Method and device for detecting a defect of a lithography system, and lithography system

Abstract

The invention relates to a method for detecting a defect (D) of a lithography system (1) which has a radiation source (3), a first mirror, and a mirror module provided downstream in the beam path, wherein each mirror (30) is paired with a respective determining device (70) for determining an indicative parameter value (P) for the intensity (I) of the radiation (S, 16) irradiated onto the mirror (30), the method involving: determining (201), by means of the determining devices (70), the indicative parameter values (P) for the intensities (I) of the radiation (S, 16) irradiated onto the mirrors (30) of the mirror module (20, 22) at a specific point in time, determining (202) a location-dependent intensity profile (IP) of the radiation (S, 16) irradiated onto the mirror module (20, 22) using the determined indicative parameter values (P), and determining (203) a defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) by comparing the determined location-dependent intensity profile (IP) with a specified reference intensity profile (R).

Description

[0001] Carl Zeiss SMT GmbH

[0002] 1

[0003] METHOD AND DEVICE FOR DETECTING A DEFECT IN A LITHOGRAPHING SYSTEM AND LITHOGRAPHING SYSTEM

[0004] The present invention relates to a method and a device for detecting a defect in a lithography system. Furthermore, the present invention relates to a lithography system with such a device for detecting a defect in the lithography system.

[0005] The content of priority application DE 102025 110444.1 is fully incorporated by reference.

[0006] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a mask (reticule) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0007] Driven by the pursuit of ever smaller structures in the production 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, particularly 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of the refracting optics, i.e., lenses, used previously.

[0008] The use of so-called MEMS mirrors in the illumination system of a lithography system is well-established. "MEMS" stands for "Micro Electro Mechanical System." Such MEMS mirrors comprise a micromirror (also called a mirror plate) and an actuator. The actuator allows the micromirror's orientation to be changed. During operation of the lithography system, radiation (also called working light, especially EUV light) strikes the surface of the micromirror and is reflected there. By changing the micromirror's orientation, the path the EUV light takes through the illumination system can be influenced. These MEMS mirrors are typically integrated onto a substrate. Carl Zeiss SMT GmbH

[0009] 2

[0010] manufactured. Advantageously, such systems require very little installation space. However, this also often results in significant space limitations for electronic components in the area behind the MEMS mirrors, i.e., on the side facing away from the working light.

[0011] The micromirrors can, for example, be mounted on a carrier plate and designed to be at least partially manipulable or tiltable, in order to allow movement of each micromirror in up to six degrees of freedom and thus highly precise positioning of the micromirrors relative to each other, especially in the pm range. This allows changes in optical properties that occur during operation of the lithography system, e.g., due to thermal influences, to be compensated for.

[0012] For the micromirror process, particularly in the six degrees of freedom, actuators are assigned to the mirrors and controlled via a feedback loop. A device for monitoring the tilt angle of each mirror is included as part of the feedback loop. For example, WO 2009 / 100856 A1 discloses a faceted mirror for a projection exposure system of a lithography system, which has a large number of individually movable mirrors. To ensure the optical quality of a projection exposure system, very precise positioning of the movable mirrors is necessary. Furthermore, document DE 102013209 442 A1 describes how the field faceted mirror can be designed as a microelectromechanical system (MEMS).

[0013] However, the photons from the EUV radiation source of the lithography system can, through the photoelectric effect, eject electrons from the mirror surfaces of the MEMS mirrors. This can lead to temporally and spatially varying current flows across the MEMS mirrors of the field facet mirror. These temporally and spatially varying current flows across the MEMS mirrors can significantly disrupt the monitoring of the tilt angle of the respective MEMS mirror.

[0014] For this purpose, DE 102023203338 A proposes a lithography system which includes a radiation source for generating radiation with a specific repetition frequency, a mirror that can be moved by a tilting angle to guide the radiation in the lithography system, and a detection device which is configured to detect the tilting angle of the mirror by means of a measuring signal with a measuring signal frequency which is greater than the repetition frequency. Carl Zeiss SMT GmbH

[0015] 3

[0016] The system is designed to acquire a discrete-time tilt angle signal and includes an evaluation unit. The evaluation unit is configured to discard certain signal values ​​of the acquired tilt angle signal based on a signal indicating the times of radiation impact on the mirror surface. This refined discrete-time tilt angle signal is used to determine the mirror's position. Because the measurement signal frequency is higher than the repetition frequency of the radiation source, the discrete-time tilt angle signal provided by the acquisition device contains more signal values ​​than necessary to determine the mirror's position. Therefore, it is possible to discard a subset of the discrete-time tilt angle signal's signal values.In this case, the evaluation unit rejects those signal values ​​of the provided discrete-time tilt angle signal whose associated acquisition times correspond to the times when the radiation strikes the surface of the mirror. Thus, the evaluation unit of DE 10 2023203338 Al is indeed suitable for providing a discrete-time tilt angle signal for specifying the tilt angle of the movable mirror with high accuracy. However, for many applications of the lighting system (including adjustments and maintenance), it would also be helpful to know the precise properties of the radiation striking the mirror.

[0017] For example, a MEMS-based illumination system can have two mirror modules, such as Mirror Module 1 (MM1) and Mirror Module 2 (MM2). Each Mirror Module MM1 and MM2 can, in turn, consist of a multitude of mirror arrays, each containing a plurality of micromirrors. The micromirrors on Mirror Module MM1 can be combined to form areas of varying sizes, known as subfields, and can image the EUV intermediate focus onto the micromirrors of Mirror Module MM2. For example, 6x6 micromirrors on Mirror Module MM2 can function as virtual pupil facets and image the sub-images in the reticular plane. The EUV intermediate focus is formed, in particular, by imaging the source plasma using the collector or collector mirror. The benefit of this approach lies primarily in light mixing.In this process, a field for mask illumination is formed from a radiation source (light source) with a specific, but not freely selectable, emission characteristic. This field is characterized primarily by high intensity homogeneity. The homogeneity ultimately achievable depends, among other things, on all real reflectivities meeting the specified expectations. Carl Zeiss SMT GmbH.

[0018] 4

[0019] Since the EUV light is generated by means of tin plasma at the focal point of the collector, the reflectivity of the collector, and to a lesser extent that of the mirror modules MM1 and MM2, can be reduced by tin deposits on the mirror surfaces. For this reason, continuous monitoring of local reflectivity changes on all mirror surfaces, especially those of the collector and the mirror modules MM1 and MM2, is desirable.

[0020] Against this background, one object of the present invention is to detect defects in a lithography system.

[0021] According to a first aspect, a method for detecting a defect in a lithography system is proposed. The system comprises a radiation source for generating radiation with a specific repetition frequency, a first mirror for guiding the radiation within the lithography system, and a mirror module downstream of the first mirror in the beam path of the lithography system for guiding the radiation within the lithography system. The mirror module includes a number of mirror arrays, each with a plurality of mirrors. Each mirror is assigned a corresponding detection device for determining an indicative parameter value for the intensity of the radiation incident on the mirror. The method includes:

[0022] a) Determining the indicative parameter values ​​for the intensities of the radiation emitted onto the mirrors of the mirror module at a specific time using the determination devices,

[0023] b) Determining a location-dependent intensity profile of the radiation incident on the mirror module using the determined indicative parameter values, and

[0024] c) Determining a defect on the first mirror or on the mirror module by comparing the determined location-dependent intensity profile with a predetermined reference intensity profile.

[0025] In this context, a defect describes in particular a change, especially an unintended change, in the reflectivity of the first mirror or the mirror module. The mirror array is in particular a micromirror array, and the respective mirror is in particular a MEMS mirror or micromirror.

[0026] In some embodiments, the mirror module is the first mirror module arranged in the beam path of the illumination system of the lithography system (mirror - Carl Zeiss SMT GmbH).

[0027] 5

[0028] module MM1) and the first mirror is the collector positioned upstream of the mirror module in the beam path. In alternative embodiments, the first mirror is the first mirror module (mirror module MM1) arranged in the beam path of the illumination system of the lithography system, and the second mirror module (mirror module MM2) is arranged in the beam path of the illumination system.

[0029] The radiation source is, for example, an EUV radiation source. The lithography system or projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The lithography system or projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm. The guided radiation can be EUV or DUV light.

[0030] The present method advantageously enables the monitoring of local reflectivity changes on all mirror surfaces of the first mirror and the mirror module. If a defect on the first mirror or on the mirror module is identified according to the present method, suitable measures, such as maintenance or adjustment, can be derived and carried out.

[0031] If, for example, the collector surface locally loses reflectivity due to debris deposits or layer damage, this can lead to local darkening at the mirror module MM1. As a result, the photocurrent detectable by the detection devices decreases locally on some micromirrors of the mirror module MM1, while the photocurrent remains constant at neighboring micromirrors. This is represented by the location-dependent intensity profile. To become independent of locally varying photocurrent sensitivities of individual micromirrors, an initial calibration is preferably performed in which the far field is recorded at the MM1 level. This is primarily represented by the predetermined reference intensity profile. As explained in detail below, the intensity profile determined by the first execution of steps a) - c) above can be used as the reference intensity profile.The selective local and temporal modification of the photocurrent allows the aforementioned defects to be distinguished from global fluctuations in source intensity or source position. Therefore, the focus here is explicitly on intensity drops or intensity variations. Carl Zeiss SMT GmbH.

[0032] 6

[0033] Reductions were sought on limited sub-areas, for example of the mirror module MM1.

[0034] Separating effects at the collector level and at the MM1 level is possible through relative motion between the radiation source or illuminator and the collector. An embodiment illustrating such a separation of effects at the collector and mirror levels by means of this relative motion is described in detail below. If the dimming propagates across the mirror module MM1, it must originate at the collector. However, if it remains on specific micromirrors of the mirror module MM1, it must be an effect on those very mirrors. Details of this are discussed in more detail below.

[0035] The photocurrent on individual micromirrors of the mirror module MM1 decreases when debris is deposited on them, as the EUV radiation is absorbed before it reaches the mirror. The observed pattern is similar to that which occurs with deposition on the collector, but remains stationary on the MM1 plane even with relative movement of the collector and radiation source (illuminator or light source).

[0036] Layer degradation with a loss of reflectivity on the mirror module MM1 can also be detected using the present method. For this purpose, the total power of individual subfields of the mirror module MM1 is preferably measured on the mirror module MM2. As described above, this power is preferably initially calibrated to be independent of the specific sensitivities of individual micromirrors. If a decrease in the measured power compared to the reference, namely the reference intensity profile, is detected (without a corresponding effect having been simultaneously measured on the collector or the mirror module MM1), this indicates a loss of reflectivity of the mirror module MM1.

[0037] According to one embodiment, step c) comprises the following steps :

[0038] Comparing the determined location-dependent intensity profile with the predetermined reference intensity profile to determine a local intensity drop on the mirror module, and

[0039] Detecting the defect on the first mirror or on the mirror module using the determined local intensity drop on the mirror module. Carl Zeiss SMT GmbH

[0040] 7

[0041] With the present embodiment, it is possible to detect whether a defect is present. However, with the present embodiment, the location of the defect—namely, whether the defect is on the first mirror or on the mirror module—cannot yet be determined. An embodiment is described below which it is also possible to detect whether the defect is actually located on the first mirror or on the mirror module.

[0042] According to another embodiment, the detection of the defect includes:

[0043] Determining the location of the defect on the first mirror or on the mirror module based on location information for the defect contained in the determined local intensity drop, and / or

[0044] Deriving a degree of reflectivity reduction of one or more adjacent mirrors on the mirror module or on the first mirror based on amplitude information for the defect contained in the determined local intensity drop.

[0045] The local intensity drop includes location information for the defect, which can be used to determine its location. Correspondingly, the determined local intensity drop also includes amplitude information about the defect, from which the degree of reflectivity reduction of one or more adjacent mirrors on the mirror module or on the first mirror can be derived.

[0046] According to a further embodiment, steps a) - c) are performed at specific times during the operation of the lithography system. Consequently, the operation of the lithography system is advantageously not restricted by the present method.

[0047] As already explained above, in embodiments the intensity profile determined by the first execution of steps a) - c) is used as the reference intensity profile.

[0048] According to another embodiment, the mirror module is the first mirror module arranged in the beam path of the illumination system of the lithography system, and the first mirror is the collector placed upstream of the mirror module in the beam path.

[0049] According to another embodiment, the first mirror is the first mirror arranged in the beam path of the illumination system of the lithography system - Carl Zeiss SMT GmbH

[0050] 8

[0051] The module and the mirror module is the second mirror module arranged in the beam path of the lighting system.

[0052] According to another embodiment, the method comprises the following steps:

[0053] Determining initial indicative parameter values ​​for the radiation intensities incident on the mirrors of the mirror module using the measurement devices at a first time point in time,

[0054] Determining a first location-dependent intensity profile of the radiation incident on the mirror module using the determined first indicative parameter values,

[0055] Comparing the determined first location-dependent intensity profile with the predetermined reference intensity profile to determine a first local intensity drop on the mirror module,

[0056] Determining second indicative parameter values ​​for the radiation intensities incident on the mirrors of the mirror module using the determination devices at a second time point after a relative movement between the radiation source and the first mirror or between the first mirror and the mirror module carried out after the first time point; determining a second location-dependent intensity profile of the radiation incident on the mirror module using the determined second indicative parameter values.

[0057] Comparing the determined second location-dependent intensity profile with the predetermined reference intensity profile to determine a second local intensity drop on the mirror module, and

[0058] Detecting the defect on the first mirror or on the mirror module using the determined first local intensity drop and the determined second local intensity drop.

[0059] According to another embodiment, the detection of the defect is formed by:

[0060] Detecting the defect on the first mirror when the determined first intensity drop and the determined second intensity drop are different from each other, and

[0061] Detecting the defect on the mirror module when the first and second intensity drops detected are identical.

[0062] Consequently, the location of the defect, namely whether the defect is on the first mirror or on the mirror module, can be advantageously determined. Carl Zeiss SMT GmbH

[0063] 9

[0064] According to another embodiment, the relative movement between the radiation source and the first mirror is carried out by means of a displacement of the radiation source and / or by means of a displacement of the first mirror at a specific time between the first time and the second time.

[0065] According to another embodiment, the relative movement between the first mirror and the mirror module is carried out by means of a displacement of the first mirror and / or by means of a displacement of the mirror module at a specific time between the first time and the second time.

[0066] Each embodiment of the first aspect can be combined with any other embodiment of the first aspect to obtain a different embodiment of the first aspect.

[0067] According to a second aspect, a detection device for detecting a defect in a lithography system is proposed. This device comprises a radiation source for generating radiation with a specific repetition frequency, a first mirror for guiding the radiation within the lithography system, and a mirror module downstream of the first mirror in the beam path of the lithography system for guiding the radiation within the lithography system. The mirror module includes a number of mirror arrays, each with a plurality of mirrors. Each mirror is assigned a corresponding detection device for determining an indicative parameter value for the intensity of the radiation incident on the mirror. The detection device has the following features:

[0068] a first unit which is set up to determine the indicative parameter values ​​for the intensities of the radiation emitted onto the mirrors of the mirror module at a specific time by means of the determination devices,

[0069] a second unit, which is designed to determine a location-dependent intensity profile of the radiation incident on the mirror module using the determined indicative parameter values, and

[0070] A third unit, which is configured to determine a defect on the first mirror or on the mirror module by comparing the specific location-dependent intensity profile with a predetermined reference intensity profile. Carl Zeiss SMT GmbH

[0071] 10

[0072] The respective unit, for example the first unit, can be implemented in hardware and / or software. In a hardware implementation, the unit can be designed as a device or as part of a device, for example as a computer, a microprocessor, or as part of the control device. In a software implementation, the unit can be designed as a computer program product, a function, a routine, part of program code, or an executable object.

[0073] Furthermore, the embodiments and features described for the method according to the first aspect also apply analogously to the detection device according to the second aspect.

[0074] According to a third aspect, a lithography system is proposed, which includes:

[0075] a radiation source for generating radiation with a specific repetition frequency,

[0076] a first mirror to guide the radiation in the lithography system,

[0077] A mirror module arranged downstream of the first mirror in the beam path of the lithography system for guiding the radiation in the lithography system, which has a number of mirror arrays with a respective plurality of mirrors, wherein each mirror is assigned a respective measuring device for determining an indicative parameter value for the intensity of the radiation incident on the mirror, and

[0078] a detection device as described above for detecting a defect in the lithography system according to the second aspect.

[0079] According to a further embodiment, the respective mirror has a mirror plate that can be displaced by a tilting angle, wherein the respective mirror plate is connected to the detection device via an electrical conductor for conducting the electric current from the mirror plate to the detection device, wherein the detection device has a capacitor coupled between the electrical conductor and ground and is configured to determine a steady-state voltage value of the voltage drop across the capacitor as an indicative parameter value for the intensity of the radiation incident on the mirror plate using the electric current supplied to the detection device. Carl Zeiss SMT GmbH

[0080] 11

[0081] By using the capacitor of the detection device, the electric current of the mirror plate can be integrated for each pulse and thus for each radiation pulse, especially EUV pulse.

[0082] The electric current from the mirror plate is either applied to a capacitor in the detection device or, alternatively, to an electrical resistor in the detection device. The indicative parameter can be a steady-state voltage value across the capacitor, a peak value across the electrical resistor, or a sampled voltage waveform across the electrical resistor.

[0083] In the first example, the electric charge applied to the mirror plate can be derived from the determined steady-state voltage across the capacitor. Additionally, the time-integrated intensity of the radiation onto the mirror plate can be determined from the electric charge. In the second example, the electric current through the mirror plate can be derived from the determined peak value of the voltage across the resistor. Subsequently, the instantaneous intensity of the radiation onto the mirror plate can also be determined from the electric current. In the third example, the time course of the electric current through the mirror plate can be derived from the sampled time course of the voltage across the resistor.Subsequently, the temporal profile of the intensity of the radiation on the mirror plate can also be determined from the temporal profile of the electric current of the mirror plate.

[0084] This allows the following properties of the radiation on the mirror plate to be determined:

[0085] the time-integrated intensity of the radiation on the mirror plate; the instantaneous value of the intensity of the radiation on the mirror plate; the time course of the intensity of the radiation on the mirror plate.

[0086] These determined properties of the radiation on the mirror plate are preferably fed to a processing unit. Based on one or more of these properties, the processing unit is configured to perform one or more of the following functions:

[0087] Suppression of disturbances in the detection device for recording the tilt angle of the mirror; Carl Zeiss SMT GmbH

[0088] 12

[0089] Measures for pulse detection and trigger suppression in the sensor system;

[0090] Adjusting the spot center for the radiation onto the mirror plate;

[0091] Monitoring of the radiation source;

[0092] Determination of the intensity distribution in the far field of the radiation source; monitoring of pollution and transmission, in particular correlating with a combination of the intensity of the incident radiation with the intensity of the absorbed radiation.

[0093] According to one embodiment, the lithography system comprises an evaluation unit which is configured to derive the electric charge that is replaced on the mirror plate from the determined steady-state voltage value of the voltage drop across the capacitor, and / or to determine the time-integrated intensity of the radiation on the mirror plate from the electric charge.

[0094] The steady-state voltage across the capacitor is indicative or representative of the electric charge displaced on the mirror plate, and thus of the intensity of the radiation incident on the mirror plate. In particular, the electric charge of the mirror plate is indicative of the time-integrated intensity of the radiation on the mirror plate.

[0095] According to another embodiment, the investigative device comprises an analog part and a digital part. The analog part has the following features:

[0096] the capacitor coupled between the electrical conductor and ground, whose input node is connected to the electrical conductor and whose output node is connected to ground,

[0097] an amplifier coupled to the input node, which is configured to provide an amplified voltage signal based on the voltage drop across the capacitor, and

[0098] an analog-to-digital converter coupled to the amplifier, which is configured to convert the voltage signal provided by the amplifier into a digital voltage signal with N bits.

[0099] According to another embodiment, the digital part comprises:

[0100] a gradient detection unit, which is configured to detect a rising edge of the voltage drop across the capacitor based on the digital voltage signal provided by the analog-to-digital converter. Carl Zeiss SMT GmbH

[0101] 13

[0102] detect and, depending on this, provide an initial trigger signal upon detection of a rising edge,

[0103] a transient detection unit which is configured to provide a second trigger signal when a stable digital voltage signal within a certain tolerance range is present, and

[0104] a storage unit which is configured to store the digital voltage signal provided by the analog-to-digital converter as the parameter value indicative of the intensity of the radiation directed onto the mirror plate, if the first trigger signal and the second trigger signal are provided.

[0105] According to another embodiment, the digital part of the detection device includes a filter unit connected between the output of the analog-to-digital converter and the storage unit. The filter unit is configured to filter the digital voltage signal provided by the analog-to-digital converter and, based on this, output a filtered digital voltage signal to the storage unit. The storage unit is configured to store the filtered digital voltage signal provided by the filter unit as the indicative parameter if the output signal of an AND gate that combines the first and second trigger signals has a positive signal state. The positive signal state is, for example, represented by a logic one, whereas a complementary negative signal state can be represented by a logic zero.

[0106] According to another embodiment, the analog part of the detection device has a controllable switch connected in parallel to the capacitor, by means of which the capacitor can be discharged using the output signal of the AND gate, particularly after storage by the memory unit. Thus, storage by the memory unit triggers the discharge of the capacitor. The discharged capacitor is then available for the next detection process. The AND gate can also be referred to as an AND circuit and represents a logical AND.

[0107] According to another embodiment, the analog section includes an overvoltage protection circuit connected between the input node and the amplifier. The overvoltage protection circuit is, for example, designed as a diode connected in parallel with the capacitor. Carl Zeiss SMT GmbH

[0108] 14

[0109] According to another embodiment, the storage unit is designed as a register array.

[0110] According to another embodiment, the gradient detection unit comprises an N-bit comparator and a register for providing a threshold value. The N-bit comparator is configured to set the first trigger signal to a positive signal state if the value of the digital voltage signal stored by the N-bit comparator is greater than the threshold value of the register.

[0111] According to another embodiment, the digital section comprises a series connection of latches between the output of the analog-to-digital converter and the register array. The latches are coupled to an N-bit comparator. In particular, the latches and the analog-to-digital converter are operated at the same clock frequency. The latches are each configured as state-controlled memory units, for example, as state-controlled flip-flops.

[0112] In this embodiment, the series connection of latches and the N-bit comparator coupled to them are part of the transient detection device.

[0113] According to a further embodiment, the respective mirror has a mirror plate that can be displaced by a tilting angle, wherein the respective mirror plate is connected to a detection device via an electrical conductor for guiding the electric current of the mirror plate to the detection device, wherein the detection device has a resistor coupled between the electrical conductor and ground and is configured to determine a peak value of the voltage drop across the resistor as an indicative parameter value for the intensity of the radiation incident on the mirror plate using the electric current guided to the detection device.

[0114] The electric current of the mirror plate can be determined by peak detection of the voltage drop across the resistor of the measuring device. Subsequently, the instantaneous intensity of the radiation on the mirror plate can also be determined from the electric current of the mirror plate. Carl Zeiss SMT GmbH

[0115] 15

[0116] According to one embodiment, the lithography system has an evaluation unit which is designed to derive the electric current of the mirror plate from the determined peak value of the voltage drop across the resistor, and / or to determine the instantaneous value of the intensity of the radiation on the mirror plate from the electric current of the mirror plate.

[0117] The measured peak value of the voltage drop across the resistor is indicative or representative of the electric current through the mirror plate. The electric current through the mirror plate, in turn, is indicative or representative of the instantaneous intensity of the radiation on the mirror plate.

[0118] According to another embodiment, the investigative device comprises an analog part and a digital part. The analog part comprises:

[0119] the resistor coupled between the electrical conductor and ground, whose input node is connected to the electrical conductor and whose output node is connected to ground,

[0120] a peak detection circuit coupled to the input node, which is configured to provide a measurement voltage at its output node representing the peak value of the voltage drop across the resistor,

[0121] a capacitor connected between the output node and ground to hold the measuring voltage,

[0122] an amplifier coupled to the output node, which is configured to amplify the measurement voltage held by the capacitor and, depending on this, to provide an amplified measurement voltage on the output side,

[0123] an analog-to-digital converter coupled to the amplifier, which is configured to convert the amplified measurement voltage provided by the amplifier into a digital voltage signal with N bits.

[0124] At the output node of the peak detection circuit, a high-value resistor is preferably connected in addition to the capacitor. The high-value resistor is configured to discharge the measurement voltage held by the capacitor, so that this voltage is supplied to the amplifier.

[0125] According to another embodiment, the digital part includes a storage unit configured to store the digital voltage signal provided by the analog-to-digital converter as the parameter value indicative of the radiation intensity projected onto the mirror plate. Carl Zeiss SMT GmbH

[0126] 16

[0127] According to another embodiment, the storage unit of the digital part is designed as a register array.

[0128] According to another embodiment, the analog-to-digital converter and the register array are operated at the same clock frequency.

[0129] According to another embodiment, the analog part of the detection device comprises an overvoltage protection circuit connected between the input node and the peak detection circuit. The overvoltage protection circuit is, for example, designed as a diode connected in parallel with the resistor.

[0130] According to another embodiment, the amplifier comprises a voltage divider coupled between the output node and ground, with a first resistor and a second resistor.

[0131] According to another embodiment, the peak detection circuit comprises an operational amplifier and a diode connected downstream of the operational amplifier. The non-inverting input of the operational amplifier is connected to the input node, and the inverting input of the operational amplifier is connected to the center tap of the voltage divider.

[0132] According to a further embodiment, the respective mirror has a mirror plate that can be displaced by a tilting angle, wherein the respective mirror plate is connected to a detection device via an electrical conductor for guiding the electric current of the mirror plate to the detection device, wherein the detection device has a resistor coupled between the electrical conductor and ground and is configured to determine a sampled time-dependent voltage profile of the voltage drop across the resistor as an indicative parameter value for the intensity of the radiation incident on the mirror plate using the electric current guided to the detection device.

[0133] The current of the mirror plate can be determined by scanning the voltage drop across the resistor of the detection device and thus by the resulting time-dependent voltage profile. Subsequently, the time profile of the Intensi-Carl Zeiss SMT GmbH can also be determined.

[0134] 17

[0135] The amount of radiation on the mirror plate can be determined from the time course of the electric current of the mirror plate.

[0136] According to one embodiment, the lithography system has an evaluation unit which is designed to derive a temporal profile of the electric current of the mirror plate from the sampled temporal voltage profile of the voltage drop across the resistor, and / or to determine a temporal profile of the intensity of the radiation on the mirror plate from the temporal profile of the electric current of the mirror plate.

[0137] The measured voltage profile across the resistor is indicative or representative of the electric current across the mirror plate over time. The electric current across the mirror plate over time, in turn, is indicative or representative of the intensity of the radiation on the mirror plate over time.

[0138] According to another embodiment, the investigative device comprises an analog part and a digital part. The analog part has the following features:

[0139] the resistor coupled between the electrical conductor and ground, whose input node is connected to the electrical conductor and whose output node is connected to ground,

[0140] an amplifier coupled to the input node and an analog-to-digital converter connected downstream of the amplifier and operated at a specific clock frequency,

[0141] wherein the amplifier is configured to amplify the voltage drop across the resistor and, depending on this, to provide an amplified voltage signal on the output side,

[0142] the analog-to-digital converter is designed to convert the amplified voltage signal provided by the amplifier into a digital voltage signal.

[0143] According to another embodiment, the digital part comprises:

[0144] A gradient detection unit operated at a specific clock frequency, which is configured to detect a rising edge of the digital voltage signal provided by the analog-to-digital converter and, based on this, to provide an initial trigger signal upon detection of a rising edge, Carl Zeiss SMT GmbH

[0145] 18

[0146] a logic circuit which is configured to provide a second trigger signal based on an AND operation of the first trigger signal and the specified clock frequency, and

[0147] a storage unit coupled to the output of the analog-to-digital converter, which is configured to store the digital voltage signal provided by the analog-to-digital converter as a time- and value-discrete signal if the second trigger signal provided by the logic circuit has a positive signal state.

[0148] According to another embodiment, the specified clock frequency is greater than 100 MHz.

[0149] According to another embodiment, the memory unit is designed as a RAM memory.

[0150] According to another embodiment, the gradient detection unit comprises an N-bit comparator and a register for providing a threshold value. The N-bit comparator is configured to set the first trigger signal to a positive signal state if the value of the digital voltage signal stored by the N-bit comparator is greater than the threshold value of the register.

[0151] According to another embodiment, the logic circuit comprises an AND gate and an address counter. In particular, the AND gate is configured to output a control signal to the address counter by means of an AND operation on the first trigger signal and the specified clock frequency. The address counter is preferably configured to output the second trigger signal to the RAM memory based on the received control signal.

[0152] According to another embodiment, the mirror is a MEMS mirror. The MEMS mirror has a mirror plate that can be displaced about the tilt angle, a support plate for supporting the mirror plate, a base plate, a solid-state joint coupling the support plate and the base plate, and a capacitive sensor arranged between the support plate and the base plate.

[0153] According to a further embodiment, a capacitive sensor is provided for measuring the tilt angle of the mirror plate of the MEMS mirror, wherein the electrodes of the capacitive sensor are comb-shaped and interlocked. Carl Zeiss SMT GmbH

[0154] 19

[0155] According to another embodiment, the comb-shaped electrodes of the capacitive sensor each have a recess through which the solid joint coupling the carrier plate and the base plate is guided.

[0156] The solid-state joint is guided through the two recesses of the comb-shaped electrodes of the capacitive sensor, thus connecting the carrier plate and the base plate of the MEMS mirror. The mirror plate of the MEMS mirror can be tilted by the specified angle via this solid-state joint.

[0157] According to another embodiment, the lithography system has a vacuum housing in which, in particular, the radiation source, the mirror array, and the detection device are arranged. For example, the vacuum housing is designed such that a pressure of 1013.25 hPa to 10 3 hPa, preferably 10 3 up to 10' 8 hPa, preferably 10' 8 up to 10 11 hPa prevails.

[0158] According to another embodiment, the lithography system has a control device arranged externally to the vacuum housing for controlling the radiation source by means of a control signal.

[0159] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise specified.

[0160] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0161] 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 further explained below with reference to preferred embodiments and the accompanying figures. Carl Zeiss SMT GmbH

[0162] 20

[0163] Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography;

[0164] Fig. 2 shows a schematic flowchart of a first implementation example of a method for detecting a defect in a lithography system;

[0165] Fig. 3 shows a schematic view of an embodiment of an aspect of a lithography system with exposure system;

[0166] Fig. 4A shows a schematic representation of part of the exposure system of Fig. 3 with radiation source, collector and mirror module;

[0167] Fig. 4B shows a schematic representation of the location-dependent intensity profile of the radiation incident on the mirror module of Fig. 4A;

[0168] Fig. 5A shows the schematic representation of Fig. 4A with a defect located on the collector;

[0169] Fig. 5B shows a schematic representation of the location-dependent intensity profile of the radiation incident on the mirror module of Fig. 5A;

[0170] Fig. 6 shows a schematic flowchart of a second implementation example of a method for detecting a defect in a lithography system;

[0171] Fig. 7 A shows a schematic representation of part of the exposure system of Fig. 3 with radiation source, collector and mirror module with a defect located on the collector to illustrate the effects of a relative movement between the collector and the radiation source;

[0172] Fig. 7B shows a schematic representation of the location-dependent intensity profile of the radiation incident on the mirror module of Fig. 7A;

[0173] Fig. 8A shows a schematic representation of part of the exposure system of Fig. 3 with radiation source, collector and mirror module with a defect located on the mirror module to illustrate the effects of a relative movement between the collector and the radiation source; Carl Zeiss SMT GmbH

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[0175] Fig. 8B shows a schematic representation of the location-dependent intensity profile of the radiation incident on the mirror module of Fig. 8A!

[0176] Fig. 9 shows a schematic block diagram of an embodiment of a detection device for detecting a defect in a lithography system!

[0177] Fig. 10 shows a schematic view of an embodiment of an aspect of the lithography system!

[0178] Fig. 11A shows a schematic view of a first embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate;

[0179] Fig. 11B shows an example of an extract of the course of the electric current supplied to the detection device of the mirror plate;

[0180] Fig. 11C shows an example of an excerpt of the course of the voltage drop across the capacitor of the measuring device according to Fig. 11A, resulting from the electric current according to Fig. 11B!

[0181] Fig. HD shows an example of an extract of the waveform of the digital voltage signal at the output of the analog-to-digital converter of the detection device according to Fig. HA!

[0182] Fig. HE shows a schematic view of a second embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate;

[0183] Fig. 12A shows a schematic view of a third embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate;

[0184] Fig. 12B shows an example of an extract of the course of the electric current supplied to the detection device of the mirror plate;

[0185] Fig. 12C shows an example of an excerpt of the course of the voltage drop across the resistance of the measuring device according to Fig. 12A, resulting from the electric current according to Fig. 12B! Carl Zeiss SMT GmbH

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[0187] Fig. 12D shows an example of an extract of the course of the digital voltage signal at the output of the analog-to-digital converter of the detection device according to Fig. 12A;

[0188] Fig. 12E shows a schematic view of a fourth embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate;

[0189] Fig. 13A shows a schematic view of a fifth embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate;

[0190] Fig. 13B shows an example of an extract of the course of the electric current supplied to the detection device of the mirror plate;

[0191] Fig. 13C shows an example of an extract of the waveform of the digital voltage signal at the output of the analog-to-digital converter of the detection device according to Fig. 13A; and

[0192] Fig. 13D shows a schematic view of a sixth embodiment of a detection device for determining a parameter value indicative of the intensity of the radiation emitted onto the mirror plate.

[0193] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0194] Fig. 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the radiation 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 include the radiation source 3. Carl Zeiss SMT GmbH

[0195] 23

[0196] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0197] Figure 1 illustrates a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x extends perpendicularly into the plane of the drawing. The y-direction y is horizontal, and the z-direction z is vertical. In Figure 1, the scan direction runs along the y-direction y. The z-direction z is perpendicular to the object plane 6.

[0198] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto 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.

[0199] A structure on the reticulum 7 is imaged onto a photosensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved, particularly along the y-direction y, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0200] Radiation source 3 is an EUV radiation source. Radiation 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. Radiation source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma, plasma generated using a laser) or a DPP source (Gas Discharged Produced Plasma, plasma generated by gas discharge). It can also be a synchrotron-based radiation source. Radiation source 3 can be a free-electron laser (FEL).

[0201] The illumination radiation 16, emanating from the radiation source 3, is focused by a collector 17. The collector 17 can be a Carl Zeiss SMT GmbH collier.

[0202] 24

[0203] The collector 17 can have one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated with the illuminating radiation 16 at grazing incidence (Gl), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0204] 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 radiation source 3 and the collector 17, and the illumination optics 4.

[0205] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be called field facets. Only a few of these first facets 21 are shown in Fig. 1 as examples.

[0206] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0207] As is known, for example, from DE 102008009600 A1, the first facets 21 themselves can each be composed of a multitude of individual mirrors, in particular a multitude of micromirrors. The first facet mirror 20 can in particular be a microelectromechanical system. Carl Zeiss SMT GmbH

[0208] 25

[0209] (MEMS system) be trained. For details, refer to DE 102008009600 Al.

[0210] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0211] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted 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 faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1614 008 B1, and US 6,573,978.

[0212] 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.

[0213] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 102008009600 Al in this regard.

[0214] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0215] The illumination optics 4 thus form a doubly faceted system. This basic principle is also known as a honeycomb condenser (EnglJ Fly's Eye Integrator).

[0216] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged at an angle to a pupil plane of the projection optics 10, as described, for example, in DE 102017220586 A1. Carl Zeiss SMT GmbH

[0217] 26

[0218] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping or indeed the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0219] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can in particular comprise one or two mirrors for normal incidence (Ni mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GF mirrors, grazing incidence mirrors).

[0220] In the embodiment shown in Fig. 1, the lighting optics 4 has exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20 and the second faceted mirror 22.

[0221] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0222] The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate imaging.

[0223] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0224] In the example shown in Fig. 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a double-obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture, which Carl Zeiss SMT GmbH

[0225] 27

[0226] is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

[0227] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, 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.

[0228] The projection optics 10 has 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.

[0229] The projection optics 10 can be anamorphic. In particular, they have different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, ± 0.125). A positive image scale β indicates a projection without image inversion. A negative sign for the image scale β indicates a projection with image inversion.

[0230] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4'1.

[0231] The projection optics 10 lead to a reduction of 8H in the y-direction y, that is, in the scan direction.

[0232] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0233] 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, depending on the design of the projection optics 10, can differ. Carl Zeiss SMT GmbH

[0234] 28

[0235] 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 Al.

[0236] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 with the help of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to each of them.

[0237] The first facets 21 are each superimposed on an associated second facet 23 to illuminate the object field 5 on the reticulum 7. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0238] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by the arrangement of the second facets 23. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0239] Another 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.

[0240] Further aspects and details of the illumination of the object field 5 and, in particular, the entrance pupil of the projection optics 10 are described below.

[0241] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0242] The entrance pupil of the projection optics 10 cannot be precisely illuminated by the second faceted mirror 22. When the projection optics 10 are projected telecentrically onto the center of the second faceted mirror 22, the following applies: Carl Zeiss SMT GmbH

[0243] 29

[0244] When projected onto wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0245] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0246] In the arrangement of the components of the illumination optics 4 shown in Fig. 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0247] Fig. 2 shows a schematic flowchart of a first embodiment of a method for detecting a defect D of a lithography system 1 or projection exposure system 1, as shown, for example, in Fig. 1.

[0248] The method according to Fig. 2 will be explained below with reference to Figs. 3 to 5B. Figure 3 shows a schematic view of an embodiment of an aspect of a lithography system 1 with exposure system 2; Figure 4A shows a schematic representation of part of the exposure system 2 of Figure 3, including radiation source 3, collector 17, and mirror module 20; Figure 4B shows a schematic representation of the location-dependent intensity profile IP of the radiation 16 incident on the mirror module 20 of Figure 4A; Figure 5A shows a schematic representation of Figure 4A with a defect D located on the collector 17; and Figure 5B shows a schematic representation of the location-dependent intensity profile IP of the radiation 16 incident on the mirror module 20 of Figure 5A. Carl Zeiss SMT GmbH

[0249] 30

[0250] In general, the method according to Fig. 2 is set up for detecting a defect D in a lithography system 1, which has a radiation source 3 for generating radiation 16 with a specific repetition frequency, a first mirror 17, 20 for guiding the radiation 16 in the lithography system 1, and a mirror module 20, 22 downstream of the first mirror 17, 20 in the beam path of the lithography system 1 for guiding the radiation S, 16 in the lithography system 1. The mirror module 20, 22 has a number of mirror arrays 24, 25, each with a plurality of mirrors 30. Each mirror 30 is associated with a respective detection device 70 (see Fig. 10 ff.) for determining an indicative parameter value P for the intensity I of the radiation 16 incident on the mirror 30.

[0251] In the example of Fig. 3, the mirror module 20, 22 is the first mirror module 20 (hereinafter also referred to as Micro-Mirror Unit 1 or MM1) arranged in the beam path of the lighting system 2, and the first mirror 17, 20 is the collector 17 arranged upstream of the mirror module 20 in the beam path. In alternative embodiments not shown, the first mirror 17, 20 is the first mirror module 20 arranged in the beam path of the lighting system 2 and the mirror module 20, 22 is the second mirror module 22 arranged in the beam path of the lighting system 2.

[0252] The procedure according to Fig. 2 comprises steps 201 - 203:

[0253] In step 201, indicative parameter values ​​P for the intensities I of the radiation 16 incident on the mirrors 30 of the mirror module 20 at a specific time are determined using the detection devices 70. The indicative parameter values ​​P are indicative of the intensities I of the radiation 16 incident on the mirrors 30 of the mirror module 20. In other words, the respective intensity I incident on the mirror 30 of the mirror module 20 can be derived or determined from the respective indicative parameter value P.

[0254] In step 202, a location-dependent intensity profile IP of the radiation 16 incident on the mirror module 20 is determined using the determined indicative parameter values ​​P. For this purpose, Fig. 4A shows a schematic representation of part of the exposure system 2 of Fig. 3 with radiation source 3, collector 17, intermediate focus 18, and mirror module 20 (also referred to as Mirror Module 1 or MM1). Fig. 4B shows a schematic representation of the location-dependent intensity profile IP of the radiation incident on the mirror module 20 of Fig. Carl Zeiss SMT GmbH

[0255] 31

[0256] 4A incident radiation 16. In Fig. 4B and Fig. 5B, the x-axis describes the position POS on the mirror module 20, and the y-axis shows the intensity I of the incident radiation 16 on the mirror module 20.

[0257] As shown in Fig. 4A, there is no defect D on either the collector 17 or the mirror module 20. Accordingly, the location-dependent intensity profile IP of Fig. 4B shows no intensity drop at any point that would be caused by such a defect D. In contrast, Fig. 5A shows a schematic representation corresponding to Fig. 4A with a defect D located on the collector 17. The defect D is, for example, a deposit, such as debris or layer damage on the collector 17. The defect D particularly alters the reflectivity at the location of the defect D on the collector 17.

[0258] As illustrated in Fig. 5B, the defect D on the collector 17 causes a decrease in intensity A in the location-dependent intensity profile IP of the radiation 16 incident on the reflector module 20 of Fig. 5A.

[0259] In step 203, a defect D on the first mirror 17 or on the mirror module 20 is determined by comparing the specific location-dependent intensity profile IP with a specific reference intensity profile R. Advantageously, step 203 detects that a defect D is present on the first mirror 17 or on the mirror module 20 downstream of the first mirror 17, but it cannot yet be determined whether the defect D is located on the first mirror 17 or on the mirror module 20. As will be discussed in detail below, the location of the defect D can be determined using the method shown in Fig. 6.

[0260] Returning to Fig. 2, step 203 includes in particular the following two steps:

[0261] Comparing the determined location-dependent intensity profile IP with the predetermined reference intensity profile R to determine a local intensity drop A on the mirror module 20, and

[0262] Detecting the defect D on the first mirror 17 or on the mirror module 20 using the determined local intensity drop A on the mirror module 20.

[0263] As the comparison of Fig. 4B and 5B shows, no intensity drop can be detected in Fig. 4B (the reason being that neither on the collector Carl Zeiss SMT GmbH

[0264] 32

[0265] (17, a defect D is still present on the mirror module 20 of Fig. 4A), whereas in the intensity profile IP of Fig. 5B, an intensity drop A can be observed. The intensity drop A of Fig. 5B is location-dependent, i.e., it lies at a specific position POS according to the x-axis and is caused by the defect D, which, according to Fig. 5A, is located on the collector 17.

[0266] In summary, according to Fig. 4B, no intensity drop A and therefore no defect D is detected on the two mirrors 17 and 20 of Fig. 4A, whereas based on the intensity drop A of Fig. 5B, a defect D is detectable on one of the mirrors 17 or 20 of Fig. 5A.

[0267] Preferably, the detection of the defect D comprises determining a location of the defect D on the first mirror 17 or the mirror module 20 based on location information for the defect D contained in the determined local intensity drop A. In this respect, Fig. 5B shows in particular that the intensity drop A is related to a specific position POS on the x-axis of the diagram of Fig. 5B and thus a location of the defect D on one of the mirrors 17 or 20 can be derived.

[0268] The detection of the defect D can preferably also be used to derive the degree of reflectivity reduction of one or more adjacent mirrors 30 on the mirror module 20 or on the first mirror 17 based on amplitude information for the defect D contained in the determined local intensity drop A. As shown in Fig. 5B, the intensity drop A has a specific amplitude from which the degree of reflectivity reduction can be derived.

[0269] In particular, steps 201-203 are performed at specific times during the operation of lithography system 1. In other words, steps 201-203 can be performed while lithography system 1 is operating. Consequently, the operation of lithography system 1 is advantageously not restricted by the present method.

[0270] Furthermore, Fig. 6 shows a schematic flowchart of a second embodiment of a method for detecting a defect D in a lithography system 1. The method according to Fig. 6 is based on the method according to Fig.

[0271] 2 and will be explained further with reference to Figs. 7A to 8B.

[0272] Fig. 7A shows a schematic representation of part of the exposure system 2 of Fig. 3 with radiation source 3, collector 17 and mirror module. Carl Zeiss SMT GmbH

[0273] 33

[0274] 20 with a defect D located on the collector 17 to illustrate the effects of a relative movement between the collector 17 and the radiation source 3 and Fig. 7B shows a schematic representation of the location-dependent intensity profile IP1 or IP2 of the mirror module 20 of the Fig.

[0275] 7A incident radiation 16.

[0276] Furthermore, Fig. 8A shows a schematic representation of part of the exposure system of Fig. 3 with radiation source 3, collector 17 and mirror module 20 with a defect D located on the mirror module 20 to illustrate the effects of a relative movement between the collector 17 and the radiation source 3, and Fig. 8B shows a schematic representation of the spatially dependent intensity profile IP1 or IP2 of the defect D located on the mirror module 20 of Fig. 3.

[0277] 8 A incident radiation 16.

[0278] The relative motion between collector 17 and radiation source 3 is represented in Figures 7A and 8A by an arrow pointing left from radiation source 3. Similarly, in Figure 7B, a leftward-pointing arrow illustrates the shift of intensity profile IP2 relative to the intensity profile IP1 shown. In Figure 8B, however, a downward-pointing arrow illustrates that intensity profile IP2 has not shifted relative to intensity profile IP1.

[0279] In the example shown in Figs. 7A-8B, the mirror module is the first mirror module 20 (hereinafter also referred to as Micro-Mirror Unit 1 or MM1) arranged in the beam path of the lighting system 2, and the first mirror is the collector 17 positioned upstream of the mirror module 20 in the beam path. In alternative embodiments not shown, the first mirror is the first mirror module 20 arranged in the beam path of the lighting system 2, and the mirror module is the second mirror module 22 arranged in the beam path of the lighting system 2.

[0280] The procedure according to Fig. 6 comprises steps 601 - 608:

[0281] In step 601, initial indicative parameter values ​​PI for the intensities I of the radiation 16 incident on the mirrors 30 of the mirror module 20 are determined at a first time tl using the measuring devices 70. As explained above, each mirror 30 is assigned a respective measuring device 70. Carl Zeiss SMT GmbH

[0282] 34

[0283] In step 602, a first location-dependent intensity profile IP1 (see Fig. 7B and 8B) of the radiation 16 incident on the mirror module 20 is determined using the determined first indicative parameter values ​​PI.

[0284] In step 603, the determined first location-dependent intensity profile IP 1 is compared with the predetermined reference intensity profile R to determine a first local intensity drop Al on the mirror module 20 (see Fig. 7B and 8B).

[0285] In step 604, a relative movement takes place between the first mirror 17, here the collector 17, and the radiation source 3. The relative movement between the first mirror 17 and the radiation source 3 is carried out in particular by means of a displacement of the first mirror 17 and / or by means of a displacement of the radiation source 3 at a specific time between the first time tl and a second time t2, at which step 605 is executed.

[0286] In step 605, second indicative parameter values ​​P2 for the intensities I of the radiation 16 incident on the mirrors 30 of the mirror module 20 are determined by means of the detection devices 70 (see Fig. 7B and Fig. 8B).

[0287] In step 606, a second location-dependent intensity profile IP2 of the radiation 16 incident on the mirror module 20 is determined using the determined second indicative parameter values ​​P2 (see Fig. 7B and 8B).

[0288] In step 607, the determined second location-dependent intensity profile IP2 is determined with the predetermined reference intensity profile R to determine a second local intensity drop A2 on the mirror module 20.

[0289] In Figures 7B and 8B, only the first local intensity drop Al is explicitly shown. The second intensity drop A2 in Figure 7B results from the first local intensity drop Al being shifted by the left-pointing arrow. In Figure 8B, the second local intensity drop A2 results from the fact that, as indicated by the downward-pointing arrow, it corresponds to the first local intensity drop Al, while the intensity profile IP2 has shifted. Carl Zeiss SMT GmbH

[0290] 35

[0291] In step 608, a defect D on the first mirror 17 or on the mirror module 20 is detected using the determined first local intensity drop Al and the determined second local intensity drop A2.

[0292] If the first measured intensity drop Al and the second measured intensity drop A2 differ from each other, it is deduced that the defect D is located on the first mirror 17, here the collector 17. Such a constellation is shown in Figures 7A and 7B. Figure 7B shows that, due to the left-pointing arrow, the first intensity drop Al and the second intensity drop A2 differ from each other. From this fact, it is then concluded that the defect D is located on the first mirror 17. This is also shown in Figure 7A.

[0293] However, if the first measured intensity drop Al and the second measured intensity drop A2 are identical, as illustrated by the downward-pointing arrow in Fig. 8B, it is concluded that the defect D is located on the mirror module 20. This constellation is again shown in Fig.

[0294] Figures 8B and 8A are shown. In detail, Figure 8B shows that the first intensity drop Al and the second intensity drop A2 are identical to each other, and Figure 8A illustrates that the defect D is located on the mirror module 20.

[0295] In summary, Figures 7A to 8B illustrate that effects on both mirrors 17, 20 can be separated by a relative movement of collector 17 and the radiation source 3. While an intensity drop Al, A2 migrates with collector defects (see Figure 7B), such disturbances induced by the mirror module 20 remain stationary (see Figure 8B).

[0296] Furthermore, Fig. 9 shows a schematic block diagram of an embodiment of a detection device 900 for detecting a defect D in a lithography system 1. As already explained above, the lithography system 1 includes a radiation source 3 for generating radiation S, 16 with a specific repetition frequency, a first mirror 17, 20 for guiding the radiation S, 16 in the lithography system 1, and a mirror module 20, 22 downstream of the first mirror 17, 20 in the beam path of the lithography system 1 for guiding the radiation S, 16 in the lithography system 1. The respective mirror module 20, 22 comprises a number of mirror arrays 24, 25, each with a plurality of mirrors 30. Each mirror 30 is equipped with a respective detection device 70 for determining an indicative parameter value P for the Radiation intensity I projected onto mirror 30 Carl Zeiss SMT GmbH

[0297] 36

[0298] S, 16 assigned. The detection device 900 comprises a first unit 901, a second unit 902 and a third unit 903.

[0299] The first unit 901 is designed to determine the indicative parameter values ​​P for the intensities I of the radiation S, 16 incident on the mirrors 30 of the mirror module 20, 22 at a specific time by means of the determination devices 70.

[0300] The second unit 902 is designed to determine a location-dependent intensity profile IP of the radiation S, 16 incident on the mirror module 20, 22 using the determined indicative parameter values ​​P.

[0301] The third unit 903 is designed to determine a defect D on the first mirror 17, 20 or on the mirror module 20, 22 by comparing the determined location-dependent intensity profile IP with a predetermined reference intensity profile R.

[0302] Fig. 10 shows a schematic view of an embodiment of an aspect of a lithography system or projection exposure system 1, as shown for example in Fig. 1.

[0303] Figure 10 shows the radiation S generated by radiation source 3 of the lithography system 1 according to Figure 1, which has a specific repetition frequency. Figure 10 also shows a mirror 30, which can be displaced by a tilt angle W, for guiding the radiation S in the lithography system 1. The mirror 30 can be designed as a MEMS mirror, for example, to be part of one of the mirrors 20, 22, M1, or M6 of the lithography system 1 of Figure 1. In particular, the mirror 30 is one of a plurality of mirrors in a mirror array, especially a MEMS mirror array.

[0304] The MEMS mirror 30 has a mirror plate 31 that can be displaced about the tilt angle W, a support plate 32 for supporting the mirror plate 31, a base plate 33, a solid-state joint 34 coupling the support plate 32 and the base plate 33, and a capacitive sensor 35 of a detection device 40 arranged between the support plate 32 and the base plate 33. The detection device 40 is configured to detect the tilt angle W of the MEMS mirror 30 by means of a measurement signal MS with a measurement signal frequency to provide a time-discrete tilt angle signal K. The measurement signal frequency is Carl Zeiss SMT GmbH

[0305] 37

[0306] greater than the repetition frequency. For example, the measurement signal frequency is at least twice as high as the repetition frequency.

[0307] The MEMS mirror 30 is displaceable in two tilting axes, preferably in two mutually orthogonal tilting axes. The sectional view of the MEMS mirror 30 in Fig. 10 shows one tilting axis. The detection device 40 of Fig. 10 comprises the aforementioned capacitive sensor 35 and two sensor units 41 and 42 per tilting axis. The capacitive sensor 35 is configured to measure the tilt angle W of the mirror plate 31 of the MEMS mirror 30. The electrodes 36, 37 of the capacitive sensor 35 are comb-shaped and interlocked. The capacitive sensor 35 has an upper electrode 36, which is coupled to the carrier plate 32. Furthermore, the capacitive sensor 35 has a lower electrode 37, which is coupled to the base plate 33. The respective sensor unit 41, 42 is designed to excite the capacitive sensor 35 by means of an excitation signal AS and to receive the measurement signal MS in response.

[0308] Two control units 51, 52 are provided per tilting axis for actuating the MEMS mirror 30. The upper electrode 36 of the capacitive sensor 35 is coupled to ground via the resistor 61. Furthermore, the mirror plate 31 is coupled to ground via the resistor 62. The mirror plate 31 is also connected to a detection device 70 via an electrical conductor 80 to conduct the electric current I from the mirror plate 31 to the detection device 70. In the example shown in Fig. 10, the electrical conductor 80 is connected to the mirror plate 31 via the resistor 62.

[0309] The measuring device 70 is designed to determine an indicative parameter value P for the intensity of the radiation S directed onto the mirror plate 31 using the electric current I supplied to the measuring device 70.

[0310] For example, the detection device 70 can have a capacitor 311 coupled between the electrical conductor 80 and ground (see Fig.

[0311] 11A, Fig. 11E). In this case, the indicative parameter value P can be formed as a steady-state voltage value of the voltage across the capacitor 311.

[0312] In alternative embodiments, the detection device 70 has a resistor 411 coupled between the electrical conductor 80 and ground. Carl Zeiss SMT GmbH

[0313] 38

[0314] (See Figs. 12A, 12E, 13A, and 13D). In these examples, the indicative parameter value P can be a determined peak value of the voltage drop across resistor 411. Alternatively, the indicative parameter value P can be a sampled time-dependent voltage waveform of the voltage drop across resistor 411. The first example, in which the indicative parameter value P is the steady-state voltage across capacitor 311, is discussed below with reference to Figs. 11A to 3E. The second example, in which the indicative parameter value P is the determined peak value of the voltage drop across resistor 411 of the detection device, is discussed with reference to Figs. 12A to 4E.The third example, in which the indicative parameter value P is formed as the sampled time-dependent voltage profile of the voltage drop across the resistor 411 of the detection device, is explained with reference to Figs. 13A to 5D.

[0315] For each of these examples, the determining device 70 can output the determined indicative parameter value P to an evaluation unit 90 (see Fig. 10). Details on this are given below with reference to the figures.

[0316] Sections 11A to 5D are explained in more detail.

[0317] Figure 11A shows a schematic view of a first embodiment of a measuring device 300 for determining an indicative parameter value P for the intensity of the radiation S incident on the mirror plate 31. The measuring device 300 of Figure 11A is an exemplary embodiment of the measuring device 70 of Figure 10.

[0318] The detection device 300 of Fig. 11A is connected to the detection device 300 via the electrical conductor 80 for conducting the electric current I of the mirror plate 31. Fig. 11B shows an example of a section of the path of the electric current I of the mirror plate 31 as it is conducted to the detection device 300. As Fig. 11B shows, the electric current I of the mirror plate 31 is formed as a current pulse, which results from the radiation S incident on the mirror plate 31.

[0319] The detection device 300 of Fig. 11A has a capacitor 311 coupled between the electrical conductor 80 and ground and is configured to use a steady-state voltage value V3 of the voltage VI dropping across the capacitor 311 as the value for the voltage applied to the mirror plate 31. - Carl Zeiss SMT GmbH

[0320] 39

[0321] The intensity of the radiation S and the indicative parameter value P were determined using the electric current I supplied to the detection device 300.

[0322] For this purpose, the detection device 300 of Fig. 11A has an analog part 310 and a digital part 320. The analog part 310 comprises the capacitor 311 coupled between the electrical conductor 80 and ground, whose input node Kl is connected to the electrical conductor 80 and whose output node K2 is connected to ground. Fig. 11C shows an example of an excerpt of the voltage VI across the capacitor 311 of the detection device 300 of Fig. 11A, resulting from the electric current I according to Fig. 11B.

[0323] Furthermore, the analog part 310 includes an amplifier 312 coupled to the input node Kl, which is configured to provide an amplified voltage signal V2 based on the voltage VI dropping across the capacitor 311.

[0324] As shown in Fig. 11A, an overvoltage protection circuit 314 can be connected between the input node Kl and the amplifier 312.

[0325] Furthermore, the analog section 310 comprises an analog-to-digital converter 313 coupled to the amplifier 312. The analog-to-digital converter 313 is configured to convert the voltage signal V2 provided by the amplifier 312 into a digital voltage signal V3 (see Fig. HD) with N bits. Fig. HD illustrates an example of a section of the waveform of the digital voltage signal V3 at the output of the analog-to-digital converter 313 of the detection device 300 according to Fig. HA.

[0326] As further illustrated in Fig. HA, the digital part 320 of the detection device 300 comprises a gradient detection unit 321, a transient detection unit 322 and a storage unit 323.

[0327] The gradient detection unit 321 can also be referred to as a gradient detection circuit or rising signal detection. The gradient detection unit 321 is designed to detect a rising edge of the voltage VI across the capacitor 311, based on the digital voltage signal V3 provided by the analog-to-digital converter 313, and, depending on this, to generate a first trigger signal TI upon detection of a rising edge. Carl Zeiss SMT GmbH

[0328] 40

[0329] to provide. The first trigger signal TI in this example is a digital signal with the possible signal states 1 and 0. The signal state 1 can also be referred to as a positive signal state, whereas the signal state 0 can also be referred to as a negative signal state.

[0330] The settling detection unit 322 can also be referred to as a settling detection circuit or settling detection. The settling detection unit 322 is designed to provide a second trigger signal T2 when a digital voltage signal V3 is stable within a specific tolerance range. "Stable within a specific tolerance range" for the digital voltage signal V3 means that the settling process is complete.

[0331] The storage unit 323 can also be referred to as memory or storage. The storage unit 323 is configured to store the digital voltage signal V3 provided by the analog-to-digital converter 313 as the parameter value P indicative of the radiation intensity S projected onto the mirror plate 31, provided that the first trigger signal TI and the second trigger signal T2 are provided, in other words, set or have a respective positive signal state.

[0332] As further illustrated in Fig. 11A, a filter unit 324 can be connected between the output of the analog-to-digital converter 313 and the storage unit 323. The filter unit 324 can also be referred to as a filter. The filter unit 324 is configured to filter the digital voltage signal V3 provided by the analog-to-digital converter 313 and, based on this, output a filtered digital voltage signal V3 to the storage unit 323. The storage unit 323 is then configured to store the filtered digital voltage signal V3 provided by the filter unit 324 as the indicative parameter P if an output signal T3 of an AND gate 325, which links the first trigger signal TI and the second trigger signal T2, has a positive signal state.

[0333] As further shown in Fig. 11A, the analog section 310 can have a controllable switch 315 connected in parallel to the capacitor 311. The capacitor 311 can be discharged by means of the switch 315, particularly using the output signal T3 of the AND gate 325, preferably after storage by the memory unit 323, so that the capacitor 311 is discharged for a new measurement process. Carl Zeiss SMT GmbH

[0334] 41

[0335] Fig. HE shows a schematic view of a second embodiment of a detection device 300 for determining a parameter value P indicative of the intensity of the radiation S incident on the mirror plate 31. The second embodiment according to Fig. HE is based on the first embodiment according to Fig. 11A. In the second embodiment according to Fig. HE, the overvoltage protection circuit 314 is designed as a diode connected in parallel to the capacitor 311.

[0336] The memory unit 323 of Fig. HE is configured as a register array. The gradient detection unit 321 of Fig. HE comprises an N-bit comparator unit 326 and a register 327 for providing a threshold value. The N-bit comparator unit 326 is configured to set the first trigger signal TI to a positive signal state if the value of the digital voltage signal V3 stored by the N-bit comparator unit 326 is greater than the threshold value of the register 327.

[0337] As further shown in Fig. HE, the digital section 320 of Fig. HE has a series connection of latches 328 between the output of the analog-to-digital converter 313 and the register array 323. The latches 328 are coupled to an N-bit comparator 329. The latches 328 and the analog-to-digital converter 313 are preferably operated at the same clock frequency. In this embodiment according to Fig. HE, the series connection of latches 328 and the N-bit comparator 329 coupled to them are part of the transient detection device 322.

[0338] In short, in the examples shown in Figures 11A-HE, the current I on the mirror plate 31 can be integrated across the capacitor 311. The radiation S, which is in the form of an EUV pulse, causes a significant increase in the capacitor voltage VI. After the EUV pulse, the capacitor voltage VI remains essentially constant (negligible for potential leakage currents). After detection of a rising edge in the capacitor voltage VI and later after the transient response, the output of the analog-to-digital converter 313 is stored in the memory unit 323. A sampling rate of approximately 1 MHz is sufficient in this case.

[0339] In summary, in the examples of Fig. 11A-3E, the indicative parameter P is designed as a steady-state voltage value V3 of the voltage VI across capacitor 311. Carl Zeiss SMT GmbH

[0340] 42

[0341] The evaluation unit 90 according to Fig. 10 is set up for the examples of Fig. 11A - 11E to derive the electric charge which is replaced on the mirror plate 31 from the determined steady-state voltage value V3 of the voltage VI dropping across the capacitor 311 and / or to determine the time-integrated intensity of the radiation S on the mirror plate 31 from the electric charge.

[0342] Furthermore, Fig. 12A shows a schematic view of a third embodiment of a measuring device 400 for determining an indicative parameter value P for the intensity of the radiation S incident on the mirror plate 31. The measuring device 400 of Fig. 12A is an exemplary embodiment of the measuring device 70 according to Fig. 10.

[0343] The detection device 400 of Fig. 12A is connected to the detection device 400 via the electrical conductor 80 for guiding the electric current I of the mirror plate 31. Fig. 12B shows an example of a section of the path of the electric current I of the mirror plate 31 guided by the detection device 400. In particular, Fig. 12B corresponds to Fig. 11B. As Fig. 12B shows, the electric current I of the mirror plate 31 is designed as a current pulse, which results from the radiation S incident on the mirror plate 31.

[0344] The measuring device 400 of Fig. 12A has an electrical resistance 411 coupled between the electrical conductor 80 and ground and is designed to determine a peak value V5 of the voltage V4 dropping across the resistance 411 as the indicative parameter value P for the intensity of the radiation S incident on the mirror plate 31 using the current I supplied to the measuring device 400.

[0345] For this purpose, the detection device 400 of Fig. 12A comprises an analog part 410 and a digital part 420. The analog part 410 includes the electrical resistor 411 coupled between the electrical conductor 80 and ground, whose input node K3 is connected to the electrical conductor 80 and whose output node K4 is connected to ground. Furthermore, the analog part 410 includes a peak value detection circuit 412 coupled to the input node K3, which is configured to provide a measuring voltage V6 at its output node K5, representing the peak value V5 of the voltage V4 across the resistor 411. Carl Zeiss SMT GmbH shows this in [reference to relevant document / document].

[0346] 43

[0347] Fig. 12C shows an example of an extract of the course of the voltage V6 resulting from the electric current I according to Fig. 12B, which drops across a resistor 417 of the measuring device 400 according to Fig. 11A.

[0348] The analog section 410 further comprises a capacitor 413 connected between output node K5 and ground for maintaining the measurement voltage V6. An amplifier 414 is coupled to output node K5, as shown in Fig. 12A. The amplifier 414 is configured to amplify the measurement voltage V6 held by the capacitor 413 and, depending on this, to provide an amplified measurement voltage V7 at its output. An analog-to-digital converter 415 is coupled to the output of the amplifier 414. The analog-to-digital converter 415 is configured to convert the amplified measurement voltage V7 provided by the amplifier 414 into a digital voltage signal V8 with N bits. Fig. 12D shows an example of a section of the waveform of the digital voltage signal V8 at the output of the analog-to-digital converter 415 of the detection device 400.

[0349] At the output node K5 of the peak detection circuit 412, the high-impedance resistor 417 is preferably coupled in addition to the capacitor 413. The high-impedance resistor 417 is configured to discharge the measurement voltage V6 held by the capacitor 413, so that this voltage can be supplied to the amplifier 414. The peak detection circuit 412 rapidly follows a rising voltage V4 across the resistor 411. The decay time of the capacitor voltage V6 is defined by the resistor 417. In this case, a sampling rate of approximately 200 kHz is sufficient for a repetition frequency of up to 100 kHz.

[0350] Furthermore, the analog part 410 of the detection device 400 according to Fig. 12A preferably has an overvoltage protection circuit 416 connected between the input node K3 and the peak value detection circuit 412.

[0351] The digital part 420 of the detection device 400 according to Fig. 12A comprises a storage unit 421. The storage unit 421 can also be referred to as memory or storage. The storage unit 421 is configured to store the digital voltage signal V8 provided by the analog-to-digital converter 415 as the parameter value P indicative of the radiation intensity S directed onto the mirror plate 31. Carl Zeiss SMT GmbH

[0352] 44

[0353] Fig. 12E shows a schematic view of a fourth embodiment of a detection device 400 for determining a parameter value P indicative of the intensity of the radiation S incident on the mirror plate 31. The fourth embodiment according to Fig. 12E is based on the third embodiment according to Fig. 12A. In the fourth embodiment according to Fig. 12E, the storage unit 421 is configured as a register array. The analog-to-digital converter 415 and the register array 421 are operated, in particular, at the same clock frequency f4.

[0354] The amplifier 414 of Fig. 12E comprises a voltage divider RI, R2 coupled between the output node K5 and ground, with a first resistor RI and a second resistor R2. The peak detection circuit 412 of Fig. 12E comprises an operational amplifier 418 and a diode 419 connected downstream of the operational amplifier 418. The non-inverting input of the operational amplifier 418 is connected to the input node K3 of the detection device 400. The inverting input of the operational amplifier 418 is connected to the center tap of the voltage divider RI, R2.

[0355] In summary, in the examples of Fig. 12A - 12E, the indicative parameter P is designed as a peak value V5 of the voltage V4 dropping across the resistor 411.

[0356] The evaluation unit 90 according to Fig. 10 is set up for the examples of Fig. 12A - 12E to derive the electric current I of the mirror plate 31 from the determined peak value V5 of the voltage V4 across the resistor 411 and / or to determine the instantaneous value of the intensity of the radiation S on the mirror plate 31 from the electric current I of the mirror plate 31.

[0357] Furthermore, Fig. 13A shows a schematic view of a fifth embodiment of a detection device 500 for determining an indicative parameter value P for the intensity of the radiation S incident on the mirror plate 31. The detection device 500 according to Fig. 13A is an exemplary embodiment of the detection device 70 according to Fig. 10.

[0358] The detection device 500 of Fig. 13A is connected to the detection device 500 via the electrical conductor 80 for conducting the electric current I of the mirror plate 31. Fig. 13B shows an example of a section of the path of the electric current I of the mirror plate 31 conducted to the detection device 500. Here, Fig. 13B corresponds to Fig. 11B and Carl Zeiss SMT GmbH

[0359] 45

[0360] Fig. 12B. As shown in Fig. 13B, the electric current I of the mirror plate 31 is designed as a current pulse, which results from the radiation S incident on the mirror plate 31.

[0361] The measuring device 500 of Fig. 13A has a resistor 511 coupled between the electrical conductor 80 and ground and is configured to determine a sampled time-dependent voltage profile V12 of the voltage V9 dropping across the resistor 511 as an indicative parameter value P for the intensity of the radiation S directed onto the mirror plate 31 using the electric current I supplied to the measuring device 500.

[0362] For this purpose, the investigation device 500 shown in Fig. 13A comprises an analog section 510 and a digital section 520. The analog section 510 includes a resistor 511 coupled between the electrical conductor 80 and ground, whose input node K6 is connected to the electrical conductor 80 and whose output node K7 is connected to ground. Furthermore, the analog section 510 includes an amplifier 512 coupled to the input node K6 and an analog-to-digital converter 513 connected downstream of the amplifier 512 and operated at a specific clock frequency f5. The amplifier 512 is configured to amplify the voltage V9 across the resistor 511 and, depending on this, to provide an amplified voltage signal V10 at its output. Furthermore, the analog-to-digital converter 513 is configured to convert the amplified voltage signal V10 provided by the amplifier 512 into a digital voltage signal VI1 with N bits. This is shown in Fig.13C is an example of an extract of the course of the digital voltage signal VI 1 at the output of the analog-to-digital converter 513 of the detection device 500 according to Fig. 13A.

[0363] The digital part 520 of the detection device 500 according to Fig. 13A comprises a gradient detection unit 521 operated at the specified clock frequency f5. The gradient detection unit 521 is configured to detect a rising edge of the digital voltage signal provided by the analog-to-digital converter 513 as Vll and, based on this, to provide a first trigger signal S1 upon detection of a rising edge.

[0364] Furthermore, the digital part 520 according to Fig. 13A includes a logic circuit 522. The logic circuit 522 is configured to generate a second trigger signal S2 based on an AND operation of the first trigger signal S1 and the be-Carl Zeiss SMT GmbH

[0365] 46

[0366] The digital section 520 comprises a memory unit 523 coupled to the output of the analog-to-digital converter 513. The memory unit 523 can also be referred to as memory or storage. The memory unit 523 is configured to store the digital voltage signal VI1 provided by the analog-to-digital converter 513 as a time- and value-discrete signal V12 if the second trigger signal S2 provided by the logic circuit 522 has a positive signal state. Preferably, the specified clock frequency f5 is greater than 100 MHz. In this case, a high-speed analog-to-digital converter 513, particularly one with a frequency greater than 100 MHz, is advantageous. Furthermore, a high-speed RAM is advantageous.

[0367] Fig. 13D shows a schematic view of a sixth embodiment of a detection device 500 for determining an indicative parameter value P for the intensity of the radiation S incident on the mirror plate 31. The sixth embodiment according to Fig. 13D is based on the fifth embodiment according to Fig. 13A.

[0368] In the sixth embodiment according to Fig. 13D, the memory unit 523 is designed as a RAM memory. The gradient detection unit 521 according to Fig.

[0369] 13D comprises an N-bit comparator 524 and a register 525 for providing a threshold value. The N-bit comparator 524 is configured to set the first trigger signal S1 to a positive signal state if the value of the digital voltage signal VI 1 stored by the N-bit comparator 524 is greater than the threshold value of the register 525.

[0370] The logic circuit 522 according to Fig. 13D comprises an AND gate 526 and an address counter 527. The AND gate 526 is configured to output a control signal S3 to the address counter 527 by means of an AND operation of the first trigger signal S1 and the specified clock frequency f5. The address counter 527 is configured to output the second trigger signal S2 to the RAM memory 523 based on the received control signal S3.

[0371] In summary, in the examples of Figs. 13A-5D, the indicative parameter P is defined as the sampled time-dependent voltage profile V12 of the voltage V9 across resistor 511. Carl Zeiss SMT GmbH

[0372] 47

[0373] The evaluation unit 90 according to Fig. 10 is set up for the examples of Fig. 13A - 5D to derive a time course of the electric current I of the mirror plate 31 from the sampled time course of the voltage V12 of the voltage V9 dropping across the resistor 511, and / or to determine a time course of the intensity of the radiation S on the mirror plate 31 from the time course of the electric current I of the mirror plate 31.

[0374] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. Carl Zeiss SMT GmbH

[0375] 48

[0376] REFERENCE MARK LIST

[0377] 1 Projection exposure system

[0378] 2 lighting systems

[0379] 3. Radiation source (light source)

[0380] 4 Lighting optics

[0381] 5 object field

[0382] 6 Object level

[0383] 7 reticles

[0384] 8 label holders

[0385] 9 Reticle displacement drive

[0386] 10 Projection optics

[0387] 11 Image field

[0388] 12 Image plane

[0389] 13 wafers

[0390] 14 wafer holders

[0391] 15 wafer transfer drive

[0392] 16 Lighting radiation

[0393] 17 Collector

[0394] 18 Intermediate focus plane

[0395] 19 deflecting mirrors

[0396] 20 First faceted mirror, mirror module (Micro-Mirror Unit 1, MM1) 21 First facet

[0397] 22 Second faceted mirror, mirror module (Micro-Mirror Unit 2, MM2)

[0398] 23 second facet

[0399] 24 mirror array

[0400] 25 mirror array

[0401] 26 frames

[0402] 30 mirrors

[0403] 31 Mirror plate

[0404] 32 Carrier plate

[0405] 33 Base plate

[0406] 34 Solid body joint

[0407] 35 capacitive sensor

[0408] 36 upper comb-shaped electrode

[0409] 37 lower comb-shaped electrode

[0410] 40 Data collection device

[0411] 41 first sensor unit Carl Zeiss SMT GmbH

[0412] 49

[0413] 42 second sensor unit

[0414] 51 Control unit

[0415] 52 Control unit

[0416] 61 Resistance

[0417] 62 Resistance

[0418] 70 Investigation Unit

[0419] 80 electrical conductors

[0420] 90 evaluation units

[0421] 201 Procedure step

[0422] 202 Procedure step

[0423] 203 Procedure step

[0424] 300 Investigation Unit

[0425] 310 analog part

[0426] 311 Capacitor

[0427] 312 amplifiers

[0428] 313 Analog-to-Digital Converter

[0429] 314 Overvoltage protection switch 315 Switch

[0430] 320 digital part

[0431] 321 Gradient detection unit 322 Transient detection unit 323 Storage unit

[0432] 324 filter unit

[0433] 325 AND gate

[0434] 326 N-bit comparison unit

[0435] 327 Register

[0436] 328 Latches

[0437] 329 N-Bit Comparator

[0438] 400 Investigation Unit

[0439] 410 analog part

[0440] 411 Resistance

[0441] 412 Peak value detection circuit 413 Capacitor

[0442] 414 amplifiers

[0443] 415 Analog-to-Digital Converter

[0444] 416 Overvoltage protection circuit 417 High-impedance resistor

[0445] 418 Operational Amplifiers

[0446] 419 Diode Carl Zeiss SMT GmbH

[0447] 50,420 digital part

[0448] 421 storage unit

[0449] 500 Investigation facility 510 Analog part

[0450] 511 Resistor

[0451] 512 amplifiers

[0452] 513 Analog-to-Digital Converter

[0453] 520 digital part

[0454] 521 Gradient detection unit 522 Logic switch

[0455] 523 memory unit

[0456] 524 N-bit comparison unit

[0457] 525 Register

[0458] 526 AND gates

[0459] 527 Address counter

[0460] 601 Procedure step

[0461] 602 Procedure step

[0462] 603 Procedure step

[0463] 604 Procedure step

[0464] 605 Procedure step

[0465] 606 Procedure step

[0466] 607 Procedure step

[0467] 608 Procedure step

[0468] 900 detection device

[0469] 901 first unit

[0470] 902 second unit

[0471] 903 third unit

[0472] A decrease in intensity

[0473] The first drop in intensity

[0474] A2 second intensity drop AS excitation signal

[0475] D Defect

[0476] f4 clock frequency

[0477] f5 Clock frequency

[0478] I Intensity of radiation

[0479] IP intensity profile

[0480] IP1 first intensity profile

[0481] IP2 second intensity profile Carl Zeiss SMT GmbH

[0482] 51

[0483] Kl Entrance Node

[0484] K2 output node

[0485] K3 Input Node

[0486] K4 Exit Node

[0487] K5 Exit Node

[0488] K6 Input node

[0489] K7 Exit node

[0490] ml mirror

[0491] M2 mirrors

[0492] M3 mirror

[0493] M4 mirrors

[0494] M5 mirror

[0495] M6 mirrors

[0496] P indicative parameter values

[0497] PI first indicative parameter values ​​P2 second indicative parameter values ​​POS position

[0498] R Reference Intensity Profile

[0499] RI first resistance

[0500] R2 second resistor

[0501] S radiation

[0502] S1 first trigger signal

[0503] S2 second trigger signal

[0504] S3 control signal

[0505] TI first trigger signal

[0506] T2 second trigger signal

[0507] T3 output signal

[0508] t time

[0509] tl first point in time

[0510] t2 first time point

[0511] VI Tension

[0512] V2 amplified voltage signal V3 steady-state voltage value V4 voltage

[0513] V5 peak value

[0514] V6 measuring voltage

[0515] V7 amplified measuring voltage

[0516] V8 digital voltage signal

[0517] V9 Voltage Carl Zeiss SMT GmbH

[0518] 52

[0519] V10 amplified voltage signal

[0520] VI 1 digital voltage signal

[0521] V12 sampled time-dependent voltage curve W tilt angle

Claims

Carl Zeiss SMT GmbH 53 PATENT CLAIMS 1. Method for detecting a defect (D) of a lithography system (1), which has a radiation source (3) for generating radiation (S, 16) with a specific repetition frequency, a first mirror (17, 20) for guiding the radiation (S, 16) in the lithography system (1), and a mirror module (20, 22) downstream of the first mirror (17, 20) in the beam path of the lithography system (1) for guiding the radiation (S, 16) in the lithography system (1), which has a number of mirror arrays (24, 25) with a respective plurality of mirrors (30), wherein each mirror (30) is assigned a respective detection device (70) for determining an indicative parameter value (P) for the intensity (I) of the radiation (S, 16) incident on the mirror (30), wherein the method comprises: a) Determining (201) the indicative parameter values ​​(P) for the intensities (I) of the radiation (S, 16) incident on the mirrors (30) of the mirror module (20, 22) at a specific time using the determination devices (70), b) Determining (202) a location-dependent intensity profile (IP) of the radiation (S, 16) incident on the mirror module (20, 22) using the determined indicative parameter values ​​(P), and c) Determining (203) a defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) by comparing the determined spatially dependent intensity profile (IP) with a predetermined reference intensity profile (R).

2. Method according to claim 1, where step c) (203) includes: Comparing the determined location-dependent intensity profile (IP) with the predetermined reference intensity profile (R) to determine a local intensity drop (A) on the mirror module (20, 22), and Detecting the defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) using the determined local intensity drop (A) on the mirror module (20, 22).

3. Method according to claim 2, where detecting the defect (D) includes: Determining the location of the defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) based on location information for the defect (D) contained in the determined local intensity drop (A), and / or Carl Zeiss SMT GmbH 54 Deriving a degree of reflectivity reduction of one or more adjacent mirrors (30) on the mirror module (20, 22) or on the first mirror (17, 20) from amplitude information for the defect (D) contained in the determined local intensity drop (A).

4. Method according to any one of claims 1 to 3, wherein steps a) - c) are carried out at specific times during the operation of the lithography system (1), where the intensity profile (IP) determined by the first execution of steps a) - c) is used as the reference intensity profile (R).

5. Method according to any one of claims 1 to 4, wherein the mirror module (20, 22) is the first mirror module (20) arranged in the beam path of an illumination system (2) of the lithography system (1) and the first mirror (17, 20) is a collector (17) placed in front of the mirror module (20, 22) in the beam path.

6. Method according to any one of claims 1 to 4, wherein the first mirror (17, 20) is the first mirror module (20) arranged in the beam path of an illumination system (2) of a lithography system (1) and the mirror module (20, 22) is the second mirror module (22) arranged in the beam path of the illumination system (2).

7. Method according to any one of claims 1 to 6, comprising: Determining (601) first indicative parameter values ​​(Pl) for the intensities (I) of the radiation (S, 16) incident on the mirrors (30) of the mirror module (20, 22) using the determination devices (70) at a first time point (tl), Determining (602) a first location-dependent intensity profile (IP1) of the radiation (S, 16) incident on the mirror module (20, 22) using the determined first indicative parameter values ​​(Pl), Comparing (603) the determined first location-dependent intensity profile (IP1) with the predetermined reference intensity profile (R) to determine a first local intensity drop (Al) on the mirror module (20, 22), determining (605) second indicative parameter values ​​(P2) for the intensities (I) of the radiation (S, 16) incident on the mirrors (30) of the mirror module (20, 22) using the determination devices (70) at a second time point (t2) after a relative measurement performed after the first time point (tl). Carl Zeiss SMT GmbH 55 movement (604) between the radiation source (3) and the first mirror (17) or between the first mirror (17, 20) and the mirror module (20, 22), Determining (606) a second location-dependent intensity profile (IP2) of the radiation (S, 16) incident on the mirror module (20, 22) using the determined second indicative parameter values ​​(P2), Comparing (607) the determined second location-dependent intensity profile (IP2) with the predetermined reference intensity profile (R) to determine a second local intensity drop (A2) on the mirror module (20, 22), and detecting (608) the defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) using the determined first local intensity drop (Al) and the determined second local intensity drop (A2).

8. Method according to claim 7, wherein the detection (608) of the defect (D) is formed by: Detecting the defect (D) on the first mirror (17, 20) when the determined first intensity drop (Al) and the determined second intensity drop (A2) are different from each other, and Detecting the defect (D) on the mirror module (20, 22) when the first intensity drop (Al) and the second intensity drop (A2) are identical.

9. Method according to claim 7 or 8, wherein the relative motion between the radiation source (3) and the first mirror (17) is carried out by means of a displacement of the radiation source (3) and / or by means of a displacement of the first mirror (17) at a specific time between the first time (tl) and the second time (t2), or wherein the relative motion between the first mirror (17, 20) and the mirror module (20, 22) is carried out by means of a displacement of the first mirror (17, 20) and / or by means of a displacement of the mirror module (20, 22) at a specific time point between the first time point (tl) and the second time point (t2).

10. Detection device (900) for detecting a defect (D) of a lithography system (1), which includes a radiation source (3) for generating radiation (S, 16) with a specific repetition frequency, a first mirror (17, 20) for guiding the radiation (S, 16) in the lithography system (1), and a mirror module (20, 22) arranged downstream of the first mirror (17, 20) in the beam path of the lithography system (1) for guiding the radiation (S, 16) in the lithography system (1). - Carl Zeiss SMT GmbH 56 graphieanlage (1) comprising a number of mirror arrays (24, 25) with a respective plurality of mirrors (30), wherein each mirror (30) is assigned a respective detection device (70) for determining an indicative parameter value (P) for the intensity (I) of the radiation (S, 16) incident on the mirror (30), wherein the detection device (900) comprises: a first unit (901) which is set up to determine the indicative parameter values ​​(P) for the intensities (l) of the radiation (S, 16) emitted onto the mirrors (30) of the mirror module (20, 22) at a specific time by means of the determination devices (70), a second unit (902) which is configured to determine a location-dependent intensity profile (IP) of the radiation (S, 16) incident on the mirror module (20, 22) using the determined indicative parameter values ​​(P), and a third unit (903) which is configured to determine a defect (D) on the first mirror (17, 20) or on the mirror module (20, 22) by comparing the determined location-dependent intensity profile (IP) with a predetermined reference intensity profile (R).

11. Lithography system (1), with a radiation source (3) for generating radiation (S, 16) with a specific repetition frequency, a first mirror (17, 20) for guiding the radiation (S, 16) in the lithography system (1), a mirror module (20, 22) downstream of the first mirror (17, 20) in the beam path of the lithography system (1) for guiding the radiation (S, 16) in the lithography system (1), which has a number of mirror arrays (24, 25) with a respective plurality of mirrors (30), wherein each mirror (30) is assigned a respective detection device (70) for determining an indicative parameter value (P) for the intensity (I) of the radiation (S, 16) incident on the mirror (30), and a detection device (900) for detecting a defect (D) of the lithography system (1) according to claim 10.

12. Lithography system according to claim 11, wherein the respective mirror (30) has a mirror plate (31) that can be displaced by a tilting angle (W), wherein the respective mirror plate (31) is connected to the detection device (300) via an electrical conductor (80) for conducting the electric current (I) of the mirror plate (31) to the detection device Carl Zeiss SMT GmbH 57 (300) is connected, wherein the detection device (300) has a capacitor (311) coupled between the electrical conductor (80) and ground and is configured to determine a steady-state voltage value (V3) of the voltage (V1) dropping across the capacitor (311) as an indicative parameter value (P) for the intensity of the radiation (S, 16) radiated onto the mirror plate (31) using the electric current (I) supplied to the detection device (300).

13. Lithography system according to claim 11, wherein the respective mirror (30) has a mirror plate (31) that can be displaced by a tilting angle (W), wherein the respective mirror plate (31) is connected to a detection device (400) via an electrical conductor (80) for conducting the electric current (I) of the mirror plate (31) to the detection device (400), wherein the detection device (400) has a resistor (411) coupled between the electrical conductor (80) and ground and is configured to determine a peak value (V5) of the voltage (V4) across the resistor (411) as an indicative parameter value (P) for the intensity of the radiation (S, 16) incident on the mirror plate (31) using the electric current (I) supplied to the detection device (400).

14. Lithography system according to claim 11, wherein the respective mirror (30) has a mirror plate (31) that can be displaced by a tilting angle (W), wherein the respective mirror plate (31) is connected to a detection device (500) via an electrical conductor (80) for conducting the electric current (I) of the mirror plate (31) to the detection device (500), wherein the detection device (500) has a resistor (511) coupled between the electrical conductor (80) and ground and is configured to determine a sampled time-dependent voltage profile (V12) of the voltage (V9) dropping across the resistor (511) as an indicative parameter value (P) for the intensity of the radiation (S, 16) incident on the mirror plate (31) using the electric current (I) supplied to the detection device (500).

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