Electrical and materials properties of AlN/ HfO2 high-k stack with a metal gate

In this study, aluminum nitride (AlN) was grown by molecular layer deposition on HfO2 that had been deposited on 200 mm Si (100) substrates. The AlN was grown on HfO2 using sequential exposures of trimethyl-aluminum and ammonia (NH3) in a batch vertical furnace. Excellent thickness uniformity on test wafers from the top of the furnace to the bottom of the furnace (across the furnace load) was obtained. The equivalent oxide thickness was 16.5-18.8 A for the AlN/HfO2 stack on patterned device wafers with a molybdenum oxynitride metal gate with leakage current densities from low 10-5 to mid 10-6 A/cm2 at threshold voltage minus one volt. There was no change in the work function with the AlN cap on HfO2 with the MoN metal gate, even with a 1000 deg. C anneal