Bottom electrode etching process in MRAM cell
First Claim
1. A method of patterning a bottom electrode layer in a MRAM structure, said bottom electrode layer is formed on a substrate including an insulation layer dielectric (ILD), comprising:
- (a) providing an array of MTJ elements on said bottom electrode layer wherein each of said MTJ elements has a bottom portion contacting the bottom electrode layer, a top portion having a top surface, and sidewalls connecting said top surface to the bottom electrode layer;
(b) forming a protective dielectric layer on the top surface and sidewalls of the MTJ elements and on the bottom electrode layer between adjacent MTJ elements;
(c) forming a stack of layers on the protective dielectric layer, comprising;
(1) a bottom anti-reflective coating (BARC) which contacts the protective dielectric layer; and
(2) a photoresist layer on the BARC layer;
(d) patterning the photoresist layer to form a plurality of openings between adjacent MTJ elements;
(e) transferring said plurality of openings through the BARC layer and through the protective dielectric layer with a dielectric etch process;
(f) transferring said plurality of openings through the bottom electrode layer with a metal etch process to form a patterned bottom electrode below each of said plurality of MTJ elements, said metal etch includes a certain amount of overetching that removes a top portion of the ILD at the bottom of each of the plurality of openings; and
(g) removing the photoresist and BARC layers with a stripping process, comprising;
(1) a first wet strip that includes immersing or spraying the substrate with a solution including one or more organic solvents;
(2) a dry ashing step that includes exposing the substrate to an O2 plasma; and
(3) a second wet strip that includes treatment of the substrate with a water based solution.
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Accused Products
Abstract
A BE patterning scheme in a MRAM is disclosed that avoids damage to the MTJ array and underlying ILD layer while reducing BE-BE shorts and BE-bit line shorts. A protective dielectric layer is coated over a MTJ array before a photoresist layer is coated and patterned on the dielectric layer. The photoresist pattern is transferred through the dielectric layer with a dielectric etch process and then through the BE layer with a metal etch that includes a certain amount of overetch to remove metal residues. The photoresist is stripped with a sequence involving immersion or spraying with an organic solution followed by oxygen ashing to remove any other organic materials. Finally, a second wet strip is performed with a water based solution to provide a residue free substrate. In another embodiment, a bottom anti-reflective coating (BARC) is inserted between the photoresist and dielectric layer for improved critical dimension control.
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Citations
20 Claims
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1. A method of patterning a bottom electrode layer in a MRAM structure, said bottom electrode layer is formed on a substrate including an insulation layer dielectric (ILD), comprising:
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(a) providing an array of MTJ elements on said bottom electrode layer wherein each of said MTJ elements has a bottom portion contacting the bottom electrode layer, a top portion having a top surface, and sidewalls connecting said top surface to the bottom electrode layer; (b) forming a protective dielectric layer on the top surface and sidewalls of the MTJ elements and on the bottom electrode layer between adjacent MTJ elements; (c) forming a stack of layers on the protective dielectric layer, comprising; (1) a bottom anti-reflective coating (BARC) which contacts the protective dielectric layer; and (2) a photoresist layer on the BARC layer; (d) patterning the photoresist layer to form a plurality of openings between adjacent MTJ elements; (e) transferring said plurality of openings through the BARC layer and through the protective dielectric layer with a dielectric etch process; (f) transferring said plurality of openings through the bottom electrode layer with a metal etch process to form a patterned bottom electrode below each of said plurality of MTJ elements, said metal etch includes a certain amount of overetching that removes a top portion of the ILD at the bottom of each of the plurality of openings; and (g) removing the photoresist and BARC layers with a stripping process, comprising; (1) a first wet strip that includes immersing or spraying the substrate with a solution including one or more organic solvents; (2) a dry ashing step that includes exposing the substrate to an O2 plasma; and (3) a second wet strip that includes treatment of the substrate with a water based solution. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of patterning a bottom electrode layer in a MRAM structure, said bottom electrode layer is formed on a substrate including an insulation layer dielectric (ILD), comprising:
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(a) providing an array of MTJ elements on said bottom electrode layer wherein each of said MTJ elements has a bottom portion contacting the bottom electrode layer, a top portion having a top surface, and sidewalls connecting said top surface to the bottom electrode layer; (b) forming a dielectric anti-reflective coating (DARC) on the top surface and sidewalls of the MTJ elements and on the bottom electrode layer between adjacent MTJ elements; (c) forming a photoresist layer on the DARC layer; (d) patterning the photoresist layer to form a plurality of openings wherein there is an opening between adjacent MTJ elements; (e) transferring said plurality of openings through the DARC layer with a dielectric etch process; (f) transferring said plurality of openings through the bottom electrode layer with a metal etch process to form a patterned bottom electrode below each of the MTJ elements in said array, said metal etch includes a certain amount of overetch to remove a top portion of the ILD at the bottom of each of the plurality of openings; and (g) removing the photoresist layer with a stripping process, comprising; (1) a first wet strip that includes immersing or spraying the substrate with a solution including one or more organic solvents; (2) a dry ashing step that includes exposing the substrate to an O2 plasma; and (3) a second wet strip that includes treatment of the substrate with a water based solution. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of patterning a bottom electrode layer in a MRAM structure, said bottom electrode layer is formed on a substrate including an insulation layer dielectric (ILD), comprising:
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(a) providing an array of MTJ elements on said bottom electrode layer wherein each of said MTJ elements has a bottom portion contacting the bottom electrode layer, a top portion having a top surface, and sidewalls connecting said top surface to the bottom electrode layer; (b) forming a spin-on carbon containing hard mask (C-SOH) on the top surface and sidewalls of the MTJ elements and on the bottom electrode layer between adjacent MTJ elements; (c) forming a spin-on silicon containing hard mask (Si-SOH) on the C-SOH layer; (d) forming a photoresist layer on the Si-SOH layer and patterning the photoresist layer to form a plurality of openings wherein there is an opening between adjacent MTJ elements; (e) transferring said plurality of openings through the Si-SOH layer with a first dielectric etch process and through the C-SOH layer with a second dielectric etch process; (f) transferring said plurality of openings through the bottom electrode layer with a metal etch process to form a patterned bottom electrode below each of the MTJ elements in said array, said metal etch includes a certain amount of overetch to remove a top portion of the ILD at the bottom of each of the plurality of openings; and (g) removing the photoresist layer with a stripping process, comprising; (1) a first wet strip that includes immersing or spraying the substrate with a solution including one or more organic solvents; (2) a dry ashing step that includes exposing the substrate to an O2 plasma; and (3) a second wet strip that includes treatment of the substrate with a water based solution. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification