Wafer Level Vacuum Packaging for Thermal Imaging Sensors
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Solution Overview
Problem
Conventional uncooled infrared (IR) detectors are complex and costly due to the need for mechanical components and bulky optical modules, making them unsuitable for compact or mobile applications and inefficient in chip-scale packaging.
Innovation Solution
The development of CMOS devices embedded with MEMS components, specifically thermoelectric-based IR sensors, using wafer-level vacuum packaging to eliminate mechanical components and simplify the packaging process, allowing for compact and cost-effective IR detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional uncooled IR detectors use mechanical components for calibration, then offset correction is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces mechanical shutters with a digital calibration approach using a dark reference pixel and offset correction circuitry. The dark reference pixel captures thermal radiation without optical components, and the offset correction circuitry digitally subtracts this reference from the sensor output, eliminating the need for mechanical moving parts while achieving the same calibration function.
Solution Approach 2:
The patent extracts and removes the mechanical shutter component from the system entirely. By implementing calibration through software/digital processing of reference pixel data, the mechanical calibration mechanism is completely eliminated, reducing device complexity and removing moving parts that require maintenance.
2Reliability
If mechanical shutters are used for microbolometer calibration, then offset correction is achieved, but manufacturing cost increases
Solution Approach 1:
The patent substitutes mechanical shutters with an integrated digital calibration system consisting of a dark reference pixel and offset correction circuitry. This approach eliminates the need for precision mechanical components, reducing manufacturing complexity and cost while maintaining calibration accuracy through digital processing.
Solution Approach 2:
The dark reference pixel serves as a self-calibrating element that continuously provides reference data for offset correction. The system automatically performs calibration using its own internal reference pixel, eliminating the need for external mechanical calibration mechanisms and reducing manufacturing costs.
3Reliability
If mechanical components are required for microbolometers, then calibration is possible, but device size increases
Solution Approach 1:
The patent replaces bulk mechanical shutters with a compact digital calibration system integrated directly into the sensor chip. The dark reference pixel and offset correction circuitry are fabricated using standard CMOS processes, achieving calibration capability without the volume requirements of mechanical components, thus enabling compact device design.
4Measurement precision
If bulky optical module assembly is used for focusing, then image sharpness increases, but device compactness decreases
Solution Approach 1:
The patent replaces bulky mechanical optical focusing modules with a focal plane array sensor that captures infrared radiation directly at the focal plane. This eliminates the need for complex mechanical optical assemblies, achieving image sharpness through precise sensor positioning and focal plane detection rather than mechanical optical components.
5Ease of manufacture
If chip scale packaging is used for IR detectors, then manufacturing is simplified, but packaging efficiency decreases
Solution Approach 1:
The patent merges the sensor chip fabrication with the packaging process by using wafer-level vacuum packaging. Multiple sensor chips are packaged simultaneously in a vacuum environment at the wafer level before singulation, combining manufacturing and packaging operations into a single integrated process, thereby improving both simplicity and efficiency.
Solution Approach 2:
The patent performs vacuum packaging at the wafer level before the chips are singulated (cut apart). This preliminary packaging action allows multiple chips to be sealed in vacuum simultaneously, improving packaging efficiency compared to sealing individual chips after fabrication. The vacuum environment is established before the chips are separated, enabling batch processing.
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 results in cost-effective, compact IR detectors with improved manufacturing efficiency and suitability for mobile applications by eliminating mechanical components and using wafer-level vacuum packaging.
Implementation Method 1
the cap creates a cap cavity over the MEMS region, the cap cavity is a vacuum cavity
Data Source
AI summary
A complementary metal oxide semiconductor (CMOS) device embedded with microelectromechanical system (MEMS) components in a MEMS region. The MEMS components, for example, are infrared (IR) thermosensors. The device is encapsulated with a CMOS compatible IR transparent cap to hermetically seal the device using wafer-level vacuum packaging techniques.