RF MEMS device based on micromachining

微机械加工是一种基于集成电路微加工的扩展技术，可以在硅芯片上制造三维微结构、传感器和驱动器。射频微电子机械系统(RFMEMS)是为生产无线系统的射频元件而开发的。开关(继电器)、可变电容器、用于时间(频率)基准的微机械谐振器或RF滤波器、RF互连和线圈，这些都是在薄的自支承膜上制造的，因此具有小的杂散电容。本研究取得了以下成果：开发了作为晶片级封装工艺的RFMEMS封装技术和用于高速信号从硅片顶端到背面的电互连的电馈通结构。研制了接触式和电容式两种静电驱动的MEMS开关。…更多的被应用于柔性平板显示器，并作为高速LSI测试仪的组件进行商业化。微机械谐振器可以具有较高的谐振频率。由于伸展模式的高弹簧常数，伸展模式能够实现比弯曲模式更高的谐振频率。通过使横向尺寸确定的谐振频率可以在一块芯片上集成具有不同谐振频率的多个谐振器。设计了一个直径为20μm的静电驱动酒杯模式硅片谐振器，其谐振频率约为100MHz.由于这种小型谐振器的谐振频率可以通过吸收气体而波动，因此在硅芯片的真空腔中制作了MEMS谐振器来稳定谐振频率。微机械谐振器存在由热机械噪声引起的固有的相位噪声问题，热机械噪声也限制了谐振式传感器的分辨率。核磁共振力显微镜(MRFM)对作为生物细胞的小样本的磁共振成像(MRI)需要极高的灵敏度。对噪声问题进行了研究，提出了通过参数压缩阻尼来降低相位噪声的方法。利用具有厚度共享模式的石英材料研制了大气中具有高品质因数的悬臂梁式谐振式传感器，并制作了高深宽比的平面线圈来减小电阻，在1.6 GHz处获得了高品质因数，可用于小样品的磁共振成像。较少

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