Backside Illuminated Image Sensor Crosstalk Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Backside illuminated image sensors face significant crosstalk issues between adjacent pixels due to light absorption and interference through insulation layers when light is incident on the front surface, leading to reduced light concentration and mixed colors in conventional image sensors.
Innovation Solution
The design includes a backside illuminated image sensor with a first semiconductor layer, a second semiconductor layer, and isolation layers to define pixels and active device regions, with a light filter layer on the rear surface and a wiring layer on the front surface, minimizing light diffusion and crosstalk by isolating photo detectors with trench-type insulation and lattice structured pixel isolation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light is incident on the front surface of the semiconductor layer, then the wiring layer can be formed on the front surface, but crosstalk between adjacent pixels occurs due to light absorption and interference through insulation layers
Solution Approach 1:
The patent inverts the conventional structure by making the semiconductor layer transparent to light and forming the wiring layer on the front surface while allowing light to incident on the rear surface. This inversion enables the wiring to be positioned in front of the photoelectric conversion region without causing crosstalk, as light travels through the transparent semiconductor layer from the rear surface directly to the photoelectric conversion region.
Solution Approach 2:
The patent changes the spatial dimension of light incidence from the front surface to the rear surface of the semiconductor layer. By forming the wiring layer on the front surface and having light incident on the rear surface, the wiring is positioned in a different spatial plane relative to the light path, eliminating interference and crosstalk between adjacent pixels.
2Reliability
If insulation layers are used to isolate pixels, then electrical isolation is achieved, but light absorption and interference occur reducing light concentration
Solution Approach 1:
The patent applies local quality by making the semiconductor layer transparent in the light incident region while maintaining its insulating properties in other regions. The semiconductor layer is selectively designed to be transparent where light passes through, allowing light to reach the photoelectric conversion region without absorption or interference from insulation layers.
Solution Approach 2:
The patent changes the optical parameter of the semiconductor layer by making it transparent to incident light. This parameter change allows the semiconductor layer to function both as an electrical insulator and as a transparent medium for light transmission, eliminating light absorption and interference issues.
3Ease of manufacture
If conventional front surface illumination is used, then wiring can be formed easily, but color mixing occurs due to light diffusion through insulation layers
Solution Approach 1:
The patent inverts the light incidence direction to the rear surface and positions the wiring layer on the front surface, creating a spatial separation between the wiring and the light path. This inversion prevents light diffusion through insulation layers, thereby maintaining color separation accuracy while preserving ease of wiring formation.
Solution Approach 2:
The patent changes the dimension of light incidence to the rear surface, positioning the wiring layer in a different spatial plane. This dimensional change eliminates light diffusion through insulation layers, ensuring accurate color separation while maintaining manufacturing ease.
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 effectively reduces crosstalk between adjacent pixels, enhancing light concentration and color separation, thereby improving the image sensor's performance by preventing light absorption and interference through insulation layers.
Implementation Method 1
each of the photo diodes of the pixels performs photoelectric conversion
Data Source
AI summary
A method of manufacturing a backside illuminated image sensor, including forming a first isolation layer in a first semiconductor layer, such that the first isolation layer defines pixels of a pixel array in the first semiconductor layer, forming a second semiconductor layer on a first surface of the first semiconductor layer, forming a second isolation layer in the second semiconductor layer, such that the second isolation layer defines active device regions in the second semiconductor layer, forming photo detectors and circuit devices by implanting impurities into a first surface of the second semiconductor layer, the first surface of the second semiconductor layer facing away from the first semiconductor layer, forming a wiring layer on the first surface of the second semiconductor layer, and forming a light filter layer on a second surface of the first semiconductor layer.