Storage Device Read Retry Logic for High-Resistance Word Lines
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Solution Overview
Problem
Storage devices face reliability issues during read operations due to failed read attempts on certain word lines, particularly those with high resistance, leading to data retrieval failures.
Innovation Solution
A storage device and method that include a memory controller capable of performing read retry operations by adjusting read voltage levels and application times, with a read retry table storing information for optimal retry conditions, ensuring successful data retrieval on vulnerable word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard read operation is performed on all word lines, then the read operation is simple and fast, but read reliability deteriorates on high-resistance word lines
Solution Approach 1:
The patent applies different read voltage levels and application times to different word lines based on their specific characteristics. High-resistance word lines receive enhanced read conditions (higher voltage, longer application time) while normal word lines use standard conditions, thereby improving read reliability where needed without unnecessarily complicating operations on all word lines.
Solution Approach 2:
The patent dynamically adjusts read voltage levels and application times based on the resistance characteristics of each word line. The memory controller modifies read parameters in real-time according to measured or pre-characterized word line properties, enabling adaptive read operations that maintain high reliability across varying conditions.
2Reliability
If read voltage level and application time are adjusted for each word line, then read reliability on high-resistance word lines improves, but operation time increases
Solution Approach 1:
The patent pre-characterizes word lines during manufacturing or initial operation to identify high-resistance word lines. This classification information is stored and used to apply appropriate read parameters from the outset, avoiding the need for repeated trial-and-error adjustments during actual read operations, thus minimizing time loss.
Solution Approach 2:
The patent changes read parameters (voltage level and application time) based on pre-determined word line categories. By establishing optimal parameter sets in advance for different word line types and selecting the appropriate set based on word line identification, the system achieves high reliability without excessive time penalties.
3Reliability
If additional read retry operations are performed on set word lines, then read reliability improves, but device complexity increases
Solution Approach 1:
The patent segments word lines into different categories (normal and set/high-resistance word lines) based on their electrical characteristics. This segmentation allows the memory controller to apply different read strategies to different segments, managing complexity by treating only the problematic segment with enhanced retry logic while keeping normal operations simple.
Data Source
AI summary
A storage device includes a memory device configured to perform a read operation on a selected word line among a plurality of word lines, and a memory controller configured to control the memory device to: perform the read operation, perform a read retry operation on the selected word line, by changing a read voltage level, when the read operation fails, and perform an additional read retry operation on the selected word line, by changing the read voltage level and an application time of voltages related to the read operation, depending on whether the selected word line is a set word line, when the read retry operation fails.