Object inspection systems and methods

• US 9,122,178 B2
• Filed: 07/02/2010
• Issued: 09/01/2015
• Est. Priority Date: 08/04/2009
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Banine, Vadim Yevgenyevich, Den Boef, Arie Jeffrey, Scaccabarozzi, Luigi, Iosad, Nikolay Nikolaevich, Ivanov, Vitalii
• Primary Examiner(s): Lyons, Michael A
• Assistant Examiner(s): DECENZO, SHAWN H
• Application Number:
  US13/388,267
• Publication Number:
  US 20120127467A1
• Time in Patent Office: 1,887 Days
• Field of Search: 356/326, 3562372-2376
• US Class Current: 1/1
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/6489 Photoluminescence of semiconductors
• CPC Class Codes: G01N 21/65 Raman scattering
• CPC Class Codes: G01N 21/94 Investigating contamination, e.g. dust G01N21/85 takes precedence
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G03F 1/24 Reflection masks; Preparation thereof
• CPC Class Codes: G03F 1/84 Inspecting

Abstract

Methods and systems for inspection of an object include the use of spectroscopic techniques for the detection of unwanted particles on an object'"'"'s surface, based on the different responses of the unwanted particles as compared with the object to be inspected due to their different materials. Time resolved spectroscopy and/or energy resolved spectroscopy of secondary photon emission from the surface of the object can be used to obtain Raman and photoluminescence spectra. The objects to be inspected can for example be a patterning device as used in a lithographic process, for example a reticle, in which case the presence of metal, metal oxide or organic particles can be detected, for example. The methods and apparatus are highly sensitive, for example, being able to detect small particles (sub 100 nm, particularly sub 50 nm) on the patterned side of an EUV reticle.

Claims

1. A method for inspection of an object, comprising:

illuminating a surface of an object with a radiation beam;

analyzing secondary photon emissions from the surface of the object with time resolved spectroscopy, wherein the analyzing comprises;

analyzing a first portion of the secondary photon emissions received through a first optical path,

analyzing a second portion of the secondary photon emissions received through a second optical path, wherein the first and second portions of the secondary photon emissions comprise wavelengths that are the same, and

performing a correlation between the analysis of the first portion and the analysis of the second portion; and

determining that a particle disposed on the surface of the object is present if the correlation indicates secondary photon emissions,

wherein said illuminating the object with a radiation beam comprises providing off-axis illumination from more than one direction.

2. The method of claim 1, wherein said off-axis illumination is provided from four different directions.

3. The method of claim 1, wherein said off-axis illumination is provided as an annular radiation beam.

4. The method of claim 1, wherein illuminating the surface of the object with a radiation beam comprises splitting said radiation beam into a plurality of split beams, each of which is incident upon the surface of the object at a different angle to the other split beams.

5. The method of claim 1, wherein the analyzing secondary photon emissions from the surface of the object with time resolved spectroscopy further comprises recording a photoluminescence signal.

6. The method of claim 1, wherein the inspected object comprises a patterning device, said patterning device being a reticle or an extreme ultraviolet (EUV) reticle.

7. The method of claim 1, further comprising analyzing secondary photon emissions from the surface of the object with energy resolved spectroscopic analysis.

8. The method of claim 1, wherein the determining further comprises determining that the particle comprises metal, metal oxide, or organic material based on the time-resolved spectroscopic signal.

9. The method of claim 1, wherein the method is performed over a first area of said surface of the object, and then repeated for sub-portions of said first area if a particle is detected.

10. The method of claim 9, further comprising performing further repetitions until a desired spatial resolution limit is reached.

11. An Apparatus for inspection of a surface of an object, comprising;

a radiation source configured to emit a radiation beam onto the surface of the object;

a spectrometer module configured to;

analyze a first portion of secondary photon emissions received through a first optical path from the surface of the object with time resolved spectroscopy,

analyze a second portion of secondary photon emissions received through a second optical path, wherein the first and second portions of the secondary photon emissions comprise wavelengths that are the same,

perform a correlation between the analysis of the first portion and the analysis of the second portion, and

determine that a particle disposed on the surface of the object is present if the correlation indicates secondary photon emissions; and

one or more optical elements configured to direct radiation onto the surface of the object from more than one direction.

12. The apparatus of claim 11, wherein the one or more optical elements comprise one or more beamsplitters configured to split said radiation beam into a plurality of split beams, each of which is incident upon the object at a different angle to the other split beams.

13. The apparatus of claim 11, comprising a controller configured to perform a detection over a first area of said surface of the object, and then to repeat the detection for sub-portions of said first area if a particle is detected.

14. A lithographic apparatus for inspection of a surface of an object, comprising:

a radiation source configured to emit a radiation beam onto the surface of the object;

a spectrometer configured to;

analyze a first portion of secondary photon emissions received through a first optical path from the surface of the object with time resolved spectroscopy,

analyze a second portion of secondary photon emissions received through a second optical path, wherein the first and second portions of the secondary photon emissions comprise wavelengths that are the same,

perform a correlation between the analysis of the first portion and the analysis of the second portion, and

determine that a particle disposed on the surface of the object is present if the correlation indicates secondary photon emissions; and

one or more optical elements configured to direct radiation onto the surface of the object from more than one direction.