Behavior and effects of fluorine in annealed n(+) polycrystalline silicon layers on silicon wafers

A comprehensive study is made of the behavior and effects of fluorine in n( +)-polysilicon layers. The polysilicon is deposited in a conventional low p ressure chemical vapor deposition furnace on (100) silicon wafers, implante d with 1 x 10(16) cm(-2) F+ and 1 x 10(16) cm(-2) As+ and annealed at 850, 950, 1015, and 1065 degrees C. Sheet resistance, transmission electron micr oscopy (TEM), and secondary ion mass spectroscopy are used to obtain quanti tative data for the breakup of the interfacial oxide, the epitaxial regrowt h of the polysilicon layer, and the fluorine and arsenic distributions. The fluorine significantly increases both the initial oxide breakup (similar t o 8x) and the initial polysilicon regrowth. It also produces inclusions in the layer which can affect the subsequent polysilicon regrowth and the arse nic distributions. Three regrowth stages and two regrowth mechanisms are di stinguished and interpreted, and a value of similar to 6 x 10(-11) cm(2) s( -1) is deduced for the effective diffusivity of fluorine in polysilicon at 950 degrees C. The amounts of regrowth determined by TEM are compared with the corresponding changes in sheet resistance. The thermal budgets required to produce polysilicon layer regrowths of 1% and 50%, important for the pe rformance of polysilicon emitter bipolar transistors, are given. All the th ermal budgets are lower when fluorine is present. (C) 2000 American Institu te of Physics. [S0021-8979(00)01410-9].