Aaron Geisberger

Electrothermal properties and modeling of polysilicon microthermal actuators

This work addresses a range of issues on modeling electrothermal microactuators, including the physics of temperature dependent material properties and Finite Element Analysis (FEA) modeling techniques. Electrical and thermal conductivity are a nonlinear function of temperature that can be explained with electron and phonon transport models, respectively. Parametric forms of these equations are developed for polysilicon and a technique to extract these parameters from experimental data is given. A modeling technique to capture the convective and conductive cooling effects on a thermal actuator in air is then presented. Using this modeling technique and the established polysilicon material properties, simulation results are compared with measured actuator responses. Both static and transient analyzes have been performed on two styles of actuators and the results compare well with measured data.

Micromachined end-effector and techniques for directed MEMS assembly

A micromachined end-effector along with techniques in micromanipulation for directed micro-electro-mechanical systems (MEMS) assembly is presented. A passive end-effector, fabricated in a 50 ?m thick single crystal silicon (SCS) deep reactive ion etched (DRIE) process, is compared with a microgripper made with the same process. With this passive tool, pick and place assembly of MEMS components can be accomplished reliably, since the end-effector is more mechanically robust than comparable microgrippers. This end-effector can withstand an order of magnitude more force than conventional MEMS based microgrippers used for microassembly. In addition, the elimination of any actuation reduces packaging complexity and allows easier integration of sensing mechanisms for feedback control. This simplified passive end-effector with an integrated electrical contact sensor is also presented, along with assembly techniques and designs used for directed pick and place MEMS assembly. Both mechanical and electrical MEMS interconnects are demonstrated.

Techniques in MEMS Microthermal Actuators and Their Applications

Micro machined transducers have been the focus of study for many groups over the past two decades and as such, a body of literature is dedicated to summarizing the field [57]. As the field has matured, a smaller group of micro transducers has been optimized to provide mechanical work into a micro system. Most notable to the authors are electrostatic, piezoelectric, electromagnetic, shape memory alloy, and thermal micro transducers. This introduction takes a brief look at these technologies and provides some metrics for evaluating a micro transducer technology, given some established requirements. The authors often find that for an application where the transducer is limited in size, powered electrically at limited voltage levels, confined to a limited micro fabrication process, and has relatively large desired mechanical output, the micro actuation technology of choice is electrothermal. These transducers convert electrical energy to mechanical work through localized Joule heating and thermal expansion.

No Physical Stimulus Testing and Calibration for MEMS Accelerometer

Conventional MEMS devices require physical stimulus for calibration and test. This is not only time consuming but also uses expensive equipment. In this paper, it is presented that an accelerometer can be tested and calibrated with no physical stimulus; this is achieved by using electrostatic forces applied at transducer test plates to excite the proof mass. It is demonstrated that gain parameters required to calibrate the device can be estimated using an extended Kalman filter algorithm provided an accurate physical system model is developed as a function of critical silicon process parameters. Our methodology is not only time efficient, but cost effective as well. This methodology may be applied to most silicon processes used for MEMS inertial sensors.

A static capacitance probe structure for resolving the sidewall skew angle of Silicon Deep Reactive-Ion Etching

This work presents a static capacitive probe structure that enables quantitative characterization of the effective sidewall skew angle of the Silicon Deep-Reactive-Ion-Etching (DRIE) using static LCR prober at ambient environment. The design is capable of resolving sidewall skew angles around both in-plane axes independently and simultaneously with the same sensitivity. The measured distributions of the sidewall skew angle across 8-inch wafers conform to empirical expectation and correlate tightly with quadrature error distributions measured gyroscopes from the same wafers. This work provides an easy, accurate and batch solution to the long existing challenge of resolving such process features in an industrial manufacturing environment.