Alignment or overlay marks for semiconductor processing

Details Alignment or overlay marks for semiconductor processing Alignment or overlay marks for semiconductor processing

2005-05-03

2005-05-03

Tran, Michael (Department: 2818)

Active solid-state devices (e.g., transistors, solid-state diode

Alignment marks

C438S401000, C438S462000, C438S975000

Reexamination Certificate

active

06888260

ABSTRACT:
An alignment or overlay mark with improved signal to noise ratio is disclosed. Improved signal-to-noise ratio results in greater depth of focus, thus improving the performance of the alignment mark. The alignment mark comprises a zone plate having n concentric alternating opaque and non-opaque rings. Light diffracted by either the odd or even rings are cancelled while light diffracted by the other of the odd or even rings are added.

REFERENCES:
patent: 4037969 (1977-07-01), Feldman et al.
patent: 4178701 (1979-12-01), Sadler
patent: 4326805 (1982-04-01), Feldman et al.
patent: 4545683 (1985-10-01), Markle
patent: 4614433 (1986-09-01), Feldman et al.
patent: 5319444 (1994-06-01), Saitoh et al.
patent: 5877562 (1999-03-01), Sur et al.

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