Characteristics of dc magnetron, reactively sputtered TiNx films for diffusion barriers in III–V semiconductor metallization

Abstract

TiNx films have been deposited on C, Si, InP, and glass substrates by reactive sputtering of Ti in a dc magnetron system. The value of x and the crystal structure varied with the deposition parameters around the pressure hysteresis loop typical of reactive sputtering. With a fixed argon flow of 5 standard cm3min−1 (sccm) and a dc current of 2 A, the total pressure P remained constant at 0.23 Pa up to nitrogen flows f(N2) of 5.2 sccm. For 0≤f(N2)<4.1 sccm, only the hcp α-Ti phase was observed by x-ray and electron diffraction, but the films tended to be amorphous for f(N2)∼4.1 sccm. At f(N2)=5.1 sccm, the fcc TiN0.8 phase was observed with a lattice constant a0 of 0.422 nm; the value of x was obtained by Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). At f(N2)=5.2 sccm, the pressure increased rapidly to 0.35 Pa; thereafter, P varied linearly with f(N2) until f(N2) was reduced to 3.0 sccm. This behavior is due to the formation of a nitride layer on the Ti target. In this condition, fcc TiN1.2 films with a0=0.428 nm were obtained for all f(N2). The diffusion barrier characteristics of these films were determined by annealing Au/TiN1.2/InP samples at different temperatures. Comparisons were made with samples where 50 nm thick TiN1.2 films were replaced by 50 nm Cr or Pt. Whereas 1 wt.% In was detected in the Au after annealing for 60 s at 500 °C for Pt and 300 s for Cr, no In was detected for the TiN1.2 barrier after 24 h.