Method of repairing lithographic mask and lithographic mask

Abstract

A method of repairing a lithographic mask is provided. The method includes receiving a lithographic mask having a capping layer, the capping layer including a damaged region, identifying a location and a size of the damaged region of the capping layer, determining a repair duration based on the size of the damaged region of the capping layer, and forming a capping patch layer in the damaged region of the capping layer. The embodiment of the invention also provides a photoetching mask.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a method of repairing a photolithography mask and a photolithography mask. Background Art

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC materials and design have produced generations of ICs, each with smaller and more complex circuits than the previous generation. Over the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased, while geometry size (i.e., the smallest component (or line) that can be created using a manufacturing process) has decreased. This scaling down has also increased the complexity of processing and manufacturing ICs, and similar developments in IC processing and manufacturing are needed to achieve these advances. Summary of the invention

[0003] Some embodiments of the present disclosure provide a method for repairing a photolithography mask, the method comprising: receiving a photolithography mask having a covering layer, wherein the covering layer includes a damaged area; identifying a location and a size of the damaged area of ​​the covering layer; determining a repair duration based on the size of the damaged area of ​​the covering layer; and forming a covering patch layer in the damaged area of ​​the covering layer.

[0004] Other embodiments of the present disclosure provide a photolithography mask, which includes: a substrate; a reflective multilayer stack located above the substrate; a covering layer located above the reflective multilayer stack; and a patterned absorption layer located above the covering layer, the patterned absorption layer defining a reflective region of the photolithography mask, wherein the covering layer includes an amorphous portion located in the reflective region of the photolithography mask and surrounded by a polycrystalline portion, the polycrystalline portion includes a first ruthenium-containing material, and the amorphous portion includes a second ruthenium-containing material.

[0005] Another embodiment of the present disclosure provides a photolithography mask, which includes: a substrate; a reflective multilayer stack located above the substrate; a covering layer located above the reflective multilayer stack, the covering layer including a ruthenium-containing material; a covering patch layer surrounded by the covering layer, the covering patch layer including an amorphous ruthenium-containing material; and a patterned absorption layer located above the covering layer, the patterned absorption layer defining a reflective region of the photolithography mask, wherein the covering patch layer is located in the reflective region of the photolithography mask. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] When read in conjunction with the accompanying drawings, aspects of the present disclosure can be best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, the dimensions of the various components may be arbitrarily increased or reduced for clarity of discussion.

[0007] Figure 1is a cross-sectional view of an extreme ultraviolet (EUV) photomask according to some embodiments.

[0008] FIG. 2A to FIG. 2D According to some embodiments, there are various defects Figure 1 Cross-sectional view of an EUV photomask.

[0009] Figure 3 is a flow chart of a method of repairing a damaged capping layer of an EUV mask according to some embodiments.

[0010] FIG. 4A to FIG. 7 According to some embodiments, Figure 3 Various views of an EUV photomask at various stages of repair of the method. DETAILED DESCRIPTION

[0011] The following disclosure provides many different embodiments or examples for implementing the different components of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component above or on a second component may include an embodiment in which the first component and the second component are directly contacted, and may also include an embodiment in which an additional component may be formed between the first component and the second component so that the first component and the second component may not be in direct contact. In addition, the present disclosure may repeat reference numerals and / or characters in various examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the individual embodiments and / or configurations discussed.

[0012] Additionally, for ease of description, spatially relative terms such as "below," "beneath," "lower," "above," and "upper" may be used herein to describe the relationship of one element or component to another element or component as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should likewise be interpreted accordingly.

[0013] When manufacturing integrated circuits, photolithography is often used to form various components, such as metal lines, in a semiconductor substrate. To form these components, a photomask is used to form a pattern in a photoresist layer. Removing areas of the photoresist layer exposes the underlying substrate to an etching process that is used to form trenches where the metal is subsequently placed.

[0014] One type of lithography is extreme ultraviolet (EUV) lithography using an EUV photomask. In one example of an EUV photomask, a patterned absorber layer is formed on a reflective multilayer stack. In order to expose the photoresist layer on the semiconductor substrate, EUV light is projected onto the photomask through a plurality of mirrors. The exposed portion of the reflective multilayer stack then reflects the light onto the semiconductor substrate on which the integrated circuit is to be formed. Thus, the light exposes the photoresist layer deposited on the semiconductor substrate.

[0015] The reflective multilayer EUV photomask architecture is extremely susceptible to surface oxidation and contamination. As a result, EUV photomasks will require regular cleaning processes to reduce defectivity—up to twenty times or more to meet the service life goals of high-volume manufacturing (HVM). EUV photomasks typically include a cover layer located between the reflective multilayer stack and the absorber layer. The cover layer protects the reflective multilayer stack from any undesirable damage that may be caused during the absorber layer etching, repair, and regular cleaning processes. However, the cover layer is also susceptible to damage and may wear out with repeated use. For example, EUV photomasks are typically cleaned after a certain number of uses. During cleaning, acids and chemicals may penetrate into the cover layer, causing damage to the cover layer. Damage to the cover layer reduces EUV reflectivity, which may cause critical dimension (CD) offset and non-uniformity. If a severely damaged cover layer is not repaired, such a damaged EUV photomask needs to be scrapped to ensure the quality of the IC.

[0016] In an embodiment of the present disclosure, the damaged covering layer is first repaired by using images obtained from a scanning electron microscope (SEM) tool and an atomic force microscope (AFM) tool to identify the position and size of the damaged area in the covering layer. The repair duration is then calculated based on the remaining thickness of the covering layer in the damaged area and the area of ​​the damaged area. Additional covering material is then deposited in the damaged area of ​​the covering layer using a combination of a focused electron beam and a precursor gas containing a Ru complex. The repair method of the present disclosure is capable of quickly repairing a damaged covering layer. Thus, the service life of the EUV photomask can be extended, thereby reducing the overall cost of the EUV photomask.

[0017] Figure 1 is a cross-sectional view of an EUV photomask 100 for EUV lithography according to various embodiments of the present disclosure.

[0018] The EUV photomask 100 includes a substrate 102. The substrate 102 is selected to minimize image distortion due to heating of the mask by enhanced illumination radiation. The substrate 102 includes a material having a low defect level and a smooth surface. In some embodiments, the substrate 102 includes a low thermal expansion material (LTEM). The LTEM may include fused silica, calcium fluoride, silicon carbide, black diamond, titanium oxide doped silicon oxide (SiO2 / TiO2), or other suitable LTEM. Optionally, the substrate 102 includes other materials, such as quartz, fused silica, or glass, depending on the design requirements of the mask. In some embodiments, the substrate 102 has a thickness in a range of about 1 mm to about 7 mm. In some examples, if the thickness of the substrate 102 is too small, the risk of cracking or warping of the EUV photomask 100 is increased. On the other hand, in some examples, if the thickness of the substrate is too large, the weight of the EUV photomask 100 is unnecessarily increased.

[0019] In addition, a conductive layer 104 may be formed on the back side of the substrate 102 for electrostatic clamping purposes. In some embodiments, the conductive layer 104 includes chromium nitride (CrN), tantalum boride (TaB), or other suitable conductive materials. In some embodiments, for example, the conductive layer 104 is formed by a deposition process such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or physical vapor deposition (PVD). The thickness of the conductive layer 104 is controlled so that the conductive layer 104 is optically transparent.

[0020] EUV photomask 100 includes a reflective multilayer stack 110 (also referred to as a multilayer mirror (MLM)) disposed over a front surface of substrate 102 (i.e., opposite to the surface on which conductive layer 104 is formed). Reflective multilayer stack 110 is designed to reflect radiation light directed toward substrate 102. In some embodiments, reflective multilayer stack 110 includes alternating layers of two materials deposited on top of substrate 102 to act as a Bragg reflector that maximizes reflection of radiation light (such as EUV light having a wavelength of 13.5 nm). In some embodiments, reflective multilayer stack 110 is configured to achieve a reflectivity of about 60% to about 75% at a peak EUV radiation wavelength.

[0021] The combination of two materials in the alternating layers is selected to provide a large refractive index difference between the two layers (e.g., to achieve a large reflectivity at the interface of the two layers according to the Fresnel equation), and also to provide a small extinction coefficient for each layer (e.g., to minimize absorption). In some embodiments, the reflective multilayer stack 110 includes molybdenum-silicon (Mo / Si) layer pairs, and in each layer pair, the molybdenum layer is located above or below the silicon layer. In some embodiments, the reflective multilayer stack 110 includes molybdenum-beryllium (Mo / Be) layer pairs, and in each layer pair, the molybdenum layer is located above or below the beryllium layer. The thickness of each layer in each layer pair in the reflective multilayer stack 110 is adjusted based on the wavelength and angle of incidence of light (e.g., EUV radiation) incident on the mask so that the mask achieves maximum constructive interference of light reflected from different interfaces of the reflective multilayer stack 110. Generally, the reflectivity of the reflective multilayer stack 110 increases as the number of layer pairs in the reflective multilayer stack 110 increases. Accordingly, in principle, if the number of layer pairs is large enough and the extinction coefficient of the layer materials is close to zero, the reflectivity of the reflective multilayer stack 110 can be close to 100% regardless of the refractive index difference of the materials of the layers in the layer pairs. However, in the EUV wavelength range, the highest reflectivity that can be achieved is limited by the extinction coefficient of the materials used for the layers in the reflective multilayer stack 110. In some embodiments, the number of layer pairs in the reflective multilayer stack 110 is 20 to 80. For example, in the illustrated embodiment, in order to achieve more than 90% of the maximum achievable reflectivity (using the selected materials) of the reflective multilayer stack 110 and minimize the blank mask manufacturing time and cost, the reflective multilayer stack 110 includes about 40 layer pairs, such as 40 Mo / Si pairs. By further example, the Mo / Si pairs include a silicon layer and a molybdenum layer, the silicon layer having a thickness of 3nm to 5nm (e.g., about 4nm), and the molybdenum layer having a thickness of 2nm to 4nm (e.g., about 3nm). Alternatively, the reflective multilayer stack 110 includes any other number of layer pairs depending on the reflectivity specification of the mask. In other alternatives, the reflective multilayer stack 110 may include a layer group, in other words, three or more layers having groups of different refractive indices and other properties to maximize reflectivity.

[0022] In the present example, the reflective multilayer stack 110 includes molybdenum-silicon (Mo / Si) layer pairs. The reflective multilayer stack 110 includes about 40 (Mo / Si) layer pairs, and each Mo / Si layer pair has a total thickness of about 7 nm.

[0023] In some embodiments, each layer in the reflective multilayer stack 110 is deposited over the substrate 102 and underlying layers using ion beam deposition or DC magnetron sputtering. The deposition method used helps ensure that the thickness uniformity of the reflective multilayer stack 110 is better than about 0.85 across the substrate 102. For example, to form the Mo / Si reflective multilayer stack 110, a Mo target is used as a sputtering target, and an argon (Ar) gas (with a thickness from 1.3×10 -2 Pa to 2.7×10 -2 Pa) as a sputtering gas, an Mo layer was deposited at a deposition rate of 0.03 nm / sec to 0.30 nm / sec with an ion acceleration voltage of 300 V to 1,500 V, and then a Si target was used as a sputtering target, and an Ar gas (with a pressure of 1.3 × 10 -2 Pa to 2.7×10 -2 The Si layer was deposited at a deposition rate of 0.03 nm / sec to 0.30 nm / sec with an ion acceleration voltage of 300 V to 1,500 V using a gas pressure of 1,400 Pa as a sputtering gas. The Mo / Si reflective multilayer stack was deposited by stacking the Si layer and the Mo layer in 40 to 50 cycles, each cycle including the above steps.

[0024] The EUV photomask 100 includes a capping layer 120 deposited on the reflective multilayer stack 110. Because the capping layer 120 has different etching characteristics from the absorption layer, the capping layer 120 provides protection for the reflective multilayer stack 110, such as as an etch stop layer in the subsequent patterning of the absorption layer or the repair process of the EUV photomask 100. In addition, the same capping layer 120 is also designed to act as an anti-oxidation barrier layer to protect the reflective multilayer stack 110 from oxidation. At the same time, the capping layer 120 will not reduce the EUV reflectivity of the reflective multilayer stack 110. The capping layer 120 may include ruthenium (Ru) or a Ru-based compound. In some embodiments, the Ru-based compound may include one or more elements, such as niobium (Nb), tantalum (Ta), zirconium (Zr), boron (B), nitrogen (N) or oxygen (O). In some embodiments, the Ru-based compound may include RuO2, RuNb, RuNbO, RuON, RuN, RuNbON, RuTaON, RuZr, RuZrO or RuB. In some embodiments, the Ru-containing compound is RuNb, wherein the atomic weight of Nb is less than or equal to 50 atomic (at) %, such as about 10 atomic %, 20 atomic %, 30 atomic % or 40 atomic %.

[0025] The capping layer 120 has a thickness that is thick enough to provide oxidation resistance and etching resistance to the underlying reflective multilayer stack 110, but not so thick as to reduce the EUV reflectivity of the reflective multilayer stack 110. In some embodiments, the capping layer 120 may have a thickness in a range of 1 nm to 10 nm. In some embodiments, the capping layer 120 has a thickness in a range of 2 nm to 4 nm. In some embodiments, the capping layer 120 has a thickness of about 2.5 nm.

[0026] In some embodiments, for example, the capping layer 120 is formed using a deposition process, such as ion beam deposition, chemical vapor deposition (CVD), physical vapor deposition (PVD) (such as DC magnetron sputtering), or atomic layer deposition (ALD). In an example in which a Ru layer is formed as the capping layer 120 using ion beam deposition, the deposition can be performed in an Ar environment by using a Ru target as a sputtering target. In some embodiments, the capping layer 120 thus formed can have a polycrystalline structure having a plurality of grains of various sizes and orientations. Optionally, the capping layer 120 is formed as an amorphous layer.

[0027] The EUV photomask 100 also includes a patterned absorption layer 130 formed on the cover layer 120. The patterned absorption layer 130 is designed to absorb radiation light (such as EUV light) during the photolithography exposure process. The radiation light passes through the openings of the patterned absorption layer 130 and is reflected by the reflective multilayer stack 110, thereby imaging the IC pattern onto an IC substrate (such as a silicon wafer). In some embodiments, the patterned absorption layer 130 includes chromium (Cr), chromium oxide (CrO), titanium nitride (TiN), tantalum nitride (TaN), tantalum (Ta), titanium (Ti), aluminum copper (Al-Cu), palladium (Pd), tantalum boron nitride (TaBN), tantalum boron oxide (TaBO), aluminum oxide (Al2O3), silver oxide (Ag2O), or other suitable materials. In another embodiment, the patterned absorption layer 130 includes multiple layers.

[0028] The patterned absorption layer 130 includes features such as IC patterns defined thereon according to an IC layout pattern. Figure 1 As shown, the patterned absorber layer 130 defines opaque regions 140 and reflective regions 150. In the opaque regions 140, the absorber layer remains on the EUV photomask 100, while in the reflective regions 150, the absorber layer is removed.

[0029] Still refer to Figure 1In some embodiments, a pellicle 160 may be located above the EUV photomask 100 to protect the pattern side of the EUV photomask 100 from contamination during storage, use, or transportation. The pellicle 160 and the EUV photomask 100 may form a closed internal space 170 enclosed by the pellicle 160 and the EUV photomask 100. The patterned surface of the EUV photomask 100 is enclosed in the internal space 170, and thus the patterned surface of the EUV photomask 100 is protected from contamination during the photolithography patterning process, mask transportation, and mask handling. In some embodiments, the pellicle 160 includes a pellicle frame 162, which may be located above the patterned absorption layer 130. In some embodiments, the pellicle frame 162 may be made of Si, SiC, SiN, glass, a low thermal expansion coefficient material (such as aluminum alloy, titanium alloy, Invar, Kovar, etc.), other suitable materials, or combinations thereof. In some embodiments, suitable processes for forming the dust-proof film frame 162 may include a machining process, a sintering process, a photochemical etching process, other applicable processes, or a combination thereof. The dust-proof film 160 may also include a dust-proof film 164, which is attached to the dust-proof film frame 162 via an adhesive. The dust-proof film 164 is a transparent film for the radiation beam used in the photolithography patterning process and also has a thermally conductive surface. In some embodiments, the dust-proof film 164 may include silicon, such as polycrystalline silicon (poly-Si), amorphous silicon (a-Si), doped silicon (such as phosphorus-doped silicon SiP or SiC) or a silicon-based compound, such as SiN or MoSixNy or a combination (SiN / MoSiN). Optionally, the dust-proof film 164 may include a polymer, graphene, a carbon network film, a carbon nanotube, a silicon carbon nanotube, a boron nitride nanotube, a carbon nanotube bundle, or other suitable materials, including a nanotube bundle. The dust film 164 has a thickness sufficient for mechanical strength, but in some embodiments, the thickness does not reduce the transparency of the film to EUV radiation from the radiation source by more than 15% in some embodiments, by more than 10% in some embodiments, or by more than 5% in some embodiments. In some examples, the dust film 164 has a thickness in a range between 30 nm and 50 nm.

[0030] As described above, the capping layer 120 of the EUV photomask 100 is susceptible to damage. FIG. 2A to FIG. 2D 1 shows various types of damage to the capping layer 120 of the EUV photomask 100 according to some embodiments of the present disclosure. For example, a strong cleaning method such as a Megasonic process may cause a partial loss of the capping material of the capping layer 120 or peeling of the capping layer 120, thereby generating pits 202 in the capping layer 120, such as Figure 2AOver time, the pit 202 may expand, eventually causing complete loss of the covering material within the pit 202, thereby exposing the reflective multilayer stack 110 below. Figure 2B In addition, with repeated use, the cover layer 120 may be etched during the cleaning process, causing the cover layer 120 to gradually become thinner over time, as shown in FIG. Figure 2C In addition, long-term use and repeated cleaning processes may cause the cover layer 120 in the reflective area 150 to be completely worn away. Figure 2D As shown, within a certain period of time, the capping layer 120 in the reflective region 150 of the EUV photomask 100 may undergo complete removal. As a result, the surface of the reflective multilayer stack 110 is no longer protected by the capping layer 120 . FIG. 2A to FIG. 2D All of these types of damage shown in may result in degradation of the reflective multilayer stack 110 and loss of EUV reflectivity.

[0031] Figure 3 1 is a flow chart of a method 300 for repairing a cover layer 120 of a photomask 400 according to some embodiments of the present disclosure. Additional operations may be provided before, during, and after the method 300, and some of the operations described may be replaced, eliminated, or moved for additional embodiments of the method. The method 300 is an example and is not intended to limit the present disclosure beyond the scope explicitly recited in the claims. FIG. 4A to FIG. 7 Method 300 is described. FIG. 4A to FIG. 7 are various views of EUV photomask 400 at various stages of repair of method 300 .

[0032] refer to Figure 3 and FIG. 4A to FIG. 4B According to some embodiments, the method 300 begins at operation 302 by providing an EUV photomask 400 having a capping layer 120 that requires repair. Figure 4A is a top view of EUV photomask 400 according to some embodiments. Figure 4B is along the line A-A' Figure 4A A cross-sectional view of an EUV photomask 400 is shown. Figure 4A As shown, the cover layer 120 includes a damaged region 402 in the reflective region 150 of the EUV photomask 400. Figure 4B As shown, within the damaged region 402, cover material has been lost, thereby creating a pit in the cover layer 120. Therefore, the damaged region 402 is also referred to as a cover material loss region.

[0033] refer to Figure 3According to some embodiments, the method 300 proceeds to operation 304, where the EUV photomask 400 is placed into a first mask inspection tool. In some embodiments, the first mask inspection tool is a scanning electron microscope (SEM) tool. The pressure of the SEM tool can be controlled at 1x10 -6 mbar to 1x10 -7 in the millibar range.

[0034] refer to Figure 3 According to some embodiments, the method 300 proceeds to operation 306, where the EUV photomask 400 is inspected using a first mask inspection tool to identify a damaged region 402. In some embodiments, inspecting the EUV photomask 400 includes scanning a surface of the cover layer 120 using a tip of the first mask inspection tool to obtain an image of the damaged region 402. After obtaining the scanned image, the scanned image is input into the algorithm. In addition, at operation 306, the location of the damaged region 402 may be recorded by coordinates in a grid based on a distance from an edge of the scanned image. The coordinates of the damaged region 402 may be represented as (x value, y value).

[0035] refer to Figure 3 According to some embodiments, method 300 proceeds to operation 308, where the scanned image is analyzed. In some embodiments, the scanned image is analyzed using, for example, an image processor to determine the size, i.e., the length and width, of damaged region 402. The area of ​​damaged region 402 is then calculated based on the size of damaged region 402.

[0036] refer to Figure 3 According to some embodiments, the method 300 proceeds to operation 310, where the EUV photomask 400 is placed into a second inspection tool and the remaining thickness (t) of the capping layer 120 in the damaged region 402 is measured using the second inspection tool. In some embodiments, the second inspection tool is an atomic force microscope (AFM) tool. Therefore, the AFM input can be used to determine the deposition height in a subsequently performed repair deposition process.

[0037] refer to Figure 3 According to some embodiments, the method 300 proceeds to operation 312, where a repair duration (i.e., required deposition time) is calculated based on the remaining thickness of the cover layer 120 in the damaged region 402 and the area of ​​the damaged region 402. In some embodiments, operation 312 may be performed before operation 310.

[0038] refer to Figure 3 and Figure 5According to some embodiments, method 300 proceeds to operation 314, at which EUV photomask 400 is placed in a mask repair tool. In some embodiments, the mask repair tool is an electron beam (E beam) based mask repair tool, in which the electron beam column is combined with a gas injection system. Operation 314 also includes injecting a precursor gas 410 including a metal complex into the mask repair tool via the gas injection system. In some embodiments, the mask repair tool is a SEM tool. In some embodiments, the mask inspection or repair operation can be performed by the same tool. In some embodiments, the precursor gas 410 also includes a reactive gas including ammonium (NH3) or nitrous oxide (N2O).

[0039] In the mask repair tool, the elements of the precursor gas 410 are adsorbed onto the surface of the cap layer 120 and further diffused into the damaged region 402 of the cap layer 120. According to some embodiments, Figure 5 is a cross-sectional view of the EUV photomask 400 after an element 412 of a precursor gas 410 is adsorbed onto the surface of the cap layer 120 in the damaged region 402 .

[0040] In embodiments of the present disclosure, the flow rate of the precursor gas 410 is selected to ensure that the repair of the EUV photomask 400 is completed within the repair duration, and to ensure that the volume repair of the EUV photomask 400 is facilitated. For example, in some embodiments, the flow rate of the precursor gas 410 can be selected in the range of 10,000 to 100,000 standard cubic centimeters per minute (sccm). In some embodiments, the flow rate of the precursor gas 410 can be in the range of 1 to 100,000 sccm. Higher pressures of the precursor gas 410 in the SEM tool generally result in faster deposition of the metal complex, and higher flow rates of the precursor gas 410 generally result in higher pressures thereof.

[0041] In some embodiments, the metal complex comprises a Ru complex having the following formula:

[0042] ML x

[0043] in:

[0044] M is Ru;

[0045] x is an integer from 1 to 6; and

[0046] L, at each occurrence, is independently acetylacetone, alkylcyclopentadienyl, benzene, carbonyl, cyclopentadienyl, cyclohexadiene, fluorinated amino alcohol, pentadienyl, pyrrolyl, trifluoroalkyl or halogen ligand, derivatives thereof, or combinations thereof.

[0047] x is the coordination number, which indicates the number of positions where the ligand L binds to the Ru ion. In some embodiments, x is 2. In some embodiments, x is 3. In some embodiments, x is 4. In some embodiments, x is 5. In some embodiments, x is 6.

[0048] In some embodiments, the Ru complex has one of the following structures:

[0049]

[0050]

[0051]

[0052] in:

[0053] R, R1 and R2 are each independently alkyl or alkoxy; and

[0054] y is an integer from 1 to 5.

[0055] In some embodiments, R, R1, and R2 are each independently methyl, ethyl, butyl, or hexyl.

[0056] In some embodiments, R, R1, and R2 are each independently methoxy, ethoxy, or 2-methoxyethyl.

[0057] In some embodiments, y is 2 or 3.

[0058] In some embodiments, the Ru complex has one of the following structures:

[0059]

[0060] refer to Figure 3 and Figure 6 According to some embodiments, the method 300 proceeds to operation 316 where a local deposition is performed to repair the cover layer 120 by forming a cover patch layer 420 in the damaged region 402 of the cover layer 120. According to some embodiments, Figure 6 is a cross-sectional view of the EUV photomask 400 after forming a cover patch layer 420 in the damaged region 402 of the cover layer.

[0061] like Figure 6As shown, the precursor gas 410 and the cover layer 120 are irradiated with a focused radiation beam 430. The focused radiation beam 430 triggers a chemical reaction of the Ru complex, and thus the Ru-containing compound can be deposited in the damaged area 402 of the cover layer 120. In some embodiments, the focused radiation beam 430 is high-energy radiation, such as an electron beam. When an electron beam is used, the deposition of the Ru complex is also referred to as electron beam induced deposition. In some embodiments, the focused radiation beam 430 is a laser beam. The cover layer 120 absorbs some of the energy of the radiation beam 430, thereby generating secondary electrons.

[0062] Since the radiation beam 430 irradiates only the damaged region 402 of the cover layer 120, the Ru-containing compound is deposited in the damaged region 402. The resulting cover patch layer 420 has a shape corresponding to the damaged region 402 in the cover layer.

[0063] The voltage of the radiation beam 430 is used to limit the charging of the surface of the EUV photomask 400. In some embodiments, the voltage of the radiation beam 430 for depositing the cover patch layer 420 is approximately in the range of about 0.4 kilovolts (kV) to 3 kV, for example, about 1 kV. Generally, the higher the voltage of the radiation beam 430, the higher the spatial resolution provided. The radiation beam 430 stays above the surface of the damaged area 402 for a predetermined time, and then moves to the next point above the surface of the damaged area 402 with a predetermined step size. The stay and movement of the radiation beam 430 are repeated until a cover patch layer 420 with a predetermined thickness is formed in the damaged area 402. In some embodiments, the predetermined time that the radiation beam 430 stays above a point on the surface of the damaged area 402 is approximately in the range of 0.05 microseconds to 10 microseconds, and the predetermined step size for moving the radiation beam 430 from one point to the next point along the surface of the damaged area 402 is approximately in the range of 1 nm to 10 nm. For an embodiment, the EUV photomask 400 may be positioned at any angle relative to the incident radiation beam 430 to allow the cover patch layer 420 to be constructed at any angle and in any orientation relative to the surface of the damaged region 402 .

[0064] The cover patch layer 420 may include a cover material that is the same as or different from the material forming the cover layer 120. In some embodiments, the cover patch layer 420 includes a Ru-containing compound that is the same as the Ru-containing compound that provides the cover layer 120. In some embodiments, the cover patch layer 420 includes a Ru-containing compound that is different from the Ru-containing compound that provides the cover layer 120. In some embodiments, the cover patch layer 420 includes Ru or RuO2. In some embodiments, the cover patch layer 420 includes an amorphous Ru-containing compound. In some embodiments, the cover patch layer 420 includes a crystalline Ru-containing compound. In this embodiment, as Figure 6As shown, the cover patch layer 420 is embedded in the cover layer 120 so that the bottom surface of the cover patch layer 420 contacts the cover layer 120. In some embodiments, both the cover layer 120 and the cover patch layer 420 are amorphous. In some embodiments, the cover layer 120 has a polycrystalline structure, and the cover patch layer 420 has an amorphous structure.

[0065] In the example where the covering material in the damaged area 402 is completely lost, so that the top surface of the reflective multilayer stack 110 is located near the damaged area 402, the covering patch layer 420 formed in the damaged area 402 is in direct contact with the top surface of the reflective multilayer stack 110, such as Figure 7 shown.

[0066] After depositing the capping patch layer 420, a cleaning process may be performed to clean the surface of the EUV photomask 400. In some embodiments, a standard acid-based wet cleaning chemistry may be used to clean the surface of the EUV photomask 400. The process includes two steps: removing organic matter by a mixture of sulfuric acid and hydrogen peroxide (SPM), and then cleaning particles with megasonic waves by an SC1 solution consisting of a mixture of NH4OH (ammonium hydroxide), H2O2 (hydrogen peroxide), and H2O.

[0067] In some embodiments, once the EUV photomask repair operation is completed, the method 300 returns to operation 304 to perform another photomask inspection operation. The inspection operation is to ensure that the cover layer has been successfully repaired. The iteration of operations 304 to 316 will continue until all damaged areas in the cover layer 120 are found and equipped.

[0068] Once the EUV photomask 400 is repaired and cleaned, the EUV photomask 400 can be used to form a pattern, such as a structure on a semiconductor substrate (not shown). For example, the EUV photomask 400 can be placed in a lithography scanner. Once in place, the EUV photomask 400 can be irradiated by an energy source, and the patterned absorption layer 130 blocks part of the light to form a patterned light pattern. The patterned light pattern can be focused and directed to the photoresist on the semiconductor substrate, thereby irradiating the photoresist with a desired pattern. Once irradiated, the photoresist can be developed and used as a mask for devices, metallization layers, isolation regions, and other structures on or within a semiconductor substrate.

[0069] One aspect of the specification relates to a method for repairing a photolithography mask. The method includes receiving a photolithography mask having a cover layer, wherein the cover layer includes a damaged area, identifying a location and a size of the damaged area of ​​the cover layer, determining a repair duration based on the size of the damaged area of ​​the cover layer, and forming a cover patch layer in the damaged area of ​​the cover layer. In some embodiments, the cover patch layer is locally formed by electron beam induced deposition. In some embodiments, identifying the location and size of the damaged area of ​​the cover layer includes: placing the photolithography mask in a first mask inspection tool; scanning the surface of the photolithography mask to obtain an image of the damaged area of ​​the cover layer; recording the location of the damaged area of ​​the cover layer; analyzing the image to calculate the area of ​​the damaged area; placing the photolithography mask in a second mask inspection tool; and measuring the remaining thickness of the cover layer in the damaged area. In some embodiments, the first mask inspection tool is a scanning electron microscope (SEM) tool. In some embodiments, the second mask inspection tool is an atomic force microscope (AFM) tool. In some embodiments, forming the cover patch layer includes: placing a photolithography mask in a mask repair tool; injecting a precursor gas including a ruthenium complex into the mask repair tool; and focusing an electron beam of the mask repair tool on the damaged area for a repair duration, wherein the electron beam strikes the precursor gas to deposit the ruthenium-containing compound onto the damaged area. In some embodiments, the mask repair tool is a SEM tool. In some embodiments, the ruthenium complex has the following formula: ML x , wherein: M is Ru; L is independently acetylacetone, alkylcyclopentadienyl, benzene, carbonyl, cyclopentadienyl, cyclohexadiene, fluorinated amino alcohol, pentadienyl, pyrrolyl, trifluoroalkyl or halogen ligand, their derivatives or combinations thereof at each occurrence; and x is an integer from 1 to 6. In some embodiments, the ruthenium complex has one of the following structures:

[0070]

[0071]

[0072]

[0073] Wherein: R, R1 and R2 are each independently alkyl or alkoxy; and y is an integer from 1 to 5. In some embodiments, R, R1 and R2 are each independently methyl, ethyl, butyl or hexyl. In some embodiments, R, R1 and R2 are each independently methoxy, ethoxy or 2-methoxyethyl.

[0074] Another aspect of the present specification relates to a photolithography mask. The photolithography mask includes a substrate, a reflective multilayer stack located above the substrate, a capping layer located above the reflective multilayer stack, and a patterned absorption layer located above the capping layer, the patterned absorption layer defining a reflection region of the photolithography mask. The capping layer includes an amorphous portion located in the reflection region of the photolithography mask and surrounded by a polycrystalline portion. The polycrystalline portion includes a first ruthenium-containing material, and the amorphous portion includes a second ruthenium-containing material. In some embodiments, the amorphous portion of the capping layer is in direct contact with the reflective multilayer stack. In some embodiments, the amorphous portion of the capping layer is in direct contact with the polycrystalline portion of the capping layer. In some embodiments, the first ruthenium-containing material includes Ru or a first ruthenium-containing compound. In some embodiments, the first ruthenium-containing compound includes ruthenium and one or more elements selected from niobium (Nb), tantalum (Ta), zirconium (Zr), boron (B), nitrogen (N) and oxygen (O). In some embodiments, the second ruthenium-containing material includes a second ruthenium-containing compound different from the first ruthenium-containing compound.

[0075] Yet another aspect of the specification relates to a photolithography mask. The photolithography mask includes a substrate, a reflective multilayer stack located above the substrate, a capping layer located above the reflective multilayer stack, the capping layer including a ruthenium-containing material, a capping patch layer surrounded by the capping layer, the capping patch layer including an amorphous ruthenium-containing material, and a patterned absorption layer located above the capping layer, the patterned absorption layer defining a reflective region of the photolithography mask. The capping patch layer is located in the reflective region of the photolithography mask. In some embodiments, the amorphous ruthenium-containing material includes ruthenium or a ruthenium-containing compound, the ruthenium-containing compound including RuO2, RuNb, RuNbO, RuON, RuN, RuNbON, RuTaON, RuZr, RuZrO, or RuB. In some embodiments, the capping patch layer is laterally surrounded by the capping layer and is in direct contact with the reflective multilayer stack.

[0076] The features of several embodiments are summarized above so that those skilled in the art can better understand aspects of the present disclosure. Those skilled in the art should understand that they can easily use the present disclosure as a basis to design or modify other processes and structures for implementing the same purpose and / or achieving the same advantages as the embodiments introduced herein. Those skilled in the art should also appreciate that such equivalent constructions do not deviate from the spirit and scope of the present disclosure, and that they can make various changes, substitutions, and modifications herein without departing from the spirit and scope of the present disclosure.

Claims

1. A method for repairing a photolithography mask, comprising: receiving a photolithography mask having a cover layer, wherein the cover layer includes a damaged region; identifying the location and size of the damaged area of ​​the cover layer; determining a repair duration based on the size of the damaged area of ​​the cover layer; and A cover patch layer is formed in the damaged region of the cover layer.

2. The method according to claim 1, wherein: The covering patch layer is locally formed by electron beam induced deposition.

3. The method according to claim 1, wherein: Identifying the location and the size of the damaged area of ​​the cover layer includes: placing the photolithography mask in a first mask inspection tool; scanning a surface of the photolithography mask to obtain an image of the damaged region of the cover layer; recording the location of the damaged area of ​​the cover layer; analyzing the image to calculate the area of ​​the damaged region; placing the photolithography mask in a second mask inspection tool; and The remaining thickness of the cover layer in the damaged area is measured.

4. The method according to claim 3, wherein: The first mask inspection tool is a scanning electron microscope (SEM) tool.

5. The method according to claim 3, wherein: The second mask inspection tool is an atomic force microscope (AFM) tool.

6. The method according to claim 1, wherein: Forming the covering patch layer comprises: placing the photolithography mask in a mask repair tool; injecting a precursor gas including a ruthenium complex into the mask repair tool; and An electron beam of the mask repair tool is focused on the damaged area for the repair duration, wherein the electron beam impacts the precursor gas to deposit a ruthenium-containing compound onto the damaged area.

7. The method according to claim 6, wherein: The mask repair tool is a SEM tool.

8. The method of claim 6, wherein the ruthenium complex has the following formula: ML x , in: M is Ru; L is independently, at each occurrence, acetylacetone, alkylcyclopentadienyl, benzene, carbonyl, cyclopentadienyl, cyclohexadiene, fluorinated amino alcohol, pentadienyl, pyrrolyl, trifluoroalkyl or halogen ligand, derivatives thereof, or combinations thereof; and x is an integer of 1-6.

9. A photolithography mask comprising: substrate; a reflective multilayer stack located above the substrate; a cover layer located above the reflective multilayer stack; as well as a patterned absorption layer located above the cover layer, the patterned absorption layer defining a reflective region of the photolithography mask, The capping layer includes an amorphous portion located in the reflective region of the photolithography mask and surrounded by a polycrystalline portion, the polycrystalline portion includes a first ruthenium-containing material, and the amorphous portion includes a second ruthenium-containing material.

10. A photolithography mask comprising: substrate; a reflective multilayer stack located above the substrate; a capping layer overlying the reflective multilayer stack, the capping layer comprising a ruthenium-containing material; a covering patch layer, surrounded by the covering layer, the covering patch layer comprising an amorphous ruthenium-containing material; as well as a patterned absorption layer located above the cover layer, the patterned absorption layer defining a reflective region of the photolithography mask, Wherein, the covering patch layer is located in the reflective area of ​​the photolithography mask.

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