Comparison of hot-carrier and radiation induced increases in base current in bipolar transistors

A comparison was made between hot-carrier stress induced and ionizing-radiation induced increases in the base current of bipolar linear microcircuit transistors from two process technologies. The comparison was made on the basis of a failure stress in seconds and a failure dose in rad(SiO/sub 2/) for a failure criterion of /spl Delta/I/sub B/=2 nA measured at an I/sub C/ of 1 /spl mu/A and V/sub CE/ of 5 V. Comparisons were made for several die on a single wafer, die from different wafers in a process lot, and die from split lots with various base oxide (also called spacer of screen oxide) hardening techniques applied. For each of these cases no correlation was found between stress-induced failure and ionizing-radiation induced failure. This result is consistent with modeling that shows different mechanisms for the degradation from hot-carriers and ionization. Hot-carrier stress induced damage is dominated by interface traps near the emitter-base junction periphery; whereas, ionizing-radiation induced damage is dominated by trapped positive charge in the base oxide over the extrinsic base region.<>