Optical module with a measuring device

An optical module, in particular for microlithography, with an optical element unit, a support device, a deformation device and a measuring device is disclosed. The support device is supported on the optical element unit, whereas for deforming an optical surface of the optical element unit, the deformation device engages a deformation section of the optical element unit comprising the optical surface. For determining the position and/or the orientation of the optical element unit with respect to an external reference in at least one degree of freedom, the measuring device comprises at least one measuring element, wherein the measuring element is arranged on a reference section of the optical element unit.

BACKGROUND OF THE INVENTION

The present invention relates to an optical module, an optical element unit for the optical module and a method for determining the position and/or the orientation of an optical element unit. The invention can be used in connection with microlithography employed in the fabrication of microelectronic circuits.

In particular in the area of microlithography, in addition to the use of components made with the highest possible accuracy, it is necessary, among other things, to position the components of the imaging device, for example the optical elements such as lenses or mirrors, as precisely as possible, in order to achieve a correspondingly high image quality. The high requirements on accuracy, which are in the microscopic range of the order of magnitude of a few nanometers or less, are not least a consequence of the constant need to increase the resolution of the optical systems used in the fabrication of microelectronic circuits, in order to drive forward the miniaturisation of the microelectronic circuits that are to be produced.

With the increased resolution and, therefore, as a rule the concomitant decrease in wavelength of the light used, it is not only the requirements on the positional accuracy of the optical elements used that increase. Naturally, there is also an increase in the requirements with respect to minimising the imaging errors of the whole optical arrangement.

To minimise the imaging errors, it is known, for example from U.S. Pat. No. 6,842,277 B2 (Watson; the complete disclosure of which is incorporated herein by reference) and U.S. Pat. No. 7,443,619 B2 (Sakino et al.; the complete disclosure of which is incorporated herein by reference), to actively deform the optically active surfaces of one or a plurality of optical elements of the imaging system, in order to correct wavefront aberrations. To this end, for example, a number of actuators supported by a support structure of the mirror engage a back side of a mirror and introduce the corresponding forces and/or moments into the mirror, in order to achieve a desired deformation of the mirror surface relative to a setpoint geometry or rigid body geometry of the mirror.

These forces and/or moments for deformation of the mirror surface may as a rule also lead to a change in the position and/or orientation of the mirror (insofar as it is regarded as an infinitely rigid body), which in its turn must be corrected. The terms rigid body position or rigid body orientation of the optical element are often used in this context.

Correction of the position and/or orientation of the optical element is typically based on the measuring signals of one or a plurality of sensors, which detect the position and/or orientation of the optical element with respect to at least one reference, as is also known from U.S. Pat. No. 6,842,277 B2. A critical factor is that the deformation can cause a relative movement in the region of the measurement point, although the rigid body position or rigid body orientation of the optical element has not changed, or not to the extent captured by the sensors, so that corrections of the position and/or orientation of the optical element are performed, although these are not required.

A disadvantage of the solution proposed in U.S. Pat. No. 7,443,619 B2 is that the optical element and the deformation device form one unit, which in its turn has to be corrected in its position and/or orientation. If this correction of the rigid body position or orientation must take place very quickly, a heavy unit is a disadvantage. Moreover, rapid correction is hampered by cables or the like, which supply the deformation device. Moreover, such a unit requires considerable space, so that attainment of a high resonant frequency of the unit, which would be necessary for favourable control behaviour, becomes much more complicated.

BRIEF SUMMARY OF THE INVENTION

The problem to be solved by the present invention is therefore to provide an optical module, an optical element unit for the optical module and a method for determining the position and/or the orientation of an optical element unit, which does not have the aforementioned disadvantages or at least has them to a smaller extent and, in particular, in a simple manner, makes it possible for imaging errors to be corrected as simply as possible.

A further object to be achieved by the present invention is to provide an optical module, an optical element unit for the optical module and a method for determining the position and/or the orientation of an optical element unit, which offers the possibility of a determination that is as simple as possible and, optionally, of a highly dynamic correction of the rigid body position or rigid body orientation of the optical element.

The present invention is based on the finding that a simple determination and, optionally, a correction of the rigid body position or rigid body orientation of the optical element are made possible if the measuring device for determining the position and/or the orientation of the optical element unit with respect to an external reference in at least one degree of freedom comprises at least one measuring element, which is arranged on a reference section of the optical element unit, which is substantially unaffected by the deformation introduced into the optical element. This can be achieved by a corresponding distance of the reference section and/or a stress decoupling of the reference section from the deformed section. Both have in each case the effect that the deformation stresses (i.e. the stresses that bring about the desired deformation of the optical element) substantially do not propagate into the region of the measuring element and do not notably influence its position and/or orientation. Accordingly, in an advantageous manner, the actual rigid body position and/or rigid body orientation of the optical element can be captured via the measuring element in one or a plurality of degrees of freedom (up to all six degrees of freedom).

One object of the present invention is therefore an optical module, in particular for microlithography, with an optical element unit, a support device, a deformation device and a measuring device. The support device supports the optical element unit, whereas for deforming an optical surface of the optical element unit, the deformation device engages a deformation section of the optical element unit comprising the optical surface. For determining the position and/or the orientation of the optical element unit with respect to an external reference in at least one degree of freedom the measuring device comprises at least one measuring element, wherein the measuring element is arranged on a reference section of the optical element unit. The reference section is arranged at a distance from the deformation section and/or decoupled from the deformation section via at least one decoupling section in such a manner that a deformation of the optical element unit introduced by the deformation device into the deformation section substantially does not propagate into the region of the measuring element.

Another object of the present invention is an optical element unit for an optical module, in particular for microlithography, with a support section for engaging a support device, a deformation section for engaging a deformation device for deforming an optical surface of the optical element unit and a measuring device. For determining the position and/or the orientation of the optical element with respect to an external reference in at least one degree of freedom the measuring device comprises at least one measuring element, wherein the measuring element is arranged on a reference section of the optical element unit. The reference section is arranged at a distance from the deformation section and/or decoupled from the deformation section via at least one decoupling section in such a manner that a deformation of the optical element unit introduced by the deformation device into the deformation section substantially does not propagate into the region of the measuring element.

Another object of the present invention is a method for determining the position and/or the orientation of an optical element unit, in particular for microlithography, in which an optical surface of a deformation section of the optical element unit is deformed and the position and/or the orientation of the optical element unit with respect to an external reference is detected, in at least one degree of freedom, via at least one measuring element, wherein the measuring element is arranged on a reference section of the optical element unit. The reference section is arranged at a distance from the deformation section and/or decoupled from the deformation section via at least one decoupling section in such a manner that a deformation of the optical element unit introduced into the deformation section substantially does not propagate into the region of the measuring element.

Further preferred embodiments of the invention become apparent from the dependent claims or from the following description of preferred embodiments, which make reference to the appended drawings. All combinations of the features disclosed, whether explicitly recited in the claims or not, are within the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Referring toFIGS. 1 to 3, a preferred embodiment of an optical imaging device101according to the invention for microlithography is described in the following, which comprises a preferred embodiment of an optical module according to the invention with a preferred embodiment of an optical element unit according to the invention. To simplify the following explanations, an xyz coordinate system is introduced in the figures, and will be referred to hereinafter.

FIG. 1shows a highly schematic representation of the optical imaging device in the form of a microlithography device101, which operates with light of a first wavelength in the EUV range (i.e. at a wavelength from 5 nm to 20 nm, typically at about 13 nm). The microlithography device101comprises an imaging unit in the form of an optical projection system102with an illuminating system103, a mask device104and an optical device in the form of an objective105. The illuminating system103comprises an optical element group106and illuminates (via a lightguide device not shown in more detail) the mask104.1of the mask device104with a projection light beam101.1(not shown in more detail in this section).

On the mask104.1, which is arranged on a mask table104.2, in an object plane there is a projection pattern, which is projected using the projection light beam101.1via the optical elements arranged in the objective105into an image plane on a substrate108.1, for example a so-called wafer, of a substrate device108.

For this purpose the objective105comprises an optical element group107, which is formed from a number of optical elements111, which are accommodated in the housing105.1of the objective105, which in turn is supported on a support structure109. The optical elements111project the projection light beam101.1onto the substrate108.1and thus image an object point of the projection pattern onto an image point on the substrate108.1.

FIG. 3shows a preferred embodiment of the optical module according to the invention110, which comprises an optical element unit in the form of one of the optical elements111. The optical element111is supported by a support device112of the optical module110, and the support device112, in turn, is supported on the support structure109(via the housing105.1).

In order to be able to correct wavefront aberrations of the projection light beam101.1during imaging of the projection pattern onto the wafer108.1, the optical module110comprises on the one hand a deformation device113. Via the deformation device113, the optical surface111.1of the optical element111interacting with the projection light beam101.1can be deformed during projection, to counteract undesirable deviations in the wave front of the projection light beam101.1.

The deformation device113comprises for this purpose a number of deformation elements in the form of first actuators113.1, which in the present example are arranged in a circumferential recess111.2provided in a main body111.3of the optical element111and extending in the circumferential direction U over the entire circumference of the optical element111.

The circumferential recess111.2forms, on the optical element111, a circumferential peripheral section111.4in the circumferential direction U and a central base section111.5. The first actuators113.1are in the present example aligned substantially in the radial direction R of the optical element111, and therefore lie in a circumferential plane defined by the circumferential direction U. The first actuators113.1are supported in each case on the one hand at a first engagement point on the peripheral section111.4and on the other hand at a second engagement point displaced inwards in the radial direction R on the base section111.5.

The recess111.2introduces a deliberate structural weakening into the optical element111, which makes it possible, in a simple manner, via the force of the first actuators113applied for example in the radial direction R, to introduce a defined deformation into a deformation section111.6of the optical element111comprising the optical surface111.1.

In particular, it is possible to make the recess111.2and therefore the deliberate weakening of the optical element111non-uniform, corresponding to the desired deformation in any directions in space, in particular in the circumferential direction U and/or the radial direction R, as indicated inFIG. 3by the dashed contours114. It will be understood, however, that in other variants of the invention, in which a substantially symmetrical deformation of the optical surface is desired, a strictly symmetrical arrangement or configuration can also be selected.

It will be understood that, in other variants of the invention, naturally any other configuration of the deformation device can also be selected, in order to achieve the desired deformation of the optical surface. In particular, some other configuration and/or orientation of the first actuators can be selected. Moreover, it is not essential to provide the recess described above. It is merely favourable if the first actuators bear on both sides directly on the optical element and not on an external support structure, as in this way the introduction of parasitic stresses from such an external support structure into the optical element can be avoided in a simple manner.

Control of the deformation of the optical surface111.1takes place in the present example via a control device115controlling the first actuators113.1. For this, a first measuring unit116of a measuring device, connected to the control device115, is provided, which comprises a first emitter device116.1and an associated first sensor device116.2. The emitter device116.1(under control by the control device115) sends a measuring light beam116.3onto the optical surface111.1, which is reflected there and is directed onto the sensor device116.2. On the basis of the signals of the sensor device116.2transmitted to the control device115, a conclusion about the existing deformation of the optical surface111.1can then be made in the control device115. Optionally the control device115then controls the first actuators113.1according to specified setpoint values, in order to adjust the deformation of the optical surface111.1.

It will be understood that, in other variants of the invention, the first measuring unit can also be constructed differently, for detecting the deformation of the optical surface. In particular, it can naturally also comprise one or a plurality of first emitter devices and/or a plurality of first sensor devices, which are assigned to the optical element corresponding to the deformation of the optical surface to be detected.

The forces introduced via the first actuators113.1into the optical element give rise to mechanical stresses in the deformation section111.6, which lead to a corresponding deformation of the deformation section and, accordingly, are designated in the sense of the present application as deformation stresses.

In addition to the deformation of the optical surface111.1, in the present example, a correction of the rigid body position (i.e. of the translation in the three translational degrees of freedom in space) and of the rigid body orientation (i.e. of the rotation about the three rotational degrees of freedom in space) is also possible. These settings of the rigid body position and rigid body orientation in all six degrees of freedom are achieved in the following example via a positioning device117, which is also controlled by the control device115.

The positioning device117comprises for this purpose a number of second actuators117.1, which, in the present example, are arranged in the manner of parallel kinematics in the form of a hexapod (which is constructed conventionally from three bipods arranged uniformly distributed in the circumferential direction U).

It will be understood, however, that in other variants of the invention, any other configuration of the positioning device, in particular any other configuration and arrangement of the second actuators, can also be selected. In particular, it can naturally also be envisaged that, depending on the requirements of the particular imaging device, the setting of the rigid body position and/or of the rigid body orientation of the optical element takes place in fewer than six degrees of freedom.

The positioning device117is supported on the one hand on the support structure112and engages a reference section111.8of the optical element111in the region of the back side111.7of the optical element111facing away from the optical surface111.1. The reference section111.8is formed on a projection, which projects on the back111.7of the optical element111from the substantially disk-shaped deformation section111.6.

The reference section111.8carries, on its outer circumference, a first measuring element118.1of a second measuring unit118of the measuring device, which serves for detecting the rigid body position and the rigid body orientation of the optical element. For this, a second measuring element118.2, which is arranged on the support structure112, is assigned to the first measuring element118.1.

At the circumference of the reference section111.8, a plurality of measuring element pairs118.3consisting of a first measuring element118.1and a second measuring element118.2are provided, so as to be able to detect the rigid body position and the rigid body orientation of the optical element111in all six degrees of freedom.

It will be understood that the number of measuring element pairs118.3depends on the number of degrees of freedom to be detected and on the redundancy that is optionally required in this context. In certain variants of the invention, optionally even a single measuring element pair may be sufficient.

In the present example, the first measuring element118.1is a simple, passive reference element, which interacts in a suitable, adequately known way with the second measuring element118.2designed as active component, in order to transmit a corresponding measuring signal to the control device115connected to the second measuring element118.2.

Based on this measuring signal and the measuring signals of the other measuring element pairs118.3, the control device115can then determine the current rigid body position and rigid body orientation of the optical element111. Depending on certain requirements arising from the current imaging process of the imaging device101, the control device115can then control the second actuators117.1, in order to correct the rigid body position and rigid body orientation of the optical element111in the desired manner.

It will be understood that the measuring element pairs can operate according to any suitable operating principle that provides suitable information about the relative position of the two measuring elements. For example, measuring element pairs operating by interferometry can be used, where the first measuring element is then in the form of a simple reflector. Measuring element pairs operating according to an encoder principle can also be envisaged, wherein the first measuring element can then for example be a corresponding one- or two-dimensional grating or the like.

It will be understood, moreover, that the first measuring element need not necessarily be a passive element. However, configuration as a passive element has the advantage that no kind of mechanical connection, for example via signal leads or the like, is necessary between the optical element and the support structure, so that the risk of introducing parasitic stresses via such a connection is eliminated in an particularly simple manner.

The deformation device113exerts, in normal operation of the optical module110, at most a specified maximum force Fmaxon the optical element111. From this maximum force Fmax, deformation stresses with a maximum first deformation stress DS1maxresult in the deformation section111.5.

To prevent the deformation introduced via the deformation device113into the optical element111affecting the measurement result of the second measuring unit118and therefore notably corrupting the measurement of the current rigid body position and rigid body orientation of the optical element111through deformation in the region of the first measuring element118.1, the reference section111.8with the first measuring element118.1is designed and arranged at a distance from the optical surface111.1in such a manner that from the maximum force effect Fmaxof the deformation device113, in the reference section111.8, a stress distribution results having a maximum second deformation stress DS2max.

The maximum second deformation stress DS2maxis in the present example less than 3% of the maximum first deformation stress DS1max. This has the advantage that, in normal operation of the imaging device101, there is no noteworthy corruption of the measurement result of the second measuring unit118, so that the correct rigid body position and rigid body orientation of the optical element111are always detected and no false corrections occur via the positioning device117.

It will be understood that, in other variants of the invention, greater deformation of the reference section can also be permitted. This may be the case, in particular, when the measurement of the second measuring unit is not sensitive to the deformation to be expected (for example when the deformation to be expected occurs in a degree of freedom that differs from or is independent from the degree of freedom to be detected).

Preferably, however, the reference section is designed and arranged in such a way that the maximum second deformation stress DS2maxis less than 20% of the maximum first deformation stress DS1max. In favourable configurations the maximum second deformation stress DS2maxis at most 10% of the maximum first deformation stress DS1max, preferably at most 3% of the maximum first deformation stress DS1max.

In the present example, the advantageously low second deformation stress DS2maxis achieved on the one hand because the reference section111.8is located at a sufficiently large distance from the deformation section111.6or the optical surface111.1, so that the deformation stresses have largely degraded before they reach the reference section111.8.

On the other hand, the reference section111.8is mechanically decoupled from the deformation section111.6via a decoupling device111.9, above all from the contact points of the deformation device113, so that direct introduction of deformation stresses into the reference section111.8, in particular into the region with the second measuring unit118, is reliably prevented.

The decoupling device111.9, in the present example, takes the form of a simple, circumferential recess in the main body111.3of the optical element111. It will be understood, however, that in other variants of the invention, instead of such a constriction of the main body of the optical element, any other mechanical decoupling can also be provided between the deformation section and the reference section.

Furthermore, it will be understood that, in other variants of the invention, this additional decoupling can also be omitted. In that case the introduction of deformation stresses into the reference section can for example be avoided simply by a sufficiently large distance between the reference section and the deformation section.

Both measures (arrangement with increased distance and decoupling of the reference section111.8from the deformation section111.6) thus have the effect that a deformation of the optical element111introduced via the deformation device113into the deformation section111.6does advantageously substantially not propagate into the region of the first measuring element118.1.

As already described above, the deformation section111.6is in the form of a substantially disk-shaped body, which in the present example defines a center axis111.10.

This center axis111.10can be an axis of symmetry of the optical element111, such as is the case for example with rotationally symmetrical elements. However, in the case of optical elements that do not have such an axis of symmetry, for example aspherical optical elements, it can also be the axis normal to the optical surface passing through the centroid of area of the optical surface.

The projection with the reference section111.8is in the present example arranged essentially concentrically with the center axis111.10. It will be understood, however, that in other variants of the invention an arrangement of the reference section differing from this can also be envisaged.

In preferred variants of the present invention (with dimensioning differing from the dimensioning shown inFIG. 3), the deformation section111.6has a maximum first longitudinal dimension L1in a longitudinal direction in the direction of the center axis111.10, whereas the projection with the reference section111.8in this longitudinal direction has a maximum second longitudinal dimension L2, wherein the second longitudinal dimension L2is more than 80% of the first longitudinal dimension L1. Preferably the second longitudinal dimension L2is more than 100% of the first longitudinal dimension L1, in particular more than 150% of the first longitudinal dimension L1. Such a configuration has the advantage that merely through the resultant large distance between the reference section111.8and the deformation section111.6, the introduction of deformations into the reference section111.8, which could corrupt the measurement result of the second measuring unit118, is reliably prevented.

Moreover, the deformation section111.6has a maximum first transverse dimension D1in a transverse direction running transversely to the center axis111.10, whereas the projection with the reference section111.8in this transverse direction has a maximum second transverse dimension D2. The second transverse dimension D2is in the present example less than 80% of the first transverse dimension D1. In further preferred variants of the invention the second transverse dimension D2is less than 60% of the first transverse dimension D1, in particular less than 40% of the first transverse dimension.

It should be mentioned at this point that it is advantageous if the recess111.9forming the decoupling device is made as deep as possible, to achieve greatest possible decoupling. In preferred variants of the invention, the main body111.3, in the region of the recess111.9, has a maximum third transverse dimension D3in the transverse direction, which is less than 80% of the second transverse dimension D2. In further preferred variants of the invention the third transverse dimension D3is less than 60% of the second transverse dimension D2, in particular less than 40% of the second transverse dimension D2.

The optical element or the optical element unit111, respectively, is designed in the present example as a monolithic element of a material with a coefficient of thermal expansion close to zero. It will be understood, however, that in other variants of the invention a multipart configuration of the optical element unit can also be envisaged. In particular, the deformation section and the reference section can be made of different components. The decoupling device can also then be formed from one or more separate elements.

FIG. 2shows a flow chart of a preferred embodiment of the method according to the invention for determining the position and/or the orientation of an optical element unit, which is carried out in the context of an imaging process in the form of a microlithography process, which for its part is carried out with the microlithography device101as shown inFIGS. 1 and 3, operating according to the so-called scanner principle.

First, in a step119.1, the procedure of the microlithography process is started, wherein the microlithography device101is provided in the configuration seen inFIGS. 1 and 3.

In a deformation step119.2, first a determination of the imaging error takes place in a determination step in parallel with the illumination of the substrate108.1. Based on the imaging error determined, a deformation of the optical element111then takes place via the deformation device113in the manner described above, in order to counteract this imaging error.

In a step119.3, the determination described above in connection withFIGS. 1 and 3and optionally correction of the rigid body position and rigid body orientation of the optical element111take place subsequent to or parallel with the deformation step119.2via the positioning device117, also serving to reduce the imaging error.

As mentioned, the determination and correction of the deformation and of the rigid body position and rigid body orientation of the optical element111takes place in parallel with the illumination of the substrate108.1. At least as long as no imaging errors are detected that would make termination of the illumination of the substrate108.1necessary, the illumination thus takes place simultaneously with and independently of the determination and correction of the imaging error.

In a further step119.4, it is then verified whether yet another correction operation should be performed. If this is not the case, the procedure is ended in step119.5. Otherwise it jumps back to step119.2.

Second Embodiment

In the following, referring toFIGS. 1,2and4, another preferred embodiment of an optical module according to the invention210is described, which can be used instead of the optical module110in the microlithography device101shown inFIG. 1.

The optical module210, in its design and functionality, basically corresponds to the optical module110inFIG. 3, so only the differences will be discussed here. In particular, components of the same kind are given a reference numeral increased by 100. Unless stated otherwise below, with regard to the properties of these components, reference is made to the explanations given above in connection with the first embodiment.

The optical module210differs from optical module110in the connection of the positioning device217to the optical element211. As can be seen fromFIG. 4, in the present example, connection takes place via a decoupling device in the form of a decoupling ring219, which is connected via decoupling elements219.1to the main body211.3of the optical element211. The decoupling elements219.1serve in a conventional manner, on the one hand, to at least reduce the introduction of parasitic stresses from the support structure212into the optical element211, and to compensate different thermal expansions of the coupled components.

The decoupling elements219.1engage the main body211.3of the optical element211in the region of the deformation section211.6. This has the advantage that the reference section211.8is located both outside of the force flux of the forces introduced by the deformation device213into the optical element211and outside of the force flux of the forces introduced by the positioning device217into the optical element211. The introduction of (as a rule dynamic) stresses, which result from the force effect of the positioning device217, into the reference section211.8is also at least largely prevented in this way, so that corruption of the measurement result of the second measuring unit218by the stresses and the resultant deformation are also avoided.

It will be understood that for connecting to the support structure, the decoupling device need not necessarily be designed as a decoupling ring. Rather, any other configuration can be selected that achieves the corresponding decoupled connection of the optical element to the support structure. Furthermore, it will be understood that, in other variants of the invention, the decoupling device can even be omitted, so that therefore the positioning device is connected directly to the main body of the optical element.

As can also be seen fromFIG. 4, the reference section211.8is formed by a projection on the back211.7of the optical element211facing away from the optical surface211.1, the maximum second transverse dimension D2of which corresponds to about 40% of the maximum first transverse dimension D1of the deformation section211.6. Furthermore, once again the dimensions described above in connection with the first example can be selected.

As can also be seen fromFIG. 4, in certain variants of the invention a coupling device of a supply device can be provided, via which contactless coupling of the control signals and/or of power for the first actuators213.1of the deformation device213takes place, as is indicated by the dashed contour220. This contactless coupling device220can operate according to any suitable operating principle. For example, an inductive operating principle can be used. Such a configuration has the advantage that the introduction of parasitic stresses, which might take place via the connecting lines to the first actuators213.1, is avoided.

For the case when in operation (for example for adjustment of the settings) large travels of the optical element211must be performed, it can be envisaged that the portion of the coupling device220supported on the support structure follows the optical element211, for always ensuring reliable coupling of the signals and/or power. For this purpose, this portion of the coupling device can be arranged on a movable carrier or the like, correspondingly controlled by the control device115.

It should be mentioned at this point that with the optical module210, which is used in the imaging device101, naturally once again the method described in connection withFIG. 2can be carried out, so that to that extent reference is merely made to the explanations given above.

Third Embodiment

In the following, referring toFIGS. 1,2and5, another preferred embodiment of an optical module according to the invention310is described, which can be used instead of the optical module110in the microlithography device101shown inFIG. 1.

The optical module310, in its design and functionality, basically corresponds to the optical module110inFIG. 3, so that only the differences will be discussed here. In particular, components of the same kind are given a reference numeral increased by200. Unless stated otherwise below, with regard to the properties of these components, reference is to be made to the explanations given above in connection with the first embodiment.

The optical module310differs from the optical module110in the connection of the positioning device317to the optical element311. As can be seen fromFIG. 5, connection takes place (as in the second embodiment) via a decoupling device in the form of a decoupling ring319, which is connected via decoupling elements319.1to the main body311.3of the optical element311. The decoupling elements319.1, in a conventional manner, serve, on the one hand, to at least reduce the introduction of parasitic stresses from the support structure312into the optical element311, and to compensate different thermal expansions of the coupled components.

The decoupling elements319.1engage the main body311.3of the optical element311in the region of the deformation section311.6. This has the advantage that the reference section311.8is located both outside of the force flux of the forces introduced by the deformation device313into the optical element311and outside of the force flux of the forces introduced by the positioning device317into the optical element311. The introduction of (as a rule dynamic) stresses, which result from the force effect of the positioning device317, into the reference section311.8is also at least largely avoided in this way, so that corruption of the measurement result of the second measuring unit318by the stresses and the resultant deformation are also avoided.

However, with a corresponding configuration of the positioning device it is also possible to omit the decoupling ring319and to connect the positioning device as in the configuration shown inFIG. 3directly to the main body311.5.

As can also be seen fromFIG. 5, the reference section311.8(as in the second embodiment) is formed by a projection on the back side311.7of the optical element311facing away from the optical surface311.1, the maximum second transverse dimension D2of which corresponds to about 40% of the maximum first transverse dimension D1of the deformation section311.6. Furthermore, once again the dimensions described above in connection with the first embodiment can be selected.

As can also be seen fromFIG. 5, another difference from the optical module110shown inFIG. 3andFIG. 4is that the deformation device313does not operate exclusively within the optical element311but between the optical element311and the support structure312. For this purpose, the first actuators313.1engage the outer circumference of the boundary region311.4and an associated projection of the support structure212.

Also in this case, the first actuators313.1(at least in the state shown inFIG. 5) operate substantially in the radial direction R in a circumferential plane of the optical element311defined by the circumferential direction U of the optical element311. It will be understood that the actuators313.1are designed in such a way that they can follow the travel movements of the optical element311produced via the positioning device317, without altering their force effect on the optical element311and therefore the deformation of the optical surface311.1. For this purpose, they can for example be constructed as force actuators (for example as so-called Lorenz actuators).

Thus, the proposed solution already overcomes the disadvantages mentioned at the beginning, in that the optical element and the deformation device form one unit. With this solution, the unit that is to be moved can be of very much lighter and more compact design. This is advantageous, in particular, with respect to the high resonant frequency of the unit, which is favourable for highly dynamic control. Correction of the rigid body position and/or rigid body orientation can therefore take place very quickly. Moreover, rapid positional correction is not hampered by supply lines to the deformation device (such as cables or the like).

It should be mentioned at this point that with the optical module310, naturally once again the procedure described in connection withFIG. 2can be carried out.

The present invention was described above on the basis of examples, operating with illumination of the substrate with wavelengths in the EUV region. However, it should be pointed out at this point that the invention can naturally also be used in connection with applications in which the illumination of a substrate or an imaging of some other kind takes place at different wavelengths.

Furthermore, it should be noted that the present invention was described above with an example from the area of microlithography. It will be understood, however, that the present invention can also be used for any other applications or imaging processes.