PLASMA PROCESSING CHAMBERS CONFIGURED FOR TUNABLE SUBSTRATE AND EDGE SHEATH CONTROL

20230132339

17/970446

October 20, 2022

Embodiments herein provide plasma processing chambers and methods configured for fine-tuning and control over a plasma sheath formed during the plasma-assisted processing of a semiconductor substrate. Embodiments include a sheath tuning scheme, including plasma processing chambers and methods, which can be used to tailor one or more characteristics of a plasma sheath formed between a bulk plasma and a substrate surface. Generally, the sheath tuning scheme provides differently configured pulsed voltage (PV) waveforms to a plurality of bias electrodes embedded beneath the surface of a substrate support in an arrangement where each of the electrodes can be used to differentially bias a surface region of a substrate positioned on the support. The sheath tuning scheme disclosed herein can thus be used to adjust and/or control the directionality, and energy and angular distributions of ions that bombard a substrate surface during a plasma-assisted etch process.

1. A substrate processing method, comprising: (a) positioning a substrate on a substrate support disposed in a processing volume of a processing chamber, the substrate support comprising a dielectric body and a plurality of first electrodes, wherein the substrate is positioned on a substrate supporting surface defined by the dielectric body and the plurality of first electrodes are disposed beneath the substrate and are spaced apart therefrom by a portion of the dielectric body; (b) igniting and maintaining a plasma from gases or vapors delivered to the processing volume; and (c) differently biasing one or more regions of the substrate by establishing, by use of a plurality of first waveform generators, pulsed voltage waveforms at individual ones or groups of the plurality of first electrodes, wherein one or more characteristics of a pulsed voltage waveform established at at least one first electrode are different from one or more characteristics of pulsed voltage waveforms established at one or more other ones of the plurality of first electrodes.

2. The method of claim 1, wherein differently biasing the one or more regions of the substrate changes a shape of a plasma sheath formed between the substrate and the plasma.

3. The method of claim 1, further comprising: (d) wherein differently biasing the one or more regions of the substrate changes a shape of a plasma sheath formed between the substrate and the plasma.

4. The method of claim 3, further comprising: (e) establishing, by use of a plurality of second waveform generators, pulsed voltage waveforms at individual ones or groups of a plurality of second electrodes, wherein the plurality of second electrodes are disposed in the dielectric body beneath an edge ring that surrounds the substrate, and one or more characteristics of at least one pulsed voltage waveforms established at one of the plurality of second electrodes are different from the characteristics of pulsed voltage waveforms established at a different one of the plurality of second electrodes.

5. The method of claim 1, wherein the one or more regions of the substrate are differently biased based on thickness variations in a layer of material formed on the substrate.

6. The method of claim 1, wherein each of the pulse voltage waveforms comprises a series of repeating cycles, a waveform period within each repeating cycle comprises a first portion that occurs during a first time interval and a second portion that occurs during a second time interval, a positive or negative voltage pulse is only present during the first time interval and has a peak-to-peak voltage pulse amplitude between consecutive waveform periods, the waveform is substantially constant or has a non-zero slope during the second time interval, a ratio of the first time interval to the second time interval is a voltage pulse duty cycle, and the voltage pulse duty cycle is less than 50%.

7. The method of claim 6, wherein the different characteristic of the pulsed voltage waveform established at the at least one first electrode at (c) comprises one or both of the voltage pulse amplitude or the voltage pulse duty cycle.

8. The method of claim 1, wherein the different characteristic of the pulsed voltage waveform established at the at least one first electrode comprises a voltage pulse amplitude, a voltage pulse frequency, a voltage pulse duty cycle, or a combination thereof.

9. The method of claim 8, wherein the different characteristic of the at least one pulsed voltage waveform comprises a difference in the voltage pulse amplitude of about 5 volts or more.

10. The method of claim 1, further comprising: (f) before, after, or concurrently with (c), electrostatically clamping the substrate to the substrate support by delivering, from a first clamping network, a clamping voltage to the plurality of first electrodes, wherein the first clamping network comprises a direct current power supply.

11. The method of claim 10, wherein the plurality of first waveform generators are respectively coupled to the individual ones or groups of the plurality of first electrodes by a corresponding plurality of transmission lines, the clamping voltage is delivered to the plurality of first electrodes through the plurality of transmission lines, and each of the plurality of first waveform generators is protected from the clamping voltage by a corresponding blocking capacitor disposed between the respective first waveform generator and the first clamping network.

12. The method of claim 10, wherein the first clamping network comprises a plurality of first clamping networks, each of the plurality of first clamping networks comprising a plurality of independently controllable direct current power supplies, and a clamping voltage delivered to at least one of the first electrodes is different from a clamping voltage delivered to one or more other ones of the plurality of first electrodes.

13. The method of claim 1, wherein the plurality of first electrodes are arranged in a repeating pattern along a portion of a radius or across a portion of a width of the dielectric body.

14. The method of claim 13, wherein the repeating pattern comprises an array pattern, a sector pattern, a concentric ring pattern, a concentric ring segments pattern, a quadrant pattern, or a combination thereof.

15. The method of claim 1, wherein differently biasing one or more regions of the substrate at (c) comprises: i.) determining a characteristic of a plasma sheath formed between the substrate and the plasma; ii.) comparing the characteristic of the plasma sheath to a desired characteristic of the plasma sheath; and iii.) based on the comparison at ii, adjusting one or more characteristics of the pulsed voltage waveform established at the at least one first electrode relative to the one or more characteristics established at the one or more other ones of the plurality of first electrodes.

16. The method of claim 15, wherein the characteristic of the plasma sheath determined at i.) comprises a sheath thickness profile.

17. The method of claim 16, wherein the desired characteristic of the plasma sheath is a non-uniform sheath thickness profile.

18. The method of claim 15, wherein determining the characteristic of the plasma sheath at i.) comprises: receiving, at a signal detection module, electrical signals from signal traces coupled to at least two of a plurality of substrate biasing circuits, wherein each of the plurality of substrate biasing circuits comprises one of the plurality of first waveform generators and the individual ones or groups of the plurality of first electrodes coupled thereto; and analyzing the electrical signals to determine characteristics of the plasma sheath formed over at least two different regions of the substrate.

19. The method of claim 18, wherein each of the pulse voltage waveforms comprises sequential reputations of burst-on periods and burst-off periods, each of the pulse voltage waveforms comprises a series of repeating waveform cycles during the burst-on periods, an output of the respective waveform generator is stopped during the burst-off periods, and determining the characteristic of the plasma sheath at i. comprises comparing characteristics of the electrical signals received during the burst-on periods to characteristics of the electrical signals received during the burst-off periods.

20. The method of claim 19, wherein igniting and maintaining the plasma comprises one of: delivering a radio frequency signal to a chamber lid or a support base having the substrate support disposed thereon; or delivering a radio frequency signal to a plasma generator assembly to generate an electromagnetic field in the processing volume.

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