US 10,475,991 B2Granted

Fabrication of large height top metal electrode for sub-60nm magnetoresistive random access memory (MRAM) devices

AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.

InventorsYi Yang, Zhongjian Teng, Jesmin Haq, Yu-Jen Wang

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Abstract

A process flow for forming magnetic tunnel junction (MTJ) cells with a critical dimension CD≤60 nm by using a top electrode (TE) hard mask having a thickness ≥100 nm prior to MTJ etching is disclosed. A carbon hard mask (HM), silicon HM, and photoresist are sequentially formed on a MTJ stack of layers. A pattern of openings in the photoresist is transferred through the Si HM with a first reactive ion etch (RIE), and through the carbon HM with a second RIE. After TE material is deposited to fill the openings, a chemical mechanical process is performed to remove all layers above the carbon HM. The carbon HM is stripped and the resulting TE pillars are trimmed to a CD≤60 nm while maintaining a thickness proximate to 100 nm. Thereafter, an etch process forms MTJ cells while TE thickness is maintained at ≥70 nm.

Claims21

Dependent claims

A method of forming magnetic tunnel junction (MTJ) cell, comprising:

(a) providing a MTJ stack of layers on a bottom electrode wherein the MTJ stack of layers comprises a reference layer, a free layer, a tunnel barrier layer between the reference layer and free layer, and an uppermost capping layer;
(b) forming a carbon hard mask layer on the capping layer, and an opening with a first width in the carbon hard mask layer;
(c) filling the opening with a top electrode (TE) material and performing a chemical mechanical polish (CMP) process to give a TE pillar with a top surface coplanar with a top surface of the carbon hard mask layer at a first height;
(d) removing the carbon hard mask layer;
(e) trimming the TE pillar such that the TE pillar has a width ≤60 nm and a thickness proximate to 100 nm;
and
(f) performing one or more MTJ etch steps to transfer a shape of the TE pillar through the MTJ stack of layers and stopping on the bottom electrode thereby forming a first sidewall on the TE pillar that is coplanar with a second sidewall on a MTJ cell and wherein the MTJ cell and TE pillar each have a first critical dimension (CD) of ≤60 nm in a widthwise direction, a second CD in a lengthwise direction, and each TE pillar has a thickness of ≥70 nm in a vertical direction.

4 more elements

A method of forming a memory device comprised of a plurality of magnetic tunnel junction (MTJ) cells, comprising:

(a) providing a MTJ stack of layers on a bottom electrode wherein the MTJ stack of layers comprises a reference layer, a free layer, a tunnel barrier layer between the reference layer and free layer, and an uppermost capping layer;
(b) sequentially forming a carbon hard mask (HM) layer, a silicon containing HM layer, and a photoresist layer on the capping layer wherein a pattern having a plurality of via openings of width d1 is formed in the photoresist layer;
(c) transferring the pattern through the silicon HM layer with a first reactive ion etch (RIE) step to yield openings of width d2 where d2 >d1, and through the carbon HM layer with a second RIE step to form openings of width d3 where d3 >d2 and where d3 ≥100 nm, and thereby removing the photoresist layer;
(d) filling the openings of width d3 with a top electrode (TE) material and performing a chemical mechanical polish (CMP) process to remove the silicon HM layer and form a plurality of TE pillars each having a first height within the carbon HM layer;
(e) removing the carbon HM layer with a third RIE step;
(f) trimming the plurality of TE pillars such that each TE pillar has a width d4 that is ≤60 nm and a thickness proximate to 100 nm;
and
(g) performing one or more MTJ etch steps to transfer a shape of each TE pillar through the MTJ stack of layers and stopping on the bottom electrode thereby forming a first sidewall on each TE pillar that is coplanar with a second sidewall on a MTJ cell and wherein each MTJ cell and overlying TE pillar has a first critical dimension (CD) of <60 nm in a widthwise direction, a second CD in a lengthwise direction, and each TE pillar has a thickness of ≥70 nm.

5 more elements

Dependencies are inferred from the claim text.