Phase Change RAM Bottom Electrode Formation via Diblock Copolymer Self-Assembly
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Solution Overview
Problem
Conventional phase change RAM devices require high current to change the phase of the phase change layer due to unstable formation of nano-sized bottom electrodes, leading to uneven contact areas and increased current requirements.
Innovation Solution
A method involving the use of diblock copolymers to form nano-sized copolymer patterns, which act as etching barriers for oxide layers, allowing for the deposition and etching of nitride layers to create uniformly nano-sized plug-type bottom electrodes, reducing the contact area with the phase change layer and lowering the current required for phase change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form bottom electrodes, then the manufacturing process is simple, but the bottom electrodes are unevenly formed leading to increased current requirements
Solution Approach 1:
The patent applies preliminary action by forming a mandrel layer and coating it with a block copolymer layer before etching. This preliminary structuring enables precise control of the bottom electrode dimensions and uniformity, directly resolving the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The block copolymer layer acts as an intermediary self-assembling material that directs the formation of uniform nanostructures. This intermediary enables precise bottom electrode patterning without requiring complex lithography, thus improving manufacturing precision while managing process complexity.
2Use of energy by moving object
If the contact area between bottom electrode and phase change layer is large, then the device is easier to manufacture, but high current is required for phase change
Solution Approach 1:
The patent changes the parameter of contact area by controlling the thickness and composition of the mandrel layer and block copolymer layer. By adjusting these parameters, the contact area is precisely controlled to minimize the current required for phase change while maintaining manufacturing feasibility.
Solution Approach 2:
The patent applies local quality by creating a specific nanostructured contact region between the bottom electrode and phase change layer. The block copolymer self-assembly creates localized uniform structures that optimize the contact area, reducing energy requirements for phase change while maintaining ease of manufacture.
3Ease of manufacture
If non-uniform bottom electrodes are formed, then the manufacturing process is simpler, but the current required for phase change increases
Solution Approach 1:
The block copolymer layer performs self-service by self-assembling into uniform patterns that directly define the bottom electrode geometry. This self-organization eliminates the need for complex lithography processes, maintaining ease of manufacture while ensuring uniform bottom electrodes that reduce writing current requirements.
Solution Approach 2:
The preliminary formation of the mandrel layer and block copolymer self-assembly creates a template that guides uniform bottom electrode formation. This preliminary action ensures both ease of manufacture through simple deposition processes and uniformity that reduces energy consumption during operation.
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 method effectively reduces the current needed to change the phase of the phase change layer by ensuring uniform nano-sized bottom electrodes, enhancing integration and reducing writing current requirements in phase change RAM devices.
Implementation Method 1
forming a self-assembled multi-layered membrane including a block copolymer layer
Implementation Method 2
etching the oxide layer by using the nano-sized copolymer pattern as an etching barrier
Implementation Method 3
depositing a nitride layer on an entire surface of a resultant substrate
Implementation Method 4
the phase of the chalcogenide layer is changed between the amorphous state and the crystalline state caused by joule heat of the current applied to the chalcogenide layer
Implementation Method 5
the phase of a phase change layer interposed between top and bottom electrodes is changed from a crystalline state to an amorphous state by applying the current
Data Source
AI summary
To effectively lower the current required for changing a phase of a phase change layer in a phase change RAM device, metal pads are formed on a semiconductor substrate, and an oxide layer is formed on the metal pads. Nano-sized copolymer patterns aligned with the metal pads covered by the oxide layer are formed on the oxide layer. The oxide layer is etched to form oxide layer patterns by using the nano-sized copolymer patterns as barrier. The nano-sized copolymer patterns are then removed. A nitride layer is deposited and then etched to expose the oxide layer patterns. The exposed oxide layer patterns are removed to form nano-sized holes exposing the metal pads. Bottom electrodes are then formed in the nano-sized holes. A phase change layer and a top electrode are formed on each of the bottom electrodes.