Photocopying – Projection printing and copying cameras – Step and repeat
Reexamination Certificate
2001-12-10
2003-10-14
Adams, Russell (Department: 2851)
Photocopying
Projection printing and copying cameras
Step and repeat
C355S067000
Reexamination Certificate
active
06633365
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of the following priority application is herein incorporated by reference:
Japanese Patent Application No. 2000-375992 filed Dec. 11, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection optical system and to an exposure apparatus to which such a projection optical system is fitted, and more particularly relates to a projection optical system which is suitable for an exposure apparatus which is used for the manufacture of semiconductor elements or liquid crystal display elements and the like by a process of photolithography.
2. Description of the Related Art
In a photolithography process for manufacture of semiconductor elements or the like, there is employed an exposure apparatus for projecting and exposing an image of a pattern upon a mask via a projection optical system onto a photosensitive substrate such as a wafer with this type of exposure apparatus, the resolving power which is required from the projection optical system is increasing along with increase of the degree of integration of the semiconductor elements or the like. Due to this, along with shortening the wavelength of the illumination light (the exposure light), a compelling necessity is experienced for raising the image side numerical aperture (NA) of the projection optical system to the ultimate limit, in order to satisfy this requirement for resolving power of the projection optical system.
However, when the numerical aperture of the projection optical system is increased, the lens outer diameter is increased in proportion to the size of the numerical aperture. As a result, the outer diameter (the glass material diameter) of the block of optical material from which this lens is manufactured also becomes great, and it becomes difficult to obtain an optical material block of the required homogeneity, and therefore it is hard to manufacture an optical system of good performance. Furthermore, when the lens outer diameter becomes great, the lens can easily be influenced by bending or distortion due to its weight, which also makes it difficult to manufacture an optical system of good performance.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a high resolution projection optical system, and an exposure apparatus to which such a projection optical system is fitted, which are capable of ensuring a large image side numerical aperture, while restraining increase in the size of the lens outer diameter. Furthermore, it is another objective of the present invention to provide a method of microdevice manufacture, which can manufacture a good quality microdevice at high accuracy by utilizing an exposure apparatus according to the present invention as defined above, to which is fitted a high resolution projection optical system which has a large image side numerical aperture.
A projection optical system according to the present invention whose image side numerical aperture is greater than or equal to 0.75, and which forms an image of a first object upon a second object using light of a predetermined wavelength less than or equal to 300 nm, comprises: a first lens group G
1
of positive refractive power; a second lens group G
2
of negative refractive power; a third lens group G
3
of positive refractive power; and a fourth lens group G
4
of positive refractive power, and: the first lens group G
1
, the second lens group G
2
, the third lens group G
3
and the fourth lens group G
4
are arranged in order from a side of the first object; and a distance D in mm along an optical axis between an optical surface of the fourth lens group G
4
closest to the second object, and the second object, satisfies a condition of 0.1<D<5.
In this projection optical system, it is preferred that the projection optical system has an image side numerical aperture greater than or equal to 0.8.
Also, it is preferred that with T being a sum of thicknesses along the optical axis of all optical members included in the fourth lens group G
4
, and with D being the distance along the optical axis between the optical surface of the fourth lens group G
4
closest to the second object, and the second object, a condition of 0.001<D/T<0.2 is satisfied.
Also, it is preferred that with T being a sum of the thicknesses along the optical axis of all optical members included in the fourth lens group G
4
, and with L being a distance along the optical axis between the first object and the second object, a condition of 0.02<T/L is satisfied.
Also, it is preferred that a distance L in mm along the optical axis between the first object and the second object satisfies a condition of 800<L<1600.
Also, it is preferred that a focal length F
2
of the second lens group G
2
and a distance L in mm along the optical axis between the first object and the second object satisfy a condition of 0.01<|F2|/L<0.15.
Also, it is preferred that at least one of a plurality of optical surfaces comprised in the projection optical system is formed in an aspherical shape.
An exposure apparatus according to the present invention, comprises: an illumination system for illuminating a mask as a first object; a projection optical system described above that forms an image of a pattern which is formed upon the mask upon a photosensitive substrate as the second object; and a prevention device that prevents gas which is generated from the photosensitive substrate from adhering to the optical surface closest to the second object of the fourth lens group G
4
of the projection optical system.
In this exposure apparatus, it is preferred that the prevention device comprises a flow forming device that forms a predetermined flow of gas or liquid in a optical path between the optical surface closest to the second object of the fourth lens group G
4
and the photosensitive substrate.
An exposure method according to the present invention, comprises: an illumination process of illuminating a mask as a first object; and an exposure process of exposing, via a projection optical system described above, an image of a pattern which is formed upon the mask upon a photosensitive substrate as the second object, and the exposure process comprises a flow formation process of forming a predetermined flow of gas or liquid in a optical path between the optical surface closest to the second object of the fourth lens group G
4
and the photosensitive substrate, in order to prevent gas which is generated from the photosensitive substrate from adhering to the optical surface closest to the second object of the fourth lens group G
4
.
A method according to the present invention for manufacturing a microdevice, comprises: an exposure process of exposing a pattern on a mask upon a photosensitive substrate, using an exposure method described above; and a development process of developing the photosensitive substrate which has been exposed by the exposure process.
REFERENCES:
patent: 5781278 (1998-07-01), Matsuzawa et al.
patent: 5856884 (1999-01-01), Mercado
patent: 5973764 (1999-10-01), McCullough et al.
patent: 6252662 (2001-06-01), Sugita
patent: 6259508 (2001-07-01), Shigematsu
patent: 6459534 (2002-10-01), Kato et al.
Adams Russell
Esplin D. Ben
Nikon Corporation
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