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This study investigated the variations in the dielectric constant with film thickness and measurement temperature of (Ba0.48Sr0.52)TiO3 thin-film capacitors with thicknesses ranging from 65 to 273 nm. The films were prepared by an on-axis rf magnetron sputtering, having Pt top and bottom electrodes. The thicker film showed a higher dielectric constant with a larger temperature dependence of the dielectric constant, and the maximum dielectric constant was observed at a higher temperature. The thickness-dependent dielectric constant at a given measurement temperature was explained by using the previously reported interfacial capacitance model, containing the intrinsic dead layer and electrode polarization. The temperature-dependent dielectric property could be explained using a modified Curie-Weiss (C-W) behavior of the film taking the nonferroelectric interfacial capacitance components into consideration. However, the C-W constant and Curie temperature of the ferroelectric layer must be modified in order to obtain a reasonable interfacial layer thickness. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) on Ta-doped SnO 2 thin films is proposed as a methodology for the fabrication of capacitor electrodes, for application in dynamic random-access memories (DRAMs). In ALD of doped materials, dopant concentration gradients inevitably occur due to the cyclic process-based characteristics of ALD. In this study, the dopant distribution improves drastically by the decrease in the growth per cycle of TaO x ALD. The modified ALD recipe exploits the low reactivity between Ta and Sn precursors to facilitate a reduction in the growth per cycle. The Ta-doped SnO 2 films grown based on this modified ALD recipe exhibit improved crystallinity and conductivity. The ALD process yields excellent conformality of the Ta-doped SnO 2 film over a hole structure with a high aspect ratio of ~10, both in terms of physical thickness and composition. Additionally, the Ta-doped SnO 2 films serve as a template for the overgrowing dielectric TiO 2 film, which induces the formation of a high-temperature phase with a high dielectric constant, rutile TiO 2 , and exhibit excellent thermal stability even after annealing at 400 °C in forming gas atmosphere. These findings demonstrate that the proposed methodology for the growth of Ta-doped SnO 2 can facilitate the fabrication of capacitor electrodes for application in DRAMs. Unlabelled Image • A new ALD process of Ta-doped SnO 2 films is demonstrated. • Potential applications include use as reduction-resistant capacitor electrode. • Dopant distribution improves by decrease in the growth per cycle of TaO x ALD. • Films reveal ease of formation of high-k rutile TiO 2 and excellent thermal stability. [ABSTRACT FROM AUTHOR]

SrTiO 3 (STO) thin films, grown by atomic layer deposition (ALD), were studied for capacitors in dynamic random access memory. The STO ALD process consisted of two steps: the growth of seed layer followed by a rapid thermal annealing (RTA) process at 650 °C to crystallize it, and the deposition of the main layer on top of the seed layer at 370 °C to induce the in-situ crystallization. During single cooling process after the RTA of the seed layer, voids and nano-cracks were formed due to the thermal expansion mismatch between STO film and Si substrate. This problem was well mitigated by adopting the stepwise cooling process, wherein the holding time of 30 s at 500, 350, and 200 °C suppressed the defect formation in the seed layer. Therefore, the main layer grown on that seed layer showed an improved microstructure with a high bulk dielectric constant of 135. However, the increase in total annealing time degraded the interface quality between the STO and the bottom electrode, which finally worsened the insulating property. As a result, the minimum equivalent oxide thicknesses with low leakage current densities (< 10 − 7 A/cm 2 at 0.8 V) for the single and stepwise cooling processes were 0.39 nm and 0.46 nm, respectively. [ABSTRACT FROM AUTHOR]