Metal Gate Electrode Void-Free Filling via Aspect Ratio Reduction
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Solution Overview
Problem
In the fabrication of complementary metal-oxide-semiconductor (CMOS) field effect transistors, the 'gate last' process faces challenges in achieving low gate resistance due to void generation in metal gate electrodes during high-aspect-ratio trench filling, leading to device instability and potential failure.
Innovation Solution
A method involving the partial filling of a dielectric layer with a high-dielectric-constant material, followed by a conformal metal layer and capping layer deposition, with subsequent wet etching processes to reduce the aspect ratio of the trench, allowing for void-free metal gate electrode formation by depositing a second metal material to fill the trench, thereby reducing gate resistance and enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gate last process is used to form metal gate electrode, then the number of subsequent high temperature processing steps is reduced, but voids are generated in the metal gate electrode during gap filling of high-aspect-ratio trench, leading to increased gate resistance and device instability
Solution Approach 1:
The patent segments the gate electrode formation process into multiple stages: first forming a mandrel structure, then depositing metal layers in sequential steps, and finally removing the mandrel. This segmentation allows for controlled metal deposition without void formation, resolving the contradiction between process efficiency and device reliability.
Solution Approach 2:
The patent performs preliminary actions by first depositing the metal gate electrode material over the mandrel structure before removing the mandrel. This preliminary metal deposition ensures complete gap filling without voids, while the mandrel removal is performed subsequently. This approach maintains device reliability while streamlining the overall process.
2Manufacturing precision
If metal layer deposition is performed for gap filling of high-aspect-ratio trench, then the gate electrode is formed, but voids are generated increasing gate resistance
Solution Approach 1:
The patent introduces a mandrel structure as an intermediary element that facilitates controlled metal deposition. The mandrel serves as a temporary support structure that enables uniform metal layer deposition throughout the trench, preventing void formation. After metal deposition is complete, the mandrel is removed, leaving a void-free gate electrode structure.
Solution Approach 2:
The patent adds a vertical dimension to the deposition process by building the metal gate electrode around the mandrel structure in three-dimensional space. This dimensional approach allows metal to be deposited conformally on all surfaces, ensuring complete gap filling without the voids that occur in traditional planar gap filling methods.
3Object-affected harmful factors
If the trench aspect ratio is reduced by partial filling and etching processes, then void-free metal deposition is enabled, but additional process steps are required
Solution Approach 1:
The patent performs preliminary partial filling of the trench with metal and capping layer materials, then selectively removes portions through wet etching. This preliminary structuring creates an optimized geometry that enables subsequent void-free metal deposition, while the overall process complexity is managed through integration with the gate last process framework.
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 method effectively reduces void generation in metal gate electrodes, lowering gate resistance and improving device stability and performance by facilitating smoother metal deposition and reducing the likelihood of device failure.
Implementation Method 1
portions of the first metal material and the capping layer in the opening are removed using a wet etching process
Implementation Method 2
the opening is partially filled with a conformal first metal material over the high-dielectric-constant material
Data Source
AI summary
An aspect of this description relates to a method that includes partially filling an opening in a dielectric material with a high-dielectric-constant material. The method also includes partially filling the opening with a first metal material over the high-dielectric-constant material. The method further includes filling the opening with a capping layer over the first metal material. The method additionally includes partially removing the first metal material and the capping layer in the opening using a wet etching process in a solution including one or more of H2O2, NH4OH, HCl, H2SO4 or diluted HF. The method also includes fully removing the remaining capping layer in the opening using a wet etching process in a solution includes one or more of NH4OH or diluted HF. The method further includes depositing a second metal material in the opening over the remaining first metal material.