METHOD OF AND APPARATUS FOR REAL-TIME CONTINUAL NANOMETER SCALE POSITION MEASUREMENT BY BEAM PROBING AS BY LASER BEAMS AND THE LIKE OF ATOMIC AND OTHER UNDULATING SURFACES SUCH AS GRATINGS OR THE LIKE RELATIVELY MOVING WITH RESPECT TO THE PROBING BEAMS

• US 6,639,686 B1
• Filed: 04/13/2000
• Issued: 10/28/2003
• Est. Priority Date: 04/13/2000
• Status: Active Grant

• Current Assignee: Nanowave Inc.
• Original Assignee: Nanowave Inc.
• Inventors: Ohara, Tetsuo
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US09/549,115
• Time in Patent Office: 1,293 Days
• Field of Search: 356/616, 356/601, 356/614, 356/615, 356/624, 250/306, 250/307
• US Class Current: 356/616
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01Q 20/02 by optical means
• CPC Class Codes: G01Q 60/22 Probes, their manufacture, or their related instrumentation, e.g. holders

Abstract

An improved method of and apparatus for real-time continual nanometer scale position measurement by beam probing as by laser beams and the like, both fixed and oscillating or scanning, over an atomic and other undulating surface such as gratings or the like, relatively moving with respect to the probing beams; and providing, where desired, increased detection speeds, improved positioning sensing response, freedom from or relaxed requirements of strict control on probing oscillation amplitude, and multi-dimensional position measurement with focused beam probes and the like.

Claims

1. A method of real-time nanometer scale position measurement of the location of a radiation beam probe relatively moving over a periodically undulating surface, that comprises, focusing and impinging the beam upon the surface during such relative movement and receiving the successive reflections of the beam from the surface;

generating substantially sinusoidal voltages through the reception of the beam reflections having the periodicity of the surface undulations;

comparing the phase and amplitude of the generated sinusoidal voltages with a reference sinusoidal voltage at a related frequency through multiplying the generated and reference voltages to develop positional signals, on a continual basis, indicative of the direction and distance of the beam probe off the apex of the nearest undulation of the surface, and thus the position of the beam probe along the surface.

2. The method of claim 1 wherein the radiation beam probe is generated by collimating laser light along a longitudinal axis and focusing the light as a probing beam upon said surface.

3. The method of claim 2 wherein beam reflections from said surface are returned first along said axis, and are then split transversely therefrom and focused upon a photodetector receiver.

4. The method of claim 1 wherein the beam probe is oscillated under the control of a controlling sinusoidal voltage the serves as said reference voltage.

5. The method of claim 4 wherein requirements in the controlling of the amplitude of the probe oscillating are relaxed through introducing multiplying the generated sinusoidal voltages by second and third order harmonics of the probe oscillation frequency and adding to the estimated probe position information in the comparing step.

6. The method of claim 5 wherein a closed loop is created according to equation (22) herein to keep error between said estimated position and the real position at substantially zero.

7. The method of claim 4 wherein increased detection speed is obtained by generating a negative reference frequency by multiplying the generated sinusoidal voltage of frequency ω

by sin (0.5 ω

t) and using such in said comparing step.

8. The method of claim 7 wherein the resultant signal is that of equation (24) herein.

9. The method of claim 4 wherein improved positioning sensing response is attained by introducing independent acceleration or speed sensing within the voltage output in the comparing step.

10. The method of claim 4 wherein multi-dimensional position measurement is effected by forming the surface in multi-layers and employing orthogonally scanning beams to focus on the respective layers.

11. The method of claim 1 wherein the beam probe consists of a single focused beam.

12. The method of claim 1 wherein the radiation beam is selected from the group consisting of laser, electron and ion beams.

13. A method of real-time nanometer scale position measurement of the location of a radiation beam probe relatively moving over a periodically undulating surface, that comprises, focusing and impinging the beam upon the surface during such relative movement and receiving the successive reflections of the beam from the surface;

generating substantially sinusoidal voltages through the reception of the beam reflections having the periodicity of the surface undulations;

comparing the phase and amplitude of the generated sinusoidal voltages with a reference sinusoidal voltage at a related frequency through multiplying the generated and reference voltages to develop positional signals, on a continual basis, indicative of the direction and distance of the beam probe off the apex of the nearest undulation of the surface, and thus the position of the beam probe along the surface and wherein the beam probe comprises a plurality of adjacent focused beams.

14. The method of claim 13 wherein the beams are fixed-focused upon adjacent points of the surface.

15. The method of claim 14 wherein the separate generated sinusoidal voltages of the reflected beams comprising the beam probe are compared to determine the beam probe position along the surface.

16. The method of claim 15 wherein said plurality comprises a main central reference beam and outer adjacent beams, separated by (2m+1)P/4, where m is an integer and P is the period of the undulations of said surface, wherein the reflected beams generate respective sinusoidal quadrature voltages with 90-degree phase difference as the beam probe and surface relatively move past one another.

17. The method of claim 16 wherein said comparing includes filtering, up/down counting and digital interpolation of the quadrature voltages to determine motion direction and beam probe position.

18. Apparatus for real-time nanometer scale position measurement of the location of a radiation beam probe relatively moving over a periodically undulating surface, having, in combination, a radiation beam source;

and optical system for focusing and impinging the beam from the source upon the surface during such relative movement and receiving the successive reflections of the beam from the surface;

detector means for generating substantially sinusoidal voltages through the reception of the beam reflections having the periodicity of the surface undulations; and

means for comparing the phase and amplitude of the generated sinusoidal voltages with a reference sinusoidal voltage at a related frequency through multiplying the generated and reference voltages to develop positional signals, on a continual basis, indicative of the direction and distance of the beam probe off the apex of the nearest undulation of the surface, and thus the position of the beam probe along the surface.

19. The apparatus claimed in claim 18 wherein oscillating means is provided for oscillating the beam probe under the control of a controlling sinusoidal voltage that serves as said reference voltage.

20. The apparatus claimed in claim 19 wherein the optical system returns the beam reflections from said surface first along said axis, and then to a beam-splitter to bend the beam transversely therefrom and then focused upon a photodetector receiver.

21. The apparatus claimed in claim 18 wherein the radiation beam is generated by a laser light source and the optical system collimates the beam along a longitudinal axis and focuses the beam as a probing laser beam upon said surface.

22. The apparatus of claim 18 wherein the beam probe is formed as a single focused beam.

23. The apparatus of claim 18 wherein the radiation beam is selected from the group consisting of laser, electron and ion beams.

24. Apparatus for real-time nanometer scale position measurement of the location of a radiation beam probe relatively moving over a periodically undulating surface, having, in combination, a radiation beam source;

and optical system for focusing and impinging the beam from the source upon the surface during such relative movement and receiving the successive reflections of the beam from the surface;

detector means for generating substantially sinusoidal voltages through the reception of the beam reflections having the periodicity of the surface undulations; and

means for comparing the phase and amplitude of the generated sinusoidal voltages with a reference sinusoidal voltage at a related frequency through multiplying the generated and reference voltages to develop positional signals, on a continual basis, indicative of the direction and distance of the beam probe off the apex of the nearest undulation of the surface, and thus the position of the beam probe along the surface and wherein the beam probe is formed as a plurality of adjacent focused beams.

25. The apparatus of claim 24 wherein the optical system fixed-focuses the beams upon adjacent points of the surface.

26. The apparatus of claim 25 wherein the separate generated sinusoidal voltages of the reflected beams comprising the beam probe are compared to determine the beam probe position along the surface.

27. The apparatus of claim 26, wherein said plurality comprises a main central reference beam and outer adjacent beams separated by (2m+1)P/4, where m is an integer and P is the period of the undulations of said surface, wherein the reflected beams generate respective sinusoidal quadrature voltages with 90-degree phase differential as the beam probe and surface relatively move past one another.

28. The apparatus of claim 27 wherein said comparing means includes means for filtering, up/down counting and digital interpolation of the quadrature voltages to determine motion direction and beam probe position.