Atomic force microscopy

Abstract

An atomic force microscope includes a tip mounted on a micromachined cantilever. As the tip scans a surface to be investigated, interatomic forces between the tip and the surface induce displacement of the tip. A laser beam is transmitted to and reflected from the cantilever for measuring the cantilever orientation. In a preferred embodiment the laser beam has an elliptical shape. The reflected laser beam is detected with a position-sensitive detector, preferably a bicell. The output of the bicell is provided to a computer for processing of the data for providing a topographical image of the surface with atomic resolution.

Description

Moreover, the size of the reflected laser beam 46 received at the bicell 40 is 5 to 7 times larger in the direction perpendicular to the deflection direction as shown in FIG. 5, thereby enabling the use of higher laser power, without exceeding the saturation limit of the bicell, and correspondingly achieving higher measurement sensitivity. Alternatively, the distance between the cantilever beam and bicell can be decreased, thus resulting in an even more compact microscope.

While there have been described and illustrated an atomic force microscope and several modifications and variations thereof, it will be apparent to those skilled in the art that further modifications and variations are possible without deviating from the broad spirit of the present invention which shall be limited solely by the scope of the claims appended hereto.

Claims

1. A method for generating a topographical image of a surface of a workpiece comprising the steps of:

moving a tip which is fixed to one end of a front side of a micromachined cantilever beam toward a surface of a workpiece to be inspected at a distance where the forces occurring between the atoms at the tip and on the workpiece surface deflect the cantilever;

transmitting a laser beam onto a back of the cantilever beam;

detecting the laser beam reflected from the cantilever beam with position-sensitive detection means for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam which change is inversely proportional to the length of the cantilever beam;

scanning the tip relative to the surface, and

processing the output signal for providing a topographical image of the workpiece surface.

2. The method as set forth in claim 1, wherein said transmitting a laser beam comprises coupling the laser beam to an optical fiber.

3. The method as set forth in claim 1, wherein said laser beam is transmitted to a reflector coupled to the back of the cantilever beam.

4. The method as set forth in claim 1, wherein said laser beam is transmitted to at least one arm supporting the tip in the region of the tip.

5. The method as set forth in claim 1, wherein said position-sensitive detector comprises a bicell.

6. The method as set forth in claim 5, wherein said bicell is a silicon bicell.

7. The method as set forth in claim 1, wherein said laser beam is in the visible light spectrum.

8. The method as set forth in claim 1, wherein the position sensitive detector is remotely positioned from the cantilevered beam.

9. The method as set forth in claim 8, A method for generating a topographical image of a surface of a workpiece comprising:

moving a tip which is fixed to one end of a front side of a micromachined cantilever beam toward a surface of a workpiece to be inspected at a distance where the forces occurring between the atoms at the tip and on the workpiece surface deflect the cantilever;

transmitting a laser beam onto a back of the cantilever beam;

detecting the laser beam reflected from the cantilever beam with position-sensitive detection means for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam which change is inversely proportional to the length of the cantilever beam;

scanning the tip relative to the surface, and

processing the output signal for providing the topographical image of the workpiece surface,

wherein the position sensitive detector is remotely positioned from the cantilevered beam, and

wherein an inertial mover remotely positions the detector.

10. The method as set forth in claim 9, wherein said moving and said detector are performed in an inaccessible environment.

11. The method as set forth in claim 10, wherein said inaccessible environment is a vacuum or ultrahigh vacuum.

12. The method as set forth in claim 8, wherein said moving and said detecting are performed in an inaccessible environment.

13. The method as set forth in claim 12, wherein said inaccessible environment is a vacuum or ultrahigh vacuum.

14. The method as set forth in claim 1 A method for generating a topographical image of a surface of a workpiece comprising:

moving a tip which is fixed to one end of a front side of a micromachined cantilever beam toward a surface of a workpiece to be inspected at a distance where the forces occurring between the atoms at the tip and on the workpiece surface deflect the cantilever;

transmitting a laser beam onto a back of the cantilever beam;

detecting the laser beam reflected from the cantilever beam with position-sensitive detection means for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam which change is inversely proportional to the length of the cantilever beam;

scanning the tip relative to the surface, and

processing the output signal for providing the topographical image of the workpiece surface,

wherein said transmitted reflected laser beam has an elliptical beam shape at said detection means.

15. An atomic force microscope for generating a topographical image of a surface of a workpiece wherein the improvement comprises:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where the forces between the atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam which change is inversely proportional to the length of the cantilever beam;

means for causing the tip and surface to undergo relative scanning motion, and

computing means coupled to said detection means for generating a topographical image of the surface.

16. An atomic force microscope as set forth in claim 15, wherein said laser means comprises an optical fiber for coupling said laser beam to said cantilever beam.

17. An atomic force microscope as set forth in claim 15, further comprising reflective means coupled to the back of the cantilever beam for reflecting the transmitted laser beam.

18. An atomic force microscope as set forth in claim 15, wherein said tip is fixed to the micromachined cantilever beam by means of at least one arm and said laser means transmits a laser beam to said at least one arm in the region of said tip.

19. An atomic force microscope as set forth in claim 15, wherein said position sensitive detection means comprises a bicell.

20. An atomic force microscope as set forth in claim 19, wherein said bicell is a silicon bicell.

21. An atomic force microscope as set forth in claim 15, wherein said laser means operates in the visible light spectrum.

22. An atomic force microscope as set forth in claim 21, where said laser means comprises a single-mode diode laser.

23. An atomic force microscope as set forth in claim 15, wherein said position-sensitive detection means is remotely positionable from the cantilever beam.

24. An atomic force microscope as set forth in claim 23, for generating a topographical image of a surface of a workpiece wherein the improvement comprises:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where the forces between the atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam, said position-sensitive detection means being remotely positionable from the cantilever beam, and wherein said position-sensitive detection means comprises an inertial mover;

means for causing the tip and surface to undergo relative scanning motion; and

computing means coupled to said detection means for generating the topographical image of the surface.

25. An atomic force microscope as set forth in claim 15, wherein said tip and said position-sensitive detection means are disposed in an inaccessible environment.

26. An atomic force microscope as set forth in claim 25, wherein said inaccessible environment is a vacuum or ultrahigh vacuum.

27. An atomic force microscope as set forth in claim 15, for generating a topographical image of a surface of a workpiece, comprising:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where the forces between the atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam;

means for causing the tip and surface to undergo relative scanning motion, and

computing means coupled to said detection means for generating the topographical image of the surface,

wherein said laser means transmits a laser beam having an elliptical shape to the back of the cantilever beam and wherein said reflected laser beam has an elliptical shape at said detection means.

28. An atomic force microscope as set forth in claim 15, further comprising display means coupled to said computing means for displaying a topographical image of the surface.

29. An atomic force microscope for generating a topographical image of a surface of a workpiece comprising:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where the forces between the atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam;

means for causing the tip and surface to undergo relative scanning motion; and

computing means coupled to said detection means for generating the topographical image of the surface,

wherein said laser means operates in the visible light spectrum,

wherein said laser means comprises a single-mode diode laser, and

wherein said reflected beam has a shape other than circular.

30. An atomic force microscope for generating a topographical image of a surface of a workpiece, comprising:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where forces between atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam, wherein the reflected laser beam has an elongated shaped light spot when incident upon the detection means;

means for causing the tip and the surface to undergo relative scanning motion; and

computing means, coupled to said detection means, for generating the topographical image of the surface.

31. The atomic force microscope of claim 30, wherein the elongated shaped light spot at said detection means moves in a direction transverse to its elongation dimension when the forces deflect the cantilever.

32. The atomic force microscope of claim 30, wherein said elongated shaped light spot is elliptical.

33. The atomic force microscope of claim 30, wherein said elongated shaped light spot is asymmetric.

34. The atomic force microscope of claim 30, wherein the laser means comprises a diode laser.

35. The atomic force microscope of claim 30, wherein the laser means produces an elongated shaped light spot when incident on said cantilever.

36. A force microscope for generating an image of a surface of a workpiece, comprising:

a tip fixed to one end of a front side of a micromachined cantilever beam adapted for being positioned in proximity to the surface of the workpiece where forces between atoms of said tip and the surface deflect the cantilever beam;

laser means for transmitting a laser beam to a back of the cantilever beam;

position-sensitive detection means for receiving said laser beam after being reflected from the cantilever beam and for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam, wherein the reflected laser beam has an elongated shaped light spot when incident upon the detection means;

means for causing the tip and the surface to undergo relative scanning motion; and

computing means, coupled to said detection means, for generating the image of the surface.

37. The force microscope of claim 36, wherein the elongated shaped light spot at said detection means moves in a direction transverse to its elongated dimension when the forces deflect the cantilever.

38. The force microscope of claim 36, wherein said elongated shaped light spot is elliptical.

39. The force microscope of claim 36, wherein said elongated shaped light spot is asymmetric.

40. The force microscope of claim 36, wherein the laser means comprises a diode laser.

41. The force microscope of claim 36, wherein the image comprises a topographical image.

42. The force microscope of claim 36, wherein the laser means produces an elongated shaped light spot when incident on said cantilever.

43. The force microscope of claim 36, wherein the force microscope comprises an atomic force microscope.

44. A method for generating an image of a surface of a workpiece comprising the steps of:

positioning a tip fixed to one end of a front side of a micromachined cantilever beam in proximity to the surface of the workpiece where the forces between the atoms of said tip and the surface deflect the cantilever beam;

transmitting a laser beam onto a back of the cantilever beam;

detecting the laser beam reflected from the cantilever beam with position-sensitive detection means for converting the reflected beam into an output signal indicative of an angular change of the cantilever beam, which change is inversely proportional to the length of the cantilever beam, wherein said reflected light beam produces an elongated shaped light spot when striking said position-sensitive detection means;

scanning the tip relative to the surface, and;

processing the output signal for providing an image of the surface of the workpiece.

45. The method of claim 44, wherein the elongated shaped light spot at said position-sensitive detection means moves in a direction transverse to its elongated dimension when the cantilever moves due to the forces.

46. The method of claim 44, wherein said elongated shaped light spot is asymmetrical.

47. The method of claim 44, wherein said elongated shaped light spot is elliptical.

48. The method of claim 44, wherein said transmitted laser beam is a beam from a diode laser.

49. The method of claim 44, wherein said transmitted laser beam produces an elongated shaped light spot when striking said cantilever.

50. The method of claim 44, wherein the image is a topographical image.