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

Abstract

A comprehensive study is made of the behavior and effects of fluorine in n ϩ -polysilicon layers. The polysilicon is deposited in a conventional low pressure chemical vapor deposition furnace on ͑100͒ silicon wafers, implanted with 1ϫ10 16 cm Ϫ2 F ϩ and 1ϫ10 16 cm Ϫ2 As ϩ and annealed at 850, 950, 1015, and 1065°C. Sheet resistance, transmission electron microscopy ͑TEM͒, and secondary ion mass spectroscopy are used to obtain quantitative data for the breakup of the interfacial oxide, the epitaxial regrowth of the polysilicon layer, and the fluorine and arsenic distributions. The fluorine significantly increases both the initial oxide breakup ͑ϳ8ϫ͒ 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 ϳ6ϫ10 Ϫ11 cm 2 s Ϫ1 is deduced for the effective diffusivity of fluorine in polysilicon at 950°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 performance of polysilicon emitter bipolar transistors, are given. All the thermal budgets are lower when fluorine is present.

The influence of BF/sub 2/ and F implants on the 1/f noise in SiGe HBTs with a self-aligned link base

“…It is possible that fluorine bubbles introduced into the buried field oxide during the BF implant might provide such a stress relief mechanism. Several researchers [29], [30] have shown the presence of inclusions when BF or F is implanted into polycrystalline silicon. These inclusions are related to the presence of the fluorine and it is postulated that they could contain gaseous [29], liquid, or solid material [30].…”

“…Several researchers [29], [30] have shown the presence of inclusions when BF or F is implanted into polycrystalline silicon. These inclusions are related to the presence of the fluorine and it is postulated that they could contain gaseous [29], liquid, or solid material [30]. To the authors' knowledge, no work has been reported on the properties of fluorine implanted into silicon dioxide.…”

Properties and benefits of fluorine in silicon and silicon-germanium devices

“…4b, the interfacial oxide layer has broken up and the bottom part of the polysilicon layer has epitaxially regrown. Detailed experiments [18] have shown that fluorine increases both the interfacial oxide break-up and the polysilicon regrowth rate.…”