Interface States and Fixed Charges in MNOS Structures with APCVD and Plasma Silicon Nitride

Abstract

The net posit ive charge density QN/q and the interface state density D~T of MNOS structures on p-Si (100) with APCVD and plasma sil icon nitr ide is studied as a funct ion of the nitr ide deposit ion temperature and the postdeposit ion anneal ing temperature. For APCVD sil icon nitride, a decrease of QN/q is accompanied by an increase of D~T with increas-ing deposit ion an d annealing temperature. E lectron irradiation (30 keV and 5 • 10-5 C/cm 2 dosage) did not affect QN/q, whereas D~T was increased for nitr ide films deposited below 800 ~ For plasma sil icon nitride, both QN/q and D~T de-creased with deposit ion and annealing temperature up to 450 ~ Very low interface state densit ies (8 • 109 cm-2 eV-~) could be achieved. These low D~T values are due to the influence of hydrogen incorporated in the PECVD sil icon nitr ide films. Very high posit ive charge densities (>1013 cm-2) could be obtained by cesium contaminat ion of the plasma nitr ide films. Pyrolyt ic chemical vapor deposited (CVD) sil icon ni-tride films are widely used as active layers in microelec-tronics, e.g., as gate dielectric in nonvolati le memory ele-ments. The performance of these metal-nitride-oxide-si l-icon (MNOS) devices is strongly dependent on the den-