SBIR-STTR Award

This Small Business Innovation Research (SBIR)Phase I project will develop a novel way to measure charge trapping in dielectrics. The feasibility of our method by applying it to the characterization of plasma enhanced chemical vapor deposition (PECVD) nitride and oxide will be demonstrated. The deposition chemistry of these materials leaves trap sites that capture charge when subjected to large electric fields. Trapped charge affects the stability and performance of micro-electro-mechanical (MEM) devices that employ these dielectrics. A novel technique that uses a resonant, electro-statically actuated mechanical structure to measure charge trapped in a suspended dielectric layer is proposed. The real part of the device impedance, measured using a network analyzer, can be correlated to changes in electric field in the dielectric resulting from trapped charge.. PECVD dielectrics are critical constituents in MEM devices that enable $3.5 Billion in annualized sales (optical components, RF components, and medical imaging components). Although the technique itself is not a commercial product, it is broadly applicable to the engineering of MEMs devices utilizing suspended PECVD dielectric layers, such as radio frequency (RF) switches and micro-mirrors. This control of charge trapping in highly process sensitive PECVD dielectrics will allow us to realize the full commercial potential of our ultrasound devices in medical imaging applications.

This Small Business Innovation Research (SBIR) Phase II project proposes to develop high quality dielectric films and structures for a family of ultrasonic transducers for medical imaging applications. The technology and methods developed in Phase I to characterize charge-trapping behavior of dielectrics are the critical innovations required to take micro-fabricated ultrasonic transducers from their current state to a commercially viable state. Charge trapping created by the high electric fields in the device is detrimental to transducer performance. Charge trapping is dependent on field polarity and causes shifts in electromechanical conversion efficiency in time. Variations in charge trapping within a transducer array are even more disruptive. A process that removes the polarity dependence of charge trapping and thereby enables a new type of bipolar ultrasound imaging array that improves image quality will be developed. Since performance and reliability are critical to successful commercialization of these ultrasound probes, the issues of how dielectric charging causes time-dependent loss in performance and material degradation that could limit lifetime will be researched. The development and commercialization of micro-fabricated ultrasound transducers (MUT) is targeted at the medical applications market. This work will also enable the development of ultrasound probes that can non-invasively provide more accurate diagnostic information for doctors, such as improved ability to distinguish between cancerous and benign tissue. The image quality to price ratio drives market share in the global $3Billion diagnostic ultrasound market. These novel ultrasonic transducers will significantly improve the image quality/price ratio, and thus realistically create market share swings of 5% upon product release. Specifically, in the $1Billion mid-to-premium segment of the radiology market most relevant to the proposed research, $50M of annual system sales would be generated by the introduction of MUT probes, of which approximately one third are direct probe sales