Non-Volatile Memory Pre-Charge Voltage Control
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Solution Overview
Problem
In flash memory systems, program disturb occurs when programming one cell on a word line inadvertently programs adjacent unselected cells, due to the application of program voltage to all cells connected to the word line, leading to errors and data integrity issues.
Innovation Solution
Unselected groups of non-volatile storage elements are pre-charged with different pre-charge enable voltages before applying a program voltage to the selected word line, ensuring a boosted potential is provided to reduce or eliminate program disturb by equalizing channel regions on both the source and drain sides of the selected word line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If program voltage is applied to all cells connected to the selected word line, then programming operation can be performed, but program disturb occurs causing adjacent unselected cells to be inadvertently programmed
Solution Approach 1:
The patent segments the word line into different regions (source side and drain side) and applies different pre-charge enable voltages to each region. This segmentation allows independent control of pre-charging conditions for cells that will be programmed versus cells that will not be programmed, thereby preventing program disturb while maintaining programming productivity.
Solution Approach 2:
The patent applies different pre-charge enable voltages to different local regions of the word line based on whether the cells are selected for programming or not. Unselected cells receive a first pre-charge enable voltage that creates a boosted potential, while selected cells receive a second pre-charge enable voltage that allows normal programming operation. This local differentiation resolves the contradiction between efficient programming and preventing disturb.
2Reliability
If pre-charge enable voltage is applied to unselected groups before programming, then program disturb is reduced, but additional voltage control complexity is introduced
Solution Approach 1:
The patent applies pre-charge enable voltages to unselected word line groups before the main programming operation begins. This preliminary action establishes the boosted potential in the channel regions of unselected cells, preventing program disturb during subsequent programming operations. The pre-charging occurs in advance, allowing the main programming to proceed without additional complex control during the programming itself.
Solution Approach 2:
The patent dynamically selects different pre-charge enable voltages based on the programming state of adjacent word lines. The control circuitry determines which pre-charge enable voltage to apply (first or second) based on whether adjacent word lines have been partially programmed, allowing the system to adapt to different programming scenarios and maintain reliability without requiring overly complex fixed control schemes.
Data Source
AI summary
Unselected groups of non-volatile storage elements are boosted during programming to reduce or eliminate program disturb for targeted, but unselected memory cells connected to a selected word line. Prior to applying a program voltage to the selected word line and boosting the unselected groups, the unselected groups are pre-charged to further reduce or eliminate program disturb by providing a larger boosted potential for the unselected groups. During pre-charging, one or more pre-charge enable signals are provided at different voltages for particular non-volatile storage elements.