Magnetic Core Structure With Protective Region for Wet-Etch Precision
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Solution Overview
Problem
The fabrication of thick magnetic cores for inductor devices faces challenges with dry-etching being impractical due to high costs and low throughput, while wet-etching results in severe undercutting, reducing inductor performance.
Innovation Solution
A semiconductor device and method involving a substrate with a protective region and a core structure etchable by a chemical solution, where the protective region is resistant to etching, allowing for isotropic wet-etching that prevents lateral etching and maintains the core's thickness and adhesion, using photo-sensitive polyimide (PSPI) for protection and patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet-etching is used to fabricate thick magnetic cores, then manufacturing cost and throughput are improved, but severe undercutting occurs that reduces inductor performance
Solution Approach 1:
A protective layer is formed over the magnetic core material before etching. This preliminary protective action prevents the etchant from attacking the sidewalls of the core, thereby avoiding undercutting while allowing the use of wet-etching for high throughput production.
Solution Approach 2:
The protective layer acts as an intermediary between the etchant and the magnetic core material. It selectively protects the core sidewalls from the etchant while allowing etching to proceed in other directions, thus maintaining core shape precision during wet-etching.
2Manufacturing precision
If dry-etching is used to fabricate thick magnetic cores, then manufacturing precision is improved, but cost increases and throughput decreases
Solution Approach 1:
A disposable protective layer is applied temporarily during the etching process to enable the use of cost-effective wet-etching. The protective layer is removed after etching, having served its purpose of preventing undercutting during the low-cost, high-throughput wet-etching process.
3Ease of manufacture
If wet-etching is used to fabricate thick magnetic cores, then manufacturing cost is reduced, but severe undercutting occurs that reduces adhesion
Solution Approach 1:
The protective layer is applied before etching to prevent undercutting at the interface between the magnetic core and the underlying layer. This preliminary protection maintains strong adhesion by preventing the etchant from creating gaps or weak interfaces during the low-cost wet-etching process.
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 enables the fabrication of thick core structures with improved adhesion and reduced side wall roughness, enhancing inductor performance by preventing lateral etching and maintaining magnetic properties, thus allowing for better inductance and reliability.
Implementation Method 1
wet-etching of a thick magnetic core may result in severe undercutting
Implementation Method 2
The protective region may include a protective material resistant to etching by the chemical solution
Data Source
AI summary
A semiconductor device may include: a substrate; a protective region provided over the substrate; and a core structure enclosed by the protective region. The core structure may include a core material etchable by a chemical solution. The protective region may include a protective material resistant to etching by the chemical solution. The core structure may have a first side and a second side opposite to the first side, the first side being closer to the substrate than the second side. The core structure may be narrowest at the first side of the core structure.