Hydrogen-Blocking Film for Ferroelectric Capacitors

An ammonia-free method of depositing silicon nitride by way of plasma-enhanced chemical vapor deposition (PECVD). Source gases of silane (SiH4) and nitrogen (N2) are provided to a parallel-plate plasma reactor, in which energy is capacitively coupled to the plasma, and in which the wafer being processed has been placed at a support electrode. Low-frequency RF energy (e.g., 360 kHz) is applied to the support electrode; high-frequency RF energy (e.g., 13.56 MHz) is optionally provided to the parallel electrode. Process temperature is above 350° C., at a pressure of about 2.5 torr. Any hydrogen present in the resulting silicon nitride film is bound by N-H bonds rather than Si-H bonds, and is thus more strongly bound to the film. The silicon nitride can serve as passivation for ferroelectric material that may degrade electrically if contaminated by hydrogen.