Interfacial Reaction of TiN/HfSiON Gate Stack in High-Temperature Annealing for Gate-First Metal-Oxide-Semiconductor Field-Effect Transistors

摘要

The interfacial reaction of a TiN/HfSiON/SiO_2 gate stack in high-temperature annealing was investigated from the viewpoint of the redistribution of the elements of gate stack materials. Oxygen incorporation enhanced the redistribution of the elements not only of the dielectric film of HfSiON/SiO_2 but also of the gate electrode film of TiN. Oxygen incorporation in high-temperature annealing enhances the partial release of Hf, N, and Si from HfSiON or the disassembly of the HfSiON film, which leads to an increase in the equivalent-oxide thickness (EOT). The EOT increase can be determined by the combination of the decrease in the HfSiON film caused by the Hf and N release from HfSiON and the increase in the interfacial layer created by the oxidation of the Si substrate surface by the penetrating oxygen. It is also found that Ti diffused from the TiN into the interfacial layer through the HfSiON/SiO_2. The suppression of oxygen incorporation is a key technique in the high-temperature annealing of metal/high-k gate stacks.