Behaviour and effects of fluorine in annealed n+ polycrystalline silicon layers on silicon wafers

摘要

A comprehensive study is made of the behaviour and effects of fluorine in n+ polysilicon layers. Sheet resistance, TEM and SIMS are used to obtain quantitative data for the breakup of the interfacial oxide, the epitaxial regrowth of the polysilicon and the fluorine and arsenic distributions. The fluorine significantly increases both the initial oxide breakup and the initial polysilicon regrowth. It also produces inclusions in the layer which can affect the subsequent polysilicon regrowth and the arsenic distributions. Three regrowth stages and two regrowth mechanisms are distinguished and interpreted and a value of approximately 6x1011cm2s-1 is deduced for the effective diffusivity of fluorine in polysilicon at 950°C.