Randhir Thakur

Effect of NH3 thermal treatment on an atomic layer deposited on tungsten films and formation of W–B–N

The effect of ammonia (NH3) ambient annealing on a tungsten (W) film deposited by atomic layer deposition at temperatures ranging from 400–700 °C is discussed. The as-deposited film contains approximately 20 at. % of boron which is chemical bound to W (W–B) having a resistivity of 128 μΩ cm. The film has an amorphous structure, which does not transform into crystalline phase during annealing. As a result of annealing in NH3 ambient, a tungsten ternary phase (W–B–N) forms at the surface; its binding configuration depends on the annealing temperature. Below 500 °C, nitrogen is chemically bonded to tungsten (W–N) while maintaining a W–B bond. Above 600 °C, nitrogen-rich W–B–N forms, in which nitrogen atoms have chemical binding with boron (B–N) and tungsten (W–N). It was found that a film annealed at higher temperatures has a resistivity of 107 μΩ cm, and thermal desorption of boron and nitrogen containing species is not observed during the thermal process. In addition, tungsten oxide formed at the surface d...