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

Patent metadata

Field	Value
Publication number	US-9316929-B2
Application number	US-201313754720-A
Country	US
Kind code	B2
Filing date	Jan 30, 2013
Priority date	Jul 30, 2010
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

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.

First claim

What is claimed is:

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 ΔT n (x,y,z)=(T n (x,y,z)−T Ref ), ΔT 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 ΔT nav , ΔT mav and ΔT nmax and ΔT 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 ΔT mav +T ref or ΔT mmax +T ref , ΔT nav +T ref or ΔT nmax +T ref , based on the respective spatial temperature distribution ΔT m (x,y,z), ΔT n (x,y,z), expressed as T 0m >max(T Ref , ΔT mav +T ref ), T 0m >max(T Ref , ΔT mmax +T ref ) or T 0n >max(T Ref , ΔT nav +T Ref ), T 0n >max(T Ref , ΔT 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 (ΔT 0m , ΔT 0n ) such that the respective real values of the zero cross temperatures are within the intervals T 0m +ΔT 0m and T 0n +ΔT 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 ΔT mav +T Ref or ΔT mmax +T Ref , ΔT nav +T Ref or ΔT nmax +T Ref , based on the respective spatial temperature distribution ΔT m (x,y,z), ΔT n (x,y,z), increased by the absolute value of the respective manufacturing tolerances ΔT 0m , ΔT 0n , expressed as T 0m >max(T Ref , ΔT mav T Ref )+|ΔT 0n |, T 0m >max(T Ref , ΔT mmax +T Ref )+|ΔT 0m | or T 0n >max(T Ref , ΔT nav +T Ref )+|ΔT 0n |, T 0n >max(T Ref , ΔT nmax +T Ref )+|ΔT 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 0

Assignees

• Zeiss Carl Smt Gmbh
• Asml Netherlands Bv

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

Classifications

• G02B17/0647

  using more than three curved mirrors (G02B17/0668, G02B17/0694 take precedence) · CPC title

• G02B3/00

  Simple or compound lenses · CPC title

• G02B5/08

  Mirrors {(vehicle mirrors involving special optical features B60R1/08)} · CPC title

• B82Y10/00 Primary

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G03B27/542

  for copying cameras, reflex exposure lighting · CPC title