3D Nonvolatile Memory Pre-Charge Control for Program Disturb
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Solution Overview
Problem
Three-dimensional nonvolatile memory devices face challenges in reliability and program disturb due to the stacking of memory cells, which affects the integration and efficiency of data storage.
Innovation Solution
A program method for nonvolatile memory devices that involves setting a pre-charge condition based on the disturb environment between cell strings, where an unselected cell string is pre-charged or not pre-charged depending on the program voltage level, number of program loops, and wear environment, to adaptively manage the pre-charge operation and prevent program disturb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If three-dimensional memory structure with vertically stacked cell strings is used to increase integration, then integration density is improved, but program disturb between adjacent cell strings increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-charging the unselected cell string before programming the selected cell string. This pre-charge operation creates a counteracting effect that prevents program disturb from propagating to the unselected cell string, thereby protecting it from harmful effects while maintaining the high integration density of the three-dimensional structure.
Solution Approach 2:
The patent implements preliminary action by performing the pre-charge operation on the unselected cell string before the actual programming operation. This preparatory step ensures that the unselected cell string is in a protected state prior to exposure to program voltage, preventing disturb effects while preserving the vertical stacking architecture for high integration.
2Reliability
If pre-charge voltage is applied to unselected cell string to prevent program disturb, then reliability is improved, but programming speed is reduced
Solution Approach 1:
The patent applies periodic action by implementing pre-charge operations selectively based on the program voltage level. The pre-charge is applied in a periodic manner - only when the program voltage exceeds a threshold value - rather than continuously for all programming operations. This approach maintains reliability by preventing program disturb when needed, while preserving programming speed by omitting pre-charge when the program voltage is low and disturb risk is minimal.
Solution Approach 2:
The patent implements dynamics by making the pre-charge operation conditional and adaptive. The control logic dynamically determines whether to apply pre-charge voltage based on real-time assessment of program voltage level and disturb risk. This dynamic approach optimizes the balance between reliability and speed by adjusting the pre-charge operation according to actual operating conditions rather than applying it uniformly.
3Reliability
If pre-charge voltage level is increased to enhance program disturb prevention, then reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by adjusting the pre-charge voltage level dynamically based on the program voltage level. When program voltage is high, the pre-charge voltage is set to a level sufficient to prevent disturb. When program voltage is low, the pre-charge voltage level is reduced or the operation is omitted entirely. This adaptive parameter adjustment maintains reliability when needed while minimizing energy consumption during low-risk operations.
Data Source
AI summary
A nonvolatile memory device includes at least two strings that are vertically stacked on a substrate and share one bit line. A program method of the nonvolatile memory device includes setting a pre-charge condition on the basis of a disturb environment between the at least two cell strings, pre-charging or not pre-charging an unselected cell string among the at least two cell strings in response to the pre-charge condition and programming memory cells in a selected cell string among the at least two cell strings.