Failure Analysis

Targeted failure analysis as applied in microelectronics is usually carried out in a five-step sequence (Table A): First is fault validation, followed by localizing the defect as accurately as possible. Then the defect location is prepared and traced for analysis; the nature of the defect is determined and, finally, an investigation of its root causes is initiated. The crucial step in this sequence is defect localization. The more accurate this is done, the less is to be spent in the subsequent examination procedure.

There are active and passive procedures for fault characterization and defect localization. Photon emission microscopy is a passive technique because it works without external stimulation, for instance by a laser source. PEM is often complemented by photon emission spectroscopy (PES) if defect location and also the emitted spectrum, especially the infrared spectrum, are of importance.

The short-wave infrared is of special interest in the case of examining silicon semiconductors, because their bandgap energy of 1.12eV between conducting and valence bands, which is of crucial importance for the recombination mechanism, equals a recombination emission wavelength of around 1107nm.

Photon emission is generally produced by a forward or reverse biased pn junction, a transistor in saturation or by dielectric breakdown. Depending on the stimulation mechanism of the charge carriers involved the emission spectrum can be fairly wide.