Growth of polycrystalline silicon films on titanium and aluminum layers
Adherent, polycrystalline silicon films were vacuum deposited onto titanium passivated steel alloy substrates at substrate temperatures between 535 and 650°C and onto aluminum films at substrate temperatures between 480 and 520°C. Silicon films deposited onto titanium layers are characterized by a sub-micron grain size and a preferential orientation of the <110> direction perpendicular to the growth surface. Resistivities of ∿104 ohm-cm are measured for the undoped films. Silicon films deposited onto aluminum layers have a larger grain size, ∿5μm, a columnar morphology and a preferential orientation of the <111> direction perpendicular to the growth surface. As-deposited resistivities of ∿102 ohm-cm are measured for these films. Boron and phosphorus doped silicon films on titanium layers were annealed. The behavior with annealing of the electrical properties of the films depended on which doping impurity was used. Silicon films on aluminum were annealed to reduce lattice damage within the silicon grains and to dope the films with aluminum from the aluminum layer. Resistivities of several ohm-cm were measured for the annealed films on aluminum.