Composition and resistivity changes of reactively sputtered W–Si–N thin films under vacuum annealing

W–Si–N layers about 200nm thick with different nitrogen content were reactively sputtered from a W5Si3 target on oxidized silicon substrates. The thermal stability of the films’ composition and resistivity was studied with ion beam analysis and four-point probe measurements. Upon vacuum annealing from 600to980°C for 1.5h, a sample with an initial 56at.% of nitrogen gradually loses nitrogen down to 36%. This composition lies close to the W–Si3N4 tie line. Concurrently, the room temperature resistivity decreases from 4.7 to about 2mΩcm. The composition changes only a little for a sample whose initial composition is near the W–Si3N4 tie line and the resistivity changes significantly less than for the nitrogen-rich film. Interpretations are discussed.