Sputtering target material, method for producing sputtering target material, mask blank, and method for producing mask blank
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- HOYA CORPORATION
- Filing Date
- 2025-12-25
- Publication Date
- 2026-07-30
Smart Images
Figure JP2025045577_30072026_PF_FP_ABST
Abstract
Description
Sputtering target material, method for manufacturing sputtering target material, mask blank, and method for manufacturing mask blank
[0001] The present invention relates to a sputtering target material, a method for manufacturing a sputtering target material, a mask blank, and a method for manufacturing a mask blank.
[0002] In recent years, there has been a growing demand for further miniaturization of devices and other components, leading to the shortening of exposure wavelengths. This shortening of exposure wavelengths has resulted in increasingly stringent requirements for the characteristics of mask blanks. For example, the semi-transparent film (halftone phase-shift film) in a halftone phase-shift mask blank must meet the required characteristics in terms of both light transmittance and phase shift amount for the exposure wavelength used.
[0003] As a sputtering target used to manufacture such mask blanks, for example, Patent Document 1 discloses a sputtering target in which silicon accounts for 70 to 97% by weight and the remainder is substantially composed of a high-melting-point metal silicide, wherein the metal structure has at least a silicon phase and a high-melting-point metal silicide phase composed of the silicon and the high-melting-point metal, and the sputtering surface has a full width at half maximum of 0.5 deg or less of the Si(111) plane peak determined by X-ray diffraction (XRD), and a full width at half maximum of 0.5 deg or less of the high-melting-point metal silicide(101) plane peak. Furthermore, Patent Document 2 discloses a method for producing a silicide target material, characterized by heating a mixed powder of silicide-forming metal element M and Si, which is blended to a composition in which a single Si phase exists and has less Si than the target composition, to form a pre-sintered body, then grinding it, adding and mixing Si powder to achieve the target composition, heating it to form a pre-sintered body, then grinding it again, and pressurizing and sintering the re-ground powder to form the target. Furthermore, Patent Document 3 discloses a Cr-Si system sintered body containing Cr (chromium) and silicon (Si), in which the total amount of impurities of Mn + Fe + Mg + Ca + Sr + Ba is 200 ppm or less, and the crystal structure assigned by X-ray diffraction is chromium silicide (CrSi ２), composed of silicon (Si), CrSi ２ The phase is present in the bulk at a concentration of 60 wt% or more, and the sintered body density is 95% or more, and CrSi ２ A Cr-Si sintered body is disclosed characterized by having an average particle size of 60 μm or less. Furthermore, Patent Document 4 discloses a titanium silicide sputtering target in which the silicon / titanium molar ratio is 2.0 to 3.0, and the structure in the cross-section of the sputtering surface of the sputtering target is a dendrite-like TiSi in which silicide particles undergo necking and connect. ２ Alternatively, it consists of a TiSi matrix phase and a Si phase discontinuously present between the matrix phase, and the dendrite-like TiSi ２ Alternatively, a titanium silicide sputtering target is disclosed, characterized in that the TiSi matrix phase has a fine structure such that the maximum length of any straight line drawn within its region is 50 μm or less.
[0004] Japanese Patent Publication No. 4509363, Japanese Unexamined Patent Publication No. 2004-204278, Japanese Unexamined Patent Publication No. 2021-143080, Japanese Patent Publication No. 3247303
[0005] In the formation of thin films in mask blanks, it was discovered that when thin films are formed using the conventional sputtering method with a target material, electric charge accumulates on the protrusions on the surface of the target material, causing abnormal discharge (arking) and scattering of particles, which increases the defect rate of the thin film.
[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a sputtering target material for mask blanks suitable for the manufacture of display devices, in which the generation of particles during sputtering is suppressed more than in conventional materials, a method for manufacturing the same, a mask blank, and a method for manufacturing the same.
[0007] The present invention has the following configuration.
[0008] (Configuration 1) A sputtering target material containing a metal and silicon, wherein the ratio of silicon content to metal content (atomic % ratio) in the sputtering target material is greater than 2, the occupied area Oa of the metal silicide phase of the sputtering target material at particle size Ds takes its maximum value within the range of particle size Ds of 2 μm or more and 10 μm or less, and the occupied area Oa at particle size Ds is calculated by multiplying the particle size Ds, in which all particles of the metal silicide phase present in an image acquired of the surface of the sputtering target material are classified in units of 1 μm, by the number of particles Nd of the metal silicide phase classified at particle size Ds.
[0009] (Configuration 2) The sputtering target material according to Configuration 1, characterized in that the ratio of the integrated value POa11 of the occupied area Oa in the range where the particle size Ds is 11 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.5 or less.
[0010] (Configuration 3) The sputtering target material according to Configuration 1 or 2, characterized in that the ratio of the integrated value POa6 of the occupied area Oa in the range where the particle size Ds is 6 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.8 or less.
[0011] (Configuration 4) The sputtering target material according to Configuration 1, characterized in that the metal is titanium.
[0012] (Configuration 5) A method for manufacturing a sputtering target material containing a metal and silicon, comprising the steps of: mixing and dissolving a metal and silicon in a ratio such that the ratio of silicon content to metal content (atomic % ratio) in the sputtering target material is greater than 2, and then generating metal silicide powder by gas atomization; and generating the sputtering target material by sintering the metal silicide powder by hot pressing and hot isostatic pressing, wherein an image of the surface of the sputtering target material is obtained, all particles of the metal silicide phase present in the image are classified in units of 1 μm for each particle size Ds, the number Nd is counted for each particle size Ds, and when the relationship between the particle size Ds and the occupied area Oa calculated by multiplying the particle size Ds by the number Nd is obtained, the occupied area Oa is maximized when the particle size Ds is in the range of 2 μm or more and 10 μm or less.
[0013] (Configuration 6) The method for manufacturing a sputtering target material according to Configuration 5, characterized in that the ratio of the integrated value POa11 of the occupied area Oa in the range where the particle size Ds is 11 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.5 or less.
[0014] (Configuration 7) A method for manufacturing a sputtering target material according to Configuration 5 or 6, characterized in that the ratio of the integrated value POa6 of the occupied area Oa in the range where the particle size Ds is 6 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.8 or less.
[0015] (Configuration 8) A method for manufacturing a sputtering target material according to Configuration 5, characterized in that the metal is titanium. (Configuration 9) A mask blank characterized in that a thin film containing metal and silicon, formed by a sputtering method using the sputtering target material according to any one of Configurations 1 to 4, is provided on a translucent substrate.
[0016] (Configuration 10) A method for manufacturing a mask blank, characterized by having a step of forming a thin film containing metal and silicon on a translucent substrate by a sputtering method using a sputtering target material described in any of Configurations 1 to 4.
[0017] A sputtering target material having such a configuration makes it possible to provide a sputtering target material in which the generation of particles during sputtering of a mask blank, which is suitable for the manufacture of a display device, is suppressed compared to conventional materials. Therefore, by using such a sputtering target material and a sputtering target material manufactured by the same manufacturing method, it is possible to provide a highly accurate mask blank and a method for manufacturing the same, which significantly reduces defects in the semi-transparent film.
[0018] This graph shows the relationship between the particle size Ds of the metal silicide phase (titanium silicide phase) and the occupied area Oa at that particle size Ds in the sputtering target material of Example 1. This graph shows the relationship between the particle size Ds of the metal silicide phase (titanium silicide phase) and the occupied area Oa at that particle size Ds in the sputtering target material of Example 2. This graph shows the relationship between the particle size Ds of the metal silicide phase (titanium silicide phase) and the occupied area Oa at that particle size Ds in the sputtering target material of Comparative Example 1. This graph shows the number of film defects in thin films deposited on a translucent substrate using the sputtering target materials of Example 1, Example 2, and Comparative Example 1. This graph shows the relationship between the arithmetic mean curvature Spc of the peaks in the sputtering target materials of Example 1, Example 2, and Comparative Example 1 and the number of film defects in thin films deposited on a translucent substrate.
[0019] First, let me explain the background to the present invention. The inventors of this invention have diligently researched sputtering target materials for mask blanks suitable for the manufacture of display devices, focusing on a sputtering target material composition that suppresses particle generation during sputtering more effectively than conventional materials. The sputtering target material of the present invention contains silicon and metal, and is a so-called silicon-rich target material in which the amount of silicon is greater than that of a stoichiometrically stable composition (the ratio of silicon content to metal content in the sputtering target material (atomic % ratio) is greater than 2). In this sputtering target material, by containing more silicon than that of a stoichiometrically stable composition of metal and silicon (making it silicon-rich), both metal silicide particles (metal silicide phase) and silicon particles (silicon phase) are present.
[0020] The inventors observed various sputtering target materials with adjusted manufacturing conditions using a scanning electron microscope (SEM) to investigate the microstructure (SEM image observed at 200x magnification: microstructure diagram). Then, they formed thin films on a substrate by sputtering using each sputtering target material, measured the number of particles (film defects) attached to the thin film, and investigated the relationship between the microstructure of the sputtering target material and the number of particles generated. As a result, it was found that the occupied area Oa, calculated by multiplying Ds (a classification of the particle size of the metal silicide phase particles on the surface of the sputtering target material in units of 1 μm) by the number of particles Nd with particle size Ds, correlates strongly with the number of particles. Note that particle size Ds is a classification value, and Ds = n [μm] (n: integer of 1 or more) indicates that the particle size is (n-1) [μm] < Ds ≤ n [μm]. On the other hand, no clear correlation was found between the number Nd of particles with particle size Ds of the metal silicide phase on the surface of the sputtering target material and the number of particles generated. The inventors then classified all particles of the metal silicide phase present in electron microscope images of each sputtering target material, for each particle size Ds, in units of 1 μm, and counted the number Nd for each particle size Ds. They then obtained the relationship between the particle size Ds and the occupied area Oa of that particle size Ds, which is calculated by multiplying the particle size Ds by the number Nd, and investigated the correlation with the number of particles generated. As a result, they found that the number of particles generated was significantly suppressed compared to conventional methods in sputtering target materials where the occupied area Oa of the metal silicide phase with particle size Ds takes its maximum value within the range of particle size Ds from 2 μm to 10 μm. The present invention was made as a result of the above-described diligent investigation.
[0021] Embodiments of the present invention will be described below. The sputtering target material of the present invention is a sputtering target material containing a metal and silicon, wherein the ratio of silicon content to metal content in the sputtering target material (atomic % ratio) is greater than 2, the occupied area Oa of the metal silicide phase of the sputtering target material at particle size Ds takes its maximum value within the range of particle size Ds of 2 μm to 10 μm, and the occupied area Oa at particle size Ds is calculated by multiplying the number of metal silicide phase particles Nd classified at particle size Ds by the particle size Ds in which all particles of the metal silicide phase present in the image acquired on the surface of the sputtering target material are classified in units of 1 μm. Examples of metals include molybdenum, titanium, tantalum, tungsten, zirconium, vanadium, niobium, nickel, and palladium. From the viewpoint of the optical properties required for the light semitransmissive film in the mask blank, titanium is more preferable as the metal.
[0022] The occupied area Oa of the metal silicide phase of the sputtering target material at particle size Ds is preferably maximized within the range of particle size Ds 2 μm to 9 μm, more preferably within the range of particle size Ds 2 μm to 7 μm, and even more preferably within the range of particle size Ds 2 μm to 5 μm. To produce a sputtering target material with a particle size Ds of less than 2 μm, it is necessary to significantly reduce the particle size of the raw material metal silicide powder.
[0023] Images of the surface of the sputtering target material can be obtained using an electron microscope. A scanning electron microscope (SEM) is preferred as the electron microscope because it allows direct observation of the target material surface (eliminating the need for thinning the object to be measured). On the other hand, other image acquisition methods may be used as long as they can acquire images of the sputtering target material surface that allow for the distinction between the metal silicide phase and the silicon phase, and the classification of the particle size of each metal silicide phase using image analysis software.
[0024] The occupied area Oa of the metal silicide phase of the sputtering target material at particle size Ds can be calculated as follows. Note that this calculation method is illustrative and does not limit the invention. The occupied area of the silicon phase at particle size can also be calculated similarly. The surface of the sputtering target material is observed with a SEM at a magnification of 200x over an arbitrary rectangular area of 476 μm × 635 μm, for example, and an SEM image is obtained. Note that the area and magnification of the image of the sputtering target material surface are not limited to this, as long as the image analysis software can distinguish between the metal silicide phase and the silicon phase and classify the particle size of each metal silicide phase. Preferably, the area of the image of the sputtering target material surface is a rectangle with sides of 400 μm or more, and the magnification is preferably 100x or more. Note that an image of the cross-section of the sputtering target material may be used as the SEM image of the sputtering target material. The acquired SEM images are binarized using the image analysis software WinROOF (manufactured by Mitani Corporation) to distinguish between the silicon phase and the metal silicide phase present in the image. Then, all particles of the metal silicide phase are classified into particle diameters Ds in 1 μm units. Here, particle diameter Ds is the diameter of a circle equal to the area of that particle (equivalent circle diameter). Classification in 1 μm units can be done by rounding up the decimal part (for example, if the calculated particle diameter is 1.2 μm, it is classified as a particle diameter Ds of 2 μm). The number Nd of particles for each classified particle diameter Ds is then counted, and the occupied area Oa of that particle diameter Ds can be calculated by multiplying the particle diameter Ds by the number Nd. Since particle diameter Ds is defined as the diameter of a circle equal to the area of each particle of the metal silicide phase (equivalent circle diameter), it is used as an evaluation quantity that represents the area distribution of each particle (an index value representing the particle size distribution).
[0025] From the viewpoint of particle reduction, the sputtering target material of the present invention preferably has a ratio (POa11 / TOa) of the integrated area Oa in the range of particle diameter Ds of 11 μm or more to the integrated area Oa TOa for all particle diameters Ds, which is 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. Furthermore, although there is no particular lower limit for this ratio (POa11 / TOa), it is preferably 0.01 or more.
[0026] From the viewpoint of particle reduction, the sputtering target material of the present invention preferably has a ratio (POa6 / TOa) of the integrated area Oa in the range of particle diameter Ds of 6 μm or more to the integrated area Oa TOa for all particle diameters Ds, which is 0.8 or less, more preferably 0.6 or less, even more preferably 0.5 or less, and particularly preferably 0.4 or less. Furthermore, although there is no particular lower limit for this ratio (POa6 / TOa), it is preferably 0.01 or more.
[0027] The metal content and silicon content in the sputtering target material of the present invention can be considered equivalent to the mixing ratio (mol%) of the raw material metal powder and silicon powder. However, they can also be obtained by methods such as ICP analysis using an ICP (inductively coupled plasma emission spectroscopy) analyzer, for example, by measuring a liquid obtained by dissolving the sputtering target material.
[0028] The sputtering target material of the present invention preferably consists of silicon and metal silicide. However, as long as the advantageous effects of the present invention are not impaired, the inclusion of a small amount of a single metal, a solid solution of silicon and a metal, or other elements is allowed. The content of components other than silicon and metal silicide is preferably 1.0% by mass or less based on the mass of the sputtering target material. Further, the sputtering target material of the present invention preferably has an oxygen content of 3000 ppm or less, more preferably 2000 ppm or less, and even more preferably 1000 ppm or less. The content of oxygen and other components of the sputtering target material can be measured using compositional analysis such as X-ray photoelectron spectroscopy (XPS).
[0029] The sputtering target material of the present invention preferably has a relative density of 97% or more. The relative density of the sputtering target material is measured based on the Archimedes method. Specifically, the mass of the target material in air is divided by the volume (mass of the target material in water / specific gravity of water at the measurement temperature), and the percentage value with respect to the theoretical density ρ (g / cm ３ ) according to the following formula (1) is defined as the relative density (unit: %). ρ = { (C1 / 100) / ρ1 + (C2 / 100) / ρ2} －１ ... (1) (In the formula, C1 and C2 respectively represent the content (% by mass) of the constituent materials of the target material, and ρ1 and ρ2 represent the densities (g / cm ３ ) of the respective constituent materials corresponding to C1 and C2.) In the case of the present invention, the constituent materials of the target material are considered as metal elements and silicon (for simplicity, metal silicide is approximated as a metal element). For example, C1: mass % of the metal element of the target material ρ1: density of the metal element (for example, in the case of titanium: 4.51 g / cm ３ ) C2: mass % of silicon in the target material ρ2: density of silicon (2.33 g / cm ３ ) By applying to formula (1), the theoretical density ρ can be calculated.
[0030] The present invention provides a method for manufacturing a sputtering target material, comprising the steps of: mixing and dissolving a metal and silicon in a ratio such that the ratio of silicon content to metal content (atomic % ratio) in the sputtering target material is greater than 2; generating metal silicide powder (more specifically, powder containing a metal silicide phase and a silicon phase) by gas atomization; and subjecting the metal silicide powder to hot pressing (hereinafter abbreviated as "HP treatment") and hot isostatic pressing (hereinafter abbreviated as "HIP treatment"). The method comprises the steps of: generating a sputtering target material by sintering it using a sintering method; acquiring an image of the surface of the sputtering target material; classifying all particles of the metal silicide phase present in the image into particle diameters Ds in units of 1 μm; counting the number Nd for each particle diameter Ds; and obtaining the relationship between the particle diameter Ds and the occupied area Oa calculated by multiplying the particle diameter Ds by the number Nd, characterized in that the occupied area Oa is maximized when the particle diameter Ds is in the range of 2 μm to 10 μm.
[0031] Gas atomization is a technique for producing spherical powder by heating and melting raw materials, then rapidly cooling the molten material with gas spray. The heating and melting conditions are preferably set to the melting temperature + 100 to 300°C. Furthermore, from the viewpoint of suppressing oxidation, it is preferable to manage the powder after gas atomization in a vacuum or an inert atmosphere such as argon. In the HP treatment, the gas atomized powder is filled into a graphite molding mold, and a sintered body is produced by pressurized sintering under an inert atmosphere. From the viewpoint of successfully obtaining the target material, the heating rate is preferably 1°C / min to 20°C / min, and more preferably 5°C / min to 15°C / min. The temperature is preferably 1150°C to 1350°C, and more preferably 1200°C to 1350°C. The pressure is preferably 5 MPa or higher, and more preferably 10 MPa or higher. There is no particular upper limit for the pressure, but it is usually 40 MPa. The holding time is preferably 30 minutes to 240 minutes, and more preferably 60 minutes to 180 minutes, provided that the temperature and pressure are within the above-mentioned range.
[0032] In HIP treatment, the purpose is to further densify the sintered body obtained by HP treatment. The heating rate is preferably 1 °C / min or more and 10 °C / min or less, and more preferably 1 °C / min or more and 5 °C / min or less. The temperature is preferably 1150 °C or more and 1350 °C or less, and more preferably 1200 °C or more and 1350 °C or less. The pressure is preferably 80 MPa or more, and more preferably 90 MPa or more. The upper limit value of the pressure is not particularly defined, but is usually 200 MPa. The holding time is preferably 30 minutes or more and 240 minutes or less, and more preferably 60 minutes or more and 180 minutes or less, provided that the temperature and pressure are within the above ranges.
[0033] The sputtering target material manufactured by the method for manufacturing a sputtering target material of the present invention has the same configuration as the sputtering target material described in the above embodiment. According to the method for manufacturing a sputtering target material of the present invention, by suitably combining a step of generating metal silicide powder by a gas atomization method and a step of sintering the metal silicide powder by HP treatment and HIP treatment to generate a sputtering target material, even for a metal that is likely to agglomerate such as titanium, a sputtering target material can be suitably manufactured such that the particle size Ds is in the range of 2 μm or more and 10 μm or less and the occupied area Oa is maximized.
[0034] The sputtering target material of the present invention is preferably manufactured using a gas atomization method. Further, the powders of metal and silicon manufactured by the gas atomization method preferably have a median diameter D50 of 10 μm or more and 100 μm or less, more preferably 15 μm or more and 80 μm or less, and even more preferably 20 μm or more and 50 μm or less.
[0035] On the other hand, the sputtering target material of the present invention is a sputtering target material after sputtering, and the arithmetic mean curvature Spc of the peak points on the surface of the erosion region of the sputtering target material is 180 mm －１ or less, preferably 160 mm －１It is more preferable that it is 150 mm or less, and －１ it is even more preferable that it is less. The arithmetic mean curvature Spc of the peak points is calculated using the following mathematical formula [Formula 1] for the surface shape data of the sputtering target material obtained by a laser microscope, a white interferometer, etc. (ISO 25178).
[0036] The peak points refer to the convex portions (peak portions, tip portions) of the unevenness on the surface of the measurement object. And the arithmetic mean curvature Spc of the peak points is the arithmetic mean value of the curvatures of the peak portions within the measurement region. Since the curvature is the reciprocal of the radius of curvature, it can be said that the steeper the peak portion is as the numerical value of the arithmetic mean curvature Spc of the peak points becomes larger. Fine unevenness exists on the surface of the sputtering target material. If the curvature at the convex portion of the surface is large and steep, abnormal discharge (arcing) is likely to occur during sputtering using this sputtering target material, and it is considered that particles resulting from this are likely to scatter.
[0037] The mask blank of the present invention includes a thin film containing metal and silicon formed on a light-transmissive substrate by a sputtering method using the sputtering target material of the present invention. Further, the method for manufacturing the mask blank of the present invention has a step of forming a thin film containing metal and silicon on a light-transmissive substrate by a sputtering method using the sputtering target material of the present invention.
[0038] The mask blank manufactured in this way can sufficiently suppress the generation of particles due to arcing from the sputtering target material during sputtering.
[0039] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.
[0040] Example 1. A titanium ingot (20 x 20 x 5 mm thick) and a silicon ingot (amorphous) were melted in a carbon crucible in such a ratio (4.26 in this example) that the ratio of silicon content to titanium content (atomic % ratio) in the sputtering target material was greater than 2. Then, a powder was prepared by gas atomization at a melting temperature of 1700°C. The resulting metal silicide powder had a median diameter D50 of 35 μm. Next, this powder was filled into a graphite molding mold. This molding mold was placed in a hot press apparatus and subjected to HP treatment by holding at a pressure of 20 MPa and 1300°C for 1 hour in a vacuum of 100 Pa or less. Then, HIP treatment was performed by holding at a pressure of 98 MPa and 1200°C for 2 hours. After that, a titanium silicide sputtering target material of 101.6 mmφ x 5 mmt was obtained by predetermined machining.
[0041] The surface of the sputtering target material of Example 1 was observed using a scanning electron microscope (SEM) at 200x magnification in an arbitrary rectangular area (476 μm × 635 μm), and an SEM image was acquired. The acquired SEM image was binarized using the image analysis software WinROOF (manufactured by Mitani Corporation) to distinguish between the silicon phase and the titanium silicide phase present in the image. Then, all particles of the titanium silicide phase were classified by particle size Ds in 1 μm units. Here, particle size Ds is the diameter of a circle equal to the area of that particle (equivalent circle diameter). Furthermore, the classification in 1 μm units was performed by rounding up the decimal part.
[0042] Figure 1 is a graph showing the relationship between the particle size Ds of the titanium silicide phase and the occupied area Oa at that particle size Ds in the sputtering target material of Example 1. As shown in the figure, the occupied area Oa of the titanium silicide phase was largest when the particle size Ds was classified as 4 μm. In other words, the maximum value was taken within the range of particle size Ds from 2 μm to 10 μm.
[0043] In the sputtering target material of Example 1, the ratio of TOa, the cumulative value of the occupied area Oa for all particle sizes Ds, to POa11, the cumulative value of the occupied area Oa in the range where the particle size Ds is 11 μm or larger, was calculated to be 0.13 (i.e., 0.5 or less). Furthermore, in the sputtering target material of Example 1, the ratio of TOa, the cumulative value of the occupied area Oa for all particle sizes Ds, to POa6, the cumulative value of the occupied area Oa in the range where the particle size Ds is 6 μm or larger, was calculated to be 0.35 (i.e., 0.6 or less).
[0044] Compositional analysis in the depth direction of the unused sputtering target material of Example 1 was performed by X-ray photoelectron spectroscopy (XPS), and the oxygen content was found to be 400 ppm. The surface roughness Ra of the unused sputtering target material of Example 1 was measured to be 1.08 μm. Furthermore, the relative density of the sputtering target material of Example 1 was measured by the Archimedes method described above and was found to be 97.2%. After sputtering using the sputtering target material of Example 1, a 3D laser microscope (Olympus OLS5100) was used to observe an arbitrary rectangular area (258 μm × 258 μm) on the surface of the erosion region of the sputtering target material at 50x magnification to obtain surface shape data. The arithmetic mean curvature Spc of the peak was calculated from the obtained surface shape data and was found to be 133.0 mm. －１ (That is, 180 mm) －１ It met the following criteria.)
[0045] Example 2. A titanium ingot (10 × 10 × 5 mm) and a silicon ingot (amorphous) were melted in a carbon crucible in such a ratio (4.26 in this example) that the ratio of silicon content to titanium content (atomic % ratio) in the sputtering target material was greater than 2. Then, a powder was prepared by gas atomization at a melting temperature of 1700°C. The resulting metal silicide powder had a median diameter D50 of 20 μm. Subsequently, this powder was filled into a graphite molding mold. The sputtering target was obtained in the same manner as in Example 1.
[0046] Figure 2 is a graph showing the relationship between the particle size Ds of the titanium silicide phase and the occupied area Oa at that particle size Ds in the sputtering target material of Example 2. As shown in the figure, the occupied area Oa of the titanium silicide phase was largest when the particle size Ds was classified as 9 μm. In other words, the maximum value was taken within the range of particle size Ds from 2 μm to 10 μm.
[0047] In the sputtering target material of Example 2, the ratio (POa11 / TOa) of the integrated value TOa of the occupied area Oa for all particle sizes Ds to the integrated value POa11 of the occupied area Oa in the range where the particle size Ds is 11 μm or larger was calculated to be 0.50 (i.e., 0.5 or less). Furthermore, in the sputtering target material of Example 2, the ratio (POa6 / TOa) of the integrated value TOa of the occupied area Oa for all particle sizes Ds to the integrated value POa6 of the occupied area Oa in the range where the particle size Ds is 6 μm or larger was calculated to be 0.79 (i.e., 0.8 or less).
[0048] Compositional analysis in the depth direction of the unused sputtering target material of Example 2 was performed by X-ray photoelectron spectroscopy (XPS), and the oxygen content was found to be 400 ppm. The surface roughness Ra of the unused sputtering target material of Example 2 was measured to be 0.56 μm. Furthermore, the relative density of the sputtering target material of Example 2 was measured by the Archimedes method described above and was found to be 99.0%. After sputtering using the sputtering target material of Example 2, surface shape data of the erosion region of the sputtering target material was obtained using the same procedure as in Example 1. The arithmetic mean curvature Spc of the peak was calculated from the obtained surface shape data and was found to be 141.0 mm. －１ (That is, 180 mm) －１ It met the following criteria.)
[0049] Comparative Example 1. Titanium particles with a median diameter D50 of 12 μm and silicon particles with a median diameter D50 of 40 μm were blended in a ratio such that the ratio of silicon content to titanium content (atomic % ratio) in the sputtering target material was greater than 2 (4.26 in this comparative example). The mixture was then mixed for 48 hours in a ball mill purged with high-purity Ar gas. Subsequently, this mixed powder was filled into a graphite molding die (powder mixing method). A sputtering target was obtained in the same manner as in Example 1.
[0050] Figure 3 is a graph showing the relationship between the particle size Ds of the titanium silicide phase and the occupied area Oa at that particle size Ds in the sputtering target material of Comparative Example 1. As shown in the figure, the occupied area Oa of the titanium silicide phase was largest when the particle size Ds was classified as 21 μm. In other words, the maximum value was not obtained within the range of particle size Ds between 2 μm and 10 μm.
[0051] In the sputtering target material of Comparative Example 1, the ratio of TOa, the cumulative value of the occupied area Oa for all particle sizes Ds, to POa11, the cumulative value of the occupied area Oa in the range where the particle size Ds is 11 μm or larger, was calculated to be 0.69 (i.e., it did not satisfy the condition of 0.5 or less). Furthermore, in the sputtering target material of Comparative Example 1, the ratio of TOa, the cumulative value of the occupied area Oa for all particle sizes Ds, to POa6, the cumulative value of the occupied area Oa in the range where the particle size Ds is 6 μm or larger, was calculated to be 0.89 (i.e., it did not satisfy the condition of 0.6 or less). Depth-direction compositional analysis of the sputtering target material of Comparative Example 1 by X-ray photoelectron spectroscopy (XPS) revealed an oxygen content of 1400 ppm.
[0052] The surface roughness Ra of the unused sputtering target material of Comparative Example 1 was measured to be 2.2 μm. Also, similar to Example 1, the relative density of the sputtering target material of Comparative Example 1 was measured to be 97.4%. Furthermore, after sputtering using the sputtering target material of Comparative Example 1, surface shape data of the erosion region of the sputtering target material was obtained using the same procedure as in Example 1. The arithmetic mean curvature Spc of the peak was calculated from the obtained surface shape data to be 198.5 mm. －１ (That is, 180 mm) －１ It did not meet the following criteria.
[0053] <Evaluation> Next, the following evaluation was performed on each of the sputtering target materials of Example 1, Example 2, and Comparative Example 1 to verify the effect of particles generated when thin films are formed by the sputtering method using these target materials. First, ten translucent substrates made of synthetic quartz glass with main surface dimensions of approximately 152 mm x 152 mm were prepared. The edges and main surfaces of these translucent substrates were polished to a predetermined surface roughness, and then subjected to predetermined cleaning and drying treatments. Next, defect inspection was performed on the main surface of all the prepared translucent substrates on the side where the thin film is formed, using a defect inspection device (Lasertec M6640). In this defect inspection, defect data related to the type of defect (convex defect, concave defect, etc.) and the location (coordinate) of the defect present on the main surface on the side where the thin film is formed was acquired and recorded in correspondence with the translucent substrate that was inspected.
[0054] Next, the translucent substrates after defect inspection were divided into sets of 10. Then, a thin film (film thickness: 100 nm) was formed on each translucent substrate in each set by sputtering using the sputtering target materials of Example 1, Example 2, and Comparative Example 1, thereby producing substrates with thin films according to Example 1, Example 2, and Comparative Example 1, respectively. Specifically, the deposition chamber was filled with argon (Ar) and nitrogen (N) ２ ) mixed gas atmosphere (flow ratio Ar:N ２ DC reactive sputtering was performed at a ratio of 1:1.
[0055] Then, a defect inspection was performed on the surface of each thin film on each thin film-attached substrate according to Example 1, Example 2, and Comparative Example 1 using a defect inspection device (Lasertec M6640). In this defect inspection, defect data related to the type of defect (convex defect, concave defect, etc.) and the location (coordinate) of the defect present on the surface of the inspected thin film was acquired and recorded in correspondence with the inspected thin film-attached substrate (translucent substrate). Finally, for each thin film-attached substrate in Example 1 and Comparative Example 1, the process of extracting only the defects (convex defects) that occurred when the thin film was formed by the sputtering method was performed.
[0056] The results of the above verification are shown in Figures 4 and 5. Figure 4 is a graph showing the number of film defects with particle sizes larger than 0.5 μm in thin films deposited on translucent substrates using the sputtering target materials in Example 1, Example 2, and Comparative Example 1. Figure 5 is a graph showing the relationship between the arithmetic mean curvature Spc of the peaks of the sputtering target materials in Example 1, Example 2, and Comparative Example 1, and the number of film defects with particle sizes larger than 0.5 μm in thin films deposited on translucent substrates. Here, the number of film defects is the average number of film defects extracted for each thin film-attached substrate in Example 1, Example 2, and Comparative Example 1. As shown in the figure, the number of film defects in Comparative Example 1 was nearly 4000. In contrast, the number of film defects in Example 1 was reduced to less than 1 / 10 of that in Comparative Example 1, and the number of film defects in Example 2 was reduced to less than 1 / 7 of that in Comparative Example 1. These results suggest that by forming thin films using the sputtering target materials of Example 1 and Example 2, the generation of particles caused by arcing from the sputtering target material during sputtering can be sufficiently suppressed.
[0057] Furthermore, when the optical properties such as phase difference and transmittance were measured for each thin film-coated substrate in Example 1 and Example 2, they were found to be particularly good as phase-shift films for phase-shift mask blanks for display devices. Therefore, it can be said that by forming thin films by sputtering using the sputtering target materials of Example 1 and Example 2, it is possible to manufacture phase-shift mask blanks for display devices that have superior optical properties compared to conventional methods. In addition, it can be said that there is a sufficient correlation between the arithmetic mean curvature Spc of the peaks in the sputtering target material and the generation of particles.
Claims
1. A sputtering target material containing a metal and silicon, wherein the ratio of silicon content to metal content (atomic % ratio) in the sputtering target material is greater than 2, the occupied area Oa of the metal silicide phase of the sputtering target material at particle size Ds takes its maximum value within the range of particle size Ds of 2 μm to 10 μm, and the occupied area Oa at particle size Ds is calculated by multiplying the particle size Ds, in which all particles of the metal silicide phase present in an image acquired of the surface of the sputtering target material are classified in units of 1 μm, by the number of particles Nd of the metal silicide phase classified at particle size Ds.
2. The sputtering target material according to claim 1, characterized in that the ratio of the integrated value POa11 of the occupied area Oa in the range where the particle size Ds is 11 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.5 or less.
3. The sputtering target material according to claim 1 or 2, characterized in that the ratio of the integrated value POa6 of the occupied area Oa in the range where the particle size Ds is 6 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.8 or less.
4. The sputtering target material according to claim 1, characterized in that the metal is titanium.
5. A method for manufacturing a sputtering target material containing a metal and silicon, comprising the steps of: mixing and dissolving a metal and silicon in a ratio such that the ratio of silicon content to metal content (atomic % ratio) in the sputtering target material is greater than 2, and then generating metal silicide powder by gas atomization; and generating the sputtering target material by sintering the metal silicide powder by hot pressing and hot isostatic pressing, wherein an image of the surface of the sputtering target material is obtained, all particles of the metal silicide phase present in the image are classified in units of 1 μm for each particle size Ds, the number Nd is counted for each particle size Ds, and when the relationship between the particle size Ds and the occupied area Oa calculated by multiplying the particle size Ds by the number Nd is obtained, the occupied area Oa is maximized when the particle size Ds is in the range of 2 μm or more and 10 μm or less.
6. The method for manufacturing a sputtering target material according to claim 5, characterized in that the ratio of the integrated value POa11 of the occupied area Oa in the range where the particle size Ds is 11 μm or more to the integrated value TOa of the occupied area Oa for all particle sizes Ds is 0.5 or less.
7. The method for manufacturing a sputtering target material according to claim 5 or 6, characterized in that the ratio of the cumulative value POa6 of the occupied area Oa in the range where the particle size Ds is 6 μm or more to the cumulative value TOa of the occupied area Oa for all particle sizes Ds is 0.8 or less.
8. The method for manufacturing a sputtering target material according to claim 5, characterized in that the metal is titanium.
9. A mask blank characterized by comprising a thin film containing metal and silicon, formed by a sputtering method using the sputtering target material described in any one of claims 1 to 4, on a translucent substrate.
10. A method for manufacturing a mask blank, characterized by comprising the step of forming a thin film containing metal and silicon on a translucent substrate by a sputtering method using a sputtering target material according to any one of claims 1 to 4.