Infrared Sensor Contact Holes for Heat Conductance Reduction

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Solution Overview

Problem

In thermal infrared solid-state image pickup apparatuses, the heat conductance of support legs increases when the pixel pitch is narrowed, leading to disconnection issues in the support leg metal wiring layer due to the vertical shape of contact holes formed using traditional PVD technology, which complicates the formation of thin film metal wiring layers.

Innovation Solution

The contact holes in the infrared sensor pixels are designed with forward tapered shapes to facilitate the formation of thin film support leg metal wiring layers, preventing heat conductance increases and ensuring stable electrical connections even when support leg lengths are short.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the pixel pitch is narrowed to downsize the apparatus, then the chip size and optical lens can be reduced, but the support leg length must be shortened which increases the heat conductance of support legs

Engineering Contradiction:

Improvechip sizeVSAvoidheat conductance of support legs

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The contact hole shape is changed from vertical to forward tapered, which modifies the deposition geometry and enables better metal film formation on inclined surfaces, allowing thin film support leg metal wiring layers to be formed effectively even with short support leg lengths

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The support leg metal wiring layer is formed as a thin film by optimizing the contact hole geometry for PVD deposition, reducing the heat conductance of the support legs while maintaining electrical connectivity

Inventive Principle:

Principle #30Flexible shells and thin films

2Loss of energy

If the support leg metal wiring layer is formed as a thin film to reduce heat conductance, then the heat conductance decreases, but disconnection occurs in the support leg metal wiring layer due to vertical contact hole side walls

Engineering Contradiction:

Improveheat conductance of support legsVSAvoidelectrical connection stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The contact hole shape parameter is changed from vertical side walls to forward tapered geometry, which enables uniform metal film deposition on inclined surfaces and prevents disconnection in thin film structures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The deposition process is optimized by changing the contact hole geometry from vertical to tapered, allowing PVD technology to effectively deposit metal films on inclined surfaces rather than vertical walls, preventing film disconnection

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If the support leg length is set to the maximum within pitch between pixels to improve heat insulation, then the heat conductance decreases, but the pixel pitch cannot be narrowed which prevents downsizing

Engineering Contradiction:

Improveheat conductance of support legsVSAvoidchip size

Core Design Contradiction:

Loss of energyVSVolume of moving object

Solution Approach 1:

The contact hole shape is changed to forward tapered, which modifies the deposition geometry and enables better metal film formation on inclined surfaces, allowing thin film support leg metal wiring layers to be formed effectively even with short support leg lengths

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Inventive Principle:

Principle #30Flexible shells and thin films

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 design balances the reduction of pixel pitch with minimized heat conductance, enhancing the reliability and efficiency of the infrared sensor while preventing disconnection issues, thus contributing to the downsizing and cost reduction of the infrared solid-state image pickup apparatus.

Implementation Method 1

the contact hole is formed by etching an insulating layer that is formed by deposition

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

the use of a known physical vapor deposition (PVD) technology in the forming of the support leg metal wiring layer

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS10274374B2Infrared sensor and infrared solid-state image pickup apparatus

Publication Date: 2019.04.30 MITSUBISHI ELECTRIC CORP

AI summary

An infrared sensor includes an infrared sensor pixel in which a contact hole is formed to electrically connect a metal wiring layer and a support leg metal wiring layer that is located inside a support leg. The metal wiring layer is electrically connected to a signal reading circuit. The contact hole is formed by etching an insulating layer that is formed by deposition so as to cover the metal wiring layer, and has a bottom portion and a side wall portion that are each shaped into a forward tapered shape.