Mirror blank for EUV lithography without expansion under EUV radiation

Patent metadata

Field	Value
Publication number	US-10732519-B2
Application number	US-201415024236-A
Country	US
Kind code	B2
Filing date	Sep 10, 2014
Priority date	Sep 30, 2013
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

A substrate for an EUV mirror which contains a zero crossing temperature profile that departs from the statistical distribution is provided. A method for producing a substrate for an EUV mirror is also provided, in which the zero crossing temperature profile in the substrate is adapted to the operating temperature of the mirror. A lithography method using the substrate is also described.

First claim

We claim:

1. A substrate for an EUV mirror, wherein the substrate comprises a surface, wherein the substrate comprises zero crossing temperatures at the surface which depart from a statistical distribution, and wherein the substrate comprises a minimal zero crossing temperature (T zcmin ) and a maximal zero crossing temperature (T zcmax ) at the surface which differ from each other by more than 1.5 K;
wherein the substrate comprises a zero crossing temperature T zc1 in regions far from an edge and a zero crossing temperature T zc2 at the edge, wherein T zc1 is at least 1.5° C. higher than T zc2 ; wherein a profile of the zero crossing temperature across the surface of the substrate is adapted to the profile of the operating temperature of the mirror;
wherein an OH profile across the surface of the substrate corresponds to the zero crossing temperature profile across the surface of the substrate; and
wherein a profile of a fictive temperature across the surface of the substrate corresponds to the zero crossing temperature profile across the surface of the substrate.

2. The substrate according to claim 1 , wherein the substrate comprises titanium oxide-doped quartz glass.

3. The substrate according to claim 1 , wherein the substrate comprises 5% by weight to 12% by weight titanium dioxide relative to a total weight of the substrate.

4. The substrate according to claim 1 , wherein the substrate comprises multiple layers.

5. The substrate according to claim 1 , wherein the difference between T zcmax and T zcmin is at least 2 K.

6. The substrate according to claim 5 , wherein the difference between T zcmax and T zcmin is in a range of from 2 to 10 K.

7. The substrate according to claim 1 , wherein the distribution of the zero crossing temperature comprises, at least partly, an essentially steady profile.

8. An EUV mirror comprising the substrate according to claim 1 .

9. The mirror according to claim 8 , wherein the profile of the zero crossing temperature across the surface of the substrate is adapted to a profile of the operating temperature of the mirror.

10. A method for producing a substrate for an EUV mirror, comprising the following steps:
a) pre-defining an inhomogeneous nominal temperature profile of a zero crossing temperature for the substrate; and
b) producing the substrate while adjusting a pre-defined location-dependent nominal profile of the zero crossing temperature, wherein the profile of the nominal temperature extends laterally;
wherein the substrate comprises a surface, wherein the substrate comprises zero crossing temperatures at the surface which depart from a statistical distribution, and wherein the substrate comprises a minimal zero crossing temperature (T zcmin ) and a maximal zero crossing temperature (T zcmax ) at the surface which differ from each other by more than 1.5 K;
wherein the substrate comprises a zero crossing temperature T zc1 in regions far from an edge and a zero crossing temperature T zc2 at the edge, wherein T zc1 is at least 1.5° C. higher than T zc2 ; wherein a profile of the zero crossing temperature across the surface of the substrate is adapted to the profile of the operating temperature of the mirror;
wherein an OH profile across the surface of the substrate corresponds to the zero crossing temperature profile across the surface of the substrate; and
wherein a profile of a fictive temperature across the surface of the substrate corresponds to the zero crossing temperature profile across the surface of the substrate.

11. The method according to claim 10 , wherein step (b) comprises:
i) depositing silicon-containing starting substances and titanium-containing starting substances while forming a TiO 2 -doped soot body;
ii) drying the soot body;
iii) sintering the soot body while forming a blank;
iv) homogenizing the blank; and
v) optionally forming a substrate.

12. The method according to claim 11 , wherein the starting substances are deposited layer-by-layer on a cylinder-shaped blank.

13. The method according to claim 11 , wherein the quantity of the titanium-containing starting substance is varied during the deposition process.

14. The method according to claim 13 , wherein the adjustment of the distribution of the zero crossing temperature is effected through doping with titanium oxide which departs from a statistical distribution.

15. The method according to claim 10 , wherein the adjustment of the distribution of the zero crossing temperature is effected through a distribution of an OH content in the soot body which departs from a statistical distribution.

16. The method according to claim 10 , wherein the adjustment of the distribution of the zero crossing temperature is effected through a distribution of a halogen co-doping agent which departs from a statistical distribution.

17. The method according to claim 10 , wherein the adjustment of the distribution of the zero crossing temperature is effected through fictive temperatures of the substrate.

18. The method according to claim 17 , wherein the adjustment of the fictive temperatures is effected through heat treatment with rings, artificial over-dimensioning and/or forced cooling.

19. An EUV mirror produced by the method according to claim 10 .

20. A lithography method comprising the following steps:
a) providing an EUV mirror having a substrate; and
b) providing at least one light source, which acts on the EUV mirror during operation, wherein the substrate comprises zero crossing temperatures at the surface which depart from a statistical distribution, and wherein the substrate comprises a minimal zero crossing temperature (T zcmin ) and a maximal zero crossing temperature (T zcmax ) at the surface which differ from each other by more than 1.5 K;
wherein the substrate comprises a zero crossing temperature T zc1 in regions far from an edge and a zero crossing temperature T zc2 at the edge, wherein T zc1 is at least 1.5° C. higher than T zc2 ;
wherein a distribution of the zero crossing temperature across the surface of the substrate is adapted to a distribution of an operating temperature of the mirror;
wherein an OH profile across the surface of the substrate corresponds to the zero cross temperature profile across the surface of the substrate; and
wherein a profile of a fictive temperature across the surface of the substrate corresponds to the zero crossing temperature profile across the surface of the substrate.

Assignees

• Heraeus Quarzglas

Inventors

• Becker Klaus
• Thomas Stephan

Classifications

• C03B2201/23

  doped with hydroxyl groups · CPC title

• C03B2201/42

  doped with titanium · CPC title

• C03B32/00

  Thermal after-treatment of glass products not provided for in groups {C03B19/00} , C03B25/00 - C03B31/00 {or C03B37/00}, e.g. crystallisation, eliminating gas inclusions or other impurities; {Hot-pressing vitrified, non-porous, shaped glass products} · CPC title

• C03B19/1415

  Reactant delivery systems · CPC title

• C03B2201/12

  doped with fluorine (C03B2201/14 takes precedence) · CPC title