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Page 1 Hannes Luyken CPR ND N e v e r s t o p t h i n k i n g. ULIS 2003 Ultimate Integration of Silicon T. Schulz, C. Pacha, R. J. Luyken, M. Städele, J. Hartwich, L. Dreeskornfeld, E. Landgraf, J. Kretz, W. Rösner, M. Specht, F. Hofmann and L. Risch Infineon Technologies AG, Corporate Research Nano Devices, Otto-Hahn-Ring 6, D-81730 Munich, Germany Session 1.1: Transistor architecture and fabrication Impact of Doping Concentration Gradient and Spacer Thickness on Device Performance of UTB-SOI CMOS
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Page 2 Motivation for the ultra thin body (UTB)-SOI device concept Simulation method Impact of technology parameters on device performance - source/drain doping concentration gradient - sidewall spacer thickness - silicon thickness - supply voltages Conclusions Outline
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Page 3 Motivation for the ultra thin body (UTB)-SOI device concept with undoped channel region Undoped channel region Increase in drive current New gate materials V th adjustment
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Page 4 green area: interconnects and wiring and geometrical aspects of gates blue area: intrinsic device and substrate material red area: coupled device and circuit simulation Simulation method
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Page 5 Device structure and technological parameters No additional source/drain series resistances were chosen NMOS and PMOS have the same structure apart from the different doping sequence
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Page 6 Simulation scheme and circuit structure 2 Inverter 4 MOSFETs (n1, p1, n2, p2) Additional R and C RC-load C-wiring Input pulse (1ps) Delay between V OUT_1 and V OUT_2
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Page 7 Transient and transfer characteristic
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Page 8 Impact of technology parameters on inverter delay - source/drain doping gradient @ constant spacer
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Page 9 Impact of technology parameters on inverter delay - source/drain doping gradient @ constant spacer Where is the effective / metallurgical channel length ? L eff as figure of merit vanish
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Page 10 Impact of technology parameters on inverter delay - source/drain doping gradient @ constant spacer Where is the effective / metallurgical channel length ? L eff as figure of merit vanish Is a relaxed doping gradient of 10 nm / decade sufficient ?
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Page 11 Steep doping profiles suppress short channel effects I OFF and I ON versus doping gradient @ constant spacer
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Page 12 Steep doping profiles suppress short channel effects Shallow doping profiles flood the channel with dopants In most cases spacer thickness of 10nm is too thin I OFF and I ON versus doping gradient @ constant spacer
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Page 13 Impact of technology parameters on inverter delay - sidewall spacer thickness @ constant gradient
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Page 14 Impact of technology parameters on inverter delay - sidewall spacer thickness @ constant gradient What is the optimal spacer thickness ?
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Page 15 Impact of technology parameters on inverter delay - sidewall spacer thickness @ constant gradient What is the optimal spacer thickness ? Thinner sidewall spacer increase short channel effects Thicker sidewall spacer increase inverter delay
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Page 16 Thin spacer leakage current increase I OFF and I ON vs. spacer thickness @ constant gradient
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Page 17 Thin spacer leakage current increase Thick spacer drive current decrease Best case for L=50nm LOP device is 20-25nm spacer thickness I OFF and I ON vs. spacer thickness @ constant gradient
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Page 18 Comparison with (bulk) roadmap trend: sidewall spacer thickness correlate with doping gradient State of the art: 50nm spacer thickness, 5nm/decade abruptness
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Page 19 Impact of technology parameters on inverter delay - combination of spacer thickness and doping gradient
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Page 20 Impact of technology parameters on inverter delay - combination of spacer thickness and doping gradient
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Page 21 Compensation of spacer thickness and doping gradient New figure of merit: doping concentration @ gate corner Impact of technology parameters on inverter delay - combination of spacer thickness and doping gradient
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Page 22 HP-device and LOP-device specs achievable I OFF spec for the LSTP-device demand thicker spacer I OFF and I ON versus different spacer / doping gradient
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Page 23 HP-device and LOP-device specs achievable I OFF spec for the LSTP-device demand thicker spacer For the presented doping profiles 10 nm/decade is the better choice I OFF and I ON versus different spacer / doping gradient
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Page 24 Transfer and output characteristics for different spacer thickness and doping gradient Figure of merit: doping concentration 1E19cm -3 @ gate corner Devices with different doping profiles but same driver performance Increase of GIDL-current due to steeper doping concentration gradient
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Page 25 Doping concentration gradient and spacer thickness can compensate each other as design parameter. Source/Drain doping concentration at the gate corner is an accurate figure of merit instead of L eff. With a steeper doping concentration gradient there is no influence on the driver performance but a significant off- current due to the increase of the GIDL-current occurs. HP- and LOP-devices can meet the roadmap targets but LSTP-devices are much harder to implement. Conclusions
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Page 26 Back up
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Page 27 Subthreshold and output characteristics
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Page 28 Impact of sidewall spacer thickness in combination with doping gradient figure of merit: doping concentration @ gate corner = 1E18cm -3
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Page 29 Impact of sidewall spacer thickness in combination with doping gradient figure of merit: doping concentration @ gate corner = 1E18cm -3 compensation of spacer thickness and doping gradient depends also from the source / drain doping concentration level (here 1E20cm -3 )
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Page 30 Silicon film thickness replace doping concentration as figure of merit Bulk: SOI: DG:
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Page 31 Gate delay metric (ITRS 2001)
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Page 32 Transit frequency (ITRS 2001)
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