STI Trench Isolation with Rounded Liner Oxide Corners
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Solution Overview
Problem
Conventional shallow trench isolation (STI) processes in semiconductor fabrication face issues such as stress-induced dislocation and thinning of the gate oxide layer due to the use of silicon nitride layers, leading to leakage currents and parasitic MOSFET formation.
Innovation Solution
The implementation of In Situ Steam Generation (ISSG) radical conversion on the silicon nitride liner layer within the STI trench to expose the top corners of the liner oxide layer, allowing the insulating layer to be formed in an oxygen-filled atmosphere and preventing dislocation, while maintaining a compact insulation layer and preserving the gate oxide layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon nitride (SiN) layer is formed over the oxide liner within the trench to prevent oxidation and enable compaction in an oxygen-filled atmosphere, then the insulation layer becomes more compact, but the gate oxide layer thickness is reduced due to thinning at the trench corners
Solution Approach 1:
The patent removes the silicon nitride layer from the trench structure, extracting the problematic element that caused gate oxide thinning. By eliminating this layer, the harmful oxidation effect at the trench corners is removed, preventing gate oxide thinning while maintaining the essential isolation function through alternative means.
Solution Approach 2:
The patent changes the chemical composition and physical properties of the liner oxide layer through controlled oxidation processes, transforming it into a material that provides both protection and rounding effects. This parameter change allows the oxide layer to serve multiple functions without requiring the problematic silicon nitride layer.
2Manufacturing precision
If the insulation layer is formed in an oxygen-filled atmosphere to achieve compactness, then the insulation quality improves, but dislocation occurs at the trench corners due to stress
Solution Approach 1:
The patent introduces rounded corners at the trench openings by controlling the oxidation process of the liner oxide layer. This curvature modification eliminates the sharp corners that concentrate stress, preventing dislocation while allowing the insulation layer to be formed in an oxygen-filled atmosphere for compactness.
Solution Approach 2:
The patent performs preliminary oxidation of the liner oxide layer to create rounded corners before depositing the insulation layer. This preliminary action pre-establishes the stress-distributing geometry, preventing subsequent dislocation when the insulation layer is formed and compacted.
3Reliability
If a liner oxide layer is formed to line the inside of the trench before oxide deposition, then the trench is protected and isolation is improved, but stress accumulates at the trench corners during compaction
Solution Approach 1:
The patent modifies the liner oxide layer by rounding its corners through controlled oxidation. This curvature change distributes stress more evenly during the compaction process, preventing stress concentration and dislocation at the trench corners while maintaining the liner's protective and isolating functions.
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 effectively reduces stress and prevents thinning of the gate oxide layer, enhancing the isolation quality and reducing leakage currents by rounding the liner oxide layer corners and maintaining a compact insulation layer within the trench.
Implementation Method 1
performing an In Situ Steam Generation (ISSG) radical conversion on a SiN liner layer within an STI trench
Implementation Method 2
performing the ISSG process at a temperature greater than 900° C.
Data Source
AI summary
A process for forming STI regions comprises performing an In Situ Steam Generation (ISSG) radical conversion on a SiN liner layer within an STI trench in order to expose the top corner of the trench and simultaneously cause rounding the top corner of a liner oxide layer within the trench. The rounding of the liner oxide layer can prevent thinning of a subsequently formed gate oxide.