摘要
化学机械抛光是实现砷化镓原子级精度表面加工的关键技术,其对材料去除的过程由摩擦化学作用主导。因此深入研究化学机械抛光中摩擦化学去除机理,有助于其加工表面质量的提升。借助原子力显微镜分别在酸性环境(pH值约为4)、中性环境(pH值约为7)、碱性环境(pH值约为10)下利用二氧化硅微球针尖对砷化镓表面在进行纳米磨损试验。采用透射电子显微镜对材料去除区域进行表征,同时结合密度泛函理论计算阐明化学机械抛光中的原子去除机制。试验结果表明,碱性环境下,砷化镓表面材料去除最为严重。透射电子显微镜分析结果显示材料去除区域晶格结构完整,表明摩擦化学反应占主导地位。密度泛函理论计算表明,碱性环境中的界面电荷转移最为明显,也表明OH-通过促进Si-O-Ga键桥形成和削弱Ga-As键的强度导致材料发生去除。研究结论还可为优化其他二元材料的化学机械抛光工艺提供指导。
Nanoprecision surface manufacturing technology has important applications in many high-tech fields,such as semiconductor photovoltaic and integrated circuit manufacturing.Chemical mechanical polishing(CMP),the most critical technology in ultraprecision surface manufacturing,guarantees and promotes the application and development of high-end technologies.Gallium arsenide(GaAs)is the most important second-generation semiconductor substrate,and it is widely used in microelectronics and optoelectronics.High-quality GaAs substrates require the absence of surface/subsurface damage,preservation of lattice integrity,and sub-nanometer level surface roughness.CMP is currently the most effective technology to achieve these requirements.As material removal in CMP is predominantly governed by tribochemical reactions,understanding these mechanisms is essential for enhancing the surface quality.In this study,the tribochemical removal mechanisms during CMP of GaAs were investigated by conducting nano-wear experiments using an atomic force microscope(AFM)equipped with a silicon dioxide(SiO2)microsphere tip under acidic(pH 4),neutral(pH~7),and alkaline(pH 10)conditions.Material-removal regions were characterized using high-resolution transmission electron microscopy(TEM).Density functional theory(DFT)calculations were employed to elucidate the atomic removal mechanisms.The results indicate that material removal on the GaAs surface is the most severe in alkaline conditions,with removal depths and volumes being significantly higher compared with those in neutral and acidic conditions.Specifically,the material removal depths in the acidic,neutral,and alkaline conditions were approximately 9.4,19.2,and 24.2 nm,respectively.Similarly,the material removal volume increased from 4.99×10°nm'in acidic conditions to 8.84x10°nm in alkaline conditions.A TEM analysis revealed that the lattice structure in the material-removal regions remained intact,suggesting that tribochemical reactions dominated the removal process without causing significant damage to the underlying atomic structure.The significant change in the charge density at the GaAs/SiO2 interface,as calculated by DFT,suggests the formation of Si-O-Ga bonds.Furthermore,interfacial charge transfer was the most pronounced in alkaline conditions,where OH-ions promoted the formation of Si-O-Ga bond bridges and weakened Ga-As bonds,facilitating material removal.The calculations showed that the charge transfers in the subsurface region of GaAs were 0.032,0.039,and 0.042 e/A3 under acidic,neutral,and alkaline conditions,respectively.This increased charge transfer in alkaline conditions leads to a more significant weakening of the Ga-As bonds,making the material more susceptible to removal.Additionally,CMP experiments conducted under the same pH conditions confirmed that the surface roughness and material removal rate(MRR)were optimal in alkaline conditions.The surface roughness(Sa)values were approximately 3.61,1.87,and 0.81 nm for acidic,neutral,and alkaline conditions,respectively.The MRR values followed a similar trend,with the highest rate observed in alkaline solutions(22.6 nm/min),compared with those in neutral(19.4 nm/min)and acidic(13.2 nm/min)conditions.This consistency between the nanowear experiments and CMP results underscores the importance of pH in controlling the tribochemical removal process.These findings suggest that the presence of OH-ions in alkaline conditions enhances the formation of Si-O-Ga bonds and increases charge transfer at the GaAs/SiO2 interface,leading to more efficient material removal.This study provides valuable insights into the pH-dependent tribochemical removal mechanisms during the CMP of GaAs,providing a foundation for optimizing CMP processes for other binary materials.The integration of single-abrasive material removal experiments based on AFM,TEM,and DFT calculations presents a comprehensive approach for understanding and improving CMP techniques for semiconductor materials.By elucidating the role of pH in the tribochemical removal process,this study contributes to the development of more efficient and precise CMP methods that ultimately enhance the performance of semiconductor devices.
作者
高健
任兴云
梁德旭
张宏林
周怀诚
江亮
余丙军
钱林茂
GAO Jian;REN Xingyun;LIANG Dexu;ZHANG Honglin;ZHOU Huaicheng;JIANG Liang;YU Bingjun;QIAN Linmao(Department of Resource and Mechanical Engineering,Lyuliang University,Liliang 033000,China;Tribology Research Institute,Southwest Jiaotong University,Chengdu 610031,China;School of Mechanical Engineering,Southeast University,Nanjing 211189,China)
出处
《中国表面工程》
北大核心
2025年第5期99-106,共8页
China Surface Engineering
基金
国家自然科学基金(52175549)。
