Lateral SCR devices with low-voltage high-current triggering characteristics for output ESD protection in submicron CMOS technology

摘要

A high-current PMOS-trigger lateral SCR (HIPTSCR) device and a high-current NMOS-trigger lateral SCR (HINTSCR) device with a lower trigger voltage but a higher trigger current are proposed to improve ESD robustness of CMOS output buffer in submicron CMOS technology. The lower trigger voltage is achieved by inserting short-channel thin-oxide PMOS or NMOS devices into the lateral SCR structures. The higher trigger current is achieved by inserting the bypass diodes into the structures of the HIPTSCR and HINTSCR devices. These HIPTSCR and HINTSCR devices have a lower trigger voltage to effectively protect the output transistors in the ESD-stress conditions, but they also have a higher trigger current to avoid the unexpected triggering due to the electrical noise on the output pad when the CMOS ICs are in the normal operating conditions. Experimental results have verified that the trigger current of the proposed HIPTSCR (HINTSCR) is increased up to 225.5 mA (218.5 mA). But, the trigger voltage of the HIPTSCR (HINTSCR) remains at a lower value of 13.4 V (11.6 V). The noise margin against the overshooting (undershooting) voltage pulse on the output pad, without accidentally triggering on the HINTSCR (HIPTSCR), can be greater than VDD+12 V (VSS -12 V). These HIPTSCR and HINTSCR devices have been practically used to protect CMOS output buffers with a 4000-V (700-V) HEM (MM) ESD robustness but only within a small layout area of 37.6/spl times/60 /spl mu/m/sup 2/ in a standard 0.6-/spl mu/m CMOS technology without extra process modification.