# US 10,319,649 B2 · Optical emission spectroscopy (OES) for remote plasma monitoring

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- Number: US 10,319,649 B2
- Document ID: US10319649B2
- Status: Granted
- Kind: B2
- Application number: 15/484,985
- Filed: 2017-04-11
- Published: 2018-10-11
- Granted: 2019-06-11
- Earliest claimed: 2017-04-11
- Assignees: Applied Materials, Inc.
- Applicants: Applied Materials, Inc.
- Inventors: Tae Seung Cho; Soonam Park; Junghoon Kim; Dmitry Lubomirsky; Shankar Venkataraman
- Web page: https://patentgrep.com/patent/US10319649B2

## CPC

- H01J 37/3411: {Constructional aspects of the reactor}
- G01J 3/0218: {using optical fibers}
- G01J 3/443: Emission spectrometry
- G01N 21/73: using plasma burners or torches
- H01J 37/32568: {Relative arrangement or disposition of electrodes; moving means}
- H01J 37/32743: {for introducing the material into processing chamber}
- H01J 37/32972: {Spectral analysis}
- H10P 50/283: {by chemical means}
- H10P 72/0604: {Process monitoring, e.g. flow or thickness monitoring}
- G01N 2201/08: Optical fibres; light guides
- G01N 2201/0833: Fibre array at detector, resolving
- H01J 37/32082: {Radio frequency generated discharge (H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence)}
- H01J 2237/3341: Reactive etching
- H10P 74/238: {comprising acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection or in-situ thickness measurement}
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Methods and systems for etching substrates using a remote plasma are described. Remotely excited etchants are formed in a remote plasma and flowed through a showerhead into a substrate processing region to etch the substrate. Optical emission spectra are acquired from the substrate processing region just above the substrate. The optical emission spectra may be used to determine an endpoint of the etch, determine the etch rate or otherwise characterize the etch process. A weak plasma may be present in the substrate processing region. The weak plasma may have much lower intensity than the remote plasma. In cases where no bias plasma is used above the substrate in an etch process, a weak plasma may be ignited near a viewport disposed near the side of the substrate processing region to characterize the etchants.

## Claims

### Claim 1

A method of etching a substrate, the method comprising:
placing the substrate in a substrate processing region of a substrate processing chamber;
flowing a fluorine-containing precursor into a remote plasma region separated from the substrate processing region by a showerhead;
forming a remote plasma having a remote plasma power in the remote plasma region;
producing plasma effluents from the fluorine-containing precursor in the remote plasma in the remote plasma region;
flowing the plasma effluents through the showerhead into the substrate processing region;
etching the substrate with the plasma effluents;
forming a local plasma having a local plasma power in the substrate processing region while maintaining the remote plasma and etching the substrate, wherein the remote plasma power of the remote plasma exceeds the local plasma power of the local plasma by a factor of ten or more;
acquiring an optical emission spectrum through a viewport affixed to a side of the substrate processing chamber and forming a border of the substrate processing region, wherein the optical emission spectrum represents intensity as a function of optical wavelength, and wherein the optical emission spectrum is acquired with an optical emission spectrometer;
determining a fluorine signal from the optical emission spectrum; and
determining an etch rate of the substrate based on the fluorine signal, wherein the fluorine signal is linearly correlated with the etch rate of the substrate.

### Claim 2 (depends on 1)

The method of claim 1, wherein the local plasma is centered over the substrate.

### Claim 3 (depends on 1)

The method of claim 1, wherein the local plasma is disposed above the substrate and outside an edge of the substrate near the viewport.

### Claim 4 (depends on 3)

The method of claim 3, wherein the local plasma is formed using an electrode that is different from electrodes used for forming the remote plasma and that is disposed on the outside of the viewport, and wherein the local plasma power is applied between the electrode and the substrate processing chamber.

### Claim 5 (depends on 3)

The method of claim 3, wherein the local plasma is formed using a first electrode and a second electrode that are different from electrodes used for forming the remote plasma, wherein the first electrode and the second electrode are each disposed on the outside of the viewport, and wherein the local plasma power is applied between the first electrode and the second electrode.

### Claim 6 (depends on 1)

The method of claim 1, wherein the local plasma is formed outside a radial edge of the substrate and proximate the viewport, and wherein a region that is within the substrate processing region and above the substrate is plasma free.

### Claim 7 (depends on 1)

The method of claim 1, further comprising etching the substrate with the local plasma, wherein the local plasma is a bias plasma.

### Claim 8

A method of etching a substrate, the method comprising:
placing the substrate in a substrate processing region of a substrate processing chamber;
flowing a fluorine-containing precursor into a remote plasma region separated from the substrate processing region by a showerhead;
forming a remote plasma having a remote plasma power in the remote plasma region;
producing plasma effluents from the fluorine-containing precursor in the remote plasma in the remote plasma region;
flowing the plasma effluents through the showerhead into the substrate processing region;
etching the substrate with the plasma effluents, wherein an electron temperature within the substrate processing region is less than 0.5 eV while etching the substrate;
forming a local plasma having a local plasma power in the substrate processing region while maintaining the remote plasma and etching the substrate, wherein the remote plasma power of the remote plasma exceeds the local plasma power of the local plasma by a factor of ten or more;
acquiring an optical emission spectrum through a viewport affixed to a side of the substrate processing chamber and forming a border of the substrate processing region, wherein the optical emission spectrum represents intensity as a function of optical wavelength and the optical emission spectrum is acquired with an optical emission spectrometer;
determining at least one signal from the optical emission spectrum; and
determining an etch rate of the substrate based on the at least one signal, wherein the at least one signal is linearly correlated with the etch rate of the substrate.

### Claim 9 (depends on 8)

The method of claim 8, wherein a pressure in the substrate processing region and in the remote plasma region while etching the substrate is between 0.01 Torr and 50 Torr.

### Claim 10 (depends on 8)

The method of claim 8, wherein a temperature of the substrate while etching the substrate is between −20° C. and 450° C.

### Claim 11 (depends on 8)

The method of claim 8, wherein the at least one signal comprises a fluorine signal from the optical emission spectrum.

### Claim 12 (depends on 8)

The method of claim 8, wherein the at least one signal comprises a fluorine signal representing a concentration of excited fluorine from both the remote plasma and the local plasma.

### Claim 13 (depends on 8)

The method of claim 8, further comprising passing an electron beam above the substrate.

### Claim 14 (depends on 8)

The method of claim 8, further comprising passing an electron beam as a laminar sheet above the substrate.

### Claim 15

A method of etching a substrate, the method comprising:
flowing a fluorine-containing precursor into a remote plasma region of a substrate processing chamber;
forming a remote plasma having a remote plasma power in the remote plasma region to produce plasma effluents;
flowing the plasma effluents into a substrate processing region separated from the remote plasma region by a showerhead, wherein the substrate is housed in the substrate processing region;
etching the substrate with the plasma effluents;
forming a local plasma having a local plasma power in the substrate processing region while maintaining the remote plasma and etching the substrate, wherein the local plasma is formed outside a radial edge of the substrate and proximate a viewport affixed to a side of the substrate processing chamber and forming a border of the substrate processing region, wherein a region that is within the substrate processing region and above the substrate is plasma free;
acquiring an optical emission spectrum through the viewport;
determining at least one signal from the optical emission spectrum; and
determining an etch rate of the substrate based on the at least one signal, wherein the at least one signal is linearly correlated with the etch rate of the substrate.

### Claim 16 (depends on 15)

The method of claim 15, wherein the remote plasma power of the remote plasma exceeds the local plasma power of the local plasma by a factor of ten or more.

### Claim 17 (depends on 15)

The method of claim 15, wherein the at least one signal comprises a fluorine signal.

### Claim 18 (depends on 15)

The method of claim 15, further comprising passing an electron beam as a laminar sheet above the substrate in the substrate processing region, and wherein an electron temperature within the substrate processing region is less than 0.5 eV while etching the substrate.