Breakdown voltage walkout effect in ESD protection devices

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.