Semiconductor device manufacturing: process – Having magnetic or ferroelectric component
Reexamination Certificate
2011-01-04
2011-01-04
Trinh, Michael (Department: 2822)
Semiconductor device manufacturing: process
Having magnetic or ferroelectric component
C438S240000, C438S671000, C257SE21665
Reexamination Certificate
active
07863060
ABSTRACT:
A method for forming a MTJ in a STT-MRAM is disclosed in which the easy-axis CD is determined independently of the hard-axis CD. One approach involves two photolithography steps each followed by two plasma etch steps to form a post in a hard mask which is transferred through a MTJ stack of layers. The hard mask has an upper Ta layer with a thickness of 300 to 400 Angstroms and a lower NiCr layer less than 50 Angstroms thick. The upper Ta layer is etched with a fluorocarbon etch while lower NiCr layer and underlying MTJ layers are etched with a CH3OH. Preferably, a photoresist mask layer is removed by oxygen plasma between the fluorocarbon and CH3OH plasma etches. A lower hard mask layer made of NiCr or the like is inserted to prevent formation and buildup of Ta etch residues that can cause device shunting.
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Belen Rodolfo
Kula Witold
Torng Chyu-Jiuh
Zhong Tom
Ackerman Stephen B.
MagIC Technologies, Inc.
Saile Ackerman LLC
Trinh Michael
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