Gate Stack Work Function Layer Protection Against Oxidation
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Solution Overview
Problem
Current semiconductor device fabrication methods face challenges in selectively etching and processing work function and barrier layers, leading to inefficiencies and poor performance due to oxidized portions of these layers, which affect the work function and gate resistance.
Innovation Solution
The method involves substrate selective atomic layer etching and deposition techniques, using precursors like tungsten fluoride and tantalum chloride to react with and remove oxidized parts of work function and barrier layers, forming protective layers that improve the work function and prevent further oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching and processing methods are used on work function and barrier layers, then the fabrication process can be completed, but oxidized portions form on these layers leading to poor performance and increased gate resistance
Solution Approach 1:
A protective layer is formed over the work function layer and barrier layer before subsequent processing steps. This preliminary protective coating prevents oxidation from occurring during fabrication, eliminating the harmful oxidized portions that would otherwise degrade device performance and increase gate resistance.
Solution Approach 2:
The protective layer creates an inert environment that shields the work function layer and barrier layer from oxidative conditions during fabrication. By maintaining this protective barrier, the method prevents oxidation without requiring complex atmospheric control throughout the entire fabrication process.
2Productivity
If work function layers are processed without protective measures, then fabrication can proceed, but work function consistency deteriorates due to oxidation
Solution Approach 1:
The protective layer is applied in advance to the work function layer and barrier layer, enabling subsequent fabrication steps to proceed without interruption while simultaneously maintaining work function consistency. This preliminary protection eliminates the need for rework or additional processing steps to correct oxidation damage.
Solution Approach 2:
The protective layer serves as a temporary, sacrificial element that is removed after serving its protective function. This disposable protective coating provides inexpensive and effective protection during fabrication, ensuring work function consistency without adding permanent complexity to the device structure.
3Device complexity
If no protective layer is formed, then the fabrication process is simpler, but aluminum diffusion and further oxidation occur
Solution Approach 1:
The protective layer acts as an intermediary barrier between the work function layer/barrier layer and the harmful external environment. This intermediate protective coating prevents aluminum diffusion and oxidation without requiring fundamental changes to the fabrication process, adding only a single deposition and removal step.
Solution Approach 2:
The harmful elements (oxygen and aluminum) are excluded from the work function layer and barrier layer by the protective layer. By extracting these harmful factors from the interaction with sensitive layers, the method maintains device reliability while keeping the added process complexity minimal.
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 resistance and reliability of semiconductor devices by selectively removing oxidized layers, improving work function consistency and reducing gate resistance, while preventing aluminum diffusion and further oxidation.
Implementation Method 1
reacting a precursor with the work function layer... to form a protective layer
Implementation Method 2
reacting the precursor with the barrier layer... to remove oxidized parts
Implementation Method 3
preventing aluminum diffusion... by the presence of fluorine
Data Source
AI summary
A semiconductor structure includes a substrate, a channel region, a gate structure, and source/drain regions. The channel region is over the substrate. The gate structure is over the channel region, and includes a high-k dielectric layer, a tungsten layer over the high-k dielectric layer, and a fluorine-containing work function layer over the tungsten layer. The source/drain regions are at opposite sides of the channel region.