Diblock Copolymer Mask for MRAM MTJ Uniformity
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Solution Overview
Problem
The challenge in fabricating magnetoresistive random access memory (MRAM) arrays lies in achieving uniformity of magnetic tunnel junction (MTJ) devices smaller than 100 nanometers in diameter, as larger MTJs require high current for switching, leading to high power consumption and non-uniformity in lithography at sub-100 nm dimensions results in impractical operation of SMT MRAM arrays.
Innovation Solution
A diblock copolymer mask is used to create uniform features down to 10 nm dimensions, self-assembling into a grid of cylinders that register with a template to ensure uniformity and size consistency, allowing for the fabrication of sub-100 nm MTJ devices with precise alignment to underlying wiring features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lithographic pattern transfer is used to form MTJ devices, then MTJ devices can be formed with defined shapes and sizes, but non-uniformity in lithography at sub-100 nm dimensions leads to undesirable non-uniformity of MTJ shapes and sizes
Solution Approach 1:
A diblock copolymer mask is introduced as an intermediary layer between the lithographic pattern and the magnetic layers. The copolymer self-assembles into uniform cylindrical structures with precise dimensions and spacing, transferring the pattern with superior uniformity compared to direct lithography. This intermediary mask layer enables formation of uniform MTJ devices at sub-100 nm dimensions.
Solution Approach 2:
The invention changes the dimensional parameters of the patterning system by using self-assembled copolymer structures with controlled molecular weights and compositions. By adjusting the copolymer block lengths and ratios, precise control over MTJ diameter (less than 100 nm) and spacing is achieved, overcoming the resolution and uniformity limits of conventional lithography.
2Use of energy by moving object
If MTJ diameter is reduced to less than 100 nm, then power consumption decreases and device density increases, but achieving uniformity at this scale becomes difficult
Solution Approach 1:
The diblock copolymer system performs self-service by automatically self-assembling into uniform cylindrical patterns through thermodynamic minimization of free energy. The block copolymer chains spontaneously organize into periodic structures with uniform spacing and dimensions, eliminating the need for complex external alignment procedures and achieving high uniformity without additional processing steps.
Solution Approach 2:
The use of diblock copolymer (a composite material consisting of two different polymer blocks) enables simultaneous achievement of small feature size and high uniformity. The immiscible blocks self-separate into distinct regions, creating well-defined cylindrical patterns with precise dimensional control that cannot be achieved with single-material systems.
3Quantity of substance
If MTJ diameter is reduced to less than 100 nm, then device density increases, but non-uniformity in lithography makes operation of SMT MRAM arrays impractical
Solution Approach 1:
The copolymer system segments the pattern formation process into self-assembled cylindrical domains separated by well-defined distances. This segmentation creates naturally uniform spacing between adjacent MTJ devices, ensuring consistent array geometry and enabling practical operation of large-scale SMT MRAM arrays with high device density.
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 enables the formation of small, uniform MTJ devices with improved power efficiency and density, addressing the issues of non-uniformity and high power consumption in SMT MRAM arrays by ensuring precise alignment and uniformity of MTJ devices.
Implementation Method 1
A diblock copolymer mask is used to create uniform features down to 10 nm dimensions, self-assembling into a grid of cylinders that register with a template
Data Source
AI summary
A device comprising a diblock copolymer mask for fabricating a magnetoresistive random access memory (MRAM) includes a magnetic layer; a mask formed on the magnetic layer; a template formed on the mask; and the diblock copolymer mask, the diblock copolymer mask comprising a first plurality of uniform shapes formed on and registered to the template.