1. Field of the Invention
The present invention is directed to a metal-to-metal antifuse structure for use in microcircuit structures such as Field Programmable Gate Arrays (FPGAs) and the like. More particularly, the antifuse structure of the present invention comprises an antifuse cell opening in which is deposited a barrier metal by means of collimated sputtering deposition over which is deposited the antifuse material layer and then another barrier metal layer. The resulting structure is advantageous in that it can be fabricated with standard CMOS process techniques plus the addition of collimated sputtering and it provides a device having a low capacitance antifuse operable at higher speeds.
2. The Prior Art
Prior art metal-to-metal antifuse structures generally comprise a planar bottom electrode on top of which is disposed a planar barrier metal layer. An interlayer dielectric layer (ILD) is disposed over the bottom electrode structure and an antifuse cell opening is formed in the ILD to expose the bottom electrode. An antifuse material layer may then be deposited in the antifuse cell opening (or "via") and appropriate layers deposited over the antifuse material layer. The problem with this approach is that it requires a thicker barrier layer on top of the bottom electrode which is not a standard process in CMOS backend technology. For manufacturability, it is desirable to have antifuse related processes impose as little change as possible on the process technology.