Memory Device Fail Cell Detection and Program Termination
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Solution Overview
Problem
The increasing number of fail cells in three-dimensional memory devices due to advancements in microfabrication technology poses a challenge in guaranteeing memory capacity, as existing methods are inadequate for effective detection and management of these defective cells.
Innovation Solution
A method for detecting fail cells during a program operation in a memory device, which involves selecting memory cells to be programmed, applying program pulses, performing a first verification operation, and then a second verification operation using an over-bit verify voltage to detect fail cells, with the option to terminate the program operation if the number of detected fail cells exceeds a reference value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If microfabrication technology is advanced to increase memory capacity, then memory capacity is improved, but the number of fail cells increases
Solution Approach 1:
The patent applies preliminary action by performing a first verification operation during the program operation to identify fail cells before they can cause read errors. The control logic circuit detects fail cells by comparing programmed values with expected values, and terminates the program operation if the fail cell count exceeds a threshold, preventing defective data from being stored
2Ease of operation
If existing verification methods are used, then program operation is simple, but fail cells cannot be reliably detected
Solution Approach 1:
The patent performs a first verification operation during the program operation as a preliminary check to identify fail cells before they can cause read errors. This preliminary detection mechanism reliably identifies defective cells by comparing programmed values with expected values, ensuring that only healthy memory cells are used for data storage
Solution Approach 2:
The patent implements feedback by continuously monitoring the number of fail cells detected during the program operation and using this information to control whether the program operation should be terminated. The control logic circuit compares the fail cell count with a threshold value and provides feedback to stop the operation when necessary, ensuring reliable detection while maintaining operational simplicity
Data Source
AI summary
An operation method of a memory device for programming memory cells to a plurality of program states includes providing a series of program pulses to selected memory cells, performing a first verification operation of verifying a target program state among the plurality of program states, performing, when the first verification operation is passed, a second verification operation of detecting fail cells among the selected memory cells to determine if these memory cells have been overprogrammed. When the number of detected fail cells is greater than or equal to a reference value, the program operation may be terminated for that location and the data may be written to another location.