Semiconductor Memory Control Logic for Word Line Voltage Optimization
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Solution Overview
Problem
Semiconductor memory devices face challenges in optimizing program operating characteristics, particularly in determining appropriate program and pass voltages based on the position of selected word lines, which affects the performance and reliability of memory cell programming.
Innovation Solution
The semiconductor memory device incorporates a control logic that determines program and pass voltages based on the position of selected word lines within the cell string, using a method that adjusts program step voltages and pass voltages to enhance programming efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed program and pass voltages are used for all word lines, then the control logic is simple, but programming efficiency and reliability deteriorate due to inability to optimize for word line position
Solution Approach 1:
The patent implements dynamic voltage adjustment where the control logic determines program and pass voltages based on the position of selected word lines in the cell string. Different voltages are applied to different word lines depending on their position (e.g., higher voltages for word lines closer to the source line), enabling optimized programming efficiency while managing complexity through position-based rules rather than arbitrary adjustments
Solution Approach 2:
The patent changes the voltage parameters dynamically based on word line position. The control logic selects from predefined voltage levels or adjusts voltage magnitudes according to the distance of each word line from the source line, transforming the fixed parameter approach into a variable parameter system that optimizes programming outcomes
2Speed
If higher program voltages are applied to all word lines, then programming speed increases, but reliability deteriorates due to excessive voltage on word lines far from source line causing cell damage
Solution Approach 1:
The patent applies different program voltages to different word lines based on their specific positions in the cell string. Word lines closer to the source line receive higher voltages for faster programming, while word lines farther from the source line receive lower voltages to prevent damage, ensuring both speed and reliability through localized voltage optimization
Solution Approach 2:
The control logic dynamically adjusts the program voltage parameter according to the word line position, selecting appropriate voltage levels from predefined ranges or calculating voltages based on distance from the source line, thereby preventing excessive voltage on distant word lines while maintaining fast programming on nearer word lines
3Reliability
If lower pass voltages are used to protect cell strings, then cell damage is prevented, but programming efficiency deteriorates due to insufficient voltage to overcome threshold variations
Solution Approach 1:
The patent applies different pass voltages to different word lines based on their position. Word lines closer to the source line receive lower pass voltages to protect the cell string, while word lines farther from the source line receive higher pass voltages to ensure programming efficiency, achieving both protection and efficiency through localized voltage control
Solution Approach 2:
The control logic dynamically adjusts the pass voltage parameter according to word line position, ensuring sufficient voltage for programming efficiency on distant word lines while maintaining protective voltage levels on nearer word lines, thereby balancing both requirements through position-based parameter adjustment
4Manufacturing precision
If uniform voltage control is used, then the control mechanism is simple, but manufacturing precision deteriorates due to inability to account for threshold voltage variations across different word line positions
Solution Approach 1:
The patent implements local quality control by applying different voltages to different word lines based on their positions. The control logic accounts for threshold voltage variations that occur with distance from the source line, ensuring precise programming control for each word line while managing complexity through systematic position-based voltage selection
Solution Approach 2:
The control logic incorporates feedback mechanisms to determine appropriate voltages based on word line position and programming outcomes. The system monitors programming results and adjusts voltages accordingly, ensuring manufacturing precision while managing complexity through learned and adaptive voltage control rather than fixed arbitrary values
Data Source
AI summary
Provided herein may be a control logic, semiconductor memory device, method of operating the control logic, and or method of operating the semiconductor memory device. The semiconductor memory device may include a control logic. The control logic may be configured to control a program voltage to be applied to the selected word line. The control logic may be configured to control a pass voltage to be applied to an unselected word line.