Variable Resistance Memory Cell Thermal Erase Control
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Solution Overview
Problem
Conventional semiconductor memory devices face inefficiencies in the erase operation of variable resistance elements due to incomplete oxygen ion migration, which results in insufficient resistance state changes, particularly because Joule heat generation is limited by the absence of current flow in regions where oxygen deficiencies have been annihilated.
Innovation Solution
The semiconductor memory device incorporates a control circuit that applies a voltage to change the resistance value of the variable resistance element and uses a wiring line layer to supply heat to the memory cell, specifically heating the word line to 400-500 K to enhance oxygen ion migration and facilitate efficient erase operations at lower voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage is applied to change resistance value of variable resistance element, then resistance state changes are achieved, but oxygen ion migration is incomplete and insufficient resistance state changes occur
Solution Approach 1:
The patent applies parameter changes by heating the word line to 400-500 K to enhance oxygen ion migration. This thermal parameter change enables more complete oxygen ion migration during erase operations, achieving sufficient resistance state changes without requiring excessive voltage application.
Solution Approach 2:
The patent uses heat as an intermediary to facilitate oxygen ion migration. By introducing thermal energy through heating the word line, the patent creates conditions that promote complete oxygen ion migration, which would not occur solely through electrical field application.
2Temperature
If Joule heat generation is used to supply heat to memory cell, then oxygen ion migration is enhanced, but current flow is required which is absent in regions where oxygen deficiencies have been annihilated
Solution Approach 1:
The patent applies preliminary action by heating the word line before and during the erase operation. This preliminary thermal preparation creates favorable conditions for oxygen ion migration without requiring high current flow, as the heating occurs in advance to establish the necessary thermal environment.
Solution Approach 2:
The patent substitutes the mechanical/electrical system (current flow-based Joule heating) with a thermal field-based system. By using external heating to raise the word line temperature to 400-500 K, the patent creates thermal energy without relying on current flow through the variable resistance element, thereby avoiding the limitation of absent current in oxygen-deficient regions.
3Reliability
If higher voltage is applied to achieve complete oxygen ion migration, then resistance state changes are improved, but voltage levels become excessively high
Solution Approach 1:
The patent resolves this contradiction by changing the temperature parameter of the word line to 400-500 K. This thermal parameter change enables complete oxygen ion migration at lower voltage levels, as the heat provides the additional energy needed for ion migration without requiring excessive electrical stress.
Solution Approach 2:
The patent introduces heat as an intermediary that mediates between the electrical field and oxygen ion migration. By using thermal energy as a mediator, the patent achieves complete oxygen ion migration without applying excessively high voltages, as the thermal field assists in overcoming the energy barriers for ion migration.
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 approach improves the migration rate of oxygen ions and enables efficient resetting operations by combining electrical field and thermal forces, allowing for effective resistance state changes at reduced voltage levels.
Implementation Method 1
a control circuit capable of executing a first operation that changes a resistance value of the variable resistance element by applying a voltage to the memory cell via the first line and the second line
Implementation Method 2
a second operation that supplies heat to the memory cell using the third line
Data Source
AI summary
A semiconductor memory device according to an embodiment comprises: a plurality of first lines extending in a first direction perpendicular to a substrate surface and arranged with a certain pitch in a second direction parallel to the substrate surface; a plurality of second lines extending in the second direction and arranged with a certain pitch in the first direction; a memory cell provided at an intersection of the first line and the second line and including a variable resistance element; a third line provided extending in the second direction between the plurality of second lines; and a control circuit capable of executing a first operation that changes a resistance value of the variable resistance element by applying a voltage to the memory cell via the first line and the second line, and a second operation that supplies heat to the memory cell using the third line.