Method and system for single ion implantation

• US 7,002,166 B2
• Filed: 08/27/2002
• Issued: 02/21/2006
• Est. Priority Date: 08/27/2001
• Status: Active Grant

• Current Assignee: NewSouth Innovations Pty Limited (University Of New South Wales)
• Original Assignee: Qucor Pty Limited
• Inventors: Clark, Robert Graham, Dzurak, Andrew Steven, Prawer, Steven, Yang, Changyi, Jamieson, David Norman
• Primary Examiner(s): Berman, Jack I.
• Application Number:
  US10/484,647
• Publication Number:
  US 20040232353A1
• Time in Patent Office: 1,274 Days
• Field of Search: None
• US Class Current: 250/492.21
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G06N 10/00 Quantum computing, i.e. information processing based on quantum-mechanical phenomena
• CPC Class Codes: H01J 2237/08 Ion sources
• CPC Class Codes: H01J 2237/20228 Mechanical X-Y scanning
• CPC Class Codes: H01J 2237/20292 Means for position and/or orientation registration
• CPC Class Codes: H01J 2237/31703 Dosimetry
• CPC Class Codes: H01J 2237/31711 using mask
• CPC Class Codes: H01J 2237/31713 Focused ion beam
• CPC Class Codes: H01J 2237/31755 using ion beams
• CPC Class Codes: H01J 2237/31788 through mask
• CPC Class Codes: H01J 37/08 Ion sources; Ion guns
• CPC Class Codes: H01J 37/20 Means for supporting or positioning the objects or the material; Means for adjusting diaphragms or lenses associated with the support introducing the objects H01J37/18
• CPC Class Codes: H01J 37/244 Detectors; Associated components or circuits therefor
• CPC Class Codes: H01J 37/3171 for ion implantation plasma immersion ion implantation H01J37/32412
• CPC Class Codes: H01J 37/3174 Particle-beam lithography, e.g. electron beam lithography
• CPC Class Codes: H01L 21/265 producing ion implantation
• CPC Class Codes: H01L 21/26513 of electrically active species

Abstract

This invention concerns a method and system for single ion doping and machining by detecting the impact, penetration and stopping of single ions in a substrate. Such detection is essential for the successful implantation of a counted number of ³¹P ions into a semi-conductor substrate for construction of a Kane quantum computer. The invention particularly concerns the application of a potential across two electrodes on the surface of the substrate to create a field to separate and sweep out electron-hole pairs formed within the substrate. A detector is then used to detecting transient current in the electrodes, and so determine the arrival of a single ion in the substrate.

Claims

1. A method for single ion doping and machining by detecting the impact, penetration and stopping of a single heavy ion in a substrate, the method comprising the steps of:

impacting an electrically active substrate with single ions to generate electron-hole pairs;

applying a potential applied across two electrodes on the surface of the substrate to create a field to separate and sweep out electron-hole pairs formed within the substrate; and

detecting transient current in the electrodes and so determine the arrival of a single ion in the substrate.

2. A method according to claim 1, where the substrate is a high resistivity silicon substrate and the ions are ³¹P.

3. A method according to claim 1, including the step of generating a focused beam of ions from a field ionisation ion source producing sub-20 nm ion beam probes.

4. A method according to claim 3, including the step of gating off the beam after a single ion arrival is detected.

5. A method according to claim 1, including a preliminary step of applying ionising radiation to cause detectable ionisation.

6. A method according to claim 5, where the ionising radiation is X-rays or electrons.

7. A method according to claim 1, including the step of measuring the polarity of the ion-impact-induced signal as a measure of the proximity of the ion strike to one or other electrode.

8. A method according to claim 1, including the step of moving a mask to a new position above the substrate for a further implant after a single ion arrival is detected.

9. A method according to claim 1, including the steps of applying a thin, ion sensitive resist to the substrate, and later processing the resist to reveal the impact sites of single ions.

10. A method according to claim 1, including the steps of applying a thick resist layer to the substrate surface, and opening apertures in the resist for the implantation of single ions.

11. A method according to claim 10, where two apertures are opened in the mask by electron beam lithography and subsequent processing.

12. A method according to claim 11, including the steps of fabricating a linear metal electrodes on the substrate surface using EBL, depositing a resist layer, drawing a cross line with the EBL system across the linear electrodes which upon development opens a path to the surface leaving the substrate exposed, and implanting ions down the paths beside the electrode.

13. A method according to claim 8, where the moveable mask is a nanomachined aperture in an AFM cantilever which is accurately positionable over the substrate surface.

14. A method according to claim 13, where the nanomachined aperture is fabricated using a Focused Ion Beam (FIB).

15. A method according to claim 14, where the Focused Ion Beam (FIB) has a diameter less than 20 nm.

16. A method according to claim 15, including the steps of imaging the cantilever tip with the FIB, and then drilling the nanomachined aperture at a known location relative to the cantilever tip.

17. A method according to claim 13, including the step of positioning the nanomachined aperture using STM or AFM to first locate and image registration marks on the substrate using the cantilever.

18. A method according to claim 13, including, between each implant step, the step of using the cantilever to image the ion impact site and verify that a single ion has been successfully delivered to the substrate.

19. A method according to claim 1, including the steps of dwelling a FIB on a location on the substrate surface where an ion is to be implanted until a single ion impact is detected, and then scanning an FIB over the substrate to a new location, and repeating the dwelling step.

20. A method according to claim 19 where the FIB is a sub-20 nm spot.

21. A method according to claim 19, including the step using a nanomachined mask and dwelling the FIB on the apertures in the mask.

22. A method according to claim 1, including the step of using a focused laser beam to anneal the ion beam induced damage from the single ion impacts.

23. A method according to claim 1, including the step of cooling the substrate to allow sufficient signal to noise ratio to detect single keV ions.

24. A system according to claim 1, including a cooling system to cool the substrate to allow sufficient signal to noise ratio to detect single keV ions.

25. A quantum computer fabricated using the method of any one of claims 1 to 23.

26. A nanomachined optical fibre fabricated using the method of any one of claims 1 to 23.

27. An integrated chip having controlled dopant implantation fabricated using the method of any one of claims 1 to 23.

28. A resist structure having controlled dopant implantation fabricated using the method of any one of claims 1 to 23.

29. A system for single ion doping and machining by detecting the impact, penetration and stopping of a single ion in a substrate, comprising:

an electrically active substrate where ion or electron impact generates electron-hole pairs;

at least two electrodes applied to the substrate;

a potential applied across the electrodes to create a field to separate and sweep out electron-hole pairs formed within the substrate; and

a current transient sensor to detect current in the electrodes and so determine the arrival of a single ion in the substrate.

30. A system according to claim 29, where the substrate is a high resistivity silicon substrate and the ions are ³¹P.

31. A system according to claim 29, including a gating subsystem to gate off the beam after a single ion arrival is detected.

32. A system according to claim 29, including source ionising radiation moveable between a first position adjacent the substrate to cause detectable ionisation, and a second position where it does not irradiate the substrate.

33. A system according to claim 32, where the ionising radiation is X-rays or electrons.

34. A system according to claim 29, including a mask moveable over the substrate to implant a single ion in different locations.

35. A system according to claim 29, including a mask having two apertures.

36. A system according to claim 34, where the mask is a nanomachined aperture in an AFM cantilever which is accurately positionable over the substrate surface.

37. A system according to claim 36, where the nanomachined aperture is fabricated using a Focussed Ion Beam (FIB).

38. A system according to claim 36, where the Focused Ion Beam (FIB) has a beam of diameter less than 20 nm.