Positive charge increase in plasma deposited oxides induced by low pressure chemical vapor deposition of silicon nitride

The origin of the positive charge observed in an interlayer dielectrics mad e of a silicon-oxide layer deposited by plasma enhanced chemical vapor depo sition (PECVD) from an O-2/tetraethoxysilane (TEOS) mixture covered by a si licon-nitride layer obtained by low pressure chemical vapor deposition (LPC VD) is studied. Charge creation during silicon-nitride deposition is eviden ced. Even though NH3 thermal decomposition is one of the main parameters of both hydrogen incorporation and the charge creation in the oxide layer, th e increase in hydrogen content and charge trapping after nitride deposition is not only due to the diffusion of hydrogen originating From ammonia frag mentation. The results show that the charge decrease observed when increasi ng the O-2/TEOS ratio and boron doping is partly related to the decrease of the carbon content in the oxide.