SiC单晶衬底的大气等离子体亚纳米级高效平坦化机理与方法研究

Surface integrity of single crystal SiC substrate impacts epitaxial film quality directly. Due to its high hardness and chemical stability, SiC surface is always machined with low efficiency and high damage by conventional planarization technologies. Atmospheric pressure plasma chemical machining provides new feasibility to solve this problem. In this project,planarization mechanism of atmospheric pressure plasma machining is analyzed,and implementation method with subnanometer accuracy and high removal rate is then studied.First, particles excitation model under atmospheric discharge is proposed with quantitative rate coefficents. Reaction path of SiC in F/O chemically reactive atmosphere is investigated to reveal the key rate control steps.Quantitative relationship between temperature and removal rate is analyzed.Then the regionally selective removal mechanism based on temperature-induced machining rate diversity is presented. By quantum chemistry simulation, reaction process between heterogeneous atoms on the gas-solid interface is investigated to reveal the selectivity of atmospheric pressure plasma chemical process on surface micro-topographies. Lucy-Richardson dwell function is proposed, and corresponding parameters optimization method is developed to make it applicable.Removal amount is considered to match with original surafce roughness to realize topography improvement,so a calculation model is proposed. Under low particle desnity, more stable status is needed to accomplish high profile accuracy, which makes a technical approach presented.To testify the proposed high-efficiency planarization mechanism, experiments are performed to demonstrate the validity of atmospheric pressure plasma machining in manufacturing subnanometer-accuracy damage-free SiC surface.The research is rather significant and valuable for developing more effective technologies for high-efficiency planarization of super-hard substrate with subnanometer accuracy.

SiC单晶衬底表面完整性直接影响到外延薄膜质量，但其高硬度、高化学稳定性等特点使得高精度无损伤SiC表面的高效加工极其困难。本项目针对SiC单晶亚纳米级表面的无损抛光，开展大气等离子体高效平坦化机理与方法的深入研究。建立大气压活性粒子放电激发模型，探索SiC的反应路径和关键速率控制步骤。建立温度-速率定量控制模型，提出基于温度诱导反应速率差异性控制的区域选择性去除机理。完成气-固界面复相化学反应的量子化学仿真分析，揭示大气等离子体化学过程对表面形貌的反应选择性机理。建立Lucy-Richardson非线性驻留函数模型，提出工艺设计量化模型和低粒子浓度条件下的稳定控制方法。针对提出的大气等离子体高效平坦化机理与方法，完成亚纳米级面型加工的实验验证。本项目有望开辟一条超硬衬底高效无损平坦化的新技术途径，对于支持高性能半导体器件在航天、国防等领域的应用推广，也具有重要的科学意义和应用价值。

SiC是第三代半导体材料的代表，被广泛应用于国防、航天等战略领域和高端民用领域，其表面完整性直接影响到半导体器件的性能、寿命和可靠性，但SiC高硬度、高化学稳定性等特点使得高精度无损伤SiC表面的高效加工极其困难。.本项目针对SiC单晶的高效无损抛光，开展大气等离子体高效平坦化机理与方法的深入研究。建立大气压活性粒子放电激发模型，探索SiC的反应路径和关键速率控制步骤。建立温度-速率定量控制模型，提出基于温度诱导反应速率差异性控制的区域选择性去除机理。完成气-固界面复相化学反应的量子化学仿真分析，揭示大气等离子体化学过程对表面形貌的反应选择性机理。建立Lucy-Richardson非线性驻留函数模型，完成纳米级面型加工的实验验证。.量子化学理论模拟计算结果显示：大气等离子体抛光的气-固界面复相化学反应，对表面形貌具有一定的选择性，即凸出于表面的微观形貌的反应速率大于凹陷于表面的微观形貌的反应速率，从统计角度分析，宏观材料表面的微观不平度将逐渐降低，直至达到一个更为光滑的新的平衡状态。实验也证明了表面粗糙度的峰谷值Rp-v逐渐减小，且在多个检测时刻粗糙度的平均峰值的减小幅度要明显大于平均谷值的减小幅度，与理论分析结果完全符合。因此，大气等离子体抛光的表面形貌选择性，是实现全局平坦化的理论基础。.SiC的高效加工机理是本项目解决的又一关键科学问题。基于Arrhenius定理建立了大气等离子体化学刻蚀的温度-去除速率定量控制模型，提出了基于温度效应的选择性去除机理，并实验验证了温度对SiC加工效率的促进作用及其可控性。明确了O元素在活性F原子刻蚀SiC反应过程中的影响机制，建立了大气压活性粒子放电激发主要基元反应的简化模型及粒子射流空间分布图，有效引导了沉积-刻蚀竞争机制的反应方向。在单晶4H-SiC上实现了约464 nm/min（深度方向）的去除速率。.建立了基于Lucy-Richardson迭代算法的非线性驻留函数模型和参数优化模型，实现了对大气等离子体化学刻蚀的纳米级控制，在单晶SiC上表面粗糙度最低达到了Ra1nm以内，面型控制精度高于λ/50，有效去除了表面损伤。