Studies of Phosphorus Pile‐Up at the Si ‐ SiO2 Interface Using Auger Sputter Profiling

Abstract

We have used Auger sputter profiling to investigate in detail the pile-up of phosphorus at the Si-SiO2 interface, which occurs during thermal oxidation of heavily doped silicon. We find that, in the early stages of oxidation, the interracial region acts as a sink for phosphorus. As oxidation proceeds, the "pile-up " within 50A of the interface saturates and the phosphorus concentra-tion in the silicon near the interface begins to rise. High temperature nitrogen anneals had little effect on the pile-up, indicating that existence of the pile-up cannot be explained by a simple diffusion mechanism. We also observed the pi le-up to be greatly diminished in a heavily boron-compen-sated sample. We discuss possible mechanisms which may be responsible for this effect. During the thermal oxidation of heavily phosphorus-doped silicon, the phosphorus, which is relatively in-soluble in SiO2, is rejected by the oxide and pushed