EUV exposure apparatus with reflective elements having reduced influence of temperature variation

• US 9,316,929 B2
• Filed: 01/30/2013
• Issued: 04/19/2016
• Est. Priority Date: 07/30/2010
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV), CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: ASML Netherlands BV (ASML Holding NV), CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Baer, Norman, Loering, Ulrich, Natt, Oliver, Wittich, Gero, Laufer, Timo, Kuerz, Peter, Limbach, Guido, Hembacher, Stefan, Walter, Holger, Kwan, Yim-Bun-Patrick, Hauf, Markus, Stickel, Franz-Josef, Van Schoot, Jan
• Primary Examiner(s): Ton, Toan
• Assistant Examiner(s): Iacoletti, Michelle M
• Application Number:
  US13/754,720
• Publication Number:
  US 20130141707A1
• Time in Patent Office: 1,175 Days
• US Class Current: 1/1
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G02B 17/0647 using more than three curved mirrors G02B17/0668, G02B17/0694 take precedence
• CPC Class Codes: G02B 27/0043 in projection exposure systems, e.g. microlithographic systems
• CPC Class Codes: G02B 3/00 Simple or compound lenses
• CPC Class Codes: G02B 5/00 Optical elements other than lenses light guides G02B6/00; optical logic elements G02F3/00
• CPC Class Codes: G02B 5/08 Mirrors vehicle mirrors involving special optical features B60R1/08
• CPC Class Codes: G02B 5/0816 Multilayer mirrors, i.e. having two or more reflecting layers G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G02B 7/1815 with cooling or heating systems cooling arrangements for laser mirrors H01S3/0401
• CPC Class Codes: G03B 27/542 for copying cameras, reflex exposure lighting
• CPC Class Codes: G03F 7/7015 Details of optical elements
• CPC Class Codes: G03F 7/702 Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems
• CPC Class Codes: G03F 7/70233 Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems
• CPC Class Codes: G03F 7/70316 Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements
• CPC Class Codes: G03F 7/70825 Mounting of individual elements, e.g. mounts, holders or supports workpiece or mask holders G03F7/707
• CPC Class Codes: G03F 7/70891 Temperature
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
• CPC Class Codes: G21K 1/062 Devices having a multilayer structure
• CPC Class Codes: G21K 2201/061 characterised by a multilayer structure
• CPC Class Codes: G21K 2201/064 having a curved surface

Abstract

A projection lens of an EUV-lithographic projection exposure system with at least two reflective optical elements each comprising a body and a reflective surface for projecting an object field on a reticle onto an image field on a substrate if the projection lens is exposed with an exposure power of EUV light, wherein the bodies of at least two reflective optical elements comprise a material with a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures, and wherein the absolute value of the difference between the zero cross temperatures is more than 6K.

Claims

1. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:

at least first and second reflective optical elements (M_m, M_n);

said reflective optical elements (M_m, M_n) having respective bodies (MB_m, MB_n) defining respective reflective surfaces (MS_m, MS_n) for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with the exposure power of the EUV light reflected from said reticle when illuminated by said illumination system;

said bodies (MB_m, MB_n) including a material having a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T_0m, T_0n);

said zero cross temperatures (T_0m, T_0n) having a difference between each other of which the absolute value is greater than 6K, expressed as abs(T_0m−

T_0n)>

6K; and

,

said projection lens being configured to be exposed with an exposure power of more than 8 W of EUV light at a wavelength lying in a wavelength range of less than 50 nm.

2. The projection lens of claim 1 further comprising:

at least four reflective optical elements Mi;

the projection lens being configured to be exposed with an exposure power of more than 10 W; and

,

said zero cross temperatures (T_0m, T_0n) having a difference between each other of which the absolute value is greater than 8K, expressed as abs(T_0m−

T_0n)>

8K.

3. The projection lens of claim 2 further comprising:

a support structure configured to passively or actively support said reflective optical elements Mi and at least a part of said support structure being at a reference temperature T_ref;

a heater configured to heat at least one of said bodies (MB_m, MB_n); and

,

a temperature control system configured to control the temperature of at least one of said heatable bodies (MB_m, MB_n) to a temperature T_k.

4. The projection lens of claim 3, wherein:

without operation of the heater, the exposure of the reflective surfaces (MS_m, MS_n) of the respective bodies (MB_m, MB_n) with EUV light being reflected by the illuminated reticle and including a spatial distribution of angular orientation, polarization and intensity in accordance with an illumination setting, resulting in temperature distributions Δ

T_n(x,y,z)=(T_n(x,y,z)−

T_Ref), Δ

T_m(x,y,z)=(Tm(x,y,z)−

T_Ref) of the bodies (MB_m, MB_n) relative to the reference temperature T_Ref with respective average and maximum temperatures Δ

T_nav, Δ

T_mav and Δ

T_nmax and Δ

T_mmax; and

,

at least one zero cross temperature (T_0m, T_0n) is higher than the maximum of the highest reference temperature T_Ref and the respective average or maximum temperature Δ

T_mav+T_ref or Δ

T_mmax+T_ref, Δ

T_nav+T_ref or Δ

T_nmax+T_ref, based on the respective spatial temperature distribution Δ

T_m(x,y,z), Δ

T_n(x,y,z), expressed as T_0m>

max(T_Ref, Δ

T_mav+T_ref), T_0m>

max(T_Ref, Δ

T_mmax+T_ref) or T_0n>

max(T_Ref, Δ

T_nav+T_Ref), T_0n>

max(T_Ref, Δ

T_nmax+T_ref).

5. The projection lens of claim 4, wherein:

the materials comprising the zero cross temperatures (T_0m, T_0n) vary regarding their real value of the zero cross temperature due to manufacturing, resulting in respective manufacturing tolerances (Δ

T_0m, Δ

T_0n) such that the respective real values of the zero cross temperatures are within the intervals T_0m+Δ

T_0m and T_0n+Δ

T_0n; and

,

at least one zero cross temperature (T_0m, T_0n) is higher than the maximum of the highest reference temperature T_Ref and the respective average or maximum temperature Δ

T_mav+T_Ref or Δ

T_mmax+T_Ref, Δ

T_nav+T_Ref or Δ

T_nmax+T_Ref, based on the respective spatial temperature distribution Δ

T_m(x,y,z), Δ

T_n(x,y,z), increased by the absolute value of the respective manufacturing tolerances Δ

T_0m, Δ

T_0n, expressed as T_0m>

max(T_Ref, Δ

T_mav T_Ref)+|Δ

T_0n|, T_0m>

max(T_Ref, Δ

T_mmax+T_Ref)+|Δ

T_0m| or T_0n>

max(T_Ref, Δ

T_nav+T_Ref)+|Δ

T_0n|, T_0n>

max(T_Ref, Δ

T_nmax+T_Ref)+|Δ

T_0n|.

6. The projection lens of claim 4, wherein the temperature Tk of the at least one heated body (M_Bm, M_Bn) is within an interval of +5K centered around the respective zero cross temperature (T_0m, T_0n).

7. The projection lens of claim 6, wherein the temperature Tk of the at least one heated body (M_Bm, M_Bn) is within an interval of ±

2K centered around the respective zero cross temperature (T_0m, T_0n).

8. The projection lens of claim 3, wherein at a time before the projection lens is exposed with the exposure power of the EUV light, the temperature T_k of the at least one heated body (MB_n, MB_m) is controlled to its value by heating the heater with a first heating power.

9. The projection lens of claim 8, wherein at the time while exposing the projection lens with the exposure power of the EUV light, the heating power of the heater is lower than the first heating power.

10. The projection lens of claim 8, wherein the temperature control system controls the temperature T_k such that the heating power of the heater, heating the at least one body (MB_m, MB_n), and the exposure power of the EUV light absorbed by the at least one heated body (MB_m, MB_n) is constant in time.

11. The projection lens of claim 3, wherein the at least one heated body (MB_m, MB_n) is connected to an actuator for translational movement of the body.

12. The projection lens of claim 3, wherein the heater for heating the at least one of the bodies (MB_m, MB_n) comprises heating elements selected from the group consisting of IR light emitting diodes, Peltier elements, optical fibers, light guide rods and IR lasers.

13. The projection lens of claim 12, wherein the heating elements are arranged in one dimension or in two dimensions at predefined spatial coordinates, forming a grid structure.

14. The projection lens of claim 12, wherein the heating elements emitting or guiding IR radiation comprise an optical arrangement to configure the IR radiation;

the optical arrangement comprises arrangement elements selected from the group consisting of collimator, focusing lens, adjustable lens, mirror and diffractive optical element; and

,

the arrangement elements are tiltable around at least one axis.

15. The projection lens of claim 12, wherein the at least one of said bodies (MB_m, MB_n) comprises a modification in or on the mirror body;

and,

the modification is selected from the group consisting of recess, blind hole, defined surface roughness, diffractive structure, spherical protrusion, spherical recess and surface curvature.

16. An EUV-lithographic projection exposure system comprising:

a reticle;

an illumination system for illuminating the reticle;

a projection lens including;

at least first and second reflective optical elements (M_m, M_n);

said reflective optical elements (M_m, M_n) having respective bodies (MB_m, MB_n) defining respective reflective surfaces (MS_m, MS_n) for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with the exposure power of the EUV light reflected from said reticle when illuminated by said illumination system;

said bodies (MB_m, MB_n) including a material having a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T_0m, T_0n);

said zero cross temperatures (T_0m, T_0n) having a difference between each other of which the absolute value is greater than 6K, expressed as abs(T_0m−

T_0n)>

6K; and

,

said projection lens being configured to be exposed with an exposure power of more than 8 W of EUV light at a wavelength lying in a wavelength range of less than 50 nm.

17. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:

at least first and second reflective optical elements (M_m, M_n);

said reflective optical elements (M_m, M_n) having respective bodies (MB_m, MB_n) defining respective reflective surfaces (MS_m, MS_n) for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with an exposure power of EUV light of more than 8 W at a wavelength lying in a range of less than 50 nm being reflected from said reticle while illuminated by said illumination system;

said bodies (MB_m, MB_n) of said reflective optical elements (M_m, M_n) including a material with a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T_0m, T_0n);

a support structure for passively or actively supporting said reflective optical elements (M_m, M_n) wherein the temperature of at least a part of the support structure is at a reference temperature T_Ref;

a heater for heating at least one of the bodies (MB_m, MB_n) including said material with said zero cross temperatures (T_0m, T_0n);

a temperature control system for controlling the temperature of the at least one heated body (MB_m, MB_n) to a temperature T_k;

without heating the bodies (MB_m, MB_n) with the heater, the exposure of said reflective surfaces MS_m and MS_n with the exposure power of the EUV light, being reflected by the illuminated reticle and including a spatial distribution of angular orientation, polarization and intensity in accordance with an illumination setting, resulting in temperature distributions Δ

T_n(x,y,z)=(T_n(x,y,z)−

T_Ref), Δ

T_m(x,y,z)=(T_m(x,y,z)−

T_Ref) of said bodies (MB_m, MB_n) relative to the reference temperature T_Ref with respective average and maximum temperatures Δ

T_nav, Δ

T_mav and Δ

T_nmax and Δ

T_mmax; and

,

at least one zero cross temperature (T_0m, T_0n) is higher than the maximum of the highest reference temperature T_Ref and the respective average or maximum temperature added by the reference temperature (Δ

T_mav+T_ref or Δ

T_mmax+T_Ref, Δ

T_nav+T_Ref or Δ

T_nmax+T_Ref), based on the respective spatial temperature distribution Δ

T_m(x,y,z), Δ

T_n(x,y,z), expressed as T_0m>

max(T_Ref, Δ

T_mav T_Ref), T_0m>

max(T_Ref, Δ

T_mmax+T_Ref) or T_0n>

max(T_Ref, Δ

T_nav+T_Ref), T_0n>

max(T_Ref, Δ

T_nmax+T_Ref).

18. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:

at least first and second reflective optical elements (M_m, M_n);

said reflective optical elements (M_m, M_n) having respective bodies (MB_m, MB_n) defining respective reflective surfaces (MS_m, MS_n) for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with an exposure power of EUV light at a wavelength lying in a range of less than 50 nm being reflected from said reticle while illuminated by said illumination system;

said bodies (MB_m, MB_n) including a material having a temperature dependent coefficient of thermal expansion which is zero at at least two zero cross temperatures T¹_0mn and T²_0mn;

a support structure for passively or actively supporting said reflective optical elements (M_m, M_n) wherein the temperature of at least a part of the support structure is at a reference temperature T_Ref;

at least two tempering devices, for independently heating and/or cooling said at least two bodies (MB_n, MB_m);

a temperature control system configured to independently control the temperature of the at least two heated or cooled bodies (MB_n, MB_m) to respective temperatures T_kn and T_km; and

,

during exposure of the lens with the exposure power of the EUV light, the temperature T_kn of the temperature controlled body MB_n is within an interval of ±

5K centered around the first zero cross temperatures T¹_0mn, and the temperature T_km of the temperature controlled body MB_m is within an interval of ±

5K centered around the second zero cross temperature T²_0mn.

19. The projection lens of claim 18, wherein during exposure of the lens with the exposure power of the EUV light, the temperature T_kn of the temperature controlled body MB_n is within an interval of ±

2K centered around the first zero cross temperature T¹_0nm, and the temperature T_km of the temperature controlled body MB_m is within an interval of ±

2K centered around the second zero cross temperature T²_0mn.

20. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:

a plurality of reflective optical elements M_i;

said reflective optical elements M_i having respective bodies MB_i defining respective reflective surfaces MS_i for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with an exposure power of EUV light of more than 8 W at a wavelength lying in a wavelength range of less than 50 nm, the EUV light being reflected from said reticle when illuminated by said illumination system;

a support structure for passively or actively supporting said reflective optical elements M_i, wherein the temperature of at least a part of the support structure is at a reference temperature T_Ref;

a heater for heating at least one optical element M_k on which a spatial temperature distribution Δ

T(x,y,z)=(T(x,y,z)−

T_Ref) relative to the reference temperature T_Ref is formed out when the projection lens is exposed with the exposure power without heating the heater, the temperature distribution Δ

T(x,y,z) having an average temperature Δ

T_av and a maximum temperature Δ

T_max; and

,

a temperature control system configured to control the temperature of said at least one reflective optical element M_k to a temperature T_k, wherein the body MB_k of said at least one heated reflective optical element M_k includes a material with a temperature dependent coefficient of thermal expansion which is zero at a temperature T_0k higher than the reference temperature T_Ref; and

,

before the exposure with the exposure power, the optical element M_k having a temperature T_k by heating it with the heater, the temperature T_k being selected from the group consisting of T_k=T_0k−

Δ

T_av;

T_k=2*T_0k−

T_Ref−

Δ

T_av;

T_k=T_Ref+3*(T_0k−

T_Ref)/2−

Δ

T_av;

T_k=T_0k−

Δ

T_max;

T_k=2*T_0k−

T_Ref−

Δ

T_max;

T_k=T_Ref+3*(T_0k−

T_Ref)/2−

Δ

T_max.

21. A projection lens of an EUV-lithographic projection exposure system including a reticle and an illumination system for illuminating the reticle, the projection lens comprising:

a plurality of reflective optical elements M_i;

said reflective optical elements M_i having respective bodies MB_i defining respective reflective surfaces MS_i for projecting an object field on said reticle onto an image field on a substrate when said projection lens is exposed with an exposure power of EUV light at a wavelength lying in a wavelength range of less than 50 nm, the EUV light being reflected from said reticle when illuminated by said illumination system;

a support unit for passively or actively supporting at least one optical element M_k;

said support unit including a temperature sensitive element selected from the group consisting of linking points, bipod structures, linking elements, support element and housing structure;

the temperature sensitive element being controlled to a constant or to a predefined temperature;

a first tempering element for heating and/or cooling the at least one optical element M_k to a temperature T_k;

a second tempering element for tempering the temperature sensitive element to the predefined temperature; and

,

said second tempering element being spatially arranged between the temperature sensitive element and the first tempering element,

wherein either the first tempering element includes a Peltier element being coupled to the second tempering element, and working as a cooler by thermally coupling one surface of the second tempering element to a surface of the Peltier element, or

wherein the first tempering element includes a radiation source, emitting a radiation to which the body MB_k of the at least one optical element M_k is semitransparent.

22. The projection lens of claim 21, wherein the radiation source is selected from the group consisting of IR light emitting diodes, optical fibers, light guide rods, and IR lasers.