Scanning kelvin microprobe system and process for analyzing a surface

• US 20030175945A1
• Filed: 02/28/2003
• Published: 09/18/2003
• Est. Priority Date: 05/24/2000
• Status: Active Grant

• Current Assignee: Sencorchem International Corporation
• Original Assignee: Sencorchem International Corporation
• Inventors: Thompson, Michael, Cheran, Larisa-Emilia
• Granted Patent: US 7,084,661 B2
• Time in Patent Office: Days
• US Class Current: 435/287.2
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01N 27/002 by investigating the work function voltage
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: G01Q 60/30 Scanning potential microscopy

Abstract

A scanning Kelvin microprobe (SKM) system capable of measuring and analyzing surface characteristics of samples is provided. Also provided is a process of measuring and analyzing surface characteristics of samples. Further, there are provided uses of the SKM system in measuring and analyzing surface characteristics of conductors, semiconductors, insulators, chemicals, biochemicals, photochemicals, chemical sensors, biosensors, biochemical microarrays, microelectronic devices, electronic imaged devices, micromachined devices, nano-devices, corroded materials, stressed materials, coatings, adsorbed materials, contaminated materials, oxides, thin films, and self assembling monolayers.

Claims

1. A scanning Kelvin microprobe system for analyzing a surface of a sample, the system comprising:

a tip with a predetermined work function for exploring a surface of the sample, and for extracting Kelvin current from the local capacitor formed between the tip and the sample;

a scan table for placing the sample thereon;

a micropositioner for moving the scan table in x and y directions;

a piezoelectric translation stage attached to the scan table for moving the sample in the z direction for maintaining a constant sample-tip distance;

a charge amplifier for converting the Kelvin current extracted by the tip into a voltage;

a first lock-in amplifier tuned at a first frequency for measuring the voltage and generating a contact potential difference image signal;

a second lock-in amplifier tuned at a second frequency for monitoring sample-tip distance and for generating a topographic image signal, the second frequency being above the first frequency; and

a controller for controlling the micropositioner.

2. The scanning Kelvin microprobe system according to claim 1, additionally comprising a data acquisition system for acquiring said contact potential difference image signal and said topographical image signal.

3. The scanning Kelvin microprobe system according to claim 1, for analysis of a sample selected from the group consisting of conductors, semiconductors, insulators, chemicals, biochemicals, photochemicals, chemical sensors, biosensors, biochemical microarrays, microelectronic devices, electronic image devices, micromachined devices, nano-devices, corroded materials, stressed materials, coatings, adsorbed materials, contaminated materials, oxides, thin films, and self assembling monolayers.

4. The scanning Kelvin microprobe system according to claim 1, wherein the tip is a microelectrode having the apex radius of curvature less than about 100 nm.

5. The scanning Kelvin microprobe system according to claim 4, wherein said radius of curvature is about 50 nm.

6. The scanning Kelvin microprobe system according to claim 1, wherein the first frequency is from about 1 to about 20 kHz.

7. The scanning Kelvin microprobe system according to claim 1, wherein the second frequency is from about 100 to about 500 kHz.

8. The scanning Kelvin microprobe system according to claim 1, wherein the controller comprises software capable of opening a file, initializing a card and a motor, starting the first and the second lock-in amplifiers, bringing the tip down, scanning the sample, bringing the tip up, writing data in a file, and closing the file.

15. Use of a scanning Kelvin microprobe system according to any one of claims 1 to 8, for assessing a surface characteristic of a sample.

9. A process for analyzing a surface of a sample using a scanning Kelvin microprobe system, comprising the steps of:

placing a sample on a scan table;

exploring a surface of the sample with a tip having a predetermined work function;

extracting Kelvin current from a local capacitor formed between the tip and the sample;

amplifying the Kelvin current extracted by the tip;

measuring the Kelvin current and generating a contact potential difference signal using a first lock-in amplifier tuned at a first frequency; and

monitoring distance between the sample and the tip and generating a topographic image signal using a second lock-in amplifier tuned at a second frequency, the second frequency being above the first frequency.

10. The process according to claim 9, wherein the steps are controlled using a software program.

11. The process according to claim 9, for analysis of a sample selected from the group consisting of conductors, semiconductors, insulators, chemicals, biochemicals, photochemicals, chemical sensors, biosensors, biochemical microarrays, microelectronic devices, electronic image devices, micromachined devices, nano-devices, corroded materials, stressed materials, coatings, adsorbed materials, contaminated materials, oxides, thin films, and self assembling monolayers.

12. The process according to claim 9, wherein the first frequency is from about 1 to about 20 kHz.

13. The process according to claim 9, wherein the second frequency is from about 100 to about 500 kHz.

14. The process according to claim 9, wherein the software program conducts the steps of opening a file, initializing a card and a motor, starting first and second lock-in amplifiers, bringing the tip down, scanning the sample, bringing the tip up, writing data in a file, and closing the file.