DE102020213837A1 - Facet mirror device - Google Patents

Abstract

A facet mirror device (20, 22) is used to reflect light (26) of a suppression wavelength to be suppressed. A multiplicity of individual mirrors (25) are arranged in or adjacent to a main arrangement plane (27). An arrangement of the individual mirrors (25) has a mirror offset (Δz) of the individual mirrors (25) to the arrangement main plane (27), which is periodic along a period direction (y). A useful light incidence plane (yz) of the facet mirror device (20, 22) is spanned by the period direction (y) and a normal (z) on the main arrangement plane (27). The mirror offset (Δz) of the individual mirrors (25) to the main plane of the arrangement (27) is such that the light (26) to be suppressed, which is reflected by the arrangement of the individual mirrors (25), is suppressed in a zero diffraction order. The result is an effective suppression of the light to be suppressed by the facet mirror device.

Description

The invention relates to a facet mirror device. Such a facet mirror device can be used in a projection exposure system for projection lithography.

From the WO 2009/100 856 A1 a facet mirror device for use in a projection exposure system is known. the WO 2013/174 644 A1 and the DE 10 2017 217 867 A1 each disclose a facet mirror for a projection exposure system.

It is an object of the present invention to design a facet mirror device in such a way that effective suppression of light of a suppression wavelength to be suppressed is ensured.

This object is achieved according to the invention by a facet mirror device with the features specified in claim 1.

According to the invention, it was recognized that a grating can be generated by offsetting individual mirrors of the facet mirror device perpendicular to a main plane of arrangement of the individual mirrors, which causes destructive interference for the reflected light of the suppression wavelength to be suppressed. Surprisingly, this grating effect also results when the individual mirrors are tilted about axes that are parallel to the main plane of the arrangement in order to ensure appropriate guidance of sub-bundles of an overall bundle of useful illuminating light. The suppression of the light to be suppressed achieved in this way can be improved by more than one order of magnitude and even by two orders of magnitude compared to the reflection on a facet mirror device without individual mirrors deliberately offset from one another perpendicular to the main plane of the arrangement. The light to be suppressed can be light of an IR wavelength. The suppression wavelength, to which the offset of the adjacent rows of mirrors is matched, can be a wavelength focal point of a wavelength bandwidth to be suppressed.

The facet mirror device is designed to reflect useful light. The useful light can be EUV light in a wavelength range between 5 nm and 30 nm.

A mirror offset can be such that the light to be suppressed, which is reflected at adjacent individual mirrors that are offset from one another, experiences an optical path length difference of half a suppression wavelength.

The individual mirror arrangement can be independent of a periodicity of the mirror offset. The individual mirror arrangement can be designed in the manner of a row / column array, but can also be designed, for example, with a different symmetry, for example as a hexagonal arrangement, or also without symmetry.

The light to be examined can in any case be partially suppressed in that the light to be suppressed is diffracted out of a target direction for the useful light to be reflected. A period length of the mirror offset of the individual mirror arrangement can be selected so that, according to the grating equation, diffracted rays of the light of the suppression wavelength to be suppressed are diffracted outside a useful beam path, for example, so that these diffracted rays are then fed to a beam dump in particular can or can be separated from the useful beam path in some other way, for example by means of diaphragms. This period of the mirror offset can accordingly be selected below a limit value of a period length.

The light to be suppressed can have precisely one suppression wavelength, can have a bandwidth of suppression wavelengths to be suppressed or can also have a plurality of specific suppression wavelengths.

A mirror offset of the individual mirrors to the main plane of the arrangement according to claim 2 is designed as an offset of at least some individual mirrors of adjacent rows of mirrors to one another.

Due to the offset of adjacent rows of mirrors with respect to one another, the facet mirror device can be designed as a line grating, each line being formed by a row of mirrors. As an alternative to an offset of individual mirrors of adjacent mirror rows to one another, it is possible to carry out the mirror offset periodically along the period direction so that the period direction does not run parallel or perpendicular to a column or row direction of an arrangement of the individual mirrors. The mirror offset, which is periodic along the period direction, is carried out in such a way that the desired diffraction suppression effect is obtained due to the periodic mirror offset.

The mirror offset of the individual mirrors with respect to one another can be designed in such a way that the individual mirrors are arranged with the same offset in each case, for example in the manner of a chessboard.

A periodicity of the mirror offset in the form of a multi-level grating is also a possible design.

An arrangement of the facet mirror device according to claim 3 can be like a chessboard, with white fields corresponding to individual mirrors with a first height perpendicular to the main arrangement plane and black fields corresponding to individual mirrors with a second offset height perpendicular to the main arrangement plane. This then results in a suppression of light to be suppressed by destructive interference which is incident under a plane of incidence which has contributions both along the row direction and along the row arrangement direction.

gegenüber einer Schachbrett-Anordnung erhöht sein. Ablenkungs- beziehungsweise Beugungswinkel sind dann gemäß der Gittergleichung um den gleichen Faktor erniedrigt.With regard to the offset of the individual mirrors perpendicular to the main plane of the arrangement, a facet arrangement according to claim 4 has a sequence along the row arrangement direction and / or along the row direction “high / low / high / low”. Such a grid can offer manufacturing advantages. The grating period of such a grating can be by a factor in the interval $\left[\text{1},\sqrt{\text{2}}\right]$

be increased compared to a checkerboard arrangement. The deflection or diffraction angles are then reduced by the same factor according to the grating equation.

In the case of an individual mirror arrangement according to claim 5, a suppression grille with a multi-level arrangement, in particular in the manner of a stair gate, can be formed.

In the case of an individual mirror arrangement according to claim 6, there are exactly three successive steps. Such a grid can offer manufacturing advantages.

The advantages of the facet mirror device are particularly effective when used as a field facet mirror and / or as a pupil facet mirror and / or as a specular reflector.

Designs according to claim 8 or 9 have proven themselves for mass production of the facet mirror device. In addition, the micromirror dimensioning results in good suppression performance in the case of destructive interference, since, according to the grating equation, the diffraction or deflection angles for the light to be suppressed are proportional to an inverse mirror size.

The advantages of an illumination optics according to claim 10, an optical system according to claim 11, an optical system with an EUV light source according to claim 12, a projection exposure system according to claim 13, a manufacturing method according to claim 14 and a micro- or nanostructured component according to claim 15 correspond to those which have already been explained above with reference to the facet mirror device.

The component or component can be a semiconductor chip, in particular a memory chip.

• 1 schematisch im Meridionalschnitt eine Projektionsbelichtungsanlage für die EUV-Projektionslithografie;
• 2 einen Abschnitt einer Ausführung eines Feldfacettenspiegels einer Beleuchtungsoptik der Projektionsbelichtungsanlage, aufgebaut aus einer Vielzahl von in einem Raster angeordneten und in Module unterteilten MEMS-Einzelspiegeln, wobei Randkonturen dreier Feldfacetten zusätzlich dargestellt sind, die durch entsprechende Gruppierung der MEMS-Einzelspiegel bei dieser Ausführung des Feldfacettenspiegels gebildet werden können und in ihrer Funktion monolithischen Feldfacettenspiegeln entsprechen;
• 3 in einer zu 2 ähnlichen Darstellung einen Abschnitt einer Ausführung eines Pupillenfacettenspiegels, dessen Pupillenfacetten wiederum aus MEMS-Einzelspiegeln mit entsprechender Gruppierung gebildet sind, wobei Randkonturen von mehreren dieser durch Gruppierung entstehenden Pupillenfacetten beispielhaft dargestellt sind;
• 4 eine Seitenansicht auf mehrere Spiegelreihen der MEMS-Einzelspiegel gemäß Blickrichtung IV in 2, wobei zusätzlich beispielhafte Einzelstrahlen von einfallendem zu unterdrückendem Licht einer Unterdrückungs-Wellenlänge, die jeweils auf einen der Einzelspiegel der jeweiligen Spiegelreihe treffen, dargestellt sind;
• 5 eine Veranschaulichung einer destruktiven InterferenzWirkung für das zu unterdrückende Licht, welches auf zwei in einer Reihen-Anordnungsrichtung zueinander benachbarte Spiegelreihen trifft;
• 6 in einer zu 4 ähnlichen Seitenansicht einen Profilquerschnitt einer Anordnungs-Einheitszelle einer weiteren Ausführung einer Anordnung von MEMS-Einzelspiegel-Reihen, wobei bei drei aufeinanderfolgenden Spiegelreihen in der Reihen-Anordnungsrichtung ein Vorzeichen eines Versatzes der benachbarten Spiegelreihen senkrecht zu einer Anordnungs-Hauptebene gleich bleibt;
• 7 in einer zu den 2 und 3 ähnlichen Aufsicht eines der MEMS-Spiegelmodule, wobei Spiegelreihen, die gegeneinander senkrecht zur Anordnungs-Hauptebene versetzt angeordnet sind, hervorgehoben dargestellt sind;
• 8 eine Aufsicht auf eine weitere Ausführung einer Anordnung von Einzelspiegeln eines Facettenspiegels, wobei jeweils ein Absolutwert eines Spiegel-Versatzes senkrecht zur Anordnungs-Hauptebene durch eine Schraffurgestaltung veranschaulicht ist, wobei gleichen Spiegel-Versatz aufweisende Einzelspiegel nach Art der weißen und schwarzen Felder eines Schachbretts verteilt angeordnet sind; und
• 9 in einem Meridionalschnitt schematisch eine Beugungswirkung einer der Facettenspiegel-Ausführungen am Ort eines Feldfacettenspiegels einer Ausführung der Beleuchtungsoptik der Projektionsbelichtungsanlage, wobei die Beugungswirkung zur Unterdrückung des zu unterdrückenden Lichts genutzt wird.

At least one embodiment of the invention is described below with reference to the drawing. In the drawing show:

• 1 schematically in meridional section a projection exposure system for EUV projection lithography;
• 2 a section of an embodiment of a field facet mirror of an illumination optics of the projection exposure system, built up from a plurality of MEMS individual mirrors arranged in a grid and subdivided into modules, with edge contours of three field facets additionally shown, which are formed by corresponding grouping of the MEMS individual mirrors in this embodiment of the field facet mirror and correspond in their function to monolithic field facet mirrors;
• 3 in one too 2 In a similar illustration, a section of an embodiment of a pupil facet mirror, the pupil facets of which are in turn formed from MEMS individual mirrors with a corresponding grouping, with edge contours of several of these pupil facets resulting from grouping being shown by way of example;
• 4th a side view of several rows of mirrors of the MEMS individual mirrors according to viewing direction IV in FIG 2 , wherein additional exemplary individual beams of incident light to be suppressed of a suppression wavelength, which impinge on one of the individual mirrors of the respective mirror row, are shown;
• 5 an illustration of a destructive interference effect for the light to be suppressed which strikes two mirror rows which are adjacent to one another in a row arrangement direction;
• 6th in one too 4th Similar side view shows a profile cross section of an arrangement unit cell of a further embodiment of an arrangement of MEMS individual mirror rows, with three successive mirror rows in the row arrangement direction having a sign of an offset of the neighboring ones Rows of mirrors perpendicular to a main plane of the arrangement remain the same;
• 7th in one to the 2 and 3 similar top view of one of the MEMS mirror modules, rows of mirrors which are offset from one another perpendicular to the main plane of the arrangement are shown highlighted;
• 8th a plan view of a further embodiment of an arrangement of individual mirrors of a facet mirror, with an absolute value of a mirror offset perpendicular to the main plane of the arrangement being illustrated by hatching, with individual mirrors having the same mirror offset arranged in a distributed manner in the manner of the white and black fields of a chessboard are; and
• 9 in a meridional section schematically a diffraction effect of one of the facet mirror designs at the location of a field facet mirror of an embodiment of the illumination optics of the projection exposure system, the diffraction effect being used to suppress the light to be suppressed.

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

A lighting system 2 the projection exposure system 1 has next to a light or radiation source 3 an illumination optics 4th for illuminating an object field 5 in one object level 6th . In this case, a is exposed in the object field 5 arranged reticle 7th . The reticle 7th is from a reticle holder 8th held. The reticle holder 8th is via a reticle displacement drive 9 especially displaceable in a scanning direction.

In the 1 a Cartesian xyz coordinate system is drawn in for explanation. The x-direction runs perpendicular to the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in the 1 along the y-direction. The z-direction runs perpendicular to the object plane 6th .

The projection exposure system 1 includes projection optics 10 . The projection optics 10 serves to map the object field 5 in an image field 11 in one image plane 12th . The image plane 12th runs parallel to the object plane 6th . Alternatively, there is also an angle between the object plane other than 0 ° 6th and the image plane 12th possible.

A structure is imaged on the reticle 7th onto a light-sensitive layer in the area of the image field 11 in the image plane 12th arranged wafers 13th . The wafer 13th is held by a wafer holder 14th held. The wafer holder 14th is via a wafer displacement drive 15th in particular displaceable along the y-direction. The displacement of the reticle on the one hand 7th via the reticle displacement drive 9 and on the other hand the wafer 13th via the wafer displacement drive 15th can be synchronized with each other.

At the radiation source 3 it is an EUV radiation source. The radiation source 3 emits EUV radiation in particular 16 , which is also referred to below as useful radiation, useful light, illuminating radiation or illuminating light or illuminating radiation. The useful radiation has, in particular, a wavelength in the range between 5 nm and 30 nm. In the case of the radiation source 3 it can be a plasma source, for example an LPP (Laser Produced Plasma) source or a DPP (Gas Discharged Produced Plasma) source. It can also be a synchrotron-based radiation source. At the radiation source 3 it can be a free electron laser (FEL).

The illuminating radiation 16 by the radiation source 3 emanates from a collector 17th bundled. At the collector 17th it can be a collector with one or more ellipsoidal and / or hyperboloid reflection surfaces. The at least one reflective surface of the collector 17th can in grazing incidence (GI), i.e. with angles of incidence greater than 45 °, or in normal incidence (normal incidence, NI), i.e. with angles of incidence less than 45 °, with the illuminating radiation 16 be applied. The collector 17th can be structured and / or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress false light.

After the collector 17th propagates the illumination radiation 16 by an intermediate focus in an intermediate focus plane 18th . The intermediate focus plane 18th can be a separation between a radiation source module comprising the radiation source 3 and the collector 17th , and the lighting optics 4th represent.

The lighting optics 4th includes a deflection mirror 19th and a first facet mirror arranged downstream of this in the beam path 20th . With the deflection mirror 19th it can be a planar deflecting mirror or, alternatively, a mirror with an effect that goes beyond the pure deflection effect act bundle influencing effect. Alternatively or in addition, the mirror can 19th be designed as a spectral filter, which is a useful light wavelength of the illuminating radiation 16 from stray light of a different wavelength. Unless the first facet mirror 20th in one plane of the lighting optics 4th is arranged to the object plane 6th is optically conjugated as a field plane, this is also referred to as a field facet mirror. The first facet mirror 20th comprises a multitude of individual first facets 21 , which are also referred to as field facets in the following. From these facets 21 are in the 1 only a few are shown as examples. These facets 21 are designed as groups of individual MEMS mirrors, as will be described below.

The first facets 21 , that is to say the groups of the MEMS individual mirrors, can be designed as rectangular facets or as facets with an arcuate or part-circular edge contour. The first facets 21 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 are the first facets 21 each composed of a large number of individual mirrors, in particular a large number of micromirrors. The first facet mirror 20th is designed as a microelectromechanical system (MEMS system). For details, refer to the DE 10 2008 009 600 A1 referenced.

Between the collector 17th and the deflection mirror 19th the illumination radiation runs 16 horizontally, i.e. along the y-direction.

In the beam path of the lighting optics 4th is the first facet mirror 20th downstream a second facet mirror 22nd . Unless the second facet mirror 22nd in a pupil plane of the illumination optics 4th is arranged, this is also referred to as a pupil facet mirror. The second facet mirror 22nd can also be spaced apart from a pupil plane of the illumination optics 4th be arranged. In this case, the combination of the first facet mirror can be used 20th and the second facet mirror 22nd also be designed 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 22nd comprises a plurality of second facets 23 . The second facets 23 are also referred to as pupil facets in the case of a pupil facet mirror.

With the second facets 23 it is facets that can be rounded, rectangular or hexagonal, for example, and are in turn designed as groups of individual MEMS mirrors. In this regard, reference is also made to the DE 10 2008 009 600 A1 referenced.

The second facets 23 can have planar or alternatively convex or concavely curved reflection surfaces.

The lighting optics 4th thus forms a double faceted system. This basic principle is also referred to as a fly's eye integrator or a honeycomb condenser.

It can be advantageous to use the second facet mirror 22nd not exactly in a plane which corresponds to a pupil plane of the projection optics 10 is optically conjugated to be arranged. In particular, the pupil facet mirror 22nd with respect to a pupil plane of the projection optics 7th be arranged in a twisted manner, for example in the DE 10 2017 220 586 A1 is described.

With the help of the second facet mirror 22nd become the individual first facets 21 in the object field 5 pictured. The second facet mirror 22nd is the last mirror that forms the beam or actually the last mirror for the illuminating radiation 16 in the beam path in front of the object field 5 .

In a further, not shown embodiment of the lighting optics 4th can in the beam path between the second facet mirror 22nd and the object field 5 a transmission optics can be arranged, in particular for imaging the first facets 21 in the object field 5 contributes. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are positioned one behind the other in the beam path of the illumination optics 4th 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 4th has when executing that in the 1 is shown after the collector 17th exactly three mirrors, namely the deflecting mirror 19th , the field facet mirror 20th and the pupil facet mirror 22nd .

In another version of the lighting optics 4th can the deflection mirror 19th also omitted, so that the lighting optics 4th after the collector 17th can then have exactly two mirrors, namely the first facet mirror 20th and the second facet mirror 22nd .

The illustration of the first facets 21 by means of the second facet 23 or with the second facet 23 and transmission optics in the object plane 6th is regularly only an approximate figure.

The projection optics 10 comprises a plurality of mirrors Mi, which according to their arrangement in the beam path of the projection exposure system 1 are numbered.

The one in the 1 The example shown includes the projection optics 10 six mirrors M1 until M6 . Alternatives with four, eight, ten, twelve or a different number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illuminating radiation 16 . With the projection optics 10 it is a doubly obscure look. The projection optics 10 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 Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflective surface shape. The mirrors Mi can, just like the mirrors of the lighting optics 4th , highly reflective coatings for illuminating radiation 16 exhibit. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 10 has a large object image offset in the y direction between a y coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11 . This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 6th and the image plane 12th .

The projection optics 10 can in particular be anamorphic. In particular, it has different imaging scales β _x , β _y in the x and y directions. The two imaging scales β _x , β _{y of} the projection optics 10 are preferably at (β _x , β _y ) = (+/- 0.25, / + - 0.125). A positive image scale β means an image without image reversal. A negative sign for the image scale β means an image with image reversal.

The projection optics 10 thus leads to a reduction in the ratio of 4: 1 in the x direction, that is to say in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8: 1 in the y-direction, i.e. in the scan direction.

Other image scales are also possible. Mapping 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 5 and the field of view 11 can be the same or can, depending on the design of the projection optics 10 , 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 the pupil facets each 23 is exactly one of the field facets 21 for the formation of an illumination channel for illuminating the object field 5 assigned. In particular, this can result in lighting according to the Koehler principle. The far field is created with the help of the field facets 21 in a variety of object fields 5 disassembled. The field facets 21 generate a plurality of images of the intermediate focus on the respective associated pupil facets 23 .

The field facets 21 are each of an assigned pupil facet 23 superimposed to illuminate the object field 5 on the reticle 7th pictured. The illumination of the object field 5 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 lighting channels.

An arrangement of the pupil facets can geometrically illuminate the entrance pupil of the projection optics 10 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 10 can be set. This intensity distribution is also referred to as an illumination setting or illumination pupil filling.

Another preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 4th can be achieved by redistributing the lighting channels.

Further aspects and details of the illumination of the object field are described below 5 and in particular the entrance pupil of the projection optics 10 described.

The projection optics 10 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 10 can be checked regularly with the pupil facet mirror 22nd not illuminate exactly. In an illustration of the projection optics 10 which is the center of the pupil facet mirror 22nd telecentrically onto the wafer 13th 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 10 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 22nd and the reticle 7th to be provided. With the aid of this optical element, 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 4th is the pupil facet mirror 22nd in one to the entrance pupil of the projection optics 10 conjugate surface arranged. The field facet mirror 20th is tilted to the object plane 6th arranged. The first facet mirror 20th is tilted to an arrangement plane arranged by the deflection mirror 19th is defined.

The first facet mirror 20th is arranged tilted to an arrangement plane that of the second facet mirror 22nd is defined.

2 shows a portion of the field facet mirror 20th . This illustrated section of a facet arrangement of the field facet mirror 20th is divided into a total of six individual mirror modules shown in dashed lines 24 . Each of these individual mirror modules 24 comprises a 10x10 grid of individual mirrors 25th , which are designed as MEMS single mirrors. The number of individual mirrors 25th each individual mirror module 24 can also be bigger. The single mirrors 25th can also be arranged in a 25x25 grid, for example.

Over the illustrated section of the field facet mirror 20th can be, at least for the most part, through appropriate grouping and interconnection of the individual mirrors 25th of the various individual mirror modules 24 for example three in the 2 Field facets shown in solid lines 21 ₁ , 21 ₂ , 21 ₃ generate, also known as virtual field facets.

3 shows in one too 2 In a similar illustration, there are six individual mirror modules 24 of the pupil facet mirror 22nd . In turn, individual mirrors are grouped by assignment and interconnection 25th the single mirror modules 24 the pupil facets 23 generated in the 3 are arranged by a hexagonal assignment.

The field facet mirror 20th , divided into the individual mirror modules 24 , as well as the pupil facet mirror 22nd , again subdivided into the individual mirror modules 24 , is an example of a facet mirror device. This facet mirror device 20th , 22nd reflected during operation of the projection exposure system 1 regularly not only the useful light 16 but also light to be suppressed 26th a suppression wavelength. In the 2 is an incident ray of the light to be suppressed 26th , which is incident in a yz plane, shown as an example. By the light to be suppressed 26th it can be, for example, infrared light, which is generated by the light source when useful light is generated 3 is used. The suppression wavelength can be, for example, 10.6 µm or 1.064 µm. Other suppression wavelengths in the range between 193 nm and 10.6 µm and, in principle, even larger suppression wavelengths are also possible. The suppression wavelength can be the wavelength center of gravity of a wavelength bandwidth to be suppressed of the light to be suppressed.

The single mirrors 25th are in or adjacent to a main level of arrangement 27 arranged. This main arrangement level 27 coincides with the plane of the drawing 2 and 3 together and runs parallel to the xy plane. Reflection surfaces of the individual mirrors 25th are for guiding sub-bundles of a total bundle of useful light 16 usually tilted about tilt axes parallel to the xy plane. This tilting of the reflection surfaces of the individual mirrors 25th plays in the following explanation of a diffraction suppression of the light to be suppressed 26th no or only a subordinate role.

The arrangement of the individual mirrors 25th has several rows of mirrors 28i on. Due to the 10x10 arrangement, each of the individual mirror modules has 24 ten rows of mirrors 28i . The rows of mirrors 28i run in a row direction running parallel to the x-direction. Each of the rows of mirrors 28i thus has several individual mirrors arranged next to one another in the row direction x 25th . Within each individual mirror module 24 are in the respective row of mirrors 28i ten individual mirrors 25th side by side in the Row direction x arranged. Per virtual field facet 21 lie in the respective row of mirrors 28i For example, thirty individual mirrors arranged next to one another in the row direction x 25th before.

The rows of mirrors 28i are in a row arrangement direction which runs parallel to the y-axis, i.e. in the main arrangement plane 27 and is perpendicular to the row arrangement direction x, arranged in rows. Individual mirrors adjacent to one another along the row arrangement direction y 25th therefore belong to adjacent rows of mirrors 28 _i , 28 _{i + i} or 28 _i , 28 _i-1 .

The facet mirror device 20th , 22nd is arranged in such a way that the plane of incidence of useful light y, z is spanned on the one hand by the row arrangement direction y and on the other hand by the normal z to the main plane of arrangement 27 (xy plane).

The single mirrors 25th adjacent rows of mirrors 28 _i , 28 _{i + 1} and in particular their reflective surfaces are, as for example in the 4th illustrated, perpendicular to the main plane of the arrangement 27 arranged offset from one another. This z-offset is in the 4th denoted by Δz.

4th also shows an example of a ray of the light to be suppressed 26th standing on a single mirror 25th one of the rows of mirrors 28 _i , 28 _{i + 1} , 28 _{i + 2} , 28 _{i + 3} falls. An angle of incidence and an angle of emergence of the light to be suppressed 26th on the arrangement of the individual mirrors 25th the facet mirror device 20th , 22nd is in the 4th denoted by α.

The z-offset of the individual mirrors 25th adjacent rows of mirrors 28 _i , 28 _{i + 1} is so great that the light to be suppressed 26th that of the neighboring rows of mirrors 28 _i , 28 _{i + 1} is reflected, experiences an optical path length difference y of half a suppression wavelength.

wobei Δz den relativen z-Versatz der Reflexionsebenen und α den Einfallswinkel der Strahlen bezeichnet 5 illustrates a destructive interference effect for the incident light to be suppressed 26th . In the 5 is also the wave character of the light to be suppressed 26th illustrated. A reflection of an incident beam of the light to be suppressed, reflected on one of the individual mirrors, is shown schematically 25th that are in the 5 is offset upwards along the z-direction (reflected ray 26 ₁ ) as well as a reflected beam, which at a single mirror 25th is reflected in the 5 is offset downwards along the z-direction (reflected ray 26 ₂ ). An optical path length difference between these two reflected rays 26 ₁ , 26 ₂ when you later hit one of the mirrors 25th parallel plane is in the 5 denoted by Y. The z-offset Δz can be chosen so that the following applies: $$\text{Y}=\text{2}\mathrm{\Delta }\text{z / cos}\mathrm{\alpha }=\mathrm{\lambda }\text{/}2$$

where Δz denotes the relative z-offset of the reflection planes and α denotes the angle of incidence of the rays

In this case, λ is the suppression wavelength at which the plane waves belonging to the rays destructively interfere. These waves are in 5 shown symbolically in p-polarization. During the reflection, a phase jump of π occurs in each case, so that the tangential components of the incoming and outgoing field cancel each other out.

Depending on the requirements for guiding the illuminating light 6th are the single mirrors 25th about axes that are parallel to the main plane of the arrangement 27 lying, tilted. Nothing changes in the mean offset Δz here.

In the offset design of successive rows of mirrors 28 _i after 4th are the rows of mirrors 28i so alternately perpendicular to the main plane of the arrangement 27 arranged offset from one another, that in the row arrangement direction y there is a sign of the offset Δz of the adjacent mirror rows 28 _i , 28 _{i + 1} perpendicular to the main plane of the arrangement 27 alternates each time. Like in the 4th shown, the rows of mirrors alternate high / low / high / low.

6th shows a variant of an offset sequence of adjacent rows of mirrors 28 ₁ until 28 ₄ in a fundamentally to 4th similar representation. A y section of a variant of the facet mirror device is delimited by dashed lines 20th , 22nd , which can be understood as a grid unit cell continuously continuing in the y-direction. The four rows of mirrors are shown 28 ₁ until 28 ₄ within a grid unit cell 29 . To illustrate this, there are also two rows of mirrors 28 ₀ and 28 ₅ adjacent grid unit cells 29 shown. The rows of mirrors 28 ₁ until 28 ₄ are in the arrangement according to 6th so offset from one another along the z-direction that in a mirror row group 30th of three consecutive rows of mirrors 28 ₂ , 28 ₃ , 28 ₄ in the row arrangement direction y, the sign of the offset Δz of the adjacent mirror rows 28 ₂ , 28 ₃ , 28 ₄ perpendicular to the main plane of the arrangement 27 is the same in each case. Between the rows of mirrors 28 ₂ and 28 ₃ on the one hand and the rows of mirrors 28 ₃ and 28 ₄ on the other hand, the same sign of the offset Δz is present in each case. The result is a stair gate with three consecutive steps.

The number of successive rows of mirrors for which the offset sign remains the same can also be greater than three and can be, for example, four or five.

7th shows a plan view of a further embodiment of one of the individual mirror modules 24 , designed as a 30x30 grid of individual mirrors 25th . The rows of mirrors running along the x-direction are highlighted in each case 28i .

A subdivision into the individual mirrors is also exemplary for one of the rows of mirrors 25th indicated within the mirror row. This is also the case within one of the rows of mirrors 28i Adjacent individual mirrors 25th can in the row direction x so perpendicular to the main plane of the arrangement 27 be arranged offset from one another, that in turn the light to be suppressed 26th that of these neighboring individual mirrors 25 _i , 25 _{i + 1} in the respective row of mirrors 28i is reflected, experiences an optical path length difference of half the suppression wavelength λ. In this case, is a direction of incidence of the light to be suppressed 26th so that a plane of incidence also has an xy component.

In the above formula, which denotes the relationship between the offset Δz and the optical path length difference, a path length difference Y in this incidence plane xz must then be set for the respective angle of incidence condition in the incidence plane xz and a corresponding offset Δz results for the side by side in the Row direction x arranged individual mirrors 25 _i , 25 _{i + 1} to generate the destructive interference for such xz incidence contributions.

As for the course of the offset along the row direction x, i.e. within one and the same mirror row 28i As far as concerns, what applies above for the offset course between adjacent rows of mirrors 28 _i , 28 _{i + 1} has been described. The course of the offset within one and the same row of mirrors can also be alternating or such that the sign of the offset for several adjacent individual mirrors 25th within one and the same row of mirrors 28i remains the same in each case.

Another embodiment of a facet mirror device that is used for the field facet mirror 20th or the pupil facet mirror 22nd can be used, is explained below based on the 8th explained. Components and functions corresponding to those described above with reference to the 1 until 7th have already been described have the same designations and reference numbers and will not be discussed again in detail.

With the mirror offset arrangement of the individual mirrors 25th after 8th these are checkerboard-like against each other perpendicular to the main arrangement plane lying in the intermediate plane 27 offset. Those individual mirrors 25 ₁ which correspond to the black fields of this checkerboard-like offset arrangement are, for example, arranged offset in the positive z-direction towards the viewer compared to the plane of the drawing, and the individual mirrors 25 ₂ corresponding to the white fields are in negative z-direction away from the viewer. Direction offset compared to the plane of the drawing. This offset arrangement is in two dimensions that form the main plane of the arrangement 27 stretch, periodically. These periods can be along the diagonals of the individual mirrors 25 ₁ , 25 ₂ run, as in the 8th by boundary lines of a unit cell 32 this two-dimensional periodic structure is indicated.

wobei g die Gitterperiode bezeichnet. Bevorzugt ist dabei die Gitterperiode g so klein gewählt, dass die in 1. Ordnung gebeugten Strahlen (Beugungswinkel α₁) außerhalb der Pupillenfacette liegen, die in 0.ter Ordnung getroffen wird (Reflexionswinkel α₀). Der Strahl 1. Ordnung des zu unterdrückenden Lichts 26 verlässt dadurch den Nutz-Strahlengang der Projektionsbelichtungsanlage 1 und kann beispielsweise durch Blenden 33 abgefangen werden.Based on 9 is subsequently the light to be suppressed 26th suppressing diffraction effect of the above-described individual mirror arrangements with the mirror offset Δz using the example of the use of such a diffraction-suppressing individual mirror arrangement at the location of the field facet mirror 20th described. The useful light 16 depends on the arrangement of the individual mirrors 25th of the field facet mirror 20th not bent, but exclusively reflected, so that the useful light 16 along a predetermined useful beam path from the field facet mirror 20th towards a selected pupillary facet 23 is performed and then subsequent optical components of the projection exposure system 1 fed. The light to be suppressed 26th is due to the individual mirror arrangement of the field facet mirror 20th flexed with the mirror offset of one of the embodiments described above. The light suppressed in the 0th order is thus _{deflected into higher diffraction orders m at diffraction angles α m} according to the grating equation $$\text{G}*\text{sin}{\mathrm{\alpha }}_{\text{m}}\text{/}\mathrm{\lambda }=\text{m}\text{, m integer}\text{,}$$

where g denotes the grating period. The grating period g is preferably selected to be so small that the rays diffracted in the 1st order (diffraction angle α ₁ ) lie outside the pupil facet that is struck in the 0th order (reflection angle α ₀ ). The beam 1 . Order of the light to be suppressed 26th thereby leaves the useful beam path of the projection exposure system 1 and can for example by blending 33 be intercepted.

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

• WO 2009/100856 A1 [0002]
• WO 2013/174644 A1 [0002]
• DE 102017217867 A1 [0002]
• DE 102008009600 A1 [0034, 0038]
• US 2006/0132747 A1 [0036]
• EP 1614008 B1 [0036]
• US 6573978 [0036]
• DE 102017220586 A1 [0041]
• US 2018/0074303 A1 [0055]

Claims (15)

Facet mirror device (20, 22) for reflecting light (26) to be suppressed at least one suppression wavelength (λ), - With a multiplicity of individual mirrors (25) which are arranged in or adjacent to a main arrangement plane (27), - wherein an arrangement of the individual mirrors (25) has a mirror offset (Δz) of the individual mirrors (25) to the arrangement main plane (27) which is periodic along a period direction (y), - wherein the facet mirror device (20, 22) is arranged such that a useful light incidence plane (yz) is spanned from the period direction (y) and a normal (z) to the main plane of arrangement (27), - The mirror offset (Δz) of the individual mirrors (25) to the main plane of the arrangement (27) is such that the light (26) to be suppressed, which is reflected by the arrangement of the individual mirrors (25), is suppressed in a zero diffraction order will. Facet mirror device according to Claim 1 , characterized in that - the arrangement of the individual mirrors (25) has several rows of mirrors (28i) each with several individual mirrors (25) arranged next to one another in a row direction (x), - the rows of mirrors (28i) in a row arrangement direction parallel to the period direction (y), which lies in the main arrangement plane (27, xy) and is perpendicular to the row direction (x), are arranged in rows, - the facet mirror device (20, 22) being arranged in such a way that the plane of incidence of useful light (yz) is spanned by the row arrangement direction (y) and the normal (z) on the arrangement main plane (27), - with at least some of the individual mirrors (25) of adjacent mirror rows (28 _i , 28 _{i + 1} ) so perpendicular to the main plane of the arrangement (27) offset from one another (Δz) are arranged so that the light (26) to be suppressed, which is reflected by the adjacent rows of mirrors (28i, 28i + i), is suppressed in a zeroth diffraction order. Facet mirror device according to Claim 2 , characterized in that adjacent one of the individual mirrors (25) are also so offset (Δz) in the row direction (x) perpendicular to the main plane (27) of the arrangement that the light (26) to be suppressed emitted by these adjacent individual mirrors ( 25 _i , 25 _{i + 1} ) is reflected in the respective row of mirrors (28i), experiences an optical path length difference (Y) of half the suppression wavelength (λ / 2). Facet mirror device according to Claim 2 or 3 , characterized in that the rows of mirrors (28i) and / or the individual mirrors (25 _i , 25 _{i + 1} ) within a row of mirrors (28i) are arranged alternately offset from one another perpendicular to the main plane (27) of the arrangement that in the row Arrangement direction (y) the sign of an offset (Δz) of the adjacent mirror rows (28 _i , 28 _{i + 1} ) and / or the individual _{mirrors (25 i} , 25 _{i + 1} ) within a mirror row (28i) perpendicular to the main arrangement plane (27 ) alternates each time. Facet mirror device according to Claim 2 or 3 , characterized in that the rows of mirrors (28 _i ) and / or the individual mirrors (25 _i ) are offset from one another within a row of mirrors (28 _i ) so that with at least three consecutive rows of mirrors (28 _i , 28 _{i + 1} , 28 _{i +2} ) in the row arrangement direction (y) and / or with at least three consecutive individual _{mirrors (25 i} , 25 _{i + 1} , 25 _{i + 2} ) in the row direction (x) the sign of an offset (Δz) of the adjacent mirror rows ( 28 _i , 28 _{i + 1} ) and / or the adjacent individual mirrors (25 _i , 25 _{i + 1} ) perpendicular to the main plane of the arrangement (27) is the same in each case. Facet mirror device according to Claim 5 , characterized in that the rows of mirrors (28 _i ) and / or the individual mirrors (25 _i ) within a row of mirrors (28 _i ) are offset from one another in such a way that in the case of groups of mirrors (30) of exactly three consecutive rows of mirrors in the row -Arrangement direction (y) and / or in the case of individual mirror groups of exactly three individual mirrors (25 _i , 25 _{i + 1} , 25 _{i + 1} ) consecutive in the row direction (x), the sign of an offset (Δz) of the adjacent mirror rows (28 _i ) and / or the adjacent individual mirror (25 _i ) perpendicular to the main plane of the arrangement (27) is the same in each case. Facet mirror device according to one of the Claims 1 until 6th , characterized in that an arrangement of the individual mirrors (25) is designed as a facet mirror of a field facet mirror (20) and / or a pupil facet mirror and / or a specular reflector of an illumination optics (4) for projection lithography. Facet mirror device according to one of the Claims 1 until 7th , characterized in that the individual mirrors (25) are designed as micromirrors. Facet mirror device according to Claim 8 , characterized by a design as a MEMS mirror array. Illumination optics (4) for guiding illumination light (16) to an object field (5) of a projection exposure system (1) for projection lithography, in which an object (7) to be imaged can be arranged, with a facet mirror device (20, 22) according to one of the Claims 1 until 9 . Optical system with lighting optics according to Claim 10 and with projection optics (10) for imaging the object field (5) in an image field (11) in which a substrate (13) can be arranged. Optical system according to Claim 11 with an EUV light source (3). Projection exposure system (1) with an optical system Claim 12 . A method for producing structured components with the following steps: - providing a wafer (13) as a substrate, on which a layer of a light-sensitive material is at least partially applied, - providing a reticle as an object (7) which has structures to be imaged, - providing a Projection exposure system (1) according to Claim 13 - Projecting at least a part of the reticle (7) onto an area of the layer of the wafer (13) with the aid of the projection exposure system (1). Structured component, produced by a method according to Claim 14 .

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