Replacement Metal Gate Stack with Halide Diffusion Blocking
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Solution Overview
Problem
In the fabrication of FinFETs, the diffusion of halide by-products from tungsten CVD deposition into the underlying gate dielectric layer degrades the gate dielectric material, leading to threshold voltage variations and dielectric leakage, reducing device reliability.
Innovation Solution
Introducing dopants into the work function metal layer to occupy diffusion routes and block halide by-products from reaching the gate dielectric layer, thereby preventing degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If tungsten CVD deposition is used to form the gate electrode layer, then the gate electrode can be successfully deposited, but halide by-products diffuse into the gate dielectric layer causing degradation
Solution Approach 1:
A titanium nitride layer is introduced as an intermediary between the gate dielectric layer and the tungsten gate electrode layer. This intermediate layer serves as a diffusion barrier that blocks halide by-products from the tungsten CVD deposition from reaching and degrading the gate dielectric layer, while still allowing the tungsten electrode to be successfully deposited.
Solution Approach 2:
The titanium nitride layer is formed in advance before the tungsten gate electrode deposition. This preliminary action establishes a protective barrier that prevents the subsequent harmful diffusion of halide by-products during the tungsten deposition process, rather than attempting to repair damage after it occurs.
2Ease of manufacture
If the dummy gate stack is removed to form the metal gate, then the metal gate structure can be formed, but the gate dielectric layer becomes exposed and vulnerable to degradation
Solution Approach 1:
The titanium nitride layer acts as a protective intermediary that remains in place after dummy gate removal. It shields the exposed gate dielectric layer from halide by-products during subsequent tungsten deposition, enabling metal gate formation without compromising dielectric integrity.
Solution Approach 2:
The titanium nitride layer provides beforehand cushioning by being present before the harmful deposition process begins. It anticipates and prevents the potential damage from halide by-products, creating a protective buffer that allows the manufacturing process to proceed safely.
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 introduction of dopants in the work function metal layer effectively blocks halide by-products, enhancing the reliability and performance of FinFETs by preventing gate dielectric degradation and maintaining consistent device operation.
Implementation Method 1
the diffusion of halide by-products from tungsten CVD deposition into the underlying gate dielectric layer
Data Source
AI summary
The semiconductor device includes a semiconductor fin, and a gate stack over the semiconductor fin. The gate stack includes a gate dielectric layer over a channel region of the semiconductor fin, a work function material layer over the gate dielectric layer, wherein the work function material layer includes dopants, and a gate electrode layer over the work function material layer. The gate dielectric layer is free of the dopants.