Alignment of mask and semiconductor wafer using linear Fresnel z

Details Alignment of mask and semiconductor wafer using linear Fresnel z Alignment of mask and semiconductor wafer using linear Fresnel z

1990-05-21

1991-03-12

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

35016216, H01J 314

Patent

active

049994875

ABSTRACT:
A system for aligning a mask and a semiconductor wafer comprises radiation source for producing a radiation beam, a dual focus linear Fresnel zone plate provided on the mask for focusing the radiation beam incident thereto on a surface of the semiconductor wafer which comprises a first part having a first focal length and a second part having a second focal length substantially smaller than the first focal length, a diffraction grating provided on the surface of the semiconductor wafer in correspondence to the dual focus linear Fresnel zone plate for diffracting the radiation beam focused thereon, a detector held with a predetermined relationship with respect to the radiation source and the mask for detecting the diffracted beam, a movable stage for supporting the semiconductor wafer, and a controller for moving the stage means responsive to an output signal of the detection means.

REFERENCES:
patent: 4600309 (1986-07-01), Fay
patent: 4936666 (1990-06-01), Futhey
patent: 4948983 (1990-08-01), Maruyama et al.

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