BSI Image Sensor Reflector for Crosstalk Reduction
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Solution Overview
Problem
Backside illuminated (BSI) image sensors face challenges in increasing sensitivity while minimizing crosstalk, as deeper photodetectors increase manufacturing costs and conductive features used for radiation reflection often cause divergence to neighboring pixels.
Innovation Solution
Incorporating a reflector positioned under the photodetector between the interconnect layer and the photodetector, which reflects radiation back to the photodetector, allowing for enhanced sensitivity with minimal crosstalk by maintaining close proximity to the photodetector and preventing radiation from reaching neighboring pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photodetectors are made deeper to increase sensitivity, then radiation absorption is improved, but manufacturing costs increase
Solution Approach 1:
A reflector is introduced as an intermediary component between the photodetector and the interconnect layer. This reflector redirects radiation that would otherwise be lost back toward the photodetector, enhancing sensitivity without requiring deeper photodetector structures, thereby avoiding increased manufacturing costs
2Reliability
If conductive features are used to reflect radiation back to photodetectors, then sensitivity is improved, but crosstalk to neighboring pixels increases
Solution Approach 1:
The reflector serves as a dedicated intermediary structure that selectively redirects radiation. Unlike conductive features that may cause divergence, the reflector is specifically designed to bounce radiation back to its originating photodetector, improving sensitivity while preventing crosstalk to neighboring pixels
Solution Approach 2:
The reflector is positioned and configured to provide localized radiation reflection specifically for each photodetector. This localized approach ensures that each photodetector receives enhanced radiation from its own incident light without interfering with or receiving radiation from neighboring pixels, thus eliminating crosstalk
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 enhances radiation absorption opportunities for the photodetector, increasing sensitivity while reducing crosstalk and manufacturing costs associated with deeper photodetectors.
Implementation Method 1
A reflector is arranged under the photodetector, between the interconnect layer and the photodetector, and is configured to reflect radiation that passes through the photodetector back towards the photodetector
Data Source
AI summary
A backside illuminated (BSI) image sensor with a reflector is provided. A pixel sensor is arranged on a lower side of a semiconductor substrate, and comprises a photodetector arranged within the semiconductor substrate. An interconnect structure is arranged under the semiconductor substrate and the pixel sensor, and comprises an interconnect layer and a contact via extending from the interconnect layer to the pixel sensor. The reflector is arranged under the photodetector, between the interconnect layer and the photodetector, and is configured to reflect incident radiation towards the photodetector. A method for manufacturing the BSI image sensor is also provided.