分子動(dòng)力學(xué)（MD）是一種重要的數(shù)值模擬方法,通過求解所有相互作用，模擬原子的運(yùn)動(dòng)方程，實(shí)現(xiàn)目標(biāo)系統(tǒng)時(shí)間演化的模擬，從而計(jì)算給定模擬時(shí)間內(nèi)組成能量與其他熱力學(xué)量等材料性質(zhì)。MD的中心問題是構(gòu)建足夠有效和準(zhǔn)確的模型，將量子尺度的相互作用適應(yīng)到經(jīng)典方程中。

Fig. 1 Comparison of the bond energies or the penalty energies on the basic test molecules.

在眾多的勢(shì)模型中，反應(yīng)力場(chǎng)（ReaxFF）勢(shì)由于其物理現(xiàn)象的再現(xiàn)性和準(zhǔn)確性，被廣泛應(yīng)用于材料領(lǐng)域的研究。然而，迄今為止，許多引起人們興趣的系統(tǒng)都沒有在文獻(xiàn)中涵蓋，即使有也需要基于先前開發(fā)的參數(shù)集進(jìn)行進(jìn)一步的調(diào)整，以組成一個(gè)可靠的MD模型來解決實(shí)際問題。因此，發(fā)展ReaxFF參數(shù)是很有必要的。

Fig. 2 Results of the c-SiO2 thermal expansion.

來自三星日本公司Junichi Noaki等，開發(fā)了Si/O/H反應(yīng)力場(chǎng)參數(shù)集，并將其應(yīng)用于硅干/濕氧化過程中，以理解Si(100)表面熱氧化的基本物理原理。

Fig. 3 Total energies calculated on small c-SiO2 test structures in different phases as a function of the volume per atom.

作者利用SiO₂晶體體積的實(shí)驗(yàn)數(shù)據(jù)作為訓(xùn)練數(shù)據(jù)，對(duì)Si/O參數(shù)進(jìn)行了系統(tǒng)開發(fā)，完成了在300-1300K溫度范圍內(nèi)的真實(shí)熱行為。通過對(duì)Si/O/H系統(tǒng)相關(guān)的參數(shù)戰(zhàn)略調(diào)整，作者進(jìn)行了濕和干過程的模擬對(duì)比。

在所得到的ReaxFF中，研究結(jié)果提供了原位蒸汽生成（ISSG）氧化過程中H原子的一些關(guān)鍵特征，包括對(duì)逐層氧化性能的影響和氧化速率的提高。通過將獲得的ReaxFF結(jié)果與其他作者最近開發(fā)的參數(shù)集獲得的結(jié)果進(jìn)行比較，深入理解了H原子在氧化過程中的作用。

Fig. 5 Time evolution of the number of O atoms retained in the system through the thermal oxidation of Si.

該工作提供的ReaxFF參數(shù)，為未來各種環(huán)境下的制造工藝的研究提供了有用的信息和見解。該文近期發(fā)表于npj Computational Materials?9:?161?(2023)。

Editorial Summary

Molecular dynamics (MD) is an important numerical simulation method, which can carry out the time evolution of the target system by solving the equation of motions for all simulated atoms that are interacting with each other, thereby investigate the properties of materials from the coordination of individual atoms in the system at a given simulation time by calculating the constituent energy and other thermodynamic quantities.

The central issue of MD is how to accommodate the quantum-scale interactions into the classical equations and construct a sufficiently effective and accurate model. Among numerous potential models, the reactive force field (ReaxFF) potential is widely used in extensive studies in the field of material because of its reproducibility of physical phenomena with great accuracy. However, so far many systems of interest are simply not covered in the literature, or, if any, further elaborate tuning is required based on previously developed parameter sets to make up a reliable MD model to answer practical questions. Therefore, it is of great importance to develop the ReaxFF parameter sets.?

Junichi Noaki et al. from Samsung Japan Corporation, developed the Si/O/H reactive force field parameter set and applied to silicon dry/wet oxidation process to understand the underlying physics of the thermal oxidation of the Si(100) surface. Employing the experimental volume of the SiO₂ crystal at different temperatures as training data, a realistic thermal behavior was accomplished, finishing the same result over the temperature range of 300–1300 K. With strategic tunings of parameters related to Si/O/H system, the authors carried out the simulation comparing the wet-and dry processes.?

In the demonstration of the resulting ReaxFF, results provided some key characteristics of the H atoms in the ‘in-situ-steam-generation (ISSG)’ oxidation processes, including the effect on the layer-by-layer oxidation property and the oxidation rate enhancement. Via comparing the results with those obtained by using parameter set recently developed by other authors, an insight into the role of H atoms in the oxidation process was acquired. ReaxFF parameters in this work provide useful information and insight into the study of manufacturing processes for various settings in the future. This article was recently published in npj Computational Materials?9:?161?(2023).

原文Abstract及其翻譯

Development of the reactive force field and silicon dry/wet oxidation process modeling (開發(fā)反應(yīng)力場(chǎng)模擬硅干/濕氧化過程)

Junichi Noaki,?Satoshi Numazawa,?Joohyun Jeon?&?Shuntaro Kochi?

Abstract

We developed the Si/O/H reactive force field parameter set and applied to silicon dry/wet oxidation process to understand the underlying physics of the thermal oxidation of the Si(100) surface. Through a systematic development of the Si/O parameter using the experimental data of the volumes of the SiO₂?crystal as a reference, we reproduced the same result over the temperature range of 300–1300?K. With strategic tunings of parameters related to Si/O/H system, we carried out the simulation comparing the wet-and dry processes. A significant acceleration of the oxide film growth seen in the ‘in-situ-steam-generation (ISSG)’ is successfully represented. These properties of our model imply its applicability in wider scope. We compare our results with those obtained by using parameter set recently developed by other authors. Investigating the configuration of atoms near the interface of the SiO₂?film, our model is found to be able to study the role of hydrogen atoms for the ISSG acceleration.

摘要

我們開發(fā)了Si/O/H反應(yīng)力場(chǎng)參數(shù)集，并將其應(yīng)用于硅干/濕氧化過程中，以理解Si(100)表面熱氧化的基本物理原理。利用SiO₂晶體體積的實(shí)驗(yàn)數(shù)據(jù)作為參考，我們對(duì)Si/O參數(shù)進(jìn)行了系統(tǒng)開發(fā)，在300-1300K溫度范圍內(nèi)重現(xiàn)了相同的結(jié)果。通過對(duì)Si/O/H系統(tǒng)相關(guān)的參數(shù)戰(zhàn)略調(diào)整，我們進(jìn)行了濕和干過程的模擬對(duì)比。在“原位蒸汽生成（ISSG）”中所看到的氧化膜增長顯著加速被成功展示。我們模型的這些特性暗示了其在更大范圍內(nèi)的適用性。我們將結(jié)果與其他作者最近開發(fā)的參數(shù)集獲得的結(jié)果進(jìn)行了比較。通過研究了二氧化硅薄膜界面附近的原子構(gòu)型，我們發(fā)現(xiàn)該模型能夠研究氫原子在ISSG加速中的作用。