No abstract

No abstract

No abstract

Tantalum oxide, nitride and metal films are of considerable interest to the semiconductor industry because of the attractive dielectric properties of the compounds and the unusual electrical conductivity of the metallic forms. For example, β-tantalum has a relatively high resistivity of 180 u ohm/cm and a temperature coefficient of essentially zero whereas α-tantalum is superconducting below 7°K and has a room temperature resistivity of 15-40 u ohm/cm depending on method of preparation. The transformation sequence in tantalum films is unusual as the film first grows in the low density bet form. At a critical thickness, about 200 nm for glass substrates at room temperature, transformation to the higher density α-form occurs with a net volume shrinkage of about 1.5%. Substrate temperature and composition markedly affect the critical thickness for transformation to bec Ta growth. At 300 C for example, the critical thickness for glass substrates is about 30 nm. For Cu substrates it is 50 nm at room temperature and on Nb it is 0 nm(2).