MRAM MTJ Pillar Patterning With Hemispherical Dielectric Hardmask
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Solution Overview
Problem
High circular edge roughness (CER) in magneto-resistive random access memory (MRAM) devices due to grain boundaries and defects in polycrystalline metal hardmasks during patterning of magnetic tunnel junction (MTJ) pillars, which negatively impacts device performance.
Innovation Solution
Employing an amorphous dielectric hardmask with a hemispherical shape instead of a polycrystalline metal hardmask to pattern MRAM stacks, reducing CER and improving MTJ pillar quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polycrystalline metal hardmask is used for patterning MTJ stacks, then the patterning process can be performed, but grain boundaries and defects are transferred into the MTJ pillar resulting in high circular edge roughness
Solution Approach 1:
The patent changes the material parameter of the hardmask from polycrystalline metal to amorphous dielectric material. This parameter change eliminates grain boundaries and defects inherent in polycrystalline structures, resulting in MTJ pillars with low circular edge roughness and improved MRAM performance.
2Manufacturing precision
If amorphous dielectric hardmask is used instead of polycrystalline metal hardmask, then circular edge roughness is reduced, but the hardmask material must be removed after patterning requiring additional process steps
Solution Approach 1:
The patent extracts the hardmask material (amorphous dielectric) after it has served its patterning function. The hardmask is removed through selective etching processes, allowing the underlying MTJ structure to be accessed while maintaining the low circular edge roughness achieved during patterning.
Data Source
AI summary
A memory device includes a magnetic tunnel junction pillar above a bottom electrode. A sidewall spacer is disposed along sidewalls of the magnetic tunnel junction pillar with an uppermost surface of the sidewall spacer being coplanar with an uppermost surface of the magnetic tunnel junction pillar. A dielectric hardmask composed of an amorphous dielectric material is disposed above a first portion of the uppermost surface of the magnetic tunnel junction pillar, the dielectric hardmask includes a hemispherical shape. A top electrode is located surrounding the dielectric hardmask and above the uppermost surface of the sidewall spacer and a second portion of the uppermost surface of the magnetic tunnel junction pillar extending outwards from the dielectric hardmask.