Mask blank, phase shift mask and semiconductor device manufacturing method

Abstract

To provide a mask blank with which phase shift effect can be enhanced by increasing permeability with respect to exposure light, a film thickness of a phase shift film is reducible, a micropattern is formable, and a phase shift mask having good optical performance is manufacturable.SOLUTION: A mask blank includes a light transmissive substrate and a phase shift film formed on the light transmissive substrate. The phase shift film includes a lower layer containing hafnium and oxygen, and an upper layer that is formed on the lower layer and contains silicon, oxygen, and nitrogen. A total content of hafnium and oxygen in the lower layer is 95 atom% or more. A nitrogen content in the upper layer is 15 atom% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mask blank for a phase shift mask, a method for manufacturing a phase shift mask and a semiconductor device. [Background technology]

[0002] In the manufacturing process of semiconductor devices, fine patterns are formed using photolithography. The formation of these fine patterns typically requires the use of multiple transfer masks. In order to miniaturize the patterns on semiconductor devices, it is necessary not only to miniaturize the mask patterns formed on the transfer masks, but also to shorten the wavelength of the exposure light source used in photolithography.

[0003] As such a photomask, Patent Document 1 discloses a dielectric mask comprising a light-transmitting substrate 1 that is transmissive to laser light, a metal film 17 laminated on the surface of the light-transmitting substrate 1 and having high reflectivity for laser light, a dielectric multilayer thin film 4 formed by alternately laminating first and second dielectric members 2 and 3, each having a different refractive index, on the metal film 17, and a plurality of openings 18 formed to penetrate the dielectric multilayer thin film 4 and the metal film 17 and arranged in a predetermined pattern. Patent Document 2 discloses an excimer laser processing mask having a structure in which a dielectric multilayer film is repeatedly formed on the surface of a glass substrate 3 transparent to ultraviolet light, opposite the ultraviolet light incident side, by combining a first dielectric layer 1 having a film thickness whose optical path length is ¼ of the wavelength of the ultraviolet light being used and a second dielectric layer 2 having an optical path length similarly of ¼ the wavelength and a refractive index smaller than that of the first dielectric layer, the first dielectric layer being laminated thereon, the top layer of which is a third dielectric layer 1' having a refractive index larger than that of the glass substrate and an optical path length of ¼ the wavelength of the ultraviolet light being used, and the top layer of which is a metal film 4.

[0004] In Patent Documents 1 and 2, a KrF excimer laser (wavelength 248 nm) is mainly used as an exposure light source when manufacturing semiconductor devices. However, in recent years, an ArF excimer laser (wavelength 193 nm) has increasingly been used as an exposure light source when manufacturing semiconductor devices.

[0005] One type of transfer mask is the halftone phase shift mask. A mask blank for a halftone phase shift mask has long been known, which has a structure in which a phase shift film made of a material containing silicon and nitrogen, a light-shielding film made of a chromium-based material, and an etching mask film (hard mask film) made of an inorganic material are stacked on a light-transmitting substrate. When manufacturing a halftone phase shift mask using this mask blank, first, the etching mask film is patterned by dry etching with a fluorine-based gas using a resist pattern formed on the surface of the mask blank as a mask. Next, the light-shielding film is patterned by dry etching with a mixed gas of chlorine and oxygen using the etching mask film as a mask. Finally, the phase shift film is patterned by dry etching with a fluorine-based gas using the pattern of the light-shielding film as a mask. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-325384 [Patent Document 2] Japanese Patent Application Publication No. 8-171197 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, with the miniaturization and increasing complexity of patterns, there is a demand for phase shift films with higher transmittance (e.g., 20% or more) to exposure light (especially ArF excimer laser exposure light) to enable higher-resolution pattern transfer. Increasing the transmittance to exposure light can enhance the phase shift effect. Furthermore, with the miniaturization of patterns (e.g., 20 nm or less), there is also a demand for the thickness of the phase shift film to be kept below a certain level (e.g., 60 nm or less) in order to prevent pattern collapse, etc.

[0008] The present invention has been made to solve the problems of the related art, and aims to provide a mask blank that can increase the transmittance to exposure light to enhance the phase shift effect, while suppressing the film thickness of the phase shift film, allowing for the formation of fine patterns and the manufacture of a phase shift mask with good optical performance. Another aim of the present invention is to provide a phase shift mask that can increase the transmittance to exposure light to enhance the phase shift effect, while suppressing the film thickness of the phase shift film, allowing for the formation of fine patterns and the manufacture of a phase shift mask with good optical performance. The present invention also aims to provide a method for manufacturing a semiconductor device using such a phase shift mask. [Means for solving the problem]

[0009] The present invention has the following configuration as a means for solving the above problems.

[0010] (Configuration 1) a light-transmitting substrate; a phase shift film formed on the light-transmitting substrate, The phase shift film is an underlayer comprising hafnium and oxygen; an upper layer formed on the lower layer, the upper layer comprising silicon, oxygen, and nitrogen; the total content of hafnium and oxygen in the lower layer is 95 atomic % or more; The mask blank, wherein the nitrogen content of the upper layer is 15 atomic % or more.

[0011] (Configuration 2) 2. The mask blank according to claim 1, wherein the upper layer has an oxygen content of 50 atomic % or less. (Configuration 3) 3. The mask blank according to claim 1, wherein the oxygen content of the lower layer is 50 atomic % or more.

[0012] (Configuration 4) 4. The mask blank according to any one of configurations 1 to 3, wherein the nitrogen content of the upper layer is 60 atomic % or less. (Configuration 5) the phase shift film includes an intermediate layer formed between the lower layer and the upper layer, 5. The mask blank according to any one of configurations 1 to 4, wherein the intermediate layer is made of a material having a total content of silicon and oxygen of 90 atomic % or more.

[0013] (Configuration 6) 6. The mask blank according to claim 5, wherein the intermediate layer is made of silicon and oxygen. (Configuration 7) 7. The mask blank according to any one of configurations 1 to 6, wherein the phase shift film has a thickness of 60 nm or less.

[0014] (Configuration 8) 8. The mask blank according to any one of configurations 1 to 7, wherein the phase shift film has a transmittance of 20% or more and a phase shift of 150 degrees or more and 210 degrees or less for ArF excimer laser exposure light. (Configuration 9) 9. The mask blank according to any one of configurations 1 to 8, further comprising a light-shielding film on the phase shift film.

[0015] (Configuration 10) a light-transmitting substrate; a phase shift film provided on the light-transmitting substrate and having a transfer pattern formed thereon; The phase shift film is an underlayer comprising hafnium and oxygen; an upper layer formed on the lower layer, the upper layer comprising silicon, oxygen, and nitrogen; the total content of hafnium and oxygen in the lower layer is 95 atomic % or more; A phase shift mask, wherein the nitrogen content of the upper layer is 15 atomic % or more. (Configuration 11) 11. The phase shift mask of claim 10, wherein the upper layer has an oxygen content of 50 atomic % or less.

[0016] (Configuration 12) 12. The phase shift mask of claim 10, wherein the oxygen content of the lower layer is 50 atomic % or more.

[0017] (Configuration 13) 13. The phase shift mask of any one of claims 10 to 12, wherein the nitrogen content of the upper layer is 60 atomic % or less.

[0018] (Configuration 14) the phase shift film includes an intermediate layer formed between the lower layer and the upper layer, 14. The phase shift mask of any one of configurations 10 to 13, wherein the intermediate layer is made of a material having a total silicon and oxygen content of 90 atomic % or more. (Configuration 15) 15. The phase shift mask of claim 14, wherein the intermediate layer is made of silicon and oxygen.

[0019] (Configuration 16) 16. The phase shift mask of any one of configurations 10 to 15, wherein the phase shift film has a thickness of 60 nm or less. (Configuration 17) 17. A phase shift mask according to any one of structures 10 to 16, wherein the phase shift film has a transmittance of 20% or more and a phase shift of 150 degrees or more and 210 degrees or less for ArF excimer laser exposure light.

[0020] (Configuration 18) 18. The phase shift mask according to any one of Structures 10 to 17, further comprising a light-shielding film having a light-shielding pattern formed on the phase shift film. (Configuration 19) 19. A method for manufacturing a semiconductor device, comprising the step of using the phase shift mask according to any one of Structures 10 to 18 to transfer the transfer pattern onto a resist film on a semiconductor substrate by exposure. [Effects of the Invention]

[0021] The mask blank of the present invention having the above configuration comprises a light-transmitting substrate and a phase shift film formed on the light-transmitting substrate, the phase shift film comprising a lower layer containing hafnium and oxygen and an upper layer formed on the lower layer and containing silicon, oxygen, and nitrogen, the lower layer having a total hafnium and oxygen content of 95 atomic % or more, and the upper layer having a nitrogen content of 15 atomic % or more. This increases the transmittance to exposure light, enhancing the phase shift effect, while also reducing the thickness of the phase shift film, allowing for the formation of fine patterns and the manufacture of phase shift masks with excellent optical performance. Furthermore, in the manufacture of semiconductor devices using this phase shift mask, it becomes possible to accurately transfer patterns onto resist films, etc., on semiconductor devices. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view of a mask blank according to a first embodiment. [Figure 2] FIG. 4 is a schematic cross-sectional view of a mask blank according to a second embodiment. [Figure 3] 2A to 2C are schematic cross-sectional views showing the manufacturing process of the phase shift masks of the first and second embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, various embodiments of the present invention will be described. The inventors of the present invention have conducted extensive research into a phase shift film that can enhance the phase shift effect by increasing the transmittance of the exposure light (particularly ArF excimer laser exposure light, hereinafter sometimes simply referred to as exposure light), while also suppressing the film thickness of the phase shift film, enabling the formation of fine patterns, and providing good optical performance. In this specification, the transmittance is calculated by assuming that the transmittance of a light-transmitting substrate (described in detail below) is 100%. A phase shift film must have both the function of transmitting exposure light at a predetermined transmittance and the function of generating a predetermined phase difference between the exposure light passing through the phase shift film and the exposure light passing through air a distance equal to the thickness of the phase shift film. If the thickness of the phase shift film is kept below a certain level, it becomes difficult to ensure the desired phase difference. A single-layer phase shift film has a low degree of design freedom, and it has not been easy to achieve a configuration that ensures the desired phase difference while increasing transmittance, enabling the formation of fine patterns, and providing good optical performance.

[0024] Therefore, the inventors of the present invention have investigated the use of a phase shift film with at least a two-layer structure. They have found that a desired phase difference and high transmittance can be achieved by configuring a phase shift film including a lower layer and an upper layer from the transparent substrate side, with the lower layer containing hafnium and oxygen and the upper layer containing silicon, oxygen, and nitrogen. However, they have found that even if the transmittance of the phase shift film is sufficiently high under these conditions, adjusting the film thickness to obtain the desired phase difference may result in an increase in the film thickness, making it impossible to form a fine pattern (e.g., 20 nm or less).

[0025] The inventors have further investigated and found that the composition of each of the lower and upper layers of the phase shift film is important for obtaining the desired retardation and high transmittance and forming a fine pattern. Therefore, after extensive investigation into the composition of each of the lower and upper layers of the phase shift film, they have found that by setting the total content of hafnium and oxygen in the lower layer to 95 atomic % or more and the nitrogen content in the upper layer to 15 atomic % or more, the desired retardation and high transmittance can be obtained while keeping the phase shift film thickness small, and a fine pattern can be formed. The present invention was made as a result of the above extensive investigation.

[0026] The detailed configuration of the present invention will be described below with reference to the drawings. Note that the same components in each drawing are denoted by the same reference numerals.

[0027] First Embodiment Fig. 1 shows a schematic configuration of a mask blank according to the first embodiment. The mask blank 100 shown in Fig. 1 has a configuration in which a phase shift film 2, a light-shielding film 3, and a hard mask film 4 are laminated in this order on one main surface of a light-transmitting substrate 1. The mask blank 100 may be configured without the hard mask film 4, if necessary. Alternatively, the mask blank 100 may have a resist film laminated on the hard mask film 4, if necessary. The main components of the mask blank 100 will be described in detail below.

[0028] [Transparent substrate] The light-transmitting substrate 1 is made of a material that has good transparency to the exposure light used in the exposure step in lithography. Examples of such materials that can be used include synthetic quartz glass, aluminosilicate glass, soda-lime glass, low-thermal expansion glass (SiO2-TiO2 glass, etc.), and various other glass substrates. Substrates made of synthetic quartz glass are particularly suitable for use as the light-transmitting substrate 1 of the mask blank 100 because they have high transparency to ArF excimer laser light (wavelength: approximately 193 nm). The exposure process in lithography referred to here is the exposure process in lithography using a phase shift mask fabricated using this mask blank 100, and the exposure light refers to ArF excimer laser light (wavelength: 193 nm) unless otherwise specified. The refractive index of the material forming the light-transmitting substrate 1 in the exposure light is preferably 1.5 or more and 1.6 or less, more preferably 1.52 or more and 1.59 or less, and even more preferably 1.54 or more and 1.58 or less.

[0029] [Phase shift film] The phase shift film 2 preferably has a function of transmitting the exposure light with a transmittance of 20% or more, more preferably 30% or more, and even more preferably 40% or more. This is to generate a sufficient phase shift effect between the exposure light that has passed through the phase shift film 2 and the exposure light that has passed through the air. The upper limit of the transmittance of the phase shift film 2 for the exposure light can be set appropriately and is not particularly limited, but is preferably 60% or less, more preferably 50% or less. This is to keep the film thickness of the phase shift film 2 within an appropriate range that ensures optical performance. Furthermore, by setting the transmittance of the phase shift film 2 for the exposure light to 60% or less, unnecessary exposure of the photosensitive material (e.g., resist film) on the transfer target object can be prevented during the exposure process.

[0030] To obtain an appropriate phase shift effect, the phase shift film 2 is preferably adjusted to have the function of generating a phase difference (phase shift amount) of 150 degrees or more and 210 degrees or less between the exposure light that has passed through this phase shift film 2 and the exposure light that has passed through air a distance equal to the thickness of this phase shift film 2. The phase difference in the phase shift film 2 is more preferably 155 degrees or more, and even more preferably 160 degrees or more. On the other hand, the phase difference in the phase shift film 2 is more preferably 195 degrees or less, and even more preferably 190 degrees or less.

[0031] The phase shift film 2 in this embodiment has a structure in which a lower layer 21 and an upper layer 22 are laminated from the light-transmitting substrate 1 side. In this embodiment, the lower layer 21 is formed in contact with the light-transmitting substrate 1, but the lower layer 21 may be formed on the light-transmitting substrate 1 via another film. In this embodiment, the upper layer 22 is formed in contact with the lower layer 21.

[0032] The thickness of the phase shift film 2 is preferably 60 nm or less, more preferably 59 nm or less, to enable the formation of a fine pattern (e.g., 20 nm or less) and ensure optical performance. The thickness of the phase shift film 2 is preferably 45 nm or more, more preferably 50 nm or more, to ensure the function of generating a desired phase difference. The thickness of each layer (lower layer 21, upper layer 22, and middle layer 23) of the phase shift film 2 described below is assumed to satisfy the thickness of the phase shift film 2 described above.

[0033] Lower layer 21 preferably contains hafnium and oxygen, and more preferably consists of hafnium and oxygen. Here, "consisting of hafnium and oxygen" refers to a material that contains only these constituent elements and elements that may be contained in lower layer 21 in very small amounts as impurities when formed by sputtering (noble gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe), hydrogen (H), carbon (C), etc.). By minimizing the presence of other elements that bond with hafnium in lower layer 21, the proportion of bonds between hafnium and oxygen in lower layer 21 can be significantly increased. For this reason, the total content of hafnium and oxygen in lower layer 21 is preferably 95 atomic % or more, and even more preferably 98 atomic % or more. The oxygen content in lower layer 21 is preferably 50 atomic % or more, and even more preferably 55 atomic % or more, and even more preferably 60 atomic % or more. The total content of the above-mentioned elements (noble gases, hydrogen, carbon, etc.) that may be contained in lower layer 21 in minute amounts as impurities is preferably 3 atomic % or less, and even more preferably 2 atomic % or less. Furthermore, it is preferable that lower layer 21 does not contain silicon except for the interface region with films (e.g., upper layer 22, intermediate layer 23) provided on lower layer 21 in contact with lower layer 21 and the interface region with light-transmitting substrate 1. This allows lower layer 21 to have high chemical resistance and cleaning resistance.

[0034] The refractive index n of the lower layer 21 to the exposure light is preferably 3.1 or less, more preferably 3.0 or less. The refractive index n of the lower layer 21 is preferably 2.5 or more, more preferably 2.6 or more. On the other hand, the extinction coefficient k of the lower layer 21 to the exposure light is preferably 0.4 or less, more preferably 0.3 or less. This is to increase the transmittance of the phase shift film 2 to the exposure light. The extinction coefficient k of the lower layer 21 is preferably 0.15 or more, more preferably 0.2 or more.

[0035] From the viewpoint of chemical resistance and cleaning resistance, the thickness of the lower layer 21 is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more. Interdiffusion may occur at the interface between the lower layer 21 and the upper layer 22 containing silicon and oxygen, or at the interface between the lower layer 21 and the light-transmitting substrate 1, potentially causing the lower layer 21 to contain hafnium, silicon, and oxygen. Thin films containing hafnium, silicon, and oxygen tend to have poor chemical resistance and cleaning resistance. However, by setting the thickness of the lower layer 21 within the above range, interdiffusion throughout the entire lower layer 21 can be suppressed, and a decrease in the chemical resistance and cleaning resistance of the lower layer 21 can be suppressed. From the viewpoint of optical properties, the thickness of the lower layer 21 is preferably 46 nm or less, and more preferably 45 nm or less.

[0036] The X-ray diffraction profile of the lower layer 21 obtained by out-of-plane measurement of the X-ray diffraction method within the diffraction angle 2θ range of 25 to 35 degrees preferably has a maximum value of diffraction intensity within the diffraction angle 2θ range of 28 to 29 degrees. That is, when out-of-plane measurement of the X-ray diffraction method is performed on the X-ray diffraction profile of the lower layer 21 within the range of 25 to 35 degrees, the X-ray diffraction profile has a maximum diffraction peak within the diffraction angle 2θ range of 28 to 29 degrees, and has no diffraction peaks in other ranges, or the diffraction peaks in other ranges are sufficiently low to be distinguishable from the maximum diffraction peak in the range of 28 to 29 degrees. Furthermore, when the maximum value of the diffraction intensity in the X-ray diffraction profile where the diffraction angle 2θ is between 28 degrees and 29 degrees is I_Lmax, and the maximum value of the diffraction intensity in the X-ray diffraction profile where the diffraction angle 2θ is between 30 degrees and 32 degrees is I_Hmax, it is preferable that I_Lmax / I_Hmax be 1.5 or more, more preferably 1.7 or more, and even more preferably 1.9 or more. The lower layer 21 having such an X-ray diffraction profile is preferable in that it can suppress the detection of false defects. The false defects referred to here are allowable irregularities on the thin film surface that do not affect pattern transfer and that would be erroneously determined to be defects when inspected with a defect inspection device. If a large number of such false defects are detected during defect inspection, fatal defects that affect pattern transfer may be buried among the numerous false defects, and fatal defects that should not be missed may not be discovered.

[0037] Furthermore, from the viewpoint of further suppressing detection of false defects, it is preferable that the lower layer 21 has crystallinity, and among the orientations of m[11-1], o

[0111] , and m

[0111] , the degree of orientation of m[11-1] is the largest. It is also preferable that the lower layer 21 has crystallinity, and among the orientations of m[11-1], o

[0111] , and m

[0111] , the degree of orientation of o

[0111] is the smallest. Here, m[11-1] and m

[0111] are the [11-1] and

[0111] planes in a simple monoclinic lattice, and have diffraction angles 2θ of 28.589 degrees and 31.811 degrees. Also, o

[0111] is the

[0111] plane in a simple rectangular lattice, and has a diffraction angle 2θ of 30.056 degrees. Note that m[11-1] is,

[0038]

number

[0039] Upper layer 22 preferably contains silicon, oxygen, and nitrogen, and more preferably consists of silicon, oxygen, and nitrogen. The total content of silicon, oxygen, and nitrogen in upper layer 22 is preferably 95 atomic % or more, and even more preferably 98 atomic % or more. As described for the lower layer, the total content of elements that may be contained in upper layer 22 in trace amounts as impurities is preferably 3 atomic % or less, and more preferably 2 atomic % or less. The nitrogen content in the upper layer 22 is preferably 15 atomic % or more, and more preferably 18 atomic % or more. This allows the overall thickness of the phase shift film to be smaller. On the other hand, the nitrogen content in the upper layer 22 is preferably 60 atomic % or less, and more preferably 50 atomic % or less. This allows the transmittance of the overall phase shift film to be higher. The oxygen content in the upper layer 22 is preferably 20 atomic % or more, and more preferably 25 atomic % or more. This allows the transmittance of the entire phase shift film to be high. On the other hand, the oxygen content in the upper layer 22 is preferably 50 atomic % or less, and more preferably 45 atomic % or less. This allows the film thickness of the entire phase shift film to be reduced while maintaining the desired optical properties.

[0040] The upper layer 22 preferably has a refractive index n of 2.3 or less, more preferably 2.2 or less, for the exposure light. The upper layer 22 preferably has a refractive index n of 1.8 or more, more preferably 1.9 or more. On the other hand, the upper layer 22 preferably has an extinction coefficient k of the exposure light that is smaller than that of the lower layer 21. Specifically, it is preferably less than 0.15, more preferably 0.13 or less. This is to increase the transmittance of the phase shift film 2 for the exposure light. Furthermore, the extinction coefficient k of the upper layer 22 for the exposure light is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.04 or more. This allows the thickness of the entire phase shift film to be reduced while maintaining the desired optical properties.

[0041] The thickness of the upper layer 22 is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more, and in order to suppress the thickness of the phase shift film 2, it is preferably 25 nm or less, and more preferably 20 nm or less.

[0042] It is more preferable that the thickness of the lower layer 21 of the phase shift film 2 is thicker than the thickness of the upper layer 22. When patterning the phase shift film 2, dry etching is continued even after the etching of the phase shift film 2 reaches the surface of the light-transmitting substrate 1, so-called over-etching, in order to increase the verticality of the sidewalls of the pattern formed. In over-etching, the sidewalls of the pattern formed in the phase shift film 2 facing the light-transmitting substrate 1 are mainly etched. If the thickness of the lower layer 21 is thick, the proportion of the lower layer 21 in the sidewalls of the pattern of the phase shift film 2 becomes relatively high. In this case, over-etching makes it easier to control the verticality of the sidewalls of the pattern of the phase shift film 2.

[0043] The refractive index n and extinction coefficient k of a thin film, including the phase shift film 2, are determined not only by the composition of the thin film. Factors that influence the refractive index n and extinction coefficient k include the film density and crystalline state of the thin film. Therefore, the conditions for forming the thin film by reactive sputtering are adjusted to ensure that the thin film has the desired refractive index n and extinction coefficient k. Setting the refractive index n and extinction coefficient k of the phase shift film 2 within the above ranges is not limited to adjusting the ratio of the mixed gas of noble gas and reactive gas (oxygen gas, nitrogen gas, etc.) during reactive sputtering. Various factors, such as the pressure in the film formation chamber, the power applied to the sputtering target, and the positional relationship between the target and the translucent substrate 1, are also involved during reactive sputtering. These film formation conditions are specific to the film formation apparatus and are adjusted appropriately so that the thin film formed has the desired refractive index n and extinction coefficient k.

[0044] [Light-shielding film] The mask blank 100 includes a light-shielding film 3 on a phase shift film 2. In a phase shift mask, the peripheral region of the region where a transfer pattern is formed (transfer pattern formation region) may be required to have an optical density (OD) of a predetermined value or higher to prevent the resist film from being affected by exposure light transmitted through the peripheral region when the resist film is exposed and transferred to a resist film on a semiconductor wafer using an exposure device. The peripheral region of the phase shift mask preferably has an OD of 2.8 or higher, more preferably 3.0 or higher. As described above, the phase shift film 2 has the function of transmitting exposure light at a predetermined transmittance, and it may be difficult to achieve the predetermined optical density using the phase shift film 2 alone. For this reason, a light-shielding film 3 may be laminated on the phase shift film 2 during the manufacturing process of the mask blank 100 to compensate for any insufficient optical density. By configuring the mask blank 100 in this manner, if the light-shielding film 3 is removed from the area where the phase shift effect is used (basically the transfer pattern formation area) during the manufacturing process of the phase shift mask 200 (see Figure 2), it is possible to manufacture a phase shift mask 200 in which a predetermined optical density value is ensured in the peripheral area.

[0045] Either a single-layer structure or a laminated structure of two or more layers can be applied to the light-shielding film 3. Furthermore, each layer of the light-shielding film 3 having a single-layer structure and a laminated structure of two or more layers may have substantially the same composition in the film or layer thickness direction, or may have a composition gradient in the layer thickness direction.

[0046] 1 has a configuration in which a light-shielding film 3 is laminated on a phase shift film 2 without any other film therebetween. In this configuration, the light-shielding film 3 is preferably made of a material that has sufficient etching selectivity with respect to the etching gas used to form a pattern in the phase shift film 2. In this case, the light-shielding film 3 is preferably made of a material containing chromium. Examples of chromium-containing materials that form the light-shielding film 3 include metal chromium and materials that contain chromium and one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine.

[0047] Generally, chromium-based materials are etched with a mixed gas of chlorine-based gas and oxygen gas, but the etching rate of chromium metal with this etching gas is not very high. In consideration of increasing the etching rate with the mixed gas of chlorine-based gas and oxygen gas, the material for forming the light-shielding film 3 is preferably a material containing chromium and one or more elements selected from oxygen, nitrogen, carbon, boron, and fluorine. Furthermore, the chromium-containing material for forming the light-shielding film 3 may contain one or more elements selected from molybdenum, indium, and tin. By containing one or more elements selected from molybdenum, indium, and tin, the etching rate with the mixed gas of chlorine-based gas and oxygen gas can be made faster.

[0048] Furthermore, if a hard mask film 4 (described later) is formed on the light-shielding film 3 using a material containing chromium, the light-shielding film 3 may be formed using a material containing silicon. In particular, a material containing a transition metal and silicon has high light-shielding performance, allowing the thickness of the light-shielding film 3 to be reduced. In this case, an etching mask film made of a material having sufficient etching resistance to the etching gas used to etch the phase shift film 2 and the light-shielding film 3 may be formed between the phase shift film 2 and the light-shielding film 3. Examples of transition metals contained in the light-shielding film 3 include molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), chromium (Cr), nickel (Ni), vanadium (V), zirconium (Zr), ruthenium (Ru), rhodium (Rh), zinc (Zn), niobium (Nb), palladium (Pd), and the like, or alloys of these metals. Examples of metal elements other than transition metal elements contained in the light-shielding film 3 include aluminum (Al), indium (In), tin (Sn), and gallium (Ga).

[0049] On the other hand, the light-shielding film 3 may have a structure in which a layer containing chromium and a layer containing a transition metal and silicon are laminated in this order from the side of the phase shift film 2. In this case, the specific materials of the layer containing chromium and the layer containing a transition metal and silicon are the same as those of the light-shielding film 3 described above.

[0050] [Hard mask film] The hard mask film 4 is provided in contact with the surface of the light-shielding film 3. The hard mask film 4 is a film formed of a material that has etching resistance against the etching gas used to etch the light-shielding film 3. This hard mask film 4 only needs to have a thickness that allows it to function as an etching mask until the dry etching for forming a pattern in the light-shielding film 3 is completed, and is not basically limited by its optical properties. Therefore, the thickness of the hard mask film 4 can be significantly thinner than the thickness of the light-shielding film 3.

[0051] When the light-shielding film 3 is made of a material containing chromium, the hard mask film 4 is preferably made of a material containing silicon. In this case, the hard mask film 4 tends to have low adhesion to resist films made of organic materials, so it is preferable to treat the surface of the hard mask film 4 with HMDS (Hexamethyldisilazane) to improve the surface adhesion. In this case, the hard mask film 4 is more preferably made of SiO2, SiN, SiON, etc.

[0052] Furthermore, when the light-shielding film 3 is formed of a material containing chromium, the hard mask film 4 can be formed of a material containing tantalum, in addition to the above. In this case, the tantalum-containing material can be tantalum metal or a material containing tantalum and one or more elements selected from nitrogen, oxygen, boron, and carbon. Examples of the tantalum-containing material include Ta, TaN, TaO, TaON, TaBN, TaBO, TaBON, TaCN, TaCO, TaCON, TaBCN, and TaBOCN. When the light-shielding film 3 is formed of a material containing silicon, the hard mask film 4 is preferably formed of the above-mentioned material containing chromium.

[0053] [Resist film] In the mask blank 100, a resist film made of an organic material is preferably formed with a thickness of 100 nm or less on the surface of the hard mask film 4. In the case of a pattern corresponding to the DRAM hp32 nm generation, a transfer pattern (phase shift pattern) to be formed on the hard mask film 4 may be provided with a sub-resolution assist feature (SRAF) with a line width of 40 nm. However, even in this case, the provision of the hard mask film 4 as described above reduces the thickness of the resist film, thereby enabling the cross-sectional aspect ratio of the resist pattern formed by this resist film to be as low as 1:2.5. This prevents the resist pattern from collapsing or detaching during development, rinsing, etc. The resist film preferably has a thickness of 80 nm or less. The resist film is preferably a resist for electron beam lithography exposure, and more preferably a chemically amplified resist.

[0054] <Second embodiment> FIG. 2 is a cross-sectional view showing the configuration of a mask blank 100 according to a second embodiment of the present invention. The mask blank 100 shown in FIG. 2 differs from the mask blank 100 shown in FIG. 1 in that the phase shift film 2 has a three-layer structure including a lower layer 21, an upper layer 22, and an intermediate layer 23 therebetween. In this embodiment, the intermediate layer 23 is formed in contact with each of the lower layer 21 and the upper layer 22. Hereinafter, explanations of points common to the mask blank 100 of the first embodiment will be omitted as appropriate. Note that the thicknesses of the layers of the phase shift film 2 shown in FIGS. 1 and 2 are illustrative, as can be understood from the above explanation, and are not limited to those shown.

[0055] Intermediate layer 23 preferably contains silicon and oxygen, and more preferably consists of silicon and oxygen. When intermediate layer 23 contains elements other than silicon and oxygen, the total content of silicon and oxygen is preferably 90 atomic % or more, more preferably 95 atomic % or more, and even more preferably 98 atomic % or more. By providing such an intermediate layer 23, it is possible to improve adhesion with lower layer 21 and upper layer 22. Furthermore, as described for the lower layer, the total content of elements that may be contained in intermediate layer 23 in trace amounts as impurities is preferably 3 atomic % or less, and more preferably 2 atomic % or less. The thickness of intermediate layer 23 is preferably greater than 1 nm, more preferably 2 nm or greater, from the viewpoint of ensuring the function of improving adhesion. Also, in order to suppress the film thickness of phase shift film 2, the thickness of intermediate layer 23 is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less.

[0056] In the phase shift film 2 including the intermediate layer 23, the thickness of the lower layer 21 is preferably 5 nm or more, more preferably 10 nm or more, and even more preferably 20 nm or more, while the thickness of the lower layer 21 is preferably 46 nm or less, and more preferably 45 nm or less. In the phase shift film 2 including the intermediate layer 23, the thickness of the upper layer 22 is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more, while the thickness of the upper layer 22 is preferably 25 nm or less, and more preferably 20 nm or less.

[0057] Although the first embodiment describes a phase shift film 2 having a two-layer structure and the second embodiment describes a phase shift film 2 having a three-layer structure, the present invention is not limited to these. As long as the desired transmittance, retardation, and film thickness are satisfied, the phase shift film 2 may have four or more layers, including films having the same structure as the lower layer, upper layer, or intermediate layer described above, or other films stacked thereon.

[0058] The phase shift film 2 in the mask blank 100 of the first and second embodiments can be patterned by a two-stage dry etching process using a chlorine-based gas and a fluorine-based gas. Preferably, the lower layer 21 is patterned by dry etching using a chlorine-based gas, and the upper layer 22 and intermediate layer 23 are patterned by dry etching using a fluorine-based gas. Etching selectivity is high between the lower layer 21 and the upper layer 22 (and intermediate layer 23). Although not particularly limited, by performing etching processes in multiple stages on a phase shift film 2 having the above characteristics, the effects of side etching can be suppressed and a good pattern cross-sectional shape can be obtained. By setting the total content of hafnium and oxygen in the lower layer 21 to 95 atomic % or more and the nitrogen content in the upper layer 22 to 15 atomic % or more, it is possible to ensure sufficient etching resistance of the upper layer 22 against the etching gas (chlorine-based gas) used when etching the lower layer 21. This makes it possible to prevent the pattern sidewalls of the upper layer 22 from being etched while the lower layer 21 is being etched. Therefore, a good pattern cross-sectional shape can be obtained.

[0059] Generally, when forming a pattern on a thin film by dry etching, additional etching (so-called over-etching) is performed to improve the verticality of the sidewalls of the pattern formed on the thin film. The over-etching is often determined based on the time it takes for the etching to reach the underside of the thin film, known as the just-etching time. By applying a multi-stage etching process to pattern the phase shift film 2 as described above, the time used as the basis for the over-etching time can be set to the just-etching time for the lower layer 21 of the phase shift film 2. This shortens the over-etching time and achieves good etching depth uniformity. Here, the chlorine-based gas is preferably a chlorine-based gas containing boron, more preferably BCl3 gas, and even more preferably a mixed gas of BCl3 gas and Cl2 gas.

[0060] [Mask blank manufacturing procedure] The mask blank 100 having the above configuration is manufactured in the following procedure: First, a light-transmitting substrate 1 is prepared. The end faces and main surface of this light-transmitting substrate 1 are polished to a predetermined surface roughness (for example, a root-mean-square roughness Rq of 0.2 nm or less within an inner region of a square with sides of 1 μm), and then the substrate is subjected to a predetermined cleaning process and drying process.

[0061] Next, the phase shift film 2 is formed on the transparent substrate 1 by sputtering in the order of lower layer 21, upper layer 22 (in the case of a phase shift film 2 having an intermediate layer 23, the lower layer 21, intermediate layer 23, and upper layer 22 are formed in that order). The lower layer 21 and upper layer 22 (and intermediate layer 23) of the phase shift film 2 are formed by sputtering, but any sputtering method such as DC sputtering, RF sputtering, or ion beam sputtering can be used. In consideration of the film formation rate, DC sputtering is preferred. When a target with low conductivity is used, RF sputtering or ion beam sputtering is preferred, but RF sputtering is more preferred in consideration of the film formation rate.

[0062] For the lower layer 21 of the phase shift film 2, either a sputtering target containing hafnium or a sputtering target containing hafnium and oxygen can be used. For the upper layer 22 (and intermediate layer 23) of the phase shift film 2, either a sputtering target containing silicon or a sputtering target containing silicon and oxygen can be used. If an annealing treatment (heat treatment) is performed after the lower layer 21 of the phase shift film 2 is formed and before the upper layer 22 is formed, the film stress of the lower layer 21 is reduced, which is preferable in that it reduces film peeling defects caused by the stress difference between the lower layer 21 and the upper layer 22 and improves the quality of the phase shift film 2. Here, in the case of a phase shift film 2 having a three-layer structure including the intermediate layer 23, it is possible to improve adhesion with the lower layer 21 and the upper layer 22. Therefore, even if the intermediate layer 23 and the upper layer 22 are formed without performing an annealing treatment for reducing film stress after forming the lower layer 21, it is possible to obtain a phase shift film 2 of good quality with few defects, which is preferable.

[0063] After the phase shift film 2 is formed, an annealing treatment is appropriately performed at a predetermined heating temperature. Next, the light-shielding film 3 is formed on the phase shift film 2 by a sputtering method. Then, the hard mask film 4 is formed on the light-shielding film 3 by a sputtering method. In the film formation by the sputtering method, a sputtering target and a sputtering gas containing the materials constituting each of the above films in a predetermined composition ratio are used, and if necessary, a mixed gas of the above-mentioned noble gas and reactive gas is also used as the sputtering gas. Thereafter, if the mask blank 100 has a resist film, the surface of the hard mask film 4 is treated with HMDS (Hexamethyldisilazane) as necessary. Then, a resist film is formed on the HMDS-treated surface of the hard mask film 4 by a coating method such as spin coating, thereby completing the mask blank 100. Thus, according to the mask blank 100 of the first and second embodiments, it is possible to increase the transmittance to exposure light (especially ArF excimer laser exposure light) to enhance the phase shift effect, while also being able to suppress the film thickness of the phase shift film, allowing for the formation of fine patterns and the manufacture of a phase shift mask 200 with good optical performance.

[0064] Phase Shift Mask and Manufacturing Method Thereof FIG. 3 shows a phase shift mask 200 according to an embodiment of the present invention, which is manufactured from the mask blank 100 of the above embodiment, and its manufacturing process. As shown in FIG. 3(g), the phase shift mask 200 is characterized in that a phase shift pattern 2a, which is a transfer pattern, is formed in the phase shift film 2 of the mask blank 100, and a light-shielding pattern 3b, which has a pattern including a light-shielding band, is formed in the light-shielding film 3. This phase shift mask 200 has the same technical features as the mask blank 100. The matters relating to the light-transmitting substrate 1, the lower layer 21, the upper layer 22 (and the intermediate layer 23) of the phase shift film 2, and the light-shielding film 3 in the phase shift mask 200 are the same as those in the mask blank 100. The hard mask film 4 is removed during the manufacturing process of this phase shift mask 200.

[0065] The method for manufacturing a phase shift mask 200 according to an embodiment of the present invention uses the mask blank 100 described above and is characterized by comprising the steps of: forming a transfer pattern in the light-shielding film 3 by dry etching; forming a transfer pattern in the phase shift film 2 by dry etching using the light-shielding film 3 having the transfer pattern as a mask; and forming a light-shielding pattern 3b in the light-shielding film 3 by dry etching using a resist film (resist pattern 6b) having the light-shielding pattern as a mask. The method for manufacturing the phase shift mask 200 according to the present invention will be described below in accordance with the manufacturing steps shown in FIG. 3 . Here, the method for manufacturing a phase shift mask 200 using a mask blank 100 in which a hard mask film 4 is laminated on the light-shielding film 3 will be described. The case where a chromium-containing material is used for the light-shielding film 3 and a silicon-containing material is used for the hard mask film 4 will be described.

[0066] First, a resist film is formed by spin coating in contact with the hard mask film 4 of the mask blank 100. Next, a first pattern, which is a transfer pattern (phase shift pattern) to be formed in the phase shift film 2, is exposed to and written on the resist film using an electron beam, and then predetermined processes such as development are performed to form a first resist pattern 5a corresponding to the phase shift pattern (see FIG. 3(a)). Subsequently, using the first resist pattern 5a as a mask, dry etching is performed using a fluorine-based gas to form a first pattern (hard mask pattern 4a) in the hard mask film 4 (see FIG. 3(b)).

[0067] Next, the resist pattern 5a is removed, and then dry etching is performed using a mixed gas of chlorine-based gas and oxygen gas with the hard mask pattern 4a as a mask, to form a light-shielding pattern 3a corresponding to the first pattern in the light-shielding film 3 (see FIG. 3(c)). Subsequently, dry etching using a fluorine-based gas and dry etching using a chlorine-based gas are alternately performed with the light-shielding pattern 3a as a mask, to form a first pattern (phase shift pattern 2a) in the phase shift film 2, and the hard mask pattern 4a is removed (see FIG. 3(d)). More specifically, dry etching using a fluorine-based gas is performed on the upper layer 22 (and the intermediate layer 23), and dry etching using a chlorine-based gas is performed on the lower layer 21.

[0068] Next, a resist film is formed on the mask blank 100 by spin coating. Next, a second pattern corresponding to the pattern (light-shielding pattern) to be formed in the light-shielding film 3 is exposed to and written on the resist film using an electron beam, and then predetermined processes such as development are performed to form a second resist pattern 6b corresponding to the light-shielding pattern (see FIG. 3(e)). Subsequently, using the second resist pattern 6b as a mask, dry etching is performed using a mixed gas of chlorine-based gas and oxygen gas to form a second pattern (light-shielding pattern 3b) in the light-shielding film 3 (see FIG. 3(f)). Furthermore, the second resist pattern 6b is removed, and after predetermined processes such as cleaning, a phase shift mask 200 is obtained (see FIG. 3(g)).

[0069] The chlorine-based gas used in the dry etching is not particularly limited as long as it contains Cl. Examples include Cl2, SiCl2, CHCl3, CH2Cl2, CCl4, and BCl3. The chlorine-based gas used in the dry etching of the lower layer 21 preferably contains boron, and more preferably contains BCl3. In particular, a mixed gas of BCl3 gas and Cl2 gas is preferred because it has a relatively high etching rate for hafnium.

[0070] Phase shift mask 200 manufactured by the manufacturing method shown in FIG. 3 is a phase shift mask having, on light-transmitting substrate 1, phase shift film 2 having a transfer pattern (phase shift pattern 2a).

[0071] By manufacturing the phase shift mask 200 in this manner, the transmittance to the exposure light (especially the exposure light of an ArF excimer laser) can be increased, thereby enhancing the phase shift effect, and the film thickness of the phase shift film can be reduced, allowing for the formation of fine patterns, resulting in a phase shift mask 200 with good optical performance. Then, when phase shift mask 200 having this phase shift film is set in an exposure tool and exposed and transferred onto a transfer target (such as a resist film on a semiconductor substrate), an exposure margin can be ensured.

[0072] Furthermore, the method for manufacturing a semiconductor device of the present invention is characterized by comprising a step of using the phase shift mask 200 to transfer a transfer pattern onto a resist film on a semiconductor substrate by exposure.

[0073] Because the phase shift mask 200 and mask blank 100 of the present invention have the effects described above, when the phase shift mask 200 is set on the mask stage of an exposure tool using an ArF excimer laser as exposure light and a transfer pattern is transferred by exposure to a resist film on a semiconductor device, the transfer pattern can be transferred to the resist film on the semiconductor device with high CD uniformity. Therefore, when a circuit pattern is formed by dry etching an underlying film using this resist film pattern as a mask, a high-precision circuit pattern can be formed without wiring shorts or breaks due to reduced CD uniformity. [Example]

[0074] In the following, examples 1 to 3 and comparative example 1 will be described in order to more specifically explain the embodiments of the present invention.

[0075] Example 1 [Mask blank manufacturing] Referring to Figure 1, a light-transmitting substrate 1 was prepared, made of synthetic quartz glass and having a main surface measuring approximately 152 mm x 152 mm and a thickness of approximately 6.35 mm. The end faces and main surfaces of this light-transmitting substrate 1 were polished to a predetermined surface roughness (Rq of 0.2 nm or less), and then subjected to predetermined cleaning and drying processes. The optical properties of light-transmitting substrate 1 were measured using a spectroscopic ellipsometer (JA Woollam M-2000D), and the refractive index for light with a wavelength of 193 nm was found to be 1.556 and the extinction coefficient was 0.000.

[0076] Next, the light-transmitting substrate 1 was placed in a single-wafer RF sputtering apparatus, and a lower layer 21 composed of hafnium and oxygen was formed on the light-transmitting substrate 1 by reactive sputtering (RF sputtering) using a HfO2 target in a mixed gas atmosphere of krypton (Kr) and oxygen (O2). The lower layer of Example 1 was formed on another light-transmitting substrate, and composition analysis revealed that the hafnium (Hf):oxygen (O) ratio was 37 atomic %:63 atomic %, and the total content of hafnium and oxygen in the lower layer 21 was 100 atomic %, or more than 95 atomic %. The oxygen content in the lower layer 21 was 63 atomic %, or more than 50 atomic %.

[0077] In addition, the lower layer of Example 1 was formed on another light-transmitting substrate and analyzed by out-of-plane measurement (θ-2θ measurement) using X-ray diffraction.The maximum diffraction intensity was found to be in the range of 28 to 29 degrees when the diffraction angle 2θ was in the range of 25 to 35 degrees. Furthermore, when the maximum value of the diffraction intensity when the diffraction angle 2θ is between 28 and 29 degrees is I_Lmax and the maximum value of the diffraction intensity when the diffraction angle 2θ is between 30 and 32 degrees is I_Hmax, the ratio I_Lmax / I_Hmax was 1.5 or more. Then, the degree of orientation at each peak of diffracted X-ray intensity was examined, and it was found that of the m[11-1], o

[0111] , and m

[0111] orientations, the degree of orientation of m[11-1] was the largest and the degree of orientation of o

[0111] was the smallest. Furthermore, to confirm that the pseudo defects in the phase shift film 2 in Example 1 were reduced, a mask blank was obtained using another light-transmitting substrate and the same treatment as above. The surface condition of the phase shift film 2 was measured using a non-contact surface profilometer, and power spectral density analysis was performed. In the power spectral density analysis, the surface condition of the phase shift film 2 in Example 1 was measured using an atomic force microscope (measurement area: 10 μm × 10 μm, number of pixels: 256 × 256). The results of power spectrum density analysis show that the spatial frequency is 0.1 μm. -1 1.0μm or more -1In the low spatial frequency range below, the maximum value of the power spectral density is 1.2 × 10 6 nm 4 The smaller the value of the power spectrum density in the low spatial frequency region, the more the false defects can be reduced. In other words, it was clear that in Example 1, the false defects were sufficiently reduced.

[0078] After forming lower layer 21 of phase shift film 2, annealing (heat treatment) was performed before forming upper layer 22. Then, for light-transmitting substrate 1 on which lower layer 21 had been formed, upper layer 22 composed of silicon, oxygen, and nitrogen was formed on lower layer 21 by reactive sputtering (RF sputtering) using a Si target in a mixed gas atmosphere of krypton (Kr), oxygen (O2), and nitrogen (N2), thereby forming phase shift film 2 consisting of lower layer 21 and upper layer 22. An upper layer was formed on another light-transmitting substrate under the same conditions, and composition analysis revealed that the Si:O:N ratio was 37%:45%:18%, with the nitrogen content being 15 atomic % to 60 atomic % and the oxygen content being 50 atomic % or less. The thickness of the lower layer 21 was 42 nm, the thickness of the upper layer 22 was 18 nm, and the thickness of the phase shift film 2 was 60 nm.

[0079] Next, the transparent substrate 1 on which the phase shift film 2 was formed was subjected to a heat treatment to reduce the film stress of the phase shift film 2. Using a phase shift amount measuring device (MPM193 manufactured by Lasertec Corporation), the transmittance and phase difference of the heat-treated phase shift film 2 for light with a wavelength of 193 nm were measured. The transmittance was 40.9%, or more than 20%, and the phase difference was 177.6 degrees (deg), or between 150 and 210 degrees. Furthermore, the optical properties of the phase shift film 2 were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). For light with a wavelength of 193 nm, the refractive index n of the lower layer 21 was 2.93 and the extinction coefficient k was 0.24. The refractive index n of the upper layer 22 was 1.92 and the extinction coefficient k was 0.04.

[0080] Next, the light-transmitting substrate 1 with the phase shift film 2 formed thereon was placed in a single-wafer DC sputtering apparatus, and reactive sputtering (DC sputtering) was performed using a chromium (Cr) target in a mixed gas atmosphere of argon (Ar), helium (He), and nitrogen (N2). As a result, a light-shielding film (CrN film) 3 composed of chromium and nitrogen was formed with a thickness of 50 nm on the phase shift film 2. A light-shielding film was formed on another light-transmitting substrate under the same conditions, and composition analysis revealed that Cr:N = 87%:13%.

[0081] Next, the light-transmitting substrate 1 on which the light-shielding film (CrN film) 3 was formed was subjected to a heat treatment. After the heat treatment, the optical density of the laminated structure of the phase shift film 2 and the light-shielding film 3 on the light-transmitting substrate 1 was measured using a spectrophotometer (Cary4000 manufactured by Agilent Technologies) at the wavelength (193 nm) of ArF excimer laser light, and it was confirmed to be 3.0 or more.

[0082] Next, the light-transmitting substrate 1 on which the phase shift film 2 and the light-shielding film 3 were laminated was placed in a single-wafer RF sputtering apparatus, and a hard mask film 4 composed of silicon, oxygen, and nitrogen was formed to a thickness of 12 nm on the light-shielding film 3 by reactive sputtering (RF sputtering) using a Si target in a mixed gas atmosphere of argon (Ar), oxygen (O2), and nitrogen (N2). Further, a predetermined cleaning process was performed, and the mask blank 100 of Example 1 was produced. Furthermore, the phase shift film of Example 1 was formed on another light-transmitting substrate, and after the desired annealing treatment, a predetermined cleaning test (chemical resistance test) was performed. After the cleaning test, the surface and side surfaces of the phase shift film of Example 1 were observed for film loss. Almost no film loss was observed on either the surface or side surfaces, indicating sufficient chemical resistance.

[0083] [Phase shift mask manufacturing] Next, to confirm that the fine pattern would not collapse, a halftone phase shift mask 200 of Example 1 having a phase shift pattern 2a with a width of 18 nm was manufactured using the mask blank 100 of Example 1 as follows: First, the surface of the hard mask film 4 was treated with HMDS. Next, a resist film made of a chemically amplified resist for electron beam lithography was formed on the surface of the hard mask film 4 by spin coating. Next, a first pattern corresponding to the phase shift pattern to be formed in the phase shift film 2 was lithographed using an electron beam on this resist film, and the resist film was subjected to predetermined development and cleaning processes to form a resist pattern 5a corresponding to the first pattern (see FIG. 3(a)).

[0084] Next, using the resist pattern 5a as a mask, dry etching was performed using CF4 gas to form a hard mask pattern 4a corresponding to the first pattern in the hard mask film 4 (see FIG. 3(b)).

[0085] Next, the resist pattern 5a was removed. Subsequently, using the hard mask pattern 4a as a mask, dry etching was performed using a mixed gas of chlorine gas (Cl2) and oxygen gas (O2), thereby forming a light-shielding pattern 3a corresponding to the first pattern in the light-shielding film 3 (see FIG. 3(c)).

[0086] Next, using the light-shielding pattern 3a as a mask, dry etching was performed to form a first pattern (phase shift pattern 2a) in the phase shift film 2, and at the same time, the hard mask pattern 4a was removed (see FIG. 3(d)). At this time, the lower layer 21 was dry-etched with a mixed gas of BCl3 gas and Cl2 gas, and the upper layer 22 was dry-etched with a fluorine-based gas (mixed gas of SF6 and He).

[0087] Next, a resist film made of a chemically amplified resist for electron beam lithography was formed on the light-shielding pattern 3a by spin coating. Next, a second pattern corresponding to the pattern to be formed in the light-shielding film (including the light-shielding band pattern) was exposed and written on the resist film, and then predetermined processes such as development were performed to form a resist pattern 6b corresponding to the light-shielding pattern (see FIG. 3(e)). Subsequently, using the resist pattern 6b as a mask, dry etching was performed using a mixed gas of chlorine gas (Cl2) and oxygen gas (O2), forming a second pattern (light-shielding pattern 3b) in the light-shielding film 3 (see FIG. 3(f)). Furthermore, the resist pattern 6b was removed, and after predetermined processes such as cleaning, a phase shift mask 200 having a phase shift pattern with a width of 18 nm was obtained (see FIG. 3(g)). No collapse of phase shift pattern 2 a was observed in phase shift mask 200 of Example 1. Furthermore, when the cross section of phase shift pattern 2 a in phase shift mask 200 of Example 1 was observed, the cross-sectional shape of phase shift pattern 2 a was good, and no film loss was observed on either the surface or side of phase shift pattern 2 a, indicating that phase shift pattern 2 a was in good condition.

[0088] [Evaluation of pattern transfer performance] Using the phase shift mask 200 fabricated according to the above procedure, a simulation of the transferred image was performed when a 20 nm fine pattern was exposed to a resist film on a semiconductor device using an AIMS193 (manufactured by Carl Zeiss) with exposure light of 193 nm wavelength. When the exposure transferred image of this simulation was verified, it was found that the CD in-plane uniformity was high and fully satisfied the design specifications. From these results, it can be said that even if the phase shift mask 200 of Example 1 is set on the mask stage of an exposure tool and a 20 nm fine pattern is exposed to a resist film on a semiconductor device, the circuit pattern ultimately formed on the semiconductor device can be formed with high precision.

[0089] Example 2 [Mask blank manufacturing] The mask blank 100 of Example 2 was manufactured using the same procedures as those of Example 1, except for the phase shift film 2. The phase shift film 2 of Example 2 was formed under different film formation conditions than the phase shift film 2 of Example 1. Specifically, the thickness of the lower layer 21 of the phase shift film 2 was first set to 39 nm (the composition, diffraction intensity, and power spectral density analysis results of the lower layer 21 were the same as those of Example 1). Annealing (heat treatment) was then performed before forming the upper layer 22. Then, the light-transmitting substrate 1 on which the lower layer 21 had been formed was subjected to reactive sputtering (RF sputtering) using a Si target in a mixed gas atmosphere of krypton (Kr), oxygen (O), and nitrogen (N). The upper layer 22, composed of silicon, oxygen, and nitrogen, was formed on the lower layer 21 to a thickness of 20 nm. Thus, the phase shift film 2 composed of the lower layer 21 and the upper layer 22 was formed to a thickness of 59 nm. An upper layer was formed on another light-transmitting substrate under the same conditions, and composition analysis revealed that the composition was Si:O:N = 41%:31%:28%, with a nitrogen content of 15 atomic % or more and 60 atomic % or less, and an oxygen content of 50 atomic % or less.

[0090] Next, the transparent substrate 1 on which this phase shift film 2 was formed was subjected to a heat treatment to reduce the film stress of the phase shift film 2. The transmittance and phase difference of the heat-treated phase shift film 2 for light with a wavelength of 193 nm were measured using a phase shift amount measuring device (MPM193 manufactured by Lasertec Corporation). The transmittance was 40.5% and the phase difference was 178.5 degrees (deg). Furthermore, the optical properties of the phase shift film 2 were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). The refractive index n of the lower layer 21 for light with a wavelength of 193 nm was 2.93, the extinction coefficient k was 0.24, and the refractive index n of the upper layer 22 was 2.10, and the extinction coefficient k was 0.10.

[0091] Next, a light-shielding film (CrN film) 3 composed of chromium and nitrogen was formed to a thickness of 50 nm on the phase shift film 2 using the same procedure as in Example 1. The optical density of the laminated structure of the phase shift film 2 and the light-shielding film 3 on the light-transmitting substrate 1 on which the phase shift film 2 and the light-shielding film 3 of Example 2 were measured using a spectrophotometer (Cary 4000 manufactured by Agilent Technologies) at the wavelength (193 nm) of ArF excimer laser light, and it was confirmed to be 3.0 or more. Furthermore, the phase shift film of Example 2 was formed on another light-transmitting substrate, and a predetermined cleaning test (chemical resistance test) was performed in the same manner as in Example 1. After the cleaning test, the surface and side surfaces of the phase shift film of Example 2 were observed for film loss, and almost no film loss was observed on either the surface or side surfaces, indicating that the film had sufficient chemical resistance.

[0092] [Phase-shift mask manufacturing and evaluation] Next, using mask blank 100 of Example 2, a phase shift mask 200 of Example 2 having phase shift pattern 2a with a width of 18 nm was manufactured in the same manner as in Example 1. No collapse of phase shift pattern 2a was observed in phase shift mask 200 of Example 2. Furthermore, when the cross section of phase shift pattern 2a in phase shift mask 200 of Example 2 was observed, the cross-sectional shape of phase shift pattern 2a was good, and no film loss was observed on either the surface or side of phase shift pattern 2a, indicating that phase shift pattern 2a was in good condition. A simulation of the transferred image was performed using phase shift mask 200 of Example 2 using AIMS193 (manufactured by Carl Zeiss) in the same manner as in Example 1, in which a 20 nm fine pattern was exposed and transferred to a resist film on a semiconductor device using exposure light with a wavelength of 193 nm. When the simulated exposure transferred image was verified, it was found that the CD in-plane uniformity was high and fully satisfied the design specifications. From these results, it can be said that even if phase shift mask 200 of Example 2 is set on the mask stage of an exposure tool and a 20 nm fine pattern is exposed and transferred to a resist film on a semiconductor device, the circuit pattern ultimately formed on the semiconductor device can be formed with high precision.

[0093] Example 3 [Mask blank manufacturing] The mask blank 100 of Example 3 was manufactured using the same procedures as in Example 1, except for the phase shift film 2. The phase shift film 2 of Example 3 was formed under different deposition conditions than the phase shift film 2 of Example 1. Specifically, the phase shift film 2 had a three-layer structure including a lower layer 21, an upper layer 22, and an intermediate layer 23. First, the thickness of the lower layer 21 of the phase shift film 2 was set to 41 nm (the composition, diffraction intensity, and power spectral density analysis results of the lower layer 21 were the same as those of Example 1). Then, using a SiO target, a 3-nm-thick intermediate layer 23 composed of silicon and oxygen was formed on the lower layer 21 of the light-transmitting substrate 1 by sputtering (RF sputtering) in an argon (Ar) gas atmosphere. An intermediate layer was formed on another light-transmitting substrate under the same conditions, and composition analysis revealed a Si:O ratio of 34%:66%, with a total silicon and oxygen content of 90 atomic % or more. Then, using a Si target, reactive sputtering (RF sputtering) was performed on the light-transmitting substrate 1 on which the lower layer 21 and intermediate layer 23 had been formed in a mixed gas atmosphere of krypton (Kr), oxygen (O2), and nitrogen (N2) to form a 15-nm-thick upper layer 22 composed of silicon, oxygen, and nitrogen on the intermediate layer 23, thereby forming a 59-nm-thick phase shift film 2 consisting of the lower layer 21, intermediate layer 23, and upper layer 22. An upper layer was formed on another light-transmitting substrate under the same conditions, and composition analysis revealed that the Si:O:N ratio was 41%:31%:28%, with the nitrogen content ranging from 15 atomic % to 60 atomic % and the oxygen content being 50 atomic % or less.

[0094] Next, the transparent substrate 1 on which the phase shift film 2 was formed was subjected to a heat treatment to reduce the film stress of the phase shift film 2. The transmittance and phase difference of the heat-treated phase shift film 2 for light with a wavelength of 193 nm were measured using a phase shift amount measuring device (MPM193 manufactured by Lasertec Corporation). The transmittance was 40.0% and the phase difference was 178.9 degrees (deg). The optical properties of the phase shift film 2 were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). For light with a wavelength of 193 nm, the refractive index n of the lower layer 21 was 2.93 and the extinction coefficient k was 0.24. The refractive index n of the intermediate layer 23 was 1.56 and the extinction coefficient k was 0.00. The refractive index n of the upper layer 22 was 2.10 and the extinction coefficient k was 0.10.

[0095] Next, a light-shielding film (CrN film) 3 composed of chromium and nitrogen was formed to a thickness of 50 nm on the phase shift film 2 using the same procedure as in Example 1. The optical density of the laminated structure of the phase shift film 2 and the light-shielding film 3 on the light-transmitting substrate 1 on which the phase shift film 2 and the light-shielding film 3 of Example 3 were measured using a spectrophotometer (Cary 4000 manufactured by Agilent Technologies) at the wavelength (193 nm) of ArF excimer laser light, and it was confirmed to be 3.0 or more. Furthermore, the phase shift film of Example 3 was formed on another light-transmitting substrate, and a predetermined cleaning test (chemical resistance test) was performed in the same manner as in Example 1. After the cleaning test, the surface and side surfaces of the phase shift film of Example 3 were observed for film loss. Almost no film loss was observed on either the surface or side surfaces, indicating that the film had sufficient chemical resistance.

[0096] [Phase-shift mask manufacturing and evaluation] Next, using mask blank 100 of Example 3, a phase shift mask 200 of Example 3 having phase shift pattern 2a with a width of 18 nm was manufactured in the same manner as in Example 1. No collapse of phase shift pattern 2a was observed in phase shift mask 200 of Example 3. Furthermore, when the cross section of phase shift pattern 2a in phase shift mask 200 of Example 3 was observed, the cross-sectional shape of phase shift pattern 2a was good, and no film loss was observed on either the surface or side of phase shift pattern 2a, indicating that phase shift pattern 2a was in good condition. A simulation of the transferred image was performed using phase shift mask 200 of Example 3, similar to Example 1, using AIMS193 (manufactured by Carl Zeiss) to transfer a 20 nm fine pattern to a resist film on a semiconductor device using exposure light with a wavelength of 193 nm. When the simulated exposure transferred image was verified, it was found to have high CD in-plane uniformity and fully meet the design specifications. From these results, it can be said that even if phase shift mask 200 of Example 3 is set on the mask stage of an exposure tool and a 20 nm fine pattern is transferred to a resist film on a semiconductor device, the circuit pattern ultimately formed on the semiconductor device can be formed with high precision.

[0097] Comparative Example 1 [Mask blank manufacturing] The mask blank of Comparative Example 1 was manufactured using the same procedures as in Example 1, except for the phase shift film. The phase shift film of Comparative Example 1 was fabricated under different deposition conditions from Phase Shift Film 2 of Example 1. Specifically, the thickness of the lower layer of the phase shift film was set to 44 nm (the composition of the lower layer was the same as in Example 1). Annealing (heat treatment) was then performed before the upper layer was deposited. An upper layer composed of silicon, oxygen, and nitrogen was deposited on the light-transmitting substrate with the lower layer by reactive sputtering (RF sputtering) using a Si target in a mixed gas atmosphere of krypton (Kr), oxygen (O), and nitrogen (N). An upper layer composed of silicon, oxygen, and nitrogen was deposited on the lower layer to a thickness of 18 nm. Phase shift film 2, consisting of the lower and upper layers, was then formed to a thickness of 62 nm. The upper layer was deposited on another light-transmitting substrate under the same conditions, and composition analysis revealed that Si:O:N = 34%:56%:10%, meaning the nitrogen content did not satisfy the range of 15 atomic % to 60 atomic %. Moreover, the oxygen content did not satisfy the requirement of 50 atomic % or less.

[0098] Next, the transparent substrate with the phase shift film formed thereon was subjected to a heat treatment to reduce the film stress of the phase shift film. The transmittance and phase difference of the heat-treated phase shift film for light with a wavelength of 193 nm were measured using a phase shift measurement device (MPM193 manufactured by Lasertec Corporation). The transmittance was 40.5% and the phase difference was 178.5 degrees (deg). Furthermore, the optical properties of the phase shift film 2 were measured using a spectroscopic ellipsometer (M-2000D manufactured by JA Woollam). The refractive index n of the lower layer 21 for light with a wavelength of 193 nm was 2.93, the extinction coefficient k was 0.24, and the refractive index n of the upper layer 22 for light with a wavelength of 193 nm was 1.76, and the extinction coefficient k was 0.01.

[0099] Next, a light-shielding film (CrN film) 3 composed of chromium and nitrogen was formed to a thickness of 50 nm on the phase shift film using the same procedure as in Example 1. The optical density of the laminated structure of the phase shift film and light-shielding film of Comparative Example 1 was measured using a spectrophotometer (Cary4000 manufactured by Agilent Technologies) at the wavelength (193 nm) of ArF excimer laser light, and was confirmed to be 3.0 or higher.

[0100] [Phase-shift mask manufacturing and evaluation] Next, using this mask blank of Comparative Example 1, a phase shift mask of Comparative Example 1 having a phase shift pattern with a width of 18 nm was manufactured in the same manner as in Example 1. In phase shift mask 200 of Comparative Example 1, collapse of phase shift pattern 2a was observed. The cause of this is presumed to be that the thickness of the phase shift film was too large compared to the width dimension of phase shift pattern 2a. From this result, it can be said that if the phase shift mask of Comparative Example 1 is set on the mask stage of an exposure tool and a fine pattern of 20 nm or less is exposed and transferred onto a resist film on a semiconductor device, it will be difficult to form the circuit pattern that will ultimately be formed on the semiconductor device with high precision. [Explanation of symbols]

[0101] 1 Translucent substrate 2 Phase shift film 21 Lower layer 22 Upper layer 23 Middle Class 2a Phase shift pattern 3. Light-shielding film 3a, 3b Light blocking pattern 4 Hard mask film 4a Hard mask pattern 5a Resist pattern 6b Resist pattern 100 mask blanks 200 Phase Shift Mask

Claims

1. a light-transmitting substrate; a phase shift film formed on the light-transmitting substrate, The phase shift film is an underlayer comprising hafnium and oxygen; an upper layer formed on the lower layer, the upper layer comprising silicon, oxygen, and nitrogen; the total content of hafnium and oxygen in the lower layer is 95 atomic % or more; The nitrogen content of the upper layer is 15 atomic % or more, The mask blank, wherein the phase shift film has a thickness of 60 nm or less.

2. 2. The mask blank according to claim 1, wherein the oxygen content of said upper layer is 50 atomic % or less.

3. 3. The mask blank according to claim 1, wherein the oxygen content of the lower layer is 50 atomic % or more.

4. 4. The mask blank according to claim 1, wherein the nitrogen content of the upper layer is 60 atomic % or less.

5. the phase shift film includes an intermediate layer formed between the lower layer and the upper layer, 5. The mask blank according to claim 1, wherein the intermediate layer is made of a material having a total content of silicon and oxygen of 90 atomic % or more.

6. The mask blank according to claim 5 , wherein the intermediate layer is made of silicon and oxygen.

7. 7. The mask blank according to claim 1, wherein the phase shift film has a transmittance of 20% or more and a phase shift of 150 degrees or more and 210 degrees or less for exposure light of an ArF excimer laser.

8. 8. The mask blank according to claim 1, further comprising a light-shielding film on the phase shift film.

9. a light-transmitting substrate; a phase shift film provided on the light-transmitting substrate and having a transfer pattern formed thereon; The phase shift film is an underlayer comprising hafnium and oxygen; an upper layer formed on the lower layer, the upper layer comprising silicon, oxygen, and nitrogen; the total content of hafnium and oxygen in the lower layer is 95 atomic % or more; The nitrogen content of the upper layer is 15 atomic % or more, A phase shift mask, wherein the phase shift film has a thickness of 60 nm or less.

10. 10. The phase shift mask according to claim 9, wherein the oxygen content of said upper layer is 50 atomic % or less.

11. 11. The phase shift mask according to claim 9, wherein the oxygen content of said lower layer is 50 atomic % or more.

12. 12. The phase shift mask according to claim 9, wherein the nitrogen content of said upper layer is 60 atomic % or less.

13. the phase shift film includes an intermediate layer formed between the lower layer and the upper layer, 13. The phase shift mask according to claim 9, wherein said intermediate layer is made of a material having a total content of silicon and oxygen of 90 atomic % or more.

14. 14. The phase shift mask of claim 13, wherein said intermediate layer is made of silicon and oxygen.

15. 15. The phase shift mask according to claim 9, wherein the phase shift film has a transmittance of 20% or more and a phase shift of 150 degrees or more and 210 degrees or less for exposure light of an ArF excimer laser.

16. 16. The phase shift mask according to claim 9, further comprising a light-shielding film on which a light-shielding pattern is formed on the phase shift film.

17. 17. A method for manufacturing a semiconductor device, comprising the step of: using the phase shift mask according to claim 9; transferring the transfer pattern onto a resist film on a semiconductor substrate by exposure.

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