Bruno Mercier

Advanced etching of silicon based on deep reactive ion etching for silicon high aspect ratio microstructures and three-dimensional micro- and nanostructures

Abstract Different processes involving an inductively coupled plasma reactor are presented either for deep reactive ion etching or for isotropic etching of silicon. On one hand, high aspect ratio microstructures with aspect ratio up to 107 were obtained on sub-micron trenches. Application to photonic MEMS is presented. Isotropic etching is also used either alone or in combination with anisotropic etching to realize various 3D shapes.

A MEMS sensor for the measurement of density-viscosity for oilfield applications

We present a sensor fabricated with MEMS (Micro-Electro-Mechanical Systems) technology that upon immersion quickly measures fluid density and viscosity. The operational principal involves the influence of the fluid on the resonance frequency and quality factor of a vibrating plate oscillating normal to its plane. By performing measurements in liquids over a wide range of temperature (20 to 150 C) and pressure (0.1 to 75 MPa), we have demonstrated a maximum inaccuracy in our density and viscosity measurements of approximately +/- 1.5 % and +/- 10 % respectively, for fluids with densities between (0.6 to 1.5) g/cc and viscosities between (0.4 to 100) cP. Such measurements are required to determine the economic feasibility of recovering hydrocarbon from subterranean strata. There are numerous examples in the literature of sensors fabricated by the methods of MEMS that are claimed to measure both density and viscosity of fluids, but in most cases, the accuracy of such sensors is not been demonstrated in a wide range of fluids and moreover, their use in non-laboratory environments has not been proven.1,2,3 Here we show that it is possible to design and package a sensor that can function with high accuracy in extreme environments while providing useful information.

Experimental Observation of Inertia-Dominated Squeeze Film Damping in Liquid

We have studied the phenomenon of squeeze film damping in a liquid with a microfabricated vibrating plate oscillating in its fundamental mode with out-of plane motion. It is paramount that this phenomenon be understood so that proper choices can be made in terms of sensor design and packaging. The influences of plate-wall distance h, effective plate radius R, and fluid viscosity and density on squeeze film damping have been studied. We experimentally observe that the drag force is inertia dominated and scales as 1/h 3 even when the plate is far away from the wall, a surprising but understandable result for a Microfluidic device where the ratio of h to the viscous penetration depth is result for a microfluidic device where the ratio of h to the viscous penetration depth is large. We observe as well that the drag force scales as R 3 , which is inconsistent with squeeze film damping in the lubrication limit. These two cubic power laws arise due to the role of inertia in the high frequency limit.

A microfluidic MEMS sensor for the measurement of density and viscosity at high pressure

We present a sensor fabricated with MEMS (Micro-Electro-Mechanical Systems) technology that quickly measures fluid density and viscosity. This sensor is fabricated inside of a microfluidic channel through which the fluid to be measured passes. The operational principal involves the influence of the fluid on the resonance frequency and quality factor of a vibrating plate oscillating normal to its plane. By performing measurements in liquids we have demonstrated operability in fluids with densities between (0.6 to 1.5) g/cc and viscosities between (0.4 to 100) cP. Such measurements are required to determine the economic feasibility of recovering hydrocarbon from subterranean strata. There are numerous examples in the literature of sensors fabricated by the methods of MEMS that are claimed to measure both density and viscosity of fluids, but in most cases, the accuracy of such sensors is not been demonstrated in a wide range of fluids and moreover, their use in non-laboratory environments has not been proven.1,2,3 Here we show that it is possible to design and package a sensor that can function with high accuracy in extreme environments while providing useful information.

SUB-0.05° precision optofluidic dual-axis inclinometer

This paper details a low-power bi-axial miniaturized inclinometer based on a mobile mass (spherical ball or fluidic droplet) positioned on a precision curved surface that is generated using a novel MEMS process. The detection of the mobile mass was implemented through an external optical system, using a quadrant photodetector. Nanotopography and chemical treatment of the curved surface have been implemented to increase accuracy when using a fluidic mobile mass, by tailoring wetting properties and minimizing contact angle hysteresis. We achieve a range of ±1° with a true linear bi-axial measurement of precision better than 0.05°.

Quantitative study of the 'M.E.M.S.N.A.S.' process for 3D microfabrication using binary lithography

In this paper, we present the results of investigations on the quantitative characterization of the previously reported MEMSNAS process, which was developed for 3D microfabrication applications using binary lithography and isotropic etching. Such characterization results are indeed of interest for the purpose of developing design rules, which are intended to help for fast prototyping of arbitrary 3D structures with good shape accuracy. Among the characteristics that have been investigated, one can mention process calibration. It is obtained using simple test structures. Silicon 3D micromachining was investigated mainly with SF/sub 6/-based dry etching using both RIE and DRIE reactors. Wet etching with an HNA mixture was also used in some experiments. The MEMSNAS 3D micromachining method was successfully applied to glass as well.