US-20260130132-A1 - DIAGONAL-TYPE PHASE CHANGE MEMORY CELL

US20260130132A1US 20260130132 A1US20260130132 A1US 20260130132A1US-20260130132-A1

Abstract

A phase change material (PCM) memory cell having a diagonal-shaped “ultrathin phase change film” channel structure approaching sub-5 nm that makes edge contact with two side electrodes, and a point contact with an ultra-thin bottom-electrode provisioned in the middle. The formed PCM memory structure includes an “angled substrate” on which the phase-change film is deposited such that the substrate is optimally etched at angles up to and exceeding 55 degrees, enabling long phase-change material channels at reduced lateral areal footprints. The diagonal-shaped ultrathin phase change film structure simultaneously enables very low programming energies in devices while achieving a small area footprint.

Inventors

Ghazi Sarwat Syed
Vara Sudananda Prasad Jonnalagadda
Timothy Mathew Philip
Abu Sebastian

Assignees

INTERNATIONAL BUSINESS MACHINES CORPORATION

Dates

Publication Date: 20260507
Application Date: 20241104

Claims (20)

1 . A phase change memory cell comprising: a first dielectric material layer; a first electrode formed above the first dielectric material layer; a second dielectric material layer formed above the first electrode; a further dielectric material structure having a first sidewall surface portion abutting a side edge of the first dielectric material layer and a second sidewall surface portion abutting a side edge of the second dielectric material layer; and a phase change material (PCM) layer having a first PCM layer portion formed on a top surface of said second dielectric material layer and having an angled PCM layer portion extending from the first PCM layer portion at an angle within said further dielectric material structure and having a slanted surface, the first electrode having an edge electrically contacting the slanted surface of the angled PCM layer.
2 . The phase change memory cell of claim 1 , wherein the angle ranges from between 5° and 75° relative to a vertical.
3 . The phase change memory cell of claim 1 , wherein the first electrode is of a length extending beyond a length of the second dielectric material layer.
4 . The phase change memory cell of claim 1 , wherein a dielectric material of the first dielectric material layer is different than a dielectric material of the second dielectric material layer.
5 . The phase change memory cell of claim 1 , wherein a dielectric material of the further dielectric material structure is the same dielectric material as the first dielectric material layer.
6 . The phase change memory cell of claim 1 , wherein the first dielectric material layer, the first electrode formed above the first dielectric material layer and the second dielectric material layer form a first stack structure, said memory cell further comprising: a second stack structure comprising a layer of the first dielectric material and the second dielectric material layer formed thereon, the second stack structure separated from said first stack by the further dielectric material structure and having a sidewall edge, wherein the angled PCM layer portion extends to a predetermined depth within the further dielectric material layer between said first and second stacks, said PCM layer further comprising: a horizontal PCM layer portion extending from said angled PCM layer portion to the sidewall edge of said second stack within said further dielectric material structure; a vertical PCM layer portion extending vertically from said horizontal PCM layer portion along the sidewall edge of said second stack; and a second PCM layer portion extended from said vertical PCM layer portion and formed on a top surface of the second stack.
7 . The phase change memory cell of claim 6 , further comprising: a second electrode having a first end electrically contacting the first PCM layer portion formed on said first stack and having a second end electrically contacting the second PCM layer portion formed on said second stack.
8 . The phase change memory cell of claim 7 , wherein the first end of said second electrode makes electrical contact with one or more of: a top surface of the first PCM layer portion or a sidewall edge of the first PCM layer portion on said second dielectric material layer of said first stack.
9 . The phase change memory cell of claim 7 , wherein the second end of said second electrode makes electrical contact with one or more of: a top surface of the second PCM layer portion or a sidewall edge of the second PCM layer portion on said second dielectric material layer of said second stack.
10 . The phase change memory cell of claim 6 , further comprising: a projection liner material layer disposed beneath the angled PCM layer portion, the projection liner material layer comprising a resistive non-switching material.
11 . A phase change memory cell comprising: a first dielectric material layer; a first electrode formed above the first dielectric material layer; a second dielectric material layer formed above the first electrode; a further dielectric material structure having a first sidewall surface portion abutting a side edge of the first dielectric material layer and a second sidewall surface portion abutting a side edge of the second dielectric material layer; a phase change material (PCM) layer having a first PCM layer portion formed on a top surface of said second dielectric material layer and having an angled PCM layer portion extending from the first PCM layer portion at an angle within said further dielectric material structure and having a second PCM layer portion extending from said angled PCM layer portion within said further dielectric material structure, said angled PCM layer having a slanted surface, wherein an edge of the first electrode electrically contacts the slanted surface of the angled PCM layer; and a second electrode having a first end electrically contacting the first PCM layer portion and having a second end electrically contacting the second PCM layer portion within said further dielectric material structure.
12 . The phase change memory cell of claim 11 , wherein the second electrode comprises an angled portion, the angled second electrode portion extending at an angle substantially parallel with the angled PCM layer portion.
13 . The phase change memory cell of claim 11 , wherein the angle ranges from between 5° and 75° relative to a vertical.
14 . The phase change memory cell of claim 11 , wherein the first electrode is of a length extending beyond a length of the second dielectric material layer.
15 . The phase change memory cell of claim 11 , wherein a dielectric material of the first dielectric material layer is different than a dielectric material of the second dielectric material layer.
16 . The phase change memory cell of claim 11 , wherein a dielectric material of the further dielectric material structure is the same dielectric material as the first dielectric material layer.
17 . The phase change memory cell of claim 11 , wherein the first end of said second electrode makes electrical contact with one or more of: a top surface of the first PCM layer portion or a sidewall edge of the first PCM layer portion on said second dielectric material layer; and the second end of said second electrode makes electrical contact with one or more of: another location of said top surface of the second PCM layer portion or a sidewall edge of the second PCM layer portion.
18 . The phase change memory cell of claim 11 , further comprising: a projection liner material layer disposed beneath the angled PCM layer portion, the projection liner material layer comprising a resistive non-switching material.
19 . A method of forming a phase change memory cell comprising: providing a first dielectric material layer having a first portion of a first thickness and a second portion of a second thickness; forming a bottom electrode on top of the first portion of the first dielectric material layer, the bottom electrode having a surface that is coplanar with a surface of the second portion of the first dielectric material layer; forming a capping dielectric material layer on top said coplanar surface, said capping dielectric material layer of a width covering an interface between a sidewall edge of the bottom electrode and the second portion of the first dielectric material layer; forming a second dielectric material layer on top of the bottom electrode, wherein a length of said second dielectric material layer is of a length less than the length of the bottom electrode, said second dielectric material layer having a surface coplanar with a surface of the capping dielectric material layer; performing a reactive ion etch at a defined angle to form an opening extending through said capping layer and said first dielectric material layer, the opening having a continuous slanted sidewall surface comprising a slanted sidewall surface portion of said capping dielectric material layer and a slanted sidewall surface portion of said first dielectric material layer, the angled etch exposing an edge of the bottom electrode on the continuous slanted sidewall surface; depositing a phase change material (PCM) layer on top said continuous slanted sidewall surface to form an angled PCM layer, whereby the edge of the first electrode electrically contacts the slanted surface of the angled PCM layer.
20 . The method of claim 19 , wherein the defined angle ranges from between 0° and 55° relative to a vertical.

Description

BACKGROUND The present application relates to a memory structure, and more particularly to a diagonal-type phase change material (PCM) memory structure, its method of manufacture, and its operation. Phase change materials (PCMs) have been pursued for a variety of applications such as, for example, storage class memory as well as storing weights of neural networks for artificial intelligence and in-memory computing. In typical PCMs formed as disc cell memory structures, the amount of PCM to melt and change phase can be relatively large requiring one or more high and/or long current pulses to melt the appropriate amount of PCM. This high and/or longer current duration can consume relatively large amounts of energy and use relatively large amounts of power. It is highly desirable to increase the PCM energy efficiency and decrease the footprint of the PCM memory device. SUMMARY A PCM device of a structure comprising an angled geometry. A PCM device of a structure comprising an angled geometry that achieves a large aspect ratio. A PCM device of a structure comprising an angled geometry that achieves a large aspect ratio with bottom electrode point of contact, i.e., the device structure enables a point contact between the PCM channel and the electrode, providing high programming efficiencies. A PCM cell device of a structure comprising a small base with a long PCM channel, wherein the PCM channel is increased without increasing the footprint of the device. In one aspect of the present disclosure, there is provided a phase change memory cell. The phase change memory cell comprises: a first dielectric material layer; a first electrode formed above the first dielectric material layer; a second dielectric material layer formed above the first electrode; a further dielectric material structure having a first sidewall surface portion abutting a side edge of the first dielectric material layer and a second sidewall surface portion abutting a side edge of the second dielectric material layer; and a phase change material (PCM) layer having a first PCM layer portion formed on a top surface of the second dielectric material layer and having an angled PCM layer portion extending from the first PCM layer portion at an angle within the further dielectric material structure and having a slanted surface, the first electrode having an edge electrically contacting the slanted surface of the angled PCM layer In a further aspect, there is provided a phase change memory cell structure. The phase change memory cell structure comprises: a first dielectric material layer; a first electrode formed above the first dielectric material layer; a second dielectric material layer formed above the first electrode; a further dielectric material structure having a first sidewall surface portion abutting a side edge of the first dielectric material layer and a second sidewall surface portion abutting a side edge of the second dielectric material layer; a phase change material (PCM) layer having a first PCM layer portion formed on a top surface of said second dielectric material layer and having an angled PCM layer portion extending from the first PCM layer portion at an angle within said further dielectric material structure and having a second PCM layer portion extending from said angled PCM layer portion within said further dielectric material structure, said angled PCM layer having a slanted surface, wherein an edge of the first electrode electrically contacts the slanted surface of the angled PCM layer; and a second electrode having a first end electrically contacting the first PCM layer portion and having a second end electrically contacting the second PCM layer portion within said further dielectric material structure In a further embodiment, there is provided a method of forming a phase change memory cell. The method comprises: providing a first dielectric material layer having a first portion of a first thickness and a second portion of a second thickness; forming a bottom electrode on top of the first portion of the first dielectric material layer, the bottom electrode having a surface that is coplanar with a surface of the second portion of the first dielectric material layer; forming a capping dielectric material layer on top the coplanar surface, the capping dielectric material layer of a width covering an interface between a sidewall edge of the bottom electrode and the second portion of the first dielectric material layer; forming a second dielectric material layer on top of the bottom electrode, wherein a length of the second dielectric material layer is of a length less than the length of the bottom electrode, the second dielectric material layer having a surface coplanar with a surface of the capping dielectric material layer; performing a reactive ion etch at a defined angle to form an opening extending through the capping layer and the first dielectric material layer, the opening having a continuous slanted sidewall surface comp