Phase change memory unit and preparation method therefor

Patent metadata

Field	Value
Publication number	US-12446478-B2
Application number	US-202118270243-A
Country	US
Kind code	B2
Filing date	Dec 24, 2021
Priority date	Dec 30, 2020
Publication date	Oct 14, 2025
Grant date	Oct 14, 2025

Abstract

The present invention is to provide a phase change memory unit and preparation method thereof. The phase change memory comprises a bottom electrode, a phase change cell, a heating electrode and a top electrode on a substrate from bottom to top. The phase change cell is a column vertically connected to the bottom electrode, which sequentially comprise a columnar phase change material layer, a hollow columnar heat dissipation layer and a hollow columnar switch layer from inside to outside. The top electrode, the heating electrode and the phase change material layer are connected sequentially from top to bottom, the switch layer is connected to the bottom electrode. The present invention adopts a heat dissipation layer wrapping around the phase change material layer to make the current density and the heat distribution more concentrated, thus to keep the effective phase transition region unchanged, reduce the volume of the effective phase transition region and the power consumption, and increase the device reliability.

First claim

What is claimed is:

1. A phase change memory unit, comprising from bottom to top: a bottom electrode, a phase change cell, a heating electrode and a top electrode which are formed on a substrate; wherein,
the phase change cell is a column vertically connected to the bottom electrode, which sequentially comprises a columnar phase change material layer, a hollow columnar heat dissipation layer and a hollow columnar switch layer from inside to outside; the top electrode, the heating electrode and the phase change material layer are connected sequentially from top to bottom, and the switch layer is connected to the bottom electrode, wherein a cross-section of the phase change cell is one or more combinations of a circle, an ellipse, a rectangle, a rhombus and a polygon.

2. The phase change memory unit of claim 1 , wherein the heating electrode is connected to a contact surface of the phase change material layer, the heat dissipation layer wraps around the remaining contact surfaces of the phase change material layer; the heating electrode is longitudinally arranged on a top surface of the phase change material layer, having a bottom arranged within an area of the top surface of the phase change material layer and a top connected to a lower end of the top electrode.

3. The phase change memory unit of claim 1 , wherein an initial state of the phase change material layer is crystalline; material of the phase change material layer comprises at least one of GeTe—Sb 2 Te 3 , GeTe—SnTe, Sb 2 Te, In 3 SbTe 2 , Sb-based material, and GeTe—Sb 2 Te 3 , GeTe—SnTe, Sb 2 Te, In 3 SbTe 2 and Sb-based material which are doped with Sc, Ag, In 2 , Al, In, C, S, Se, N, Cu, W elements.

4. The phase change memory unit of claim 1 , wherein a cross-section of the heating electrode comprises one or more combinations of a ring, a circle, an ellipse, a rectangle, a rhombus and a polygon.

5. The phase change memory unit of claim 1 , wherein thermal conductivity of the material of the heat dissipation layer is greater than 100 W/mK.

6. The phase change memory unit of claim 1 , wherein a switch formed by the switch layer is one of a two-dimensional material transistor, an ovonic threshold switch and a metal oxide thin film resistance switch.

7. The phase change memory unit of claim 1 , wherein material of the heat dissipation layer comprises at least one of graphene, carbon-containing compounds, two-dimensional materials, Ti, W, Ta, Cu, WCN, WN and TaN.

8. A method for preparing a phase change memory unit, comprising:
S1: providing a substrate, depositing a first dielectric layer on the substrate, and forming a bottom electrode in the substrate and the first dielectric layer;
S2: depositing a second dielectric layer on the first dielectric layer, forming a first trench or via in the second dielectric layer on the bottom electrode, the first trench or via penetrating the second dielectric layer;
S3: forming a hollow columnar switch layer, a hollow columnar heat dissipation layer and a columnar phase change material layer sequentially on the second dielectric layer to fill the first trench or via;
S4: removing the switch layer, the heat dissipation layer and the phase change material layer on the second dielectric layer by chemical mechanical polishing to form a phase change cell in the second dielectric layer;
S5: depositing a third dielectric layer on the second dielectric layer, and forming a heating electrode connected to the phase change material layer in the third dielectric layer;
S6: depositing a fourth dielectric layer on the third dielectric layer, and forming a top electrode connected to the heating electrode in the fourth dielectric layer; wherein, the top electrode, the heating electrode and the phase change material layer are connected sequentially from top to bottom, the switch layer is connected to the bottom electrode;
wherein a cross-section of the phase change cell is one or more combinations of a circle, an ellipse, a rectangle, a rhombus and a polygon.

9. The method of claim 8 , wherein in step S2, a horizontal dimension of the first trench or via is less than or equal to a horizontal dimension of a top surface of the bottom electrode; in step S5, a horizontal dimension of the heating electrode is less than a horizontal dimension of a top surface of the phase change material layer.

Assignees

• Shanghai Ic R&D Ct Co Ltd

Inventors

• Zhong Min
• Feng Gaoming

Classifications

• H10B63/10

  Phase change RAM [PCRAM, PRAM] devices · CPC title

• H10N70/231 Primary

  based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect · CPC title

• H10N70/066

  by filling of openings, e.g. damascene method · CPC title

• H10N70/8265

  on sidewalls of dielectric structures, e.g. mesa-shaped or cup-shaped devices · CPC title

• H10N70/8413 Primary

  adapted for resistive heating · CPC title