Effects of hydrogen and carbon co-implantation on boron activation in germanium at low temperatures

Boron activation in germanium at low temperatures is crucial for enabling device stacking through back-end-of-line processes in the development of three-dimensional integrated circuits. In this study, hydrogen and carbon were co-implanted with boron to analyze the correlation between boron activation and damage induced by light ions. Differential Hall measurements revealed high activation efficiency near the surface for samples subjected to subamorphizing boron implantation, even without post-implantation annealing. The implantation sequence was found to strongly affect boron activation. During annealing at 500 °C, enhanced boron activation was observed when hydrogen implantation preceded boron implantation. Activation with the reversed implantation order did not exceed that achieved with boron implantation alone. Carbon co-implantation negatively impacted boron activation regardless of the implantation sequence. These results suggest that implantation damage generated by carbon ions adversely governed boron activation in germanium at low temperatures.