Preparation and Properties of Ta205 Films by LPCVD for ULSI Application

Preparation and electrical properties of tantalum pentoxide (Ta20~) films have been studied for the application to ultra large scale integrated circuits (ULSIs). Ta205 films were deposited by a cold wall-type low-pressure chemical vapor depo-sition (LPCVD) at temperatures of 340~176 and then annealed at temperatures ranging from 600 ~ to 900 ~ in 02. It can be found that for the films grown by the present method, a high-temperature annealing is exceedingly effective for an in-crease in dielectric onstant and a decrease in leakage current flowing through the film. Relative dielectric onstants of 25-35 are achieved for the annealed Ta205 films with the thickness above 40 nm, which are about 1.4 times larger than those reported previously. The annealing forms a transition oxide layer at the Ta2Os-Si interface, which results in excellent C-V characteristics of metal-insulator-semiconductor (MIS) capacitors as applied to ULSI. In recent years, tantalum pentoxide (Ta205) films have received much attention as a promising dielectric for a storage capacitor in scaled-down memory cells and a gate insulator of metal-oxide-semiconductor (MOS) devices, because of a much larger dielectric onstant than that of silicon dioxide (SIO2). The usage of materials with such