Thermistor Element with [111] Orientation for Miniaturization

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Solution Overview

Problem

The high resistance value of thermistor films in current thermistor elements poses a challenge for miniaturization, making it difficult to extract detection signals effectively, particularly in electromagnetic wave sensors where further miniaturization is desired.

Innovation Solution

A thermistor element with a thermistor film having a spinel crystal structure and a [111] preferred orientation in the film thickness direction, employing a current-perpendicular-to-plane (CPP) structure with electrodes, which reduces the resistance value and enables miniaturization, is used in conjunction with an electromagnetic wave sensor that includes an array of these thermistor elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a current-in-plane (CIP) structure is employed in a thermistor element, then the thermistor element can be manufactured with conventional processes, but the resistance value becomes excessively high and miniaturization becomes difficult

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidminiaturization

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The patent inverts the conventional current flow direction from in-plane (CIP) to perpendicular-to-plane (CPP). By changing the current measurement direction from parallel to perpendicular relative to the film plane, the resistance value is dramatically reduced, enabling miniaturization while maintaining manufacturability through standard sputtering processes.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the measurement parameter configuration by switching from in-plane current flow to perpendicular-to-plane current flow. This parameter change fundamentally alters the resistance characteristics, reducing resistance by several orders of magnitude and enabling the thermistor element to be miniaturized to practical dimensions.

Inventive Principle:

Principle #35Parameter changes

2Volume of moving object

If the thermistor film is miniaturized to reduce sensor size, then the sensor becomes more compact, but the resistance value increases making signal extraction difficult

Engineering Contradiction:

Improvesensor sizeVSAvoidsignal extraction capability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent inverts the current measurement geometry from in-plane to perpendicular-to-plane direction. This inversion causes the resistance to decrease as the film area decreases (opposite to conventional behavior), allowing miniaturized sensors to maintain low resistance values and reliable signal extraction capability.

Inventive Principle:

Principle #13The other way round (Inversion)

3Ease of manufacture

If a thermistor film with random crystal orientation is used, then the manufacturing process is simpler, but the resistance value is high and miniaturization is limited

Engineering Contradiction:

Improveprocessing simplicityVSAvoidminiaturization

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The patent applies local quality control by inducing specific crystallographic orientation ([111] direction) in the spinel structure of the thermistor film. This localized crystallographic arrangement perpendicular to the film plane reduces resistance anisotropy and enables miniaturization, while the overall manufacturing process remains compatible with conventional sputtering techniques.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the crystallographic parameter by establishing a specific [111] preferred orientation in the spinel crystal structure. This parameter change in crystal orientation fundamentally alters the electrical resistance characteristics, reducing resistance and enabling miniaturization while maintaining manufacturing simplicity.

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 configuration allows for reduced resistance values and enhanced miniaturization of thermistor elements, improving the detection capabilities of electromagnetic wave sensors by enabling more efficient signal extraction and further miniaturization.

Implementation Method 1

In an electromagnetic wave sensor, infrared rays (electromagnetic waves) incident on a thermistor film are absorbed by the thermistor film or materials around the thermistor film, and thereby a temperature of the thermistor film changes.

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 2

The electrical resistance of a thermistor film included in a thermistor element changes according to change in temperature of the thermistor film.

Methodology Applied

Scientific EffectThermistor effect: Thermistor

Data Source

PatentUS11668607B2Thermistor element and electromagnetic wave sensor

Publication Date: 2023.06.06 TDK CORP

AI summary

A thermistor element includes a thermistor film, a first electrode provided in contact with one surface of the thermistor film, and a pair of second electrodes provided in contact with the other surface of the thermistor film, wherein the thermistor film includes an oxide having a spinel crystal structure and having a [111] preferred orientation in a film thickness direction.