RRAM cell structure with conductive etch-stop layer
First Claim
1. A method of forming a resistive random-access memory (RRAM) device comprising:
- providing a semiconductor base surface comprising a metal interconnect structure disposed within a low-k dielectric layer, wherein outer sidewalls of the metal interconnect structure are spaced apart by a first length;
forming a conductive etch-stop layer (CESL) abutting an upper surface of the metal interconnect structure;
forming a bottom RRAM electrode layer above the CESL;
forming a variable resistive dielectric layer above the bottom RRAM electrode layer;
forming a top RRAM electrode layer above the variable resistive dielectric layer;
forming a mask over the top RRAM electrode layer, the mask covering some portions of the top RRAM electrode layer while leaving other portions of the top RRAM electrode layer exposed;
performing a first etch to remove the exposed portions of the top RRAM electrode layer and to thereby form a top electrode structure;
forming sidewall spacers about outer sidewalls of the top electrode structure, wherein the sidewall spacers and top electrode structure cover some portions of the variable resistive dielectric layer and leave other portions of the variable resistive dielectric layer exposed; and
performing a second etch with the sidewall spacers and the top electrode structure in place to remove the exposed portions of the variable resistive dielectric layer as well as underlying portions of the bottom RRAM electrode layer, to thereby form a bottom electrode structure and a variable resistive dielectric structure which have outer sidewalls that are aligned, wherein outer sidewalls of the bottom electrode structure are spaced apart by a second length and outer sidewalls of the variable resistive dielectric structure are spaced apart by the second length, the second length being greater than the first length.
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Accused Products
Abstract
The present disclosure relates to a resistive random access memory (RRAM) device architecture, that includes a thin single layer of a conductive etch-stop layer between a lower metal interconnect and a bottom electrode of an RRAM cell. The conductive etch-stop layer provides simplicity in structure and the etch-selectivity of this layer provides protection to the underlying layers. The conductive etch stop layer can be etched using a dry or wet etch to land on the lower metal interconnect. In instances where the lower metal interconnect is copper, etching the conductive etch stop layer to expose the copper does not produce as much non-volatile copper etching by-products as in traditional methods. Compared to traditional methods, some embodiments of the disclosed techniques reduce the number of mask step and also reduce chemical mechanical polishing during the formation of the bottom electrode.
53 Citations
20 Claims
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1. A method of forming a resistive random-access memory (RRAM) device comprising:
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providing a semiconductor base surface comprising a metal interconnect structure disposed within a low-k dielectric layer, wherein outer sidewalls of the metal interconnect structure are spaced apart by a first length; forming a conductive etch-stop layer (CESL) abutting an upper surface of the metal interconnect structure; forming a bottom RRAM electrode layer above the CESL; forming a variable resistive dielectric layer above the bottom RRAM electrode layer; forming a top RRAM electrode layer above the variable resistive dielectric layer; forming a mask over the top RRAM electrode layer, the mask covering some portions of the top RRAM electrode layer while leaving other portions of the top RRAM electrode layer exposed; performing a first etch to remove the exposed portions of the top RRAM electrode layer and to thereby form a top electrode structure; forming sidewall spacers about outer sidewalls of the top electrode structure, wherein the sidewall spacers and top electrode structure cover some portions of the variable resistive dielectric layer and leave other portions of the variable resistive dielectric layer exposed; and performing a second etch with the sidewall spacers and the top electrode structure in place to remove the exposed portions of the variable resistive dielectric layer as well as underlying portions of the bottom RRAM electrode layer, to thereby form a bottom electrode structure and a variable resistive dielectric structure which have outer sidewalls that are aligned, wherein outer sidewalls of the bottom electrode structure are spaced apart by a second length and outer sidewalls of the variable resistive dielectric structure are spaced apart by the second length, the second length being greater than the first length. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of forming a resistive random-access memory (RRAM) device comprising:
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providing a semiconductor substrate with a metal interconnect structure disposed over the semiconductor substrate, wherein outer sidewalls of the metal interconnect structure are spaced apart by a first length; forming a conductive etch-stop layer (CESL) over the metal interconnect structure, wherein the CESL directly contacts a metal line and a low-k dielectric which are disposed in an upper conductive layer of the metal interconnect structure; forming a bottom RRAM electrode layer to directly contact the CESL; forming a variable resistive dielectric layer to directly contact the bottom RRAM electrode layer; forming a top RRAM electrode layer to directly contact the variable resistive dielectric layer; forming a mask over the top RRAM electrode layer, and performing a first etch to remove portions of the top RRAM electrode layer exposed through openings in the mask, and wherein the first etch stops at an uppermost surface of the variable resistive dielectric layer to thereby form a top electrode structure; forming sidewall spacers about outer sidewalls of the top electrode structure, wherein the sidewall spacers and top electrode structure cover some portions of the variable resistive dielectric layer and leave other portions of the variable resistive dielectric layer exposed; and with the sidewall spacers and top electrode structure in place and without forming another mask over the top electrode structure, performing a second etch to remove the exposed portions of the variable resistive dielectric layer as well as underlying portions of the bottom electrode, to thereby form a variable resistive dielectric structure and a bottom electrode structure which have outer sidewalls that are aligned, wherein the aligned outer sidewalls of the bottom electrode structure are spaced apart by a second length and outer sidewalls of the variable resistive dielectric structure are spaced apart by the second length, the second length being greater than the first length. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method of forming a resistive random-access memory (RRAM) device comprising:
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providing a semiconductor substrate with a metal interconnect structure disposed over the semiconductor substrate, wherein outer sidewalls of the metal interconnect structure are spaced apart by a first length; forming a conductive etch-stop layer (CESL) over the metal interconnect structure; forming a bottom RRAM electrode layer, a variable resistive dielectric layer, and a top RRAM electrode layer in that order over the CESL; performing a first etch to the top RRAM electrode layer to form a top electrode structure; forming sidewall spacers about outer sidewalls of the top electrode structure; and performing a second etch to remove exposed portions of the variable resistive dielectric layer and underlying portions of the bottom electrode that are not covered by the top electrode structure and the sidewall spacer, to thereby form a variable resistive dielectric structure and a bottom electrode structure whose outer sidewalls are aligned, wherein the outer sidewalls of the bottom electrode structure are spaced apart by a second length and outer sidewalls of the variable resistive dielectric structure are spaced apart by the second length, the second length being greater than the first length; and performing a third etch to remove exposed portions of the CESL not covered by the bottom electrode structure, while leaving at least a substantial portion of the CESL covered by the bottom electrode structure in place between the bottom electrode structure and the metal interconnect structure; wherein the second etch comprises dry etching while the third etch comprises alkali base wet etching. - View Dependent Claims (19, 20)
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Specification