Micromachined hybrid integrated receiver modules for 38 GHz and 77 GHz, on silicon substrate, technology and manufacturing

This paper present the fabrication process for the manufacturing of hybrid integrated receiver modules for 38GHz and 77GHz operating frequency, on micromachined silicon substrate. The hybrid receiver structures consists in a membrane-supported antenna as well as a GaAs Schottky detector diode, a matching network and a low-pass filter on a bulk material area of the chip. The technological process as well as the manufacturig characteristics are presented. AFM, SEM, and White Light Interferometry have been used. for microphysical characterizatio

Design and Optimization of Microwave Lumped Elements Fllters using mixed Circuital-Electromagnetic Simulations

This paper presents the design, fabrication and experimental results of the switchable band-pass lumped elements filters. The design is based on a new optimization approach that integrates mixed circuital and electromagnetic simulations. The use of horizontal internal ports and the connection of external capacitors at circuital level make the optimization procedure very efficient. A very good agreement between measurements and simulations validate the new design approach

Design of Coplanar Micromachined Microwave Circuits

An approach to the design of microwave and millimeter wave coplanar waveguide (CPW) circuits is here described, stressing the advantages and the drawbacks in using a commercial software package, namely the Hewlett Packad Microwave Design System (HP-MDS). It will be shown that satisfactory results in the modeling of lumped elements and filters can be obtained by using coupled microstrips as an approximation of CPW configurations at least up to 40 GHz

Resistive pressure sensing structures on polymide membranes on GaAs substrate

This paper presents the manufacture of a simple pressure sensing structure supported on polymide membranes obtained by micromachining of a GaAs substrate. The sensing element is a gold on chromium resistor on the polymide membrane. The technological process for the manufacturing of this structure is presented. The sensing element shows high linearity, absence of hysteresis, good sensitivity, and can be used in high-temperature application

Dielectric Membranes Supported Millimeter-Wave Passive Circuits

In the last years a lot of studies were focused on micromachining for high-performance microwave and millimeter-wave circuits. A substantial improvement in circuits’ characteristics has been achieved by integration of antennas, components and transmission lines on thin dielectric and semiconductor membranes. Several types of membranes have been developed during the past few years. It is the purpose of this presentation to compare the membranes’ quality and the performances of the circuits manufactured on each type of membrane. The following types of membranes have been successfully manufactured: three-layer (SiO2/Si3N4/SiO2) dielectric membranes on high-resistivity and silicon wafers by means of wet anisotropic and, respectively, isotropic substrate removal; polyimide membranes on semi-insulator GaAs wafers. Comparative results will be presented, including AFM and SEM photos, details about average and maximum roughness of the top and bottom side of the membranes. Lumped elements: meander and S-line inductors, interdigitated capacitors (with 8 and 16 fingers) have been successfully manufactured on these membranes. Experimental comparative microwave measurements on S11 and S21 parameters are presented for the circuits manufactured on three-layer and polyimide membrane as well as for the same circuits on bulk substrate in order to notice the differences and to choose the optimum choice. A substantial improvement of microwave performances has been noticed for the micromachined structures. This work has been supported by the Commission of the European Communities under COPERNICUS Grant No. 97713

Micromachined filters for 38 and 77 GHz supported on thin membranes

This paper presents the fabrication processes for micromachined millimetre-wave devices, on two different types of semiconductor substrates. The first process uses micromachining on high-resistivity (100) oriented silicon. A three-layer dielectric membrane, with a total thickness of 1.5 um is used as support for the millimetre-wave structures. This process was used for the manufacturing of two coupled line filters, wih central operating frequencies of 38 and 77 GHz, respectively. The second process is based on GaAs micromachining. For the first time, a 2.2 um thin GaAs/AIGaAs membrane, obtained by molecular beam epitaxy growth and micromachining of semi-insulating (100) GaAs, is used as support for millimetre-wave filter structures. Cascaded coplanar waveguide open-end series stubs filter type structures, with central frequences of 38 and 77 GHz, respectively, were designed and manufactured on a GaAs micromachined substrate. 'On wafer' measurements for the filter structures were performed. Losses of less than 1.5 dB at 38 GHz and less than 2 dB at 77 GHz have been obtained for both the silicon as well as for the GaAs-based micromachined filter