Tungsten Nitride Liner for Low-Resistance Gate Electrodes
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Solution Overview
Problem
Conventional TiN-based film stacks in semiconductor device fabrication face issues such as high deposition temperatures, poor diffusion resistance, and increased resistivity due to halide element diffusion, particularly in sub-micron feature sizes where space for low resistance CVD W bulk is limited, and the need for a nucleation layer complicates the process.
Innovation Solution
A method involving the deposition of a tungsten nitride layer on a substrate, followed by a nitridation treatment using active nitrogen species and the direct deposition of a conductive bulk layer without a tungsten nucleation layer, using halogen-free MOCVD or MOALD processes to form WN, WN(Wrich), or WN(Wpure) film stacks, which serve as a barrier and growth site for subsequent bulk W, reducing resistivity and eliminating the need for a high resistive nucleation layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If TiN liner/barrier is used, then step coverage is improved, but deposition temperature becomes much greater than 400°C which is incompatible with many device integration processes
Solution Approach 1:
The patent removes the TiN liner/barrier layer from the conventional film stack and replaces it with a tungsten nitride (WN) layer. This extraction of the problematic TiN component eliminates the need for high-temperature deposition processes while maintaining the barrier function against halide diffusion.
Solution Approach 2:
The patent changes the material parameter from TiN to tungsten nitride (WN), which allows for low-temperature deposition compatible with device integration processes. The WN layer provides the necessary barrier properties at temperatures much lower than 400°C, resolving the temperature contradiction.
2Reliability
If TiN is used as barrier film, then barrier function is provided, but diffusion resistance is poor allowing halide elements to diffuse into the device increasing resistivity
Solution Approach 1:
The patent extracts and removes the TiN barrier layer that exhibits poor diffusion resistance. Instead, it introduces a tungsten nitride (WN) layer that provides superior barrier properties against halide element diffusion, eliminating the harmful diffusion effect while maintaining the barrier function.
Solution Approach 2:
The patent employs a composite film stack structure consisting of tungsten nitride (WN) and tungsten-rich tungsten nitride (WN(Wrich)) layers. This composite structure provides enhanced barrier properties against halide diffusion compared to single-layer TiN, improving the reliability of the film stack.
3Productivity
If feature sizes are decreased to sub-micron dimensions, then circuit density is increased, but space for low resistance CVD W bulk is limited or nonexistent
Solution Approach 1:
The patent removes the high-resistivity nucleation layer from the film stack, which traditionally occupied valuable space in sub-micron features. By eliminating this layer, more space is available for the low-resistance CVD W bulk material, allowing circuit density increases without compromising electrical performance.
Solution Approach 2:
The patent changes the material composition and structure of the barrier layer from conventional TiN to tungsten nitride (WN) with controlled stoichiometry. This parameter change enables the barrier layer to be thinner while maintaining effective barrier properties, thereby freeing up space for the conductive CVD W bulk in sub-micron features.
4Ease of manufacture
If nucleation layer is deposited as growth site for W bulk film, then W bulk film growth is enabled, but film stack resistivity is increased due to high resistivity of nucleation layer
Solution Approach 1:
The patent extracts and eliminates the high-resistivity nucleation layer from the film stack. Instead of using a separate nucleation layer to enable W bulk film growth, the tungsten nitride (WN) layer itself is engineered to serve as both the barrier layer and the growth substrate for the CVD W bulk, thereby removing the source of high resistivity.
Solution Approach 2:
The tungsten nitride (WN) layer is designed to perform multiple functions simultaneously: it acts as the barrier layer against halide diffusion, provides a growth site for the CVD W bulk film, and maintains low resistivity. This multi-functionality eliminates the need for a separate high-resistivity nucleation layer.
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 achieves void-free gap fill with high aspect ratio features, reduces film stack resistivity, and provides more space for low resistance gate metallization, while preventing fluorine penetration and eliminating halide diffusion issues, particularly beneficial for feature sizes below 40 nm.
Implementation Method 1
subjecting the substrate to a nitridation treatment using active nitrogen species from a remote plasma
Implementation Method 2
subjecting the substrate to a nitridation treatment using active nitrogen species from a remote plasma
Implementation Method 3
depositing a tungsten nitride layer on the substrate... and depositing a conductive bulk layer directly on the tungsten nitride layer using halogen-free MOCVD or MOALD processes
Data Source
AI summary
The invention provides a method of forming a film stack on a substrate, comprising depositing a tungsten nitride layer on the substrate, subjecting the substrate to a nitridation treatment using active nitrogen species from a remote plasma, and depositing a conductive bulk layer directly on the tungsten nitride layer without depositing a tungsten nucleation layer on the tungsten nitride layer as a growth site for tungsten.