JPH0757992A - Projection aligner - Google Patents

Abstract

PURPOSE:To increase the depth of focus even for an isolated pattern by disposing a coherence suppressing member on a plane, or a nearby plane, in a projection optical system having optical Fourier transform relationship with the pattern plane of a mask. CONSTITUTION:An coherence suppressing member CCM, disposed on a plane or a nearby plane in a projection optical system having optical Fourier transform relationship with the pattern plane of a mask, is prepared by applying a parallel planar transmissive object to an annular transmission part FB of radius from the center CC on a transparent parallel plate having high ultraviolet transmittance. In this regard, coherence is reduced between an imaging light distributed over the first and third regions FA, FC and the imaging light distributed over the second region FB. A phase difference of (2m+1) IV (m is an integer) is imparted between the imaging light distributed over the first region FA and the imaging light distributed over the third region FC. In the constitution, beta=0.85.alpha+0.58 (0.2<=alpha<=0.4) is satisfied when r1=alpha.r3 and r2=beta.r3.

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 such as a semiconductor integrated circuit or a liquid crystal display.

[0002]

2. Description of the Related Art A projection optical system used in a projection type exposure apparatus of this type is incorporated into the apparatus through advanced optical design, careful selection of glass materials, ultra-precision processing of glass materials, and precise assembly and adjustment. Currently, in the semiconductor manufacturing process, the i-line (wavelength 365 nm) of a mercury lamp is used as illumination light for a reticle (mask).
A stepper that mainly irradiates the light and forms an image of the transmitted light of the circuit pattern on the reticle on a photosensitive substrate (a wafer coated with a photoresist or the like) via a projection optical system is mainly used. In addition, a so-called excimer stepper that uses an excimer laser (KrF laser having a wavelength of 248 nm or the like) as illumination light is also used for evaluation or research. When the projection optical system for the excimer stepper is composed of only a refracting lens, usable glass materials are limited to quartz and fluorite.

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: depth of focus) of the projection optical system are important factors. Has become.
Among the projection optical systems currently in practical use, those for the i-line having a numerical aperture (NA) of about 0.6 have been obtained. When the wavelengths of the illumination light used are the same, increasing the numerical aperture of the projection optical system improves the resolution accordingly. However, depth of focus (DOF) is numerical aperture NA
Decrease with increasing. The depth of focus is the wavelength of the illumination light λ
Is defined by DOF = ± λ / NA ² .

FIG. 1 schematically shows an image forming optical path of a conventional projection optical system. The projection optical system is a lens system G of the front group.
A lens system GB of the rear group. As a projection optical system of this type, a system in which both the reticle R side and the wafer W side are telecentric or a system in which only the wafer W side is telecentric is generally used. Now, in FIG. 1, arbitrary three points A, B, and C are assumed on the pattern surface of the reticle R (the object surface of the projection optical system).
Rays L ₁ , L ₂ , L ₃ , L traveling from point A in various directions
Of a, La ′, La ″, the light ray L ₁ is generated at an angle so that it cannot be incident on the lens system GA of the projection optical system.
₂ and L ₃ cannot pass through the pupil ep located on the Fourier transform plane FTP of the projection optical system. On the other hand, the other ray L
a, La ′, La ″ pass through the pupil ep, enter the lens system GB of the rear group, and converge on the point A ′ on the surface of the wafer W (image plane of the projection optical system). Among the light rays generated from the point A, the light rays that have passed through the pupil ep (the circular area centered on the optical axis AX) of the projection optical system contribute to forming a point image at the point A ′. Of the rays traveling from A to the point A ′, the center point CC of the pupil ep (position on the optical axis AX)
A ray La that passes through is called a principal ray, and in the case of a telecentric projection optical system on both sides, this principal ray La is parallel to the optical axis AX in the respective spaces on the object plane side and the image plane side.

The same applies to the light rays generated from the other points B and C on the reticle R, and only the light rays passing through the pupil ep contribute to the formation of the point images B'and C '.
Similarly, the light rays Lb and Lc that travel from the points B and C in parallel with the optical axis AX and enter the lens system GA are principal rays that pass through the center point CC of the pupil ep. As described above, the pupil ep has a Fourier transform and an inverse Fourier transform relationship with respect to the pattern surface of the reticle R and the surface of the wafer W, and the light rays from the pattern on the reticle that contribute to image formation are All the pupils ep will overlap and pass.

The numerical aperture of such a projection optical system is generally expressed as a value on the wafer side. In FIG. 1, among the rays that contribute to the formation of the point image A ′, the angles θw formed by the rays La ′ and La ″ passing through the outermost part in the pupil ep with the principal ray La on the wafer W are the projection optical system. Corresponding to the numerical aperture NAw on the wafer (image plane) side of the reticle R, and is represented by NAw = sin θw. It is called the numerical aperture NAr on the (object surface) side and is represented by NAr = sin θr. Further, if the image forming magnification of the projection optical system is M (M = 0.2 in the case of ⅕ reduction), there is a relation of NAr = M · NAw.

By the way, in order to increase the resolution, the numerical aperture NAw (NAr) is increased. In other words, this means that the diameter of the pupil ep is increased and the effective diameters of the lens systems GA and GB are increased. It is nothing but an increase in.
However, since the depth of focus DOF decreases in inverse proportion to the square of the numerical aperture NAw, even if a projection optical system with a high numerical aperture can be manufactured, the required depth of focus cannot be obtained, It becomes a big obstacle in practical use.

For example, the wavelength of the illumination light is 365 nm for the 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 within one shot area (about 20 mm square to 30 mm square) on the wafer W, the surface unevenness or curvature is resolved at a depth of focus DOF or more. It will cause defects. In addition, even on the stepper system, it becomes necessary to perform focusing, leveling, etc. for each shot area of the wafer W with extremely high precision, and the mechanical system, electrical system, and software burden (measurement resolution, servo control accuracy) , Efforts to improve the set time, etc.) will increase.

Therefore, the applicant of the present invention has solved the problems of the projection optical system as described above, and has a high resolution and a large power without using the phase shift reticle disclosed in JP-A-62-50811. A new projection exposure technique capable of obtaining both depth of focus is disclosed in Japanese Patent Application Laid-Open No. 4-101.
It was proposed in Japanese Patent Laid-Open No. 148, Japanese Patent Laid-Open No. 4-225358 and the like. This exposure technique increases the resolving power and the depth of focus by controlling the reticle illumination method to a special form while maintaining the existing projection optical system.
(Super High Resolution by IllumiNation Control) method. The SHRINC method is a line and space pattern (L & S pattern) on the reticle R.
Of two illumination lights (or 4
Illuminating the reticle with two illuminating lights), the 0th-order diffracted light component and one of the ± 1st-order diffracted light components generated from the L & S pattern are passed symmetrically with respect to the center point CC in the pupil ep of the projection optical system, and two-beam interference is caused. By utilizing the principle of (interference between one first-order diffracted light and one zero-order diffracted light), a projected image (interference fringe) of the L & S pattern is generated.

According to the image formation utilizing the two-beam interference in this way, the occurrence of the wavefront aberration at the time of defocusing can be suppressed more than in the case of the conventional method (normal vertical illumination), so that the depth of focus becomes large. . However, this SHRIN
The C method has an intended effect when the pattern formed on the reticle R has a periodic structure like an L & S pattern (lattice), and is effective for an isolated pattern such as a contact hole pattern. No effect. Generally, in the case of an isolated minute pattern, the diffracted light from the minute pattern is generated as Fraunhofer diffraction that is almost uniform in the diffraction angle direction, so that the 0th-order diffracted light and the higher-order diffracted light are clearly separated in the pupil ep of the projection optical system. This is because it does not.

Therefore, as an exposure method for expanding the apparent depth of focus with respect to 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 W is exposed between each exposure. A method of moving a fixed amount in the optical axis direction is disclosed in, for example, Japanese Patent Laid-Open No. 63-4.
No. 2122. This exposure method is FLEX
(Focus Latitude enhancement EXposure) method,
A sufficient depth of focus expansion effect can be obtained for isolated patterns such as contact hole patterns. However, F
Since the LEX method requires multiple exposure of a slightly defocused contact hole pattern image, the resist image obtained after development inevitably has a reduced sharpness. The problem of sharpness deterioration (profile deterioration) is that a photoresist with a high gamma value is used, a multilayer resist is used, or CEL (Contrast Enhancem) is used.
ent Layer).

As an attempt to expand the depth of focus when projecting the contact hole pattern without moving the wafer W in the optical axis direction during the exposure operation as in the FLEX method,
1991 Spring Applied Physics Society Proceedings 29a-ZC-
The Super-FLEX method announced in 8 and 9 is also known. In this Super-FLEX method, a transparent phase plate is provided in the pupil ep of the projection optical system, and the complex amplitude transmittance given to the imaging light by the phase plate changes sequentially from the optical axis AX toward the periphery. Is to have. By doing so, the image formed by the projection optical system maintains sharpness with a constant width (wider than before) around the best focus surface (the surface conjugate with the reticle R) in the optical axis direction. , The depth of focus increases.

A method of increasing the depth of focus by changing the transmittance distribution or the phase difference by filtering on the pupil plane of the projection optical system like the Super-FLEX method is generally known as a multi-focus filter method. There is. Regarding the multi-focus filter, pages 41 to 55 in a paper entitled "Study on imaging performance in optical system and its improvement method" of Mechanical Testing Laboratory Report No. 40 issued on January 23, 1936. See page for details.

[0014]

Among the various conventional techniques described above, the FLEX method and the Super-FLEX method can obtain a sufficient depth of focus increasing effect for an isolated contact hole pattern. .. However, it is difficult to apply the scanning exposure type exposure apparatus by the FLEX method of the type in which the wafer is continuously moved or vibrated in the optical axis direction during the exposure work, and the exposure is performed by the first exposure and the second exposure. In the method of dividing the wafer into two and moving the wafer in the optical axis direction between each exposure, there is a disadvantage that the throughput is largely lowered and the throughput is significantly lowered.

In view of the above point, the present invention has an object to provide a projection exposure apparatus having an increased depth of focus in projection exposure of an isolated pattern such as a contact hole pattern. It is an object of the present invention to provide a projection exposure apparatus that enables faithful transfer to an isolated pattern and at the same time obtains a depth of focus expansion effect.

[0016]

A projection exposure apparatus according to the present invention is, for example, as shown in FIGS. 8 and 10, an illumination for irradiating a mask (R) on which a transfer pattern is formed with exposure illumination light. Projection exposure apparatus including means (1 to 14) and a projection optical system (PL) for projecting an image of a pattern of a mask (R) onto a photosensitive substrate (W) under the illumination light thereof In the projection optical system (PL), the projection optical system (PL) on the optical Fourier transform surface (FTP) with respect to the pattern forming surface of the mask (R) or on the passing surface of the imaging light in the vicinity thereof.
An area having a radius r ₃ centered on the optical axis (AX) of the projection optical system (PL) and having a radius r ₁ centered on the optical axis (AX), A ring-shaped second region (FB) having a radius r ₁ to r ₂ centered on the optical axis (AX) and a ring-shaped second region having a radius r ₂ to r ₃ centered on the optical axis (AX). It is divided into three areas (FC) (however, r ₁ <r ₂ <r ₃ ).

Then, the coherence between the image forming light distributed in the first area (FA) and the third area (FC) and the image forming light distributed in the second area (FB) is reduced. With the first
Light distributed in the area (FA) and the third area (FC)
(2m + 1) π phase difference (m
A coherence reducing member (CCM) that gives an integer) is provided, and the radii r ₁ and r ₂ are represented as follows using the radius r ₃ and predetermined coefficients α and β, respectively.

R ₁ = α · r ₃ and r ₂ = β · r ₃ (1) In this case, in the present invention, the following two relations are simultaneously established for the coefficients α and β. β = 0.85 · α + 0.58 (2) 0.2 ≦ α ≦ 0.4 (3) In this case, an example of the coherence reducing member (CCM) is the first area (FA) and the third area. Temporal coherency that gives an optical path difference of a coherence length or more determined according to the wavelength range of the illumination light between the imaging light distributed in (FC) and the imaging light distributed in the second region (FB). It is a reduction member.

Another example of the coherence reducing member (CCM) is a polarization state of the image forming light distributed in the first area (FA) and the third area (FC) and the second area (FB). It is a polarization control member that makes the polarization states of the image-forming light distributed in the state not interfere with each other. Also, as the illumination means (1-14),
An annular illumination system or a modified light source system may be used.

[0020]

According to the present invention, a plane in the projection optical system (hereinafter referred to as "pupil plane") that optically has a Fourier transform relationship with the pattern plane of the mask (hereinafter referred to as "reticle"). (Abbreviated) or a surface in the vicinity thereof is provided with a coherence reducing member (CCM), and a part of the imaging light distributed in a circular or ring-shaped region (FA, FC) in the pupil plane, and other The imaging lights distributed in the region (FB) are set in a state where they do not interfere with each other. As a result, the exposure illumination light (image forming light) in the reticle pattern, which has been transmitted through the contact hole pattern and diffracted, is spatially divided into two types of light beams that do not interfere with each other in the pupil plane, and the exposed object is exposed. As a photosensitive substrate (hereinafter referred to as a “wafer”).

Since the two kinds of light beams do not interfere with each other (incoherently) even on the wafer, an intensity combined image of the images (contact hole pattern images) produced by the respective light beams can be obtained. In the conventional exposure method, when the light flux that has transmitted through the minute contact hole pattern on the reticle and diffracted reaches the wafer surface through the projection optical system, all of them are amplitude-wise combined (coherent addition), and the reticle pattern image (optical image ) Was formed. Conventional Sup
Also in the er-FLEX method, since the imaging light distributed on the pupil plane is only partially phase-shifted, it is still coherent addition.

Assuming that the projection optical system has no phase shift plate on the pupil plane, in the best focus state (focus state), the optical path from any one point on the reticle to the corresponding image point on the wafer. The lengths are the same regardless of which optical path in the projection optical system (Fermat's principle). Therefore, the amplitude composition on the wafer is the composition of light with no phase difference, and all the directions increase the intensity of the contact hole pattern. Act on.

However, when defocusing (deviation in the optical axis direction between the wafer surface and the best focus surface) occurs on the wafer, the above optical path length becomes different depending on the optical path in the projection optical system. As a result, the above-described amplitude synthesis is the addition of light having an optical path difference (phase difference), and a canceling effect is partially generated, which weakens the central strength of the contact hole pattern. The optical path difference generated at this time is defined by the incident angle of an arbitrary light ray incident on one image point on the wafer as θ, and the optical path length of the light ray (main ray) perpendicularly incident on the wafer as a reference (=
0), it is expressed as approximately (1/2) (ΔF · sin ² θ). Here, ΔF represents the defocus amount. sin
Since the maximum value of θ is the numerical aperture NAw on the wafer side of the projection optical system, when all the light that has passed through the pupil ep among the diffracted light from the minute contact hole pattern is amplitude-combined on the wafer as in the conventional case, Up to (1/2) (△ F ・ NAw
The optical path difference of ² ) will occur. At this time, assuming that the depth of focus allows an optical path difference of λ / 4,
The following relationship holds.

(1/2) (ΔF · NAw ² ) = λ / 4 (4) When this equation is put together, ΔF = λ / (2NAw ² ), which is in agreement with the generally-known depth of focus. To do. For example, i-line (wavelength 0 ..
365 μm), the numerical aperture NAw is 0.50
, The depth of focus ± ΔF / 2 is ± 0.73 μm, which is a value with almost no margin for a process step difference of 1 μm on the wafer.

FIG. 6 schematically shows the above principle. The horizontal axis of FIG. 6 represents the distance in the radial direction of the pupil with the optical axis as the center (0). The rectangular distribution curve tc in FIG. 6 (A) represents the amplitude transmittance of the pupil, but in a normal image formation, a phase shift plate and a light absorbing substance are not placed on the pupil surface, so that it is constantly +.
The amplitude transmittance is 1. FIG. 6B shows the angular range of the light beam incident on the wafer, sin θn = NA (wafer side numerical aperture), and the maximum values of the angle θn and the numerical aperture NA are θw and NAw, respectively.

Now, there is no phase plate on the pupil plane, and -θn
When the light in the incident angle range from to + θn reaches the wafer,
That is, in the best focus (ΔF = 0) state, as shown in FIG.
As shown in (C), the optical path length difference ΔLCO between one point on the reticle and the image point on the wafer becomes equal regardless of the incident angle on the wafer or its sine (ΔLCO = 0).
On the other hand, when the wafer W is defocused by F (ΔF =
F), the above optical path length difference differs by (1/2) ΔFsin ² θ depending on the sine of the incident angle (θ). This is shown in FIG. Between θ = 0 and sin θ = NAw, the optical path difference is only ΔLCF (wavefront aberration due to defocus).
Occurs. This optical path difference (wavefront aberration) deteriorates the profile of the image. This is the deterioration of the image due to defocus.

On the other hand, FIG. 7 schematically shows the principle of image formation by a double focus filter as an example of a so-called multi-focus filter. Here, as shown in FIG. 7A, a filter that makes the phase of the transmitted light different by π [rad] between the central portion and the peripheral portion of the pupil plane is used as the bifocal filter. That is, the amplitude transmittance of the filter is the center (circular area)
Is negative and positive in the periphery (ring zone), but this sign relationship is relative, and it is of course possible to reverse the sign.

The region where the amplitude transmittance is negative is shown in FIG.
As described above, the incident angle on the wafer is −θ ₁ <θ <θ ₁ , and the range of the incident angle θ on the wafer is −θw <θ <θ ₁ and θ in the region where the amplitude transmittance is positive. ₁ <θ <θw (sin θ ₁ = NA ₁ ). Now, the optical path length difference from one point on the reticle to the image point on the wafer is shown in FIG.
Even in the best focus (ΔF = 0) due to the bifocal filter used as described above, the optical path difference of ΔLF0 = λ / 2 is included. Therefore, the best focus (△
The image at F = 0 is degraded rather than the normal (no bifocal filter used) image. However, in the defocus state of ΔF = F, as shown in FIG.
The phase difference ΔLFF caused by the phase shift effect of the dual focus filter as shown in (D) can be made smaller than the normal optical path length difference ΔLCF in FIG. 6 (D). Therefore, the image at a position defocused to some extent can be improved by the bifocal filter, and the depth of focus can be increased.

In the above description, defocusing on only one side (positive direction) is considered, but the effect of the bifocal filter also appears for defocusing on the opposite side (negative direction). In the defocus on the opposite side, FIG. 6 (D) and FIG. 7 (D)
Although both parabola is convex upward, -NA ₁ light flux corresponding to during this time -NAw~-NA ₁ in FIG. 6 (D), the and NA ₁ ~NAw is shown in FIG. 7 (D) shifted one wavelength than the light beam between the ～NA ₁ - interferes with (side) light flux, thus the optical path difference in the case of △ F = -F becomes likewise △ LFF.

On the other hand, in the present invention, as shown in FIG. 2, a coherence reducing member CCM is provided on the pupil plane (FTP) of the projection optical system. At this time, an imaging light beam (the principal ray is LLp) diffracted by the isolated pattern Pr formed on the pattern surface of the reticle R
Enters the front lens group GA of the projection optical system PL and then reaches the Fourier transform plane FTP. And the Fourier transform plane F
In TP, the luminous flux (each LF) that passes through the circular transmissive portion FA at the center and the annular transmissive portion FC at the peripheral portion in the pupil
a and LFc) and the light flux (LFb) transmitted through the ring-shaped transmission portion FB in the middle portion are controlled (converted) to a state where they do not interfere with each other. Therefore, on the wafer W, the light fluxes LFa and LFc that have passed through the circular transmissive portion FA of the coherence reducing member CCM and the peripheral annular transmissive portion FC and the light flux LFb that has passed through the intermediate transmissive portion FB interfere with each other. Do not wake up. As a result, the luminous flux L from the central transmitting portion FA and the peripheral transmitting portion FC
Fa and LFc and the light beam LFb from the intermediate transmitting portion FB independently interfere with each other by themselves to form contact hole pattern images (intensity distribution) Pr ′. That is, a contact hole obtained by the present invention is obtained by simply adding in intensity the image generated on the wafer W by the interference of only the light beams LFa and LFc and the image generated by the interference of only the light beams LFb. An image Pr ′ of an isolated pattern such as

Illumination light ILB to reticle R is assumed to have a constant numerical aperture sin ψ / 2 as in the conventional case.
However, the numerical aperture NAr on the reticle side of the projection optical system PL is set to the condition of NAr> sin ψ / 2. Therefore, the principle of image formation in the present invention will be described with reference to FIGS. 3, 4, and 5. FIG. 3 shows a plan view and an amplitude transmittance of a coherence reducing member CCM as a pupil filter used in the present invention.

As described above, the circular transmitting portion F having the center radius r ₁
A and an annular transmissive portion FC having an inner radius r _{2 in} the periphery, an annular transmissive portion F having an inner radius r ₁ and an outer radius r _{2 in} the middle portion
B is provided with a member that reduces the coherence with the transmitted light of the transmission parts FA and FC. Therefore, the transparent portion F
It does not make much sense to represent the amplitude transmittances of A and FC and the transmission part FB on the same coordinate. Because the transmitted light (LFa, LFc) of each of the two transmission parts FA and FC and the transmission part FB
This is because they do not amplitude-wise combine (interfere) with the transmitted light (LFb). Therefore, in FIG. 3, FIG.
As in (C), the respective amplitude transmittances are separately represented as | a> (ket a) and | b> (ket b). These | a> and | b> mean lights that do not interfere with each other.

In this case, with respect to | a> (amplitude transmissivity of the transmissive portions FA and FC), the present invention uses the phase shift means for imparting a phase difference of (2m + 1) π [rad] to the transmitted light of both portions. , The central part (FA) and the peripheral part (FC) have opposite signs. In FIG. 3B, the center is negative and the outer periphery is positive, but since this sign relationship is relative, positive and negative may be reversed. Further, as shown in FIG. 3 (C), the amplitude transmittance of the intermediate annular zone FB is positive here, but this value may be any value as long as its absolute value is 1. . Further, the amplitude transmittance of FIG. 3C and the amplitude transmittance of FIG. 3B are completely unrelated.

As shown in FIG. 4, in the amplitude composition within the light flux LFb passing through the intermediate ring-shaped transmission portion FB, the incident angle θ of the light flux LFb on the wafer corresponds to the radii r ₁ , r ₂ of the ring-shaped transmission portion FB. Then, the range of θ ₁ <θ <θ _{2 is established} , and the optical path length difference ΔLBF when ΔF = F is as follows as shown in FIG. ΔLBF = (1/2) F (sin ² θ ₂ −sin ² θ ₁ ) (5) Of course, when ΔF = 0, the optical path length difference ΔL is as shown in FIG. 4C.
B0 is 0.

On the other hand, in the images (amplitude synthesis) of the transmitted light LFa and LFb of the central transmission part FA and the peripheral transmission part FC as shown in FIG. ing. Therefore, even in the best focus state (ΔF = 0), as shown in FIG.
The optical path length difference is equal to λ / 2, but the optical path length difference is about ΔLAF as shown in FIG. 5D when ΔF = F is defocused, and is smaller when defocused (ΔF = ± F). An image with a small wavefront aberration, that is, a good profile can be obtained. Since the first light flux LFa and LFc and second beam LFb do not interfere each other, the light beam LFa, LFc image Pr by interference of only degradation of _{2 '1,} and the light beam LFb interference image Pr by only' is , Optical path length difference within each luminous flux ΔLB
It is caused only by F, ΔLAO, and ΔLAF.

Of these optical path length differences, ΔLBF, ΔL
Regarding AF, as is clear from FIGS. 4 and 5, the optical path length difference ΔLCF (=
It is smaller than (1/2) F · NAw ² ). Also, ΔLA0 =
λ / 2 is the optical path length difference for the bifocal filter, and does not generally deteriorate the image. As a result, in the present invention, when the same amount of defocus is applied, the optical path length difference can be made smaller than that of the conventional image formation, that is, a larger depth of focus can be obtained. In this way, in the pupil plane FTP of the projection optical system PL or the surface in the vicinity thereof,
A method for converting an imaging light flux into a plurality of light fluxes that do not interfere with each other will be described below in SFINCS (Spatial Filter for INCohere).
nt Stream) method.

Further, according to the present invention, ringing, which is a problem when only the conventional bifocal filter or trifocal filter as described above is used, has no problem at all. Describe.
Further, according to the present invention, the first area (FA), the second area (FB) and the third area on the pupil plane of the projection optical system or on the surface in the vicinity of the pupil plane.
Regarding the shape of the region (FC), the conditions of the formulas (1) to (3) are imposed, and when this condition is satisfied, the expansion width of the depth of focus becomes particularly large.

Furthermore, when a ring-shaped illumination system or a modified light source system is used as the illumination means (1 to 14), the effect of expanding the depth of focus by the use of the ring-shaped illumination system or the modified light source system is added. As a result, the depth of focus further expands.

[0039]

Embodiments of the projection exposure apparatus according to the present invention will be described below with reference to the drawings. FIG. 8 shows the overall configuration of the projection exposure apparatus according to the embodiment of the present invention. In FIG. 8, the brightness light emitted from the mercury lamp 1 is converged on the second focal point by the elliptical mirror 2 and then becomes divergent light and enters the collimator lens 4. The rotary shutter 3 is arranged at the position of the second focus, and the rotary shutter 3
Controls the 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 a desired spectrum required for exposure, for example, only the i-line is extracted. The illumination light (i-line) emitted from the interference filter 5 enters a fly-eye lens 7 as an optical integrator.
Of course, a wavelength other than the i-line or a plurality of wavelengths may be used, and the light source itself may be a laser light source or the like. Figure 8
Among them, the polarization control member 6 between the interference filter 5 and the fly-eye lens 7 may be used according to the embodiment of the present invention, and will be described in detail later.

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 image (mercury) is provided on the exit side of each lens element. An image of the light emitting point of the lamp 1) is formed. Therefore, the same number of point light source images as the number of lens elements are distributed on the exit side of the fly-eye lens 7 to form a surface light source image. 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 this diaphragm 8
After being reflected by the mirror 9 and entering the condenser lens system 10, the rectangular opening of the reticle blind 11 is illuminated with a uniform illuminance distribution. In FIG. 8, among the plurality of secondary light source images (point light sources) formed on the exit side of the fly-eye lens 7,
Only the illumination light from one secondary light source image located on the optical axis AX is representatively shown. Further, by the condenser lens system 10, the exit side of the fly-eye lens 7 (the surface on which the secondary light source image is formed) is a Fourier transform surface with respect to the rectangular aperture surface of the reticle blind 11. Therefore, the respective illumination lights that diverge from the plurality of secondary light source images of the fly-eye lens 7 and enter the condenser lens system 10 are superimposed on the reticle blind 11 as parallel light beams having slightly different incident angles. To be done.

The illumination light passing through the rectangular opening of the reticle blind 11 enters the condenser lens 14 via the lens system 12 and the mirror 13, and the light emitted from the condenser lens 14 reaches the reticle R as the illumination light ILB. Here, the rectangular opening surface of the reticle blind 11 and the pattern surface of the reticle R are arranged conjugate with each other by a composite system of the lens system 12 and the condenser lens 14,
The image of the rectangular opening of the reticle blind 11 is the reticle R
The image is formed so as to include a rectangular pattern formation region formed in the pattern surface of the. As shown in FIG. 8, the illumination light ILB from one secondary light source image side located on the optical axis AX in the secondary light source image of the fly-eye lens 7 tilts on the reticle R with respect to the optical axis AX. There is no parallel light flux because this is because the reticle side of the projection optical system PL is telecentric. Of course, a large number of secondary light source images (off-axis point light sources) that are displaced from the optical axis AX are formed on the exit side of the fly-eye lens 7, so that any illumination light from them is on the reticle R. Then, it becomes a parallel light beam inclined with respect to the optical axis AX and is superimposed in the pattern formation region.

The pattern surface of the reticle R and the exit side surface of the fly-eye lens 7 are optically Fourier-transformed by a composite system including a condenser lens system 10, a lens system 12, and a condenser lens 14. Needless to say Further, the incident angle range ψ (see FIG. 2) of the illumination light ILB to the reticle R changes depending on the aperture diameter of the diaphragm 8. If the aperture diameter of the diaphragm 8 is reduced to reduce the substantial area of the surface light source, the incident light ILB is incident. The angle range ψ also becomes smaller. Therefore, the diaphragm 8 adjusts the spatial coherency of the illumination light. As a factor indicating the degree of spatial coherency, the maximum incident angle ψ / 2 of the illumination light ILB is set.
The ratio (σ value) between the sine of σ and the numerical aperture NAr of the projection optical system PL on the reticle side is used. This σ value is usually σ =
It is defined by sin (ψ / 2) / NAr, and most of the steppers currently in operation are used in the range of σ = 0.5 to 0.7. In the present invention, the σ value may be any value, and in an extreme case, σ may be about 0.1 to 0.3.

A predetermined reticle pattern is formed of a chrome layer on the pattern surface of the reticle R. Here, the chrome layer is vapor-deposited on the entire surface and a minute rectangular opening (transparent without the chrome layer is formed therein). It is assumed that there are a plurality of contact hole patterns formed in part).
The contact hole pattern may be designed to have a size of 0.5 μm square (or diameter) or less when projected onto the wafer W, and the projection magnification M of the projection optical system PL may be designed.
The size of the reticle R is determined in consideration of the above. The dimension between adjacent contact hole patterns is
Since the size of each contact hole pattern is usually considerably larger than that of one contact hole pattern, each contact hole pattern exists as an isolated minute pattern. That is, the two adjacent contact hole patterns are often separated to the extent that the light (diffraction, scattered light) generated from each of them does not strongly influence each other like a diffraction grating. However, as will be described later in detail, there is also a reticle in which contact hole patterns are formed in close proximity to each other.

In FIG. 8, the reticle R is held on the reticle stage RST, and the optical image (light intensity distribution) of the contact hole pattern of the reticle R is formed on the photoresist layer on the surface of the wafer W via the projection optical system PL. To be imaged. Here, the optical path from the reticle R to the wafer W in FIG. 8 is shown only by the chief ray of the imaging light flux. The Fourier transform plane FTP in the projection optical system PL is provided with the coherence reducing member CCM described in FIGS. 2 and 3 above. The coherence reducing member CCM has a diameter that covers the maximum diameter of the pupil ep, and can be moved out of the optical path or into the optical path by the slider mechanism 20. If the stepper is used exclusively for exposing the contact hole pattern, the coherence reducing member CCM may be fixed in the projection optical system PL.

However, when the exposure work in the lithography process is performed by a plurality of steppers, considering the most efficient operation of each stepper, hesitating to assign a specific stepper to the exposure dedicated to the contact hole pattern. It Therefore, the interference reduction member CCM
It is desirable that the stepper be provided so that it can be inserted into and removed from the pupil ep of the projection optical system PL so that the stepper can be used even during exposure of a reticle pattern other than the contact hole pattern. Depending on the projection exposure system, a circular aperture diaphragm (NA variable diaphragm) for changing the effective pupil diameter may be provided at the pupil position (Fourier transform plane ETP).
In this case, the aperture stop and the coherence reducing member CCM are arranged as close as possible without mechanical interference.

The wafer W moves two-dimensionally in the plane perpendicular to the optical axis AX (hereinafter referred to as "XY movement"), and moves slightly in the direction parallel to the optical axis AX (hereinafter "Z movement"). The wafer is held on the wafer stage WST. The XY movement and the Z movement of wafer stage WST are controlled by stage drive unit 22, and the XY movement is controlled according to the coordinate measurement value by laser interferometer 23.
The movement is controlled based on the detection value of the focus sensor 24 for autofocus. The stage drive unit 22, the slider mechanism 20, etc. operate according to a command from the main control unit 25. This 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 to open the aperture control unit 2
7 to send a command to the diaphragm 8 or the reticle blind 11
Control the size of each opening. In addition, the main control unit 2
Reference numeral 5 allows the reticle name read by the bar code reader 28 provided in the reticle transport path to the reticle stage RST to be input. Therefore, the main control unit 25 comprehensively controls the operation of the slider mechanism 20, the operation of the aperture drive unit 27, and the like according to the input reticle name, and the aperture size of each of the diaphragm 8 and the reticle blind 11 and the interference reducing member. Whether or not CCM is required can be automatically adjusted according to the reticle.

Here, the structure of a part of the projection optical system PL in FIG. 8 will be described with reference to FIG. Figure 9 shows a partial cross section of the projection optical system PL made in all refractive glass material, the top of the lens GB ₁ lens system GB at the bottom of the lens GA ₁ and the rear group lens system GA of the front lens group The Fourier transform plane FTP exists in the space between and. Although the projection optical system PL holds a plurality of lenses by a lens barrel, the coherence reducing member CC
An opening is provided in a part of the lens barrel for inserting and removing M. Further, a cover 20B that does not directly expose the coherence reducing member CCM and the slider mechanism 20 in whole or in part is extended from the opening of the lens barrel. This cover 2
0B prevents minute dust floating in the outside air from entering the pupil space of the projection optical system PL. An actuator 20A such as a rotary motor, a pen cylinder, and a solenoid is coupled to the slider mechanism 20. Further, a flow path Af communicating with the pupil space is provided in a part of the lens barrel, and clean air whose temperature is controlled is supplied to the pupil space through the pipe 29, so that a part of the exposure light of the coherence reducing member CCM is exposed. The temperature rise due to absorption and the temperature rise of the entire pupil space are suppressed. If the clean air forcibly supplied to the pupil space is forcibly discharged via the slider mechanism 20 and the actuator 20A, the slider mechanism 20
It is possible to prevent dust generated due to the like from entering the pupil space.

FIG. 10 shows a structure of the coherence reducing member CCM according to the first embodiment, FIG. 10 (A) is a sectional view taken along a point passing through the optical axis AX, and FIG. 10 (B) is a plan view. Now, Fig. 8
The light source (water source lamp 1) inside has a random polarization state (light that is a combination of light of various polarization states and that polarization state changes with time), and its coherent length ΔLc is extremely high. short. Now, with the illumination light as the i-line, the central wavelength λ ₀ = 365 nm and the wavelength width Δλ = 5n
If m, the coherent length ΔLc is obtained as follows.

ΔLc = λ ₀ ² / Δλ≈26 [μm] (6) The coherence reducing member CCM shown in FIG. From the radius r ₁ to the radius r _{2 in} the annular transparent portion FB, the thickness h
The transparent object of ₁ parallel plate is attached. At this time, if the refractive index of the transparent object to be pasted is n ₁ ,
The thickness h ₁ should satisfy the following equation.

(N₁ -1) h₁ ≧ ΔLc (coherent length) (7) Then, the transmitted light of the transmission parts FA and FC and the transmission part FB
Between transmitted light (n ₁ -1) h₁ , That is, coherent
An optical path difference of length ΔLc or more is given, and the light flux between both light beams is
Loss of communication. Transparent objects are glass, quartz, fluorite, etc.
And the refractive index n₁ Is about 1.5, so the thickness h₁ Is 5
It may be 2 μm or more.

Further, the central transmitting portion FA has a central transmitting portion F.
Between the transmitted light of A and the transmitted light of the peripheral transmitting portion FC (2 m +
1) A phase shifter that gives a phase difference of π [rad] is attached (m is an integer). This phase shifter is made of SiO
A thin film such as ₂ is formed by vapor deposition, sputtering, CVD (chemical vapor deposition) or the like. If the refractive index of the phase shifter is n ₂ , the thickness d of the phase shifter may be set so as to satisfy the following equation.

(N ₂ −1) d = (m + ½) λ ₀ (8) In this embodiment, λ ₀ is 0.365 μm. Refractive index n ₂
Is about 1.5, for example, when m = 0,
From the formula (8), the thickness d may be 0.365 μm. The thickness d can be made thicker corresponding to m = 1, 2, 3, ..., However, there arises a problem of light absorption due to the material of the thin film as the phase shifter, or the thickness d is transmitted. Since there is a problem that coherence remains between the transmitted light of the portion FB and the transmitted light of the transmitting portion FA, a thickness corresponding to about m = 0, 1, 2 is practically set. Better Similarly, if the thickness h ₁ of the transmission parallel plate adhered to the transmission portion FB is too thick, it will adversely affect absorption and geometrical optics aberrations.

As a modification of the example shown in FIG.
The flat plate-shaped substrate itself is processed so that it protrudes into the annular transmission part FB.
You may give the step of a part or a recessed part. Also in this case, the step h₁'
(That is, the difference in thickness between the transparent portions FA, FC and the transparent portion FB)
Is the refractive index of the substrate n₀ As (n₀ -1) h₁'≧ △
Lc is satisfied. FIG. 11 shows the interference reduction member No. 1
Two examples will be shown. In the example of FIG. 11, the intermediate annular zone F
Instead of attaching another parallel plate to B, its transparent part F
Part of B has a higher refractive index than others due to ion implantation etc.
Make a high area. The refractive index of this part is n ₃ , The other part
The refractive index of n₀ And the depth is h₂ Then, (n₃ 
-N₀ ) H ₂ If ≧ ΔLc, the transmitted light of the transmission part FB is
The coherence with the transmitted light of other transmission parts FA and FC disappears.
To do. Also in this example, the phase of the thickness d is formed in the transmission part FA at the center.
A shifter is provided. The conditions for the thickness d are the same as in the example of FIG.
is there.

FIG. 12 shows the structure of the interference reducing member CCM according to the third embodiment. As shown in FIG. 12B, a cover glass for preparation of a sample under a microscope, a thin film (pellicle) made of a polymer, or a thin transparent substrate (thickness h ₃ ) such as an acrylic thin plate is used as shown in FIG. 12B. The cut-out portion corresponds to the intermediate transparent portion FB. In order to prevent the central transmission part FA from being separated from the peripheral transmission part FC, the two are connected by some columns e. Assuming that the thickness of the thin transparent substrate is h ₃ and the refractive index is n ₅ , if (n ₅ −1) h ₃ ≧ ΔLc, the transmissive portion FA,
The coherence between each transmitted light of FC and the transmitted light of the transmission part FB disappears. Also in this example, a phase shifter having a thickness d is added to the central transmission portion FA. It is desirable that the pillar e has a light-shielding property, but even if it is transparent, since the area of the pillar part is small, there is almost no adverse effect on the imaging performance, and a metal film or the like may be attached to form the light-shielding part. it can.

In the example of FIG. 12, the interference reducing member CC
Since the thickness h ₃ of M can be thinned (≈52 μm), a conventional projection optical system designed and manufactured without assuming that a parallel flat plate such as a coherence reducing member CCM is provided on the pupil plane. Even if it is inserted in, the geometrical-optical aberrations generated by the coherence reducing member CCM can be suppressed to be small. On the other hand, as shown in FIGS. 10 and 11, in the coherence reducing member CCM having a certain thickness (thickness of the substrate), it is premised that the coherence reducing member CMP is used as a projection optical system. As the above, the one designed and manufactured will be used. In this case, conversely, from the pupil plane, the coherence reducing member CCM
Since various geometrical optics aberrations are aggravated in the state excluding
When it is used in a process other than the contact hole pattern process, the coherence reducing member CCM may be removed from the optical system, and a parallel plate having substantially the same thickness may be inserted instead.

In each of the above-mentioned embodiments, a member that gives an optical path difference equal to or longer than the temporal coherence length between the light beams is used as the coherence reducing member, but a member of another system may be used. FIG. 13 is a fourth diagram showing the structure of the interference reducing member according to another method.
FIG. 13A and FIG. 13B are examples and show a cross-sectional view and a plan view of the coherence reducing member CCM, respectively. Center transmission part F
As shown in FIG. 13 (C), A and the peripheral transmissive portion FC are configured by a polarizing plate that transmits only linearly polarized light in a direction orthogonal to the intermediate transmissive portion FB, and the polarization direction of the transmitted light of the transmissive portion FB. Is orthogonal to the linear polarization direction of the transmitted light of the transmission parts FA and FC. Since the linearly polarized lights whose polarization directions are orthogonal to each other do not interfere with each other, even by controlling the polarization characteristics in this way,
It is possible to eliminate (reduce) the coherence of both light fluxes.

Incidentally, as shown in FIG. 13A, in this case as well, a phase shifter of thickness d is provided in the central transmitting portion FA.
As a result, the transmissive portion FA and the transmissive portion FC form a bifocal filter, which is exactly the same as the previous embodiments. The conditions for the thickness d are the same as described above. Alternatively, the phase shifter of FIG. 13 (A) may be omitted, and instead, the thicknesses of the respective polarizing plates of the transmissive portions FA and FC may be different to give a phase difference of (2m + 1) π [rad]. .

Further, a quarter wavelength plate (λ / 4) is provided on the wafer side of the coherence reducing member CCM using the polarizing plate of the example of FIG.
A plate) may be provided to convert the above two orthogonal linearly polarized lights into circularly polarized lights having mutually opposite rotations. Also in this case, since the circularly polarized lights having mutually opposite rotations do not interfere with each other, it can be used as a coherence reducing member in which a polarizing plate and a ¼ wavelength plate are combined. At this time, the axial direction of the quarter-wave plate (the direction in which the refractive index is high) is shifted by 45 ° with respect to the polarization directions of the two orthogonally polarized lights.

In the embodiment using the above-mentioned polarizing plate, since the coherence reducing member CCM in the projection optical system PL is composed of a polarizing plate, a half of the original light amount to be transmitted through the projection optical system PL. Will be absorbed by the polarizing plate as the coherence reducing member CCM. This also means a decrease in exposure power, but heat (energy of the exposure light absorbed) accumulates in the projection optical system, which poses a problem in terms of stability of the optical system and glass material.

Therefore, an embodiment for solving this heat problem (exposure power loss) is shown in FIGS. 14, 15, 16 and 1.
This will be described with reference to FIG. In the present embodiment, the polarization characteristic of the illumination light ILB is important, so that will be described first. FIG. 14 shows some examples of the polarization control member 6 (see FIG. 8) provided in the illumination optical system. 14
(A) is an example in which a polarizing plate 6A is used as the polarization control member 6, and the incident light from the mercury lamp 1, which is random polarized light, is emitted as specific linearly polarized light. FIG. 14B shows an example in which a polarizing plate 6A and a quarter-wave plate 6B are combined as the polarization control member 6. Also at this time, the incident light which is randomly polarized light is first linearly polarized by the polarizing plate 6A,
Next, by the quarter-wave plate 6B, either clockwise or counterclockwise circularly polarized light is emitted. Also at this time 1/4
The axial direction of the wave plate 6B is set to the axial direction for converting the linearly polarized light from the polarizing plate 6A into circularly polarized light.

When the light flux from the light source (incident light flux) itself is linearly polarized light, for example, when a laser light source is used, the illumination light ILB reaching the reticle R is linearly polarized light without providing the polarization control member 6. Has become. However, depending on the configuration of the polarization state control member in the projection optical system described later, as shown in FIG.
Only the polarization control member 6 may be provided so that circularly polarized light is formed. The axial direction of the quarter-wave plate 6B in this case is also set as described above.

Now, if the polarization characteristics of the illumination light ILB to the reticle R are made uniform by using the polarization control member 6 as shown in FIG. 14, the light is transmitted through the contact hole pattern, diffracted, and is projected in the projection optical system PL. The image-forming light flux reaching the coherence reducing member CCM is also in the state of being aligned with the linearly polarized light or the circularly polarized light having the characteristic. Therefore, the illumination light ILB is, for example, as shown in FIG.
A structure of a coherence reducing member CCM suitable for the case where linearly polarized light is aligned as in (A) is shown in FIG. 15 as a fifth embodiment. FIG. 15 (A) shows 1 / as a coherence reducing member CCM.
This is an example of using a two-wave plate. FIG. 15 (A) shows the polarization state of the light (illumination light ILB) immediately before entering the coherence reducing member CCM, and here it is assumed that it is linearly polarized light having a vibration plane of the electric field in the vertical direction in the figure. . FIG. 15B shows a planar structure of the coherence reducing member CCM, which has radii r _{1 to} r _2.
The ring-shaped transmission part FB of is composed of a half-wave plate (λ / 2 plate), and the central transmission part FA and the peripheral ring-shaped transmission part FC are almost the same as the middle transmission part FB (half-wave plate). It is an ordinary transparent plate (for example, quartz) having a thickness (optical thickness) of.

As shown in FIG. 15C, the polarization state of the light immediately after passing through the coherence reducing member CCM of FIG. 15 is such that the polarization state of the intermediate ring-shaped transmission portion FB is a straight line in the left-right direction. It is converted into polarized light, and the polarization state does not change at all in the central transmission part FA and the peripheral annular transmission part FC.
For this reason, it is possible to divide the image forming light beams into polarization states that do not interfere with each other, as in the first embodiment. here,
The axial direction (in-plane rotation) of the half-wave plate as the transmission part FB is set to the axial direction that converts the direction of the incident linearly polarized light into the direction orthogonal thereto, but the axis of the half-wave plate is In order to optimize the direction and the polarization direction of the illumination light ILB, the coherence reduction member CCM and the polarization control member 6 may be relatively adjustable in the plane in the rotation direction.

Alternatively, as the interference reducing member CCM, a ring-shaped transparent portion FB having a radius r _{1 to} r ₂ and a circular transparent portion F at the center.
Both A and the peripheral ring-shaped transmission portion FC may be formed of a quarter wavelength plate (having substantially the same thickness). In this case as well, the incident light beams are all linearly polarized as shown in FIG. 15A, so that the axial directions of the quarter-wave plates of the transmission parts FA and FB are circularly polarized in directions opposite to each other with respect to the polarization state of the incident light beams. By optimizing so that the light flux that has passed through the annular transmissive portion FB becomes a clockwise circularly polarized light, and the light flux that has passed through the central circular transmissive portion FA and the peripheral annular transmissive portion FC, a counterclockwise circularly polarized light. It can be converted into polarized light, and light beams having different polarization states (not interfering with each other) can be obtained. In this case as well, the polarization direction of the illumination light ILB is adjusted in accordance with the axial direction of the quarter-wave plate serving as the coherence reducing member CCM, as in the above-described embodiment.
It is better to be able to adjust by. Note that FIG.
1/2 as the intermediate ring-shaped transmission part FB shown in (B)
The wave plate may be replaced with an optical rotatory substance such as quartz, and even in that case, the direction of linearly polarized light can be converted in the same manner.

Further, for the above embodiment using the half-wave plate or the quarter-wave plate, the illumination light is not linearly polarized light but circularly polarized light as shown in FIGS. 14 (B) and 14 (C). Can also be used. That is, the circularly polarized light is converted by the coherence reducing member as shown in FIG. 15B into the circularly polarized light having the reverse rotation, and the transmitted light from the other transparent portions FA and FC is the original circularly polarized light. It remains.

Alternatively, also in the example in which the transmissive portions FA and FC and the transmissive portion FB are quarter-wave plates having different axial directions, the incident circularly polarized lights are converted into orthogonal linearly polarized lights, which also do not interfere with each other. It is divided into two light beams. Further, if the incident light flux (illumination light ILB) is circularly polarized light, there is no need to rotate and adjust the axial direction of the ½ wavelength plate or the ¼ wavelength plate in accordance with the polarization characteristic of the illumination light, which is advantageous.

As described above, when the polarization control member 6 shown in FIG. 14 and the coherence reducing member CCM shown in FIG. 15 are used, the coherence reducing member C using the polarizing plate as described above is used.
This is extremely convenient in that the problem of absorption of the exposure energy in the CM is eliminated and the heat accumulation in the projection optical system PL is suppressed. However, this time, in the illumination optical system, the illumination light I
The light amount loss (more than half) associated with aligning LB to one polarization state remains a problem. Therefore, an example of an illumination system in which the light amount loss of illumination light is reduced will be described with reference to FIG. The system of FIG. 16 is provided instead of the polarization control member 6 of FIG. First, in FIG. 16A, the incident light beam is divided and combined by the two polarization beam splitters 6C and 6D. That is, the first polarization beam splitter 6C transmits the P-polarized component (vertical polarization) and the second polarization beam splitter 6D also transmits straight. On the other hand, the S-polarized light component (polarized light component in the direction perpendicular to the paper surface of FIG. 16A) split by the beam splitter 6C is combined by the beam splitter 6D via mirrors 6E and 6F separated by a distance d ₁ to produce P-polarized light. It goes coaxially with the ingredients. At this time, an optical path difference of 2 × d ₁ is given to the P-polarized light and the S-polarized light by the optical paths of the mirrors 6E and 6F. Therefore, if the temporal coherence length ΔLc of the incident light flux is shorter than 2d ₁ , the combined P organization component and S polarization component are complementary in polarization direction and also temporally incoherent (non-coherent). Interference).

When illumination light having these two polarization components is used and the coherence reducing member CCM shown in FIG. 15B is used, as shown in FIG. 17A, the coherence reducing member CCM is changed. The incident P-polarized component (for example, a white arrow direction) and the S-polarized component (for example, a black arrow direction) interfere with each other after passing through the coherence reducing member CCM as shown in FIG. 17C. There are four light beams that do not match.
That is, the original polarization direction is rotated by 90 ° in the intermediate annular transmission part FB (1/2 wavelength plate). The four light beams have different polarization directions, and the transmission parts FA and F
Even if the polarization directions of C and the transmissive part FB are the same, they do not interfere with each other because they are temporally incoherent.
That is, the S-polarized light component that has passed through the transmissive portion FB is converted into a P-polarized light component and has the same polarization direction as the P-polarized light component that has passed through the transmissive portions FA and FC, but the two lights are temporally incoherent. So do not interfere. If the illumination light from the polarization control member having the structure shown in FIG. 16A is not used,
Since the P-polarized light and the S-polarized light in FIG. 17 remain coherent with respect to time, each light flux after passing through the coherence reducing member CCM will also interfere with each other if the polarization directions are the same. The effect of the invention diminishes. The system shown in FIG. 16 (A) can make a large difference in optical path length between the two polarization components to be combined, and is therefore suitable for a light source having a relatively long temporal coherence length, for example, a laser light source with a narrow band. There is.

When linearly polarized light is used as the laser light source, the effect of the present invention can be obtained without using the polarization control means having the structure shown in FIG. However, when the polarization control means as shown in FIG. 16A is used for a linearly polarized laser light source, the illumination light can be made into two light fluxes that are temporally incoherent, which is a problem when using the laser light source. Speckles and interference fringes (illuminance unevenness)
Is effective. in this case,
The polarization direction of the linearly polarized light incident on the first-stage beam splitter 6C in FIG.
As shown in FIG. 16A with respect to C, the P polarization direction and S
Polarization direction L intermediate to the polarization direction (45 ° direction from both)
PL is recommended.

By the way, when the light source is a light source having a comparatively large spectral width such as a mercury lamp, its temporal coherence length is short. Therefore, a simple member as shown in FIG. It can be used as the control member 6. This member is a transparent parallel plate 6G made of quartz or the like with a polarizing reflection film 6H attached to the surface thereof, and a total reflection film 6J made of metal or the like on the back surface thereof so that the collimated light flux from the mercury lamp is reflected at a predetermined angle. Is located in. At this time, of the randomly polarized incident light from the mercury lamp, the S polarization component (direction perpendicular to the paper surface of FIG. 16B) is the film 6H on the surface.
And the P-polarized component is reflected by the surface film 6H and the parallel plate 6G.
Is reflected by the film 6J on the back surface, and an optical path difference corresponding to approximately twice the thickness (optical thickness) of the parallel plate 6G is given between the S-polarized component and the P-polarized component. For example, in the case of i-line from a mercury lamp, the coherent length ΔL as described above
c is about 26 μm. Therefore, even with a sufficiently thin parallel plate 6G (for example, with a thickness of about 1 mm), it is possible to give a sufficient optical path length difference for eliminating temporal coherence.

As another embodiment, a quarter wave plate is provided on the exit side of the system of FIG. 16A or 16B to convert two linearly polarized lights into circularly polarized lights in opposite directions. Good. At this time, the light beam after passing through the coherence reducing member CCM of FIG. 17B is similarly divided into four light beams which do not interfere with each other. Then, they either do not interfere with each other temporally, or do not interfere with each other because they are circularly polarized lights of opposite rotations.

Although the description of the coherence reducing member using the half-wave plate or the quarter-wave plate is omitted in the embodiment, the center transmission part FA and the peripheral transmission part F are naturally also here again.
A phase shifter that gives a phase difference of (2m + 1) π [rad] between the transmitted light with C is provided. Although the phase shifter is provided in the central transmission part FA in any of the above embodiments, the phase shifter is relative, and therefore the same effect can be obtained even if the phase shifter is provided in the peripheral transmission part FC.

Further, in the embodiment using the half-wave plate and the quarter-wave plate, only the ring-shaped transmission part FB as in the configuration of FIGS. It is also possible to adopt a configuration in which a ½ wavelength plate or a ¼ wavelength plate is attached to a transparent plate that serves as a substrate. Further, in all of the above embodiments, the outer radius of the central circular transmissive portion FA and the inner radius of the ring-shaped transmissive portion FB in the middle portion are r ₁ , the outer radius of the ring-shaped transmissive portion FB in the middle portion and the ring in the peripheral portion. The inner radius of the band-shaped transparent portion FC is r _2, and the values of the radii r ₁ and r ₂ are
Radius r _{3 of the} pupil plane corresponding to the numerical aperture (NA) of the projection optical system
Is set as follows using predetermined coefficients α and β.

R ₁ = α × r ₃ , r ₂ = β × r ₃ (9) In this case, the coefficient β is expressed as follows using the coefficient α. β = 0.85 · α + 0.58 (10) Further, the value of the coefficient α is set within the following range. 0.2 ≦ α ≦ 0.4 (11) The reason for this will be described later. The radius r ₃ has a value corresponding to the effective maximum numerical aperture (NAw) of the projection optical system.

By the way, the wafer stage W shown in FIG.
In the ST drive unit 22, the function of the conventional FLEX method may be provided in the control for finely moving the wafer W in the optical axis direction. By using the FLEX method together, the effect of increasing the depth of focus according to the present invention can be further increased. Further, the present invention can be applied to any type of projection type exposure apparatus. For example, it may be a stepper type using a projection lens, a step-and-scan type using a catadioptric system, or a 1: 1 mirror projection type. In particular, in the scan type (step and scan) and mirror projection methods, it is said that it is difficult to apply the conventional FLEX method because the reticle and the wafer are exposed by scanning while moving in a plane perpendicular to the optical axis of the projection optical system. But,
The present invention has an advantage that it can be applied to such a scanning type exposure apparatus very easily.

Therefore, a case where the present invention is applied to a mirror projection type aligner of the same size will be described with reference to FIGS. In FIG. 18, the illumination light from the mercury lamp (Xe-Hg) lamp 1 is the illumination optical system IL.
The light is projected on the reticle (mask) R via S in an arc slit-shaped illumination area. The reticle R is held on the reticle stage RST capable of one-dimensional scanning, and moves at the same speed in synchronization with the wafer stage WST. The projection optical system includes a trapezoidal optical block having reflection surfaces MR ₁ and MR ₄ on the reticle side and the wafer side, and a large concave mirror MR.
₂ and a small convex mirror MR _3, and the radius of curvature of the concave mirror MR ₂ is set to about twice the radius of curvature of the convex mirror MR ₃ . In the case of the system shown in FIG. 18, the surface of the convex mirror MR ₃ often coincides with the Fourier transform surface FTP with respect to the reticle pattern surface (or wafer surface).

At this time, the imaging light flux generated from the point Pr on the reticle R is reflected along the principal ray LLP by the reflecting surface MR ₁ ,
Proceed in the order of the upper side of the concave mirror MR ₂ , the entire surface of the convex mirror MR ₃ , the lower side of the concave mirror MR ₂ , and the reflecting surface MR ₄ ,
It converges on the point Pr ′ on the wafer W. Thus, even when the surface of the concave mirror MR ₃ is the pupil plane of the system, the coherence reducing member CCM used in each of the embodiments described so far.
Can be used as it is or with a slight modification.

Specifically, as shown in FIG. 19A, the interference
Consistency reduction member CCM is a convex mirror MR ₃ Placed in the immediate vicinity of
Concave mirror MR₂ From convex mirror MR₃ Incident on
Time and the convex mirror MR₃ From concave mirror MR₂ Injection to
With the optical path of 2 times (reciprocating) with the time of
Luminous flux passing through the excess FA and peripheral transmission FC and the intermediate zone
The luminous flux that has passed through the transmission part FB has a coherent length of ΔLc or more.
It suffices to configure the optical path length difference.

Alternatively, as shown in FIG. 19B, a minute step with a predetermined radius (area) is provided on the surface of the convex mirror MR ₃ ′ serving as a Fourier transform surface, and the upper surface and the lower surface of the step are formed. May give an optical path length difference (twice the step amount) of a coherent length ΔLc or more to the reflected light flux. In this case, the step may be formed integrally with the mirror MR ₃ ′, but in any case, the step corresponds to the coherence reducing member CCM. The stepped portion formed on the surface of the convex mirror MR ₃ ′ shown in FIG. 19B may be a transparent object (thin film). In that case, the step between the surface of the convex mirror MR ₃ ′ and the surface of the transmissive object (corresponding to the transmissive part FA), that is, the thickness d of the transmissive object is determined by the fact that the light beam reciprocates in the transmissive object having the refractive index n. Optical path length difference 2 (n-1)
It is determined that d is larger than the coherent length ΔLc.

When a half-wave plate or a quarter-wave plate is combined with any of the transmissive parts FA, FB, and FC to control the polarization state, a double polarization effect should be applied in the round-trip optical path. Considering that, the half-wave plate becomes a quarter-wave plate,
It is necessary to change the wave plate to a 1/8 wave plate.
Further, in a projection exposure apparatus using an excimer laser as a light source, a secondary light source surface (a large number of point light sources) formed on the exit side of a fly-eye lens or the like is re-imaged on the pupil surface of the projection optical system. Optical elements (lens, reflecting surface, aperture stop,
If the coherence reducing member CCM or the like) is arranged, the optical element may deteriorate due to a converged light source image due to long-term use. Therefore, it is preferable that the coherence reducing member CCM or the like is not strictly arranged on the pupil plane, but rather is slightly displaced.

In each of the above embodiments, when the coherence reducing member CCM is used as a transmissive member, its interface (surface) should be coated with an antireflection coating. As described above, in each of the embodiments of the present invention, the optical path length difference between the image forming light beams split by the coherence reducing member CCM of the type that gives an optical path difference of not less than the temporal coherence length ΔLc of the light beam (illumination light ILB). Is significantly larger than the optical path length difference (1/2 of wavelength to several wavelengths) given by the conventional Super-FLEX method. Furthermore, in the Super-FLEX method, all of the image-forming light flux that has passed through the filter (complex amplitude transmissivity) arranged on the pupil plane of the projection optical system interferes (amplitude synthesis) on the wafer W, which is the same. Invention and Sup
In principle, this is completely different from the er-FLEX method.
Due to the difference in its principle, in the present invention,
New effects not obtained by the r-FLEX method can be obtained. This will be described with reference to the simulation described below.

The interference reducing member CC used in the present invention
M is for the purpose of dividing an imaging light flux passing through the pupil plane (in the case of a contact hole pattern, distributed substantially uniformly) into a plurality of portions in the radial direction of the pupil, and reducing coherence between the respective partial light fluxes. Acts only on. Therefore, in the coherence reducing member CCM used in each embodiment, the best focus position (focus position) of each of a plurality of images (Pr ′ ₁ , Pr ′ ₂ etc.) formed independently of each other by partial light fluxes, Optical axis AX of projection optical system
There is no effect of offsetting the directions relative to each other, i.e. giving some sort of spherical aberration.

Next, the products obtained by the respective embodiments of the present invention
Explanation of effects and effects based on simulation results
To do. FIG. 20 (A) was used for the following simulation
Square contour with one side corresponding to 0.3 μm on the wafer
It is the cthole pattern PA and the simulation
In FIG. 20A, on the wafer of the cross section taken along the line AA ′ in FIG.
The image intensity distribution at is treated. FIG. 20 (B) shows
It shows the interference reduction member CCM shown in FIG. 3 etc.
Radius r of the circular transmission part FA of the heart₁ And the middle transparent zone F
Outer radius r of B₂ And the numerical aperture NAw of the projection optical system
Radius r of the pupil plane ₃ And the above equations (9) to (11)
, R₁ = Αr₃ , R₂ = Βr₃ , Β = 0.85 · α
+0.58 (0.2≤α≤0.4),
And In addition, all of the following simulations are NA
w = 0.57, exposure illumination light is i-line (wavelength λ is 0.36)
5 μm). In addition,
The σ value which is a coherence factor was set to 0.6.

Now, in FIG. 20C, α = 0.3 and β =
The image intensity distribution on the wafer of the pattern PA under the condition of 0.835 is shown. The solid curve represents the intensity distribution at the best focus position, and the alternate long and short dash curve represents the intensity distribution at the defocus position of 1 μm (almost solid line). The curve of the two-dot chain line is the intensity distribution at the defocus position of 2 μm. In addition, Eth in FIG. 20C indicates the intensity (exposure amount) required to completely remove (photosensitize) the positive photoresist on the wafer, and Ec indicates that the positive photoresist is dissolved (film reduction). The starting intensity (exposure amount) is shown. The vertical magnification (exposure amount) of each intensity distribution was set so that the diameter of the contact hole pattern image (the width of the slice crossing Eth) in the best focus state was 0.3 μm.
For comparison, FIG. 21 shows an intensity distribution at the best focus position (solid curve) by an ordinary exposure apparatus (with the coherence reducing member CCM removed), and an intensity distribution at a defocus position of 1 μm (dashed line curve). ), And the intensity distribution at the defocus position of 2 μm (curved with two-dot chain line).
Similarly, the simulation condition at this time is NAw =
0.57, wavelength λ = 0.365 μm, and σ = 0.6. Comparing FIG. 21 with FIG. 20C, it can be seen that in the SFINCS method according to the present invention, the change in image intensity during defocusing (contrast decrease) is reduced and the depth of focus is increased.

On the other hand, FIG.
It shows a change in image intensity distribution when the LEX method is combined. The exposure conditions of the FLEX method are that the best focus position and the position defocused by ± 1.25 μm each perform a total of three divided exposures. Comparing the simulation result of FIG. 22 with the simulation result of FIG. 20C, it can be seen that the effect of increasing the depth of focus in the present invention can be obtained to the same extent as in the FLEX method.

Next, simulation results under other conditions according to this embodiment are shown in FIGS. The simulation result shown in FIG. 23 shows that α = 0.20, β = 0.
24, and in FIG. 24, α = 0.40, β = 0.
92 conditions. Other conditions are the same as those shown in FIG. 20 (C). Even under these conditions, an image of the contact hole pattern having a sufficient depth of focus can be obtained as in the case of the above-mentioned conditions.

In addition to the above three conditions, (1
Using the coefficients α and β that satisfy the equations (0) and (11), a number of simulations are performed for the radii r ₁ and r ₂ determined by the relationship of r ₁ = α · r ₃ and r ₂ = β · r _3. However, as long as the radii r ₁ and r ₂ satisfy the above relational expressions, a good depth of focus can be obtained. In addition,
Expression (10) above, that is, (β = 0.85 · α + 0.5)
The relational expression of 8) does not necessarily have to be established exactly, and the effect of the present invention is sufficient if the value of the coefficient β is within a range of about ± 5% with respect to the value determined by the relational expression. Can be demonstrated. However, if the values of the coefficients α and β deviate significantly from the above equation (10), the effect of the present invention is weakened.

Incidentally, FIGS. 25 and 26 show the above (1
0) shows a simulation result under the condition that the expression (0) is not satisfied. FIG. 25 shows α = 0.3, β = 0.75 (β <0.85
.Alpha. + 0.58), and FIG.
0.3, β = 0.92 (β> 0.85 ・ α + 0.58)
It is the result under the condition of. In the case of FIG. 25, the double focus effect (effect of coherent addition between the transmission parts FA and FC) by the pupil filter is too strong, and it is ± 1 μm defocused state (indicated by a chain line) from the best focus state (solid line curve). Curve), the peak intensity of the image is stronger and the level Et
The slice width at h also becomes wider. Therefore ± 1 μm
At the time of defocusing, the size of the transferred contact hole pattern becomes larger than the design value (0.3 μm), and the desired pattern cannot be obtained.

On the other hand, in the case of FIG. 26, as compared with the best focus state (solid curve), the image deterioration in the ± 1 μm defocus state (dashed line curve) is large, and the increase in the depth of focus is not sufficient. I understand. 27 and 28 satisfy the relationship of the above equation (10), but are simulation results when α = 0. 1 and α = 0.94, respectively, and both are of the equation (11). Relationship, ie (0.2
≦ α ≦ 0.4) is not satisfied. Even in such a case, as compared with the best focus state (solid curve), ± 1 μm defocused state (dashed line curve)
It can be seen that the deterioration of the image is large and a sufficient depth of focus cannot be obtained.

FIG. 29 shows a conventional Super for comparison.
-This is a simulation result by the FLEX method, and the condition of the pupil filter is r for the radius r _{3 of} the pupil.
_A phase filter was used in which the phase of transmitted light within a circular region within a radius r ₄ determined by ₄ = 0.38 × r ₃ was shifted by π [rad] with respect to the phase of transmitted light outside the circular region. Transmittance is 100% radius r ₁ within the area and the radius r ₁ other regions both. Since the value of the radius r ₄ is optimized for the Super-FLEX filter based on various simulations, it is possible to obtain a good depth of focus as good as the projected image according to the present embodiment. But,
As can be seen from FIG. 29, there is a problem that the image of the contact hole pattern has strong sub-peaks (ringing) in the periphery. However, in the isolated contact hole pattern used in the simulation, the ringing does not pose a problem. However, when there are two contact hole patterns that are close to each other to some extent, the ringing of the images of both contact hole patterns overlaps each other, and the exposure amount due to ringing exceeds the level Ec at which the film thickness is reduced, and it is unnecessary for the photoresist. It causes film loss.

FIG. 30 shows an example of such a pattern. Two 0.30 μm square contact hole patterns are arranged close to each other with a center-to-center distance of 1.05 μm. The dimensions in this case are also converted into the values on the wafer. FIG. 31 shows the same Super as in the case of FIG.
30 is a simulation result of a projected image of the pattern of FIG. 30 when a FLEX type pupil filter is used.
The image intensity distribution (best focus state) in the cross section taken along the line AA 'is shown. As can be seen from FIG. 31, Supe
The ringing by the r-FLEX type pupil filter overlaps in the middle of the images of both contact hole patterns, and the ringing intensity exceeds the level Ec. Therefore, even in the transferred image on the photoresist, unnecessary film loss occurs in an unnecessary portion, which may cause a short circuit in the wiring of the LSI or the like. Therefore, in order to actually use the Super-FLEX type pupil filter, it is necessary to take some measures against a plurality of adjacent isolated patterns.

On the other hand, FIG. 32 shows a case of using the same pupil filter of this embodiment as that of FIG.
FIG. 31 is a simulation of projected images of individual contact hole patterns, and represents an image intensity distribution (best focus state) in a cross section taken along the line AA ′ in FIG. 30. As can be seen from FIG. 32, in the pupil filter of the present embodiment, unlike the conventional Super-FLEX type pupil filter, since the ringing around the original image is small, the image intensity between both contact hole pattern images is also sufficient. It is very dark, and there is no risk of unnecessary erroneous transfer.

Although the respective embodiments of the present invention and the operation thereof have been described above, when the illumination light ILB to the reticle R has a specific polarization direction, it is judged whether the polarization direction is appropriate or not, or there is interference. A means for photoelectrically detecting a part of the light flux that has passed through the projection optical system may be provided on the wafer stage WST in FIG. 8 in order to determine whether the polarization state of the image-forming light flux after passing through the property reducing member CCM is good or bad. Good. Further, when using a reticle having a line-and-space pattern, the coherence reducing member CCM may be moved out of the projection optical system PL, and a part of the illumination system may be exchanged so as to be suitable for the SHRINC method. In addition, the coherence reducing member CCM is used at the time of projection exposure of the contact hole pattern, and S
A modified illumination system such as the HRINC method or an annular illumination light source may be used together. In that case, when changing the reticle to be exposed from the contact hole pattern to the line and space pattern, the interference reducing member CC
Only M should exit.

Further, the interference reducing member CCM shown in each of the embodiments of the present invention is composed of a circular or annular transmissive portion or a light shielding portion, but this is not limited to a literal shape. For example, the circular transmissive portion or the light shielding portion may be deformed into a polygon including a rectangle, and the annular transmissive portion or the light shielding portion may be deformed into a shape surrounding the polygon in an annular shape.

Further, in each of the above embodiments, the circular shape at the center
Transparent part FA, intermediate transparent part FB, and peripheral annular part
Each boundary of the transparent portion FC has a radius r₁ And r₂ Place of
However, for example, the interference reduction member
Due to manufacturing reasons, etc., light-shielding parts (rings
Shape) may be provided. In this case, as shown in FIG. 4 and FIG.
The wavefront aberration due to the defocus is further reduced by the light shield.
Therefore, the effect of increasing the depth of focus according to the present invention is further increased.
You can In this case, the radius r₁ , R ₂ Is a husband
It is good to consider it as the middle of each light-shielding part (ring-shaped). Well
In addition, by blocking the light near the optical axis in the central transmission area FA,
In the same way as above, the effect of increasing the depth of focus can be further increased.
It is possible.

Further, the present invention may be further combined with the FLEX method to further increase the depth of focus. As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0097]

According to the present invention, the depth of focus during projection exposure of an isolated pattern such as a contact hole pattern is
It can be expanded to the same extent as the FLEX method or the Super-FLEX method, and it does not move or vibrate the photosensitive substrate in the optical axis direction unlike the FLEX method, and it is complicated like the Super-FLEX method. The advantage is that it is not necessary to create a spatial filter having a function of complex complex amplitude transmittance.

In particular, in the present invention, the pupil plane (Fourier transform plane) of the projection optical system or a surface in the vicinity thereof satisfies the predetermined condition 3
The ringing itself, which is likely to occur due to spatial filtering, is divided into individual areas and the coherence reducing member sets the coherence between the illumination lights passing through these three areas to a predetermined state. Is sufficiently small. Therefore, even when a plurality of contact hole patterns are arranged relatively close to each other, there is no adverse effect (such as generation of a ghost image) caused by superposition of ringing sub-peak portions as in the Super-FLEX method. Such a great effect can be obtained.

Further, when the illumination means is a ring illumination system or a modified light source system, the effect of expanding the depth of focus is further enhanced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a normal projection exposure method.

FIG. 2 is an optical path diagram for explaining the principle of the projection exposure apparatus according to the present invention.

FIG. 3 is a diagram for explaining the principle configuration of a coherence reducing member used in the projection exposure apparatus according to the present invention.

FIG. 4 is a diagram for explaining the principle of increasing the depth of focus by the coherence reducing member of FIG.

5 is a diagram for explaining the principle of increasing the depth of focus by the coherence reducing member of FIG.

FIG. 6 is a diagram for explaining the concept of depth of focus in a conventional projection exposure method.

FIG. 7 is a diagram for explaining the concept of depth of focus in a conventional dual focus filter.

FIG. 8 is a configuration diagram showing an entire embodiment of a projection exposure apparatus according to the present invention.

9 is a sectional view showing in detail the structure of a part of the projection optical system PL of FIG.

FIG. 10 is a coherence reducing member CCM according to the first embodiment of the present invention.
It is a figure which shows the structure of.

FIG. 11 is a coherence reducing member CCM according to a second embodiment of the present invention.
3 is a cross-sectional view showing the configuration of FIG.

FIG. 12 is a coherence reducing member CCM according to a third embodiment of the present invention.
It is a figure which shows the structure of.

FIG. 13 is a coherence reducing member CCM according to a fourth embodiment of the present invention.
FIG. 7 is a diagram for explaining the configuration and action of FIG.

FIG. 14 is a diagram showing a modification of some members of the illumination optical system applied to the embodiment of the present invention.

FIG. 15 is a coherence reducing member CCM according to a fifth embodiment of the present invention.
FIG. 7 is a diagram for explaining the configuration of FIG.

FIG. 16 is a diagram showing a configuration example of some members in the illumination optical system in which the polarization direction is controlled.

17 is a coherence reduction member C according to the fifth embodiment of FIG.
FIG. 17 is a diagram for explaining a state when the CM and the illumination optical system of FIG. 16 are combined.

FIG. 18 is a configuration diagram showing a mirror projection type aligner to which each embodiment of the present invention is applied.

FIG. 19 is a diagram showing a main part when the coherence reducing member CCM of each embodiment of the present invention is applied to the aligner of FIG. 18.

FIG. 20 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by the SFINCS method (α = 0.3, β = 0.835) of this example.

FIG. 21 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by a conventional ordinary exposure method.

FIG. 22 shows a conventional F with a single contact hole pattern.
It is a figure which shows the simulation result of the intensity distribution of the optical image obtained by projection by the LEX method.

FIG. 23 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by the SFINCS method (α = 0.20, β = 0.75) of this embodiment.

FIG. 24 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by the SFINCS method (α = 0.40, β = 0.75) of this embodiment.

FIG. 25 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by the SFINCS method (α = 0.3, β = 0.75) of the present embodiment.

FIG. 26 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting a single contact hole pattern by the SFINCS method (α = 0.3, β = 0.92) of this example.

FIG. 27 shows a single contact hole pattern formed by the SFINCS method (α = 0.1, β = 0.85 · α +) of this embodiment.
It is a figure which shows the simulation result of the intensity distribution of the optical image obtained by projecting at 0.58).

FIG. 28 shows a single contact hole pattern formed by the SFINCS method (α = 0.494, β = 0.85 · α) of this embodiment.
It is a figure which shows the simulation result of the intensity distribution of the optical image obtained by projecting at +0.58).

FIG. 29 shows a conventional S with a single contact hole pattern.
It is a diagram illustrating a simulation result of the intensity distribution of the optical image obtained by projecting the uper-FLEX method _{(r 4 = 0.38 · r 3} ).

FIG. 30 is an enlarged view showing two contact hole patterns arranged close to each other.

FIG. 31 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting two adjacent contact hole patterns by the same conventional Super-FLEX method as in the case of FIG. 29.

FIG. 32 is a diagram showing a simulation result of intensity distribution of an optical image obtained by projecting two adjacent contact hole patterns by the same SFINCS method as in the case of FIG. 20.

[Explanation of symbols] R reticle W Wafer PL Projection optical system FTP Fourier transform plane (pupil surface) AX Optical axis PA Contact hole pattern CCM Coherence reducing member FA Circular transmissive part FB, FC Annular transmissive part ILB Illumination light 1 Mercury lamp 5 Interference filter 6 Polarization control member 7 Fly-eye lens 8 Variable aperture 11 Reticle blind 20 Slider mechanism 25 Main control unit

Claims (4)

[Claims] 1. A mask on which a transfer pattern is formed
Illumination means for illuminating with the illumination light for exposure, and
To form an image of the mask pattern on a photosensitive substrate
In a projection exposure apparatus including a projection optical system for projecting, a pattern forming surface of the mask in the projection optical system is provided.
Optical Fourier transform plane or a plane through which imaged light passes
Above, the projection optics centered on the optical axis of the projection optics
Radius r corresponding to the numerical aperture of the system₃The area of
Radius r as the heart ₁Centered on the first region of
Radius is r₁To r₂Second zone in the form of an annulus up to the front
Radius r centered on the optical axis₂To r₃Zonal up to
It is divided into a third region (however, r₁<R₂<R₃), Imaging light distributed in the first region and the third region,
The coherence with the imaging light distributed in the second region is reduced.
And the imaging light distributed in the first region and
(2m + 1) π between the imaging light distributed in the third region
A coherence reducing member that gives a phase difference (m is an integer) is provided, and the radius r₁And r₂Is the radius r₃And a predetermined coefficient
r using α and β respectively₁= Α ・ r₃, R₂= Β · r₃ , Β = 0.85 · α + 0.58 and 0.2 ≦ α ≦ 0.
A projection exposure apparatus characterized in that the relationship of 4 is established. 2. As the coherence reduction member, the illumination light between the imaging light distributed in the first area and the third area and the imaging light distributed in the second area 2. The projection exposure apparatus according to claim 1, wherein a temporal coherency reduction member that gives an optical path difference equal to or longer than a coherence length determined according to a wavelength range is used. 3. The polarization state of the image forming light distributed in the first region and the third region and the polarization state of the image forming light distributed in the second region are mutually defined as the coherence reducing member. The projection exposure apparatus according to claim 1, wherein a polarization control member that does not interfere is used. 4. The projection exposure apparatus according to claim 1, wherein the illuminating unit is an annular illumination system or a modified light source system.