No abstract

In the last few years, several Low Temperature Cofired Ceramics (LTCC) materials with a silicon adapted Coefficient of Thermal Expansion (CTE) have been developed for direct wafer bonding to silicon. BGK (special type designation of Fraunhofer IKTS), a sodium containing LTCC was originally developed for anodic bonding of the sintered LTCC whereas BCT (Bondable Ceramic Tape) tailored for direct silicon bonding of green LTCC tapes to fabricate a quasi-monolithic silicon ceramic compound substrate. This so-called SiCer technique is based on homogeneous nano-structuring of a silicon substrate, a lamination step of BCT and silicon and a subsequent pressure assisted sintering. We present a new approach for an integrated RF-platform-setup combining passive, active and mechanical elements on one SiCer substrate. In this context RF parameters of the silicon adapted LTCC tapes are investigated. We show first technological results of creating cavities at the silicon ceramic interface for SiCer-specific contacting options as well as windows in the ceramic layer of the SiCer substrate for additional silicon processing. A further investigated platform technology is deep reactive ion etching of the silicon-ceramic-composite-substrate. The etching behavior of silicon on BCT will be demonstrated and discussed. With the SiCer technique it is possible to reduce the silicon content at the setup of RF MEMS to a minimum (low signal damping).

No abstract

Abstract:The behavior of molten glass on nanostructured silicon surface is of essential importance for the fabrication of a strong bond interface between glass (or glass-based ceramic tapes) and silicon. It was found that typical glasses do not wet the silicon surface that is always coated with a thin silica layer. It is shown that the high surface tension of molten glasses at high temperatures in combination with the dewetting surface of the structured silicon prohibits the formation of an interlocking bond between the two substrates. The theory of wetting can be applied to molten glasses, too. As a consequence, a similar solution as for liquids is investigated: the surface has to be chemically modified to become wettable. Investigations with sputtered metals on the nanostructured silicon improve wetting of the surface and result in a better bond homogeneity of the SiCer compound during sintering with low pressure.

No abstract