Work Function Metal Stack Repair for Gate Threshold Control
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Solution Overview
Problem
The scaling down of semiconductor IC manufacturing increases complexity and leads to device defects due to damage of work function metal layers during etching or implanting operations, affecting threshold voltage and yield.
Innovation Solution
A method is introduced to remove damaged work function metal layers and re-deposit new layers with similar composition, using a tungsten-containing residue as evidence of the process, which is compatible with current semiconductor manufacturing and reduces device defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If work function metal layers are adjusted by depositing multiple layers or removing portions, then device performance is improved, but manufacturing complexity increases
Solution Approach 1:
The work function metal layer is divided into multiple sub-layers (first work function metal layer, second work function metal layer, third work function metal layer) with different materials and thicknesses. Each sub-layer contributes differently to the overall work function, allowing precise control of device performance while maintaining manufacturing feasibility through standardized deposition processes.
Solution Approach 2:
Different portions of the work function metal structure have different material compositions and thicknesses tailored to specific local requirements. The first work function metal layer has greater thickness than the second layer, creating local variations in work function characteristics across the gate structure to optimize device performance.
2Reliability
If work function metal layers are removed during etching or implanting operations, then device performance can be adjusted, but device defects increase
Solution Approach 1:
A protective layer is deposited over the work function metal layers before subsequent etching or implanting operations. This protective layer acts as a cushion that prevents damage to the work function metal layers during these operations, reducing device defects while still allowing performance adjustment through controlled removal of the protective layer or selective etching.
Solution Approach 2:
The protective layer serves as an intermediary between the work function metal layers and the harmful etching or implanting processes. It mediates the interaction by absorbing the impact of these operations, preventing direct damage to the work function metal layers while allowing the desired performance adjustments to be made.
3Manufacturing precision
If multiple work function metal layers are deposited, then work function control is improved, but process time increases
Solution Approach 1:
Multiple work function metal layers are deposited in a continuous process sequence without breaking the vacuum or stopping the deposition system. The first, second, and third work function metal layers are deposited consecutively in one continuous operation, reducing process time while maintaining precise work function control through the multi-layer structure.
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 semiconductor device performance and yield by minimizing defects and maintaining process compatibility without requiring additional masks, ensuring sufficient strength for subsequent patterning processes.
Implementation Method 1
A first work function metal layer is deposited over the gate dielectric layer. A dummy layer is deposited over the first work function metal layer.
Data Source
AI summary
A device includes a pair of gate spacers on a substrate, and a gate structure on the substrate and between the gate spacers. The gate structure includes an interfacial layer, a metal oxide layer, a nitride-containing layer, a tungsten-containing layer, and a metal compound layer. The interfacial layer is over the substrate. The metal oxide layer is over the interfacial layer. The nitride-containing layer is over the metal oxide layer. The tungsten-containing layer is over the nitride-containing layer. The metal compound layer is over the tungsten-containing layer. The metal compound layer has a different material than a material of the tungsten-containing layer.