Automated atomic force microscope and the operation thereof

• US 9,383,388 B2
• Filed: 04/21/2015
• Issued: 07/05/2016
• Est. Priority Date: 04/21/2014
• Status: Active Grant

• Current Assignee: Oxford Instruments Asylum Research Inc (Oxford Instruments PLC)
• Original Assignee: Oxford Instruments Asylum Research Inc (Oxford Instruments PLC)
• Inventors: Stetter, Frank, Proksch, Roger, Callahan, Roger C., Limpoco, Ted, Hohlbach, Sophia, Bemis, Jason, Cleveland, Jason
• Primary Examiner(s): Ippolito, Nicole
• Assistant Examiner(s): Chang, Hanway
• Application Number:
  US14/692,270
• Publication Number:
  US 20150301080A1
• Time in Patent Office: 441 Days
• Field of Search: 850/5, 850/6, 850/7, 850/21, 850/33
• US Class Current: 1/1
• CPC Class Codes: G01Q 10/065 Feedback mechanisms, i.e. wherein the signal for driving the probe is modified by a signal coming from the probe itself
• CPC Class Codes: G01Q 40/00 Calibration, e.g. of probes
• CPC Class Codes: G01Q 60/24 AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
• CPC Class Codes: G01Q 60/32 AC mode
• CPC Class Codes: G01Q 70/08 Probe characteristics

Abstract

Improvements for rapidly calibrating and automatically operating a scanning probe microscope are disclosed. A central component of the SPM is the force transducer, typically a consumable cantilever element. By automatically calibrating transducer characteristics along with other instrumental parameters, scanning parameters can be rapidly and easily optimized, resulting in high-throughput, repeatable and accurate measurements. In contrast to dynamic optimization schemes, this can be accomplished before the surface is contacted, avoiding tip or sample damage from the beginning of the measurement process.

Claims

1. A method of operating a cantilever based measuring instrument, comprising:

obtaining a relationship between an optical lever sensitivity of a cantilever of the cantilever based instrument in a dynamic environment where the sensitivity depends on distances to a sample, and using said relationship to determine a dynamic optical lever sensitivity called invOLS of said cantilever; and

measuring surfaces of the surface being measured using said invOLS value, by using a tip of the cantilever to measure characteristics of the surface and by estimating parameters of gain in the measurement, based on the invOLS value.

2. The method as in claim 1, wherein said obtaining said invOLS value comprises measuring a sensitivity of the cantilever of the cantilever based measuring instrument.

3. The method as in claim 2, wherein said obtaining said invOLS value comprises measuring the sensitivity without making contact between a tip of the cantilever and the sample.

4. The method as in claim 3, wherein said obtaining a relationship comprises obtaining a frequency spectrum of Brownian movement, and using said frequency spectrum to determine said sensitivity.

5. The method as in claim 3, wherein the sensitivity is measured by estimating a first spring constant of the cantilever using one technique that depends on detection sensitivity and estimating a second spring constant with a second technique different than the first technique, and estimating a sensitivity of the cantilever detection by inverting the first spring constant against the second spring constant.

6. The method as in claim 1, further comprising determining a spring constant of the cantilever.

7. The method as in claim 1, wherein said measuring comprises adjusting a gain of the feedback system that controls a separation between a tip and the sample based on an error signal, that is based on at least one gain parameter that is estimated from the measured sensitivity.

8. The method as in claim 1, wherein said cantilever based instrument is an Atomic Force Microscope.

9. A cantilever based measuring instrument apparatus, comprising:

a cantilever based instrument that has a cantilever, operating to measure a surface,

a controller that controls measuring information about the cantilever, in a dynamic environment where the sensitivity depends on distances to a sample, and using said relationship to determine a dynamic optical lever sensitivity called invOLS of said cantilever; and

said cantilever based instrument operating for measuring surfaces of the surface being measured using said invOLS value, by using a tip of the cantilever to measure characteristics of the surface and by estimating parameters of gain in the measurement, based on the invOLS value.

10. The apparatus as in claim 9, wherein said obtaining said invOLS value comprises measuring a sensitivity of the cantilever of the cantilever based measuring instrument.

11. The apparatus as in claim 10, wherein said obtaining said invOLS value comprises measuring the sensitivity without making contact between a tip of the cantilever and the sample.

12. The apparatus as in claim 11, wherein said obtaining a relationship comprises obtaining a frequency spectrum of Brownian movement, and using said frequency spectrum to determine said sensitivity.

13. The apparatus as in claim 11, wherein the sensitivity is measured by estimating a first spring constant of the cantilever using one technique that depends on detection sensitivity and estimating a second spring constant with a second technique different than the first technique, and estimating a sensitivity of the cantilever detection by inverting the first spring constant against the second spring constant.

14. The apparatus as in claim 9, further comprising determining a spring constant of the cantilever.

15. The apparatus as in claim 9, wherein said measuring comprises adjusting a gain of the feedback system that controls a separation between a tip and the sample based on an error signal, that is based on at least one gain parameter that is estimated from the measured sensitivity.

16. The apparatus as in claim 9, wherein said cantilever based instrument is an Atomic Force Microscope.

17. A method of operating a cantilever based measuring instrument, comprising:

obtaining a first relationship between an optical lever sensitivity of a cantilever of the cantilever based instrument in a first environment to determine a parameter of said cantilever in said first environment;

obtaining a second relationship between an optical lever sensitivity of a cantilever of the cantilever based instrument in a second environment to determine a parameter of said cantilever in said second environment; and

determining an optical lever sensitivity InvOLS for the cantilever, based on the spring constants in both environments being the same as

18. The method as in claim 17, wherein the first environment is in gas, and the second environment is in water.