Pre-Charging ReRAM Bit Lines for Fast Programming
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Solution Overview
Problem
In unipolar-type ReRAM, it is challenging to apply a required program voltage to a selected memory cell in a short time due to high capacitance and resistance of the bit line and word line, leading to long charging and discharging times, and cross-talk disturbances in non-selected cells occur due to reverse voltage application.
Innovation Solution
The method involves pre-charging all word lines and bit lines to a certain voltage before applying a program voltage to the selected memory cell, with a program-block voltage applied to non-selected lines, allowing for a high-rate voltage boost and reducing program disturbance by minimizing the reverse voltage applied to non-selected cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a program voltage is applied to a selected memory cell in unipolar-type ReRAM, then data can be written to the selected cell, but the high capacitance and resistance of the bit line and word line cause long charging and discharging times, preventing short pulse width application
Solution Approach 1:
The patent applies preliminary action by pre-charging the bit line and word line to a specific voltage level before applying the program voltage pulse to the selected memory cell. This pre-charging step reduces the voltage swing required during the actual programming operation, thereby decreasing the charging and discharging time of the high-capacitance bit line and word line, and enabling shorter pulse width application.
2Productivity
If a program voltage is applied to a selected memory cell, then data writing is achieved, but reverse voltage application causes cross-talk disturbances in non-selected cells
Solution Approach 1:
The patent applies preliminary anti-action by pre-charging the bit line and word line to a specific voltage level before applying the program voltage. This pre-charging creates a voltage baseline that prevents reverse voltage application to non-selected cells during the programming operation. By establishing this preliminary voltage state, the method counteracts the harmful reverse voltage effect before it can cause cross-talk disturbances in non-selected memory cells.
3Adaptability or versatility
If the capacitance and resistance of bit line and word line are increased to support higher integration, then more memory cells can be addressed, but the charging and discharging time becomes longer
Solution Approach 1:
The patent resolves this contradiction by applying preliminary action through pre-charging the bit line and word line to a specific voltage level before the programming operation. This pre-charging reduces the voltage swing required during programming, enabling fast charging and discharging even with the high capacitance and resistance inherent in highly integrated memory cell arrays. The method thus maintains adaptability for high integration while overcoming the time penalty.
Data Source
AI summary
A method of programming a non-volatile memory device with memory cells formed of variable resistance elements and disposed between word lines and bit lines, includes: previously charging a selected word line and a selected bit line together with a non-selected word line and a non-selected bit line up to a certain voltage; and further charging the selected word line and the non-selected bit line up to a program voltage higher than the certain voltage and a program-block voltage, respectively, and simultaneously discharging the selected bit line.