Ferroelectric Semiconductor Structure for Low-Voltage Polarization Switching

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Solution Overview

Problem

Conventional ferroelectric field effect transistors face challenges in changing the polarization direction of the ferroelectric layer at low voltages due to insufficient minority carriers, resulting in small memory windows and poor retention characteristics.

Innovation Solution

A semiconductor device design with a semiconductor substrate having a lower doping concentration than the channel layer, combined with a thin channel layer, allows for the change in polarization direction of the ferroelectric layer by supplying minority carriers, enhancing memory window size and retention characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional ferroelectric field effect transistors are used, then the device structure is simple, but the memory window is small and retention characteristics are poor due to insufficient minority carriers

Engineering Contradiction:

Improveretention characteristicsVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The device is segmented into distinct functional layers: a semiconductor substrate providing minority carriers, a channel layer for charge transport, and a ferroelectric layer for polarization storage. This segmentation allows each layer to be optimized independently, with the substrate specifically designed to supply minority carriers to enhance retention characteristics without complicating the overall device structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining a semiconductor substrate (e.g., Si, Ge, SiGe) with a channel layer (oxide semiconductor or 2D material) and a ferroelectric layer (hafnium oxide, zirconium oxide). This composite material approach enables the substrate to supply minority carriers while maintaining device structural simplicity, thereby improving retention characteristics without significant complexity increase

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If high doping concentration is used in the semiconductor substrate, then the device can operate at low voltages, but the memory window becomes small due to insufficient minority carriers

Engineering Contradiction:

Improveoperating voltageVSAvoidmemory window

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention changes the doping concentration parameter of the semiconductor substrate to a specific range (10^16 to 10^19 cm^-3) that optimizes minority carrier supply. This parameter adjustment allows the device to achieve both low operating voltage and large memory window by balancing the substrate's ability to supply minority carriers with its electrical characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The semiconductor substrate is pre-doped with appropriate concentration before device fabrication to ensure sufficient minority carrier supply during operation. This preliminary action of doping the substrate establishes the foundation for both low-voltage operation and large memory window without requiring additional structures or processes

Inventive Principle:

Principle #10Preliminary action

3Reliability

If a thick channel layer is used, then the device has good electrical characteristics, but the polarization direction cannot be changed effectively due to insufficient minority carrier supply

Engineering Contradiction:

Improveelectrical characteristicsVSAvoidpolarization switching

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The invention applies local quality by creating a specific doping concentration gradient: the semiconductor substrate has a lower doping concentration (10^16 to 10^19 cm^-3) specifically in the region that contacts the channel layer, while maintaining other regions at conventional doping levels. This localized doping approach enables effective minority carrier supply for polarization switching in the channel region without compromising the overall electrical characteristics of the device

Inventive Principle:

Principle #3Local quality

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 achieves a large memory window and improved retention characteristics by effectively changing the polarization direction of the ferroelectric layer at low voltages, while also improving durability through the use of two-dimensional semiconductor materials.

Implementation Method 1

allows for the change in polarization direction of the ferroelectric layer by supplying minority carriers

Methodology Applied

Scientific EffectCarrier supply:

Implementation Method 2

A ferroelectric material is a material that has ferroelectricity and thus maintains a spontaneous polarization due to aligning of an internal electric dipole moment

Methodology Applied

Scientific EffectFerroelectricity:

Data Source

PatentUS20230275150A1Semiconductor device including ferroelectric material and electronic device including the semiconductor device

Publication Date: 2023.08.31 SAMSUNG ELECTRONICS CO LTD

AI summary

A semiconductor device may include a semiconductor substrate including a dopant having a polarity; a channel layer on the semiconductor substrate and including majority carriers having a polarity opposite to a polarity of the semiconductor substrate; a ferroelectric layer on the channel layer; and a gate on the ferroelectric layer. A doping concentration of the semiconductor substrate may be less than a concentration of the majority carrier of the channel layer.