Backside-Illuminated Photosensor Array With Junction Depth Spectral Selectivity
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Solution Overview
Problem
Conventional backside-illuminated photosensor arrays require color filters on the backside surface with different light transmission and absorption properties for each pixel, which complicates the manufacturing process and may affect circuit performance.
Innovation Solution
A monolithic backside-sensor-illumination image sensor with pixel sensors having junction depths that determine their spectral sensitivity, allowing for red, yellow, and panchromatic sensitivity without the need for color filters, where red and green signals are derived from specific pixel sensors and blue signals are calculated by subtracting yellow from white signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If color filters are deposited on the backside surface of BSI photosensor arrays, then spectral selectivity for color detection is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent changes the physical parameter of junction depth in the photodiode structure to achieve spectral selectivity. By creating photodiodes with different junction depths (shallow, intermediate, deep), each photodiode becomes sensitive to different wavelengths of light, eliminating the need for color filters on the backside surface.
2Adaptability or versatility
If color filters are used on the backside surface, then color detection capability is improved, but light absorption characteristics are degraded
Solution Approach 1:
The invention changes the operational parameter by utilizing different junction depths within the semiconductor substrate to achieve wavelength-selective detection. This approach allows direct detection of different colors without energy loss through filter materials, as each photodiode naturally responds to specific wavelengths based on its junction depth.
3Measurement precision
If color filters are deposited on the backside surface, then spectral separation is improved, but circuit performance is affected
Solution Approach 1:
The patent changes the structural parameter of photodiode junction depth to achieve spectral separation, eliminating the need for backside color filters that could interfere with circuit performance. The different-depth photodiodes provide inherent spectral filtering through their physical structure, maintaining circuit reliability while achieving color detection.
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 eliminates the need for color filters on the backside surface, simplifying the manufacturing process and improving light absorption characteristics, enabling efficient color signal generation without affecting circuit performance.
Implementation Method 1
one deep junction, of depth about 2 microns, sensing red light, another intermediate-depth junction, of depth about 0.6 microns, sensing green light, and another shallow junction, of depth about 0.2 microns, sensing blue light
Data Source
AI summary
A monolithic backside-sensor-illumination (BSI) image sensor has a sensor array is tiled with a multiple-pixel cells having a first pixel sensor primarily sensitive to red light, a second pixel sensor primarily sensitive to red and green light, and a third pixel sensor having panchromatic sensitivity, the pixel sensors laterally adjacent each other. The image sensor determines a red, a green, and a blue signal comprising by reading the red-sensitive pixel sensor of each multiple-pixel cell to determine the red signal, reading the sensor primarily sensitive to red and green light to determine a yellow signal and subtracting the red signal to determine a green signal. The image sensor reads the panchromatic-sensitive pixel sensor to determine a white signal and subtracts the yellow signal to provide the blue signal.