DE102015208571A1 - Illumination optics for EUV projection lithography - Google Patents

Abstract

An illumination optics for EUV projection lithography has a field facet mirror and a pupil facet mirror. Via a respective illumination channel, a respective useful illumination light partial bundle (16i) is guided between a light source and an object field via exactly one field facet and exactly one pupil facet (29). At least some pupil facets (29), which can be used as correction pupil facets, are arranged in the beam path of the illumination light sub-beam (16i) acting on them, so that an image of the light source arises at a location which is spaced along the illumination channel (16i) from the pupil facet (29) lies. Correction control means (32) for controlled displacement of at least some field facets usable as correction field facets which are in signal communication with the displacement actuators (31) are designed such that a correction displacement path for the correction field facets is so large, a respective correction illumination channel (16i) is trimmed on the edge side by the correction pupil facet (29) such that the illumination light partial bundle (16i) is not transferred completely from the correction pupil facet (29) into the object field. With the illumination optics, a method for predetermining a minimal illumination intensity of illumination light (16) via a transverse field coordinate (x) of an object field of the illumination optics (4) can be carried out.

Description

The invention relates to an illumination optical system for EUV projection lithography for illuminating an object field, in which an object to be imaged can be arranged, with illumination light. Furthermore, the invention relates to a lighting system with such illumination optics, an optical system with such illumination optics and a projection exposure apparatus with such an optical system. Furthermore, the invention relates to a method for specifying a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of illumination optics for projection lithography. Furthermore, the invention relates to a method for producing a microstructured or nanostructured component with such a projection exposure apparatus and to a microstructured or nanostructured component produced by such a method.

An illumination optics of the type mentioned is known from the US 2011/0001947 A1 , of the WO 2009/132756 A1 , of the WO 2009/100 856 A1 as well as from the US Pat. No. 6,438,199 B1 and the US Pat. No. 6,658,084 B2 ,

It is an object of the present invention to develop an illumination optical system of the type mentioned at the outset such that a flexible field-dependent correction of illumination parameters is ensured.

This object is achieved by an illumination optical system with the features specified in claim 1.

According to the invention, it has been recognized that a specific spacing of a light source image from the pupil facets impinged by the illumination light leads to a field-dependent spatial distribution of an illumination light impingement on the pupil facets, which can be used for illumination parameter correction purposes. The distance between the correction pupil facets and the light source image causes the correction pupil facets to form a light spot of the illumination light sub-beam which acts on them, which represents a convolution of a field facet edge contour with a source edge contour of the light source. Trimming the illumination light sub-beam as part of the correction results in illumination light being transferred from this correction pupil facet with different intensity to the object field, depending on the location on the object field. By a controlled displacement of the correction field facets, a field-dependent correction of an illumination angle distribution over the object field can be achieved. All field facets of the field facet mirror can represent correction field facets. All pupil facets of the pupil facet mirror can represent correction pupil facets.

The controlled displacement that may be brought about by the correction controller may be a controlled tilt. Accordingly, the correction actuators can be correction tilt actuators. The correction displacement path may be a correction tilt angle of the correction field facets that is so large in a correction tilt angle range that a respective correction illumination channel is trimmed from an edge of the correction pupil facet such that the illumination light sub-beam is not completely transferred from the correction pupil facet to the object field. In addition to a tilt, the displacement may also be a translation or the targeted production of a defocus.

For flexible specification of illumination settings, the number of pupil facets can be greater than the number of field facets, it being possible to switch between different pupil facets acted on via these field facets via actuation of corresponding tilt actuators and corresponding tilting of the field facets. Despite this possibility of change, each of the field facets transmits illuminating light from the light source to exactly one of the pupil facets in a specific set illumination geometry. Correspondingly, in this illumination situation, a respective illuminating light partial bundle is guided via the respective illumination channel via a field facet and exactly one pupil facet between the light source and the object field. The change-over between different pupil facets which can be acted upon via a respective field facet can be actuators independent of the correction actuators. Alternatively, it is possible that the AC-Tilt actuators are designed to perform both "alternate lighting setting" and "lighting parameter correction" functions.

The field facet mirror need not be located exactly in the field plane. It is sufficient if the field facet mirror is arranged close to the field. The pupil facet mirror need not be located exactly in a pupil plane. It is sufficient if the pupil facet mirror is arranged close to the pupil.

To characterize these terms "close to the field", "close to the pupil", the following parameter P can be used; WO 2009/024164 A also explained: P (M) = D (SA) / (D (SA) + D (CR))

Where:
D (SA) is the diameter of a sub-aperture, that is to say a partial beam, of the useful illumination light originating from exactly one field point, on a beam-forming surface of the component M, thus for example the field facet mirror or the pupil facet mirror;
D (CR) is the maximum distance of principal rays of an effective object field imaged by the objective, measured in a reference plane (eg, in a plane of symmetry or meridional plane), on the beam-forming surface of M;
in a field level: P = 0, because D (CR) is not 0 and D (SA) = 0;
in a pupil plane: P = 1, because D (CR) = 0 and D (SA) not equal to 0.

"Near the pupil" means: P is at least 0.7, e.g. 0.75, at least 0.8, e.g. 0.85 or at least 0.9, e.g. 0.95.

"Field close" means: P is at most 0.3, e.g. 0.25, at most 0.2, e.g. 0.15 or at most 0.1, e.g. 0.05.

For certain illumination geometries, illumination light can also be transferred simultaneously to a plurality of pupil facets via exactly one field facet. However, useful illumination light is transferred exactly to a pupil facet. The possibly still other pupil facets striking illumination light is no useful illumination light and is not transferred from these other pupil facets to the illumination field, but either used for other purposes or disposed of in a controlled manner.

Some or all of the field facets and / or the pupil facets may in turn be constructed from a plurality of individual mirrors. In particular, the field facet mirror and / or the pupil facet mirror can be constructed as a MEMS (microelectromechanical mirror) array, wherein each of the field facets or each of the pupil facets can then be constructed from a plurality of MEMS mirrors. An example of such a MEMS structure provides the WO 2009/100 856 A1 ,

In such a MEMS design, a targeted defocus can be brought about as a possibility for the correction shift to be generated by prescribing a change in a bending angle of the respective field facet.

The subordinate transmission optics in the respective illumination channel of the field facets can be formed exclusively by the respective pupil facets within the illumination channel. Alternatively, the transmission optics may also have further components, in particular further mirrors, which are arranged downstream of the pupil facet of a respective illumination channel and are arranged upstream of the object field.

Displacement actuators according to claim 2 allow a fine influence of correcting illumination parameters. Alternatively, it is possible to design the displacement actuators such that a plurality of discrete tilt states of the correction field facets can be achieved. Such a design of the displacement actuators can ensure, for example, reliably reproducible displacement positions. A continuous shift of the correction field facets leads to a stepless specification of a displacement path.

Correction actuators according to claim 3 allow particularly flexible correction shift of the correction field facets.

Embodiments of the illumination optics according to claims 4 to 6 enable a flexible illumination correction, via which influence on different field dependencies and / or influence on different field-dependent illumination parameters can be taken.

With arcuate field facets according to claim 7, a correspondingly arcuate light spot of the illumination light partial beam on the correction pupil facets resulting from the convolution with the source structure whose edge contour is particularly suitable for circumcision correction can be achieved since, depending on the direction of displacement of the light spot, a trimming on Edge of the correction pupil facet results, which leads to a different field-dependent illumination parameter correction effect. Alternatively, the field facets may also be straight, that is not arcuate, and rectangular, for example.

The advantages of a lighting system according to claim 8, an optical system according to claim 9, a projection exposure apparatus according to claim 10, a manufacturing method according to claim 14 and a micro- or nanostructured component according to claim 15 correspond to those already explained above with reference to the illumination optical system according to the invention were.

Another object of the invention is to provide a method for specifying a minimum illumination intensity of illumination light over a transverse field coordinate of an object field of illumination optics for projection lithography, which can be used for illumination light throughput increase in the projection exposure.

This object is achieved by a method having the features specified in claim 11.

According to the invention, it has been recognized that by increasing the illumination intensity of the respectively identified illumination channel at the minimum intensity transverse field coordinate, the minimum overall illumination intensity present at the minimum intensity transverse field coordinate can be increased. As a result, when it is required that the same illumination intensity be present across all transverse field coordinates, less illuminating light must remain unused by shading, for example, by using a UNICOM type field intensity presetting device. This results in a higher illumination light throughput. The default method starts at the global intensity minimum, which results from superimposing the illumination intensities of all illumination light sub-beams on the transverse field coordinate. The two facet mirrors may be a field facet mirror and a pupil facet mirror.

The illumination channels, which can be used for alignment when using the predefined method, can be illumination channels with correction facets of the illumination optics according to the invention. In the inventive method, a plurality of illumination channels can be identified and their first facets can be aligned accordingly. All illumination channels can also be identified and aligned accordingly. An identification of individual illumination channels can, as far as this identification is done by measurement, for example by shading all other illumination channels and intensity measurement of an illumination light intensity, which is guided over the remaining illumination channel to the object field, via the transverse field coordinate. This can be done with a spatially resolved sensor.

In a method according to claim 12, in each individual illumination channel, where this is possible via a corresponding cropping variation, its minimum illumination intensity can be raised above the transverse field coordinate. The cross-field coordinate of a corresponding single beacon channel minimum need not be the minimum intensity cross-field coordinate. Also in the method of claim 12, a plurality of illumination channels can be identified and aligned. In extreme cases, all illumination channels can be identified and aligned.

In the method according to claim 13, an actuator displacing the facet, in particular the correction actuator, can be used. Alternatively, an alignment of the first facet can also take place statically in the basic structure of the field facet mirror.

• 1. Bestimmung eines Beleuchtungslicht-Teilbündels mindestens eines zur Korrektur ausgewählten Ausleuchtungskanals durch Messung und/oder durch Berechnung. Bei der Messung kann das Beleuchtungslicht-Teilbündel in einer vorgegebenen Korrekturebene beispielsweise durch Einsatz eines ortsaufgelösten Intensitätsdetektors vermessen werden. Eine Berechnung des Beleuchtungslicht-Teilbündels kann durch rechnerische Bestimmung einer Point-Spread-Function (Punktausbreitungsfunktion) beispielsweise mit Hilfe eines optischen Designprogramms erfolgen. Diese Berechnung kann analytisch oder numerisch oder auch im Wege einer Simulation geschehen.
• 2. Bestimmung einer Korrekturinformation, insbesondere eines Satzes von Aktorpositionen der Korrektur-Aktoren der Korrektur-Feldfacetten. Bei der Korrekturinformation kann es sich insbesondere um einen Satz von Kippwinkeln der Korrektur-Feldfacetten handeln. Diese Korrekturinformations-Bestimmung kann durch ein numerisches und/oder durch ein analytisches Rechenverfahren erfolgen.
• 3. Verwendung der Korrekturinformation zur Korrekturverlagerung der Korrektur-Feldfacetten. Dies kann durch Ansteuerung der Korrektur-Aktoren geschehen.
• 4. Verifikation der Wirkung der Korrekturinformation als optionaler Schritt. Diese Verifikation kann durch Messung und/oder durch Simulation erfolgen.

When setting the actual illumination setting within the manufacturing process, a field-dependent single-channel intensity correction can be used. The field-dependent single-channel intensity correction can include the following sequence of method steps:

• 1. Determination of an illumination light sub-beam of at least one illumination channel selected for correction by measurement and / or by calculation. During the measurement, the illumination light sub-beam can be measured in a predetermined correction plane, for example by using a spatially resolved intensity detector. A computation of the illumination light sub-beam can be carried out by arithmetic determination of a point spread function, for example with the aid of an optical design program. This calculation can be done analytically or numerically or also by means of a simulation.
• 2. Determining a correction information, in particular a set of actuator positions of the correction actuators of the correction field facets. The correction information may in particular be a set of tilt angles of the correction field facets. This correction information determination can be carried out by a numerical and / or by an analytical calculation method.
• 3. Use of the correction information for correction displacement of the correction field facets. This can be done by controlling the correction actuators.
• 4. Verification of the effect of the correction information as an optional step. This verification can be done by measurement and / or by simulation.

The component can be manufactured with extremely high structural resolution. In this way, for example, a semiconductor chip with extremely high integration or storage density can be produced.

Embodiments of the invention will be explained in more detail with reference to the drawing. Show it:

1 schematically a meridional section through a projection exposure system for EUV projection lithography;

2 and 3 Arrangement variants of field facet mirrors, which may be implemented with monolithic field facets, but also Field facets may have, each of which is constructed from a plurality of individual mirrors;

4 schematically a plan view of a pupil facet mirror, which is part of an illumination optical system of the projection exposure system together with the field facet mirror.

5 a variant of a pupil facet following the pupil facet mirror 4 can be used, wherein on the Pupillenfacette an edge contour of an illumination light partial bundle is shown, with which the pupil facet is acted upon by exactly one of the field facets and a predetermined illumination channel, the illumination light partial bundle acts on the pupil facet such that the illumination light partial bundle completely is reflected from the pupil facet;

6 in a diagram, an intensity dependence of a channel intensity I _K of illumination light exposure of the object field of a field height x, that is, a dimension or coordinate perpendicular to a Objektverlagerungsrichtung, the intensity I _K , plotted for exactly one illumination channel, is applied scan integrated and wherein the Effect of displacement and trimming of the illumination light sub-beam on the pupil facet in the -x direction is shown;

7 in one too 6 similar representation of the effect of a shift of the illumination light partial beam on the pupil facet in the + x direction on the field height dependence of the channel intensity I _K (x);

8th in one too 6 similar view showing the effect of a displacement of the illuminating light beam on the pupil part in the + y-direction of the field height function of the channel intensity I _K (x);

9 in one too 6 similar representation of the effect of a shift of the illumination light partial beam on the pupil facet in the -y direction on the field height dependence of the channel intensity I _K (x);

10 schematically in a diagram dependency of an x-telecentricity T _x of the field height x before a correction by targeted displacement of illumination light partial beams on correction pupil facets on the type of pupil facet after 5 in the + x direction (cf. 7 ); and

11 schematically an intensity distribution over a pupil of the illumination optics for an object field point at location x = x _max before a correction of the x-telecentricity, wherein pupil spots are highlighted, which are illuminated via pupil facets, which are as correction pupil facets on which a + x displacement to 7 is brought about;

12 schematically the object field and a sensor unit for detecting an intensity of the illumination light depending on the field height x;

13 very schematically a flowchart of a method for specifying a minimum illumination intensity of the illumination light over the field height x, that is, over a transverse field coordinate of the object field;

14 in a diagram, a dependence of a gas office illumination intensity of all guided over their respective illumination channels illumination light sub-beam depending on the field height before performing the default method after 13 ; and

15 in one too 14 Similarly, the dependence of the overall illumination intensity of the field height after performing the default method after 13 ,

1 schematically shows in a meridional section a projection exposure system 1 for micro lithography. To the projection exposure system 1 belongs to a light or radiation source 2 , A lighting system 3 the projection exposure system 1 has a lighting look 4 to expose one with an object field 5 coincident illumination field in an object plane 6 , The illumination field can also be larger than the object field 5 , An object in the form of an object field is exposed in this case 5 arranged reticle 7 that of an object or reticle holder 8th is held. The reticle 7 is also called lithography mask. The object holder 8th is about a object displacement drive 9 displaceable along an object displacement direction. A projection optics 10 serves to represent the object field 5 in a picture field 11 in an image plane 12 , A structure is shown on the reticle 7 on a photosensitive layer in the area of the image field 11 in the picture plane 12 arranged wafers 13 , The wafer 13 is from a wafer holder 14 held. The wafer holder 14 is via a wafer displacement drive 15 synchronized to the object holder 8th displaceable parallel to the object displacement direction.

At the radiation source 2 It is an EUV radiation source with an emitted useful radiation in the range between 5 nm and 30 nm. It can be a plasma source, for example a GDPP source (plasma generation by gas discharge, gasdischarge-produced plasma) or an LPP source. Source (plasma generation by laser, laser-produced plasma) act. Also, a radiation source based on a synchrotron or on a free electron laser (FEL) is for the radiation source 2 used. Information about such Radiation source is the expert, for example from the US Pat. No. 6,859,515 B2 , EUV radiation 16 coming from the radiation source 2 goes out, in particular the object field 5 Lighting utility lighting light, is from a collector 17 bundled. A corresponding collector is from the EP 1 225 481 A known. After the collector 17 propagates the EUV radiation 16 through an intermediate focus level 18 before moving to a field facet mirror 19 meets. The field facet mirror 19 is a first facet mirror of the illumination optics 4 , The field facet mirror 19 has a plurality of reflective field facets included in the 1 are not shown. The field facet mirror 19 is in a field level of the illumination optics 4 arranged to the object level 6 is optically conjugated.

The EUV radiation 16 is hereinafter also referred to as illumination light or as imaging light.

After the field facet mirror 19 becomes the EUV radiation 16 from a pupil facet mirror 20 reflected. The pupil facet mirror 20 is a second facet mirror of the illumination optics 4 , The pupil facet mirror 20 is in a pupil plane of the illumination optics 4 arranged to the Zwischenfokusebene 18 and to a pupil plane of the illumination optics 4 and the projection optics 10 is optically conjugated or coincides with this pupil plane. The pupil facet mirror 20 has a plurality of reflective pupil facets included in the 1 are not shown. With the help of the pupil facets of the pupil facet mirror 20 and a subsequent imaging optical assembly in the form of a transmission optics 21 with mirrors in the order of the beam path 22 . 23 and 24 become the field facets of the field facet mirror 19 overlapping each other in the object field 5 displayed. The last mirror 24 the transmission optics 21 is a grazing incidence mirror.

To facilitate the description of positional relationships is in the 1 a Cartesian xyz coordinate system as a global coordinate system for the description of the positional relationships of components of the projection exposure apparatus 1 between the object plane 6 and the picture plane 12 located. The x-axis runs in the 1 perpendicular to the drawing plane into this. The y-axis runs in the 1 to the right and parallel to the direction of displacement of the object holder 8th and the wafer holder 14 , The z-axis runs in the 1 down, that is perpendicular to the object plane 6 and to the picture plane 12 ,

The x-dimension over the object field 5 or the image field 11 is also called field height. The object displacement direction is parallel to the y-axis.

The further figures show local Cartesian xyz coordinate systems.

The x-axes of the local coordinate systems run parallel to the x-axis of the global coordinate system 1 , The xy planes of the local coordinate systems represent arrangement planes of the component shown in the figure. The y and z axes of the local coordinate systems are tilted by a certain angle about the respective x-axis.

The 2 and 3 show examples of different facet arrangements for the field facet mirror 19 , Each of the field facets displayed there 25 can be constructed as a single-mirror group of a plurality of individual mirrors, such as from WO 2009/100 856 A1 known. In each case one of the individual mirror groups then has the function of a facet of a field facet mirror, as this example in the US Pat. No. 6,438,199 B1 or the US 6,658,084 B2 is disclosed.

The field facet mirror 19 to 2 has a variety of curved executed field facets 25 , These are in groups in field facet blocks 26 on a field facet carrier 27 arranged. Overall, the field facet mirror has 19 to 2 twenty-six field faceted blocks 26 to which three, five or ten of the field facets 25 grouped together.

Between the field facet blocks 26 there are gaps 28 in front.

The field facet mirror 19 to 3 has rectangular field facets 25 , in turn, groupwise field facet blocks 26 are arranged, between which spaces 28 available.

4 schematically shows a plan view of the pupil facet mirror 20 , pupil facets 29 of the pupil facet mirror 20 are in the range of an illumination pupil of the illumination optics 4 arranged. The number of pupil facets 29 is greater in reality than in 4 shown. The pupil facets 29 are on a pupil facet-bearer of the pupil facet mirror 20 arranged. A distribution of over the field facets 25 with the illumination light 16 applied pupil facets 29 within the illumination pupil gives an actual illumination angle distribution in the object field 5 in front.

Each of the field facets 25 serves to transfer part of the illumination light 16 , that is, an illumination light sub-beam 16 _i , from the light source 2 towards one of the pupil facets 29 ,

In the field facets 25 So it is in the beam path of the illumination light 16 each first facets of the illumination optics 4 , Accordingly, the pupil facets are concerned 29 around in the beam path of the illumination light 16 second facets of the illumination optics 4 ,

The following is a description of illumination light sub-beams 16 _i assumed that the associated field facet 25 each maximum, so over their entire reflection surface is illuminated. In this case, an edge contour of the illumination light sub-beam drops 16 _{i together} with a Randkontor the illumination channel, which is why the illumination channels below with 16 _{i be} designated. The respective illumination channel 16 _i represents a possible light path of the associated field facet 25 maximum illuminating illumination light sub-beam 16 _i about the other components of the illumination optics 4 represents.

The transmission optics 21 points to each of the illumination channels 16 _i one each of the pupil facets 29 for transferring the illumination light partial bundle 16 _i from the field facet 25 towards the object field 5 on.

In each case a lighting light partial bundle 16 _i , of which in the 1 schematically two illumination light sub-beams 16 _i (i = 1, ..., N; N: number of field facets) is between the light source 2 and the object field 5 over exactly one of the field facets 25 and about exactly one of the pupil facets 29 each guided by a lighting channel.

At least some of the pupil facets 29 , In the considered embodiment, all pupil facets 29 of the pupil facet mirror 20 , are used as correction pupil facets. These correction pupil facets are thus in the beam path of the illumination light sub-beam acting on them 16 _i arranged that a picture 2 ' the light source 2 arises at a picture location along the illumination channel 16 _i spaced from the pupil facet 29 lies.

In the 1 are two variants of such an arrangement of light source images 2 ' shown schematically. A first light source image 2 ' ₁ is arranged at a picture location in the beam path of the associated illumination light partial beam 16 _i before reflection on the pupil facet of the pupil facet mirror 20 lies. A second light source image 2 ' ₂ is in the beam path of another illumination light sub-beam 16 _i at a location after reflection on the pupil facet of the pupil facet mirror 20 arranged.

At least some of the field facets 25 , in the illustrated embodiment all field facets 25 , are used as correction field facets, each via one of the illumination channels 16 _i a respective correction pupil facet 29 assigned. The correction field facets 25 are with correction or displacement actuators in the form of tilt actuators 31 connected, of which in the 2 only a few relocation actuators 31 are shown schematically. The relocation actuators 31 are for continuous displacement, namely for continuous tilting of the correction field facets 25 educated. The relocation actuators 31 are for tilting the correction field facets 25 formed about two mutually perpendicular axes, parallel to the x-axis and the y-axis, for example, by a respective center or by a center of gravity of a reflection surface of the correction Feldfacette 25 run.

The relocation actuators 31 are connected via a signal connection, not shown, with a correction control device 32 the projection exposure system 1 in signal connection (cf. 1 ). The correction control device 32 serves for the controlled tilting of the correction field facets 25 ,

The correction control device 32 and the relocation actuators 31 are designed so that a correction displacement path, namely a correction tilt angle of the correction field facets 25 in a correction displacement area, namely in a correction tilt angle range is so large that a respective correction illumination channel 16 _i from one edge of the associated correction pupil facet 29 is trimmed so that the illumination light sub-beam 16 _i not completely from the correction pupil facet 29 in the object field 5 is transferred. This will be explained below with reference to 5 ff. explained in more detail.

5 shows one of the pupil facets 29 at the pupil facet mirror 20 can be used. The pupil facet 29 to 5 has no circular edge contour, as in the 4 shown, but an approximately square edge contour with rounded corners. Such a border contour, which can be designed without rounded corners, so square or rectangular, allows the pupil facet carrier 30 relatively close to the pupil facets 29 to prove.

The pupil facet 29 to 5 is from an arcuate field facet 25 of the field facet mirror 19 to 2 with the illumination light sub-beam 16 _i charged.

The 5 shows a position of the pupil facet 29 reflected illumination light sub-beam 16 _i in a tilt angle position of this pupil facet 29 associated field facet 25 in which no illumination correction takes place. At this, in the 5 illustrated arrangement is an entire cross section of the illumination light sub-beam 16 _i on the pupil facet 29 so that the lighting sub-beam 16 _i not on the edge from the edge of the pupil facet 29 is cropped. An edge contour of the cross section of the illumination light partial bundle 16 _i on the pupil facet 29 has an approximate arcuate, bean or kidney-shaped shape and can be understood as folding the arcuate field facets 25 to 2 with a round source surface of the light source 2 , This folding arises due to the fact that, as already stated above, the image 2 ' the light source 2 arises at a picture location along the illumination channel 16 _i spaced from the pupil facet 29 , in the beam path either before or after the pupil facet 29 , lies.

The arcuate edge contour of the illumination light partial bundle 16 _i on the pupil facet 29 represents a light spot of the illumination light sub-beam 16 _i dar.

Dashed are in the edge contour of the illumination light sub-beam 16 _i on the pupil facet 29 three subbundles 16 _i ¹ , 16 _i ² and 16 _i ³ drawn. The illumination light sub-beam 16i consists of a large number of such subbundles 16 _i ^j together. The illumination light sub-beam 16 _i can, if the optical parameters of light are known, for example by means of an optical design program, are calculated and is referred to herein as the "point spread function" (point spread function).

The illumination light 16 this subbundel 16 _i ¹ to 16 _i ³ starts from a left edge point 25 ¹ , from a central point 25 ² and from a right edge point 25 ^{3 of} the associated field facet 25 , In the 2 are exemplary of these starting points 25 to 25 ³ on one of the field facets 25 located.

By corrective tilting of the field facet 25 that the pupil facet 29 to 5 applied, a field-dependent correction of an illumination angle distribution over the object field 5 be achieved.

6 shows a dependence of a scan-integrated intensity I _K , one of the illumination channels 16 _i for illumination of the object field 5 contributes, from the field height x. A scan integration means an integration of the illumination intensity along the y-coordinate of the object field 5 ,

Dashed lines show a nominal field profile that results when the entire illumination light sub-beam 16 _i from the pupil facet 29 towards the object field 5 is reflected.

Is pulled through in the 6 a field profile of the channel intensity I _K , which arises when the illumination light sub-beam 16 _i by tilting the correction actuator 31 the associated correction field facet 25 in -x-direction so on the pupil facet 29 is shifted that the associated correction illumination channel 16 _i - and thus also the illumination light partial bundle 16 _i - from the edge of the correction pupil facet 29 is cropped. This, in the 5 and 6 left edge of the illumination light sub-beam 16 _i no longer supports the illumination of the object field 5 at, so that in the 6 solid field response results in which the channel intensity I _K at small field height values x falls faster to the value 0 than the dashed, nominal field profile. The result is a field-dependent course of illumination over this pupil facet via this illumination channel 29 , ie a field-dependent course of the intensity of the associated illumination angle. In the correction tilt position after 6 An object field point "sees" illumination light at the x value x _min 16 from the direction of the pupil facet 29 practically not, because illumination light 16 , that of a prototype corresponding to this field height x _min of the associated field facet of the illumination channel 16 _i , not from the pupil facet 29 is reflected. Above a limit field height x _G , the correction field profile of the channel intensity I _K returns to the nominal field profile.

7 Correspondingly shows a correction effect when the tilt actuator 31 the correction field facet 25 tilted so that the illumination light sub-beam 16 _i in the positive x-direction on the correction pupil facet 29 shifted and from the edge of the correction pupil facet 29 is cropped. The progression of the channel intensity I _K is shown again across the field height x after the displacement has taken place in comparison to the nominal field course represented by dashed lines. In the region of a maximum field height x _max , the object field points then see virtually no illumination light, which is emitted by the associated correction pupil facet 29 emanates. Below a limit field height x _G , the solid correction field course follows 7 again in the dashed, nominal field profile over.

For shifting the illumination light partial bundle 16 _i in the +/- x direction becomes the associated correction field facet 25 about the associated tilt actuator to one to the y-axis in the 2 tilted parallel axis.

An arrangement geometry of a guide of the illumination light 16 over the illumination channels 16 _i is thus such that a cross section of the illumination channel 16 _i on the correction pupil facets 29 a border contour has such that over a size of the correction tilt angle a randseitiges Cropping the cross section in a direction +/- x perpendicular to the object displacement direction y can be specified.

8th shows the result of a correction shift of the illumination light sub-beam 16 _i on the correction pupil facet 29 to 5 in the positive y-direction, caused by a corresponding correction tilting of the associated correction field facet 25 around an axis parallel to the x-axis. Due to the arc shape of the illumination light sub-beam 16 _i on the correction pupil facet 29 Due to this + y displacement, the edge of the illumination light sub-beam leading in the + y direction first becomes 16 _i in the range of the subbundle 16 _i ² from the edge of the correction pupil facet 29 circumcised. The result is a reduction or a dip of the channel intensity I _K in the region of a central field height x ₀ . Above a field height x ₀ + x _A2 and below a field height x ₀ - x _A1 is in the 8th drawn through the correction field characteristic of the channel intensity I _K again in the dashed, nominal field profile over.

9 shows the correction effects of a shift of the illumination light sub-beam 16 _i according to 5 in the negative y-direction, caused by a tilt of the associated correction field facet 25 around a tilting axis parallel to the x-axis.

It results due to a truncation of both ends of the arc shape of the illumination light sub-beam 16 _i in the range of subbundles 16 _i ¹ and 16 _i ^{3 is} a drop of the channel intensity I _K at both field height edges, ie simultaneously in the field height x _min and x _max . In the area of the central field height x ₀ , the corrected, in the 9 solid field shape again into the dashed, nominal field profile of the channel intensity I _K.

An arrangement geometry of a guide of the illumination light 16 over the illumination channels 16 _i is thus such that a cross section of the illumination channel 16 _i on the correction pupil facets 29 has an edge contour such that over a size of the correction tilt angle edge-side trimming of the cross-section in a direction +/- y along or parallel to the object displacement direction y can be specified.

Via a direction +/- y of the correction tilt angle, it is therefore possible to specify whether a trimming of the cross section of the illumination channel 16 _i , seen in a dimension x perpendicular to a trimmed edge +/- y centrally (ie in the range x ₀ ) or edge (ie in the ranges x _min and x _max ).

A trimming of the illumination light sub-beam 16 _i thus causes, depending on the location on the object field 5 illumination light 16 from this correction pupil facet 29 with different intensity towards the object field 5 is transferred. By controlled tilting of the correction field facets 25 Thus, a field-dependent correction of an illumination intensity distribution over the object field can be achieved 5 achieve.

A correspondingly trimmed illumination channel 16 _i represents a correction illumination channel.

The correction shifts of the illumination light sub-beam 16 _i in the positive or negative x direction can be combined with the correction displacements in the negative or positive y direction. This can be done by simultaneously tilting the correction field facet 25 , those of the considered correction pupil facet 29 is assigned to the y- and around the x-axis by a corresponding correction tilt angle. The resulting correction field profiles of the channel intensity I _K arise as overlays, for example, the correction field courses after the 6 and 8th , after the 6 and 9 , after the 7 and 8th or after the 7 and 9 , In this way even more complex correction field courses can be generated.

Based on 10 and 11 Below, by way of example, a concrete correction application of the illumination optical system described above 4 explained.

wobei x den Feldpunkt beschreibt, K ein Normierungsfaktor ist, und I_C (x, ρ_x, ρ_y) die Intensität in der Pupille des c-ten Kanals am Ort ρ_x, ρ_y am Feldpunkt x bezeichnet. 10 shows a field course to be corrected of an x-telecentricity T _x . The following applies:

where x denotes the field point, K is a normalization factor, and I _C (x, ρ _x , ρ _y ) denotes the intensity in the pupil of the c-th channel at the location ρ _x , ρ _y at the field point x.

The telecentricity value T _x increases between a minimum value T _{x, min} at the field height x _min over the field height x monotonically up to a value T _{x, max} at the maximum field height x _max .

A course of the x-telecentricity T _x is in the 10 at 33 shown in solid lines. 11 shows an illumination pupil of the illumination optics 4 that are from points of the object field 5 is seen at the maximum field height x _max . Shown schematically and not to scale is an x-dipole setting. A left pole 34 this dipole Lighting settings are formed by intensity contributions or pupil spots 35 , by applying this field height x _max with corresponding pupil facets 29 is produced. The intensity contributions 35 are relatively weak, which is in the 11 through small radii of these intensity contributions 35 is illustrated.

A right pole 36 of the dipole lighting bezel 11 includes intensity contributions or pupil spots 37 , starting from corresponding pupil facets 29 of the pupil facet mirror 20 , The intensity contributions 37 are stronger than the intensity contributions 35 what in the 11 by correspondingly larger radii of the intensity contributions 37 is clarified. Due to the stronger intensity contributions 37 is the integrated illumination intensity across the pole 36 greater than the integrated illumination intensity across the pole 34 , which at location x _{max leads} to the positive x telecentricity value T _{x, max} .

It can now be in the 11 Intensity contributions highlighted by a dashed border 37 by selecting the corresponding pupil facets 29 corrected as a correction pupil facets, so be reduced in terms of their intensities. In these associated pupil facets 29 then takes place a shift of the illumination light sub-beams 16 _i in the positive x-direction, so that a field correction according to the 7 results. An integral intensity across the illumination pole 36 and thus the value T _{x, max} can thus be reduced.

11 shows this, scan-integrated illumination pupil at the field coordinate x, plotted on pupil coordinates σx, σy.

In the projection exposure using the projection exposure machine 1 First, a predetermined lighting setting is set and measured with regard to its lighting parameters. Subsequently, a selection of correction pupil facets takes place and, via the controlled specification of corresponding correction tilt angles of the assigned correction field facets, a correction of default values of not observed illumination parameters takes place until they lie within predefined tolerance limits around predefined desired values of the illumination parameters.

The illumination optics 4 further comprises a sensor unit 40 (see. 1 and 12 ) for detecting an intensity of the illumination light 16 as a function of the field height x, that is, as a function of a transverse field coordinate x of the object field 5 , The sensor unit 40 includes a ballast optics 41 and a spatially resolved measuring sensor 42 ,

The ballast optics 41 in the 12 is shown schematically, has a detection area 43 that the entire object field 5 covers. The ballast optics 41 forms the object field 5 on the sensor 42 from. At the sensor 42 it can be a line array or a row and column array of individually illuminated photosensitive sensor pixels. In particular, it is the sensor 42 around a CCD array. By means of appropriate wavelength conversion devices, for example with the aid of a scintillation coating, the EUV wavelength for measuring the illumination light intensity dependence is converted from the field height x into a guide wavelength for which the sensor 42 is sensitive. Alternatively, it is possible to measure the dependence of the illumination light intensity of the field height x, the EUV light source 2 be simulated by a measuring light source, the emission characteristic of which corresponds to that of the EUV light source, but which emits a measuring wavelength for which the sensor 42 is sensitive.

Using the sensor unit 40 , the central control device 32 and the tilt actuators 31 For example, a method described below for specifying a minimum illumination intensity I _min (cf. 14 and 15 ) are carried out over the field height x, which hereinafter in particular based on the 13 will be described in more detail.

This is done in an identification step 44 First, a _minimum intensity transverse field coordinate x _{min is} identified, in which a total illumination intensity I _{Ges, 0} of all illumination channels 16 _i led lighting light sub-beam 16 _{i is} minimal. This identification is carried out by measuring the total illumination intensity I _Ges over the field height x using the sensor unit 40 at a first set of tilt positions of the tilt actuators 31 of the field facet mirror 19 , An exemplary result of this measurement is in the 14 shown. The result is the _minimum intensity transverse field coordinate x _min at the right edge of the field of the object field 5 , The associated intensity I (x _min ) is I _min .

Subsequently, in an illumination channel identification step 45 at least one illumination channel 16 _i identifies in which a variation of a marginal trimming of the illumination light sub-beam guided over it 16 _i at the respective pupil facet 29 leads to an increase of an illumination intensity I (x _min ) at the _minimum intensity transverse field coordinate x _min . This illumination channel identification can be done by measuring the respective I (x) variation of the respective illumination channel 16 _i when the tilt actuator is actuated 31 the this illumination channel 16 _i associated field facet 25 done, which basically for all illumination channels 16 _i can be performed metrologically.

Here, individual illumination channels can 16 _{i be} measured, in which case all other illumination channels 16 _{i be} shaded.

Alternatively, a corresponding I (x) variation can also be achieved by simulating the light-guiding conditions of the respective illumination light sub-beam 16 _i via the illumination channel 16 _i take place.

For those illumination channels 16 _i , in which the illumination channel identification step 45 was successful, is subsequently carried out in an alignment step 46 an alignment of the respective field facet 25 of the identified illumination channel 16 _i for increasing the illumination intensity of the associated illumination light sub-beam 16 _i at the _minimum intensity cross field coordinate x _min . The alignment is done by a corresponding actuation of the tilt actuator 31 of the at least one identified illumination channel 16 _i .

The result of this default procedure with the steps 44 to 46 shows by way of example the 15 , As a result, the minimum illumination intensity I _{min, k} is compared to the initial minimum illumination intensity I _min (cf. 14 ) raised. I _{min, k} can be 1 percent, 2 percent, 3 percent, 5 percent, 10 percent, or a higher percentage greater than I _min .

Due to the new orientation of the field facets 25 in the alignment step 46 has a dependence of an illumination intensity I _{Ges, k of} the entire illumination light 16 changed over the field height x compared to the original intensity distribution I _{Ges, 0} , so that in the example of the 15 the now predetermined minimum illumination intensity I _{min, k is present} not only at the right edge of the field, ie at the minimum intensity transverse field coordinate x _min , but also at the left edge of the field.

In the method described above, the global intensity minimum is set over the field height x, which is determined by superimposing the illumination intensities of all the illumination light sub-beams 16 _i over the field height x, ie over the transverse field coordinate.

The default procedure can have exactly one illumination channel 16 _{i can be} identified or it can be a plurality of illumination channels 16 _{i be} identified. It can all illumination channels 16 _be identified, in which by varying the marginal trimming of the guided over this illumination light partial bundle 16 _i at the pupil facet 29 gives the desired illumination light intensity magnification at the _minimum intensity transverse field coordinate x _min .

In addition, a further illumination channel identification step and a further facet alignment step may be performed during the predefining method explained above. These further identification and alignment steps may be performed in parallel or sequentially to the above-identified identification and alignment steps.

In the further illumination channel identification step, at least one illumination channel is formed 16 _i identifies in which a variation of a marginal trimming of the illumination light sub-beam guided over it 16 _i at the pupil facet 29 to an increase of a minimum illumination intensity I _{min, i of} this illumination light sub-beam 16 _i over the transverse field coordinate, ie over the field height x leads. In the 14 is a dashed line in relative intensity units, a dependence of an intensity curve I _i an illumination intensity of a so identified illumination channel 16 _i drawn. This identification is again performed by measurement using the sensor unit 40 in which all other illumination channels 16 _{i are} shadowed. In this intensity course I _i on the field height x the illumination channel intensity I _i is not at the minimum intensity Querfeldkoordinate x _min minimal, but on the other, the left edge of the field, so at the coordinate x _{min, i.} The minimum intensity of this illumination channel 16 _i at the individual minimum coordinate x _{min, i} is in the 14 denoted by I _{min, i} . In reality, I _{min, i is, of} course, orders of magnitude smaller than I _min . By way of illustration, the course I _i, however, as mentioned above, in relative intensity units in the 14 located.

After this further illumination channel identification step, an alignment of the illumination channel takes place in the further facet alignment step 16 _i associated field facet 25 for increasing the minimum illumination intensity I _{min, i of} this illumination channel 16 _i , adding the corresponding circumcision variation to the associated pupil facet 29 of the illumination channel 16 _{i is} set.

The alignment in the alignment steps is carried out according to the above-described embodiments using the tilt or correction actuators 31 , The field facets 25 can be tilted dynamically for alignment. Alternatively, such alignment can also be static already in the basic design of the field facet mirror 19 be done so tiltable field facets using tilt actuators 25 not mandatory for carrying out the methods described above.

Result of the further illumination channel identification step and also further Alignment step is a raising of the illumination intensity not only in the area of the _minimum intensity transverse field coordinate x _min , but also in the range of others and in their possibly low illumination intensity of critical field coordinates, in the 14 and 15 embodiment shown, thus in the region of the minimum intensity Querfeldkoordinate x _min opposing left field coordinate x _{min, i.} Performing the further illumination channel identification and facet alignment steps accordingly ensures that when the illumination intensity is increased to the intensity I _{min, k} at the _minimum intensity transverse field coordinate x _min using the above-described steps 44 to 46 the illumination intensity is not undesirably lower than I _{min, k} at another field coordinate.

In the projection exposure using the projection exposure system 1 First, an illumination geometry is set with the aid of the above-explained adjustment method. Then at least part of the reticle becomes 7 in the object field 5 on a portion of the photosensitive layer on the wafer 13 in the image field 11 for the lithographic production of a microstructured or nanostructured component, in particular a semiconductor component, for example a microchip. This will be the reticle 7 and the wafer 13 synchronized in time in the y-direction continuously in scanner operation.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• US 2011/0001947 A1 [0002]
• WO 2009/132756 A1 [0002]
• WO 2009/100856 A1 [0002, 0014, 0053]
• US 6438199 B1 [0002, 0053]
• US 6658084 B2 [0002, 0053]
• WO 2009/024164 A [0009]
• US Pat. No. 685,951 B2 [0046]
• EP 1225481A [0046]

Claims (15)

Illumination optics ( 4 ) for the EUV projection lithography for the illumination of an object field ( 5 ), in which an object to be imaged ( 7 ), - with a field facet mirror ( 19 ) with a plurality of field facets ( 25 ) arranged in the region of a field plane of the illumination optics ( 4 ), - with a pupil facet mirror ( 20 ) having a plurality of pupil facets ( 29 ), arranged in the region of a pupil plane of the illumination optics ( 4 ), Wherein each of the field facets ( 25 ) for the transfer of useful illumination light ( 16 ) from a light source ( 2 ) to each one of the pupil facets ( 29 ), wherein a respective useful illumination light partial bundle (in each case via one illumination channel 16 _i ) between the light source ( 2 ) and the object field ( 5 ) over exactly one field facet ( 25 ) and exactly one pupil facet ( 29 ), - one in the respective illumination channel ( 16 _i ) the field facet ( 25 ) downstream transmission optics ( 21 ) for superimposing the field facets ( 25 ) in the object field ( 5 ), the transmission optics ( 21 ) for each illumination channel ( 16 _i ) in each case one of the pupil facets ( 29 ) for transferring the illumination light partial bundle ( 16 _i ) of the field facet ( 25 ) to the object field ( 5 ), wherein at least some pupil facets ( 29 ), which can be used as correction pupil facets, in the beam path of the illumination light sub-beam (FIG. 16 _i ) are arranged so that an image (2 ') of the light source ( 2 ) arises at a picture location along the illumination channel ( 16 _i ) spaced from the pupil facet ( 29 ), - with a correction control device ( 32 ) for controlled displacement of at least some of the field facets ( 25 ), via respective illumination channels ( 16 _i ) the correction pupil facets ( 29 ) and can be used as correction field facets, with the correction field facets ( 25 ) associated correction actuators ( 31 ), - wherein the correction control device ( 32 ) and the correction actuators ( 31 ) are carried out such that a correction displacement path of the correction field facets ( 25 ) is so large in a correction displacement area that a respective correction illumination channel ( 16 _i ) from an edge of the correction pupil facet ( 29 ) is trimmed so that the illumination light sub-beam ( 16 _i ) not completely from the correction pupil facet ( 29 ) in the object field ( 5 ) is transferred. Illumination optics according to claim 1, characterized in that the correction actuators ( 31 ) for continuously shifting the correction field facets ( 25 ) are formed. Illumination optics according to claim 1 or 2, characterized in that the correction actuators ( 31 ) for shifting the correction field facets ( 25 ) are formed around two mutually perpendicular axes (x, y). Illumination optics according to one of claims 1 to 3, characterized in that the object ( 7 ) along an object displacement direction (y) is displaceable, wherein an arrangement geometry of a guide of the illumination light ( 16 ) via the illumination channels ( 16 _i ) is such that a cross section of the respective illumination channel ( 16 _i) (to the correction-pupil facet 29 ) has an edge contour such that over a size of the correction displacement path, a marginal cutting of the cross section in a direction (+/- x) perpendicular to the object displacement direction (y) can be specified. Illumination optics according to one of claims 1 to 4, characterized in that the object ( 5 ) along an object displacement direction (y) is displaceable, wherein a Geordnungsgeomtrie a guide of the illumination light ( 16 ) via the illumination channels ( 16 _i ) is such that a cross section of the respective illumination channel ( 16 _i) (to the correction-pupil facet 29 ) has an edge contour such that over a size of the correction displacement path edge-side trimming of the cross-section in one direction (+/- y) parallel to the object displacement direction (y) can be specified. Illumination optics according to one of Claims 1 to 5, characterized in that it is possible to specify via a direction (+/- y) of the correction displacement path whether a trimming of the cross section of the illumination channel ( 16 _i ), seen in a dimension (x) perpendicular to a trimmed edge centrally (x ₀ ) or edge (x _min , x _max ) takes place. Illumination optics according to one of Claims 1 to 6, characterized by arcuate field facets ( 25 ). Lighting system ( 3 ) with an illumination optics ( 4 ) according to claims 1 to 7 and with a light source ( 2 ) for generating the illumination light ( 16 ). Optical system with illumination optics ( 4 ) according to one of claims 1 to 7 and with a projection optics ( 10 ) for mapping the object field ( 5 ) in an image field ( 11 ). Projection exposure apparatus ( 1 ) with an optical system according to claim 9 and a light source ( 2 ) for generating the illumination light ( 16 ) - with an object holder ( 8th ) with an object displacement drive ( 9 ) for relocating the object ( 7 ) along an object displacement direction (y), - with a wafer holder ( 14 ) with a wafer displacement drive ( 15 ) with the object displacement drive ( 9 ) synchronized displacement of a wafer ( 13 ). Method for specifying a minimum illumination intensity (I _{min, k} ) of illumination light ( 16 ) over a transverse field coordinate (x) of an object field ( 5 ) an illumination optics ( 4 ) for the projection lithography, - where in the object field ( 5 ) an object to be imaged ( 7 ), wherein the transverse field coordinate (x) extends transversely to an object displacement direction (y) along which the object ( 7 ) is displaceable, - wherein the illumination optics ( 4 ) two in the beam path of the illumination light ( 16 ) successively arranged facet mirrors ( 19 . 20 ) that via each one illumination channel ( 16 _i ) a respective useful illumination light sub-beam ( 16 _i ) between a light source ( 2 ) and the object field ( 5 ) about exactly one facet ( 25 ) of the first facet mirror ( 19 ) and exactly one facet ( 29 ) of the second facet mirror ( 20 ), with the following steps: identifying ( 44 ) of a _minimum intensity transverse field coordinate (x _min ) at which the total illumination intensity (I _{Ges, 0} ) of the illumination channels ( 16 _i ) guided illumination light partial bundle ( 16 _i ) is minimal, - identify ( 45 ) at least one illumination channel ( 16 _i ), in which a variation of marginal trimming of the illumination light sub-bundle ( 16 _i ) at the second facet ( 29 ) to increase an illumination intensity of this illumination light sub-beam ( 16 _i) leads to the minimum intensity Querfeldkoordinate (x _min), - aligning ( 46 ) of the first facet ( 25 ) of this illumination channel ( 16 _i ) to increase its illumination intensity (I _{min, k} ) at the _minimum intensity transverse field coordinate (x _min ). Method according to claim 11, characterized by the following further steps: - identification of at least one illumination channel ( 16 _i ), in which a variation of marginal trimming of the illumination light sub-bundle ( 16 _i ) at the second facet ( 29 ) to increase a minimum illumination intensity (I _{min, i} ) of this illumination light sub-beam ( 16 _i ) via the transverse field coordinate (x) leads, - aligning the first facet ( 25 ) of this illumination channel ( 16 _i ) to increase this minimum illumination intensity (I _{min, i} ). Method according to claim 11 or 12, characterized in that the first facet ( 25 ) is tilted dynamically for alignment. Method for producing a microstructured or nanostructured component comprising the following steps: - providing a projection exposure apparatus ( 1 ) according to claim 10, - setting an actual illumination setting of an illumination angle distribution over the object field ( 5 ) in accordance with predetermined tolerance limits with a target illumination setting by specifying appropriate correction displacement paths for selected correction field facets ( 25 ) via the correction control device ( 32 ), - providing a wafer ( 13 ), - providing a lithography mask ( 7 ), - projecting at least a part of the lithographic mask ( 7 ) to a portion of a photosensitive layer of the wafer ( 13 ) with the aid of the projection optics ( 10 ) of the projection exposure apparatus ( 1 ). Component produced by a method according to claim 14.

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