Control and manipulation of residual gases during RF magnetron sputter deposition of calcium phosphate coatings

In this paper we report on the development of an integrated RGA-based diagnostic and control facility used as part of an RF magnetron sputtering system for depositing calcium phosphate (CaP) thin film coatings. The RGA-based equipment continually collects information regarding the gases present within the vacuum chamber throughout the complete sputter deposition cycle. In addition, the system incorporates the simultaneous recording of the key processing conditions of RF power density, chamber pressure, gas flow and temperature. A comprehensive record is made of the deposition conditions and becomes part of a subsequent control routine. The system described above has been operated under a set of standard sputtering conditions in order to validate the deposition facility. Results are presented here for a series of benchmarking experiments for a range of in situ partial pressures of key residual gases such as H2O, CO2, etc. Variations in RF power density, chamber gas pressure and gas flow rate have then been used to identify how these parameters effect the quality of the coatings which have been extensively characterised by FTIR, XPS, and AFM.