An anti-snapback circuit technique for inhibiting parasitic bipolar conduction during EOS/ESD events

In this work, an anti-snapback circuit technique called Source Injection (SI) is presented for the first time ever, which is shown to inhibit parasitic bipolar conduction during EOS/ESD events. The design is presented for a fully salicided, 0.25 mu m, 35 Angstrom/70 Angstrom dual gate oxide, thin-epi, retrograde nwell, bulk CMOS technology. The technique is shown to greatly extend the snapback voltage of NMOS devices in this technology, which are usually destroyed instantaneously once snapback occurs. The design also has the benefit of controlling output buffer impedances for impedance matching to transmission-line loads. The design is fully compatible with the baseline process and has been shown to increase ESD robustness for positive discharge stress modes, which are the most difficult to protect for in epi processes. An increase of >1.5kV is demonstrated for HBM, an increase of 550V is shown for MM, and an increase of >550V is exhibited for CDM, over non-SI and SI iopad designs, respectively.