Metal Gate Work Function Tuning via Ion Diffusion
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Solution Overview
Problem
The conventional gate last process for semiconductor devices is complex and faces integrity and reliability challenges due to the need for multiple steps in forming and removing work function metal layers, particularly in filling gate trenches with high thermal budget processes.
Innovation Solution
A manufacturing method that involves forming a first work function metal layer in a gate trench, followed by an etch stop layer and a filling metal layer, where ion diffusion from the filling metal layer transmutes the first work function metal layer into a second work function metal layer, simplifying the process by eliminating the need for multiple work function metal layers and reducing process complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the conventional gate last process is used to form metal gates with different work functions, then the semiconductor device can achieve different conductivity types, but the process complexity increases due to multiple steps of forming and removing work function metal layers
Solution Approach 1:
The patent changes the work function parameter of the metal layer through ion diffusion from the filling metal layer. By controlling the diffusion process, a single metal layer is transformed into multiple work function metal layers with different conductivity types, eliminating the need to form and remove multiple separate metal layers.
Solution Approach 2:
The patent extracts the work function differentiation function from the structural composition. Instead of using multiple physical metal layers, the work function variation is achieved through chemical composition modification (ion diffusion) of a single metal layer, simplifying the structural complexity while maintaining functional versatility.
2Adaptability or versatility
If multiple work function metal layers are formed in gate trenches using conventional processes, then different conductivity types are achieved, but the integrity and reliability deteriorate due to high thermal budget processes
Solution Approach 1:
The patent uses ion diffusion to modify the chemical composition parameter of the metal layer in-situ within the gate trench. This avoids high thermal budget processes that would compromise the integrity of surrounding structures, while still achieving the required work function differentiation for different conductivity types.
Solution Approach 2:
The patent introduces ion diffusion as an intermediary mechanism to achieve work function modification. Instead of directly forming multiple metal layers through high-temperature processes, ion diffusion acts as a mediator that transforms a single metal layer into multiple functional layers with different work functions, preserving structural integrity.
3Ease of manufacture
If conventional processes are used to fill gate trenches with work function metals, then metal gates are formed, but the manufacturing precision deteriorates due to complicated process steps
Solution Approach 1:
The patent uses ion diffusion to change the chemical composition parameter of the metal layer, transforming it into different work function metal layers. This single-step transformation improves manufacturing precision by eliminating multiple deposition and removal steps, while maintaining ease of manufacture through a streamlined 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 method simplifies the metal gate process, improves gap-filling results, and enhances the yield of the metal gate process by directly converting the first work function metal layer into a second work function layer through ion diffusion, reducing the complexity and number of steps required.
Implementation Method 1
ion diffusion from the filling metal layer transmutes the first work function metal layer into a second work function metal layer
Data Source
AI summary
A manufacturing method for semiconductor device having metal gate includes providing a substrate having a first semiconductor device and a second semiconductor device formed thereon, the first semiconductor device having a first gate trench and the second semiconductor device having a second gate trench, forming a first work function metal layer and an etch stop layer in the first gate trench and the second gate trench, forming a metal layer having a material the same with the first work function metal layer in the second gate trench, and forming a filling metal layer in the first gate trench and the second gate trench to form a second work function metal layer in the first gate trench.