Study to establish data sheets for CMOS devices in space and nuclear applications

Threshold voltage shifts from RCA Series 4000 CMOS hex inverters, irradiated to dose levels up to 3 megarads (SiO2) were measured during and after irradiation. The asymptotic values were found to be the same whether the exposure was carried out in small increments or all at once. Three different phenomena (hole trapping, negative interface state formation, and electron injection) occurring with different time constants, appear to be responsible for the time-dependent response of the N-channel threshold voltage. Hole trapping seems to be the dominant effect in the P-channel. For hardness assurance testing, space applications require only the asymptotic measurements; nuclear applications also require measuring the minimum value, as a function of time, of the threshold voltage.