JPH09260260A - Projection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To faithfully transfer a plurality of isolating patterns which are very adjacently arranged with each other on a wafer, with large focal depth via a projection optical system. SOLUTION: An illumination light from an ArF excimer laser light source 1 is made to enter a fly's eye lens 3. The illumination light IL passing an illumination aperture iris 4 of an output surface of the fly's eyes lens 3 illuminates a reticle R via a convergence lens system 6, a reticle blind 7, a condenser lens system 8, etc. In the illumination light, the image of a pattern of the reticle R is imaged and projected on the wafer W via a projection optical system PL. A shield type pupil filter PF whose radius is almost 35-45% of a radius corresponding to the numerical aperture of the projection optical system PL is arranged on a pupil surface FTP of the projection optical system PL. Exposure is performed by making an aperture of the illumination aperture iris 4 as a ring belt wherein a coherence factor of the outer periphery is 0.35-0.45 and a coherence factor of an inner periphery is 0.20-0.30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photolithography process for manufacturing, for example, a semiconductor element, an image pickup element (CCD or the like), a liquid crystal display element, a thin film magnetic head or the like, and a mask pattern is passed through a projection optical system. The present invention relates to a projection exposure apparatus for transferring onto a photosensitive substrate.

[0002]

2. Description of the Related Art For example, when manufacturing a semiconductor device, a reticle pattern as a mask is coated with a photoresist as a photosensitive substrate through a projection optical system under exposure illumination light (exposure light). In addition, a projection exposure apparatus that transfers to each shot area on the wafer is used. As such a projection exposure apparatus, i-line (wavelength 365 nm) of a mercury lamp is used.
A so-called i-line stepper is mainly used for sequentially projecting and exposing an image of a reticle pattern through a projection optical system on each shot area on a wafer under the illumination light. Further, a so-called excimer stepper, which uses an excimer laser light such as a KrF excimer laser light (wavelength 248 nm) or an ArF excimer laser light (wavelength 193 nm) as exposure illumination light, is also used for evaluation or research.

Recently, it has been required to transfer a pattern of a reticle having a larger area onto a wafer with high throughput (productivity) without increasing the burden on the projection optical system. Therefore, after stepping the shot area of the wafer to be exposed to the scanning start position, the reticle and the wafer are synchronously scanned with respect to the projection optical system.
A projection exposure apparatus of a scanning exposure type, such as a so-called step-and-scan method, which sequentially exposes a pattern image of a reticle to the shot area has also been proposed.

The projection optical system used in these projection type exposure apparatuses is incorporated into the apparatus through advanced optical design, careful selection of glass materials, ultra-precision processing of glass materials, and precise assembly and adjustment. Generally, in order to faithfully transfer a fine pattern of a reticle onto a wafer by exposure using a projection optical system, the resolution and depth of focus (DOF) of the projection optical system are important factors. The resolution of the projection optical system is proportional to λ / NA, where λ is the wavelength of the illumination light for exposure and NA is the numerical aperture. On the other hand, since the depth of focus is proportional to λ / NA ^2, there is a problem that if the numerical aperture NA is increased to improve the resolution, the required depth of focus cannot be obtained.

In this case, the depth of focus obtained by the projection optical system also differs depending on the type of pattern to be transferred,
In particular, a fine aperture pattern (bright pattern) called a contact hole is a pattern in which it is difficult to obtain a large depth of focus. Therefore, in particular, as an exposure method for increasing the apparent depth of focus for a contact hole, the exposure for one shot area on the wafer is divided into a plurality of times, and the wafer is moved by a certain amount in the optical axis direction between each exposure. A method of doing so has been proposed in, for example, Japanese Patent Laid-Open No. 63-42122. This exposure method is based on FLEX (Focus Latitude enhancem
ent EXposure) method, which can obtain a sufficient depth of focus expansion effect for isolated patterns such as contact holes. However, since the FLEX method requires multiple exposure of a slightly defocused contact hole image, the sharpness of the resist image obtained after development is inevitably reduced.

Further, as an attempt to expand the depth of focus when projecting a contact hole without moving the wafer in the optical axis direction during the exposure operation as in the FLEX method, 1991.
The Super-FLEX method presented in the 29th Spring Society of Applied Physics, 29a-ZC-8, 9 is also known. In this Super-FLEX method, a transparent phase plate is arranged in the pupil of the projection optical system, and the complex amplitude transmittance given to the imaging light by this phase plate has a characteristic that it sequentially changes from the optical axis toward the periphery. It is what I had. This way,
The image formed by the projection optical system has a constant sharpness in the optical axis direction with a wider width than before, centered on the best focus surface (the surface that is conjugate with the reticle pattern surface), and the depth of focus increases. Of.

However, according to the Super-FLEX method,
Subpeaks (ringing) having a relatively high intensity occur near the image of the contact hole to be transferred, and this causes a ghost pattern, which is problematic for practical use. In addition, as a pupil filter, a phase change is not added, but coherence (coherence) of an image forming light beam is reduced (see JP-A-6-120110 and JP-A-6-124870), or Among the image-forming light fluxes, the light fluxes distributed in the vicinity of the optical axis in the pupil plane are blocked by a so-called light-shielding type pupil filter (Japanese Patent Application Laid-Open No. 4-179598).
The present applicant has also proposed methods for increasing the depth of focus of the image of the contact hole, respectively. With these pupil filters, the ringing that occurs is relatively weak, and the sharpness reduction that is a problem when used in combination with the FLEX method is small. Especially,
The light-shielding pupil filter is expected to be most practically used because it does not generate new aberrations in the conventional projection optical system and has a simple structure.

[0008]

Recently, with the further miniaturization of circuit patterns of VLSI and the like, it has been required to further miniaturize not only the pattern size but also the interval between adjacent patterns. Has been. In an extreme case, for example, two contact holes each having a width close to the resolution limit may be arranged such that the center distance is twice the resolution limit, that is, the length from edge to edge is the resolution limit. ,
It will be necessary to arrange them in close proximity.

When the distance between the two contact holes comes close to each other in this way, for example, the above-mentioned Japanese Patent Laid-Open No. 7-29807.
Even if exposure is performed under the optical condition (a numerical aperture NA, a so-called σ value which is a coherence factor, etc.) that also uses the FLEX method together with a light-shielding pupil filter as disclosed in Japanese Patent Publication No. So-called film loss occurs in the resist between the projected images of the holes. Furthermore, the size of the transferred image is large due to both contact holes being formed in a continuous manner, and among the various contact hole patterns existing in the same reticle pattern, those that exist independently and those that are close to each other. Inconvenience such as being different occurs.

In view of the above problems, it is an object of the present invention to provide a projection exposure apparatus capable of increasing the depth of focus when transferring an isolated pattern such as a contact hole through a projection optical system. Further, the present invention also provides a projection exposure apparatus that can faithfully transfer a plurality of isolated patterns arranged very close to each other onto a wafer through a projection optical system and also obtain an effect of expanding the depth of focus. To aim.

[0011]

The projection exposure apparatus according to the present invention is, for example, as shown in FIGS. 1 and 2, an illumination optical system for illuminating a mask (R) on which a transfer pattern is formed with exposure illumination light. A system (1 to 3, 5 to 8) and a projection optical system (PL) for projecting an image of the pattern of the mask (R) on the photosensitive substrate (W) under the illumination light by the illumination optical system. In the projection exposure apparatus including the projection optical system (PL), the projection optical system (PL) is formed on the optical Fourier transform plane (pupil plane FTP) with respect to the pattern surface of the mask (R) in the projection optical system (PL) or on a surface in the vicinity thereof. A substantially circular light-shielding member (PF) having a radius centered on the optical axis of, within the range of 25% to 45% of the radius corresponding to the numerical aperture of the projection optical system (PL),
The illumination optical system has a coherence factor of 0.
In the range of 35 to 0.45, the inner peripheral coherence factor is in the range of 0.20 to 0.30.

According to the present invention, the light shielding member (PF) provided on the surface (FTP) in the projection optical system (PL) having an optical Fourier transform relationship with the pattern surface of the mask (R). However, it acts in the same manner as a conventional light-shielding pupil filter to improve the sharpness and depth of focus of an image of an isolated pattern such as a contact hole. Further, assuming that two adjacent contact holes are transferred as a plurality of isolated patterns arranged very close to each other, in the present invention, the illumination for the mask pattern is an annular illumination, and the annular illumination is the annular illumination. (R) by optimizing the coherence factor by optimizing the outer diameter and the inner diameter of the aperture stop (4) for
The coherence (the degree of complex coherence) between the illumination lights that have passed through the two contact hole patterns arranged close to each other is optimized. Therefore, while satisfactorily separating (resolving) the images of both contact holes, the intensity of the optical image of both contact holes can be made substantially equal to the image intensity when the contact holes exist alone.
That is, the size of the transferred image of both contact holes (image size on the photosensitive material) can be made substantially equal to the size of the transferred image of the contact holes that exist independently.

In this case, the radius of the light shielding member (PF) is 35, which corresponds to the numerical aperture of the projection optical system (PL).
% To 45% is desirable. Thereby, the radius of the light blocking member (PF) is further optimized.
Relative displacement means (10, 11, 12A to 12C) for relatively displacing the image surface of the projection optical system (PL) and the exposure surface of the photosensitive substrate (W) in the optical axis direction of the projection optical system (PL). Is provided, and the image plane of the projection optical system (PL) and the exposed surface of the photosensitive substrate (W) are relatively moved or vibrated via the relative displacement means during the exposure of the photosensitive substrate (W). May be. This means that exposure is performed by further using the FLEX method in combination with the above-described present invention, and the depth of focus becomes deeper by using the FLEX method in combination.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a projection exposure apparatus according to the present invention will be described below with reference to the drawings. In this example, the present invention is applied to a stepper type projection exposure apparatus. FIG. 1 shows the entire configuration of the projection exposure apparatus of this example. In FIG. 1, an ArF excimer laser light source (oscillation wavelength 193 nm) 1 is used as an exposure light source. However, a KrF excimer laser light source, a metal vapor laser light source, a harmonic generator of a YAG laser, or the like may be used as the exposure light source. Furthermore, when a bright line lamp such as a mercury lamp is used as the exposure light source. The present invention also applies.

The illumination light composed of the laser beam emitted from the ArF excimer laser light source 1 is used as the beam shaping optical system 2.
After the cross-sectional shape is shaped by, the light enters the fly-eye lens 3 as an optical integrator. Illumination light that is incident on the fly-eye lens 3 and is composed of substantially parallel light beams is divided by a plurality of lens elements of the fly-eye lens 3, and a secondary light source image (a converging point of a laser beam is formed on each exit side of each lens element). ) Is formed. An illumination aperture stop (σ stop) 4 for adjusting the size and shape of the entire surface light source image in the illumination optical system is provided on the exit side of the fly-eye lens 3. In this example, the illumination aperture stop 4 is a ring-shaped stop (details will be described later).
The illumination light IL (divergent light) that has passed through the σ stop 4 is reflected by the mirror 5, reaches the reticle blind (illumination field stop) 7 via the condenser lens system 6, and reaches the reticle blind 7.
The illumination light IL that has passed through the aperture of the condenser lens system 8
Through the illumination area 9 on the pattern surface (lower surface) of the reticle R.
Illuminate with a uniform illuminance distribution.

At this time, the pattern surface of the reticle R and the exit side surface of the fly-eye lens 3 are optically Fourier-transformed by a synthetic system including the condenser lens system 6 and the condenser lens system 8. There is. Then, according to the position of each secondary light source image on the exit side surface of the fly-eye lens 3, the incident angle and the direction of the light flux emitted from the secondary light source image on the reticle R are determined.

In order to make the illuminance distribution of the illumination light IL on the reticle R more uniform, the fly-eye lens 3 may be provided in two stages along the traveling direction of the illumination light. In that case, the illumination aperture stop 4 is provided on the exit side surface of the fly-eye lens closer to the reticle R than the second stage. Under the illumination light IL, the reticle R
Optical image of pattern in upper illumination area 9 (light intensity distribution)
Is imaged on the photoresist layer on the surface of the wafer W via the projection optical system PL. The projection optical system PL is telecentric on both sides (or one side on the wafer W side), and has a reticle R.
The projection magnification M from the wafer W to the wafer W is, for example, 1/5, or 1 /
It is 4 mag. Further, the optical Fourier transform surface (hereinafter referred to as “pupil surface”) FTP for the pattern surface of the reticle R in the projection optical system PL has a radius r _PF within a radius r _PF with the optical axis AX of the projection optical system PL as the center. A light blocking pupil filter PF that blocks the light flux is provided. Therefore, of the diffracted light generated from the pattern on the reticle R, the light flux of the component with a small diffraction angle is blocked by the light blocking pupil filter PF, and only the light flux of the component with a large diffraction angle reaches the wafer W.

Incidentally, depending on the configuration of the projection optical system PL,
A circular aperture diaphragm (NA variable diaphragm) for changing the effective pupil diameter may be provided on the pupil plane FTP. In this case, it is desirable that the circular aperture stop and the light-shielding type pupil filter PF are arranged so as not to mechanically interfere with each other and as close as possible in the optical axis AX direction. In the following, the Z-axis is taken in parallel with the optical axis AX of the projection optical system PL, the X-axis is taken in a plane perpendicular to the Z-axis, parallel to the plane of FIG. 1, and the Y-axis is taken perpendicular to the plane of FIG. explain.

At this time, the reticle R is held by the reticle stage RST, and the reticle stage RST positions the reticle R in the X direction, the Y direction, and the rotation direction. On the other hand, the wafer W is held on the sample table 10, and the sample table 10 is provided with three fulcrums 12 which are respectively expandable and contractible in the Z direction.
It is mounted on the Z leveling stage 11 through A to 12C, and the Z leveling stage 11 is mounted on the XY stage 13. And the Z leveling stage 11
By driving the three fulcrums 12A to 12C in parallel via a driving unit inside, the Z of the sample stage 10 (wafer W) is
Directional position (focus position) can be adjusted and 3 fulcrums 12A
It is possible to adjust the tilt angle of the sample table 10 by independently driving .about.12C. Further, the Z leveling stage 11 (wafer W) is configured to be movable in the X direction and the Y direction on the XY stage 13 by the stage drive unit 16.

Then, the movable mirror 14m fixed to the upper end of the sample table 10 and the laser interferometer 14 fixed to the outside measure the coordinates of the sample table 10 in the X and Y directions. Main control system 15 that controls the entire device
The main control system 15 positions the sample stage 10 (wafer W) via the stage drive unit 16 based on the supplied measurement result.

Further, the side surface of the projection optical system PL is obliquely projected onto the surface of the wafer W in the exposure field of the projection optical system PL by using, for example, a slit image by using illumination light having low photosensitivity to the photoresist. An optical system 18 and a condensing optical system 19 that condenses the reflected light from the wafer W to re-image the slit image and generates a focus signal corresponding to the lateral deviation amount of the slit image. An incident type autofocus sensor is arranged. The focus signal is also supplied to the main control system 15. Wafer W
When the focal position of the surface of the optical system changes, the position of the slit image re-imaged in the condensing optical system 19 shifts laterally, the focus signal changes, and at the same time, the imaging plane of the projection optical system PL (best The calibration is performed so that the focus signal becomes 0 level when the surface of the wafer W matches the (focus surface). for that reason,
The main control system 15 can obtain the defocus amount from the image plane of the surface of the wafer W from the focus signal.

The main control system 15 controls the amount of expansion and contraction of the fulcrums 12A to 12C via the drive unit in the Z leveling stage 11 based on the focus signal.
Normally, autofocus control is performed so that the surface of the wafer W matches the image plane of the projection optical system PL. However, in this example, the FLEX method is used together during the exposure of the wafer W, if necessary. When the FLEX method is also used in this way,
While exposing the pattern image of the reticle R on the wafer W, the main control system 15 controls the expansion and contraction amounts of the three fulcrums 12A to 12C based on the focus signal thereof, as shown by the arrow 21. The surface of the wafer W to Z
The wafer W is oscillated with a predetermined amplitude in the direction, or the surface of the wafer W is moved in the Z direction by a predetermined width.

Thus, during the exposure of the wafer W, the FLEX
When the method is used together, the amount of discrete or continuous movement of the wafer W in the Z direction is optimally set to the amount disclosed in JP-A-7-29807. Further, the main control system 15 can perform on / off control of oscillation of the ArF excimer laser light source 1 via the laser power supply 17.

Although the projection exposure apparatus of FIG. 1 is a stepper type, the reticle stage RST is provided with a function of scanning the reticle R in a predetermined direction, and each shot area on the wafer W is exposed. On the occasion, the reticle stage RS
It may be a step-and-scan projection exposure apparatus that drives the T and XY stages 13 to scan the reticle R and the wafer W relative to the projection optical system PL. To apply the FLEX method at this time, for example, scanning may be performed in a state in which the wafer W is tilted with respect to the image forming surface of the pattern of the reticle R.

In FIG. 1, a predetermined reticle pattern is formed on the pattern surface of the reticle R by a light-shielding film such as a chrome layer. Here, the light-shielding film is vapor-deposited on the entire surface, and a minute reticle is formed therein. It is assumed that there are a plurality of contact hole patterns each having a rectangular opening (a transparent portion having no light shielding film). The size of the contact hole pattern on the reticle R is 0.15 μm for the transferred image on the wafer W.
The projection magnification M of the projection optical system PL is determined in consideration of the angle (or the diameter of 0.15 μm).

Since the interval between the plurality of contact hole patterns is usually considerably larger than the width of the opening of one contact hole pattern, these contact hole patterns may exist as individual minute patterns. Many. In order to transfer such a contact hole pattern with a high resolution and a large depth of focus, it is desirable to use a projection exposure apparatus under the optical conditions as disclosed in the above-mentioned JP-A-7-29807. That is, a light blocking pupil filter PF having a radius of about 0.4 times the substantial pupil radius of the projection optical system PL (proportional to the numerical aperture of the projection optical system PL) is provided, and the FLEX method is used in combination. It is preferable to use an exposure apparatus capable of

However, as described above, it is necessary to form the contact hole patterns such that the distance from the edge of one contact hole pattern to the edge of the adjacent contact hole pattern is as close as the width of each contact hole pattern. There may be FIG.
3 shows a state in which two contact hole patterns arranged in close proximity on the reticle R of FIG. 1 are projected on the wafer W, and in FIG. 3, the width d in the X direction and the width in the Y direction are respectively shown in FIG. Two square contact hole images 20A and 20B of d are projected at an interval d in the X direction. Further, in this example, the width (interval) d is set to 0.15 μm, which is close to the resolution limit of the projection optical system PL.

When the distances between the contact holes are close to each other as described above, in the apparatus having the structure disclosed in Japanese Patent Laid-Open No. 7-29807, as described above, the contact hole images 20A and 20B are located in the middle. There is a risk that the "half-shadow blur" will be synthesized, the photoresist will be thinned (photosensitized), and in extreme cases, both contact holes will be connected and formed. In addition, even if such a bad influence does not occur, the size of two adjacent contact hole images is independent by adding the penumbra of other contact hole images to the contact hole image. There is also a problem that it becomes larger than the size of.

Therefore, in the present embodiment, as shown in FIG. 1, the illumination optical system from ArF excimer laser light source 1 to condenser lens system 8 is changed to an annular zone by forming the illumination aperture stop 4 into an annular zone. The numerical aperture and the like are optimized by using the illumination system and optimizing the aperture shape of the illumination aperture stop 4. 2 shows the shape of the aperture 4a of the illumination aperture stop 4 in FIG. 1. In this FIG. 2, the illumination aperture stop 4 is arranged on the Fourier transform plane with respect to the pattern plane of the reticle R of FIG. 1 as described above. ing. Further, since the pupil plane FTP of the projection optical system PL is also a Fourier transform plane with respect to the pattern plane of the reticle R, the illumination aperture stop 4 and the pupil plane FTP have an image forming relationship (conjugate). In FIG. 2, a broken line circle 22 indicates a virtual illumination aperture stop 4
The effective area of the pupil plane FTP of the projection optical system PL projected above is shown. That is, the radius r ₀ of the dashed circle 22 corresponds to the numerical aperture NA of the projection optical system PL. The numerical aperture NA of the projection optical system PL of this example is about 0.6.

In the projection exposure apparatus of this example, the aperture 4a of the illumination aperture stop 4 is formed into a ring shape, and the aperture 4 is formed.
The outer radius r ₂ and the inner radius r ₁ of a are about 0.4 times and 0.25 times the radius r ₀ corresponding to the numerical aperture NA of the projection optical system PL, respectively. These outer radius r _2, and 0.4 indicating the ratio to the radius r ₀ of the inner radius r _1, and 0.
The value of 25 corresponds to a so-called σ value which is a coherence factor in an ordinary illumination optical system, that is, a value of a ratio of the numerical aperture of the illumination optical system to the numerical aperture of the projection optical system. When such an illumination condition is adopted, the coherence (complex coherence degree) of the illumination light between two adjacent contact hole patterns as described above is optimized, the resolution between adjacent contact hole patterns is improved, and Multiple contact hole patterns arranged in
It was found that it is possible to make the sizes of the transfer images of both one contact hole pattern existing independently and the same.

Even in this example provided with the illumination conditions as described above, the radius r _PF of the light-shielding pupil filter PF arranged on the pupil plane FTP of the projection optical system PL of FIG. 1 is equal to the effective radius of the pupil plane FTP. About 0.4 times r _NA (radius corresponding to numerical aperture NA of projection optical system PL) is preferable. Of course, the value is not limited to 0.4 times, but may be within a range satisfying the following expression, that is, within a range of 0.35 to 0.45 times the radius r _NA .

0.35r_NA≤r_PF≤0.45r_NA (1) Radius r of the light-shielding pupil filter PF_PFBut the radius r_NAOf 0.3
If it is less than 5 times, the effect as a pupil filter is difficult to obtain.
And the sharpness of the image deteriorates. On the other hand, the radius r _PFBut half
Diameter r_NAIf it becomes larger than 0.45 times of
As the intensity of ringing around the image is increased,
Both are not preferable. However, the sharpness of the contact hole image
For applications where is not a problem,
Radius r_NAAbout 0.25 times.

The outer radius r ₂ and the inner radius r ₁ of the aperture 4a of the illumination aperture stop 4 are not limited to the above values, and the outer radius r ₂ is the radius r as shown in the following equation. It may be 0.35 to 0.45 times ₀ , and the inner radius r
₁ may be about 0.2 to 0.3 times the radius r ₀ .

0.35r ₀ ≦ r ₂ ≦ 0.45r ₀ (2), 0.2r ₀ ≦ r ₁ ≦ 0.3r ₀ (3) In this case, the outer radius r ₂ is 0.45 times the radius r ₀ . When it is larger, the transferred image (resist pattern) of two contact hole patterns adjacent to each other becomes larger than the transferred image of one contact hole pattern existing independently. On the contrary, if the outer radius r ₂ is smaller than 0.35 times the radius r ₀ ,
The transferred images of the two contact hole patterns adjacent to each other are smaller, and the separated (resolution) transfer images of both contact holes are not sufficient.

Similarly, when the inner radius r ₁ is larger than 0.3 times the radius r ₀ , the transferred image of two contact hole patterns adjacent to each other becomes a transferred image of one contact hole pattern existing independently. Compared to the inner radius r
_{When 1} is smaller than 0.2 times the radius r ₀ , the transferred image of two contact hole patterns adjacent to each other becomes smaller,
Moreover, the separation (resolution) of the transferred images of both contact holes becomes insufficient.

Next, as shown in FIG.
An example of the computer simulation result of the light intensity distribution of the optical image of one contact hole pattern will be described. The optical conditions in this simulation are shown in Fig. 1.
Of the illumination light IL of 193 nm, the numerical aperture NA of the projection optical system PL of 0.60, the coherence factor σ value of the illumination optical system (corresponding to the outer radius r ₂ of the aperture 4a of the illumination aperture stop 4 of FIG. 2). Is 0.4, and the σ value corresponding to the inner radius r ₁ of the aperture 4a of the illumination aperture stop 4 is 0.2668 (=
0.4 / 0.667), the radius r of the light-shielding pupil filter PF
Magnification for radius r _NA corresponding to numerical aperture NA of _PF is 0.
And 4. Further, the FLEX method was applied, and double exposure was performed at two points by shifting the surface of the wafer W by ± 0.5 μm in the Z direction with respect to the best focus image of the pattern of the reticle R. The light intensity distribution of the resulting optical image was calculated.

FIG. 4A shows an optical image of one contact hole pattern that exists independently (for example, the optical image when the contact hole image 20A exists in one of FIG. 3) under the above-mentioned optical conditions. FIG. 4B shows the simulation result of the intensity distribution, and FIG. 4B shows the simulation result of the light intensity distribution of the optical images of the two contact hole patterns arranged in close proximity shown in FIG. 4A and 4B, the horizontal axis represents the position in the X direction in the cross section passing through the center of the contact hole image, and the vertical axis represents the light intensity distribution I at the position X.
(X) is shown. In addition, the magnification on the vertical axis in FIGS. 4A and 4B is obtained by comparing the light intensity distribution I (X) with a predetermined threshold Eth.
When sliced by, the slice width d1 of the light intensity distribution of FIG. 4A corresponding to the pattern existing independently is set to be the design value of 0.150 μm. FIG. 4 corresponding to the two adjacent patterns at this time.
The slice width d2 of the light intensity distribution in (b) is 0.152 μm.
m. This is because when two contact hole patterns arranged close to each other are projected under the above-mentioned optical conditions, that is, the optical conditions described in the above-described embodiments, the line widths of the respective contact hole images exist almost independently. This shows that the line width of the image obtained by projecting the contact hole pattern is about the same, and that good imaging characteristics can be obtained.

In the above-described embodiment, the projection optical system PL is a refractive optical system in which all optical members are transmissive members (lenses), but all optical members are reflective members (mirrors). It may be a catadioptric system, or may be a catadioptric system that is a combination of them. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention.

[0039]

According to the projection exposure apparatus of the present invention, a light blocking member having a predetermined size is arranged near the optical Fourier transform plane (pupil plane) in the projection optical system with respect to the pattern surface of the mask, and a predetermined light blocking member is provided. Since the illumination is performed by the annular illumination system having the coherence factor, there is an advantage that the depth of focus can be increased when an isolated pattern such as a contact hole is transferred through the projection optical system. In particular, according to the present invention, a plurality of fine isolated patterns (contact holes or the like) having a size close to the resolution limit of the projection optical system are arranged closely on the mask at a minute interval close to the resolution limit. In this case, there is an advantage that the images of the plurality of isolated patterns can be faithfully transferred at a high resolution and with a large depth of focus onto the photosensitive substrate.

When the radius of the light shielding member is within the range of 35% to 45% of the radius corresponding to the numerical aperture of the projection optical system, the radius of the light shielding member is optimized,
The depth of focus is increased for isolated patterns. Further, relative displacement means for relatively displacing the image surface of the projection optical system and the exposure surface of the photosensitive substrate in the optical axis direction of the projection optical system is provided, and the relative displacement means is used during the exposure of the photosensitive substrate. By moving or vibrating the image plane of the projection optical system and the exposure surface of the photosensitive substrate relatively.
Since the method is used together, there is an advantage that the depth of focus becomes deeper.

[Brief description of drawings]

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

FIG. 2 is an enlarged view showing a shape of an aperture of an illumination aperture stop 4 in FIG.

FIG. 3 is an enlarged plan view showing a projected image of two contact hole patterns arranged close to each other.

FIG. 4A is a diagram showing a simulation result of a light intensity distribution of an optical image of one contact hole pattern which exists independently, and FIG. 4B is an optical image of two contact hole patterns arranged in close proximity. It is a figure which shows the simulation result of light intensity distribution.

[Explanation of symbols]

 1 ArF excimer laser light source 3 fly eye lens 4 illumination aperture stop 7 reticle blind 8 condenser lens system R reticle PL projection optical system PF light blocking pupil filter FTP Fourier transform surface (pupil surface) W wafer 10 sample stage 11 Z leveling stage 12A ~ 12C Support point 13 XY stage 14 Main control system 18 Irradiation optical system of autofocus sensor 19 Condensing optical system of autofocus sensor

Claims (3)

[Claims] 1. An illumination optical system for illuminating a mask having a transfer pattern formed thereon with exposure illumination light, and forming an image of the mask pattern on a photosensitive substrate under the illumination light from the illumination optical system. In a projection exposure apparatus provided with a projection optical system for projecting an image, an optical Fourier transform surface for the pattern surface of the mask in the projection optical system, or a surface in the vicinity thereof, an optical axis of the projection optical system. A substantially circular light-shielding member whose center has a radius within a range of 25% to 45% of a radius corresponding to the numerical aperture of the projection optical system is arranged, and the illumination optical system has a coherence factor of an outer periphery. 0.
A projection exposure apparatus characterized in that an annular illumination system having an inner coherence factor in the range of 35 to 0.45 and in the range of 0.20 to 0.30 is used. 2. The projection exposure apparatus according to claim 1, wherein a radius of the light shielding member is within a range of 35% to 45% of a radius corresponding to a numerical aperture of the projection optical system. Projection exposure system. 3. The projection exposure apparatus according to claim 1, wherein the image plane of the projection optical system and the exposure plane of the photosensitive substrate are relatively displaced in the optical axis direction of the projection optical system. Relative displacement means is provided, and during exposure of the photosensitive substrate, the image plane of the projection optical system and the exposed surface of the photosensitive substrate are relatively moved or vibrated via the relative displacement means. Projection exposure device.