Pixel Isolation Trench Structure for Low-Noise Light Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In light detection devices with deep trenches separating pixels, the suppression of dark current leakage and noise characteristics is challenging due to the potential for electrical shorts and worsening noise characteristics when the trench side walls are not effectively isolated.
Innovation Solution
A light detection device with a semiconductor layer having photoelectric conversion regions, where trenches partition these regions, and a separation part with a first and second separation part, where the first surface of the second separation part faces a material that suppresses etching, preventing electrical shorts and maintaining the intended distance between the fixed charge film and charge accumulation region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trenches are used to completely separate pixels, then electron or hole leakage between pixels is suppressed, but dark current leakage through trench side walls worsens
Solution Approach 1:
The patent applies composite materials by forming a multilayer separation structure consisting of a first separation part (insulating film) and a second separation part (semiconductor layer with different conductivity type) in the trench. This composite structure combines the electrical isolation properties of the insulating film with the carrier blocking properties of the oppositely doped semiconductor layer, effectively suppressing both pixel leakage and dark current through the trench side walls.
Solution Approach 2:
The patent applies local quality by creating a region with different conductivity type (second separation part) specifically at the trench side walls where dark current leakage occurs. This localized modification of electrical properties targets the specific problem area without affecting the overall pixel structure, suppressing dark current at the critical interface while maintaining photoelectric conversion efficiency in the bulk.
2Reliability
If pixels are separated by trenches, then cross-pixel electron leakage is reduced, but noise characteristics worsen
Solution Approach 1:
The composite separation structure of insulating film plus oppositely doped semiconductor layer creates enhanced electrical isolation that reduces both carrier leakage and noise-generating defects. The second separation part with different conductivity type passivates interface states and reduces generation-recombination noise at the trench boundaries while maintaining effective pixel isolation.
3Object-generated harmful factors
If separation structure is added to suppress dark current, then dark current leakage is reduced, but device complexity increases
Solution Approach 1:
The patent merges the dark current suppression function with the existing pixel separation trench structure. The second separation part is formed within the same trench that already provides physical separation between pixels, combining multiple functions (pixel isolation and dark current suppression) into a single integrated structure rather than adding separate components.
Solution Approach 2:
The separation structure including the second separation part is formed preliminarily during the manufacturing process before final device operation. The oppositely doped semiconductor layer is created in advance to establish the dark current suppression mechanism, eliminating the need for additional post-processing steps or complex assembly operations.
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 worsening of noise characteristics and prevents electrical shorts, maintaining the integrity of the photoelectric conversion regions and improving the overall performance of the light detection device.
Implementation Method 1
the first material being a material of which an etching rate relative to a selected etchant is lower than that of a material constituting the sacrificial layer
Data Source
AI summary
A light detection device capable of suppressing the worsening of noise characteristics is provided. The light detection device includes a semiconductor layer having photoelectric conversion regions, one surface of the semiconductor layer forming a light incident surface, the other surface of the semiconductor layer forming an element forming surface, a trench positioned to partition the photoelectric conversion regions and penetrating the semiconductor layer in a direction of thickness thereof, and a separation part formed in the trench and including a first separation part and a second separation part, the first separation part being positioned on the side of the light incident surface, the second separation part being positioned on the side of the element forming surface. A first surface of the second separation part on the side of the first separation part faces a first material.