Impact of heavy doping with donors on CZ silicon properties

Abstract

This work reports a detailed characterization of 200 mm silicon wafers heavily doped with antimony, arsenic or phosphorus, in the range 1–50 mΩ•cm, corresponding to 7 × 1019 – 2 × 1017 at·cm−3. Grown‐in voids (revealed as light‐scattering objects on the wafer surface) are shown to be controlled by the dopant concentration. For As‐doped wafers the voids show a pronounced increase in their density up to [As] = 1.7 × 1019 cm−3, but at higher concentration the void density drops sharply. The same behaviour was found for P‐doped wafers where a sharp drop occurs at [P] > 2.9 × 1019 cm−3. In the case of antimony, the explored concentration range was sufficient only to reveal the increasing side of the curve. AFM characterization confirmed the morphology of voids as also seen in lightly‐doped silicon. Both single and double voids were observed. The oxygen precipitate density (BMD) was measured after submitting the wafers to a stabilization and growth thermal cycle. Overall it ranges from 1 × 106 ( = detection limit) to 1.5 × 1010 counts/cm3. The relationship between BMD density and oxygen concentration follows the classical S‐shaped curve, indicating that also for heavily doped N+ type wafers the oxygen content plays a major role on BMD formation.