Phase Change Memory Cell Filling via Melt Expansion
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Solution Overview
Problem
Conventional plasma vapor deposition processes are impractical for filling small pores with phase change materials in phase change memory cells, and atomic layer deposition processes are difficult to control, limiting the use of additives in these materials.
Innovation Solution
A method involving the formation of a memory cell with a phase change element, where a phase change material is confined within a structure and heated to expand, filling a hole in an insulator, with capping materials ensuring the phase change material moves into the hole and becomes electrically connected to the bottom electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional plasma vapor deposition processes are used to fill small pores with phase change materials, then the deposition process can be performed, but it is impractical for filling very small pores (e.g., 17 nm×7.5 nm×30 nm)
Solution Approach 1:
The patent changes the physical state parameter of the phase change material from solid to liquid by heating it above its melting point. This parameter change enables the material to flow and fill very small pores that cannot be filled by conventional vapor deposition processes, thereby resolving the impracticality of filling sub-20nm pores.
Solution Approach 2:
The patent utilizes the phase transition of the phase change material from solid to liquid state through heating. This phase transition allows the material to become fluid and infiltrate the small pore space, then solidifies upon cooling to fill the pore completely. This resolves the limitation of conventional deposition methods for very small pores.
2Volume of moving object
If atomic layer deposition or chemical vapor deposition processes are used to fill small holes with phase change materials, then filling can be achieved, but it is very difficult to control the phase change material compositions and cannot use many additives
Solution Approach 1:
The patent replaces the complex chemical vapor deposition or atomic layer deposition processes with a simpler physical process: melting the phase change material and allowing it to flow into the pore by capillary action and gravity. This substitution eliminates the difficulty of controlling material composition and using additives, as the material is deposited in a controlled melt state rather than through complex chemical reactions.
Solution Approach 2:
The patent changes the deposition method from vapor-phase chemical processes to liquid-phase physical processes by melting the material. This parameter change from vapor to liquid state simplifies composition control and enables the use of various additives that are difficult to incorporate through CVD or ALD processes.
3Use of energy by moving object
If the pore size is reduced to confine the active region to improve power efficiency and speed, then power consumption decreases and speed improves, but it becomes difficult to consistently and uniformly fill the pores
Solution Approach 1:
The patent uses the phase transition from solid to liquid and back to solid to achieve uniform filling of reduced-size pores. The liquid phase allows the material to flow uniformly into the small pore, and the subsequent solidification ensures complete and consistent filling, resolving the difficulty of uniform pore filling at reduced dimensions.
Solution Approach 2:
The patent changes the physical state of the phase change material to liquid during the filling process, enabling it to flow into and uniformly fill small pores. This parameter change from solid to liquid state, controlled by temperature, ensures consistent filling uniformity even as pore size is reduced for lower power consumption.
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 method allows for consistent and uniform filling of small holes with phase change materials, enabling efficient electrical connection and improving the operational speed and power efficiency of phase change memory cells.
Implementation Method 1
The phase change material is characterized by expansion in volume when melted by a characteristic percentage. The phase change material is heated causing the phase change material to expand into the hole
Implementation Method 2
The phase change material is characterized by expansion in volume when melted by a characteristic percentage. The void volume is less than the characteristic percentage of the volume of phase change material inside the confining structure
Data Source
AI summary
To form a memory cell with a phase change element, a hole is formed through an insulator to a bottom electrode, and a phase change material is deposited on the insulator surface covering the hole. A confining structure is formed over the phase change material so the phase change material expands into the hole when heated to melting to become electrically connected to the bottom electrode. A top electrode is formed over and electrically connects to the phase change material. The bottom electrode can include a main portion and an extension having a reduced lateral dimension. The confining structure can include capping material having a higher melting temperature than the phase change material, and sufficient tensile strength to ensure the phase change material moves into the hole when the phase change material melts and expands. The hole can be a J shaped hole.