Photodiode Charge Transfer via Localized n-- Region
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Solution Overview
Problem
The charge transfer efficiency in semiconductor devices, such as CMOS image sensors, is hindered by the deep and wide n-type semiconductor region formation, which reduces the performance of photoelectric conversion elements due to increased depletion potential and potential energy barriers.
Innovation Solution
The introduction of an n−− type semiconductor region with lower impurity density than the n− type semiconductor region, and a p type semiconductor region with lower impurity density than the p type semiconductor region, facilitates improved charge transfer by reducing potential barriers and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an n type semiconductor region is formed deeply and widely in a p type semiconductor substrate, then the internal quantum efficiency and capacitance of the photodiode are improved, but the charge transfer efficiency deteriorates
Solution Approach 1:
The patent applies local quality by creating an n−− type semiconductor region with lower impurity density specifically in the channel length direction of the transfer transistor, while maintaining the deep and wide n type semiconductor region structure. This localized modification reduces potential energy barriers in the charge transfer path without compromising the overall photodiode capacitance and internal quantum efficiency.
Solution Approach 2:
The patent changes the impurity density parameter by introducing an n−− type semiconductor region with lower impurity density than the surrounding n type semiconductor region. This parameter change reduces the depletion potential and potential energy barriers in the charge transfer path, thereby improving charge transfer efficiency while maintaining the deep junction structure for high internal quantum efficiency.
2Quantity of substance
If an n type semiconductor region is formed deeply and widely in a p type semiconductor substrate, then the capacitance of the photodiode is improved, but the charge transfer efficiency deteriorates
Solution Approach 1:
The patent applies local quality by creating an n−− type semiconductor region with lower impurity density specifically in the channel length direction of the transfer transistor, while maintaining the deep and wide n type semiconductor region structure. This localized modification reduces potential energy barriers in the charge transfer path without compromising the overall photodiode capacitance and internal quantum efficiency.
Solution Approach 2:
The patent changes the impurity density parameter by introducing an n−− type semiconductor region with lower impurity density than the surrounding n type semiconductor region. This parameter change reduces the depletion potential and potential energy barriers in the charge transfer path, thereby improving charge transfer efficiency while maintaining the deep junction structure for high internal quantum efficiency.
3Productivity
If the impurity density of the n type semiconductor region is reduced, then the charge transfer efficiency is improved, but the sensitivity of the photodiode deteriorates
Solution Approach 1:
The patent applies local quality by creating an n−− type semiconductor region with lower impurity density specifically in the channel length direction of the transfer transistor, while maintaining the deep and wide n type semiconductor region structure. This localized modification reduces potential energy barriers in the charge transfer path without compromising the overall photodiode capacitance and internal quantum efficiency.
Solution Approach 2:
The patent changes the impurity density parameter by introducing an n−− type semiconductor region with lower impurity density than the surrounding n type semiconductor region. This parameter change reduces the depletion potential and potential energy barriers in the charge transfer path, thereby improving charge transfer efficiency while maintaining the deep junction structure for high internal quantum efficiency.
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 configuration enhances charge transfer efficiency and sensitivity of the photodiode, improving the overall performance of the semiconductor device by reducing depletion potential and potential energy barriers.
Implementation Method 1
a photoelectric conversion element such as a photodiode for detecting a light, and generating electric charges is formed
Data Source
AI summary
The performances of a semiconductor device are improved. A semiconductor device has a transfer transistor and a photodiode. The photodiode has an n type semiconductor region, an n+ type semiconductor region, and a second p type semiconductor region surrounded by a first p type semiconductor region of an interpixel isolation region. The n+ type semiconductor region is formed on the main surface side of the semiconductor substrate, and the n type semiconductor region is formed under the n+ type semiconductor region via the second p type semiconductor region. In the channel length direction of the transfer transistor, in the n type semiconductor region, an n−− type semiconductor region having a lower impurity density than that of the n type semiconductor region is arranged, to improve the transfer efficiency of electric charges accumulated in the photodiode.