ESD protection for output pad with well-coupled field-oxide device in 0.5-/spl mu/m CMOS technology

A well-coupled field-oxide device (WCFOD) is first proposed to effectively improve Electrostatic Discharge (ESD) robustness of the output pad in a 0.5-/spl mu/m CMOS process. ESD-transient voltage is coupled to the bulk of field-oxide device through a parasitic capacitor to trigger on the lateral bipolar action of the field-oxide device. This WCFOD has been practically implemented in a 256-K high-speed SRAM product to sustain HBM ESD stress up to 6500 V.