JPH0774090A - Manufacture of circuit and aligner - Google Patents

Abstract

PURPOSE:To form a clear image on a wafer by constituting a demagnified image formation optical system of refractive optical member out of single glass material excellent in light transmittance, and correcting coma-aberration by this refractive optical member. CONSTITUTION:For a demagnified image formation optical system, a first image formation system is constituted of the three reflecting mirrors of a concave mirror M11, a convex mirror M12, and a concave mirror M13, so that they may have the center of curvature in the same direction in order from the side of an object and that they may be positioned on the same optical axis, and a lens L11 in meniscus shape. And, the second image formation system is constituted of lenses L21 and L22 in meniscus shape, a concave mirror M21, and two lenses L'22 and L'21 in meniscus shape. Here, the correction of the aberration outside the axis and the comma-aberration is improved by arranging the lens L11 in meniscus shape so that only the beam reflected with a concave mirror M13 may transmit it. Moreover, the correction of the aberration of the second image formation system becomes easy by negating the chromatic aberration caused by the refraction system arranged in the second image formation system with each other with the lens L11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a circuit such as IC and LSI and an exposure apparatus used when manufacturing a circuit such as IC and LSI.

[0002]

2. Description of the Related Art When manufacturing a circuit such as an IC or an LSI, there is a step of using an exposure apparatus to reduce a circuit pattern of a mask onto a wafer to form an image and transfer it.

[0003]

In order to increase the resolution of this exposure apparatus, the wavelength of the exposure light may be shortened. However, if the wavelength is shortened, the light of each lens made of different glass materials that constitutes the reduction imaging optical system will be used. Due to the absorption, the optical characteristics (focus position, magnification) of the reduction imaging optical system change greatly.

In order to avoid such light absorption, it is not necessary to use a lens in the reduction image-forming optical system, but with such a configuration, important aberrations such as coma aberration cannot be corrected, and it becomes clear on the wafer. Cannot form a perfect image.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit manufacturing method and an exposure apparatus capable of forming a clear image on a wafer.

A method of manufacturing a circuit according to the present invention is a method of manufacturing a circuit, which includes a step of reducing and imaging a circuit pattern on an object to be exposed by a reduction imaging optical system. It is characterized in that the member is composed of a single glass material having a good light transmittance, and the refracting optical member corrects coma aberration. A circuit pattern image is formed.

The exposure apparatus of the present invention is an exposure apparatus for reducing and forming an image of a mask pattern on an object to be exposed by a reduction image forming optical system, wherein the image forming optical system is made of a single glass material having a high light transmittance. It is characterized in that it comprises a refracting optical member configured to correct coma aberration by the refracting optical member, thereby forming a clear mask pattern image while reducing a change in optical characteristics of the reduction imaging optical system. .

SiO ₂ and CaF ₂ are preferable as the glass material when the exposure light in the short wavelength region is used.

A sharper mask pattern image can be formed by limiting the field of view of the reduction image-forming optical system to a slit shape and taking out a good image area for exposure.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view of an optical system of an embodiment of an exposure apparatus for the step of forming an image of a circuit pattern on an object to be exposed by the reduction imaging optical system of the present invention. The reduction imaging optical system in the figure has a center of curvature in the same direction in order from the object side, and a concave mirror M ₁₁ and a convex mirror M so that they are positioned on the same optical axis.
₁₂ and the three reflecting mirrors of the concave mirror M ₁₃ and the meniscus-shaped lens L ₁₁ constitute a first imaging system, and two meniscus-shaped lenses L ₂₁ and L ₂₂ , a concave mirror M ₂₁ and two meniscus-shaped lenses L 11. ₂₂ ', L _21' constitutes a second imaging system in.

In the figure, a light beam from an off-axis object point within a predetermined area above the optical axis, that is, an off-axis object point P ₁ having a predetermined slit width shown in a numerical example described later, is reflected by a reflecting mirror M ₁₁ ,
The light is reflected in the order of M ₁₂ and M ₁₃ , passed through the lens L _11, and then imaged at the first image point P ₁ ′. The first image point P ₁ 'is object point P ₂ next to the second imaging system, the object point P ₂ light beams from the two lenses L _21, L _22, the concave mirror M ₂₁ and the two lenses L
_An image is formed on the second image point P ₂ ′ via ₂₂ ′ and L ₂₁ ′.

In the present embodiment, the first imaging system uses a concave mirror M ₁₁ , a convex mirror M _12, and a concave mirror M ₁₃ for reflecting the light flux from the object point P ₁ , three reflecting mirrors having so-called positive, negative and positive refractive powers and a meniscus. The image is formed on the first image point P ₁ ′ after passing through the shaped lens L _11, and aberrations generated by the respective reflecting mirrors are corrected in a well-balanced manner.

Particularly, the off-axis aberration and the coma aberration (asymmetrical aberration) which often occur when a reduction system is constructed by arranging the meniscus lens L ₁₁ so that only the light flux reflected by the concave mirror M ₁₃ is transmitted. Corrected well. The lens L ₁₁ cancels out the chromatic aberration caused by the refraction system arranged in the second image forming system, thereby facilitating the aberration correction of the second image forming system.

A light beam from the object point P ₂ passes through the second image forming system first through two meniscus-shaped lenses L ₂₁ and L ₂₂ , and then a concave mirror M ₂₁ and two meniscus-shaped lenses L ₂₂ ′,
After passing L ₂₁ ′, the image is formed on the second image point P ₂ ′, and the residual aberration and the chromatic aberration in the first image forming system are corrected well.

In particular, the glass material of each lens has a short wavelength (wavelength 2
Despite being composed only of quartz glass having a good transmittance on the (30 to 400 nm) side, by specifying the lens shape as described above, good chromatic aberration correction is achieved as shown in the aberration charts described later.

In particular, the light flux from the object point P _{2 is} passed through the two lenses L.
₂₁ and L ₂₂ and similarly two lenses L ₂₂ ′ and L ₂₁ ′ are used to increase the aperture ratio and reduce the amount of aberrations such as coma and off-axis halo as a whole. The chromatic aberration is satisfactorily corrected together with the image system lens L ₁₁ . And despite using a reflective system,
Vignetting of the light flux is minimized.

In this embodiment, the imaging magnification of the first imaging system is set to 0.
11 times, the imaging magnification of the second imaging system is 2.26 times, and the reduction imaging optical system of the reduction system of 0.25 times is configured as a whole.

As described above, by constructing one of the image-forming systems as the magnifying system and the other image-forming system as the reducing system so that the entire system becomes the reducing system, the off-axis spherical surface generated in each of the image-forming systems is formed. Aberrations, coma, distortion, and other aberrations are well corrected, and a large-aperture-ratio reduction imaging optical system is easily achieved despite a simple configuration.

Incidentally, in this embodiment, in order to satisfactorily correct the off-axis spherical aberration, the coma aberration and the chromatic aberration, and to achieve a reduction system of higher resolution, the lens L ₁₁ is a meniscus whose concave surface faces the concave mirror M ₁₃ side. It is preferable that each of the lenses L ₂₁ , L ₂₂ , L ₂₁ ′ and L ₂₂ ′ is a meniscus lens having a convex surface facing the concave mirror M ₂₁ side.

Further, it is possible to achieve good aberration correction by forming the lenses L ₁₁ and L ₂₁ , and the lens L ₂₁ ′ with positive refractive power, and the lenses L ₂₂ and L ₂₂ ′ with negative refractive power. Is preferred.

In this embodiment, the lens L ₂₁ and the lens L ₂₁ ′ are the same lens, and the lens L ₂₂ and the lens L ₂₂ ′ are the same lens. However, each lens is a separate lens. In this case, the degree of freedom is increased, and aberration correction can be achieved better. Further, the object of the present invention can be achieved even if the lens L ₁₁ is composed of two or more meniscus lenses.

In this embodiment, the chief ray from the object point P ₁ intersects with the optical axis between the convex mirror M ₁₂ and the concave mirror M ₁₃ and between the concave mirror M ₂₁ and the lens L ₂₂ ′. , The entire optical system is made compact, and a high-performance reduction imaging optical system is achieved while reducing the vignetting of the light flux.

In this embodiment, each lens is set to S as described later.
Although a case of using iO ₂ is shown, CaF ₂ or the like, which has a high transmittance on the short wavelength side, may be used.

Next, a numerical example of the embodiment shown in FIG. 1 will be shown. Ri represents a radius of curvature of the i-th reflector and lens surface counted in order of progress of the light from the object point P _1, Di is the i-th and the (i + 1) th lens thickness counting the order of progress of the light from the object point P ₁ and Air space, SiO ₂ is quartz glass. The air gap and the refractive index are shown as positive when measured from the left to the right in the light traveling direction and as negative when measured in the opposite direction.

Numerical Example NA = 0.25 Slit width 1.5mm Magnification
1/4

[0026]

[Table 1]

[0027]

According to the present invention, the refraction optical member of the reduction imaging optical system is composed of a single glass material having a good light transmittance, and the refraction optical member is used to correct coma aberration. As a result, a clear pattern image is formed while reducing the change in the optical characteristics of the reduction imaging optical system.

[Brief description of drawings]

FIG. 1 is an optical sectional view of a numerical example of the present invention.

FIG. 2 is an aberration diagram of numerical examples of the present invention.

[Explanation of symbols]

A Sagittal image plane B Meridional image plane Y ₀ Object height P ₁ 1st object point P ₂ 2nd object point P ₁ ′ 1st image point P ₂ ′ 2nd image point

Claims (10)

[Claims] 1. A method of manufacturing a circuit including a step of reducing a circuit pattern onto an object to be exposed to form an image by a reduction imaging optical system, wherein a refractive optical member of the reduction imaging optical system has a high light transmittance. A method of manufacturing a circuit, comprising a single glass material, and correcting the coma aberration by the refractive optical member. 2. The method for manufacturing a circuit according to claim 1, wherein the reduction imaging optical system includes a concave mirror. 3. The method of manufacturing a circuit according to claim 1, wherein the field of view of the reduction imaging optical system is limited to a slit shape. 4. The method of manufacturing a circuit according to claim 1, wherein the glass material comprises SiO ₂ . 5. The method for manufacturing a circuit according to claim 1, wherein the glass material comprises CaF ₂ . 6. An exposure apparatus for reducing and imaging a mask pattern on an object to be exposed by a reduction imaging optical system,
The exposure apparatus, wherein the reduction imaging optical system includes a refractive optical member made of a single glass material having a high light transmittance, and the coma aberration is corrected by the refractive optical member. 7. The exposure apparatus according to claim 6, wherein the reduction imaging optical system includes a concave mirror. 8. The exposure apparatus according to claim 6, wherein the field of view of said reduction imaging optical system is limited to a slit shape. 9. The exposure apparatus according to claim 6, wherein the glass material comprises SiO ₂ . 10. The exposure apparatus according to claim 6, wherein the glass material comprises CaF ₂ .