Ferroelectric Memory Gate Insulator Segmentation for Polarization Stability
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Solution Overview
Problem
Ferroelectric memories face degradation of memory cell characteristics due to polarization instability, leading to fluctuating threshold voltages and increased leak currents, which degrade the read disturb characteristic and reduce reliability.
Innovation Solution
A semiconductor memory device with a gate insulating layer containing a ferroelectric region of hafnium or zirconium oxide, and paraelectric regions, where the length of the gate electrode layers is larger than the ferroelectric region, and paraelectric regions are provided at the ends to stabilize polarization, preventing electric field concentration and stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a one-transistor type memory cell with MFS structure is used, then high integration and large capacity are achieved, but polarization instability occurs leading to degraded memory cell characteristics
Solution Approach 1:
The gate insulating layer is segmented into three distinct regions along the thickness direction: a first paraelectric region adjacent to the semiconductor layer, a ferroelectric region in the middle, and a second paraelectric region adjacent to the gate electrode layer. This segmentation allows each region to perform its specific function - the paraelectric regions suppress electric field concentration and stabilize polarization, while the ferroelectric region provides the necessary switching capability, thereby resolving the contradiction between high integration and polarization stability.
Solution Approach 2:
Different regions of the gate insulating layer are assigned different material compositions and functional properties. The paraelectric regions contain materials with high dielectric constants to suppress electric fields, while the central ferroelectric region contains materials with switchable polarization. This local differentiation of quality allows the structure to simultaneously achieve high integration density and stable polarization characteristics.
2Ease of manufacture
If the gate insulating layer has uniform structure, then manufacturing is simplified, but electric field concentration occurs at the ends leading to polarization instability
Solution Approach 1:
The gate insulating layer is divided into three functional segments with different material compositions. The paraelectric regions are positioned at the ends to suppress electric field concentration, while the ferroelectric region is positioned centrally for switching. This segmentation can be implemented through sequential deposition processes, maintaining manufacturing feasibility while dramatically improving polarization stability.
Solution Approach 2:
The paraelectric regions act as intermediary layers between the semiconductor layer/gate electrode and the ferroelectric region. These intermediary paraelectric regions suppress electric field concentration at the interfaces, preventing polarization instability while allowing the ferroelectric region to maintain its switching function. This mediator approach resolves the contradiction between manufacturing simplicity and polarization stability.
3Volume of moving object
If the gate electrode layer length matches the ferroelectric region length, then device structure is compact, but electric field concentration at the ends causes polarization instability and increased leak current
Solution Approach 1:
The gate insulating layer is segmented into paraelectric and ferroelectric regions, with the paraelectric regions extending beyond the ferroelectric region boundaries. This segmentation allows the gate electrode to be shorter than the overall gate insulating layer, preventing electric field concentration at the ends while maintaining compact device footprint. The paraelectric regions act as field-suppressing extensions that improve read disturb characteristics.
Solution Approach 2:
The solution addresses the length mismatch problem by extending the gate insulating layer in the thickness dimension rather than increasing the planar dimensions. The paraelectric regions extend beyond the ferroelectric region in the thickness direction, allowing the gate electrode to be shorter while maintaining proper electric field distribution. This dimensional approach improves reliability without increasing device footprint.
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 solution stabilizes polarization, improves read disturb characteristics, and enhances the reliability of ferroelectric memory by suppressing degradation of memory cell characteristics.
Implementation Method 1
the gate insulating layer including a first region containing a first oxide including at least one of a hafnium oxide and a zirconium oxide
Implementation Method 2
paraelectric regions are provided at the ends to stabilize polarization, preventing electric field concentration and stress
Data Source
AI summary
Provided is a semiconductor memory device according to an embodiment including: a stacked body including gate electrode layers stacked in a first direction; a semiconductor layer provided in the stacked body and extending in the first direction; and a gate insulating layer provided between the semiconductor layer and at least one of the gate electrode layers, and the gate insulating layer including a first region containing a first oxide including at least one of a hafnium oxide and a zirconium oxide, in which a first length of the at least one of the gate electrode layers in the first direction is larger than a second length of the first region in the first direction.