Aluminum nitride substrates for thin film hybrid integrated circuits report II - Thin film deposition and pattern generation studies.

We are evaluating aluminum nitride (AlN) substrates because of their favorable thermal properties. Material characteristics relevant to thin film substrate application were reported in an earlier memorandum. Data on compatibility of AlN substrates with thin film processes are presented in this report. AlN substrates, cleaned with a modified procedure, were compatible with the standard thin film deposition and pattern generation processes. Thin film adhesion on AlN was adequate as confirmed by soldered lead pull test. However, the definition of 3 mil wide resistor line pattern was not satisfactory. Poor resistor line definition was attributable to surface roughness of AlN substrates, which was fourfold higher than that of alumina. The definition of fine lines is expected to improve by using substrates of smoother surface. Future efforts must include evaluation of AlN substrates with smoother surfaces, evaluation of Hybrid Integrated Circuits on AlN substrates and development of process flexibility.