Image Sensor Light Balancing Structure for Green Pixel Crosstalk
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Solution Overview
Problem
Conventional image sensors experience asymmetric optical crosstalk, particularly affecting adjacent green pixels, leading to non-uniform signal readout and performance issues, which current compensation methods fail to adequately address.
Innovation Solution
Implementing a light balancing structure between the metal layer and photodiodes, comprising discrete segments that redirect longer wavelength light to mitigate asymmetric optical crosstalk by balancing crosstalk between adjacent green pixels, taking into account factors like chief ray angle and pixel position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional image sensors are used without light balancing structure, then device complexity is low, but asymmetric optical crosstalk occurs between adjacent green pixels causing non-uniform signal readout
Solution Approach 1:
A light balancing structure is introduced as an intermediary component between the color filter layer and the photodiode layer. This structure includes light balancing layers with specific refractive indices and thicknesses that mediate the optical interaction between adjacent pixels, redirecting longer wavelength light to balance crosstalk between green pixels while maintaining overall device functionality
Solution Approach 2:
The light balancing structure is divided into multiple discrete layers (first light balancing layer and second light balancing layer) with different optical properties. Each layer serves a specific function in managing different wavelength ranges, allowing precise control over optical crosstalk without requiring complete redesign of the entire sensor structure
2Measurement precision
If light balancing structure is implemented, then asymmetric optical crosstalk is reduced and pixel sensitivity uniformity is enhanced, but device complexity increases
Solution Approach 1:
The light balancing structure is designed with spatially varying properties - the first light balancing layer has different refractive index characteristics than the second layer, and their thicknesses are optimized for specific wavelength ranges. This local differentiation allows precise control over optical crosstalk in different regions of the spectrum without uniformly increasing complexity across the entire device
3Ease of manufacture
If conventional structures are used, then manufacturing process is simple, but optical crosstalk compensation is inadequate
Solution Approach 1:
The light balancing structure is designed to perform multiple functions simultaneously: it manages optical crosstalk between adjacent pixels, controls light distribution across different wavelength ranges, and maintains compatibility with existing semiconductor manufacturing processes. The layers can be integrated into standard fabrication sequences without requiring entirely new manufacturing approaches
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
The light balancing structure effectively reduces asymmetric optical crosstalk, enhancing the uniformity of pixel sensitivity and improving image sensor performance by minimizing signal discrepancies between adjacent green pixels.
Implementation Method 1
asymmetric optical crosstalk from light propagating through the first type of pixel cells towards the second type of pixel cells
Implementation Method 2
discrete segments optically aligned with the first type of pixel cells to redirect light
Data Source
AI summary
An image sensor is described. The image sensor includes a plurality of pixel cells arranged to form an image sensor array disposed in or on a semiconductor substrate, a proximal metal layer, and a light balancing structure. Each pixel cell included in the plurality of pixel cells includes one or more photodiodes disposed between a first side and a second side, opposite of the first side, of the semiconductor substrate. The proximal metal layer is included in an interconnect stack disposed proximate to the second side of the semiconductor substrate. The light balancing structure is disposed between the second side of the semiconductor substrate and the proximal metal layer. The light balancing structure includes a plurality of discrete segments optically aligned with a first type of pixel cells included in the plurality of pixel cells.