Fully integrated CMOS-MEMS resonators as a biosensing platform
[eng] Functional diversification in the More than Moore era has attracted an increasing attention on MEMS resonators as sensing devices for system-on-chip applications thanks to its miniaturization capabilities, simple readout schemes, and integration with current ICs fabrication technologies. These...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/673937 |
| Acceso en línea: | http://hdl.handle.net/10803/673937 |
| Access Level: | acceso abierto |
| Palabra clave: | CMOS-MEMS VOCs System-on-Chip Lab-on-Chip Microfluidics Calorimeter Ressonadors CMOS-MEMS per a aplicacions de bio-sensat 53 |
| Sumario: | [eng] Functional diversification in the More than Moore era has attracted an increasing attention on MEMS resonators as sensing devices for system-on-chip applications thanks to its miniaturization capabilities, simple readout schemes, and integration with current ICs fabrication technologies. These advantages make them the perfect candidates to develop biosensing applications in the chemical and biological domains provided its portability, high-throughput, reduced footprint, and minimal processing time. This thesis focuses on analyzing, designing, and developing MEMS resonators oriented and optimized for VOCs detection and calorimetric sensing that are monolithically integrated with a commercial 0-35-μm CMOS technology with on-chip readout via a CMOS-MEMS fabrication approach. An electrostatic actuation scheme and a capacitive readout allow the MEMS structures to operate as a self-sustained oscillator when coupled to a specific amplifier providing a quasidigital output signal. The MEMS resonators are defined using the available CMOS layers. The adopted fabrication approach uses an intra-CMOS post-fabrication wet-etching step to release the mechanical moving parts by removing the surrounding sacrificial oxide, while the readout circuit is protected thanks to the passivation layer. Extensive analytical studies and FEM simulations, together with experimental characterization in open-loop and closedloop configuration of the fabricated CMOS-MEMS devices are addressed, offering an invaluable source of information for design optimization. Four-anchored plate resonators operating in the MHz range are designed and evaluated to work as a gas sensor with specific surface functionalization (via dip-cast immersion and inkjet polymer deposition) achieving a mass resolution per unit area as low as 213 pg·cm-2·Hz-1 and an Allan deviation below 0.5 ppm. Tolerance against environment perturbations such as temperature, humidity and fluid flow are discussed in detail for multiple anchor topologies, providing an optimum folded flexure alternative that alleviates such disturbances by 20-times. After P4V polymer coating, the fabricated system demonstrated acetone detection with a resolution down to 20 ppb that directly points towards non-invasive exhaled breath diagnosis for diabetic patients. In the case of calorimetric sensing, CC-Beams resonators in the MHz range have been designed as the temperature sensor providing extremely high temperature sensitivity up to -7900 ppm·ºC-1 that, together with a fair sub-ppm Allan deviation, achieves an outstanding temperature resolution of 300 μK. In this line, a cointegration of the resonator within a microfluidics PDMS-based platform has been developed that enables a Lab-on-Chip CMOS-compatible system capable of routing a fluid of interest to interact with a CMOS electrode. A conformal 2D planarization process is proposed to increase the IC active surface, combined with a standard wire bonding technique for socket connection. The obtained results confirm micro-calorimetric operation with an experimentally measured thermal efficiency from sample to resonator of 20%, conducting to an energy and heat resolutions as low as of 150 pJ and 630 nW, respectively. |
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