Modified Profile Metal Gate for Void-Free Trench Filling
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Solution Overview
Problem
The semiconductor industry faces challenges in filling trenches with a high aspect ratio in gate-last processes for metal gate stacks, leading to voiding issues during the replacement of dummy gate stacks.
Innovation Solution
A method is introduced to modify the profile of the gate structure by re-shaping the layers within the trench, using etching processes to create a modified entry profile that allows for improved gap filling of the trench, reducing voiding and enhancing the filling efficiency of the fill metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy gate stack is removed and replaced with a metal gate stack in a gate-last process, then device performance is improved with decreased feature sizes, but voiding issues occur during trench filling due to high aspect ratio
Solution Approach 1:
The patent applies preliminary action by forming a mandrel structure before removing the dummy gate stack. This mandrel serves as a temporary support structure that maintains trench integrity during the metal gate filling process, preventing voiding issues that would otherwise occur due to the high aspect ratio of the trench. The mandrel is removed after filling, having served its purpose of enabling precise manufacturing.
Solution Approach 2:
The patent uses an intermediary mandrel structure that acts as a mediator between the trench walls and the metal gate filling material. This mandrel provides mechanical support and facilitates uniform metal deposition throughout the trench, ensuring complete filling without voids. The intermediary structure is temporarily present during the critical filling operation and is removed afterward.
2Length of moving object
If the trench aspect ratio is high for metal gate filling, then device scaling is achieved, but voiding occurs during the filling process
Solution Approach 1:
The mandrel structure is formed in advance before the metal gate filling operation. This preliminary structure provides internal support that enables uniform metal deposition even in high aspect ratio trenches, allowing device scaling while maintaining filling quality. The mandrel ensures that metal fills the entire trench volume uniformly.
Solution Approach 2:
The patent changes the structural parameters of the trench by introducing a mandrel, effectively transforming the filling problem from a high aspect ratio challenge to a manageable configuration. The mandrel modifies the effective geometry, allowing uniform filling parameters to be achieved even when the original trench aspect ratio would cause voiding.
3Device complexity
If conventional gap filling is used in high aspect ratio trenches, then process simplicity is maintained, but voiding issues arise
Solution Approach 1:
The mandrel formation is added as a preliminary step before metal gate filling. While this adds a process step, it significantly improves filling reliability by preventing voiding in high aspect ratio trenches. The temporary mandrel structure ensures that the subsequent filling operation produces reliable, void-free metal gates.
Solution Approach 2:
The mandrel acts as an intermediary structure that enables reliable filling in high aspect ratio trenches. This temporary mediator facilitates uniform metal deposition and prevents voiding, with the added process complexity justified by the significant improvement in filling reliability and device performance.
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
The modified profile approach effectively reduces voiding and improves the filling of the trench, ensuring a more reliable and efficient metal gate structure formation in semiconductor devices.
Implementation Method 1
using etching processes to create a modified entry profile
Data Source
AI summary
A semiconductor device has a semiconductor substrate with a dielectric layer disposed thereon. A trench is defined in the dielectric layer. A metal gate structure is disposed in the trench. The metal gate structure includes a first layer and a second layer disposed on the first layer. The first layer extends to a first height in the trench and the second layer extends to a second height in the trench; the second height is less than the first height.