FinFET Gate Stack Protection Against Oxidation and Gate Resistance
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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 performance issues 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, using precursors like tungsten fluoride and tantalum chloride to react with and remove oxidized parts of work function and barrier layers, forming protective layers to improve the work function and prevent further oxidation, while depositing metal gate electrodes over these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove oxidized portions of work function and barrier layers, then the work function consistency can be improved, but the processing time and complexity increase
Solution Approach 1:
A protective layer is deposited over the work function and barrier layers before etching occurs. This protective layer is designed to be selectively removed only in regions where etching is desired, allowing the etching process to proceed quickly without requiring complex masking steps. The preliminary deposition of this protective layer enables subsequent rapid selective etching of oxidized portions.
Solution Approach 2:
The protective layer acts as an intermediary element that facilitates selective etching. It is deposited over the entire surface but can be selectively removed through targeted processing, serving as a mediator between the etching chemistry and the underlying work function and barrier layers. This intermediary layer enables precise control of where etching occurs without requiring complex direct patterning.
2Reliability
If selective etching is performed to remove oxidized portions of work function and barrier layers, then gate resistance can be reduced, but the device complexity increases
Solution Approach 1:
The protective layer is segmented or patterned to provide different protection levels in different regions. This allows selective access to the work function and barrier layers in specific areas where oxidized portions need to be removed. The segmentation enables complex selective etching patterns to be achieved through relatively simple protective layer deposition and removal steps.
Solution Approach 2:
The protective layer is deposited in advance to define which areas will be etched. This preliminary action simplifies the overall process by pre-determining the etching pattern, allowing the actual etching step to be performed rapidly without complex real-time control or multiple sequential etching steps.
3Manufacturing precision
If protective layers are deposited to prevent oxidation of work function and barrier layers, then work function consistency is improved, but the manufacturing process complexity increases
Solution Approach 1:
The protective layer serves multiple functions: it prevents oxidation of the work function and barrier layers during processing, acts as a mask for selective etching operations, and can be selectively removed to expose specific regions. This multi-functionality consolidates what would otherwise require multiple separate process steps into a single versatile layer, simplifying the overall manufacturing process while maintaining work function consistency.
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 work function consistency and reduces gate resistance by removing oxidized layers and preventing aluminum diffusion, thereby improving the performance and reliability of semiconductor devices.
Implementation Method 1
reacting a precursor with the work function layer... forming a protective layer over the work function layer
Implementation Method 2
reacting the precursor with the barrier layer... removing reaction products between the precursor and the barrier layer
Implementation Method 3
removing reaction products between the precursor and the work function layer, and reaction products between the precursor and the barrier layer, by using an inert gas
Data Source
AI summary
A semiconductor device includes a substrate, a semiconductor fin, a gate structure, and source/drain structures. The semiconductor fin extends upwardly from the substrate. The gate structure is across the semiconductor fin and includes a high-k dielectric layer over the semiconductor fin, a fluorine-containing work function layer over the high-k dielectric layer and comprising fluorine, a tungsten-containing layer over the fluorine-containing work function layer, and a metal gate electrode over the tungsten-containing layer. The source/drain structures are on the semiconductor fin and at opposite sides of the gate structure.