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

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 (Mm, Mn);
• said reflective optical elements (Mm, Mn) having respective bodies (MBm, MBn) defining respective reflective surfaces (MSm, MSn) 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 (MBm, MBn) including a material having a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T0m, T0n);
• said zero cross temperatures (T0m, T0n) having a difference between each other of which the absolute value is greater than 6K, expressed as abs(T0m−T0n)>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.

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 (Mm, Mn);
• said reflective optical elements (Mm, Mn) having respective bodies (MBm, MBn) defining respective reflective surfaces (MSm, MSn) 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 (MBm, MBn) of said reflective optical elements (Mm, Mn) including a material with a temperature dependent coefficient of thermal expansion which is zero at respective zero cross temperatures (T0m, T0n);
• a support structure for passively or actively supporting said reflective optical elements (Mm, Mn) wherein the temperature of at least a part of the support structure is at a reference temperature TRef;
• a heater for heating at least one of the bodies (MBm, MBn) including said material with said zero cross temperatures (T0m, T0n);
• a temperature control system for controlling the temperature of the at least one heated body (MBm, MBn) to a temperature Tk;
• without heating the bodies (MBm, MBn) with the heater, the exposure of said reflective surfaces MSm and MSn 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 ΔTn(x,y,z)=(Tn(x,y,z)−TRef), ΔTm(x,y,z)=(Tm(x,y,z)−TRef) of said bodies (MBm, MBn) relative to the reference temperature TRef with respective average and maximum temperatures ΔTnav, ΔTmav and ΔTnmax and ΔTmmax;
• and,
• at least one zero cross temperature (T0m, T0n) is higher than the maximum of the highest reference temperature TRef and the respective average or maximum temperature added by the reference temperature (ΔTmav+Tref or ΔTmmax+TRef, ΔTnav+TRef or ΔTnmax+TRef), based on the respective spatial temperature distribution ΔTm(x,y,z), ΔTn(x,y,z), expressed as T0m>max(TRef, ΔTmav TRef), T0m>max(TRef, ΔTmmax+TRef) or T0n>max(TRef, ΔTnav+TRef), T0n>max(TRef, ΔTnmax+TRef).

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 (Mm, Mn);
• said reflective optical elements (Mm, Mn) having respective bodies (MBm, MBn) defining respective reflective surfaces (MSm, MSn) 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 (MBm, MBn) including a material having a temperature dependent coefficient of thermal expansion which is zero at at least two zero cross temperatures T10mn and T20mn;
• a support structure for passively or actively supporting said reflective optical elements (Mm, Mn) wherein the temperature of at least a part of the support structure is at a reference temperature TRef;
• at least two tempering devices, for independently heating and/or cooling said at least two bodies (MBn, MBm);
• a temperature control system configured to independently control the temperature of the at least two heated or cooled bodies (MBn, MBm) to respective temperatures Tkn and Tkm;
• and,
• during exposure of the lens with the exposure power of the EUV light, the temperature Tkn of the temperature controlled body MBn is within an interval of ±5K centered around the first zero cross temperatures T10mn, and the temperature Tkm of the temperature controlled body MBm is within an interval of ±5K centered around the second zero cross temperature T20mn.

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 Mi;
• said reflective optical elements Mi having respective bodies MBi defining respective reflective surfaces MSi 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 Mi, wherein the temperature of at least a part of the support structure is at a reference temperature TRef;
• a heater for heating at least one optical element Mk on which a spatial temperature distribution ΔT(x,y,z)=(T(x,y,z)−TRef) relative to the reference temperature TRef is formed out when the projection lens is exposed with the exposure power without heating the heater, the temperature distribution ΔT(x,y,z) having an average temperature ΔTav and a maximum temperature ΔTmax;
• and,
• a temperature control system configured to control the temperature of said at least one reflective optical element Mk to a temperature Tk, wherein the body MBk of said at least one heated reflective optical element Mk includes a material with a temperature dependent coefficient of thermal expansion which is zero at a temperature T0k higher than the reference temperature TRef;
• and,
• before the exposure with the exposure power, the optical element Mk having a temperature Tk by heating it with the heater, the temperature Tk being selected from the group consisting of Tk=T0k−ΔTav;
• Tk=2*T0k−TRef−ΔTav;
• Tk=TRef+3*(T0k−TRef)/2−ΔTav;
• Tk=T0k−ΔTmax;
• Tk=2*T0k−TRef−ΔTmax;
• Tk=TRef+3*(T0k−TRef)/2−ΔTmax.

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 Mi;
• said reflective optical elements Mi having respective bodies MBi defining respective reflective surfaces MSi 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 Mk;
• 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 Mk to a temperature Tk;
• 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 MBk of the at least one optical element Mk is semitransparent.