Energetic negative ion impact ionization plasma

Patent metadata

Field	Value
Publication number	US-2016293386-A1
Application number	US-201615088930-A
Country	US
Kind code	A1
Filing date	Apr 1, 2016
Priority date	Apr 3, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

A processing method and system are provided for processing a substrate with a plasma in the presence of an electro-negative gas. A processing gas is injected into a processing chamber. The gas includes a high electron affinity gas species. A surface is provided in the plasma chamber onto which the gas species has a tendency to chemisorb. The gas species is exposed to the surface, chemisorbed onto it, and the surface is exposed to energy that causes negative ions of the chemisorbed gas species, that interact in the plasma to release secondary electrons. A neutralizer grid may be provided to separate from the chamber a second chamber in which forms a low energy secondary plasma for processing the substrate that is dense in electrons and contains high energy neutrals of the gas species and high energy positive ions of processing gas. Pulsed energy may be used to excite plasma or bias the substrate. A hollow cathode source is also provided.

First claim

What is claimed is:

1 . A method of processing a substrate with a plasma in the presence of an electro-negative gas, comprising:
injecting a processing gas that includes a high electron affinity gas species into the plasma chamber; exposing the high electron affinity gas species in the plasma chamber to a surface onto which the high electron affinity gas species has a tendency to chemisorb; igniting a plasma in the plasma chamber; exposing the surface to energy to cause the emission of negative ions from chemisorbed high electron affinity gas species into the plasma; and processing the substrate using the plasma.

2 . The method of claim 1 further comprising:
igniting the plasma by applying a pulsed RF signal to an electrode operably coupled to the plasma chamber.

3 . The method of claim 1 further comprising:
applying a pulsed voltage to the substrate that alternates the bias of the substrate between a negative bias voltage level and a less negative or positive bias voltage level.

4 . The method of claim 1 wherein:
the exposing of the surface includes applying a time average negative potential on the surface.

5 . The method of claim 1 , wherein:
the exposing of the surface includes impacting the surface with radiation from the high-energy pulsed plasma to release negative ions of the high electron affinity gas species into the high-energy pulsed plasma and interacting the negative ions with unionized processing gas to emit energized electrons.

6 . The method of claim 5 , wherein the interacting includes neutralizing the negative ions to emit energized electrons.

7 . The method of claim 6 further comprising:
energizing a second plasma with the emitted energized electrons.

8 . The method of claim 7 , further comprising:
exposing a substrate on a substrate holder is exposed to the second plasma; applying a pulsed DC bias to the substrate positioned on a substrate support in the processing chamber; and periodically biasing the substrate positioned on the substrate support between first and second bias levels, the first bias level being more negative than the second bias level, wherein the substrate and substrate support, when biased at the first bias level, attracts mono-energetic positive ions from the plasma toward the substrate and operable to enhance a selected chemical etch process at a surface of the substrate.

9 . The method of claim 1 , further comprising:
increasing an electron density of the high-energy pulsed plasma by emitting negative ions from the secondary electron source that are reactive to non-ionized process gas.

10 . The method of claim 9 , further comprising:
neutralizing the negative ions to emit energized electrons.

11 . The method of claim 10 , further comprising:
energizing a secondary plasma in a portion of the chamber between the plasma and the substrate with the emitted energized electrons.

12 . The method of claim 11 , further comprising:
positioning the substrate on a substrate holder and applying a pulsed DC bias to the substrate on the substrate support; and periodically biasing the substrate between first and second bias levels, the first bias level being more negative than the second bias level, wherein the substrate, when biased at the first bias level, attracts mono-energetic positive ions from the high-energy pulsed plasma toward the substrate.

13 . The method of claim 1 , wherein:
the exposing of the high electron affinity gas species and the igniting of the plasma are carried out in a first plasma sub-chamber within the plasma chamber having a said surface therein, the ignited plasma being a primary plasma, the negative ions increasing an electron density in the primary plasma by being neutralized in the primary plasma to thereby emit energized secondary electrons; and the processing of the substrate is carried out in a second plasma sub-chamber having the substrate therein by forming a secondary plasma in the second sub-chamber with the energized secondary electrons.

14 . The method of claim 13 , wherein the substrate is positioned on a substrate holder in the second plasma sub-chamber, the method further comprising:
applying a pulsed DC bias to the substrate positioned on the substrate holder; and periodically biasing the substrate between first and second bias levels, the first bias level being more negative than the second bias level, wherein the substrate, when biased at the first bias level, attracts mono-energetic positive ions from the plasma toward the substrate.

15 . A processing system, comprising:
a first plasma chamber configured to contain a first plasma; a gas source operably coupled to the first plasma chamber and configured to inject a process gas and a high electron affinity species into the first plasma chamber; a secondary electron source disposed within the first plasma chamber, the secondary electron source having a surface that has a tendency to chemisorb the high electron affinity species, the high electron affinity species having a tendency to chemisorb onto said surface; and a power source coupled to the secondary electron source and configured to supply a negative time-average potential to the secondary electron source.

16 . The system of claim 15 , wherein said surface is effective to emit negative ions of the chemisorbed high electron affinity species when impacted by radiation.

17 . The system of claim 16 , wherein the negative ions are effective to react with unionized process gas within the primary plasma to yield energetic electrons.

18 . The system of claim 15 , further comprising:
a second plasma chamber being in fluid communication with the first plasma chamber; and a neutralizer positioned between the first plasma chamber and the second plasma chamber, the neutralizer having a plurality of openings therein, each opening of the plurality configured to permit energetic electrons to pass while the negative ions impact the neutralizer at least once so as to release another energetic electron.

19 . The system of claim 18 , wherein said surface of the secondary electron source comprises aluminum, the high electron affinity species is oxygen gas, and the neutralizer comprises silicon.

20 . The system of claim 18 , wherein said surface of the secondary electron source comprises doped-silicon, the high electron affinity species includes at least one of fluorine gas, chlorine gas, bromine gas, tetrachlorosilane, and tetrafluorosilane, and the neutralizer comprises silicon.

21 . The system of claim 18 , further comprising:
a substrate support in said second plasma chamber for supporting a substrate thereon for processing; a plasma generating electrode; a power supply operably coupled to the plasma generating electrode and configured to energize the plasma generating electrode so as to capacitively couple power into the plasma processing chamber to form a plasma between the substrate and the plasma generating electrode; and a DC pulse generator operably coupled to the substrate support and configured to apply a pulsed DC bias voltage to a substrate on the substrate support, wherein the DC pulse generator is configured to apply a first voltage to the substrate support that is operable to attract positive ions from the plasma and onto the substrate and, periodically, to apply a second voltage to the substrate support that is operable to attract electrons from the plasma and onto the substrate, the first voltage being more negative than th

Assignees

• Tokyo Electron Ltd

Inventors

• Chen Lee
• Funk Merritt

Classifications

• H10P50/242

  of Group IV materials · CPC title

• H01J37/32467

  Material · CPC title

• H01J37/32422

  Arrangement for selecting ions or species in the plasma · CPC title

• H01J37/32357

  Generation remote from the workpiece, e.g. down-stream · CPC title

• C23C16/517

  using a combination of discharges covered by two or more of groups C23C16/503 - C23C16/515 · CPC title