JPH06124870A - Projection exposure apparatus and exposure method - Google Patents

Abstract

PURPOSE:To enlarge the depth of focus by providing a coherence-reducing member in the Fourier transform surface or its neighboring surface in the image- formation optical path between a mask and sensitive substrate. CONSTITUTION:The pupil surface FTP of a projection optical system between a reticle R and sensitive substrate W is provided with a coherence-reducing member CCM. An image-formation luminous flux LLp diffracted by an isolated pattern Pr formed on the pattern surface of the reticle R enters the pre-group lens system GA of the projection optical system PL and thereafter reaches a Fourier transform surface FTP. In the Fourier transform surface FTP, then, luminous fluxes respectively passing through the circular transmission part FA and zonal transmission part FB of the central part in the pupil surface ep are controlled to a state where both fluxes do not interfere with each other. Consequently, Line luminous fluxes LFa and LFb respectively passing through the circular transmission part FA and peripheral transmission part FB of the coherence-reducing member CCM do not interfere with each other on a wafer W. Thus, it is possible to enlarge the depth of focus of the isolated pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type exposure apparatus used for forming fine patterns in semiconductor integrated circuits, liquid crystal displays and the like.

[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 by 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 (wafer or the like) through a projection optical system is mainly used. An excimer stepper using an excimer laser (KrF laser having a wavelength of 248 nm) 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, the depth of focus (DOF) decreases with increasing numerical aperture NA. The depth of focus is defined by DOF = ± λ / NA ² where λ is the wavelength of the illumination light.

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. This type of projection optical system is generally one in which both the reticle R side and the wafer W side are telecentric, or one in which only the wafer W side is telecentric. Now, in FIG. 1, three arbitrary 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 , La, L traveling from point A in various directions
a ', of the La ", light L ₁ occurs at an angle that can not enter the lens system GA of the projection optical system. Moreover, of the light incident on the lens system GA of the front group, ray L _2, L ₃
Is a pupil e located on the Fourier transform plane FTP in the projection optical system.
cannot pass p. And the other rays La, L
a ′ and La ″ pass through the pupil ep, enter the lens system GB of the rear group, and converge at the point A ′ on the surface of the wafer W (pupil surface of the projection optical system). Among the light rays generated from A, the light rays that have passed through the pupil ep of the projection optical system (a circular area centered on the optical axis AX) contribute to forming a point image at the point A ′. A ray La that passes through the center point CC (position of the optical axis AX) of the pupil ep among the rays directed to the point A ′ is called a principal ray, and this principal ray La is, in the case of a telecentric projection optical system on both sides, the object plane side, It is parallel to the optical axis AX in each space on 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 both chief rays passing through the center point CC of the pupil ep. In this way, the pupil ep has a Fourier transform and an inverse Fourier transform with respect to the pattern surface of the reticle R and the surface of the wafer W, and the light rays that contribute to image formation among the light rays from the pattern on the reticle 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 NA _W on the wafer (image plane) side, and is represented by NAw = sin θw Therefore, the angle θr formed by the light rays La ′ and La ″ with the principal ray La on the reticle R side is ) Side numerical aperture NAr, which is represented by NAr = sin θr. Further, the image forming magnification of the projection optical system is M (M for 1/5 reduction
= 0.2), NAr = M · NAw.

In order to increase the resolution, the numerical aperture NAw (NAr) must be increased. In other words, this means increasing the diameter of the pupil ep and further increasing the effective diameters of the lens systems GA and GB. It is nothing but making it bigger.
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. , Becomes a big obstacle in practical use.

When the wavelength of the illumination light is 365 nm of the i-line and the numerical aperture NAw is 0.6, the depth of focus DOF becomes about 1 μm (± 0.5 μm) in width, and one shot on the wafer W is obtained. In a region (20 mm square to 30 mm square), unevenness or curvature of the surface causes DOF or more in a portion having a DOF or more. Also on the stepper system, focusing for each shot area of the wafer W,
Since it becomes necessary to perform leveling and the like with extremely high accuracy, the load on the mechanical system, the electrical system, and the software (measurement resolution, servo control accuracy, setting time, etc.) will increase.

Therefore, the applicant of the present invention has solved such problems of the projection optical system, and has a high resolution and a large focus without using a phase shift reticle disclosed in Japanese Patent Publication No. 62-50811. A new projection exposure technique capable of obtaining both depth and depth is disclosed in JP-A-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 apparent resolving power and the depth of focus by controlling the reticle illumination method to a special shape while maintaining the existing projection optical system.
HRINC (S uper H igh R esoluti
on by I llumi N ation C ontro
l) We call it the law. The SHRINC method irradiates the reticle with two illumination lights (or four illumination lights) symmetrically inclined in the pitch direction of the line and space pattern (L & S pattern) on the reticle R, and is generated from the L & S pattern. The 0th-order diffracted light component and one of the ± 1st-order diffracted light components are passed symmetrically with respect to the center point CC in the pupil ep of the projection optical system, and two-beam interference (interference between one 1st-order diffracted light and the 0th-order diffracted light) occurs. The principle is utilized to generate a projected image (interference fringe) of an L & S pattern.

According to the image formation utilizing the two-beam interference as described above, 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 apparently becomes large. Of. However, in the SHRINC method, the desired effect can be obtained when the pattern formed on the reticle R has a periodic structure like an L & S pattern (lattice). Can't get the effect.
In general, in the case of an isolated minute pattern, most of the diffracted light from it occurs as Franforfer diffraction, so that it is not clearly separated into zero-order diffracted light and higher-order diffracted light in the pupil ep of the projection optical system.

Therefore, as an exposure method for increasing the apparent depth of focus for an isolated pattern such as a contact hole, the exposure for one shot area of the wafer W is divided into a plurality of times, and the wafer W is subjected to the optical axis between the exposures. A method of moving a certain amount in a certain direction has been proposed, for example, in Japanese Patent Laid-Open No. 63-42122. This exposure method is FLEX ( F ocu
s L attitude enhancement EX
This is called the "posure) method, and a sufficient depth of focus expansion effect can be obtained for isolated patterns such as contact holes. However, since the FLEX method requires multiple exposure of a slightly defocused contact hole image, the sharpness of the resist image obtained after development is inevitably reduced. The problem of deterioration of sharpness (profile deterioration) is to use a resist with a high gamma value,
Multi-layer resist is used, or CEL (Contr
It can be compensated by using ast Enhancement Layer).

As an attempt to increase the depth of focus when projecting a contact hole pattern without moving the wafer W in the optical axis direction during the exposure operation as in the FLEX method, 1
991 Spring Applied Physics Society Proceedings 29a-ZC-8,
The Super-FLEX method announced in 9 is also known. This Super FLEX method uses the pupil e of the projection optical system.
A transparent phase plate is provided on p, and the phase plate has such a characteristic that the complex amplitude transmittance given to the image-forming light sequentially changes from the optical axis AX toward the periphery. 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.

[0013]

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 has been found that in the case of a plurality of contact hole patterns that are close to each other to some extent, both methods cause an unnecessary film slip in the photoresist between the holes, which makes it practically difficult to use.

Further, in the FLEX method, even for an isolated contact hole pattern, the sharpness of the image (synthesized optical image obtained by multiple exposure) is inevitably deteriorated. There is also the problem that the degree decreases. Further, 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 divided into the first exposure and the second exposure. In the method in which the wafer is moved in the optical axis direction between the exposures, there is a problem that the processing capacity is largely reduced and the throughput is significantly reduced.

Therefore, the present invention has an object to obtain a projection exposure apparatus having an increased depth of focus when projecting and exposing isolated patterns such as contact holes, and particularly for a plurality of isolated patterns which are relatively close to each other. An object of the present invention is to provide an apparatus and an exposure method that enable faithful transfer and at the same time obtain the effect of increasing the depth of focus.

[0016]

In order to solve the above problems, in the present invention, an illuminating means (1 to 1) for irradiating a mask (reticle R) on which a fine pattern is formed with illuminating light for exposure.
4) and a projection optical system (PL) for injecting light generated from the pattern of the mask and projecting an image of the pattern onto the sensitive substrate (wafer W) by imaging, the mask and the sensitive substrate. A circular area (FA) which is arranged on the Fourier transform plane (FTP) in the image forming optical path between and or near the Fourier transform plane, and which is centered on the optical axis of the projection optical system on the Fourier transform plane or on the near plane. A coherence reducing means (coherence reducing member CCM) for reducing coherence between the image forming light (LFa) distributed inside and the image forming light (LFb) distributed in the area (FB) outside thereof is provided. I chose

[0017]

In the present invention, a coherence reducing member is provided on a surface (hereinafter referred to as a pupil surface) in the projection optical system which has an optical Fourier transform relationship with the reticle pattern surface, or a surface in the vicinity thereof. A part of the image-forming light distributed in a circular or annular shape on the pupil plane and an image-forming light distributed in the other part are set not to interfere with each other. As a result, the exposure light beam (imaging light) that has been transmitted and diffracted in the reticle pattern, particularly through the contact hole pattern, is spatially divided into two light beams that do not interfere with each other in the pupil plane and reach the exposure target such as a wafer. To do. Even on the wafer, the two light beams do not interfere with each other (are incoherent), so that an intensity combined image of the images (contact hole images) produced by the respective light beams can be obtained. In the conventional exposure method, when the light beams that have passed through the minute contact hole pattern on the reticle and are diffracted reach the wafer surface through the projection optical system, they are all combined amplitude-wise (coherent addition) and the reticle pattern image (optical image ) Was formed. Conventional Super-FLE
Also in the X method, since the imaging light distributed on the pupil plane is only partially phase-shifted, it is still coherent addition.

Now, assuming that there is no phase shift plate or the like on the pupil plane of the projection optical system, the optical path length from any one point on the reticle to the corresponding image point on the wafer in best focus (in focus). Are the same regardless of which optical path in the projection optical system passes (Fermat's principle), so amplitude synthesis on the wafer is the synthesis of light with no phase difference,
All act in the direction of increasing the strength of the contact hole pattern.

However, when the wafer is defocused (deviation in the optical axis direction between the wafer surface and the best focus surface),
The above optical path length varies depending on the optical line in the projection optical system. As a result, the above-mentioned amplitude synthesis is the addition of light having an optical path difference (phase difference), and a canceling effect occurs in part,
The central strength of the contact hole pattern is weakened. If the incident angle of an arbitrary ray incident on one image point on the wafer is θ and the optical path length of the ray (chief ray) incident vertically on the wafer is a reference (= 0), the optical path difference generated at this time is It is expressed as approximately 1/2 (ΔF · sin ² θ). Here, ΔF represents the defocus amount. Since the maximum value of sin θ is the numerical aperture NAw on the wafer side of the projection optical system, when all the light passing through the pupil ep among the diffracted light from the minute hole pattern is amplitude-synthesized on the wafer as in the conventional case,
The maximum optical path difference is 1/2 (ΔF · NAw ² ). At this time, assuming that an optical path difference of λ / 4 is allowed as the depth of focus, the following relationship holds.

1/2 (ΔF · NAw ² ) = λ / 4 When this equation is recombined, ΔF = λ / (2NAw ² ), which is in agreement with the generally-known depth of focus. For example, i-line (wavelength 0.3
65 μm), numerical aperture NAw = 0.50
Assuming that, 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.

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 circular transparent portion F at the center in the pupil plane ep
The light fluxes transmitted through A and the annular transmission portion FB are controlled (converted) to a state where they do not interfere with each other. Therefore, on the wafer W, the light flux LFa transmitted through the circular transmissive portion FA of the coherence reducing member CCM and the light flux LFb transmitted through the peripheral transmissive portion FB do not interfere with each other. As a result, the luminous flux LFa from the circular transmitting portion FA and the luminous flux LF from the peripheral portion FB are formed.
b independently interfere with each other by themselves to form an image (intensity distribution) Pr ′ of a hole pattern. That is, an image obtained by the interference of only the light beam LFa and an image produced by the interference of only the light beam LFb is simply added in terms of intensity, and an isolated contact hole or the like obtained by the present invention is obtained. It becomes a pattern image Pr '.

The illumination light ILB to the reticle R has 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 NAr> sin ψ / 2. Therefore, the principle of image formation in the present invention will be described with reference to FIG. FIG. 3 shows a structure of the coherence reducing member CCM and a state of an image-forming light flux that forms an image Pr ′ of the contact hole,
3 schematically shows each relationship with the optical path difference ΔZ of each light flux at the time of defocusing.

Light flux LFa passing through the central portion as shown in FIG.
In the amplitude combination in the above, since the light flux LFa includes a light ray in the angle range from the vertically incident light ray (main light ray LLp) to the incident angle θ ₁ , the maximum value Δ of the optical path difference when the defocus amount is ΔF.
Z ₁ is ΔZ ₁ = 1/2 (ΔF · sin ² θ ₁ ). The horizontal axis of the graph at the bottom of FIG. 3 represents the sine of the incident angle.
Let nθ ₁ = NA ₁ . On the other hand, in the amplitude synthesis in the light flux LFb passing through the peripheral portion as shown in FIG. 3B, the light flux LFb has a light ray in the incident angle range from the incident angle θ ₁ to the numerical aperture NAw (sin θw). Is ΔF, the maximum optical path length difference ΔZ ₂ is ΔZ ₂ = 1/2 (ΔF) (NAw ² −sin ² θ ₁ ).

Since the first light beam LFa and the second light beam LFb do not interfere with each other, the deterioration of the image Pr ' ₁ due to the interference of only the light beam LFa and the deterioration of the image Pr' ₂ due to the interference of only the light beam LFb are different. This is caused only by the optical path length differences ΔZ ₁ and ΔZ ₂ in the light flux. For example, if sin θ ₁ is set so that sin ² θ ₁ = 1/2 (NAw ² ), that is, if the radius of the first transmission part FA is set so as to substantially satisfy this relational expression, the first light flux LFa The maximum optical path difference ΔZ _{1 due} to
The maximum optical path difference ΔZ ₂ due to the light flux LFb is as follows.

ΔZ ₁ = 1/2 (ΔF · sin ² θ ₁ ) =
1/4 (ΔF · NAw ² ) ΔZ ₂ = 1/2 (ΔF) (NAw ² −sin ² θ ₁ ) = 1/4
(ΔF · NAw ² ) Thus, the two incoherent light beams LFa and L
Each of the Fbs has substantially the same maximum optical path difference, 1/4 (ΔF · NAw ² ), when defocused by ΔF, and this value is half that in the conventional case. In other words, even if the defocus amount (2ΔF) is twice as large as the conventional one, the same maximum optical path length difference as in the case of the defocus amount ΔF in the conventional projection method will suffice, resulting in the isolated pattern Pr.
The depth of focus at the time of imaging is increased about twice. The pupil plane ep of the projection optical system PL, a method of exchanging a plurality of light beams do not interfere with imaging light beam from each other, thereafter SFINCS (S patial F ilter for
It will be referred to as INC oherent S tream) method.

[0026]

FIG. 4 shows the overall construction of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 4, the high-intensity 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. A rotary shutter 3 is arranged at the position of the second focal point, and controls passage and blocking of illumination light. The illumination light converted into a substantially parallel light flux by the collimator lens 4 is
It is incident on the interference filter 5, where only the desired spectrum required for exposure, eg, 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.

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 the diaphragm 8 is reflected by a mirror 9 and enters a condenser lens system 10, and then illuminates the rectangular opening of the reticle blind 11 with a uniform illuminance distribution. In FIG. 4, of the plurality of secondary light source images (point light sources) formed on the exit side of the fly-eye lens 7, the optical axis A
Only illumination light from one secondary light source image located on X is representatively shown. Moreover, 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 for the rectangular aperture surface of the reticle blind 11. Therefore, fly eye lens 7
From each of the plurality of secondary light source images of the condenser lens system 1
The respective illumination lights that have entered 0 are superimposed on the reticle blind 11 as parallel light beams having slightly different incident angles.

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. 4, the illumination light ILB from one secondary light source image located on the optical axis AX of the secondary light source image of the fly-eye lens 7 has an inclination with respect to the optical axis AX on the reticle R. There is no parallel light flux, but
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.
It goes without saying that the pattern surface of the reticle R and the exit side surface of the fly-eye lens 7 are optically Fourier-transformed by the combined system of the condenser lens system 10, the lens system 12, and the condenser lens 14. . Further, the incident angle range ψ of the illumination light ILB on the reticle R (see FIG. 2)
Varies depending on the aperture diameter of the diaphragm 8. When the aperture diameter of the diaphragm 8 is reduced to reduce the substantial area of the surface light source, the incident angle range ψ also decreases. Therefore, the diaphragm 8 adjusts the spatial coherency of the illumination light. As a factor representing the degree of spatial coherency, a ratio (σ value) between the sine of the maximum incident angle ψ / 2 of the illumination light ILB and the numerical aperture NAr of the projection optical system PL on the reticle side is used. This σ value is usually defined by σ = sin (ψ / 2) / NAr, and most steppers currently in operation have σ = 0.
It is used in the range of 5 to 0.7. In the present invention, the σ value may be any value, and in an extreme case σ =
It may be about 0.1 to 0.3.

A predetermined reticle pattern is formed by 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 dimensions on the reticle R are determined in consideration of the above. Further, since the dimension between adjacent contact hole patterns is usually considerably larger than the dimension of the opening of one contact hole pattern, it exists as an isolated minute pattern. That is, the two adjacent contact hole patterns are often separated to the extent that the light (diffracted and 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. 4, 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 imaged on the photoresist layer on the surface of the wafer W via the projection optical system PL. To be done.
Here, the optical path from the reticle R to the wafer W in FIG. 4 is shown only by the chief ray of the imaging light flux. And the projection optical system P
The Fourier transform plane FTP in L 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 performing exposure work in a lithography process by a plurality of steppers, in consideration of the most efficient operation of each stepper, it is hesitant to assign one specific stepper to the exposure dedicated to the contact hole pattern. Therefore, the coherence reducing member CCM is the projection optical system PL.
It is desirable that the stepper be provided so that it can be inserted into and removed from the pupil ep so that the stepper can be used even when exposing a reticle pattern other than the contact hole pattern. Depending on the projection optical system, its pupil position (Fourier transform plane FT
A circular aperture stop (NA) for changing the effective pupil diameter
A variable diaphragm may be provided. 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 (hereinafter referred to as XY movement) in a plane perpendicular to the optical axis AX, and
The wafer is held on a wafer stage WST that is slightly moved (hereinafter, referred to as Z movement) in a direction parallel to the optical axis AX. The XY movement and the Z movement of the wafer stage WST are performed by the stage drive unit 22, the XY movement is controlled according to the coordinate measurement value by the laser interferometer 23, and the Z movement is set to the detection value of the focus sensor 24 for autofocus. It is controlled based on. Stage drive unit 2
2. The slider mechanism 20 and the like 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, and the shutter 3
In addition to controlling the opening and closing of the aperture, a command is sent to the aperture control unit 27 to control the size of each aperture of the diaphragm 8 or the reticle blind 11. Further, the main control unit 25 can input the reticle name read by a bar code reader 28 provided in the reticle transport path to the reticle stage RST. Therefore, the main control unit 2
5 is a slider mechanism 20 according to the input reticle name.
And the operation of the aperture drive unit 27 are comprehensively controlled to automatically adjust the size of each aperture of the diaphragm 8 and the reticle blind 11 and the necessity / non-necessity of the interference reducing member CCM according to the reticle. be able to.

Here, the structure of a part of the projection optical system PL in FIG. 4 will be described with reference to FIG. FIG. 5 shows a partial cross section of the projection optical system PL, which is made entirely of a refractive glass material. The lowermost lens GA ₁ of the front lens group GA and the uppermost lens GB ₁ of the rear lens system GB are shown. 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. In addition, 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 20
B prevents minute dust floating in the outside air from entering the pupil space of the projection optical system PL. The slider mechanism 20 has
An actuator 20A such as a rotary motor, a pen cylinder, and a solenoid is connected. Further, a channel 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 supplied. The temperature rise due to absorption and the temperature rise of the entire pupil space are suppressed. In addition, the clean air forcibly supplied to the pupil space,
By forcibly discharging it through the slider mechanism 20 and the actuator 20A, it is possible to prevent dust generated in the slider mechanism 20 and the like from entering the pupil space. 6A and 6B show the structure of the coherence reducing member CCM according to the first embodiment. FIG. 6A is a sectional view taken along a point passing through the optical axis AX, and FIG. 6B is a plan view. As described previously in conjunction with FIG. 3, the maximum radius r ₂ circular transmitting portion radius r ₁ of the FA is a effective pupil ep in the center of the pupil, r ₂
The relationship is set to ² = 2r ₁ ² , but in reality it is better to be several percent larger than that. As is clear from this equation,
The area πr ₁ ² of the circular transmission part FA is the effective area π of the pupil aperture.
It is about half of r ₂ ² .

The light from the light source (mercury lamp 1) in FIG. 4 is in a random polarization state (light is a composite light of various polarization states, and the polarization state changes with time). At the same time, its coherent length ΔLc is extremely short. Now, with the illumination light as the i-line, the central wavelength λ ₀ = 36
When the wavelength width is 5 nm and the wavelength width is Δλ = 5 nm, the coherent length ΔLc is obtained as follows.

ΔLc = λ ₀ ² / Δλ≈26 μm A coherence reducing member CCM shown in FIG. 6 is a parallel flat plate glass having a refractive index of n ₁ and a thickness of t in a circular transmission part FA having a radius r ₁ from a center point CC. Alternatively, a parallel plate-shaped crystal element is used, and the ring-shaped peripheral transmission part FB coaxial with the center point CC is formed of a parallel plate glass having a refractive index of n ₂ and a thickness of t, or a crystal element. With such a configuration, the optical path difference between the imaging light beam LFa that has passed through the circular transmissive portion FA and the imaging light beam LFb that has passed through the peripheral annular zone transmissive portion FB must be at least the coherent length ΔLc of the light. For example, the two light beams LFa and LFb are temporally incoherent light beams. That is, | (n
_{The two} glass materials (refractive indexes n ₁ and n ₂ ) and the thickness t may be determined so as to satisfy the relationship of ₂ −n ₁ ) t | ≧ ΔLc. Here, assuming that the circular transmission part FA is a glass having a refractive index n ₁ = 1.50 and the ring-shaped transmission part FB is a glass having a refractive index n ₂ = 1.60, the i-line (Δλ = 5 nm) of the mercury lamp is If
| (1.60-1.50) t | ≧ 26 μm, the thickness t
Is 260 μm or more. There is no particular upper limit for the thickness t, and a glass plate having a thickness of several mm is sufficient.
However, when the illumination light from the light source is extreme ultraviolet light (for example, a wavelength band of 240 nm to 250 nm by a xenon mercury lamp), absorption is large in general optical glass, so it is a good idea to increase the thickness t more than necessary. is not. In any case, the imaging light fluxes that have passed through the circular transmissive portion FA and the annular transmissive portion FB become luminous fluxes (LFa, LFb) that do not interfere with each other. Both central and peripheral light fluxes that do not interfere with each other reach the wafer W, and each of them amplitude-synthesizes only with itself, and separates images (intensity distribution).
The principle of increasing the depth of focus of the composite image (composite intensity distribution) by forming Pr ₁ 'and Pr ₂ ' is as described in the section of action.

FIG. 7 shows the structure of the interference reducing member CCM according to the second embodiment. In this embodiment, as in the case of FIG. 6, the central circular transmissive portion FA and the peripheral annular transmissive portion FB are the same in that they are optical glasses having a thickness t and refractive indices n ₁ and n ₂ , respectively. However, the difference is that a transparent plate FC having a more uniform thickness is provided on the entire surface of the exit side (or the entrance side). As the material of the transparent plate FC, quartz glass or fluorspar that transmits extreme ultraviolet light is used, and as shown in FIG. Placed with a gap maintained. Also in this embodiment, the light flux that has passed through the circular transmissive portion FA and the transparent plate FC and the light flux that has passed through the annular transmissive portion FB and the transparent zone FC have a temporal incoherent relationship.

FIG. 8 collectively shows some sectional structures of other modified examples of the coherence reducing member (optical path length difference controlling member) CCM used in each embodiment of the present invention.
FIG. 8A shows a transparent circular substrate (glass, quartz, etc.) OP ₁ of uniform thickness having a diameter slightly larger than the effective maximum radius r ₂ of the pupil ep, and glass or resin with a minute thickness ta. The thin plate OP ₂ is placed or attached. This thin plate OP ₂ constitutes a circular transmission part FA having a radius r ₁ , and when its refractive index is n ₁ , a light beam passing through both the thin plate OP ₂ and the substrate OP ₁ and a light beam passing through only the substrate OP ₁ (ring The difference in the optical path length between the transmitted light of the band transmission portion FB) is (n
₁ -1) given by ta. Therefore, from the relationship with the coherent length ΔLc of the luminous flux (illumination light), (n ₁ −1) ta ≧
The thickness ta of the thin plate OP ₂ may be determined so as to satisfy ΔLc.

This thin plate OP₂As the material of the glass,
High transmittance for crystals or ultraviolet light (exposure light)
Resins such as C manufactured and sold by Asahi Glass Co., Ltd.
YTOP (trade name) etc. can be used. In addition, in FIG.
As a method of manufacturing the interference reducing member CCM, a substrate OP is used.₁
Thin OP on top₂After pasting, the thin plate OP₂The surface of
It is desired to polish to obtain flatness and uniformity of the total thickness of the member CCM.
You may finish it. Or substrate OP₁Spat on top
Thin plate OP by a vacuum deposition method, a vapor deposition method, or a CVD method ₂Film formation
You may. Further thin plate OP₂When using as a resin,
Liquid of the resin of spin coating method (substrate OP₁Rotate
Then, drop the liquid resin at the center and apply centrifugal force to the desired thickness.
It may be formed by a method of stretching to the maximum).

In FIG. 8B, the radius of the center of at least one surface of a single circular transparent parallel substrate (quartz or the like) is r ₁
A circular transmission part FA is shown by etching the peripheral ring zone by the step tb. If the refractive index of this circular transparent substrate is n ₂ , then (n ₂ −1) tb
The step tb is determined so as to satisfy the relationship of ≧ ΔLc.
In general, fused silica has a refractive index of about 1.5 in the ultraviolet region, so the i-line coherent length ΔLc of a mercury lamp is 26 μm.
When m, the step tb may be 52 μm or more. When fluorspar is used, its refractive index is about 1.46, so the step tb may be 57 μm or more.

8C, a circular transparent parallel substrate (quartz or the like) OP ₁ is formed with a circular concave portion having a radius r ₁ and a depth tc at the central portion, and a thin plate OP made of glass or resin is formed therein.
₂ is placed or pasted together. This Figure 8
The configuration of (C) is only complementary to that of FIG. Here, let the refractive index of the thin plate OP _{2 be} n.
₁ and the refractive index of the substrate OP ₁ is n ₂ , (n ₁ −n
₂ ) The depth tc is determined so as to satisfy tc ≧ ΔLc. Although the surface of the thin plate OP ₂ is shown to be the same as the surface of the substrate OP ₁ , this is not always necessary.

FIG. 8D shows a circular transparent substrate OP.₁Heart of
Radius r₁Ion implantation, or
Refractive index differs due to thermal diffusion of impurity ions
Area OP₃It shows what formed. In this case, the substrate OP
₁The refractive index of n₂, Region OP ₃The refractive index of n₃, And
Area OP₃Is defined as td, | (n₃-N₂) T
The amount of change in the refractive index (n₃-N
₂), Or the thickness td is controlled.

Similar to FIG. 8B, in FIG. 8E, a circular transparent substrate OP ₄ and a ring-shaped transparent substrate OP ₅ which have the same refractive index but different thicknesses are manufactured separately, and later. It is a combination. The circular transparent substrate OP ₄ has a radius r ₁ and constitutes a circular transparent portion FA. Further, assuming that the thickness of the circular substrate OP ₄ is te, the thickness of the annular substrate OP ₅ is tf, and the refractive indices of both substrates are n ₂ , | (te-tf) (n ₂ −1) |
The relationship between the thicknesses is determined so as to satisfy ≧ ΔLc. Further, if the refractive index of the circular substrate OP ₄ is ne and the refractive index of the annular substrate OP ₅ is nf, then | (ne-1)
The relationship of te- (nf-1) tf | ≧ ΔLc may be satisfied. Therefore the two substrates OP _4, OP each refractive index of the ₅ ne, Different nf, two substrates OP _4, OP ₅
It is also possible to make the respective thicknesses te and tf the same, and in that case, the structure is the same as the structure of the coherence reducing member CCM in FIG. Further, in the case of the structure of FIG. 8E, te, ne, t
The relationship between f and nf is te (1-1 / ne) = tf (1-1
/ Nf), the effect on the optical aberration of the projection system can be minimized.

FIG. 8 (F) shows the surrounding annular zone FB.
An annular thin plate (quartz, etc.) with a thickness of tg is installed only on the contacting part.
The case of kicking is shown. At this time, the thickness tg is as shown in FIG.
Thin plate OP₂It may be considered under the same conditions as the thickness ta. Now,
FIG. 9 shows the structure of the interference reducing member CCM according to the third embodiment.
FIG. 9A shows a cross section at a point passing through the optical axis AX.
However, FIG. 9B shows a plane. In this embodiment, the optical axis AX
Centered on the center point CC of the pupil ep through which the radius r passes₁Round
Transmission part FA ₁And its outer diameter r₃First ring-shaped transparent
FB₂And the outer diameter r of the outer side₂(Effective of the pupil
Second zonal transparent part FB with various maximum diameters₃And three areas
Divided into each transparent part FA₁, FB₂, FB₃Imaging through
An optical path with a temporal coherence length ΔLc or more for each light flux
Give a length difference. The concrete structure is as shown in FIG.
The thing shown in FIG. 8 can be applied suitably. In the case of this embodiment,
Three transparent parts FA₁, FB₂, FB₃After passing through each of
It is necessary to prevent the image forming light beams of
It However, as is the case with the first and second embodiments,
It is not necessary to completely reduce the coherence to zero,
Just go. Further, in FIG. 9, the central circular transmission part FA₁Something
Although it is shown that the quality exists, the method of FIG.
When applied, circular transmission part FA₁The radius r₁The opening of
It can be (space).

Further, the interference reducing member CCM shown in FIG.
As a modified example, a transparent thin film (phase shifter) is provided in either one of the central circular transmissive portion FA ₁ and the outermost annular transmissive portion FB _3, and the transmitted light flux of the circular transmissive portion FA ₁ and the annular zone A phase difference of λ / 2 (that is, an opposite phase) may be given to the transmitted light flux of the transmission part FB ₃ . However, even in this case, an optical path length difference of coherent length ΔLc or more is given to the respective transmitted light fluxes of the other two transmissive portions FA ₁ and FB ₃ with respect to the transmitted light flux of the intermediate annular zone transmissive portion FB _2. There is.

Therefore, when the thicknesses and materials of the transmissive portions FA ₁ and FB ₃ are made equal, the transmissive luminous fluxes of the transmissive portions FA ₁ and FB ₃ interfere with each other, but these two luminous fluxes are mutually caused. Since they are in the opposite phase relationship, they act as a sort of bifocal filter, and the effect of expanding the depth of focus is obtained. Such a Fourier transform plane (pupil) divides the image-forming light beam into several parts, and the method of the multi-focus filter that gives a predetermined phase difference to each of these divided light beams is
Published on January 23, 1964. Mechanical Testing Laboratory Report No. 40, "Study on Imaging Performance in Optical Systems and Methods for Improving It", pp. 41-55.

By the way, in the case of the embodiment of FIG.
The image-forming light flux (point image) reaching the upper portion passes through the light flux LFa including the chief ray LLp that has passed through the circular transmissive portion FA ₁ and the annular zone transmissive portions FB ₂ and FB ₃ , respectively, as shown in FIG. The light beams LFb ₂ and LFb ₃ are divided into three. In the configuration described above in which the phase shifter is not provided, these three light beams LFa, LFb ₂ and LFb ₃ have extremely low coherence with each other.

In FIG. 11 (A), the incident angle θw of the light ray passing through the position of the effective outermost diameter (radius r ₂ ) of the pupil ep.
Corresponds to the numerical aperture NAw of the projection optical system PL on the wafer W side. Now, the light beam LFa is distributed in the angle range from the vertically incident light beam (main light beam) LLp to the incident angle θ ₁ , the light beam LFb ₂ is distributed in the angle range from the incident angle θ ₁ to θ ₃ , and the light beam LFb ₃ is incident. It is distributed in the angle range from the angles θ ₃ to θw. Assuming that the focal length of the lens group GB on the rear side of the projection optical system PL is f, the transmission parts FA ₁ and F ₁ on the pupil ep are
The radii r ₁ and r ₃ of B ₂ are r ₁ = f sin θ ₁ and r ₃ =
There is a relationship of fsin θ ₃ .

FIG. 11B shows a graph of the optical path length difference ΔZ that occurs in FIG. 11A. The defocus amount is ΔF, and the vertical and horizontal axes are the same as in FIG. Therefore, with respect to the defocus amount ΔF, the maximum optical path length difference generated in the light beam LFa is ΔZ ₁ , the maximum optical path length difference generated in the light beam LFb ₂ is ΔZ ₂ , and the maximum optical path length difference generated in the light beam LFb ₃ is ΔZ _3. Then, they are respectively expressed as follows.

ΔZ ₁ = (ΔF · sin ² θ ₁ ) / 2 =
(ΔF ・ NA ₁ ² ) / 2 ΔZ ₂ = (ΔF (sin ² θ ₃ −sin ² θ ₁ ) / 2 = (ΔF (NA ₃ ² −
NA ₁ ² )) / 2 ΔZ ₃ = (ΔF (sin ² θw −sin ² θ ₃ ) / 2 = (ΔF (NAw ² −
NA ₃ ²⁾⁾ / ² where the incident angle theta _1, as follows, and defining the radius r _1, r ₃ such that theta ₃ relationship.

Sin²θ₁= NA₁ ²= 1/3 (NAw²) Sin²θ₃= NA₃ ²= 2/3 (NAw²) Then, the three light beams LFa and LFb₂, LFb₃Each of
The optical path length differences at are all equal as follows. ΔZ₁= ΔZ₂= ΔZ₃= (ΔF ・ NAw²/ 3) / 2 This condition applies to the transmission part FA₁Area πr₁ ², Transparent part FB
₂Area of π (r₃ ²-R ₁ ²), And the transparent portion FB₃Fruit
Effective area π (r₂ ²-R₃ ²) All three are equal
That is nothing but saying.

As described above, in the conventional normal projection exposure, the optical path length difference ΔZ in the defocus amount ΔF is Δ.
It was represented by Z = (ΔF · NAw ² ) / 2. However, in this embodiment, when the allowable value of the optical path length difference is λ / 4, the defocus amount 3ΔF is three times as large as that in the conventional case.
It will be accepted as a good image. That is, the depth of focus is tripled as compared with the conventional one.

As described above, in the embodiment shown in FIG.
Coherence reducing member CCM so as to be divided into three light beams by p
However, the number of divisions may be m (natural number) of 4 or more, and the circular transmission portion or the ring transmission portion may be configured so that the m division light beams do not interfere with each other. In this case, the central circular transmission portion and (m-1) are arranged so as to divide the entire area determined by the effective maximum diameter of the pupil ep (the aperture diameter of the diaphragm when limited by the NA diaphragm) into m equal parts. By determining each area (radius) with the annular transmission part, the depth of focus can be increased by m times as compared with the conventional case.

That is, the incident angle of the light ray passing through the position of the maximum diameter in the light flux passing through one transmitting portion is θ _out , and the incident angle of the light ray passing through the position of the minimum diameter is θ _in (for the principal ray LLp, θ _in = 0), if sin ² θ _out −sin ² θ _in = NAw ² / m, each of the optical path length differences ΔZ due to defocus in each divided light flux is 1 in the conventional case. / M
Therefore, the maximum depth of focus can be obtained.

Next, the structure of the coherence reducing member CCM according to the fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, a circular light-shielding portion FD having a radius r ₄ is provided in the central portion in the vicinity of (or in close contact with) the coherence reducing member CCM shown in FIG. FIG. 10A shows a cross section of the coherence reducing member CCM of the present embodiment, and FIG. 10B shows a plane. In the case of the present embodiment, as shown in FIG. 10 (B), the imaging light flux incident on the pupil ep has a circular light-shielding portion FD at the center of a radius r ₄ , an annular transmission portion FA having an inner diameter r ₄ and an outer diameter r _{1. 1} , an inner diameter r ₁ , an outer diameter r _3, an annular transmission portion FB ₂ , and an inner diameter r ₃ an annular transmission portion FB ₃
It is considered that each of the light beams is divided into four, and only the three light beams other than the light shielding portion FD reach the wafer W among them.

FIG. 12 shows the relationship between the division of the image forming light beam and the optical path length difference ΔZ in the embodiment of FIG. Here, the relationship between the radius of the circular light-shielding portion FD at the center and the respective ring-shaped transmission portions FA ₁ , FB ₂ and FB _{3 around it} is shown in FIG.
As shown in (A), it is assumed that r ₄ <r ₁ <r ₃ <r ₂ . In the present embodiment, the central light shielding portion FD
Because of this, the chief ray LLp does not exist in the actual light flux.
Also, the light fluxes LFa, LFb ₂ , LFb ₃ that have passed through the respective transmission parts
And the maximum incident angle of each is θ ₁ , θ ₃ , θw, and the luminous flux L
The minimum incident angle of Fa is θ ₄ .

By dividing the luminous flux as shown in FIG.
The light beams LFa, LFb _2, the optical path length difference between the defocus in each of _{LFb 3 ΔZ 1, ΔZ 2,} ΔZ 3 is 1
2 (B). Also in this case, ΔZ ₁ = ΔZ ₂
= ΔZ ₃ is satisfied, that is, the annular zone F
The area π (r ₁ ² −r ₄ ² ) of A ₁ , the area π (r ₃ ² −r ₁ ² ) of the ring zone transmitting portion FB ₂ , and the area π (r ₂ ² −r of the ring zone transmitting portion FB _{3 If the} radii r ₄ , r ₁ , and r ₃ are determined so that ₃ ² ) is substantially equal to each other, the effect of expanding the depth of focus can be maximized.

By the way, as shown in FIG. 10, a circular light-shielding portion is provided at the center.
When FD is provided, the optical path length difference due to the defocus amount ΔF
ΔZ₁, ΔZ₂, ΔZ₃Is the area of the circular light shield FD,
Nominal radius r_FourIt will change according to. So the figure
12 (B), the optical path length difference ΔZ₁, ΔZ₂, ΔZ₃To
Three transmission parts FA to be equal₁, FB₂, FB ₃
Assuming that the area of
Radius r_FourAnd the effective radius r of the pupil ep₂Ratio r_Four/ R
₂Let k be ΔZ₁= ΔZ₂= ΔZ₃= (NAw²-K²・ NA
w²) / 3. K in this formula²・ NAw²Is the light-shielding part FD
It corresponds to the area, and its value is NA_Four ²= Sin
²θ_FourIt is none other than. Therefore, the light-shielding portion FD should have a predetermined area.
(Radius r_Four) In the embodiment of FIG.
Compared with the case, the optical path length difference ΔZ₁, ΔZ₂, ΔZ₃The value of
Since it can be made smaller, the depth of focus will increase.
It

As described above, in the embodiment of FIG. 10, the circular light-shielding portion FD
Is provided around the optical axis AX, but even if it is provided as a ring-shaped light-shielding portion, the effect of increasing the depth of focus can be obtained according to the area. As an example, a configuration as shown in FIG. 13 can be considered. 13A is a plan view and FIG. 13B is a sectional view. In this embodiment, a ring-shaped light shielding portion FD having an inner diameter r ₁ and an outer diameter r ₃ is provided. Further, the inside of the light-shielding portion FD is a circular transmission portion FA having a radius r ₁ , and the outside is an annular transmission portion FB having an inner diameter r _3.
Then, the optical path difference of the coherent length ΔLc or more is given to the light flux passing through each of the transmission portions FA and FB.

Also in the case of the present embodiment, as shown in FIG. 13C, the optical path length difference ΔZ ₁ at the time of defocusing of the light flux passing through the transparent portion FA and the defocusing of the light flux passing through the transparent portion FB. So as to make the optical path length difference ΔZ ₂ of each of them substantially equal to each other, the transmission portions FA and FB and the light shielding portion F with respect to the effective diameter r ₂ of the pupil.
If the radii r ₁ and r ₃ of D are determined, the effect of increasing the depth of focus is maximized.

The structure of the coherence reducing member CCM according to each of the embodiments of the present invention has been described above. In these, the image forming light beam from the contact hole pattern on the reticle R is substantially uniform at the pupil ep of the projection optical system. This is because it is assumed to be distributed in. That is, the diameters of the transmissive portions FA, FA ₁ , FB, FB ₂ , FB ₃ and the light shielding portion FD are determined on the assumption that the image forming light flux distributed to the pupil ep exists up to the effective maximum radius r _2. It was Such conditions are generally determined by the reticle-side numerical aperture NAr of the projection optical system PL, the wavelength λ of the illumination light ILB, and the size of the contact hole pattern Pr. Therefore, it is more practical for the exposure apparatus to insert the coherence reducing member CCM into the image forming light flux when the size of the contact hole pattern Pr becomes a certain value or less.

Next, the structure of the coherence reducing member CCM according to the fifth embodiment of the present invention will be described with reference to FIG. In each of the embodiments described so far, the temporal coherent length ΔL is set for each of the circular and annular light fluxes divided by the pupil ep.
Although the optical path length difference of c or more is given, the coherence can be reduced by another method. For example, in an exposure apparatus having a projection optical system configured by only a reflection mirror or a combination of a reflection mirror and a refraction element (lens), since the projection optical system itself has a small chromatic aberration, the illumination light has a wide wavelength range. Light or a plurality of bright line components close to each other (eg, g-line and h-line of mercury lamp) may be used.

Another person who applies the present invention to such a device
As a method, as shown in FIG.
Center radius r₁Of the circular transparent part FA of
The wavelength band of the transmitted light is different for each of the excess portion FB.
A bandpass filter may be formed. This bandpass
The filter is made of, for example, a multilayer dielectric thin film and
It is formed by vapor deposition on a transparent circular substrate. Implementation
In the example, a dielectric thin film is used as the center circular transmission part FA.
It is vapor-deposited on one surface of the plate, and the ring-shaped transparent portion FB (inner diameter r₁)When
A thin dielectric film on the other side of the substrate
Part FA, for example, should pass only h-line of wavelength 405 nm
However, the transmissive part FB of the ring zone passes only the g-line with a wavelength of 436 nm.
To do so. In addition, here, the light flux passing through the pupil ep is defined as the central portion.
It is divided into two light fluxes LFa and LFb that pass through the periphery.
The effective radius r of the pupil ep ₂In contrast, the transparent portion F
Radius r of A₁Is r₂ ²= 2r₁ ²Has been set in a relationship
It

Thus, the transmitted light LFa of the circular transmitting portion FA
When the transmitted light LFb of the ring-shaped transmission portion FB is divided into wavelength bands by a bandpass filter, these two light beams LFa and LFb are converted into light beams which do not interfere with each other, and as in the previous embodiments. The depth of focus is enlarged.
The bandpass filter may be made of absorptive colored glass.

As another method, the light beam distributed on the pupil is polarized.
It is also possible to split by light to eliminate coherence.
It The method in that case is shown in FIG. 15 as the sixth embodiment.
explain. In this embodiment, two transparent circular substrates CCM are used.
Coherency reduction member CCM is composed of a and CCMb as one set.
The substrate CCMa has a radius r centered on the optical axis AX.₁of
Circular transmission part PCa and inner diameter r₁And outer diameter is r₂(Effective
And a ring-shaped transparent portion PCb having a different pupil diameter. And transparent
Both or one of the excess PCa and PCb
Change the polarization state between the light beams passing through it so that they do not interfere with each other.
Any of a polarizing plate, a 1/4 wavelength plate, a 1/2 wavelength plate, etc.
Made in. On the other hand, the substrate CCMb is centered on the optical axis AX.
Radius r_FourMade of annular quartz plate with circular opening of
Inside diameter r_Four, Outer diameter r₃The first thickness of the ring
-Shaped transparent part and inner diameter r₃, Outer diameter r ₂The second and above
An annular transparent portion having a thickness is formed.

Where radius r₁~ R_FourIs r_Four<R₁<R₃
<R₂And r_Four ²= (R₁ ²-R_Four ²)
= (R₃ ²-R₁ ²) = (R₂ ²-R₃ ²) Is set to
It is assumed that In addition, two substrates CCMa and CCMb
May be placed close to each other with the Fourier transform plane FTP in between.
You can stick them together. In the case of such a configuration
Radius r_FourLight flux LFa passing through the circular transmission part FA of
Diameter r_Four~ R₁Ring zone transparent part FB₁Luminous flux LFb that passed through₁
Means that the polarization states are the same, but the optical path length difference is coherent.
Since the length is ΔLc or more, they do not interfere with each other. Also radius
r₁~ R₃Ring zone transparent part FB₂Luminous flux LFb that passed through₂When
Luminous flux LFb₁, LFa have different polarization states from each other.
Will not interfere with. Further radius r₃~ R₂The torus
FB ₃Luminous flux LFb that passed through₃And luminous flux LFb₂Is light
Since the path length difference is more than the coherent length ΔLc,
Light flux LFb at the same time without interference₃And luminous flux LFb₁, LFa
And do not interfere with each other because they have different polarization states.

After all, the luminous fluxes LFa and LF divided into four are
Each of b ₁ , LFb ₂ and LFb ₃ is converted into light having no interference with each other, and in the case of the present embodiment, the theoretical depth of focus is expanded to 4 times the conventional depth. by the way,
The light-shielding portion FD in FIGS. 10 and 13 may be, for example, a light-shielding film obtained by vapor-depositing a metal film or the like on a transparent substrate, or may be a metal plate or the like provided apart from the coherence reducing member CCM.

Further, the light-shielding portion FD, or the light-shielding plate equivalent to the light-shielding portion FD, needs to shield only the exposure wavelength.
An optical sharp cut filter made of a dielectric thin film or the like may be used to absorb a short wavelength region such as an exposure wavelength (ultraviolet light). In this way, for example He
-When using a TTL type alignment system that irradiates an alignment mark on the wafer W with a Ne laser as a light source and detects the reflected light or the like via a projection optical system PL, a light-shielding portion FD located on the pupil plane, or light-shielding There is no problem that the plate gives a bad influence (shielding) to the reflected light from the mark. Alternatively, only the position on the light shielding plate or the light shielding portion FD of the above-mentioned metal or the like through which the laser beam for illuminating the wafer mark or the reflected light from the mark passes may be a transmissive region, and if the area is small, the effect of the present invention is particularly impaired. Does not mean

FIG. 16 shows an example of a TTL alignment system as a seventh embodiment, in which a lattice mark G is formed on the wafer W.
It is assumed that R is formed and the positional deviation of the mark GR in the grating pitch direction is detected. Here, FIG. 16A is a view of the alignment system viewed from a direction in which the left-right direction on the paper is the pitch direction, and FIG. 16B is a view obtained by rotating the system of FIG. 16A by 90 °. I saw it. A coherent laser beam (He-N) is emitted from the objective lens OBJ of the alignment optical system provided above the reticle R.
e) _Two of ALB ₁ and ALB ₂ are reflected by the mirror MR and intersect at the surface CF, and then enter the projection optical system PL through the window RM around the reticle R. First, as shown in FIG. 16 (A), the two beams ALB ₁ and ALB ₂ are incident on each of the bendability correction elements PG ₁ and PG ₂ formed on the coherence reducing member CCM located at the pupil, Here, two beams ALB are used in an amount corresponding to the axial chromatic aberration of the projection optical system PL.
₁ , change the ALB ₂ direction. As a result, the two beams ALB ₁ and ALB ₂ are separated by the lattice mark G on the wafer W.
Irradiate R at an angle that is symmetrically inclined with respect to the pitch direction. At this time, the pitch Pg of the grating mark GR, the wavelengths λa of the beams ALB ₁ and ALB ₂ , and the beam AL
The incident angle θa of B ₁ and ALB ₂ is sin θa = λa / P
When g is satisfied, the + _{1st order} diffracted light generated from the grating mark GR by the irradiation of the beam ALB ₁ and the beam AL
The −1st-order diffracted light generated from the mark GR by the irradiation of B ₂ is the two beams ALB ₁ ,
Interfering beam A becomes coaxial with the optical path just in the middle of ALB _2.
Go backward as DL. The interference beam ADL is changed in traveling direction by the bendability correction element PG ₃ formed on the coherence reducing member CCM, and returns to the alignment optical system through the window RM of the reticle R. At this time, FIG. 16 (B)
As also shown, since the two beams ALB ₁ and ALB ₂ reaching the mark GR on the wafer W are inclined with respect to the direction (non-measurement direction) orthogonal to the pitch direction, the interference beam ADL is also generated with inclination. . Further, as shown in FIG. 16A, the two beams ALB ₁ and ALB ₂ intersect with each other on the plane CF, but the plane CF can actually be aligned with the position of the window RM. That is, the two beams ALB ₁ and AL
The axial chromatic aberration component generated with respect to B ₂ can be almost completely compensated. Further, as shown in FIG. 16B, the two beams ALB ₁ and ALB ₂ are made to enter the window RM while being displaced from the telecentric condition in the non-measurement direction, so that the chromatic aberration of magnification can be compensated. The optical axis AXa of the objective lens OBJ is set perpendicular to the reticle R.

When measuring the positional deviation of the mark GR,
There are two ways. One of them is two beam AL
B₁, ALB₂Is formed on the mark GR by the intersection of
Position of the mark GR in the pitch direction based on the interference fringes
This is to detect this. For that, alignment
The returned interference beam ADL is photoelectrically detected in the optical system.
Equipped with a photoelectric sensor and measure the output signal level
Yes. One way to have two beams ALB₁, ALB
₂A slight frequency difference between the two (eg 20-100 KHz
Degree) to determine the interference fringes generated on the mark GR.
It is a heterodyne method that runs at a speed according to the frequency difference.
It In this case, two beam ALB₁, ALB ₂Frequency
Create a reference AC signal with a number difference and output from the photoelectric sensor.
Force signal (for heterodyne, the interfering beam ADL is
Since the intensity changes at the frequency, it becomes an AC signal)
By calculating the phase difference between the
Can be measured.

As described above, when the bending correction elements PG ₁ , PG ₂ , and PG ₃ for compensating for chromatic aberration are provided on the pupil plane of the projection optical system PL, depending on their arrangement, the light shielding portion FD shown in FIGS. It may also interfere with the shape of (or the light shielding plate) in position. However, this type of alignment type beam ALB ₁ , ALB ₂ , or interference beam A
Since DL has an extremely small spot diameter, the correction element P
The dimensions of G ₁ , PG ₂ and PG ₃ may also be extremely small. Usually, the correction elements PG _{1 to} PG ₃ are formed as a phase grating on the surface of a transparent glass material by etching or the like.
Therefore, as described above, when the light-shielding portion FD interferes in position, only the light-shielding portion at that position needs to be a transparent portion.

Further, in FIG. 16, the correction elements PG _{1 to} PG _{3 are}
Is shown to be formed directly on the coherence reducing member CCM, a normal quartz plate on which the correction elements PG _{1 to} PG ₃ are formed is fixedly arranged on the pupil plane, and the coherence reducing member CCM is the quartz plate. It may be arranged so that it can be inserted and removed in the immediate vicinity of.
Incidentally, a method of providing a correction lens (convex lens) having a small diameter in the center of the pupil plane of the projection optical system PL and compensating for the chromatic aberration component of the alignment beam by such a correction lens is disclosed in USP.
5,100,237. In this case, the correction lens portion has a small transmittance for the exposure wavelength,
By depositing a dichroic film having a very high transmittance for the wavelength of the alignment beam, a component substantially equivalent to the central light shielding part FD of the coherence reducing member CCM shown in FIG. 10 can be easily constructed. However, the above USP. 5, 10
0 and 237 have transmission parts FA ₁ and F ₁ as shown in FIG.
There is no suggestion of providing B ₂ and FB ₃ at the same time.

Further, in the drive unit 22 of wafer stage WST shown in FIG. 4, the function of the conventional FLEX method may be provided in the control for finely moving wafer W in the optical axis direction. The combined use of the FLEX method can dramatically increase the effect of increasing the depth of focus according to the present invention. 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. However, 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 equal magnification is explained as an eighth embodiment with reference to FIGS. In FIG. 17, the illumination light from the mercury lamp (Xe-Hg) lamp 1 is projected on the reticle (mask) R into an illumination area having an arc slit shape via the illumination optical system ILS. The reticle R is held on the reticle stage RST capable of one-dimensional scanning,
It moves at the same speed in synchronization with wafer stage WST.
The projection optical system has a reflective surface MR on each of the reticle side and the wafer side.
₁ , a trapezoidal optical block having MR ₄ , a large concave mirror MR ₂ and a small convex mirror MR _3, and a concave mirror M with respect to the radius of curvature of the convex mirror MR _3.
The radius of curvature of R ₂ is set to about twice. This FIG.
In the case of such a system, the surface of the convex mirror MR _{3 is} the Fourier transform surface F with respect to the reticle pattern surface (or wafer surface).
Often matches TP.

At this time, the imaging light beam 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 convex 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. 18A, the interference
Consistency reduction member CCM is a convex mirror MR ₃Placed in the immediate vicinity of
Concave mirror MR₂From convex mirror MR₃Incident on
Time and the convex mirror MR₃From concave mirror MR₂Injection to
The optical path is twice (round-trip) with the time of going, and the center circle
(Or annular zone) Light flux passing through the transmission part FA and surrounding annular zone transmission
Light having a coherent length ΔLc or more with the light flux that has passed through the section FB
It may be configured to have a difference in road length.

Alternatively, as shown in FIG. 18 (B), a minute step with a predetermined radius (area) is provided on the surface of the convex mirror MR ₃ ′ serving as the 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 difference) 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. 18B may be a transparent object (thin film). In that case, the step between the surface of the convex mirror MR and the surface of the transmissive object (corresponding to the transmissive part FA), that is, the thickness d of the transmissive object, is the optical path length generated by the reciprocation of the light beam in the transmissive object having the refractive index n. Difference 2 (n-
1) d is set to be larger than the coherent length ΔLc.

Further, in the case of FIG. 15 in which a half-wave plate or a quarter-wave plate is combined with a part of the transmission parts FA and FB, it is considered that the polarization effect is doubled in the round-trip optical path. It is necessary to change the two-wave plate to a quarter-wave plate and the quarter-wave plate to a one-eighth 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. When an optical element (lens, reflecting surface, aperture stop, CCM, etc.) is arranged on the pupil surface, there is a possibility that the optical element deteriorates due to a converged light source image after long-term use. Therefore, it is preferable that the coherence reducing member CCM and the like are not strictly arranged on the pupil plane, but rather are slightly displaced.

As described above, the optical path length difference between the image-forming light beams divided by the coherence reducing member CCM described in each embodiment of the present invention is equal to or longer than the temporal coherence length ΔLc of the light beam (illumination light ILB). However, its value is the conventional Super
The difference is significantly larger than the optical path length difference (wavelength 1/2 to several wavelengths) given by the FLEX method. Further Supe
In the r FLEX method, there is no change due to interference (amplitude synthesis) of all of the imaging light flux that has passed through the filter (complex amplitude transmissivity) arranged on the pupil plane of the projection optical system on the wafer W. In principle, it is completely different from the Super FLEX method. Due to the difference in principle, a new effect that cannot be obtained by the Super FLEX method in the present invention can be obtained. This will be described with reference to the simulation described below.

The coherence reducing member CCM used in the present invention
Is only for the purpose of dividing the imaging light flux passing through the pupil plane (in the case of a contact hole pattern, distributed almost uniformly) into multiple parts in the radial direction of the pupil and reducing the coherence between the partial light fluxes. To work. 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, There is no effect of mutually shifting in the optical axis AX direction of the projection optical system, that is, an effect of giving a certain kind of spherical aberration.

In each of the above embodiments, when the pupil plane ep of the projection optical system is divided into m areas, which are a circular area or an annular area,
Although it is assumed that the areas of the respective divided regions are equal, this is not necessarily an essential condition. In particular, an optical path difference of not less than the temporal coherence length ΔLc is not given between the pair of circular regions and the annular regions, or between the pair of annular regions and the annular regions, and
In the case of a configuration that gives an optical path difference of ½ wavelength (an example using a phase shifter or the like), it is better to make each area of the pair of regions different. This is because, if the light quantities (corresponding to the respective areas) of both light fluxes (each corresponding to the transmitted light of the above both areas) having an optical path length of ½ wavelength are substantially equal, both light fluxes on the wafer (image position) This is because they cancel out and the strength becomes zero. Alternatively, the transmittance of either one of the regions may be lowered instead of making the areas of the two regions different. Of course, both the area and the transmittance may be changed. In each of the above embodiments, the interference reducing member C
When CM is used as a transmissive member, its interface (surface) may be coated with an antireflection coating.

Next, the operation and effect obtained by each embodiment of the present invention will be described based on simulation results. FIG. 19A is a square contact hole pattern PA having one side corresponding to 0.3 μm on the wafer used in the following simulation. In the following simulation, the cross section taken along the line AA ′ in FIG. Image intensity distribution on the wafer. FIG. 19B is the same as FIG.
(Or FIGS. 7 and 8) shows the coherence reducing member CCM, which has a ratio r ₁ / r ₂ (of the radius r ₁ of the central circular transmission part FA to the effective maximum radius r ₂ of the pupil ep) NA ₁ / NA
w) is set to be 0.707 as described in the explanation of the principle. That is, if the maximum incident angle of the image forming light flux passing through the transmitting portion FA is θ ₁ , then sin ² θ
It is determined to satisfy ₁ = 1/2 (NAw ² ). In the following simulations, NAw = 0.
57, the exposure wavelength was i-line (wavelength 0.365 μm). The σ value, which is the coherence factor of the illumination light flux, was set to 0.6. Now, FIG. 19 (C),
(D) and (E) show image intensity distributions on the wafer of the pattern PA, which are intensity distribution I ₁ at the best focus position, intensity distribution I ₂ at the defocus position of 1 μm, and I ₂ and 2, respectively.
It is the intensity distribution I ₃ at the defocus position of μm. Further, Eth in FIGS. 19C, 19D, and 19E indicates the strength required to completely remove (photosensitize) the positive photoresist on the wafer, and Ec dissolves the positive resist (film verification).
Indicates the strength at which to start. The vertical magnification (exposure amount) of each intensity distribution is the contact hole diameter (Et
The width of the slice portion that crosses h) was set to 0.3 μm. 20 (A), (B), (C) for comparison
The intensity distribution I ₇ at the best focus position and the intensity distribution I ₈ at the defocus position of 1 μm by an ordinary exposure apparatus (without the reduction member CCM), respectively.
The intensity distribution I ₉ at the defocus position of μm is shown. The simulation condition at this time is also NAw = 0.5.
7, wavelength λ = 0.365 μm, and σ = 0.6.

20A to 20C and the above FIG.
Comparing (D) to (F), the SFIN according to the present invention
It can be seen that in the CS method, the change in image intensity (decrease in contrast) during defocus is reduced and the depth of focus is increased.
On the other hand, FIG. 21 shows changes in the image intensity distributions I ₁₀ , I ₁₁ , and I ₁₂ when the FLEX method is combined with a normal projection exposure apparatus. The exposure conditions of the FLEX method were a total of three divided exposures, one for each of the best focus position and the position defocused by ± 1.25 μm. This Figure 2
Comparing the simulation result of No. 1 with the simulation results of FIGS. 19C to 19E, 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 the FLEX method. 22 shows a simulation result in the case where the configuration of FIG. 6 is provided with the light shielding part FD based on the same idea as the coherence reducing member CCM shown in FIG. 10 in the embodiment of the present invention. At this time, as shown in FIG. 26B, the interference reducing member CCM
The radius r ₄ of the circular light-shielding portion FD at the center of is determined to be 0.31r ₂ (that is, sin θ ₄ = 0.31NAw), and the ring-shaped transmissive portion FA having an inner diameter r ₄ and an outer diameter r _{1 on} the outer side thereof is determined.
Has an outer diameter r ₁ of 0.74r ₂ (ie sin θ ₁ = 0.
74 NAw). That is, it is set to satisfy (r ₁ ² −r ₄ ² ) = (r ₂ ² −r ₁ ² ). Of course, as the exposure condition, NA
w = 0.57, σ = 0.6, and λ = 0.365 μm remain unchanged. A reduction member CCM as shown in FIG. 22 (B)
However, as shown in FIGS. 22 (C), (D), and (E), the intensity distribution I ₄ at the best focus position, the intensity distribution I ₅ at the defocus position of 1 μm, and the intensity distribution I ₅ at the defocus position of 2 μm. _{As shown in 6} , a sufficient effect of increasing the depth of focus can be obtained.

FIG. 23 shows a conventional Super for comparison.
9 shows a result of simulation by the FLEX method. 23 (A), (B), and (C) show a numerical aperture NAw of 0.57 and a filter in which the complex amplitude transmittance of the portion within the radius of 0.548 NAw from the pupil center point is -0.3. The intensity distribution I ₁₃ at the best focus position, the intensity distribution I ₁₄ at the defocus position of 1 μm, and the intensity distribution I ₁₅ at the defocus position of 2 μm, which are obtained when the image is provided in FIG. In the Super FLEX method, the center intensity at the best focus position is high and the profile is sharp as shown in FIG. 23, but the decrease in center intensity due to the defocus amount occurs abruptly from a certain amount. However, the effect of increasing the depth of focus is approximately the same as the effect of the present invention shown in FIGS. However, Super F
In the LEX method, the area around the original image (center intensity) is shown in FIG.
Sub-peaks (ringing) as shown in (A) occur. This is not a problem for the isolated contact hole pattern PA used as the simulation model in FIG. 23, but is a serious problem when applied to a plurality of adjacent contact hole patterns described later.

In order to prevent such ringing, FIGS. 24A, 24B, and 24C use a filter having a weaker action than the pupil filter of the Super FLEX method used as the simulation model in FIG. The simulation result in the case is shown. In this case, the numerical aperture NAw of the projection optical system is 0.57, and the radius of the pupil center is 0.447 NA.
A filter with a complex amplitude transmittance of -0.3 in the portion corresponding to w is used. 24 (A) to (C) show the intensity distribution I ₁₆ at the best focus position, the intensity distribution I ₁₇ at the defocus position of 1 μm, and the intensity distribution I ₁₈ at the defocus position of 2 μm. Although ringing is weaker than in the case of No. 23, the effect of increasing the depth of focus is also reduced at the same time.

In FIGS. 25A to 25D, two adjacent contact hole patterns PA ₁ and PA ₂ are shown in FIG.
5E shows the results of simulating the image intensity distributions obtained by various exposure methods when the lines are spaced apart by a center-to-center distance of 0.66 μm (on the wafer) as in FIG. Figure 25
22A shows S under the same simulation condition as FIG.
FIG. 25 (B) shows an image intensity distribution obtained by the FINCS method (present invention), FIG. 25 (B) shows an image intensity distribution obtained by the conventional FLEX method, and FIG. 25 (C) shows Super under the same conditions as FIG. FIG. 25 (D) shows the image intensity distribution obtained by the FLEX method (1), and FIG. 25 (D) shows the image intensity distribution obtained by the Super FLEX method (2) under the same conditions as in FIG. 24. It is at the best focus position. As can be seen from the results of this simulation, the images obtained in FIGS. 25 (A), (C), and (D) are 2
Since the strength between two hole images is lower than the film-verification strength Ec, the resist (positive type) between both holes is completely left,
The resist images in both holes are separated and formed well. However, in the FLEX method shown in FIG. 25 (B), the intensity between the two hole images is not sufficiently low, the resist between both holes is film-verified, and a good pattern cannot be formed. That is, the images of the two contact holes may be connected to each other due to a slight difference in the exposure amount. As described above, the depth of focus at the time of projecting an isolated contact hole pattern was obtained by the SFINCS method of the present invention and the conventional FLEX method to the same extent, but the resolution (fidelity) of adjacent hole patterns was In terms of points, the SFINC of the present invention
It can be seen that the S method is superior to the FLEX method.

In the simulations of FIGS. 25C and 25D, two hole patterns PA ₁ and PA ₂ are provided under the condition that the peak portion of ringing due to one hole pattern overlaps with the central intensity portion of the other hole pattern. Since the center-to-center distance is determined, the ringing effect does not appear between the two hole pattern images. This means that, conversely, when the distance between the centers of the _two hole patterns PA ₁ and PA ₂ is different from the previous condition (0.66 μm on the wafer), the effect of ringing appears.

FIG. 26 is a simulation result of the intensity distribution at the best focus position of two contact hole images arranged with the center-to-center distance of 0.96 μm (converted on the wafer). The image intensity distribution I _{23 obtained} by the SFINCS method (present invention) under the conditions shown in FIG. 22 is 2 as shown in FIG.
The space between two hole images is sufficiently dark, and a good resist pattern can be formed. However, S under the conditions shown in FIG.
In the upper FLEX method (1), ringing due to each of the two hole patterns is synthesized (added) like the intensity distribution I ₂₄ in FIG. 26B, and a bright sub-peak (film) is formed in the middle of the two hole images. The verifying strength Ec or more) occurs, and the resist in this part is film-verified. Therefore, a good resist image cannot be obtained. On the other hand, when two hole patterns with a center-to-center distance of 0.96 μm are projected by the Super FLEX method (2) under the conditions shown in FIG. 24, the image intensity distribution I ₂₅ becomes as shown in FIG. 26 (C). . In this way, Supe is relatively weak
In the case of the r FLEX method (2), a good resist image can be obtained because the ringing is small and the film is free from the film. However, under this condition, as described with reference to FIG. 24, a sufficient depth of focus expansion effect cannot be obtained as compared with the SFINCS method of the present invention.

FIG. 27 shows another projection exposure method in which 0.7 is used for the effective radius r ₂ of the pupil on the pupil plane of the projection optical system.
Image intensity distribution I _{26 of} an isolated hole pattern obtained when only a circular light-shielding plate having a radius of 07 times (NAw × 0.707), that is, an area approximately half the effective area of the pupil is arranged at the center of the pupil. Is shown. In this case as well, ringing still occurs around the original image, and it is difficult to apply the contact hole patterns adjacent to each other to projection exposure.

FIG. 28 shows contact hole patterns PA ₁ , PA ₂ , PA ₃ , PA used in a memory cell portion in a DRAM as an example of a plurality of contact holes adjacent to each other.
₄ shows an example of a two-dimensional array of ₄ . When the Super FLEX method is used for such a hole pattern group, ringing (sub-peak) occurs around each hole.
Ra, Rb, Rc, Rd occur, and the region R where they overlap
At o, the peak intensities of the four ringings will overlap. In such a case, in the case of only two hole patterns (two ringings overlap each other), the film VERY did not occur.
Even in the X method (2), the size of the sub-peak is as shown in FIG.
About twice as much as the state shown in (C), and again the film-verification strength E
Since it is c or more, good pattern transfer cannot be performed. That is, an image of a hole (ghost image) that originally does not exist on the reticle is formed at the position of the region Ro on the wafer.

On the other hand, in the case of the SFINCS method according to the present invention, as shown in FIG. 26A, the light intensity distribution in the middle of the two hole patterns is 1/2 or less of the film-verification intensity Ec. In the region Ro shown, even if the added intensity further doubles from the state of FIG. 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 determined whether the polarization direction is appropriate or not, or the coherence reducing member. C
A means for photoelectrically detecting a part of the light flux passing through the projection optical system may be provided on the wafer stage WST in order to judge whether the polarization state of the image-forming light flux after passing through the CM is good or bad. Further, when using a reticle having a line and space, 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 during the projection exposure of the contact hole pattern,
A modified illumination system such as the SHRINC method or an annular illumination light source may be used together. In that case, when the reticle to be exposed is exchanged from the contact hole to the line and space, only the coherence reducing member CCM needs to be withdrawn.

Further, the coherence 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 it is not limited to the 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.

[0091]

As described above, according to the present invention, the depth of focus during projection exposure of an isolated pattern such as a contact hole is set to F
It can be expanded to the same extent as the LEX 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.
Further, there is an advantage that it is not necessary to prepare a spatial filter having a complex function of complex amplitude transmittance as in the Super FLEX method. In particular, in the present invention, the ringing itself, which is likely to occur due to spatial filtering on the pupil plane (Fourier transform plane) of the projection optical system, is suppressed sufficiently small, so that a plurality of contact hole patterns are arranged relatively close to each other. Even if it is
It is possible to obtain a great effect that the adverse effect (occurrence of a ghost image) caused by the superposition of the ringing sub-peak portions unlike the FLEX method is eliminated.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a conventional projection exposure method.

FIG. 2 is a diagram showing a principle configuration for carrying out the projection exposure method of the present invention.

FIG. 3 is a diagram illustrating the principle of increasing the depth of focus by the exposure method of the present invention.

FIG. 4 is a diagram showing an overall configuration of a projection exposure apparatus suitable for implementing the present invention.

FIG. 5 is a partial sectional view showing a partial structure of a projection optical system.

FIG. 6 is a coherence reduction member C according to the first embodiment of the present invention.
The figure which shows the structure of CM.

FIG. 7 is a coherence reducing member C according to a second embodiment of the present invention.
The figure which shows the structure of CM.

FIG. 8 is a view showing some modifications of the coherence reducing member CCM according to the first and second embodiments of the present invention.

FIG. 9 is a coherence reducing member C according to a third embodiment of the present invention.
The figure which shows the structure of CM.

FIG. 10 is a diagram showing the configuration of a coherence reducing member CCM according to a fourth embodiment of the present invention.

FIG. 11 is a diagram for explaining an image forming action by the coherence reducing member CCM shown in FIG. 9.

12A and 12B are views for explaining an image forming action by the coherence reducing member CCM shown in FIG.

FIG. 13 is a view for explaining the structure of a coherence reducing member CCM according to the fifth embodiment of the present invention and its imaging action.

FIG. 14 is a diagram showing the configuration of a coherence reducing member CCM according to a sixth embodiment of the present invention.

FIG. 15 is a diagram showing the configuration of a coherence reducing member CCM according to a seventh embodiment of the present invention.

FIG. 16 is a diagram showing a configuration according to an eighth example of the present invention, showing a configuration of a projection optical system when an alignment system is used.

FIG. 17 is a diagram showing the structure of a mirror projection aligner according to a ninth embodiment of the present invention.

FIG. 18 is a view showing a state where the coherence reducing member CCM according to each embodiment of the present invention is applied to the aligner of FIG.

FIG. 19: SF of the present invention for a single hole pattern
The graph which simulated the effect by the INCS method as image intensity distribution.

FIG. 20 is a graph simulating the effect of the conventional normal exposure method on a single hole pattern as an image intensity distribution.

FIG. 21: Conventional FLE for a single hole pattern
The graph which simulated the effect by X method as image intensity distribution.

FIG. 22: SF of the present invention for a single hole pattern
The graph which simulated the effect by the INCS method as image intensity distribution.

FIG. 23: Conventional Sup for a single hole pattern
er is a graph in which the effect of the FLEX method (1) is simulated as an image intensity distribution.

FIG. 24: Conventional Sup for a single hole pattern
er is a graph simulating the effect of the FLEX method (2) as an image intensity distribution.

FIG. 25 is a graph simulating the effect of various exposure methods on two close hole patterns as an image intensity distribution.

FIG. 26 shows the distance between two hole patterns that are close to each other.
The graph which simulated the effect by various exposure methods when changing from the case of 5, and was made as image intensity distribution.

[FIG. 27] When only a circular light-shielding portion is provided in the center of the pupil,
6 is a graph showing that ringing occurs in the image intensity distribution of a single hole pattern.

FIG. 28 is a diagram showing a relationship between two-dimensionally distributed contact hole patterns and ringing generation positions.

[Explanation of symbols]

R ... Reticle W ... Wafer PL ... Projection optical system AX ... Optical axes PA, PA ₁ , PA ₂ ... Hole pattern CCM ... Coherence reducing member FA ... Circular transmission Part FB: annular transmissive part ILB: illumination light

Claims (4)

[Claims] 1. An illuminating means for irradiating a mask on which a fine pattern is formed with an illuminating light for exposure, and an image of the pattern is projected onto a sensitive substrate by injecting light generated from the pattern of the mask. In a projection exposure apparatus including a projection optical system for performing a Fourier transform plane in an image forming optical path between the mask and the sensitive substrate, or a plane near the Fourier transform plane, or a plane near the Fourier transform plane. Coherence reducing means for reducing coherence between the imaging light distributed in a circular area centered on the optical axis of the projection optical system and the imaging light distributed in an area outside thereof are provided. And a projection exposure apparatus. 2. An illuminating means for irradiating a mask on which a fine pattern is formed with an illuminating light for exposure, and a light generated from the pattern of the mask is incident to project an image of the pattern on a sensitive substrate. In a projection exposure apparatus including a projection optical system for performing a Fourier transform plane in an image forming optical path between the mask and the sensitive substrate, or a plane near the Fourier transform plane, a plane on the Fourier transform plane, or a plane near the Fourier transform plane. Coherence for reducing coherence between the imaging light distributed in the annular zone centered on the optical axis of the projection optical system and the imaging light distributed inside or outside the annular zone. A projection exposure apparatus comprising a reducing means. 3. A projection optical system in which a mask having a plurality of isolated minute hole patterns is uniformly irradiated with exposure illumination light having a predetermined incident angle range, and the light from the mask is projected. In the method of exposing each projected image of the plurality of hole patterns onto the photosensitive substrate by projecting as an image-forming light beam onto the photosensitive substrate via, a Fourier transform plane in the projection optical system, or When the image-forming light flux distributed on the near surface is divided into a circular area centered on the optical axis of the projection optical system and a ring-shaped area surrounding the outside, each of the circular area and the ring-shaped area is divided. A coherence reducing member that makes the optical path length between the image-forming light fluxes that pass through and reaches the photosensitive substrate more than the coherent length of the illumination light is provided in the projection optical system, and a Fourier transform surface in the projection optical system is provided. of An exposure method, which comprises exposing the projected image of the hole pattern in a state where the area of the circular region is approximately halved with respect to the effective opening area. 4. A mask having a plurality of isolated fine hole patterns is uniformly irradiated with exposure illumination light having a predetermined incident angle range, and the light from the mask is projected into an optical projection system. In the method of exposing each projected image of the plurality of hole patterns onto the photosensitive substrate by projecting as an image-forming light beam onto the photosensitive substrate via, a Fourier transform plane in the projection optical system, or When the image-forming light flux distributed on the near surface is divided into a circular region centered on the optical axis of the projection optical system and n ring-shaped regions surrounding the outside at least doubly, the circular region The projection optical means includes a coherence reducing member that makes the optical path length between the image-forming light fluxes that reach the photosensitive substrate through at least two regions of the n ring-shaped regions different by at least the coherent length of the illumination light. Within the system And exposing the projected image of the hole pattern in a state where the areas of the at least two regions are made substantially equal to each other.