Pt/SrBi_2Ta_2O_9/Hf-Al-O/Siダイオードの素子特性に及ぼすHf-Al-O層への窒素導入の効果

概要

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A metal/ferroelectric/insulator/semiconductor Pt/SrBi2Ta2O9(SBT)/Hf-Al-O(HAO)/Si is a promising gate structure for a ferroelectric-gate transistor. Effects of adding nitrogen into the HAO were investigated. Pt/SBT/HAO(N)/Si and Pt/SBT/HAO(O)/Si were prepared by depositing the HAO in N2 and O2, respectively. Nitrogen inclusion in the HAO(N) was confirmed by secondary ion mass spectrometry (SIMS). The SIMS results also indicated that diffusions of Sr, Bi and Ta into the HAO(N) were much more suppressed than those into HAO(O). Scanning transmission electron microscope (STEM) images showed that the HAO(N) was amorphous and fine while the HAO(O) was polycrystallized and rugged. The STEM image also showed an interfacial layer (IL) between the HAO and Si, grown mainly during an annealing process at 800°C for 1h for SBT polycrystallization. The major components of the IL were Si and O. The IL thicknesses of the HAO(N) and the HAO(O) were 3.4 nm and 7.4 nm respectively. Capacitance-voltage measurements of the Pt/SBT/HAO(N)/Si showed a 0.9V memory window at ±6V gate-voltage swing, which was three times larger than the memory window of the Pt/SBT/HAO(O)/Si. We concluded that adding nitrogen into the HAO of Pt/SBT/HAO/Si was effective for obtaining a large memory window by suppressing material diffusions and the IL layer growth.
社団法人粉体粉末冶金協会の論文
2008-01-15