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Structural and electrical evidence for a ferroelectric phase in yttrium doped hafnium oxide thin films is presented. A doping series ranging from 2.3 to 12.3 mol% YO1.5 in HfO2 was deposited by a thermal atomic layer deposition process. Grazing incidence X-ray diffraction of the 10 nm thick films revealed an orthorhombic phase close to the stability region of the cubic phase. The potential ferroelectricity of this orthorhombic phase was confirmed by polarization hysteresis measurements on titanium nitride based metal-insulator-metal capacitors. For 5.2 mol% YO1.5 admixture the remanent polarization peaked at 24 μC/cm2 with a coercive field of about 1.2 MV/cm. Considering the availability of conformal deposition processes and CMOS-compatibility, ferroelectric Y:HfO2 implies high scaling potential for future, ferroelectric memories. [ABSTRACT FROM AUTHOR]

We report the observation of ferroelectricity in capacitors based on hafnium-zirconium-oxide. Hf0.5Zr0.5O2 thin films of 7.5 to 9.5 nm thickness were found to exhibit ferroelectric polarization-voltage hysteresis loops when integrated into TiN-based metal-insulator-metal capacitors. A remnant polarization of 16 μC/cm2 and a high coercive field of 1 MV/cm were observed. Further proof for the ferroelectric nature was collected by quasi-static polarization-voltage hysteresis, small signal capacitance-voltage, and piezoelectric measurements. Data retention characteristics were evaluated by a Positive Up Negative Down pulse technique. No significant decay of the initial polarization state was observed within a measurement range of up to two days. [ABSTRACT FROM AUTHOR]

The authors report the relationship between HfO2 crystalline phase and the resulting electrical properties. Crystallization of amorphous HfO2 into the monoclinic phase led to a significant increase in leakage current and formation of local defects. Admixture of 10% SiO2 avoided formation of these defects by stabilization of the tetragonal phase, and concurrently increased the permittivity to 35. This understanding enabled fabrication of crystalline HfO2 based metal-insulator-metal capacitors able to withstand a thermal budget of 1000 °C while optimizing capacitance equivalent thickness (<1.3 nm) at low leakage [J(1 V)<10-7 A/cm2]. [ABSTRACT FROM AUTHOR]

Rare earth (RE) doping (Gd, Er, Dy) of HfO2 reduces leakage current by three orders of magnitude compared with pure HfO2. The key to reducing HfO2 leakage current and equivalent oxide thickness (EOT) is stabilization of the higher permittivity tetragonal phase. RE doping of 10–20 at. % stabilizes tetragonal HfO2 and increases permittivity. The maximum permittivity achieved for HfREOx is 28. The maximum permittivity for ZrREO is 32. HfGdO metal-insulator-semiconductor capacitors with EOT=1.93 nm and leakage current <1×10-8 A/cm2 after 1070 °C have been demonstrated. [ABSTRACT FROM AUTHOR]