Mobility improvement of n-MOSFET's with nitrided gate oxide by backsurface Ar+ bombardment

Abstract

Low-energy (550 eV) argon-ion beam was used to bombard directly, the backsurface of nitrided n-MOSFET's after the completion of all conventional nMOS processing steps. The interface characteristics and inversion layer mobility of the MOS devices were investigated. The results show that, as bombardment time increases, interface state density and fixed charge density decrease first, and then the change slows down or even turns around. Correspondingly, the carrier mobility and drain conductance of the MOS devices are found to enhance first, and then saturate or turn around. Therefore, this simple technique, which is readily compatible with existing IC processing, is effective for restoring some of the lost device performance associated with gate-oxide nitridation.