Memory Cell Pass Voltage Control for Low-Temperature Programming
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Solution Overview
Problem
At low program temperatures, memory devices experience increased program interference and read errors due to slow electron flow rates, making it difficult to suppress program interference in non-selected memory cells, leading to higher probabilities of incorrect programming.
Innovation Solution
Applying specific pass voltages to target word lines based on program temperature and sequence, using compensation voltages to enhance the pass voltages for memory cells, thereby reducing program interference and read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard pass voltage is applied to turn on the channel of non-selected memory cells, then the channel conduction is sufficient at high temperatures, but at low program temperatures the electron flow rate is slow and program interference cannot be suppressed
Solution Approach 1:
The patent applies a first pass voltage that is higher than the standard third pass voltage when the program temperature is below the temperature threshold. This parameter change compensates for the slow electron flow rate at low temperatures, ensuring sufficient channel conduction and suppressing program interference in non-selected memory cells during cold programming operations.
Solution Approach 2:
The patent determines whether the program temperature is below the threshold before applying the program voltage, and preemptively applies the elevated first pass voltage to counteract the anticipated program interference. This preliminary anti-action prevents programming errors before they occur by compensating for the temperature-dependent electron flow characteristics.
2Reliability
If the pass voltage is increased to suppress program interference at low temperatures, then programming accuracy improves, but the voltage difference between target word lines increases
Solution Approach 1:
The patent applies different pass voltages to different target word lines based on their specific conditions. The first pass voltage is applied selectively to the first target word line that is closer to the selected word line, while a different voltage strategy is used for the second target word line. This local differentiation suppresses program interference at the most vulnerable location without unnecessarily increasing voltage differences across all word lines.
Solution Approach 2:
The patent divides the target word lines into different groups (first target word line and second target word line) based on their distance from the selected word line. This segmentation allows for differentiated voltage application, applying the elevated first pass voltage only where most needed (first target word line) while using a different approach for the second target word line, thereby managing voltage stress more effectively.
Data Source
AI summary
An operation method of a memory device includes: when a program temperature of a memory device is less than a temperature threshold, and during a process of programming a selected memory cell coupled with a first selected word line, applying a first program voltage to the first selected word line, applying a first pass voltage to a first target word line, and applying a second pass voltage to a second target word line, wherein the first selected word line is any one of lines of the memory device that is selected after a reference word line, the first pass voltage is greater than a third pass voltage, and the third pass voltage is a voltage that is utilized to turn on a channel of a memory cell coupled with the first target word line.