Semiconductor Isolation Structure With Closed-Loop Dielectric Barrier
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Solution Overview
Problem
As semiconductor feature sizes decrease, existing technologies face challenges in effectively forming isolation structures that prevent impurity diffusion and enhance device reliability and yield, particularly due to issues with void formation and nitride layer placement affecting transistor performance.
Innovation Solution
The semiconductor structure incorporates a dielectric barrier structure formed by a combination of nitride layers surrounding an oxide fill layer in a closed loop, which blocks impurities and improves manufacturing yield by maintaining the nitride layer away from the active region, thereby preventing electron trapping and enhancing leakage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the nitride layer is placed directly in the trench to form isolation structure, then the isolation structure can be formed simply, but the nitride layer may trap electrons and degrade transistor performance
Solution Approach 1:
The patent extracts the nitride layer from direct contact with the active region by removing it from the trench bottom and retaining it only on the trench sidewalls. This is achieved through selective etching processes that remove the nitride layer from areas that would cause electron trapping while preserving it on sidewalls where it provides beneficial isolation without harming transistor performance.
Solution Approach 2:
The patent introduces an oxide layer as an intermediary between the nitride layer and the active region. The oxide layer is formed on the trench bottom and serves as a barrier that prevents direct interaction between the nitride layer and the semiconductor substrate, thereby preventing electron trapping while still allowing the nitride layer to provide isolation functionality on the sidewalls.
2Object-affected harmful factors
If the oxide fill layer is used to fill the trench, then impurity diffusion can be blocked, but voids may form affecting manufacturing yield
Solution Approach 1:
The patent uses a composite isolation structure combining multiple materials: oxide layers for impurity blocking, nitride layers for additional isolation and sidewall protection, and selective removal of nitride portions to prevent void formation. The multi-material approach allows each layer to perform its optimal function while compensating for the limitations of individual materials.
Solution Approach 2:
The patent segments the isolation structure into multiple functional layers with distinct roles. The oxide fill layer is divided into different regions (first oxide layer in the trench, second oxide layer overhanging the trench), and the nitride layer is segmented into sidewall portions and bottom portions that are selectively retained or removed. This segmentation allows precise control over where each material is present to optimize both impurity blocking and void prevention.
3Productivity
If the isolation structure is formed with traditional methods, then the process can be completed quickly, but the device yield and reliability are compromised
Solution Approach 1:
The patent performs preliminary actions by forming the oxide layer and nitride layer in specific sequences before final trench filling. The oxide layer is formed first to establish the base isolation structure, followed by nitride layer deposition on sidewalls. Selective removal of nitride from the trench bottom is performed as a preliminary step before final oxide filling, preventing void formation in advance and ensuring high device yield without requiring additional corrective processing steps.
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate and an isolation structure disposed in the semiconductor substrate. The isolation structure includes a lining layer disposed along a boundary between the semiconductor substrate and the isolation structure, a first oxide fill layer disposed over the lining layer, a dielectric barrier structure surrounding the first oxide fill layer in a closed loop, and a second oxide fill layer disposed over the dielectric barrier structure and adjacent to the lining layer.