The fabrication of planar microwave devices is becoming very promising for many applications. It is well known that the use of silicon substrates and the well established microelectronics technologies allows in general devices integration, high throughput and reduced cost. The fabrication of planar microwave devices can take great advantages from these peculiarities, On the other hand it has been shown that the bulk silicon is not the best choice in terms of devices performances. To reduce dispersion and avoid the propagation losses in the semiconductor substrate, the devices can be built on thin dielectric membranes obtained by micromachining technique. To obtain flat membranes the fabrication process has to be carefully controlled, especially as far as the membrane stress is concerned. Flat membranes have been produced on high resistivity Si substrate: a SiO2/Si3N4/SiO2 sandwich structure has been chosen as dielectric membrane. The membranes has been obtained by anisotropic etching using TMAH as etchant. The deposition process and the thickness of the dielectric layers was chosen in order to obtain a slightly tensile ‘global’ stress. The flatness of the membranes was tested both by Laserscan, AFM and Makyoh topography. To demonstrate the effectiveness of the process, some coplanar waveguides have been also produced both on membrane and high resistivity Si substrate. The electrical measurement have shown a satisfactory improvement in terms of device performances.

Micromachined Dielectric Membranes for Microwave Applications

Giacomozzi, Flavio;Guarnieri, Vittorio;Margesin, Benno;Zen, Mario;
2000

Abstract

The fabrication of planar microwave devices is becoming very promising for many applications. It is well known that the use of silicon substrates and the well established microelectronics technologies allows in general devices integration, high throughput and reduced cost. The fabrication of planar microwave devices can take great advantages from these peculiarities, On the other hand it has been shown that the bulk silicon is not the best choice in terms of devices performances. To reduce dispersion and avoid the propagation losses in the semiconductor substrate, the devices can be built on thin dielectric membranes obtained by micromachining technique. To obtain flat membranes the fabrication process has to be carefully controlled, especially as far as the membrane stress is concerned. Flat membranes have been produced on high resistivity Si substrate: a SiO2/Si3N4/SiO2 sandwich structure has been chosen as dielectric membrane. The membranes has been obtained by anisotropic etching using TMAH as etchant. The deposition process and the thickness of the dielectric layers was chosen in order to obtain a slightly tensile ‘global’ stress. The flatness of the membranes was tested both by Laserscan, AFM and Makyoh topography. To demonstrate the effectiveness of the process, some coplanar waveguides have been also produced both on membrane and high resistivity Si substrate. The electrical measurement have shown a satisfactory improvement in terms of device performances.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11582/1913
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