CMOS Infrared Detector Multi-Layer Structure
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Solution Overview
Problem
The existing infrared detectors face challenges due to process incompatibility between the CMOS measuring circuit and the MEMS infrared sensing structure, leading to performance inconsistencies, low productivity, high cost, and limitations in miniaturization.
Innovation Solution
An infrared detector with a multi-layer structure based on the CMOS process is developed, where both the CMOS measuring circuit system and the CMOS infrared sensing structure are fabricated using the CMOS process, eliminating the need for a sacrificial polyimide layer and enhancing process compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the infrared sensing structure is fabricated by MEMS process with polyimide sacrificial layer, then the sensing structure can be formed, but the process is incompatible with CMOS process and release is incomplete
Solution Approach 1:
The patent changes the sacrificial layer material from polyimide to silicon oxide, altering the chemical and physical parameters to achieve complete release via CF4 plasma etching while maintaining CMOS process compatibility. This material substitution resolves both the incompatibility issue and the incomplete release problem.
Solution Approach 2:
The patent uses silicon oxide as a disposable sacrificial layer that is completely removed after serving its temporary purpose of defining the cavity structure. This approach eliminates the need for polyimide and enables complete release without affecting the final device performance.
2Ease of manufacture
If polyimide is used as sacrificial layer, then the sensing structure can be released, but the vacuum degree is affected and film growth temperature is limited
Solution Approach 1:
The patent changes the sacrificial layer material from polyimide to silicon oxide, which allows for higher film growth temperatures without compromising the release process. Silicon oxide can be completely removed by CF4 plasma etching, enabling subsequent high-temperature processing steps that were previously limited by polyimide's thermal stability.
3Ease of manufacture
If polyimide sacrificial layer is used, then the sensing structure can be formed, but the resonator height is inconsistent affecting main wavelength
Solution Approach 1:
The patent changes the sacrificial layer material to silicon oxide, which can be deposited with atomic layer precision using PECVD or sputtering techniques. This material enables consistent resonator height control and maintains uniform cavity dimensions, thereby ensuring accurate main wavelength performance that was difficult to achieve with polyimide.
4Ease of manufacture
If MEMS process is used for infrared sensing structure, then the structure can be fabricated, but the control is worse than CMOS process restricting performance consistency
Solution Approach 1:
The patent merges the infrared sensing structure fabrication with the CMOS process by using silicon oxide sacrificial layer and PECVD/sputtering techniques that are standard in CMOS manufacturing. This integration allows both the sensing structure and readout circuit to be fabricated in the same cleanroom environment using compatible processes, significantly improving performance consistency and yield.
5Ease of manufacture
If MEMS process is used for infrared sensing structure, then the structure can be fabricated, but the productivity is low and cost is high preventing mass production
Solution Approach 1:
The patent combines the infrared sensing structure fabrication with the CMOS process flow, allowing both to be manufactured in the same cleanroom environment using standard CMOS equipment. This integration eliminates the need for separate MEMS processing lines, significantly improving productivity and enabling cost-effective mass production while maintaining sensing structure quality.
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 solution achieves high yield, low cost, and high productivity, enabling large-scale integrated production of chips with improved detection sensitivity, longer detection distance, and better performance consistency.
Implementation Method 1
the heat-sensitive dielectric layer is configured to convert a temperature change corresponding to infrared radiation absorbed by the heat-sensitive dielectric layer into a resistance change
Implementation Method 2
the absorption plate is configured to convert an infrared signal into an electrical signal
Implementation Method 3
the CMOS infrared sensing structure includes a resonant cavity composed of the reflecting layer and the heat-sensitive dielectric layer
Implementation Method 4
the suspended micro-bridge structure for controlling heat transfer
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
An infrared detector with a multi-layer structure based on a CMOS process. A CMOS measuring circuit system (1) and a CMOS infrared sensing structure (2) in the infrared detector are both fabricated by using the CMOS process, and a CMOS manufacturing process comprises a metal interconnection process, a through hole process, an IMD process and an RDL process. In the infrared detector with the multi-layer structure, a first columnar structure (61) comprises at least one layer of solid columnar structure and/or at least one layer of hollow columnar structure, a second columnar structure (62) comprises at least one layer of solid columnar structure and/or at least one layer of hollow columnar structure, at least one hole-shaped structure is formed in an absorption plate (10), and the hole-shaped structure at least penetrates a dielectric layer in the absorption plate (10); and/or, at least one hole-shaped structure is formed in a beam structure (11). Problems of low performance, low pixel scale, low yield and poor consistency of a conventional infrared detector based on an MEMS process are solved, a degree of planarization of the absorption plate (10) is optimized, a thermal conductivity of the beam structure (11) is reduced, and a performance of the infrared detector is optimized.