Patent Description:
The invention relates to a projection exposure apparatus for semiconductor lithography.

Such apparatuses are used for producing extremely small structures, in particular on semiconductor components or other microstructured component parts. The operating principle of said apparatuses is based on the production of very small structures down to the nanometres range by way of generally reducing imaging of structures on a mask, using what is referred to as a reticle, on an element to be structured that is provided with photosensitive material. The minimum dimensions of the structures produced are directly dependent on the wavelength of the light used. Recently, light sources having an emission wavelength in the range of a few nanometres, for example between <NUM> and <NUM>, in particular in the region of <NUM>, have increasingly been used. The described wavelength range is also referred to as the EUV range. These highly complex projection exposure apparatuses, in particular for the EUV range, comprise inter alia an illumination optical unit and a projection optical unit, which are embodied as mechatronic systems and thus have highly complex actuators, sensors and also cooling and decoupling systems. Projection optical units typically have <NUM> to <NUM> mirrors, a large portion of the mirrors being adjustable in up to six degrees of freedom. As a result, these systems include up to <NUM> actuators and more than <NUM> sensors. Besides the highly accurate sensors for mirror positioning, a large number of sensors are used for temperature measurements, system start, acceleration measurements and further detection of physical properties. On account of the large number of systems and subsystems it is practically impossible to guarantee the function and imaging quality of the overall system over the lifetime. It should therefore be assumed that, for example, the positional control of a mirror will fail during the lifetime on account of a failed actuator. A redundant construction of the system is possible only to a limited extent on account of the requirement in respect of controllability and also the real structural space situation. A further requirement of highly complex projection exposure apparatuses is a fundamental capability for the retrofitting of functions and components, such as, for example, a deformable optical element or optical elements having further developed layers for the projection optical unit. As a result, firstly the quality and the imaging properties of the projection exposure apparatus can be improved, and secondly it is possible to react to effects that are still unknown at the time of development. Projection exposure apparatuses in the prior art already comprise the possibility of exchanging components defined in advance, which are usually selected in an early optical design status, such that a preferred accessibility can be taken into account during the development of the projection exposure apparatus. In this case, it is possible to exchange preferably the first and last optical elements in the beam path and only few elements within the beam path. The proportion of exchangeable optical elements in the systems in the prior art is in the range of <= <NUM>%. All other optical elements are no longer alterable over the lifetime of the system without the exchange of the projection optical unit, of some other system or of the overall system.

Concerning exchanging optical elements, US Patent Application Publication <CIT> discloses an exposure apparatus with removable modules; International Patent Application <CIT> discloses a projection exposure apparatus with modules comprising an infrastructure for coupling.

On account of complex process developments and costly commissioning for a projection exposure apparatus, wherein the differences between different projection exposure apparatuses that are within the scope of the specifications, the so-called fingerprint, and in particular the imaging properties that are greatly influenced by the projection optical unit are also taken into account, the trivial solution for retrofitting, namely the exchange of an entire system, such as the projection optical unit, is unacceptable. Other prior art documents are <CIT> and <CIT>.

It is an object of the present invention to provide an apparatus which resolves the above-described disadvantages of the prior art. It is a further object of the invention to specify a method for exchanging components in a projection lens and in a projection exposure apparatus.

This object is achieved by means of an apparatus and a method having the features of the independent claims. The dependent claims relate to advantageous further developments and variants of the invention.

A projection exposure apparatus according to the invention for semiconductor lithography having a projection optical unit comprises a sensor frame, a carrying frame, a module having an optical element and actuators for positioning and/or orienting the optical element. In this case, the module is arranged on the carrying frame and the sensor frame is embodied as a reference for the positioning and/or orientation of the optical element. The module comprises an infrastructure, which is embodied according to the invention such that it comprises interfaces for separating the module from the projection optical unit. The modular construction of the projection optical unit has the advantage that the individual modules can be exchanged in the field, that is to say where the end customer has installed them, and in this case the so-called fingerprint, that is to say the imaging features inherent to each projection exposure apparatus, can be maintained to the greatest possible extent. This is of particular relevance in so far as during the production of electronic components, besides the imaging quality of the projection optical unit itself, the exposure process and, in particular, the process for the light-sensitive coating can also have a crucial influence on the quality of the structure. The inherent features of each individual projection exposure apparatus are therefore taken into account in these processes. Furthermore, an individual module can be transported more easily on account of its smaller geometry and the complexity for an exchange is also advantageously simplified vis à vis the exchange of a projection optical unit.

Furthermore, the infrastructure can comprise electrical and/or optical lines and/or lines for a fluid. The modules can be separated from all these lines independent of the other modules, that is to say that it is possible to remove only one module from the projection optical unit, without the other modules losing their position in the process.

In addition, the infrastructure of a plurality of modules can be connected in parallel with one another. The lines of the infrastructure are thus embodied in a continuous fashion and comprise a branching for each module, such that a plurality or all of the modules can be supplied in parallel by an infrastructure line.

Alternatively, the infrastructure of a plurality of modules can be connected in series with one another. In this case, the lines of the infrastructure can at least partly comprise the lines of the modules, such that the infrastructure line extends from one module to the other and connects them in series. If a module is demounted, then the interfaces of the infrastructure between the modules are released and the module is removed. The modules and in particular the sensors of the modules remaining in the projection exposure apparatus are not altered mechanically upon the demounting of the one module, and can therefore be put into operation again without renewed setting up and/or calibration of the modules and/or sensors after the demounted module has been reinstalled.

In one variant of the invention, at least one module can comprise a module carrying frame. In this case, the module carrying frame can be embodied such that it can determine the stiffness of the module and can function as a central mechanical component of the module.

Furthermore, the actuators can be arranged on the module carrying frame. Said actuators are demounted with the module carrying frame in the case of a module being demounted. As a result, it is possible to carry out an exchange of the actuators on the demounted module, which advantageously simplifies the exchange of an actuator on account of the better accessibility.

In particular, the actuators can be exchanged without the module carrying frame being demounted. This has the advantage that, in the case of a defective actuator, the outlay for an exchange can be reduced to a minimum since all the other components, in particular the sensors, are not moved mechanically and, as a result, the commissioning of the module after the exchange of the actuator is also greatly simplified.

In a further variant of the invention, at least one module can comprise a sensor. The sensor can be constructed in a bipartite fashion and comprise a sensor element and a sensor reference, wherein the sensor element can be connected to the module.

In addition, the reference of the sensor can be arranged on the sensor frame.

In particular, the reference of the sensor can be embodied such that it is not altered as a result of the module being demounted. This has the advantage that the commissioning of the module and of the entire projection exposure apparatus after the exchange of a module is advantageously simplified and the outage times of the projection exposure apparatus can be reduced to a minimum.

In this case, the sensor can be embodied in particular as an interferometer or as an encoder. It is also conceivable for one portion of the sensors arranged in modules to be embodied as an interferometer and another portion of the sensors to be embodied as an encoder. In this case, the choice for the type of sensor depends predominantly on the arrangement of the module with respect to the sensor frame and the usually limited structural space conditions. Furthermore, any other type of a sensor suitable for the task is also conceivable.

In case the sensor is embodied as an interferometer it can comprise a sensor reference and a sensor element which are arranged at a distance in the range of <NUM> to <NUM> from each other.

Furthermore, the module carrying frame can comprise mechanical interfaces for positioning and orienting on the carrying frame. The carrying frame can be embodied as a central component of the projection exposure apparatus, to which all the modules can be mechanically connected.

In particular, the module carrying frame can be embodied such that when the module carrying frame is connected to the carrying frame, the stiffness of the carrying frame is increased. As a result, the carrying frame and the module carrying frame can be embodied with a low stiffness and can advantageously be embodied more easily as a result. The connection of the module carrying frame to the carrying frame is realized by means of a screw connection.

Furthermore, the module carrying frame can be connected to the carrying frame in an overdetermined manner (having excessive or redundant connections). As a result of the overdetermined mounting of the module carrying frame, for example, the screw-on forces can be increased and the overall stiffness of the modules screwed to the carrying frame can thus be increased. The force-locking connection brought about by friction can also be designed for higher operating loads and/or also transport loads, such as shocks, for example. A deformation possibly caused by the overdetermined mounting is decoupled by the actuators and not transferred to the optical element.

In one variant of the invention, the sensor frame can be arranged in the volume defined by the carrying frame. This has the advantage that the sensor frame can be constructed compactly and, as a result, has low moments of inertia, as a result of which in turn the vibrations brought about by external excitation can advantageously be reduced to a minimum.

In particular, the sensor frame can comprise a plurality of subframes. The multipartite construction of the sensor frame has the advantage that firstly manufacture and assembly, and secondly the transport of the individual parts can be simplified.

In this case, the subframes among one another can be referenced with respect to one another by way of sensors. The referencing of the subframes among one another has the effect that the positions of the individual frames with respect to one another, said positions varying as a result of movements of the frames with respect to one another, are always known and, as a result, the sensor frame can be used as a common reference for all of the modules.

In one variant of the invention, each optical element of the projection optical unit can be arranged in a dedicated module. This has the advantage that irrespective of the optical element or module at which a fault or damage occurs, the projection exposure apparatus can be ready for operation again with a minimal outage time.

Furthermore, the projection exposure apparatus can be embodied such that the module can be exchanged with a projection optical unit mounted in the projection exposure apparatus. An exchange of a module while the projection optical unit is still installed in the projection exposure apparatus reduces the outlay for the exchange and thus the outage time of the projection exposure apparatus, which in turn advantageously reduces the production costs of the electronic components.

In a method according to the invention for exchanging a module of a projection optical unit of a projection exposure apparatus for semiconductor lithography, wherein the module comprises an optical element, according to the invention a reference for positioning and/or orienting the optical element remains in the projection exposure apparatus during the exchange of the module. This reduces the outlay for the exchange of an optical element, such as, for example, a mirror, an actuator or any other component of a module, advantageously to a minimum.

In addition, the exchange of the module is carried out without an alteration on any of the other modules and the module to be exchanged is located between two other modules of the projection optical unit.

As a result, the referencing of the other modules can remain unchanged, which advantageously reduces the commissioning duration after an exchange.

Furthermore, the module can be calibrated after the exchange. The calibration of a module is less complex in comparison with the calibration of an entire projection optical unit.

The projection exposure apparatus can in particular be ready for operation again after the exchange and calibration of the module. It is therefore not necessary for any other module or a group of modules of the projection exposure apparatus to be put into operation.

In one variant of the invention, the exchange of the module can be carried out without an alteration on a sensor frame. As a result, optionally, a part of the calibration of the module is obviated and the commissioning duration is advantageously reduced further.

Furthermore, a mount in a reticle module and/or wafer module can be moved into a parking position for the exchange of the module. In order to transfer a reticle and/or wafer, it is possible to move to so-called parking positions in the reticle module and/or wafer module, as a result of which the access to the modules arranged below and/or respectively above the reticle and/or wafer, respectively, can be simplified. As a result, despite the arrangement of the optical elements with respect to the reticle module or wafer module and the given structural space conditions, a module can be exchanged without additional outlay.

In addition, the reticle module or wafer module can be demounted for the exchange of the module.

Furthermore, the projection optical unit can be removed from the projection exposure apparatus for the exchange of the module. This is the case whenever accessibility to the modules with the projection optical unit installed is not possible.

In one variant of the invention, the exchange of a module can have no influence on the process for exposing wafers which is optimized for the projection exposure apparatus. During the production of electronic components, besides the imaging quality of the projection optical unit, the exposure process and, in particular, the process in the light-sensitive coating during the exposure and in the subsequent processing thereof can also influence the quality of the structure. Therefore, these processes are optimized to the properties specific to each imaging. The imaging can already be significantly altered as a result of demounting of a projection optical unit and renewed mounting with the same optical elements, such that the process has to be optimized once again. By virtue of only one module being exchanged, with the arrangement of all the other modules simultaneously being maintained, the change of the individual imaging properties can be kept small enough that the existing process can continue to be used without adaptation.

In one variant of the invention, more than <NUM>%, in particular more than <NUM>%, in particular <NUM>%, of the optical elements of the projection optical unit can be exchanged without an alteration on any of the other modules.

Exemplary embodiments and variants of the invention are explained in more detail below with reference to the drawing. In the figures:.

<FIG> shows an example of the basic construction of a microlithographic EUV projection exposure apparatus <NUM> in which the invention can be used. An illumination system of the projection exposure apparatus <NUM> has, in addition to a light source <NUM>, an illumination optical unit <NUM> for the illumination of an object field <NUM> in an object plane <NUM>. EUV radiation <NUM> in the form of optical used radiation generated by the light source <NUM> is aligned by means of a collector, which is integrated in the light source <NUM>, in such a way that it passes through an intermediate focus in the region of an intermediate focal plane <NUM> before it is incident on a field facet mirror <NUM>. Downstream of the field facet mirror <NUM>, the EUV radiation <NUM> is reflected by a pupil facet mirror <NUM>. With the aid of the pupil facet mirror <NUM> and an optical assembly <NUM> having mirrors <NUM>, <NUM> and <NUM>, field facets of the field facet mirror <NUM> are imaged into the object field <NUM>.

A reticle <NUM> arranged in the object field <NUM> and held by a schematically illustrated reticle holder <NUM> is illuminated. A merely schematically illustrated projection optical unit <NUM> serves for imaging the object field <NUM> into an image field <NUM> in an image plane <NUM>. A structure on the reticle <NUM> is imaged on a light-sensitive layer of a wafer <NUM> arranged in the region of the image field <NUM> in the image plane <NUM> and held by a likewise partly represented wafer holder <NUM>. The light source <NUM> can emit used radiation in particular in a wavelength range of between <NUM> and <NUM>.

The invention can likewise be used in a DUV apparatus, which is not illustrated. A DUV apparatus is set up in principle like the above-described EUV apparatus <NUM>, wherein mirrors and lens elements can be used as optical elements in a DUV apparatus and the light source of a DUV apparatus emits used radiation in a wavelength range of <NUM> to <NUM>.

<FIG> shows a basic construction of a projection optical unit <NUM> according to the invention in a sectional illustration. The projection optical unit <NUM> comprises six optical modules <NUM> and is connected to a reticle module <NUM> and a wafer module <NUM>. The modules <NUM>, <NUM>, <NUM> are arranged around a central sensor frame <NUM> and are connected to a carrying frame <NUM>. The modules <NUM>, <NUM>, <NUM> can also additionally be connected among one another. In this case, the modules <NUM>, <NUM>, <NUM> are embodied such that they can be separated from the projection optical unit <NUM> in the direction of the arrows, without any other module <NUM>, <NUM>, <NUM> having to be altered as a result. The remaining modules <NUM>, <NUM>, <NUM> do not have to be calibrated or oriented anew after the demounted module <NUM>, <NUM>, <NUM> or an identical replacement module <NUM>, <NUM>, <NUM> has been reinstalled, with the result that only the exchanged module <NUM>, <NUM>, <NUM> has to be calibrated anew, if appropriate.

The modules <NUM>, <NUM>, <NUM> are embodied such that they can be demounted and installed again without the other modules <NUM>, <NUM>, <NUM> or the module <NUM>, <NUM>, <NUM> itself being influenced.

The optical modules <NUM> comprise at least one sensor <NUM>, wherein the latter comprises a sensor element <NUM> and a sensor reference <NUM>. While the sensor element <NUM> is arranged on the optical element <NUM>, the sensor reference <NUM> is arranged on the sensor frame <NUM> and thus determines the position and location of the optical element with respect to the sensor frame <NUM> and thus with respect to all the other optical modules <NUM>, the reticle module <NUM> and the wafer module <NUM>. In this case, the sensors <NUM> can be embodied in particular as interferometers or as encoders.

In case interferometric sensors <NUM> are used, the sensor element <NUM> may comprise a mirror which reflects optical radiation emitted by a sensor reference <NUM> which can be embodied as a sensor head of the interferometric sensor <NUM>. In this case, it is possible to arrange the sensor reference <NUM> and the sensor element <NUM> at a greater distance from each other, in particular up to <NUM> - <NUM> centimeters. Using interferometric sensors makes it possible to realize a more compact sensor frame <NUM> which is more advantageous in respect of the excitation of oscillations. Furthermore, a more compact sensor frame <NUM> effectuates more free installation space. In particular, a more compact sensor frame <NUM> reduces the complexity of an exchange or a removal of an optical module <NUM>.

The sensor frame <NUM> and the carrying frame <NUM> are decoupled from one another (not illustrated), such that reaction forces of the actuators (not illustrated) of the optical modules <NUM> cannot dynamically excite the sensor frame <NUM>. The sensor frame <NUM> and the carrying frame <NUM> are additionally also mounted in a decoupled manner vis à vis the projection exposure apparatus <NUM> (likewise not illustrated), as a result of which excitations from the ground or other systems of the projection exposure apparatus have no or only a negligibly small influence on the imaging quality of the projection exposure apparatus.

The EUV radiation <NUM> emitted by the light source <NUM> illustrated in <FIG> and guided onto the reticle <NUM> by way of the illumination optical unit <NUM> likewise illustrated in <FIG> is reflected at the reticle <NUM> and is reflected by the individual modules <NUM> via the optical elements <NUM> embodied as mirrors <NUM> and is imaged onto the wafer <NUM>. The reticle <NUM> is arranged in a reticle holder <NUM> and can be moved with the latter parallel to the object plane <NUM>. The wafer <NUM> is arranged in a wafer holder <NUM> and can likewise be moved parallel to an image plane <NUM>.

<FIG> shows a detail view of the invention, illustrating an exert from the carrying frame <NUM> with an optical module <NUM> in a sectional illustration. The optical module <NUM> typically comprises three actuators <NUM>, which are embodied as bipods and can position the optical element <NUM> in six degrees of freedom. In the example shown, only one actuator <NUM> is illustrated for reasons of clarity. The actuators <NUM> are connected to a module carrying frame <NUM>, which is fixed to a flange <NUM> of the carrying frame <NUM> by screws <NUM>, whereby a mechanical interface <NUM> is formed between module carrying frame <NUM> and carrying frame. By virtue of this arrangement, it is easily possible for the optical module <NUM> to be released from the carrying frame <NUM> and demounted. The optical module <NUM> stiffens the carrying frame <NUM> by virtue of the screw connection, embodied as an overdetermined screw connection, with the result that the eigenmodes of the carrying frame <NUM> are advantageously increased. In this case, the actuators <NUM> are embodied, or arranged in the module carrying frame <NUM>, such that they can be exchanged even without the optical module <NUM> being demounted (see arrow). The optical element <NUM> comprises the sensor element <NUM> of the sensor <NUM>, which together with the actuator <NUM> and an open-loop or closed-loop control (not illustrated) can position and orient the optical element <NUM> with an accuracy in the range of less than one nanometre.

<FIG> shows a further detail view of the invention, illustrating the optical module <NUM> in a sectional illustration. Besides the actuators <NUM> and sensors <NUM> illustrated in <FIG>, the optical module <NUM> also comprises end stops <NUM>, which restrict the movement of the optical element, as a result of which the actuators, embodied as Lo-renz actuators, for example, and also the optical element <NUM> itself are protected against damage. Actuators and sensors are not illustrated in <FIG> for reasons of clarity. The end stops <NUM> are held in mounts <NUM> arranged on the module carrying frame <NUM>, wherein the end stops <NUM> are embodied such that they are easily accessible and exchangeable with the module <NUM> having been demounted.

<FIG> shows a further detail view of the invention, illustrating an exert from the carrying frame <NUM> and an optical module <NUM> in a sectional illustration. The actuators, sensors and also the end stops shown in <FIG> are illustrated in <FIG> for reasons of clarity. The transport securing means <NUM> are connected to the module carrying frame <NUM> by way of screws <NUM>, wherein the transport securing means <NUM> are illustrated in the transport position, that is to say the position used for transporting the optical modules <NUM>. The transport securing means <NUM> presses, for example by way of a spring force, the optical element <NUM> into the end stops thereof (not illustrated), as a result of which the optical element <NUM> is fixed. In this case, the transport securing means <NUM> are also embodied such that they can be exchanged even without the optical module <NUM> being demounted.

All the functional elements required for the positioning and orientation of the optical element <NUM>, that is to say actuators, sensors, end stops and transport securing means, are arranged on the module and can thus be exchanged in a simple manner and without the module being disassembled, in part even without the module being demounted from the projection optical unit.

<FIG> shows a further detail view of the invention, illustrating the optical module <NUM> installed in the carrying frame <NUM> from the rear side facing away from the optical element (not visible). The optical module <NUM> comprises three actuators <NUM>, which are arranged at an angle of <NUM>° in each case, three transport securing means <NUM>, which are arranged offset with respect to the actuators <NUM> by <NUM>° in each case, and three interfaces <NUM> for an exchange device (not illustrated) for exchanging the optical module <NUM>. Furthermore, interfaces <NUM>, <NUM> for the infrastructure <NUM> of the optical module <NUM> are also arranged on the rear side of the optical module <NUM>. In two of the four corners of the module carrying frame <NUM> embodied in a rectangular fashion, there is embodied in each case an interface <NUM> for fluid lines, by means of which the optical module <NUM> can be connected to a compressed air line or a hydraulic line. An interface <NUM> for cables, that is to say for electrical or optical lines, is arranged in direct proximity, a plurality of plug connections being arranged next to one another. A plurality of screws <NUM> - arranged in a row - of the screw connection <NUM> of the optical module <NUM> to the carrying frame <NUM> are arranged on two sides of the module carrying frame <NUM>. By virtue of this overdetermined connection, the contact stiffness can be designed such that the module carrying frame <NUM> as part of the carrying frame positively increases the eigenmodes of the carrying frame <NUM> and the module carrying frame <NUM> is prevented from slipping on the carrying frame <NUM>, for example as a result of shock events during transport.

<FIG> shows a further detail view of the invention, illustrating an optical module <NUM> having an optical element <NUM> in a plan view from the front side of the optical module <NUM>. Actuators, sensors, end stops and transport securing means are not illustrated for reasons of clarity, or are concealed by the optical element <NUM>. Furthermore, three mechanical interfaces <NUM> are arranged at an angle of <NUM>° with respect to one another, which mechanical interfaces are embodied such that the optical module <NUM> can be positioned on the carrying frame (not illustrated) with an accuracy of below <NUM>, in particular below <NUM> and in particular below <NUM>. In this case, the travel of the actuators (not illustrated) is designed such that the optical element <NUM> can be positioned in its desired position and desired orientation after the optical module <NUM> has been screwed to the carrying frame. After the module carrying frame <NUM> has been oriented on the carrying frame (not illustrated), it is connected to the carrying frame by the screw connection <NUM>, only the through holes <NUM> of the screw connection <NUM> being illustrated in <FIG>.

<FIG> shows a further detail view of the invention, illustrating an interface <NUM> for fluid lines <NUM>. In this case, the interface <NUM> comprises two adapters <NUM>, <NUM>', which are respectively arranged in a cutout <NUM>, <NUM>' on the module carrying frame <NUM> and on the carrying frame <NUM>. The line <NUM> is guided in a receptacle <NUM> in the module carrying frame <NUM> and the end of said line bears against the adapter <NUM>. The latter is additionally sealed vis à vis the cutout <NUM> by way of a seal <NUM> and fixed by screws <NUM> in the module carrying frame <NUM>. A conically tapering tube section <NUM> is embodied on that side of the adapter <NUM> which is directed towards the corresponding adapter <NUM>' of the carrying frame <NUM>, which tube section, when the module <NUM> is screwed to the carrying frame <NUM>, descends into a corresponding opening <NUM> in the adapter <NUM>' of the carrying frame <NUM> and creates a tight connection as a result of the conical embodiment. A seal <NUM> is arranged outside the opening <NUM> and brings about an additional sealing between the adapter <NUM>'. The adapter <NUM>' is arranged in a cutout <NUM>' of the carrying frame <NUM> and is connected to the latter by means of screw <NUM>.

<FIG> shows a further detail view of the invention, illustrating an interface <NUM> for lines <NUM> embodied as electrical or optical cables <NUM>. The sockets <NUM> of the plug connection <NUM> are arranged in a socket receptacle <NUM>', which in turn is arranged in a cutout <NUM>' of the carrying frame <NUM> and is connected to the latter by screws <NUM>. The plugs <NUM> corresponding to the sockets <NUM> are arranged in a plug receptacle <NUM>, which is connected to the module carrying frame <NUM> in a cutout <NUM> by way of an elastic mount <NUM> embodied as a spring. For aligning the plugs <NUM> and sockets <NUM> during the connection of the module carrying frame <NUM> and the carrying frame <NUM>, depressions <NUM> are formed in the plug receptacle <NUM>, and pins <NUM> having a corresponding geometry, which are arranged on the socket receptacle <NUM>', can enter into said depressions. As a result, the plugs <NUM> and sockets <NUM> are prealigned and can be plugged together in a simple manner. An encoding can also be established by the pins <NUM>, such that different receptacles <NUM>, <NUM>' can be plugged only at the positions provided for them and in the correct orientation, as a result errors owing to incorrect plug connections <NUM> can advantageously be avoided.

Claim 1:
Projection exposure apparatus (<NUM>) for semiconductor lithography having a projection optical unit (<NUM>) comprising
- a sensor frame (<NUM>),
- a carrying frame (<NUM>),
- a module (<NUM>) having an optical element (<NUM>) and actuators (<NUM>) for positioning and/or orienting the optical element (<NUM>), wherein the module (<NUM>) is arranged on the carrying frame (<NUM>) and the sensor frame (<NUM>) is embodied as a reference for the positioning and/or orientation of the optical element (<NUM>), and wherein the module (<NUM>) comprises an infrastructure (<NUM>),
characterized in that
the infrastructure (<NUM>) is embodied such that it comprises interfaces (<NUM>, <NUM>) for separating the module (<NUM>) from the projection optical unit (<NUM>), wherein at least one module (<NUM>) comprises a module carrying frame (<NUM>) and wherein the module carrying frame (<NUM>) is fixed to a flange (<NUM>) of the carrying frame (<NUM>) by screws (<NUM>), whereby a mechanical interface (<NUM>) is formed between module carrying frame (<NUM>) and carrying frame (<NUM>) and wherein the module carrying frame (<NUM>) is connected to the carrying frame (<NUM>) in an overdetermined manner.