CMOS Compact Modeling for Cryogenic PDK Re-Centering

Solution Overview

Problem

The lack of foundry Process Development Kits (PDKs) for CMOS devices designed for cryogenic temperatures poses challenges in ensuring consistent transistor characteristics, as conventional re-centering methods fail to guarantee accuracy between typical-typical transistors and those fabricated on silicon chips.

Innovation Solution

A method involving the use of room-temperature TCAD models, fitting structural and carrier transport parameters to measured characteristics, and calibrating at cryogenic temperatures to determine compact model parameters for CMOS devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional re-centering methods are used to adapt room-temperature PDKs to cryogenic temperatures, then some level of cryogenic operation is enabled, but the transistor characteristics cannot be guaranteed to match typical-typical specifications

Engineering Contradiction:

Improvecryogenic operation capabilityVSAvoidtransistor characteristic consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The method performs preliminary fitting of structural parameters to room-temperature measured characteristics before cryogenic operation. This preliminary calibration ensures that the TCAD model accurately represents actual device characteristics at room temperature, which then serves as a reliable foundation for extracting cryogenic compact model parameters, thereby guaranteeing characteristic consistency across temperature ranges.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The method changes the temperature parameter from room temperature to cryogenic temperature in a controlled manner. By fitting structural parameters at room temperature and then using these fitted parameters to determine carrier transport parameters at cryogenic temperatures, the method systematically adapts the model parameters to different temperature conditions while maintaining characteristic consistency.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If cryogenic PDK development is pursued to ensure accurate transistor characteristics at cryogenic temperatures, then modeling accuracy is improved, but the development cost becomes prohibitive

Engineering Contradiction:

Improvecryogenic transistor characteristic accuracyVSAvoidPDK development cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The method introduces a TCAD model as an intermediary between room-temperature measurements and cryogenic compact models. Instead of directly developing cryogenic PDKs through expensive cryogenic measurements and model fitting, the TCAD model serves as a mediator that translates room-temperature fitted parameters into accurate cryogenic compact model parameters, significantly reducing development cost while maintaining accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The method creates a virtual copy of the transistor behavior through TCAD simulation. By fitting the TCAD model to room-temperature measured characteristics and then using this virtual model to predict cryogenic behavior, the method avoids the need for expensive physical cryogenic measurements and PDK development, achieving accurate cryogenic modeling through simulation copying.

Inventive Principle:

Principle #26Copying

3Ease of manufacture

If foundry PDKs are designed for room-temperature operation, then standard manufacturing processes can be used, but the PDKs cannot guarantee accurate characteristics for cryogenic applications

Engineering Contradiction:

Improvestandard manufacturing process compatibilityVSAvoidcryogenic transistor characteristic accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The method performs preliminary fitting of structural parameters to room-temperature measured characteristics before cryogenic operation. This preliminary calibration ensures that the TCAD model accurately represents actual device characteristics at room temperature, which then serves as a reliable foundation for extracting cryogenic compact model parameters, thereby guaranteeing characteristic consistency across temperature ranges.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The method changes the temperature parameter from room temperature to cryogenic temperature in a controlled manner. By fitting structural parameters at room temperature and then using these fitted parameters to determine carrier transport parameters at cryogenic temperatures, the method systematically adapts the model parameters to different temperature conditions while maintaining characteristic consistency.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250328711A1Determining compact model parameters for modelling CMOS devices at cryogenic temperatures

Publication Date: 2025.10.23 SEMIWISE

AI summary

The method is directed to determining compact model parameters for modelling CMOS devices at cryogenic temperatures. The method includes: obtaining (110) a room-temperature TCAD model of CMOS devices: fitting (118) a structural parameter of the room-temperature TCAD model to room-temperature measured characteristics of first CMOS devices, to produce a shifted TCAD model: fitting (128) a carrier transport parameter of the shifted TCAD model to cryogenically measured characteristics of the first CMOS devices, to determine a cryogenically-fitted carrier transport parameter; and running (132, 136) a room-temperature TCAD model of CMOS devices using the cryogenically-fitted carrier transport parameter to determine compact model parameters. The method allows measurement data from a ‘non-ideal’ silicon wafer to be used in a TCAD-based cryogenic PDK recentering process, which may also be used to generate target data for the corner transistors in the recentered PDK.