Benefits of Damage Engineering for PMOS Junction Stability

As CMOS devices continue to shrink, the formation of ultra shallow junction (USJ) in the source/drain extension remains to be a key challenge requiring high dopant activation, shallow dopant profile and abrupt junctions. The next generations of sub nano-CMOS devices impose a new set of challenges such as elimination of residual defects resulting in higher leakage, difficulty to control lateral diffusion, junction stability post anneal and junction formation in new materials. To address these challenges for advanced technological nodes beyond 32 nm, it is imperative to explore novel species and techniques. Molecular species such as Carborane (C2B10H12), a novel doping species and a promising alternative to monomer Boron is of considerable interest due to the performance boost for 22 nm low power and high performance devices. Also, to reduce residual defects, damage engineering methodologies have generated a lot of attention as it has demonstrated significant benefits in device performance. Varian proprietary techniques to perform implants at cold temperatures (PTC II) have demonstrated lower junction leakage, enhanced activation, reduced dopant diffusion and less dopant deactivation due to the reduction of self-interstitial atoms present at the end-of-range (EOR) with low implant temperatures. In this paper, for the first time, there is a comprehensive study of the effect of implant temperature on defect engineering affecting deactivation/reactivation, and it is well established in this paper that colder the implant temperature the better it is for damage engineering with reduced EOR defects and better amorphization. The effect has been studied over a wide range of implant temperature. To understand any difference in deactivation between molecular and monomer Boron and to provide direct comparison equivalent Boron implants, co-implanted with Carbon were also studied. Implants with wide range of temperatures are implemented using PTC II. This paper will also show how damage reduction correlates with optimum junction formation and stability.