Diode-based ESD concept for DEMOS protection

摘要

The invention relates to an ESD protection circuit for an integrated circuit including a drain-extended MOS device and an output pad that requires protection. The ESD protection circuit includes a first diode coupled to the output pad and to a bias voltage rail, a second diode coupled to the output pad and to another bias voltage rail, and an ESD power clamp coupled between the two bias voltage rails. The ESD power clamp is formed as a vertical npn transistor with its base and emitter coupled together. The collector of the npn transistor is formed using an n-well implantation and a DEMOS n-drain extension to produce a snapback-based voltage limiting characteristic. The diodes are formed with a lightly p-doped substrate region over a buried n-type layer, and a p-well implant and an n-well implant separated by intervening substrate. A third diode may be coupled between the two bias voltage rails.