JP3526042B2 - Projection exposure equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a lithography process for manufacturing, for example, a semiconductor device, an image pickup device (CCD or the like), a liquid crystal display device, a thin film magnetic head, etc. The present invention relates to a projection exposure apparatus that transfers onto a photosensitive substrate.

[0002]

2. Description of the Related Art A projection exposure apparatus for manufacturing semiconductor elements such as IC and LSI includes a reticle as a mask and
Positioning each shot area of a wafer (or a glass plate, etc.) as a photosensitive substrate in a predetermined positional relationship through a projection optical system, and exposing the entire reticle pattern image to each shot area collectively. It is roughly classified into a repeat method and a step-and-scan method in which the reticle and each shot area of the wafer are sequentially scanned with respect to the projection optical system to sequentially expose the pattern image of the reticle to each shot area. It Both of these methods are common in that the pattern of the reticle is projected through the projection optical system, and it is important how accurately the image of the pattern of the reticle can be projected on the wafer.

Generally, when designing a projection optical system, the optical aberrations are designed to be substantially zero under predetermined conditions. However, the environment during projection exposure changes and the vicinity of the projection optical system is changed. If the atmospheric pressure or temperature of the image changes, or if there is heat absorption due to the irradiation of the exposure illumination light, the refractive index change of the gas between the lenses forming the projection optical system, the lens expansion, the refractive index change of the lens, and Expansion of the lens barrel occurs. For this reason,
When the reticle pattern is projected onto the wafer, the position (focus position) in the optical axis direction of the projection optical system of the image forming plane (best focus plane) of the projected image shifts, and the wafer surface becomes the image forming plane. There was a defocus out of focus. This defocus is divided into linear defocus (a component in which the defocus amount changes linearly with the image height) and non-linear defocus (a component other than linear defocus). Then, as a means for correcting linear defocus than in the past, an autofocus mechanism for controlling the focus position of the wafer in the direction of the image plane, and an auto-leveling control for adjusting the tilt angle of the wafer to match the image plane. The mechanism is known.

[0004]

In the prior art as described above, it is possible to correct the non-linear defocus component of the defocus on the image plane of the projection optical system caused by the environmental change or the like. There was an inconvenience that it could not be done. The main part of the non-linear defocus component is the field curvature in which the defocus amount changes with a curve approximate to a quadratic or higher function according to the image height of the projected image. That is, in the state that serves as a design reference, as shown in FIG. 15A, the focus position Z _F of the image plane of the projection optical system is almost in the vicinity of the design target position regardless of the image height H. is there.

However, when a change in atmospheric pressure with respect to the reference state or heat absorption due to irradiation of exposure illumination light occurs, the defocusing characteristic of the image plane is shown in FIG. 15 (b).
The field curvature is as shown in. When such field curvature occurs, the width of the depth of focus (DOF) on the entire image plane becomes narrow, and as a result, it becomes difficult to obtain a desired resolution for the entire projected image of the reticle pattern.

When the field curvature as shown in FIG. 15 (b) occurs in the step-and-repeat system (collective exposure system) projection exposure apparatus, as shown in FIG. 16 (a), the original projected image is obtained. The focus position of the image forming surface 72 changes non-linearly according to the image height to form the image forming surface 73A, and the width of the depth of focus as a whole is narrowed. On the other hand, when the field curvature as shown in FIG. 15B occurs in the step-and-scan type (scanning exposure type) projection exposure apparatus, FIG.
As shown in FIG. 6 (b), although defocus does not occur in the Y direction, which is the scanning direction, with respect to the original image plane 72 of the projected image, image deterioration occurs due to the averaging effect. Has occurred. Also, non-scanning direction (X direction)
In the same manner as in the batch exposure method, defocusing according to the image height occurs, and the substantial image plane after the scanning exposure is the image plane 73.
Since it is B, it can be confirmed that a so-called "kamaboko-shaped" field curvature is generated as a result.

Further, in recent years, the size of the reticle has been increasing, and the inconvenience that the curvature of field is further increased when a large reticle is used. For example, assuming that the periphery of the reticle is held by vacuum suction or the like, as shown in FIG.
As shown in FIG. 7A, when the reticle RA having a small size (each side is about 5 inches or less) is supported by the four support portions 74A, the reticle RA does not bend, and there is no particular problem. However, as shown in FIG. 17B, when a large size reticle RB (for example, one side is about 6 to 9 inches) is supported by the four support parts 74B, the reticle RB moves in the longitudinal direction of the support part 74B. There is an inconvenience that it bends "kamaboko" by its own weight in the direction (X direction) orthogonal to the (Y direction), and the field curvature of the image forming surface increases correspondingly. In particular, when the reticle RB of FIG. 17B is used in a step-and-scan type (scanning exposure type) projection exposure apparatus in which the Y direction is the scanning direction, FIG.
The "kamaboko-shaped" field curvature shown in (1) may be amplified.

When nonlinear defocus such as field curvature is present on the image plane of the projection optical system as described above, either the step-and-repeat method or the step-and-scan method is finally used. However, the depth of focus of the image plane obtained as a result becomes narrow as a whole, and the resolution is degraded. In view of such a point, the present invention takes into account the change in environment such as atmospheric pressure around the projection optical system, absorption of exposure illumination light,
Another object of the present invention is to provide a projection exposure apparatus capable of correcting defocus of an image plane of a projection optical system, which is deteriorated due to bending of a reticle, in particular, non-linear defocus such as field curvature.

[0009]

In a projection exposure apparatus according to the present invention, as shown in FIGS. 1 and 2, for example, a pattern of a mask is placed on a photosensitive substrate (W) via a projection optical system. in a projection exposure apparatus for projecting, the projection optical system (PL1) is a
A plurality of optical members (25 to 34, 35) made of one glass material
A, 38A ) and the temperature characteristics related to the refractive index are
At least one optic consisting of a second glass material different from the glass material
With the members ( 36A, 37A) and from the second glass material
At least one optical element (36A, 37A) temperature control means for controlling the temperature of the (13) is provided, the image plane of the projection optical system of a projection optical system using the temperature control means (PL1) made of (PL1) It controls the position in the direction of the optical axis.

An example of the object controlled by the temperature control means (13) is the field curvature of the projection optical system (PL1). In this case, the magnification error control means (controls the magnification error of the projection optical system (PL1) ( 12) is provided, and temperature control means (13) is provided.
It is desirable to reduce the magnification error that occurs when the field curvature of the projection optical system (PL1) is controlled by using the magnification error control means (12).

Further, the temperature of the optical members (36A, 37A) to be controlled is controlled within a range of ± 1 ° C. or less by the temperature control means (13), so that the projection optical system (PL1)
It is desirable to correct the field curvature of within the range of ± 0.3 μm or less. Further, a storage means (18) for storing the amount of change in the position of the image plane of the projection optical system (PL1) according to the change in the usage condition of the projection optical system (PL1) is provided, and the projection optical system (PL1) is used. Storage means (18) according to changes in conditions
In order to cancel out the amount of change in the position of the image plane stored in the projection optical system (PL) via the temperature control means (13).
It is desirable to control the position of the image plane of 1).

Further, there is provided focus position control means (2) for relatively moving the image plane of the projection optical system (PL1) and the photosensitive substrate (W) in the optical axis direction of the projection optical system (PL1),
It is desirable to reduce the offset of the focus position remaining when the position of the image plane of the projection optical system (PL1) is controlled using the temperature control unit (13) via the focus position control unit (2). .

According to the present invention, when light near the far ultraviolet region such as KrF excimer laser light (wavelength 248 nm) or ArF excimer laser light (wavelength 193 nm) is used as the exposure light, the temperature characteristic of the refractive index is obtained. Examples of the plurality of glass materials having different materials include quartz and fluorite. In this case, quartz does not expand even if the temperature rises because it has a small expansion coefficient, but it has the property of increasing the refractive index.
Therefore, as shown in FIG. 6B, a positive quartz lens 49
In B, when the temperature rises, the image plane FB moves toward the positive lens 49B.
It is displaced in the direction of approaching. On the other hand, fluorite has the property that it expands with increasing temperature and its refractive index decreases. Therefore, as shown in FIG. 6A, when the temperature of the fluorite positive lens 49A rises, the image plane FA is displaced in a direction away from the positive lens 49A. The temperature characteristic of the refractive index of the glass material described above is not only obtained when the temperature changes in consideration of not only the temperature characteristic of the refractive index itself but also the thermal expansion of the lens made of the glass material and the expansion of the lens barrel. It is a characteristic determined by the direction in which the image plane changes.

If, for example, quartz is used as the first glass material and fluorite is used as the second glass material, and most of the lenses of the projection optical system (PL1) are made of the first glass material, the projection is performed. Considering the distribution of the focus position on the image plane of the optical system, the tendency of the distribution of the focus position Z _{F due} to the lens of the first glass material according to the image height H is shown by a curve 61A in FIG. 7A. As described above, the field curvature is convex downward, and the state of the field curvature changes due to environmental changes, absorption of exposure illumination light, and the like. On the other hand, the distribution of the focus position of the image plane due to the lens of the second glass material is shown in FIG.
As shown by the curve 62C in (1), there is a tendency that an offset amount common to all image heights H is added to the upwardly convex field curvature having the opposite tendency to the curve 61A.

Therefore, the temperature of the lens of the second glass material is controlled, for example, in accordance with environmental changes or absorption of illumination light for exposure, and the field curvature of the curve 61A is offset by the field curvature of the curve 62C. As a result, the field curvature, which is a non-linear defocus of the projection optical system (PL1), can be reduced. However,
When the temperature of the lens made of the second glass material is controlled, a linear magnification error may occur. Therefore, such a linear magnification error is controlled by, for example, a magnification error control means (12) for controlling the pressure in the gas chamber between predetermined lenses in the projection optical system.
Projection optical system (PL1)
The distortion does not remain in the projected image.

Further, as it is, the distribution of the focus positions on the image forming plane is as shown by a straight line 63A in FIG.
A certain offset remains. However, such a focus position offset can be almost completely removed by adjusting the height of the substrate (W) by the focus position control means (2) such as a stage for controlling the height of the substrate (W). . As a result, the distribution of the focus position Z _F of the image plane with respect to the surface of the substrate (W) becomes as shown by the curve 65A in FIG. 8, and the defocus becomes almost zero.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a projection exposure apparatus according to the present invention will be described below with reference to FIGS. 1, 2 and 6 to 14. In this example, the present invention is applied to a step-and-scan projection exposure apparatus that uses an excimer laser beam as an illumination light for exposure. However,
The projection optical system used in this example has such a performance that it can be used in a step-and-repeat system (collective exposure system) projection exposure apparatus.

FIG. 1 shows the projection exposure apparatus of this embodiment. In FIG. 1, the illumination light IL consisting of a laser beam pulsed from an excimer laser light source 16 is reflected by a mirror 15.
It is deflected by and is incident on the illumination optical system 14. As the excimer laser light source 16, a KrF excimer laser light source (oscillation wavelength: 248 nm), an ArF excimer laser light source (oscillation wavelength: 193 nm), or the like can be used. As a light source for exposure, a YAG laser harmonic generator, a metal vapor laser light source, a mercury lamp, or the like can be used.

The illumination optical system 14 includes a beam expander,
Consists of a dimming system, fly-eye lens, relay lens, field stop (reticle blind), movable blade for avoiding unnecessary exposure before and after scanning, condenser lens, etc. Shaped to uniform illuminance distribution by illumination optical system 14. The illumination light IL thus illuminated illuminates an illumination region having a predetermined shape on the pattern forming surface (lower surface) of the reticle R. In this case, the main controller 18, which controls the operation of the entire device,
Through the illumination control system 17, the timing of pulse emission of the excimer laser light source 16 and the control of the extinction ratio in the extinction system in the illumination optical system 14 are performed. Illumination light transmitted through the pattern of the reticle R in the illumination area is projected onto the wafer W coated with the photoresist via the projection optical system PL1, and the pattern is magnified by β (β is, for example, ¼, or 1
The projected image reduced by / 5 etc.) is transferred onto the wafer W.
Here, the Z axis is taken parallel to the optical axis AX of the projection optical system PL1, the Y axis is taken parallel to the paper surface of FIG. 1 in the plane perpendicular to the Z axis, and the X axis is taken perpendicular to the paper surface of FIG. .

The reticle R is held on the reticle stage 6, and the reticle stage 6 is movably mounted in the Y direction on the reticle support base 5 via an air bearing. A movable mirror 7 fixed to the upper end of the reticle stage 6,
And the Y coordinate of the reticle stage 6 measured by the laser interferometer 8 on the reticle support 5 is the stage control system 11
Is supplied to. The stage control system 11 includes a main controller 18
The position and the moving speed of the reticle stage 6 are controlled according to the command from.

On the other hand, the wafer W is held on the wafer stage 2, and the wafer stage 2 moves in the X, Y, and Z directions.
And the wafer W is positioned in the rotation direction, and Y
The wafer W is scanned in the direction. The movable mirror 9 is fixed to the upper end of the wafer stage 2, and the X coordinate and the Y coordinate of the wafer stage 2 are constantly measured by the movable mirror 9 and an external laser interferometer 10, and the measurement result is supplied to the stage control system 11. There is. The stage control system 11 follows a command from the main controller 18 to perform a stepping operation of the wafer stage 2.
Also, the scanning operation is controlled in synchronization with the reticle stage 6. That is, during scanning exposure, the reticle stage 6 is moved to -Y relative to the projection optical system PL1 under the control of the stage control system 11 using the magnification β from the reticle side of the projection optical system PL1 to the wafer side. The wafer stage 2 is moved in the + direction in synchronization with the scanning in the direction (or + Y direction) at the speed V _R.
Y is scanned in the direction (or the -Y direction) in the speed _{V W (= β · V R} ). As a result, the pattern of the reticle R is sequentially transferred to each shot area on the wafer W.

An image-forming characteristic measuring sensor 3 is fixed near the wafer W on the wafer stage 2. As shown in FIG. 9B, the image-forming characteristic measuring sensor 3 has a light-shielding film 50 having a rectangular opening 50a formed on the surface set at the same height as the surface of the wafer W. It has a glass substrate 51, a photoelectric conversion element 52 for photoelectrically converting the illumination light for exposure that has passed through the opening 50a, and a signal processing section 53 for processing the detection signal S1 from this photoelectric conversion element 52. The processing result of the signal processing unit 53 is supplied to the main controller 18 of FIG. In the present example, as will be described later, by driving the wafer stage 2, the projected image of the pattern of the reticle R is formed into the opening 50a of the imaging characteristic measuring sensor 3.
The signal processing unit 53 uses the detection signal S1 output from the photoelectric conversion element 52 at that time to determine the distribution of focus positions (field curvature) at various image heights on the image forming surface of the projection optical system PL1. I am asking for it.

Next, referring to FIG. 1, the projection optical system P of the present example.
Most of the plurality of lens elements constituting L1 are made of quartz, the remaining part of the lens elements is made of fluorite, and the lens elements are formed between a predetermined pair of lens elements made of quartz. A lens control device 12 for controlling the gas pressure in a predetermined gas chamber is provided. The magnification, the focus position (best focus position), and the field curvature of the projection optical system PL1 according to the environmental change such as atmospheric pressure change or temperature change, or the history of the irradiation amount of the exposure illumination light with respect to the projection optical system PL1. When the image forming characteristics such as the above change, the lens controlling apparatus 12 corrects the image forming characteristics based on a command from the main controller 18. As the lens control device 12, in addition to the pressure control device, for example, a lens position control device that controls the position or inclination angle of a predetermined lens element made of quartz or fluorite in the optical axis AX direction, or the light of the reticle R. A reticle position control device or the like for controlling the position and tilt angle in the axis AX direction may be used.

Further, the projection optical system PL1 is connected to a lens temperature control device 13 for controlling the temperature of one or a plurality of lens elements made of a part of fluorite. In this example, when the non-linear defocus (field curvature etc.) of the projection optical system PL1 is deteriorated according to the environmental change, the history of the irradiation amount, or the like, the lens based on the command from the main controller 18 is used. The temperature control device 13 is adapted to correct the non-linear defocus. Moreover, the projection optical system PL is corrected by the non-linear defocus correction.
When the linear magnification error of 1 worsens, the lens controller 12 corrects the linear magnification error.

Further, in the projection exposure apparatus of this example, a projection optical system 68 for obliquely projecting spot light onto the wafer W at a plurality of measurement points in the exposure area by the projection optical system PL1, and the measurement points A focus position detection system is provided which includes a light receiving optical system 69 that receives the reflected light of each of the two and re-images the spot light, and outputs a focus signal corresponding to the lateral shift amount of the re-formed spot light. Has been. A plurality of focus signals from the light receiving optical system 69 are supplied to the main controller 18. In this case, the projection optical system PL on the surface of the wafer W
When the position (focus position) of 1 in the optical axis direction (Z direction) changes, the level of the corresponding focus signal changes, so the main controller 18 monitors the focus position of the wafer W. In the main controller 18, the stage control system 1
By controlling the operation of the driving mechanism in the Z direction in the wafer stage 2 via the projection optical system PL1, the focus position at the center of the average surface of the shot area of the exposure target of the wafer W is obtained in advance. The focus position is maintained at the center of the average surface of the image forming plane.

Further, in this example, when the field curvature of the projection optical system PL1 is corrected, an offset may occur in the focus position at the center of the average surface of the image forming plane, so such an offset occurs. At this time, the wafer stage 2 is driven to correct the focus position of the wafer W by the offset, thereby preventing defocus between the image plane and the surface of the wafer W. Further, the wafer stage 2 of this example is also provided with a mechanism (leveling stage) for correcting the tilt angle of the wafer W, and the main controller 18 moves the wafer W from the focus positions at a plurality of measurement points of the focus position detection system. The tilt angle is obtained, and the tilt angle of the wafer W is adjusted to the tilt angle of the image plane.

Further, on the side surface of the projection optical system PL1 of the present example, an off-axis type image pickup type alignment sensor for detecting the position of an alignment wafer mark attached to each shot area on the wafer W. 70 is also provided. Next, the configuration of the projection optical system PL1 of this example and the configuration of the lens temperature control device 13 and the like will be described in detail with reference to FIG.

FIG. 2 shows an internal structure of the projection optical system PL1 of this example and a control system of image forming characteristics. In FIG. 2, the projection optical system PL1 is, as an example, in the lens barrel 4 from the wafer W side. Six lens elements 25 arranged in order
˜30, four lens elements 31 to 34, and four lens elements 35A to 38A. Further, only the lens elements 36A and 37A are made of fluorite, and the other lens elements are made of quartz. Then, the lens elements 33, 3
4 is fixed in the lens barrel 4 via the lens frame G1, the lens elements 35A to 38A are fixed in the lens barrel 4 via the lens frame G2, and the other lens elements are also respectively inserted in the lens frame not shown. It is fixed in the lens barrel 4.

In this case, the gas chamber surrounded by the lens elements 33 and 34 and the lens frame G1 is hermetically sealed, and the gas chamber is connected to the bellows mechanism 12b via the pipe 12c so that the bellows mechanism 12b expands and contracts. It is controlled by the controller 12a. This control unit 12
The lens control device 12 of FIG. 1 is configured by a, the bellows mechanism 12b, and the pipe 12c, and the gas (for example, air) in the gas chamber is adjusted by adjusting the expansion / contraction amount of the bellows mechanism 12b.
The pressure can be controlled.

The lens element 3 made of fluorite
In the gas chamber surrounded by 6A, 37A and the lens frame G2,
The temperature control device 13b supplies a gas at an arbitrary temperature instructed to the main control device 18 via the pipe 21, and the gas circulated in the gas chamber is supplied via the pipe 22 to the temperature control device 1
It is configured to be returned to 3b. If the gas flowing in the gas chamber has the same composition as the atmosphere (air) around the projection optical system PL1, the gas that has passed through the gas chamber must be returned to the temperature control device 13b via the pipe 22. However, for example, when a gas whose temperature is easily controlled (for example, nitrogen gas) is used, it is necessary to use the pipe 22 to perform temperature control in a closed loop.

Further, in this embodiment, since the temperature control device 13b controls the temperature of the lens elements 36A and 37A, the temperature of these lens elements 36A and 37A is controlled by the lens frame G2, the lens barrel 4, and the quartz before and after the gas. It is necessary to prevent conduction to the lens elements 35A, 38A made of Therefore, the lens element 3
A gas chamber surrounded by 7A, 38A and the lens frame G2,
And lens elements 35A and 36A and lens frame G2
The gas chambers surrounded by
A gas at a constant temperature is flown from the temperature control device 13a via the. A gas having a low temperature conductivity (air or the like) is used as the gas having a constant temperature, and the gas circulated in these gas chambers is returned to the temperature control device 13a via the pipes 23A and 24A, respectively. Temperature control device 13a, 1
The lens temperature control device 13 of FIG. 1 is configured by 3b and the pipes 19 to 22, 23A, and 24A.

Further, in the projection exposure apparatus of this example, in order to expose various patterns with high resolution, the illumination conditions by the illumination optical system 14 of FIG. 1 are set to the normal state, the modified light source, the annular illumination, and the coherence factor. It can be switched to a state in which the σ value is small. FIG. 12 shows the state of the illumination light that passes through the projection optical system PL1 when the illumination optical system 14 is switched. First, the 0th-order light that has passed through the reticle R in the normal state is shown in FIG. like,
It passes through a predetermined substantially circular area on the pupil plane (Fourier transform plane for reticle R) of projection optical system PL1. Next, when the illumination optical system 14 is in the modified light source state, the 0th-order light that has passed through the reticle R is separated on the pupil plane of the projection optical system PL1 as shown in the sectional view of FIG. Pass through multiple areas. When the illumination optical system 14 is in the annular illumination state, the 0th-order light that has passed through the reticle R passes through a substantially annular zone on the pupil plane of the projection optical system PL1.
Further, the illumination optical system 14 is set to a coherence factor σ
When the value is small, the 0th-order light that has passed through the reticle R is projected onto the projection optical system PL as shown in FIG.
It passes through a substantially small circular area on the pupil plane of 1. The imaging characteristics of the projected image also change depending on these illumination conditions.

Next, an example of the operation for removing the field curvature of the projection optical system PL1 in this example will be described. The glass material of the lens element of the projection optical system PL1 of this example is quartz and fluorite. Here, quartz has a characteristic that the index of refraction becomes large, although it hardly expands even if the temperature rises because the coefficient of expansion is small. Therefore, as shown in FIG. 6B, when the temperature of the quartz positive lens 49B rises, the image forming surface F
B is displaced in the direction toward the lens. On the other hand, fluorite has the property that it expands with increasing temperature and its refractive index decreases. Therefore, as shown in FIG. 6A, when the temperature of the fluorite positive lens 49A rises, the image plane FA is displaced in the direction away from the lens. The temperature characteristic of the refractive index of the glass material described above is not only obtained when the temperature changes in consideration of not only the temperature characteristic of the refractive index itself but also the thermal expansion of the lens made of the glass material and the expansion of the lens barrel. It is a characteristic determined by the direction in which the image plane changes.

Further, the field curvature of the projection optical system PL1 will be described with reference to FIGS. 7 and 8. 7 and 8, the vertical axis represents the image height H and the horizontal axis represents the focus position Z _F of the image plane of the projection optical system PL1 at the image height H, and the focus position on the optical axis (H = 0). Is shown as the designed focus position. In this case, the projection optical system PL after the exposure is continuously performed for a certain time under a certain environment.
The image plane formed by the lens element 1 made of quartz has a field curvature that is convex downward as shown by a curve 61A in FIG. 7A.

On the other hand, in this example, the projection optical system PL1 is adjusted by adjusting the temperatures of the lens elements 36A and 37A made of fluorite in the projection optical system PL1 via the lens temperature control device 13 of FIG. The field curvature due to the lens element made of fluorite is set so as to have a field curvature having characteristics substantially opposite to the curve 61A of FIG. 7A. However, even if the field curvature of the lens element made of fluorite is set in such a manner, a constant offset is superimposed on the focus position of the image forming surface in the entire range of the predetermined image height H. Therefore, the distribution of the focus positions of the image plane due to the lens element made of fluorite of the projection optical system PL1 is shown in FIG.
As shown by the curve 62C in FIG. 7B, the predetermined offset has a characteristic in which the field curvature having a characteristic almost opposite to that of the curve 61A in FIG. 7A is superimposed.

Therefore, the focus position Z _F of the image plane as a whole of the projection optical system PL1 is determined by the straight line 6 in FIG.
As shown by 3A, the value is almost constant over the entire range of the image height H, and defocus occurs with the surface of the wafer W. Therefore, the focus position on the surface of the wafer W is corrected by the defocus amount with respect to the projection optical system PL1 using the drive mechanism in the Z direction in the wafer stage 2 in FIG.
This substantially corresponds to the image plane of the projection optical system PL1.
This means adding an offset of the focus position as shown by a straight line 64A in FIG. 7 (c). As a result, the distribution of the focus position Z _F of the image plane of the projection optical system PL1 of this example with reference to the surface of the wafer W becomes as shown by the curve 65A in FIG. Have also been removed. Therefore, the width of the depth of focus is wider on the entire image plane than that of the conventional example, and the projection image is projected and exposed with a high resolution as a whole.

Further, the lens element 36 made of fluorite
By adjusting the temperatures of A and 37A, the linear magnification error of the image plane (error in which the magnification changes in proportion to the image height H)
May worsen. When a linear magnification error occurs in this way, a linear magnification error that substantially cancels the generated linear magnification error is given to the image forming plane via the lens control device 12 of FIG. As a result, the image forming characteristics of the projection optical system PL1 of this example are good characteristics with no field curvature and no distortion.

Here, an example of a method for measuring the distribution of focus positions on the image plane of the projection optical system PL1 will be described with reference to FIGS. 9 and 10. Therefore, as the reticle R in FIG. 1, a test reticle in which a predetermined number of pairs of evaluation marks (for example, 16 pairs) are uniformly distributed in the illumination area is used. The evaluation marks of each pair are X-axis evaluation marks composed of line-and-space patterns arranged at a predetermined pitch in the X-direction, and Y-axis evaluation marks in which the evaluation marks are rotated by 90 °. FIG. 9A shows a projected image MY (i) of the i-th (i = 1 to 16) Y-axis evaluation mark composed of the marks. In the following, the focus position of the image plane (best image plane) is detected using the projected image of the Y-axis evaluation mark, but both of the X-axis evaluated mark projection images are also used. The difference in focus position obtained by the method may be obtained.

In FIG. 9A, the projected image MY (i) is a pattern in which the bright portions P1 to P5 are arranged in the Y direction at a predetermined pitch. First, the position of the wafer stage 2 in the Z direction is set to a predetermined initial value. Wafer stage 2 of FIG.
Is driven, the projected image MY (i) is scanned in the Y direction by the rectangular opening 50a of the imaging characteristic measuring sensor 3. At that time, the detection signal S1 output from the photoelectric conversion element 52 of FIG. 9B is analog / digital (A / D) converted inside the signal processing unit 53, and the wafer stage 2
Is stored corresponding to the Y coordinate of.

FIG. 10A shows the detection signal S1 of this example, and since the opening 50a of this example is rectangular, FIG.
As shown in (a), the obtained detection signal S1 becomes a signal that changes stepwise according to the Y coordinate. Therefore, as an example, in the signal processing unit 53, the detection signal S1 is differentiated by the Y coordinate (difference calculation is performed in actual processing), and FIG.
A differential signal dS1 / dY as shown in (b) is obtained. Position Y ₁ on the Y-axis where this differential signal dS1 / dY has a peak
To Y ₅ are projected images M of the evaluation marks in FIG.
It corresponds to the bright portions P1 to P5 of Y (i). When the imaging surface of the imaging characteristic measuring sensor 3 is at the focus position (best focus position) of the imaging surface, the differential signal dS1 / d
The contrast of the waveform corresponding to the bright portions P1 to P5 of Y becomes maximum, and the average value ΔS of the heights of the waveforms corresponding to the bright portions P1 to P5 (corresponding to the slope of the detection signal S1 in FIG. 10A). Is the maximum. Therefore, the signal processing unit 53 obtains the average value ΔS of the heights of the peak portions of the differential signal dS1 / dY. Then, for example, the average value ΔS of the heights of the peak portions of all 16 projected images is obtained. After that, while changing the position of the surface of the imaging characteristic measuring sensor 3 in the Z direction by a predetermined step width via the Z direction driving unit of the wafer stage 2 of FIG. The average value ΔS of the heights of the peaks is calculated.

As a result, the measurement data as shown by the dot sequence in FIG. 10C is obtained for the projection image of a certain image height among the 16 projection images. In FIG. 10C, the horizontal axis represents the position in the Z direction of the image pickup surface of the imaging characteristic measuring sensor 3, and the vertical axis represents the average value ΔS of the peak heights. Then, in the signal processing unit 53, the point sequence shown in FIG.
The least square approximation is performed with 1, and the position Z _{F in the} Z direction where the quadratic curve 71 has a peak is regarded as the focus position of the image forming surface at that image height. By obtaining the focus position Z _F of the image plane for each of the marks having various image heights, the distribution of focus positions (field curvature) as shown in FIG. 8 in the current environment can be measured. Further, since the focus positions at a plurality of predetermined measurement points on the image height H are measured,
For the focus position at the image height between them, a value obtained by interpolating the focus positions at the front and rear measurement points may be used.

Next, an example of a method for determining the set values of the temperatures of the lens elements 36A and 37A made of fluorite in FIG. 2 will be described. First, assuming that the pressure (atmospheric pressure) of the air around the projection optical system PL1 is x, the atmospheric pressure x is the reference value x _0.
When the field curvature exceeding the allowable value is generated in the projection optical system PL1 due to the change from, the set value of the temperature y of the lens elements 36A and 37A for canceling the field curvature will be described. In this case, the atmospheric pressure x is the reference value x ₀
The curvature of field of the projection optical system PL1 caused by the change from is calculated by optical calculation. Then, the temperature y of the lens elements 36A and 37A for generating the field curvature thus obtained and the field curvature having the opposite characteristic is calculated.

The solid curve in FIG. 11 indicates the temperature y obtained as a function FA (x) of the atmospheric pressure x in advance.
(Y = FA (x)), and in FIG. 11, the horizontal axis represents the atmospheric pressure x and the vertical axis represents the lens element 36 made of fluorite.
The temperature y is A, 37A, and the temperature of the lens elements 36A, 37A for minimizing the field curvature at the reference atmospheric pressure x ₀ is y ₀ . In practice, the function FA
The temperature y may be set based on (x).

However, in reality, the projection optical system PL1
The curvature of field may not be sufficiently reduced at the temperature y determined by the function FA (x) due to the manufacturing error of each optical element. Furthermore, in the illumination optical system 14 of FIG.
As described in 2, the illumination conditions such as normal illumination, modified light source method, and illumination with a small coherence factor (σ value) can be switched and used in various ways. Therefore, the above-mentioned function FA (x) also needs to be calculated for each illumination condition, but the reliability of the calculation result may be low particularly in the modified light source method or illumination with a small coherence factor (σ value). Therefore, in order to make the field curvature smaller, it is desirable to calibrate the function FA (x) as follows.

That is, in order to find a function that actually fits well, the atmospheric pressure x at any one point different from the reference atmospheric pressure x _{0.
In 1} , the field curvature of the projection image of the projection optical system PL1 is obtained by using the imaging characteristic measuring sensor 3 of FIG. Next, the temperature of the lens elements 36A and 37A made of fluorite is controlled via the lens temperature control device 13 to obtain the temperature y ₁ when the field curvature of the projected image becomes 0 (minimum).
At this time, the lens elements 36A, 37 made of fluorite
The temperature of A is changed near the temperature y defined by the theoretical function FA (x). Then, the lens control device 12 is also used to obtain the pressure in the gas chamber for making the remaining linear magnification error zero. At the same time, the offset of the remaining focus position is also obtained.

The atmospheric pressure x₁Other atmospheric pressure different from
x₂Also in the same way, the field curvature of the projected image is actually
The temperature of the lens element made of fluorite to make it almost zero
Degree y ₂, And the remaining linear scaling error to zero.
The pressure in the gas chamber of
Ask for a set. And the atmospheric pressure is x₀, X₁, X₂of
Measured temperature of a fluorspar lens element at a point
Therefore, as shown by the dotted line in FIG.
Of the lens element made of fluorite for atmospheric pressure x
The function FA '(x) representing the temperature y can be obtained.
Furthermore, in order to make the linear magnification error remaining at this time 0
The pressure of the gas chamber of is also obtained as a function of the atmospheric pressure x.
You can At the same time, the focus position remaining
The fuss can also be obtained as a function of the atmospheric pressure x.
In addition, increasing the number of measurement points,
As a number, determine the temperature y etc. of the lens element made of fluorite.
You may stop. By using the function FA '(x)
Therefore, the field curvature of the projected image can be further reduced.

Further, the function FA ′ (x) in FIG. 11 is a function obtained under normal illumination conditions (method of FIG. 12A), but other two types of illumination conditions (FIG. 12 ( The calibration is similarly performed under the methods (b) and (c). Under the illumination conditions of FIGS. 12B and 12C,
Results FA1 (x) and FA3 (x) of FIG. 13 are obtained by obtaining the temperature y for minimizing the field curvature of the lens element made of fluorite as a function of the atmospheric pressure x. Further, the function FA2 (x) in FIG.
Function FA ′ (x), that is, a function obtained under normal illumination conditions. When the functions are obtained in this way, the three functions FA1 (x) to FA3 (x) of FIG. 13 are stored in the storage unit in the main controller 18 of FIG. Then, in the main controller 18, according to the measured atmospheric pressure x,
The target value of the temperature y of the fluorspar lens element is obtained from a function according to the illumination condition being used, and the temperature of the lens element is set to the target value via the lens temperature control device 13.

In the above example, the correction of the field curvature due to the atmospheric pressure has been described, but in addition to that, each lens element expands due to the irradiation energy when the illumination light for exposure passes through the projection optical system. The refractive index of each lens element may change, and this also causes field curvature. Therefore, it is necessary to set the irradiation energy passing through the projection optical system PL1 per unit time to e, and to obtain the temperature y of the lens element made of fluorite for minimizing the field curvature as a function of the irradiation energy e. .
Furthermore, the function in this case also needs to be obtained for each illumination condition.

FIG. 14 shows the temperature y of the lens elements 36A and 37A made of fluorite obtained by performing calibration so that the curvature of field is minimized with respect to the irradiation energy e. The horizontal axis represents the irradiation energy e of the illumination light for exposure that passes through the projection optical system PL1,
The vertical axis represents the temperature y for minimizing the field curvature of the lens element made of fluorite. In this case, the irradiation energy e is converted in advance into a signal obtained by photoelectrically converting a light beam obtained by separating a part of the illumination light for exposure in the illumination optical system 14 in FIG. 1, for example. It is calculated by multiplying the coefficient. Then, the functions gA1 (e), gA2 (e) and gA3 of the irradiation energy e in FIG.
(E) is the temperature y for minimizing the field curvature obtained for each of the illumination conditions in FIGS. 12 (b), 12 (a) and 12 (c).
Is a function that indicates.

To summarize the above, in the end, by using the function Q (e, x, I) with the irradiation energy e, the atmospheric pressure x, and the illumination condition I as parameters, fluorite for minimizing the curvature of field is obtained. It is necessary to obtain the temperature y of the lens element. The function Q (e, x, I) is also stored in the storage unit in the main control unit 18 of FIG. 1, and the main control unit 18 is responsive to the irradiation energy e during exposure, the atmospheric pressure x, and the illumination condition I. It is desirable to obtain the target temperature of the lens element made of fluorite from the function Q (e, x, I).

Further, as described with reference to FIG.
When the reticle used becomes large, the bending of the reticle becomes large, and the field curvature of the image plane is deteriorated. Therefore,
The field curvature of the image plane is calculated in advance by using the above-described image-forming characteristic measuring sensor 3 for each size or type of reticle used, and the field curvature is minimized according to the reticle used. It is desirable to control the temperature of the lens element made of fluorspar. As a result, even if a reticle having a large area is used, it is possible to cancel the bending of the reticle and the curvature of field.

Although an excimer laser light source is used as the exposure light source in this example, the irradiation energy of the exposure illumination light is the i-line (wavelength: 365) of the mercury lamp.
(nm) has a larger absorption in the projection optical system than the excimer laser light, and the field curvature of the projection optical system also largely changes. Therefore, the method of controlling the temperature of the lens element made of fluorite according to the irradiation energy is applied to a projection exposure apparatus (stepper or the like) that uses the i-line of a mercury lamp to improve the field curvature. There is a great advantage that it can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. 3, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The projection optical system of this example is particularly suitable for use in a step-and-scan projection exposure apparatus. Figure 3
3 shows the projection optical system PL2 of this example. In FIG. 3, the projection optical system PL2 includes six lens elements 25 to 30 and four lens elements arranged in order in the lens barrel 4 from the wafer W side. 31 to 34 and four lens elements 35B to 38B. The lens elements 35B to 37B are fixed in the lens barrel 4 via a lens frame G3, and the lens element 38B is also fixed in the lens barrel 4 via a lens frame (not shown).

In this case, only the lens element 36B is made of fluorite and the other lens elements are made of quartz. Then, a pair of temperature control elements 40A and 40B are fixed to both surfaces of one end in the Y direction, which is the scanning direction of the lens element 36B, and a pair of temperature control is also applied to both surfaces of the other end in the Y direction. The elements 40C and 40D are fixed. In this case, if the width in the Y direction of the slit-shaped illumination area on the pattern forming surface of the reticle R by the illumination optical system is L, the temperature of the illumination light that has passed through the illumination area of the width L does not pass through them. Control element 40A-
40D is fixed.

As the temperature control elements 40A to 40D, a heater, a Peltier element or the like can be used. The Peltier element may be used for heating or heat absorption. Although not shown, a temperature sensor is fixed to the end of the lens element 36B in the Y direction, the detection signal of this temperature sensor is supplied to an external temperature control device 39, and the temperature control device 39 detects it. The heating or heat absorption operation of the temperature control elements 40A to 40D is controlled so that the temperature becomes the set temperature instructed by the main controller 18.

Further, in this example, a heat exhausting mechanism is provided for preventing the heat generated by controlling the temperature of the lens element 36B from affecting the adjacent lens elements. That is, the lens element 36
Gas of a predetermined temperature is supplied from the temperature control device 13a to the gas chamber surrounded by B and 37B and the lens frame G3 through the pipe 19, and the gas circulated in the gas chamber is pipe 23B.
A gas of a predetermined temperature is supplied from the temperature control device 13a through the pipe 20 to the gas chamber which is returned to the temperature control device 13a through and is surrounded by the lens elements 35B and 36B and the lens frame G3. The gas circulated in the chamber is returned to the temperature control device 13a via the pipe 24B. Then, based on the command from the main control device 18, the temperature control device 13a uses forced air-conditioning to cause the lens elements 35B and 37 before and after the lens element 36B.
The temperature of B is kept constant. The other configuration is the same as the example of FIG.

As described above, according to this example, the lens element made of fluorite is effectively used by using the temperature control elements 40A to 40D by effectively utilizing the space which is not irradiated with the illumination light passing through the slit-shaped illumination region. Since the temperature of 36B is directly controlled, there is an advantage that the temperature of the lens element 36B can be set to a desired target temperature at high speed and with high accuracy. Thereby, the field curvature of the projection image of the projection optical system PL2 can be corrected quickly and with high accuracy.

Next, a third embodiment of the present invention will be described with reference to FIG. 4, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The projection optical system of this example is a suitable optical system to be applied to any projection exposure apparatus of the step-and-repeat method and the step-and-scan method. FIG. 4 shows the projection optical system PL3 of this example. In FIG. 4, the projection optical system PL3 is arranged in the lens barrel 4 in order from the wafer W side.
It is composed of four lens elements 25 to 30, four lens elements 31, 32, 33A and 34A, and four lens elements 35C to 38C. The lens elements 33A and 34A are fixed in the lens barrel 4 through the lens frame G4, and the lens elements 35C and 36C are fixed.
Is fixed in the lens barrel 4 via a lens frame G5, and other lens elements are also fixed via a lens frame (not shown).

In this case, only the lens elements 33A and 36C are made of fluorite, and the other lens elements are made of quartz. In this case, the field curvature characteristics mainly change due to the temperature change of the upper fluorite lens element 36C, and the lower fluorite lens element 3
The characteristics of the linear magnification error change mainly due to the temperature change of 3A. In addition, the lens element 35
A gas having a variable temperature is supplied from the temperature control device 13c to the gas chamber surrounded by C and 36C and the lens frame G5 via the pipe 41A, and the gas circulated in the gas chamber is pipe 41B.
The temperature of the variable temperature is supplied to the temperature chamber 13c from the temperature controller 13d via the pipe 42A to the gas chamber which is returned to the temperature controller 13c through the lens element 33A, 34A and the lens frame G4. The gas circulated in the gas chamber is returned to the temperature control device 13d via the pipe 42B. Then, based on the command from the main controller 18, the temperature controllers 13c and 13d respectively set the temperatures of the lens elements 36C and 33A to the target temperatures.

In this example, when correcting the field curvature of the projection image of the projection optical system PL3, the temperature control device 13c is used.
The temperature of the lens element 36C is controlled via the, and the linear magnification error generated at that time is offset by controlling the temperature of the lens element 33A via the temperature control device 13d. Further, in this method, the characteristics of the field curvature due to atmospheric pressure and the characteristics of the field curvature due to the temperature change at the time of irradiation of the illumination light for exposure to the projection optical system are different,
It can also be used when the field curvature control is independently performed by the lens elements made of fluorite at two locations corresponding to each, when a large error in focus position of the third order or higher remains. That is, for example, the lens element 36C made of fluorite on the upper side corrects the field curvature due to atmospheric pressure, and the lens element made of fluorite on the lower side corrects the field curvature caused by irradiation of the illumination light. Good.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 5, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The projection optical system of the present example is an optical system suitable for use in any projection exposure apparatus of step-and-repeat type and step-and-scan type. FIG. 5 shows a projection optical system PL4 of this example. In FIG. 5, the projection optical system PL4 includes six lens elements 25, 26, 27A, 28A, 29A in the lens barrel 4A in order from the wafer W side. Three
0, 4 lens elements 31, 32, 33B, 34
B and two lens elements 35D and 36D are fixed, and a support base 45 holding the lens element 37D and a support base 46 holding the lens element 38D are fixed on the lens barrel 4A. . The lens elements 28A and 29A are fixed in the lens barrel 4A via a lens frame G6, and the other lens elements are also fixed in the lens barrel 4A via a lens frame (not shown).

In this example, only the lens elements 28A and 29A are made of fluorite, and the other lens elements are made of quartz. Further, the gas chamber surrounded by the lens elements 28A and 29A and the lens frame G6 is supplied with a variable temperature gas from the temperature control device 13e via the pipe 43, and the gas circulated in the gas chamber is pipe 4
It is returned to the temperature control device 13e via 4. Then, based on a command from the main controller 18, the temperature controller 13e sets the temperature of the lens elements 28A and 29A to the target temperature. In addition, the support base 45
And 46 are configured so that they can be moved independently of each other by a drive device 47 in a direction parallel to the optical axis AX of the projection optical system PL4 and can be tilted at a desired angle. The operation of the drive device 47 is controlled by the imaging characteristic control device 48 based on a command from the main control device 18.

Also in this example, the field curvature of the projection image of the projection optical system PL4 is corrected by controlling the temperature of the lens elements 28A and 29A made of fluorite via the temperature control device 13e, but this occurs. The linear magnification error that causes the lens elements 37D and 38D to pass through the supports 45 and 46.
Is corrected by tilting or moving up and down. By combining the movements of the two supports 45 and 46, not only the magnification error but also the defocus of the focus position can be corrected, so most of the other aberrations that occur during field curvature correction are the temperature control device 13e and the drive. This can be offset by optimizing the control of the device 47.

[0064]

EXAMPLES Next, the results of a numerical analysis of the actual numerical model of the projection optical system showing how the field curvature changes due to temperature control are shown. In this case, for example, when the projection optical system PL1 shown in FIG.
There are, for example, two lens elements in 1 in which the imaging characteristics may be corrected by forming them from fluorite. Therefore, when the two lens elements formed of fluorite and effective as the lens elements L1 and L2 are not used,
And when the lens element L1 or L2 is made of fluorite and the other lens elements are made of quartz, the magnification error βA [μ at the position where the image height is 100% of the maximum value]
m] and the shift amount of the focus position in the Z direction (that is,
The field curvature) βB [μm] was determined. Further, with reference to the focus position at the image height of 0, the magnification error βA [μm] and the focus position shift amount βB [μ when the temperature of one lens element made of fluorite is changed by 1 ° C.
m] is shown in Table 1 below.

[0065]

[Table 1]

From Table 1 above, by changing the temperature of one lens element made of fluorite by ± 1 ° C., about ±
It can be seen that the field curvature of about 0.2 μm can be corrected. Further, generally, the resolution of the temperature control can be about 0.01 ° C. Therefore, when the field curvature is corrected by changing the temperature of the lens element made of fluorite by about 1 ° C., the correction of the field curvature can be performed. The resolution is approximately ± 2 nm (= ± 0.2 /
100 [μm]). Further, by inserting fluorite lens elements at a plurality of positions, it is possible to narrow the temperature control range, reduce the linear magnification error additionally generated, and correct a larger field curvature. .

The present invention is not limited to the above-described embodiments and examples, and it goes without saying that various configurations can be made without departing from the gist of the present invention.

[0068]

According to the present invention, since the temperature control member for controlling the temperature of at least one optical member made of the second glass material is provided, a large area around the projection optical system is provided. The advantage is that it is possible to correct defocus of the image plane of the projection optical system, which is deteriorated due to environmental changes such as atmospheric pressure, absorption of exposure illumination light, or deflection of the reticle, and in particular non-linear defocus. is there. As a result, the width of the depth of focus of the entire projected image is widened, and the resolution of the entire projected image is improved.

The object to be controlled by the temperature control means is the field curvature of the projection optical system, and a magnification error control means for controlling the magnification error of the projection optical system is provided, and the projection optical system is controlled by using the temperature control means. When the magnification error that occurs when the field curvature is controlled by the magnification error control means, the magnification error such as the linear magnification error that occurs due to the correction of the field curvature is reduced, and the overall result is reduced. The image characteristics are maintained well.

Further, by controlling the temperature of the optical member to be controlled within the range of ± 1 ° C. or less by the temperature control means, the field curvature of the projection optical system is corrected within the range of ± 0.3 μm. At times, as shown in the above-mentioned numerical analysis, it is possible to perform correction within that range by controlling the temperature of one lens element made of, for example, fluorite, which is practical.

Further, a storage means for storing the amount of change in the position of the image plane of the projection optical system according to the change in the use condition of the projection optical system is provided, and the storage means is provided in accordance with the change in the use condition of the projection optical system. When the position of the image plane of the projection optical system is controlled via the temperature control unit so as to cancel out the amount of change in the position of the image plane stored in the storage unit, the use condition changes. Also, there is an advantage that the field curvature and the like can be corrected quickly and with high accuracy.

Further, there is provided focus position control means for relatively moving the image plane of the projection optical system and the photosensitive substrate in the optical axis direction of the projection optical system, and the projection optical system is provided by using the temperature control means. When the focus position control means is used to reduce the remaining focus position offset when the position of the image forming surface is controlled, the defocus caused by the correction of the field curvature is corrected and the photosensitive substrate The exposure is carried out with the surface conforming to the image plane.

[Brief description of drawings]

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

FIG. 2 is a partially cutaway configuration diagram showing a projection optical system and an image forming characteristic correction mechanism used in the first embodiment.

FIG. 3 is a partially cutaway configuration diagram showing a projection optical system used in a second embodiment and a mechanism for correcting an imaging characteristic.

FIG. 4 is a partially cutaway configuration diagram showing a projection optical system and an image forming characteristic correction mechanism used in a third embodiment.

FIG. 5 is a partially cutaway configuration diagram showing a projection optical system and an image forming characteristic correction mechanism used in a fourth embodiment.

FIG. 6 is a graph showing characteristics 2 different from each other with respect to temperature change.
It is an optical-path figure which shows the lens of two glass materials.

7A is a diagram showing a field curvature due to a lens element made of quartz, FIG. 7B is a diagram showing a focus position distribution due to a lens element made of fluorite whose temperature is controlled, and FIG. It is a figure which shows the correction amount of the remaining focus position.

FIG. 8 is a diagram showing a focus position distribution (field curvature) obtained by combining a lens element made of quartz, a lens element made of fluorite whose temperature is controlled, and a focus position control mechanism (wafer stage). .

9A is a plan view showing a projected image of an opening of the image-forming characteristic measuring sensor 3 and an evaluation mark, and FIG. 9B is a partial cross-sectional view showing the configuration of the image-forming characteristic measuring sensor 3. FIG. FIG.

10A is a waveform diagram showing a detection signal detected by the imaging characteristic measuring sensor 3, FIG. 10B is a waveform diagram showing a differential signal of the detection signal, and FIG. 10C is a focus position determination method. FIG.

FIG. 11 is a diagram showing the relationship between atmospheric pressure and the temperature of a lens element made of fluorite.

FIG. 12 is a conceptual diagram showing the distribution of 0th-order light from a reticle passing through the projection optical system when the illumination conditions are variously switched.

FIG. 13 is a diagram showing the relationship between the atmospheric pressure and the temperature of the lens element made of fluorite when the illumination conditions are switched.

FIG. 14 is a diagram showing the relationship between the irradiation energy passing through the projection optical system and the temperature of the lens element made of fluorite.

FIG. 15 is a diagram showing field curvature in a conventional projection exposure apparatus.

FIG. 16A is a diagram showing the influence of field curvature when performing collective exposure, and FIG. 16B is a diagram showing the influence of field curvature when performing scanning exposure.

FIG. 17A is a perspective view showing the flexure of a small size reticle, and FIG. 17B is a perspective view showing the flexure of a large size reticle.

[Explanation of symbols]

R Reticle PL1, PL2, PL3, PL4 Projection optical system W Wafer 2 Wafer stage 3 Imaging characteristic measurement sensor 4 Lens barrel G1, G2 Lens frame 6 Reticle stage 8, 10 Laser interferometer 12 Lens controller 13 Lens temperature controller 13a, 13b Temperature control device 14 Illumination optical system 18 Main control device 25 to 34, 35A, 38A Lens element 36A, 37A made of quartz Lens element 36B made of fluorite Lens element 33A, 36C made of fluorite Lens made of fluorite Elements 28A and 29A Lens elements 40A to 40D made of fluorite Temperature control element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 21/30 516E 516F (56) References JP-A-4-86668 (JP, A) JP-A-5-347239 (JP, A ) JP-A-60-159748 (JP, A) JP-A-6-5490 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03B 13/36 G03F 7 / 20 521

Claims (9)

(57) [Claims] 1. A projection exposure apparatus which a pattern of a mask through a projection optical system for projecting onto the photosensitive substrate, the projection optical system, a plurality of optical members made of a first glass material
And the temperature characteristics regarding the refractive index are different from those of the first glass material.
At least one optical member made of a second glass material, temperature control means for controlling the temperature of at least one optical member made of the second glass material is provided, and the projection optical system is provided by using the temperature control means. A projection exposure apparatus, characterized in that the position of the image plane of the system in the optical axis direction of the projection optical system is controlled. 2. The temperature control means controls a field curvature of the projection optical system, a magnification error control means for controlling a magnification error of the projection optical system is provided, and the projection is performed by using the temperature control means. wherein the magnification error generated when controlling the curvature of the optical system in claim 1, characterized in that to reduce via the magnification error control means
Projection exposure apparatus. 3. The temperature control unit controls the second
The temperature of at least one optical member made of glass is ± 1 ℃
The projection exposure apparatus according to claim 2 , wherein the field curvature of the projection optical system is corrected within a range of ± 0.3 μm or less by controlling within the range below. 4. A storage unit is provided for storing the amount of change in the position of the image plane of the projection optical system according to the change in the use condition of the projection optical system, and the storage unit is provided in accordance with the change in the use condition of the projection optical system. claim 1, wherein the controller controls the to cancel the variation of the position of the focal plane stored in the storage means, the position of the focal plane of the projection optical system via the temperature control means ~ 3 Izu
The projection exposure apparatus according to any one of the above . 5. A focus position control means for relatively moving an image forming surface of the projection optical system and the photosensitive substrate in an optical axis direction of the projection optical system is provided, and the projection optical system is provided by using the temperature control means. wherein the offset of the focus position remaining when controlling the position of the focal plane of the system in any one of claims 1 to 4, characterized in that to reduce through the focus position control means
Projection exposure apparatus. 6. The projection exposure apparatus according to claim 1, wherein the temperature control unit has a temperature control element fixed to the surface of the at least one optical member. 7. The projection optical system has two optical members made of the second glass material, and the temperature control means controls the temperature of one of the two optical members to obtain the projection optical system. The linear magnification error of the projection optical system is corrected by correcting the field curvature of the system and controlling the temperature of the other of the two optical members. The projection exposure apparatus according to. 8. The first glass material is quartz, and the second glass material is fluorite.
The projection exposure apparatus according to claim 1. 9. A mask stage for holding the mask and a substrate stage for holding the photosensitive substrate are further provided, and scanning exposure is performed by synchronously moving the mask stage and the substrate stage. Claim 1
9. The projection exposure apparatus according to claim 8.