Browsing by Author "Mohan, Jaidah"
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Item Ferroelectric HfxZr1-xO2 for Next Generation Non-volatile Memory Applications and Its Reliability(December 2021) Mohan, Jaidah; Kim, Jiyoung; Harabagiu, Sanda; Wallace, Robert M; Summerfelt, Scott R; Young, Chadwin D; Gnade, BruceTo keep up with the increasing memory demands, developing memories with higher densities, speed and energy efficiency is necessary at different levels of the memory hierarchy. Ferroelectric materials have been considered alternative memory components; however, the conventional perovskite-based ferroelectric materials pose several challenges due to CMOS integration, high thermal budget, and scaling to sub 70 nm thicknesses. In this regard, the discovery of ferroelectricity in doped HfO2 thin films was revolutionary as HfO2 is already employed in front end CMOS as a high-k dielectric material for scaled thicknesses (<10 nm) . Additionally, doping HfO2 films with ZrO2, i.e., Hf0.5Zr0.5O2 (HZO) showed stable ferroelectric phase crystallization at back-end of line compatible temperatures (<450 °C). This dissertation addresses some critical issues on the stress-induced crystallization of the ferroelectric phase in HZO films, the reliability properties of metal-ferroelectric-metal (MFM) structures, scaling ferroelectric HZO films on silicon substrates, and their reliability. First, the driving forces for the crystallization of pure ferroelectric phase in HZO thin films were addressed and the role of the TiN top electrode in phase crystallization at low process temperatures (400 °C) is studied. Then, the reliability of 10 nm thick HZO films was studied, and the various ferroelectric device reliability properties and mechanisms were evaluated for metal-ferroelectricmetal structures. Finally, the ferroelectric HZO films were integrated directly on silicon for FeFET applications and the effect of ferroelectric device reliability based on scaling HZO films on silicon structures was studied.Item Ferroelectric Hf₀․₅Zr₀․₅O₂ Thin Films: A Review of Recent Advances(Springer, 2018-09-28) Kim, Si Joon; Mohan, Jaidah; Summerfelt, Scott R.; Kim, Jiyoung; 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Mohan, Jaidah; Kim, JiyoungFerroelectricity in HfO₂-based materials, especially Hf₀․₅Zr₀․₅O₂ (HZO), is today one of the most attractive topics because of its wide range of applications in ferroelectric random-access memory, ferroelectric field-effect transistors, ferroelectric tunneling junctions, steep-slope devices, and synaptic devices. The main reason for this increasing interest is that, when compared with conventional ferroelectric materials, HZO is compatible with complementary metal-oxide-semiconductor flow [even back-end of the line thermal budget] and can exhibit robust ferroelectricity even at extremely thin (<10nm) thicknesses. In this report, recent advances in the ferroelectric properties of HZO thin films since the first report in 2011, including doping effects, mechanical stress effects, interface effects, and ferroelectric film thickness effects, are comprehensively reviewed.Item Ferroelectric TiN/Hf₀.₅Zr₀.₅O₂/Tin Capacitors with Low-Voltage Operation and High Reliability for Next-Generation FRAM Applications(Institute of Electrical and Electronics Engineers Inc.) Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, Jiyoung; Summerfelt, S. R.; San, T.; 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Mohan, Jaidah; Young, Chadwin D.; Colombo, Luigi; Kim, JiyoungIn this study, we investigated the ferroelectric properties of Hf₀.₅Zr₀.₅O₂ (HZO) thin films with different thicknesses (5-20 nm) deposited by atomic layer deposition for the development of future ferroelectric random access memory cells. HZO-based capacitors with a thickness of 5 nm exhibited a switching polarization of ~13 μC/cm² and a ferroelectric saturation voltage of 1.0 V as extracted from the pulse write/read measurements. Furthermore, we performed fatigue measurements and we found no degradation up to 10¹⁰ switching cycles at 1.2 V.Item Large Ferroelectric Polarization of TiN/Hf₀․₅Zr₀․₅0₂ Capacitors Due to Stress-Induced Crystallization at Low Thermal Budget(Amer Inst Physics, 2018-10-22) Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Summerfelt, Scott R.; San, Tamer; Colombo, Luigi; Kim, Jiyoung; 0000-0001-7335-1053 (Lee, JS); 0000-0001-9477-5728 (Byun, Y-C); 0000-0003-0690-7423 (Young, CD); 0000-0003-2781-5149 (Kim, J); 70133685 (Kim, J); Kim, Si Joon; Narayan, Dushyant; Lee, Jae-Gil; Mohan, Jaidah; Lee, Joy S.; Lee, Jaebeom; Kim, Harrison S.; Byun, Young-Chul; Lucero, Antonio T.; Young, Chadwin D.; Kim, JiyoungWe report on atomic layer deposited Hf₀․₅Zr₀․₅0₂ (HZO)-based capacitors which exhibit excellent ferroelectric (FE) characteristics featuring a large switching polarization (45 μC/cm²) and a low FE saturation voltage (~1.5V) as extracted from pulse write/read measurements. The large FE polarization in HZO is achieved by the formation of a non-centrosymmetric orthorhombic phase, which is enabled by the TiN top electrode (TE) having a thickness of at least 90nm. The TiN films are deposited at room temperature and annealed at 400 ⁰C in an inert environment for at least 1 min in a rapid thermal annealing system. The room-temperature deposited TiN TE acts as a tensile stressor on the HZO film during the annealing process. The stress-inducing TiN TE is shown to inhibit the formation of the monoclinic phase during HZO crystallization, forming an orthorhombic phase that generates a large FE polarization, even at low process temperatures.