CMOS Image Sensor Light Shield Wall for Pixel Spillover Reduction
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Solution Overview
Problem
Existing solid-state imaging apparatuses, particularly back-illuminated CMOS image sensors, face inadequate light-shielding properties, leading to significant spillover of light from adjacent unit pixels, which affects image quality.
Innovation Solution
A solid-state imaging apparatus is designed with a semiconductor layer containing photoelectric conversion units and charge retention units, featuring a light shield wall within a trench formed between these units and an insulation layer on the opposite side with an opening surrounding the trench, enhancing light shielding efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shield wall is formed between adjacent unit pixels, then light spillover is reduced, but the light-shielding properties remain inadequate
Solution Approach 1:
The light shielding function is divided into multiple components: a light shield wall formed in a trench between adjacent photoelectric conversion units, and an insulation layer with openings that surround the trench. This segmentation allows each component to contribute to light shielding from different aspects, with the light shield wall providing primary blocking and the insulation layer openings providing additional shielding coverage, thereby resolving the inadequacy of single-component light shielding.
Solution Approach 2:
The insulation layer with openings is positioned on the opposite side of the semiconductor layer from the light-incident side, creating a three-dimensional light shielding structure. This dimensional approach allows light to be blocked from multiple directions and paths, not just at the surface level but also from light that may travel through or around the initial shield wall, thereby enhancing overall light-shielding properties.
2Object-affected harmful factors
If the light shield wall is made deeper to block more light, then light spillover is reduced, but device complexity increases
Solution Approach 1:
The light shield wall and the insulation layer with openings are merged into a unified light shielding system. The insulation layer is integrated with the trench structure, and the openings are positioned to surround the trench. This merging allows the combination of simpler structural elements to achieve enhanced light shielding without requiring excessively deep individual components, thereby reducing overall device complexity while maintaining effective light spillover prevention.
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 proposed solution effectively reduces light spillover between adjacent unit pixels, improving image quality by blocking direct or indirect light incidence, thereby minimizing optical noise and enhancing pixel characteristics.
Implementation Method 1
The light shield wall is provided inside a trench formed in a depth direction from a light-incident side between the photoelectric conversion units and the charge retention units adjacent to each other in the semiconductor layer
Implementation Method 2
a semiconductor layer provided with a plurality of photoelectric conversion units and a plurality of charge retention units that retain charge generated by the photoelectric conversion units
Data Source
AI summary
The solid-state imaging apparatus (1) according to the present disclosure includes a semiconductor layer (51), a light shield wall (60b), and an insulation layer. The semiconductor layer (51) is provided with a plurality of photoelectric conversion units and a plurality of charge retention units that retain charge generated by the photoelectric conversion units (26). The light shield wall (60b) is provided inside a trench (51a) formed in a depth direction from a light-incident side between the photoelectric conversion units and the charge retention units (26) adjacent to each other in the semiconductor layer (51). The insulation layer is provided on a side of the semiconductor layer (51) opposite from the light-incident side, and having an opening (53a) that surrounds the trench (51a).