Back-Illuminated Sensor Infrared Shielding via Dual Light-Blocking Films
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Solution Overview
Problem
Infrared light penetration into the optical black portion of back surface incidence type solid-state image sensing apparatuses leads to incorrect black level detection and increased costs due to the need for expensive IR cut filters, especially in applications where infrared light is utilized.
Innovation Solution
A solid-state image sensing apparatus with a sensor portion on a semiconductor substrate featuring a first light-shielding film closer to the back surface and a second light-shielding film closer to the front surface, utilizing wiring lines as light-shielding layers to prevent infrared light from entering the optical black portion, thereby ensuring accurate black level detection without the need for expensive filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an IR cut filter is used to prevent infrared light from entering the optical black portion, then black level detection accuracy is improved, but the cost of the image sensing apparatus increases significantly
Solution Approach 1:
The patent divides the light-shielding function into multiple segments: a first light-shielding film on the back surface and a second light-shielding film on the front surface. This segmentation allows each film to be optimized for specific wavelengths and angles, providing effective infrared light blocking without requiring an expensive broad-spectrum IR cut filter.
Solution Approach 2:
The patent adds a spatial dimension to the light-shielding approach by placing light-shielding films on both the back surface and front surface of the semiconductor substrate. This multi-layer arrangement at different depths creates multiple barriers that infrared light must penetrate, significantly improving blocking effectiveness while using inexpensive materials.
2Area of stationary object
If a back surface incidence type structure is used to improve aperture ratio, then the aperture ratio is improved, but infrared light enters the optical black portion in larger amounts
Solution Approach 1:
The light-shielding function is segmented into multiple films at different surfaces, with each film addressing specific infrared light paths. The first film on the back surface blocks light before it enters the substrate, while the second film on the front surface blocks reflected light, together solving the infrared contamination problem while maintaining the back-illuminated structure's high aperture ratio.
Solution Approach 2:
The light-shielding films act as intermediary elements that intercept infrared light at strategic points in its path. By placing these films at the back and front surfaces, the patent creates intermediate barriers that prevent infrared light from reaching the optical black portion, allowing the back-illuminated structure to maintain both high aperture ratio and effective infrared blocking.
3Device complexity
If wiring lines are used as light-shielding layers, then the device complexity is reduced and cost is lowered, but the shielding effectiveness against oblique infrared light may be insufficient
Solution Approach 1:
The patent makes the wiring lines serve multiple functions: they act as both electrical conductors for signal transmission and as light-shielding layers for blocking infrared light. This multi-functionality reduces the need for separate light-shielding structures, simplifying the overall device design while providing effective infrared blocking through the inherent properties of the metal wiring layers.
Solution Approach 2:
The wiring lines automatically provide light-shielding functionality as part of their inherent structure, without requiring additional dedicated light-shielding components. The metal wiring layers naturally block infrared light, and by strategically positioning them, the patent enables them to serve dual purposes: electrical connectivity and optical shielding, thereby reducing 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
Effectively shields infrared light from entering the optical black portion, allowing for correct black level detection and reducing costs by eliminating the need for IR cut filters, while maintaining image sensing quality even in applications that utilize infrared light.
Implementation Method 1
a first light-shielding film formed closer to the back surface side of the semiconductor substrate than the sensor portion, and a second light-shielding film formed closer to a front surface side of the semiconductor substrate than the sensor portion
Implementation Method 2
a sensor portion that performs photo-electric conversion
Data Source
AI summary
This invention provides a solid-state image sensing apparatus in which a sensor portion that performs photo-electric conversion and plural layers of wiring lines including a signal line for the sensor portion are formed on a semiconductor substrate; which includes an effective pixel portion configured such that light enters the sensor portion, and an optical black portion shielded so that the light does not enter the sensor portion; and which has a light-receiving surface on the back surface side of the semiconductor substrate. The optical black portion includes the sensor portion, a first light-shielding film formed closer to the back surface side of the semiconductor substrate than the sensor portion, and a second light-shielding film formed closer to the front surface side of the semiconductor substrate than the sensor portion.