TaN to Ta Conversion for Semiconductor Barrier Layers
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Solution Overview
Problem
In high-speed and high-integration semiconductor devices, the use of copper wiring is hindered by signal delay due to resistance and capacitance, and existing barrier layers like Tantalum Nitride have low adhesive strength and allow copper diffusion, while dual-film barriers face complications in formation, especially with large aspect ratios and impurities affecting resistivity.
Innovation Solution
A method involving the formation of a dual film of Tantalum (Ta) and Tantalum Nitride (TaN) using atomic layer deposition (ALD) and conversion of TaN to Ta using a diluted Nitric Acid solution to prevent overhanging and impurity incorporation, ensuring adequate diffusion barrier and adhesive properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Tantalum Nitride (TaN) film is used as a barrier layer, then copper diffusion is prevented, but adhesive strength with Copper is reduced
Solution Approach 1:
The barrier layer is segmented into a dual-film structure with a TaN film (for diffusion prevention) and a Ta film (for adhesion). This segmentation allows each layer to perform its specialized function independently, resolving the contradiction between diffusion barrier performance and adhesive strength.
2Ease of manufacture
If a dual-film barrier layer is formed by PVD, then formation is simpler, but overhanging occurs blocking the via
Solution Approach 1:
The mechanical PVD deposition process is replaced with ALD (Atomic Layer Deposition), which uses chemical vapor deposition mechanisms. This substitution eliminates the overhanging problem inherent in PVD while maintaining process feasibility, as ALD provides superior conformal coverage in high aspect ratio structures.
3Manufacturing precision
If a dual-film barrier layer is formed by ALD, then overhanging is prevented, but formation process becomes more complicated
Solution Approach 1:
The process parameters are optimized by forming the TaN film with controlled thickness (50-200 nm) and subsequently converting it to Ta through nitric acid soaking. This parameter control simplifies the overall process by eliminating the need for separate Ta deposition steps while maintaining the dual-film functionality.
4Ease of manufacture
If Carbon (C) and Oxygen (O) are present in a TaN film during ALD, then film formation is easier, but resistivity becomes relatively large
Solution Approach 1:
The Carbon and Oxygen impurities incorporated during ALD are converted into a benefit through nitric acid soaking. The nitric acid treatment transforms the TaN film into Ta while removing the impurities, thereby reducing resistivity and improving electrical conductivity without requiring separate purification steps.
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 prevents copper diffusion and enhances adhesion, reducing signal delay and resistivity, while simplifying the processing steps and maintaining cost-effectiveness by forming a stable and high-purity barrier layer structure.
Implementation Method 1
converting a TaN film into a Ta film by soaking the TaN film in a diluted Nitric Acid (HNO3) solution
Implementation Method 2
forming a TaN film over a semiconductor substrate by atomic layer deposition (ALD)
Data Source
AI summary
A method for forming a thin film of a semiconductor device, which may include at least one of the following steps: Forming a Tantalum Nitride (TaN) film over a semiconductor substrate by atomic layer deposition. Forming a Tantalum (Ta) film by converting at least a portion of a Tantalum Nitride (TaN) film into Tantalum (Ta) by soaking the TaN film in a diluted HNO3 solution.