vlsi - Single Crystal Silicon MEMS Fabrication Technology...

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Single Crystal Silicon MEMS Fabrication Technology Using Proton-Implantation Smart-Cut Technique Jiangang Du, Darrin J. Young, Wen H. Ko EECS Department, Case Western Reserve University Cleveland, Ohio, USA Email: jxd77@po.cwru.edu Abstract A novel single crystal silicon MEMS fabrication process is proposed using proton-implantation smart-cut technique. Compared to conventional SOI wafer fabrication processes for MEMS applications, this technology can potentially result in a significant substrate and processing cost reduc- tion. A single crystal silicon layer with 1.78 µ m thickness has been achieved using the proposed technique. Prototype structures such as cantilever beams and clamped-clamped micro-bridges have been successfully fabricated as demon- stration vehicles for future micro-system implementations. Keywords MEMS; micromachining; single crystal silicon; smart-cut; wafer splitting; proton implantation. INTRODUCTION Single crystal silicon material is highly desirable for im- plementing MicroElectroMechanical devices and systems due to its reliable and reproducible mechanical and electri- cal properties. Silicon on insulator (SOI) wafers have been used to realize single crystal silicon MEMS inertial sen- sors, optical devices, field emission components, etc. [1, 2, 3, 4]. The silicon structural layer is typically obtained through wafer bonding followed by a grinding and chemi- cal mechanical polishing (CMP) step [2, 5]. This tech- nique, however, results in a substantial amount of silicon material loss through the grinding and CMP process, hence increasing the substrate and processing cost. In this paper, we present a novel single crystal silicon MEMS fabrication technology based on proton-implantation smart-cut tech- nique. This technique has been proposed to produce low cost SOI wafers, with a typical silicon thickness on the order of nanometers, for low power microelectronics appli- cations [6, 7]. At present most MEMS devices, however, call for silicon structural layer with a thickness of at least 1 µ m, sometimes a few tens of micrometers, to achieve cer- tain performance requirements. In this research we have demonstrated that single crystal silicon layer with mi- crometer thickness can be obtained through increasing the proton implantation energy using the smart-cut technique for MEMS applications. The silicon film thickness, critical for precision micro-system fabrication, can be accurately determined through implantation energy control. Further- more, the proposed fabrication technique eliminates the grinding and CMP processes required in conventional MEMS SOI wafer preparation, potentially resulting in a significant substrate and processing cost reduction. MEMS prototype structures such as cantilever beams and clamped- clamped micro-bridges with a silicon thickness of 1.78 µ m have been fabricated as demonstrated vehicles for future
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This note was uploaded on 11/03/2009 for the course ECE EE560 taught by Professor Alsaba during the Spring '09 term at S. Alabama.

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vlsi - Single Crystal Silicon MEMS Fabrication Technology...

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