Pixel Light Guide Structure for Autofocus Image Sensors
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Solution Overview
Problem
Existing image sensing devices face challenges in achieving high light reception efficiency and accurate autofocus functions due to isolation structures between photoelectric conversion elements, which can lead to light reception efficiency deterioration and manufacturing inefficiencies.
Innovation Solution
The image sensing device incorporates a light guide unit that divides incident light into multiple beams without forming isolation structures between photoelectric conversion elements, using layers with varying refractive indices to guide light efficiently to multiple conversion elements, enhancing light reception and autofocus accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation structures are formed between photoelectric conversion elements, then crosstalk between adjacent pixels is reduced, but light reception efficiency deteriorates
Solution Approach 1:
A light guide structure is introduced as an intermediary element between photoelectric conversion elements. This light guide has a refractive index lower than the surrounding layers, creating optical contrast that isolates light paths while allowing efficient light guidance to individual photodiodes, thus reducing crosstalk without sacrificing light reception efficiency
Solution Approach 2:
The refractive index parameter is strategically manipulated by introducing a light guide material with refractive index lower than both the upper cladding layer and the photodiode layer. This parameter change creates optical confinement and directionality, enabling light to be guided efficiently to the intended photodiode while preventing lateral spread that would cause crosstalk
2Reliability
If isolation structures are formed between photoelectric conversion elements, then pixel separation is improved, but manufacturing complexity increases
Solution Approach 1:
The light guide structure serves multiple functions simultaneously: it acts as an optical waveguide for efficient light transmission, provides isolation between adjacent pixels through refractive index contrast, and can be integrated with the existing layer structure. This merging of functions reduces the need for separate isolation structures, simplifying the manufacturing process while maintaining pixel separation
Solution Approach 2:
The light guide layer performs multiple roles within the image sensor stack: guiding incident light to photodiodes, isolating optical paths between adjacent pixels, and potentially serving as a structural support layer. This multi-functionality eliminates the need for dedicated isolation structures, reducing manufacturing complexity
3Manufacturing precision
If light guide unit is introduced, then light distribution control is improved, but device structure becomes more complex
Solution Approach 1:
The light guide structure is positioned locally between specific photoelectric conversion elements where light distribution control is needed. By confining the light guide to specific regions rather than implementing a global complex structure, the patent achieves precise light distribution control while minimizing overall device complexity
Solution Approach 2:
The light guide structure utilizes the vertical dimension by being disposed between layers at different heights (between the upper cladding layer and photodiode layer). This three-dimensional arrangement enables effective light control through refractive index contrast in the vertical direction, achieving precise light distribution without requiring complex lateral structures
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 design improves light reception efficiency and autofocus accuracy by uniformly distributing light to multiple conversion elements, reducing the impact of isolation structures and increasing manufacturing efficiency.
Implementation Method 1
the light guide includes a material having a refractive index smaller than a refractive index of the first anti-reflection layer
Data Source
AI summary
An image sensing device includes: a plurality of photoelectric conversion elements included in a unit pixel and located in a substrate layer; an isolation structure configured to isolate the plurality of photoelectric conversion elements from photoelectric conversion elements included in another unit pixel; a first anti-reflection layer configured to overlap the plurality of photoelectric conversion elements and disposed to be in contact with one surface of the substrate layer; a light guide disposed between the plurality of photoelectric conversion elements and disposed to be in contact with one surface of the substrate layer and the first anti-reflection layer; a grid layer configured to overlap the isolation structure; and a second anti-reflection layer disposed to be in contact with the first anti-reflection layer, the light guide, and the grid layer, wherein the light guide includes a material having a refractive index smaller than a refractive index of the first anti-reflection layer.