Optimization of standard As ion implantation for NMOS Si bulk FinFETs extension

Abstract

Extension doping for FinFETs is more difficult compared with planar devices due to fin geometry. An amorphization problem for NMOS FinFETs and photo resist shadowing for CMOS FinFETs are pointed out when standard ion implantation (I/I) is used. Amorphization of the fin results in poor recrystallization during subsequent annealing. The whole fin can easily be amorphized when As is implanted at high dose to form source and drain extensions, especially for narrow FinFETs. Fin sputter erosion can be seen when narrow tilt angle standard As I/I is employed. These are serious concerns because they degrade the device performance and increase the variability. In this study, the improvement of the fin amorphization and the fin sputter erosion of standard I/I is reported. The optimization procedure and the optimized result of standard I/I are discussed. In addition, the difference between the device performance for 7 degrees tilt As I/I and the optimized 30 degrees tilt As I/I, which is almost -conformal doping, has been quantified.