Serhan Ardanuc

Chip-scale sonic communication using AlN transducers

On-chip wired interconnects presents a bottleneck for VLSI integrated circuits. An additional channel with which to communicate information would be beneficial to supplement traditional wired designs. Utilizing virtual, reconfigurable ultrasonic interconnects operating at high bit rate could open new vistas for computer architecture and low power computing. The first step to this goal has been demonstrated in this paper by using ultrasonic pulses to communicate between two aluminum nitride thin film transducers on a silicon wafer representative of a VLSI substrate. Direct output voltages on receive pixels were on the order of 40-60 μVpp for a drive voltage on transmit pixels of 0.5 Vpp at 900 MHz. An FEA model was used to verify the time-of-flight and signal amplitudes to demonstrate that the primary mechanism is bulk acoustic waves travelling through the silicon substrate.

Planar laser-micro machined bulk PZT bimorph For in-plane actuation

We demonstrate a PZT bimorph technology for integrated chip-scale in-plane nano-motion actuators. Bulk PZT actuators are micro-machined to define beams by laser-cutting through a PZT-4 plate while also defining arbitrary 2D electrode patterns on top and bottom surface of the beams by using a commercial laser cutting tool with backside alignment capability. Lateral actuators that are 5, 10 and 20 mm long, 0.45 mm wide, and 0.5 mm thick were characterized with single and dual side laser patterned electrodes. The in-plane bimorph displacements are in the range of 0.02 to 0.64 microns/volt. The out of plane displacement sensitivity of these actuators were simulated to be ~ 100s ppm/V compared to the desired in plane actuation. We also report doubling of the actuator tip displacement for the same applied voltages in the dual side electrode actuators, when compared to the single sided actuators.

DOME-DISC: Diffractive optics metrology enabled dithering inertial sensor calibration

We demonstrate 107-ppm accurate scale-factor and bias calibration of a commercial Coriolis force gyroscope, in which the typical un-calibrated scale factor variations are ~100,000-ppm. In this paper, we present a proof-of-concept result on calibration architecture - Diffractive Optics Metrology Enabled Dithering Inertial Sensor Calibration (DOME-DISC). DOME-DISC consists of a piezoelectric dither stage to provide built-in mechanical stimulus to the gyroscope attached to it. The motion of the dithering stage is measured by imaging an optical diffraction pattern created by an incident laser off diffraction gratings on the dither stage. In order to calibrate the gyroscope, the stage motion needs to be measured accurately and precisely. The motion of the stage is measured using the Nano Optical Ruler Imaging System (NORIS), with absolute accuracy of ~30nm over several millimeters, stable over several hours. NORIS provides parts-per-million stage motion measurement accuracy. In this paper, an angular dither motion of 0.1 to 0.5 degrees was optically measured with ~ 0.1 millidegree resolution. By measuring the scale factor and bias for a gyroscope on the dither stage mounted directly on a commercial rate table, and matching the gyroscope input-output curve to 100ppm, we demonstrate the capability to measure in-package gyroscope characteristics within the error limits of the commercial rate table.

Towards ultrasonic through-silicon vias (UTSV)

3D interconnects between stacked silicon chips in 3D integrated circuits (3DICs) have been realized with through-silicon vias (TSVs). These call for special processing microfabriation techniques requiring through wafer etching and metal filling, which add to the cost and can lead to lower chip reliability due to thermal expansion mismatch related strain fields. In this paper, we present a novel interconnect for 3DICs - an ultrasonic TSV implemented with piezoelectric aluminum nitride (AlN) thin film transducers on silicon. Whereas TSVs require a physical via through the entire thickness of a wafer, the ultrasonic TSV works by propagating signals from one aluminum nitride (AlN) transducer to another with bulk acoustic waves through the silicon wafer. This technology has the potential to simplify processing in 3DIC manufacturing and integration and increase TSV density.

Monolithic piezoelectric in-plane motion stage with low cross-axis-coupling

We present a rotary dither stage that can provide rotation stimulus to objects mounted on it. The stage is in planar form-factor allowing compatibility with planar packages that can house both the stage and the inertial sensor. We used laser micromachining of bulk PZT-4 plates to form PZT beams to achieve monolithic integration of lateral actuators and flexures. This process enables high-aspect ratio PZT beams (500μm thick, 150μm wide) resulting in high out-of-plane stiffness, helping in reducing the out-of-plane motion to parts-per-thousand of the inplane motion. The micro stage technology opens up a new design space of 100-micron scale lateral bimorphs for mm-scale stages with large motion. A dither stage was designed and fabricated that can achieve in plane dither of ~ 1.2 millidegree/V and dither rates up to 1800 degree/s. Low dither rates of 20-60 millidegree/s are demonstrated and measured.

Chip-scale reconfigurable phased-array sonic communication

As CMOS electronics scale to smaller dimensions, wired interconnect density, power consumption, and delays have introduced bottlenecks in performance. Ultrasonic communication links integrated within the silicon substrate offer an opportunity to create low power high data rate channels. We have utilized ultrasonic phased arrays, micro-sonars, for reconfigurable communication links. Brand new vistas in computer architecture and low power computing are enabled by these links, including brain inspired computing. This paper demonstrates the use of phased array elements to create a reconfigurable 120 Mbit per second channel in silicon. The array is capable of selectively communicating to four different locations on chip.

Graphene one-shot micro-valve: Towards vaporizable electronics

One-shot micro-valves are key to applications that require leak-proof sealing of micro-cavities before they are irreversibly triggered to expose the cavity content to the outside environment. Here, we report a novel micro-scale one-shot valve made of graphene transferred on to silicon-nitride (SixNy) membranes. The valve triggers thermo-mechanically in 15.4±3.9 msec consuming 142.1±13.5 mW electrical power, corresponding to 2.2 mJ input energy. The valve membrane can sustain a differential pressure of 2 bars. The graphene serves multiple purposes in the device, acting as an atomically thin barrier to gas-diffusion, a resistive heater, and a source of stress in triggering the valve owing to its negative thermal expansion coefficient (TEC). The valve is designed to trigger and expose arrays of nanogram micro-packets of reactive alkali metal atoms such as rubidium, exposing it to atmospheric oxygen causing it generate heat. This heat can be used for massively parallel vaporization of vaporizable polymer electronics. A 1 mm3 Li-battery can trigger 1580 valves on a single chip for enabling transient electronics.

Multi-modal mechanical stimuli stage for in-situ calibration of MEMS gyroscopes

We report a multi-axis piezoelectric multi-modal mechanical stimuli stage capable of in-situ calibration of MEMS gyroscopes attached to the stage. The system is fully self-contained with electronics for portable operation. In this work, we demonstrate active calibration of a commercial Z-axis gyroscope ADXRS646 for high bandwidth applications. The dithered stage is capable of pure sinusoidal angular rates at 0-300 deg/s even after being loaded with a gyroscope die, to extract the scale factor and the bias. The stage has the added capability of X-Y in-plane acceleration stimulus 0-90 m/s2 to extract the cross-axis sensitivities which are essential parameters. The measured maximum in-plane cross-axis sensitivity for unpackaged gyro ~ 13.64% (Sx/Sy x 100) operated at ~800Hz bandwidth, providing high bandwidth calibration data useful for personal navigation. The maximum power consumption of the unloaded calibration stage is ~396mWatts during calibration.

Micro-Einzel lens for wafer-integrated electron beam actuation

Miniaturizing charged particle beam actuator systems to the wafer-scale Si-based micromachined platforms, requires devices such as micro-Einzel lenses, which are used to control beam trajectory and focusing in targeted small volumes. In this paper, we present a highly versatile 3D fabrication process that provides high aspect ratio multi-electrode structures that enable electrostatic Einzel lenses, quadrupoles, and hexapoles, for in-plane and out-of-plane particle motion-control. We demonstrate 3 wafer-layer Einzel lens with predicted focal length shifts of up to 167mm for voltages up to 300V. This lens actuator technology paves the way for integrated charged particle beam systems such as parallel e-beam lithography that offers much faster writing times than conventional single-beam systems.

Process-Independent, Ultrasound-Enhanced, Electrostatic Batch Assembly

This paper describes a batch assembly method for 3D microsystems that is based on combining electrostatic forces and ultrasonic actuation. Simplicity of the setup, applicability to a broad range of surface micromachining processes, and the lack of any additional fabrication steps or exotic materials are the foremost advantages of this method. These attributes distinguish it from other popular assembly methods that rely on surface tension, magnetic coatings, robotics, etc.