Fabrication and testing of an integrated thermal flow sensor employing thermal isolation by a porous silicon membrane over an air cavity

Abstract

In this work, an integrated thermal gas flow sensor was fabricated and evaluated using a new thermal isolation technique based on a porous silicon membrane over an air cavity in silicon. The fabrication process of a thermal gas flow sensor employing this type of micro-hotplate is described together with the theoretical estimation of the thermal distribution around the heater of the sensor. Experimental results of the thermal isolation achieved are shown. A flow evaluation of the sensor is presented and discussed. All the results obtained are compared with the corresponding ones for an identical sensor using a micro-hotplate made of porous silicon membrane but without the air cavity underneath. The improvement achieved by the air cavity is evaluated.

Stress control of porous silicon films for microelectromechanical systems

“…Further, the effect of oxidation under ambient conditions is unclear. While stress is known to affect the resonant frequency of non-porous microbeams [11,12], the relative impacts of stress when using low modulus PS films [13,14] is not yet known. Thus the extent of stress changes after typical processing steps must be determined.…”

Dielectric characterization of macroporous thick silicon films in the frequency range 1 Hz–1 MHz

“…On-chip applications include both DC and RF isolation by silicon integrated porous silicon micro-plates. So far, for these last applications, mainly mesoporous silicon has been investigated [6][7][8]. The dielectric properties of both meso-and macroporous silicon depend strongly on the structural and morphological properties of the material.…”

Platinum Micro-Hotplates on Thermal Insulated Structure for Micro-Thermoelectric Gas Sensor

“…Micro-hotplates are used nowadays in many applications such as micro-fluidics (1) , infrared emission (2) and thermal flow sensing (3) . However, from the early time the main application of micro-hotplates is the gas sensing field (4) .…”