ELECTRICAL AND STRUCTURAL-PROPERTIES OF ULTRATHIN SIO2 GATE DIELECTRICS PREPARED UNDER VARIOUS CONDITIONS

We have fabricated ultrathin SiO2 layers between 5 and 10 nm. Conventional thermal and rapid thermal oxide forming processes were applied, as well as a low temperature chemical vapor deposition (CVD) process. With these dielectrics, single layers have been produced for structural investigations by infrared (IR) absorbance spectroscopy. The IR-spectra of the thermal oxides and the postannealed CVD-oxide revealed nearly the same vibrational properties. Metal oxide semi-conductor devices such as capacitors and field effect transistors (FETs) have been fabricated with these dielectrics. Breakdown measurements revealed a reduced high field breakdown voltage with a broadened distribution for CVD layers as compared to the results obtained for thermal oxides. This effect was reduced with decreasing thickness. From transfer characteristics and charge pumping measurements on FETs, no considerable difference in the number of fixed oxide charge and interface trapped charge density was observed for all oxides. The device properties appear to be more strongly effected by substrate dopant concentrations and the oxide thickness than by the intrinsic properties of the oxide.