DE102014217608A1 - Method for assigning a second facet of a second faceted element of an illumination optical system in the beam path - Google Patents

Abstract

A method for assigning a second facet of a second faceted element (10) of an illumination optics (23) of a projection exposure system (1) in the beam path to an area (7) on a first facetted element (6) of the illumination optics (23) in the beam path to define a The illumination channel for a partial bundle of illuminating light (3) has the following steps: First, at least one illumination parameter is identified. The dependence of the lighting parameter on design specification data, on individual part acceptance data, on overall system acceptance data, on calibration data and / or online measurement data of the light source and / or the lighting optics is determined. An evaluation function dependent on the illumination channel is then specified for evaluating a possible illumination channel. An evaluation target range of evaluation variables is then specified as the result of the evaluation function, and the evaluation variable for at least selected ones of the possible illumination channels is calculated on the basis of the specified evaluation function. Those illumination channels whose evaluation size reaches the evaluation target range are preselected. At least one disturbance variable which influences an illumination of the object field and a dependency of the lighting function on this disturbance variable are identified. The disturbance variable is varied for the preselected illumination channels within a predefined disturbance variable variation range and the respective following variation of the evaluation variable is calculated using the evaluation function. Those illumination channels are selected whose varied assessment variable remains within the assessment target range in the entire variation range.

Description

The invention relates to a method for assigning a second facet of a second facetted element of an illumination optical unit of a projection exposure apparatus to an area on a first faceted element of the illumination optical unit for defining an illumination channel for a partial bundle of illumination light which starts from a light source at the area on the first faceted element and is reflected at the second facet associated with the method towards an illuminated by the illumination optical object field. Furthermore, the invention relates to a computer program for implementing such a mapping method on a computer, a data carrier having stored thereon such a computer program and a computer with a computer program implemented thereon.

An illumination system for EUV projection lithography with a first faceted element in the beam path and a second faceted element in the beam path is known from US Pat DE 103 17 667 A1 , of the US 2010/0231882 A1 and from the US Pat. No. 6,507,440 B1 , A second facetted element, which is arranged at a distance to a pupil plane of the illumination system and whose illuminated facets contribute both to specifying a direction of illumination direction and to specifying a field shape, is known as a so-called specular reflector, for example from US Pat DE 103 17 667 A1 and from the US 2010/0231882 A1 known. A projection exposure apparatus with an illumination optical system including a field facet mirror and a pupil facet mirror is known from US Pat WO 2009/132756 A1 , of the DE 10 2006 059 024 A1 , of the DE 10 2006 036 064 A1 , of the WO 2010/037 453 A1 , of the DE 10 2008 042 876 A , of the DE 10 2008 001 511 A1 , of the DE 10 2008 002 749 A1 and the DE 10 2009 045 694 A1 ,

The faceted mirrors of an illumination optical unit of a projection exposure apparatus often each have several hundred facets. In an illumination optical system with N regions to be selected on the first faceted element and N second facets theoretically exist with N! scaling possibilities of assigning the areas on the first faceted element to the second facets. This number of assignment options quickly becomes unmanageably large as the number of facets or facets to be selected increases.

It is an object of the present invention to provide an association method of the type mentioned above, which ensures a reproducible selection of an assignment of the second facet to the area on the first faceted element and thus a reproducible specification of the illumination channels of the illumination optics on the basis of an illumination parameter to be optimized.

This object is achieved by a method with the steps specified in claim 1.

According to the invention, it has been recognized that it is important to specify a suitable evaluation function in which the influence of properties of the bundle guidance on an individual illumination channel is received by the illumination parameter to be considered. The assignment method makes it possible to associate all the illumination channels of an illumination optical system with regions on the first faceted element and second facets with an identified, optimized illumination parameter. The method can be flexibly adapted to the respective lighting task. This adaptation takes place by selecting the illumination parameter to be considered and by selecting and adapting the evaluation function to be provided, for example by inserting weighting terms, and by specifying the evaluation target area.

Design assignment data, ie setpoints for a production process, in particular of main components of the projection exposure apparatus, that is to say a light source, an illumination optics and a projection optics, enter into the assignment method. In simple terms, the design specification data are specification data recorded in a datasheet prior to the manufacture of the main components of the projection exposure apparatus. Furthermore, the individual acceptance data, that is to say the setup values of the components of the projection exposure apparatus actually achieved during manufacture, are included in the assignment method. B. measurement data for a reflective surface shape (Passe) or for a mirror reflectivity, resulting in a component or item decrease. Furthermore, the assignment procedure includes the total acceptance data, that is, the data that is collected when the entire projection exposure system is removed after assembly. Furthermore, calibration data, ie measurement data that specify a specific useful configuration of the projection exposure apparatus, a so-called setup, are included in the assignment method. Finally, online measurement data, ie the current measured values that characterize an actual state of the light source, the illumination optics and possibly a projection optics, are included in the assignment process.

Of these different data sets, ie the design specification data, the individual part acceptance data, the overall system acceptance data, the calibration data and the online measurement data, it is not absolutely necessary for all data records to be included in the assignment process. Depending on the quality requirements or the manageability of the assignment method, only a single data record can be used or some of these data records can be used. The assignment method can therefore flexibly take into account the originally given design, the component quality attained in the production, the assembly quality attained during assembly, the currently used setup and the current actual state of the projection exposure apparatus. Further data, for example data on the object to be imaged by the projection exposure apparatus, or data on the substrate or wafer on which the object is to be imaged can also be included in the assignment process.

The second facet may be a facet of a specular reflector, hereinafter also referred to as an SR facet. The respective illuminated areas on the first faceted element are in turn subdivided into a plurality of individual micro-mirrors.

The second facets may in turn be subdivided into a multiplicity or multiplicity of individual micro-mirrors.

When specifying an arrangement of the second facets or according to claim 2, a size of the facets and / or a position of the facets to one another on the facet mirror and / or a radius of curvature of the facets can be predetermined. Such an arrangement specification of the facets can take place, in particular, when the facet mirror is designed as a MEMS mirror array. Part of a facet placement constraint may be an alignment of the number of areas on the first faceted element with the number of available sets of the second facets.

An evaluation function according to claim 3 allows independent of the lighting setting specification of a valuation function. In particular, different environments of the second facets may be used to generate different illumination intensity sums, for example an environment in which only the nearest neighbors of the selected second facet are considered, and an environment in which also more distant neighbors of the selected second facet are considered. When summing the illumination intensities, weighting factors may be included. Shades, especially between adjacent facets, can be accommodated by including tilt angles of the adjacent facets.

Specifications according to claims 4 and 5 have been found to be particularly suitable for optimizing a illumination channel assignment. Alternatively or additionally, radii of curvature for the regions on the first facetted element and / or z-positions of the regions on the first facetted element can also be specified in the context of the assignment method.

A tilt angle set default according to claims 6 and 7 can be directly converted into control signals for an actuator tilt control of the areas on the first faceted element and / or second facets.

A data set according to claims 8 or 9 can quantitatively describe the illumination settings possible for a given illumination channel assignment. From this a set of pre-set lighting settings can be selected. It is also possible to compare the illumination settings of the data set with preset setting values.

A tuning method according to claim 10 may be performed initially without specifying a lighting setting. In this case, illumination channel assignments are made which prove to be particularly suitable for imaging the characterized object structure. The suitability is determined by the respective evaluation function. A lighting setting results in this voting procedure as a result.

A voting method according to claim 11 can be performed at the time of the method still unknown, imaged object structure. The illumination setting to be provided may include extended areas in an illumination pupil covered by groups of the second facets. Alternatively or additionally, the illumination setting to be specified may include individual second facets to be acted upon by illumination light whose nearest neighbors are unlit.

The advantages of a method according to claim 12, a data carrier according to claim 13 and a computer according to claim 14 are similar to those already explained above with reference to the matching method.

A stability of the evaluation quantity for a lighting channel to be evaluated may be considered depending on a given disturbance become. Such an allocation method makes it possible to associate all the illumination channels of an illumination optical unit with areas on the first faceted element and second facets with optimized stability. This adaptation additionally takes place by selection and adaptation of the disturbance variable used in each case and the specification of the disturbance variable variation range.

The evaluation variable can be precalculated for at least selected of the possible illumination channels on the basis of the predetermined evaluation function before the actual selection of the illumination channel. In this way, a preselection of possible target configurations of illumination channels can be made with less computational effort. In particular, from the outset unsuitable configurations can be excluded via a pre-selection. Symmetry considerations can, for example, enter into the pre-selection so that, for example, in the assignment process, configurations are first checked on the basis of the evaluation function, which have certain symmetry properties. Such configurations can be used in particular as start configurations for the disturbance variable variation.

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

1 schematically and with respect to a lighting system in the meridional section, a projection exposure apparatus for microlithography;

2 a schematic plan view of a first faceted element of the illumination optics of the projection exposure system according to 1 ;

3 an excerpt from 2 in which a subdivision of illuminated areas on the first faceted element is illustrated, to which second facets of a second faceted element arranged downstream in the illumination optical system are assigned via illumination channels;

4 a plan view of the second faceted element of the illumination optics; and

5 a schematic flow diagram of a method for assigning a second facet of a second faceted element of illumination optics of a projection exposure system for EUV lithography to an area on the first faceted element of a field facet mirror of the illumination optics for defining an illumination channel for a subset of illumination light.

A projection exposure machine 1 for microlithography is used to produce a micro- or nanostructured electronic semiconductor device. A light source 2 emits EUV radiation used for illumination in the wavelength range, for example between 5 nm and 30 nm. For the light source 2 it can be a GDPP source (plasma discharge by gas discharge, gas discharge produced plasma) or an LPP source (plasma generation by laser, laser produced plasma). Also, a radiation source based on a synchrotron is for the light source 2 used. Information about such a light source is the expert, for example in the US 6,859,515 B2 , For illumination and imaging within a lighting system of the projection exposure apparatus 1 becomes EUV illumination light or illumination radiation 3 used. The EUV lighting light 3 goes through the light source 2 first a collector 4 , which may be, for example, a nested collector with a known from the prior art multi-shell structure or alternatively an ellipsoidal shaped collector. A corresponding collector is from the EP 1 225 481 A2 known. After the collector 4 passes through the EUV illumination light 3 first an intermediate focus level 5 , what about the separation of the EUV illumination light 3 can be used by unwanted radiation or particle fractions. After passing through the Zwischenfokusebene 5 meets the EUV lighting light 3 first on a first faceted element 6 , The first faceted element 6 in the form of a facet mirror is in a field plane of a lighting optical system of the projection exposure system 1 arranged.

To facilitate the description of positional relationships, a Cartesian global xyz coordinate system is shown in the drawing. The x-axis runs in the 1 perpendicular to the drawing plane and out of it. The y-axis runs in the 1 to the right. The z-axis runs in the 1 up.

To facilitate the description of positional relationships in individual optical components of the projection exposure apparatus 1 In each of the following figures, a Cartesian local xyz or xy coordinate system is used. Unless otherwise described, the respective local xy coordinates span a respective main assembly plane of the optical component, for example a reflection plane. The x-axes of the xyz global coordinate system and the local xyz or xy coordinate systems are parallel. The respective y-axes of the local xyz or xy coordinate systems have an angle to the y-axis of the global xyz- Coordinate system that corresponds to a tilt angle of the respective optical component about the x-axis.

3 shows a plan view of the first faceted element 6 , The number of individual mirrors designed as micromirrors 6a (see. 3 ) on the first faceted element 6 is so big that single micromirrors 6a in the 2 are not recognizable. The micromirrors 6a are in two approximately semicircular facet areas 6b . 6c arranged with a far field of illumination light 3 be lit up.

3 shows in a section of the 2 a group assignment of micromirrors 6a in areas 7 on the first faceted element 6 , The areas 7 be about a second faceted element described below 10 (see. 1 and 4 ) each in an object field 18 (see. 1 ). All micromirrors 6a each one of the areas 7 illuminate one and the same second facet on the second faceted element 10 , The second faceted element 10 is not located in a pupil plane of the illumination system.

The areas 7 on the first faceted element 6 have different arrangements, shapes and sizes depending on the illumination setting to be selected, that is, depending on a given illumination angle distribution and illumination intensity distribution over the object field, and depending on the illumination geometry and on the object field dimensions.

The first faceted element 6 is a MEMS mirror array with a variety of tiltable micromirrors 6a built, each of the areas 7 by a plurality of such micromirrors 6a is formed. Such a construction of the field facet mirror 6 is basically known from the US 2011/0001947 A1 ,

A radius of curvature of an area 7 given single-mirror group of the MEMS mirror array can be adjusted by shifting the individual mirror perpendicular to a mirror array arrangement plane and corresponding tilt of the individual mirror, as also in the US 2011/0001947 A1 described. Also, by tilting the individual mirror without a corresponding displacement perpendicular to a mirror array arrangement plane a curvature radius adjustment can be achieved, which then effectively z. B. gives a Fresnel mirror.

After reflection at the field facet mirror 6 This is the case in bundles of rays or partial bundles, which are the individual areas 7 on the first faceted element 6 allocated, split EUV lighting light 3 on the second faceted element 10 ,

The areas 7 on the first faceted element 6 are tiltable between multiple illumination tilt positions, so that thereby a beam path of the respective area 7 on the first faceted element 6 reflected illumination light 3 changed in his direction and thus the point of impact of the reflected illumination light 3 on the second faceted element 10 can be changed. Corresponding facets which can be displaced between different illumination tilt positions are known from US Pat US 6,658,084 B2 and the US 7,196,841 B2 ,

4 shows an exemplary facet arrangement of round second facets 11 of the second faceted element 10 , The second facets 11 are arranged hexagonally. The channel-wise assignment of the second facets 11 to the areas 7 on the first faceted element 6 occurs depending on a desired illumination by the projection exposure system 1 ,

About the respective illumination tilt positions of the respective area 7 on the first faceted element 6 is this area 7 on the first faceted element 6 a disjoint set of second facets 11 of the second faceted element 10 assigned. Each of the second facets 11 One of these sets is about exactly one of the different tilt positions of the assigned areas 7 on the first faceted element 6 with the illumination light 3 acted upon, so that depending on the tilt position of the area 7 on the first faceted element 6 a certain illumination channel between this area 7 on the first faceted element 6 and one of the second facets 11 the quantities of the second facets is formed. The illumination channels, which depending on the tilt position exactly one of the areas 7 on the first faceted element 6 can be used, so over the second facets 11 the area 7 on the first faceted element 6 associated disjoint set of second facets 11 can be acted upon with the illumination light sub-beam form an illumination channel group. An area 7 on the first faceted element 6 may have more tilting positions, which can be adjusted by means of an actuator connected to it, as tilting positions, which lead to the formation of a lighting channel. Only one tilted position, which leads to the formation of an illumination channel, will be referred to below as a tilted position.

The field facet mirror 6 has several hundred of the areas 7 on the first faceted element 6 for example, 300 areas 7 on the first faceted element 6 , In a variant, not shown, the second faceted element 10 constructed as a MEMS mirror array with a plurality of tiltable individual mirrors, wherein each of the second facets 11 is formed by a plurality of such individual mirrors. Such a construction of the second faceted element 10 is known from US 2011/0001947 A1 , Also, a radius of curvature of a single-mirror group that is one of the second facets 11 is built on such a MEMS mirror array, by moving the individual mirrors perpendicular to a mirror array arrangement plane and corresponding to the tilt of the individual mirror can be adjusted, as above in connection with the first faceted element 6 already described.

About the second faceted element 10 (see. 1 ) and a subsequent one, from three EUV mirrors 12 . 13 . 14 existing transmission optics 15 become the areas 7 on the first faceted element 6 in an object plane 16 the projection exposure system 1 displayed. The EUV level 14 is designed as a grazing incidence mirror. In the object plane 16 is an object in the form of a reticle 17 arranged, of which with the EUV illumination light 3 an illumination area is illuminated in the form of a lighting field, which is illuminated with an object field 18 a downstream projection optics 19 the projection exposure system 1 coincides. The object field illumination channels are in the object field 18 superimposed. The EUV lighting light 3 is from the reticle 17 reflected.

The projection optics 19 forms the object field 18 in the object plane 16 in a picture field 20 in an image plane 21 from. In this picture plane 21 is a wafer 22 which carries a photosensitive layer during projection exposure with the projection exposure apparatus 1 is exposed. In the projection exposure, both the reticle 17 as well as the wafer 22 scanned synchronized in y-direction. The projection exposure machine 1 is designed as a scanner. The scanning direction y is also referred to below as the object displacement direction.

The field facet mirror 6 , the second faceted element 10 and the mirrors 12 to 14 the transmission optics 15 are components of a lighting system 23 the projection exposure system 1 , In a variant of the illumination optics 23 in the 1 not shown, the transmission optics 15 also partially or completely omitted, so that between the second faceted element 10 and the object field 18 no further EUV level, exactly one other EUV mirror or even exactly two further EUV mirrors can be arranged.

Together with the projection optics 19 forms the illumination optics 23 an optical system of the projection exposure apparatus 1 ,

Based on 5 is a method for assigning a second facet in the following 11 of the second faceted element 10 the illumination optics 23 the projection exposure system 1 to each one of the areas 7 on the first faceted element 6 the illumination optics 23 for defining in each case an illumination channel for a sub-beam of the illumination light 3 described. The guided over the illumination channel sub-beam of the illumination light 3 is starting from the light source 2 at the assigned area 7 on the first faceted element 6 and then at the second facet associated with the method 11 of the second faceted element 10 , if necessary via the transmission optics 15 , to the object field 18 reflected.

In an identification step 26 In the context of the assignment process, at least one illumination parameter is initially identified, with which illumination of the object field 18 can be characterized. For example, a uniformity, a telecentricity or an ellipticity of the illumination can be used as the illumination parameter. Definitions of these illumination parameters uniformity, telecentricity and ellipticity can be found in the WO 2009/132756 A1 and in the DE 10 2006 059 024 A1 , Alternatively, an achievable by the illumination structure resolution in the image of the illuminated object field 18 be used in an image field as lighting parameters. Instead of the telecentricity or the ellipticity can be used as lighting parameters z. B. a variation of a line width of an imaged structure over the image field are used.

The illustrated feature size may be a critical dimension (CD). The object structure image size is the size of a distance value in the image plane of a typical reference structure, which is imaged into the image field with the aid of the projection optics. An example of this is the so-called "pitch", ie the distance between two adjacent lines in the image field. In the structural image size variation (ΔCD), when linear object structures are imaged, it may be the variation of a line width in which an intensity of the image light is above a threshold intensity required to develop a photosensitive layer on the substrate or wafer , This line width, ie the illustrated structure size, can be independent of a distance between two adjacent lines, ie independent of a pitch of the object structure as an example of the further object feature size, vary over a field height.

In the identification step 26 is first queried as the requirements for a lighting of the object field 18 for the respective exposure task. Depending on this exposure task, a particularly homogeneous intensity distribution over the object field 18 be desired. In this case, the uniformity is the one in the identification step 26 identified illumination parameters. Alternatively, for example, overlay requirements for multiple exposure of the wafer 22 with the projection exposure system 1 to be made manageable, to set a predetermined telecentric value. In this case, telecentricity becomes the illumination parameter in the identification step 26 identified. The same applies to cases in which a certain weighting of illumination angle distributions over the object field 18 is desired. In this case, the ellipticity is called the illumination of the object field 18 characterizing illumination parameter in the identification step 26 selected. As an illumination parameter, alternatively or additionally, the imagable line width and / or a depth of focus and / or a defocusing of the image of the regions 7 on the first faceted element 6 into the object plane 16 be used. Also a throughput of the projection exposure system 1 that is, the number of exposed wafers achievable in a given period of time 22 , can be used.

In a determination step 27 For example, in the assignment method, a dependency of the identified illumination parameter, or possibly a combination of identified illumination parameters, which may be a weighted combination, on design specification data of the optical parameters of the light source 2 and / or the illumination optics 23 certainly.

The design default data may be specification data of the optical parameters of the light source 2 or the illumination optics 23 act, ie intervals within which the corresponding quantities must lie. They may also be expected values for these optical parameters. With regard to the light source, optical parameters are, for example, the size of a luminous spot or luminous volume of the light source, a distribution of a radiation intensity over this luminous spot or the luminous volume, a radiation direction characteristic of the light source, a useful wavelength including a useful wavelength distribution, a useful light intensity radiated within a useful aperture angle , an optionally existing pulse frequency of the light source, an optionally present pulse duration of the light source and information on the temporal behavior of a usable light source intensity including a temporal behavior of the emission intensity itself and a temporal behavior of a radiation direction stability.

Alternatively or additionally, in the allocation process in a further determination step 28 a dependence of the identified illumination parameter of item decrease data of the optical parameters of the light source 2 and / or the illumination optics 23 be determined. Item acceptance data showing the lighting optics 23 are the optical parameters of the components of the illumination optics 23 So the arrangement of the lighting optics 23 constituent components including the radii of curvature, the reflectivities, the distances of the components to one another and the relative position of the regions 7 on the first faceted element 6 to each other and the second facets 11 to each other. For the tiltable areas 7 on the first faceted element 6 The manufacturing data include the location of centers of the respective facet reflection angle and a spatial characterization of each of the micromirrors 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 reachable tilt positions. Item acceptance data may be determined once a particular component has been manufactured. These data are thus individual to that particular component, as opposed to design default data, which is identical for each component of the same type.

To the optical parameters of the illumination optics 23 may also include information on temporal drifts, so for example information on the thermal dependence of a behavior of the illumination optics 23 , To the optical parameters of the illumination optics 23 Also include reflectivity data of the respective mirror surfaces for given angles of incidence.

Also data of the projection optics 19 may belong to the optical parameters, that is information about the shape of the illumination bundle leading surfaces of the components of the projection optics 19 , in particular specular reflection surface forms, the distances between the components of the projection optics to each other and information on any existing coatings on the components of the projection optics 19 to optimize their throughput.

The design default data is that data specified independently of the actual projection exposure equipment actually produced. The item acceptance data is data relating to a particular actually manufactured component and thus to the particular one Projection exposure system in which this particular component is installed.

After completion of the projection exposure system or a larger assembly, such as the illumination optics 23 Also, optical parameters of this individual assembly and / or projection exposure equipment may be determined, which are then overall system acceptance data determined at the point of manufacture.

In an alternative and additional determination step 28a Thus, a dependence of the identified illumination parameter on the overall system acceptance data of the optical parameters at the place of manufacture of the light source 2 and / or the illumination optics 23 be determined. Overall system acceptance data relate in particular to assemblies which are transported in their entirety but separately from other assemblies to the operating site.

After installation and adjustment of the projection exposure system at the place of operation, further determinations of optical parameters can be carried out. These are called calibration data. In a further or alternative additional determination step 28b becomes a dependence of the identified illumination parameter on the calibration data of the optical parameters of the light source 2 and / or the illumination optics 23 at the place of installation of the projection exposure apparatus 1 certainly.

During operation of the projection exposure apparatus, optical parameters can be determined with the aid of at least one measuring device in or on the projection exposure apparatus, which are referred to here as online measured data. In a further alternative or additional determination step 29 becomes a dependence of the identified illumination parameter on the online measurement data of the optical parameters of the light source 2 and / or the illumination optics 23 certainly.

The later in the chain of determining operations described herein, the value of an optical parameter is determined to be more consistent with the value of the optical parameter during operation of the projection exposure apparatus, and thus with the value of the optical parameter used to produce a microlithographic Structure is relevant. However, certain optical parameters are more easily determinable at the beginning of the chain described here.

In the determination step 27 certain design default data become the optical parameters of the light source 2 , the lighting optics 23 or the projection optics 19 given and the dependence of the in step 26 The illumination parameters identified by this design specification data are checked.

In the alternative or additionally performed further determination step 28 becomes a dependency of the respectively identified illumination parameter on the individual part acceptance data of the optical parameters of the light source 2 and / or the illumination optics 23 checked. The determination step 28 requires an initial measurement of the components that make up a light source 2 or an illumination optics 23 will be built. The individual part acceptance data of the optical parameters are those values of the optical parameters of the concretely manufactured components of the projection exposure apparatus 1 , These are therefore those specifications of the specific components of the light source 2 and the concrete lighting optics 23 which deviate from the design specification data, that is to say the values of the optical parameters, which as a rule indicate value ranges, required by the optical design in comparison to the fact that concrete individual case data are now available. Insofar as the design specification data are available as area specifications, the individual parts acceptance data now represent concrete data within these areas.

In the further determination step 28a becomes a dependence of the respectively identified illumination parameter of total system acceptance data of the optical parameters of the light source 2 and / or the illumination optics 23 checked. The determination step 28a sets an initial measurement of the light source 2 or the illumination optics 23 after mounting the projection exposure machine 1 at the place of manufacture. The overall system acceptance of the optical parameters are those values of the optical parameters of the specifically produced projection exposure apparatus 1 , These are therefore those specifications of the specific light source 2 and the concrete lighting optics 23 that deviate from the design specifications, that is, the specifications given by the manufacturer, which generally indicate ranges of values, that concrete individual case data is now available. Insofar as the design specification data exist as area specifications, the overall system acceptance data now represent concrete data within these areas.

In the further determination step 28b is a dependence of the respectively identified illumination parameter from the calibration data of the optical parameters of the light source 2 and / or the illumination optics 23 checked. The determination step 28b sets an initial measurement of the light source 2 or the illumination optics 23 after mounting the projection exposure machine 1 at the Operating location ahead. The calibration data of the optical parameters are those values of the optical parameters of the specifically produced projection exposure apparatus 1 which may differ from those measured at the place of manufacture due to transport and readjustment. These are therefore those specifications of the specific light source 2 and the concrete lighting optics 23 that deviate from the design specifications, that is, the specifications given by the manufacturer, which generally indicate ranges of values, that concrete individual case data is now available. As far as the design specification data is available as area data, the calibration data now represent concrete data within these areas.

The optical parameters include the reflectivities of the mirror surfaces of the illumination optics 23 working on a concrete projection exposure machine 1 , ie the angles of incidence given there, are present. With regard to checking the dependence of the identified illumination parameter on its optical parameters, the determination steps correspond 28 . 28a and 28b the determination step 27 ,

In the further determination step 29 becomes a dependence of the identified illumination parameter on the online measurement data of the optical parameters of the light source 2 , the lighting optics 23 or the projection optics 19 checked. The online measurement data of the optical parameters are actual measured values which are displayed on the projection exposure apparatus 1 were measured. The verification step 29 So sets a current measurement of the projection exposure system 1 ahead. It is thus a day form of the projection exposure system 1 determines and it is, for example, the useful light intensity of the light source 2 , which is currently available, measured and also determines the useful light wavelength. In the illumination optics 23 For example, a throughput of the illumination optics 23 certainly. Such a throughput determination can be a reflectivity measurement of all the reflective surfaces of the illumination optics involved 23 include. Accordingly, online measurement data for the projection optics 19 be collected.

In a default step 30 will after the identification step 26 and performing at least one of the determining steps 27 . 28 . 28a . 28b and 29 depending on the identified lighting parameter and depending on the result of the in steps 27 . 28 . 28a . 28b and 29 determined dependencies of the identified illumination parameter an illumination channel-dependent evaluation function for the evaluation of a possible illumination channel. The result of the step 30 predetermined evaluation function thus correlates with that in the step 26 identified illumination parameters and their dependencies on the design specification data of the optical parameters of the light source, the illumination optics or the projection optics, the item acceptance data of the optical parameters of the light source, the illumination optics or the projection optics, the overall system acceptance data of the optical parameters of the light source, the illumination optics or the projection optics, the calibration data of the optical parameters of the light source, the illumination optics or the projection optics and of the online measurement data of the light source, the illumination optics or the projection optics. The evaluation function thus allows the evaluation of a possible combination of one of areas 7 on the first faceted element 6 with one of the second facets 11 for guiding a partial bundle of the illumination light 3 over the illumination channel defined thereby.

• – eine gegebenenfalls inhomogene Ausleuchtung der Bereiche 7 auf dem ersten facettierten Element 6 mit dem Beleuchtungslicht 3; in die Bewertungsfunktion kann dann eine Abweichung einer Intensität einer Ausleuchtung der Bereiche 7 auf dem ersten facettierten Element 6 mit dem Beleuchtungslicht 3 von einer homogenen Ausleuchtungsintensität für den jeweils betrachteten Ausleuchtungskanal eingehen;
• – eine vom Einfallswinkel des Beleuchtungslichts 3 auf die Mikrospiegel 6a der Bereiche 7 auf dem ersten facettierten Element 6 und der zweiten Facetten 11 des zweiten facettierten Elements 10 des zu bewertenden Ausleuchtungskanals abhängige Reflektivität der Mikrospiegel 6a der Bereiche 7 auf dem ersten facettierten Element 6 und der zweiten Facetten 11 des zweiten facettierten Elements 10 für das Beleuchtungslicht 3; in die Bewertungsfunktion kann also ein Einfallswinkel des jeweiligen Teilbündels des Beleuchtungslichts 3 auf die Mikrospiegel 6a der Bereiche 7 auf dem ersten facettierten Element 6 und der zweiten Facetten 11 des zweiten facettierten Elements 10 des betrachteten Ausleuchtungskanals eingehen;
• – eine vom zu bewertenden Ausleuchtungskanal abhängige Reflektivität der den beiden facettierten Elementen 6, 10 nachfolgenden Übertragungsoptik 15;
• – ein Spotbild der Bereiche 7 auf dem ersten facettierten Element 6 beziehungsweise ein lokaler geometrischer Pupillenfehler, wobei als Spotbild die Form und Intensitätsverteilung des längs genau eines Ausleuchtungskanals geführten Teilbündels genau auf der zweiten Facette bezeichnet wird, was weiter unter noch erläutert wird.
• – eine Parametrisierung einer ausleuchtungskanalabhängigen Verzeichnung der Abbildung der Bereiche 7 auf dem ersten facettierten Element 6 in die Objektebene 16, beispielsweise durch den Spiegel 14 in streifenden Einfall;
• – eine ausleuchtungskanalabhängige Variation einer Strukturbildgröße, also beispielsweise eine Variation einer abgebildeten Linienbreite. Diese Linienbreite-Variation kann für verschiedene Verläufe der abzubildenden Linien unterschiedlich ausgewertet werden. Es kann beispielsweise erfasst werden, wie groß der Unterschied zwischen der abgebildeten Linienbreite horizontal und vertikal verlaufender Strukturlinien ist, die objektseitig den gleichen Abstand zueinander haben. Alternativ oder zusätzlich kann die Strukturgrößen-, also beispielsweise Linienbreiten-Variation von diagonal verlaufenden, abzubildenden Objektlinien als Bewertungsfunktion oder als Teil von dieser betrachtet werden;
• – ein ausleuchtungskanalabhängiger Effekt der Lichtquelle 2, beispielsweise eine ausleuchtungskanalabhängige Inhomogenität einer Emission der Lichtquelle 2, hervorgerufen beispielsweise durch eine variable Abschattung, durch eine nicht perfekte Abbildung der Bereiche 7 auf dem ersten facettierten Element 6 in das Objektfeld 18 oder durch einen variablen Emissionsschwerpunkt der Lichtquelle 2, abhängig von deren Emissionsrichtung;
• – eine Fokusstabilität des Projektionsobjektivs 19, also Informationen darüber, ob und wie sich eine Lage der Feldebene 21 relativ zur Lage der Objektebene 16 ändert und/oder welchen Einfluss eine Lagevariation des Retikels 17 zur Objektebene 16 auf eine Bildlage in der Bildebene 21 hat;
• – Informationen zu einem Höhenprofil einer Schichtstruktur auf den Wafer 22, insbesondere Informationen zu einem Höhenprofil von in einem früheren Belichtungsschritt bereits belichteten Schichten auf den Wafer 22. Diese Daten können Teil der Kalibrierdaten sein. Aus diesen Höhenprofil-Daten können im Rahmen des Vorgabeschritts 30 und auch im Rahmen eines nachfolgend noch erläuterten, nachgeschalteten Vorgabeschritts Angaben über eine erforderliche Tiefenschärfe der Projektionsoptik 19 abgeleitet werden.
• – Informationen zu einer Lackbeschichtung auf dem Wafer 22, insbesondere Informationen zur notwendigen Belichtungsdosis zur Lackentwicklung und Informationen zum Entwicklungs-Ansprechverhalten des Lacks. Hieraus lassen sich z. B. im Vorgabeschritt 30 Angaben über eine einzuhaltende Belichtungsdosis des Wafers 22, also Informationen darüber, welche Dosis des Beleuchtungslichts 3 auf einen zu belichtenden Bereich des Wafers 22 treffen soll, ableiten.

In the default step 30 given evaluation function can enter into the following characteristics of the respective illumination channel to be evaluated:

• - an optionally inhomogeneous illumination of the areas 7 on the first faceted element 6 with the illumination light 3 ; in the evaluation function can then a deviation of an intensity of illumination of the areas 7 on the first faceted element 6 with the illumination light 3 of a homogeneous illumination intensity for the considered illumination channel;
• - one of the angle of incidence of the illumination light 3 on the micromirrors 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 the reflectivity of the micromirrors depending on the illumination channel to be evaluated 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 for the illumination light 3 ; in the evaluation function can therefore an angle of incidence of the respective sub-beam of the illumination light 3 on the micromirrors 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 enter the considered illumination channel;
• A reflectivity of the two faceted elements dependent on the illumination channel to be evaluated 6 . 10 subsequent transmission optics 15 ;
• - a spot picture of the areas 7 on the first faceted element 6 or a local geometric pupil error, wherein the form and intensity distribution of the longitudinally exactly one illumination channel guided partial bundle exactly on the second facet is referred to as a spot image, which will be explained further below.
• - A parameterization of an illumination channel dependent distortion of the mapping of the areas 7 on the first faceted element 6 into the object plane 16 for example through the mirror 14 in grazing incidence;
• An illumination channel-dependent variation of a structure image size, that is, for example, a variation of an imaged line width. This line width variation can be evaluated differently for different courses of the lines to be imaged. For example, it can be detected how large the difference between the imaged line width of horizontal and vertical structure lines, which have the same distance from each other on the object side. Alternatively or additionally, the structure size, ie, for example, line width variation of diagonally extending object lines to be imaged can be considered as a valuation function or as part of it;
• - An illumination channel dependent effect of the light source 2 , For example, an illumination channel dependent inhomogeneity of an emission of the light source 2 , caused for example by a variable shading, by a non-perfect mapping of the areas 7 on the first faceted element 6 in the object field 18 or by a variable emission centroid of the light source 2 , depending on their emission direction;
• - Focus stability of the projection lens 19 That is, information on whether and how a situation at the field level 21 relative to the location of the object plane 16 changes and / or what influence a position variation of the reticle 17 to the object level 16 on an image layer in the image plane 21 Has;
• - Information about a height profile of a layer structure on the wafer 22 in particular information on a height profile of layers already exposed in an earlier exposure step on the wafer 22 , This data can be part of the calibration data. From this height profile data can be used in the context of the default step 30 and also in the context of a subsequently explained subsequent step, information about a required depth of focus of the projection optics 19 be derived.
• - Information about a paint coating on the wafer 22 , in particular information on the necessary exposure dose for paint development and information on the development response of the paint. From this can be z. B. in the default step 30 Information on the exposure dose of the wafer to be observed 22 , that is information about what dose of illumination light 3 on a region of the wafer to be exposed 22 should meet, deduce.

These characteristics arise as dependencies of the respective lighting parameter on design specification data of the optical parameters of the light source 2 , the lighting optics 23 or the projection optics 19 In addition, the respective illumination parameter may depend on the individual data of the optical parameters of the light source 2 , the lighting optics 23 or the projection optics 19 , depending on the total system acceptance data, depending on the calibration data as well as on the online measurement data of the optical parameters of the light source 2 , the lighting optics 23 or the projection optics 19 be.

A not perfect illustration of the areas 7 on the first faceted element 6 in the object field 18 In addition to aberrations introduced via the imaging optics, it may also be due to the fact that the light source 2 is not punctiform. Ultimately, therefore, there is always a washed-out at the edges image of the areas 7 on the first faceted element 6 in the object plane 16 , The quality of this figure depends on the assignment of the areas 7 on the first faceted element 6 and the second facets 11 to the respective illumination channel. Certain mappings lead to better quality mappings than others. In addition, see in a non-point or spherical light source different of the areas 7 on the first faceted element 6 the light source 2 in different form.

Error contributions due to distortion effects of a transmission optics between the field facet mirror and the object plane, which can be parameterized via the evaluation function, are discussed as examples in FIG WO 2010/037 453 A1 , Pupil effects, which can also be illumination channel-dependent and can go into the evaluation function, are for example in the DE 10 2006 059 024 A explained.

The evaluation function may include several of the lighting parameters that may be weighted differently in the evaluation function.

In a further specification step 31 In the context of the allocation procedure, a valuation target range of valuation parameters is given which represents the result of the valuation function. The evaluation function therefore includes the pairing belonging to an illumination channel to be evaluated (areas 7 on the first faceted element 6 , second facet) and, depending on this, the evaluation parameter is determined by means of the evaluation function. In the default step 31 A target range of this rating is specified, which must be reached in order for a configuration of illumination channels to be evaluated to come into a further selection.

In an optional calculation step 32 is now in the context of the allocation process the Evaluation variable for at least selected of the possible illumination channels calculated by inserting into the evaluation function.

In an optionally optional pre-selection step 33 become those illumination channels, ie those pairings of areas 7 on the first faceted element 6 to second facets 11 , preselected, in step 32 calculated evaluation variable in the default step 31 predetermined rating target range.

In an optional identification step 34 of the assignment method, at least one disturbance variable is identified, which illuminates the object field 18 through the illumination optics 23 or by a the illumination optics 23 and the light source 2 affecting lighting system influenced.

As a disturbance, for example, a variation of a positioning of the light source 2 in x, y or z direction. Also a variation of a source size of the light source 2 can be used as a disturbance variable. Also a change of a type of light source 2 , for example between an LPP source and a GDPP source, can be used as a disturbance. Furthermore, a simulated life-time effect, for example with respect to an age of reflective layers, of the illumination light can be used as a disturbance variable 3 leading components, are used. Also, an increase in stray light as a result of simulated aging of the illumination optics 23 can be used as a disturbance variable. As a disturbance can continue to act on the second facets 11 of the illumination channel to be evaluated by illuminating light not used for illumination 3 and thus an additional heating of the second facet 11 be used.

After the disturbance identification step 34 is in a further optional identification step 35 a dependence of the evaluation function of the at least one identified disturbance identified.

In an optional variation step 36 The identified disturbance variable for the preselected illumination channels is then varied within a predefined disturbance variable range of variation and the resulting variation of the evaluation variable via the evaluation function and that in the identification step 35 identified dependence calculated.

In a selection step concluding the assignment process 37 those illumination channels are selected whose varied evaluation value remains within the entire range of variation within the evaluation target range.

The assignment procedure with the steps 26 to 37 is repeated until a predetermined number of areas 7 on the first faceted element 6 a still free second facet 11 of the second faceted element 10 assigned. The result of the assignment process may also be a plurality of assignments of the areas 7 on the first faceted element 6 to each other second facets 11 provided all of these assignments meet the evaluation criteria within the steps 27 to 34 of the allocation procedure.

In a variant of the assignment method, it is ensured that the assignment of the second facets 11 to the sets of the second facets, which in particular tilt-dependent on exactly one area 7 on the first faceted element 6 can be acted upon with an illumination light sub-beam, so each this exactly one area 7 on the first faceted element 6 are assigned such that desired groups of second facets 11 can be acted upon at the same time with illumination light. This will be discussed later.

In a variant of the assignment method, input values, in addition to the setpoint values of the design specification data, the actual values of the design specification data and the calibration data, may also be entered as user input.

The assignment method gives as the output data the to-be-controlled tilt angles of the second facets 11 out. These tilt angles are then at the second faceted element 10 either manually or actorically specified. For this purpose, the individual second facets 11 be tilted via individually controllable actuators. A realization of the second faceted element 10 As MEMS mirror array with individually aktorisch tiltable micromirrors corresponds in their effect so individually controllable actuators.

In the assignment process can also about the illumination optics 23 Preset lighting settings, ie the illumination angle distribution for the reticle 17 in the object field 18 received. In this case, based on the result of the selection step 37 now an adjustment of the tilt illumination positions of the areas 7 on the first faceted element 6 and a corresponding adjustment of the second facets assigned via the selected illumination channels 11 , In this variant of the assignment method, in which a lighting setting is also set, the design specification data, the individual part acceptance data, the overall system acceptance data, the calibration data and / or the online measurement data are more optical in the assignment process as input data Parameters as well as user data, namely the lighting setting to be selected. Output data of the allocation method are the tilt angles of the second facets 11 and the respective tilting position of the areas to be set 7 on the first faceted element 6 ,

Optionally, the output data of the assignment method may also include a data record that characterizes a set actual illumination setting. This can then be compared with the user request, that is to say, the desired lighting setting to be specified.

Alternatively or additionally, after completion of the assignment process, a data record can also be output which is based on the result of the selection step 37 , each on the specification of the areas 7 on the first faceted element 6 and that about the respective tilt positions of the associated micromirrors 6a associated second facets 11 adjustable lighting settings characterized.

The characterization of the illumination setting may include information about the expected intensity that reaches each object field point from each illumination direction.

The selection of the illumination channels via the assignment method can use a simulated annealing algorithm. It starts with a certain illumination channel and in the variation step 33 the disturbance varies and the resulting variation of the evaluation variable is calculated. In the following, a lighting channel, which is used initially, can be used with regard to the guidance of the partial bundle of the illumination light 3 only slightly different further illumination channel are selected for evaluation, in which, for example, a slight modification of an assignment of the area 7 on the first faceted element 6 to the second facet 11 of the second faceted element 10 or an assignment of this area 7 to an adjacent second facet 11 is made. Now again the variation step 36 for all illumination channels that result then performed. The change made is accepted provided that the evaluation criteria of the allocation procedure are met. Based on such change steps, the evaluation quantity is calculated taking into account the disturbance variable variation by successive application of the variation step 36 optimized.

The assignment of the individual areas 7 on the first faceted element 6 to the individual second facets 11 Corresponding illumination channels at the beginning of the implementation of the assignment method are also referred to below as a start assignment or as an output assignment.

When selecting a start assignment of all illumination channels at the beginning of the assignment process or after specifying a modification step, symmetry considerations can be incorporated. For example, the boot assignment may be pairs of ranges 7 on the first faceted element 6 with mutually complementary intensity profile of an exposure of the areas on the first faceted element 6 through the light source 2 consider. Such pairs of areas 7 on the first faceted element 6 can neighboring second facets 11 apply. The complementary field profiles then compensate each other when superimposing the field facet images in the object field 18 , leaving a field dependency on the object field 18 can be minimized. Changes in the allocations of the illumination channels in the context of the search for an optimum of the evaluation variable are then carried out only in such a way that a corresponding pairing of facets with complementary field profiles is maintained. The disturbance variation ensures that even with changes, for example, the light source 2 the desired complementarity is maintained.

A start assignment of the illumination channels, which is optimized via the assignment method, can also start from a point-symmetrical arrangement of illumination channels, in which thus assigned illumination channels by rotation by a predetermined angle φ about a center of support plates of the field facet mirror 6 on the one hand and the second faceted element 10 on the other hand merge into each other. Again, a change in the assignment is performed so that the symmetry is maintained. The point symmetry thus represents a parameter that enters into the evaluation function.

For example, the start map may be in polar coordinates rotated by 90 ° positions of areas 7 on the first faceted element 6 , the same intensity profile of exposure to the light source 2 and their associated second facets 11 in polar coordinates at 90 ° to each other twisted in the pupil are arranged have. There can be two such areas each 7 on the first faceted element 6 are present in the start assignment whose associated second facets are arranged in polar coordinates at 90 ° to each other twisted in the pupil. Another mapping strategy that can be used as a start mapping and where the areas 7 on the first faceted element 6 with the same intensity gradient four second facets 11 are assigned in polar coordinates by 90 ° are arranged twisted against each other, is in the DE 10 2006 036 064 A1 described.

A start assignment can be the mirror symmetry of the illumination optics 23 to 1 with regard to the local drawing plane, ie the meridional plane. For alternative designs of lighting optics 23 which are at least approximately also mirror-symmetric with respect to further planes, for example in a design of the illumination optics according to the DE 103 29 141 A1 , this corresponding additional mirror symmetry can also be taken into account when specifying an output channel assignment.

Further examples of pairwise assignments which can be chosen for an output assignment of the illumination channels before the start of the assignment method are described, for example, in US Pat WO 2009/132756 A1 ,

Alternatively, an assignment of the areas 7 on the first faceted element 6 to second facets 11 be designed at the beginning of the assignment process so that neighboring of the areas 7 on the first faceted element 6 non-adjacent second facets 11 that is, by a given number of additional second facets 11 separate second facets 11 illuminate. Such a start assignment minimizes scattered light, which can occur when illumination channels have an overall closely adjacent course, so that illumination light guided along the one illumination channel undesirably scatters into the other illumination channel. The scattered light criterion can therefore also be a criterion that enters into the evaluation function.

Further criteria which are associated with the selection of a suitable output allocation of the illumination channels or with the specification of a strategy for changing the channel assignment in the context of, for example, a simulated annealing optimization method are a minimization of the angles of incidence on the individual micromirrors 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 or a minimization of a switching stroke in the case of the use of displaceable between at least two illumination tilt positions micromirrors 6a the areas 7 on the first faceted element 6 and the second facets 11 of the second faceted element 10 ,

When specifying an output assignment of the illumination channels at the beginning of the assignment process, the areas 7 on the first faceted element 6 that is the edge of the area on which the areas 7 on the first faceted element 6 are arranged, for example, the edge of the carrier plate 24 , are adjacent, to be particularly taken into account. For these marginal areas 7 on the first faceted element 6 can select the assigned second facets allowed in the start map 11 for example, by specifying a list of permitted second facets 11 be restricted. This selection can be made such that a picture of the marginal areas 7 on the first faceted element 6 through the second facets 11 and the subsequent transmission optics 15 no unwanted aberrations, in particular no unwanted rotation or displacement learns.

Insofar as set values for presettable lighting settings are included in the assignment method, a subsequent optimization step for the illumination channel assignment can be carried out by comparing the at least one desired illumination setting with actual illumination settings resulting from the illumination channel assignment found , During post-processing, the illumination channel assignment found is again varied with the aim of further reducing any desired / actual deviations in the illumination settings.

To prepare for the default step 30 for the evaluation function, a position specification of the second facets 11 respectively. This happens in the cases where the second faceted elements 10 is designed so that the second facets 11 are variable in their position and / or size and / or number. This is the case, for example, when the second facets 11 are formed as individual mirror groups of a MEMS mirror array.

As far as it is possible to specify a position and / or size and / or number of the second facets, this may take into account a size of a luminous volume of the light source 2 , especially at the location of the Zwischenfokusebene 5 , be made. From this size of the luminous volume or the light spot of the light source 2 can be a necessary minimum size of the second facets 11 be derived.

Within the allocation process, it is possible to check to what extent the size of a light spot image, that is to say a secondary light source, on the respectively given second facets 11 depends on the specific assignment of the illumination channels. This is usually the case if, for example, due to different light paths of the illumination light sub-beams on the illumination channels different imaging qualities in the transmission of the Zwischenfokusebene 5 in the plane of arrangement of the second faceted element 10 result.

Depending on a found minimum size of the second facets then an arrangement of the second facets 11 on a support plate of the second faceted element 10 or an assignment of the individual mirrors of a MEMS mirror array of the second facets are made.

As far as in an embodiment of the second faceted element 10 As a MEMS mirror array, a size of the formed as a single mirror groups second facets results in a number of the second facets or to a number of over different areas 7 on the first faceted element 6 triggerable amounts of second facets greater than the number of regions 7 on the first faceted element 6 , can increase the effective number of areas 7 on the first faceted element 6 Predetermined of the areas 7 on the first faceted element 6 two second facets 11 be assigned, with the respective areas 7 on the first faceted element 6 , which may then also be implemented as individual mirror groups of a MEMS mirror array, the illumination light 3 on two different further facets 11 to distribute. About exactly one of the areas 7 on the first faceted element 6 can then have two second facets 11 be acted upon with the illumination light.

As far as the assignment of the individual mirror groups of the second faceted element 10 to second facets 11 shows that the number of resulting second facets 11 or the number of sets of second facets 11 less than the number of areas 7 on the first faceted element 6 , this is taken into account in the illumination channel assignment, for example by areas 7 on the first faceted element 6 disregarded by the light source 2 only be dimly lit.

• – annulares (ringförmiges) Beleuchtungssetting mit kleinen Beleuchtungswinkeln;
• – annulares Beleuchtungssetting mit mittelgroßen Beleuchtungswinkeln;
• – annulares Beleuchtungssetting mit großen Beleuchtungswinkeln;
• – x-Dipolsetting;
• – y-Dipolsetting;
• – Dipolsetting mit vorgegebenem Dipol-Drehwinkel um ein Pupillenzentrum, beispielsweise 45°;
• – Quadrupolsetting;
• – Hexapolsetting.

The illumination channel assignment can take into account user presets for lighting settings that are compatible with the projection exposure system 1 should be set. If corresponding user specifications are not available, standard lighting settings are used. Such standard lighting settings can be:

• - annular (annular) illumination setting with small illumination angles;
• - annular illumination setting with medium illumination angles;
• - annular illumination setting with large illumination angles;
• - x-dipole setting;
• - y-dipole setting;
• - Dipolsetting with a given dipole angle of rotation about a pupil center, for example 45 °;
• - quadrupole setting;
• - Hexapolsetting.

Corresponding standard illumination settings are known from the prior art, for example from the DE 10 2008 021 833 A1 ,

Alternatively or additionally, individual lighting settings can be used in accordance with user specifications. Prioritization, for example by using weighting factors, can be undertaken between the standard illumination settings and / or the user-dependent, ie customer-specific illumination settings.

At the selection step 37 are then given in the context of a start-assignment of the illumination channels first the respective lighting settings, ie arrangements or groups of the second facets 11 on the second faceted element 10 given on the basis of different areas 7 on the first faceted element 6 the illumination light 3 can be distracted. The second facets 11 are arranged according to the particular set of lighting settings. Subsequently, when selecting the start assignment, an assignment of the areas 7 on the first faceted element 6 7 to the second facets 11 with appropriate specification of arrangements of sets of the second facets 11 performed such that in each group second facets 11 (second facets 11 , the different areas 7 on the first faceted element 6 assigned to the specification of a specific lighting setting) exclusively second facets 11 different sets of second facets (second facets 11 , the different tilt positions of the same areas 7 on the first faceted element 6 are assigned) are arranged.

Also the areas 7 on the first faceted element 6 are given in terms of their location and / or size and / or number, as described above with reference to the second facets 11 has already been explained. This is possible in particular during the start selection.

A necessary size of the respective areas 7 on the first faceted element 6 can be dependent on the illumination channel as an enlargement scale of a picture of the areas 7 on the first faceted element 6 in the object field 18 depending on the precise guidance of the illumination channel in the illumination optics 23 is. This can be done by means of post-processing in an optimization of the selection step 37 be considered.

Here are the areas 7 on the first faceted element 6 the selected one Illumination channel assignments still laterally shifted and / or adjusted in size.

Also a radius of curvature of the areas 7 on the first faceted element 6 can be customized, as in the US 2011/0001947 A1 is described.

To determine a size specification of the respective areas 7 on the first faceted element 6 can be a back projection of the object field 18 about the respectively assigned second facets 11 in an assembly plane of the first faceted element 6 in the range of sizes to be determined areas 7 on the first faceted element 6 respectively. A standard size of the areas 7 on the first faceted element 6 can be a bit bigger, z. For example, a few percent larger than the size of the areas 7 on the first faceted element 6 that results from such a back projection. This contributes to an effective reduction of a facet projection in tilting the areas 7 on the first faceted element 6 Invoice and any resulting shading effects between adjacent areas 7 on the first faceted element 6 Bill. It can be beneficial to the size of the areas 7 on the first faceted element 6 along the object displacement direction y to select something smaller than according to the back projection, while transverse to an object displacement direction y, ie in the x direction, the size of the areas 7 on the first faceted element 6 slightly larger than that chosen according to the rear projection.

If, after a sizing of the areas 7 on the first faceted element 6 shows that the number of areas 7 on the first faceted element 6 of the particular size on the first faceted element 6 smaller than the number on the second faceted element 10 available second facets 11 , each other can overlap areas 7 on the first faceted element 6 be used, with one and the same individual mirror of the MEMS mirror array then z. B. is assigned two individual mirror groups, each one of the areas 7 on the first faceted element 6 build up. Alternatively, the MEMS areas 7 on the first faceted element 6 be scaled down in their y-dimension, so that they no longer have a full y-dimension of the object field 18 illuminate.

The in the default step 30 The evaluation function to be specified can be the weighted sum of an illumination intensity of the second facets 11 within at least one environment of the second facets 11 contain. In this case, with an illumination channel allocation currently to be evaluated, it is considered with which intensity of the illumination light 3 those second facets 11 be illuminated, that of a respective considered second facet 11 are adjacent within a given environment. In the evaluation function can enter several predetermined environmental variables. Depending on the neighborhood ratio, the illumination intensities of the second facets present within the environment can 11 weighted for their part.

In the start selection, it can be considered that only certain lighting settings are actually used in the projection exposure. These selected lighting settings then enter the rating function.

Channel-dependent reflectivities of the optical components, that between the second facet, can enter into the evaluation function 11 of the considered illumination channel and the object field 18 lie. In the case of the illumination optics 23 these are the mirrors 12 to 14 ,

In the evaluation function, the shape of a source image on the second facet 11 of the considered illumination channel. In the evaluation function, a magnification of a map of the areas 7 on the first faceted element 6 of the considered illumination channel into the object field 18 received.

In the evaluation function can be a picture of the area 7 on the first faceted element 6 of the considered illumination channel into the object field 18 to enter descriptive size. This includes, in particular, an aberration, for example a distortion, an image tilt, an image shading, a filing of an image of an area 7 on the first faceted element 6 from the object plane 16 , a deposit (defocusing) of the second facet 11 of the considered illumination channel of an entrance pupil of the projection optics 19 or one of these entrance pupil corresponding, in particular conjugate plane or a depth of field of the image.

In the evaluation function, a symmetry variable, a scattered light size, can be a line width to be imaged in the object field 18 arranged object or may be a position of the area 7 on the first faceted element 6 of the considered illumination channel within a far field of the light source 2 at the location of the field facet mirror 6 received.

Due to the fact that the picture of the light source 2 or the intermediate focus 5 on the second facet 11 is not perfect, so results depending on the considered place on the object field 18 a slightly different lighting direction, starting from the considered second facet 11 ,

Spots on the second facets 11 can from different points on the object field 18 seen differently on the second facet 11 lie. The respective spot picture on the object field 18 can by geometrical analysis of the optical design of the illumination optics 23 be accurately determined. Each assignment of a specific area 7 on the first faceted element 6 to a specific second facet 11 leads to a different spot image variation, so that the spot image is a characteristic of the default step 27 suitable for the assignment procedure.

As a result of the allocation process, an allocation of the areas 7 on the first faceted element 6 to the second facets 11 result in an inhomogeneous illumination of the areas 7 on the first faceted element 6 is used to compensate for the shift of the spot image. The geometric shift of an illumination angle distribution resulting from superposition of the spot images on all second facets 11 can be achieved by adjusting the intensities of each EUV sub-package accordingly 48 , which are guided over the illumination channels, be compensated. This is comparable to a telecentric compensation, since the telecentricity value also includes a product from the direction of the individual partial beams and their intensity or a product of distance and intensity.

• – Verteilung der Beleuchtungswinkel, die diesen Feldpunkt ausleuchten,
• – Beleuchtungsintensitäten bei den einzelnen Beleuchtungswinkeln.

During the assignment, a data record can be calculated, which corresponds to each field point of the object field 18 and thus also the image field 20 assign the following data:

• - Distribution of the illumination angles that illuminate this field point,
• - Illumination intensities at the individual illumination angles.

Before the assignment process described above, the object structure, ie the structure of the reticle to be imaged, can still be used 17 to be characterized. This characterization can enter the evaluation function. This object structure characterization step is in the 6 as a step 46 before the identification step 26 specified.

The characterization of the object structure can also be included in the selection of at least one lighting setting to be specified. This, in turn, influences the implementation of the assignment method, as already explained above. This lighting setting selection step is in 6 as a step 47 specified.

The specification of the tilt angle of the micromirrors 6a the areas 7 on the first faceted element 6 and the tilt angle of the second facets 11 can by a corresponding control of tilt angle actuators via a central control device of the illumination optics 23 respectively.

The assignment procedure takes place on an assignment computer.

The central control device is in signal connection with the allocation computer.

QUOTES INCLUDE IN THE DESCRIPTION

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

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• DE 102008021833 A1 [0105]

Claims (14)

Method for assigning a second facet ( 11 ) of a second faceted element in the beam path ( 10 ) an illumination optics ( 23 ; 40 ) of a projection exposure apparatus ( 1 ) to an area ( 7 ) on a first faceted element in the beam path ( 6 ) of the illumination optics ( 23 ; 40 ) for defining an illumination channel for a sub-beam ( 48 ) of illumination light ( 3 ), which, starting from a light source ( 2 ) at the area ( 7 ) on the first faceted element ( 6 ) and at the second facet ( 11 ) to one of the illumination optics ( 23 ; 40 ) illuminated object field ( 18 ), with the following steps a) to i), wherein at least one of the determination steps of the subsequent determination steps b) to f) is mandatory: a) Identification ( 26 ) of at least one illumination parameter with which illumination of the object field ( 18 ), b) determining ( 27 ) a dependence of the illumination parameter on design specification data of the optical parameters of the light source ( 2 ) and / or the illumination optics ( 23 ; 40 ), c) determining ( 28 ) a dependency of the illumination parameter on item acceptance data of the optical parameters of the light source ( 2 ) and / or the illumination optics ( 23 ; 40 ), d) determining ( 28a ) a dependence of the illumination parameter on total system acceptance data of the optical parameters at the location of the production of the light source ( 2 ) and / or the illumination optics ( 23 ; 40 ), e) determining ( 28b ) a dependence of the illumination parameter on calibration data of the optical parameters of the light source ( 2 ) and / or the illumination optics ( 23 ; 40 ) at the place of installation of the projection exposure apparatus, f) determining ( 29 ) a dependence of the illumination parameter on online measurement data of the optical parameters of the light source ( 2 ) and / or the illumination optics ( 23 ; 40 g) Predict ( 30 ) of an illumination channel-dependent evaluation function for evaluating a possible illumination channel group, that is to say a possible combination of exactly one area ( 7 ) on the first faceted element ( 6 ) with exactly one disjoint set of second facets ( 11 ) for guiding the sub-beam of the illumination light ( 3 ), depending on the selected illumination parameter, h) Predict ( 31 ) of a valuation target range of valuation items as a result of the valuation function, i) selecting ( 37 ) of those channels whose scoring size remains within the scoring target range. Method according to claim 1, characterized by predetermining an arrangement of the second facets ( 11 ) of the second faceted element ( 10 ) in selecting ( 37 ) of the illumination channels. Method according to one of claims 1 and 2, characterized in that for the weighting function a weighted sum of an illumination intensity of the second facets ( 11 ) within at least one environment around at least one selected second facet ( 11 ) is used. Method according to one of claims 1 to 3, characterized by the specification of radii of curvature for the second facets ( 11 ) of the second faceted element ( 10 ) to prepare the selection ( 37 ) of the illumination channels. Method according to one of claims 1 to 4, characterized by specifying a z-position of the second facets ( 11 ) relative to an assembly plane of the second facets ( 11 ) on a support plate of the second faceted element ( 10 ) to prepare the selection ( 37 ) of the illumination channels. Method according to one of claims 1 to 5, characterized by specifying a set of tilt angles of the second facets ( 11 ) resulting from the illumination channel selection ( 37 ). Method according to one of Claims 1 to 6, characterized by specifying a set of tilt angles of the regions ( 7 ) on the first faceted element ( 6 ) resulting from the illumination channel selection ( 37 ). Method according to one of Claims 1 to 7, characterized by the provision of a data set corresponding to each field point (x) of the object field ( 18 ) assigns the following data: - distribution of the illumination angles that illuminate this field point (x), - illumination intensities (I) at the respective illumination angles. Method according to one of Claims 1 to 8, characterized by the provision of a data record having the following content: quantities of the second facets as a result of the assignment method, tilts of tiltable regions 7 ) on the first faceted element ( 6 ), which depending on the tilt angle, a partial bundle ( 48 ) of the illumination light ( 3 ) to a given second facet ( 11 ), including the data on the amount of those second facets that exceed the tilt angles of exactly one area ( 7 ) on the first faceted element ( 6 ) can be acted upon with the sub-bundle, - for each possibility of tilting settings of the areas ( 7 ) on the first faceted element ( 6 ) the distribution of the illumination angles for each field point (x) illuminating this field point (x), - illumination intensities (I) at the respective illumination angles. Method for adjusting a lighting system to one having a projection system ( 1 ) to be imaged object structure, wherein the lighting system ( 1 ) a light source ( 2 ) and an illumination optics ( 23 ; 40 ), comprising the following steps: characterizing ( 46 ) of the object structure, - performing the assignment method according to one of claims 1 to 9, depending on the object structure to be specified. Method for tuning an illumination system to a projection exposure apparatus ( 1 ) to be imaged object structure, wherein the lighting system ( 1 ) a light source ( 2 ) and an illumination optics ( 23 ; 40 ), comprising the following steps: 47 ) of a presetting lighting setting, - performing the allocation method according to one of claims 1 to 9, depending on the lighting setting to be provided. Method for tuning an illumination system to a projection exposure apparatus ( 1 ) to be imaged object structure, wherein the illumination system to the light source ( 2 ) and an illumination optics ( 23 ; 40 ), comprising the following steps: characterizing ( 46 ) of the object structure, - Select ( 47 ) of a lighting setting to be provided, depending on the object structure characterization, - performing the assignment method according to one of claims 1 to 9, depending on the lighting setting to be specified. Data carrier with a computer program stored thereon for implementing the method according to one of Claims 1 to 12. Computer with a computer program implemented thereon for implementing the method according to one of Claims 1 to 12.

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