Window cleaning and fluorine incorporation by XeF2 in photochemical vapor deposition

A new method of maintaining window transparency in photochemical vapor deposition (photo‐CVD) has been developed in which the window is continuously etched clean during the deposition process. This technique is demonstrated in the deposition of a‐Si:H(F) by direct photo‐CVD of Si2H6 using XeF2 as an etchant. XeF2 is also used to clean the chamber between runs. Fluorine may be incorporated in the films via either gas phase or surface reactions with XeF2. The optoelectronic quality of a‐Si:H:F decreases with F incorporation, which suggests that this technique may be particularly suited to the deposition of μc‐Si:H(F) and a‐SiGe :H(F) and a‐SiC :H(F) alloys wherein fluorinated process gases are preferentially employed.