JPH06349703A - Projection exposure device - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a projection exposure apparatus capable of excellent correction for a change in optical characteristics, that is, a change in image formation state caused by thermal deformation of a mask. A projection exposure apparatus of the present invention illuminates a mask on which a predetermined pattern is formed with illumination light in a predetermined wavelength range, and forms an image of the predetermined pattern on a projection substrate through a projection optical system. In a projection exposure apparatus that forms an image in the image formation state,
A temperature measuring unit for optically measuring a temperature change of the mask due to absorption of the illumination light, and a change amount of the imaging state generated according to a thermal deformation amount of the mask due to the temperature change. And a correcting means for correcting at least one of a magnification change and a distortion change based on the amount of change in the image formation state in order to perform projection exposure in a predetermined image formation state. It is characterized by

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, such as a pattern exposure apparatus for manufacturing semiconductors, which requires a high degree of image forming characteristics, and more particularly to maintaining the image forming characteristics thereof.

[0002]

2. Description of the Related Art Conventionally, as a pattern of a semiconductor integrated circuit is miniaturized, in a projection exposure apparatus, a change in imaging characteristics (for example, magnification, focal length) caused by absorption of exposure light by a projection optical system. Need to be corrected. For example, as disclosed in Japanese Patent Laid-Open No. 60-78455 or Japanese Patent Laid-Open No. 63-58349, the amount of light incident on the projection optical system is detected, and the optical characteristics of the projection optical system fluctuate due to absorption of illumination light. Was equipped with a mechanism to correct the.

A brief description of this correction mechanism is as follows.
A model (function) corresponding to the variation characteristics of the imaging characteristics (for example, projection magnification, focus position, etc.) due to heat accumulation is created in advance, and the amount of energy incident on the projection optical system is calculated by the photoelectric sensor on the stage. The amount of fluctuation of the imaging characteristic is calculated over time according to this model. That is, the signal of the shutter OPEN during the exposure operation is received, the variation amount of the optical characteristic is constantly calculated according to the model, and at least one optical element forming the projection optical system is determined based on the variation amount of the imaging characteristic. This is to move or seal a space sandwiched between two optical elements and control the pressure in this sealed space to correct the imaging characteristics to a predetermined value.

In the above technique, the problem of absorption of exposure light of the projection optical system has been solved for the time being. However,
Since the exposure light beam also passes through the mask, there is a disadvantage that the mask is thermally deformed by absorption of the exposure light, which causes a change in imaging characteristics. In particular, since the pattern of the mask is drawn with chrome or the like, heat absorption in the chrome portion is large unlike the glass portion having high transmittance. Further, in recent years, there has been a tendency to adopt a technique of reducing the reflection of chromium on the mask for the purpose of preventing flare of the optical system, but this further increases the heat absorption of the chromium portion.

It is conceivable that the temperature of the glass portion of the mask also rises due to the heat absorption of the chromium portion, and the entire mask thermally expands. According to actual measurement, the temperature rise of the mask rises by about 5 ° C. under the worst condition. When the temperature rises by about 5 ° C, the material of the mask is generally quartz glass, and its expansion coefficient is 0.4 ppm / ° C, so a deviation of 0.02 μm occurs with respect to a 10 mm interval. This causes distortion or magnification errors on the surface.

Further, the chrome pattern of the mask is not always uniformly distributed over the entire mask, but may have a biased distribution state. In this case, the temperature of the mask locally rises and anisotropic strain may occur. Also, when exposing only a part of the mask using a light-shielding band (variable field stop) or the like, anisotropic distortion may similarly occur.
The distortion of the mask thus generated causes anisotropic distortion in the projected image. In this case,
It is not sufficient to correct only the magnification component.

[0007]

As described above, when the thermal deformation of the mask occurs, the conventional technique causes a shift in the imaging characteristics depending on the type of mask used. That is,
The thermal deformation of the specific mask used for the adjustment at the time of shipment has been corrected because it is recognized as a change characteristic of the optical characteristics of the projection optical system, but if other masks are used, the thermal deformation characteristics will generally differ, so the correction I can't run out. Further, when the masks are exchanged one after another for exposure, the conventional technique has a problem that a large error occurs because the thermal deformation characteristics of each mask are not taken into consideration.

As a countermeasure against this, for example, a method of cooling the mask to a constant temperature can be considered, but since the glass surface temperature of the mask and the temperature of chromium cannot be made constant,
It is impossible to cool the whole so as to have a uniform heat distribution. Further, since cooling is a phenomenon involving heat conduction, the response is poor and it is not possible to quickly follow the OPEN and CLOSE of the shutter.

It is considered that these points, which have not been a problem in terms of accuracy in the past, will become important for projection patterns that are becoming finer in recent years or in the future. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a projection exposure apparatus that can perform favorable correction for a change in optical characteristics, that is, a change in image formation state caused by thermal deformation of a mask. And

[0010]

In order to solve the above-mentioned problems, in the present invention, a mask having a predetermined pattern is illuminated with illumination light in a predetermined wavelength range, and the predetermined light is passed through a projection optical system. In a projection exposure apparatus for forming an image of a pattern on a projection substrate in a predetermined image formation state, temperature measuring means for optically measuring a temperature change of the mask due to absorption of the illumination light, and the temperature change. Calculation means for calculating the amount of change in the image formation state that occurs according to the amount of thermal deformation of the mask, and the amount of change in the image formation state for projection exposure in a predetermined image formation state. And a correction means for correcting at least one of a change in magnification and a change in distortion based on the above.

Further, according to a preferred aspect of the present invention, the temperature measuring means receives the infrared ray generated by the mask through the light splitter provided in the illumination optical system and the light splitter. The photoelectric sensor means and the temperature data processing means for obtaining the temperature change of the mask based on the temperature data sensed by the photoelectric sensor means. Also,
The correction means includes magnification correction means for moving at least one optical element in the projection optical system to correct a change in magnification, or between two adjacent optical elements in the projection optical system. It is preferable to include a magnification correction unit for changing the pressure in the space enclosed by and correcting the change in magnification. Further, it is preferable that the correction means includes a distortion correction means for correcting the distortion change by moving the mask along the optical axis.

[0012]

Since the present invention is constructed as described above, the temperature distribution of the mask due to absorption of the illumination light can be sequentially and accurately obtained by the temperature measuring means, and the thermal deformation amount of the mask can be calculated based on the temperature distribution. Can be obtained with high accuracy. Furthermore, based on the amount of thermal deformation of the obtained mask,
For example, it is possible to obtain the change in the image formation state by a formulation based on optical calculation or actual measurement. In general, changes in the imaging state can be roughly classified into magnification changes corresponding to isotropic deformation of the mask and distortion changes corresponding to anisotropic deformation of the mask. Therefore, by appropriately controlling at least one of the magnification correction means and the distortion correction means, which are conventionally known correction means for the image formation characteristic, it is possible to perform the correction so that the image formation state becomes optimum. As described above, in the present invention, since the fluctuation of the image forming characteristic due to the thermal deformation of the mask is offset and corrected by the means for correcting the image forming characteristic, a good image forming state is always maintained regardless of the type of mask used. It becomes possible to do.

[0013]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 1, an illumination light source 1 for exposure such as an ultra-high pressure mercury lamp and an excimer laser light source
Is g-line, i-line or ultraviolet pulsed light (eg KrF
Illumination light IL having a wavelength (exposure wavelength) that exposes the resist layer, such as an excimer laser, is generated. Illumination light I
L is an illumination including an optical integrator (fly-eye lens) after passing through a shutter 2 that closes and opens the optical path of the illumination light, and a semi-transmissive mirror 4 that allows most (90% or more) of the illumination light to pass. Reach the optical system 6.

The shutter 2 is driven by a drive unit 3 so as to control passage and blocking of illumination light. A part of the illumination light reflected by the semi-transmissive mirror 4 enters a photoelectric detector (power monitor) 5 such as a PIN photodiode. The power monitor 5 photoelectrically detects the illumination light IL and outputs light information (intensity value) PS to the main control system 20. This information P
S is basic data for obtaining the amount of variation in the image forming characteristics due to the exposure light absorption of the projection optical system PL in the main control system 20.

The illumination light IL, which has been made uniform in luminous flux and reduced in speckles in the illumination optical system 6, is reflected by the mirror 7 through the diaphragm, and the relay lens 9a, the variable blind 10 and the relay lens 9b. After passing through, the light is reflected by the dichroic mirror 12 in the vertical direction in the drawing to reach the main condenser lens 13, and illuminates the pattern area PA of the reticle R with uniform illuminance. Since the surface of the variable blind 10 is in an image-forming relationship with the reticle R, the drive motor 11
Thus, the illumination field of the reticle R can be arbitrarily selected by opening and closing the movable blade that constitutes the variable blind 10 to change the opening position and the opening shape. Further, in this embodiment, the dichroic mirror 12 is obliquely provided at an angle of 45 ° above the reticle R. The dichroic mirror 12 has, for example, a reflectance of 90% or more for light having a short wavelength (ultraviolet region including an exposure wavelength) and 50% for light having a long wavelength (infrared region longer than the exposure wavelength).
It has the above transmittance.

Further, in the present embodiment, the reflected light generated from the wafer W by the illumination of the illumination light IL passes through the mirror 7 and is incident on the photodetector (reflection amount monitor) 8. . The reflection amount monitor 8 photoelectrically detects the reflected light and outputs optical information (intensity value) RS to the main control system 20. This information RS serves as basic data for the main control system 20 to obtain the amount of change in the imaging characteristics due to the exposure light absorption of the projection optical system PL.

Further, in this embodiment, the infrared ray generated by the reticle R is received to measure the temperature change (temperature distribution) of the reticle R caused by the absorption of the illumination light IL. Infrared rays generated by the reticle R are transmitted through the dichroic mirror 12, reflected by the mirror 51 in the horizontal direction in the figure, and then incident on the temperature sensor 53 by the lens 52.
If an infrared camera is used as the temperature sensor 53, the temperature distribution of the reticle R can be easily detected.
However, as the temperature sensor 53, a photoelectric sensor (Si, G
e, PbS, CdS, etc.) may be arranged two-dimensionally to detect the temperature.

Receiving the temperature data detected by the temperature sensor 53, the temperature data processing unit 54 determines the temperature distribution of the reticle R. The obtained temperature distribution information TS is output to the main control system 20, and this information TS serves as basic data for obtaining a variation amount of the image forming characteristic due to the exposure light absorption of the reticle R in the main control system 20 (details). Is described later). In this way, the dichroic mirror 12 is arranged above the reticle R so that the infrared rays emitted from the reticle R are detected by the temperature sensor 5.
Since the temperature measurement means of the present invention is configured so as to lead to No. 3, the temperature distribution in the reticle R can always be obtained with high accuracy without interfering with the projection exposure process (that is, even during exposure).

The reticle R is mounted on a reticle stage Rst which is two-dimensionally movable in a horizontal plane and is held by a reticle table RT which can be moved up and down via expandable / contractible drive elements 50a to 50c. Pattern area PA
The reticle R is positioned so that its center point coincides with the optical axis AX. Initialization of the reticle R is performed by finely moving the reticle stage Rst based on a mark detection signal from a reticle alignment system RA that photoelectrically detects an alignment mark (not shown) around the reticle. The reticle R is used after being appropriately replaced by a reticle exchanger (not shown). Reticle replacement is frequently performed, especially when performing high-mix low-volume production.

The illumination light IL that has passed through the pattern area PA enters the projection optical system PL that is telecentric on both sides. The projection optical system PL superimposes the projected image of the circuit pattern of the reticle R on one shot area on the wafer W, which has a resist layer formed on the surface and is held so that the surface substantially coincides with the image plane IM. To project (image).
The wafer W is moved in the optical axis direction (Z direction) by the drive motor 17.
It is mounted on a Z stage 14 that can be slightly moved. Furthermore, the Z stage 14 is mounted on an XY stage 15 which can be two-dimensionally moved by a step-and-repeat method by a drive motor 18. When the transfer exposure of the reticle R onto one shot area on the wafer W is completed, the XY stage 15 is stepped to the next shot position.

The two-dimensional position of the XY stage 15 is constantly detected by the interferometer 19 with a resolution of, for example, about 0.01 μm, and a movable mirror for reflecting the laser beam from the interferometer 19 is provided at the end of the Z stage 14. 14m is fixed. A dose monitor (for example, a photoelectric detector having a light-receiving surface having substantially the same area as the image field of the projection exposure system PL or the projection area of the reticle pattern) 16 is substantially aligned with the surface position of the wafer W on the Z stage 14. The information LS regarding the irradiation amount is also sent to the main control system 20. This information LS is used by the main control system 20.
In (1), it becomes basic data for obtaining the variation amount of the image forming characteristic caused by the exposure light absorption of the projection optical system PL.

Further, FIG. 1 shows an image forming plane I of the projection optical system PL.
Irradiation optical system 22a for supplying an image forming light beam or a parallel light beam for forming an image of a pinhole or a slit toward M from an oblique direction with respect to the optical axis AX, and the wafer surface of the image forming light beam or the parallel light beam. Oblique-incident-light type surface detection system 2 including a light-receiving optical system 22b for receiving the reflected light beam at
Two are provided. Here, the configuration of the surface detection system 22 is disclosed in, for example, Japanese Patent Publication No. 2-10361, and the position of the wafer surface in the vertical direction (Z direction) with respect to the image plane IM is detected and the wafer W is detected. Projection optical system PL
This is a combination of a focus detection system that detects the in-focus state with and a horizontal position detection system that detects the inclination of a predetermined region on the wafer W with respect to the image plane IM.

In the present embodiment, the angle of the parallel flat glass (plane parallel) (not shown) provided inside the light receiving optical system 22b is adjusted in advance so that the image plane IM becomes the zero point reference, and the focus is adjusted. When the detection system is calibrated and when the surface of the wafer W and the image plane IM coincide with each other, the parallel light flux from the illumination optical system 22a is a four-division light receiving element (not shown) inside the light receiving optical system 22b. It is assumed that the horizontal position detection system has been calibrated so that the light is focused at the center position of.

Next, the structure of the correction means for correcting the image formation state will be described. In the present embodiment, as will be described later in detail, the configuration is such that the imaging characteristics (projection magnification, distortion, etc.) are corrected by driving the lens elements of the projection optical system PL. A part of the optical element is movable so that the characteristics can be adjusted. As shown in FIG. 1, the lens element (30, 31) of the first group closest to the reticle R is fixedly supported by the support member 32, and the lens element 33 of the second group is fixedly supported by the support member 34. Further, the lens element 35 of the third group is the support member 3
6 is fixedly supported. In addition, the lens element 35
The lower lens elements are respectively the projection optical system P
It is fixedly supported by the L lens barrel portion 37.

In the present embodiment, the optical axis AX of the projection optical system PL refers to the optical axis of the lens element fixed to the lens barrel 37. Now, the support member 36
Is connected to the lens barrel portion 37 of the projection optical system PL by extendable drive elements 40a, 40b, 40c. Also,
The support member 34 is a drive element 39a, 39b, 3
While being connected to the support member 36 by 9c,
The support member 32 includes drive elements 38a, 38b, 3 that can expand and contract.
It is connected to the support member 34 by 8c. In this embodiment, the drive element control unit 23 controls the lens elements (30, 31), (33) and (3) close to the reticle R.
5) is movable, and those lens elements are selected so that their influences on the magnification and distortion characteristics are greater and easier to control than other lens elements.

Further, in this embodiment, since the movable lens elements are composed of three groups, it is possible to increase the moving range of the lens elements while suppressing the fluctuations of other various aberrations, and to obtain various shape distortions (trapezoids). , Diamond shape, barrel shape, pincushion shape, etc., and it is possible to sufficiently cope with fluctuations in the image forming characteristics of the projection optical system PL caused by thermal deformation of the reticle R due to absorption of exposure light. It should be noted that the movement of the lens element is performed within a range in which the influence exerted on other various aberrations (eg, astigmatism) of the projection optical system PL can be ignored. Alternatively, by adjusting the distance between the lens elements, it is possible to employ a method in which the magnification and distortion characteristics are controlled and other various aberrations are also corrected.

FIG. 2 is a view of the projection optical system PL seen from above (reticle side). The drive elements 38a to 38c are arranged at positions rotated by 120 °, respectively, and can be independently controlled by the drive element control section 23. Has become. Also,
Similarly, the driving elements 39a to 39c and 40a to 40c are also rotated by 120 ° and arranged,
Independent control is possible by the drive element control unit 23.
The drive elements 38a, 39a and 40a are arranged offset from each other by 40 °, and the drive elements 38b, 39b and 40b and 38c, 39c and 40c are also arranged offset from each other by 40 °. In addition,
The drive elements 50a to 50c described above are arranged in the same manner as the drive elements 38 to 40, and can be independently controlled by the drive element control unit 23.

As the driving elements 38 to 40 and 50, for example, an electrostrictive element or a magnetostrictive element is used, and the displacement amount of the driving element according to the voltage or magnetic field applied to the driving element is previously obtained. Although not shown here, a capacitive position sensor as a position detection device, a differential transformer, and the like are provided near the drive element in consideration of the hysteresis of the drive element. Therefore, the position of the drive element corresponding to the voltage or the magnetic field applied to the drive element can be monitored, so that highly accurate driving can be performed.

With the above construction, the periphery 3 of the lens elements (30, 31), (33) and (35) of the three groups.
The points can be independently moved in the optical axis AX direction of the projection optical system PL by an amount according to a drive command given from the main control system 20. As a result, the lens elements (3
0, 31), (33) and (35) are respectively set to the optical axis AX.
It is possible to make a parallel movement along substantially the same as, and to arbitrarily tilt with respect to a plane substantially perpendicular to the optical axis AX. The lens elements are assumed to be tilted with the optical axis AX as a virtual tilt reference. Further, the reticle R can be moved via the drive element 50 as necessary.

The main control system 20 receives information PS and R from the power monitor 5, the reflection amount monitor 8 and the irradiation amount monitor 16, respectively.
After obtaining S and LS, the variation amount of the imaging characteristic due to the exposure light absorption of the projection optical system is calculated according to the conventional technique. The main control system 20 also receives the temperature distribution information TS of the reticle R from the temperature data processing unit 54, and calculates the variation amount of the imaging characteristic due to the exposure light absorption of the reticle R according to the present invention as described later. . Furthermore, the main control system 20
Controls the entire device including the drive element controller 23. On the other hand, reference numeral 21 denotes a memory, which also stores a mathematical formula or a table for calculating the amount of thermal deformation of the mask based on the measured temperature distribution, and by extension, the amount of change in the image formation state.

Next, a method of calculating the variation amount of the image forming characteristic will be described. The present invention focuses on and corrects the change in the image forming characteristic caused by the thermal deformation of the reticle R. When calculating the change amount of the image forming characteristic, the thermal deformation amount of the reticle R is first calculated. Need to ask. Reticle R
Since it can be considered that the heat deformation occurs in proportion to the temperature distribution of the reticle R, it is sufficient to know the temperature distribution of the reticle R at a certain time in order to calculate the heat deformation amount. In the present invention, the temperature distribution can be accurately obtained by the above-mentioned temperature measuring means without interfering with the projection exposure process.

3 and 4 show typical temperature distributions of the reticle R captured by, for example, an infrared camera. FIG. 3 shows a temperature distribution symmetrical about the optical axis, and FIG. 4 shows an asymmetrical temperature distribution about the optical axis. Shows a wide temperature distribution. Although the reticle R is uniformly irradiated with the illumination light IL during the projection exposure, it has already been described above that the temperature distribution changes depending on the arrangement of the chrome portions forming the pattern and the like. As shown in FIG. 3, when the temperature distribution of the reticle R is symmetrical with respect to the optical axis, that is, isotropic, the deformation of the reticle is also isotropic as a whole. As a result, the change in magnification becomes dominant on the image plane. On the other hand, as shown in FIG. 4, when the temperature distribution of the reticle R is asymmetric with respect to the optical axis, that is, anisotropic, the deformation of the reticle is also anisotropic as a whole. As a result, the distortion change becomes dominant on the image plane.

In general, the deformation of the reticle can be determined exactly from the temperature distribution by calculation based on, for example, the finite element method, and the amount of change in the imaging state can be obtained from the above deformation by optical calculation or actual measurement. However, as a simpler method, for some typical temperature distribution shapes, the temperature average value (or temperature peak value), temperature peak position (or temperature distribution center of gravity position), the magnification change amount of the projection optical system, and the like. The relationship with the distortion change amount is obtained in advance, and the magnification change amount or distortion change amount corresponding to the average temperature (or peak temperature), temperature peak position (or temperature distribution center of gravity position), etc., during actual projection exposure. There is also a method of directly obtaining. In any case, the amount of change in the imaging characteristics of the projection optical system (that is, the amount of deformation of the projected image) according to the thermal deformation of the reticle R is obtained from the obtained temperature distribution, and the amount of change in magnification and the distortion change are calculated. It will be calculated separately from the ingredients.

Next, a method of correcting the image formation state will be described. Basically, as described above, the lens elements (30, 31), (33) and (35) or the reticle R of the three groups of the projection optical system PL are used as the optical axis direction or the axis perpendicular to the optical axis as the rotation axis. A desired image formation state is obtained by driving in the tilt direction. Here, only the correction of the magnification change and the distortion change will be described, but the field curvature and the like can be corrected by this method. For example, a change in magnification and a change in distortion caused by driving the lens elements (30, 31) will be described with reference to FIGS. 5 and 6, respectively. 5 and 6, the dotted line shows the image plane when there is no thermal deformation of the reticle, and the solid line shows how the image plane is deformed by thermal deformation. In order to clearly show the deformation, we focus on the points divided into grids. Actually, the manner of change varies depending on the configuration of the lens element, and therefore the diagram shown here is an example and not a general one.

First, when the lens element (30, 31) is moved in the optical axis direction, the magnification changes with the optical axis as the center CT. The manner in which the magnification is changed is shown in FIG. Further, when the lens element (30, 31) is tilted about an axis perpendicular to the optical axis, the distortion changes as shown in FIG. 6, for example. In this example,
The image portion distant from the rotation axis RX changes in the direction perpendicular to the rotation axis RX. In this way, each lens element group (3
It is possible to correct various magnification changes or distortion changes by combining the driving methods of 0, 31), (33) and (35). In addition, even if the reticle R is moved up or down or tilted, distortion (particularly a spool type,
The barrel type) can be changed. Driving a lens element (or reticle) to correct magnification changes and distortion changes may worsen other aberrations (eg coma, astigmatism), but drives multiple lens elements. Therefore, it is possible to perform desired magnification correction or distortion correction while correcting various aberrations.

The memory 21 stores the movement of each of a plurality of points (lattice points) on the image plane accompanying the driving of the lens element or reticle as shown in FIGS. 5 and 6 in the form of a mathematical expression or a table. The main control system 20 calculates the optimum magnification correction amount or distortion correction amount according to the amount of change in the image forming characteristics of the projection optical system PL due to the thermal deformation of the reticle R. As a calculation method, for example, a condition that minimizes the maximum value of the deviation with respect to an ideal grid point, that is, a grid point when the reticle R is cold (shown by a dotted line in FIGS. 5 and 6), or the sum of squares of the deviation is minimized. A magnification correction or a distortion correction that satisfies the condition

The above is the magnification correcting means and the distortion correcting means in the present embodiment, but the image plane is changed (vertical movement, inclination) by driving the lens element groups (30, 31), (33) and (35). There is a possibility that it will happen. In this case, if an offset is given to the wafer surface detection system 22 according to the change of the image surface, the wafer W is always set to the best image surface, and this influence can be prevented. As described above, the wafer surface detection system 22 irradiates the wafer surface with a light beam and detects the position or inclination of the wafer surface in the optical axis direction by the reflected light. The main control system 20 controls the Z stage 14 according to the output of the wafer surface detection system 22, and the Z stage is driven so that the wafer W and the image plane always match.

As another means for correcting the image formation state, a method of moving, tilting or bending the reticle R in the optical axis direction, or providing an airtight space between adjacent lens elements in the projection optical system, A method of adjusting the pressure, a method of bending the glass by installing parallel flat plate glass above or below the projection optical system and controlling the inside, and the like can be considered. Generally, in order to correct a so-called anisotropic deformation that is not symmetric with respect to the optical axis such as a distortion change, a method of moving the reticle R along the optical axis AX by the driving elements 50a to 50c, and the present embodiment. The method of driving the lens element is preferable.

As described above, in the projection exposure apparatus of the present invention,
Reticle R based on temperature distribution during device manufacturing
Each parameter for calculating the thermal deformation of, and consequently the fluctuation of the image formation state is stored in the memory 21. During the exposure operation, the power monitor 5, the reflection amount monitor 8, and the irradiation amount monitor 16 output light information (intensity values), respectively, and the temperature data processing unit 54 outputs reticle temperature distribution information to the main control system 20. It In the main control system 20, based on these information and each data stored in the memory 21, the change in the image formation state due to the absorption of the exposure light of the reticle R and the absorption of the exposure light of the projection optical system PL are caused. The change in the imaging state is calculated and the total change amount is calculated.

When the image forming state of the projection optical system PL changes due to other factors such as a change in atmospheric pressure, these changes can be summed up if necessary. An optimum correction amount is calculated for the total change amount of the image formation state, and the lens element driving elements 38 to 40 are driven to perform the correction. Further, in this case, other correction means, for example, the drive element 50 may be driven for correction as necessary. Here, regarding the focal position and the image plane inclination, the wafer W is detected using the wafer surface detection system 22 and the Z stage 14.
By vertically moving and tilting the projection lens P
It is also possible to match the best image plane of L with the wafer surface.

[0041]

As described above, according to the present invention, the temperature distribution of the mask caused by the absorption of the illumination light of the mask can be accurately obtained without obstructing the projection exposure operation by the optical temperature measuring means. Based on the temperature distribution, it becomes possible to obtain the thermal deformation of the mask and, consequently, the change in the image formation state with high accuracy. In this way, a change in magnification, a change in distortion, etc. corresponding to the obtained change in the image formation state can be appropriately corrected by a known correction means. As a result, regardless of the type of mask used, a good image formation state can always be maintained, and the image overlay accuracy and the like are significantly improved.

[Brief description of drawings]

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

FIG. 2 is a plan view of the projection optical system of FIG. 1 seen from above.

FIG. 3 is a diagram showing a temperature distribution symmetrical with respect to an optical axis.

FIG. 4 is a diagram showing a temperature distribution asymmetric with respect to the optical axis.

FIG. 5 is a diagram showing movement of points in the image plane by the magnification correction means according to the embodiment of the present invention.

FIG. 6 is a diagram showing movement of points in the image plane by the distortion correction means according to the embodiment of the present invention.

[Explanation of symbols]

 R Reticle PL Projection optical system W Wafer TS Temperature distribution information 1 Light source 5 Power monitor 8 Reflection amount monitor 10 Variable blind 12 Dichroic mirror 16 Irradiation amount monitor 20 Main control system 22 Surface detection system 23 Drive element control section 53 Temperature sensor 54 Temperature data Processing unit

Claims (5)

[Claims] 1. A mask on which a predetermined pattern is formed is illuminated with illumination light in a predetermined wavelength range, and an image of the predetermined pattern is formed on a projection target substrate in a predetermined image formation state through a projection optical system. In the projection exposure apparatus, a temperature measuring unit for optically measuring a temperature change of the mask due to absorption of the illumination light; and an image formation state generated according to a thermal deformation amount of the mask due to the temperature change. And a correction means for correcting at least one of a magnification change and a distortion change based on the change amount of the image formation state in order to perform projection exposure in a predetermined image formation state. And a projection exposure apparatus. 2. The temperature measuring means includes a light divider provided in an illumination optical system, a photoelectric sensor means for receiving infrared rays generated by the mask through the light divider, and the photoelectric sensor. The projection exposure apparatus according to claim 1, further comprising: temperature data processing means for obtaining a temperature change of the mask based on temperature data sensed by the means. 3. The correction unit comprises a magnification correction unit for moving at least one optical element in the projection optical system to correct a change in magnification. The projection exposure apparatus described. 4. The correcting means includes a magnification correcting means for correcting a magnification change by changing a pressure in a space sealed between two adjacent optical elements in the projection optical system. The projection exposure apparatus according to claim 1 or 2. 5. The correction means comprises a distortion correction means for correcting the distortion change by moving the mask along the optical axis. The projection exposure apparatus according to item.