Plasma chamber and chamber component cleaning methods
Embodiments provided herein generally include plasma processing systems configured to preferentially clean desired surfaces of a substrate support assembly by manipulating one or more characteristics of an in-situ plasma and related methods. In one embodiment, a plasma processing method includes generating a plasma in a processing region defined by a chamber lid and a substrate support assembly, exposing an edge ring and a substrate supporting surface to the plasma, and establishing a pulsed voltage (PV) waveform at the edge control electrode.
1 . A plasma processing method, comprising:
(a) generating a plasma in a processing region defined by a chamber lid and a substrate support assembly, the substrate support assembly comprising:
a first portion of dielectric material that forms a substrate supporting surface;
an edge ring surrounding the substrate supporting surface, the edge ring comprising a plasma-facing surface and one or more edge pocket surfaces inwardly disposed from the plasma-facing surface;
a bias electrode that is spaced apart from the substrate supporting surface by the first portion of dielectric material; and
an edge control electrode that is disposed a distance from the center of the bias electrode, wherein
the bias electrode is electrically coupled to a first bias generator configured to establish a first pulsed voltage (PV) waveform at the bias electrode;
the edge control electrode is electrically coupled to a second bias generator configured to establish a second pulsed voltage (PV) waveform at the edge control electrode;
(b) exposing the edge ring and the substrate supporting surface exposed by the absence of a substrate to the plasma; and
(c) concurrent with the step (b), establishing the second pulsed voltage (PV) waveform at the edge control electrode.
2 . The method of claim 1 , wherein the first pulsed voltage (PV) waveform generator does not establish the first pulsed voltage (PV) waveform at the bias electrode during at least a portion of exposing the edge ring and the substrate supporting surface to the plasma.
3 . The method of claim 1 , wherein the first and second pulsed voltage (PV) waveforms have a frequency of about 1 MHz or less.
4 . The method of claim 1 , wherein
the second pulsed voltage (PV) waveform comprises a series of repeating cycles,
a waveform within each cycle has a first portion that occurs during a first time interval and a second portion that occurs during a second time interval,
the voltage during the second time interval is lower than the voltage during at least a portion of the first time interval.
5 . The method of claim 4 , wherein a voltage established at the bias electrode is maintained at about 0+/−1 volts (V) by electrically coupling the bias electrode to ground.
6 . The method of claim 4 , wherein a voltage established at the bias electrode is maintained at about 0+/−1 volts (V) by controlling the first pulsed voltage (PV) bias generator.
7 . The method of claim 4 , further comprising:
(d) adjusting one or more characteristics of the second pulsed voltage (PV) waveform relative to one or more characteristics of the first pulsed voltage (PV) waveform to control a shape of a plasma sheath boundary formed over the substrate supporting surface and the edge ring.
8 . The method of claim 7 , wherein
the shape of the plasma sheath boundary is at least partially determined by a difference in a frequency, duration, and/or amplitude of the voltage pulse between the first and second pulsed voltage (PV) waveforms.
9 . The method of claim 8 , wherein
the plasma is generated using a radio frequency (RF) signal from an RF waveform generator,
the RF signal has a frequency of about 1 MHz or greater, and
the RF generator is electrically coupled to:
the chamber lid or a support base having the substrate support disposed thereon, wherein the RF generator is configured to deliver an RF signal to ignite and maintain the plasma; or
a plasma generator assembly configured to generate an electromagnetic field used to ignite and maintain the plasma.
10 . The method of claim 9 , wherein (d) adjusting one or more characteristics of the second pulsed voltage (PV) waveform relative to one or more characteristics of the first pulsed voltage (PV) waveform causes a bend in a plasma sheath boundary to preferentially direct plasma generated ions towards an edge pocket region of the substrate support assembly.
11 . A plasma processing method, comprising:
(a) igniting and maintaining a plasma in a processing region of a processing chamber, the plasma comprising a first portion disposed between a substrate supporting surface of a substrate support assembly and a chamber lid and a second portion disposed between an edge ring and the chamber lid, the substrate support assembly comprising:
a first portion of dielectric material that forms the substrate supporting surface;
a bias electrode that is spaced apart from the substrate supporting surface by the first portion of dielectric material, wherein the bias electrode is electrically coupled to a first pulsed voltage waveform generator configured to establish a first pulsed voltage (PV) waveform at the bias electrode;
an edge control electrode that is disposed a distance from the center of the bias electrode, wherein the edge control electrode is electrically coupled to a second pulsed voltage (PV) waveform generator; and
the edge ring that surrounds the substrate supporting surface, the edge ring comprising one or more edge pocket surfaces that define an edge pocket region with an at least partially lifted substrate disposed over the substrate supporting surface;
(b) establishing, using the second pulse voltage (PV) waveform generator, a second pulsed voltage (PV) waveform at the edge control electrode; and
(c) exposing the at least partially lifted substrate to the plasma.
12 . The method of claim 11 , wherein
the second pulsed voltage (PV) waveform established at the edge control electrode comprises a series of repeating cycles,
a waveform within each cycle has a first portion that occurs during a first time interval and a second portion that occurs during a second time interval,
the voltage during the second time interval is lower than the voltage during at least a portion of the first time interval.
13 . The method of claim 12 , wherein a voltage established at the bias electrode using the first pulsed voltage (PV) waveform generator is maintained at between about −1 volts (V) and about 1 V for at least a portion of a time period where the partially lifted substrate is exposed to the plasma.
14 . The method of claim 12 , wherein the first pulsed voltage (PV) waveform generator does not establish the first pulsed voltage (PV) waveform at the bias electrode during at least a portion of a time period while the partially lifted substrate is exposed to the plasma.
15 . The method of claim 12 , wherein the repeating cycles of the second pulsed voltage (PV) waveform have a frequency of about 1 MHz or less.
16 . The method of claim 12 , further comprising:
(d) adjusting one or more characteristics of the first pulsed voltage (PV) waveform, the second pulsed voltage (PV) waveform, or both to change a shape of a plasma sheath formed over the substrate support.
17 . The method of claim 16 , wherein (e) comprises increasing a frequency, duration, and/or amplitude of the voltage pulse in the second pulsed voltage (PV) waveform.
18 . The method of claim 17 , wherein
the plasma is ignited and maintained using a radio frequency (RF) signal from an RF generator, and
the RF signal has a frequency of about 1 MHz or greater.
19 . The method of claim 18 , wherein
the substrate support assembly further comprises a support base and a second portion of dielectric material disposed over the support base,
the radio frequency (RF) generator is electrically coupled to the support base, and
the bias electrode is spaced apart from the support base by the second portion of dielectric material.
20 . The method of claim 19 , wherein changing the shape of the plasma sheath at (d) causes a bend in a plasma sheath boundary to preferentially direct plasma generated ions towards surfaces of the edge pocket region.