Impact of crystallization behavior of SrxTiyOz films on electrical properties of metal-insulator-metal capacitors with TiN electrodes

Pawlak, Małgorzata; Kaczer, B.; Kim, Min‐Soo; Popovici, Mihaela; Tomida, Kazuyuki; Swerts, J.; Opsomer, Karl; Polspoel, Wouter; Favia, P.; Vrancken, C.; Demeurisse, C.; Wang, W. C; Afanasʼev, Valeri; Vandervorst, Wilfried; Bender, Hugo; Debusschere, I.; Altimime, L.; Kittl, J. A.

doi:10.1063/1.3505323

Cited by 27 publications

(35 citation statements)

References 6 publications

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“…13 After these findings, the authors' group has focused on a high-temperature (>350°C) ALD process by adopting precursors that can withstand high temperatures, such as Ti(O i Pr) 2 (tmhd) 2 as a Ti-precursor. 1,2,14 In contrast, a research group in Interuniversity Microelectronics Centre (IMEC) focused on the low temperature ALD (∼250°C) process to make use of the facile ALD reactions between the Sr( t Bu 3 Cp) 2 and Ti(OMe) 4 with H 2 O, where Bu and Me correspond to butyl and methyl groups, respectively, which required PDA at a higher temperature to crystallize STO films. 4,15,16 Similar to the current authors' case, such high-temperature PDA induced micro-and nanocracking problems; as a result, they introduced a double-layer structured ALD process.…”

Section: ■ Introductionmentioning

confidence: 96%

Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Lee

Jeon

et al. 2015

Chem. Mater.

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An atomic layer deposition (ALD) process for SrTiO 3 (STO) thin film growth was developed using a newly designed and synthesized heteroleptic Sr-precursor, {Sr(demamp)(tmhd)} 2 (demampH = 1-{[2-(dimethylamino)ethyl](methyl)amino}-2-methylpropan-2-ol, tmhdH = 2,2,6,6-tetramethyl-3,5-heptanedione), which offered an intermediate reactivity toward oxygen between Sr(tmhd) 2 and Sr( i Pr 3 Cp) 2 . Because of the appropriate reactivity of {Sr(demamp)(tmhd)} 2 toward oxygen, the abnormal initial growth behavior (due to interaction between the Sr-precursor and active oxygen contained in the underlying oxidized Ru layer) became negligible during the growth of the SrO and STO films on the Ru electrode, which allowed the growth of the SrO and STO films to be highly controllable with a moderate growth rate. Using Ti(CpMe 5 )(OMe) 3 as the Ti-precursor and O 3 as the oxygen source in the TiO 2 ALD subcycle, the ALD process of the STO film revealed a growth rate of 0.05 nm/cycle and ∼85% of step coverage in terms of the thickness and cation composition on a capacitor hole structure with an aspect ratio of 10 (opening diameter of 100 nm and depth of 1 μm). The minimum achievable equivalent oxide thickness (t ox ) with a low leakage current (<10 −7 A/cm 2 at 0.8 V) was limited to 0.46 nm. The damage effect on the underlying Ru electrode by the prolonged ALD process time appears to affect the limited scalability of t ox . ■ INTRODUCTIONSrTiO 3 (STO) has been considered to be a promising candidate for a dielectric layer in the next-generation dynamic random access memory (DRAM) capacitors because of its high permittivity (∼300 in bulk material) compared with that of other dielectric materials, such as HfO 2 and ZrO 2 . Many studies have reported a high dielectric constant of >100 for metal− insulator−metal (MIM) capacitors that contain an STO insulator, in which the insulators are thinner than 20 nm. 1−6 Considering the extremely tiny three-dimensional (3D) structure of the DRAM capacitors, 7 atomic layer deposition (ALD) appears to be the only feasible thin film growth technique that can fulfill the stringent requirements of thickness and composition step coverage in the DRAM capacitors. Despite the acute requirement for a suitable ALD process of the STO films, the development has been hindered for two main reasons: first, the lack of a suitable Sr-precursor for feasible STO ALD, although that for Ti is abundant; second, because of the low temperature of the ALD, ensuring a suitable crystalline quality of the STO film is challenging in general. Because such problems and possible solutions have already been extensively reviewed in previous reports from the authors' group, 3,7,8 more recent reports that are directly related to the present work are described in this section.The first viable report in this field was published by the Helsinki group in the late 1990s. Vehkamaki et al. deposited STO films with Sr( i Pr 3 Cp) 2 (Pr and Cp are propyl and cyclopentadienyl group, respectively) and Ti(O i Pr) 4 [TTIP] as Sr-and Ti-precursors,...

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Section: ■ Introductionmentioning

confidence: 96%

Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Lee

Jeon

et al. 2015

Chem. Mater.

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“…The cracks at the grain boundaries can be either formed due to densification caused by solid-state diffusion or to tensile stress between grains. 13,14 and dielectric properties. [10][11][12][13]18 This example shows the importance of resolving the correct process and temperature window to obtain the desired film properties for the specific application targeted.…”

mentioning

confidence: 99%

Crystallization Study by Transmission Electron Microscopy of SrTiO₃Thin Films Prepared by Plasma-Assisted ALD

Longo

Verheijen

Roozeboom

et al. 2013

ECS J. Solid State Sci. Technol.

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The crystallization behavior of thin strontium titanate (SrTiO3, STO) films with ∼15 nm thickness was studied by Transmission Electron Microscopy (TEM). Amorphous STO films with [Sr]/([Sr]+[Ti]) ratio ranging from 0.50 to 0.63 were deposited at 350°C by plasma-assisted ALD and subsequently treated by rapid thermal annealing in flowing N2 for crystallization. Different temperatures and annealing durations were employed to fully characterize the crystallization process. TEM analysis showed that transrotational crystals were formed and evidenced the influence of the STO composition and of the thermal budget applied on the grain size, crack and void formation. In particular, Sr-rich layers ([Sr]/([Sr]+[Ti] ≥ 0.59) showed a finer crystalline structure which was imputed to a higher nucleation probability at the onset of the crystallization process. Crystallization into the perovskite structure was confirmed for all the film compositions studied. By tuning the STO composition and the thermal budget of the annealing step it was demonstrated that it is possible to control the microstructure of the crystallized film as a further step in optimizing the STO film properties.

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“…76 Pawlak et al at IMEC, Belgium, extensively studied the PDA effects on the crystallization behavior of stoichiometric or Sr-rich Sr x Ti y O z ALD films. 72 After thermal annealing at 500-600 1C under N 2 , stoichiometric STO films (9-10 nm) showed a dielectric constant of 4200, although they suffered from a high leakage current (10 À2 to 10 À3 A cm À2 at 1 V), due to the formation of nanocracks induced by large crystalline grains. Sr-rich STO (Sr/(Sr + Ti) = B64 at%, 9-10 nm), however, showed a dielectric constant of B50 with a low J G of 10 À6 A cm À2 at 1 V, which is a largely improved leakage current with some sacrifice of the dielectric constant due to its different crystallization behavior.…”

Section: Thermal Annealing (Annealing During Every Ald Cycle or Post-mentioning

confidence: 99%

“…In this section, we review characterization strategies that researchers have pursued to understand the morphology of thin-film perovskites and how they linked their findings to the obtained properties (Table 5). 15,46,[64][65][66]70,72,[76][77][78][79][80][81]83,[85][86][87]90,94,97,98,102,[104][105][106] To obtain compositional information, XPS is the most common technique. The information that can be obtained ranges from film contamination to the elemental composition within the topmost 1-10 nm of the film and its uniformity, chemical and electronic states, binding information, and depth information.…”

Section: Characterization Of Ultrathin Perovskite Filmsmentioning

confidence: 99%

Process–property relationship in high-k ALD SrTiO₃ and BaTiO₃: a review

et al. 2017

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bfPerovskites exhibit a wide range of remarkable material properties that have the potential to advance various scientific fields. These properties originate in their unique structure and composition. To leverage these properties in the ultrathin film regime, atomic-level control of thickness, composition, and crystal structure will be essential for creating next-generation perovskite devices. Atomic layer deposition (ALD) has the potential to enable these design prospects. However, its future use in the field will be dependent on the quality of the link between ALD process parameters and the perovskite phase.In this overview, we present work on barium and strontium titanate (BTO and STO) ultrathin films for high-k applications. We present ALD process strategies developed and optimized to achieve both desired composition and phase, yielding high dielectric constants and low leakage currents at the same time. We discuss thermal annealing, plasma treatment, and the use of seed layers and specialized precursors to improve the properties of BTO and STO by different enhancement mechanisms. In the ultrathin film regime, the understanding of macroscopic material properties will be dependent on the knowledge of the atomic scale arrangement. In conjunction with advances in manufacturing, we therefore also discuss novel strategies and techniques for characterization that will likely be significant in establishing a valid and reliable ALD process parameter-thin film dielectric property relationship.

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Impact of crystallization behavior of SrxTiyOz films on electrical properties of metal-insulator-metal capacitors with TiN electrodes

Cited by 27 publications

References 6 publications

Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Crystallization Study by Transmission Electron Microscopy of SrTiO₃Thin Films Prepared by Plasma-Assisted ALD

Process–property relationship in high-k ALD SrTiO₃ and BaTiO₃: a review

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Impact of crystallization behavior of SrxTiyOz films on electrical properties of metal-insulator-metal capacitors with TiN electrodes

Cited by 27 publications

References 6 publications

Improved Initial Growth Behavior of SrO and SrTiO3 Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}2 as Sr-Precursor

Improved Initial Growth Behavior of SrO and SrTiO3 Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}2 as Sr-Precursor

Crystallization Study by Transmission Electron Microscopy of SrTiO3Thin Films Prepared by Plasma-Assisted ALD

Process–property relationship in high-k ALD SrTiO3 and BaTiO3: a review

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Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Improved Initial Growth Behavior of SrO and SrTiO₃ Films Grown by Atomic Layer Deposition Using {Sr(demamp)(tmhd)}₂ as Sr-Precursor

Crystallization Study by Transmission Electron Microscopy of SrTiO₃Thin Films Prepared by Plasma-Assisted ALD

Process–property relationship in high-k ALD SrTiO₃ and BaTiO₃: a review