Actel Corporation, Inc.

Huang-Chung Tseng

Wenn-Jei Chen

The present invention is directed to an antifuse structure and fabrication process wherein the bottom oxide of the ONO antifuse material layer is grown over a small area of N- diffusion surrounded by an N+ diffusion area where the N- diffusion could be patterned as N- 'islands' or as N- 'stripes', or the like, with the active N- area controlled by the formation and drive-in of the N+ diffusion layer. In this way, the bottom oxide layer of the ONO antifuse material layer is thinner at its center (above the N- region) than at its edges because oxide grows slower on the less doped N- region at the center of the antifuse than at the more heavily doped N+ regions at the edges of the antifuse. Forcing the center of the antifuse material layer to be thinner causes the antifuse to preferentially break down at its center and away from its edges. The opening in the antifuse cell opening mask is wider than the width of the N- diffusion area so that both N- and N+ areas are exposed in the antifuse cell opening step. Since the N+ diffusion can be very accurately dimensionally controlled with known techniques, it is thus possible to reduce the dimension of the active N- diffusion down to 0.2 .mu.m or below, comparing favorably with the linear dimension of 1.0 .mu.m used in currently available state-of-the-art manufacturing processes for antifuses. This represents a factor of 25 reduction in the active antifuse area, which in turn can dramatically reduce the defect density of antifuses over current technology and/or dramatically increase the number of antifuses that may be disposed in a given area of silicon.

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Santa Clara, CA, United States of America

Huang-Chung Tseng