JP3099933B2 - Exposure method and exposure apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for manufacturing a semiconductor integrated circuit, and more particularly to an exposure method and an exposure apparatus used for transferring an integrated circuit pattern.

[0002]

2. Description of the Related Art In recent years, the progress of photolithography has been remarkable, and the wavelength of exposure light has been shortened (i-line: 365 nm).
With the excimer laser (248 nm) and the high performance of the projection exposure apparatus, especially the high NA of the lens, it has become possible to form a finer resist pattern on a wafer.

FIG. 12 shows a schematic configuration of a conventional projection exposure apparatus generally used. From the light source side, the light source 10
1, first condensing optical system 102, uniformizing optical system 103, second
Condensing optical system 104, reticle 105, projection optical system 10
6, wafers 107 in this order. The first condensing optical system 102 is a portion corresponding to an elliptical reflecting mirror and an input lens. In addition to the elliptical mirror, a spherical mirror, a plane mirror, a lens, and the like are appropriately arranged, and a light beam emitted from the light source 101 is made uniform as efficiently as possible. Has the role of putting in system 103. Also,
The homogenizing optical system 103 is a portion corresponding to an optical integrator (a rope-eye lens), and an optical fiber, a polyhedral prism, or the like may be used as another component.

[0004] The second condensing optical system 104 is a portion corresponding to an output lens and a collimation lens.
The light emitted from the uniformizing optical system 103 is superimposed, and the image plane telecentricity is further ensured. In addition, a filter that transmits only the wavelength of which the aberration is corrected is inserted at a position where the light beam is close to the optical axis parallel, and a cold mirror is also inserted although the position is not unique.

In the apparatus having such a configuration, the reticle 1
When viewing the side from which the light comes from 05, the property of the light becomes the property of the light coming out of the homogenizing optical system 103 through the second condensing optical system 104, and the exit side of the homogenizing optical system 103 is the apparent light source. Looks like. Therefore, in the case of the above configuration,
Generally, the exit side 108 of the homogenizing optical system 103 is called a secondary light source. When the reticle 105 is projected on the wafer 107, the formation characteristics of the projection exposure pattern, that is, the resolution, the depth of focus, and the like, depend on the numerical aperture NA of the projection optical system 106 and the properties of the light irradiating the reticle 105, that is, the secondary light source 108. Determined by the nature of

However, since a fine pattern is formed on the resist, the wavelength of the exposure light is reduced, and the NA of the projection optical device is increased.
When the resolution is increased by the conversion, the practical resolution is not much improved because the depth of focus is reduced. Therefore, in the projection exposure apparatus, improvement in resolution and depth of focus has been considered by changing the secondary light source intensity distribution, the reticle, and the complex transmittance distribution on the pupil plane of the projection optical system from those in the related art.

In order to improve the resolving power, in particular, LS
For a pattern having a one-dimensional periodicity (hereinafter abbreviated as L / S) such as the wiring pattern in I, the phase difference between the exposure light passing through the opening adjacent to the opening of the mask and the exposure light passing through the opening is approximately 180. By using a mask formed so as to have a high resolution, the resolution can be improved about twice as much as that of a conventional mask in which an L / S pattern is formed on a transparent substrate using a light-shielding material such as chrome. Known (JP-A-57-620)
No. 52).

Further, as a device utilizing the difference in the coherence property depending on the polarization direction of light, an improved light source (JP-A-5-109601) and an improved pupil (JP-A-5-901)
No. 28, and an improved mask (JP-A-5-88356) are known. However, in the method in which only the light source is polarized, the resolving power improvement effect can be improved only for a one-dimensional periodic pattern having sides in the polarization direction of the light source, and for a pattern having sides in a direction perpendicular to the polarization direction. ,
On the contrary, it is known that the resolution is reduced. Furthermore, it can be said that the method of forming a polarizer on a mask is very difficult. Further, the method of forming the polarizer concentrically at the pupil position has a disadvantage that the loss of the light amount of the polarization component orthogonal to the polarization transmission direction of the polarizer increases.

On the other hand, in a miniaturized mask pattern, the resolution line width of the pattern approaches the wavelength of the exposure light. It becomes difficult to secure a sufficient difference in light amount between light and dark in the mask pattern projected image, and the contrast at the boundary between light and dark is also reduced. In order to solve this problem, there has been proposed a method of improving the limit resolution by changing the shape of a light source for illuminating a mask (Japanese Patent Laid-Open No. 4-10148).

FIG. 13A shows a conventional exposure apparatus and exposure method based on this proposal. In FIG. 13A, a typical example of a fine pattern is shown on a mask 121.
A one-dimensional lattice pattern 122 having a duty ratio of 0.5 is formed vertically and horizontally. The illumination optical system for illuminating the mask 121 includes a mercury lamp 111, an ellipsoidal mirror 112, a cold mirror 113, a condensing optical element 114, and an integrator. 11
5, relay lens 118 (pupil relay system), mirror 11
9, a condenser lens 120, which is a pupil plane of an illumination optical system (a Fourier transform plane, in this case, a mercury lamp 11
In the vicinity of the exit end surface of the integrator 115 where the first secondary light source image is formed, a light-shielding plate having four openings whose off-axis amounts are determined from the optical axis according to the fineness of the mask pattern 122 116 is arranged.

FIGS. 13B and 13C show the light shielding plate 1 respectively.
16 is a diagram of the mask 121 as viewed from above. The hatched portions indicate light-shielding portions. FIG. 13D shows the projection optical system 1.
23 shows an exposure light distribution on a pupil plane (corresponding to a substantially conjugate plane at the position of the light-shielding plate 116) in the reference numeral 23. In an actual exposure apparatus, the coordinates (X, Y), (x, y),
They are arranged so that the directions of (X ', Y') coincide. The optimum position of the center coordinates of the circular opening in FIG. 13B is determined by the fineness of the mask pattern. For example, if the pitch of the mask pattern is p, the lattice pattern 12
In No. 2, since both the vertical pattern and the horizontal pattern exist, the optimal center coordinates (X, Y) of the opening are (1 / 2p, 1/2).
p), (1 / 2p, -1 / 2p), (-1 / 2p, 1 /
2p) and (-1 / 2p, -1 / 2p). Further, the four peak position coordinates (X ′, Y ′) of the exposure light distribution in FIG.

As can be seen, when the pitch p of the mask pattern becomes smaller, the coordinates of the position of the opening of the light shielding plate 116 and the coordinates of the peak position of the exposure light at the pupil position of the projection optical system 123 become farther from the optical axis. I understand. Assuming that the numerical aperture of the projection optical system is NA and the exposure wavelength is λ, FIG.
The radius of the pupil from expressed by NA / λ, 1 / 2p = NA / (2 1/2 λ) p = 2 1/2 minute pattern represented by lambda / 2NA is said to be the limit that can be resolved. Actually, since the opening of the light-shielding plate 116 has a certain area, the marginal resolution is slightly different depending on the size of this area. If the pitch p of the mask pattern is smaller than the above expression, the diffracted light deviates from the pupil and the image cannot be formed.

[0013]

As described above, in a typical LSI pattern, since a one-dimensional lattice pattern is arranged vertically and horizontally, both the vertical pattern and the horizontal pattern are formed at a high resolution. In order to form an image, four openings of the light-shielding plate arranged at the secondary light source position had to be arranged at a position of 45 degrees with respect to the pattern. Therefore, the critical resolution in the vertical pattern and the horizontal pattern is 2 ^1/2
It was limited by λ / 2NA.

A pattern group having one-dimensional periodicity (L
/ S) is applied to a mask arranged so as to have its periodicity in a plurality of directions, and an exposure method using polarized light based on the above method produces an effect only in a certain direction. There is a problem that a reverse effect is produced for a pattern having a periodicity in the orthogonal direction, a mask is difficult to form, or a loss of light amount is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an exposure method and an exposure method capable of further improving the limit resolution and substantially increasing the limit resolution to λ / 2NA. It is to provide a device.

Further, another object of the present invention is to provide a pattern group (L / S) having one-dimensional periodicity in any direction with respect to a mask arranged so as to have the periodicity in a plurality of directions. Another object of the present invention is to provide an exposure method and an exposure apparatus that can obtain an effect of improving resolution.

[0017]

In order to solve the above problems, the present invention employs the following configuration.

That is, according to the present invention (claim 1), an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane between a photomask and a pupil plane of a projection optical system. The directions are optically coincident, and a pattern long in the X direction and Y
In an exposure method of illuminating the photomask on which a pattern long in a direction is formed and projecting and exposing the pattern on the photomask onto a substrate to be exposed by a projection optical system, the exposure method corresponds to a conjugate plane of a pupil plane of the projection optical system. Two positions symmetric on the X axis with respect to the origin in the plane of the illumination optical system
A region where the intensity of the illumination light is higher than the other positions is formed at each of two positions symmetrical on the axis, and a component in the Y direction is formed at the region where the intensity of the illumination light is higher at the position symmetrical on the X axis. While passing polarized light having a component in the X direction in a region formed at a symmetrical position on the Y axis, and passing a pattern long in the X direction on the photomask. Only polarized light having a component in the X direction of the polarized light is transmitted, and only light polarized in the polarized light having a component in the Y direction is transmitted for a pattern long in the Y direction.

Further, according to the present invention (claim 2), an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane between a photomask and a pupil plane of a projection optical system. The directions are optically coincident, and a pattern long in the X direction and Y
In an exposure apparatus that illuminates the photomask on which a pattern long in a direction is formed and projects and exposes the pattern on the photomask onto a substrate to be exposed by a projection optical system, the exposure apparatus corresponds to a conjugate plane of a pupil plane of the projection optical system. A light-shielding plate disposed in the plane of the illumination optical system to be illuminated and having openings respectively at positions symmetrical on the X-axis with respect to the origin and at positions symmetrical on the Y-axis; Means for defining a plane of polarization of light incident on an opening formed at a symmetrical position to be polarized light having a component in the Y direction, and light incident on an opening formed at a position symmetrical on the Y axis with respect to the origin of the light shielding plate. Means for defining the polarization plane of the light to be polarized to have a component in the X direction; means for passing only polarized light having a component in the X direction for light incident on a pattern long in the X direction of the mask; Incident on long pattern in mask Y direction That it is characterized by being provided with means for passing only the polarized light having a Y-direction component for light.

Here, preferred embodiments of the present invention include the following. (1) The light shielding plate has two openings formed at symmetrical positions shifted from the optical axis in the X direction and two openings formed at symmetrical positions shifted from the optical axis in the Y direction. . (2) A polarizing member is formed on the opening of the light shielding plate, or on the light incident side or the light emitting side of the opening. (3) A polarizing member is formed on the pattern (opening) of the mask or on the light incidence side or light emission side of the pattern.

Further, according to the present invention (claim 3), an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane between a photomask and a pupil plane of a projection optical system. The directions are optically coincident, and a pattern long in the X direction and Y
In an exposure method of illuminating the photomask on which a pattern long in a direction is formed and projecting and exposing the pattern on the photomask onto a substrate to be exposed by a projection optical system, the exposure method corresponds to a conjugate plane of a pupil plane of the projection optical system. The polarization plane of the illumination light is defined at an angle of θ ° with respect to the X direction within the plane of the illumination optical system to illuminate the photomask, and the illumination light passing through the photomask is projected onto the pupil plane of the projection optical system. In two regions symmetric on the X axis with respect to the origin, the polarization direction of the illumination light is set to 90.
The polarization direction of the illumination light is rotated by θ ° in two regions symmetric on the Y-axis with respect to the origin, by rotating by − °°.

Further, according to the present invention (claim 4), an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane between a photomask and a pupil plane of a projection optical system. The directions are optically coincident, and a pattern long in the X direction and Y
An exposure apparatus that illuminates the photomask on which a pattern long in a direction is formed and projects and exposes the pattern on the photomask onto a substrate to be exposed by a projection optical system, wherein the polarization plane of the illumination light is θ ° with respect to the X direction. And the polarization direction of the illumination light is 90 ° −θ in two regions provided on the pupil plane of the projection optical system and symmetrical on the X axis with respect to the origin. By rotating the polarization direction of the illumination light by θ ° in two regions symmetrical on the Y axis with respect to the origin while rotating the polarization direction, the polarization state is controlled so that the polarization direction is aligned on the pupil plane. And a member.

Here, preferred embodiments of the present invention include the following. (1) As means or a polarization member for controlling the polarization state, the polarization direction of the light source light is rotated by 90 degrees within a peripheral region on the pupil plane restricted by the polarization direction of the light source light. (2) The polarization member for controlling the polarization at the light source and the pupil position
/ 2 wavelength plate. (3) The mask pattern shall be composed of a group of one-dimensional periodic patterns. (4) Use a phase shift mask as a mask. (5) The special aperture that forms the effective light source intensity distribution can change the light intensity distribution arbitrarily according to the pattern size and pitch of the mask to be transferred.

[0024]

According to the present invention (claims 1 and 2), X from the optical axis.
A light-shielding plate having an opening is provided at a position shifted in the direction and a position shifted in the Y direction, a polarization plane of light is defined as linearly polarized light for each opening, and a pattern long in the X direction of the mask and in the Y direction. By defining the plane of polarization of the light as linearly polarized for each of the long patterns, the X
A pattern that is long in the direction is exposed only with linearly polarized light in the X direction from the opening shifted from the optical axis in the Y direction, and a pattern that is long in the Y direction is only linearly polarized light in the Y direction from the opening that is shifted in the X direction from the optical axis. Can be exposed. As a result, it is possible to improve the limit resolution and substantially increase the resolution to λ / 2NA.

According to the present invention (claims 3 and 4),
By using almost linearly polarized light as the light source,
In the polarization component of the diffracted light on the pupil plane, anisotropy occurs in the resolution characteristics depending on the pattern period direction. By rotating the polarization direction of the component diffracted in the polarization direction of the light source on the pupil plane by the polarizing plate, it is possible to prevent the degradation of the resolution characteristic due to the vector interference effect during imaging. . Therefore, the contrast of the image can be increased, and thereby a fine pattern group having high resolution can be obtained.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view showing a schematic structure of a projection exposure apparatus according to a first embodiment of the present invention. In the mask 11, as a typical fine pattern example,
A one-dimensional lattice pattern 12 with a duty ratio of 0.5 is formed vertically and horizontally. Further, on or near the lattice pattern 12, a polarizing member 14 that allows only light having a predetermined polarization plane to pass therethrough is formed. An illumination optical system for illuminating the mask 11 includes a mercury lamp 1, an ellipsoidal mirror 2, a cold mirror 3, a condensing optical element 4, an integrator 5, a relay lens 8 (pupil relay system), a mirror 9, and a condenser lens 10. In the vicinity of the pupil plane of the illumination optical system (the Fourier transform plane, here, the exit end face of the integrator 5 where the secondary light source image of the mercury lamp 1 is formed), the optical axis is set according to the fineness of the mask pattern 12. A light-shielding plate 6 having four openings, the amount of which is shifted from the axis, is arranged. Further, a polarizing member 7 that allows only light having a predetermined polarization plane of the exposure light to pass therethrough is formed in or near the opening.

In the exposure apparatus configured as described above,
Exposure light generated by the mercury lamp 1 arranged at the first focal point of the elliptical mirror 2 is reflected by the elliptical mirror 2 and the cold mirror 3 and condensed at the second focal point of the elliptical mirror 2, and then collimated. After passing through a condenser optical element 4 composed of a lens, a cone-shaped prism for correcting light flux distribution, and the like, a substantial surface light source is formed at the position of the light shielding plate 6 by an integrator 5 composed of a fly-eye lens group. This surface light source is to provide exposure light which is incident on the mask 11 from above at various incident angles as in the related art. However, since the light shielding plate 6 is provided, the light is emitted through the four openings of the light shielding plate 6. Only the luminous flux that can be transmitted. The light to be transmitted through the four openings has a polarization plane defined by a polarizing member, and illuminates the mask 11 via the relay lens 8, the mirror 9, and the condenser lens 10.

The polarization plane of the illuminating light is further defined by the polarizing member 14, and the light incident on the pattern 12 of the mask 11 is diffracted after passing through the mask, enters the projection optical system 13 and is incident on the pupil plane for each order. To form spots. Thereafter, the light further passes through the projection optical system 13 to form a reduced image on the substrate 17 to be exposed.

Here, of the above-described apparatus configuration in the present embodiment, what differs from the conventional example is the method of installing the light shielding plate 6 and the newly provided polarizing members 7 and 14. 2A and 2B are views of the light-shielding plate 6 and the polarizing member 7, the mask 11, the grating pattern 12, and the polarizing member 14, respectively, as viewed from above. The hatched portions indicate light-shielding portions. Also, the directions in which the polarization planes defined by the polarization members 7 and 14 are defined are indicated by arrows. That is, only light whose electric field is vibrating in the direction of the arrow can pass through the polarizing members 7 and 14.

FIG. 2C shows an exposure light distribution on a pupil plane (corresponding to a substantially conjugate plane at the position of the light shielding plate 6) in the projection optical system 13. The arrows in the figure indicate the polarization plane of the exposure light that has reached the pupil plane. Diffraction light in which two peaks on the X 'axis have reached from the y pattern 12y, and two peaks on the Y' axis
Two peaks indicate diffraction light that has reached from the x pattern 12x. In an actual exposure apparatus, they are arranged such that the directions of the respective coordinates (X, Y), (x, y), (X ', Y') in the figure coincide. As described above, in the conventional example, the opening of the light shielding plate 6 exists at a position of 45 degrees with respect to the grid patterns 12x and 12y, whereas in the present embodiment, the openings are parallel and perpendicular to the grid patterns 12x and 12y. Is different.

The optimum position of the center coordinates of the circular opening in FIG. 2A is determined by the fineness of the mask pattern. For example, assuming that the pitch of the mask pattern is p, the opening center coordinates (X, Y) are (1 / 2p, 0), (-1/2).
p, 0), (0, 1 / 2p), and (0, -1 / 2p). Further, the four peak position coordinates (X ′, Y ′) of the exposure light distribution in FIG. As can be seen, when the pitch p of the mask pattern becomes smaller, the coordinates of the opening position of the light shielding plate 6 and the coordinates of the exposure light peak position at the pupil position of the projection optical system 13 move away from the optical axis. Assuming that the numerical aperture of the projection optical system 13 is NA and the exposure wavelength is λ, the radius of the pupil in FIG. 2C can be represented by NA / λ, so that ｐp = NA / λ p = λ / 2NA. This can be said to be the limit at which a fine pattern can be resolved. Actually, since the opening of the light-shielding plate 6 has a certain area, the size of this area causes a slight deviation in the limit resolution, but the difference is almost the same. According to the prior art, p = 2 ^1/2 λ / 2NA is the limit resolution, whereas according to the present embodiment, p = λ / 2NA, and the limit resolution is substantially improved by 2 ^1/2 times. Was completed. Further, unlike the conventional example, both the y pattern and the x pattern
Since the image is formed only with the polarized light component (s-polarized light component) perpendicular to the plane of incidence, the critical resolution and the depth of focus are further improved.

Here, the principle of exposure according to the present embodiment will be described in more detail with reference to FIG. FIG. 3 is a conceptual perspective view of the exposure apparatus of the present embodiment. The illumination light from 6a and 6c among the four openings of the light-shielding plate 6 contributes to the exposure of the lattice pattern 12y (referred to as y-pattern) parallel to the y-axis by the same action, and improves the limit resolution. 6b and 6
The illumination light from d contributes to the exposure of the grating pattern 12x (referred to as x pattern) parallel to the x axis by the same action,
Improve the limit resolution. Therefore, representatively, exposure by illumination from the openings 6a and 6b will be described. FIG. 3A is a view for explaining exposure by illumination light from the opening 6a.
(B) is a diagram for explaining exposure by illumination light from an opening 6b.

First, exposure by illumination from the opening 6a will be described with reference to FIG. The illumination light emitted from the opening 6a illuminates the mask 11 via an illumination optical system. The illumination light at this time is linearly polarized in the y-axis (Y-axis) direction by a polarizing member (not shown) arranged near the opening 6a.
On the other hand, a polarizing member 14 is disposed on the mask 11 and in the vicinity of the mask 11 in correspondence with the directionality of the mask pattern. Specifically, the y-pattern 12y receives only linearly polarized light parallel to the y-axis. Let the polarizing member 14y that passes through be x
A polarizing member 14x that allows only linearly polarized light parallel to the x-axis to pass is arranged on the pattern 12x. Then opening 6
Since the illumination light from a is linearly polarized in the y-axis (Y-axis) direction, it can pass through the polarizing member 14y in the y pattern 12y, but is shielded by the polarizing member 14x in the x pattern 12x. The illumination light that has passed through the y pattern 12y is diffracted, and after passing through the pupil position 13a of the projection optical system,
7 is formed.

As described above, in the image formation by the illumination light from the openings 6a and 6c, only the y pattern 12y is transferred, and the x pattern 12x is not transferred at all. In this exposure, since an image is formed only by a polarized light component perpendicular to the plane of incidence on the substrate 17 to be exposed, an image with a very high contrast is obtained.

Next, exposure by illumination from the opening 6b will be described with reference to FIG. The illumination light from the opening 6b is
By a polarizing member (not shown) arranged near the opening 6b,
Since the light is linearly polarized in the x-axis (X-axis) direction, it can pass through the polarizing member 14x in the x pattern 12x, but is shielded by the polarizing member 14y in the y pattern 12y. The illumination light that has passed through the x pattern 12x is diffracted and forms an image on the substrate 17 after passing through the pupil position 13a of the projection optical system. Thus, in the image formation by the illumination light from the openings 6b and 6d,
Only the x pattern 12x is transferred, and the y pattern 12y is not transferred at all. In the same manner as described above, this exposure forms an image with only a polarization component perpendicular to the plane of incidence on the substrate to be exposed, so that an image with a very high contrast can be obtained.

FIG. 4 shows the result of this embodiment.
(A) and (b) are plan views of a light shielding plate used in the exposure of this embodiment and the conventional exposure, respectively. In this embodiment, the coordinates (X, Y) of the opening are (0.9 NA / λ,
0), (−0.9 NA / λ, 0), (0, 0.9 NA /
λ), (0, −0.9 NA / λ), the conventional case (0.9
× 2 ^1/2 NA / 2λ, 0.9 × 2 ^1/2 NA / 2λ),
(0.9 × 2 ^1/2 NA / 2λ, -0.9 × 2 ^1/2 NA /
2λ), (−0.9 × 2 ^1/2 NA / 2λ, 0.9 × 2
^1/2 NA / 2λ), (-0.9 × 2 ^1/2 NA / 2λ,-
0.9 × 2 ^1/2 NA / 2λ).

As shown in FIG. 4A, in this embodiment, the polarizing member is arranged near the opening so that the polarization plane of the exposure light passing through the opening is defined in the direction shown. The radius of each of the circular openings is 0.1 NA / λ.
Calculate the image intensity distribution (for one cycle) on a substrate to be exposed when a line and space pattern having a line width of 0.17 μm is exposed as a mask pattern under exposure conditions of NA = 0.5 and λ = 250 nm. The results obtained are shown in FIG. As described above, it was found that the exposure according to the present embodiment has a remarkable effect of improving the limit resolution as compared with the conventional example.

FIG. 5 shows the structure of the mask used in this embodiment. FIG. 5 is a cross-sectional view of a part of the mask 11 shown in FIGS. As shown in FIGS. 5A and 5B, the periphery of the lattice pattern is covered with a polarizing film (polarizing member) 14, and a resist pattern is formed at a position corresponding to the periodic opening using a negative resist. When a negative type mask is used, the polarizing member 14 may be formed on the light shielding film of the mask as shown in FIG. 5A, or may be formed on the mask as shown in FIG. 5B. It may be formed on the back surface.

On the other hand, when a positive type mask is used in which the periphery of the lattice pattern is not covered with the light shielding film and a resist pattern is formed at a position corresponding to the periodic light shielding portion using a positive type resist. When the polarizing member 14 is formed on the light-shielding film, a phase difference of the exposure light occurs at the edge portion, and an unnecessary dark portion is formed. For this reason, as shown in FIG. 5 (c), it is preferable to dispose it at a position off the imaging plane. Further, as shown in FIG. 5D, a method of inserting a flat plate made of the polarizing member 14 independently of the mask may be adopted.

In the above embodiment, the light shielding plate 6
Although a circular opening is used as the opening, the present invention is not limited to this and may be a shape other than a circle, for example, a square or a fan. Further, the opening position of the light-shielding plate and the polarization direction of the polarizing member provided in the opening and the pattern of the mask are not always strict, and may be slightly shifted as long as the effects of the present invention can be obtained. (Embodiment 2) FIG. 6 is a perspective view showing a schematic configuration of an exposure apparatus according to a second embodiment of the present invention. The basic configuration of the exposure apparatus used in this embodiment is the same as that of a conventional apparatus,
The difference is the pupil and light source in FIG. FIG. 6 particularly shows a configuration diagram for transferring the L / S group.

As shown in FIG. 6, a linearly polarized light source 21 is used. The polarization direction is set to a direction substantially equal to one direction of the periodic direction of the L / S pattern. At the pupil position 29, a polarizing plate 30 for rotating the polarization direction by about 90 degrees is provided in a region limited by the polarization direction of the light source 21.

The principle of improving the resolving power according to this embodiment will be described below. When the L / S pattern on the reticle 25 is illuminated by a point light source from the optical axis of the illumination optical system (corresponding to coherent illumination), the diffraction light distribution on the pupil plane 29 of the projection optical system is shown in FIG. (B). This is nothing but a distribution obtained as a result of Fourier transforming the pattern on the reticle 25. Here, it is assumed that the pattern extends infinitely while maintaining the periodicity, so that the diffraction light distribution is discretely distributed. This is sufficiently established as an approximation if the size of the pattern group is sufficient. Further, in this figure, higher-order components of the diffraction light are omitted, and not all are drawn. Of these diffracted light components, only those components that pass inside the pupil are involved in the image formation.

After passing through the pupil, a case where an image is formed in a polarization state (s-polarized light) as shown in FIG. 8A and a case where an image is formed in a state (p-polarized light) in FIG. An image having a higher contrast can be formed by forming an image in the s-polarized state where the directions of the electric field vectors are aligned than in the p-polarized state. In an ordinary exposure apparatus, the light source 21 can be said to be in a non-polarized state as a polarized state. In this case, the unpolarized light can be treated as two linearly polarized lights that are incoherent and orthogonal to each other. Therefore, it can be said that the image quality is degraded by the p-polarized light component even in the ordinary exposure apparatus.

Therefore, by using the light source as linearly polarized light and making the polarization direction coincide with the pattern periodic direction, it is possible to suppress image quality deterioration due to the p-polarized light component. However, in this case, the image quality deteriorates for a pattern having periodicity in different directions on the same reticle. Therefore, in order to remedy this, the wave plate 30 that rotates the polarization direction by about 90 degrees at the pupil position as shown in FIG.
Is provided in a region through which diffraction light of the pattern whose image quality is degraded by the linearly polarized light passes, so that the resolution of a pattern having periodicity in this direction can be improved.

Further, by using the wave plate, it is possible to solve the problem of the loss of light amount caused by placing the polarizer at the pupil position in the conventional example. When using linearly polarized light as the light source, when using laser light, it is possible to extract linearly polarized light in the first place by attaching a Brewster window or the like to the laser resonator. As shown in FIG. 10, the non-polarized light can be effectively used by suppressing the light quantity loss by the polarizing beam splitter 33 and the half-wave plate 30. (Embodiment 3) FIG. 11 is a perspective view showing a schematic configuration of an exposure apparatus according to a second embodiment of the present invention. This embodiment is different from the first embodiment in that:
With respect to the linear polarization direction of the light source, the insertion position of the wave plate at the pupil position and the polarization rotation direction thereof. The same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, for simplicity, the light source 21 is installed in a state where the polarization direction of the light source 21 is inclined by about 45 degrees with respect to the main period direction of the L / S group. Then, using a wave plate 31 as shown in FIG.
By setting the angle to 45 degrees, the same effect as in the first embodiment can be obtained. In this case, since there is no presence / absence of passage through the wave plate in the L / S periodic direction, the light passes through the wave plate equally, so that it is possible to suppress the influence on the resolution due to the difference in light amount loss due to the passage through the wave plate 31. .

In the second and third embodiments, the polarization characteristics of the light source need not always be linearly polarized light, but may be elliptically polarized light having a large ratio between the major axis and the minor axis. Further, the light source does not necessarily have to be circular, and there is no problem even if a modified illumination method such as a ring shape or a fourth shape can be arranged at a position on the pupil corresponding to the modified illumination method. Furthermore, there is no need to binarize the light intensity distribution,
The intensity distribution may change continuously.
Further, the light source distribution may be formed by, for example, an optical fiber bundle.

Further, in the structure of the embodiment, even if modulation is applied to the complex transmittance distribution on the pupil plane, or multiple exposure is performed by changing the focal plane position on the image plane side, the present invention does not impose any problem. Is not the place to go. Forming a compensating plate at the pupil position to compensate for a phase change due to the wave plate is one of the preferred embodiments. Further, even if the shape of the wave plate is other than the shape shown in the figure, it does not hurt at all. Further, by using a Levenson-type phase shift mask as a mask, it becomes possible to arrange a diffraction light distribution on a pupil plane at a rim of the pupil. Thereby, it is possible to obtain an improvement in resolution using more polarization characteristics.

[0050]

As described above, the present invention (claim 1,
According to 2), light-shielding plates having openings are provided at positions shifted from the optical axis in the X direction and at positions shifted in the Y direction, and the polarization plane of light is defined as linearly polarized light with respect to each opening.
By limiting the polarization plane of the light to linearly polarized light for each of the pattern long in the X direction and the pattern long in the Y direction of the mask, the critical resolution is improved, and substantially λ / 2.
It becomes possible to raise to NA.

According to the present invention (claims 1 and 2),
Irrespective of the direction of the pattern period, it is possible to adjust the polarization direction dependence of interference at the time of image formation, and thus it is possible to improve the image contrast.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a projection exposure apparatus according to a first embodiment.

FIG. 2 is a plan view of a light shielding plate and a mask in the first embodiment and an exposure light distribution diagram at a pupil position.

FIG. 3 is a conceptual perspective view of an exposure apparatus for explaining an exposure principle according to the first embodiment.

FIG. 4 is a plan view of a light shielding plate of an example and a conventional example, and a diagram showing a calculation comparison result.

FIG. 5 is a sectional view showing the structure of a mask used in the first embodiment.

FIG. 6 is a perspective view showing a schematic configuration of a projection exposure apparatus according to a second embodiment.

FIG. 7 is a schematic diagram showing a state of light diffracted by a reticle pattern.

FIG. 8 is a schematic diagram showing interference of light in an s-polarized state and a p-polarized state.

FIG. 9 is a schematic diagram showing an example using 1/2 and 1/4 wavelength plates.

FIG. 10 is a diagram illustrating an example in which a light amount loss is suppressed by a polarizing beam splitter and a half-wave plate.

FIG. 11 is a perspective view showing a schematic configuration of a projection exposure apparatus according to a second embodiment.

FIG. 12 is a schematic view showing a schematic configuration of a projection exposure apparatus generally used conventionally.

FIG. 13 is a perspective view showing a conventional exposure apparatus in which the shape of a light source is changed to improve the limit resolution.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mercury lamp 2 ... Ellipsoidal mirror 3 ... Cold mirror 4 ... Condensing optical element 5 ... Integrator 6 ... Shielding plate 7 ... Polarizing member 8 ... Relay lens (pupil relay system) 9 ... Mirror 10 ... Condenser lens 11 ... Mask 12 ... Mask pattern 13 ... Projection optical system 14 ... Polarizing member

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-67914 (JP, A) JP-A-5-188576 (JP, A) JP-A-5-210232 (JP, A) JP-A-5-210232 241324 (JP, A) JP-A-6-53120 (JP, A) JP-A-6-124872 (JP, A) JP-A-5-55110 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027

Claims (4)

(57) [Claims] 1. A direction of an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane of a photomask and a pupil plane of a projection optical system. An exposure method for illuminating the photomask on which a pattern long in the direction and a pattern long in the Y direction are formed, and projecting and exposing the pattern on the photomask onto a substrate to be exposed by a projection optical system; In the plane of the illumination optical system corresponding to the conjugate plane of the plane, a region where the intensity of the illumination light is greater than the other positions at two positions symmetrical on the X axis and two positions symmetrical on the Y axis with respect to the origin. Are formed, and in the region where the intensity of the illumination light formed at the position symmetrical on the X axis is high, the polarized light having the component in the Y direction is allowed to pass, and at the position symmetrical on the Y axis. Region has component in X direction On the photomask, on the photomask, only a polarized light having a component in the X direction of the polarized light is transmitted for a pattern that is long in the X direction, and the polarized light is transmitted for a pattern that is long in the Y direction. An exposure method characterized in that only polarized light having a component in the Y direction among light is transmitted. 2. The direction of an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane of a photomask and a pupil plane of a projection optical system, and X An exposure apparatus that illuminates the photomask on which the pattern long in the direction and the pattern long in the Y direction are formed and projects and exposes the pattern on the photomask onto a substrate to be exposed by a projection optical system; A light-shielding plate disposed in a plane of the illumination optical system corresponding to a conjugate plane of the surface and having openings at positions symmetrical on the X-axis and on the Y-axis with respect to the origin, respectively; Means for defining the plane of polarization of light incident on the opening formed at a position symmetrical on the X axis to polarized light having a component in the Y direction, and a means symmetrical on the Y axis with respect to the origin of the light shielding plate. The polarization plane of the light incident on the formed aperture Means for defining polarized light having a component in the direction; means for passing only polarized light having a component in the X direction for light incident on the pattern long in the X direction of the mask; An exposure apparatus comprising means for passing only polarized light having a component in the Y direction with respect to light incident on the exposure apparatus. 3. The directions of an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane of a pupil plane of a photomask and a projection optical system optically coincide with each other; An exposure method for illuminating the photomask on which a pattern long in the direction and a pattern long in the Y direction are formed, and projecting and exposing the pattern on the photomask onto a substrate to be exposed by a projection optical system; The polarization plane of the illumination light is defined at an angle of θ ° with respect to the X direction in the plane of the illumination optical system corresponding to the conjugate plane of the plane, illuminates the photomask, and projects the illumination light passing through the photomask. In two regions on the pupil plane of the optical system that are symmetric on the X axis with respect to the origin, the polarization direction of the illumination light is rotated by 90 ° -θ °, and in two regions that are symmetric on the Y axis with respect to the origin, The polarization direction of the illumination light may be rotated by θ °. An exposure method characterized by the following. 4. The directions of an XY coordinate system having an optical axis defined as an origin in a plane of an illumination optical system corresponding to a conjugate plane of a pupil plane of a photomask and a projection optical system optically coincide with each other; An exposure apparatus that illuminates the photomask on which a pattern long in the direction and a pattern long in the Y direction are formed and projects and exposes the pattern on the photomask onto a substrate to be exposed by a projection optical system, wherein the polarization plane of the illumination light is The light source of the projection optical system defined at an angle of θ ° with respect to the X direction, and the polarization of the illumination light in two regions provided on a pupil plane of the projection optical system and symmetric with respect to the origin on the X axis. While rotating the direction 90 ° -θ °,
In two regions symmetrical on the Y axis with respect to the origin, a polarization member whose polarization state was controlled so that the polarization direction of the illumination light was rotated by θ ° to align the polarization direction on the pupil plane was provided. An exposure apparatus comprising: