Read Window Adjustment for Memory Cell Data Retention
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Solution Overview
Problem
Existing memory systems fail to effectively determine a read window tailored to the operating characteristics of individual memory devices and their environments, leading to decreased data retention over program/erase cycles, as they do not consider the specific operating conditions and characteristics of memory cells.
Innovation Solution
The solution involves subjecting memory cells to high quantities of program/erase cycles in a shorter time span than their service life, determining a read window based on these cycles, and adjusting trim parameters to improve data retention by compensating for the effects of extensive program/erase cycles, thereby enhancing the data retention capacity of memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory cells are subjected to high quantities of program/erase cycles to determine read window, then data retention capability is improved, but service life is reduced
Solution Approach 1:
The patent applies preliminary action by subjecting a first group of memory cells to a high quantity of program/erase cycles before determining the read window. This accelerated testing allows the system to establish trim parameters and read window characteristics that account for degradation over time, without requiring the entire service life to elapse. The read window determined from these pre-tested cells is then applied to a second group of memory cells, improving their data retention capability without subjecting them to the full cycle count.
2Measurement precision
If read window is determined based on accelerated program/erase cycles, then measurement precision is improved, but time consumption is reduced
Solution Approach 1:
The patent uses copying by subjecting a first group of memory cells to accelerated program/erase cycles to create a model or representation of degraded memory characteristics. The read window determined from this first group serves as a copied characteristic that is then applied to a second group of memory cells. This allows the system to obtain accurate read window measurements that reflect long-term degradation without actually waiting for the full service life to pass with the second group of cells.
Data Source
AI summary
A first group of memory cells of a memory device can be subjected to a particular quantity of program/erase cycles (PECs) in response to a programming operation performed on a second group of memory cells of the memory device. Subsequent to subjecting the first group of memory cells to the particular quantity of PECs, a data retention capability of the first group of memory cells can be assessed.