Reflective mask and method for manufacturing the same

Abstract

To provide: a reflective mask having a coating film that is uniformly formed along an outermost face and a side face of a transfer pattern and has a high EUV transmittance and high washing resistance; and a production method for the reflective mask.SOLUTION: A reflective mask 100 comprises: a substrate 1; a multilayer reflective film 2 that is formed on the substrate 1 and reflects incoming EUV light; an absorbent layer 4 that is formed on at least a portion of the multilayer reflective film 2 and absorbs incoming EUV light; and a coating film 5 that is formed on the multilayer reflective film 2 and the absorbent layer 4 and transmits incoming EUV light. The coating film 5 has an extinction coefficient k of 0.04 or less with respect to EUV light, is resistant to washing with a washing chemical liquid, and is formed on the front face and side face of the absorbent layer 4 with a uniform thickness.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reflective mask and a method for manufacturing a reflective mask. [Background technology]

[0002] In the manufacturing process of semiconductor devices, the demand for miniaturization of photolithography technology is increasing along with the miniaturization of semiconductor devices. In photolithography, the minimum resolution dimension of the transfer pattern is highly dependent on the wavelength of the exposure light source, and the shorter the wavelength, the smaller the minimum resolution dimension can be. For this reason, in the manufacturing process of semiconductor devices, the conventional exposure light source using ArF excimer laser light with a wavelength of 193 nm is being replaced by an EUV (Extreme UltraViolet) exposure light source with a wavelength of 13.5 nm.

[0003] Since EUV light has a short wavelength, most materials have high optical absorption. For this reason, photomasks for EUV (EUV masks) are reflective masks, unlike conventional transmissive masks. The reflective mask blank that is the basis for reflective masks is formed by sequentially forming a multilayer reflective layer that exhibits high reflectance to the wavelength of the exposure light source and an absorption layer for the wavelength of the exposure light source on a low thermal expansion substrate, and further forming a back conductive film for the electrostatic chuck in the exposure machine on the back surface of the substrate. There are also EUV masks that have a structure with a buffer layer between the multilayer reflective layer and the absorption layer.

[0004] When processing a reflective mask blank into a reflective mask, the absorbing layer is partially removed by EB (Electron Beam) lithography and etching technology, and in the case of a structure having a buffer layer, this is also partially removed to form a circuit pattern consisting of an absorbing part and a reflecting part. The light image reflected by the reflective mask thus produced is transferred onto a semiconductor substrate via a reflection optical system. In addition, as mentioned above, EUV lithography cannot use refractive optics that utilize the transmission of light, so the optical components of the exposure machine are mirrors rather than lenses. This creates a problem in that the light incident on the EUV mask and the light reflected from the EUV mask cannot be designed to be on the same axis, so EUV lithography normally employs a method in which the EUV light is incident with the optical axis tilted 6 degrees from the vertical direction of the EUV mask, and the reflected light reflected at an angle of minus 6 degrees is irradiated onto the semiconductor substrate.

[0005] In this way, because EUV lithography tilts the optical axis, the EUV light incident on the EUV mask casts a shadow on the circuit pattern of the EUV mask, which can cause a problem called the "projection effect," which deteriorates the transfer performance. Note that the circuit pattern formed on the EUV mask described above is also called the transfer pattern or the absorbing layer pattern. To address this problem, Patent Document 1 discloses a method of reducing the film thickness and the projection effect by adopting a compound material that has a high absorption property (extinction coefficient) for EUV light compared to a conventional absorption layer or phase shift film mainly composed of Ta.

[0006] Furthermore, if a photomask is highly reactive to acidic or alkaline cleaning chemicals, it will not be able to withstand repeated cleaning, shortening the lifespan of the photomask. Therefore, the photomask needs to be made of a compound material that has high resistance to acid and alkaline cleaning (hereinafter also simply referred to as "cleaning resistance"). However, the method of Patent Document 1 uses an absorption layer having two or more different compositions containing Ta as a main component, but does not mention washing resistance.

[0007] In addition, the method of Patent Document 2 discloses a method for improving the cleaning resistance of an absorbing layer by forming a top surface protective layer made of a component containing Ta and O on an absorbing layer mainly composed of Ta, Cr, and Pd. However, Patent Document 2 does not describe the protection of the sidewall of the absorbing layer during the formation of a transfer pattern, and the cleaning resistance including the sidewall is not clear. Furthermore, if the absorbing layer is mainly composed of a substance other than the above, the cleaning resistance of the absorbing layer and the top surface part will naturally be different. Therefore, when the photomask is repeatedly cleaned, damage occurs because the sidewall of the absorbing layer is not protected, which may cause a problem that adversely affects the pattern transferability.

[0008] In the technical field of optical masks, not EUV masks, a protective film is formed on a transfer pattern for the purpose of physical protection when the optical mask is exposed to close contact with a stepper, according to the method of Patent Document 3. Similarly, it is considered that cleaning resistance can be improved by forming a protective film on a transfer pattern, but in the field of EUV masks, when a protective film is formed on a multilayer film, a problem may occur in which the pattern transferability is reduced due to the absorption of EUV light by the protective film. Therefore, it is necessary to select a material with high transmittance to EUV light as the protective film. Furthermore, if the thickness of the protective film differs for each pattern, it may have a negative effect on the transferability, so it is necessary to form the protective film uniformly along the surface and side of the transfer pattern. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2007-273678 A [Patent Document 2] JP 2014-45075 A [Patent Document 3] Japanese Patent Application Publication No. 60-87327 Summary of the Invention [Problem to be solved by the invention]

[0010] Thus, in order to use an EUV mask repeatedly, the outermost layer of the EUV mask needs to be resistant to cleaning. For this purpose, it is effective to form a protective film on the outermost layer and sides of the transfer pattern formed on the EUV mask. However, if the protective film is formed of a protective film material with low EUV light transmittance, the projection effect may adversely affect the pattern transferability. Furthermore, if the protective film is not uniform on the outermost layer and sides of the transfer pattern, the pattern transferability may deteriorate. In other words, there were few protective films for conventional EUV masks that had both high EUV transmittance and high cleaning resistance.

[0011] Therefore, an object of the present invention is to provide a reflective mask having a coating film that is uniformly formed along the outermost surface and side surfaces of a transfer pattern, has high EUV transmittance, and is highly resistant to cleaning, and a method for manufacturing the same. [Means for solving the problem]

[0012] In order to achieve the above object, a reflective mask according to one embodiment of the present invention comprises a substrate, a reflective portion formed on the substrate for reflecting incident light, an absorbing portion formed on at least a portion of the reflective portion for absorbing the incident light, and a coating film formed on the reflective portion and the absorbing portion for transmitting the incident light, wherein the coating film has an extinction coefficient k of 0.04 or less for EUV (Extreme UltraViolet: wavelength 13.5 nm) light and is resistant to cleaning with a cleaning solution, and is formed with a uniform thickness on the outermost surface and side surfaces of the absorbing portion. Effect of the Invention

[0013] According to the present invention, by uniformly covering the outermost surface layer and side surfaces of the absorbing part with a material that has high EUV transmittance and high cleaning resistance, it is possible to maintain the dimensional accuracy and shape accuracy of the pattern transferred onto the wafer and use the mask for a long period of time. [Brief description of the drawings]

[0014] [Figure 1]1 is a schematic cross-sectional view showing a structure of a reflective mask according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing a structure of a reflective mask blank according to an embodiment of the present invention. [Diagram 3] 5A to 5C are schematic cross-sectional views showing a manufacturing process of a reflective mask according to an embodiment of the present invention. [Figure 4] 5A to 5C are schematic cross-sectional views showing a manufacturing process of a reflective mask according to an embodiment of the present invention. [Diagram 5] 1 is a schematic plan view showing the shape of a design pattern of a reflective mask according to an embodiment of the present invention. [Figure 6] 1 is a schematic cross-sectional view showing a structure of a reflective mask according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the structure of a reflective mask according to an embodiment of the present invention will be described with reference to the drawings. (Overall structure) FIG. 1 is a schematic cross-sectional view showing the structure of a reflective photomask with a coating film (hereinafter, also simply referred to as a "reflective mask") 10. The reflective mask 10 includes a substrate 1, a multilayer reflective film (reflective portion) 2, a capping layer 3, an absorbing layer (absorbing portion) 4, and a covering film 5. The reflective mask 10 includes an absorbing layer pattern (transfer pattern) which is a fine pattern formed by the absorbing layer 4. The substrate 1 according to this embodiment is, for example, a substrate with low thermal expansion. Specifically, a flat Si substrate, a synthetic quartz substrate, or the like can be used as the substrate 1. Alternatively, low thermal expansion glass with added titanium can be used as the substrate 1. Thus, the substrate 1 may be made of any material having a small thermal expansion coefficient, and is not limited to these materials.

[0016] (Multilayer reflective film) The multilayer reflective film 2 according to this embodiment is a film (layer) formed on the substrate 1. This multilayer reflective film 2 is a film for reflecting EUV light (extreme ultraviolet light) which is the exposure light, and is, for example, a multilayer reflective film formed by combining materials having significantly different refractive indices for EUV light. As the multilayer reflective film 2, for example, a laminated film in which a layer containing Mo (molybdenum) and a layer containing Si (silicon) are laminated, or a laminated film in which a layer containing Mo (molybdenum) and a layer containing Be (beryllium) are laminated, is preferably formed by repeatedly laminating about 40 periods of the laminated film.

[0017] (capping layer) The capping layer 3 according to this embodiment is a layer formed on the multilayer reflective film 2. The capping layer 3 is formed of a material that is resistant to the dry etching performed when forming the absorbing layer 4. In other words, the capping layer 3 functions as an etching stopper that prevents damage to the multilayer reflective film 2 when the absorbing layer 4 is etched to form a transfer pattern (low-reflection portion pattern). Here, depending on the material of the multilayer reflective film 2 and the etching conditions, the capping layer 3 may not be provided.

[0018] (Absorption layer) The absorption layer 4 according to this embodiment is preferably formed of a single material such as tantalum, tin, indium, nickel, osmium, hafnium, tungsten, platinum, tellurium, cobalt, or palladium, or a compound material such as an oxide or nitride containing at least one of the above elements. In addition, the material constituting the absorption layer 4 itself preferably contains the above elements in an atomic ratio of 50% or more. Moreover, the absorbing layer 4 preferably contains a compound material containing the above-mentioned element in an amount of 50 mass % or more based on the mass of the entire absorbing layer 4.

[0019] If the absorbing layer 4 is made of the above-mentioned material, the transfer pattern formed by the absorbing layer 4 can reduce (suppress) the projection effect. The thickness of the absorbing layer 4 may be in the range of 10 nm to 50 nm, more preferably in the range of 20 nm to 40 nm, and further preferably in the range of 25 nm to 35 nm. When the thickness of the absorbing layer 4 is in the above-mentioned range, it is possible to effectively absorb EUV light and to realize a thin absorbing layer 4.

[0020] (Coating film) The absorbing layer 4 is required to have washing resistance as a reflective mask, and the types of materials are limited. However, by covering the absorbing layer 4 with the coating film 5, which has high washing resistance, a material with poor washing resistance can also be used as the constituent material of the absorbing layer 4. Even if the constituent material of the absorbing layer 4 is a material with washing resistance, the absorbing layer 4 is protected by the coating film 5, and therefore does not come into direct contact with the chemical solution, and therefore can withstand repeated washing.

[0021] The cleaning resistance required for the reflective mask is determined by immersing the reflective mask 10 in sulfuric acid at 80°C for 10 minutes, and then immersing the mask in a cleaning bath filled with a cleaning solution of ammonia, hydrogen peroxide, and water in a ratio (mass ratio) of 1:1:20 for 10 minutes using megasonics at 500 W. The amount of film loss of the transfer pattern (low reflection portion pattern) is measured with an electronic balance, and a compound material with no mass change is defined as a material with high cleaning resistance in this embodiment. Here, "no mass change" means that the amount of film loss (mass) is 10% or less of the total mass of the transfer pattern (low reflection portion pattern).

[0022] In the case of the reflective mask 10 according to this embodiment, since the covering film 5 is the outermost layer of the reflective mask 10, it is preferable that it does not interfere with the optical paths of the incident light and the reflected light. In order to keep the deterioration of resolution due to the projection effect within 25%, it is desirable that the extinction coefficient k of the covering film 5, which is the outermost layer, is 0.04 or less, and the film thickness of the covering film 5 is 10 nm or less. A more preferable range of the film thickness of the covering film 5 is 1 nm or more and 8 nm or less, and even more preferably, 2 nm or more and 6 nm or less. Within the above numerical ranges, it is possible to further reduce the interference with the optical paths of the incident light and the reflected light.

[0023] As the main material of the coating film 5 for reducing the above-mentioned projection effect, it is preferable that the material is a compound material having a small extinction coefficient k for EUV light so as not to obstruct the optical path. For example, the extinction coefficient k of silicon (Si) is 0.0018, which satisfies the above-mentioned condition. Silicon dioxide is known to have high resistance to acids and alkalis, and applying silicon dioxide to the outermost layer can provide the reflective mask 10 with the necessary cleaning resistance. A compound material that has an atomic ratio of silicon (Si) and oxygen (O) of 1:1.5 to 1:2, and the total content of silicon and oxygen is 50% or more of the entire compound material, and satisfies the above-mentioned optical conditions, is preferable as the main material of the coating film 5 because it has sufficient cleaning resistance.

[0024] Thus, the coating film 5 is preferably made of a compound material having cleaning resistance and an extinction coefficient k of 0.04 or less. Therefore, the coating film 5 may be made of, for example, a simple material such as silicon dioxide, silicon nitride, aluminum oxide, ruthenium, zirconium, chromium, hafnium, niobium, rhodium, tungsten, vanadium, or titanium, or a compound material such as an oxide or nitride containing at least one of the above elements. In addition, the material constituting the coating film 5 itself preferably contains the above elements in an atomic ratio of 50% or more. Moreover, the coating film 5 preferably contains compound materials containing the above-mentioned elements in an amount of 50 mass % or more relative to the mass of the entire coating film 5.

[0025] If the coating film 5 is formed from the above-mentioned material, the transfer pattern formed by the coating film 5 can increase the efficiency of absorbing EUV light. 1, in the reflective mask 10 according to this embodiment, a back conductive film can be formed on the surface of the substrate 1 opposite to the surface on which the multilayer reflective film 2 is formed. The back conductive film is a film for fixing the reflective mask 10 by utilizing the principle of an electrostatic chuck when the reflective mask 10 is placed in an exposure machine.

[0026] (Method of forming coating film) When manufacturing the reflective mask 10 according to this embodiment, the coating film 5 may be formed using an atomic layer deposition method in which a gas containing at least one of silicon, aluminum, zirconium, ruthenium, chromium, hafnium, niobium, rhodium, tungsten, vanadium, and titanium and a gas containing one of oxygen, nitrogen, and fluorine are alternately supplied. Atomic layer deposition is capable of forming a thin film in atomic layer units, and therefore the coating film 5 formed by this method has high thickness uniformity and high shape conformability.

[0027] In order to prevent deterioration of transfer performance due to cleaning, the coating film 5 needs to be formed along the transfer pattern formed on the surface and side of the absorption layer 4, and further on the capping layer 3 or the multilayer reflective film 2, that is, on the capping layer 3 or the multilayer reflective film 2 whose surface is exposed. Furthermore, as described above, in order to prevent deterioration of transferability due to the coating film 5, the allowable film thickness is limited, and the coating film 5 to be formed is required to have a uniform film thickness. Therefore, by forming the coating film 5 by the atomic layer deposition method, which has excellent film thickness uniformity and shape followability, it is possible to manufacture a reflective mask 10 having high cleaning resistance without deterioration of pattern transferability. Here, "uniform film thickness" means that the thickness of the thinnest part is within a range of -2 nm and the thickness of the thickest part is within a range of +2 nm with respect to the average thickness of the coating film 5 formed on the surface and side of the absorption layer 4. That is, in this embodiment, the layer thickness of the coating film 5 formed on the surface of the absorption layer 4 is within a range of ±2 nm with respect to the average thickness. Moreover, the layer thickness of the coating film 5 formed on the side of the absorption layer 4 is within a range of ±2 nm with respect to the average thickness.

[0028] In this manner, in the reflective mask 10 according to this embodiment, the coating film 5 with high cleaning resistance is formed by atomic layer deposition on the front and side surfaces of the absorption layer 4. This reduces the erosion of the absorption layer 4 caused by the cleaning chemicals used in the reflective mask 10, and can suppress deterioration of the pattern transferability. Moreover, since the coating film 5 is uniformly formed from a material with high EUV transmittance, it is possible to suppress deterioration of transferability due to the formation of the coating film 5. Therefore, even when an absorber layer material with low cleaning resistance is used, high pattern transfer accuracy can be achieved.

[0029] [Example 1] Hereinafter, a reflective mask according to an embodiment of the present invention will be described with reference to figures and tables. As shown in Fig. 2, a multilayer reflective film 12 was formed by stacking 40 layers of a laminate film, each layer being made of a pair of silicon (Si) and molybdenum (Mo), on a substrate 11 made of synthetic quartz having low thermal expansion. The thickness of the multilayer reflective film 12 was set to 280 nm. For simplicity, the multilayer reflective film 12 is shown in Fig. 2 as a laminate film made up of several pairs of layers.

[0030] Next, a capping layer 13 made of ruthenium (Ru) was formed as an intermediate film to a thickness of 2.5 nm on the multilayer reflective film 12. As a result, a reflective layer (reflective portion) 16 having the multilayer reflective film 12 and the capping layer 13 was formed on the substrate 11. On the capping layer 13, an absorbing layer 14 made of tin oxide was formed to a thickness of 26 nm. Next, a back surface conductive film 15 made of chromium nitride (CrN) was formed to a thickness of 100 nm on the side of the substrate 11 on which the multilayer reflective film 12 was not formed. A multi-target sputtering device was used to deposit each film on the substrate 11. The thickness of each film was controlled by the sputtering time.

[0031] Next, a positive chemically amplified resist (SEBP9012: manufactured by Shin-Etsu Chemical Co., Ltd.) was formed on the absorbing layer 14 by spin coating to a thickness of 120 nm, and baked at 110° C. for 10 minutes to form a resist film 17. Next, a predetermined pattern was written on the positive chemically amplified resist by an electron beam writing machine (JBX3030: manufactured by JEOL Ltd.). Thereafter, the resist was baked at 110° C. for 10 minutes, and then spray-developed (SFG3000, manufactured by Sigma Meltec Co., Ltd.) to form a resist pattern 17a as shown in FIG.

[0032] Next, using the resist pattern as an etching mask, the absorbing layer 14 was patterned by dry etching mainly using a chlorine-based gas to form an absorbing layer pattern 14a. Next, the remaining resist pattern 17a was peeled off, thus forming an absorber layer pattern 14a in which the surface and side surfaces of the absorber layer 14 were exposed, as shown in FIG. In this embodiment, the absorbing layer pattern 14a formed in the absorbing layer 14 functioning as a low reflection layer was a line and space (LS) pattern with a line width of 64 nm. This LS pattern with a line width of 64 nm was designed in the x and y directions as shown in FIG. 5 so that the influence of the projection effect due to EUV irradiation could be easily seen.

[0033] Next, a coating film 18 made of silicon dioxide was formed on the exposed surface and side of the absorption layer 14 and on the reflective layer 16 by atomic layer deposition using silicon gas and oxygen gas to a thickness of 2 nm, 5 nm, and 10 nm, respectively. The atomic ratio of silicon to oxygen was measured by XPS (X-ray photoelectron spectroscopy) to be 1:1.9. In this way, a reflective photomask (hereinafter also simply referred to as a "reflective mask") 100 as shown in FIG. 6 was produced.

[0034] [Example 2] In the same manner as in Example 1, an absorption layer pattern 14a shown in FIG. Next, by atomic layer deposition using organic aluminum gas and oxygen gas, coating films 18 made of aluminum oxide were formed on the front and side surfaces of the absorption layer 14 and on the reflective layer 16 to thicknesses of 2 nm, 5 nm, and 10 nm, respectively. The atomic ratio of aluminum to oxygen was measured by XPS (X-ray photoelectron spectroscopy) to be 1:1.6. In this way, a reflective mask 100 as shown in FIG. 6 was produced.

[0035] [Example 3] In the same manner as in Example 1, an absorption layer pattern 14a shown in FIG. Next, by atomic layer deposition using an organic titanium gas and oxygen gas, coating films 18 made of titanium oxide were formed on the front and side surfaces of the absorption layer 14 and on the reflective layer 16 to thicknesses of 2 nm, 5 nm, and 10 nm, respectively. In this way, a reflective mask 100 as shown in FIG. 6 was produced.

[0036] [Comparative Example 1] In the same manner as in Example 1, an absorption layer pattern 14a shown in FIG. Next, by atomic layer deposition using an organic molybdenum gas, coating films 18 made of molybdenum were formed on the front and side surfaces of the absorption layer 14 and on the reflective layer 16 to thicknesses of 2 nm, 5 nm, and 10 nm, respectively. In this way, a reflective mask 100 as shown in FIG. 6 was produced.

[0037] [Comparative Example 2] In the same manner as in Example 1, an absorption layer pattern 14a shown in FIG. Next, by atomic layer deposition using an organic platinum-based gas, coating films 18 each containing platinum were formed to thicknesses of 2 nm, 5 nm, and 10 nm on the front and side surfaces of the absorption layer 14 and on the reflective layer 16. In this way, a reflective mask 100 as shown in FIG. 6 was produced. In the above-mentioned examples and comparative examples, the thickness of the coating film 18 was measured by a transmission electron microscope.

[0038] (Washing resistance) The reflective mask 100 was cleaned using SPM cleaning using hot sulfuric acid and water peroxide with a weight concentration of 90% and a liquid temperature of 80° C., and SC1 cleaning using ammonia water and water peroxide. The film loss was confirmed from the mass change using an electronic balance. In this example, if the amount of film loss was 10% or less of the mass of the coating film 18, there was no problem in use, and the mask was evaluated as "resistant to cleaning." On the other hand, if the amount of film loss was more than 10% of the mass of the coating film 18, there was a problem in use, and the mask was evaluated as "not resistant to cleaning."

[0039] (Wafer exposure evaluation) Using an EUV exposure device (NXE3300B: manufactured by ASML), the absorption layer pattern 14a of the reflective mask 100 produced in the examples and comparative examples was transferred and exposed onto a semiconductor wafer coated with an EUV positive chemically amplified resist. At this time, the exposure dose was adjusted so that the LS pattern in the x direction shown in FIG. 5 was transferred as designed. The transferred resist pattern was observed and line width was measured using an electron beam dimension measuring device to confirm the resolution. More specifically, in this example, the resolution was evaluated based on whether the LS pattern in the y direction was properly transferred. That is, in a state where the exposure conditions were adjusted so that the LS pattern in the x direction shown in FIG. 5 was transferred as designed, the case where the resolution deterioration of the LS pattern in the y direction was within 25% of the resolution without the coating film was determined as "pass", and the case where the resolution deterioration exceeded 25% (the LS pattern in the y direction was not resolved) was determined as "fail". In Tables 1 to 5, the case where the LS pattern in the y direction was not resolved is indicated by "-".

[0040] The evaluation results are shown in Tables 1 to 5. Table 1 shows the cleaning resistance and the resist pattern dimensions on the wafer for the reflective mask 100 of Example 1, i.e., the reflective mask 100 in which the absorption layer 14 is made of tin oxide and has a thickness of 26 nm, and the coating film 18 is made of silicon dioxide and has a thickness of 2 nm, 5 nm, and 10 nm, respectively.

[0041] In the reflective mask 100 of Example 1, no film loss due to cleaning was observed. In other words, the reflective mask 100 of Example 1 had cleaning resistance. When the thickness of the coating film 18 was 2 nm, 5 nm, and 10 nm, the LS pattern dimensions in the y direction were 12.4 nm, 11.9 nm, and 11.7 nm, respectively, compared to the design value of 16.0 nm. As described above, as the thickness of the coating film 18 increased, a deterioration in dimensional accuracy due to the projection effect was observed, but the deterioration in resolution was within approximately 25%. In other words, the reflective mask 100 of Example 1 had pattern transferability that was problem-free in use.

[0042] [Table 1]

[0043] Table 2 shows the cleaning resistance and the resist pattern dimensions on the wafer for the reflective mask 100 of Example 2, i.e., the reflective mask 100 in which the absorption layer 14 is made of tin oxide and has a thickness of 26 nm, and the coating film 18 is made of aluminum oxide and has a thickness of 2 nm, 5 nm, and 10 nm, respectively.

[0044] In the reflective mask 100 of Example 2, no film loss due to cleaning was observed. In other words, the reflective mask 100 of Example 1 had cleaning resistance. When the thickness of the coating film 18 was 2 nm, 5 nm, and 10 nm, the LS pattern dimensions in the y direction were 12.3 nm, 11.5 nm, and 10.4 nm, respectively, with respect to the design value of 16.0 nm, and the results were equivalent to those of Example 1. As described above, as in Example 1, a deterioration in dimensional accuracy due to the projection effect was observed as the thickness of the coating film 18 increased, but the deterioration in resolution was within approximately 25%. In other words, the reflective mask 100 of Example 2 had pattern transferability that was problem-free in use.

[0045] [Table 2]

[0046] Table 3 shows the cleaning resistance and the resist pattern dimensions on the wafer for the reflective mask 100 of Example 3, i.e., the reflective mask 100 in which the absorption layer 14 is made of tin oxide and has a thickness of 26 nm, and the coating film 18 is made of titanium oxide and has a thickness of 2 nm, 5 nm, and 10 nm.

[0047] In the reflective mask 100 of Example 3, no film loss due to cleaning was observed. In other words, the reflective mask 100 of Example 1 had cleaning resistance. When the thickness of the coating film 18 was 2 nm, 5 nm, and 10 nm, the LS pattern dimensions in the y direction were 12.5 nm, 11.2 nm, and 10.5 nm, respectively, with respect to the design value of 16.0 nm, and the results were equivalent to those of Example 1. As described above, as in Example 1, a deterioration in dimensional accuracy due to the projection effect was observed as the thickness of the coating film 18 increased, but the deterioration in resolution was within approximately 25%. In other words, the reflective mask 100 of Example 2 had pattern transferability that was problem-free in use.

[0048] [Table 3]

[0049] Table 4 shows the cleaning resistance and the resist pattern dimensions on the wafer for the reflective mask 100 of Comparative Example 1, i.e., the reflective mask 100 in which the absorption layer 14 is made of tin oxide and has a thickness of 26 nm, and the coating film 18 is made of molybdenum and has thicknesses of 2 nm, 5 nm, and 10 nm.

[0050] In the reflective mask 100 of Comparative Example 1, a film loss due to the cleaning chemical was confirmed, and it was found that the cleaning resistance was low. When the film thickness of the coating film 18 was 2 nm, 5 nm, and 10 nm, the LS pattern dimensions in the y direction were 12.7 nm, 11.1 nm, and 10.5 nm, respectively, with respect to the design value of 16.0 nm, and the results were equivalent to those of Examples 1 to 3. Thus, as in Examples 1 to 3, a deterioration in dimensional accuracy due to the projection effect was observed as the film thickness of the coating film 18 increased. Meanwhile, unlike Examples 1 to 3, the coating film 18 formed of molybdenum is a material with low cleaning resistance, and is therefore unsuitable for use as a reflective mask.

[0051] [Table 4]

[0052] Table 5 shows the cleaning resistance and the resist pattern dimensions on the wafer for the reflective mask 100 of Comparative Example 2, i.e., the reflective mask 100 in which the absorption layer 14 is made of tin oxide and has a thickness of 26 nm, and the coating film 18 is made of platinum and has thicknesses of 2 nm, 5 nm, and 10 nm.

[0053] No film loss due to cleaning was observed in the reflective mask 100 of Comparative Example 2. When the thickness of the coating film 18 was 2 nm, the LS pattern dimension in the y direction was 12.4 nm compared to the design value of 16.0 nm, but the pattern was not resolved when the thickness was 5 nm or 10 nm. In other words, the reflective mask 100 of Comparative Example 2 did not have sufficient pattern transferability. Thus, unlike in Examples 1 to 3, when coating film 18 was formed from a material with a large extinction coefficient k, the projection effect became stronger as the thickness of coating film 18 increased, and the y-direction pattern was not resolved at a thickness of 5 nm or more.

[0054] [Table 5]

[0055] From the above, it was found that even if the absorption layer 14 is made of a material with poor cleaning resistance, a reflective mask 100 in which the coating film 18 is formed of silicon dioxide, aluminum oxide, or titanium oxide does not deteriorate the projection effect and has good cleaning resistance, resulting in a reflective mask with a long life and high transfer performance. [Industrial Applicability]

[0056] The reflective mask according to the present invention can be suitably used for forming fine patterns by EUV exposure in the manufacturing process of semiconductor integrated circuits and the like. [Explanation of symbols]

[0057] 1...Substrate 2…Multilayer reflective film 3…Capping layer 4…Absorption layer 5…Coating film 10...Reflective photomask 11...Substrate 12…Multilayer reflective film 13…Capping layer 14…Absorption layer 14a…Absorption layer pattern 15…Back conductive film 16...Reflection part (reflection layer) 17...Resist film 17a...Resist pattern 18...Coating film 100...Reflective photomask

Claims

1. A substrate; A reflecting portion formed on the substrate for reflecting incident light; a capping layer formed on the reflective portion; an absorbing portion formed on at least a portion of the capping layer so as to be in contact with the capping layer and absorbing the incident light; a coating film formed on the capping layer and the absorbing portion to transmit the incident light, the capping layer is formed of ruthenium; the coating film has an extinction coefficient k of 0.04 or less with respect to EUV (Extreme UltraViolet: wavelength 13.5 nm) light, is resistant to cleaning with a cleaning solution, and is formed with a uniform film thickness on an outermost surface and a side surface of the absorbing portion; 4. A reflective mask, wherein the coating film is formed from a compound containing at least chromium.

2. 2. The reflective mask according to claim 1, wherein the absorbing portion is formed of a compound containing at least one of tantalum, tin, indium, nickel, osmium, hafnium, tungsten, platinum, tellurium, cobalt, and palladium.

3. 2. The reflective mask according to claim 1, wherein the absorbing portion is formed of a compound containing at least one of indium, nickel, osmium, hafnium, tellurium, cobalt, and palladium.

4. 2. The reflective mask according to claim 1, wherein the absorbing portion is made of a compound containing at least tungsten.

5. 5. The reflective mask according to claim 1, wherein the coating film has a thickness within a range of 5 nm to 10 nm.

6. 6. The reflective mask according to claim 1, wherein the absorbing portion is a single layer.

7. A method for manufacturing a reflective mask according to any one of claims 1 to 6, comprising the steps of: A method for producing a reflective mask, comprising the step of forming the coating film by atomic layer deposition.

8. 8. The method for manufacturing a reflective mask according to claim 7, wherein in the step of forming the coating film, the coating film is formed by atomic layer deposition using a metal hydride, a metal halide, or an organometallic compound as a source gas.

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