Nano-Structured Non-Polarizing Beamsplitter

Patent metadata

Field	Value
Publication number	US-2019107727-A1
Application number	US-201816138092-A
Country	US
Kind code	A1
Filing date	Sep 21, 2018
Priority date	Oct 10, 2017
Publication date	Apr 11, 2019
Grant date	—

Abstract

A beamsplitter includes a substrate formed from a material transparent to wavelengths of light at least above a selected cutoff wavelength and reflective structures distributed across a surface of the substrate. The reflective structures split incident light having wavelengths above the selected cutoff wavelength into a reflected beam formed from portions of the incident light reflected from the reflective structures and a transmitted beam formed from portions of the incident light transmitted through the substrate. A splitting ratio of a power of the reflected beam to a power of the transmitted beam is based on a ratio of surface area of the reflective surfaces to an area of the incident light on the substrate. Separation distances between neighboring reflective structures are smaller than the cutoff wavelength such that diffracted power of the incident light having wavelengths above the selected cutoff wavelength is maintained below a selected tolerance.

First claim

What is claimed:

1 . A beamsplitter comprising:
a substrate formed from a material transparent to wavelengths of light at least above a selected cutoff wavelength; and a plurality of reflective structures distributed across a surface of the substrate, wherein the plurality of reflective structures are configured to split incident light having wavelengths above the selected cutoff wavelength into a reflected beam formed from portions of the incident light reflected from the plurality of reflective structures and a transmitted beam formed from portions of the incident light transmitted through the substrate, wherein a splitting ratio of a power of the reflected beam to a power of the transmitted beam is based on a ratio of surface area of the reflective surfaces to an area of the substrate not covered by the reflective structures, wherein separation distances between neighboring reflective structures of the plurality of reflective structures are smaller than the cutoff wavelength, wherein the plurality of reflective structures are configured to maintain power of non-zero diffracted orders of the incident light having wavelengths above the selected cutoff wavelength below a selected tolerance.

2 . The beamsplitter of claim 1 , wherein the plurality of reflective structures comprises:
metallic films on the surface of the substrate.

3 . The beamsplitter of claim 1 , wherein the plurality of reflective structures includes planar surfaces parallel to the surface of the substrate.

4 . The beamsplitter of claim 1 , wherein the plurality of reflective structures is distributed in a square lattice pattern having a common pitch in a first direction and a second direction perpendicular to the first direction.

5 . The beamsplitter of claim 1 , wherein the plurality of reflective structures is distributed in at least one of a hexagonal lattice pattern, an oblique lattice pattern, or an equilateral triangle lattice pattern.

6 . The beamsplitter of claim 1 , wherein the substrate comprises:
at least one of fused silica, Suprasil, Heralux, CaF 2 , MgF 2 , LiF, quartz, or sapphire.

7 . The beamsplitter of claim 1 , wherein the selected cutoff wavelength comprises:
a wavelength in the range of approximately 120 nm to approximately 200 nm.

8 . The beamsplitter of claim 1 , wherein the selected cutoff wavelength comprises:
at least one of an ultraviolet wavelength, a deep ultraviolet wavelength, a vacuum ultraviolet wavelength, or an extreme ultraviolet wavelength.

9 . The beamsplitter of claim 1 , wherein sizes of the plurality of reflective structures are less than 1 micrometer.

10 . The beamsplitter of claim 1 , wherein the separation distances between neighboring reflective structures are less than 1 micrometer.

11 . The beamsplitter of claim 1 , wherein the splitting ratio is independent of wavelength above the selected cutoff wavelength.

12 . The beamsplitter of claim 1 , wherein the splitting ratio is independent of polarization of the incident light, wherein the beamsplitter comprises:
a non-polarizing beamsplitter.

13 . The beamsplitter of claim 1 , wherein the substrate and the plurality of reflective structures are configured as a plate beamsplitter.

14 . The beamsplitter of claim 1 , further comprising:
an additional substrate disposed on the plurality of reflective structures, wherein the second substrate is transparent to wavelengths at least above the selected cutoff wavelength.

15 . The beamsplitter of claim 14 , wherein the substrate, the plurality of reflective structures, and the additional substrate are configured as a cubic beamsplitter.

16 . The beamsplitter of claim 1 , wherein the surface of the substrate is a planar surface.

17 . The beamsplitter of claim 1 , wherein the surface of the substrate is a curved surface.

18 . The beamsplitter of claim 1 , wherein the curved surface provides a selected focal power.

19 . A metrology system comprising:
an illumination source configured to generate an illumination beam having wavelengths above a selected cutoff wavelength; an objective lens; a detector; and a beamsplitter, wherein the beamsplitter splits the illumination beam into a first illumination beam and a second illumination beam, wherein the objective lens directs the first illumination beam to a sample, wherein the objective lens collects radiation emanating from the sample in response to the first illumination beam, wherein the beamsplitter splits the radiation emanating from the sample from the objective lens into a first detected beam and a second detected beam, wherein the detector receives the first detected beam, wherein the beamsplitter comprises:
a substrate formed from a material transparent to wavelengths of light at least above the selected cutoff wavelength; and
a plurality of reflective structures distributed across a surface of the substrate, wherein the plurality of reflective structures are configured to split incident light having wavelengths above the selected cutoff wavelength into a reflected beam formed from portions of the incident light reflected from the plurality of reflective structures and a transmitted beam formed from portions of the incident light transmitted through the substrate, wherein a splitting ratio of a power of the reflected beam to a power of the transmitted beam is based on a ratio of surface area of the reflective surfaces to an area of the substrate not covered by the reflective structures, wherein separation distances between neighboring reflective structures of the plurality of reflective structures are smaller than the cutoff wavelength, wherein the plurality of reflective structures are configured to maintain power of non-zero diffracted orders of the incident light having wavelengths above the selected cutoff wavelength below a selected tolerance.

20 . The metrology system of claim 19 , wherein the plurality of reflective structures comprises:
metallic films on the surface of the substrate.

21 . The metrology system of claim 19 , wherein the plurality of reflective structures includes planar surfaces parallel to the surface of the substrate.

22 . The metrology system of claim 19 , wherein the plurality of reflective structures is distributed in a square lattice pattern having a common pitch in a first direction and a second direction perpendicular to the first direction.

23 . The metrology system of claim 19 , wherein the plurality of reflective structures is distributed in at least one of a hexagonal lattice pattern, an oblique lattice pattern, or an equilateral triangle lattice pattern.

24 . The metrology system of claim 19 , wherein the substrate comprises:
at least one of fused silica, Suprasil, Heralux, CaF 2 , MgF 2 , LiF, quartz, or sapphire.

25 . The metrology system of claim 19 , wherein the selected cutoff wavelength comprises:
a wavelength in the range of approximately 120 nm to approximately 200 nm.

26 . The metrology system of claim 19 , wherein the selected cutoff wavelength comprises:
at least one of an ultraviolet wavelength, a deep ultraviolet wavelength, a vacuum ultraviolet wavelength, or an extreme ultraviolet wavelength.

27 . The metrology system of claim 19 , wherein the sizes of the plurality of reflective structures are less than 1 micrometer.

28 . The metrology system of claim 19 , wherein the separat

Assignees

• Kla Tencor Corp

Inventors

• Gorelik Dmitry
• Hill Andrew V
• Bachar Ohad
• Manassen Amnon
• Negri Daria

Classifications

• G02B27/147 Primary

  using averaging effects by spatially variable reflectivity on a microscopic level, e.g. polka dots, chequered or discontinuous patterns, or rapidly moving surfaces (G02B27/1086 takes precedence) · CPC title

• G02B27/142

  Coating structures, e.g. thin films multilayers · CPC title

• G02B27/14 Primary

  operating by reflection only · CPC title

• G02B27/143

  using macroscopically faceted or segmented reflective surfaces · CPC title

• G02B27/0955

  Lenses (lenses per se G02B3/00) · CPC title