Thermal stability and chemical bonding states of AlO _x N _y /Si gate stacks revealed by synchrotron radiation photoemission spectroscopy

Annealing-temperature dependence of the thermal stability and chemical bonding states of AlO _x N _y /SiO ₂ /Si gate stacks grown by metalorganic chemical vapor deposition (MOCVD) using new chemistry was investigated by synchrotron radiation photoemission spectroscopy (SRPES). Results have confirmed the formation of the AlN and AlNO compounds in the as-deposited samples. Annealing the AlO _x N _y samples in N ₂ ambient in 600-800 °C promotes the formation of SiO ₂ component. Meanwhile, there is no formation of Al-O-Si and Al-Si binding states, suggesting no interdiffusion of Al with the Si substrate. A thermally induced reaction between Si and AlO _x N _y to form volatile SiO and Al ₂ O is suggested to be responsible for the full disappearance of the Al component that accompanies annealing at annealing temperature of 1000 °C. The released N due to the breakage of the Al-N bonding will react with the SiO ₂ interfacial layer and lead to the formation of the Si ₃ -N-O/Si ₂ -N-O components at the top of Si substrate. These results indicate high temperature processing induced evolution of the interfacial chemistry and application range of AlO _x N _y /Si gate stacks in future CMOS devices.