New system offers zero-stress coatings in MEMS and nano-fabrication

Microelectronics International

ISSN: 1356-5362

Article publication date: 1 April 2002




(2002), "New system offers zero-stress coatings in MEMS and nano-fabrication", Microelectronics International, Vol. 19 No. 1.



Emerald Group Publishing Limited

Copyright © 2002, MCB UP Limited

New system offers zero-stress coatings in MEMS and nano-fabrication

Keywords: Coatings, MEMS

Recent MEMS applications demand completely tension-free PECVD coatings of silicon nitride, silicon oxynitride and silicon carbide films with special thicknesses. For sensors, free-standing structures are fabricated by initially depositing a layer of nitride, oxynitride or silicon carbide onto a suitable substrate (typically silicon) and then etching away some areas of the underlying supporting substrate. Films with high internal stress used for these applications will rupture once the underlying supporting material is removed. It is essential that the stress produced during the deposition has to be minimized and/or accurately controlled from compressive through zero to tensile stress levels. Therefore, deposition of films with accurately controlled internal stress is a must. Sensor structures made by UltraDep II preserve their shape because of the stress-controlled deposition and will result in stable, free-standing structures with minimal curvature.

Group Sciences uses a unique mixing of high and low frequencies rather than pulsing each frequency as some other systems do in order to attain a fully adjustable range of controlled stress from compressive through tensile. Thus, by varying the percentage of one frequency into the other, there is a possibility to alter the film stress from compressive stress through to tensile stress. These PECVD coatings are particularly suited for a wide variety of applications due to their excellent adhesion, step coverage, scratch resistance, and barrier properties, i.e. resistance to ion migration and moisture penetration.

Recently, some new coating processes were developed, e.g. for silane oxide,TEOS oxide, silicon nitride, silicon carbide3MS on 2"-8" wafers of silicon, gallium arsenide, indium phosphide, sapphire and quartz. UltraDep II offers multiple layer stack in-situdeposition.

Most of these processes have been applied in cooperation with the National Nanofabrication Users Network (NNUN) including five U.S. universities, with Cornell University as headquarters for the program.

The processes are directly transferable to the mass production market leader, PECVD systems. Therefore, the UltraDep systems are perfectly suited for back-up, process development and pilot- line production.

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