Method and system for single ion implantation

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 31 P.

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 31 P.

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.