Deep Trench Isolation for CMOS Image Sensor Leakage
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Solution Overview
Problem
As semiconductor image sensors evolve with smaller and more complex pixels, excessive current leakage becomes difficult to control, leading to white spot problems (white pixels) in CMOS image sensors due to increased proximity between pixels.
Innovation Solution
The implementation of deep trench isolation (DTI) structures using silicon oxycarbonitride (SiOCN) dielectric layers, formed through atomic layer deposition, provides effective separation between neighboring pixels, preventing light crosstalk and reducing unwanted current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to increase resolution, then image quality is improved, but current leakage increases causing white spot problems
Solution Approach 1:
The patent applies segmentation by introducing deep trench isolation structures that physically divide and separate adjacent photodiode regions. These trenches extend deeply into the substrate, creating independent isolation zones that prevent current leakage between neighboring pixels, thereby resolving the white spot problem while maintaining high-resolution imaging capability
Solution Approach 2:
The patent uses deep trench isolation structures as intermediary elements positioned between adjacent photodiodes. These isolation trenches act as mediators that block unwanted current paths and electrical interference, allowing pixels to be placed closer together for higher resolution without suffering from current leakage issues
2Productivity
If separation between pixels is reduced to increase pixel density, then productivity is improved, but light crosstalk increases causing white pixels
Solution Approach 1:
The patent transitions from two-dimensional surface separation to three-dimensional deep trench isolation. By extending isolation structures vertically deep into the substrate, the patent creates separation in the depth dimension, enabling high horizontal pixel density while maintaining effective optical isolation between adjacent pixels
Solution Approach 2:
The deep trench isolation structures serve as intermediary barriers between adjacent photodiodes. These trenches filled with dielectric material act as optical and electrical mediators that prevent light crosstalk and charge carrier diffusion between neighboring pixels, enabling higher pixel density without compromising image quality
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 approach significantly reduces white pixels by 36% and enhances image sensor performance by minimizing crosstalk between pixels, ensuring better image quality.
Implementation Method 1
formed through atomic layer deposition
Data Source
AI summary
A plurality of radiation-sensing doped regions are formed in a substrate. A trench is formed in the substrate between the radiation-sensing doped regions. A SiOCN layer is filled in the trench by reacting Bis(tertiary-butylamino)silane (BTBAS) and a gas mixture comprising N2O, N2 and O2 through a plasma enhanced atomic layer deposition (PEALD) method, to form an isolation structure between the radiation-sensing doped regions.