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This work presents the characterization of a thermal vacuum sensor, directly integrated on a printed circuit board (PCB) substrate. The sensor consists of a thin platinum strip, in direct electrical contact with the patterned Cu tracks of the FOB.; The platinum resistor that resides on a thick SU-8 layer on the PCB, acts as both heating and temperature sensing element. Both PCB substrate and SU-8 have low thermal conductivity values, therefore ensuring a high degree of thermal isolation. Under electrical current flow through the Pt heater, an elevated temperature field is developed in its vicinity due to Joule heating. The overall heat exchange rate is a function of the surrounding gas pressure in certain pressure regimes due to the contribution of different heat transfer mechanisms. The determination of heat transfer allows for the 0 extraction of the corresponding vacuum value. The sensor operation was tested in a pressure range from 10 3 to 10∼5 mbar for three different operation modes, namely that of constant current (CI), constant temperature (CT) and constant power (CP).

In this paper we present results of the evaluation of a thermal gas flow sensor device implemented on a printed circuit board (PCB) substrate by a combination of PCB and MEMs technologies. The device consists of 3 parallel Pt strip resistors in direct electrical contact to patterned copper tracks of the PCB. For planarization purposes, the Pt strips reside on a thick polymer layer (SU8). The central resistor plays the role of a heater and the two other resistors, situated symmetrically on both sides of the heater, are temperature dependent sensing elements. The three main advantages of this specific sensor are: the low thermal conductivity of the substrate materials (FR4 and SU8, with thermal conductivity ∼0.2 W(m·K)) which permits high sensitivity at low power, its robustness compared to suspended membrane sensors and its simple fabrication process. The sensor can operate in both hot wire and calorimetric modes. The sensor was mounted inside a 1.5m long tube with 25 mm2 cross sectional area and was evaluated in nitrogen flow up to 100 SLPM, which corresponds to Reynolds numbers up to 25.000. The sensor signal in both the calorimetric and the hot-wire modes is a monotonous function of the flow rate. A very high sensitivity is obtained in the calorimetric mode at very low flow rates (

This work concerns the fabrication, modeling and characterization of a novel microfluidic flow sensor based on a microchannel capped with a porous silicon membrane, on top of which the sensor active elements are integrated. The microchannel is formed through a two-step anodization process. In the first step a mesoporous silicon layer is formed on a lithographically defined area, while in the second step a channel is formed underneath the porous layer by electropolishing. The channel is buried into bulk silicon and capped with a free-standing porous silicon layer, which is co-planar with the Si substrate. The overall developed process for the formation of the device will be described and simulation and device characterization results will be presented.

A non-destructive method for evaluation of the thickness of films over bulk substrates is presented. This method is based on evaluation of the parameters of the decay part of the x-ray signal ratio. For a selected energy range of each film thickness it is demonstrated that the decay part follows an exponential law. The physical parameters involved in this law are the energy exponent and a constant that depends mainly upon the film thickness. The values found for the energy exponent are in the range 2.0–3.0. This is confirmed in a variety of cases (Al/Si, Ti/Si, Cu/Si, Pt/Si, Cu/Ni, Ti/Au and Pt/Au) for film thicknesses larger than a critical value. The experimental results are compared to those obtained by two theoretical methods and a Monte-Carlo approach. The first method is based on solution of the Boltzmann transport equation for the electron beam, an approach developed by one of the authors for e-beam lithography. The second is based on a previously developed semi-empirical formula for the x-ray depth distribution function. The energy dependence of the signal ratio is also discussed using this approach. © 1998 John Wiley & Sons, Ltd.

Erbium silicide thin films are grown on Si(100) substrates under high vacuum by single deposition of Er or co-deposition of Er and Si, followed by annealing. Electron microscopy revealed for both preparations the existence of at least three new types of structural phases of erbium silicide. One has a tetragonal ThSi 2 type structure; the other two are orthorhombic superstructures of the first one resulting from ordering of vacancies on the Si sublattice, which leads to a composition of ErSi 2-x (0 < x < 0.5).