Low Reflective Film on Substrate Backside for Image Sensor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Infrared light reflection into the optical black portion of solid-state image pickup devices causes fluctuations in the optical black level, leading to changes in image color or brightness, and existing solutions like infrared-cut filters are costly or impractical for all applications.
Innovation Solution
A low reflective film with low infrared reflectance is formed on the backside of the semiconductor substrate, reducing infrared light reflection and absorption in the optical black portion, thereby stabilizing the optical black level and allowing for the potential removal or cost reduction of infrared-cut filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an infrared-cut filter is provided to block infrared light transmission, then infrared light entering the optical black portion is reduced, but the device becomes expensive and complex
Solution Approach 1:
A low-reflective film is introduced as an intermediary layer on the back surface of the semiconductor substrate. This film mediates the interaction between infrared light and the substrate by reducing infrared reflectance, thereby preventing infrared light from entering the optical black portion without requiring a complex infrared-cut filter structure.
Solution Approach 2:
The reflectance parameter of the semiconductor substrate back surface is changed by forming a low-reflective film with specific optical properties. This parameter change reduces infrared light reflection and transmission into the optical black portion, achieving the desired effect through material property modification rather than structural complexity.
2Reliability
If an infrared-cut filter is provided to block infrared light transmission, then infrared light entering the optical black portion is reduced, but the manufacturing cost increases
Solution Approach 1:
The low-reflective film serves as a cost-effective alternative to expensive infrared-cut filters. This film can be formed using standard semiconductor manufacturing processes, making it a cheaper solution that achieves the same functional goal of preventing infrared light contamination in the optical black portion.
Solution Approach 2:
By modifying the optical parameters of the substrate back surface through film formation, the solution achieves infrared light control through a simpler, more manufacturable process compared to traditional infrared-cut filters, thereby reducing manufacturing costs.
3Reliability
If the semiconductor substrate back surface has high infrared reflectance, then infrared light reflects and enters the optical black portion causing photoelectric conversion, but forming a low-reflective film adds manufacturing steps
Solution Approach 1:
The low-reflective film acts as an intermediary layer that modifies the optical interaction at the substrate back surface. It reduces infrared reflectance without requiring fundamental changes to the substrate structure or complex multi-step processes, achieving the desired optical control through a single functional layer.
Solution Approach 2:
The low-reflective film is formed using composite material structures (such as alternating layers of materials with different refractive indices) that provide superior infrared reflectance control. This composite approach achieves the desired optical performance while maintaining manufacturing simplicity.
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 image pickup characteristics by preventing infrared light-induced changes in the optical black level, enabling high-quality imaging without the need for expensive infrared-cut filters, even in applications where they are not available.
Implementation Method 1
a low reflective film with low reflectance of infrared light formed on the back of the semiconductor substrate
Implementation Method 2
infrared light which entered obliquely the effective pixel portion reflects on the back of a substrate and enters the sensor portion of the optical black portion
Implementation Method 3
a photoelectric-conversion sensor portion formed on the surface of the semiconductor substrate
Data Source
AI summary
A solid-state image pickup device includes a semiconductor substrate 11, a photoelectric-conversion sensor portion 13 formed on the surface of the semiconductor substrate 11, a pixel area including an effective pixel portion 31 and an optical black portion 32 and a low reflective film 21 with low reflectance of infrared light formed on the back of the substrate 11. The solid-state image pickup device has satisfactory image pickup characteristics by suppressing an optical black optical level of the optical black portion from being fluctuated due to incidence of infrared light.