Planar Lens Structure for Back-Illuminated Imaging Optical Noise Reduction
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Solution Overview
Problem
Back-illuminated solid-state imaging apparatuses face issues with optical noise due to light leakage into adjacent pixels, which degrades pixel signals, as light can be reflected by the interface between the semiconductor substrate and the wiring layer or wires, causing indirect entry into adjacent pixels.
Innovation Solution
A photoelectric conversion apparatus with a planar lens structure composed of alternating first and second insulating parts with different refractive indices, disposed on the wiring layer, which creates a cyclic or concentric pattern to prevent light reflection and increase sensitivity by refracting light away from adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the opening ratio of the light-receiving portion is increased in back-illuminated imaging apparatus to improve sensitivity, then more light enters the photodiodes, but optical noise from light leakage into adjacent pixels increases
Solution Approach 1:
The patent segments the optical control function into two parts: the trench structure handles direct light containment, while the planar lens structure with its segmented insulating parts handles reflected light management. This segmentation allows the opening ratio to be maximized for sensitivity while maintaining effective light isolation.
Solution Approach 2:
The patent applies different optical properties to different regions: the trench provides strong light blocking at critical interfaces, while the planar lens structure provides gradual refraction control in the wiring layer region. This local differentiation of optical control strategies enables high sensitivity with reduced optical noise.
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
The planar lens structure effectively reduces light entry into adjacent pixels, enhancing pixel signal quality by mimicking a concave or convex lens effect, thereby improving the sensitivity and reducing optical noise.
Implementation Method 1
the optical structure includes a plurality of first insulating parts and a plurality of second insulating parts, wherein a refractive index of the first insulating part is lower than a refractive index of the second insulating part
Data Source
AI summary
A photoelectric conversion apparatus, including: a photoelectric conversion unit that converts received light into charges; and an optical structure that is disposed on the opposite side of a light-receiving surface of the photoelectric conversion unit, wherein the optical structure includes a plurality of first insulating parts and a plurality of second insulating parts, wherein a refractive index of the first insulating part is lower than a refractive index of the second insulating part, wherein at least one of the first insulating part and the second insulating part is disposed at intervals shorter than a wavelength of a detection target light, and wherein an effective refractive index of the optical structure is lowest at a reference point and increases as the distance from the reference point increases, or is highest at the reference point and decreases as the distance from the reference point increases.