Simple and Accurate Approach to Implement the Complex Trans-Conductance in Time- Domain Simulators M. Homayouni, D. Schreurs, and B. Nauwelaers K.U.Leuven, Belgium

Outline Introduction to Table-Based ModelIntroduction to Table-Based Model Microwave and mm-Wave IssuesMicrowave and mm-Wave Issues ImplementationImplementation Linear ModelLinear Model Non-Linear ModelNon-Linear Model ConclusionConclusion AcknowledgementAcknowledgement

Introduction to Table-Based Model Layout and equivalent circuit of CMOS FinFET transistor.Layout and equivalent circuit of CMOS FinFET transistor.

Introduction to Table-Based Model Equivalent Circuit Intrinsic Network: Parameters that are bias-dependent, representing active channel. Extrinsic Network: Parasitic elements that are bias-independent, originating from layout pads.

Introduction to Table-Based Model Model (equivalent circuit parameters) is extracted from measurements carried out on actual device.Model (equivalent circuit parameters) is extracted from measurements carried out on actual device. DC-measurementsDC-measurements S-parameter measurementsS-parameter measurements Thermal measurementsThermal measurements Noise measurementsNoise measurements –Intrinsic Network Parameters Bias-dependentBias-dependent Extracted from S-parameters at hot bias condition (Vgs and Vds non-zero)Extracted from S-parameters at hot bias condition (Vgs and Vds non-zero) Tabulated in table-filesTabulated in table-files –Extrinsic Network Parameters Bias-independentBias-independent Extracted from S-parameters at cold bias condition (Vds=0)Extracted from S-parameters at cold bias condition (Vds=0) Tabulated in table-filesTabulated in table-files

Microwave and mm-Wave Issues Microwave and mm-Wave Issues Complex Trans-ConductanceComplex Trans-Conductance gm, represents the gaingm, represents the gain  represents the channel time-delay  represents the channel time-delay Complex Trans-conductance

Microwave and mm-Wave Issues Influence of channel time-delay on model accuracy.Influence of channel time-delay on model accuracy. Most sensitive parameter: S21.Most sensitive parameter: S21. Error (difference between model and measurement ) in percentage Error (difference between model and measurement ) in percentage in S-parameters due to ignorance of channel time-delay. in S-parameters due to ignorance of channel time-delay. mm-Wave application:mm-Wave application: 38GHz fast Ethernet, 60GHz WLAN, 77GHz car-radar38GHz fast Ethernet, 60GHz WLAN, 77GHz car-radar Significant features: gain (S21), fmax, ftSignificant features: gain (S21), fmax, ft

Implementation Do microwave software support complex trans-conductance (time- delay)? ADS (Advance Design System)Yes Spectre (Cadence)No Verilog-ANo SpiceNo Complex trans-conductance in ADS Gain: gm = 45mS time delay: t = 5.2psec

Implementation   represents the channel time-delay   represents the channel time-delay Virtual implementation of time-delayVirtual implementation of time-delay Introduction of transmission lineIntroduction of transmission line Gate terminal to delay the sampling voltage Drain terminal to delay the current of voltage-controlled current source (VCCS) current source (VCCS) Delayed Voltage

Implementation How to determine and implement the t-line?How to determine and implement the t-line? T-line should be terminated with match-load to guarantee no reflection.T-line should be terminated with match-load to guarantee no reflection. Input impedance of t-line should be orders of magnitudes larger than impedance seen from connection point (Zin should be much larger than Zout).Input impedance of t-line should be orders of magnitudes larger than impedance seen from connection point (Zin should be much larger than Zout). Electrical length of t-line corresponds to time-delay.Electrical length of t-line corresponds to time-delay. Zin Zout

Implementation Implementation Issues for SimulatorsImplementation Issues for Simulators T-lines are not very convenient for time-domain simulators.T-lines are not very convenient for time-domain simulators. T-lines are approximated by lumped LC-networkT-lines are approximated by lumped LC-network –Simpler to extract the values –Simpler to develop them in model –Limited in terms of frequency range

Implementation Approximate LC-NetworkApproximate LC-Network If  then the LC-network is performing as a t-line that delays the input signal.If  then the LC-network is performing as a t-line that delays the input signal.  is in order of tenth of psec.  is in order of tenth of psec. Z0 is in order of M Z0 is in order of M  In our case (FinFET transistor):In our case (FinFET transistor): – 300MHz < f < 50GHz –  psec  < , acceptable but limited in terms of frequency range

Implementation Comparison between model and measurement in both cases, with time- delay and without time-delay.Comparison between model and measurement in both cases, with time- delay and without time-delay. Accuracy of model is improved due to implementation of time-delay.Accuracy of model is improved due to implementation of time-delay. Improvement in model accuracy

Implementation Non-linear table-based model Integration

Implementation Implementation of time-delay in non-linear model Different from linear model No need for t-line or equivalent lumped network Complex trans-conductance can be split into real and imaginary parts Non Quasi-Static non-linear model can be implemented Real trans-conductance: modeled as normal Negative capacitance

Conclusion Channel time-delay is significant at microwave and mm- wave frequencies.Channel time-delay is significant at microwave and mm- wave frequencies. Accurate technique was introduced to introduce complex trans-conductance in time-domain simulators.Accurate technique was introduced to introduce complex trans-conductance in time-domain simulators. Simple and accurate approximation was introduced to ease the time-delay implementation in model for time- domain simulators.Simple and accurate approximation was introduced to ease the time-delay implementation in model for time- domain simulators. Simple method was introduced to implement non quasi- static non-linear table-based models.Simple method was introduced to implement non quasi- static non-linear table-based models.

Acknowledgements Nano-RF project IST FinFET team at IMEC Andries Scholten from NXP