Application of physics-based device models for circuit simulation

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Application of physics-based device models for
circuit simulation
MOS-AK Meeting, September 22, 2006

• Victor Spitsyn, Ilya Lisichkin
• Cadence Design Systems LLC, Moscow

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A Model equations and parameters

• The model derivation includes discretization
  mesh, Poison and continuity equations integration
  steps. A circuit representation is derived. Some
  simplifying assumptions were done.
• dQkp
• Ckp ----------------
• d(Vkp Vki)
• Jkp e gkmn (Vk-1i Vki)
• gkdn (Vk-1i Vk-1n, Vki Vkn )
• gkvn (Vk-1n Vkn)

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Pn junction circuit model

• Three-block equivalent circuit of a pn junction.
  The elements drawn in black are those which
  implement the minimum device functionality. The
  elements drawn in grey are only required for
  accurate high-injection and high-frequency
  modeling. The heavy dark lines highlight elements
  which reduce to short circuits in the
  low-injection case.

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Simulation of pn junction

• Small-signal conductance and capacitance at
  100kHz for a symmetric pn junction with 5µm long
  p and n regions of doping 1016cm-3. The order
  parameter indicates the number of partitions on
  each side of the junction.

• Frequency response (real and imaginary part of
  the small-signal admittance) for the first- and
  second-order model, at a forward bias of 0.7V.

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Npn bipolar transistor circuit model

• Equivalent circuit of the npn bipolar transistor.
  The elements drawn in black are those which
  implement the minimum device functionality. The
  elements drawn in grey are only required for
  accurate high-injection and high-frequency
  modeling. The heavy dark lines highlight elements
  which reduce to short circuits at low injection

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Simulation of bipolar transistor

• Frequency dependence of the real and imaginary
  parts (absolute values) of the Y parameters for a
  0.25 µm npn bipolar transistor at a current
  density of 430 µA/ µm2 (ft 16 GHz, fmax 30
  GHz)

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Whats next performance and accuracy gain
measurement

• Using common benchmarks and typical engineering
  tasks to measure performance and compare accuracy
  wrt compact models

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Summary

• Considered models are good to apply for
  small-signal analyses.
• For successful implementation, parameter
  extraction tool is needed, because optimization
  procedure is an essential part of the entire
  flow.
• Assessment of performance impact and accuracy
  gain as compared to the compact models is
  reasonable to complete.

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References

• J. G. Linvill, Lumped models of transistors and
  diodes, Proc. IRE, vol. 46, pp. 11411152, June
  1958.
• C. T. Sah, The equivalent circuit model in
  solid-state electronicsPart I The single energy
  level defect centers, Proc. IEEE, vol. 55, pp.
  654671, May 1967
• A. Pacelli, M. Mastrapasqua, and S. Luryi,
  Generation of equivalent circuits from
  physics-based device simulation, IEEE Trans.
  Computer Aided Design of Integrated Circuits,
  vol. 19, pp. 12411250, Nov. 2000.