Sub-millisecond optical detection of pulsed plasma processes

Patent metadata

Field	Value
Publication number	US-2025157801-A1
Application number	US-202318505810-A
Country	US
Kind code	A1
Filing date	Nov 9, 2023
Priority date	Nov 9, 2023
Publication date	May 15, 2025
Grant date	—

Abstract

An optical emission spectroscopy (OES) detection device includes an optical collector configured to be optically coupled to a plasma in a plasma processing apparatus, an adjustable wavelength filter optically coupled to the optical collector, and a photodetector optically coupled to the adjustable wavelength filter. The optical collector receives an optical signal from the plasma. The adjustable wavelength filter is configured to automatically adjust a passband of the adjustable wavelength filter to include a selected wavelength in response to receiving a wavelength selection signal, and allow a filtered portion of the optical signal to pass through while excluding a remaining portion of the optical signal. The filtered portion includes the selected wavelength. The photodetector is configured to generate an OES measurement in response to detecting the filtered portion of the optical signal with a response time that is less than one millisecond.

First claim

What is claimed is:

1 . An optical emission spectroscopy (OES) detection device comprising:
an optical collector configured to be optically coupled to a plasma in a plasma processing apparatus, the optical collector receiving an optical signal from the plasma; an adjustable wavelength filter optically coupled to the optical collector and configured to
automatically adjust a passband of the adjustable wavelength filter to include a selected wavelength in response to receiving a wavelength selection signal, and
allow a filtered portion of the optical signal to pass through while excluding a remaining portion of the optical signal, the filtered portion comprising the selected wavelength; and
a photodiode optically coupled to the adjustable wavelength filter and configured to generate an electric current as an OES measurement in response to detecting the filtered portion of the optical signal, the photodiode having an active area diameter less than about one millimeter.

2 . The OES detection device of claim 1 , wherein rise and fall times of the electric current generated by the photodiode are less than about a nanosecond.

3 . The OES detection device of claim 1 , further comprising:
a timing circuit electrically coupled to the photodiode and configured to
generate a setup delay in response to receiving a synchronization signal from the plasma processing apparatus,
generate a clock signal having a frequency greater than 1 kHz,
cause the OES detection device to collect a series of OES measurements from the photodiode by switching the photodiode off and on after the setup delay according to the clock signal.

4 . The OES detection device of claim 1 , wherein the adjustable wavelength filter comprises a Fabry-Pérot interferometer with a tunable air gap.

5 . The OES detection device of claim 1 , further comprising:
a collimator optically coupled between the optical collector and the adjustable wavelength filter, the collimator being configured to form a parallel beam from the optical signal; a fiber optic optically coupled to the photodiode and configured to transmit the filtered optical signal to the photodiode; and a focusing lens optically coupled between the adjustable wavelength filter and the fiber optic, the focusing lens being configured to focus the filtered optical signal on an input of the fiber optic.

6 . The OES detection device of claim 1 , further comprising one or more additional optical paths, each comprising:
an additional adjustable wavelength filter optically coupled to the optical collector and configured to
automatically adjust a passband of the additional adjustable wavelength filter to include an additional selected wavelength in response to receiving an additional wavelength selection signal, and
allow a filtered portion of the optical signal to pass through while excluding a remaining portion of the optical signal, the filtered portion comprising the additional selected wavelength; and
an additional photodiode optically coupled to the adjustable wavelength filter and configured to generate an electric current as an OES measurement in response to detecting the additional filtered portion of the optical signal, the additional photodiode having an active area diameter less than about one millimeter.

7 . A pulsed plasma optical emission spectroscopy (OES) system comprising:
a pulsed plasma processing apparatus comprising
a plasma processing chamber, and
a source power (SP) coupling element configured to generate a plasma contained by the plasma processing chamber;
an SP control path electrically coupled to the SP coupling element and configured to supply a sequence of SP pulses to the SP coupling element to generate the plasma; an OES detection device optically coupled to the plasma and comprising an adjustable wavelength filter and a photodetector; a control and data acquisition circuit electrically coupled to the adjustable wavelength filter and the photodetector, the control and data acquisition circuit being configured to
adjust a passband of the adjustable wavelength filter to a selected wavelength using a wavelength selection signal, and
cause the photodetector to collect a series of OES measurements of the plasma, the series of OES measurements comprising a temporal resolution less than a millisecond so that multiple OES measurements of the series are collected for each SP pulse of the sequence.

8 . The pulsed plasma OES system of claim 7 , wherein the control and data acquisition circuit is further configured to set an integration time of the photodetector to between about 2 microseconds and about 100 microseconds.

9 . The pulsed plasma OES system of claim 7 , further comprising:
a timing circuit electrically coupled to the control and data acquisition circuit, the timing circuit being configured to generate a clock signal having a frequency greater than 1 kHz in response to receiving a synchronization signal corresponding to the sequence of SP pulses; and wherein the control and data acquisition circuit is further configured to cause the OES detection device to collect the series of OES measurements using the photodetector by switching the photodetector off and on after the setup delay according to the clock signal.

10 . The pulsed plasma OES system of claim 9 , wherein the control and data acquisition circuit is further configured to use the synchronization signal to cause the OES detection device to collect the series of OES measurements during a selected portion of each power cycle of the sequence of SP pulses.

11 . The pulsed plasma OES system of claim 9 , further comprising:
a bias power (BP) control path configured to supply a sequence of BP pulses to a substrate holder of the pulsed plasma processing apparatus disposed within the plasma processing chamber and configured to support a substrate; wherein the control and data acquisition circuit is further configured to use the synchronization signal to cause the OES detection device to collect the series of OES measurements during a selected portion of each power cycle of the sequence of BP pulses.

12 . The pulsed plasma OES system of claim 7 , further comprising:
a bias power (BP) control path configured to supply a sequence of BP pulses to a substrate holder of the pulsed plasma processing apparatus disposed within the plasma processing chamber and configured to support a substrate; a timing circuit electrically coupled to the control and data acquisition circuit, the timing circuit being configured to trigger the control and data acquisition circuit to cause the photodetector to collect the series of OES measurements in response to receiving a synchronization signal from at least one of the SP control path and the BP control path; wherein the control and data acquisition circuit is further configured to process, amplify, and digitize the series of OES measurements for output to a computing system.

13 . The pulsed plasma OES system of claim 7 , wherein the adjustable wavelength filter is a Fabry-Pérot interferometer with a tunable air gap, and wherein the photodetector is a photodiode having an active area diameter less than about one millimeter.

14 . A method of collecting optical emission spectroscopy (OES) data of a pulsed plasma process, the method comprising:
selecting a first wavelength for an adjustable wavelength filter of an OES detection device optically coupled to a plasma processing chamber of a plasma processing apparatus, the plasma processing chamber being configured to contain a plasma for the pulsed plasma process; and collecting a series of OES measurements of the plasm

Assignees

• Tokyo Electron Ltd

Inventors

• Machuca Francisco
• Ng Joel
• Mihaylov Mihail
• Tian Xinkang

Classifications

• H01J37/32972 Primary

  Spectral analysis · CPC title

• H01J37/32146

  Amplitude modulation, includes pulsing · CPC title

• H01J37/32963 Primary

  End-point detection · CPC title