Optical: systems and elements – Light dispersion
Reexamination Certificate
1997-12-16
2001-11-27
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Light dispersion
C355S067000, C355S071000, C372S100000, C372S101000, C372S102000, C372S103000
Reexamination Certificate
active
06322220
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to an exposure apparatus and a device manufacturing method. More particularly, the invention is concerned with an exposure apparatus and a device manufacturing method, suitably usable for the manufacture of devices such as ICs, LSIs, CCDs, liquid crystal panels or magnetic heads, for example.
With the increasing degree of integration of semiconductor devices, exposure apparatuses of high resolution and having a large exposure area are desired. As an apparatus which meets these requirements, a scan type reduction projection exposure apparatus for exposing a mask and a wafer while scanning them has attracted a great deal of attention.
On the other hand, on the point of reducing the resolvable line width, the use of shorter wavelength light as exposure light is desired. In this respect, the use of an excimer laser, for example, which emits intense light in the deep ultraviolet region, in a scan type reduction projection exposure apparatus, has been proposed.
However, as regards the emission spectrum of an excimer laser, in a case of a KrF excimer laser, it is about 0.3 nm in terms of half full width (FWHM). Thus, the band width is not sufficiently narrow.
This problem may be solved by using a band narrowing unit for narrowing the band width of the laser light. However, the use of a band narrowing unit raises another problem that the exposure apparatus has to be operated fixedly with exposure light of a narrow spectrum. Thus, the latitude of the exposure apparatus with respect to the exposure light is limited considerably.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an exposure apparatus having a large latitude with respect to exposure light.
In accordance with an aspect of the present invention, there is provided an exposure apparatus having means for changing the band width of laser light. Particularly, the apparatus is provided with dispersing means for dispersing laser light with respect to wavelength, an optical system for collecting each of laser lights of wavelength units being dispersed and wavelength selecting means for changing the band width of laser light to be provided thereby, by changing a blocking portion for intercepting the collected laser light. With this arrangement, the spectrum of exposure light is made variable, and thus, the latitude of the apparatus with respect to the exposure light is enlarged. This assures optimum exposure processes best suited to different types of wafer processes, respectively.
The dispersing element, the optical system and the wavelength selecting means may be provided within a resonator and, on that occasion, a decrease of intensity of the laser light is avoided irrespective of the provision of the band narrowing unit.
A Brewster window for transforming laser light into linearly polarized light as well as a reflector for turning the laser light back into a chamber may be provided within the resonator.
The dispersing element may comprise a prism or a diffraction grating. The laser may comprise an excimer laser.
One preferred form of the present invention comprises a first unit for making the spectral width of the laser light smaller than a natural emission spectrum, and a second unit for setting the spectral width of the laser light at the natural emission spectrum, the first and second units being able to be used alternately, such that a larger latitude with respect to exposure light is assured.
In one preferred form of the present invention, the wavelength selecting means may comprise a slit of a variable opening width.
In one preferred form of the present invention, the second unit for setting the spectral width of laser light at the natural emission spectrum may comprise a total reflection mirror which may be interposed between the chamber of the resonator and the pair of the dispersing means and the wavelength selecting means.
In accordance with this aspect of the present invention, there is provided a high-resolution scan type exposure apparatus for scanning a mask and a substrate with laser light from a wavelength selecting means to thereby project a pattern of the mask onto the substrate.
In accordance with another aspect of the present invention, there is provided an exposure apparatus which comprises a first dispersing element for dispersing substantially parallel laser light, from a laser, with respect to the wavelength to provide light beams in wavelength units, a first optical system for collecting each laser light beam of a wavelength unit from the first dispersing element, wavelength selecting means for passing a desired wavelength region of laser light, of the light beams of the wavelength units each being collected by the first optical system, a second optical system for receiving the laser light from the wavelength selecting means and providing parallel light beams of wavelength units, and a second dispersing element for combining the parallel laser light beams of the wavelength units from the second optical system, the second dispersing element having substantially the same angular dispersion as that of the first dispersing element, but having a direction of dispersion opposite to that of the first dispersing element. The dispersing elements may be disposed out of a resonator of the laser, to narrow the band width of the laser light, such that the emission strength of the laser light is stable.
Also, the provision of the second optical system and the second dispersing element is effective to avoid or reduce eccentricity of the wavelength distribution along the section of the laser light.
The wavelength selecting means may change the size of the region through which the laser light can pass, such that the supply of laser light having a desired band width best suited to wafer processes is allowed. For example, the wavelength selecting means may comprise slit means having a variable slit width.
Each of the first and second dispersing elements may comprise a prism or a diffraction grating. The laser may comprise an excimer laser.
In accordance with this aspect of the present invention, there is provided a high resolution scan type exposure apparatus for scanning a mask and a substrate with laser light from the second dispersing element by which a pattern of the mask is projected onto the substrate.
Also, in accordance with another aspect of the present invention, there is provided a device manufacturing method by which the manufacture of devices of a large area and a high integration is allowed.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
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R. L. Sheffield, et al., “An Independently Controllable Multiline Laser Resonator and Its Use in Multifrequency Injection Locking,” Appl. Phys. Lett., vol. 29, No
Ouchi Chidane
Sano Naoto
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Jr. John Juba
Spyrou Cassandra
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