Method for qualifying a defect structure on an object utilizable in projection lithography

Abstract

To verify the defect structure of an object usable in projection lithography, at least one target contour (20) of the structure to be measured is first assigned to the object. Furthermore, the actual contour (22) of the structure is measured. The deviation (23) between the target contour (20) and the actual contour (22) is determined perpendicular to the profile of the target contour (20). The assigned value (23max) of the determined deviation (23) is documented as a defect verification parameter for the structure to be measured. The additional verification method may omit the assigned target contour. The significance of the defect verification is increased by this verification method, and this can be performed particularly with a measurement system.

Description

Technology Field

[0001] The contents of German patent application DE 10 2024 203 208.5 are incorporated by reference.

[0002] The present invention relates to a method for verifying the defect structure of an object usable in projection lithography. Background Technology

[0003] The metrology systems disclosed in US 2017 / 0131 528 A1 (WO 2016 / 0124 425 A2 parallel filing), WO 2016 / 012 426 A1, US 2017 / 0132782 A1 and DE 10 2009 016 858 B4 are used particularly for analyzing defects in structured parts in the form of a reticle or lithography mask. A method for determining the characteristics of a structure formation process is known in US 2022 / 0229374 A1.

[0004] The objective of the present invention is to improve the significance of defect qualification, which can be performed particularly using a measurement system.

[0005] According to the present invention, this objective is achieved by a method having the features specified in claim 1.

[0006] With respect to the defect structure, the subject of verification may be a structured component (e.g., a lithography mask or reticle) or a component that is likely not structured (e.g., a mask blank or wafer blank). In other words, the subject may be a wafer to be exposed or a wafer that has already been exposed.

[0007] Multilayer reflective layers and / or multilayer absorbing layers may also represent targets to be verified in relation to defect structures.

[0008] In the determination step (35), a maximum part-field-actual difference corresponding to a predetermined multiple of the standard deviation of the normal distribution of the intensity distribution measured in imaging of a structure-free ROI can be determined. The multiple of the standard deviation selected in the determination step (35) may be a multiple between 1.5 and 5, particularly a multiple within the range of 3.

[0009] The verification method enables the reproducible identification and recording of deviations based on reproducible defect verification parameters. This can be utilized to separate compliant objects from waste. A specific value of the recorded deviation may be the maximum value of the deviation. Alternatively, the average deviation can be recorded as a defect verification parameter, thereby allowing the use of a weighted average in particular.

[0010] Before determining the deviation between the target contour and the actual contour, the measured actual contour value, specifically the measured intensity value of the imaging light, can be normalized to the specified target value of the target contour during actual imaging of the structure of interest. This prevents systematic errors caused by the absolute difference between the specified target value and the measured actual value on the one hand.

[0011] This verification method can be used for imaging wavelengths in the EUV range or other lithography exposure wavelengths, particularly imaging in the DUV range. This verification method can be used in the aerial metrology category or the SEM (Scanning Electron Microscope) image category.

[0012] The verification method can be used, for example, for a full inspection of a lithography mask to determine whether the lithography mask is defective. Alternatively, or additionally, the verification method can be performed as part of a mask review, that is, in the context of investigating whether potential defects found in the preliminary stage are actual defects.

[0013] In the verification method according to the present invention, the deviation is determined regardless of the exact shape of the specified target contour. Therefore, this verification method can be applied to completely different target contours and, in this sense, can be generally applied regardless of the type and size of the specified target contour.

[0014] The designated variations for the target contour according to claims 2 to 4 have been proven to be practical and may be combined with each other depending on current boundary conditions.

[0015] The target contour may be specified through a simulated image of the defect-free structure to be imaged. The mask design or reticle parameters of the reticle and / or mask (e.g., material and thickness of the layer structure of the mask or coating) may be included in these simulations.

[0016] For example, specifying the average value of the target contour can take into account the object's roughness and error contribution.

[0017] Another objective of the present invention is to specify an important verification method even when the target contour of the object structure to be measured cannot be specified due to a lack of ideally existing structures.

[0018] According to the present invention, this objective is achieved by a method having the features specified in claim 5.

[0019] This additional verification method does not require target contour designation. For each part-field of the image field, if the deviation between the maximum and minimum values ​​of image intensity exceeds a set target difference, it is considered a defect. Part-field measurements can be performed by scanning the entire image field. During the preparation phase, the Region of Interest (ROI) can be imaged assuming it is defect-free. The maximum target difference can be specified based on the imaging results of this type of defect-free ROI, which is typically much larger than the difference between the maximum and minimum intensity values ​​when imaging a defect-free ROI. Alternatively, during the initial designation phase, the maximum target difference can be estimated as a generally expected difference value or calculated based on simulation.

[0020] In the additional method, a defect structure is a set of partial fields where the difference between the maximum and minimum imaging intensity values ​​is greater than the target intensity difference, resulting in excessive intensity fluctuation. Such defect structures can occur, for example, due to the deposition of unwanted particles on the object to be verified. For instance, coating defects or material or microstructural defects, particularly those in semiconductor materials, can cause corresponding intensity deviations that exceed the specified target intensity difference. Other object defects that do not manifest as deviations from the target contour can also be identified in this manner.

[0021] The designation of the maximum target difference according to claim 6 may be made using an empirical value for the intensity noise value. In particular, speckle noise may be used as the intensity noise value. Contributions to the designation of the maximum target difference, in particular noise contributions, may be contributions from the measurement system, contributions from the object under verification (e.g., object roughness), and in particular measurement contributions from the detection device. Contributions from the measurement system other than the detection device may arise, for example, from positional errors and / or drift.

[0022] In the method according to claim 7, defect structures smaller than the specified minimum size are not considered. The minimum size is generally larger than the roughness of a typical object.

[0023] The advantages of the software product according to claim 8 are consistent with those already described with reference to the defect analysis method.

[0024] The same description applies to the advantages of the measurement system according to claim 9. The measurement light of the measurement system may have a wavelength in the EUV range, particularly between 5 nm and 30 nm, for example, a wavelength of 13.5 nm. Alternatively, the measurement system may operate using measurement light in the DUV range, for example, a measurement light with a wavelength of 193 nm or 248 nm.

[0025] The components of the measurement system may include a light source for illumination and imaging light, an illumination optical unit that illuminates the object field, an imaging optical device that images the object field into an image field, and a spatial resolution detection device that detects the illuminance distribution within the image field. The measurement system may also include an open-loop / closed-loop control device. The open-loop / closed-loop control device may be used to perform individual steps of each verification method.

[0026] The measurement system can be used to measure the lithography mask provided for projection exposure to produce semiconductor components with very high structural resolution, which, for example, can be better than 500 nm or better than 100 nm, and especially better than 30 nm and better than 10 nm. Brief explanation of the drawing

[0027] Exemplary embodiments of the present invention will be described in more detail with reference to the drawings. In the drawings: FIG. 1 schematically illustrates a measurement system that performs defect analysis by assisting in the determination of a production aerial image of a measurement target object obtained as a result of illumination and imaging under illumination and imaging conditions corresponding to the illumination and imaging conditions of an optical production system, wherein a plan view of the object field and a plan view of the measurement or image field at the current Z position are additionally illustrated; Figure 2 is a plan view showing a portion of the imaging intensity measurement results within a measurement field using a defect-free round structural object in the form of a semiconductor column, where the predetermined target contour of the structural object following the imaging intensity contour is highlighted by a dotted line. Figure 3 is a drawing similar to Figure 2, showing a defective structural object with a deformed contour compared to a structural object according to Figure 2, where the actual contour of the defective structural object along the strength contour lines of the drawing is highlighted with a solid line. FIG. 4 illustrates the deviation between the target contour according to FIG. 2 and the actual contour according to FIG. 3 by superimposing the top view according to FIG. 2 and FIG. 3, and the defect verification parameters of the structural object to be measured that result from this deviation, where the difference in imaging intensity according to FIG. 2 and FIG. 3 is also illustrated. FIG. 5 illustrates a schematic sequence of a method for verifying a defect structure on an object usable for projection lithography, for example, a lithography mask or blank, for example, a defect structure according to FIG. 3. FIG. 6 illustrates another measured structural object in the form of a defect-free linear structure with a representation similar to FIG. 2, wherein a vertically extending linear protrusion is shown in the center, and in each case, a linear concave is shown adjacent to the right and left, and in the lateral area, a nominal contour of the linear structure in the form of an imaging intensity is highlighted by a dotted line between the protrusion and the concave adjacent to the protrusion. FIG. 7 is a drawing similar to FIG. 6, illustrating a line structure having a defect structure in the central area of ​​the right boundary of the linear protrusion shown in the center of FIG. 7, wherein the actual contour of this defect structure is particularly highlighted as a solid line in FIG. 7. Figure 8 is a drawing similar to Figure 4, showing the visualization of defect verification parameters of the line structure to be measured by superimposing the contour drawings according to Figures 6 and 7 and recording the deviation between the target contour and the actual contour. FIG. 9 is a drawing similar to FIG. 5, illustrating the schematic sequence of an additional method for verifying a defect structure, in which case the target contour cannot be utilized, and this method is an alternative or additional verification method. FIG. 10 illustrates the imaging intensity measurement results when imaging a structure-free region of interest (ROI) of an object to be measured in order to prepare for defect-independent designation of the maximum target difference between the maximum imaging intensity and the minimum imaging intensity in the context of the verification method according to FIG. 9. Figure 11 illustrates an imaged ROI having a defect structure defined in the context of the verification method according to Figure 9. FIG. 12 illustrates an overlay figure for visualizing a defect verification parameter that records the deviation between the actual contour of the array structure to be measured and the target contour, similar to FIG. 4 and FIG. 8. Specific details for implementing the invention

[0028] FIG. 1 illustrates the beam path of EUV illumination light or EUV imaging light (1) in a measurement system (2) having an imaging optical unit (3) schematically represented by the box of FIG. 1 on a plane corresponding to a meridional cross-section. The illumination light (1) is generated in the illumination system (4) of the projection exposure device (2).

[0029] Below, the measurement system (2) is described using an EUV measurement system as an example. Depending on the requirements for measurement, the measurement system can also be used as a DUV measurement system having a measurement light wavelength of, for example, 193 nm or 248 nm.

[0030] To facilitate the explanation of relative positions, the Cartesian xyz coordinate system is used below. The x-axis of FIG. 1 is perpendicular to the drawing plane and points outward from the drawing plane. The y-axis of FIG. 1 points to the right, and the z-axis of FIG. 1 points upward.

[0031] The illumination system (4) includes an EUV or DUV light source (5) and an illumination optical unit (6), which are schematically illustrated in each case. The light source may be a laser-producing plasma (LPP) or a discharge-producing plasma (DPP). In principle, a synchrotron-based light source, for example, a free electron laser (FEL), may also be used. The available wavelength of the illumination light (1) is in the range of 5 nm to 30 nm. In principle, in a modified version of the measurement system (2), a light source for other available light wavelengths, for example, 193 nm or 248 nm, may also be used.

[0032] The lighting light (1) is adjusted in the lighting optical unit (6) of the lighting system (4) to provide a specific lighting setting, that is, a specific lighting angle distribution. The lighting setting corresponds to a specific intensity distribution of the lighting light (1) in the lighting pupil of the lighting optical unit of the lighting system (4). A pupil stop (7) placed on the pupil plane (8) of the lighting optical unit (6) serves to provide the corresponding lighting setting.

[0033] The pupil stop (7) is fixed to a stop holder (7a). This holder may be a quick-change stop holder capable of replacing the pupil stop (7) currently used for lighting with at least one change pupil stop. Such a quick-change holder may include multiple pupil stops (7), particularly cartridges having different pupil stops, to specify various lighting settings.

[0034] The stop holder (7a) may also be displaced by a stop displacement drive (7b) schematically illustrated in FIG. 1, which is intended to displace the pupil stop (7) in the pupil plane (8) on one side in the direction of displacement or on the other side in two displacement directions perpendicular to each other. Alternatively, or in addition to this, the stop displacement drive (7b) may be designed so that the pupil stop (7) is displaced in a direction perpendicular to the pupil plane (8), i.e., in the z-direction.

[0035] The image proximal numerical value of the imaging optical unit (3) is 0.7. Depending on the implementation example of the imaging optical unit (3), the image proximal numerical value may be greater than 0.5, and may be 0.55, 0.6, 0.65, 0.75, 0.8, or greater. This image proximal numerical value of the imaging optical unit (3) is adjusted to match the image proximal numerical value of the production projection exposure device to be simulated through imaging by the measurement system. Accordingly, the lighting setting set by the dipole pupil stop (7) is also adjusted to match the production lighting setting of this production projection exposure device.

[0036] The measurement system (2) is used as follows. First, on one hand, the imaging optical unit (3) is used, and on the other hand, the image proximal aperture and lighting settings corresponding to the lighting and imaging conditions of the production projection exposure device to be measured are set through the corresponding pupil stop (7) or by setting the stop displacement drive (7b).

[0037] When each lighting setting is configured, the lighting light (1) illuminates the object field (9) of the object plane (10) of the measurement system (2). Thus, a lithography mask (11), also called a reticle, is placed on the object plane (10) as an object to be illuminated during the production process. The lithography mask (11) represents an object in the form of a structured part that needs to be measured using the measurement system (2). The measurement system (2) is used to perform defect analysis on the lithography mask (11). Defect analysis is implemented through aerial image measurement of the measurement system (2).

[0038] In FIG. 1, the structural portion of the lithography mask (11) is schematically shown as an inset on the object plane (10) extending parallel to the xy plane. This structural portion is described to be positioned on the drawing plane of FIG. 1. The actual arrangement of the lithography mask (11) is perpendicular to the drawing plane of FIG. 1 on the object plane (10).

[0039] As schematically illustrated in FIG. 1, illumination light (1) is reflected from the lithography mask (11) and incident on the incident pupil (12) of the imaging optical unit (3) at the incident pupil plane (13). The incident pupil (12) of the imaging optical unit (3) is round or has an elliptical periphery as schematically illustrated in FIG. 1.

[0040] Within the imaging optical unit (3), the illumination or imaging light (1) propagates between the incident pupil plane (13) and the exit pupil plane (14). The circular exit pupil (15) of the imaging optical unit (3) is located in the exit pupil plane (14). The imaging optical unit (3) may be anamorphic and generates a circular exit pupil (15) from a circular or elliptical incident pupil (12).

[0041] The imaging optical unit (3) images the object field (9) into the measurement field or image field (16) from the image plane (17) of the projection exposure device (2). In the inset below the image plane (17), FIG. 1 shows the value z in the z direction on the image plane (17). W The imaging light intensity distribution (I) measured in a plane at a distance of that amount, i.e., the defocus value z W Schematically illustrates the imaging light intensity at.

[0042] Imaging light intensity I(x, y, z) at various z-values ​​around the image plane (17) w ) is also called a 3D aerial image of a projection exposure device (2).

[0043] A spatial resolution detection device (18), which may be a CCD camera or a CMOS camera, is placed on an image plane (17) representing a measurement plane of the measurement system (2). The detection device (18) has an imaging light intensity I (x, y, z W ) detects and registers.

[0044] The imaging optical unit (3) may have a magnification imaging magnification greater than 100 when imaging the object field (9) to the image field (16). This imaging magnification may be greater than 200, greater than 250, greater than 300, greater than 400, or greater than 500. The imaging magnification of the imaging optical unit (3) is generally less than 2000.

[0045] FIG. 2 illustrates an exemplary portion of an image field (16) having a structural image (19) of a structure to be measured in a reticle (11) displayed as an intensity profile of image light (1) as an enlarged section. The intensity profile of the structural image (19) shows the greatest intensity I at the center of FIG. 2. max It has, and this intensity decreases continuously outward in a rotational symmetric manner, so that the surrounding value I min It decreases to.

[0046] In FIG. 2, the rounded target outline (20) of the structural image (19) is highlighted with a dotted line. The structural image (19) is a structural image of a defect-free object structure. This defect-free object structure can be determined in the context of a preliminary inspection.

[0047] The target contour (20) follows the intensity contour of the intensity profile of the structure image (19), that is, the image of the corresponding circular object structure of the reticle (11). This object structure can be a pillar structure with a diameter ranging from 10 nm to 100 nm.

[0048] FIG. 3 again illustrates a portion of the image field (16) having an additional imaged structural image (21) of the defect structure, similar to FIG. 2.

[0049] In FIG. 3, the actual contour (22) of the defect structure image (21) is highlighted with a solid line, and this solid line follows the contour line of image intensity over part of the image field (16).

[0050] The contour lines of the target curve (20) of the defect-free structure image (19) and the actual contour line (22) of the defect structure image (21) are all connected at the same level of relative strength value I0, which is 0.2 and 0.8 I depending on the designation. max The range between, for example, 0.3 I max or 0.5 I max It may be in.

[0051] FIG. 4 illustrates a superposition of a defect-free target curve (20) (dotted line) and an actual curve (22) (solid line) of a defective structure. FIG. 4 also illustrates a deviation (23) between the target curve (20) and the actual curve (22) that is perpendicular to the profile of the target contour (20). This deviation (23) is also referred to as an edge placement error.

[0052] Due to the rounded shape of the target contour (20), the deviation (23) proceeds in the radial direction. Maximum value (23) of the deviation (23) max ) , That is, the maximum deviation between the target curve (20) and the actual curve (22) perpendicular to the path of the target contour (20) is highlighted in FIG. 4. This 23 max The maximum value represents the defect verification parameter of the defect structure to be measured using the defect structure image (21).

[0053] With respect to imaging intensity values, FIG. 4 simultaneously illustrates the difference images between FIG. 2 and FIG. 3. In the deviation region between the actual contour (22) and the target contour (20), the intensity difference shown in FIG. 4 has the absolute largest value.

[0054] FIG. 5 visualizes a method of verifying a defect structure using an image (21) of a defect structure on an object that is capable of being used for projection lithography on a reticle (11).

[0055] In the step (28) of the verification method, the target contour (20) of the structure to be measured on the reticle (11) is specified. As described above in relation to FIG. 2, this can be done by measuring the column structure verified as defect-free in the context of the preliminary inspection of the reticle (11) with the structure image (19).

[0056] Alternatively, the target contour (20) may be designated as the average value of multiple object structures measured in the context of the preliminary inspection process of the reticle (11). All structures within the captured field (view of sight) and / or all identical structures of objects existing within this captured field and another selected captured field that have the same nominal shape and size as a given structure type may be considered. Not all measured object structures need to be defect-free. Thanks to averaging, the statistical significance of the designated target contour is enhanced.

[0057] Additionally, alternatively or additionally, the target contour (20) may be specified as a specific value of the structural result obtained by projection lithography, for example, a target image size such as "a circular structure with a diameter of 80 nm." Additionally, it may be taken into account that a smooth or accurately specified target contour does not actually appear. The fundamental roughness occurring in real objects with a small length scale in the nm range may be taken into account when specifying the target contour.

[0058] After the step (28) of specifying the target contour (20), the (defect) structure to be measured is measured in the measurement step (29), where the actual contour (22) in this measurement step appears as an isoline of imaging intensity as described above in relation to FIG. 3.

[0059] In the subsequent determination step (30) of the verification method, the deviation (23) between the target contour (20) and the actual contour (22) is determined perpendicular to the profile of the target contour (20) as described above with reference to FIG. 4.

[0060] The maximum value (23) of the deviation (23) in the recording step (31) max ) is recorded as a defect verification parameter of the object structure to be measured.

[0061] Recorded defect verification parameters (23 max ) can be compared to the tolerance value 230 of the defect verification parameter. For example, the result is 23 max If > 230, the structure generated from the defect structure image (21) according to FIG. 3 is verified as a defect structure. 23 max If ≤ 230, the verification result is that the structure object (21) deviates from the target value but is still usable.

[0062] FIGS. 6 to 8 illustrate the verification conditions for a defective structure on a defect-free line structure, similar to FIGS. 2 to 4 described above. Components and functions corresponding to those already described with reference to FIGS. 2 to 4 use the same reference numerals and are not described in further detail.

[0063] According to FIG. 6, a defect-free line structure image (25) has a plurality of structural protrusions (26) that extend to maintain equal distances from each other in the y-direction, which represent the maximum intensity of the imaging intensity across a portion of the image field (16). One of these structural protrusions (26) extends from the center at the x-value 0 position in FIG. 6.

[0064] Between the structural protrusions, the x distance may be in the range of 10 nm to, for example, 200 nm, there is a structural depression (27) that also extends in the y direction.

[0065] The target contour (20), which represents the boundary line between each structural protrusion (26) and an adjacent structural recess (27), extends along the y-direction along the image intensity contours, as described above with particular reference to FIGS. 2 and 3. Unlike the example according to FIG. 2, the target contour (20) is not closed due to the linear structure.

[0066] FIG. 7 illustrates the actual contour (22) of a defective central structural protrusion (26) in the positive x direction at y = 0, similar to FIG. 3. Excluding the defective area that appears as a protrusion with an increased x-structural width, the actual curve (22) is an extension of the target curve (20) according to FIG. 6.

[0067] FIG. 8 is a drawing corresponding to FIG. 4, showing the target curve (20) according to FIG. 6 and the actual curve (22) according to FIG. 7 superimposed, with a maximum deviation value 23 maxThe deviation (23) including is shown again. The deviation (23) extends perpendicularly to the profile (dotted line in FIG. 8) of the target contour (20) of FIG. 8.

[0068] Referring to FIG. 5, the verification method described above is used in the same way as described above with respect to the curves (20, 22) according to FIG. 2 to 4, and is also used with respect to the curves (20, 22) of FIG. 6 to 8.

[0069] If a target contour cannot be used, an alternative or additional method to verify the defect structure of an object available in projection lithography may be used, which is described with reference to Fig. 9 below. Such defects without a specified target contour may, for example, be foreign matter attached to a particle-free surface if desired.

[0070] In the verification method according to FIG. 9, the maximum target difference between the maximum intensity value Imax and the minimum intensity value Imin of the intensity measurement is initially designated as an allowable limit in the designation step (32) when imaging a structure-free or defect-free region of interest (ROI) (33) of the reticle (11). Such a structure-free ROI (33) is shown in the lower right of FIG. 2.

[0071] FIG. 10 illustrates an example of the imaging result of such a structureless ROI (33). The imaged object (11) is a multilayer reflective object and is partially coherently illuminated through the object field (9) by illumination light (1). The ROI (33) represents a part or the entire image field (16). In the image of the structureless ROI (33), a general spot pattern of imaging intensity appears, which varies between relative intensity values ​​of 0.9 and 1.08 in the example according to FIG. 10.

[0072] FIG. 11 is a difference diagram comparable to FIG. 4 and FIG. 8, illustrating the difference in intensity between the current ROI of interest (33) with a defect structure in the form of a structural image (42) (maximum defect intensity range) and the defect-free intensity image according to FIG. 10. The peripheral contour (43) of the defect structure belonging to the structural image (42) in 431, 432, and 433. i Three examples of ) are shown as intensity contour lines in FIG. 11, which is the result of implementing the verification method according to FIG. 9 as a result of various part-field-real differences (e.g., multiples of the standard deviation (σ) of the normal distribution of image intensity of a defect-free ROI (33) according to FIG. 10).

[0073] Since the peripheral contour (431) occurs at the smallest predetermined part-field-actual difference (e.g., 3σ), the resulting peripheral contour (431) of the resulting defect structure occupies the largest surface as a result of the determination step (38). The additional peripheral contours (432 and 433) are the result of the implementation of the verification method according to FIG. 9, in which the maximum part-field-actual difference (e.g., 2σ and 1σ) specified in the determination step (35) gradually increases.

[0074] The result is the corresponding surrounding contour (43) of the verified defect structure. i ) and through this, the comparison step (37) and the definition step (38) are used to conclude, for example, the presence of particles and especially the type of particles.

[0075] In the ROI (33), the maximum intensity I within the ROI is due to, for example, the contribution of the measurement system (2), the contribution of the object to be measured, that is, the contribution of the roughness of the structureless area of ​​the reticle (11) or the roughness of the blank, or the contribution of the detection device (18). max and minimum strength I min There is a difference in imaging intensity that causes an intensity difference between. max Wow I min The maximum allowable target difference between them is specified. In step (32), the maximum target difference is specified. The maximum target difference can be specified specifically based on the intensity-noise value.

[0076] Next, in the imaging step (34) of the verification method, imaging of the ROI (33) or other selected region of interest is performed, and an image field point (16) within the ROI (33) i An image field corresponding to the ROI (33) having an intensity measurement value assigned to ) is obtained.

[0077] In the determination step (35) of the verification method, the maximum partial field actual difference (TID) is determined. This is the maximum intensity value of the measured intensity value I present in each case in the partial field of the image field (16) when imaging each partial field of the image field (16). Imax and minimum strength I min This is the difference between. These partial fields, which can be scanned in the context of a measurement scan within the image field (16), are reproduced in FIG. 361 to 364 in the context of a row of partial fields extending in the x direction.

[0078] In the comparison step (37) of the verification method, the actual difference of each partial field is compared with the target difference specified in the specification step (32).

[0079] In the regulation stage (38), all partial fields 36 where the actual partial field difference is greater than the target difference i It is defined as a defective structure.

[0080] In the case of a defect structure that occurred in the context of the specification step (38), range measurements can now be performed in the x direction and / or y direction. To prepare for these range measurements, the minimum range of the defect structure verified at that time is first specified. This is performed in the specification step (39) of the verification method according to FIG. 9. This minimum range is generally larger than, for example, the general roughness of the object to be verified.

[0081] In the comparison step (40), the defect structure defined in the regulation step (38) is compared with the minimum range specified in the designation step (39) in relation to the defect structure range.

[0082] In the output step (41), the defect structure defined in the definition step (38) is output as a verified defect structure if the defect structure defined in the definition step (38) is greater than the minimum range specified in the designation step (39).

[0083] The verification method described above can appear as a software product of the storage medium itself.

[0084] A software algorithm for performing defect verification according to one of the methods described above may be designed as a computer program and may be part of a computer program product that includes a program means that is computer-readable and stored on a medium suitable for a computer, which enables the computer to perform various steps of defect verification.

[0085] Each verification method may be part of a measurement program performed by a measurement system (2) to inspect each object used in projection lithography.

[0086] FIG. 12 shows another example of a deviation (23) between a target contour (20) and an actual contour (22) determined and recorded by the method according to FIG. 5, which is a structural rectangle (44) with spherical radius corners ij Use an example of a target contour (20) in the form of an X / Y array of ).

[0087] The defect structure is a structural rectangle (44) representing the strength contour in the example of FIG. 12. ij Adjacent structural rectangles (44) within a column in the array assembly of ) 11 and 44 21 ), directly adjacent structural rectangles within the row (44 21 and 44 22 ), and diagonally adjacent structural rectangles (44 11 and 4422 ) three structural rectangles (44) that are undesirably connected to each other through the actual contour (22), that is, are not separated from each other as in the case of the target contour (20). l, 44 21 and 44 22 ) appears in a converging form. Due to this convergence, the defect structure (44 D ) is generated.

[0088] structural rectangle (44 21 Starting from the target contour (20) of ), the deviation (23) between this target contour (20) and the actual contour (22) is determined in the determination step (30) of the verification method according to FIG. 5.

[0089] In the example according to FIG. 12, the maximum value (23) of the deviation (23) max ) consists of two adjacent structural rectangles 44 ij It is greater than the row or column distance d. In the example according to FIG. 12, a portion of this row-column distance d, e.g. d / 2, d / 4, d / 8, or d / 10, may be used as a specified value for the determined deviation (23). In the example according to FIG. 12, 23 max Since > d / 2, the maximum deviation (23) determined by the verification method according to Fig. 5 max ) is verified as a defect structure, and the deviation value (23 max ) is verified as a defect verification parameter of the object structure to be measured.

Claims

Claim 1 A defect structure (21; 26) on an object (11) that can be used for projection lithography D ; 44 D As a method for verifying ), the following steps: - specifying a target contour (20) of at least one structure (19; 26) to be measured on the object (11) (28), - the defective structure (21; 26 D ; 44 D A step (29) of measuring the actual contour (22) of the target contour (20), a step (30) of determining the deviation (23) between the actual contour (22) perpendicular to the profile of the target contour (20), and a specified value (23) of the determined deviation (23). max ) to be measured, the defect structure (21; 26 D ; 44 D A method comprising the step (31) of recording as a defect verification parameter of ), wherein the measured actual contour values ​​are normalized to specified target values ​​of the target contour (20) before determining the deviation (23) between the target contour (20) and the actual contour (22). Claim 2 In claim 1, the structure verified as defect-free in the context of a preliminary inspection (19; 26; 44 ij A method characterized by measuring ) and designating the target contour (20) in the context of a preliminary inspection of an object (11). Claim 3 In claim 1 or claim 2, the target contour (20) is a plurality of object structures (19; 21; 26; 26) measured in the context of a preliminary inspection of the object (11). D ; 44 ij A method characterized by being designated as the average value of ). Claim 4 A method according to claim 1 or claim 2, characterized in that the target contour (20) is designated as a specified value of the structural result to be achieved in the projection lithography. Claim 5 A method for verifying a defect structure on an object (11) that is applicable to projection lithography, comprising the following steps: - a maximum intensity value (I) of an intensity value (I) measured when imaging a region of interest (ROI: 33) of the object (11). max ) and minimum strength value(I min Maximum target difference (I) between max - I min Step (32) of designating ) as an allowable limit, - Step (34) of imaging the ROI (33) of the object (11) to detect the image field (16) corresponding to the ROI (33) having the measured intensity value (I) assigned to the image field point (16i), - Each partial field (36 i When imaging ), the partial field (36) of the image field (16) i Step (35) of determining the maximum partial field actual difference between the maximum and minimum strength values ​​of the measured strength values ​​present in each case, - each partial field actual difference all partial fields (36 i Step of comparing with the target difference for ) (37), - all partial fields (36) where the actual difference of the partial field is greater than the target difference i The defect structure (42; 43) as the sum of ) i A method including a step (38) of defining ) Claim 6 A method according to claim 5, characterized in that the maximum target difference is surrounded by an intensity noise value. Claim 7 A method according to claim 5 or claim 6, characterized by the following additional steps: - specifying a minimum range of a verified defect structure (39), - comparing the range of the defect structure with the specified minimum range (40), - outputting the defined defect structure as a verified defect structure if the defined range of the defect structure is greater than the minimum range (41). Claim 8 A computer program stored in a non-transient computer-readable storage medium for executing a program sequence corresponding to the method described in any one of claims 1, 2, 5, and 6. Claim 9 A measuring system for performing the method described in any one of claims 1, 2, 5, and 6.

Images