A comparison of graphite and AlN caps used for annealing ion-implanted SiC

The SiC wafers implanted with Al were capped with AIN, C, or AIN and C and were annealed at temperatures as high as 1700degreesC to examine their ability to act as annealing caps. As shown previously, the AIN film was effective up to 1600degreesC, as it protected the SiC surface, did not react with it, and could be removed selectively by a KOH etch. However, it evaporated too rapidly at the higher temperatures. Although the C did not evaporate, it was not a more effective cap because it did not prevent the out-diffusion of Si and crystallized at 1700degreesC. The crystalline film had to be ion milled off, as it could not be removed in a plasma asher, as the C films annealed at the lower temperatures were. A combined AIN/C cap also was not an effective cap for the 1700degreesC anneal as the N or Al vapor blew holes in it, and the SiC surface was rougher after the dual cap was removed than it was after annealing at the lower temperatures.