JP2884950B2 - Projection exposure apparatus, exposure method, and method of manufacturing semiconductor integrated circuit - Google Patents

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 such as semiconductor integrated circuits and liquid crystal displays.

[0002]

2. Description of the Related Art A projection optical system used in a projection type exposure apparatus of this kind is incorporated into the apparatus through advanced optical design, careful selection of glass materials, ultra-precision processing of glass materials, and precise assembly adjustment. . At present, in a semiconductor manufacturing process, a reticle (mask) is used with i-line (wavelength 365 nm) of a mercury lamp as illumination light.
, And a stepper is mainly used in which a transmitted light of a circuit pattern on the reticle is imaged on a photosensitive substrate (a wafer or the like) via a projection optical system. 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 an excimer stepper is constituted by only a refraction lens, usable glass materials are limited to quartz, fluorite and the like.

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) of the projection optical system are important factors. Has become.
Among projection optical systems currently in practical use, those having an aperture of about 0.6 for i-line have been obtained. When the wavelength of the illumination light to be used is the same, if the numerical aperture of the projection optical system is increased, the resolving power is correspondingly improved. 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.
A and a rear lens group GB. In general, this type of projection optical system has both the reticle R side and the wafer W side telecentric, or has only the wafer W side telecentric. 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). Light rays L ₁ , L ₂ , L ₃ , La, L traveling in various directions from point A
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 through p. And the other rays La, L
a ′ and La ″ pass through the pupil ep, enter the rear lens system GB, and converge on a point A ′ on the surface of the wafer W (pupil plane of the projection optical system). Of the light rays generated from A, the light rays that have passed through the pupil ep (a circular area centered on the optical axis AX) of the projection optical system contribute to forming a point image at the point A ′. The ray La passing through the center point CC (the position of the optical axis AX) of the pupil ep among the rays directed to the point A ′ is called a principal ray. Each space on the image plane side is parallel to the optical axis AX.

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

The numerical aperture of such a projection optical system is generally expressed as a value on the wafer side. In FIG. 1, among the light beams contributing to the formation of the point image A ′, the angle θw formed by the light beams La ′ and La ″ passing through the outermost part in the pupil ep and the principal light beam La on the wafer W is determined by the projection optical system. Corresponds to the numerical aperture NA _W on the wafer (image plane) side, and is expressed by NAw = sin θw. Therefore, the angle θr formed by the rays La ′ and La ″ with the principal ray La on the reticle R side is determined by the reticle (object plane) ) Side is referred to as a numerical aperture NAr, and is represented by NAr = sin θr. Further, the imaging magnification of the projection optical system is set to M (in the case of 1/5 reduction, M
= 0.2), there is a relationship of NAr = M · NAw.

In order to increase the resolution, the numerical aperture NAw (NAr) is increased. In other words, the diameter of the pupil ep must be increased, and the effective diameters of the lens systems GA and GB must be increased. There is no other way to make it bigger.
However, the depth of focus DOF decreases in inverse proportion to the square of the numerical aperture NAw, so that even if a projection optical system having a high numerical aperture can be manufactured, the required depth of focus cannot be obtained. This is a major 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 is about 1 μm (± 0.5 μm) in width, and one shot on the wafer W In a region (about 20 mm square to 30 mm square), a portion having a surface irregularity or curvature equal to or larger than DOF causes poor resolution. Also on the stepper system, focus adjustment for each shot area of the wafer W,
It becomes necessary to perform leveling and the like with extremely high accuracy, and the burden on the mechanical system, the electric system, and the software (improvement in measurement resolution, servo control accuracy, setting time, and the like) increases.

Therefore, the present applicant has solved the problems of the projection optical system, and has a high resolution and a large focus without using a phase shift reticle as disclosed in Japanese Patent Publication No. 62-50811. A new projection exposure technique that can obtain both the depth and
No. 148, Japanese Patent Application Laid-Open No. 4-225358, and the like. This exposure technique increases the apparent resolving power and depth of focus by controlling the illumination method for the reticle 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) It is called the law. In the SHRINC method, two illumination lights (or four illumination lights) symmetrically inclined in a pitch direction of a line-and-space pattern (L & S pattern) on a reticle R are irradiated on the reticle, and are generated from the L & S pattern. One of the 0th-order diffracted light component and one of the ± 1st-order diffracted light components passes symmetrically with respect to the center point CC in the pupil ep of the projection optical system. The projection image (interference fringe) of the L & S pattern is generated using the principle.

As described above, according to the image formation utilizing the two-beam interference, the generation of the wavefront aberration at the time of defocus is suppressed as compared with the case of the conventional method (normal vertical illumination), so that the apparent depth of focus becomes large. It is. However, according to the SHRINC method, an intended effect can be obtained when the pattern formed on the reticle R has a periodic structure like an L & S pattern (lattice). Does not have that effect.
In general, in the case of an isolated micropattern, the diffracted light from the micropattern is generated almost as a Fraunhofer diffraction, so that the 0th-order diffracted light and the higher-order diffracted light are not clearly separated 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, exposure to one shot area of the wafer W is divided into a plurality of times, and the wafer W A method of moving the lens by a certain amount in the direction has been proposed, for example, in Japanese Patent Application Laid-Open No. 63-42122. This exposure method FLEX (F ocu
s L attitude enhancement EX
This method is called a “posture” method, and a sufficient effect of increasing the depth of focus can be obtained for isolated patterns such as contact holes. However, since the FLEX method requires multiple exposures of a slightly defocused contact hole image, the resist image obtained after development necessarily has a reduced sharpness. The problem of the decrease in sharpness (deterioration of profile) is that a resist having a high gamma value is used,
Use a multilayer resist, or use CEL (Contr
This can be compensated for by using a first enhancement layer.

As an attempt to increase the depth of focus at the time of 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
Proceedings 29a-ZC-8 of the Japan Society of Applied Physics Spring, 991,
The Super-FLEX method published in No. 9 is also known. This Super FLEX method uses a pupil e of the projection optical system.
A transparent phase plate is provided on p, and a characteristic is provided such that the complex amplitude transmittance given to the imaging light by this phase plate sequentially changes from the optical axis AX toward the periphery. In this way, the image formed by the projection optical system is kept sharp at a constant width (wider than the conventional one) in the optical axis direction around the best focus plane (a plane conjugate with the reticle R). This increases the depth of focus.

[0013]

Among the various conventional techniques described above, the FLEX method and the Super FLEX method can obtain a sufficient effect of increasing the depth of focus for an isolated contact hole pattern. However, it has been found that, with a plurality of contact hole patterns which are close to each other, unnecessary film loss occurs in the photoresist between the holes in both methods, which makes it practically difficult to use.

Further, in the FLEX method, even with an isolated contact hole pattern, the sharpness of the image (composite optical image obtained by multiple exposure) is necessarily deteriorated. There is also a problem that the degree decreases. Further, it is difficult to apply the FLEX method in which the wafer is continuously moved or vibrated in the optical axis direction during the exposure operation to a scanning exposure type exposure apparatus, and the exposure is divided into a first exposure and a second exposure. In the method in which the wafer is moved in the optical axis direction between each exposure, there is a problem that the processing capacity is greatly reduced and the throughput is significantly reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a projection exposure apparatus with an increased depth of focus when projecting an isolated pattern such as a contact hole. It is an object of the present invention to provide an apparatus and an exposure method which enable a faithful transfer and at the same time obtain an effect of increasing the depth of focus.

[0016]

According to the present invention, there is provided a projection exposure apparatus which illuminates a mask on which a pattern is formed with illumination light and guides light from the pattern onto a substrate. Provided between the mask and the substrate,
A conversion unit is provided for converting light from the pattern into a plurality of lights having an optical path difference equal to or longer than a coherence distance determined by a wavelength range of the illumination light.

[0017]

The operation of the present invention will be described based on the description of the embodiment. A plane in the projection optical system (hereinafter abbreviated as a pupil plane) that optically has a Fourier transform relationship with respect to the reticle pattern plane;
Or a state in which a coherence reducing member is provided on a surface in the vicinity thereof, and a part of the imaging light distributed in a circular or annular shape in the pupil plane and an imaging light distributed in other parts do not interfere with each other. And As a result, the exposure light flux (imaging light) transmitted and diffracted especially in the contact hole pattern in the reticle pattern.
Is spatially divided into two light beams that do not interfere with each other in the pupil plane, and reaches an object to be exposed such as a wafer. Since the two light beams do not interfere with each other even on the wafer (they are incoherent), an intensity-combined image in terms of the light amount of the image (the image of the contact hole) created by each light beam is obtained. In the conventional exposure method, the light flux transmitted and diffracted through the minute contact hole pattern on the reticle reaches the wafer surface via the projection optical system, where it is all synthesized in amplitude (coherent addition).
Thus, an image (optical image) of the reticle pattern was formed. Even in the conventional Super-FLEX method, the imaging light distributed on the pupil plane is only partially phase-shifted, so that it is still coherent addition.

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 the best focus (focused state). Are the same regardless of which optical path in the projection optical system they pass through (Felmer's principle), so that the amplitude synthesis on the wafer becomes a light synthesis without a phase difference,
All work in the direction of increasing the strength of the contact hole pattern.

However, when the wafer is defocused (difference in the optical axis direction between the wafer surface and the best focus surface),
The optical path length varies depending on the optical path in the projection optical system. As a result, the above-described amplitude synthesis is the addition of light having an optical path difference (phase difference), and a cancellation effect occurs in part,
This weakens the center strength of the contact hole pattern. The optical path difference generated at this time is as follows, where θ is an incident angle of an arbitrary ray incident on one image point on the wafer, and the optical path length of a ray (principal ray) incident perpendicularly on the wafer is a reference (= 0). It is approximately expressed as （(ΔF · sin ² θ). Here, ΔF represents the defocus amount. Since the maximum value of sin θ is the numerical aperture NAw of the projection optical system on the wafer side, when all the lights that have passed through the pupil ep among the diffracted light from the minute hole pattern are amplitude-combined on the wafer as in the related art,
An optical path difference of 1/2 (ΔF · NAw ² ) will occur at the maximum. At this time, assuming that an optical path difference of λ / 4 is allowed as the depth of focus, the following relationship is established.

1/2 (ΔF · NAw ² ) = λ / 4 When this expression is re-arranged, ΔF = λ / (2NAw ² ), which is equivalent to the commonly known depth of focus. For example, i-line (wavelength 0.3
65 μm) and the numerical aperture NAw = 0.50
Is assumed, the depth of focus ± ΔF / 2 is ± 0.73 μm, which is a value with little allowance for a process step difference of about 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 a pupil plane (FTP) of the projection optical system. At this time, an image forming light beam diffracted by the isolated pattern Pr formed on the pattern surface of the reticle R (the principal ray is LLp)
Enters the front group lens system GA of the projection optical system PL and then reaches the Fourier transform plane FTP. And the Fourier transform plane F
At TP, a circular transmission portion F at the center in the pupil plane ep
The light beams transmitted through A and the annular transmission portion FB are controlled (converted) so that the light beams do not interfere with each other. Therefore, on the wafer W, the light beam LFa transmitted through the circular transmission portion FA of the coherence reducing member CCM and the light beam LFb transmitted through the peripheral transmission portion FB do not cause interference. As a result, the light beam LFa from the circular transmitting portion FA and the light beam LF from the peripheral portion FB
b independently interfere with each other and form an image (intensity distribution) Pr ′ of the hole pattern. That is, an image generated on the wafer W by interference of only the light beam LFa and an image generated by interference of only the light beam LFb are simply added in terms of intensity to obtain an isolated image such as a contact hole obtained by the present invention. An image Pr 'of the pattern is obtained.

The illuminating light ILB for the reticle R has a constant numerical aperture sinψ / 2 as in the prior art. However, for the numerical aperture NAr on the reticle side of the projection optical system PL, the condition of NAr> sinψ / 2 is set. Therefore, the principle of image formation according to the present invention will be further described with reference to FIG. FIG. 3 shows the structure of the coherence reducing member CCM, the state of the image forming light beam that generates the image Pr ′ of the contact hole,
4 schematically shows the relationship between each light beam and the optical path difference ΔZ at the time of defocusing.

A light beam LFa passing through the center as shown in FIG.
Since the light beam LFa includes a light beam in the angle range from the normal incident light beam (principal light beam LLp) to the incident angle θ ₁ in the amplitude synthesis within the range, the maximum value Δ of the optical path difference when the defocus amount is ΔF
Z ₁ is ΔZ ₁ = １ ／ (ΔF · sin ² θ ₁ ). Note that the horizontal axis of the graph at the bottom of FIG.
Let nθ ₁ = NA ₁ . On the other hand, in the amplitude synthesis in the light beam LFb passing through the peripheral portion as shown in FIG. 3B, the light beam LFb has a light ray in the range of the incident angle 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 ／ (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 caused by the interference of the light beam LFa alone and the deterioration of the image Pr ′ ₂ caused by the interference of the light beam LFb alone are This is due to only the optical path length differences ΔZ ₁ and ΔZ ₂ in the light beam. For example, when sin θ ₁ is set so that sin ² θ ₁ = １ ／ (NAw ² ), that is, when the radius of the first transmission part FA is set so as to substantially satisfy this relational expression, the first light beam LFa The maximum optical path difference ΔZ _{1 due} to
The maximum optical path difference ΔZ ₂ due to the luminous flux LFb is as follows.

ΔZ ₁ = １ ／ (ΔF · sin ² θ ₁ ) =
４ (ΔF · NAw ² ) ΔZ ₂ = １ ／ (ΔF) (NAw ² −sin ² θ ₁ ) = 1/4
(ΔF · NAw ² ) Thus, the two incoherent light beams LFa, L
Each of Fb has substantially the same maximum optical path difference, 1/4 (ΔF · NAw ² ) at the time of defocusing of ΔF, and this value is half that of the conventional case. In other words, even if the defocus amount is twice as large as the conventional one (2ΔF), the same maximum optical path length difference as in the case of the defocus amount ΔF in the conventional projection method is sufficient, and as a result, the isolated pattern Pr
Will be approximately doubled during imaging. 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 configuration of a projection exposure apparatus according to an embodiment of the present invention. In FIG. 4, high-luminance light emitted from a mercury lamp 1 is converged to a second focal point by an elliptical mirror 2 and then becomes divergent light and enters a collimator lens 4. A rotary shutter 3 is disposed at the position of the second focal point, and controls passage and cutoff of illumination light. The illumination light converted into a substantially parallel light beam by the collimator lens 4 is
The light enters the interference filter 5 where only the desired spectrum required for exposure, for example, 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 light beam) 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 each 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, and a surface light source image is created. On the exit side of the fly-eye lens 7, a variable stop 8 for adjusting the size of the surface light source image is provided. Illumination light (divergent light) passing through the stop 8 is reflected by a mirror 9 and enters a condenser lens system 10 to irradiate a rectangular opening of the reticle blind 11 with a uniform illuminance distribution. 4, among 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 the illumination light from one secondary light source image located on X is representatively shown. Also, by the condenser lens system 10,
The exit side (the surface on which the secondary light source image is formed) of the fly-eye lens 7 is a Fourier transform surface with respect to the rectangular opening surface of the reticle blind 11. Therefore, fly-eye lens 7
From each of the plurality of secondary light source images
The illumination lights incident on 0 are superimposed on the reticle blind 11 as parallel light beams having slightly different incident angles from each other.

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 illumination light ILB. Here, the rectangular opening surface of the reticle blind 11 and the pattern surface of the reticle R are conjugated to each other by a combined 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 plane of FIG. As shown in FIG. 4, the illumination light ILB from one secondary light source image located on the optical axis AX among the secondary light source images of the fly-eye lens 7 has a tilt with respect to the optical axis AX on the reticle R. There is no parallel light flux,
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 offset from the optical axis AX are formed on the exit side of the fly-eye lens 7, and any illumination light from these secondary light source images is on the reticle R. In this case, a parallel light beam inclined with respect to the optical axis AX 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. . Also, the incident angle range of the illumination light ILB on the reticle R (see FIG. 2)
Varies depending on the aperture diameter of the stop 8, and when the aperture diameter of the stop 8 is reduced to reduce the substantial area of the surface light source, the incident angle range な る also decreases. Therefore, the aperture 8 adjusts the spatial coherency of the illumination light. As a factor representing the degree of the 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 on the reticle side of the projection optical system PL is used. This σ value is usually defined as σ = sin (ψ / 2) / NAr, and most steppers currently in operation have σ = 0.
It is used in the range of about 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 on the pattern surface of the reticle R by a chromium layer. Here, a chromium layer is vapor-deposited on the entire surface, and a minute rectangular opening (a transparent film without a chrome layer) is formed therein. It is assumed that there are a plurality of contact hole patterns formed in section (1).
The contact hole pattern may be designed to have a dimension of 0.5 μm square (or diameter) or less when projected onto the wafer W.
In consideration of the above, the size on the reticle R is determined. In addition, since the dimension between the contact hole patterns adjacent to each other is usually much larger than the dimension of the opening of one contact hole pattern, it exists as an isolated minute pattern. That is, two adjacent contact hole patterns are often separated to such an extent that light (diffraction, scattered light) generated from each does not strongly influence each other unlike a diffraction grating. However, as will be described in detail later, there is also a reticle in which a contact hole pattern is formed in a very close arrangement.

In FIG. 4, reticle R is held on reticle stage RST, and an optical image (light intensity distribution) of a contact hole pattern of reticle R is formed on a photoresist layer on the surface of wafer W via projection optical system PL. Is done.
Here, the optical path from the reticle R to the wafer W in FIG. 4 is indicated only by the principal ray of the imaging light beam. And the projection optical system P
The Fourier transform plane FTP in L is provided with the coherence reducing member CCM described with reference to FIGS. 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 enter 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 the exposure operation of the lithography process using a plurality of steppers, it is hesitant to assign a specific one stepper to the exposure dedicated to the contact hole pattern in consideration of the most efficient operation of each stepper. Therefore, the coherence reducing member CCM is provided in the projection optical system PL.
It is desirable that the stepper can be used even when exposing a reticle pattern other than the contact hole pattern, so that the stepper can be used. Note that, depending on the projection optical system, the pupil position (Fourier transform plane FT)
P) to change the effective pupil diameter
(Variable aperture) may be provided. In this case, the aperture stop and the coherence reducing member CCM are arranged so as not to mechanically interfere with each other and as close as possible.

The wafer W moves two-dimensionally (hereinafter referred to as XY movement) in a plane perpendicular to the optical axis AX.
It is held on wafer stage WST that slightly moves (hereinafter, referred to as Z movement) in a direction parallel to 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 based on the detection value of the auto-focusing focus sensor 24. 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. The main control unit 25 further sends a command to the shutter drive unit 26,
Of the aperture 8 and the size of each aperture of the aperture 8 or the reticle blind 11 are controlled. Further, the main control unit 25 can input a reticle name read by a bar code reader 28 provided in a 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.
, The operation of the aperture driving unit 27, and the like, and automatically adjusts the aperture size of the aperture 8, the reticle blind 11, and the necessity / unnecessity of the coherence 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. Figure 5 shows a partial cross section of the projection optical system PL made in all refractive glass material, the top of the lens GB ₁ lens system GB at the bottom of the lens GA ₁ and the rear group lens system GA of the front lens group A Fourier transform plane FTP exists in the space between. Although the projection optical system PL holds a plurality of lenses in 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 all or a part of the interference reducing member CCM and the slider mechanism 20 to the outside air 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 includes
An actuator 20A such as a rotary motor, a pen cylinder, and a solenoid is connected. Further, a flow path Af communicating with the pupil space is provided in a part of the lens barrel, and clean air whose temperature is controlled is supplied to the pupil space via the pipe 29, so that a part of the exposure light of the coherence reducing member CCM is provided. The temperature rise due to absorption and the temperature rise in the entire pupil space are suppressed. In addition, clean air forcibly supplied to the pupil space,
By forcibly discharging the dust through the slider mechanism 20 and the actuator 20A, it is possible to prevent dust generated by the slider mechanism 20 and the like from entering the pupil space. 6A and 6B show the structure of the first embodiment of the coherence reducing member CCM. FIG. 6A is a sectional view taken along 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
² = 2r ₁ ² a is set in a relationship, in fact better several% greater than that. As is clear from this equation,
Area pi] r ₁ ² of circular transmitting portion FA is the effective area of the pupil aperture π
It has become about half of the r _{² 2.}

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

ΔLc = λ ₀ ² / Δλ ≒ 26 μm The coherence reducing member CCM shown in FIG. 6 is a parallel plate glass having a refractive index of n ₁ and a thickness of t in a circular transmitting portion FA having a radius r ₁ from the center point CC. Alternatively, the peripheral transmission portion FB in the form of an annular zone coaxial with the center point CC is formed of a parallel plate-shaped crystal element having a refractive index of n ₂ and a crystal element having a thickness of t. With such a configuration, the optical path difference between the imaging light beam LFa transmitted through the circular transmission portion FA and the imaging light beam LFb transmitted through the peripheral annular transmission portion FB is not less than the coherent length ΔLc of the light. For example, the two light beams LFa and LFb become temporally incoherent light beams. That is, | (n
₂₋ n ₁ ) t | ≧ ΔLc The two glass materials (refractive indices n ₁ and n ₂ ) and the thickness t may be determined so as to satisfy the relationship. Here, assuming that the circular transmission part FA is made of glass having a refractive index n ₁ = 1.50 and the annular transmission part FB is made of glass having a refractive index n ₂ = 1.60, the i-line (Δλ = 5 nm) of a mercury lamp is used. If
| (1.60-1.50) t | ≧ 26 μm, the thickness t
Is 260 μm or more. Note that there is no particular upper limit for the thickness t, and a glass plate having a thickness of several mm may be used.
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 increased in general optical glass, so that it is advisable to increase the thickness t more than necessary. is not. In any case, the imaging light fluxes that have passed through each of the circular transmission part FA and the annular transmission part FB become light fluxes (LFa, LFb) that do not interfere with each other. Both the central beam and the peripheral beam that do not interfere with each other reach the wafer W, and each of them combines amplitude only with itself and separately forms an image (intensity distribution).
The principle of increasing the depth of focus of the combined image (combined intensity distribution) by forming Pr ₁ ′ and Pr ₂ ′ is as described in the section of the operation.

FIG. 7 shows the structure of a coherence reducing member CCM according to a second embodiment. In the present embodiment, similarly to FIG. 6, the central circular transmission part FA and the peripheral annular transmission part FB are completely the same in that the optical glass has a thickness t and refractive indexes 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 emission side (or the incidence side). The material of the transparent plate FC is quartz glass or fluorite that transmits extreme ultraviolet light, and is bonded to the optical glass forming the transmission parts FA and FB as shown in FIG. It is arranged with the gap maintained. Also in this embodiment, the light beam transmitted through the circular transmission portion FA and the transparent plate FC and the light beam transmitted through the annular transmission portion FB and the transparent band FC have a temporally incoherent relationship.

FIG. 8 shows some cross-sectional structures of other modified examples of the coherence reducing member (optical path difference control member) CCM used in each embodiment of the present invention.
FIG. 8 (A) is effective maximum radius uniform thickness of the transparent circular substrate r having slightly larger diameter than the _second pupil ep (glass, quartz) in OP _1, glass fine thickness ta, or resin a thin plate OP ₂ are those placed, or were stuck. The thin plate OP ₂ constitutes a circular transmitting portion FA of radius r _1, when the refractive index n _1, a light beam (wheel passing through only a light beam and the substrate OP ₁ passing through both of the thin plate OP ₂ and the substrate OP ₁ The optical path length difference between the optical path length and the transmitted light of the band transmitting portion FB is (n)
Given by ₁ -1) ta. Therefore, from the relationship with the coherent length ΔLc of the light beam (illumination light), (n ₁ −1) ta ≧
It may be determined thickness ta of the thin plate OP ₂ so as to satisfy the DerutaLc.

This thin plate OP_TwoThe material is glass,
High transmittance for crystals or ultraviolet light (exposure light)
Resins, such as C manufactured and sold by Asahi Glass Co., Ltd.
YTOP (product name) can be used. 8 (A)
As a method of manufacturing the interference reducing member CCM, the substrate OP₁
OP on thin plate_TwoAfter sticking, thin plate OP_TwoPolished surface
Polishing to achieve flatness and uniformity of the overall thickness of the member CCM
You may finish it. Or board OP₁On top
Thin plate OP by a vacuum method, a vapor deposition method, or a CVD method. _TwoFilm
May be. Further thin plate OP_TwoWhen resin is used,
Liquid resin and spin coating method (substrate OP₁Rotate
And drop the liquid resin at the center, and centrifugally apply the desired thickness.
May be formed by a method of stretching to the maximum.

FIG. 8B shows the center of at least one surface of a single circular transparent parallel substrate (such as quartz) with a radius r _1.
This shows that the peripheral orbicular zone is etched by the step tb so as to obtain the circular transmitting portion FA. Assuming that the refractive index of this circular transparent substrate is n ₂ , here also (n ₂ -1) tb
The step tb is determined so as to satisfy the relationship of ≧ ΔLc.
In general, since the refractive index of fused silica is about 1.5 in the ultraviolet region, the coherent length ΔLc of the i-line of the mercury lamp is 26 μm.
Assuming that m, the step tb may be 52 μm or more. When fluorite is used, its refractive index is about 1.46, so that the step tb may be 57 μm or more.

[0039] Now, FIG. 8 (C) to form a circular recess depth tc a radius r ₁ in the center of the circular transparent parallel substrate (quartz) OP _1, there glass, or sheet of a resin OP
₂ shows what is placed or bonded. This FIG.
The configuration of FIG. 8C is only complementary to that of FIG. Here, the refractive index of the thin plate OP ₂ is n
_1, when the refractive index of the substrate OP ₁ was 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 substrate OP _1, this is not a requirement.

FIG. 8D shows a circular transparent substrate OP.₁Heart of
Radius r₁Ion implantation within the circular area of
Differs in refractive index due to thermal diffusion of impurity ions
Area OP_ThreeAre shown. In this case, the substrate OP
₁The refractive index of_Two, Area OP _ThreeThe refractive index of_ThreeAnd
Area OP_Three| (N) where td is the thickness of_Three-N_Two) T
d | ≧ ΔLc so that the refractive index change amount (n_Three-N
_Two) Or the thickness td is controlled.

FIG. 8 (E) is the refractive index in the same manner as FIG. 8 (B) is the same, and a circular transparent substrate OP ₄ and annular transparent substrate OP ₅ of different thicknesses manufactured separately, later It is a combination. Circular transparent substrate OP ₄ is the radius r _1, constituting the circular transmitting portion FA. Moreover, te thickness of the circular substrate OP _4, the thickness of the annular substrate OP ₅ and tf, and the refractive index of the substrates and _{n 2, | (te-tf} ) (n 2 -1) |
The relationship between the thicknesses is determined so as to satisfy ≧ ΔLc. Further, when varying the refractive index of the circular substrate OP ₄ ne, the refractive index of the annular substrate OP ₅ as nf is, | (ne-1)
What is necessary is to satisfy the relationship of te− (nf−1) tf | ≧ ΔLc. Therefore the two substrates OP _4, OP each refractive index of the ₅ ne, Different nf, two substrates OP _4, OP ₅
May be the same, and in this case, the structure is the same as the structure of the coherence reducing member CCM of FIG. Further, in the case of the structure of FIG.
The relationship between f and nf is expressed by te (1-1 / ne) = tf (1-1)
/ Nf), the effect on the optical aberration of the projection system can be minimized.

FIG. 8 (F) is a view showing the surrounding annular zone transmitting portion FB.
A ring-shaped thin plate (quartz, etc.) with a thickness of tg
It shows the case where At this time, the thickness tg of FIG.
Sheet OP_TwoMay be considered under the same conditions as the thickness ta. Now,
FIG. 9 shows a configuration of a third embodiment of the coherence reducing member CCM.
FIG. 9A shows a cross section at a point passing through the optical axis AX.
FIG. 9B shows a plane. In this embodiment, the optical axis AX
Radius r about the center point CC of the pupil ep through which₁Round
Transmission part FA ₁And its outer diameter r_ThreeFirst ring-shaped transparent
Excess FB_TwoAnd the outer diameter r_Two(Effective of the eyes
The largest annular diameter) of the second annular transmission portion FB_ThreeThree areas with
And the transmission part FA₁, FB_Two, FB_ThreeImaging through
Each of the light beams has an optical path longer than the temporal coherent length ΔLc.
Give a length difference. The specific structure is shown in FIG.
The one shown in FIG. 8 can be applied as appropriate. In the case of this embodiment,
Three transmission parts FA₁, FB_Two, FB_ThreeAfter passing each of
It is necessary to prevent the imaging light beams from
You. However, as in the first and second embodiments,
It is not necessary to completely reduce the coherence to zero,
I just need to be. In FIG. 9, the central circular transmitting portion FA is shown.₁Thing
Although it is shown that the quality exists, the method of FIG.
When applied, the circular transmission part FA₁Is the radius r₁Opening
(Space).

Further, the coherence reducing member CCM shown in FIG.
As a modification of, the transparent thin film (phase shifter) either one of the regions of the provided circular transmitting portion FA ₁ and the outermost annular transmitting portion FB ₃ of the center, the transmitted light beam of the circular transmitting portion FA ₁ and zonal phase difference of lambda / 2 between the transmitted light beam of the transmitting portion FB ₃ (i.e. antiphase) may be given. However, even in this case, the transmitted light flux of the other two transmitting parts FA ₁ and FB ₃ is given an optical path length difference greater than or equal to the coherent length ΔLc with respect to the transmitted light flux of the intermediate annular transmission part FB _2. I have.

Accordingly, when the thicknesses and materials of the transmission portions FA ₁ and FB ₃ are made equal, the transmitted light beams of the transmission portions FA ₁ and FB ₃ cause interference. Since they have an anti-phase relationship, they act as a kind of bifocal filter, and an effect of increasing the depth of focus can be obtained. A method of a multifocal filter that divides an imaged light beam into several parts on such a Fourier transform plane (pupil) and gives a predetermined phase difference to each of the divided light beams is as follows.
It was issued on January 23, 1961. This is described in detail in pages 41 to 55 of a paper entitled "Study on Image Forming Performance in Optical System and Improvement Method Thereof" in Report No. 40 of Mechanical Testing Laboratory.

By the way, in the case of the embodiment shown in FIG.
Imaging light beam which reaches the top (point image) is passed through a respective 11 light beams LFa and zonal transmitting portion FB ₂ including a main ray LLp passing through the circular transmitting portion FA ₁ as shown in (A), FB ₃ The light beams LFb ₂ and LFb ₃ are divided into three. In the configuration in which the phase shifter is not provided as described above, these three light beams LFa, LFb ₂ , and LFb ₃ have extremely low coherence with each other.

In FIG. 11A, the incident angle θw of a 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 are distributed in an angular range of up to an incident angle theta ₁ from the vertical incident light (main beam) LLP, the light flux LFb ₂ is distributed in the angular range of the incident angle theta ₁ to theta _3, the light flux LFb ₃ is incident distributed in an angular range of from the corner θ ₃ to θw. Assuming that the focal length of the rear lens group GB on the rear side of the projection optical system PL is f, each of the transmission parts FA ₁ , F ₁ on the pupil ep
The radii r ₁ and r ₃ of B ₂ are given by r ₁ = f sin θ ₁ , r ₃ =
fsin θ ₃ .

FIG. 11B is a graph of the optical path length difference ΔZ generated in FIG. 11A, where the defocus amount is ΔF, and the vertical and horizontal axes are the same as FIG. Therefore, for the defocus amount ΔF, the maximum optical path length difference generated in the light flux LFa is ΔZ ₁ , the maximum optical path length difference generated in the light flux LFb ₂ is ΔZ ₂ , and the maximum optical path length difference generated in the light flux LFb ₃ is ΔZ ₃ Then, each is 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 It is assumed that the radii r ₁ and r ₃ are determined so as to satisfy the following relationship between the incident angles θ ₁ and θ ₃ .

[0049] sin^Twoθ₁= NA₁ ^Two= 1/3 (NAw^Two) Sin^Twoθ_Three= NA_Three ^Two= 2/3 (NAw^TwoThen, the three light beams LFa and LFb_Two, LFb_ThreeEach of
Are all equal as follows. ΔZ₁= ΔZ_Two= ΔZ_Three= (ΔF · NAw^Two/ 3) / 2₁Area πr₁ ^Two, Transmission part FB
_TwoArea π (r_Three ^Two-R ₁ ^Two) And transmission part FB_ThreeFruit
Effective area π (r_Two ^Two-R_Three ^Two) Equal to all three
There is nothing to say.

As described above, in the conventional ordinary projection exposure, the optical path length difference ΔZ at the defocus amount ΔF is ΔΔ
Z = (ΔF · NAw ² ) / 2. However, in this embodiment, if the allowable value of the optical path length difference is λ / 4, the defocus amount 3ΔF which is three times that of the conventional case.
Until then, it will be accepted as a good image. That is, the depth of focus is tripled as compared with the related art.

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

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

Next, the structure of a coherence reducing member CCM according to a fourth embodiment of the present invention will be described with reference to FIG. In the present embodiment close to the coherence reducing member CCM shown in FIG. 9 (or adhesion) to provide a circular shielding portion FD of radius r ₄ in the central portion. FIG. 10A shows a cross section of the coherence reducing member CCM of the present embodiment, and FIG. 10B shows a plan view. In the case of the present embodiment, as shown in FIG. 10B, the imaging light flux incident on the pupil ep is a circular light-shielding portion FD at the center of a radius r ₄ , and an annular transmission portion FA having an inner diameter r ₄ and an outer diameter r _{1. 1,} the inner diameter r _1, annular transmitting portion FB ₂ having an outer diameter r _3, and the annular transmitting portion FB ₃ of the inner diameter r ₃
, And only the light beam divided into three parts other than the light shielding portion FD reaches the wafer W.

FIG. 12 shows the relationship between the state of division of the imaging light beam and the optical path length difference ΔZ in the embodiment of FIG. Here, the relationship between the radius of the central circular light-shielding portion FD and the radius of each of the annular transmission portions FA ₁ , FB ₂ , 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
Therefore, the principal ray LLp does not exist in the actual light beam.
Further, the light fluxes LFa, LFb ₂ , LFb ₃ that have passed through the respective transmission portions
Are the maximum incident angles θ ₁ , θ ₃ , θw, and the luminous flux L
The minimum incident angle of Fa is θ ₄ .

By dividing the light beam 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 , that is, the annular transmission portion F
Area of ^{_{A 1 π (r 1 2 -r}} 4 2), the area ^{_{π (r 3 2 -r 1 2}} ) of the annular transmitting portion FB _2, and annular area of the transmissive portion FB ₃ π (r _{² 2} -r _{If the} radii r ₄ , r ₁ , and r ₃ are determined so that ₃ ² ) is made substantially equal, the effect of increasing the depth of focus can be maximized.

By the way, as shown in FIG.
When the FD is provided, the optical path length difference due to the defocus amount ΔF
ΔZ₁, ΔZ_Two, ΔZ_ThreeIs the area of the circular light-shielding portion FD,
That is, radius r_FourWill change in accordance with So figure
The optical path length difference ΔZ as shown in FIG.₁, ΔZ_Two, ΔZ_ThreeTo
Three transmission parts FA to make them equal₁, FB_Two, FB _Three
Assuming that the area of the circular light-shielding portion FD is set,
Radius r_FourAnd the effective radius r of the pupil ep_TwoAnd the ratio r_Four/ R
_TwoIs k, ΔZ₁= ΔZ_Two= ΔZ_Three= (NAw^Two-K^Two・ NA
w^Two) / 3. In this equation, k^Two・ NAw^TwoIs the light shielding part FD
It corresponds to the area, and its value is NA_Four ^Two= Sin
^Twoθ_FourNothing else. Therefore, the light-shielding portion FD has a predetermined area.
(Radius r_Four9), the above-described embodiment of FIG.
Optical path length difference ΔZ₁, ΔZ_Two, ΔZ_ThreeThe value of
Since it can be made smaller, the depth of focus will be further increased.
You.

As described above, in the embodiment shown in FIG.
Is provided around the optical axis AX, but if provided as a ring-shaped light-shielding portion, the effect of increasing the depth of focus can be obtained according to the area thereof. As an example, a configuration as shown in FIG. 13 can be considered. FIG. 13A is a plan view, and FIG. 13B is a cross-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 transmitting portion FA having a radius r ₁ , and the outside is an annular transmitting portion FB having an inner diameter r _3.
A light path difference equal to or longer than the coherent length ΔLc is given to a light beam passing through each of the transmission parts FA and FB.

Also in the case of this embodiment, as shown in FIG. 13C, the optical path length difference ΔZ ₁ when the light beam passing through the transparent portion FA is defocused and the light path length difference ΔZ ₁ when the light beam passing through the transparent portion FB is defocused. of the optical path length difference [Delta] Z ₂ so as to be substantially equal, the transmitting portion FA for effective diameter r ₂ of the pupil, FB, shielding portion F
If the radii r ₁ and r ₃ of D are determined, the effect of expanding the depth of focus is maximized.

As described above, the configuration of the coherence reducing member CCM according to each embodiment of the present invention has been described. However, the imaging light flux from the contact hole pattern on the reticle R is substantially uniform at the pupil ep of the projection optical system. Is assumed to be distributed in That is, the diameters of the transmission parts FA, FA ₁ , FB, FB ₂ , FB ₃ and the light shielding part FD are determined on the assumption that the imaging light flux distributed on the pupil ep exists up to the effective maximum radius r _2. 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 imaged light beam when the size of the contact hole pattern Pr becomes smaller than a certain value.

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

Another method of applying the present invention to such an apparatus
As a method, as shown in FIG.
Center radius r₁Circular transmission part FA and its surrounding annular zone
Each of the FBs has a different wavelength range for the transmitted light.
A low pass filter may be formed. This band pass
The filter is formed of, for example, a multilayer dielectric thin film, and
It is constituted by vapor deposition on a transparent circular substrate. This implementation
In the example, a dielectric thin film is used as the central circular transmission part FA.
Vapor deposition is performed on one surface of the plate, and the annular transmission portion FB (inner diameter r₁)When
The dielectric thin film on the other side of the substrate
The part FA is, for example, to pass only the h-line having a wavelength of 405 nm.
And the annular transmission portion FB passes only the g-line having a wavelength of 436 nm.
To do. Here, the light beam passing through the pupil ep is referred to as the central portion.
It is split into two light beams LFa and LFb passing through
Therefore, the effective radius r of the pupil ep _Two, The transmission part F
Radius r of A₁Is r_Two ^Two= 2r₁ ^TwoSet in a relationship
You.

As described above, the transmitted light LFa of the circular transmitting portion FA
When the light and the transmitted light LFb of the annular transmission part FB are divided in a wavelength range by a band-pass filter, the two light beams LFa and LFb are converted into light having no interference with each other. The depth of focus is increased.
Note that the bandpass filter may be made of absorptive colored glass.

As another method, the luminous flux distributed to the pupil is polarized.
It is also conceivable that light is split by light to eliminate coherence
You. The method in that case is shown as a sixth embodiment in FIG.
explain. In this embodiment, two transparent circular substrates CCM
a, CCMb constitutes a set to form the coherence reduction member CCM
The substrate CCMa has a radius r about the optical axis AX.₁of
Circular transmitting part PCa and inner diameter r₁And the outer diameter is r_Two(Effective
(A pupil diameter). And transparent
Excess PCa and / or PCb
Change the polarization state of the light beams passing through them so that they do not interfere with each other.
Polarizing plate, quarter-wave plate, half-wave plate, etc.
Made with On the other hand, the substrate CCMb is centered on the optical axis AX.
Radius r_FourMade of an annular quartz plate with a circular opening of
The inner diameter there_Four, The outer diameter is r_ThreeRing zone of the first thickness
And the inner diameter is r_Three, The outer diameter is r _TwoThe second
An annular transmission portion having a thickness is formed.

Where the radius r₁~ R_FourIs r_Four<R₁<R_Three
<R_TwoAnd r_Four ^Two= (R₁ ^Two-R_Four ^Two)
= (R_Three ^Two-R₁ ^Two) = (R_Two ^Two-R_Three ^Two) Is set to
It is assumed that In addition, two substrates CCMa, CCMb
May be arranged close to each other across the Fourier transform plane FTP.
They may be pasted together. In such a configuration
The radius r_FourAnd half of the light beam LFa that has passed through the circular transmission portion FA
Diameter r_Four~ R₁Zone transmission part FB₁Light beam LFb passing through₁
Means that the polarization state is the same, but the optical path length difference is coherent
Since they are longer than the length ΔLc, they do not interfere with each other. Also radius
r₁~ R_ThreeZone transmission part FB_TwoLight beam LFb passing through_TwoWhen
Luminous flux LFb₁, LFa are different from each other because of their different polarization states.
Does not interfere. Further radius r_Three~ R_TwoRing of Toru
Excess FB _ThreeLight beam LFb passing through_ThreeAnd luminous flux LFb_TwoIs light
Since the path length difference is greater than the coherent length ΔLc,
Without interference, light flux LFb at the same time_ThreeAnd luminous flux LFb₁, LFa
And do not interfere with each other because of their different polarization states.

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

The light-shielding portion FD or a light-shielding plate equivalent to the light-shielding portion FD only needs to shield light for the exposure wavelength.
It may be one that absorbs a short wavelength region such as an exposure wavelength (ultraviolet light) by using an optical sharp cut filter made of a dielectric thin film or the like. In this case, for example, He
When a TTL 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 the projection optical system PL is used, a light shielding unit FD located on the pupil plane or a light shielding unit The problem that the plate exerts an adverse effect (light blocking) on the reflected light from the mark is eliminated. Alternatively, only the position on the light-shielding plate or light-shielding portion FD of the above-described metal or the like through which the reflected light from the laser beam or the mark for illuminating the wafer mark passes may be used as the transmission region. Does not.

FIG. 16 shows an example of a TTL alignment system as a seventh embodiment, in which a lattice mark G
An R is formed, and it is assumed that the positional deviation of the mark GR in the lattice pitch direction is detected. Here, FIG. 16A is a view of the alignment system from a direction in which the horizontal direction on the paper surface is the pitch direction, and FIG. 16B is a view from the direction in which the system of FIG. Is what I saw. A coherent laser beam (He-N) is emitted from an objective lens OBJ of an alignment optical system provided above the reticle R.
e) The two light beams 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 via the window RM around the reticle R. First, as shown in FIG. 16A, the two beams ALB ₁ and ALB ₂ are incident on the bending correction elements PG ₁ and PG ₂ formed on the coherence reducing member CCM located at the pupil, respectively. Here, the two beams ALB have an amount corresponding to the axial chromatic aberration of the projection optical system PL.
_1. Change the traveling direction of ALB ₂ . As a result, the two beams ALB ₁ and ALB ₂ are converted into the lattice mark G on the wafer W.
R is irradiated at an angle symmetrically inclined with respect to the pitch direction. At this time, the pitch Pg of the grating mark GR, the wavelength 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
g, the + _1st-order diffracted light generated from the grating mark GR by the irradiation of the beam ALB ₁ and the beam ALB ₁
The -1st-order diffracted light generated from the mark GR by the irradiation of the B _2, 2 beams ALB ₁ as shown in FIG. 16 (A), the
Interference beam A by making the optical path just in the middle of ALB ₂ coaxial
Reverse as DL. The interference beam ADL is changed the traveling direction by bending correction device PG ₃ formed on the coherence reducing member CCM, go back towards the alignment optical system through the window RM of the reticle R. At this time, FIG.
As shown in FIG. 2, the two beams ALB ₁ and ALB ₂ reaching the mark GR on the wafer W are inclined with respect to a direction (non-measurement direction) orthogonal to the pitch direction, so that the interference beam ADL is also generated with an inclination. . Also, as shown in FIG. 16A, the two beams ALB ₁ and ALB ₂ intersect at the surface CF, but the surface CF can actually coincide with the position of the window RM. That is, two beams ALB ₁ and AL
It can be substantially completely compensating the longitudinal chromatic aberration fraction raised against B _2. Further, as shown in FIG. 16B, the two beams ALB ₁ and ALB ₂ are shifted from the telecentric condition in the non-measurement direction and enter the window RM to compensate for the chromatic aberration of magnification. The optical axis AXa of the objective lens OBJ is set perpendicular to the reticle R.

In measuring the displacement of the mark GR,
There are two ways. One of them is two beams AL
B₁, ALB_TwoFormed on the mark GR by the intersection of
Of the mark GR in the pitch direction with respect to the interference fringes
This is to detect this. For that, alignment
The returned interference beam ADL is photoelectrically detected in the optical system.
A photoelectric sensor and measure its output signal level.
No. One method is to use two beams ALB₁, ALB
_TwoSlight frequency difference between (eg 20-100 KHz
Degree), and the interference fringes generated on the mark GR are
Heterodyne method that runs at a speed corresponding to the frequency difference
You. In this case, two beams ALB₁, ALB _TwoFrequency
Create a reference AC signal with a number difference and output from the photoelectric sensor.
Force signal (in the case of heterodyne, the interference beam ADL is
Signal because the intensity changes at the same frequency)
By calculating the phase difference between
Can be measured.

As described above, when the bending correction elements PG ₁ , PG ₂ , and PG ₃ for chromatic aberration compensation are provided on the pupil plane of the projection optical system PL, the light shielding portion FD shown in FIGS. (Or a light shielding plate) in some cases. However, this type of alignment beam ALB ₁ , ALB ₂ or the 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 built as a phase grating correction element PG ₁ ~PG ₃ by etching or the like on the surface of a transparent glass material.
Therefore, as described above, when the light-shielding portion FD interferes with the position, only the light-shielding portion at that position needs to be a transparent portion.

In FIG. 16, the correction elements PG _{1 to} PG ₃
Is formed directly on the coherence reducing member CCM, but 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 May be removably disposed in the very vicinity of.
A method of providing a correction lens (convex lens) having a small diameter at the center of the pupil plane of the projection optical system PL to compensate for the chromatic aberration of the alignment beam is disclosed in, for example, USP.
5,100,237. In this case, the transmittance for the exposure wavelength is small in the portion of the correction lens,
If a dichroic film having an extremely high transmittance with respect to the wavelength of the alignment beam is deposited, a film substantially equivalent to the center light shielding portion FD of the coherence reducing member CCM shown in FIG. 10 can be easily formed. However, the above USP. 5,10
0 and 237 have transmission portions FA ₁ and F as shown in FIG.
There is no suggestion about providing B ₂ and FB ₃ at the same time.

In the drive unit 22 of the wafer stage WST shown in FIG. 4, the function of the conventional FLEX method may be provided in the control for finely moving the wafer W in the optical axis direction. By using the FLEX method together, the effect of increasing the depth of focus according to the present invention can be dramatically increased. The present invention can be applied to any type of projection 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 a scan type (step-and-scan) or mirror projection system, exposure is performed while scanning and moving a reticle or a wafer in a plane perpendicular to the optical axis of a projection optical system, and it has been considered difficult to apply the conventional FLEX method. However, the present invention has an advantage that it can be applied to such a scanning type exposure apparatus very easily.

The case where the present invention is applied to an aligner of the same size mirror projection system will be described as an eighth embodiment with reference to FIGS. In FIG. 17, illumination light from a mercury lamp (Xe-Hg) lamp 1 is projected on a reticle (mask) R via an illumination optical system ILS into an illumination area in the shape of a circular arc slit. The reticle R is held on a 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, the optical block trapezoidal with MR _4, is composed of a large concave mirror MR ₂ with a small convex mirror MR _3, the concave mirror with respect to the radius of curvature of the convex mirror MR ₃ M
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 coincides with TP.

At this time, the image forming light flux generated from the point Pr on the reticle R is reflected along the principal ray LLP along the reflecting surface MR ₁ ,
Upper concave mirror MR _2, the entire surface of the convex mirror MR _3, the lower side of the concave mirror MR _2, and proceeds in the order of the reflection surface MR _4,
It converges to a point Pr ′ on the wafer W. Thus even when the surface of the convex mirror MR ₃ is a pupil plane of the system, the coherence reducing member CCM used in the embodiments have been described until now
Can be used as it is or with some modifications.

More specifically, as shown in FIG.
Convergence reducing member CCM _ThreePlaced in the immediate vicinity of
Concave mirror MR_TwoTo convex mirror MR_ThreeIncident on
Time and convex mirror MR_ThreeFrom concave mirror MR_TwoInjection to
The optical path of twice (round trip) with the time when going
(Or orbicular zone) Light flux passing through the transmission part FA and surrounding orbicular zone transmission
The light beam passing through the portion FB is light having a coherent length ΔLc or more.
What is necessary is just to comprise so that there may be a path length difference.

Alternatively, as shown in FIG. 18 (B), a minute step is provided with a predetermined radius (area) on the surface of the convex mirror MR ₃ ′ serving as a Fourier transform surface, and the upper and lower portions of the step are formed. May give an optical path length difference (twice the step amount) greater than or equal to the coherent length ΔLc to the reflected light beam. 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. Incidentally, the stepped portion formed in the convex mirror MR _'3 of the surface shown in FIG. 18 (B) may be a transparent object (film). In this case, the step between the surface of the convex mirror MR and the surface of the transmitting object (corresponding to the transmitting portion FA), that is, the thickness d of the transmitting object is the optical path length generated by the reciprocation of the light beam in the transmitting object having the refractive index n. Difference 2 (n-
1) d is determined so as 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, considering the fact that the light is reciprocally polarized twice in the reciprocating optical path, 1 / It is necessary to change the two-wavelength plate to a 波長 wavelength plate and the １ ／ wavelength plate to a ８ wavelength plate. In a projection exposure apparatus using an excimer laser as a light source, a secondary light source surface (many point light sources) formed on the exit side of a fly-eye lens or the like is re-imaged on a pupil surface of a projection optical system. When an optical element (a lens, a reflecting surface, an aperture stop, a CCM, or the like) is arranged on the pupil plane, the optical element may be deteriorated due to a converged light source image due to long-term use. For this reason, it is preferable that the coherence reducing members CCM and the like not be strictly arranged on the pupil plane, but rather be slightly shifted.

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 coherent length ΔLc of the light beam (illumination light ILB). However, the value is the same as the conventional Super
This is much larger than the optical path length difference (wavelength 1/2 to several wavelengths) given by the FLEX method. In addition, Supe
In the r FLEX method, all the imaging light fluxes that have passed through a filter (complex amplitude transmittance) disposed on the pupil plane of the projection optical system interfere with (combine the amplitude) on the wafer W and remain unchanged from the present invention. It is completely different in principle from the Super FLEX method. Due to the difference in principle, a new effect not obtained by the Super FLEX method in the present invention can be obtained. This will be described with reference to a simulation described below.

The coherence reducing member CCM used in the present invention
Is to divide the imaging light flux passing through the pupil plane (distributed almost uniformly in the case of a contact hole pattern) into a plurality of portions in the radial direction of the pupil, and only to reduce the coherence between the respective partial light fluxes Works. Therefore, in the coherence reduction member CCM used in each embodiment, the best focus position (focal position) of each of a plurality of images (Pr ′ ₁ , Pr ′ _2, etc.) independently formed by each partial light beam is There is no effect of shifting the projection optical system in the direction of the optical axis AX, that is, an effect of giving a certain type of spherical aberration.

In each of the above embodiments, when the pupil plane ep of the projection optical system is divided into m areas of a circular area or an annular area,
Although it is assumed that the areas of the respective divided regions are equal, this is not always an essential condition. In particular, an optical path difference of not less than the temporal coherent length ΔLc is given between a pair of circular regions and an annular region, or between a pair of annular regions and an annular region, and
In the case of a configuration that gives an optical path difference of 波長 wavelength (an example using a phase shifter or the like), it is preferable that the areas of the pair of regions be different. This is because if the light quantities (corresponding to each area) of both light fluxes (each corresponding to the transmitted light in both regions) having an optical path length of 波長 wavelength are substantially equal, the two light fluxes are on the wafer (image position). This is because the offset cancels out and the intensity becomes zero. Alternatively, instead of making the areas of the two regions different, the transmittance of one of the regions may be reduced. Of course, both the area and the transmittance may be changed. In each of the above embodiments, the coherence reducing member C
When CM is used as a transmission member, an antireflection coat is preferably applied to the interface (surface).

Next, the operation and effect obtained by each embodiment of the present invention will be described based on simulation results. FIG. 19A shows a square contact hole pattern PA whose one side corresponds 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. 19A is shown. Of the image intensity distribution on the wafer. FIG. 19B is the same as FIG.
(Or FIGS. 7 and 8) showing the coherence reducing member CCM, wherein the ratio r ₁ / r ₂ between the radius r ₁ of the central circular transmitting portion FA and the effective maximum radius r ₂ of the pupil ep ( NA ₁ / NA
w) is determined to be 0.707 as described in the explanation of the principle. That is, assuming that the maximum incident angle of the image forming light beam passing through the transmission part FA is θ ₁ , sin ² θ
It is determined to satisfy ₁ = 1/2 (NAw ² ). In the following simulations, NAw = 0.
57. The exposure was performed under the condition of i-line (wavelength 0.365 μm). The σ value, which is the coherence factor of the illumination light beam, was set to 0.6. Now, FIG. 19 (C),
(D), (E) shows the image intensity distribution on the wafer of the pattern PA, the intensity distribution I ₁ at the best focus position, respectively, the intensity distribution I ₂ at the defocus position of 1 [mu] m, 2
This is an intensity distribution I ₃ at a defocus position of μm. Eth in FIGS. 19C, 19D, and 19E indicates the strength required to completely remove (expose) the positive photoresist on the wafer, and Ec indicates the dissolution of the positive resist (film burrs).
Indicates the strength at which to start. The vertical magnification (exposure amount) of each intensity distribution is the contact hole diameter (Et) at the best focus.
h (width of the slice portion crossing h) was set to 0.3 μm. For comparison, FIGS. 20 (A), (B), (C)
Intensity distribution I ₈ in the intensity distribution I _7, 1 [mu] m defocus position of the best focus position by conventional exposure device (minus the reducing member CCM) respectively, 2
₉ shows an intensity distribution I ₉ at a defocus position of μm. The simulation condition at this time is also NAw = 0.5.
7, wavelength λ = 0.365 μm, σ = 0.6.

FIGS. 20 (A) to 20 (C) and 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) at the time of defocusing decreases, and the depth of focus increases.
On the other hand, FIG. 21 shows changes in image intensity distributions I ₁₀ , I ₁₁ and I ₁₂ when the FLEX method is combined with a normal projection exposure apparatus. The exposure condition of the FLEX method was 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 FIG. 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 degree as in the FLEX method. FIG. 22 shows a simulation result in the case where the configuration of FIG. 6 is provided with a light shielding portion FD based on the same concept as the coherence reducing member CCM shown in FIG. 10 in the embodiment of the present invention. At this time, as shown in FIG.
Radius r ₄ of the circular light shielding portion FD of central 0.31r ₂ (i.e. sinθ ₄ = 0.31NAw) is the determined relationship, the outside inner diameter r _4, the outer diameter r ₁ annular transmitting portion FA
Has an outer diameter r ₁ of 0.74r ₂ (that is, sin θ ₁ = 0.
74NAw). That ^{_{(r 1 2 -r 4 2)}} = is set to satisfy the ^{_{(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 as they are. The reduction member CCM as shown in FIG.
However, as shown in FIGS. 22C, 22D and 22E, the intensity distribution I ₄ at the best focus position, the intensity distribution I _{5 at} the 1 μm defocus position, and the intensity distribution I _{5 at} the 2 μm defocus position. _{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 simulation result by the FLEX method. 23 (A), (B) and (C) show filters having a numerical aperture NAw of 0.57 and a complex amplitude transmittance of -0.3 within a radius of 0.548 NAw from the pupil center point. 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 are obtained. In the Super FLEX method, the central intensity at the best focus position is high and the profile is sharp as shown in FIG. 23, but the central intensity decreases sharply due to the defocus amount from a certain amount. However, the effect of increasing the depth of focus is almost the same as the effect of the present invention shown in FIGS. However, Super F
In the LEX method, the image shown in FIG.
A sub-peak (ringing) as shown in FIG. Although this is not a problem in the isolated contact hole pattern PA serving as a simulation model in FIG. 23, it is a serious problem when applied to a plurality of close contact hole patterns described later.

FIGS. 24 (A), 24 (B) and 24 (C) show a filter which has a weaker effect than the pupil filter of the Super FLEX method used as a simulation model in FIG. 23 to prevent such ringing. 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 0.447NA.
A filter having a complex amplitude transmittance of −0.3 in a portion corresponding to w is used. Figure 24 (A) ~ (C) the intensity distribution at the best focus position, respectively I _16, the intensity distribution I ₁₇ at the defocus position of 1 [mu] m, show an intensity distribution I ₁₈ at the defocus position of 2 [mu] m, indeed FIG Although ringing is weaker than in the case of 23, the effect of increasing the depth of focus is also reduced.

FIGS. 25A to 25D show two contact hole patterns PA ₁ and PA ₂ adjacent to each other, for example, as shown in FIG.
The results of simulating the image intensity distribution obtained by various exposure methods when the lines are separated by a center-to-center distance of 0.66 μm (converted on the wafer) as shown in FIG. FIG.
(A) shows S under the same simulation conditions as in FIG.
FIG. 25B shows an image intensity distribution obtained by the conventional FLEX method, and FIG. 25C shows a Super under the same conditions as FIG. 23. FIG. 25D shows the image intensity distribution obtained by the FLEX method (1), and FIG. 25D 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 simulation results, the images obtained in FIGS. 25A, 25C, and 25D
Since the intensity between the two hole images is lower than the film bulging intensity Ec, the resist (positive type) between the two holes completely remains,
The resist images of both holes are separated and well formed. However, in the FLEX method shown in FIG. 25B, the intensity between the two hole images is not sufficiently low, and the resist between the two holes is filmed, and a good pattern cannot be formed. That is, the images of the two contact holes may be connected due to a slight difference in the exposure amount. As described above, although the SFINCS method of the present invention and the conventional FLEX method can obtain the same depth of focus when projecting an isolated contact hole pattern, the resolution (fidelity) of the close hole pattern can be improved. In terms of the SFINC of the present invention
It can be seen that the S method is superior to the FLEX method.

In the simulations shown in FIGS. 25C and 25D, two hole patterns PA ₁ and PA ₂ are set under the condition that the peak of ringing due to one hole pattern overlaps with the center intensity portion of the other hole pattern. , The effect of ringing does not appear between the two hole pattern images. This means that if 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 influence of ringing appears.

FIG. 26 is a simulation result of the intensity distribution at the best focus position of two contact hole images arranged at a center-to-center distance of 0.96 μm (converted on the wafer). The image intensity distribution I ₂₃ according to the SFINCS method (the present invention) under the conditions shown in FIG. 22 is 2 as shown in FIG.
The space between the two hole images is sufficiently dark, and a good resist pattern can be formed. However, S under the conditions shown in FIG.
In uper FLEX method (1), as the intensity distribution I ₂₄ in FIG. 26 (B), ringing due each of two hole pattern will be synthesized (added), two intermediate bright sub peak (film hole images (Veri strength Ec or more) is generated, and the resist in this portion is film-verified. Therefore, a good resist image cannot be obtained. On the other hand, when two hole patterns having 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. 26C. . As described above, the comparatively weak Supe
In the case of the r FLEX method (2), a good resist image can be obtained since there is little ringing and no film burrs. 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 the effective radius r ₂ of the pupil is 0.7 mm 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, approximately half the effective area of the pupil is arranged at the center of the pupil. It is shown. In this case as well, ringing occurs around the original image, and it is difficult to apply the contact hole pattern close to the 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 close 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 are generated, and the region R in which they overlap
At o, the respective peak intensities of the four ringings overlap. In such a case, when only two hole patterns (two ringings overlap), Super FLE, which is relatively ineffective and has no film burrs, is generated.
Even with the X method (2), the size of the sub-peak
This is about twice as large as the state shown in FIG.
c or more, good pattern transfer cannot be performed. That is, an image (ghost image) of a hole that does not originally 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 between the two hole patterns is not more than の of the film vertex intensity Ec. In the region Ro shown, even if the added intensity is further doubled from the state shown in FIG. Although the 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 or not the polarization direction is appropriate, or the coherence reducing member is determined. C
In order to determine the quality of the polarization state of the imaging light beam after passing through the CM, means for photoelectrically detecting a part of the light beam that has passed through the projection optical system may be provided on the wafer stage WST. When a reticle having a line and space is used, the coherence reducing member CCM may be moved out of the projection optical system PL, and a part of the illumination system may be exchangeable so as to be suitable for the SHRINC method. In addition, while using the coherence reduction member CCM at the time of 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 in combination. In this case, when the reticle to be exposed is changed from the contact hole to the line and space, only the interference reducing member CCM needs to be withdrawn.

Further, the coherence reducing member CCM shown in each embodiment of the present invention is constituted by a circular or annular transmission portion or light shielding portion, but this is not limited to the literal shape. For example, the circular transmission portion or light shielding portion may be deformed into a polygon including a rectangle, and the annular transmission portion or light shielding portion may be deformed into a shape surrounding the polygon in a ring shape.

[0091]

As described above, according to the present invention, the depth of focus at the time of projection exposure of an isolated pattern such as a contact hole is set to F.
It can be enlarged to the same extent as the LEX method or the Super FLEX method, and without moving or vibrating the photosensitive substrate in the optical axis direction unlike the FLEX method,
Another advantage is that it is not necessary to create a spatial filter having a complex function of complex amplitude transmittance unlike 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 kept sufficiently small, so that a plurality of contact hole patterns are arranged relatively close. Even if it is done, Super
As in the case of the FLEX method, there is obtained a great effect that there is no adverse effect (such as generation of a ghost image) caused by superimposition of the ringing subpeak portion.

[Brief description of the drawings]

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

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

FIG. 3 is a view for explaining the principle of increasing the depth of focus by the exposure method of the present invention.

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

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

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

FIG. 7 shows 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 modified examples of the coherence reducing member CCM according to the first and second embodiments of the present invention.

FIG. 9 shows 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 a configuration of a coherence reducing member CCM according to a fourth embodiment of the present invention.

FIG. 11 is a diagram illustrating an image forming operation by the coherence reducing member CCM illustrated in FIG. 9;

FIG. 12 is a view for explaining an image forming operation by the coherence reducing member CCM shown in FIG. 10;

FIG. 13 is a diagram illustrating a configuration of an interference reducing member CCM according to a fifth embodiment of the present invention and its imaging operation.

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

FIG. 15 is a diagram showing a 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 embodiment of the present invention, and showing a configuration of a projection optical system when an alignment system is used.

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

FIG. 18 is a view showing a state in which the coherence reducing member CCM according to each embodiment of the present invention is applied to the aligner of FIG. 17;

FIG. 19: SF of the present invention for a single hole pattern
9 is a graph simulating the effect of the INCS method as an image intensity distribution.

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

FIG. 21 shows a conventional FLE for a single hole pattern.
9 is a graph simulating the effect of the X method as an image intensity distribution.

FIG. 22 shows SF of the present invention for a single hole pattern.
9 is a graph simulating the effect of the INCS method as an image intensity distribution.

FIG. 23 shows a conventional Sup for a single hole pattern.
5 is a graph simulating the effect of the FLEX method (1) as an image intensity distribution.

FIG. 24 shows a conventional Sup for a single hole pattern.
3 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 close hole patterns in FIG.
5 is a graph simulating, as an image intensity distribution, the effects of various exposure methods when changed from the case of FIG.

FIG. 27 shows a case where only a circular light-shielding portion is provided at the center of the pupil.
9 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 contact hole patterns distributed two-dimensionally and ringing occurrence positions.

[Explanation of symbols]

R · · · reticle W · · · wafer PL · · · projection optical system AX · · · optical axis PA, PA _1, PA ₂ ··· hole pattern CCM · · · coherence reducing member FA · · · circular transparent Part FB: annular transmission part ILB: illumination light

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (18)

(57) [Claims] 1. A projection exposure apparatus that illuminates a mask on which a pattern is formed with illumination light and guides light from the pattern onto a substrate, wherein the light from the pattern is provided between the mask and the substrate. A projection exposure apparatus comprising: a conversion unit that converts a plurality of lights having a light path difference equal to or longer than a coherence distance determined from a wavelength range of the illumination light. 2. The apparatus according to claim 1, wherein said converting means has a first region and a second region through which light from said pattern passes, and converts light passing through said first region and light passing through said second region. 2. The projection exposure apparatus according to claim 1, wherein the light is converted into light having an optical path difference equal to or longer than a coherent distance determined by a wavelength range of the illumination light. 3. A projection optical system for forming an image of light from the pattern on the substrate, wherein the conversion means includes an optical Fourier transform surface on the mask pattern surface in the projection optical system or in the vicinity thereof. The projection exposure apparatus according to claim 1, wherein the projection exposure apparatus is arranged. 4. The method according to claim 1, wherein the conversion unit includes a first area and a second area.
The projection exposure apparatus according to claim 2, further comprising an optical element having a different refractive index from the region. 5. The method according to claim 1, wherein the conversion unit includes a first area and a second area.
4. The projection exposure apparatus according to claim 2, further comprising an optical element having a thickness in a direction of an optical axis of the projection optical system different from the region. 6. The apparatus according to claim 2, wherein the first area is an area centered on an optical axis of the projection optical system, and the second area is an area outside the first area. 6. The projection exposure apparatus according to any one of claims 1 to 5, 7. The apparatus according to claim 6, wherein the first area is a circular area centered on the optical axis of the projection optical system, and the second area is an area outside the circular area. 3. The projection exposure apparatus according to claim 1. 8. The projection exposure apparatus according to claim 7, wherein the area of the circular region is substantially half the effective opening area of the Fourier transform surface in the projection optical system. 9. The apparatus according to claim 1, wherein the first area is an annular area centered on an optical axis of the projection optical system, and the second area is inside or outside the annular area. Item 6. The projection exposure apparatus according to any one of Items 2 to 5. 10. The first area is a circular area centered on the optical axis of the projection optical system, and the second area is an annular area surrounding at least double the outside of the circular area, 3. The apparatus according to claim 2, wherein each of the annular zones has an optical element having a different refractive index or a different thickness in the optical axis direction of the projection optical system.
6. The projection exposure apparatus according to any one of claims 1 to 5, 11. A circular or annular light-shielding member centered on the optical axis of the projection optical system is provided at or near the Fourier transform plane. Projection exposure equipment. 12. A projection exposure apparatus according to claim 11, further comprising a drive mechanism for enabling at least one of said conversion means or said light shielding member to be inserted and removed between said mask and said substrate. . 13. A projection according to claim 1, further comprising a moving mechanism for relatively moving said substrate and said projection optical system in an optical axis direction of said projection optical system. Exposure equipment. 14. A projection exposure method for illuminating a mask on which a pattern is formed with illumination light and guiding light from the pattern onto a substrate, wherein the light from the pattern is interposed between the mask and the substrate. A projection exposure method, comprising: converting a plurality of lights having an optical path difference equal to or longer than a coherence distance determined from a wavelength range of illumination light; and guiding the converted plurality of lights onto the substrate. 15. An image forming apparatus according to claim 14, wherein when the plurality of lights are imaged on the substrate, the substrate and the projection optical system are relatively moved in an optical axis direction of the projection optical system.
3. The projection exposure method according to 1. 16. A method for manufacturing a semiconductor integrated circuit using the device according to claim 1. 17. A method for manufacturing a semiconductor integrated circuit by the method according to claim 14. 18. A projection exposure apparatus which illuminates a mask on which a pattern is formed with illumination light and guides light from the pattern onto a substrate, wherein the light from the pattern is provided between the mask and the substrate. Characterized by having conversion means for converting light into a plurality of lights having different wavelengths from each other.