Solid-State Imaging Device Refractive Index Layer Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging devices suffer from reduced sensitivity due to crystal defects in silicon or semiconductor layers, leading to issues like white blemishes and optical crosstalk, which limit their performance in image quality and downsizing.
Innovation Solution
A solid-state imaging device is designed with a semiconductor layer on an insulator layer, where the refractive index of the insulator layer is lower than that of the semiconductor layer, reducing crystal defects and enhancing sensitivity by reflecting incident light off the interface between the layers, and incorporating features like grooves and polysilicon films to prevent optical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silicon layer or semiconductor layer including a photoelectric converter is formed on a reflector structure, then sensitivity to long wavelength light is enhanced, but crystal defects occur in the silicon or semiconductor layer leading to white blemishes
Solution Approach 1:
A semiconductor layer is introduced as an intermediary between the reflector structure (insulator layer) and the silicon layer containing the photoelectric converter. This intermediary layer prevents direct contact between the silicon layer and the reflector structure, thereby avoiding crystal defects and white blemishes while still allowing the reflector to enhance sensitivity to long wavelength light through the semiconductor layer.
2Area of stationary object
If the pixel size is reduced to achieve downsizing, then device size is reduced, but sensitivity decreases significantly
Solution Approach 1:
The device is segmented into multiple functional layers (insulator layer, semiconductor layer, silicon layer) with distinct roles. The semiconductor layer acts as a dedicated light-guiding and reflecting structure that enhances light absorption efficiency, allowing smaller pixel sizes to maintain high sensitivity through improved optical path management rather than relying solely on larger pixel area.
Solution Approach 2:
The refractive index parameter is utilized by selecting materials with appropriate refractive indices for the insulator and semiconductor layers. This creates optimal light reflection and guidance conditions that enhance sensitivity even in reduced-size pixels, allowing sensitivity to be maintained or improved despite pixel downsizing.
3Object-affected harmful factors
If a shallow photoelectric converter is formed to reduce optical crosstalk, then optical crosstalk between adjacent pixels is reduced, but sensitivity is compromised
Solution Approach 1:
The semiconductor layer serves as an intermediary that guides and reflects light, enabling the photoelectric converter to be positioned shallower while still effectively capturing light. This intermediary structure improves light collection efficiency, compensating for the reduced depth of the photoelectric converter and maintaining sensitivity while reducing optical 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
The solution effectively prevents white blemishes and optical crosstalk, improving image quality and sensitivity, particularly for long wavelength light, while maintaining high crystal quality and reducing noise.
Implementation Method 1
since the refractive index of the insulator layer is lower than that of the semiconductor layer, and incident light can be reflected off the interface between the insulator layer and the semiconductor layer, this can enhance the sensitivity, in particular, to long wavelength light
Implementation Method 2
a photoelectric converter configured to convert light into signal charge
Data Source
AI summary
A solid-state imaging device includes: a substrate; an insulator layer formed on the substrate; a semiconductor layer formed on the insulator layer; and a silicon layer formed on the semiconductor layer. The silicon layer includes a plurality of pixels each including a photoelectric converter configured to convert light into signal charge, and a circuit configured to read the signal charge, and a refractive index of the insulator layer is lower than a refractive index of the semiconductor layer.