Technology Transfer SSC Pacific
Optimized Model and Standard Cell Logic Library for Subthreshold Circuit Design 
 

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The U.S. Navy seeks to commercialize a method and standard cell logic library for developing circuits that operate in the subthreshold region.

Background

The subthreshold region is a rarely used operating region for Metal Oxide Field Effect Transistor (MOSFET) devices. Generally, circuits operate in the higher voltage region known as the saturation region. Voltage in the subthreshold region is characterized by being below the threshold voltage. This results in much lower power consumption due to a lower applied electric field. Thus, subthreshold circuits are ideal for low power applications such as remote and unattended sensors that favor reduced energy consumption over system performance. Unfortunately, due to the subthreshold region’s limited use, Simulation Program with Integrated Circuit Emphasis (SPICE) models provided by foundries do not properly characterize the region. This results in undependable subthreshold simulations and circuit designs. A proper model is needed for the accurate design of subthreshold circuits.

The Technology

Scientists and Engineers at SSC Pacific completed fabrication runs that included specific test vehicles needed to characterize the TSMC 0.25 µm process in the subthreshold region. The data collected by measuring the devices was used to optimize the foundry’s SPICE model. SSC Pacific test data shows that the optimized model can properly characterize the process throughout the entire operating range better than the foundry model, especially in the subthreshold region of operation. The optimized model was used to create a subthreshold standard cell library. The library enables the design of an Application Specific Integrated Circuit (ASIC) or System on Chip (SoC) having a power savings of up to 6 orders of magnitude for some applications.

Key Benefits

  • Aids in fabrication of model-accurate transistors that consume less power
  • Benefits ASICs that favor low power over performance
  • Leverages known simulation models (SPICE, BSIMv3.3, UTMOST IV)
  • Could apply to other fabrication processes (not limited to TSMC 0.25 µm)
  • Ideal applications include remote sensors, RFID tags, biomedical devices
  • Development Status

  • U.S. Patent Applications 13/917036 and 13/564902
  • Total R&D: $350K over 2 years
  • DoD 5000 Series TRL 3: characteristic proof of concept
  • Available for licensing. Seeking collaborators to use model to develop other fabrication sizes and/or create low power versions of their designs.
  • Publications

  • Subthreshold SPICE model optimization. AIP Conf. Proc. 1339, 314 (2011), 21-24 September 2010.  
  • For more information on technology transfer, please contact us at (619) 5535118 or email ssc_pac_t2@navy.mil       
    SD 1172, November 2013. SSC Pacific, San Diego, CA 921525001. Approved for public release; distribution is unlimited.

    SSC Pacific
     
    Updated: 12/9/2013 6:26 PM EST   Published (1.0)