Independent Study.ppt

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2014 Synopsys, Inc. All rights reserved. 1

DUAL GATE SINGLE MATERIAL JLFET

MODELLING

9thMay 2014


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GOALS

Motivation

DGSMJLFET Device Operation

Surface potential modelingtheoretical

Creating Model

Surface potentialsimulation results

Correlating Model vs Simulation results


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MOTIVATION

Aggressive Scaling.

Difficult to control Abrupt junction profiles.


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DGSMJLFET Device Operation

The device works in two mode full-depletion and accumulation

In Full-Depletion mode there are no mobile charges present in

channel for conduction hence the device is in off state

As the voltage starts to increase on gate (assuming N device) the

device starts to move from fully depleted mode to accumulationmode

In accumulation mode, as there are mobile charges present in

channel so the device is turned on

Figures 1 and 2 shows conc. Of carriers at off and on states


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Carrier Conc. Vg=0V (Off state)


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Carrier Conc. Vg=1V ( On State)


7/26 2014 Synopsys, Inc. All rights reserved. 7

SIMULATION RESULTS



DEVICE PROPERTY

DEVICE PROPERTY

TYPE N+ Si

DOPING 1*1E+19

SUBSTRATE THICKNESS 10nm

ToX 1nm

GATE PPOLY

GATE LENGTH 1um



Surface Potential @ VG=0V



Surface Potential @ Vg=1.0V



Energy Band Diagram @ Vg=0V



Id-VgsCurve Vg(-0.5V to 1V)


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Analytical Model


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1-D Poisson Equation

()

(1)


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Energy Band Diagram

Symmetrical behavior of gates.

Figure: [2]


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Boundary Conditions

()

() . (2)

()

|x=0

(3)

(0) =0 , for gate voltages above

threshold voltage of device.

Figure: [2]


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Integral Solution

()

= ()

= ()2

()/ ()/ + /

()/ ()/ (0)

(4)


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Bulk Charge

2 ( 0 ) (5)

(6)


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Solving for (s)

Equation 4 , using equation 2,3,5 and 6 reduces to: (0) = VgVFB; for Vg< threshold voltage of device.

(0) = 0; for Vg> threshold voltage of device.

Finally (s) :

0

(7)


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Approximations

(0) = 0 , if the device is conducting. (s) = 0 , for Flat band conditions.

For Vg> VFB, charge term still taken as that of fully

depleted.

Behavior of both gates is symmetrical.


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Correlation Model vs. Simulation


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Simulation data

SURFACE POTENTIAL (V)

Vgate(V) X=-5nm X=-4 X=-2 X=-1 X=-0.5 X=-0.1 X=0 X=0.1 X=0.5 X=1 X=2 X=4 X=5nm

0 -0.795 -0.743 -0.634 -0.611 -0.605 -0.604 -0.604 -0.604 -0.605 -0.611 -0.634 -0.743 -0.795

0.25 -0.504 -0.4762 -0.384 -0.361 -0.356 -0.355 -0.354 -0.355 -0.356 -0.361 -0.384 -0.4762 -0.504

0.5 -0.297 -0.256 -0.138 -0.116 -0.11 -0.108 -0.108 -0.108 -0.11 -0.116 -0.138 -0.256 -0.297

0.75 -0.082 -0.095 -0.036 -0.028 -0.026 -0.025 -0.025 -0.025 -0.026 -0.028 -0.036 -0.095 -0.082

1 -0.017 -0.017 -0.016 -0.016 -0.016 -0.016 -0.016 -0.016 -0.016 -0.016 -0.016 -0.017 -0.017

1.2 0.036 0.003 -0.012 -0.014 -0.014 -0.014 -0.014 -0.014 -0.014 -0.014 -0.012 0.003 0.036


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Analytical Model data

SURFACE POTENTIAL (V)

Vgate(V) X=-5nm X=-4 X=-2 X=-1 X=-0.5 X=-0.1 X=0 X=0.1 X=0.5 X=1 X=2 X=4 X=5nm

0 -0.78969 -0.7214 -0.63035 -0.60759 -0.6019 -0.60008 -0.6 -0.60008 -0.6019 -0.60759 -0.63035 -0.7214 -0.78969

0.25 -0.53969 -0.4714 -0.38035 -0.35759 -0.3519 -0.35008 -0.35 -0.35008 -0.3519 -0.35759 -0.38035 -0.4714 -0.53969

0.5 -0.28969 -0.2214 -0.13035 -0.10759 -0.1019 -0.10008 -0.1 -0.10008 -0.1019 -0.10759 -0.13035 -0.2214 -0.28969

0.75 0.189692 0.121403 0.030351 0.007588 0.001897 7.59E-05 7.59E-07 7.59E-05 0.001897 0.007588 0.030351 0.121403 0.189692

1 0.189692 0.121403 0.030351 0.007588 0.001897 7.59E-05 7.59E-07 7.59E-05 0.001897 0.007588 0.030351 0.121403 0.189692

1.2 0.189692 0.121403 0.030351 0.007588 0.001897 7.59E-05 7.59E-07 7.59E-05 0.001897 0.007588 0.030351 0.121403 0.189692


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Comparison

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

-5 -4 -2 -1 -0.5 -0.1 0 0.1 0.5 1 2 4 5

MODEL , VG=0

MODEL , VG=0.25

MODEL , VG=0.5

MODEL , VG=0.75

MODEL , VG=1

MODEL , VG=1.2

SIM , VG=0

SIM , VG=0.25

SIM , VG=0.5

SIM , VG=0.75

SIM , VG=1

SIM , VG=1.2


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Future Targets

Model Drain current using model developed for (s). Develop model for Dual gate dual material device.

Add second order effects to the model.[7][8][9][10]


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2014 Synopsys Inc All rights reserved 26

References

1. Sleight, Jeffrey W., and Rafael Rios. "A continuous compact MOSFET model for fully-and partially-depleted SOI

devices." Electron Devices, IEEE Transactions on 45.4 (1998): 821-825.

2. Sallese, J-M., et al. "Charge-based modeling of junctionless double-gate field-effect transistors." Electron Devices,

IEEE Transactions on58.8 (2011): 2628-2637.

3. Duarte, Juan Pablo, Sung-Jin Choi, and Yang-Kyu Choi. "A full-range drain current model for double-gate

junctionless transistors." Electron Devices, IEEE Transactions on58.12 (2011): 4219-4225.

4. Taur, Yuan, et al. "A continuous, analytic drain-current model for DG MOSFETs." Electron Device Letters,

IEEE25.2 (2004): 107-109.

5. Atlas Users Manual: Device Simulation Software, Silvaco Int., Santa Clara, CA, 2008.

6. Pradeep Agarwal, Govind Saraswat and M. Jagadesh Kumar, "Compact Surface Potential Model for FD SOI

MOSFET Considering Substrate Depletion Region," IEEE Trans. on Electron Devices, Vol.55, pp.789-795,

March 2008.

7. H. Park, P. Ko, and C. Hu, A charge sheet capacitance model of shortchannel MOSFETs for SPICE, IEEE Trans.

Computer-Aided Design, vol. 10, pp. 376389, Mar. 1991.

8. N. D. Arora, R. Rios, C.-L. Huang, and K. Raol, PCIM: A physically based continuous short-channel IGFET model

for circuit simulation, IEEE Trans. Electron Devices, vol. 41, pp. 988997, June 1994.9. R. Rios, N. D. Arora, and C.-L. Huang, An analytic polysilicon depletion effect model for MOSFETs,IEEE

Electron Device Lett., vol. 15, pp. 129131, Apr. 1994.

10. R. Rios, N. D. Arora, C.-L. Huang, N. Khalil, J. Faricelli, and L. Gruber, A physical compact MOSFET model,

including quantum mechanical effects, for statistical circuit design applications, inIEDM Tech. Dig., Dec. 1995, pp.

937940.

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