Hydrofluoric acid (HF) is commonly used in Si wafer processing as a surface treatment to remove surface oxide and provide a H-terminated surface passivation that resists contamination within short time scales. During silicon heterojunction (SHJ) device fabrication a similar oxide removal and surface passivation is desired for doped and intrinsic hydrogenated amorphous silicon (aSi) films and therefore studied as follows. X-ray photoelectron spectroscopy is employed to evaluate surface chemical composition, especially with regard to oxygen removal, resistance to hydrocarbon adsorption, and fluorine incorporation post HF treatment. Variable angle spectroscopic ellipsometry is used to determine the growth rate of native oxide and terminal oxide thickness. The electrical effects of aSi native oxide at contact interfaces of SHJ cells are evaluated with current-voltage measurements. HF treatment is effective for oxide removal and provides surface passivation of aSi similar to the crystalline counter-part. Further, fluorine bonding is enhanced for p-type aSi films and control of native oxide thickness below 20Å is not essential for typical electrical contacts of the SHJ photovoltaic cell.