DEPOSITION METHOD TO CONTROL PLASMA-ENHANCED CHEMICAL VAPOR-DEPOSITION TETRAETHYLORTHO-SILICATE OXIDE CHARGE

A deposition method to control the postanneal positive oxide charge in undoped plasma-enhanced chemical vapor deposition (PECVD) tetraethylortho silicate (TEOS) oxide is demonstrated. The method uses the preanneal oxide film stress as the determining characteristic for predicting the resulting post-anneal oxide film stress as the determining characteristic for predicting the resulting post-anneal oxide charge. The undoped TEOS oxide, deposited by PECVD techniques, exhibits a positive charge after high temperature anneal (900-degrees-C) in an O2/HCl ambient. The charge is not observed in PECVD TEOS oxide films annealed in nitrogen at 900-degrees-C or in LPCVD TEOS oxide films annealed in O2/HCl at 900-degrees-C. The post-anneal oxide charge can be controlled with the as-deposited (pre-anneal) oxide film stress. Depositing an oxide with tensile stress, rather than a compressive stress, can reduce or eliminate the positive oxide charge. Lower post-anneal oxide charge is correlated with higher tensile stress in the pre-anneal oxide film. The as-deposited (pre-anneal) tensile-film has compressive film characteristics after a high temperature anneal. The as-deposited film stress can be controlled with the amount of ion bombardment by either varying the total RF power or amount of low frequency power in commercial PECVD deposition systems.