April 19, 2022

Towards Open-Source Models of Cryogenic CMOS

Brian Hoskins and Pragya Shrestha

National Institute of Standards and Technology, MD, USA

NIST Mission

To promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life

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©Nicholas McIntosh Photography

©Robert Rathe

Credit: J.Burrus/NIST

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e.g., opto-electronics

Cryogenic Electronics : Applications

Supercomputer : 77 K

• High Performance Computing

• LT Source/Sensor Electronics

High Performance Computing

• Speed
• High mobility, higher saturation velocity
• Lower noise
• Better reliability
• lower thermally assisted degradations
• Reduced susceptibility to latch-up
• Increased integration density due to higher thermal conductivity of materials used in circuits
• Less power consumption due to lower supply voltage

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Gutierrez-D et all Low temperature electronics : physics, devices, circuits, and applications, 2001; Balestra, F. Et al, Device and circuit cryogenic operation for low temperature electronics, 2001.

Low Temperature Sensor Electronics

Satellite

Space mission

Dark matter physics

Magnetometry

• Measuring tiny magnetic fields

Gravitational wave research

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Gutierrez-D et all Low temperature electronics : physics, devices, circuits, and applications, 2001

• Due to environment
• To improve sensitivity
• Low temperature required for it to work

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Sensors operated at low temperatures

Mix of AC and DC signal required to control and read the Qubits

Digital

• Inverters, ring oscillators

Analog

• Voltage reference, Low Noise Amplifiers

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Control Electronics for Quantum Computers

https://phys.org/news/2020-08-google-largest-chemical-simulation-quantum.html ; https://www.cnet.com/news/google-quantum-supremacy-only-first-taste-of-computing-revolution, Amundson, J.; Sexton-Kennedy, E. J. E. W. C., Quantum Computing. 2019

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Quantum processor

MUX

DEMUX

Read

Control

Digital Control

ASIC/FPGA

ADC

DAC

OSC

1 - 4 K

<100 mK

300 K

Amp

Low power operation

Requirement of Low Operating Power

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• Do devices work at low temperatures?
• YES!!! Devices function at cryogenic temps (4 K)
• MOSFETs
• In general: |V_th|increases, I_ON increases (mobility), and SS improves

10 x 0.36 μm² Si/SiO₂ (4 nm)

Device at Low Temperature

Gutierrez-D et all Low temperature electronics : physics, devices, circuits, and applications, 2001

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Problem?

Proper Device Characterization for Accurate PDK

• Cryo-CMOS models
• Build device model
• Necessary for circuit design
• Commercial device model
• Down to 233 K ( - 40 ⁰C)
• Does not account for
• Kink effect
• SS saturation
• Accurate transistor mismatch and variability
• Incomplete ionization mechanism
• Low temperature noise effects
• Understanding device physics
• Extrapolating parameters
• Down selecting relevant technologies
• Account for reliability issues

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Akturk, A. et al, TED 2010; Beckers, A. et al JEDS 2018; Hart, P. A. T. et al, JEDS 2020, Grill, A. et al, 2020 IEEE International Reliability Physics Symposium (IRPS)

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Amplifier

Cryogenic Fast IV Setup for Device Reliability and Physics Measurements

Time + Temperature dependent characterization

P. R. Shrestha et. al (submitted JEDS)

Low Temperature Device Characterization Setup : Memory

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Zaslavsky et al. APL 2021; Richter et al. APS 2022.

Low Temperature Circuits Characterization

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Prashansa Mukim, Jabez McClelland.

• Setup
• Temperature dependence (multi temp. measurements)
• Special board layout
• On board temperature sensor
• CMOS Circuit (Collective Pulse Oscillators)
• Noise
• Power
• Frequency

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Reliable Time + Temperature Measurement

Partners and Plan

Cryogenic Models and Data of Open Sky130

Raw Data

Fit Models

Useful Devices

Si-Proven IP@4k

Mehdi Saligane, Tuohang Zeng, David Fleischer, Akin Akturk, Advait Madhavan, Tim Edwards, Jeff DiCorpo, Tim Ansell, Ethan Mahintorabi, Aaron Cunningham, Steve Kosier

Test Structure Interface

60 µm

Probe Card

Basic Test Structure Forms

MOSCAP Arrays

Transistor Arrays

Overlap

MOSCAP Arrays

Precision Resistors

Line

Resistance

Via

Resistance

Diode Modules

MIM

Capacitor Modules

To Validation Modules

Modeling Validation Modules

1,024 Frequency Divider

10 Flipflops

Parametric Extraction

Model Parastics

Predict Oscillator Frequency

Validate Performance

Close Timing in Real Circuit?

From Parametric Modules

V

fast Pulses

V

slow Pulses

Resultant Test Die

Major Highlights!

• Over 1400 Pads
• 400+ Transistor Structures
• 30 Capacitor Test Structures
• 24 Ring Oscillators
• 18 line and via chain modules
• 7 Diode Test Structures

https://github.com/tuohangzeng/openfasoc_cryo_caravel/tree/main/gds

GDS Images

MOSCAP Arrays

Transistor Arrays

Precision Resistors

Line Resistance

Via Resistance

Diode Modules

MIM

Capacitor Modules

Validation Modules

Implemented 3 Standard Cell Inverter Classes:

9 Additional OSU Standard Cell Inverters

12T_hs, 12T_ls, 12T_ms,15T_hs,15T_Is, 15T_Is, 15T_ms, 18T_hs, 18T_Is, 18T_ms

HD, HS, and HVL inverters

Preliminary Results: 118 Transistor @ 4k!

Cryogenic Electronics at NIST

Device

Circuits

Packaging

• Physics
• Application Specific Reliability/understanding

• Circuits
• Standardize Testing

• Applications
• Testing/Metrology