# US 10,770,305 B2 · Method of atomic layer etching of oxide

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- Number: US 10,770,305 B2
- Document ID: US10770305B2
- Status: Granted
- Kind: B2
- Application number: 16/401,441
- Filed: 2019-05-02
- Published: 2019-11-14
- Granted: 2020-09-08
- Earliest claimed: 2018-05-11
- Assignees: Tokyo Electron Limited
- Applicants: Tokyo Electron Limited
- Inventors: Sonam D. Sherpa; Alok Ranjan
- Web page: https://patentgrep.com/patent/US10770305B2

## CPC

- H10P 50/283: {by chemical means}
- H01J 37/32009: {Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources (plasma generation in general H05H1/24)}
- H01J 2237/3174: Etching microareas
- H10P 76/4085: {characterised by the processes involved to create the masks}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

In one exemplary embodiment, described herein is an ALE process for etching an oxide. In one embodiment, the oxide is silicon oxide. The ALE modification step includes the use of a carbon tetrafluoride (CF4) based plasma. This modification step preferentially removes oxygen from the surface of the silicon oxide, providing a silicon rich surface. The ALE removal step includes the use of a hydrogen (H2) based plasma. This removal step removes the silicon enriched monolayer formed in the modification step. The silicon oxide etch ALE process utilizing CF4 and H2 steps may be utilized in a wide range of substrate process steps. For example, the ALE process may be utilized for, but is not limited to, self-aligned contact etch steps, silicon fin reveal steps, oxide mandrel pull steps, oxide spacer trim, and oxide liner etch.

## Claims

### Claim 1

A method for etching a substrate, comprising:
providing a first layer comprising silicon oxide, the first layer to be etched selective to a second layer;
exposing the first layer to a first plasma comprising carbon tetrafluoride (CF4) to modify at least a surface of the first layer to form a modified surface layer, the modified surface layer being silicon rich compared to a remainder of the first layer; and
exposing the modified surface layer to a second plasma comprising hydrogen (H2), the plasma comprising H2 removing at least a portion of the modified surface layer,
wherein a combination of use of the first plasma and the second plasma reduces at least a portion of a thickness of the first layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein multiple cycles of the exposing the first layer to the first plasma comprising CF4 and exposing the modified surface layer to the second plasma comprising H2 are performed.

### Claim 3 (depends on 1)

The method of claim 1, wherein the method for etching the substrate is part of a self-aligned contact application.

### Claim 4 (depends on 1)

The method of claim 1, wherein the method for etching the substrate is part of a fin reveal application.

### Claim 5 (depends on 1)

The method of claim 1, wherein the method for etching the substrate is part of an oxide mandrel pull application.

### Claim 6 (depends on 1)

The method of claim 1, wherein the method for etching the substrate is part of a silicon oxide spacer trim application.

### Claim 7 (depends on 1)

The method of claim 1, wherein the method for etching the substrate is part of a silicon oxide liner etch application.

### Claim 8

A method for etching a substrate, comprising:
providing a first layer comprising silicon oxide; and
performing an atomic layer etch process to etch the first layer, the atomic layer etch process comprising, multiple cycles of (1) a surface modification step comprising a first plasma, the first plasma comprising carbon tetrafluoride (CF4) and (2) a removal step following the surface modification step, the removal step comprising a second plasma, the second plasma comprising hydrogen (H2).

### Claim 9 (depends on 8)

The method of claim 8, wherein the method for etching the substrate is part of a self-aligned contact application.

### Claim 10 (depends on 8)

The method of claim 8, wherein the method for etching the substrate is part of a fin reveal application.

### Claim 11 (depends on 8)

The method of claim 8, wherein the method for etching the substrate is part of an oxide mandrel pull application.

### Claim 12 (depends on 8)

The method of claim 8, wherein the method for etching the substrate is part of a silicon oxide spacer trim application.

### Claim 13 (depends on 8)

The method of claim 8, wherein the method for etching the substrate is part of a silicon oxide liner etch application.

### Claim 14

A method for reducing a thickness of a silicon oxide layer on a substrate, comprising:
performing at least one cycle of (a) exposing the silicon oxide layer to a perfluorinated hydrocarbon plasma to modify a surface of the silicon oxide substrate followed by (b) exposing a product of step (a) to an elemental hydrogen (H2) plasma to remove at least a portion of the surface modified in step (a).

### Claim 15 (depends on 14)

The method of claim 14, wherein the method is part of a self-aligned contact application.

### Claim 16 (depends on 14)

The method of claim 14, wherein the method is part of a fin reveal application.

### Claim 17 (depends on 14)

The method of claim 14, wherein the method is part of an oxide mandrel pull application.

### Claim 18 (depends on 14)

The method of claim 14, wherein the method is part of a silicon oxide spacer trim application.

### Claim 19 (depends on 14)

The method of claim 14, wherein the method is part of a silicon oxide liner etch application.

### Claim 20 (depends on 14)

The method of claim 14, wherein the perfluorinated hydrocarbon is carbon tetrafluoride (CF4).