JPH08148411A - Projecting aligner - Google Patents

Abstract

PURPOSE: To build an optimum projecting optical system responsive to an exposure pattern without using a filter inserting and removing mechanism. CONSTITUTION: Optical members (PF1 , PF2 ) having an air gap of a protruding section are installed on the Fourier transformed surface or its vicinity surface of a projecting optical system PL, fluid having a refractive index responsive to the pattern of a reticle for exposing is filled in the gap, and hence the members can be functioned as a parallel flat plate glass material or a phase difference type or interference reducing type pupil filter in response to an exposure pattern.

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 used for forming a fine pattern on a semiconductor integrated circuit, a liquid crystal display substrate or the like, and in particular, it is possible to optimize an optical system according to the pattern to be exposed. The present invention relates to a projection exposure apparatus.

[0002]

2. Description of the Related Art A projection optical system mounted on a projection exposure apparatus of this type is incorporated into the apparatus through an advanced optical design, careful selection of glass materials, precision processing of glass materials, and precise assembly and adjustment.
Currently, in the semiconductor manufacturing process, i-line (wavelength 3
The mainstream is a stepper that irradiates a reticle (mask) with (65 nm) as illumination light and forms an image of the transmitted light of a circuit pattern on the reticle on a photosensitive substrate (wafer or the like) via a projection optical system.

Generally, in order to faithfully transfer a fine reticle pattern onto a photosensitive substrate by exposure using a projection optical system, the resolution and depth of focus (DOF: De) of the projection optical system are used.
pth Of Focus) is an important factor. As for the projection optical system for the i-line, the one having the image side numerical aperture NA adjusted to about 0.6 is currently put into practical use.

By the way, if the wavelength of the illumination light is λ between the numerical aperture NA and the depth of focus DOF of the projection optical system, D
It is known that the relation of OF = ± λ / (2 × NA ² ) is established. Then, when the wavelengths λ of the illumination light used are the same, in order to enhance the resolution of the projection optical system, the numerical aperture NAw on the photosensitive substrate side (image side) of the projection optical system (or the numerical aperture NAr on the mask side NAr ), In other words, it is necessary to increase the pupil diameter of the projection optical system and the effective diameter of the lens diameter or the mirror diameter. However, as described above, the depth of focus DOF decreases in inverse proportion to the square of the numerical aperture NAw. Therefore, even if a projection optical system with a high numerical aperture can be manufactured, the required depth of focus can be obtained. This was a big obstacle for practical use.

For example, the wavelength of the illumination light is 365 nm for i-line.
And the numerical aperture NAw is 0.6, the depth of focus DOF
Is about 1 μm (± 0.5 μm) in width, and one shot area (20
mm square to about 30 mm square), there is a possibility that the unevenness or curvature of the surface may cause poor resolution in a portion having a depth of focus DOF or more.

In order to solve such a problem, the phase shift method (Japanese Patent Publication No. 62-50811) and the SHRINC method (Japanese Patent Laid-Open No. 4-101148, Japanese Patent Laid-Open No. 4-180612, Japanese Patent Laid-Open No. 4-180613, etc.) ) And so-called super-resolution techniques have been proposed. However, these techniques are extremely effective for improving the resolution and increasing the depth of focus for a pattern having a relatively high pattern density and a periodic pattern, for example, a line and space pattern. It was not possible to obtain the effect for the discrete and isolated pattern called ".

Therefore, as an exposure method for increasing the apparent depth of focus even for an isolated pattern such as a contact hole pattern, the exposure for one shot area of the wafer W is divided into a plurality of times, and the wafer is separated between each exposure. A method of moving W in the optical axis direction by a certain amount, so-called FLEX
(Focus Latitude enhance
nt EXPOSURE) method is disclosed in, for example, JP-A-63-4.
It is proposed in Japanese Patent No. 2122. However,
Since this FLEX method requires multiple exposure of a slightly defocused contact hole image, the resist image obtained after development inevitably had a sharpness lowered.

Further, as an attempt to expand the depth of focus at the time of projecting the contact hole pattern without moving the wafer W during the exposure operation as in the FLEX method, 199
The Super-FLEX method is proposed in Proceedings 28a-ZC-8, 9 of the 1st Spring Society of Applied Physics. In this Super-FLEX method, a filter having a concentric amplitude transmission distribution centered on the optical axis is provided on the pupil plane of the projection optical system (that is, the Fourier transform plane for the reticle), and the resolution and focus are adjusted by the action of this filter. It increases the depth.

It is desirable that the amplitude transmittance distribution formed in the above filter continuously changes in the radial direction of the pupil plane, but since such a filter is difficult to manufacture, it is actually specified. An optical filter whose amplitude transmittance, that is, phase difference, changes stepwise from negative to positive at the radius of (hereinafter, referred to as “phase difference pupil filter”), and the phase difference pupil filter is projected. Attempts have been made to install it on the Fourier transform plane of an optical system.

Further, an optical filter (hereinafter referred to as a "coherence reduction type pupil filter") for exchanging the image-forming light beams into a plurality of light beams which do not interfere with each other is installed on the pupil plane of the projection optical system PL. A method for increasing the depth of focus during projection exposure of an isolated pattern such as a contact hole, so-called S
FINCS method (Spatial Filter for)
INCherent Stream) is disclosed in Japanese Patent Laid-Open No. 6-
It is proposed in Japanese Patent No. 120110, Japanese Patent Application Laid-Open No. 6-124870, and the like.

The phase type pupil filter or the coherence reduction type pupil filter F having the above optical characteristics is shown in FIG.
As shown in, a circular transmissive area FA having a radius r ₂ is formed at the center of at least one surface of a circular transparent parallel substrate having a radius r ₁ slightly larger than the effective radius of the pupil plane of the projection optical system PL. As described above, the peripheral annular transmission region FB is configured as an optical filter having a convex cross section by etching by the step d, and is installed on the pupil plane of the projection optical system PL, that is, the Fourier transform plane FTP or in the vicinity thereof. It had been. The value of the radius r _{2 and} the value of the step d that define the circular transmissive portion FA are optimally determined according to the required phase difference and the coherence reduction state.

By the way, each of the optical filters F provided on the pupil plane of the projection optical system PL as described above has a minute transmissive aperture pattern in a light-shielding region (chrome vapor deposition or the like) of the reticle, such as a contact hole pattern. Works effectively for patterns that are discrete and isolated,
Line and space pattern (brightness width is about 1: 1
With respect to the repetition and the proximity pattern), the depth of focus may be decreased or the resolution may be decreased (false resolution).

Therefore, in the conventional projection exposure apparatus, the optical filter F as described above is adapted to the pattern to be exposed by the filter insertion / removal mechanism FD provided adjacent to the projection optical system PL as shown in FIG. It is configured so that it can be inserted into and removed from the Fourier transform plane FTP of the projection optical system PL. Then, for example, when exposing the contact hole pattern, the optical filter F is inserted into the projection optical system PL, and when exposing the line and space pattern, for example, the optical filter F is inserted into the projection optical system PL. There has been an attempt to always obtain high resolution and depth of focus regardless of the type of exposure pattern.

[0014]

However, in the above-mentioned configuration, it is necessary to provide a mechanical portion for attaching and detaching the optical filter F (that is, the filter inserting / removing mechanism FD), and the apparatus is large in size corresponding to the installation space. There was a problem of becoming. Further, since the drive unit of the filter insertion / removal mechanism FD serves as a dust source, it is necessary to take measures to prevent the dust from being mixed into the pupil surface. Further, when the optical filter F is inserted into the pupil plane of the projection optical system PL, strict positioning accuracy is required, so that control is difficult and stable imaging performance is difficult to obtain.

The present invention has been made in view of the above problems of an exposure apparatus having a conventional filter insertion / removal mechanism, and an object thereof is to reduce mechanical parts.
It is possible to save space, suppress dust generation, and eliminate the need for mechanical insertion / removal of the optical filter, which clears the problem of pupil filter positioning accuracy and reduces the type of pattern to be exposed. Nevertheless, it is an object of the present invention to provide a new and improved projection exposure apparatus capable of obtaining stable image forming performance.

[0016]

In order to solve such a problem, a projection exposure apparatus constructed according to the present invention, that is, a fine pattern (for example, a contact hole pattern or a line and space pattern) is formed. Illuminating means (1 to 14) for illuminating the formed mask (reticle R) with exposure illumination light, and projecting an image of the pattern onto a photosensitive substrate (eg, wafer W) by injecting light generated from the pattern of the mask. Projection optical system (PL) and an optical Fourier transform plane (F) in the imaging optical path between the mask and the photosensitive substrate.
TP), or imaging light distributed in the vicinity thereof and distributed in a circular area (FA) centered on the optical axis (AX) of the projection optical system and imaging light distributed in an area (FB) outside thereof. Is a projection exposure apparatus provided with an optical filter (PF) that reduces coherence between the optical filter and the optical filter (PF), and the circular region is convex on at least one side with respect to the incident side or the exit side. A light-transmissive member (PF ₁ , PF ₂ ) having a refractive index of n ₁ and having an entrance surface and an exit surface of the light-transmissive member and the air gap. It is formed as a plane parallel to the optical axis of the system as a vertical line, and the voids thereof are exchangeably filled with fluids (for example, liquid or gas) having different refractive indexes (n ₂ ).

Then, for example, a line and space pattern
In the case of exposure processing that does not require a pupil filter such as turn
Is a fluid (e.g.
Chi, n ₁= N₂) Is preferred, for example
Dew that requires a pupil filter, such as the pattern for tact holes.
In the case of light treatment, use a fluid with a refractive index different from that of the translucent member.
Filling is preferred.

Further, the step d of the convex portion of the gap of the transparent member.
When a phase difference type pupil filter is constructed, the phase difference to be given between two image forming lights is PC, the refractive index of the transparent member is n ₁ , and the refraction of one fluid filled in the void is Rate n ₂ ,
When the wavelength of the illumination light is λ, d = λ · PC / {2π (n ₁ −n ₂ )} is set.

Alternatively, in the case of constructing a pupil filter with reduced interference, the step d of the convex portion of the void of the transparent member has a refractive index of n ₁ of the transparent member and a fluid filled in the void. When the refractive index is n ₂ and the coherent length of the illumination light is ΔLc,

[0020]

[Equation 2]

Is set as follows.

[0022]

In the projection exposure apparatus configured as described above, a fluid having a different refractive index depending on, for example, the pattern of the mask to be exposed is put in or taken out of the gap formed in the translucent member. Regardless of the type, it is possible to build an optimal projection optical system that always has a high depth of focus and resolution. Further, since the mechanical filter insertion / removal mechanism of the conventional device can be omitted, it is possible to simplify the structure and save the space of the device, and to be free from the dust countermeasures caused by the filter insertion / removal mechanism. . Also,
Since it is not necessary to perform the alignment for each insertion / removal operation, stable image forming performance can be obtained only by the initial setting adjustment.

More specifically, for example, when exposure is performed with a line-and-space pattern, as shown in FIG. 4, the light-transmissive member is placed in a space formed in the light-transmissive member. By filling with a fluid having a refractive index substantially equal to that of the refractive index (that is, n ₁ = n ₂ ), it becomes possible to cause the light-transmissive member to function substantially like flat glass, and to achieve high resolution and It is possible to obtain the depth of focus. On the other hand, for example, when performing exposure with a pattern for a contact hole, as shown in FIG. 5, a refractive index different from the refractive index of the transparent member is provided in the void formed in the transparent member. By filling the fluid (that is, n ₁ ≠ n ₂ ) with, the void can be made to function as a phase difference type pupil filter or a coherence reduction type pupil filter, and the depth of focus can be expanded. Becomes

The step d of the convex portion of the void of the transparent member is
According to the phase difference PC to be given between the two image-forming lights, the refractive index of the transparent member is n ₁ , the refractive index of one fluid filled in the void is n ₂ , and the wavelength of the illumination light is λ. Then, by setting so that d = λ · PC / {2π (n ₁ −n ₂ )}, a phase difference type pupil filter capable of enhancing the resolution and expanding the depth of focus should be constructed. You can

Alternatively, the step d of the convex portion of the gap of the transparent member is such that the refractive index of the transparent member is n ₁ , the refractive index of the fluid filled in the gap is n ₂ , and the coherent length of the illumination light is ΔLc. And when

[0026]

(Equation 3)

By setting so that it becomes possible to construct a coherence reduction type pupil filter capable of increasing the resolution and expanding the depth of focus with a simpler configuration.

[0028]

1 shows the overall construction of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 1, the high-intensity light emitted from the mercury lamp 1 is converged on the second focal point by the elliptic mirror 2 and then becomes divergent light and enters the collimator lens 4. A rotary shutter 3 is arranged at the position of the second focal point, and controls passage and blocking of illumination light. The illumination light converted into a substantially parallel light flux by the collimator lens 4 is incident on the interference filter 5, where only a desired spectrum required for exposure, for example, i-line (wavelength 365 nm) is extracted. The illumination light (i-line) emitted from the interference filter 5 is
Fly's eye lens 7 as an optical integrator
Incident on. The light source used in the exposure apparatus according to the present invention is not limited to a bright line lamp such as a mercury lamp, but a laser light source or the like can be used, for example.

The illumination light (substantially parallel luminous flux) incident on the fly-eye lens 7 is divided by a plurality of lens elements of the fly-eye lens 7, and a secondary light source (mercury lamp) is provided on each emission side of each lens element. 1) is formed. That is, the fly-eye lens 7
A surface light source image in which the same number of point light source images as the number of lens elements are distributed is formed on the exit side of. A variable diaphragm 8 for adjusting the size of the surface light source image is provided on the exit side of the fly-eye lens 7. Illumination light (divergent light) that has passed through the variable diaphragm 8 is reflected by a mirror 9 and enters a condenser lens system 10 and then an illumination field diaphragm (reticle blind) 11
Irradiate the opening with a uniform illuminance distribution. The reticle blind 1 is provided on the exit side of the fly-eye lens 7 (that is, the surface on which the secondary light source image is formed) by the condenser lens system 10.
It is a Fourier transform plane for the aperture plane of 1. Therefore, the respective illumination lights that have diverged from each of the plurality of secondary light source images of the fly-eye lens 7 and have entered the condenser lens system 10 are superimposed on the reticle blind 11 as parallel light beams having slightly different incident angles. It

The illumination light passing through the opening of the reticle blind 11 passes through the lens system 12 and the mirror 13 and enters the condenser lens 14, and the light emitted from the condenser lens 14 reaches the reticle R as illumination light ILB. Here, the opening surface of the reticle blind 11 and the pattern surface of the reticle R are arranged so as to be conjugate with each other by the synthetic optical system of the lens system 12 and the condenser lens 14, and the image of the opening of the reticle blind 11 is the pattern surface of the reticle R. An image is formed so as to include a pattern formation region formed inside. Since the pattern surface of the reticle R and the exit side surface of the fly-eye lens 7 have a Fourier transform relationship by the synthetic optical system of the condenser lens system 10, the lens system 12, and the condenser lens 14, a plurality of fly-eye lenses 7 are arranged. On the reticle R, the respective illumination light from the secondary light source image becomes a parallel light flux that is slightly inclined with respect to the optical axis AX and is superimposed in the pattern formation area.

On the pattern surface of the reticle R, a predetermined reticle pattern is formed by a chrome layer. This reticle pattern has a relatively high density in the chrome layer, and in addition to the line-and-space pattern in which the light transmission openings are periodically formed, the reticle pattern is discrete and isolated from the chrome layer deposited on the entire surface. Pattern for contact holes with a very small aperture for light transmission is
It is appropriately selected and used according to the lithography process.

As shown in FIG. 1, the reticle R is held on the reticle stage RST, and the optical image (light intensity distribution) of the pattern of the reticle R is transferred to the wafer through the projection optical system PL which is telecentric on at least the reticle side. An image is formed on the photoresist layer on the surface of W. Then, by supplying or discharging a predetermined fluid to or from the Fourier transform plane FTP in the projection optical system PL via the fluid supply mechanism 20 and the fluid discharge mechanism 21, the reticle R is removed.
An optical filter PF capable of forming an optimum optical system is installed according to the type of pattern, and its detailed structure will be described later.

The wafer W moves two-dimensionally in the plane perpendicular to the optical axis AX (hereinafter referred to as XY movement), and also moves slightly in the direction parallel to the optical axis AX (hereinafter referred to as Z movement). ) Is held on the wafer stage WST. The XY movement and the Z movement of the wafer stage WXT are performed by the stage drive unit 22, the XY movement is controlled according to the coordinate measurement value by the laser interferometer 23, and the Z movement is performed by the focus sensor 2 for autofocus.
It is controlled based on the detected value of 4. The stage drive unit 22 operates according to a command from the main control unit 25. The main control unit 25 further sends a command to the shutter drive unit 26 to control the opening / closing of the shutter 3 and also sends a command to the aperture control unit 27 to stop the aperture 8.
Alternatively, the size of each opening of the reticle blind 11 is controlled. Further, the main control unit 25 uses the reticle stage RS
Information about each reticle read by the bar code reader 28 provided in the conveyance path of the reticle R to the T can be input. Therefore, the main control unit 25
The operations of the fluid supply mechanism 20, the fluid discharge mechanism 21, the aperture drive unit 27, and the like are comprehensively controlled according to the input information about the reticle, and the diaphragm 8 and the reticle blind 1 are controlled.
Each aperture size 1 and the type of pupil filter PF can be automatically adjusted according to the reticle.

Next, the optical filter PF installed on the pupil plane of the projection optical system PL will be described with reference to FIGS. As shown in FIG. 2 (A), the optical filter PF is formed by attaching transparent circular substrates (glass, quartz, etc.) PF ₁ and PF ₂ having a diameter r ₃ larger than the effective maximum diameter r ₁ ′ of the pupil. It is configured by The optical axis AX of the projection optical system PL is attached to the attachment surface of the upper transparent circular substrate PF _1.
A cylindrical void having a radius r ₂ centered at and a depth of d is formed by etching. Similarly, a cylindrical void having an appropriate depth with a radius r ₁ centered on the optical axis AX of the projection optical system is formed on the attachment surface of the lower transparent circular substrate PF ₂ by etching. Therefore, the upper and lower two transparent circular substrates PF
By laminating ₁ and PF ₂ , an optical filter PF having a void with a convex cross section in the center is formed.

The outer diameter r ₁ of the ring-shaped transparent region (FB) having the convex cross section shown in FIG. 2B is selected to be slightly larger than the effective radius r ₁ ′ of the pupil. The inner diameter of the ring-shaped light-transmitting region (FB), that is, the radius r ₂ of the circular light-transmitting region (FA), which is the convex portion of the convex cross section, is selected to be optimum according to the required optical characteristics. It For example, when forming a phase difference type pupil filter, the projection exposure system PL
In the type in which the amplitude transmittance in the vicinity of the optical axis of -1 is −1 and the peripheral transmittance changes stepwise to +1, the ratio of the radius r _{2 to} the pupil plane radius r ₁ ′ is set to about 0.2 to 0.25. It has been proved by the applicant's simulation that good results can be obtained. When constructing a coherence reduction pupil filter based on the SFNICS method, it is necessary to set so that the effective maximum radius r ₁ ′ of the pupil is r ₁ ' ² = 2r ₂ ^2. preferable. In other words, the area of the area pi] r ₂ ² of circular transmitting portion of the radius r ₂ is the effective pupil aperture pi] r ₁ ^'2
It is possible to configure about half.

The convex step d of the convex cross section is selected so as to be optimum according to the required optical characteristics or the type of the optical filter to be constructed. For example, in the case of configuring a phase difference pupil filter, the step d of the convex portion has a refractive index n ₁ of the translucent member and a gap of a gap depending on the phase difference PC to be given between the two image forming lights. It is possible to set d = λ · PC / {2π (n ₁ −n ₂ )}, where n _{2 is} the refractive index of one fluid to be filled and λ is the wavelength of the illumination light. . Therefore, the i-line (wavelength λ = 365 nm) of the mercury lamp is used as the illumination light, and the glass having the refractive index n ₁ of 1.5 is used as the translucent member (PF ₁ and PF ₂ ) to fill the space. , Which has a refractive index of about 1, is used as the phase difference PC = π [ra
In order to obtain d], the step d is (1.5) × 365 =
It may be 182.5 nm.

Further, in the case of constructing the pupil filter for reducing interference, the step d of the convex portion of the void of the transparent member has a refractive index of n ₁ of the transparent member, and When the refractive index is n ₂ and the coherent length of the illumination light is ΔLc,

[0038]

[Equation 4]

It is possible to set as follows.
For example, when the i-line of a mercury lamp (wavelength λ = 365 nm) is used as a light source, the wavelength width Δλ of this light source is 5 nm.
Therefore, the coherent length ΔLC is ΔLC = λ ² /
Δλ = 26 μm. Therefore, glass having a refractive index n ₁ of 1.5 is used as the translucent member (PF ₁ and PF ₂ ),
When air having a refractive index of about 1 is used as the fluid to fill the gap, the step d may be set to 52 μm or more.

Further, the transparent circular substrate PF₁And PF₂Pasting
At least one on at least one of the surfaces
The groove of the book is diametrically cut through
The convex cross section formed on the attachment surface of the transparent circular substrate.
At least two places inside and outside the void are connected.
It is configured to pass through. And these communication grooves
(However, transparent circular substrate PF₁And PF₂After attaching
Through holes) 20a, 21a, as shown in FIG.
The through hole 20a is connected to the fluid supply mechanism 20, and
The other communication hole 21a is connected to the fluid discharge mechanism 21,
As will be described later, the type of reticle R pattern to be exposed
Refractive index (n₂Supply or discharge fluid with
It is possible to It should be noted that all of FIG. 3 are made of refractive glass material.
2 shows a partial cross section of the projected projection optical system PL,
Lens GA at the bottom of lens system GA ₁And rear lens system G
Fourier transform to the space between the top lens GB1 of B
There is a surface FTP, and this Fourier transform surface FTP or its
A pupil filter PF having the above configuration is installed in the vicinity.
It The projection optical system PL holds a plurality of lenses with a lens barrel.
However, the communication provided in the pupil filter PF of FIG.
The communication hole 20 is provided in a part of the lens barrel facing the holes 20a and 21a.
b and 21b are drilled. Then, in the communication hole 20b
Is a fluid supply mechanism via a conduit 20c and a valve 20d.
20 is connected, and the conduit 2 is provided in the communication hole 21b.
Fluid discharge mechanism 21 is connected via 1c and valve 21d
Has been done.

Next, referring to FIG. 4 and FIG.
The operation of the projection exposure apparatus according to the example will be described. Sude
As described above, the pattern of the reticle R to be exposed is
Type (for example, line and space pattern or
Pattern for contact holes) is the reticle stage RS
By a bar code reader 28 provided in the transport path to T
Information is input to the main control unit 25
It And the pattern to be exposed has a relatively high pattern density.
High and periodic line and space pattern
If it is, the pupil plane is
It is better not to install the filter PF for better resolution and wider focus.
Since the point depth can be obtained, the main control unit 25
Sends a command to the fluid supply mechanism 20 and the fluid discharge mechanism 21.
As shown in FIG. 4, a transparent circular base forming the pupil filter PF
Board PF₁And PF₂Refractive index n of₁Refractive index n equal to₂(sand
That ’s n₁= N₂) Is supplied to the void of convex cross section,
After bubbles etc. are completely removed, valves 20d and 21d
Close. As a result, the transparent circular substrate PF ₁And PF₂of
Refractive index n₁And the refractive index n of the filled fluid₂Is equal to
Then, the pupil filter PF is equivalent to parallel plate glass, and
-Reducing the phase difference or coherence in the transmitted light that passes through the Fourier conversion surface
Pattern for line and space that does not cause a state
It is possible to configure a projection optical system PL that is optimal for transferring
Become.

On the other hand, when the type of reticle R identified by the barcode reader 28 is a discrete and isolated pattern, for example, a contact hole pattern, a phase difference type pupil filter or interference is formed on the pupil plane. It is preferable to interpose the pupil reduction filter PF. Therefore, the main control unit 25 sends a command to the fluid supply mechanism 20 and the fluid discharge mechanism 21, and already has a refractive index equal to the refractive index n ₁ of the transparent circular substrates PF ₁ and PF _{2 in} the void of the convex cross section of the optical filter PF. When the fluid of n ₂ (that is, n ₁ = n ₂ ) is filled, the valve 21d is opened and the fluid inside is discharged to be emptied (that is, filled with air) as shown in FIG. By making the refractive index n _{1 of the} transparent circular substrates PF ₁ and PF ₂ different from the refractive index n ₂ of the space in the convex cross-section void, the central circular transmission area FA and the ring-shaped transmission area FB around it are transmitted. It is possible to improve the depth of focus and the resolution by configuring a pupil filter PF that gives a predetermined phase difference or reduces coherence between the lights. When constructing the pupil filter PF for the pattern processing for contact holes, the fluid is discharged from the void of the convex cross-section as described above so that the void is simply a cavity, that is, the refractive index is approximately 1. Although it is possible to fill only with air, depending on the application, another fluid having a desired refractive index n ₂ may be introduced, or air having a predetermined pressure may be introduced to form a desired refractive index n _2. It is also possible to adopt.

Thus, according to one embodiment of the present invention,
The step d of the convex portion of the void of the transparent member (PF ₁ and PF ₂ ).
The refractive index of the transparent member is n ₁ , the refractive index of one fluid filled in the void is n ₂ , and the wavelength of the illumination light is When λ is set, a phase difference pupil filter having a desired phase difference can be configured by setting d = λ · PC / {2π (n ₁ −n ₂ )}. And
With the pupil filter, it is possible to superimpose the amplitudes of the images formed at different points in the optical axis direction with an appropriate phase difference, and to improve the depth of focus and the resolution even for the contact hole pattern.

Alternatively, according to another embodiment of the present invention,
The step d of the convex portion of the void of the transparent member (PF ₁ and PF ₂ ).
Where n _{1 is} the refractive index of the transparent member, n ₂ is the refractive index of the fluid filled in the void, and ΔLc is the coherent length of the illumination light.

[0045]

(Equation 5)

The coherence reduction type pupil filter PF can be configured by setting such that Then, by the pupil filter, the imaging light fluxes that respectively pass through the circular transmission area FA and the annular transmission area FB around the circular transmission area FA are made to reach the wafer W as light rays that do not interfere with each other, and intensity combination that does not interfere with each other is performed. By obtaining the image, it is possible to obtain the effect of improving the depth of focus and the resolution of the contact hole pattern.

As described above, in the present invention, the transparent circular substrates PF ₁ and P ₁ having the refractive index n ₁ are used.
Fluids having different refractive indexes n ₂ are exchanged and filled in the voids of the convex cross section of F _2. However, when the fluid to be filled is a liquid, bubbles are mixed in the liquid and the optical characteristics are Care must be taken not to damage it. As a countermeasure against such bubbles, it is preferable to provide bubble removing means on the fluid supply mechanism 20 side. Alternatively, as shown in FIG. 6, the stepped portions of the voids formed in the transparent circular substrates PF ₁ ′ and PF ₂ ′, for example, the steps E ₁ , E ₂ formed in the convex portion FA ′ and the fluid to the voids. It is also possible to adopt a configuration in which the steps E ₃ and E ₄ formed in the introduction portion are formed in a round shape instead of a square shape, and bubbles are less likely to stay in the step portion. Alternatively, as shown in FIG. 7, the convex portions (FA ") of the voids formed on the transparent circular substrates PF ₁ ″ and PF ₂ ″ are formed downward along the optical axis, that is, on the wafer side, and the upper surface U of the void is formed. It is also possible to adopt a configuration in which bubbles are less likely to stay on the upper surface U of the void by structuring the plane.

The transparent circular substrates PF ₁ and PF ₂ can be made of an appropriate translucent material, for example, any material such as glass, quartz, and fluorite. For the fluid to be filled in the voids of the convex cross-section during exposure, a material having a refractive index equal to that of the transparent material is used depending on the type of the transparent material forming the transparent circular substrates PF ₁ and PF _2. It is necessary to select it. For example, when the transparent circular substrates PF ₁ and PF ₂ are made of glass having a refractive index of 1.5, as a fluid to be filled, imadineoin having a refractive index of about 1.5, carbon tetrachloride or the like is used. It is possible to

In the above embodiment, the case where the phase difference type pupil filter or the coherence reduction type pupil filter is independently configured has been described, but the present invention is not limited to the embodiment and the phase difference type pupil filter and the phase difference type pupil filter are used. Of course, it can be applied to a pupil filter that is a combination of coherence reduction pupil filters. Further, in the above-described embodiment, the configuration is such that one fluid introduction through hole and one fluid discharge through hole are provided, but the number and size of these through holes may be set arbitrarily according to the application. It goes without saying that you can do it.

[0050]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, the translucent members (PF ₁ , PF ₂ ) arranged in the Fourier transform plane (FTP) of the projection optical system (PL) or in the vicinity thereof can be used. It is possible to construct an optimal projection optical system that always has a high depth of focus and resolution, regardless of the type of pattern, simply by inserting and removing fluids (air, etc.) with different refractive indices into and from the formed voids. is there. Further, since the mechanical filter insertion / removal mechanism of the conventional device can be omitted, it is possible to simplify the structure and save the space of the device, and to be free from the dust countermeasures caused by the filter insertion / removal mechanism. . Further, since it is not necessary to perform the alignment every time the inserting / removing operation is performed, stable image forming performance can be obtained by only the initial setting adjustment.

[Brief description of drawings]

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

2 is an optical filter PF that can be mounted on the projection optical system PL of the projection exposure apparatus shown in FIG.
2A is a side view of the optical filter PF, and FIG. 3B is a plan view of the optical filter PF.

3 is a partial sectional view showing a partial structure of a projection optical system PL of the projection exposure apparatus shown in FIG.

FIG. 4 is a diagram showing a usage state of the optical filter PF according to the present invention, and is a diagram showing a state in which a fluid is introduced into a convex cross-section void and, for example, a line-and-space pattern is exposed.

FIG. 5 is a diagram showing a usage state of the optical filter PF according to the present invention, which is a diagram showing a state in which a convex cross-section void is emptied and a contact hole pattern is exposed, for example.

FIG. 6 is a diagram showing the configuration of another embodiment of the optical filter PF according to the present invention.

FIG. 7 is a diagram showing the configuration of still another embodiment of the optical filter PF according to the present invention.

FIG. 8 is a diagram showing a schematic configuration of a conventional projection exposure apparatus.

[Explanation of symbols]

R Reticle W Wafer PL Projection optical system AX Optical axis FA Circular transmission area FB Ring-shaped transmission area ILB Illumination light FTP Fourier transform surface PF Optical filters PF ₁ and PF ₂ Translucent member d Step 20 Fluid supply mechanism 21 Fluid ejection mechanism

Claims (5)

[Claims] 1. An illuminating means for illuminating a mask on which a fine pattern is formed with an illuminating light for exposure, and a projection for projecting an image of the pattern onto a photosensitive substrate by injecting light generated from the pattern of the mask. The optical system is arranged on an optical Fourier transform surface in an image forming optical path between the mask and the photosensitive substrate, or a surface in the vicinity thereof, and distributed in a circular region centered on the optical axis of the projection optical system. In the projection exposure apparatus provided with an optical filter for reducing coherence between the image forming light and the image forming light distributed in the area outside thereof, or for making the phase different, in the optical filter, the circular area is incident. Of the light-transmissive member and the air-gap, the incident surface and the emission surface of the light-transmissive member and the air-gap are the projection optical system. The optical axis of That together are formed as parallel planes, a projection exposure apparatus characterized by fluid having different refractive index is filled in replacement to the air gap. 2. The fluid includes a material having a refractive index substantially equal to that of the translucent member.
The projection exposure apparatus according to. 3. The projection exposure apparatus according to claim 1, wherein the fluid filled in the gap has a refractive index different from that of the translucent member. 4. The step d of the convex portion of the gap is filled with the phase difference PC to be provided between the two image-forming lights, the refractive index of the transparent member is n ₁ , and the gap ₁ is filled. When the refractive index of one fluid is n ₂ and the wavelength of the illumination light is λ, d = λ · PC / {2π (n ₁ −n ₂ )} is set. The projection exposure apparatus according to 1 or 3. 5. The step d of the convex portion of the void has a refractive index n ₁ of the translucent member, a refractive index n ₂ of one fluid filled in the void, and a coherent length of the illumination light. ΔLc
When, The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is set so that