Thermally Insulated Phase Change Memory Cell Structure
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Solution Overview
Problem
Manufacturing high-density memory devices with small dimensions and low reset currents is challenging due to variations in process specifications needed for large-scale memory devices, particularly in phase change based memory materials where reducing the reset current magnitude is desirable.
Innovation Solution
A memory cell structure with a thermal insulating layer surrounding a phase change material element, where the thermal insulating material is at least 10% better than the dielectric layer in thermal insulation and has a similar thermal expansion coefficient, and a method for forming this structure involving multiple electrode layers and etching processes to minimize the size of the phase change material element and reduce reset current requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the size of the phase change material element is reduced to minimize reset current, then the reset current magnitude is reduced, but the manufacturing precision requirements increase due to tight specifications needed for large-scale memory devices
Solution Approach 1:
The patent applies local quality by creating a tapered contact structure where the contact area between the electrode and phase change material is smaller at the interface with the phase change material compared to the electrode bulk. This localized geometric modification concentrates the current density precisely where needed at the phase change material interface, enabling lower reset currents without requiring uniform size reduction throughout the entire device structure, thereby easing manufacturing precision requirements.
Solution Approach 2:
The patent changes the geometric parameters of the contact structure by implementing a tapered profile with specific angle ranges (30-60 degrees). This parameter change optimizes the current density distribution and thermal confinement, allowing the device to achieve low reset current operation while maintaining manufacturability through well-defined geometric specifications that can be controlled within standard fabrication tolerances.
2Use of energy by moving object
If the contact area between electrodes and phase change material is reduced to achieve higher current densities, then the reset current magnitude is reduced, but the device complexity increases due to additional manufacturing steps
Solution Approach 1:
The patent segments the electrode structure into distinct regions with different functions: a broader electrode body for electrical connection and a tapered contact region for localized current concentration. This segmentation allows the device to achieve high current density at the phase change material interface through the tapered geometry alone, without requiring additional complex structures such as separate contact pads or interlayer routing, thus minimizing the increase in device complexity.
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 solution effectively reduces the reset current needed for phase change from crystalline to amorphous state by minimizing the size of the phase change material element and using a better thermal insulator, enhancing the operational efficiency of memory cells in phase change random access memory (PCRAM) devices.
Implementation Method 1
A thermal insulating layer surrounds the memory material element. The thermal insulating layer comprises a second memory material.
Implementation Method 2
Phase change based memory materials have at least two solid phases, including for example a generally amorphous solid phase and a generally crystalline solid phase. These materials can be caused to change phase by application of electrical current
Implementation Method 3
The change from crystalline to amorphous, referred to as reset herein, is generally a higher current operation, which includes a short high current density pulse to melt or breakdown the crystalline structure
Data Source
AI summary
A memory cell, the memory cell includes first and second electrodes and a memory material element electrically coupling the first and second electrodes. The memory material element comprises a first memory material, such as GST, the first memory material having an electrical property that can be changed by the application of energy. A thermal insulating layer surrounds the memory material element. The thermal insulating layer comprises a second memory material. A dielectric layer separates the thermal insulating material from the memory material element. A method for making a thermally insulated memory cell device is also disclosed.