Backside Illumination CMOS Image Sensor Dark Current Suppression
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Solution Overview
Problem
The existing solid-state imaging devices face degradation in Dark characteristics due to weakened pinning on the silicon substrate, leading to issues like white spots and dark currents, as charges flow into the photodiode.
Innovation Solution
A solid-state imaging device is designed with a PN junction region including a P-type and an N-type region on the light incident surface, where the N-type solid-phase diffused layer does not contact the backside Si interface, preventing charge pinning and degradation, and forming an intense electric field region to hold charges effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a P-type diffused layer and an N-type diffused layer are formed on a side wall of a trench between pixels to improve saturated charge amount, then charge holding capability is improved, but pinning on the silicon substrate is weakened causing Dark characteristic degradation
Solution Approach 1:
The invention transitions from two-dimensional planar diffused layers to a three-dimensional structure by forming the PN junction region on the side wall of the trench, creating a vertical intense electric field region that simultaneously achieves charge holding and pinning maintenance
Solution Approach 2:
The light shielding wall acts as an intermediary structure that isolates the intense electric field region from direct contact with the photodiode, preventing charge leakage while maintaining the electric field for charge holding
2Quantity of substance
If diffused layers are formed to increase charge capacity, then saturated charge amount increases, but charge leakage into photodiode occurs causing white spots and dark currents
Solution Approach 1:
The invention segments the charge holding region from the photodiode by introducing a trench with light shielding wall, dividing the structure into distinct functional zones that prevent harmful charge leakage while maintaining charge capacity
Solution Approach 2:
The invention uses a composite structure combining the P-type and N-type diffused layers with the light shielding wall material to create a multi-functional structure that provides both charge holding capability and electrical isolation
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 effectively suppresses the degradation of Dark characteristics by preventing charge flow into the photodiode, thereby reducing the occurrence of white spots and dark currents.
Implementation Method 1
a photoelectric converting unit configured to perform photoelectric conversion
Implementation Method 2
a PN junction region including a P-type region and an N-type region on a side of a light incident surface of the photoelectric converting unit
Data Source
AI summary
The present technology relates to a solid-state imaging device and electronic equipment to suppress degradation of Dark characteristics. A photoelectric converting unit configured to perform photoelectric conversion, and a PN junction region including a P-type region and an N-type region on a side of a light incident surface of the photoelectric converting unit are included. Further, on a vertical cross-section, the PN junction region is formed at three sides including a side of the light incident surface among four sides enclosing the photoelectric converting unit. Further, a trench which penetrates through a semiconductor substrate in a depth direction and which is formed between the photoelectric converting units each formed at adjacent pixels is included, and the PN junction region is also provided on a side wall of the trench. The present technology can be applied, for example, to a backside irradiation type CMOS image sensor.