Rounded Ferroelectric Gate for FeFET Memory
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Solution Overview
Problem
Ferroelectric field effect transistors (FeFETs) face significant variations in electrical parameters due to fringing fields from the gate corner, leading to area and geometry dependencies, which affect the performance and reliability of non-volatile memory devices.
Innovation Solution
The use of a circular or elliptic shape ferroelectric material for the gate electrode, which overlaps into an adjacent isolation region, optimizes the perimeter-to-area ratio, reducing depolarization field effects and enhancing robustness and density in non-volatile memory arrays by minimizing edge-driven depolarization fields and maximizing volume-driven remnant polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional rectangular gate structure is used, then manufacturing is simpler, but fringing fields from gate corners cause significant variation in electrical parameters
Solution Approach 1:
The patent applies spheroidality by replacing the conventional rectangular gate structure with a circular or elliptic gate structure. This curvature eliminates the sharp corners that generate fringing fields, thereby reducing significant variations in electrical parameters and improving reliability of the FeFET device.
2Object-affected harmful factors
If the ferroelectric material is confined to the active area, then isolation is improved, but the perimeter-to-area ratio increases causing stronger depolarization field effects
Solution Approach 1:
The circular or elliptic shape of the ferroelectric material reduces the perimeter-to-area ratio compared to rectangular shapes, thereby minimizing edge-driven depolarization fields while still containing the material within the active area boundaries.
Solution Approach 2:
The patent changes the geometric parameters of the ferroelectric material from rectangular to circular/elliptic shape, which optimizes the perimeter-to-area ratio and reduces depolarization field effects without requiring additional active area.
3Productivity
If the gate structure overlaps into the isolation region, then area utilization is maximized, but manufacturing precision requirements increase
Solution Approach 1:
The circular or elliptic gate structure provides smoother edges compared to rectangular shapes, which can be more tolerant to manufacturing variations and alignment errors, thereby reducing the stringency of manufacturing precision requirements while still achieving maximum area utilization through overlap into the isolation region.
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 design results in reduced variation and back-switching effects, leading to more robust and denser non-volatile memory arrays with improved performance, as demonstrated by the minimized perimeter-to-area ratio and enhanced memory window stability.
Implementation Method 1
Fringing fields from the internal depolarization field at the FeFETs gate corner, though, can cause significant variation of the electrical parameters
Implementation Method 2
A ferroelectric field effect transistor (FeFET) can be used for memory devices. The FeFET typically uses a high-k dielectric material such as hafnium oxide in its gate structure
Implementation Method 3
The FeFET typically uses a high-k dielectric material such as hafnium oxide in its gate structure, which allows the device to be scaled down
Implementation Method 4
the FeFET can maintain its logic state even when power is removed
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to rounded shaped transistors and methods of manufacture. The structure includes a gate structure composed of a metal electrode and a rounded ferroelectric material which overlaps an active area in a width direction into an isolation region.