Invention Grant
US07863060B2 Method of double patterning and etching magnetic tunnel junction structures for spin-transfer torque MRAM devices 有权
双重图案化和蚀刻用于自旋转移转矩MRAM器件的磁性隧道结结构的方法

Method of double patterning and etching magnetic tunnel junction structures for spin-transfer torque MRAM devices
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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