DE102015215223A1 - EUV lithography system - Google Patents

Abstract

The invention relates to an EUV lithography system (1), comprising: an EUV light source (5) for generating EUV radiation (7), which passes through the EUV lithography system (1) along an EUV beam path (6), at least one optical element (8, 9, 10, 11, 13, 14) whose optical surface (8a, 9a, 10a, 11a, 13a, 14a) is arranged in the EUV beam path (6), at least one electrically conductive structure (17a C) which annularly surrounds the EUV beam path (6) in at least one section (6a-c) and / or which forms a grid structure (17a-c) comprising a plurality of electrical conductors connected to nodes, and at least one voltage source (18a-c) for generating an electrical charge (-) of the at least one electrically conductive structure (17a-c) for deflecting electrically charged contaminating particles (P) from the EUV beam path (6).

Description

Background of the invention

The invention relates to an EUV lithography system, comprising: an EUV light source for generating EUV radiation, which passes through the EUV lithography system along an EUV beam path, and at least one optical element whose optical surface is arranged in the EUV beam path.

For the purposes of this application, an EUV lithography system is understood to mean an optical system for EUV lithography, i. an optical system that can be used in the field of EUV lithography. In addition to an EUV lithography system, which is used for the production of semiconductor devices, the optical system can be, for example, an inspection system for inspecting a photomask used in an EUV lithography system (also referred to below as a reticle) for inspection of a semiconductor substrate to be patterned (in FIG Hereinafter also referred to as wafers) or a metrology system which is used for measuring an EUV lithography system or parts thereof, for example for measuring a projection system. In such an EUV lithography system, reflective optical elements, for example reflective multilayer mirrors, are typically arranged in a vacuum environment in one or more housings or vacuum chambers.

When using EUV radiation at wavelengths in the range between about 5 nm and about 30 nm, e.g. In EUV lithography systems, the contamination of optical elements by contaminating substances or particles is a particular problem. Contaminating substances can be produced, for example, in an EUV light source, in which a target material, for example in the form of tin droplets, is produced the EUV radiation is used. The target material in the form of the tin droplets can be converted into a plasma state by means of a laser beam, as a result of which the tin droplets partially evaporate and tin particles are formed. The tin particles can spread in the EUV lithography system and attach either directly or in the form of a tin layer to the optical and mechanical or mechatronic surfaces of the optical elements of the EUV lithography system.

The contamination of the optical surfaces by tin particles can be done in different ways: The tin particles can be deposited directly from the gas phase on the optical surfaces or a tin layer can be formed by surface diffusion of tin. Tin contaminations may also be due to outgassing effects on tin-containing components in the EUV lithography equipment caused by hydrogen present in the EUV lithography equipment or a hydrogen plasma. The deposition of tin on the optical surfaces of the optical elements can also lead to the formation of bubbles in a reflective coating of the optical elements, which in the worst case results in delamination of the coating. Mechatronic components can also be severely limited or destroyed in their mode of operation by penetrating Sn particles.

In the US 8721778 B2 For example, a foil trap is disclosed having a plurality of spaced apart foils which are rotated about a common axis of rotation to collect contaminating particles on the walls of the foils, thereby preventing the contaminating particles from becoming optical components.

From the WO 2008/034582 A2 It is known to the Applicant to carry out a local encapsulation of contaminated components, in particular optical surfaces, of an EUV lithography system in partial housings with limited partial volumes (mini-environments) which are flushed with a purge gas, eg with hydrogen, in order to prevent contaminants from penetrating To complicate substances from the environment of a respective sub-housing. The vacuum housings, which each form a mini-environment, can be made of a gas-binding material at least on a partial area on their inner side. An optical element of the EUV lithography system may comprise a contaminant absorbing material adjacent to the optical surface, which may be a catalytic material, such as rhodium, palladium, molybdenum, iridium, osmium, rhenium, silver, zinc oxide or their alloys, or Ruthenium can act.

From the US 2004/0119394 has become known a device for reducing the transport of dirt particles that arise in an electrical discharge source. The reduction of the transport of the dirt particles can be effected by a thermoporetic and / or electrostatic deposition of the dirt particles. In order to promote electrostatic deposition, a body may be disposed adjacent to a front electrode of the electric discharge source and an electric field may be generated between the (conical) body and the front electrode. The conical body can be made of an electrically insulating material and as a support body for an electrically conductive material, for example for a metal cone or for a metallic mesh material serve.

From the US 2013/0070218 A1 For example, a system for removing contaminating particles from the EUV beam path of an EUV lithography system has been disclosed in which at least one pair of electrodes are arranged on mutually opposite sides of the EUV beam path and in which there is a voltage source having a controllable voltage generated between the electrodes. In a first phase of the control, an AC voltage is applied and in a second phase of the control, a DC voltage is applied to the pair of electrodes.

Object of the invention

The object of the invention is to provide an EUV lithography system in which the transport of contaminating particles to the optical surfaces of the EUV lithography system is reduced.

Subject of the invention

This object is achieved by an EUV lithography system of the aforementioned type, further comprising: at least one electrically conductive structure which surrounds the EUV beam path in at least one section annularly or in the manner of an enclosure and / or forms a lattice structure which a plurality of electrical conductors connected to each other at nodes, and a voltage source for generating an electrical charge of the electrically conductive structure for deflecting electrically charged contaminating particles from the EUV beam path.

According to the invention, it is proposed to surround at least a portion of the EUV beam path with an electrically conductive structure annularly (ie by 360 ° in the circumferential direction) or to encapsulate the EUV beam path in the section with the aid of the electrically conductive structure and / or an electrically conductive structure To use structure that forms a lattice structure in which a plurality of electrical conductors are connected to each other at nodes.

In the first case, the electrically conductive structure surrounds the generally substantially cylindrical or cone-shaped EUV beam path (more precisely its cross section) in a ring-shaped manner and can for this purpose have one or more electrical conductors which are for example in the form of wires or the like are. The electrically conductive structure may, for example, comprise one or more electrical conductors that surround the EUV beam path in a spiral shape. The electrically conductive, e.g. Metallic structure does not necessarily surround the cross section of the EUV beam path annularly, but can surround the EUV beam path, for example in the manner of a rectangular or elliptical ring or frame, in particular if the EUV beam path itself has a rectangular or elliptical geometry in cross section.

With the aid of the voltage source, an electrical charge is applied to the electrically conductive structure, as a result of which the entire electrically conductive structure is typically at the same electrical potential. The voltage source may generate a voltage or potential between the ground potential of the EUV lithography system and the electrically conductive structure to apply the electrical charge to the electrically conductive structure. If necessary, a plurality of electrical conductors of the electrically conductive structure can be connected to one another in an electrically conductive manner only via the voltage source, which holds the electrical conductors at the same electrical potential.

The generation of a positive or negative charge of the electrically conductive structure makes it possible to redirect electrically charged particles having a charge of opposite sign in the direction of the electrically conductive structure, so that the contaminating particles ideally leave the EUV beam path before these pass on one of the arranged in EUV beam path electrically conductive optical surfaces. The contaminating particles may, for example, be the tin particles mentioned above, which are typically ionized and thus positively charged by the EUV radiation present in the EUV beam path. Due to a negatively charged electrically conductive structure, a well-defined electric field is generated in the EUV beam path, which influences the trajectories of the tin particles so that they leave the EUV beam path of the EUV lithography system.

In the second case, the electrically conductive structure forms a lattice structure which has a plurality of electrical conductors connected to one another at nodes. The electrical conductors are in electrical and mechanical connection with one another at the nodes, so that it is sufficient to electrically connect the voltage source to the electrically conductive grid structure only at one location in order to keep the grid structure at the same potential. An electrically conductive structure in the form of a lattice structure allows the contaminating particles, which are deflected to the lattice structure, to pass through the space or openings formed between the electrical conductors, so that only a small amount is typically present the contaminating particles strike the lattice structure itself. The lattice structure may annularly surround the EUV beam path, for example in the manner of a cage, from which the contaminating particles emerge to the outside.

In a further development, the electrical conductors of the grid structure are formed as metallic wires. The metallic wires are typically dimensionally stable so that the grid structure is cantilevered so that the grid structure theoretically only has to be fastened at one point to a housing or to a housing component of the EUV lithography system. The attachment is typically via an electrically insulating component. The attachment of the lattice structure can be carried out, for example, at the two mutually opposite ends of the portion of the EUV beam path, which surrounds the lattice structure in an annular manner. In a further embodiment, the electrically conductive structure, in particular the lattice structure, has at least one closed, in particular annular, conductor loop which surrounds the EUV beam path. Contaminating particles in the EUV beam path, which do not pass through the conductor loop exactly in their middle, experience a force effect due to the electric field within the conductor loop to the outside, i. out of the EUV beam path. Several such conductor loops can be arranged one behind the other along the EUV beam path and be kept at the same potential either by the voltage source or by a mechanical connection to further conductors running, for example, substantially parallel to the propagation direction of the EUV radiation along the EUV beam path.

In a further embodiment, the EUV lithography system additionally comprises at least one vacuum chamber, which is arranged in an interior of a housing forming a vacuum environment, wherein the vacuum chamber surrounds the EUV beam path at least in a section which is typically adjacent to an optical surface of an optical element is arranged. The vacuum chamber can form a so-called mini-environment, as in the cited above WO 2008/034582 A2 which is incorporated herein by reference in its entirety. The vacuum chamber is typically purged with a purge gas, eg, hydrogen, to impede the entry of contaminants from the interior of the housing into the vacuum chamber, and thus the partial pressure of contaminants on the optical surface of the optical chamber Element to reduce the partial pressure of contaminants in the interior.

In a further development, the electrically conductive structure, in particular the lattice structure, is arranged in the vacuum chamber. In this case, the electrically conductive structure between the EUV beam path and the inside of the wall of the vacuum chamber is arranged, which also encapsulates the EUV beam path or typically annular surrounds. In this way, the contaminating particles can be deflected by means of the electrically conductive structure to the surfaces on the inside of the vacuum chamber.

Optionally, the electrically conductive structure may also be formed by the wall of the vacuum chamber itself, i. the vacuum chamber is directly exposed to a potential. In this case, it is typically necessary to electrically isolate the vacuum chamber, more specifically its typically annular annular chamber wall, from the housing or vacuum vessel in which the vacuum chamber is located.

In a further embodiment, the electrically conductive structure and / or at least one surface of the EUV lithography system arranged outside the EUV beam path has / have at least one material which adsorbs the contaminating particles. The adsorbent material may be applied to the surface, in particular in the form of a coating, but it is also possible that the component on which the surface is formed itself is formed from a material adsorbing the contaminating particles, so that dispensing with a coating can. Ideally, at least during operation of the EUV lithography system, the contaminating particles should adhere to the electrically conductive structure itself and / or to a surface located outside the EUV beam path (and outside the electrically conductive structure).

In one development, the adsorbent material is selected from the group comprising: noble metals, in particular Ru, Pd, Pt, Rh, Ir, Au or semi-precious metals, in particular Cu. The use of these adsorbent materials has proved to be favorable, since metallic particles, in particular tin particles, have a high affinity to attach to the above-mentioned materials.

In a further embodiment, the EUV lithography system has at least one cooling device for cooling the electrically conductive structure and / or for cooling at least one surface of the EUV lithography system arranged outside the EUV beam path. The cooling device makes it possible to bind the contaminating particles to the electrically conductive structure and / or to a surface arranged outside the EUV beam path, for this purpose to a temperature of less than 290 K, preferably less than 80 K, in particular of less than 20 K is cooled. The cooling device may for example comprise one or more Peltier elements. The cooling device may have cooling channels to allow gas and / or liquid cooling. The cooling device can be used to freeze the contaminating particles, for example in the form of liquid tin, which have been removed during the heating of the electrically conductive structure, on at least one surface arranged outside the EUV beam path. The cooling device may also be used to additionally or alternatively to surfaces having an adsorbent material freeze contaminating particles on the at least one cooled surface during operation of the EUV lithography system.

In a further embodiment, the surface is formed with the adsorbent material or the cooled surface in the vacuum chamber, in particular on an inner wall of the vacuum chamber or on a non-optical component in the vacuum chamber. When the electrically conductive structure is disposed in the vacuum chamber, the contaminating particles may be redirected to an inner wall surrounding the lattice structure, typically a substantially tubular vacuum chamber, and collected on the adsorbent material. Also, on non-optical and non-functional components disposed in the vacuum chamber, a coating of at least one adsorbent material may be applied to prevent the contaminating particles from being exposed to the optical surface of the at least one in the vacuum chamber be transported arranged optical element.

In another embodiment, the vacuum chamber has an outlet connecting the vacuum chamber to the interior of the housing, i. of the vacuum vessel surrounding the optic, connects and the surface with the adsorbent material or the cooled surface is formed in the interior of the housing, in particular on an inner wall of the housing. The typically flushed with a purge gas vacuum chamber generally has at least one outlet to transport the purge gas and possibly contained in this contaminants in the interior. If necessary, contaminating particles can also enter the interior through the outlet. In order to prevent the contaminating particles from accumulating uncontrollably on the components present in the interior or, if necessary, entering another vacuum chamber at which an electrically conductive structure is present, it is favorable to target the particles in a targeted manner on the surface Accumulate housing having at least one adsorbent material or which is cooled by means of a cooling device.

In a further embodiment, the voltage source is designed to generate a positive or negative electrical charge of the electrically conductive structure, wherein preferably the absolute amount (and possibly the sign) of the electrical charge of the electrically conductive structure is variable with time. As described above, the charge of the electrically conductive structure can be generated, for example, by generating a voltage between the electrically conductive structure and the ground potential of, for example, the housing of the EUV lithography system. The negatively charged charge carriers (electrons), which are present in excess in the electrically conductive structure, generate a static electric field which attracts positively charged contaminating particles. Accordingly, it is also possible to positively charge the electrically conductive structure to attract negatively charged contaminating particles. The absolute amount of the charge or the voltage which is applied to the electrically conductive structure can vary over time, in particular as a function of the strength of the EUV radiation-induced plasma of the purge gas, for example in the form of hydrogen: The (conductive ) Hydrogen plasma may possibly shield the contaminating particles, so that they are not deflected to the electrically conductive structure. In particular, the plasma may, in particular, possibly convert the positive charge of the contaminating particles generated by the EUV radiation due to the photoelectric effect into a negative charge. During operation of the voltage source, the plasma and thus the negative charge of the contaminating particles can be amplified in a first step by the time-dependent change in the charge of the electrically charged structure, for example by the application of an alternating voltage, so that in a second step, in which the charge of the electrically conductive structure remains constant over time, are deflected in this case positively charged electrically conductive structure, as in the above-cited US 2013/0070218 A1 which is incorporated herein by reference in its entirety. If several, eg four, grating structures are used which only partially surround the EUV beam path, eg in an angular range of 90 ° or less, adjacent grating structures can be set to a different (positive or negative) potential, so that both positively charged ions as well as negatively charged ions can be deflected simultaneously and removed from the EUV beam path. For example, four grid structures in the manner of a quadrupole can be arranged around the EUV beam path.

In a further embodiment, the EUV lithography system comprises a heating device for heating the electrically conductive structure. In Depending on the absolute number of contaminating particles which are deflected by the electrically conductive structure, it may be favorable to heat the electrically conductive structure to an elevated temperature, at least during maintenance work or during breaks in operation of the EUV lithography system. For this purpose, the heating device can be designed, for example, to generate a current in the electrically conductive structure, so that it is itself used as a heating resistor. It is understood that other types of heating, such as radiant heating, the electrically conductive structure is possible to replace contaminating particles of the electrically conductive structure.

In a further development, the heating device is designed to heat the electrically conductive structure to a temperature which is greater than the melting temperature of the contaminating particles, for example to a temperature of more than 232 ° C (melting temperature of tin) or more than 300 ° C. If the heating device is heated to a temperature which is greater than the melting temperature of the contaminating particles, they can detach from the electrically conductive structure or be transferred into the gas phase. In this way, the electrically conductive structure can be cleaned of the contaminating particles, wherein the heating of the electrically conductive structure preferably takes place during a break in operation of the EUV lithography system. The EUV lithography system preferably has a collecting device in order to collect the contaminating particles, for example in the form of liquid tin, after detachment. The catcher may be e.g. tubular device having at least one surface cooled by means of a cooling device and / or an adsorbing surface to bind the contaminating particles. For example, the component may be introduced into the EUV lithography system during a break in operation and removed after collecting the particles from the EUV lithography system before the EUV lithography system is put into operation again.

In another embodiment, the contaminating particles have a positive charge and the electrically conductive structure has a negative charge. As described above, contaminating particles are typically ionized or lost electrons by the EUV radiation due to the photoelectric effect and are therefore positively charged unless the plasma prevailing in the EUV beam path is too intense (see above). Due to the negatively charged electrically conductive structure, the positively charged contaminating particles are deflected from the EUV beam path, as described in detail above.

In another embodiment, the EUV lithography system comprises a beam generation system, an illumination system, and a projection system, and the at least one electrically conductive structure surrounds a portion of the EUV beam path in the beam generation system, the illumination system, or the projection system. The electrically conductive structure can in principle surround any section of the EUV beam path of the EUV lithography system, which in the embodiment described here is designed as an EUV lithography system. As has been described above, contaminating particles in the form of tin particles can be generated in the EUV light source and first pass into the beam generation system and from there, if necessary, into the optically downstream illumination system and optionally into the optically downstream projection system. It is therefore advantageous to remove the contaminating particles or at least a large part of the contaminating particles as close as possible to the EUV light source from the EUV beam path. As an alternative or in addition to the EUV beam path in the beam generation system, the EUV beam path in the illumination system can therefore also have at least one electrically conductive structure, in particular. The transition of the EUV radiation from the beam generating system into the lighting system takes place via an intermediate focus, if necessary. An electrically conductive structure may therefore for example be arranged between the intermediate focus at the entrance of the illumination system and the first reflective optical element of the illumination system in order to encapsulate the EUV beam path in this section. It is understood, however, that possibly the entire portion of the EUV beam path that runs in the illumination system can be encapsulated with one or more electrically conductive structures. The same applies to the section of the EUV beam path in the beam generation system and in the projection system.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawing, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

drawing

Embodiments are illustrated in the schematic drawing and will be explained in the following description. It shows

1 a schematic representation of an EUV lithography system with three lattice structures for the deflection of contaminating particles from an EUV beam path of the EUV lithography system,

2a , b schematic representations of one of the lattice structures of 1 , which are electrically neutral ( 2a ) or negative ( 2 B ) is loaded.

In the following description of the drawings, identical reference numerals are used for identical or functionally identical components.

In 1 is schematically an EUV lithography system 1 in the form of an EUV lithography system, which is a beam generation system 2 , a lighting system 3 and a projection system 4 that has separate housings 2a . 3a . 4a housed and consecutively in one of an EUV light source 5 the beam generating system 2 outgoing EUV beam path 6 that of the EUV light source 5 generated EUV radiation 7 are arranged.

As an EUV light source 5 For example, a plasma source can be used. The from the EUV light source 5 leaking EUV radiation 7 , which has an intensity maximum at an operating wavelength λ _B , which in the present example is about 13.5 nm, is determined by means of a collimator mirror 8th bundled to further increase the energy density. The in the beam generation system 2 EUV radiation treated for spatial distribution 7 gets into the lighting system 3 introduced, which a first and second reflective optical element 9 . 10 having. The two reflective optical elements 9 . 10 direct the radiation onto a photomask 11 (Reticle) as another reflective optical element, which has a structure by means of the projection system 4 on a smaller scale on a wafer 12 is shown. For this purpose, a first and second reflective optical element 13 . 14 in the projection system 4 intended. The mask 11 is in one with the lighting system 3 and the projection system 4 via openings for the passage of the EUV beam path 6 connected housing 15 arranged. Also the wafer 12 is in its own, with the projection system 4 connected housing 16 accommodated. It is understood that both the number of optical elements in each system 2 . 3 . 4 as well as their arrangement is to be understood only as an example and that in a real EUV lithography system 1 both the number and the arrangement of the optical elements differ from those in FIG 1 shown EUV lithography system 1 can distinguish.

The reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 each have an optical surface 8a . 9a . 10a . 11a . 13a . 14a on top of that, the EUV radiation 7 the light source 5 is exposed. The reflective optical elements 8th . 9 . 10 . 13 . 14 are in a respective interior 2 B . 3b . 4b in the cases 2a . 3a . 4a the beam generating system 2 , the lighting system 3 and the projection system 4 the EUV lithography system 1 arranged. As described above, the reflective mask is 11 in a separate housing 15 the EUV lithography system 1 arranged.

The reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 are in the example shown each with one for the EUV radiation 7 reflective coating, which may be, for example, a reflective multilayer coating having alternating layers of materials with a high and a low refractive index. The optical surfaces 8a . 9a . 10a . 11a . 13a . 14a the reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 are in the EUV beam path 6 arranged and can be contaminated by contaminating particles in the EUV lithography system 1 available. Such contaminating particles may be from, for example, the EUV light source 5 be generated. If it is the EUV light source 5 is a plasma light source in which a target material in the form of tin droplets is bombarded with laser radiation, tin particles P are typically generated. The passage of tin particles from the EUV light source 5 into the beam generating system 2 can not be completely prevented as a rule. The tin particles P can be used in the vacuum environment in the respective housings 2a . 3a . 4a is formed, propagate and adhere to the surfaces 8a . 9a . 10a . 11a . 13a . 14a the reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 settle and contaminate them.

To the deposition of contaminating particles P at least on the optical surfaces 9a . 10a . 11a . 13a . 14a the reflective optical elements 9 . 10 . 11 . 13 . 14 of the lighting system 3 and the projection system 4 counteract are in the EUV lithography system 1 In the example shown three electrically conductive structures attached, which are in the form of lattice structures 17a -C are formed. Each of the three lattice structures 17a -C surrounds a respective section 6a -C of the EUV beam path 6 completely in the manner of a tube or a cage. The first grid structure 17a is in the housing of the beam generating system 2 arranged and surrounds a first section 6a of the EUV beam path 6 in the case 2a the beam generating system 2 between the collimator mirror 8th and an intermediate focus Z _{F of} the EUV beam path 6 runs. The second lattice structure 17b is in the lighting system 3 arranged and runs along a second section 6b of the EUV beam path 6 between the intermediate focus Z _F and the first reflecting optical element 9 of the lighting system 3 , The third lattice structure 17c is in the projection system 4 arranged and runs along a third section 6c of the EUV beam path 6 between the first and second reflective optical elements 13 . 14 of the projection system 4 ,

At the in 1 Example shown is each of the three grid structures 17a -C with one voltage source each 18a -C electrically conductively connected. The voltage sources generate a potential or a voltage between the ground potential, for example, on the housings 2a . 3a . 4a is applied, and the respective lattice structure 17a c. The grid structures 17a -C are by means of voltage sources 18a C are thus electrically charged and have an electrical charge or an electrical potential which depends on the polarity or on the setting of the respective voltage source 18a -C can be positive (+) or negative (-).

2a , b show a trajectory 19 a contaminating particle P, which in the region of the intermediate focus Z _F in the illumination system 3 enters and the second grid structure 17b goes through, in the event that the second lattice structure 17b is electrically neutral ( 2a ) or in the event that the second grid structure 17b is negatively charged ( 2 B ). As in 2a , b, has a single contaminating particle P, which is in the EUV beam path 6 runs, due to the EUV radiation 7 a positive charge (+). At the in 2a As shown, the contaminating particle P passes through the second lattice structure 17b along a straight trajectory 19 , When in 2 B shown example, in which the second lattice structure 17b has a negative charge (-), the contaminating particle P from the EUV beam path 6 deflected and passes through the openings in the cage-like second lattice structure 17b therethrough. Accordingly, the first and the third lattice structure 17a . 17c by generating a negative charge (-) or possibly a positive charge (+) contaminating particles P within the EUV beam path 6 run, from the EUV beam path 6 distracted.

The deflected particles P occur at the first lattice structure 17a directly into the interior 2 B of the housing 2a the beam generating system 2 one. To prevent the contaminating particles P back into the EUV beam path 6 can get back to is in the in 1 shown an annular shield 20 in the interior 2 B arranged, which is the first lattice structure 17a surrounds annularly. On the inside 20a the shield 20 is a coating 21 which has at least one material adsorbing the contaminating particles P. In the example shown, the adsorbent material is ruthenium, but other noble metals, eg, in particular Ru, Pd, Pt, Rh, Ir, Au or semiprecious metals, in particular Cu, can also be used as constituents of the adsorbing coating 21 be used. Typically, the shield is 20 on which the coating 21 is applied, formed of stainless steel or aluminum. Optionally, however, the shield 20 itself be formed of an adsorbent material, such as Cu. In this case, on the coating 21 if necessary completely omitted.

Both the second lattice structure 17b as well as the third grid structure 17c are each in a vacuum chamber 23 . 24 arranged, which in the interior 3b of the housing 3a of the lighting system 3 or in the interior 4b of the housing 4a of the projection system 4 is arranged. The first vacuum chamber 23 surrounds the second section 6b of the EUV beam path 6 in the lighting system 3 , the third vacuum chamber 24 surrounds the third section 6c of the EUV beam path 6 in the projection system 4 , In the example shown, the second and third lattice structures are 17b . 17c each at opposite ends of the vacuum chambers 23 . 24 secured by means of insulator components, so that the electric charge (+) or (-) on the lattice structures 17b . 17c remains limited.

In the example shown, the first vacuum chamber 23 between the intermediate focus Z _F and the first optical element 9 of the lighting system 3 formed, ie the first optical element 9 and thus also its optical surface 9a is in the first vacuum chamber 23 arranged. Accordingly, in the example shown, the first and the second optical element 13 . 14 of the projection system 4 in the second vacuum chamber 24 housed in the interior 4b of the projection system 4 is arranged. Each of the vacuum chambers 23 . 24 has an outlet 25 . 26 on top of the inside of each vacuum chamber 23 . 24 with the interior 3b of the housing 3a of the lighting system 3 or with the interior 4b of the housing 4a of the projection system 4 combines. With the help of the interior 3b . 4b of the respective housing 3a . 4a arranged vacuum chamber 23 . 24 becomes the EUV beam path 6 between the intermediate focus Z _F and the first optical element 9 or between the two optical elements 13 . 14 encapsulated, ie from the interior 3b . 4b of the respective housing 3a . 4a separated.

The first vacuum chamber 23 points in addition to the outlet 25 , outside the EUV beam path 6 is formed, a first opening through which the EUV beam path 6 in the region of the intermediate focus Z _F in the first vacuum chamber 23 enters, as well as a second opening through which the EUV radiation 7 attached to the first reflective optical element 9 was reflected, the first vacuum chamber 23 leaves. Accordingly, also the second vacuum chamber 24 a first Opening on, over which the EUV beam path 6 or the EUV radiation 7 in the second vacuum chamber 24 enters, as well as a second opening, through which the EUV beam path 6 or the EUV radiation 7 the vacuum chamber 24 leaves. In the example shown, the second vacuum chamber 24 both at the first opening and at the second opening with another, in 1 unillustrated vacuum chamber in conjunction to substantially the entire EUV beam path 6 from the respective interiors 3b . 4b of the lighting system 3 and the projection system 4 encapsulate. Unlike in 1 can also be shown the EUV beam path 6 in the beam generating system 2 by means of one or possibly more vacuum chambers from the interior 2 B of the housing 2a the beam generating system 2 be encapsulated.

At the in 1 shown vacuum chambers 23 . 24 will connect the interior 3b . 4b of the respective housing 3a . 4a and the interior of the respective vacuum chamber 23 . 24 in which the respective section 6b . 6c of the EUV beam path 6 runs, so not on the openings, but only on the respective outlet 25 . 26 produced. As in 1 also can be seen, each opens a supply line 27 . 28 for supplying a purge gas, in the example shown in the form of hydrogen H ₂ , inside the first vacuum chamber 23 or inside the second vacuum chamber 24 , The purge gas leaves the respective vacuum chamber 23 . 24 over the outlet 25 . 26 and enters the respective interior 3b . 4a a housing 3a . 4a one. Through the outlet 25 . 26 can therefore possibly contaminating particles P in the interior 3b . 4b of the respective housing 3a . 4a reach. On a surface 22 in the interior of the housing 3a of the lighting system 3 more precisely on an inner wall of the housing 3a of the lighting system 3 , In the example shown is an adsorbent coating 21 attached to receive the contaminating particles P. The EUV lithography system 1 has a cooling device 33b on to a surface 34 on an inner wall of the housing 4a of the projection system 4 to cool to a temperature sufficient to bind the contaminating particles P. For this purpose, the surface can be 34 with the help of the cooling device 33b be cooled to a temperature of, for example, less than about 290 K, 80 K or 50 K.

On the surface 23a on the inner wall of the tubular first vacuum chamber 23 is a coating in the example shown 21 made of an adsorbent material, such as ruthenium, applied to the EUV beam path 6 deflected contaminating particles P to adsorb or absorb. Accordingly also has a surface 29a a non-optical and non-functional component 29 placed in the first vacuum chamber 23 is arranged, an adsorbent coating 21 on. It is understood that other non-optical components in the vacuum chambers 23 . 24 can be provided with an adsorbing coating. In particular, on all in the respective vacuum chamber 23 . 24 arranged surfaces an adsorbent coating 21 be upset. Also the grid structures 17a - 17c even can with a coating 21 be provided, which has at least one adsorbent material to adsorb the contaminating particles P.

In the 1 shown EUV lithography system 1 has a cooling device 33a on to the surface 24a on the inner wall of the second tubular vacuum chamber 24 to cool and in this way to bind the contaminating particles P. The cooling device 33a can for this purpose the surface 24a on the inner wall of the second vacuum chamber 24 Cool to a temperature of less than about 290 K, 80 K or 50 K. Also the grid structures 17a -C may optionally be cooled by means of suitable cooling means to temperatures which are sufficiently low to bind the contaminating particles P.

The purge gas, which in the form of hydrogen of the respective vacuum chamber 23 . 24 is supplied by the EUV radiation 7 typically converted to a plasma state. A plasma is understood to mean all charged species, ie both electrons and ionic species. The hydrogen plasma can cause the electric field, which is within the respective lattice structure 17b . 17c is generated, is shielded by the electrically conductive hydrogen plasma, so that the deflection effect of the lattice structures 17b . 17c is reduced for the contaminating particles P. To prevent this, if necessary, the amount of electrical charge, which by means of the voltage sources 18b . 18c on the grid structures 17b . 17c is applied, be changed time-dependent, ie it may be an AC voltage to the grid structures 17b . 17c can be created, which acts on the hydrogen plasma suitable. For example, in a first step, the hydrogen plasma can be amplified in this way so that the contaminating particles P have a magnitude greater negative charge than the (positive) charge that can be achieved by the photoelectric effect. In a second step, you can click on the respective grid structure 17b . 17c a constant voltage can be applied to the contaminating particles P from the EUV beam path 6 divert the effect of the deflection by the greater absolute amount of charge is enhanced.

Alternative to the grid structures shown 17a -C, which the EUV beam path 6 each surrounded annularly, the EUV beam path 6 are surrounded by a plurality, for example four, grid structures which are not electrically conductively connected to each other and each only a portion of the entire circumference of the EUV beam path 6 surrounded, for example in an angular range of 90 ° or less. Adjacent grating structures in this case can be set to a different (positive or negative) potential by means of one or more voltage sources, so that both positively charged ions and negatively charged ions can be simultaneously deflected and removed from the EUV beam path. For example, four grating structures in the manner of a quadrupole around the EUV beam path 6 be arranged around.

The geometry of a particular grid structure 17a - 17c is typically the geometry of the section 6a -C of the EUV beam path 6 adapted by the respective grid structure 17a -C is surrounded. To specifically a desired electric field distribution within the respective lattice structure 17a - 17c can generate the geometry or the design of the grid structure 17a - 17c be selected suitable. At the in 1 shown example, the lattice structures 17a C a plurality of electrical conductors in the form of metallic wires 30 . 31 on (cf. 2a , b). A first group of metallic wires 30 each form closed conductor loops which the EUV beam path 6 surrounded by a ring. A second group of metallic wires 31 runs essentially parallel to the propagation direction of the EUV beam path 6 and is with the wires 30 in the form of conductor loops at conductor nodes 32 connected together so that a total of a cage-like or lattice-shaped structure is formed. The distance between the wires designed as conductor loops 30 along the EUV beam path 6 can as well as the number and arrangement of the in the direction of the EUV beam path 6 extending wires 31 be chosen or varied suitably. It is not mandatory that the respective grid structure 17a -C wires 30 In the form of conductor loops, but rather two or more wires that are connected to each other at conductor nodes, the EUV beam path 6 enclose annular.

Optionally, instead of a grid structure 17a C another electrically conductive structure can be used, which the EUV beam path 6 surrounds. For example, one or, if appropriate, a plurality of spiral-shaped electrical conductors, for example in the form of metallic wires, form an electrically conductive structure, which forms the EUV beam path 6 completely, typically annular surrounds. In general, all conductors of the electrically conductive structure in this case, the same potential or the same charge, even if this may not be mechanical, but only on the respective voltage source 18a C are electrically connected.

To the grid structure 17a -C especially in the case that this is an adsorbent coating 21 has to clean from the accumulated contaminating particles P is in the in 2a shown example, a heater 35 in the EUV lithography system 1 intended. The heater 35 is at opposite ends to the grid structure 17b connected and formed, a current flow through the grid structure 17b to produce so that it acts as a heating resistor. By the heater 35 can the grid structure 17b be heated to a temperature T _G , which is greater than the melting temperature T _{S of} the contaminating particles P. If the contaminating particles P to tin particles, the melting temperature T _S is about 232 ° C, so that the heater 35 the second lattice structure 17b to a temperature T _G of more than 232 ° C heats. It is understood that the material of the metallic wires 30 . 31 for cleaning the grid structure 17b must have a melting temperature which is greater than the melting temperature T _{S of} the contaminating particles P. The cleaning of the lattice structure 17b typically occurs during a break in operation of the EUV lithography system 1 in which the respective voltage source 18a -C no electrical charge at the respective grid structure 17a -C, since the distraction of contaminating particles P during a break in operation is not required.

The of the respective lattice structure 17a -C detached contaminating particles P can be taken up by a collecting device, wherein as a receiving device, for example, a cooled by means of a cooling device surface or a surface of a contaminating particle P adsorbing material can be used. Optionally, for collecting the contaminating particles P, a component to which a cooled or a surface provided with an absorbent material is attached during a break in operation in the EUV lithography system 1 are introduced and removed after collecting the contaminating particles P again from the EUV lithography system.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• US 8721778 B2 [0005]
• WO 2008/034582 A2 [0006, 0017]
• US 2004/0119394 [0007]
• US 2013/0070218 A1 [0008, 0025]

Claims (15)

EUV lithography system ( 1 ), comprising: an EUV light source ( 5 ) for generating EUV radiation ( 7 ), the EUV lithography system ( 1 ) along an EUV beam path ( 6 ) passes through, at least one optical element ( 8th . 9 . 10 . 11 . 13 . 14 ), whose optical surface ( 8a . 9a . 10a . 11a . 13a . 14a ) in the EUV beam path ( 6 ), characterized by at least one electrically conductive structure ( 17a -C), the EUV beam path ( 6 ) in at least one section ( 6a C) surrounds annularly and / or the one grid structure ( 17a -C) forming several nodes ( 32 ) interconnected electrical conductors ( 30 . 31 ), and at least one voltage source ( 18a C) for generating an electrical charge (+, -) of the at least one electrically conductive structure ( 17a -C) for deflecting electrically charged contaminating particles (P) from the EUV beam path ( 6 ). EUV lithography system according to claim 1, wherein the electrical conductors of the grid structure ( 17a -C) as metallic wires ( 30 . 31 ) are formed. EUV lithography system according to one of the preceding claims, in which the electrically conductive structure ( 17a -C) at least one closed conductor loop ( 30 ) having the EUV beam path ( 6 ) surrounds annularly. EUV lithography system according to one of the preceding claims, further comprising: at least one vacuum chamber ( 23 . 24 ), which in a vacuum environment forming interior ( 3b . 4b ) of a housing ( 3a . 4a ), wherein the vacuum chamber ( 23 . 24 ) the EUV beam path ( 6 ) at least in one section ( 6b . 6c ) surrounds. EUV lithography system according to claim 4, in which the electrically conductive structure ( 17b . 17c ) in the vacuum chamber ( 23 . 24 ) is arranged. EUV lithography system according to one of the preceding claims, in which the electrically conductive structure ( 17a -C) and / or at least one outside the EUV beam path ( 6 ) arranged surface ( 20a . 23a . 24a . 22 ) of the EUV lithography system ( 1 ) has at least one contaminating particle (P) adsorbing material. EUV lithography system according to claim 6, wherein the adsorbent material is selected from the group comprising: noble metals, in particular Ru, Pd, Pt, Rh, Ir, Au or semi-precious metals, in particular Cu. EUV lithography system according to one of the preceding claims, further comprising: at least one cooling device ( 33a . 33b ) for cooling the electrically conductive structure ( 17a C) and / or for cooling at least one outside the EUV beam path ( 6 ) arranged surface ( 24a . 34 ) of the EUV lithography system ( 1 ). EUV lithography system according to one of Claims 6 to 8, in which the surface ( 23a . 29a ) with the adsorbent material or the cooled surface ( 24a . 34 ) in the vacuum chamber ( 23 . 24 ), in particular on an inner wall of the vacuum chamber ( 23 . 24 ) or on a non-optical component ( 29 ) in the vacuum chamber ( 23 . 24 ) is formed. EUV lithography system according to one of claims 6 to 9, wherein the vacuum chamber ( 23 . 24 ) an outlet ( 25 . 26 ) having the vacuum chamber ( 23 . 24 ) with the interior ( 3b . 4b ) of the housing ( 3a . 3b ) and in which the surface ( 22 ) with the adsorbent material or the cooled surface ( 34 ) in the interior ( 3b . 4b ) of the housing ( 3a . 4a ), in particular on an inner wall of the housing ( 3a . 4a ) is formed. EUV lithography system according to one of the preceding claims, in which the voltage source ( 18a C) for generating a positive or negative electric charge (+, -) of the electrically conductive structure ( 17a C), wherein preferably the absolute value of the electrical charge (+, -) of the electrically conductive structure ( 17a -C) is time-dependent variable. EUV lithography system according to one of the preceding claims, further comprising: a heating device ( 35 ) for heating the electrically conductive structure ( 17a c). EUV lithography system according to claim 12, in which the heating device ( 35 ), the electrically conductive structure ( 17b ) to a temperature (T _G ) which is greater than the melting temperature (T _S ) of the contaminating particles (P). EUV lithography system according to one of the preceding claims, in which the contaminating particles (P) have a positive charge (+) and in which the electrically conductive structure ( 17a -C) has a negative charge (-). EUV lithography system according to one of the preceding claims, which comprises a beam generation system ( 2 ), a lighting system ( 3 ) and a projection system ( 4 ), wherein the at least one electrically conductive structure ( 17a -C) a section ( 6a -C) of the EUV beam path ( 6 ) in the beam generating system ( 2 ), by doing Lighting system ( 3 ) or in the projection system ( 4 ) surrounds.

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