Plasma-Enhanced Atomic Layer Deposition of Ta(C)N Thin Films for Copper Diffusion Barrier

Abstract

Ta(C)N thin films were deposited by plama-enhanced atomic layer deposition using an alternate supply of tertiary amyl imido-tris(dimethylamido) tantalum [TAIMATA] and hydrogen plasma at 230°. Hydrogen plasma acted as an effective reducing agent for TAIMATA. The film thickness/cycle was saturated at 0.132nm/cycle, when the source pulse time exceeds 5 sec. The resistivity of Ta(C)N films was 1000 μΩ-cm, which is higher value as the application of Cu diffusion barrier material. However, the resistivity of TaN films improved with the increase of hydrogen plasma time because of the decrease of Ta3N5 (>106 μΩ-cm) phase formed by insufficient active hydrogen radical to reduce alkyl groups in TAIMATA, the formation of Ta-C (30 μΩ-cm) phase, and the increase of crystallinity of cubic-TaN. By applying higher plasma power, the lattice mismatch between Ta(C)N and CVD-Cu can be minimized. As a result, Ta(C)N films showed an improved adhesion to CVD-Cu.