Changhwan Shin Department of Electrical Engineering and Computer Sciences

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Suppression of Random Dopant-Induced Threshold Voltage Fluctuations in Sub-0.1 m MOSFETs with Epitaxial and -Doped Channels A. Asenov and S. Saini, IEEE Trans. on Electron Devices , Aug 1999. Changhwan Shin Department of Electrical Engineering and Computer Sciences - PowerPoint PPT Presentation

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  • Suppression of Random Dopant-Induced Threshold Voltage Fluctuations in Sub-0.1m MOSFETs with Epitaxial and -Doped ChannelsA. Asenov and S. Saini, IEEE Trans. on Electron Devices, Aug 1999Changhwan ShinDepartment of Electrical Engineering and Computer Sciences University of California, Berkeley, CA 94720March 2, 2009

  • *OutlineIntroductionBulk MOSFET and its scaling challengesRandom Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFsAdjusting the channel doping profileSummary

  • *OutlineIntroductionBulk MOSFET and its scaling challengesRandom Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFsAdjusting the channel doping profileSummary

  • *Incommensurate gains in ION with scalinglimited carrier mobilitiesstrain Si to enhance meffparasitic resistanceuse metallic (silicide) source/drain extensionsBulk-Si MOSFET Scaling ChallengesLeffNsubXJ LgTox Performance variationLeakagedrain currentreduce Tox,eq and Xjgate currentuse high-k gate dielectric

  • *Sources of VariabilitySub-wavelength lithography:Resolution enhancement techniques are costly and increase process sensitivityStatistical dopant fluctuationsAtomistic effects become significant in nanoscale FETsA. Asenov, Symp. VLSI Tech. Dig., p. 86, 2007SiO2GateA. Brown et al., IEEE Trans. Nanotechnology, p. 195, 2002SourceDrain

  • *OutlineIntroductionBulk MOSFET and its scaling challengesRandom Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFsAdjusting the channel doping profileSummary

  • Random Dopant Fluctuations (RDFs)*Intrinsic variation in MOSFET parametersArising from the small number of discrete dopants and their random position in the channel depletion regionsSiO2GateA. Brown et al., IEEE Trans. Nanotechnology, p. 195, 2002SourceDrain

  • *OutlineIntroductionBulk MOSFET and its scaling challengesRandom Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFsAdjusting the channel doping profileSummary

  • MOSFET designs to suppress RDFs*Fluctuation-resistant architectures via appropriate tailoring of the channel doping profileThin, low doped layer in the channelRadical solutionsUn-doped channel MOSFET (UTB, FinFET, DG, gate-all-around)More demanding of technological modification

    Conventional Epitaxial Epitaxial w/ -doping

  • 3D atomistic simulation results*Epitaxial MOSFETVt is evaluated via 3D atomistic simulatorResultsVt dramatically reduced for the first 10nm of epilayerMaximum depi should be considered with Tox, Xj, LeffLeff/depi > 5Boron diffusion into epi-layer; tolerable up to 1017cm-3Dependence of Vt on the back-doping; Screening effect The holes in the heavily doped region screen the charge of the discrete random acceptors in the thin depletion layer

  • 3D atomistic simulation results*Epitaxial MOSFET with the delta dopingResultsIf the -doping is only partially depleted (i.e. depi is deep enough, or screen effect is valid), the doping concentration NAb increase will result in Vt reduction.Additional degree of freedom in tailoring the threshold voltageConventional Epitaxial Epitaxial w/ -doping

  • *OutlineIntroductionBulk MOSFET and its scaling challengesRandom Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFsAdjusting the channel doping profileSummary

  • Summary*Fundamental issue; RDFs in deep sub-micron MOSFET3D statistical atomistic simulations to study RDFsRandom dopant-induced threshold voltage fluctuations can be significantly suppressed in MOSFETs with low-doped epitaxial channels.

  • Q & AThank you for your attention!!!Questions?