Norisato Shimizu

Approach to higher reliability in 3D micromechanisms

A micro-reducer characterized in its small size, high resolution ration and high reliability has been developed to achieve sufficient performance after 5,000,000 high-speed rotations1. A 3K-type mechanical paradox planetary gear reduction system was chosen in mechanical design. The size of a reducing part is 3 x 3.8 x 1.3 mm, and its reduction ratio is about 200. The module of the fine gears is 0.03. Alloy tool steel and WC-Ni-Cr super hard alloy were selected for the materials. The mechanical, thermal and environmental attributes were investigated by the properties of the materials suitable for micro fabrication on the specific strength and resistance to thermal distortion as the functional performance, and energy content of the material as the environmental impact. Micro-EDM process was optimized to accurately shape such a microscopic components. Surface modification by DLC, CrN, and MoS+-2) thin film was applied by rotating deposition technique to improve the surface-based attributes such as hardness, friction coefficient and resistance to wear. Several kinds of lubrication and bearing systems were evaluated to understand their internal energy dissipation and durability. This report presents such a synthetic approach for the micro-reducer to be steady, efficient and durable.

Application of a silicon-enriched nitride diaphragm to a condenser microphone

LSI process compatible materials are important in the MEMS field. To add on MEMS fabrication processes after circuit fabrication, it is necessary the process temperature must be kept less than about 350 degrees C. The stress control of the film is also important for actual devices. The individual silicon enriched nitride (SEN) film has been developed, and the film properties have been clarified. The deposition temperature of SEN film is 250 degrees C, and that temperature is enough low to perform deposition process after LSI fabrication. The stress of SEN film is proportional to H2 gas flow, and it can be controlled from tensile stress of 30 MPa to compressive stress of 360 MPa. It is thought that the SEN film stress depends on the hydrogen content. The deposition rate and buffered HF etching rate also depend on H2 gas flow. From the RBS analysis, the composition ratio of Si/N is about 2.1. The SEN film is adopted to a condenser microphone. The membrane profile is well controlled by using tensile stressed SEN film. The sensitivity of fabricated microphone increased 0.5 mV/Pa in the half area diaphragm. The noise level is also improved over 12 dBSPL.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.