基于室温离子液体的高硬晶体基片化学机械抛光新方法

Currently the polishing slurry in chemical mechanical polishing (CMP) is mainly water-based. There exist problems of low material removal rate and poor machining quality while machining high-hardness crystal substrates, such as single crystal sapphire, SiC and GaN, using CMP due to the high hardness and the chemical inertness of the material. The innovation of this project is to put forward a new CMP technology based on the deep eutective solvent (DES). As a newly developed room temperature ionic liquid, DES has unique qualities such as high ion concentration, good thermostability, excellent catalytic ability and wide temperature range of liquid state. The matching ability of DES and the high-hard crystal will be studied to develop the new CMP polishing slurry containing DES, oxidants, catalysts and surfactants. The proper poishing pad will be selected. The micro-mechanical behavior and the physicochemical properties between the high hard crystal surface and the slurry under the friction will be studied to reveal the material removal and surface formation mechanism. This project aims to develop new CMP technology with independent intellectual property.

现行化学机械抛光（CMP）技术主要采用水基抛光液体系，在加工单晶蓝宝石、SiC和GaN等高硬晶体时，由于这些材料的硬度高、化学稳定性好，水基抛光液环境中化学作用有限，存在材料去除率极低、加工质量不稳定等问题。本项目创新地提出采用室温离子液体体系的CMP新原理。以新型可工业化的离子液体——深共熔溶剂（DES）为基液，利用DES所具有的离子浓度高、液程宽、催化能力强、热稳定性好等不同于水基溶液的独特性质，开发高硬晶体高效CMP新方法。针对高硬晶体的特性，研究晶体材料与DES之间物理化学性质的适配性，研制以DES为基液、并含有氧化剂、表面活性剂等的CMP抛光液，优选适用于新型CMP体系的抛光垫；研究DES环境中摩擦作用下高硬晶体表面与新抛光液之间的物理化学效应和微观力学行为，揭示新CMP体系加工高硬晶体的材料去除和表面形成机理。通过系统的理论研究和工艺开发，发展具有自主知识产权的CMP新技术

针对三类高硬、高化学惰性晶体材料（蓝宝石（Al2O3）、氮化镓（GaN）、碳化硅（SiC））在传统化学机械抛光（CMP）加工过程中材料去除速率低下，加工成本高的问题。进行了三类晶片在深共溶剂（DES）环境中的纯化学刻蚀，研究了对三类晶片产生化学刻蚀的组分及添加剂；研究了以DES为基液的抛光液基本特性，特别是磨粒在基液中的分散情况，设计并搭建了可与DES基液相配合使用的CMP平台进行三类晶片CMP加工实验；重点研究了GaN晶片在不同溶液组分、添加剂及紫外光照情况下的光化学和光电化学刻蚀机理；将GaN晶片的光化学氧化机理和光电化学氧化机理与机械抛光进行组合，创新性地提出了GaN晶片的光化学机械抛光加工（PCMP）和光电化学机械抛光加工（PECMP）方法；基于PCMP加工和PECMP加工方法，设计并搭建了相应的加工实验平台，开展了对GaN晶片的PCMP和PECMP实验研究和机理研究。研究结果表明：GaN晶片的PECMP加工可获得约1.2 um/h的材料去除速率和超光滑晶片表面。