Image Sensor Grid Structure for Lower DTI Light Absorption
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Image sensors, particularly CMOS image sensors, face light loss due to absorption by polysilicon regions in deep trench isolation structures, leading to reduced light conversion efficiency and image quality.
Innovation Solution
The image sensor design incorporates a substrate with a pixel separating pattern, multiple photoelectric conversion layers, and grid patterns with varying heights and refractive indices to minimize light absorption, enhancing light reception and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If deep trench isolation structure with polysilicon region is used, then pixel separation and structural stability are improved, but light absorption increases causing light loss
Solution Approach 1:
An intermediary layer with graded refractive index is introduced between the polysilicon DTI structure and the incident light. This intermediate layer acts as a mediator that gradually transitions the refractive index from high (polysilicon) to low (air), reducing abrupt refraction and minimizing light absorption by the polysilicon region while maintaining pixel separation stability.
Solution Approach 2:
The refractive index parameter is changed by introducing a graded refractive index layer that transitions from high to low refractive index. This parameter change allows light to pass through the DTI structure more efficiently by reducing the abrupt refractive index mismatch, thereby decreasing light absorption and improving light transmission to the photodiodes.
2Power
If one pixel includes two or more photodiodes, then photoelectric conversion capability is improved, but light absorption by DTI structure increases
Solution Approach 1:
A graded refractive index intermediary layer is placed between the multi-photodiode structure and the incident light path. This intermediary structure mediates the optical interaction, allowing light to reach multiple photodiodes effectively while minimizing absorption by the surrounding DTI polysilicon structures.
3Illumination intensity
If grid patterns with varying heights and refractive indices are used, then light distribution is improved, but device complexity increases
Solution Approach 1:
The grid pattern is designed with local quality variations, where different regions have different heights and refractive indices optimized for their specific functions. This local differentiation improves light distribution by directing light appropriately to different photodiode regions while managing the complexity through localized rather than global modifications.
Solution Approach 2:
The solution moves from a two-dimensional planar grid to a three-dimensional structure with varying heights and refractive indices. This dimensional change allows for more sophisticated light control and distribution while the systematic arrangement of the 3D grid patterns keeps the manufacturing complexity manageable.
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 reduces light loss and improves image sensor performance by optimizing light distribution and absorption within the sensor, leading to enhanced image quality and sensitivity.
Implementation Method 1
The CIS may convert light energy into electrical energy and may read image information
Implementation Method 2
a first grid pattern on the pixel separating pattern; and a second grid pattern on the first separating pattern and having a lower height than the first grid pattern
Data Source
AI summary
An image sensor includes: a substrate including a first side configured to receive light and a second side that is opposite the first side; a pixel separating pattern configured to at least partially define a unit pixel in the substrate; a first photoelectric conversion layer and a second photoelectric conversion layer arranged in a first direction in the pixel separating pattern; a first separating pattern configured to at least partially define the first photoelectric conversion layer and the second photoelectric conversion layer in the substrate between the first photoelectric conversion layer and the second photoelectric conversion layer; a first grid pattern on the pixel separating pattern; and a second grid pattern on the first separating pattern and having a lower height than the first grid pattern.