FeFET Gate Stack With Buffer Oxide for Ferroelectric Endurance
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Solution Overview
Problem
The existing semiconductor devices face challenges in maintaining ferroelectricity in thin films, leading to deterioration of characteristics such as charge trapping and breakdown, particularly when hafnium-based oxides are used as gate insulating films, due to the formation of an interface film between the substrate and the gate insulating film.
Innovation Solution
A semiconductor device structure is developed with a substrate, a gate electrode film, a gate insulating film made of hafnium-based oxide, an interface film, a buffer film, and a buffer oxide film, where the thickness of the interface film is minimized through an annealing process, and the buffer film and gate electrode film apply mechanical stress to induce an orthorhombic phase in the gate insulating film, enhancing ferroelectricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hafnium-based oxide is used as gate insulating film to maintain ferroelectricity in thin films, then ferroelectricity is maintained, but charge trapping and breakdown occur due to interface film formation
Solution Approach 1:
A buffer oxide film is introduced as an intermediary layer between the hafnium-based oxide gate insulating film and the gate electrode film. This buffer oxide film prevents direct contact between the gate electrode and the ferroelectric layer, thereby eliminating charge trapping and breakdown issues while preserving the ferroelectric properties of the hafnium-based oxide.
Solution Approach 2:
The gate insulating film structure is segmented into multiple layers: a bottom gate insulating film (hafnium-based oxide) for ferroelectricity and a top buffer oxide film for charge isolation. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between maintaining ferroelectricity and preventing charge trapping.
2Reliability
If interface film thickness is reduced to improve device characteristics, then endurance and memory window improve, but manufacturing precision requirements increase
Solution Approach 1:
The buffer oxide film serves as a mediator that decouples the interface quality from the ferroelectric layer thickness. By introducing this intermediate layer, the system can achieve thin effective interface thickness for improved device characteristics without requiring extremely precise control of the direct interface between gate electrode and ferroelectric layer.
Solution Approach 2:
The harmful interface film formation is extracted and isolated into a dedicated buffer oxide layer. This allows the interface film thickness to be controlled independently as a separate parameter, enabling optimization of device characteristics without compromising manufacturing feasibility.
3Reliability
If buffer film and gate electrode film apply mechanical stress to induce orthorhombic phase, then ferroelectricity is enhanced, but device structure complexity increases
Solution Approach 1:
The crystal phase of the hafnium-based oxide is changed from non-ferroelectric phases to orthorhombic ferroelectric phase by applying mechanical stress through the buffer film and gate electrode film. This parameter change (phase transformation) enhances ferroelectricity while the stress application mechanism is achieved through standard thin film deposition processes.
Solution Approach 2:
The gate stack forms a composite structure with multiple materials (hafnium-based oxide, buffer oxide, gate electrode) where each material contributes specific properties. The buffer oxide film provides mechanical stress to induce the orthorhombic phase in the ferroelectric layer, creating a functional composite that enhances overall device performance.
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 improves the endurance and memory window of the ferroelectric field effect transistor (FeFET) by reducing the interface film thickness, thereby enhancing the ferroelectricity and stability of the semiconductor device.
Implementation Method 1
the buffer film and gate electrode film apply mechanical stress to induce an orthorhombic phase in the gate insulating film, enhancing ferroelectricity
Implementation Method 2
the thickness of the interface film is minimized through an annealing process
Data Source
AI summary
A semiconductor device including a ferroelectric field effect transistor (FeFET) and a method for fabricating the same are provided. The semiconductor device includes a substrate, a gate electrode film including a metal element, on the substrate, a gate insulating film including a ferroelectric material between the substrate and the gate electrode film, and a buffer oxide film including an oxide of a semiconductor material between the gate insulating film and the gate electrode film, the buffer oxide film being in contact with the gate insulating film.