US 8,133,745 B2Granted

Method of magnetic tunneling layer processes for spin-transfer torque MRAM

AssigneeMagIC Technologies, Inc.

InventorsTom Zhong, Rongfu Xiao, Chyu-Jiuh Torng, Adam Zhong

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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 and two etch steps to form a post in a hard mask which is transferred through a MTJ stack of layers by a third etch process. Optionally, the third etch may stop on the tunnel barrier or in the free layer. A second embodiment involves forming a first parallel line pattern on a hard mask layer and transferring the line pattern through the MTJ stack with a first etch step. A planar insulation layer is formed adjacent to the sidewalls in the line pattern and then a second parallel line pattern is formed which is transferred by a second etch through the MTJ stack to form a post pattern. Etch end point may be controlled independently for hard-axis and easy-axis dimensions.

Claims24

Dependent claims

A method of fabricating a MTJ element having essentially vertical sidewalls and with a top surface having an area determined by a first dimension along a first axis and a second dimension along a second axis, said MTJ element has stack of layers comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and hard mask layer formed in order from bottom to top, comprising:

(a) forming an unpatterned MTJ stack of layers on a substrate;
(b) patterning a first photoresist layer on the hard mask layer to form a first parallel line pattern wherein each line has a width that is the first dimension along the first axis;
(c) transferring said first parallel line pattern through the hard mask layer with a first etch step to form parallel hard mask lines on the hard mask spacer layer;
(d) patterning a second photoresist layer on the parallel hard mask lines and hard mask spacer layer to form a second parallel line pattern wherein each line intersects the parallel hard mask lines and has a width that is the second dimension along the second axis, said second photoresist layer contacts a top surface of the parallel hard mask lines;
(e) transferring said second parallel line pattern through the hard mask layer with a second etch step to form a post pattern in the hard mask layer wherein each post has an area determined by the first dimension and second dimension;
and
(f) performing a third etch step to transfer the hard mask post pattern through the hard mask spacer and remaining unpatterned layers in the MTJ stack of layers to form a plurality of MTJ elements, said first and second dimensions are formed simultaneously in the MTJ stack of layers below the hard mask layer, and said hard mask layer remains as an uppermost layer in the MTJ stack.

4 more elements

A method of fabricating a MTJ element with a top surface having an area determined by a first dimension along a first axis and a second dimension along a second axis, said MTJ element has stack of layers comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and hard mask layer formed in order from bottom to top, comprising:

(a) forming an unpatterned MTJ stack of layers on a substrate;
(b) patterning a first photoresist layer on the hard mask layer to form a first parallel line pattern wherein each line has a width that is the first dimension along the first axis;
(c) transferring said first parallel line pattern through the hard mask layer with a first etch step to form parallel hard mask lines on the hard mask spacer layer;
(d) patterning a second photoresist layer on the parallel hard mask lines and hard mask spacer layer to form a second parallel line pattern wherein each line intersects the parallel hard mask lines and has a width that is the second dimension along the second axis, said second photoresist layer contacts a top surface of the parallel hard mask lines;
(e) transferring said second parallel line pattern through the hard mask layer with a second etch step to form a post pattern in the hard mask layer wherein each post has an area determined by the first dimension and second dimension;
and
(f) performing a third etch step to transfer the hard mask post pattern through the unpatterned hard mask spacer layer and at least a portion of the unpatterned free layer to form a plurality of MTJ elements, said first and second dimensions are formed simultaneously in the hard mask spacer and at least a portion of the free layer, said hard mask layer remains as an uppermost layer in the MTJ stack.

4 more elements

A method of fabricating a MTJ element with a top surface having an area determined by a first dimension along a first axis and a second dimension along a second axis, said MTJ element has a stack of layers and is comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and hard mask layer formed in order from bottom to top, comprising:

(a) forming an unpatterned MTJ stack of layers with a first thickness on a substrate;
(b) patterning a first photoresist layer on the hard mask layer to form a first parallel line pattern wherein each line has a width that is the first dimension along the first axis;
(c) transferring said first parallel line pattern through the unpatterned MTJ stack of layers with a first etch step to form a parallel line pattern wherein each line has two sidewalls;
(d) forming a planar insulation layer on the substrate and adjacent to the two sidewalls of each line and with a thickness that is equal to or greater than said first thickness;
(e) patterning a second photoresist layer on the insulation layer and above the parallel line pattern to form a second parallel line pattern wherein each second photoresist line has a width that is the second dimension along the second axis and contacts a top surface of the parallel line pattern;
and
(f) transferring said second parallel line pattern through the MTJ stack of layers with a second etch step to form a post pattern comprised of a plurality of posts wherein each post has an area determined by the first dimension and second dimension, said hard mask layer remains as an uppermost layer in the MTJ stack.

4 more elements

A method of fabricating a MTJ element with a top surface having an area determined by a first dimension along a first axis and a second dimension along a second axis, said MTJ element has a stack of layers and is comprised of a seed layer, AFM layer, pinned layer, tunnel barrier, free layer, hard mask spacer layer, and hard mask layer formed in order from bottom to top, comprising:

(a) forming an unpatterned MTJ stack of layers with a first thickness on a substrate;
(b) patterning a first photoresist layer on the hard mask layer to form a first parallel line pattern wherein each line has a width that is the first dimension along the first axis;
(c) transferring said first parallel line pattern through the hard mask layer, unpatterned hard mask spacer layer, and at least an upper portion of the unpatterned free layer with a first etch step to form a parallel line pattern wherein each line has two sidewalls;
(d) forming a planar insulation layer adjacent to the two sidewalls of each line and with a thickness that is equal to or greater than said first thickness;
(e) patterning a second photoresist layer on the insulation layer and above the parallel line pattern to form a second parallel line pattern wherein each second photoresist line has a width that is the second dimension along the second axis and contacts a top surface of the parallel line pattern;
and
(f) transferring said second parallel line pattern through the hard mask layer, hard mask spacer layer, and at least an upper portion of the free layer with a second etch step to form a post pattern comprised of a plurality of posts wherein each post has an area determined by the first dimension and second dimension, said hard mask layer remains as an uppermost layer in the MTJ stack.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/975,045Filed 17 Oct 2007
Published: US 2009/0104718 A123 Apr 2009
Granted: 13 Mar 2012
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H10N 50/01
Galvanomagnetic devices: manufacture or treatment
B82Y 10/00
Nanotechnology for information processing, storage or transmission
H10B 61/22
Comprising components having three or more electrodes, e.g. transistors: of the field-effect transistor [FET] type
H10N
Electric solid-state devices not otherwise provided for