Dark field wafer nano-defect inspection system with a singular beam
Provided is a method, system, and apparatus for inspecting a substrate. The method comprises illuminating the substrate with a singular laser beam, the singular laser beam forming an illuminated spot on the substrate and a bright fringe at a surface of the substrate, the bright fringe extending over at least a portion of the illuminated spot, and detecting, by an optical detection system, scattered light from nano-defects present on the substrate within the illuminated spot.
1. A method for inspecting a substrate, comprising:
illuminating the substrate with a laser beam having a spatial phase singularity forming an illuminated spot on the substrate and a standing wave, the standing wave having at least one bright fringe and at least one dark fringe on the substrate, the at least one bright fringe extending over at least a portion of the illuminated spot; and
detecting, by a dark field optical detection system, scattered light from nano-defects present on the substrate within the illuminated spot.
2. The method of claim 1 , wherein the laser beam has at least two beam portions separated by a phase difference.
3. The method of claim 2 , wherein the phase difference is π radians.
4. The method of claim 2 , wherein the phase difference of the laser beam is formed using a phase mask or a phase retarder.
5. The method of claim 1 , wherein the laser beam has an s polarization orientation at the substrate or a p polarization orientation at the substrate.
6. The method of claim 1 , wherein an angle of incidence of the singular laser beam at the substrate is from about 1° to about 90°.
7. The method of claim 1 , wherein the laser beam includes a light wavelength in the extreme ultraviolet (EUV), deep ultraviolet (DUV), ultraviolet (UV), or visible portions of the light spectrum, or a combination of two or more thereof.
8. The method of claim 1 , wherein the dark field optical detection system is configured to detect scattered light from the nano-defects in a direction substantially perpendicular to the substrate.
9. The method of claim 1 , wherein the dark field optical detection system comprises:
an objective lens;
a configurable imaging aperture;
relay optics;
a bandpass filter; and
a detector array.
10. The method of claim 9 , wherein the detector array comprises a photomultiplier tube (PMT) array or a time delay integration charge-coupled device (TDI CCD) array.
11. The method of claim 9 , wherein the objective lens is optimized to minimize chromatic aberrations.
12. The method of claim 9 , wherein the dark field optical detection system further comprises:
an autofocus system for maintaining focus during detection of scattered light from nano-defects on the substrate.
13. The method of claim 9 , wherein the dark field optical detection system further comprises:
an image computer for signal processing an acquired optical signal from scattered light from illuminated nano-defects and for determining if a nano-defect occurs within the field of view of the dark field optical detection system.
14. The method of claim 1 , wherein the nano-defects include defects located atop the substrate and all layers formed on the substrate.
15. A system for inspection a substrate, comprising:
a substrate stage for receiving the substrate;
a laser light source;
illumination optics for directing light from the laser light source on the substrate, wherein the illumination optics are configured to form a laser beam having a spatial phase singularity for forming an illuminated spot on the substrate and a standing wave having at least one bright fringe and at least one dark fringe on the substrate; and
a dark field optical detection system for detecting illuminated nano-defects by detecting scattered light from the illuminated nano-defects on the substrate.
16. The system of claim 15 , further comprising:
a purge chamber, wherein the substrate stage is deposited in the purge chamber.
17. The system of claim 15 , wherein the dark field optical detection system comprises:
an objective lens;
a configurable imaging aperture;
relay optics;
a bandpass filter and
a detector array.
18. The system of claim 17 , wherein the detector array includes a photomultiplier tube (PMT) array or a time delay integration charge-coupled device (TDI CCD) array.
19. The system of claim 17 , wherein the dark field optical detection system further comprises:
an autofocus system for maintaining focus during detection of scattered light from nano-defects on the substrate.
20. An apparatus for inspecting a substrate, comprising:
an illumination system for forming a laser beam having a spatial phase singularity from a laser light source and directing the laser beam to the substrate, the laser beam forming an illuminated spot and a standing wave having at least one bright fringe and at least one dark fringe on the substrate; and
a dark field optical detection system for detecting illuminated nano-defects by detecting scattered light from the illuminated nano-defects on the substrate.