Projection optical system, exposure apparatus incorporating this projection optical system, and manufacturing method for micro devices using the exposure apparatus

Abstract

In a projection optical system which forms an image of a first plane on a second plane, using extreme ultraviolet illumination light, an object of the invention is to form an image on the first plane on the second plane under suitable conditions. This projection optical system comprises a first diffractive optical element arranged in an optical path between the first plane and the second plane; a second diffractive optical element arranged in the optical path on the side of the second plane from the first diffractive optical element; and an optical system having a negative power, arranged in the optical path between the first diffractive optical element and the second diffractive optical element.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a projection optical system for forming an image of a first plane on a second plane, an exposure apparatus incorporating this projection optical system and used at the time of transferring a mask pattern onto a substrate in a lithography process for manufacturing devices or micro devices, such as semiconductor devices or liquid-crystal display devices, and a manufacturing method for micro devices using this exposure apparatus to manufacture micro devices such as semiconductor devices, imaging devices, liquid-crystal display devices or thin film magnetic heads.[0003] 2. Description of the Related Art[0004] When micro devices such as semiconductor devices are manufactured, there are used a batch exposure type projection exposure apparatus (stepper or the like) in which a minute pattern image formed on a reticle as a mask is transferred onto a wafer (or a glass plate) on which a resist is applied, via a projection ...

AI Technical Summary

Problems solved by technology

However, even if the numerical aperture of the projection optical system is increased over and above what is required, if illumination light having a long wavelength is used, there is naturally a limit to improvement of the resolution.

However, even if the numerical aperture is high, if aberration occurs, there is a problem in forming minute patterns.

This method however, requires a multiplicity of lenses, and hence invites a reduction in transmittance, and an increase in the cost for manufacturing the projection optical system cannot be avoided.

As a result, this is not desirable in view of improving transmittance and cost reduction.

With the diffractive optical element having a cross-section in a saw-tooth pattern or a stepwise pattern, occurrence of unnecessary diffracted light which does not contribute to image forming cannot be avoided due to form error or the like.

When the wavelength of illumination light becomes short with shortening of the wavelength of the light source, the kinds of usable glass material are limited due to absorption of light, and if the wavelength becomes 180 nm or below, the only glass material practically usable is fluorite.

Therefore, under illumination light having such a short wavelength, correction of chromatic aberration becomes impossible with a construction having only dioptric lenses.

Hence the production thereof becomes difficult.

However, for a projection optical system for forming a pattern having a resolution of 0.1 .mu.m or less, using extreme ultraviolet illumination light having a large numerical aperture, measures have not heretofore been taken for exhibiting sufficient imaging performance, taking into consideration incident angle characteristics and manufacturing error of the diffractive optical element.

Images