JPH0950952A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the nonlinear magnification error (high order magnification error) of a projection optical system which is deteriorated by the change of environmental conditions such as the atmospheric pressure and the ambient temperature of the projection optical system or by the absorption of an exposure lighting light, etc. SOLUTION: Among lens elements 25-38A of which a projection optical system is composed, the lens elements 36A and 37A only are made of fluorite and the other lens elements are made of quarts. Gas whose temperature is controlled is supplied to a gas chamber surrounded by the lens elements 36A and 37A and a lens frame G2 from a temperature controller 13a and the gas which is made to flow through the gas chamber is returned to the temperature controller 13a. A nonlinear magnification error which is produced by the lens elements made of quartz is eliminated by the temperature control of the lens elements 36A and 37A and, further, the residual nonlinear magnification error is eliminated by the pressure control of gas in a gas chamber between the lens elements 33 and 34.

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 element, an image pickup element (CCD or the like), a liquid crystal display element, a thin film magnetic head or the like, and a mask pattern is passed through a projection optical system. 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 a reticle pattern is projected on a wafer, distortion occurs, which is a phenomenon in which the projected image shifts in a direction perpendicular to the optical axis of the projection optical system. This distortion is divided into a linear error (a component in which the imaging position changes as a linear function with respect to the image height) and a non-linear error (a component other than the linear error), and the linear error is a linear magnification error (with respect to the image height). It is also called a component whose magnification changes as a linear function). A lens control system that drives some of the lenses in the projection optical system and controls the gas pressure between some of the lenses has been used as a means for correcting the linear magnification error.

[0004]

The conventional projection exposure apparatus as described above has a disadvantage in that it cannot correct a non-linear error in the distortion of the projection optical system caused by a change in the environment. The main part of the non-linear error is a non-linear magnification error (higher-order magnification error) in which the magnification changes with a characteristic such as a function of a second or higher order according to the image height of the projected image. However, even in a design reference state, a slight non-linear magnification error remains in the projection optical system within a practically unproblematic range, and as shown in FIG. The magnification (projection magnification from the reticle to the wafer) β of the optical system slightly changes nonlinearly from the design value β ₀ . Furthermore, if atmospheric pressure changes or heat absorption due to irradiation of exposure illumination light occurs with respect to the reference state, the nonlinear magnification error shown in FIG. 15A is generated.
It becomes large as shown in. As shown in FIG. 15B, a nonlinear magnification error in which the magnification β changes once in the negative direction and then in the positive direction with respect to the image height H is “C
It is also called "letter distortion".

The non-linear magnification error as shown in FIG. 15B is caused by the step-and-repeat method (collective exposure method).
16A, the original projected images 66 and 67 are changed non-linearly according to the image height to become projected images 66A and 67A, as shown in FIG. The alignment accuracy deteriorates. On the other hand, if a non-linear magnification error as shown in FIG. 15B occurs in the step-and-scan (scanning exposure) projection exposure apparatus, the original projected images 66 and 67 change non-linearly depending on the image height. Then, projection images 66B and 67B are obtained, and similarly, overlay accuracy between the two layers deteriorates. FIG.
In (b), the scanning direction of the wafer during scanning exposure is the Y direction indicated by the arrow, and although the distortion of the projected image does not occur in the scanning direction due to the averaging effect, the image deterioration occurs due to the averaging effect. Is occurring. Further, it can be confirmed that a magnification error corresponding to the image height occurs in the non-scanning direction (X direction) as in the batch exposure method.

If there is a non-linear magnification error in the projection optical system as described above, the projected image finally obtained by either the step-and-repeat method or the step-and-scan method will be distorted, and the overlapping will occur. There is an inconvenience that the alignment accuracy deteriorates. The present invention in view of such a point,
Distortion of the projection optical system that deteriorates due to changes in the environment such as atmospheric pressure and the ambient temperature of the projection optical system, or absorption of exposure illumination light, especially nonlinear magnification error (higher-order magnification error)
It is an object of the present invention to provide a projection exposure apparatus capable of correcting the above.

[0007]

A projection exposure apparatus according to the present invention is a projection exposure apparatus for projecting a mask pattern (R) onto a photosensitive substrate (W) through a projection optical system as shown in FIGS. 1 and 2, for example. In the exposure apparatus, its projection optical system (PL1)
Is a plurality of sets of optical members (25 to 34, 35A, 38A and 36A, made of glass materials having different refractive index temperature characteristics).
37A), and temperature control means (13) for controlling the temperature of at least one optical member (36A, 37A) in the plurality of sets of optical members is provided, and the projection optical system (PL1 is used by using this temperature control means. ) Is used to control the imaging characteristics.

In this case, an example of the imaging characteristic of the projection optical system (PL1) controlled by the temperature control means (13) is a non-linear magnification error. Further, the temperature of the optical members (36A, 37A) to be controlled is controlled by the temperature control means (13).
It is desirable to correct the nonlinear magnification error of the projection optical system (PL1) within a range of ± 50 nm by changing it by 1 ° C.

Further, a linear magnification control means (12) for correcting a linear magnification error of the projection optical system (PL1) is provided, and a non-linear magnification error of the projection optical system (PL1) is controlled by a temperature control means (13) within a predetermined allowable range. It is desirable to reduce the linear magnification error that remains after being stored inside by means of the linear magnification control means (12). In addition, a storage unit (18) for storing the amount of change in the imaging characteristics of the projection optical system (PL1) according to the change in the usage conditions of the projection optical system (PL1) is provided, and the storage condition (18) of the usage conditions of the projection optical system (PL1) is provided. The storage means (1
8) via the temperature control means (13) so as to cancel the amount of change in the imaging characteristics stored in 8).
It is desirable to control the imaging characteristic of 1).

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 FB 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 the temperature characteristic of the refractive index itself, but also the direction of the image plane when the temperature changes in consideration of the thermal expansion of the lens made of the glass material. It is a characteristic determined by whether it changes to.

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 composed of the first glass material, the projection is performed. Considering the distortion in the image forming characteristics of the optical system, the tendency of the distortion due to the lens of the first glass material becomes non-linear as shown by the curve 61 in FIG. 7A, and the distortion is due to environmental changes or exposure. It changes depending on the absorption of illumination light. On the other hand, the distortion due to the second glass lens is shown in FIG.
As shown by the curve 62A in (b), there is a tendency that the offset amount of the linear magnification error shown by the straight line 62B is added to the nonlinear magnification error having the opposite tendency to the curve 61.

Therefore, the non-linear magnification error of the curve 61 is canceled by the non-linear magnification error of the curve 62A, for example, by controlling the temperature of the lens of the second glass material according to environmental changes, absorption of exposure illumination light, and the like. Therefore, the projection optical system (PL1)
The non-linear magnification error of can be reduced. However, since the linear magnification error remains as it is, the distortion of the projection optical system (PL1) is almost completely removed by reducing the remaining error through the linear magnification control means (12). .

[0013]

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 a projection exposure apparatus of this example. 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,
Light intensity adjustment system, fly-eye lens, relay lens,
Illumination light IL formed by a field stop (reticle blind), a movable blade for avoiding unnecessary exposure before and after scanning, a condenser lens, etc., and shaped into a uniform illuminance distribution by the illumination optical system 14 is a pattern of the reticle R. An illumination area of a predetermined shape on the formation surface (lower surface) is illuminated. In this case, the main controller 18 that controls the operation of the entire device
However, the timing of pulse emission of the excimer laser light source 16 and the control of the extinction ratio in the light amount adjusting mechanism in the illumination optical system 14 are performed via the illumination control system 17. The illumination light transmitted through the pattern of the reticle R in the illumination area is projected by the projection optical system PL.
1 is projected onto the wafer W coated with the photoresist, and the projected image obtained by reducing the pattern at a magnification β (β is, for example, 1/4 or 1/5) 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.

A distortion measuring sensor 3 is fixed near the wafer W on the wafer stage 2. The distortion measuring sensor 3 is shown in FIG.
As shown in FIG. 5, a glass substrate 51 having 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, and an exposure substrate that has passed through the opening 50a for exposure. A photoelectric conversion element 52 for photoelectrically converting the illumination light of
The signal processing unit 53 that processes the detection signal S1 from the photoelectric conversion element 52 is provided, and the processing result of the signal processing unit 53 is supplied to the main controller 18 of FIG. In this example, as described later, by driving the wafer stage 2,
The projected image of the pattern of the reticle R is scanned by the opening 50a of the distortion measuring sensor 3, and the signal processing unit 5 uses the detection signal S1 output from the photoelectric conversion element 52 at that time.
3 determines the magnification error (distortion) of the projection optical system PL1 at various image heights.

Next, most of the plurality of lens elements constituting the projection optical system PL1 of the present example are made of quartz, and the remaining part of the lens elements are made of fluorite, which is made of quartz. A lens control device 12 for controlling the gas pressure in a predetermined gas chamber formed between the pair of lens elements is provided. Atmospheric pressure change,
Alternatively, according to environmental changes such as temperature changes, or the history of the irradiation amount of the exposure illumination light with respect to the projection optical system PL1, the magnification of the projection optical system PL1, the focus position (best focus position), image formation such as field curvature, etc. When the characteristics change, the lens controller 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 magnification error (higher-order magnification error) of the projection optical system PL1 is deteriorated due to environmental changes, the history of irradiation amount, or the like, the lens temperature control is performed based on a command from the main controller 18. The device 13 is adapted to correct the non-linear magnification error. Further, when the linear magnification error of the projection optical system PL1 is deteriorated due to the correction of the nonlinear magnification error, the linear magnification error is corrected by the lens control device 1.
2 is designed to correct.

Next, the configuration of the projection optical system PL1 and the configuration of the lens temperature control device 13 of this example will be described in detail with reference to FIG. FIG. 2 shows the projection optical system PL of this example.
2 shows an internal structure of No. 1 and a control system of the image forming characteristic. In FIG. 2, the projection optical system PL1 includes six lens elements 25 in the lens barrel 4 in order from the wafer W side as an example.
˜30, four lens elements 31 to 34, and four lens elements 35A to 38A are fixed. Further, only the lens elements 36A and 37A are made of fluorite, and the other lens elements are made of quartz. Then, the lens element 33,
34 is fixed in the lens barrel 4 via a lens frame G1, lens elements 35A to 38A are fixed in the lens barrel 4 via a lens frame G2, and the other lens elements are also respectively inserted via a 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, and the expansion and contraction amount of the bellows mechanism 12b is increased. 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.

In the projection exposure apparatus of this example, the illumination optical system 14 is used to expose various patterns with high resolution.
The illumination conditions can be switched to a normal state, a deformed light source, an annular illumination, a state where the coherence factor σ value is small, and the like. 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. As described above, the light 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. Furthermore,
When the illumination optical system 14 has a small σ value, the 0th-order light that has passed through the reticle R has a substantially small circular area on the pupil plane of the projection optical system PL1 as shown in FIG. 12C. Pass through. The imaging characteristics of the projected image also change depending on these illumination conditions.

Next, an example of the operation for removing the non-linear magnification error 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 element 49B rises, the image formation plane FB is displaced in a direction approaching the lens element. On the other hand, fluorite has the property that it expands with increasing temperature and its refractive index decreases. Therefore, FIG.
As shown in (a), fluorite positive lens element 49
In A, when the temperature rises, the image plane FA is displaced in a direction away from the lens element. The temperature characteristic of the refractive index of the glass material described above is not only the temperature characteristic of the refractive index itself but also the thermal expansion of the lens element made of the glass material. It is a characteristic determined by whether the direction changes.

Further, the distortion of the projection optical system PL1 will be described with reference to FIGS. 7 and 8, the vertical axis represents the image height H and the horizontal axis represents the magnification β of the projection optical system PL1 at the image height H, which is on the optical axis (H = 0).
The magnification at is shown as the designed magnification β ₀ . In this case, the distortion due to the lens element made of quartz of the projection optical system PL1 after continuous exposure for a certain time under a certain environment is the curve 61 in FIG.
As indicated by, the non-linear error (higher-order magnification error) is such that the magnification β once becomes smaller than the design value and then increases almost monotonically as the image height H increases.

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 distortion due to the lens element made of fluorite is set so as to have a non-linear magnification error having a characteristic substantially opposite to that of the curve 61 of FIG. 7A. However, even if the distortion of the lens element made of fluorite is set in such a manner, a predetermined linear magnification error is superimposed as an offset on the distortion. Therefore, the distortion due to the lens element made of fluorite of the projection optical system PL1 is as shown in FIG.
As indicated by the curve 62A in (b), the linear magnification error indicated by the straight line 62B has a characteristic in which a non-linear magnification error having a characteristic substantially opposite to that of the curve 61 in FIG. 7A is superimposed.

Therefore, when the lens controller 12 of FIG. 1 does not correct the image forming characteristic, the distortion of the projection optical system PL1 as a whole is a straight line 6 of FIG. 7 (c).
As shown by 3, the magnification β has a characteristic that it can be approximated by a linear magnification error that linearly increases from the design value according to the image height H. Therefore, the lens control device 12 of FIG. 1 linearly magnifies the projection optical system PL1 with a linear magnification error represented by a straight line 64 that substantially cancels out the residual magnification error approximated by the straight line 63 of FIG. 7C. Is given. As a result, the distortion of the projection optical system PL1 of this example becomes as shown by the curve 65 in FIG. 8, and the linear magnification error is removed together with the nonlinear magnification error.

Here, an example of a method of measuring the distortion 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 (for example, 16 pairs) of evaluation marks are evenly distributed in the illumination area is used. In this case, the evaluation marks of each pair have an image height H in the projected state.
There 10% of the maximum value H _max (i.e., H _max itself), and 80% (i.e., 0.8H _max) preferably includes a mark that the various image height as such. The evaluation marks of each set are X-axis evaluation marks formed of line and space patterns arranged at a predetermined pitch in the X direction,
And the evaluation mark of the Y-axis having a configuration obtained by rotating the evaluation mark by 90 °, of which the i-th (i = 1 to 16)
9A shows a projected image MY (i) of the evaluation mark on the Y-axis of FIG.
Shown in

In FIG. 9A, a projected image MY (i) is a pattern in which bright portions P1 to P5 are arranged in the Y direction at a predetermined pitch, and distortion measurement is performed by driving the wafer stage 2 in FIG. The projected image MY (i) is scanned in the Y direction by the rectangular opening 50a of the sensor 3 for use. 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 corresponds to the Y coordinate of the wafer stage 2. Will be remembered.

FIG. 10A shows the detection signal S1 of this example, and since the opening 50a of this example has a rectangular shape, that 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.
After obtaining the differential signal dS1 / dY as shown in (b), the value Y _{1 of the} Y coordinate at which the differential signal dS1 / dY has a peak.
~ Calculate Y ₅ . These values Y _{1 to} Y ₅ are respectively shown in FIG.
Bright portions P1 to 1 of the projected image MY (i) of the evaluation mark in (a)
Since it corresponds to P5, the signal processing unit 53 calculates the Y coordinate Y _i of the projected image MY (i) from the following equation.

Y _i = (Y ₁ + Y ₂ + Y ₃ + Y ₄ + Y ₅ ) / 5 (1) Further, regarding the projection image of the i-th X-axis evaluation mark, with respect to the projection image By scanning the opening 50a of the distortion measuring sensor 3 in the X direction, the X coordinate X _i can be obtained. As a result, the X coordinate X _i and the Y coordinate Y _i of the projected image of each pair of evaluation marks are obtained, and the obtained coordinates are supplied to the main controller 18. Further, when there is no magnification error in the projection optical system PL1, the position of the projected image of each pair of evaluation marks (designed position) (X
D _i , YD _i ) is stored in advance in the storage device in the main controller 18.

In this case, the actually measured position (X _i , Y _i ) of the projected image of each evaluation mark includes the influence of the rotation error of the test reticle. In order to remove the influence, in the main controller 18, the rotation error is set to Δφ,
Designed position of the projected image of each pair of evaluation marks (XD _i ,
YD _i ) is rotated by its rotation error Δφ, and the calculated position (XC _i , YC _i ) and the actually measured position (XC _i , YC _i ).
The rotation error Δφ is determined by the least square method so that the sum of squares of the difference between _i and Y _i ) is minimized. Therefore, the shift amount of the projected images of the evaluation marks of each pair due to the magnification error of the projection optical system PL1 is (X _i −XC _i , Y _i −YC _i ). The range of the subscript i in this case is, for example, 1 to 16.

Next, in order to separate the deviation amount of the projected image into a linear magnification error and a non-linear magnification error, the magnification β is given by the following equation using a predetermined coefficient k for the image height H, for example. And β = k · H + β ₀ (2) Then, the calculated positions (XC _i , YC _i ) of the projected images of the evaluation marks of each pair are corrected by using the magnification β of the equation (2). The least squares method is used so that the sum of squares of the difference between the position (XC _i ', YC _i ') and the measured position (X _i , Y _i ) of the projected image of the evaluation mark of each pair is minimized. The value of the coefficient k is determined. As a result, the linear magnification error is obtained. As a result, the deviation amount of the projected image of each pair of evaluation marks due to the non-linear magnification error of the projection optical system PL1 becomes (X _i −XC _i ′, Y _i −YC _i ′), and these deviation amounts are The calculated image height H (position (XC _i ', YC
_The remaining non-linear magnification error (higher-order magnification error) is obtained as a function of the image height H by dividing by the image height at _i ′). Further, since it is the magnification error at a plurality of predetermined measurement points on the image height H that is measured, the magnification error at the image height between them is obtained by interpolating the magnification errors at the front and rear measurement points. You may use the value that is given.

In addition to the above-described method of determination, for example, the linear magnification error is located at a position where the image height H is 100% of the maximum radius H _max of the exposure area of the projection optical system (that is, H = H _max ).
The linear magnification error may be obtained from the average value of the positional deviation amounts of the projected images of the evaluation marks near the image height H _max . In this case, the linear magnification error at an image height H smaller than that is a value proportional to the image height H.

Further, after removing the linear magnification error thus obtained, the position where the image height H becomes 70% of the maximum radius H _max of the exposure area by the projection optical system (that is, H = 0.7H).
_The remaining magnification error of ( _max ) may be defined as a non-linear magnification error, and the non-linear magnification error may be obtained from the average value of the positional deviation amounts of the projected images of the evaluation marks near the image height 0.7H _max .

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 a non-linear magnification error 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 non-linear magnification error will be described. In this case, the nonlinear magnification error of the projection optical system PL1 caused by the change of the atmospheric pressure x from the reference value x ₀ is obtained by optical calculation. Then, the lens elements 36A and 37A for generating the nonlinear magnification error having the opposite characteristic to the nonlinear magnification error thus obtained
The temperature y of is calculated. In this case, for the sake of simplicity, as described above, after removing the linear magnification error based on the magnification error at the maximum image height H _max , 70% of the image height (0.
The magnification error at 7H _max ) may be the non-linear magnification. However, the temperatures of the lens elements 36A and 37A for causing the nonlinear magnification error having the opposite characteristic may be obtained from the magnification errors at a plurality of image heights H by the method of least squares.

The solid curve in FIG. 11 indicates the temperature y (y) obtained as a function F (x) of the atmospheric pressure x in advance.
= F (x)), in which the horizontal axis represents atmospheric pressure x and the vertical axis represents lens elements 36A, 3 made of fluorite.
The temperature y is 7 A, and the temperatures of the lens elements 36A and 37A for minimizing the nonlinear magnification error at the reference atmospheric pressure x ₀ are y ₀ . Even in practice, the function F (x)
You may make it set temperature y based on.

However, in reality, the projection optical system PL1
The non-linear magnification error may not be sufficiently small at the temperature y obtained by the function F (x) due to the manufacturing error of each optical element. Further, in the illumination optical system 14 of FIG. 1 of the present example, as described with reference to FIG. 12, various illumination conditions such as normal illumination, modified illumination, and illumination with a small coherence factor (σ value) are switched. Ready to use. Therefore, the above-mentioned function F (x) also needs to be calculated for each illumination condition, but the reliability of the calculation result may be low especially for modified illumination or illumination with a small coherence factor (σ value). Therefore, in order to further reduce the nonlinear magnification error, it is desirable to calibrate the function F (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 non-linear magnification error of the projection image of the projection optical system PL1 is obtained using the distortion 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 nonlinear magnification error of the projected image becomes 0 (minimum). At this time, the temperature of the lens elements 36A and 37A made of fluorite is the theoretical function F
The temperature is changed near the temperature y defined by (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.

Also, at other atmospheric pressures x ₂ different from the atmospheric pressure x ₁ , the temperature y _{2 of the} lens element made of fluorite for actually making the nonlinear magnification error of the projected image 0, and The pressure of the gas chamber for making the remaining linear magnification error zero is obtained. And the atmospheric pressure is x ₀ , x
_From the measured temperatures of the lens element made of fluorspar at the points ₁ and x ₂ , as shown by the dotted line in FIG.
As a next function, a function F ′ (x) representing the temperature y of the lens element made of fluorite with respect to the atmospheric pressure x can be obtained. Furthermore, the pressure of the gas chamber for making the remaining linear magnification error zero at this time can also be obtained as a function of the atmospheric pressure x. The number of measurement points may be increased to determine the temperature y of the lens element made of fluorite as a function of the third or higher order of the atmospheric pressure x. Its function F '
By using (x), the nonlinear magnification error of the projected image can be made smaller.

The function F '(x) in FIG. 11 is a function obtained under normal illumination conditions (method of FIG. 12 (a)), but other two types of illumination conditions (FIG. 12 ( b) and (c)
Method) and so on. Under the illumination conditions of FIGS. 12 (b) and 12 (c), the result of obtaining the temperature y for minimizing the nonlinear magnification error of the lens element made of fluorite as a function of the atmospheric pressure x is
These are represented by the functions F1 (x) and F3 (x) in FIG. 13, respectively. Further, the function F2 (x) in FIG. 13 is the same function as the function F ′ (x) in FIG. 11, that is, the function obtained under normal illumination conditions. When the function is obtained in this way,
The three functions F1 (x) to F3 (x) of No. 3 are stored in the storage unit in the main controller 18 of FIG. Then, the main controller 18 obtains a target value of the temperature y of the fluorite lens element from a function corresponding to the illumination condition being used, in accordance with the measured atmospheric pressure x, and via the lens temperature controller 13, The temperature of the lens element is set to the target value.

In the above example, the correction of the non-linear magnification error 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, which also causes a nonlinear magnification error. Therefore, it is necessary to determine the irradiation energy passing through the projection optical system PL1 per unit time as e, and obtain the temperature y of the lens element made of fluorite for minimizing the nonlinear magnification error 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 lens elements 36A, 3 made of fluorite which are obtained by performing calibration so as to minimize the nonlinear magnification error with respect to the irradiation energy e.
In FIG. 14, the horizontal axis indicates the irradiation energy e of the illumination light for exposure that passes through the projection optical system PL1, and the vertical axis indicates the nonlinear magnification error of the lens element made of fluorite. The temperature y is shown. 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 g1 (e), g2 (e) and g of the irradiation energy e in FIG.
3 (e) is shown in FIGS. 12 (b), (a) and (c), respectively.
Is a function indicating the temperature y for minimizing the nonlinear magnification error obtained for each illumination condition.

To summarize the above, finally, the nonlinear error of the lens element made of fluorite is minimized by the function Q (e, x, I) using the irradiation energy e, the atmospheric pressure x, and the illumination condition I as parameters. It is necessary to find the temperature y for doing so. The function Q (e, x, I) is also stored in the storage unit in the main controller 18 of FIG.
Then, the irradiation energy e, the atmospheric pressure x, the illumination condition I at the time of exposure
It is desirable to obtain the target temperature of the lens element made of fluorite from the function Q (e, x, I) according to

In the above example, the lens element 36 is used.
Although the method of performing temperature control on A and 37A has been described, the same effect can be obtained because the distance between lens elements changes even when the temperature of the lens barrel 4 or the lens frame G2 itself is controlled. Become. Therefore, a mechanism for controlling the temperature of the lens barrel 4 or a predetermined lens frame may be provided. Further, even when the temperature of the lens elements 36A and 37A is controlled as described above, the temperature change of the lens barrel 4 and the lens frame G2 occurs and the distance between the lens elements expands and contracts. Is desirable.

In this example, an excimer laser light source is used as the exposure light source, but 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 nonlinear magnification error 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 or the like to improve the nonlinear magnification error. 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. FIG.
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 31 to 34 in the lens barrel 4 in order from the wafer W side. , And four lens elements 35
B to 38B are fixed. The lens elements 35B to 37B are connected to the lens barrel 4 via the lens frame G3.
The lens element 38B is also fixed inside 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. This makes it possible to reduce the non-linear magnification error of the projection image of the projection optical system PL2 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 includes six lens elements 25 to 30 and four lens elements 31 in the lens barrel 4 in order from the wafer W side. ，
32, 33A, 34A, and 4 lens elements 3
5C to 38C are fixed. The lens elements 33A and 34A are fixed in the lens barrel 4 via the lens frame G4, the lens elements 35C and 36C are fixed in the lens barrel 4 via the lens frame G5, and other lens elements are also not shown. It is fixed through the lens frame.

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 characteristic of the non-linear magnification error changes mainly due to the temperature change of the upper fluorite lens element 36C, and the characteristic of the linear magnification error mainly changes due to the temperature change of the lower fluorite lens element 33A. It has become. In addition, a gas having a variable temperature is supplied from the temperature control device 13c to the gas chamber surrounded by the lens elements 35C and 36C and the lens frame G5 via the pipe 41A, and the gas circulated in the gas chamber passes through the pipe 41B. Is returned to the temperature control device 13c and is surrounded by the lens elements 33A and 34A and the lens frame G4. A gas having a variable temperature is supplied from the temperature control device 13d through the pipe 42A to the gas chamber. The gas circulated in the 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 nonlinear magnification error (higher-order magnification error) of the projection image of the projection optical system PL3, the lens element 36 is passed through the temperature controller 13c.
A method of controlling the temperature of C and canceling the linear magnification error generated at that time by controlling the temperature of the lens element 33A via the temperature control device 13d is adopted. Further, this method is different in the characteristic of the high-order magnification error due to the atmospheric pressure and the characteristic of the high-order magnification error due to the temperature change at the time of irradiating the projection optical system with the illumination light for exposure, and the third-order or higher magnification error is large. In the case of remaining, it can be used also when performing high-order magnification control independently with lens elements made of fluorite corresponding to two places. That is, for example, the non-linear magnification error due to atmospheric pressure is corrected by the lens element 36C made of fluorite on the upper side, and the non-linear magnification error caused by irradiation of the illumination light is corrected by the lens element made of fluorite on the lower side. 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 temperature of the lens elements 28A and 29A made of fluorite is controlled via the temperature controller 13e to correct the nonlinear magnification error (higher-order magnification error) of the projection image of the projection optical system PL4. However, the linear magnification error generated at that time is corrected by inclining or vertically moving the lens elements 37D and 38D via the support bases 45 and 46. By combining the movements of the two supports 45 and 46, not only the magnification error but also the defocus of the focus position, the field curvature, etc. can be corrected.
Most of the other aberrations that occur during the correction of the nonlinear magnification error can be canceled by optimizing the control of the temperature control device 13e and the drive device 47.

[0060]

EXAMPLES Next, the results of numerical analysis of the actual numerical model of the projection optical system showing how the nonlinear magnification error changes due to temperature control will be shown. In this case, for example, FIG.
When the projection optical system PL1 shown in (1) is used as an analysis target, there are nine lens elements in the projection optical system PL1 that may be formed of fluorite to correct the imaging characteristics. Therefore, the nine lens elements that can be formed from fluorite in this way are designated as lens elements L1 to L9, and no lens element made of fluorite is used, and
When the one lens element is made of fluorite and the other lens element is made of quartz, the magnification error βA [μm] at the position where the image height is 100% of the maximum value and the image height when it is 70% of the maximum value Magnification error βB [μm] and the magnification error at the position where the image height is 100% of the maximum value are corrected to almost 0, the magnification error that remains at the position where the image height is 70% of the maximum value (non-linear magnification Error) βC [μm] was determined. When one lens element is made of fluorite, the lens elements L1 to L9 are sequentially made of fluorite and the magnification when the temperature of one lens element made of the fluorite is changed by 1 ° C. Error βA [μm], magnification error βB [μ
m] and residual magnification error (non-linear magnification error) βC [μ
m] is shown in Table 1 below.

[0061]

[Table 1] βA [μm] βB [μm] βC [μm] No fluorite -0.0144 -0.0204 +0.0100 L1 +0.0436 +0.0135 -0.0067 L2 -0.2797 -0.1862 +0.0199 L3 -0.2254 -0.1529 +0.0152 L4 -0.2576 -0.1739 +0.0167 L5 +0.1602 +0.0926 -0.0092 L6 +0.1045 +0.0572 -0.0056 L7 +0.2371 +0.1447 -0.0110 L8 +0.2911 +0.1793 -0.0142 L9 +0.3854 +0.2406 -0.0192

In Table 1 above, for example, when the lens element L4 is made of fluorite, the residual magnification error (non-linear magnification error) βC is larger than that when no fluorite is used.
It is 0.0067 μm, that is, about 7 nm larger. Further, when the lens element L9 is made of fluorite, the residual magnification error (non-linear magnification error) βC changes by 0.0292 μm, that is, about 29 nm, as compared with the case where fluorite is not used. Therefore, by changing the temperature of one lens element made of fluorite by ± 1 ° C, the maximum is approximately ± 2.
It can be seen that it is possible to correct the nonlinear magnification error of about 0 nm.

Further, generally, the resolution of temperature control is 0.01
Since a temperature of about 1 ° C is possible, when the temperature of the lens element made of fluorite is changed by about 1 ° C to correct the non-linear magnification error, the resolution of the non-linear magnification error correction is approximately ±
It becomes 0.2 nm (= ± 20/100 [nm]). Further, it can be seen from Table 1 that a linear magnification error of about ± 0.2 μm occurs when the temperature of the lens element made of fluorite is changed by 1 ° C. Therefore, the control resolution of the linear magnification error when the temperature of the lens element made of fluorite is changed by about 1 ° C. is approximately ± 2 nm (= ± 0.
2/100 [μm]).

Further, by inserting fluorite lens elements at a plurality of positions, the temperature control range can be narrowed, the linear magnification error additionally generated can be reduced, and a larger nonlinear magnification error can be corrected. It will be possible. In addition,
The present invention is not limited to the above-described embodiments and examples,
Of course, various configurations can be adopted without departing from the scope of the present invention.

[0065]

According to the present invention, the projection optical system has a plurality of sets of optical members (lens elements) made of glass materials having different temperature characteristics of refractive index, and temperature control of at least one of the optical members. By performing the above, the image forming characteristic of the projection optical system is controlled. Therefore, it is possible to correct the distortion of the projection optical system that is deteriorated due to environmental changes such as atmospheric pressure and the ambient temperature of the projection optical system, changes in illumination conditions (normal or modified light source, etc.), or absorption of exposure illumination light. There is. As a result, it is possible to improve the overlay accuracy of the projected images on the photosensitive substrate.

When the imaging characteristic of the projection optical system controlled by the temperature control means is a non-linear magnification error,
There is an advantage that a non-linear magnification error that cannot be corrected by the conventional method can be corrected. In this case, when the temperature of the optical member to be controlled is changed by ± 1 ° C. by the temperature control means to correct the nonlinear magnification error of the projection optical system within the range of ± 50 nm, it is shown by the above numerical analysis. Thus, for example, by controlling the temperature of one or two lens elements made of fluorite, the correction can be performed within that range, which is practical.

Further, linear magnification control means for correcting the linear magnification error of the projection optical system is provided, and the linear magnification remaining after the non-linear magnification error of the projection optical system is kept within a predetermined allowable range by the temperature control means. When reducing the error through the linear magnification control means, the distortion of the projection optical system can be made substantially zero. Further, a storage means is provided for storing the amount of change in the image forming characteristics of the projection optical system in accordance with the change in the use condition of the projection optical system,
In order to cancel out the amount of change in the imaging characteristics stored in the storage means according to the change in the use condition of the projection optical system,
When controlling the image forming characteristic of the projection optical system via the temperature control means, when the use condition of the projection optical system changes, the image forming characteristic such as distortion of the projection optical system can be obtained with almost no waiting time. There is an advantage that it can be returned to a good condition.

[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 element of two glass materials.

7A is a diagram showing a non-linear magnification error due to a lens element made of quartz, and FIG. 7B is a diagram showing a magnification error due to a lens element made of fluorite whose temperature is controlled;
(C) is a figure which shows the correction amount of a linear magnification error.

FIG. 8: Magnification error (distortion) obtained by combining a lens element made of quartz, a lens element made of fluorite whose temperature is controlled, and a lens control device.
FIG.

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

10A is a waveform diagram showing a detection signal detected by the distortion measuring sensor 3, and FIG. 10B is a waveform diagram showing a differential signal of the detection signal.

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 a non-linear magnification error in a conventional projection exposure apparatus.

16A is a diagram showing an influence of a non-linear magnification error when performing batch exposure, and FIG. 16B is a diagram showing an influence of a non-linear magnification error when performing scanning exposure.

[Explanation of symbols]

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

Claims (5)

[Claims] 1. A projection exposure apparatus for projecting a mask pattern onto a photosensitive substrate via a projection optical system, wherein the projection optical system has a plurality of sets of optical members made of glass materials having different temperature characteristics of refractive index. Projection exposure, characterized in that temperature control means for controlling the temperature of at least one optical member in the plurality of sets of optical members is provided, and the imaging characteristic of the projection optical system is controlled using the temperature control means. apparatus. 2. The projection exposure apparatus according to claim 1, wherein the imaging characteristic of the projection optical system controlled by the temperature control means is a non-linear magnification error. 3. The projection exposure apparatus according to claim 2, wherein the temperature control means changes the temperature of the optical member to be controlled by ± 1 ° C., so that the nonlinear magnification error of the projection optical system is ± 50 nm. A projection exposure apparatus characterized by correction within a range. 4. The projection exposure apparatus according to claim 2, further comprising a linear magnification control unit that corrects a linear magnification error of the projection optical system, and the temperature control unit causes a nonlinear magnification of the projection optical system. A projection exposure apparatus characterized in that the linear magnification error remaining after the error is within a predetermined allowable range is reduced through the linear magnification control means. 5. The projection exposure apparatus according to claim 1, 2, 3, or 4, wherein the amount of change in the image forming characteristic of the projection optical system is stored according to the change in the usage condition of the projection optical system. A storage unit is provided so as to offset the change amount of the imaging characteristic stored in the storage unit according to the change of the usage condition of the projection optical system.
A projection exposure apparatus, characterized in that it controls an image forming characteristic of the projection optical system via the temperature control means.