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-SiC implanted with 3 x 10(15) cm(-2) nitrogen ions to a depth of 2800 Angstrom, the minimum sheet resistance observed is 534 Omega/rectangle. The minimum sheet resistance in 4H-SiC implanted with 4 x 10(15) cm(-2) phosphorus ions 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 resistances are observed following anneals at 1700 degrees C far nitrogen and phosphorus samples. Lower temperature anneals produce sheet resistances which decrease monotonically with increasing time of anneal. Overall, sheet resistances from phosphorus-implanted 4H-SiC are an order of magnitude below those measured from nitrogen implanted samples,The response of phosphorus to low-temperature annealing is significant;, and sheet resistances below 500 Omega/rectangle are achieved at 1200 degrees C. Activation of phosphorus is attempted in an oxidizing atmosphere with and without prior argon annealing. 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 about 20% compared to samples subjected solely to argon annealing, It is also found that, oxide rates are much higher over phosphorus implanted than over unimplanted 4H-SiC. Reasons for the disparity in sheet resistances between nitrogen and phosphorus implants, and for the difference in oxide growth rates are suggested.