THERMAL-STABILITY OF COPPER AMORPHOUS HYDROGENATED CARBON-NITROGEN THIN-FILM BILAYERS

In order to investigate the effectiveness and failure of amorphous hyd rogenated carbon-nitrogen thin films (a-C:H(N)) as diffusion barriers against diffusion of copper in silicon, we performed a systematic stud y of films 10-100 nm thick. The a-C:H(N) films were grown by plasma-en hanced chemical vapour deposition onto unpatterned p-type (100) Si waf ers and overlaid with 100 nm Cu films. The films were annealed in a va cuum quartz tube at temperatures in the range 300-800 degrees C. The a nnealing time was fixed at 30 min and no kind of sequential annealing was involved for each sample. The structural modifications and thin fi lm reactions were followed as a function of the annealing temperature and characterized by nuclear techniques (Rutherford backscattering spe ctrometry, elastic recoil detection analysis and nuclear reaction anal ysis), Auger electron spectroscopy and hydrogen effusion experiments. In situ sheet resistance measurements were also performed. Whereas Cu films react completely with Si at 200 degrees C to form Cu3Si, the a-C :H(N) film prevents Cu-Si interaction up to 700 degrees C despite the degradation of the a-C:H(N) film and hydrogen and nitrogen losses that begin at temperatures as low as 400 degrees C.