Ferroelectric Memory Gate Structure With Control Transistor Discharge
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Solution Overview
Problem
Existing ferroelectric field effect transistors face reliability issues due to repeated program and erase operations leading to the breakdown of the gate dielectric layer, and ferroelectric metal field effect transistors suffer from reduced reliability due to electron leakage affecting the channel threshold voltage.
Innovation Solution
A semiconductor device design incorporating a ferroelectric memory structure with a control transistor and a control connection structure, where the ferroelectric memory structure includes a switching gate dielectric layer, a switching gate electrode, and ferroelectric layers connected in series, and a control transistor structure with a control gate dielectric layer and electrode, allowing for controlled voltage distribution and electron discharge to maintain reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If repeated program and erase operations are performed in existing ferroelectric field effect transistors, then memory functionality is achieved, but gate dielectric layer breakdown occurs reducing reliability
Solution Approach 1:
The gate structure is segmented into a first gate electrode connected to the control transistor and a second gate electrode connected to the ferroelectric capacitor, with a gate insulating layer between them. This segmentation allows independent voltage control and discharge paths for each gate electrode, preventing voltage stress accumulation that causes dielectric breakdown during repeated operations.
Solution Approach 2:
A control transistor is introduced as an intermediary component to control the voltage applied to the first gate electrode. The control transistor includes a control gate that can be independently controlled, allowing precise management of voltage distribution and discharge timing, thereby protecting the gate dielectric layer from excessive stress during program and erase operations.
2Reliability
If ferroelectric metal field effect transistors are used, then memory operation is enabled, but electron leakage affects channel threshold voltage reducing reliability
Solution Approach 1:
The harmful effect of electron leakage is extracted and redirected by providing a dedicated discharge path through the control transistor. The control transistor's channel region serves as an electron collection path that removes leaked electrons from the first gate electrode, preventing them from affecting the channel threshold voltage and maintaining reliability.
3Reliability
If voltage is applied to ferroelectric memory structure, then polarization is written, but voltage stress on dielectric layers increases risk of breakdown
Solution Approach 1:
The control transistor is configured to preliminarily discharge electrons from the first gate electrode before or during the voltage application process. The control gate of the control transistor can be set to a voltage level that ensures the channel is conductive, creating a safe discharge path that prevents voltage stress accumulation on the gate insulating layer during polarization writing operations.
Solution Approach 2:
The control transistor provides feedback control by monitoring and adjusting the voltage distribution across the ferroelectric memory structure. The control gate voltage can be dynamically adjusted based on the operation state (program, erase, or discharge), ensuring optimal voltage distribution that minimizes stress on dielectric layers while maintaining effective polarization writing.
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 design reduces the voltage stress on the dielectric layers, enhancing the operational reliability of the ferroelectric memory by minimizing breakdown and maintaining consistent channel threshold voltages through controlled voltage distribution and electron discharge.
Implementation Method 1
the electrical polarization can exhibit hysteresis behavior when the external electric field is applied. Accordingly, by controlling the external electric field applied to the ferroelectric material, polarization states having various magnitudes and orientations following the hysteresis behavior can be reversibly implemented within the ferroelectric material
Implementation Method 2
the polarization can be preserved within the ferroelectric material in the form of remanent polarization after the external electric field is removed
Implementation Method 3
a control transistor structure with a control gate dielectric layer and electrode, allowing for controlled voltage distribution and electron discharge to maintain reliability
Data Source
AI summary
A semiconductor device according to an embodiment of the present disclosure includes a ferroelectric memory structure, a control transistor, and a control connection structure that electrically connects the control transistor with the ferroelectric memory structure. The ferroelectric memory structure includes a switching gate dielectric layer, a switching gate electrode layer, and a first memory electrode layer, a ferroelectric memory layer, and a second memory electrode layer, the first memory electrode layer being connected to the switching gate electrode layer. The control transistor structure includes a control source electrode and a control drain electrode, a control gate dielectric layer and a control gate electrode layer. The control connection structure electrically connects the control drain electrode and the switching gate electrode layer to each other over the substrate.