Abstract
In this study the impact of the defect tails generated by germanium implantation into n-type silicon wafers on the deep energy states, the doping profiles and mobilities, are investigated. 100 mm (100) silicon wafers with a base doping concentration of 3×1015/cm3 have been Implanted with 80 keV germanium on the Danfysik DF1090 high current implanter using instantaneous current density of 5 μA/cm2-95 μA/cm2, which correspond to power loading values of 0.4 and 7.6 W/cm2 respectively. Channelling Rutherford Backscattering analysis of a wafer implanted with 1×1016 Ge/cm2 and a dose rate of 80 μA/cm2 indicates a defect tail extending to 0.65 μm compared with 0.35 μm from a similar implant using 20 μA/cm2. Deep Level Transient Spectroscopy (DLTS) measurements of samples implanted with 3×1014 Ge/cm2 followed by a regrowth anneal of 700 °C for 20 mins reveal a high concentration of deep levels beyond the projected range of germanium of 58 nm at depths extending from 0.15 μm to depths greater than 0.4 μm. The main peak indicate a deep level at 0.35 eV. The increase in the dose rate from 5 μA/cm2 to 95 μA/cm2 is accompanied by a 5 times reduction of the 0.35 eV trap concentration. This difference could be attributed to the dynamic annealing effects during the implant using 95 μA/cm2.