CAREER: advanced temperature compensation techniques for integrated bulk-mode micro and nano mechanical resonators

Issued as final reportNational Science Foundation (U.S.

A high aspect-ratio high-performance polysilicon vibrating ring gyroscope.

Design, fabrication and testing of a micromachined, high aspect-ratio high-performance polysilicon vibrating ring gyroscope are presented. The polysilicon vibrating ring is 1mm in diameter, 80mum thick and 4mum wide. It is supported by eight semi-circular springs to a center post that is 120mum in diameter. Sixteen electrodes are evenly located around the structure to drive, sense and electronically tune the ring structure. To sense rotation, the ring is electrostatically vibrated into its first in-plane flexural vibration mode and the position of the node lines are capacitively monitored. In this dissertation, a detailed analysis has been performed to determine the overall sensitivity of the vibrating ring gyroscope and identify its scaling limits. Several aspects of this analysis apply to other gyroscope sensing structures. Based on this analysis, a new single-wafer, high aspect ratio, dry-release poly-silicon microfabrication technology has been developed to implement sensor structures that provide all the features required for achieving the desired high performance. This process utilizes polysilicon as the structural element with its superior and homogenous material properties and is capable of producing very thick vertical polysilicon and silicon structures using Deep Reactive Ion Etching of silicon. Various size capacitive air-gaps ranging from sub-micron to tens of micron can be realized in this technology. This process is capable of producing silicon electrodes as tall as the main body structure with a simple fabrication process that eliminates the limitations of the previous technologies. Using a bent-beam strain gauge sensor, residual stress in 80mum thick, 4mum wide trench-refilled vertical polysilicon beams has been measured to be zero. 300mum long clamped-clamped beam resonators have shown quality factors as high as 85,000 in 1mTorr vacuum. A prototype 1.7 x 1.7 mm2 Polysilicon Ring Gyroscope (PRG) fabricated using the above technology has been tested in hybrid format. An open-loop sensitivity of 200muV/deg/sec in a dynamic range of +/-250 deg/sec was measured under low vacuum level for a prototype device. The resolution of the sensor is currently limited by the noise from the circuitry and for a prototype sensor with a quality factor (Q) of 1150 and parasitic capacitances of 2pF was measured to be less than 1 deg/sec in 1Hz bandwidth. Elimination of the parasitic capacitances and improvement in the quality factor of the ring structure are expected to reduce the resolution to 0.01 deg/sec in 1Hz bandwidth. By increasing the drive amplitude to 1mum in an asymmetric single ring gyroscope design, a minimum detectable signal of 5 x 10 -3 deg/sec (18 deg/h) in a 10Hz bandwidth can be achieved. Recommendations for improving the sensor performance to tactical and inertial grade levels are discussed at the end.Ph.D.Applied SciencesAutomotive engineeringElectrical engineeringMechanical engineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/132299/2/9963737.pd

IMU-on-a-Chip: MEMS and CMOS Microsystems

Presented on February 27, 2015 at 12:00 p.m. in room 1116 of the Marcus Nanotechnology Building.Farrokh Ayazi is a professor of Electrical and Computer Engineering and the director of the Center for MEMS and Microsystems Technologies at Georgia Tech. His main research interest lies in the area of integrated micro and nano electromechanical systems (MEMS and NEMS), with a focus on resonators and inertial sensors.Runtime: 63:45 minutesThe motion of an object in space can be mapped through the use of an inertial measurement unit (IMU), which comprises of accelerometers and gyroscopes. Accelerometers measure linear motion (axial acceleration) while gyroscopes measure rotation (angular velocity). IMUs are sometimes augmented by magnetometers, which provide heading information by measuring the earth magnetic field, and barometers for measuring atmospheric pressure to determine the relative altitude of an object. Such motion and position measurement and processing units can be used in a myriad of applications including robotics, gaming, user interfaces, unmanned air vehicles, and IoT. They can also enable in-door navigation through sensor fusion when GPS is not reliably available or where higher resolution is required. The gyroscope resolution and drift have been the bottleneck in achieving accurate and extended periods of navigation using silicon IMU chips. High-Q bulk acoustic wave (BAW) modes of a silicon resonator can be used to sense rotation around all three axes without being affected by linear motion. If these modes have identical frequencies and are coupled through Coriolis effect (i.e. gyroscopic modes), the sensitivity of the device is amplified by the Q-factor of the modes, which can reach a few millions, reducing power consumption and improving sensitivity. This talk will discuss strategies to integrate, operate and self-calibrate high performing MEMS inertial sensors using CMOS interface ICs and present a scalable manufacturing platform that enables the co-integration of a wide array of MEMS and NEMS sensors and actuators with CMOS for creation of 3D Integrated Microsystems. The nano-gap capacitive transducers implemented using the HARPSSTM process enable system-on-chip (SOC) integration of all IMU components with many more sensor and actuator using a foundry-compatible monolithic process

Through-silicon-via process development

Issued as final reportGoodrich Corporatio

Finite Ground Coplanar Lines on CMOS Grade Silicon with a Thick Embedded Silicon Oxide Layer Using Micromachining Techniques

Finite Ground Coplanar (FGC)waveguide transmission lines on CMOS grade silicon wafer (U<0.01 ohm-cm)with a thick embedded silicon oxide layer have been developed using micromachining techniques.Lines with different lengths were designed,fabricated and measured.Measured attenuation and s-parameters are presented in the paper.Results show that the attenuation loss of the fabricated FGC lines is as low as 3.2 dB/cm at 40 GHz