TEM studies of the microstructure evolution in plasma treated CVD TiN thin films used as diffusion barriers

Abstract

In semi-conductor technology, TiN thin films elements are used as diffusion barriers between a copper interconnect layer and a silicon oxide dielectric. Plasma treatment application, by modifying the film microstructure, can improve the film barrier properties and its electrical conductivity. But details of the plasma application effect on the film microstructure evolution and correlations of this evolution with the physical properties are still unclear. To clarify the correlations, the microstructure of a series of TiN thin films deposited using an OMCVD (organo-metallic chemical vapor deposition) technique has been analyzed by transmission electron microscopy (TEM). The films were obtained by cycling a basic synthesis sequence including first a limited film growth and then application of a N 2/H 2 gaseous plasma with various powers and duration times. Films are actually stackings of plasma-treated elementary layers. TEM analyses show that films are made of nanocrystallites and that whereas no texture is observed when no plasma is applied, short-time plasma treatment induces a tendency to 〈100〉 texture and if treatment is longer, the direction of texture progressively rotates to 〈110〉. A tentative interpretation of this texture evolution has been made in terms of nucleation and growth and correlations between this evolution and the effect on the physical properties have been obtained.