Ion mass separation using RF extraction

Patent metadata

Field	Value
Publication number	US-10068758-B2
Application number	US-201715417767-A
Country	US
Kind code	B2
Filing date	Jan 27, 2017
Priority date	Jan 27, 2017
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

An apparatus which has the capability of filtering unwanted species from an extracted ion beam without the use of a mass analyzer magnet is disclosed. The apparatus includes an ion source having chamber walls that are biased by an RF voltage. The use of RF extraction causes ions to exit the ion source at different energies, where the energy of each ion species is related to its mass. The extracted ion beam can then be filtered using only electrostatic energy filters to eliminate the unwanted species. The electrostatic energy filter may act as a high pass filter, allowing ions having an energy above a certain threshold to reach the workpiece. Alternatively, the electrostatic energy filter may act as a low pass filter, allowing ions having an energy below a certain threshold to reach the workpiece. In another embodiment, the electrostatic energy filter operates as a bandpass filter.

First claim

What is claimed is:

1. An apparatus for extracting an ion beam, comprising:
an ion source having a plurality of chamber walls defining an ion source chamber, wherein one of the chamber walls comprises an extraction plate having an extraction aperture, wherein the extraction plate is biased using an RF voltage;
extraction optics, disposed outside the ion source chamber, to extract an ion beam from the ion source chamber through the extraction aperture; and
an electrostatic energy filter disposed downstream from the extraction optics to selectively allow certain ions from the ion beam to reach a workpiece.

2. The apparatus of claim 1 , wherein the extraction optics are DC biased.

3. The apparatus of claim 1 , wherein the electrostatic energy filter uses only electric fields to manipulate the ion beam.

4. The apparatus of claim 3 , wherein the electrostatic energy filter functions as a high pass filter, passing ions having an energy greater than a first predetermined value.

5. The apparatus of claim 3 , wherein the electrostatic energy filter functions as a low pass filter, passing ions having an energy less than a second predetermined value.

6. The apparatus of claim 3 , wherein the electrostatic energy filter functions as a band pass filter, passing ions having an energy between a first predetermined value and a second predetermined value.

7. The apparatus of claim 3 , further comprising a second electrostatic energy filter disposed between the electrostatic energy filter and the workpiece.

8. An apparatus for extracting an ion beam, comprising:
an ion source having a plurality of chamber walls defining an ion source chamber, wherein one of the chamber walls comprises an extraction plate having an extraction aperture, wherein the extraction plate is biased using an RF voltage;
extraction optics, disposed outside the ion source chamber, to extract an ion beam from the ion source chamber through the extraction aperture; and
an electrostatic energy filter disposed downstream from the extraction optics, wherein the electrostatic energy filter comprises at least one electrode comprising an aperture therethrough, to selectively allow ions from the ion beam having a certain energy to pass through the aperture and to reach a workpiece.

9. The apparatus of claim 8 , wherein the electrostatic energy filter comprises a first electrode biased at a first positive voltage, such that ions having an energy less than the first positive voltage are repelled by the first electrode, so that ions having an energy greater than the first positive voltage pass through the aperture.

10. The apparatus of claim 9 , further comprising a second electrode biased at a negative voltage disposed between the first electrode and the workpiece to accelerate ions passing through the aperture of the first electrode.

11. The apparatus of claim 8 , wherein the electrostatic energy filter comprises an entry electrode, an exit electrode and at least one central electrode, each electrode comprising an upper plate and a lower plate, defining an aperture therebetween, where the upper plate and lower plate are independently biased, and wherein apertures of the electrodes are not linearly aligned.

12. The apparatus of claim 11 , wherein the electrostatic energy filter comprises a plurality of central electrodes.

13. The apparatus of claim 8 , wherein the electrostatic energy filter comprises an entry electrode, an exit electrode and at least one central electrode, each electrode comprising two independently biased spaced apart conductive rods, defining an aperture therebetween, wherein apertures of each electrode are not linearly aligned.

14. The apparatus of claim 13 , wherein the electrostatic energy filter comprises a plurality of central electrodes.

15. An apparatus for extracting an ion beam, comprising:
an ion source configured to extract an ion beam, wherein each species of ions in the ion beam has a unique ion energy distribution function; and
an electrostatic energy filter, disposed downstream from the ion source, to selectively pass certain species of ions toward a workpiece, based on the unique ion energy distribution function.

16. The apparatus of claim 15 , wherein the electrostatic energy filter comprises a resolving aperture, such that only ions having a desired energy pass through the resolving aperture and are directed toward the workpiece.

17. The apparatus claim 15 , further comprising a second electrostatic energy filter, disposed between the electrostatic energy filter and the workpiece, to selectively pass certain species of ions toward the workpiece, based on the unique ion energy distribution function.

Assignees

• Varian Semiconductor Equipment Ass Inc

Inventors

• Likhanskii Alexandre

Classifications

• H01J49/061

  Ion deflecting means, e.g. ion gates · CPC title

• H01J49/22 Primary

  Electrostatic deflection · CPC title

• H01J37/05 Primary

  Electron or ion-optical arrangements for separating electrons or ions according to their energy {or mass}(particle separator tubes H01J49/00) · CPC title

• H01J49/48

  using electrostatic analysers, e.g. cylindrical sector, Wien filter · CPC title

• H01J27/024

  Extraction optics, e.g. grids · CPC title