Photon source, metrology apparatus, lithographic system and device manufacturing method

Patent metadata

Field	Value
Publication number	US-9357626-B2
Application number	US-201414548734-A
Country	US
Kind code	B2
Filing date	Nov 20, 2014
Priority date	Jun 12, 2012
Publication date	May 31, 2016
Grant date	May 31, 2016

Abstract

A laser driven light source comprises laser and focusing optics. These produce a beam of radiation focused on a plasma forming zone within a container containing a gas (e.g., Xe). Collection optics collects photons emitted by a plasma maintained by the laser radiation to form a beam of output radiation. Plasma has an elongate form (L>d) and collecting optics is configured to collect photons emerging in the longitudinal direction from the plasma. The brightness of the plasma is increased compared with sources which collect radiation emerging transversely from the plasma. A metrology apparatus using the light source can achieve greater accuracy and/or throughput as a result of the increased brightness. Back reflectors may be provided. Microwave radiation may be used instead of laser radiation to form the plasma.

First claim

The invention claimed is:

1. A plasma-based photon source apparatus comprising:
a container configured to contain a gaseous atmosphere;
a driving system configured to form a driving radiation beam focused on a plasma forming zone within the container and maintain, by the driving radiation beam, a plasma;
a collecting optical system configured to collect photons emitted from the plasma along a longitudinal axis and to form the collected photons into at least one beam of output radiation; and
a reflector configured to reflect photons emitted in at least one of a direction reverse to the longitudinal axis and a direction transverse to the longitudinal axis back into the plasma.

2. The apparatus of claim 1 , wherein the reflector is located between the driving system and the plasma and includes an aperture to pass the driving radiation beam through the reflector.

3. The apparatus of claim 1 , wherein the reflector is one of a spherical reflector, a cylindrical reflector, or a compound of a spherical reflector and a cylindrical reflector.

4. The apparatus of claim 1 , wherein the driving system is configured to maintain, by the driving radiation beam, the plasma in an elongated form.

5. The apparatus of claim 4 , wherein the plasma in the elongated form has a length along the longitudinal axis that is substantially greater than a diameter of the elongated form in the direction transverse to the longitudinal axis.

6. The apparatus of claim 1 , further comprising:
two or more electrodes, positioned on opposite sides of the plasma forming zone, configured to ignite the plasma prior to operation, the electrodes being disposed from the longitudinal axis.

7. The apparatus of claim 6 , wherein the electrodes are positioned on an axis orthogonal to the longitudinal axis.

8. The apparatus of claim 7 , wherein the electrodes, the driving system and the collecting optical system are arranged on three axes that are mutually orthogonal.

9. The apparatus of claim 1 , wherein the driving system is configured to deliver the driving radiation beam along the longitudinal axis at an end of the plasma opposite to the end from which the collected photons emerge.

10. The apparatus of claim 1 , wherein the driving system is configured to deliver the driving radiation beam to the plasma forming zone in a direction transverse to the longitudinal direction.

11. An inspection apparatus comprising:
a support configured to support a substrate, the substrate having a structure thereon;
an optical system configured to illuminate the structure under predetermined illumination conditions and to detect radiation diffracted by the structure under the predetermined illumination conditions; and
a processor configured to process information characterizing the detected radiation to obtain a measurement of a property of the structure, wherein the optical system includes a photon source apparatus comprising:
a container configured to contain a gaseous atmosphere;
a driving system configured to form a driving radiation beam focused on a plasma forming zone within the container and maintain, by the driving radiation beam, a plasma;
a collecting optical system configured to collect photons emitted from the plasma along a longitudinal axis and to form the collected photons into at least one beam of output radiation; and
a reflector configured to reflect photons emitted in at least one of a direction reverse to the longitudinal axis and a direction transverse to the longitudinal axis back into the plasma.

12. The inspection apparatus of claim 11 , wherein the driving system is configured to maintain, by the driving radiation beam, the plasma in an elongated form having a length along the longitudinal axis that is substantially greater than a diameter of the elongated form in the direction transverse to the longitudinal axis.

13. A method comprising:
generating a driving radiation beam focused on a plasma forming zone within a container containing a gaseous atmosphere;
maintaining, by the driving radiation beam, a plasma;
reflecting, by a reflector, photons emitted in at least one of a direction reverse to a longitudinal axis and a direction transverse to the longitudinal axis back into the plasma;
collecting, by a collecting optical system, photons emitted from the plasma along the longitudinal axis; and
forming the collected photons into at least one beam of output radiation.

14. The method of claim 13 , wherein the maintaining a plasma comprises maintaining the plasma in an elongated form.

15. The method of claim 14 , wherein the plasma in the elongated form has a length along the longitudinal axis that is substantially greater than a diameter of the elongated form in the direction transverse to the longitudinal axis.

16. The method of claim 13 , further comprising:
igniting the plasma prior to operation using two or more electrodes positioned on opposite sides of the plasma forming zone away off the longitudinal axis.

17. The method of claim 13 , further comprising:
placing the reflector between the driving system and the plasma, wherein the reflector includes an aperture to pass the driving radiation beam through the reflector.

18. The method of claim 13 , further comprising:
illuminating structures using the beam of output radiation;
detecting radiation diffracted by the structures; and
determining, from a property of the diffracted radiation, a property of the structure.

19. The method of claim 13 , further comprising:
delivering the driving radiation beam to the plasma forming zone in a direction transverse to the longitudinal direction.

20. The method of claim 19 , further comprising:
focusing the driving radiation beam into a substantially line focus corresponding to the elongated form of the plasma.

Assignees

• Asml Netherlands Bv

Inventors

• Pellemans Henricus Petrus Maria
• Antsiferov Pavel Stanislavovich
• Krivtsun Vladimir Mihailovitch
• De Wit Johannes Matheus Marie
• Smeets Ralph Jozef Johannes Gerardus Anna Maria
• Van Der Zouw Gerbrand

Classifications

• G01N21/956 Primary

  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 H10P74/20)} · CPC title

• H01J65/04

  Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating {plasma display panels} · CPC title

• G03F7/70616

  Monitoring the printed patterns · CPC title

• G03F7/70033

  by plasma extreme ultraviolet [EUV] sources · CPC title

• H01J61/545

  using an auxiliary electrode inside the vessel (H01J61/542 takes precedence) · CPC title