Piezoelectric Resonant Body Transistor (PRBT)

Technology #14912

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 FIG. 1 a shows a top view of a piezoelectric electromechanical transistor, according to some embodiments.  FIG. 1 b shows a cross-sectional view of the piezoelectric electromechanical transistor of FIG. 1 a. FIG. 2 shows an equivalent circuit model for the piezoelectric electromechanical transistor.FIG. 3 shows a plot of iout and the RMS (root mean square) distortion of iout as a function of the quality factor.
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Inventors
Professor Dana Weinstein
Department of Electrical Engineering-Computer Science, MIT
External Link (www.eecs.mit.edu)
Radhika Marathe
Department of Electrical Engineering-Computer Science, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Piezoelectric electromechanical devices

US Patent 8,841,818
Publications
Resonant Body Transistors in Standard CMOS Technology
Ultrasonics Symposium (IUS, 2012 IEEE International

Applications

This technology improves piezoelectric electromechanical devices, such as piezoelecric electromechanical transistors, by integrating both a transistor and a resonator in the same device. Applications for this technology include wireless communication, telecommunication, microprocessors, clocking, and transceiver circuitry.

Problem Addressed

Resonant Body Transistors (RBT) integrate a field effect transistor (FET) with a microelectromechanical (MEMS) dielectric resonator. The integration allows decoupling of the drive and sense mechanisms for low-noise and an efficient sensing mechanism for amplification of the mechanical signal at resonance. While this leads to increased operating frequencies for Complementary Metal-Oxides (CMOS)-integrated resonators, such dielectric-based MEMS resonators suffer from high insertion losses and low power handling capability. On the other hand, piezoelectric based MEMS resonators have much lower insertion loss and larger power handling capability due to higher breakdown voltage than the dielectric MEMS resonator, but these suffer from lower quality factors (q) and lack of in-line switching. As piezoelectrics have an inherently higher coupling coefficient as compared to the dielectrics, the Piezoelectric Resonant RBT has a much improved insertion loss over the RBT. This allows for larger power handling defined by the breakdown voltage across piezoelectric films, and ease of packing and integration into transceiver circuitry. 

Technology

This technology integrates piezoelectric material into an active MEMS resonator, such as an RBT. This allows manufacture of FET-sensed piezoelectric devices operating at >10 GHz band frequency with reduced insertion loss, high Q (due to Si body), and higher power handling capability, making the device suitable for communication systems and low-noise clocking sources. Materials, such as AlN or ZnO allow CMOS-compatible manufacturing techniques, and the sensing FET allows for switching the device on and off as well as integrating non-linear behavior for signal amplification and rectification.

Advantages

  • Fully CMOS compatible
  • Multiple resonators with different frequencies may be fabricated on the same device with a single mask
  • Very high quality factor (Q > 10,000)
  • Small footprint
  • Low power consumption
  • Reduces spurious modes