Infrared Detector Optical Window for Small-Pixel Vacuum Packaging
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Solution Overview
Problem
Existing infrared detector manufacturing techniques face challenges in achieving a low detection surface area without compromising performance and vacuum level, particularly when using SOI wafers with limited silicon layer thickness, leading to degraded vacuum and performance due to complex and expensive processes.
Innovation Solution
Combining a multilayer interference filter with a periodic diffraction grating on the cover substrate, allowing anodic bonding with a spacer to increase hermetic package volume while maintaining performance by using a periodic diffraction grating that resists high bonding temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the detection surface area is decreased to form smaller pixels, then the infrared detector can achieve higher resolution, but the vacuum level in the hermetic package degrades due to increased proportion of desorbed molecules
Solution Approach 1:
The patent increases the height dimension of the hermetic package by bonding the cover substrate to the base substrate, thereby expanding the package volume in the vertical direction. This dimensional change compensates for the reduced detection surface area, maintaining an adequate vacuum level by providing more space relative to the fixed quantity of desorbed molecules.
2Reliability
If a multilayer interference filter is used to attenuate wavelengths from 2 to 8 micrometers, then the infrared detector performance is improved, but the manufacturing process becomes more complex and costly
Solution Approach 1:
The patent changes the filtering mechanism from multilayer interference filters to a periodic diffraction grating structure. This parameter change in the optical filtering approach simplifies the manufacturing process while maintaining the ability to attenuate unwanted wavelengths, as the diffraction grating can be formed through direct patterning rather than complex multi-layer deposition.
3Volume of stationary object
If the hermetic package volume is increased to maintain vacuum level, then the detection surface area can be reduced, but the package height must be increased which complicates the structure
Solution Approach 1:
The patent merges the cover substrate and base substrate into a single hermetic package structure through direct bonding. This combination allows the package volume to be increased by utilizing the full height between the two substrates, achieving the required vacuum maintenance without adding separate structural elements or complicating the overall package design.
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
Enables the production of infrared detectors with a low footprint and high vacuum level, reducing manufacturing complexity and costs by using a single shipping process, while ensuring effective radiation filtering and structural integrity.
Implementation Method 1
said periodic diffraction grating of the lower surface being configured to attenuate the incident radiation in a second wavelength interval in the range from y to 8 micrometers
Implementation Method 2
said multilayer interference filter or said periodic diffraction grating of the upper surface being configured to attenuate the incident radiation in a first wavelength interval in the range from 2 to x micrometers
Implementation Method 3
anodic bonding of a spacer onto a lower surface of said cover substrate
Data Source
AI summary
A method of forming an infrared detector includes defining an optical window in a cover substrate. Defining the optical window includes forming a multilayer interference filter or a periodic diffraction grating on an upper surface of the optical window and a periodic diffraction grating on the lower surface of the optical window. The method also includes performing anodic bonding of a spacer onto the cover substrate, transferring the cover substrate provided onto a base substrate, and hermetically bonding the spacer onto the base substrate.