Millisecond annealing induced by atmospheric pressure thermal plasma jet irradiation and its application to ultra shallow junction formation

Abstract

We have developed millisecond annealing technique using an atmospheric pressure DC arc discharge thermal plasma jet (TPJ). Noncontact monitoring of wafer surface temperature is performed on the basis of transient reflectivity of silicon wafer observed during TPJ irradiation. As and B implanted silicon wafers were annealed and the impurity activation was investigated. In the case of As⁺-implanted samples, efficient dopant activation was observed at a temperature higher than 1000 K, while it was observed at a temperature higher than 1400 K in the case of B-implanted samples. The sheet resistance (RS) of B-implanted samples monotonically decreases with temperature, and no significant dependence on heating rate (Rh) or cooling rate (Rc) is observed. On the other hand, As⁺-implanted samples show significant dependence of RS on Rh and Rc. We have performed TPJ annealing on an As2⁺-implanted sample, and obtained an ultrashallow junction (USJ) with a junction depth (Xj) of 11.9 nm and a RS of 1095 Ω/sq. B USJ is also obtained with a Xj of 23.5 nm and a RS of 392 Ω/sq. Precise control of Rh and Rc in addition to annealing temperature is quite important for achieving highly efficient doping in USJ.