Transcript topic5
半導體量測技術 Semiconductor Materials and Device Characterization Topic 5: oxide trapped charge and poly-depletion effect in MOSFET Instructor: Dr. Yi-Mu Lee Department of Electronic Engineering National United University Determine Qot or Qm: D. K. Schroder, p. 363 effect on both sweeping direction Qot no effect has effect Qm D. K. Schroder, p. 363 Finite gate doping density: Typical doping densities: 1019~1020/cm3 D. K. Schroder, p. 351 Poly depletion effect on C-V curve (PMOS device): Why? D. K. Schroder, p. 351 Lf and hf C-V: both showing capacitance drop Poly depletion effects: 1. Change Vt 2. Reduce the drain current 3. Increase gate resistance 1~3: reduce circuit speed D. K. Schroder, p. 360 VFB-tox plot: determine work function and Qf D. K. Schroder, p. 361 D. K. Schroder, p. 339 D. K. Schroder, p. 340 Fig 6.4 (a) D. K. Schroder, p. 341 Fig 6.4 (b) and (c) (b) –Vg, surface: accumulated, Qp dominates, Cp is very high, so Cp, Cb, Cn, Cit are shorted (c) Small +Vg, depleted surface, Qb dominates Depletion to weak inversion Fig. from D. K. Schroder, p. 341 Fig 6.4 (d) and (e) (d) Strong inversion: Cn can follow applied ac voltage, low-freq (e) Inversion charge can’t follow ac voltage, high-freq Fig. from D. K. Schroder, p. 341 Interface trapped charge (Qit) • Low-freq (quasistatic) method • Effect of Qit on lf and hf C-V • acceptor-like and donor-like trap density High-freq CV Fig. from D. K. Schroder, p. 369 Qit doesnot contribute capacitance Distorted C-V stretch-out due to gate-voltage axis Low-freq CV Fig. from D. K. Schroder, p. 369 Donor-like trap Qit does contribute capacitance acceptor-like trap inversion delay additional capacitance: Qit respond low-frequency Review: • • • • P. 346 (exercise 6.1) Band structure (equilibrium, non-equilibrium) P. 368~372 Derive eq (6.44) and (6.47)