Optical arrangement for determining a beam caustic of a laser beam, method for determining a beam caustic of a laser beam with an optical arrangement, EUV driver laser, EUV light generation system and method for producing a semiconductor intermediate product or a microchip
A fixed detection device with a deformable deflection surface in the optical arrangement addresses the space and speed limitations of prior systems, enabling precise and compact beam caustic determination for EUV driver lasers, enhancing EUV light generation efficiency.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TRUMPF LASERSYSTEMS FOR SEMICONDUCTOR MANUFACTURING SE
- Filing Date
- 2026-01-12
- Publication Date
- 2026-07-23
AI Technical Summary
Existing optical arrangements for determining the beam caustic of a laser beam, particularly for EUV driver lasers, have a large space requirement and slow image determination speed due to the need for a translationally movable detection device and complex actuator systems.
The optical arrangement features a fixed detection device with a reversibly deformable deflection surface, allowing for adjustable focal lengths and rapid image generation, reducing the device's footprint and enabling precise beam caustic determination.
The solution provides a compact and efficient method for determining beam caustics with high speed and accuracy, minimizing thermal effects and imaging errors, suitable for use in EUV light generation systems for semiconductor manufacturing.
Smart Images
Figure EP2026050589_23072026_PF_FP_ABST
Abstract
Description
[0001] Optical arrangement for determining a beam caustic of a laser beam, method for determining a beam caustic of a laser beam using an optical arrangement, EUV driver laser, EUV light generation system and method for manufacturing a semiconductor intermediate or a microchip
[0002] BACKGROUND OF THE INVENTION
[0003] 1. Field of the invention
[0004] The invention relates to an optical arrangement for determining a beam caustic of a laser beam, with
[0005] a) a coupling device designed to couple a measuring beam separated from a laser beam to be measured into a measuring beam path,
[0006] b) a detection device having an imaging plane, wherein the detection device is configured to detect a plurality of images of the measuring beam in the imaging plane,
[0007] c) an evaluation device by means of which the beam caustic of the laser beam can be determined on the basis of the plurality of images of the measuring beam,
[0008] d) a deflecting device having a deflecting surface and positioned to deflect the measuring beam from the direction of the coupling device towards the imaging plane of the detection device by means of the deflecting surface.
[0009] The invention further relates to a method for determining a beam caustic of a laser beam with an optical arrangement, an EUV driver laser, an EUV light generation system and a method for producing a semiconductor intermediate or a microchip.
[0010] 2. State of the art
[0011] In the production of integrated circuits, so-called microchips, semiconductor substrates (hereinafter referred to as "wafers"), which are often monocrystalline, are coated with a layer in a relatively early manufacturing step. This layer is then structured in subsequent manufacturing steps. Such structuring acts as a mask in further downstream manufacturing steps, enabling the functional layer beneath the coating to be etched, doped with foreign atoms (e.g., by ion implantation), or introduced into the structure by foreign materials (e.g., by LIGA and lift-off).
[0012] The aim of these process steps is, among other things, to fabricate transistors and conductive areas that connect the transistors on the wafers. The structuring can be introduced into the coating using various methods.
[0013] In photolithography, for example, the coating is a photosensitive coating, specifically a photoresist. Here, the photoresist is exposed to light of a specific wavelength, to which it is sensitive, in a particular pattern. This allows the chemical properties of the exposed areas of the photoresist, such as its solubility in a developer solution, to be influenced. Some photoresists polymerize the exposed areas, meaning their solubility increases compared to the unexposed areas (so-called negative resists). Others become more soluble in the exposed areas compared to the unexposed areas (so-called positive resists).In any case, to form the structure in the photoresist and thus the mask for the functional layer located under the photoresist, the more soluble areas of the photoresist are removed using the developer solution.
[0014] To introduce the specific pattern into the photoresist, a masking element (hereinafter referred to as "photomask") is usually placed between the light source and the wafer, which, depending on the photoresist used (negative or positive), is designed as a negative or positive of the structure to be formed on the photoresist.
[0015] In conventional photolithography, the photomask either lies directly on the photoresist or is positioned just above it, i.e., spaced apart from it, resulting in a 1:1 relationship between the photomask and the resulting pattern on the photoresist. Since photomasks can only be scaled to a finite size, this method is essentially limited to feature sizes of a few hundred nanometers. Because smaller patterns enable microchips with significantly higher performance per unit area or volume (since more transistors can be implemented on the same small area), there is a general drive to reduce the size of the pattern to its absolute physical limits.For this reason, projection exposure systems are generally used nowadays, in which a focusing optic is usually positioned between the photomask and the photoresist. This allows the photomask to be drastically reduced in size and projected onto the photoresist. This enables the photomasks to be manufactured more cheaply, as the structures of the photomask do not need to be as small. Furthermore, it allows for significantly smaller structures to be imaged onto the wafers compared to conventional photolithography. The photomask and the resulting structure on the photoresist can then be present in a ratio of, for example, 5:1 or greater. The photomask itself can be designed as an absorptive or a reflective photomask.
[0016] Since the reduced image size of the photomask on the photoresist does not allow the entire wafer to be covered, prior art methods often employ a so-called "step-and-repeat" process: the wafer is exposed at a first exposure position, moved a certain distance, and then exposed again at a second exposure position. This process is repeated until the wafer is largely covered with instances of the same pattern.
[0017] After the areas of the photoresist that are more soluble than the developer solution have been removed and the underlying functional layer has been treated, for example by etching, the photoresist is often removed from the functional layer by a process called "stripping".
[0018] For multi-layered microchips, the projection exposure method described above can be performed up to one hundred times for the same microchip.
[0019] EUV lighting system and EUV generation
[0020] Besides reducing the size of the photomask and using focusing optics, another way to reduce the size of the pattern on the wafers is to use light with a shorter wavelength for exposure.
[0021] In methods known from the prior art, extreme ultraviolet light (EUV light) with a wavelength in the range of about 8 to about 15 nm is generated, with a main proportion of the EUV light being at 13.5 nm, which is directed onto the photoresist by means of an EUV projection optic and an EUV focusing optic of the projection exposure system.
[0022] An EUV light generation system used for this purpose essentially comprises an EUV driver laser, which can generate at least one excitation light beam, a target material generator, and an EUV light generation chamber. Typically, a pulsed high-power laser is used as the EUV driver laser, and a droplet generator serves as the target material generator, which injects droplets of a target material into the EUV light generation chamber. To prevent damage to the system due to particle contamination, a high vacuum under a process gas atmosphere can be maintained within the EUV light generation chamber in prior art implementations. Hydrogen (H₂) or helium (He) are particularly suitable process gases.
[0023] In prior art processes, tin (Sb) is frequently used as the target material. However, in addition to tin (Sb), target materials including xenon (Xe), gold (Au), and / or lithium (Li) are also possible. To increase the amount of emitted EUV light, the droplets generated by the droplet generator can, for example, first be excited with a pre-pulse and then with a main-pulse. The two excitation beams can be independent or generated by splitting a single beam. In principle, EUV light could be generated with only a single excitation beam; a second excitation beam is therefore not strictly necessary. However, using a second excitation beam increases the conversion efficiency.the ratio of input laser power to generated EUV power is significant.
[0024] This is because, in this known method, the pre-pulse excitation causes a preconditioning of the target material droplet. Currently, this preconditioning involves the target material droplet forming an approximately disk-like shape due to the energy input from the pre-pulse, thereby comparatively increasing the surface area of the target material droplet that can be excited by the second excitation light beam. The main pulse then strikes the preconditioned target material droplet, thereby exciting it. In known methods, this excitation includes the generation of an ionized gas of the target material—if the target material is a tin material, this generates a tin plasma. This tin plasma then emits the EUV light required for the formation of the structure in the photoresist.
[0025] In another known method, a third excitation light beam, in the form of a so-called rarefaction pulse, can be used for further preconditioning. This pulse strikes the target material droplet between the pre-pulse and the main pulse. In this known method, the rarefaction pulse causes a dilution or volume increase of the target material droplet, which has been shaped into a disc by the pre-pulse, towards a target material cloud. The term "cloud" here is not to be equated with a gaseous or vapor state of the target material. The use of such a rarefaction pulse further increases the conversion efficiency.
[0026] The dilution pulse can be generated by splitting the initial excitation beam into the pre-pulse and the dilution pulse. Alternatively, a separate light source can be used for the dilution pulse, or even a single excitation beam can be split into the pre-pulse, the dilution pulse, and the main pulse. Furthermore, the dilution pulse can be designed as a temporally preceding segment of the main pulse, both in terms of timing and intensity distribution over time. In this case, it is often referred to as a "pedestal."
[0027] EUV driver lasers are also conceivable, in which more than three excitation light beams are used to excite the target material and generate EUV light.
[0028] In each of the above cases, the main pulse hits the target material droplet with a power in the range of 20 to 50 kW.
[0029] EUV driver laser
[0030] Prior art EUV driver lasers, sometimes also referred to as EUV drivelasers, can have a beam source, a pump source, an amplifier arrangement with a plurality of optical amplifiers and a focusing unit.
[0031] The beam source can generate the excitation light beam, which is then amplified at a specific point along the optical path by the multitude of optical amplifiers to form an amplified excitation light beam.
[0032] If more than one light beam is used to generate EUV light in the prior art methods, individual beam sources can be provided for each excitation beam (pre-pulse, dilution pulse and main pulse), i.e. a pre-pulse beam source, a dilution pulse beam source and a main pulse beam source.
[0033] In known methods, the term "pulse" refers to a light beam with a relatively short duration, and therefore a start and end point. It is part of a series of temporally successive light beams of the same type (pulse sequence) and is generated by a pulsed laser. The pulse duration can be in the micro-, nano-, pico-, or femtosecond range. Lasers operating in continuous wave (CW) mode should be distinguished from these.
[0034] If one, two, three or more individual beam sources are used to generate the excitation light beam or the pre-, dilution and / or main pulse, these can generate the excitation light beams with the same or different wavelength and the same or different intensity, mode, beam caustics and / or polarization, or the excitation light beams can strike the target material droplet with the same or different wavelength and the same or different intensity, mode, beam caustics and / or polarization.
[0035] In conventional EUV excitation light generation systems, the use of a solid-state laser as a pre-pulse beam source is known. Such a known solid-state laser generates the pre-pulse with a wavelength in the range of approximately 1 pm. A solid-state laser can also be used as the dilution pulse beam source, preferably with a wavelength different from the pre-pulse, also in the range of approximately 1 pm, for metrological purposes.
[0036] A CO2 laser is often used as the main pulse beam source for the main pulse, generating the main pulse with a wavelength in the range of about 10.6 µm.
[0037] Problem arising from the state of the art
[0038] Optical arrangements for determining the beam caustic of a laser beam, particularly for use in an EUV driver laser, are known from the prior art. These arrangements include a coupling device configured to couple a measurement beam, split off from the laser beam to be measured, into a measurement beam path. Furthermore, the prior art optical arrangements include a detection device having an imaging plane, the detection device being configured to capture an image of the measurement beam in the imaging plane. In the prior art optical arrangements, the detection device is designed to be translationally displaceable and configured to be moved to different positions within the measurement beam path in order to capture an image of the measurement beam at those positions.Using an evaluation unit, the beam caustics of the measuring beam can be determined in these known optical arrangements based on the plurality of images of the measuring beam. A problem with such optical arrangements known from the prior art for determining the beam caustics is their comparatively large space requirement, since the various positions of the detection device for capturing the images of the measuring beam in the measuring beam path necessitate a relatively space-consuming actuator system. Furthermore, the various positions along the measuring beam to be measured must be relatively far apart for the translationally movable detection device in order to ensure a sufficiently accurate determination of the beam caustics.
[0039] Furthermore, the comparatively slow speed of determining the images of the measuring beam is problematic due to the complex and comparatively slow positioning of the detection device at different positions in the measuring beam path using the actuators.
[0040] SUMMARY OF THE INVENTION
[0041] The object of the present invention is therefore to provide the optical arrangement mentioned at the outset for determining a beam caustic of a laser beam, which addresses the disadvantages described above in the prior art.
[0042] This problem is solved according to the invention by means of the optical arrangement mentioned at the outset, in which
[0043] e) the detection device is fixed in a stationary position and the imaging plane of the detection device is fixed,
[0044] f) the deflection surface is designed to be reversibly deformable at least in certain areas, such that a focal length of the deflection device can be adjusted by means of at least partial deformation of the deflection surface, so that, in particular at different focal lengths, a plurality of images of the measuring beam can be generated in the imaging plane of the detection device.
[0045] This optical arrangement has a particularly small footprint, since the detection device is fixed in place and the imaging plane of the detection device is fixed.
[0046] A deflection device, which includes a deflection surface, is positioned to redirect the measuring beam along the beam path from the direction of the coupling device towards the imaging plane of the detection device. This makes the optical arrangement for determining the beam caustic of a laser beam particularly compact and space-saving. Furthermore, in different installation spaces, the deflection device can be advantageously adapted to the specific installation situation by appropriately positioning it, thus allowing the beam path to be adjusted to the given space constraints.
[0047] The deflection surface of the deflecting device is designed to be reversibly deformable, at least in certain areas, so that the focal length of the deflecting device can be adjusted by means of at least partial deformation of the deflection surface. This allows for the generation of multiple images of the measuring beam in the imaging plane of the detection device at different focal lengths. Since the adjustment of the focal length by means of at least partial deformation of the deflection surface can be performed particularly quickly, a particularly high speed is possible for determining the images of the measuring beam and thus for determining the beam caustic of the laser beam.
[0048] The detection device can advantageously include a camera. The camera can include an active area for generating the image of the measuring beam, in particular a camera chip, e.g., a gallium arsenide quantum well (QWIP) detector, a mercury cadmium telluride (MCT) detector, or a microbolometer array for higher wavelengths from approximately 8 pm; an indium gallium arsenide (InGaAs) detector or a lead sulfide (PbS) detector for lower wavelengths in a range of approximately 1 pm to approximately 2 pm; or an indium antimony (InSb) detector or a mercury cadmium telluride (MCT) detector; and optionally, a deuterated triglycine sulfate (DTGS) detector for medium wavelengths in a range of approximately 3 pm to approximately 5 pm, which exhibits comparatively low absorption for the measuring beam. Due to the comparatively low absorption, images of the measuring beam with particularly high accuracy are possible.
[0049] Advantageously, the deflection device is designed as a mirror. The deflection surface of the deflection device can consist of a material that is highly reflective for the wavelength of the measuring beam, or be coated with such a material, such as silver, copper, or gold.
[0050] It is advantageous if the deflection surface of the deflecting device exhibits comparatively low absorption of the measuring beam. The deflection surface can be made of, or coated with, a material that exhibits this comparatively low absorption of the measuring beam. The material can include silver.
[0051] It is advantageous if the power of the measuring beam separated by the coupling device is less than 50%, preferably less than 25%, and particularly preferably less than 5% of the power of the laser beam. Due to such a comparatively low power of the measuring beam, changes in thermal expansion in components of the optical arrangement can be kept particularly small, and particularly accurate images of the measuring beam can be obtained.
[0052] It is advantageous if the coupling device is designed as a beam splitter, at least partially a transmitting mirror, or at least a partially reflective diamond window.
[0053] Advantageously, the measuring beam separated from the laser beam to be measured by means of the coupling device has a substantially identical beam caustic to the laser beam to be measured. In other words, the measuring beam is preferably as exact a duplicate as possible of the laser beam with respect to the beam caustic.
[0054] Preferably, the deflection device has a counter-surface opposite the deflection surface, which is configured to effect at least a partially reversible deformation of the deflection surface under pressure. This allows for particularly simple deformation of the deflection surface. The counter-surface can be designed as a uniform and / or continuous surface, so that the pressure is applied to the uniform and / or continuous counter-surface. Alternatively, the counter-surface can be designed with distinct, and in particular, separate areas, so that a different pressure can act on the counter-surface in these distinct, and in particular, separate areas, thus causing reversible deformations of the deflection surface corresponding to the deformation forces acting on the deflection surface in each respective area.This allows for the realization of freeform deflection surfaces, which in turn enables the compensation of even more complex beam aberrations. These freeforms can be approximated by Zernike polynomials.
[0055] It is advantageous if the deflection device comprises a plurality of piezoelectric actuators configured to reversibly deform the deflection surface, at least in certain areas. These piezoelectric actuators allow for the setting of a deformation state of the deflection surface that differs from an undeformed normal state. The piezoelectric actuators can be configured such that all piezoelectric elements exert the same deformation force on the deflection surface. Alternatively, the piezoelectric elements can also be configured to exert different deformation forces on the deflection surface.Another advantageous possibility is to group the piezo actuators into at least a first group and a second group, where the first group is configured to exert a first deformation force on the deflection surface and the second group is configured to exert a second deformation force, different from the first. More than two groups of piezo actuators are also possible. This also allows for the realization of freeform deflection surfaces that can be described, at least approximately, by Zernike polynomials.
[0056] Advantageously, in a deformed configuration deviating from its normal state, the deflecting surface exhibits the same radius of curvature in a direction parallel to a reflection plane formed by a measuring beam incident on the deflecting surface and a measuring beam emitted from the deflecting surface as in a direction perpendicular to the reflection plane. In other words, the deflecting surface is symmetrical with respect to the reflection plane and a plane perpendicular to the reflection plane in a deformed state. Identical, and therefore symmetrical, deformation parallel and perpendicular to the reflection plane is particularly easy to implement.
[0057] Preferably, the angle of incidence between a normal and the measuring beam incident on the deflecting surface lies in a range of 1° to 15°, preferably from 1° to 8°, and particularly preferably from 1° to 5°. For these angles of incidence, imaging errors of the measuring beam in the imaging plane of the detection device are particularly low, and a particularly accurate determination of the beam caustic is possible.
[0058] Advantageously, in a deformed configuration deviating from its normal state, the deflecting surface exhibits a different radius of curvature in a direction parallel to a reflection plane formed by a measuring beam incident on the deflecting surface and a measuring beam emitted from the deflecting surface, compared to a direction perpendicular to the reflection plane. In other words, the shape of the deflecting surface in a deformed state is asymmetrical with respect to the reflection plane and a plane perpendicular to the reflection plane. In particular, the deflecting surface in the deformed configuration can be parabolic. The deflecting surface in the deformed configuration can be such that a first radius of curvature with respect to the direction parallel to the reflection plane is smaller than a second radius of curvature with respect to the direction perpendicular to the reflection plane.This allows for the correction of an undesired change in the cross-sectional profile of the measuring beam exiting the deflecting surface compared to the cross-sectional profile of the measuring beam entering the deflecting surface, such that the cross-sectional profile of the measuring beam exiting the deflecting surface essentially corresponds to the cross-sectional profile of the measuring beam entering the deflecting surface. In this way, imaging errors of the measuring beam in the imaging plane of the detection device can be reduced. The cross-sectional profile of the measuring beam can be understood as a profile of the measuring beam that lies in a plane perpendicular to the propagation direction of the measuring beam. In particular, the cross-sectional profile can be understood as the roundness of the measuring beam. The cross-sectional profile can have a relatively round, elliptical, or arbitrarily free shape.Preferably, the beam cross-sectional profile of the measuring beam exiting the deflecting surface has a comparatively round shape.
[0059] It is advantageous if the angle of incidence between a normal and the measuring beam incident on the deflecting surface lies in a range of 25° to 60°, preferably 35° to 55°, particularly preferably 40° to 50°.
[0060] Preferably, a focusing element, in particular a lens, with a constant focal length is arranged in the measuring beam path between the detection device and the deflecting device. Due to the focusing element, the detection device can be positioned closer to the deflecting device than in an optical arrangement without such a focusing element, since the constant focal length of the focusing element can be selected such that focused images of the measuring beam in the imaging plane of the detection device can be generated at a comparatively short distance between the detection plane and the deflecting device. In this way, the optical arrangement can be designed to be particularly compact. The constant focal length of the focusing element is preferably in the range of 1 m to 2 m.
[0061] An advantage arises when the optical arrangement includes a second deflection device that is translationally movable and / or rotatable about at least one axis of rotation and / or has a second deflection surface that is at least partially reversibly deformable, wherein the second deflection device is configured to set an angle and / or a position of the measuring beam relative to a reference area on the imaging plane. Using such a second deflection device, the position of the measuring beam relative to the reference area on the imaging plane can be corrected, for example, during initial commissioning and / or referencing of the optical arrangement. This ensures that the measuring beam strikes the imaging plane of the detection device at a desired angle and position, and that images of the measuring beam on the imaging plane are generated with as few errors as possible.
[0062] According to a further aspect of the invention, the aforementioned problem is solved by a method for determining a beam caustic of a laser beam with an optical arrangement, comprising the steps: a) coupling a measuring beam separated from a laser beam to be measured into a measuring beam path by means of a coupling device and deflecting the measuring beam towards an imaging plane of a detection device by means of a deflecting device,
[0063] b) at least partially reversible deformation of a deflecting surface of the deflecting device, thereby setting different focal lengths f(n) of the deflecting device and in turn thereby generating a plurality of images of the measuring beam D( (n)) in the imaging plane E det the detection device,
[0064] c) Capturing the majority of images of the measuring beam D (n)) in the imaging plane E det by means of the detection device,
[0065] d) using the evaluation unit, determining virtual images of the measuring beam D( / (n)) virt in virtual mapping planes £' (n)) virt based on the majority of images of the measuring beam
[0066]
[0067] in the image plane E det the detection device and the different focal lengths f(n) of the deflection device,
[0068] e) Determining the beam caustics of the laser beam from the virtual images D( / (n)) virt by means of the evaluation unit.
[0069] Preferably, the virtual images are determined according to
[0070] D
[0071]
[0072] (f(n)) virt = β(f(n)) * D(f(n)),
[0073] where
[0074] D( / (n)) virtdenotes a virtual image of the measuring beam, ß(J n)~) denotes a lateral magnification and D (n)) denotes an image of the measuring beam.
[0075] Advantageously, lateral magnifications β(f(n)~) and virtual lateral positions of the virtual imaging planes E( (nβ) can be used. virt from transfer matrices
[0076]
[0077] The optical arrangement can be determined using the virtual lateral position s(f(n)~). virt The distance of the virtual mapping plane E(f (n)) virt designated by the coupling device.
[0078] The optical arrangement can be mathematically described by transfer matrices M(f(n)~) as a function of the different focal lengths fn) of the deflection device. Transfer matrices are also frequently referred to as beam matrices or ABCD matrices. In addition to the different focal lengths fn) of the deflection device, other optical components of the optical arrangement, such as one or more lenses, mirrors, free propagation paths of the measuring beam, and the virtual lateral position, can also be included in the transfer matrices M(f( )).
[0079]
[0080] This must be taken into account. Transfer matrices are preferred.
[0081]
[0082] all optical components of the optical device, free propagation paths of the measuring beam and the virtual lateral position
[0083]
[0084] taken into account.
[0085] It is advantageous if at least six, in particular at least eight, preferably at least ten virtual images D( (n)~) are available. virt of the measuring beam in virtual imaging planes £' (n)) virt based on images of the measuring beam D (n)) in the imaging plane E det The detection device determines the beam caustic. This allows for a particularly precise determination of the beam caustic.
[0086] Preferably, a first half of a number of the virtual mapping planes D( (n)~) virt in a first region within the Rayleigh length and a second half of a number of virtual mapping planes D(f(n)) virt in a second area outside twice the Rayleigh length. This allows for a particularly precise determination of the ray caustic.
[0087] According to a further aspect of the invention, the problem mentioned at the outset is solved by an EUV driver laser for exciting a target material with a laser beam to generate an EUV light-emitting plasma of the target material, comprising an optical arrangement with some or all of the features mentioned above for the optical arrangement.
[0088] According to a further aspect of the invention, the aforementioned problem is solved by an EUV light generation system for generating EUV light, comprising an EUV driver laser with some or all of the features mentioned above for the EUV driver laser, a target material generator for generating units of the target material that can be excited by the laser beam, and an EUV light generation chamber within which the units of the target material can be excited by the laser beam and thereby generate EUV light.
[0089] According to a further aspect of the invention, the aforementioned problem is solved by a method for producing a semiconductor intermediate or a microchip, comprising the steps of:
[0090] a) Providing an EUV driver laser with some or all of the features mentioned above for the EUV driver laser and generating the laser beam;
[0091] b) Providing a target material generator and generating units of the target material that can be excited by the laser beam;
[0092] c) By means of the EUV driver laser, excitation of the units of the target material with a laser beam and thereby generation of the EUV light-emitting plasma of the target material;
[0093] d) Exposure of a semiconductor substrate coated with a photosensitive coating with EUV light emitted by the plasma of the target material. List of figures
[0094] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. These show:
[0095] Fig. 1 shows a schematic representation of an EUV driver laser with an exemplary optical arrangement for determining a beam caustic of a laser beam of the EUV driver laser;
[0096] Fig. 2 shows an embodiment of an EUV light generation system according to the invention in a schematic representation.
[0097] The invention is not limited to the embodiments shown. The embodiments shown in the figures merely represent specific examples of the invention. Within the scope of their expert knowledge, a person skilled in the art can recognize embodiments of the invention that are not explicitly shown. 2024P00380WO
[0098] Reference symbol list
[0099] 8 EUV driver lasers
[0100] 9 Ray cauterization
[0101] 10 optical arrangement
[0102] 12 Laser beam
[0103] 14 Coupling device
[0104] 16 Measuring beam
[0105] 18 Detection device
[0106] 20 Image plane
[0107] 22 Image of the measuring beam
[0108] 24 Evaluation unit
[0109] 26 Deflection device
[0110] 28 Deflection area
[0111] 30 piezo actuators
[0112] 32 focusing element
[0113] 34 virtual image of the measuring beam
[0114] 36 virtual mapping plane
[0115] 38 EUV lighting system
[0116] 40 EUV light
[0117] 42 Target material generator
[0118] 44 Target material
[0119] 46 EUV Light Generation Chamber DESCRIPTION OF PREFERRED EXECUTION EXAMPLES
[0120] Fig. 1 shows a schematic representation of an EUV driver laser 8, with an exemplary optical arrangement 10 for determining a beam caustic of a laser beam 12 of the EUV driver laser 8.
[0121] The optical arrangement 10 comprises a coupling device 14, which is configured to couple a measuring beam 16, separated from a laser beam 12 to be measured, into a measuring beam path. The measuring beam 16 separated from the laser beam 12 to be measured is coupled into the measuring beam path by means of the coupling device 14 such that the beam caustic of the laser beam 12 to be measured is essentially identical to a beam caustic of the measuring beam 16 separated from the laser beam 12 to be measured.
[0122] A detection device 18, having an imaging plane 20, is configured to capture a plurality of images of the measuring beam 22 in the imaging plane 20. The beam caustic of the laser beam 12 can be determined from the plurality of images of the measuring beam 22 by means of an evaluation device 24.
[0123] According to the invention, the detection device 18 is fixed in a stationary position, and the imaging plane 20 of the detection device 18 is also fixed. A deflecting device 26, which in this case is designed as a mirror, has a deflecting surface 28 and is positioned such that it deflects the measuring beam 16 from the direction of the coupling device 14 towards the imaging plane 20 of the detection device 18 by means of the deflecting surface 28. According to the invention, the deflecting surface 28 is designed to be reversibly deformable, at least in certain areas, so that the focal length of the deflecting device 26 can be adjusted by means of at least partial deformation of the deflecting surface 28.
[0124] This makes it possible to generate a plurality of images of the measuring beam 22 in the imaging plane 20 of the detection device 18 at different focal lengths.
[0125] The deflection device 26 comprises a plurality of piezo actuators 30, which are configured to deform the deflection surface 28 at least partially and reversibly. In the present embodiment, the individual piezo actuators 30 can be controlled independently of one another, so that each individual piezo actuator 30 can assume independent and / or different positions. As a result, free spatial deformation of the deflection surface 28 of the deflection device 26 is possible. In the present embodiment, the deflection surface 28, in a deformed configuration deviating from its normal state, has the same radius of curvature in a direction parallel to a reflection plane formed by a measuring beam 16 incident on the deflection surface 28 and a measuring beam 16 emitted from the deflection surface 28 as in a direction perpendicular to the reflection plane.
[0126] The angle of incidence between the normal and the measuring beam 16 incident on the deflecting surface 28 is 7.5°. At such an angle of incidence, imaging errors of the images of the measuring beam 22 in the imaging plane 20 of the detection device 18 can be minimized.
[0127] In the measuring beam path, a focusing element 32 with a constant focal length is arranged between the detection device 18 and the deflecting device 26. The focusing element 32 is designed as a lens. The constant focal length of the lens is selected such that images of the measuring beam 22 with as few errors as possible can be generated in the imaging plane 20 of the detection device 18, while maintaining comparatively short distances s2 and / or s3. The distance s2 describes the distance between the deflecting surface 28 of the deflecting device 26 and the focusing element 32 along the measuring beam path. The distance s3 describes the distance between the focusing element 32 and the imaging plane 20 of the detection device 18 along the measuring beam path.
[0128] The exemplary optical arrangement 10 is set up to carry out a method for determining the beam caustic of the laser beam 12.
[0129] In the method for determining the beam caustic of the laser beam 12, the measuring beam 16, split off from a laser beam 12 to be measured, is coupled into the measuring beam path by means of the coupling device 14. The measuring beam 16 is deflected towards the imaging plane 20 of the detection device 18 by means of the deflecting device 26. By deforming the deflecting surface 28 of the deflecting device 26, at least partially reversibly, different focal lengths f(n) of the deflecting device 26 are achieved, resulting in a plurality of images of the measuring beam 22.
[0130]
[0131] in the image plane 20 E det The detection device 18 generates the majority of images of the measuring beam 22.
[0132]
[0133] in the image plane 20 E detrecorded. Based on the majority of images of the measuring beam 22 D( (n)) in the imaging plane 20 E det The detection device 18 and the different focal lengths f(n) of the deflection device 26 are used to create virtual images of the measuring beam 34 in virtual imaging planes 36£' (n)) by means of the evaluation device 24. virt The beam caustic of the laser beam 12 is determined from the virtual images 34 D(f(n)) using the evaluation unit 24. virt certainly.
[0134] The virtual images of the measuring beam
[0135]
[0136] 34 can be determined according to
[0137] D( / (n)) virt = ß f nß) * D (n)),
[0138] where lateral magnifications β(f(nβ) and virtual lateral positions s( (n)) virt the virtual mapping planes E( (nß) virt from transfer matrices
[0139]
[0140] The optical arrangement 10 can be determined. The distances sO, s1, s2 and s3 can be assumed to be known.
[0141] In the present embodiment, the transfer matrices can depend on the different focal lengths f(n) of the deflection device.
[0142]
[0143] expressed as
[0144]
[0145] — ^s(f(n)) virt * M S1 * M Spiegel (f(n)) * M s2 * M lens *
[0146] with
[0147] M S3 : Transfer matrix of route s3
[0148] M S2 : Transfer matrix of the route s2
[0149] M S1 : Transfer matrix of route s1
[0150] M Linse : Transfer matrix of the focusing element 32, in this case a lens M Spiegel (f(n)): Transfer matrix of the deflection device 26, in this case a mirror M
[0151]
[0152] s( y(n)) virt '■ Transfer matrix of the virtual lateral position s(J(n)~) virt
[0153] Figure 2 shows a schematic representation of an embodiment of an EUV light generation system 38 according to the invention. The EUV light generation system 38 for generating EUV light 40 comprises an EUV driver laser 8 with an optical arrangement 10 according to Figure 1. The EUV light generation system 38 also includes a target material generator 42 for generating units of the target material 44 that can be excited by the laser beam 12, and an EUV light generation chamber 46. Within the EUV light generation chamber 46, the units of the target material 44 can be excited by the laser beam 12, thereby generating EUV light (40).
Claims
Patent claims 1. Optical arrangement (10) for determining a beam caustic of a laser beam (12), with a) a coupling device (14) which is configured to couple a measuring beam (16) separated from a laser beam (12) to be measured into a measuring beam path, b) a detection device (18) having an imaging plane (20), wherein the detection device (18) is configured to detect a plurality of images of the measuring beam (22) in the imaging plane (20), c) an evaluation device (24) by means of which the beam caustic of the laser beam (12) can be determined on the basis of the plurality of images of the measuring beam (22), d) a deflecting device (26) having a deflecting surface (28) and positioned to deflect the measuring beam (16) from the direction of the coupling device (14) by means of the deflecting surface (28) towards the imaging plane (20) of the detection device (18), characterized by the fact that e) the detection device (18) is fixed in a stationary position and the imaging plane (20) of the detection device (18) is fixed, f) the deflecting surface (28) is designed to be at least partially reversibly deformable, such that a focal length of the deflecting device (26) can be adjusted by means of at least partial deformation of the deflecting surface (28), so that a plurality of images of the measuring beam (22) can be generated in the imaging plane (20) of the detection device (18).
2. Optical arrangement (10) according to claim 1, characterized in that the deflecting device (26) has a counter surface opposite the deflecting surface (28) which is designed to cause the deflecting surface (28) to deform at least partially reversibly under pressure on the counter surface.
3. Optical arrangement (10) according to claim 1, characterized in that the deflecting device (26) comprises a plurality of piezo actuators (30) which are configured to deform the deflecting surface (28) at least partially and reversibly.
4. Optical arrangement (10) according to any one of the preceding claims, characterized in that the deflecting surface (28), in a deformed configuration deviating from a normal state, has the same radius of curvature in a direction parallel to a reflection plane formed by a measuring beam (16) incident on the deflecting surface (28) and a measuring beam (16) emitted from the deflecting surface (28) as in a direction perpendicular to the reflection plane.
5. Optical arrangement (10) according to claim 4, characterized in that a value of an angle of incidence between an incident normal and the measuring beam (16) incident on the deflecting surface (28) lies in a range of 1° to 15°, preferably from 1° to 8°, particularly preferably from 1° to 5°.
6. Optical arrangement (10) according to one of the preceding claims, characterized in that the deflecting surface (28) in a deformed configuration deviating from a normal state has a different radius of curvature in a direction parallel to a reflection plane formed by a measuring beam (16) incident on the deflecting surface (28) and a measuring beam (16) emerging from the deflecting surface (28) as in a direction perpendicular to the reflection plane.
7. Optical arrangement (10) according to claim 6, characterized in that a value of an angle of incidence between a normal and the measuring beam (16) incident on the deflecting surface (28) lies in a range of 25° to 60°, preferably from 35° to 55°, particularly preferably from 40° to 50°.
8. Optical arrangement (10) according to one of the preceding claims, characterized in that a focusing element (32), in particular a lens, with a constant focal length is arranged in the measuring beam path between the detection device (18) and the deflecting device (26).
9. Optical arrangement (10) according to one of the preceding claims, characterized in that the optical arrangement (10) comprises a second deflection device (26) which is translationally movable and / or rotatable about at least one axis of rotation and / or which has a second deflection surface (28) which is at least partially reversibly deformable, wherein the second deflection device (26) is configured to set an angle and / or a position of the measuring beam (16) with respect to a reference area on the imaging plane (20).
10. Method for determining a beam caustic of a laser beam (12) with an optical arrangement (10), comprising the steps: a) Coupling a measuring beam (16) separated from a laser beam (12) to be measured into a measuring beam path by means of a coupling device (14) and deflecting the measuring beam (16) towards an imaging plane (20) of a detection device (18) by means of a deflecting device (26), b) at least partially reversible deformation of a deflecting surface (28) of the deflecting device (26), thereby setting different focal lengths f(n) of the deflecting device (26) and in turn thereby generating a plurality of images of the measuring beam (22) D(f(n)) in the imaging plane (20) E det the detection device (18), c) Capturing the majority of images of the measuring beam (22) D(f(n)) in the imaging plane (20) E det by means of the detection device (18), d) using the evaluation device (24), determining virtual images of the measuring beam (34) D( / (n)) V[rt ' n virtual mapping planes (36) £' (n)) virt based on the plurality of images of the measuring beam (22) D (n)) in the imaging plane (20) E det the detection device (18) and the different focal lengths f(n) of the deflection device (26), e) Determining the beam caustics of the laser beam (12) from the virtual images (34) D(f(n)) virt by means of the evaluation unit (24).
11. Method according to claim 10, characterized in that the virtual images of the measuring beam (34) D(f(n)) virt will be determined according to D (f(n)) virt = β(f(n)) * D(f(n)), where D(f(n)) virt a virtual image of the measuring beam (34), β(f(n)) denotes a lateral magnification and D(f(n)) denotes an image of the measuring beam (22).
12. Method according to claim 11, wherein the lateral magnification β(f(n)) and virtual lateral positions s(f(n)) virt the virtual mapping planes E(f(n)) virtfrom transfer matrices M(f(n)) of the optical arrangement (10).
13. Method according to one of claims 10 to 12, characterized in that the optical arrangement (10) is an optical arrangement (10) according to one of claims 1 to 9.
14. Method according to claims 10 to 13, characterized in that at least six, in particular at least eight, preferably at least ten virtual images of the measuring beam (34) in virtual imaging planes (36) are determined on the basis of images of the measuring beam (22) in the imaging plane (20) of the detection device (18).
15. Method according to claim 14, characterized in that a first half of a number of virtual imaging planes (36) is located in a first region within the Rayleigh length and a second half of a number of virtual imaging planes (36) is located in a second region outside twice the Rayleigh length.
16. EUV driver laser (8) for exciting a target material (44) with a laser beam (12) for generating an EUV light (40) emitting plasma of the target material (44), comprising an optical arrangement (10) according to any one of claims 1 to 9.
17. EUV light generation system (38) for generating EUV light (40), comprising an EUV driver laser (8) according to claim 16, a target material generator (42) for generating units of the target material (44) that can be excited by the laser beam (12) and an EUV light generation chamber (46) in which the units of the target material (44) can be excited by the laser beam (12) and thereby EUV light (40) can be generated.
18. Method for manufacturing a semiconductor intermediate or a microchip, comprising the steps of: a) Providing an EUV driver laser (8) according to claim 16 and generating a laser beam (12); b) Providing a target material generator (42) and generating units of the target material (44) that can be excited by the laser beam (12); c) By means of the EUV driver laser (8), excitation of the units of the target material (44) with a laser beam (12) and thereby generating an EUV light (40) emitting plasma of the target material; d) Exposure of a semiconductor substrate coated with a photosensitive coating with the EUV light (40) emitted by the plasma of the target material (44).