Stability of boron and phosphorus implanted tungsten silicide structures at high temperatures

We report on the stability of sputter-deposited tungsten silicide (WSi_2.6) films that were implanted with boron or phosphorus and annealed at high temperatures using rapid thermal annealing. Depending on process conditions, some films were found to be unstable, resulting in peeling and lifting from the substrate. The regime of stability was experimentally determined and found to be a function of the implant dose, species, and anneal temperature. Films implanted with boron were found to be more stable than those implanted with phosphorus. With the appropriate choice of dopant dose, anneal temperature, and capping layer type, the film stacks were found to be stable upon subsequent furnace annealing steps at 900°C.