ELECTRO-OPTICAL SEMICONDUCTOR DEVICE WITH A POLYIMIDE/SILICON OXIDE BI-LAYER BENEATH A METAL CONTACT LAYER

摘要

An electro-optical, ridge-waveguide device (10) and method for its fabricati on utilizes a polyimide ridge-protection layer (116), which provides good ridge protection/planarization while minimizing parasitic capacitance. A silicon oxide interlayer (118) is used between a metal contact layer (112) and the polyimide. This interlayer facilitates the adhesion between the metal contac t layer (112) and the underlying device (108) since good adhesion can be obtained between the silicon oxide layer and the polyimide layer and between the metal layer and silicon oxide layer. Preferably, the polyimide is roughened to increase the surface area contact between the polyimide layer (116) and silicon oxide layer (118) to further increase adhesion and thus th e pull-off force required to separate the metal contact layer (122) from the device. While such roughening can be achieved through plasma etching, in a preferred embodiment, the polyimide layer (116) is roughened by patterned etching. Specifically, a patterned photoresist (154) is used as an etch- protection layer to form a series of wells in the polyimide layer that have a pitch between 1 and 20 microns.