DE102023128365A1 - Method and control device for controlling a position of a substrate holder of a lithography system, positioning system and lithography system - Google Patents

Abstract

Method for controlling a position (r) of a substrate holder (202) of a lithography system (1), wherein the lithography system (1) is designed to image an image (400) of a mask (7) on a substrate (204) arranged on the substrate holder (202), comprising the steps:
a) receiving (S2) one or more pressure values (w) of a liquid (304) in a liquid line (306) of the lithography system (1), wherein the liquid line (306) is configured to control the temperature of a position-sensitive component (108) of the lithography system (1),
b) determining (S3) a control variable (u) based on the one or more received pressure values (w) and a pre-determined function (G) of the pressure (P) of the liquid (304) as a function of an imaging error (F) of the lithography system (1) at the location of the substrate (204), and
c) controlling (S4) an actuator device (206) for positioning the substrate holder (202) based on the manipulated variable (u).

Description

The present invention relates to a method and a control device for controlling a position of a substrate holder of a lithography system, a positioning system for positioning a substrate holder and a lithography system with such a control device or such a positioning system.

Microlithography is used to produce microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system that has an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, that is coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system in order to transfer the mask structure onto the light-sensitive coating of the substrate.

Driven by the pursuit of ever smaller structures in the manufacture of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, in particular 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e. mirrors, instead of - as previously - refractive optics, i.e. lenses.

The requirements for the accuracy and precision of the imaging properties of lithography systems are constantly increasing. From a dynamic point of view, it is therefore important to minimize the influence of interference on the movement of various components of the lithography system. For example, very precise positioning of optical components, in particular mirrors, and mechanical components, in particular sensor frames, of the lithography system is required. Dynamic interference from optical and mechanical components can be generated, for example, by the movement of other components of the lithography system. Furthermore, due to increasing thermal requirements, it is necessary to cool optical and mechanical components of the lithography system, in particular mirrors and sensor frames. For cooling, a cooling device with cooling lines is required, through which a coolant is transported to the component to be cooled. This leads to another source of dynamic interference in the form of acoustic interference. Acoustic interference is transmitted, for example, as longitudinal waves through the coolants in the cooling lines to the component to be cooled.

Against this background, it is an object of the present invention to provide an improved method for operating a lithography system.

1. a) Empfangen eines oder mehrerer Druckwerte einer Flüssigkeit in einer Flüssigkeitsleitung der Lithographieanlage, wobei die Flüssigkeitsleitung zum Temperieren einer positionssensitiven Komponente der Lithographieanlage eingerichtet ist,
2. b) Ermitteln einer Stellgröße basierend auf dem einen oder den mehreren empfangenen Druckwerten und einer vorermittelten Funktion des Druckes der Flüssigkeit in Abhängigkeit eines Abbildungsfehlers der Lithographieanlage am Ort des Substrats, und
3. c) Ansteuern einer Aktoreinrichtung zum Positionieren des Substrathalters basierend auf der Stellgröße.

According to a first aspect, a method for controlling a position of a substrate holder of a lithography system is proposed. The lithography system is designed to image an image of a mask on a substrate arranged on the substrate holder. The method also comprises the steps:

1. a) receiving one or more pressure values of a liquid in a liquid line of the lithography system, wherein the liquid line is configured to control the temperature of a position-sensitive component of the lithography system,
2. b) determining a control variable based on the one or more received pressure values and a pre-determined function of the pressure of the liquid as a function of an imaging error of the lithography system at the location of the substrate, and
3. c) Controlling an actuator device for positioning the substrate holder based on the manipulated variable.

If pressure fluctuations occur in the liquid in the liquid line used to temper (e.g. cool) the position-sensitive component, the position of the position-sensitive component can be changed in an undesirable way by acoustic interference. This leads to an imaging error when imaging the mask (e.g. lithography mask) on the substrate. The imaging error can be at least partially compensated by controlling the position of the substrate holder depending on measured instantaneous pressure values of the cooling liquid in the cooling line.

The lithography system is, for example, an EUV or a DUV lithography system. EUV stands for "extreme ultraviolet" (EUV) and describes a wavelength of the working light in the range of 0.1 nm to 30 nm, in particular 13.5 nm. DUV also stands for "deep ultraviolet" (DUV) and describes a wavelength of the working light between 30 nm and 250 nm.

The EUV or DUV lithography system includes an illumination system and a projection system. In particular, the EUV or DUV lithography system projects the image of the mask (reticle) illuminated by means of the illumination system by means of the projection system onto a substrate coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system, for example a wafer and/or silicon wafer, in order to transfer the mask structure to the light-sensitive coating of the substrate.

The lithography system has, for example, a temperature control device (e.g. cooling device) which comprises the liquid line for transporting the liquid to the position-sensitive component.

The position-sensitive component of the lithography system can be an optical or a mechanical component of the lithography system, e.g. a projection optics of the lithography system. The position-sensitive component is in particular a component that must be held in a precise position with only small tolerances during operation of the lithography system.

A cooling device is set up, for example, to cool one or more position-sensitive components of the lithography system. The cooling device is used in particular to avoid high temperatures and temperature fluctuations of the component(s) to be cooled. In particular, mirrors of an EUV lithography system (as an example of an optical component) heat up as a result of absorption of the high-energy EUV radiation. The high temperatures and temperature fluctuations in the mirror caused by this and the associated thermal deformations of the mirror can lead to wavefront aberrations and thus impair the imaging properties of the mirrors. To avoid thermally induced deformations, optical components of the lithography system are actively cooled.

The cooling device can also be used (in addition to or instead of) cooling, for example, a sensor frame (as an example of a position-sensitive component). This can prevent the sensor frame from heating up due to thermal radiation. Thermal radiation is caused in particular by working light of the lithography system absorbed by mirror surfaces or structural elements. Other heat sources can be, for example, actuators and heating heads. The cooling device can be used to create a stable temperature environment for the sensor frame. This allows a position measurement of the mirror or the multiple mirrors to be carried out with greater accuracy using the sensor device held by the sensor frame.

The liquid is in particular a tempering liquid (e.g. cooling liquid). The liquid is, for example, water.

The temperature control device (e.g. cooling device) has, for example, a temperature control unit (e.g. cooling unit) for temperature control (e.g. cooling) of the liquid. The temperature control device comprises the liquid line and can also have further liquid lines for transporting the liquid. The temperature control device also comprises one or more pumps for generating a required flow rate of the liquid in the line and one or more valves for controlling the flow through the line.

The tempering device can be a cooling device for cooling the position-sensitive component or a heating device for heating the position-sensitive component.

The liquid line(s) is/are made of metal, such as stainless steel.

The one or more pressure values of the fluid comprise, for example, an amplitude of a pressure fluctuation. The one or more pressure values of the fluid comprise, for example, an amplitude of a longitudinal pressure fluctuation.

The lithography system is designed to image an image of a mask (reticle) on a substrate (e.g. a wafer) arranged on the substrate holder. The substrate has in particular a light-sensitive layer. The substrate is further arranged in particular in the region of an image field in an image plane of the lithography system (e.g. the projection optics of the lithography system).

The substrate holder (e.g. wafer holder) of the lithography system is designed to hold the substrate. The substrate holder has in particular a surface on which the substrate is arranged.

The lithography system also has, for example, an actuator device (e.g. a substrate displacement drive) which comprises one or more actuators. The substrate holder can be moved together with the substrate by means of the actuator device.

The actuator device is designed, for example, to move the substrate holder in all of its six rigid body degrees of freedom. The six rigid body degrees of freedom include, in particular, three translational degrees of freedom with respect to three Directions that span a three-dimensional space (e.g. are arranged perpendicular to each other). The six rigid body degrees of freedom also include three rotational degrees of freedom with respect to a respective rotation around the three directions.

In the method, a control variable is determined based on the one or more received pressure values and a pre-determined function of the pressure of the liquid as a function of an imaging error of the lithography system at the location of the substrate. In particular, the pre-determined function of the pressure of the liquid as a function of the imaging error of the lithography system indicates an extent of the imaging error that is caused by a pressure fluctuation of a certain size (e.g. a certain amplitude) when the substrate is exposed.

By controlling the actuator device for positioning the substrate holder based on the control variable, the imaging error, which depends on the pressure fluctuation, is compensated. This positioning (i.e. moving) of the substrate holder to compensate for the imaging error is carried out in particular in addition to a movement of the substrate holder during normal operation of the lithography system, which serves to expose different areas on the substrate.

The actuation of the actuator device for positioning the substrate holder based on the manipulated variable can, for example, be carried out in such a way that the substrate holder is moved in one, in several or in all of its six rigid body degrees of freedom.

For example, a pressure fluctuation can lead to a shift in structures imaged on the substrate (so-called line-of-sight error). In this case, the substrate holder with the substrate is shifted in such a way that the imaged structures still appear in the correct place on the substrate.

According to one embodiment, the liquid line is designed to control the temperature of a position-sensitive component of a projection system of the lithography system, and/or
the position-sensitive component is a mechanical component, in particular a sensor frame, or an optical component, in particular a mirror, of the lithography system.

The position-sensitive component of the lithography system is, for example, a mirror of the lithography system, e.g. a mirror of the projection system or the projection optics of the lithography system. The mirrors of a projection optics of an EUV lithography system are usually movably attached to a support frame by means of actuators in order to be able to precisely adjust the position of the respective mirror.

The position-sensitive component of the lithography system can also be a frame structure that serves as a (e.g. optical) reference. The position-sensitive component can be, for example, a sensor frame of the lithography system, e.g. the projection optics of the lithography system. A sensor frame usually has a sensor device for measuring a current position of one or more optical components of the lithography system relative to the sensor frame. The sensor frame is, for example, mounted in a vibration-decoupled manner with respect to a support frame of the optical component(s). The sensor device comprises, for example, one or more sensors, such as interferometers and/or other measuring devices for detecting a position of the optical component(s). The optical component(s) can, for example, have reflector elements for reflecting light emitted by the sensors (e.g. laser light). For example, the one or more sensors serve to detect a position of the optical component(s) in six degrees of freedom. The six degrees of freedom include in particular three translational degrees of freedom (e.g. in three mutually perpendicular spatial directions) and three rotational degrees of freedom (e.g. with respect to a rotation around the three mutually perpendicular spatial directions).

According to a further embodiment, the liquid line is configured to cool the position-sensitive component of the lithography system.

According to a further embodiment, the substrate has a main extension plane that extends in a first direction and a second direction perpendicular to the first direction. In addition, the imaging error of the lithography system is an imaging error by which the image of the mask on the substrate shifts in the first and/or second direction, and/or the imaging error of the lithography system is an imaging error that is generated by a tilting of a wave front impinging on the substrate in the first and/or second direction.

A (lateral) shift of structures imaged on the substrate is referred to as a so-called line-of-sight error. The line of sight of the lithography system, in particular the projection optics of the lithography system, is shifted from a target position on the substrate. The line-of-sight error of a lithography system usually has a decisive Share of the error budget of a lithography system. In particular, the line-of-sight error is one of the most important variables for characterizing the accuracy of a lithography system. The line-of-sight error also plays a key role in the coverage accuracy in the sequence of several photolithographic structurings of the substrate.

Here, it is proposed to move the substrate holder with the substrate in such a way that a line-of-sight error can be compensated (e.g. reduced and/or completely compensated).

According to a further embodiment, the substrate holder has a surface for supporting the substrate, which extends in a first direction and a second direction perpendicular to the first direction. In addition, the actuator device is controlled such that the substrate holder is moved in the first direction, the second direction and/or a third direction perpendicular to the first and second directions, and/or that the substrate holder is rotated about the first direction, the second direction and/or the third direction.

Thus, based on the manipulated variable, the substrate holder can be moved in three translational degrees of freedom and three rotational degrees of freedom with respect to the first, second and third directions.

According to a further embodiment, the pre-determined function of the pressure of the liquid as a function of the imaging error of the lithography system is determined by repeatedly imaging the mask on the substrate with a stationary substrate holder and for several different pressure fluctuations induced in the liquid.

The pre-determined function of the pressure of the liquid as a function of the imaging error is in particular a pre-determined calibration function. The calibration function is in particular determined before steps a) to c). The calibration function can be determined, for example, before the lithography system is first put into operation. The calibration function can also be determined, for example - instead or in addition - immediately before an exposure of a specific substrate.

During normal operation of the lithography system, the substrate holder is moved to expose different areas on the substrate. In addition, the substrate holder is moved in this case to compensate for an imaging error. However, to determine the calibration function, the substrate holder remains stationary, i.e. is not moved by the actuator device.

To determine the function of the pressure of the liquid as a function of the imaging error, several different pressure fluctuations are induced in the liquid. The several different pressure fluctuations have, for example, different pressure amplitudes. The several different pressure fluctuations are induced (i.e. emitted) in the liquid using, for example, a loudspeaker (e.g. water loudspeaker).

In embodiments, the method comprises, before step a), a step of determining the function of the pressure of the liquid as a function of the imaging error of the lithography system by repeatedly imaging the mask on the substrate with a stationary substrate holder and for a plurality of different pressure fluctuations induced in the liquid.

According to a further embodiment, the pre-determined function of the pressure of the liquid as a function of the imaging error of the lithography system is a linear function.

In other embodiments, the pre-determined function of the pressure of the liquid as a function of the imaging error of the lithography system can also be a non-linear function, have non-linear components and/or be frequency-dependent.

According to a further embodiment, the one or more pressure values of the liquid in the liquid line are received by one or more pressure sensors arranged on the liquid line.

The one or more pressure sensors are designed to detect a pressure of the liquid in the liquid line. The one or more pressure sensors are in particular in fluid communication with the liquid line. The one or more pressure sensors are, for example, piezoelectric pressure sensors, liquid manometers, piston manometers, spring manometers or other pressure measuring devices for measuring a pressure of a liquid in the liquid line.

According to a further embodiment, the one or more pressure sensors are arranged in a projection system of the lithography system and/or with respect to a flow direction of the liquid at the inlet and/or at the outlet of the projection system.

This is particularly advantageous if the position-sensitive component to be tempered is a component of the projection system. This is because the pressure can then be detected close to the position-sensitive component to be tempered.

According to a further embodiment, the liquid line is configured to temper a sensor frame of the lithography system, and the one or more pressure sensors are arranged directly in front of the sensor frame with respect to a flow direction of the liquid.

This allows the pressure of the liquid to be measured as close as possible to the sensor frame to be tempered by the liquid.

According to a further embodiment, the liquid line is configured to control the temperature of a mirror of the lithography system, and the one or more pressure sensors are arranged directly in front of the mirror with respect to a flow direction of the liquid.

This allows the pressure of the liquid to be measured as close as possible to the level to be tempered by the liquid.

• Ermitteln einer weiteren Stellgröße basierend auf dem einen oder den mehreren empfangenen Druckwerten, und
• Ansteuern der weiteren Aktoreinrichtung zum Positionieren der positionssensitiven Komponente basierend auf der Stellgröße.

In embodiments, the method can also be used to control and/or regulate a position of the position-sensitive component of the lithography system. For this purpose, a further actuator device is provided for positioning the position-sensitive component. The method also comprises:

• Determining a further manipulated variable based on the one or more received pressure values, and
• Controlling the further actuator device for positioning the position-sensitive component based on the manipulated variable.

This allows pressure fluctuations at the location of the position-sensitive component to be compensated. This makes it even easier to avoid imaging errors.

For example, the pressure values in supply lines of the tempered position-sensitive component are measured.

• eine Empfangseinrichtung zum Empfangen eines oder mehrerer Druckwerte einer Flüssigkeit in einer Flüssigkeitsleitung der Lithographieanlage, wobei die Flüssigkeitsleitung zum Temperieren einer positionssensitiven Komponente der Lithographieanlage eingerichtet ist,
• eine Ermittlungseinrichtung zum Ermitteln einer Stellgröße basierend auf dem einen oder den mehreren empfangenen Druckwerten und einer vorermittelten Funktion des Druckes der Flüssigkeit in Abhängigkeit eines Abbildungsfehlers der Lithographieanlage am Ort des Substrats, und
• eine Ansteuereinrichtung zum Ansteuern einer Aktoreinrichtung zum Positionieren des Substrathalters basierend auf der Stellgröße.

According to a second aspect, a control device for controlling a position of a substrate holder of a lithography system is proposed. The lithography system is designed to image a mask on a substrate arranged on the substrate holder. The control device also has:

• a receiving device for receiving one or more pressure values of a liquid in a liquid line of the lithography system, wherein the liquid line is configured for tempering a position-sensitive component of the lithography system,
• a determination device for determining a control variable based on the one or more received pressure values and a pre-determined function of the pressure of the liquid as a function of an imaging error of the lithography system at the location of the substrate, and
• a control device for controlling an actuator device for positioning the substrate holder based on the manipulated variable.

The respective device described above or below, such as the control device, the receiving device, the detection device and the control device, can be implemented using hardware and/or software. In a hardware implementation, the respective device can be designed as a computer or as a microprocessor, for example. In a software implementation, the respective device can be designed as a computer program product, as a function, as a routine, as an algorithm, as part of a program code or as an executable object. Furthermore, the corresponding device can also be designed as part of a higher-level control system of the lithography system.

• einen Substrathalter,
• eine Aktoreinrichtung zum Bewegen des Substrathalters, und eine wie vorstehend beschriebene Steuervorrichtung.

According to a third aspect, a positioning system for positioning a substrate holder of a lithography system is proposed. The positioning system comprises:

• a substrate holder,
• an actuator device for moving the substrate holder, and a control device as described above.

In embodiments, the positioning system further comprises a liquid line for tempering a position-sensitive component and/or one or more pressure sensors for detecting a pressure value of the liquid in the liquid line.

According to a fourth aspect, a lithography system, in particular an EUV lithography system, is proposed. The lithography system has a control device as described above and/or a positioning system as described above.

The position-sensitive component is preferably a position-sensitive component of a pro projection optics of the lithography system (projection exposure system). However, the position-sensitive component can also be a position-sensitive component of an illumination system of the lithography system.

In this case, "one" is not necessarily to be understood as being limited to just one element. Rather, several elements, such as two, three or more, can also be provided. Any other counting word used here is also not to be understood as being limited to the exact number of elements mentioned. Rather, numerical deviations upwards and downwards are possible, unless otherwise stated.

The embodiments and features described for the method according to the first aspect apply accordingly to the second to fourth aspects and vice versa.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt einen schematischen Meridionalschnitt einer Projektionsbelichtungsanlage für die EUV-Projektionslithographie gemäß einer Ausführungsform;
• 2 zeigt ein Projektionssystem der Projektionsbelichtungsanlage aus 1 gemäß einer Ausführungsform;
• 3 zeigt ein Flussablaufdiagramm eines Verfahrens zum Steuern einer Position eines Substrathalters einer Projektionsbelichtungsanlage gemäß einer Ausführungsform;
• 4 zeigt eine Abbildung von Strukturen auf einem Substrat gemäß einer Ausführungsform;
• 5 zeigt eine Kalibrierfunktion gemäß einer Ausführungsform;
• 6 zeigt ein Blockschaltbild einer Steuerung einer Position eines Substrathalters gemäß einer Ausführungsform; und
• 7 zeigt funktionelle Komponenten einer Steuervorrichtung des Projektionssystems aus 2 gemäß einer Ausführungsform.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. The invention is explained in more detail below using preferred embodiments with reference to the attached figures.

• 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography according to an embodiment;
• 2 shows a projection system of the projection exposure system from 1 according to one embodiment;
• 3 shows a flow diagram of a method for controlling a position of a substrate holder of a projection exposure apparatus according to an embodiment;
• 4 shows an illustration of structures on a substrate according to an embodiment;
• 5 shows a calibration function according to an embodiment;
• 6 shows a block diagram of a control of a position of a substrate holder according to an embodiment; and
• 7 shows functional components of a control device of the projection system 2 according to one embodiment.

In the figures, identical or functionally equivalent elements have been given the same reference symbols unless otherwise stated. It should also be noted that the representations in the figures are not necessarily to scale.

1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. An embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not comprise the light source 3.

A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced via a reticle displacement drive 9, in particular in a scanning direction.

In the 1 For explanation, a Cartesian coordinate system with an x-direction x, a y-direction y and a z-direction z is drawn. The x-direction x runs perpendicularly into the drawing plane. The y-direction y runs horizontally and the z-direction z runs vertically. The scanning direction runs in the 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the area of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced via a wafer displacement drive 15, in particular along the y-direction y. The displacement of the reticle 7 on the one hand via the reticle displacement drive 9 and the wafer 13 on the other hand via the wafer displacement drive 15 can be synchronized with one another.

The light source 3 is an EUV radiation source. The light source 3 emits in particular EUV radiation 16, which is also referred to below as useful radiation, illumination radiation or illumination light. The useful radiation 16 has in particular a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source, for example an LPP source (Laser Produced Plasma, plasma generated with the aid of a laser) or a DPP source (Gas Discharged Produced Plasma, plasma generated by means of gas discharge). It can also be a synchrotron-based radiation source. The light source 3 can be a free-electron laser (FEL).

The illumination radiation 16 that emanates from the light source 3 is bundled by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 in grazing incidence (GI), i.e. with angles of incidence greater than 45°, or in normal incidence (NI), i.e. with angles of incidence less than 45°. The collector 17 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.

After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

The illumination optics 4 comprise a deflection mirror 19 and a first facet mirror 20 arranged downstream of this in the beam path. The deflection mirror 19 can be a flat deflection mirror or alternatively a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be designed as a spectral filter which separates a useful light wavelength of the illumination radiation 16 from false light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 which is optically conjugated to the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, only one is shown in the 1 only a few examples are shown.

The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or alternatively as convex or concave curved facets.

As for example from the EN 10 2008 009 600 A1 As is known, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, please refer to the EN 10 2008 009 600 A1 referred to.

Between the collector 17 and the deflection mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from the US 2006/0132747 A1 , the EP 1 614 008 B1 and the US$6,573,978 .

The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

The second facets 23 can also be macroscopic facets, which can be round, rectangular or hexagonal, for example, or alternatively facets composed of micromirrors. In this regard, reference is also made to the EN 10 2008 009 600 A1 referred to.

The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 4 thus forms a double faceted system. This basic principle zip is also called a fly's eye integrator.

It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugated to a pupil plane of the projection optics 10. In particular, the second facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as is the case, for example, in the EN 10 2017 220 586 A1 described.

With the help of the second facet mirror 22, the individual first facets 21 are imaged in the object field 5. The second facet mirror 22 is the last bundle-forming or actually the last mirror for the illumination radiation 16 in the beam path in front of the object field 5.

In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to the imaging of the first facets 21 in the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for vertical incidence (NI mirrors, normal incidence mirrors) and/or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

The lighting optics 4 have in the version shown in the 1 As shown, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the first facet mirror 20 and the second facet mirror 22.

In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

In the 1 In the example shown, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The projection optics 10 is a double obscured optics. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has a numerical aperture on the image side that is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, just like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 10 have a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

The projection optics 10 can in particular be anamorphic. In particular, it has different image scales βx, βy in the x and y directions x, y. The two image scales βx, By of the projection optics 10 are preferably (βx, βy) = (+/- 0.25, +/- 0.125). A positive image scale β means an image without image inversion. A negative sign for the image scale β means an image with image inversion.

The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction x, i.e. in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8:1 in the y-direction y, i.e. in the scanning direction.

Other image scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions x, y, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or can be different depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018/0074303 A1 .

Each of the second facets 23 is assigned to exactly one of the first facets 21 to form a respective illumination channel for illuminating the object field 5. This can result in particular in illumination according to the Köhler principle. The far field is broken down into a plurality of object fields 5 using the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

The first facets 21 are each imaged onto the reticle 7 by an associated second facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by superimposing different illumination channels.

By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be defined geometrically. By selecting the illumination channels, in particular the subset of the second facets 23 that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be set. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

In the following, further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described.

The projection optics 10 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 10 cannot usually be illuminated precisely with the second facet mirror 22. When the projection optics 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimal. This surface represents the entrance pupil or a surface conjugated to it in spatial space. In particular, this surface shows a finite curvature.

It is possible that the projection optics 10 have different positions of the entrance pupil for the tangential and the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the 1 In the arrangement of the components of the illumination optics 4 shown, the second facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The first facet mirror 20 is arranged tilted to the object plane 6. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the second facet mirror 22.

2 shows an example of a projection system 100 with a projection optics 102 of the lithography system 1 from 1 according to one embodiment.

In 2 several exemplary frame structures (support structures) 104, 106, 108 and an exemplary mirror 110 of the projection system 200 are schematically illustrated. For example, the mirror 110 is one of the mirrors M1 to M5 from 1 For example, reference numeral 108 designates a sensor frame of projection system 100. A sensor device (not shown) is arranged on sensor frame 108, for example, for measuring a current position of mirror 110 relative to sensor frame 108. Furthermore, reference numeral 106 designates a support frame (English: force frame) of mirror 110, for example. Sensor frame 108 is mounted in a vibration-decoupled manner with respect to support frame 106, for example. Support frame 106 of the exemplary mirror 110 is mounted in a vibration-decoupled manner with respect to a floor, for example.

Furthermore, in 2 a positioning system 200 for positioning a substrate holder 202 of the lithography system 1 is shown. A substrate 204 is arranged on the substrate holder 202 (similar to that on the wafer holder 14 in 1 arranged wafer 15). The substrate holder 202 has in particular a surface 228 for supporting the substrate 204.

The positioning system 200 comprises, in addition to the substrate holder 202, an actuator device 206 (similar to the wafer displacement drive 15 in 1 ) for moving the substrate holder 202. The actuator device 206 comprises, for example, one or more actuators 208, e.g. piezo actuators or other actuators, for moving the substrate holder 202 relative to a base 210.

The actuator device 206 is, for example, configured to move the substrate holder 202 relative to the base 210 in three translational degrees of freedom with respect to the x-, y- and z-directions in 2 and to move in three rotational degrees of freedom with respect to rotation about the x, y and z directions (ie, in all six rigid body degrees of freedom of the substrate holder 202).

The positioning system 200 also has a control device 212 for controlling a position r of the substrate holder 202. The control device 212 is designed, for example, to control the position r of the substrate holder 202 in the x- and y-direction in 2 The control device 212 is in particular designed to control the position r of the substrate holder 202 as a function of a pressure P of a liquid 304 in a liquid line 306 of a temperature control device 300, which pressure P is detected by one or more pressure sensors 214. For example, the control device 212 is connected to the one or more pressure sensors (wirelessly or wired) for data transmission of the detected pressure P (see reference numeral 216).

An embodiment of a tempering device 300 for tempering various components 108, 110 of the projection system 100 is shown in 2 shown. In the following, the temperature control device 300 is described by way of example as a cooling device 300, wherein the temperature control device 300 can also be used in other embodiments for heating components 108, 110 of the projection system 100. In addition, the temperature control device 300 is in 2 as an example for tempering the sensor frame 108 as an example of a component of the projection system 100 to be tempered. However, the tempering device 300 can also be set up for tempering other components of the projection system 100, such as one or more mirrors 110, in addition to or instead of tempering the sensor frame 108.

The cooling device 300 (as an example of a temperature control device 300) comprises a cooling unit 302 for cooling a cooling liquid 304. The cooling device 300 also comprises one or more liquid lines 306 for transporting the cooling liquid 304 from the cooling unit 302 to the component 108 to be cooled and back to the cooling unit 302. The cooling device 300 also comprises one or more pumps (not shown) for generating a required flow rate of the cooling liquid 304. The cooling device 300 further comprises one or more valves (not shown) for controlling the cooling flow.

In 2 Only one pressure sensor 214 is shown as an example, which is arranged in the flow direction S of the cooling liquid 304 directly in front of the component 108 to be cooled. However, more than one pressure sensor 214 can also be arranged on the liquid line 306. In addition, the one or more pressure sensors 214, 218 can also be arranged at a location other than directly in front of the component 108 to be cooled. As a further example, a pressure sensor 218 is shown with dashed lines, which is arranged at the inlet 230 of the projection system 100. In other examples, one or more pressure sensors (not shown) can also be arranged at the outlet of the projection system 100 in addition or instead.

3 shows a flowchart of a method for controlling the position r of the substrate holder 202.

In the following, only a control of the position r of the substrate holder 202 for compensating an imaging error of the lithography system is described. In addition, the substrate holder 202 can also be moved in a controlled manner to expose different areas of the substrate 204, as in a conventional lithography system - although not explained in more detail in connection with the method described here.

As in connection with 1 As described, the lithography system 1 is designed to produce an image of a mask 7 ( 1 ) on the substrate 204, which is arranged on the substrate holder 202. The substrate 204 has, for example, a main extension plane E (xy plane in 2 ) with a first direction x and a second direction y perpendicular to the first direction x.

In 4 an example of an image 400 with structures 402 imaged on the substrate 204 is shown. The reference numeral 404 indicates the structures 402 imaged at a target position. Furthermore, the reference numeral 406 designates the structures 402 imaged at an actual position due to an imaging error F. The imaging error F is caused in particular by a tilting of a wave front 112 ( 2 ) around the x- and y-axis. Due to the imaging error F, structures of the mask 7 ( 1 ) is imaged on the substrate 204 such that it extends from the target position 404 to the actual position in the negative x and negative y directions in 4 The imaging error F can, for example, be a vector with an x-component F _x and a y-component F _y , as shown.

In a first optional step S1 of the method, a calibration function G is determined. An example of a calibration function G is shown in 5 The calibration function G is a (e.g. linear) function of a pressure P ( 2 ) of the liquid 304 in the liquid line 306 depending on the imaging error F ( 4 ) of the lithography system. The calibration function G is determined, for example, by repeatedly imaging the mask 7 using the projection system 100 on the substrate 204 with the substrate holder 202 stationary and for several different pressure fluctuations induced in the liquid 304. In 5 The x-component F _x of the aberration F is shown as an example. Furthermore, 5 by way of example, two different pressure values P ₁ , P ₂ of a pressure fluctuation induced in the liquid 304 (e.g. with a water loudspeaker, not shown) are marked. Furthermore, the x-components F _x of the imaging errors F ₁ , F ₂ determined for these pressure values P ₁ , P ₂ are shown. Although not shown in the figures, the calibration function can also be, for example, a three-dimensional function that specifies both the x-component F _x and the y-component F _y of an imaging error F as a function of the pressure P. The imaging error F can, for example, be specified in the position space. Alternatively, the imaging error can also be specified in the frequency space.

In a second step S2 of the method, one or more pressure values w(t) of the liquid 304 in the liquid line 306 of the lithography system 1 are determined, e.g. by the control device 212 ( 2 ), for example, the pressure values w(t) from the one or more pressure sensors 214, 218 ( 2 ) by means of data transmission 216. The pressure value or pressure values w(t) are, for example, time-dependent values, where t denotes a time.

In a third step S3 of the method, a manipulated variable u(t) is determined based on the one or more received pressure values w(t) and the pre-determined calibration function G.

In a fourth step S4 of the method, the actuator device 206 ( 2 ) for positioning the substrate holder 202 based on the manipulated variable u(t).

The manipulated variable u(t) in step S3 is determined, for example, such that the actuator device 206 in step S4 moves the substrate holder 202 and thus the substrate 204 based on the manipulated variable u(t) such that the structures 402 to be imaged ( 4 ) from the actual position 406 to the target position 404. The arrow K indicates this shift, by which the imaging error F is compensated.

6 shows a block diagram of a control of the position r of the substrate holder 202 for compensating (see arrow K in 4 ) of an imaging error F of the lithography system 1. The control is in particular a feedforward control without feedback.

The control device 212 receives the detected pressure values w(t) (i.e. actual values) of a pressure fluctuation of the liquid 304 in the liquid line 306. A setpoint value for the pressure of a pressure fluctuation of the liquid 304 is zero and can be stored in a memory unit of the control device 212.

The control device 212 can optionally also receive the pre-determined calibration function G, as in 6 illustrated. Alternatively, the pre-determined calibration function G can also already be stored in a memory unit of the control device 212. The control device 212 determines a control signal u(t) for controlling the actuator device 206 based on the received pressure values w(t) and the pre-determined calibration function G. The reference number 220 in 6 identifies a control path of the controller. The control path 220 comprises, for example, an actuator (e.g. actuator device 206), a sensor (e.g. pressure sensor(s) 214, 218) and/or the substrate holder 202.

By controlling the actuator device 206 based on the control signal u(t), the substrate holder 202 and the substrate 204 are moved such that the imaging error F ( 4 ), see arrow K in 4 and reference symbol k(t) in 6 .

In the exemplary figures shown and described herein, the substrate holder 202 is controlled by controlling the actuator device 206 based on the control signal u(t) in the x- and/or y-direction (ie in the xy plane) in the figures. In other examples, however, the substrate holder 202 can also be moved additionally or instead in the z direction and/or rotated about the x, y and/or z direction by controlling the actuator device 206 based on the control signal u(t).

7 schematically shows functional components of the control device 212 according to an embodiment.

The control device 212 comprises a receiving device 222 for receiving one or more pressure values w(t) of the liquid 304 in the liquid line 306 ( 2 ). The control device 212 also comprises a determination device 224 for determining the manipulated variable u(t) based on the received pressure value(s) w(t) and the pre-determined calibration function G. The control device 212 also has a control device 226 for controlling the actuator device 206 based on the determined manipulated variable u(t). For example, the control device 226 sends a corresponding control signal a(t) to the actuator device 206.

In addition to the control of the position of the substrate holder described herein to compensate for imaging errors caused by pressure fluctuations of a tempering liquid, pressure fluctuations of a tempering liquid can also be actively dampened by other known measures (e.g. so-called silencers).

Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

LIST OF REFERENCE SYMBOLS

1

Projection exposure system

2

Lighting system

3

Light source

4

Lighting optics

5

Object field

6

Object level

7

Reticle

8

Reticle holder

9

Reticle displacement drive

10

Projection optics

11

Image field

12

Image plane

13

Wafer

14

Wafer holder

15

Wafer relocation drive

16

Illumination radiation

17

collector

18

Intermediate focal plane

19

Deflecting mirror

20

first faceted mirror

21

first facet

22

second facet mirror

23

second facet

100

Projection system

102

Projection optics

104

Frame structure

106

Frame structure

108

Frame structure

110

Mirror

112

Wavefront

200

Positioning system

202

Substrate holder

204

Substrat

206

Actuator device

208

Actuator

210

base

212

Control device

214

Pressure sensor

216

Data transfer

218

Pressure sensor

220

Control path

222

Reception facility

224

Investigation facility

226

Control device

228

surface

230

Entrance

300

Tempering device

302

Tempering unit (cooling unit)

304

liquid

306

Liquid line

400

Picture

402

structure

404

structure

406

Structure

a

signal

E

level

F

Mistake

Fx, Fy

Mistake

F1, F2

Mistake

G

function

K, k

correction

M1-M6

Mirror

P

Pressure

P1, P2

Pressure

S

Direction

S1-S4

Process steps

t

Time

u

Control variable

w

Pressure value

x

Direction

x1, x2

position

y

Direction

y1, y2

position

z

Direction

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102008009600 A1 [0075, 0079]
• US 20060132747 A1 [0077]
• EP 1614008 B1 [0077]
• US6573978 [0077]
• DE 102017220586 A1 [0082]
• US 20180074303 A1 [0096]

Claims (14)

Method for controlling a position (r) of a substrate holder (202) of a lithography system (1), wherein the lithography system (1) is set up to image an image (400) of a mask (7) on a substrate (204) arranged on the substrate holder (202), with the steps: a) receiving (S2) one or more pressure values (w) of a liquid (304) in a liquid line (306) of the lithography system (1), wherein the liquid line (306) is set up for tempering a position-sensitive component (108) of the lithography system (1), b) determining (S3) a control variable (u) based on the one or more received pressure values (w) and a pre-determined function (G) of the pressure (P) of the liquid (304) depending on an imaging error (F) of the lithography system (1) at the location of the substrate (204), and c) controlling (S4) an actuator device (206) for positioning the substrate holder (202) based on the manipulated variable (u). Procedure according to Claim 1 , wherein the liquid line (306) is designed to control the temperature of a position-sensitive component (108) of a projection system (100) of the lithography system (1), and/or the position-sensitive component (108) is a mechanical component (108), in particular a sensor frame (108), or an optical component (110), in particular a mirror (110), of the lithography system (1). Procedure according to Claim 1 or 2 , wherein the liquid line (306) is arranged to cool the position-sensitive component (108) of the lithography system (1). Procedure according to one of the Claims 1 until 3 , wherein the substrate (204) has a main extension plane (E) which extends in a first direction (x) and a second direction (y) perpendicular to the first direction (x), and the imaging error (F) of the lithography system (1) is an imaging error (F) by which the image (400) of the mask (7) on the substrate (204) shifts in the first and/or second direction (x, y), and/or the imaging error (F) of the lithography system (1) is an imaging error (F) which is generated by a tilting of a wave front (112) impinging on the substrate (204) in the first and/or second direction (x, y). Procedure according to one of the Claims 1 until 4 , wherein the substrate holder (202) has a surface (228) for supporting the substrate (204), which extends in a first direction (x) and a second direction (y) perpendicular to the first direction (x), and the actuator device (206) is controlled such that the substrate holder (202) is moved in the first direction (x), the second direction (y) and/or a third direction (z) perpendicular to the first and second directions (x, y), and/or that the substrate holder (202) is rotated about the first direction (x), the second direction (y) and/or the third direction (z). Procedure according to one of the Claims 1 until 5 , wherein the pre-determined function (G) of the pressure (P) of the liquid (304) is determined as a function of the imaging error (F) of the lithography system (1) by repeatedly imaging the mask (7) on the substrate (204) with a stationary substrate holder (202) and for several different pressure fluctuations (P ₁ , P ₂ ) induced in the liquid (304). Procedure according to one of the Claims 1 until 6 , wherein the pre-determined function (G) of the pressure (P) of the liquid (304) as a function of the imaging error (F) of the lithography system (1) is a linear function. Procedure according to one of the Claims 1 until 7 , wherein the one or more pressure values (w) of the liquid (304) in the liquid line (306) are received by one or more pressure sensors (214, 218) arranged on the liquid line (306). Procedure according to Claim 8 , wherein the one or more pressure sensors (214, 218) is/are arranged in a projection system (100) of the lithography system (1) and/or with respect to a flow direction (S) of the liquid (304) at the inlet (230) and/or at the outlet of the projection system (100). Procedure according to Claim 8 , wherein the liquid line (306) is configured to control the temperature of a sensor frame (108) of the lithography system (1), and the one or more pressure sensors (214) is/are arranged directly in front of the sensor frame (108) with respect to a flow direction (S) of the liquid (304). Procedure according to Claim 8 , wherein the liquid line (306) is configured to control the temperature of a mirror (110) of the lithography system (1), and the one or more pressure sensors is/are arranged directly in front of the mirror (110) with respect to a flow direction (S) of the liquid (304). Control device (212) for controlling a position (r) of a substrate holder (202) of a lithography system (1), wherein the lithography system (1) is designed to image an image (400) of a mask (7) on a substrate (204) arranged on the substrate holder (202), comprising: a receiving device (222) for receiving one or more pressure values (w) of a liquid (304) in a liquid line (306) of the lithography system (1), wherein the liquid line (306) is designed to control the temperature of a position-sensitive component (108) of the lithography system (1), a determining device (224) for determining a manipulated variable (u) based on the one or more received pressure values (w) and a pre-determined function (G) of the pressure (P) of the liquid (304) depending on an imaging error (F) of the lithography system (1) at the location of the substrate (204), and a control device (226) for controlling an actuator device (206) for positioning the substrate holder (202) based on the manipulated variable (u). Positioning system (200) for positioning a substrate holder (202) of a lithography system (1), comprising: a substrate holder (202), an actuator device (206) for moving the substrate holder (202), and a control device (212) according to Claim 12 . Lithography system (1), in particular EUV lithography system, with a control device (212) according to Claim 12 or a positioning system (200) according to Claim 13 .

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