Phase Change Memory Electrode Structure for Thermal Efficiency
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Solution Overview
Problem
Conventional phase change memory devices face issues with thermal efficiency due to heat dissipation through upper metal electrodes, leading to increased reset current and reduced memory cell size, especially in high-integration phase change memory LSI, and pose challenges in manufacturing with problems like line pollution, composition changes, and complex processing.
Innovation Solution
A novel electrode structure without an upper electrode, using a landing electrode that contacts the phase change layer off from the heater electrode, embedded in the interlayer insulating film, with a patterned landing electrode layer and adhesion layer to improve adhesion and thermal efficiency, allowing for reduced reset current and flexible layout design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an upper electrode is used in conventional phase change memory devices, then electrical connection is achieved, but heat dissipation increases leading to reduced thermal efficiency
Solution Approach 1:
The invention removes the upper electrode from the phase change memory device structure. By extracting the upper electrode that causes heat dissipation, the patent achieves improved thermal efficiency without compromising the essential electrical connection function, as the lower electrode and landing electrode configuration maintains necessary electrical pathways.
Solution Approach 2:
Instead of the conventional sandwich structure with electrodes on both upper and lower sides, the invention inverts the approach by using only a lower electrode with a landing electrode configuration. This structural inversion eliminates the heat-dissipating upper electrode while maintaining electrical functionality through alternative pathways.
2Reliability
If the phase change layer is contacted directly by the electrode, then electrical connection is established, but composition changes and line pollution occur during manufacturing
Solution Approach 1:
The invention introduces a landing electrode as an intermediary component between the lower electrode and the phase change layer. This landing electrode serves as a mediator that establishes reliable electrical connection while preventing direct contact between the electrode and phase change layer, thereby avoiding line pollution and composition changes during manufacturing processes.
3Temperature
If reset current is increased to overcome heat dissipation, then phase transition can be achieved, but energy consumption increases
Solution Approach 1:
The invention converts the potential harm of electrode removal (which could reduce heat conduction to the phase change layer) into a benefit by utilizing the landing electrode configuration. The landing electrode provides sufficient thermal coupling to achieve phase transition while eliminating the parasitic heat dissipation pathway through the upper electrode, thereby reducing the reset current required.
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 enhances thermal efficiency, reduces reset current, and enables mass production of large-scale phase change memory LSI by eliminating heat dissipation issues and simplifying the manufacturing process while maintaining rewritable characteristics.
Implementation Method 1
Joule heat is used as heat to supply to the chalcogenide alloy for phase transition. In other words, by supplying pulses with different peak values and different durations to the chalcogenide alloy, Joule heat is generated in a contact face between an electrode and the chalcogenide alloy and its vicinity.
Implementation Method 2
the chalcogenide alloy becomes an amorphous state when supplied with heat near its melting point for a short time and cooled rapidly. Meanwhile, the chalcogenide alloy becomes a crystalline state when supplied with heat of its crystallization point lower than the melting point for a long time and then cooled.
Data Source
AI summary
The invention provides a novel structure of a phase change memory device. In the phase change memory device of the invention, an electrode acting as a radiating fin does not exit immediately above a phase change area of a phase change layer (115). A heater electrode (111) and landing electrode layer (113a, 114a) both contact the bottom of the phase change layer (115) made of GST. The landing electrode layer (113a, 114a) contacts the bottom of the phase change layer (115) to partially overlap in a region off from a portion immediately above the contact face (Y) of the phase change layer and heater electrode. The contact electrode (116, 118) is directly connected to the landing electrode layer (113a, 114a) in a portion off from a portion immediately above the heater electrode (111). The phase change layer of GST or the like does not exist immediately below the contact electrode.