The concentration profiles of B which had been diffused, from polycrystalline material, into underlying monocrystalline material were analyzed by means of secondary ion mass spectrometry. The co-diffusion of As and B was studied in an emitter and extrinsic base configuration. Simulations indicated that diffusion of the dopant at the lowest fluence was slowed much more by in-depth inhomogeneous grain growth that was induced by amorphization and annealing, than by a built-in electric field. It was assumed that the dopant, at the highest doses, saturated the grain-boundary traps. This was true of B. In a first poly-Si layer, the diffusivity (table 31) could be described by:

D (cm2/s) = 1.9 x 10-2exp[-2.5(eV)/kT]

In a second poly-Si layer, the diffusivity could be described by:

D (cm2/s) = 3.2 x 10-5exp[-1.86(eV)/kT]

Dopant Redistribution during Rapid Thermal Annealing in a Self-Aligned Polysilicon Emitter Bipolar Structure Compatible with a Complementary Metal-Oxide-Semiconductor Technology. A.Merabet, C.Gontrand: Physica Status Solidi A, 1994, 145[1], 77-88

Table 30

Diffusion Parameters for B in Si, as a Function of the B Composition