Resistive Memory Forming With Dense Switching for Filament Stability
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Solution Overview
Problem
The forming operation in resistive memory devices can cause multi-conductive filaments and ionization of excess oxygen ions, leading to degradation during high temperature data retention and asymmetry in set and reset operations, resulting in reliability issues and reduced efficiency.
Innovation Solution
A pre-forming operation followed by a dense switching forming operation and a normal set operation is performed, using specific voltage configurations to control filament formation and prevent over-forming, thereby avoiding multi-conductive filaments and oxygen ion ionization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a strong forming operation is used to pull out oxygen ions and produce conductive filaments, then the resistive memory can be turned into a low resistance state, but multi-conductive filaments are generated causing over-forming and degradation during high temperature data retention test
Solution Approach 1:
The forming operation is segmented into three distinct stages: pre-forming operation with lower voltage to initiate filament formation, dense switching forming operation with alternating set/reset to refine filament structure, and normal set operation to complete the process. This segmentation prevents over-forming and multi-conductive filament generation while ensuring reliable LRS state.
Solution Approach 2:
A pre-forming operation is performed before the main forming process to prepare the oxygen ion distribution and create initial conductive pathways. This preliminary action reduces the strength required in subsequent forming operations, preventing excessive filament growth and multi-conductive filament formation that would degrade reliability.
2Reliability
If a strong forming operation is used to produce conductive filaments, then the resistive memory can be turned into a low resistance state, but the forming time is extended reducing production efficiency
Solution Approach 1:
The dense switching forming operation uses periodic alternating set and reset operations to progressively refine the conductive filament structure. This periodic action efficiently shapes the filaments without requiring excessively long forming times, balancing reliability improvement with production efficiency by limiting the number of alternating cycles.
Solution Approach 2:
The pre-forming operation prepares the material structure in advance by initiating oxygen ion migration and creating initial conductive pathways. This preliminary preparation reduces the time required for the main forming operation, as subsequent operations only need to refine rather than create the filaments from scratch, thus improving productivity while maintaining filament stability.
3Reliability
If excess oxygen ions are present near electron holes, then the resistive memory can be reset to high resistance state, but oxygen ions are ionized and backfilled into oxygen vacancies during heat provided test causing set-complementary switching
Solution Approach 1:
The pre-forming operation redistributes oxygen ions before the main forming process, creating a more uniform oxygen ion distribution and reducing excessive concentration near electron holes. This preliminary redistribution prevents ionization and backfilling during subsequent operations, eliminating set-complementary switching while maintaining reset reliability.
Solution Approach 2:
The dense switching forming operation applies localized voltage stress to specific regions during alternating set and reset cycles, precisely controlling oxygen ion migration to desired locations. This local quality control ensures oxygen ions are positioned appropriately in the conductive filaments without excessive accumulation near electron holes, preventing ionization and backfilling that would cause set-complementary switching.
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 enhances filament stability, reduces the risk of over-setting and set-complementary switching, and shortens the forming process, improving production efficiency and reliability of resistive memory devices.
Implementation Method 1
a forming operation, which is much stronger than a general set operation, needs to be used to pull out oxygen ions in the transition metal oxide to produce conductive filaments
Implementation Method 2
an initial reset operation with an intensity equivalent to the forming operation but with a different polarity is performed to reset most of the oxygen ions to block the conductive filaments
Implementation Method 3
the ionization of excess oxygen ions near electron holes causes the oxygen ions to be backfilled into the oxygen vacancies of the conductive filaments from the heat provided during the HTDR test
Data Source
AI summary
A forming operation of resistive memory device is provided. The operation includes: applying a pre-forming gate voltage and a pre-forming bit line voltage to a target memory cell; performing a dense switching forming operation, wherein the dense switching forming operation includes alternately performing dense set operations and dense reset operations on the target memory cell, wherein the dense set operation includes applying a dense switching gate voltage and a dense set bit line voltage; and performing a normal set operation on the target memory cell, wherein the normal set operation includes applying a normal set gate voltage and a normal set bit line voltage to the target memory cell, the normal set gate voltage is greater than the pre-forming gate voltage and the dense switching gate voltage, and the normal set bit line voltage is less than the pre-forming bit line voltage and the dense set bit line voltage.