Differential Hall Effect Metrology (DHEM) Sub-Nm Profiling and Its Application to Dopant Activation in n-Type Ge

摘要

Accurate characterization of dopant activation at the near-surface region is essential to understanding and developing doping schemes to achieve low contact resistance for Ge NMOS. Differential Hall Effect Metrology (DHEM) was employed to study dopant activation with sub-nm resolution on n-type Ge layers epitaxially grown on Si substrates. Two different capping layers, Al_2O_3 and SiO_2, were deposited on Ge and the samples were implanted with Sb and P, then subsequently annealed. Carrier concentration depth profiles as measured by DHEM showed one order of magnitude higher dopant activation at the surface for the SiO_2 capped samples. SIMS measurements indicated Al in-diffusion for the Al_2O_3 capped films, suggesting a highly defective Ge surface. This indicates that annealing is insufficient to repair damage caused by ion implantation, necessitating alternative approaches to achieve high dopant activation in n-type Ge.