Self-Aligned MRAM Top Electrode Via for MTJ Protection
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Solution Overview
Problem
As MRAM technology nodes shrink from 28 nm to N5 or beyond, aligning a top electrode via with the top electrode of the MRAM cell becomes increasingly difficult, leading to overlay shifts and potential damage to the MTJ structure during the etching process, which affects the electrical and magnetic properties of the MRAM cells.
Innovation Solution
A self-aligned via approach is developed using a patterned etch stop layer deposited on spacers and a first dielectric layer, which protects the MTJ structure during via hole formation, ensuring precise alignment and preventing damage during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional via alignment methods are used, then manufacturing process is simpler, but manufacturing precision deteriorates due to overlay shifts at advanced technology nodes
Solution Approach 1:
The patent applies preliminary action by forming the etch stop layer and spacers before via hole etching. The etch stop layer is deposited conformally on the spacers and first dielectric layer, creating a protective structure in advance that defines the via hole location and protects the MTJ structure during subsequent etching processes, thereby achieving self-aligned via formation with high precision.
2Reliability
If etching process is performed without protection, then manufacturing process is simpler, but reliability deteriorates due to damage to MTJ structure
Solution Approach 1:
The patent uses the etch stop layer as an intermediary protective element between the etching process and the MTJ structure. The etch stop layer is selectively deposited on the spacers and first dielectric layer, acting as a mediator that protects the underlying MTJ structure from direct exposure to the etching process while allowing precise via hole formation through the second dielectric layer.
Solution Approach 2:
The patent implements beforehand cushioning by depositing the etch stop layer and forming spacers prior to the via hole etching process. This protective structure is prepared in advance to cushion and protect the MTJ structure from potential damage during the etching process, ensuring the integrity of the magnetic tunnel junction while enabling precise via alignment.
3Area of moving object
If technology nodes are shrunk to N5 or beyond, then device density is improved, but manufacturing precision deteriorates due to increased overlay shifts
Solution Approach 1:
The patent applies self-service by creating a self-aligned via formation process where the etch stop layer and spacers automatically define the via hole location. The conformal deposition of the etch stop layer on the spacers and first dielectric layer creates a structure that self-aligns with the MTJ, eliminating the need for additional alignment steps and photoresist rework, thereby maintaining high manufacturing precision at advanced N5 and beyond technology nodes.
Data Source
AI summary
An MRAM device includes a bottom electrode over a substrate, a magnetic tunnel junction (MTJ) structure on the bottom electrode and a top electrode on the MTJ structure. The MRAM device also includes spacers on sidewalls of the top electrode and the MTJ structure. The MRAM device further includes a first etch stop layer on the spacers. A bottommost surface of the first etch stop layer covers a topmost surface of the spacers. In addition, the MRAM device includes a top electrode via on the top electrode and the first etch stop layer.