Memory Controller Test Read for Open Block Reliability
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Solution Overview
Problem
Existing semiconductor memory devices face reliability issues due to increased threshold voltages of memory cells in open blocks, leading to unreliable data storage, especially when the number of memory cells with threshold voltages higher than a test read voltage exceeds a preset value.
Innovation Solution
A method and system for a semiconductor memory device that includes a controller to determine if a memory block is an open block and uses a test read voltage to assess the target page, performing programming on the target page only when the number of data bits with a first logic value is equal to or less than a preset value, and redirecting programming to another page if the number exceeds the preset value, thereby ensuring reliable data storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If programming is performed on memory blocks with increased threshold voltages, then storage capacity is utilized, but data reliability deteriorates
Solution Approach 1:
The controller performs a test read operation before programming to check the threshold voltage state of memory cells. This preliminary action identifies unsuitable memory blocks (open blocks with excessive threshold voltages) before programming occurs, preventing unreliable data storage while maintaining efficient programming of suitable blocks
Solution Approach 2:
The controller uses feedback from the test read operation to determine whether to proceed with programming. Based on the read data indicating threshold voltage levels, the controller dynamically decides to program or skip the target page, ensuring reliability while optimizing programming efficiency through selective programming
2Productivity
If all pages in a memory block are programmed, then storage utilization increases, but threshold voltage instability increases
Solution Approach 1:
The controller applies different treatment to different pages within the same memory block based on their individual states. Pages that pass the test read criterion are programmed, while pages indicating open block conditions are skipped. This local differentiation maintains threshold voltage stability by preventing programming in vulnerable areas while utilizing suitable pages
Data Source
AI summary
A method of programming a memory system includes: reading a target page included in a selected memory block in response to a program request when at least one of the pages included in the selected memory block contains data; and performing a program for the target page when, among the data bits included in the data read from the target page, the number of data bits having a first logic value is equal to or less than a preset value.