A new aluminum pattern formation using substitution reaction of aluminum for polysilicon and its application to MOS device fabrication

This paper describes a new aluminum pattern formation process using the substitution reaction of aluminum for polysilicon (APSP), and its application to the fabrication of self-aligned aluminum-gate MOSFET´s. The APSP method uses the intensive interdiffusion reaction between aluminum and polysilicon observed for contact structure where the aluminum film overlaps polysilicon and is heat treated below the eutectic temperature (577°C). The basic idea in the fabrication of self-aligned aluminum-gate MOSFET´s using APSP is to replace the polysilicon gate with an aluminum gate in the final step following fabrication of the self-aligned polysilicon-gate MOSFET. It is shown that the new fabrication process can be followed by almost all of the conventional polysilicon-gate processes. It is also shown that the electrical characteristics of the aluminum-gate MOSFET fabricated using APSP are nearly the same as those of polysilicon-gate MOSFET´s fabricated on the same wafer.