Image Sensor Pixel With Color Filter Window
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Solution Overview
Problem
Conventional image sensors have limited dynamic range and low sensitivity to long wavelengths of light, which affects the quality of images captured, especially in varying light conditions.
Innovation Solution
The implementation of pixels with a color filter window and an additional photosensitive layer positioned deeper in the substrate, allowing for improved light sensitivity and dynamic range by guiding light through dielectric materials and using microlenses to focus light on both layers, enabling separate or combined signal readout for high dynamic range image production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixels are used, then the image sensor can capture images, but the dynamic range is limited and sensitivity to long wavelengths is low
Solution Approach 1:
The pixel is divided into multiple photosensitive layers (first and second photosensitive layers) positioned at different depths in the substrate. Each layer captures light at different wavelengths and intensities, with the first layer capturing shorter wavelengths and the second layer capturing longer wavelengths. This segmentation allows the sensor to achieve high dynamic range by combining signals from multiple layers, effectively solving the limited dynamic range problem of conventional single-layer pixels.
Solution Approach 2:
The invention transitions from a conventional two-dimensional pixel structure to a three-dimensional stacked structure by adding depth dimension with multiple photosensitive layers at different depths. The first photosensitive layer is positioned at a first depth and the second photosensitive layer is positioned at a second depth greater than the first depth. This dimensional change enables simultaneous capture of multiple wavelength bands and light intensities, dramatically improving dynamic range and long wavelength sensitivity.
2Reliability
If a color filter window is added to improve light sensitivity, then sensitivity to long wavelengths improves, but the device structure becomes more complex
Solution Approach 1:
The color filter is segmented into multiple regions including a first color filter region and a second color filter region positioned at different locations. The second color filter region is positioned to allow light to reach the second photosensitive layer through the first photosensitive layer. This segmentation of the color filter structure enables selective wavelength transmission to different photosensitive layers, improving light sensitivity while maintaining a systematic and manufacturable structure.
Solution Approach 2:
The first photosensitive layer serves multiple functions: it captures light for color information, allows transmission of certain wavelengths to the second photosensitive layer, and acts as a structural element in the stacked configuration. The color filter similarly serves multiple functions by selectively filtering wavelengths for different layers. This multi-functionality reduces the need for additional separate components, thereby improving light sensitivity without proportionally increasing device complexity.
3Reliability
If multiple photosensitive layers are used to improve dynamic range, then sensitivity to varying light conditions improves, but manufacturing precision requirements increase
Solution Approach 1:
The pixel structure is segmented into distinct functional layers (first photosensitive layer, second photosensitive layer, color filter regions) that can be manufactured and positioned independently. Each layer has specific positioning requirements relative to others, with the second photosensitive layer positioned deeper in the substrate than the first. This segmentation approach, combined with standard semiconductor manufacturing techniques, enables controlled positioning while maintaining manufacturing feasibility.
Solution Approach 2:
The invention utilizes vertical positioning (depth parameter) as a key differentiator between layers, with the first photosensitive layer at a first depth and the second photosensitive layer at a second depth greater than the first depth. This parameter-based differentiation (using depth rather than lateral positioning) simplifies manufacturing precision requirements, as vertical layering can be more easily controlled through standard semiconductor fabrication processes than precise lateral alignment of multiple sensitive elements.
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 configuration enhances the sensitivity to both low and high light conditions and longer wavelengths, allowing for the production of high dynamic range images with reduced saturation and blooming cross-talk, thereby improving image sensor performance.
Implementation Method 1
Each pixel includes a photosensitive layer that receives incident photons (light) and converts the photons into electrical signals
Implementation Method 2
using microlenses to focus light on both layers
Data Source
AI summary
An imaging pixel may include an upper substrate layer with a photosensitive layer and a lower substrate with a photosensitive layer. A color filter layer may be formed over the upper substrate layer. The color filter layer may include a color filter window that allows light to pass through the upper substrate layer to the photosensitive layer in the lower substrate. The color filter window may be formed from a dielectric material or from a color filter element with a different color than the surrounding color filter element. A metal interconnect layer may couple the lower substrate layer to the upper substrate layer. The color filter window may be formed in the central portion of a pixel, or between multiple pixels in an image sensor.