Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/ Semiconductor Device Modeling and Characterization EE5342, Lecture 23 -Sp 2002 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/ L23 02Apr09

Extracting RB and RE from fg data iB = (IS/BF)exp[(vBE,X - iB(RB+RE) - iCRE)/NF•Vt] + negligible terms. iB/iB = 1 = (iB/NF•Vt) (vBE,X/iB - (RB+RE) - REiC/iB) NF•Vt/iB = vBE,X/iB -(RB+RE) -REiC/iB y=vBE,X/iB-NF•Vt/iB=REiC/iB+(RB+RE) plot y vs. iC/iB, slope=RE, int.= RB+RE L23 02Apr09

Extraction of RE and RB from fg data The figure shows [vBE,X/iB-NF•Vt/iB] versus iC/iB From the slope, we have RE = 32 ohms. The intercept (RE = RB) is 77 ohms so RB = 45 ohm. Data generated from RB = 100 and RE = 1 L23 02Apr09

Extracting RB and RE from rg data iB = (IS/BR)exp[(vBC,X - iB(RB+RC) - iERC)/NR•Vt] + negligible terms. iB/iB = 1 = (iB/NR•Vt) (vBC,X/iB - (RB+RC) - RCiE/iB) NR•Vt/iB = vBC,X/iB -(RB+RC) -RCiE/iB y=vBC,X/iB-NR•Vt/iB=RCiE/iB+(RB+RC) plot y vs. iE/iB, slope=RC, int.= RB+RC L23 02Apr09

MOSFET equivalent circuit elements Fig 10.51* L23 02Apr09

MOS small-signal equivalent circuit Fig 10.52* L23 02Apr09

MOS channel- length modulation Fig 11.5* L23 02Apr09

Analysis of channel length modulation L23 02Apr09

Channel length mod- ulated drain char Fig 11.6* L23 02Apr09

Fully biased n- channel VT calc L23 02Apr09

Q’d,max and xd,max for biased MOS capacitor Fig 8.11** |Q’d,max|/q (cm-2) xd,max (microns) L23 02Apr09

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Values for fms with silicon gate L23 02Apr09

I-V relation for n-MOS ohmic ID non-physical ID,sat saturated VDS,sat L23 02Apr09

Analysis of channel length modulation L23 02Apr09

Associating the output conductance ID ID,sat VDS,sat VDS L23 02Apr09

n-channel enhancement MOSFET in ohmic region 0< VT< VG e- channel ele + implant ion Channel VS = 0 0< VD< VDS,sat EOx,x> 0 n+ e-e- e- e- e- + + + + + + + + + + + + n+ Depl Reg p-substrate Acceptors VB < 0 L23 02Apr09

Ion implantation L23 02Apr09

“Dotted box” approx L23 02Apr09

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Mobilities L23 02Apr09

Fully biased n- channel VT calc L23 02Apr09

Subthreshold conduction Below O.S.I., when the total band-bending < 2|fp|, the weakly inverted channel conducts by diffusion like a BJT. Since VGS>VDS, and below OSI, then Na>nS >nD, and electr diffuse S --> D Electron concentration at Source Concentration gradient driving diffusion L23 02Apr09

Subthreshold current data Figure 10.1** Figure 11.4* L23 02Apr09

Mobility variation due to Edepl Figures 11.7,8,9* L23 02Apr09

Velocity saturation effects Figure 11.10* L23 02Apr09

References *Semiconductor Physics and Devices, by Donald A. Neamen, Irwin, Chicago, 1997. **Device Electronics for Integrated Circuits, 2nd ed., by Richard S. Muller and Theodore I. Kamins, John Wiley and Sons, New York, 1986 L23 02Apr09