Ultrashallow (<10nm) p+∕n junction formed by B18H22 cluster ion implantation and excimer laser annealing

In order to form an ultrashallow p+∕n junction, incorporation of a top amorphous-silicon (a-Si) layer is necessary so as to avoid channeling and to fully activate the dopant. Conventional ultrashallow junction processes require two-step implantation such as preamorphization by Si+ or Ge+ implantation and ultralow (<0.5keV) energy B+ implantation. In this report, the authors investigate B18H22+ implantation. Due to the heavy mass of cluster ions, one-step ion implantation at 5keV readily forms a 5-nm-thick a-Si layer and an ultrashallow junction without B channeling. By employing excimer laser annealing, the authors have obtained a shallow junction depth (∼9nm) and low Rs (∼830Ω∕◻).