expanding the apparent depth of focus for an isolated pattern such as a contact hole pattern, it was announced in a proceedings 29a-ZC-8, 9 of the Japan Society for Applied Physics 1991. Super F
The LEX method is known. In this Super FLEX method, a phase filter having a concentric amplitude transmittance distribution centered on the optical axis is provided on the pupil plane of the projection optical system (that is, the Fourier transform plane for the reticle), and by the action of this filter, It increases the effective resolution and depth of focus of the projection optical system.

A method of increasing the depth of focus by changing the transmittance distribution or the phase difference by filtering on the pupil plane of the projection optical system like the above Super FLEX method is generally known as a multi-focus filter method (for example, , Machine Testing Laboratory Report No. 4, issued January 23, 1964
No. 0, pp. 41-55 in the paper entitled "Study on Imaging Performance in Optical Systems and Improvement Methods Therefor").
In addition, the method of improving image quality by spatial filtering in the pupil plane is generally called "pupil filter method".
It is called. Therefore, an optical filter arranged near the pupil plane of the projection optical system and having a predetermined transmittance distribution, phase distribution, polarization characteristic distribution, or the like with respect to the image-forming light beam is hereinafter referred to as a “pupil filter”.

As a new type of the pupil filter method, the applicant of the present application proposed a filter of a type that shields only a circular region near the optical axis (hereinafter referred to as "shading filter") in Japanese Patent Laid-Open No. 4-179958. did. Further, the applicant of the present application previously filed Japanese Patent Application No. 4-263521 for a pupil filter named SFINCS method for reducing the spatial coherency of an image-forming light flux from a contact hole pattern that passes through the pupil plane. , Japanese Patent Application No. 4-2717
Proposed in No. 23.

In addition to the above-mentioned pupil filter for contact hole pattern, line and space (L &
S) A pupil filter effective for relatively dense periodic patterns such as patterns is also described in "Projection Exposure Method Using Oblique Incident Illumination", which was concentrated in the 1991 Autumn Society of Applied Physics.
I. Principle ”(Matsuo et al .: 12a-ZF-7), and 199
It is reported in "Optimization of annular illumination and pupil filter" (Yamanaka et al .: 30p-NA-5), etc., which was concentrated in the 2nd Spring Society of Applied Physics. These filters are a method of reducing the transmittance (amount of transmitted light) in a circular area or an annular area centered on the optical axis (hereinafter referred to as “L & S pattern filter”), and unlike the Super FLEX method, The phase of transmitted light does not change.

[0014]

As described above, by using a pupil filter such as a phase filter, a light-shielding filter, or an L & S pattern filter, the resolution and the depth of focus when exposing a predetermined pattern are improved. it can. However, for example, when a light-shielding filter or an L & S pattern filter is used, the intensity distribution of the illumination light on the pupil plane changes, and the same inconvenience as that of the conventional high resolution technique occurs. That is, there is a change in the image forming characteristic due to the fluctuation of the irradiation energy, or a change in the image forming characteristic due to the difference in the light beam passage position. Therefore, it is necessary to correct the change in the image forming characteristic through the correction mechanism.

Further, the pupil filter method has no effect except for the contact hole pattern, and has a bad effect on the contrary. Therefore, it is necessary to insert and remove the pupil filter according to the pattern to be exposed. Alternatively, when a light-shielding filter is used for an isolated pattern and an L & S pattern filter is used for a dense periodic pattern, the pupil filter is replaced according to the pattern to be exposed. There is a need. The fluctuation state of the imaging characteristics changes depending on whether or not such a pupil filter is used or the type of the pupil filter.

Further, there may be a case in which the presence / absence and type of the pupil filter and the switching of the illumination condition (change of σ value, use of annular illumination, etc.) are combined, and the fluctuation state of the imaging characteristic changes under each condition. . In addition to this, when the pupil filter method and the conventional high-resolution technique are applied in combination, the fluctuation state of the imaging characteristic changes. If such a change in the image forming characteristic is corrected through the correction mechanism using the parameters corrected as described above, there is no problem from a long-term standpoint.

However, the phenomenon of heat accumulation in the projection optical system has a past history. Therefore, when the illumination condition or the pupil filter is changed in accordance with the reticle or its pattern, even if the amount of change in the imaging characteristic is calculated and corrected immediately according to the corrected parameter under the new condition, While the history according to the condition before the change remains in the projection optical system, the image forming characteristic cannot be corrected accurately. This inconvenience is roughly divided into the following two.

First, the first disadvantage is that the illumination condition before the change and the heat distribution generated by the pupil filter cause the imaging characteristics under the new (after the change) illumination condition and the pupil filter to be changed. That is, even if it is obtained by taking the offset component of into consideration, it does not match the actual imaging characteristics. In other words, since the offset component is in a state where the projection optical system is not affected by the absorption of the illumination light, if the effect of the absorption of the illumination light before the condition change remains, it is necessary to offset the offset component further. . That is, since the amount of change in the image formation characteristic before and after the change of the illumination condition and the pupil filter becomes discontinuous, the image formation characteristic cannot be accurately corrected following the change of the illumination condition and the pupil filter.

Next, the second inconvenience occurs even if the first inconvenience is solved by some method if the exposure is performed under a new illumination condition and a pupil filter. That is, immediately after changing the illumination condition and the pupil filter, the heat distribution state under the previous condition and the heat distribution state under the new condition overlap in the lens element near the pupil plane of the projection optical system. Therefore, even if the amount of change in the imaging characteristics is calculated with the parameters under any illumination condition, the calculation result is the actual amount of change in the imaging characteristics. Does not match. The image forming characteristic in such a transitional state (that is, the heat distribution state of the projection optical system) cannot be simply expressed as the sum of the two, and the change amount of the image forming characteristic in this transitional state can be accurately expressed. Calculation,
It is very difficult to correct.

In view of the above point, the present invention applies the pupil filter method to control the resolution and the depth of focus, and when the pupil filter is inserted into or removed from the projection optical system or the pupil filter is replaced. However, it is an object of the present invention to provide a projection exposure apparatus capable of performing pattern exposure on a photosensitive substrate while always maintaining the image formation characteristic close to a desired state.

[0021]

A projection exposure apparatus according to the present invention comprises an illumination means (1) for illuminating a mask (R) on which a transfer pattern is formed, as shown in FIGS. 1 and 2, for example.
˜4, 11A, 11B) and a projection optical system (PL) for projecting an image of the pattern of the mask on the photosensitive substrate (W) with a predetermined image forming characteristic under the illumination light from the illumination means. In a projection exposure apparatus, at least one optical characteristic of an optical characteristic group including a polarization characteristic distribution, a transmittance distribution, and a phase distribution is changed on a pupil plane in a projection optical system (PL) or on a surface in the vicinity thereof. Optical characteristic changing means (31),
Imaging state adjusting means (24, 14, 1) for adjusting the imaging state of the projected image on the photosensitive substrate by the projection optical system (PL).
8, 21, 36, 38) and a predetermined image forming characteristic of a projected image on the photosensitive substrate (W) by the projection optical system (PL) which occurs when the corresponding optical characteristic is changed by the optical characteristic changing means. And an image forming characteristic correcting means (6) for correcting the change of (1) through the image forming state adjusting means.

In this case, an example of the image forming characteristic correcting means (6) calculates the amount of change of the predetermined image forming characteristic according to the optical characteristic changed by the optical characteristic changing means (30A, 31). Parameter switching means (62) for changing the parameters for the image formation, image forming characteristic calculation means (64) for obtaining the amount of change of the predetermined image forming characteristic using the parameters switched by the parameter switching means, and this image forming And a control means (65) for correcting the change in the predetermined image forming characteristic through the image forming state adjusting means on the basis of the change amount of the image forming characteristic obtained by the characteristic calculating means.

In this case, accumulated energy measuring means (27, 24) for determining accumulated energy in the projection optical system (PL) by the illumination light emitted from the illumination means is provided,
It is desirable that the image formation characteristic calculation means (64) calculates a change in the predetermined image formation characteristic based on the stored energy obtained by the stored energy measurement means and the parameter that can be switched.

Further, the stored energy measuring means (27, 24) for obtaining the stored energy in the projection optical system (PL) by the illumination light emitted from the illuminating means and the corresponding optical characteristic by the optical characteristic varying means. And an exposure determining means (64) for stopping the exposure of the mask pattern until the stored energy obtained by the stored energy measuring means falls below a predetermined allowable amount due to thermal diffusion. You may

Further, in each of the above cases, the distortion of the projected image on the photosensitive substrate (W) by the projection optical system (PL), which occurs when the corresponding optical characteristic is changed by the optical characteristic changing means, is corrected. The distortion correction plate (33A) for the mask (R) and the photosensitive substrate (W)
May be inserted between and.

[0026]

According to the present invention, the optical characteristic changing means (3
When a predetermined pupil filter (30A) is installed near the pupil plane of the projection optical system (PL) according to 1), the absorption amount of illumination light in the projection optical system changes due to the change of the light amount distribution on the pupil surface, The image forming characteristics may change. Further, even if the illumination light is not absorbed, the predetermined image forming characteristic may change depending on the pupil filter. By correcting such a change in the image forming characteristic via the image forming state adjusting means, the pattern exposure is performed on the photosensitive substrate while always keeping the image forming characteristic close to a desired state.

Further, the installed pupil filter (30
According to A), the parameter is changed by the parameter switching means (62), the changed amount of the image forming characteristic is obtained by the image forming characteristic calculating means (64) using the changed parameter, and based on the changed amount. By correcting the image forming characteristic via the image forming state adjusting means, the image forming characteristic can be corrected quantitatively and accurately. Immediately after the pupil filter is taken in and out, or immediately after the pupil filter is exchanged, the offset determined by the history up to that point is added to the change amount of the image forming characteristic calculated by the image forming characteristic calculating means (64). May be.

Further, the imaging characteristics of the projection optical system (PL) are
It changes depending on the stored energy by the illumination light in the projection optical system. Therefore, the image formation characteristic calculation means (64) performs calculation by using the accumulated energy measured by the accumulated energy measurement means (27, 24), whereby the change amount of the image formation characteristic can be calculated more accurately. As a result, the image forming characteristics can be maintained in a state closer to a desired state.

On the other hand, since the change of the imaging characteristics due to the accumulated energy is complicated, when the pupil filter is changed, the exposure is stopped until the accumulated energy becomes less than a predetermined allowable amount due to diffusion or the like. Good. Further, the distortion in the image forming characteristics may be deteriorated due to the withdrawal or replacement of the pupil filter. In such a case, the deterioration of the imaging characteristics can be prevented by inserting a distortion correction plate that cancels the changed distortion, for example, between the mask (R) and the projection optical system (PL). .

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the projection exposure apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a projection exposure apparatus according to the present embodiment. In FIG. 1, an ultrahigh pressure mercury lamp 1 generates illumination light (i-line etc.) IL in a wavelength range that exposes a photoresist layer. To do. As the illumination light source for exposure, in addition to the bright line of a mercury lamp or the like, Kr
Laser light source such as F or ArF excimer laser, or Y
A harmonic such as an AG laser may be used. The illumination light IL is
Through the shutter 2 that opens and closes the optical path of the illumination light IL,
The light enters the illuminance distribution uniforming optical system 3 including a collimator lens and an optical integrator (fly-eye lens).

A large number of light source images are formed on the exit surface of the illuminance distribution uniformizing optical system 3, and an aperture stop on the turret plate 4 is arranged on this exit surface. As shown in FIG.
As shown in FIG. 1, a normal aperture stop 7 (which increases the numerical aperture of the illumination system, that is, increases the coherence factor σ value), an annular stop 8 for annular illumination, and a small aperture stop 9 (illumination system). The aperture stop 10 for the modified light source is arranged in which four small circular apertures are eccentrically arranged. Returning to FIG. 1, the main control system 6 controls the rotation angle of the turret plate 4 via the drive motor 5, so that a desired aperture stop is set on the exit surface thereof. The main control system 6 determines the type of reticle pattern to be exposed (for example, the presence / absence of a phase shifter,
Presence / absence of periodic pattern or isolated pattern) and reticle pattern formation conditions (line width, pitch, duty, etc.)
The optimum aperture stop is selected according to the situation. The change of the aperture stop is the change of the illumination condition of the reticle R.

The illumination light that has passed through the aperture stop of the turret plate 4 reaches the mirror 12 after passing through the relay optical system 11A including the first relay lens, the field stop, and the second relay lens, and the condenser lens 11B. 12
The illumination light reflected substantially vertically downward at illuminates the pattern area PA of the reticle R with a substantially uniform illuminance. The reticle R is held by the reticle holder 13, and the reticle holder 1
3 is mounted on a reticle stage 15 which is two-dimensionally movable in a horizontal plane via a plurality of expandable and contractible drive elements (only two of which are shown in FIG. 1) 14 (comprising piezoelectric elements). In the present embodiment, the sub-control system 24 controls the expansion and contraction amounts of the drive element 14 to move the reticle R in parallel with the optical axis AX of the projection optical system PL and at the same time to the plane perpendicular to the optical axis AX. On the other hand, it can be tilted in any direction. As will be described in detail later, the above-described configuration can correct the image forming characteristics of the projection optical system PL, in particular, the pincushion type and barrel type distortions. The reticle R is positioned so that the center point of the pattern area PA coincides with the optical axis AX.

A projection optical system PL is arranged below the reticle R, and the projection optical system PL is composed of a first projection optical system PL1 and a second projection optical system PL2 from the reticle R side. In this embodiment, the reticle R and the first projection optical system PL
If necessary, a distortion correction plate 33A is installed between the distortion correction plate 33A and the setting device 1. The sub control system 24
The setting of the distortion correction plate 33A is controlled via the setting device 34. Further, the setting device 34 can replace the distortion correction plate 33A with another distortion correction plate. Distortion correction plate 33
Each of A and the other correction plates is made by polishing the whole or only a part of the glass substrate into a spherical surface or an aspherical surface,
It is used to correct distortion in the imaging characteristics.

The illumination light IL that has passed through the pattern area PA of the reticle R and the distortion correction plate 33A (when inserted) enters the projection optical system PL that is telecentric on both sides, and the projection optical system PL is the circuit of the reticle R. The projected image of the pattern is projected (imaged) by superimposing it on one shot area on the wafer W, on which a photoresist layer is formed on the surface and which is held so that the surface substantially coincides with the best image plane. Further, in the present embodiment, it is possible to drive each of some of the lens elements (one lens element 16 and 20 in FIG. 1) that configure the projection optical system PL independently, which allows the projection optical system to be driven. It is possible to correct the imaging characteristics of the system PL, such as projection magnification, distortion, field curvature, astigmatism, etc. (details will be described later).
Further, a variable aperture stop 25A is provided on the pupil plane of the projection optical system PL (Fourier transform plane of the reticle R) or in the vicinity thereof, and the main control system 6 controls the variable aperture stop 25A via the drive unit 25B. The numerical aperture NA of the projection optical system PL can be changed by adjusting the aperture diameter.

Further, the pupil plane or this near plane is arranged between the first projection optical system PL1 and the second projection optical system PL2, and the pupil filter 30A is inserted in the pupil plane or this near plane. Main control system 6 for controlling imaging conditions
Controls the entrance and exit of the pupil filter 30A via the setting device 31. The pupil filter 30A is, for example, as shown in FIG.
As shown in (a), a light-shielding filter having a light-shielding portion 31 that shields 0th-order light that passes through the central portion including the optical axis of the projection optical system PL, and a transmissive portion 32 that allows diffracted light to pass around it. Is. However, as shown in FIG. 4B, a pupil where the optical path length difference with respect to the illumination light exceeds the coherence length between the central portion 41 through which the 0th-order light passes and the annular zone 42 through which the diffracted light in the periphery passes. The filter 30B may be used instead of the pupil filter A. These pupil filters are usually phase-shifted, annular illumination, or modified light source (SH) methods.
In the super-resolution technology such as the RING method), an isolated pattern (mainly a contact hole pattern) that is not very effective
It is used when performing the exposure. However, as described above, the pupil filter such as the L & S pattern filter is effective for the periodic pattern.

Depending on the type of reticle pattern to be exposed and the forming conditions, the type of aperture stop in the turret plate 4 and the presence / absence of the pupil filter 30A, or the type of another pupil filter used as necessary, are used as the main control system 6. It is judged by.
Then, the main control system 6 rotates the turret plate 4 through the drive motor 5 to set a desired aperture stop, and
Putting in and out the pupil filter 30A via the installation device 31,
Alternatively, set another pupil filter. However, the selection of the combination of the aperture stop and the pupil filter may be designated by the operator via a keyboard (not shown).

The wafer W is a wafer holder (θ table) 2
The wafer holder 26 is vacuum-adsorbed on the wafer 6, and is fixed on the wafer stage WS. The Z axis is taken parallel to the optical axis AX of the projection optical system PL, and the Cartesian coordinate system of a plane perpendicular to the Z axis is taken as the X axis and the Y axis. In this case, the wafer stage W
S is a leveling stage that tilts the wafer W in an arbitrary direction with respect to the best image plane of the projection optical system PL, a Z stage that slightly moves the wafer W in the optical axis direction (Z direction) of the projection optical system PL, and its light. It is composed of an XY stage and the like that two-dimensionally positions the wafer W by a step-and-repeat method in an XY plane perpendicular to the axis AX, and transfers the pattern of the reticle R onto one shot area on the wafer W. When the exposure is completed, the wafer W is stepped to the next shot position. Also, the wafer stage WS
An irradiation amount monitor 27 including a photoelectric detector is provided above the light receiving surface of the wafer W so as to substantially coincide with the exposure surface of the wafer W.

The dose monitor 27 is, for example, a projection optical system P.
The photoelectric detector is provided with a light-receiving surface having substantially the same area as the L image field or the projection area of the reticle pattern. The photoelectric conversion signal of the irradiation amount monitor 27 is supplied to the sub-control system 24. This photoelectric conversion signal is used in the projection optical system PL.
This is basic data for obtaining the amount of change in the image forming characteristic of.
Further, in FIG. 1, an irradiation optical system for projecting an image of a pinhole, a slit pattern or the like obliquely with respect to the optical axis AX toward the exposure surface of the wafer W near the best image plane of the projection optical system PL. 28 and a light receiving optical system 2 for receiving the reflected light flux of the projected image on the surface of the wafer W through the slit.
An oblique incidence type focus position detection system composed of 9 and 9 is provided. The focus position detection system detects the position (focus position) of the surface of the wafer W in the Z direction with respect to the best image plane, and detects the focus state of the wafer W with respect to the projection optical system PL. A focus signal indicating the amount of deviation of the focus position of the wafer W from the best image plane is supplied from 29 to the sub-control system 24. In the present embodiment, it is assumed that the focus position detection system is calibrated in advance so that the best image plane becomes the zero point reference, that is, the focus signal becomes 0 on the best image plane. . Specifically, for example, parallel plate glass (plane parallel) (not shown) provided inside the light receiving optical system 29.
Calibration is performed by adjusting the angle of.

Next, this embodiment is also provided with a mechanism for correcting spherical aberration in the projection optical system PL. Figure 3
3 shows in detail the configuration in the vicinity of the pupil plane of the projection optical system PL in FIG. 1, and in FIG. 3, the lens system 35 closest to the pupil plane FTP of the first projection optical system PL1 is driven by the drive device 36 to the optical axis AX. It is supported so that it can be moved in any direction. Similarly, the lens system 37 of the second projection optical system PL2 closest to the pupil plane FTP is also supported via the drive device 38 so as to be finely movable in the optical axis AX direction. When the sub-control system 24 of FIG. 1 instructs the control device 32 about the necessary correction amount of spherical aberration, the control device 32 finely adjusts the positions of the corresponding lens systems 35 and 37 via the drive devices 36 and 38. Thereby, the spherical aberration is corrected. At this time, the pupil plane FTP
By finely adjusting the positions of the lens systems 35 and 37 close to, the spherical aberration can be accurately corrected.

By the way, as described above, in the projection exposure apparatus of FIG. 1, the correction amount of the image forming characteristic of the projection optical system PL is determined,
A sub-control system 24 for controlling each correction mechanism to always maintain good imaging characteristics, and an optimum exposure condition is selected according to the type of reticle pattern, formation conditions, and in some cases photoresist type, etc. And a main control system 6 for controlling the changing mechanism.

FIG. 2 is a functional block diagram of the main part of the main control system 6. As shown in FIG. 2, the illumination condition / pupil filter setting unit 63 first sets the illumination condition (exposure condition) and the pupil filter. I do. The setting condition is the parameter changing unit 6
2, the parameter changing unit 62 obtains a parameter corrected in accordance with the setting condition from the supplied setting condition and the imaging characteristic calculation parameter read from the memory 61, and the corrected parameter is set as the corrected parameter. It is supplied to the imaging characteristic calculation unit 64. Information on the thermal energy of the illumination light accumulated in the projection optical system PL is also supplied from the sub-control system 24 to the image formation characteristic calculation unit 64, and the image formation characteristic calculation unit 64 is based on the corrected parameters and heat energy. Reference numeral 64 calculates the amount of change in the imaging characteristics (magnification, distortion, position of the best imaging surface, etc.) of the projected image by the projection optical system PL.
Then, this change amount is transmitted via the control unit 65 to the sub control system 24.
Is supplied to. The sub-control system 24 corrects the change in the image formation characteristic due to the change in the exposure condition, based on the information on the amount of change in the image formation characteristic from the control unit 65 in the main control system 6. Further, the sub control system 2
Reference numeral 4 indicates environmental changes such as atmospheric pressure and temperature, and the projection optical system PL.
It also corrects the change in the imaging characteristics caused by the absorption of the illumination light IL. Therefore, the main control system 6 includes a projection optical system P
Measurement data from an environment sensor (not shown) for measuring atmospheric pressure and temperature around L is also supplied.

Next, the image forming characteristic adjusting mechanism (image forming state adjusting means) of the projection optical system PL in this embodiment will be described. As shown in FIG. 1, in this embodiment, the sub-control system 24 includes a reticle R, lens elements 16 and 2 via a driving element.
The projection optical system PL is driven by independently driving each
It is possible to correct the image forming characteristic of. The imaging characteristics of the projection optical system PL include the position of the best imaging surface, projection magnification, distortion, field curvature, spherical aberration, astigmatism, etc., and these values can be individually corrected. However, in the present embodiment, in order to simplify the description, the case of correcting the position of the best image plane, the projection doubling, the distortion, and the curvature of field in the projection optical system that is telecentric on both sides will be described. Further, in this embodiment, barrel-shaped or pincushion-shaped distortion is corrected by moving the reticle R.

The lens element 16 of the first group closest to the reticle R is fixed to the lens frame 17, and the lens element 20 of the second group is fixed to the lens frame 19. The lens element 23 and the like below the lens element 20 are fixed to the lens barrel portion 22 of the first projection optical system PL1. In the present embodiment, the optical axis AX of the projection optical system PL
Is the optical axis of the lens element fixed to the lens barrel portion 22.

The lens frame 17 has a plurality of expandable and contractible (for example, 3
Then, it is connected to the lens frame 19 via two driving elements 18 in the drawing), and the lens frame 19 is connected to the lens barrel portion 22 via a plurality of expandable / contractible driving elements 21.
As the driving elements 14, 18 and 21, for example, an electrostrictive element (piezo element or the like) or a magnetostrictive element is used, and the displacement amount of the driving element according to the voltage applied to each driving element or the magnetic field is obtained in advance. Although not shown here, a position detector such as a capacitive displacement sensor or a differential transformer is provided in the drive device in consideration of the hysteresis of the drive device, and these position detectors correspond to the voltage or magnetic field applied to the drive device. The position of the driven element is monitored to drive with high accuracy.

Here, when each of the lens elements 16 and 20 is translated in the direction of the optical axis AX, the projection magnification M, the field curvature C, and the position F of the best imaging plane are changed at a rate of change corresponding to the amount of movement. Each of the changes. If the driving amount of the lens element 16 is x ₁ and the driving amount of the lens element 20 is x ₂ , the projection magnification M, the field curvature C, and the change amounts ΔM, ΔC, and ΔF of the position F of the best imaging plane. Is expressed by the following equation.

[0046]

[Equation 1] ΔM = C _M1 · x ₁ + C _M2 · x ₂

[0047]

[Expression 2] ΔC = C _C1 · x ₁ + C _C2 · x ₂

[0048]

[ _Formula 3] ΔF = C _F1 · x ₁ + C _F2 · x ₂ Coefficients C _M1 , C _M2 , C _C1 , C _C2 , C _F1 , and C _F2 are change rates of the displacement amount with respect to the driving amount of the lens element. It is a constant to represent. By the way, as described above, the focus position detection system 2
Reference numerals 8 and 29 are for detecting the amount of deviation of the wafer surface with respect to the best image forming plane, with the position of the best image forming plane of the projection optical system PL as a zero point reference. Therefore, the focus position detection system 28,
An appropriate electrical or optical offset amount x _{3 is applied} to 29, and the focus position detection systems 28 and 29 are used to position the wafer surface, so that the focus associated with the driving of the lens elements 16 and 20 is increased. It is possible to correct the positional deviation. At this time, the above equation (3) is expressed as the following equation.

[0049]

[ _Formula 4] ΔF = C _F1 · x ₁ + C _F2 · x ₂ + x ₃ Similarly, when the reticle R is translated in the direction of the optical axis AX, the distortion D and the best result are obtained at the rate of change corresponding to the amount of movement. Each of the positions F on the image plane changes. Assuming that the driving amount of the reticle R is x ₄ , the distortion D and the changes ΔD and ΔF of the position F of the best imaging plane are represented by the following equations.

[0050]

[Equation 5] ΔD = C _D4 x ₄

[0051]

[Equation 6] ΔF = C_F1・ X₁+ C_F2・ X₂+ X₃+ C_F4・ X_Four The coefficient C_D4, C_F4Is the drive amount of the reticle R for each change amount
Is a constant representing the rate of change with respect to. From the above,
Driving in (Equation 1), (Equation 2), (Equation 5), (Equation 6)
Quantity x ₁~ X_Four By setting the change amount ΔM, Δ
It can be seen that C, ΔD, and ΔF can be arbitrarily corrected. still,
Here, let us consider the case of simultaneously correcting four types of imaging characteristics.
As described above, the illumination light absorption is one of the imaging characteristics of the projection optical system PL.
The amount of change in imaging characteristics due to
If so, it is not necessary to perform the above correction. On the other hand, in this example,
Large imaging characteristics (eg spherical aberration) other than the four solid types
If it changes, use the mechanism shown in Fig. 3, for example.
It is necessary to correct the image forming characteristics of.

In the above description, the case where the reticle R and the lens elements 16 and 20 are moved in parallel is dealt with. However, in reality, the expansion and contraction amounts of the driving elements at three or four points on the periphery of the reticle R are set. By adjusting, the reticle R can be tilted in any direction with respect to the plane perpendicular to the optical axis AX. Similarly, the lens elements 16 and 20 can be tilted in any direction with respect to the plane perpendicular to the optical axis AX. This makes it possible to correct other imaging characteristics as well.

Here, in this embodiment, the sub control system 24 can move the reticle R, the lens elements 16 and 20, and the lens systems 35 and 37.
6 and 20, the influences on the characteristics such as projection magnification, distortion, field curvature, and astigmatism are greatly controlled compared to other lens elements. Similarly, the lens systems 35 and 37 have a larger influence on spherical aberration than other lens elements. However, the number of movable lens elements may be three groups or more, or the number of movable lens systems may be three or more. In these cases, the movement range of the lens element or lens system can be reduced while suppressing variations in other aberrations. It is possible to increase the size, and it is possible to deal with various distortions (such as trapezoidal and rhombic distortions), field curvature, and astigmatism. By adopting the image forming characteristic adjusting mechanism having the above structure, it is possible to sufficiently cope with a change in the image forming characteristic of the projection optical system PL due to absorption of exposure light.

As described above, in this embodiment, the reticle R and the lens elements 16 and 2 are used as the image forming characteristic adjusting mechanism.
Although the example in which the image forming characteristic is corrected by 0 and the movement of the lens systems 35 and 37 is shown, the adjusting mechanism used in this embodiment may be of any other type, for example, sandwiched between two lens elements. A method may be adopted in which the closed space is sealed and the gas pressure in the sealed space is adjusted.

Next, in FIG. 1, the sub-control system 24 moves the distortion correction plate 33A in and out or replaces it via the setting device 34. This is due to the high-order distortion or the higher-order distortion which cannot be removed by the adjusting mechanism. It is used to correct an asymmetrical aberration component or a random aberration component. For this reason, it is not versatile and is not used as a normal adjusting mechanism of the imaging characteristics, but is used for initial adjustment. In this embodiment,
The distortion that occurs due to the use of the pupil filter is corrected by using the distortion correction plate 33A in synchronism with the taking in or out of the pupil filter 30A. Naturally, the position of the best imaging plane and the distortion (pincushion, barrel-shaped distortion) also change when the pupil filter 30A is moved in and out, so these must be corrected by the above-mentioned mechanism for adjusting the imaging characteristics.

Next, the main operation of this embodiment will be described.
Although the projection optical system PL is originally highly corrected for aberrations, it is normal that aberrations that cannot be eliminated by manufacturing remain. This is due to, for example, an aberration (spherical aberration) in which the position of the best imaging plane is different from the position where the illumination light IL1 passes through the pupil plane of the projection optical system PL as shown in FIG. 6A, or FIG. ), There is an aberration (coma aberration, spherical aberration) in which the position where the illumination light IL2 passes through the pupil plane of the projection optical system PL is exposed, that is, the distortion is different. Therefore, as in this embodiment, the projection optical system P
When the pupil filter 30A is inserted in the L pupil plane, the position of the best image plane and the distortion change. The intensity distribution of the exposure light on the pupil plane of the projection optical system also changes depending on the aperture diaphragms 7 to 10 of the illumination system.
5A and the type of reticle R also change.

Therefore, in this embodiment, these states are shown in FIG.
The illumination condition / pupil filter setting unit 63 informs the parameter changing unit 62, the parameter changing unit 62 corrects the parameters read from the memory 62, and supplies the corrected parameters to the imaging characteristic calculation unit 64. Then, the sub-control system 24 corrects the change in the image formation characteristic calculated by the image formation characteristic calculation unit 64. The relationship between the illumination condition, the pupil filter, the state of the aperture stop 25A, and the type of the reticle R and the imaging characteristics is previously obtained through experiments or simulations, and is stored in the internal memory of the main control system 6 in the form of a table or a mathematical formula. It is stored in 61.

In the above description, the projection optical system PL is in a static state, but in reality, it is subject to changes in atmospheric pressure, changes in temperature, and changes caused by absorption of the illumination light IL by the projection optical system PL. . The memory 61 of the main control system 6 also stores parameters for these changes in advance, and the imaging characteristic calculation unit 64 uses atmospheric pressure, temperature information, etc. from an environment sensor (not shown) and the parameters to combine them. The change amount of the image characteristic is calculated, and the calculated change amount is supplied to the sub control system 24 via the control unit 65. In response to this, the sub control system 2
The correction 4 cancels the change in the image forming characteristic. It is also necessary to change those parameters depending on the conditions such as the illumination conditions, the pupil filter, the aperture stop 25A of the pupil plane, etc. In this embodiment, the parameter changing unit 62 changes the corresponding parameters.

Among these, the change of the image forming characteristic due to the absorption of the illumination light will be described. Here, the change of the position of the best image forming surface is taken as the changing image forming characteristic, but the same applies to the magnification, the distortion and the like. For example, in FIG.
(A) shows the change characteristic of the position of the best imaging plane when the pupil filter 30A is not inserted in the projection optical system PL. When the exposure operation is performed from the time point of time t ₁ ,
Since the projection optical system PL gradually absorbs the illumination light IL, the deviation amount ΔF of the position of the best image plane with respect to the initial position gradually increases as shown by the curve 43. Actually step
Although the smooth curve 43 as shown in FIG. 7A is not obtained due to the drive operation by the and repeat method, the wafer W exchange operation, and the like, it is almost correct as a whole. After that, when the predetermined exposure period T _EXP ends and the exposure is stopped, the displacement amount ΔF of the position of the best imaging plane gradually returns to zero.

That is, the shift amount ΔF during exposure can be approximately expressed as follows using a predetermined time constant T _P1 and a coefficient a _P1 .

[0061]

## EQU00007 ## .DELTA.F = _a.sub.P1 (1-exp (-t / _T.sub.P1 )) On the other hand, FIG. 7B shows the amount of deviation of the position of the best image plane when the pupil filter 30A is inserted. The change in ΔF is shown. In this case, when the exposure operation is performed from the time t ₂ to t ₂ , the shift amount ΔF is as shown by the curve 45 in FIG.
It changes similarly to (a), but the characteristics are slightly different.
Further, the origin of the shift amount ΔF (the shift amount when not affected by the absorption of the illumination light) is different, but this is because the illumination light distribution on the pupil plane of the projection optical system PL is different. is there. The change characteristic of the absorption of the illumination light has the same energy of the illumination light (measured by the dose monitor 27 of FIG. 1) E
Of the amount of deviation ΔF, ΔF / E, and FIG.
It can be represented by the rising characteristics of the curves of (a) and (b). These two types of characteristics may be obtained in advance by experiments or the like and stored as parameters in the memory 61, and the parameter changing unit 62 may change the parameters when the conditions change.

Specifically, those parameters are, for example, the time constant T _P1 and the coefficient a _P1 in (Equation 7). Therefore, when the pupil filter 30A is used, the time constant T _P1 and the coefficient a _P1 are set to different time constants T _P2 ,
And the coefficient a _P2 may be (Equation 7). Figure 2
The memory 61 stores the time constant T _P1 and the coefficient a _P1 as parameters.

Next, by absorbing the illumination light, aberrations other than the correctable aberrations are aggravated, so even if the imaging characteristics are corrected by the sub-control system 24, the image is formed at a certain point. Since the characteristic deteriorates and there is a limit (exposure) that exposure cannot be performed as it is, the conventional exposure apparatus is provided with a predetermined energy limit so that the projection optical system PL does not absorb the illumination light above the energy limit. Some had functions. Aberrations other than the correctable aberrations (such as astigmatism and spherical aberration in this embodiment) also differ depending on various conditions including the pupil filter 30A. If it is obtained by simulation or the like and rewritten according to the conditions and used, it is possible to perform exposure under more accurate imaging characteristics.

This state is shown by dotted curves 44 and 46 in FIGS. 7 (a) and 7 (b). In FIGS. 7A and 7B, the deviation amount ΔF of the best imaging plane at the energy limit is La and Lb, respectively. The curve in FIG. 7 represents the change in the position of the best image plane, but if it is assumed that other aberrations also show the same change characteristics, then it can be converted into the amount of change in the position of the best image plane to obtain a limit value. , It is not necessary to calculate another change characteristic of aberration again. Of course, other aberration change characteristics may be calculated separately. In the solid line curve 43, there is no problem because the deviation amount is always equal to or less than the limit La. However, when the incident illumination light amount is large (for example, when the transmittance of the reticle R is high), the deviation amount is represented by a dotted curve 44. The deviation amount ΔF changes up to the limit La. At this time, the exposure apparatus temporarily stops the exposure operation as in the latter half of the curve 44 and repeats the operation of performing exposure again after a while so that the deviation amount limit La is not exceeded. In contrast to this limit La, in FIG. 7B, if the exposure operation is performed by using another limit Lb, the exposure can be performed in a range in which the imaging characteristics are not deteriorated in each case, and the exposure is performed by a lower limit than necessary. There is an advantage that the throughput (productivity) of the device is not reduced.

Conventionally, as shown in FIGS. 7 (a) and 7 (b), when the presence or absence of the pupil filter is switched or replaced (the same applies when other conditions are not changed), the exposure is temporarily stopped,
This was done after a certain amount of time had passed until the effect of absorption of illumination light could be ignored. On the other hand, in the present embodiment, the conditions are switched while the influence of the absorption of the illumination light remains sufficient. At this time, there is a problem in the calculation of the imaging characteristics due to the absorption of the illumination light. That is, as described above, there is a problem due to the influence of the heat distribution generated by the condition before the change and a problem due to the fact that the heat distributions before and after the change overlap.

In the control method in this case, as shown in FIG.
At the time t without the pupil filter₃And the pupil filter
-Continued to change to "Yes". In this case, first
Time t when the pupil filter 30A is inserted₃And the best image plane
The amount of deviation ΔF of the position of is discontinuous. The amount of deviation is
The change amount dF when there is no bright light absorption
The aberration state of the projection optical system PL changes compared to when there is no absorption
Change amount dF₂Is added. This
This is inconvenient. Further, at time t in FIG. ₃from
Period T_mThen, the attenuation and change of the heat distribution according to the condition before the change
The effect of increasing the heat distribution due to the latter condition overlaps.
It This effect is not a simple addition and can be easily calculated.
Absent. This is an inconvenience.

The first method for avoiding the above inconvenience is that the above inconvenience does not occur unless the influence before the condition change disappears as shown in FIGS. 7 (a) and 7 (b). That is, in this method, the exposure operation with the pupil filter 30A inserted is stopped until the thermal energy due to the illumination light absorbed without the pupil filter 30A is attenuated. However, if the exposure stop time becomes long, the throughput deteriorates. Therefore, the exposure operation is stopped until an inconvenience can be neglected in accuracy by experiments or the like.

This will be described with reference to FIG. The limit La that can be ignored for the accuracy of the deviation amount ΔF of the best imaging plane is La.
_2, and after the exposure, the deviation amount ΔF is stopped only exposure operation period T _L as the limit La ₂ below. Limit La
_{Although 2} may be a constant value, it may be changed depending on the conditions for the next exposure. As a result, it is possible to set a value of the limit La ₂ for each condition for performing the next exposure and perform finer control, and in this case, deterioration of throughput can be minimized. However, during the period _TL , it is possible to perform an operation (for example, an alignment operation) other than the exposure operation in which accuracy is relatively unimportant.

The second method is a method for obtaining and correcting the offset dF ₂ of the positional deviation of the best image plane in FIG. 8 through experiments, simulations or the like. This eliminates the inconvenience. On the other hand, the inconvenience of still exists,
Ignore this case because it is small enough to ignore. Note that the actual change in characteristics is not as large as in the example of FIG. 8, so even a simple sum will not cause a large error.

Since the amount of the offset dF ₂ differs between the conditions before and after the time point t ₃ , it is necessary to carry out the experiment with the required combination. The value of offset dF ₂ is
It is a parameter of the amount of illumination light absorption, since it depends on how much the illumination light is absorbed. As an example of a simple method for expressing this, the positional deviation amount ΔF of the best image plane at the time t ₃
It is also possible to use a method of using the value ΔF _{a of the above} and storing the ratio (dF ₂ / ΔFa) of the _two quantities as a coefficient. That is, the offset dF ₂ is obtained based on the amount of deviation ΔFa of the position of the best image plane at the time t ₃ when the condition changes before and after, and the correction is continued using this offset. With this method, there is an advantage that exposure can be continuously performed without deteriorating the throughput unlike the first method, and inconvenience at the time of switching the conditions is eliminated.

In the above-mentioned example, the parameters are stored in advance in the main control system 6 and the parameters are switched according to the conditions to deal with them. However, this method is similar to the projection exposure apparatus of FIG. In addition, there is a disadvantage that the number of combinations of conditions becomes complicated and adjustment of the device takes time. As a method of solving this, for example, a method of simply measuring the position of the best image plane, distortion, etc. in an aerial image and using it for correction can be considered. Although this is not shown in FIG. 1, for example, a photoelectric sensor (C
CD, a light receiving element having a slit-shaped opening, etc. are provided, the reference pattern of the reticle is received by this photoelectric sensor, distortion and magnification are obtained from the light receiving position, and the position of the best image plane is detected from the contrast. Various methods are already known. Using this method, correction is frequently performed for a while after the condition is changed, and the correction value is data-processed to find the parameter in the main control system 5 under the new condition, and the parameter is found. After that, the measurement may be stopped and the correction may be performed according to the new parameter.

Further, once the parameters have been obtained, the parameters are stored, and when the next exposure is carried out under the same conditions, if the stored ones are used, especially when the exposure is repeated under the same conditions. The measurement for obtaining the parameters can be omitted. According to this method, the throughput drops in the aerial image measurement only at the beginning, after that it can be corrected with the usual throughput, and it is not necessary to obtain the parameters under all conditions in advance. There is.

Furthermore, as another method, it is possible to use a method that does not have parameters corresponding to the respective conditions but has parameters according to the intensity distribution on the pupil plane of the projection optical system. Specifically, it has a parameter according to the shape of a typical pupil filter on the pupil plane, and a parameter in an intermediate state is obtained by interpolation calculation and used. This method does not necessarily have parameters in all conditions, and when conditions are given, whether the illumination light distribution on the pupil plane under those conditions is calculated or actually measured,
The parameter is obtained by comparing the intensity distribution pattern stored in advance. The stored intensity distribution pattern may not match the actual intensity distribution, but it may be obtained by the above-described interpolation calculation, estimation by fuzzy theory, or the like. As a method for obtaining the light intensity distribution on the pupil plane, for example, a photoelectric sensor is moved in and out of the pupil plane, or the aperture diameter of the aperture stop 25A is continuously changed on the irradiation amount monitor 27 on the wafer stage to perform irradiation. There is a method of detecting the output of the quantity monitor 27.
This method also has an advantage that it is possible to save the trouble of previously obtaining the parameters for each condition.

The present invention is not limited to the above embodiment,
Various configurations can be adopted without departing from the scope of the present invention.

[0075]

According to the present invention, when the pupil filter of the projection optical system is moved in or out of the projection optical system by the optical characteristic changing means or the pupil filter is exchanged, the change of the image forming state due to the change. However, since it is corrected by the image formation state correction means, there is an advantage that the pattern formation can be performed on the photosensitive substrate while always maintaining the image formation characteristic close to a desired state.

Further, the image-formation characteristic correcting means changes the parameter for calculating the predetermined amount of change in the image-forming characteristic according to the optical characteristic changed by the optical-characteristic varying means, and the parameter switching means. An image forming characteristic calculating means for obtaining a change amount of the predetermined image forming characteristic using the parameter changed by the changing means, and an image forming operation based on the change amount of the image forming characteristic obtained by the image forming characteristic calculating means. In the case where the control means for correcting the change of the predetermined image forming characteristic is provided via the state adjusting means, the image forming characteristic can be corrected easily and at high speed simply by switching the parameter.

Further, there is provided accumulated energy measuring means for obtaining accumulated energy in the projection optical system by the illumination light emitted from the illuminating means, and the image formation characteristic calculating means has the accumulated energy obtained by the accumulated energy measuring means. When correcting the change in the predetermined image forming characteristic based on the switched parameters, the image forming characteristic can be corrected more accurately in consideration of the influence of the accumulated energy of the illumination light.

Furthermore, the accumulated energy measuring means for obtaining the accumulated energy in the projection optical system by the illumination light emitted from the illuminating means and the accumulated energy since the corresponding optical characteristic is changed by the optical characteristic changing means. When the exposure determining means for stopping the exposure of the mask pattern until the stored energy obtained by the measuring means becomes equal to or less than a predetermined allowable amount due to thermal diffusion, throughput is slightly reduced, but it is complicated. It is possible to prevent exposure without deteriorating the imaging characteristics without performing calculation.

Next, a distortion correction plate for correcting the distortion of the projected image on the photosensitive substrate by the projection optical system, which occurs when the corresponding optical characteristic is changed by the optical characteristic changing means, is provided on the mask and the photosensitive substrate. If it is placed between the two, there is an advantage that even a complicated distortion can be accurately corrected.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a projection exposure apparatus according to an embodiment of the present invention with a part cut away.

FIG. 2 is a functional block diagram showing a configuration of a main control system 6 in FIG.

FIG. 3 is a partially cutaway configuration diagram showing a spherical aberration correction mechanism of the projection optical system PL of FIG.

FIG. 4 is an enlarged plan view showing a configuration example of a pupil filter in FIG.

5 is an enlarged plan view showing an example of an aperture stop arranged on the turret plate 4 in FIG.

FIG. 6 is an explanatory diagram showing that the image forming characteristic changes depending on the intensity distribution of the illumination light on the pupil plane of the projection optical system.

FIG. 7 is a diagram showing a change in the positional shift amount of the best imaging plane when the exposure state without the pupil filter is switched to the exposure state with the pupil filter through the exposure stop state.

FIG. 8 is a diagram showing a change in the amount of positional deviation of the best imaging plane immediately after switching the presence / absence of a pupil filter without going through an exposure stop state.

FIG. 9 is an explanatory diagram of an effect of providing an exposure stop state when switching the presence / absence of a pupil filter.

[Explanation of symbols]

 R Reticle PL Projection optical system W Wafer WS Wafer stage 4 Turret plate 6 Main control system 14, 18, 21 Drive element 24 Sub control system 25A Aperture stop 28 Projection optical system 29 Light receiving optical system 30A, 30B Pupil filter 31 Setting device 33A Distortion Correction plate 62 Parameter changing unit 64 Imaging characteristic calculation unit

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/30 515 D 526 A

Claims (5)

[Claims] 1. An illuminating device for illuminating a mask on which a transfer pattern is formed, and an image of the pattern of the mask is projected on a photosensitive substrate with a predetermined image forming property under illumination light from the illuminating device. In a projection exposure apparatus having a projection optical system, at least one of an optical characteristic group consisting of a polarization characteristic distribution, a transmittance distribution and a phase distribution on a pupil plane in the projection optical system or on a surface in the vicinity thereof. Optical characteristic changing means for changing the optical characteristic, image forming state adjusting means for adjusting the image forming state of the projected image on the photosensitive substrate by the projection optical system, and changing the corresponding optical characteristic by the optical characteristic changing means. An image forming characteristic correcting means for correcting a change in a predetermined image forming characteristic of a projected image on the photosensitive substrate by the projection optical system caused by the image forming state adjusting means. Characterized by Projection exposure system. 2. The image forming characteristic correcting means includes a parameter switching means for changing a parameter for calculating a change amount of the predetermined image forming characteristic according to the optical characteristic changed by the optical characteristic changing means. An image forming characteristic calculating means for obtaining a change amount of the predetermined image forming characteristic by using the parameter changed by the parameter changing means, and an image forming characteristic changing means obtained by the image forming characteristic calculating means, The projection exposure apparatus according to claim 1, further comprising a control unit that corrects a change in the predetermined image formation characteristic via the image formation state adjustment unit. 3. An accumulated energy measuring means for determining accumulated energy in the projection optical system by the illumination light emitted from the illuminating means is provided, and the imaging characteristic calculating means is obtained by the accumulated energy measuring means. The projection exposure apparatus according to claim 2, wherein a change in the predetermined image formation characteristic is corrected based on the stored energy and the switched parameter. 4. A stored energy measuring means for obtaining stored energy in the projection optical system by illumination light emitted from the illuminating means, and the corresponding optical characteristic being changed by the optical characteristic changing means, The exposure determination means for stopping the exposure of the pattern of the mask until the stored energy obtained by the stored energy measuring means becomes less than a predetermined allowable amount due to thermal diffusion. Projection exposure device. 5. A distortion correction plate for correcting distortion of a projected image on the photosensitive substrate by the projection optical system, which occurs when the corresponding optical characteristic is changed by the optical characteristic changing means, and the mask. It is inserted between the photosensitive substrate and the photosensitive substrate.
4. The projection exposure apparatus according to claim 4.