Cylindrical Heating Electrode Phase Change Memory
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Solution Overview
Problem
Phase change memory devices require high operation currents to generate heat for state changes in GST film patterns, limiting device integration and power consumption efficiency due to the isotropic heat distribution and large contact hole sizes, which are constrained by photolithography processes.
Innovation Solution
A phase change memory device with a substantially cylindrical heating electrode and a filling insulation pattern, where the phase change material pattern contacts the sidewalls of the heating electrode, reducing the contact area and program region volume, thereby minimizing operation current and achieving high integration and low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional planar heating electrode and large contact hole are used, then sufficient Joule heat can be generated to change the state of GST film, but the operation current is large and device size cannot be reduced
Solution Approach 1:
The heating electrode is transformed from a planar structure to a vertically extended cylindrical structure. The electrode extends downward from the contact hole bottom surface along the inner walls of the contact hole, creating a three-dimensional structure that increases the heating surface area without increasing the contact hole opening size. This dimensional change allows sufficient heat generation with reduced operation current.
Solution Approach 2:
The cylindrical heating electrode is nested within the contact hole structure, with the electrode occupying the vertical space inside the contact hole. The insulating film is formed between the electrode and the contact hole walls, creating a nested configuration where the electrode is contained within the contact hole boundary. This nesting allows the electrode to utilize the vertical dimension for heat generation without increasing the lateral footprint.
2Use of energy by moving object
If the contact hole width is reduced to decrease operation current, then power consumption decreases, but the width is limited by photolithography process capabilities
Solution Approach 1:
The heating electrode utilizes the vertical dimension by extending downward from the contact hole bottom, compensating for the limited reduction in contact hole width. This vertical extension provides additional heating surface area that allows the use of smaller contact holes (within photolithography limits) while still generating sufficient heat for GST state change.
Solution Approach 2:
The electrode geometry is changed from a thin planar layer to a vertically extended cylindrical structure with significant height. This parameter change in the electrode's three-dimensional configuration allows the system to achieve sufficient heating capacity with smaller contact hole dimensions, effectively decoupling the operation current from the contact hole width constraint.
3Use of energy by moving object
If a vertically extended cylindrical heating electrode is used, then operation current is minimized and device size is reduced, but the electrode structure becomes more complex
Solution Approach 1:
The insulating film is formed as a thin conformal layer surrounding the cylindrical heating electrode. This thin film structure provides electrical isolation between the electrode and the contact hole walls while maintaining a simple overall device architecture. The use of thin films minimizes the added complexity introduced by the vertical electrode structure.
Solution Approach 2:
The cylindrical heating electrode structure serves multiple functions: it generates Joule heat for GST state change, it defines the program region through its geometry, and it provides a scalable template for high-density memory cell arrays. This multi-functionality reduces the need for additional specialized structures, thereby limiting the increase in device complexity.
4Use of energy by moving object
If the program region volume is reduced by using a cylindrical electrode, then operation current decreases, but the heat distribution becomes more challenging
Solution Approach 1:
The cylindrical heating electrode provides localized heat generation at the contact hole bottom and along its inner walls. The heat is concentrated in the immediate vicinity of the electrode surface, creating a well-defined program region. This local quality of heat distribution allows precise control over which GST regions are programmed, compensating for the reduced overall program region volume.
Solution Approach 2:
The vertical extension of the electrode into the contact hole creates a three-dimensional heat distribution pattern. Heat is generated along the entire length of the electrode, not just at a single planar interface. This volumetric heat distribution ensures uniform heating of the GST film in the program region, addressing the heat distribution challenge despite the smaller overall program region volume.
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 significantly reduces the operation current and heat required for programming or erasing, allowing for smaller device sizes and improved integration while maintaining efficient data storage.
Implementation Method 1
Joule heat is used as the heat supplied to the phase change material. That is, when the current is supplied to an electrode connected to the phase change material, the Joule heat is generated from the electrode and supplied to the phase change material.
Implementation Method 2
The phase change material has two stable states (amorphous state and crystalline state) by a provided heat. When the GST is heated for a short time at a temperature close to a melting point and is then sharply cooled, the GST has an amorphous state. If the GST is heated for a long time at a crystallization temperature lower than the melting point and slowly cooled, the GST has a crystalline state.
Data Source
AI summary
A phase change memory device includes a mold layer disposed on a substrate, a heating electrode, a filling insulation pattern and a phase change material pattern. The heating electrode is disposed in an opening exposing the substrate through the mold layer. The heating electrode is formed in a substantially cylindrical shape, having its sidewalls conformally disposed on the lower inner walls of the opening. The filling insulation pattern fills an empty region surrounded by the sidewalls of the heating electrode. The phase change material pattern is disposed on the mold layer and downwardly extended to fill the empty part of the opening. The phase change material pattern contacts the top surfaces of the sidewalls of the heating electrode.