Solid-State Imaging Device Thinner Metallization Light Scattering
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Solution Overview
Problem
CMOS image sensors face challenges in efficiently guiding incident light to pixels due to multilevel metallization structures, leading to light scattering and attenuation, which complicates fabrication and hinders larger-scale integration and smaller chip size designs.
Innovation Solution
A solid-state imaging device is designed with a thinner multilevel metallization structure over the pixel array portion and a thicker structure over the peripheral circuitry portion, forming a single trench structure that minimizes light scattering and attenuation, and simplifies the fabrication process by using a uniformly thin metallization structure over the pixel array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multilevel metallization structure is used to achieve larger-scale integration and smaller chip size, then integration density is improved, but light scattering and attenuation increase
Solution Approach 1:
The chip is divided into two distinct regions: a pixel array portion with a thinner metallization structure optimized for light transmission, and a peripheral circuitry portion with a thicker metallization structure optimized for high-density integration. This spatial segmentation allows each region to have metallization thickness optimized for its specific function, resolving the contradiction between integration density and light transmission efficiency.
2Productivity
If a thicker multilevel metallization structure is used over the pixel array to support larger-scale integration, then integration capability is improved, but incident light guidance efficiency deteriorates
Solution Approach 1:
Different metallization thicknesses are applied to different locations on the chip. The pixel array portion receives a thinner metallization structure with fewer layers to maintain high light transmission efficiency, while the peripheral circuitry portion receives a thicker metallization structure with more layers to achieve larger-scale integration. This local differentiation of metallization quality allows each region to have properties optimized for its specific requirements.
3Manufacturing precision
If a trench structure is formed in the multilevel metallization over each pixel to guide light, then light guidance is improved, but fabrication complexity increases
Solution Approach 1:
Instead of forming complex trench structures within the metallization layers over each pixel, the invention extracts the upper metallization layers entirely from the pixel array region. This creates a naturally light-guiding structure without requiring additional trench formation steps, thereby simplifying the fabrication process while still achieving effective light guidance to the photoelectric convertors.
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
This design enables higher integration density, smaller chip size, and reduced light scattering and attenuation, improving image quality while simplifying the fabrication process.
Implementation Method 1
a photoelectric convertor and transistors which reset and amplify the convertor
Data Source
AI summary
A solid-state imaging device has a substrate in which are formed a pixel array portion having a plurality of pixels, and a peripheral circuitry portion. The device is characterized in that a first multilevel metallization structure is formed over the peripheral circuitry portion, and a second multilevel metallization structure thinner than the first multilevel metallization structure is formed over the pixel array portion.