Emmanuel Quévy

A modified Bosch-type process for precise surface micromachining of polysilicon

We report on the study of a new plasma process for precise surface micromachining of polysilicon. The principle is based on the adaptation of the well-known Bosch process to polysilicon, alternating etch and passivation steps under inductively coupled plasmas (ICPs). However, instead of using ICPs for both steps, we chose to keep a C4F8-based ICP for the passivation step, while using a standard RF plasma with SF6 chemistry during etching. The effect of ICP power and gas flux over etch rates, etch profiles and selectivity was studied. It showed the ability to easily control the anisotropy angle using very few parameters, and was dedicated to the realization of micromechanical structures.

Ultimate technology for micromachining of nanometric gap HF micromechnical resonators

We demonstrate in this paper a fabrication process for the realization of nanometric lateral gap micromechanical resonators. This two-masks self-aligned process relies on surface micromachining of silicon to achieve high aspect ratio lateral capacitive gaps between a mobile resonator and its fixed electrodes down to 60nm. Two structural materials were used for the vibrating parts : Single crystal silicon and disilane-based LPCVD polysilicon. Thanks to this process, resonating devices have been demonstrated, among which lateral clamped-clamped beam resonators, impact-driven resonators, and paralleled identical resonators structures, with resonance frequency ranging from 5MHz to 35MHz.

Stiction-controlled locking system for three-dimensional self-assembled microstructures: Theory and experimental validation

The premise of our study lies in the controlled use of the phenomenon of stiction to lock three-dimensional self-assembled polycrystalline silicon (polysilicon) microstructures. The stiction refers to the permanent adhesion of the microstructures to adjacent surfaces. It can occur either during the final stage of the micromachining process, that is to say the releasing of the microstructural material, or after the packaging of the device, due to overrange input signals or electromechanical instability. As a result, we often regard stiction as a major failure issue in the microelectromechanical systems fabrication. This letter reports both the theory of our stiction-controlled locking system operation mode and the validation of our original concept through the stiction-locking of a three-dimensional self-assembled device.

IF MEMS filters for mobile communication

For the past few years, the mobile phone market has been facing fast growth. However, the first generations of mobile telecommunications were based on several different standards over the world, and even at the time major operators negotiate for the third generation licenses, it seems UMTS, CDMA2000 and TD-SCDMA cannot achieve one single standard. A great challenge would be to develop flexible, re-configurable mobile phone handsets that could switch from one standard to another. To do so, MEMS technology is expected as a promising solution to provide tiny, low-consumption tunable components. Moreover, enhancing MEMS technologies to be compatible with IC processing, a novel architecture can be used for a MEMS-based transceiver that could reach the ultimate goal of a fully-integrated single-chip system. Indeed, it has been recently demonstrated that every off-chip, bulky, and expensive passive component present in a typical superheterodyne transceiver front-end could be advantageously replaced by an RF-MEMS counterpart. For example, micro-mechanical resonators could avoid the use of ceramic, SAW, and quartz off-chip resonators to allow low-loss filtering, mixing and carrier generation. But that kind of micro-scale resonators requires high quality factor and temperature stability to achieve highly selective filtering and low phase-noise frequency references. So, to demonstrate this ability, resonators and filters with center frequency up to 300 MHz were designed, and for their fabrication, two processes have been undertaken: an epitaxial thick-film polysilicon industrial technology and a thin-film polysilicon-based technology made compatible with a CMOS-SOI technology.

Realization and actuation of continuous-membrane by an array of 3D self-assembling micro-mirrors for adaptive optics

This paper proposes and experimentally demonstrates a novel technique for the realization and the actuation of continuous-membrane for adaptive optics application. This original device demonstrates, for the first time, both positive and negative deflection with individual pixel displacement of +/- 10 /spl mu/m, which is one order of magnitude larger than in usual approaches. The deformable mirror is constituted by a thin film bulk-micromachined membrane which covers an original set of actuators composed of an array of self-assembling/self-locking 3D polysilicon electrostatic micro-structures.

Vacuum and cryogenic station for microelectromechanical systems probing and testing

We have developed a flexible station for probing and testing microelectromechanical systems (MEMS) and relative integrated circuits. The system allows testing devices under vacuum condition ranging from 10−6 to 760 Torr and at variable temperatures from −100 to +150 °C. Electrical measurements up to 3 GHz and optical measurements through glass windows can be performed simultaneously on MEMS devices. Either packaged devices mounted on printed circuit boards or diced or undiced chips are acceptable. Chips are probed using manual probe heads or probe cards. If needed, two separable parts of a MEMS device, for example, an electromechanical part and an electronic integrated circuit, can be tested simultaneously in different temperature conditions. The setup has been successfully used to characterize electromechanical resonators which exhibit quality factors close to 100 000 in high vacuum.

3D Self-assembled Micro-actuators for Optical Applications

This paper proposes an advanced 3D self-assembling technique of surface polysilicon structures micro-machining for the realisation of actuators dedicated to optical applications such as micro-mirrors array with large deflection angles. The novelty relies on the use on both integrated mechanical latches or electrostatic induced stiction to permanently keep the 3D shapes. The assembled actuator characteristics were measured and their mechanical behavior was successfully analysed by means of electromechanical simulations.

New actuation structure for the deformation of continuous mirrors for adaptive optics

This work demonstrates a novel technique for the realization and the actuation of continuous-membrane for adaptive optic applications. This original device exhibits, for the first time, both positive and negative membrane deflection with individual pixel displacement of +/- 10 micrometers , which is one order of magnitude larger than usual approaches, without diffractive interference.

Stiction-controlled locking system for three-dimensional self-assembled microstructures: theory and experimental validation

The novelty of our study lies in the first controlled use of the phenomenon of stiction to lock three-dimensional self- assembled polysilicon microstructures. The stiction refers to the permanent adhesion of the microstructures to adjacent surfaces. It can occur either during the final stage of the micromachining process, that is to say the releasing of the microstructural material, or after the packaging of the device, due to overrange input signals or electromechanical instability. As a result, we often regard stiction as a major failure issue in the MEMS field of research. This paper reports both the theory of our stiction-controlled locking system operation mode and the validation of our original concept through the stiction-locking of a 3-D self-assembled device.

Reliability of self-assembled 3D microstructures: Dynamic Snap-Through modeling and experimental validation

This work considers the reliability of an elementary 3D structure, and particularly the response of a homogeneous, clamped-clamped polysilicon microfabricated beam, buckling under the compressive force produced by Scratch-Drive Actuators (SDA). First, using Galerkins method, the governing partial differential equation reduced to a modified Duffing equation and was solved by the harmonic balance method. Besides the solution of simple harmonic motion (SHM) and superharmonic motion (SPHM) were found numerically using a Newton iteration method. Then, the study of continuity -- of these solutions -- allowed to analyze the stability boundaries. Finally, Runge-Kutta numerical integration method was used to investigate the snap-through problem. Intermittent, as well as continuous, snap-through behavior was obtained. The theoretical results agreed well with the experiments.