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Characterization of subthreshold MOS mismatch in transistors for VLSI systems

Journal of VLSI signal processing systems for signal, image and video technology volume 8, pages 75–85 (1994)Cite this article

Abstract

MOS transistor mismatch is revisited in the context of subthreshold operation and VLSI systems. We report experimental measurements from large transistor arrays with device sizes typical for digital and analog VLSI systems (areas between 9 and 400μm2). These are fabricated at different production qualified facilities in 40-nm gate oxide,n-well andp-well, mask lithography processes. Within the small area of our test-strips (3 mm2), transistor mismatch can be classified into four categories: random variations, “edge,” “striation,” and “gradient” effects. The edge effect manifests itself as a dependence of the transistor current on its position with reference to the surrounding structures. Contrary to what was previously believed, edge effects extend beyond the outer most devices in the array. The striation effect exhibits itself as a position-dependent variation in transistor current following a sinusoidal oscillation in space of slowly varying frequency. The gradient effect is also a position-dependent spatial variation but of much lower frequency. When systematic effects are removed from the data, the random variations follow an inverse linear dependence on the square root of transistor area.

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Authors and Affiliations

  1. Electrical and Computer Engineering, Johns Hopkins University, 21218, Baltimore, Maryland

    Aleksandra Pavasović, Andreas G. Andreou & Charles R. Westgate

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  1. Aleksandra Pavasović
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  2. Andreas G. Andreou
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  3. Charles R. Westgate
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Pavasović, A., Andreou, A.G. & Westgate, C.R. Characterization of subthreshold MOS mismatch in transistors for VLSI systems. Journal of VLSI Signal Processing 8, 75–85 (1994). https://doi.org/10.1007/BF02407112

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  • DOI: https://doi.org/10.1007/BF02407112

Keywords

  • Test Strip
  • Density Plot
  • Subthreshold Region
  • VLSI System
  • Analog Circuit Design