Energy distribution and depth profile in BF3 plasma doping

Plasma doping (PD) is intrinsically different from beam-line doping (BD), a s there is no mass filtering and the ion impact angle depends on the target geometry and plasma conditions. There are several ways to alter the impact energy of the incident ions and consequently the dopant depth profile when a BF3 plasma is used, because the plasma consists of ion species with diff erent masses, compositions, and charge states. The rise and fall times of t he sample voltage pulse also contribute to the overall energy distribution, since a long rise or fall time will increase the low-energy component. In this work, a particle-in-cell model is employed to simulate BF3 PD into sil icon under typical plasma doping conditions. The energy distributions of th e implanted B and F, as well as the effects of the rise/fall time and other factors are discussed. The PD profiles are compared to ED depth profiles a cquired by the TRIM simulation code. Our results reveal that the plasma con ditions and pulse shape can be altered to obtain the desired B depth profil e. In addition, PD gives rise to a low-energy surface component that is lar ger for a longer rise and fall time. (C) 2001 Elsevier Science B.V. All rig hts reserved.