DEPENDENCE OF MECHANICAL STRENGTH OF CZOCHRALSKI SILICON-WAFERS ON THE TEMPERATURE OF OXYGEN PRECIPITATION ANNEALING

Dependence of mechanical strength of Czochralski silicon (CZ-Si) wafer s on the temperature of oxygen precipitation annealing has been studie d both experimentally and theoretically. Thermal stress was applied to CZ-Si wafers after oxygen precipitation annealing at 1100 degrees C o r 1000 degrees C after preannealing at 800 degrees C. The warpages and the densities of slip dislocations in the wafers annealed at 1100 deg rees C are much higher than those in the wafers annealed at 1000 degre es C, nevertheless each precipitate density is almost equal. Transmiss ion electron microscopy observations of the 1100 degrees C samples sho wed that both platelet and polyhedral precipitates were generated, but very few of these precipitates actually generated punched-out disloca tions. In contrast, in the 1000 degrees C samples, only platelet preci pitates were generated, many of which generated punched-out dislocatio ns. Further studies showed that slip dislocations formed only from pla telets which did not punch out dislocations, i.e., slip dislocations f ormed only in the 1100 degrees C samples. The mechanism of the generat ion of slip dislocation by oxide precipitates is discussed With calcul ated results of the system energy change due to slip dislocation gener ation.