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

US7863060B2 · kind B2 · utility

Assignee

• MagIC Technologies, Inc. · US

Inventors

• Rodolfo P. Belen · San Francisco, US
• Tom Zhong · Saratoga, US
• Witold Kula · Gilroy, US
• Chyu-Jiuh Torng · Pleasanton, US

Key dates

• Filing date: Mar 23, 2009
• Grant date: Jan 4, 2011
• Expiry date: Jul 18, 2029

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10N50/01

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.