Mask Pattern Fabrication via Selective Trench Etching
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Solution Overview
Problem
Over-etching occurs during the formation of trench patterns in semiconductor fabrication, particularly in shallow trench isolation (STI) structures, leading to inefficiencies and inaccuracies in device isolation.
Innovation Solution
A method involving multiple mask layers and materials is employed to prevent over-etching, where a first trench with a wider width than a second trench is filled with a first mask material, and a third mask material is used to protect the second mask material, allowing for controlled etching and alignment to form precise trench patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching process is used to transfer trench patterns, then the etching process can be completed, but over-etching occurs on the masks leading to loss of mask material and reduced manufacturing precision
Solution Approach 1:
The patent applies preliminary action by forming a protective mask material layer before the etching process. This protective layer is deposited conformally over the mask patterns and trenches, creating a buffer that prevents over-etching damage to the underlying mask structures. The protective layer is then selectively removed after etching, ensuring mask integrity is maintained throughout the process.
Solution Approach 2:
The protective mask material layer serves as an intermediary between the etching process and the mask patterns. This intermediate layer absorbs the excessive etching energy that would otherwise damage the mask materials, allowing the etching to proceed to completion without compromising mask pattern accuracy or causing over-etching.
2Manufacturing precision
If multiple mask layers are used to prevent over-etching, then mask pattern accuracy is improved, but process complexity increases
Solution Approach 1:
The protective mask material layer performs multiple functions: it protects underlying mask patterns from over-etching, serves as an etch stop layer, and provides a planar surface for subsequent processing. By combining these functions into a single universal layer, the patent reduces the need for multiple separate protective layers, thereby simplifying the overall process while maintaining high manufacturing precision.
3Reliability
If conformal coating is applied to fill trenches, then trench coverage is improved, but material usage increases
Solution Approach 1:
The patent applies local quality by using selective removal processes after conformal coating. The protective mask material layer is deposited conformally to ensure complete trench coverage and reliability, but then selectively removed from specific areas using targeted etching or lifting processes. This approach maintains the benefits of conformal coverage while minimizing unnecessary material consumption in regions where full coverage is not required.
Data Source
AI summary
A method of fabricating a mask pattern includes providing numerous masks on a substrate. A wider trench and a narrower trench are respectively defined between the mask. Subsequently, a mask material is formed to fill in the wider trench and the narrower trench. The top surface of the mask material overlapping the wider trench is lower than the top surface of the mask material overlapping the narrower trench. A photoresist layer is formed on the mask material overlapping the wider trench. Later, the mask material overlapping the narrower trench is etched while the mask material overlapping the wider trench is protected by the photoresist layer.