LOCOS-induced stress effects on thin-film SOI devices

LOCOS-induced stress effects on thin-film SOI devices are investigated. We show that as the field oxide thickness increases, degradation (enhancement) of nMOSFET's (pMOSFET's) I-V characteristics becomes increasingly pronounced. The total degradation or enhancement of I-V characteristics can reach /spl sim/40% of drive current for devices under certain processing conditions. Estimated stress results using four-point bending measurement show that the stress level on the silicon film is of order 1200 MPa for devices with /spl sim/40% of I-V degradation/enhancement. We attribute the stress phenomenon to the volumetric expansion of field oxide during the LOCOS process.