点载荷对应变硅晶体管载流子迁移率增强机理及结构优化设计

It is a hot research topic to use strain technology to modify the optical and electrical properties of semiconductor silicon and othe quantum structural materials. Strained silicon technology, which has become an very important trend in the development of new generation of microelectronics and photonics technology, has been thus called as strain engineering. Its essence is that strain significantly enhance the carrier mobility of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), thereby it drastically improve the performance of the electric device. Most of the previous researches employed lattice mismatch technology to induce strain in silicon, but with limitations of small strain. Its process is complex and expensive. This project proposes to apply the point loads on elastic structure together with optimization design to induce larger strain in the silicon channel of the MOSFET, and to do theoretical and experimental study on carrier mobility enhancement mechanism of the strained silicon. The method is mainly following the natural connections among the point loads, the non-uniform deformation of strained silicon channel of the MOSFET, the quantum electronic structure and charge carrier mobility. Not only the theory of elasticity is employed to study the microstructure deformation evolution process and strength of strained silicon MOSFETs, but the quantum mechanics and energy band theory are also used to study the effect of inhomogeneous strain field on the quantum electronic structure and the charge carrier mobility enhancement mechanism. The research results of the project can provide theoretical and experimental basis for the concept design method for strained silicon devices.

通过应变调控半导体硅及其它量子结构材料光电性质是目前国际研究热点问题。应变硅技术已经成为新一代微电子和光电子技术发展的一个重要趋势而被称为应变工程。其本质是应变会显著增强晶体管载流子迁移率, 从而显著提高器件性能。目前大部分研究是通过外延晶格失配技术产生应变，而局限性是产生的应变较小，工艺复杂且造价昂贵。此项目提出采用点载荷及弹性结构优化设计在晶体管应变硅沟道中产生较大应变，以点载荷、晶体管及应变硅沟道不均匀微结构变形和应变硅量子化电子结构及其载流子迁移率之间的内在关联为主线，致力于应变硅载流子迁移率增强机理的理论与实验研究。不仅采用弹性力学研究应变硅材料微结构形变演化过程及强度，而且应用量子力学理论和能带理论进一步深入研究不均匀应变场对量子化电子结构影响和载流子迁移率增强机理。寻找一套通过点载荷和弹性结构优化调控硅器件光电性质的新概念设计方法，可为新型应变硅器件设计提供理论和实验基础。

此项目提出采用施加点载荷和弹性结构优化设计在应变硅结构中产生较大应变，以点载荷作用下应变的不均匀微结构变形及其量子化电子结构之间的内在关联为主线，致力于通过施加点载荷改变量子化电子结构和迁移率及其机理研究。主要研究内容和成果如下：（1）设计了多功能三维空心壳结构，得到了点载荷下空心半导体量子弹性球应变硅结构内应变分布的解析解，相关研究已经在Archive of Applied Mechanics刊出。（2）提出了采用巴西实验研究二维应变对硅能带结构以及对导带底与价带顶劈裂值的影响,得到了巴西实验中有限圆柱体内应力分布的3-D精确解析解，研究结果不仅为利用巴西实验间接测试脆性材料拉伸强度提供了理论支撑，而且为研究双轴拉伸应变对硅能带结构以及对导带底与价带顶劈裂值的影响,进而研究双轴拉伸应变能带结构的改变对载流子有效质量与散射概率的影响奠定基础。相关研究结果已经在International Journal of Solids and Structures刊出。（3）开展了一维平板压缩下半导体量子空心硅球结的应力分析，得到了平板压缩作用下半导体量子弹性空心硅球结构应力的解析解及其弹性常数的确定方法。相关研究已经在International Journal of Mechanical Sciences刊出。（4）设计了两层壳应变硅新结构，得到了点载荷下两层壳半导体量子弹性球应变硅结构内应力和应变分布的解析解，研究了不均匀应变对量子化电子结构和迁移率影响。相关研究已经在European Journal of Mechanics A/Solids刊出。