Method and apparatus for mask repair

Abstract

To provide a method, an apparatus and a computer program for processing an object for lithography.SOLUTION: A method for processing an object for lithography includes (a) providing a first gas, (b) providing a second gas including a second molecule capable of performing a reversal oscillation, and (c) providing a particle beam to a working area of the object to produce deposited material in the working area based at least in part on the first gas and the second gas. The second gas is supplied at a gas flow of less than 5sccm, preferably less than 2sccm, more preferably less than 0. 5sccm.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method, an apparatus and a computer program for processing objects for lithography. More particularly, the invention relates to a method for generating a deposition material, a method for passivating a surface material, a corresponding apparatus, a method for lithographic processing of a wafer, and a computer program for carrying out these methods. [Background technology]

[0002] In the semiconductor industry, increasingly smaller structures are being formed on wafers to ensure increased integration. Methods used here to form the structures include lithographic methods that image these structures onto the wafer. Lithographic methods can include, for example, photolithography, ultraviolet (UV) lithography, DUV lithography (i.e., lithography in the deep ultraviolet spectral region), EUV lithography (i.e., lithography in the extreme ultraviolet spectral region), X-ray lithography, nanoimprint lithography, etc. Here, a mask is typically used as a lithographic object (e.g., a photomask, exposure mask, reticle, stamp in the case of nanoimprint lithography, etc.) that contains a pattern, for example, to image the desired structures onto the wafer.

[0003] As integration density increases, the demands on mask manufacturing also increase (e.g., as a result of the concomitant reduction in feature dimensions on the mask or as a result of higher material requirements in lithography). As a result, the mask manufacturing process becomes increasingly complex, time-consuming, and costly, yet it is not always possible to avoid mask errors (e.g., defects, missing material, poorly formed material, etc.). Therefore, mask errors are typically repaired or repaired in a separate processing operation.

[0004] For example, mask errors can be repaired by particle beam-based or particle beam-induced deposition processes, which typically involve electron beam-induced or ion beam-induced deposition of material onto localized sites in the region of the mask error. Here, a deposition gas can be used as a precursor gas, which is crucial in defining the composition of the deposited material (i.e., the repair material).

[0005] However, the (repaired) mask may be subjected to high physical and even chemical stresses during lithography and downstream processes (e.g., during mask exposure, mask cleaning operations, etc.), and therefore the strength, durability and stability of the repair material against these aggressive influences are of great importance.

[0006] For example, it is known that additive gases can be added to the deposition gas in a masking operation, which can further affect the properties of the repair material.

[0007] Furthermore, U.S. Patent Application Publication No. 2020 / 103751 discloses the deposition of a material using a first particle beam and at least one deposition gas. The deposition gas can include a metal carbonyl, and the metal carbonyl can include chromium hexacarbonyl. The deposition gas is typically used to replace missing portions of pattern elements of a photomask. Furthermore, at least one additive gas including an oxidizer can be added to the deposition gas, where the oxidizer can include, for example, oxygen, water vapor, or nitrogen dioxide. Furthermore, the additive gas can include a gas with a reducing effect. The gas with a reducing effect can include hydrogen, ammonia, or methane. An EUV mask is also disclosed. One possible material for the buffer layer of the EUV mask is chromium nitride. The buffer layer is deposited on a capping layer, which protects the multilayer structure of the EUV mask. One possible material for the absorber layer of the EUV mask is chromium. One possible material for the anti-reflective layer of the EUV mask is tantalum oxynitride. Structuring in such a manner is also disclosed that a structure of absorbing pattern elements formed from a buffer layer, an absorbing layer and an anti-reflective layer is produced.

[0008] However, due to the technical complexity of particle beam-based deposition processes, the properties of the repair material are not always optimal.

[0009] The problem solved by the present invention is therefore to specify a method and an apparatus for optimizing the processing of objects for lithography. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent Application Publication No. 2020 / 103751 Summary of the Invention

[0011] This objective is achieved, at least in part, by various aspects of the present invention.

[0012] A first aspect of the present invention relates to a method for processing an object for lithography. The method includes supplying a first gas and a second gas containing second molecules capable of performing inversion oscillations. The method further includes supplying a particle beam to a working region of the object to generate a deposition material at the working region based at least in part on the first gas and the second gas. The second gas can be supplied at a gas flow rate of less than 5 sccm, preferably less than 2 sccm, and more preferably less than 0.5 sccm.

[0013] The concept of the present invention is based primarily on the fact that molecular inversion oscillations can have a decisive effect on the generation of deposition materials using particle beams. Molecules capable of inversion oscillations are also referred to herein as inverted molecules. The present invention takes advantage of the fact that inverted molecules can have an average dipole moment μ that is zero when averaged over time. Due to this inversion oscillation, the integral of the dipole moment μ of an inverted molecule is essentially zero for a specific time interval (e.g., the integral of the dipole moment μ can be zero for a time interval including one or more oscillation periods, or can mathematically approach zero as the selected time interval tends to infinity). Therefore, as a result of this mechanism, inverted molecules can have a lower dipole character than molecules that cannot perform inversion oscillations. It has now been discovered that this lower dipole character of inverted molecules can have a decisive effect on the interaction of inverted molecules with material surfaces. When generating deposition materials, complex interactions can occur between a first gas, a second gas, and a particle beam, during which deposition materials are generated on material surfaces within the working area of ​​a lithographic object. For example, the generation of deposition materials can involve particle-beam-induced deposition (e.g., by a beam of non-zero mass particles). Therefore, the properties of the working area and the object's environment, including the properties of these gases, are crucial to the generation of deposition materials. These (local) properties of the gases can include the (local) gas concentration of the gas in the working area or the object's environment. This (local) gas concentration can include, for example, the concentrations of the first gas, the second gas, and / or the gaseous reaction products of the generation of the deposition material. Furthermore, this (local) gas concentration can include the concentrations of various molecules (e.g., the concentration of the second molecule, the concentration of another molecule contained in the first gas, the second gas, and / or the reaction products). Furthermore, the (local) gas concentrations described herein can include any gas parameters associated with the first gas, the second gas, and / or the gaseous reaction products (e.g., gas pressure, gas flow rate, etc.).

[0014] When producing a deposition material, a defined (local) gas concentration is typically required over a specific period of time to allow the reaction to produce the deposition material to proceed in a controlled manner, thereby establishing defined physical and / or chemical properties of the deposition material. Therefore, it can be useful to control this defined (local) gas concentration. This defined (local) gas concentration can be of a static or dynamic type. Here, a static (local) gas concentration can mean that an essentially constant (local) gas concentration (e.g., a constant ratio of the concentrations of a first gas, a second gas, and / or a reaction product) can exist or that such a (local) gas concentration is established. Here, a dynamic (local) gas concentration can mean that a dynamic process of (local) gas concentration (e.g., controlled outward transport of a reaction product, controlled switching between two static (local) gas concentrations, alternating (local) gas concentrations, etc.) is performed in a controlled manner.

[0015] However, due to chemical and / or physical interactions during the production of the deposition material, this defined (local) gas concentration may vary to a technically undesirable extent, for example, this may include (local) depletion of the second gas (and / or the first gas) in the working area in such a way that the process of producing the deposition material is undesirably affected.

[0016] The present inventors have now realized that in the case of particle beam-based production of deposition materials, the use of inverted molecules, which may have the low dipole moment described herein, can be highly advantageous. This is because the low dipole moment of inverted molecules can affect the absorption probability of the inverted molecules relative to the material in the working region. As a result of the low dipole moment, for example, the absorption probability of second molecules of a second gas (i.e., inverted molecules) can be more favorable than the material in the working region. This favorable absorption probability cannot be achieved using molecules that cannot perform inverted oscillations, for example. These molecules that cannot perform inverted oscillations are referred to herein as non-inverted molecules. Non-inverted molecules can have, for example, a non-zero permanent dipole moment. Non-inverted molecules can also include, for example, polar molecules (e.g., NO, NO, HO) with a non-zero dipole moment. Specifically, due to their low dipole moment, inverted molecules can have a lower absorption probability relative to the material (in the working region) than non-inverted molecules. Therefore, inverted molecules may be absorbed less by the material (within the working region) than non-inverted molecules. Therefore, when using inverted molecules in the second gas, it is possible to minimize depletion of the second gas within the working region. Thus, for example, the concentration of the second gas within the working region can be higher or maintained longer than if non-inverted molecules were used (exclusively) in the second gas. Therefore, the need to technically readjust the concentration of the second gas or to consider a decrease in the concentration of the second gas due to a high absorption probability can be significantly reduced.

[0017] The use of inverted molecules as second molecules can therefore make it possible to optimize the ratio of defined (local) gas concentrations during the production of the deposited material, and thus optimize the production of the deposited material. Furthermore, this use can optimize the establishment of defined physical and / or chemical properties of the produced deposited material, since these properties can depend to a crucial extent on the (local) gas concentrations during the production of the deposited material.

[0018] The ability of the second molecule to undergo inversion oscillation can be defined as the ability of the second molecule to undergo inversion oscillation at a specific temperature, including temperatures above zero Kelvin. For example, this can be defined as the ability of the second molecule of the second gas to undergo inversion oscillation at a temperature prevailing during the production of the deposition material. For example, the specific temperature at which the second molecule can undergo inversion oscillation can include typical room temperature (e.g., 20°C or 25°C). This specific temperature can also be within a temperature range between -60°C and 600°C, which may prevail during the production of the deposition material.

[0019] Furthermore, the inventors of the present invention have discovered a parameter space for the gas flow rate of the second gas (including inverted molecules) that is favorable for producing deposited materials through a series of tests. The second gas can be supplied at a gas flow rate of less than 5 sccm (sccm means standard cubic centimeters per minute). Furthermore, the second gas can be supplied at a gas flow rate of preferably less than 2 sccm, more preferably less than 0.5 sccm. In another example, the second gas can be supplied at a gas flow rate of less than 0.3 sccm. Within these ranges, it is possible to deposit materials with a certain stability against external influences (e.g., irradiation with UV, DUV, or EUV radiation under reduced pressure, use in a reactive gas atmosphere, cleaning cycles of EUV or DUV masks, etc.).

[0020] The interaction of the gas flow rates described herein and the interactions of the inverted molecules with the material (in the working region) elucidated herein can produce particularly favorable properties of the deposited material. One property is the material's composition. For example, Auger electron spectroscopy and / or X-ray photoelectron spectroscopy (abbreviated as XPS) can enable the determination of the chemical composition of the deposited material.

[0021] The inventors of the present invention have now realized that an optimum for the chemical composition of the deposited material can be found within the described ranges. Alternatively, advantageous properties may relate to the durability of the deposited material. For example, the deposited material can essentially withstand a certain number of cleaning cycles (e.g., of an EUV or DUV mask), such as at least 10, at least 50, or at least 100, or at least 1000 cleaning cycles (e.g., after this number of cleaning cycles, transparent defects repaired by the deposited material essentially cannot be printed).

[0022] However, in principle, examples are also conceivable that include supplying a second gas at a different gas flow rate, e.g., <0.01 sccm or >5 sccm. Particularly advantageous deposition materials can then be produced, for example, alternatively or additionally, by other embodiments described herein. Correspondingly, a method for depositing chromium nitride or a chromium nitride-containing material can be considered an embodiment of the present invention, in which a particle beam and first and second gases described in general terms herein are used (without being limited to a specific interval of gas flow rates). The first gas can be a chromium-containing gas. The second gas can include a second molecule capable of performing inversion oscillation.

[0023] Regardless, it should be clarified that the expression sccm relates to standard cubic centimeters per minute, a unit known to those skilled in the art. This indicates the flow rate in units of volume per unit time, and these volume units correspond to the volume units under standard conditions (temperature T=0°C, pressure p=1013.25 hPa). Standard densities, known to those skilled in the art, can be used to calculate, for example, the mass flow rate (e.g., kg / min) required for a particular gas flow rate at different pressures or temperatures. For example, the standard density of air is, for example, approximately 1.29 mg / cm. 3 , the standard density of NH3 is, for example, about 0.77 mg / cm 3 is.

[0024] The method can further include locally supplying the first gas and / or the second gas to a working region of the object. Thus, the first and / or second gas can be locally directed onto the working region (e.g., via a gas line, nozzle, etc.) to generate the deposition material. The method can further include locally generating the deposition material within the working region in a manner such that the generation of the deposition material is essentially limited to the working region of the lithographic object. The method can further include using a localized particle beam, e.g., a focused particle beam, where the generation includes local generation essentially limited to the region of the localized particle beam.

[0025] The lithographic objects described herein can include lithography masks. The lithography masks can be designed for use in lithography (e.g., in exposing semiconductor-based wafers) for manufacturing semiconductor-based chips. The lithography masks can also include any type of lithography mask capable of imaging an image based on a source of electromagnetic radiation (of any wavelength) and a pattern contained in the lithography mask. The image can include a variation of the pattern. The lithography masks can include, for example, EUV masks, DUV masks, X-ray lithography masks, binary masks, phase-shift masks, etc. Furthermore, the lithography masks can also include nanoimprint lithography stamps or lithography masks capable of imaging a pattern based on a particle source.

[0026] A working area as specified herein may include a localized area of ​​a lithographic object. However, it is also contemplated that the working area may include the entire lithographic object. A working area may further include any area dimension, shape, and / or geometry. For example, a working area may be within a range of magnitude related to a (critical) dimension of the object. For example, the (critical) dimension may include a specific dimension CD of a pattern element of the object. A working area may, for example, cover an area A based on the specific dimension CD (e.g., A may be proportional to the specific dimension CD, e.g., A=CD 2 Additionally, materials can be generated within a work area in a manner such that the generated material does not necessarily cover the entire area of ​​the work area, but is generated only in a small area of ​​the work area. Alternatively, materials can be generated within a work area in a manner such that the generated material covers the entire area of ​​the work area.

[0027] In one example, the method includes supplying the second gas at a gas flow rate of less than 0.01 sccm, preferably less than 0.05 sccm, and more preferably less than 0.1 sccm, these minimum amounts allowing for particularly advantageous stability of the deposited material.

[0028] The method can further include supplying the second gas at a gas flow rate between 0.1 sccm and 0.5 sccm, more preferably between 0.2 sccm and 0.3 sccm, and most preferably between 0.24 sccm and 0.26 sccm, within which it has been found that particularly advantageous stability of the deposited material can be achieved.

[0029] In one example, the method includes providing a particle beam with a particle beam dwell time of at least 0.1 microseconds, preferably at least 0.3 microseconds, and most preferably at least 0.5 microseconds. In one example, the method includes providing a particle beam with a particle beam dwell time of at least 1 microsecond, preferably at least 3 microseconds, and most preferably at least 5 microseconds. In another example, the process includes providing a particle beam with a particle beam dwell time of 0.1 microseconds to 10 microseconds, preferably 0.3 microseconds to 7 microseconds, and most preferably 0.4 microseconds to 6 microseconds. Multiple cycles are performed at this dwell time to deposit material to the desired height.

[0030] In one example, the method includes supplying the first gas and / or the second gas in such a way that the deposition material at least partially forms in the gas phase without the influence of the particle beam. The use of inverted molecules in the second gas in the present invention can ensure a higher concentration of the second gas in the environment of the working region of the object compared to the use of non-inverted molecules (as described herein). This condition can therefore enable a reaction between the first gas and the second gas even without the influence of the particle beam. Therefore, it is possible to significantly increase the probability of the deposition material forming on the surface of the working material, even in the gas phase. This can, for example, create favorable boundary conditions for the reaction during particle beam-induced generation of the deposition material. Therefore, upon activation of the particle beam, the generation of the deposition material in the form of a deposit of the deposition material in the working region can occur in a manner favorable for making its generation more efficient. The above-mentioned condition can be further promoted by controlled adjustment of the gas parameters of the first gas and / or the second gas (e.g., by the corresponding gas flow rates, gas concentrations, gas pressures, etc. of the first and / or second gases).

[0031] In one example, the method includes supplying a second gas so that reaction products of the material formation are removed from the working region. This can be achieved, for example, by using inverted molecules as the second molecules. As described herein, a higher concentration of the second gas in the environment of the working region of the object can be ensured compared to using non-inverted molecules. The resulting higher supply of second molecules in the gas phase can increase the probability that reaction products are removed from the surface of the working region.

[0032] In one example, the first gas can be considered the primary deposition gas for producing the deposition material. This first gas can be designed to have a significant effect on the metal content of the produced deposition material. In one example, the first gas of this method includes a first molecule that includes a metal atom. Thus, in this example, the first gas (as the primary deposition gas) can affect the process of producing the deposition material in such a way that the first gas determines whether the deposition material contains a particular metal. Furthermore, the first gas (as the primary deposition gas) can determine whether the deposition material contains a particular complex metal.

[0033] In this context, the second gas described herein can be considered an additive gas relative to the primary deposition gas (i.e., the first gas). The additive gas can further tailor the chemical composition and physical properties (e.g., the stoichiometry, hardness, chemical stability, etc.) of the deposited material. For example, by using the second gas as an additive gas, components of the second gas can be incorporated into the deposited material. Furthermore, the use of the second gas can reduce the molar fraction within the deposited material (compared to exclusively using the first gas to generate the deposited material using a particle beam). The inventors of the present invention have realized that additive gases containing inverted molecules are particularly advantageous over additive gases containing non-inverted molecules due to the relationships described herein.

[0034] In one example, the method includes at least partially simultaneously supplying a first gas and a second gas. For example, the first gas and the second gas can be introduced simultaneously into the environment of the working area or the environment of the object, for example, during the generation of the deposition material. This can further include (at least partially) having a first gas flow rate of the first gas and a second gas flow rate of the second gas during the generation in a manner that ensures that both the first gas and the second gas are present in the environment of the working area / object. Here, for example, the first gas flow rate and the second gas flow rate can be essentially identical. Alternatively, in other examples, the gas flow rates can be different. Simultaneously supplying the first gas and the second gas can further include varying the first gas flow rate and the second gas flow rate (during the generation of the deposition material).

[0035] In one example, the method includes supplying a first gas and a second gas at least partially separated in time. For example, to generate a deposition material, it may be necessary to supply or introduce only one of these two gases into the environment of the work area / object during one step of the generation process. For example, to begin generating the deposition material, it may be necessary to initially introduce only the first gas (or the second gas) into the environment of the work area / object. Subsequently, at a later point in time, the second gas (or the first gas) can be fed or supplied. Furthermore, it is conceivable that during generation, the (exclusive) supply / introduction of the first gas (without the second gas) and the (exclusive) supply / introduction of the second gas (without the first gas) may be alternated in stages. Furthermore, the end of the process of generating a deposition material may include the exclusive supply / introduction of one of these two gases. For example, it is conceivable that the end of the generation process is defined by the exclusive supply / introduction of the second gas.

[0036] In another example, the first gas of the method includes a first molecule that includes a carbonyl compound. This can also be interpreted as the first molecule of the first gas having a carbonyl group. For example, the first molecule can include a carbon monoxide ligand.

[0037] In one example, the first molecule of this method includes a metal carbonyl. For example, the metal carbonyl can include a complex of a metal containing carbon monoxide as a ligand. The metal carbonyl can, in principle, include a complex of any charge, any number and type of central atom, and any number and type of ligands and their bonding modes. For example, the metal carbonyl can include an uncharged complex, a positively charged metal carbonyl cation, and / or a negatively charged metal carbonylate anion. The generation of the deposition material can generate carbon monoxide molecules (i.e., CO molecules) as a reaction product. In another example, the first molecule of this method includes an organometallic compound.

[0038] In one example, the metal carbonyl comprises chromium carbonyl. For example, the chromium carbonyl can comprise chromium hexacarbonyl, Cr(CO).

[0039] In one example, the resulting deposition material includes chromium nitride, which has been found to achieve unique durability in the deposition material. In another example, the resulting deposition material includes metal nitrides and / or metal oxynitrides.

[0040] In one example, the chromium nitride (or deposited material) of this method comprises at least 10 atomic percent nitrogen, preferably at least 15 atomic percent nitrogen, and more preferably at least 20 atomic percent nitrogen. The unit "atomic percent" can refer to the molar fraction of the chromium nitride (or deposited material), where the atomic percentage indicates, for example, the relative number of particles (e.g., nitrogen atoms) to the total number of particles of a substance (e.g., the total number of atoms in the chromium nitride or the total number of atoms in the deposited material). The atomic percentage can be detected, for example, by Auger electron spectroscopy and / or X-ray photoelectron spectroscopy (and further, for example, by photoelectron spectroscopy (PES)).

[0041] In one example, the method includes generating a deposition material in a manner that repairs a defect in the object. For example, this can include first detecting the location of the defect (e.g., by a scanning electron microscope, an optical microscope, etc.). Here, a working area used to generate the deposition material can be defined based on at least one characteristic of the defect whose location is detected (e.g., based on the location, shape, size, type, etc. of the defect). Repairing the defect in the object can further include generating a repair shape that includes the defect. In one example, the repair shape can serve as the working area of ​​the method specified herein. The repair shape can have, for example, a pixel pattern that can enable location detection of the defect site. The pixel pattern can be, for example, designed to follow the contour of the defect in such a manner that every pixel in the pixel pattern essentially corresponds to a site in the defect and thus constitutes a defect pixel. In another example, the pixel pattern has a fixed geometric shape (e.g., a polygon, rectangle, circle, etc.) that completely contains the defect, in which case not every pixel necessarily constitutes a defect site. Here, the pixel pattern can include defective pixels corresponding to the defect site and non-defective pixels corresponding to the site that does not cover the defect. In one example, the method includes directing a particle beam onto at least the defective pixels of the pixel pattern of the repair shape when generating the material. Furthermore, the particle beam can be configured to be directed onto any defective pixels when generating the deposition material. This can ensure that the generation of the deposition material is limited to the defective pixels and therefore only the defects are treated.

[0042] In one example, the defects of the method include transparent defects. A transparent defect here refers to a fault location on a lithographic object that, according to the object's design, should actually be opaque (e.g., opaque or highly absorbing to radiation of a particular wavelength). Specifically, opacity may be defined with respect to the lithographic method for the object. For example, the lithographic object may include an EUV mask for an EUV lithographic method, in which case "opaque" may refer to a radiation wavelength of 13.5 nanometers. "Opaque" could also refer to a DUV lithographic method (e.g., with a radiation wavelength of 193 nanometers or 248 nanometers), an i-line lithographic method (e.g., with a radiation wavelength of 265 nanometers), or any other lithographic method depending on the object. Furthermore, a transparent defect may include, for example, a fault location where an opaque pattern element of a lithographic mask has lost material. The method may include forming a deposition material such that the fault location is opaque. For example, the method can include producing an absorber material as a deposited material by a method specified herein. The absorber material can be designed to be opaque with respect to wavelengths at which the pattern element is also opaque. The produced absorber material can, for example, correspond to the material of a layer of the pattern element or can include a material composition having optically similar properties (e.g., refractive index n, absorption coefficient k) as the material of the layer of the pattern element. In one example, to repair a transparency defect, an absorber material that is substantially chromium nitride or essentially comprises chromium nitride is deposited by a method specified herein. Furthermore, this method according to the present invention can include producing the material of any layer of the pattern element by a method specified herein.

[0043] A second aspect of the present invention relates to a method for treating a surface material of a lithographic object, the method comprising: supplying a second gas containing second molecules capable of performing inversion oscillations; the method of the second aspect further comprises supplying a particle beam to the working region of the object to passivate the surface material in the working region based at least in part on the second gas; thus, the method of the second aspect can comprise particle beam-assisted or particle beam-induced passivation based at least in part on the second gas; the surface material can comprise any material contained in the lithographic object; for example, the surface material can be the material of any structure and / or layer of a lithography mask; for example, the surface material can be present on the object.

[0044] The second embodiment can also include features described herein with respect to the first embodiment. Specifically, the second gas can be a second gas described herein with respect to the first embodiment. Similarly, the first embodiment can include features described herein with respect to the second embodiment. Furthermore, the first embodiment can include the second embodiment, and similarly, the second embodiment can include the first embodiment.

[0045] In the method of the second embodiment, the passivation of the surface material can be designed so that only the localized portion of the surface material on which the particle beam acts is passivated. For example, the particle beam can be directed (e.g., by controlled deflection and / or focusing of the particle beam) onto the localized portion of the surface material in such a manner that the localized portion is passivated in cooperation with the supplied second gas. The size of the localized portion to be passivated can correspond, for example, to the size of the particle beam on the surface. For example, this passivation can be performed within a portion having a diameter proportional to the diameter (e.g., FWHM) of the particle beam on the surface (e.g., 5 to 0.2 times the diameter of the particle beam, or 2 to 0.5 times the diameter of the particle beam). Thus, by positioning the particle beam, the passivation of the surface material can be localized with any degree of freedom. Thus, the surface material can be passivated locally (i.e., geometrically enclosed) in a controlled manner. For example, in the context of the method of the second embodiment, a particle beam can be scanned along the surface of a surface material in a specific pattern, resulting in the surface material being passivated along this pattern. This is in contrast to conventional, purely gas-based, global passivation, which can passivate a material (e.g., a material of a lithography object) over a large area alone (e.g., in the case of conventional, purely gas-based passivation, the entire surface exposed to the gas is passivated). Thus, this method according to the present invention allows for a high degree of configuration of the geometry of the passivated or passivated regions, and also allows for the controlled exclusion of regions that are not passivated (for example, because this method allows for passivation of only the regions scanned by the particle beam).

[0046] In one example, the passivation of the second embodiment includes passivation of the side of the surface material. The side may include, for example, localized areas / surfaces such as edges, corners, heights, recesses, etc. of the surface material. The method according to the present invention can therefore enable passivation of side areas of the material of a lithographic object that are usually difficult to access. Here, it is possible to align the particle beam with the surface material at a lateral angle. When passivating the side, it is also conceivable to angle / tilt the object (and thus the surface material), or even to combine tilting the object and aligning the particle beam from the side. In another example, the surface material of the present invention includes the material of the side of the object.

[0047] The passivation of the surface material can be designed to make it physically and / or chemically more stable against external influences than it would be without the passivation according to the present invention. This passivation can be optimized in particular with respect to the external influences to which the object is exposed during lithography processing (e.g., electromagnetic radiation, purge gas, cleaning chemicals, immersion medium, etc.). This passivation can be performed in a particularly advantageous manner because the second molecules used are inverted molecules that promote the formation of a defined (local) gas concentration of the second gas in the working area (as described herein). Furthermore, this passivation can particularly serve to passivate reactive sites of the structured lithography mask that can be (preferentially) attacked by the process gas (e.g., edges, previously damaged structures, easily damaged critical structures, etc.). This passivation can be performed in a particularly preventative manner to prevent possible damage in advance.

[0048] In one example, in the method of the second aspect, this passivation assists the etching process. For example, the surface material can be passivated (as described herein) during or between etching processes (e.g., in the case of localized etching in a region of the surface material). This etching process can include, for example, etching of an absorber material containing chromium and / or chromium oxide. The etching gas used can be, for example, XeF2 and HO. The edges generated in this etching process can be considered as the surface material (or side surface of the surface material) described herein. Therefore, in the present invention, the edges described herein can be passivated by the method of the second aspect. This can be performed, for example, after the etching process is completed for basic (e.g., final) passivation of the surface material. Furthermore, it is also conceivable to perform passivation to adjust the process rate of the etching process. This passivation can be performed at least partially during this etching process.

[0049] In one example, the method of the second embodiment further includes generating a surface material in the working region based at least in part on supplying a first gas and a particle beam prior to passivating the surface material. The first gas of the second embodiment can correspond to one of the examples specified herein for the first gas of the first embodiment of the present invention. The method of the second embodiment can further include controlled (e.g., particle beam-induced) deposition of the surface material, which can then be passivated in accordance with the present invention. For example, the passivation can be performed immediately after generating the surface material, in which case it is also possible to perform the generation and passivation of the surface material separately (e.g., as separate processing operations).

[0050] In another example, a surface material may be produced by one of the methods of the first aspect described herein, in which case the surface material of the second aspect may be similar to or correspond to the deposited material produced in the first aspect.

[0051] In another example, the generation of the surface material can further be based at least in part on an added gas (hereinafter, additive gas). The additive gas can be supplied as an additive gas together with the first gas when generating the surface material. For example, the additive gas can include an oxidizing agent, a halide, and / or a gas having a reducing effect. The oxidizing agent can include an oxygen-containing gas. For example, the oxidizing agent can include at least one of the following: oxygen (O), ozone (O), water (H), hydrogen peroxide (H), nitrous oxide (N), nitrous oxide (NO), nitrogen dioxide (N), and nitric acid (HNO). The halide can include a halogen-containing gas. For example, the halide can include at least one of the following: Cl, HCl, XeF, HF, I, HI, Br, HBr, NOCl, PCl, PCl, and PF. The gas having a reducing effect (e.g., a reducing agent) can include a hydrogen-containing gas. For example, the gas having a reducing effect can include at least one of the following: H2, NH3, H2N-NH2, CH4. In one example, generating the surface material includes supplying a first gas including chromium hexacarbonyl and supplying an additive gas including nitrogen dioxide as an oxidizing agent. In another example, generating the surface material includes supplying a first gas including chromium hexacarbonyl and supplying an additive gas including water and / or oxygen as an oxidizing agent.

[0052] In one example, in the method of the second aspect, the surface material comprises an absorber material, which, as described herein, can be one designed to be opaque to the wavelengths of the lithographic method in which the lithographic object may be used.

[0053] In one example, in the method of the second aspect, the passivation includes generating a passivation layer on the surface material. For example, generating the passivation layer can include chemical / physical alteration of at least one upper layer of the surface material. Furthermore, generating the passivation layer can include depositing the passivation layer as a separate layer on the surface material. It is also contemplated that the present invention can generate a combination of an altered upper layer of the surface material and a deposited separate layer on the surface material. In one example, in the method of the second aspect, the generated passivation layer includes a nitride of the surface material.

[0054] In one example, in the method of the second aspect, the surface material produced comprises chromium. For example, the surface material produced may be a chromium oxide-containing material or a chromium-containing material, the surface of which is passivated by nitridation.

[0055] In one example, in the method of the second embodiment, the passivation layer produced comprises chromium nitride.

[0056] In one example, the method of the second embodiment includes, following this passivation, creating another surface material on the passivated surface material. This other surface material can be created in a manner similar to the surface material (described herein). Furthermore, the method of the second embodiment can include passivating this other surface material (as described herein). In another example, the method of the second embodiment includes alternating between creating this other surface material and its passivation. Here, the alternating between creating and passivating can be repeated as frequently as desired. For example, this example can result in a layer stack of alternating (other) surface materials and their passivation layers.

[0057] In one example, in the method of the second embodiment, the chromium nitride comprises at least 10 atomic percent nitrogen, preferably at least 15 atomic percent nitrogen, more preferably at least 20 atomic percent nitrogen.

[0058] In one example, the method of the second aspect includes generating a surface material in a manner that repairs a defect in the object. For example, this can be performed in a manner similar to the example described in the first aspect. In one example, in the method of the second aspect, the defect includes a transparent defect.

[0059] In one example, in the method of the first and / or second aspect, the inversion vibration comprises a pyramidale inversion of the second molecule.

[0060] In one example, in the method of the first and / or second aspect, the second molecule comprises a trigonal-pyramidale geometry.

[0061] In one example, in the method of the first and / or second embodiment, the second molecule comprises nitrogen and hydrogen in the compound. For example, the second molecule can essentially comprise nitrogen and hydrogen. It is also possible that the second molecule exclusively comprises nitrogen and hydrogen.

[0062] In one example, in the method of the first and / or second embodiment, the second molecule comprises ammonia NH3. For example, the inversion vibration of ammonia occurs at a high frequency of about 23 gigahertz (GHz) at typical room temperature. The inventors have recognized that this is advantageous for the method according to the present invention.

[0063] In one example, in the method of the first and / or second embodiment, the second molecule comprises H2N-NH2.

[0064] In one example, in the method of the first and / or second embodiment, the second molecule comprises nitrogen and a halogen in a compound. For example, the second molecule can essentially comprise nitrogen and a halogen. It is also possible that the second molecule exclusively comprises nitrogen and a halogen.

[0065] In one example, in the method of the first and / or second embodiment, the second molecule comprises at least one of the following molecules: NF3, NCl3, NI3, NBr3.

[0066] In one example, in the method of the first and / or second embodiment, the second molecule comprises nitrogen, hydrogen, and a halogen in a compound. For example, the second molecule can essentially comprise nitrogen, hydrogen, and a halogen. It is also possible that the second molecule exclusively comprises nitrogen, hydrogen, and a halogen.

[0067] In one example, in the method of the first and / or second embodiment, the second molecule comprises at least one of the following molecules: NH2X (wherein X comprises a halogen), NHX2 (wherein X comprises a halogen).

[0068] In one example, in the methods of the first and / or second aspects, the second molecule has a lower absorption probability than the NO molecule in the working area, and the lower absorption probability may ensure better availability of the second molecule.

[0069] In one example, in the methods of the first and / or second aspects, the particle beam comprises an electron beam. For example, the deposition material of the first aspect and / or the surface material of the second aspect may be produced by electron beam induced deposition (e.g., known as (F)EBID, i.e., (focused) electron beam induced deposition).

[0070] However, it is also contemplated that the particle beam may comprise an ion beam (such as gallium ions, etc.). For example, the deposition material of the first aspect and / or the surface material of the second aspect may be produced by ion beam induced deposition (e.g. known as (F)IBID, i.e. (focused) ion beam induced deposition).

[0071] Furthermore, it is also conceivable to use multiple particle beams as the particle beam.

[0072] In one example, in the method of the first and / or second aspect, an additive gas (as an additive gas) is also provided. For example, the second gas can include an additive gas (or molecules thereof). The additive gas can include an oxidizing agent, a halide, and / or a gas having a reducing effect (i.e., a reducing agent). The oxidizing agent can include, for example, an oxygen-containing gas. For example, the oxidizing agent can include at least one of the following: oxygen (O), ozone (O), water (H), hydrogen peroxide (H), nitrous oxide (N), nitric oxide (NO), nitrogen dioxide (N), and nitric acid (HNO). The halide can include a halogen-containing gas. For example, the halide can include at least one of the following: Cl, HCl, XeF, HF, I, HI, Br, HBr, NOCl, PCl, PCl, and PF. The gas having a reducing effect can include a hydrogen-containing gas. For example, the gas having a reducing action may include at least one of the following: H2, NH3, H2N-NH2, CH4.

[0073] In a preferred example, the method of the first and / or second embodiment includes supplying a first gas containing chromium hexacarbonyl and a second gas containing an inverting molecule (as described herein) as the second molecule and containing nitrogen dioxide as the oxidant. In another preferred example, the method of the first and / or second embodiment includes supplying a first gas containing chromium hexacarbonyl and a second gas containing an inverting molecule (as described herein) as the second molecule and containing oxygen and / or water as the oxidant. In another preferred example, the method of the first and / or second embodiment includes supplying a first gas containing chromium hexacarbonyl and a second gas containing an inverting molecule (as described herein) as the second molecule and containing H2 as the reductant.

[0074] A third aspect of the present invention relates to an apparatus for processing a lithographic object, the apparatus comprising: means for supplying a first gas; means for supplying a second gas containing second molecules capable of performing inversion oscillation; and means for supplying a particle beam. The apparatus is further configured to perform a method according to the examples of the first and / or second aspects of the present invention described herein. Furthermore, the apparatus may comprise a computer system.

[0075] In some instances, for example when the apparatus is intended to be used only for passivation as described herein, the apparatus does not necessarily include means for supplying the first gas.

[0076] A fourth aspect of the invention relates to a lithographic object, which has been processed by the method of the first and / or second aspect.

[0077] A fifth aspect of the present invention relates to a method for lithographic processing of semiconductor-based wafers. The method of the fifth aspect further comprises lithographically transferring a pattern associated with a lithographic object onto the wafer, the object having been processed according to one of the examples of the first and / or second aspects of the present invention described herein. The lithographic transfer can include a lithographic method for which the object is designed (e.g., EUV lithography, DUV lithography, i-line lithography, etc.). For example, the method of the fifth aspect can include providing a beam source of electromagnetic radiation (e.g., EUV radiation, DUV radiation, i-line radiation, etc.). This can further include applying a developable resist layer onto the wafer. The lithographic transfer can further be based, at least in part, on a radiation source and on applying a developable resist layer. Here, the pattern can be imaged (in a modified form) onto the resist layer, for example by radiation from the radiation source.

[0078] The methods described herein can be recorded, for example, in the form of a document. This can be achieved, for example, by a digital file, in an analog manner (e.g., in the form of a paper document), in a user handbook, or in a format (e.g., recorded on a device and / or computer at a semiconductor fab). It is also contemplated that a written protocol may be compiled during the performance of one of the methods described herein. This protocol may, for example, allow for verification of the execution of the method and its details (e.g., formulas) at a later point in time (e.g., during a fault evaluation, audit, etc.). This protocol may, for example, include a protocol file (i.e., a log file), which may, for example, be recorded on a device and / or computer.

[0079] A sixth aspect of the present invention relates to a computer program comprising instructions which, when executed by a computer system, cause the computer system to perform a method according to one of the examples of the first, second and / or fourth aspects of the present invention.

[0080] Another aspect relates to the above-mentioned device, which includes a memory containing a computer program. The device may further include means for executing the computer program. Alternatively, the computer program may be stored elsewhere (e.g., in the cloud), and the device may simply include means for receiving instructions resulting from the program being executed elsewhere. In any case, this may allow the method to be performed automatically or autonomously within the device. As a result, intervention, for example by an operator, may be minimized, thereby minimizing both the cost and complexity of processing the mask.

[0081] The method features (and further examples) specified herein may also apply to or be applicable to the above-mentioned apparatus accordingly, and similarly, the apparatus features (and further examples) specified herein may also apply to or be applicable to the apparatus described herein accordingly.

[0082] The following detailed description provides background information and working examples of the invention with reference to the figures. [Brief explanation of the drawings]

[0083] [Figure 1] 1A and 1B are schematic top views of exemplary repair situations of lithographic objects according to the prior art; [Figure 2] 1A-1C are schematic diagrams illustrating, by way of example, cross-sections of a process for repairing defects in a lithographic object. [Figure 3] 1 is a schematic diagram of an exemplary method of the present invention. [Figure 4a] 1 shows scanning electron micrographs of five test structures, some of which were produced by a method according to the present invention. [Figure 4b] FIG. 4b shows Auger electron spectroscopy results for the five test structures of FIG. 4a. [Figure 5] 1 is a schematic cross-sectional view of an exemplary device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0084] FIG. 1 schematically illustrates a top view of an exemplary repair situation of a lithography object. The lithography object may include a lithography mask suitable for a lithography method (e.g., EUV lithography, DUV lithography, i-line lithography, nanoimprint lithography, etc.). In one example, the lithography mask may include an EUV mask, a DUV mask, an i-line lithography mask, and / or a nanoimprinting stamp. Furthermore, the lithography object may include a binary mask (e.g., a chrome mask, an OMOG mask), a phase mask (e.g., a chrome-free phase mask), an alternating phase mask (e.g., a rim phase mask), a half-tone phase mask, a tri-tone phase mask, and / or a reticle (e.g., a reticle with a pellicle). The lithography mask may be used, for example, in a lithography method for manufacturing semiconductor chips.

[0085] Lithographic objects can contain (unwanted) defects. For example, defects can occur during the manufacturing of the object. Furthermore, defects can occur during the (lithographic) processing of the object, process deviations during the (lithographic) processing, transportation of the object, etc. Because manufacturing lithographic objects is usually expensive and complex, defects are usually repaired.

[0086] In the working examples described herein, for illustrative purposes, an EUV mask is often used as an example of a lithographic object, however, any object for lithography (e.g., as described herein) is contemplated rather than an EUV mask.

[0087] FIG. 1 may schematically illustrate two local states D, R of a mask detail 1000 during repair of an EUV mask defect. The detail 1000 illustrates a portion of a pattern element PE of the EUV mask. The pattern element PE may also be considered a pattern element of the EUV mask. The pattern element PE may be a portion of a designed pattern that can be transferred to a wafer, for example, by a lithography method. Local state D illustrates a transparent defect 110 in the pattern element PE. (As described herein) The transparent defect 110 may be characterized, for example, by a lack of opaque material in the pattern element PE. With respect to FIG. 1 (state D), it is clear that a defect-free pattern element PE of the detail 1000 should have a square shape, but as a result of the defect 1010, this targeted state does not exist. Therefore, the repair procedure RV typically generates repair material 1020 in the area of ​​the transparent defect 1010 in such a manner that a repaired state R of the pattern element PE can be established. For example, in state R of FIG. 1, it is clear that the targeted square state of the pattern element has already been re-established. The repair material 1020 may include a material that has the effect of imparting an opacity effect at the site of the (original) defect 1010 corresponding to the opacity effect of the pattern element. The opacity effect of the pattern element is particularly caused by at least one absorber material of the pattern element. Therefore, the repair material 1020 usually includes an absorber material, which may, for example, be essentially identical to the absorber material of the pattern element or may have similar absorption properties (e.g., a similar material) as the absorber material of the pattern element. However, a technical challenge here is that the locally generated repair material may be affected in the same way as the material of the pattern element originally present on the EUV mask. Therefore, this repair material with its local boundaries may be subject to high chemical and physical stresses.

[0088] Lithography masks can be exposed to extreme physical and chemical environmental conditions within a lithography tool or during use in a lithography process, which can, for example, alter the material properties of the mask. This is particularly true for exposure of EUV masks during UV lithography processes, where absorbing materials can be particularly susceptible to these effects. EUV, which uses high-energy EUV radiation, is typically performed in a hydrogen atmosphere. Furthermore, DUV masks in DUV lithography processes can be particularly exposed to environmental conditions that can potentially alter the material.

[0089] Therefore, high demands are placed on repair materials, which may contain absorber materials, such as stability against these lithography environmental conditions. Electron-beam-induced deposition is typically used to repair defects resulting in material loss (e.g., in UV, DUV, and EUV masks). Electron-beam-induced deposition can produce absorbing (e.g., chromium-containing) deposits. Often, a chromium precursor gas is used in conjunction with an oxidizing additive gas (e.g., NO, O, HO, etc.). The primary purpose of adding the oxidizing additive gas is to reduce the carbon content in the deposit, since residual carbon can further reduce the stability of the deposit. However, the resulting chromium oxide-containing material (i.e., the repair material) often only partially meets the stability requirements against the aggressive ambient conditions prevailing in lithography processes (e.g., in UV, DUV, and EUV lithography methods). Therefore, damage to the repair material (and mask) cannot always be prevented.

[0090] Damage to the repair material (and mask) may involve chemical and / or physical changes in the material, which may have various causes. First, this cause may be due to operations during the lithography process (e.g., exposure operations). For example, this cause may be radiation (e.g., EUV radiation, DUV radiation, etc.), (process) temperature, reactions with hydrogen and / or other reactive hydrogen species (e.g., free radicals, ions, plasma) during exposure, and / or reactions of the mask with purge gas (e.g., N2, extreme clean dry air (XCDA®), noble gases) associated with the radiation during exposure. Second, this cause may be due to downstream processes (e.g., processing of the mask after the lithography process). This downstream process may include, for example, mask cleaning. Here, the repair material (and mask) previously damaged by chemical and / or physical processes during the lithography process may be further damaged by downstream processes.

[0091] FIG. 2 shows an example cross-sectional view of a process for repairing defects in a lithography object. Furthermore, FIG. 2 also shows a cross-sectional view of a reflective lithography mask 200 for the EUV wavelength range (i.e., an EUV mask or EUV photomask). The exemplary EUV mask 200 may be designed for an exposure wavelength in the 13.5 nm range. The EUV mask 200 may include a substrate 210 made of a material with a low thermal expansion coefficient, such as quartz. Similarly, other dielectric, glass, or semiconductor materials, such as ZERODUR®, ULE®, or CLEARCERAM®, may be used as the substrate for the EUV mask. The backside 215 or backside surface 215 of the substrate 210 of the EUV mask 200 may serve to hold the substrate 210 in an EUV photolithography apparatus during the creation and operation of the EUV mask 200. A thin conductive layer 220 is preferably applied to the backside 215 of the substrate 210 for holding the substrate 210 on an electrostatic chuck (ESC).

[0092] The front surface 225 of the substrate 210 may include a deposited multilayer film or structure 270, e.g., having 20-80 alternating pairs of molybdenum (Mo) layers 230 and silicon (Si) layers 235. This alternating layer may also be referred to as a MoSi layer. Instead of molybdenum, a layer of another element with a high mass number, such as cobalt (Co), nickel (Ni), tungsten (W), rhenium (Re), zirconium (Zn), or iridium (Ir), may be used for the MoSi layer. To protect the multilayer structure 270, a capping layer 240, e.g., silicon dioxide, may be applied over the top silicon layer 235. Similarly, other materials, e.g., ruthenium (Ru), may also be considered for the capping layer 240.

[0093] A structured pattern element PE may be present on the capping layer 240. The pattern element PE may include several layers. For example, the pattern element PE may include a buffer layer 245 on the capping layer 240. Furthermore, the pattern element PE may include an absorbing layer 250 on the buffer layer 245. Furthermore, the pattern element PE may include an anti-reflective layer 255 on the absorbing layer 250. The pattern element PE may be designed to be opaque (i.e., not transmissive to light or highly absorbing) to optical radiation used, for example, in EUV lithography (e.g., optical radiation having a wavelength of 13.5 nm). Here, all layers of the pattern element PE may be designed to be opaque to this optical radiation. Specifically, the absorbing layer 250 may have a major proportion of the absorption of (EUV) optical radiation, and the buffer layer 245 and / or the anti-reflective layer 255 may also contribute to the absorption. Thus, by virtue of the provided pattern elements PE, the EUV mask 200 has absorptive regions 280 and reflective regions 285 .

[0094] Possible materials for the buffer layer 245 may include quartz (SiO2), silicon oxynitride (SiON), Ru, chromium (Cr), chromium oxide, and / or chromium nitride (CrN). In particular, chromium nitride may be preferred as a material for the buffer layer 245 of the EUV mask. Possible materials for the absorber layer 250 may include chromium nitride, chromium, chromium oxide, titanium nitride (TiN), and / or tantalum nitride (TaN). In particular, chromium nitride may be preferred as a material for the absorber layer 250 of the EUV mask. The anti-reflective layer may include, for example, tantalum oxynitride (TaON) and / or chromium nitride.

[0095] During repair, it may be necessary to replace lost material of the pattern element PE. Here, it may be necessary to generate any material of the layers of the pattern element PE. For example, the repair operation RV may include generating material of the absorber layer 250, as schematically shown by A in FIG. 2. For example, it may be necessary to repair an absorber layer 250 that is only partially missing. Here, the repair material may be generated directly on the (partially present) absorber layer 250. In this case, the boundary layer of the generated repair material is defined with respect to the absorber layer 250 (and not with respect to, for example, the buffer layer 245 or the substrate). Furthermore, the repair operation RV may include generating material of the buffer layer 245, as schematically shown by B in FIG. 2. Here, it is also conceivable that the repair operation RV generates material for the anti-reflection layer 255 and / or material for the capping layer 240. Furthermore, combinations of generating different materials for different layers of the pattern element PE are also conceivable (for example, the repair operation RV may generate material for the buffer layer 245 and also material for the absorber layer 250). Furthermore, it is possible that in the repair operation RV only an absorber material is produced that corresponds to the material of the absorber layer 250, for example, or that has similar opaque properties to the absorber layer 250. Correcting a (transparent) defect does not necessarily require correction of missing cross sections of the buffer material 245 and / or the anti-reflection layer 255.

[0096] 3 shows a schematic diagram of an exemplary method 300. Method 300 can be used to generate missing material of a pattern element PE. As described herein, this method can be used to repair, for example, a transparency defect.

[0097] The method can include providing a first gas 310. The first gas can include, for example, a chromium-containing gas, preferably chromium hexacarbonyl.

[0098] Further, the method 300 may include supplying 320 a second gas containing a second molecule capable of performing the inversion oscillation. The second gas may include, for example, ammonia, since ammonia is capable of performing the inversion oscillation. Specifically, the second gas may be supplied at a gas flow rate of less than 5 sccm, preferably less than 2 sccm, and more preferably less than 0.5 sccm.

[0099] The method 300 further includes providing 330 a particle beam to the working region to generate a deposition material based at least in part on the first gas and the second gas. Specifically, generating can include electron beam-induced deposition, which is performed in a gas atmosphere including, for example, chromium hexacarbonyl (as the first gas) and ammonia (as the second gas). The method can further include generating within a specific parameter space. For example, this parameter space can include generating the second gas at a gas flow rate described herein. Further, other parameter spaces for this method are contemplated, which may relate, for example, to the first gas, the second gas, and / or the particle beam or their parameters. Some parameter spaces of the exemplary method 300 enabled particularly advantageous properties of the generated deposition material. In particular, when a second gas including nitrogen is used, the specified parameter space can be advantageous for achieving a high nitride content of the deposition material (compared to deposition using only the first gas). The carbon content of the deposition material can be reduced (compared to deposition using only the first gas).

[0100] FIG. 4a shows scanning electron micrographs of the top surfaces of five test structures, some of which were produced by the method according to the present invention. Here, the five test structures S1, S2, S3, S4, and S5 are cubic structures, and test structures S2, S3, S4, and S5 were produced using different parameter spaces of the method according to the present invention. Common to all test structures S1-S5 is that chromium hexacarbonyl was supplied as the first gas and that the production of the deposited material was based on electron beam induced deposition. Common to test structures S2-S5 is that the method according to the present invention was carried out with ammonia supplied as the second gas. Test structure S1 was produced as a reference structure, while test structure S1 was produced without the supply of a second gas (e.g., ammonia) according to the present invention (i.e., in the presence of only the first gas). The process parameters are described in detail below.

[0101] Test structure S1 was produced using only chromium hexacarbonyl supply and electron beam-induced deposition. A relatively short electron beam dwell time of 0.5 microseconds was selected. Test structure S2 was produced using a gas flow rate of the second gas (ammonia in this example) of 0.1 sccm and the same electron beam dwell time. Test structure S3 was produced using a gas flow rate of the second gas of 0.25 sccm and the same electron beam dwell time. Test structure S4 was produced using a gas flow rate of the second gas of 0.25 sccm and a relatively long electron beam dwell time (10 times longer than for S1). Test structure S5 was produced using a gas flow rate of the second gas of 0.4 sccm and the same electron beam dwell time as for S1.

[0102] For test structures S2-S5, the electron beam scanning technique used in particle beam-induced deposition was selected so that the height dimensions of test structures S2-S5 were similar (approximately 50 nm). The height dimension of test structure S1 was approximately 130 nm. This can be attributed to the lack of a second gas supply during the creation of reference structure S1. Furthermore, during the processing of test structures S1, S2, S3, S4, and S5, the pixel pattern that geometrically defined the test structures was scanned. The electron beam was directed at least once over every pixel of the pixel pattern for each test structure. This scanning can be considered as creating a partial layer, and repeated scanning defines the height of the test structure. Scanning is sometimes referred to as a loop or cycle. Test structures S1, S2, S3, and S5 were each created using a similar number of loops. The number of loops for test structure S4 was significantly less due to its longer dwell time.

[0103] FIG. 4b shows Auger electron spectroscopy results for the five test structures in FIG. 4a. Therefore, the Auger electron spectroscopy (or Auger spectroscopy) results allow for relative comparison of test results. The vertical axis of FIG. 4b shows the mole fraction in atomic percent. The horizontal axis of FIG. 4b shows the materials evaluated by Auger spectroscopy. The results for all test structures S1, S2, S3, S4, and S5 are summarized by material. The analyzed materials shown in FIG. 4b are carbon (C) and nitrogen (N). Oxygen and chromium were also analyzed but are not shown in FIG. 4b. As can be seen from FIG. 4b, when the method of the present invention was used (i.e., for test structures S2 to S5), the nitrogen content was clearly higher than that of the reference structure S1. The method of the present invention can achieve a nitrogen content of at least 10 atomic percent, whereas no significant nitrogen content was detected in the material deposited by the conventional method for the reference structure S1. This suggests that chromium nitride was preferentially produced by the method of the present invention using ammonia compared to the conventional method. For structures S4 and S5, it was also possible to achieve nitrogen contents of >20 atomic percent. For an exemplary method according to the present invention (using chromium hexacarbonyl and ammonia), Cr(CO)6 + bNH3 → cCr x O y N z The basic chemical reaction of +dCO +eH2O +fCH4 +gCO2 +hN2 is assumed (in contrast, for subsequent passivation, this equation is x O y C z +dNH3→Cr x O y-a C z-b N c + eH2O + fCO2). The exact reaction can be affected by the parameter space of the method.

[0104] Furthermore, it is clear that the carbon content is significantly lower when using the method according to the present invention (i.e., for test structures S2-S5) compared to the reference structure S1. It can be shown here that the method according to the present invention can result in a carbon content of less than 40 atomic percent, preferably less than 30 atomic percent, and more preferably less than 20 atomic percent. Thus, the method according to the present invention achieves a clear reduction in the carbon content of 25 percent, preferably 40 percent, and more preferably 60 percent (compared to deposition without the supply of a second gas). A possible explanation for this is that the use of ammonia as an inversion molecule results in advantageous effects that can be enhanced by appropriate parameter spacing. In the case of electron-beam-induced deposition of chromium using chromium hexacarbonyl, CO molecules can remain on the surface. A high supply of NH3 in the gas phase, which can be ensured, for example, by the properties of NH3 as an inversion molecule, can increase the probability of CO removal from the surface by NH3. This can have the effect of depositing less carbon in the deposited material. These two effects (i.e., preferential formation of chromium nitride or high nitrogen content and reduced carbon content in the deposited material) may enable optimized repair materials in mask repair that are more tolerant to the effects specified herein. Furthermore, there is a clear trend for nitrogen content to increase with increasing gas flow rate of the second gas. Because the nitrogen content is reduced relatively slightly in the case of the relatively high gas flow rate of ammonia (0.4 sccm) for test structure S5, it can be concluded that the favorable gas flow rate of the second gas is 0.25 sccm.

[0105] As noted herein, the analyzed chromium content is not shown in FIG. 4b. The chromium contents of the test structures S1, S2, S3, S4, and S5 were measured to be in the range of approximately 15 to 25 atomic percent without significant differences or variations. Therefore, it was shown that the method according to the present invention does not significantly affect the chromium content. It should be noted that the method according to the present invention also allowed for the detection of higher chromium contents (e.g., chromium contents of at least 25 atomic percent, at least 30 atomic percent, or at least 35 atomic percent). It is also contemplated that the chromium content of the deposited material may even be at least 50 atomic percent, at least 70 atomic percent, or at least 80 atomic percent (or between 35 atomic percent and 99 atomic percent). It is also contemplated that the chromium content may be less than 15 atomic percent. Furthermore, a higher oxygen content was also detected in the test structures S2, S3, S4, and S5 compared to the reference structure S1 (without the supply of the second gas). The oxygen content increased, for example, by at least 1.5 or at least 2 times.

[0106] Furthermore, it was shown that a relatively long dwell time of the electron beam (for test structure S4) can produce a higher nitrogen content in the deposited material compared to shorter dwell times of the electron beam (for test structures S2, S3, and S5).

[0107] 4, it is therefore possible to achieve or aim for a nitrogen content of at least 5 atomic %, preferably at least 10 atomic %, more preferably at least 20 atomic % in the produced material by the method according to the invention. The method according to the invention can also increase the nitrogen content of the produced material by at least 2, 3, 4 and / or 10 times compared to production by prior art methods (e.g., without supplying a second gas).

[0108] The low dipolarity of ammonia, compared to nitrogen dioxide, can reduce the probability of absorption of ammonia at the substrate surface. As a result, the concentration of ammonia molecules in the gas phase above the substrate surface can be increased. This can increase the probability that the desired nitrogen-containing deposition material is already formed in the gas phase. This can probably be explained by the exchange of CO ligands with NH3 ligands on the chromium atoms already occurring in the gas phase. One possible reaction is as follows: Cr(CO)6 + nNH3 → Cr(CO) 6-n (NH3) n +nCO, where n = 1 to 6.

[0109] Two other test structures, E1 and E2, were fabricated for further analysis. Test structure E2 was fabricated using the parameter space of the method according to the present invention. Test structures E1 and E2 were fabricated to have lengths and widths of 20 μm × 20 μm and heights ranging from 10 nm to 20 nm. These test structures were analyzed by X-ray photoelectron spectroscopy (abbreviated as XPS). The test structures were analyzed for carbon (C), oxygen (O), chromium in oxide compounds (Cr-Ox), metallic chromium (Cr-Met), nitrogen (N), and total chromium content (Cr-sum). Test structure E1 was fabricated as a reference structure by a known method, which involves supplying chromium hexacarbonyl as the first gas and nitrogen dioxide as the second gas, which cannot perform inversion oscillations (at the process temperature of electron beam-induced deposition). Test structure E1 was fabricated using a gas flow rate of 0.5 sccm of the second gas (i.e., nitrogen dioxide) and a dwell time of 5 microseconds for the electron beam. Test structure E2 was fabricated by electron beam-induced deposition using chromium hexacarbonyl as the first gas and ammonia as the second gas. The process parameter space for fabricating test structure E2 was as follows: a gas flow rate of 0.25 sccm for the second gas (i.e., ammonia), a process temperature of 17°C, an electron beam dwell time of 5 microseconds, and a frame refresh rate of 2500 microseconds. Furthermore, the process for fabricating test structure E2 was performed with an electron beam acceleration voltage between 0.3 kV and 1 kV, e.g., about 0.6 kV (kV: kilovolts), and an electron beam current between 1 pA and 100 pA, e.g., about 28 pA (pA: picoamperes). The pixel pattern was scanned in such a way that the height of the test structure ranged from 10 nm to 20 nm. To minimize process gas depletion, a scanning pattern was selected in which every 10 rows were sequentially addressed. In some examples, to generate test structure E2, the gas flow rate of the second gas (e.g., ammonia) can be between 0.1 sccm and 2 sccm, between 0.1 sccm and 1 sccm, and / or between 0.1 sccm and 0.5 sccm. The process temperature can include a (preset) temperature of the first gas and a (preset) temperature of the second gas.In some examples, to generate test structure E2, the electron beam dwell time can range between 0.1 microseconds and 10 microseconds, between 0.3 microseconds and 7 microseconds, and / or between 1 microsecond and 6 microseconds. In some examples, the frame refresh rate can be between 0.5 milliseconds and 5 milliseconds, between 0.7 milliseconds and 4 milliseconds, and / or between 1 millisecond and 3 milliseconds. Furthermore, the process temperature (of the first and / or second gas) can be in the range of 0°C to 60°C, or between 10°C to 40°C, between 12°C to 30°C, and / or between 12°C to 20°C.

[0110] This further analysis revealed that test structure E2 contained approximately 23 atomic percent (at. %) nitrogen. Therefore, it was shown that the parameter space of the method according to the present invention allows for achieving a high nitrogen content for test structure E2. This also suggests that the method according to the present invention allows for the production of a high chromium nitride content in the deposited material. This effect can be particularly advantageous in the context of repair operations RV, since chromium nitride can be a resistant material to aggressive chemical / physical environmental conditions.

[0111] Furthermore, the oxygen content of test structure E2 was significantly lower than that of reference structure E1. The reduction in oxygen content roughly corresponded to the nitrogen content observed in test structure E2. Therefore, it can be concluded that a reduction in oxygen content can increase the nitrogen content roughly corresponding to this reduction.

[0112] The increase in carbon content of test structure E2 compared to reference structure E1 was minimal, with both test structures exhibiting low levels (single-digit percent range). It should be noted that the carbon content (oxygen content) of reference structure E1 was lower (higher) than that of reference structure S1 of FIG. 4b. In this regard, it should be noted that reference structure E1 was produced by a deposition method using nitrogen dioxide as an additive gas (and chromium hexacarbonyl as the first gas), while reference structure S1 of FIG. 4b was produced by a deposition method without an additive gas (and thus exclusively using chromium hexacarbonyl as the deposition gas). This demonstrates that using an inverting molecule (ammonia in this case) rather than nitrogen dioxide as the additive gas does not significantly change the carbon content (and that the carbon content can remain low using the method according to the present invention). Furthermore, it was possible to increase the metallic chromium content of test structure E2 by a factor of seven compared to E1. The percentage of chromium in the oxide compounds of test structure E1 was slightly lower than that of test structure E2.

[0113] Reducing the chromium oxide content can be advantageous for EUV lithography processes. Possible chemical reactions that can occur between chromium oxide (e.g., Cr2O3) and hydrogen within an EUV lithography tool include, for example, the partial reduction of chromium (Cr2O3 + 3H2 → 2Cr + 3H2O) and a local change in the oxidation state of the chromium atoms. For example, the oxidation state can change from Cr(III) to Cr(II), Cr(I), and / or Cr(0). Similarly, it is conceivable that the oxidation state can change from Cr(IV) to Cr(III), Cr(II), Cr(I), and / or Cr(0). This local change in the oxidation state of the chromium atoms can increase the heterogeneity of the material in such a way that the chemical and physical durability of the material is reduced. For example, reactive hydrogen species within an EUV lithography tool can remove oxygen from materials containing chromium oxide, which can cause defects in the solid material. These defects can accelerate erosion of the material during subsequent cleaning processes. Therefore, reducing the chromium oxide content by the method according to the invention may minimize the above-mentioned effects. It is also conceivable that the high chromium nitride content that can be produced by the method according to the invention may further minimize the above-mentioned effects associated with a particular chromium oxide content.

[0114] In summary, the repair material produced by the method according to the present invention may be more stable or more resistant to influences that the EUV mask may be subjected to during processing (e.g., as described herein) in repairing the EUV mask.

[0115] Testing of the resulting deposited metals, including chromium nitride, suggests that the durability, resistance, and stability of the material to external chemical / physical influences are increased compared to materials produced by conventional methods. In the case of repairing an EUV mask by method 300 (or a method according to the first and / or second embodiment), this can be particularly advantageous when the repaired EUV mask is used in a lithography method. For example, this can enable an increased number of DUV and / or EUV exposure cycles (of a lithography method) that the repaired lithography mask can undergo before the optical properties of the repaired feature change to the extent that the feature no longer meets the required specifications for the critical dimension CD. Furthermore, this can lead to reduced damage from downstream processes, such as mask cleaning operations. In particular, there may be resistance to cleaning processes comprising at least one of the following steps: removal of contamination, removal of carbon-containing contamination, removal of particles, use of oxidizing agents, use of acids, use of oxidizing acids, use of acids and oxidizing agents, use of cleaning solutions with a pH < 7, use of H2SO4 (and e.g. HO2), use of UV light, use of light that may react with and activate cleaning chemicals, use of plasma, use of oxygen plasma, use of basic solutions, use of solutions with a pH < 7, use of solutions containing NH3. Furthermore, the method according to the invention (of the first and / or second aspects) may allow for a reduction in erosion or deterioration of the deposit (at the repaired site). This deterioration may in particular comprise at least one of the following: global progressive erosion, (gradual) leafing, localized erosion, simultaneous loss of large areas of the deposit, loss of desired optical properties.

[0116] Furthermore, the following working examples are possible for the method of the first and / or second aspect according to the present invention. For example, it is conceivable that the second gas comprises at least one of the following: a reducing additive precursor, a hydrogen-containing additive precursor, an additive precursor comprising at least one nitrogen atom and at least one hydrogen atom. In another example, it is conceivable that the deposition material and also the (passivated) surface material produced according to the present invention can be consolidated or stabilized by electron beam bombardment (e.g. in a separate processing operation).

[0117] In some instances, electron beam accelerating voltages of 0.1 to 2 kV, 0.2 to 1.5 kV, or 0.3 to 1 kV can be used. In each case, an electron beam current of 28 pA can be used. Alternatively, currents in other ranges are also contemplated, such as 1 to 100 pA, 5 to 80 pA, or 10 to 60 pA.

[0118] FIG. 5 shows a schematic cross-sectional view of an exemplary apparatus 500 according to the present invention. The apparatus 500 may be configured to perform the method 300 or the methods of the first and / or second aspects of the present invention. In one example, the apparatus 500 of FIG. 5 includes a mask repair apparatus for repairing or processing a lithography mask. The apparatus 500 may be used to detect the location of mask defects and to repair or repair the mask defects. The apparatus 500 may include portions such as those described in U.S. Patent Application Publication No. 2020 / 103751 (see corresponding FIG. 3A therein).

[0119] The exemplary apparatus 500 of FIG. 5 can include, for example, a scanning electron microscope (SEM) 501 for providing a particle beam, which in this example is an electron beam 509. An electron gun 506 can generate the electron beam 509, which can be directed by beam shaping elements 508 and 512 as a focused electron beam 510 onto a lithography mask 502 disposed on a specimen stage 504 (or chuck). Furthermore, the scanning electron microscope can be used to control the parameters / characteristics of the electron beam (e.g., acceleration voltage, dwell time, current, focus, spot size, etc.). The electron beam parameters can be adjusted, for example, with respect to the parameter space of the methods described herein. The electron beam 509 can serve as an energy source to initiate a local chemical reaction in a working area of ​​the lithography mask 502. The electron beam 509 can be utilized, for example, for the methods described herein (e.g., to perform electron-beam-induced deposition of the first embodiment, electron-beam-assisted passivation of the second embodiment). Additionally, the electron beam 509 may be utilized to image the lithography mask 502. The apparatus 500 may include a detector 514 for detecting the electrons.

[0120] To implement the corresponding methods described herein, the exemplary apparatus 500 of FIG. 5 can include at least two reservoir containers for at least two different process or precursor gases. The first reservoir container G1 can store a first gas. The second reservoir container G2 can store a second gas containing molecules capable of performing inversion oscillation. The second gas can also be considered an additive gas. Furthermore, in the exemplary apparatus 500, each reservoir container G1, G2 can have its own gas inlet system 532, 547, which can include a nozzle at the end near the incident point of the electron beam 510 on the lithography mask 502. To control the amount of the corresponding gas supplied per unit time, i.e., the gas flow rate of the corresponding gas, each reservoir container G1, G2 can have its own control valve 546, 531. This control can be performed in such a way that the gas flow rate at the incident point of the electron beam 510 is controlled. Additionally, in one example, the apparatus 500 can include a separate reservoir container for additional gases (e.g., oxidizers, reductants, halides as described herein) that can be added as one or more (additive) gases to the process of the first and / or second embodiments. The apparatus 500 of Figure 5 can include a pump system 522 for generating and maintaining the required pressure within the process chamber 585.

[0121] Apparatus 500 can further comprise a control unit 518, which can be, for example, part of a computer system 520. In one example, apparatus 500 can be configured such that computer system 520 and / or control unit 518 control process parameters of the methods disclosed herein. This configuration can enable controlled or automated performance of the inventive methods specified herein, e.g., performance without manual intervention. This configuration of apparatus 500 can be achieved or enabled, for example, by a computer program according to the present invention, as described herein.

[0122] Additionally, at least one of the following can be included as a first gas (e.g., as a deposition gas) in the present invention: (metal, transition element, main group) alkyls, such as cyclopentadienyl (Cp) or methylcyclopentadienyl (MeCp), trimethylplatinum (CpPtMe3 or MeCpPtMe3), tetramethyltin (SnMe4), trimethylgallium (GaMe3), ferrocene (Cp2Fe), bisarylchromium (Ar2Cr), and other compounds of this type. Additionally, at least one of the following can be included as a first gas in the present invention: (metal, transition element, main group) carbonyls, such as chromium hexacarbonyl (Cr(CO)6), molybdenum hexacarbonyl (Mo(CO)6), tungsten carbonyl (W(CO)6), dicobalt octacarbonyl (Co2(CO)8), triruthenium dodecacarbonyl (Ru3(CO)). 12 , iron pentacarbonyl Fe(CO)5, and other compounds of this type. Additionally, one of the following can be included as the first gas in the present invention: (metal, transition element, main group) alkoxides, such as tetraethoxysilane Si(OC2H5)4, tetraisopropoxytitanium Ti(OC3H7)4, and other compounds of this type.

[0123] Additionally, at least one of the following can be included as a first gas in the present invention: (metal, transition element, main group) halides, such as WF6, WCl6, TiCl6, BCl3, SiCl4, and other compounds of this type. Additionally, at least one of the following can be included as a first gas in the present invention: (metal, transition element, main group) complexes, such as copper bis(hexafluoroacetylacetonate) Cu(CF6HO2)2, dimethyl gold trifluoroacetylacetonate Me2Au(CF3H4O2), and other compounds of this type. Additionally, at least one of the following can be included as a first gas in the present invention: organic compounds, such as CO, CO2, aliphatic or aromatic hydrocarbons, components of vacuum pump oil, volatile organic compounds, and other such compounds. [Explanation of symbols]

[0124] 1000 EUV Mask Details 1010 Transparent defect 1020 Repair materials D. Defective local state R the repaired local state PE Pattern Elements RV Repair Procedures 200 Reflective lithography mask (EUV mask) 210 Substrate 215 Back side of the board 220 Thin Conductive Layer 225 Front of the board 230 Molybdenum (Mo) layer 235 Silicon (Si) layer 240 Capping Layer 245 Buffer layer 250 Absorbing Layer 255 Anti-reflection layer 270 Deposited multilayer structure 280 Absorbent Area 285 Reflective Area S1 Test Structure S2 test structure S3 Test Structure S4 test structure S5 Test Structure 500 devices 501 Scanning Electron Microscope 502 Lithography Mask 504 Sample stage 506 Electron Gun 508 Beam Shaping Elements 509 Electron Beam 510 Focused electron beam 512 Beam Shaping Elements 514 detector 518 Control Unit 520 Computer Systems 522 Pump System 531 Control Valve 532 Gas Inlet System 546 Control Valve 547 Gas Inlet System 585 Process Chamber G1 First reservoir G2 Second reservoir

Claims

1. A method for processing objects for lithography, To supply the first gas, Supplying a second gas containing a second molecule capable of reverse vibration, Supplying a particle beam to the work area of ​​the lithography object to generate a deposit material in the work area, based at least partially on the first gas and the second gas, The second gas is supplied at a gas flow rate of 0.1 sccm to 0.5 sccm, method.

2. The method according to claim 1, wherein the second molecule comprises ammonia NH3.

3. The method according to claim 1 or claim 2, wherein the particle beam is supplied with a residence time of 0.1 microseconds to 10 microseconds, preferably 0.3 microseconds to 7 microseconds.

4. The method according to claim 1 or 2, wherein the first gas and / or the second gas are supplied so that the deposited material is at least partially formed in the gas phase without the influence of the particle beam.

5. The method according to claim 1 or claim 2, wherein the first gas comprises a first molecule containing a carbonyl compound.

6. The method according to claim 5, wherein the first molecule comprises a metal carbonyl.

7. The method according to claim 6, wherein the metal carbonyl includes chromium carbonyl.

8. The method according to claim 1 or claim 2, wherein the deposited material contains chromium nitride.

9. The method according to claim 8, wherein the chromium nitride contains at least 10 atomic percent nitrogen, preferably at least 15 atomic percent nitrogen, and more preferably at least 20 atomic percent nitrogen.

10. The method according to claim 1 or 2, wherein the deposited material is produced such that defects in the object for lithography are repaired.

11. The method according to claim 10, wherein the defect includes a transparency defect.

12. A method for processing the surface material of an object for lithography, Supplying a second gas containing a second molecule capable of reverse vibration, In order to passivate the surface material in the work area based at least partially on the second gas, a particle beam is supplied to the work area of ​​the object for lithography, Includes, The second molecule contains NH3, method.

13. The method according to claim 12, further comprising generating the surface material in the work area based at least partially on the supply of a first gas and the particle beam, prior to the passivation of the surface material.

14. The method according to claim 12 or claim 13, wherein the passivation includes generating a passivation layer on the surface material.

15. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the inversion vibration includes a pyramidal inversion of the second molecule.

16. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the second molecule includes a trigonal pyramidal structure.

17. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the second molecule contains nitrogen and hydrogen in the compound.

18. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the object for lithography includes a lithography mask.

19. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the second molecule comprises H₂N-NH₂.

20. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the second molecule contains nitrogen and halogen in the compound.

21. The method according to claim 20, wherein the second molecule comprises at least one of NF3, NCl3, NI3, and NBr3.

22. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the second molecule contains nitrogen, hydrogen, and halogen in the compound.

23. The method according to claim 22, wherein the second molecule comprises at least one of the following molecules: NH 2 X (where X contains halogen), NHX 2 (where X contains halogen).

24. The second molecule is NO 2 The method according to claim 1, claim 2, claim 12, or claim 13, having an absorption probability in the work area that is lower than that of a molecule.

25. The method according to claim 1, claim 2, claim 12, or claim 13, wherein the particle beam includes an electron beam.

26. An apparatus for processing objects for lithography, A means for supplying the first gas, A means for supplying a second gas containing a second molecule capable of performing inversion vibrations, Means for supplying a particle beam, Equipped with, The apparatus is configured to perform the method according to claim 1, claim 2, claim 12, or claim 13. Device.

27. A lithography object, wherein the lithography object is processed by the method described in claim 1, claim 2, claim 12, or claim 13.

28. A method for lithography of a semiconductor-based wafer, comprising lithographically transferring a pattern associated with a lithographic object onto the wafer, wherein the lithographic object is processed by the method of claim 1, claim 2, claim 12, or claim 13.

29. A computer program including an instruction, wherein when the instruction is executed by a computer system, the instruction causes the computer system to execute the method according to claim 1, claim 2, claim 12, or claim 13.

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