Annealing ion implanted SiC with an AlN cap

An AlN cap was used to try to prevent the preferential evaporation of Si du ring the high temperature anneals required to activate N implanted into a S iC substrate. The process was essentially successful as the electrical meas urements showed that the resistivity continued to decrease with increasing annealing temperatures up to 1600 degrees C and times up to 120 min. The ch anges were, however, marginal when compared to a 1500 degrees C, 30 min ann eal suggesting that this anneal would be sufficient to activate most of the N implants. There is evidence for a small amount of Si being lost near the surface. This could occur where the AlN pulled away locally from the SIC w afer; this effect was stronger for patterned substrates where stress concen trations can occur at steps. For the most part, however, the SiC surface re tained its integrity even during the process of removing the AIN film with a hot KOH etch. Also, there was no evidence that Al from the AIN contaminat ed the N implanted region by diffusing in during the anneals. The surface o f the AIN retained its integrity during the anneal although topographical c hanges suggested that considerable atomic motion had occurred. This coincid ed with the formation of an amorphous AIN layer in the film. (C) 1999 Elsev ier Science S.A. All rights reserved.