Memory Read Pass Voltage Switching Across Temperature
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Solution Overview
Problem
Existing memory devices experience read errors due to temperature-induced threshold voltage drift in unselected memory cells, leading to reduced read accuracy and sense margin differences at varying temperatures.
Innovation Solution
The peripheral circuit adjusts pass voltages applied to unselected word lines based on working temperature, using different pass voltages at high and low temperatures to minimize read disturbance and maintain accurate read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed pass voltage is applied to unselected word lines regardless of temperature, then the device structure remains simple, but read errors increase due to temperature-induced threshold voltage drift
Solution Approach 1:
The pass voltage applied to unselected word lines is made dynamic rather than fixed. The voltage control circuit adjusts the pass voltage level based on detected temperature conditions, applying a first pass voltage at high temperatures and a second pass voltage at low temperatures. This dynamic adaptation resolves the contradiction by maintaining read accuracy across temperature variations without requiring complete redesign of the device structure.
Solution Approach 2:
The patent changes the voltage parameter of unselected word lines based on temperature conditions. By detecting temperature and switching between different pass voltage levels (first pass voltage at high temperature, second pass voltage at low temperature), the system compensates for temperature-induced threshold voltage drift in memory cells, thereby maintaining read accuracy without increasing fundamental device complexity.
2Reliability
If different pass voltages are applied at different temperatures, then read accuracy is maintained, but the control circuit complexity increases
Solution Approach 1:
The voltage control circuit incorporates temperature detection and feedback mechanisms. It detects the current temperature condition and uses this information to determine the appropriate pass voltage level to apply to unselected word lines. This feedback loop enables automatic adaptation to temperature changes, maintaining read accuracy while keeping the control circuit design systematic and manageable rather than arbitrarily complex.
Solution Approach 2:
The temperature operating range is segmented into different conditions (high temperature and low temperature), with each condition having a designated pass voltage level. The voltage control circuit is designed to switch between these predefined voltage levels based on temperature detection, rather than continuously adjusting voltage. This segmentation approach simplifies the control logic and reduces peripheral circuit complexity compared to continuous voltage regulation.
3Reliability
If high pass voltage is always applied to unselected word lines, then sense margin is maintained at low temperature, but read errors increase at high temperature due to excessive read disturbance
Solution Approach 1:
The pass voltage parameter is changed based on temperature conditions to optimize the balance between maintaining sense margin and minimizing read disturbance. At high temperatures, a first pass voltage is applied that is sufficient to maintain sense margin but limited to prevent excessive read disturbance. At low temperatures, a second pass voltage is applied that provides adequate sense margin without causing harmful disturbance. This parameter adaptation resolves the contradiction by making the pass voltage temperature-dependent.
Solution Approach 2:
Different voltage quality levels are applied to unselected word lines based on local temperature conditions. Rather than using a uniform high pass voltage across all conditions, the system applies appropriately scaled voltage levels matched to the local thermal environment. This ensures that each operating condition receives the precise voltage quality needed to maintain sense margin without introducing harmful read disturbance, resolving the contradiction between these competing requirements.
Data Source
AI summary
The present application provides a memory device and an operation method thereof, and a memory system. The memory device includes a memory array and a peripheral circuit. The peripheral circuit is coupled with the memory array, and is configured to: apply a read voltage to a selected first word line of the plurality of word lines; apply a first pass voltage to an unselected second word line of the plurality of word lines in response to determining that a working temperature is a first temperature; and apply a second pass voltage to the second word line in response to determining that the working temperature is a second temperature, wherein the first temperature is greater than the second temperature, and the first pass voltage is less than the second pass voltage.