Defect detection using energy spectrometer

• US 7,276,694 B1
• Filed: 03/29/2005
• Issued: 10/02/2007
• Est. Priority Date: 03/29/2005
• Status: Active Grant

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Bertsche, Kirk J.
• Primary Examiner(s): Wells; Nikita
• Assistant Examiner(s): SMITH, JOHNNIE L
• Application Number:
  US11/092,545
• Time in Patent Office: 917 Days
• Field of Search: 250/310, 250/397, 250/307, 250/306
• US Class Current: 250/311
• CPC Class Codes: H01J 2237/2446 Position sensitive detectors
• CPC Class Codes: H01J 2237/24475 Scattered electron detectors
• CPC Class Codes: H01J 2237/2448 Secondary particle detectors
• CPC Class Codes: H01J 2237/24485 Energy spectrometers
• CPC Class Codes: H01J 2237/24495 Signal processing, e.g. mixing of two or more signals
• CPC Class Codes: H01J 37/244 Detectors; Associated components or circuits therefor

Abstract

One embodiment disclosed relates to an apparatus for detecting defects in substrates. An irradiation source is configured to generate an incident beam, and a lens system configured to focus the incident beam onto a target substrate so as to cause emission of electrons. A multiple-bin detector is configured to detect the emitted electrons, and each bin of the detector detects the emitted electrons within a range of energies. A processing system configured to process signals from the multiple-bin detector. Other embodiments are also disclosed.

Claims

1. An apparatus for detecting defects in substrates, the apparatus comprising:

an irradiation source configured to generate an incident beam;

a lens system configured to focus the incident beam onto a target substrate so as to cause emission of electrons;

a multiple-bin detector configured to detect the emitted electrons directly from the target substrate, wherein each bin of the detector detects the emitted electrons within a range of energies; and

a processing system configured to process signals from the multiple-bin detector.

2. The apparatus of claim 1, wherein the multiple-bin detector comprises a higher-energy detector, a lower-energy detector, and an energy filter, wherein the detector is configured such that electrons with sufficiently high energy to pass the energy filter are detected by the higher-energy detector, and wherein the detector is configured such that electrons without sufficient energy to pass the energy filter are detected by the lower-energy detector.

3. The apparatus of claim 2, wherein the energy filter comprises a first conductive mesh and a second conductive mesh, wherein the second conductive mesh is at a voltage level more negative than the first conductive mesh.

4. The apparatus of claim 2, wherein the multiple-bin detector further comprises a mechanism to generate a magnetic field, and wherein the magnetic field is configured to direct the emitted electrons towards the energy filter and to direct the electrons without sufficient energy to pass the energy filter towards the lower-energy detector.

5. The apparatus of claim 1, wherein the multiple-bin detector comprises an energy dispersive element configured to disperse trajectories of the emitted electrons based upon the energies of the emitted electrons.

6. The apparatus of claim 5, wherein the energy dispersive element comprises an electrostatic dispersive element.

7. The apparatus of claim 5, wherein the energy dispersive element comprises an magnetic dispersive element.

8. The apparatus of claim 5, wherein the energy dispersive element comprises combined electric and magnetic elements.

9. The apparatus of claim 5, wherein the multiple-bin detector further comprises a segmented detector configured to receive the emitted electrons.

10. The apparatus of claim 1, wherein the multiple-bin detector comprises a plurality of electrostatic depressors, and wherein each electrostatic depressor is configured to redirect those emitted electrons with insufficient energy to pass the depressor towards a corresponding detector unit.

11. The apparatus of claim 1, wherein the apparatus comprises equipment for automated inspection of the substrates in a semiconductor manufacturing environment.

12. The apparatus of claim 1, wherein the apparatus comprises equipment for metrology of features on a semiconductor wafer.

13. The apparatus of claim 1, wherein the apparatus comprises equipment for defect review of semiconductor wafers.

14. A method of imaging defects in substrates, the method comprising:

generating an incident beam of irradiation;

focusing the incident beam onto a target substrate so as to cause emission of electrons;

detecting the emitted electrons directly from the target substrate into multiple energy bins, wherein each energy bin counts the emitted electrons within a range of energies; and

processing signals from the multiple energy bins,

wherein said processing includes determining an indication of a shift in surface charge.

15. The method of claim 14, wherein the shift in surface charge is used to dynamically adjust an energy threshold level.

16. The method of claim 15, wherein image data is selected using the dynamically-adjusted energy threshold level.

17. An automated inspection apparatus for detecting defects in substrates, the apparatus comprising:

means for creating an incident beam of irradiation;

means for impinging the incident beam onto a target substrate so as to cause emission of electrons;

means for detection of the emitted electrons directly from the target substrate into multiple energy bins, wherein each energy bin counts the emitted electrons within a range of electron energies; and

means for processing data signals derived from the multiple energy bins,

wherein the means for processing is configured to determine an indication of a shift in surface charge.

18. The apparatus of claim 17, wherein the apparatus is configured to use the shift in surface charge to dynamically adjust an energy threshold level.

19. The apparatus of claim 18, wherein the apparatus is further configured to select image data using the dynamically-adjusted energy threshold level.