CAREER: High-Temperature Thermal Transport in LPCVD Polysilicon for MEMS

本研究计划探讨低压化学气相沉积（LPCVD）多晶硅的高温显微结构变化对微机电系统（MEMS）中微尺度热输运现象的影响。热传导物理学、材料科学和硅微机械加工的应用为多晶硅基热传感器和执行器的设计及其可靠性预测提供了新的科学知识。为了实现在高温下的研究，利用MEMS技术开发了一种新的片上仪器。该仪器用于测量多晶硅薄膜的热传递特性，并允许在现场观察晶粒尺寸的演变。根据获得的实验数据，通过考虑晶粒尺寸、晶粒构型、杂质浓度和微观结构动力学，进行理论工作来模拟热输运。所开发的模型用于理解基于多晶硅的MEMS器件和CMOS晶体管的缩放规律和设计规则。该教育计划解决了对MEMS工程师传热教育的重大要求，目的是为学生“优化产品设计”做好准备。利用校内信息技术资源，该项目开发了一门基于MEMS热设计竞赛的新传热课程。热设计项目要求学生团队提出一种MEMS设计，该设计应该为受传热现象强烈影响的特定器件产生更好的性能值。本课程是为来自不同工程专业的高年级学生和研究生设计的。本课程采用网页教学，以促进学员之间的有效沟通。

This research program investigates the impact of high-temperature microstructural changes in Low Pressure Chemical Vapor Deposited (LPCVD) polysilicon on microscale thermal transport phenomena in microelectromechanical systems (MEMS). An application of thermal conduction physics, materials science, and silicon micromachining is made for generating new scientific knowledge needed for the design of polysilicon-based thermal sensors and actuators, and for their reliability predictions. To achieve studies at high-temperatures, a novel on-chip instrument is developed using MEMS techniques. The instrument is to measure thermal transport property of polysilicon films and allows for in situ observation of grain size evolution. Based on the acquired experimental data, theoretical work is performed to model thermal transport by accounting for grain size, grain configuration, impurity concentrations, and microstructural kinetics. The developed model is to serve for understanding scaling laws and design rules for polysilicon-based MEMS devices and CMOS transistors. The education program addresses the significant demands on heat transfer education for MEMS engineers with the purpose of preparing students for "optimizing a product design." Using on-campus information technology resources, this program develops a new heat transfer course based on a MEMS thermal design competition. The thermal design project asks student teams to propose a MEMS design that should yield a better figure of merit for a particular device, which is strongly influenced by heat transfer phenomena. The course is designed for senior and graduate students from various engineering programs. A web-page-based instruction is implemented for this course to promote effective communications among the participants.