Wafer-scale integration of piezoelectric actuation capabilities in nanoelectromechanical systems resonators

In this work, we demonstrate the integration of piezoelectric actuation means on arrays of nanocantilevers at the wafer scale. We use lead titanate zirconate (PZT) as piezoelectric material mainly because of its excellent actuation properties even when geometrically constrained at extreme scal

Wafer-scale integration of piezoelectric actuation capabilities in nanoelectromechanical systems resonators

In this work, we demonstrate the integration of piezoelectric actuation means on arrays of nanocantilevers at the wafer scale. We use lead titanate zirconate (PZT) as piezoelectric material mainly because of its excellent actuation properties even when geometrically constrained at extreme scal

Nanoelectromechanical systems for biodetection : development of an integrated transducer and biofunctionalization strategies

Avec une limite de détection ultime pouvant atteindre le yoctogramme (1 yg = 10-24 g), les nanosystèmes électromécaniques (NEMS) employés comme capteurs gravimétriques présentent un fort potentiel pour la détection ultra-sensible et sans marquage de molécules biologiques. A l’heure actuelle, plusieurs défis restent cependant à relever avant de pouvoir envisager de manière réaliste leur utilisation comme outils de biodétection. Ces travaux de thèse adressent en particulier l’intégration du moyen de transduction et le développement de stratégies de biofonctionnalisation. En vue de répondre à la première problématique, l’intégration d’une couche piézoélectrique à base de Titano-Zirconate de Plomb (PZT) selon une approche de fabrication collective de réseaux de NEMS par voie descendante a été développée et caractérisée.Deux approches de biofonctionnalisation adaptées à une organisation de NEMS en réseaux,respectivement basées sur le dépôt localisé de matériel biologique par impression moléculaire et sur la structuration par photolithographie d’une couche bioréceptrice à base de polymères à empreintes moléculaires (MIP), ont ensuite été mises en oeuvre et ont permis de démontrer une première preuve de concept. Ces différentes contributions constituent un premier pas dans le développement des NEMS pour des applications de biodétection.With an ultimate limit of detection down to the yoctogram regime (1 yg = 10-24 g),nanoelectromechanical systems (NEMS) resonators used as ultra-sensitive and label-free gravimetric sensors have a high potential for biodetection applications. To date, several challenges currently limit their wide spread use as viable biosensing tools. This PhD thesis addresses the issues related to the transducer integration and the biofunctionnalization. A Lead Zirconate Titatane (PZT)-based piezoelectric transducer has been implemented according to a top-down approach compatible with collective fabrication of NEMS arrays. Two biofunctionnalization strategies, suitable for a NEMS array organization and based on the localized deposition of biological material assisted by microcontact printing and the patterning of molecularly imprinted polymers (MIP) by photolithography, have also been investigated and first proof-of-concept biosensors were demonstrated. These various contributions have the potential to drive future advancements in the realm of NEMS as effective biosensing tools

Nanosystèmes électromécaniques pour la biodétection : intégration d'un moyen de transduction et stratégies de biofonctionnalisation

With an ultimate limit of detection down to the yoctogram regime (1 yg = 10-24 g),nanoelectromechanical systems (NEMS) resonators used as ultra-sensitive and label-free gravimetric sensors have a high potential for biodetection applications. To date, several challenges currently limit their wide spread use as viable biosensing tools. This PhD thesis addresses the issues related to the transducer integration and the biofunctionnalization. A Lead Zirconate Titatane (PZT)-based piezoelectric transducer has been implemented according to a top-down approach compatible with collective fabrication of NEMS arrays. Two biofunctionnalization strategies, suitable for a NEMS array organization and based on the localized deposition of biological material assisted by microcontact printing and the patterning of molecularly imprinted polymers (MIP) by photolithography, have also been investigated and first proof-of-concept biosensors were demonstrated. These various contributions have the potential to drive future advancements in the realm of NEMS as effective biosensing tools.Avec une limite de détection ultime pouvant atteindre le yoctogramme (1 yg = 10-24 g), les nanosystèmes électromécaniques (NEMS) employés comme capteurs gravimétriques présentent un fort potentiel pour la détection ultra-sensible et sans marquage de molécules biologiques. A l’heure actuelle, plusieurs défis restent cependant à relever avant de pouvoir envisager de manière réaliste leur utilisation comme outils de biodétection. Ces travaux de thèse adressent en particulier l’intégration du moyen de transduction et le développement de stratégies de biofonctionnalisation. En vue de répondre à la première problématique, l’intégration d’une couche piézoélectrique à base de Titano-Zirconate de Plomb (PZT) selon une approche de fabrication collective de réseaux de NEMS par voie descendante a été développée et caractérisée.Deux approches de biofonctionnalisation adaptées à une organisation de NEMS en réseaux,respectivement basées sur le dépôt localisé de matériel biologique par impression moléculaire et sur la structuration par photolithographie d’une couche bioréceptrice à base de polymères à empreintes moléculaires (MIP), ont ensuite été mises en oeuvre et ont permis de démontrer une première preuve de concept. Ces différentes contributions constituent un premier pas dans le développement des NEMS pour des applications de biodétection

PFM Performances Analysis of PZT Piezoelectric Nano Cantilevers Fabricated on Si Wafer

International audienceWe present in this work and for the first time a high level of integration of piezoelectric nano-cantilevers on a silicon substrate (4 inches in diameter). We use lead titanate – zirconate material as piezoelectric material mainly because of its excellent piezoelectric activity at macro scale. However, its integration within a silicon technological process is limited by the difficulty of structuring this material with sub micrometer resolution at the wafer scale. At the nano-scale many questions still remain unanswered. For example: what becomes of the piezoelectric activity? What are the limitations of the integration level process? What are the best electrodes (bottom and top) for piezoelectric film actuation? In this study we have tried to answer some of these fundamental questions. To this end, we have developed a specific patterning method based on deep UV lithography to fabricate nano cantilevers with a high density of integration. The main objective is to obtain sub-micron features by lifting off a 70-nm thick PZT layer while preserving the material’s piezoelectric properties. We show that for the actuation of a very thin film the choice of the bottom and top electrodes has a strong influence. To analyse the piezoelectric activity at nano scale we use the Piezo Force Microscopy, this measurement approach is a good characterization tool for piezoelectric nano device

Additively patterned ferroelectric thin films with vertical sidewalls

International audienceThe functional properties of electroceramic thin films can be degraded by subtractive patterning techniques used for microelectromechanical (MEMS) applications. This work explores an alternative deposition technique, where lead zirconate titanate (PZT) liquid precursors are printed onto substrates in a desired geometry from stamp wells (rather than stamp protrusions). Printing from wells significantly increased sidewall angles (from ~1 to >35 degrees) relative to printing solutions from stamp protrusions. Arrays of PZT features were printed, characterized, and compared to continuous PZT thin films of similar thickness. Three-hundred-nanometer-thick printed PZT features exhibit a permittivity of 730 and a loss tangent of 0.022. The features showed remanent polarizations of 26 μC/cm2, and coercive fields of 95 kV/cm. The piezoelectric response of the features produced an e31,f of −5.2 C/m2. This technique was also used to print directly atop prepatterned substrates. Optimization of printing parameters yielded patterned films with 90° sidewalls. Lateral feature sizes ranged from hundreds of micrometers down to one micrometer. In addition, several device designs were prepatterned onto silicon on insulator (SOI) wafers (Si/SiO2/Si with thicknesses of 0.35/1/500 μm). The top patterned silicon was released from the underlying material, and PZT was directly printed and crystallized on the free-standing structures

Determination of the effective mass and stiffness of a micro resonator from a single optical characterization

International audienceWe propose a method for the experimental determination of the effective mass and stiffness of a micro mechanical resonator using optical interferometry in a Fabry-Perot configuration. The method relies on the spectral analysis of the photodiode signal, which is ruled by the Jacobi-Anger expansion, allowing the absolute calibration of the vibration amplitude. Effective parameters are then calculated from the thermomechanical noise spectrum of the resonator. As an example of application, the method is applied to the determination of the effective parameters of an AFM probe

PZT Nanofilm-Based Wafer Scale Nanoresonators

International audienceIn this work, we present an unprecedented level of integration of piezoelectric actuation means on arrays of functional nanoresonators at the wafer scale. We use 150-nm thin lead titanate zirconate (PZT) as piezoelectric material mainly because of its excellent actuation properties even when geometrically constrained at extreme scale. This work paves promising ways for NEMS to be used in configurations where transduction capabilities are integrated at the nanodevice level providing effective fabrication process flow at the wafer-scale

Multiplexed functionalization of nanoelectromechanical systems with photopatterned molecularly imprinted polymers

International audienceImplementing dedicated and reliable biochemical recognition functionalities onto nanoelectromechanical systems (NEMS) is of primary importance for their development as ultra-sensitive and highly-integrated biosensing devices. In this paper, we demonstrate the large-scale and multiplexed integration of molecularly imprinted polymers (MIPs) as highly stable biomimetic receptors onto arrays of nanocantilevers. Integration is carried out by spin-coating and photopatterning the polymer layers before releasing the nanostructures. We demonstrate that these biomimetic layers are robust enough to withstand the wet-etch of the sacrificial layer making this functionalization strategy compatible with further MEMS/NEMS processing. As a proof of concept, we fabricate NEMS resonators coated with a MIP using Boc-L-phenylalanine as the template molecule. We demonstrate the preserved molecular recognition ability of the patterned sensitive layer through the fluorescence detection of dansyl-L-phenylalanine, a fluorescent derivative of the template, and the mechanical integrity of the resonators by means of resonant frequency measurements

Fabrication and characterization of mechanical resonators integrating microcontact printed PZT films

International audienceWe report on the fabrication and characterization of lead zirconate titanate (PZT)-coated cantilever resonators for the realization of piezoelectric nanoelectromechanical systems (NEMS) with integrated actuation and detection capabilities. PZT is deposited by microcontact printing, resulting in a relatively thin PZT film without deterioration of its piezoelectric properties induced by etching damage. The cantilever fabrication process is based on stepper ultraviolet lithography and standard micromaching. Electrical characterization was carried out with a dedicated electrical set-up enabling the devices' resonance frequency to be detected through the piezoelectric response. These characterizations validate the simultaneous actuation and detection capability of the PZT layer. Finally, modeling of the PZT cantilever results in the estimation of the piezoelectric coupling coefficient d*31. We have found excellent large signal d*31 of around 200 pm/V, even for PZT cantilevers with reduced dimensions