JP5414968B2 - Measuring device and operating method of optical imaging system - Google Patents

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention includes an optical measurement device for optical measurement, such as an interferometer, for an optical imaging system intended for imaging effective patterns, and imaging error correction for such an optical imaging system. , Related to the operation method.

2. Description of Related Art The imaging quality of optical imaging systems is becoming increasingly demanding. One example of this is a projection objective for microlithographic manufacture of semiconductor components and finely structured components that are required to be completely imaging error free in the submicrometer range. Due to the complex optical design, it is generally impossible to derive the optical properties of the objective lens from theoretical calculations, so reliable measurement of the optical properties can be performed before use in, for example, a so-called wafer scanner for wafer exposure. Or in some cases during operation.

  Interferometer measurement methods are often used for this purpose. An apparatus that operates in the same way as a shearing interferometer for wavefront detection and enables high-speed, high-accuracy measurement of a high-resolution photolithographic projection objective is described in Japanese Patent Application Laid-Open No. DE 101 09 929 A1. Such a measuring device typically includes a wavefront source on its object side, i.e. on the object side of the optical imaging system to be measured, thereby producing at least one radiating wavefront and its wavefront. Provides interferometer information indicating the imaging system, the image side, i.e., the image side diffraction grating of the optical imaging system being measured, and the downstream of the diffraction grating and indicating imaging errors in the system being measured and Pass the position-resolved detector to detect. The imaging error can be determined from the detected interference information by an appropriate evaluation means.

  As an example, a so-called source or wavefront module can be used as an illumination module as a wavefront source, which has a measurement mask in the form of a so-called hole or coherent mask connected to the illumination part and having an appropriate measurement pattern. If necessary, the illumination portion may correspond to a portion associated with the optical imaging system at a location intended for its use, such as in a microlithography system. In this case, the measurement device can be integrated into the microlithography system, and in each case all that is necessary is to replace the effective mask to which the effective pattern is applied with an illumination module and a detector instead of the wafer It is only introducing.

  Furthermore, the prior art German patent application No. 102 17 242.0 proposes a function for measuring an optical imaging system during its normal operation by means of using a sharing interferometer, and for that purpose, A mask is provided for the surface source, and a measurement pattern is formed on the mask in addition to the effective pattern. Interference information obtained in this way during the normal imaging operation of the optical imaging system and indicating the aberration of the imaging system is evaluated by the evaluation unit and used to correct the found aberrations for that purpose. A suitable aberration closed loop or open loop control system is provided.

  In addition to such interferometer measurement methods, non-interferometer measurement methods are also used for determining aberrations for projection objectives of microlithographic projection exposure systems, such as, for example, the Shack-Hartmann method. Is done.

  As imaging quality requirements have become more stringent, especially for microlithographic projection objectives, imaging errors or aberrations due to so-called heating effects or “lens heating” effects can no longer be essentially ignored. Imaging of microlithographic projection objectives or some other optical imaging system due to the radiation used and the interaction between the objective lens and / or those system components that are active for imaging purposes It means a change in characteristics. One of the difficulties in determining these heat-dependent imaging errors is that this effect often collapses rapidly when irradiation is complete. In this way, system components that are active for imaging purposes are first and foremost intensely irradiated with a radiation intensity comparable to that during normal operation, for example, which then causes heating-dependent imaging errors. When stopped for measurement, these measurement results will represent imaging errors that occur during normal illumination operations only in a very limited range.

  The object of the present invention includes a measurement device of the type described above and imaging error correction, the imaging error of which can be determined using such a measuring device, so that heating-dependent imaging errors are compared. It is to provide a method of operating an optical imaging system that can be determined easily and reliably and can be taken into account for the purpose of correction.

SUMMARY OF THE INVENTION The present invention achieves this task by providing a measuring device having the features of claim 1 or claim 3 or claim 5 or claim 7. Such an apparatus comprises an apparatus for the production of radiation information indicative of imaging errors in a measurement operation, the apparatus comprising a mask structure mechanism having a measurement pattern for detecting and evaluating radiation information indicative of imaging errors. A detection / evaluation device is provided. The apparatus further comprises a heating irradiation mechanism for radiant heating of the optical imaging system during the measurement operation, so that the heating effect of the radiation applied to the optical imaging system to be measured is within a tolerance that can be determined in advance. During the imaging operation of the optical imaging system, the heating effect of the radiation passing through the effective pattern is equal to the measured value.

  In this way, the measuring device of the present invention is such that the heating effect of the radiation passing through the imaging system in the measurement operation is within an allowable range that can be determined in advance, and the radiation that passes through the effective pattern during the normal imaging operation of the optical imaging system. A heating irradiation mechanism selected to correspond to the heating effect is included. Thus, the optical imaging system is actually subjected to a typical beam load during the measurement process, which is the load that the optical imaging system receives during normal imaging operations. Thus, heating-dependent imaging errors and imaging errors that depend on radiation intensity are substantially the same during the measurement process as those that occur during normal operation of the imaging system. Imaging errors caused by radiation loads during normal operation of the optical imaging system can thus be determined very realistically and accurately by this measuring device, preferably on a position-resolved and / or time-resolved basis. it can. The measuring apparatus according to the present invention is suitable for both interferometer and non-interferometer optical measurement methods.

  In one embodiment of the present invention, the heating irradiation mechanism is configured such that the heating effect of radiation passing through this heating irradiation pattern is substantially the same as the heating effect of radiation used during normal imaging operations within the tolerance range described above. A heating irradiation pattern on the mask structure elements selected to be equal is provided. Both the heating irradiation pattern and the measurement pattern may be provided on a common mask, and the measurement pattern preferably occupies a relatively small mask sub-region, while the heating irradiation pattern spans the remaining effective mask region. It has spread. Alternatively, the measurement pattern may be provided on its own mask placed on the object side or on the image side, along or in front of or behind the mask to which the heating irradiation pattern is adapted.

  In another embodiment, the heating illumination mechanism comprises a beam forming assembly adapted to simulate the illumination conditions in normal imaging operations when an effective pattern is applied, the simulation particularly comprising an angular distribution. And hence spatial coherence, and at the same time spatial dependence and thus field dependent radiation intensity. In this embodiment, the heating effect caused by radiation passing through the effective pattern in normal imaging operations is thus simulated in the measurement operation by a suitably formed radiant heating beam and uses a heated irradiation mask pattern. do not have to.

  The tolerance that the radiation load acting on the optical imaging system must correspond to the radiation load during normal operation is preferably an effective pattern or multiple effective patterns typically used during operation of the optical imaging system. Based on the pattern, it can be selected appropriately according to the application. Thus, for example, the heating illumination pattern is representative of the individual effective pattern used or a group of different effective patterns that are to be imaged by the optical imaging system (typically from a radiation transmission perspective). May be the same. Furthermore, a rough structure that is simpler than the structure of a typical effective pattern is that the effect of the radiation transmitted thereby with respect to “lens heating” causing imaging errors is such that the radiation passes through an effective pattern within a predetermined limit. As long as it corresponds, it can be used as a heating irradiation pattern. This can be determined, for example, by simple calculations or experiments.

  In a further improvement of the invention, the heating illumination mechanism is based on a criterion for producing a diffraction pattern in the pupil plane of the optical imaging system corresponding to a diffraction pattern produced by an effective pattern within a predeterminable tolerance. Selected. This ensures that heating-dependent imaging errors during the measurement process are essentially the same as errors during operation of the imaging system.

  In a further improvement, the measuring device comprises a screen mechanism in front of the detection / evaluation means, thereby allowing a radiation component containing radiation information indicative of imaging errors to pass through and simultaneously produced by a heating irradiation mechanism, the detection means Masking the radiation used to achieve a heating effect in front of and thereby avoid overlap in the detector of radiation information indicative of imaging errors. The screen mechanism can be adapted to block the specially polarized light of the heating illumination mechanism while passing through differently polarized measurement radiation. According to yet another embodiment, the screen mechanism provides the necessary separation of the measurement radiation from the heating irradiation, either spatially or time-switched, i.e. in the latter case the measurement radiation and the heating irradiation are alternately applied with respect to time. Can be provided as is.

  According to a further preferred embodiment of the invention, there are various possibilities for directing the measurement radiation on the one hand and the heating radiation on the other hand through the optical imaging system to be measured. In one type of measuring device, the heating radiation is coupled laterally to a system on the object side of the optical imaging system, while the measuring radiation is incident in a longitudinal direction parallel to the optical axis of the optical imaging system. In another type of measurement device, measurement radiation is coupled laterally to the system, while the heating radiation is incident parallel to the optical system axis. For both of these types, the measurement radiation and heating radiation pass through the optical imaging system being measured in the same direction. In yet another embodiment, the measurement radiation passes through the optical imaging system in a direction opposite to the direction of the heated illumination. This can be performed, for example, by directing measurement radiation from the image side of the optical imaging system to the object side, while directing heating radiation from the object side to the image side, or vice versa. In these embodiments too, measurement radiation and / or heating radiation can be coupled into the system from the lateral direction or can be incident in the longitudinal optical axis direction.

  In a further refinement, the measuring device includes a unit for calculating error correction information from imaging error information obtained by evaluating the measurement results. The error correction information can be used during normal operation of the optical imaging system to compensate for heating-dependent imaging errors in whole or in part by appropriate error correction means.

  This is achieved in a specific way by the operating method of the present invention. That is, firstly, the optical imaging system is measured with the aid of a measuring device according to the invention, in particular heating-dependent imaging errors are also taken into account during this process. To compensate for the latter, appropriate error correction information is calculated, so that the optical imaging system uses an appropriate error correction procedure or method to compensate for heating-dependent imaging errors in whole or in part. Then, it is driven in the imaging mode. The heating dependent imaging error and, in a corresponding manner, the compensation error correction means are preferably determined on the basis of time resolution, i.e. as a function of the time profile of the radiation load on the optical imaging system. If necessary, provide imaging error information obtained by evaluating stored measurement results and drive the imaging system for the intended use of error correction information at different times from the determination of imaging error information Provide error correction information determined by this at a later time required for, or call until computed imaging error information obtained and needed for imaging operation of the imaging system Error correction information stored in such a manner as to be able to be provided can be provided.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS Advantageous embodiments of the present invention are described below and illustrated in the figures.

Detailed Description of the Preferred Embodiments The measuring device shown in FIG. 1 may in particular be a projection objective of a microlithography system, for simplicity it is represented as objective 1 in FIG. Used for interferometer measurements in optical imaging systems. The layout of the measurement device is designed to perform sharing interferometer measurements, but other conventional and non-interferometric measurements such as point diffraction interferometers or Shack-Hartmann measurements. It can also be used to implement the technique.

  As can be seen from FIG. 1, on the object side of the imaging system 1 to be measured, the measuring device comprises a conventional illuminator 2 that produces a partially coherent radiation 3 at a desired angle with respect to the optical axis 4. For this purpose, the illumination unit 2 may include, for example, a light source (not shown), a perforated diaphragm 2a, and an illumination optical system 2b.

  The illumination unit 2 is followed by a mask 5 that is preferably located on the object plane of the imaging system 1. In the application of the lithographic object to be measured, the position of the mask 5 corresponds to the position of the focusing plate on which the focusing plate with an effective pattern is placed, usually during the exposure operation, so that the image The effective pattern on the wafer located on the surface is imaged.

In the effective and irradiation region, the mask 5 is provided with a measurement pattern 6 and a heating irradiation pattern 7. The measurement pattern 6 is limited to a small sub-region 8 and is shown in FIG. 1 as a black-out region, preferably smaller than about 1 cm ² , while the heating irradiation pattern 7 is in the remaining effective mask region 9. Spread across. According to requirements, the measurement pattern 6 and the heating irradiation pattern 7 can also be provided on two different masks arranged alongside each other or side by side, in which case the overlap of the two patterns can also be applied depending on the application. If permitted and necessary, the measurement pattern 6 may also be arranged on the image side instead of the object side.

  The measurement pattern 6 is suitably selected for performing the intended interferometer measurement, for example as a so-called coherence mask pattern for sharing interferometer measurements or as a pinhole pattern for point diffraction interferometer measurements. The heating irradiation pattern 7 is received by the imaging system 1 by radiation during normal imaging operation so that the radiation component 3a passing therethrough results in heating, that is, essentially within an allowable range that can be determined in advance. Selected to correspond to the one. As a reference for this, the heating irradiation pattern 7 is selected to result in the same radiation load on the imaging system 1 on the pupil plane as the load that occurs during normal imaging operations. In the case of a lithographic objective, this is the radiation load from the exposure process with a focusing plate having a predetermined effective pattern. This criterion is guaranteed, for example, when the heating irradiation pattern 7 produces the same diffraction pattern in the pupil of the imaging system 1 within a predetermined allowable range.

  The illumination unit 2 of the measuring device preferably corresponds to the same one used in the illumination system for the imaging operation of the imaging system 1. As an example, the effective pattern selected for the normal exposure process can be used identically as the heating irradiation pattern of the mask 5, but the corresponding small subregion in which the measurement pattern 6 is formed is removed. Alternatively, a simpler structure than the effective pattern can be used as a heating irradiation pattern having the same heating effect on the imaging system 1 within an allowable range that can be determined in advance. For example, the allowable range can be determined in advance as an upper limit value and a lower limit value for the radiation intensity or temperature. If it is intended to image different effective patterns during normal operation of the imaging system 1, the heating irradiation pattern is preferably within a predetermined tolerance range, which is the heating effect of these multiple effective patterns, or , Representing all the heating effects of these effective patterns, and is selected to require only one heating irradiation pattern for one entire group of effective patterns. For many applications, it is sufficient to use a periodic grating structure as the heating illumination pattern, which results in uniform pupil illumination over a very wide range.

  On the image side of the imaging system 1, the measuring device shown in FIG. 1 is matched to the type of measurement technique used and is for example arranged with a front detection surface on the image plane of the imaging system 1. And an evaluation unit or measuring head 10. The screening plate 11 is located in front of the measuring head 10 and exits from the measuring pattern 6, and in this case, through the opening 12 that only allows the passage of the light component 3b having radiation information indicating imaging errors in the form of interference information. Have. The radiation component 3a that creates the heating effect is masked as opposed to this, so that it does not impose an additional thermal load on the measuring head 10 and does not interfere with the detection and evaluation of interference information.

  In particular, the interferometer measurement of the imaging system 1, which is a system with high accuracy imaging characteristics and very high resolution, is used for high accuracy determination of imaging errors in this system. For this purpose, the measurement system part on the object side preferably forms a so-called wavefront source, in which case the wavefront interference occurring on the image side contains the desired image error information, which information is detected. It can be extracted from this information by appropriate evaluation of the interferograms made.

  The object-side measurement system layout shown in FIG. 2 is suitable, for example, to provide such a wavefront source for that part of the system associated with the measurement pattern 6. In the example of FIG. 2, a binary coherence mask pattern is used as measurement pattern 6, which can be used as a sharing interferometer measurement in a known manner. In this case, the measurement pattern 6 forms between the diffuser 14 and the coherence mask pattern 6 a so-called source or illumination module exit side part further comprising an entrance side diffuser 14 and an imaging optical instrument 15. The illumination module 13 is preferably arranged behind the illumination unit 2 so that the measurement pattern 6 is at the same height as the object plane of the imaging system 1 to be measured, and the illumination module 13 is arranged in the measurement pattern subregion 8 of the mask 5. A function of providing coherence mask measurement for sharing in interferometer measurement, a function of destroying spatial coherence on an object surface, and a radiation angle spectrum that illuminates the pupil of the imaging system 1 as uniformly as possible It has a function. The optical instrument 15 is optional and may be omitted in other embodiments of the illumination module.

  The measurement apparatus as shown in FIG. 1 and FIG. 2 has a wavefront aberration generated by the heating effect in each case of field points defined by the measurement pattern sub-region 8 of the mask 5 at intervals of, for example, a few seconds. Detect, record and store on a time resolved basis. In particular, heating-dependent imaging errors of the imaging system 1 can be detected on a time-resolved basis even in the phase in which they are being created, which is because the imaging system 1 is actually subjected to a thermal load before the start of the measurement. This is because the thermal load due to the heating light component 3a that does not contribute to the interferometer measurement occurs simultaneously with the interferometer measurement. The imaging error determination measurement can be performed on any desired number of field points by the lateral movement of the mask 5 and the measuring head 10 with the screening plate 11 in synchronism with it.

  FIG. 3 illustrates the use of the present invention for a non-interferometric measurement method. In particular, FIG. 3 illustrates a Shack-Hartmann mechanism essentially according to the prior art design, showing only the system part of interest here from the mask 5a to the detector plane 10a. Show. This system part is in a part in front of the conventional illumination system part, for example of the type described above with reference to FIG. The mechanism shown in FIG. 3 again allows aberrations of the projection objective 1a of, for example, the microlithographic projection exposure system to be measured or any other optical imaging system. The mask 5a corresponds to the mask 5 in the example shown in FIG. 1, but a conventional Shack-Hartmann opening 6a is used as a measurement pattern, and more in a corresponding relatively small measurement pattern sub-region 8a. The heating irradiation pattern 7a is different in that it is spread over the remaining effective mask region 9a. The heating irradiation pattern 7a corresponds to the heating irradiation pattern 7 in the example shown in FIG. 1, thereby going to the above description relating to the heating irradiation pattern 7 as shown in FIG. 1 for its possible implementation and characteristics. Can be referenced. As described above with reference to FIG. 1, in order to take into account the heating effect caused by the representative heating irradiation pattern 7a, the mask 5a is exposed over its entire effective area, ie, the heating irradiation pattern, during the measurement process. It is clear that even at the location where 7a is located, it is clearly illuminated by the upstream illuminator, but for clarity, FIG. 3 only shows the beam profile 16 passing through the Shack-Hartmann mask opening 6a. Is shown.

  On the image side, a measuring device shown in FIG. 3 and based on the Shack-Hartmann principle is used for measuring radiation 16 downstream of an image 17 of a wafer surface of a unit under test, for example a microlithographic projection objective. A Shack-Hartmann having a detector element having a micro objective lens 19 for collimation, a perforated diaphragm or microlens field 20 for selecting the sub-pupil region of the unit 1a under test, and the detector surface 10a described above. ) Includes a sensor 18; Based on the Shack-Hartmann method, horizontal deflections of the individual sub-pupil beam bundles from their ideal locations, each marked with a point in FIG. 3, are detected. In the case of this non-interferometer measurement method, the aberration of the unit 1a during the test is based on the heating irradiation pattern 7a used, and realistically considers the “lens heating” effect, as in FIG. Derived from this. The detected radiation information indicative of imaging errors is evaluated by a suitable evaluation algorithm that is known per se to various interferometer and non-interferometer measurement techniques and therefore does not need to be described in further detail here. The In particular, the aberrations induced by heating effects are appropriately field dependent and time dependent Zernike coefficients, in a sufficient number of field points, in such a relationship, as described above. Can be described by time-dependent measurement.

  The heating irradiation pattern 7 used in the measurement process will result in substantially the same radiation and thus the same heating effect, as in the corresponding effective pattern or multiple effective patterns used during normal imaging operations. And, as a result, are selected to result in the same heating-dependent change to the imaging characteristics of the imaging system 1, so that in the measurement process for individual field points, the imaging error determined based on the time-resolved criterion is In particular, the changes in imaging characteristics caused by the radiation load will also be the same as those that occur during normal imaging operations, which are taken into account based on position and time resolved criteria. As a result, the imaging error information obtained based on the position resolution and time resolution criteria in the measurement process can be used as correction means during the subsequent normal imaging operation. As an example, the manufacturer of a projection objective for a microlithography system can record appropriate imaging error information on the test equipment, taking into account the effects of radiation loads based on position-resolved and time-resolved criteria, thereby This information can later be used to provide correction and compensation driving for the projection objective when used in a microlithography system. This causes, for example, the various manipulators of the projection objective to be heated during wafer exposure, which had to be continuously readjusted based on the time-resolved aberration information criteria previously recorded by the measurement. It becomes possible to correct spherical aberration in whole or in part.

  FIG. 4 shows a method for operating the optical imaging system, including imaging error correction, in the form of a schematic flowchart. As can be seen from FIG. 4, the imaging error of the optical imaging system is measured in a first step 20 by a suitable measuring device according to the invention, such as one of the measuring devices shown in FIGS. The In the next step 21, the desired time-resolved and position-resolved imaging error information is determined from the stored radiation information so that it is recorded by the measurement process, indicating the imaging error and stored.

  In the case of the intended use of the optical imaging system for normal imaging operations, the stored imaging error information is then recalled and used to derive error correction information, which information specifically indicates the imaging error that has occurred. One or more imaging activations of the optical imaging system so that is fully or partially compensated, including fluctuations in imaging behavior (step 22) caused by the “lens-heat” effect Used for open-loop or closed-loop control of imaging behavior on the element, whose imaging behavior can be varied in a controllable manner. In the case of projection objectives used in microlithography scanners, for example, for the correction of spherical aberrations during wafer exposure under the assumption that aberrations are caused by heating effects and fluctuate with time in a corresponding manner. In particular, it is possible in particular to make a permanent readjustment of the z-manipulator.

  Apart from the procedure for deriving the error correction information from the stored imaging error information when it is necessary for the open loop or closed loop control of the correction of the imaging system 1 described above, the error correction information indicates the imaging error. It is possible to derive from imaging error information obtained by evaluation of radiation information and store this information until it is necessary for imaging error correction during the imaging operation.

  From the above, FIG. 1 to FIG. 1 show an embodiment generated using a heating irradiation pattern, in which the measurement radiation and the heating irradiation are provided by a common illumination source, and the heating irradiation is preferably provided with a measurement pattern on a single mask. 3 was described. Measurement radiation and heating radiation are thus both guided along the longitudinal direction of the system, i.e. in the direction of the optical system axis, and pass through the optical imaging system to be measured from its object side to its image side. Various other embodiments of the measuring device of the present invention are also possible, and FIGS. 5 and 8 show some examples. For convenience, the same reference numbers are used in FIGS. 5 to 8 for the same or functionally equivalent elements, as in FIGS. Omitted.

  As a feature common to the embodiments of FIGS. 5-8, the heating irradiation mechanism is configured to generate a heating irradiation beam that appropriately simulates the lens heating effect of an effective pattern used during a normal imaging operation in a measurement operation. A beam shaping assembly 30 configured. That is, the heated irradiation beamforming assembly 30 fully inherits the function of the heated irradiation pattern used in the embodiment of FIGS. For this purpose, the beam shaping assembly 30 is designed to adjust the heated irradiation beam 32, and thus in particular the angular distribution, and thus spatial coherence, as well as the field-dependent intensity of the beam line, so that the measurement operation The heating effect of the heating irradiation beam 31 is equal to the heating effect of the imaging radiation provided by the effective pattern in the normal imaging operation of the imaging system 1 within a predetermined allowable range. This involves pre-monitoring the typical angular distribution and field-dependent intensity of any effective pattern used in normal imaging operations and adjusting the beam shaping assembly 30 so that the heated illumination beam 31 is exactly the same as the beam line. It may also be included to simulate the same heating effect caused by this imaging radiation on the imaging system 1 by providing an angular distribution and a field dependent intensity. In these embodiments, it is thus sufficient that the mask 5 includes a measurement pattern 6 for generating the measurement radiation 3b.

  The heated irradiation beam shaping assembly 30 may have a substantially conventional illumination source structure, while a special beam shaping element such as a heated irradiation diaphragm 30a placed on the surface of the object and the beam shaping. A variable light transmission element 30b placed on the pupil plane of the objective lens unit of the assembly 30 may be included to appropriately adjust the angular distribution of the beam line and the field-dependent intensity. Any conventional beam shaping means can be used in the beam shaping assembly 30 for elements 30a and 30b such as, for example, hologram elements, diaphragms, diffractive optical elements, filter elements, mirror arrays, and / or movable mirrors.

  In the embodiment of FIG. 5, the measurement radiation 3 b is guided from the object side to the image side of the imaging system 1 in the longitudinal direction parallel to the optical system axis 4 via the imaging system 1 to be measured. A heated illumination beam 31 is also directed from the object side to the image side through the imaging system 1 but is laterally coupled to the system using a deflection or scanning mirror 32 as shown. The The deflection mirror 32 is placed in the optical path behind the mask 5 so as not to block the measurement radiation 3b in a direction of substantially 45 degrees.

  Other means such as beam splitting elements, pellicle elements, etc. can be used in place of the deflecting mirror 32 to couple the heating radiation 31 to the system in the desired lateral direction between the mask 5 and the imaging system 1. .

  In the mechanism as shown in FIG. 5, it is possible to simulate the scanning mode of heating irradiation. This is particularly suitable for simulating the heating effects of normal imaging radiation in scanner-type wafer exposure systems. In this scanning mode, the heating irradiation beam 31 may be scanned through the entire image area by moving a beam deflection element such as a scanning mirror 32 correspondingly.

  In an embodiment where the beam shaping assembly is used for lens heating simulation during a measurement operation, the measurement radiation 3b and the lens heating simulating beam 31 are measured separately from the simultaneous application of the heating radiation 31 and the measurement radiation 3b. By switching between radiant illumination and lens heating beam illumination, an alternate mode of operation may be provided that is applied alternately over time. This switching may be performed, for example, by alternately starting and stopping the corresponding light source, or using a deformed scan or a deflecting mirror instead of the deflecting mirror 32. This deformed scanning mirror has a first position where the measurement radiation 3b is blocked while guiding the lens heating beam 31 to the imaging system 1, and the lens heating beam 31 blocks while allowing the measurement radiation 3b to enter the imaging system 1. It is movably arranged so that it can be quickly switched between the second positions.

  As can be seen from FIG. 5, in comparison to FIG. 1, in the embodiment using the heated beam shaping assembly 30, the need to separate lens heating illumination and measurement radiation produces measurement radiation 3b and lens heating illumination 3a. Therefore, it is avoided by using different field points, as achieved in FIG. 1 using different regions of the mask 5. In addition, this allows multi-channel measurements at multiple or all field points considered.

  As another advantage, the use of a separation assembly 30 that provides a lens heating simulation beam 31 allows for greater freedom for generating heating illumination. For example, the heating radiation 31 may have a different wavelength, a different wavelength spectral distribution, a different pulse frequency, a different pulse shape, and / or compared to the measurement radiation and also to the effective radiation used during normal imaging operations. Different pulse lengths may be used. For example, a simpler light source, a higher energy dose, and / or a shorter exposure duration may be used for the lens heating simulation beam 31.

  The use of the separate heating beam shaping assembly 30 further allows the measurement radiation 3b and the lens heating beam 31 to be directed through the imaging system 1 in various directions during the measurement operation. In this regard, FIG. 6 shows an embodiment which basically corresponds to FIG. 5, but the direction of the measurement radiation 3b is reversed. In detail, in the embodiment of FIG. 6, the mask 5 having the measurement pattern 6 is arranged on the image side of the imaging system 1, but the measuring head 10 and the associated screen plate 11 are objects of the optical imaging system 1. Located on the side. Accordingly, in this embodiment, the measurement radiation 3b is guided from the image side to the object side via the imaging system 1, but the lens heating simulation beam 31 is transmitted via the imaging system 1 to the object side. It is guided from the object side to the image side.

  In a further embodiment as shown in FIG. 7, the lens heating beam shaping assembly 30 is similar to a normal illumination source in normal imaging operation, ie on the object side of the imaging system 1 along its optical axis 4. Is arranged. Furthermore, the measurement radiation 3b is a system using a deflection or scanning mirror 32a that deflects the measurement radiation emitted laterally from the mask to pass through the imaging system 1 from its object side to the image side. Are coupled horizontally. In this case, the mask 5 is displaced laterally from the optical system axis 4 and its mask surface is positioned parallel to it.

  In the embodiment described above, the lens heating irradiation is separated from the measurement radiation at the front of the measuring head 10 by the lateral displacement and the use of the screening plate 11. Other types that prevent entry into the measuring head 10 are also covered. A corresponding embodiment is shown in FIG. In this embodiment, the separation of the heating radiation from the measurement radiation is achieved by using different polarizations and appropriate polarization elements. The embodiment of FIG. 8 basically corresponds to the embodiment of FIG. 6, but was designed to produce a heated irradiation beam 31a having a special first polarization, for example a linear polarization in the x direction. A modified beam shaping assembly 30a is used. On the other hand, the measurement radiation 3b is generated with another distinct second polarization, such as a linear polarization in the y-direction orthogonal to the x-direction, for example using a corresponding polarization filter 33 in front of the mask 5 Is done.

  By using different polarizations, the measurement radiation 3b and the heating radiation 31a can be guided through the imaging system 1 in common, ie in the same field region, from the object side to the image side. For this purpose, an illumination source of the measurement radiation 3b is provided along the optical system axis 4 and a specially polarized measurement radiation 3b is passed using the beam splitting cube element 34 behind the mask 5; At the same time, the heating irradiation 31a polarized differently is deflected. A polarizing cube element can be used in place of the beam splitting cube element 34 to achieve the desired matched illumination of the imaging system 1 with the measurement radiation 3b and the heating radiation 31a polarized differently.

  Another polarizing filter 35 is placed in front of the measuring head 10 and behind the optical measuring instrument 36, allowing the heating radiation 31a to be measured while allowing differently polarized measuring radiation to enter the measuring head 10. Preventing entry into the head 10.

  In the variant of the embodiment of FIG. 8, other polarization states are also selected for the heating radiation 31a and / or the measuring radiation 3b so that they prevent the heating radiation 31a from reaching the measuring head 10. It can be used as long as it is. For example, the measurement radiation polarization filter 33 may not be used, while a clear polarization state is selected for the heating radiation 31a, and the polarization filter 35 at the front of the measurement head 10 blocks the heating radiation 31a. Adjusted appropriately. In this case, the measurement radiation component having a polarization state different from that of the heating irradiation 31 a passes through the polarization filter 35 and enters the measurement head 10.

  As will be appreciated by those skilled in the art, if necessary, any effect of the beam splitting element 34 on the measurement imaging can be corrected computationally from the measurement results or the appropriate geometry of the measurement assembly. You may compensate by changing a parameter or combining both means.

  Depending on the requirements, the measuring device used to measure the imaging system, for example, the measuring device of any of the embodiments described above, can be designed as an autonomous device, or within the system for which the imaging system is intended. You may integrate. In the case of integration, the same lighting part can be used on the one hand for measurements and on the other hand for normal imaging operations, thus ensuring the same lighting conditions up to this range. Yes. In the application of a wafer scanner corresponding to the apparatus shown in FIG. 1 or FIG. 3, what is necessary when changing from measurement to normal wafer exposure mode or vice versa is the measurement mask unit and / or object side The illumination module is simply replaced with an effective pattern focusing plate, and the measurement head on the image side is replaced with the wafer to be exposed. In any case, in both the case of integration and the case of an autonomous device, the effects of heating-dependent image errors can be detected on a time-resolved basis immediately after the start of imaging or exposure processing, and likewise on the time-resolved basis. It can be corrected by negative feedback. From the above it is clear that the procedure according to the invention can be carried out not only with different heating radiation patterns, but also with different so-called “lighting settings”, ie with different lighting system parts and lighting wavelengths.

  The above description of the preferred embodiment is given by way of example. From the disclosure made herein, those skilled in the art will not only understand the present invention and its attendant advantages, but will also find apparent various modifications and variations to the disclosed structures and methods. Accordingly, it is required that all modifications and variations be covered as falling within the spirit and scope of the invention as defined by the appended claims and their equivalents.

It is a schematic side view of the measuring apparatus for interferometer measurement of the optical imaging system. FIG. 2 is a schematic side view of one possible embodiment of the measurement system section on the object side of the measurement apparatus shown in FIG. 1. 1 is a schematic side view of a part of a measuring device for measurement of an optical imaging system based on Shack-Hartmann. 3 is a flowchart of an operation method of an optical imaging system including image error correction. FIG. 2 shows a variant of the measuring device of FIG. 1 with beam-shaped heating irradiation coupled laterally to the object-side system. FIG. 6 shows a variant of the measuring device of FIG. 5 with measuring radiation guided from the image side to the object side. FIG. 6 shows a variant of the measuring device of FIG. 5 including different polarizations of measuring radiation and heating irradiation, respectively. FIG. 2 shows a variant of the measuring device of FIG. 1 with measuring radiation laterally coupled to the object-side system.

Claims (13)

A measurement device for optical measurement of an optical imaging system intended to image an effective pattern in an imaging operation,
An apparatus for manufacturing radiation information indicating an imaging error in a measurement operation, the apparatus having a mask structure mechanism including a measurement pattern for providing measurement radiation;
A detection / evaluation device for detection and evaluation of radiation information indicating imaging errors;
A heating irradiation mechanism for radiation heating of the optical imaging system during a measurement operation, wherein the heating effect of radiation applied to the optical imaging system to be measured is within an allowable range that can be determined in advance. A heating irradiation mechanism that is equivalent to the heating effect of the radiation passing through the effective pattern during the imaging operation,
The heating irradiation mechanism comprises a heating irradiation supply unit adapted to couple heating radiation to the optical imaging system laterally on its object side or image side, and / or the apparatus for producing radiation information A measuring device comprising a measuring radiation supply unit adapted to couple measuring radiation to the optical imaging system laterally on its object side or image side.   At least one of the heating irradiation supply unit and the measurement radiation supply unit is a light for deflecting the heating radiation or measurement radiation incident from the lateral direction in an emission direction substantially parallel to the optical axis of the optical imaging system. The measuring device according to claim 1, comprising a deflection element. A measurement device for optical measurement of an optical imaging system intended to image an effective pattern in an imaging operation,
An apparatus for manufacturing radiation information indicating an imaging error in a measurement operation, the apparatus having a mask structure mechanism including a measurement pattern for providing measurement radiation;
A detection / evaluation device for detection and evaluation of radiation information indicating imaging errors;
A heating irradiation mechanism for radiation heating of the optical imaging system during a measurement operation, wherein the heating effect of radiation applied to the optical imaging system to be measured is within an allowable range that can be determined in advance. A heating irradiation mechanism that is equivalent to the heating effect of the radiation passing through the effective pattern during the imaging operation,
The heating irradiation mechanism has a heating irradiation beam having an angular distribution and a field dependent intensity so as to correspond to radiation passing through an effective pattern during an imaging operation of the optical imaging system, in a heating effect on the optical system to be measured. And / or a heating illumination mechanism is used during normal imaging operations in at least one of wavelength, wavelength spectrum, pulse frequency, pulse shape, and pulse length. A measuring device comprising a heated irradiation light source adapted to generate a heated irradiation different in at least one of the measuring radiation and the radiation.   The heated irradiation beam shaping assembly adjusts at least the angular distribution and / or field dependent intensity of a beam line selected from the group comprising a hologram element, a diaphragm, a diffractive optical element, a filter element, a mirror array element, and a movable mirror element The measuring device according to claim 3, comprising one optical element. A measurement device for optical measurement of an optical imaging system intended to image an effective pattern in an imaging operation,
An apparatus for manufacturing radiation information indicating an imaging error in a measurement operation, the apparatus having a mask structure mechanism including a measurement pattern for providing measurement radiation;
A detection / evaluation device for detection and evaluation of radiation information indicating imaging errors;
A heating irradiation mechanism for radiation heating of the optical imaging system during a measurement operation, wherein the heating effect of radiation applied to the optical imaging system to be measured is within an allowable range that can be determined in advance. A heating irradiation mechanism that is equivalent to the heating effect of the radiation passing through the effective pattern during the imaging operation,
A measuring device provided with a switching device for passing measuring radiation and heating radiation alternately with respect to time through an optical imaging system during a measuring operation.   The switching device moves between a first position that blocks measurement radiation and directs heating radiation to the optical imaging system and a second position that blocks heating radiation and directs measurement radiation to the optical imaging system. 6. A measuring device according to claim 5, comprising a adapted movable optical element. A measurement device for optical measurement of an optical imaging system intended to image an effective pattern in an imaging operation,
An apparatus for manufacturing radiation information indicating an imaging error in a measurement operation, the apparatus having a mask structure mechanism including a measurement pattern for providing measurement radiation;
A detection / evaluation device for detection and evaluation of radiation information indicating imaging errors;
A heating irradiation mechanism for radiation heating of the optical imaging system during a measurement operation, wherein the heating effect of radiation applied to the optical imaging system to be measured is within an allowable range that can be determined in advance. A heating irradiation mechanism that is equivalent to the heating effect of the radiation passing through the effective pattern during the imaging operation,
A polarization mechanism is provided that includes a polarizing element at the front of the detection / evaluation device that is adapted to generate measurement radiation and heating radiation of different polarization states, blocks the heating radiation and at least partially transmits the measurement radiation. measuring device.   The heating irradiation mechanism has an effective pattern during an imaging operation of the optical imaging system, within a tolerance that a heating effect of radiation passing through the heating irradiation pattern on the optical imaging system to be measured can be determined in advance. The measuring device according to any one of claims 1 to 7, comprising a mask structure element including a heating irradiation pattern selected to be equal to a heating effect of radiation passing therethrough.   The measurement apparatus according to claim 8, wherein the mask structure mechanism includes a mask formed by bonding a measurement pattern and a heating irradiation pattern.   The radiant heating mechanism produces a diffraction pattern corresponding to a diffraction pattern produced on the pupil plane during normal imaging operation by an effective pattern within an allowable range that can be determined in advance on the pupil plane of the optical imaging system to be measured. The measuring apparatus according to claim 1, wherein the measuring apparatus is selected to be performed.   11. A screen mechanism according to any one of the preceding claims, further comprising a screen mechanism in front of the detection / evaluation device for passing radiation components coming from the measurement pattern and blocking radiation components coming from the heating irradiation mechanism. The measuring device according to item.   The detection / evaluation device performs open-loop or closed-loop control of the optical imaging system during normal imaging operation together with an effective pattern for correcting imaging error from imaging error information obtained by evaluating radiation information indicating imaging error. The measuring apparatus according to claim 1, further comprising a unit that calculates error correction information to be used. A method of operating an optical imaging system, including imaging error correction,
The pre SL optical imaging system, optically measured using a measurement pattern, the measuring device according to any one of claims 1 to 12, to determine the radiation-dependent imaging error information, then,
Imaging an effective pattern with the optical imaging system having an open-loop or closed-loop control of the imaging system to correct imaging errors as a function of the imaging error information determined in a measurement step and dependent on radiant heating ,Method of operation.

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