The invention relates to a lighting optical system for microlithography
according to your preamble of claim 1. Furthermore, the invention relates
a lighting system with such illumination optics, a
Projection exposure system with such a lighting system,
a measuring device for measuring an optical parameter of the
Illumination system and / or the projection optics of a projection exposure apparatus,
a method for producing a micro- or nanostructured component
with such a projection exposure system and a with
this method produced micro- or nanostructured device.
Corresponding illumination optics are known from the WO 2006/002859 A2
, of the US 2006/0109533 A1
and the US Pat. No. 6,859,263 B2
It is an object of the present invention to provide an illumination optics
of the type mentioned in such a way that the number
the bundling components is minimized.
The object is achieved by
an illumination optical system with the features specified in claim 1.
According to the invention was
recognized that an object field illumination is possible by
the object field not altogether in one go, ie simultaneously,
is illuminated, but by sections of the object field sequentially
be scanned. It can be used a radiation source,
their light intensity for simultaneous illumination of the entire
Object field is not sufficient. In addition, it was recognized
that such scanning with exactly one optical bundle guide component
it is possible that it is not necessary, the degrees of freedom of movement
for scanning the object field on various optical Bün delführungskomponenten
to distribute. The result is the possibility of an illumination optics
with exactly one optical bundle guide component
to realize. This minimizes reflection losses within the
Lighting optics and also saves costs. Such reflection losses
are especially in the use of illumination wavelengths
relevant to the production of highly reflective layers
is problematic. The use of several reflective layers
each with non-negligible reflection losses
would then lead to high light losses altogether.
Ellipsoid mirror according to claim 2 is a particularly efficient embodiment
the optical bundle guide component. The ellipsoidal mirror can
so arranged and so guided when scanning the object field
be that in one of its focal points the radiation source and
in the other of its focal points, each to be illuminated during the scanning
Field point is arranged.
degrees of freedom
according to claim 3 of the optical bundle guide component
are depending on the selected arrangement of the illumination optics
to achieve an object field illumination within predetermined
Tolerance limits are preferably provided.
optical bundle guide component according to the claims
4 or 5 allows scanning of the object field with over
the object field of homogeneous intensity.
Configuration of the optical bundle guide component
with five degrees of freedom of movement according to claim 6
within narrow limits constant illumination parameters, in particular
the focus size and the divergence of the over
the object field guided radiation beam, safe.
Advantages of a lighting system according to claim 7 and a projection exposure apparatus
according to claim 8 correspond to those described above with respect to the
Inventive illumination optics executed
were. The radiation source is in particular
an EUV radiation source with a useful wavelength in the range
between 5 nm and 30 nm. In principle, radiation sources are also used
can be used that emit light of other wavelengths.
Measuring device according to claim 9 with an inventive
Illumination optics allow a defined illumination of a measuring field
within the object plane for measuring optical parameters of the
Lighting system and / or the projection optics. A survey
can be done with a radiation source whose light intensity
is not sufficient for the simultaneous illumination of the entire object field.
Advantages, as above, in particular in connection with the illumination optics
executed, apply to the manufacturing process
according to claim 10 and the microstructured thereby produced
Component according to claim 11.
Embodiment of the invention will be described below
explained in detail the drawing. In this show:
1 schematically a projection exposure apparatus for EUV microlithography;
2 schematically a lighting system of the projection exposure system according to 1 ;
3 greatly magnified a view of a arranged in an object field of the projection exposure reticle with a total of nine arranged thereon coherence masks for wavefront measurement;
4 - 7 the dependence of a bundle shape of an illumination radiation beam generated in front of the illumination system in the object plane on adjustment degrees of freedom of an ellipsoidal mirror of an illumination optics of the illumination system;
8th a trajectory for the illumination beam bundle scanned across the object field for generating an object field illumination with a homogeneous intensity distribution over the object field for scan illumination of a surveying diffusing disc arranged there as an example of a structure for a scattered light measurement;
9 in one too 8th similar representation an alternative scan illumination of the object field.
A projection exposure machine 1 for microlithography has a radiation source 2 to produce one in the 1 and 2 schematically illustrated illumination beam 3 , At the radiation source 2 it is an EUV radiation source, in particular a plasma source. An EUV issue volume 4 the radiation source 2 is in the 2 shown schematically. The issue volume 4 has approximately the shape of an ellipsoid. This ellipsoid, for example, has a diameter of 0.5 mm and a length of 15 mm. The illumination radiation beam 3 is emitted in the direction of a long semiaxis of this ellipsoid. At the radiation source 2 it is an EUV radiation source that generates light in a wavelength range, in particular between 5 nm and 30 nm. Other EUV wavelengths are possible.
To guide the illumination beam 3 from the radiation source 2 towards an object field 5 in an object plane 6 serves a lighting optics 7 , Together with the radiation source 2 represents the illumination optics 7 an illumination system of the projection exposure apparatus 1 represents.
With a projection optics 8th becomes the object field 5 in an unspecified image field in an image plane 9 mapped with a given reduction scale. In the object field 5 is a structure to be imaged in the form of a reticle 10 arranged. The image is taken on the surface of a substrate 11 in the form of a wafer made by a substrate holder 12 worn.
2 shows further details of the lighting system. Based on the issue volume 4 becomes the illumination beam 3 on an ellipsoidal mirror 13 reflected. Between the issue volume 4 and the ellipsoidal mirror 13 no further bundle-forming element is arranged. Starting from the ellipsoidal mirror 13 meets the illumination beam 3 on the reticle designed as a reflection mask 10 , An angle o between a main beam of the illumination beam 3 and the object plane 6 is 84 °. The illumination radiation beam 3 so hits the reticle 10 with an angle of incidence of 6 °.
The ellipsoid mirror 13 is dimensioned so that at a given basic adjustment of the ellipsoidal mirror 13 a center 14 the issue volume 4 in a first focal point of the ellipsoidal mirror 13 lies and that a central object field point 15 in the other focal point of the ellipsoidal mirror 13 lies.
In order to facilitate the explanation of positional relationships, both a Cartesian xyz coordinate system and a Cartesian x'y'z 'coordinate system are used below (cf. 2 ). The in the 2 horizontally extending z-axis is the rotational symmetry axis of the base ellipsoid, of which the reflective surface of the ellipsoidal mirror 13 represents a section, and goes through both focal points 14 . 15 , The y-axis runs in the 2 up. The x-axis is perpendicular to the plane of the 2 into this. The x'-axis runs in the 2 also perpendicular to the drawing plane. The y'-axis is perpendicular to the object plane 6 , The z'-axis, on the one hand in the object plane 6 and on the other hand, in the drawing plane of 2 lies, runs to the top right. The reticle 10 lies in the x'z'-plane.
A distance x1 between the source center 14 and a point of impact 16 a main beam of the illumination beam 3 on the ellipsoidal mirror 13 is 1120 mm. A distance x2 between the point of impact 16 and your central object field point 15 is 700 mm. A distance x3 between the source center 14 and the central object field point 15 is 931.442 mm.
The lighting system after 2 can be used for projection exposure of the reticle 10 and / or for measuring exposure of the object field 5 be used. In the measurement exposure, optical parameters of the illumination system and / or the projection optics 8th measured, for example, the wavefront of the illumination beam 3 , the wavefront of the projection optics 8th , the homogeneity of the illumination of the object field 5 as well as components of the illumination system and / or the projection optics 8th caused stray light fect.
3 shows a measuring reticle 17 which instead of the reticle 10 can be used for measuring exposure. The measuring reticle 17 is square with an edge length of 8 mm. In a 4 mm grid are on the measuring reticle 17 a total of nine coherence masks 18 arranged. The coherence masks 18 lie in the corners, in the center and on the medians of the measuring reticle 17 , The coherence masks 18 are used to facilitate the following description line by line from top to bottom of 19 to 27 numbered. The top left coherence mask 18 So get the number 19 and the coherence mask arranged at the bottom right is the number 27 ,
The coherence masks 18
have a diameter between 50 and 200 mm. The coherence masks 18
serve for wave front shaping of the illumination radiation beam 3
and thus for measuring the optical parameters of the illumination system and / or the projection optics 8th
, The associated measuring technology is explained in the DE 101 09 929 A1
whose content is fully incorporated here.
In connection with this measurement technique can still be used:
- Shear interferometry,
- - PDI (Point Diffraction Interferometer, Point Diffraction Interferometer),
- - Shack Hartmann sensor.
Details of the shear interferometry are known from the US 6,707,560
, Details of the point diffraction interferometer are known from the US 6,100,978
, Details about the Shack Hartmann Sensor are known from the US 5,898,501
To perform the measurement, the ellipsoidal mirror 13 so shifts that the nine coherence masks 18 be illuminated sequentially.
The ellipsoid mirror 13 can be shifted by a total of six degrees of freedom. The ellipsoid mirror 13 First, a translation Tx, Ty, Tz along the axes x, y, z learn. In addition, the ellipsoidal mirror 13 a tilt Rx, Ry, Rz learn about the axes x, y, z. The Rz tilt, which does not affect the imaging properties of the ellipsoidal mirror 13 has, becomes the alignment of the ellipsoidal mirror 13 between the radiation source 3 and the object field 5 ,
The driven displacement by the six degrees of freedom mentioned is the ellipsoidal mirror 13 with six actuators 28 . 29 . 30 . 31 . 32 . 33 connected, via a common and not shown central control device of the projection exposure system 1 be controlled. Each of the actuators is for a displacement of the ellipsoidal mirror 13 responsible for one of the degrees of freedom Tx, Ty, Tz, Rx, Ry, Rz. Alternatively, it is possible to move the six actuators 28 to 33 to specify that six independent linear combinations of the degrees of freedom Tx, Ty, Tz, Rx, Ry, Rz result, so that the degrees of freedom by combinations of the movements of the actuators 28 to 33 can be generated.
The ellipsoid mirror 13 is manipulated by the degrees of freedom Tx, Ty, Tz, Rx, Ry, Rz such that on the coherence masks 19 to 27 on the one hand, a defined intensity illumination in the object plane 6 and on the other hand a defined illumination angle distribution on the respective coherence mask 18 takes place.
4 shows a size of a spot 34 , So the cross section of the illumination beam 3 in the object plane 6 for the mapping of the source center 14 to the central object field point 15 , This spot size is shown dependent on the translation Ty of the ellipsoidal mirror 13 , With basic adjusted ellipsoidal mirror 13 (Ty = 0), the spot size is minimal. When Ty is displaced in both directions (negative / positive sign), a symmetrical enlargement of the spot size results, which remains round.
5 shows the spot size when illuminating the coherence mask 20 , This was the ellipsoidal mirror 13 shifted in positive z-direction (Tz). 5 shows the dependence of the spot size of the illumination beam 3 at this z position depending on Ty. This results in an astigmatic spot 34 because by the Tz shift the source center 14 from the focal point of the ellipsoidal mirror 13 has emigrated.
6 shows the situation in which to illuminate the coherence mask 20 in addition to the Tz shift an Rx tilt was made.
In turn, the dependence of the spot size on the translation Ty of the ellipsoid mirror is shown 13 , The result is a round spot on the coherence mask 20 , However, the minimum value of the spot size is no longer exactly in the object plane when using these degrees of freedom. Ty fitting is required. In addition, the minimum value of the spot size in the situation is after 6 greater than the one after 4 ,
7 shows the situation when illuminating the coherence mask 20 using both degrees of freedom Tz and Rx and Ty. This will be a round spot 34 with a diameter that demjeni according to the situation 4 corresponds, achieved, whose minimum diameter in the object plane 6 lies.
The coherence masks 22 and 24 can therefore be illuminated by varying the degrees of freedom Ty, Tz and Rx so that a virtually diffraction-limited imaging is possible. The thus illuminated coherence masks 18 then couple from the issue volume 4 the illumination beam 3 with defined shape and illumination angle distribution in the projection optics 8th one. These default parameters for the illumination beam 3 on the coherence masks 19 to 27 are practically the same, so for all nine coherence masks 18 the same lighting conditions are achieved so that an exact wavefront survey over that of the nine coherence masks 18 spanned area in the object plane 6 is possible.
In a similar way, the coherence masks can be 20 and 26 Illuminate defined by using the degrees of freedom Tx and Ry. The coherence masks arranged in the four corners 19 . 21 . 25 and 27 can be illuminated by overlapping the degrees of freedom Tx, Ty, Tz and Rx and Ry.
In connection with the 8th
is subsequently also a by displacement of the ellipsoidal mirror 13
realizable scanning illumination of defined fields in the object plane 6
described. This scanning illumination can be used on the one hand for projection exposure. On the other hand, the scanning illumination is also for another measurement technique for determining optical parameters of the illumination system and / or the projection objective 8th
can be used in the object level 6
Structures are arranged for the scattered light measurement. The associated measurement technique is described for example in the WO 2005/015313 A1
whose contents are fully included here.
8th shows a trajectory 35 in the object plane 6 with snapshots showing the spot 34 along the trajectory 35 represent. The scanning movement starts, for example, in the 8th left above, first passing through a top line from left to right, then zigzags down line by line until the scan illumination ends in the lower right corner of the illuminated area. The object field relevant for the homogeneous field illumination or for the projection exposure 5 lies within the entire scanned area of the object plane 6 , The homogeneously illuminated object field 5 is square with a side of 8 mm.
In the homogeneous field illumination, it mainly comes to a homogeneous intensity illumination of the object field 5 at.
The trajectory 35 to 8th is solely due to displacement of the ellipsoidal mirror 13 realized with the degrees of freedom Tx and Tz. The ellipsoid mirror 13 is thus shifted translation along only two axes. For this shift, only two of the actuators 28 to 33 required. When scania lighting can therefore on a total of four of the six actuators 28 to 33 be waived.
8th shows the situation with basic adjusted ellipsoidal mirror 13 , By a displacement of the ellipsoidal mirror 13 from the basic adjustment by a predetermined value along the y-axis is achieved that the spot size of the scan spot 34 opposite to the illustration 8th further increases that the trajectory 35 opposite to the 8th so it is further lubricated. This can be achieved that the entire object field 5 is illuminated homogeneously.
9 shows a corresponding trajectory 36 , which is achieved exclusively by shifting over the degrees of freedom Rx and Ry. The ellipsoid mirror 13 is thus tilted by two degrees of freedom. So only two of the actuators are for this illumination 28 to 33 required.
The trajectory 36 starts in the 9 bottom left, where first a left column in the object plane 6 is illuminated. Subsequently, the object plane becomes 6 in a predetermined range column by column in zigzag illuminated until the trajectory 36 in the 9 right top ends. The actual field of interest for the illumination 5 lies within the total illuminated scan area. By defocusing about a translation in y-direction can be achieved that the size of the spots 34 opposite to the illustration 9 is still significantly increased, so that the trajectory 36 further lubricated. This allows a homogeneous intensity illumination of the object field 5 be achieved.
The further the spot 34 from the center of the object field 5 removes the object plane 6 pierces, the larger is the spot there 34 , Due to astigmatic effects, this spot size is deformed all the more in comparison to a round spot, the farther the spot 34 from the center of the object field 5 is spaced.
When using one of the measuring methods, ie when using the coherence masks 18 or the structures for scattered light measurement in the object plane 6 , is instead of the substrate 11 in the picture plane 9 a spatially resolved for the wavelength of the lighting tung radiation bundle 3 sensitive detection unit 37 arranged in the 1 is shown in dashed lines. This may be, for example, a CCD camera, which is sensitive by using a corresponding attachment element for the EUV wavelength. This results in a measuring device for measuring at least one optical parameter of the illumination system and / or the projection optics 8th ,
The projection exposure apparatus is used to produce a microstructured or nanostructured component 1 used as follows: First, the reflection mask 10 or the reticle and the substrate or the wafer 11 provided. Subsequently, a structure on the reticle 10 on a photosensitive layer of the wafer 11 with the help of the projection exposure system 1 projected. This is where the object field becomes 5 by shifting the ellipsoidal mirror 13 scanned. By developing the photosensitive layer, a microstructure or nanostructure then becomes on the wafer 11 and thus produces the micro- or nanostructured component.
In the illumination of the object plane 6 for example via a trajectory illumination, as described above in connection with the 8th and 9 shown, there may be deviations from one over the object field 5 homogeneous lighting come. Such homogeneity error influences result, for example, from distortion errors, that is to say a deviation of the trajectories generated as a result of distortion 35 . 36 of straight-line procedural sections. Further homogeneity error influences are a point image variation, that is to say a change in the shape of the spot produced as a result of distortion 34 over the trajectories 35 or 36 , a movement error or a speed error of the actuators 28 to 33 of the ellipsoidal mirror 13 ,
These homogeneity error effects can be at least partially eliminated or compensated individually or in their combined effect. For this it is possible to fine tune the shape of the trajectories. Alternatively or additionally, it is possible the point image, so the shape of the spot 34 , as well as the position and / or the travel speed of the actuators 28 to 33 to correct. A correction of the total error caused by the various homogeneity error effects discussed above with respect to the homogeneity of the illumination of the object field 5 is generated, it is possible the trajectories 35 respectively. 36 and to measure the dot images by field illumination and to perform an iterative optimization depending thereon.
QUOTES INCLUDE IN THE DESCRIPTION
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Cited patent literature
- - WO 2006/002859 A2 
- US 2006/0109533 A1 
- US 6859263 B2 
- - DE 10109929 A1 
- US 6707560 
- US 6100978 
- US 5898501 
- WO 2005/015313 A1