Infrared Detector Silicon Layer Diode Connection
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Solution Overview
Problem
Conventional infrared solid state imaging devices experience mechanical distortion and reliability issues due to thermal expansion coefficient differences between metal interconnection layers and silicon substrates, leading to increased 1/f noise and vulnerability to mechanical vibration and impact.
Innovation Solution
The solution involves forming first and second PN junction diodes in a silicon layer separated from a support substrate, with a metal film connection on a concave portion spanning both P-type and N-type regions, reducing mechanical distortion and noise by dispersing stress and increasing stiffness against thermal and mechanical forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal silicide or metal layers are used to connect diodes, then electrical connectivity is achieved, but thermal expansion coefficient difference causes mechanical distortion and reliability degradation
Solution Approach 1:
The patent applies homogeneity by using a silicon layer (same material as the substrate) to form the connection structure between diodes. This eliminates the material heterogeneity that causes thermal expansion mismatch, thereby preventing mechanical distortion while maintaining electrical connectivity and improving mechanical strength.
2Measurement precision
If diodes are connected in series to enhance temperature sensitivity, then sensitivity improves, but 1/f noise increases due to crystal defects from distortion
Solution Approach 1:
By using a homogeneous silicon layer for connections, the patent eliminates thermal expansion-induced distortion that creates crystal defects. This allows diodes to be connected in series to enhance temperature sensitivity without generating 1/f noise from mechanical stress-related crystal defects.
3Measurement precision
If the temperature sensor portion is separated from the substrate to improve heat sensitivity, then heat sensitivity improves, but mechanical strength is reduced
Solution Approach 1:
The patent uses a thin silicon layer (separated from the substrate to improve heat sensitivity) and reinforces it with a silicon oxide film. This thin-film structure maintains mechanical strength while allowing thermal separation for improved heat sensitivity, resolving the contradiction between sensitivity and strength.
4Area of moving object
If picture elements are downsized to reduce device size, then miniaturization is achieved, but mechanical distortion increases due to thermal expansion differences
Solution Approach 1:
The patent uses a homogeneous silicon layer for interconnections, eliminating material mismatch that causes thermal expansion distortion. This allows picture elements to be downsized for miniaturization without increasing mechanical distortion, as the uniform silicon structure accommodates size reduction without stress concentration.
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 reduces noise and mechanical vulnerability, enhancing the sensitivity and reliability of infrared detectors, making them suitable for portable and monitoring applications while maintaining high sensitivity and low noise levels.
Implementation Method 1
connecting the first PN junction diode and the second PN junction diode by a metal film formed on a surface of a concave portion spreading both of the P-type first region and the N-type second region
Implementation Method 2
it is necessary that an infrared temperature sensor portion composed of an infrared absorption portion that incident infrared rays are converted to heat and a thermoelectric conversion portion is separated from the substrate which has large heat capacity to improve the heat sensitivity
Implementation Method 3
an infrared absorption portion that incident infrared rays are converted to heat
Implementation Method 4
converts infrared rays absorbed by an infrared absorption structure to heat and temperature changes caused by the heat convert electric signals
Data Source
AI summary
An infrared detector includes a first PN junction diode and a second PN junction diode which are formed in a silicon layer formed apart from a support substrate, the silicon layer having a P-type first region and an N-type second region, wherein the first PN junction diode is composed of the P-type first region and an N-type first region formed in the P-type first region at a position separated from the N-type second region, and the second PN junction diode is composed of the N-type second region and a P-type second region formed in the N-type second region at a position separated from the P-type first region, and wherein the first PN junction diode and the second PN junction diode are connected by a metal film formed on a surface of a concave portion spreading both of the P-type first region and the N-type second region.