ION BEAM INCIDENT ANGLE DETECTOR FOR ION IMPLANT SYSTEMS

• US 20040195528A1
• Filed: 04/01/2003
• Published: 10/07/2004
• Est. Priority Date: 04/01/2003
• Status: Active Grant

• Current Assignee: Axcelis Technologies Incorporated
• Original Assignee: Axcelis Technologies Incorporated
• Inventors: Parrill, Thomas, Graf, Michael A., Reece, Ronald N., Freer, Brian S.
• Granted Patent: US 6,828,572 B2
• Time in Patent Office: Days
• US Class Current: 250/492.21
• CPC Class Codes: H01J 2237/24528 Direction of beam or parts thereof in view of the optical axis, e.g. beam angle, angular distribution, beam divergence, beam convergence or beam landing angle on sample or workpiece means for deflecting or directing discharge H01J2237/15
• CPC Class Codes: H01J 2237/24578 Spatial variables, e.g. position, distance
• CPC Class Codes: H01J 2237/30455 Correction during exposure
• CPC Class Codes: H01J 37/244 Detectors; Associated components or circuits therefor
• CPC Class Codes: H01J 37/304 Controlling tubes by information coming from the objects or from the beam, e.g. correction signals
• CPC Class Codes: H01J 37/3045 Object or beam position registration
• CPC Class Codes: H01J 37/3171 for ion implantation plasma immersion ion implantation H01J37/32412

Abstract

The present invention facilitates semiconductor device fabrication by monitoring and correcting angular errors during ion implantation procedures via an incident ion beam angle detector. Additionally, the present invention facilitates semiconductor device fabrication by calibrating a process disk with respect to an incident ion beam without measuring implantation results on wafers prior to an ion implantation process.

Claims

1. An ion beam incident angle detector for ion implantation systems comprising:

a structure having a hole therethrough defining an aperture, the aperture extending through the structure along an axis and having a selected aspect ratio that selectively prevents ions in the ion beam from passing therethrough according to an angle of incidence between the ion beam and the structure; and

a sensor mechanism configured to receive the ions that pass through the aperture in the structure, the sensor providing a signal as a function of an amount of the charged ions that pass through the aperture.

2. The angle detector of claim 1, wherein the sensor mechanism comprises a charge collector.

3. The angle detector of claim 2, wherein the charged ions that pass through the aperture build up charge on the charge collector.

4. The angle detector of claim 1, wherein a portion of the structure having the aperture associated therewith is manufactured in a material selected from the group consisting of aluminum, aluminum coated with silicon, graphite and anodized aluminum.

5. The angle detector of claim 3, wherein the charge collector is operable as a charge monitor.

6. The angle detector of claim 1, wherein the aspect ratio of the aperture yields a suitable signal to noise ratio.

7. The angle detector of claim 1, wherein the structure comprises a tube.

8. The angle detector of claim 1, wherein the structure is substantially grounded such that ions striking an interior surface of the aperture become substantially neutral or the interior surface of the aperture is configured to collect or trap ions that strike the interior surface.

9. The angle detector of claim 1, wherein the sensor mechanism comprises a faraday that measures beam current as a function of the angle of incidence.

10. The angle detector of claim 9, wherein the structure comprises a process disk having the hole therethrough that defines at least a portion of the aperture.

11. The angle detector of claim 1, further comprising a process disk onto which the structure is mounted, wherein the structure comprises a tube generally centered and extending along the axis, and wherein the structure is substantially grounded such that ions striking an interior surface of the aperture become substantially neutral or the interior surface of the aperture is configured to collect or trap ions that strike the interior surface.

12. An end station of an ion implantation system comprising:

a process chamber configured to accommodate one or more ion beam angle detectors; and

a process support structure adjustable about one or more axes, and configured to accommodate one or more wafers,

wherein each of said ion beam angle detectors includes a beam discriminating structure mounted on said process support structure.

13. The end station of claim 12, further comprising a chamber mount that supports the process chamber and supports adjustment of the process support structure about the one or more axes.

14. The end station of claim 12, wherein the process support structure comprises a multi-wafer process disk operable to support a plurality of wafers or a single-wafer platen for implantation thereof.

15. The end station of claim 12, wherein the one or more axes comprise an alpha axis and a beta axis, respectively.

16. The end station of claim 12, wherein the one or more ion beam angle detectors respectively comprise:

a charge collector;

an insulative layer formed on charge collector, the insulative layer having an aperture of a first diameter along an axis that exposes a portion of the charge collector; and

a tube portion as the beam discriminating structure formed on the insulative layer, the tube portion being grounded and having an aperture along the axis, wherein the aperture permits ions traveling substantially in-line with the axis to impact the exposed portion of the charge collector and build up charge thereon and wherein ions traveling substantially off-line with the axis impact the tube portion and lose at least a portion of charge associated therewith.

17. The end station of claim 12, wherein the one or more ion beam angle detectors respectively comprise:

a charge collector;

an insulative layer formed on charge collector, the insulative layer having an aperture of a first diameter along an axis that exposes a portion of the charge collector; and

a tube portion as the beam discriminating structure formed on the insulative layer, the tube portion having an aperture along the axis, wherein the aperture permits ions traveling substantially in-line with the axis to impact the exposed portion of the charge collector and build up charge thereon and wherein ions traveling substantially off-line with the axis impact the tube portion and are collected thereby.

18. The end station of claim 12, the process support structure being calibrated via the one or more ion beam angle detectors about the one or more axes.

19. The end station of claim 12, the process support structure being adjusted in situ via the one or more ion beam angle detectors about the one or more axes.

20. The end station of claim 12, the ion beam angle detectors being located within a scanning range of an ion beam.

21. The end station of claim 12, the ion beam angle detectors being located outside a scanning range of an ion beam.

22. The end station of claim 12, wherein the one or more angle detectors respectively comprise:

a tube portion as the beam discriminating structure mounted on the process support structure and aligned with a an aperture defined in the process support structure, wherein the tube portion and aperture define a passageway for allowing ions to pass therethough; and

a sensor mechanism configured to receive the ions that pass through the tube portion and aperture, the sensor mechanism providing a signal as a function of an amount of the ions passing through the tube portion and aperture.

23. The end station of claim 22, wherein the sensor mechanism comprises a faraday located downstream of the process support structure that measures beam current as a function of charged ions that maintain their charge after passing through the aperture defined in the process support structure.

24. The end station of claim 22, wherein the sensor mechanism comprises a charge collector located downstream of the process support structure that collects charge as a function of charged ions that maintain their charge after passing through the aperture defined in the process support structure.

25. The end station of claim 12, wherein the one or more angle detectors respectively comprise:

an array of tubes as the beam discriminating structure mounted on the process support structure aligned with an array of apertures defined in the process support structure wherein the array of tubes and the array of apertures define an array of passageways for allowing ions to pass therethough; and

a sensor mechanism configured to receive the ions that pass through the array of passageways for collectively measuring beam current as a function of charged ions that maintain their charge after passing therethrough.

26. The end station of claim 12, wherein the one or more angle detectors respectively comprise:

an array of tubes as the beam discriminating structure mounted on the process support structure and in-line with an array of holes through the process support structure, wherein apertures are defined by the tube portions and the holes; and

a plurality of faradays each associated with one of the array of tubes, that collectively measure beam current as a function of charged ions that maintain their charge after passing through the apertures, wherein each of the plurality of faradays are associated with a portion of the ion beam.

27. The end station of claim 12, wherein the one or more angle detectors respectively comprise:

an array of holes extending through the process support structure as the beam discriminating structure, wherein apertures are defined by profile holes; and

a sensor mechanism configured to receive the ions that pass through the profile holes, the sensor providing a signal as a function of an amount of the charged ions that pass through the profile holes.

28. The end station of claim 12, wherein the one or more angle detectors respectively comprise:

an array of holes extending through the process support structure as the beam discriminating structure, wherein apertures are defined by profile holes; and

a plurality of sensor mechanisms each associated with one of the profile holes configured to receive the ions that pass through the profile holes, the sensors each providing a signal as a function of an amount of the charged ions that pass through the profile holes, wherein each of the plurality of sensors is associated with a portion of the ion beam.

29. A method of aligning an incident ion beam comprising:

providing a process support structure configured to support one or more wafers and having one or more angle detectors;

aligning the process support structure along one or more axes to initial first and second angle settings;

determining a plurality of first angle offset values and second angle offset values;

performing ion implantations for the plurality of second angle offset values and obtaining a plurality of second angle charge values;

performing ion implantations for the plurality of first angle offset values and obtaining a plurality of first angle charge values; and

determining a first angle calibration value according to the plurality of first angle charge values and a second angle calibration value according to the plurality of second angle charge values.

30. The method of claim 29, further comprising applying the first angle calibration value and the second angle calibration value to the process support structure and verifying alignment of the process support structure.

31. The method of claim 30, further comprising the following on a failed verification of the alignment:

determining a plurality of second first angle offset values and second angle offset values;

performing ion implantations for the plurality of second angle offset values and obtaining a plurality of second angle charge values;

performing ion implantations for the plurality of second first angle offset values and obtaining a plurality of second first angle charge values;

determining existence of angular error; and

determining a second first angle calibration value according to the plurality of second first angle charge values and a second angle calibration value according to the plurality of second angle charge values;

applying the second first angle calibration value and the second angle calibration value to the process support structure and verifying alignment thereof.

32. The method of claim 31, wherein the method is completed iteratively until the alignment is successfully verified.

33. A method of aligning an incident ion beam comprising:

providing a process support structure configured to support one or more wafers and having one or more angle detectors;

aligning the process support structure to initial first and second angle values;

determining a plurality of first angle offset values and second angle offset values;

performing ion implantations for the plurality of second angle offset values and obtaining a plurality of second angle beam current values;

performing ion implantations for the plurality of first angle offset values and obtaining a plurality of first angle beam current values; and

determining an first angle calibration value according to the plurality of first angle beam current values and a second angle calibration value according to the plurality of second angle beam current values.

34. The method of claim 33, further comprising applying the first angle calibration value and the second angle calibration value to the process support structure and verifying alignment of the process support structure.

35. The method of claim 34, further comprising the following on a failed verification of the alignment:

determining a plurality of second first angle offset values and second angle offset values;

performing ion implantations for the plurality of second angle offset values and obtaining a plurality of second angle beam current values;

performing ion implantations for the plurality of second first angle offset values and obtaining a plurality of second first angle beam current values;

determining existence of angular error; and

determining a second first angle calibration value according to the plurality of second first angle beam current values and a second angle calibration value according to the plurality of second angle beam current values;

applying the second first angle calibration value and the second angle calibration value to the process support structure and verifying alignment thereof.

36. The method of claim 35, wherein the method is completed iteratively until the alignment is successfully verified.

37. A method of aligning a process support structure and incident ion beam in situ comprising:

selecting ion implantation process parameters, the process parameters including at least an angle of implant;

determining a range of acceptable charge values for one or more angle detectors based at least partly on the process parameters and angle implantation charge data;

initiating an ion implantation process in accordance with the ion implantation process parameters;

monitoring charge values from the one or more angle detectors during the ion implantation process; and

appropriately modifying the ion implantation process parameters during the ion implantation process on obtaining charge values outside of the acceptable range of charge values.

38. The method of claim 37, further comprising calibrating the process disk prior to initiating the ion implantation process.

39. The method of claim 37, wherein modifying the process parameters comprises adjusting first and second angle values by determined offset values.

40. A method of aligning an incident ion beam comprising:

providing a process support structure configured to support one or more wafers and having one or more angle detectors;

aligning the process support structure to initial first and second angle values;

determining a plurality of first angle offset values and second angle offset values;

performing ion implantations for the plurality of second angle offset values and obtaining a plurality of second angle signal values;

performing ion implantations for the plurality of first angle offset values and obtaining first angle signal values; and

determining an first angle calibration value according to the plurality of first angle signal values and a second angle calibration value according to the plurality of second angle signal values.

41. The method of claim 40, wherein the first angle signal values and the second angle signal values are based on accumulated charges obtained by a charge collector.

42. The method of claim 41, wherein the first angle signal values and the second angle signal values are based on beam current values measured by a faraday.