# US 9,431,255 B2 · Method for etching high-k metal gate stack

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- Number: US 9,431,255 B2
- Document ID: US9431255B2
- Status: Granted
- Kind: B2
- Application number: 14/738,343
- Filed: 2015-06-12
- Published: 2016-06-23
- Granted: 2016-08-30
- Earliest claimed: 2014-12-19
- Assignees: SK hynix Inc.
- Applicants: SK hynix Inc.
- Inventors: Su-Bum Shin; Hae-Jung Lee
- Web page: https://patentgrep.com/patent/US9431255B2

## CPC

- H10D 64/01328: {by defining the conductor using a sidewall spacer mask, a transformation under a mask or a plating at a sidewall}
- H10B 41/43: comprising only one type of peripheral transistor
- H10D 64/01: Manufacture or treatment
- H10D 64/01318: {the conductor comprising a layer of alloy material, compound material or organic material contacting the insulator, e.g. TiN (comprising a layer of alloys of Si, Ge or C H10D64/01314)}
- H10D 64/667: {the conductor comprising a layer of alloy material, compound material or organic material contacting the insulator, e.g. TiN workfunction layers (having lateral variation H10D64/671)}
- H10D 84/0181: {Manufacturing their gate insulating layers}
- H10D 84/038: {using silicon technology, e.g. SiGe}
- H10P 50/267: {using plasmas}
- H10P 50/268: {of silicon-containing layers}
- H10P 50/283: {by chemical means}
- H10P 50/285: {of materials not containing Si, e.g. PZT or Al2O3}
- H10P 50/73: {using masks for insulating materials}
- H10P 70/23: {during, before or after processing of insulating materials}
- H10D 64/685: {being perpendicular to the channel plane}
- H10D 64/691: {comprising metallic compounds, e.g. metal oxides or metal silicates (insulators comprising nitrogen H10D64/693)}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10B: ELECTRONIC MEMORY DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A method for etching a gate includes forming a high-k material layer over a substrate; forming an overlying layer over the high-k material layer; performing a first etching process for etching the overlying layer to form an overlying layer pattern; forming a spacer on a sidewall of the overlying layer pattern; and performing a second etching process using plasma including a etch gas and an additive gas, to etch the high-k material layer, wherein an amount of the additive gas is substantially the same as the main etch gas to increase an etch selectivity with respect to the substrate.

## Claims

### Claim 1

A method for forming a gate, the method comprising:
forming a high-k material layer over a substrate;
forming an overlying layer over the high-k material layer;
performing a first etching process for etching the overlying layer to form an overlying layer pattern;
forming a spacer on a sidewall of the overlying layer pattern; and
performing a second etching process using plasma including a etch gas and an additive gas, to etch the high-k material layer,
wherein an amount of the additive gas is substantially the same as the main etch gas to increase an etch selectivity with respect to the substrate,
wherein the second etching process is performed at a temperature higher than the first etching process.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the main etch gas includes BCl3.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the additive gas includes argon.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the high-k material layer includes a hafnium-containing layer.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the first etching process and the second etching process are performed in inductively coupled plasma equipment.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the second etching process is performed by applying bias power larger than 10 W.

### Claim 7 (depends on 1)

The method according to claim 1, further comprising:
performing hydrogen fluoride (HF)-based wet cleaning after the second etching process.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the first etching process is performed at 50 degrees Celsius, and
wherein the second etching process is performed at 220 degrees Celsius.

### Claim 9 (depends on 1)

The method according to claim 1, wherein the overlying layer includes a work function adjustment layer, a silicon-based capping layer over the work function adjustment layer, and a metal gate electrode layer over the silicon-based capping layer.

### Claim 10 (depends on 9)

The method according to claim 9, wherein the first etching process includes:
a first sub etching process for etching the silicon-based capping layer; and
a second sub etching process for etching the work function adjustment layer.

### Claim 11 (depends on 10)

The method according to claim 10,
wherein the first sub etching process includes a main etching process and an over etching process, and
wherein the over etching process is performed using an etchant which has a selectivity equal to or higher than 10 with respect to the work function adjustment layer.

### Claim 12 (depends on 11)

The method according to claim 11, wherein the over etching process is performed using plasma including a bromine-containing gas and an oxygen-containing gas.

### Claim 13 (depends on 10)

The method according to claim 10, wherein the second sub etching process is performed using plasma including a chlorine-containing gas and argon gas.

### Claim 14 (depends on 1)

The method according to claim 1, wherein the overlying layer includes a rare earth metal-based capping layer, a work function adjustment layer over the rare earth metal-based capping layer, a silicon-based capping layer over the work function adjustment layer, and a metal gate electrode layer over the silicon-based capping layer.

### Claim 15 (depends on 14)

The method according to claim 14, wherein the first etching process includes:
a first sub etching process for etching the silicon-based capping layer;
a second sub etching process for etching the work function adjustment layer; and
a third sub etching process for etching the rare earth metal-based capping layer.

### Claim 16 (depends on 15)

The method according to claim 15,
wherein the first sub etching process includes (i) a main etching process which is performed until the work function adjustment layer is exposed and (ii) an over etching process which is performed after the work function adjustment layer is exposed, and
wherein the over etching process is performed using plasma which has a selectivity equal to or higher than 10 with respect to the work function adjustment layer.

### Claim 17 (depends on 16)

The method according to claim 16, wherein the over etching process is performed using plasma including a bromine-containing gas and oxygen gas.

### Claim 18 (depends on 15)

The method according to claim 15, wherein the second sub etching process is performed using plasma including a chlorine-containing gas and argon gas.

### Claim 19 (depends on 15)

The method according to claim 15, wherein the third sub etching process is performed using plasma including HCl.