A new diffusion algorithm during oxidation which can handle both phosphorus pile-up and boron segregation at Si-SiO/sub 2/ interface

A new simulation algorithm during oxidation which can handle both the phosphorus (P) pile-up and the boron (B) segregation has been proposed. In this algorithm, an interlayer (IL) is placed at Si-SiO/sub 2/ interface in order to have P pile-up. The interface is moved according to the Si consumption during a time step and a new interface is generated at the end of the consumed Si region. A region between an old and a new IL is defined as a transition layer (TL). A diffusion equation is solved inside the TL using local effective diffusion constants in order to fully redistribute the impurities. By using this "diffusion in the TL", the P piled up in the old IL may move through the TL and re-piles up into the new IL, and B segregation can be simulated accurately. The V/sub th/-V/sub sub/ characteristics of an actual buried channel pMOSFET which is simulated using the proposed algorithm agrees well with the experiment.