In this paper we address the degradation of oxide reliability after annealing the phosphorusdoped polysilicon of MOS structures. The oxide reliability was studied in terms of X-ray radiation sensitivity as well as breakdown characteristics.

We found that annealing the polysilicon increased the radiation sensitivity of the gate oxide. We believe that this increase is a result of the phosphorus out-diffusion from the polysilicon into the oxide and a result of the creation of phosphorus related traps in the oxide bulk. We also found that the oxide charge to breakdown (Qbd ) degradation correlates well with the density of the phosphorus in the oxide.

A silicon nitride membrane growth process has been characterized. The films were grown by LPCVD on 100 mm diameter silicon substrates using ammonia and dichlorosilane as reactant gases. The films were grown using a range of gas ratios at three different temperatures. The film composition was determined by elastic recoil detection. The silicon-nitrogen absorption bands were characterized by FTIR spectroscopy. The photon transmission of the films was measured in the visible region from 350 – 850 nm, and in the x-ray region for photon energies from 1000 to 3000 eV. The film stresses were determined using the wafer bow technique. An increase in the silicon content of the films was observed for increased dichlorosilane gas flow and for increasing growth temperatures. The increased silicon content of the films is correlated to a decrease in the tensile stress and a decrease in the optical transmission of the films.