SU-8胶薄膜应力梯度测量方法研究

发布时间：2018-11-16 16:48

【摘要】：SU-8胶是一种在微机电系统(MEMS)中广泛应用的负性光刻胶。由于其独特的光学性能、力学性能和化学性能,以及SU-8胶光刻技术相对于LIGA(lithographie, galvanoformung and abformung)技术成本低,已被广泛的应用于MEMS传感器与执行器的制作中,在微细制造领域正受到了越来越多的关注。在MEMS工艺中,SU-8胶薄膜尤其是作为结构层使用时,其力学性能对MEMS器件制作的成败及性能的好坏至关重要。在MEMS薄膜材料力学参数中,主要包括材料的内应力,应力梯度,泊松比以及杨氏模量等。本文在基于圆形薄膜结构测量应力梯度原理的基础上提出了一种乒乓球拍形测试结构测量SU-8薄膜的应力梯度,并通过CoventorWare软件对乒乓球拍形结构测量理论的正确性进行了仿真验证。仿真计算得到,当圆膜的最大形变小于圆膜厚度的1/4倍时,应力梯度的测量误差小于1%。本文还提出了一种基于牺牲层技术的SU-8胶MEMS结构加工工艺,加工出的SU-8乒乓球拍测试结构中没有裂纹,且被释放的结构层未与衬底发生粘连。采用显微干涉技术拍摄测试结构释放后的干涉图,由干涉图通过最小二乘法拟合计算出释放后测试结构的曲率半径,从而计算出应力梯度。显微干涉测量方法属于非接触式测量,不仅重复性好,不会损害测试结构,而且适用于导电材料与非导电材料力学参数的在线测量。本文分别制作了SU-8胶的乒乓球拍形测试结构和悬臂梁测试结构,并测量计算出它们的应力梯度进行比较,实验结果表明,采用乒乓球拍结构测量应力梯度的重复性很好,而已有的采用悬臂梁测试结构测量应力梯度的重复性较差,因此,乒乓球拍形测试结构要比悬臂梁测试结构更适用于应力梯度测量。本文还采用微梁旋转法对SU-8薄膜的应力进行了测量。通过显微镜拍摄出形变的照片,测量出SU-8测试结构释放后指针的偏转量,从而计算出SU-8薄膜的应力。
[Abstract]:SU-8 adhesive is a kind of negative photoresist widely used in MEMS (MEMS). Because of its unique optical, mechanical and chemical properties, and the low cost of SU-8 photoetching compared with LIGA (lithographie, galvanoformung and abformung), it has been widely used in the fabrication of MEMS sensors and actuators. More and more attention has been paid in the field of micro manufacturing. In MEMS process, the mechanical properties of SU-8 film, especially when used as a structure layer, are very important to the success or failure of MEMS device fabrication and the quality of its performance. The mechanical parameters of MEMS films mainly include internal stress, stress gradient, Poisson's ratio and Young's modulus. Based on the principle of stress gradient measurement of circular thin film structure, a table tennis bat structure is proposed to measure the stress gradient of SU-8 film. The correctness of table tennis racket shape structure measurement theory is verified by CoventorWare software. Simulation results show that when the maximum deformation of the circular film is less than 1 / 4 times of the thickness of the circular film, the measurement error of the stress gradient is less than 1 / 1. This paper also presents a process of SU-8 MEMS structure based on sacrificial layer technology. There is no crack in the tested structure of SU-8 ping-pong bat, and the released layer does not adhere to the substrate. The interferogram of the test structure was taken by means of microinterferometry, and the curvature radius of the structure was calculated by least square method, and the stress gradient was calculated. The micro-interferometry is a non-contact measurement, which not only has good repeatability and does not damage the testing structure, but also is suitable for on-line measurement of mechanical parameters of conductive materials and non-conductive materials. In this paper, the test structure of ping-pong bat shape of SU-8 glue and the test structure of cantilever beam are made, and their stress gradients are measured and calculated. The experimental results show that the repeatability of measuring stress gradient with table tennis racket structure is very good. However, the repeatability of using cantilever beam to measure stress gradient is poor. Therefore, the test structure of table tennis bat shape is more suitable for measuring stress gradient than cantilever beam test structure. The stress of SU-8 thin film was measured by microbeam rotation method. The deformation photographs were taken by microscope and the deflection of the pointer after the release of the structure was measured by SU-8, and the stress of the SU-8 film was calculated.
【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB383.2;TB302

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