Infrared Imaging Element Room-Temperature Bonding
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Solution Overview
Problem
Conventional uncooled infrared sensors face challenges in cost reduction and thermal stress during the seal process due to the use of silicon seal plates and thermal melting, which complicates vacuum sealing and affects reliability.
Innovation Solution
The infrared imaging element employs a Silicon On Insulator (SOI) substrate with a buried oxide layer as the infrared absorption film and uses the silicon support substrate as an infrared transmission window, allowing for direct bonding at room temperature without solder, and selecting a less expensive seal substrate like quartz, thereby reducing thermal stress and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon seal plates are used for vacuum sealing, then infrared transmission is achieved, but manufacturing cost increases and thermal stress occurs during soldering
Solution Approach 1:
The patent replaces expensive silicon seal plates with inexpensive glass seal plates. Glass is a cheaper material that can perform the sealing function effectively without requiring the same thermal processing as silicon, thereby reducing manufacturing cost while maintaining vacuum sealing capability.
Solution Approach 2:
The patent changes the joining temperature parameter from high temperature (soldering at several hundred degrees) to low temperature (adhesive bonding at room temperature or slightly elevated temperatures). This parameter change eliminates thermal stress during assembly while maintaining reliable vacuum sealing.
2Strength
If thermal melting of solder is used for joining sensor substrate and seal plate, then strong bonding is achieved, but temperature rise of several hundred degrees causes great thermal stress
Solution Approach 1:
The patent replaces the thermal-mechanical soldering process with a chemical bonding process using adhesives. Instead of relying on thermal melting and mechanical interlocking of solder, the system uses chemical adhesion to achieve strong bonding between the sensor substrate and seal plate without high temperature exposure.
Solution Approach 2:
The patent fundamentally changes the temperature parameter from high temperature (soldering) to low temperature (adhesive bonding). This parameter change maintains adequate joining strength while eliminating the thermal stress that compromises reliability.
3Use of energy by moving object
If silicon seal plates are used, then infrared transmission is achieved, but drastic cost down in the seal process is difficult
Solution Approach 1:
The patent substitutes expensive silicon with inexpensive glass for the seal plate. Glass provides adequate infrared transmission for the application while being significantly cheaper than silicon, enabling drastic cost reduction in the sealing process.
Solution Approach 2:
The patent uses glass as a substitute material that copies the essential function of silicon (infrared transmission and sealing) without requiring the same expensive processing. Glass can be sealed using simpler, lower-cost processes while maintaining the necessary optical and sealing properties.
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 enhances infrared absorption efficiency, stabilizes the vacuum environment, and lowers manufacturing costs by eliminating the need for thermal soldering, thus improving the reliability and productivity of the infrared imaging element.
Implementation Method 1
a first insulation film on the first cavity absorbing the incident infrared rays and converting the incident infrared rays to heat
Implementation Method 2
the diodes converting the heat obtained by the first insulation film to an electric signal
Implementation Method 3
uses the silicon support substrate as an infrared transmission window
Data Source
AI summary
An infrared imaging element according to an embodiment includes: a semiconductor substrate including a stacked structure of a silicon first substrate, and a first insulation film, first cavities being provided on a surface of the first substrate; an infrared detection unit provided in the semiconductor substrate and including, detection cells provided respectively over the first cavities, each of the detection cells having diodes and a second insulation film, the first insulation film converting incident infrared rays to heat, the diodes converting the heat obtained by the first insulation film to an electric signal, a third insulation film having a top face located at a greater distance from the semiconductor substrate as compared with a top face of the second insulation film; and a second substrate provided over the third insulation film. A second cavity is formed between the second substrate and the infrared detection unit.