A comparison of the AIN annealing cap for 4H-SiC annealed in nitrogen versus argon atmosphere

AlN deposited on 4H-SiC by pulsed laser deposition (PLD) did not noticeably deteriorate when it was annealed in an Ar atmosphere at 1500 degreesC for 30 min, but it contained numerous thermal etch pits when it was annealed at 1600 degreesC as determined by SEM and AFM, and it completely evaporated at the higher annealing temperatures thereby allowing the silicon to evaporate preferentially that produced a pitted SiC surface. When the AlN film was annealed in nitrogen for 30 min, the film formed a protective cover up to 1650 degreesC, and when a sapphire cover was employed, it protected the SiC surface up to 1700 degreesC. The AlN surface was altered when it was annealed in nitrogen by both the evaporation of N from the surface and reactions with the N in the atmosphere. This produced a rougher surface as determined by SEM and AFM that was composed of more randomly oriented crystallites as determined by X-ray and TEM analyses, but it still protected the SiC surface below. Thermodynamic calculations are in qualitative agreement with these analyses. Published by Elsevier Ltd.