Effect of Si and He implantation in the formation of ultra shallow junctions in Si

Abstract

He, Si and B implantation are successively combined in order to produce ultra shallow junctions (USJs). Si is implanted at 180 keV to create a ‘vacancy-rich’ layer. Such a layer is however followed by a deeper interstitial rich one. He implantation is performed at a dose high enough (5 × 10 16 cm − 2 ) to create a cavity layer in Si sample. Eventually, B is introduced by low energy ion implantation. Since cavities are known to be sinks for self-interstitials (Is), they might be able to decrease the transient enhanced diffusion (TED) of B during the dopant activation annealing in all processes investigated in this study. The samples are divided in two groups (named S1 and S2) to check the benefits of defect engineering of each implantation element. Hence, sample 1 is first implanted with He, followed by cavity formation annealing and second with B. Si implantation is performed on S2 after cavity formation, and followed by B implantation in the same condition as S1. All samples are characterized by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM) and Hall effect measurements. Results show that, in all cases, boron TED is suppressed while working with a cavity layer created before activation annealing. This layer acts as an Is barrier. Finally, an USJ with a low junction depth ( X j = (13 ± 1) nm, determined at 10 18 cm − 3 boron level) is successfully realized.