Photocopying – Projection printing and copying cameras – Illumination systems or details
Reexamination Certificate
1999-10-01
2002-05-28
Mathews, Alan A. (Department: 2851)
Photocopying
Projection printing and copying cameras
Illumination systems or details
C355S053000, C355S067000
Reexamination Certificate
active
06396568
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an exposure method and an exposure device for transferring a mask pattern to a photosensitive substrate during a photolithography process for manufacturing such things as semiconductor elements, imaging elements (such as CCDs), liquid crystal display elements, or thin-film magnetic heads.
DISCUSSION OF THE RELATED ART
During the manufacture of semiconductor elements an exposure device transfers an image of a pattern to a reticle. The reticle which acts as a mask, transfers the image to a wafer which is coated with photoresist, forming a photosensitive substrate by the projection exposure system. In the past, projection exposure devices of the collective exposure type, such as steppers, have been used as exposure devices. In recent years the projection exposure method of the scanning exposure type, such as the step-and-scan method where a reticle and a wafer is scanned in sync by the projection exposure system which allows the transfer of large-area patterns without overly stressing the projection exposure system has been gaining attention.
FIG. 13
shows a schematic diagram of an example of a conventional projection exposure device, where the illumination light from the illumination optical system
101
illuminates the pattern formation region of the pattern formation surface (bottom surface) of the reticle (R). Under that illumination light, the projection image, where the pattern is formed upon reticle (R) is reduced a designated magnification by the projection exposure system
102
, exposes the photoresist coated on wafer (W) under the illumination light. The numerical aperture of projection exposure system
102
is defined by the aperture diaphragm
103
. By developing the photoresist, the projected image appears as a raised resist pattern. However, to increase the resolution of the image, has in the past, required expensive and inconvenient light sources and exposure devices.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a projection exposure apparatus and method that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a projection exposure method includes the steps of illuminating a transfer pattern and forming an image of the transfer pattern upon a mask for exposure from an illumination light and transfer exposing the image of the pattern of the mask under the illumination light onto a photosensitive surface. Selectively switching between a normal illumination condition and a modified illumination condition based upon a numerical aperture of the illumination light, wherein the normal illumination condition occurs when a light quantity distribution at an illumination pupil plane is in a first region including an optical-axis, and the modified illumination condition occurs when the light quantity distribution at the illumination pupil plane is in a second region not including the optical-axis.
A further object of the invention is to provide a projection exposure apparatus and method for illuminating a transfer pattern and forming an image of the transfer pattern upon a mask for exposure from an illumination light and transfer exposing the image of the pattern of the mask under the illumination light. Switching a projection condition for changing a numerical aperture of the illumination light and switching an illumination condition between multiple illumination conditions, wherein a normal illumination condition occurs when a light quantity distribution at an illumination pupil plane is in a first region including an optical-axis, and a modified illumination condition occurring when the light quantity distribution at the illumination pupil plane is in a second region not including the optical-axis.
Another object of the present invention is to provide a luminous flux splitting system which splits the illumination light for exposure into a first and a second luminous flux wherein the first luminous flux magnification system, for spreading a cross section of the first luminous flux in a ring shape, and a second luminous flux magnification system for spreading a cross section of the second luminous flux in a ring shape; and a luminous flux synthesis system which synthesizes the luminous flux from the first and second luminous flux systems in front of the illumination pupil plane, wherein the switching of the illumination condition guides the luminous flux synthesized in the luminous flux synthesis system to the illumination system pupil system and carries out an annular illumination when the modified illumination condition is set.
A still further object of the present invention provides a projection exposure apparatus and method for illuminating a transfer pattern and forming an image of the transfer pattern upon a mask for exposure from an illumination light and transfer exposing on a photosensitve circuit board, from an illumination light, detecting an image of a position matching mark on the photosensitive substrate under the illumination light, position matching and aligning the photosensitive substrate based on a detection result, transferring the image formed on the mask and exposing the photosensitive substrate under the illumination light, and switching an alignment optical system between two detection conditions based upon a numerical aperture of the illumination light, wherein the projection exposure system is equipped with two condition detectors, a normal condition detector where an imaging luminous flux is uniformly transmitted on an alignment system pupil plane and an outline emphasis detector, which carries out outline emphasis by transmitting the imaging luminous flux at a designated distribution on the alignment system pupil plane.
A still further object of the present invention provides a projection exposure apparatus and method for transferring a transfer pattern by an exposure illumination light onto a mask, transfer exposing the transfer pattern onto a circuit board coated with a photosensitive material under the exposure illumination light for exposure, controlling an integrated exposure quantity of the exposure illumination light according to the thickness of the photosensitive material coated on the circuit board.
A final object of the present invention provides a projection exposure method including the steps of transferring a transfer pattern by an exposure illumination light onto a mask, transfer exposing the transfer pattern onto a circuit board coated with a photosensitive material under the exposure illumination light for exposure, controlling a switching operation of a numerical aperture of the projection exposure system according to thickness of the photosensitive material coated on the circuit board.
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Shinichi Nakamura, et al., Image Quality of Higher NA i-line Projection Lens, SPIE vol. 1264, Optical/Laser Microlithography III (1990), pp. 84-93.
Hiroaki Kawata, et al., Optical Projection Lithography Using Lenses With Numerical Apertures Greater Than Unity, Microelectronic Engineering, May 9, 1989, Nos. 1-4, Amsterdam, NL., pp. 31-36.
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Mathews Alan A.
Morgan & Lewis & Bockius, LLP
Nguyen Henry Hung
Nikon Corporation
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