Metal Gate Trench Barrier Sublayers to Prevent Premature Sealing
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Solution Overview
Problem
The critical dimension of semiconductor devices becomes smaller with the use of metal gates, leading to a reduced process window for filling metal materials, resulting in void defects and poor electrical performance due to premature sealing and lateral overhang of diffusion barrier layers.
Innovation Solution
A method involving physical vapor deposition with a negative bias power less than a preset power to form a first diffusion barrier sublayer almost entirely on the bottom of the metal gate trench, followed by a second diffusion barrier sublayer on the sidewalls, mitigating lateral overhang and enhancing the electrical performance of the metal gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal materials are used to fill the metal gate to reduce resistance, then the electrical performance is improved, but the critical dimension becomes smaller and the process window reduces, resulting in void defects
Solution Approach 1:
The diffusion barrier layer is divided into two sublayers: a first diffusion barrier sublayer formed at the bottom of the metal gate trench and a second diffusion barrier sublayer formed on the sidewalls. This segmentation allows each sublayer to be optimized for its specific location, preventing premature sealing at the bottom while controlling lateral overhang on the sidewalls, thereby improving the process window for metal filling.
Solution Approach 2:
Different regions of the diffusion barrier layer are formed with different properties by using separate sublayers. The first sublayer at the bottom provides diffusion barrier protection, while the second sublayer on the sidewalls controls lateral growth. This local differentiation prevents the uniform lateral overhang that causes premature sealing, enabling effective metal filling even at reduced critical dimensions.
2Ease of manufacture
If the diffusion barrier layer is formed with conventional methods, then the metal gate structure is completed, but lateral overhang occurs causing premature sealing and void defects
Solution Approach 1:
The diffusion barrier layer formation process is segmented into two distinct steps: forming the first sublayer at the bottom followed by forming the second sublayer on the sidewalls. This segmentation eliminates the lateral overhang problem inherent in conventional single-step formation methods, preventing premature sealing while maintaining ease of manufacture through sequential deposition processes.
3Productivity
If the critical dimension is reduced to improve device integration, then the device density increases, but the process window for filling metal material becomes smaller resulting in void defects
Solution Approach 1:
By segmenting the diffusion barrier layer into bottom and sidewall sublayers, the invention creates additional process flexibility that compensates for the reduced critical dimension. The separated formation steps allow independent optimization of each region, effectively widening the process window for metal filling even at smaller critical dimensions, thereby supporting higher device integration.
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 solution effectively prevents premature sealing and improves the electrical performance of the metal gate by reducing lateral overhang, ensuring proper filling and reducing resistance.
Implementation Method 1
forming a first diffusion barrier sublayer via a physical vapor deposition process with a negative bias power less than a preset power to form a first diffusion barrier sublayer on the work function layer at the bottom of the metal gate trench
Data Source
AI summary
The present disclosure provides a semiconductor structure and a method for forming the same. The method includes: providing a substrate having a metal gate trench with a work function layer on the bottom and sidewalls of the metal gate trench; forming a diffusion barrier layer on the work function layer, including: performing a physical vapor deposition process with a negative bias power less than a preset power to form a first diffusion barrier sublayer on the work function layer at the bottom of the metal gate trench. The present disclosure can reduce the possibility of premature sealing.