Phosphorus implantation into 4H-silicon carbide

Sheet resistances in nitrogen- and phosphorus-implanted 4H-SiC are measured to assess the time and temperature dependencies of this variable. in 4H-Si C implanted with 3 x 10(15) cm(-2) nitrogen ions to a depth of 2800 Angstro m, the minimum sheet resistance observed is 534 Omega/rectangle. The minimu m sheet resistance in 4H-SiC implanted with 4 x 10(15) cm(-2) phosphorus io ns to a depth of 4000 Angstrom is 51. Ohm/rectangle, a record low value for any implanted element into any polytype of Sie. Time-independent sheet res istances are observed following anneals at 1700 degrees C far nitrogen and phosphorus samples. Lower temperature anneals produce sheet resistances whi ch decrease monotonically with increasing time of anneal. Overall, sheet re sistances from phosphorus-implanted 4H-SiC are an order of magnitude below those measured from nitrogen implanted samples,The response of phosphorus t o low-temperature annealing is significant;, and sheet resistances below 50 0 Omega/rectangle are achieved at 1200 degrees C. Activation of phosphorus is attempted in an oxidizing atmosphere with and without prior argon anneal ing. A three-hour gate oxidation in wet O-2 at 1150 degrees C, followed by a 30 min argon anneal, produced a sheet resistance of 1081 Omega/rectangle. Oxidation after argon annealing caused sheet resistances to increase by ab out 20% compared to samples subjected solely to argon annealing, It is also found that, oxide rates are much higher over phosphorus implanted than ove r unimplanted 4H-SiC. Reasons for the disparity in sheet resistances betwee n nitrogen and phosphorus implants, and for the difference in oxide growth rates are suggested.