HIGH-SENSITIVITY DEFECT EVALUATION BY A NEW PREFERENTIAL ETCHING TECHNIQUE FOR HIGHLY AS-DOPED SI CRYSTALS

A high-sensitivity preferential etching technique is presented to eval uate crystal defects in a highly As-doped silicon crystal with a resis tivity lower than 0.01 Omega.cm. For highly doped n-type Si, a convent ional preferential etching technique, such as Secco etching, Wright et ching or Dash etching becomes less useful because of a significant dec rease in defect detection sensitivity. The new method is quite sensiti ve to dislocations, stacking faults and oxygen precipitates in highly As-doped crystals with a surface of either (111) or (100). In this met hod, copper is first decorated at the defect site, then the defect is preferentially etched by a dilute alkaline solution. The technique thu s offers us a sensitive and Cr-free method, attractive from an environ mental aspect. A correlation between the laser scattering method is al so obtained for the oxygen precipitate density.