TWI747806B - Illumination optical unit for a projection exposure system - Google Patents

Abstract

An illumination optical unit (17_i) for a projection exposure system (1) comprises a plurality of radiation-reflecting components, wherein all of the radiation-reflecting components are arranged in such a way that a beam (10_i) with illumination radiation (5) is deflected at these in the same sense.

Description

Illumination optical unit for projection exposure system [Cross-reference related applications]

This application claims the priority of German patent application DE 10 2014 221 175.1, the content of which is hereby incorporated as a reference.

The present invention relates to an illumination optical unit used in a projection exposure system, and particularly relates to a projection exposure system in which a free electron laser (FEL) is used as a radiation source. The present invention further relates to an illuminating system including at least one such illuminating optical unit, an optical system including an illuminating optical unit and a projection optical unit, and a projection exposure system including at least one such illuminating optical unit. Finally, the present invention relates to a method of producing a microstructure or nanostructure component, and a component produced according to this method.

In a projection exposure device, the illuminating radiation emitted by the radiation source is conventionally deflected many times during the journey to the mask to be illuminated in the object field, which may cause undesired radiation loss and/or undesired Polarization effect.

The purpose of the present invention is to improve an illuminating optical unit for guiding illuminating radiation to an object field.

This objective is achieved by an illumination optical unit containing a plurality of radiation reflecting components In this way, all the radiation reflecting components are configured so that the light beam containing the illuminating radiation will be deflected in the same way on these components.

The illuminating optical unit is particularly used to transmit illuminating radiation from an intermediate focal point to an object field, and is suitable for a projection exposure device with a single scanner. It can be used in a particularly advantageous manner in a projection exposure system containing a plurality of scanners, especially a projection exposure system in which illumination radiation from a common radiation source, especially a free electron laser (FEL) is supplied to the plurality of scanners . In particular, the illuminating radiation may be EUV radiation, i.e. radiation having a wavelength in the range from 2 nm to 30 nm, especially in the range from 2 nm to 15 nm, especially having a wavelength of 13.5 nm.

What can be identified according to the present invention is that by selecting a particularly optimized configuration of the radiation reflection component in a targeted manner, especially from the perspective of the deflection caused by the illuminating radiation, the optical performance of an illuminating optical unit can be improved. characteristic. In particular, it can reduce radiation loss and/or maintain the degree of polarization within a specific range, especially less than 20%.

According to one aspect of the present invention, at least two of the radiation reflecting components, especially both, are embodied as faceted elements, especially faceted mirrors. In particular, it can be a field facet mirror and a pupil facet mirror.

The radiation reflecting components further include at least one advanced reflector. In particular, the at least one advanced mirror is arranged downstream of the second facet mirror in the beam path. In addition, the at least one advanced mirror is arranged upstream of the first facet mirror in the beam path.

According to a further aspect of the present invention, in the beam path direction, the radiation reflecting components include a first facet mirror, a second facet mirror, and precisely only one advanced mirror. The latter is arranged in the beam path between the second facet mirror and the object field or upstream of the first facet mirror.

In particular, the illumination optical unit has been specifically implemented, so that only one reflector is arranged in the beam path between the second facet mirror and the object field.

In particular, the illumination optical unit contains only three mirror elements. Here, the two facet mirrors include multiple radiation reflection independent facets.

In particular, the advanced mirrors arranged downstream of the second facet mirror or upstream of the first facet mirror in the beam path are not faceted, that is, they have a single specific embodiment.

In particular, it is embodied as an imaging mirror, that is, a mirror with imaging effects. In particular, it has a non-planar reflective surface.

According to a further aspect of the present invention, the third reflector in the beam path of the illumination optical unit is particularly used to form the second facet mirror, in particular to form a pupil facet mirror, to form an image to be arranged in the illumination optical unit. A machine in a projection optical unit downstream of the unit cannot touch the plane, especially a machine that is imaged to the projection optical unit cannot touch the pupil plane.

In view of the results of the specific embodiment of the illumination optical unit, the design of the optical system including the illumination optical unit and the projection optical unit assigned thereto can be simplified, especially the design of the scanner including the optical system.

According to a further aspect of the present invention, the light beam with illuminating radiation is deflected to a deflection angle on each of the radiation reflecting components of the illuminating optical unit, and has a ratio between any two deflection angles not exceeding 1.5 . The ratio between any two deflection angles is defined as positive or negative according to the deflection direction, especially positive. The ratio between any two deflection angles of the radiation reflecting components of the illumination optical unit is particularly not more than 1.3, especially not more than 1.2, especially not more than 1.1, especially not more than 1.05, especially not more than 1.03, especially not more than More than 1.01. Preferably, all deflection angles are equal.

This results in a particularly high, especially the highest total transmission of the illumination optical unit. In this regard, please note that this is a general term, especially this does not apply to any angular dependence of the reflectivity of the radiation reflecting components. However, this result has been established and confirmed for the known angular dependence of the reflectivity of the radiation reflecting components provided.

Furthermore, at least one of these deflection angles can be advantageously selected in this way, which is different from the two other deflection angles due to further boundary conditions, especially optical aberration factors. This can be detrimental to overall transmission and is only provided where needed.

According to a further aspect of the present invention, the radiation reflecting components are configured such as This results in the overall deflection range of the illuminating radiation beam from 45° to 135°. The overall deflection is in particular in the range from 60° to 120°, in particular in the range from 80° to 100°, in particular in the range from 85° to 95°, in particular 90°.

Here, the overall deflection from the entering direction of the beam, especially in the area of the intermediate focal point, to the direction of the chief ray in the object field area is measured.

According to the present invention, it can be understood that this overall deflection is particularly advantageous for illuminating a horizontal angle mask. Especially when using a radiation source with a horizontal output direction of illuminating radiation, especially a FEL radiation source, has advantages.

According to a further aspect of the present invention, all the radiation reflecting components are configured so that the light beam with illuminating radiation has an incident angle of no more than 25°, especially no more than 22.5°, especially no more than 20°, especially It is not more than 17.5°, especially not more than 15°. Advantageously, all angles of incidence, especially all three angles of incidence, are equal.

This results in a particularly high overall transmission and/or is particularly advantageous, especially a sufficiently low degree of polarization of the illumination radiation.

According to a further aspect of the present invention, one of the radiation reflection components is configured and specifically implemented, so that the other radiation reflection component is imaged in the pupil plane of a downstream projection optical unit. In particular, it can be used for the radiation reflection component to be imaged in the mechanically inaccessible pupil plane of the downstream projection optical unit. In particular, the reflecting mirror that is prepared to be arranged between the second facet mirror and the object field, and the second facet mirror is imaged to a pupil plane of the projection optical unit.

According to a further aspect of the present invention, one of the radiation reflecting components has a switchable facet. In particular, the first radiation reflection component in the beam path is prepared to be implemented as a facet mirror with switchable facets.

Here, the cut surface can be switched to understand the rotation capabilities representing the cut surfaces, especially regarding the same configuration as a second facet mirror with different cut surfaces. The cut planes of the first facet mirror can also be switched to a position, where it does not contribute to the illumination of the object field.

According to a further aspect of the present invention, the two first ones of the radiation reflecting components in the beam path are separated from each other by a distance d ₁ , which is smaller than the distance between the second and third ones of the radiation reflecting components in the beam path. A distance d ₂ .

This is quite advantageous when the installation space is limited. The advantageous possibility of arranging many components is presented in the exemplary embodiments.

A further object of the present invention consists of improving an optical system, especially a scanner of a projection exposure system. This can be achieved by using an optical system including an illumination optical unit and a projection optical unit, wherein the illumination optical unit has at least two tangent elements and at least one advanced mirror, which is implemented and/or configured in the illumination optical In the light beam path of the unit, the second tangent element of the illumination optical unit is thus imaged into a pupil plane of the projection optical unit upstream of the first tangent element.

As a result, the optical design of the optical system can be significantly simplified. In particular, the advanced mirror rendering can image the second facet mirror, especially a pupil facet mirror, to a mechanically inaccessible pupil plane of the projection optical unit, especially a mechanically inaccessible pupil plane. Enter the pupil. The configuration of the advanced mirror upstream of the first slicing element in the beam path of the illuminating optical unit makes the configuration of the slicing mirrors in the available space easier. Furthermore, the heat load on the mirror can be reduced. It can reduce the incident angle on the first facet mirror. It can be further used to homogenize the far-field brightness distribution of the radiation source. In this way, the resolution of the illumination optical unit can be enhanced. In particular, the image change of the radiation source on the second slices can be reduced. Furthermore, the packaging density of the cut surfaces on the first cut surface element can be enhanced. Finally, out-of-band radiation, especially radiation having a wavelength less than 13.5nm and/or in the range of 13.5nm to 100nm, can be absorbed, or directed away from the main beam path, especially so that such radiation will not strike the first facet mirror.

In particular, the illumination optical unit corresponds to the above one. In particular, the illuminating optical unit is implemented so that all the radiation reflecting components that are the same are configured so that the light beam containing the illuminating radiation will be deflected in the same way on these components.

According to an alternative embodiment, the illumination optical unit is specifically implemented so that there is only one reflector in the beam path between the second tangent element and the object field, or There is only one mirror in the beam path upstream of the first slicing element.

A further object of the present invention consists of improving an illumination system, especially a projection exposure system including a plurality of scanners.

This can be achieved by using an illumination system that includes a radiation source in the form of a free electron laser (FEL) and at least one illumination optical unit according to the previous description.

A corresponding illuminating optical unit is particularly suitable for deflecting the illuminating radiation from a free electron laser (FEL) or synchrotron radiation source to a horizontally arranged mask.

According to one aspect of the present invention, the radiation source is specifically implemented and/or configured so as to emit a light beam with illuminating radiation extending in the horizontal direction.

In particular, the lighting system has a light beam entry direction, which is not more than 45° inclination relative to the object field, especially not more than 30°, especially not more than 15°, especially not more than 10°, especially not more than 5 °, especially not more than 3°, especially not more than 1°. Here, the object field is arranged in the object plane. In particular, the entry direction of the light beam extends parallel to the plane of the object.

A further object of the present invention consists of improving a projection exposure system. A projection exposure system including at least one illuminating optical unit according to the above, and at least one projection optical unit is used to image the object field to the image field to achieve this objective. The advantages are presented in these illumination optical units.

A further objective of the present invention is achieved by improving a method for producing a microstructure or nanostructure component, and a component produced according to this method. These objectives can be achieved by using a projection exposure system prepared to include an illumination optical unit according to the above. The advantages are presented above.

1: Projection exposure system

2: Radiation source module

3: Scanner

4: Radiation source

5: Illumination radiation

6: Original beam

7: Beam shaping optical unit

8: Concentrated output beam

9: Output link optical unit

10: Individual output beam

11: Object field

12: Individual partial beam

13: Beam guiding optical unit

14: Projection optical unit

15: Deflection optical unit

16: input link optical unit

17: Illumination optical unit

18: Lighting device

19: Lighting system

20: Optical system

21: Object plane

22: Mask

23: image field

24: Image plane

25: Wafer

26: middle focus

27: Intermediate focal plane

28: The first facet mirror

29: The second facet mirror

30: cut noodles

31: Cut Noodles

37: Advanced mirror

38: Shell

39: negative pressure device

40: entrance pupil

41: Mirror

The further advantages and details of the present invention come from the description of the exemplary embodiments based on the drawings. Detailed drawings: Figure 1 shows a schematic diagram of the components and subsystems of a projection exposure system; Figure 2 shows a schematic diagram of an optical system according to the projection exposure system in Figure 1 Figure; Figure 3A shows a graph of the reflectivity of the radiation reflecting element in view of the p-polarized EUV radiation depending on the most likely to be loaded into the stack thickness after the average incident angle and half-angle bandwidth; Figure 3B shows a diagram according to Figure 3A but for s polarization Diagram of EUV radiation; Figure 4 shows a diagram of the overall transmission of EUV radiation when the overall deflection of the three radiation reflecting elements is about 90° and the half-angle bandwidth of 3° depends on the first and second incident angles. Figure 5 shows the corresponding diagram of the polarization degree of an original unpolarized EUV beam; Figure 6 shows that the polarization degree of the illumination radiation depends on the numerical aperture to achieve the minimum slope of the spatial image side, expressed as "NILS> 2" schematic diagram; Figure 7 shows the diagram according to Figure 4, using the normalization of the overall transmission value that should occur when perpendicularly incident on all three radiation reflecting surfaces; Figure 8 shows the deflection on the three radiation reflecting elements And the overall deflection is 90°, depending on the predetermined incident angle, the relative maximum overall transmission diagram; Figure 9 shows the diagram corresponding to Figure 8 for the degree of polarization; Figure 10 shows the illumination optical unit and in its The geometry diagram in a downstream projection optical unit; Figure 11 shows that the maximum radius of the pupil facet mirror is used to show that it depends on the distance between the third beam deflecting mirror of the illumination optical unit and the light cover, And a diagram that depends on the distance between the mask and the entrance pupil of the projection optical unit; and FIG. 12 shows a schematic diagram of an alternative specific embodiment of an illumination optical system according to the projection exposure system in FIG. 1.

The basic components of a projection exposure system 1 are described below with reference to FIG. 1.

The division of the projection exposure system 1 into subsystems is mainly carried out under the terms of the division. These subsystems can form separate structural subsystems. However, the division into subsystems is not necessarily reflected in the structural division.

The projection exposure system 1 includes a radiation source module 2 and a plurality of scanners 3 _i .

The radiation source module 2 includes a radiation source 4 for generating illumination radiation 5.

The radiation source 4 is particularly a free electron laser (FEL), which can also be a synchrotron radiation source or a synchrotron radiation source, which generates coherent radiation with very high brightness. For this type of radiation source, refer to US 2007/0152171 A1 and DE 103 58 225 B3 by way of example.

By way of example, the average power of the radiation source 4 ranges from 1kW to 30kW, and has a pulse frequency ranging from 10MHz to 1.3GHz. Each individual radiation pulse can generate 83μJ of energy. In the case of a radiation pulse length of 100 fs, this corresponds to a radiation pulse power of 833 MW.

The radiation source 4 has a repetition rate in the kilohertz range, such as 100 kHz, in the low megahertz range, such as 3 MHz, in the medium megahertz range, such as 30 MHz, in the high megahertz range, such as 300 MHz, or in the gigahertz range, such as 1.3 GHz.

In particular, the radiation source 4 may be an EUV radiation source. In particular, the radiation source 4 emits EUV radiation having a wavelength range of, for example, between 2 nm and 30 nm, especially between 2 nm and 15 nm.

The radiation source 4 emits illuminating radiation 5 in the form of an original beam 6, which has a very low divergence. The divergence of the original light beam 6 is less than 10 milliradians, particularly less than 1 milliradians, particularly less than 100 microradians, and particularly less than 10 milliradians.

The radiation source module 2 further includes a beam shaping optical unit 7 which is arranged downstream of the radiation source 4. The beam shaping optical unit 7 is used to generate a concentrated output beam 8 from the original beam 6. The concentrated output beam 8 has very low divergence. The divergence of the concentrated output light beam 8 is less than 10 milliradians, particularly less than 1 milliradians, particularly less than 100 microradians, and particularly less than 10 microradians.

Furthermore, the radiation source module 2 includes an output connection optical unit 9 which is arranged downstream of the beam shaping optical unit 7. The output coupling optical unit 9 is used to generate multiple, in other words n, individual output light beams 10 _i (i=1 to n) from the concentrated output light beam 8. In each case, the individual output light beams 10 _i form light beams for illuminating an object field 11 _i . In each case, the light beams include a plurality of individual partial light beams 12 _i . In particular, there is a one-to-one correspondence between the individual output beams 10 _i and the illumination optical unit 17 _i or the scanner 3 _i.

The scanner 3 _i includes a beam guiding optical unit 13 _i and a projection optical unit 14 _i in each case.

The optical beam directing means 13 _i 5 for illumination radiation, in particular individual output beam 10 _i, guided to the individual object field scanner 3 _i 11 _i.

In each case, the projection optical unit 14 _{i is} used to image a mask 22 _i arranged in one of the object fields 11 _i to an image field 23 _i , especially to a mask 22 i arranged in the image field 23 _i Wafer _25i on.

The beam guiding optical unit 13 _i in the order of the beam path of the illuminating radiation 5 in each case includes a deflection optical unit 15 _i , an input link optical unit 16 _i , especially in the form of a focusing assembly, and an illumination optics Unit 17 _i . The input link optical unit 16 _i can be embodied in particular as a Wolter III collector.

According to a variation, the deflection optical unit 15 _i can be omitted. In addition, the deflection optical unit 15 _i can be specifically implemented, so that the individual output beam 10 _i can only be deflected at a small angle, especially the deflection angle is less than 30°, especially the deflection angle is less than 10°, especially the deflection angle is less than 5°, and especially The deflection angle is less than 2°.

In particular, the input connecting optical unit 16 _{i is} used to connect the illuminating radiation 5, especially one of the individual output light beams 10 _i generated by the output connecting optical unit 9 to an individual one of the illuminating optical unit 17 _i . In this way, the input connection optical unit 16 _i can also be omitted.

The beam guiding optical unit 13 _i, the beam shaping optical unit 7 and the output coupling optical unit 9 together form a part of an illuminating device 18.

The lighting device 18, like the radiation source 4, is a part of a lighting system 19.

Each illumination optical unit 17 _i is assigned to one of the projection optical units 14 _i , respectively. The illumination optical unit 17 _i and the projection optical unit 14 _i assigned to each other are also referred to as an optical system 20 _i .

In each case, the illuminating optical unit 17 _{i is} used to transmit the illuminating radiation 5 to a mask 22 _{i arranged within the object field 11 i} in an object plane 21. The projection optical unit 14 _i is used for imaging the photomask 22 _{i , especially for imaging the structure on the photomask 22 i,} on a wafer 25 _i arranged in an image field 23 _i in an image plane 24.

The projection exposure system 1 includes especially at least two, especially at least three, especially at least four, especially at least five, especially at least six, especially at least seven, especially at least eight, especially at least Nine, especially at least ten scanners 3 _i . The projection exposure system 1 can contain up to twenty scanners 3 _i .

The shared radiation source module 2, especially the shared radiation source 4, supplies the illuminating radiation 5 to the scanner 3 _i .

The projection exposure system 1 is used to produce microstructure or nanostructure components, especially electronic semiconductor components.

The illuminating radiation 5, in particular the individual output beams 10 _i , each pass through an intermediate focal point 26 _{i in the} intermediate focal plane 27. The intermediate focal point 26 _i can be respectively arranged in the area of the passage opening of the housing of the _{optical system 20 i} or the scanner 3 _{i, in particular, the housing can be evacuated.}

In each case, the illumination optical unit 17 _i includes a first facet mirror 28 _i and a second facet mirror 29 _i , which in each case depends on functions known from the prior art. The first facet mirror 28 _i can be a single field facet mirror, and the second facet mirror 29 _i can be a pupil facet mirror in particular. However, the second facet mirror 29 _i can also be arranged at a distance from the pupil plane of the _{illumination optical unit 17 i.} In general, it is also designated as a specular reflector.

The facet mirrors 28 _i and 29 _i also include multiple cut surfaces 30 and 31 in each case. During the operation of the projection exposure system 1, each first slice 30 is assigned to one of the second slices 31, respectively. In each case, the cut surfaces 30 and 31 are assigned to each other to form an illumination channel for the illumination radiation 5, which is used to illuminate the object field 11 _i at a specific illumination angle.

According to the desired lighting, especially the predetermined lighting settings, the channel assignment from the second section 31 to the first section 30 is performed one by one. In each case, the cut surface 30 of the first facet mirror 28 _i can be embodied to be replaceable, especially tiltable, especially with two tilting degrees of freedom. The cut surface 30 of the first facet mirror 28 _i can be particularly switched between different positions. In different switching positions, different second cutting surfaces 31 are assigned to different second cutting surfaces 31. In each case, at least one switching position of the first cut surface 30 can also be provided, in which the illumination radiation 5 colliding with it does not contribute to the illumination of the _{object field 11 i.} The cut surface 30 of the first facet mirror 28 _i can be embodied as a virtual cut surface 30, which should be understood as being formed by a plurality of individual mirrors, especially a variable group of a plurality of micro mirrors. For related details, please refer to WO 2009/100856 A1, the entire content of which is hereby incorporated into this application as a part.

The cut surface 31 of the second facet mirror 29 _i can be specifically implemented as a virtual cut surface 31 accordingly, and it can also be specifically implemented accordingly, so that it can be replaced, especially can be tilted.

With the second facet mirror 29 _i and an advanced mirror 37 _i , the first cut surface 30 is imaged into the object field 11 _i in the mask plane or object plane 21.

These individual lighting channels result in illuminating the object field 11 _i at a specific lighting angle. By using the illumination optical unit 17 _{i in this way} , all the illumination channels result in the illumination angle distribution of the illumination of the _{object field 11 i.} This illumination angle distribution is also called illumination setting.

The mask 22 _i has a structure that reflects the illuminating radiation 5 and is arranged in the object plane 21 in the area of the object _{field 11 i.} Photomask 22 _i is carried by a reticle holder, which mask holder can be replaced by a replacement device.

In each case, the projection optical unit 14 _i images the object field 11 _i into the image field 23 _i in the imaging plane 24. The wafer 25 _{i is} arranged in the imaging plane 24 during the projection exposure. The wafer 25 _i has a photosensitive coating which is exposed by the projection exposure system 1 during the projection exposure. The wafer 25 _{i is} carried by a wafer holder, and the wafer holder can be replaced by a replacement device.

The replacement device of the photomask holder and the replacement device of the wafer holder can be signal-connected to each other, especially synchronized. The photomask 22 _i and the wafer 25 _i can be replaced with each other in a synchronized manner in particular.

The further details and special features of the optical system 20 _i or the illumination system 19, especially the illumination optical unit 17 _{i, are described below.}

The illumination optical unit _{17i is} arranged in a housing 38, which is schematically indicated in FIG. 2. In particular, the housing 38 can be evacuated by the negative pressure device 39.

Illuminating radiation 5 to form one or more individual output beam 10 _i enters the illumination optical unit 17 _i, thus forming an illumination beam of radiation. The central ray of the illuminating radiation 5 enters an illuminating optical unit 17 _i , defining a beam direction. This illuminating radiation can continue to be referred to as the individual output beam 10 _i , even within the illuminating optical unit 17 _i .

The illumination radiation 5, in particular the individual output beam 10 _i , enters the illumination optical unit 17 _i horizontally. In particular, the illuminating radiation 5 enters the illuminating optical unit 17 _{i in} the _{region of the intermediate focal length 26 i.} The horizontal entry direction of the illuminating radiation 5 into the illuminating optical unit 17 _i has advantages, especially in combination with the radiation source 4 embodied as a free electron laser (FEL). In particular, the radiation reflecting element can be omitted in the beam path between the radiation source 4 and the illumination optical unit 17 _i.

If the individual output light beam 10 _i does not actually enter the illumination optical unit 17 _i , but only enters approximately horizontally, the advantages _{of the illumination optical unit 17 i according to the present invention also exist.} In this way, it is possible to continuously use a beam reflecting element in the beam path between the _{radiation source 4 and the illumination optical unit 17 i , in particular in order to achieve a favorable geometric configuration of the scanner 3 i with} respect to the output coupling optical unit 9.

The object plane 21 in which the mask 22 _{i is arranged extends horizontally.}

In an alternative embodiment, _{the object plane 21 in which the mask 22 i} is disposed is inclined to the horizontal direction, and the angle may be between 1° and 30°, especially between 2° and 8°. The individual output light beam 10 _i does not actually enter the illumination optical unit 17 _i , but only enters approximately horizontally. The deviations of the individual output light beam 10 _i from the horizontal direction and the object plane 22 from the horizontal direction are the same, that is _{, the angle between the individual output light beam 10 i} and the object plane is smaller than the two angles in the first example.

The illuminating radiation 5, especially the individual output beams 10 _i , will be deflected multiple times within the illuminating optical unit 17 _i. The individual output light beams 10 _{i are} specifically deflected on the first facet mirror 28 _i , the second facet mirror 29 _i and the advanced mirror 37 _i. In particular, it is precisely deflected three times within the beam path 26 _{i to the object field 11 i.} The three mirrors 28 _i , 29 _i and 37 _{i are} configured such that the individual output beam 10 _i is deflected in the same manner on all three mirrors 28 _i , 29 _i and 37 _i. Below, the incident angles and reflection angles on the three mirrors 28 _i , 29 _i and 37 _{i are denoted as α 1} , α ₂ and α ₃ .

The three mirrors 28 _i , 29 _i and 37 _i are all configured so that the overall transmission reaches the minimum and/or the desired degree of polarization of the illumination radiation. The overall transmission and/or degree of polarization to be achieved can be predetermined as boundary conditions, especially the three mirrors 28 _i , 29 _i and 37 _{i are} configured so that the overall transmission is maximized.

In particular, the illuminating optical unit 17 _i can be embodied as a compound eye condenser commonly called. The first facet mirror 28 _i can form a one-field facet mirror, the second facet mirror 29 _i can form a pupil facet mirror, and the advanced mirror 37 _i can be used to image the second facet mirror 29 _i to the projection optics. Inside the entrance pupil 40 of the unit 14 _i. In this way, a projection optical unit 14 _i having an inaccessible entrance pupil 40 can be used. _{Using the illumination optical unit 17 i} according to the present invention, a compound-eye condenser having _{a projection optical unit 14 i} with an inaccessible entrance pupil 40 can be used in particular. _{In particular, a projection optical unit 14 i} having a large numerical aperture can be used in this way. The specific embodiment in which the illumination optical unit 17 _i has a compound eye condenser simplifies the optical design of _{the optical system 20 i.}

The illumination optical unit 17 _i contains exactly three radiation deflection elements: a first facet mirror 28 _i , a second facet mirror 29 _i and an advanced mirror 37 _i . The advanced mirror 37 _{i is} arranged in the beam path between the second facet mirror 29 _i and the mask 22 _i. According to the present invention, it has been proven that the advanced mirror 37 _i can be used to achieve additional optical functions, in particular, even if it is located in a mechanically inaccessible plane, it can still be used to image the second facet mirror 29 _i to the projection optical unit 14 _i Inside the entrance pupil 40.

The illumination optical unit three mirrors 28 _i 17 _i's, 29 _i and 37 _i between the radiation leads to the inlet of the illumination optical unit 17 _i, 26 _i especially a middle focal object field with illumination between the optical unit 17 _i 11 _i, The overall deflection of the illumination radiation 5 at 90°.

The projection optical unit 14 _i includes a plurality of mirrors 41 _i . The mirror 41 _{i of the} projection optical unit 14 _i is numbered from 1 to n according to its order within the beam path of the illumination radiation 5 advancing from the mask 22 _i. The number n of the reflecting mirror 41 _i is at least two, and can be three, four, five, six, seven, eight or more.

To describe the present invention, FIGS. 3A and 3B illustrate the dependence of the reflectivity of individual mirrors with multiple layers on the average incident angle (ew) (x-axis) and half-angle bandwidth (wbb) (y-axis). Figure 3A illustrates the reflectivity for p-polarized radiation. Figure 3B illustrates the reflectivity for s-polarized radiation. The contour line with internal reflectance values ranging from 10% to 60% has been regenerated.

For a known incident direction, the reflectivity of the multilayer depends on the thickness of the individual layers. If light is incident with a specific angular bandwidth of approximately the average incident angle, the layer stack thickness must be adjusted according to the average incident angle and the half-angle bandwidth in order to optimize the overall reflectivity.

From a specific reflection value, it can be determined how high the overall transmission is in a system with multiple reflections, especially in a system with three reflections, that is, three radiation deflection.

This specific embodiment of the illumination optical unit 17 _i has been optimized to take the following boundary conditions into consideration: _{the overall deflection on the three mirrors 28 i} , 29 _i and 37 _i is 90°. The individual output beam 10 _i has a half-angle bandwidth of 3°, which is 52 mrad.

Generally speaking, the overall transmission depends on three average incident angles, which can be represented by the angle-dependent reflectance values for the individual reflections of p-polarized and S-polarized light.

The boundary condition, according to which the overall deflection is 90°, can be rewritten as a range where the sum of the three incident angles is 45°. One angle can be removed in this way, so the overall transmission presented depends on the two remaining angles. Corresponding pictures are shown in Figure 4. The contour lines in each case correspond to the overall transmission with a certain degree of transmission.

Figure 5 accordingly describes the degree of polarization after three reflections. The innermost contour corresponds to a degree of polarization of 20%; the outermost contour corresponds to a degree of polarization of 80%.

According to the present invention, what is to be identified and considered is that the degree of polarization has a substantial influence on the resolution line width. The relevant parameter in this range is the so-called NILS value (normalized intensity recording squared value), which represents a measure of the steepness of the side surface of the spatial image. For rough instructions, that is to say in space The intra-image stabilization lithography process should reach a NILS value of at least 2, that is, the impedance diffusion is not considered.

Figure 6 illustrates in an exemplary manner that the regions with NILS>2 and NILS<2 depend on the numerical aperture (NA) and the degree of polarization (DOP). Here, tangential polarization is expressed as DOP>0, and radial polarization is expressed as DOP<0. The meaning of the tangent and the radial depends on _{the structure of the mask 22 i} , so the deflection position of the beam is not known. Therefore, by precautions, it is necessary to assume the worst case when DOP≠0. It can be found from Figure 6 that when the numerical aperture (NA) is 0.6, the degree of polarization (DOP) is up to 20% to determine a stable lithography process (NILS>2). Consider 20% of the polarization degree as the maximum acceptable value.

In order to better compare the _{overall transmission with other systems in the case of reflection on the three mirrors 28 i} , 29 _i and 37 _i , Fig. 7 again describes the diagram from Fig. 4, and the overall transmission under the condition of three reflections at normal incidence The value is normalized. The maximum relevant overall transmission exceeds 70%.

Aiming at the current angular dependence of the reflectivity of these individual layers, it is found that when all three angles α ₁ , α ₂ and α ₃ are consistent, it is 15°, and α ₁ = α ₂ = α ₃ =15°, which will reach The maximum overall transmission.

In a specific environment, one of the three deflection angles can be selected to be less than 30°, that is, for optical aberration, so the corresponding incident angle should be selected to be less than 15°. Therefore, the other two angles increase, and thus the overall transmission decreases. _{Fig. 8 shows the relative overall transmission T rel.} which can be achieved with three deflections, which is related to the maximum possible overall transmission of a system with an overall deflection of 90°, depends on this incident angle. Figure 9 presents the corresponding degree of polarization DOP.

10 schematically describes the geometry of the optical system within the environment 20 _i, 17 _i within the particular illumination optical unit. The relevant variables are the distance d between the components, the focal length of the components, defined as f below, and the radius r of the components. In this respect, we should refer to the fact that r _PF represents the radius of the entire pupil facet mirror 29 _{i , and r FF} represents the radius of each of the field facet 30, d _FF,PF represents the field facet mirror 28 _i and the pupil The distance between the facet mirror 29 _{i ; d PF,N} represents the distance between the pupil facet mirror 29 _i and the advanced reflector 37 _i ; d _N,Ret represents the advanced reflector 37 _i and the mask 22 _i The distance between; d _{Ret, Pup} represents the distance between the mask 22 _i and the pupil plane 40.

The field cut surface 30 has been imaged on the mask 22 _i , which is precisely based on the dual mirror system composed of one of the pupil cut surface 31 and the advanced mirror 37 _i. This can be represented by the corresponding imaging situation and the corresponding back focus situation.

The pupil section 31 has been imaged to _{the entrance pupil 40 of the projection optical unit 14 i} , which can also be represented by imaging conditions and back focus conditions. Here, the numerical aperture NA on the mask is included in the back focus condition of the later imaging case.

The focal lengths of the pupil facet mirror 29 _i and the field facet mirror 28 _i of the advanced mirror 37 _i can be freely selected as the largest possible range, and therefore are not further related to the construction conditions. If many clear dependencies on the focal length f have been eliminated, the following conditions will arise from the imaging and back focus conditions: d _N,Ret r _PF =d _Ret,Pup (d _PF,N NA-r _PF )

r _FF r _PF =d _FF,PF NA r _Ret

d _FF,PF d _N,Ret r _Ret =d _Ret,Pup (d _PF,N r _FF -d _FF,PF -r _Ret )

These conditions can be further shortened: d _PF,N d _Ret,Pup NA=(d _Ret,Pup +d _N,Ret )r _PF

d _PF,N d _Ret,Pup r _FF =d _FF,PF (d _Ret,Pup +d _N,Ret )r _Ret

According to the present invention, it is further confirmed that the geometric boundary conditions can be divided into the following groups: pupil facet mirror 29 _i , field facet mirror 28 _i and advanced mirror 37 _i cannot be too large or too small, that is, r _FF and r _PF must be Within a certain interval. The advantageous dimensions of the field sections have a radius of 5 mm to 200 mm, in particular between 20 mm and 70 mm. The advantageous dimensions of the pupil cut surfaces have a radius of 1 mm to 10 mm, in particular between 2 mm and 5 mm.

The distance between these components cannot be particularly large or small, and must be within a specific interval.

_{In particular, the distance d FF,PF} between the two facet mirrors 28 _i and 29 _i is in the range from 500 mm to 1500 mm. _{In particular, the distance d PF,N} between the second facet mirror 29 _i and the advanced mirror 37 _i is in the range from 650 mm to 1800 mm. In particular, _{the distance d N,Ret between the advanced mirror 37 i} and the mask 22 _i is in the range from 1000 mm to 3000 mm. The difference d _{PF, N-} d _{FF, PF is} at least 150 mm, especially if it lies in the range from 150 mm to 1000 mm. In particular, the difference d _{N, Ret-} d _{PF, N is} greater than -100 mm. In particular, it lies in the range from -100 mm to 150 mm.

c₁以及d_N,Ret-d_FF,PF

c₂，具有正常數c₁和c₂。 The distance between these components must meet certain conditions between them to avoid installation space conflicts. In particular, the pupil facet mirror 29 _i cannot exceed the object plane 21 containing the mask 22 _i , because this volume is already occupied by the mask step. With an example, it can be expressed by the following conditions: d _N,Ret -d _PF,N

c ₁ and d _N,Ret -d _FF,PF

c ₂ , with normal numbers c ₁ and c ₂ .

If the size of the field section 30 does not matter, and only the radius r _{PF of the pupil facet 29 i} is important, the following appears:

Omitting d _N,Ret in the denominator results in an estimate: r _PF <d _PF,N NA.

If the distance between the inner pupil facet 29 _i and the mask 22 _{i of the optical system 20 i} with the projection optical unit 14 _i that can reach the entrance pupil 40 is used instead of _{d PF,N} , this prediction should accurately result in the pupil The radius r _{PF of the} facet mirror 29 _i .

Other estimates are derived from the fact that due to the aforementioned installation space conditions, the following applies: d _PF,N <d _N,Ret . This leads to the following:

A graphical representation of this dependency relationship is presented in Figure 11.

Therefore, the pupil facet mirror 29 _{i is} significantly smaller than the size that should be in the lithography system with the accessible entrance pupil of the projection optical unit. If the size of the individual pupil sections is reduced due to production factors, it means that the number of pupil sections must be reduced.

Also because of this factor, the radiation source 4 is advantageously embodied as a free electron laser (FEL). Within the FEL, the smallest possible pupil filling must be provided and it is not limited by the concentration of the radiation source. Therefore, the requirement for a specific minimum number of pupil sections 31 is less significant, _{and the distance between a possible intermediate focus and the field facet mirror 28 i} is not directly related, and is only included in the necessary diopter of the field section 30.

Table 1 presents example-specific values that may be achieved. All implementations assume that the radius of the mask is 52mm, and all length units are mm. In order to be comparable with the data from the known EUV optical unit, Table 1 specifies the numerical aperture NA on the _{wafer 25 i} and the imaging ratio of the _{projection optical unit 14 i.}

Since the focal lengths f _PF , f _FF and f _N are not related to the realization statement, they are not listed in the table.

It can be implemented in a non-diopter field section 30 and/or pupil section 31, that is, in a plane aspect. The result can be cost savings. In this case, the demonstration design is summarized in Table 2:

In the following, an alternative specific embodiment of the _{illumination optical unit 17 i will be} described with reference to FIG. 12. This specific embodiment basically corresponds to the previously described specific embodiment shown in FIG. 2 and is incorporated by reference at this time. Compared with the specific embodiment shown in Figure 2, the three mirrors 28 _i , 29 _i and 37 _i are rearranged, which are specifically arranged in the beam path, so that the advanced mirror 37 _i is located in front, that is, the first Upstream of facet mirror 28 _i.

With this configuration, it is easier to configure the facet mirrors 28 _i and 29 _i , especially the first facet mirror 28 _i in the available space.

With this configuration, no facet mirrors 28 _i and 29 _{i are} imaged into the pupil plane 40 of the downstream projection optical unit 14 _i.

The reflecting mirror 37 _i may have an aspherical reflecting surface, and it may particularly have a reflecting surface corresponding to a conical section. The reflective surface of the mirror 37 _i may not have rotational symmetry, and in particular, it may also be called a free-form surface.

The surface of the reflector 37 _i can be designed to homogenize the far-field brightness distribution of the radiation source 4. This can reduce the heat load, especially the heat load on the _{facet mirrors 28 i} and 29 _i. Furthermore, the resolution of the illumination optical unit 17 _{i can be enhanced.} This can be caused by the reduction in the size of the image of the radiation source 4 on the cut surface 31 of the second facet mirror 29 _i.

In particular, _{the reflecting surface of the reflector 37 i} can be designed to correct the change in the regeneration ratio _{for imaging the radiation source 4 to the intermediate focus 26 i} due to the shape of the collector reflector of the radiation source module. In this way, the _{size of the cut surface 31 of the second facet mirror 29 i} is reduced and the pupil filler can be reduced, resulting in an enhanced resolution of the _{optical unit 17 i.}

The reflecting surface of the reflecting mirror 37 _i can also be designed to enhance the efficiency of the upper cut surface 30 of the _{first facet mirror 28 i.} For this purpose, the reflecting surface of the mirror 37 _i can in particular be a free-form surface. In this way, the _{luminous intensity} at the intermediate focal point 26 i can be changed, so that the far field of the radiation source 4 is assumed to be rectangular or at least approximately rectangular in shape.

Using a continuous differentiable surface, the boundary of the mirror will be mapped to the boundary of the far field. Because the boundary of the mirror is continuously differentiable, the boundary of the far field must also be different. Therefore, a far-field boundary without corners will be realized. By appropriately defining the mapping, the corner can be approximated to a continuous differentiable curve using a large curvature (for example ^{, the behavior of x n} where n is larger). If the mirror is the only piecewise continuous differentiable, it means that there are kinks in the surface, and the far field boundary will have corners.

The image shape of the radiation source 4 in the intermediate focal point 26 _i can be specifically transformed into the shape of the cut surface 30 of the _{first facet mirror 28 i.}

According to another aspect of the present invention, _{the reflecting surface of the reflecting mirror 37 i} can be designed to reduce the incident angle of the illumination radiation on the tangent surface 30 of the _{first facet mirror 28 i.} To this end, _{the reflecting surface of the reflecting mirror 37 i} may have the shape of a paraboloid of revolution or a segment thereof. In this way, the intermediate focus 26 _i can be imaged to infinity. This allows collimating the radiation beam diverging on the first facet mirror 28 _i , thereby reducing the angle of incidence of the illuminating radiation 5 on the tangent plane 30. At the same time, the angle of incidence of the illuminating radiation 5 on the cut surface 30 is reduced, resulting in a reduction in the shadow effect.

According to another aspect of the present invention, out-of-band radiation, especially radiation having a wavelength of less than 13.5 nm and/or a wavelength between 13.5 nm and 100 nm, can be absorbed or directed _{by the reflector 37 i,} In particular, the reflection is away from the first facet mirror 28 _i . In this way, the appearance of the _{first facet mirror 28 i can be reduced.} This is particularly advantageous because it is easy to cool because of the single embodiment of the _{mirror 37 i.}

_{Furthermore, the configuration of the mirrors 37 i} , 28 _i and 29 _i according to FIG. 12 has the advantage that the mirrors can be easily exchanged with replacement mirrors, which may be necessary when the radiation source 4 has been replaced. Generally speaking, _{the space required by the reflecting mirror 37 i} is smaller than that of the first facet mirror 28 _i . Even if the incident angle distribution of the illuminating radiation 5 on this mirror 37 _i is changed, the illumination of the _{first facet mirror 28 i} will change, the light collector _{including the two facet mirrors 28 i} and 29 _{i can still be kept from following} The channel assignment from the second cut surface 31 to the first cut surface 30 varies. This can be used to demodulate the reflective layer so that only the total transmission is reduced according to the local enhanced absorption.

The different specific embodiments of the illumination optical unit 17 _i described here are not only advantageous when using a FEL and radiation source 4, but also when combined with a plasma source, especially when compared with the horizontal or approximately horizontal illumination radiation 5 When the plasma source of the beam path is combined.

5: Illumination radiation

10: Individual output beam

14: Projection optical unit

17: Illumination optical unit

20: Optical system

21: Object plane

22: Mask

24: Image plane

25: Wafer

26: middle focus

28: The first facet mirror

29: The second facet mirror

30: cut noodles

31: Cut Noodles

37: Advanced mirror

38: Shell

39: negative pressure device

41: Mirror

Claims (12)

A way for a projection exposure system (1) illuminating radiation guide (5) to an object field (11 _i) an illumination optical unit (17 _i), comprising 1.1 a plurality of radiation-reflector assembly 1.2. All such radiation-reflector assembly wherein _{Are configured so that a beam (10 i} ) with illuminating radiation (5) is deflected in the same manner on these components, wherein all the radiation reflecting components are configured so that the beam (16 i) containing illuminating radiation (5) _i ) each has an incident angle (α _i ), which does not exceed 25° on each of the radiation reflecting components; wherein the light beam (10 _i ) with the illuminating radiation (5) is on each of the radiation reflecting components One is deflected by a deflection angle, and the ratio between any two deflection angles does not exceed 1.5; wherein the radiation reflecting components include a first facet mirror (28 _i ), a second facet mirror (29 _i ), and At least one advanced mirror (37 _i ), which is arranged downstream of the second facet mirror (29 _i ) or upstream of the first facet mirror (28 _i ) in the beam path. A way for a projection exposure system (1) illuminating radiation guide (5) to an object field (11 _i) an illumination optical unit (17 _i), comprising 2.1 a plurality of radiation-reflector assembly 2.2. All such radiation-reflector assembly wherein Are configured so that a beam (10i) with illuminating radiation (5) is deflected in the same manner on these components, wherein all the radiation reflecting components are configured such that the beam (16 _{i) containing illuminating radiation (5)} ) Respectively have an incident angle (α _i ), which does not exceed 25° on each of the radiation reflecting components; wherein the radiation reflecting components cause the overall deflection of the light beam containing the illuminating radiation (5) to be from 45° Within the range of 135°; wherein the radiation reflecting components include a first facet mirror (28 _i ), a second facet mirror (29 _i ) and at least one advanced mirror (37 _i ), the mirror It is arranged downstream of the second facet mirror (29 _i ) or upstream of the first facet mirror (28 _i ) in the beam path. _{The illumination optical unit (17 i} ) described in item 1 or 2 of the aforementioned patent application is characterized in that the radiation reflecting components include a first facet mirror (28 _i ) and a first facet mirror (28 i) in the direction of the beam path A second facet mirror (29 _i ) and an advanced mirror (37 _i ), the latter being arranged in the beam path between _{the second facet mirror (29 i} ) and the object field (11 _i) , Or in the beam path before the first facet mirror (28 _{i ). The illumination optical unit (17 i} ) described in item 1 or 2 of the aforementioned patent application is characterized in that one of the radiation reflecting components images the other of the radiation reflecting components to a downstream projection optical unit ( 14 _i ) within a pupil plane (40). _{The illumination optical unit (17 i} ) described in item 1 or 2 of the aforementioned patent application is characterized in that the first of the radiation reflection components in the beam path of the illumination radiation (5) is embodied as a The facet mirror (28 _i ), which has a switchable section (30). _{The illumination optical unit (17 i} ) described in item 1 or 2 of the aforementioned patent application is characterized in that the two first ones of the radiation reflection components in the beam path are separated from each other by a distance (d1), which is smaller than the A distance (d2) between the second and third of the radiation reflecting components in the beam path. An optical system (20 _i ), including 7.1. An illuminating optical unit (17 _i ), used to guide the illuminating radiation (5) to an object field (11 _i ), including 7.1.1. A first cut surface element (28 _i ), 7.1.2 a second tangent element (29 _i ), and 7.1.3 at least one advanced mirror (37 _i ), 7.2. a projection optical unit (14 _i ), used in an image field (23 _i ) imaging the object field (11 _i ), 7.3. wherein the at least one advanced mirror (37 _i ) has been implemented and/or arranged in the optical path of _{the illumination optical unit (17 i ),} 7.3.1. Thus imaging the second facet mirror (29 _i ) to a pupil plane of the projection optical unit (14 _i ), or 7.3.2 upstream of the first facet element (28 _{i ),} And 7.4. Wherein all the radiation reflection components of the illumination optical unit (17 _{i ) are configured so that a light beam (10 i} ) with illuminating radiation (5) is deflected in the same manner on these components, wherein all the radiation reflection components The radiation reflecting components are all configured so that the light beam (16 _i ) containing the illuminating radiation (5) has an angle of incidence (α _i ), which does not exceed 25° on each of the radiation reflecting components; there is an illumination _{The beam (10 i} ) of the radiation (5) is deflected by a deflection angle on each of the radiation reflecting components, and the ratio between any two deflection angles does not exceed 1.5. An illumination system (19) comprising 8.1. A radiation source (4) in the form of a free electron laser (FEL), and 8.2. At least one illumination optics as in any one of items 1 to 6 in the scope of the patent application Unit (17 _i ). The lighting system (19) described in item 8 of the scope of patent application is characterized in that the radiation source (4) is specifically implemented and/or configured so as to emit a beam of illuminating radiation (5) extending in the horizontal direction. A projection exposure system (1), including 10.1. At least one illumination optical unit (17 _i ) as in any one of items 1 to 6 in the scope of the patent application, and 10.2. at least one projection optical unit (14 _i ), used in Image the object field (11 _i ) into an image field (23 _i ). A method for producing a microstructure or nanostructure component. The method includes the following steps: -providing a substrate, on which at least a part of which is coated with a layer made of photosensitive material, -providing a photomask (22 _i ), which It has the structure to be imaged, -provides the projection exposure system (1) as in the tenth item of the scope of patent application, -projects at least part of the mask (22 _i ) to the projection exposure system (1) with the help of the On the photosensitive layer area of the substrate. A component produced by the method described in item 11 of the scope of the patent application.

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