3-LEVEL CHARGE-PUMPING STUDY OF RADIATION-INDUCED DEFECTS AT SI-SIO2 INTERFACE IN SUBMICROMETER MOS-TRANSISTORS

The charge pumping response of interface traps and near-interfacial ox ide traps (border traps) induced by Co-60 gamma rays in submicrometer (0.5 mu m channel length) metal-oxide-semiconductor transistors has be en studied. Using an improved three-level charge pumping technique, th e energy distribution of interface trap parameters (emission times, ca pture cross-sections and interface state density) has been determined after irradiation in both the upper and lower parts of the silicon ban d gap on n-channel devices. The influence of border traps on three-lev el charge pumping measurements is demonstrated for the first time. Goo d agreement has been found between standard charge pumping and three-l evel charge pumping characteristics in terms of 'breakpoint frequency' at which the charge recombined per cycle deviates from the fast inter face state response, The distance of border traps from the interface h as been estimated to be similar to 15-20 Angstrom from a trap-to-trap tunneling model. In addition, a new technique is presented based on th ree-level charge pumping measurements to determine a border trap distr ibution in the silicon band gap.