Work Function Metal Stack Rework for Lower Gate Defect Yield Loss
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Solution Overview
Problem
The existing methods for forming semiconductor devices with metal gate stacks face challenges in removing damaged work function metal layers without causing further damage, leading to device defects and reduced yield.
Innovation Solution
The proposed solution involves removing the damaged work function metal layer and re-depositing a new work function metal layer with similar composition, using a tungsten-containing residue as evidence of the removal and re-deposition process, thereby avoiding the need for additional masks and ensuring compatibility with current semiconductor manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the damaged work function metal layer is removed using conventional methods, then the work function can be adjusted, but device defects increase and yield decreases
Solution Approach 1:
A protective capping layer is deposited over the work function metal layer before any removal or adjustment processes. This preliminary protective action prevents damage to the underlying metal layer during subsequent etching or removal operations, thereby reducing device defects and improving yield while still allowing work function adjustment.
Solution Approach 2:
An intermediate protective layer is introduced between the damaged work function metal layer and the removal process. This intermediary layer acts as a buffer that protects the metal layer from direct damage during removal, enabling work function adjustment without increasing device defects.
2Manufacturing precision
If multiple work function metal layers with different materials are deposited, then the work function can be precisely adjusted, but the manufacturing process complexity increases
Solution Approach 1:
Instead of depositing multiple different metal materials, the invention adjusts the work function by changing the thickness or composition ratio of a single work function metal layer. This parameter-based approach achieves precise work function control while avoiding the complexity of multiple material deposition processes.
Solution Approach 2:
A single work function metal layer is designed to perform multiple functions: providing the necessary work function adjustment and serving as a protective layer during subsequent processing. This multi-functional design eliminates the need for separate protective layers and multiple material depositions, reducing manufacturing complexity while maintaining precision.
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 reduces device defects, enhances yield, and improves the performance of semiconductor devices by ensuring the integrity of the work function metal layers throughout the manufacturing process.
Implementation Method 1
re-depositing a new work function metal layer with similar composition, using a tungsten-containing residue as evidence of the removal and re-deposition process
Data Source
AI summary
A device includes gate spacers over a substrate, and a gate structure between the gate spacers. The gate structure includes an interfacial layer over the substrate, a metal oxide layer over the interfacial layer, a metal oxide layer over the interfacial layer, a first metal nitride layer over the metal oxide layer, a second metal nitride over the first metal nitride layer, and a tungsten-containing material interposing the first metal nitride layer and the second metal nitride layer.