A Heavily Boron-Doping Method for Fabrication of Thick MEMS Structural Layer

在MEMS器件中,浓硼掺杂层通常为器件的结构层.但由于受表面固溶度及浓度梯度影响,该掺杂层(硼原子浓度≥5x1019CM-3)厚度越大所需的扩散时间越长.为了能在同等扩散工艺条件下,制备出更厚的浓硼掺杂层以满足器件要求,提出了多步扩散法.即在保证总的累计扩散时间不变的前提下,将传统的扩散过程分为两个相对短的扩散周期.并且这两个周期连续进行,每个周期各包含一次预扩散和再分布.与传统的两步扩散相比,多步扩散法可为硅基底引入更大量的硼杂质,并且具有一定能力使硼杂质留在一定深度范围内.因此该方法可以获得更大的有效节深.实验中采用该方法成功制备出21μM厚的浓硼掺杂层.然而在文献中提到的采用传统两步法在同样条件下得到的厚度则小于15μM.从而验证了该方法可在同等扩散工艺条件下,可以制备出更厚的浓硼掺杂层.In MEMS devices,heavily boron-doped layers are usually used as structural layers.Due to the influence of solid solubility and concentration gradient in area near surface,the fabrication of a thicker layer(boron concentration≥5 × 10 19 cm-3) needs a longer diffusion duration.In order to fabricate the thicker layer under the same diffusion condition,multi-step diffusion method is put forth.It divides conventional diffusion process into two relatively short periods while maintaining the same cumulative diffusion duration.The two periods are performed continuously and each diffusion period includes one predeposition and one drive-in.Compared with conventional two-step diffusion method,this multi-step diffusion method can bring a larger quantity of boron dopants to silicon substrate and possesses the potential to trap dopants at a certain depth.Thus,it is possible to obtain thicker heavily boron-doped layers.In the experiment,a 21 μm thick heavily boron-doped layer was obtained by this method,6 μm thicker than that obtained in references(less than 15 μm) using conventional two-step method under the same diffusion condition,which demonstrates that this method can fabricate thicker heavily boron-doped layers under the same diffusion condition.thesupportfromAviationScienceFoundationofChina(20110868001); AviationKeyLaboratoryofScienceandTechnologyonInertia~

Application of Aerosol Jet Technology on Through Hole Metal Interconnection for MEMS Wafer Level Package

在微机电系统(MEMS)圆片级封装中,通孔缺陷极有可能降低芯片与外界电互联的可靠性.采用气浮沉积的方法,在通孔底部沉积纳米银浆,形成低电阻的Ag/Al/SI欧姆接触结构,解决了电极间的电学连接问题.根据AJTM300气溶胶喷射系统的特点,选择50nM粒径的纳米银浆制作通孔Ag/Al/SI欧姆接触结构;在平面圆形Al电极上气浮沉积纳米银浆,改变银浆的烧结温度,用以验证Ag对Al/SI接触电阻的影响;将此法应用于通孔互联结构中,并探究得出最优沉积时间,测量两通孔间的I-V特性.试验结果表明,采用超声雾化方式的气浮沉积方法,在通孔底部沉积15S的纳米银浆,经过300℃的烧结,可以有效填充通孔底部缺陷,并形成较低电阻的Ag/Al/SI接触结构.采用按需喷印的气浮沉积方案对通孔进行沉积,为实现MEMS芯片与外界的电互联提供了新思路.In MEMS wafer level package,the reliability of electrical interconnection between the chip and external environment may be reduced by the breakage of the through-hole.The breakages of the through-hole deteriorate the reliability of electrical interconnection between internal device and external circuit.In order to solve the problem,the Aerosol Jet technique is adopted in this paper,which deposits nano-silver ink at the bottom of the through hole,forming Ag/Al/Si contact structure with low resistance.First,nanosilver ink with particle diameter of 50 nm is deposited on planar round electrodes with Aerosol Deposition to verify the influence of Ag on Al/Si contact resistance.Then,the bottoms of the through holes are filled with silver ink to form Ag/Al/Si contact structure.The I-Vcharacteristics between two through holes are also tested.The experimental result shows that aerosol jet method with ultrasonic atomizer is able to fill the breakage in through hole and form Ag/Al/Si contact structure with low resistance after depositing nano-silver ink for 15 sand sintering under 300 ℃.The Aerosol Deposition method which is deposit on demand,provides a new thinking to achieve the electrical interconnection.国家自然科学基金(51105320

Design and Simulation of Fully-symmetrical Resonant Pressure Sensor

提出了一种基于侧向驱动的全对称谐振式压力传感器结构.谐振结构采用侧向梳齿电容驱动,既保证了驱动力的线性特性,又由于本身的空气阻尼为滑膜阻尼,可以取得较高的品质因子.另外,设计的差分电容结构能进一步提高器件的检测灵敏度.经过AnSyS 10.0的仿真分析总结出谐振结构固有频率受结构参数影响的规律,确定了量程为0~550kPA的谐振式压力传感器具体尺寸,其灵敏度达到了22.602Hz/kPA;分析了温度对谐振结构固有频率的影响,得到-20~60℃下的热灵敏度温度系数为-1.823 3Hz/℃,为后续的温度补偿提供依据;最后通过分析谐振结构的频域响应特性,最终确定了传感器的频域特性曲线以及不同阻尼比下传感器的品质因子,为谐振式压力传感器真空封装的真空度选择提供参考.A fully-symmetrical resonant pressure sensor based upon lateral drive is presented.Resonant structure adopts lateral comb capacitance drive,which can ensure the linear characteristic of driving force,and obtain higher quality factors because its air damping is a kind of slide-film damping.In addition,the differential capacitance structure of the design can further improve the detection sensitivity of device.According to the simulation analysis by ANSYS 10.0,the law by which the natural frequency of the resonator is influenced by the structural parameters can be summarized,the specific size of resonant pressure sensor with a range of 0 to 550 kPa is confirmed,and its sensitivity has reached up to 22.602 Hz/kPa;the impact of temperature on the natural frequency of the resonator is analyzed,knowing that the temperature coefficient of thermal sensitivity is-1.823 3 Hz/℃ and on the condition that temperature is-20 ℃ to 60 ℃,it provides basis for temperature compensation;Finally,based on the analysis on the frequency domain response characteristics of the resonator,ultimately the curve of frequency domain characteristics has been drawn up and the quality factors of sensor under different damping ratios are identified,it offers reliable reference for the choice of vacuum whose vacuum encapsulation of resonant pressure sensor.国家自然科学基金项目(51035002;50875222);中央高校基本科研业务费专项资金项目(2010121039