R. Shane Fazzio

Accelerating Development of a MEMS Piezoelectric Microphone

MEMS projects are well known for their lengthy development times, hindering a company’s ability to make MEMS product development profitable. This paper describes a three-pronged methodology for rapid development of a piezoelectric MEMS microphone, utilizing concurrent design and prototyping, leveraged process technology, and a modified version of Quality Function Deployment (QFD). Avago Technologies has produced more than 300 million Film Bulk Acoustic Resonator (FBAR) piezoelectric band pass filters. FBAR uses Aluminum Nitride (AlN) as the piezoelectric film. Volume production of FBAR makes Avago the world’s only high volume producer of thin-film AlN products. This high-volume FBAR production process was greatly leveraged to enable fast prototyping of piezoelectric MEMS microphones. The concurrent design concept of simultaneously iterating on technical theory, finite element modeling, and prototyping with confirmation from testing was employed as another means of enabling swift development progress. QFD helps designers utilize the ‘voice of the customer’ to determine which product specifications are the most essential, and has long been used as a successful design methodology in the heavy industrial and automotive industries [1]. QFD and most other design methodologies have rarely been applied to MEMS products [2]. The second phase of QFD was modified for better application to MEMS products. Both Phase I and Phase II of QFD were then employed to guide the development process, giving insight into which elements of the design to focus on, which design concepts had the most merit, and which potential applications were the best fit to the technology. The combined effect of these three methods was extremely rapid development, enabling prototyping of hundreds of design variations and brisk improvement of measured results during the first eight months of the program. Achieving technical results quickly while assessing potential applications can aid in identifying a fast path to market. The methods used in this case study can easily be generalized for application to other MEMS development programs, potentially enabling MEMS products to reach production more quickly and generate increased profitability through addressing applications that best fit the technology and design.Copyright

Analysis of Micromachined Piezoelectric Transducers Operating in a Flexural Mode

Micromachined acoustic transducers have recently emerged in multiple application domains. Bulk acoustic resonators, for example, are extensively used as filters in the cellular handset industry. As another example, silicon capacitive microphones are rapidly replacing electret-condenser devices in consumer electronics platforms. Piezoelectric materials are commonly used in acoustic sensing applications. Combining micromaching with piezoelectric thin-films opens up possibilities of multiple new applications, in addition to the miniaturization of existing sensors. Applications may be as diverse as nondestructive test, acoustic imaging, vibration sensing, acceleration/force sensing, or electroacoustics. This paper presents analysis and measured behavior of micromachined devices constructed as a molybdenum, aluminum nitride, molybdenum trilayer and operating in a flexural mode. A theoretical analysis is derived using thin-plate bending theory. Finite-element simulation results of plate dynamics are examined, and sensitivities and linearity of manufactured devices are shown.Copyright