Method of controlling ion energy distribution using a pulse generator with a current-return output stage
Embodiments of this disclosure describe an electrode biasing scheme that enables maintaining a nearly constant sheath voltage and thus creating a mono-energetic IEDF at the surface of the substrate that consequently enables a precise control over the shape of IEDF and the profile of the features formed in the surface of the substrate.
1. A processing chamber, comprising:
a pulsed DC biasing system, comprising:
a substrate support assembly comprising a biasing electrode and a substrate-supporting surface, wherein the biasing electrode is electrically coupled to a first electrical conductor;
a bias generator that is electrically coupled to a second electrical conductor, wherein the bias generator is configured to establish a pulsed voltage waveform at the biasing electrode, the bias generator comprising:
a pulse generator that is electrically coupled to the second electrical conductor; and
a current-return output stage, wherein a first end of the current-return output stage is electrically coupled to the second electrical conductor, and a second end of the current-return output stage is electrically coupled to ground; and
a blocking capacitor coupled between the first electrical conductor and the second electrical conductor.
2. The processing chamber of claim 1 , wherein the biasing electrode is spaced apart from the substrate-supporting surface by a layer of dielectric material.
3. The processing chamber of claim 1 , wherein the blocking capacitor has a capacitance of between about 40 nF and about 80 nF.
4. The processing chamber of claim 1 , wherein a high-voltage module is electrically coupled to the first electrical conductor at a connection point disposed between the biasing electrode and the blocking capacitor.
5. The processing chamber of claim 4 , further comprising a resistor disposed between the high-voltage module and the connection point.
6. The processing chamber of claim 5 , wherein the resistor has a resistance of more than about 1 MOhm.
7. The processing chamber of claim 1 , further comprising a high-voltage module electrically coupled between ground and the first electrical conductor, wherein the high-voltage module is configured to apply a voltage to the first electrical conductor relative to the ground.
8. The processing chamber of claim 7 , wherein the blocking capacitor has a capacitance of between about 40 nF and about 80 nF.
9. The processing chamber of claim 7 , wherein
the high-voltage module is electrically coupled to a first end of the first electrical conductor,
the biasing electrode is coupled to a second end of the first electrical conductor, and
the blocking capacitor is disposed between the first end of the of the first electrical conductor and the bias generator.
10. The processing chamber of claim 1 , further comprising a non-transitory computer readable medium having instructions stored thereon for performing a method of processing a substrate when executed by a processor, the method comprising:
generating a plasma over a surface of a substrate disposed on the substrate-supporting surface, wherein the substrate is spaced apart from the biasing electrode by a layer of dielectric material of the substrate support assembly;
establishing a pulsed voltage waveform at the biasing electrode using the bias generator; and
chucking the substrate to the substrate support assembly by delivering a chucking voltage to the biasing electrode from a high-voltage module,
wherein the blocking capacitor is disposed between the high-voltage module and the bias generator.
11. A method of processing a substrate, comprising:
generating a plasma over a surface of a substrate disposed on a substrate support assembly, the substrate support assembly comprising a biasing electrode and a layer of dielectric material disposed between the biasing electrode and the substrate;
establishing a pulsed voltage waveform at the biasing electrode using a bias generator that is electrically coupled to the biasing electrode through a blocking capacitor and one or more electrical conductors; and
chucking the substrate to the substrate support assembly by delivering a chucking voltage from a high-voltage module to the biasing electrode through one of the one or more electrical conductors,
wherein the blocking capacitor is disposed between the high-voltage module and the bias generator.
12. The method of claim 11 , wherein the blocking capacitor has a capacitance of between about 40 nF and about 80 nF.
13. The method of claim 11 , wherein
the pulsed voltage waveform comprises a series of repeating cycles,
a waveform within each cycle of the series of repeating cycles has a first portion that occurs during a first time interval and a second portion that occurs during a second time interval, and
a positive voltage pulse is only present during the first time interval.
14. The method of claim 13 , wherein
the one or more electrical conductors comprises a first electrical conductor coupled to the biasing electrode and a second electrical conductor coupled to the bias generator, and
the blocking capacitor is coupled between the first electrical conductor and the second electrical conductor.
15. The method of claim 14 , wherein the bias generator comprises:
a pulse generator that is electrically coupled to the second electrical conductor; and
a current-return output stage, wherein
a first end of the current-return output stage is electrically coupled to the second electrical conductor,
a second end of the current-return output stage is electrically coupled to ground, and
a current flows from the biasing electrode to ground through the current-return output stage during at least a portion of the second time interval.
16. The method of claim 14 , wherein
the high-voltage module is electrically coupled between ground and the first electrical conductor, and
the chucking voltage is applied to the first electrical conductor relative to the ground.
17. A processing chamber, comprising:
a pulsed DC biasing system, comprising:
a substrate support assembly comprising a biasing electrode and a substrate-supporting surface; and
a bias generator electrically coupled to the biasing electrode using one or more electrical conductors and a blocking capacitor; and
a non-transitory computer readable medium having instructions stored thereon for performing a method of processing a substrate when executed by a processor, the method comprising:
generating a plasma over a surface of a substrate disposed on the substrate-supporting surface, wherein the substrate is spaced apart from the biasing electrode by a layer of dielectric material of the substrate support assembly;
using the bias generator to establish a pulsed voltage waveform at the biasing electrode through the blocking capacitor; and
chucking the substrate to the substrate support assembly by delivering a chucking voltage from a high-voltage module to the biasing electrode through one of the one or more electrical conductors,
wherein the blocking capacitor is disposed between the high-voltage module and the bias generator.
18. The processing chamber of claim 17 , wherein
the pulsed voltage waveform comprises a series of repeating cycles,
a waveform within each cycle of the series of repeating cycles has a first portion that occurs during a first time interval and a second portion that occurs during a second time interval, and
a positive voltage pulse is only present during the first time interval.
19. The processing chamber of claim 18 , wherein
the one or more electrical conductors comprises a first electrical conductor coupled to the biasing electrode and a second electrical conductor coupled to the bias generator, and
the blocking capacitor is coupled between the first electrical conductor and the second electrical conductor.
20. The processing chamber of claim 19 , wherein
the bias generator comprises:
a pulse generator that is electrically coupled to the second electrical conductor; and
a current-return output stage, wherein
a first end of the current-return output stage is electrically coupled to the second electrical conductor,
a second end of the current-return output stage is electrically coupled to ground, and
a current flows from the biasing electrode to ground through the current-return output stage during at least a portion of the second time interval.