A method of forming a magnetic tunneling junction (MTJ) MRAM device and a tunneling magnetoresistive (TMR) read head

Abstract

An MTJ (magnetic tunneling junction) device particularly suitable for use as an MRAM (magnetic random access memory) or a tunneling magnetoresistive (TMR) read sensor, is formed on a seed layer which allows the tunneling barrier layer to be ultra-thin, smooth, and to have a high breakdown voltage. The seed layer is a layer of NiCr which is formed on a sputter-etched layer of Ta. The tunneling barrier layer for the MRAM is formed from a thin layer of Al which is radically oxidized (ROX), in-situ, to form the layer with characteristics described above. The tunneling barrier layer for the read sensor formed from a thin layer of Al or a HfAl bilayer which is naturally oxidized (NOX), in-situ, to form the barrier layer. The resulting device has generally improved performance characteristics in terms of GMR ratio and junction resistance.

Description

RELATED PATENT APPLICATION [0001] This application is related to Docket No. HT 02-019, Ser. No. 10 / 371,841, filing date Feb. 20, 2003, Docket No. HT 03-016, Ser. No. 10 / 820,391, filing date Apr. 8, 2004, and Docket No. HT 02-032, Ser. No. 10 / 768,917, filing date Jan. 30, 2004, assigned to the same assignee as the current invention.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates generally to magnetic tunneling junction (MTJ) devices such as MRAMs and read-heads and more particularly to the use of a novel seed layer that allows the formation of a junction layer of superior physical properties. [0004] 2. Description of the Related Art [0005] The magnetic tunneling junction device (MTJ device) is essentially a variable resistor in which the relative orientation of magnetic fields in an upper and lower very thin dielectric layer (the tunneling barrier layer) formed between those electrodes. As electrons pass through the upper electrode they are ...

AI Technical Summary

Benefits of technology

The present invention provides a method for improving the topography of a bottom electrode or pinned layer in a TMR read head or MTJ MRAM element by reducing its roughness. This allows for the formation of a smooth and flat tunneling barrier layer that meets various requirements such as low junction resistance, high GMR ratio, and high breakdown voltage. The invention also provides a method for forming an MTJ MRAM element with a very smooth bottom electrode and a flat pinned layer. The invention achieves these technical effects by using a NiCr buffer layer as a seed layer on a Ta layer, followed by the deposition of an antiferromagnetic pinning layer, an MnPt layer, and a second NiCr seed layer. The resulting MTJ MRAM element has a high GMR ratio, low junction resistance, and high breakdown voltage.

Problems solved by technology

Whether it is used as an MRAM or as a TMR read head, fabrication of a high quality MTJ device presents considerable difficulties due to the necessity of forming layers of extreme thinness.

This is itself a problem, since the layers are exceptionally thin.

Second, the resistance of the tunneling barrier layer is typically high, which results in a poor ratio of signal-to-noise (S / N) in read head applications.

If the resistance of the barrier layer is lowered by excessively thinning that layer, then fabrication processes such as lapping the air-bearing surface of the read head can create shorts through the barrier layer.

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