等离子体刻蚀建模中的电子碰撞截面数据

Electron collision cross section data in plasma etching modeling

半导体芯片是信息时代的基石,诸如大数据、机器学习、人工智能等新兴技术领域的快速发展离不开源自芯片层面的算力支撑.在越来越高的算力需求驱动下,芯片工艺不断追求更高的集成度与更小的器件体积.作为芯片制造工序的关键环节,刻蚀工艺因此面临巨大的挑战.基于低温等离子体处理技术的干法刻蚀工艺是高精细电路图案刻蚀的首选方案,借助等离子体仿真模拟,人们已经能够在很大程度上缩小实验探索的范围,在海量的参数中找到最优工艺条件.电子碰撞截面是等离子体刻蚀模型的关键输入参数,深刻影响着模型预测结果的可靠性.本文主要介绍了低温等离子体建模的基本理论,重点强调电子碰撞截面数据在数值模拟中的重要作用.与此同时,本文概述了获取刻蚀气体截面数据的理论与实验方法.最后总结了刻蚀相关原子分子的电子碰撞截面研究现状,并展望了未来的研究前景.

Semiconductor chips are the cornerstone of the information age,which play a vital role in the rapid development of emerging technologies such as big data,machine learning,and artificial intelligence.Driven by the growing demand for computing power,the chip manufacturing industry has been committed to pursuing higher level of integration and smaller device volumes.As a critical step in the chip manufacturing processes,the etching process therefore faces great challenges.Dry etching(or plasma etching)process based on the low-temperature plasma science and technology is the preferred solution for etching the high-precision circuit pattern.In the low-temperature plasma,electrons obtain energy from the external electromagnetic field and transfer the energy to other particles through collision process.After a series of complex physical and chemical reactions,a large number of active particles such as electrons,ions,atoms and molecules in excited states,and radicals are finally generated,providing the material conditions for etching the substrate.Dry etching chamber is a nonlinear system with multiple space-time dimensions,multiple reaction levels and high complexity.Facing such a complex system,only by fully understanding the basic physical and chemical reaction of the etching process can we optimize the process parameters and improve the etching conditions,so as to achieve precision machining of the semiconductor and meet the growing demand of the chip industry for etching rate and yield.In the early days,the process conditions of dry etching were determined through the trial-and-error method,which is characterized by high cost and low yield.However,with the help of plasma simulation,nowadays people have been able to narrow the scope of experiment to a large extent,and find out efficiently the optimal process conditions in a large number of parameters.In this review,we first introduce the basic theory of the mostly used models for plasma simulation including kinetic,fluid dynamic,hybrid and global models,in which the electron collision cross sections are the key input parameters.Since the formation of the low-temperature plasma is driven by the electron-heavy particle collision processes,and the active species for plasma etching are generated in the reactions induced by electron impact,the accuracy and completeness of the cross-section data greatly affect the reliability of the simulation results.Then,the theoretical and experimental methods of obtaining the cross-section data of etching gases are summarized.Finally,the research status of the electron collision cross sections of etching atoms and molecules is summarized,and the future research prospect is discussed.