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identifier&Analysis of quantum effect in NMOSFETs2001Y0 Y YtTŐYP Y0 YMasterMaster's ThesisMOSFET device is scaled to deep submicron region in VLSI system for high speed and efficient integrated circuit (IC). This deep submicron MOSFET shows a short channel effect (SCE), which decreases the device ability. To reduce the SCE and maximize the device performance, oxide thickness should be reduced and substrate doping should be increased.
Because these MOSFETs have very high vertical electric field at Si/SiO interface, electrons in the inversion layer reside in strong potential well. In that case, it is impossible to calculate the electron resided in potential well by Poisson equation. Therefore, device property analysis founded Poisson equation is not valid anymore. We need a new method, Schrodinger equation solver, which calculates electron state in quantum mechanics. In this thesis, the variation of device property by quantum effect was analyzed using the self-consistent method converging Poisson equation and Schrodinger equation at the same time. The results, which consider quantum effect shows higher threshold voltage and smaller gate capacitance in comparison with classical mechanics results.
In this thesis, quantum effect is analyzed using the self-consistent method. However, the change of oxide thickness didn't affect the amount of quantum effect. Just the increment of threshold voltage by quantum effect is proportional to the oxide thickness. This appearance results from oxide potential. And the variation of device characteristics due to the change of substrate doping by quantum effect was analyzed. It is found that, as the substrate doping increases, the increment of threshold voltage due to quantum effect increases.
As transverse electric field by quantum effect is increased, mobility in inversion layer is decreased. Especially, as substrate doping is increased, device speed is decreased by decrement of mobility. To improve this defect, delta-doped device is used in modern technologies. This device has an efficient mobility, because of the lower impurity scattering in the inversion layer. Quantum effect of uniform and delta-doped device with same threshold voltage in classical mechanics is the same. However, because of different impurity scattering of two devices, mobility by quantum effect is different. As Tepi of delta-doped device is increased, impact by quantum effect is decreased. And, because of decreasing surface roughness scattering, mobility is improved.
Therefore, to diminish quantum effect in high substrate doping, using the delta-doped device in modern technologies is better in view of quantum effect and mobility.;ٳ ĳ@ ĳX t XՌ t踴 ǔ VLSI system MOSFET deep submicron <\ scaling . t\ deep submicron MOSFETX 1 XՔ short-channel | \͌TXt X lٳ %D \TX0 X, TɹX Pخ ɍ<\ ɴ, 0X doping ĳ X .
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