Christophe Poulain

Breakdown in Argon at nanoscale interelectrode gaps is studied to highlight the deviation from Paschen's law prediction. The discharge occurs between gold-plated electrodes in a setup similar to a planar configuration. A fast cutoff system allows the measurement of up to one hundred breakdowns for each experimental condition. A statistical study is then conducted on the probability distribution of breakdown voltages. The presence of two peaks in the breakdown distribution shows a competition between two different elementary discharge processes. One of it always occurs around a field value of 7.7×10^{8}V/m and does not seem to be affected by the pressure: this is the field emission breakdown mechanism. The other pressure-dependent mechanism is present only when the electrode gap is sufficiently large: this is the Townsend avalanche breakdown mechanism. The statistical method introduced in this work allows for a better interpretation of the processes involved in breakdown in submicrometer interelectrode spaces.

Flexible hybrid electronics (FHE) is becoming a disruptive technology in the packaging of electronic components. Indeed, thanks to the thinness and flexibility of devices, it is conceivable to add a function to any object without changing its aspect. However, this approach faces critical issues such as the management of ultrathin components from different sources and the cost of individual operations. In this paper, a wafer-level packaging (WLP) process for integrated silicon dies coming from various foundries in a flexible label is presented. The process is performed in a microelectronic component manufacturing line on a 200 mm temporary wafer carrier, thus achieving a high level of integration. The purpose of this article is to present results for different hybridization methods of ultrathin silicon dies inside a flexible label. In addition, the process was applied to two demonstrators. The first comprises an ultrathin silicon strain sensor based on a doped crystalline (100) silicon piezoresistive effect that is embedded in a flexible label and bonded to a printed circuit board. When the printed circuit board is mechanically stressed, the die resistances are changed as a result of the piezoresistive effect, and a Wheatstone bridge circuit is used to measure the change in resistance. The second demonstrator is a heterogeneous flexible system including an ultrathin radio frequency identification die integrated within a small flexible label and bonded to a flexible antenna. The functionality of the two demonstrators has been successfully demonstrated.

We present a study of the effect of electrically induced cracks on both the ferroelectric and piezoelectric properties of Pt/PbZr_0.52Ti_0.48O₃ (PZT)/Pt capacitors and correlations with domain structures of PZT films. Above a threshold bipolar electric field, cracks appear inside the PZT layer thickness leading to an increase in the ferroelectric polarization (+50% for the remnant polarization, from 16 to 25 μC/cm²) and the longitudinal piezoelectric coefficient d_33,f (from ∼150 to ∼220 pm/V). The use of x-ray diffraction during in situ biasing provides direct evidence for a modification of the PZT crystalline structure as well as the a/c domain configuration. After cracking, the fraction of c-domains is strongly increased, thus contributing to higher polarization and larger strain in the out-of-plane direction.

We propose a method to evaluate the Total Harmonic Distortion generated by a cantilever-based PZT loudspeaker inside an IEC 60318-4 coupler. The model is validated using experimental data of a commercial loudspeaker. Using the time domain equations of the equivalent electrical circuit of the loudspeaker inside the coupler and a state space formulation, the acoustic pressure response is calculated and compared to the measurement of the manufacturer. Next, the stiffness, transduction and capacitance nonlinear functions are evaluated with a Double-Beam Laser Interferometer (DBLI) and a nanoindenter on test devices and on the commercial loudspeaker. By introducing the nonlinear functions into the model as amplitude-dependent parameters, the THD generated by the loudspeaker is calculated and compared to the value provided by the manufacturer. The good agreement between the measurement and the simulation could allow for a rather quick simulation of the performance of similarly designed loudspeakers at the early stage of the design, by only estimating the static linearity of the main nonlinearity sources.

This paper proposes a stiffness correction method to improve the resilience to vibration of a dual-mass MEMS gyroscope with a particular focus near the resonance frequency of the anti-phase drive mode (f_Da), i.e., its operational mode. Because of its balanced shape, this operating mode is ideally insensitive to vibrations. However, fabrication imperfections generates a residual sensitivity to parasitic vibrations that can disturb normal operation of the sensor. This work shows that the application of a DC voltage (V_tr) at the drive actuation electrode enables to decrease this sensitivity by a factor of at least 30 because of the stiffness tuning of the dual-mass structure. Experiments are performed to confirm this assumption and an efficient stiffness correction method is proposed to improve device operation.

This paper qualitatively explores the performance limits, i.e., energy vs. frequency, of adiabatic logic circuits based on nanoelectromechanical (NEM) switches. It is shown that the contact resistance and the electro-mechanical switching behavior of the NEM switches dictate the performance of such circuits. Simplified analytical expressions are derived based on a 1-dimensional reduced order model (ROM) of the switch; the results given by this simplified model are compared to classical CMOS-based, and sub-threshold CMOS-based adiabatic logic circuits. NEMS-based circuits and CMOS-based circuits show different optimum operating conditions, depending on the device parameters and circuit operating frequency.