Failure Analysis of JFET IC by Corona Charging.

Previous applications of corona discharges for analysis of failure due to surface ion motion and for design evaluation have generally involved high voltage devices operating above one hundred volts. Devices operating at lower voltages, however, also may be subject to surface ion failure mechanisms, as described here. A corona discharge controlled by a grid electrode is shown to be a sensitive technique for evaluating devices operating at tens of volts. A procedure for calibrating the surface voltage of the device after corona charging is also described. In the application to a JFET IC, the technique confirmed the susceptibility of defective devices to net surface charge and demonstrated the effectiveness of the process changes instituted to prevent failure due to surface charge accumulation. The technique also showed that a device is ``good'' by design (immune to contamination) and not because its surface is free of ions.