Trench Isolation Structure Using Oxidation Barrier Layer
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Solution Overview
Problem
Conventional trench isolation structure manufacturing methods using TEOS as an etching hardmask result in large grooves and soft connections due to polysilicon residue, leading to unfavorable flatness and increased critical dimensions.
Innovation Solution
A method involving the formation of an oxidation barrier layer and an ethyl orthosilicate layer, where the oxidation barrier layer shields the non-trench region during oxidation, reducing wet-etching volume and avoiding lateral etching, allowing for a smaller critical dimension and improved flatness by using these layers as masking and barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet-etching is performed at a large scale to remove oxidation layer, then the oxidation layer can be completely removed, but lateral etching occurs and critical dimension increases
Solution Approach 1:
The patent segments the etching process into two distinct stages: first, dry etching is used to remove the oxidation layer with precise control over critical dimensions; second, wet-etching is applied only to remove residual oxidation layer at the trench bottom. This segmentation eliminates lateral etching while maintaining complete oxidation layer removal.
Solution Approach 2:
The patent changes the etching parameters by transitioning from wet-etching to dry etching for the main oxidation layer removal step. Dry etching provides better anisotropy and etch profile control, preventing lateral etching and maintaining accurate critical dimensions while still achieving complete oxidation layer removal.
2Manufacturing precision
If wet-etching is performed extensively, then oxidation layer can be removed, but a large groove is formed on the trench top resulting in poor flatness
Solution Approach 1:
The patent divides the oxidation layer removal into two parts: dry etching for the bulk removal with controlled depth, and wet-etching only for residual removal at the trench bottom. This prevents the formation of large grooves on the trench top while ensuring complete oxidation layer removal.
Solution Approach 2:
The patent replaces extensive wet-etching with dry etching for the primary oxidation layer removal. Dry etching provides better etch profile control and reduces groove formation, improving the flatness of the trench top surface while maintaining complete oxidation layer removal.
3Reliability
If TEOS layer is used as etching hardmask, then the etching process can be performed, but polysilicon residue causes soft connection affecting product performance
Solution Approach 1:
The patent extracts the problematic TEOS hardmask layer and replaces it with a photoresist-based masking system. This eliminates the polysilicon residue issue that causes soft connections, while the etching process remains effective through the use of photoresist as the masking layer.
Solution Approach 2:
The patent uses photoresist as a disposable masking layer that can be easily applied, patterned, and removed without leaving residues. The photoresist serves its masking function during etching and is then completely removed, avoiding the polysilicon residue problems associated with TEOS hardmasks.
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 method achieves a trench isolation structure with reduced critical dimension and enhanced flatness by minimizing wet-etching and preventing polysilicon residue, thereby improving the structural integrity and performance of the trench isolation structure.
Implementation Method 1
oxidizing a sidewall of the trench using the oxidation barrier layer as a barrier layer
Implementation Method 2
etching the substrate to form a trench using the etched oxidation barrier layer and the ethyl orthosilicate layer as masking layers
Implementation Method 3
filling polysilicon in the trench, and then performing an etchback process to the polysilicon to remove the polysilicon on the surface
Data Source
AI summary
A method for preparing a trench isolation structure, which comprises the following steps of: providing a substrate; forming an oxide layer on the substrate; successively generating an oxidation barrier layer and an ethyl orthosilicate layer on the surface of the oxide layer; etching the oxidation barrier layer and the ethyl orthosilicate layer; corroding the substrate to form a trench by using the oxidation barrier layer and the ethyl orthosilicate layer as mask layers; removing the ethyl orthosilicate layer, and oxidizing a side wall of the trench by using the oxidation barrier layer as a barrier layer; filling the trench with a polysilicon and then etching back the polysilicon, and removing the polysilicon on the surface of the oxidation barrier layer; and removing the oxidation barrier layer and the oxide layer on the surface of the substrate.