Measuring setup for position determination and projection exposure system

Abstract

The invention relates to an optical measuring arrangement (100) for measuring the distance of a component relative to a reference along at least one measuring axis, comprising a sensor (101) with a sensor head (102) and a measuring target (103) connected or connectable to the component, wherein the sensor head (102) has an input mirror (104) for coupling a measuring beam (106) and an end mirror (105) enclosing a resonator cavity (107) of an optical resonator, and wherein the measuring target (103) is configured to deflect the measuring beam (106) back and forth between the mirrors (104, 105, 108, 109) of the sensor head (102). The sensor head (102) additionally has at least two retroreflectors (108, 109).

Description

[0001] The invention relates to an optical measuring arrangement, in particular for a lithography system or a projection exposure system, for measuring the distance of a component relative to a reference along at least one measuring axis, comprising a sensor with a sensor head and a measuring target connected or connectable to the component, wherein the sensor head has an input mirror for coupling a measuring beam and an end mirror enclosing a resonator cavity of an optical resonator, and wherein the measuring target is configured to deflect the measuring beam back and forth between the mirrors of the sensor head. The invention further relates to a projection exposure system, a lithography system, an inspection system, and a coordinate measuring machine.

[0002] Projection exposure systems are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on the creation of ultra-fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, onto a wafer, which is coated with photosensitive material. The minimum dimensions of the generated structures depend directly on the wavelength of the light used. This light is shaped in an illumination optic to optimally illuminate the reticle. Recently, light sources with emission wavelengths in the nanometer range, for example between 1 nm and 120 nm, particularly in the 13.5 nm range, have been increasingly used. This wavelength range is also known as the EUV range.

[0003] The microstructured components are manufactured not only using EUV systems but also with established DUV systems operating at wavelengths between 100 nm and 400 nm, particularly 193 nm. With the increasing demand for ever smaller structures, the requirements for optical correction in these systems have also risen. To improve efficiency, each new generation of projection exposure systems in the EUV or DUV range increases throughput.

[0004] In the operation of microlithographic projection exposure systems, where the mask and wafer are typically moved relative to each other in a scanning process, the positions of the mirrors, which are sometimes movable in all six degrees of freedom, must be set with high accuracy and their position maintained in order to avoid or at least reduce aberrations and associated impairments of the imaging result or image shifts.

[0005] Various approaches are known in the prior art for measuring the position of individual mirrors, as well as the wafer or wafer stage and the reticular plane. Besides interferometric or encoder-based measurement setups, frequency-based position and / or distance measurement using an optical resonator in which a standing wave is generated is also known.

[0006] This is described, for example, in DE 10 2012 212 663 A1. This patent discloses an optical resonator with two resonator mirrors, a first resonator mirror being attached to a reference element in the form of a measuring frame rigidly connected to the housing of the projection lens of the projection exposure system, and a second resonator mirror (as a "measuring target") being attached to a mirror whose position is to be measured. The actual distance measuring device comprises a radiation source whose optical frequency is tunable, which generates a coupling radiation that passes through a beam splitter and is coupled into the optical resonator. The radiation source is controlled by a coupling device such that the optical frequency of the radiation source is tuned to the resonance frequency of the optical resonator and thus coupled to this resonance frequency.The coupled-in radiation, extracted via a beam splitter, is analyzed using an optical frequency measuring device, which may include, for example, a frequency comb generator for highly accurate determination of the absolute frequency. If the position of the EUV mirror changes in the x-direction, the resonant frequency of the optical resonator also changes with the distance between the resonator mirrors, and thus—due to the coupling of the frequency of the tunable radiation source to the resonator's resonant frequency—the optical frequency of the coupled-in radiation also changes, which is then directly registered by the frequency measuring device.

[0007] Alternatively, instead of a tunable radiation source, a frequency-based position and / or distance measurement can also include a highly stable radiation source whose frequency is tracked and stabilized or locked to the resonance frequency of the optical resonator using a frequency shifter (for example, using an IQ modulator) and Pound Drive Hall technique.

[0008] US 11,274,914 B2 discloses a measuring arrangement for frequency-based distance and / or position detection with an optical resonator, which additionally has a convolution mirror connected or connectable to the component to be measured, which is configured to deflect the measuring beam back and forth between the resonator mirrors.

[0009] Essential for the functionality of an optical resonator in distance measurement is, firstly, that the measuring beam can complete as many revolutions as possible within the optical resonator (without leaving the cavity formed by the resonator) so that eigenmodes can develop within the resonator. Equally important is the coupling capability of the external radiation field applied at the entrance of the resonator path (the "coupling field") to the mode field of the optical resonator (the "resonator field"). The coupling efficiency characteristic of this coupling is defined by the overlap integral between the coupling field and the resonator field, so that to achieve high coupling efficiency, the coupling field and the resonator field must match as closely as possible in all relevant parameters.

[0010] WO 2019 / 223968 A1 discloses various resonators for frequency-based position detection of a moving component. The German patent application with file number 102023208513.5 discloses a resonator cavity that is insensitive to tilting and has two curved resonator mirrors, as well as a measuring target arranged between the curved resonator mirrors, which is configured to deflect the beam back and forth between the two mirrors.

[0011] To expand the application possibilities of frequency-based position and / or distance measurement, higher demands are being placed on the detection of increasingly larger distances. A technical challenge lies in enabling length changes over larger ranges with the highest possible resolution, as the stability of the cavity becomes a limiting factor with increasing length adjustment range. One possible design of an optical resonator for detecting larger distances is disclosed in DE 10 2023 209 192 A1. This patent discloses an optical resonator with a parallel beam path and a measuring target designed as a multi-part retroreflector. The larger the distance to be measured, the larger the retroreflectors must be to ensure that the measuring beam is still reflected by the partial retroreflectors. This results in a comparatively large and heavy measuring target.

[0012] It is therefore the object of the present invention to provide a measuring arrangement, a projection exposure system, a lithography system, an inspection system and a coordinate measuring machine that can detect the distance of a component relative to a reference over a large measuring range with high accuracy.

[0013] The problem relating to the optical measuring arrangement is solved by an optical measuring arrangement according to the features of claim 1. The problem relating to the projection exposure system is solved by a projection exposure system with the features of claim 14. The problem relating to the lithography system is solved by a lithography system with the features of claim 15, the problem relating to the inspection system is solved by an inspection system with the features of claim 16, and the problem relating to the coordinate measuring machine is solved by a coordinate measuring machine according to the features of claim 17. Advantageous embodiments with expedient further developments are specified in the dependent claims.

[0014] The optical measuring arrangement is characterized in particular by the fact that the sensor head additionally features at least two retroreflectors. This enables simpler manufacturing and, in particular, a smaller design of the measuring target, thereby increasing the measuring accuracy. Preferably, at least one of the retroreflectors is designed as a 2D retroreflector, whereby a 2D retroreflector is understood to be one whose cross-section or contour is unchanged or constant along its longitudinal extent, i.e., its function is defined by its two-dimensional shape. Each 2D retroreflector preferably has two reflective surfaces or mirror surfaces that are aligned at a predetermined angle of preferably 90° to each other. This angle is also constant or unchanged along the longitudinal extent of the respective partial retroreflector.Training as a 2D retroreflector achieves the aforementioned advantages in a beneficial way.

[0015] In this context, it is particularly advantageous if the measuring target is designed as a plane mirror. Designing the measuring target as a plane mirror allows for particularly simple manufacturing and design of the measuring target.

[0016] Furthermore, it is preferred if at least one of the retroreflectors is designed as a roof edge mirror, in particular as a 90° roof edge mirror, or as a prism, preferably as a 90° prism with total internal reflection or with a metallic reflective layer, or as a triple mirror or as a triple prism.

[0017] Furthermore, at least one of the retroreflectors can be multi-part, with two separately formed reflective surfaces arranged at an angle to each other. The reflective surfaces can be manufactured separately and connected or connectable to one another. Alternatively, the surfaces can also be spaced apart from each other.

[0018] Furthermore, it is preferred if the longitudinal extent of one retroreflector l = G + f · Δd · sin α is or at least is , where Δd is the change in distance between the retroreflector and the measurement target, α is the opening angle of the measurement beam at the measurement target, and G is the total beam diameter. The total diameter G is defined as a multiple n of the individual beam diameters g that impinge on the retroreflector (i.e., the diameter of each point of impact of the measurement beam on the retroreflector). An ideal Gaussian beam is assumed to determine the individual beam diameter. The individual beam radius (half the individual beam diameter) along the propagation axis z is defined as the radius at which the intensity is reduced to 1 / e 2(approximately 13.5%). Preferably, n ≥ 4 and f between 1.0 and 1.4. This allows the retroreflector to be made smaller by f · sin α than in the prior art, or in other words: the movement of the measuring beam on the retroreflector, when the measuring target moves along the measuring axis, is at most Δd · sin α, where α is the opening angle of the measuring beam at the measuring target and Δd is the change in distance between the retroreflector and the measuring target. This allows for a smaller retroreflector design than in the prior art and thus a smaller sensor head design, which in turn has a beneficial effect on the dynamics of the sensor head and the object to which the sensor head is attached, e.g., a support structure.

[0019] Furthermore, it is advantageous if one coupling mirror and end mirror are curved, and the other is flat. Preferably, the end mirror is flat and the coupling mirror is curved. The end mirror is preferably configured to reflect the beam back onto itself. Thus, the end mirror is preferably configured so that the measuring beam strikes the reflecting surface perpendicularly, causing the measuring beam to return to its point of origin.

[0020] Furthermore, it is preferred if the retroreflectors are aligned in such a way that the measuring beam is reflected more frequently by one retroreflector than by the other during a passage through the optical resonator.

[0021] In a preferred embodiment, the measuring target is configured to direct the measuring beam from the coupling mirror to one retroreflector, and from one retroreflector to the other. Furthermore, the measuring target is configured to direct the measuring beam from the other retroreflector to the first retroreflector, and from the first retroreflector to the final mirror. The measuring target is thus configured to direct the measuring beam back and forth between the coupling mirror and one retroreflector. In addition, the measuring target is further configured to direct the measuring beam back and forth between the retroreflectors, and the measuring target is also configured to direct the measuring beam back and forth between the other retroreflector and the final mirror.

[0022] Preferably, the area of ​​the reflective surface of one retroreflector differs from the area of ​​the reflective surface of the other retroreflector, but they can also be the same. In particular, it is preferred if the longitudinal extent of one retroreflector differs from the longitudinal extent of the other retroreflector. Of course, they can also be of the same length. In particular, it is preferred that the longitudinal extent of the retroreflector on which the measuring beam first strikes, after passing through or being reflected from the coupling mirror, is longer.

[0023] Preferably, the retroreflectors are aligned with respect to the measuring target such that the position of the reflection point of the measuring beam on the retroreflector changes when the measuring target is moved along the measuring axis, while the position of the reflection point on the other retroreflector remains constant or approximately constant.

[0024] Alternatively, it is also possible that the retroreflectors are aligned relative to the measuring target in such a way that the position of the reflection point of the measuring beam changes on both retroreflectors when the measuring target is moved along the measuring axis.

[0025] Furthermore, it is advantageous if the sensor is configured to detect a distance to a measuring target movable in two axes, and if the mirrors of the sensor head are arranged such that the partial beams of the measuring beam passing between the mirrors of the sensor head and the measuring target are parallel or approximately parallel to a plane defined by the two axes. If the measuring target moves along, for example, the x-axis and the z-axis, the mirrors of the sensor head are preferably arranged such that the partial beams of the measuring beam passing between the mirrors of the sensor head and the measuring target are parallel or approximately parallel to a plane defined by the x-axis and the z-axis.In particular, the partial beams running between the mirrors of the sensor head and the measuring target can run in different planes, each of which is parallel or approximately parallel to a plane defined by the two axes.

[0026] In this context, it is preferred if the extent of the measuring target along the further axis is adapted to the maximum possible adjustment range of the measuring target along this axis. The adjustment range of the measuring target (i.e., the object being measured) is the distance Δd. x , which the measuring target can maximally extend along the further axis. Preferably, the extent of the measuring target along the further axis is at least the sum of the distance Δd. x, and the total beam diameter, which corresponds to n times the individual beam diameter of the measuring beam g, where preferably n ≥ 4. The individual beam diameter is preferably obtained by considering the individual beam as a Gauss beam.

[0027] Furthermore, it is advantageous to have multiple sensors configured for distance measurement along linearly independent measurement axes. This allows the measurement setup to detect the distance and / or position of the object along multiple degrees of freedom.

[0028] Preferably, the measuring arrangement comprises a laser stabilized on a resonator mode of the optical resonator. This laser is coupled into the resonator, in particular, by an optical fiber and the first resonator mirror.

[0029] Furthermore, it is particularly preferred if the optical resonator has at least one optical element configured to control the beam radius of the measuring beam at the coupling mirror and / or a Gouy phase of the measuring beam propagating in the optical resonator, preferably as a function of the length change of the resonator cavity, particularly within a length adjustment range of the optical resonator. The optical element of the optical resonator can be one of the mirrors enclosing the resonator cavity, for example, the coupling mirror or the end mirror, and / or at least one additional optical element associated with the optical resonator, i.e., arranged in the resonator cavity in addition to the coupling mirror and the end mirror. The optical element can also be located upstream of the coupling mirror.The optical element allows the beam radius at the coupling mirror and / or the Gouy phase to be controlled such that the coupling efficiency of the measuring beam into the resonator cavity is high. This leads to higher measurement accuracy, especially with large length differences in the resonator cavity. The length adjustment range, i.e., the range within which the cavity can change its length from an initial length l0, is at least ±5 cm, preferably at least ±10 cm, and most preferably at least ±30 cm or ±50 cm. The length adjustment range thus indicates which changes in distance and / or position of the component to be measured can be detected by the optical measuring arrangement. In order to be able to accurately measure the position and / or distance of the component relative to a reference, it is preferred that the resonator cavity is stable at least within this length adjustment range and / or that the coupling efficiency at the coupling mirror is high.The term "stable" means that primarily the fundamental mode is excited in the resonator and that the excitation of higher mode orders is sufficiently suppressed. In particular, an optical resonator is stable within the meaning of the application if the beam radius of the measuring beam at the coupling mirror corresponds to the beam radius of the resonant beam of the resonator cavity incident on the coupling mirror, or deviates by a maximum of 10%, preferably by a maximum of 5%, and particularly preferably by a maximum of 3%, and / or the Gouy phase is constant or approximately constant, and the quality factor is at least 5, preferably at least 10, and particularly preferably at least 50.This can be achieved, among other things, by maximizing the overlap between the measuring beam coupled into the resonator cavity via the coupling mirror and the resonant measuring beam striking the coupling mirror within the resonator cavity (i.e., the measuring beam already reflected within the resonator cavity). The quality factor of a resonator for a given resonator mode is defined as the quotient of the energy stored in the resonator and the energy loss occurring per oscillation period (i.e., revolution). Assuming an exponential decrease in the energy of the resonator mode over time, the quality factor of the resonator is the quotient of the resonance frequency and the resonance width (bandwidth of the resonance frequency).The optical element allows the beam radius and / or the Gouy phase to be controlled such that the overlap with the resonant measurement beam on the coupling mirror is as large as possible, meaning that the positions and beam radii of the coupled and resonant measurement beams at the coupling mirror are approximately the same. If the optical resonator consists of exactly two resonator mirrors, one of the resonator mirrors is connected to the reference and the other resonator mirror, which serves as the measurement target, is connected to the component or can be connected to it.

[0030] To provide a measurement setup that is additionally insensitive to tilting of the component and thus of the measurement target, it is advantageous to have a mirror element adjustable within the resonator cavity, configured to deflect the measurement beam back and forth between the final mirror and the coupling mirror. The mirror element can be a planar convolutional mirror or a retroreflector. The mirror element can also be multi-part, in particular a multi-part retroreflector, wherein a first partial retroreflector is connected to or connectable with the component (i.e., movable with the component) and the second partial retroreflector is stationary.The two partial retroreflectors are preferably aligned with each other such that the measuring beam, after passing through the coupling mirror, is reflected by the partial retroreflectors to the final mirror and from there back through the partial retroreflectors to the coupling mirror. The coupling mirror and / or the final mirror are preferably curved.

[0031] In this context, it is particularly advantageous if the at least one optical element is configured to keep the beam radius of the measuring beam at the coupling mirror and / or the Gouy phase of the measuring beam propagating in the resonator cavity constant or approximately constant, at least within a length adjustment range of the resonator cavity. The larger the length adjustment range, the greater the change in the Gouy phase and the beam radius difference at the coupling mirror between the coupled and the resonant measuring beam reflected in the resonator cavity.Therefore, it is particularly preferred that, if the at least one optical element is configured, at least within the length adjustment range of the resonator cavity, the beam radius of the measuring beam at the coupling mirror and / or a Gouy phase of the measuring beam propagating in the resonator cavity can be controlled such that the measurement error is less than a predetermined or predefinable limit value or is minimal. Accordingly, it can also be advantageous not to keep the Gouy phase and / or the beam radius constant, but to adjust them to values ​​that produce a small or the smallest possible measurement error.

[0032] In particular, it is preferred if the resonator cavity is configured for position and / or distance detection of the component relative to the reference along two linearly independent measurement axes. An optical resonator configured to determine the position and / or distance of a component along two linearly independent measurement axes is disclosed in DE 10 2023 209 192 A1, the contents of which are fully incorporated into the present application (incorporated by reference). The optical resonator comprises a multi-part retroreflector, wherein a first partial retroreflector serves as the measurement target and is movably arranged with the component within the optical cavity, and a second partial retroreflector is stationary.The two parts are aligned such that the measuring beam, after passing through the coupling mirror, is reflected through the two parts of the retroreflector to the final mirror and from there back through the two parts of the retroreflector to the coupling mirror. The two parts can be configured as 2D retroreflectors, and in particular as 90° roof mirrors or 90° prisms. Preferably, the two parts are aligned perpendicular to each other. However, the optical measuring arrangement can also be used to detect the position and / or distance along only one measuring axis. The optical resonators can be of any design, but must be configured to form a standing wave within the optical resonator cavity. Further examples of suitable optical resonators are described in WO 2019 / 223968 A1, or in the German patent application with application number 10 2023 208 513.5 revealed, which are also fully incorporated into the present revelation (incorporated by reference).

[0033] Furthermore, it is preferred if the optical resonator is designed such that the beam radius of the measuring beam directed from the final mirror to the coupling mirror increases, in particular monotonically increases.

[0034] Furthermore, it is advantageous if a property of the optical element, in particular its position, deformation, and / or refractive power, is selected or adjustable in relation to a change in the length of the resonator cavity such that the measurement error in position and / or distance detection is less than a predetermined or predefinable limit. This property can be the position and / or deformation of a surface and / or the refractive index of the optical element. Consequently, it is advantageous if the position of the optical element within the resonator cavity is adjustable such that the measurement error is less than the predetermined or predefinable limit or is minimal.Alternatively or additionally, a surface of the optical element arranged in the resonator cavity, or of an additional optical element arranged in the resonator cavity, is deformable, at least in certain areas, such that the measurement error is less than the predetermined or predefinable limit. Alternatively or additionally, it is preferred that the refractive power of the optical element or of an additional optical element is selected such that the measurement error in position and / or distance detection is less than the predetermined or predefinable limit or minimal. The properties such as the position, deformation, and / or refractive power of the optical element are preferably adaptable to the change in length of the resonator cavity such that the measurement error is less than the predetermined or predefinable limit.Furthermore, several optical elements can be provided to control the Gouy phase and / or the beam radius of the measuring beam at the coupling mirror. These can be configured differently, i.e., as lenses and / or mirrors. The optical elements can also be designed as deformable lenses, so that the refractive power and deformation can be adjusted to changes in the length of the resonator cavity. Additionally, the deformable lens can be adjustable within the resonator cavity, so that its position, deformation, and refractive power can be adjusted to changes in the length of the resonator cavity.

[0035] It is particularly preferred if the optical element is a deformable optical element. For this purpose, the deformable optical element comprises at least one actuator configured to deform the surface of the optical element, at least in certain areas. Preferably, the deformable optical element has actuators, in particular solid-state actuators such as piezostrictive, electrostrictive, or magnetostrictive actuators, located away from the optically active area. Alternatively, the actuator can also be a heat-induced actuator or an electrostatic, electromagnetic, or mechanical actuator. The deformable optical element is preferably a mirror, but can also be a lens.

[0036] In this context, it is advantageous if the radius of curvature of the deformable optical element is adapted or adaptable to changes in the length of the resonator cavity. The radius of curvature of the deformable optical element is preferably selected such that the beam radius of the measuring beam at the coupling mirror corresponds to the beam radius of the resonant beam from the resonator cavity incident on the coupling mirror, or deviates by a maximum of 10%, preferably by a maximum of 5%, and most preferably by a maximum of 3%, and / or the Gouy phase is constant or approximately constant. In particular, the radius of curvature of the deformable optical element is selected such that the measurement error in position and / or distance detection is less than the predetermined or predefinable limit value or is minimal.

[0037] The deformable optical element preferably comprises a deformable region and an actuator-free region. In particular, the deformable optical element has a boundary region that at least partially encloses the optically active area. The optically active area is the area illuminated by the measuring beam. Preferably, at least one actuator is arranged on or at the boundary region, particularly in a planar arrangement. The actuator-free region is preferably formed away from the boundary region. Alternatively or additionally, the deformable region comprising at least one actuator can also be a lateral surface of the optical element; that is, the at least one actuator is arranged on the lateral surface of the at least one optical element.

[0038] Within the scope of the invention, it is particularly preferred if the coupling mirror is formed as the optical element and, in particular, as the deformable optical element.

[0039] Alternatively or additionally, it is advantageous if the optical element is designed as a refractive optical element. The refractive optical element is preferably designed as a lens.

[0040] In this context, it is particularly preferred if the refracting optical element is adjustable within the resonator cavity by means of an actuator such that the beam radius of the measuring beam at the coupling mirror corresponds to the beam radius of the resonant beam of the optical cavity incident on the coupling mirror, or deviates by a maximum of 10%, preferably by a maximum of 5%, and most preferably by a maximum of 3%, and / or the Gouy phase of the measuring beam propagating in the resonator cavity is constant or approximately constant. The position of the optical element formed as the refracting optical element is preferably adaptable to, or adapted to, a change in the length of the resonator cavity. In particular, the position of the refracting optical element can be adjusted such that the measurement error in the position and / or distance detection of the component is less than a predetermined or predeterminable measurement error, or is minimal.

[0041] Furthermore, it is advantageous if the at least one optical element, i.e., the refracting or deformable optical element, is arranged or adjustable in a region of the resonator cavity where the radius of the measuring beam increases monotonically. The optical element can also be fixed within the resonator cavity.

[0042] Furthermore, it is preferred if the refractive optical element is connected or connectable to the coupling mirror by means of an actuator, or if the coupling mirror and the refractive element are mounted on a common support structure.

[0043] Furthermore, it is advantageous if the adjustable property of the optical element is controlled by a control unit that tracks and locks a frequency of the measuring beam to the resonant frequency of the resonator cavity. It is particularly advantageous if the control unit is configured to adjust the property of the optical element based on a resonant frequency of the resonator cavity determined by a pound-driver-Hall method or on a quantity derived from the resonant frequency. Consequently, if the resonant frequency of the resonator cavity changes because the length within the length adjustment range changes, the property of the optical element—i.e., a deformation (radius of curvature), refractive index (e.g., due to temperature change), or position within the resonator cavity—can be adjusted. The control unit can regulate the adjustment of the property by sending a voltage signal to, for example, an actuator.A calibration procedure can be performed beforehand to determine the optimal adaptation of the optical element's properties for various resonator cavity lengths. This involves identifying the deformation, position, and / or refractive index at which the measurement error is less than a predefined or predefinable limit value or minimal. Alternatively, the control variable for the actuator or for adapting the optical element's properties can be determined directly from the resonance frequency or a derived quantity. Additionally, the optical element can be controlled using a feedforward control system.

[0044] The projection exposure system is characterized in particular by the fact that it includes at least one optical measuring arrangement. The component of the projection exposure system to be measured can preferably be at least one or more optical elements or a supporting structure of the projection exposure system. By detecting the position of the optical elements, their position or orientation, or even a deformation of the optical surface, can be detected, and the position or deformation can preferably be adjusted by means of actuators. This improves the image quality of the projection exposure system. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the projection exposure system comprising at least one optical measuring arrangement.

[0045] Furthermore, at least one optical measuring arrangement according to the invention can also be used in a projection lens, in particular in a projection lens of a projection exposure system, for determining the position and / or distance of a movable or immovable component of the projection lens.

[0046] The optical measuring arrangement according to the invention can also be used in a lighting system, in particular in a lighting system for a projection exposure system. The lighting system preferably has at least one optical measuring arrangement. This arrangement is configured to detect the position or distance of a movable or immovable component. The at least one optical measuring arrangement is directly or indirectly connected to, or connectable to, the component to be measured. The component can, in particular, be an optical element or a support structure.The lighting system of a lithography system comprises, in particular, a light source configured to generate light in an EUV or DUV wavelength range and a plurality of optical elements configured to redirect the light generated by the light source and couple it into the projection exposure system. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the lighting system comprising at least one optical measuring arrangement.

[0047] The lithography system is characterized in particular by the fact that it has at least one optical measuring arrangement. The component of the lithography system can preferably be at least one or more optical elements, support structures, stages, or masks of the lithography system. By detecting the position of the components, which are formed, for example, as optical elements, using the optical measuring arrangement, their position or orientation, or even a deformation of the optical surface, can be detected, and the position or deformation can preferably be adjusted by means of actuators. The advantages and embodiments mentioned for the optical measuring arrangement are also applicable to the lithography system comprising at least one optical measuring arrangement.

[0048] The inspection system according to the invention for checking an optical element (preferably a lithography system) or a wafer or wafer stage or a reticle or reticle stage comprises at least one optical measuring arrangement according to the invention. The optical measuring arrangement is configured to detect the position or distance of a component, for example, an optical element, a wafer, a wafer stage, or a reticle or reticle stage. Preferably, an evaluation unit is provided that compares the detected positions or distances, in particular of structures of the component, with predetermined distances or positions of the structures or components and, in the event of a deviation by a predetermined limit value, initiates corrective action. The at least one optical measuring arrangement is directly or indirectly connected to, or connectable to, the component to be measured.The advantages and embodiments mentioned for the optical measuring arrangement also apply to the inspection system comprising at least one measuring arrangement. An example of such an inspection system for mask or wafer inspection (without the measuring arrangement according to the invention) is known from publication DE 102012205181A1, the entire content of which is incorporated into the present application by reference.

[0049] The invention can also be used in a measuring machine for detecting the position, geometry, or shape of a component. The measuring machine then comprises at least one optical measuring arrangement according to the invention. The at least one optical measuring arrangement is preferably connected to the component, either directly or indirectly. The measuring machine can be used, in particular, in manufacturing technology or industrial metrology in mechanical engineering, for example, in the automotive or aerospace industries. The at least one optical measuring arrangement is connected, or connectable, directly or indirectly to the component to be measured. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the measuring machine comprising the at least one measuring arrangement.

[0050] The coordinate measuring machine according to the invention comprises at least one optical measuring arrangement according to the invention. Coordinate measuring machines are used for the inspection or measurement of components, whereby the component is typically scanned and distances or positions are determined based on the scanning. For this purpose, an optical system as well as a movable frame structure and / or a high-precision positioning system are provided, which carries the component or object to be inspected. The optical measuring arrangement is preferably connected directly or indirectly to this movable component, i.e., frame structure or positioning system. By means of the at least one optical measuring arrangement, the position or distance of the movable component can be determined, thereby controlling the scanning of the object.Furthermore, the optical measuring arrangement can also be used to detect and thus inspect the distance or position of the component itself. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the coordinate measuring machine comprising at least one optical measuring arrangement. An example of such a coordinate measuring machine (without the measuring arrangement according to the invention) is known from publication DE10 2019 213 794A1, the entire content of which is incorporated into the present application by reference.

[0051] Further features, properties, and advantages of the present invention are described in more detail below with reference to exemplary embodiments and the accompanying figures. All features described so far and below are advantageous both individually and in any combination. The exemplary embodiments described below are merely examples and do not limit the scope of the invention. The following are shown: Fig. 1a a schematic representation of a microlithographic projection exposure system designed for operation in the EUV, Fig. 1b a schematic representation of a microlithographic projection exposure system designed for operation in DUV, Fig. 2 a schematic representation of a first embodiment of an optical measuring arrangement, Fig. 3 a schematic representation of the first embodiment with a larger measuring distance than in Fig. 1, Fig. 4 a schematic representation of a second embodiment of an optical measuring arrangement and Fig. 5 a schematic representation of a third embodiment of an optical measuring arrangement.

[0052] Fig. Figure 1a shows a schematic representation of an exemplary projection exposure system 600 designed for operation in EUV, in which the present invention can be implemented. However, the invention can also be used in other nanopositioning systems.

[0053] According to Fig. Figure 1a comprises a field faceted mirror 603 and a pupil faceted mirror 604 in a projection exposure system 600 designed for EUV. The light from a light source unit, comprising a plasma light source 601 and a collector mirror 602, is directed onto the field faceted mirror 603. A first telescope mirror 605 and a second telescope mirror 606 are arranged in the light path downstream of the pupil faceted mirror 604. A deflecting mirror 607 is arranged further down the light path, which directs the incident radiation onto an object field in the object plane of a projection lens comprising six mirrors 651-656. At the location of the object field, a reflective structure-bearing mask 621 is arranged on a mask table 620, which is imaged into an image plane by means of the projection lens, in which a substrate 661 coated with a light-sensitive layer (photoresist) is located on a wafer table 660.

[0054] The invention can be used in a DUV system as well as in Fig. 1b is shown. A DUV system is basically the same as the EUV system described above. Fig. 1a constructed, wherein mirrors and lenses can be used as optical elements in a DUV system and the light source of a DUV system emits useful radiation in a wavelength range of 100 nm to 400 nm.

[0055] The in Fig. The DUV lithography system 700 shown in Figure 1b has a DUV light source 701. For example, an ArF excimer laser can be used as the DUV light source 701, emitting radiation 702 in the DUV range at, for example, 193 nm. A beam shaping and illumination system 703 directs the DUV radiation 702 onto a photomask 704. The photomask 704 is designed as a transmissive optical element and can be located outside the system 703. The photomask 704 has a structure which is reduced in size and projected onto a wafer 706 or the like by means of the projection system 705. The projection system 705 has several lenses 707 and / or mirrors 708 for imaging the photomask 704 onto the wafer 706. Individual lenses 707 and / or mirrors 708 of the projection system 705 can be arranged symmetrically to the optical axis 709 of the projection system 705.It should be noted that the number of lenses 707 and mirrors 708 of the DUV lithography system 700 is not limited to the number shown. More or fewer lenses 707 and / or mirrors 708 may be used. In particular, the beam shaping and illumination system 703 of the DUV lithography system 700 has several lenses 707 and / or mirrors 708. Furthermore, the mirrors are typically curved on their front surface for beam shaping. An air gap 710 between the last lens 707 and the wafer 706 can be replaced by a liquid medium with a refractive index > 1. The liquid medium can be, for example, highly purified water. Such a setup is also called immersion lithography and offers increased photolithographic resolution.

[0056] Fig. Figure 2 shows an optical measuring arrangement 100, in particular for a lithography system, a projection exposure system, a measuring machine, an inspection system, or a coordinate measuring machine, for measuring the distance of a component relative to a reference along at least one measuring axis, in this case the z-axis. The measuring arrangement 100 comprises a sensor 101 with a sensor head 102, and a measuring target 103, which is connected or connectable to the component (not shown in detail), for example, a mirror, a wafer, a wafer stage, a reticle, or a reticle stage.

[0057] The sensor head 102 comprises a coupling mirror 104 for coupling a measuring beam 106 and an end mirror 105, which enclose a resonator cavity 107 of an optical resonator. The sensor head 102 also has two retroreflectors 108, 109. The measuring target 103 is configured to deflect the measuring beam 106 back and forth between the mirrors 104, 105, 108, 109 of the sensor head 102. This allows for simpler manufacturing and, in particular, a smaller design of the measuring target, thereby increasing the measuring accuracy. The measuring target is therefore designed without a retroreflector. Preferably, the retroreflectors 108, 109 are designed as a 2D retroreflector, whereby a 2D retroreflector is understood to be one whose cross-section or contour is unchanged or constant in its longitudinal extent, i.e., its function is defined by its two-dimensional shape.Each 2D retroreflector preferably has two reflective surfaces or mirror surfaces aligned at a predetermined angle, preferably 90°, to each other. This angle is also constant or unchanged along the longitudinal extent of the respective partial retroreflector. The retroreflectors 108, 109 are configured as roof edge mirrors, in particular as 90° roof edge mirrors, but can also be configured as prisms, preferably as a 90° prism with total internal reflection or with a metallic reflective layer, or as a triple mirror or triple prism. Furthermore, at least one of the retroreflectors 108, 109 can be formed in multiple parts, with two separate reflective surfaces arranged at an angle to each other.

[0058] The measuring target 103 is formed as a plane mirror. One mirror, consisting of the coupling mirror 104 and the end mirror 105, is curved, while the other mirror, also consisting of the coupling mirror 104 and the end mirror 105, is flat. In this configuration, the end mirror 105 is flat and the coupling mirror 104 is curved. The end mirror 105 is preferably configured to reflect the measuring beam 106 back onto itself. This means that the measuring beam strikes the reflective surface of the end mirror perpendicularly and is reflected back to its point of origin.

[0059] The retroreflectors 108 and 109 are aligned such that the measuring beam 106 is reflected more frequently by one retroreflector 108 than by the other retroreflector 109 during one pass through the optical resonator. In this case, one resonator mirror 108 reflects the measuring beam 106 eight times and the other resonator mirror 109 four times per revolution.

[0060] After passing through the coupling mirror 104, the measuring beam 106 is directed onto the measuring target 103 and from there reflected onto a first reflective surface of one retroreflector 108. The first reflective surface of the retroreflector 108 reflects the measuring beam 106 onto the second reflective surface, which then directs the measuring beam 106 back onto the measuring target 103. The measuring target 103 is in turn configured to direct the measuring beam 106 onto a first reflective surface of the other retroreflector 109. From there, the measuring beam 106 is reflected onto the second reflective surface of the other retroreflector 109 and from there back onto the measuring target 103. The measuring beam 106 is directed from the measuring target 103 to the second reflective surface of one retroreflector 108 and from there reflected to the first reflective surface of one retroreflector 108, in order to be directed from there back to the measuring target 103.Finally, the measuring target 103 reflects the measuring beam onto the end mirror 105. From the end mirror 105, the measuring beam 106 is directed back onto the measuring target 103 and from there onto the first reflective surface of one retroreflector 108, and from there onto the second reflective surface of one retroreflector 108, and from there back onto the measuring target 103. The measuring target 103 reflects the measuring beam 106 onto the second reflective surface of the other retroreflector 109. This reflector directs the measuring beam 106 onto the first reflective surface of the other retroreflector 109, and from there the measuring beam 106 is directed back onto the measuring target 103, in order to be reflected from there onto the second reflective surface of one retroreflector 108. From there, the measuring beam 106 is directed again to the first reflective surface of one retroreflector 108 and from there reflected via the measuring target 103 onto the coupling mirror 104.Reflection of the measuring beam 106 onto the coupling mirror 104 starts a new cycle in the resonator cavity 107.

[0061] Preferably, the area of ​​the reflective surface of one retroreflector 108 differs from the area of ​​the reflective surface of the other retroreflector 109. In this case, one retroreflector 108 has a greater longitudinal extent 110 than the other retroreflector.

[0062] By integrating the retroreflectors 108, 109 into the sensor head 102, the longitudinal extent 110 of at least one retroreflector 108 can be chosen to be smaller. The longitudinal extent 110 of one retroreflector 108 is given by l = G + f · Δd · sin α, where Δd is the change in distance between the retroreflector and the measurement target, α is the opening angle of the measuring beam at the measurement target, and f is between 1.0 and 1.4. G is the total beam diameter, which is defined as a multiple n of the individual beam diameters g that impinge on the retroreflector 108 (i.e., the diameter of each point of impact of the measuring beam on the retroreflector 108), where n ≥ 4 is preferred. An ideal Gaussian beam is assumed to determine the individual beam diameter. The single-beam radius (half the single-beam diameter) along the propagation axis z is defined as the radius at which the intensity is reduced to 1 / e 2(approx. 13.5%). The retroreflector 108 can therefore be made smaller by f sin α than in the prior art, or in other words: the movement of the measuring beam 106 on the one retroreflector 108, when the measuring target 103 moves along the measuring axis (z-axis), is at most Δd · sin α, where α is the opening angle of the measuring beam 106 at the measuring target 106 and Δd is the change in the distance between the retroreflector 108 and the measuring target 103. The in the Fig. The illustrated embodiment 3 shows how the reflection position of the measuring beam on one retroreflector 108 changes when the distance d2 between the retroreflector 108 and the measuring target (here compared to the distance d1 of the Fig. 2) changes.

[0063] In the exemplary embodiments according to the Fig. 2 and Fig. 3 The retroreflectors 108, 109 are aligned relative to the measuring target 103 in such a way that the position of the reflection point of the measuring beam 106 on one retroreflector 108 changes when the measuring target 103 is moved along the measuring axis (z-axis), while the position of the reflection point on the other retroreflector remains constant or approximately constant.

[0064] The one in Fig. The embodiment shown in Figure 4 differs in that the retroreflectors 108, 109 are aligned relative to the measuring target 103 in such a way as to the examples of Fig. 2 and Fig. 3 are rotated so that the position of the reflection point of the measuring beam on both retroreflectors 109 changes when the measuring target 103 is moved along the measuring axis 103 (z-axis).

[0065] Fig. Figure 5 shows a further embodiment, which differs from the embodiment according to the Fig. 2 and Fig.3 differs in that the sensor 101 is configured to detect the distance of a measuring target 103 that is movable in two (linearly independent) axes (in this case, the measuring target 103 is movable in the x and z directions). This enables a distance determination of the object being measured, even if it does not only move along the measuring axis (z-axis), but also along another axis (the x-axis) that deviates from the measuring axis. In order to provide a sensor 101 that is as compact as possible, it is preferred that the mirrors 104, 105, 108, 109 of the sensor head 102 are arranged such that the partial beams 106a,b,c,d,e,f,g,h of the measuring beam running between the mirrors 104,105, 108, 109 of the sensor head and the measuring target 103 run parallel or approximately parallel to a plane defined by the two axes (axis of movement of the measuring target 103).(xz-plane) In this case, the partial beams 106a, b running between one retroreflector 108 and the measuring target 103, the partial beam 106c running between the coupling mirror 104 and the measuring target, and the partial beam 106d running between the final mirror 105 and the measuring target 103 all run in a common plane that is parallel or approximately parallel to the plane defined by the x-axis and the z-axis. The partial beams 106e, f of the measuring beam 103 running between the other retroreflector 109 and the measuring target 103 run in a further common plane that is parallel or approximately parallel to the plane defined by the x-axis and the z-axis. The partial beams 106g, h, which run between one retroreflector 108 and the measuring target 109, preferably also run in this further common plane.Preferably, all partial beams 106a,b,c,d,e,f,g,h which run between the mirrors 104,105,108,109 of the sensor head 102 and the measuring target 103 run in one of at least two planes or in exactly two planes, each of which is parallel or approximately parallel to the plane defined by the axes of the measuring target 103.

[0066] In this context, the extent of the measuring target 103 along the further axis (x-axis) is adapted to the maximum possible adjustment range of the measuring target 103 along this axis. The adjustment range of the measuring target 103 (i.e., the object being measured) is the distance Δd. x "which the measuring target 103 can maximally extend along the further axis. Preferably, the extent of the measuring target 103 along the further axis is at least the sum of the distance Δd." x, and the total beam diameter G, i.e., the multiple n of the individual beam diameters of the measuring beam 106, where n ≥ 4. Additionally—and not shown in detail—the optical resonator can have at least one optical element configured to control the beam radius of the measuring beam 106 at the coupling mirror 104 and / or a Gouy phase of the measuring beam 106 propagating in the resonator cavity 107 as a function of a change in the length of the resonator cavity 107. The optical element can be a refracting optical element (e.g., a lens) or a reflective optical element whose radius of curvature is adjustable. The optical element can be the coupling mirror 104 or the end mirror 105, or an additional optical element that is arranged in the resonator cavity, is adjustable in position, or is located upstream of the coupling mirror.This makes it possible to provide a more stable resonator cavity, even for large measurement distances.

[0067] In order to determine distances of the measuring target 103 relative to a reference along several linearly independent measuring axes, and in particular for determining the position of the measured object, the measuring axis can have a plurality of sensors 102 which are set up to detect a distance in linearly independent measuring axes.

[0068] The invention, i.e. the measuring arrangement 100 according to the invention, can be used, among other things, in a projection exposure system, a lighting system, a projection lens, a lithography system, an inspection system, a measuring machine and a coordinate measuring machine. REFERENCE MARK LIST 100 measuring setup 101 Sensor 102 Sensor head 103 measuring target 104 coupling mirrors 105 End mirrors 106 Measuring beam 107 Resonator cavity of an optical resonator 108 the one retroreflector 109 the other retroreflector 110 Longitudinal extent 600 Projection exposure system 601 Plasma light source 602 Collector mirrors 603 Field faceted mirror 604 pupil facet mirrors 605 first telescope mirror 606 second telescope mirror 607 Deflection mirror 620 mask table 621 Mask 651 Mirror (projection lens) 652 Mirror (projection lens) 653 Mirror (projection lens) 654 Mirror (projection lens) 655 Mirror (projection lens) 656 Mirror (projection lens) 660 wafer table 661 coated substrate 700 DUV lithography system 701 DUV light source 702 DUV radiation / beam path 703 Beam shaping and illumination system (DUV) 704 Photomask 705 Projection System 706 wafers 707 lens 708 mirrors 709 optical axis QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 212 663 A1

[0006] US 11,274,914 B2

[0008] WO 2019 / 223968 A1 [0010, 0032] DE 10 2023 209 192 A1 [0011, 0032] WO 10 2023 208 513.5

[0032] DE 102012205181A1

[0048] DE 10 2019 213 794A1

[0050]

Claims

Optical measuring arrangement (100) for distance detection of a component relative to a reference along at least one measuring axis comprising a sensor (101) with a sensor head (102) and a measuring target (103) connected or connectable to the component, wherein the sensor head (102) has an input mirror (104) for coupling a measuring beam (106) and an end mirror (105) enclosing a resonator cavity (107) of an optical resonator, and wherein the measuring target (103) is configured to deflect the measuring beam (106) back and forth between the mirrors (104, 105, 108, 109) of the sensor head (102), characterized in that the sensor head (102) additionally has at least two retroreflectors (108, 109). Optical measuring arrangement (100) according to claim 1, characterized in that the measuring target (103) is formed as a plane mirror. Optical measuring arrangement (100) according to one of claims 1 or 2, characterized in that at least one of the retroreflectors (108, 109) is formed as a roof edge mirror or as a prism or as a triple mirror or as a triple prism. Optical measuring arrangement (100) according to one of claims 1 to 3, characterized in that at least one of the retroreflectors (108, 109) is formed in multiple parts, as two separate reflective surfaces arranged inclined to each other. Optical measuring arrangement (100) according to one of claims 1 to 4, characterized in that the longitudinal extent (110) of one retroreflector (108) is l = f · d · sin α, where d is the distance between one retroreflector (108) and the measuring target (103), α is the opening angle of the measuring beam at the measuring target (103) and f is between 1.0 and 1.

4. Optical measuring arrangement (100) according to one of claims 1 to 5, characterized in that one is formed in a curved manner from the coupling mirror (104) and the end mirror (105) and the other is formed in a planar manner from the coupling mirror (104) and the end mirror (105). Optical measuring arrangement (100) according to one of claims 1 to 6, characterized in that the retroreflectors (108, 109) are aligned to each other such that the measuring beam (106) is reflected more frequently by one retroreflector (108) than by the other retroreflector (109) when passing through the optical resonator. Optical measuring arrangement (100) according to one of claims 1 to 7, characterized in that the measuring target (103) is configured to direct the measuring beam (106) from the coupling mirror (104) to one retroreflector (108) and to direct the measuring beam (106) from one retroreflector (108) to the other retroreflector (109), and that the measuring target (103) is configured to direct the measuring beam (106) from the other retroreflector (109) back to one retroreflector (108) and to direct the measuring beam (106) from one retroreflector (108) to the end mirror (105). Optical measuring arrangement (100) according to one of claims 1 to 8, characterized in that the area of ​​the reflective surface of one retroreflector (108) differs from the area of ​​the reflective surface of the other retroreflector (109). Optical measuring arrangement (100) according to one of claims 1 to 9, characterized in that the retroreflectors (108, 109) are aligned with respect to the measuring target (103) such that the position of the reflection point of the measuring beam on one retroreflector (108) changes when the measuring target is moved along the measuring axis, while the position of the reflection point on the other retroreflector (109) is constant or approximately constant. Optical measuring arrangement (100) according to one of claims 1 to 10, characterized in that the sensor (102) is configured to detect a distance to a measuring target (103) movable in two axes and that the mirrors (104, 105, 108, 109) of the sensor head (102) are arranged such that the partial beams (106a,b,c,d,e,f,g,h) of the measuring beam (106) which run between the mirrors (104, 105, 108, 109) of the sensor head and the measuring target (103) run parallel or approximately parallel to a plane defined by the two axes. Optical measuring arrangement (100) according to one of claims 1 to 11, characterized in that a plurality of sensors (102) are provided which are set up for distance detection along linearly independent measuring axes. Optical measuring arrangement (100) according to one of claims 1 to 12, characterized in that the optical resonator has at least one optical element which is configured to control the beam radius of the measuring beam (106) at the coupling mirror (104) and / or a Gouy phase of the measuring beam (106) propagating in the resonator cavity (107) as a function of a change in length of the resonator cavity (107). Projection exposure system (600, 700) with at least one optical measuring arrangement (100) according to one of claims 1 to 13 . Lithography system with at least one optical measuring arrangement (100) according to one of claims 1 to 13 . Inspection system for inspecting the shape, position or geometry of an object with at least one optical measuring arrangement (100) according to one of claims 1 to 13. Coordinate measuring machine with at least one optical measuring arrangement (100) according to one of claims 1 to 13 .

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