CMOS Temperature Sensor Layout Using a Floating Field Plate

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Solution Overview

Problem

The challenge of measuring active device temperatures in advanced CMOS transistors is complicated by increased thermal junction temperatures and the risk of electrostatic discharge (ESD) due to direct electrical connections, which also introduce thermal resistance and inaccuracy in temperature measurements.

Innovation Solution

A method and apparatus for ambient temperature sensing in a CMOS process using a floating contact field plate with a dielectric layer between the plate and the active device terminal, providing thermal contact without electrical connection, thus reducing ESD risk and thermal resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a direct electrical connection is made to measure active device temperature, then temperature measurement is enabled, but the risk of electrostatic discharge (ESD) increases and thermal resistance is introduced

Engineering Contradiction:

Improvetemperature measurement accuracyVSAvoidelectrostatic discharge risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

A floating metal plate is introduced as an intermediary element between the measurement system and the active device. This plate is positioned one interlayer dielectric layer away from the transistor, allowing thermal contact while preventing direct electrical connection. The intermediary plate enables temperature sensing without creating an electrical pathway that could conduct ESD to the sensitive active device.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a non-connected (floating) metal is placed one interlayer dielectric layer away from the transistor, then ESD protection is improved, but thermal resistance increases

Engineering Contradiction:

ImproveESD protectionVSAvoidthermal resistance

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The thickness of the interlayer dielectric is optimized to balance thermal resistance and ESD protection. By controlling the dielectric layer thickness parameter, the design achieves sufficient thermal conductivity for accurate temperature sensing while maintaining adequate electrical isolation for ESD protection. The parameter optimization allows the floating metal to be thermally coupled to the active device without creating a direct electrical connection.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables accurate temperature sensing with improved electrostatic discharge protection and reduced thermal resistance, enhancing the sensitivity and reliability of temperature measurements in CMOS devices.

Implementation Method 1

a dielectric layer between the floating contact field plate and the terminal of the active/passive device

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20250210438A1Method and apparatus for ambient temperature sensor design in a complementary metal oxide semiconductor (CMOS) process

Publication Date: 2025.06.26 QUALCOMM INC

AI summary

An integrated circuit (IC) structure is described. The IC structure includes a substrate having an active/passive device in the substrate. The IC structure also includes a terminal of the active/passive device in the substrate. The IC structure further includes a floating contact field plate above the terminal. The IC structure also includes a dielectric layer between the floating contact field plate and the terminal of the active/passive device.