DE102014207894B4 - Illumination optics, measuring system for characterizing at least one component of an exposure system and method for characterizing at least one component of an exposure system - Google Patents

Abstract

Illumination optics (3) for guiding a light radiation (18) of a light source (2) onto an object plane (4), in particular for guiding an EUV radiation, wherein the illumination optics (3) is designed to form a planar light radiation (18) of the light source (2) to focus in at least two light channels (11) and to direct the two light channels (11) to at least two predetermined field points (10) in an object plane (4), the illumination optics directing at least two arrays (13, 15) of light And wherein a membrane (17) with openings (19) is provided, and wherein the membrane (17) between the arrays (13, 15) is arranged, wherein the elements (14) of the first array ( 13) direct the light channels (10) through the openings (19) of the membrane (17) to the elements (16) of the second array (15), wherein the second array (15) is arranged in an object plane (4), and wherein the elements (16) of the second array (15) the light channels (10) through the Open openings (19) of the membrane (17) in the direction of an image plane (6).

Description

The invention relates to an illumination optical system for guiding a light radiation of a light source onto an object plane, in particular for guiding an EUV radiation, a method for exposing an object plane, a measuring system for characterizing at least one component of an exposure system, and a method for characterizing at least one component of an illumination system exposure apparatus.

Out DE 10 2011 077 223 A1 a measuring system for characterizing at least one component of a projection exposure apparatus is known, wherein the projection exposure apparatus has a measuring device for measuring an optical parameter, a positioning device for positioning the at least one measuring device, wherein the positioning device is displaceably connected to a lens of the projection exposure apparatus. The projection exposure apparatus has a light source which generates a light that is directed onto a reticle with a lighting system. The reticle is arranged in an object plane. The reticle deflects the light in the direction of projection optics, with the projection optics imaging the light onto an image plane.

The object of the invention is to propose an improved illumination optics.

The object of the invention is achieved by the illumination optics according to claim 1, the method according to claim 10, the measuring system according to claim 11 and the method according to claim 12.

A core of the invention consists in that the illumination optics is designed to concentrate a planar light radiation onto at least two predetermined field points in an object plane. In this way, it is possible to concentrate the light output provided by a light source to predetermined field points of an object plane. As a result, a sufficient irradiation of predetermined field points of an object plane can also be achieved by means of a weak light source. Thus, using the proposed illumination optics, measurements can also be performed with a weak light source. Furthermore, the illumination optics offers the advantage that selected field points are irradiated simultaneously and measurements can be carried out at these field points simultaneously. This significantly reduces the requirements for the stability of the measuring device. This is particularly important for the measurement of the image shell and the distortion of the lens.

Thus, despite a low light output, a punctual high light output at predetermined field points can be achieved, thereby improving a measurement of at least one optical property of the illumination optics.

In one embodiment, the illumination optics has at least two arrays of light-directing elements. This embodiment offers the possibility to concentrate the light of the light source in a simple manner in at least two light channels and to direct to at least two field points.

Depending on the chosen embodiment, the elements of the arrays may be in the form of mirrors and / or lenses. Depending on the light radiation used, mirrors and / or lenses with the desired optical properties can be used. As a result, an individual adaptation of the illumination optics to the light radiation used can be achieved.

In a further embodiment, an efficient concentration of the light radiation on the light channels and the steering of the light channels on the predetermined field points is achieved. This is achieved in that each element of the first array directs a portion of the light radiation to at least one element of the second array, wherein the elements of the second array direct the light radiation in the form of light channels on the predetermined field points of the object plane.

In a further embodiment, a membrane is provided with openings, wherein the membrane is arranged between the arrays. With this arrangement, a defined exposure of the field points in the object plane can be achieved.

In a further embodiment, a mirror is provided. In this way, a variability between the arrangement of the two arrays and the object plane can be achieved. For this purpose, the mirror is preferably arranged in the light path between the second array and the object plane.

Another embodiment has the advantage that a precise exposure of the field points is achieved. For this purpose, the illumination optics on a plane mirror with holes, which is arranged between the two arrays. By arranging the plane mirror with the holes further clarification of the leadership of the light channels can be achieved.

In one embodiment, the plane mirror is arranged between the arrays such that each element of the first array directs a portion of the light radiation through the opening of the plane mirror onto at least one element of the second array, wherein the elements of the second array direct the light radiation in the form of light channels onto a reflective rear side of the plane mirror, wherein the rear side of the plane mirror directs the light channels through the second array to the object plane, and the light channels are returned from the object plane, in particular from a reticle Openings of the plane mirror are directed to a projection optics.

In a further embodiment, the second array is designed in the form of a specular reflector. In this embodiment, a plurality of elements of the first array direct the light radiation to at least one element of the specular reflector, wherein the elements of the specular reflector direct the light radiation in the form of multiple light channels to a plurality of predetermined field points of the object plane.

In a further embodiment, a further improvement of the illumination optics is achieved. This is possible because the elements of the first array and the elements of the second array are arranged in such a way that the light channels hit the object plane at defined angles in such a way that the light channels are deflected by a reticle arranged in the object plane in this way in that the light channels in a surface of an entrance pupil are superimposed on a projection optical unit.

In a further embodiment, the elements of the first and / or the second array are designed to be movable. For this purpose, corresponding actuators are provided which can change a position and / or an angle of at least one element or a group of elements. As a result, increased flexibility is achieved in the creation of patterns of field points to be irradiated or in the angular distribution during the irradiation of the field points.

The illumination optics described is preferably used as part of a measuring system in order to characterize at least one component of an exposure system, in particular the illumination optics or a projection optics.

The described illumination optics can be used to illuminate an object plane in a desired pattern or grid of field points. With the help of the proposed illumination optics, it is possible to achieve an increased light output at predetermined field points by means of a weak areal light radiation.

Furthermore, the illumination optics described can be used to characterize a method for characterizing at least one component of an exposure system, in particular an optical property of illumination optics or projection optics.

The invention will be explained in more detail below with reference to FIGS. Show it

1 a schematic structure of an exposure system,

2 an example of a lighting look,

3 Examples of two arrays and a membrane,

4 another example of lighting optics,

5 a third example of an illumination optics and

6 a fourth example of an illumination optics.

1 shows a schematic representation of an exposure system 1 , which as essential components a light source 2 , an illumination optics 3 , an object plane 4 , a projection optics 5 and an image plane 6 having. The light source 2 can z. B. be an EUV radiation source with a wavelength between 5 and 100 nm. It can be a plasma source, for example plasma generation by gas discharge or plasma generation by laser. Similarly, a synchrotron radiation as a light source 2 be used. The light source 2 For example, it can produce light of various wavelengths, especially short wavelength light, for example, ultraviolet light or extreme ultraviolet light having a wavelength of 13.5 nm and smaller. The light source 2 can also produce longer wavelength light between 13.5 nm and 365 nm and larger.

The exposure system 1 for example, can be used to using a reticle 7 that in the object plane 4 is arranged, a desired exposure structure in the image plane 6 to create. The reticle 7 may represent an exposure mask for a layer of electronic circuit or mechanical structure. For example, in the image plane 6 a wafer may be arranged with a photosensitive layer. Using the of the reticle 7 a desired exposure pattern may be formed on the photosensitive layer of the wafer.

In addition, the exposure system 1 be used to at least one optical parameter of the exposure system 1 to eat. This is in the picture plane 6 not a wafer, but an optical sensor 9 arranged with which an optical image in the image plane 6 is detected. In addition, the sensor can 9 with a computing unit 40 be connected, which is an evaluation of the sensor 9 detected light information performs.

For example, by means of the described arrangement, the arithmetic unit 40 Perform interferometric measurements to capture the quality or quality of the illumination optics and / or the projection optics. This can be done, for example, in the image plane 6 Masks are used, which have a certain structure and for the detection of optical parameters such. As a wavefront curve, a spatial resolution, a spatial coherence, overlapping surfaces and a Stör- / Nutzverhältnis suitable. For example, by means of the arrangement described, Zernike coefficients can be determined with which optical properties of the exposure system can be described. For carrying out the measuring methods, in particular of Schermessverfahren is a high light intensity at least in certain field points 10 the object level 4 required.

One aspect of the present exposure system 1 is that the illumination optics 3 is formed in the manner to a flat light radiation of the light source 2 in at least two light channels 11 to concentrate and the at least two light channels 11 to at least two predetermined field points 10 in the object plane 4 to steer.

In the object plane 4 is the reticle 7 having a predetermined structure to produce a desired exposure pattern in the image plane. For this, the reticle 7 as in the illustrated embodiment of the light channels 11 be irradiated, so from the reticle 7 outgoing light rays 12 using the projection optics 5 on the picture plane 6 be projected.

Depending on the chosen embodiment, the exposure system 1 However, also be formed in such a way that the projection optics 5 and the picture plane 6 with the sensor 9 like the illumination optics 3 above the object plane 4 is arranged. In this arrangement, the reticle reflects 7 the rays of light 12 back to the top on the projection optics 5 into the picture plane 6 that are above the object plane 4 is arranged.

The exposure system 1 has the advantage that, despite a light source 2 , which has a low light output, in predetermined field points 10 the picture plane 6 a high light output on a reticle 7 can be generated. In this way, in spite of the low light output, for example, at least one optical parameter of the illumination optics 3 and / or the projection optics 5 be measured.

2 shows a schematic representation of a first embodiment of a lighting optical system 3 , The illumination optics 3 includes in this embodiment a first array 13 with first elements 14 , a second array 15 with second elements 16 and a flat membrane 17 , The first array 13 is shown only schematically in cross-section one-dimensional, but with the first array 13 in the form of a surface, for example, rectangular. The first array 13 consists of several first elements 14 , which have a surface light radiation 18 the light source 2 to several light channels 11 concentrate and through openings 19 the membrane 17 to second elements 16 of the second array 15 to steer. The second array 15 is also shown one-dimensionally only in cross-section, with the second array 15 also has a planar extension, for example, a rectangular extension having. In the illustrated embodiment, the second array is 15 in the object plane 4 arranged. The second elements 16 are formed in the way that of the first array 13 received light channels 11 redirected and over openings 19 through the membrane in the direction of a schematically shown projection optics 5 be guided.

The membrane 17 has a corresponding two-dimensional planar surface with corresponding openings 19 on to allow the desired beam passages. The Elements 14 . 16 of the first and second arrays 13 . 15 are for example in the form of mirrors or lenses, in particular in the form of spot lenses. The openings 19 For example, they may be circular, arranged in a certain pitch, and have a diameter in the range of, for example, 100 μm. Depending on the chosen design, the openings may 19 also have other shapes and / or larger or smaller diameter.

The light channels 11 according to the 2 For example, they may have a diameter at a field point of 100 μm. The arrangement of 2 ensures that a main beam angle of the illumination optics 3 is manipulated by the position of the individual elements of the first and the second array so that the main beam angle of the projection optics is hit for the respective field point in the object field. The magnification of the mirror system defines the numerical aperture and the spot size, ie the diameter of the light channel 11 at the field point 10 in the object plane 4 or on the reticle 7 , In the illustrated embodiment, the second array is 15 firmly with the reticle 7 connected. Likewise, the membrane 17 firmly with the reticle 7 connected.

3 shows a schematic representation of a first array 13 with first elements 14 , There is also a second array 15 with second elements 16 shown. The first elements 14 of the first array 13 border directly on each other. In this way, as much as possible of the surface light radiation 18 collected and into individual light channels 11 concentrated. The second array 15 has second elements 16 on, which are spaced from each other in a predetermined grid. Furthermore, a membrane 17 with openings 19 shown schematically. The openings 19 are also spaced apart in a grid.

4 shows in a schematic representation of another embodiment in which the light source 2 a flat light radiation 18 over a first array 13 with first elements 14 , a second array 15 with second elements 16 on a mirror 20 directs. The mirror 20 reflects the received light channels 11 towards the object plane 4 at which a reticle 7 is arranged. About the reticle 7 become the light channels 11 in the direction of a schematically illustrated projection optics 5 distracted. After the projection optics 5 is in the picture plane 6 a sensor 9 with a computing unit 40 intended.

The use of the mirror 20 has the advantage that the arrangement of the first and the second array 13 . 15 in the geometric position decoupled from the arrangement of the object plane 4 and thus increased flexibility in the construction of the exposure system 1 given is. The mirror 20 preferably has a free-form surface. The mirror 20 represents an imaging mirror in the form of a large mirror.

Due to the arrangement of 4 It is through the provision of the mirror 20 possible, the second array 15 spatially separate from the reticle. In addition, in the arrangement of 4 the reticle 7 also a membrane 17 according to the execution of 2 exhibit.

5 shows a further embodiment of a lighting optical system, in which a light source 2 a flat light radiation 18 on a first array 13 sends. The array 13 has a variety of first elements 14 on, the surface light radiation 18 in light channels 11 focus and move towards an object plane 4 to steer. In the object plane 4 is a reticle 7 arranged. Between the first array 13 and a second array 15 is a plane mirror 21 arranged. In the example shown, the second array is 15 in front of the object plane 4 at a fixed distance from the reticle 7 arranged. The distance may be, for example, in the range of 1 mm or smaller. In addition, the second array 15 on a second membrane 22 arranged. The second membrane 22 has a plurality of second elements 16 on that the light channels 11 distracted. For example, the second elements 16 formed in the form of ellipsoidal mirrors. Furthermore, the second membrane 22 between the ellipsoidal mirrors 16 second openings 23 on. Furthermore, the plane mirror 21 on a back a reflective surface 24 on. In addition, in the mirror 21 third openings 25 brought in. The third openings 25 are larger in diameter than the second openings 23 , In addition, the third openings 25 slightly laterally offset to the second openings 23 arranged. In 5 is the second array 15 and the plane mirror 21 additionally shown in a front view.

For example, the first elements 14 of the first array 13 and the second elements 16 of the second array 15 be formed in the form of ellipsoidal mirrors.

The light channels 11 be from the first array 13 through the third openings 25 on a front side of the second array 15 steered, on which the second elements 16 are arranged. The second elements 16 reflect the light channels 11 on the reflecting surface 24 the back of the plane mirror 21 , The reflecting surface 24 is the object plane 4 facing and reflecting the light channels 11 in the form of through the second openings 23 the second membrane 22 in field points 10 on the reticle 7 , The reticle 7 reflects light rays 12 back over the second openings 23 the second membrane 22 and the third openings 25 the plane mirror 21 towards a not shown projection optics 5 with a sensor arranged behind it 9 with arithmetic unit 40 ,

The openings 19 the membrane 17 , the second openings 23 the second membrane 22 and the third openings 25 the plane mirror 21 represent through holes.

6 shows a further embodiment of an exposure system 1 in which a light source 2 a flat light radiation 18 on a first array 13 sends. The first array 13 has a variety of first elements 14 on, which are formed in the form of lenses and / or mirrors. The first array 13 is areal trained and in 6 only shown in cross section. The first elements 14 of the first array 13 stand with an actor 26 in connection. The actor 26 is provided to the position and / or an angle of each first element 14 adjust. The first elements 14 shapes from the surface light radiation 18 light channels 11 and steer them towards a second array 15 , Depending on the angular position of the individual elements 14 become the light channels 11 in different angles of radiation 27 in relation to the first array 13 distracted. In the illustrated embodiment, for example, two superimposed first elements steer 14 her light channel 11 on a common area 28 of the second array 15 , In a corresponding manner, the two first elements arranged underneath guide it 14 also their light channels 11 on another common area 29 of the second array 15 ,

The second array 15 has a plurality of second elements 16 on, which are formed in the form of lenses or mirrors. Depending on the chosen embodiment, the second elements 16 with a second actor 30 communicate with the second actor 30 the local position and / or an angle of each individual second element 16 can adjust. In the illustrated embodiment, the second elements are 16 formed in the form of lenses and direct the light channels 11 of different areas 28 . 29 to the same field point 10 . 31 . 32 in the object plane 4 at which a reticle 7 is arranged. The reticle 7 is from the light channels 11 radiates through, the field points 10 . 31 . 32 light rays 12 towards a projection optics 5 submit. The second elements 16 of the second array 15 steer the light channels 11 at a second angle 34 with respect to the plane of the second array 15 towards the object plane 4 from.

The first array 13 and the second array 15 are built in the way and arranged so that the first angle 27 and the second angle 34 are formed in such a way that the light rays 12 in an area of an entrance pupil 35 the projection optics 5 overlap. Preferably, the light rays 12 aligned in such a way that no light is sideways next to the entrance pupil 35 past radiates.

In the illustrated embodiment, the second elements 16 formed in the form of lenses, so that the second array 15 represents a specular reflector. The arrangement of 6 can of course also with a reflection of the light channels 11 from the reticle 7 be applied.

One size and one pitch of the first array 13 should be chosen such that the size and the pitch multiplied by a magnification just equal to the size and pitch of the given field points 10 on the mask or the reticle 7 correspond.

Using the actuators 26 . 30 can be a variable exposure of different field points 10 on the reticle by a corresponding adjustment of the tilt angle and / or positions of the elements 14 . 16 of the first and / or the second array 13 . 15 be achieved. This can be done by the actuators 26 . 30 with a control unit 33 communicate with the actors 26 . 30 controls, so given pattern of field points 10 at the object level 4 be illuminated with light channels.

Depending on a selected embodiment, with an unchanged first array 13 different second arrays 15 be used to create different patterns of field points 10 on the reticle 7 to illuminate.

Claims (13)

Illumination optics ( 3 ) for a guidance of a light radiation ( 18 ) of a light source ( 2 ) on an object level ( 4 ), in particular for guiding an EUV radiation, wherein the illumination optics ( 3 ) is formed to a flat light radiation ( 18 ) of the light source ( 2 ) in at least two light channels ( 11 ) and the two light channels ( 11 ) to at least two predetermined field points ( 10 ) in an object plane ( 4 ), wherein the illumination optics at least two arrays ( 13 . 15 ) of light-directing elements ( 14 . 16 ) and wherein a membrane ( 17 ) with openings ( 19 ), and wherein the membrane ( 17 ) between the arrays ( 13 . 15 ), the elements ( 14 ) of the first array ( 13 ) the light channels ( 10 ) through the openings ( 19 ) of the membrane ( 17 ) on the elements ( 16 ) of the second array ( 15 ), the second array ( 15 ) in an object plane ( 4 ), and wherein the elements ( 16 ) of the second array ( 15 ) the light channels ( 10 ) through the openings ( 19 ) of the membrane ( 17 ) in the direction of an image plane ( 6 ) to steer. Illumination optics according to claim 1, wherein as elements ( 14 . 16 ) for the two arrays ( 13 . 14 ) Mirrors and / or lenses are provided. Illumination optics according to one of claims 1 or 2, wherein each element ( 14 ) of the first array ( 13 ) a part of the light radiation ( 18 ) in the form of a light channel ( 11 ) on at least one element ( 16 ) of the second array ( 15 ) and where the elements ( 16 ) of the second array ( 15 ) the light channels ( 11 ) to the given field points ( 10 ) of the object level ( 4 ) to steer. Illumination optics according to one of claims 1 to 3, wherein a mirror ( 20 ), the mirror ( 20 ) in an optical path between the second array ( 15 ) and the object level ( 4 ), and wherein the mirror ( 20 ) the light channels ( 11 ) of the second array ( 15 ) to the given field points ( 10 ) of the object plane directs. Illumination optics ( 3 ) for a guidance of a light radiation ( 18 ) of a light source ( 2 ) on an object level ( 4 ), in particular for the management of an EU Radiation, whereby the illumination optics ( 3 ) is formed to a flat light radiation ( 18 ) of the light source ( 2 ) in at least two light channels ( 11 ) and the two light channels ( 11 ) to at least two predetermined field points ( 10 ) in an object plane ( 4 ), wherein the illumination optics at least two arrays ( 13 . 15 ) of light-directing elements ( 14 . 16 ) and wherein a plane mirror ( 21 ) with holes ( 25 ) is provided, and wherein the plane mirror ( 21 ) between the two arrays ( 13 . 15 ) is arranged. Illumination optics according to claim 5, wherein the holes ( 25 ) of the plane mirror ( 21 ) are arranged in such a way that each element ( 14 ) of the first array ( 13 ) a part of the light radiation as a light channel ( 11 ) through a hole ( 25 ) of the plane mirror ( 21 ) on an element ( 16 ) of the second array ( 15 ), whereby the elements ( 16 ) of the second array ( 15 ) the light channels ( 11 ) on a reflective back ( 24 ) of the plane mirror ( 21 ), with the back ( 24 ) of the plane mirror ( 21 ) the light channels ( 11 ) through holes ( 23 ) a second membrane ( 22 ) on which the second array ( 15 ), to field points ( 10 ) in the object plane ( 4 ), and wherein from the object plane, in particular from a reticle ( 7 ) the light beams ( 12 ) back through the holes ( 25 ) of the plane mirror to a projection optics ( 5 ) are steered. Illumination optics according to one of claims 1 to 3, wherein the second array ( 15 ) is designed as a specular reflector, wherein a plurality of elements ( 14 ) of the first array ( 13 ) the light radiation in the form of several light channels ( 11 ) on a surface ( 28 . 29 ) of the specular reflector ( 15 ), whereby one surface ( 28 . 29 ) of the specular reflector ( 15 ) the light channels ( 11 ) to several predetermined field points ( 10 . 31 . 32 ) of the object level ( 4 ) steers. Illumination optics according to claim 7, wherein the elements ( 14 ) of the first array ( 13 ) and the elements ( 16 ) of the second array ( 15 ) are arranged in such a way that the light channels ( 11 ) at defined angles so on the object plane ( 4 ), that the light channels ( 11 ) of one in the object plane ( 4 ) arranged reticles ( 7 ) in the way as light rays ( 12 ) are deflected, that the light rays ( 12 ) in an area of an entrance pupil ( 35 ) of a projection optics ( 5 overlay). Illumination optics according to one of the preceding claims, wherein the elements ( 14 . 16 ) of the first and / or the second array ( 13 . 15 ) using actuators ( 26 . 30 ) are designed to be movable. Method for exposing an object plane with an illumination optical system according to one of claims 1 to 9, wherein a planar light radiation of a light source, in particular an EUV radiation, is concentrated on at least two predetermined field points in an object plane. Measuring system for characterizing at least one component of an exposure system ( 1 ) comprising a) a light source ( 2 ) for providing a surface light radiation ( 18 ), b) an illumination optics ( 3 ) according to one of claims 1 to 9 for concentrating the surface light radiation ( 18 ) on at least two light channels ( 11 ) and for guiding the two light channels to at least two predetermined field points ( 10 ) in an object plane ( 4 ), c) a projection optics ( 5 ) for mapping one of the object plane ( 4 ) outgoing light rays on an image plane ( 6 ), and d) a measuring device ( 9 . 40 ) for measuring at least one optical parameter in the image plane ( 6 ). A method for characterizing at least one component of an exposure system, wherein by means of an illumination optical system according to one of claims 1 to 9, a surface light radiation is concentrated on at least two light channels, wherein the two light channels are guided to at least two predetermined field points in an object plane, wherein by means of a projection optics imaging of the object plane outgoing light beams on an image plane, and wherein at least one optical parameter in the image plane is measured by means of a measuring device. The method of claim 12, wherein in a first measurement first field points of the object plane are irradiated, and wherein in a second measurement second field points are irradiated, wherein the first field points at least partially different from the second field points, and wherein the first measurement and the second measurement be evaluated as a total measurement.

Images