Optical: systems and elements – Diffraction – Using fourier transform spatial filtering
Patent
1997-04-07
1998-09-15
Henry, Jon W.
Optical: systems and elements
Diffraction
Using fourier transform spatial filtering
359572, G02B 518, G03B 2754
Patent
active
058087966
ABSTRACT:
A projection method uses a modified illumination method for a lithography process of semiconductor device, and a projection system and mask use the projection method. An object is exposed by removing the vertical incident component of light passed through a condenser lens. Zero-order diffracted light interferes destructively and the oblique component of -/+ first-order diffracted light, interferes constructively. The obliquely incident component light illuminates a mask having a pattern formed thereon. The vertical incident component of the light is removed by a phase difference of light due to a grating mask or a grating pattern formed on the back surface of the conventional mask. The resolution of a lithography process is improved due to the increased contrast, and the depth of focus is also increased. Thus, patterns for 64 Mb DRAMs can be formed using a conventional projection exposure system.
REFERENCES:
patent: 5145212 (1992-09-01), Mallik
Choi Seong-oon
Han Woo-sung
Kang Ho-young
Kim Cheol-hong
Sohn Chang-jin
Henry Jon W.
Samsung Electronics Co,. Ltd.
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