Energy Conversion Layer for Image Sensor Blue Light Absorption
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Solution Overview
Problem
Current image sensors are inefficient in absorbing light with higher energy wavelengths, such as blue wavelengths, compared to lower energy wavelengths like red.
Innovation Solution
Incorporating an energy conversion layer in the image sensor fabrication process, which converts higher energy light (e.g., blue) into lower energy light (e.g., red, yellow, or green) to enhance light absorption, using materials like YAG:Ce crystals or cesium iodide scintillators, and positioning this layer under the color filter to direct converted light to the photodiode layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an energy conversion layer is added to convert high-energy light to low-energy light, then light absorption efficiency for blue wavelengths is improved, but device complexity increases
Solution Approach 1:
An energy conversion layer comprising scintillator crystals (such as cesium iodide or YAG:Ce) is introduced as an intermediary component between the blue color filter and the photodiode. This layer converts high-energy blue photons into lower-energy photons with wavelengths better matched to the photodiode's spectral response, thereby improving light absorption efficiency without requiring fundamental changes to the existing sensor architecture
Solution Approach 2:
The energy conversion layer utilizes composite scintillator materials such as cesium iodide crystals or yttrium aluminum garnet doped with cerium (YAG:Ce). These composite materials are specifically selected for their ability to convert blue light wavelengths into wavelengths that align with the photodiode's peak sensitivity, thus resolving the spectral mismatch issue while maintaining a relatively simple structural integration
2Productivity
If the energy conversion layer is positioned directly under the color filter, then light conversion efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The energy conversion layer is positioned and integrated during the fabrication process at an early stage, specifically between the formation of the color filter layer and the photodiode layer. This preliminary positioning ensures optimal alignment and light path configuration before subsequent processing steps, maximizing light conversion efficiency while establishing a reproducible manufacturing sequence that manages precision requirements
3Measurement precision
If scintillator crystals are used for energy conversion, then detection capability for blue light is improved, but cost of materials increases
Solution Approach 1:
The patent evaluates and selects scintillator materials based on key parameters including conversion efficiency, spectral match to photodiode response, and material cost. By optimizing the crystal composition (such as using YAG:Ce as an alternative to cesium iodide) and controlling crystal size and distribution within the energy conversion layer, the solution achieves improved blue light detection capability while managing material costs through parameter optimization rather than simply using the most expensive available materials
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 significantly increases the light absorption efficiency of the image sensor across specific light spectra, improving detection capabilities for wavelengths previously difficult to sense, like blue light, thereby enhancing image capture quality.
Implementation Method 1
converting the electromagnetic radiation into electromagnetic radiation having a second wavelength range
Implementation Method 2
an energy conversion layer to receive the light of the first color and to convert the light of the first color into light of a second color
Data Source
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AI summary
A system and method for applying a layer of material in the image sensor fabrication process in order to increase the absorption of specific range light spectrum by the image sensor is described. The mechanism adopted is by converting light rays from higher energy range (shorter wavelength) to lower energy range (longer wavelength) such that the light absorption by the image sensor can be increased.