FinFET TaN Gate Layer Protection During Tungsten Wet Etching
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Solution Overview
Problem
In the manufacturing of FinFETs, the challenge lies in maintaining the integrity and thickness of the TaN layer during wet etching processes, as existing methods can cause significant loss due to chemical reactions or physical interactions with subsequent metal layers, particularly with tungsten, leading to suboptimal device performance.
Innovation Solution
A protective layer, doped with boron or other elements like silicon and nitrogen, is introduced on the surface of the TaN layer to prevent thickness loss during wet etching operations, using gases such as B2H6 for doping and WF6 for forming metallic layers, which are then removed using solutions like H3PO4 without damaging the TaN layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If wet etching process is used to remove metallic layers, then the metallic layer can be effectively removed, but the TaN layer thickness is significantly reduced due to chemical reactions and physical interactions
Solution Approach 1:
A protective layer is introduced as an intermediary between the TaN layer and the wet etching solution. This protective layer selectively resists the etching solution, preventing direct contact and chemical reactions between the solution and the TaN layer, thereby preserving the TaN layer thickness while still allowing the metallic layers to be removed.
Solution Approach 2:
The protective layer is formed in advance before the wet etching process to preemptively prevent the harmful chemical reactions and physical interactions that would otherwise occur between the etching solution and the TaN layer. This preliminary protective action ensures the TaN layer maintains its intended thickness throughout the etching process.
2Ease of manufacture
If no protective layer is used, then the manufacturing process is simpler, but the TaN layer thickness is lost during wet etching
Solution Approach 1:
The protective layer serves as a temporary intermediary structure that adds a controlled step to the manufacturing process. While this increases process complexity slightly, it enables precise control over the TaN layer thickness by preventing unwanted material loss during wet etching, thereby achieving better manufacturing precision.
3Reliability
If the protective layer is made highly resistant to the etching solution, then the TaN layer is better protected, but the protective layer itself becomes harder to remove
Solution Approach 1:
The protective layer is designed with spatially varying properties: it exhibits high resistance to the etching solution when in contact with the TaN layer to provide effective protection, but has specific regions or characteristics that allow for selective removal after the metallic layers are stripped. This local differentiation enables both effective protection and subsequent removal.
Solution Approach 2:
The protective layer's resistance to the etching solution is optimized to specific parameter ranges that balance protection effectiveness with removability. By controlling the composition, thickness, and structural parameters of the protective layer, it achieves sufficient resistance to protect the TaN layer while maintaining the capability to be removed under controlled conditions after serving its protective function.
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 protective layer effectively suppresses chemical reactions and physical interactions, resulting in minimal thickness loss of the TaN layer, thereby maintaining device integrity and performance.
Implementation Method 1
The protective layer is resistant to the solution of the wet etching operation, thereby suppressing a chemical reaction and/or a physical interaction between the solution and the TaN layer
Implementation Method 2
a protective layer, doped with boron or other elements like silicon and nitrogen, is introduced on the surface of the TaN layer
Data Source
AI summary
In a method of manufacturing a semiconductor device, a gate dielectric layer is formed over a channel region, a first conductive layer is formed over the gate dielectric layer, a protective layer is formed at a surface region of the first conductive layer, a metallic layer is formed by applying a metal containing gas on the protective layer, and the metallic layer is removed by a wet etching operation using a solution. The protective layer is resistant to the solution of the wet etching operation.