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Electrical and Computer Engineering and Network for Computational Nanotechnology

IEEE Central NC EDS/MTT/SSC Society Friday, Nov. 5th, 2010 The Nanoscale MOSFET: Physics and Limits Mark Lundstrom. Electrical and Computer Engineering and Network for Computational Nanotechnology Birck Nanotechnology Center Purdue University, West Lafayette, Indiana USA.

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Electrical and Computer Engineering and Network for Computational Nanotechnology

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  1. IEEE Central NC EDS/MTT/SSC Society Friday, Nov. 5th, 2010The Nanoscale MOSFET:Physics and LimitsMark Lundstrom Electrical and Computer Engineering and Network for Computational Nanotechnology Birck Nanotechnology Center Purdue University, West Lafayette, Indiana USA

  2. 21st Century: microelectronics  nanoelectronics transistors per cpu chip Lundstrom

  3. nanoscale MOSFETs 2010 gate electrode channel ~ 32 nm gate oxide EOT~ 1.1 nm S G D source drain SiO2 silicon

  4. gate-voltage controlled current source gate-voltage controlled resistor MOSFET IV characteristic circuit symbol D G S (Courtesy, Shuji Ikeda, ATDF, Dec. 2007)

  5. gate-voltage controlled resistor MOSFET IV: low VDS VG>VT 0 VD

  6. MOSFET IV: “pinch-off” at high VDS 0 VG VD

  7. gate-voltage controlled current source 2 MOSFET IV: high VDS 0 VG VD

  8. velocity saturation 107 velocity cm/s ---> 105 104 electric field V/cm --->

  9. (Courtesy, Shuji Ikeda, ATDF, Dec. 2007) MOSFET IV: velocity saturation 0 VG VD

  10. carrier transport nanoscale MOSFETs Velocity (cm/s)  D. Frank, S. Laux, and M. Fischetti, Int. Electron Dev. Mtg., Dec., 1992. Lundstrom

  11. ~1995 - 2000 Moore’s Law? Molecular electronics http://www.eng.yale.edu/reedlab/ Lundstrom

  12. objectives Present a simple, physical picture of the nanoscale MOSFET (to complement, not supplement simulations). Discuss ballistic limits, velocity saturation, and quantum limits in nanotransistors. Compare to experimental results for Si and III-V FETs Discuss scattering in nano-MOSFETs Lundstrom

  13. outline 1) Introduction 2) The nano-MOSFET 3) The ballistic MOSFET 4) Scattering in nano-MOSFETs 5) Summary Lundstrom

  14. how transistors work 2007 N-MOSFET electron energy vs. position electron energy vs. position (Courtesy, Shuji Ikeda, ATDF, Dec. 2007) E.O. Johnson, “The IGFET: A Bipolar Transistor in Disguise,” RCA Review, 1973

  15. MOSFETs are barrier controlled devices 2) region under strong\ control of gate 1) “Well-tempered MOSFET” 3) Additional increases in VDS drop near the drain and have a small effect on ID M. Lundstrom, IEEEEDL, 18, 361, 1997. A. Khakifirooz, O. M. Nayfeh, D. A. Antoniadis, IEEE TED, 56, pp. 1674-1680, 2009.

  16. current flows when the Fermi-levels are different gate Lundstrom

  17. LDOS “device” contact 1 contact 2 “top of the barrier model” energy position Lundstrom

  18. outline 1) Introduction 2) The nano-MOSFET 3) The ballistic MOSFET 4) Scattering in nano-MOSFETs 5) Summary Lundstrom

  19. ballistic MOSFET: linear region near-equilibrium Lundstrom

  20. linear region with MB statistics Boltzmann statistics: (MOS electrostatics) ✔ Lundstrom

  21. ballistic MOSFET: linear region near-equilibrium Lundstrom

  22. relation to conventional expression ballistic MOSFET conventional MOSFET Lundstrom

  23. ballistic MOSFET: on-current Lundstrom

  24. saturated region with MB statistics Boltzmann statistics: ✔ Lundstrom

  25. under low VDS Lundstrom

  26. under high VDS Lundstrom

  27. velocity vs. VDS Lundstrom

  28. velocity vs. VDS Velocity saturates in a ballistic MOSFET but at the top of the barrier, where E-field = 0. Lundstrom

  29. 2007 N-MOSFET (Courtesy, Shuji Ikeda, ATDF, Dec. 2007) velocity saturation in a ballistic MOSFET velocity saturation Lundstrom

  30. aside: relation to conventional expression ballistic MOSFET conventional MOSFET Lundstrom

  31. the ballistic IV (Boltzmann statistics) ballistic on-current ballistic channel resistance K. Natori, JAP, 76, 4879, 1994. Lundstrom

  32. comparison with experiment: Silicon • Si MOSFETs deliver > one-half of the ballistic on-current. (Similar for the past 15 years.) • MOSFETs operate closer to the ballistic limit under high VDS. A. Majumdar, Z. B. Ren, S. J. Koester, and W. Haensch, "Undoped-Body Extremely Thin SOI MOSFETs With Back Gates," IEEE Transactions on Electron Devices, 56, pp. 2270-2276, 2009. Device characterization and simulation: Himadri Pal and Yang Liu, Purdue, 2010.

  33. comparison with experiment: InGaAs HEMTs Jesus del Alamo group (MIT) Lundstrom

  34. outline 1) Introduction 2) The nano-MOSFET 3) The ballistic MOSFET 4) Scattering in nano-MOSFETs 5) Summary Lundstrom

  35. X X X transmission and carrier scattering λ0 is the mean-free-path for backscattering Lundstrom

  36. the quasi-ballistic MOSFET Lundstrom

  37. on current and transmission Lundstrom

  38. the quasi-ballistic MOSFET Lundstrom

  39. scattering under high VDS Lundstrom

  40. connection to traditional model (low VDS) Lundstrom

  41. connection to traditional model (high VDS) how do we interpret this result? Lundstrom

  42. the MOSFET as a BJT “base” ‘bottleneck’ “collector” Lundstrom

  43. outline 1) Introduction 2) The nano-MOSFET 3) The ballistic MOSFET 4) Scattering in nano-MOSFETs 5) Summary Lundstrom

  44. 3) The on-current is controlled by the ballistic injection velocity - not the high-field, bulk saturation velocity. 2) The channel resistance has a lower limit - no matter how high the mobility is. physics of nanoscale MOSFETs 4) Channel velocity saturates near the source, not at the drain end. 1) Transistor-like I-V characteristics are a result of electrostatics. Lundstrom

  45. limits to barrier control: quantum tunneling 4) 3) 1) 2) from M. Luisier, ETH Zurich / Purdue

  46. 21st Century electronics? Moore’s Law? Lundstrom

  47. 21st Century electronics 1) Information processing dominated by “Si CMOS” 2) SOC’s complemented by “CMOS+” technologies 3) and….. macroelectronics, power electronics, PV, solid-state lighting, thermoelectrics, … Lundstrom

  48. for more information 1) “Physics of Nanoscale MOSFETs,” a series of eight lectures on the subject presented at the 2008 NCN@Purdue Summer School by Mark Lundstrom, 2008. http://nanohub.org/resources/5306 2) “Electronic Transport in Semiconductors,” Lectures 1-7, by Mark Lundstrom, 2009. http://nanohub.org/resources/7281 Lundstrom

  49. questions 1) Introduction 2) The nano-MOSFET 3) The ballistic MOSFET 4) Scattering in nano-MOSFETs 5) Summary Lundstrom

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