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Cntfet copy
- 1. CNTFET Substitute of MOSFET GonuguntaSaiphani kumar M.Tech VLSI 2nd sem 14219008 NIT Jalandhar-144011 1
- 2. Introduction When furtherscaling down MOSFET, serious limits in fabrication& performance In particular five different short-channel effects can be distinguished: 1. drain-induced barrier lowering and punchthrough 2. surface scattering 3. velocity saturation 4. impact ionization 5. hot electrons And also self oscillation of MOSFET due to parasitic capacitances 2
- 3. Solutions to overcome Modification on existing structures & technologies High - K insulating material, metal gate electrode Using new materials to replace silicon MOSFETs 3
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- 5. Role of chiralityvector depending on angle of arrangement along the tube If n=m or n-m = 3i then it behaves like a metal Otherwise it behaves like a semiconductor Diameter SWCNT(~1nm) ; where a0 = 0.142nm 5
- 6. CNTFET Formed byCNT connecting two metal electrodes. Gate electrode is separated CNT by thin oxide film. There is no scattering in the CNT channell The net current is carried by carriers with energy between μ1 and μ2 that travel from contact 1 to contact 2. L = |Ch| = a * 6
- 7. Why carbon nanotubes? Single walled carbon nanotube is a potential channel material for future high performance logic circuits. High carrier mobility from 3000 to 10000 cm2/v-s Excellent electrostatics Excellent gate control. 7
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- 9. advantages Better controlover channel formation Better threshold voltage Better subthreshold slope High electron mobility High current density High transconductance Good stiffness, strength 9
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- 11. Implementation of fulladder using 10nm CNTFET 11
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- 13. Drawbacks of CNTFET Manufacturing CNTFET-based circuits will differ from current practice with conventional silicon Technologies so the fault/defect models must be revisited. the defect and failure rate at device and circuit level is expected to be much higher than with traditional CMOS. The carbon nanotube degrades in a few days when exposed to oxygen. There have been several works done on passivating the nanotubes with different polymers and increasing their lifetime. So many difficulties in mass production, production cost. The multi-channeled CNTFETs can keep a stable performance after several months, while the single-channeled CNTFETs are usually out of work after a few weeks in the ambient atmosphere.The multi-channeled CNTFETs keep operating when some channels break down, this won’t happen in the single-channeled ones. 13
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