Method and device for determining a repair shape for processing a defect in a photolithographic mask

Abstract

A method for determining a repair shape (195) for processing at least one defect (140) of a photolithographic mask (100), the method comprising the following steps: a. Determining at least two location-dependent correction values (185) for the repair shape (195) of the at least one defect (140), wherein the at least two location-dependent correction values (185) take into account a position (175) of at least one pattern element (130) of the photolithographic mask (100) that does not contact the at least one defect (140); and b. Correcting the repair shape (195) by applying the at least two location-dependent correction values (185).

Description

1. Technical area

[0001] The present invention relates to a method and a device for determining a repair shape for processing a defect of a photolithographic mask. 2. State of the art

[0002] As a result of the growing integration density in the semiconductor industry, photolithographic masks must image increasingly smaller structures. Therefore, the production of photomasks is becoming increasingly complex and therefore more expensive. The decreasing feature sizes of photomasks lead to the occurrence of new, additional errors or defects on the photomasks. The increasing effort involved in creating photomasks with ever smaller structures and the associated cost pressure force the repair of defects that arise during mask production or during mask use to avoid the costly, complete remanufacture of the masks.

[0003] Before defects on photomasks can be repaired, they must be localized. This is done by optical inspection, preferably using short-wavelength photons. In a second step, the localized defects are analyzed by scanning them with a particle beam (ions or electrons) from a focused ion beam (FIB) scanning microscope or a scanning electron microscope (SEM). When using an electron beam, the backscattered electrons and secondary electrons released by the electrons from the photomask surface to be examined are used to create an image of the photomask surface. When using a focused ion beam, in addition to the secondary electrons, the secondary ions released by the ions from the substrate surface, which are analyzed for their mass (SIMS, Secondary Ion Mass Spectroscopy), depict the composition of the irradiated surface.

[0004] The published patent application DE 10 2007 054 994 A1 relates to a method for repairing phase shift masks for photolithography, in which a phase shift mask is examined for the presence of defects and, if defects are present, (i) it is analyzed which of the defects impair the imaging properties of the phase shift mask, (ii) these defects are repaired, (iii) the imaging properties of the repaired phase shift mask are analyzed and compliance with a predetermined tolerance criterion is checked and (iv) the two previous steps (ii) and (iii) are repeated several times if necessary, if the imaging properties do not correspond to the predetermined tolerance criterion.In such a method, the imaging properties are analyzed by determining a test size for each of the defects to be repaired as a function of focus and exposure for the defect and at least one other non-defective location on the phase shift mask in the immediate vicinity of the defect, and by specifying a minimum permissible deviation of the test size for the defect and the non-defective location as a tolerance criterion.

[0005] German Patent Application DE 10 2008 062 928 A1 describes a defect repair method, in particular for repairing quartz defects on alternating phase masks. To repair defects occurring on one and the same component, both defect repair steps—essentially based on mechanical processes—in particular nanomachining steps—and defect repair steps—essentially based on etching processes, in particular FIB (Focused Ion Beam) steps—are used. Furthermore, this patent application relates to a component—repaired using such a defect repair method—in particular a photomask.

[0006] German Patent Application DE 103 04 674 A1 describes a circuit layout in which, in a first structural pattern, which is electronically stored in a data format and represents a first lithographic level, a partial area is defined in which a lower limit for the length of a serif to be added to a structural element in an OPC correction can be undercut in order to locally increase the resolution. The partial area in the electronically stored circuit layout can, for example, be an active region to be contacted, which was selected as a structural element in a second structural pattern in a further lithographic level. Within such a partial area of an integrated circuit, increased requirements for dimensionally accurate imaging are thus met, while the required data volume overall increases only insignificantly.

[0007] US Patent No. 6,982,136 B1 describes a system for determining optimal proximity corrections (OPCs) for a mask pattern. The system comprises a photomask having a plurality of mask areas formed on the mask, each mask area having the same mask pattern of polygons modified with corresponding different OPC perturbations; a photolithographic system for producing a corresponding patterned area from each mask area of the mask; and a microscope system for generating a corresponding microscope image of each corresponding mask area to determine a corresponding error function for each mask area.

[0008] US 6,187,483 B1 describes a system and method for characterizing patterns comprising optical proximity correction designs by applying a mathematical transformation to the OPC designs and evaluating the transformed patterns with a metric associated with the pattern transmission system. Furthermore, US 6,187,483 B1 relates to a system and method for determining an optimal mask manufacturing process by applying a mathematical transformation to mask patterns formed by different manufacturing processes and evaluating the transformed mask patterns with a metric associated with the pattern transmission system.

[0009] Published patent application DE 10 2011 079 382 A1 describes a method for analyzing a defect in an element for the extreme ultraviolet wavelength range; the element has at least one substrate and at least one multilayer structure. The method comprises the steps of: (a) determining first data by exposing the defect to ultraviolet radiation; (b) determining second data by scanning the defect with a scanning probe microscope; (c) determining third data by scanning the defect with a scanning particle microscope; and (d) linking the first, second, and third data.

[0010] US Patent No. 8,316,698 B2 describes difficulties that can arise when analyzing a defect adjacent to a pattern element of a photomask. The defect analysis provides a repair shape for a detected defect. The repair shape defines the projection of an identified defect onto the surface of the photomask substrate. The projection is performed perpendicular to the surface of the photolithographic mask substrate.

[0011] Identified defects in photolithographic masks are preferably corrected using particle beam-induced processes. Defects that arise because material is present at locations on the mask substrate that should be transparent (so-called opaque defects) are typically corrected using a particle beam-induced etching process. Defects that indicate locations where absorbing pattern material is missing (so-called clear defects) are preferably corrected using a particle beam-induced deposition process. These particle beam-induced etching or deposition processes are highly localized processes. Ideally, these localized machining processes are limited to the diameter of the particle beam on the defect or repair shape. However, a particle beam cannot be focused to a point-like diameter in the mathematical sense. In addition, due to the movement of the molecules of the etching or deposition agent,of the deposition gas - the particle beam-induced processes are not limited to the focus of the particle beam.

[0012] A repair or correction of defects in photolithographic masks based solely on the repair shape can therefore not only result in the desired defect correction but also in damage to the photomask substrate surrounding the defect. Furthermore, the repair of a defect adjacent to a pattern element can also affect that pattern element.

[0013] This problem has already been recognized. The applicant's publication "ebeam Initiative, April 20, 2015 in Yokohama - Japan" (www.ebeam.org / docs / ebeam initiative zeiss.pfd) describes how a low-energy electron beam is suitable for repairing small, isolated defects on the substrate of a photomask, essentially based on the repair shape, without correcting the repair shape, while the area in which the mask substrate is damaged by the electron beam-induced etching process is small.

[0014] In Chapter 4: “Ion beam techniques” of the book “Beam Processing Technologies”, edited by NG Einspruch, SS Cohen and RN Singh in the series VLSI Electronics Microstructure Science, Vol. 21, Academic Press, author LR Harriot describes scanning an ion beam across the defect to remove it, keeping the ion beam one beam diameter away from the edge of the defect.

[0015] US Patent No. 6,591,154 B2 describes a method for maintaining a certain distance from the edge of the defect when correcting defects on wafers or masks. To do this, the operator of a repair device draws a polygon around the defect to be corrected. The line thickness of the polygon is used to adjust the distance of an ion beam or laser beam from the edge of the defect, thus adjusting or correcting (biasing) the repair shape of the defect.

[0016] In the cited publications, a correction value or bias is used to adapt the entire repair shape of a defect, or at least a portion of the repair shape adjacent to the mask substrate or a pattern element, to the subsequent repair process. Due to the decreasing size of photomask structures or pattern elements, this approach to adapting the repair shape is no longer sufficient for future masks.

[0017] The present invention is therefore based on the problem of specifying a method and a device for determining a repair shape for a defect in a photolithographic mask, which at least partially avoid the above-mentioned disadvantages when determining the repair shape. 3. Summary of the invention

[0018] According to one embodiment of the present invention, this problem is solved by a method according to claim 1. In one embodiment, the method for determining a repair shape for processing at least one defect of a photolithographic mask comprises the following steps: (a) determining at least one correction value for the repair shape of the at least one defect, wherein the correction value takes into account a position of at least one pattern element of the photolithographic mask that does not contact the at least one defect; and (b) correcting the repair shape by applying the at least one correction value.

[0019] A method according to the invention therefore takes into account not only the pattern element(s) of a photomask that border a defect, but also pattern elements that are located near the defect. The method according to the invention does not require any additional equipment, since a particle beam apparatus is required anyway to locate and process the defect. The term "near the defect" refers to a distance of the pattern element from the defect that is only so small that the pattern element lies at least partially in the processing zone of the defect during a processing process of the defect and can therefore be changed by the processing process. The term "near the defect" therefore depends on the equipment capabilities of the defect processing apparatus under consideration.

[0020] According to a further embodiment, the problem specified in the preceding section is solved by a method according to claim 2. In one embodiment, the method for determining a repair shape for processing at least one defect of a photolithographic mask comprises the following steps: (a) determining at least one correction value for the repair shape of the at least one defect, wherein the correction value takes into account a lateral extent of the at least one defect on a surface of a substrate of the photolithographic mask; and (b) correcting the repair shape by applying the at least one correction value.

[0021] A method according to the invention takes the lateral extent of a defect into account when determining correction values for the repair shape of the defect. This takes into account the effort required for the defect processing process or the defect correction process when correcting the repair shape. This takes into account the duration of the defect processing process, since the area surrounding the defect can be influenced at least during part of this time period. Thus, a method according to the invention goes beyond correcting the repair shape, in which the edge of a defect is reduced by a certain amount, depending on whether the defect borders a pattern element or ends on the substrate of the mask.

[0022] In this application, the term "lateral extension" describes a projection of the defect onto the plane forming the undisturbed surface of the substrate of the photolithographic mask. The projection is essentially perpendicular to the substrate surface.

[0023] The term “essentially” in this application describes a measured variable within the error specification when measuring instruments according to the state of the art are used.

[0024] According to another embodiment, the problem explained above is solved by a method according to claim 3. In one embodiment, the method for determining a repair shape for processing at least one defect of a photolithographic mask comprises the following steps: (a) determining at least one correction value for the repair shape of the at least one defect, wherein the correction value takes into account a shape of the at least one pattern element of the photolithographic mask that contacts the at least one defect; and (b) correcting the repair shape by applying the at least one correction value.

[0025] A method according to the invention not only considers the boundary of a defect with a pattern element by applying a constant correction value for the repair shape, but also considers the shape of the common boundary between the defect and the pattern element. This is particularly advantageous because, during defect repair, the particle beam of the scanning particle microscope causes increased secondary electron emission or secondary ion emission at the edges of a pattern element, which can lead, for example, to so-called "riverbedding." Thus, the correction of the repair shape determined using a method according to the invention goes far beyond the state of the art.

[0026] The at least one correction value may take into account a lateral dimension of the at least one pattern element.

[0027] The processing of a defect adjacent to a pattern element represents a trade-off between the degree of correction of the defect along the boundary and the extent of damage to the adjacent pattern element. By considering the lateral dimension of the pattern element along the common boundary, the trade-off can be optimized locally.

[0028] The term “lateral dimension of the pattern element” in this application means the extent of the pattern element in a plane that is parallel to the surface of the substrate of the photolithographic mask.

[0029] The at least one correction value can take into account at least one corner of the at least one pattern element.

[0030] In addition to the lateral dimension of the pattern element adjacent to a defect, the correction of the repair shape can also take into account the specifics that occur at a corner of the pattern element.

[0031] The at least one correction value can lead to a reduction in the size of the repair shape in the vicinity of the at least one corner of the at least one pattern element in comparison with a correction value in the vicinity of a rectilinear region of the pattern element when the corner protrudes into the at least one defect and / or the at least one correction value can lead to an enlargement of the repair shape in the vicinity of the at least one corner of the at least one pattern element in comparison with a correction value in the vicinity of a rectilinear region of the pattern element when the at least one defect protrudes into the corner of the at least one pattern element.

[0032] The at least one correction value may take into account the lateral dimension of the at least one pattern element and the at least one corner of the at least one pattern element.

[0033] Determining the at least one correction value may further comprise: taking into account a thickness and / or a material composition of the at least one pattern element.

[0034] The thickness of the pattern element that shares a common boundary with the defect influences the defect repair process. The material composition of the pattern element influences the extent of damage the pattern element suffers during a defect repair process. The methods described here allow these aspects to be taken into account when correcting the repair shape to find the best possible compromise between defect correction and modifying the pattern element along the common boundary.

[0035] Determining the at least one correction value may further comprise: taking into account the thickness and / or a material composition of the at least one defect.

[0036] The thickness and material composition have a decisive influence on the effort required to eliminate the defect. By incorporating these parameters into the correction values of the repair mold, the defect repair process is optimized while minimizing the impact on the photomask.

[0037] Processing the at least one defect may comprise: performing a particle beam-induced etching process and / or a particle beam-induced deposition process on the corrected repair shape of the at least one defect.

[0038] Defects in the form of excess material, such as excess absorber material of a pattern element (so-called opaque defects), are typically treated using a particle beam-induced etching process. A particle beam-induced etching process can be corrected, for example, using an electron beam and one or more etching gases provided locally at the location of the electron beam impact. An etching gas can, for example, comprise xenon difluoride (XeF2), a halogen, and / or a halogen-containing gas.

[0039] Defects in the form of missing material, for example, missing absorber material from a pattern element (a so-called clear defect), are typically corrected using a particle beam-induced deposition process. A particle beam-induced deposition process can be corrected, for example, using an electron beam and one or more deposition gases that are applied locally at the electron beam impingement site. Chromium hexacarbonyl (Cr(CO)6) is an example of a deposition gas.

[0040] Determining the at least one correction value may include approximating the at least one correction value on an empirical basis. For this purpose, the defects to be analyzed are preferably assigned to different defect classes that have different parameters. Based on a progressive number of defect processing cycles, the defect classes and their parameter sets can be updated.

[0041] Determining the at least one correction value may comprise analyzing a test mask.

[0042] Applying the at least one correction value may include: reducing an area of the repair shape by correcting at least a portion of an edge of the repair shape.

[0043] This allows the outer contour of the repair shape to be locally adapted to the defect itself and the surrounding area. This not only considers the area adjacent to the defect, but also the area surrounding the defect, which lies within the interaction zone of the machining process.

[0044] Determining the at least one correction value may comprise combining the at least one correction value according to the second and third embodiments described above.

[0045] Determining the at least one correction value may comprise combining the at least one correction value according to the first and second embodiments.

[0046] Combining the at least one correction value of two embodiments may comprise linear combining.

[0047] Determining the at least one correction value may comprise: averaging at least a portion of the edge of the at least one defect that does not contact the at least one pattern element; and determining a perpendicular to the tangent to the averaged edge of the at least one defect to determine the distance of the averaged edge from the at least one pattern element that does not contact the at least one defect and the lateral extent of the at least one defect on the surface of the substrate.

[0048] Determining the at least one correction value may comprise: forming a perpendicular in the region of the at least one pattern element that contacts the at least one defect to determine the lateral extent of the at least one defect and the lateral extent of the at least one pattern element that contacts the at least one defect.

[0049] A computer program may contain instructions which, when executed by a computer system, cause the computer system to perform the method steps of the aspects set out above.

[0050] In one embodiment, a device for determining a repair shape for processing at least one defect of a photolithographic mask comprises: (a) a measuring unit configured to determine the repair shape; (b) a computing unit configured to determine at least one correction value for the repair shape of the at least one defect, wherein: (i) the at least one correction value takes into account a position of at least one pattern element of the photolithographic mask that does not contact the at least one defect; (ii) the at least one correction value takes into account a lateral extent of the at least one defect on a surface of a substrate of the photolithographic mask; and / or (iii) the at least one correction value takes into account a shape of the at least one pattern element of the photolithographic mask that contacts the at least one defect;and wherein (c) the computing unit is further configured to correct the repair shape by applying the at least one correction value;

[0051] The device can be designed to carry out the method steps of the aspects described above. 4. Description of the drawings

[0052] In the following detailed description, currently preferred embodiments of the invention are described with reference to the drawings, wherein Fig. 1 shows, in the right-hand part, the correction of a repair shape of a defect in a photolithographic mask according to the prior art, and, in the left-hand part, schematically shows the correction of a repair shape according to two of the methods described in this application; Fig. 2 schematically presents correction values of a repair shape for a defect adjacent to a pattern element, wherein the lateral dimensions of the defect and the pattern element vary perpendicular to the boundary line of the defect and the pattern element; Fig. 3 schematically indicate correction values for a repair shape, wherein a pattern element has two corners in the area where the defect contacts the pattern element; Fig. 4 shows a schematic representation of a test structure for determining correction values of a repair shape for a test defect which is adjacent to a pattern element, has a stepped lateral dimension and whose distance from a pattern element varies; Fig. 5 the test structure of the Fig. 4 presented after removal of the test defect; and Fig. 6 presents a flowchart of the methods for determining a repair shape for processing a defect of a photolithographic mask. 5. Detailed description of preferred embodiments

[0053] Preferred embodiments of the inventive methods and the inventive device are explained in more detail below. However, the inventive methods are not limited to the exemplary applications explained below. Rather, the methods described here can be used to determine a repair shape for defects that can occur in all types of photomasks. Furthermore, the methods described in this application are not limited to correcting defects in photomasks. Rather, these methods and the corresponding device can also be used, for example, to determine a repair shape for defects in integrated circuits.

[0054] The Fig. 1 shows the correction of a repair shape according to the prior art in the right-hand part of the image, ie to the right of the vertical line 142. The mask 100 comprises a substrate 110 and the pattern elements 120 and 130. In the example of Fig. 1, the photomask 100 is a transmissive mask. The substrate 110 of the mask 100 often comprises quartz. The pattern elements 120 and 130 essentially completely absorb optical radiation in the actinic wavelength range of the photolithographic mask. The pattern elements 120 and 130 comprise chromium or opaque MoSiON-based (molybdenum silicon oxynitride) absorbers as the absorbing material. The methods described below for determining correction values for a repair shape can be used for all types of photomasks 100, including masks for the extreme ultraviolet (EUV) wavelength range and so-called NIL masks, i.e., masks for the nano-imprint technique (in the Fig. 1 not shown).

[0055] Adjacent to the pattern element 120, the mask 100 has a defect 140. The defect 140 can, for example, comprise excess absorber material (opaque defect). If this is the case, the defect 140 could have substantially the same height as the pattern elements 120, 130. However, the opaque defect 140 can have any desired height. It is also possible for the defect to have a different material or a different material composition than the pattern elements 120, 130. Furthermore, it is possible for the defect 140 to be a defect of missing absorber material (clear defect; in the Fig. 1 not shown). In addition, the defect 140 may comprise a defect of excess or missing substrate material (in the Fig. 1 also not shown).

[0056] The defect 140 is preferably detected with an inspection tool and analyzed with a scanning particle microscope, frequently a scanning electron microscope. The defective location is then compared with a defect-free location of the photomask 100 that has the same pattern structure as the defective location. Alternatively, the defective location can be compared with design data of the defective mask section. By subtracting the defect-free mask section from the section that has the defect, the repair shape 145 of the defect 140 is obtained. The repair shape 145 is thus the projection of the defect 140 onto the plane of the surface of the substrate 110 of the mask 100. In this representation, an image of the repair shape contains only the defect itself without the pattern elements 120 and 130 of the corresponding mask section. For illustrative purposes, the exemplary representation of the Fig. 1 and the following figures, however, the pattern elements 120 and 130 are shown. A computing unit of a scanning particle microscope can be used to determine the repair shape 145 of the defect 140.

[0057] As explained in the introductory part of the description, processing of the defect 140 on the basis of the repair shape 145 leads to a substantial correction of the defect 140. However, due to the lateral extent of the processing zone, the defect processing damages both the substrate 110 of the mask 100 and the pattern element 120 adjacent to the defect 140. Furthermore, processing of the defect 140 can change the pattern element 130, which does not have a common boundary with the defect 140 but is at least partially located near the defect 140.

[0058] In the prior art, the repair shape 145 of the defect 140 is therefore corrected. This is done, firstly, by correcting the repair shape 145 of the defect 140 along the boundary of the defect 140 to the surrounding substrate 110 by a fixed distance 157, so that the corrected repair shape along the substrate 110 has the new boundary 155. This correction of the repair shape 145 is also called edge bias.

[0059] Along the common edge of defect 140 and pattern element 120, the repair shape 145 is also corrected by a fixed amount 162, so that the corrected repair shape along pattern element 120 has the new edge 160. This correction of the repair shape 145 is also referred to as volume bias. The volume bias and the edge bias can have the same distances 157 and 162. Typically, however, the distances 157 and 162 are different correction values for the repair shape 145. The repair shape 145 of the defect 140 thus has two correction values, with the help of which the entire outer contour of the repair shape 145 of the defect 140 is corrected.

[0060] The left part of the Fig. 1 shows the mask section of the mask 100 and the defect 140, axially mirrored at the vertical line 142. This partial image now explains part of the method described in this application for determining correction values for the repair shape 145 of the defect 140. In the first step, the tangent of the edge 162 is determined at predetermined points 165 of the repair shape 145 or of the defect 140, which borders the substrate 110. If the defect 140, unlike in the Fig. 1, does not have a smooth edge 162, is averaged over a predetermined section of the edge 162 before determining the tangent.

[0061] Then the perpendicular 170 is drawn to the tangent and its intersection points are determined with the pattern elements 120 and 130. The distance a i175 of the point 165 of the edge 162 is taken into account when determining the correction values for the repair shape 145, even though the pattern element 130 has no direct contact with the repair shape 145 of the defect 140. The size of the local correction value C i 185 depending on the distance a i 175 of the pattern element 130 from the edge 162 of the repair shape 145 at the point 165: Ci=f1(ai)

[0062] The function f1 can calculate the distances a i to the pattern element 130 in a non-linear manner. However, in a first approximation, f1 is a linear function of the distances a i . In addition, the correction values C i contain a constant correction contribution, which is, however, suppressed in equation (1). For the accuracy of the correction values 185, it is advantageous if, in addition to the distances a i to the pattern element 130, also the distances b i180 of the points 165 of the edge 162 of the repair shape 145 to the pattern element 120 that is in contact with the defect 140 must be taken into account. This is particularly important at those locations of the repair shape 145 where the lateral dimension 180 of the defect 140 and thus of the repair shape 145 is small. Equation (1) is thus expanded to: Ci=f1(ai)+f2(bi)

[0063] Unlike in the prior art, equation (2) describes local, location-dependent correction values 185 of the defect 140. The correction values 185 of equation (2) can be supplemented to form a continuous curve 190. In the Fig. In the example shown in Figure 1, the correction values 185 and / or the closed curve 190 are used to generate a corrected repair shape 195.

[0064] It is also possible to determine correction values for the defect 140 that only take into account the lateral extent of the defect 140, ie based on f2 (bi) and ignore the influence of the defect processing on the pattern element 130.

[0065] The Fig. 2 shows how the Fig. 1, a section of a photomask 100. Using this example, the determination of a part of a repair shape for the defect 240 along the common boundary of the pattern element 220 and the defect 240 will be discussed. Fig. 2 shows the left part of the Fig. 1 with two differences. Firstly, defect 240 on the left edge has a different shape than defect 140 of the Fig. 1. On the other hand, the pattern element 220 has a different shape than the pattern element 120 of the Fig. 1.

[0066] To determine the correction values for the repair shape, a perpendicular 270 is determined at various points 265 of the edge 250 on the edge 250 of the pattern element 220. The distances d i 275 describe the distance of the edge 262 of the defect 240 from the points 265 of the common edge 262 of the defect 240 and the pattern element 220. The distances e i 280 denote the distance of the edge 230 of the rear end of the pattern element 220 from the points 265 of the common edge 250 of the defect 240 and the pattern element 220. Based on these definitions, correction values K i 285 are introduced, which take into account the local lateral extensions of both the defect 240 and the pattern element 220: Ki=f3(di)+f4(ei)

[0067] The corrections K i285 along the common edge 250 of the defect 240 with the pattern element 220 at the points 265 can in turn be supplemented to form a continuous line 290. The corrections K i 285 and 290 respectively along the line of contact of the defect 240 with the pattern element 220 is part of the repair shape 295 for the defect 240. As already explained in the discussion of equation (1), the functions f3 and f4 can determine the distances d i of the defect 240 and the lateral dimensions e i of the pattern element 220 in a non-linear manner. However, as a first approximation, it is often sufficient to consider f3 and f4 as a linear function of the lateral dimensions d i and e i to be taken into account.

[0068] As long as the dimensions d i 275 and e i280 are much larger than the diameter of the machining zone of the defect machining process, a single correction value is sufficient to correct the repair shape of the defect 240 in this area of the common boundary line. This situation is at the right edge of the Fig. 2. In this limiting case, the correction of repair form 295 discussed here merges into the correction previously used for the volume bias.

[0069] In the middle part of the image Fig. 2, the defect 240 borders only on a narrow web 255 of the pattern element 220. The correction values K i 285 are significantly enlarged in this area to avoid irreparable damage to the pattern element 220 in the area of the narrow web 255 when processing the defect 240. This means that the small distances e i and thus the function f4 determine the correction values K in the area of the narrow bar 255 of the pattern element 220 i285 and thus correcting the repair form 295.

[0070] In the area on the left edge of the Fig. 2 is the lateral dimension e i 280 of the pattern element 220 is significantly lower than in the right part of the Fig. 2. On the other hand, the lateral dimensions d vary in this area i 275 of the defect 240. Therefore, in this part of the common boundary of the pattern element 220 and the defect 240, the correction values K i 285 depends on both the function f3 and f4 of equation (3).

[0071] Based on the correction values 195 of the Fig. 1 along the substrate 110 of the photolithographic mask 100 (ie the above-mentioned edge bias) as well as the correction values 295 of the Fig. 2 along the area in which the defect 240 contacts the pattern element 220 (ie the above-mentioned volume bias), a corrected repair shape for a defect can be determined, which takes into account the lateral dimensions of the defect 140, 240, the pattern element 120, 220 to which the defect 140, 240 borders, and the distance of the pattern element 130 that is not in contact with the defect 140.

[0072] The Fig. 3 illustrates an example of the correction of a repair shape of a pattern element that contacts the defect in an area where the pattern element has a corner. Fig. 3 shows an enlarged section of the left part of the Fig. 1 in the area of the corners of the pattern element 120 as well as the defect 140, which borders the pattern element 120. Furthermore, the Fig. 3 shows a correction according to the prior art. The curve 160 follows the common boundary line 330 of the pattern element 120 and the defect 140 at a fixed distance 162. The corner points P1 and P2 of the pattern element 120 are mapped by the curve 160 into the corner points P1' and P2'.

[0073] The curve 385 of the Fig. 3 shows the course of the correction values 385 for the repair shape 395, when the problems of defect processing in the area of the two corner points P1 and P2 are taken into account when determining correction values for the repair shape. Fig. In the example shown in Figure 3, an ellipse function is used to determine correction values in the area of the two corner points P1 and P2. The angle α serves as a parameter. n the vertices P n . The angles α n the vertices P n are measured in the area of the defect 140, ie outside the pattern element 120. As the Fig. 3, angles 1° ≤ α n ≤ 179° reducing parts of an ellipse compared to the state-of-the-art correction value. Angle of the range 181° ≤ α n ≤ 359°, however, generate additive parts of an ellipse compared to the state-of-the-art correction value. The parameters of the reducing and adding ellipse parts are approximately equal for α1 = 270° and α2 = 90°. The parameters characterizing the ellipse parts are determined experimentally.

[0074] Equation (3), which describes a volume bias, ie the correction of a repair shape 295 of a defect 140 bordering a pattern element 120, is extended by the corner correction: Ki′=Ki+f5(αn) where K i the correction values of equation (3).

[0075] A precise determination of the course of the repair shape 395 of the defect 140 along the common boundary line 330 or the edge 330 of the pattern element 120 is very important for the repair of the defect 140. The particle beam used to repair a defect 140 may have an increased emission rate of secondary electrons in the region of the edge 330, which, when they impinge on the substrate 110 of the photolithographic mask, can lead to so-called "riverbedding."

[0076] With the correction values C i 190 and K i 290 or K i ' the repair form 195, 295 of the defect can be corrected in the best possible way 140, 240 without significantly damaging the substrate 110 or the pattern elements 120, 140, 220.

[0077] The diagram 400 of the Fig. 4 schematically presents a test structure 410 for determining the correction values C i of equation (2) and K iof equation (3). The test structure 410 comprises the two pattern elements 420 and 430 as well as a test defect 440 made of absorbing material, which is Fig. 4 is deposited on the substrate 110 of the test structure 410. The test defect 440 borders on the pattern element 430 and has a lateral dimension 475 that increases stepwise from left to right until the test defect 440 is in the last step at the right edge of the Fig. 4 contacts the pattern element 420. The test defect 440 creates the repair shape 445. The test defect 440 is removed from the substrate 110 of the test structure 410 using a particle beam-induced etching process. The processing process of the test defect 440 is based on the uncorrected repair shape 445.

[0078] The diagram 500 of the Fig. 5 shows the test structure 410 of the Fig. 4 after etching the test defect 440 based on the uncorrected repair shape 445. Only the effects of the particle beam-induced etching process on the pattern elements 420 and 430 of the test structure 410 are considered. Adverse effects of the processing process of the test defect 440 on the substrate 110 of the test structure are not considered. The etching process of the uncorrected repair shape 445 extends beyond the repair shape due to the non-point-shaped processing zone. For the pattern elements 520 and 530, this means that in the area where the test defect 440 comes close to the pattern elements 520 and 530 or the test defect 440 touches a part of the pattern elements 520 and 530, it is also removed in the particle beam-induced etching process compared to the edge 550 of the original pattern elements 420 and 430.From the removed parts 540 and 545 or the deviations 540 and 545 with respect to the original pattern elements 420 and 430, the correction values C can be determined. i the equation (2).

[0079] The pattern elements 520 and 530 of the Fig. 5 illustrate the dependence of the machining process on the lateral dimensions of the test defect 440 by the deviations 540 and 545 compared to the original pattern elements 420 and 430. Based on the deviations 540 and 545 of the pattern elements 520 and 530 induced by the machining process, the correction values K i the equation (3).

[0080] The flowchart 600 of the Fig.Figure 6 presents a method for determining a repair shape for processing a defect in a photolithographic mask. The method begins at step 610. In the second step 620, at least one correction value for the repair shape of at least one defect is determined, where: (i) the correction value takes into account a position of at least one pattern element of the photolithographic mask which does not contact the at least one defect; (ii) the correction value takes into account a lateral extent of the at least one defect on the surface of a substrate of the photolithographic mask; and / or (iii) the correction value takes into account a shape of the at least one pattern element of the photolithographic mask which contacts the at least one defect.

[0081] In the next step 630, the repair shape is corrected by applying the at least one correction value. The method finally ends in step 640.

Claims

[1] A method for determining a repair shape (195) for processing at least one defect (140) of a photolithographic mask (100), the method comprising the following steps: a. Determining at least two location-dependent correction values (185) for the repair shape (195) of the at least one defect (140), wherein the at least two location-dependent correction values (185) take into account a position (175) of at least one pattern element (130) of the photolithographic mask (100) that does not contact the at least one defect (140); and b. Correcting the repair shape (195) by applying the at least two location-dependent correction values (185). [2] A method for determining a repair shape (195) for processing at least one defect (140) of a photolithographic mask (100), the method comprising the following steps: a. Determining at least two location-dependent correction values (185) for the repair shape (195) of the at least one defect (140), wherein the at least two location-dependent correction values (185) take into account a lateral extent (180) of the at least one defect (140) on a surface of a substrate (110) of the photolithographic mask (100); and b. Correcting the repair shape (195) by applying the at least two location-dependent correction values (185). [3] A method for determining a repair shape (295) for processing at least one defect (240) of a photolithographic mask (100), the method comprising the following steps: a. Determining at least one correction value (285, 385) for the repair shape (295, 395) of the at least one defect (240), wherein the correction value (285, 395) takes into account a shape of at least one pattern element (220) of the photolithographic mask (100) that contacts the at least one defect (140, 240); and b. Correcting the repair shape (295) by applying the at least one correction value (285). [4] The method of claim 3, wherein the at least one correction value (285) takes into account a lateral dimension (280) of the at least one pattern element (220). [5] Method according to claim 3 or 4, wherein the at least one correction value (385) takes into account at least one corner (340, 350) of the at least one pattern element (220). [6] The method according to claim 5, wherein the at least one correction value (385) results in a reduction in the size of the repair shape (395) in the vicinity of the at least one corner (350) of the at least one pattern element (120) in comparison with a correction value in the vicinity of a rectilinear region of the pattern element (120) when the corner (350) protrudes into the at least one defect (140), and / or wherein the at least one correction value (385) results in an enlargement of the repair shape (395) in the vicinity of the at least one corner (340) of the at least one pattern element (120) in comparison with a correction value in the vicinity of a rectilinear region of the pattern element (120) when the at least one defect (140) protrudes into the corner (340) of the at least one pattern element (120). [7] Method according to claim 4 or 5, wherein the at least one correction value (285, 385) takes into account the lateral dimension (280) of the at least one pattern element (220) and the at least one corner (340, 350) of the at least one pattern element (120, 220). [8] Method according to one of the preceding claims, wherein the determination of the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) further comprises: taking into account a thickness and / or a material composition of the at least one pattern element (120, 130, 220). [9] Method according to one of the preceding claims, wherein determining the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) further comprises: taking into account the thickness and / or a material composition of the at least one defect (140, 240). [10] Method according to one of the preceding claims, wherein processing the at least one defect (140, 240) comprises: performing a particle beam-induced etching process and / or a particle beam-induced deposition process on the corrected repair shape (195, 295, 395) of the at least one defect (140, 240). [11] Method according to one of the preceding claims, wherein determining the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) comprises analyzing a test mask (410, 610). [12] Method according to one of the preceding claims, wherein applying the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) comprises: reducing an area of the repair shape (195, 295, 395) by correcting at least a portion of an edge of the repair shape (195, 295, 395). [13] Method according to one of the preceding claims, wherein determining the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) comprises combining the at least two location-dependent correction values (185) of claim 2 and the at least one correction value (285, 385) of claim 3. [14] Method according to one of the preceding claims, wherein determining the at least two location-dependent correction values (185) comprises combining the at least two location-dependent correction values (185) of claims 1 and 2. [15] Method according to claim 13 or 14, wherein combining the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) of two claims comprises linear combining. [16] The method of claim 1 or 2, wherein determining the at least two location-dependent correction values (185) comprises: averaging at least a portion of the edge (162) of the at least one defect (140) that does not contact the at least one pattern element (130); and determining a perpendicular to the tangent to the averaged edge of the at least one defect (140) to determine the distance (175) of the averaged edge from the at least one pattern element (130) that does not contact the at least one defect and the lateral extent (180) of the at least one defect (140) on the surface of the substrate (110). [17] Method according to claim 2 or 3, wherein the determination of the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185) comprises: forming a perpendicular in the region of the at least one pattern element (120, 220) which contacts the at least one defect (140, 240) for determining the lateral extent (180, 270) of the at least one defect (140, 240) and the lateral extent of the at least one pattern element (120, 220) which contacts the at least one defect (140, 220). [18] A computer program containing instructions which, when executed by a computer system, cause the computer system to carry out the method steps of claims 1 to 17. [19] Device for determining a repair shape (195, 295, 395) for processing at least one defect (140, 240) of a photolithographic mask (100), the device comprising: a measuring unit configured to determine the repair shape (145); b. a computing unit configured to determine at least one correction value (285, 385) for the repair shape (295, 395) and / or at least two location-dependent correction values (185) for the repair shape (195) of the at least one defect (140, 240), wherein: (i) the at least two location-dependent correction values (185) take into account a position of at least one pattern element (130) of the photolithographic mask (100) which does not contact the at least one defect (140); (ii) the at least two location-dependent correction values (185) take into account a lateral extent (180) of the at least one defect (140) on a surface of a substrate (110) of the photolithographic mask (100); and / or (iii) the correction value (285, 395) takes into account a shape of at least one pattern element (120, 220) of the photolithographic mask (100) which contacts the at least one defect (140, 220); and wherein c. the computing unit is further configured to correct the repair shape (195, 295, 395) by applying the at least one correction value (285, 385) and / or the at least two location-dependent correction values (185). [20] Apparatus according to claim 19, which is designed to carry out the method steps of claims 1 to 17.

Images