Adjacent Wordline Corrective Reads for Memory Vt Shift Compensation
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Solution Overview
Problem
Cell-to-cell interference in memory devices leads to Vt distribution widening, resulting in read window budget degradation and reduced memory device reliability.
Innovation Solution
Perform corrective reads implementing incremental reads with respect to adjacent wordlines, utilizing page buffers to store information from adjacent cells and performing incremental read loops to determine appropriate read level offsets for target wordlines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corrective reads are performed to compensate for Vt distribution shifts, then memory device reliability is improved, but read operation time increases
Solution Approach 1:
The patent performs preliminary reads on adjacent wordlines before reading the target wordline. By reading adjacent wordlines first and determining their Vt distribution characteristics, the system can pre-calculate appropriate read levels for the target wordline, avoiding the need for multiple iterative reads and thus reducing total read time while maintaining reliability
Solution Approach 2:
The patent applies partial corrective reads by selectively reading only adjacent wordlines that are likely to cause interference based on their physical proximity and programming status. This partial action approach compensates for the most significant sources of Vt distribution shift without performing exhaustive reads on all wordlines, thereby balancing reliability improvement with time efficiency
2Measurement precision
If incremental read loops are performed to determine read level offsets, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the read operation into distinct phases: reading adjacent wordlines, analyzing their Vt distributions, calculating read level offsets, and applying these offsets to read the target wordline. This segmentation allows each phase to be optimized independently and simplifies the control logic by breaking down the complex measurement process into manageable steps
Solution Approach 2:
The patent introduces an intermediary calculation step that uses the read results from adjacent wordlines to determine the appropriate read levels for the target wordline. This intermediary process acts as a mediator between the raw read data and the final data retrieval, enabling precise measurement without requiring complex direct measurement circuits
Data Source
AI summary
A system includes a memory device including a memory array and control logic operatively coupled with the memory array. The control logic may perform operations including causing a first read to be performed with respect to a first cell of the memory array, storing, to a first primary data cache, a first bit of a first read result of the first read, storing, to a secondary data cache, a second bit of the first read result, causing a second read to be performed with respect to a second cell of the memory array, storing, to a second primary data cache, a second read result of the second read, and causing a third read to be performed with respect to a target cell of the memory array, wherein the target cell is adjacent to the first cell and the second cell.