JPH09148234A - Projection exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection exposure device which compensates for variations in distortion with changes in the lighting condition. SOLUTION: When a rotational drive 64 rotates an aperture stop 48 for a change from one aperture to another to change lighting conditions, a main controller 16 instructs a replacement drive 24 to replace a distortion corrective member. The replacement drive 24 operates a rotational drive 28 to rotate a disc 26 so that a distortion corrective member suited to the lighting condition can be set in the optical path of exposure light. Therefore, nonlinear variations in distortion of a projection optical system PL with changes in intensity distribution of exposure light are compensated for if the lighting condition is changed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and more particularly to a projection exposure apparatus capable of changing illumination conditions according to required resolution, depth of focus and the like.

[0002]

2. Description of the Related Art Conventionally, in a projection exposure apparatus such as a so-called stepper, a mask (or reticle) is operated under a single illumination condition.
Pattern has been transferred onto a photosensitive substrate such as a wafer via a projection optical system. However, as the pattern on the wafer becomes finer, recently, the intensity distribution of the exposure light is changed near the position conjugate with the pupil plane of the projection optical system in accordance with the required pattern resolution and depth of focus. Therefore, a projection exposure apparatus capable of changing illumination conditions has been developed. As such a projection exposure apparatus capable of changing the illumination condition, there is known a projection exposure apparatus which changes the illumination condition by variously changing the shape of the aperture of the aperture stop.

[0003]

However, in the conventional projection exposure apparatus capable of changing the illumination conditions, the above-mentioned conventional projection exposure apparatus is particularly susceptible to the change of the image forming characteristics when the aperture stop is changed to change the illumination conditions. Since it was not taken into consideration, a variation in the imaging characteristics, especially distortion, causes a total misalignment between the process and layer under different illumination conditions such as overprinting, resulting in finer patterns and higher resolution. It is no longer sufficient in the present situation where improvement of the demand is required.

The present invention has been made under such circumstances, and an object of the invention is to provide a projection exposure apparatus capable of correcting the amount of distortion variation due to switching of illumination conditions.

[0005]

A variation amount of distortion due to a change in illumination condition includes a linear component that can be corrected by fine movement and tilt adjustment of a lens element that constitutes a projection optical system, and a non-correctable nonlinear component. There is. The present invention is constructed as follows on the basis of such fact.

The invention described in claim 1 is a projection exposure apparatus for illuminating a mask with exposure light from an illumination optical system and exposing and transferring an image of a pattern on the mask onto a photosensitive substrate through a projection optical system. An illumination condition switching means for switching the illumination condition by changing the intensity distribution of the exposure light in the vicinity of a position conjugate with the pupil plane of the projection optical system; and a case of switching the illumination condition by the illumination condition switching means. A first distortion correction means for correcting a non-linear change amount of distortion of the projection optical system due to a change in intensity distribution of exposure light.

According to this, when the illumination condition is switched by changing the intensity distribution of the exposure light in the vicinity of the position conjugate with the pupil plane of the projection optical system by the illumination condition switching means, the first distortion correction means is operated. By using this, it is possible to correct the non-linear change amount of the distortion of the projection optical system due to the change of the intensity distribution of the exposure light when switching the illumination conditions.

In this case, as in the second aspect of the invention, the illumination condition switching means is set by the aperture diaphragm switching setting means for switching and setting a plurality of aperture diaphragms having different sizes or shapes on the optical path of the exposure light. Can be configured.

The invention described in claim 3 is the first or second invention.
The projection exposure apparatus described in (1) further includes second distortion correction means for correcting a linear change amount of distortion by adjusting an optical distance between the mask and the projection optical system.

According to this, when the illumination condition is switched by changing the intensity distribution of the exposure light in the vicinity of the position conjugate with the pupil plane of the projection optical system by the illumination condition switching means, the first distortion correction means is used. The amount of nonlinear change in the distortion of the projection optical system due to the change in the intensity distribution of the exposure light when switching the illumination conditions is corrected, and the second distortion correction means adjusts the optical distance between the mask and the projection optical system. By doing so, the linear change amount of distortion can be corrected.

According to a fourth aspect of the invention, in the projection exposure apparatus according to any one of the first to third aspects, the first distortion correction corresponding to each illumination condition switched by the illumination condition switching means. The means performs trial baking in a state in which a parallel plate is arranged between the mask and the projection optical system under each of the illumination conditions, and based on the result, the nonlinear change amount of distortion is corrected. It is characterized in that the parallel flat plates are made to have different thicknesses. According to this, only by switching the parallel plate corresponding to the switching of the illumination condition by the illumination condition switching unit, the nonlinear change amount of the distortion of the projection optical system due to the change of the intensity distribution of the exposure light at the time of switching the illumination condition can be obtained. It can be easily corrected.

According to a fifth aspect of the present invention, in the projection exposure apparatus according to the fourth aspect, when the illumination conditions are switched by the illumination condition switching means, the parallel flat plate corresponding to the illumination conditions after the switching is applied. It further has a changing means for changing.
According to this, when the illumination condition is switched by the illumination condition switching unit, the changing unit changes the parallel plate to the parallel plate corresponding to the switched illumination condition. Therefore, the non-linear change amount of the distortion of the projection optical system due to the change of the intensity distribution of the exposure light at the time of switching the illumination condition is automatically corrected.

According to a sixth aspect of the present invention, in the projection exposure apparatus according to any one of the third to fifth aspects, the distortion linearity obtained based on the result of the trial baking under each of the illumination conditions is performed. A storage unit that stores the correction value of the change amount, and when the illumination condition is switched by the illumination condition switching unit, the correction value of the linear change amount of the distortion corresponding to the illumination condition after the switching is read from the storage unit, It further has a control means for controlling the second distortion correction means based on the correction value.

According to this, when the illumination condition is switched by the illumination condition switching means, the changing means changes to the parallel plate corresponding to the switched illumination condition. At this time, the control unit reads out the correction value of the linear change amount of distortion corresponding to the illumination condition after the switching from the storage unit, and controls the second distortion correction unit based on the correction value. Therefore, the non-linear change amount and the linear change amount of the distortion of the projection optical system due to the change of the intensity distribution of the exposure light when the illumination condition is switched are automatically corrected.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a projection exposure apparatus 1 according to an embodiment.
A 0 configuration is shown. The projection exposure apparatus 10 includes a wafer stage 12 on which a wafer as a photosensitive substrate (not shown) is mounted, a projection optical system PL disposed above the wafer stage 12, and a projection optical system PL disposed above the projection optical system PL. Reticle R as a mask and this reticle R
An illumination optical system 14 that illuminates the device with exposure light, and a main controller 16 that controls the entire apparatus.

The wafer stage 12 is constructed so as to be movable in a two-dimensional direction of an X axis parallel to the paper surface and a Y axis orthogonal thereto in a horizontal plane orthogonal to the paper surface in FIG. The drive system 18 drives the wafer stage 12 in the two-dimensional X and Y directions. In addition, this wafer stage 12
The XY two-dimensional position of the laser interferometer is measured by a laser interferometer (not shown).
To be entered. That is, the main controller 16 monitors the output of the laser interferometer while monitoring the drive system 18
The position of the wafer stage 12 in the XY two-dimensional directions is controlled via the.

The projection optical system PL has a Z-axis orthogonal to the XY plane.
It is composed of a plurality of lens elements arranged in a predetermined interval in the axial direction and having a common optical axis and a lens barrel holding these lens elements. In FIG. 1, a part of the projection optical system PL near the reticle R is shown. , Distortion correction mechanism 20
Are shown separately.

The distortion correction mechanism 20 portion has at least two lens elements, and at least two of these lens elements are arranged in the Z-axis direction (optical axis direction) at intervals and positions, in the X-direction, and in the Y-direction. The inclination of is configured to be adjustable. Each lens element that constitutes the distortion correction mechanism 20 is supported at, for example, the outer peripheral portion at three points at intervals of approximately 120 degrees, and each support point can be driven in the Z-axis direction by an actuator such as a piezo element. This distortion correction mechanism 2
Zero is controlled by the distortion correction control unit 22.

Further, in this embodiment, a plurality of distortion correction members (which will be described in detail later including the manufacturing method thereof) are arranged between the reticle R and the distortion correction mechanism 20 at substantially equal intervals. A rotation plate 26 for a distortion correction member, which is a disk-shaped member, is arranged. This distortion correction member rotary plate 26
Are rotated by the first rotary drive mechanism 28. The first rotation drive mechanism 28 is controlled by the distortion correction member exchange drive unit 24.

The distortion correction control section 22 and the distortion correction member exchange driving section 24 are
It is under the control of the main controller 16.

The illumination optical system 14 includes a mercury lamp 36, an elliptical mirror 38, mirrors 40, 44, 54, 58 and a shutter 4.
2, a fly-eye lens 46 as an optical integrator, an aperture diaphragm plate 48, a blind 52, and a condenser lens 56. Here, each component of the illumination optical system 14 will be described together with its operation.

In the “open” state of the shutter 42, the exposure light (i-line or g-line) emitted from the mercury lamp 36 is condensed by the elliptical mirror 38, reflected by the mirror 40, and the shutter 4 is released.
After passing through the second position, it is reflected again by the mirror 44, passes through the fly-eye lens 46 and the aperture stop of the aperture stop plate 48 (which will be described later in detail), and reaches the blind 52. Here, the arrangement surface of the blind 52 is conjugate with the pattern formation surface of the reticle R, and the blind 52
The shape of the illumination area on the reticle R is defined by the opening of. Exposure light whose shape is defined by the blind 52 is reflected by a mirror 54, condensed by a condenser lens 56, reflected by a mirror 58, and illuminates the reticle R from above. As a result, the image of the circuit pattern formed on the pattern formation surface of the reticle R is transferred onto the wafer (not shown) on the wafer stage 12 at a predetermined reduction magnification via the projection optical system PL. On the other hand, the shutter 42 is “closed”
In this state, the exposure light is blocked by the shutter 42, so that the reticle R is not illuminated.

The aperture stop plate 48 is made of, for example, a disc-shaped member as shown in FIG.
On the upper side, an aperture stop 49A composed of a normal circular aperture at substantially equal intervals, an aperture stop 49B composed of a small circular aperture, for reducing the σ value which is a coherence factor, and a ring-shaped aperture stop 49C for annular illumination. And a modified aperture stop 49 having a plurality of apertures eccentrically arranged for the modified light source method.
D is arranged. In this embodiment, the aperture stop plate 4
8, the four aperture stops 49A to 49A-4
A desired aperture stop in 9D can be selected. The aperture diaphragm plate 48 is rotationally driven about the Z axis by the second rotary drive mechanism 64 controlled by the aperture diaphragm exchange control unit 66. The aperture stop replacement controller 66 is also under the control of the main controller 16.

Further, in the present embodiment, a hard disk 68 as a storage unit is installed in the main controller 16. In the hard disk 68, the four aperture stops 49A are provided.
The correction values of the linear change amount of distortion obtained by the test exposure under the respective illumination conditions corresponding to .about.49D are stored in the form of a data file.

Next, a method of creating a distortion correction member and a data file corresponding to each aperture stop will be described.

First, the normal illumination diaphragm 49 A is first set on the optical path of the exposure light, and the normal parallel plate is set at a predetermined height position between the reticle R and the distortion correction mechanism 20 (the distortion correction member in FIG. 1). It is arranged orthogonal to the optical axis of the projection optical system PL at the position of the rotary plate 26) and so-called test exposure is performed in this state.

Based on the result of this test exposure, the amount of distortion during normal illumination is measured.

Next, based on this measurement result, a distortion correction value of linear and non-linear components that makes the distortion amount at the time of normal illumination zero is obtained.

Next, using the correction value of the non-linear component of the distortion, the surface of the parallel plate is processed so that this becomes zero, and the distortion correction member corresponding to the normal illumination diaphragm 49A, that is, the non-linearity of the distortion, is processed. A parallel plate having a partially different thickness is prepared so that the variation is corrected.

Then, the distortion correction mechanism 20 is used by using the correction value of the linear component of the distortion.
A data file of the amount of movement of the lens / elements that compose the above is created and stored in the hard disk 68.

With respect to the illumination conditions in which the other aperture diaphragms 49B to 49D are set, the test exposure is performed for each illumination condition, the distortion amount is measured, the correction value is obtained, and the distortion correction member and the data are obtained in the same manner as the above. Create a file.

In this way, the distortion correction member prepared in advance on the basis of the result of the test exposure under the illumination condition using each of all the aperture diaphragms is mounted on the distortion correction member rotating plate 26 and prepared in advance. The stored data file is stored in the hard disk 68.

Next, the main operation of the projection exposure apparatus 10 of the present embodiment constructed as described above prior to the actual exposure will be described focusing on the control operation of the main controller 16.

When an external command, specifically, a command from the operator or a command to change the aperture diaphragm from the host computer is input to the main controller 16, the main controller 16 issues a command to the aperture diaphragm replacement controller 66. Out the second
By rotating the aperture stop plate 48 via the rotary drive mechanism 64, the aperture stop is replaced with the aperture stop corresponding to the command.

At the same time, the main controller 16 gives a command for changing the distortion correction member to the distortion correction member exchange control unit 24, and the movement amount of the lens element corresponding to the aperture stop shape is calculated from the data file in the hard disk 68. It is read and given to the distortion correction control unit 22. As a result, the distortion correction member replacement drive unit 24 rotationally drives the distortion correction member rotation plate 26 to correct the non-linear component of the distortion, and the distortion correction control unit 22 controls the distortion correction mechanism 20 to control the linear component of the distortion. Is corrected.

As described above, after the variation of the distortion due to the change of the aperture stop is corrected, the exposure is started.

As is clear from the above description, in the present embodiment, the first distortion correcting means is constituted by each distortion correcting member mounted on the distortion correcting member rotary plate 26, and the distortion correcting mechanism 20 and the distortion correcting member are constituted. A second distortion correction means is constituted by the control section 22,
The distortion correction member exchange drive unit 24 and the first rotation drive mechanism 28 constitute a changing unit, and the aperture stop plate 48, the second rotation drive mechanism 64, and the aperture stop exchange control unit 66 constitute the illumination condition switching unit, that is, the aperture. The aperture switching setting means is configured, and the control means is realized by the function of the main control device 16.

As described above, according to this embodiment,
It is possible to automatically correct the distortion change that occurs when the illumination condition using one aperture stop is changed to the illumination condition using another aperture stop. Also,
By correcting the distortion change, it is possible to prevent deterioration of the total overlay (total overlay deviation) between the process layers under different illumination conditions using different aperture stops.

In the above embodiment, as the distortion correction mechanism for correcting the linear component of the distortion change amount, the one for adjusting the position and the inclination of the lens element in the projection optical system PL in the optical axis direction is exemplified. However, the reticle R is not limited to this, and, for example, means for changing the position of the reticle R in the Z direction, and the reticle R
The distortion adjusting means may be configured using any means as long as it can change the optical distance (optical path length) between the projection optical system PL and the projection optical system PL.

In the above embodiment, the illumination condition switching means is composed of the aperture diaphragm plate 48, the second rotary drive mechanism 64 and the aperture diaphragm exchange control section 66. There is no limitation, and any configuration of illumination condition switching means may be used as long as it is a means for switching the illumination condition by changing the intensity distribution of the exposure light near the position conjugate with the pupil plane of the projection optical system PL. Is also good.

[0042]

As described above, claims 1 to 4
According to the invention described in (1), there is an unprecedented excellent effect that it is possible to correct the variation amount of distortion due to switching of illumination conditions.

Further, according to the invention described in claims 5 to 6, there is an effect that it is possible to automatically correct the variation amount of the distortion due to the switching of the illumination conditions.

In particular, according to the third, fourth and sixth aspects of the invention, not only the non-linear component of the amount of distortion variation due to switching of the illumination conditions but also the linear component can be corrected. There is an effect.

[Brief description of the drawings]

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

FIG. 2 is a plan view showing an example of an aperture stop plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Projection exposure apparatus 14 Illumination optical system 16 Main controller (control means) 20 Distortion correction mechanism (a part of second distortion correction means) 22 Distortion correction control section (a part of second distortion correction means) 24 Distortion correction Member exchange drive unit (change unit) 26 Rotation plate for distortion correction member (first distortion correction unit) 28 First rotation drive mechanism (part of change unit) 48 Aperture diaphragm plate (part of illumination condition switching unit, Part of aperture stop switching setting means 49A to 49D Aperture stop 64 Second rotation drive mechanism (part of illumination condition switching means,
Aperture stop switching setting unit) 66 Aperture stop replacement control unit (part of illumination condition switching unit, part of aperture stop switching setting unit) 68 Hard disk (storage unit) R reticle (mask) PL projection optical system

Claims (6)

[Claims] 1. A projection exposure apparatus for illuminating a mask with exposure light from an illumination optical system and exposing and transferring an image of a pattern on the mask onto a photosensitive substrate via the projection optical system. Illumination condition switching means for switching the illumination condition by changing the intensity distribution of the exposure light in the vicinity of a position conjugate with the pupil plane; and a change in the intensity distribution of the exposure light when the illumination condition is switched by the illumination condition switching means. A projection exposure apparatus comprising: first distortion correction means for correcting a non-linear change amount of distortion of the projection optical system. 2. The illumination condition switching means is an aperture diaphragm switching setting means for switching and setting a plurality of aperture diaphragms having different sizes or shapes on the optical path of the exposure light. Projection exposure device. 3. The second distortion correction means according to claim 1, further comprising a second distortion correction means for correcting a linear change amount of distortion by adjusting an optical distance between the mask and the projection optical system. Projection exposure device. 4. The first distortion correction unit corresponding to each illumination condition switched by the illumination condition switching unit arranges a parallel plate between the mask and the projection optical system under each illumination condition. 4. The parallel flat plate having a partially different thickness so that the non-linear change amount of the distortion is corrected based on the result of the trial baking in this state. The projection exposure apparatus according to claim 1. 5. The projection exposure apparatus according to claim 4, further comprising, when the illumination condition is switched by the illumination condition switching unit, a changing unit that changes to the parallel plate corresponding to the switched illumination condition. 6. A storage unit storing a correction value of a linear change amount of distortion, which is obtained based on a result of trial baking under each illumination condition, and when the illumination condition is switched by the illumination condition switching unit. And a control unit that reads out a correction value of a linear change amount of distortion corresponding to the illumination condition after the switching from the storage unit and controls the second distortion correction unit based on the correction value. 6. The projection exposure apparatus according to any one of items 5 to 5.