# US 12,225,834 B2 · Method for forming semiconductor structure

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- Number: US 12,225,834 B2
- Document ID: US12225834B2
- Status: Granted
- Kind: B2
- Application number: 17/335,831
- Filed: 2021-06-01
- Published: 2021-09-16
- Granted: 2025-02-11
- Earliest claimed: 2017-11-21
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Company Ltd.
- Inventors: Hsing-Lien Lin; Hai-Dang Trinh; Fa-Shen Jiang
- Web page: https://patentgrep.com/patent/US12225834B2

## CPC

- H10N 70/231: {based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect}
- H10N 70/011: {Manufacture or treatment of multistable switching devices}
- H10N 70/066: {by filling of openings, e.g. damascene method}
- H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices}
- H10N 70/841: {Electrodes}
- H10N 70/8413: {adapted for resistive heating}
- H10N 70/8613: {Heating or cooling means other than resistive heating electrodes, e.g. heater in parallel}
- H10B 63/30: {comprising selection components having three or more electrodes, e.g. transistors}
- H10N 70/8828: {Tellurides, e.g. GeSbTe}
- H10N 70/884: {based on at least one element of group IIIA, IVA or VA, e.g. elemental or compound semiconductors (compounds of sulfur, selenium or tellurium, e.g. chalcogenides H10N70/882; oxides or nitrides H10N70/883)}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

A method for forming a semiconductor structure includes following operations. A first conductive layer is formed. A first dielectric layer is formed over the first conductive layer, and the first dielectric layer includes at least one trench exposing the first conductive layer. A second conductive layer is formed in the trench. A third conductive layer is formed in the trench, and a resistivity of the third conductive layer is greater than a resistivity of the second conductive layer. A second dielectric layer is formed over the third conductive layer. A phase change material is formed over the first dielectric layer.

## Claims

### Claim 1

A method for forming a semiconductor structure, comprising:
forming a first metal layer, wherein a material of the first metal layer is selected from the group consisting of tungsten (W), aluminum (Al), and aluminum copper (AlCu);
forming a first dielectric layer over the first metal layer, the first dielectric layer comprising at least one trench exposing the first metal layer, wherein a bottom surface of the first dielectric layer is aligned with a top surface of the first metal layer;
forming a second metal layer in the trench, wherein a material of the second metal layer is selected from the group consisting of tantalum (Ta), titanium nitride (TiN), tungsten nitride (WN), tungsten (W), palladium (Pd), nickel chromium (NiCr), zirconium (Zr), and niobium (Nb);
forming a third metal layer in the trench, wherein a resistivity of the third metal layer is greater than a resistivity of the second metal layer, and a material of the third metal layer is selected from the group consisting of titanium nitride (TiN), tantalum nitride (TaN), and tantalum aluminum nitride (TaAlN);
forming a second dielectric layer over the third metal layer; and
forming a phase change material over the first dielectric layer,
wherein a top surface of the third metal layer is entirely in contact with the phase change material.

### Claim 2 (depends on 1)

The method of claim 1, wherein the material of the first metal layer is different from the material of the second metal layer.

### Claim 3 (depends on 1)

The method of claim 1, wherein the material of the second metal layer is different from the material of the third metal layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the material of the second metal layer and the material of the third metal layer are the same.

### Claim 5 (depends on 1)

The method of claim 1, further comprising forming a fourth metal layer over the phase change material.

### Claim 6

A method for forming a semiconductor structure, comprising:
forming a first dielectric layer over a first metal layer, wherein a material of the first conductive layer is selected from the group consisting of W, Al and AlCu;
exposing the first metal layer through a bottom of a trench in the first dielectric layer;
forming a second metal layer in the trench and covering a top surface of the first dielectric layer, wherein a material of the second metal layer is selected from the group consisting of Ta, TiN, WN, W, Pd, NiCr, Zr, and Nb;
removing a portion of the second metal layer such that a top surface of the second metal layer is lower than the top surface of the first dielectric layer;
forming a third metal layer in the trench and covering the first dielectric layer, wherein a material of the third conductive layer is selected from the group consisting of TiN, TaN, and TaAlN;
forming a second dielectric layer over the third metal layer and the first dielectric layer;
removing a portion of the third metal layer and a portion of the second dielectric layer to expose the top surface of the first dielectric layer; and
forming a phase change material over the first dielectric layer, the second dielectric layer and the third metal layer,
wherein a top surface of the third metal layer is entirely in contact with the phase change material.

### Claim 7 (depends on 6)

The method of claim 6, wherein the material of the first metal layer is different from the material of the second metal layer.

### Claim 8 (depends on 6)

The method of claim 6, wherein a top surface of the second dielectric layer is in contact with the phase change material.

### Claim 9 (depends on 6)

The method of claim 6, wherein a resistivity of the third metal layer is greater than a resistivity of the second metal layer.

### Claim 10 (depends on 6)

The method of claim 6, wherein a thickness of the second metal layer is greater than a thickness of the third metal layer.

### Claim 11 (depends on 6)

The method of claim 6, further comprising forming a fourth metal layer over the phase change material.

### Claim 12 (depends on 11)

The method of claim 11, further comprising forming a fifth metal layer over the fourth metal layer, and the fifth metal layer is in contact with the fourth metal layer.

### Claim 13 (depends on 11)

The method of claim 11, further comprising:
forming a conductor over the fourth metal layer; and
forming a fifth metal layer over the conductor,
wherein the fourth metal layer is electrically connected to the fifth metal layer by the conductor.

### Claim 14

A method for forming a semiconductor structure, comprising:
forming a first dielectric layer over a lower conductive layer, the first dielectric layer comprising at least one trench exposing the lower conductive layer, wherein a bottom surface of the first dielectric layer is aligned with a top surface of the lower conductive layer, wherein a material of the lower conductive layer is selected from the group consisting of tungsten (W), aluminum (Al), and aluminum copper (AlCu);
forming a heat-buffering layer in the trench, wherein a material of the heat-buffering layer is selected from the group consisting of tantalum (Ta), titanium nitride (TiN), tungsten nitride (WN), tungsten (W), palladium (Pd), nickel chromium (NiCr), zirconium (Zr), and niobium (Nb);
stacking a heat-spreading layer over the heat-buffering layer in the trench;
filling the trench with a second dielectric layer;
disposing a phase change material over the first dielectric layer; and
forming a top electrode over the phase change material,
wherein the second dielectric layer, the heat-spreading layer, and the heat-buffering layer form a bottom electrode, and a resistivity of the heat-buffering layer is less than a resistivity of the heat-spreading layer.

### Claim 15 (depends on 14)

The method of claim 14, wherein a thickness of the heat-buffering layer is greater than a thickness of the heat-spreading layer.

### Claim 16 (depends on 14)

The method of claim 14, wherein a top surface of the second dielectric layer is entirely in contact with the phase change material.

### Claim 17 (depends on 14)

The method of claim 14, further comprising forming an upper conductive layer over the top electrode.

### Claim 18 (depends on 17)

The method of claim 17, wherein the top electrode is in contact with the upper conductive layer.

### Claim 19 (depends on 17)

The method of claim 17, further comprising a conductor electrically connecting the top electrode and the upper conductive layer.

### Claim 20 (depends on 14)

The method of claim 14, wherein a sidewall of the heat-spreading layer is aligned with a sidewall of the heat-buffering layer.