Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1999-08-26
2001-07-10
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C430S296000
Reexamination Certificate
active
06258492
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
This invention relates to a mask and a method of making the same, suitable for use in the manufacture of semiconductor devices, for example. In another aspect, the invention is concerned with an exposure method and a device manufacturing method which use such a mask.
For further improvement of integration density and operation speed of a semiconductor device such as an LSI, miniaturization of a circuit pattern has been continuously pursued. In an exposure process of lithography for the device manufacture, a higher resolution is attainable with a shorter exposure wavelength. In this respect, fine-pattern formation which is based on high-luminance x-rays from a synchrotron radiation (SR) light source, for example, becomes attractive.
As an example of x-ray exposure, Japanese Patent Application Laid-Open No. 100311/1990 discloses a proximity unit-magnification x-ray exposure method which uses soft x-rays of about 0.5-2 nm. In principle, a high resolution of not greater than 0.1 micron may be attainable. This x-ray exposure method uses a transmission-type mask called an “x-ray mask” (which may be called a “reticle”). The portion of this mask through which x-rays pass is called a “membrane”, and generally it comprises a thin film of a thickness of about 2 microns and a size of 35-50 mm square. A circuit pattern formed on this membrane is made of an x-ray absorbing material having a thickness of about 0.5 micron. For projection of the mask circuit pattern onto a wafer substrate, the x-rays from a light source are projected to the x-ray mask, whereby the mask pattern is transferred to the wafer which is placed opposed to and in proximity with the mask.
In the x-ray unit-magnification exposure method, however, since the mask and the wafer are placed close to each other and there is no reduction projection optical system therebetween, it is difficult to adjust the transfer magnification of a pattern to be transferred to the wafer.
SUMMARY OF THE INVENTION
An external force may be applied to an x-ray mask to change the magnification of the mask pattern (to adjust the mask pattern size) formed on the x-ray mask, in accordance with the wafer pattern magnification. It is accordingly an object of the present invention to provide a method and/or a structure which accomplishes this on a practical level.
It is another object of the present invention to provide an improved method of making a mask by which high precision pattern transfer can be accomplished.
It is a further object of the present invention to provide a high-precision device manufacturing method using such a mask.
These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 6007948 (1999-12-01), Cummings
patent: 2-100311 (1990-04-01), None
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Rosasco S.
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