JPH08288213A - Projection aligner - Google Patents

Abstract

PURPOSE: To obtain a projection aligner by which various fine patterns can be transferred extremely stably without lowering the resolution of a projection optical system so much. CONSTITUTION: A projection aligner is provided with an illumination optical system 1 used to illuminate a reticle 3 having a prescribed pattern and with a projection optical system 4 which is used to project the pattern on the reticle onto the face of a wafer and which has a prescribed numerical aperture. In the projection aligner, two wedge prisms which are installed so as to be movable to a direction crossing an optical axis are arranged in an optical path between the reticle and the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for transferring a pattern on a reticle onto a wafer.

[0002]

2. Description of the Related Art Conventionally, a reduction projection type exposure apparatus has been used for manufacturing a semiconductor element having an extremely fine pattern such as an LSI and a VLSI, and in order to accurately and stably transfer a finer pattern. A great deal of effort continues. For example, efforts are being made to use light with a shorter wavelength depending on the exposure wavelength and to increase the NA (numerical aperture) of the projection optical system. For stable transfer of such a fine pattern, it is necessary not only that the resolution of the projection optical system is excellent, but also that the contrast of the projection image is high. Efforts have also been made to investigate and find the optimum exposure conditions. Regarding the illumination condition, by adjusting a so-called σ value corresponding to the ratio of the NA of the illumination optical system to the NA (numerical aperture) of the projection optical system, it is possible to obtain an appropriate balance between the resolution and the contrast for a given pattern. Adjusting the NA of the system is known, for example, from Japanese Utility Model Publication No. 61-151.

[0003]

However, in the conventional apparatus as described above, although the illumination optical system can be optimized to some extent, the projection optical system itself has not been optimized. It is an object of the present invention to solve the above-mentioned problems and to perform extremely stable transfer to various fine patterns without significantly reducing the resolving power of the projection optical system. To provide a device.

[0004]

In order to achieve the above object, a projection exposure apparatus according to the present invention includes an illumination optical system for illuminating a reticle having a predetermined pattern, and a pattern on the reticle on a wafer. A projection exposure apparatus having a projection optical system having a predetermined numerical aperture for projecting onto a surface, wherein an optical path between the reticle and the wafer is:
Two wedge prisms are arranged so as to be movable in a direction crossing the optical axis.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The projection type exposure apparatus according to the present invention as described above will be explained based on the configuration of the embodiment shown in FIG. As shown in FIG. 1, the exposure illumination light supplied from the illumination optical device 1 uniformly illuminates the reticle 3 having a predetermined projection pattern via the condenser lens 2. The pattern on the reticle 3 is reduced by the reduction projection objective lens 4.
The image is reduced and projected onto the wafer 6 placed on the stage 5.
Here, in the illumination optical device 1, illumination information such as the wavelength λ of the exposure light and the numerical aperture (NA) of the illumination system is input to the computing means 20 via the illumination information input means 11 and formed on the reticle 3. Information of the projection pattern regarding the line width of the pattern is input from the projection pattern information input means 12 to the computing means 20. Further, information on the exposed object such as the material of the wafer, the resist material, and the thickness of the resist is input to the calculation means 20 by the exposed object information input means 14. Then, the aperture value (NA) information of the reduction projection objective lens 4 is also input to the calculation means 20 via the aperture information input means 13.

Based on such various kinds of information, the calculating means 20 obtains the optimum spherical aberration amount, and the desired aberration is generated by the aberration varying means 40 via the aberration varying driving means 30. It is possible to obtain a proper depth of focus. By the way, the fineness of the reticle pattern from the projection pattern information input means 12 and the illumination information input means 11
Based on the information of the illumination conditions from, the calculating means 20 can obtain the optimum aperture value of the reduction projection objective lens 4 by calculation, and the aperture control means 21 can set the aperture of the reduction projection objective lens 4 to the optimum aperture value. In this case, the excess amount of spherical aberration can be set to the optimum value by the aberration varying means 30 based on the optimum aperture value calculated by the calculating means 20 without using the aperture information inputting means 13.

As the aberration varying means 40 in the present invention,
The phenomenon that a positive spherical aberration is generated when a spherical wave passes through a plane-parallel plate is used. That is, in a projection objective lens that is ideally aberration-corrected, spherical aberration can be excessively generated by inserting a plane-parallel plate into a condensed or divergent light beam, and the thickness of the plane-parallel plate can be changed. It is possible to arbitrarily control the excessive spherical aberration amount.

Specifically, as shown in FIG. 2, it is possible to change the amount of spherical aberration by alternately inserting parallel plane plates 41 and 42 having different thicknesses in the optical path, as shown in FIG. As described above, it is also possible to continuously change the combined center thickness by moving the two wedge prisms 43 and 44 in the opposite directions. Also, as shown in FIG. 4, two parallel flat plates 4
Fill the space between 5,46 with a transparent fluid, and place two parallel plane plates 45,46.
It is possible to change the substantial optical path length between the plane-parallel plates by changing the distance between, and it is possible to give a desired amount of spherical aberration even with such a configuration.

As the spherical aberration varying means, various concrete means as described above can be used, but in any case, the reduction projection objective lens 4 has a telecentric configuration also on the reticle 3 side, and the projection objective lens It is preferably arranged on the reticle side. This is because if a plane-parallel plate is inserted in a portion where the light flux is telecentric, only spherical aberration will change and other aberrations (coma, astigmatism, etc.) will not be affected. In other words,
By inserting a plane-parallel plate in a portion where the light flux is not telecentric and changing its thickness, not only spherical aberration but also other aberrations (coma aberration, astigmatism, etc.) can be changed. In the reduction projection exposure apparatus, since the space between the projection objective lens and the wafer is generally telecentric, it is conceivable to insert spherical aberration varying means on the wafer side of the projection objective lens. Since the working distance of the projection objective lens becomes short, it imposes a serious constraint on the optical design for increasing the working distance. Further, on the wafer side of the projection objective lens, since the NA (numerical aperture) is large, the tolerance of the thickness of the plane-parallel plate becomes extremely strict in order to control the amount of spherical aberration generated by the plane-parallel plate. Practical control becomes difficult.

[0010]

As described above, according to the projection exposure apparatus of the present invention, since two wedge prisms are provided so as to be movable in the direction crossing the optical axis of the projection optical system, the optical paths of these two wedge prisms are provided. The length can be changed. This makes it possible to extremely stably transfer a fine pattern without significantly reducing the resolution of the projection optical system.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a specific example of spherical aberration varying means.

FIG. 3 is a cross-sectional view showing a specific example of spherical aberration varying means.

FIG. 4 is a sectional view showing a specific example of spherical aberration varying means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Illumination optical device 4 ... Projection objective lens 3 ... Reticle 6 ... Wafer 20 ... Calculation means 30 ... Aberration variable drive means 40 ... Aberration variable means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Matsumoto 1-6-3 Nishioi, Shinagawa-ku, Tokyo Inside Nikon Oi Manufacturing Co., Ltd. (72) Inventor Kyoichi Suwa 1-3-6 Nishioi, Shinagawa-ku, Tokyo Shares Inside Nikon Oi Manufacturing Co., Ltd. (72) Inventor Koichi Ohno 1-6-3 Nishioi, Shinagawa-ku, Tokyo Inside Nikon Oi Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A projection exposure apparatus having an illumination optical system for illuminating a reticle having a predetermined pattern, and a projection optical system having a predetermined numerical aperture for projecting the pattern on the reticle onto a wafer surface. In the projection exposure apparatus, in the optical path between the reticle and the wafer, two wedge prisms provided so as to be movable in a direction crossing the optical axis are arranged. 2. The projection exposure apparatus according to claim 1, wherein the two wedge prisms are arranged in an optical path between the reticle and the projection optical system. 3. The projection optical system is a telecentric optical system, and the two wedge prisms are arranged in a portion where a light beam is telecentric. Projection exposure device.