Analog Integrated Circuits (ECE 4530 / 5530) | Fall 2022

Heterogeneously Integrated CMOS systems for electrophysiological monitoring and high-speed wirelines.Select Publications:1) M.F. Reynolds, A. J. Cortese, Q. Liu, Z. Zheng, W. Wang, S.L. Norris, S. Lee, et al., “Microscopic Robots with Onboard Digital Control,” Science Robotics. (2022).2) S. Daudlin, A. Rizzo, N. C. Abrams, S. Lee, et al., “A Compact 3-D Integrated CMOS-Silicon Photonic Transceiver for DWDM,” The Optical Networking and Communication Conference & Exhibition. (2021).3) E. C. Szoka, J. C. Werth, S. Lee, et al., “Neural Probe Utilizing Programmable Micro-coil Magnetic Stimulation,” IEEE EMBS Conference on Neural Engineering. (2021).4) A. C. Molnar, S. Lee, et al., “Nanoliter-Scale Autonomous Electronics Advances, Challenges, and Opportunities,” IEEE CICC. (2021).5) A. Khalifa, S. Lee, et al., “Injectable Wireless Microdevices: Challenges and Opportunities,” Bioelectronic Medicine. (2021).6) S. Lee, et al., “Fabrication of Injectable Micro-Scale Opto-Electronically Transduced Electrodes (MOTEs) for Physiological Monitoring,” IEEE JMEMS. (2020).7) A.J. Cortese, C. L. Smart, T. Wang, M. F. Reynolds, S. L. Norris, Y. Ji, S. Lee, A. Mok, C. Wu, F. Xia, N. I. Ellis, A. C. Molnar, C. Xu, and P. L. McEuen., “Microscopic sensors using optical wireless integrated circuits,” PNAS (2020).

Implantable, Microscale Opto-electrically Transduced Electrodes Site (MOTES) for In Vivo Monitoring of Electrophysiological Signals in Nervous Systems:1) Built a heterogeneous μ-System, an untethered electrode unit on the same physical size as the neurons themselves, powered by, and communicating through micro light emitting diode (μLED) that can dual-function as micro photovoltaic (μPV), to combine many benefits of optical techniques with high temporal-resolution recording of electrical signals. 2) Demonstrated that the MOTES can indeed function as an untethered neural probe, optically powered and communicated through the integrated μPV-μLED (PVLED), and showed that the neural signals of an earthworm can been measured with high fidelity.Select Publications:1) S. Lee, et al., “A 250 μm × 57 μm Microscale Opto-Electronically Transduced Electrodes (MOTEs) for Neural Recording,” IEEE TBioCAS. (2018).2) S. Lee. et al., “A 300μm x 90μm Opto-electronically Integrated Wireless System on Chip for Recording of Neural Activities,” 2018 IEEE International Solid-State Circuits Conference (ISSCC), February 11-15, 2018.

[Advisors: Professors James Hone, Kenneth Shepard, and Ioannis Kymissis]1) Graphene NEMS for CMOS-Compatible Filters and Oscillators• Fabricated suspended graphene resonators at the Cornell Nanofabrication Facility and Columbia University Cleanroom using contact, photo and electron beam lithography, plasma and chemical etching, furnace growth, and thermal and e-beam evaporation• Adapted methods for growing graphene on copper foil using chemical vapor deposition (CVD) and to make large arrays of suspended graphene resonators• Measured forward transmission coefficient (S21) of graphene resonators under high vacuum and performed two-tone test to evaluate filter characteristics• Demonstrated electrically tunable self-oscillation of graphene resonator with an external amplifier and a phase shifter• Applied strain on the suspended graphene membrane using SU-8 polymer to increase the resonant frequency of the resonator by factor of 5 (250MHz – the final goal is 1GHz) with associated quality factor close to 300 at room temperature. *Supported by Qualcomm Innovation Fellowship 2012• Designed a layout in TSMC 0.18um technology where graphene resonators can be built on top with post-processing, for tunable graphene filter array (in collaboration with Changhyuk Lee in Prof. Alyosha Molnar’s Group at Cornell) *Supported by Qualcomm Innovation Fellowship 20132) Metallization of High-Q Dielectric NEMS Using Graphene• Fabricated suspended graphene – silicon nitride heterostructure for high Q tunable NEMS• Measured quality factors close to 1,000,000 at room temperature using electrical actuation and optical detection.• Developed fabrication processes for full electrical integration using shadow masks, and demonstrated electrical actuation and detection based on capacitive transduction.• Demonstrated the electrostatic tuning of the graphene-metallized Si3N4, and showed the trade-off between the electro-mechanical coupling and the quality factor.

[Advisors: Professor James Hone, Kenneth Shepard, and Ioannis Kymissis]1) Worked as a teaching assistant for thermodynamics class in mechanical engineering department at Columbia University.*Rewarded an Outstanding TA Award2) Nano-pillars for Understanding T-cell Activation• Fabricated Nano-pillars (diameters ranging from 200nm to several microns), to study the correlation between different mechanical surroundings and immune cell activation• Developed an algorithm for image analysis to track the nanoscale movements of the nano-pillars using Matlab

Design and Evaluation of Next Generation MEMS Gyroscopes[Managers: Dr. See-Ho Tsang, Dr. Igor Prikhodko, Dr. Jeffrey Gregory, and Dr. Michael Judy]• Set up an evaluation system for MEMS gyroscopes by integrating a rate table with a thermal chamber, and designing a mobile electronics module capable of DC and r.f. characterization.• Designed a probe card for wafer scale evaluation, as well as a PCB for die-level testing.• Automated trimming procedures to improve characterization efficiency.• Implemented a PID-controlled real-time mode-matching scheme for enhanced device stability.

High Quality CVD Graphene for Spintronics Applications[Managers: Dr. Ching-Tzu Chen and Dr. Daniel Worledge]• Optimized the CVD graphene growth process to achieve four-point mobility as high as 30,000 cm2/V-s at room temperature. • Fabricated graphene-based spintronics devices for high Non-Local Resistance (NLR) at low magnetic field.• Automated the measurement setup using Matlab to control a parameter analyzer, voltage/current sources, superconducting magnets, a helium monitor, and lock-in amplifiers.

Tapered Fiber and Grating Coupler for Low Loss Waveguide Coupling for the Study of Optomechanics[Advisor: Professor Michal Lipson]• Set up and optimized tapered fiber fabrication, and automated using LabView• Developed method of flexible waveguide coupling for microcavity-characterization with low insertion loss using a tapered fiber• Modeled thermal optomechanical properties of microcavities using Mathematica• Fabricated low loss grating coupler to implement VECSL for on-chip photonics

Tin-Solder Electroplating for 3D Flip Chip Integration[Manager: Ms. Gordana Zupanski-Nielsen]• Set up Tin-Solder plating baths for Solder Bump Interconnect for 3D System Integrations Group• Reduced the plating thickness variation by a factor of three over previous method to enhance device yield

Fabrication Process Characterization and Optimization Magnetic Random Access Memory (MRAM) Devices[Advisor: Professor Santosh Kurinec]• Conducted design of experiments (DOE) to show that tantalum (Ta) minimizes the resistance-area product of the bottom electrode• Developed a curing process for Spin-On-Glass (SOG) for an interlayer dielectric (ILD)