The dependence of silicon nitride film composition and properties on the flow rates of ammonia and silane gases during deposition and on subsequent thermal annealing has been investigated for films deposited from a reactive plasma in a commercially available reactor. Ammonia-to-silane flow ratios were varied between 1.3:1 and 4.4: 1, and determinations were made of the refractive index, etch rate, charge transport, absorption edge, Si/N ratio, Si-N bonds, and of chemically bound hydrogen. Increasing the ammonia-tosilane ratio during deposition has the following effects upon the films: decreases excess Si concentration, Si-H bond concentration, refractive index, and charge transport; and increases the concentrations of N-H and Si-N bonds, the energy of the absorption edge, and the etch rate. Isochronal annealing between the deposition temperature (300~ and 900~ causes a loss of chemically bound hydrogen, decreases the film thickness, etch rate, and the energy of the absorption edge, and increases the refractive index and the charge transport. Excess Si in the film composition is a major factor in determining the properties of plasma-deposited silicon nitride films, but the 20 to 25 atomic percent chemically bound hydrogen also plays a role. The importance of hydrogen is particularly apparent in the parallel behavior between an annealing induced shift of the absorption edge and the loss of Sill centers from Si-rich films. The annealing effects are analogous to those for hydrogenated amorphous Si.

Thin film layers of Cr–Au were subjected to temperatures in the range 423–573 K for various periods of time and the morphology of the Cr layer was examined with optical and scanning electron microscopy. A preferential depletion of Cr was found beneath the Au grain boundaries and intergranular spaces which was not fully compensated by diffusion of Au into the Cr. Since the Au grain boundaries intersect, this results in islands of remaining Cr surrounded by a labyrinth of voids or channels. This phenomenon renders the entire Cr–Au interface vulnerable to the entry of corrosives. By using transmission optical microscopy in conjunction with a photometer, the optical transmission of the Cr layer was measured and related to the Cr depletion as a function of time and temperature. From these measurements two mathematical models were devised to calculate the activation energy for the Cr diffusion resulting in values of 1.30 and 1.36 eV, respectively.

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