Dual Semiconductor Phase Change Device for Multi-State Memory
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Solution Overview
Problem
There is a need for structures and methods to enable the creation of high-density phase change devices (PCDs) and multi-state PCD structures, particularly in the back end of the line (BEOL) regions, where the complexity of dielectric substrate layers poses challenges in fabricating dense arrays of PCDs.
Innovation Solution
A phase change device is constructed with two semiconductor layers made of different materials that can transition between amorphous and crystalline states under distinct conditions, allowing for the control of resistance by varying the thickness of epitaxial and remainder layers through thermal and electrical processes, enabling multiple resistance states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple dielectric substrate layers are used in BEOL regions, then device integration is enabled, but fabrication of dense PCD arrays becomes difficult
Solution Approach 1:
The device is segmented into two separate semiconductor layers (first semiconductor layer and second semiconductor layer) with different materials, each capable of independent phase transitions. This segmentation allows the layers to be processed and controlled independently, simplifying fabrication in BEOL regions while maintaining integration capability.
Solution Approach 2:
Different semiconductor materials are used in the first and second layers, each with distinct phase transition properties. This local quality differentiation enables tailored phase change behavior in each layer, allowing dense array fabrication with controlled resistance states despite the complexity of multiple dielectric layers.
2Device complexity
If single-state PCDs are used, then device simplicity is maintained, but memory density and functionality are limited
Solution Approach 1:
Two semiconductor layers with different phase change materials are merged into a single device structure, enabling multiple resistance states (multi-state operation) while maintaining a relatively simple overall device architecture. This combining approach increases memory density without significantly increasing device complexity.
Solution Approach 2:
The device uses composite material structure with first semiconductor material and second semiconductor material in separate layers. Each material contributes different resistance characteristics when in amorphous or crystalline states, enabling multiple resistance states and enhanced memory density while keeping the device structure manageable.
3Manufacturing precision
If epitaxial layer thickness is increased, then resistance control precision is improved, but manufacturing complexity increases
Solution Approach 1:
The resistance state is controlled by changing the thickness parameter of the epitaxial layer. By precisely controlling the epitaxial layer thickness during fabrication, different resistance states can be achieved. This parameter-based control method provides precise resistance tuning while using standard semiconductor manufacturing techniques.
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 approach allows for the creation of phase change devices with multiple resistance states, enhancing the density and functionality of PCD arrays in BEOL regions by controlling resistance through epitaxial and remainder layer thickness variations.
Implementation Method 1
The first semiconductor material can transition between a first amorphous state and a first crystalline state at one or more first conditions
Implementation Method 2
The second semiconductor material can transition between a second amorphous state and a second crystalline state at one or more second conditions
Implementation Method 3
the first semiconductor layer is divided or split into a first epitaxial crystalline layer and a first amorphous remainder layer
Data Source
AI summary
According to some embodiments of the present invention a phase change device (PCD) has a first and second semiconductor layer. The first semiconductor layer made of a first semiconductor material and has a first semiconductor thickness, a first interface surface, and a first electrode surface. The first interface surface and first electrode surface are on opposite sides of the first semiconductor layer. The first semiconductor material can transition between a first amorphous state and a first crystalline state at one or more first conditions. The second semiconductor layer is made of a second semiconductor material and has a second semiconductor thickness, a second interface surface, and a second electrode surface. The second interface surface and second electrode surface are on opposite sides of the second semiconductor layer. The first interface surface and the second interface surface are in electrical, physical, and chemical contact with one another at an interface. The second semiconductor material can transition between a second amorphous state and a second crystalline state at one or more second conditions. A first electrode in physical and electrical contact with the first electrode surface of the first semiconductor layer and a second electrode in physical and electrical contact with the second electrode surface of the second semiconductor layer. The first conditions and second conditions are different. Therefore, in some embodiments, the first and second semiconductor materials can be in different amorphous and/or crystalline states. The layers can have split amorphous/crystalline states. By controlling how the layers are split, the PCD can be in different resistive states.