US Patent 7601991 On-chip structure for electrostatic discharge (ESD) protection

A complementary SCR-based structure enables a tunable holding voltage for robust and versatile ESD protection. The structureare n-channel high-holding-voltage low-voltage -trigger silicon controller rectifier (N-HHLVTSCR) device and p-channel high-holding-voltage low-voltage -trigger silicon controller rectifier (P-HHLVTSCR) device. The regions of the N-HHLVTSCR and P-HHLVTSCR devices are formed during normal processing steps in a CMOS or BICMOS process. The spacing and dimensions of the doped regions of N-HHLVTSCR and P-HHLVTSCR devices are used to produce the desired characteristics. The tunable HHLVTSCRs makes possible the use of this protection circuit in a broad range of ESD applications including protecting integrated circuits where the I/O signal swing can be either within the range of the bias of the internal circuit or below/above the range of the bias of the internal circuit.