Semiconductor Barrier Metal Layer Nitrogen Trapping
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Solution Overview
Problem
The diffusion of nitrogen atoms from the TiN layer in semiconductor devices can decompose TiSi2, leading to increased contact resistance, while fluorine and silicon atom diffusion through grain boundaries in the TiN layer can cause voids and conversion of the W layer, respectively, reducing the yield of semiconductor devices.
Innovation Solution
A semiconductor device structure with a barrier metal layer comprising a Ti layer and a second metal nitride layer with a lower nitride formation free energy, which traps nonbonding nitrogen atoms and prevents diffusion of fluorine and silicon atoms, thereby maintaining low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TiN layer is heated at high temperature to form a barrier metal layer, then the barrier metal layer can provide good electrical conductivity, but nonbonding nitrogen atoms diffuse outwardly from the TiN layer and decompose TiSi2, increasing contact resistance
Solution Approach 1:
A second metal nitride layer is introduced between the TiN layer and the TiSi2 layer to act as an intermediary barrier. This intermediate layer has lower nitride formation free energy than TiN, enabling it to trap nitrogen atoms and prevent their outward diffusion to the TiSi2 layer, thus resolving the contradiction between maintaining electrical conductivity and preventing nitrogen diffusion.
Solution Approach 2:
The barrier metal layer is designed as a composite structure combining TiN layer and second metal nitride layer. This composite structure leverages the high electrical conductivity of TiN while the second metal nitride component provides enhanced nitrogen trapping capability, achieving both good electrical conductivity and effective prevention of nitrogen diffusion.
2Ease of manufacture
If the TiN layer structure is used without additional barriers, then the manufacturing process is simple, but fluorine atoms and silicon atoms diffuse along grain boundaries, causing voids and W layer conversion, reducing device yield
Solution Approach 1:
The second metal nitride layer serves as a diffusion barrier intermediary that blocks fluorine atoms from reaching the substrate and prevents silicon atoms from diffusing into the W layer. This intermediate barrier layer effectively stops harmful diffusion along grain boundaries while adding minimal complexity to the manufacturing process.
3Reliability
If a second metal nitride layer with lower nitride formation free energy is added to trap nitrogen atoms, then contact resistance is maintained low by preventing nitrogen diffusion, but the barrier metal layer structure becomes more complex
Solution Approach 1:
The invention changes the key parameter of nitride formation free energy by selecting a second metal with lower nitride formation free energy than titanium. This parameter change enables the second metal nitride layer to thermodynamically favor nitrogen trapping, effectively preventing nitrogen diffusion and maintaining low contact resistance. The layer is formed to a thickness of 1 nm or more to ensure adequate barrier 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 solution effectively prevents the increase in contact resistance by trapping nitrogen atoms and blocking the diffusion of fluorine and silicon atoms, ensuring stable semiconductor device performance.
Implementation Method 1
nonbonding nitrogen atoms in the TiN layer diffuse outwardly from the TiN layer
Implementation Method 2
fluorine atoms generated in forming a tungsten (W) layer functioning as a plug material layer can diffuse to a substrate along a grain boundary in the TiN layer, or that silicon atoms in the substrate can diffuse to the W layer along the grain boundary in the TiN layer
Data Source
AI summary
According to some embodiments, a semiconductor device includes a substrate and an insulating film that is provided on the substrate. The device further includes a contact plug which includes a barrier metal layer provided in the insulating film, and a plug material layer provided in the insulating film, the barrier metal layer disposed between the plug material layer and the insulating film. The barrier metal layer includes at least a first layer including a first metal element and nitrogen, and a second layer including a second metal element different from the first metal element, and nitrogen.