Projection exposure systems

Details Projection exposure systems Projection exposure systems

1998-03-30

1999-11-02

Henry, Jon

Optical: systems and elements

Diffraction

Using fourier transform spatial filtering

359566, 430 5, 355 53, G02B 2444, G02B 518, G03F 900, G03B 2754

Patent

active

059781386

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

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