TiN diffusion barriers for copper metalization

Abstract

The requirements of future integrated circuits will result in shrinking dimensions and consequently new materials like copper or low k materials. TIN films are an interesting candidate as diffusion barriers because of their well known compatibility to semiconductor technology. Moreover TiN films were already shown to be stable barriers against copper diffusion [ 1,2].Based on a series of tests including the stochiometry variation (0,59 N/Ti 1) of films deposited by reactive magnetron sputtering on Si and SiOz and annealing in different atmospheres the interaction between film properties and barrier stability is studled. The applicability of optical, mechanical and analytical thickness measurement methods for thin TIN films is investigated. Advantages and drawbacks of the used measurement techniques given by method related boundary conditions are shortly discussed.It is found that texture and roughness of the deposited films is independent of the N/Ti ratio. Moreover the underlaying substrates (Si, Si02) did not affect the texture of the films. The effect of annealing in different atmospheres (N2, H2) on resistivity, stress and film composition is studied for films of different stochiometry.Finally the barrier stability after annealing in N2, H2 or in vacuum is investigated by analytical and electrical investigations on n' p diodes. The barrier stability clearly depends on the annealing atmosphere. It is observed, that the barrier fails already after annealing at 45OOC in N2 independent of the film stochiometry. This is accompained by a strong peeling of the Cu film. By contrast the failure occurs at higher temperatures, if the samples are annealed in H2 or vacuum.