Gate Electrode Barrier Structure to Suppress Al Diffusion
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Solution Overview
Problem
The existing semiconductor element manufacturing process risks Al diffusion from the gate electrode into the gate insulating film through the surface protective film during heat treatment and under operating conditions, leading to unstable operation such as threshold voltage fluctuation and leakage current generation.
Innovation Solution
A semiconductor element design that includes a first barrier layer to prevent Al diffusion, a metal layer made of Al or its alloy on the barrier layer, and a second barrier layer to protect the metal layer, with the side surface of the metal layer recessed inside the side surfaces of both barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a surface protective film is added to protect the gate electrode, then the gate electrode is protected from oxidation, but Al may diffuse into the gate insulating film through the surface protective film during heat treatment
Solution Approach 1:
The gate electrode is divided into multiple functional layers: a first barrier layer (TiN) between the metal layer and gate insulating film to prevent Al diffusion, a metal layer (Al) for electrical conductivity, and a second barrier layer (TiN) on the outer surface for oxidation protection. This segmentation allows each layer to perform its specific function independently.
Solution Approach 2:
The first barrier layer acts as an intermediary between the metal layer and the gate insulating film, preventing direct contact and diffusion of Al into the insulating film. The second barrier layer serves as an intermediary between the metal layer and the external environment, protecting against oxidation while the recessed structure prevents direct diffusion paths to the gate insulating film.
2Ease of manufacture
If the gate electrode uses a simple Al structure, then the manufacturing process is simple, but Al diffuses into the gate insulating film causing threshold voltage fluctuation and leakage current
Solution Approach 1:
The gate electrode is divided into multiple functional layers: a first barrier layer (TiN) between the metal layer and gate insulating film to prevent Al diffusion, a metal layer (Al) for electrical conductivity, and a second barrier layer (TiN) on the outer surface for oxidation protection. This segmentation allows each layer to perform its specific function independently.
Solution Approach 2:
The gate electrode uses a composite structure combining TiN and Al layers, where TiN provides diffusion barrier and oxidation protection properties, while Al provides high electrical conductivity. The composite structure leverages the advantageous properties of each material to achieve both manufacturing feasibility and operational reliability.
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 configuration effectively suppresses Al diffusion into the insulating film, thereby stabilizing the semiconductor element's operation by reducing threshold voltage fluctuations and leakage currents.
Implementation Method 1
a first barrier layer to prevent Al from diffusing into the insulating film
Implementation Method 2
a structure is known, in which TiN, Al, and TiN are deposited in this order on a gate insulating film
Data Source
AI summary
Provided is a semiconductor element in which Al in an electrode on an insulating film is suppressed from diffusing into an insulating film via a surface protective film. The semiconductor element includes a semiconductor layer, an insulating film (gate insulating film) disposed on the semiconductor layer, an electrode (gate electrode) disposed on the insulating film, and a surface protective film covering the semiconductor layer, the insulating film, and the electrode. The electrode includes a first barrier layer preventing Al diffusion into the insulating film, a metal layer formed on the first barrier layer and made of Al or an alloy mainly composed of Al, and a second barrier layer formed on the metal layer and protecting the metal layer. A side surface of the metal layer is disposed inside a side surface of the first barrier layer and inside a side surface of the second barrier layer.