Methods for minimizing silicon regrowth in aluminum films

The transport of polycrystalline silicon into an overlying aluminum film and silicon regrowth in the metal medium under heating at 500 °C was examined as a function of doping level and grain size of the silicon. Such regrowth was eliminated through phosphorus doping and was substantially reduced for increased grain size. These results are consistent with a mechanism of silicon grain-boundary transport in the films. The necessity for a silicon oxide layer at the aluminum-silicon interface, if regrowth is to occur, is also indicated.