Plasma-Treated Diffusion Barrier for FinFET Metal Gates
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Solution Overview
Problem
The formation of metal gates in semiconductor devices, particularly in FinFETs, faces challenges due to thermal instability and the need for blocking layers to inhibit metal diffusion, which can result in defects like pitting when using conventional thermal atomic layer deposition methods.
Innovation Solution
A method involving the formation of a high integrity, pinhole-free diffusion barrier layer using a plasma treatment with argon and hydrogen, followed by depositing a metal gate material over the diffusion barrier layer, which is compatible with high-k gate dielectrics and allows for conformal deposition within high aspect ratio openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal atomic layer deposition is used to form the blocking layer, then the blocking layer can be formed conformally within high aspect ratio openings, but the films typically include pitting which adversely affects device functionality
Solution Approach 1:
The patent changes the deposition parameters by using plasma-enhanced atomic layer deposition (PE-ALD) instead of thermal ALD, and by modifying the deposition temperature and precursor flow rates. These parameter changes result in films deposited at lower temperatures with improved morphology that are free of pitting while maintaining conformal coverage in high aspect ratio openings.
Solution Approach 2:
The patent replaces the thermal deposition mechanism with a plasma-enhanced deposition mechanism. The plasma activation allows for lower deposition temperatures and better film quality, eliminating the pitting defect while maintaining the ability to form conformal layers in high aspect ratio structures.
2Reliability
If metal gates are used instead of polysilicon gates, then charge carriers are not depleted and gate contact resistance is reduced, but metal gates are not thermally robust and cannot be exposed to high temperatures during processing
Solution Approach 1:
The patent segments the gate structure into multiple functional layers: a thermally stable blocking layer (tantalum nitride) that protects the metal gate from diffusion and thermal damage, and a metal gate layer (aluminum or copper) that provides low resistance and high carrier density. This segmentation allows each layer to perform its optimal function while protecting the metal from thermal exposure.
Solution Approach 2:
The patent introduces a blocking layer as an intermediary between the metal gate and the high-k dielectric, and between the metal gate and the surrounding environment. This blocking layer serves as a protective mediator that prevents metal diffusion during subsequent high-temperature processing while allowing the metal gate to maintain its electrical advantages.
3Ease of manufacture
If aluminum is used as metal gate material, then ease of processing using damascene planarization technology is improved, but aluminum diffusion must be inhibited using a blocking layer
Solution Approach 1:
The blocking layer serves multiple functions simultaneously: it acts as a diffusion barrier to prevent aluminum from migrating into the high-k dielectric, it provides a planarization surface for subsequent processing steps, and it serves as an adhesive layer between the metal gate and the dielectric. This multi-functionality reduces the need for additional separate layers.
4Manufacturing precision
If the blocking layer is formed using thermal ALD, then conformal deposition is achieved, but the films include pitting defects
Solution Approach 1:
The patent changes the deposition parameters by using plasma-enhanced atomic layer deposition (PE-ALD) instead of thermal ALD, and by modifying the deposition temperature and precursor flow rates. These parameter changes result in films deposited at lower temperatures with improved morphology that are free of pitting while maintaining conformal coverage in high aspect ratio openings.
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 enhances the film morphology and reduces resistivity of the diffusion barrier layer, preventing pinholes and ensuring effective filling of the metal gate material, thereby improving device performance and reliability.
Implementation Method 1
treating the diffusion barrier layer in a plasma treatment operation using at least one of argon and hydrogen
Implementation Method 2
depositing a diffusion barrier layer on the high-k gate dielectric and within the opening
Data Source
AI summary
A structure and method for replacement metal gate technology is provided for use in conjunction with semiconductor fins or other devices. An opening is formed in a dielectric by removing a sacrificial gate material such as polysilicon. The surfaces of the semiconductor fin within which a transistor channel is formed, are exposed in the opening. A replacement metal gate is formed by forming a diffusion barrier layer within the opening and over a gate dielectric material, the diffusion barrier layer formation advantageously followed by an in-situ plasma treatment operation. The treatment operation utilizes at least one of argon and hydrogen and cures surface defects in the diffusion barrier layer enabling the diffusion barrier layer to be formed to a lesser thickness. The treatment operation decreases resistivity, densifies and alters the atomic ratio of the diffusion barrier layer, and is followed by metal deposition.