DE102018200955A1 - Mirror assembly for beam guidance of imaging light in projection lithography - Google Patents

Abstract

A mirror assembly is used for beam guidance of imaging light (3) in projection lithography. The mirror assembly has at least one mirror (M9, M10) with an optical surface (20) each supported by a base body (18). At least one limiting body (24) serves to limit at least one correction pressure compartment (33). The limiting body (24) and the mirror (M10) constitute boundary walls of the correction pressure compartment (33). A gas source of the mirror assembly for gas for applying the correction pressure compartment (33) is in fluid communication with the correction pressure compartment (33) , The result is a mirror assembly that can be provided with the least possible pass deformation of belonging to this assembly at least one mirror.

Description

The invention relates to a mirror assembly for beam guidance of imaging light in projection lithography. Furthermore, the invention relates to an imaging optics with at least one such mirror assembly, an imaging optics with at least one mirror assembly, an optical system with such imaging optics, a projection exposure system with such an optical system, a method for producing a micro- or Nanostructured component with such a projection exposure system and a manufactured with this method micro- or nanostructured component. Furthermore, the invention relates to a measuring device with at least one such mirror assembly.

Such a mirror assembly is known from the DE 10 2013 214 989 A1 , Imaging optics of the type mentioned are known from the WO 2016/188934 A1 and the WO 2016/166080 A1 ,

It is an object of the invention to provide a mirror assembly with the least possible pass deformation of the at least one mirror of the assembly at the site.

This object is achieved by a mirror assembly with the features specified in claim 1.

According to the invention, it has been recognized that with the use of a correction pressure, a pressure difference can be predetermined which can act on a mirror of the mirror assembly to be corrected with regard to its pass. The correction pressure can be adjusted so that, for example, a gravitational difference between a place of manufacture and a place of use can be compensated very precisely. Other pass deformations can also be corrected or compensated by using such a correction pressure. In particular, a defined pressure difference between a pressure within the correction pressure compartment and an environment outside the correction pressure compartment is possible with the mirror module. The correction pressure can act from the back side of the mirror main body.

A limiting body according to claim 2 combines the functions of a mirror for beam guidance on the one hand and a limiting body for a correction pressure compartment on the other hand. Alternatively, it is possible to perform the limiting body as a non-beam guiding body. This increases the flexibility of the design possibilities for the limiting body in terms of its shape and its arrangement.

In an embodiment according to claim 3, the limiting body combines the functions of a holder for the mirror on the one hand and the boundary of the correction pressure compartment on the other hand. Alternatively, the mirror may be carried independently of the limiting body.

A seal according to claim 4 has been found to be specified for defined pressure difference ratios particularly suitable. The seal can be designed as a labyrinth seal and can also be designed as a leaky seal. Reference is made to seal designs that from the WO 2007/031413 A2 are known.

A design of the seal according to claim 5 avoids disturbances of the imaging beam path due to a gas flow.

A design according to claim 6 is adapted to the conditions for certain imaging optics in projection lithography, the component of which may be the mirror assembly. The correction pressure compartment may be configured so that the imaging light passage opening does not limit the correction pressure compartment. The correction pressure compartment may, for example, be designed as an annular space around the passage opening.

A plurality of correction pressure compartments according to claim 7 increase the degrees of freedom in setting a correction pressure for setting a desired pass deformation of the optical surface.

The plurality of correction pressure compartments may be configured as multiple coaxial annular spaces. Alternatively, the plurality of correction pressure compartments can also be arranged distributed in the form of a grid or arranged in the form of a multiple symmetry over the reflection surface or opposite over the back of the mirror, so that a corresponding grid-like or a multiple symmetry having pressurization and thus deformation effect on the mirror surface can be.

Own fluid connections according to claim 8 allow a very flexible pressurization of the correction pressure Kompartiments.

The advantages of an imaging optical system according to claim 9, an optical system according to claim 10, a projection exposure apparatus according to claim 11, a manufacturing method for micro- or nanostructured components according to claim 12 and a micro- or nanostructured component according to claim 13 corresponding to those mentioned above Reference to the optical element according to the invention have already been explained. In particular, a semiconductor component, for example a memory chip, can be produced with the projection exposure apparatus.

With the aid of a measuring device according to claim 14, an influence of a gas pressure in the correction pressure compartment of the mirror assembly can be foreseen. By means of this it is possible to collect information for compensating a gravitational pass deformation due to a gravitational difference between a place of manufacture and a place of use of a mirror. The measuring device may in particular be an interferometric measuring device.

The light source of the projection exposure apparatus may be an EUV light source. A DUV light source, for example a light source with a wavelength of 193 nm, can also be used as an alternative.

• 1 schematisch eine Projektionsbelichtungsanlage für die EUV-Mikrolithographie;
• 2 in einem Meridionalschnitt eine Ausführung einer abbildenden Optik, die als Projektionsobjektiv in der Projektionsbelichtungsanlage nach 1 einsetzbar ist, wobei ein Abbildungsstrahlengang für Hauptstrahlen und für einen oberen und einen unteren Komastrahl dreier ausgewählter Feldpunkte dargestellt ist;
• 3 perspektivisch ein Spiegel der abbildenden Optik nach 2;
• 4 eine Abweichung einer Ist-Oberflächenform einer Reflexionsfläche eines Spiegelsubstrats des Spiegels nach 3 von einer Soll-Oberflächenform;
• 5 stark schematisch einen Meridionalschnitt durch eine Spiegel-Baugruppe, nämlich eines vorletzten und eines letzten Spiegels im Abbildungsstrahlengang, wobei die beiden dargestellten Spiegel Teile einer abbildenden Optik sind, die alternativ zur abbildenden Optik nach 2 als Projektionsobjektiv in der Projektionsbelichtungsanlage nach 1 einsetzbar ist;
• 6 die Spiegel-Baugruppe nach 5, wobei zusätzlich ein Begrenzungskörper zur Begrenzung eines Druck-Kompartiments dargestellt ist, wobei ein Korrekturdruck im Druck-Kompartiment größer ist als ein Spiegel-Normaldruck in einem weiteren Kompartiment zwischen den beiden Spiegeln der Spiegel-Baugruppe, wobei ausschließlich eine Druckwirkung auf eine Passedeformation des das Korrekturdruck-Kompartiment begrenzenden Spiegels dargestellt ist;
• 7 eine zu 6 ähnliche Darstellung, wobei in diesem Fall der Spiegel-Normaldruck gleich dem Korrekturdruck ist und wobei zusätzlich eine Gravitationswirkung auf die Passedeformation des das Korrekturdruck-Kompartiment begrenzenden Spiegels dargestellt ist;
• 8 in einer zu den 6 und 7 ähnlichen Darstellung eine weitere Ausführung einer Spiegel-Baugruppe, die grundsätzlich vergleichbar ist mit der Spiegelanordnung der beiden im Abbildungsstrahlengang letzten Spiegel der abbildenden Optik nach 2, wiederum mit einem zusätzlichen Begrenzungskörper zur Begrenzung eines Korrekturdruck-Kompartiments in Form eines Ringraums;
• 9 eine Ausschnittvergrößerung der 8, die Strömungsverhältnisse insbesondere zwischen dem Korrekturdruck-Kompartiment, einem Spiegel-Normaldruck-Kompartiment und einem zwischenliegenden, ebenfalls ringraumförmigen Spiegel-Normaldruck-Kompartiment verdeutlicht;
• 10 in einer zu 9 ähnlichen Darstellung eine weitere Ausführung einer Spiegel-Baugruppe mit einer Mehrzahl von Korrekturdruck-Kompartiments, die koaxial zueinander jeweils als Ringraum gestaltet sind;
• 11 einen der Spiegel der vorstehend angesprochenen Ausführungen der Spiegel-Baugruppen in einer schematischen Seitenansicht zur Verdeutlichung einer Passedeformation, die druck-, herstellungs- und/oder gravitationsbedingt sein kann;
• 12 der Spiegel nach 11, gefertigt mit einem Vorhalt zur Berücksichtigung eines Gravitationskonstanten-Unterschiedes, schematisch an drei alternativen Einsatzorten mit drei verschiedenen Einsatzorten-Gravitationskonstanten.

An embodiment of the invention will be explained in more detail with reference to the drawing. In this show:

• 1 schematically a projection exposure system for EUV microlithography;
• 2 in a meridional section, an embodiment of an imaging optic, which follows as a projection objective in the projection exposure apparatus 1 is usable, wherein an imaging beam path for main beams and for an upper and a lower Komastrahl three selected field points is shown;
• 3 perspective a mirror of the imaging optics 2 ;
• 4 a deviation of an actual surface shape of a reflection surface of a mirror substrate of the mirror after 3 from a target surface shape;
• 5 very schematically a meridional section through a mirror assembly, namely a penultimate and a last mirror in the imaging beam path, the two mirrors shown are parts of an imaging optics, the alternative to the imaging optics after 2 as a projection objective in the projection exposure apparatus 1 can be used;
• 6 the mirror assembly after 5 , wherein additionally a limiting body for limiting a pressure compartment is shown, wherein a correction pressure in the pressure compartment is greater than a normal mirror pressure in a further compartment between the two mirrors of the mirror assembly, wherein only a pressure effect on a pass deformation of the Correction pressure compartment limiting mirror is shown;
• 7 one too 6 similar representation, in which case the mirror normal pressure is equal to the correction pressure and in addition a gravitational effect on the fitting deformation of the correction pressure compartment limiting mirror is shown;
• 8th in one of the 6 and 7 similar representation of a further embodiment of a mirror assembly, which is basically comparable to the mirror arrangement of the two in the imaging beam path last mirror of the imaging optical system 2 again with an additional limiting body for limiting a correction pressure compartment in the form of an annulus;
• 9 a section enlargement of the 8th , the flow conditions in particular between the correction pressure compartment, a mirror normal pressure compartment and an intermediate, also annular space mirror normal pressure compartment illustrates;
• 10 in one too 9 similar representation of another embodiment of a mirror assembly having a plurality of correction pressure compartments, which are designed coaxially with each other as an annular space;
• 11 one of the mirrors of the above-mentioned embodiments of the mirror assemblies in a schematic side view to illustrate a pass deformation, which may be due to pressure, manufacturing and / or gravitational;
• 12 the mirror after 11 , made with a guideline to account for a gravitational constant difference, schematically at three alternative sites with three different site-gravity constant.

A projection exposure machine 1 for microlithography has a light source 2 for illumination light or imaging light 3 , At the light source 2 it is an EUV light source that generates light in a wavelength range, for example between 5 nm and 30 nm, in particular between 5 nm and 15 nm. At the light source 2 it can be a plasma-based light source (laser-produced plasma (LPP), gas-generated plasma (GDP) or even a synchrotron-based light source, for example a free-electron laser (FEL) light source 2 in particular, it may be a light source having a wavelength of 13.5 nm or a light source having a wavelength of 6.9 nm act. Other EUV wavelengths are possible. In general, even arbitrary wavelengths, for example visible wavelengths or also other wavelengths which can be used in microlithography (for example DUV, deep ultraviolet) and for the suitable laser light sources and / or LED light sources are available (for example 365 nm, 248 nm) nm, 193 nm, 157 nm, 129 nm, 109 nm) for the in the projection exposure apparatus 1 led lighting light 3 possible. A beam path of the illumination light 3 is in the 1 shown very schematically.

For guiding the illumination light 3 from the light source 2 towards an object field 4 in an object plane 5 serves a lighting optics 6 , With a projection optics or imaging optics 7 becomes the object field 4 in a picture field 8th in an image plane 9 mapped with a given reduction scale.

To facilitate the description of the projection exposure apparatus 1 as well as the different versions of the projection optics 7 in the drawing, a Cartesian xyz coordinate system is given, from which the respective positional relationship of the components shown in the figures results. In the 1 the x-direction is perpendicular to the plane of the drawing. The y-direction runs to the left and the z-direction to the top.

The object field 4 and the picture box 8th are in the projection optics 7 bent or curved and executed in particular partially annular. A radius of curvature of this field curvature can be 81 mm on the image side. A corresponding ring field radius of the image field is defined in FIG WO 2009/053023 A2 , A basic shape of a border contour of the object field 4 or the image field 8th is bent accordingly. Alternatively it is possible to use the object field 4 and the picture box 8th rectangular shape. The object field 4 and the picture box 8th have an xy aspect ratio greater than 1 , The object field 4 thus has a longer object field dimension in the x direction and a shorter object field dimension in the y direction. These object field dimensions run along the field coordinates x and y.

The projection optics 7 has an x-dimension of the image field of 26 mm and a y-dimension of the image field 8th of 1.2 mm.

The object field 4 is accordingly spanned by the first Cartesian object field coordinate x and the second Cartesian object field coordinate y. The third Cartesian coordinate z, which is perpendicular to these two object field coordinates x and y, is also referred to below as the normal coordinate.

For the projection optics 7 can that be in the 2 illustrated embodiment can be used. The optical design of the projection optics 7 after the 2 and 3 is known from the WO 2016/188934 A1 , the contents of which are fully incorporated by reference.

The picture plane 9 is in the projection optics 7 in the execution after 2 parallel to the object plane 5 arranged. Here, one is shown with the object field 4 coincident section of a reflection mask 10 , which is also called reticle. The reticle 10 is from a reticle holder 10a carried. The reticle holder 10a is powered by a reticle displacement drive 10b relocated.

The picture through the projection optics 7 takes place on the surface of a substrate 11 in the form of a wafer made by a substrate holder 12 will be carried. The substrate holder 12 is from a wafer or substrate displacement drive 12a relocated.

In the 1 is schematically between the reticle 10 and the projection optics 7 an incoming into this bundle of rays 13 of the illumination light 3 and between the projection optics 7 and the substrate 11 one from the projection optics 7 leaking beam 14 of the illumination light 3 shown. An image field-side numerical aperture (NA) of the projection optics 7 is in the 1 not reproduced to scale.

The projection exposure machine 1 is the scanner type. Both the reticle 10 as well as the substrate 11 be during operation of the projection exposure system 1 scanned in the y direction. Also a stepper type of the projection exposure system 1 in which between individual exposures of the substrate 11 a gradual shift of the reticle 10 and the substrate 11 in the y-direction is possible. These displacements are synchronized with each other by appropriate control of the displacement drives 10b and 12a ,

The 2 shows the optical design of the projection optics 7 , The 2 shows the projection optics 7 in a meridional section, ie the beam path of the imaging light 3 in the yz plane. The projection optics 7 to 2 has a total of ten mirrors, in the order of the beam path of the individual beams 15 , starting from the object field 4 , With M1 to M10 are numbered.

Shown in the 2 the beam path in each case three individual beams 15 , of three in the 2 go out to each other in the y-direction spaced object field points. Shown are main rays 16 , so individual rays 15 passing through the center of a pupil in a pupil plane of the projection optics 7 run, and in each case an upper and a lower coma beam of these two object field points. Starting from the object field 4 close the main beams 16 with a normal to the object plane 5 an angle CRA of 5.2 °.

The object plane 5 lies parallel to the image plane 9 ,

Shown in the 2 Detail of the calculated reflection surfaces of the mirrors M1 to M10 , A subarea of these calculated reflection surfaces is used. Only this actually used area of the reflection surfaces is plus a supernatant in the real mirrors M1 to M10 actually present.

The mirror M10 has a passage opening 17 to the passage of the imaging light 3 , the third last mirror M8 to the penultimate mirror M9 is reflected. The mirror M10 becomes the passage opening 17 around used reflectively. All other mirrors M1 to M9 have no passage opening and are used in a coherently coherent area reflective.

The mirror M1 to M10 are designed as free surfaces which can not be described by a rotationally symmetrical function. There are also other versions of the projection optics 7 possible, where at least one of the mirrors M1 to M10 is designed as a rotationally symmetric asphere. An aspherical equation for such a rotationally symmetric asphere is known from US Pat DE 10 2010 029 050 A1 , Also all mirrors M1 to M10 may be embodied as such aspheres.

A free-form surface can be defined by the following free-form surface equation (equation 1 ) to be discribed: $$\begin{array}{l}Z=\frac{c_x{x}^2+{\mathrm{<figure-callout\; id="2"\; label="c\; y\; y"\; filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0007.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_y{y}^{}{}^2}{1+\sqrt{1-\left(1+k_x\right){\left(c_{x}x\right)}^2-\left(1+k_y\right){\left(c_{y}y\right)}^2}}\hfill \\ +C_{1}x+C_{2}y\hfill \\ +{\text{C}}_2{\text{x}}^2+{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0003.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\text{xy}+{\text{C}}_5{\text{<figure-callout id="2" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0007.png" state="{{state}}">y</figure-callout>}}^2\hfill \\ +{\text{C}}_6{\text{x}}^3+...+{\text{C}}_9{\text{<figure-callout id="3" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0003.png" state="{{state}}">y</figure-callout>}}^3\hfill \\ +{\text{C}}_{10}{\text{x}}^4+...+{\text{C}}_{12}{\text{x}}^2{\text{<figure-callout id="2" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0007.png" state="{{state}}">y</figure-callout>}}^2+...+{\text{C}}_{14}{\text{<figure-callout id="2" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0007.png" state="{{state}}">y</figure-callout>}}^2\hfill \\ +{\text{C}}_{15}{\text{x}}^5+...+{\text{C}}_{20}{\text{<figure-callout id="5" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0003.png" state="{{state}}">y</figure-callout>}}^5\hfill \\ +{\text{C}}_{21}{\text{x}}^6+...{\text{C}}_{24}{\text{x}}^3{\text{<figure-callout id="3" label="y" filenames="DE102018200955A1\_0002.png,DE102018200955A1\_0003.png" state="{{state}}">y</figure-callout>}}^3+...+{\text{C}}_{27}{\text{<figure-callout id="6" label="y" filenames="DE102018200955A1\_0002.png" state="{{state}}">y</figure-callout>}}^6\hfill \\ +...\hfill \end{array}$$

• Z ist die Pfeilhöhe der Freiformfläche am Punkt x, y, wobei x² + y² = r². r ist hierbei der Abstand zur Referenzachse der Freiformflächengleichung
• (x = 0; y = 0).

For the parameters of this equation ( 1 ) applies:

• Z is the arrow height of the freeform surface at point x, y, where x ² + y ² = r ² . Here r is the distance to the reference axis of the free-form surface equation
• (x = 0, y = 0).

In the free-form surface equation ( 1 ) C ₁ , C ₂ , C ₃ ... denote the coefficients of free-form surface series expansion in the powers of x and y.

In the case of a conical base, c _x , c _{y is} a constant that corresponds to the vertex curvature of a corresponding asphere. So c _x = 1 / R _x and c _y = 1 / R _y . k _x and k _y each correspond to a conical constant of a corresponding asphere. The equation (1) thus describes a biconical freeform surface.

An alternatively possible free-form surface can be generated from a rotationally symmetrical reference surface. Such free-form surfaces for reflecting surfaces of the mirrors of projection optics of projection exposure apparatuses for microlithography are known from US Pat US 2007/0058269 A1 ,

Alternatively, freeform surfaces can also be described using two-dimensional spline surfaces. Examples include Bezier curves or nonuniform rational base splines (NURBS). For example, two-dimensional spline surfaces may be described by a network of points in an xy plane and associated z-values or by these points and their associated slopes. Depending on the particular type of spline surface, the complete surface is obtained by interpolation between the mesh points using, for example, polynomials or functions that have certain continuity and differentiability properties. Examples of this are analytical functions.

The used reflection surfaces of the mirrors M1 to M10 are carried by basic bodies.

The main body 18 can be made of glass, ceramic or glass ceramic. The material of the base 18 may be tuned so that its thermal expansion coefficient at a selected operating temperature of the mirror M is very close to the value 0 lies and ideally exactly 0 is. An example of such a material is Zerodur ^®.

3 shows in perspective one of the mirrors of the projection optics 7 namely, the mirror M10 , wherein the passage opening 17 is omitted.

A mirror substrate or basic body 18 of the mirror M10 has three mounting holes 19 , The bearings for holding the mirror substrate 18 pretend to a mirror holder.

4 illustrates a pass of the mirror M10 , ie a deviation of an actual surface shape of a reflection surface 20 or optical surface of the mirror M10 from an optimal target surface shape. This passport or pass deformation can be due to gravity and / or production-related and / or pressure-related, as will be explained below. An entire absolute value range of the illustrated pass is subdivided into a plurality of value range sections, each of which has a different shaded representation, between which pass-iso-pass lines run.

Due to the threefold arrangement of the mounting points of the mirror substrate 18 over the mounting holes 19 results in a corresponding threefold course of the pass. In the area of mounting holes 19 the pass is minimal and increases continuously to the center of the reflection surface 20 where the pass is maximum. In the circumferential direction around the mirror substrate 18 is the passe in the circumferential positions between each two mounting holes 19 maximum and is there about half of the maximum Passe in the center of the reflection surface 20 ,

5 shows in a highly schematic Meridionalschnitt a mirror assembly, which in an alternative embodiment of the projection optics 7 without a passage in the last mirror M10 can be used in the imaging beam path. Shown are the last two mirrors in the imaging beam path in front of the image field 8th for comparability with the design of the projection optics 7 to 2 again with M9 and M10 be designated. The reflection surfaces 20 these two mirrors M9 and M10 are facing each other.

Between the two mirrors M9 and M10 is a mirror normal pressure compartment 21 arranged in which a normal pressure p _i prevails, which is greater than an ambient pressure p _a . The normal pressure p _i prevails along the entire imaging beam path of the projection optics 7 , Since the mirror normal pressure p _{i is} higher than the ambient pressure p _a , the reflection surfaces are 20 the mirror M1 to M10 protected from contamination by otherwise possibly penetrating from the outside particles.

The normal pressure compartment 21 is from the two mirrors M9 and M10 and additionally by a compartment seal 22 limited. The compartment seal 22 can be shaped so that it follows in sections the imaging beam path. Basic examples of such compartment seals are known from the WO 2007/031413 A2 ,

The compartment seal 22 may be made of a flexible material or of a plastically deformable material. The compartment seal 22 or one of the other seals described may be made of stainless steel or ceramic.

The compartment seal 22 has in the execution after 5 the shape in about a hollow cylinder with a tapered shell wall. In this shell wall is at least one in the 5 not shown passage opening for the passage of the imaging light 3 executed along the imaging beam path. The compartment seal 22 is on both sides of the mirrors M9 and M10 not on, so there each overflow passages 23 are formed by a stream of a normal pressure compartment 21 Present gas is possible to the environment outwards.

Schematically are in the 5 also bearings 19a for mounting the mirror M9 and M10 over the mounting holes, not shown 19 on the support frame of the projection exposure system 1 shown.

6 shows the mirror assembly 5 with an additional limiting body 24 in the form of a printing plate. The limiting body 24 serves to limit at least one correction pressure compartment 25 , in which a correction pressure p _c prevails. The limiting body 24 one hand, and the mirror M10 on the other hand, make boundary walls of the correction pressure compartment 25 dar. The pressure plate 24 is separate from the mirrors M9 and M10 stored. Alternatively, it is possible in principle, the pressure plate 24 also on one of the mirrors, for example on the mirror M10 to fix.

The correction pressure compartment 25 is also limited by another compartment seal 22 , The compartment seal 22 the correction pressure compartment 25 is designed as a hollow cylinder and in turn has overflow passages 23 in the manner of those of the above-described compartment seal 22 of the standard pressure compartment 21 on. Due to the overflow passages 23 is also a defined gas flow from the correction pressure compartment 25 outward possible.

The limiting body 24 is not a body for the beam guidance of the imaging light. Alternatively, it is possible as the limiting body 24 another mirror, for example one of the mirrors M1 to M7 in the execution of the projection optics 7 to 2 , to use.

To mirror assembly after 6 still belongs to a gas source 27 for applying the correction pressure compartment 25 with gas. The gas source 27 is via a feed line 28 passing through the correction pressure compartment seal 26 passed through, with the correction pressure compartment 25 in fluid communication.

About the gas source 27 connected to a central control device, not shown, of the projection exposure apparatus 1 is in signal communication is a specification in particular a defined pressure difference between the pressure p _c in the correction pressure compartment 25 and the ambient pressure p _a outside the correction pressure compartment 25 possible. Also a defined pressure difference between the pressure p _c in the correction pressure compartment 25 and the mirror normal pressure p _i and / or the specification of a defined pressure difference between the mirror normal pressure p _i and the ambient pressure p _a is possible.

6 shows the effect of such a correction pressure p _c , which is greater than the mirror normal pressure p _i . An effect of gravity on the mirrors is neglected. In the 6 the following applies: p _c > p _i > p _a . Due to the pressure difference (p _c > p _i ) results in a deflection of the mirror M10 in the 6 is greatly exaggerated. This deflection of the mirror M10 causes its reflection surface 20 deforms convex.

7 shows in an otherwise to 6 identical representation of a gravitational effect on the most sensitive because of its dimensions last mirror M10 in the imaging beam path of the projection optics. This gravitational effect, which in the 7 acting downward in the direction of the gravitational vector g, is comparable to the pressure effect, which in connection with the 6 was explained. In the case after 7 only gravity acts and p _c = p _i > p _a .

By a compensating effect of the correction pressure p _c , the gravitational effect after 7 be compensated, so that no gravitational pass deformation of the mirror M10 results. In this case, p _i > p _c > p _a . Compared to the mirror normal pressure compartment 21 then lies in the correction pressure compartment 25 a negative pressure that causes a force on the mirror M10 leads, which acts exactly opposite to the gravitational force in the direction and, depending on the pressure difference, can have the same amount, so that the on the mirror M10 acting gravitational force is being compensated. The reflection surface 20 of the mirror M10 experiences in this case due to the pressure compensation of the gravitational conditional pass deformation just no more passiefeformation.

PA = mΔg.

• p: der Druckunterschied beziehungsweise die Druckdifferenz zwischen p_c und p_i,
• A: die Spiegelfläche, auf die der Druckunterschied wirkt,
• m: die Masse des Spiegels
• Δg: die Gravitationsdifferenz zwischen dem Herstellort und dem Einsatzort.

Here is

• p: the pressure difference or the pressure difference between p _c and p _i ,
• A: the mirror surface on which the pressure difference acts,
• m: the mass of the mirror
• Δg: the gravitational difference between the place of manufacture and the place of use.

For the adjustable pressure difference, ie the amount of the difference between p _c and p _i , it holds that this amount can be between 1 Pa and 5,000 Pa.

In particular, by adjusting the correction pressure p _c, a gravitational difference between a place of manufacture and a place of use of the optical assembly can be compensated or compensated. A gravitational difference of 0 , 3% between the place of manufacture and the place of use corresponds to an assumed dead weight of the mirror M10 of 400 kg of a mass change of about 1 kg, ie a force of 10 N. At a mirror surface of about 1 m ² , a necessary pressure difference between p _c and p _i of about 10 Pa results.

Based on 8th is explained another embodiment of a mirror assembly, which in a projection optics in the projection exposure system 1 can be used, which represents an alternative to the projection optics, in which the mirror assembly according to 5 to 7 is used. Components and functions associated with the 1 to 7 and especially in connection with the 5 to 7 have already been explained in the 8th the same reference numbers and will not be discussed again in detail.

For the mirror assembly after 8th has the last mirror M10 in the imaging beam path according to the embodiment according to 2 a passage opening 17 for the imaging light 3 ,

The mirror normal pressure compartment 21 extends along the imaging beam path of the imaging light 3 , ie from a passage opening 29 for the imaging light 3 in the limiting body 24 first to the passage opening 17 in the mirror M10 and then extends further between the mirrors M9 and M10 and then follows the imaging light beam path after reflection of the imaging light 3 at the last mirror M10 towards the picture field 8th , Accordingly, the normal pressure compartment seal 22 designed in several parts and includes a first normal pressure sealing portion 30 . designed as a hollow cylinder between the mirror M10 and the restriction body 24, another normal pressure seal portion 31 between the mirrors M9 and M10 and another normal pressure seal portion 32 looking at the imaging beam path after reflection at the mirror M10 towards the picture field 8th follows.

A correction pressure compartment 33 is in the execution after 8th designed as an annular space and in addition to the limiting body 24 and to the back of the mirror M10 limited by an external correction pressure compartment seal 34 and an internal correction pressure compartment seal 35 , The internal correction pressure compartment seal 35 surrounds the normal pressure seal section 30 between the limiting body 24 and the back of the mirror M10 , This normal pressure seal section 30 , the inner correction pressure compartment seal 35 and the outer correction pressure compartment seal 34 extend coaxially to the imaging beam path between the mirrors M8 (in the 8th not shown) and M9 ,

The pressure effect of a correction pressure p _c in the correction pressure comparator 33 to 8th corresponds to that in the correction pressure compartment 25 , which in connection with the 5 to 7 has already been explained. This effect of the annular correction pressure compartment 33 is rotationally symmetric.

9 shows a cutout of the 8th in the area of the mirror M10 and the limiter body 24 , where only the left half of these two components compared to 8th is shown.

Shown are flow paths of the gas between the various compartments and the environment. Gas initially flows through the feed line 28 in the correction pressure compartment 33 as indicated by an arrow in the 9 indicated. Between the internal correction pressure compartment seal 35 and this adjacent normal pressure seal portion 30 There is also a ring-shaped connection space 36 before, which is in fluid communication with the environment, so the ambient pressure p _a . Since p _c > p _a , the gas flows from the correction pressure compartment 33 via the overflow passages 23 between the inner correction pressure compartment seal 35 and the mirror M10 on the one hand and the limiting body 24 on the other hand by corresponding, in the 9 not shown passages in the limiting body 24 in the area, what in the 9 indicated by arrows. As is also true
p _i > p _a , the gas also flows out of the mirror normal pressure compartment 21 with pressure p _i in the connection space 36 , An overflow of gas between the correction pressure compartment 33 and the normal pressure compartment 21 does not take place.

This gas routing ensures that a defined gas flow is exclusively from the correction pressure compartment 33 to the outside and / or from the outside into the correction pressure compartment 33 is possible without flowing through the imaging beam path with the gas.

In particular, the normal pressure sealing section 30 , but also at least one of the other above-explained seals or sealing portions may be designed as a labyrinth seal.

The design of the compartment seals 22 . 26 . 34 and 35 can be done in the manner of a leaky seal. In this regard, reference is made to the WO 2007/031413 A2 ,

10 shows in one too 9 similar representation, a further embodiment for a correction pressure compartment 37 between the mirror M10 and the limiting body 24 , Components and functions corresponding to those described above with reference to FIGS 1 to 9 and especially with reference to the 9 have already been explained, bear the same reference numbers and not discussed again in detail.

In the execution after 10 is a correction pressure compartment divided into total 3 Correction pressure Kompartimentabschnitte 38 . 39 and 40 , The correction pressure compartment sections 38 to 40 are as coaxial annuli around the imaging beam path between the mirrors M8 and M9 educated.

The correction pressure compartment section 40 is designed as an annulus, which is directly connected to the connection space 36 followed. In the correction pressure compartment section 40 there is a correction pressure p _c3 . Outward connects to the correction pressure compartment section 40 the correction pressure compartment section 39 on, which is designed as a middle annulus. The latter is in turn surrounded on the outside by the correction pressure compartment section 38 , In the mean correction pressure compartment section 39 there is a correction pressure p _c2 and in the outer correction pressure compartment section 38 a correction pressure p _c1 . Between the inner correction pressure compartment section 40 and the connection room 36 lies the inner correction pressure compartment seal 35 in front.

The correction pressure compartment sections 38 to 40 are each from a section of the back of the mirror M10 limited.

Between the inner correction pressure compartment section 40 and the mean correction pressure compartment section 39 is a correction pressure compartment seal 41 and between the mean correction pressure compartment section 39 and the outer correction pressure compartment section 38 another correction pressure compartment seal 42 in front. Outward is the outer correction pressure compartment section 38 again through the correction pressure compartment seal 34 limited. Between the correction pressure compartment seals 35 . 41 . 42 and 34 and the adjacent boundary surfaces of the limiting body 24 and the mirror M10 in turn are overflow passages 23 in front.

The correction pressure compartment sections 38 to 40 each have their own feeders 28a . 28b and 28c with the in the 10 not shown gas source 27 in fluid communication.

Shown in the 10 a situation in which p _c1 ~ p _c3 and p _c2 <p _c1 , p _c3 . In addition, p _c1 , p _c3 > p _i and p _c2 <p _i . Force effects that result from these pressure conditions are in the 10 by force arrows 43 shown. In the internal correction pressure compartment section 40 and also in the correction pressure compartment section 38 a resulting force acts on the mirror from above M10 , In the mean correction pressure compartment section 39 a force acts 43 in the opposite direction, ie upwards in the direction of the limiting body 24 to. This can be a rotationally symmetrical about the imaging beam path between the mirrors M8 and M9 extending wave in the yoke of the reflection surface 20 of the mirror M10 be phoned.

Since all correction pressures p _c1 , p _c2 and p _{c3 are} each greater than the ambient pressure p _a , a gas flow takes place from the correction pressure Komparti-ment sections 38 to 40 towards the surroundings, as again in the 10 indicated by flow arrows.

The possibilities of gravitational compensation using the correction pressure p _c are described below with reference to FIG 11 and 12 further clarified.

11 shows an example of the mirror M10 with the reflection surface 20 and, for example, a gravitational pass deformation P thus a deviation of the actual surface shape of the reflection surface 20 from the target surface shape due to a gravitational difference between the place of manufacture and the place of use mirror M10 can come.

12 shows the mirror M10 with effect of different gravitational constants. At a gravitational constant of 9.80 m / s ^{2 there} is currently no pass deformation. In this case, it is not necessary to use the correction pressure to compensate for gravitational pass deformation.

Above shows the 12 the same mirror M10 When used in a place with in comparison to the place of manufacture of higher gravity in the range of 9.83 m / s ² . It results in a stronger gravitational effect, ie a greater deflection of the body 18 and a maximum pass deformation P _max . This pass deformation, as explained above, can be compensated for by setting p _c <p _i .

12 Below shows the situation when using the mirror M10 in a place with compared to the place of manufacture of smaller gravitational constant of 9.77 m / s ² . It results in a reverse deflection, so that in the 12 exaggerated concave reflection surface 20 results. This deflection can be compensated for by means of the correction pressure p _c > p _i , as explained above.

Instead of the embodiments described above, in which the mirror assembly was in each case part of a projection optics of a projection exposure apparatus, the described mirror assemblies can also be used in a measuring apparatus. Such a measuring device includes a measuring device for measuring the optical surface of at least one mirror of the mirror assembly. In this way, with the measuring device, the influence of a gas pressure, especially in the correction pressure compartment 25 . 33 or 38 to 40 be measured. It can thus be determined a correction pressure p _c , which is required to compensate for a predetermined gravitational deformation. The measuring device of the measuring device can be designed, for example, as an interferometric measuring device.

The projection exposure apparatus is used to produce a microstructured or nanostructured component 1 used as follows: First, the reflection mask 10 or the reticle and the substrate or the wafer 11 provided. Subsequently, a structure on the reticle 10 on a photosensitive layer of the wafer 11 using the projection exposure system 1 projected. By developing the photosensitive layer, a micro or nanostructure is then formed on the wafer 11 and thus produces the microstructured component.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102013214989 A1 [0002]
• WO 2016/188934 A1 [0002, 0024]
• WO 2016/166080 A1 [0002]
• WO 2007/031413 A2 [0008, 0049, 0074]
• WO 2009/053023 A2 [0021]
• DE 102010029050 A1 [0034]
• US 2007/0058269 A1 [0039]

Claims (14)

Mirror assembly for beam guidance of imaging light (3) in projection lithography, with at least one mirror (M9, M10) with an optical surface (20) carried by a base body (18), - having at least one limiting body (24) for limiting at least one correction pressure compartment (25; 33; 38, 39, 40), the limiting body (24) and the mirror (M10) limiting walls of the correction pressure compartment (25; , 39, 40), - with a gas source (27) for gas for pressurizing the correction pressure compartment (25; 33; 38, 39, 40) in fluid communication with the correction pressure compartment (25; 33; 38, 39, 40). Mirror assembly after Claim 1 , characterized in that the limiting body (24) constitutes a further mirror for beam guidance of the imaging light (3). Mirror assembly after Claim 1 , characterized in that the limiting body (24) carries the mirror (M10). Mirror assembly according to one of Claims 1 to 3 characterized in that the correction pressure compartment (25; 33; 38,39,40) is further limited by at least one seal (26; 34,35; 34,42,41,35) which is designed such that in defined gas flow from the correction pressure compartment (25; 33; 38,39,40) to the outside and / or from the outside into the correction pressure compartment (25; 33; 38,39,40) is possible. Mirror assembly after Claim 4 , characterized in that the seal (26; 34, 35; 34, 42, 41, 35) is designed so that the defined gas flow exclusively from the pressure compartment (25; 33; 38, 39, 40) to the outside and / or or from the outside into the correction pressure compartment (25; 33; 38, 39, 40) is possible without flowing through an imaging beam path with the gas. Mirror assembly according to one of Claims 1 to 5 , characterized in that the mirror (M10) and / or the limiting body (24) has a passage opening (17; 29) for the imaging light (3). Mirror assembly according to one of Claims 1 to 6 characterized by a plurality of correction pressure compartment sections (38, 39, 40) delimited by a respective portion of the at least one delimiting body (24) and by a respective portion of the at least one mirror (M10). Mirror assembly after Claim 7 , characterized in that each of the correction pressure compartment sections (38 to 40) is connected to the gas source (27) via its own fluid connection (28a, 28b, 28c). Imaging optics (7) with at least one mirror assembly according to one of Claims 1 to 8th for imaging an object field (4), in which an object (10) to be imaged can be arranged, into an image field (8), in which a substrate (11) can be arranged. Optical system - with an imaging optic Claim 9 , - with an illumination optical system (6) for illuminating the object field (4) with illumination light (3) of a light source (2). Projection exposure system with an optical system after Claim 10 and a light source (2) for generating the illumination light (3). A method of fabricating a patterned device comprising the steps of: providing a reticle (10) and a wafer (11), projecting a pattern on the reticle (10) onto a photosensitive layer of the wafer (11) using the projection exposure apparatus Claim 11 , - Generating a micro or nanostructure on the wafer (11). Structured component produced by a method according to Claim 12 , Measuring device with at least one mirror assembly according to one of Claims 1 to 8th and with a measuring device for measuring the optical surface.

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