MRAM Cell Blocking Layer Prevents Contact Short Circuits
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Solution Overview
Problem
Conventional MRAM cell structures are prone to undesired short circuits during the formation of contacts, particularly due to misalignment issues during the etching process, which can cause the MRAM cells to fail.
Innovation Solution
Incorporating a blocking layer wider than the magnetic tunnel junction unit on the top electrode to prevent short circuits between contacts and the magnetic tunnel junction unit, along with a cap layer to protect the MTJ unit from over-etching, and using a process that does not require additional masks, maintaining compatibility with standard backend processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a via contact is formed on the top electrode in the inter-metal dielectric layer, then electrical connection is established, but misalignment during etching can cause short circuits between the contact and the MTJ unit
Solution Approach 1:
A blocking layer is introduced as an intermediary element between the top electrode and the contact. This blocking layer extends laterally beyond the top electrode edges, creating a protective barrier that prevents misaligned contacts from shorting to the MTJ unit. The blocking layer acts as a mediator that absorbs the misalignment error without causing functional failure.
2Ease of manufacture
If the top electrode is directly exposed for contact formation, then electrical connection is simplified, but the MTJ unit becomes vulnerable to over-etching and short circuits
Solution Approach 1:
The blocking layer is formed in advance before contact formation, extending laterally beyond the top electrode. This preliminary action creates a protective barrier that is already in place when contacts are formed, preventing over-etching from reaching the MTJ unit. The blocking layer is positioned and sized beforehand to anticipate potential misalignment issues.
3Reliability
If additional blocking layers and cap layers are added to prevent short circuits, then reliability is improved, but device structure becomes more complex
Solution Approach 1:
The blocking layer serves multiple functions simultaneously: it provides lateral extension to prevent misaligned contacts from reaching the MTJ unit, it acts as a cap layer to protect the top electrode during etching processes, and it maintains electrical isolation where needed. By combining multiple protective functions into a single layer, the design avoids the need for separate blocking and capping structures.
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 proposed MRAM cell structure effectively prevents short circuits, enhancing the reliability of the memory cells and maintaining cost-effectiveness by avoiding the need for additional masks and being compatible with existing processes.
Implementation Method 1
Each MRAM cell includes a magnetic tunnel junction (MTJ) unit whose resistance can be adjusted to represent a logic state '0' or '1.' The resistance of the MTJ unit can be adjusted by changing the direction of the magnetic moment of the free magnetic layer.
Implementation Method 2
The MTJ unit is comprised of a fixed magnetic layer, a free magnetic layer, and a dielectric tunnel layer disposed there between.
Data Source
AI summary
A MRAM cell structure includes a bottom electrode; a magnetic tunnel junction unit disposed on the bottom electrode; a top electrode disposed on the magnetic tunnel junction unit; and a blocking layer disposed on the top electrode, wherein the blocking layer is wider than the magnetic tunnel junction unit for preventing against formation of a short circuit between a contact and the magnetic tunnel junction unit.