Radiation source

Patent metadata

Field	Value
Publication number	US-9516732-B2
Application number	US-201214241986-A
Country	US
Kind code	B2
Filing date	Jul 27, 2012
Priority date	Sep 2, 2011
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

According to a first aspect of the present invention, there is provided a radiation source comprising: a nozzle configured to direct a stream of fuel droplets ( 70 ) along a trajectory towards a plasma formation location; a laser configured to direct laser radiation at a fuel droplet at the plasma formation location to generate, in use, a radiation generating plasma; wherein the laser comprises: a seed laser ( 50 ) for providing a seed laser beam ( 52 ); a beam splitter ( 54 ) for receiving the seed laser beam from the seed laser; an optical amplifier ( 58 ) for receiving the seed laser beam from the beam splitter and performing optical amplification; a first reflector ( 60 ) located downstream of the optical amplifier, configured to direct the seed laser beam back through the optical amplifier and on to the beam splitter; and a second reflector ( 70 ) located further downstream of the beam splitter, configured to receive the seed laser beam from the beam splitter and to direct at least a portion of the seed laser beam back toward the beam splitter.

First claim

The invention claimed is:

1. A radiation source comprising:
a nozzle configured to direct a stream of fuel droplets along a trajectory towards a plasma formation location; and
a laser system configured to direct a laser beam at a fuel droplet at the plasma formation location to generate, in use, a radiation generating plasma,
wherein the laser system comprises:
a seed laser configured to provide a seed laser beam;
a beam splitter configured to receive the seed laser beam from the seed laser;
an optical pre-amplifier configured to receive the seed laser beam from the beam splitter and provide an amplified seed laser beam;
a first reflector configured to receive the amplified seed laser beam and to direct the amplified seed laser beam to the beam splitter via the optical pre-amplifier to provide twice amplified seed laser beam; and
a further optical amplifier configured to receive the twice amplified seed laser beam via the beam splitter and to further amplify the twice amplified seed laser beam in a single pass through the further optical amplifier to generate the laser beam.

2. The radiation source of claim 1 , wherein the beam splitter is a polarizing or polarized beam splitter.

3. The radiation source of claim 1 , wherein a wave plate is located in a beam path between the beam splitter and the first reflector.

4. The radiation source of claim 3 , wherein the wave plate is a quarter wave plate.

5. The radiation source of claim 1 , wherein the beam splitter is arranged to direct approximately 10% of the seed laser beam to the optical pre-amplifier.

6. A laser system for generating a laser beam, comprising:
a seed laser configured to provide a seed laser beam;
a beam splitter configured to receive the seed laser beam from the seed laser;
an optical pre-amplifier configured to receive the seed laser beam from the beam splitter and provide an amplified seed laser beam;
a first reflector configured to receive the amplified seed laser beam and to direct the amplified seed laser beam to the beam splitter via the optical pre-amplifier to provide twice amplified seed laser beam; and
a further optical amplifier configured to receive the twice amplified seed laser beam via the beam splitter and to further amplify the twice amplified seed laser beam in a single pass through the further optical amplifier to generate the laser beam.

7. A method of generating a laser beam radiation, the method comprising:
directing a seed laser beam toward a beam splitter;
directing the seed laser beam using the beam splitter to an optical pre-amplifier to provide an amplified seed laser beam;
after the seed laser beam has passed through the optical pre-amplifier, directing the amplified seed laser beam off a first reflector and to the beam splitter again via the optical pre-amplifier to provide twice amplified seed laser beam; and
further amplifying the twice amplified seed laser beam in a single pass through a further optical amplifier to generate the laser beam.

8. A lithographic apparatus comprising a laser system for generating a laser beam, the laser system comprising:
a seed laser configured to provide a seed laser beam;
a beam splitter configured to receive the seed laser beam from the seed laser;
an optical pre-amplifier configured to receive the seed laser beam from the beam splitter and provide an amplified seed laser beam;
a first reflector configured to receive the amplified seed laser beam and to direct the amplified seed laser beam to the beam splitter via the optical pre-amplifier to provide twice amplified seed laser beam; and
a further optical amplifier configured to receive the twice amplified seed laser beam via the beam splitter and to further amplify the twice amplified seed laser beam in a single pass through the further optical amplifier to generate the laser beam.

9. The lithographic apparatus of claim 8 , further comprising:
an illumination system for providing a radiation beam;
a patterning device for imparting the radiation beam with a pattern in its cross-section;
a substrate holder for holding a substrate; and
a projection system for projecting the patterned radiation beam onto a target portion of the substrate.

Assignees

• Wagner Christian
• Loopstra Erik Roelof
• Asml Netherlands Bv

Inventors

• Wagner Christian
• Loopstra Erik Roelof

Classifications

• G03F7/70025

  by lasers · CPC title

• G03F7/70033

  by plasma extreme ultraviolet [EUV] sources · CPC title

• H01S3/2333

  Double-pass amplifiers · CPC title

• H01S3/0064

  Anti-reflection devices, e.g. optical isolaters (absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955) · CPC title

• H01S3/2316

  Cascaded amplifiers · CPC title