Nano-imprint Lithography for MRAM MTJ Alignment and Flatness
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Solution Overview
Problem
The manufacturing of magnetic random access memory (MRAM) faces challenges in achieving the flatness of magnetic tunnel-junction (MTJ) elements and aligning them with lower electrodes, which affects memory-cell size and characteristic, and in forming wirings for embedded memory that differ in height from logic section wirings without misalignment.
Innovation Solution
The use of nano-imprint lithography templates with specific patterns allows for simultaneous patterning and etching of MTJ elements and electrodes, and the formation of wirings with different heights in the same plane by using templates with step structures and recesses to define patterns for resist curing and metal deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography is used for patterning MTJ elements and lower electrodes separately, then alignment margin can be selected, but manufacturing precision and process complexity increase
Solution Approach 1:
The patent combines the patterning of MTJ elements and lower electrodes into a single nano-imprint lithography step. The template contains both the MTJ element pattern and the lower electrode pattern, allowing both structures to be formed simultaneously in one process, thereby improving alignment precision while reducing process complexity
Solution Approach 2:
The template serves multiple functions: it defines both the MTJ element pattern and the lower electrode pattern, and it establishes the alignment relationship between them. This multi-functional template eliminates the need for separate patterning steps and alignment procedures
2Area of moving object
If MTJ elements are formed immediately above contacts, then device area is reduced, but flatness of MTJ elements deteriorates
Solution Approach 1:
The lower electrode is formed with a pattern that extends beyond the contact area, creating a platform structure before the MTJ elements are formed. This preliminary formation of the lower electrode pattern provides a flat surface for subsequent MTJ element deposition, ensuring both compact area and adequate flatness
3Adaptability or versatility
If wirings of memory section and logic section are formed at different heights, then functional requirements are met, but alignment and manufacturing complexity increase
Solution Approach 1:
The patent uses nano-imprint lithography to create patterns that incorporate vertical dimension considerations directly in the template design. The template patterns account for different wiring heights by defining etch depths and layer thicknesses, allowing height differentiation while maintaining planar alignment precision
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 enhances the flatness and alignment of MTJ elements, reduces process costs, decreases memory-cell area, and maintains a broad write/read margin while preventing characteristic degradation and misalignment, allowing for efficient and cost-effective manufacturing of MRAM with increased storage capacity.
Implementation Method 1
forming a first pattern or a second pattern in the resist by setting a first template or a second template into contact with the resist and curing the resist
Implementation Method 2
setting a first template or a second template into contact with the resist and curing the resist
Data Source
AI summary
A magnetic material of a magnetoresistive element is formed on a lower electrode. An upper electrode is formed on the magnetic material. A resist for nano-imprint lithography is formed on the upper electrode. A first pattern or a second pattern is formed in the resist by setting a first template or a second template into contact with the resist and curing the resist. The first template has the first pattern that corresponds to the magnetoresistive element and the lower electrode. The second template has the second pattern that corresponds to the magnetoresistive element and the upper electrode. The magnetic material and the lower electrode are patterned at the same time by using the resist having the first pattern, or the magnetic material and the upper electrode are patterned at the same time by using the resist having the second pattern.