Electrical fuses and electrical antifuses are used in the semiconductor industry to implement array redundancy, field programmable arrays, analog component trimming circuits, and chip identification circuits. Once programmed, the programmed state of an electrical fuse or an electrical antifuse does not revert to the original state on its own, that is, the programmed state of the fuse is not reversible. For this reason, electrical fuses and electrical antifuses are called One-Time-Programmable (OTP) memory elements.
Programming or lack of programming constitutes one bit of stored information in fuses or antifuses. The difference between fuses and antifuses is the way the resistance of the memory element is changed during the programming process. Semiconductor fuses have a low initial resistance state that may be changed to a higher resistance state through programming, i.e., through electrical bias conditions applied to the fuse. In contrast, semiconductor antifuses have a high initial resistance state that may be changed to a low resistance state through programming.
Continuous advances in the semiconductor technology oftentimes require changes in the material employed in semiconductor structures. Of particular relevance is the advent of a metal gate electrode, which, in addition to the gate dielectric, a polysilicon layer, and a metal silicide layer, contains a metal gate layer in a gate stack. Typically, the metal gate layer is employed in conjunction with a high-k gate dielectric material. This is because high gate leakage current of nitrided silicon dioxide and depletion effect of polysilicon gate electrodes limits the performance of conventional silicon oxide based gate electrodes. High performance devices for an equivalent oxide thickness (EOT) less than 1 nm require a high-k gate dielectric material and a metal gate electrode to limit the gate leakage current and provide high on-currents.
The high-k gate dielectric materials refer to dielectric metal oxides or dielectric metal silicates having a dielectric constant that is greater than the dielectric constant of silicon oxide of 3.9 and capable of withstanding relatively high temperatures, e.g., above 600° C., and preferably above 800° C. The metal gate layer may comprise a metal, a metal alloy, or a metal nitride, and typically has an even higher conductivity than the metal silicide.
In view of the above, there exists a need for an electrical antifuse structure compatible with fabrication of other semiconductor devices employing metal gate electrodes and methods of manufacturing the same.