Shadow Programming for TLC/QLC NAND Read Window Reliability
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Solution Overview
Problem
Current reprogramming methods are inadequate for reduced tier pitch triple-level cell (TLC) or quad-level cell (QLC) memory arrays, leading to lower performance in high-reliability and high-performance applications, and require larger write buffers and narrower read windows.
Innovation Solution
Implementing single command shadow programming for TLC or QLC memory arrays, which includes a one-pass programming operation with dual pulse programming and read level offset voltages to improve reliability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reprogramming methods are used for reduced tier pitch TLC or QLC memory arrays, then manufacturing is simpler, but programming efficiency and reliability deteriorate
Solution Approach 1:
The programming operation is divided into multiple passes, with each pass programming a specific subset of word lines. The method segments the memory array into different programming groups and uses separate programming operations for each group, allowing complex reduced-tier-pitch arrays to be programmed systematically without requiring overly complex single-pass methods
Solution Approach 2:
The method performs preliminary programming of lower page data to shadow buffers before final programming operations. This preliminary action ensures data is prepared and verified before committing to the final programming state, improving reliability without requiring complex real-time programming methods
2Reliability
If conventional reprogramming methods are used, then write buffer size can be smaller, but read window budget narrows and reliability decreases
Solution Approach 1:
The method introduces shadow buffers as intermediary storage structures that temporarily hold programming data during the multi-pass operation. These shadow buffers act as mediators between the input data and the final memory state, allowing verification and correction operations without requiring excessively large write buffers
Solution Approach 2:
The method incorporates read operations between programming passes to verify data integrity and detect programming errors. This feedback mechanism allows the system to detect and correct issues before finalizing the programming operation, improving reliability without proportionally increasing buffer requirements
3Quantity of substance
If reduced tier pitch is implemented to increase density, then storage capacity increases, but programming performance deteriorates with conventional methods
Solution Approach 1:
The memory array is segmented into programming groups where each group contains a manageable subset of word lines that can be programmed together. This segmentation allows the high-density reduced tier pitch array to be programmed in organized batches, maintaining programming speed despite increased density
Solution Approach 2:
The multi-pass programming method ensures continuous productive work by overlapping operations where possible and minimizing idle time between passes. Each pass is designed to be self-contained and productive, avoiding wasted cycles while handling the complexity of reduced tier pitch structures
Data Source
AI summary
Methods, systems, and devices for techniques for single command shadow programming are described herein. A one-pass programming operation is performed by programming lower page data of an (N+1)-th program loop word line to memory cells of the memory array. Lower page data of an N-th program loop word line is read from the memory cells, and higher page data of the N-th program loop word line is programmed to the memory cells.