new version 5.0 of ufsoi model released in smartspice · of the parasitic (coupled) bjt (current...

TCAD Driven CAD A Journal for Circuit Simulation and SPICE Modeling Engineers

IntroductionThe University of Florida SOI Group firstreleased version 5.0 of UFSOI model inAugust 1999 and then in November 1999.To keep backward compatibility withprevious versions, two model parameters(VERSION, REVISION) have been added inSmartSpice to select the desired model. Bydefault, the value of VERSION is 5.0 andthe value of REVISION is 1 .0 whichcorresponds to the last release ofNovember, 1999.

Features

Global Features (prior to version 5.0)

The UFSOI NFD (Non-Fully Depleted) andFD (Fully Depleted) charge-based SOIMOSFET models have been developedfrom the basic modeling of thin-filmdevices. The principal improvements are:

� the UFSOI NFD (Non-Fully Depleted) and FD (FullyDepleted) charge-based SOI MOSFET models areselected according to the value of the NFDMODmodel parameter

� the model for the FD SOI MOSFET, which physicallyaccounts for the charge coupling between the frontand back gates, includes a two-dimensional analysisor the subthreshold region of operation

� the model for the NFD SOI MOSFET properlyaccounts for DC as well as dynamic floating-bodyeffects in all regions of operation

� both UFSOI models have improved quasi-2D modelingof the parasitic (coupled) BJT (current and charge),GIDL, junction tunneling, and impact-ionization currents

� recent improvements (introduced in version 4.5) takeaccount of polysilicon-gate depletion, energyquantization, junction tunneling, GIDL, RSCE(Reverse short Channel Effect)/halo effect andnarrow-width effects

� charge modeling has been improved

Volume 11, Number 4, April 2000

New Version 5.0 of UFSOI Model Released in SmartSpice

INSIDE

JFET/MESFET TRIQUINT Models . . . . . . . . . . . . . . . . 3

RF MOSFET Small Signal SPICE Model . . . . . . . . . . . 5

Calendar of Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Hints, Tips, and Solutions . . . . . . . . . . . . . . . . . . . . . . . . 10

Continued on page 2....

Figure 1. Influence of the velocity overshoot with FD model

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� all terminal charges and their derivativesare now continuous for all bias conditions,as are all currents and their derivatives

� substrate depletion charge under thesource and drain regions is included ascomponents of the source, drain andback-gate charges

� temperature depended effects are modeled

New Features (introduced in version 5.0)

New features and improvements have beenadded to enhance the accuracy of the modeland speed up the simulation.

Release of August [1]

� the physical noise modeling has been expanded toaccount for hot-carrier effects on the channel thermalnoise

� the most noteworthy improvement is the run-timereduction for the NFD model : by switching from dif-ference approximations to approximate analyticalderivatives, DC and transient simulation times for theNFD model have been reduced by about a factor ofthree (Table 1)

� bug fixes related to Iweak

Release of November [2]

� a physical accounting for carrier-velocity overshoothas been added (Figures 1 and 2);

� for the NFD model, the difference approximationshad to be retained for the Vbs-derivatives because ofthe numerical accuracy required for reliable simula-tion of floating body effects. The simulation time hasnow been reduced by a factor of 2-3 (Table 1)

� the FD model is also valid for asymmetrical double-gate (DG) MOSFETs having one predominant chan-nel in strong inversion

� diffusion capacitance for Cdds has been added (need-ed for high Vbd)

� dIbjt/dVds has been refined regarding Xlbjt

� bug fixes related to Fvbjt

New Model Parameters

The default value of VSAT has changed to 7.0e6. VSATshould be set to its physical value (default) when thevelocity-overshoot option is used (VO > 0).

References

[1] UFSOI MOSFET MODELS (Ver. 5.0), User’s Guide, SOIGroup, University of Florida, August 1999.

[2] UFSOI MOSFET MODELS (Ver. 5.0), User’s Guide, SOI

Group, University of Florida, November 1999

The Simulation Standard April 2000

Parameter Description Units Default

VERSION Version selector - 5.0

REVISION Revision selector - 1.0

VO Velocity overshoot - 0.0parameter

Figure 2 : Influence of the velocity overshoot with NFD model

v4.5 v5.0, rev0.0 v5.0, rev1.0

FD x1 x0.73 x0.79

NFD x1 x0.33 x0.44

Table 1: Comparison of run times.

IntroductionUntil now, SmartSpice has supported the TriQuintmodel designated TOM using the Level=5 modelparameter. SmartSpice now supports the TriQuint-2MESFET model designated TOM-2. This model isaccessible as a standard MESFET model, using theLevel=7 model parameter. It is an incrementalimprovement based on TriQuint’s original MESFETmodel. All current analyses are currently supported(dc, ac, transient and noise).

Physical EffectsRefinements to improve accuracy in the knee andsubthreshold region have been added. Particularattention has been given to temperature effects. TOM-2retains the desirable features of TOM-1 while improvingperformance in the subthreshold characteristics nearthe cut-off and knee regions. Additional temperaturecoefficients are included relating to the drain current andmajor deficiencies in the behavior of the capacitance as afunction of temperature have been corrected.

Simulation ModelThe parameters of the TOM-2 MESFET model arerepresented in Table 1.

The model parameters BETA, VTO, ALPHA, GAMMA,DELTA, Q are common for both the original andimproved TriQuint models. An important aspect ofmodeling the MESFET is a correct description of thebehavior as a function of temperature.

April 2000 The Simulation Standard

JFET/MESFET TRIQUINT Models (Level=5 and Level=7)

Parameter Description Units Default Area

BETA Transconductance parameter A/V2 0.1 ( W e f f /Leff)· M

VTO Quadratic equation gate threshold voltage V -2.5

ALPHA Coefficient of vds 1/V 2.0

GAMMA (GAMDS) Static feedback parameter 0

DELTA Output feedback parameter 1/(A·V) 0.2

Q (VGEXP) Power law parameter 2.0

VBI Gate diode built-in potential V 1.0

VMAX Gate diode capacitance limiting voltage V 0.95

LAMBDA Channel length modulation parameter 1/V 0

K1 Bulk bias sensitivity for thresh-old voltage 0

VBITC Temperature coefficient for VBI 1/K 0

ALPHATCE Temperature coefficient for ALPHA 1/K 0

GAMMATC Temperature coefficient for GAMMA 1/K 0

Table 1. Parameters of the TOM-2 TriQuint MESFET model.

Figure 1. Ids versus Vds for different Vgs voltages.

The basic equations including the current source equationsand the capacitance equations can be found in [1]. Theessentials of the subthreshold model are described in [2]where the formulae are used to describe the CMOS sub-threshold behavior.

DC ResultsTests have been performed for a variety of temperaturesand device widths to check proper scaling andtemperature dependencies. Drain-source current Ids,gate-drain and gate-source capacitances respectivelyCgd and Cgs (CAPMOD and CAPDC=1) are representedversus bias for the depletion mode. A comparison

between TOM-1 and TOM-2 dc characteristics (Ids-Vds)are plotted in Figure 1. The drain current is plottedversus Vgs for different temperatures in Figure 2.Improved accuracy in the knee region is observed in theTOM-2 model characteristic. Similar results can befound in reference [3].

Reference

[1] SmartSpice/UTMOST Modeling Manual Volume 2.

[2] M. Godfrey "CMOS device modeling for subthreshold circuits"IEEE Transactions on Circuits and Systems II : Analog and DigitalSignal Processing, 39(8), August 1992.

[3] N. SCHEINBERG, R. BAYRUNS, P. WALLACE "An accurateMESFET Model for linear and microwave circuit design" IEEE

Journal of Solid-State Circuits, vol. 24, n. 2, April 1989.


Figure 2. Ids versus Vgs for Vds=1V for different temperatures. Figure 3. Cgs versus Vds for different Vgs.

Figure 4. Cgd versus Vds for different Vgs.

IntroductionWith the advent of ever increasingoperation frequencies, Silvaco isintroducing a new high frequencymodel for MOSFETs that will beimplemented into the SmartSpicecode. This article describing thesenew models will be in two parts.The first part describes themathematical detail concerning theextraction of the "Y" parametersthat contain the necessary frequencyterms and part two, in the Julyissue, describes the conversion ofthe "Y" parameters into therequired elements for the Spicemodel itself.

When extracting frequencydependent parameters for highfrequency MOSFETs and other active devices frommeasured data, it is important to isolate the elementsthat are due to the device alone, from the "parasitics"that are inevitably present from bonding pads,packaging and the like. To this end, the user has tohave two types of structure. One structure type

contains all the active elements and the other structuretype consists of identical bond pads and packaging butwithout the active devices. By measuring both types ofstructure, the frequency dependent parameters of theactive device can be isolated by subtracting the effectsof the package without the active devices. Thisprocedure is called "de-embedding. The followingarticle describes the method for extracting an accuratehigh frequency Spice model from just such measured data.

1.1 Parameter Extraction Requirement

Measured S-parameters of MOSFET devices andS-parameters of de-embedding patterns (open, short)are needed to extract small signal parameters of RFMOSFET. De-embedding patterns are used to de-embedparasitics of pad and interconnection line. Gate is port 1and drain is port 2. Source and body are grounded.The characteristic impedance is 50 Ohm.

The data is stored in standard sequential ASCII files.One line of data is a set of data for one frequency and,for example, can be written as

Frequency Mag(S11) Phase(S11) Mag(S21)

Phase(S21) Mag(S12)

Phase(S12) Mag(S22) Phase(S22)


New RF MOSFET Small Signal SPICE Model Part 1

Ickjin Kwon, Minkyu Je, Kwyro Lee, and Hyungcheol ShinDepartment of Electrical Engineering, Korea Advanced Institute of Science and Technology

Figure 1. The proposed common-source equivalent circuit of a MOSFET after de-embeddingparasitics of on-wafer pads and interconnection lines. Four independent intrinsiccapacitances Cgs, Cgd, Cdg, and Cds are needed for charge conservation. The definitionsof each capacitance are also shown.

Symbol Physical Meaning

Measured S-parameters of MOSFET device

Measured S-parameters of open dummy pattern

Measured S-parameters of short dummy pattern

[YD] Y-parameters of MOSFET devices

[YO] Y-parameters of open de-embedding pattern

[YS] Y-parameters of short de-embedding pattern

[YDO] =[YD] – [YO]

[YSO] =[YS] – [YO]

[ZDO] Z-parameters converted from [YDO]

[ZSO] Z-parameters converted from [YSO]

[ZF] =[ZDO] – [ZSO]

[YF] Y-parameters converted from[ZF]

S11D S12D[SD] =S21D S22D

S11O S12O[SO] =S21O S22O

S11S S12S[SS] =S21S S22S

Table 1. The symbol definitions for the de-embedding procedure.

In an S-Parameter file, a typical line might be

500 0.64 -23 12.5 98 0.03 70 0.8 -37

In this case, 500 is the frequency in megahertz. Themagnitudes of S11, S21, S12 and S22 are 0.64, 12.5, 0.03and 0.8, and the phases are –23, 98, 70 and –37 degrees,respectively.

S-parameter of devices will have to be measured underDC bias condition of Vgs, Vds. One routine of extractionprocedure extracts small-signal parameters under oneDC bias condition of Vgs, Vds. De-embedding patterns(open, short) are measured under zero DC bias conditionof Vgs = 0 V, Vds = 0 V.

The symbol definitions for the de-embedding procedureare listed in Table 1.

1.2 S-parameter Measurement(1) S-parameters of MOSFET device are represented as

The magnitudes and the phases of S11D, S21D, S12D andS22D are converted to real and imaginary format.

Then, S11D, S21D, S12D and S22D are represented as real andimaginary format as following.

(2) S-parameters of open de-embedding pattern arerepresented by

The magnitudes and the phases of S11O, S21O, S12O andS22O are converted to real and imaginary format.

Then, S11O, S21O, S12O and S22O are represented as realand imaginary format as following.

(3) Measured S-parameters of short de-embeddingpattern are represented by

The magnitudes and the phases of S11S, S21S, S12S and S22S

are converted to real and imaginary format.


*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

*

Then, S11S, S21S, S12S and S22S are represented as real andimaginary format as following.

1.3 De-embedding Procedure

(1) Measured S-parameters of MOSFET device areconverted to Y-parameters. (([SD]�[YD] ) )

Then, MOSFET device Y-parameters are represented asreal and imaginary parts.

(2) Measured S-parameters of open de-embeddingpattern are converted to Y-parameters. ([S0]�[Y0] )

Then, open pattern Y-parameters are represented asreal and imaginary parts.

(3) Subtract open pattern Y-parameters from MOSFETdevice Y-parameters. ([YDO] = [YD] – [YO] )

If only open de-embedding pattern is used withoutusing short-pattern, following (4)-(9) procedures areomitted. In this case, Y11DO, Y21DO, Y12D0, Y22DO are usedfor parameter extraction.

(4) Measured S-parameters of short de-embeddingpattern are converted to Y-parameters. ([SS]�[YS] )

Then, short pattern Y-parameters are represented asreal and imaginary parts.


(5 ) Subtract open pat tern Y-parameters f romshort pattern Y-parameters. ([YSO] = [YS] – [YO] )

(6) ([YSO]�[ZSO] )

(7) ([YDO]�[ZDO] )

(8) ([ZF] = [ZDO] – [ZSO] )

(9) ([ZF]�[YF] )

D e - e m b e d d i n g p r o c e d u r e u s i n g o p e n a n dshort de-embedding pattern is finished.

Note that, Y11F, Y21F, Y12F, Y22F are used in the followingparameter extraction procedure and Y-parameters inthe extraction equation is same as Y11F, Y21F, Y12F, Y22F .(i.e. [Y] = [YF] )

If only open pattern is used, Y11DO, Y21DO, Y12DO, Y22DO

are used instead of Y11F, Y21F, Y12F, Y22F. (i.e. [Y] = [YDO] )

For the parameter extraction, Y-parameters arerepresented as real and imaginary format as follows.

ConclusionThis concludes the extraction of the "Y" parameters thatare required for generating the equivilent circuitelements in the high frequency Spice model forMOSFETs. In the July issue, the conversion of thede-embedded "Y"parameters into the frequencydependent circuit elements is described.



Calendar of Events

12 ESMC - Munich,Germany3 ESMC - Munich,Germany45678 SLIP2000 - San Diego, CA9 SLIP2000 - San Diego, CA10111213141516171819 14th Microelectronics

Show Oomiya, Japan20 14th Microelectronics

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April1 GaAs MANTECH -

Washington DC2 GaAs MANTECH -



Washington DC56789 1011121314 IPRM Williamsburg, VA15 IPRM Williamsburg, VA16 IPRM Williamsburg, VA17 IPRM Williamsburg, VA18 IPRM Williamsburg, VA19202122 ISPSD Toulouse, France

IWCE Glasgow, Scotland23 ISPSD Toulouse, France

IWCE Glasgow, Scotland24 ISPSD Toulouse, France

IWCE Glasgow, Scotland25262728293031

May

The Simulation Standard, circulation 18,000 Vol. 11, No. 4, April 2000 is copyrighted by Silvaco International. If you, or someone you know wants a subscription tothis free publication, please call (408) 567-1000 (USA), (44) (1483) 401-800 (UK), (81)(45) 341-7220 (Japan), or your nearest Silvaco distributor.

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For more information on any of our workshops, please check our web site at http://www.silvaco.com

East Coast DoubleheaderMay is stacked with two big conferences on theEast Coast. The GaAs Conference will be heldin Washington DC on May 1-4. On May 14-18in Williamsburg, Virginia the staff fromSilvaco’s Boston office will be showcasing ourproducts at the Indium Phosphide Conference.

SLIP2000This year’s System-Level InterconnectPrediction Workshop will be held in San Diego,California. We are looking forward to display-ing our comprehensive line of DISCOVERY andCELEBRITY toolsets. Silvaco’s parasitic extrac-tion tools continue to lead the way for theinterconnect community.

ISPSDSilvaco’s European office will be demonstratingthe trend-setting capabilities of Silvaco productsat this year’s 12th International Symposium onPower Semiconductor Devices & IC’s. Maketime to join us May 22nd through 25th inToulouse, France.

B u l l e t i n B o a r d


The RC_sat routine uses the flyback method to extractthe constant part of the RC (RCX) and RE for the VBICmodel. The RC has two parts in the VBIC model. Theparameter RCX is the constant extrinsic collectorresistance and RCI is the intrinsic modulated collector

resistance. After the data collection the usercan press the "fit" option to extract both para-meters RCX and RE. The results will becopied to the "parameters" screen. (Figure 1.)The parameter RCI will be used later forquasi-RC region modeling.

The ALL_DC routine can be used to extractsome of the fundamental DC parameters ofthe VBIC model. The forward and reversecharacteristics of the bipolar device shouldbe measured ( The "All DC" selection in the"set measurement/To Model" button selec-tion). After the data collection the "fit" buttonshould be pressed to extract the DC parameters(Figure 2.). The extracted parameters will becopied to the parameters screen.

The extracted parameters are:

IS, NF, NR, IBEI, IBEN, NEI, IBCI, IBCN,NCN, IKF and IKR.

Q. How can I extract VBIC bipolar modelparameters using UTMOST III?

A. UTMOST III Bipolar module can be utilized toextract and optimize the VBIC model parametersfor bipolar devices.

The VBIC model extraction strategy is similar tothe Gummel-Poon model parameter extraction.For DC modeling the measured data should becollected using routines "RC_sat" (For RC and REextraction), and ALL_DC (forward and reversecharacteristics should be collected). The RBextraction can be accomplished using the DC orAC methods. However the extracted RB resultsusually requires further optimization.

The user should load the VBIC model parametersand their default values using the "Spice ModelFile". The Spice Model File is located under theworking directory of "<user_home_directory/vyper_data/ utmost_data/bip/" For theUTMOST III III version of 16.3.0.R the Spice Model Filename would be: BIP.16.3.0.R.s. The Spice Model Filecan be loaded by selecting the Spice Model File menuoption from the files menu of UTMOST III.

Hints, Tips and SolutionsMustafa Taner, Applications and Support Engineer

Figure 1. RC_sat routine graphics screen.

Figure 2. ALL_DC routine with extracted VBIC parameters.


In order to model the substrate current, the ALL_DC orGummel routine data should be collected withIsub_flag in the measurement setup screen set to "1".When this flag is set to "1" the gummel curves willinclude the measured substrate current (Figure 3.)

For NPN devices the substrate current will be moredominant under reverse bias operation. Therefore thereverse bias gummel curves should also include thesubstrate current. The following parameters shouldbe optimized on the reverse gummel curve withsubstrate current:

ISP, IBENP, IBCIP, IBCNP, NFP, NCIP, NCNP,IKP, RS and RBP

The VBIC model can be utilized to model theavalanche effect on IC/VCE characteristics.Parameters AVC1 and AVC2 should be optimizedat the high VCE region where the avalanche effectbecomes visible (Figure 4.)

The quasi saturation region modeling can also beaccomplished using the VBIC model parametersRCX, RCI, GAMM and HRCF. These parametersshould be optimized using the IC/VCE characteristicswhich demonstrates the Quasi-RC effect (Figure 5).

The parameter values used for this example are:

RCI = 22

RCX = 55

VO = 0.4

GAMM = 1E-10

HRCF = 111

Call for QuestionsIf you have hints, tips, solutions or questions to contribute, please

contact our Applications and Support DepartmentPhone: (408) 567-1000 Fax: (408) 496-6080

e-mail: [email protected]

Hints, Tips and Solutions ArchiveCheck our our Web Page to see more details of this example

plus an archive of previous Hints, Tips, and Solutionswww.silvaco.com

Figure 4. IC/VCE measured vs simulated data.

Figure 5. IC/VCE measured versus simulated (including theQuasi-RC effect)

Figure 3. Measured Gummel curves including the substrate current.

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new version 5.0 of ufsoi model released in smartspice · of the parasitic (coupled) bjt (current...

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