Guardwall structures for esd protection

Abstract

A semiconductor circuit for protecting an I/O pad against ESD events comprising a pMOS transistor (510) in a first n-well (511) having its source connected to Vdd and the first n-well, and its drain connected to the I/O pad; the transistor has a finger-shaped contact (513) to the first n-well. Further a finger-shaped diode (520) with its cathode (521) located in a second n-well and connected to the I/O pad, and its anode connected to ground. The anode is positioned between the cathode and the first n-well, whereby the finger-shaped anode and cathode are oriented approximately perpendicular to the finger-shaped transistor n-well contact. Further a third finger-shaped n-well (551) positioned between the first n-well and the diode, the third n-well connected to ground and approximately perpendicular to the first n-well contact, acting as a guard wall (550).

Dependencies are inferred from the claim text.