Imaging Sensor Photodiode Groove Structure for Lower kTC Noise
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Solution Overview
Problem
Existing imaging devices face challenges in achieving high signal-to-noise ratio and reducing kTC noise due to junction capacitance and noise generation in photodiodes covered by line layers, leading to impaired image quality and frequent line disconnections.
Innovation Solution
The photodiode semiconductor layers are partially etched to remove the upper impurity-doped semiconductor layer in regions covered by line layers, reducing junction capacitance and kTC noise, while maintaining effective light absorption and preventing line disconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the photodiode is covered by a line layer to maintain structural integrity, then mechanical strength is improved, but junction capacitance increases and kTC noise is generated
Solution Approach 1:
The patent extracts the harmful upper impurity-doped semiconductor layer from the photodiode structure in regions where line layers are formed. By removing this layer, the source of kTC noise and excessive junction capacitance is eliminated, while the line layer remains in place to provide mechanical support and electrical connectivity.
Solution Approach 2:
The patent applies different structural configurations to different regions of the photodiode. In regions covered by line layers, the upper impurity-doped layer is removed to reduce noise, while in light-receiving regions, the complete photodiode structure is maintained for optimal light detection. This local differentiation resolves the contradiction between mechanical strength and noise reduction.
2Measurement precision
If the upper impurity-doped semiconductor layer is removed in line-covered regions, then junction capacitance is reduced and sensitivity is improved, but structural complexity increases
Solution Approach 1:
The patent implements local quality by creating grooves that selectively remove the upper impurity-doped semiconductor layer only in regions where line layers are formed, while preserving the complete photodiode structure in light-receiving regions. This approach improves signal-to-noise ratio by reducing junction capacitance in non-light-receiving areas without compromising light detection capability, and the groove structure itself is a relatively simple geometric modification.
3Reliability
If the photodiode structure is modified to prevent line disconnections, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming grooves to remove the upper impurity-doped semiconductor layer before depositing the line layers. This pre-preparation creates a favorable surface condition that prevents line disconnections during subsequent manufacturing steps, thereby improving reliability without significantly complicating the overall manufacturing process.
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 image quality by increasing sensitivity and reducing noise, while improving the yield and reliability of the imaging device by minimizing line disconnections.
Implementation Method 1
An imaging element including a p-n or p-i-n junction photodiode effectively produces drift of the electric charges generated from incident light when the photodiode is kept in a reverse-biased state
Implementation Method 2
a non-light-transmissive line included in a layer upper than the upper electrode
Data Source
AI summary
An imaging device includes a substrate, photodiode semiconductor layers on the substrate, an upper electrode and a lower electrode sandwiching the photodiode semiconductor layers, and a non-light-transmissive line included in a layer upper than the upper electrode, defining the substrate as the lowermost layer. The photodiode semiconductor layers include a first semiconductor layer, and a second semiconductor layer located between the first semiconductor layer and the lower electrode. The photodiode semiconductor layers have a groove in which the first semiconductor layer is removed in a region covered with the non-light-transmissive line in a planar view. A region overlapping the groove in the planar view does not include the upper electrode. The region overlapping the groove in the planar view includes a part of the second semiconductor layer and a part of the lower electrode.