LASER ABLATION APPARATUS AND METHOD

• US 20090273782A1
• Filed: 05/05/2009
• Published: 11/05/2009
• Est. Priority Date: 05/05/2008
• Status: Active Grant

• Current Assignee: Applied Spectra, Inc.
• Original Assignee: Applied Spectra, Inc.
• Inventors: Liu, Chunyi, Tribe, Randolph S., Yoo, Jong Hyun
• Granted Patent: US 8,199,321 B2
• Time in Patent Office: Days
• US Class Current: 356/318
• CPC Class Codes: B23K 26/03 Observing, e.g. monitoring, the workpiece
• CPC Class Codes: B23K 26/048 by controlling the distance between laser head and workpiece
• CPC Class Codes: B23K 26/0861 in at least in three axial directions
• CPC Class Codes: G01J 3/443 Emission spectrometry
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma
• CPC Class Codes: H01J 49/0463 Desorption by laser or particle beam, followed by ionisation as a separate step sample holder per se H01J49/0418

Abstract

Provided is a laser ablation spectroscopy apparatus and method. A pulse laser is focused on the sample site to generate a plasma plume during a laser ablation process. The plasma plume is detected with a spectrometer and an intensified charge coupled device. A sample of material is coupled to a stage movable in the x, y and z directions using an array of x-y-z motors. A change in the height of the sample is detected using a triangulation sensor. The apparatus includes a system computer for synchronizing the movement of the stage in the x, y and z direction during the laser ablation process. The method includes a protocol of generating one or more laser ablations per sample site. The spectral data of the total number of laser ablations for each sample site are averaged together. The protocol includes laser ablating additional sample sites and averaging the spectral data of the total number of sample sites.

Claims

1. Method of ablation spectroscopy, comprising:

ablating a location of a material coupled to a stage movable in any of an x-y-z direction;

generating spectral data associated with the ablated material;

averaging spectral data of two or more ablations of the location to generate a ‘

site sum’

, automatically adjusting a height of the material; and

ablating one or more additional locations to generate additional site sums and averaging the spectral data of the total number of site sums to generate a ‘

sample sum’

, automatically adjusting the height of the material.

2. The method of claim 1, further comprising completing the method of claim 1 on a known standard material to generate a calibrated spectral data before completing the method of claim 1 on the ‘

material’

, and using the calibrated spectral data to generate the ‘

spectral data’

.

3. The method of claim 2, wherein the calibrated spectral data comprises spectral intensity values, wavelength values and composition values, wherein the spectral data comprises spectral intensity values and wavelength values.

4. The method of claim 3, wherein the spectral data is generated by comparing the spectral intensity values of the ‘

spectral data’

with the spectral intensity values of calibrated spectral data and approximating composition values for the spectral data.

5. The method of claim 1, wherein ablation spectroscopy comprises laser induced breakdown spectroscopy.

6. The method of claim 1, wherein the stage is movable using an array of stepper motors coupled thereto, the array of stepper motors controlled by a system computer.

7. The method of claim 1, wherein the generated spectral data is presented on a graphical user interface.

8. The method of claim 1, wherein a sensor generates a displacement signal proportional to a change in the height of the material.

9. The method of claim 8, wherein the sensor comprises a laser triangulation sensor.

10. The method of claim 8, wherein a computer coupled with the sensor is used in automatically adjusting the height.

11. The apparatus of claim 8, wherein the sensor comprises a laser triangulation sensor, the triangulation sensor generating a visible spot on a surface of the material, the visible spot being coincident with an ablation impact point of the ablation source.

12. An apparatus for ablation spectroscopy, comprising:

an ablation source configured to ablate a material on a stage movable in any of an x-y-z direction;

a sensor generating a displacement signal proportional to a change in height of the movable stage;

a spectrometer and detector configured for detecting spectral data and generating intensity values, wavelength values and composition values of one or more elements of the material; and

a system computer coupled with the sensor and the movable stage automatically adjusting the height of the material.

13. The apparatus of claim 12, wherein ablation spectroscopy comprises laser induced breakdown spectroscopy.

14. The apparatus of claim 12, wherein the ablation source comprises a laser.

15. The apparatus of claim 12, wherein the stage comprises an array of stepper motors coupled thereto, the array of stepper motors being controlled by the system computer.

16. The apparatus of claim 12, wherein the sensor comprises a laser triangulation sensor, the triangulation sensor generating a visible spot on a surface of the material, the visible spot being coincident with an ablation impact point of the ablation source.

17. The apparatus of claim 12, wherein the generated spectral data is presented on a graphical user interface.

18. The apparatus of claim 12, wherein the spectrometer comprises a monochromator or a polychromator.

19. The apparatus of claim 12, wherein the detector comprises a photomultiplier or a charge couple device (CCD).

20. The apparatus of claim 12, wherein the detector comprises an ‘

intensified’

CCD or ICCD.

21. The apparatus of claim 12, wherein the system computer includes a controller configured to synchronize the ablation source, the movable stage, the sensor, the spectrometer, and the detector.

22. The apparatus of claim 21, further comprising a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) apparatus.

23. Method of ablation spectroscopy, comprising:

ablating a location of a material;

generating spectral data associated with the ablated material to generate a ‘

site sum’

; and

ablating one or more additional locations to generate additional site sums and averaging the spectral data of the total number of site sums to generate a ‘

sample sum’

, automatically adjusting the height of the material.

24. The method of claim 23, wherein the ablating the location comprises averaging spectral data of two or more ablations of the location, automatically adjusting a height of the material.

25. The method of claim 23, wherein the ablating the location comprises a single ablation of the location, automatically adjusting a height of the material.

26. The method of claim 23, further comprising completing the method of claim 23 on a known standard material to generate a calibrated spectral data before completing the method of claim 23 on the ‘

material’

, and using the calibrated spectral data to generate the ‘

spectral data’

.

27. The method of claim 26, wherein the calibrated spectral data comprises spectral intensity values, wavelength values and composition values, wherein the spectral data comprises spectral intensity values and wavelength values.

28. The method of claim 27, wherein the spectral data is generated by comparing the spectral intensity values of the ‘

spectral data’

with the spectral intensity values of calibrated spectral data and approximating composition values for the spectral data.

29. The method of claim 23, wherein the location of the material is coupled to a stage movable in any of an x-y-z direction.

30. The method of claim 29, wherein the stage is movable using an array of stepper motors coupled thereto, the array of stepper motors controlled by a system computer.

31. The method of claim 23, wherein ablation spectroscopy comprises laser induced breakdown spectroscopy.

32. The method of claim 23, wherein the generated spectral data is presented on a graphical user interface.

33. The method of claim 23, wherein a sensor generates a displacement signal proportional to a change in the height of the material.

34. The method of claim 33, wherein the sensor comprises a laser triangulation sensor.

35. The method of claim 33, wherein a computer coupled with the sensor is used in automatically adjusting the height.

36. The apparatus of claim 33, wherein the sensor comprises a laser triangulation sensor, the triangulation sensor generating a visible spot on a surface of the material, the visible spot being coincident with an ablation impact point of the ablation source.

37. Method of ablation spectroscopy using an ablation apparatus having an adjustable

ablation impact point, comprising:

ablating a location of a material;

generating spectral data associated with the ablated material;

averaging spectral data of two or more ablations of the location to generate a ‘

site sum’

, automatically adjusting the ablation impact point to optimize a plasma lumina; and

ablating one or more additional locations to generate additional site sums and averaging the spectral data of the total number of site sums to generate a ‘

sample sum’

, automatically adjusting the ablation impact point to optimize the plasma lumina.

38. The method of claim 37, further comprising completing the method of claim 37 on a known standard material to generate a calibrated spectral data before completing the method of claim 37 on the ‘

material’

, and using the calibrated spectral data to generate the ‘

spectral data’

.

39. The method of claim 38, wherein the calibrated spectral data comprises spectral intensity values, wavelength values and composition values, wherein the spectral data comprises spectral intensity values and wavelength values.

40. The method of claim 39, wherein the spectral data is generated by comparing the spectral intensity values of the ‘

spectral data’

with the spectral intensity values of calibrated spectral data and approximating composition values for the spectral data.

41. The method of claim 37, wherein the location of the material is coupled to a stage movable in any of an x-y-z direction.

42. The method of claim 41, wherein the stage is movable using an array of stepper motors coupled thereto, the array of stepper motors controlled by a system computer.

43. The method of claim 37, wherein ablation spectroscopy comprises laser induced breakdown spectroscopy.

44. The method of claim 37, wherein the generated spectral data is presented on a graphical user interface.

45. The method of claim 37, wherein a sensor generates a displacement signal proportional to a change in the height of the material.

46. The method of claim 45, wherein the sensor comprises a laser triangulation sensor.

47. The method of claim 45, wherein a computer coupled with the sensor is used in automatically adjusting the height.

48. The apparatus of claim 45, wherein the sensor comprises a laser triangulation sensor, the triangulation sensor generating a visible spot on a surface of the material, the visible spot being coincident with the ablation impact point of the ablation source.