Efficient Output Esd Protection Of High-speed Sram Ic With Well-coupled Technique In Sub-pm Cmos Technology

A yell-coupled field-oxide device (WCFOD) has been proposed to effectively improve ESD robustness of output buffers in a 0.5-pm CMOS process. ESD-transient voltage is coupled to the bulk of the field-oxide device through a parasitic capacitor to trigger on the lateral bipolar action of the field-oxide device. A 0.5-pm high-speed 256K SRAM product had been fabricated with this WCFOD to practically verify the excellent efficiency for output ESD protection. The HBM ESD failure voltage of this SRAM product has been improved up to above 6.5KV without using any extra ESD-modification process, whereas the original output buffer just can sustain the HBM ESD stress of 1KV only.