System and method for processing a wafer including stop-on-alumina processing

Abstract

Magnetic tunnel junction (MTJ) devices can be fabricated by a stop-on-alumina process whereby the tunnel junction layer serves as the stop layer during plasma overetching of the upper magnetic layer. The resulting side walls of the MTJ device are non-vertical in the vicinity of the tunnel junction layer which serves to electrically isolate the upper magnetic layer from the lower magnetic layer. The gas employed during plasma overetching excludes halogen containing species which results in highly selective etching of the magnetic layer vis-à-vis the alumina tunnel barrier layer. The introduction of oxygen in the gas may enhance the reproducibility of the overetch process. Finally, plasma treatment with He and H2 followed by rinsing and baking subsequent to removal of the photoresist mask during the fabrication process enhances yield.

Description

[0001] This application is a Divisional of U.S. patent application Ser. No. 10 / 937,660 entitled SYSTEM AND METHOD FOR PROCESSING A WAFER INCLUDING STOP-ON-ALUMINA PROCESSING, by Robert Ditizio, filed Sep. 9, 2004 (Attorney Docket No: TEGL-01172US0), which application is incorporated herein by reference.BACKGROUND OF THE INVENTION [0002] Magnetic multilayer films are employed as a storage element in memories, such as magnetic random access memories (MRAM) and the like. The memory element for the MRAM technology is a patterned structure (memory bit) of multilayer material. The magnetic multilayer material is usually composed of a stack of different materials, such as permalloy (NiFe), cobalt-iron, copper, tantalum, etc. and may include some insulator like materials, such as Al2O3. A typical stack may contain as many as ten different or more overlying layers of these materials. To fabricate a storage element, it is necessary to deposit the materials in overlying blanket films, layer by...

AI Technical Summary

Benefits of technology

"The present invention is about making magnetic tunnel junction (MTJ) devices. The invention uses a process where the alumina tunnel barrier layer acts as a stop layer during plasma overetching of the upper magnetic layer. This results in MTJ devices with non-vertical side walls and better electrical isolation. The use of specific gases during plasma overetching helps to selectively etch the upper magnetic layer without damaging the alumina tunnel barrier layer. Additionally, a corrosion plasma treatment with He and H2 gas followed by rinsing and dehydration baking can be employed to improve the quality of the MTJ devices."

Problems solved by technology

Ion beam milling operates with relatively low selectivity, and the portions of the stack that are near to the edges of the mask or the boundaries of an MRAM cell body can be easily damaged.

One of the drawbacks of current etching techniques is that the vertical profiles of MRAM structure are susceptible to electrical shorting across the thin tunnel junction.

The vertical walls adjacent the thin alumina insulator layer separating the upper magnet and the lower magnetic is inadequate to prevent electrical shorting.

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