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 substrate support assembly comprising a biasing electrode and a substrate supporting surface, wherein
the biasing electrode is separated from the substrate supporting surface by a layer of a dielectric material, wherein the layer has a thickness of between about 0.1 mm and about 1 mm; and
a bias generator that is electrically coupled to a generator end of an electrical conductor using a generator coupling assembly, and an electrode end of the electrical conductor is electrically coupled to the biasing electrode using an electrode coupling assembly,
wherein the bias generator is configured to establish a pulsed voltage waveform at the biasing electrode, and comprises:
a pulse generator that is electrically coupled to the generator end of the electrical conductor; and
a current-return output stage, wherein
a first end of the current-return output stage is electrically coupled to the electrical conductor, and
a second end of the current-return output stage is electrically coupled to ground.
2. The processing chamber of claim 1 , further comprising:
a chucking power supply that is electrically coupled to the generator end of the electrical conductor using a supply coupling assembly.
3. The processing chamber of claim 2 , wherein the supply coupling assembly comprises a blocking resistor that has a resistance of more than about 1 MOhm.
4. The processing chamber of claim 1 , wherein a parallel plate like structure comprising the biasing electrode and the layer of the dielectric material has an effective capacitance of between about 5 nF and about 50 nF.
5. The processing chamber of claim 1 , wherein the substrate support assembly further comprises a substrate support and a support base, wherein the substrate support comprises a dielectric material.
6. The processing chamber of claim 5 , wherein
the substrate support has a second surface that is positioned opposite to the substrate supporting surface,
the support base is positioned adjacent to the second surface and comprises a plurality of cooling channels that are configured to receive a fluid from a coolant source, and
the substrate support assembly further comprises an insulator plate that is disposed between a ground plate and the support base.
7. The processing chamber of claim 5 , wherein the biasing electrode is disposed within the substrate support of the substrate support assembly.
8. The processing chamber of claim 5 , wherein the substrate support has a second surface that is positioned below and opposite to the substrate supporting surface, and the biasing electrode is disposed below the second surface.
9. The processing chamber of claim 5 , wherein the support base is configured to be used as a biasing electrode.
10. The processing chamber of claim 1 , wherein a first end of the pulse generator is electrically coupled to the generator end of the electrical conductor, and a second end of the pulse generator is electrically coupled to ground.
11. The processing chamber of claim 1 , wherein the generator coupling assembly comprises one of the components selected from the group consisting of a capacitor, a capacitor and an electrical conductor in series, an inductor, and an inductor and an electrical conductor in series.
12. The processing chamber of claim 1 , wherein the generator coupling assembly or the electrode coupling assembly comprise an electrical conductor.
13. The processing chamber of claim 1 , wherein the electrode coupling assembly comprises one of the components selected from the group consisting of a capacitor, a capacitor and an electrical conductor in series, an inductor, and an inductor and an electrical conductor in series.
14. The processing chamber of claim 1 , wherein the generator coupling assembly comprises a capacitor having a capacitance in a range of about 40 nF to about 80 nF.
15. The processing chamber of claim 1 , wherein the electrical conductor comprises a first electrical conductor and a second electrical conductor that are electrically coupled in series, wherein one end of the first electrical conductor is electrically coupled to an output of the bias generator using the generator coupling assembly and one end of the second electrical conductor is electrically coupled to the biasing electrode using the electrode coupling assembly.
16. A method of processing of a substrate, comprising:
generating a plasma over a surface of a substrate disposed on a substrate supporting surface of a substrate support assembly; and
biasing a biasing electrode disposed within the substrate support assembly using a bias generator that is electrically coupled to a generator end of an electrical conductor using a generator coupling assembly, and a second end of the electrical conductor is electrically coupled to the biasing electrode using an electrode coupling assembly, wherein:
the biasing electrode is separated from the substrate supporting surface by a layer of the dielectric material, wherein the layer has a thickness of between about 0.1 mm and about 1 mm;
the bias generator is configured to establish a pulsed voltage waveform at the biasing electrode, and 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,
a positive voltage pulse is only present during the first time interval, and
the bias generator comprises:
a pulse generator that is electrically coupled to the generator end of the electrical conductor; and
a current-return output stage, wherein
a first end of the current-return output stage is electrically coupled to the electrical conductor, and
a second end of the current-return output stage is electrically coupled to ground, and
wherein 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.
17. The method of claim 16 , wherein a parallel plate like structure comprising the biasing electrode and the layer of the dielectric material has an effective capacitance of between about 5 nF and about 50 nF.
18. The method of claim 16 , further comprising:
a chucking power supply that is electrically coupled to the generator end of the electrical conductor using a supply coupling assembly.
19. The method of claim 18 , wherein the supply coupling assembly comprises a blocking resistor that has a resistance of more than about 1 MOhm.
20. The method of claim 16 , wherein the electrical conductor comprises a first electrical conductor and a second electrical conductor that are electrically coupled in series, wherein one end of the first electrical conductor is electrically coupled to an output of the bias generator using the generator coupling assembly and one end of the second electrical conductor is electrically coupled to the biasing electrode using the electrode coupling assembly.
21. The method of claim 16 , wherein the substrate support assembly further comprises a substrate support and a support base, wherein the substrate support comprises a dielectric material.
22. The method of claim 21 , wherein
the substrate support has a second surface that is positioned opposite to the substrate supporting surface,
the support base is positioned adjacent to the second surface and comprises a plurality of cooling channels that are configured to receive a fluid from a coolant source, and
the substrate support assembly further comprises an insulator plate that is disposed between a ground plate and the support base.
23. The method of claim 21 , wherein the biasing electrode is disposed within the substrate support of the substrate support assembly.
24. The method of claim 21 , wherein the substrate support has a second surface that is positioned below and opposite to the substrate supporting surface, and the biasing electrode is disposed below the second surface.
25. The method of claim 21 , wherein the support base is configured to be used as a biasing electrode.
26. The method of claim 16 , wherein a first end of the pulse generator is electrically coupled to the generator end of the electrical conductor, and a second end of the pulse generator is electrically coupled to ground.
27. The method of claim 16 , wherein the generator coupling assembly comprises one of the components selected from the group consisting of a capacitor, a capacitor and an electrical conductor in series, an inductor, and an inductor and an electrical conductor in series.
28. The method of claim 16 , wherein the generator coupling assembly or the electrode coupling assembly comprise an electrical conductor.
29. The method of claim 16 , wherein the electrode coupling assembly comprises one of the components selected from the group consisting of a capacitor, a capacitor and an electrical conductor in series, an inductor, and an inductor and an electrical conductor in series.
30. The method of claim 16 , wherein the generator coupling assembly comprises a capacitor having a capacitance in a range of about 40 nF to about 80 nF.