Investigation of an ECR plasma source used for the deposition of diamond-like carbon films

Abstract

Summary form only given, as follows. Diamond-like carbon (DLC) films are generating technological interest as protective optical and tribological coatings. In this study the deposition of DLC films using a low pressure (1-10 mTorr) electron cyclotron resonance (ECR) microwave plasma system is investigated. The purpose of this work is to investigate variations in an ECR plasma source design and operation with respect to DLC film properties produced in the deposition process. Such a parameter space quantification is useful for obtaining desired film properties for various applications. In this study, a methane-argon discharge is generated in a microwave ECR plasma source and the substrate is placed on an unheated, rf-biased substrate holder approximately 10 cm downstream from the plasma source. The plasma source used is a resonant cavity, ECR source operated at 2.45 GHz. The input parameter space variations for this study include a methane concentration of 30-70% in argon, total flow rate of 10-100 seem, operating pressure of 1-8 mTorr, and rf induced substrate bias of 25-100 volts. The DLC films are deposited on glass, polycarbonate, and silicon substrates. The film thickness is measured using an ellipsometer and by using the transmission/interference of infrared light. The optical band-gap, Raman spectrum, and infrared transmission spectrums are also measured. Within this input parameter range, films have been deposited which are transparent, adhere to the substrate, and have an optical band gap of 1.1-1.5 eV. The deposition rate across this input parameter space is as high as 6 micrometers/hour.