Laser Scanning Tomography: A Non Destructive Qualification Test for Semiconductors

Among the various physical approaches of the semiconductor wafer defect characterization a special attention is to be payed to the infra red imaging techniques which are prefectly non destructive Recent developement of the Laser Scanning Tomography will be emphasized because it gives highly resolved images of decorated dislocations and microprecipitates Three dimensional exploration of the material is allowed with a large accuracy and possibly close to the active regions of the circuits. Observation of micro defects are reviewed especially concerning GaAs materials of various origins and constitutions. Microscale images enable us to reveal very small scatterers even if their sie is much smaller than the optical diffraction limit. Results obtained on other semi conductors such as InP, CdTe or Si will also be reviewed : most of the conventional semiconductors are relevant to this powerful technique which is a unique means of investigation.