Charge relaxation in nitrided and non-nitrided sputtered oxide

The charge relaxation of nitrided silicon oxide was studied in an MOS struc ture. Oxynitrides were formed by reactive sputtering in an Ar/O-2/N-2 plasm a from a silicon oxide target. The nitrogen mixing ratio was varied from 0% to 20%, with the argon mixing ratio kept at 80%. The electrical stress was performed with injection from an aluminium gate and the relaxation of stre ss-induced charge under floating and gate bias conditions was monitored via mid-gap voltage and interface states density measurement in a time interva l from 1 min to about four months. A trend that nitrided oxides experience more relaxation of mid-gap voltage was observed while non-nitrided oxide ha d the largest relaxation of interface states density in the same time inter val. We suggest that relaxation under applied bias due to the stress-induce d charge is, in part, due to the slow states. (C) 1999 Elsevier Science B.V . All rights reserved.