Oct 17, 2026

[paper] ACM3 Compact MOSFET Model

Deni Germano Alves Neto; Márcio Cherem Schneider; Manuel J. Barragan; 
Sylvain Bourdel; Carlos Galup-Montoro,
ACM3 - An Advanced Compact MOSFET Model for Analog IC Design and Simulation
in IEEE Access, DOI: 10.1109/ACCESS.2026.3742180

1.) Federal University of Santa Catarina, 88040-900 Florianópolis (BR)
2.) Univ. Grenoble Alpes, CNRS, Grenoble INP, TIMA F-38000 Grenoble (F)

Abstract: This paper presents ACM3, an advanced compact MOSFET model that extends the designoriented ACM2 formulation by introducing gate-voltage dependencies for the slope factor n, the draininduced barrier lowering (DIBL) coefficient σ, and inversion charge dependence for the specific current IS. ACM3 preserves a single-piece, charge-based description of the drain current, valid from weak to strong inversion and from the linear to the saturation regions, while relying on an efficient analytical approximation of the Lambert W -function suitable for Verilog-A implementation. A robust yet straightforward parameterextraction flow is proposed, in which all eight DC parameters (VT 0, IS0, Φ, γ, θ, σWI , σSI and ζ) are obtained directly from ID–VGB and ID–VDS curves through a differential evolution (DE) algorithm that minimizes the root-mean-square percentage error between the reference and the modeled drain current. A distinctive feature of this flow is that the reference curves may originate either from silicon measurements or from another compact model, making the extraction equally applicable to measured and simulated data. At the device level, the parameters are extracted from silicon measurements of an open-source 130 nm BiCMOS technology, yielding agreement with the measured data for both short- and long-channel transistors across all regions of operation. At the circuit level, ACM3 is validated through simulations of a common-source amplifier, a self-biased current source, and a CMOS latch in a 180 nm CMOS technology, where the ACM3 parameters are extracted from BSIM4-generated characteristics and the results are compared against the foundry BSIM4 model. Representative process, voltage, and temperature (PVT) robustness is also evaluated against BSIM4. The ACM3 model has been implemented in Verilog-A and integrated into open-source circuit simulators, via OpenVAF, enabling accurate and intuitive analog IC design within fully open design flows.

TAB: Comparison of ACM3 with representative industrial 
and design-oriented compact MOSFET models

Aknowlegements: This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, (BRAZIL), Conselho Nacional de Desenvolvimento Científico e Tecnológico, (BRAZIL), and TIMA laboratory, Grenoble (FRANCE).

Oct 15, 2026

eSim 2.6 Release

A Big Milestone for FOSSEE eSim - eSim 2.6 IS HERE!


The release of eSim 2.6 is bringing exciting improvements, enhanced workflows, and new capabilities to our open-source Electronic Design Automation (EDA) tool developed by the FOSSEE Project, IIT Bombay.

Download eSim 2.6: https://esim.fossee.in/downloads
Explore eSim 2.6 Release Notes: https://github.com/FOSSEE/eSim/releases/tag/v2.6

What's New in eSim 2.6?
  • Refreshed User Interface
  • Enhanced Simulation and Waveform Analysis
  • Improved HDL Workflows and Icarus Verilog Support
  • Compatibility with Newer KiCad Versions
  • IHP OpenPDK Support
  • Native Windows Installer
  • Reduced Installer Size
  • OpenROAD Integration (Work in Progress)
Celebrating the Team Behind the Release:

A special shout-out to Varadha RS, Akshat Sharma, and more than 100 hardworking interns for their dedication and contributions to eSim 2.6. From implementing new features and resolving issues to testing workflows and improving usability, their efforts have helped bring this release to life.

A heartfelt thank you to all eSim and FOSSEE team members for their invaluable contributions, technical expertise, guidance, and continued support. Every contribution matter, and milestones like this are the result of collaboration, persistence, and teamwork.
Acknowledging Our Supporters

Our sincere gratitude goes to the FOSSEE Project, Indian Institute of Technology Bombay, National Mission on Education Through ICT (NMEICT), and the Ministry of Education, Government of India, New Delhi, for their continued support in advancing open-source engineering tools and education.
Building the Future of Open-Source EDA

At FOSSEE, IIT Bombay, we are committed to making circuit design, simulation, PCB design, and semiconductor design more accessible through open-source technologies.

Thank you to everyone who has been part of this journey. Special thanks to our collaborators and the wider open-source community:
  • Wladek Grabinski, 
  • Steve Hoover, 
  • Indira Iyer Almeida
  • OpenPDK IHP - Leibniz Institute for High-Performance Microelectronics
  • The OpenROAD Project

Oct 13, 2026

[paper] Self-Heating Effects in 55-nm SiGe HBTs

Abdelaaziz Boulgheb1, Billel Smaani2, Taha Housseyn Nouibat1
Physics-Based Electro-Thermal Modeling and Analysis 
of Self-Heating Effects in 55-nm SiGe HBTs
physica status solidi (a), 2026; 223:e70563 
https://doi.org/10.1002/pssa.70563

1. USTHB, Bab Ezzouar, Algeria 
2. University of Mila, Mila, Algeria

Abstract: This work investigates spatially resolved electrothermal behavior in scaled SiGe HBTs under self-heating conditions, emphasizing its impact on temperature distribution and RF performance. Unlike conventional lumped thermal resistance approaches assum- ing uniform temperature rise, the present analysis resolves the internal temperature field to capture nonuniform heat propagation effects. A physics-based electrothermal framework combining drift–diffusion transport, temperature-dependent semiconductor properties, and heat conduction equations is used to study hotspot formation and thermal confinement in a 55 nm SiGe HBT structure. Three operating conditions are considered: nominal operation at 300 K, self-heating at 300 K ambient temperature, and elevated ambient temperature of 320 K. The results reveal localized hotspot formation near the base–collector junction due to current crowding and geometrical confinement, leading to RF performance degradation. The cutoff frequency decreases from 320 to 285 GHz, while the maximum oscillation frequency reduces from 486 to 458.5 GHz. The current gain decreases from 2000 to 1500, and the maximum junction temperature reaches 417 K under the highest thermal stress condition. These findings highlight the importance of spatial thermal effects in governing RF limitations of SiGe HBTs and provide insight into the coupling between heat propagation and electrical performance in BiCMOS technologies.
FIG: Device structure of 55 nm SiGe HBT simulated with multiphysics TCAD: (a) log of electron and hole concentration highlighting emitter/base/SIC pedestal (b) TEM cross section of a fabricated BiCMOS 55nm HBT. Impact of self-heating on high-frequency performance of the 55-nm SiGe HBT under three thermal conditions: (c) parasitic delay parasitic (d) forward transit time τF , (e) cutoff frequency fT, and (f) maximum oscillation frequency fmax.

Oct 12, 2026

[paper] BSIM4 CryoModel-4K

Mohammed Saleh Alshaikh
CryoModel-4K: physics-based BSIM4 extension for28 nm bulk CMOS compact modeling at 4K
Nature Scientific Reports (Article in Press) DOI: 10.1038/s41598-026-69962-w

* Device Simulation Laboratory, Department of Electrical Engineering, College of Engineering and Architecture, Umm Al-Qura University, Makkah (SA)

Abstract: Accurate compact transistor models for 28nm bulk CMOS at cryogenic temperatures are essential for reli-able quantum computing interface circuit design. Existing room-temperature BSIM4 models fail to capture carrier mobility freeze-out, subthreshold swing saturation, current kink effects, and threshold voltage shifts at 4K. These failures produce post-fabrication performance deviations exceeding 300% in cryo-CMOS circuits designed using room-temperature models. This paper presents CryoModel-4K, a physics-based compact model that extends BSIM4 to accurately capture 28nm bulk CMOS behavior from 300 to 4K through three integrated correction modules. The Phonon Freeze-Out Mobility Enhancement Module (PFMEM) models the 3 to 8× car-rier mobility enhancement at liquid helium temperatures through a Matthiessen’s-rule combination of phonon, impurity, and surface roughness scattering. It is validated against published 4 K Hall effect measurements. The Cryogenic Subthreshold Swing Saturation Model (CSSM) replaces the classical kT/q thermal voltage with aband-tail tunneling-corrected expression. It accurately reproduces the observed 15 to 25 mV/dec subthreshold swing plateau below 30K. The Impurity Band Transport Kink Model (IBTK) captures the characteristic drain current kink arising from impact ionization triggered floating body effects in the partially frozen bulk substrate. Validation against published wafer-level characterization data for TSMC 28 nm bulk CMOS spanning 300 to 4K across 380 devices on three wafer splits demonstrates less than 5% RMS prediction error for all DC char-acteristics and less than 8% for RF S-parameters up to 10 GHz. Ring oscillator frequency is predicted within6.2% of measured values at 4K, compared to 312.5% error for standard BSIM4. The total SPICE simulation overhead relative to standard BSIM4 is approximately 25%.

FIG: a) Fig. 5 Complete small-signal equivalent circuit of CryoModel-4K for RF simulation, showing the intrinsic MOSFET withPFMEM-modified transconductance, CSSM-corrected output conductance, IBTK kink current source, temperature-depen-dent gate and substrate resistances, and parasitic interconnect elements. Small-signal equivalent circuit valid for operation from 100 MHz to 10 GHz at temperatures from 300 to 4 K. All substrate network elements are temperature-dependent 
b) Output characteristics (𝐼𝐷𝑉D) of a 28 nm NMOS device at 4 K for multiple 𝑉𝐺 values: measured data (symbols) ,CryoModel-4K with IBTK (solid lines), and BSIM4 without kink correction (dashed lines). Device: NMOS Lg = 28 nm, W =  um at T = 4K. VGS stepped from Vth to Vth + 0.5V in 0.1V increments. VDS swept from 0 V to 1.0 V in 25 mV steps. The IBTK captures the characteristic current kink at 𝑉𝐷≈0.5–0.7V

Acknowledgements: The author extends his sincere gratitude to the Umm Al-Qura University, for the invaluable resources and sup-portive environment that made this research possible.

Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License

APCI Program: SBMicro Projects

APCI Program
Support for SBMicro Integrated Circuit Projects



TAB: Universities Involved in IC Design and EDA/CAD Tool Development

University #Profs #PhDs #MSCs
CEFET-MG - Centro Federal de Educação Tecnológica de Minas Gerais803
CEFET-RJ - Federal Center for Technological Education Celso Suckow da Fonseca210
FEI - Centro Universitário da FEI203
FURG - Universidade Federal do Rio Grande311
IFSP - Instituto Federal de São Paulo500
ITA - Instituto Tecnológico de Aeronáutica1005
PUCRS - Pontifícia Universidade Católica do Rio Grande Do Sul8159
UCPEL - Universidade Católica de Pelotas306
UEA - Universidade do Estado do Amazonas100
UERGS - State University of Rio Grande do Sul500
UFABC - Federal University of ABC602
UFAM - Universidade Federal de Manaus440
UFBA - Universidade Federal da Bahia5138
UFC - Universidade Federal do Ceará353
UFERSA - Mossoró104
UFERSA - Pau dos Ferros513
UFG - Federal University of Goiás810
UFMG - Universidade Federal de Minas Gerais639
UFPB - Universidade Federal da Paraíba112
UFPEL - Universidade Federal de Pelotas13132
UFPR - Universidade Federal do Paraná725
UFRGS - Universidade Federal do Rio Grande do Sul173245
UFRJ - Federal University of Rio de Janeiro624
UFRN - Federal University of Rio Grande do Norte432
UFS - Universidade Federal do Sergipe301
UFSC - Universidade Federal de Santa Catarina111211
UFSM - Universidade Federal de Santa Maria805
UFV - Universidade Federal de Viçosa233
UNB - Universidade de Brasília939
UNESP - Universidade Estadual Paulista401
UNICAMP - Universidade Estadual de Campinas81621
UNIFEI - Universidade Federal de Itajubá723
UNIFEI - Itabira303
UNIPAMPA - Universidade Federal do Pampa402
UNISANTOS - Universidade Católica de Santos100
UNISINOS - Universidade do Vale do Rio dos Sinos303
UNIVALI - Universidade do Vale do Itajaí303
USP - Universidade de São Paulo8112
USP-EESC - Escola de Engenharia de São Carlos312
UTFPR - Universidade Tecnológica Federal do Paraná100