In Situ Memory Re-Programming via Hole Pre-Charge
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Solution Overview
Problem
NAND memory devices face challenges in efficiently re-programming data without inducing program disturb, especially when dealing with word lines that have a high failed bit count due to leakage, as existing methods can cause unintentional programming in neighboring cells during the pre-charge operation.
Innovation Solution
The method involves a 'hole pre-charge' operation where a low voltage is applied to all word lines to make memory cells conductive to holes, and a weak erase voltage is applied to the source line to inject gate-induced drain leakage (GIDL) holes, allowing for re-programming of selected word lines without disturbing adjacent cells, thereby avoiding program disturb.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pre-charge operation is applied to re-program word lines with high failed bit counts, then the memory cells can be re-programmed, but program disturb occurs in neighboring cells causing unintentional programming
Solution Approach 1:
The patent applies different voltage levels to different word lines during the pre-charge operation. Specifically, a first voltage level is applied to the selected word line to be re-programmed, while a second, lower voltage level is applied to non-selected word lines. This localized voltage differentiation allows the selected cell to be properly pre-charged for re-programming while preventing program disturb in neighboring cells, thus resolving the contradiction between re-programming success and preventing harmful side effects.
2Object-generated harmful factors
If data is moved to another memory block for re-programming, then program disturb is avoided, but device complexity and operation time increase
Solution Approach 1:
The patent extracts and isolates the pre-charge operation for the selected word line from the conventional block-wide pre-charge process. By separating the voltage application to the selected word line from the non-selected word lines, the method eliminates the need to move data to another memory block while still preventing program disturb. This extraction of the problematic element (high voltage pre-charge) from the broader context resolves both the program disturb issue and avoids the complexity of data relocation.
3Ease of operation
If a conventional pre-charge voltage is applied to all word lines, then all memory cells are properly pre-charged, but neighboring cells experience program disturb
Solution Approach 1:
The patent implements local quality by applying different voltage levels to different spatial locations (word lines) within the memory block. The selected word line receives a first voltage level sufficient for proper pre-charge, while non-selected word lines receive a second, lower voltage level that prevents program disturb. This spatial differentiation of voltage quality maintains ease of operation for the target cell while eliminating harmful effects in neighboring cells.
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 enables in-situ re-programming of memory cells with high failed bit counts without moving data to another memory block, improving performance and extending the device's operating life by eliminating the need for a program-erase cycle, while preventing program disturb in neighboring cells.
Implementation Method 1
a weak erase voltage is applied to the source line to inject gate-induced drain leakage (GIDL) holes
Data Source
AI summary
The memory device includes a memory block with a plurality of memory cells that are arranged in a plurality of word lines and in a plurality of channels. The memory device also includes circuitry that is configured to conduct a hole pre-charge operation to inject holes into the plurality of channels. The hole pre-charge operation includes applying a first voltage to the plurality of word lines to make the plurality of memory cells conductive to holes and applying a voltage to the channels from one side of the memory block to inject holes into the channels.