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高性能MEMS射频无源器件与三维硅微机械加工技术

High-performance MEMS RF Passive Components and Silicon Micromachined Technology

【作者】 顾磊

【导师】 李昕欣;

【作者基本信息】 中国科学院研究生院(上海微系统与信息技术研究所) , 微电子学与固体电子学, 2007, 博士

【摘要】 本论文工作主要研究硅基三维微机械结构制造及关键器件的研制技术。一方面将技术针对目前电讯用RFIC的高性能无源元件,所开发的低温工艺可以与RFIC的CMOS工艺相兼容,同时利用MEMS技术解决了硅衬底损耗等问题,实现了高性能的RF电感、互感和可变电容等关键元件,另一方面还针对微纳操纵和精确定位系统需求的X-Y微移动平台,用深沟侧壁隔离(Trench-sidewall)MEMS工艺形成了具有微米级移动范围和纳米级定位精度的高性能X-Y微移动平台,同时电绝缘技术使该微平台可以在普通硅片上制作,大大降低了制作成本。国际上首次报道一种采用低温CMOS兼容工艺制造嵌入式悬浮螺管(CSS)结构电感与互感。为了便于封装以及后续加工,电感或互感线圈嵌入在硅片内部,这种新型结构能显著降低衬底损耗,并且制造出的器件悬浮结构能够抵抗住10000g的冲击试验,在100g的加速度环境下,ANSYS分析得到的器件形变比目前国际上报道最好的悬浮结构低一个量级。制造出的电感在电感值为2.47nH,Q值在5.3GHz时为54,自谐振频率超过15GHz,优于大多数微机械电感。互感的有效增益为0.89是目前国际上互感性能报道中最好的。利用低应力电镀技术制造出悬浮可变梳齿电容。在4V的驱动电压下可变电容值变化3.18:1即218%,1GHz时的Q值可达103。国际上首次报道一种旋转式可变电容,外界加速度所带来的位移变化比此前国际上所报道的传统微机械梳齿电容低两个量级,旋转式可变电容结构既满足低电压的需要又能够削弱外界加速度的影响。采用深槽侧壁隔离技术制造两维微位移平台,微位移平台的位移精度优于18nm,该技术能够实现单一硅片上不同功能单元的电绝缘,并具备将压阻、电容敏感单元与静电执行器集成在一块单硅片上的能力。

【Abstract】 In this dissertation, we mainly study the 3-D micromachined process and research of key RF passive components. On the one hand, this technology is performed in RFIC for communication. The novel process could be compatible with CMOS process with low temperature. Moreover, the substrate effect is suppressed deeply to get high-performance inductors, transformers and tunable capacitors. On the other hand, a nano-precision XY-stage is designed and fabricated with trench-sidewall technology. Moreover, the XY-stage is performed on a sigle wafer instead of SOI wafer to reduce the cost of the fabrication.The concave-suspended inductors and transformers are performed with CMOS compatible process under a low temperature. The embedded structures facilitate the post-fabricated and package such as flip-chip. The suspended structures survive the 10000g shock. Moreover, 100g acceleration is sequentially applied to X, Y and Z axes by using ANSYS software. The deformation is an order lower than other robust suspended spiral inductor. In consequence, the 2.74nH inductor shows a high peak Q-factor of about 54 at 5.35GHz. The self-resonance frequency is over 15GHz. To my best knowledge, the available gain of the transformer is the highest among the reported paper as 0.89.Suspended tunable capacitors are performed by using low stress electroplating and isotropic release process. The tuning ratio is about 3.18:1, namely 218%, under 4V driving voltage. The Q factor is about 103 at 1 GHz. We also propose a rotational tunable capacitor to suppress the circumstance acceleration and vibration. The deformation under acceleration is two orders lower than the conventional MEMS comb tunable capacitor. The rotational structure keeps not only low driving voltage but robust structure.A XY-stage is fabricated with trench-sidewall process. The precision of the displacement is better than 18nm. Using the trench-sidewall technology, piezoresistive, capacitive sensing and electrostatic driving could be integrated on single wafer to reduce the cost.

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