DE102020201558A1 - Device for cleaning a plasma radiation source - Google Patents

Abstract

A device (33) for cleaning a plasma radiation source (21) in a radiation source module of a projection exposure system (13) has a laser radiation source (31) for generating a processing beam (38) and an end effector (32) for targeted guidance of the processing beam (38) ) within the radiation source module, the end effector (32) having at least one mirror (54) which can be tilted on the one hand around a tilting axis (56) running perpendicular to a mirror normal (55) and on the other hand around a tilting axis (56) running perpendicular to the tilting axis (56) Rotation axis (7) is rotatable.

Description

The invention relates to a device for cleaning a plasma radiation source, in particular an EUV radiation source in a radiation source module of a mask inspection system or a projection exposure system. The invention also relates to a method for cleaning a plasma radiation source, in particular an EUV radiation source in an illumination system of a mask inspection system or a projection exposure system. The invention further relates to a radiation source module, a lighting system and a mask inspection system or a projection exposure system with a corresponding cleaning device.

When operating plasma radiation sources, the problem arises that the plasma target material (e.g. tin) contaminates the source chamber or components surrounding the plasma are sputtered off by ion bombardment, thereby contaminating the source chamber.

A device for cleaning a source chamber of a plasma radiation source is from the DE 10 2017 212 351 A1 known.

It is an object of the present invention to develop a device for cleaning a plasma radiation source, in particular to improve it.

This object is achieved by the features of claim 1.

The essence of the invention is to provide the device with a laser radiation source for generating a machining beam, with an end effector for targeted guidance of the machining beam within the radiation source module, and with the end effector having at least one displaceable mirror. The mirror is preferably tiltable, on the one hand, about a tilting axis running perpendicular to a mirror normal and, on the other hand, rotatable about an axis of rotation running perpendicular to the tilting axis.

With the aid of a corresponding end effector, the processing beam can be guided quickly and precisely to predetermined areas of a wall of the source chamber of the radiation source. In particular, it is possible to reach the entire surface of the inside of the source chamber with the processing jet.

The wall can in particular be a side wall, a top wall or a bottom wall of the source chamber. In other words, the term is not to be understood as restrictive.

The at least one mirror of the end effector can also be linearly displaceable along the axis of rotation. This further increases the flexibility of the displaceability of the end effector mirror.

In general, the end effector has at least one displaceable beam guiding element.

The mirror can in particular at a rotation speed of more than 100 revolutions per minute (rpm), in particular more than 200 rpm, in particular more than 300 rpm, in particular more than 500 rpm, in particular more than 1000 rpm min be rotatable around the axis of rotation.

The number of laser pulses per surface area is also determined via the speed of rotation. As a result, the removal can be adapted to different thicknesses of the contamination layer. Adjusting the speed of rotation enables, in particular, the targeted removal of thicker and thinner layers of contamination (thick layer - low rotation speed, thin layer - high rotation speed).

The mirror can in particular be operated via a stepper motor, micro-stepper motor, DC motor or piezo drive. Sliding contacts can be provided for power transmission.

In particular, the device enables a plasma radiation source to be cleaned in situ, that is to say while it is installed in a radiation source module, in particular in an illumination system of a mask inspection system or a projection exposure system.

The radiation source is in particular a plasma radiation source, for example an EUV radiation source or a radiation source for generating X-rays, in particular soft X-rays (so-called soft X-ray radiation source). In particular, it can be a radiation source for a projection exposure system or a mask inspection system or a metrology system or an EUV microscope. It can also be a radiation source for an X-ray microscope, in particular for a water window microscope with a wavelength range between 2.4 nm and 4.4 nm.

The device also comprises an outer optic, which is preferably arranged outside the radiation source module, and a Coupling device for coupling the outer optics to the end effector.

According to a further aspect of the invention, the end effector has an element for detecting the position of the at least one displaceable mirror. The position of the mirror can in particular be recorded, in particular read out and evaluated, by means of one or more encoders. In particular, it is possible to detect a tilted position of the mirror by means of a first encoder and a rotational position of the mirror and thus the point of impact of the laser spot on the chamber wall by means of a second encoder.

This enables the mirror position to be determined particularly quickly and precisely. This in turn enables a particularly fast and precise detection of the guidance of the machining beam. The positioning accuracy of the processing beam on the inner wall of the source chamber is in particular better than 100 μm, in particular better than 50 μm.

According to a further aspect of the invention, the end effector has a partially transparent element for partially reflecting an adjustment beam. The partially permeable element can in particular be a coated window.

As will be explained in more detail below, the adjustment beam and the processing beam can have different wavelengths.

The partially transparent element has a high transmission with regard to the processing beam. The transmittance of the partially transparent element of the end effector is in particular at least 90%, in particular at least 95%, in particular at least 97%, in particular at least 99%, at the wavelength of the processing beam.

The degree of reflection of the partially transparent element for the wavelength of the adjustment beam is, for example, in the range from 0.5% to 10%, in particular in the range from 1% to 3%.

The partially transparent element is arranged on the input side on the end effector in the beam direction of the processing beam. This enables the relative alignment, in particular the relative angular position of the end effector to the adjustment beam and directly or indirectly to the processing beam, to be determined in a simple manner.

This further improves the precision of the beam guidance of the processing beam in the source chamber.

According to a further aspect of the invention, the device has a device for detecting process lighting.

This makes it possible to monitor the cleaning process.

This aspect can also be advantageous regardless of the details of the end effector. It can represent an independent invention. In particular, independently of the details of the end effector, it can form the core of a claim directed to the cleaning device.

The invention also relates to a device for cleaning a plasma radiation source in a radiation source module of a projection exposure system with a device for detecting process lighting.

According to a further aspect of the invention, the device for detecting or evaluating a process light is part of the external optics, which are arranged outside the radiation source module.

According to a further aspect of the invention, the device for monitoring the cleaning process has at least one filter for selecting a wavelength range and at least one photodiode.

The spectrum of the process lighting provides information about the material removed. The spectrum can be evaluated either with a spectrometer or, in particularly advantageous arrangements, by selecting a wavelength band with grating, low-, band- and / or high-pass filters and a photodiode.

This makes it possible to collect large amounts of data at a time. For example, more than 10,000 recordings per second, in particular more than 20,000 recordings per second, in particular more than 30,000 recordings per second, in particular more than 50,000 recordings per second, in particular more than 100,000 recordings per second, are possible.

This enables a high spatial resolution of the process monitoring.

To monitor the cleaning process, the process light is guided from the processing surface along the same beam path as the processing beam, but in the opposite direction to this. The process lighting is guided in particular through the end effector, the coupling device and part of the external optics.

By correlating the detected process light with the position of the processing beam on the source chamber wall or the position of the displaceable mirror of the end effector, spatially resolved process monitoring is possible.

According to a further aspect of the invention, the process lighting is detected in a wavelength range which deviates from the wavelength of the processing beam and / or from the wavelength of the adjustment beam. The process glow can be detected in particular at a shorter wavelength.

The low-pass filter is at least partially permeable, in particular permeable, up to a limit wavelength λ _limit. In particular, it can have a limit wavelength λ _limit of, for example, 850 nm.

A partially transparent mirror, for example, can serve as the low-pass filter. The low-pass filter, in particular the partially transparent mirror, is arranged in particular in the beam path of the processing beam.

According to a further aspect of the invention, the monitoring device has two photodiodes. Here, one of the photodiodes can detect portions of the process lighting in the wavelength range above the cut-off wavelength λ _{limit of} the low-pass filter, the other of the photodiodes can detect the process lighting in the wavelength range below the cut-off wavelength λ _limit . The two components can be spatially separated from one another by means of a beam splitter, in particular a beam splitter cube.

According to a further aspect of the invention, the device for monitoring the cleaning process has an evaluation unit in which data recorded by the at least one photodiode of the monitoring device are coupled with position data of the displaceable mirror of the end effector.

For this purpose, the evaluation unit is in signal-transmitting connection with the at least one photodiode of the monitoring device. It is also in signal-transmitting connection with the element for detecting the position of the at least one displaceable mirror of the end effector.

This enables spatially resolved process monitoring.

According to a further aspect of the invention, the device has an adjustment device by means of which the precise alignment of the processing beam relative to the source chamber can be adjusted.

This aspect is also advantageous regardless of the details of the end effector and / or the details of the monitoring device. In particular, it can independently form the core of a corresponding claim. The invention thus also relates to a device for cleaning a plasma radiation source in a radiation source module of a mask inspection system or a projection exposure system with a laser radiation source for generating a processing beam and an adjustment device by means of which the precise alignment of the processing beam relative to the source chamber can be adjusted.

The adjustment of the alignment of the processing beam relative to the source chamber can in particular take place in an automated manner.

According to one aspect of the invention, the adjustment device relates to an adjustment laser. In particular, the alignment laser has a wavelength which differs from that of the machining laser. The wavelength of the adjustment beam can in particular be smaller than the wavelength of the machining beam. In particular, it can be at least 10 nm, in particular at least 20 nm, in particular at least 50 nm less than that of the processing beam. For example, a laser with a wavelength of 975 nm or more can serve as the alignment laser. The alignment laser has, in particular, a wavelength which does not overlap with that of the alignment laser, in particular which is separated from this area.

According to a further aspect of the invention, the adjustment wavelength differs by at least 5% from the machining wavelength.

According to an alternative, the adjustment laser can be dispensed with if the adjustment takes place separately from the actual cleaning process. The processing laser can also be used for adjustment, preferably with a low radiation intensity.

The alignment laser generates a back reflection on the reflective coated window on the end effector. This back reflection is directed back in the beam path, directed to the position photodiode, the position is detected and evaluated and the adjustment of the tilting mirror is changed. This is repeated iteratively until the back reflection on the position photodiode assumes a desired position.

The adjustment device can have a beam splitter, in particular a beam splitter cube.

The adjustment device can have a position photodiode, in particular a lateral photodiode, in particular a four-quadrant diode. It can also have a camera, in particular a CCD camera.

The adjustment device has in particular a displaceable, in particular a tiltable, optical element, in particular in the form of a beam guiding element, in particular in the form of a deflecting mirror.

To adjust the device, this displaceable element, in particular the deflection mirror, can be displaced until an incident beam and an emergent beam overlap, in particular have the same center of gravity, in particular have a concentric, in particular congruent beam cross-section. The displaceable element can in particular be displaced until the emerging beam assumes a previously adjusted target position.

The adjustment device has, in particular, a control unit which is connected in a signal-transmitting manner to the displacement mechanism of the displaceable element.

The displaceable element can in particular form the last optical element, in particular the last mirror in the beam path of the processing and / or adjustment beam in front of the end effector.

The adjustment beam reflected by the displaceable element, in particular by the displaceable deflecting mirror, hits the partially transparent window arranged on the input side of the end effector next, from which it is at least partially reflected and returned to the deflecting mirror.

The displaceable deflection mirror of the adjustment device can in particular have a piezoelectric drive, a stepper motor or a micro-stepper motor. In particular, it can be moved very precisely. The displacement of the deflecting mirror can in particular have a resolution of, for example, 1.5 μrad / step.

The deflection mirror can have an adjustment range in the range from 1 ° to 10 °, in particular in the range from 2 ° to 5 °, for example from 3 ° to 4 °.

The displaceable deflecting mirror of the adjustment device can be part of the coupling device. It can also be part of the external appearance.

The adjustment device can have a further deflecting mirror. This can be designed or arranged to be fixed or also displaceable.

Another deflection mirror opens up a further degree of freedom for adjusting the adjustment beam and / or the processing beam.

This makes it possible to separate the processing beam and the adjustment beam from one another by means of a low-pass filter, in particular in the form of a partially transparent mirror.

According to a further aspect of the invention, the processing beam can be focused by means of one or more focusing optics on a spot size with a diameter in the range from 10 μm to 100 μm, in particular in the range from 20 μm to 50 μm, for example approximately 30 μm. The outer optics can in particular have a focusing unit for focusing the machining beam. The focusing unit can have a plurality of lenses and / or lens groups. The lenses and / or lens groups can in particular be displaceable relative to one another in the direction of the machining beam.

The focus of the processing beam can be tracked by means of the focusing unit. In particular, it can be controlled in such a way that it lies within predetermined tolerances in the area of the swelling chamber wall. In this way it can be achieved in particular that the processing beam leads to a spot size in the area of the source chamber wall which has at most a maximum predetermined diameter.

According to a further aspect of the invention, the laser radiation source of the processing laser has a pulsed infrared fiber laser with an output power of at least 20 W, in particular at least 50 W, in particular at least 70 W. The beam quality in particular has a K factor of at least 0.4, in particular at least 0.5, in particular at least 0.55, in particular at least 0.57. Other values are also possible.

The processing laser can in particular have a processing wavelength of more than 1000 nm, in particular more than 1050 nm.

The processing laser can in particular be operated in a pulsed manner. The pulse frequency is in particular at least 100 kHz, in particular at least 200 kHz, in particular approximately 400 kHz.

A positioning of the focus on the corresponding area in the beam path is necessary due to the installation space specifications.

According to a further aspect of the invention, the cleaning device comprises a suction device for suctioning off contaminants from the source chamber.

It preferably has a suction capacity greater than 100 m ³ / h with a vacuum of 100 mbar, in particular greater than 150 m ³ / h with a vacuum of 200 mbar. A targeted distribution of the suction over the processing area is possible.

Another object of the invention is to develop a method for cleaning a plasma radiation source, in particular to improve it.

• - Bereitstellen einer Plasma-Strahlungsquelle in einem Beleuchtungssystem einer Projektionsbelichtungsanlage/oder eines Maskeninspektionssystems,
• - Bereitstellen einer Vorrichtung zur Reinigung der Plasma-Strahlungsquelle mittels eines Bearbeitungsstrahls,
• - Beaufschlagen eines vorbestimmten Bereichs einer Quellkammer der Plasma-Strahlungsquelle mit dem Bearbeitungsstrahl,
• - wobei der Bearbeitungsstrahl mittels eines Endeffektors mit mindestens einem verlagerbaren Spiegel zu bestimmten Bereichen der Quellkammer geführt wird.

This task is solved by a method with the following steps:

• - Provision of a plasma radiation source in an illumination system of a projection exposure system / or a mask inspection system,
• - Provision of a device for cleaning the plasma radiation source by means of a processing beam,
• - exposure of a predetermined area of a source chamber of the plasma radiation source with the processing beam,
• - wherein the processing beam is guided to certain areas of the source chamber by means of an end effector with at least one displaceable mirror.

The method is used in particular to clean a plasma radiation source in situ, that is to say in the installed state in an illumination system of a projection exposure system or a mask inspection device.

The process is also suitable for cleaning other sources of radiation that are subject to operational contamination.

The cleaning device is in particular a cleaning device according to the preceding description.

The advantages result from those already described.

With the aid of the cleaning device according to the invention, in particular, very precise and thorough cleaning of the source chamber of the EUV radiation chamber is possible. It has been found that the source chamber can be cleaned in less than an hour. With the aid of the cleaning device according to the invention or the cleaning method according to the invention, the downtime of the radiation source is thus considerably reduced.

According to one aspect of the invention, the cleaning is monitored by detecting and evaluating a process light. For details, reference is made to the previous description of the monitoring device.

The monitoring takes place in particular with a high clock frequency. The recording rate of the process lighting is in particular at least 10 kHz, in particular at least 20 kHz, in particular at least 30 kHz, in particular at least 50 kHz, in particular at least 100 kHz.

According to one aspect of the invention, the alignment of the cleaning device for cleaning the plasma radiation source is adjusted relative to the latter, in particular adjusted automatically. In particular, it can be adjusted before the start of the cleaning process and / or at predetermined intervals during the cleaning process, in particular continuously.

Further objects of the invention consist in improving a radiation source module for a projection exposure system or for a mask inspection tool, in particular with regard to its service life. Further objects of the invention consist in improving an illumination system for a mask inspection tool or a projection exposure system and a mask inspection tool or a projection exposure system.

These objects are each achieved by a radiation source module, an illumination system and a projection exposure system with a cleaning device according to the preceding description.

The advantages result from those of the cleaning device.

The radiation source is in particular a plasma radiation source, in particular an EUV radiation source.

The use of the cleaning device according to the invention makes it possible to clean the source chamber of the radiation source between the exposure of two wafers or between the inspection of two masks, in particular in situ.

This significantly reduces the time required to clean the source chamber.

It should be explicitly made clear again at this point that the present invention has a plurality of aspects, which independently of one another or in combination with one or more of the other aspects can form the subject of a claim. In particular, the aspects of the end effector, the aspects of the device for monitoring the cleaning process and the aspects of the adjustment device lead to advantages independently of one another and / or in combination with one another.

• 1 schematisch in einem Meridionalschnitt eine Projektionsbelichtungsanlage für die Mikrolithographie,
• 2 einen schematischen Schnitt durch eine Quellkammer einer EUV -S trahlungsquelle,
• 3 eine schematische Ansicht auf eine Bodenplatte der Quellkammer gemäß 2 entlang der Linie III-III,
• 4 schematisch einen Schnitt durch einen Quellkopf einer EUV-Strahlungsquelle oder eine in die Quellkammer eingebrachte Reinigungsvorrichtung,
• 5 exemplarisch die Anordnung der Bestandteile einer Reinigungsvorrichtung an einer EUV-Strahlungsquelle in einem Strahlungsquellen-Modul einer Projektionsbelichtungsanlage,
• 6 schematisch Ausschnitte aus den Strahlengängen in der Reinigungsvorrichtung gemäß 5 mit schematischer Darstellung einer Auswahl von optischen Bauelementen der Reinigungsvorrichtung,
• 7 schematisch Bestandteile einer Justage-Vorrichtung, welche einen Bestandteil der Reinigungsvorrichtung bildet ohne die übrigen Bestandteile der Reinigungsvorrichtung,
• 8 schematisch Bestandteile einer Überwachungs-Einrichtung, welche einen Bestandteil der Reinigungsvorrichtung bildet ohne die übrigen Bestandteile der Reinigungsvorrichtung
• 9 schematisch einen Schnitt durch einen Endeffektor welcher durch eine zentrale Bohrung in die Quellkammer eingeführt werden kann,
• 10 schematisch einen Schnitt durch die Quellkammer mit in diese eingeführten Endeffektor und
• 11 schematisch einen Verfahrensablauf eines Verfahrens zur Reinigung einer Quellkammer einer EUV-Strahlungsquelle.

Further details and advantages of the invention emerge from the description of exemplary embodiments on the basis of the figures. Show it:

• 1 schematically in a meridional section a projection exposure system for microlithography,
• 2 a schematic section through a source chamber of an EUV radiation source,
• 3 a schematic view of a base plate of the source chamber according to 2 along the line III-III,
• 4th schematically a section through a source head of an EUV radiation source or a cleaning device introduced into the source chamber,
• 5 an example of the arrangement of the components of a cleaning device on an EUV radiation source in a radiation source module of a projection exposure system,
• 6th schematically sections from the beam paths in the cleaning device according to FIG 5 with a schematic representation of a selection of optical components of the cleaning device,
• 7th schematically components of an adjustment device, which forms a component of the cleaning device without the other components of the cleaning device,
• 8th schematically, components of a monitoring device which forms a component of the cleaning device without the other components of the cleaning device
• 9 schematically a section through an end effector which can be introduced into the source chamber through a central bore,
• 10 schematically a section through the source chamber with the end effector introduced into it and
• 11 schematically a process sequence of a method for cleaning a source chamber of an EUV radiation source.

1 shows a schematic example of a projection exposure apparatus in a meridional section 13th for microlithography. A lighting system 1 the projection exposure system 13th has in addition to a plasma radiation source, in particular in the form of an EUV radiation source 21 an illumination optics 2 for exposing an object field 3 in one object level 4th . Here, a is exposed in the object field 3 arranged and in the 1 Reticle, not shown, the one with the projection exposure system 13th carries the structure to be projected for the production of micro- or nano-structured semiconductor components. A projection lens 5 serves to map the object field 3 in an image field 6th in one image plane 7th . The structure on the reticle is imaged on a light-sensitive layer in the area of the image field 6th in the image plane 7th arranged wafer, which is not shown in the drawing.

As an EUV radiation source 21 a plasma source is used, which is used in the operation of the projection exposure system 13th Usable radiation in the form of EUV radiation 8th emitted. The EUV radiation 8th is from a collector 9 bundled. A corresponding collector is for example from the EP 1 225 481 A known. After the collector 9 propagates EUV radiation 108 through an intermediate focus plane 10 before looking at a field facet mirror 11 meets. The field facet mirror 11 is in one plane of the lighting optics 2 arranged to the object plane 4th is optically conjugated. According to the field facet mirror 11 becomes the EUV radiation 8th from a pupil facet mirror 12th reflected. The pupil facet mirror 12th is in one plane of the lighting optics 2 arranged to a pupil plane of the projection optics 5 is optically conjugated. With the help of the pupil facet mirror 12th and an imaging optical assembly in the form of transmission optics with in the order of the beam path for the EUV radiation 8th designated mirrors 14th , 15th and 16 become field facets of the field facet mirror 11 superimposed in the object field 3 pictured. The transmission optics are used together with the pupil facet mirror 12th also as follow-up optics for transferring EUV radiation 8th from the field facet mirror 11 towards the object field 3 designated.

The lighting system 1 is via a vacuum pump 17th evacuable.

The design of the projection exposure system described here 100 is to be understood as purely exemplary and not restrictive. Alternatively, other configurations of a projection exposure system, an illumination system and / or illumination optics can also be used.

The plasma radiation source can also be one for a mask inspection tool not shown in the figures.

In the following, with reference to the 2 and 3 the EUV radiation source 21 (Plasma radiation source) described in more detail.

The EUV radiation source 21 includes the source chamber 22nd . The source chamber 22nd is through a chamber wall 23 limited. The chamber wall 23 includes a top wall, lid 24 and a bottom wall, bottom plate 25th . The chamber wall 23 is made of an electrically conductive material, in particular copper, in particular aluminum, in particular an alloy of the metals mentioned, made of a copper compound, in particular of CDA 110 , manufactured.

The source chamber 22nd is substantially cylindrical with a cylinder axis perpendicular to the bottom plate 25th runs. The bottom plate 25th is circular and can, for example, have a diameter of 250 mm. An expansion of the source chamber 22nd perpendicular to the base plate 25th can for example be 120 mm.

The EUV radiation source 21 is part of the projection exposure system 13th or a mask inspection system. In particular, it is part of the lighting system 1 . In the exemplary embodiment shown here, the EUV radiation source is in the projection exposure system 13th integrated.

Access to the EUV radiation source 21 is limited. However, the installation allows access to the EUV radiation source, albeit limited 21 over the base plate 25th . The bottom plate 25th has several openings for this purpose. The openings can be used for maintenance purposes and, as will be explained later, for cleaning purposes.

In 3 is a plan view of an exemplary floor panel 25th the source chamber 22nd according to 2 shown. The bottom plate 25th has three openings 26th and a central opening 27 on. The openings 26th , 27 are as holes in the base plate 25th executed. The openings 26th are equidistant from the central opening 27 arranged. The openings 26th , 27 can operate the EUV radiation source 21 serve as flow openings for source plasma. At least when the EUV radiation source is in operation 21 can the central opening 27 also contain a central part, for example in the form of a ladder tube. The central opening 27 is therefore usually occupied. The cleaning of the source chamber 22nd can through the eccentric openings 26th respectively. It is also possible to use the central opening for cleaning 27 perform. For example, after removing the contents, cleaning can take place through the central opening. When cleaning by means of a laser beam, cleaning is ensured through the central opening 27 better coverage of the chamber wall 23 the source chamber 22nd .

During operation of the EUV radiation source 21 is in the source chamber 22nd the source plasma is generated. For this purpose, a process gas is passed through a in the 2 Plasma generating device (not shown) is ionized to form the source plasma and excited to emit useful radiation in the EUV range. The process gas is supplied via a mass flow controller and a feed line to the source chamber 22nd .

When operating the EUV radiation source 21 Debris may build up in the source chamber 22nd come. The debris can be particularly on an inner surface 28 the chamber wall 23 in the form of a contamination layer 29 deposit. The contamination layer 29 grows with the number of operating hours of the EUV radiation source 21 . The contamination layer 29 poses a functional risk for the EUV radiation source 21 To ensure safe and precise operation of the EUV radiation source 21 to ensure the source chamber 22nd from the contamination layer 29 getting cleaned.

The contamination layer 29 may for example comprise tin or other materials deposited by the operation of the plasma source. The cleaning of the source chamber 22nd from the contamination layer 29 should preferably take place in such a way that the contamination layer without damaging the chamber wall below 23 is removed.

What is known is the source chamber 22nd to be cleaned by the EUV radiation source 21 from the projection exposure system 13th is removed and disassembled into individual parts. However, this is only possible with a large expenditure of time. The productivity of the projection exposure system 100 and thus the throughput of the semiconductor components to be manufactured are considerably reduced as a result. It is therefore beneficial when cleaning the source chamber 22nd is made in situ, ie without the EUV radiation source 21 must be removed from the projection exposure system and / or dismantled.

In the following, a system is made up of the EUV radiation source 21 and a cleaning module for in situ cleaning of the source chamber 22nd described. The cleaning module can be used in particular to clean the inner surface 28 the chamber wall 23 through the openings 26th , 27 possible. The cleaning process enables the source chamber to be cleaned 22nd without the inner surface 28 the chamber wall 23 to damage. The cleaning process enables in situ cleaning of the source chamber 22nd through an opening in the source chamber 22nd .

The following are general details of a cleaning procedure for cleaning the EUV radiation source 21 described. For further details please refer to the example DE 10 2017 212 351 A1 referenced, which is hereby fully integrated into the present application.

The process described below is a laser cleaning process 108 . In the laser cleaning process 108 becomes the contamination layer 29 on the inner surface 28 the chamber wall 23 removed with the help of laser radiation. The laser cleaning process 108 in particular uses a targeted laser ablation of the contamination on the inner surface 28 the chamber wall 23 the source chamber 22nd to remove the contamination layer 29 . For this purpose, as described in more detail below, laser radiation is specifically focused on the contamination. It also removes the ablated contamination from the source chamber 22nd sucked off.

For the cleaning are first in a preparation step 109 the lighting system 1 the projection exposure system 13th provided with the cleaning module described in more detail below.

The cleaning process can be a pre-cleaning 110 and / or post-cleaning 111 include. The pre-cleaning 110 and / or post-cleaning 111 are carried out in particular with XCDA. For this purpose, there is a radiation step in each case 112 provided in which the inner surface 28 the chamber wall 23 is blasted with compressed air. Before and / or during and / or after the blasting step 112 can be a suction step 113 connect, in which the source chamber 22nd is sucked off. The pre-cleaning 110 can have a suction step 113 before and one during and one after the blasting step 112 include. With a subsequent cleaning 111 becomes the suction step 113 preferably only after the blasting step 112 carried out. The suction step 113 is particularly suitable for removing by means of the compressed air in the blasting step 112 radiated particles from the source chamber 22nd . A suction step is preferably performed during the blasting step 112 carried out.

To carry out the pre-cleaning 110 and / or post-cleaning 111 the cleaning module comprises a compressed air generator and compressed air nozzles. The compressed air generator is connected to one of the openings 26th , 27 can be coupled, in particular coupled in such a way that the respective opening 26th , 27 can be acted upon with compressed air.

After pre-cleaning 110 is in a control step 114 the degree of soiling of the source chamber 22nd determined.

After pre-cleaning 110 and the control step 114 is in one ablation step 115 electromagnetic energy in the form of laser radiation pulses targeted at the inner surface 28 the source chamber 22nd , especially on the source chamber 22nd limiting chamber wall 23 irradiated. For this purpose, the laser radiation pulses are transmitted by a processing laser 36 generated and by means of a beam manipulator, which is hereinafter referred to as the end effector 32 is referred to, spatially targeted on the inner surface 28 irradiated.

A direction of incidence of the laser radiation pulses can be set by means of the beam manipulator, so that during the ablation step 115 the entire inner surface 28 the chamber wall 23 is scanned by the laser radiation pulses. This ensures thorough cleaning.

There is also a removal step 116 intended. In the distance step 116 contaminations are detached from the source chamber due to the radiation of the laser light pulses 22nd through at least one of the openings 26th , 27 away. The removal step 116 takes place by suctioning off the source chamber 22nd . In the event that the impurities detached by the laser radiation pulses are sublimed, the detached particles do not interfere with subsequent laser radiation pulses. The suction prevents disturbances. The removal step 116 can therefore after the ablation step 115 be performed. In an alternative embodiment, the removing step 116 at the same time as the ablation step 115 carried out. This ensures that non-sublimated particles detached by the irradiation of the laser radiation pulses do not scatter or absorb subsequent laser radiation pulses, which would adversely affect the cleaning process.

Using the ablation step 115 can be a cleaning of the source chamber 22nd take place in less than 120 minutes, in particular less than 90 minutes, in particular in about 60 minutes.

The ablation step 115 and the removal step 116 close the post-cleaning 111 and then another control step 114 at.

In the following, with reference to the 5 to 10 further details of a cleaning device 33 for in situ cleaning of the EUV radiation source 21 , especially their source chamber 22nd described.

In the 5 is a schematic of a possible arrangement of the components of the cleaning device 33 shown on an illumination system of a projection exposure system, the Components of the radiation source are not explicitly shown for reasons of clarity. In particular, a frame is shown 34 a service chamber 35 a source head 36 the radiation source 21 (please refer 4th ). The service chamber 35 is with a lid 37 lockable. By opening the lid 37 can access the service chamber 35 getting produced.

The source chamber 22nd includes according to the in 4th shown variant an upper chamber 22 ₁ and a lower chamber 22 ₂ .

The source head 36 is safe, but preferably releasable, with a frame of the radiation source 21 and / or the lighting system 1 connected. This enables a precise arrangement of the swelling head 36 and thus the radiation source 21 to the other components of the lighting system 1 be ensured.

The cleaning device 33 includes the machining laser 31 . By means of the processing laser 31 is a machining beam 38 producible.

As a processing laser 31 In particular, an infrared laser, in particular an infrared fiber laser, can be used. The processing laser 31 is preferably operated in a pulsed manner. For example, it can have a pulse frequency of 400 kHz. By varying the pulse frequency, the selectivity of the contamination to be removed from the base material can be adjusted; for example, at a lower frequency, more energy is introduced and, as a result, more base material is removed. The high frequency of 400 kHz preferably removes contamination, for example SiC. In the case of homogeneous and / or particularly thick contamination, a lower frequency is also expedient.

The processing laser 31 preferably has an output power of at least 30 W, in particular at least 50 W, in particular at least 70 W. It can also have a lower output power, in which case the cleaning takes longer.

The processing radiation 38 has a wavelength of more than 850 nm, in particular more than 900 nm, in particular more than 1000 nm. The wavelength λ _Bearb can be 1064 nm, for example.

The processing laser 31 has a high beam quality. The diffraction index M ^{2 of} the processing beam 38 is preferably less than 1.7. The machining beam 38 in particular has a K factor of at least 0.5, in particular at least 0.55, in particular at least 0.6.

The cleaning device 33 includes an external appearance 39 . The external look 39 is outside the radiation source module, in particular outside the lighting system 1 , arranged. It can also be arranged within the beam source module.

The external look 39 includes, among other things, optical elements for shaping and / or focusing the machining beam 38 .

The external look 39 preferably comprises optical elements of an adjustment device 40 .

The external look 39 comprises in particular optical components of a device 41 for monitoring the cleaning process.

The external look 39 includes a low pass filter 42 .

The low pass filter 42 is in the beam path of the machining beam 38 arranged.

The low pass filter 42 has a cutoff wavelength which is lower than the wavelength of the machining beam 38 . The cutoff wavelength of the low pass filter 42 is greater than a wavelength λ _{adjustment of} an alignment laser 43 . The alignment laser 43 is part of the adjustment device 40 .

The low pass filter 42 is designed in particular as a partially transparent mirror. It reflects radiation with a wavelength which is greater than the cutoff wavelength. For wavelengths which are smaller than the cutoff wavelength, it is at least partially transparent.

The low pass filter 42 is used in particular to couple and uncouple the alignment laser 43 emitted adjustment radiation 45 into the beam path of the machining radiation 38 .

The external look 39 has a second low pass filter 44 on.

As a low pass filter 44 A partially transparent mirror also serves in particular. The cutoff wavelength of the low pass filter 44 is lower than that of the low pass filter 42 . The cutoff wavelength of the low pass filter 44 is in particular less than the wavelength of the alignment laser 43 . Thus, both the machining beam 38 as well as one from the alignment laser 43 emitted adjustment beam 45 from the low pass filter 44 reflected.

The cutoff wavelength of the low pass filter 44 lies in particular in the red range that is barely visible or in the near infrared range. It can be, for example, 850 nm.

The low pass filter 44 is at least partially transparent in particular for wavelengths that are generated during process lighting, in particular for light in the visible range. For wavelengths less than 850 nm, it has, in particular, a transmittance of at least 70%, in particular at least 90%, in particular at least 95%.

The low pass filter 44 serves in particular to separate, in particular to decouple, radiation generated during process lighting, which is directed in the opposite direction to the processing beam 38 through the cleaning device 33 spreads.

The external look 39 includes a facility 46 for focusing the processing beam 38 . With the help of the focusing device 46 can in particular focus the machining beam 38 be tracked.

The focusing device 46 includes a plurality of lenses 47 and / or lens groups.

The focusing device 46 includes in particular lenses 47 and / or lens groups, which relative to one another in the direction of the machining beam 38 are relocatable.

The cleaning device 33 also has a coupling device 48 for coupling the external optics 39 to the end effector 32 on.

The coupling device 48 can in the service chamber 35 to be ordered.

The coupling device 48 is especially in the evacuable area of the lighting system 1 arranged.

The coupling device 48 comprises focusing optics, in particular relay optics 49 . The relay optics 49 is used for mapping from one intermediate focus to the next in order to extend the length of the tube.

The coupling device 48 comprises a first deflecting mirror 50 and a second deflecting mirror 51 .

The second deflection mirror 51 is relocatable. In particular, it is designed to be tiltable. The second deflection mirror 51 is in particular tiltable piezoelectrically. Other adjustment mechanisms are also possible.

The second deflection mirror 51 can in particular be displaced very precisely. The resolution of the piezoelectric displaceability of the second deflecting mirror 51 is, for example, 1.5 µrad / step.

The second deflection mirror 51 can have an adjustment range of 4 °.

The second deflection mirror 51 can be part of the adjustment device 40 form.

The second deflection mirror 51 in particular forms the last mirror in the beam path of the machining beam 38 before the end effector 32 .

With the help of the second deflection mirror 51 can determine the exact alignment of the machining beam 39 relative to the end effector 32 influenced, in particular controlled, preferably regulated.

The displaceability of the second deflection mirror 51 is in particular via a control unit, not shown in the figures, of the adjustment device 40 controllable.

The first deflection mirror 50 can be fixed in the coupling device 48 be arranged. According to an alternative, there is also the first deflection mirror 50 displaceable, in particular tiltable, in particular arranged piezoelectrically tiltable.

The end effector 32 has a window on the entrance side 52 on. In general, the window forms a partially permeable element. In particular, it serves to partially reflect the adjustment beam 45 . In particular, it has a degree of _{reflection at the wavelength λ adjustment of the adjustment beam} 45 of approx. 1%.

The window 52 is preferably for the wavelength λ _{Mach of} the machining beam 38 permeable. In particular, it has a degree of transmission for the wavelength λ _{Mach of} the processing beam 38 of at least 90%, in particular at least 95%, in particular at least 97%, in particular at least 99%.

The end effector 32 has a focusing optics 53 on.

Also, the end effector instructs 32 at least one mirror 54 on which one is perpendicular to a mirror normal 55 running tilt axis 56 tiltable, on the other hand about a perpendicular to the tilt axis 56 running axis of rotation 57 is rotatable.

In the 6th is also an example of the one on the chamber wall 23 generated spot 58 of the machining beam 38 shown. The spot 58 preferably has a largest diameter of at most 200 μm, in particular at most 100 μm, in particular at most 50 μm, in particular at most 30 µm. This leads to a particularly high radiation intensity of the machining beam 38 in the area of the chamber wall 23 .

Like in the 6th is also shown by way of example, comprises the cleaning device 33 a suction device 59 for suction of the detached contaminants from the source chamber 22nd .

The suction device 59 in particular has one or more suction lines 60 on, by means of which, for example, through the openings 26th Contamination from the source chamber 22nd are aspirated.

The suction lines 60 are in the vacuum area of the lighting system 1 arranged.

As part of 34 is a connection 61 for connecting a vacuum generator 62 to the suction lines 60 intended.

Further details of the adjustment device are given below 40 described.

The adjustment device 40 serves to adjust the processing beam 38 relative to the end effector 32 . With the help of the adjustment device 40 In particular, it can be ensured that the machining beam 38 A precise alignment to the end effector within specified tolerances 32 , especially towards the window 52 of the end effector 32 , having.

The adjustment device 40 can in particular comprise a control unit, not shown in the figures, by means of which the adjustment of the alignment of the machining beam 38 can be controlled in an automated manner, in particular regulated.

For adjusting the alignment of the processing beam 38 is used in particular by the window 52 reflected portion of the adjustment beam 45 .

By means of the adjustment device 40 can in particular the position or orientation of the window 52 reflected portion of the adjustment beam 45 evaluated or monitored. Depending on this, the second deflecting mirror can 51 be displaced, in particular tilted, in such a way that the incident adjustment beam 45 and the one at the window 52 reflected portion of the same in the area of the second deflection mirror 51 overlap. The positioning of the second deflection mirror 51 can in particular be controlled, in particular regulated, in such a way that the incident and the one at the window 52 reflected beam in the area of the second deflecting mirror 51 Have beam cross-sections such that the smaller of the beam cross-sections lies completely within the larger beam cross-section. The beam cross-sections can in particular have identical centroids.

For evaluating the reflected portion of the adjustment beam 45 has the adjustment device 40 a photodiode 63 on. As a photodiode 63 A lateral photodiode, in particular a four-quadrant diode, is used in particular. Instead of the photodiode 63 a camera can also be provided.

The adjustment device 40 also includes a lens 64 for focusing the reflected part of the adjustment beam 45 on the photodiode 63 .

The adjustment device 40 also includes a beam splitter cube 67 to separate the outgoing and the reflected part of the adjustment beam 45 .

The adjustment device also includes 40 two deflection mirrors 65 , 66 for redirecting the adjustment beam 45 .

The low pass filter 42 , which is in the beam path of the machining beam 38 is arranged, can also be part of the adjustment device 40 be considered.

The second deflection mirror 51 can also be used as part of the adjustment device 40 be considered.

The focusing device 46 can also be part of the adjustment device 40 form. In particular, it can be used in a signal-transmitting manner with the control unit of the adjustment device 40 be connected. As an alternative or in addition to this, it can be used in a signal-transmitting manner with an element for detecting the position of the mirror 54 of the end effector 32 be connected.

The following are details of the monitoring device 41 described. The monitoring device 41 is used to record and evaluate a process light generated during the cleaning process.

The same beam path is used for coupling out the process lighting as for coupling in the processing beam 38 into the source chamber 22nd .

The process lighting is via the low-pass filter 44 from the beam path of the machining beam 38 decoupled. After the low pass filter 44 the radiation generated during process lighting is achieved by means of a beam splitter, in particular in the form of a beam splitter cube 67 , divided into a long-wave and a short-wave part. The beam splitter cube 67 can in particular have the same cut-off wavelength as the low-pass filter 44 . It is also possible to arrange a spectrometer directly behind the beam splitter.

Two photodiodes are used to record the process lighting 68 , 69 .

The monitoring device also includes 41 two lenses 70 , 71 , by means of which the process lighting on the photodiodes 68 , 69 is focusable.

Furthermore are in front of the photodiodes 68 , 69 Spectral filter, especially a short pass filter 72 or a long pass filter 73 arranged.

Via the short pass filter 72 and the photodiode 68 the evaluation of the process lighting takes place.

Via the long pass filter 73 and the photodiode 69 the lighting of the processing laser can be monitored.

By the arrangement of the filters 72 , 73 and the diodes 68 , 69 large amounts of data can be recorded at a time. In particular, recording rates of at least 10 kHz, in particular at least 20 kHz, in particular at least 30 kHz, in particular at least 50 kHz, in particular at least 100 kHz are possible. This enables even with a very rapid displacement of the mirror 54 a high spatial resolution of the process monitoring. The cleaning process can in particular be monitored with a positioning accuracy of better than 100 μm, in particular better than 50 μm.

The following are details of the end effector 32 described.

The end effector 32 forms part of a beam manipulator for the targeted introduction of the machining beam 38 into the source chamber 22nd the EUV radiation source 21 , especially for guiding the machining beam 38 inside the source chamber 22nd , especially for guiding the machining beam 38 on predetermined areas of the inner surface 28 the chamber wall 23 the source chamber 22nd .

By means of the end effector 32 is the machining beam 38 despite the difficult accessibility of the source chamber 22nd can be introduced precisely into this and, in particular, within the same, specifically to predetermined areas of the inner surface 28 the chamber wall 23 manageable. Here the mirror can 54 are shifted in such a way that at least 90%, in particular at least 95%, in particular at least 97%, in particular at least 99%, in particular the entire inner surface 28 the source chamber 22nd with the machining beam 38 is scannable.

For the arrangement of the end effector 32 at the source chamber 22nd instructs the end effector 32 a fastening ring 81 on.

The end effector 32 includes the tiltable and rotatable mirror 54 .

The mirror 54 can also be in the direction of the axis of rotation 57 be shifted linearly. The speed of the laser beam on the chamber wall can be up to 12 m / s. The mirror 54 can for this purpose with a rotation speed of up to 10 revolutions per second, in particular up to 20 revolutions per second, in particular 30 revolutions per second around the axis of rotation 57 be rotated.

To detect the position of the mirror 54 two encoders 74 ₁ , 74 _{2 are} provided. With the help of the first encoder 74 ₁ , the mirror is tilted 54 detectable. The rotational position of the mirror is determined by means of the second encoder 74 ₂ 54 detectable.

To rotate the mirror 54 around the axis of rotation 57 is a gear drive 75 with two interlocking gears 76 , 77 intended. This enables a very precisely adjustable and rapid rotation of the mirror 54 .

The end effector 32 has two sliding contacts 78 , 79 for power transmission to an actuator 80 for tilting the mirror 54 on.

The end effector 32 can be purposefully purged with gas, preferably N ₂ , CDA or XCDA. A flushing line, not shown in the figures, can be provided for this purpose. The flushing line can be through the central opening 27 in the base plate 25th into the source chamber 22nd be introduced. You can also use one of the openings 26th into the source chamber 22nd be led.

In the following, further details of the invention are described in key words.

The external look 39 comprises optical elements for shaping and / or focusing the processing beam 38 . The external look 39 can in particular have one or more lens packages. These can be arranged on a linear axis. In particular, they enable focus tracking, in particular with high positioning accuracy. The focus tracking can be adjusted to the position of the mirror 54 be coupled. The position of the mirror 54 can be determined in particular via the two encoders 74 ₁ , 74 ₂ .

The focus tracking can also be controlled depending on the result of the process observation.

The external look 39 also includes components of the adjustment device 40 .

The external look 39 also includes components of the monitoring device 41 . The monitoring device 41 can in particular completely outside the vacuum range of the lighting system 1 be arranged.

In the area between the low pass filter 42 and the window 52 run the machining beam 38 and the adjustment beam 45 parallel.

For adjusting the processing beam 38 relative to the end effector 32 can the second deflecting mirror 51 be shifted in a controlled manner, in particular regulated, that the on the window 52 incident adjustment beam 45 as well as possible with the one at the window 52 reflected portion of the adjustment beam 45 coincides. Because the reflected portion is essentially due to the entire optics of the cleaning device 33 is returned, the alignment of all functional units of the cleaning device 33 with the help of the adjustment device 40 monitored, in particular adjusted. In particular, the position of the reflected portion of the adjustment beam is used for this purpose 45 by means of the diode 63 monitored, especially evaluated. Instead of the photodiode 63 a camera can also be provided.

The photodiode 63 is connected in particular in a signal-transmitting manner to the control unit of the adjustment device.

The deflection mirror 50 , 51 the coupling device 48 are also known as deflection spiders. The deflection spider is used to correctly couple the machining beam 38 in the end effector 32 . With the help of the deflection spider it can be ensured that the angle error and / or the lateral offset of the machining beam 38 when coupling into the end effector 32 lie within a specified tolerance range. To adjust the lateral offset, a further adjustable, in particular actuatable, mirror can in particular be provided.

The tolerance range for the alignment of the machining beam 38 when coupling into the end effector 32 is in particular at most +/- 1.5 ° angle error and / or +/- 1.5 mm lateral offset.

The tolerance range can depend on the geometry of the radiation source 21 , especially the source chamber 22nd can be specified.

The projection exposure system is used to produce micro- or nano-structured components 13th provided. A reticle with structures to be imaged is then created in the object field 3 arranged. In addition, a wafer with a radiation-sensitive coating is in the image field 6th arranged. The structures of the reticle to be imaged are then imaged on the wafer with the aid of the projection exposure system. The source chamber can be used between the exposure of two wafers 22nd the radiation source 21 cleaned in situ.

The cleaning device according to the invention can advantageously also be used for cleaning a radiation source, in particular a plasma source, of a mask inspection system.

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• DE 102017212351 A1 [0003, 0105]
• EP 1225481 A [0090]

Claims (15)

Having a device (33) for cleaning a plasma radiation source (21) in a radiation source module of a projection exposure system or a mask inspection system (13) 1.1. a laser radiation source (31) for generating a machining beam (38) and 1.2. a device for the targeted guidance of the machining beam (38) onto predetermined areas of a wall (23, 24, 25) of a source chamber (22) of a plasma radiation source (21) 1.2.1. outer optics (39) for shaping and / or focusing the processing beam (38), 1.2.2. an end effector (32) for targeted guidance of the processing beam (38) within the radiation source module and 1.2.3. a coupling device (48) for coupling the outer optics (39) to the end effector (32), 1.3. wherein the end effector (32) has at least one mirror (54) which can be tilted on the one hand around a tilt axis (52) running perpendicular to a mirror normal (55) and on the other hand rotatable around a rotation axis (57) running perpendicular to the tilt axis (52). Device (33) according to Claim 1 , characterized in that the end effector (32) has at least one element (74 ₁ , 74 ₂ ) for detecting the position of the at least one displaceable mirror (54). Device (33) according to one of the preceding claims, characterized in that the end effector (32) has a partially transparent element (52) for partially reflecting an adjustment beam. Device (33) according to one of the preceding claims, characterized in that the device (33) has a device (41) for detecting process lighting. Device (33) according to Claim 4 , characterized in that the device (41) for detecting the process lighting has at least one filter (44) for selecting a wavelength range and at least one photodiode (68, 69). Device (33) according to one of the Claims 1 to 5 , characterized in that the device (41) for detecting the process lighting has an evaluation unit in which data recorded by the at least one photodiode (68, 69) are coupled with position data of the displaceable mirror (54) of the end effector (32). Device (33) according to one of the preceding claims, characterized in that the device (33) has an adjustment device (40) by means of which the precise alignment of the processing beam relative to the source chamber (22) can be adjusted. Device (33) according to Claim 7 , characterized in that the adjustment device (40) has at least one displaceable mirror (52) which is arranged in the beam path of the machining beam (38). Device (33) according to Claim 8 , characterized in that the adjustment device (40) has an adjustment laser (43) with an adjustment wavelength (λ _adjustment ) which differs from the wavelength of the processing beam (38). Device (33) according to one of the preceding claims, characterized in that the laser radiation source (31) has a pulsed IR fiber laser with an output power of at least 70 W and a beam quality with a K factor of at least 0.58. A method for cleaning a plasma radiation source (21) comprising the following steps: - Provision of a plasma radiation source (21) in an illumination system (1) of a projection exposure system (13) or a mask inspection tool, - Provision of a device (33) for cleaning the plasma radiation source (21) by means of a processing beam (38), - Exposing a predetermined area of a source chamber (22) of the plasma radiation source (21) with the processing beam (38). - wherein the processing beam (38) is guided to certain areas of the source chamber (22) by means of an end effector (32) with at least one displaceable mirror (52). Radiation source module for a projection exposure system (13) or a mask inspection system with - a radiation source (21) for generating illumination radiation (8) and - a device (33) according to one of the Claims 1 to 10 . Illumination system (1) for a projection exposure system (13) or a mask inspection system with - a radiation source module according to FIG Claim 12 and - illumination optics (2) for transferring illumination radiation (8) to an object field (3). Projection exposure system (13) with - an illumination system (1) according to Claim 13 and - a projection optics (5) for projecting the object field (3) into an image field (6). Mask inspection system with a lighting system (1) according to Claim 13 .

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