Passive integrated optical systems and methods for reduction of spatial optical coherence

Patent metadata

Field	Value
Publication number	US-2025341781-A1
Application number	US-202318859981-A
Country	US
Kind code	A1
Filing date	Apr 18, 2023
Priority date	May 16, 2022
Publication date	Nov 6, 2025
Grant date	—

Abstract

Passive integrated optical systems and methods are described. The present systems and methods facilitate reduction of spatial optical coherence in source radiation used for metrology, for example. Current coherence scramblers used for metrology typically include one or more (moving) mechanical components configured to reduce the coherence of source radiation. However, these mechanical coherence scramblers occupy volume within a system and introduce the threat of mechanical wear and/or failure. In contrast, the present systems and methods utilize a combination of passive integrated optical elements to form a coherence scrambler. This reduces or eliminates the use of mechanical components and increases durability, among other advantages.

First claim

1 . A system configured to convert spatially coherent radiation to completely or partially spatially incoherent radiation, the system comprising:
a splitter configured to receive and split the spatially coherent radiation into channels; optical pathways having different lengths coupled to the channels, the different lengths configured to convert the spatially coherent radiation to the completely or partially spatially incoherent radiation; and a combiner coupled to the optical pathways and configured to combine the completely or partially spatially incoherent radiation from the optical pathways into a single multimode output.

2 . The system of claim 1 , wherein the optical pathways are configured such that radiation in a single channel does not become incoherent since it is single mode radiation, but with an appropriate path difference, radiation in the single channel becomes incoherent with respect to radiation in neighboring channels.

3 . The system of claim 1 , wherein the splitter, the optical pathways, and the combiner are integrated into an integrated optical body.

4 . The system of claim 3 , wherein the integrated optical body comprises a microchip fabricated using complementary metal-oxide-semiconductor (CMOS) and/or indium phosphide fabrication techniques.

5 . The system of claim 3 , wherein a waveguiding layer of the integrated optical body is formed from silicon, silicon-on-oxide, indium phosphide, silicon nitride, and/or aluminum oxide.

6 . The system of claim 1 , comprising stacked integrated optical bodies that form a multidimensional array of waveguide emitters.

7 . The system of claim 1 , wherein the system is passive, having no moving parts or electrically controlled components.

8 . The system of claim 1 , wherein the splitter is configured to split the spatially coherent radiation into at least 2-100 channels.

9 . The system of claim 1 , wherein the splitter is a binary tree beam splitter or a non-binary beam splitter.

10 . The system of claim 1 , wherein the splitter is a multimode interference (MMI) device.

11 . The system of claim 1 , wherein each optical pathway comprises a waveguide and forms a portion of a corresponding channel.

12 . The system of claim 1 , wherein the different lengths are configured to reduce or eliminate interference between radiation traversing different optical pathways, which converts the spatially coherent radiation to the completely or partially spatially incoherent radiation.

13 . The system of claim 1 , wherein an optical path length difference from a first optical pathway to a second optical pathway is larger than a coherence length of the spatially coherent radiation.

14 . The system of claim 1 , wherein the combiner comprises an optical fiber array.

15 . The system of claim 1 , wherein the combiner comprises a photonic lantern.

16 . The system of claim 1 , wherein the combiner comprises a micro lens array and/or one or more macroscopic lenses.

17 . The system of claim 1 , wherein the spatially coherent radiation comprises visible light.

18 . The system of claim 1 , further comprising a multimode fiber configured to receive the single multimode output from the combiner.

19 . The system of claim 1 , further comprising a controller configured to actively control output from individual optical pathways.

20 . The system of claim 1 , wherein the spatially coherent radiation is converted to the completely or partially spatially incoherent radiation for metrology associated with a semiconductor manufacturing process.

Assignees

• Asml Netherlands Bv

Inventors

• Setija Irwan Dani
• Sokolov Sergei

Classifications

• G03F7/70633

  Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching · CPC title

• G03F7/70075 Primary

  Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection · CPC title

• G03F7/706847

  Production of measurement radiation, e.g. synchrotron, free-electron laser, plasma source or higher harmonic generation [HHG] · CPC title

• G03F7/70091 Primary

  Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA] · CPC title

• G03F7/70025

  by lasers · CPC title