面向柔性电子制造的空间隔离原子层沉积系统基础研究

Atomic layer deposition (ALD) is a powerful thin film growth technique that employs a sequence of self-limiting chemisorption surface reaction steps, affording sub-nm control of the growth process and uniformity over large areas. For its outstanding performance in fabricating nanoscale, pinhole free films for both packaging and functional layers, ALD has drawn significant attentions in the field of flexible electronics. However, in the conventional temporal atomic layer deposition system, the size of the substrate is limited due to the vacuum deposition environment. The production rate is relatively low with alternating precursor pulses. . Spatially-separated atomic layer deposition (SALD) technology is developed to enable the continuous manufacturing mode for flexible electronics, from "sample preparation" to "mass production". It also enables fast and uniform thin film depositing on the over-large flexible substrate. The rapidly developing SALD technique could meet the requirements for large scale and low cost manufacturing. Yet the SALD process and equipment are much more complex than the conventional temporal ALD ones. For SALD, the process parameters are coupled with each other to influence the process jointly, including gas flow, precursor concentration, substrate moving speed, nozzle structural design, and substrate temperature distribution. The goal of this study is to achieve uniform film with high-speed growth rate by optimizing these interlinked parameters. In conjunction with experimental verifications through our custom built SALD prototype, it is aimed to establish a chemical reaction coupled computational fluid dynamics model. The simulation on gas phase reaction probability enables the analysis of gas separations with high sensitivity. The multi-scale numerical model analysis could guide the process and structural optimizations on the deposition yield and precursor usage. The uniformity and stability of temperature distributions are to be improved through the closed loop predictive control algorithm and the optimization of heating hardware. Finally, we plan to design a modular nozzle that has higher versatility and expandability. The success of this project could provide both experimental and theoretical guidance for the further design of high efficient SALD systems, and promote the key technology and equipment development in the fast growing flexible electronic field in our country.

原子层沉积（ALD）薄膜制造方法因其优良的均匀一致性和厚度可控性，在柔性电子器件的封装层、功能层等具有突出表现和潜在应用。近年迅速发展的空间隔离原子层沉积（SALD）方法可以进一步满足柔性电子大面积、批量化、低成本的制造需求，但其工艺参数与装备较为复杂，涉及到流量、压力、浓度等流体状态参数，衬底移动速度，设备结构参数，以及衬底温度分布的综合影响。本项目旨在通过研究这些参数之间的规律，实现均匀一致、快速高效的沉积。主要包括通过仿真分析和实验验证，在自主设计搭建的SALD系统上进行耦合化学反应的动态流体动力学仿真来分析隔离效果；建立跨尺度数值分析模型来指导产率和前驱体利用率的优化；通过闭环预测控制算法及优化硬件加热方式，实现具有较强抗外界干扰性的快速稳定控制系统，以获得衬底表面温度的均匀分布。为高效空间隔离原子层沉积系统的扩展设计提供理论和实验指导，推进我国柔性电子领域关键工艺与装备的发展。

本课题研究按项目计划书执行，围绕着动态基底薄膜快速均匀生长与饱和吸附间的难题，逐步建立了微间隙带内耦合物质传输、化学反应、基底运动的流体动力学模型，提出了高速动态复杂流场状态下前驱体有效隔离的判定准则, 发明了空间隔离原子层沉积反应单元模块化设计方法, 攻克了薄膜快速均匀制备难题，并成功研制平动式（包括原型机与模块化装备）、卷对卷式系列空间隔离ALD装备。通过对模块化反应单元的拓展与集成，自主研制的常压空间隔离原子层沉积装备实现了纳米叠层薄膜的快速制备以及精确调控，在薄膜沉积不均性保持在±3%以内的前提条件下，沉积速率达到100 nm/min，相较传统时间隔离0.2 nm/min的沉积速率提升2~3个数量级，是所见报道的国际最好水平。通过集成模型预测闭环温度控制、自整定多项式运动曲线、背压精密控制等一系列核心关键技术，装备温度切换速度可达40 ℃/min，较PID算法效率提升67%，同时展现出优良的抗干扰鲁棒性和动态稳定性；基底残余振动小于25μm，较T型运动曲线下降80%以上；自主研发的密封组件可实现反应区域压力精确控制。相关理论成果受到了国内外学术人员的高度评价。法国国家科学研究中心化学研究所负责人Constantin Vahlas研究员认为申请人所采取“数值模拟方法是ALD腔体设计的有力工具”。项目执行期间，在国际知名期刊Chem. Mater., Small等上累计发表论文48篇，代表性论文成果入选Nanoscale期刊封面。申请发明专利47项（含国际专利4项，授权21项），相关成果荣获2018年第46届日内瓦国际发明展评审团特别嘉许金奖、2016年华中科技大学年度知识产权奖。基于上述学术影响，项目负责人在重要国际会议上做大会/主旨/邀请学术报告20余次。在完成项目预定计划的同时，本项目还针对柔性电子封装层和功能层的需求，将装备推广应用于太阳能电池、柔性显示等领域。与武汉华星光电半导体显示技术有限公司就柔性OLED器件的高效封装开展产学研合作研究，制备的复合纳米叠层膜将OLED器件的封装可靠性提升至1000小时，对比商用SiNx封装可靠性提升10倍；在保持高透光性的同时，封装层弯折30000次无裂纹，具有良好的柔韧性，有力地支撑了第六代AMOLED柔性显示面板的研制与应用。