Eric Joseph

Toward Standard Method for Microelectromechanical Systems Material Measurement through On-Chip Electrostatic Probing of Micrometer Size Polysilicon Tensile Specimens

Polysilicon deposited by low pressure chemical vapor deposition is the most widely used structural material for surface-micromachined microelectromechanical systems. Thus, investigations are still needed in order to identify polysilicon mechanical characteristics as a function of the deposition conditions. The following work focuses on new micrometer size monolithic test cells combining polysilicon tensile specimens and ultra-high driving force electrostatic actuators fabricated from a common process flow. The proposed approach allows intrinsic material properties such as polysilicon tensile fracture to be measured through electrostatic probing, using on-chip micrometer size uniaxial tensile test cells.

On-Chip Investigation of Torque/Speed Characteristics on New High-Torque Micrometer-Size Polysilicon Electrostatic Actuators

In this study, we investigate new-generation high-torque/low-speed electrostatic micromotors as well as original on-chip testing methods for the mechanical characterization of silicon-based microactuators. Torque/speed characteristics of micrometer-size electrostatic actuators are measured for the first time using real-time elastic braking video analysis of polysilicon rotors that are monolithically coupled with elastic mechanical sensors. Loading characteristics measured through on-chip electrostatic probing indicate the potentialities of emerging actuator design methodologies involving frictional stator/rotor contact interactions on the micrometer scale.

Investigation of Output Mechanical Power Limits on High-Torque Electrostatic Actuators Using High-Frequency Complementary Metal Oxide Semiconductor (CMOS) Camera Combined with Image Processing Software

The following work investigates output mechanical power limits of electrostatic micromotors using stator/rotor contact interactions. Loading characteristics of micrometer size motors monolithically coupled with elastic polysilicon torque sensors are measured through an high-frequency complementary metal oxide semiconductor (CMOS) camera combined with a specific image processing software. Short duration video sequences recorded during the rotor braking are analyzed by tracking of a target pixel attached to the tested devices. Output mechanical power limits are measured through electrostatic probing on the wafer level within a few milliseconds. Experiments point out an unusual mechanical power per mass unit which is as high as 100 W/gr, considering driving frequencies on the order of 100 kHz.

Electromechanical characterization of screen-printed PZT thick films

Thick soft and hard-PZT films have been fabricated on different geometries of Alumina substrates using a screen-printing technique. Three mechanical characterization tests were set up to determine Youngs modulus of the films: dynamic, quasi-static and nanoindentation tests. A Youngs modulus around 52+/- 7 Gpa was calculated. The piezoelectric coefficient d31 was also investigated and is found to be close to -33pC/N. The fabricated films showed also good performances when used in damping control.