Work Function Metal Stack Recovery After Gate Trench Etch Damage
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Solution Overview
Problem
The challenge in semiconductor device manufacturing is the risk of structure loss and device defects due to damage from etching or implanting operations in the work function metal layers of the metal gate stack, which can impact threshold voltage and yield.
Innovation Solution
The method involves removing the damaged work function metal layer and re-depositing a new layer with similar composition, using a tungsten-containing residue as evidence of the process, which eliminates the need for additional masks and is compatible with current semiconductor processes, ensuring stronger re-deposited layers for subsequent patterning and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etching or implanting operations are performed on work function metal layers, then device performance can be adjusted, but structure loss and device defects occur
Solution Approach 1:
A protective capping layer is deposited over the work function metal layer before etching or implanting operations. This preliminary protective action prevents direct exposure of the work function metal layer to harmful processes, thereby avoiding structure loss and device defects while still allowing device performance adjustment through the capping layer modification
Solution Approach 2:
The capping layer serves as an intermediary between the etching/implanting operations and the work function metal layer. It absorbs the harmful effects of these operations, protecting the underlying work function metal layer from damage while enabling the necessary process adjustments for device performance
2Manufacturing precision
If work function metal layers are removed and re-deposited, then defects are reduced, but additional process steps are required
Solution Approach 1:
The capping layer is deposited in advance to protect the work function metal layer during subsequent processing. This preliminary protective measure eliminates the need for complete removal and re-deposition of the work function metal layer, reducing defects while avoiding additional complex process steps
Solution Approach 2:
Instead of removing and re-depositing the entire work function metal layer, only the damaged portions are selectively removed through the protective capping layer approach. This extracts only the necessary corrective action while preserving the intact portions of the work function metal layer, simplifying the overall process
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 results in higher yielding and better-performing semiconductor devices with fewer defects, maintaining the integrity of the metal gate stack and enhancing the semiconductor device's performance.
Implementation Method 1
removing the damaged work function metal layer
Implementation Method 2
re-depositing a new layer with similar composition
Data Source
AI summary
A method includes removing a dummy gate to form a gate trench. A gate dielectric layer is deposited over a bottom and sidewalls of the gate trench. 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. An impurity is introduced into the dummy layer and the first work function metal layer after the dummy layer is deposited. The dummy layer is removed after the impurity is introduced into the dummy layer and the first work function metal layer. The gate trench is filled with a conductive material after the dummy layer is removed.