Method and apparatus for processing DC marks for the repair of lithography masks

Abstract

Method for processing an object for lithography comprising: processing a mark (M) deposited on the object (O) with a particle beam (102) and an etching gas (EG) to reduce the volume of the mark, wherein the mark remains on the object after processing the mark.

Description

1. Technical area

[0001] The present invention relates to processing a marking of an object, e.g. an object for lithography, with a particle beam, as well as corresponding methods, a corresponding computer program and a corresponding device. 2. State of the art

[0002] In the semiconductor industry, increasingly smaller structures are being produced on a wafer to ensure increased integration density. Lithographic processes, among others, are used to produce the structures, which map them onto the wafer. The lithographic processes can include, for example, photolithography, UV lithography, DUV lithography, EUV lithography, X-ray lithography, nanoimprint lithography, etc. Lithography usually uses masks (e.g., photomasks, exposure masks, reticles, stamps in nanoimprint lithography, etc.), which contain a pattern to map the desired structures, for example, onto a wafer.

[0003] As integration density increases, the demands on mask manufacturing also increase (e.g., due to the associated reduction in feature sizes on the mask or the higher material requirements of lithography). The mask manufacturing processes are thus becoming increasingly complex, time-consuming, and costly. Mask errors (e.g., defects) cannot always be avoided.

[0004] It may therefore be necessary to precisely process a mask within a (predefined) work area, e.g., to correct or repair mask defects. For example, this can be done using a particle beam-based processing process in which a particle beam is used to process the mask. The particle beam-based processing process can, for example, include particle beam-induced deposition and / or etching. The particle beam-based processing process can also include imaging the mask via the particle beam.

[0005] To perform particle beam-based processing of a mask in a defined manner, it may be necessary to use markings. For example, the markings can be (local) reference markings, which are rasterized with the particle beam, for example, for (drift) correction and / or control of the processing process. It may be common practice to deposit the markings on the mask in order to be able to perform defined processing at any location on the mask.

[0006] It may happen that a deposited mark can be used effectively for particle beam-based processing, but subsequently becomes a disruptive element of the mask. For example, a mark deposited on the mask can cause an optical defect (e.g., a violation of an optical specification) during a lithographic process. The mark itself can therefore correspond to a defect on the mask.

[0007] Known approaches usually rely on the markings being removed completely after the machining process in order to avoid optical defects.

[0008] However, with the advancement of mask technology, this approach cannot (always) be applied to all lithographic objects. For example, a process to completely remove a mark may compromise the lithographic object.

[0009] The present invention is therefore based on the object of providing improved or alternative possibilities for processing objects for lithography. 3. Summary of the invention

[0010] This object is at least partially achieved by the various aspects of the present invention.

[0011] A first aspect of the invention relates to a method for processing an object for lithography, comprising: processing a mark deposited on the object with a particle beam and an etching gas to reduce the volume of the mark, wherein the mark remains on the object.

[0012] The object for lithography (as described herein) may, for example, comprise a mask for a lithographic process. For example, the object may comprise an EUV mask for EUV lithography. For example, the EUV mask may comprise an absorbing and / or phase-shifting EUV mask. However, it is also conceivable for the object to comprise a mask for any other lithographic process. For example, the object may comprise a mask for DUV lithography, UV lithography, X-ray lithography, or nanoimprint lithography.

[0013] In one example, the object for lithography may also include a mask blank. Mask blanks are a well-known starting material for a mask in the lithography industry. The mask blank may, for example, not include imaging structures like the mask itself, but rather its layer material.

[0014] For example, the marking may have been deposited as a reference structure for correcting a particle beam for processing (e.g., repair) of the object. The marking may, for example, comprise a reference structure for drift correction of the particle beam.

[0015] It should be mentioned that objects for lithography can include, for example, electrically insulating samples. Scanning the object with charged particles (e.g. electrons from an electron beam, ions from an ion beam) can therefore cause the object to become electrostatically charged. This charge can unintentionally deflect the particle beam from the intended point of impact. This effect is called drift of a particle beam, although other mechanisms can also influence it. For example, the particle beam can also be influenced by thermal drift. For example, the particle beam can also be influenced by (mechanical) vibrations of one or more components. For example, the vibrations of the object, an object holder, particle beam optics and / or a particle beam deflection unit (e.g. a column), and / or any vibrations of the particle beam device can (unintentionally) influence the particle beam.

[0016] To enable defined processing of the object, a marker deposited on the object can be used as a reference structure. During processing, the marker can be rasterized to determine or track its position. Based on this, the particle beam can be corrected to ensure defined processing at a desired location on the object. Processing can include, for example, particle beam-induced etching and / or deposition, or image acquisition with the particle beam.

[0017] However, a mark deposited on the object can cause an optical defect in the object during lithography due to its geometric dimensions. For example, the mark may be geometrically designed in such a way that the optical properties of the object are locally disrupted. This may, for example, cause a critical dimension in an aerial image of the object (e.g., during lithography and / or during examination in an inspection device) to be violated in an area of ​​the deposited mark.

[0018] The optical error can occur, for example, if the dimensions of the marking are on the same order of magnitude as the structural dimensions of the object for lithography. For example, it may be necessary for a marking to have a specific minimum width and / or minimum height in order to be used as a functional reference structure for drift correction (e.g. for contrast purposes during image recognition of the marking). This way, the rasterization of the marking and its position determination can be reliably ensured. If the marking is on the same order of magnitude as the structural dimension, the marking can have an optical influence on lithography. For example, the marking (like a structure of the mask) can have an absorbing and / or phase-shifting effect and thus cause an optical error. This effect is all the more critical the smaller the structural dimensions of the object for lithography are.

[0019] For example, it is known that photolithography masks of the 32 nm technology node can have a structural dimension (e.g., a line width) of approximately 130 nm. This can be in a similar order of magnitude to known (drift correction) markings, whose dimensions can range, for example, between 50 and 100 nm. The markings in this example can therefore cause undesirable effects. It is known that these (interfering) markings can be removed without residue (e.g., via etching).

[0020] However, with the continued technical development of lithography, this approach may not always be applicable or advantageous. Firstly, if the mark is to be completely removed, the object for lithography may be over-etched (i.e., over-processed) for a certain period of time to ensure complete (e.g., essentially residue-free) removal of the mark material. However, this may increase the risk of the object being attacked and / or damaged in the process.

[0021] Overetching can comprise a process in which the object is exposed to an etching component for a comparatively long time, at least in the area of ​​the marking. This can, for example, ensure that any material of the marking is completely removed or is only (still) present in traces. Attacking and / or damaging the structures of the object cannot always be ruled out, since overetching can also influence the material of the structures of the object. For previous comparatively wide structure dimensions (e.g. greater than 130 nm) and optically less complex lithography processes, such overetching does not always have to have a critical effect. For example, with such wide structures, overetching can attack the material of the structures (e.g. slight etching of mask structures).However, this may be a smaller percentage due to the wide structural dimensions, so the risk of causing an optical defect of the object in the area of ​​the marking may be low.

[0022] However, in the course of technical development, the dimensions of, for example, imaging structures of objects for lithography can become significantly smaller, e.g., smaller than 100 nm, than 80 nm, than 70 nm and / or smaller than 60 nm. This can be the case, for example, with objects for EUV lithography (e.g., for absorbing and / or phase-shifting masks for EUV lithography and / or for masks for high-NA EUV lithography). For example, structure widths of EUV masks can now be in the range of 60 nm, although the trend in the future may be towards even more delicate (e.g., even narrower) structure dimensions. Overetching markings on objects with smaller structure dimensions (e.g., below 100 nm) can increase the risk that the structures of the object can be attacked and / or influenced much more easily than comparatively larger structures.For example, with such narrower structures, overetching can cause attack on the structural material (e.g., slight etching of mask structures), which accounts for a comparatively higher percentage due to the narrower structure dimensions. The risk of causing an optical defect in the object in the marking area can therefore be higher.

[0023] It should also be noted that the requirements for the properties of the materials used in lithography objects are becoming increasingly complex as lithographic processes are becoming increasingly optically complex. For example, increasingly stringent optical requirements are being placed on the absorbing and / or phase-shifting properties of masks (or mask blanks). Objects for lithography are, for example, increasingly being designed for more complex optical exposures, where, for example, tilted exposure (also known as oblique illumination) takes place and / or a defined phase-shifting property of the object is desired. As lithographic processes become increasingly complex, the requirements for the reliability of the real and / or imaginary refractive indices of the mask structures are also becoming higher.

[0024] Overetching of a mark may involve a relatively long exposure of the object to an etching component, which may conceivably affect the complex optical properties of the object for lithography in a disruptive manner.

[0025] To meet these complex properties, there is increasing discussion about using novel materials or material combinations for lithographic objects (and their structures). This can lead, for example, to the fact that a sufficiently high etch selectivity for removing the marking relative to the object's materials cannot always be guaranteed. Removing the marking (e.g., by overetching) can therefore significantly damage the object's structures and induce defects.

[0026] Furthermore, overetching represents an extended time component for complete removal, since, for example, the removal of the mark is only completed when it can be assumed that (essentially) no residue of the mark remains. However, for the processing of objects for lithography within mass production in the semiconductor industry, a long or unnecessary processing time is not advantageous. Instead, processes are typically designed to save time, for example, to enable high throughput, cost reduction, and / or simplify technical complexity.

[0027] The well-known over-etching and complete removal of a marking is therefore not always an optimal solution.

[0028] The idea of ​​the invention, in contrast, is to reduce the volume of the deposited marking, whereby the marking remains on the object after processing. The volume of the marking can therefore be reduced without completely removing the marking. For example, the volume can be reduced to such an extent that it can be examined with a scanning electron microscope after processing. The volume can therefore, for example, be reduced to such an extent that it can be recognized in a scanning electron image. For example, if the marking is completely removed, a material of the marking might no longer be visible in the scanning electron image.

[0029] The approach of the invention can enable increasingly complex lithographic objects to be protected when a marking on the object is processed. The processing of the marking according to the method of the first aspect can, for example, take place after its functional use (e.g., as drift correction marks for a particle beam). The inventive approach can enable a shorter processing time for the marking. This can prevent the object from being exposed to an etching component for an unnecessarily long time during lithography.

[0030] By reducing the processing time, the risk of negative effects on the structures and / or materials of the object being induced during removal can be minimized. Disruptive effects on the optical properties of the object can thus be minimized. As described herein, in the course of technical development, the structural dimensions can become increasingly smaller and / or the materials for lithography objects can become more complex. The method described here can take this development into account and offer a gentle processing process which minimizes the risk of impairing the optical properties of (increasingly complex) lithography objects. According to the invention, the object can therefore be processed for lithography with a lower risk than if the markings were completely removed.

[0031] Furthermore, reducing processing time can represent a significant time advantage in mass production. For example, in mass production in the semiconductor industry, a reduction in any process times can be of enormous importance. As described herein, the method of the first aspect can be carried out after a repair of the object (e.g., a mask repair). It may be common practice for mask repairs to be carried out in industrial mass production with a comparatively high throughput (e.g., in shift operation), since critical mask defects can regularly occur in semiconductor manufacturing (especially in complex lithographic processes). Any time saved in removing the marks can (in total) represent a huge advantage for a semiconductor factory (e.g., an increase in throughput and / or a significant cost reduction).

[0032] Furthermore, the invention can also save material, as less etching gas is required. This can be primarily due to the fact that there is no overetching, but rather a targeted etching of the marking for a comparatively short time (compared to overetching). In industrial mass production, the savings in etching gas (in total) can be a significant factor and, for example, represent a significant cost reduction.

[0033] The risks and / or disadvantages mentioned when completely removing the marking can thus be reduced.

[0034] In one example, the volume (of the mark) may be reduced such that the processed mark does not cause a deviation from a predetermined specification during lithography.

[0035] One idea of ​​the invention can, for example, be understood as meaning that the volume of the marking is reduced at least to the extent that the marking cannot have a technically disadvantageous effect during lithography. The predetermined specification can, for example, be defined for an optical image of the object in a reference plane (e.g. an aerial image of a mask). For example, the predetermined specification can comprise a critical dimension in the optical image (e.g. a distance between characteristic lines in an aerial image of the mask, as is known in the industrial environment). The predetermined specification can, for example, also be defined for a resist image, wherein the resist image was generated via an optical image of the object. For example, a substrate (e.g. a wafer) with a developable resist layer can have been exposed and developed via the object. The resist image can, for example, be referred to in industry as a wafer print.For example, the predetermined specification may include a critical dimension in the resist image (e.g., a distance between characteristic lines in the resist image of the mask, as known in the industrial environment). The predetermined specification may also be defined (analogously) for an etching, where the etching may, for example, correspond to an etching of the resist image.

[0036] Figuratively speaking, the invention can be understood as meaning that the marking is removed in the optical image of the object for lithography, but not physically on the object itself. The marking is therefore (only) optically removed, so that an optical specification of the object is not violated.

[0037] According to the invention, unnecessarily lengthy processing of the marking can be avoided. At the same time, the method can be used in such a way that the marking no longer has a negative impact on the lithography process.

[0038] However, the advantages of the invention can also be accompanied by more extensive preparatory measures for the method of the first aspect. For example, it can be determined experimentally to what volume the marking must be reduced so that no deviation from the predetermined specification occurs. For example, in a relay experiment with different processing times (e.g., different etching times), it can be determined at which processing time of the marking with the particle beam and etching gas no deviation from the predetermined specification occurs.

[0039] In one example, the volume of the marking can be reduced from a first volume to a second (predetermined target) volume. The first volume can correspond to the volume of the marking that it had before carrying out the method of the first aspect. The first volume can therefore correspond to the volume of the marking that it had before processing the marking with the particle beam and the etching gas. The first volume can, for example, correspond to an original volume of the marking that it had after deposition. For example, the first volume of the marking can also deviate from the original volume of the marking. For example, it is conceivable that the marking is rasterized with the particle beam after deposition for specific purposes, thereby causing a change in the original volume of the marking. For example, the marking can be used for processing the object (e.g.a mask repair), whereby the volume of the marking may have increased compared to the original volume due to deposition processes or decreased due to etching processes.

[0040] The second volume may correspond to the volume that the marking has according to the method of the first aspect.

[0041] In one example, the volume of the marker may be reduced by at least 10%, (preferably) at least 30%, (more preferably) at least 50%, (most preferably) at least 90%. It is also conceivable that the volume of the marker may also be reduced by at least 95%.

[0042] In one example, at least 5%, (preferably) at least 10%, (more preferably) at least 20%, (most preferably) at least 30% of the volume of the marker may remain. In one example, further, at least 40%, (preferably) at least 50%, (more preferably) at least 70%, (most preferably) at least 90% of the volume of the marker may remain.

[0043] For example, the second volume of the marking may comprise (substantially) 10% of the first volume. For example, the second volume may comprise (substantially) 20% of the first volume. For example, the second volume may also comprise (substantially) 30%, 40%, and / or 50% of the first volume.

[0044] According to the invention, a significant residue of the marking material can remain, which does not correspond to a trace residue of the marking material. For example, this residue can be detected using a scanning electron microscope.

[0045] In one example, the mark may be deposited on an imaging structure of the object. The imaging structure may, for example, be a radiation-absorbing and / or phase-shifting structure for lithography. For example, the imaging structure may comprise a pattern element of a mask. For example, the imaging structure may comprise a linear structure with a specific width. The imaging structure may, for example, comprise one or more layers. The mark may, for example, be applied to an (upper) plateau of the imaging structure (e.g., on an uppermost layer of the imaging structure). For example, the imaging structure may be in the form of a mesa, with the mark deposited on the mesa. In one example, the mark may be applied directly to the imaging structure, without a layer (e.g., a sacrificial layer) having to be applied between the mark and the imaging structure.Due to the advantages mentioned herein in reducing the volume of the marking, for example, an easily removable sacrificial layer which is present between the imaging structure and the marking can be dispensed with.

[0046] According to the invention, the particle beam and the etching gas can be directed at the mark on the imaging structure to reduce the mark in volume, wherein the mark remains on the imaging structure. In one example, the etching gas can be introduced locally in the vicinity of the mark (e.g., via a gas nozzle). In one example, a pixel grid can be superimposed over the mark, wherein one or more pixels can cover the mark. When processing the mark, the particle beam can be directed at the one or more pixels to perform the method described herein.

[0047] In one example, the imaging structure can be adjacent to a cover layer of the object. The cover layer can comprise ruthenium, for example, although other materials are also conceivable. For example, the cover layer can comprise quartz. Areas of the object where the cover layer is exposed can be regarded as clear areas, for example, since exposure radiation is not absorbed at these locations. Areas of the object where material of the imaging structure is present can be regarded as opaque areas, for example, since exposure radiation is absorbed at these locations. The marking can be applied to an opaque area, for example.

[0048] In one example, the volume may be reduced such that a height of the processed mark relative to the imaging structure is less than a height of the imaging structure relative to the object. The height of the (processed) mark relative to the imaging structure may be defined, for example, as a height of the (processed) mark relative to the (upper) plateau of the imaging structure. The height of the imaging structure relative to the object may be, for example, the height of the imaging structure relative to the cover layer to which the imaging structure may be adjacent.

[0049] According to the invention, a reduction in the height of the marking can therefore be achieved. In one example, the height of the marking can be reduced from a first height to a second height (e.g., a second predetermined target height). The first height can, for example, correspond to the height of the marking before carrying out the method of the first aspect. The first height can, for example, correspond to the original height of the marking after deposition on the object. The first height can, for example, also deviate from the original height (e.g., caused by deposition and / or etching processes during rasterization of the marking, as described herein).

[0050] The second height may correspond to the height of the mark which it has according to the method of the first aspect.

[0051] In one example, the marking may be edited such that the height of the edited marking (relative to the imaging structure) is at least 10%, (preferably) at least 30%, (more preferably) at least 50%, (most preferably) at least 90% less than the height of the imaging structure (relative to the object). In one example, the marking may be edited such that the height of the edited marking is at least 95% less than the height of the imaging structure.

[0052] In one example, the processing of the mark may be performed such that the height of the processed mark (relative to the imaging structure) corresponds to at least 5%, preferably at least 7%, more preferably at least 10%, most preferably at least 12% of the height of the imaging structure (relative to the object).

[0053] In one example, the volume is reduced such that the second height of the marker corresponds to at least 5%, (preferably at least) 10%, (more preferably) at least 20%, (most preferably) at least 40% of the first height of the marker. In one example, the volume is reduced such that the second height corresponds to at least 50%, (preferably at least) 60%, (more preferably) at least 70%, (most preferably) at least 90% of the first height.

[0054] Height reduction can be useful, for example, if the object is used for lithography with an inclined exposure. The object can be exposed with a radiation incident at an angle relative to the object plane. This means that the radiation incident during exposure can be oblique relative to the object's cover layer. Furthermore, the radiation can be reflected at an appropriate angle from the object. Inclined exposure can be used, for example, in EUV lithography.

[0055] Against this background, a critical height of the marking can cause shadowing upon incidence of the inclined exposure. The shadowing can, for example, extend beyond the imaging structure, e.g., onto the cover layer. This can thus induce an optical error. Likewise, a critical height of the marking (due to the inclined exposure) can shadow radiation reflected obliquely from the object. This mechanism can also induce an optical error (e.g., a deviation from a predetermined specification during lithography). According to the invention, a height reduction can, for example, be achieved in such a way that even with inclined exposure, no (significant) optical errors are generated during lithography.

[0056] In one example, the imaging structure may comprise a lateral dimension (e.g., a width) of at most 100 nm, (preferably) at most 80 nm, (more preferably) at most 60 nm, and (most preferably) at most 40 nm. In one example, the imaging structure may also comprise a lateral dimension (e.g., a width) of at most 30 nm or at most 20 nm. For example, the width of the imaging structure may have a width between 10 nm and 100 nm. As described herein, the width of the imaging structure may, for example, comprise a lateral dimension of the imaging structure (e.g., a line width, as known in the industrial environment). The width may, for example, correspond to a line width of a pattern element (e.g., an absorber structure). As mentioned, objects for lithography may comprise imaging structures with structure dimensions below 100 nm. This may, for example, be the case for objects for EUV lithography.

[0057] For such delicate structures with dimensions below 100 nm, complete removal of a marking (e.g., present on the structure) may not always be advantageous (as described herein). Masks for EUV lithography, for example, may have imaging structures with a width in the range of 60 nm (e.g., less than or equal to 60 nm). The method according to the first aspect can ensure, by reducing the volume of the marking, that the disruptive effect of the marking for lithography can be reliably eliminated even for such objects. The risk of damage to structures with dimensions below 100 nm can thereby be minimized.

[0058] In one example, a lateral dimension (e.g., a width) of the marking before processing can correspond to at least 50% of a lateral dimension (e.g., a width) of the imaging structure. In this case, a dimension of the marking would be on the order of magnitude of a structure dimension. In such an example, it can happen during lithography that, for example, even with vertical exposure or transillumination of the object, shadowing by the marking occurs, which can cause an optical error in a lateral effective area around the marking. Such optical phenomena can also be minimized or eliminated using the method described herein. It should be mentioned that the lateral optical error can also occur with an inclined exposure of the object (e.g., preferentially in one direction). The lateral dimension of the marking can, for example,a lateral dimension of the marking, which it has at an interface with a surface on which the marking is deposited. For example, the lateral dimension of the marking can comprise a diameter of the marking. For example, the marking can have a circular or elliptical shape at the interface with the surface on which the marking is deposited. The lateral dimension of the marking can comprise, for example, a diameter of this circle or a diameter of the elliptical shape.

[0059] In one example, a lateral dimension of the marking may comprise at least 60%, (preferably) at least 70%, (more preferably) at least 80%, (most preferably) at least 90% of a width (or lateral dimension) of the imaging structure.

[0060] In one example, the imaging structure may comprise a maximum width of 70 nm, wherein the marking comprises a width of at least 25 nm. In one example, the imaging structure may comprise a maximum width of 60 nm, wherein the marking comprises a width of at least 30 nm.

[0061] In one example, the volume of the mark may be reduced such that a width of the mark is reduced. In one example, a width of the mark may be reduced from a first width to a second width. The first width of the mark may correspond to the mark it has before performing the method of the first aspect. The first width may, for example, correspond to the original width of the mark it had after deposition. The first width may, for example, also deviate from the original width (e.g., caused by deposition and / or etching processes when rasterizing the mark, as described herein). The second width may correspond to the width the mark has after the method of the first aspect. The second width may be less than the first width.

[0062] In one example, a mark may be deposited with an offset on an imaging structure. For example, one side of the mark may be closer to an edge of the imaging structure than another side of the mark. It may, for example, be useful to edit the width of the mark. For example, the mark may be edited on the side that is closer to an edge of the imaging structure. Thus, for example, lateral effects on the corresponding side can be minimized (as described herein). However, it is also conceivable that the width of the mark is reduced homogeneously (i.e., evenly). For example, in the case of a circular diameter of a mark, this may represent a reduction of the radius of the circular diameter.

[0063] In one example, the method further comprises processing a processing location of the object with the particle beam. The processing may, for example, comprise a repair of the object (e.g., the repair of missing and / or excess material on the mask, and / or an optical correction of the mask). At least one correction of the particle beam may be performed based at least in part on a position of the marking. The processing of the processing location may further comprise providing a gas (e.g., providing an etching gas and / or a deposition gas).

[0064] In one example, the method may further comprise processing a foreign material of the object in an environment of the marking with the particle beam and the etching gas to reduce the volume of the foreign material. The idea of ​​the invention is therefore also to remove interfering material around the marking. In one example, the foreign material may depend on the presence of the marking. For example, during the deposition of the marking and / or rasterization of the marking (e.g., as a reference structure), foreign material may be generated around (and / or on) the marking.

[0065] This foreign material, due to its geometric dimensions, can also cause an optical defect in the object during lithography (as described analogously for a marking). The features and aspects of the method described herein for processing the marking can therefore also apply to processing the foreign material.

[0066] In one example, the foreign material can be reduced in volume while the foreign material remains on the object.

[0067] The features described herein for the relative reduction in the volume of the marker may also apply or be applied accordingly to the reduction in the volume of the foreign material. For example, when reducing the volume of the foreign material, the percentage reductions in the volume of the marker described herein may also correspond to the percentage reduction in the foreign material.

[0068] In another example, the foreign material can be removed from the object. For example, the foreign material can be removed (essentially) without leaving any residue. For example, the foreign material can have different properties than the material of the marking. It can be the case, for example, that the foreign material was deposited parasitically (e.g. based on an actually undesired but nevertheless existing deposition condition). To eliminate the optical defect induced by the foreign material, it can therefore be (e.g. absolutely) necessary to remove the foreign material (essentially without leaving any residue). In such a case, for example, the risk that over-etching the foreign material may entail disadvantages can be accepted, since the advantages of an optically defect-free mask can outweigh the disadvantages.

[0069] In one example, the environment of the mark where the foreign material is present may be within a radius of 1 µm or less from the mark (and / or within a radius of 10 µm or less, and / or within a radius of 100 nm or less). However, the environment of the mark where the foreign material is present may also depend on the deposition of the mark and / or the processing during rasterization of the mark, so the environment need not (necessarily) be limited to absolute values.

[0070] In one example, the foreign material may comprise a deposition material that was generated during the deposition of the marking. For example, the deposition of the marking may comprise particle beam-induced deposition. This may, for example, comprise electron beam-induced and / or ion beam-induced deposition. In such deposition processes, it may happen that particles additionally accumulate or collect at local locations due to the effect of the particle beam on the object (e.g., due to reflection, diffraction, and / or secondary emission of particles, etc.). These local locations may be offset from the actual point of impact of the particle beam. The presence of particles at these local locations may also lead to deposition there. However, this may not be technically desirable.Technically, it is usually intended that deposition material should be generated only at the point of impact of the particle beam in order to create a deposition geometry defined by the orientation of the particle beam. Due to the effect described here, in addition to the desired deposition geometry (e.g., at locations where the particle beam was directed during deposition), a parasitic foreign material may be deposited locally offset from it (e.g., at a location where the particle beam was not directed during deposition).

[0071] According to the invention, this foreign material displaced from the marking can be processed using one of the methods described herein.

[0072] In one example, the foreign material may comprise foreign material around (and / or on) the mark. For example, the foreign material may be radially spaced from the mark. For example, the foreign material may be in the form of a halo around the mark. For example, foreign material around the mark may not always have a defined shape or thickness. For example, the foreign material may appear like a halo around the mark in an image (e.g., a scanning electron image). As described herein, the foreign material in the form of a halo may, for example, have been parasitically generated during electron beam-induced deposition of the mark, because electrons had accumulated around the mark during deposition. The foreign material in the form of a halo may, for example, comprise a material whose thickness decreases exponentially (e.g., in the radial direction starting from the mark).This thickness gradient can appear as a halo (e.g. around the marking) in a scanning electron image.

[0073] It is also conceivable that the foreign material is arranged around the marking, for example in a ring shape and / or in the form of an ellipse.

[0074] In one example, the foreign material may comprise a deposition material that was generated during rasterization of the marking within a raster field, preferably during a repair of the object. For example, the marking may be rasterized as a reference structure for drift correction of the particle beam during processing of the object (e.g., a particle beam-induced repair of a defect).

[0075] As described herein, charging effects can occur during repair and / or processing of the object with the particle beam, so that the particle beam is unintentionally deflected (and does not hit a desired position). Therefore, the position of a marking is usually used as a reference structure in order to adjust or correct the particle beam based on the position of the marking. This correction can ensure that the particle beam can strike a desired position (e.g., a desired processing and / or repair point on the object). During repair and / or processing, for example, a position of the marking must be determined several times to correct the particle beam.

[0076] In order to effectively use the marking as a reference structure, a local grid field can be arranged around the marking, whereby the grid field is completely scanned with the particle beam to determine the position of the marking. The reason for this is that when the position of the marking is determined, its position can also drift (or fluctuate) due to charging effects. By placing a grid field with a defined size (initially) around the marking, a position drift of the marking within the grid field can be addressed with the particle beam. If, for example, the entire local grid field is scanned, it can be assumed that the particle beam should ultimately hit the marking for imaging purposes, even if the position of the marking (within the grid field) drifts. During processing of the object, the particle beam can therefore be moved to a desired processing location, e.g.for particle beam-induced etching and / or deposition at the processing site. For drift correction, the particle beam can then scan the grid field around the marking in addition to the actual processing site in order to target or determine the position of the marking.

[0077] It may happen that the processing of the object includes particle beam-induced deposition using a deposition gas at a processing location. This can be, for example, a mask repair, where the processing location may include a defect in the mask (e.g., a defect where material is missing from the mask, e.g., a clear defect in the mask). For particle beam-induced deposition at the processing location of the object, a deposition gas can be provided there. The deposition gas can, for example, be introduced locally above the processing location, although it is also conceivable that a deposition gas is introduced globally above the object. By directing the particle beam at the processing location, a corresponding deposition reaction can be induced via the deposition gas present there.

[0078] During such processing, it can happen that, due to the provision of a deposition gas at the processing location of the object, this deposition gas is also present in the area of ​​the marking. Thus, for example, the grid field around the marking can also contain the deposition gas. If, during such processing of the object, the grid field surrounding the marking is scanned to correct the particle beam, particle beam-induced deposition of foreign material can occur in the grid field.

[0079] This foreign material can be present around the marking (or even on the marking). For example, this foreign material can (essentially) correspond to the lateral dimensions of the grid field. This can be detectable in a scanning electron image, for example, a rectangular foreign material can be detected containing a drift-correcting marking.

[0080] According to the invention, such foreign material can also be reduced in volume and / or completely removed from the object.

[0081] In one example, the foreign material may be present next to an imaging structure of the object and / or on an imaging structure of the object. The idea of ​​the invention is therefore also to remove interfering foreign material in clear areas and / or opaque areas of the object. The foreign material next to and / or on the imaging structure of the object may, for example, result from the grid field around the marking.

[0082] In one example, the marking can be applied to the imaging structure. With comparatively larger structural dimensions of imaging structures (e.g., with widths greater than 130 nm), the grid field (described here), for example, can be designed such that it only encompasses an area in which material of the imaging structure is present. Therefore, if a deposition occurs there during scanning of the grid field, the corresponding deposition material can only be present on the imaging structure. Since the deposition material in this approach is only present on the (e.g., radiation-absorbing) imaging structure, it was previously assumed that no (significant) optical error could be induced.

[0083] However, for optimal positioning of the marking, a certain minimum size of the grid field is (usually) required. With the increasingly smaller dimensions of the imaging structures (e.g., below 100 nm), it can therefore happen that the grid field not only comprises an area that covers material of the imaging structure, but also (necessarily) comprises a second area that covers an area adjacent to the imaging structure. The second area of ​​the grid field can therefore comprise a clear area of ​​the object in which no material of the imaging structure is present. When scanning the grid field, foreign material can also be deposited in the second area and thus directly onto a clear area of ​​the object (e.g., if deposition gas is present in the grid field, as described herein).According to the methods described herein, this parasitically generated foreign material can be reduced and / or removed in volume next to the imaging structure in order to avoid, for example, optical errors during lithography.

[0084] With the increasingly smaller dimensions of the imaging structures and / or the increasingly complex requirements for objects for lithography, the foreign material on the imaging structure (which was generated, for example, during scanning of the grid field) can no longer be neglected. For example, this foreign material can also cause a deviation in a lithography specification during an inclined exposure during lithography. According to the methods described herein, parasitically generated foreign material on the imaging structure can be reduced in volume and / or removed, for example, to avoid optical errors during lithography.

[0085] In one example, the method may further comprise: selecting the etching gas, wherein the etching gas is selected at least in part based on a provided deposition gas with which the mark and / or a foreign material was deposited on the object in an environment of the mark. The etching gas for processing the mark and / or for processing the foreign material may thus, for example, be based on a deposition material of the mark and / or the foreign material. In one example, the method may thus comprise: selecting the etching gas, wherein the etching gas is selected at least in part based on a material comprised in the mark and / or the foreign material.

[0086] As described herein, the parasitically deposited foreign material may result from a deposition gas present in the grid field with which the object was processed at a processing location (e.g., when repairing a defect in the object). The composition of the foreign material may therefore, for example, have a different composition than the material of the marking. However, the features and / or aspects described herein for the assignment of etching gas to deposition gas can also be applied accordingly to this case.

[0087] In one example, the mark is processed with a first etching gas and the foreign material is processed with a second etching gas, wherein the second etching gas is different from the first etching gas.

[0088] In one example, the method may comprise generating the marking on the object using a particle beam and a deposition gas provided, preferably for repairing the object (e.g., a mask repair). The deposition gas provided for generating the marking may, for example, be stored in a memory and / or a database. Likewise (analogously), the deposition gas used for processing at the processing site may, for example, be stored in a memory and / or a database.

[0089] Selecting the etching gas may include retrieving the provided deposition gas from the memory and / or the database. The components and / or the one or more chemical compounds of the provided deposition gas can then be determined. Based on the components and / or the one or more chemical compounds, a corresponding etching gas can be selected. For example, this can be done via a look-up table and / or a database. For example, one column of the look-up table can include the components and / or the one or more chemical compounds of the deposition gas. Another column can include the possible assigned etching gases. Based on the determination of the components and / or the one or more chemical compounds, a corresponding etching gas for processing the marking can be selected via the look-up table.Furthermore, any database is conceivable in which an assignment of deposition gas (or deposition gas composition) and possible etching gases is stored.

[0090] For example, the method may also (correspondingly) comprise automatically setting or storing an etching gas in a database and / or look-up table, e.g. after the marking has been deposited with a specific deposition gas.

[0091] This can enable an automated process for processing the marking with a suitable etching gas.

[0092] In one example, the etching gas may comprise a halogen. For example, the etching gas may comprise at least one halogen atom.

[0093] In one example, the halogen (of the etching gas) may comprise chlorine if the deposition gas comprises chromium. For example, the database and / or the look-up table may store that a chlorine-containing etching gas is associated with a chromium-containing deposition gas.

[0094] For example, the chromium-comprising deposition gas may comprise chromium hexacarbonyl, Cr(CO)6.

[0095] In one example, if the deposition material of the mark and / or foreign material comprises chromium, the halogen (of the etching gas) may (analogously) comprise chlorine.

[0096] In one example, the etching gas may further comprise nitrogen and oxygen (if the deposition gas comprises chromium). In one example, the etching gas may (analogously) further comprise nitrogen and oxygen if the deposition material of the mark and / or the foreign material comprises chromium.

[0097] In one example, the etching gas may comprise chlorine, nitrogen, and oxygen in a compound, preferably nitrosyl chloride, NOCl (if the deposition gas comprises chromium). For example, the database and / or the look-up table may store that a chromium-containing deposition gas is assigned nitrosyl chloride as the etching gas.

[0098] In one example, the etching gas may (analogously) comprise nitrosyl chloride if the deposition material of the mark and / or foreign material comprises chromium.

[0099] In one example, the halogen may comprise fluorine if the deposition gas comprises chromium and / or if the deposition gas comprises silicon and oxygen and / or if the deposition gas comprises molybdenum. For example, the database and / or the look-up table may store that a fluorine-containing etching gas is associated with a deposition gas comprising silicon and oxygen and / or a deposition gas comprising molybdenum.

[0100] For example, the deposition gas containing silicon and oxygen may comprise tetraethylorthosilicate, TEOS.

[0101] For example, the molybdenum deposition gas may comprise molybdenum hexacarbonyl, Mo(CO)6.

[0102] In one example, the halogen (of the etching gas) may (analogously) comprise fluorine if the deposition material of the mark and / or the foreign material comprises chromium. In one example, the halogen (of the etching gas) may (analogously) comprise fluorine if the deposition material of the mark and / or the foreign material comprises silicon and oxygen. In one example, the halogen (of the etching gas) may (analogously) comprise fluorine if the deposition material of the mark and / or the foreign material comprises molybdenum.

[0103] In one example, the etching gas may further comprise xenon (if the deposition gas comprises chromium and / or if the deposition gas comprises silicon and oxygen and / or if the deposition gas comprises molybdenum). In one example, the etching gas may further comprise xenon if the deposition material of the mark and / or the foreign material comprises chromium. In one example, the etching gas may further comprise xenon if the deposition material of the mark and / or the foreign material comprises silicon and oxygen. In one example, the etching gas may further comprise xenon if the deposition material of the mark and / or the foreign material comprises molybdenum.

[0104] In one example, the etching gas may comprise fluorine and xenon in a compound, preferably xenon difluoride, XeF2 (if the deposition gas comprises chromium and / or if the deposition gas comprises silicon and oxygen and / or if the deposition gas comprises molybdenum). For example, the database and / or the look-up table may store that a deposition gas containing silicon and oxygen (e.g., tetraethyl orthosilicate) is assigned xenon difluoride as the etching gas.

[0105] For example, it can be stored in the database and / or in the look-up table that a deposition gas containing chromium (e.g. chromium hexacarbonyl) is assigned xenon difluoride as the etching gas.

[0106] For example, the database and / or the look-up table may contain information that a deposition gas containing molybdenum (e.g. molybdenum hexacarbonyl) is assigned xenon difluoride as the etching gas.

[0107] In one example, the etching gas may (analogously) comprise xenon difluoride if the deposition material of the mark and / or foreign material comprises chromium.

[0108] In one example, the etching gas may (analogously) comprise xenon difluoride if the deposition material of the mark and / or the foreign material comprises silicon and oxygen.

[0109] In one example, the etching gas may (analogously) comprise xenon difluoride if the deposition material of the mark and / or the foreign material comprises molybdenum.

[0110] In one example, the etching gas may comprise oxygen if the deposition gas comprises molybdenum. In this example, the etching gas does not necessarily have to comprise a halogen. In one example, the etching gas may (analogously) comprise oxygen if the deposition material of the marking and / or the foreign material comprises molybdenum. A molybdenum-containing marking and / or a molybdenum-containing foreign material may also be etched with an oxygen-containing gas within the scope of the method, which does not necessarily have to contain a halogen.

[0111] In one example, the (oxygen-containing) etching gas may comprise water (if the deposition gas comprises molybdenum). For example, the etching gas may (analogously) comprise water if the deposition material of the marking and / or foreign material comprises molybdenum. A molybdenum-containing marking and / or a molybdenum-containing foreign material may also be etched within the scope of the process using water as the etching gas, which does not necessarily require the presence of a halogen.

[0112] In one example, the processing of the mark and / or the foreign material can further be performed with an additive gas containing oxygen. The additive gas can, for example, be added to the etching gas as an oxidative component.

[0113] In one example, the additive gas may comprise water and / or nitrogen dioxide.

[0114] In one example, the etching gas may comprise nitrosyl chloride, wherein the additive gas may comprise water if the deposition material of the mark and / or foreign material comprises chromium.

[0115] In one example, the etching gas may comprise xenon difluoride, wherein the additive gas may comprise water and nitrogen dioxide if the deposition material of the mark and / or foreign material comprises chromium.

[0116] In one example, the etching gas may comprise xenon difluoride, wherein the additive gas may comprise water if the deposition material of the mark and / or foreign material comprises tetraethyl orthosilicate.

[0117] In one example, the etching gas may comprise xenon difluoride, wherein the additive gas may comprise water if the deposition material of the mark and / or the foreign material comprises a silicon oxide.

[0118] In one example, the etching gas may comprise xenon difluoride, wherein an additive gas may be omitted if the deposition material of the marking and / or the foreign material comprises tetraethyl orthosilicate and / or a silicon oxide.

[0119] In one example, the etching gas may comprise xenon difluoride, wherein the additive gas may comprise water if the deposition material of the mark and / or foreign material comprises molybdenum.

[0120] In one example, the etching gas may comprise water, but an additive gas may be omitted if the deposition material of the mark and / or foreign material comprises molybdenum.

[0121] A second aspect relates to processing a foreign material of the object (described herein) in an environment of the marking with the particle beam and the etching gas to reduce the volume of the foreign material. The features and aspects described herein for processing the foreign material (e.g., with regard to the method of the first aspect) can apply or be applied accordingly to the method according to the second aspect. In the method according to the second aspect, the foreign material (described herein) can be processed separately, without, for example, significantly processing the marking. Further features and / or aspects of the first method can also apply accordingly to the method of the second aspect. For example, the method of the second aspect can also comprise processing a processing location of the object with the particle beam. The processing can, for example, comprise repairing the object (e.g.,the repair of missing and / or excess material on the mask, and / or an optical correction of the mask). Furthermore, the method of the second aspect can also comprise generating the marking on the object with a particle beam and a provided deposition gas, preferably for a repair of the object (e.g., a mask repair).

[0122] A third aspect relates to a method according to the second aspect, wherein the foreign material comprises (only) a foreign material in the form of a halo around the marking (as described herein). According to the method of the third aspect, a halo around the marking can therefore be reduced in volume or removed (essentially without residue), wherein further foreign material does not necessarily have to be processed. For example, in the context of a mask repair, it can be useful to only reduce the volume and / or remove the halo in a separate step. For example, the deposition material of the halo can have a different geometry and / or composition than the marking, so that processing the halo and the marking in a coherent process step is not always advantageous.

[0123] A fourth aspect relates to a method according to the second aspect, wherein the foreign material comprises (only) a deposition material that was generated during rasterization of the marking within a raster field, preferably during a repair of the object (as described herein). According to the method of the fourth aspect, a deposition material that was generated in the raster field can thus be reduced in volume or removed (essentially without residue), wherein further foreign material does not necessarily have to be processed. For example, in the context of a mask repair, it can be useful to only minimize and / or remove the foreign material of the raster field in volume in a separate step. For example, the deposition material of the raster field can have a different geometry and / or composition than the marking (and / or the halo).Processing the deposition material of the grid field and the marking in a single process step may therefore not always be advantageous.

[0124] A fifth aspect relates to a method according to the second aspect, wherein the foreign material comprises (only) a foreign material in the form of a halo around the marking (as described herein), and wherein the foreign material comprises a deposition material that was generated during rasterization of the marking within a raster field, preferably during a repair of the object (as described herein). For example, in the context of a mask repair, it may be useful to only minimize and / or remove the halo and the foreign material of the raster field in a separate step. Processing the deposition material of the raster field, the halo, and the marking in a single process step may not always be advantageous due to different geometries and / or compositions of these materials.

[0125] A sixth aspect relates to a method for processing an object for lithography, comprising processing a foreign material of the object in an environment of a deposition material using a particle beam and an etching gas to reduce the volume of the foreign material. The deposition material can, for example, comprise any (e.g., locally limited) deposition material. This deposition material can, for example, have been deposited using a particle beam induced method. One idea of ​​the invention can therefore also be to remove interfering foreign material around any deposition material using a particle beam induced method. The invention therefore does not necessarily have to be limited to removing foreign material in an environment of a deposited marking. The features of the other aspects of the invention described herein can also be applied or apply accordingly to the method of the sixth aspect.For example, according to the method of the sixth aspect, the foreign material can be (substantially) completely removed from the object (e.g., removed substantially without residue). For example, according to the method of the sixth aspect, the foreign material can be reduced in volume, while the foreign material remains on the object.

[0126] For example, the foreign material processed by a method of the sixth aspect (as described analogously for the other aspects) may depend on the presence of the (e.g., locally limited) deposition material. For example, during particle beam-induced deposition of the (e.g., locally limited) deposition material, foreign material may be generated around (and / or on) the deposition material.

[0127] For example, the foreign material may comprise a halo present around the (e.g., locally limited) deposition material (as described herein analogously for the halo of the fiducial mark).

[0128] For example, the (e.g., locally limited) deposition material of the sixth aspect may comprise a repair material with which the object is repaired for lithography. During the particle beam-induced deposition of the repair material, a halo may, for example, have formed in the vicinity of the repair material (as described analogously herein for the halo around the marking). This halo of the repair material may represent the foreign material, which is reduced in volume using a method of the sixth aspect.

[0129] For example, the repair material of the sixth aspect may be deposited to repair an opaque defect of the object for lithography. For example, the repair material of the sixth aspect may also be deposited to repair any other defect of the object, such as the mask.

[0130] In one example, the particle beam mentioned herein may comprise an electron beam and / or an ion beam.

[0131] A seventh aspect relates to a computer program having instructions for performing a method according to any of the aspects described herein when the instructions are executed. For example, the computer program may comprise instructions that, when executed by a computer, can cause a method according to any of the aspects described herein to be performed by a computer and / or a device.

[0132] The features of the methods described herein can be incorporated correspondingly in the computer program. The features (as well as examples) of the methods (of the first to fifth aspects) mentioned herein can therefore also be applied or apply to the mentioned computer program in a corresponding manner.

[0133] A further aspect relates to a memory comprising the computer program of the sixth aspect.

[0134] An eighth aspect relates to an apparatus for processing an object for lithography, comprising: means for processing a mark deposited on the object with a particle beam and an etching gas for reducing the volume of the mark so that the mark remains on the object; a computer unit that causes the apparatus to perform a method according to any one of the aspects described herein based at least in part on an execution of a computer program of the fifth aspect.

[0135] In one example, the device comprises a memory that includes the computer program according to any of the aspects described herein. In this example, the computer unit may be capable of executing the computer program. The computer program may, for example, be installed on the computer unit and thus on the device (physical / material).

[0136] The computer unit may, for example, comprise a computer, a processing unit, a microprocessor, etc. The computer unit may, for example, be communicatively coupled to the components of the device such that a signal output from the computer unit may cause a change in a component of the device.

[0137] Upon execution, the computer program may, for example, issue an instruction that causes the device to reduce the volume of a marker (as described herein). Similarly, upon execution, the computer program may, for example, select an etching gas based on a deposition gas (as described herein).

[0138] For example, the device may be configured to receive a value from the user on the basis of which the volume of the marking is automatically reduced to or by a predetermined value.

[0139] In one example, it is also possible for the computer program to be stored elsewhere (e.g., in a cloud) and for the device to merely have means for receiving instructions resulting from the execution of the program elsewhere. In this case, the computer program can therefore be executed externally (e.g., on an external computer unit, on a server unit, etc.), with the instructions of the computer program being sent to the means for receiving the device. The means for receiving the instructions can, for example, be communicatively coupled to the computer unit of the device. The means for receiving can, for example, comprise a receiving unit configured to receive and / or process instructions via a wireless and / or wired connection.

[0140] The synergy between the computer program and the corresponding device can, for example, enable the process to run automatically or autonomously within the device. This minimizes intervention, for example, by an operator, thus minimizing both the costs and complexity of processing objects (for lithography).

[0141] It should be noted that, in principle, the features (and examples) of the methods mentioned herein can be applied or applied accordingly to the device mentioned. Likewise, the features (and examples) of the device mentioned herein can be applied or applied accordingly to the methods described herein.

[0142] A ninth aspect relates to an object for lithography which has been processed by a method according to one of the methods described herein.

[0143] A tenth aspect relates to a method for processing a semiconductor-based wafer, comprising: lithographically transferring a pattern associated with an object for lithography onto the wafer, wherein the object has been processed using a method of the aspects described herein. The lithographic transfer may comprise a lithography method for which the object is designed (e.g., EUV lithography, DUV lithography, i-line lithography, etc.). For example, the method of this aspect may comprise providing a beam source of electromagnetic radiation (e.g., EUV radiation, DUV radiation, i-line radiation, etc.). Furthermore, providing a developable resist layer on the wafer may be included. The lithographic transfer may further be based at least partially on the beam source and the provision of the developable resist layer. For example,The pattern is imaged onto the lacquer layer (in a transformed form) using the radiation from the beam source. 4. Short description of the characters

[0144] In the following detailed description, technical background information and embodiments of the invention are described with reference to the figures: Fig. Figure 1 shows, in the left part, a scanning electron image of a defect in a mask and reference marks used to correct a particle beam during processing of the defect. The right part illustrates the complete removal of a reference mark according to the state of the art. Fig. 2 schematically illustrates in a plan view an exemplary reference marking on an imaging structure which can be processed using a method according to the invention. Fig. 3 schematically illustrates in a side view the exemplary reference marking of the Fig. 2, which can be processed using a method according to the invention. Fig. 4 schematically illustrates in a side view a reduction of a volume of a reference mark according to a method according to the invention. Fig. 5 schematically illustrates in a plan view a grid field which is used to determine the position of the reference marking for a correction of the particle beam. Fig. 6 shows schematically in a plan view a foreign material which was generated during rasterization of the raster field and which can be processed according to a method according to the invention. Fig. 7 shows schematically in a side view the foreign material which was generated during rasterization of the raster field and which can be processed according to a method according to the invention. Fig. Figure 8 shows schematically in plan view a foreign material in the form of a halo which is present around the marking and which can be processed according to a method according to the invention. Fig. Figure 9 shows schematically in a side view the foreign material in the form of a halo that is present around the marking and can be processed according to a method according to the invention. Fig. 10 schematically shows an exemplary device according to the invention. 5. Detailed description of possible embodiments

[0145] Fig. 1 shows in the left part a scanning electron image of a defect D of a mask for lithography and reference marks (M1, M2, M3, M4) which are used to correct a particle beam during processing of the defect D. Fig. 1 illustrates a procedure according to the state of the art.

[0146] In Fig. 1, defect D corresponds to excess mask material. For example, material from an imaging structure is present in the area of ​​defect D, although this should not be the case according to the mask design. Defect D can therefore represent an opaque defect, as the defect area has a radiation-absorbing and / or phase-shifting effect. However, according to the mask design, the defect area should represent a clear area where targeted radiation absorption is not intended.

[0147] The defect D can, for example, be repaired using a known repair process. For example, the defect D can be repaired using an electron beam induced etching process, which etches and thus removes the excess material of the defect D. It should be noted that the defect D in the Fig. 1 represents only one example defect. Mask defects can also occur where a material from the mask is missing. For example, a material from an imaging structure of the mask may be missing. Such defects can, for example, represent clear defects, since the defect area does not have a radiation-absorbing and / or phase-shifting effect. However, according to the mask design, such a defect area should represent an opaque area in which targeted radiation absorption (or phase shifting) is intended. Clear defects can be repaired, for example, via electron beam-induced deposition in the defect area.

[0148] Typically, a repair mold, such as a pixel grid, can be used for defect processing. The repair mold can encompass the defect (e.g., its surface), with the electron beam being directed onto the pixels of the pixel grid, for example, to cause electron beam-induced deposition and / or etching there. For defect repair, the defect can be exposed to a suitable deposition gas and / or etching gas.

[0149] As described herein, particle beam-induced repair may require correcting the particle beam (e.g., the electron beam) using reference markers. For example, this may involve drift correction of the particle beam based on a position determination of the reference marker during the processing of the defect.

[0150] In the left part of the Fig. 1, four reference marks M1, M2, M3, M4 are arranged around the defect D. The reference marks M1, M2, M3, M4 may, for example, have been deposited on the mask before the repair of the defect D.

[0151] In the middle part of the Fig. 1 shows an enlarged view of a first reference mark M1 of the four reference marks M1, M2, M3, and M4. In this example, the first reference mark M1 is applied to an imaging structure L. Next to the imaging structure L is a clear area, where a cover layer C of the mask can be recognized in the scanning electron image by a different contrast.

[0152] As described herein, the reference markings M1, M2, M3, and M4 can cause an optical defect during a lithographic process of the mask. For example, exposing the mask may result in a deviation in the optical image in the area of ​​the reference markings M1, M2, M3, and M4. For example, the reference markings can lead to a violation of a specification in an aerial image of the mask.

[0153] In the prior art it is known to completely remove the reference markings (e.g. by etching and / or wet chemical cleaning).

[0154] In the right part of the Fig. Figure 1 illustrates, by way of example, the result of a complete removal of the first reference mark M1 according to the prior art. It can be seen that a (substantially) residue-free removal of the material of the first reference mark M1 has taken place. This can be seen from the fact that in the scanning electron image of the right-hand part of the image, Fig. 1 no material of the first reference mark M1 can be seen.

[0155] As described herein, with the increasingly smaller dimensions of the mask structures (e.g., the imaging structures) and / or the increasingly complex requirements of the mask materials, complete removal of the reference markings may not always be optimal. For example, as the imaging structures of the mask are reduced in size, the dimensions of the reference markings become increasingly closer to the dimensions of the imaging structures. However, a certain minimum dimension of the reference markings may be technically necessary to reliably determine the position of a reference marking for particle beam correction. As described herein, complete removal of the reference markings may therefore not always be suitable for all masks and / or reference markings.

[0156] However, if left unprocessed, the reference marks can lead to optical errors during lithography. For mask structure widths similar to the reference marks (e.g., structure widths below 60 nm), shadowing effects can occur, for example, during vertical exposure or transillumination, due to a (optical) lateral overlap of the structures. This can be the case, for example, with masks for UV lithography and / or DUV lithography.

[0157] With increasingly smaller structure widths (e.g. with structure widths below 60 nm), shadowing effects can also occur, for example, during inclined exposure due to the vertical extent of the reference markings. In this case, for example, the radiation incident on the mask and / or the radiation reflected by the mask can be shadowed. It should be mentioned in this regard that due to the ever smaller dimensions of the mask structures, the reference marking (due to the necessary minimum dimension) can be, for example, twice as high as the height of an imaging structure (e.g. an absorber of the mask). The reference markings can therefore cause comparatively strong shadowing effects during inclined exposure. For example, inclined exposure of the mask can take place in EUV lithography. The invention therefore also relates, for example, to EUV masks for EUV lithography.

[0158] Fig. Figure 2 schematically illustrates, in a top view, an exemplary reference mark on an imaging structure that can be processed using a method according to the invention. A reference mark M can be seen, which was deposited on an imaging structure L. In addition to the imaging structure L, two further exemplary imaging structures of the mask are sketched.

[0159] The reference mark M may have a reference mark width BM. The imaging structure L may have a feature width BL. As mentioned herein, the feature widths BL of imaging structures may become increasingly smaller, while minimum widths for the reference mark width BM may still be technically required. Such a situation is exemplified in Fig. 2. It can be seen that the reference marking width BM accounts for more than 50% of the structural width BL.

[0160] For example, in such a case, the reference mark width BM can be at least 20 nm, at least 30 nm, or at least 50 nm. For example, the reference mark width can be between 20 and 100 nm.

[0161] In such a case, the structure width BL of the imaging structure L on which the reference mark M is deposited can, for example, comprise a width of a maximum of 100 nm, a maximum of 70 nm, a maximum of 60 nm, a maximum of 40 nm and / or a maximum of 30 nm.

[0162] For example, the feature width BL can be in the range of 100 nm, while the reference mark width BM can be 50 nm. For example, the feature width BL can be in the range of 60 nm, while the reference mark width BM can be in the range between 30 and 40 nm.

[0163] Fig. 3 schematically illustrates in a side view the exemplary reference marking of the Fig. 2, which can be processed using a method according to the invention. A simplified side view is shown through a mask O. The illustration is primarily intended to schematically illustrate the dimensions of the imaging structure L and the reference marking M.

[0164] Thus, the imaging structure L can have a structure height HL. The structure height HL can be defined with respect to a cover layer of the mask O to which the imaging structure L is adjacent (as in Fig. 3 schematically illustrated). The structure height HL can, for example, be a height of maximum 100 nm, maximum 80 nm, maximum 50 nm, maximum 30 nm. Also in Fig. 3 the structural width BL of the reference marking is drawn (as already in Fig. 2 explained).

[0165] The reference mark M may, for example, have a substantially circular shape in a plan view (as in Fig. 2). In one example, the reference mark M may also have an elliptical shape in a plan view.

[0166] Furthermore, in Fig. 3, the reference mark M, which was deposited on the imaging structure L, can be seen. It can be seen in the side view that the reference mark can have a reference mark height HM. The reference mark height HM can be defined with respect to the plateau of the imaging structure on which the reference mark is deposited (as in Fig. 3). The reference mark height HM can, for example, be a maximum of 200 nm, a maximum of 100 nm, a maximum of 80 nm, a maximum of 70 nm, or a maximum of 40 nm. The reference mark height HM can, for example, also have a maximum height of 10 nm or a maximum of 30 nm. It should therefore be noted that the reference mark height HM can, for example, have a height between 10 nm and 200 nm.

[0167] The reference mark M may have a conical shape in cross-section in a side view, for example (as in Fig. 3). However, the reference marking M can also have a cylindrical shape, e.g. in cross-section in a side view, and / or an at least partially formed elliptical shape. A width of the reference marking at its tip can be smaller than the width of the reference marking at the plateau of the imaging structure L (as in Fig. 3). The width of a marking or the reference marking width BM (described herein) can refer to the maximum width of the reference marking. It is also conceivable that the reference marking width BM corresponds to a width of the reference marking, which can be seen in a top view of a scanning electron microscope image.

[0168] It should be noted that the reference mark M can also have a cylindrical and / or cuboid shape. Furthermore, any other shape is also conceivable.

[0169] As described herein, a complete removal of the reference mark M may not always be optimal if the structure dimensions (e.g., the structure width BL and / or the structure height HL) of the mask are in the order of magnitude of the dimensions of the reference mark M (e.g., in the order of magnitude of the reference mark width BM and / or the reference mark height).

[0170] Fig. 4 schematically illustrates, in a side view, a reduction of the volume of a reference marking M according to a method according to the invention. In the left-hand partial image, a first reference marking height HM1 of the reference marking can be seen. Furthermore, a first reference marking width BM1 of the reference marking can also be seen in the left-hand partial image. In general, the reference marking in the left-hand partial image can comprise a first volume. The first volume can, for example, correspond to the volume of the reference marking which it had after the repair of the defect in the mask (or directly after the deposition of the reference marking). Subsequently, the first volume can be reduced according to the method described herein. The result of the reduction of the volume is shown in the right-hand partial image of the Fig. 4 shown.

[0171] It can be seen, for example, that the height of the reference mark M has been reduced. After the volume reduction, the reference mark has a second reference mark height HM2, which is lower than the first reference mark height. An optical error during mask exposure can thus be avoided. For example, an optical error can be avoided in particular during an inclined exposure of the mask, since the height reduction can prevent shadowing effects during an inclined exposure.

[0172] It can also be seen that, for example, the width of the reference mark M has been reduced. After the volume reduction, the reference mark has a second reference mark width BM2, which is smaller than the first reference mark width. This prevents an optical error during mask exposure. For example, a lateral optical error, which can arise from an overly wide reference mark, can be avoided.

[0173] The volume reduction can be achieved, for example, via electron beam-induced etching with an etching gas. It is conceivable that the electron beam is directed statically at the reference mark. In another example, the electron beam can be directed dynamically at the reference mark in a temporal interaction (e.g., the electron beam can be directed at two or more locations on the reference mark M during the volume reduction).

[0174] Furthermore, it is also conceivable that reducing the volume merely comprises reducing the height of the reference marking. For example, reducing the volume may merely comprise reducing the width of the reference marking. In another example, reducing the volume may comprise a first step for reducing the height and a second step for reducing the width of the reference marking.

[0175] An exemplary workflow of the method according to the invention will be explained once again below. First, the method may comprise detecting a defect on a mask. Subsequently, one or more reference marks may be deposited, which can be used to repair the defect (e.g., for correcting an electron beam). The defect may then be repaired. This may comprise electron beam-induced etching and / or electron beam-induced deposition in the defect region. Subsequently, the volume of the reference marks may be reduced, as described herein.

[0176] As described herein, the method need not be limited to reducing the volume of fiducials, but may also include machining foreign material in the vicinity of a fiducial.

[0177] Fig. 5 schematically illustrates a plan view of a grid field S which can be used to determine the position of the reference marking M for correcting the particle beam. It can be seen that the grid field S is placed around a reference marking M. To determine the position of the reference marking M, the entire grid field S can be scanned. Via the grid field S, a position drift of the reference marking M within the grid field S can be addressed, which can be induced when processing the mask with an electron beam. However, in order to address the position drift of the reference marking M, a minimum size of the grid field S may be required. If the grid field is too small, for example, the risk that the electron beam will not hit the reference marking M due to drift may increase. Determining the position of the reference marking M (and the associated drift correction) would therefore not be possible.

[0178] With the ever-smaller dimensions of mask structures (e.g. ever-smaller structure widths BL of the imaging structures L), the grid field S can therefore extend beyond the width of a mask structure. This is exemplified in Fig. 5. The grid field S can, for example, comprise a first grid field area S1. The first grid field area S1 comprises Fig. 5 a region in which a material of the imaging structure L is located. The grid field S can further comprise, for example, a second grid field region S2. The second grid field region S2 projects beyond the imaging structure L. The second grid field region S2 can be Fig. 5 comprises a region in which no material of the imaging structure L is present. For example, the second grid area S2 can comprise a region that covers a cover layer of the mask. The second grid area S2 can thus correspond to a clear area of ​​the mask in which no radiation absorption should occur according to the mask design. As mentioned, however, a deposition gas may be present in the grid area S. When scanning the grid area S with an electron beam, (unwanted) electron beam-induced deposition from the deposition gas can thus occur in the grid area S.

[0179] As described herein, this can be the case if the position of the correction marks is determined as part of an electron beam-induced deposition. For example, a defect in the mask can be repaired via electron beam-induced deposition using at least one deposition gas. To correct the drift of the electron beam, the grid field S of a reference mark M is usually scanned several times. The deposition gas for repairing the defect can, for example, also reach the location of the grid field (e.g., via diffusion). This can also occur if the deposition gas is only provided locally above the defect. For example, the reference marks M are placed as close as possible to the defect, so that the deposition gas usually has a comparatively short diffusion path from the defect to the reference marks.It may also happen that the deposition gas cannot be technically confined to the defect, meaning that the reference marks may be exposed to the deposition gas. This means that foreign material may be deposited in the grid field.

[0180] Fig. 6 schematically shows a top view of a foreign material F that was generated during scanning of the grid field S and that can be processed according to a method according to the invention. It can be seen that foreign material is deposited throughout the entire grid field S. Furthermore, it can be seen that foreign material F is present in the first grid field region S1 as well as in the second grid field region S2. The foreign material F was deposited on the imaging structure L in the first grid field region S1 and next to the imaging structure L in the second grid field region S2 (e.g., on the cover layer of the mask).

[0181] Fig. Figure 7 shows schematically in a side view the foreign material F of the Fig. 6. The side view shows that the foreign material F is deposited on the reference mark M. Furthermore, the foreign material can be present on the plateau of the imaging structure L and on its side walls. It can also be seen that the foreign material F is located next to the imaging structure L (e.g. on the cover layer of the mask). In particular, the foreign material F next to the imaging structure L (in the second grid field region S2) can be problematic for lithography with the mask. According to the mask design, this region represents a clear area in which no radiation absorption (and / or no phase shift) should occur. The foreign material F in this area can therefore lead to an optical defect.

[0182] However, it is also conceivable that the foreign material F causes an optical defect on the imaging structure L. For example, the reason for this may be that this foreign material F extends to the edge (and / or side walls) of the imaging structure (as in Fig. 7). The foreign material F can therefore, for example, exert a lateral influence on the imaging structure and lead to a lateral optical error.

[0183] According to the invention, the foreign material F in the grid field S can therefore be reduced in volume and / or completely removed.

[0184] In another example, it is also conceivable that a foreign material F generated by the grid field is removed only next to the imaging structure (e.g. only in the second grid field area S2).

[0185] In a further example, it is also conceivable that in a first step, only the foreign material F adjacent to the imaging structure L is removed (e.g., foreign material F in the second raster field region S2). In a second step, the foreign material F can be removed on the imaging structure L and / or at the reference marking M (e.g., foreign material F in the first raster field region S1).

[0186] In one example of a method, only a foreign material present in the grid field S can be reduced in volume and / or completely removed.

[0187] In another example of a method, the reference mark M and the foreign material F in the raster field S may be reduced in volume such that the reference mark M and the foreign material F remain on the mask.

[0188] In another example of a method, the reference mark M may be reduced in volume such that the reference mark remains, wherein the foreign material F in the grid field S is completely removed from the mask (substantially residue-free).

[0189] Fig. Figure 8 schematically shows a plan view of a foreign material in the form of a halo H, which is present around the reference mark M and can be processed according to a method according to the invention. As described herein, the halo H can have been generated during the electron beam-induced deposition of the reference mark M. For example, electrons can concentrate locally around the reference mark (e.g., due to scattered electrons). Thus, an electron beam-induced deposition reaction can also occur around the mark, which can lead to the formation of the halo H.

[0190] Fig. Figure 9 shows schematically the halo H of the Fig. 8 in a side view. It can be seen that the halo H can have a lower height than the reference mark M. It should be noted that the halo H does not necessarily have to have a homogeneous layer height (as in Fig. 9). For example, the layer height of the halo H can also fluctuate or be irregular. Furthermore, it can be seen that the halo can be located in the immediate vicinity of the reference marking M. According to the invention, the halo H can be reduced in volume and / or removed.

[0191] In one example of a method, only the halo H may be reduced in volume (with the halo H otherwise remaining) and / or removed completely.

[0192] In another example of a method, the fiducial mark M may be reduced in volume such that the fiducial mark remains, with the halo H being completely removed from the mask (essentially residue-free).

[0193] In another example of a method, the fiducial mark M may be reduced in volume such that the fiducial mark remains, wherein the halo H is completely removed from the mask (substantially residue-free), and the foreign material F in the grid field S is reduced in volume and / or completely removed.

[0194] In another example of a method, the reference mark M and the halo H may be reduced in volume such that the reference mark M and the halo H remain on the mask.

[0195] For the sake of completeness, it should be noted that the methods described herein are not necessarily limited to the stated feature widths and / or feature heights. Thus, the method can also be applied to feature widths greater than 100 nm.

[0196] Fig. 10 schematically shows a device 100 according to the invention. The device 100 may comprise a mask repair device adapted according to the invention. The device 100 may, for example, be designed so that electron beam-induced etching and / or deposition can be performed on a mask O. The device 100 may, for example, comprise an electron source 101. The electron source 101 may emit an electron beam 102 with which electron beam-induced etching or deposition can be performed on a mask O. The means for deflecting, focusing and / or adapting the electron beam are shown in the Fig. 10 is not shown. The device 100 can be configured so that the electron beam can impinge on a defined impact point 103 on the mask O.

[0197] Furthermore, the device can provide one or more deposition gases DG on the object O. These can be supplied to the object via a corresponding gas line 104. Likewise, the device can provide one or more etching gases EG on the object. These can be supplied to the object O, for example, via a corresponding gas line 105. Furthermore, additive gases can be supplied to the one or more deposition gases DG and / or the one or more etching gases EG. For the sake of simplicity, the containers for the one or more additive gases are shown in Fig. 10 not listed.

[0198] The device 100 may further comprise a user interface via which, for example, an operator may operate the device 100 and / or read data.

[0199] Furthermore, the device may include a computer unit 106. The computer unit 106 may cause the device 100 to perform one of the methods described herein, based at least in part on an execution of a corresponding computer program.

[0200] Shown in Fig.10 also includes a database 107, which may be included, for example, in the device 100. As described herein, the etching gas for reducing the volume of the reference mark M and / or the foreign material may be based on a deposition gas with which the reference mark and / or the foreign material was deposited. A deposition gas may, for example, be assigned to an etching gas. Analogously, the etching gas for processing the reference mark and / or the foreign material may be based on the material composition of the reference mark and / or the foreign material. The database may, for example, comprise a look-up table, as described herein. In the database, a corresponding etching gas may, for example, be assigned to the deposition gas. If an etching gas is to be selected within the scope of the method, this may be based on which deposition gas was previously used to generate the reference mark and / or the foreign material.For example, it can be stored in the database 107 that when using a first deposition gas DG1, a first etching gas EG1 is to be used to reduce the volume. Accordingly, it can be stored that when using a second deposition gas DG2, a different second etching gas EG2 is to be used to reduce the volume, etc. For example, the database 107 can be communicatively coupled to the computer unit 106. Furthermore, the computer unit 106 can also include the database 107.

[0201] The reference mark can, for example, have been created using a focused electron beam-induced deposition with a deposition gas DG. As mentioned, the repair of a defect can also include an electron beam-induced deposition with a deposition gas DG, which can accordingly result in the deposition of the foreign material F (in the grid field S). For both types of deposition, one of the following deposition gases DG (or gas mixture) can be used: Cr(CO)6, Cr(CO)6 and NO2, TEOS, TEOS and NO2, Mo(CO)6, Mo(CO)6 and NO2. The substances of these deposition gases or gas mixtures can be present in the corresponding deposition material. In one example, the database can store the deposition gas DG used to deposit the reference mark or the deposition gas DG used for the repair. Based on the database, the appropriate etching gas can then be selected to reduce the volume.

[0202] A chromium-based reference mark M or a chromium-based foreign material F can be removed or reduced in volume (e.g., reduced in height) using the precursors NOCl and H2O, for example. Chromium-based reference marks M or chromium-based foreign material F can also be processed or reduced in volume (e.g., reduced in height) using XeF2 and H2O, or XeF2 and H2O and NO2, for example. The process with NOCl and H2O can exhibit high selectivity in the removal of the deposited material compared to damage to the mask material, e.g., compared to molybdenum silicide (e.g., MoSi and / or MoSi2), OMOG (Opaque MoSi on Glass), CPL, and EUV mask materials.

[0203] The mentioned methods are also suitable for removing and / or reducing the height of chromium-based foreign material at a repair site (a defect) or in its vicinity. For example, as described herein (for the sixth aspect of the invention), foreign material in the vicinity of a repair material can be processed according to the invention. For example, a chromium-based halo (as foreign material) can occur in the vicinity of a repair site (or a repair material), which can be processed according to the methods described herein.

[0204] A reference mark and / or a foreign material containing TEOS and / or silicon oxide can be removed or reduced in volume using the precursors XeF2 or XeF2 and H2O, for example.

[0205] The mentioned methods are also suitable for removing and / or reducing the height of TEOS-based or silicon oxide-based foreign material at a repair site (of a defect) or in its vicinity. For example, as described herein (for the sixth aspect of the invention), foreign material in the vicinity of a repair material can be processed according to the invention. For example, a halo comprising TEOS and / or silicon oxide can also occur in the vicinity of a repair site (or a repair material), wherein the halo can be processed according to the methods described herein.

[0206] A reference mark and / or a foreign material containing molybdenum can be removed or reduced in volume using, for example, the precursors XeF2 and H2O or H2O. The process with H2O can exhibit high selectivity in removing the deposited material compared to damaging the mask material, e.g., molybdenum silicide (e.g., MoSi and / or MoSi2), OMOG (Opaque MoSi on Glass), CPL, and EUV mask materials.

[0207] The mentioned methods are also suitable for removing and / or reducing the height of molybdenum-based deposition material at a repair site (of a defect) or in its vicinity. For example, as described herein (for the sixth aspect of the invention), foreign material in the vicinity of a repair material can be processed according to the invention. Thus, a halo comprising molybdenum can also occur in the vicinity of a repair site (or of a repair material), and the halo can be processed according to the methods described herein.

[0208] The invention may further enable an automated, software-based workflow for processing a reference mark and / or foreign material.

[0209] As mentioned, the method may initially comprise a repair of a defect in which the position of the reference marks is used, for example, for drift correction.

[0210] After the repair process is completed, the quality of the repair can be evaluated. This can be done, for example, by an operator of the device 100. For example, the repair location can be displayed to the operator on the user interface. Furthermore, it is also conceivable for the quality of the repair to be assessed using an internal and / or external evaluation program. The evaluation program can, for example, be installed on the device 100. Furthermore, it is also conceivable for repair data to be transmitted to the external evaluation program for quality control.

[0211] If the repair or its quality has been assessed as successful, the operator can, if necessary, start automatic processing of the reference markings and / or the foreign material according to one of the methods described herein. To do so, the operator can, for example, make a corresponding input on the user interface of the device 100. It is also conceivable that the internal and / or external evaluation program (if the repair is successful) automatically starts processing the reference markings and / or the foreign material according to one of the methods described herein. In both cases, one of the methods described herein can be prepared and started automatically. For the automated execution of the methods described herein, reference can be made, for example, to the database 107, from which it can be seen which etching gas (with regard to the deposition gas used) is to be used.

Claims

[1] A method for processing an object for lithography comprising: Processing a mark deposited on the object using a particle beam and an etching gas to reduce the volume of the mark while leaving the mark on the object. [2] The method according to claim 1, wherein the volume is reduced such that the processed mark does not cause a deviation from a predetermined specification during lithography. [3] A method according to any one of claims 1 or 2, wherein the volume of the marking is reduced by at least 10%, at least 30%, at least 50%, or at least 90%. [4] Method according to one of claims 1-3, wherein the marking is deposited on an imaging structure of the object. [5] The method of claim 4, wherein the volume is reduced such that a height of the processed mark relative to the imaging structure is less than a height of the imaging structure relative to the object. [6] Method according to claim 5, wherein the processing of the marking is carried out such that the height of the processed marking is at least 10%, at least 30%, at least 50%, or at least 95% less than the height of the imaging structure. [7] Method according to one of claims 4-6, wherein the imaging structure comprises a lateral dimension of at most 100 nm, at most 80 nm, at most 60 nm, or at most 40 nm. [8] Method according to one of claims 4-7, wherein a lateral dimension of the marking before processing corresponds to at least 50% of a lateral dimension of the imaging structure. [9] A method according to any one of claims 1-8, further comprising: Processing a foreign material of the object in a marking environment with the particle beam and the etching gas to reduce the volume of the foreign material. [10] The method of claim 9, wherein the foreign material comprises a deposition material produced during deposition of the marker. [11] A method according to any one of claims 9 or 10, wherein the foreign material comprises a foreign material around the marker. [12] Method according to one of claims 9-11, wherein the foreign material comprises a deposition material which was generated during rasterization of the marking within a raster field, preferably during a repair of the object. [13] Method according to one of claims 9-12, wherein the foreign material is present adjacent to an imaging structure of the object and / or on an imaging structure of the object. [14] The method of any one of claims 1-13, further comprising: Selecting the etching gas, wherein the etching gas is selected based at least in part on a provided deposition gas with which the mark and / or a foreign material in an environment of the mark was deposited on the object. [15] The method of claim 14, wherein the etching gas comprises a halogen. [16] The method of claim 15, wherein if the deposition gas comprises chromium, the halogen comprises chlorine. [17] The method of claim 16, wherein the etching gas further comprises nitrogen and oxygen. [18] A method according to claim 16 or 17, wherein the etching gas comprises chlorine, nitrogen and oxygen in one compound, preferably nitrosyl chloride, NOCl. [19] The method of claim 15, wherein, if the deposition gas comprises chromium and / or if the deposition gas comprises silicon and oxygen and / or if the deposition gas comprises molybdenum, the halogen comprises fluorine. [20] The method of claim 19, wherein the etching gas further comprises xenon. [21] A method according to claim 20, wherein the etching gas comprises fluorine and xenon in a compound, preferably xenon difluoride, XeF2. [22] The method of claim 14, wherein if the deposition gas comprises molybdenum, the etching gas comprises oxygen. [23] The method of claim 22, wherein the etching gas comprises water. [24] The method according to any one of claims 1-23, wherein the processing of the marking and / or the foreign material is further carried out with an additive gas comprising oxygen. [25] The method of claim 24, wherein the additive gas comprises water and / or nitrogen dioxide. [26] A computer program comprising instructions for performing a method according to any one of claims 1-25 when executed. [27] Apparatus for processing an object for lithography comprising: means for processing a mark deposited on the object with a particle beam and an etching gas to reduce the volume of the mark so that the mark remains on the object; a computer unit that causes the device to perform a method according to any one of claims 1-25 based at least in part on an execution of a computer program according to claim 26.

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