Frank Kahlenberg

Low Si-OH ORMOCER ®s for Dielectrical and Optical Interconnection Technology

ORMOCER ®* s (inorganic-organic hybrid polymers) with low Si-OH content were synthesized by a new sol-gel route. Optimization of the sol-gel process parameters (catalyst, temperature etc.) was performed in order to achieve reproducible low cost materials which are photo-patternable even in higher layer thicknesses up to 150 μm within one step without cracking or delamination. The materials combine low losses in the NIR region (0.2 dB/cm at 1310 nm and 0.5 dB/cm at 1550 nm without fluorination!) with low dielectric constants (3.3 at 10 kHz). Beside the dielectric and optical properties the materials have a variety of additional advantages for interconnection technology: good wetting and adhesion on various substrates (e.g. glass, silicon and several polymers), low processing temperatures (postbake below 160 °C), high thermal stability (up to 270 °C) and a tunable refractive index. Details of chemical synthesis and characterization as well as photo-lithographic processing of ORMOCER ® materials are presented.

ORMOCER®s (Organic-Inorganic Hybrid Polymers) for Telecom Applications: Structure/Property Correlations

The development and characterization of fluoroaryl functionalized organic-inorganic hybrid polymers for optical waveguide applications is presented. The materials are prepared from organoalkoxysilanes in a two-step process. The first step is the formation of the inorganic polysiloxane network by hydrolysis and polycondensation in order to obtain a soluble resin. This can be mixed with a photo initiator and applied onto a substrate as a photo-sensitive film. Micro patterns (waveguides with core and cladding) are then manufactured in a second step by exposure to UV-light through a mask. The polymers are characterized with respect to application in the fabrication of telecom optical waveguide devices. Thus, special attention is turned to optical losses in the telecom wavelengths at 1310 nm and 1550 nm as well as to refractive indices. During all stages of ORMOCER ® preparation, structure-property correlations are deduced from presented characterization data.Various spectroscopic tools give an insight into network structures of polycondensate resins and cured hybrid polymer samples. 29 Si-NMR in particular is used for the quantitative analysis of siloxane species. With the aid of molecular modeling, structural characteristics of oligomeric intermediates as determined by experiment are visualized. ORMOCER ® resins with low optical losses of 0.28 dB/cm at 1310 nm and 0.42 dB/cm at 1550 nm, respectively, are prepared. Subsequent micropatterning by means of photolithography results in waveguide and other test patterns. A low optical loss of 0.51 dB/cm at 1550 nm is measured on a waveguide manufactured from a photopatternable fluoroaryl functionalized ORMOCER ® .

Electrical and Optical Interconnection-Technology based on Ormocer - Inorganic-Organic Hybrid Materials

Photopatternable hybrid inorganic-organic polymers with negative resist behaviour have been developed and tested for evaluation in optical and electrical interconnection technology. They are composed of inorganic oxidic structures cross-linked or substituted by organic groups. The synthesis starts from organosilane precursors reacted by sol-gel-processing in combination with organic crosslinking of polymerisable organic functions. As a result of these functionalities the properties of the ORMOCER®s are adjusted to the particular applications. Systematic variation of composition combined with adaptation to micro system technology allows great flexibility in processing. The main features of these materials are: • Combined use as dielectric and passivation layers in electrical systems and devices as well as core and cladding for optical applications enables e/o applications with high integration levels. • Postbaking at moderate temperatures (120 - 170 °C) enables processing on low-cost substrates such as FR-4 (a glass-fibre reinforced epoxy-polymer). • Easily adaptable to thin film technology: spin-on with planarisation > 90 %, via diameters down to 20 μm and high aspect ratio for optical waveguides have been achieved. Synthesis, modification of the resins towards technological needs, their thin film technology and the resulting demonstrators will be discussed.