الفهرس 
ABSTRACT
Label vs. Label-Free bio-detectionOnly 14 pages are availabe for public view
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Abstract
Miniaturizing biomedical labs into a Lab-On-A-Chip is the focus of a lot of bio-medical research in the last years. The need to detect genetically-modified organisms, the rapid spreading of infectious agents and many other diseases has led to an increasing interest to research and build new sensitive diagnostic tools such as bio-sensors for DNA identification. Recently, the use of Micro (Nano) Electro-Mechanical (MEM/NEM) resonators, as label-free biosensors, promised to provide highly sensitive devices. It is envisaged that such sensor will be integrated with a microfluidics device designed to handle the required biological sample preparation prior to the detection exercise. Research at imec demonstrated the advantage of using poly-SiGe in allowing direct MEMS-CMOS monolithic integration, which allows for cost-effective MEMS-based biosensors. Since a MEMS-based resonator is expected to operate under atmospheric pressure and/or in the presence of fluids, ensuring its flawless and reliable performance over device lifetime is of paramount importance for successful commercialization.
The research reported in this thesis focuses on measuring the performance of MEMS-based biosensors, studying their reliability and identifying design, fabrication and functionalization steps responsible for specific reliability failure modes. Therefore, we developed an experimental setup, using the research and measurement facilities at imec laboratories, to measure the bio-resonator’s performance under conditions similar to its typical use model, i.e. under atmospheric pressure. Compared to the standard MEMS performance measurements done in vacuum, utilizing MEM resonator in ambient pressure is challenging due to the difficulty in detecting resonance peaks. We conducted the first detailed and systematic study on the impact of each step in the functionalization process, where the resonator surface is chemically modified to attract a specific biomolecule, on the shift in resonance frequency and reliability of the resonator. It was found that the blocking agent ’Bovine Serum Albumin’ (BSA) was a major cause of resonator’s failure during the functionalization step. As a result of an optimization plan that was triggered by our finding, Hexylamine was selected and confirmed as an alternative blocking agent that yields the best reliability results at high sensitivity.
from the design perspective, it was found that long double clamped beam (DCB) resonators, as well as, bulk acoustic wave (BAW) resonators with low perforation density were more susceptible to failure due to stiction. Based on the tested structures of 4μm width, DCBs with surface area less than 3000μ2 are recommended for a stiction-resilient design. Also, results show that for best reliability performance a normalized effective density in the range between 0.24 and 0.36 is recommended for future BAW resonator designs.
We investigated the sensitivity of the first electrically actuated/sensed SiGe MEM-based DNA sensor where numerous experiments we performed on DCB resonators as well as solid and perforated Bulk Acoustic Wave (BAW) resonators. We report a minimum DNA concentration sensitivity of 500nM using perforated (BAW) resonators.
This thesis represented the performance and reliability assessment part of an integrated project to develop a sensitive and reliable MEMS-based biosensor that included tasks like MEMS design, fabrication and surface engineering. Therefore, in addition to performing the measurements and reliability assessment, a focused and disciplined coordination and integration effort was required.