High quality thin films are required for modulator, wavelength converter, filter, and MEMS applications. This technology outlines a method for fabricating localized thin film membranes which are partially attached to an original crystal substrate. Processing techniques create a hollow space separating the membrane from the substrate. This air-isolates the materials, making the film useful as an optical waveguide. The membrane-substrate spacing also makes this technology useful for lab-on-a-chip applications in chemical processing and biological analysis.
A free-standing thin film is very fragile, difficult to handle, and impossible to form at a sub-micron thickness. This technology forms a thin film membrane in localized surface regions of a crystal substrate. Photo-masks are used to precisely pattern and implant hydrogen or helium ions into sub-surface layers of the substrate, which can made from LiNbO3, LiTaO3, LiIO3, or similar. The ions modify the chemical or structural properties of the sub-surface layers of the substrate, which are subsequently removed by selective etching. This process preserves layers of the crystal as an intact membrane above a hollow space and the original substrate. Because the thin film is partially attached to the original substrate it is possible to fabricate sub-micron thickness membranes, which are required for improved membrane performance. The cavity between the membrane and substrate can also be utilized to diversify application of the film to chemical and biological analytics.
This methodology has been tested and resultant thin films have been characterized with imaging and scanning electron microscopy.
US Patent (US 7,312,092 B2)
Tech Ventures Reference: IR M03-066