Ion source for multiple charged species

Patent metadata

Field	Value
Publication number	US-9818570-B2
Application number	US-201514972412-A
Country	US
Kind code	B2
Filing date	Dec 17, 2015
Priority date	Oct 23, 2015
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

An indirectly heated cathode (IHC) ion source having improved life is disclosed. The IHC ion source comprises a chamber having a cathode and a repeller on opposite ends of the ion source. Biased electrodes are disposed on one or more sides of the ion source. The bias voltage applied to at least one of the cathode, the repeller and the electrodes, relative to the chamber, is varied over time. In certain embodiments, the voltage applied to the electrodes may begin at an initial positive voltage. Over time, this voltage may be reduced, while still maintaining the target ion beam current. Advantageously, the life of the cathode is improved using this technique.

First claim

What is claimed is:

1. An indirectly heated cathode ion source, comprising:
a chamber into which a gas is introduced;
a cathode disposed on one end of the chamber;
a repeller disposed at an opposite end of the chamber;
an electrode disposed along a side of the chamber; and
a second electrode on a side opposite the electrode, where the second electrode is electrically connected to the chamber,
wherein a voltage applied to at least one of the cathode, the repeller and the electrode relative to the chamber varies over time to maintain a desired ion beam current.

2. The indirectly heated cathode ion source of claim 1 , wherein the voltage decreases over time.

3. The indirectly heated cathode ion source of claim 1 , further comprising a controller, wherein the controller monitors hours of operation of the indirectly heated cathode ion source and determines the voltage to be applied based on hours of operation.

4. The indirectly heated cathode ion source of claim 1 , further comprising a controller in communication with a current measurement system, wherein the measurement system measures current of an ion beam extracted from the indirectly heated cathode ion source through an extraction aperture, and the controller adjusts the voltage to be applied based on measured current of the ion beam.

5. The indirectly heated cathode ion source of claim 1 , wherein the voltage is applied to the electrode.

6. The indirectly heated cathode ion source of claim 1 , wherein at least one of the cathode, the repeller and the electrode is initially formed with a front surface having a concave surface.

7. An indirectly heated cathode ion source, comprising:
a chamber into which a gas is introduced;
a cathode disposed on one end of the chamber;
a repeller disposed at an opposite end of the chamber;
at least one electrode disposed along a side of the chamber; and
a controller, configured to determine a voltage to be applied to the at least electrode,
wherein the voltage applied to the at least one electrode decreases over time to maintain a desired ion beam current.

8. The indirectly heated cathode ion source of claim 7 , wherein the controller monitors hours of operation of the indirectly heated cathode ion source and determines the voltage based on the hours of operation of the indirectly heated cathode ion source.

9. The indirectly heated cathode ion source of claim 8 , wherein the controller decreases the voltage by a first rate during a burn-in phase and decreases the voltage by a second rate during an operational phase, wherein the first rate is greater than the second rate.

10. The indirectly heated cathode ion source of claim 7 , wherein the controller is in communication with a current measurement system, wherein the measurement system measures a current of an ion beam extracted from the indirectly heated cathode ion source, and the controller adjusts the voltage based on measured current of the ion beam.

11. The indirectly heated cathode ion source of claim 7 , further comprising a second electrode on a side opposite the at least one electrode, where the second electrode is electrically connected to the chamber.

12. The indirectly heated cathode ion source of claim 7 , wherein at least one of the cathode, the repeller and the at least one electrode is initially formed with a front surface having a concave surface.

13. The indirectly heated cathode ion source of claim 7 , wherein the cathode and the repeller are negatively biased relative to the chamber and the at least one electrode is initially positively biased relative to the chamber.

14. The indirectly heated cathode ion source of claim 13 , wherein the voltage initially applied to the at least one electrode is between 60 and 150 volts.

15. An indirectly heated cathode ion source, comprising:
a chamber;
a cathode disposed on one end of the chamber, in communication with a cathode power supply;
a repeller disposed on an opposite end of the chamber, in communication with a repeller power supply;
an electrode disposed within the chamber and on a side of the chamber, in communication with an electrode power supply;
an extraction aperture disposed on another side of the chamber; and
a controller, in communication with at least one of the cathode power supply, the repeller power supply and the electrode power supply, wherein the controller modifies a voltage applied to one of the cathode, the repeller and the electrode relative to the chamber over time, and wherein the controller decreases the voltage by a first rate during a burn-in phase and decreases the voltage by a second rate during an operational phase, wherein the first rate is greater than the second rate.

16. The indirectly heated cathode ion source of claim 15 , further comprising a second electrode disposed on a second side of the chamber, wherein the second electrode is in electrical contact with the chamber.

17. The indirectly heated cathode ion source of claim 15 , wherein the cathode power supply and the repeller power supply are one power supply.

18. The indirectly heated cathode ion source of claim 15 , wherein the controller varies the voltage as a function of hours of operation of the indirectly heated cathode ion source.

19. The indirectly heated cathode ion source of claim 15 , wherein the voltage applied to the electrode is modified.

20. The indirectly heated cathode ion source of claim 15 , wherein at least one of the cathode, the repeller and the electrode is initially formed with a front surface having a concave surface.

Assignees

• Varian Semiconductor Equipment Ass Inc

Inventors

• Alvarado Daniel
• Becker Klaus
• Ackerman David

Classifications

• H01J27/024

  Extraction optics, e.g. grids · CPC title

• H01J27/205 Primary

  with electrons, e.g. electron impact ionisation, electron attachment · CPC title

• H01J27/08

  using arc discharge · CPC title

• H01J1/22

  Heaters · CPC title

• H05H1/03

  using electrostatic fields · CPC title