The redistribution of iron implanted into the oxide layer of silicon-on-insulator structures has been measured using the secondary ion mass spectroscopy technique after annealing at 900–1050 °C. Iron diffusion has been found to be much faster in the oxide prepared by the separation-byimplantation-of-oxygen (SIMOX) procedure compared to the thermally grown oxide in the bonded and etched-back structures. In the latter case, the Fe diffusivity exhibits a thermal activation with an energy of 2.8 eV, confirming the literature data on silica glass. In the SIMOX oxide, the diffusivity depends only weakly on temperature, indicative of an essentially activation-free diffusion mechanism. Gettering of Fe at below-the-buried-oxide defects in SIMOX wafers has been observed. No iron segregation has been detected at the SiO2–Si interfaces.

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Using experimental and numerical simulation analysis the breakdown voltage walkout effect has been studied in 40 V ESD protection devices based on extended drain MOS devices implemented in a 5 V CMOS process. A similar effect has been observed in 100 V and 24 V BiCMOS processes. The physical mechanism of this effect is revealed as the result of hot electron capture in the thick field oxide of the extended drain region. To address this, a method to reduce the walkout effect in high voltage ESD devices is proposed and experimentally validated.