Suppression of Random Dopant-Induced Threshold Voltage Fluctuations in Sub-0.1μm MOSFET’s with Epitaxial and δ-Doped Channels A. Asenov and S. Saini, IEEE Trans. on Electron Devices, Aug 1999OutlineSlide 3Bulk-Si MOSFET Scaling ChallengesSources of VariabilitySlide 6Random Dopant Fluctuations (RDFs)Slide 8MOSFET designs to suppress RDFs3D atomistic simulation resultsSlide 11Slide 12SummaryQ & ASuppression of Random Dopant-Induced Threshold Voltage Fluctuations in Sub-0.1μm MOSFET’s with Epitaxial and δ-Doped ChannelsA. Asenov and S. Saini, IEEE Trans. on Electron Devices, Aug 1999Suppression of Random Dopant-Induced Threshold Voltage Fluctuations in Sub-0.1μm MOSFET’s with Epitaxial and δ-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, 20092OutlineOutlineIntroduction»Bulk MOSFET and its scaling challenges»Random Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFs»Adjusting the channel doping profileSummary3OutlineOutlineIntroduction»Bulk MOSFET and its scaling challenges»Random Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFs»Adjusting the channel doping profileSummary4Incommensurate gains in ION with scaling»limited carrier mobilitiesstrain Si to enhance eff»parasitic resistanceuse metallic (silicide) source/drain extensionsBulk-Si MOSFET Scaling ChallengesBulk-Si MOSFET Scaling ChallengesSubstrateGateSource DrainLeffNsubXJ LgTox Performance variationLeakage»drain currentreduce Tox,eq and Xj»gate currentuse high- gate dielectric5Sources of VariabilitySources of VariabilitySub-wavelength lithography:»Resolution enhancement techniques are costly and increase process sensitivityStatistical dopant fluctuations»Atomistic effects become significant in nanoscale FETsA. Asenov, Symp. VLSI Tech. Dig., p. 86, 2007SiO2GateA. Brown et al., IEEE Trans. Nanotechnology, p. 195, 2002SourceDrain6OutlineOutlineIntroduction»Bulk MOSFET and its scaling challenges»Random Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFs»Adjusting the channel doping profileSummaryRandom Dopant Fluctuations (RDFs)Random Dopant Fluctuations (RDFs)7“Intrinsic” variation in MOSFET parameters»Arising from the small number of discrete dopants and their random position in the channel depletion regionsSiO2GateA. Brown et al., IEEE Trans. Nanotechnology, p. 195, 2002SourceDrain8OutlineOutlineIntroduction»Bulk MOSFET and its scaling challenges»Random Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFs»Adjusting the channel doping profileSummaryMOSFET designs to suppress RDFsMOSFET designs to suppress RDFs9Fluctuation-resistant architectures via appropriate tailoring of the channel doping profile»Thin, low doped layer in the channelRadical solutions»Un-doped channel MOSFET (UTB, FinFET, DG, gate-all-around)»More demanding of technological modificationConventional Epitaxial Epitaxial w/ δ-doping3D atomistic simulation results3D atomistic simulation results10Epitaxial MOSFET»σVt is evaluated via 3D atomistic simulatorResults»σVt dramatically reduced for the first 10nm of epilayer»Maximum depi should be considered with Tox, Xj, Leff»Leff/depi > 5»Boron diffusion into epi-layer; tolerable up to 1017cm-3»Dependence of σVt 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 layer3D atomistic simulation results3D atomistic simulation results11Epitaxial MOSFET with the delta dopingResults»If the δ-doping is only partially depleted (i.e. depi is deep enough, or screen effect is valid), the doping concentration NAb increase will result in σVt reduction.»Additional degree of freedom in tailoring the threshold voltageConventional Epitaxial Epitaxial w/ δ-doping12OutlineOutlineIntroduction»Bulk MOSFET and its scaling challenges»Random Dopant Fluctuations (RDFs)MOSFET design to suppress the RDFs»Adjusting the channel doping profileSummarySummarySummary13Fundamental issue; RDFs in deep sub-micron MOSFET3D statistical atomistic simulations to study RDFsRandom dopant-induced threshold voltage fluctuations can be significantly suppressed in MOSFET’s with low-doped epitaxial channels.Q & AQ & AThank you for your
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