Method of performing lithography using cantilever array

• US 5,666,190 A
• Filed: 12/04/1995
• Issued: 09/09/1997
• Est. Priority Date: 04/12/1994
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.)
• Inventors: Quate, Calvin F., Minne, Stephen Charles
• Primary Examiner(s): Gellner, Michael L.
• Assistant Examiner(s): MALLEY, DANIEL PATRICK
• Application Number:
  US08/566,621
• Time in Patent Office: 645 Days
• Field of Search: 355/71, 354/227.1, 250/234
• US Class Current: 355/71
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G01Q 20/02 by optical means
• CPC Class Codes: G01Q 70/06 Probe tip arrays
• CPC Class Codes: G01Q 80/00 Applications, other than SPM, of scanning-probe techniques manufacture or treatment of nanostructures B82B3/00; recording or reproducing information using near-field interaction G11B9/12, G11B11/24, G11B13/08
• CPC Class Codes: G03F 7/0002 Lithographic processes using patterning methods other than those involving the exposure to radiation, e.g. by stamping
• CPC Class Codes: G03F 7/2049 using a cantilever
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 7/70375 Multiphoton lithography or multiphoton photopolymerization; Imaging systems comprising means for converting one type of radiation into another type of radiation
• CPC Class Codes: Y10S 977/856 including etching/cutting
• CPC Class Codes: Y10S 977/857 including coating

Abstract

A lithography system includes a plurality of cantilevers, preferably formed in a silicon wafer. Each cantilever includes a tip located near the free end of the cantilever and an electrical conduction path which extends along the length of the cantilever to the tip. A switch is included in the conduction path to control the voltage at the tip of the cantilever.

The array of such cantilevers is positioned adjacent a wafer which is to be patterned, in the manner of an atomic force microscope operating in either the contact or noncontact mode. The cantilever array is scanned over the wafer, preferably in a raster pattern, and the individual switches are operated so as to control an electric current or electric field at the tip of each cantilever. The electric current or field is used to write a pattern on a layer of resist coating the wafer or on the surface of the wafer itself. Alternatively, the lithographic pattern may be formed by using the tip to scribe lines in a thin layer of soft material coating the wafer.

Claims

1. A method of performing lithography on a substrate using a layer of resist, said method comprising the following steps:

providing an array of cantilevers, said cantilevers being formed in a first substrate, each of said cantilevers including a tip located near a free end of said cantilever and a conductive path extending to said tip;

providing a second substrate, said second substrate being coated with a layer of resist;

bringing said first and second substrates together such that said tips of said cantilevers are adjacent a surface of said layer of resist;

scanning said cantilevers above said surface, said step of scanning comprising the step of causing one of said first and second substrates to oscillate back and forth along a first axis while causing the other of said first and second substrates to advance along a second axis generally perpendicular to said first axis; and

causing an electric current to flow between said tips and said layer of resist and then interrupting said electric current whereby said layer of resist is exposed in a plurality of selected lithographic patterns by said electric current.

2. The method of claim 1 wherein said layer of resist comprises a material selected from the group consisting of self-assembled monolayers, multilayered surface imaging resists, and poly(methylmethacrylate).

3. The method of claim 1 wherein said tips are in contact with said surface during said scanning.

4. The method of claim 1 wherein said tips are not in contact with said surface during said scanning.

5. The method of claim 4 further comprising the steps of:

causing said cantilevers to vibrate; and

detecting the respective frequencies at which said cantilevers are vibrating.

6. The method of claim 5 wherein the step of causing said cantilevers to vibrate includes the step of applying an AC signal to a piezoelectric element attached to each of said cantilevers.

7. The method of claim 5 further comprising the step of using the detected frequency of vibration of each cantilever to adjust a separation between said tip of said cantilever and said surface of said layer of resist.

8. The method of claim 7 wherein the steps of causing said cantilever to vibrate and adjusting said separation include the step of applying a superimposed AC/DC signal to a piezoelectric element attached to said cantilever.

9. The method of claim 1 wherein the step of interrupting said electric current comprises causing said cantilever to bend in a direction away from said surface of said layer of resist.

10. The method of claim 1 wherein the step of interrupting said electric current comprises opening a switch that is connected in an electric conduction path extending to said tip.

11. The method of claim 1 wherein said step of scanning comprises oscillating said first substrate along said first axis and advancing said second substrate along said second axis.

12. The method of claim 1 wherein said step of scanning comprises oscillating said second substrate along said first axis and advancing said first substrate along said second axis.

13. The method of claim 1 wherein a piezoelectric element is used to cause said one of said substrates to oscillate along said first axis.

14. The method of claim 1 wherein a piezoelectric element is used to cause said one of said substrates to advance along said second axis.

15. The method of claim 1 wherein the other of said first and second substrates is advanced along said second axis in steps such that each of said tips describes a raster pattern on said second substrate.

16. A method of performing lithography on a substrate, said method comprising the steps of:

providing an array of cantilevers, said cantilevers being formed in a first substrate, each of said cantilevers including a tip located near a free end of said cantilever and a conductive path extending to said tip;

providing a second substrate;

bringing said first and second substrates together such that said tips of said cantilevers are adjacent a surface of said second substrate;

scanning said cantilevers above said surface, said step of scanning comprising the step of causing one of said first and second substrates to oscillate back and forth along a first axis while causing the other of said first and second substrates to advance along a second axis generally perpendicular to said first axis; and

electrically biasing each of said tips so as to create an electric field between said tip and said second substrate and then interrupting said electric field whereby said electric field causes an oxide layer to form in a plurality of selected lithographic patterns on said second substrate.

17. The method of claim 16 wherein said second substrate comprises a material selected from the group consisting of silicon, silicon dioxide, aluminum, chromium and titanium.

18. The method of claim 16 wherein said tips are in contact with said surface during said scanning.

19. The method of claim 16 wherein said tips are not in contact with said surface during said scanning.

20. The method of claim 19 further comprising the steps of:

causing said cantilevers to vibrate; and

detecting the respective frequencies at which said cantilevers are vibrating.

21. The method of claim 20 wherein the step of causing said cantilevers to vibrate includes the step of applying an AC signal to a piezoelectric element attached to each of said cantilevers.

22. The method of claim 20 further comprising the step of using the detected frequency of vibration of each cantilever to adjust a separation between said tip of said cantilever and said surface of said substrate.

23. The method of claim 22 wherein the steps of causing said cantilever to vibrate and adjusting said separation include the step of applying a superimposed AC/DC signal to a piezoelectric element attached to said cantilever.

24. The method of claim 16 wherein the step of interrupting said electric current comprises causing said cantilever to bend in a direction away from said surface of said substrate.

25. The method of claim 16 wherein the step of interrupting said electric current comprises opening a switch that is connected in an electric conduction path extending to said tip.

26. The method of claim 16 wherein said step of scanning comprises oscillating said first substrate along said first axis and advancing said second substrate along said second axis.

27. The method of claim 16 wherein said step of scanning comprises oscillating said second substrate along said first axis and advancing said first substrate along said second axis.

28. The method of claim 16 wherein a piezoelectric element is used to cause said one of said substrates to oscillate along said first axis.

29. The method of claim 16 wherein a piezoelectric element is used to cause said one of said substrates to advance along said second axis.

30. The method of claim 16 wherein the other of said first and second substrates is advanced along said second axis in steps such that each of said tips describes a raster pattern on said second substrate.

31. A method of performing lithography on a substrate, said method comprising the steps of:

providing an array of cantilevers, said cantilevers being formed in a first substrate, each of said cantilevers including a tip located near a free end of said cantilever and a conductive path extending to said tip;

providing a second substrate, said second substrate including a surface layer of a material that is softer than a material at a surface of said tip;

bringing said first and second substrates together such that said tips of said cantilevers are adjacent said surface layer;

scanning said cantilevers across said surface, said step of scanning comprising the step of causing one of said first and second substrates to oscillate back and forth along a first axis while causing the other of said first and second substrates to advance along a second axis generally perpendicular to said first axis; and

causing each of said cantilevers to bend in a direction toward said substrate such that said tip of said cantilever scribes a trench in said surface layer.

32. The method of claim 31 wherein the other of said first and second substrates is advanced along said second axis in steps such that each of said tips describes a raster pattern on said second substrate.