MRAM Programming Method Continuous Bit Line Voltage
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Solution Overview
Problem
Magnetic random access memory (MRAM) devices face a high write error rate due to manufacturing process issues, which limits the yield and reliability of nonvolatile semiconductor memory devices, despite increased write voltage.
Innovation Solution
A programming method for MRAM devices that involves maintaining bit line and source line voltages continuously through both program operations, allowing for extended programming time and reducing the write error rate by eliminating the need for voltage ramp-up time between operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write voltage is increased to reduce write error rate, then reliability improves, but manufacturing defects increase causing write error rate to remain high
Solution Approach 1:
The patent applies preliminary action by maintaining bit line and source line voltages at programming levels before the actual program operation begins. This pre-charging eliminates the voltage ramp-up time during programming, providing immediate high voltage stress to the memory cell to overcome manufacturing defects and reduce write error rates.
Solution Approach 2:
The patent implements continuity of useful action by continuously maintaining the bit line and source line at programming voltages throughout the programming period, including during intervals between word line pulses. This continuous voltage application ensures sustained programming effect without interruption, improving reliability despite manufacturing variations.
2Productivity
If voltage is applied continuously to reduce programming time, then productivity improves, but energy consumption increases
Solution Approach 1:
The patent uses preliminary action by pre-charging the bit line and source line to programming voltages before word line activation. This eliminates the need for slow voltage ramp-up during each programming cycle, significantly reducing programming time while the energy is efficiently utilized during the active programming window.
Solution Approach 2:
The patent employs periodic action by applying word line pulses in periodic intervals while maintaining continuous bit line and source line voltages. This allows the memory cell to receive repeated programming stimuli without continuously charging the bit line and source line, reducing energy consumption while maintaining high programming speed.
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 significantly decreases the write error rate, improving the reliability and yield of MRAM devices by utilizing the time typically spent on voltage charging for additional programming, thereby enhancing the overall performance of the memory device.
Implementation Method 1
A representative example of such a nonvolatile element is a magnetic random access memory (MRAM) using a tunneling magneto-resistive (TMR) layer
Implementation Method 2
a magnetic random access memory (MRAM) using a tunneling magneto-resistive (TMR) layer
Data Source
AI summary
Disclosed is a memory device. The memory device includes a memory cell array that includes a target cell, a row decoder that drive a word line, and a write driver and sense amplifier that are configured to drive a bit line and a source line. The row decoder is configured to drive the word line in a first program operation and a second program operation. Between a start of the first program operation and an end of the second program operation, the write driver and sense amplifier are configured to continuously drive a bit line connected to the target cell with a second driving voltage or drive a source line connected to the target cell with a third driving voltage.