杂质磷对单晶硅微结构疲劳特性的影响

发布时间：2018-02-12 08:01

本文关键词： MEMS 单晶硅掺磷疲劳可靠性弯曲测试结构片外弯曲测试装置疲劳寿命模型　出处：《国防科学技术大学》2012年硕士论文　论文类型：学位论文

【摘要】：硅是微机电系统（MEMS: Microelectromechanical Systems）中最常用的功能结构材料之一，，其疲劳特性在硅基MEMS可靠性中有着重要地位。通过疲劳试验数据和现象来认知硅疲劳是目前普遍采用的方法，但由于影响硅疲劳的因素繁多，因此效果并不理想。尽管对硅疲劳特性的研究已有二十载，在测试手段、疲劳寿命建模、疲劳机理等方面取得了一些进展，但没能给出广为接受的硅疲劳理论。本文着眼于提高单晶硅微结构的疲劳可靠性，着重研究了单因素——掺磷（一种常用的电活性杂质）——对单晶硅疲劳特性的影响。主要研究内容及结论如下： 1．针对各向异性湿法体硅工艺的特点，设计了一种既新颖又经济的试样结构，利用有限元分析确定结构的尺寸；设计掩膜版和工艺流程，制备了六组不同掺磷浓度的试样；设计了一种简易的片外弯曲测试系统，通过调整和改进，整个系统的测试性能可满足使用要求。 2．研究了杂质磷对单晶硅微梁弯曲强度的影响。由强度测试数据可知，掺磷对单晶硅微梁的弯曲强度有明显的增强作用。其作用机理为：杂质磷能提高部分原子键的断裂难度和产生新表面的能量。 3．研究了杂质磷对单晶硅微梁弯曲疲劳特性的影响。首先根据强度信息确定疲劳加载应力，进行疲劳测试；然后建立疲劳断裂概率模型；最后由疲劳测试数据和疲劳模型拟合得到材料常数C和n，通过对C和n随掺磷浓度变化趋势的分析得知，掺磷对单晶硅的疲劳特性有比较明显的改善。其机理是：杂质磷能提高单晶硅阻碍裂纹萌生和扩展的能力。经上述研究，本文发现了掺磷对单晶硅强度及疲劳特性的影响规律，这对硅基MEMS的相关可靠性设计有一定的参考价值。
[Abstract]:Silicon is one of the most commonly used functional structural materials in MEMS (Microelectromechanical Systems), and its fatigue characteristics play an important role in the reliability of silicon-based MEMS. But because there are many factors that affect the fatigue of silicon, the effect is not satisfactory. Although the research on the fatigue characteristics of silicon has been 20 years, some progress has been made in testing methods, fatigue life modeling, fatigue mechanism, etc. However, the widely accepted theory of silicon fatigue has not been given. The purpose of this paper is to improve the fatigue reliability of monocrystalline silicon microstructures. The effect of single factor -doped phosphorus (a commonly used electrically active impurity) on the fatigue properties of monocrystalline silicon is studied. The main contents and conclusions are as follows:. 1. According to the characteristics of anisotropic wet bulk silicon process, a new and economical sample structure is designed, the size of the structure is determined by finite element analysis, and six groups of samples with different phosphorus concentration are prepared by designing mask plate and technological process. A simple out-of-chip bending testing system is designed. Through adjustment and improvement, the testing performance of the whole system can meet the requirements of application. 2. The influence of impurity phosphorus on the bending strength of monocrystalline silicon microbeam is studied. Phosphorus doping can obviously enhance the bending strength of monocrystalline silicon microbeams. The mechanism is that phosphorus impurity can increase the fracture difficulty of some atomic bonds and produce the energy of new surface. 3. The influence of phosphorus impurity on the bending fatigue characteristics of single crystal silicon microbeam is studied. Firstly, the fatigue loading stress is determined according to the strength information, and then the fatigue fracture probability model is established. Finally, the material constants C and n were obtained by fitting the fatigue test data and fatigue model, and the change trend of C and n with the concentration of phosphorus was analyzed. The mechanism is that phosphorus impurity can improve the ability of single crystal silicon to prevent crack initiation and propagation. Based on the above studies, the influence of phosphorus doping on the strength and fatigue characteristics of monocrystalline silicon has been found, which has a certain reference value for the reliability design of silicon-based MEMS.
【学位授予单位】：国防科学技术大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH-39;TB34

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