ACED Fab: On-chip CMOS-MEMS Infrared Spectroscopy Systems

Metabolites, gases, and many chemicals are structurally unique and exhibit distinctive absorptive fingerprints in the infrared spectrum band. The accurate detection and tracking of such spectrum using portable devices carry enormous potential and would enable many applications, including real-time health monitoring, gas detection, spectroscopy, imaging, the identification of hazardous materials, etc. Common infrared spectrometers rely on Fourier Transform system (FTIR) that are bulky, expensive, incompatible with integrated circuits, and unsuitable for real-life applications. Here, rooted on a synergetic collaborative effort between U.S. and Taiwan groups, an on-chip infrared spectroscopy system operating at room temperature and able to scan from ~ 1.5μm to 10 μm using a large number of channels will be demonstrated. The system relies on the integration of an array of miniaturized and spectrally-selective infrared sensors fabricated in the US, and CMOS chips fabricated in Taiwan that implement state of the art noise-suppression and interrogation techniques. The proposed on-chip infrared spectroscopy platform constitutes a significant step forward in the field of infrared technologies, moving beyond bulky and expensive Fourier Transform-based spectrometers into miniaturized, affordable, and mass-production ready devices. The potential applications enabled by such systems include sensing, communications, imaging, and spectroscopy, among many others. On the educational front, this project will provide multidisciplinary training to graduate and undergraduate students on a variety of scientific areas such as CMOS technologies, infrared sensing, mechanical resonators, metamaterials, and device fabrication and characterization; integrate research results with education activities, including the incorporation of research content in graduate courses and its broad dissemination through journal papers and scientific conferences; and encourage the participation and retention of women and Hispanic students - the PIs can serve as role model- in STEM and research. Moving beyond, this program will foster the collaboration between US and Taiwan researchers and set the foundations for long-term partnerships and scientific interactions. The goal of this project is to demonstrate an on-chip infrared spectroscopy system able to scan from ~ 1.5μm to 10 μm using a massive number of parallel channels while exhibiting a performance able to surpass competing technologies operating at room temperature. To this purpose, a large array spectrally-selective infrared sensors will be fabricated on a single chip at the UC Davis cleanroom, whereas RF interrogating and noise-suppression schemes will be implemented on a CMOS chip that will be fabricated at the Taiwan Semiconductor Research Institute (TSRI). Heterogeneous integration and packaging will also be carried out at the TSRI. The key building-block is an infrared detector based on nano-patterning ultrathin and high-Q metasurfaces on top of free-space standing microelectromechanical systems (MEMSs) to efficiently absorb light with desired spectral distribution. Each MEMS, designed to achieve a high mechanical quality factor and to absorb targeted wavelengths, will be excited at resonance by a RF signal whose phase and amplitude changes with the absorbed infrared power. To enhance the system performance, the detector will include two MEMS per released cavity, one serving as the reference and the other as the sensor. Exploiting I/Q signals for reference/sensing paths, the phase/amplitude variations of both units will be obtained and processed to highly suppress common mode and environmental noises (electrical, mechanical, optical, thermal) as well as the electronic readout circuit noises and non-idealities. In addition to significant noise reduction, the use of CMOS technology will permit to interrogate simultaneously a larger array of parallel sensors on a chip, and to multiplex their signals towards an output channel. This program will lay the foundational groundwork and demonstrate miniaturized, ultra-sensitive, low-noise, on-chip IR spectroscopy systems able to compete with state-of-the-art FTIR technologies operating at room temperature while strengthening the partnership and scientific interactions between USA and Taiwan. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.