The Nano-Precision HARPSS-CMOS Process for RF and Sensory Microsystems

本提案旨在将高纵横比、亚100nm垂直气隙mems /NEMS技术与1um门长CMOS工艺集成，并将由此产生的高纵横比CMOS- mems工艺应用于高性能射频传感微系统，以及混合信号电路。提出了以下两个试验台的实施方案，作为技术示范：1。高性能传感器系统测试平台：实现一种具有直接数字输出的新型cmos集成惯性级（亚ug分辨率）加速度/振动传感器系统。与目前的集成微系统相比，这种单芯片传感器系统将具有3-4个数量级的灵敏度。它由一个纳米精度横向加速度计和一个高性能混合信号接口电路组成，该电路采用200um高的垂直多聚电容，在模具面积上减少了2个数量级。无线射频组件测试平台：实现基于mems的高q片上频率参考，“在扩展到GHz的宽频率范围内”与cmoseleconics（基于mems的VCO）集成。在过去的几十年里，CMOS和类似CMOS的工艺在Si衬底表面沉积层的数量和厚度上都有了实质性的增长（所谓的后端工艺）。然而，前端工艺并没有按比例增长，仍然局限于制造晶体管所需的步骤。cmos的硅外厚度已经增长到几乎比它的硅内厚度大一个数量级。集成MEMS工艺的发展遵循与表面微加工结构集成相同的模式。问题是：能否修改cmos工艺的前端，通过提高性能和提供更高水平的功能，为集成MEMS带来新的生命？所提出的活动的智力优点是使用深度反应离子蚀刻和填充技术修改cmos工艺的前端，以利用硅的第三维度并在cmos级硅衬底内嵌入功能（包括电气和机械）。所提出的工艺将通过其独特的创造亚100nm垂直间隙和亚微米硅特征的能力，允许微机械结构的缩放到纳米领域。高纵横比多晶硅和单晶硅结构（具有高品质因子）以纳米级的间隙分隔，将集成到CMOS电路中。所提议的活动产生的更广泛的影响是能够为集成MEMS和混合信号电路带来更高水平的性能和集成。更高的性能水平和在单个硅芯片上进行无线通信的能力可以为新的机会和应用打开大门。想象一下，有一个微小的MEMS-CMOS硅芯片，不仅可以监测环境中的微小变化，还可以将监测到的数据以数字形式实时传输到接收器，或者与无线传感节点网络进行通信。这种无线传感节点可以在各种形式的环境监测和节能系统中找到许多应用。

0301900AyaziThis proposal is aimed at the integration of a high aspect-ratio, sub-100nm vertical airgapMEMS/NEMS technology with a 1um gate-length CMOS process, and the application of theresulting high aspect ratio CMOS-MEMS process to high-performance RF-sensory microsystems,as well as mixed-signal circuits. The implementation of the following two testbeds is proposed astechnology demonstrators:1. The high-performance sensor system testbed: Implementation of a novel CMOS-integratedinertial-grade (sub-ug resolution) acceleration/vibration sensor system with direct digital output.This single-chip sensor system will have 3-4 orders of magnitude higher sensitivity compared tothe current state of the art integrated microsystem. It consists of a nano-precision lateralaccelerometer and a high-performance mixed-signal interface circuit which utilizes 200um tallvertical poly-poly capacitors, yielding 2 orders of magnitude reduction in the die area.2. The wireless RF components testbed: Implementation of MEMS-based high-Q on-chipfrequency references "over a wide frequency range extending into GHz" integrated with CMOSelectronics (MEMS-based VCO).Over the past few decades, CMOS and CMOS-like processes have substantially grown in thenumber and thickness of the deposited layers on the surface of the Si substrate (the so-calledback-end processes). However, the front-end processes have not grown proportionally andremained limited to the steps necessary to create the transistors. The out of silicon thickness ofCMOS has grown to be almost an order of magnitude larger than the inside silicon thickness of it.The development of the integrated MEMS processes has followed the same model withintegration of surface micromachined structures. The question is: can the front-end of the CMOSprocess be modified to bring new life to integrated MEMS by enhancing the performance andproviding higher levels of functionality?The intellectual merit of the proposed activity is to modify the front-end of the CMOSprocess using the deep reactive ion etching and refill technique to make use of the thirddimension into the silicon and embed functionality (both electrical and mechanical) inside theCMOS-grade silicon substrate. The proposed process will allow the scaling of micromechanicalstructures into the nanometer domain through its unique ability to create sub-100nm vertical gapsand sub-micron silicon features. High aspect ratio poly and single crystal silicon structures (withhigh quality factors) separated by nanometer in size gaps will be integrated with CMOS circuits.The broader impact resulting from the proposed activity is the ability to bring about significantly higher levels of performance and integration to the integrated MEMS and mixed-signal circuits. Higher performance levels and the ability to communicate wireless on a single silicon chip can open up the door to new opportunities and applications. Imagine having a tiny MEMS-CMOS silicon chip that can not only monitor very small changes in the environment, but also can transmit the monitored data real time in digital form to a receiver base, or communicate with a network of wireless sensory nodes. Such wireless sensory nodes can find numerous applications in various forms of environmental monitoring and energy-efficient systems.