Electron beam exciter for use in chemical analysis in processing systems

• US 9,997,325 B2
• Filed: 07/16/2009
• Issued: 06/12/2018
• Est. Priority Date: 07/17/2008
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System), Verity Instruments Incorporated
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System), Verity Instruments Incorporated
• Inventors: Hosch, Jimmy W., Goeckner, Matthew J., Whelan, Mike, Kueny, Andrew Weeks, Harvey, Kenneth C., Thamban, P.L. Stephan
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): LUONG, HENRY T
• Application Number:
  US12/460,462
• Publication Number:
  US 20100032587A1
• Time in Patent Office: 3,253 Days
• Field of Search: 2504923, 2504931, 25033907, 25039007, 31511101, 31511121, 31511131, 31511171, 31511181
• CPC Class Codes: H01J 37/06 Electron sources; Electron guns electron sources in general H01J1/02, H01J19/02; electron guns in general H01J3/02
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32972 Spectral analysis

Abstract

The present invention is directed to a gas line electron beam exciter, gas line electron beam excitation system and method for exciting a gas using an electron beam exciter. The electron beam exciter generally comprises a variable density electron source for generating a cloud of electrons in an electron chamber and a variable energy electron extractor for accelerating electrons from the electron chamber as an electron beam and into an effluent stream for fluorescing species in the effluent. The electron density of the electron beam is variably controlled by adjusting the excitation power applied to the variable density electron source. The electrons in the electron chamber reside at a reference electrical potential of the chamber, typically near ground electrical potential. The electron energy of the electron beam is variably controlled by adjusting an electrical potential across the variable energy electron extractor, which energizes the electrons through an extraction hole of the chamber and toward the extractor. The greater the difference in the electrical potential between the electron extractor and the electron source, the higher the energy imparted to the electrons in the electron beam. The excitation power applied to the electron source can be adjusted independently from the electron energy of the electron beam, thereby altering the electron density of the electron beam without changing the energy level of the electrons of the electron beam.

Claims

1. A method of determining an endpoint in an etching process by monitoring excited gas particles undergoing a relaxation from an excited energy state to a lower energy state, comprising:

identifying a spectral profile of an emission wavelength of a target gas species within a plurality of gas species when the plurality of gas species is excited by an electron beam;

identifying an electron scattering cross section for the target gas species;

setting an extractor voltage of an electron beam source for exciting the target gas species to emit the spectral profile based on an electron energy associated with a maximum value of the electron scattering cross section for the target gas species;

adjusting an energy distribution and concentration of the electron beam based on the electron energy associated with the maximum value of the electron scattering cross section for the target gas species and sufficient to excite the target gas species into an energy state to undergo emission relaxation to produce the spectral profile detectable for determining the endpoint; and

monitoring the etching process and ending the etching process based upon change of the spectral profile of the target gas species.

2. The method of claim 1, further comprising:

adjusting the energy distribution and concentration of the electron beam based on the electron energy associated with the maximum value of the electron scattering cross section sufficient to excite a second target gas species into a second energy state to undergo emission relaxation to produce a second spectral profile detectable for determining the endpoint.

3. The method recited in claim 1, wherein adjusting the energy distribution of the electron beam further comprises adjusting the electron beam only to excite the target gas species.

4. The method recited in claim 3, wherein adjusting the energy distribution of the electron beam comprises holding a density of electrons in the electron beam constant at a first concentration of electrons;

altering the energy state of the electron beam to a second mean electron energy state; and

receiving light from relaxation of the excited target gas species.

5. The method recited in claim 4, further comprising:

holding an energy level of electrons in the electron beam constant at the second mean electron energy state;

adjusting the density of electrons in the electron beam to a second concentration of electrons; and

receiving light emissions from relaxation of the excited target gas species.

6. The method recited in claim 1, wherein the target gas species is a first target gas species, and the method further comprising:

identifying a spectral profile of an emission wavelength for a second, different target gas species within the plurality of gas species;

setting an extractor voltage for exciting the second different target gas species to emit the spectral profile based on the electron energy associated with the maximum value of the electron scattering cross section for the second different target gas species;

adjusting the energy distribution and concentration of the electron beam based on the electron energy associated with the maximum value of the electron scattering cross section for the second different target gas species and sufficient to excite the second different target gas species into the energy state to undergo emission relaxation to produce the spectral profile detectable for determining the endpoint; and

monitoring the etching process and ending the etching process based upon change of the spectral profile of the second different target gas species.

7. The method recited in claim 1, further comprising:

monitoring a density of electrons in the electron beam and verifying the density of electrons in the electron beam at a first concentration of electrons.

8. A method of determining an endpoint in an etching process by monitoring excited gas particles undergoing a relaxation from an excited energy state to a lower energy state, comprising:

providing a first excitation energy level for an electron source;

establishing a reference potential at the electron source;

providing a first extractor voltage for an electron beam source for exciting a target gas species to emit a spectral profile based on an electron energy associated with a maximum value of an electron scattering cross section of the target gas species, wherein the first extractor voltage is greater than the reference potential;

generating an electron beam along a beam axis based on the first extractor voltage and sufficient to excite the spectral profile of the target gas species within a plurality of gas species when the plurality of gas species is excited by the electron source;

adjusting an energy distribution and concentration of the electron beam based on the electron energy associated with the maximum value of the electron scattering cross section for the target gas species and sufficient to excite the target gas species into an energy state to undergo emission relaxation to produce an identifying spectral profile detectable for determining the endpoint; and

monitoring the etching process and ending the etching process based upon change of the spectral profile of the target gas species.

9. The method recited in claim 8

wherein the target gas species is a first target gas species, and the method further comprising:

identifying a spectral profile of an emission wavelength for a second, different target gas species within the plurality of gas species;

identifying an electron scattering cross section for the second target gas species;

setting an extractor voltage for exciting the second target gas species to emit the spectral profile for the second target gas species based on the electron energy associated with a maximum value of the electron scattering cross section for the second target gas species;

adjusting an energy distribution and concentration of the electron beam based on the electron energy associated with the maximum value of the electron scattering cross section for the second target gas and sufficient to excite the second target gas species into an energy state to undergo emission relaxation to produce the spectral profile detectable for determining the endpoint; and

monitoring an etching process and ending the etching process based upon change of the spectral profile of the second target gas species.