June 18, 2006
June 18, 2006
June 21, 2006
11.844.1 - 11.844.8
Introductory MEMS technology using Bulk Micromachining in the Semiconductor Manufacturing Curriculum
Microelectromechanical systems (MEMS) are small, integrated devices or systems that combine electrical and mechanical components. They range in size from sub micrometer (or sub micron) to millimeter. MEMS extends the fabrication techniques developed for integrated circuit industry to micromachining and manufacturing by adding mechanical elements such as beams, gears, diaphragms, and springs to devices. These systems can sense, control, and activate mechanical processes on the micro scale, and function individually or in arrays to generate effects on the macro scale. Consequently, the micro fabrication technology enables fabrication of large arrays of devices, which individually perform simple tasks, but in combination can accomplish complicated functions1.
Although MEMS is relatively a new technology introduced in industry, significant teaching potential of introductory MEMS technology is identified in the Semiconductor Manufacturing Technology (SMT) curriculum. The SMT class (TECH4392) taught at Engineering and Technology Department covers broad spectrum of SMT technologies from the crystallographic structure of the silicon substrate to IC inspection. It consists of 5 lab sessions of semiconductor fabrication in the class 10,000 cleanroom in the department. Primary lab activities include silicon oxide growth, aluminum PVD (Physical Vapor Deposition), photolithography, etching and surface inspection.
To introduce fundamentals of MEMS technology in SMT class, we used statements by leading researchers such as Kaigham (Ken) J. Gabriel, a Carnegie Mellon University professor who illustrates the fabrication of MEMS simply as “we deposit materials and remove them,” essentially the same as ICs manufacturing process. However, “the films put down are thicker by an order of magnitude,” he added. These films can grow several microns thick, sometimes up to 10 microns, while IC thin-film layers are typically measured in angstroms these days. In addition, MEMS fabrication calls for deeper etches. “The whole point of MEMS is to wind up with a mechanical structure that moves,” said Gabriel, who once led the DARPA MEMS program3. These remarks unveil any fear or hesitation on the part of students and allow us to introduce a whole new area of study different from the main class curriculum, but at the same time similar in many manufacturing aspects.
In spring 2005, a group of students who registered in TECH4392 for research credits went through entire bulk micromachining processes from design to fabrication (in section III). While taking the SMT course, they reported their works at each significant milestone and provided full presentation at the end of the semester. Due to the analogy in terminologies and processes between MEMS technology and SMT, students in two different groups seem to experience minimal difficulties for teaching and communication. In order to introduce the fundamentals of the MEMS technology in the SMT curriculum, a bulk micromachining process of pure silicon is considered. Although brittle in macro scale, Si has higher intrinsic yield strength (7 Gpa) than steel (4.2 Gpa), thus often being considered for micro structure fabrication material such as beam
Um, D. (2006, June), Introductory Mems Technology Using Bulk Micromachining In The Semiconductor Manufacturing Curriculum Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. https://peer.asee.org/46
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