Semiconductor Structure with Dopant Gradient for Hot Cluster Suppression
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Solution Overview
Problem
Current semiconductor technologies lack a universal solution to suppress hot clusters in CMOS image sensors, which can lead to total die failure due to the spread of abnormal pixel defects, as existing approaches are mostly case-specific and ineffective in preventing the formation of hot clusters.
Innovation Solution
A semiconductor structure is developed with a dopant gradient region and a shallow trench isolation region, where the isolation doping region is adjacent to the dopant gradient region, forming a potential barrier to restrict the spread of dark current and prevent hot clusters by creating a conductivity gradient between epitaxial layers and substrate, thereby isolating abnormal pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional isolation methods are used, then manufacturing simplicity is maintained, but hot cluster suppression effectiveness deteriorates
Solution Approach 1:
The patent implements local quality by creating a dopant gradient region with varying dopant concentrations at different locations within the semiconductor substrate. The gradient transitions from a first dopant concentration in the first region to a second dopant concentration in the second region, providing location-specific electrical properties that suppress hot cluster formation where needed while maintaining normal operation in other areas.
Solution Approach 2:
The patent applies parameter changes by modifying the dopant concentration parameter across different regions of the substrate. The dopant gradient region features a continuous transition in dopant concentration from the first region through the gradient region to the second region, creating varying electrical characteristics that prevent hot cluster propagation without requiring complex structural modifications.
2Object-generated harmful factors
If dopant gradient region is created, then dark current flow is restricted, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the dopant gradient region through a thermal process performed before subsequent manufacturing steps. The gradient region is created in advance to establish the desired dopant concentration profile, which then serves to restrict dark current flow throughout the remaining manufacturing process and device operation.
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
The proposed solution effectively suppresses hot clusters by creating a potential barrier that restricts dark current flow, preventing the formation of cross-shaped or block-shaped clusters and avoiding total die failure from single hot cluster incidents.
Implementation Method 1
a dopant gradient region in the epitaxial layer so that the dopant gradient region has a dopant gradient decreasing from the substrate toward the epitaxial layer
Implementation Method 2
the shallow trench isolation region and the dopant gradient region together form a potential barrier to suppress a hot cluster caused by a dark current travelling from the first element region through the epitaxial layer to the second element region
Implementation Method 3
a thermal step is carried out after the formation of the epitaxial layer to form a dopant gradient region in the epitaxial layer
Implementation Method 4
an isolation doping region surrounding the shallow trench isolation so that the isolation doping region is substantially adjacent to the dopant gradient region
Data Source
AI summary
A semiconductor structure for suppressing hot clusters includes a substrate of a first dopant concentration, an epitaxial layer having a second dopant concentration smaller than the first dopant concentration and directly disposed on the substrate, a dopant gradient region disposed in the epitaxial layer and having a gradient decreasing from the substrate to the epitaxial layer, a shallow trench isolation disposed between a first element region and a second element region, and a shallow trench doping region surrounding the shallow trench isolation and near the dopant gradient region to suppress a hot cluster formed by the first element region to jeopardize the second element region.