# US 8,647,439 B2 · Method of epitaxial germanium tin alloy surface preparation

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- Number: US 8,647,439 B2
- Document ID: US8647439B2
- Status: Granted
- Kind: B2
- Application number: 13/456,500
- Filed: 2012-04-26
- Published: 2013-10-31
- Granted: 2014-02-11
- Earliest claimed: 2012-04-26
- Assignees: Applied Materials, Inc.
- Applicants: Errol Antonio C. Sanchez; Yi-Chiau Huang
- Inventors: Errol Antonio C. Sanchez; Yi-Chiau Huang
- Web page: https://patentgrep.com/patent/US8647439B2

## CPC

- H10P 14/3602: {In-situ cleaning}
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/3211: {Silicon, silicon germanium or germanium}
- H10P 14/3212: {including tin}
- H10P 14/3411: {Silicon, silicon germanium or germanium}
- H10P 14/3412: {including tin}
- H10P 14/3442: {N-type}
- H10P 14/3444: {P-type}
- H10P 50/242: {of Group IV materials}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Methods of preparing a clean surface of germanium tin or silicon germanium tin layers for subsequent deposition are provided. An overlayer of Ge, doped Ge, another GeSn or SiGeSn layer, a doped GeSn or SiGeSn layer, an insulator, or a metal can be deposited on a prepared GeSn or SiGeSn layer by positioning a substrate with an exposed germanium tin or silicon germanium tin layer in a processing chamber, heating the processing chamber and flowing a halide gas into the processing chamber to etch the surface of the substrate using either thermal or plasma assisted etching followed by depositing an overlayer on the substantially oxide free and contaminant free surface. Methods can also include the placement and etching of a sacrificial layer, a thermal clean using rapid thermal annealing, or a process in a plasma of nitrogen trifluoride and ammonia gas.

## Claims

### Claim 1

A method of preparing a clean GeSn or SiGeSn surface, comprising:
positioning a substrate in a processing chamber, wherein the substrate comprises an exposed GeSn or SiGeSn layer;
heating the processing chamber to a first temperature;
flowing an etching gas into the processing chamber at the first temperature, wherein the etching gas comprises a halide gas;
etching the surface of the substrate at the first temperature using either thermal etching or plasma assisted etching to create a cleaned surface; and
depositing an overlayer on top of the cleaned surface, wherein the overlayer comprises one of Ge, doped Ge, a GeSn layer, a SiGeSn layer, a doped GeSn layer, a doped SiGeSn layer, an insulator, or a metal.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first temperature is from 300° C. to 400° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein the halide gas is chlorine or hydrogen chloride.

### Claim 4 (depends on 1)

The method of claim 1, wherein the dopant comprises one of phosphorus (P), boron (B), or arsenic (As).

### Claim 5

A method of preparing a clean GeSn or SiGeSn surface, comprising:
positioning a substrate in a first processing chamber, wherein the substrate comprises a GeSn or SiGeSn layer with a sacrificial protective Ge cap, and wherein the sacrificial protective Ge cap is formed after GeSn or SiGeSn formation but before exposure to oxygen or contaminants;
transferring the substrate to a second processing chamber;
heating the second processing chamber to a first temperature;
flowing an etching gas into the second processing chamber at the first temperature, wherein the etching gas comprises a halide gas;
etching the sacrificial cap at the first temperature using either thermal etching or plasma assisted etching, as to expose a clean GeSn or SiGeSn layer; and
depositing an overlayer on top of the cleaned surface, wherein the overlayer comprises one of Ge, doped Ge, a GeSn layer, a SiGeSn layer, a doped GeSn layer, a doped SiGeSn layer, an insulator, or a metal.

### Claim 6 (depends on 5)

The method of claim 5, wherein the sacrificial protective Ge cap is from 20 Å to 40 Å thick.

### Claim 7 (depends on 5)

The method of claim 5, wherein the first temperature is from 300° C. to 400° C.

### Claim 8 (depends on 5)

The method of claim 5, wherein the halide gas is chlorine or hydrogen chloride.

### Claim 9 (depends on 5)

The method of claim 5, wherein the dopant comprises one of phosphorus (P), boron (B), or arsenic (As).

### Claim 10

A method of preparing a clean GeSn or SiGeSn surface, comprising:
positioning a substrate in a processing chamber, wherein the substrate comprises an exposed GeSn or SiGeSn layer;
flowing H2 into the chamber while maintaining a constant pressure; heating the chamber to a first temperature while maintaining the flow of H2 to create a cleaned surface, wherein the temperature is higher than 450° C. and is maintained for a period of time;
cooling the chamber to a temperature below 400° C.; and
depositing an overlayer on top of the cleaned surface, wherein the overlayer comprises one of Ge, doped Ge, a GeSn layer, a SiGeSn layer, a doped GeSn layer, a doped SiGeSn layer, an insulator, or a metal.

### Claim 11 (depends on 10)

The method of claim 10, wherein the first temperature is from 450° C. to 650° C.

### Claim 12 (depends on 10)

The method of claim 10, wherein the dopant comprises one of phosphorus (P), boron (B), or arsenic (As).

### Claim 13 (depends on 10)

The method of claim 10, wherein the period of time is less than 1 minute.

### Claim 14 (depends on 10)

The method of claim 10, further comprising applying UV light while heating to the first temperature.

### Claim 15

A method of preparing a clean GeSn or SiGeSn surface, comprising:
positioning a substrate in a processing chamber, wherein the substrate comprises an exposed GeSn or SiGeSn layer with one or more surface contaminants;
adjusting the processing chamber to a first temperature;
flowing an NF3 and NH3 plasma gas mixture into the processing chamber at the first temperature to form a salt mixture, wherein the salt mixture comprises the surface contaminants;
heating the substrate to a second temperature to sublimate the salt mixture, creating a cleaned surface;
positioning the cleaned substrate to a deposition chamber, wherein a vacuum is maintained; and
depositing an overlayer on top of the cleaned surface, wherein the overlayer comprises one of Ge, doped Ge, a GeSn layer, a SiGeSn layer, a doped GeSn layer, a doped SiGeSn layer, an insulator, or a metal.

### Claim 16 (depends on 15)

The method of claim 15, wherein the first temperature is from 20° C. to 60° C.

### Claim 17 (depends on 15)

The method of claim 15, wherein the second temperature is from 80° C. to 150° C.

### Claim 18 (depends on 15)

The method of claim 15, wherein the dopant comprises one of phosphorus (P), boron (B), or arsenic (As).