Illumination System

• US 20090168072A1
• Filed: 12/04/2008
• Published: 07/02/2009
• Est. Priority Date: 12/02/2005
• Status: Active Grant

• Current Assignee: ASML Holding NV, ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Vink, Rob, Shmarev, Yevgeniy, Coston, Scott D., Ryzhikov, Lev, Joobeur, Adel, VISSER, Huibert, Klinkhamer, Jacob Fredrik Friso
• Granted Patent: US 8,159,651 B2
• Time in Patent Office: Days
• US Class Current: 356/497
• CPC Class Codes: G02B 27/0905 Dividing and/or superposing multiple light beams
• CPC Class Codes: G03F 7/70075 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 Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting

Abstract

A coherence remover includes a first partially reflective surface and a second partially reflective surface. The coherence remover is configured to receive an input beam. Each of the first and second reflective surfaces is configured to reflect a respective portion of the input beam to produce respective one or more intermediate beams. The intermediate beams collectively form an output beam that has a reduced coherence compared to the input beam.

Claims

1. A coherence remover, comprising:

a first partially reflective surface; and

a second partially reflective surface;

wherein the coherence remover is configured to receive an input beam, wherein each of the first and second reflective surfaces is configured to reflect a respective portion of the input beam to produce respective one or more intermediate beams, and wherein the intermediate beams collectively form an output beam that has a reduced coherence compared to the input beam.

2. The coherence remover of claim 1, wherein at least one of the first and second partially reflective surfaces is angled with respect to a normal axis of the first and second partially reflective surfaces.

3. The coherence remover of claim 1, further comprising:

a beam splitter configured to output the input beam at a first port such that the input beam is incident on the first partially reflective surface, wherein the beam splitter is configured to receive the output beam and output the output beam at a second port that is different than the first port.

4. The coherence remover of claim 3, wherein the beam splitter is a polarized beam splitter that is configured to output beams having a first polarization at the first port and beams having a second polarization at the second port.

5. The coherence remover of claim 4, further comprising:

a wave plate configured to alter a polarization state of the output beam such that the output beam is incident on the beam splitter having the second polarization, whereby the output beam is output at the second port of the beam splitter.

6. The coherence remover of claim 5, wherein the wave plate is a quarter wave plate.

7. The coherence remover of claim 1, further comprising:

a substantially fully reflective mirror configured to reflect a portion of the input beam to produce one or more of the intermediate beams.

8. The coherence remover of claim 7, wherein the substantially fully reflective mirror is angled with respect to the normal axis of the first and second partially reflective mirrors.

9. The coherence remover of claim 1, wherein the coherence remover is configured to output the output beam to a homogenizer or a patterning device.

10. An lithographic apparatus, comprising:

a coherence remover, comprising;

a first partially reflective surface; and

a second partially reflective surface;

wherein the coherence remover is configured to receive an input beam, wherein each of the first and second reflective surfaces is configured to reflect a respective portion of the input beam to produce respective one or more intermediate beams, and wherein the intermediate beams collectively form an output beam that has a reduced coherence compared to the input beam; and

a homogenizer configured to convert the output beam into a plurality of beams.

11. The lithographic apparatus of claim 10, further comprising:

a patterning device configured to modulate the plurality of beams such that a pattern is formed on a substrate that receives the modulated plurality of beams.

12. The lithographic apparatus of claim 10, wherein the homogenizer comprises first and second homogenizer plates that are angled relative to one another.

13. The lithographic apparatus of claim 12, wherein the homogenizer plates are rotatably mounted, such that an angular orientation of the homogenizer plates is adjustable.

14. The lithographic apparatus of claim 12, wherein the homogenizer comprises:

a first homogenizer module configured to homogenize the output beam in a first direction; and

a second homogenizer module configured to homogenize an output of the first homogenizer module in a second direction, wherein the first direction is perpendicular to the second direction.

15. The lithographic apparatus of claim 14, wherein at least one of the first homogenizer module and the second homogenizer module comprises at least one of a plate or two parallel mirrors.