High-Robustness and Low-Capacitance Silicon-Controlled Rectifier for High-Speed I/O ESD Protection

A high-robustness and low-capacitance clamp for on-chip electrostatic discharge (ESD) protection is developed. The low capacitance is obtained by mitigating the capacitance associated with the lightly doped n-well/p-well junction. In addition to minimizing the capacitance, the high ESD robustness is achieved by optimizing independently within the same structure a silicon-controlled rectifier and a diode for the forward and reverse conduction processes, respectively. The new clamp with an area of
$\hbox{50} \times \hbox{10} \ \mu\hbox{m}^{2}$
is able to handle an ESD current in excess of 1.5 A, whereas the capacitance at zero bias is kept at 94 fF.