Nitrogen induced states at the CNx/Si interface

The deposition of carbon nitride (CNx) films onto n-type silicon wafers by rf magnetron sputtering at room temperature produces insulating films suita ble for electronic applications. The traps at the CNx/Si interface may hamp er the creation of electronic devices especially in VLSI applications. Whil e amorphous carbon films have been studied for that purpose, the introducti on of nitrogen inside the growth chamber adds an extra parameter in the pro cess. CNx films were grown with the N-2 concentration ranging between 1 and 25%. The effect of various N-2 concentrations on the interface states is i nvestigated in the present work. The interface states were characterized by admittance spectroscopy on metal-insulator-semiconductor (MIS) devices cre ated by the deposition of A1 contacts. The density of interface states (D-i t) and the corresponding time constants were obtained by the conductance te chnique. The D-it was found to extend between 5.5 x 10(12) and 2.0 x 10(13) eV(-1) cm(-2) depending on the N-2 concentration. Annealing at 350 degrees C reduced these values. Typical values for the time constants were around 10(-4) s indicating that the traps are located close to the silicon midgap. (C) 2000 Elsevier Science S.A. All rights reserved.