Influences of postimplantation annealing conditions on resistance lowering in high-phosphorus-implanted 4H-SiC

The dependences of sheet resistance (R-s), sheet carrier concentration, and carrier mobility on postimplantation annealing temperature and time have been investigated in high-phosphorus (P)-implanted 4H-SiC using Hall effect measurement. At an annealing temperature below 1200degreesC, R-s decreases with an increase in annealing time due to the increases in sheet carrier concentration and carrier mobility, but the R-s available for SiC device applications is not obtained using even a long annealing time of 500 min. At an annealing temperature above 1600degreesC, annealing for 30 min causes the R-s to increase due to an evaporation of the implanted layer. In addition, the precipitation of P donors occurs by long-time annealing regardless of annealing temperature, thereby reducing sheet carrier concentration in implanted layer. On the contrary, a R-s of less than 100 Omega/sq has been achieved at a short annealing time of 30 s because of the extremely high electrical activation of P donors exceeding its solubility limit. Based on these results, it is revealed that the decrease in R-s of the P-implanted 4H-SiC is necessary to satisfy the three requisites: (1) sufficient crystal recovery, (2) suppression of implanted layer evaporation, and (3) prevention of P precipitation, and is achieved by rapid thermal annealing at high temperature for a short time. (C) 2003 American Institute of Physics.