Ferroelectric Tunnel Junction With Internal Metal Gate
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Solution Overview
Problem
Conventional ferroelectric tunnel junctions (FTJs) face challenges in forming high-performance non-volatile memory devices due to poor endurance caused by dielectric layer breakdown, requiring improvements in endurance, TER ratio, programming voltage, and area efficiency.
Innovation Solution
The design incorporates an internal metal gate structure with a high-K dielectric layer and a ferroelectric film, where the top electrode and ferroelectric layer have a smaller surface area than the internal metal layer and dielectric layer, respectively, reducing the electric displacement field in the dielectric layer and allowing for lower programming voltages, thus enhancing endurance and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional FTJ structure is used, then the device can achieve basic memory functionality, but the dielectric layer breaks down leading to poor endurance
Solution Approach 1:
The patent segments the electric field distribution by introducing an internal metal layer that divides the dielectric layer into two regions with different areas. This segmentation allows the electric displacement field to be concentrated in a smaller area under the internal metal layer, preventing widespread dielectric breakdown and improving endurance.
Solution Approach 2:
The patent applies local quality by creating a non-uniform area configuration where the internal metal layer has a larger area than the top electrode. This local variation in geometry creates a localized electric field distribution that protects the dielectric layer from breakdown while maintaining the desired memory functionality.
2Device complexity
If the top electrode and ferroelectric layer have the same area as the internal metal layer, then the structure is simple, but the electric displacement field causes dielectric breakdown
Solution Approach 1:
The patent introduces asymmetry by making the internal metal layer area different from the top electrode area. Specifically, the internal metal layer has a larger area, creating an asymmetric geometry that redistributes the electric displacement field and prevents dielectric breakdown without significantly complicating the overall device structure.
3Ease of operation
If high programming voltages are used, then the FTJ can be programmed, but power consumption increases and endurance decreases
Solution Approach 1:
The patent changes the geometric parameters of the device, specifically the area relationship between the internal metal layer and top electrode. This parameter change modifies the electric field distribution and reduces the programming voltage requirement from conventional high voltages to lower voltages, thereby reducing power consumption and improving endurance.
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 of FTJs by preventing dielectric layer breakdown, achieving a higher TER ratio, and enabling lower programming voltages, which enhances the performance and reliability of non-volatile memory devices.
Implementation Method 1
a ferroelectric layer over the internal metal layer
Implementation Method 2
a dielectric layer between the internal metal layer and the bottom electrode
Implementation Method 3
The electrical resistance of the FTJ, also referred to as the tunneling electroresistance (TER) of the FTJ, is determined by the orientation of the electric polarization of the ferroelectric layer
Data Source
AI summary
A device includes a bottom electrode that includes a first electrically conducive material; a dielectric layer over the bottom electrode; an internal metal layer over the dielectric layer; a ferroelectric layer over the internal metal layer; and a top electrode over the ferroelectric layer, the top electrode including a second electrically conductive material, an area of the top electrode being smaller than an area of the internal metal layer.