Bandwidth demand is still growing and it is becoming more difficult for copper based interconnect technologies to meet system requirements. Considerable progress is being made in the development of optical interconnect technology. Recent publications have shown improved integration of turning mirrors and connectors for board level applications. This paper presents recent work on a siloxane-based waveguide material that is optimized for 850nm board level optical interconnect applications. The material under development is a negative acting photoimageable material that can be processed with conventional Printed Wire Board (PWB) or CMOS processing techniques and chemistries. Meter long waveguides have been fabricated on both silicon and FR4 substrates with optical loss performance of 0.027dB/cm and 0.067dB/cm respectively. Data illustrating the effect of bend radii and splitter performance is reported. Lastly, the ability of the siloxane material to withstand PWB fabrication and assembly processes such as lamination, metallization and reliability is demonstrated.
There are a number of organic, inorganic, and hybrid inorganic waveguide materials that are currently being used for a wide variety of optical interconnect applications. Depending upon the approach, waveguide formation is performed using a combination of lithographic and/or reactive ion etch (RIE) techniques. Often the processes involved with waveguide formation require unique processing conditions, hazardous process chemicals, and specialized pieces of capital equipment. In addition, many of the materials have been optimized for silicon substrates but are not compatible with printed wire board (PWB) substrates and processes. We have developed compositions and processes suitable for the creation of optical, planar waveguides on both silicon and PWB substrates. Based on silicate technology, these compositions use lithographic techniques to define waveguides, including aqueous, alkaline development. The resulting planar waveguides take advantage of the glass-like nature of silicate chemistry wedded with the simplicity of standard lithographic processes. Attenuation at typical wavelengths has been found to compete well with the non-silicate-based technologies available today. Single-mode (SM) and multi-mode (MM) waveguides with losses ranging from 0.6 dB/cm @ 1550nm, 0.2 dB/cm @1320nm, and <0.1 @ 850nm are feasible. Composition, process, and physical properties such as optical, thermal and mechanical properties will be discussed.