Polysilicon Disk Research Articles

RF Channel-Select Micromechanical Disk Filters-Part II: Demonstration.

This Part II of a two-paper sequence presents fabrication and measurement results for a micromechanical disk-based RF channel-select filter designed using the theory and procedure of Part I. Successful demonstration of an actual filter required several practical additions to an ideal design, including the introduction of a 39-nm-gap capacitive transducer, voltage-controlled frequency tuning electrodes, and a stress relieving coupled array design, all of which combine to enable a 0.1% bandwidth 223.4-MHz channel-select filter with only 2.7 dB of in-band insertion loss and 50-dB rejection of out-of-band interferers. This amount of rejection is more than 23 dB better than a previous capacitive-gap transduced filter design that did not benefit from sub-50-nm gaps. It also comes in tandem with a 20-dB shape factor of 2.7 realized by a hierarchical mechanical circuit design utilizing 206 micromechanical circuit elements, all contained in an area footprint of only [Formula: see text]. The key to such low insertion loss for this tiny percent bandwidth is Q 's >8800 supplied by polysilicon disk resonators employing for the first time capacitive transducer gaps small enough to generate coupling strengths of Cx/Co ∼ 0.1 %, which is a 6.1× improvement over previous efforts. The filter structure utilizes electrical tuning to correct frequency mismatches due to process variations, where a dc tuning voltage of 12.1 V improves the filter insertion loss by 1.8 dB and yields the desired equiripple passband shape. Measured filter performance, both in- and out-of-channel, compares well with predictions of an electrical equivalent circuit that captures not only the ideal filter response, but also parasitic nonidealities that distort somewhat the filter response.

Characterization of Oxide-Coated Polysilicon Disk Resonator Gyroscope Within a Wafer-Scale Encapsulation Process

In this paper, we present the fabrication and test results of an oxide-coated polysilicon disk resonator gyroscope in a wafer-scale encapsulation process. We demonstrate the effects of an oxide coating on the device structure and the key performance parameters of resonant-based sensors, such as the temperature coefficient of frequency and quality factor ( $Q$ ). Results from the as-fabricated device show that a thin oxide coating reduces the surface roughness of a fully encapsulated device by $10\times $ , compared with a polysilicon device without the oxide coating. This increases the uniformity across the wafer, providing higher process yield. The open-loop rate measurement mode reveals an angle random walk of 0.18°/ $\surd $ hr and a bias instability of 1.43°/hr. [2015-0124]

An effective approach for restraining electrochemical corrosion of polycrystalline silicon caused by an HF-based solution and its application for mass production of MEMS devices

This paper presents a novel method to effectively protect the structural material polycrystalline silicon (polysilicon) from electrochemical corrosion, which often occurs when the MEMS device is released in HF-based solutions, especially when the device contains a noble metal. This corrosion seriously degrades the electrical and mechanical performance as well as the reliability of MEMS devices. In this method, a photoresist (PR) is employed to cover the noble metal, which is electrically coupled with the underlying polysilicon layer. This PR cover can effectually prevent an HF-based solution from diffusing through and arriving at the surface of the noble metal, thus cutting off the electrical current of the electrochemical corrosion reaction. The polysilicon is well protected for longer than 80 min in 49% concentrated HF solutions by a 3 µm-thick AZ 6130 PR film. This fabrication process is simple, reliable and suitable for mass production of high-end micromechanical disk resonators. Benefiting from the technology breakthrough mentioned above, a novel low-cost microfabrication method for disk resonators with high performance has been developed, and the VHF polysilicon disk resonators with resonance frequencies around 282 MHz and Q values larger than 2000 at atmosphere have been produced at wafer level.

Investigation of peptide based surface functionalization for copper ions detection using an ultrasensitive mechanical microresonator

Abstract In the framework of developing a portable label-free sensor for multi arrayed detection of heavy metals in drinking water, we present a mechanical resonator-based copper ions sensor, which uses a recently synthesized peptide Cysteine–Glycine–Glycine–Histidine (CGGH) and the l -Cysteine (Cys) peptide. In this work we combine the selectivity of two different functionalization layers with the very high distributed mass to frequency sensitivity of our bulk mechanical resonator. The resonator is a polysilicon disk which shows a Q-factor of 6500 in air at 65.3 MHz, while the two capturing chelating peptides CGGH and Cys have been immobilized via thiol groups on its surface. Insight on the interaction between the novel CGGH peptide and copper ions is obtained, demonstrating a 4.8 times larger binding efficiency than expected compared to a precedent model. After demonstrating the ability of the functionalized devices to detect a concentration of 10 μM of copper in water, we regenerate the surface by removing the copper ions from the functionalization layer using EDTA.

Ultrasensitive bulk disk microresonator-based sensor for distributed mass sensing

In the framework of the development of an ultrasensitive microfabricated mass sensor for distributed mass sensing applications we present a bulk resonator-based mass sensor. The two devices presented are based on a polysilicon disk resonating at 132 and 66 MHz, respectively, actuated electrostatically in a wine-glass mode. By using bulk mode resonators it has been possible to reduce the thickness of the sensor layer without affecting the resonance frequency, reaching an extremely high distributed mass to a frequency shift sensitivity of 11.3 kHz µm2 fg−1 and a markedly small mass resolution of 8.7 pg cm−2 in air and at room temperature.