INFLUENCE OF TIAS PRECIPITATE FORMATION ON MORPHOLOGY DEGRADATION OF THE TISI2/AS-DOPED POLYSILICON SYSTEM

Abstract

The formation of TiAs precipitates between TiSi2 with C54 structure and arsenic-doped polysilicon and the influence of TiAs and silicon resulting from the reaction TiSi2 + As --> TiAs + 2Si on layer morphology degradation have been studied. The formation of TiAs precipitates has been revealed by X-ray diffraction in a sample annealed at 900-degrees-C for 60 min and a sequential increase in sheet resistance with increasing annealing time has been observed. Cross-sectional scanning electron microscopy of the sample annealed for 60 min has shown irregular-shaped protrusions. Point analyses by Auger electron spectroscopy and cross-sectional transmission electron microscopy of the same sample have shown the presence of TiAs precipitates and extra silicon near the TiSi2 - polysilicon interface under the protrusion area. From the results it has been found that TiAs precipitates and extra silicon resulting from the reaction TiSi2 + As --> TiAs + 2Si lead to morphology degradation of this system.