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EE130/230A Discussion 9

EE130/230A Discussion 9. Peng Zheng. MOS Electrostatics (n-type Si). Decrease V G toward more negative values  the gate electron energy increases relative to that in the Si. Inversion V G < V T Surface inverted to p-type. decrease V G. decrease V G. Accumulation V G > V FB

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EE130/230A Discussion 9

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  1. EE130/230A Discussion 9 PengZheng

  2. MOS Electrostatics (n-type Si) Decrease VG toward more negative values  the gate electron energy increases relative to that in the Si • Inversion • VG < VT Surface inverted to p-type decrease VG decrease VG • Accumulation • VG > VFB • Electrons accumulated at Si surface • Depletion • VG < VFB • Electrons depleted from Si surface EE130/230A Fall 2013 Lecture 15, Slide 2 R. F. Pierret, Semiconductor Device Fundamentals, Fig. 16.5

  3. PMOS Capacitor Energy Band Diagrams

  4. PMOS Capacitor Energy Band Diagrams

  5. Sample Problem- PMOS Capacitor VT

  6. Sample Problem- PMOS Capacitor VT

  7. Sample Problem- PMOS Capacitor VT Pay attention to the sign of each term! Compare PMOS and NMOS Capacitor.

  8. Threshold Voltage • For p-type Si: • For n-type Si: C. C. Hu, Modern Semiconductor Devices for ICs, Figure 5-8 EE130/230A Fall 2013 Lecture 16, Slide 8

  9. MOS Capacitor vs. MOS Transistor C-V(p-type Si) C MOS transistor at any f, MOS capacitor at low f, or quasi-static C-V Cmax=Cox CFB MOS capacitor at high f Cmin VG accumulation depletion inversion VFB VT EE130/230A Fall 2013 Lecture 17, Slide 9

  10. MOS C-V Characteristic for n-type Si C MOS transistor at any f, MOS capacitor at low f, or quasi-static C-V Cmax=Cox CFB MOS capacitor at high f Cmin VG inversion depletion accumulation VT VFB EE130/230A Fall 2013 Lecture 17, Slide 10

  11. MOSCapvs MOSFET Channel Gate Gate Insulator Insulator Source Channel Drain Substrate Substrate Minority carriers generated within the depletion region Majority carriers pulled in from S/D (fast !!) So Cinv can be << Cox if fast gate switching (~ GHz) Cinv = Cox Adapted from UVA ECE 663

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