FABRICATION OF LARGE-AREA CCD DETECTORS ON HIGH-PURITY, FLOAT-ZONE SILICON

One of the problems with the fabrication of radiation detectors on hig h-purity, float-zone silicon is that such material is more susceptible to the formation of dislocations during high-temperature processing t han Czochralski-grown material. We describe here the impact of disloca tions on the electrical performance of a 1024 x 1024-pixel CCD imager that we have developed as the principal detector for the Advanced X-ra y Astrophysical Facility. A technique has been developed to determine both the location (to within one gate of a pixel) and the trapping par ameters of a dislocation. The processes giving rise to dislocation for mation and propagation will be discussed, and techniques will be descr ibed for maintaining wafers free of dislocations even after the many h igh-temperature steps necessary for CCD fabrication.