RF MEMS device based on micromachining

微机械加工是集成电路微加工的一种扩展技术，可以在硅芯片上制造三维微结构、传感器和执行器。射频微机电系统（RF MEMS）是一种为无线系统生产射频元件的技术。开关（继电器）、可变电容器、用于时间（频率）参考或射频滤波器的微机械谐振器、射频互连和线圈，这些都是在薄的自支撑膜上制造的，因此具有小的杂散电容。本研究项目取得了以下成果：研究了射频MEMS的晶圆级封装技术和从硅芯片顶部到背面高速信号的电气互连馈电结构。开发了静电驱动的接触式和电容式MEMS开关。MEMS开关…更多应用于柔性平板显示器，并作为高速LSI测试器的元件商业化。微机械谐振器可以具有高谐振频率。由于延伸模式的高弹簧常数，延伸模式比弯曲模式能够实现更高的谐振频率。通过使谐振频率由横向尺寸决定，可以在一个芯片上集成多个不同谐振频率的谐振器。一个直径为20 μm的静电驱动酒杯型硅盘谐振器的谐振频率约为100 MHz。由于这种小型谐振器的谐振频率会因吸收气体而波动，因此在硅片的真空腔中制造MEMS谐振器以稳定谐振频率。微机械谐振器存在由热机械噪声引起的相位噪声问题。热机械噪声也限制了共振传感器的分辨率。MRFM（磁共振力显微镜）对生物细胞等小样本的MRI（磁共振显微镜）要求极高的灵敏度。对噪声问题进行了研究，提出了采用参数挤压阻尼来降低相位噪声的方法。采用厚度共享模式的石英材料，研制了具有高大气质量因子的悬臂谐振传感器。高纵横比刨床线圈。都是为了降低电阻而制造的。在1.6 GHz下，小样本核磁共振成像的质量因子高达85。少

Three-dimensional microstructures, sensors and actuators can be fabricated on a silicon chip using micromachining which is an extended technology based microfabrication for integrated circuits. RF MEMS (Radio Frequency Micro Electro Mechanical Systems) has been developed to produce RF components for wireless systems. Switches (relays), variable capacitors, micromechanical resonators for time (frequency) references or RF filters, RF interconnection and coils which are fabricated on thin self supported membranes and hence have small stray capacitances can be made by this technology. Following achievements are obtained in this research program.Packaging technologies for the RF MEMS as wafer level packaging processes and electrical feedthrough structures for an electrical interconnection for high speed signal from the top side to the backside of silicon chips were developed. MEMS switches as contact type and capacitive type which are actuated electrostatically were developed.MEMS switches … More were applied for a flexible flat panel display and commercialized as components for high speed LSI testers.Micromechanical resonators can have high resonant frequencies. The extension mode enables higher resonant frequency than the bending mode because of the high spring constant of the extension mode. By making the resonant frequency determined by the lateral dimension multiple resonators with different resonant frequencies can be integrated on a chip. An electrostatically driven wine glass mode silicon disk resonator of witch diameter is 20 μm demonstrated a resonant frequencies of approximately 100 MHz. Since the resonant frequency of such small resonators can be fluctuated by absorbing gas MEMS resonator was fabricated in a vacuum cavity in a silicon chip to stabilize the resonant frequency. Micromechanical resonators have an inherent problem of phase noise caused by thermomechanical noise.The thermomechanical noise also limit the resolution of resonating sensors. Extreme sensitivity is required for MRFM (Magnetic Resonance Force Microscopy) for the MRI (Magnetic Resonance Microscopy) of small samples as biological cell. The noise problems were studied and the phase noise could be reduced by a parametric squeeze damping. Cantilever resonant sensors which have high quality factor in atmosphere were.developed by using quartz material with thickness share mode.High aspect ratio planer coils.were fabricated to reduce the resistance.and high quality factor as high as 85 at 1.6 GHz was achieved for the purpose of the MRI for the small samples. Less