Semiconductor Image Sensor Reflective Isolation for Low-Light Crosstalk
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Solution Overview
Problem
Semiconductor image sensors face challenges with optical crosstalk, particularly as their size decreases, leading to increased sensitivity to noise from neighboring pixel sensors, which affects light absorption efficiency, especially at low light levels.
Innovation Solution
The implementation of a semiconductor device design that includes a first light sensing unit and a second light sensing unit, with a first isolation structure and a reflective layer to reduce crosstalk, where the first light sensing unit receives less radiation and is surrounded by the second light sensing unit, and the use of a third light sensing unit to further minimize interference, along with surface roughening and varying isolation structure sizes to enhance light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of semiconductor image sensors is decreased, then the device becomes more compact and integration density increases, but optical crosstalk between neighboring pixel sensors increases and light absorption efficiency deteriorates
Solution Approach 1:
The sensor surface is divided into distinct first pixel sensors and second pixel sensors with different light-receiving characteristics. First pixel sensors have larger light-receiving areas optimized for low-light conditions, while second pixel sensors have smaller areas optimized for high-light conditions. This segmentation allows each pixel type to be optimized for its specific function without compromise.
Solution Approach 2:
Different regions of the sensor are assigned different pixel types with locally optimized properties. First pixel sensors are positioned in regions where low-light sensitivity is prioritized, while second pixel sensors are positioned where high-light performance is prioritized. Each pixel type has tailored light-receiving characteristics suited to its local functional requirements.
2Reliability
If the light-receiving area of pixel sensors is increased to improve light absorption efficiency, then sensitivity improves, but optical crosstalk from neighboring pixels increases
Solution Approach 1:
The sensor is segmented into first pixel sensors with larger light-receiving areas for high light absorption efficiency, and second pixel sensors with smaller light-receiving areas for reduced crosstalk. This segmentation allows simultaneous optimization of both light absorption and crosstalk reduction in different pixel regions.
Solution Approach 2:
The patent converts the potential harm of optical crosstalk into a benefit by using second pixel sensors with smaller light-receiving areas that inherently generate less crosstalk. These second pixel sensors act as crosstalk-reducing elements that protect the first pixel sensors while maintaining overall sensor sensitivity.
3Object-affected harmful factors
If isolation structures are added between pixel sensors to reduce crosstalk, then optical interference decreases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of adding complex isolation structures between all pixels, the patent segments pixels into two types with inherently different light-receiving characteristics. The second pixel sensors' smaller areas naturally provide optical isolation, reducing the need for additional isolation structures and simplifying device complexity.
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 effectively reduces crosstalk interference, enhancing the light sensitivity of the first light sensing unit by minimizing noise from neighboring sensors, thereby improving light absorption efficiency, especially in low-light conditions.
Implementation Method 1
a reflective layer to reduce crosstalk
Implementation Method 2
photodiodes and transistors that can absorb radiation projected toward the substrate and convert the sensed radiation into electrical signals
Data Source
AI summary
A method of manufacturing a semiconductor device includes disposing a plurality of a first type of light sensing units on a substrate; and disposing a plurality of a second type of light sensing units arranged on the substrate. Each of the first type of light sensing units is operable to receive less radiation than each of the second type of light sensing units. At least one of the second type of light sensing units is adjacent to a portion of at least one of the first type of light sensing units. The method includes disposing a first isolation structure between one of the first type of light sensing units and one of the second type of light sensing units; and disposing a second isolation structure between the adjacent first type of light sensing units. The method includes disposing a reflective layer above the first type of light sensing units.