Vertical Transfer Gate Image Sensor for High Integration Density
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is to create an image sensor with improved performance that can provide high resolution images while maintaining pixel characteristics, as increasing integration density leads to deterioration of pixel characteristics due to reduced physical size.
Innovation Solution
The image sensor design includes a photoelectric conversion element with complementary impurity regions, a vertical transfer gate, and a channel layer, along with a color filter layer and light condensing member, which facilitates high integration and prevents characteristic deterioration by optimizing the structure and materials used in the pixel array, such as polysilicon channel layers and high-K gate dielectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If integration density is increased to improve resolution, then productivity and image quality are improved, but pixel characteristics deteriorate due to reduced physical size
Solution Approach 1:
The patent transitions from a planar pixel structure to a three-dimensional stacked structure with vertical channels extending through multiple layers. This vertical dimension allows multiple photoelectric conversion elements to be stacked above each other, increasing integration density while maintaining adequate physical dimensions for each pixel element to preserve its characteristics.
Solution Approach 2:
The patent implements a nested structure where channel layers are positioned within and between photoelectric conversion elements, and transfer gates are formed around vertical channels. This nested arrangement maximizes space utilization, allowing multiple functional elements to coexist in a compact volume without compromising individual element performance.
2Productivity
If physical size of pixel is reduced to increase integration density, then productivity is improved, but manufacturing precision and pixel characteristics deteriorate
Solution Approach 1:
The patent divides the pixel structure into distinct functional segments: photoelectric conversion elements, channel layers, transfer gates, and floating diffusion regions. Each segment is independently formed and optimized, allowing precise control over the dimensions and properties of each component even as overall pixel size decreases.
Solution Approach 2:
The patent employs polysilicon channel layers with controlled doping concentrations and high-k gate dielectric materials with specific dielectric constants to maintain electrical performance. By carefully controlling material parameters such as doping levels, layer thicknesses, and dielectric constants, the patent achieves reliable pixel characteristics despite reduced physical dimensions.
3Ease of manufacture
If conventional structures are used to maintain simplicity, then ease of manufacture is improved, but integration density and performance are limited
Solution Approach 1:
The patent designs vertical channels and transfer gates that serve multiple functions: they enable charge transfer between stacked photoelectric conversion elements, provide structural support, and facilitate electrical connections through multiple layers. This multi-functionality reduces the need for separate dedicated structures, maintaining manufacturing simplicity while achieving high integration density.
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 high integration density without compromising pixel characteristics, enhancing quantum efficiency and dark current characteristics, thus facilitating the production of high-resolution images.
Implementation Method 1
An image sensor converts an optical image into an electrical signal
Implementation Method 2
a channel layer formed between the transfer gate and the pillar and contacting the photoelectric conversion element, wherein the channel layer contacts the first impurity region and has the same conductivity as the second impurity region
Data Source
AI summary
An image sensor includes a photoelectric conversion element including a first impurity region and a second impurity region, wherein the first impurity region contacts a first surface of a substrate, wherein the second impurity region has conductivity complementary to the first impurity region and is formed in the substrate and below the first impurity region; a pillar formed over the photoelectric conversion element; a transfer gate formed over the photoelectric conversion element to surround the pillar; and a channel layer formed between the transfer gate and the pillar and contacting the photoelectric conversion element, wherein the channel layer contacts the first impurity region and has the same conductivity as the second impurity region.