08. MOS Charges

08. MOS Charges - D.K. Schroder, Semiconductor...

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Unformatted text preview: D.K. Schroder, Semiconductor Characterization MOS Charges MOS Capacitor Basics Fixed Charge Mobile Charge Interface Trapped Charge Characterization Techniques D.K. Schroder, Semiconductor Characterization SiO 2 and SiO 2 /Si Interface Si D B Hydrogen A C A : Si-Si Bond (Oxygen Vacancy) B : Dangling Bond C : Si-H Bond D : Si-OH Bond Oxygen Dangling Bond This looks really messy! D.K. Schroder, Semiconductor Characterization Oxide Charges / Interface Traps Charge Type Location Cause Effect on Devices (1) Interface SiO 2 /Si Dangling Junction Leakage Current D it (cm-2 eV-1 ) Trapped Interface Bonds Noise, Threshold Voltage N it , Q it Charge Shift, Subthreshold Slope (2) Fixed Close to Si + (?) N f , Q f Charge SiO 2 /Si Threshold Voltage Shift (cm-2 , C/cm 2 ) Interface (3) Oxide In SiO 2 Trapped N ot , Q ot Trapped Electrons Threshold Voltage Shift Charge & Holes (4) Mobile In SiO 2 Na, K, Li N m , Q m Charge Threshold Voltage Shift x x x x + + + + + + (1) (2) (3) (4) SiO 2 Si D.K. Schroder, Semiconductor Characterization MOS Capacitor MOS Capacitor (MOS-C) can be used to determine Oxide charge Interface trapped charge Oxide thickness Flatband voltage Threshold voltage Substrate doping density Generation lifetime Recombination lifetime D.K. Schroder, Semiconductor Characterization MOS Capacitor MOS capacitor cross section and band diagram E c /q E F /q t ox t ox +W E i /q E v /q S F x V G V G V ox D.K. Schroder, Semiconductor Characterization MOS Capacitor Capacitance consists of C ox : oxide capacitance C p : accumulation capacitance C b : bulk (space-charge region) capacitance C n : inversion capacitance C it : interface trap capacitance C ox C p C b C n C it p D.K. Schroder, Semiconductor Characterization MOS Capacitor The capacitance is G G dV dQ C = it n b p s it s ox dQ dQ dQ dQ d dQ dQ dV C + + + + + = 1 it n b p ox C C C C C C + + + + = 1 1 1 s ox it s G it s G G d dV dQ dQ dV dQ dQ dV dQ C + + = + = = The charge is ) ( it n b p it s G Q Q Q Q Q Q Q + + + = = This gives D.K. Schroder, Semiconductor Characterization MOS Capacitance Accumulation C p >> C ox Depletion C b C ox C it Inversion low frequency C n >> C ox Inversion high frequency C b C ox C ox Accumulation C ox C p C b C...
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This note was uploaded on 05/25/2011 for the course EEE 536 taught by Professor Schroder during the Spring '11 term at ASU.

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08. MOS Charges - D.K. Schroder, Semiconductor...

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