Semiconductor Isolation Trenches for CMOS Noise Reduction
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Solution Overview
Problem
Complementary metal oxide semiconductor (CMOS) image sensors face inefficiencies and noise issues due to lack of proper isolation between devices, particularly as pixel size scales down, leading to undesirable junction leakage.
Innovation Solution
The formation of isolation regions using a process involving gate dielectric and conductive layers, hardmask layers, advanced patterning films, and ion implantation to create trenches and dielectric layers, which effectively separate devices and reduce leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size and pitch are scaled down to increase resolution, then image sensor resolution is improved, but noise between devices increases and junction leakage occurs due to insufficient isolation
Solution Approach 1:
The patent applies segmentation by dividing the semiconductor substrate into isolated pixel regions using deep isolation trenches. These trenches physically separate adjacent pixels and devices, preventing electrical interference and noise coupling. The trenches extend through multiple layers including gate dielectric and interlayer dielectric, creating distinct isolated zones for each pixel while maintaining high resolution through compact pixel design.
Solution Approach 2:
The patent introduces isolation trenches filled with dielectric material as an intermediary structure between adjacent pixels and devices. This intermediary layer acts as an electrical barrier that blocks noise and leakage currents from propagating between neighboring devices, while allowing each pixel to function independently at high resolution.
2Reliability
If isolation structures are added to reduce noise and leakage, then device isolation is improved, but manufacturing complexity increases due to additional process steps
Solution Approach 1:
The patent merges the formation of isolation trenches with existing manufacturing processes. The trenches are created using the same gate dielectric deposition and patterning steps already required for transistor fabrication. By combining isolation structure formation with standard process flows, the patent achieves effective device isolation without proportionally increasing manufacturing complexity.
Solution Approach 2:
The isolation trenches serve multiple functions simultaneously: they provide electrical isolation between devices, act as mechanical support structures, and define pixel boundaries. This multi-functionality reduces the need for separate dedicated isolation processes, thereby limiting the increase in manufacturing complexity while achieving reliable device 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 solution enhances the operational efficiency of CMOS image sensors by reducing noise and junction leakage, ensuring proper isolation between components and improving image capture capabilities.
Implementation Method 1
a first type of dopants with a first conductivity is implanted into the substrate using a first dielectric layer as a mask, the implanting first ions forming an isolation region within the substrate
Data Source
AI summary
A system and method for isolating semiconductor devices is provided. An embodiment comprises an isolation region that is laterally removed from source/drain regions of semiconductor devices and has a dielectric material extending over the isolation implant between the source/drain regions. The isolation region may be formed by forming an opening through a layer over the substrate, depositing a dielectric material along the sidewalls of the opening, implanting ions into the substrate after the deposition, and filling the opening with another dielectric material.