Interface state analysis in MOS devices

A DLTS apparatus was set up in a computer-controlled version, which made possible the measurement of bulk traps by DDLTS and the measurement of interface traps by CC-DLTS (Constant Capacitance DLTS), which was newly developed. By CC-DLTS, an interface state density as low as Dsub(it)=3 x 108 cm-2 eV-1 could be resolved for the first time. The following measurement problems have been dealt with: Oxygen implantation in MOS structures showed little influence on stochiometry and interface state density after annealing; however, a number of bulk traps in Si in the interface region have been found, which are related to oxygen and the annealing of MOS structures. In MNOS structures, interface traps at the Si-SiO2 interface are observed and separated from traps in the nitride. IR-excitation of interface traps showed a low absorption cross-section sigmasub(n)0=10-19 cm2. The newly proposed VE-model can explain all the observed properties of interface traps. In ICs, an increased density of interface traps is observed at the boundary of microstructures. Interstitial Si generates bulk traps in Si at Esub(C) -0.07 eV and Esub(C) -0.49 eV which are identified for the first time in Si containing A-swirls and after oxygen-deficient oxidation in MOS structures. (orig.)