Evaluation of High Voltage ICs by Corona Charging

Many high voltage integrated circuits are sensitive to surface ions. The accumulation of net charge to these ions over certain regions of the device results in decreased breakdown voltage or increased leakage current. The deliberate deposition of surface ions on a device from at atmospheric pressure discharge can be used to determine the surface ion sensitivity of devices. This technique is described and is shown to be useful in evaluating device designs and process variations and in failure analysis. The effects on surface ion sensitivity of variations in dielectrically-isolated tub depth, of field plate dimension, and of length of field-grading diffusions have been examined using this method. Three examples of this technique for failure analysis are also presented.