AN EXPERIMENTAL-STUDY OF SIOXNY SI INTERFACES PREPARED BY RAPID THERMAL-PROCESSING - EVIDENCE FOR 2 GROUPS OF INTERFACE STATES/

Three types of MIS capacitors are prepared by rapid thermal processing of n-Si: rapid thermal oxidation (RTO), rapid thermal oxidation follo wed by rapid thermal nitridation (RTN) in N2O, and rapid thermal oxyni tridation in N2O (RTON) at temperatures of 1100 to 1150 degrees C. The resulting densities of interface states above the midgap are reconstr ucted from measurements of charge transient spectroscopy (QDLTS) and t he feedback charge C-V method (FCM) of Mego. The midgap-level density is assessed from quasistatic C-V measurements, while the related surfa ce generation velocities can be deduced from the well-known C-t method of Zerbst. The QDLTS and FCM data point to a superior SiOxNy/Si inter face quality after the two-step (RTO + RTN) processing. Contrary to th is, a minimum density of the midgap levels is found in devices prepare d by the RTON procedure. The surface generation velocity of minority c arriers (holes) seems to be insensitive to the type of processing, bei ng in the 10(-)4 ms(-1) range. The resolved two branches of interface states may be of different origin and are to be treated separately. Fi nally, in the samples prepared by the RTON a discrete trap level at E( c) - E(t) approximate to 0.34 eV with a capture cross section of 1.6 x 10(-15) cm(2) can be resolved, in addition to the two branches of int erface states distributed in energy.