MRAM SOT Protective Layer Structure Against Oxidation Damage
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Solution Overview
Problem
Conventional MRAM fabricating processes often result in oxidation or damage to conductive layers and material surfaces, which affects the integrity and performance of the magnetic tunnel junctions.
Innovation Solution
An MRAM structure with a protective insulator layer covering the spin orbit torque (SOT) elements, along with a specific method of forming conductive vias through these layers to prevent oxidation and damage during the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fabricating processes are used without protective layers, then the fabrication process is simpler and more direct, but the conductive layers and material surfaces suffer from oxidation and damage
Solution Approach 1:
An inert material layer (such as silicon nitride or silicon oxide) is introduced as an intermediary between the conductive layers and the ambient environment. This intermediary layer prevents direct contact between oxygen/moisture and the conductive materials, thereby preventing oxidation and surface damage while maintaining fabrication feasibility.
Solution Approach 2:
The patent utilizes plasma-based processes (pneumatic/chemical environment control) to deposit the inert protective layer and to perform subsequent fabrication steps in a controlled atmosphere that prevents oxidation of exposed surfaces.
2Reliability
If the protective layer is added to cover SOT elements, then oxidation and damage are prevented, but the fabrication process becomes more complex with additional steps
Solution Approach 1:
The protective layer formation is merged with subsequent fabrication steps by using the protective layer as an etch stop layer and as a barrier during trench formation. Multiple functions (protection, etch stopping, process integration) are combined into a single layer, reducing the need for separate process steps.
Solution Approach 2:
The inert material layer serves multiple functions: (1) protective barrier against oxidation, (2) etch stop layer during trench formation, (3) structural support layer, and (4) isolation layer. This multi-functionality reduces overall process complexity despite adding initial fabrication steps.
3Reliability
If conductive vias are formed through the protective layer, then electrical connection is achieved, but the protective layer may be damaged or compromised
Solution Approach 1:
Conductive vias are formed by selectively removing (extracting) material through defined pathways. The protective layer is locally removed via etching to create via holes, allowing electrical connection while preserving the protective layer integrity in surrounding areas. The protective layer acts as an etch stop to define via boundaries precisely.
Solution Approach 2:
The protective layer maintains its protective function in all areas except where conductive vias are formed. The local removal of the protective layer at via locations allows electrical connection without compromising the overall protective coverage. Each region of the protective layer has different functionality: intact in most areas (protection), removed at via locations (conduction).
Data Source
AI summary
An MRAM structure includes an MTJ, a first SOT element, a conductive layer and a second SOT element disposed from bottom to top. A protective layer is disposed on the second SOT element. The protective layer covers and contacts a top surface of the second SOT element. The protective layer is an insulator. A conductive via penetrates the protective layer and contacts the second SOT element.