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.
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