SILVER DIFFUSION IN AG2SE/GESE2 INORGANIC RESIST SYSTEM

The Ag concentration depth profile in 3000- and 6000-A-thick films of GeSe//2 on substrates consisting of 300 A of Ta on silicon wafers has been studied by SIMS, using an O** plus //2 primary beam. The Ag//2Se/GeSe//2 resist was exposed by an unfiltered mercury arc source and received doses ranging from 0 to 2 J/cm**2. The unreacted Ag//2Se was stripped prior to the SIMS analysis. The Ag incorporation was found to increase rapidly with exposure first, and then saturate about 1 J/cm**2. However, its concentration peaks both near the top surface and at the substrate interface. The anomalous Ag peak at the substrate interface indicates that Ag diffuses far beyond the penetration depth of the radiation and presumably piles up in front of the Ta diffusion barrier. Moreover, with the same exposure, the anomalous Ag peaks are identical in both the 3000- and 6000-A-thick films. These results are consistent with the model of Ag diffusion through the columnar structure of GeSe//2, an extremely fast path in regions between the columns extending through the film, and a slower diffusion component in the denser regions within the columns.