Thermal Stability of Stacked high-κ Dielectrics on Silicon and Its Improvement by Helium Annealing(<Special Section>High-κ Gate Dielectrics)

概要

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Thermal stability of stacked high-k dielectrics, especially ZrO_2, HfO_2 and ZrSiO_4/SiO_2 layered structures, on silicon has been investigated in terms of ultrahigh vacuum (UHV), 1 Torr N_2 and helium (He) gas annealing with controlled oxygen partial pressure (Po_2) at 920℃ Comparison of 2 nm and 20 nm ZrO_2 films under UHV annealing revealed that the trigger of silicidation is the contact of ZrO_2, SiO and Si accompanying disappearance of interfacial SiO_2 layer due to SiO desorption. In the contact position, a small amount of SiO gas can easily change ZrO_2 to ZrSi_2. This reaction model is also applicable to the silicidation of HfO_2 and ZrSiO_4, at not only stacked high-pr film/Si substrate interface, but also at gate poly-Si/high-k film interface. Moreover, comparison of UHV, N_2 and He annealing with controlled PO_2 revealed that the optimal PO_2 ranges in He at which the thermal stability of layered structure can be achieved are wider than those in UHV and N_2. This result suggests that He gas physically may obstruct SiO creation due to the quenching of atomic vibration at degradation-prone sites in the SiO_2/Si interface, thus reducing probability of bond breaking process, which is the first step of silicidation.
一般社団法人電子情報通信学会の論文
2004-01-01