Optical and physicochemical properties of hydrogenated silicon nitride thin films: Effect of the thermal annealing

ABSTRACT

The effect of thermal annealing on the optical and physicochemical properties of hydrogenated silicon nitride films was studied. These films were deposited by plasma-enhanced chemical vapor deposition from a mixture of silane, ammonia, and nitrogen. Subsequently, the films were annealed at various temperatures ranging from 400°C to 1000°C. The properties of the films were studied using ellipsometry and Fourier transform infrared spectroscopy. The Maxwell Garnet model considers the silicon nitride material as heterogeneous with three distinct phases: silicon, stoichiometric silicon nitride, and hydrogen. Based on the ellipsometric analysis, the annealing treatment leads to reduce the volume fraction of both hydrogen and silicon. As a result, the stoichiometry parameter significantly increases from 1.24 to 1.32 making it closer to the stoichiometric silicon nitride one. According to the infrared data, a noticeable decrease in the total hydrogen concentration in the films was obtained with respect to the annealing temperature.

KEYWORDS:

• Ellipsometry
• infrared spectroscopy
• silicon nitride
• thermal annealing

Acknowledgments

We are indebted to all members of the LAAS team of France for their services and technical assistance, also to team-researcher in LEMEAMED and to all who directly or indirectly contributed to the achievement of this work.