Semiconductor Memory Device Temperature-Adaptive Read Voltage Control
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Solution Overview
Problem
Semiconductor memory devices face challenges in maintaining reliable read operations due to temperature variations, which affect the accuracy of threshold voltage determination in memory cells.
Innovation Solution
The semiconductor memory device incorporates a peripheral circuit with a voltage generator, address decoder, read and write circuit, and temperature sensor to adjust read and pass voltages based on temperature, ensuring optimal voltage levels for read operations across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed read voltage and pass voltage are applied to memory cells, then the device structure remains simple, but read performance deteriorates under temperature variations
Solution Approach 1:
The patent applies dynamic voltage adjustment by modifying the pass voltage applied to unselected word lines based on detected temperature conditions. The voltage generator dynamically changes the magnitude of pass voltages (first pass voltage for adjacent unselected word lines, second pass voltage for non-adjacent unselected word lines) according to temperature, rather than using fixed voltages. This dynamic adaptation resolves the contradiction by maintaining reliable read performance across temperature variations while keeping the overall device structure relatively simple.
Solution Approach 2:
The patent changes the voltage parameter (pass voltage magnitude) in response to temperature changes. Specifically, the voltage generator adjusts the pass voltage levels based on temperature detection, changing the electrical parameters to compensate for temperature-induced variations in memory cell characteristics. This parameter change approach allows the system to maintain accurate threshold voltage determination despite temperature fluctuations, resolving the reliability issue without requiring fundamental structural changes.
2Reliability
If temperature compensation is implemented for read operations, then read performance under temperature variations improves, but the device complexity increases due to additional temperature sensing and voltage adjustment circuits
Solution Approach 1:
The voltage generator is designed to perform multiple functions: it generates read voltages for selected word lines, generates pass voltages for unselected word lines, and dynamically adjusts these voltages based on temperature conditions. By making the voltage generator multi-functional, the patent avoids adding separate dedicated temperature compensation circuits, thus improving threshold voltage determination accuracy while minimizing the increase in device complexity.
Solution Approach 2:
The system uses its own existing temperature detection capability (through the temperature sensor already present in the device) to automatically adjust its operating parameters. The voltage generator uses temperature information to self-adjust the pass voltages, making the temperature compensation process self-service rather than requiring external control systems. This approach improves reliability while keeping the peripheral circuit complexity manageable by utilizing existing device resources.
Data Source
AI summary
Provided herein may be a semiconductor memory device. The semiconductor memory device may include a memory cell array, a peripheral circuit, and control logic. The memory cell array includes a plurality of memory cells. The peripheral circuit performs a read operation on the memory cells. The control logic controls the read operation of the peripheral circuit. During the read operation, the control logic controls the peripheral circuit so that a read voltage is applied to a selected word line among a plurality of word lines coupled to the memory cells, a first pass voltage is applied to an unselected word line disposed adjacent to the selected word line and a second pass voltage is applied to an unselected word line that is not disposed adjacent thereto. The peripheral circuit adjusts a magnitude of the first or second pass voltage based on a temperature of the semiconductor memory device.