Latchup in CMOS Devices from Heavy Ions

Complementary metal oxide semiconductor (CMOS) microcircuits are inherently latchup prone. The four layer n-p-n-p structures formed from the parasitic pnp and npn transistors comprise a silicon controlled rectifier (SCR) which, if properly biased, may be triggered "ON" by electrical transients, ionizing radiation or a single heavy ion. This latchup phenomenon might cause loss of functionality or device burnout. For space applications cosmic ray heavy ions are a significant threat and the latchup of a CMOS circuit is a major system concern because of its catastrophic nature. This paper presents the results of testing nineteen different device types from six manufacturers to investigate their latchup sensitivity with argon and krypton beams. The parasitic npnp paths have been generally identified, and a qualitative rationale for latchup susceptibility and a latchup cross section is given for each device type. The correlation between bit-flip sensitivity and latchup susceptibility is also presented.