Polysilicon Anti-Reflection Structure for CMOS Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face performance degradation due to Fresnel reflection, and existing anti-reflection structures (ARS) using limited materials struggle to effectively mitigate this issue across the visible spectrum.
Innovation Solution
A solid-state image sensing device with an anti-reflection structure comprising polysilicon and silicon oxide materials, where anti-reflection layers are alternately formed using these materials to match refractive indexes and dispersions, reducing Fresnel reflection and maintaining constant transmittance across the visible spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional anti-reflection structures with limited materials are used, then manufacturing simplicity is maintained, but Fresnel reflection cannot be effectively reduced across the visible spectrum
Solution Approach 1:
The patent employs a composite anti-reflection structure consisting of multiple layers with different materials (polysilicon and silicon oxide) having different refractive indexes. This multi-material approach enables effective reduction of Fresnel reflection across the visible spectrum by creating optical interference that cancels reflected light, while still using materials that are readily available in semiconductor manufacturing processes.
2Reliability
If anti-reflection structure is added to reduce Fresnel reflection, then sensing performance is improved, but device structure becomes more complex
Solution Approach 1:
The anti-reflection structure is segmented into multiple discrete layers (polysilicon layer and silicon oxide layer) with different optical properties. Each layer is designed with specific thickness and refractive index to create constructive interference for light transmission. This segmentation allows independent optimization of each layer's properties to achieve broad-spectrum anti-reflection while maintaining a systematic manufacturing approach.
3Illumination intensity
If multi-layer anti-reflection structure is implemented, then transmittance consistency across spectrum is improved, but manufacturing process becomes more complex
Solution Approach 1:
The polysilicon and silicon oxide materials serve multiple functions: they provide anti-reflection properties across the visible spectrum, are compatible with standard CMOS manufacturing processes, and can be deposited using conventional semiconductor fabrication techniques. This multi-functionality enables the anti-reflection structure to be integrated into existing manufacturing lines without requiring entirely new process equipment or materials.
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 Fresnel reflection and maintains consistent transmittance across the visible spectrum, including the blue wavelength region, enhancing the sensing performance of CMOS image sensors.
Implementation Method 1
Fresnel reflection originating from the characteristics of the materials used for manufacturing a CIS is a crucial factor that reduces the sensing performance of the CIS
Implementation Method 2
each of the first anti-reflection layer and the top layer is formed of a different second material
Data Source
AI summary
A solid-state image sensing device including an anti-reflection structure that uses polysilicon and a method of manufacturing the same, in which the solid-state image sensing device includes a photodiode region and a transistor region. The photodiode region includes a semiconductor substrate, a first anti-refection layer, a second anti-reflection layer, and a top layer. The first anti-reflection layer is formed on the semiconductor substrate, and the second anti-reflection layer is formed on the first anti-reflection layer. The top layer is formed on the second anti-reflection layer. Each of the semiconductor substrate and the second anti-reflection layer is formed of a first material, and each of the first anti-reflection layer and the top layer is formed of a second material different from the first material.