We have investigated the effects of substrate ion bombardment and microwave electron cyclotron resonance (ECR) assisted processing on the microstructural and electrical properties of ion beam sputtered Y1Ba2Cu3Ox thin films. Substrate bombardment was performed using a Kaufman-type ion source or a microwave ECR gridless ion source. While substrate bombardment has been found to change the properties of the films, only in the case of ECR-assisted deposition was any sign of superconductivity observed in the as-deposited films. Results indicate that low energy oxygen ion bombardment, at low ambient pressures, simulates a high oxygen pressure ambient. © 1990.