DE102020211359A1 - Assembly of an optical system for microlithography - Google Patents

Abstract

The invention relates to an assembly of an optical system for microlithography, having a first component (130) and a second component (160), the first component (130) and the second component (160) having independent functionalities during operation of the optical system , which are each associated with the emission of parasitic heat, and a cooling unit with at least one channel system (150) through which a cooling fluid can flow, this channel system (150) being configured in such a way that the cooling fluid flowing in the channel system (150) parasitic during operation of the optical system Dissipates heat from both the first component (130) and the second component (160).

Description

BACKGROUND OF THE INVENTION

field of invention

The invention relates to an assembly of an optical system for microlithography.

State of the art

Microlithography is used to produce microstructured components such as integrated circuits or LCDs. The microlithographic process is carried out in a so-called projection exposure system, which has an illumination device and a projection lens. The image of a mask (= reticle) illuminated by means of the illumination device is projected by means of the projection objective onto a substrate (e.g. a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection objective in order to project the mask structure onto the light-sensitive coating of the to transfer substrate.

Mask inspection systems are used to inspect reticles for microlithographic projection exposure systems.

In optical systems designed for the EUV range for microlithography, i.e. at wavelengths of e.g. about 13 nm or about 7 nm, mirrors are used as optical components for the imaging process due to the lack of availability of suitable light-transmitting refractive materials.

Optical systems for microlithography often contain components that have to be actively cooled to avoid thermally induced deformations and associated optical imaging errors during operation of the optical system. In this case, parasitic heat to be dissipated can be caused not only by the exposure of the respective optical components or mirrors to useful optical (e.g. EUV) radiation, but possibly also by electrical power loss occurring within assemblies of the optical system. Examples of this are actuator arrangements on adaptive mirrors or mirror arrangements to which electrical current is applied (whereby such actuator arrangements can include, for example, current-carrying coils or electromagnets) as well as components of any control electronics that may be present.

The components mentioned above are used, for example, in mirror arrangements which, in order to implement specific illumination angle distributions, are constructed from a plurality of mirror elements designed to be tiltable independently of one another via flexure joints. Such mirror arrangements or facet mirrors are designed for the operation of a microlithographic projection exposure system designed in EUV, for example DE 10 2008 009 600 A1 known, and for example in the VUV range (ie at wavelengths less than 250 nm, in particular less than 200 nm). WO 2005/026843 A2 famous.

Other application examples of components that give off parasitic heat caused by electrical power loss during operation of the respective optical system and may therefore require active cooling are (e.g. CCD) camera systems and associated evaluation devices, such as those used in a mask inspection system.

Typically, separate cooling units are assigned to the respective assemblies in the optical system, which can be caused by the specific structural conditions depending on the specific application situation. A resulting disadvantage in practice, however, is the correspondingly high complexity of the structure (typically comprising a plurality of soldered or welded joints), which on the one hand increases the equipment complexity and costs and on the other hand leads to considerable leakage due to the correspondingly high number of cooling fluid connections -risks.

The prior art is only given as an example DE 10 2018 216 645 A1 referred.

SUMMARY OF THE INVENTION

Against the above background, it is an object of the present invention to provide an assembly of an optical system for microlithography, which enables the operation of the optical system to reduce or avoid the above-described problems caused by parasitic heat occurring during operation.

This object is solved by the assembly according to the features of independent patent claim 1 .

• - einer ersten Komponente und einer zweiten Komponente, wobei die erste Komponente und die zweite Komponente im Betrieb des optischen Systems voneinander unabhängige Funktionalitäten besitzen, welche jeweils mit einer Abgabe parasitärer Wärme einhergehen; und
• - einer Kühleinheit mit wenigstens einem von einem Kühlfluid durchströmbaren Kanalsystem,
• - wobei dieses Kanalsystem derart konfiguriert ist, dass das im Kanalsystem strömende Kühlfluid im Betrieb des optischen Systems parasitäre Wärme sowohl von der ersten Komponente als auch von der zweiten Komponente abführt.

According to one aspect of the invention, the invention relates to an assembly of an optical system for microlithography, with

• - A first component and a second component, the first component and the second component being independent of one another during operation of the optical system Possess functionalities, each of which is accompanied by the emission of parasitic heat; and
• - a cooling unit with at least one channel system through which a cooling fluid can flow,
• - This channel system being configured in such a way that the cooling fluid flowing in the channel system dissipates parasitic heat both from the first component and from the second component during operation of the optical system.

The invention is based in particular on the concept of using one and the same channel system to cool a plurality of components in an assembly of an optical system for microlithography, which have different functionalities and each emit parasitic heat during operation of the optical system. In other words, the present invention includes in particular the principle of suitably adapting a cooling unit in an assembly such that a plurality of components whose operation is associated with parasitic heat emission (typically in the form of electronic waste heat) are cooled together. In this way, the result is efficient heat dissipation while reducing the complexity of the apparatus structure and reducing the risk of leakage.

According to one embodiment, the channel system is configured in such a way that the cooling fluid flowing in the channel system flows successively along the first component and along the second component.

According to one embodiment, the channel system is configured such that the flow along the first component and the flow along the second component are in opposite directions.

According to one embodiment, the channel system is configured in such a way that the cooling fluid flowing in the channel system flows in parallel along the first component and the second component.

According to one embodiment, the assembly has a cooling fluid inlet and a cooling fluid outlet, the cooling fluid inlet and the cooling fluid outlet being arranged on the same side of the assembly.

In the above-described configurations, a realization of the cooling fluid supply and cooling fluid discharge on one and the same side of the assembly, which is necessary for reasons of installation space, for example, can be used to channel the cooling fluid flowing through the assembly (to a certain extent on the “way” through the assembly) through a suitable configuration of the channel system. on the first component and (on the "return" through the assembly) along the second component and thus at the same time to realize the inventive joint cooling of the multiple components.

At the same time, it can be ensured according to the invention by a suitable configuration of the channel system - in particular in the sense of the smallest possible distance between the channel system or the flowing cooling fluid on the one hand and the first or second component on the other hand - that the respective heat conduction path, which is located within the assembly from the respective component to be cooled to which the parasitic heat dissipating cooling fluid extends, is kept as low as possible. In this way, the fact can be taken into account that the "combination" according to the invention of the components to be cooled in relation to the cooling unit is fundamentally associated with an increased risk of the occurrence of undesirable bimetal effects, which result from the fact that different components with different thermal expansion from one another are mechanically and thermally coupled to one another in the assembly according to the invention. Such undesired bimetal effects can then also be minimized according to the invention due to the minimization of the respective heat conduction path within the assembly.

According to one embodiment, the assembly has a carrier for the first component and/or for the second component, this carrier being made of a material with a thermal conductivity of at least 300 (W/m·K). This material can be copper (Cu), in particular (but without the invention being limited thereto).

According to one embodiment, a distance between the channel system and the carrier is less than 5 cm, in particular less than 1 cm, more particularly less than 0.1 cm.

According to one embodiment, the first component has an electronic control arrangement with at least one electronic control unit.

According to one embodiment, the second component has an actuator arrangement with at least one actuator.

According to one embodiment, the control electronics arrangement is configured for this ated to control a plurality of actuators of the actuator assembly independently.

According to one embodiment, the assembly also has a third component, with this third component having a functionality that is independent of the first component and the second component during operation of the optical system, which is associated with the emission of parasitic heat, with the channel system also being configured in such a way that the cooling fluid flowing in the channel system dissipates parasitic heat from the third component during operation of the optical system.

In yet further embodiments, more than three components with functionalities that are independent of one another can also be present and can be cooled together via the channel system or the cooling fluid flowing through it.

All components can alternatively be cooled "in series" (so that the cooling fluid flowing in the channel system flows past the individual components one after the other) or in parallel (so that the cooling fluid flowing in the channel system flows past all components in parallel).

According to one embodiment, the assembly has a mirror arrangement with a plurality of mirror elements, which can be adjusted by independently adjustable tilt angles, for generating a desired light distribution of the light emanating from the mirror arrangement.

The invention also relates to an optical system for microlithography, characterized in that it has an assembly with the features described above.

According to one embodiment, the optical system is designed for a working wavelength of less than 30 nm, in particular less than 15 nm.

Furthermore, the invention also relates to a microlithographic projection exposure system, which has an illumination device and a projection lens, wherein the illumination device, during operation of the projection exposure system, illuminates a mask that is arranged in an object plane of the projection lens and has structures to be imaged with useful light of a working wavelength, and wherein the projection lens converts these structures to an in a substrate arranged in an image plane of the projection objective, the illumination device having an optical system with the features described above.

Further configurations of the invention can be found in the description and in the dependent claims.

The invention is explained in more detail below with reference to exemplary embodiments illustrated in the attached figures.

character list

• 1-2 schematische Darstellungen zur Erläuterung eines möglichen Aufbaus einer erfindungsgemäßen Baugruppe in einer beispielhaften Anwendung; und
• 3 eine schematische Darstellung einer für den Betrieb im EUV ausgelegten mikrolithographischen Projektionsbelichtungsanlage, in welcher die Erfindung beispielsweise realisierbar ist.

Show it:

• 1-2 schematic representations to explain a possible structure of an assembly according to the invention in an exemplary application; and
• 3 a schematic representation of a microlithographic projection exposure system designed for operation in the EUV, in which the invention can be implemented, for example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

3 1 shows a schematic representation of a projection exposure system 300 designed for operation in the EUV, in which the invention can be implemented, for example.

According to 3 an illumination device of the projection exposure system 300 has a field facet mirror 303 and a pupil facet mirror 304 . The light of a light source unit, which in the example comprises an EUV light source (plasma light source) 301 and a collector mirror 302, is directed onto the field facet mirror 303 . A first telescope mirror 305 and a second telescope mirror 306 are arranged in the light path after the pupil facet mirror 304 . A deflection mirror 307 is arranged downstream in the light path, which deflects the radiation striking it onto an object field in the object plane of a projection objective comprising six mirrors 321-326. At the location of the object field, a reflective structure-bearing mask 331 is arranged on a mask table 330, which is imaged with the aid of the projection lens in an image plane in which a substrate 341 coated with a light-sensitive layer (photoresist) is located on a wafer table 340.

The assembly according to the invention described below can, for example, include the field facet mirror 303 and can be used to dissipate the parasitic heat emitted there.

However, the invention is not limited to this application or to the general application in a projection exposure system designed for operation in the EUV. Especially the invention can also be advantageously used in a projection exposure system designed for operation in DUV (ie at wavelengths less than 250 nm, in particular less than 200 nm) or in another optical system for microlithography (for example a mask inspection system).

1 serves to explain the possible structure of an assembly which, in an exemplary application of the invention, comprises a mirror arrangement 100 in the form of a facet mirror. In the 1 The mirror arrangement 100 (only indicated) has, in a manner known per se, a plurality of mirror elements (not shown in detail), of which each mirror element is mechanically connected to a base via a joint arrangement. A plunger is typically attached to the back of each mirror element and is fixed to a magnet at its end opposite the mirror element. A drive and sensor unit consisting of an actuator 161 and a sensor 162 is assigned to each of the mirror elements, with the drive and sensor units in turn being fastened to a common carrier 120 . By suitably controlling the actuators 161 or electromagnets, the respective magnet and thus the mirror element connected via the plunger can be tilted into a desired position as a result of the magnetic force acting on the respectively assigned magnet, with the position being determined via the respectively assigned sensors 162 of each drive and sensor unit is controlled.

The actuators 161 or electromagnets of the drive and sensor units are controlled via a control electronics arrangement with control electronics units 131. This control electronics arrangement is supplied with target position data (target tilt angle) for the individual mirror elements, and the control electronics arrangement transmits them corresponding control signals to the drive and sensor units.

Both the actuators 161 and the control electronics units 131 emit unwanted parasitic heat during operation of the optical system, which can be attributed to the respective electrical power loss in these components. A cooling unit with a channel system 150 through which a cooling fluid can flow, to which a cooling fluid inlet 151 and a cooling fluid outlet 152 are connected, is used to dissipate this parasitic heat.

The cooling unit or the duct system 150 are now configured according to the invention in such a way that the cooling fluid flowing in the duct system 150 in the direction of the arrows drawn dissipates parasitic heat both from the plurality of actuators 161 and from the plurality of electronic control units 131 . The actuator arrangement formed by the plurality of actuators 161 is referred to below as the “first component” 160 , whereas the electronic control arrangement formed by the plurality of electronic control units 131 is referred to as the “second component” 130 .

Furthermore, according to the control electronics units 131 1 a common carrier 140 is assigned, which is made of a material with a thermal conductivity of at least 300 (W/m·K), in particular copper (Cu).

As in 1 is shown schematically, the cooling fluid in the channel system 150, after entering via the cooling fluid inlet 151, first flows along the actuators 161 forming the first component 160 and then flows along the control electronics units 131 forming the second component 130 or the associated carrier 140 back to the cooling fluid outlet 152 The cooling fluid outlet 152 is typically located on one and the same side of the assembly as the cooling fluid inlet 151 due to the space available.

2 shows a section along the dot-dash line 1 . How out 1 As can be seen, the cooling fluid flows in the region of the actuator 161 shown on the left, on the one hand along the arrows shown around this actuator 161 and, on the other hand, downwards via transfer ports 153 in the negative z-direction. Furthermore, upon reaching the actuator 161 shown on the right, the cooling fluid flows upwards via further overflows 153 in the positive z-direction and then along the arrows shown around this actuator 161 . From there, the cooling fluid flows further to in 2 further actuators 161 (not shown) until it is deflected in order to return to the cooling fluid outlet 152 along the control electronics units 131 forming the second component 130 or the associated carrier 140 .

According to the cooling unit according to the invention 1 The flow pattern realized, in which successive sections of the channel system 150 are flown through in series, is off as such DE 10 2018 216 645 A1 known and advantageous in that (in contrast to a parallel flow through channel sections) a uniform flow velocity distribution can be achieved. Said serial flow pattern has, however, in accordance with 1 selected placement of cooling fluid inlet 151 and cooling fluid outlet 152 on one and the same side of the assembly also necessarily means that the Duct system 150 after going through the assembly once (in 1 from left to right) back again (i.e. in 1 from right to left). This return of the channel system 150 or the cooling fluid flowing through the channel system 150 is now advantageously carried out according to the invention in such a way that the remaining distance from the second component 130 or the associated carrier 140 is kept as small as possible. The distance between channel system 150 and carrier 140 is preferably less than 5 cm, in particular less than 1 cm, more particularly less than 0.1 cm. In this way, the thermal conduction path between the second component 130 or associated carrier 140 on the one hand and the channel system 150 or cooling fluid on the other hand is kept low, thus ensuring effective heat dissipation. At the same time, by separating the carrier 140 of the second component 130 from the cooling fluid flowing through the channel system 150 (which is the case in the specific application example of 1 is achieved via a comparatively thin wall of the carrier 120), a corrosion of components occurring elsewhere in the system with the material of the carrier 120 (eg copper, Cu) different electrochemical potential (eg aluminum, Al) can be avoided.

Depending on the specific application situation (e.g. if there is no risk of corrosion), the carrier 140 for the second component 130 can also be in direct contact with the cooling fluid flowing through the channel system 150 (without, as in 1 to be separated therefrom by a comparatively thin wall of the carrier 120).

Although in the embodiment of 1 the geometry of the channel system 150 runs meandering along the actuators 161, the invention is not limited to this. In principle, other configurations of the cooling unit should also apply as covered by the invention, in which the cooling fluid flowing in a channel system dissipates heat from a number of components with different functionality.

These components can also be other components (e.g. a CCD camera system or an associated evaluation device). Accordingly, the invention can also be advantageously implemented in other application situations of microlithography (e.g. in a mask inspection system) in which parasitic heat is efficiently dissipated from several components and thermally induced deformations and associated impairments of the imaging quality of the optical system are to be prevented.

Although the invention has also been described on the basis of specific embodiments, numerous variations and alternative embodiments will become apparent to the person skilled in the art, e.g. by combining and/or exchanging features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be encompassed by the present invention, and the scope of the invention is limited only in terms of the appended claims and their equivalents.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited 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 102008009600 A1 [0006]
• WO 2005/026843 A2 [0006]
• DE 102018216645 A1 [0009, 0046]

Claims (15)

Assembly of an optical system for microlithography, with • a first component (130) and a second component (160), wherein the first component (130) and the second component (160) have functionalities that are independent of one another during operation of the optical system, each of which is associated with the emission of parasitic heat; and • a cooling unit with at least one channel system (150) through which a cooling fluid can flow, • wherein this channel system (150) is configured such that the cooling fluid flowing in the channel system (150) dissipates parasitic heat both from the first component (130) and from the second component (160) during operation of the optical system. assembly claim 1 , characterized in that the channel system (150) is configured such that the cooling fluid flowing in the channel system (150) sequentially flows along the first component (130) and the second component (160). assembly claim 2 characterized in that the duct system (150) is configured such that the flow along the first component (130) and the flow along the second component (160) are in opposite directions. assembly claim 1 , characterized in that the channel system (150) is configured in such a way that the cooling fluid flowing in the channel system (150) flows parallel to the first component (130) and to the second component (160). Assembly according to one of the preceding claims, characterized in that it has a cooling fluid inlet (151) and a cooling fluid outlet (152), the cooling fluid inlet (151) and cooling fluid outlet (152) being arranged on the same side of the assembly. Assembly according to one of the preceding claims, characterized in that it has a carrier (140) for the first component (130) and/or for the second component (160), this carrier (140) being made of a material with a thermal conductivity of at least 300(W/m·K) is produced. assembly claim 6 , characterized in that a distance between the channel system (150) and the carrier (140) is less than 5 cm, in particular less than 1 cm, more particularly less than 0.1 cm. Assembly according to one of the preceding claims, characterized in that the first component (130) has an electronic control arrangement with at least one electronic control unit (131). Assembly according to one of the preceding claims, characterized in that the second component (160) has an actuator arrangement with at least one actuator (161). assembly claim 8 and 9 , characterized in that the control electronics arrangement is configured to control a plurality of actuators (161) of the actuator arrangement independently. Assembly according to one of the preceding claims, characterized in that it also has a third component, this third component having a functionality independent of the first component and the second component during operation of the optical system, which is associated with the emission of parasitic heat, the Channel system is further configured such that the cooling fluid flowing in the channel system dissipates parasitic heat from the third component during operation of the optical system. Assembly according to one of the preceding claims, characterized in that it has a mirror arrangement (100) with a plurality of mirror elements adjustable by independently adjustable tilting angles for generating a desired light distribution of the light emanating from the mirror arrangement (100). Optical system for microlithography, characterized in that it has an assembly according to one of the preceding claims. Optical system after Claim 13 , characterized in that it is designed for a working wavelength of less than 30 nm, in particular less than 15 nm. Microlithographic projection exposure system, which has an illumination device and a projection objective, wherein the illumination device illuminates a mask which is arranged in an object plane of the projection objective and has structures to be imaged and wherein the projection objective images these structures onto a substrate arranged in an image plane of the projection objective, characterized during operation of the projection exposure apparatus , that the projection exposure system follows an optical system Claim 13 or 14 having.

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