RRAM Forming Sequence Inversion for Voltage Drop Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The voltage drop issue during the forming operation of resistive random access memory (RRAM) cells leads to reduced voltage, increased time, and higher operating voltage requirements, potentially resulting in failed filament formation.
Innovation Solution
A forming operation method where a positive pulse and a negative pulse are sequentially applied to RRAM cells from the farthest location to the nearest location relative to the bit line/source line driver, reducing the voltage drop and facilitating faster conductive filament formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the forming operation is performed sequentially from nearest location to farthest location, then the conductive filament can be formed in earlier cells, but the voltage drop increases for later cells requiring higher operating voltage and more retries
Solution Approach 1:
The patent inverts the conventional forming operation sequence by performing forming operations from the farthest location to the nearest location relative to the bit line/source line driver, rather than the traditional nearest-to-farthest approach. This reversal ensures that cells closer to the driver (which would otherwise experience maximum voltage drop) are formed first when voltage is still sufficient, thereby improving forming success rate without requiring excessive voltage increases.
Solution Approach 2:
The patent applies preliminary action by performing forming operations on distant cells first, before the voltage drop from previously formed near cells accumulates. This ensures that all cells receive adequate forming voltage regardless of their position in the array, preventing forming failures due to voltage depletion and reducing the need for retry operations.
2Reliability
If higher operating voltage is applied to compensate for voltage drop, then the conductive filament can be formed in distant cells, but the energy consumption and device stress increase
Solution Approach 1:
By inverting the forming sequence to process distant cells first, the patent eliminates the need for excessive voltage compensation. Distant cells are formed when the voltage drop across the conductive wire is still minimal, allowing the use of standard forming voltages without requiring elevated operating voltages that would waste energy and stress the device.
3Reliability
If the resistance value of formed resistive elements is greatly reduced, then data storage is enabled, but the leakage current of series transistors affects subsequent forming operations
Solution Approach 1:
The patent performs forming operations on distant cells before near cells, ensuring that the leakage current from formed near cells does not interfere with the forming process of distant cells. By completing distant cell formation first when leakage current is still low, the patent prevents the harmful effect of leakage current from compromising the forming success of subsequent cells.
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 method reduces the overall voltage drop experienced by RRAM cells, allowing for faster conductive filament formation, fewer retries, and reduced maximum voltage requirements, thereby improving the reliability and efficiency of the forming operation.
Implementation Method 1
a positive pulse and a negative pulse are sequentially applied, by a bit line/source line driver, to multiple resistive random access memory cells in a direction from a farthest location to a nearest location based on the bit line/source line driver through a bit line and a source line to break down a dielectric film of each of the resistive random access memory cells and generate a conductive filament
Implementation Method 2
the resistance value of the resistive element may be changed by applying an electric field to store data. After forming the conductive filament, the resistance value of the resistance element of the resistive random access memory is reduced from hundreds of millions of ohms to tens of thousands of ohms
Data Source
AI summary
A forming operation method of a resistive random access memory is provided. The method includes the following steps. A positive pulse and a negative pulse are sequentially applied, by a bit line/source line driver, to multiple resistive random access memory cells in a direction form a farthest location to a nearest location based on the bit line/source line driver through a bit line and a source line to break down a dielectric film of each of the resistive random access memory cells and generate a conductive filament of each of the resistive random access memory cells.