MTJ Pillar Fabrication via Protective Layer Etching
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Solution Overview
Problem
During the physical etching process of magnetic tunnel junction (MTJ) structures in MRAM devices, conductive layers are often etched together, leading to electrical shorts and the need for cost-effective and time-efficient methods to form MTJ structures without etching the conductive layers, while maintaining self-alignment and avoiding planarization-induced structural nonconformities.
Innovation Solution
A method involving the formation of MTJ layers over a substrate, with a protective layer and sacrificial material, creating via holes, depositing conductive material, and forming a hard mask to etch the MTJ layers into pillar structures without planarizing the conductive material, ensuring self-alignment and avoiding electrical shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If physical etching process is used to form MTJ structures, then MTJ layers can be etched to form pillar structures, but conductive layers are also etched together causing electrical shorts
Solution Approach 1:
A protective layer is introduced as an intermediary between the MTJ layers and the etching process. This protective layer prevents the etchant from reaching and damaging the conductive layers beneath, thereby eliminating electrical shorts while still allowing MTJ pillar structures to be formed through the protective layer via selective etching
Solution Approach 2:
The etching process is segmented into selective steps: first etching through the protective layer to form openings, then etching the MTJ layers to form pillar structures. This segmentation allows different layers to be etched at different stages, preventing simultaneous etching of conductive layers and MTJ layers
2Manufacturing precision
If conductive layers are etched together with MTJ layers, then pillar structures can be formed, but re-deposited conductive by-products generate electrical shorts
Solution Approach 1:
The protective layer serves as a barrier that prevents conductive material from being re-deposited onto the sidewalls of forming structures. By blocking the etchant and preventing material migration, it eliminates the generation of conductive by-products that would cause electrical shorts
Solution Approach 2:
The protective layer transforms the potentially harmful etching process into a beneficial selective formation process. It allows the etchant to selectively remove material where needed while preventing unwanted side effects like conductive by-product formation, turning a harmful process into a controlled fabrication step
3Manufacturing precision
If planarization is performed on conductive material, then surface flatness is improved, but structural nonconformities are introduced
Solution Approach 1:
The planarization step is completely removed from the fabrication process. Instead of performing planarization that would damage the conductive material structure, the process extracts this unnecessary step and relies on self-alignment and conformal deposition to achieve the desired surface characteristics without introducing structural nonconformities
4Manufacturing precision
If conventional etching methods are used, then MTJ structures can be formed, but the process is costly and time-consuming
Solution Approach 1:
The protective layer is deposited in advance before the etching process begins. This preliminary action simplifies subsequent fabrication steps by providing built-in protection and self-alignment features, eliminating the need for complex masking and alignment procedures that would increase cost and time
Solution Approach 2:
The protective layer provides self-alignment for the etching process, automatically defining the pattern locations without requiring additional alignment steps. The process is self-service in that the protective layer itself guides the etching, eliminating the need for external alignment equipment and procedures
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 fabrication of integrated circuits with self-aligned MTJ structures and conductive pillars, reducing critical dimensions and top electrode resistance, enhancing process margin and performance while being cost-effective and time-efficient.
Implementation Method 1
etching the protective layer and the MTJ layers to form a pillar structure
Implementation Method 2
depositing conductive material in the via hole in contact with the upper surface of the MTJ layers
Data Source
AI summary
Integrated circuits and methods for fabricating magnetic tunnel junction (MTJ) structures and integrated circuits are provided. An exemplary method for fabricating an integrated circuit including a magnetic tunnel junction (MTJ) structure includes forming magnetic tunnel junction (MTJ) layers over a substrate. Further, the method includes forming a conductive pillar over the MTJ layers, wherein the conductive pillar is formed with an uppermost surface, and wherein the uppermost surface is not planarized. Also, the method includes etching the MTJ layers to form a pillar structure from portions of the MTJ layers underlying the conductive pillar.