SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 437 eφ 1 eφ^2 e(φ 1 −φ 2 ) EVAC EV(1) EV(2) EC(1) EC(2) −eVbi=EC(1)−EC(2) Figure 9.5: A ...

438 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET (a) (b) (c) dox M O S fs fM fM fs FB Metal Metal Oxide (Oxide) Oxide (insulator) ...

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 439 1.0 0.8 0.6 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 1014 1015 1016 1017 1018 p+ poly (n- ...

440 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET p p 0 n 0 Z n W p Na p^0 Z n W p p 0 n 0 Z n W Na Inversion Depletion Accumulati ...

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 441 Ec EFi EF Ev Oxide Semiconductor z Vs = 2 φF at inversion Vs Channel with elect ...

442 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET negative bias is needed to cause inversion. From Chapter 2, using Boltzmann stat ...

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 443 Ec Ei EF Ev M O Semiconductor EF eVG W d z Charge density under inversion Qm Q (cha ...

444 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET Also ΔVox =ΔEox·dox= sΔEsdox ox = sΔEs Cox (9.3.8) whereCoxis the oxide capac ...

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 445 If the body is at a biasVSBwith respect to the inversion region, then the surface p ...

446 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET Parameter NMOS PMOS Substrate p-type n-type φms Al-gate – – n+ Si-gate – – p+ Si ...

9.3. METAL-OXIDE-SEMICONDUCTOR CAPACITOR 447 The potentialVfbis given by eVfb=eφm−(eχs+(Ec−EF)) The position of the Fermi level ...

448 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET Example 9.4Consider ann-MOSFET made from Si-dopedp-type at Na=5× 1016 cm−^3 at 3 ...

9.4. CAPACITANCE-VOLTAGE CHARACTERISTICS OF THE MOS 449 Oxide Silicon Cs MOS CAPACITOR Capacitance per unit area Cox =εdox ox Fi ...

450 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET whereWmaxis defined by equation 9.3.13. At the onset of strong inversion, free e ...

9.4. CAPACITANCE-VOLTAGE CHARACTERISTICS OF THE MOS 451 Low frequency (~1Hz) High frequency (10^3 Hz) Inversion Accumulation Cmo ...

452 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET Qss = 0 Vfb(2) Vfb(0) Cmos(min) Cox C VG Gate bias Positive charge at interface ...

9.4. CAPACITANCE-VOLTAGE CHARACTERISTICS OF THE MOS 453 Example 9.5Derive the relation for the semiconductor capacitance per uni ...

454 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET The maximum depletion width (assumingVs=− 2 φF)is Wmax= ( 4 |φF| eNa ) 1 / 2 = ...

9.5. MOSFET OPERATION 455 Oxide p-Si z y x (b) (a) Source Gate Drain n-channel p-Si n+ n+ L Z Gate width x = 0 x = L S G D n-cha ...

456 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET value ofQsgives (Vc(L)=VDS) ID= μnZCox L [{ VGS−VT− VDS 2 }] VDS (9.5.5) Let us ...