DE102012207511A1 - Facet mirror e.g. field facet mirror, for channel-wise reflection of light radiation in UV micro-lithographic projection exposure system, has displaceable micro mirrors whose facet reflecting surfaces exhibit specific area - Google Patents

Abstract

The mirror e.g. field facet mirror (19), has a set of simple facets (38e) and a set of composite facets (38z) comprising two sets of facet reflecting surfaces, respectively. The facet reflecting surfaces of the composite facets are assembled to a set of single reflecting surfaces of displaceable micro mirrors (28). Facet reflecting surfaces of the simple facets and the single reflecting surfaces of the displaceable micro mirrors exhibit areas of about 10 and 5 square mm, respectively, where number of simple facets lies within a range of 20-1000. Independent claims are also included for the following: (1) a lighting system (2) a method for lighting an object field (3) an optical system (4) a method for manufacturing a micro or nano-structured component.

Description

The invention relates to a facet mirror for channelwise reflection of illumination radiation. The invention also relates to an illumination optics for illuminating an object field and to a method for illuminating an object field. Furthermore, the invention relates to a lighting system for a projection exposure apparatus, a projection exposure apparatus, a method for producing a micro- or nanostructured component and a component produced in this way.

Illumination optics with faceted mirrors are from the DE 10 2008 009 600 A1 and the DE 10 2009 045 694 A1 known.

It is an object of the present invention to improve a facet mirror for illumination optics.

This object is solved by the features of claim 1.

The essence of the invention is to realize a plurality of facets by macroscopic facets in a faceted mirror, while a plurality of facets of a plurality of displaceable micromirrors is composed. In particular, it is envisaged to form the majority of the facets, in particular at least 80% of the total number of facets, as macroscopic, simple facets.

Such a facet mirror is on the one hand much easier to produce than a facet mirror, which is predominantly or exclusively composed of micromirrors. On the other hand, it has surprisingly been found that even a comparatively small number of displaceable micromirrors is sufficient to significantly improve the imaging properties of the facet mirror.

The micromirrors are in particular combined into modules. These modules are preferably each designed as a micro-electro-mechanical system (MEMS). The modules each have at least 16, in particular at least 64, in particular at least 144 individual mirrors.

Advantageously, at least a subset of the micromirrors, in particular all of the micromirrors, can be grouped into a plurality of groups in such a way that a group reflection surface formed from the entirety of the individual reflection surfaces of a group in each case approximates the shape of a simple facet. The group reflection surface, which forms the facet reflection surface of a composite facet, has in particular dimensions in a longitudinal and a transverse direction which deviate at most by the extent of two micromirrors, in particular at most the extent of a micromirror, from those of a simple facet. The approximation of the shape of the simple facets can be flexibly adapted by displacing individual micromirrors. This makes it possible to vary the effectively used reflection area of the composite facets. As a result, a very flexible adaptation of the overall intensity and intensity distribution of the reflected illumination radiation is possible. This can advantageously be used, for example, to correct deviations in the scan-integrated overall intensity, a so-called uniformity, the illumination of an object field.

The number of micromirrors per compound facet is in the range of 150 to 20,000, in particular in the range of 400 to 1,500.

The total number of micromirrors of the facet mirror is at least 1000, in particular at least 5000, in particular at least 20 000.

The number of simple facets of the facet mirror is in the range of 20 to 1000, in particular in the range of 50 to 500.

The facets are preferably arranged in columns, in particular in half-columns. According to one aspect of the invention, it is provided to form exactly one or more of these half-slits as composite facets. The remaining half-columns are preferably formed from simple facets.

Another object of the invention is to improve an illumination optics for illuminating an object field and an illumination system for a projection exposure apparatus. These objects are achieved by the features of claims 7 and 8. The advantages correspond to those described above for the facet mirror.

Another object of the invention is to improve a method for illuminating an object field. This object is solved by the features of claim 9. The essence of the invention is to adapt the illumination of an object field by displacing a number of the micromirrors of the composite facets with the facet mirror according to the invention such that the illumination has a high uniformity and at the same time the image of a composite field facet illuminates at least 80% of the object field. The images of the composite facets in the object plane have, in particular, dimensions which are not more than 20%, in particular not more than 10%, in particular by at most 5% of those of the object field to be illuminated. They deviate, in particular in the direction perpendicular to the scanning direction, by at most 20%, in particular at most 10%, in particular at most 5%, from those of the object field to be illuminated.

In other words, with the facet mirror according to the invention, an illumination setting of an object field can be achieved in which the illumination of the object field has a high degree of uniformity and at the same time a given illumination channel largely illuminates the given object field without significant loss of light.

Further objects of the invention are to improve a method for producing a micro- or nanostructured component and a corresponding component. These objects are achieved by the features of claims 10, 11 and 12.

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 schematically a plan view of a section of a Feldfacettenspiegels for use in the projection exposure system according to 1 ;

3 Representations of the scan-integrated intensity of a lighting channel for a known from the prior art EUV lighting system and a lighting system with a facet mirror according to 2 ,

1 schematically shows in a meridional section a projection exposure system 1 for micro-lithography. To the projection exposure system 1 belongs to a 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 , This carries outside of the object field 5 falling radiation not for imaging the object field 5 in a picture field 11 at. 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 object holder 8th is about a object displacement drive 9 displaceable along a 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, also not shown 14 held. The wafer holder 14 is about a wafer displacement drive 15 synchronized to the object holder 8th also displaceable along the 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 a 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 emanating 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 with a variety of field facets 38 meets. The field facet mirror 19 is a first facet mirror of the illumination optics 4 , The field facet mirror 19 is in a plane of illumination optics 4 arranged to the object level 6 is optically conjugated.

The EUV radiation 16 is hereinafter also referred to as illumination radiation, illumination light or 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 projection optics 10 is optically conjugated or coincides with this pupil plane. The pupil facet mirror 20 has a plurality of pupil facets 37 in the 1 are not shown. With the help of the pupil facets 37 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 field facets 38 in the object field 5 displayed. The last mirror 24 the transmission optics 21 is a grazing incidence mirror.

The field facets 38 of the field facet mirror 19 are the pupil facets 37 of the pupil facet mirror 20 for the education of Illumination channels for illuminating the object field 5 individually assignable with certain angles of incidence.

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. Here, the z-direction is in each case parallel to the optical axis, that is aligned to the central main radiation direction. The x-direction runs in 1 perpendicular to the drawing plane into this. The y direction is in the 1 shown running to the right. It is in the area of the object plane 6 parallel to the direction of displacement of the object holder 8th and in the area of the image plane 12 parallel to the direction of displacement of the wafer holder 14 ,

A pupil facet 37 generates an image of the assigned field facet 38 in the object plane 6 , The image of the field facets 38 in the object plane 6 in this case has dimensions which are advantageously at most 20%, in particular at most 10% of those of the object field 5 differ. For the operation of the projection exposure machine 1 It is beneficial if the image of a field facet 37 the object field 5 each as completely as possible. In other words, the illumination channels are advantageously designed such that the object field 5 with each of the illumination channels as completely as possible, in particular at least 80%, in particular at least 90%, in particular at least 95%, can be illuminated. This is especially true in the y direction. Will the object field 5 in y-direction from an image of a field facet 38 only partially filled, so is the Lichtleitwert, the projection optics 10 can transport, only a part exploited. With a fixed optical conductivity of the radiation source 2 and fixed tolerance and stability requirements for the projection exposure equipment 1 The pupil filling would then increase, which can adversely affect the imaging quality of the projection exposure apparatus. This strength of this undesirable effect can be quantified by indicating what proportion of the object field 5 from the picture of a field facet 38 each filled out. This value is understood to mean that the difference between the largest y-coordinate in the object field 5 (relative to the y-coordinate of the center of the object field 5 for the corresponding x-coordinate) and the smallest y-coordinate in the object field 5 (relative to the y-coordinate of the center of the object field 5 for the corresponding x-coordinate) is formed. This definition effectively means that the light conductance loss caused by the rotation of the image of the field facet 38 due to the aberrations of the pupil facet 37 occurs, is not considered.

The following is with reference to the 2 the inventive structure of the facet mirror 19 described in more detail. The field facet mirror 19 has a x0 / y0 extent, which, depending on the design, for example, 300 mm × 300 mm or 600 mm × 600 mm. The facet mirror 19 includes a variety of simple facets 38e , The simple facets 38e have simply contiguous facet reflection surfaces. With the simple facets 38e these are macroscopic mirrors with a facet reflection surface of at least 10 mm ² , in particular at least 50 mm ² . The facet reflection surface of the simple facets 38e corresponds, apart from a possible scaling, the dimensions of the object field 5 , In particular, it has an aspect ratio of at least 8: 1, in particular at least 13: 1. The simple facets 38e are preferably rectangular or arcuate.

The number of simple facets 38e is in the range of 20 to 1000, in particular in the range of 50 to 500. They are preferably in several columns 25 on the field facet mirror 19 arranged. The columns 25 are each through a central, non-reflective area 26 in half columns 27 divided.

Like in the 2 is shown schematically, the invention provides the simple facets 38e the central upper half-column 27 through compound facets 38z to replace. The facet mirror according to the invention 19 thus comprises a plurality of composite facets 38z , The number of compound facets 38z ranges from 1% to 20% of the total number of facets 38 of the facet mirror 19 , The composite facets 38z have faceted reflection facets consisting of a plurality of individual reflection surfaces of displaceable micromirrors 28 are composed. The micromirrors 28 have dimensions in the range of 10 μm × 10 μm to 2 mm × 2 mm. In particular, they have individual reflection surfaces with an area of at most 5 mm 2, in particular at most 10 ^-6 m 2, in particular at most 10 ^-8 m 2, in particular at most 10 ^-10 m 2. They are designed such that a portion of the illumination radiation reflected by it 16 each a section of the object field 5 whose area is at most 1%, in particular at most 1 ‰, in particular at most 0.1 ‰ of the area of the entire object field 5 is. The micromirrors 28 have in particular identical dimensions. For details of the micromirrors 28 and the formation of compound facets 38z through the micromirrors 28 be on the WO 2009/100 856 A1 referenced, which should be fully incorporated into this application.

The micromirrors 28 are in modules 29 arranged. Each of the modules 29 comprises at least 16, in particular at least 64, in particular at least 256 micromirrors 28 , The micromirrors 28 are displaceable by means of actuators. In particular, they are controllably displaceable in modules by a central control device. The modules 29 are each designed as a micro-electro-mechanical system (MEMS).

The total number of micromirrors 28 of the facet mirror 19 is at least 1000, in particular at least 10000.

The micromirrors 28 are square shaped. Other forms, the most complete occupation of the reflection surface of the composite facets 38z are possible. Such alternative micromirror forms are known from the mathematical theory of tiling.

The micromirrors 28 every module 29 are arranged in a matrix, that is an array, of rows and columns. The arrangement of the rows and columns of the arrays of micromirrors 28 may be rotated relative to the xyz coordinate system, in particular relative to the direction of displacement. In particular, they can be twisted by 45 °.

The micromirrors 28 are trained plan. Your reflection surface thus has no curvature. They each have an EUV-reflecting coating, in particular a multi-layer coating.

The distance between two adjacent micromirrors 28 same module 29 is at most 100 .mu.m, in particular at most 50 .mu.m, preferably at most 10 .mu.m. The micromirrors 28 a module 29 are thus essentially seamless, that is arranged densely packed.

The distance between adjacent modules 29 may be greater than the spacing of adjacent micromirrors 28 same module 29 ,

Each of the micromirrors 28 is independently tiltable about two mutually perpendicular tilting axes. The two tilt axes lie in the individual reflection surfaces of the respective micromirrors 28 ,

The micromirrors 28 are in particular designed individually tiltable between at least two tilt positions. This carries the from the respective micromirrors 28 reflected illumination radiation 16 in the first tilted position to a total intensity of the illumination radiation 16 of the respective illumination channel in the object field 5 at. There may be several first tilt positions in which the illumination radiation 16 about different pupil facets 37 to the object field 5 to be led. In the second tilt position of the micromirrors 28 becomes that of the respective micromirrors 28 reflected radiation 16 not to the object field 5 and thus does not contribute to the overall intensity of the illumination radiation 16 of the respective illumination channel in the object field 5 at. It is thus possible in other words, all micromirrors 28 a composite field facet 38z for guiding the illumination radiation 16 from the radiation source 2 to the object field 5 to use or single of the micromirrors 28 off. This makes it possible, the total intensity of the individual radiation channels in the field of the object field 5 by tilting a suitable selection of micromirrors 28 to adapt to a predetermined value. As a result, the uniformity of each individual radiation channel can be improved. In particular, it is possible to reduce the field dependence of the pupil.

Preferably, by means of the actuators also an individual displacement of the micromirrors 28 in z-direction possible. The micromirrors 28 are therefore separately controllable along a normal to the reflection surface displaced. As a result, the topography of the reflection surface can be changed overall.

In principle it is also possible to use a part of the micromirrors 28 rigid, that is, not displaceable. Generally, at least some of the micromirrors are 28 displaced. Preferably, all micromirrors are 28 displaced.

The micromirrors 28 are each grouped into groups such that one of the totality of the individual reflection surfaces of one of the groups formed group reflection surface each have the shape of one of the simple facets 38e approximated.

The micromirrors 28 a composite field facet 38z can belong to different individual mirror groups.

The number of micromirrors 28 a composite field facet 38z is in the range of 1 to 10 ⁶ , in particular in the range of 150 to 20,000, in particular in the range of 400 to 1500.

The group reflection surface of the composite facets 38z is thus the discrete sum of the individual reflection surfaces of the associated micromirrors 28 , By individual displacement of the micromirrors 28 , in particular in the edge region of the composite facets 38z , the approximation may be the shape of the simple facets 38e be flexibly adapted. This makes it possible, in particular, the number of micromirrors 28 . which to each of the compound facets 38z contribute, adapt flexibly. By tilting individual micromirrors 28 can thus be that of a compound facet 38z into the object field 5 reflected intensity of the illumination radiation 16 be varied depending on location. This can be used for a so-called uniformity correction.

In a known from the prior art facet mirror, which has only simple facets, it comes in the field of the object field 5 to a location dependence of the intensity of a radiation channel. The relevant quantity for characterizing such a location dependence is the so-called uniformity. In a trained as a scanner projection exposure system 1 In this case, in particular, the integral of the intensity perpendicular to the direction of displacement is relevant. The scan-integrated intensity in the area of the object plane 6 results from integration of the intensity of the illumination light 16 along the direction of displacement of the object holder 8th , ie by integration over the y-coordinate, over the illuminated area of the object plane 6 , The scan-integrated intensity is the relevant quantity for the quantification of the uniformity of the illumination of the object plane 6 , The value of the scan-integrated intensity depends on the position perpendicular to the direction of displacement in the object plane 6 from the x-coordinate. In addition to the total scan-integrated intensity, ie the integral over the entire intensity of the illumination light 16 in the object plane 6 , it is also possible to define a scan-integrated intensity, which is only the illumination light 16 which is about a particular composite field facet 38z of the field facet mirror 19 was led.

For some applications, it is crucial to have the object field 5 to illuminate with a high uniformity. To improve the uniformity of the lighting is usually a example of the EP 0 952 491 A2 known uniformity correction device based on spatial dimming used. However, such a uniformity correction device limits the imaging quality of a lighting system 3 significant. In particular, it results in that only a small part of the optical conductivity of such a lighting system 3 is being used. Reason is that the pictures of the field facets 38 in the object field 5 are shifted against each other and therefore can not be superimposed. Thus, each image can only be part of the object field 5 illuminate.

Without a uniformity correction device, the intensity of the illumination radiation is indicative 16 in the object field 5 , as exemplified by the curve 31 in 3 is shown to have a strong unevenness or non-uniformity. One main reason for this unevenness is the characteristic of the light source.

In the inventive design of the facet mirror 19 Moreover, this unevenness is a fine structure due to the inevitable spacing of adjacent micromirrors 28 same module 29 on the one hand, and in particular adjacent modules 29 on the other hand superimposed.

Because every micromirror 28 however, only a small area of the object field 5 Illuminated, by turning off individual micromirrors 28 , that is, by tilting the same, can be achieved that the illumination radiation reflected by them 16 no longer the object field 5 reached. Thus, the intensity in the object field 5 locally reduced, that is adapted. This makes it possible, the uniformity of the illumination of the object field 5 significantly improve. This is an example in the curve 32 of the 3 shown.

According to the invention, it has been found that it is sufficient to correct the uniformity, only a part of the facets 38 as compound facets 38z train. It is sufficient in particular, only 20%, in particular only 15% of the facets 38 , in particular only 10%, in particular only 5% thereof as composite facets 38z train.

It turned out that a total uniformity, that is the scan integrated total intensity of the illumination radiation 16 after summation of the scan-integrated intensity over all field facets 38 , better than 1%, in particular better than 0.5%, in particular better than 0.2% can be guaranteed.

The formation of the facet mirror 19 simple facets 38e and compound facets 38z was previously described with reference to the field facet mirror 19 and the field facets 38 described. An appropriate training is also for the pupil facet mirror 20 with the pupil facets 37 possible.

In the following, the inventive method for illuminating the object field 5 with the illumination system described above 3 described. First, the reticle to be imaged 7 , which generally forms a structure to be illuminated, in the object field 5 the illumination optics 4 provided. Then, an illumination setting is set with illumination channels of a specific intensity and angle of incidence distribution. Here are at least some of the compound facets 38z by shifting a number of their micromirrors 28 adjusted so that the scan-integrated intensity in the object field 5 depending on location at most 5%, in particular at most 1%, in particular at most 0.5%, in particular at most 0.2%, deviates from an average value, with its image in the object field 5 in each case at least 80%, in particular at least 90%, in particular at least 95% of the object field 5 fills.

The wafer is used to produce a microstructured or nanostructured component 13 on which at least partially a layer of a photosensitive material is applied, provided, and then at least a portion of the reticle 7 with the help of the projection exposure system 1 projected onto it. Subsequently, the with the illumination radiation 16 exposed photosensitive layer on the wafer 13 developed. The microstructured or nanostructured component is, for example, a semiconductor chip.

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

• DE 102008009600 A1 [0002]
• DE 102009045694 A1 [0002]
• US Pat. No. 685,951 B2 [0022]
• EP 1225481 A [0022]
• WO 2009/100856 A1 [0030]
• EP 0952491 A2 [0047]

Claims (13)

Facet mirror ( 19 . 20 ) for channelwise reflection of illumination radiation ( 16 ) comprising a. a multitude of simple facets ( 38c ) with simply contiguous facet reflection surfaces and b. a plurality of compound facets ( 38z ) with facet reflection surfaces, which consist of a plurality of individual reflection surfaces of displaceable micromirrors ( 28 ), c. the facet reflection surfaces of the simple facets ( 38e ) have an area of at least 10 mm ² , and d. wherein the individual reflection surfaces of the micromirrors ( 28 ) each have an area of at most 5 mm ² . Facet mirror ( 19 . 20 ) according to one of the preceding claims, characterized in that at least a subset of the micromirrors ( 28 ) is groupable into a plurality of groups in such a way that a group reflection surface formed from the totality of the individual reflection surfaces of one of the groups has the shape of one of the single facets ( 38e ) approximates. Facet mirror ( 19 . 20 ) according to one of the preceding claims, characterized in that the number of micromirrors ( 28 ) is at least 3000. Facet mirror ( 19 . 20 ) according to one of the preceding claims, characterized in that the number of simple facets ( 38e ) is in the range of 20 to 1000. Facet mirror ( 19 . 20 ) according to one of the preceding claims, characterized in that the facets ( 38 ) in several half columns ( 27 ), and the facets ( 38 ) an integer number of these half columns ( 27 ) as compound facets ( 38z ) are formed. Facet mirror ( 19 . 20 ) according to one of the preceding claims, characterized in that the number of compound facets ( 38z ) in the range of 2% to 20% of a total number of facets ( 38 ) lies. Illumination optics ( 4 ) for illuminating an object field ( 5 ) with a. a facet mirror ( 19 . 20 ) according to one of the preceding claims. Lighting system ( 3 ) for a projection exposure apparatus ( 1 ) comprising a. a radiation source ( 2 ) and b. an illumination optics ( 4 ) according to claim 7. Method for illuminating an object field ( 5 ) comprising the following steps: a. Providing a lighting system ( 3 ) according to claim 8, b. Providing a structure to be illuminated ( 7 ) in an object field ( 28 ) of the illumination optics ( 4 c. Illuminate the object field ( 5 ) with a lighting setting having a certain intensity and angle of incidence distribution, d. where the composite facets ( 38z ) in each case by a pupil facet ( 37 ) into an object plane ( 6 ) that the dimensions of the image of the individual field facets ( 38z ) in each case by at most 20% of dimensions of the object field ( 5 ) and e. wherein at least some of the compound facets ( 38z ) by displacing a number of their micromirrors ( 28 ) are adapted such that i. a scan-integrated intensity in the object field ( 5 ) deviates from the mean by a maximum of 1% depending on the location, and ii. the picture of this field facet ( 38z ) in the object plane 6 at least 80% of the area of the object field ( 5 ) covered. Optical system comprising - an illumination optics ( 4 ) according to one of claims 1 to 7 and, - a projection optics ( 10 ) for projecting an object field ( 5 ) in an image field ( 11 ). Projection exposure apparatus ( 1 ) for microlithography with - a lighting system ( 3 ) according to claim 9 and, - a projection optics ( 10 ) for projecting an object field ( 5 ) in an image field ( 11 ). Method for producing a microstructured or nanostructured component comprising the following steps: providing a substrate on which at least partially a layer of a photosensitive material is applied, providing a reticle ( 7 ) having structures to be imaged, - providing a projection exposure apparatus ( 1 ) according to claim 11, - projecting at least part of the reticle ( 7 ) to a region of the photosensitive layer of the substrate by means of the projection exposure apparatus ( 1 ). Component produced by the method according to claim 12.

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