Self-Limiting Isotropic Wet Etching Technique with a Tape as an Etch Mask for the Fabrication of Micromachined Devices and Semiconductor Devices

Description A novel process for fabricating micromachined devices and semiconductor devices has been developed at the College of Engineering of the University of Hawaii. The process uses isotropic etching to form structures on substrates such as silicon, glass or metal. During the formation of a spherical cavity in a silicon wafer, a self-limiting etching behavior of an isotropic silicon etchant is observed when a tape was used as an etch mask. Such self-limiting behavior is due to the presence of gas bubbles which close the etch window and limit the mass transport of the etchant to the silicon surface. Because of this behavior, the spherical cavity size has been found to depend on the size of the etch-mask opening and to be independent of the etching time. Using the self-limiting etching phenomenon in an isotropic etching, the dimensions of a spherical cavity are controlled precisely by a photolithographically delineated pattern. Applications Acoustic lenses for a scanning acoustic microscope Optical lenses and fusion target Dome-shaped diaphragm acoustic transducer Numerous arbitrarily shaped structures on silicon wafer
(Circular diaphragm, crossed narrow channel, etc) Usage of Tape (polyethylene backing) as for general mask layer for isotropic etching Pattern-able passivation layer in silicon package Main Advantages Allows precise and uniform control on the etch dimension in isotropic etching process Produces isotropic-etching pattern and structure without any restriction on etching time Simplifies fabrication process due to its fast and easy process technique which requires no vacuum system (usage of polyethylene tape as for isotropic etching mask) Greatly reduces cost (with the low cost materials)

Type of Offer: Licensing

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