DE102023206428A1 - Apparatus and method for producing an optical element and lithography system - Google Patents

Abstract

The invention relates to a device (1) for producing a mirror body (2) for an optical element (116, 118, 119, 120, 121, 122, Mi) of an EUV projection exposure system (100), which has an optical surface (2a), by means of bonding at least two components (3a, 3b) to a contact surface (4) of the components (3a, 3b). For this purpose, an oven (5) is provided for heating the mirror body (2). According to the invention, at least one reflection surface (6) is provided for reflecting thermal radiation (7) and is designed to homogenize a temperature profile of the mirror body (2) during bonding in an area along the optical surface (2a) and/or the contact surface (4) in such a way that the mirror body (2) has the same temperature in the entire area along the optical surface (2a) and/or the contact surface (4). The at least one reflection surface (6) is arranged such that the reflection surface (6) runs at least approximately perpendicular to the optical surface (2a) and/or the contact surface (4).

Description

The invention relates to a device for producing a mirror body for an optical element of an EUV projection exposure system, which has an optical surface, by means of bonding at least two components to a contact surface of the components, with a furnace for heating the mirror body.

The invention further relates to a method for producing a mirror body for an optical element of an EUV projection exposure system, which has an optical surface, by means of bonding at least two components to a contact surface of the components, wherein the mirror body is heated with an oven

The invention also relates to a lithography system, in particular an EUV projection exposure system for semiconductor lithography, with an illumination system with a radiation source and an optics which has at least one optical element.

It is known from the prior art that when producing water-cooled mirrors for EUV lithography systems, structures such as cooling channels are introduced into a mirror body or a mirror blank. Milling processes, drilling processes or the like are known for introducing the cooling channels into the mirror body.

In particular for processing steps, such as those that can be part of a milling process, it is known to break the mirror body down into at least two components. This allows the structures, in particular the cooling channels, to be advantageously incorporated into the interior of the mirror.

In practice, the individual components are reassembled in a thermal process, particularly through a high-temperature process in an oven. Bonding can be used as a thermal joining process.

A disadvantage of the methods known from the prior art is that the material properties of the mirror body can change during the thermal joining process, which can lead to inhomogeneous properties of the mirror body after the thermal joining process.

This can limit the reliability of the mirror body or of the mirror based on the mirror body, for example when the mirror is operated in an EUV projection exposure system.

The present invention is based on the object of creating a device for producing a mirror body for an optical element, which avoids the disadvantages of the prior art, in particular enables the production of reliably shaped mirror bodies.

According to the invention, this object is achieved by a device having the features mentioned in claim 1.

The present invention is further based on the object of creating a method for producing a mirror body for an optical element, which avoids the disadvantages of the prior art, in particular enables the production of reliably shaped mirror bodies.

According to the invention, this object is achieved by a method having the features mentioned in claim 6.

The present invention is also based on the object of creating a lithography system, in particular an EUV projection exposure system, which avoids the disadvantages of the prior art, in particular has reliably shaped optical elements.

According to the invention, this object is achieved by a lithography system, in particular a projection exposure system, having the features mentioned in claim 10.

The device according to the invention for producing a mirror body for an optical element of an EUV projection exposure system, which has an optical surface, by means of bonding at least two components to a contact surface of the components, with a furnace for heating the mirror body, comprises at least one reflection surface for reflecting thermal radiation, which is designed to homogenize a temperature profile of the mirror body during bonding in an area along the optical surface and/or the contact surface in such a way that the mirror body has the same temperature in the entire area along the optical surface and/or the contact surface. For this purpose, the at least one reflection surface is arranged in such a way that the reflection surface runs at least approximately perpendicular to the optical surface and/or the contact surface.

According to the invention, each of the provided reflection surfaces is arranged at least approximately perpendicular to the optical surface and/or the contact surface.

However, a configuration not according to the invention is also disclosed here, in which several reflection surfaces are provided, wherein at least one of the several reflection surfaces runs perpendicular to the optical surface and/or the contact surface. This can also contribute to homogenization.

By means of the device according to the invention, heating of the mirror body can be carried out in such a way that material properties of the mirror body, in particular a zero-crossing temperature (ZCT), do not change negatively or change as little as possible.

In particular, by means of the device according to the invention it can be achieved that every point along the optical surface and/or the contact surface in the mirror body undergoes an identical temporal temperature curve.

By means of the device according to the invention, it can be avoided that the optical element, in particular the mirror, deforms disadvantageously during operation due to its changed material properties.

By means of the device according to the invention, the optical element can further be reliably shaped in such a way that after production with the device according to the invention, it has a shape during operation which, although it inevitably deviates from an ideal shape, is tolerably deformed and/or easily correctable.

The inventors have recognized that a deviation from the optimal state, according to which every point in the entire mirror body optimally runs through the same temporal temperature curve, is acceptable provided that this condition is met for all points along the optical surface and/or the contact surface. Using the device according to the invention, a temperature distribution that is as spatially homogeneous as possible can therefore be achieved in a relevant part of the mirror body.

It is particularly advantageous if the at least one reflection surface is arranged such that the reflection surface runs at least approximately perpendicular to the optical surface.

In a case where the contact surface or a bonding plane is arranged obliquely to the optical surface, it is advantageous if a homogeneous temperature distribution on the optical surface is prioritized over a homogeneous temperature distribution on the contact surface.

In the context of the invention, the optical surface is also understood to include its precursor surfaces in the relevant manufacturing stage of the optical element.

The device according to the invention is particularly suitable for mirror bodies which have cooling channels, in particular if the cooling channels run in the region of the contact surface.

By means of the device according to the invention, a later performance of the mirror based on the mirror body can be achieved in that a homogeneous temperature distribution can be achieved, especially in a material layer between a later optical surface of the mirror and preferably provided cooling channels.

The material layer, also referred to as the “critical zone”, is located particularly in the area of the optical surface and/or the contact surface.

Areas and/or zones in the optical element or components tend to be more critical the closer they are to the optical surface.

To produce optical elements that are designed as cooled mirrors, it can be provided that the contact surface or the bonding plane is arranged as close to the optical surface as possible. This allows it to be cooled as effectively as possible when the mirror is in operation.

By arranging the at least one reflection surface such that the reflection surface extends at least approximately perpendicular to the optical surface and/or the contact surface, it can be achieved that lateral surfaces of the mirror body are kept as adiabatic as possible.

The use of reflective surfaces enables a reduction in radiation exchange on the side surfaces of the mirror body. This is particularly advantageous because heat exchange between a surface of the mirror body and the furnace at the process temperatures present during bonding mainly takes place via radiation.

In the device according to the invention, the reduction of the radiation exchange is achieved by introducing at least one reflection surface into the furnace.

The at least one reflection surface is preferably a mirror surface and/or a surface with a low emissivity, in particular an emissivity of less than 0.1, preferably less than 0.06.

The at least one reflection surface can be oriented such that the reflection of the heat radiation occurs towards or away from the mirror body.

In an advantageous development of the device according to the invention, it can be provided that several reflection surfaces are provided and configured to enclose the mirror body on all sides perpendicular to the optical surface and/or the contact surface and/or to completely cover an extension of the mirror body perpendicular to the optical surface and/or the contact surface.

If the mirror body is surrounded on all sides by the reflection surfaces and at least approximately completely covered along its extension perpendicular to the optical surface and/or the contact surface, the temperature distribution in the mirror body can be homogenized in such a way that a homogeneous temperature profile is formed in the mirror body along layers parallel to the optical surface and/or the contact surface, or within layers parallel to the optical surface and/or the contact surface.

A temperature distribution in the mirror body during heating and/or cooling of the mirror body in the furnace is therefore homogeneous parallel to the optical surface and/or the contact surface and has a layering perpendicular to the optical surface and/or the contact surface.

It can be provided that the reflection surfaces are at least as “high” as the workpiece or mirror body formed from the components.

It can also be intended to make the reflective surfaces or the reflective frame, which will be discussed later, higher than the workpiece or the mirror body. This can serve to shield the side surfaces of the mirror body even more effectively against obliquely incident heat radiation.

In an advantageous development of the device according to the invention, it can be provided that the at least one reflection surface is designed as a coating of the mirror body.

The advantage of applying the reflection surface as a coating directly to the mirror body is that it avoids radiation losses in a gap between the mirror body and the reflection surface.

The inventors have recognized that the arrangement of the at least one reflection surface claimed according to the invention, such that it runs at least approximately perpendicular to the optical surface and/or the contact surface, is particularly advantageous. However, it should be noted that even if a side surface of the mirror body does not run completely perpendicular to the optical surface and/or the contact surface, i.e. at an angle to the optical surface and/or the contact surface, an advantageous homogenization of the temperature profile within the optical surface and/or the contact surface can occur.

It is particularly advantageous if the at least one reflection surface is applied as a reflective layer on the side surfaces of the mirror body.

In an advantageous development of the device according to the invention, it can be provided that the at least one reflection surface is formed on a structure that can be positioned in the oven, preferably a frame.

If a reflective structure is introduced into the oven, leading laterally around the mirror body, in particular in the form of a frame, this results in a high degree of flexibility for different geometries of the mirror body. Furthermore, this makes it possible to achieve a distance, preferably a small one, between the reflective surface of the reflection area and the side surfaces of the mirror body. This can prevent contamination of the mirror body by substances that may evaporate from the structure at the high temperatures present in the oven.

In an advantageous development of the device according to the invention, it can be provided that at least one first reflection surface oriented towards the mirror body and at least one second reflection surface oriented away from the mirror body are provided.

In this way, reflection both internally and externally is made possible.

Preferably, the first and second reflection surfaces abut one another and are parallel to one another.

Preferably, the at least one reflection surface and/or a reflective material The material of the at least one reflection surface and/or the reflection surface designed as a coating has a low emissivity and/or a high reflectivity for thermal radiation in the furnace.

In addition to the use of two reflection surfaces, a single reflection surface can also be used, which allows the heat radiation to be reflected towards the mirror body and towards the oven.

It can be provided that the reflection surface comprises a metal.

It can be provided that the reflection surface is designed as a metal coating, in particular as an aluminum coating of the side surfaces of the mirror body.

A further development of the device in which the reflection surface and/or the structure are heat-resistant can also be advantageous.

In particular, the reflection surface and/or the structure or the material used for the structure have such a temperature resistance that contamination of the mirror material of the mirror body is avoided.

The invention further relates to a method having the features mentioned in claim 6.

In the method according to the invention for producing a mirror body for an optical element of an EUV projection exposure system, which has an optical surface, by means of bonding at least two components to a contact surface of the components, the mirror body is heated using an oven. According to the invention, a temperature profile of the mirror body during bonding is homogenized in an area along the optical surface and/or the contact surface by at least one reflection surface in such a way that the mirror body is kept at the same temperature in the entire area along the optical surface and/or the contact surface. The mirror body and the at least one reflection surface are arranged relative to one another in the oven in such a way that the optical surface and/or the contact surface runs at least approximately perpendicular to the at least one reflection surface.

By means of the method according to the invention, an advantageously homogeneous temperature distribution can be achieved, especially in a material layer between a later optical surface of the mirror and cooling channels, preferably formed in the mirror body. The cooling channels are generally formed along a plane of the contact surface or adjacent to the contact surface. A homogeneous temperature distribution in the area between the contact surface and the optical surface of the mirror is particularly relevant for the later performance of the mirror. The optical surface and/or the contact surface can therefore be referred to as a "critical zone".

The method according to the invention makes it possible to heat the mirror body only on the top and bottom and reduces heat conduction via the side surfaces. This results in an advantageously homogeneous temperature distribution within the critical zone.

In the method according to the invention, it can be provided that a temperature of 800 °C to 1,000 °C prevails in the furnace during bonding. This can, under certain circumstances, influence the ZCT and hydrogen-induced outgassing of the mirror body. The method according to the invention enables the advantageous mirror properties to be maintained even at the high temperatures described above.

Furthermore, thermal stresses, which can arise at the aforementioned high temperatures, can be reduced by the method according to the invention.

The method according to the invention is particularly suitable for producing mirrors for operation at a normal incidence (“normal incidence mirror”) and/or mirrors for operation at a grazing incidence (“grazing incidence mirror”).

In an advantageous development of the method according to the invention, it can be provided that the mirror body is enclosed on all sides by a plurality of reflection surfaces perpendicular to the optical surface and/or the contact surface and/or is completely covered perpendicular to the optical surface and/or the contact surface.

If the emissivity is reduced on the side surfaces of the mirror body, a temperature profile is created that is layered along the height of the mirror body. Only small temperature gradients occur in the lateral direction, so that a much more homogeneous temperature profile is created in a direction parallel to the optical surface and/or the contact surface.

This can reduce the risk of inhomogeneous changes in the ZCT.

Furthermore, the risk of introducing unwanted stresses and deformations during the bonding process can be reduced.

In an advantageous development of the method according to the invention, it can be provided that the mirror body is arranged in a frame, the outer surface of which is formed by the at least one reflection surface.

The use of a frame results in a high degree of flexibility in the relative arrangement of the mirror body relative to the at least one reflection surface.

In an advantageous development of the method according to the invention, it can be provided that at least one recess, preferably a groove, is introduced into at least one of the components before bonding on the contact surface, and wherein at least one cooling channel is formed in the mirror body by bonding the components.

It can be provided that the at least one mirror body is made of a titanium silicate glass.

Preferably, exactly two components are provided.

In the case of mirrors which have at least one cooling channel, the application of the method according to the invention is associated with particular advantages, since above all the material layer between the later optical surface of the mirror and the at least one cooling channel is relevant for the later performance of the mirror.

The invention also relates to a lithography system having the features mentioned in claim 10.

The lithography system according to the invention, in particular an EUV projection exposure system for semiconductor lithography, comprises an illumination system with a radiation source and an optics which has at least one optical element. According to the invention, at least one mirror body of at least one of the optical elements is produced at least partially by means of the above-described device according to the invention and/or by means of the above-described method according to the invention.

The lithography system according to the invention is characterized by advantageously reliable optical elements. This enables high production stability in the manufacture of semiconductor components.

In an advantageous development of the lithography system according to the invention, it can be provided that the at least one mirror body produced at least partially by means of the device according to the invention and/or by means of the method according to the invention has at least one cooling channel.

In particular, mirrors whose mirror bodies have at least one cooling channel benefit particularly from production by means of the method according to the invention and/or the device according to the invention.

The method according to the invention and/or the device according to the invention are particularly suitable for producing mirror bodies or mirrors of EUV projection exposure systems.

However, the device according to the invention and/or the method according to the invention can also be used advantageously in the production of other optical elements, such as reticles and/or lenses.

Both EUV projection exposure systems and DUV projection exposure systems benefit from optical elements produced using the device according to the invention and/or the method according to the invention. In general, the device according to the invention and the method according to the invention are suitable for producing optical elements which have a bonded body with cooling channels.

Features that have been described in connection with one of the objects of the invention, namely given by the device according to the invention, the method according to the invention or the lithography system according to the invention, can also be implemented advantageously for the other objects of the invention. Likewise, advantages that have been mentioned in connection with one of the objects of the invention can also be understood to relate to the other objects of the invention.

In the following, embodiments of the invention are described in more detail with reference to the drawing.

The figures each show preferred embodiments in which individual features of the present invention are shown in combination with one another. Features of an embodiment can also be implemented separately from the other features of the same embodiment and can therefore be easily combined by a person skilled in the art to form further useful combinations. and sub-combinations with features of other embodiments.

In the figures, functionally identical elements are provided with the same reference symbols.

• 1 eine EUV-Projektionsbelichtungsanlage im Meridionalschnitt;
• 2 eine DUV-Projektionsbelichtungsanlage;
• 3 eine schematische Darstellung einer möglichen Ausführungsform einer erfindungsgemäßen Vorrichtung;
• 4 eine schematische Darstellung eines mit der erfindungsgemäßen Vorrichtung temperierten Spiegelkörpers;
• 5 eine blockdiagrammartige Darstellung einer möglichen Ausführungsform eines erfindungsgemäßen Verfahrens;
• 6 eine schematische Darstellung eines auf herkömmliche Weise temperierten Spiegelkörpers;
• 7 eine schematische Darstellung einer Temperaturkurve eines Spiegelkörpers;
• 8 eine schematische Darstellung von Wärmeübergangskoeffizienten eines Spiegelkörpers; und
• 9 eine schematische Darstellung von Temperaturkurven eines Spiegelkörpers unter dem erfindungsgemäßen Verfahren.

Show it:

• 1 an EUV projection exposure system in meridional section;
• 2 a DUV projection exposure system;
• 3 a schematic representation of a possible embodiment of a device according to the invention;
• 4 a schematic representation of a mirror body tempered with the device according to the invention;
• 5 a block diagram representation of a possible embodiment of a method according to the invention;
• 6 a schematic representation of a conventionally tempered mirror body;
• 7 a schematic representation of a temperature curve of a mirror body;
• 8th a schematic representation of heat transfer coefficients of a mirror body; and
• 9 a schematic representation of temperature curves of a mirror body using the method according to the invention.

In the following, with reference to 1 The essential components of an EUV projection exposure system 100 for microlithography are described as an example of a lithography system. The description of the basic structure of the EUV projection exposure system 100 and its components should not be understood as limiting.

An illumination system 101 of the EUV projection exposure system 100 has, in addition to a radiation source 102, illumination optics 103 for illuminating an object field 104 in an object plane 105. A reticle 106 arranged in the object field 104 is exposed. The reticle 106 is held by a reticle holder 107. The reticle holder 107 can be displaced via a reticle displacement drive 108, in particular in a scanning direction.

In 1 For explanation purposes, a Cartesian xyz coordinate system is shown. The x-direction runs perpendicular to the drawing plane. The y-direction runs horizontally and the z-direction runs vertically. The scanning direction runs in 1 along the y-direction. The z-direction is perpendicular to the object plane 105.

The EUV projection exposure system 100 comprises a projection optics 109. The projection optics 109 are used to image the object field 104 into an image field 110 in an image plane 111. The image plane 111 runs parallel to the object plane 105. Alternatively, an angle other than 0° between the object plane 105 and the image plane 111 is also possible.

A structure on the reticle 106 is imaged onto a light-sensitive layer of a wafer 112 arranged in the area of the image field 110 in the image plane 111. The wafer 112 is held by a wafer holder 113. The wafer holder 113 can be displaced via a wafer displacement drive 114, in particular along the y-direction. The displacement of the reticle 106 on the one hand via the reticle displacement drive 108 and the wafer 112 on the other hand via the wafer displacement drive 114 can be synchronized with one another.

The radiation source 102 is an EUV radiation source. The radiation source 102 emits in particular EUV radiation 115, which is also referred to below as useful radiation or illumination radiation. The useful radiation 115 has in particular a wavelength in the range between 5 nm and 30 nm. The radiation source 102 can be a plasma source, for example an LPP source (“laser produced plasma”, plasma generated using a laser) or a DPP source (“gas discharged produced plasma”, plasma generated by means of gas discharge). It can also be a synchrotron-based radiation source. The radiation source 102 can be a free-electron laser (FEL).

The illumination radiation 115 that emanates from the radiation source 102 is bundled by a collector 116. The collector 116 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 116 can be exposed to the illumination radiation 115 in grazing incidence (GI), i.e. with angles of incidence greater than 45°, or in normal incidence (NI), i.e. with angles of incidence less than 45°. The collector 116 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation 115 and on the other hand to suppress stray light.

After the collector 116, the illumination radiation 115 propagates through an intermediate focus in an intermediate focus plane 117. The intermediate focal plane 117 may represent a separation between a radiation source module, comprising the radiation source 102 and the collector 116, and the illumination optics 103.

The illumination optics 103 comprises a deflection mirror 118 and a first facet mirror 119 arranged downstream of this in the beam path. The deflection mirror 118 can be a flat deflection mirror or alternatively a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 118 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation 115 from false light of a different wavelength. If the first facet mirror 119 is arranged in a plane of the illumination optics 103 that is optically conjugated to the object plane 105 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 119 comprises a plurality of individual first facets 120, which are also referred to below as field facets. Of these facets 120, only one is shown in the 1 only a few examples are shown.

The first facets 120 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 120 can be designed as flat facets or alternatively as convex or concave curved facets.

As for example from the EN 10 2008 009 600 A1 As is known, the first facets 120 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 119 can in particular be designed as a microelectromechanical system (MEMS system). For details, please refer to the EN 10 2008 009 600 A1 referred to.

Between the collector 116 and the deflection mirror 118, the illumination radiation 115 runs horizontally, i.e. along the y-direction.

In the beam path of the illumination optics 103, a second facet mirror 121 is arranged downstream of the first facet mirror 119. If the second facet mirror 121 is arranged in a pupil plane of the illumination optics 103, it is also referred to as a pupil facet mirror. The second facet mirror 121 can also be arranged at a distance from a pupil plane of the illumination optics 103. In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also referred to as a specular reflector. Specular reflectors are known from the US 2006/0132747 A1 , the EP 1 614 008 B1 and the US$6,573,978 .

The second facet mirror 121 comprises a plurality of second facets 122. In the case of a pupil facet mirror, the second facets 122 are also referred to as pupil facets.

The second facets 122 can also be macroscopic facets, which can be round, rectangular or hexagonal, for example, or alternatively facets composed of micromirrors. In this regard, reference is also made to the EN 10 2008 009 600 A1 referred to.

The second facets 122 may have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 103 thus forms a double-faceted system. This basic principle is also called the fly's eye integrator.

It may be advantageous not to arrange the second facet mirror 121 exactly in a plane which is optically conjugated to a pupil plane of the projection optics 109.

With the help of the second facet mirror 121, the individual first facets 120 are imaged into the object field 104. The second facet mirror 121 is the last bundle-forming or actually the last mirror for the illumination radiation 115 in the beam path in front of the object field 104.

In a further embodiment of the illumination optics 103 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 121 and the object field 104, which contributes in particular to the imaging of the first facets 120 in the object field 104. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 103. The transmission optics can in particular comprise one or two mirrors for perpendicular incidence (NI mirrors, “normal incidence” mirrors) and/or one or two mirrors for grazing incidence (GL mirrors, “grazing incidence” mirrors).

The illumination optics 103 has in the design shown in the 1 As shown, after the collector 116 there are exactly three mirrors, namely the deflection mirror 118, the field facet mirror 119 and the pupil facet mirror 121.

In a further embodiment of the illumination optics 103, the deflection mirror 118 can also be omitted, so that the illumination optics 103 can then have exactly two mirrors after the collector 116, namely the first facet mirror 119 and the second facet mirror 121.

The imaging of the first facets 120 by means of the second facets 122 or with the second facets 122 and a transmission optics into the object plane 105 is usually only an approximate imaging.

The projection optics 109 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the EUV projection exposure system 100.

In the 1 In the example shown, the projection optics 109 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 115. The projection optics 109 are doubly obscured optics. The projection optics 109 have a numerical aperture on the image side that is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, just like the mirrors of the illumination optics 103, can have highly reflective coatings for the illumination radiation 115. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 109 have a large object-image offset in the y-direction between a y-coordinate of a center of the object field 104 and a y-coordinate of the center of the image field 110. This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 105 and the image plane 111.

The projection optics 109 can in particular be anamorphic. In particular, it has different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 109 are preferably (βx, βy) = (+/- 0.25, +/- 0.125). A positive image scale β means an image without image inversion. A negative sign for the image scale β means an image with image inversion.

The projection optics 109 thus leads to a reduction in the ratio 4:1 in the x-direction, i.e. in the direction perpendicular to the scanning direction.

The projection optics 109 leads to a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

Other image scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x and y directions in the beam path between the object field 104 and the image field 110 can be the same or can be different depending on the design of the projection optics 109. Examples of projection optics with different numbers of such intermediate images in the x and y directions are known from US 2018/0074303 A1 .

Each of the pupil facets 122 is assigned to exactly one of the field facets 120 to form an illumination channel for illuminating the object field 104. This can result in particular in illumination according to the Köhler principle. The far field is broken down into a plurality of object fields 104 using the field facets 120. The field facets 120 generate a plurality of images of the intermediate focus on the pupil facets 122 assigned to them.

The field facets 120 are each imaged onto the reticle 106 by an associated pupil facet 122, superimposing one another, to illuminate the object field 104. The illumination of the object field 104 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by superimposing different illumination channels.

By arranging the pupil facets, the illumination of the entrance pupil of the projection optics 109 can be defined geometrically. By selecting the illumination channels, in particular the subset of the pupil facets that guide light, the intensity distribution in the entrance pupil of the projection optics 109 can be set. This intensity distribution is also referred to as the illumination setting.

A preferred pupil uniformity in the area of defined illuminated sections an illumination pupil of the illumination optics 103 can be achieved by redistributing the illumination channels.

In the following, further aspects and details of the illumination of the object field 104 and in particular the entrance pupil of the projection optics 109 are described.

The projection optics 109 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 109 cannot usually be illuminated precisely with the pupil facet mirror 121. When the projection optics 109 images the center of the pupil facet mirror 121 telecentrically onto the wafer 112, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimal. This surface represents the entrance pupil or a surface conjugated to it in spatial space. In particular, this surface shows a finite curvature.

It is possible that the projection optics 109 have different positions of the entrance pupil for the tangential and the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 121 and the reticle 106. With the help of this optical component, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the 1 In the arrangement of the components of the illumination optics 103 shown, the pupil facet mirror 121 is arranged in a surface conjugated to the entrance pupil of the projection optics 109. The first field facet mirror 119 is arranged tilted to the object plane 105. The first facet mirror 119 is arranged tilted to an arrangement plane that is defined by the deflection mirror 118.

The first facet mirror 119 is arranged tilted to an arrangement plane which is defined by the second facet mirror 121.

In 2 an exemplary DUV projection exposure system 200 is shown. The DUV projection exposure system 200 has an illumination system 201, a device called a reticle stage 202 for receiving and precisely positioning a reticle 203, by means of which the later structures on a wafer 204 are determined, a wafer holder 205 for holding, moving and precisely positioning the wafer 204 and an imaging device, namely a projection optics 206, with several optical elements, in particular lenses 207, which are held via mounts 208 in an objective housing 209 of the projection optics 206.

Alternatively or in addition to the lenses 207 shown, various refractive, diffractive and/or reflective optical elements, including mirrors, prisms, end plates and the like, can be provided.

The basic functional principle of the DUV projection exposure system 200 provides that the structures introduced into the reticle 203 are imaged onto the wafer 204.

The illumination system 201 provides a projection beam 210 in the form of electromagnetic radiation required for imaging the reticle 203 onto the wafer 204. A laser, a plasma source or the like can be used as a source for this radiation. The radiation is shaped in the illumination system 201 via optical elements such that the projection beam 210 has the desired properties with regard to diameter, polarization, shape of the wave front and the like when it strikes the reticle 203.

An image of the reticle 203 is generated by means of the projection beam 210 and is transferred to the wafer 204 in a correspondingly reduced size by the projection optics 206. The reticle 203 and the wafer 204 can be moved synchronously so that areas of the reticle 203 are imaged onto corresponding areas of the wafer 204 practically continuously during a so-called scanning process.

Optionally, an air gap between the last lens 207 and the wafer 204 can be replaced by a liquid medium having a refractive index greater than 1.0. The liquid medium can be, for example, high-purity water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

The use of the invention is not limited to use in projection exposure systems 100, 200, in particular not with the described structure. The invention is suitable for any lithography systems or microlithography systems, but in particular for projection exposure systems with the described structure. The invention is also suitable for EUV projection exposure systems which have a lower image-side numerical aperture than those associated with 1 described, and do not have an obscured mirror M5 and/or M6. In particular, the invention is also suitable for EUV projection exposure systems which have an image-side numerical aperture of 0.25 to 0.5, preferably 0.3 to 0.4, particularly preferably 0.33. The invention and the following embodiments are also not to be understood as being limited to a specific design.

The following figures represent the invention merely by way of example and in a highly schematic manner.

3 shows a schematic representation of a possible embodiment of a device 1 for producing a mirror body 2.

The device 1 for producing the mirror body 2, in particular for an optical element 116, 118, 119, 120, 121, 122, Mi for the projection exposure system 100, which has at least one optical surface 2a, by means of bonding from at least two components 3a, 3b (see 4 ) on a contact surface 4 (see 4 of the components 3a, 3b), comprises an oven 5 for heating the mirror body 2. In the device 1, at least one reflection surface 6 is provided for reflecting a thermal radiation 7 and is designed to homogenize a temperature profile of the mirror body 2 during bonding in an area along the optical surface 2a and/or the contact surface 4 such that the mirror body 2 has the same temperature in the entire area along the optical surface 2a and/or the contact surface 4. In this case, the at least one reflection surface 6 is arranged such that the reflection surface 6 runs at least approximately perpendicular to the optical surface 2a and/or the contact surface 4.

In the 3 In the embodiment shown, a plurality of reflection surfaces 6 are provided and designed to enclose the mirror body 2 on all sides perpendicular to the optical surface 2a and/or the contact surface 4 and/or to at least approximately completely cover an extension of the mirror body 2 perpendicular to the optical surface 2a and/or the contact surface 4.

In the 3 In the embodiment of the device 1 shown, the at least one reflection surface 6 is on a structure positionable in the oven 5 in the 3 illustrated embodiment preferably formed of a frame 8.

In an embodiment not shown, the at least one reflection surface 6 can alternatively or additionally be formed as a coating of the mirror body 2.

According to the embodiment of the device 1 according to 3 the reflection surface 6 and the frame 8 are heat-resistant, preferably up to a temperature of at least 1000°C.

According to an embodiment not shown, at least one first reflection surface 6 oriented towards the mirror body 2 and at least one second reflection surface 6 oriented away from the mirror body 2 can be provided.

It can be provided that the reflection surface 6 is spaced from a side surface of the mirror body 2 by a distance which is 1% to 10%, preferably 5% +/- 2%, of an extension of the mirror body 2 perpendicular to the optical surface 2a and/or the contact surface 4.

In the top view 3 an upper side of the mirror body 2 is shown.

4 shows a schematic representation of a mirror body 2 which is tempered with the device 1 according to the invention.

In 4 an embodiment of the mirror body 2 is shown in which the mirror body 2 is formed from the two components 3a and 3b, which are connected to one another along the contact surface 4. A homogeneous temperature profile has been formed along the optical surface 2a and/or the contact surface 4 by the temperature control by means of the device 1. The temperature profile is layered perpendicular to the optical surface 2a and/or the contact surface 4.

In the 4 In the example shown, the heat exchange between the mirror body 2 and the furnace 5 occurs predominantly from above and below or under a reduced emissivity on the side surfaces of the mirror body 2.

5 shows a block diagram of a possible embodiment of a method for producing the mirror body 2.

In the method for producing the mirror body 2 for the optical element 116, 118, 119, 120, 121, 122, Mi, in particular a mirror, of an EUV projection exposure system 100, which has the optical surface 2a, by means of bonding at least two components 3a, 3b to the contact surface 4 of the components 3a, 3b, in a heating The mirror body 2 is heated with the furnace 5 in the heating block 20.

In a homogenization block 21, a temperature profile of the mirror body 2 is homogenized during bonding in a region along the optical surface 2a and/or the contact surface 4 by the at least one reflection surface 6 such that the mirror body 2 is kept at the same temperature in the entire region along the optical surface 2a and/or the contact surface 4.

In an arrangement block 22, the mirror body 2 and the at least one reflection surface 6 are arranged relative to one another in the furnace 5 such that the optical surface 2a and/or the contact surface 4 runs at least approximately perpendicular to the at least one reflection surface 6.

Within the framework of the homogenization block 21 and/or the arrangement block 22, the mirror body 2 is preferably surrounded on all sides by a plurality of reflection surfaces 6 perpendicular to the optical surface 2a and/or the contact surface 4 and/or completely covered perpendicular to the optical surface 2a and/or the contact surface 4.

Within the arrangement block 22, the mirror body 2 is further preferably arranged in a frame 8, the outer surface of which is formed by the at least one reflection surface 6.

In the embodiment of the method according to 5 Furthermore, at least one recess, preferably a groove, is preferably introduced into at least one of the components 3a, 3b before bonding on the contact surface 4, whereby the bonding of the components 3a, 3b creates at least one cooling channel 9 (see 4 ) is formed in the mirror body 2.

Preferably, the at least one recess is introduced, in particular by milling, such that the at least one recess in the contact surface 4 is open.

In the 5 The blocks shown are preferably chronological, as in 5 However, other arrangements are also possible and useful.

6 shows a schematic representation of a conventionally tempered mirror body 2.

Due to the absence of the laterally arranged reflection surfaces 6 according to the invention, a temperature gradient also occurs within the optical surface 2a and/or the contact surface 4.

In the conventional case of uniform heating from all sides, the 6 shown hot core inside the mirror body 2 with temperature gradients to the entire surface of the mirror body in all spatial directions.

In the 6 In the example shown, there is a uniform heat exchange from all sides of the mirror body 2 and thus a uniform emissivity on the entire surface of the mirror body 2.

7 shows an exemplary representation of a temperature curve for bonding a mirror body 2 made of titanium silicate glass from two components 3a, 3b.

8th shows a schematic representation of heat transfer coefficients by radiation and by convection at the mirror body 2 as a function of temperature.

8th shows in particular a comparison of the heat transfer by radiation and by convection as a function of the temperature of the mirror body 2. The heat transfer by radiation, in 8th marked as S, was estimated based on common emissivities for titanium silicate glass and furnace materials and a temperature difference of 10 K between the furnace wall and mirror body 2. For comparison, heat transfer coefficients are shown, in 8th marked as V, which result from radiation with an emissivity of 0.05, as occurs for example on polished metallic surfaces, or are to be expected for natural convection.

8th clearly shows that the heat transfer at the temperatures prevailing in the furnace 5 during bonding is strongly dominated by radiation from the mirror body 2. Furthermore, it can be clearly seen that the heat transfer by radiation can be greatly reduced by a reflective surface or reflection area 6 with a low emissivity of 0.05.

9 shows a schematic representation of temperature curves of the mirror body 2 in the method according to the invention.

In 9 Results of finite element simulations are shown, in which different heat transfer coefficients were assumed for the side surfaces of the mirror body 2. On the one hand, the heat transfer coefficient was determined according to the heat transfer that an emissivity of titanium silicate glass, and once simulated with an emissivity of 0.05.

In both cases, a cooling process was simulated, whereby the entire mirror body 2 was assumed to be completely heated to a starting temperature at the beginning of the simulation.

9 shows the temperature profile of a maximum temperature, a minimum temperature and an average temperature in the mirror body 2 over time for both cases described above. The temperature profiles of the two cases are very similar. The case in which the heat exchange takes place predominantly via the top and bottom of the mirror body 2 cools down somewhat more slowly.

In 9 The temperature profiles, which were simulated on the assumption of a uniform emissivity for titanium silicate glass on the entire surface of the mirror body 2, are shown with solid lines. The temperature profiles, which were simulated on the assumption of a reduced emissivity on the side surfaces of the mirror body 2, ie with a heat transfer which takes place practically exclusively on the top and bottom of the mirror body 2, are shown with dashed lines.

The invention is particularly suitable for mirror bodies 2, which are preferably mirror bodies 2 for the mirrors 116, 118, 119, 120, 121, 122, Mi of an EUV projection exposure system, in particular the one shown in 1 EUV projection exposure system 100 shown in principle. The projection exposure system 100 according to 1 For semiconductor lithography, preferably at least one of the mirror bodies of the mirrors 116, 118, 119, 120, 121, 122, Mi is produced using the device described above. Alternatively and/or additionally, at least one of the mirror bodies of the mirrors 116, 118, 119, 120, 121, 122, Mi is produced using the method described above.

The mirror body 2 of the lithography system according to the invention can in particular be the mirror body 2 for the mirror M2 of the 1 This may be the EUV projection exposure system 100 shown.

The invention can also be used in connection with optical elements, in particular lenses 207 of DUV projection exposure systems 200. The embodiment is to be understood analogously in such a way that the optical element is a lens 207 of the DUV projection exposure system 200.

List of reference symbols

1

contraption

2

Mirror body

2a

optical surface

3a,b

Component

4

Contact surface

5

Oven

6

Reflection surface

7

Thermal radiation

8th

Frame

9

Cooling channel

20

Heating block

21

Homogenization block

22

Arrangement block

100

EUV projection exposure system

101

Lighting system

102

Radiation source

103

Lighting optics

104

Object field

105

Object level

106

Reticle

107

Reticle holder

108

Reticle displacement drive

109

Projection optics

110

Image field

111

Image plane

112

Wafer

113

Wafer holder

114

Wafer relocation drive

115

EUV / useful / illumination radiation

116

collector

117

Intermediate focal plane

118

Deflecting mirror

119

first facet mirror / field facet mirror

120

first facets / field facets

121

second facet mirror / pupil facet mirror

122

second facets / pupil facets

200

DUV projection exposure system

201

Lighting system

202

Reticle stages

203

Reticle

204

Wafer

205

Wafer holder

206

Projection optics

207

lens

208

Version

209

Lens housing

210

Projection beam

Wed

Mirror

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was 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 accepts no liability for any errors or omissions.

Cited patent literature

• DE 102008009600 A1 [0096, 0100]
• US 20060132747 A1 [0098]
• EP 1614008 B1 [0098]
• US6573978 [0098]
• US 20180074303 A1 [0117]

Claims (11)

Device (1) for producing a mirror body (2) for an optical element (116, 118, 119, 120, 121, 122, Mi) of an EUV projection exposure system (100), which has an optical surface (2a), by means of bonding from at least two components (3a, 3b) to a contact surface (4) of the components (3a, 3b), with a furnace (5) for heating the mirror body (2), characterized in that at least one reflection surface (6) is provided for reflecting thermal radiation (7) and is designed to homogenize a temperature profile of the mirror body (2) during bonding in a region along the optical surface (2a) and/or the contact surface (4) in such a way that the mirror body (2) has the same temperature in the entire region along the optical surface (2a) and/or the contact surface (4), wherein the at least one reflection surface (6) is arranged in such a way is that the reflection surface (6) runs at least approximately perpendicular to the optical surface (2a) and/or the contact surface (4). Device (1) according to Claim 1 , characterized in that a plurality of reflection surfaces (6) are provided and arranged to enclose the mirror body (2) on all sides perpendicular to the optical surface (2a) and/or the contact surface (4) and/or to completely cover an extension of the mirror body (2) perpendicular to the optical surface (2a) and/or the contact surface (4). Device (1) according to Claim 1 or 2 , characterized in that the at least one reflection surface (6) is designed as a coating of the mirror body (2). Device (1) according to one of the Claims 1 or 2 , characterized in that the at least one reflection surface (6) is formed on a structure positionable in the furnace (5), preferably a frame (8). Device (1) according to one of the Claims 1 until 4 , characterized in that at least one first reflection surface (6) oriented towards the mirror body (2) and at least one second reflection surface (6) oriented away from the mirror body (2) are provided. Method for producing a mirror body (2) for an optical element (116, 118, 119, 120, 121, 122, Mi) of an EUV projection exposure system (100), which has an optical surface (2a), by means of bonding at least two components (3a, 3b) to a contact surface (4) of the components (3a, 3b), wherein the mirror body (2) is heated with an oven (5), characterized in that a temperature profile of the mirror body (2) during bonding in a region along the optical surface (2a) and/or the contact surface (4) is homogenized by at least one reflection surface (6) in such a way that the mirror body (2) is kept at the same temperature in the entire region along the optical surface (2a) and/or the contact surface (4), wherein the mirror body (2) and the at least one reflection surface (6) are arranged relative to one another in the oven (5) in such a way that the optical surface (2a) and/or the contact surface (4) runs at least approximately perpendicular to the at least one reflection surface (6). Procedure according to Claim 6 , characterized in that the mirror body (2) is enclosed on all sides by a plurality of reflection surfaces (6) perpendicular to the optical surface (2a) and/or the contact surface (4) and/or is completely covered perpendicular to the optical surface (2a) and/or the contact surface (4). Procedure according to Claim 6 or 7 , characterized in that the mirror body (2) is arranged in a frame (8), the outer surface of which is formed by the at least one reflection surface (6). Method according to one of the Claims 6 until 8th , characterized in that at least one recess, preferably a groove, is introduced into at least one of the components (3a, 3b) before bonding to the contact surface (4), and wherein by bonding the components (3a, 3b) through the recess at least one cooling channel (9) is formed in the mirror body (2). Lithography system, in particular EUV projection exposure system (100) for semiconductor lithography, with an illumination system (101) with a radiation source (102) and an optics (103, 109) which has at least one optical element (116, 118, 119, 120, 121, 122, Mi), characterized in that at least one mirror body (2) of at least one of the optical elements (116, 118, 119, 120, 121, 122, Mi) at least partially - by means of a device (1) according to one of the Claims 1 until 5 and/or - by means of a method according to one of the Claims 6 until 9 is manufactured. Lithography system according to Claim 10 , characterized in that the at least one at least partially - by means of a device (1) according to one of the Claims 1 until 5 and/or - by means of a method according to one of the Claims che 6 until 9 manufactured mirror body (2) has at least one cooling channel (4).

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