Method for treating a reflective optical element for the EUV wavelength range, method for producing same, and treating apparatus

Patent metadata

Field	Value
Publication number	US-11328831-B2
Application number	US-201816050541-A
Country	US
Kind code	B2
Filing date	Jul 31, 2018
Priority date	Jul 31, 2017
Publication date	May 10, 2022
Grant date	May 10, 2022

Abstract

Treating a reflective optical element (104) for the EUV wavelength range that has a reflective coating on a substrate. The reflective optical element in a holder (106) is irradiated with at least one radiation pulse of a radiation source (102) having a duration of between 1 μs and 1 s. At least one radiation source (102) and the reflective optical element move relative to one another. Preferably, this is carried out directly after applying the reflective coating in a coating chamber (100). Reflective optical elements of this type are suitable in particular for use in EUV lithography or in EUV inspection of masks or wafers, for example.

First claim

What is claimed is:

1. A method for treating a reflective optical element for an extreme ultraviolet (EUV) wavelength range comprising a reflective coating on a substrate, comprising:
irradiating the reflective optical element with at least one radiation pulse having a duration of between 1 μs and 1 s, wherein the irradiating is carried out with at least one radiation source and at a wavelength between 800 nm and 1100 nm; and
moving the at least one radiation source and the reflective optical element relative to one another to perform a relative movement,
wherein the relative movement is performed with a linear component having a velocity of between 1 cm/s and 600 cm/s adapted at least in part to achieve an artificial ageing of the reflective coating on the substrate with respect to a state of the reflective optical element directly after coating,
wherein the reflective optical element includes a substrate and a plurality of stacks, each having an absorber-spacer pair,
wherein saturated stress relaxation of the reflective optical element that was irradiated is approximately 250 MPa or wherein stress overcompensation of the reflective optical element that was irradiated is between −50 MPa to −150 MPa, and
wherein compaction of at least one layer of the reflective optical element is approximately 0.1 to 1.5% relative to an original layer thickness.

2. The method according to claim 1 , wherein the relative movement is further performed as a superimposition of at least one linear movement and at least one rotational movement.

3. The method according to claim 1 , wherein the at least one radiation pulse is directed onto the reflective coating.

4. The method according to claim 1 , wherein the irradiating is performed with at least one radiation pulse having an energy density of between 0.01 J/cm 2 and 15 J/cm 2 .

5. A method for producing a reflective optical element for EUV lithography comprising a reflective coating on a substrate, comprising:
coating the substrate; and
treating the coated substrate according to the method claimed in claim 1 .

6. The method according to claim 5 , wherein the coating of the substrate is performed in a coating chamber, and wherein the treating is performed in the coating chamber.

7. The method according to claim 5 , wherein both the coating and the treating are performed under vacuum or protective atmosphere.

8. The method according to claim 5 , wherein the treating is performed directly after the coating.

9. The method according to claim 1 , wherein the radiation source is operated with varying power depending on the relative movement.

10. The method according to claim 1 , wherein the irradiating is performed with at least one radiation pulse having an energy density of between 0.01 J/cm 2 and 5 J/cm 2 .

11. The method according to claim 1 , wherein the irradiating is performed with at least one radiation pulse having a duration of between 250 μs to 2 ms.

12. The method according to claim 1 , wherein the at least one radiation source is operated in a pulsed manner with a pulse duration between 100 μs and 500 μs and an energy density between 0.01 J/cm 2 and 15 J/cm 2 , wherein the pulse duration and the energy density is set based on a desired stress relaxation of at least one layer of the optical element and wherein the energy density is set to increase homogenous ageing.

13. The method according to claim 1 , wherein the velocity is between 10 cm/s to 200 cm/s.

14. The method according to claim 1 , wherein the irradiation source has a radiation spot size of 1 mm 2 to 1 cm 2 , is operated at a power of 5 W to 500 W, and passes through 1 to 1000 cycles in a pulsed operation at a repetition rate of approximately 0.1 Hz to 1000 Hz.

15. The method according to claim 1 , wherein the velocity of the linear component is adapted at least in part to achieve densification of individual layers of the reflective optical element in comparison to the state of the reflective optical element directly after coating and the artificial ageing including density changes and saturated stress relaxation.

16. The method according to claim 1 , wherein the velocity of the linear component is adapted at least in part to achieve one or more structural changes of the reflective optical element on account of interdiffusion at layer boundaries of the reflective optical element.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Grasse Christian
• Hermann Martin
• Six Stephan
• Weber Joern
• Winter Ralf
• Dier Oliver
• Shklover Vitaliy
• Hild Kerstin
• Strobel Sebastian

Classifications

• G02B5/0891

  Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06) · CPC title

• G21K1/062 Primary

  Devices having a multilayer structure · CPC title

• G03F1/52

  Reflectors · CPC title

• G03F7/70958

  Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties · CPC title

• G02B1/12

  by surface treatment, e.g. by irradiation · CPC title