WO2024199972A1 - Method and system for irradiating a lithographic object - Google Patents

Abstract

The invention relates to a method for irradiating a lithographic object (14, 40, 50), in which the lithographic object (14, 40, 50) is coated with a lacquer layer (20). The irradiation properties of the lacquer are determined in a spatially resolved manner. According to the irradiation properties determined for a first surface region of the lithographic object (14, 40, 50), an irradiation device (21, 52) is set to a first irradiation state in order to irradiate the first surface region. According to the irradiation properties determined for a second surface region of the lithographic object (14, 40, 50), the irradiation device (21, 52) is set to a second irradiation state in order to irradiate the second surface region. The lithographic object (14, 40, 50) is irradiated by guiding a spot, which is generated using an irradiation beam path (23), along a specified path over the lithographic object (14, 40, 50) in order to generate an irradiation track (25) in the lacquer layer (20). The invention also relates to a system for irradiating a lithographic object (14, 40, 50).

Description

Method and system for irradiating a lithography object

The present patent application takes priority from the German patent application filed on 30 March 2023

DE 10 2023 202 896 . 4, to which reference is made and the contents of which are fully incorporated herein ( "incorporation by reference") .

The invention relates to a method and a system for irradiating a lithographic object, in which the lithographic object is coated with a layer of lacquer.

In lithography applications, partial areas of the lithography object coated with a varnish are irradiated in order to define the surface areas in which the lithography object is subjected to structuring in a subsequent processing step. Depending on the type of varnish, the irradiated areas are either processed or excluded from processing.

The effect of the irradiation step depends on the irradiation properties of the lacquer at the irradiation location. Possible irradiation properties of the lacquer to be structured are, for example, the local, frequency-dependent refractive index, a local layer thickness, a local solvent content, or a local concentration of a photo-active component (PAC concentration). For example, the greater the layer thickness of the lacquer, the more intensive the interaction between the irradiation light and the lacquer layer must be in order to penetrate to the substrate of the lithography object. In addition to the properties listed above, In principle, a variety of other properties are suitable for influencing the irradiation step of the paint.

The invention is based on the object of presenting a method and a system with which a lithography object can be structured spatially homogeneously via an irradiation step. The object is achieved with the features of the independent claims. Advantageous embodiments are specified in the subclaims.

In the method according to the invention, irradiation properties of the lacquer are determined in a spatially resolved manner. Depending on the irradiation properties determined for a first partial area of the lithographic object, an irradiation device is set to a first irradiation state in order to irradiate the first partial area. Depending on the irradiation properties measured for a second partial area of the lithographic object, the irradiation device is set to a second irradiation state in order to irradiate the second partial area.

By irradiating the lithography object in a spatially resolved manner depending on the locally determined properties, it is possible to carry out the irradiation step with increased spatial homogeneity in relation to the structuring result. Possible irradiation properties of the resist to be structured include, for example, the local, frequency-dependent refractive index, a local layer thickness, a local solvent content, or a local concentration of a photo-active component (PAC concentration). A lithographic object can be, for example, an optical element. For example, it can be a mirror, a lens, a diffractive optical element (e.g. a grating), or something similar. The method is not restricted to optical elements and can be used on any type of surface to be structured lithographically. The surface of a lithographic object can be concave-curved, convex-curved, designed as a free-form surface or as a planar substrate.

In one embodiment, the surface of the lithography object coated with the resist layer is a free-form surface. The lithography object can be a mirror, for example a mirror of a projection lens of an EUV projection exposure system, a mirror of an illumination system of an EUV projection exposure system or a mirror of an EUV radiation source. The lithographic production of integrated circuits with particularly small structures requires the use of very short-wave, extreme ultraviolet radiation (EUV radiation) with a wavelength between 5 and 30 nm and the provision of appropriately designed EUV projection exposure systems.

The surface structuring can be produced lithographically. For this purpose, a surface of the substrate is coated with a lacquer and irradiated in such a way that the surface structure is defined.

The varnish can be applied to the substrate in liquid form and hardened there. Depending on the method of application, as well as subsequent varnish-related process steps and subform-dependent influences of the lithographic object, local inhomogeneities in the properties of the varnish can occur. After the varnish has been applied and during hardening, the paint, which can lead to local inhomogeneities in the properties of the paint.

In one embodiment of the invention, the layer thickness of the paint is used as a measure of the irradiation properties. The irradiation properties can be determined by measuring the layer thickness of the paint. In addition or alternatively, other properties of the paint layer can also be measured, such as the proportion of photo-optically active substances or the residual solvent content.

The thickness of the paint layer can be determined using a suitable optical measuring method or another non-destructive measuring method. The measurement can be, for example, an absorptive measurement, an interferometric measurement, an ellipsometric measurement or an X-ray reflectometric measurement. Other types of measurement are also possible, such as photothermal measurements or tactile measurements.

The layer thickness of the lacquer can be measured at a large number of points on the lithography object, for example at least 100 points, preferably at least 500 points, more preferably at least 1000 points. In the case of an optical measuring method, the measurement can be carried out in such a way that the measuring beam path forms a spot on the lacquer layer, which is directed successively at the various points. In one embodiment, the measuring beam path can be directed non-perpendicularly, i.e. at an angle other than 90° to the tangent of the optical surface, onto a surface section of the lithography object, so that a reflected beam leaves the lacquer at a defined exit point. In another embodiment, the measuring beam path can be directed perpendicularly onto the lithography object, so that the measuring beam path is reflected in itself. Another possibility, a To obtain spatially resolved information about the layer thickness, it is necessary to direct the measuring radiation onto a larger surface area of the lithography object and to evaluate the measuring signal in spatially resolved form using a suitable detector.

A first positioning system can be provided to position the measuring device of the optical method, with which the lacquer layer thickness is measured, relative to the lithography object, so that the measuring beam path of the measuring device is directed successively to different points on the lithography object. The first positioning system can be designed so that the lithography object is held in a fixed position and the measuring device is moved relative to the lithography object, or vice versa. A first positioning system is also possible in which both the measuring device and the lithography object are moved. If the lithography object is a surface of a body that has a symmetry, the symmetry can be exploited to keep the movements of the positioning system as simple as possible.

The lithography object can have a plurality of unit cells which are subjected to uniform irradiation in the irradiation step. This means that during the irradiation of a unit cell, the irradiation device is not switched between different irradiation states. On the other hand, different unit cells can be treated with different irradiation states. The lithography object can, for example, have at least 20, preferably at least 50, more preferably at least 100 unit cells.

In each unit cell, the layer thickness of the paint can be measured at several points, for example at least two points, preferably at least five points, further preferably at least ten locations. The layer thickness for the unit cell can be obtained by averaging the measured values.

Each unit cell can form a continuous area on the lithography object. Any two unit cells can be separated by an area that is not subjected to irradiation. In this way, the lithography object can be provided with a surface structure that has two levels. In order to produce a surface structure with more than two levels, unit cells that are a multiple of the width of an adjacent unirradiated area can be defined in a first lithography step. After material has been removed from the lithography object in the area of the unit cells, unit cells for the next level can be defined in a second lithography step. This can be repeated if more than two levels are to be produced.

During the irradiation step, the resist is changed by the influence of radiation, so that in a subsequent step the desired mask can be created on the lithograph object. The radiation acting in the irradiation step has a wavelength to which the resist is sensitive. If the resist is a positive resist, the resist layer is removed in the irradiated areas, while the resist layer in the non-irradiated areas remains. With a negative resist, it is the other way round. It is also possible that the resist is a reversal resist, which can be processed either as a positive resist or, alternatively, with the aid of further process steps, as a negative resist. In the areas in which the resist layer was removed, the material of the lithograph object can be influenced in a subsequent processing step and, for example, material can be removed from the lithograph object. The properties and the The spatial structure of the irradiated parts of the paint layer depend essentially on the radiation dose acting on a given surface section of the paint layer. The radiation dose corresponds to the product of radiation power and time related to the relevant surface section.

The irradiation device can be set up so that the lithographic object is irradiated over its entire surface or with a scanning irradiation process. A scanning irradiation process means that the radiation is emitted in the form of a locally limited beam and that the radiation is directed in a time sequence onto those surface sections of the lithographic object that are to be subjected to irradiation.

A spot generated with an irradiation beam path can be guided along a predetermined path over the lithograph object in order to generate an irradiation track in the resist layer. The irradiation spot can be generated, for example, with a suitable laser. The irradiation spot on the lithograph object can, for example, have a diameter between 1 pm and 100 pm, preferably between 5 pm and 50 pm, more preferably between 10 pm and 30 pm. In principle, the irradiation spot can be diffraction-limited in its extent beyond the physical limit of the respective irradiation method.

Various intensity distributions are possible across the cross-section of the beam path. If a beam is used in which the radiation intensity decreases from the center to the outside, a higher radiation dose is effective in the center of the spot than at the edge of the spot. This results in a funnel-shaped gradient of the radiation efficiency in the lacquer layer. If such a spot is moved over the surface of the lithography object, the result for a defined radiation dose is an irradiation track with a funnel-shaped cross-section. The radiation dose can be adjusted so that the entire thickness of the paint layer is irradiated in the center of the irradiation track. By superimposing several such irradiation tracks, a continuous area of the paint layer can be irradiated.

A transition region can be formed at the edge of an irradiation track, which forms a transition to non-irradiated parts of the lacquer layer. The transition region can extend between the back and the front of the lacquer layer and have subregions that have an approximately linear course. An approximately linear subregion can enclose an angle with the surface of the lithography object, which can be between 20° and 90°, for example, preferably between 20° and 40°. In addition to a subregion with an approximately linear course, the transition region can also have subregions that include a curved course, e.g. a sigmoidal, a logarithmic, or an exponential course.

There are various ways of influencing the radiation dose. For example, the power of the radiation source of the irradiation device can be adjusted. With a higher power, the radiation dose becomes greater and vice versa. The radiation dose can also be changed over the duration of the irradiation. With increasing duration, the radiation dose becomes greater and vice versa. In a scanning process in which an irradiation track is created in the paint layer using a beam path, the duration of the irradiation depends on the speed at which the irradiation spot is moved. If the scanning process is carried out in such a way that a first section of the irradiation track overlaps with a second section of the irradiation track, the spatial profile of the total radiation dose used depends on the degree of overlap. The more the tracks overlap, the greater the radiation dose in the overlap region. One way to switch between the first state and the second state of the irradiation device is to change the degree of overlap between the sections of the irradiation track, while the other parameters of the irradiation device remain unchanged.

In an irradiation state within the meaning of the invention, the parameters of the irradiation device are defined such that a predetermined radiation dose acts on the lacquer layer. In an irradiation state, the parameters mentioned are therefore set such that a partial area of the lithograph object is treated with a specific radiation dose. The radiation dose can be constant over the partial area of the lithograph object, apart from the reduction in the radiation dose which may occur in a transition region of an irradiation track. The partial area can correspond to a unit cell on the lithograph object.

The irradiation device can comprise a second positioning system to position the radiation source relative to the lithography object. The second positioning system can be designed as a scanning device with which a spot of the irradiation beam path is guided along a predetermined path over the lithography object in order to produce an irradiation track in the lacquer layer. The second positioning system can be designed so that the lithography object is held in a fixed position and the radiation source is moved relative to the lithography object or vice versa. A second positioning system is also possible in which both the radiation source and the lithography object are moved. If the lithography object has a rotational symmetry, the lithography object can be rotated about its optical axis. The radiation source can be moved within a plane. which coincides with the axis in order to be able to direct the radiation onto different sections of the lithograph object. The radiation source can be aligned in such a way that the beam path hits the surface of the lithograph object perpendicularly. If the lithograph object is rotated while the radiation source is in a fixed position, the resist layer can be irradiated along a circumferential line of the lithograph object.

By moving the radiation source while the lithograph object rotates, a spiral path on the surface of the lithograph object can be irradiated. The speed at which the radiation source is moved can be adjusted so that the distance by which the spot of the beam path is displaced on the surface of the lithograph object during one revolution is smaller than the spot diameter, i.e. the portion of a cross-section of the spot primarily used for irradiation. Typically, the spot diameter corresponds to the FWHM width of the beam. This results in overlapping irradiation in which a point on the surface of the lithograph object is irradiated during two or more revolutions. In one embodiment, the radiation dose with which the paint layer is treated is adjusted by changing the speed of movement of the radiation source, while the other parameters of the irradiation device remain constant. Other trajectories, such as linear trajectories, are possible.

The path speed with which the radiation source is moved relative to the surface of the lithography object can be, for example, between 5 m/s and 28 m/s. The lithography object can be rotated during irradiation at a speed of between, for example, 200 rpm and 800 rpm, preferably between 300 rpm and 500 rpm. The speed can be kept constant during irradiation. Possible is also to vary the speed during irradiation in order to adjust the radiation dose. With the spiral movement of the irradiation spot, a unit cell extending over the circumference of the lithograph object can be irradiated. Distributed over the lithograph object, a large number of such unit cells, for example between 100 and 200 unit cells, can be irradiated in this way. Within each unit cell, the irradiation state can be readjusted depending on the thickness of the resist layer.

The invention also encompasses, in addition to or as an alternative to the movement of the radiation source, changing one or more other parameters of the irradiation device in order to adjust the radiation dose. For example, the power of the radiation source can be adjusted while the irradiation spot remains unchanged. It is also possible to change the irradiation state by changing the shape of the beam, for example by focusing the irradiation light more or less strongly. In an alternative embodiment, the focusing of the beam can be kept constant, wherein the distance of the beam focus relative to the surface of the lithography object is varied while the beam is moved over the surface of the lithography object.

The first positioning system and the second positioning system can be designed as a uniform positioning device in which the measuring means of the optical method and the radiation source are held on a common carrier. The radiation source in this sense is the element from which the radiation is directed onto the lithography object. The radiation source can, for example, be the exit end of a light guide. The method can be carried out in such a way that in a first process phase the measured values for the layer thickness of the paint are obtained and in a subsequent second process phase the partial areas of the lithography object are irradiated. Alternatively, it is also possible for partial areas of the lithography object to be irradiated before all measured values for the paint layer thickness are available. In particular, measured values for the paint layer thickness can be obtained while the lithography object is being irradiated, so that the irradiation state can be changed during the irradiation process depending on the measured values for the paint layer thickness obtained.

In the case of a plurality of unit cells, one possibility is to first obtain all measured values for the resist layer thickness within a first unit cell, then to irradiate the first unit cell before continuing in a corresponding manner with the second unit cell and further unit cells.

In another embodiment of the invention, the lithography object is a planar surface, for example a planar surface of a wafer. In a first method step, a first mask can be imaged with an imaging optics onto a first partial surface of the lithography object, and in a second method step, a second mask can be imaged with the imaging optics onto a second partial surface of the lithography object. The second mask can be identical to the first mask or different from the first mask. Between the first method step and the second method step, the lithography object is moved relative to the imaging optics so that the second partial surface assumes the position relative to the imaging optics that the first partial surface previously occupied. Depending on the irradiation properties of the first partial surface, the irradiation is The radiation device is set to the first irradiation state in order to irradiate the first partial surface. Depending on the irradiation properties of the second partial surface, the radiation device is set to the second irradiation state in order to irradiate the second partial surface. This method can also be carried out with a larger number of partial surfaces on the lithography object, for example at least 10, preferably at least 50 partial surfaces.

The invention also relates to a system for irradiating a lithographic object. The system comprises a measuring device and an irradiation device. The measuring device is designed to determine the irradiation properties of the varnish in a spatially resolved manner for the lithographic object coated with a varnish. The irradiation device is set to a first irradiation state depending on the irradiation properties determined for a first partial area of the lithographic object in order to irradiate the first partial area. The irradiation device is set to a second irradiation state depending on the irradiation properties determined for a second partial area of the lithographic object in order to irradiate the second partial area.

The measuring device can comprise a measuring means of an optical measuring method, for example in the form of an interferometer. The irradiation device can comprise a radiation source. The system can have a uniform positioning system with which both the measuring means and the radiation source are positioned relative to the lithography object. In particular, the positioning system can have a single carrier that carries both the measuring means and the radiation source. Additionally or alternatively, the measuring device can be designed to measure other properties of the lacquer layer, such as refractive index, residual solvent content, dill parameters and/or the content of photo-optically active components.

The invention also relates to an optical element, wherein the optical element is produced from a lithography object and wherein the lithography object has been treated according to the method according to the invention. The invention further relates to a semiconductor technology system which comprises such an optical element. The system can be a microlithographic projection exposure system, i.e. a projection exposure system for EUV or DUV semiconductor lithography. It is also possible for the system to be a wafer inspection system or a mask inspection system.

The disclosure includes further developments of the system which are described in connection with the method according to the invention. The disclosure includes further developments of the method which are described in connection with the system according to the invention.

The invention is described below by way of example with reference to the accompanying drawings using advantageous embodiments. They show:

Fig. 1: an embodiment of an inventive

measuring device;

Fig. 2: an embodiment of an irradiation device according to the invention;

Fig. 3: a lithographic object according to the invention in a

cross-sectional view;

Fig. 4: a measurement obtained with the measuring device from Fig. 1.

measurement result; Fig. 5: an irradiation pattern generated with the irradiation device from Fig. 2;

Fig. 6: a section of the surface of a lithographic object;

Fig. 7: the view from Fig. 6 in a different state of the lithograph object;

Fig. 8-10: the view according to Fig. 3 in different states of the lithograph object;

Fig. 11: an EUV lithography system;

Fig. 12: an embodiment of a system according to the invention;

Fig. 13: an alternative embodiment of a system according to the invention.

In Fig. 1, a lithography object 14 is arranged on a support surface of a measuring device 15 according to the invention. The measuring device 15 comprises a first positioning system in the form of an X-Y positioner 16, which carries a measuring device 17 of an optical measuring method. The measuring device 17 generates a measuring beam path 18, which strikes the lithography object 14 perpendicularly. By moving the measuring device 17 with the X-Y positioner 16, the lithography object 14 can be scanned with the measuring beam 18.

According to Fig. 3, the lithography object 14 comprises a substrate 19 on which a lacquer layer 20 is applied, the lacquer layer 20 having a desired layer thickness of 1 to 20 pm, preferably 5 to 15 pm, more preferably 8 to 12 pm. The lacquer is sensitive to irradiation with wavelengths of up to 450 nm. The measuring beam 18 of the measuring device 17 has a wavelength that is longer than the wavelength at which the paint is sensitive. In order to obtain an interference signal between light components reflected on the front and back of the paint layer 20 for different layer thicknesses, the measuring beam 18 is broadband and in the present embodiment covers a wavelength range from 500 nm to 800 nm. By scanning the lithography object 14 with the measuring beam 18, information about the thickness of the paint layer 20 is obtained for each measured point. In the diagram in Fig. 4, areas of the same layer thickness are colored the same and areas of different layer thicknesses are colored differently.

If the desired information on the thickness of the lacquer layer 20 is available, the lithograph object 14 is transferred from the measuring device 15 to an irradiation device 21, see Fig. 2. The irradiation device 21 comprises a radiation source 22 in the form of a laser which emits radiation with a wavelength of 450 nm in the form of a beam path 23. The beam path 23 is directed onto the lithograph object 14 in the form of a Gaussian beam. With a second positioning system in the form of an X-Y positioner 24, the radiation source 22 is positioned relative to the lithograph object 14 so that the beam path 23 hits the desired areas of the lithograph object 14.

The parameters of the radiation source 22 and the speed at which the radiation source 22 is moved relative to the lithography object 14 are coordinated in such a way that an irradiation track 25 with a funnel-shaped cross-section is produced. The irradiation track 25 has a width of approximately 30 pm on the surface of the lacquer layer and tapers towards the substrate 19. In order for the lacquer layer 20 to be irradiated in this way, the focus of the laser is at a distance of approximately 1000 pm from the lacquer layer 20. The power of the radiation source 22 is limited so that a smooth flank of the irradiation track 25 is established. The fact that the lacquer layer 20 is activated over its entire thickness is achieved by suitable adjustment of the speed of the XY positioner 24. The flank of the irradiation track 25 encloses a flank angle 12 of approximately 30° with the surface of the substrate 19.

If the lithograph object 14 is repeatedly covered with the irradiation spot so that the irradiated areas overlap with one another, a larger, continuous area of the lithograph object 14 can be irradiated. Fig. 9 shows an irradiation area extending over a larger width, which was created by overlapping irradiation tracks 25. Fig. 10 shows the lithograph object 14 in a state in which the resist in the irradiated areas has been removed so that the surface of the substrate 19 is accessible for a subsequent processing step.

According to the invention, the irradiation state is set depending on the local irradiation properties of the paint layer. In the example in Fig. 4, the thickness of the paint layer is a measure of the irradiation properties. In one embodiment, the dose of irradiation light is increased when the paint layer is thicker. This can be particularly useful for surface areas that are completely irradiated. In the sense of the invention, the irradiation state of the irradiation device defines the dose of irradiation light with which the paint layer 20 is treated.

In another embodiment, in which not primarily a continuous area of the lacquer layer 20 is completely and uniformly irradiated over the entire thickness of the lacquer layer 20, but in which primarily the flank angle 12 at the transition between irradiated and non-irradiated surface sections is to be kept constant, it can happen that the radiation dose does not have to be increased for a greater layer thickness, but rather reduced, in order to achieve a uniform structuring of the lacquer layer 20 that is independent of the layer thickness. The background is as follows: Starting from a first state with a first lacquer thickness to a second state with a second lacquer thickness, where the first lacquer thickness is smaller than the second lacquer thickness, a critical dose increases, i.e. the dose that is at least required to completely irradiate the lacquer layer 20 over its entire thickness. Since the flank angle 12 in the transition region between a completely exposed area and a completely unexposed area depends on the gradient of the profile of the Gaussian beam of the irradiation light in the region in which the Gaussian beam interacts with the resist, the flank angle 12 changes when the critical dose changes with a change in the resist thickness. Such an undesirable change in the flank angle 12 with a spatially changing layer thickness can be compensated for by scaling the dose profile in relation to the changed resist thickness between the first state with a first resist thickness and the second state with a second resist thickness.

In an advantageous variant of the invention, the dose profile is scaled by changing the laser power. If a corresponding scaling of the dose profile is carried out for a series of scaling factors at a defined value of the critical dose for the second state with a second lacquer thickness and the slope of the profile of the Gaussian radiation beam found for this value of the critical dose is plotted against the scaling factor, the result is unexpected at first glance that for a compared to a first state with a first Due to the increased paint thickness for the second state, the radiation dose used for irradiation in the area of the flank must be reduced in order to keep the flank angle 12 constant for the first state and the second state. The physical reason for this is that with increasing scaling factor, the critical dose is reached in a lower area of the profile of the Gaussian beam. However, the scaling results in a strongly non-linear dependence of the slope values of the profile of the Gaussian beam at the critical dose, with this non-linearity causing an absolute increase in the slope value of the profile of the Gaussian beam at the necessary critical dose of the second state with a second paint thickness. However, when scaling the dose profile it must be taken into account that with a scaled laser power the irradiated surface area and thus the absolute position of the flank can change. However, this effect can be easily calculated and compensated by shifting the irradiation spot.

According to the embodiments defined above, starting from the measurement of the thickness of the lacquer layer 20 shown in Fig. 4, one aim of the method according to the invention is to treat the lithography object 14 with a higher dose of irradiation light at those locations where a greater layer thickness was measured, and to treat it with a lower dose of irradiation light at those locations where a smaller layer thickness was measured. For this purpose, a basic setting of the irradiation state is defined for the irradiation device 21. The power of the radiation source 22 and the diameter of the irradiation spot are therefore set to a fixed value. The XY positioner 24 is given a basic speed so that the desired Irradiation track 25 within the lacquer layer 20 is set. Based on the information about the local layer thickness, the speed of the XY positioner 24 is varied so that the beam path 23 is moved over the lithograph object 14 at a lower speed in areas of greater layer thickness and at a higher speed in areas of lesser layer thickness. In Fig. 5, the speed at which the XY positioner 24 is moved in certain areas of the lithograph object 14 is indicated by a grayscale. Areas of the same speed are each shown with the same grayscale. The result is a pattern that corresponds to the layer thickness pattern in Fig. 4.

Based on the measurement of the thickness of the resist layer 20 shown in Fig. 4, the aim is to treat the lithography object 14 with a higher dose of irradiation light at those locations where a greater layer thickness was measured, and to treat it with a lower dose of irradiation light at those locations where a smaller layer thickness was measured. For this purpose, a basic setting of the irradiation state is defined for the irradiation device 21. The power of the radiation source 22 and the diameter of the irradiation spot are therefore set to a fixed value. A basic speed is specified for the XY positioner 24 so that the desired irradiation track 25 is established within the resist layer 20 with the given setting of the radiation source 22. Based on the information about the local layer thickness, the speed of the XY positioner 24 is varied so that the beam path 23 is moved over the lithography object 14 at a lower speed in areas of greater layer thickness and at a higher speed in areas of lesser layer thickness. In Fig. 5, the speed at which the XY positioner 24 is moved in certain areas of the lithograph object 14 is indicated by a color scale. Areas of the same speed are each shown with the same color. This results in a pattern that corresponds to the pattern of the layer thickness in Fig. 4.

In Fig. 6, the lithographic object 14 is divided into strips between first regions 26 which are to be subjected to irradiation and second regions 27 which are not to be irradiated. The first regions 26 form unit cells 26 within which the irradiation state remains constant. Between the various unit cells 26, the irradiation state is changed.

The thickness of the paint layer 20 is measured at several points for each of the unit cells 26 using the measuring device 15. The thickness of the paint layer 20 within the unit cell 26 is determined as an average of the measured values, so that a measured value for the thickness of the paint layer 20 is available for each unit cell 26.

In the subsequent irradiation step, the power of the radiation source 22 and the diameter of the irradiation spot are kept constant across the various unit cells 26. The XY positioner 24 is controlled so that the area of a unit cell 26 is covered with multiple overlapping irradiation tracks 25. The speed at which the radiation source 22 is moved remains constant. The dose of the irradiation light is adapted to the layer thickness within the relevant unit cell 26 by changing the degree of overlap between adjacent irradiation tracks. The higher the degree of overlap, the greater the irradiation dose with which the paint layer in the unit cell 16 is treated. When irradiating a subsequent unit cell 26, the parameters of the radiation source 22 remain constant. The speed at which the XY positioner 24 moves the radiation source 22 also remains constant. The irradiation state is adjusted by changing the degree of overlap between the irradiation tracks 25.

In Fig. 11, a projection exposure system for microlithography is shown schematically. The projection exposure system comprises an illumination system 30 and a projection system 31. With the aid of the illumination system 30, an object field 33 in an object plane 32 is illuminated.

The illumination system 30 comprises an irradiation source 34 which emits electromagnetic radiation in the EUV range, i.e. in particular with a wavelength between 5 nm and 30 nm. The radiation emanating from the irradiation source 34 is first bundled in a collector 35 into an intermediate focal plane 36.

The illumination system 30 comprises a deflection mirror 37, with which the radiation emitted by the radiation source 34 is deflected onto a first facet mirror 38. A second facet mirror 39 is arranged downstream of the first facet mirror 38. The first facet mirror and the second facet mirror 39 each comprise a plurality of micromirrors that can be individually pivoted about two axes running perpendicular to one another. The individual facets of the first facet mirror 38 are imaged into the object field 33 using the second facet mirror 39.

With the help of the projection system 31, the object field 33 is imaged into an image plane 29 via a plurality of mirrors 28. In the object plane 32, a mask (also called a reticle) is which is imaged onto a light-sensitive layer of a wafer arranged in the image plane 29.

The various mirrors of the projection exposure system, on which the illumination radiation is reflected, are designed as EUV mirrors. The EUV mirrors are provided with highly reflective coatings, for example in the form of multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The EUV collector 35 has a reflection surface in the form of a rotational ellipsoid, resulting in a near focus point and a far focus point. In the area of the near focus point, EUV radiation is generated by means of a laser-produced plasma (LPP), the plasma being excited by a CO2 laser with a wavelength of 10.6 pm. For this purpose, the concave mirror has a recess in the area of the optical axis through which the laser radiation can pass. The EUV radiation generated is bundled by the concave mirror and focused on the far focus point 36. The second focus point 36 forms the intermediate focus 36, after passing through which the EUV radiation enters the illumination optics of the illumination system 30.

In order to prevent the remainder of the 10.6 pm radiation emitted by the CO2 laser from being focused on the distant focus point, the reflection surface of the concave mirror is provided with a surface structure that deflects the 10.6 pm radiation from the distant focus point. The surface structure can be produced lithographically. The concave mirror on which the surface structure is to be produced can form a lithographic object within the meaning of the invention. Fig. 12 shows an integrated measuring and irradiation device 43 which is suitable for use with a concave mirror 40 as a lithography object. The concave mirror 40 is mounted on a carrier 41 which is equipped with a rotary drive in order to rotate the concave mirror 40 about its optical axis 42. The measuring and irradiation device 43 comprises a measuring means 17 and a radiation source 22 which are accommodated in a common housing 44. The housing 44 is mounted on a guide rail 45 along which the housing 44 can be moved up and down. In the view of Fig. 12, the movement of the housing 44 extends in the plane of the page.

Depending on the operating state of the measuring and irradiation device 43, the measuring beam path 18 and the irradiation beam path 23 emerge from the housing 44. The measuring and irradiation device 43 is adjusted so that in any position of the housing 44 relative to the guide rail 45, the measuring beam path 18 and the irradiation beam path 23 impinge perpendicularly on the reflection surface of the concave mirror 40.

Several unit cells 26 are defined on the reflection surface 46, which extend along circumferential lines over the reflection surface 46. Each of the unit cells 26 is to be irradiated with the radiation source 22, whereby the irradiation state within each unit cell 26 remains constant. To do this, in a first step, several measured values distributed over the circumference are recorded for each unit cell 26 on the thickness of the paint layer. The layer thickness within the unit cell 26 is assumed to be the average of the measured values. In order to obtain the measured values within a unit cell 26, the housing 44 with the measuring device 17 can be held in a fixed position relative to the guide rail 45, while the concave mirror 40 rotates once around the optical Axis 42 is rotated. In this way, the desired number of measured values distributed over the circumference can be obtained within the unit cell 26.

The irradiation state is then set by first suitably adjusting the diameter of the irradiation spot acting on the paint and the power of the radiation source 22. For the irradiation step, the concave mirror 40 is rotated again. If the radiation source 22 is moved along the guide rail 45 while the concave mirror 40 is rotating, this results in a spiral path along which the irradiation beam path 43 moves over the reflection surface 46 of the concave mirror 40. By adjusting the overlap between adjacent revolutions, the dose with which the paint layer 20 is treated can be adjusted. Within a unit cell 26, the dose remains constant. For the transition to the next unit cell 26, the dose is adjusted by changing the degree of overlap within the spiral path. The degree of overlap is adjusted by changing the speed at which the housing 44 moves along the guide rail 45.

An alternative embodiment of a measuring and irradiation device 43 according to the invention is shown in Fig. 13. The lithography object here is a planar surface of a substrate 50 coated with lacquer, on the surface of which a plurality of unit cells 26 are defined, which are to be subjected to irradiation. The measuring and irradiation device 43 comprises a measuring means 17, with which the thickness of the lacquer layer 20 within a unit cell is determined. The measured value is sent to a controller 51, which evaluates the measured value and uses it to determine a control specification for an irradiation device 52. The irradiation device 52 is used to image a mask (not shown) onto a unit cell 26 via an imaging optics 53. The wafer 50 remains in a fixed position until the relevant unit cell 26 has been treated with a sufficient dose of radiation. After the irradiation of this unit cell 26 has been completed, the wafer 50 is shifted one position to the right so that the radiation hits the next unit cell 26. The thickness of the resist layer 20 of this unit cell 26 is known from the previous interferometric measurement. The irradiation device 52 receives a control specification from the controller 51, with which the duration of the irradiation is set so that the unit cell is treated with the appropriate dose of irradiation light.

Claims

patent claims 1. Method for irradiating a lithography object (14, 40, 50), in which the lithography object (14, 40, 50) is coated with a lacquer layer (20), in which irradiation properties of the lacquer (20) are determined in a spatially resolved manner, in which, depending on the irradiation properties determined for a first partial area of the lithography object (14, 40, 50), an irradiation device (21, 52) is set to a first irradiation state in order to irradiate the first partial area, and in which, depending on the irradiation properties determined for a second partial area of the lithography object (14, 40, 50), the irradiation device (21, 52) is set to a second irradiation state in order to irradiate the second partial area, wherein the lithography ieobj ekt (14, 40, 50) is irradiated by guiding a spot generated with an irradiation beam path (23) along a predetermined path over the lithograph ieobj ekt (14, 40, 50) in order to generate an irradiation track (25) in the resist layer (20). 2. The method according to claim 1, wherein the irradiation properties of the lacquer layer (20) are determined by measuring the layer thickness of the lacquer. 3. The method according to claim 2, wherein the layer thickness of the paint is measured using an optical measuring method. 4. Method according to one of claims 1 to 3, wherein the lithography object has a plurality of unit cells (26) and wherein the irradiation state of the irradiation device (21, 52) remains constant when irradiating a unit cell (26). 5. Method according to one of claims 1 to 4, wherein the irradiation beam path (23) is adjusted such that an approximately linear section of a flank of the irradiation track (25) encloses an angle (12) between 20° and 90°, preferably between 20° and 40°, with the lithography object (14, 40, 50). 6. The method according to any one of claims 1 to 5, wherein a first portion of the irradiation track (25) overlaps with a second portion of the irradiation track (25). 7. The method according to claim 6, wherein the first irradiation state of the irradiation device (21, 52) is changed to the second state of the irradiation device (21, 52) by changing the degree of overlap between the first section of the irradiation track (25) and the second section of the irradiation track (25). 8. Method according to one of claims 1 to 7, wherein the lithograph object (40) has a rotational symmetry and wherein the lithograph object (40) is rotated about its optical axis (42). 9. The method according to claim 8, wherein a radiation source (22) of the irradiation device (21, 52) and the lithography object (40) are moved relative to each other to produce a spiral irradiation track (25). 10. System for irradiating a lithographic object (14, 40, 50), with a measuring device (15) and an irradiation device (21), wherein the measuring device (15) is designed to determine the irradiation properties of the lacquer in a spatially resolved manner in the lithographic object (14, 40, 50) coated with a lacquer layer (20), and wherein the irradiation device (21, 52) is dependent on the irradiation properties determined for a first partial area of the lithography object (14, 40, 50) are set to a first irradiation state in order to irradiate the first partial area, and in which the irradiation device (21, 52) is set to a second irradiation state in dependence on the irradiation properties determined for a second partial area of the lithography object (14, 40, 50) in order to irradiate the second partial area (26), wherein the irradiation device is designed to irradiate the lithography object (14, 40, 50) by guiding a spot generated with an irradiation beam path (23) along a predetermined path over the lithography object (14, 40, 50) in order to generate an irradiation track (25) in the resist layer (20). 11. System according to claim 10, wherein the measuring device (15) comprises a measuring means (17) of an optical method, wherein the irradiation device (21, 52) comprises a radiation source (22) and wherein a uniform positioning system (43) is provided with which both the measuring means (17) and the radiation source (22) are positioned relative to the lithography object (14, 40, 50). 12. Optical element made from a lithograph object (14, 40, 50), wherein the lithograph object (14, 40, 50) has been treated according to the method according to any one of claims 1 to 9. 13. A semiconductor technology system comprising an optical element (19, 28, 35, 38), wherein the optical element is designed according to claim 12. 14. System according to claim 13, wherein the system is a microlithographic projection exposure system, a wafer inspection system or a mask inspection system.