OXYGEN INCORPORATION AND PRECIPITATION BEHAVIOR IN HEAVILY BORON-DOPED CZOCHRALSKI SILICON-CRYSTALS

To understand the effect of heavy boron-doping, p(+)-type (100) silicon crystals doped with boron in the order of 1X10(19) atoms cm(-3) (0.006-0.01 Omega cm) and a p-type (100) silicon crystal doped with boron in the order of 1 X 10(15) atoms cm(-3) (12-16 Omega cm) were grown in a Czochralski puller and studied. The oxygen contents in the p(+)-type crystals were determined by gas fusion analysis and shown to be on the average about 23% higher than those in a comparable p-type crystal. Etch pit features of oxide precipitates after a high-low-high annealing were generally different between the two types of silicon, and three distinct regimes of behavior about the critical boron and oxygen concentrations were identified. Those are: with resistivity greater than or similar to 0.007 Omega cm or oxygen concentration less than or similar to 30 ppma (Old ASTM), the oxide precipitate density, in the order of 10(10) cm(-3), is basically unaffected by heavy boron-doping and dependent on oxygen concentration; with resistivity less than or similar to 0.007 Omega cm and oxygen concentration greater than or similar to 37 ppma, however, large platelets, which are 10-15 mu m in size and in the order of 10(7) cm(-3) in density, are formed instead and completely gettered oxide precipitates. In a medium-oxygen range of about 28-30 ppma, both p- and p(+)-type (100) silicon wafers formed an ideal internal gettering structure, consisting of a well-defined precipitate-free zone (PFZ) to a depth of about 15 mu m from the surface and dense bulk oxide precipitates in the order of 10(10) cm(-3) below the PFZ, after a high-low-high annealing.