Phase-Change Memory Device with Zn-Ge-Te Material for High-Temperature Operation
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Solution Overview
Problem
Current phase-change memory materials used in semiconductor non-volatile memory lack sufficient heat resistance for high-temperature applications, particularly in devices requiring operation above 120°C, such as vehicle-mounted systems.
Innovation Solution
A phase-change memory device utilizing a chalcogenide material composition with 2-25 at% of Ge and Sb, 40-65 at% of Te, and 20-50 at% of elements from group 2b, group 1b, groups 3a to 7a, and group 8 elements, specifically Zn or Cd, which provides high crystallization and melting points, enabling stable operation at elevated temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional phase-change memory materials (e.g., Ge2Sb2Te5) are used, then the memory device can operate at standard temperatures, but the heat resistance is insufficient for high-temperature applications above 120°C
Solution Approach 1:
The patent modifies the chemical composition parameters of the phase-change material by incorporating group 2b elements (Zn, Cd) at 20-50 at%, group 1b elements at 10-30 at%, and Ge/Sb at 2-25 at% with Te at 40-65 at%. This compositional parameter change increases the melting point and crystallization temperature, enabling reliable operation at temperatures up to 145°C while maintaining phase-change functionality for memory storage
Solution Approach 2:
The patent creates a composite phase-change material by combining multiple elements (group 2b elements like Zn/Cd, group 1b elements, Ge, Sb, and Te) in specific ratios. This composite structure synergistically improves heat resistance and oxidation resistance while preserving the reversible phase-change properties necessary for non-volatile memory operation at elevated temperatures
2Speed
If the phase-change material contains high concentrations of Ge and Sb, then the crystallization speed improves, but the oxidation resistance decreases
Solution Approach 1:
The patent optimizes the concentration parameters by limiting Ge and Sb to 2-25 at% each (preventing excessive oxidation susceptibility) while incorporating 20-50 at% group 2b elements and 10-30 at% group 1b elements. This parameter optimization maintains sufficient crystallization speed by preserving some Ge/Sb content while the dominant group 2b and 1b elements provide oxidation resistance, solving the trade-off between speed and stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed memory device exhibits high heat resistance and can operate continuously at temperatures up to 145°C, meeting the requirements for high-temperature applications like vehicle engine control systems, with improved oxidation resistance and extended rewriting capabilities.
Implementation Method 1
memory information is written by the change of the state of crystallization of a memory device in accordance with a Joule heat caused by current flowing through the memory device per se
Implementation Method 2
recording information by causing a reversible phase-change between a crystal phase and an amorphous phase
Implementation Method 3
high crystallization temperature... can operate continuously at temperatures up to 145°C
Data Source
AI summary
A phase-change memory device including a memory cell having a memory element and a select transistor is improved in heat resistance so that it may be operable at 145° C. or higher.The memory layer is used which has a content of Zn or Cd of 20 at % or more and 50 at % or less, a content of Ge or Sb of 5 at % or more and 25 at % or less, and a content of Te of 40 at % or more and 65 at % or less in Zn-Ge-Te.