Trimmable Silicon Thermistor Orthogonal Segments

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Solution Overview

Problem

Thermistors are sensitive to stress imposed by device packaging and mounting, leading to unpredictable resistance changes and increased design tolerance, making it impractical to accurately reflect environmental temperature.

Innovation Solution

The use of split resistor segments in semiconductor substrates, oriented in orthogonal crystallographic directions to reduce the net resistance change under stress, with one segment conducting in the [011] direction and the other in the [001] or [110] and [112] directions, allowing for reduced sensitivity to mechanical stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single thermistor is used, then the device structure is simple, but the resistance changes unpredictably under stress, increasing design tolerance and reducing measurement precision

Engineering Contradiction:

Improvedevice structureVSAvoidtemperature measurement accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent divides the single thermistor into multiple resistor segments (at least two segments) with different crystallographic orientations. Each segment experiences stress differently due to its orientation, and their resistance changes partially compensate each other, reducing the overall stress sensitivity while maintaining structural simplicity.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If resistor segments are oriented in orthogonal crystallographic directions, then stress sensitivity is reduced and resistance stability is improved, but the device complexity increases

Engineering Contradiction:

Improveresistance stabilityVSAvoidresistor configuration

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent assigns different crystallographic orientations to different resistor segments locally. Specifically, at least one segment has a first crystallographic orientation while another segment has a second crystallographic orientation that is orthogonal to the first. This local differentiation in orientation provides different stress responses in different parts of the device, achieving compensation without requiring complex overall structure.

Inventive Principle:

Principle #3Local quality

3Reliability

If multiple resistor segments with different orientations are used, then the resistance tolerance is tighter and reliability is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvedevice reliabilityVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent combines multiple resistor segments with different crystallographic orientations into a single integrated device structure. The segments are formed within the same semiconductor substrate and packaged together as one unit, allowing them to experience similar packaging and mounting stresses simultaneously. This merging approach ensures that the stress compensation effect is maintained while simplifying the manufacturing process compared to using separate devices.

Inventive Principle:

Principle #5Merging (Combining)

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 results in a more stable total resistance value, reducing the impact of packaging and mounting stress, leading to improved device yield, fewer field failures, and tighter resistance tolerance.

Implementation Method 1

Each of the resistor segments has a respective doped resistive region formed in a semiconductor substrate. The resistor segments are connected between first and second terminals. The first resistor body is configured to conduct a current in a first direction, and the second resistor body is configured to conduct the current in a second different direction.

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

Thermistors are sensitive to stress imposed by device packaging and mounting, leading to unpredictable resistance changes. The use of split resistor segments in semiconductor substrates, oriented in orthogonal crystallographic directions to reduce the net resistance change under stress.

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS11004929B2Trimmable silicon-based thermistor with reduced stress dependence

Publication Date: 2021.05.11 TEXAS INSTRUMENTS INC

AI summary

Various examples provide an electronic device that includes first and second resistor segments. Each of the resistor segments has a respective doped resistive region formed in a semiconductor substrate. The resistor segments are connected between first and second terminals. The first resistor segment is configured to conduct a current in a first direction, and the second resistor segment is configured to conduct the current in a second different direction. The directions may be orthogonal crystallographic directions of the semiconductor substrate.