SiOF films were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) on Si(100) substrates as a function of both the SiF4/O-2 flow ratio, as well as the Ar flow rate. The formation of Si-O and Si-F bonds was then confirmed using Fourier transform infrared spectroscopy (FTLR), and the residual stress in the SiOF thin films was also measured. While the SiOF thin films deposited in a SiF4/O-2 ECR plasma were in tensile intrinsic stress, the films deposited in a SiF4/O-2/Ar ECR plasma had compressive intrinsic stress. This transition between tensile and compressive stress was interpreted to result from Ar ion bombardment of the growing film. In the cases where films had compressive intrinsic stress, the magnitude of the compressive stress decreased with increasing SiF4/O-2 ratio. The relaxation of the compressive stress for a given Ar flow rate is related to an F- ion related open structure.