DOPANT REDISTRIBUTION DURING RAPID THERMAL ANNEALING IN A SELF-ALIGNED POLYSILICON EMITTER BIPOLAR STRUCTURE COMPATIBLE WITH A COMPLEMENTARY METAL-OXIDE-SEMICONDUCTOR TECHNOLOGY

Arsenic and boron concentration profiles, diffused from polycrystallin e silicon (polysilicon) into an underlying single crystalline silicon, are analyzed by secondary ion mass spectrometry. This bilayer is the basic structure of a self-aligned bipolar transistor, compatible with a complementary metaloxide-semiconductor; arsenic and boron codiffusio ns are studied in an emitter and extrinsic base configuration of bipol ar transistors. Rapid thermal annealings are performed to obtain shall ow junctions, with temperature and annealing plateau duration as param eters. Finally, the codiffusion process is investigated using simulati ons. It indicates that diffusion of the dopant at the lowest fluence i s slowed, much more because of the in-depth inhomogeneous grain growth induced by amorphization and annealing, than a built-in electric fiel d. Then, it should be assumed that the dopant at the highest dose satu rates the grain boundary traps. This hypothesis concerns essentially a rsenic, but also boron, to a less extent.