Thomas D. DuBois

Integrated force array: interface to external systems

Integrated Force Arrays (IFAs) are thin film linear actuators which operate with substantial displacement and force. The methods of attachment of these devices to external systems are under development. Our current methods to incorporate IFAs in an scanning ultrasound imaging systems as well as a new material and method for attachment will be described.

Integrated force array: positioning drive applications

Integrated Force Arrays (IFAs) are thin film membrane actuators that act as transfer devices for electrostatic force. They are capable of large amplitude motion and evidence significant energies per unit volume (eg. 8.2 erg/mm3). Devices which use IFAs as drivers to scan PZT acoustic imaging transducers are under development and will be discussed here.

Measured forces and displacements of integrated force arrays

IFAs are MEMS actuators which are powered by the electrostatic forces between the plates of many microscopic deformable capacitors arranged in monolithic arrays. IFAs are fabricated using standard techniques of VLSI electronics. The IFAs reported here resemble thin, flexible plastic membranes 10 mm long and either 1 or 3 mm wide, which contain from 75,000 to 200,000 cells. They are low-weight, high-efficiency actuators with low power consumption, silent operation, and absence of sliding friction. Testing methods applicable to these free- standing MEMS structures are discussed, along with experimental observations and measurements of forces and displacements. We have measured forces in excess of 6 dynes and displacements of over 700 micrometers . The force/cross-sectional area of this MEMS structure is 2800 dynes/mm2, and the work done by the IFA divided by its volume is in excess of 7 ergs/mm3. A rate over 20,000 contractions/second has been observed, as well as lifetimes of greater than 108 contractions. The metalization of the IFA strongly affects the performance. Experimental results are presented demonstrating the improvements in the performance with a Cr/Au metal system compared to the Cr/Pd metal system originally used.

Integrated force arrays: scaling methods for extended range and force

Integrated Force Arrays (IFAs) are thin, flexible, metallized membranes which may be configured as actuators or sensors. The current prototype structures are approximately 1 cm long by 1 mm wide and designed for deformations of 2 mm. In this paper we will discuss how the devices may be scaled-up for extended range and force.

Micro-electro-mechanical actuator with extended range and enhanced force: fabrication, test, and application as a mechanical scanner

A miniature ultrasound scanner has been constructed using a MEMS actuator called an Integrated Force Array. A second type of actuator called a Spiral Wound Transducer (SWT) is under development and shows significant promise for this application. Both the scanner and SWT will be discussed.

Entrenched Metal Liftoff Using A Novel Bilayer Process

This paper will discuss the preparation and characterization of a modified photoresist and describe its use in a novel bilayer process. The modified photoresist solutions are prepared by dissolving enough cyclic phosphonitrilic chloride trimer, PNCT, in commercially available photoresist solutions to achieve phosphorus concentrations of 10 to 12 weight percent in the resulting films. FTNMR and FTIR data will be presented which demonstrate that the cyclic phosphonitrilic chloride trimer does not undergo chemical reaction with the components of the photoresist in the photoresist solutions or photoresist films. The exposure threshold of the PNCT modified photoresist films is 1.5 times greater than that of the unmodified films. Experimental data will be discussed which suggests the decrease in exposure threshold is the result of a relatively lower concentration of photoactive compound in the PNCT modified films. The PNCT modified films will be shown to provide resolution comparable to that of the unmodified photoresist films and yield a process window of better than 20%. A mechanism for the formation of the 02/N2 plasma resistant etch barrier formed during 02/N2 plasma etching will be discussed. Finally, a bilayer process which uses the PNCT modified photoresist in generating metal features entrenched in polyimide will be presented.