PMOSFET Work-Function Layer for Aluminum Diffusion Blocking
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Solution Overview
Problem
As semiconductor devices continue to shrink in size, the challenge of reducing aluminum diffusion in transistors becomes significant, affecting the threshold voltage and performance of p-type transistors.
Innovation Solution
The formation of a ternary p-type work-function layer comprising a first metal nitride, such as titanium nitride (TiN), mixed with a second metal nitride, such as tungsten carbonitride (WCN), is used to reduce aluminum diffusion in n-type work-function layers, thereby stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum is used in the n-type work-function layer, then the work function is adjusted appropriately, but aluminum diffusion occurs which worsens transistor performance
Solution Approach 1:
A ternary metal nitride layer (e.g., WCN/TiN) is introduced as an intermediary barrier between the aluminum-containing n-type work-function layer and the underlying layers. This intermediate layer effectively blocks aluminum diffusion while allowing the system to maintain appropriate work function characteristics, thus resolving the contradiction between using aluminum for work function adjustment and preventing its harmful diffusion.
Solution Approach 2:
The patent employs a composite ternary metal nitride material combining two or more metal nitrides (such as tungsten carbonitride and titanium nitride). This composite material provides both the necessary work function properties and superior aluminum diffusion blocking capability compared to single metal nitrides, addressing the technical contradiction through material composition optimization.
2Productivity
If feature size is reduced to increase integration density, then more components fit in given area, but aluminum diffusion control becomes more difficult
Solution Approach 1:
The patent changes the material parameters by introducing ternary metal nitrides with specific compositional ratios and thicknesses. By adjusting the composition and thickness parameters of the barrier layer, effective aluminum diffusion control is achieved at reduced feature sizes, enabling continued scaling while maintaining manufacturing precision.
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 use of a WCN/TiN ternary layer effectively blocks aluminum diffusion, leading to improved transistor performance by lowering the threshold voltage and maintaining the integrity of the p-type transistor's functionality.
Implementation Method 1
The second metal nitride in the ternary p-type work-function layer is configured to reduce the downward diffusion of the aluminum in the overlying n-type work-function layer
Data Source
AI summary
A method includes forming a p-type transistor. The method includes forming a gate dielectric on a semiconductor region, and depositing a p-type work-function layer on the gate dielectric. The p-type work-function layer includes a metal nitride, which includes a first metal and a second metal. An n-type work-function layer is deposited over the p-type work-function layer. A p-type source/drain region is formed aside of the semiconductor region.