Silicon nitride overcoats for thin film magnetic recording media
Abstract
A plasma enhanced chemical vapor deposition (PECVD) process for silicon nitride films which can be used as overcoats for thin film magnetic recording disks has been developed. The most wear resistant coatings are deposited at low concentrations of silane diluted with nitrogen, low deposition frequencies (100–400 kHz), low power densities (0.1 W/cm<sup>2</sup>), low total pressure (30 Pa), and temperatures above 250°C. Stoichiometric materials with hydrogen content down to 10 at % are obtained. Increased deposition temperature leads to an increase in hardness and a decrease in hydrogen content in the films. The stress is compressive and increases linearly with increasing temperature. Wear rates drop by three orders of magnitude as the deposition temperature is raised from 100 to 250°C. Uniubricated disks deposited above 250°C exhibit low static friction without detectable wear for thousands and tens of thousands of start/stop cycles in dry and ambient environments, respectively. These disks lubricated with polyperfluoroethers have lifetimes in excess of ten thousand cycles even in dry conditions. © 1991 IEEE