Scanning probe microscope and method for increasing a scan speed of a scanning probe microscope in the step-in scan mode

Patent metadata

Field	Value
Publication number	US-11054439-B2
Application number	US-201916395542-A
Country	US
Kind code	B2
Filing date	Apr 26, 2019
Priority date	Oct 28, 2016
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

The present invention relates to a scanning probe microscope having: (a) a scan unit embodied to scan a measuring probe over a sample surface in a step-in scan mode; and (b) a self-oscillation circuit arrangement configured to excite the measuring probe to a natural oscillation during the step-in scan mode.

First claim

What is claimed is:

1. A scanning probe microscope comprising:
a. a scan unit embodied to scan a measuring probe over a sample surface in a step-in scan mode; and
b. a self-oscillation circuit arrangement configured to excite the measuring probe to a natural oscillation during the step-in scan mode;
c. wherein the self-oscillation circuit arrangement comprises a phase shifter configured to set a phase of the excitation relative to the natural oscillation of the measuring probe, wherein the phase shifter is configured to set the excitation with a phase difference in relation to a best possible excitation of the natural oscillation of the measuring probe in a range of ±30°; and
wherein the self-oscillation circuit arrangement comprises an automatic gain closed-loop control configured to set an amplitude of the natural oscillation of the measuring probe.

2. The scanning probe microscope according to claim 1 , wherein the phase shifter is configured to set the excitation with a phase difference in relation to the best possible excitation of the natural oscillation of the measuring probe in the range of ±20°.

3. The scanning probe microscope according to claim 1 , wherein the automatic gain closed-loop control comprises at least one amplifier, a scan-hold circuit arrangement and a control unit, wherein the control unit is configured to switch the scan-hold circuit arrangement between a scan mode and a hold mode.

4. The scanning probe microscope according to claim 1 , wherein the self-oscillation circuit arrangement is embodied as a digital circuit.

5. The scanning probe microscope according to claim 1 , wherein the self-oscillation circuit arrangement is embodied as at least one of a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

6. The scanning probe microscope according to claim 3 , further having a first actuator configured to transfer the excitation of the self-oscillation circuit arrangement to a cantilever of the measuring probe and a second actuator configured to transfer a signal from the control unit of the automatic gain closed-loop control to the cantilever of the measuring probe.

7. The scanning probe microscope according to claim 6 , further having a first laser system configured to transfer the excitation of the self-oscillation circuit arrangement to the first actuator and a second laser system configured to transfer the signal from the control unit to the second actuator.

8. The scanning probe microscope according to claim 6 , wherein the first actuator and the second actuator are embodied as a bimorph actuator.

9. The scanning probe microscope according to claim 8 , wherein the cantilever of the measuring probe comprises the bimorph actuator.

10. The scanning probe microscope according to claim 6 , further having a detector configured to detect a deflection of the cantilever of the measuring probe and a detection unit configured to detect a vertical position of a free end of the cantilever of the measuring probe.

11. The scanning probe microscope according to claim 1 , further having a control device which comprises the scan unit and an excitation unit, wherein the excitation unit is configured to control the self-oscillation circuit arrangement.

12. The scanning probe microscope according to claim 1 , wherein the amplitude of the natural oscillation of the measuring probe comprises a range of 1 nm to 1000 nm.

13. A method for increasing a scan speed of a scanning probe microscope operating in a step-in scan mode, the method comprising the following steps:
a. scanning a measuring probe over a sample surface in a step-in scan mode;
b. exciting the measuring probe to carry out a natural oscillation during the step-in scan mode by way of a self-oscillation circuit arrangement; and
c. setting a phase of the excitation relative to the natural oscillation of the measuring probe by use of a phase shifter of the self-oscillation circuit arrangement, wherein the phase shifter is configured to set the excitation with a phase difference in relation to a best possible excitation of the natural oscillation of the measuring probe in a range of ±30°; and
wherein the self-oscillation circuit arrangement comprises an automatic gain closed-loop control configured to set an amplitude of the natural oscillation of the measuring probe.

14. The method according to claim 13 , wherein steps a. and b. comprise:
d. in step b.: activating a first actuator configured to transfer the excitation of the self-oscillation circuit arrangement to the measuring probe;
e. in step a.: activating a second actuator configured to change a distance between a measuring tip of the measuring probe and a sample surface; and
f. in step a.: detecting a contact between the measuring tip of the measuring probe and the sample surface.

15. The method according to claim 14 , wherein steps a. and b. further comprise the sequence of steps:
g. in step b.: activating the second actuator;
h. in step b.: deactivating an amplitude closed-loop control by switching a scan-hold circuit arrangement from a scan mode to a hold mode;
i. in step b.: deactivating the first actuator if an amplitude of the natural oscillation of the measuring probe drops below a predetermined threshold;
j. in step a.: determining a vertical position of the measuring tip of the measuring probe after detecting a contact of the measuring tip with the sample surface;
k. in step a.: deactivating the second actuator and awaiting a predetermined time duration until there is a loss of contact between the measuring tip of the measuring probe and the sample surface;
l. in step b.: activating the first actuator in phase; and
m. in step b.: activating the amplitude closed-loop control by switching the scan-hold circuit arrangement from the hold mode to the scan mode.

16. The method according to claim 14 , wherein detecting a contact between the measuring tip of the measuring probe and the sample surface comprises the determination of a vertical position of the measuring tip of the measuring probe at this point.

17. The method according to claim 13 , further having the step of:
determining a switch-on time for the in-phase activation of a first actuator from a decay curve of the natural oscillation of the measuring probe without activation of the first actuator.

18. A non-transitory computer-readable medium storing a computer program comprising instructions which, when executed by a computer system, prompt the computer system in combination with a scanning probe microscope to carry out a method for increasing a scan speed of the scanning probe microscope operating in a step-in scan mode, the method comprising the following steps:
(a) scanning a measuring probe over a sample surface in a step-in scan mode;
(b) exciting the measuring probe to carry out a natural oscillation during the step-in scan mode by way of a self-oscillation circuit arrangement; and
(c) setting a phase of the excitation relative to the natural oscillation of the measuring probe by use of a phase shifter of the self-oscillation circuit arrangement, wherein the phase shifter is configured to set the excitation with a phase difference in relation to a best possible excitation of the natural oscillation of the measuring probe in the range of ±30°; and
wherein the self-oscillation circuit arrangement comprises an automatic gain closed-loop control configured to set an amplitude of the natural oscillation of the measuring probe.

19. The non-transitory computer-readable medium of claim 18 in wh

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Baur Christof

Classifications

• G01Q10/06 Primary

  Circuits or algorithms therefor · CPC title

• G01Q10/045 Primary

  Self-actuating probes, i.e. wherein the actuating means for driving are part of the probe itself, e.g. piezoelectric means on a cantilever probe · CPC title