Memory Device Pre-fill Operation for Charge Control
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Solution Overview
Problem
In memory devices, particularly those using high threshold voltage levels, there is a challenge in controlling short-term vertical and lateral charge spreading and suppressing long-term retention charge loss caused by fast charge lateral movement, which affects memory storage density and reliability.
Innovation Solution
The solution involves a memory device operation method that includes a pre-fill operation with multiple voltage phases and an erase operation, where selected and unselected word lines are alternately applied with specific voltages in sequential loops to control charge distribution and retention, effectively reducing threshold voltage spreading and retention charge loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high threshold voltage levels are used to increase memory storage density, then memory storage capacity is improved, but charge lateral movement increases causing threshold voltage spreading and retention charge loss
Solution Approach 1:
The patent applies a pre-fill operation before the main programming operation. This preliminary action involves applying a first voltage to selected word lines and a second voltage to unselected word lines to pre-establish charge distribution patterns. By performing this preparatory charge arrangement, the patent prevents excessive charge lateral movement during subsequent programming, thereby reducing threshold voltage spreading while maintaining high storage density capabilities
Solution Approach 2:
The patent employs multiple programming operations divided into different loops (first loop, second loop, etc.). Each loop applies voltage patterns periodically to different word line groups. This periodic action allows controlled charge distribution over time, preventing uncontrolled lateral charge movement that would cause threshold voltage spreading, while still achieving the required storage density through cumulative programming effects
2Quantity of substance
If programming operations are performed to increase storage capacity, then memory capacity is improved, but fast charge lateral movement causes retention charge loss in the long term
Solution Approach 1:
The pre-fill operation serves as a preliminary action that establishes proper charge distribution before main programming. By pre-applying voltages to selected and unselected word lines, the patent creates a charge configuration that minimizes subsequent lateral charge movement during programming and retention phases, thereby reducing long-term charge loss while maintaining programming effectiveness for increased capacity
Solution Approach 2:
The patent applies different voltages to different word line groups (selected vs. unselected) during both pre-fill and programming operations. This local differentiation of voltage application creates localized charge distribution patterns that confine charges to their intended regions, preventing widespread lateral charge movement that would cause retention loss, while still achieving overall increased memory capacity
Data Source
AI summary
Provided are a memory device and an operation method thereof. The memory device includes a plurality of word lines. The operation method comprising: performing a pre-fill operation on the word lines, in a first loop, applying a selected word line voltage on a first selected word line group and applying an unselected word line voltage on a first unselected word line group, and in a second loop, applying the selected word line voltage on a second selected word line group and applying the unselected word line voltage on a second unselected word line group, the first selected word line group being different from the second selected word line group, and the first unselected word line group being different from the second unselected word line group; performing an erase operation on the word lines; and performing a programming operation on the word lines.