SELF-ALIGNED MEMORY CELL CONTACT
In various embodiments, a memory storage element for storing two or more bits of information is formed by connecting two resistive change elements in series whereby the first resistive change element is made of a first material and the second resistive change element is made of a second material and the melting point of the first resistive change element material is greater than the melting point of the second resistive change element material such that the set and reset states of the two elements can be written and read.
1 . A method of making a memory cell, comprising:
etching the layer of barrier or adhesion or conductive material that is disposed in a hole to remove a portion of the barrier or adhesion or conductive material from the hole;
depositing information storage material into the hole onto remaining barrier or adhesion or conductive material; and
removing a portion of the information storage material.
2 . The method of claim 1 , wherein the removing a portion of the information storage material comprises etching.
3 . The method of claim 2 , wherein the information storage material comprises phase change material.
4 . The method of claim 3 , wherein the phase change material comprises Chalcogenide elements.
5 . The method of claim 1 , wherein the removing a portion of the information storage material comprises CMP.
6 . The method of claim 1 , wherein the information storage material comprises phase change material.
7 . The method of claim 6 , wherein the phase change material comprises Chalcogenide elements.
8 . The method of claim 1 , wherein the barrier or adhesion or conductive material comprises a layer of titanium salicide and a layer of TiN.
9 . The method of claim 8 , wherein the information storage material comprises phase change material.
10 . The method of claim 1 , further comprising:
depositing a between-element barrier material over remaining information storage material in the hole;
removing a portion of the between-element barrier material from the hole;
depositing top information storage material in the hole over remaining between-element barrier material;
removing a portion of the top information storage material from the hole;
depositing a top contact over remaining top information storage material in the hole;
removing a portion of the top contact; and
depositing a top dielectric layer over remaining top contact.
11 . The method of claim 10 , wherein the top contact comprises TiN.
12 . The method of claim 10 , wherein the between-element barrier material comprises TiN.
13 . The method of claim 10 , wherein removing a portion of the top contact comprises etching.
14 . The method of claim 10 , wherein removing a portion of the top contact comprises CMP.
15 . The method of claim 10 , wherein the information storage material and the top information storage material have different melting points.
16 . The method of claim 15 , wherein the top information storage material has a higher melting point than the information storage material.
17 . The method of claim 16 , wherein the information storage material and the top information storage material comprise Chalcogenide elements.
18 . A method, comprising the steps:
(i) partially etching a barrier and/or adhesion and/or conductive material disposed in a cup, wherein a portion of the barrier and/or adhesion and/or conductive material remains in a first portion of the cup; and
(ii) filling at least a second portion the cup with an information storage material.
19 . The method of claim 18 , wherein the information storage material comprises GST.
20 . The method of claim 18 , further comprising:
(iii) etching the information storage material with an etch that selectively removes the information storage material at a faster rate than surrounding dielectric material;
(iv) stopping the etch before removing all of the information storage material in the cup; and
(v) filling at least a third portion of the area of the cup from which the information storage material was etched with a barrier and/or adhesion and/or conductive material.