One of the major challenges towards scaling down of the electronic devices to the nm-regime is attaining controlled doping of semiconductor materials with atomic accuracy. At such small scales, the various existing technologies suffer from a number of setbacks, including an inability to achieve junction abruptness down to nm range, stochastic distribution of the dopant atoms, crystal damage, and incompatibility with nanomaterials. In this work, We report the formation of sub-5 nm ultrashallow junctions in 4â€ Si wafers enabled by the molecular monolayer doping of phosphorous and boron atoms and the use of conventional spike annealing. The junctions are characterized by secondary ion mass spectrometry and non-contact sheet resistance measurements. It is found that the majority (~70%) of the incorporated dopants are electrically active, therefore, enabling a low sheet resistance for a given dopant areal dose. The wafer-scale uniformity is investigated and found to be limited by the temperature homogeneity of the spike anneal tool used in the experiments. Notably, minimal junction leakage currents (<1 uA/cm2) are observed which highlights the quality of the junctions formed by this process. The results clearly demonstrate the versatility and potency of the monolayer doping approach for enabling controlled, molecular-scale ultrashallow junction formation without introducing defects in the semiconductor.
Project end date: 08/11/09