Memory Array Pass-Voltage Sequencing for Program Disturbance Control
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Solution Overview
Problem
Non-volatile memory devices suffer from programming disturbance effects, such as hot-electron injection and electrostatic field-induced charge changes, due to shared word lines causing unintended data alterations in unselected memory cells during programming operations.
Innovation Solution
Implementing a control logic that increases the pass voltage on unselected wordlines during the initial phase of a program operation to expel residual electrons, followed by a controlled reduction in pass voltage to prevent hot-electron injection and maintain read margin stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a constant pass voltage is applied to all word lines during programming, then the programming operation is simple to implement, but hot-electron injection and programming disturbance occur in unselected memory cells
Solution Approach 1:
The patent applies dynamics by making the pass voltage time-dependent rather than constant. The pass voltage is increased during the initial phase of programming to expel residual electrons, then reduced to a lower level for the remainder of the programming operation. This dynamic adjustment of voltage over time resolves the contradiction by preventing hot-electron injection while maintaining operational simplicity.
Solution Approach 2:
The patent changes the voltage parameter dynamically during the programming operation. Specifically, the pass voltage transitions from an initial higher level to a subsequent lower level based on the programming phase. This parameter change allows the system to mitigate programming disturbance effects without complicating the overall operation.
2Reliability
If the pass voltage is increased to expel residual electrons, then programming disturbance is reduced, but the voltage distribution becomes more complex
Solution Approach 1:
The dynamic voltage adjustment resolves the contradiction between reliability and device complexity. By implementing a time-dependent pass voltage that transitions from high to low based on programming phase, the system achieves accurate data retention while maintaining relatively simple voltage distribution control through phased timing.
Solution Approach 2:
The patent employs periodic action by dividing the programming operation into distinct phases (initial phase and subsequent phase) with different voltage levels. This phased approach simplifies voltage distribution management while ensuring reliable electron expulsion and data retention.
3Reliability
If the pass voltage is reduced to prevent hot-electron injection, then data retention is improved, but residual electrons may remain in the channel
Solution Approach 1:
The patent applies preliminary action by first increasing the pass voltage during the initial phase of programming to expel residual electrons from the channel before reducing it to a lower level. This preliminary high-voltage action prevents subsequent hot-electron injection and maintains read margin stability without leaving harmful residual electrons.
Solution Approach 2:
The dynamic voltage transition from high to low resolves the contradiction between preventing hot-electron injection and removing residual electrons. The initial high voltage expels residual electrons, then the reduced voltage prevents hot-electron injection during the rest of the programming operation, achieving both goals through time-dependent control.
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
Mitigates programming disturbance effects, ensuring accurate data retention and read stability by preventing hot-electron injection and maintaining optimal voltage distributions in memory arrays.
Implementation Method 1
hot-electron injection and electrostatic field-induced charge changes
Implementation Method 2
hot-electron injection and electrostatic field-induced charge changes
Data Source
AI summary
A memory device includes a memory array with a plurality of wordlines and control logic operatively coupled with the memory array. The control logic determines, during an initial phase of a program operation, whether a program voltage being applied to a selected wordline of the memory array satisfies a threshold program voltage. The control logic increases, in response to the program voltage not satisfying the threshold program voltage, an initial pass voltage to generate a higher pass voltage. The control logic causes the higher pass voltage to be applied to unselected wordlines of the plurality of wordlines before programming one or more memory cells associated with the selected wordline.