Tungsten Contact Plug Dual Barrier Layer Adhesion
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Solution Overview
Problem
The challenge in semiconductor devices is to shrink the diameter of contact plugs without degrading their reliability and increasing electric resistance, as existing chemical vapor deposition methods result in poor adhesion and worse electro-migration resistance compared to physical vapor deposition methods, and the barrier layer's high resistivity limits further thinning.
Innovation Solution
A semiconductor device structure featuring a tungsten contact plug with a two-layer barrier system, including a titanium-based first bottom barrier layer formed by Physical Vapor Deposition (PVD) for enhanced adhesion and a tungsten nitride barrier metal, allowing for thinner film thickness while maintaining functionality, and a titanium nitride second bottom barrier layer, which helps in reducing electric resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a chemical vapor deposition method is used to form a contact plug in a small diameter contact hole, then the contact plug can be formed with good step coverage, but the adhesion to the lower conductor layer becomes poor and electro-migration resistance deteriorates
Solution Approach 1:
The barrier layer is divided into a stacked structure consisting of a first barrier layer (formed by PVD) and a second barrier layer (formed by CVD). The first barrier layer provides strong adhesion and electro-migration resistance, while the second barrier layer provides good step coverage. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between adhesion reliability and step coverage.
Solution Approach 2:
The first barrier layer acts as an intermediary between the lower conductor layer and the second barrier layer. It provides a transition zone that ensures strong adhesion to the conductor layer while allowing the second barrier layer to provide the necessary step coverage for the contact plug formation.
2Reliability
If the barrier layer film thickness is increased to realize its functions, then adhesion and electro-migration resistance improve, but the electric resistance of the contact plug increases due to the high resistivity of the barrier layer material
Solution Approach 1:
The barrier layer is segmented into two layers with different thicknesses and functions. The first barrier layer has a greater thickness to provide the necessary adhesion and electro-migration resistance, while the second barrier layer has a smaller thickness to minimize its contribution to the overall electric resistance. This segmentation allows the barrier layer to fulfill its protective functions while minimizing the harmful effect of high resistivity.
3Productivity
If the diameter of the contact plug is shrunk to achieve further miniaturization, then integration density increases, but the electric resistance of the contact plug increases extremely
Solution Approach 1:
The invention changes the material parameters of the barrier layer by using a stacked structure with different materials and thicknesses. This allows optimization of the balance between adhesion, electro-migration resistance, and electric resistance, enabling smaller contact plug diameters without excessive resistance increase.
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 improves the adhesion and reliability of the contact plug while allowing for a larger diameter, thereby reducing electric resistance without degrading the semiconductor device's performance, even when the contact plug diameter is shrunk.
Implementation Method 1
a first bottom barrier layer comprising titanium and formed by a physical vapor deposition method
Implementation Method 2
it is desirable to use a chemical vapor deposition method rather than a physical vapor deposition method from the viewpoint of a deposition phenomenon such as step coverage
Data Source
AI summary
Disclosed herein is a semiconductor device that comprises a plug including an upper portion, a lower portion and a side surface and comprising tungsten, a barrier metal comprising tungsten nitride and covering the side surface and the lower portion of the contact plug, a conductive layer, and a barrier layer comprising titanium and intervening between the barrier metal and the first conductive layer.