Phase-Change Memory Contact Plug with Segmented Materials
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Solution Overview
Problem
Phase-change memory devices face reduced thermal efficiency due to heat radiation from metal layers above and below the memory cell, which becomes a significant issue in highly integrated and mass-produced memory ICs, affecting the ability to reduce reset current and maintain high storage capacity.
Innovation Solution
A phase-change memory device with a different-material contact plug and an extension electrode layer is introduced, where the first electrically conductive material plug has a higher specific resistance and lower thermal conductivity, and the second plug has lower resistance and higher conductivity, reducing heat radiation from both above and below the phase-change layer by eliminating the heat sink effect of metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal layers are used above and below the phase-change layer for electrical connection, then electrical conductivity is improved, but thermal efficiency deteriorates due to heat radiation from the metal layers
Solution Approach 1:
The contact plug is divided into two distinct segments: a lower contact plug made of highly conductive metal (e.g., tungsten) for electrical connection, and an upper contact plug made of low-thermal-conductivity material (e.g., titanium nitride) for thermal insulation. This segmentation allows each segment to perform its specific function optimally, resolving the contradiction between electrical conductivity and thermal efficiency.
Solution Approach 2:
Different regions of the contact plug structure are assigned different material properties: the lower region uses high-conductivity metal for electrical connection, while the upper region uses low-thermal-conductivity material for heat radiation prevention. This local differentiation of material quality enables simultaneous achievement of electrical connectivity and thermal efficiency.
2Reliability
If highly conductive metal is used for contact plugs, then electrical resistance is reduced, but heat radiation increases reducing thermal efficiency
Solution Approach 1:
The contact plug is divided into two distinct segments: a lower contact plug made of highly conductive metal (e.g., tungsten) for electrical connection, and an upper contact plug made of low-thermal-conductivity material (e.g., titanium nitride) for thermal insulation. This segmentation allows each segment to perform its specific function optimally, resolving the contradiction between electrical conductivity and thermal efficiency.
Solution Approach 2:
The contact plug structure uses a composite of two different materials: a metal material (tungsten) for high electrical conductivity and a metal nitride material (titanium nitride) for low thermal conductivity. This composite structure combines the advantageous properties of both materials, achieving low electrical resistance while minimizing heat radiation.
3Ease of manufacture
If conventional electrode structure is used, then manufacturing is simplified, but thermal efficiency is reduced due to heat sink effect
Solution Approach 1:
The contact plug is divided into two distinct segments: a lower contact plug made of highly conductive metal (e.g., tungsten) for electrical connection, and an upper contact plug made of low-thermal-conductivity material (e.g., titanium nitride) for thermal insulation. This segmentation allows each segment to perform its specific function optimally, resolving the contradiction between electrical conductivity and thermal efficiency.
Solution Approach 2:
The upper contact plug made of low-thermal-conductivity material acts as an intermediary layer between the phase-change layer and the external environment. This intermediary structure blocks heat radiation from the metal layers while maintaining electrical connectivity, thereby improving thermal efficiency without significantly complicating the manufacturing process.
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
This configuration enhances thermal efficiency during phase changes, allows for reduced reset current, and facilitates the mass production of high-capacity phase-change memory devices by minimizing heat radiation and maintaining low electrical resistance.
Implementation Method 1
the first electrically conductive material plug has a higher specific resistance and lower thermal conductivity
Implementation Method 2
the second plug has lower resistance and higher conductivity
Implementation Method 3
pulses having different peak values and different pulse durations are applied to the chalcogenide semiconductor to generate Joule heat in the vicinity of contact surfaces of the electrodes and the chalcogenide semiconductor
Implementation Method 4
A chalcogenide semiconductor may take one of two stable states at one time, i.e., an amorphous semiconductor state and a crystalline state
Data Source
AI summary
A phase-change memory device has a different-material contact plug having a first electrically conductive material plug made of a first electrically conductive material, and a second electrically conductive material plug made of a second electrically conductive material having a specific resistance smaller than the first electrically conductive material, the first electrically conductive material plug and the second electrically conductive material plug being buried in a common contact hole. The different-material contact plug is effective for reducing the radiation of heat from a contact plug beneath a phase-change layer. The phase-change memory device also includes an extension electrode layer held in contact with a portion of the bottom surface of the phase-change layer in an area displaced off a position directly above a contact surface through which the phase-change layer and the heater electrode contact each other. The extension electrode layer reduces the radiation of heat from an electrode above the phase-change layer.