Reliable HICUM implementation in Eldo Mohamed Selim Device Modeling Team Mentor Graphics HICUM Workshop, June. 2004

Reliable HICUM implementation in Eldo

Mohamed SelimDevice Modeling TeamMentor Graphics

HICUM Workshop, June . 2004

HICUM in Eldo, June 2004 Copyright ©1999-2001, Mentor Graphics.

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Overview

HICUM status in Eldo. Stability issues in the standard model. Enhancements done to improve stability. Current work done. Conclusion.


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Status Model implemented since 1999 in Eldo v5.3_1.1. The model accuracy was reviewed versus DEVICE

simulator and some major accuracy issues had been resolved in Eldo v5.8_1.1, released 2001.

In the 2001 workshop, ST presented a comparison between different commercial simulators showing that Eldo had the best implementation of the model for the DC results .

Since then, no modifications were done in the standard model, hence in Eldo just minor bug fixes were done.


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Stability Issues

Currents, Charges and their derivatives (conductances and capacitances) are needed from model for proper simulation for all types of analysis; DC, AC and TRANSIENT.

Convergence problems were seen using the standard model implemented in Eldo due to missing or incorrect derivatives (from the numerical point of view).

The standard model focuses on DC and small signal behavior mainly, many derivatives were not taken into account.


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Stability Issues 4 Major points of instability exist:

— Self heating derivatives.— Diffusion capacitance modeling.— NQS model.— RBI dependencies.

Some modifications in the existing derivatives were done and some derivatives were added to the standard model in Eldo to enhance the stability.

In the following slide a summary of the work done will be presented.


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Enhancements Diode junction currents derivatives w.r.t. self

heating (thermal) voltage. Avalanche current derivative w.r.t. self heating

(thermal) voltage. RBI derivatives w.r.t. VBE and VCE. Changing the expression for CDCI calculation. Adding the new derivative of QDEI w.r.t. VCEI. Applying the NQS effect on all derivatives of ITF

(forward transfer current) and QDEI (base emitter depletion charge).


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Enhancements These added features are added in AMS2004.2

release corresponding to Eldo v6.3_2.1. A new parameter called AMSVER is added. It can take 2 values.

— 2004.1 -> Standard AC results are maintained.— 2004.2 -> AC results are changed (default).

For both values of AMSVER, the newly added derivatives are always used used to enhance convergence for DC and TRANSIENT analysis.


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Enhancements

1e12H

1e12H

0.01F

0.01F

0.5v DC

1.0v DC

V1 = 1mv AC

Temp = 27

FREQ = 10MHz, 100MHz, 1 GHz, 10 GHz

AC setup

I2


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Enhancements

1e12H

1e12H

0.01F

0.01F

0.5v DC

1.0v DC

V1 = sinusoidal source with peak value 1mv , frequency = FREQ

Temp = 27

FREQ = 10MHz, 100MHz, 1 GHz, 10 GHz

TRANSIENT setup

I2


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Enhancements

From the results the AC values with AMSVER = 2004.2 match those obtained from the TRANSIENT analysis and they are both different from the standard AC results with AMSVER = 2004.1.

All the testcases that showed convergence problems are working fine with the new modifications.


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Current Work

We are currently enhancing the speed of the HICUM model in Eldo.

This will be available in the AMS 2004.3 release.


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Conclusion

AMS 2004.2 (Eldo v6.3_2.1) which was released few weeks ago has a fully stable HICUM model with NO convergence issues.

AMS 2004.3 (Eldo v6.4_1.1) planned to be released by the end of the year will have the speed enhanced version of the model.

MG is always looking to keep the models in the very best shape from both accuracy compared to standard models point of view and model speed.


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Documents

Reliable HICUM implementation in Eldo Mohamed Selim Device Modeling Team Mentor Graphics HICUM Workshop, June. 2004