Next articleElectro-optic, polymer-based integrated optic devices for high-speed communication and computing applications offer potentially significant advantages over conventional inorganic electro-optic crystals. One key area of integrated optical technology--primary processing and fabrication--may particularly benefit from the use of polymer materials. However, as efforts concentrate on the miniaturization of electro-integrated circuit pattern geometries, the ability to etch fine features and smoothly sloped sidewalls is essential to make polymers useful for electro-integrated circuit applications. There are many existing processes available to etch polymer materials, but they all yield nearly vertical sidewalls. Vertical sidewalls are too difficult to reliably cover with a metal layer, and incomplete metalization degrades microwave performance, particularly at high frequency. However, obtaining a very sloped sidewall greatly improves the deposition of metal on the sidewall, leading to low-loss characteristics, which are essential to integrating these devices in high-speed electro-optic modulators.
The NASA Lewis Research Center has developed in-house an inexpensive etching technique that uses a photolithography method followed by a simple, wet chemical etching process to etch through polymer layers. In addition to being simpler and inexpensive, this process can be used to fabricate smoothly sloped sidewalls by using a commercial nonerodible mask: Spin-On-Glass. A commercial transparent material, Spin-On-Glass, uses processes and equipment similar to that for photoresist techniques.
This new etching technique offers a simpler fabrication process and a cost-effective method of generating the moderately sized patterns typically encountered in low and medium density interconnection applications. In addition, it yields high-resolution patterns and smooth sidewalls, resulting in low optical scattering losses. With this technique, measured microwave losses have been found to be very low. The new technique offers low-loss performance comparable to that found with conventional reactive ion etching techniques, which have considerably higher costs.
Lewis contact: Hung D. Nguyen, (216) 443-6590,
Hung.D.Nguyen@grc.nasa.gov
Author: Hung D. Nguyen
Headquarters Program Office: OSS (ATMS)
Program/Projects: Space Communications Project
Last updated June 16, 1999, by Nancy.L.Obryan@nasa.gov
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