Electrical behaviour associated with defect tails in germanium implanted silicon

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/spl times/10/sup 15//cm/sup 3/ have been implanted with 80 keV germanium on the Danfysik DF1090 high current implanter using instantaneous current density of 5 /spl mu/A/cm/sup 2/-95 /spl mu/A/cm/sup 2/, which correspond to power loading values of 0.4 and 7.6 W/cm/sup 2/ respectively. Channelling Rutherford Backscattering analysis of a wafer implanted with 1/spl times/10/sup 16/ Ge/cm/sup 2/ and a dose rate of 80 /spl mu/A/cm/sup 2/ indicates a defect tail extending to 0.65 /spl mu/m compared with 0.35 /spl mu/m from a similar implant using 20 /spl mu/A/cm/sup 2/. Deep Level Transient Spectroscopy (DLTS) measurements of samples implanted with 3/spl times/x10/sup 14/ Ge/cm/sup 2/ followed by a regrowth anneal of 700/spl deg/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 /spl mu/m to depths greater than 0.4 /spl mu/m. The main peak indicates a deep level at 0.36 eV. The increase in the dose rate from 5 /spl mu/A/cm/sup 2/ to 95 /spl mu/A/cm/sup 2/ 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 /spl mu/A/cm/sup 2/.