Abstract
It has been already demonstrated that the orthorhombic phase transformation of Zr or Si doped HfO2 (induced by annealing) is responsible for its ferroelectricity but the use of capping top electrodes is usually required [1-4]. Here, we show that by using NiSi2 as bottom electrode (suggesting an orthorhombic structure after annealing), moderate ferroelectric properties of Si-doped HfO2 thin films (8.7 nm in thickness) deposited on NiSi2 electrodes can be generated during post-deposition annealing (PDA). For this Si:HfO2/NiSi2 structure, the bottom and top metallic films are deposited by sputtering at room temperature while atomic-layer deposition is used for deposition of Si:HfO2 with a cycle ratio of 1:16 (SiO2:HfO2), see figs. 1-2. Annealing in argon, forming gas and oxygen atmospheres for temperatures ranging from 1000°C down to 400°C, was done on structures having NiSi2 or TiN (used as reference) as bottom electrodes in order to correlate the influence of these processing conditions to the electrical and ferroelectric properties of the resulting MIM devices. For this, leakage current, capacitance, remanent polarization and fatigue measurements with applied voltage were obtained. Moderate ferroelectric behavior was obtained for PDA samples having NiSi2 as bottom electrode in the temperature range of 750°C–500°C, see figs. 3-4. This result shows the advantage of the use of NiSi2 bottom electrode, broadening the processing window for CMOS-compatible ferroelectric materials. AcknowledgementThis research is supported by the Center of Innovation Program from Japan Science and Technology Agency, JST.
Published Version
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