JPH0883761A - Projection exposing device - Google Patents

Abstract

PURPOSE: To give excellent exposing conditions to all exposing processes including the exposing time and aligning time of isolated patterns. CONSTITUTION: In a projection exposing device provided with a lighting optical system which projects illuminating light ILB for exposure upon a mask M and a projection optical system which makes the light from the pattern of the mask M to form an image on a photosensitive substrate, a variable-pupil filter 15 means which is provided on a Fourier transformation surface in an image forming optical path between the mask M and photosensitive substrate or its vicinity and variable operating means 14 which changes the filter characteristic of the filter 15 means so as to change the projecting state of the image forming light upon the photosensitive substrate are provided.

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, for example, a projection exposure apparatus used when manufacturing a semiconductor element, a liquid crystal display element, a thin film magnetic head, etc. in a photolithography process.

[0002]

2. Description of the Related Art Conventionally, in a projection exposure apparatus which transfers a desired circuit pattern onto a photosensitive substrate coated with a photosensitizer (photoresist) when manufacturing a semiconductor device or a liquid crystal display device, the circuit pattern is A photomask or reticle (hereinafter collectively referred to as “mask”) provided is irradiated with illumination light from an illumination optical system, and an image of a circuit pattern is formed on a photosensitive substrate via the projection optical system.

In recent years, miniaturization of semiconductor integrated circuit elements has been strongly demanded in order to realize high integration and high performance of semiconductor integrated circuits. Generally, when a fine pattern is transferred onto a photosensitive substrate by such a projection exposure apparatus, the resolution and depth of focus (DOF) of the projection optical system are important factors for transferring with high accuracy.

The resolution of the projection optical system and the DOF have a contradictory relationship. When the numerical aperture NA is increased to improve the resolution of the projection optical system, the DOF decreases in inverse proportion to the square of the numerical aperture NA. Become. Therefore, even if a projection optical system having a high numerical aperture can be obtained, it is not possible to obtain a projection optical system having a required depth of focus (DOF), which is a big practical problem.

Particularly, as an exposure method for increasing the apparent depth of focus for an isolated pattern such as a contact hole, the exposure for one shot area of the wafer is divided into a plurality of times, and the wafer is moved in the optical axis direction during each exposure. For example, a method of moving a fixed amount is proposed in JP-A-63-42122.

This exposure method is based on FLEX (Focus Latitude en
This is called the hancement EXposure) method and exhibits a sufficient depth of focus expansion effect for isolated patterns such as contact holes. However, since the FLEX method multiple-exposes a slightly defocused contact hole image, the sharpness of the resist image obtained after development is inevitably reduced.

The problem of deterioration of the sharpness (deterioration of profile) is that a resist having a high gamma value is used, a multilayer resist is used, or CEL (Contrast Enhancement Lath) is used.
yer) can be used to compensate.

Further, a so-called Super-FLEX method is also proposed in JP-A-5-259035 as a method for expanding the depth of focus when projecting a contact hole pattern without moving the wafer in the optical axis direction during the exposure operation. ing.

In this Super-FLEX method, a transparent phase plate is provided at the position of the pupil plane (Fourier transform plane for the pattern) of the projection optical system, and the complex amplitude transmittance given to the image-forming light by this phase plate is from the optical axis. This is a method in which the characteristics are given so that the characteristics gradually change toward the periphery. In this method, the image formed by the projection optical system maintains sharpness with a certain width wider than before in the optical axis direction, centering on the best focus surface that is a surface conjugate with the mask, so the depth of focus is Will increase.

As another exposure method for enlarging the apparent depth of focus for an isolated pattern such as a contact hole, a Fourier transform plane may be provided at the pupil plane (Fourier transform plane for the pattern) or near plane position of the projection optical system. An optical filter was provided to make the phase or polarization state different between the imaging light in the circular area centered on the optical axis of the projection optical system on the upper or near surface and the imaging light in the annular zone outside the circular area. A projection exposure apparatus having a structure is proposed in, for example, Japanese Patent Laid-Open No. 6-120110.

In this projection exposure apparatus, the imaging light that has passed through a circular area centered on the optical axis of the projection optical system on the Fourier transform surface or a near surface and the imaging light that has passed through an area outside the circular area are Since each of them independently interferes with each other to form an image (intensity distribution) of the hole pattern, the interference image of the light flux passing through the circular area and the interference of the light flux passing through the outer area. An image obtained by simply adding intensities to the image can be obtained as an image of an isolated pattern such as a contact hole. Further, the light blocking filter corresponding to the circular region blocks light passing through the circular region.

[0012]

However, since the projection exposure apparatus that is generally used must be compatible with all exposure steps for manufacturing semiconductor elements and the like, a pupil filter is always installed in the projection optical system. I can't.

Further, in this type of apparatus, exposure is usually performed after the mask and the wafer are aligned. Therefore, the alignment mark provided on the wafer is detected by, for example, a through-the-lens (TTL) type alignment method in which the alignment mark is detected through a projection optical system to perform alignment between the mask and the wafer. In the case of such TTL type alignment, there is a problem that the pupil filter blocks the alignment light during the alignment of the wafer.

The present invention has been made in view of the above problems, and provides a projection exposure apparatus which gives good exposure conditions in all exposure steps as well as during exposure and alignment of isolated patterns. With the goal.

Further, it is an object of the present invention to provide a projection exposure apparatus in which the pupil filter means can be easily provided on a predetermined Fourier transform plane or a nearby plane, which saves time and labor and is excellent in manufacturing efficiency.

[0016]

In order to solve the above-mentioned problems, in the projection exposure apparatus according to the first aspect of the present invention, an illumination optical system for irradiating a mask having a predetermined pattern with illumination light for exposure. A projection optical system that forms an image of the pattern on a photosensitive substrate by light generated from the pattern of the mask, a Fourier transform in an imaging optical path between the mask and the photosensitive substrate. A variable pupil filter means arranged at or near the conversion surface, and a variable operation means for changing the filter characteristic of the variable pupil filter means so as to change the irradiation state of the imaging light on the photosensitive substrate. It is what

Also, in the projection exposure apparatus according to the second invention, in the first invention, the variable pupil filter means is used to vary the 0th-order light distributed in a predetermined region centered on the optical axis of the projection optical system. It is assumed that it is selectively removed based on the operation of the operation means.

Further, in the projection exposure apparatus according to the third invention, in the first invention, the variable pupil filter means has a polarization state of 0th order light distributed in a predetermined region centered on the optical axis of the projection optical system. Is selectively changed based on the operation of the variable operation means.

Further, in the projection exposure apparatus according to the fourth aspect of the present invention, in the first or second aspect of the invention, the variable pupil filter means is a transmission type provided corresponding to the 0th-order light transmission region at or near the Fourier transform plane. An electro-optical element is provided, and the variable operating means selectively energizes the transmissive electro-optical element to selectively make the transmissive electro-optical element at least partially shielded.

Further, in the projection exposure apparatus according to the fifth aspect of the present invention, in the first or second aspect of the invention, the variable pupil filter means is a light transmitting member provided corresponding to the 0th order light transmitting region at or near the Fourier transform plane. And a variable operating means for changing the filter characteristics by selectively introducing a fluid into the fluid receiving chamber.

[0021]

Since the invention according to the present application is configured as described above, it has the following effects. First, according to a first aspect of the invention, an illumination optical system for irradiating a mask on which a predetermined pattern is formed with illumination light for exposure, and light generated from the pattern of the mask forms an image of the pattern on a photosensitive substrate. In a projection exposure apparatus having a projection optical system for forming an image,
Variable pupil filter means disposed at or near the Fourier transform plane in the image forming optical path between the mask and the photosensitive substrate, and the variable pupil filter so as to change the irradiation state of the image forming light on the photosensitive substrate. There is proposed a projection exposure apparatus provided with a variable operating means for changing the filter characteristic of the means.

That is, all the principal rays from the mask pattern, which contribute to the image formation, pass through the pupil at the Fourier transform plane position or in the vicinity of the plane plane, so that the irradiation state of these image formation rays is at this position. By providing a pupil filter for changing the value, the exposure of an isolated pattern such as a contact hole pattern can be improved.

In the exposure apparatus of the present invention, variable pupil filter means is provided as this pupil filter. The variable pupil filter means has a configuration capable of changing the irradiation state of the image forming light on the photosensitive substrate, and is further provided with a variable operation means for changing the filter characteristic of the variable pupil filter means, so that the variable pupil filter means can be freely changed. The filter characteristics can be adjusted. Therefore, as well as exposure of an isolated pattern such as a contact hole pattern,
It is possible to provide good exposure conditions even for periodical pattern exposure such as & S pattern.

For example, during exposure of an isolated pattern such as a contact hole pattern, the variable operating means adjusts the filter characteristics of the variable pupil filter means to form a pupil filter, or a periodic pattern such as an L & S pattern. It is possible to easily switch the irradiation state of the image-forming light according to the purpose of exposure such that the variable operation means does not form the pupil filter by adjusting the filter characteristic of the variable pupil filter means at the time of exposure.

Of course, the filter characteristics of the variable pupil filter means may be such that the incident illumination light is not allowed to pass at all, or the incident illumination light (or a predetermined wavelength) is not allowed to pass partially. Good
Allow (or do not allow) only light of a predetermined wavelength
Further, the intensity distribution in the cross section of the incident illumination light may be changed, depending on factors such as the characteristics of the photosensitive material such as a resist provided on the substrate to be exposed and the exposure time. Anything that freely changes the optical characteristics of the illumination light may be used.

Further, since the variable pupil filter means works like a plane-parallel plate, it is desirable in the optical design to design the entire projection optical system so as to minimize the influence of defocus and aberration. As a result, the projection exposure apparatus can be used in the optimal imaging state in each process.

In addition, even in the case of TTL type wafer alignment, alignment light is not blocked because the pupil filter is not formed at the time of alignment by the variable operation means, so that alignment can always be performed with high accuracy.

Here, as the variable pupil filter means, for example, an electro-optical element such as an electrochromic element or a liquid crystal is used, and the variable operation means energizes the variable pupil filter means to form a pupil filter. Alternatively, the variable pupil filter means may be a mechanically formed one such as an opening / closing blind structure or a rolling shutter structure, and the variable operation means may be the opening / closing state of the variable pupil filter means. The pupil filter may be formed by performing an assembling operation such as a combination or a combination state, but the first invention is not particularly limited thereto.

The second invention is the variable pupil filter means provided in the projection exposure apparatus as described above, wherein the 0th-order light distributed in a predetermined region centered on the optical axis of the projection optical system is described above. It has been proposed to selectively remove it based on the operation of the variable operation means.

That is, at the time of exposure of an isolated pattern such as a contact hole pattern, it is distributed in a circular region centered on the optical axis of the projection optical system at or near the Fourier transform plane position in the imaging optical path. Since the depth of focus can be increased by removing the 0th-order light, the variable pupil filter means for removing the 0th-order light is arranged in the second invention.

Examples of the variable pupil filter means include those in which a variable filter section is formed by an electro-optical element such as an electrochromic element or a liquid crystal element in a circular area centered on the optical axis of the projection optical system. However, it is not particularly limited as long as it removes the 0th-order light in the circular region.

Since the variable operation means for changing the filter characteristics of the variable pupil filter means is provided, it is not limited to the exposure of an isolated pattern such as a contact hole pattern, but a cycle such as an L & S pattern (lattice). It is possible to secure a good illumination state even at the time of pattern exposure having a structure, alignment, and the like, and it is possible to deal with all exposure steps for manufacturing a semiconductor element or the like.

Furthermore, the third aspect of the invention is a variable pupil filter means provided in the projection exposure apparatus as described above, which is for the 0th-order light distributed in a predetermined area centered on the optical axis of the projection optical system. It has been proposed to selectively change the polarization state based on the operation of the variable operation means.

As described above, at the time of exposure of an isolated pattern such as a contact hole pattern, a Fourier transform plane position or a position near the Fourier transform plane is formed within a predetermined area centered on the optical axis of the projection optical system. Although the depth of focus can be increased by removing the distributed zeroth-order light, blocking the inside of the region reduces the effective light amount of the entire image-forming light, so that the exposure is performed for good exposure. The exposure efficiency will be impaired because the time must be lengthened.

Therefore, according to the present invention of claim 3, by disposing variable pupil filter means for making the polarization state of the 0th-order light different from the polarization state of other higher-order lights (± first-order diffracted light or more), An interference image is formed by the interference of the diffracted light itself. Thereby, sufficient exposure energy can be secured without causing a loss of light quantity.

As the variable pupil filter means, for example, a polarizing plate having a liquid crystal in the 0th-order light passing region,
A polarizing plate or the like provided with a ceramic polarization element (PLZT) in the next light passage region can be used, but it is not particularly limited as long as it changes the polarization state of the 0th order light.

Further, since the variable operation means for freely forming the variable pupil filter means is provided, it is not necessary to attach or replace the pupil filter according to the purpose of exposure, and the variable pupil filter means can be easily operated. The filter characteristics are changed to secure a good exposure state not only when exposing an isolated pattern such as a contact hole pattern, but also when exposing a pattern having a periodic structure such as an L & S pattern (lattice) or during alignment. Therefore, it is possible to correspond to all the exposure steps for manufacturing a semiconductor element or the like.

Further, in the fourth invention, the first invention or the second invention
In the invention, as the variable pupil filter means, one having a transmission type electro-optical element provided corresponding to a 0th-order light transmission region at the Fourier transform surface or a position in the vicinity thereof is used, and as the variable operation means, A projection exposure apparatus has been proposed which uses a device which selectively energizes the transmissive electro-optical element to selectively make the transmissive electro-optical element at least partially shielded.

That is, at the time of exposure of an isolated pattern such as a contact hole, the variable operation means forms a pupil filter for blocking the 0th-order light passage region by energizing the variable pupil filter means, but the L & S pattern is used. As described above, during the exposure of the periodic pattern, the variable pupil filter means is not energized, and the pupil filter is not formed, so that the formation state of the pupil filter can be electrically switched as necessary. .

A typical example of the variable pupil filter means is an optical element which shields light when energized, such as one having an electrochromic element or one having a liquid crystal. Any element (member) having characteristics can be applied to other elements (members).

Further, even if the variable pupil filter means is constructed such that the light-shielding state is entirely changed when the variable operation means is energized, the variable operation means has a predetermined portion for the variable pupil filter means. It is also possible to adopt a structure in which the light-shielding state of only that portion changes when electricity is supplied to only that portion. Further, the light blocking area of the variable pupil filter means may be configured to be able to change into various patterns in accordance with the circuit pattern to be exposed.

With this, it is possible to obtain an illumination state that always suits the circuit pattern to be exposed, and it is easy to carry out without performing a process having a very bad workability such as attaching a pupil filter from the outside or taking it out from the inside. It is possible to form a pupil filter in.

Furthermore, in the fifth invention, in the first invention or the second invention, the variable pupil filter means is provided with a light-transmitting property provided corresponding to a zero-order light transmission region at the Fourier transform plane or a position in the vicinity thereof. There is proposed a projection exposure apparatus using the one having a fluid receiving chamber and changing the filter characteristic by selectively introducing a fluid into the fluid receiving chamber as the variable operating means.

That is, at the time of exposure of an isolated pattern such as a contact hole, the variable operation means forms a pupil filter by introducing a fluid into the fluid receiving chamber of the variable pupil filter means, but like the L & S pattern. At the time of periodic pattern exposure, the fluid is not introduced by the variable operation means, and the pupil filter is not formed.

Of course, the fluid receiving chamber into which the fluid is introduced may be one chamber having a size including the entire pupil or may be a plurality of chambers. When the fluid receiving chamber is divided into a plurality of portions, various light blocking states can be formed by partially introducing the fluid, and therefore the division pattern of the fluid receiving chamber may be determined according to the exposure pattern.

Here, examples of the fluid forming the pupil filter include liquids such as magnetic fluids, dyes, and black ink, but are not particularly limited as long as they have a property of blocking incident light. As a result, it is possible to achieve an illumination state that always matches the circuit pattern to be exposed, and it is possible to easily perform the pupil filter without performing steps with extremely poor workability, such as attaching or removing the pupil filter from the outside. Can be formed.

Furthermore, in any one of the first to third inventions, the variable pupil filter means is provided with a planar member having first and second filter portions having different light-shielding characteristics or polarization characteristics, and the variable operation means is provided. May change the filter characteristics by selectively arranging the first filter portion and the second filter portion of the planar member at the Fourier transform plane or a position in the vicinity thereof so as to be positioned.

In this case, the variable pupil filter means
It has at least a light-shielding (or polarizing) first filter section and a second filter section that transmits all the incident light, and the variable operating means can freely switch the filter section according to the exposure pattern. Thus, it is possible to cope with both the exposure state during the periodic pattern exposure and the exposure state during the isolated pattern exposure. Of course,
The variable pupil filter means may be composed of a plurality of filter parts, and in this case, the exposure condition can be finely controlled.

Here, for example, as the variable pupil filter means, one in which several filter parts having different optical characteristics are provided in one plane is used, and the variable pupil filter means is adjusted according to the mask pattern exposed by the variable operation means. An example is a configuration in which one filter unit is selected by rotation or parallel movement.

As another configuration example, the variable pupil filter means is provided with several filter parts having different optical characteristics in one plane, and the variable pupil filter means such as a take-up shutter has a shutter structure. In addition, the variable operation means winds (or sends out) the variable pupil filter means to move the position of the filter portion to select one filter portion.

Further, the variable pupil filter means is made into a tape shape, and the pupil filter transporting section composed of the sending reel and the take-up reel and the filter table for mounting the filter section at the Fourier transform plane position or a position in the vicinity thereof. And a configuration in which a filter unit having desired optical characteristics is selected by rotating each reel.

In this variable pupil filter means, when performing exposure of a periodic pattern such as an L & S pattern, the filter transport section exposes a transmission section having no light-shielding (or polarization) pattern, and a contact hole or the like. When performing the exposure of an isolated pattern such as, for example, a desired light-shielding (or polarization) pattern, such as deleting the 0th-order light in a predetermined area by rotating the delivery reel, appears, and again. When performing periodic pattern exposure, a configuration may be employed in which the light-transmitting portion (winding reel) is rotated in the reverse direction to expose a transparent portion having no light-shielding (or polarization) pattern.

Further, the rotation direction of the delivery reel may be fixed, and the light-shielding (or polarization) pattern corresponding to each pattern to be exposed and the transmitting portion may be exposed.

Of course, as the filter part, for example, one that blocks all (or part) of the incident light, one that does not block it at all, and one that blocks only the 0th-order light distributed in a predetermined region. Examples of the structure include a structure in which the polarization direction of 0th-order light distributed in a predetermined region and the polarization direction of light incident from another region are different, and the optical properties are provided as necessary. You can use one.

Further, in any one of the first to third inventions, the variable pupil filter means comprises a combination of a plurality of filter elements, and the variable operation means changes the combination arrangement of the plurality of filter elements. The filter characteristics may be changed by.

Since the space available for holding the variable pupil filter means is relatively small in the projection optical system, in this case, the variable pupil filter means is composed of a plurality of filter elements so as to correspond to this small space. It is divided and held.

Therefore, the variable operating means has a guide mechanism for guiding these plural elements to the 0th-order light passage region and combining them with a predetermined arrangement. Of course, when the pupil filter is not formed, the variable operation means is divided into a plurality of filter elements again and each filter element is guided to the space for holding the variable pupil filter means.

As a simple example of dividing the variable pupil filter means as described above and forming it when necessary, the variable pupil filter means has a blind structure in which a predetermined light-shielding pattern is drawn. An example is one in which the operation means controls the opening / closing operation of the plurality of elements forming the blind structure to form the pupil filter.

As a result, the pupil filter does not get in the way at the time of alignment, and the pupil filter can be easily formed without performing a process having a very bad workability such as attaching the pupil filter from the outside or taking it out from the inside. It is possible.

[0060]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the schematic construction of the entire projection exposure apparatus according to an embodiment of the present invention. In FIG. 1, the illumination light from the light source 1 converges on the second focal point by the elliptical mirror 2 and then becomes divergent light and enters the collimator lens 4. Here, a mercury lamp is used as a light source to obtain high-luminance illumination light. Further, a rotary shutter 3 is arranged at the second focus position, and the irradiation amount (passing or blocking) of illumination light is adjusted by the rotary shutter 3.

The illumination light converted into a substantially parallel light flux by the collimator lens 4 enters the interference filter 5.
The interference filter 5 transmits only the light of a desired wavelength (for example, i-line) required for exposure, and only the light of the required wavelength (i-line) is transmitted through the fly-eye lens 6 here. Will be incident on.

The fly-eye lens 6 is an optical member composed of a plurality of lens elements, and the illumination light (substantially parallel light flux) incident on the fly-eye lens 6 is divided by the plurality of lens elements of the fly-eye lens 6. A secondary light source image (image of the light emitting point of the mercury lamp 1) is formed on each exit side of each lens element. In other words,
On the exit side of the fly-eye lens 6, the same number of point light source images as the number of lens elements are distributed, and a surface light source image is formed.

Further, on the exit side of the fly-eye lens 6, a variable diaphragm 7 for adjusting the size of this surface light source image.
Is provided, the illumination light that is divided by the fly-eye lens 6 and converted into a light flux having a constant intensity distribution is adjusted in the incident angle range to the mask M by the diaphragm 7.

The illumination light (divergent light) that has passed through the diaphragm 7 is
After being reflected by the mirror 8 and entering the condenser lens system 9, the rectangular opening of the mask blind 10 is illuminated with a uniform illuminance distribution. Here, among the plurality of secondary light sources (point light sources) formed on the exit side of the fly-eye lens 6, only the illumination light from one secondary light source located on the optical axis AX is representatively shown.

The exit side of the fly-eye lens 6 (the surface on which the secondary light source image is formed) by the condenser lens system 9 is a Fourier transform surface with respect to the opening surface of the mask blind 10. Therefore, the respective illumination lights diverging from the plurality of secondary light sources of the fly-eye lens 6 and incident on the condenser lens system 9 are superimposed on the mask blind 10 as parallel light fluxes having slightly different incident angles. It

The illumination light that has passed through the opening of the mask blind 10 enters the condenser lens 13 via the relay lens system 11 and the mirror 12, and the condenser lens 13
The light emitted from becomes the illumination light ILB and reaches the mask M. Here, the opening surface of the mask blind 10 and the pattern surface of the mask M are arranged so as to be conjugate with each other by a combination system of the relay lens system 11 and the condenser lens 13, and the image of the opening of the mask blind 10 is the pattern surface of the mask M. An image is formed so as to include a rectangular pattern formation region formed inside.

The illumination light ILB from one secondary light source image located on the optical axis AX in the secondary light source image of the fly-eye lens 6 has no inclination with respect to the optical axis AX on the mask M. Although it is a parallel light beam, this is due to the projection optical system PL.
This is because the mask M side of is made telecentric.

Of course, on the exit side of the fly-eye lens 6,
Since a large number of secondary light source images (off-axis point light sources) that are displaced from the optical axis AX are formed, the illumination light from these large number of secondary light source images are all on the mask M on the optical axis AX. The parallel luminous flux is inclined with respect to and is superimposed in the pattern formation region.

It should be noted that the pattern surface of the mask M and the exit side surface of the fly-eye lens 6 are optically in a Fourier transform relationship by the combined system of the condenser lens system 9, the relay lens system 11, and the condenser lens 13. Needless to say.

Further, when the aperture diameter of the diaphragm 7 is reduced to reduce the substantial area of the surface light source, the incident angle range of the illumination light ILB is also reduced. That is, since the incident angle range of the illumination light ILB on the mask M changes depending on the aperture diameter of the diaphragm 7,
It can be said that the diaphragm 7 adjusts the spatial coherency of the illumination light.

A predetermined mask pattern is formed by a chrome layer on the pattern surface of the mask M. Here, the chrome layer is vapor-deposited on the entire surface and a minute rectangular opening (transparent without a chrome layer is formed therein). A plurality of contact hole patterns are formed.

The mask M is held on the mask stage MST, and the optical image (light intensity distribution) of the contact hole pattern of the mask M is imaged on the photoresist layer on the surface of the wafer W via the projection optical system PL. Here, the mask M
The optical path from the wafer to the wafer W is shown only by the chief ray of the image forming light beam. Then, the Fourier transform plane F in the projection optical system PL
The variable pupil filter 15 is arranged in TP.

In the first embodiment, the variable pupil filter 15
As an example, one using an electrochromic element that blocks incident light will be described. FIG. 2 shows a specific example of such a variable pupil filter 15, which is a schematic explanatory diagram when the variable pupil filter 15 is viewed from the mask M side. The variable pupil filter 15 is made of a transparent substrate and has a circular area 1 centered on the optical axis of the projection optical system PL.
5b is composed of an electrochromic element.

The variable pupil filter 15 is provided with a transparent electrode 15a whose voltage is controlled by the variable operation unit 14, and when a voltage is applied to the transparent electrode 15a, the electrochromic element serves as a light-shielding portion and within the circular area 15b. Blocks light that passes through.

Here, an example in which the incident light is shielded by using an electrochromic element is shown as an example, but the invention is not limited to the electrochromic element, and any element can be used as long as it changes the optical characteristics by changing the voltage. Other members such as liquid crystals may be used.

Further, the polarization direction of the light passing through the circular region 15b on the Fourier transform plane FTP centered on the optical axis of the projection optical system PL may be changed. In this case, another auxiliary member may be used in accordance with the property of the polarization control member provided in the circular area, such as providing a polarization adjusting member such as a polarizing plate in a part of the illumination optical system.

As described above, the variable pupil filter 15 blocks the central region including the optical axis AX on the Fourier transform plane FTP by converting the photochromic element forming region into a light-shielding portion or a light-transmitting portion according to the exposure pattern. It is shining. Specifically, in response to a command from the main control unit 19, the variable operation unit 14 causes the variable pupil filter 1 to operate.
The voltage applied to the photochromic element 5 is controlled to convert the central portion of the variable pupil filter 15 corresponding to the central portion of the Fourier transform surface FTP into a light shielding portion or a light transmitting portion.

The illumination light from the illumination optical system forms an image on the surface of the wafer W through the variable pupil filter 15, and the mask M
An image of the pattern is formed on the wafer W. The wafer W is held by the wafer stage WST, but the wafer stage WST can be two-dimensionally moved in the XY plane perpendicular to the optical axis AX, and is in the direction parallel to the optical axis AX (Z direction). Fine movement is possible.

The movement of the wafer stage WST in the XY direction and the Z direction is performed by the stage drive unit 16, and the movement in the XY direction is controlled according to the coordinate measurement value by the laser interferometer 17, and the Z movement is performed. Is controlled by the main control unit 19 based on the detection value of the focus sensor 18 for autofocus disclosed in, for example, JP-A-60-168112.

Further, in the apparatus of FIG. 1, a through-the-lens (TTL) type alignment sensor AS for detecting an alignment mark on a wafer via a projection optical system PL (see, for example, JP-A-60-130742). Disclosure T
A TL type sensor) is provided.

The signal from the alignment sensor AS and the coordinate measurement value by the laser interferometer 17 are sent to the main control unit 19, and the main control unit 19 receives the alignment sensor AS.
The position of the mark is detected based on the signal of 1 and the coordinate measurement value of the laser interferometer 17. The main control unit 19 controls the movement of the stage WST so that the wafer W is aligned with the mask M based on the mark position.

Further, the stage drive unit 16 is controlled by a main control unit 19, and the main control unit 19 drives not only the stage drive unit 16 but also the variable operation unit 14 and the shutter for controlling the rotary shutter 3. Unit 20, variable diaphragm 7 and mask blind 10 for adjusting the size of the surface light source image
The control of the aperture control unit 21 for adjusting the aperture of the device is performed.

The main control unit 19 also has a memory for inputting a mask name read by a bar code reader 22 provided in a mask transfer system (not shown) for transferring a mask to the mask stage MST. With this, the main control unit 19 comprehensively controls the operation of the variable operation unit 14, the operation of the shutter drive unit 20, the operation of the aperture control unit 21, etc. according to the input mask name, and the variable operation is performed. Whether or not a pupil filter PF (Pupil Filter) is formed by the unit 14 and the diaphragm 7
The size of each opening of the mask blind 10 and the intensity of the illumination light can be automatically adjusted according to the mask to be exposed.

That is, the mask M transferred from the mask transfer system (not shown) has its mask name read by the bar code reader 22 and stored in the memory of the main control unit 19 before being placed on the mask stage MST. .

The main control unit 19 reads the mask name to be arranged next on the mask stage from this memory, and drives the variable operation unit 14 and the stage based on the optimum exposure conditions for exposing the mask M. Commands are issued to the unit 16, the shutter drive unit 20, the aperture control unit 21, and the like.

As a result, the pattern of the mask M can be always exposed under the optimum exposure conditions. That is,
When performing exposure of an isolated pattern such as a contact hole pattern, for example, the variable operation unit 14 is used.
Issues a command to apply a voltage to the photochromic element of the variable pupil filter 15, controls the variable pupil filter 15, and causes the Fourier transform plane FTP to form a pupil filter PF (for example, a central light shielding type filter).

When the exposure time is lengthened, or when a periodic pattern such as an L & S pattern is exposed or when alignment is performed, the pupil filter PF is formed on the variable pupil filter 15 without applying a voltage to the photochromic element. Shorten the exposure time without doing so. In this way, it is possible to always perform exposure under optimum exposure conditions regardless of the mask pattern.

Further, the TTL type alignment sensor S
Since the variable operation unit 14 does not apply a voltage to the variable pupil filter 15 during wafer alignment using A, the pupil filter PF is not formed during alignment. As a result, the alignment light can be executed without the alignment light being blocked by the pupil filter PF.

Next, FIG. 3 shows a second configuration example of the variable pupil filter. FIG. 3 shows the schematic diagram of the projection optical system in the projection exposure apparatus as shown in FIG. FIG. 3 (a)
In, the Fourier transform plane FTP ₂ position of around the optical axis AX ₂ of the projection optical system PL ₂ in the projection optical system PL _2, variable pupil filter 25 is provided.

The variable pupil filter 25 is composed of a pupil filter surface 25a and a rotary drive system 24 such as a motor for rotating the pupil filter surface 25a. A variable operation unit (not shown) controls the rotary drive system 24 to form the pupil filter PF on the Fourier transform plane FTP ₂ . A perspective view of the variable pupil filter 25 is shown in FIG.

That is, when a variable operation unit (not shown) receives a command from a main control unit (not shown), the rotary shaft 24a of the rotary drive system 24 rotates by 90 degrees, and the pupil filter surface 25a moves. It is disposed at the position of the Fourier transform plane FTP ₂ or is removed from the Fourier transform plane FTP ₂ .

Although the structure of the pupil filter surface 25a is not particularly limited, for example, the Fourier transform surface FT is used.
P ₂ or the optical axis AX of the projection optical system PL _{2 in} the vicinity thereof
_It is preferable to use a light shielding plate, a polarizing plate, or the like so as to correspond to the 0th-order light transmission region distributed in the circular region centered on ₂ .

As a pupil filter using such a rotation axis, as shown in FIG. 3C, a variable pupil filter having a plurality of pupil filters around the rotation axis 24'a can also be mentioned. In this case, fine adjustment can be performed according to the exposure state. Further, when wafer alignment is performed using the TTL alignment sensor SA, the pupil filter PF is not formed during alignment by the variable operation unit.

Various methods are conceivable for mechanically forming the pupil filter PF, as shown in FIG.
FIG. 5 shows a simple perspective view of the third and fourth configuration examples. FIG. 4 is a perspective view of an example in which the variable pupil filter is configured like a fence. FIG. 4 shows two fences 35a of exactly the same size,
The variable pupil filter 35 has a structure in which 35b are overlapped, and the width w _{3 of} this fence is about 2 to avoid unevenness of the light amount as much as possible.
It is 3 μm.

In this figure, when the X fence 35a is on the front side of the drawing and the Y fence 35b is on the other side, the X fence is moved in the arrow direction (or the Y fence is moved in the arrow direction). As shown in the figure, since the gaps formed in each fence and the width of the fence are almost equal, if the gap of X fence is closed by Y fence in the Fourier transform plane, all the light incident on the pupil filter will be It is shielded from light.

When the X fence (or the Y fence) is moved in the direction opposite to the arrow direction, the fence portions of the X fence and the Y fence overlap each other. Therefore, in this state on the Fourier transform plane, the X filter enters the pupil filter. Half of the emitted light will be transmitted.

Of course, even if the light amount of about half of the incident light is lost, the decrease of the light amount can be compensated by lengthening the exposure time. Therefore, by using this fence-shaped pupil filter, the contact hole pattern can be sufficiently formed. It is possible to perform the exposure of the isolated pattern as described above and the exposure of the periodic pattern as the L & S pattern.

Of course, the variable operation unit (not shown)
The movement of the X fence (or the Y fence) is controlled by a drive system (not shown) to form or remove the pupil filter PF on the Fourier transform plane.

Further, FIG. 5 shows an example of a case where the variable pupil filter is configured in a blind shape. In this case, when the pupil filter PF is formed, it is closed as shown in FIG. 5, and when the pupil filter PF is not formed,
As shown by the dotted line in FIG. 5, the open state creates an exposure state that matches the pattern to be exposed.

Of course, the variable operation unit (not shown)
The opening / closing operation of the variable pupil filter 45 is controlled by a drive system (not shown) to form or remove the pupil filter PF on the Fourier transform plane.

FIG. 6 shows another configuration example of the variable pupil filter. 6, on the Fourier transform plane FTP ₅ of the optical axis AX ₅ projection optical system PL within ₅ around the projection optical system PL _5, it is provided with a variable pupil filter 55 which can form a pupil filter PF .

The variable pupil filter 55 is of a foldable type such as a roll-up shutter type. The variable operation unit, transport unit 5 for transporting the pupil filter 55 and the storage unit 54a for storing a variable pupil filter 55 to the Fourier transform plane FTP ₅
4b and the Fourier transform plane FT
Holding means 54 for holding the pupil filter 55 on P _5.
It consists of c and.

That is, when the pupil filter PF is required by a command from the main control unit (not shown), the guide means takes out the variable pupil filter 55 from the accommodating portion 54a to the outside and conveys it. It is transported to the Fourier transform plane FTP ₅ by section 54b. Wherein the Fourier transform plane FTP _5, the holding means 54c are provided, the holding means 54c has a configuration in which to hold the variable pupil filter 55 which is carried by the guide means.

On the contrary, when the pupil filter PF is unnecessary,
The guide means keeps the variable pupil filter 55 in the housing portion 54a when the variable pupil filter 55 is in the housing portion 54a, and when the variable pupil filter 55 is in the holding means 54c. The holding means 54
By storing the variable pupil filter 55 on c in the storage portion 54a by the transport portion 54b, the pupil filter P
F is removed.

Although the structure of the variable pupil filter 55 is not particularly limited, for example, the Fourier transform plane FT is used.
P ₅ or an optical axis A of the projection optical system PL _{5 on} the surface in the vicinity of P ₅ .
It is preferable to use a light shielding plate, a polarizing plate, or the like so as to correspond to the 0th-order light transmitting region distributed in the circular region centering on X ₅ .

As described above, another variable pupil filter is housed inside the projection optical system, and is taken out from the housing portion when necessary to form a pupil filter at the Fourier transform plane FTP position or at a position in the vicinity thereof. An example is shown in FIG.

FIG. 7A shows a variable pupil filter 6 for storing the pupil filter PF in the storage portion when it is unnecessary.
5 shows a state in which 5 is divided into a plurality of filter elements a to f. In this case, the individual filter elements a to f are equilateral triangles having exactly the same size, but the variable pupil filter 65 is not limited to this shape, as a matter of course.
For example, any shape such as a dodecagonal shape may be used as long as it functions as the pupil filter PF when all the filter elements are combined.

In FIG. 7A, the individual filter elements a to f are integrally formed by the guide portion 64 so as not to fall apart, and are housed in a projection optical system (not shown) so as not to interfere. There is.

At the time of forming the pupil filter PF, as shown in FIG. 7 (b), the Fourier transform surface FTP ₆ can be easily formed by connecting the peripheral edge of the guide portion 64 and the other peripheral edge.
Alternatively, the pupil filter PF can be formed on the surface in the vicinity thereof. Of course, it is possible to easily obtain the pupil filter PF having such a configuration by using an elastic member such as rubber or a flexible member as the guide means. Of course,
The guide means may have another structure.

FIG. 8 shows another example of the configuration of the variable pupil filter. In FIG. 8, a light blocking tape 75 having a plurality of light blocking patterns drawn as a variable pupil filter.
The holding means 74c for holding the light shielding tape 75 on the Fourier transform surface FTP ₇ , the delivery reel 74a for carrying the light shielding tape 75 toward the holding means 74c, and the light shielding tape 75 from the holding means 74c are used. And a take-up reel 74b for taking up the film are provided in the projection optical system PL ₇ .

The light-shielding tape 75 has a light-shielding pattern drawn according to the pattern to be exposed, and the pattern is moved by the rotation of the delivery reel 74a and the take-up reel 74b. In this figure, the delivery reel 74a and the take-up reel 74b are configured to be rotatable in one direction. By moving a long light-shielding tape on which various patterns are drawn in one direction,
A pupil filter PF is formed on the Fourier transform plane,
The exposure conditions such as light intensity distribution and intensity are finely adjusted.

As a matter of course, as a structure which can rotate in the opposite direction,
The light shielding tape 75 is provided with at least two types of patterns such as an area for an isolated pattern and an area for a periodic pattern, and the rotation directions of the delivery reel 74a and the take-up reel 74b are changed. It is also possible to easily control the exposure conditions by just using this. In this case, since the tape to be wound is short, the pupil filter PF can be housed compactly in the projection optical system PL ₇ .

Further, FIG. 9 shows an example of a variable pupil filter provided with a plurality of filter parts in one plane. FIG. 9 is a top view of such a variable pupil filter. The variable pupil filter 85 in FIG. 9 includes five types of filter parts. The optical characteristics of the respective filter parts are, for example, a filter part that blocks the light that is incident on the entire surface and a light shield that partially blocks the light that is incident. The filter unit has a configuration in which the filter characteristics can be selected and used in accordance with the pattern to be exposed, such as a filter unit that controls light, a filter unit that does not block light at all, and a filter unit that changes the polarization direction of only the incident 0th order light.

Therefore, a variable operation unit (not shown)
Is the variable pupil filter 85.
The pupil filter PF is formed on the Fourier transform surface by rotating the surface around the rotation axis 84 in the plane including the, and the exposure conditions such as the distribution and intensity of the light quantity are finely adjusted.

Further, FIG. 10A shows still another configuration example of the variable pupil filter used in the projection exposure apparatus as shown in FIG. In FIG. 10A, in the Fourier transform surface FTP ₉ in the projection optical system PL ₉ , a region corresponding to the 0th-order light transmitting region of the Fourier transform surface or a surface in the vicinity thereof is a fluid receiving chamber. The boards are arranged.

The fluid receiving chamber is connected to a liquid introducing pipe 94a and a liquid outlet pipe 94b extending from the liquid holding tank 94c in the projection optical system PL ₉ , and the liquid introducing pipe 94 is provided.
The liquid a and the liquid outlet pipe 94b are connected to the liquid controller 94, respectively.

The liquid control section 94 includes a liquid holding tank 9
The liquid sucked from 4c is introduced into the fluid receiving chamber, or the liquid drawn out from the fluid receiving chamber is returned to the liquid holding tank 94c to control the pupil filter PF on the Fourier transform plane FTP. It plays the role of a variable operation unit that is formed and removed.

FIG. 10B is an explanatory diagram showing the schematic structure of the pupil filter PF shown in FIG. 10A. Figure 10
In (b), a fluid receiving chamber 92 for introducing a liquid is provided in the central portion of the transparent substrate 91, and the fluid receiving chamber 92 communicates with the liquid introducing pipe 94a and the liquid outlet pipe 94b. Has been done. The liquid introduction pipe 94a
Is connected to one peripheral edge of the fluid receiving chamber 92, and a liquid outlet pipe 94b is provided at a peripheral edge position facing the peripheral edge.

Further, the other ends of the liquid introduction pipe 94a and the liquid discharge pipe 94b which are not connected to the fluid receiving chamber 92 are connected to the liquid control unit 94, and the liquid control unit 94 further includes It is connected to a liquid holding tank (not shown).

Therefore, when the pupil filter PF is formed, the liquid control unit 94 sucks the liquid from the liquid holding tank and guides it to the liquid introduction pipe 94a, and at the same time, the air is ejected from the fluid receiving chamber 92 through the liquid discharge pipe 94b. By sucking
The fluid receiving chamber 92 is filled with a liquid.

On the contrary, when the pupil filter PF is not formed, the liquid controller 94 sucks the liquid from the fluid receiving chamber 92 through the liquid outlet pipe 94b and returns it to the liquid holding tank, and the liquid inlet pipe 94a. The liquid in the fluid receiving chamber 92 is removed by sucking air through the.

[0122]

As described above, according to the present invention,
A good exposure condition can be given not only in the exposure of an isolated pattern but also in all the exposure steps. Therefore, it is possible to obtain a projection exposure apparatus which can be applied to all the exposure steps of manufacturing a semiconductor device or the like. You can

Further, since the pupil filter means can be easily provided on the Fourier transform plane or the neighboring plane, it is possible to obtain a projection exposure apparatus which saves labor and shortens the total exposure time. As a result, it is possible to obtain a projection exposure apparatus with good manufacturing efficiency.

In addition, even in the TTL type wafer alignment, the alignment filter is not blocked by the variable operation means so that alignment light is not blocked by the variable operation means, and good alignment is always possible.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a variable pupil filter according to the first embodiment of this invention.

FIG. 3 is a schematic diagram of a projection optical system including a variable pupil filter according to a second embodiment of the present invention and an explanatory diagram of the variable pupil filter.

FIG. 4 is a perspective view of a fence-shaped variable pupil filter according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a main part of a blind variable pupil filter according to a fourth embodiment of the present invention.

FIG. 6 is a schematic diagram of a projection optical system including a variable pupil filter according to a fifth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a variable pupil filter according to a sixth embodiment of the present invention, and FIG. 7A is an explanatory diagram showing a shape for storing the pupil filter by dividing it into a plurality of elements; FIG. 7B is an explanatory diagram showing a state in which FIG. 7A is formed as a pupil filter.

FIG. 8 is a schematic diagram of a projection optical system including a tape-shaped variable pupil filter according to a seventh embodiment of the present invention.

FIG. 9 is a top view of a variable pupil filter according to an eighth embodiment of the present invention.

FIG. 10A is a schematic view of a projection optical system including a variable pupil filter according to a ninth embodiment of the present invention,
FIG. 10B is an explanatory diagram showing a schematic configuration of the target pupil filter used at this time.

[Explanation of symbols]

 1 Light Source 2 Elliptical Mirror 3 Rotary Shutter 4 Collimator Lens 5 Interference Filter 6 Fly Eye Lens 7 Aperture 8 Mirror 9 Condensing Lens System 10 Mask Blind 11 Relay Lens System 12 Mirror 13 Condenser Lens 14 Variable Operation Unit 15, 25, 55, 65 , 85, 95 Pupil filter 15a Transparent electrode 15b Circular area 16 Stage drive unit 17 Laser interferometer 18 Focus sensor 19 Main control unit 20 Shutter drive unit 21 Aperture control unit 22 Bar code reader 24, 84 Rotation axis 25a, 85a to 85e Pupil Filter surface 54a Storage part 54b Transport parts 54c, 74c Holding means 64 Guide part 75 Light-shielding tape 74a Sending reel 74b Take-up reel 91 Transparent substrate 92 Fluid receiving chamber 94 Liquid system Part 94a liquid introducing pipe 94b the liquid outlet pipe 94c liquid holding tank FTP Fourier transform plane PL projection optical system AX optical axis ILB illumination light M mask W wafer MST mask stage WST wafer stage a~f filter element

Claims (5)

[Claims] 1. An illumination optical system for irradiating a mask on which a predetermined pattern is formed with illumination light for exposure, and an image of the pattern is formed on a photosensitive substrate by the light generated from the pattern of the mask. In a projection exposure apparatus including a projection optical system, variable pupil filter means arranged at or near a Fourier transform plane in an image forming optical path between the mask and the photosensitive substrate, and image forming light for the photosensitive substrate. And a variable operating means for changing the filter characteristic of the variable pupil filter means so as to change the irradiation state of the projection exposure apparatus. 2. The variable pupil filter means selectively removes 0th-order light distributed in a predetermined area centered on the optical axis of the projection optical system based on an operation of the variable operation means. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is a device. 3. The variable pupil filter means selectively selects a polarization state of 0th-order light distributed in a predetermined area centered on the optical axis of the projection optical system based on an operation of the variable operation means. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is changed. 4. The variable pupil filter means includes a transmissive electro-optical element provided corresponding to a 0th-order light transmission region at or near the Fourier transform plane, and the variable operation means comprises the transmission means. The projection exposure according to claim 1 or 2, wherein the transmission type electro-optical element is selectively made at least partially in a light-shielding state by controlling energization to the transmission type electro-optical element. apparatus. 5. The variable pupil filter means comprises a light-transmissive fluid receiving chamber provided corresponding to a 0th-order light transmission region at or near the Fourier transform plane, and the variable operation means comprises: 3. The projection exposure apparatus according to claim 1, wherein the filter characteristic is changed by selectively introducing a fluid into the fluid receiving chamber.