Ion chemistry and ionic thin film deposition from HMDS-photochemistry induced by VUV-radiation from an atmospheric plasma

Injection of precursor molecules into a plasma often results in particle generation or deposition in the source, compromising film quality and plasma operation. We present here a study of ion chemistry and ionic film deposition from hexamethyldisilane (HMDS) using a novel device utilizing vacuum ultraviolet (VUV)-radiation from a remote atmospheric plasma. Infrared spectroscopy showed that -like films were obtained at the lowest admixture, where impurities are more important and VUV-photons reach the substrate, while only slightly oxidized films were deposited at high admixtures. Photoionization mainly forms the monomer ion due to collisional stabilization and possibly slow polymerization reactions as found by ion mass spectrometry. The more detailed photochemistry of HMDS-related ions is discussed based on mass spectra for different admixtures.