RF-MEMS-platform based on silicon-ceramic-composite-substrates

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).

Systematic design strategies for multi-physical RF systems using the example of MEMS oscillator

“…This will enable an optimal integration of micromechanical sensor and actuators together with electronics into large systems on a RF-MEMS-Platform [2].…”

“…• Depending on which case was calculated, xmax must be assigned with (2) for the other case, to make sure the pullin point is not reached. It may be necessary to increase k.…”

Electrostatic parallel-plate MEMS switch on silicon-ceramic-composite-substrates

“…Next the mechanical layout of the switch is transferred with help of a photoresist mask on the silicon. After etching the silicon on the SiCer composite using an adapted DRIE process [7] (e), the sacrificial layer under the etched silicon structures is removed using HF-vapor (f). The non-conformal deposition of silica by PECVD in small trenches results in bulges near the surface.…”

Thermal analysis of the ceramic material and evaluation of the bonding behavior of silicon-ceramic composite substrates

“…Ceramic substrates like low-temperature cofired ceramics (LTCC) require in contrast an own technology set for microfabrication comprising thick film manufacturing, e.g. pattern punching, laser cutting and screen-printing [2]. LTCC tapes enable a manufacturing of functional devices at relatively low cost with small footprint by processing each single layer followed by their stacking prior to a thermal sintering process.…”

“…LTCC tapes enable a manufacturing of functional devices at relatively low cost with small footprint by processing each single layer followed by their stacking prior to a thermal sintering process. In this way, passive components, wiring and vias can be effectively realized [2]. Especially the dielectric properties of the LTCC render it as a superior material for high frequency applications [2].…”