Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2002-03-25
2004-06-15
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S066000
Reexamination Certificate
active
06750948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection optical system for a projection exposure apparatus to be employed when a semiconductor element or a liquid crystal display element is to be manufactured by the photolithographic process, a projection exposure apparatus provided with the projection optical system, Projection Method thereof, Exposure Method thereof and Fabricating Method for fabricating a device using the projection exposure apparatus, and, more particularly, to a projection optical system for a scanning type projection exposure apparatus and having a resolution of 0.1 microns or less in an ultraviolet region
2. Related Background Art
In the photolithographic process for manufacturing a semiconductor element or the like, there has been employed a projection exposure apparatus for projecting and exposing a pattern image formed on a photo mask or reticle (as will be generally called the “reticle”), through a projection optical system to a wafer or glass plate to which a photoresist or the like is applied. As the degree of integration of the semiconductor element or the like grows higher, there rises higher the resolution which is demanded for the projection optical system employed in the projection exposure apparatus. In order to satisfy this demand, it is necessary to shorten the wavelength of an illumination radiation (or exposure radiation) and to enlarge the numerical aperture (as will be abbreviated into the “NA”) of the projection optical system, or to effect the-both. When the illumination radiation has a wavelength of 180 nm or less, for example, it is possible to achieve a high resolution of 0.1 microns or less.
As the wavelength of the illumination radiation is the-shorter, the kind of a practical glass material is the-more limited by the optical absorption. Especially when the wavelength is as short as 180 nm or less, what can be practiced as the glass material is limited to only fluorite. When the wavelength is shorter than 100 nm, moreover, there is no glass material to be employed as the refractive lens. It is, therefore, necessary to develop an optical system employing no refractive lens or only an extremely small number of refractive lenses.
Several techniques for constructing the projection optical system have been proposed by the reflection type optical system employing no refractive lens or the reflection type optical system employing an extremely small number of refractive lenses. For example, an optical system having an aperture as large as the NA exceeding 0.2 on the image side has been disclosed in U.S. Pat. Nos. 5,815,310 and 5,686,728.
However, the optical systems disclosed are not sufficiently corrected in aberration when the numerical aperture on the image side exceeds 0.3 and when an emitted radiation in a soft X-ray range of a wavelength of 100 nm or less is used. Therefore, the optical systems thus far described cannot provide a sufficient optical performance if employed as the projection optical system having a resolution of 30 nm or less.
SUMMARY OF THE INVENTION
The object of the invention is to provide a projection optical system having a large numerical aperture in a soft X-ray wavelength range of 200 nm or less, specifically 100 nm or less and a resolution drastically lower than 50 nm, and a projection exposure apparatus provided with the projection optical system.
In order to solve the above-specified problem, according to the invention, there is provided a projection optical system for projecting the image of a first plane on a second plane, comprising: an arcuate field area spaced away from the optical axis of the projection optical system; and a shading area in a pupil plane of the projection optical system.
In the invention, on the other hand, the projection optical system further comprises: a first imaging optical system for forming an intermediate image of said first plane; and a second imaging optical system for forming the final image of said first plane on said second plane on the basis of an emitted radiation from said intermediate image. Said first imaging optical system includes at least two reflecting surfaces, and said second imaging optical system includes at least one reflecting surface having an optically transmissive portion.
In the invention, on the other hand, said shading area has a ring shape (doughnut shape).
According to the invention, on the other hand, there is provided a projection optical system for projecting the image of a first plane on a second plane, comprising: a first imaging optical system for forming an intermediate image of said first plane; and a second imaging optical system for forming the final image of said first plane on said second plane on the basis of an emitted radiation from said intermediate image, wherein said first imaging optical system includes at least two reflecting surfaces, and said second imaging optical system includes at least one reflecting surface having an optically transmissive portion.
In the invention, on the other hand, the projection optical system further comprises: a first imaging optical system for forming an intermediate image of said first plane; and a second imaging optical system for forming the final image of said first plane on said second plane on the basis of an emitted radiation from said intermediate image, wherein said first imaging optical system includes at least one reflecting surface of a positive power, and at least one reflecting surface of a negative power, wherein said second imaging optical system includes a primary mirror disposed in the vicinity of said intermediate image, and an auxiliary mirror disposed closer to said second plane than said primary mirror, wherein said primary mirror has a first optically transmissive portion and a first reflecting surface of a positive power (a concave shape), and wherein said auxiliary mirror has a second optically transmissive portion and a second reflecting surface, whereby: the emitted radiation from said intermediate image is reflected through said first optically transmissive portion of said primary mirror on said second reflecting surface of said auxiliary mirror; the emitted radiation, as reflected on said second reflecting surface of said auxiliary mirror, is reflected on said first reflecting surface of said primary mirror; and the emitted radiation, as reflected on said first reflecting surface of said primary mirror, is transmitted through said second optically transmissive portion of said auxiliary mirror to form said final image on said second plane. Further, the power on the reflecting surface is an inverse number of a focal distance of said reflecting surface.
In the invention, on the other hand, all the optical elements composing said projection optical system are reflecting surfaces.
In the invention, on the other hand, the projection optical system further comprises: a first imaging optical system for forming an intermediate image of said first plane; and a second imaging optical system for forming the final image of said first plane on said second plane on the basis of an emitted radiation from said intermediate image, wherein said first imaging optical system includes at least one refractive lens component, and wherein said projection optical system is a telecentric optical system on the sides of said first plane and said second plane.
In the invention, on the other hand, all the optical elements composing said projection optical system are positioned to have their optical axes on a common straight line.
In the invention, on the other hand, the projection optical system further comprises: a first imaging optical system for forming an intermediate image of said first plane; and a second imaging optical system for forming the final image of said first plane on said second plane on the basis of an emitted radiation from said intermediate image, wherein said projection optical system is a telecentric optical system on the side of said second plane, and wherein a shading member for forming said shading area is arranged in the vicinity
Adams Russell
Nikon Corporation
Oliff & Berridg,e PLC
LandOfFree
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