MEMS微梁粘着动力分析

针对严重影响MEMS性能和可靠性的微梁粘着问题,根据W-S微观连续介质理论,建立了粘着力数学模型;针对粘着力对微梁刚度的强非线性影响,利用单元离散法,通过对粘着力时空变量相分离,对500μm×1μm×0.1μm表面镀金的微悬臂梁粘着进行了动力仿真,发现了“跳跃粘着”现象,从而为微梁的系统研究提供理论基础。     

AFM稳定性研究

“突跳”现象严重影响着原子力显微镜(AFM)的性能。根据W igner-Seitz模型微观连续介质理论,建立了AFM针尖同试样面接触力包含斥力的数学模型;由分析力学的稳定平衡条件,发现了引起AFM“突跳”的本质是不稳定平衡点的存在;通过增加AFM悬臂梁刚度,提出了一种避免AFM“突跳”现象发生的方法,并给出仿真结果。     

Hamaker微观连续介质理论的数字密度和Hamaker常数分析

针对Hamaker微观连续介质理论在微观接触力计算中存在的问题,根据Hamaker假设,用连续介质法计算2个原子之间的相互作用力,发现作用力同经典的Lennard-Jones势所反映的作用力不一致.通过分析数字密度,发现数字密度并非是如Hamaker所认为的常数,而是随间距变化的;并得到Hamaker微观连续介质理论仅在间距大于7倍的原子半径时才成立的结论.通过分析Hamaker常数,发现Hamaker常数也随间距变化.     

Hamaker连续介质假设分析

针对Hamaker理论在工程实际中存在的问题，从物质结构出发分析晶体结构，发现晶体结构存在空隙，Hamaker连续介质假设不成立.为实现介质的连续性，根据物质结构理论，提出体心立方体和面心立方体的Wigner-Seitz密实拼构模型.通过分析双Wigner-Seitz模型同经典Lennard-Jones势，推导出Hamaker介质修正系数，对Hamaker可加性假设和均质材料假设进行了修正，同时修正了Hamaker提出的用连续方法计算微观物质间相互作用力的表达式，对斥力进行了分析，将微观连续介质的应用范围 关键词： Hamaker假设 Wigner-Seitz模型 Lennard-Jones势 微观连续介质     

Hamaker均质材料假设修正

Hamaker三个假设条件是用连续方法解离散问题的理论基础.根据Hamaker三个假设条件，利用连续方法计算两个原子之间的相互作用力，发现作用力同经典的Lennard-Jones势所反映的作用力不一致.通过分析得出Hamaker均质材料假设条件仅适用于微观物质间距较大的范围以及数字密度随间距变化的结论；推导出数字密度随间距变化的表达式，修正了Hamaker提出的用连续方法计算微观物质间相互作用力的表达式.最后对Hamaker常数进行分析，得出Hamaker常数本身就是随物质间距变化的结论，从而对目前存在的 关键词： Hamaker假设 数字密度 Hamaker常数 Lennard-Jones势     

微机械纳米接触连续方法的建模和计算

为解决微机械中“微碰撞”、“纳米接触”问题,建立了纳米接触的刚性球-面模型,根据Hamaker3个假设和Lennard-Jones势,利用连续方法推导出球同平面第1和第Ⅳ层原子之间的作用力表达式,仿真出粘着力同原子层之间的关系,得出影响纳米接触的主要原子为接触区域少数几层原子的结论,从而为纳米接触、纳米摩擦的进一步研究提供理论基础。     

Casimir力、Hamaker力及黏附“突跳”研究

针对微观黏附中出现的"突跳"问题,建立了正弦分布粗糙面黏附模型;基于Casimir效应推导出Casimir力表达式;基于Wigner-Seitz微观理论,推导出包含斥力项的Hamaker力表达式;经过对黏附过程数值仿真,发现存在两个"突跳"过程,曲线存在两个拐点,而非目前研究所得的单个"突跳"过程;仿真结果同相关实验对比,结果符合较好.从而为微纳器件检测和原子分子操纵等提供理论基础.     

The study on mechanism and model of negative bias temperature instability degradation in P-channel metal-oxide-semiconductor field-effect transistors

Negative Bias Temperature Instability (NBTI) has become one of the most serious reliability problems of metal- oxide-semiconductor field-effect transistors (MOSFETs). The degradation mechanism and model of NBTI are studied in this paper. From the experimental results, the exponential value 0.25-0.5 which represents the relation of NBTI degradation and stress time is obtained. Based on the experimental results and existing model, the reaction-diffusion model with H+ related species generated is deduced, and the exponent 0.5 is obtained. The results suggest that there should be H+ generated in the NBTI degradation. With the real time method, the degradation with an exponent 0.5 appears clearly in drain current shift during the first seconds of stress and then verifies that H+ generated during NBTI stress.     

Effect of Channel Length and Width on NBTI in Ultra Deep Sub-Micron PMOSFETs

The effects of channel length and width on the degradation of negative bias temperature instability （NBTI） are studied. With the channel length decreasing, the NBTI degradation increases. As tile channel edges have more damage and latent damage for the process reasons, the device can be divided into three parts： the gate and source overlap region, the middle channel region, and the gate and drain overlap region. When the NBTI stress is applied, the non-uniform distribution of the generated defects in the three parts will be generated due to the inhomogeneous degradation. With tile decreasing channel length, tile channel edge regions will take up a larger ratio to the middle channel region and the degradation of NBTI is enhanced. The channel width also plays an important role in the degradation of NBTI. There is an inflection point during the decreasing channel width. There are two particular factors： the lower vertical electric field effect for the thicker gate oxide thickness of the sha/low trench isolation （STI） edge and the STI mechanical stress effecting on the NBTI degradation. The former reduces and the latter intensifies the degradation. Under the mutual compromise of the both factors, when the effect of the STI mechanical stress starts to prevail over the lower vertical electric field effect with the channel width decreasing, the inflection point comes into being.     

Wigner-Seitz模型微观连续性分析

针对Wigner-Seitz单元模型同微观连续介质理论体积无限小的连续性矛盾，通过比较面心立方体和体心立方体双Wigner-Seitz单元和经典Lennard-Jones双原子势函数之间引力（长程力）和斥力（短程力）的相对误差，发现当双Wigner-Seitz模型相互重合一半后，相对误差仍满足工程要求；将Wigner-Seitz模型同离散模拟法计算得到的铝单原子球-面作用力结果相比较，两者结果符合；根据Wigner-Seitz模型，建立包含黏附的数字微镜（DMD）动力方程，仿真并同试验结果比较；从而得到Wigner-Seitz模型满足微、纳技术工程分析中微观连续性要求的结论，为微、纳技术的研究提供理论基础. 关键词： Wigner-Seitz模型 微观连续介质 Lennard-Jones势