Semiconductor Memory De-Trap Control for Threshold Voltage Stability
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Solution Overview
Problem
Non-volatile memory devices face reliability issues due to deteriorating threshold voltage distribution of memory cells with increasing program and erase operations, necessitating improved methods to maintain data integrity.
Innovation Solution
A semiconductor device with a control circuit that performs a de-trap operation on memory cells during programming, selectively fixing or changing voltage levels based on program completion status to improve threshold voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If program operations are performed repeatedly to increase storage capacity utilization, then data storage capability is improved, but threshold voltage distribution deteriorates and reliability decreases
Solution Approach 1:
The de-trap operation is performed in advance during the programming process (between program pulse application and verification) to prevent threshold voltage distribution deterioration before it occurs. This preliminary action removes trapped charges that would otherwise degrade memory cell reliability after repeated program operations.
Solution Approach 2:
The patent converts the harmful effect of trapped charges (which cause threshold voltage distribution deterioration) into a beneficial process by intentionally inducing controlled charge trapping during programming and then removing it through de-trap operations. This controlled cycle actually improves reliability by preventing uncontrolled charge accumulation.
2Reliability
If de-trap operation is performed on all memory cells, then threshold voltage distribution is improved, but operation complexity increases
Solution Approach 1:
The de-trap operation is applied selectively only to memory cells that require it, based on their individual programming status. The control circuit identifies which cells have incomplete program operations and applies de-trap only to those specific cells, rather than uniformly to all cells, thereby reducing unnecessary operations.
Solution Approach 2:
The system uses program verification results as feedback to determine whether de-trap operation is needed. The control circuit monitors the completion status of program operations and dynamically adjusts de-trap application accordingly, creating a closed-loop control system that optimizes operation complexity.
3Reliability
If program verification is performed frequently to ensure data integrity, then reliability is improved, but operation time increases
Solution Approach 1:
The de-trap operation is performed preliminarily during the programming phase to prevent threshold voltage shifts that would require additional verification cycles. By addressing potential reliability issues early, the system reduces the need for repeated verification operations, thereby reducing total operation time.
Data Source
AI summary
Disclosed is a semiconductor device including a plurality of strings connected between a plurality of bit lines and a source line, a plurality of page buffers connected to the plurality of bit lines, respectively, and configured to adjust a voltage level of each of the plurality of bit lines, and a control circuit configured to control the plurality of page buffers to fix a voltage level of a bit line connected to a string including a memory cell on which a program operation has been completely performed and to change a voltage level of a bit line connected to a string including a memory cell on which the program operation has not been completely performed, during a de-trap operation.