Semiconductor junction antifuse circuit

DETAILED DESCRIPTION A junction antifuse is formed by one or more reverse-biased semiconductor junctions.
In one embodiment of the invention, two n+ regions are spaced apart in a p-type substrate with a small section of the p-type substrate therebetween.
Input and output conductors coupled to each of the n+ regions provide signal lines for application of electrical signals to the n+ regions.
If a positive input voltage is applied to one of the n+ regions, the junction between the n+ region and the p-type substrate is reverse-biased, blocking any current from flowing.
If, however, the input voltage is sufficiently high, it breaks down the reverse-biased junction, causing current flow.
Continuous application of the high voltage causes continuous current flow that, in turn, causes carrier migration through the gap between the n-wells.
As carriers migrate through the gap, they produce a conductive path extending between the n-wells.
Once the conductive path is formed, the integrated structure no longer forms an open circuit and the junction antifuse is "blown.
" Thus, the unblown junction antifuse forms an open circuit and the blown antifuse forms a conductive path.
In a second embodiment of the invention, the junction antifuse is formed by adjacent n+ and p+ regions in an n-well.
The n+ and p+ regions are highly doped, having an abrupt junction boundary with a relatively low breakdown voltage.
The p+ region is connected to an input line and the n+ region is connected to a reference potential.
If a positive voltage is applied to the n+ region, the junction between the p+ and n+ regions forms an open circuit, blocking current flow.
A sufficiently high voltage to break down the reverse-biased p-n junction causes current to flow from the n+ region to the p+ region.
Continuous application of the high voltage causes continuous current flow that, in turn, causes carrier migration producing a conductive path.
The conductive path effectively bypasses the reverse-biased p-n junction and the junction antifuse conducts