Infrared Sensor Structure with Substrate Light Blocking
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Solution Overview
Problem
Existing infrared (IR) radiation sensors are large, expensive, fragile, and require packaging with windows to block visible light, limiting their size, cost-effectiveness, sensitivity, and robustness for applications like non-contact temperature measurement and remote gas concentration detection.
Innovation Solution
A CMOS-processing-compatible IR sensor chip with first and second thermopile junctions connected in series, where the first junction is thermally insulated from the substrate by a cavity, and bonded to a printed circuit board using bump conductors, eliminating the need for a large package with an infrared window, and featuring a robust dielectric membrane reinforced with a cap layer to prevent contamination and enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional packaging with infrared windows is used, then visible light blocking is achieved, but device size and cost increase
Solution Approach 1:
The patent extracts the visible light blocking function from the traditional package window and relocates it to the substrate level. The silicon substrate itself is used to block visible light while allowing infrared radiation to pass through to the thermopile junctions, eliminating the need for separate package windows and reducing overall device size.
Solution Approach 2:
The silicon substrate serves multiple functions simultaneously: it provides mechanical support, blocks visible light, and allows infrared transmission. This multi-functionality eliminates the need for additional packaging components, reducing device complexity and size while maintaining the required optical filtering.
2Object-affected harmful factors
If traditional packaging with infrared windows is used, then visible light blocking is achieved, but manufacturing cost increases
Solution Approach 1:
The patent removes the expensive package window component and integrates the visible light blocking function directly into the silicon substrate. This eliminates the need for separate infrared-transparent window materials and complex packaging assembly, significantly reducing manufacturing costs.
Solution Approach 2:
By making the silicon substrate multi-functional (mechanical support, visible light blocking, infrared transmission), the patent eliminates the need for additional expensive packaging components and assembly steps, thereby reducing overall manufacturing cost.
3Measurement precision
If the first thermopile junction is thermally insulated from the substrate, then sensitivity to IR radiation is improved, but device complexity increases
Solution Approach 1:
The patent extracts the thermal insulation function and implements it through a simple cavity structure beneath the first thermopile junction. This cavity isolates the junction from the substrate thermally while maintaining structural simplicity, allowing the junction to respond sensitively to infrared radiation without complex insulation layers.
Solution Approach 2:
Instead of adding complex thermal insulation layers in the vertical dimension, the patent uses a cavity structure that provides thermal isolation through spatial separation. This dimensional approach achieves thermal insulation with minimal added complexity.
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
The solution results in smaller, more economical, and more accurate IR sensors with improved sensitivity and robustness, capable of measuring IR radiation without the need for expensive packaging, while maintaining high accuracy and reliability.
Implementation Method 1
the first junction is thermally insulated from the substrate by a cavity
Implementation Method 2
The silicon substrate transmits IR radiation to the thermopile while blocking visible light
Implementation Method 3
The silicon substrate transmits IR radiation to the thermopile while blocking visible light
Implementation Method 4
first and second thermopile junctions connected in series to form a thermopile
Data Source
AI summary
A radiation sensor (27) includes a radiation sensor chip (1) including first (7) and second (8) thermopile junctions connected to form a thermopile (7,8). The first thermopile junction is disposed in a floating portion of a dielectric membrane (3) thermally insulated from a silicon substrate (2) of the chip, and the second thermopile junction is disposed in the dielectric membrane directly adjacent to the substrate. Bump conductors (28) are bonded to corresponding bonding pads (28A) coupled to the thermopile (7,8) to physically and electrically connect the chip to conductors on a printed circuit board (23). The silicon substrate transmits infrared radiation to the thermopile while blocking visible light.