Stacked Infrared Imaging Pixels With In-Pixel Readout Circuits
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Solution Overview
Problem
Conventional thermal infrared solid-state imaging elements face limitations due to a hollow heat insulation structure, which restricts the area for temperature detection, supporting legs, and wiring, making it difficult to provide a correction circuit for each pixel and increasing chip area as the readout circuit is formed outside the pixel array region.
Innovation Solution
The solution involves stacking the circuit region, supporting leg region, and infrared detection region as separate layers, allowing for increased diode density in the detection region, longer supporting leg wiring for improved thermal time constant, and integrating the readout and correction circuits within the pixel, enabling miniaturization and high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hollow heat insulation structure is used with temperature detection part, supporting legs, and wiring arranged in the same plane, then the structure is simple to manufacture, but the area for temperature detection is limited and the chip area increases
Solution Approach 1:
The patent transitions from a planar arrangement to a three-dimensional stacked structure. The temperature detection part is positioned on a first substrate, supporting legs extend vertically to connect to a second substrate, and wiring is arranged in multiple layers. This vertical stacking enables the detection area to expand in the thickness direction rather than being constrained to a single plane, effectively increasing the detection area without complicating the manufacturing process.
2Ease of manufacture
If a hollow heat insulation structure is used with components arranged in the same plane, then the structure is easy to manufacture, but correction circuits cannot be provided for each pixel
Solution Approach 1:
The stacked configuration provides vertical space between the first and second substrates, allowing correction circuits to be integrated within this three-dimensional structure. The supporting legs and wiring can be routed through multiple layers, enabling each pixel to have its own correction circuit without requiring external placement, thus achieving both manufacturing simplicity and per-pixel correction capability.
3Device complexity
If the readout circuit is formed outside the pixel array region, then the pixel array can be simplified, but the chip area increases
Solution Approach 1:
The patent merges the readout circuit with the pixel array by integrating it within the stacked structure. The second substrate and the space between substrates are utilized to house readout circuit components, allowing them to occupy the same vertical volume as the pixel array rather than requiring additional horizontal space. This integration maintains pixel array simplicity while preventing chip area expansion.
4Measurement precision
If the number of diodes is increased to improve detection sensitivity, then the detection sensitivity increases, but the area required for arranging diodes increases
Solution Approach 1:
The patent arranges diodes in a three-dimensional configuration across multiple substrates and layers rather than confining them to a single plane. This vertical stacking allows a larger number of diodes to be packed into a compact volume, increasing detection sensitivity through higher diode density without proportionally increasing the horizontal chip area.
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 approach enhances infrared detection sensitivity, allows for miniaturization of the imaging element, and provides the capability to form correction circuits within each pixel, reducing the chip area and eliminating the need for external readout circuits.
Implementation Method 1
an infrared detection part 13 held on the supporting leg wiring 4 and provided with a diode 2
Implementation Method 2
a semiconductor element such as a diode is used as a temperature sensor constituting a pixel
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
This infrared imaging element includes: a substrate (31) which has a front surface and a back surface and to which a circuit unit (32) is provided; a support leg wiring line (4) that is disposed above the front surface of the substrate (31); and an infrared-ray detection unit (13) which is held on the support leg wiring line (4) and to which a diode (2) electrically connected to the circuit unit (32) via the support leg wiring line (4) is provided, wherein a temperature change of the infrared-ray detection unit (13) is detected as an electrical signal change of the diode (2) by the circuit unit (32). The substrate (31), the support leg wiring line (4), and the infrared-ray detection unit (13) are laminated at intervals in a direction perpendicular to the front surface of the substrate (31).