Wafer-Level Getter Reflector for Microbolometer Vacuum Packaging
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Solution Overview
Problem
In microbolometer focal plane arrays, the non-imaging areas used for thin film getters become inadequate as the arrays are miniaturized, failing to maintain the package vacuum over the required lifetime, necessitating a reduction in thin film getter area without degrading sensor performance.
Innovation Solution
Combining the functions of the thin film getter and quarter wave reflector using opaque, reflective metals within the pixel structure, allowing the getter material to be placed under the sensor pixels, thereby reducing non-imaging areas while maintaining vacuum integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the focal plane array is miniaturized by reducing non-imaging areas, then the imaging sensor size is reduced, but the thin film getter area becomes inadequate to maintain package vacuum over the required lifetime
Solution Approach 1:
The patent combines the getter function and reflector function into a single integrated component. The quarter-wave reflector is modified to include getter material, allowing it to perform both optical reflection and vacuum maintenance functions simultaneously. This eliminates the need for separate getter areas in non-imaging regions.
Solution Approach 2:
The quarter-wave reflector is transformed into a multi-functional component that serves both as an optical reflector and as a getter. By incorporating getter material into the reflector structure, a single component performs multiple critical functions: reflecting infrared radiation and maintaining vacuum pressure.
2Reliability
If thin film getters are placed in non-imaging areas, then they do not interfere with sensor operation, but the available area becomes insufficient as the array is miniaturized
Solution Approach 1:
The patent moves the getter function from the lateral plane (non-imaging areas around the pixel array) to the vertical dimension (within the pixel structure itself). By placing getter material in the quarter-wave reflector beneath the pixel, the solution utilizes the third dimension to resolve the area constraint.
3Area of moving object
If the thin film getter area is reduced, then the imaging sensor size can be minimized, but the vacuum lifetime cannot be maintained
Solution Approach 1:
The getter and reflector are merged into a single integrated component, allowing sufficient getter material to be incorporated within the imaging array footprint without requiring additional non-imaging area. This maintains both compact size and adequate vacuum lifetime.
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 enables reliable vacuum maintenance and high pixel density, reducing the imaging sensor size while preserving resolution, enabling the use of tiled sensors with minimal gaps and maintaining pixel sensitivity.
Implementation Method 1
a quarter wave reflector beneath the pixel that reflects radiation back to the pixel
Implementation Method 2
a getter is used within the vacuum cavity to maintain low vacuum levels
Data Source
AI summary
An apparatus and method for a wafer level vacuum package uncooled microbolometer focal plane array (FPA) on a wafer level substrate with a thin film getter-reflector (G-R). The G-R removes gas from the vacuum package and is reflective in the frequency band of the FPA. Sensor pixels are supported about a quarter-wavelength above the G-R which is within the perimeter of the imaging array. The package is evacuated through a single aperture, and vacuum is maintained for the lifetime of the FPA. Imaging sensor size is reduced while maintaining resolution by reducing non-imaging area.