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 made of a silicon-oxide layer deposited by plasma enhanced chemical vapor deposition (PECVD) from an O2/tetraethoxysilane (TEOS) mixture covered by a silicon-nitride layer obtained by low pressure chemical vapor deposition (LPCVD) is studied. Charge creation during silicon-nitride deposition is evidenced. Even though NH3 thermal decomposition is one of the main parameters of both hydrogen incorporation and the charge creation in the oxide layer, the increase in hydrogen content and charge trapping after nitride deposition is not only due to the diffusion of hydrogen originating from ammonia fragmentation. The results show that the charge decrease observed when increasing the O2/TEOS ratio and boron doping is partly related to the decrease of the carbon content in the oxide.