Photodiode Structure with Segmented Impurity Gradients
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Solution Overview
Problem
In CMOS image sensors, the charge transfer efficiency is compromised when light is incident on the deeper portion of the p-type well, leading to degraded performance due to the inability to increase charge transfer efficiency while maintaining internal quantum efficiency.
Innovation Solution
A semiconductor device configuration with a p-type well, an n-type semiconductor region closer to the surface, and a p-type region between the n-type and n-type regions, where the net impurity concentration in the n-type region is lower than in the p-type region, allowing for improved charge transfer and internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple semiconductor regions with different conductivity types are formed to improve charge transfer efficiency, then charge transfer efficiency improves, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the photodiode into distinct functional regions: a first-conductivity-type semiconductor region and a second-conductivity-type semiconductor region, each with optimized impurity concentrations. This segmentation allows independent optimization of charge generation and charge transfer functions in different spatial zones, improving overall charge transfer efficiency while maintaining a relatively simple integrated structure that can be manufactured using standard semiconductor processing techniques.
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
Enhances charge transfer efficiency and internal quantum efficiency, improving the overall performance of the semiconductor device by optimizing the impurity concentration and region placement within the photodiode structure.
Implementation Method 1
the efficiency with which the incident light is absorbed by the photodiode and electrons are generated by photoelectric conversion
Data Source
AI summary
An improvement is achieved in the performance of a semiconductor device. A semiconductor device includes an n−-type semiconductor region formed in a p-type well, an n-type semiconductor region formed closer to a main surface of a semiconductor substrate than the n−-type semiconductor region, and a p−-type semiconductor region formed between the n−-type semiconductor region and the n-type semiconductor region. A net impurity concentration in the n−-type semiconductor region is lower than a net impurity concentration in the n-type semiconductor region. A net impurity concentration in the p−-type semiconductor region is lower than a net impurity concentration in the p-type well.