Cup-Shaped Conductor for Phase Change Memory Reset Current
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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 size of the phase change material element and contact area is essential to minimize reset current.
Innovation Solution
A memory cell device structure featuring a bottom electrode, a top electrode, and a cup-shaped conductive member with a rim contacting the top electrode and an opening that contacts the phase change memory material, allowing for a self-aligned, scalable manufacturing process with a small contact area between the memory material and the bottom electrode, reducing the reset current required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the size of the phase change material element and contact area are 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 device is segmented into distinct functional regions: a bottom electrode, a phase change material element confined within a cavity, and a cup-shaped conductive member with a rim. This segmentation allows the phase change material to be precisely contained in a small volume, reducing the contact area and reset current while maintaining manufacturing feasibility through modular fabrication steps
Solution Approach 2:
The cup-shaped conductive member acts as an intermediary structure between the bottom electrode and the phase change material. Its rim provides a defined contact interface that limits the contact area, thereby reducing the reset current magnitude while the cavity structure ensures precise positioning of the phase change material element
2Power
If the size of the phase change material element is reduced to achieve high current density with small absolute current values, then the reset current is minimized, but the device complexity increases due to the need for small pores and precise material placement
Solution Approach 1:
The phase change material element is nested within a cavity formed by the cup-shaped conductive member, which itself is positioned over the bottom electrode. This nested structure achieves compact dimensions and high current density while maintaining a systematic fabrication approach that reduces overall device complexity
Solution Approach 2:
The cup-shaped conductive member extends vertically to form a rim that contacts the top electrode, utilizing the vertical dimension to define the contact area and confine the phase change material. This three-dimensional structure achieves small contact area without requiring excessively small lateral dimensions, simplifying manufacturing
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 enables the creation of memory cells with small dimensions and low reset currents, improving the scalability and efficiency of phase change based memory devices by confining current flow to a small area, thus effectively addressing the challenges of manufacturing small-scale memory devices.
Implementation Method 1
Phase change based memory materials are widely used in read-write optical disks. These materials have at least two solid phases, including for example a generally amorphous solid phase and a generally crystalline solid phase.
Implementation Method 2
Laser pulses are used in read-write optical disks to switch between phases and to read the optical properties of the material after the phase change. Phase change based memory materials, like chalcogenide based materials and similar materials, also can be caused to change phase by application of electrical current
Data Source
AI summary
A memory cell device has a bottom electrode and a top electrode, a plug of memory material in contact with the bottom electrode, and a cup-shaped conductive member having a rim that contacts the top electrode and an opening in the bottom that contacts the memory material. Accordingly, the conductive path in the memory cells passes from the top electrode through the conductive cup-shaped member, and through the plug of phase change material to the bottom electrode. Also, methods for making the memory cell device include steps of forming a bottom electrode island including an insulative element and a stop element over a bottom electrode, forming a separation layer surrounding the island, removing the stop element to form a hole over the insulative element in the separation layer, forming a conductive film in the hole and an insulative liner over conductive film, etching to form a cup-shaped conductive film having a rim and to form an opening through the insulative liner and the bottom of the cup-shaped conductive film to the surface of the bottom electrode, forming a plug of phase change memory material in the opening, and forming a top electrode in contact with the rim of the cup-shaped conductive film.