A LOCOS process for an electrostatic microfabricated motor
1990; Elsevier BV; Volume: 23; Issue: 1-3 Linguagem: Inglês
10.1016/0924-4247(90)87054-m
ISSN1873-3069
AutoresLee S. Tavrow, Stephen F. Bart, Jeffrey H. Lang, Martin F. Schlecht,
Tópico(s)Force Microscopy Techniques and Applications
ResumoAbstract A novel process based on local oxidation of silicon (LOCOS) for fabricating planar electric micron-scale radial-gap motors is described. Issues relating to the design, fabrication and performance of these micromotors are discussed, with particular emphasis given to the LOCOS process. Functioning variable-capacitance motors with rotors of 50 μm radii are described in detail and qualitative results of their operation with air levitation are presented. Finally, the integration of electronics with the micromotors on the same substrate is discussed. We have discussed the main issues involved in designing and fabricating electric variable-capacitance motors. Radial-gap motors have been selected for controllable instability and ease of fabrication. Furthermore, by examining the fabrication requirements of high-precision thick structures, we conclude that planarization is required unless greatly increased process complexity can be tolerated. The LOCOS-based process has thus been developed because it is inherently planar, unlike standard surface micromachining processes. Micron-scale motors and other structures have been successfully fabricated using the new LOCOS-based process. These motors were spun electrostatically up to speeds over 10 00O rpm, without visible signs of wear, when levitated by an externally generated air bearing. We are investigating the use of reduced-friction coatings such as Si 3 N 4 [2] or Teflon [19] in the bearing structure to eliminate the need for external air levitation. The inherent planarization of the motor not only facilitates the fabrication but may also facilitate the development of certain applications that require some form of direct cover or package. Starting and load transients must be sensed and controlled for stable VC motor performance. Closed-loop control, however, is virtually impossible witho
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