The Suppression of the Interfacial Reaction between HfAlOx/Interfacial Layers during Post Deposition Annealing

The reaction behavior of the Interfacial Layer (IL) in an HfAlOx/SiO2 and SiON structure during a post deposition annealing (PDA) in an N2-diluted oxygen ambient was examined. After a PDA at 1,050oC for 1 s, the 0.7 nm-thick IL was reduced if the O2 concentration was lower than 0.02%. The reduction of the IL led to the formation of defects and the Si migration to the HfAlOx surface, resulting in an increase in the C-V hysteresis. The amount of Si migrated to HfAlOx surface decreases with increasing the O2 concentrations during PDA and changing the interfacial layer from SiO2 to SiON. Even if SiON is used for interfacial layer, the decreasing of mobility was caused by nitrogen which stay in interface between SiON and substrate. Optimization of nitrogen in SiON interfacial layer is necessary. Electron and hole mobility of 75/77% of that for SiO2 were obtained for HfAlOx/SiON with EOT = 1.6 nm because of optimization of PDA O2 concentration and nitrogen profile in SiON.