US 8,133,809 B2Granted

Method to fabricate thin metal via interconnects on copper wires in MRAM devices

AssigneeMagIC Technologies, Inc.

InventorGuomin Mao

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Abstract

A scheme for forming a thin metal interconnect is disclosed that minimizes etch residues and provides a wet clean treatment for via openings. A single layer interlayer dielectric (ILD), BARC, and photoresist layer are successively formed on a substrate having a copper layer that is coplanar with a dielectric layer. In one embodiment, the ILD is silicon nitride with 100 to 600 Angstrom thickness. After a via opening is formed in a photoresist layer above the copper layer, a first RIE process including BARC main etch and BARC over etch steps is performed. Then a second RIE step transfers the opening through the ILD to uncover the copper layer. Photoresist and BARC are stripped with oxygen plasma and a low DC bias. Wet cleaning may involve a first ST250 treatment, ultrasonic water treatment, and then a third ST250 treatment. A bottom electrode layer may be deposited in the via opening.

Claims20

Dependent claims

A method of fabricating thin metal via interconnects, comprising:

(a) providing a substrate comprised of a copper layer formed in a first dielectric layer, said copper layer has a top surface that is coplanar with a top surface of the first dielectric layer;
(b) depositing a thin single layer of interlayer dielectric (ILD) on the substrate;
(c) sequentially forming a bottom anti-reflective coating (BARC) and a photoresist layer on the ILD;
(d) forming a pattern in the photoresist layer comprised of a via opening that is aligned above a portion of the copper layer and exposes a portion of a top surface of the BARC;
(e) performing a first reactive ion etch (RIE) process, comprising:
(1) a BARC main etch step that removes a substantial thickness of BARC in regions exposed by the via opening;
and
(2) a BARC over etch step that completely uncovers a top surface of ILD aligned below the via opening
(f) performing a second RIE etch process comprised of a low bias power, a fluorocarbon gas, and an initial end point detect signal thereby removing the ILD below the via opening and uncovering a portion of copper layer and first dielectric layer below the via opening;
(g) stripping the BARC and any remaining portions of the photoresist layer with an oxygen plasma in an etch chamber with a wafer pedestal temperature, DC bias, and minimum time beyond an end point signal that avoid copper oxidation and damage to copper;
and
(h) performing a wet clean treatment.

9 more elements

A method of fabricating thin metal via interconnects, comprising:

(a) providing a substrate comprised of a copper layer formed in a first dielectric layer, said copper layer has a top surface that is coplanar with a top surface of the first dielectric layer;
(b) depositing a thin single layer of interlayer dielectric (ILD) on the substrate;
(c) sequentially forming a bottom anti-reflective coating (BARC) and a photoresist layer on the ILD;
(d) forming a pattern in the photoresist layer comprised of a via opening that is aligned above a portion of the copper layer and exposes a portion of a top surface of the BARC;
(e) performing a first reactive ion etch (RIE) process that removes the BARC layer exposed by the via opening, and removes a portion of the ILD layer that is exposed by etching the BARC layer;
said first RIE process includes an initial end point detect signal and uncovers a portion of the copper layer below the via opening;
(f) stripping the BARC and any remaining portions of the photoresist layer with an oxygen plasma in an etch chamber with a wafer pedestal temperature, DC bias, and minimum time beyond an end point signal that avoid copper oxidation and damage to copper;
and
(g) performing a wet clean treatment.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/806,381Filed 11 Aug 2010
Published: US 2012/0040531 A116 Feb 2012
Granted: 13 Mar 2012
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H10P 70/234
During, before or after processing of insulating materials: the processing being the formation of vias or contact holes
H10P 50/283
Of inorganic materials: by chemical means
H10P 50/287
Of organic materials: by chemical means
H10W 20/081
Of dielectric parts thereof: by forming openings in the dielectric parts