DE102021200114A1 - Mirror projection optics, method for checking an optical element, optical element and lithography system - Google Patents

Abstract

The invention relates to mirror projection optics (1) with pupil obscuration (2) for useful radiation (3), in particular EUV radiation, having at least one optical element (4) which has an optically reflecting surface (5) with an optical useful area (6) and an optical shadow area (7), wherein the optical useful area (6) interacts with the useful radiation (3) and is rotationally asymmetrical and wherein the optical shadow area (7) does not interact with the useful radiation (3). According to the invention, the optical shadow area (7) has at least one partial area (13) that is rotationally symmetrical with respect to at least one axis of rotation (8).

Description

The invention relates to mirror projection optics with pupil obscuration for useful radiation, in particular EUV radiation, having at least one optical element which has an optically reflective surface with an optical useful area and an optical shadow area, the optical useful area interacting with the useful radiation and being rotationally asymmetrical and wherein the optical shadow area does not interact with the useful radiation.

In the context of the invention, the useful radiation is to be understood as meaning radiation which contributes to the imaging of the projection optics.

In the context of the invention, the optical shadow area is to be understood as an area on the optically reflective surface that does not interact with the useful radiation and / or the radiation occurring there does not propagate into the image plane and thus does not contribute to the imaging of the projection optics. In summary, such an optical shadow area is characterized in that it does not interact with the useful radiation in the sense of the radiation used for imaging.

The invention also relates to a method for checking at least one optical property of an optical element which has at least one optical useful area that interacts with useful radiation, in particular EUV radiation, and at least one optical shadow area that does not interact with the useful radiation on an optically reflective surface.

The invention further relates to an optical element which has at least one optical useful area that interacts with a useful radiation and at least one optical shadow area that does not interact with the useful radiation on an optical surface, the optical useful area being rotationally asymmetrical.

The invention further relates to a lithography system, in particular a projection exposure system for microlithography, with an illumination system which has a radiation source for generating radiation, in particular an illumination radiation or a projection beam, an illumination optics and a projection optics, in particular a mirror projection optics, wherein the illumination optics and / or the projection optics have at least one optical element.

Optical elements as parts of lithography systems for shaping and guiding useful radiation are known from the prior art.

Projection optics are known from the prior art for imaging a reticle in a wafer plane of the lithography system. For this purpose, the DE 10 2019 203 423 A1 referenced.

In particular in EUV (extreme ultraviolet) projection exposure systems, it is known to use mirror projection optics. The use of mirrors as optical elements in mirror projection optics has the advantage that it is possible to shape and guide EUV radiation with high efficiency through the use of mirrors.

To enable high numerical apertures of the mirror projection optics, it is also known from the prior art that the mirror projection optics have a pupil obscuration. Here, the useful radiation is introduced into the mirror projection optics through a cutout or an opening in an optical element. For this purpose, the DE 10 2019 203 423 A1 referenced.

This enables an advantageously compact geometry of the mirror projection optics.

The pupil obscuration creates a flaw in the reflected light which emanates from that optical element which has the recess or opening.

All subsequent and / or preceding optical elements therefore have at least one optical shadow area which corresponds to the recess or the defect and which does not interact with the useful radiation.

It is also known from the prior art that the optical elements of mirror projection optics are rotationally asymmetrical, in particular aspherical.

By means of an aspherical or non-rotationally symmetrical shape of the reflective surface of the optical elements, for example, imaging errors can be corrected and / or high numerical apertures can be achieved.

To check whether a surface of an optical element has a desired, in particular not rotationally symmetrical, shape, the use of interferometric methods is known from the prior art.

Test wave devices are known for checking the optical properties of the optical element.

In the case of an advantageously designed test wave device, in particular a CGH (computer-generated hologram), a test radiation or test wave is directed onto the optical element to be measured in such a way that the test radiation or test wave occurs at every point on the optically relevant part of the reflective surface of the optical element this strikes perpendicularly and is reflected by this. The reflected test wave is superimposed with a reference wave and the resulting interferogram is used to determine the extent to which the actual shape of the reflective surface corresponds to the desired shape of the reflective surface.

Such a quality determination of the shaping of the optical element in turn depends on a quality of the test shaft device. In particular when using electron beam written CGHs, it is known from practice that these have typographical errors and / or degradation errors.

To determine such errors in test shaft devices for rotationally symmetrical optical elements, rotary calibration is known from the prior art.

Here, the test shaft device and the rotationally symmetrical optical element are rotated against each other and it is determined to what extent a relative rotation leads to a change in the interferogram.

Deviations that are changed by the relative rotation indicate errors such as degradations and / or writing errors.

The disadvantage of the state of the art is that the rotary calibration of optical elements of mirror projection optics which are rotationally asymmetrical is made more difficult by the fact that, when there is a relative rotation between the test shaft device and the optical element, changes occur regularly due to the lack of rotational symmetry faulty design of the test shaft device can be concluded.

The present invention is based on the object of creating mirror projection optics which avoid the disadvantages of the prior art, in particular have optical elements with a rotationally asymmetrical shape that has been checked particularly reliably.

According to the invention, this object is achieved by mirror projection optics with the features mentioned in claim 1.

The present invention is also based on the object of creating a method for checking at least one optical property of an optical element which avoids the disadvantages of the prior art, in particular enables a particularly reliable checking of rotationally asymmetrical optical elements.

According to the invention, this object is achieved by a method having the features mentioned in claim 5.

The present invention is also based on the object of creating an optical element with a rotationally asymmetrical useful area in which the disadvantages of the prior art are avoided, in particular in which the optical properties are checked particularly reliably.

According to the invention, this object is achieved by an optical element having the features mentioned in claim 12.

The present invention is also based on the object of creating a lithography system which avoids the disadvantages of the prior art, in particular has mirror projection optics with reliably checked optical elements.

According to the invention, this object is achieved by a lithography system having the features mentioned in claim 17.

The mirror projection optics according to the invention, with pupil obscuration, for radiation, in particular EUV radiation, has at least one optical element which has an optically reflective surface with an optical useful area and an optical shadow area, the optical useful area interacting with the useful radiation and rotationally asymmetrical is formed and wherein the optical shadow area does not interact with the useful radiation. According to the invention, it is provided that the optical shadow area has at least one partial area that is rotationally symmetrical with respect to at least one axis of rotation.

The mirror projection optics according to the invention has the advantage that a rotary calibration of the test shaft device is made possible in that the optical element to be tested has an optical shadow area with at least one rotationally symmetrical sub-area. The presence of the rotationally symmetrical sub-area does not conflict with the rotationally asymmetrical configuration of that part of the optical element which is in the Usable radiation guided by the mirror projection objective guides and forms, since the rotationally symmetrical sub-area is arranged in the optical shadow area, ie an area which is not involved in guiding and shaping the useful radiation guided by the mirror projection optics.

The at least one rotationally symmetrical sub-area can completely or partially fill the optical shadow area. A plurality of rotationally symmetrical partial areas can also be formed in the optical shadow area. Furthermore, it can also be provided that two or more partial areas are arranged symmetrically with respect to the axis of rotation and are used in cooperation to calibrate the test shaft device.

Within the scope of the invention, the sub-area can be understood as rotationally symmetrical with respect to the axis of rotation if, for example, a wavefront formed by the sub-area, in particular reflected, does not change its shape and / or spatial position when the sub-area rotates, or only changes it insignificantly.

In the context of the invention, the optical shadow area is to be understood as that area of the optical element which does not interact with the useful radiation or on which no useful radiation generated by the radiation source impinges. In particular, within the scope of the invention, the shadow area has no influence on an image of the mask in a propagation of the usable radiation.

In an advantageous development of the mirror projection optics according to the invention, it can be provided that at least one of the rotationally symmetrical subregions is arranged in a central region of the optical element and / or at least one of the rotationally symmetrical subregions is completely enclosed by the usable optical region.

Arranging the optical shadow area and in particular the rotationally symmetrical sub-area of the optical shadow area in a central area of the optical element has the advantage that optical properties can be determined from areas on the test shaft device that correspond to the central area. In particular, errors detected in an area of the test shaft device corresponding to the central area of the optical element, such as writing errors and / or degradations, allow a particularly reliable conclusion about the presence of such errors on the entire test shaft device, for example by extrapolation.

A rotationally symmetrical sub-area completely enclosed by the usable optical area has a relatively small average distance to points in the usable optical area and therefore allows large conclusions to be drawn about areas on the test shaft device that correspond to the usable optical area.

Furthermore, a central arrangement of rotationally symmetrical sub-area enables the axis of rotation to run through a central area of the optical element and thus often in particular to run the axis of rotation in the vicinity of a center of gravity of the optical element.

If, during the rotary calibration, the optical element is rotated about an axis of rotation which is close to its center of gravity, the rotation can advantageously be carried out in a simple manner, in particular without applying unnecessarily high torques.

In particular, it can be provided that a centrally arranged rotationally symmetrical partial area is circular and is arranged coaxially with the axis of rotation.

In an advantageous development of the game projection optics according to the invention, it can be provided that at least one of the rotationally symmetrical sub-areas is arranged in a peripheral area of the optical element and / or at least one of the rotationally symmetrical sub-areas is radially further spaced from the axis of rotation than the useful optical area.

Another possibility for inferring from areas of the test shaft device corresponding to the at least one rotationally symmetrical sub-area to areas of the test shaft device corresponding to the useful optical area, for example by means of extrapolation, is an arrangement of the at least one rotationally symmetrical sub-area in a peripheral area or edge area of the optical element. An edge area of the optical element is to be understood as an area which is arranged adjacent to the useful optical area on the edge of the optical element.

If necessary, a sufficiently large edge can already be provided during the design and / or manufacture of the optical element.

If the axis of rotation runs through the central region of the optical element, the optical shadow region is spaced further apart from the axis of rotation in the radial direction.

In particular with the presence of a rotationally symmetrical sub-area of the optical shadow area both in a central area and in a peripheral area of the optical element, it is particularly advantageous to extrapolate reliably from the central area and the peripheral area to the useful optical area.

The properties of the area on the test shaft device that corresponds to the usable optical area can accordingly be extrapolated both from a radial inside and from a radial outside of the usable optical area.

Rotary calibration can also be carried out for mirror projection optics without the pupil obscuration if, at least in sections, rotationally symmetrical partial areas are arranged on the peripheral area.

In an advantageous development of the mirror projection optics according to the invention, it can be provided that the optical shadow area has at least one alignment mark.

An alignment marking has the advantage that the optical element with the optical useful area and the optical shadow area as well as the test shaft device and the axis of rotation can be reliably aligned relative to one another.

The invention also relates to a method for checking at least one optical property of an optical element with the features mentioned in claim 5.

The method according to the invention for checking at least one optical property of an optical element which has at least one optical useful area that interacts with radiation, in particular EUV radiation, and at least one optical shadow area that does not interact with the useful radiation on an optically reflective surface is provided that an incident test wave is formed by a test wave device and is radiated at least partially perpendicularly onto the optical shadow area and is reflected by the optical shadow area. It is also provided that the test wave reflected by the optical shadow area is compared interferometrically with a reference test wave, after which the test wave device and the optical element are rotated relative to one another about an axis of rotation and a new interferometric comparison is carried out. According to this, at least one optical property of the test shaft device is determined, according to which the optical property of the test shaft device is taken into account when determining the optical property of the optical element.

The inventive method for checking the optical element has the advantage that the correct formation of the surface shape of the optical element can be checked by means of a test wave device, the optical properties of which, in particular degradations and / or writing errors, can also be taken into account when checking the optical element. The method according to the invention enables the test shaft device to be taken into account and, if necessary, to be calibrated.

Within the scope of the invention, it has proven to be possible and particularly advantageous to extrapolate from optical properties found and determined for areas of the test wave device corresponding to the optical shadow area also to the areas of the test wave device corresponding to the useful wave areas.

Here, for example, specially prepared partial areas can be arranged in the optical shadow area, which simplify the calibration and / or make it more reliable.

This is possible because errors in test shaft devices, in particular CGHs, often occur globally and homogeneously or at least vary slowly over all areas of the test shaft device.

Even if only local defects occur in areas on the test shaft device that correspond to the optical shadow area, the probability increases that such local defects will also occur in an area of the test shaft device that corresponds to the useful optical area.

In any case, the method according to the invention can be used to obtain valuable information about the state of the test shaft device, which can be taken into account when checking the optical element in order to be able to use particularly reliably checked optical elements, for example in mirror projection optics and / or a projection exposure system.

In particular in the case of optical elements which are provided for use in mirror projection optics with a pupil obscuration, there is an optical shadow area advantageously arranged in and / or on the optical element.

Advantageously, it can be provided that at least approximately only the test wave reflected by the rotationally symmetrical partial area is compared interferometrically with the reference test wave, after which the test shaft device and the optical element are rotated several times relative to one another around the axis of rotation, and a new interferometric comparison is carried out each time,

In an advantageous development of the method according to the invention, it can be provided that a rotation of the optical shadow area around the axis of rotation is at least partially rotationally invariant with respect to the incident test shaft and / or at least one partial area that is rotationally symmetrical with respect to the axis of rotation is formed in the optical shadow area.

The calibration of the test shaft device takes place via rotationally symmetrical partial areas of the optical element, which are not required for the function of the optical element in its intended use. This optical shadow area can be shaped rotationally symmetrically at least in sections, regardless of a desired shape of the optical useful area, in order to enable a rotary calibration of the test shaft device.

Strictly speaking, the optical properties, in particular errors, of the test shaft device are determined only for those areas of the test shaft device which correspond to the rotationally symmetrical partial areas of the optical shadow area.

The optical properties of the test shaft device are then inferred by extrapolation.

In an advantageous development of the method according to the invention, it can be provided that at least one of the rotationally symmetrical partial areas is completely surrounded by the optical useful area and / or is centrally received by the optical useful area.

The rotationally symmetrical sub-area located in the central area is always completely located in the optical shadow area as part of the optical shadow area. Accordingly, when the rotationally symmetrical sub-area located in the central area is present, the optical shadow area extends at least in the circumference of the rotationally symmetrical sub-area into the central area of the optical element.

An arrangement of the optical shadow area and in particular the rotationally symmetrical sub-area of the optical shadow area within the optical useful area has the advantage that this allows optical properties of areas corresponding to the central area on the test shaft device to be determined. In particular, errors detected in an area of the test shaft device corresponding to the central area of the optical element, such as writing errors and / or degradations, allow a particularly reliable conclusion about the presence of such errors on the entire test shaft device, for example by extrapolation.

In an advantageous development of the method according to the invention, it can be provided that at least one of the rotationally symmetrical subregions is formed peripherally on the optical useful region and / or at least one of the rotationally symmetrical subregions is radially further spaced from the axis of rotation than the optical useful region.

In an advantageous development of the method according to the invention, it can be provided that an at least partially rotationally symmetrical optical reference element is used to determine the at least one optical property of the test shaft device.

To obtain additional information about the optical properties of the test shaft device, the rotary calibration can also be carried out in a separate step with a rotationally symmetrical reference element.

In an advantageous development of the method according to the invention, it can be provided that at least one marker area is formed on the test shaft device, which is at least partially arranged in areas of the test shaft device, preferably corresponding to the optical useful area, which are not used to check the optical element.

The information collected for calibration of the test shaft device can be supplemented by the formation of at least one marker area on the test shaft device.

Such marker areas can in particular be arranged at least partially in areas of the test shaft device that are not used to measure the optical element.

The marker areas are used to check the optical element or the test wave device to the extent that test waves emanating from the marker areas point to the hit optical element and are reflected by this and are superimposed with a reference test wave, from which an interferometric determination of the correspondence between test wave device and optical element can be created.

According to this definition, those areas can also be referred to as marker areas which correspond to the optical shadow area or rotationally symmetrical partial areas of the optical shadow area of the optical element.

However, it can be provided in particular that the marker areas correspond to areas of the optical useful area and not the optical shadow area.

However, this requires that the marker areas only play a subordinate role in checking the shaping of the optical useful area.

Areas of this type on the test shaft device can occur, for example, in locations which can occur, for example, due to scattered light effects such as resonances in test shaft devices that are encoded several times, in particular CGHs.

Since the requirements for rotary calibration of the marker area are essentially similar to those for other areas of the test shaft device, it is advantageous if the marker area corresponds to a rotationally symmetrical area on the optical element to be checked.

Since within the scope of the invention a rotationally asymmetrical optical useful area of the optical element to be checked is assumed, the marker areas can advantageously be measured with the aforementioned rotationally symmetrical optical reference element.

The knowledge gained from this can then be used for an even more precise check of the optical properties or errors of the test shaft device.

In other words, the checking of the test shaft device by means of marker areas and a rotationally symmetrical optical reference element is an implementation of a method known from the prior art for rotational calibration with a rotationally symmetrical optical element and an associated corresponding to the rotationally symmetrical optical element Test shaft device.

In the context of the invention, however, this method known from the prior art is initially carried out only on a partial area of the test shaft device, namely the marker areas. These are designed to correspond to the rotationally symmetrical reference element.

Second, the method known from the prior art is modified within the scope of the invention in such a way that it only comprises a time segment of the entire method for checking the optical element. For example, at the beginning of the rotary calibration, information about the properties of the test shaft device is recorded by means of a rotary calibration with a rotationally symmetrical reference element with areas which correspond to the optical useful area of the optical element to be ultimately checked.

Thereafter, further information about the state of the test shaft device is collected by means of the aforementioned method using rotationally symmetrical subregions of the optical shadow region of the optical element to be checked.

The information collected with regard to the marker areas can serve as further support points for extrapolating the information obtained from the at least one rotationally symmetrical sub-area of the optical shadow area about the state of the test shaft device into the useful optical area.

This can advantageously be done efficiently in that the marker areas do not correspond to the optical shadow area, but to areas located in the optical useful area of the optical element to be checked.

It is advantageous here if the marker areas correspond to rotationally symmetrical areas of the reference element.

This in turn is made possible by the fact that the marker areas are arranged in those regions of the test shaft device which, for various reasons, cannot be used for interferometric checking of the optical element to be checked.

It can also be provided that a calibration based on markers or marker areas, in particular a rotary calibration, of the test shaft device is carried out as an independent method for checking an optical element, even without using the method according to the invention.

In an advantageous development of the method according to the invention, it can be provided that a plurality of marker areas are formed on the test shaft device as congruent island areas arranged equidistantly along an axis of rotation.

Such an arrangement and geometry of the marker areas has proven to be particularly advantageous within the scope of the invention. A point-symmetrical design and arrangement of the marker areas, in particular in resonance areas, has proven to be particularly advantageous.

The invention also relates to an optical element having the features mentioned in claim 12.

The optical element according to the invention has at least one optical useful area that interacts with a useful radiation and at least one optical shadow area that does not interact with the useful radiation on an optical surface, the optical useful area being rotationally asymmetrical. According to the invention, it is provided that the optical shadow area has at least one partial area which is rotationally symmetrical with respect to at least one axis of rotation and which is set up for the, preferably reflective, interaction with a test shaft.

The optical element according to the invention has the advantage that the implementation of a rotational calibration based on rotational symmetry of a test shaft device from which test shafts emanate that fall perpendicularly onto the optical element is made possible, although the usable optical range is rotationally asymmetrical and thus a rotational calibration of the test shaft device by means of the optical usable area is prevented.

In the context of the invention, the useful optical area of the optical element is to be understood as that area which, when the optical element is used as intended, guides and shapes the useful radiation to be guided and shaped by the optical element.

The optical shadow area, on the other hand, is not or only insignificantly involved in the intended use of the optical element in guiding and shaping the useful radiation.

However, the optical shadow area is at least partially set up, in particular in the rotationally symmetrical sub-area, to interact with a test radiation or test wave, which can also be used in a similar form and / or the same form for checking the optical element.

The rotationally symmetrical sub-area can accordingly preferably have optical properties that are similar, but not completely identical, to the optical usable area. In particular, it can be provided that the optical shadow area differs from the optical useful area in a spatial-physical manner only through the presence of rotationally symmetrical partial areas, in addition to the interaction with the useful radiation when the optical element is used as intended.

The optical element is preferably a reflective optical element, in particular a mirror.

In the context of the invention it can also be provided that the optical element is, for example, a lens. Such a lens accordingly has a rotationally asymmetrical optical usable area and a rotationally symmetrical partial area in the optical shadow area. The optical useful area and the optical shadow area can accordingly also be understood to belong to the surface within the scope of the invention if they are arranged in layers of the optical element that are remote from the surface. For example, an inclusion and / or a cut of a lens can be understood as belonging to the surface.

In an advantageous development of the optical element according to the invention, it can be provided that at least one of the rotationally symmetrical subregions is arranged in a central region of the optical element and / or at least one of the rotationally symmetrical subregions is completely enclosed by the useful optical region.

The rotationally symmetrical sub-area located in the central area is always completely located in the optical shadow area as part of the optical shadow area. Accordingly, when the rotationally symmetrical sub-area located in the central area is present, the optical shadow area extends at least in the circumference of the rotationally symmetrical sub-area into the central area of the optical element.

A rotationally symmetrical sub-area of the optical shadow area that is completely enclosed by the usable optical area can often advantageously be implemented simply and inexpensively, since a pupil obscuration is often formed in close proximity to the optical axis.

In an advantageous development of the optical element according to the invention, it can be provided that the optical shadow area has at least one alignment mark.

One or more alignment markings can simplify a relative positioning of the optical element and the test shaft device to one another and in particular also to the axis of rotation.

It can be of particular advantage here if the alignment mark is arranged on the axis of rotation.

The alignment marking can furthermore be an optical marking or else a physical marking, for example a notch and / or a hole.

It can also be advantageous if the optical shadow area has a calibration structure.

In an advantageous development of the optical element according to the invention, this is provided or set up or configured for use in a mirror projection optics according to the invention according to one of claims 1 to 4 and / or is checked according to a method according to the invention according to one of claims 5 to 11.

The invention also relates to a lithography system having the features mentioned in claim 17.

The lithography system according to the invention, in particular a projection exposure system for microlithography, comprises an illumination system which has a radiation source for generating the radiation, in particular an illumination radiation or a projection beam, illumination optics and projection optics, in particular mirror projection optics. Here, the illumination optics and / or the projection optics have at least one optical element. According to the invention it is provided that the projection optics is designed according to one of claims 1 to 4 and / or at least one of the optical elements of the projection optics is checked according to one of claims 5 to 11 and / or at least one of the optical elements is an optical element according to one of the Claims 12-16 is.

The lithography system according to the invention has the advantage that, due to a particularly reliable calibration of the test shaft device, a check of the optical elements used in the lithography system by means of the particularly precisely calibrated test shaft device is in turn particularly reliable and precise.

In this way, the lithography system according to the invention enables a particularly reliable and precise function and thus a particularly reliable and precise microlithographic production, in particular in the semiconductor industry.

It can further be provided that at least one of the optical elements of the lighting system has a rotationally symmetrical sub-area in the shadow area. Instead of the pupil obscuration, such a shadow area can be caused, for example, by an expansion of the optical element which exceeds the expansion of the illuminating radiation.

However, for optical elements of the lighting system, an arrangement of the shadow area in a central area can be less advantageous. For this reason, in the case of an optical element, in particular a mirror, of the lighting system, it is particularly advantageous to form the shadow area and in particular the rotationally symmetrical sub-area on the peripheral area of the optical element.

Features that have been described in connection with one of the objects of the invention, namely given by the mirror projection optics according to the invention, the method according to the invention, the optical element according to the invention and the lithography system according to the invention can also be advantageously implemented for the other objects of the invention. Likewise, advantages that were mentioned in connection with one of the subjects of the invention can also be understood in relation to the other subjects of the invention.

In addition, it should be pointed out that terms such as “comprehensive”, “having” or “with” do not exclude any other features or steps. Furthermore, terms such as “a” or “that” which refer to a single number of steps or features do not exclude a plurality of features or steps - and vice versa.

In a puristic embodiment of the invention, however, it can also be provided that the features introduced in the invention with the terms “comprising”, “having” or “with” are finally enumerated. Accordingly, one or more lists of features can be regarded as complete within the scope of the invention, for example, considered for each claim. The invention can consist exclusively of the features mentioned in claim 1, for example.

It should be mentioned that designations such as “first” or “second” etc. are primarily used for reasons The distinguishability of respective device or process features are used and are not necessarily intended to indicate that features are mutually dependent or related to one another.

Exemplary embodiments of the invention are described in more detail below with reference to the drawing.

The figures each show preferred exemplary embodiments in which individual features of the present invention are shown in combination with one another. Features of an exemplary embodiment can also be implemented separately from the other features of the same exemplary embodiment and can accordingly be easily combined by a person skilled in the art to form further meaningful combinations and sub-combinations with features of other exemplary 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 erfindungsgemäßen Spiegelprojektionsoptik;
• 4 eine schematische Darstellung eines erfindungsgemäßen optischen Elements in einer ersten Ausführungsform;
• 5 eine schematische Darstellung eines erfindungsgemäßen optischen Elements in einer zweiten Ausführungsform;
• 6 eine schematische Darstellung einer ersten beispielhaften Vorrichtung zur Durchführung eines erfindungsgemäßen Verfahrens;
• 7 eine schematische Darstellung einer zweiten beispielhaften Vorrichtung zur Durchführung eines erfindungsgemäßen Verfahrens; und
• 8 eine schematische Darstellung eines optischen Elements mit zu Markerbereichen gehörenden Korrespondenzbereichen.

Show it:

• 1 an EUV projection exposure system in meridional section;
• 2 a DUV projection exposure system;
• 3 a schematic representation of a mirror projection optics according to the invention;
• 4th a schematic representation of an optical element according to the invention in a first embodiment;
• 5 a schematic representation of an optical element according to the invention in a second embodiment;
• 6th a schematic representation of a first exemplary device for performing a method according to the invention;
• 7th a schematic representation of a second exemplary device for performing a method according to the invention; and
• 8th a schematic representation of an optical element with corresponding areas belonging to marker areas.

In the following, first with reference to 1 exemplarily the essential components of an EUV projection exposure system 100 for microlithography as an example of a lithography system. The description of the basic structure of the EUV projection exposure system 100 as well as their components are not to be understood as restrictive here.

A lighting system 101 the EUV projection exposure system 100 has next to a radiation source 102 an illumination optics 103 for illuminating an object field 104 in one object level 105 on. Here, a is exposed in the object field 104 arranged reticle 106 . The reticle 106 is from a reticle holder 107 held. The reticle holder 107 is via a reticle displacement drive 108 especially displaceable in a scanning direction.

In 1 a Cartesian xyz coordinate system is drawn in for explanation. The x-direction runs perpendicularly into the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in 1 along the y-direction. The z-direction runs perpendicular to the object plane 105 .

The EUV projection exposure system 100 includes projection optics 109 . The projection optics 109 serves to map the object field 104 in an image field 110 in one image plane 111 . The image plane 111 runs parallel to the object plane 105 .

Alternatively, there is also an angle between the object plane other than 0 ° 105 and the image plane 111 possible.

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

At the radiation source 102 it is an EUV radiation source. The radiation source 102 emits EUV radiation in particular 115 , which is also referred to below as useful radiation or illuminating radiation. The useful radiation 115 in particular has a wavelength in the range between 5 nm and 30 nm. In the case of the radiation source 102 it can be a plasma source, for example an LPP source (“Laser Produced Plasma”) or a DPP source (“Gas Discharged Produced Plasma”). It can also be a synchrotron-based radiation source. At the radiation source 102 it can be a free-electron laser ("Free-Electron-Laser", FEL).

The illuminating radiation 115 by the radiation source 102 emanates from a collector 116 bundled. At the collector 116 it can be a collector with one or more ellipsoidal and / or hyperboloid reflection surfaces. The at least one reflective surface of the collector 116 can in grazing incidence ("Grazing Incidence", GI), ie with angles of incidence greater than 45 °, or in normal incidence ("Normal Incidence", NI), ie with angles of incidence smaller than 45 °, with the illuminating radiation 115 be applied. The collector 116 can on the one hand to optimize its reflectivity for the useful radiation 115 and on the other hand, structured and / or coated to suppress stray light.

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

The lighting optics 103 includes a deflection mirror 118 and a first facet mirror arranged downstream of this in the beam path 119 . With the deflection mirror 118 it can be a plane deflecting mirror or, alternatively, a mirror with an effect that influences the bundle beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror can 118 be designed as a spectral filter that has a useful light wavelength of the illuminating radiation 115 from stray light of a different wavelength. Unless the first facet mirror 119 in one plane of the lighting optics 103 is arranged to the object plane 105 is optically conjugated as a field plane, this is also referred to as a field facet mirror. The first facet mirror 119 comprises a multitude of individual first facets 120 , which are also referred to as field facets in the following. From these facets 120 are in the 1 only a few are shown as examples.

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

For example from the DE 10 2008 009 600 A1 known can be the first facets 120 itself can also be composed of a large number of individual mirrors, in particular a large number of micromirrors. The first facet mirror 119 can in particular be designed as a microelectromechanical system (MEMS system). For details, refer to the DE 10 2008 009 600 A1 referenced.

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

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

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

With the second facets 122 it can also be macroscopic facets, which can for example be round, rectangular or also hexagonally edged, or alternatively facets composed of micromirrors. In this regard, reference is also made to the DE 10 2008 009 600 A1 referenced.

The second facets 122 can have planar or alternatively convex or concavely curved reflection surfaces.

The lighting optics 103 thus forms a double faceted system. This basic principle is also known as the fly's eye integrator.

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

With the help of the second facet mirror 121 become the individual first facets 120 in the object field 104 pictured. The second facet mirror 121 is the last mirror that forms the beam, or actually the last mirror for the illuminating radiation 115 in the beam path in front of the object field 104 .

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

The lighting optics 103 has when executing that in the 1 is shown after the collector 116 exactly three mirrors, namely the deflecting mirror 118 , the field facet mirror 119 and the pupil facet mirror 121 .

In another version of the lighting optics 103 can the deflection mirror 118 also omitted, so that the lighting optics 103 after the collector 116 can then have exactly two mirrors, namely the first facet mirror 119 and the second facet mirror 121 .

The illustration of the first facets 120 by means of the second facet 122 or with the second facets 122 and transmission optics in the object plane 105 is regularly only an approximate figure.

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

The one in the 1 The example shown includes the projection optics 109 six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or a different number of mirrors Wed are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illuminating radiation 115 . With the projection optics 109 it is a doubly obscure look. The projection optics 109 has an image-side numerical aperture which is greater than 0.5 and which can also be greater than 0.6 and which can be 0.7 or 0.75, for example.

Reflection surfaces of the mirrors Wed can be designed as free-form surfaces without an axis of rotational symmetry. Alternatively, the reflecting surfaces of the mirror Wed be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirror Wed can, as well as the mirrors of the lighting optics 103 , highly reflective coatings for lighting radiation 115 exhibit. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 109 has 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 imaging scales βx, βy in the x and y directions. The two imaging scales βx, βy of the projection optics 109 are preferably at (βx, βy) = (+/- 0.25, +/- 0.125). A positive image scale β means an image without image reversal. A negative sign for the imaging scale β means imaging with image reversal.

The projection optics 109 thus leads to a reduction in the ratio in the x direction, that is to say in the direction perpendicular to the scanning direction 4th :1.

The projection optics 109 leads to a reduction of 8: 1 in the y-direction, i.e. in the scan 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 field of view 110 can be the same or can, depending on the design of the projection optics 109 , be different. Examples of projection optics with different numbers of such intermediate images in the x and y directions are known from US 2018/0074303 A1 .

One of each of the pupil facets 122 is exactly one of the field facets 120 to form one lighting channel for illuminating the object field 104 assigned. In particular, this can result in lighting based on Koehler's principle. The far field is created with the help of the field facets 120 in a variety of object fields 104 disassembled. The field facets 120 generate a plurality of images of the intermediate focus on the respective associated pupil facets 122 .

The field facets 120 are each of an assigned pupil facet 122 superimposed to illuminate the object field 104 on the reticle 106 pictured. 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 uniform can can be achieved by superimposing different lighting channels.

An arrangement of the pupil facets can geometrically illuminate the entrance pupil of the projection optics 109 To be defined. 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 can be achieved 109 can be set. This intensity distribution is also referred to as the lighting setting.

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

Further aspects and details of the illumination of the object field are described below 104 and in particular the entrance pupil of the projection optics 109 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 can be checked regularly with the pupil facet mirror 121 not illuminate exactly. In an illustration of the projection optics 109 which is the center of the pupil facet mirror 121 telecentrically onto the wafer 112 images, the aperture rays often do not intersect in a single point. However, an area can be found in which the distance between the aperture rays, which is determined in pairs, is minimal. This surface represents the entrance pupil or a surface conjugate to it in spatial space. In particular, this surface shows a finite curvature.

It may be that the projection optics 109 has different positions of the entrance pupil for the tangential and for the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be between the second facet mirror 121 and the reticle 106 to be provided. 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 case of the 1 illustrated arrangement of the components of the lighting optics 103 is the mirror of the pupil facet 121 in one to the entrance pupil of the projection optics 109 conjugate surface arranged. The first field facet mirror 119 is tilted to the object plane 105 arranged. The first facet mirror 119 is arranged tilted to an arrangement plane, that of the deflecting mirror 118 is defined.

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

In 2 is an exemplary DUV projection exposure system 200 shown. The DUV projection exposure system 200 has a lighting system 201 , a reticle day 202 said device for receiving and exact positioning of a reticle 203 , through which the later structures on a wafer 204 be determined, a wafer holder 205 for holding, moving and exact positioning of the wafer 204 and an imaging device, namely projection optics 206 , with several optical elements, especially lenses 207 that over sockets 208 in a lens housing 209 the projection optics 206 are kept on.

As an alternative or in addition to the lenses shown 207 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 that provides for the reticle 203 introduced structures on the wafer 204 can be mapped.

The lighting system 201 provides one for imaging the reticle 203 on the wafer 204 required projection beam 210 in the form of electromagnetic radiation. A laser, a plasma source or the like can be used as the source for this radiation. The radiation is in the lighting system 201 Shaped via optical elements so that the projection beam 210 when hitting the reticle 203 has the desired properties in terms of diameter, polarization, shape of the wavefront and the like.

By means of the projection beam 210 becomes an image of the reticle 203 generated and by the projection optics 206 correspondingly reduced on the wafer 204 transfer. The reticle 203 and the wafer 204 are moved synchronously so that areas of the reticle are practically continuous during a so-called scanning process 203 on corresponding areas of the wafer 204 can be mapped.

Optionally, there can be an air gap between the last lens 207 and the wafer 204 be replaced by a liquid medium which has a refractive index greater than 1.0. The liquid medium can be ultrapure water, for example. Such a Structure is also known as immersion lithography and has an increased photolithographic resolution.

The use of the invention is not restricted to use in projection exposure systems 100 , 200 , in particular not limited to the structure described. The invention is suitable for any lithography systems, but in particular for projection exposure systems, with the structure described. Furthermore, the invention and the exemplary embodiments below are not to be understood as being restricted to a specific design. The following figures show the invention merely by way of example and in a highly schematic manner and serve to disclose projection optics according to the invention, a method according to the invention, an optical element according to the invention and a lithography system according to the invention.

3 shows a schematic representation of mirror projection optics 1 with a pupil obscuration 2 for a useful radiation 3 , especially EUV radiation.

With the useful radiation 3 In particular, it can be from the radiation source 102 generated EUV illumination radiation 115 Act. The mirror projection optics 1 can in particular be part of the lighting optics 103 being. The mirror projection optics 1 can in particular be part of the lighting optics 103 being. A use of the invention in a DUV system, for example as we see in 2 shown, requires a different structure of the projection optics. In this case it can be useful radiation 3 around the projection beam 210 Act.

The mirror projection optics 1 points in the in 3 illustrated embodiment an optical element 4th on which an optically reflective surface 5 with an optical usable area 6th and with an optical shadow area 7th having.

The optical usable area 6th is parallel to the optical element for better visibility 4th shown as a solid line. The optical shadow area 7th is parallel to the optical element for better visibility 4th shown as a dashed line.

The usable optical area interacts here 6th with the usable radiation 3 and is rotationally asymmetrical. The optical shadow area 7th does not interact with the usable radiation 3 . The optical shadow area 7th here has at least one rotationally symmetrical with respect to an axis of rotation 8th trained sub-area 13th on.

In the case of the optical element 4th the mirror projection optics 1 in the in 3 The illustrated embodiment can in particular be one of the optical elements Wed the in 1 illustrated projection exposure system 100 Act.

It can also be the case with the optical element 4th also an optical element 207 the in 2 illustrated projection exposure system 200 Act. A different construction of the projection optics can be used for this 1 to be required.

The pupil obscuration 2 is used in the in 3 illustrated embodiment through an opening in a last mirror 9 realized. The one through the pupil obscuration 2 penetrated useful radiation 3 is from the optical element 4th which is a penultimate mirror 10 corresponds to one image plane 11th directed.

In the in 3 illustrated embodiment of the mirror projection optics 1 the optical shadow area interacts 7th with an obscured radiation which has no influence on the creation of an image of the reticle 106 , 203 in the image plane 11th has. In 3 are as dashed lines two rays of an obscured marginal radiation 3a shown. The obscured marginal radiation 3a is the outermost part of the obscured radiation which is a border of the shadow area 7th to the optical usable area 6th and a limit of the obscured radiation to the usable radiation 3 trains. The through the optical element 4th reflected obscured marginal radiation 3a leaves the mirror projection optics 1 through the pupil obscuration 2 and thus has no influence on the formation of the image of the reticle 106 , 203 in the image plane 11th .

The last mirror 9 points in the in 3 illustrated embodiment instead of a shadow area 7th the pupil obscuration 2 in the form of an opening or a hole. This allows the last mirror in the form shown 9 no rotationally symmetrical sub-area 13th exhibit. However, it can be provided within the scope of the invention that the last mirror 9 before formation of pupillary obscuration 2 in their place a shadow area 7th with a rotationally symmetrical sub-area 13th has, which only after a review of the last mirror 9 is removed, thereby obscurating the pupil 2 is trained. Such a trained final mirror 9 , as well as other such optical elements in projection optics 1 , 109 , 206 , e.g. the mirrors Wed according to 1 , are within the scope of the invention also as optical elements according to the invention 4th to understand, even if they are at the time of intended use in the mirror projection optics 1 are spatially and physically changed, for example by the Formation of a hole instead of the shadow area 7th .

The in 3 The illustrated embodiment of the mirror projection optics is in the optical element 4th also the rotationally symmetrical sub-area 13th in a central area of the optical element 4th arranged and at least the rotationally symmetrical sub-areas 13th is of the optical useful range 6th completely enclosed.

In 3 A possible embodiment of the mirror projection optics is not shown 1 in the case of at least one of the rotationally symmetrical subregions 13th in a peripheral region of the optical element 4th is arranged and / or at least one of the rotationally symmetrical subregions 13th radially further from the axis of rotation 8th is spaced apart than the useful optical area 6th .

4th shows a schematic representation of an optical element according to the invention 4th .

This in 4th illustrated optical element 4th shows one with the useful radiation 3 interacting optical usable area 6th and one, if the optical element is used as intended 4th , not with the useful radiation 3 interacting optical shadow area 7th on the optical surface 5 on. The optical usable area 6th is here rotationally asymmetrical. Furthermore, the optical shadow area 7th at least one rotationally symmetrical with respect to at least one axis of rotation 8th trained sub-area 13th on which for, preferably reflective, interaction with a test wave 17th (please refer 6th ) is set up.

The optical usable area 6th is in the in 4th illustrated embodiment is circular, for example as a concave mirror.

In the in 4th The illustrated embodiment has the optical shadow area 7th a rotationally symmetrical sub-area 13th and is therefore rotationally symmetrical in sections.

In particular, in the in 4th illustrated embodiment of the optical shadow area 7th a circular, rotationally symmetrical sub-area 13th through whose center the axis of rotation 8th runs

This in 4th illustrated optical element 4th can, for example, be found in the in 3 mirror projection optics shown 1 Find use.

The in 4th illustrated embodiment of the optical element 4th is also the rotationally symmetrical sub-area 13th in a central area of the optical element 4th arranged and at least the rotationally symmetrical sub-areas 13th is of the optical useful range 6th completely enclosed.

Such an optical element 4th can especially in the in 3 mirror projection optics shown 1 with the properties described above are used.

In the in 4th illustrated embodiment of the optical element 4th indicates the optical shadow area 7th also an alignment mark 14th on, which is preferably cross-shaped and on the axis of rotation 8th is arranged.

Such an alignment mark 14th in the optical shadow area 7th is particularly for the optical element 4th for the in 3 mirror projection optics shown 1 intended.

5 shows a further schematic representation of an optical element 4th . In the in 5 The exemplary embodiment shown are further rotationally symmetrical subregions 13th in a peripheral region of the optical element 4th arranged and at least the additional rotationally symmetrical sub-areas 13th are radially further from the axis of rotation 8th spaced apart than the usable optical area 6th .

Such an optical element 4th is particularly suitable in connection with the in 3 explained mirror projection optics 1 .

In the in 5 illustrated embodiment of the optical element 4th are next to the central, rotationally symmetrical sub-area 13th even more rotationally symmetrical sub-areas 13th at the edge of the usable optical area 6th in the form of circular ring sections, which are point-symmetrical to the axis of rotation 8th are arranged, formed.

One possible embodiment of the optical element is not shown 4th which is only in the peripheral area of the optical element 4th having arranged rotationally symmetrical subregions.

6th shows a schematic representation of an exemplary device 15th for performing a method for checking at least one optical property of the optical element 4th .

The optical element 4th indicates here with the useful radiation 3 , in particular an EUV radiation, interacting optical usable area 6th as well as not with the useful radiation 3 interacting optical shadow area 7th on the optically reflective surface 5 on. From a test shaft device 16 becomes the incident test wave 17th formed and on the optical shadow area 7th irradiated at least partially perpendicularly and from the optical shadow area 7th reflected. After that, that of the optical shadow area 7th reflected test wave 17 ' with a reference test shaft 18th compared interferometrically. After this, the test shaft devices 16 and the optical element 4th relative to each other around the axis of rotation 8th rotates and another interferometric comparison is carried out. This is followed by at least one optical property of the test shaft device 16 , in particular the presence of errors in the test shaft device 16 , definitely. When determining the optical property of the optical element 4th the determined optical property of the test shaft device 16 taken into account.

In the in 6th illustrated embodiment of the device 15th the method can be carried out in such a way that a rotation of the optical shadow area 7th around the axis of rotation 8th at least partially rotationally invariant with respect to the incident test shaft 16 works. In particular, this is done in the optical shadow area 7th at least one opposite the axis of rotation 8th rotationally symmetrical sub-area 13th educated.

In particular, in the in 6th illustrated embodiment of the optical useful area 6th rotationally asymmetrical with respect to the axis of rotation 8th .

In the in 6th illustrated embodiment of the device 15th becomes the rotationally symmetrical sub-area 13th of the optical useful range 6th completely surrounded and by the optical usable area 6th centrally recorded.

An exemplary embodiment of the device is not shown 15th , in which at least one of the rotationally symmetrical sub-areas 13th peripheral to the optical useful area 6th is formed and / or at least one of the rotationally symmetrical subregions 13th radially further from the axis of rotation 8th is spaced apart as the useful optical area 6th .

7th shows a schematic representation of a further exemplary device 15th to carry out the procedure described above.

This is used to determine the at least one optical property of the test shaft device 16 an at least partially rotationally symmetrical optical reference element 19th used.

Furthermore, in the test shaft device 16 two marker areas 20th formed, which in with the optical useful area 6th corresponding areas of the test shaft device 16 are arranged. These areas are not used to check the optical element 4th used.

In particular, the test shaft device 16 several marker areas 20th designed as congruent island areas arranged equidistantly along a direction of rotation, in particular in the circumferential direction of rotation.

8th shows a schematic representation of an optical element 4th with to marker areas 20th corresponding correspondence areas 21 .

In contrast to the in 7th on the test shaft device 16 shown marker areas 20th is in 8th the optical element to be checked 4th shown.

On the optical element 4th is the optical shadow area in a central location 7th with the rotationally symmetrical sub-area 13th as well as alignment mark 14th educated. In the rotationally asymmetrical usable optical area 6th are those areas of correspondence 21 which are the marker areas 20th on the associated test shaft device 16 correspond. In these correspondence areas 21 will not check the optical element 4th carried out, since resonances can occur at these points, for example. For a reference element 19th , which has a similar outer contour to the one in 8th illustrated example of the optical element 4th has go from the correspondence areas arranged in the same position 21 the reflected test waves 17 ' and fall back on the marker areas 20th the test shaft device.

How out 8th obviously favors the location of the correspondence areas 21 between a central area and a peripheral area of the optical element 4th an extrapolation of the optical properties of the test shaft device 16 of the rotationally symmetrical sub-areas 13th in the optical shadow area 7th and the marker areas 20th on the optical usable area that is not directly accessible for inspection 6th corresponding area of the test shaft device 16 .

The ones in the 4th , 5 and 8th illustrated embodiments of the optical element 4th are particularly suitable for use in mirror projection optics 1 , especially in mirror projection optics 109 an EUV projection exposure system 100 .

The invention is particularly suitable for a lithography system for microlithography, in particular for the EUV projection exposure system 100 , which in the 1 is shown. The EUV projection exposure system 100 includes the lighting system 101 that is the radiation source 102 to generate the useful radiation 3 , especially the illumination radiation 115 , the Lighting optics 103 and the projection optics 1 , 109 , especially the mirror projection optics 1 , 109 , having. Here are the lighting optics 103 and / or the projection optics 1 , 109 at least one optical element 4th , Wed on. It is also provided that the projection optics 1 , 109 according to one of claims 1 to 4 with those in connection with the 3 illustrated features is formed and at least one of the optical elements 4th , Wed , 207 the projection optics 1 , 109 with the 6th exemplified method is checked according to one of claims 5 to 11 and at least one of the optical elements 4th , Wed one of the based on the 4th , 5 and 8th explained optical element 4th according to any one of claims 12 to 16.

The invention is also suitable for a lithography system for microlithography, in particular for the DUV projection exposure system 200 , which in the 2 is shown with the lighting system 201 to generate the useful radiation 3 , especially the projection beam 210 , and the projection optics 206 . The projection optics 1 , 109 , 206 at least one optical element 4th , 207 on. It is also provided that the projection optics 1 , 206 according to one of claims 1 to 4 with those in connection with the 3 illustrated features is formed and at least one of the optical elements 4th , 207 the projection optics 1 , 206 with the 6th exemplified method is checked according to one of claims 5 to 11 and at least one of the optical elements 4th , 207 one of the based on the 4th , 5 and 8th explained optical element 4th according to any one of claims 12 to 16.

List of reference symbols

1

Mirror projection optics

2

Pupil obscuration

3

Usable radiation

3a

Obscured marginal radiation

4th

Optical element

5

Reflective surface

6th

Usable optical area

7th

Optical shadow area

8th

Axis of rotation

9

Last mirror

10

Penultimate mirror

11th

Image plane

13th

Rotationally symmetrical sub-area

14th

Alignment mark

15th

Device for carrying out the method

16

Test shaft device

17th

Incident test wave

17 '

Reflected test wave

18th

Reference test shaft

19th

Reference element

20th

Marker areas

21

Correspondence area

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

Field of view

111

Image plane

112

Wafer

113

Wafer holder

114

Wafer displacement drive

115

EUV / useful / lighting radiation

116

collector

117

Intermediate focus plane

118

Deflection 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 days

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 the 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 assumes no liability for any errors or omissions.

Patent literature cited

• DE 102019203423 A1 [0008, 0010]
• DE 102008009600 A1 [0137, 0141]
• US 2006/0132747 A1 [0139]
• EP 1614008 B1 [0139]
• US 6573978 [0139]
• US 2018/0074303 A1 [0158]

Claims (17)

Mirror projection optics (1), with a pupil obscuration (2), for a useful radiation (3), in particular an EUV radiation, having at least one optical element (4) which has an optically reflective surface (5) with an optical useful area (6) and an optical shadow area (7), wherein the optical useful area (6) interacts with the useful radiation (3) and is rotationally asymmetrical and wherein the optical shadow area (7) does not interact with the useful radiation (3), characterized in that the optical shadow area (7) has at least one partial area (13) which is rotationally symmetrical with respect to at least one axis of rotation (8). Mirror projection optics (1) according to Claim 1 , characterized in that at least one of the rotationally symmetrical subregions (13) is arranged in a central region of the optical element (4) and / or at least one of the rotationally symmetrical subregions (13) is completely enclosed by the useful optical region (6). Mirror projection optics (1) according to Claim 1 or 2 , characterized in that at least one of the rotationally symmetrical subregions (13) is arranged in a peripheral region of the optical element (4) and / or at least one of the rotationally symmetrical subregions (13) is spaced further radially from the axis of rotation (8) than the useful optical region ( 6). Mirror projection optics (1) according to one of the Claims 1 until 3 , characterized in that the optical shadow area (7) has at least one alignment mark (14). Method for checking at least one optical property of an optical element (4) which has at least one optical useful area (6) that interacts with a useful radiation (3), in particular EUV radiation, and at least one optical shadow area ( 7) on an optically reflective surface (5), characterized in that an incident test wave (17) is formed by a test wave device (16) and irradiated at least partially perpendicularly onto the optical shadow area (7) and from the optical shadow area (7) is reflected, after which the test wave (17 ') reflected by the optical shadow area (7) is compared interferometrically with a reference test wave (18), after which the test wave device (16) and the optical element (4) relative to one another about an axis of rotation (8) are rotated, and a renewed interferometric comparison is carried out, after which little At least one optical property of the test shaft device (16) is determined, after which the optical property of the test shaft device (16) is taken into account when determining the optical property of the optical element (4). Procedure according to Claim 5 , characterized in that a rotation of the optical shadow area (7) about the axis of rotation (8) acts at least partially in a rotationally invariant manner with respect to the incident test shaft (17) and / or in the optical shadow area (7) at least one sub-area that is rotationally symmetrical with respect to the axis of rotation (8) (13) is formed. Procedure according to Claim 6 , characterized in that at least one of the rotationally symmetrical partial areas (13) is completely surrounded by the optical useful area (6) and / or is centrally received by the optical useful area (6). Procedure according to Claim 5 or 6th , characterized in that at least one of the rotationally symmetrical partial areas (13) is formed peripherally on the optical useful area (6) and / or at least one of the rotationally symmetrical partial areas (13) is spaced radially further from the axis of rotation (8) than the optical useful area (6) ). Method according to one of the Claims 5 until 8th , characterized in that an at least partially rotationally symmetrical optical reference element (19) is used to determine the at least one optical property of the test shaft device (16). Procedure according to Claim 9 , characterized in that at least one marker area (20) is formed on the test shaft device (16), which is at least partially arranged in areas of the test shaft device (16) which preferably correspond to the optical useful area (6) and which are not used for checking the optical Elements (4) are used. Procedure according to Claim 10 , characterized in that a plurality of marker areas (20) are formed on the test shaft device (16) as congruent island areas which are arranged equidistantly along a direction of rotation. Optical element (4) which has at least one optical useful area (6) that interacts with useful radiation (3) and at least one optical shadow area (7) that does not interact with useful radiation (3) on an optical surface (5), the optical useful area (6) is rotationally asymmetrical, characterized in that the optical shadow area (7) is at least one rotationally symmetrical with respect to at least one axis of rotation (8) formed sub-area (13) which is set up for, preferably reflective, interaction with a test shaft (17). Optical element (4) according to Claim 12 , characterized in that at least one of the rotationally symmetrical subregions (13) is arranged in a central region of the optical element (4) and / or at least one of the rotationally symmetrical subregions (13) is completely enclosed by the useful optical region (6). Optical element (4) according to Claim 12 or 13th , characterized in that at least one of the rotationally symmetrical subregions (13) is arranged in a peripheral region of the optical element (4) and / or at least one of the rotationally symmetrical subregions (13) is spaced further radially from the axis of rotation (8) than the useful optical region ( 6). Optical element (4) according to one of the Claims 12 until 14th , characterized in that the optical shadow area (7) has at least one alignment mark (14). Optical element according to one of the Claims 12 until 15th , for a mirror projection optics (1) according to one of the Claims 1 until 4th . Lithography system, in particular a projection exposure system (100, 200) for microlithography, with an illumination system (101, 201) which has a radiation source (102) for generating a useful radiation (3), in particular an illumination radiation (115) or a projection beam (210) Illumination optics (103) and projection optics (1, 109, 206), in particular mirror projection optics (1, 109), wherein the illumination optics (103) and / or the projection optics (1, 109, 206) have at least one optical element (4 , Mi, 207), characterized in that the projection optics (1, 109, 206) according to one of the Claims 1 until 4th is formed and / or at least one of the optical elements (4, Mi, 207) of the projection optics (1, 109, 206) according to one of the Claims 5 until 11th is checked and / or at least one of the optical elements (4, Mi, 207) is an optical element (4) according to one of the Claims 12 until 16 is.

Images