Variable Resistor with Oxygen-Deficient HfO2 and Self-Rectification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current non-volatile memory devices, such as NAND flash memories, face limitations in scaling down due to increasing integration density, and there is a need for a low-power memory device with a simplified cell configuration that can replace NAND flash without requiring an electroforming process and having self-rectification characteristics.
Innovation Solution
A variable resistor with a stacked structure comprising a titanium electrode, an oxygen-deficient hafnium oxide film, an oxygen-deficient titanium oxide film, and a stoichiometric tantalum oxide film, which exhibits self-rectification and allows for resistive switching without an electroforming process, enabling a non-volatile memory device with multiple resistance states and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NAND flash memory integration density is increased, then storage capacity is improved, but scaling-down limits are reached
Solution Approach 1:
The patent changes the fundamental operating parameter from charge storage (NAND flash) to resistance state storage (ReRAM). By utilizing multiple resistance levels in the HfO2-based variable resistor, the device achieves multi-bit storage capability without requiring further scaling of transistor dimensions, thus avoiding scaling-down limits while maintaining high storage capacity.
Solution Approach 2:
The patent employs a composite material structure consisting of HfO2 film combined with TiN electrode and SiO2 interlayer. This composite structure enables the variable resistor to exhibit multiple resistance states and self-rectification characteristics, allowing high-density storage without increasing device complexity or requiring advanced scaling.
2Reliability
If electroforming process is used in ReRAM, then reversible resistance change is achieved, but power consumption increases and process complexity increases
Solution Approach 1:
The patent performs preliminary action during the fabrication process by forming oxygen-deficient regions in the HfO2 film through controlled oxidation of TiN electrode and oxygen diffusion during sputtering. This preliminary creation of oxygen vacancies eliminates the need for subsequent electroforming process, reducing both power consumption and process steps while maintaining reliable reversible resistance switching.
Solution Approach 2:
The TiN electrode serves a dual function: as an electrical contact and as an oxygen source that automatically creates oxygen-deficient regions in the HfO2 film during deposition. This self-service mechanism eliminates the need for external electroforming process, reducing power consumption and simplifying the manufacturing process.
3Reliability
If current steering devices are added to achieve self-rectification, then rectification characteristic is improved, but device complexity increases
Solution Approach 1:
The patent extracts the rectification function from separate current steering devices and integrates it directly into the variable resistor structure itself. By forming asymmetric oxygen-deficient regions at the TiN/HfO2 interface through controlled oxidation, the device achieves self-rectification without requiring external diodes or transistors, thereby reducing device complexity while maintaining reliable rectification characteristics.
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 provides a reliable variable resistor with multiple resistance states, low power consumption, and self-rectification, enabling the development of a non-volatile memory device that can replace NAND flash memories with a simplified structure and improved performance.
Implementation Method 1
The resistive switching is adjusted by trapping and de-trapping of charges at trap centers formed in the hafnium oxide film
Implementation Method 2
a second electrode for forming a Schottky barrier
Implementation Method 3
no current may flow until a voltage difference exceeds a predetermined value when potential of the second electrode is lower than that of the first electrode
Data Source
AI summary
Provided are a semiconductor technique, and more particularly, to a variable resistor, a non-volatile memory device using the same, and a method of fabricating the same. The variable resistor may include a first electrode including titanium (Ti); a second electrode for forming a Schottky barrier; and a stacked structure including an oxygen-deficient hafnium oxide film (HfO2-x, 0<x<2) between the first electrode and the second electrode, an oxygen-deficient titanium oxide (TiOx) film between the oxygen-deficient hafnium oxide film and the first electrode, and a stoichiometric tantalum oxide (Ta2O5) film between the oxygen-deficient hafnium oxide film and the second electrode.