# US 10,873,023 B2 · Using aluminum as etch stop layer

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- Number: US 10,873,023 B2
- Document ID: US10873023B2
- Status: Granted
- Kind: B2
- Application number: 15/468,847
- Filed: 2017-03-24
- Published: 2017-10-05
- Granted: 2020-12-22
- Earliest claimed: 2016-03-31
- Assignees: Crossbar, Inc.
- Applicants: Crossbar, Inc.
- Inventors: Sundar Narayanan; Natividad Vasquez; Zhen Gu; Yunyu Wang
- Web page: https://patentgrep.com/patent/US10873023B2

## CPC

- H10N 70/826: {adapted for essentially vertical current flow, e.g. sandwich or pillar type devices}
- H10N 70/063: {by etching of pre-deposited switching material layers, e.g. lithography}
- H10N 70/20: Multistable switching devices, e.g. memristors
- H10N 70/841: {Electrodes}
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A two-terminal resistive switching device (TTRSD) such as a non-volatile two-terminal memory device or a volatile two-terminal selector device can be formed according to a manufacturing process. The process can include forming an etch stop layer that is made of aluminum and can include forming a buffer layer below the etch stop layer and/or between the etch stop layer and a top electrode of the TTRSD.

## Claims

### Claim 1

A method, comprising:
forming layers of a two-terminal resistive switching device;
forming a buffer layer overlaying and in contact with a top electrode layer of the layers of the two-terminal resistive switching device, wherein the top electrode layer at least in part comprises an aluminum material;
forming an etch stop layer comprising at least in part the aluminum material and overlaying and in contact with the buffer layer;
forming a top cap layer comprising TiN or TaN overlaying and in contact with the etch stop layer;
etching with a first etch procedure of a two-step etch at least a portion of the top cap layer and terminating the first etch procedure when the etch stop layer comprising aluminum is reached, wherein the first etch procedure comprises employing a chemical etch procedure, and wherein the terminating the etching comprises terminating the chemical etch procedure in response to an indication that the aluminum of the etch stop layer has been exposed; and
etching with a second etch procedure of the two-step etch a portion of the etch stop layer exposed by the first etch procedure and respective portions of the buffer layer and of the top electrode layer underlying the portion of the etch stop layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein the two-terminal resistive switching device is a non-volatile two-terminal memory device.

### Claim 3 (depends on 1)

The method of claim 1, wherein the forming the layers of the two-terminal resistive switching device comprises forming the top electrode layer from a material selected from a group consisting of: aluminum (Al), an aluminum compound, and an aluminum mixture.

### Claim 4 (depends on 1)

The method of claim 1, wherein the buffer layer comprises titanium nitride (TiN) and the top cap layer comprises TiN.

### Claim 5 (depends on 1)

The method of claim 1, wherein the forming the buffer layer further comprises providing the buffer layer with a thickness in a first range of between 100 angstroms to 150 angstroms, and wherein the forming the etch stop layer further comprises providing the etch stop layer with a thickness in a second range of between 100 angstroms to 200 angstroms, and wherein the forming the top cap layer comprises providing the top cap layer with a thickness in a third range of between 300 angstroms to 500 angstroms.

### Claim 6 (depends on 1)

The method of claim 1, further comprising determining the indication that aluminum of the etch stop layer has been exposed using a spectral emission measurement device.

### Claim 7 (depends on 1)

The method of claim 1, wherein the employing the chemical etch procedure further comprises employing an etchant selected from a group consisting of: boron trichloride (BCl3), chlorine (Cl), and a compound comprising Cl, Cl2, or BCl3.

### Claim 8 (depends on 1)

The method of claim 1, wherein the second etch procedure comprises a physical etch procedure utilizing an argon plasma etch or a H2 plasma etch that removes the portion of the etch stop layer and the respective portions of the buffer layer and of the top electrode layer.

### Claim 9 (depends on 8)

The method of claim 8, wherein the implementing the second etch procedure comprising the physical etch procedure further comprises removing respective portions of materials of all of the layers of the two-terminal resistive switching device underlying the portion of the etch stop layer exposed by the etching of the portion of the top cap layer.

### Claim 10

A method, comprising:
forming layers of a two-terminal resistive switching device, comprising a top electrode layer comprising aluminum, a bottom electrode layer, and an interface layer;
forming an etch stop layer comprising aluminum overlaying the top electrode layer;
forming a top cap layer from a material selected from a group consisting of: TiN and TaN overlaying and in contact with the etch stop layer;
employing a first chemical etching procedure comprising etching at least a portion of the top cap layer and stopping the etching in response to the first chemical etching procedure exposing aluminum material of the etch stop layer; and
employing a second etching procedure comprising removing a portion of the etch stop layer exposed by the first chemical etching procedure and a portion at least of the top electrode layer of the two-terminal resistive switching device underlying the portion of the etch stop layer.

### Claim 11 (depends on 10)

The method of claim 10, further comprising forming a buffer layer overlaying and in contact with the top electrode layer.

### Claim 12 (depends on 10)

The method of claim 10, wherein the employing the first chemical etching procedure further comprises employing a chemical etching procedure utilizing an etchant selected from a group consisting of: boron trichloride (BCl3), chlorine (Cl), and a compound comprising Cl, Cl2, or BCl3.

### Claim 13 (depends on 10)

The method of claim 10, wherein the second etching procedure comprises an argon plasma etch or a H2 plasma etch that removes the portion of the etch stop layer and the portion at least of the top electrode layer of the two-terminal resistive switching device.

### Claim 14 (depends on 13)

The method of claim 13, wherein forming the layers of the two-terminal resistive switching device further comprise forming a buffer layer overlying and in contact with the top electrode layer and underlying and in contact with the etch stop layer, wherein the employing the second etching procedure further comprises removing a portion of the buffer layer together with the portion of the etch stop layer and the portion at least of the top electrode layer of the two-terminal resistive switching device.

### Claim 15 (depends on 13)

The method of claim 13, wherein the employing the second-etching procedure further comprises removing respective portions of the bottom electrode layer and the interface layer of the two-terminal resistive switching device underlying the portion of the etch stop layer exposed by the first chemical etching procedure.

### Claim 16 (depends on 14)

The method of claim 14, further comprising forming the buffer layer of a second material selected from the group consisting of: TiN and TaN.

### Claim 17 (depends on 16)

The method of claim 16, further comprising forming the buffer layer with a thickness in a first range of between 100 angstroms to 150 angstroms.

### Claim 18 (depends on 17)

The method of claim 17, further comprising forming the etch stop layer with a second thickness in a second range of between 100 angstroms to 200 angstroms.

### Claim 19 (depends on 18)

The method of claim 18, further comprising forming the top cap layer with a third thickness in a third range of between 300 angstroms and 500 angstroms.

### Claim 20 (depends on 10)

The method of claim 10, further comprising utilizing the same material containing aluminum for the top electrode layer and for the etch stop layer.