FABRICATION OF LARGE-AREA SI CYLINDRICAL DRIFT DETECTORS

The processing of an advanced silicon detector, a large area cylindric al drift detector (CDD), was carried out in the BNL Instrumentation Di vision Fabrication Facility. The double-sided planar process technique was developed for the fabrication of the CDD. Important improvements of the double-sided planar process in this fabrication include the int roduction of an A1 implantation protection mask and implantation of bo ron through an 1000 angstrom oxide layer in the step of opening the p- window. Another important aspect of the design of the CDD is the struc ture called ''river,'' which allows the current generated on the Si-Si O2 interface to ''flow'' into the guard anode, and thus minimize the l eakage current at the signal anode. The test result showed that for th e best detector most of the signal anodes have leakage currents of abo ut 0.3 nA/cm2.