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EP-4740002-A1 - DEVICE FOR INSPECTING SUBSTRATES

EP4740002A1EP 4740002 A1EP4740002 A1EP 4740002A1EP-4740002-A1

Abstract

The invention relates to an inspection device (100, 200, 300, 400, 500) for detecting defects on substrates, such as wafers, comprising : - an illumination module (10) comprising at least one light source (12) configured to illuminate at least one region of a substrate (30) to be inspected with at least one illumination beam (20, 21); - at least one detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55-2, 56-1, 56-2) configured to detect light issued from the substrate (30) and to produce an inspection signal; - a light collection module; and - a processing module configured to produce an inspection information from the inspection signal, wherein the light collection module comprises at least one collection lens (40) with a nanostructured surface (90), the nanostructured surface (90) comprising at least one light collection region (91, 92, 92', 93, 94, 95, 96, 97, 98) configured to collect light issued from the substrate (30) within a predetermined solid angle (81, 82, 83, 84, 85) and to direct the collected light towards a corresponding detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55- 2, 56-1, 56-2), a light collection region and a corresponding detector forming a collection channel (61, 62, 63, 64, 65, 66, 67, 68).

Inventors

  • VIENNE, GUILLAUME
  • HAKOBYAN, Davit
  • GENEVET, Patrice

Assignees

  • UNITY SEMICONDUCTOR
  • Centre National de la Recherche Scientifique

Dates

Publication Date
20260513
Application Date
20230706

Claims (15)

  1. 1. An inspection device (100, 200, 300, 400, 500) for detecting defects on substrates, such as wafers, comprising: - an illumination module (10) comprising at least one light source (12) configured to illuminate at least one region of a substrate (30) to be inspected with at least one illumination beam (20, 21); - at least one detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55-2, 56-1, 56-2) configured to detect light issued from the substrate (30) and to produce an inspection signal; - a light collection module; and - a processing module configured to produce an inspection information from the inspection signal, wherein the light collection module comprises at least one collection lens (40) with a nanostructured surface (90), the nanostructured surface (90) comprising at least one light collection region (91, 92, 92', 93, 94, 95, 96, 97, 98) configured to collect light issued from the substrate (30) within a predetermined solid angle (81, 82, 83, 84, 85) and to direct the collected light towards a corresponding detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55- 2, 56-1, 56-2), a light collection region and a corresponding detector forming a collection channel (61, 62, 63, 64, 65, 66, 67, 68).
  2. 2. The inspection device (100, 200, 300, 400, 500) according to claim 1, characterized in that it comprises at least two collection channels (61, 62, 63, 64, 65, 66, 67, 68), the collection channels corresponding to different solid angles (81, 82, 83, 84, 85).
  3. 3. The inspection device (100, 200, 300, 400, 500) according to claim 1 or 2, characterized in that the collection channel comprises a plurality of polarization sub-channels (64-1, 64-2, 65-1, 65-2, 66-1, 66-2, 67-1, 67-2), each corresponding to a different polarization of the light issued from the substrate (30), the light of each polarization sub-channel being directed in a different direction.
  4. 4. The inspection device (100, 200, 300, 400, 500) according to the preceding claim, characterized in that the polarization sub-channels (64-1, 64-2, 65-1, 65-2, 66-1, 66-2, 67-1, 67-2) are implemented by a birefringent nanostructured surface (90) of the collection lens (40).
  5. 5. The inspection device (100, 200, 300, 400, 500) according to claim 1 or 2, characterized in that the collection channel comprises a plurality of chromatic sub-channels (64-1, 64-2, 65-1, 65-2, 66-1, 66-2, 67-1, 67-2), each corresponding to a different spectral range of the light issued from the substrate (30), the light of each chromatic sub-channel being directed in a different direction.
  6. 6. The inspection device (100, 200, 300, 400, 500) according to the preceding claim, characterized in that the chromatic sub-channels (64-1, 64-2, 65-1, 65-2, 66-1, 66-2, 67-1, 67-2) are implemented by a chromatic nanostructured surface (90) of the collection lens (40).
  7. 7. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, characterized in that the collection lens (40) comprises a region (94, 97) without nanostructures such that the illumination light passes through that region of the collection lens to illuminate the substrate (30).
  8. 8. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, characterized in that the illumination module (10) and the at least one detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55-2, 56-1, 56-2) are configured to operate in a dark-field configuration.
  9. 9. The inspection device (100, 200, 300, 400, 500) according to any one of claims 1 to 7, characterized in that the illumination module (10) and the at least one detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55-2, 56-1, 56-2) are configured to operate in a bright-field configuration.
  10. 10. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, characterized in that the collection module comprises a focusing lens (71, 72, 73, 74, 74-1, 74-2, 75, 75-1, 75-2, 76-1, 76-2, 77- 1, 77-2) for each collection channel (61, 62, 63, 64, 65, 66, 67, 68) configured to focus the collected light on the detector (51, 52, 53, 54, 54-1, 54-2, 55, 55-1, 55-2, 56-1, 56-2), the at least one light collection region being configured to collimate the collected light.
  11. 11. The inspection device (100, 200, 300, 400, 500) according to any one of claims 1 to 9, characterized in that the at least one light collection region is configured to focus the collected light on the detector (51, 52, 53).
  12. 12. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, further comprising displacement means (22, 31) configured to displace the illuminated region on the substrate (30).
  13. 13. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, characterized in that an angle of incidence of the illumination beam on the substrate (30) varies between grazing incidence and normal incidence.
  14. 14. The inspection device (100, 200, 300, 400, 500) according to any one of the preceding claims, characterized in that at least two illumination beams (20, 21) intersect each other in the illuminated region on the substrate (30).
  15. 15. The inspection device (100, 200, 300, 400, 500) according to the preceding claim, characterized in that two illumination beams (20, 21) form an interference pattern in the illuminated region.

Description

Device for inspecting substrates Field of the invention [0001] The present invention relates to a device for inspecting substrates, such as semiconductor wafers. [0002] The field of the invention is the field of the inspection, characterization, and quality control of substrates, such as semiconductor wafers. Background [0003] Inspection devices or defect detection devices are used to characterize samples such as semiconductor substrates, or wafers, in particular during fabrication. Defects include, for example, pits and particles, such as metal particles. Defects can also include, for example, crystalline defects inducing photoluminescence. [0004] A dark-field light collection architecture of an inspection device of the prior art is illustrated in FIGURE 1. A dashed line 10 indicates an illumination beam. In the illustrated example, the device 1 comprises two or three optical radiation collection channels. A narrow-angle collection channel with a collection lens 3 detects light issued from the illumination area M in a solid angle close to the normal z of the substrate 2, for example between 0 to 0.095 sr, corresponding to 0° - 10° (degree) in plane angles. A wide-angle collection channel with a collection mirror 4 detects light at wide solid angles with respect to the normal z, for example corresponding to 60° - 89° plane angles. The wide-angle collection channel may further be split in two channels, a forward detection channel in the direction of the forward scattering of the light issued from the illumination area, and a backward detection channel in the direction of the backward scattering. The device comprises one detector 6 for the narrow-angle detection, and one or two further detectors 7 for the wide- angle detection. [0005] In the illustrated example, the device 1 is in a dark-field configuration for the detection of the scattered light. The collection channels are indeed arranged to avoid collecting light of specular reflections from the substrate 2. [0006] The collection channels convey light from a detection area. In the example of FIGURE 1, the detection area is located around the illumination area M. The detection area can be identical or different for the respective collection channels. In the example of FIGURE 1, the device 1 comprises a collection fiber bundle 5. The detection area of the respective collection channels can then be defined as an optical conjugate of the core of the respective fibers 5 by the optical system of the collection channel. The light is then guided by the fibers 5 towards the detectors. [0007] However, the device 1 uses bulky components, such as the collection mirrors, that have to be able to collect the light notably under the wide solid angles. Such components have several drawbacks, including, but not limited to, bulkiness, inflexibility, non-versatility, and cost of fabrication. [0008] In particular, it is difficult to design them such as they may be used for collecting light under extremely narrow and wide solid angles, or under many different solid angles. Also, the collection optics collects indistinctively all the light, including scattered light and photoluminescence light, regardless of the polarization of this radiation. If a better selectivity is sought, it has to be added afterwards by splitting the channels with polarizers and/or spectral filters, leading to complex architectures. Summary of the invention [0009] A purpose of the present invention is to overcome at least one of the drawbacks of the known techniques. [0010] Another purpose of the present invention is to provide an inspection device combining several light collection functions in a compact, flexible, versatile, and cost effective manner. [0011] At least one of these aims is achieved by an inspection device for detecting defects on substrates, such as wafers, comprising : - an illumination module comprising at least one light source configured to illuminate at least one region of a substrate to be inspected with at least one illumination beam; - at least one detector configured to detect light issued from the substrate and to produce an inspection signal; - a light collection module; and - a processing module configured to produce an inspection information from the inspection signal, wherein the light collection module comprises at least one collection lens with a nanostructured surface, the nanostructured surface comprising at least one light collection region configured to collect light issued from the substrate within a predetermined solid angle and to direct the collected light towards a corresponding detector, a light collection region and a corresponding detector forming a collection channel. [0012] The inspection device according to the present invention comprises a light collection lens with a nanostructured surface. Such a nanostructured surface comprises subwavelength-scale elements and allows for wavefront shaping of incident light. These surfaces are also called metasurfac