耦合超高频激振技术制备低应力薄膜的调控机制

Large stress exists in SiNx thin film which prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD), it seriously affects the mechanical performances of the film-forming device. There is found in our previous study that stress within microminiature device can be eliminated when it works in the resonance state. Accordingly, a new technology is proposed that PECVD synchronous coupling the ultrahigh frequency (UHF) vibration technology on the MEMS scale. It uses the vibration energy to regulate the Si-N bonding structure, and improves the uniformity and compactness of the deposited film. The main research contents of this project are as follows. Firstly, the dynamic process and evolution law of the UHF energy influence on the Si-N bonding structure are investigated, furthermore, the affecting law of the Si-N bonding structure and morphology on the film stress will be revealed. Secondly, the regulatory mechanism of the compound effect of the multi-physical fields including temperature, vibration force, pressure and plasma after PECVD environment coupling UHF vibration, also the preparation condition of low-stress SiNx film will be obtained which affected by the coupling of vibration force, vibration frequency and vibration waveform. Finally, the experimental PECVD system will be built which coupling UHF vibration, and the transmitting channel will be designed through which the vibration energy effectively propagates in the micro devices, also the process specification of the in-site preparation of low-stress SiNx film will be gained. This research results will reveal the physical mechanism of the low-stress SiNx film prepared by PECVD coupling vibration energy, and will provide innovative ideas for the preparation of low-stress film.

等离子增强化学气相沉积（PECVD）制备SiNx薄膜存在较大应力，严重影响成膜器件的力学性能。我们前期研究发现微小型器件在共振状态下应力能被消除，据此提出微尺度下PECVD同步耦合超高频激振的新技术，利用振动能量调控Si-N键合结构，改善沉积薄膜的均匀性和致密性。主要研究内容有：考察超高频振动能量影响Si-N键合结构的动态过程和演变规律，揭示Si-N键合结构和形态对薄膜应力的作用规律；研究PECVD环境耦合超高频激振后，温度、振动力、气压和等离子体等多物理场复合作用对成膜应力的调控机制，获得多种激振力、激振频率和激振波形等耦合作用制备低应力SiNx膜的条件；构建耦合超高频激振的PECVD实验系统，设计振动能量在微器件的有效传递通道，试验获取在线制备低应力SiNx薄膜的工艺规范。研究成果将揭示PECVD耦合振动能量调控制备低应力SiNx膜的物理机制，为低应力薄膜的制备提供崭新的思路。

高频振动时效技术消除薄膜应力，克服了传统时效方法的应力消除周期长、工艺参数复杂、实验条件要求严格等缺点，为快速有效的制备低应力薄膜提供了一种新方法。.（1）研究了高频振动时效机理及实验装置的组建。首先，从光刻胶薄膜交联网络的形成和高频振动能量改变分子链形态来分析时效机理；其次，组建了用于薄膜振动时效的高频激振装置；最后，分析了表面轮廓法测量薄膜应力的原理，组建了用于测量样品表面轮廓的轮廓测量装置。.（2）研究了小孔法中校准系数的有限元数值标定技术和逐层钻孔构建非均匀残余应力的测量技术。首先，用有限元数值分析的方法模拟力学拉伸实验的校准过程，在ANSYS中构造试件和应变花粘合的三维模型，分析了试件贴片平面的边长、试样的厚度、钻孔直径和钻孔深度对校准系数的影响规律；其次，采用逐层钻孔的小孔法测量构建非均匀的残余应力，用分层加载的方法标定出分步逐层钻孔所需的校准系数矩阵，建立了一种实用的逐层钻孔的应力测试技术。.（2）研究了高频振动时效的激振参数对AZ 4620薄膜应力消除率的影响。首先，研究了样品的模态仿真结果与应力消除率的对应关系，并根据激振加速度与应力消除率的关系确定了激振加速度临界值为8 g；其次，根据时效规律，对薄膜在混合频率激振6932 Hz、4524 Hz、2581 Hz、1114 Hz、激振电流5 A、时效56 min下振动时效，获得最佳应力消除率为69.28%；最后，分析了薄膜厚度及振动时效的热作用对应力消除率的影响。.（3）以PI光刻胶为例，研究了高频振动时效对其它聚合物光刻胶薄膜应力消除的适用性。首先，概述了PI薄膜的制备参数及其模态分析；其次，基于正交实验结果及AZ 4620薄膜的应力消除规律选定激振功率20 W、时效时间15 min；最后，对PI薄膜在混合激振频率6894 Hz、4499 Hz、2567 Hz、1107 Hz、激振功率20 W、时效60 min下振动时效，获得应力消除率为46.42%。