Cooperative Roles of Chemical Reactions and Mechanical Friction in Chemical Mechanical Polishing of Gallium Nitride Assisted by OH Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations
Cooperative Roles of Chemical Reactions and Mechanical Friction in Chemical Mechanical Polishing of Gallium Nitride Assisted by OH Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations
复制标题
OH自由基辅助氮化镓化学机械抛光中化学反应和机械摩擦的协同作用：紧束缚量子化学分子动力学模拟
DOI：
10.1039/d0cp05826b
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
M. Kubo
中科院分区：
文献类型：
--
作者：
K. Kawaguchi;Y. Wang;J. Xu;Y. Ootani;Y. Higuchi;N. Ozawa;M. Kubo
化学机械抛光（CMP）是将氮化镓（GaN），特别是Ga面GaN应用于半导体器件（例如激光二极管）的关键制造工艺。然而，由于GaN的高硬度和化学稳定性，其CMP效率非常低。实验上，OH自由基似乎能够提高CMP效率的GaN抛光的SiO2磨料颗粒，而OH自由基辅助CMP过程的机制仍然不清楚，因为实验阐明的复杂的化学反应之间发生的GaN衬底，磨料颗粒，和OH自由基是困难的。在这项工作中，我们使用我们以前开发的紧束缚量子化学分子动力学模拟研究OH自由基辅助CMP过程中广泛使用的Ga面GaN衬底抛光的非晶SiO2磨料颗粒，努力了解OH自由基如何协助CMP过程，然后帮助下一代CMP技术的发展。我们的模拟结果表明，GaN的OH自由基辅助CMP过程通过以下三个基本反应步骤进行：（i）首先，GaN表面上的所有氢终端通过与OH自由基的连续反应被OH终端取代;（ii）在基质被OH完全封端后，这些OH封端的氢原子通过与新加入的OH自由基反应而除去，其形成H2O分子并在表面上留下具有悬挂键的高能氧原子;以及（iii）最后，这些高能氧原子侵入衬底内部，伴随Ga-N键的解离和N2和氢氧化镓分子的产生，这累积地导致N和Ga原子从衬底上去除。
Chemical mechanical polishing (CMP) is a key manufacturing process for applying gallium nitride (GaN), especially the Ga-face GaN, to semiconductor devices such as laser diodes. However, the CMP efficiency for GaN is very low due to its high hardness and chemical stability. Experimentally, OH radicals appear able to improve the CMP efficiency of GaN polished by a SiO2 abrasive grain, whereas the mechanisms of the OH-radical-assisted CMP process remain unclear because experimental elucidation of the complex chemical reactions occurring among GaN substrate, abrasive grain, and OH radicals is difficult. In this work, we used our previously developed tight-binding quantum chemical molecular dynamics simulator to study the OH-radical-assisted CMP process of the widely employed Ga-face GaN substrate polished by an amorphous SiO2 abrasive grain in an effort to understand how OH radicals assist the CMP process and then aid the development of next-generation CMP techniques. Our simulations revealed that the OH-radical-assisted CMP process of GaN occurs via the following three basic reaction steps: (i) first, all hydrogen terminations on the GaN surface are replaced by OH terminations through continuous reactions with OH radicals; (ii) after the substrate is fully terminated by OH, the hydrogen atoms of these OH terminations are removed by reacting with newly added OH radicals, which forms H2O molecules and leaves energetic oxygen atoms with dangling bonds on the surface; and (iii) finally, these energetic oxygen atoms intrude inside the substrate with concomitant dissociation of Ga–N bonds and the generation of N2 and gallium hydroxide molecules, which accumulatively lead to the removal of N and Ga atoms from the substrate.