Micromechanical GaAs Hot Plates for Gas Sensors

This paper discusses the design, simulation and fabrication of new Micromachined Thermal Hot Plates (MTHPs) based on GaAs, which were designed for Gas sensors. High sensitivity and low power are expected for present metal oxide Gas sensors, which generally work in high temperature mode (which is essential for chemical reactions to be performed between molecules of the specified gas and the surface of sensing material). Because low power consumption is required, even for operation temperatures in the range of 200 to 500 oC, high thermal isolation of these devices are necessary. The problem can be solved by designing free standing micromechanical hot plates. Mechanical stability and a fast thermal response are especially significant parameters that can not be neglected. These characteristics can be achieved with a new concept of GaAs based thermal converter

Recent challenges in micromachining of wide-bandgap materials and fabrication of mems for harsh environments

The properties of SiC and diamond make them attractive materials for MEMS and sensor devices. We innovated specific laser ablation techniques to fabricate membranes and cantilevers made of SiC or nano-(micro-) crystalline diamond films grown on Si/SiO2 substrates by microwave chemical vapour deposition (MWCVD). We started research to generate surface moulds to grow corrugated diamond films for membranes and cantilevers. A software tool was developed to support the design of micromechanical cantilevers. We can measure deformation and resonant frequency of diamond cantilevers and identify the global mechanical properties. A benchmark against finite element simulations enables an inverse identification of the specific system parameters and simplifies the characterization procedure

Diamond cantilevers for MEMS sensor applications fabricated by laser ablation and optimized etching techniques

The properties of diamond make it an attractive material for MEMS and sensor devices. We present the feasibility to fabricate membranes and cantilevers made of nano-(micro-) crystalline diamond films grown on Si/SiO2 substrates using microwave chemical vapour deposition (MWCVD). The patterning of micromechanical structures was performed by a combined process of femtosecond laser ablation and wet etching. We designed cantilever structures with varying lengths and widths (25, 50, 100, 200 and 300 μm). The cantilevers were made in a symmetric left- and right-hand configuration. An additional laser treatment was used to modify the mechanical properties of the left-hand cantilever. The deflection of the laser-treated, and non-treated sections was measured. The global mechanical system properties were simulated and corresponded with high accuracy to the measured results of deflection