&lt;italic&gt;In Situ&lt;/italic&gt; Process Control of Trilayer Gate-Stacks on p-Germanium With 0.85-nm EOT

Zheng, Yongping; Agrawal, Ashish Kumar; Rayner, G. B.; Barth, Michael; Ahmed, K.; Datta, Suman; Engel‐Herbert, Roman

doi:10.1109/led.2015.2459663

Cited by 12 publications

(7 citation statements)

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“…This will enable future studies to assess ALD of Al 2 O 3 , as well as other feasible high-ĸ candidates and passivation strategies (such as hafnia, zirconia, tantalum, germanium oxynitride [96][97][98][99][100] and bi/tri-layer dielectrics [101][102][103][104] ) on pristine and oxidised Ge surfaces. As such, ReaxFF can be instrumental in identifying optimal processing conditions to form high quality high-ĸ dielectrics/non-Si semiconductor interfaces.…”

Section: Applications Of Reaxffmentioning

confidence: 99%

The ReaxFF reactive force-field: development, applications and future directions

et al. 2016

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The reactive force-field (ReaxFF) interatomic potential is a powerful computational tool for exploring, developing and optimizing material properties. Methods based on the principles of quantum mechanics (QM), while offering valuable theoretical guidance at the electronic level, are often too computationally intense for simulations that consider the full dynamic evolution of a system. Alternatively, empirical interatomic potentials that are based on classical principles require significantly fewer computational resources, which enables simulations to better describe dynamic processes over longer timeframes and on larger scales. Such methods, however, typically require a predefined connectivity between atoms, precluding simulations that involve reactive events. The ReaxFF method was developed to help bridge this gap. Approaching the gap from the classical side, ReaxFF casts the empirical interatomic potential within a bond-order formalism, thus implicitly describing chemical bonding without expensive QM calculations. This article provides an overview of the development, application, and future directions of the ReaxFF method. INTRODUCTIONAtomistic-scale computational techniques provide a powerful means for exploring, developing and optimizing promising properties of novel materials. Simulation methods based on quantum mechanics (QM) have grown in popularity over recent decades due to the development of user-friendly software packages making QM level calculations widely accessible. Such availability has proved particularly relevant to material design, where QM frequently serves as a theoretical guide and screening tool. Unfortunately, the computational cost inherent to QM level calculations severely limits simulation scales. This limitation often excludes QM methods from considering the dynamic evolution of a system, thus hampering our theoretical understanding of key factors affecting the overall behaviour of a material. To alleviate this issue, QM structure and energy data are used to train empirical force fields that require significantly fewer computational resources, thereby enabling simulations to better describe dynamic processes. Such empirical methods, including reactive force-field (ReaxFF), 1 trade accuracy for lower computational expense, making it possible to reach simulation scales that are orders of magnitude beyond what is tractable for QM.Atomistic force-field methods utilise empirically determined interatomic potentials to calculate system energy as a function of atomic positions. Classical approximations are well suited for nonreactive interactions, such as angle-strain represented by harmonic potentials, dispersion represented by van der Waals potentials and Coulombic interactions represented by various polarisation schemes. However, such descriptions are inadequate for modelling changes in atom connectivity (i.e., for modelling chemical reactions as bonds break and form). This motivates the

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Section: Applications Of Reaxffmentioning

confidence: 99%

The ReaxFF reactive force-field: development, applications and future directions

et al. 2016

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“…38 It is therefore expected that a direct Al 2 O 3 deposition on Ge:H will result in inferior electrical characteristics of dielectric/Ge interface in the application in field effect transistors. 39 To experimentally confirm the ReaxFF predictions, in situ SE experiments were performed during the Al 2 O 3 ALD on Ge(100):H (Figure 3a). The Al 2 O 3 thickness during ALD was extracted in real time by fitting the SE spectra using a layered model of Al 2 O 3 /Ge.…”

Section: ■ Results and Discussionmentioning

confidence: 87%

“…A nominally 5 Å-thick GeO x overlayer was formed prior to ALD deposition by exposing the hydrogenated Ge surface to a remote oxygen plasma. 39 The ALD nucleation behavior (Figure 6a) is also nonlinear but with distinctively different characteristics of TMA adsorption and GPC compared to those of Ge:H surfaces. The nucleation can be categorized into four regions (Figure 6b).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Modeling and in Situ Probing of Surface Reactions in Atomic Layer Deposition

Zheng

Hong

Psofogiannakis

et al. 2017

ACS Appl. Mater. Interfaces

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Atomic layer deposition (ALD) has matured into a preeminent thin film deposition technique by offering a highly scalable and economic route to integrate chemically dissimilar materials with excellent thickness control down to the subnanometer regime. Contrary to its extensive applications, a quantitative and comprehensive understanding of the reaction processes seems intangible. Complex and manifold reaction pathways are possible, which are strongly affected by the surface chemical state. Here, we report a combined modeling and experimental approach utilizing ReaxFF reactive force field simulation and in situ real-time spectroscopic ellipsometry to gain insights into the ALD process of AlO from trimethylaluminum and water on hydrogenated and oxidized Ge(100) surfaces. We deciphered the origin for the different peculiarities during initial ALD cycles for the deposition on both surfaces. While the simulations predicted a nucleation delay for hydrogenated Ge(100), a self-cleaning effect was discovered on oxidized Ge(100) surfaces and resulted in an intermixed AlO/GeO layer that effectively suppressed oxygen diffusion into Ge. In situ spectroscopic ellipsometry in combination with ex situ atomic force microscopy and X-ray photoelectron spectroscopy confirmed these simulation results. Electrical impedance characterizations evidenced the critical role of the intermixed AlO/GeO layer to achieve electrically well-behaved dielectric/Ge interfaces with low interface trap density. The combined approach can be generalized to comprehend the deposition and reaction kinetics of other ALD precursors and surface chemistry, which offers a path toward a theory-aided rational design of ALD processes at a molecular level.

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“…The peak electron μ eff is experimentally found to be ~750 cm 2 /V·s using GeO x passivation and Al 2 O 3 barrier layer, [6], [7] which gate structure has been considered as one of the most feasible routes for realizing both low density of interfacial states (D it ) and low equivalent oxide thickness. [3], [4], [8], [9] Furthermore, to maximize the channel on-state current drivability, the scattering mechanisms that limit the μ eff are of great concern. Developing a process technology that improves the mobility requires understanding the mechanism of Ge mobility degradation.…”

Section: Introductionmentioning

confidence: 99%

Electron Mobility Degradation Due to Remote Coulomb Scattering in Ge MOSFET

Xu¹,

Zhang²,

Wei³

et al. 2016

Proceedings of the 2016 International Conference on Computer Science and Electronic Technology

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Abstract-Remote13 cm -2 . The origin of this mobility dependence on GeO x thickness is attributed to the RCS due to electric dipole at Al 2 O 3 /GeO x interface. And this remote dipole scattering is found to play a significant role on mobility degradation. The discovery of this new scattering mechanism indicates that engineering of Al 2 O 3 /GeO x interface is key for mobility enhancement and device performance improvement. These results are helpful for understanding and engineering the Ge mobility enhancement.

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<italic>In Situ</italic> Process Control of Trilayer Gate-Stacks on p-Germanium With 0.85-nm EOT

Cited by 12 publications

References 11 publications

The ReaxFF reactive force-field: development, applications and future directions

The ReaxFF reactive force-field: development, applications and future directions

Modeling and in Situ Probing of Surface Reactions in Atomic Layer Deposition

Electron Mobility Degradation Due to Remote Coulomb Scattering in Ge MOSFET

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