Effects of NH 3 Annealing on High-k HfSiON/HfO 2 Gate Stack Dielectrics

INTRODUCTION HfSiON has recently proven to be a promising high-k dielectrics.[1] Nitrogen in HfSiON was reported to enhance the dielectric constant and prevent boron diffusion and crystallization [2, 3]. However, relatively low dielectric constant and channel mobility of HfSiON material limit its application. In this study, HfSiON was evaluated as a capping layer of HfO2 for improved thermal stability and boron blocking. Although our previous work on HfON/HfO2 showed that top HfON layer was partially effective in suppressing both oxygen and boron diffusion [4], the amount of nitrogen incorporated is limited to very low value. In this work, the nitrogen concentration was controllably increased with Si incorporation. Post-deposition annealing (PDA) gas of NH3 was used to achieve even higher nitrogen concentration in HfSiON and the effects of its use on HfSiON/HfO2 gate dielectrics were investigated.