JP2004190120A - Method of producing sputtering target, and sputtering target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a sputtering target by which a resist layer capable of corresponding to the requirement for increasing the recording capacity of various devices can be formed with high precision in such a manner that the oxidizing degree of metal unsaturated oxide composing the resist layer can easily be stabilized, and to provide a sputtering target. <P>SOLUTION: At least one kind of metal powder and at least one kind of metal oxide powder are mixed, or a plurality of metal oxide powders different in valences are mixed, and the mixture is subjected to pressure sintering to obtain the sputtering target. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and a method for manufacturing a sputter target made of a metal unsaturated oxide, and more particularly to a method and a method for manufacturing a sputter target for forming an inorganic resist thin film.
[0002]
[Prior art]
In recent years, optical disks such as DVDs (Digital Versatile Discs) have been used as recording media in a wide range of fields.
In this optical disk, a fine uneven pattern such as pits and grooves indicating information signals is formed on one principal surface of an optically transparent substrate such as polycarbonate, and a reflective film made of a metal thin film such as aluminum is formed thereon. Further, it has a structure in which a protective film is formed on the reflective film, and is manufactured by a conventionally known lithography technique using an organic resist (for example, see Patent Document 1).
[0003]
As an optical disk having such a structure, a read-only optical disk (DVD-ROM) having a diameter of 12 cm and having an information capacity of 4.7 GB on one side has appeared. In recent years, a recording capacity several times larger than that is required. ing.
[0004]
In the recording medium having the above structure, it is possible to increase the recording density by making the concavo-convex pattern finer, thereby increasing the recording capacity. Using the formed stamper, it is manufactured by a process of faithfully and immediately replicating the pattern on the substrate, and if it goes back, the resist layer is exposed to laser light to form a latent image. It is determined by how fine a concavo-convex pattern can be formed by so-called cutting.
[0005]
For example, in the aforementioned read-only DVD (DVD-ROM) having an information capacity of 4.7 GB, a pit row having a shortest pit length of 0.4 μm and a track pitch of 0.74 μm is formed in a spiral shape on a stamper. Cutting has been applied. A laser having a wavelength of 413 nm and an objective lens having a numerical aperture NA of about 0.90 (for example, 0.95) are used for the cutting.
[0006]
Assuming that the wavelength of the light source is λ (μm) and the numerical aperture of the objective lens is NA, the shortest pit length P (μm) to be exposed is represented by the following equation (1). Note that K is a proportional constant.
P = K · λ / NA (1)
Here, the wavelength λ of the light source and the numerical aperture NA of the objective lens are items determined by the specifications of the laser device serving as the light source, and the proportionality constant K is an item determined by the combination of the laser device and the resist master.
[0007]
When an optical disk having the information capacity of 4.7 GB is manufactured, since the wavelength is 0.413 μm, the numerical aperture NA is 0.90, and the shortest pit length is 0.40 μm, the proportional constant K = 0 from the above equation (1). .87.
[0008]
On the other hand, in order to meet the requirements of the above 25 GB optical disk, it is necessary to reduce the minimum pit length to about 0.17 μm and the track pitch to about 0.32 μm.
[0009]
In general, it is effective that the above-described miniaturization of the concavo-convex pattern (formation of extremely fine pits) is achieved by shortening the laser wavelength. That is, in order to obtain the shortest pit length of about 0.17 μm required for a high-density optical disk having 25 GB on one side, the proportionality constant is K = 0.87 and the numerical aperture NA = 0.95. = 0.18 μm light source is required.
[0010]
The required wavelength of 0.18 μm is shorter than the 193 nm wavelength ArF laser developed as a light source for next-generation semiconductor lithography. An exposure apparatus that achieves such a short wavelength requires a special optical component such as a lens as well as a laser as a light source, and is very expensive. In other words, the method of responding to ultra-fine processing by increasing the optical resolution by shortening the exposure wavelength λ and increasing the numerical aperture NA of the objective lens requires the use of an existing exposure apparatus as the miniaturization progresses. Since an expensive exposure apparatus must be introduced instead of being unusable, it is extremely unsuitable for achieving inexpensive device supply. Therefore, there is a limit to the increase in the storage capacity of the optical disk due to the enhancement of the function of the laser device in the exposure apparatus.
[0011]
At present, an exposure method in which an organic resist such as a novolak-based resist or a chemically amplified resist is combined with ultraviolet light as an exposure source is generally widely used. Organic resists are versatile and widely used in the field of photolithography. However, due to their high molecular weight, the pattern at the boundary between exposed and unexposed areas becomes unclear, resulting in a level of 25 GB. There is a problem in terms of precision in the micromachining corresponding to the high capacity optical disk.
[0012]
In contrast, inorganic resists, especially amorphous inorganic resists, have a minimum structural unit of atomic size, so a clear pattern can be obtained at the boundary between exposed and unexposed parts, compared to organic resists. High-precision fine processing is possible, and application to a high-capacity optical disk is considered promising. This includes MoO₃And WO₃And the like as a resist material, and there is a fine processing example using an ion beam as an exposure source (for example, see Non-Patent Document 1). In addition, SiO₂Is used as a resist material, and there is a processing example using an electron beam as an exposure source (for example, see Non-Patent Document 2).
). Further, a method of using chalcogenide glass as a resist material and using lasers having a wavelength of 476 nm and 532 nm as an exposure source and ultraviolet light from a mercury xenon lamp has been studied (for example, see Non-Patent Document 3).
[0013]
[Patent Document 1]
JP 2001195791 A (paragraphs [0002] to [0006])
[Non-patent document 1]
Nobuyoshi Koshida, Kazuyoshi Yoshida, Shinichi Watanuki, Masanori Komuro and Nobufumi Atoda: “50-nm Metal Line Fabrication by Focused Ion Beam and Oxide Resists”, Jpn.J.Appl.Phys.Vol.30 (1991) pp3246
[Non-patent document 2]
Sucheta M. Gorwadkar, Toshimi Wada, Satoshi Hiraichi, Hiroshi Hiroshima, Kenichi Ishii and Masanori Komuro: “SiO_Two/ c-Si Bilayer Electron-Beam Resist Process for Nano-Fabrication ”, Jpn.J.Appl.Phys.Vol.35 (1996) pp6673
[Non-Patent Document 3]
S. A. Kostyukevych: “Investifations and modeling of physical processes in inorganic resists for the use in UV and laser lithography”, SPIE Vol. 3424 (1998) pp20
[0014]
[Problems to be solved by the invention]
However, when an ion beam or electron beam is used as an exposure source, various types of inorganic resist materials can be combined as described above, and a fine concavo-convex pattern can be obtained by narrowing the electron beam or ion beam. However, an apparatus equipped with an electron beam and ion beam irradiation source is complicated in structure and extremely expensive, and is not suitable for supplying an inexpensive optical disk.
[0015]
In that regard, it is desirable that light such as a laser device mounted on an existing exposure apparatus, that is, ultraviolet light or visible light can be used, but materials that can be cut with ultraviolet light or visible light among inorganic resist materials are limited. However, only a chalcogenide material has been reported so far. This is because ultraviolet or visible light is transmitted through inorganic resist materials other than chalcogenide materials, and the absorption of light energy is extremely small, which is not practical.
[0016]
Although the combination of an existing exposure apparatus and a chalcogenide material is a practical combination in terms of economy, the chalcogenide material is Ag.₂S₃, Ag-As₂S₃, Ag₂There is a problem of containing materials harmful to the human body such as Se-GeSe, and its use is difficult from the viewpoint of industrial production.
As described above, the production of an optical disk with a high recording capacity using an existing exposure apparatus has not been realized so far.
[0017]
The present invention has been proposed in order to solve such conventional problems, and is a safe resist that realizes high-precision fine processing without using an expensive irradiation device such as an electron beam or an ion beam. It is an object of the present invention to provide a method of manufacturing a sputter target used for manufacturing an optical disk master capable of realizing a higher storage capacity of an optical disk using a material and an existing exposure apparatus, and a sputter target. I do.
[0018]
[Means for Solving the Problems]
A method for manufacturing a sputter target according to the invention of claim 1, which is provided to solve the above-mentioned problem, comprises mixing at least one kind of metal powder and at least one kind of metal oxide powder, or a method of mixing a plurality of kinds having different valences. The metal oxide powder is mixed, and the mixture is sintered under pressure to obtain a sputter target composed of a metal unsaturated oxide.
[0019]
The present inventors have found that, when the oxygen content deviates even slightly from the stoichiometric composition of the transition metal oxide in the inorganic resist material, the absorption of the oxide for ultraviolet or visible light suddenly increases, and the ultraviolet or visible light is reduced. Based on the idea that the chemical properties change due to absorption, a new resist material and a method for manufacturing an optical disc master that can respond to the demand for higher recording capacity with the current exposure apparatus have been developed.
[0020]
In the resist layer forming step of this manufacturing method, a resist layer is formed by a reactive sputtering method in which a film is formed by a sputtering method in an atmosphere of argon and oxygen using a sputter target composed of a single transition metal. In this case, the degree of oxidation of the transition metal unsaturated oxide is controlled by changing the oxygen gas concentration in the vacuum atmosphere. In some cases, a resist layer containing a transition metal unsaturated oxide containing two or more transition metals may be used. Is generally mixed during film formation. The mixing ratio is controlled by changing the sputter input power.
[0021]
According to the method for manufacturing an optical disk master using the thus formed resist layer made of a transition metal unsaturated oxide, a 25 GB information capacity is secured on one side of an optical disk having a diameter of 12 cm by the same signal processing method as before. Has been achieved.
[0022]
Here, regarding the formation of a resist layer, in the reactive sputtering method, highly accurate control is performed on changes in the amount of introduced oxygen gas and changes over time in the exhaust performance of the film forming apparatus in order to keep the degree of oxidation constant. In particular, in reactive sputtering using an alloy target composed of two or more transition metals, the rate of reaction with oxygen differs depending on the type of metal, and therefore adjustment of the reaction is necessary.
[0023]
Therefore, the present invention makes it easier to control the sputter deposition conditions such as the introduction gas and the input power, thereby more stabilizing the state of the unsaturated oxide in the thickness direction of the resist layer. It has been developed for the purpose of stabilizing the sensitivity and eventually stabilizing the pit size after development.
[0024]
According to the first aspect of the present invention, it is possible to manufacture a sputter target capable of forming a metal unsaturated oxide layer without requiring introduction of an oxygen gas during sputtering film formation.
Note that the metals referred to here include atomic numbers 21 (Sc) to 30 (Zn), atomic numbers 39 (Y) to 48 (Cd), atomic numbers 57 (La) to 80 (Hg), and Si. Say.
Although the optical disk has been described as an example here, a method of manufacturing a sputter target and a sputter target used for photolithography technology from resist layer formation to development developed by the inventors include a DRAM (Dynamic Random Access Memory), Flash memory, semiconductor devices such as CPU (Central Processing Unit), ASIC (Application Specific IC), magnetic devices such as magnetic heads, liquid crystal, display devices such as EL (Electro Luminescence), PDP (Plasma Display Panel), optical recording media And various devices such as optical devices such as light modulation elements.
[0025]
A method for manufacturing a sputter target according to a second aspect of the present invention, which is provided to solve the above-mentioned problem, is characterized in that, in the first aspect of the invention, a mixture ratio of the metal powder and the metal oxide powder or a plurality of different valences are different. It is characterized in that the oxygen content after the above-mentioned pressure sintering is adjusted by the mixing ratio of the kinds of metal oxide powders.
[0026]
In this method, the degree of oxidation of the resist layer formed at the time of sputtering film formation can be accurately determined by adjusting the mixture ratio of the mixture to form a sputter target having a predetermined oxygen content. The target oxidation degree can be easily and stably obtained as compared with the sputtering method.
Note that the oxygen content after the pressure sintering here is generally the target oxygen content of the resist layer.
[0027]
According to a third aspect of the present invention, there is provided a method for manufacturing a sputter target according to the third aspect of the present invention, wherein the metal is a transition metal.
[0028]
According to this method, it is possible to manufacture a sputter target capable of forming a resist layer which is an unsaturated oxide of a transition metal without requiring introduction of oxygen gas at the time of film formation by sputtering.
[0029]
According to a fourth aspect of the present invention, there is provided a method for manufacturing a sputter target, wherein the transition metal is Ti, V, Cr, Mn, Fe, Nb, Cu, Ni. , Co, Mo, Ta, W, Zr, Ru, and Ag.
[0030]
According to this method, a resist layer (unsaturated oxide of a transition metal) corresponding to a photolithography technique that enables high recording capacity of various devices can be formed without requiring introduction of oxygen gas at the time of film formation by sputtering. A sputter target that can be manufactured can be manufactured.
[0031]
According to a fifth aspect of the present invention, there is provided a method of manufacturing a sputter target according to the third aspect of the present invention, wherein the transition metal is one or both of Mo and W. .
[0032]
According to this method, a resist layer (unsaturated oxide of a transition metal) corresponding to a photolithography technique that enables high recording capacity of various devices can be formed without requiring introduction of oxygen gas at the time of film formation by sputtering. A sputter target that can be manufactured can be manufactured.
[0033]
According to a sixth aspect of the present invention, there is provided a method for manufacturing a sputter target according to the fourth aspect of the present invention, wherein the transition metal has a melting point in an oxide state lower than that in a metal state. When a metal powder and an oxide powder of a metal are mixed and the mixture is sintered under pressure, the firing temperature at which the transition metal oxide powder is sintered under pressure to form a sputter target of a saturated oxide It is characterized by firing at a higher temperature.
[0034]
According to this method, when a mixture of a metal powder of a transition metal of the same element and an oxide powder is used as a raw material, the firing temperature is determined in consideration of the relationship between the melting point of the metal state of the transition metal and the melting point of the oxide state. By setting, a sputter target with sufficient density and strength can be obtained.
[0035]
The method for producing a sputter target according to the invention of claim 7, which is provided to solve the above problem, is a method according to any one of claims 3 to 6, wherein the mixture further includes a powder of an element other than a transition metal. Is added.
[0036]
By this method, the crystal grains of the transition metal unsaturated oxide constituting the resist layer formed at the time of sputtering film formation are reduced, and the resolution is greatly improved by reducing the surface roughness of the resist layer. A sputter target with improved exposure sensitivity can be manufactured.
Here, the element other than the transition metal is at least one of Al, C, B, Si, Ge and the like.
[0037]
A sputter target according to the invention of claim 8 provided to solve the above problem is a mixture of at least one kind of metal powder and at least one kind of metal oxide powder, or a mixture of a plurality of kinds of metals having different valences. It is characterized by comprising a metal unsaturated oxide obtained by mixing oxide powder and sintering the mixture under pressure.
[0038]
Thus, a metal unsaturated oxide layer can be formed without the need for introducing an oxygen gas during sputtering film formation.
Note that the metals referred to here include atomic numbers 21 (Sc) to 30 (Zn), atomic numbers 39 (Y) to 48 (Cd), atomic numbers 57 (La) to 80 (Hg), and Si. Say.
[0039]
According to a ninth aspect of the present invention, there is provided a sputtering target according to the eighth aspect, wherein a relative density after pressure sintering is 80% or more.
[0040]
As a result, a stable sputter rate of the unsaturated metal oxide can be secured, and a resist layer of stable quality can be formed.
[0041]
According to a tenth aspect of the present invention, there is provided a method of manufacturing a sputter target according to the tenth aspect, wherein the metal is a transition metal.
[0042]
This makes it possible to form a resist layer that is a transition metal unsaturated oxide without requiring introduction of oxygen gas during sputtering film formation.
[0043]
In order to solve the above-mentioned problem, a sputter target according to the invention of claim 11 is the invention according to claim 10, wherein the transition metal is Ti, V, Cr, Mn, Fe, Nb, Cu, Ni, Co, It is characterized by being at least one of Mo, Ta, W, Zr, Ru, and Ag.
[0044]
This makes it possible to form a resist layer composed of a transition metal unsaturated oxide without the need of introducing oxygen gas during film formation by sputtering, and it is applied to photolithography technology that can increase the recording capacity of various devices. can do.
[0045]
A sputter target according to a twelfth aspect of the present invention provided to solve the above problem is characterized in that, in the tenth aspect of the present invention, the transition metal is one or both of Mo and W.
[0046]
This makes it possible to form a resist layer composed of a transition metal unsaturated oxide without the need of introducing oxygen gas during film formation by sputtering, and it is applied to photolithography technology that can increase the recording capacity of various devices. can do.
[0047]
According to a thirteenth aspect of the present invention, there is provided a sputter target according to any one of the tenth to twelfth aspects, wherein a powder of an element other than a transition metal is further added to the mixture. It is characterized by having.
[0048]
Thereby, in the resist layer formed using this target, the crystal grains of the transition metal unsaturated oxide are reduced, and the surface roughness of the film is reduced, so that the boundary between the exposed portion and the unexposed portion is further increased. It becomes clear and the resolution is greatly improved. Further, the exposure sensitivity can be improved.
Here, the element other than the transition metal is at least one of Al, C, B, Si, Ge and the like.
[0049]
According to a fourteenth aspect of the present invention, there is provided a sputter target comprising an unsaturated metal oxide and having a relative density of 80% or more.
[0050]
This makes it possible to secure a stable metal unsaturated oxide sputter rate without the need of introducing oxygen gas during sputtering film formation, and to form a stable quality metal unsaturated oxide layer. it can.
Note that the metals referred to here include atomic numbers 21 (Sc) to 30 (Zn), atomic numbers 39 (Y) to 48 (Cd), atomic numbers 57 (La) to 80 (Hg), and Si. Say.
[0051]
BEST MODE FOR CARRYING OUT THE INVENTION
First, a method for manufacturing an optical disk using an inorganic resist material as a premise of the present invention will be described. This production method includes an unsaturated oxide of a transition metal, wherein the unsaturated oxide has an oxygen content smaller than the oxygen content of a stoichiometric composition corresponding to the possible valence of the transition metal. After a resist layer made of such a resist material is formed on a substrate, the resist layer is selectively exposed to light corresponding to a recording signal pattern and developed to form a predetermined concavo-convex pattern.
[0052]
An outline of the manufacturing process will be described below with reference to FIG.
First, a resist layer 102 made of a predetermined inorganic resist material is uniformly formed on a substrate 100 (resist layer forming step, FIG. 1A). Further, a predetermined intermediate layer 101 may be formed between the substrate 100 and the resist layer 102 in order to improve the recording sensitivity of the resist layer 102. FIG. 1A shows this state. The thickness of the resist layer 102 can be arbitrarily set, but is preferably in the range of 10 nm to 80 nm.
[0053]
Then, the resist layer 102 is selectively exposed to light corresponding to the signal pattern by using an existing exposure apparatus equipped with a laser device, and exposed (resist layer exposure step, FIG. 1B). At this time, the unsaturated oxide of the transition metal, which is the resist layer 102, absorbs ultraviolet light or visible light, and changes its chemical property when irradiated with ultraviolet light or visible light.
Further, by developing the resist layer 102, a master 103 on which a predetermined concavo-convex pattern is formed is obtained (resist layer developing step, FIG. 1C). Here, development is performed by utilizing the fact that a so-called selectivity is obtained in which an etching rate differs between an exposed portion and an unexposed portion with respect to an acid or alkali aqueous solution even though the resist is an inorganic resist.
[0054]
Next, a metal nickel film is deposited on the concave / convex pattern surface of the master 103 by electroforming (FIG. 1D). The transferred mold stamper 104 is obtained (FIG. 1E).
[0055]
Using the molding stamper 104, a resin disk 105 made of polycarbonate, which is a thermoplastic resin, is duplicated by an injection molding method (FIG. 1F). Subsequently, an optical disk is obtained by forming a reflective film 106 (FIG. 1 (h)) and a protective film 107 of an Al alloy on the uneven surface of the resin disk 105 (FIG. 1 (i)).
[0056]
Hereinafter, a sputter target used for forming a resist material according to the present invention will be described in detail.
(Sputter target)
The sputter target of the present invention is formed by firing a mixture of a transition metal powder and a transition metal oxide powder, or a mixture of transition metal oxide powders having different valences under pressure. Takes a disk shape with a diameter and thickness.
Here, the unsaturated oxide of the transition metal is a compound shifted in the direction of decreasing the oxygen content from the stoichiometric composition corresponding to the maximum possible valence of the transition metal, that is, the unsaturated oxide of the transition metal. Is defined as a compound in which the oxygen content in is smaller than the oxygen content of the stoichiometric composition corresponding to the maximum possible valence of the transition metal.
[0057]
For example, as a transition metal oxide, the chemical formula MoO_ThreeWill be described as an example. Chemical formula MoO₃The oxidation state of the composition Mo_1-xO_xWhen x = 0.75, the saturated oxide is a saturated oxide. On the other hand, when 0 <x <0.75, the unsaturated oxide whose oxygen content is less than the stoichiometric composition when x <0.75. You can say that.
[0058]
Some transition metals can form oxides having different valences with one element. For example, Mo has a maximum valence of 6 as described above and also has a divalent oxide (MoO). Also exists. In this case, the composition ratio Mo_1-xO_xX = 0.5, which corresponds to less than x = 0.75, it can be said that the oxide is a non-saturated oxide. The valence of the transition metal oxide can be analyzed with a commercially available analyzer.
[0059]
Specific transition metals constituting the sputter target include Ti, V, Cr, Mn, Fe, Nb, Cu, Ni, Co, Mo, Ta, W, Zr, Ru, Ag and the like. Among them, it is preferable to use Mo, W, Cr, Fe, and Nb, and particularly preferable to use Mo and W from the viewpoint that a large chemical change can be obtained by ultraviolet light or visible light.
[0060]
Examples of the unsaturated oxide of a transition metal include, in addition to the unsaturated oxide of one type of transition metal, those added with a second transition metal, those added with a plurality of types of transition metals, those other than the transition metal. Any of the elements to which the element (1) is added is included in the scope of the present invention.
In addition, in the case of adding a second transition metal in addition to one kind of unsaturated oxide of a transition metal, and further adding three or more kinds of transition metals, in the case of one kind of transition metal atom having a crystal structure, It is considered that some of these transition metals are substituted with other transition metal atoms. I will decide whether or not.
[0061]
Further, as an element other than the transition metal, at least one of Al, C, B, Si, Ge and the like may be contained. By sintering a combination of two or more transition metals, or by adding other elements other than the transition metal, the resist layer formed using this target is formed of a transition metal unsaturated oxide. Since the crystal grains become smaller and the surface roughness of the film becomes smaller, the boundary between the exposed portion and the unexposed portion becomes clearer, and the resolution is greatly improved. Further, the exposure sensitivity can be improved.
[0062]
(Production method)
The procedure for manufacturing the sputter target according to the present invention will be described below.
(S1) Weighing and mixing
After weighing a predetermined amount of each of the powders of two or more types of raw materials, dry mixing is performed. The raw material powder used here includes at least a combination of a transition metal metal powder and an oxide powder of the same element, or a combination of two transition metal oxide powders of the same element but different valences. In addition, a metal powder or an oxide powder of a transition metal different from the above-mentioned transition metal may be included, and a metal powder of an element other than the transition metal may be included.
The predetermined amount of each powder to be weighed is determined in consideration of the mixing ratio so that the target oxygen content of the unsaturated oxide is obtained after mixing and pressure sintering.
[0063]
(S2) Pressure sintering
The obtained mixed powder is put into a carbon mold and pressed and fired by a hot press device. Here, a hot press apparatus may be generally used, and firing is performed at a constant pressure and a constant firing temperature in a non-oxygen atmosphere for a predetermined time.
For transition metals whose melting point in the oxide state is lower than the melting point in the metal state, the firing temperature in the case where the metal powder and the oxide powder are mixed and fired under pressure is only the oxide powder of the transition metal. The firing temperature is set to be higher than the firing temperature for obtaining a sputter target by firing under pressure. Transition metals to which this setting is applied are Ti, V, Fe, Nb, Mo, Ta, W, and the like.
When a mixture of two kinds of transition metal oxide powders having the same element but different valences is sintered under pressure, the kind of the transition metal, the mixing ratio of the oxide powder, and the firing temperature determined in advance are used. The firing temperature is set such that the target oxygen content of the unsaturated oxide after the pressure sintering is obtained from the relationship between and the oxygen content after sintering.
[0064]
(S3) Finishing
The sintered body after the pressure sintering is machined so as to have a disk shape of a predetermined size, and is completed as a sputter target.
[0065]
Hereinafter, the transition metal W and Mo are formed by the production method of the present invention (WMo)._1-xO_xAn example in which an oxide sputter target is actually manufactured and an example in which an optical disc is manufactured using the sputter target will be described.
When each of W and Mo becomes a saturated oxide, WO_ThreeAnd MoO_ThreeHaving the following composition: Therefore, in the case of a WMo alloy and a case of a saturated oxide, (WMo) O_ThreeThe composition becomes (W_100-yMo_y)_100-xO_xIf it is described in the form of (x, y: atomic%), x = 75.
[0066]
(Example 1)
In Example 1, an unsaturated oxide of a WMo alloy (target target composition (W₈₀Mo₂₀)₃₀O₇₀, And (W₈₀Mo₂₀)₃₅O₆₅2) shows an example in which a sputter target was produced.
In the fabrication, the conditions of each step were as follows according to the above-described manufacturing steps of the present invention.
(1) Raw materials: W powder, WO_ThreePowder, MoO_ThreePowder
(2) Target target composition:
(W₈₀Mo₂₀)₃₀O₇₀, And (W₈₀Mo₂₀)₃₅O₆₅Two types
(3) Sintering conditions:
-Pressure: 24.5 MPa
-Firing temperature: constant temperature between 873K and 1263K
(Prepared by changing the firing temperature)
(4) Target size: diameter 38 mm, thickness 5 mm
As Comparative Example 1, WO_ThreePowder and MoO_ThreeFrom the mixture with the powder, a saturated oxide was obtained under the same conditions as in the example (W₈₀Mo₂₀)_{twenty five}O₇₅Was prepared.
[0067]
The prepared sputter target was measured for relative density (%) with respect to theoretical density, flexural strength (MPa) as an index of mechanical strength, and composition analysis. The results are shown in FIGS.
(Relative density)
In the case of the unsaturated oxide according to Example 1, the relative density tended to decrease with decreasing oxygen content at the same firing temperature. Here, the relative density is the ratio of the density calculated from the diameter, thickness, and weight of the created target to the theoretical density.Theoretical density is calculated by calculating the weight of each element of the target composition, It was determined by dividing by the target volume.
From the viewpoint of the relative density of 80% or more, which is desirable for keeping the sputtering rate and the like stable as a sputter target, the result of Example 1 shows that the target target composition (W₈₀Mo₂₀)₃₀O₇₀In the case of the above, it was achieved at a firing temperature of 873K (FIG. 2). Target target composition (W₈₀Mo₂₀)₃₅O₆₅In the case of (1), a higher firing temperature was required, and this was achieved at 1033 K or higher (FIG. 3).
In addition, in the case of the saturated oxide containing two kinds of metal elements (W, Mo) as Comparative Example 1, the relative density was 100% even at a relatively low firing temperature of 873K (FIG. 4). .
[0068]
(Bending strength)
Regarding the transverse rupture strength, a similar tendency was observed in the case of the unsaturated oxide according to Example 1 (FIGS. 2 and 3). If the oxygen content was low and the firing temperature was low, sufficient strength could not be obtained. It was necessary to fire at a temperature higher than the firing temperature of Comparative Example 1 (saturated oxide target) (FIG. 4).
The mixture in Example 1 (W + WO_Three+ MoO_Three) In order to obtain a predetermined relative density and flexural strength, the mixture (WO_Three+ MoO_Three) Requires a higher firing temperature than the sintered body of_ThreeIt is presumed that metal W (melting point: 3673K) having a higher melting point than (melting point: undetermined at 1746K or less) is included.
[0069]
(composition)
FIG. 5 shows a composition analysis result of the target manufactured in Example 1. In any of the compositions of Example 1, the same composition as the raw material mixture ratio (target target composition) was stably obtained regardless of the firing temperature. However, for the composition of Comparative Example 1 shown in FIG. 6, the oxygen content varied depending on the firing temperature, and a difference from the raw material mixture ratio (target target composition) was observed.
[0070]
(Example 2)
In Example 2, an unsaturated oxide of a WMo alloy (target target composition (W₈₀Mo₂₀)₃₀O₇₀2) shows an example in which a sputter target was produced.
In the fabrication, the conditions of each step were as follows according to the above-described manufacturing steps of the present invention.
(1) Raw material: WO_TwoPowder, WO_ThreePowder, MoO_ThreePowder
(2) Target target composition: (W₈₀Mo₂₀)₃₀O₇₀
(3) Sintering conditions:
-Pressure: 24.5 MPa
-Firing temperature: constant temperature between 1193K and 1473K
(Prepared by changing the firing temperature)
(4) Target size: diameter 38 mm, thickness 5 mm
[0071]
FIG. 7 shows the result of analyzing the composition of the produced sputter target.
Unlike the case of Example 1, a tendency was observed that the oxygen content decreased as the firing temperature increased, and the W and Mo contents relatively increased. When a metal powder such as W powder is added as in Example 1, as a result of the metal powder reacting with desorbed oxygen and being oxidized, the oxygen content does not change in the whole sintered body. Seem. On the other hand, when no metal powder such as W powder is used as in Example 2 and Comparative Example 1, oxygen is released in the environment during firing, and the oxygen content of the entire sintered body decreases. It is thought to be.
[0072]
In preparing a sputter target of a transition metal unsaturated oxide, availability and cost vary greatly depending on the type of metal and the state of the powder (oxide powder, metal powder). Various types of powder mixtures may be used as raw materials depending on the method of adding oxide powder, etc., but simply sintering them at a general firing temperature as a mixture that matches the target composition will make the composition stable. However, it is not possible to obtain a sputter target having sufficient density or strength.
[0073]
When a mixture of a metal powder and an oxide powder of a transition metal of the same element is used as a raw material, as shown in Example 1 of the present invention, the melting point of the transition metal in the metal state and the melting point of the oxide state thereof By setting the firing temperature in consideration of the relationship, the oxygen content as a mixture and the target oxygen content as the final sintered body are equalized, and a sputter target with sufficient density and strength is obtained. It is possible.
[0074]
When a mixture of two kinds of transition metal oxide powders having the same element but different valences is used, as shown in Example 2 of the present invention, a mixture determined by the mixing ratio of the transition metal oxide powders By setting the firing temperature in consideration of the oxygen content as a target and the target oxygen content as a final sintered body, a sputter target having a stable composition can be obtained. Specifically, the mixing ratio of the raw materials is determined to a desired value first, and then the firing temperature is changed from the mixing ratio to a target oxygen content. Alternatively, the sintering temperature may be determined first, and then the mixing ratio of the raw materials may be changed to a mixing ratio that takes into account the amount changed by sintering.
[0075]
(Example 3)
The target composition (W₈₀Mo₂₀)₃₀O₇₀After a resist material was formed on the substrate using the above sputtering target, a predetermined process was performed to manufacture an optical disk having a recording capacity of 25 GB.
Specifically, an optical disk was manufactured in the following procedure.
[0076]
First, a silicon wafer was used as a substrate, and an intermediate layer made of amorphous silicon was uniformly formed with a thickness of 80 nm on the substrate by a sputtering method. Next, a resist layer 102 composed of an unsaturated oxide of W and Mo was uniformly formed thereon by a sputtering method. At this time, the target composition (W₈₀Mo₂₀)₃₀O₇₀Was sputtered in an argon atmosphere using the above sputtering target. Although the degree of vacuum in the chamber of the sputtering apparatus fluctuated during the sputter deposition, the composition of the resist layer was stable because the composition of the sputter target was deposited as it was by argon sputtering. I was
[0077]
When the deposited resist layer was analyzed by EDX, the ratio of W to Mo in the formed unsaturated oxide of W and Mo was 80:20, and the oxygen content was 70 at.%. there were. The thickness of the resist layer was 55 nm. From the analysis result of the electron beam diffraction by the transmission electron microscope, it was confirmed that the crystalline state of the WMoO unsaturated oxide before the exposure was amorphous.
[0078]
Next, the substrate on which the resist layer was formed was set in the exposure apparatus shown in FIG. 8, and the turntable 11 was rotated simultaneously with the irradiation of the laser beam from the beam generation source 12 to record a 25 GB signal on the resist layer. Exposure was performed. In this exposure, the turntable 11 is continuously moved by a small distance in the radial direction of the resist substrate 1 while rotating the turntable 11, thereby forming a concave and convex pit for information data and a guide groove as a latent image of fine irregularities. A meander was formed.
[0079]
The exposure conditions at this time are shown below.
-Exposure wavelength: 0.405 nm
-Numerical aperture NA of exposure optical system: 0.95
・ Modulation: 17PP
-Bit length: 112 nm
・ Track pitch: 320 nm
-Linear velocity at the time of exposure: 4.92 m / s
-Exposure irradiation power: 6.0 mW
・ Write method: Simple write method similar to phase change disk
[0080]
Next, the exposed resist substrate was developed by a wet process using an alkali developing solution. In this development step, while the resist substrate is immersed in the developing solution, development is performed in a state where ultrasonic waves are applied to improve the uniformity of etching, and after the development is completed, the substrate is sufficiently washed with pure water and isopropyl alcohol, The process was completed by drying with air blow or the like. A tetramethylammonium hydroxide solution was used as the alkali developer, and the development time was 30 minutes.
[0081]
FIG. 9 shows the result of observing the pit shape on the surface of the resist substrate after development by SEM. The resist material made of the unsaturated oxide of W and Mo is a positive type resist. In FIG. 9, the pit portions correspond to the exposed portions and are concave with respect to the unexposed portions of the resist layer. The formed pit length (diameter) was about 130 nm, and it was confirmed that the shortest pit length of 170 nm (0.17 μm) or less required for a 25 GB single-sided high-density optical disk was achieved. Further, it was observed that pits were formed in a state where pits having a length of 150 nm, linear pits having a width of 130 nm, and the like corresponded to actual signal patterns as resist patterns.
[0082]
Next, a metal nickel film is deposited on the concave-convex pattern surface of the resist master by electroforming, and is subjected to predetermined processing after being separated from the resist master, and a molding stamper onto which the concave-convex pattern of the resist master has been transferred. Obtained.
Finally, a resin disk made of polycarbonate, which is a thermoplastic resin, was duplicated by injection molding using the obtained molding stamper, and a reflective film of Al alloy and a film thickness of 0.1 mm were formed on the uneven surface of the resin disk. An optical disk (DVD-ROM) having a diameter of 12 cm was obtained by forming the above protective film. The steps up to obtaining the optical disk from the resist master are manufactured by a conventionally known technique.
[0083]
(Comparative Example 2)
In the manufacturing process of the optical disk in the above embodiment, the sputtering target of the present invention is not used in the resist layer forming step, and a sputtering target composed of a single element of W and a sputtering target composed of a single element of Mo are arranged side by side as in the related art, Sputtering was performed in a mixed atmosphere of argon and oxygen while rotating the substrate on them to form a resist layer made of a WMoO unsaturated oxide with the target of the same composition as in Example 3.
[0084]
At this time, in order to keep the degree of oxidation of the WMo unsaturated oxide constant, the sputter input power of the sputtering apparatus, the exhaust speed in the chamber, and the introduced amount of the mixed gas of argon and oxygen were adjusted. In principle, the amount of mixed gas introduced was controlled so that the degree of vacuum in the chamber was constant, but the degree of vacuum could fluctuate within the range of 1 to 10 Pa during sputter deposition, and oxygen content in the resist film was increased. This suggests that the amount may fluctuate. An optical disk was manufactured under the same manufacturing conditions as in Example 3 except for the above.
When the state of the resist substrate surface was observed after the completion of the resist layer developing step, it was observed that pits equivalent to a 25 GB single-sided high-density optical disk were formed on the single-sided surface in the visual field of SEM observation as in Example 3. .
[0085]
The optical disk having a recording capacity of 25 GB obtained in Example 3 was read out under the following conditions, the RF signal was obtained as an eye pattern, and the signal was evaluated. The result is shown in FIG.
・ Tracking servo: Push-pull method
・ Modulation: 17PP
-Bit length: 112 nm
・ Track pitch: 320 nm
・ Reading linear velocity: 4.92m / s
・ Reading irradiation power: 0.4 mW
[0086]
The jitter value of the eye pattern (FIG. 10B) obtained by performing the conventional equalization processing on the eye pattern (FIG. 10A) as read is 8.6%, and the eye pattern obtained by performing the limit equalization processing (FIG. 10B). The jitter value at 10 (c)) was a sufficiently low value of 4.9%, and a good result having no practical problem was obtained as a ROM disk having a recording capacity of 25 GB.
In the optical disk obtained in Comparative Example 2, the jitter value in the eye pattern subjected to the conventional equalization processing was 8.0%, and the jitter value in the eye pattern subjected to the limit equalization processing was 4.6%. A jitter value almost equal to 3 was shown.
[0087]
【The invention's effect】
According to the first aspect of the present invention, it is possible to manufacture a sputter target capable of forming a metal unsaturated oxide layer without requiring introduction of oxygen gas during sputtering film formation.
Further, in the method according to the second aspect of the present invention, the degree of oxidation of the resist layer formed at the time of film formation by sputtering can be accurately determined by adjusting the mixture ratio of the mixture to form a sputter target having a predetermined oxygen content. Thus, the target oxidation degree can be easily and stably obtained as compared with the conventional reactive sputtering method.
Further, according to the method of the third aspect, it is possible to manufacture a sputter target capable of forming a resist layer that is an unsaturated oxide of a transition metal without requiring introduction of an oxygen gas during film formation by sputtering. .
According to the invention of claim 4 or claim 5, a resist layer (unsaturated oxide of a transition metal) corresponding to a photolithography technique capable of increasing the recording capacity of various devices is formed by oxygen gas deposition. It is possible to manufacture a sputter target that can be formed without requiring the introduction of sapphire.
Further, according to the invention of claim 6, when a mixture of a metal powder of a transition metal of the same element and an oxide powder is used as a raw material, a relation between a melting point of the transition metal in a metal state and a melting point of an oxide state thereof. By setting the firing temperature in consideration of the above, it is possible to obtain a sputter target having sufficient density and strength.
According to the invention of claim 7, the resolution of the resist layer is reduced by reducing the crystal grains of the unsaturated oxide of the transition metal constituting the resist layer formed at the time of film formation by sputtering, and reducing the surface roughness of the resist layer. Is greatly improved, and a sputter target with improved exposure sensitivity can be manufactured.
[0088]
According to the invention of claim 8, a metal unsaturated oxide layer can be formed without the need of introducing an oxygen gas at the time of film formation by sputtering.
According to the ninth aspect of the present invention, a stable sputtering rate of a metal unsaturated oxide can be secured, and a resist layer of stable quality can be formed.
According to the tenth aspect of the present invention, it is possible to form a resist layer which is a transition metal unsaturated oxide without requiring introduction of an oxygen gas at the time of sputtering film formation.
According to the invention of claim 11 or claim 12, a resist layer made of a transition metal unsaturated oxide can be formed without the need of introducing an oxygen gas at the time of film formation by sputtering. The present invention can be applied to a photolithography technology that enables the formation of a semiconductor device.
According to the invention of claim 13, the resist layer formed using this target has a smaller crystal grain of the transition metal unsaturated oxide and a smaller surface roughness of the film. And the boundary between them becomes clearer, and the resolution is greatly improved. Further, the exposure sensitivity can be improved.
Further, according to the invention of claim 14, it is possible to secure a stable sputtering rate of a metal unsaturated oxide without requiring introduction of oxygen gas during sputtering film formation, and to obtain a stable quality of a metal unsaturated oxide. Layers can be formed.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram of an optical disk using a resist substrate having a transition metal unsaturated oxide as a resist layer.
FIG. 2 shows a mixture (W + WO) in the method for producing a sputter target according to the present invention._Three+ MoO_Three) And sintering the target composition (W₈₀Mo₂₀)₃₀O₇₀FIG. 7 is a view showing the results of relative density and bending strength when the sputter target of Example 1 is formed.
FIG. 3 shows a mixture (W + WO) in the method for producing a sputter target according to the present invention._Three+ MoO_Three) And sintering the target composition (W₈₀Mo₂₀)₃₅O₆₅FIG. 7 is a view showing the results of relative density and bending strength when the sputter target of Example 1 is formed.
FIG. 4 is a view showing the results of relative density and bending strength when a sputter target of Comparative Example 1 was formed.
FIG. 5 shows a mixture (W + WO) in the method for producing a sputter target according to the present invention._Three+ MoO_Three) And sintering the target composition (W₈₀Mo₂₀)₃₀O₇₀FIG. 4 is a diagram showing a composition analysis result when a sputter target was formed.
FIG. 6 is a diagram showing a composition analysis result when a sputter target of Comparative Example 1 was formed.
FIG. 7 shows a mixture (WO) in the method for producing a sputter target according to the present invention._Two+ WO_Three+ MoO_Three) And sintering the target composition (W₈₀Mo₂₀)₃₀O₇₀FIG. 4 is a diagram showing a composition analysis result when a sputter target was formed.
FIG. 8 is a diagram schematically showing an exposure apparatus used in a fine processing method using a resist substrate having a transition metal unsaturated oxide as a resist layer.
FIG. 9 is a photograph of the surface of a resist layer made of an unsaturated oxide formed using the sputter target of the present invention, which was subjected to 25 GB cutting, developed, and then observed with an SEM.
FIG. 10 is a diagram illustrating a signal evaluation result of an optical disc having a recording capacity of 25 GB manufactured in Example 3.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Resist substrate, 11 ... Turntable, 12 ... Beam generation source, 13 ... Collimator lens, 14 ... Beam splitter, 15 ... Objective lens, 16 ... Condensing lens, 17 ... Split photodetector, 18 ... Focus error signal, 19 ... Focus actuator, 20 data signal, 21 reflected light signal, 22 tracking error signal, 23 laser drive circuit, 24 spindle motor control system

Claims (14)

A mixture of at least one kind of metal powder and at least one kind of metal oxide powder, or a mixture of plural kinds of metal oxide powders having different valences, and sintering the mixture under pressure. A method for producing a sputter target comprising a metal unsaturated oxide. The oxygen content after the pressure sintering is adjusted by the mixing ratio of the metal powder and the metal oxide powder, or the mixing ratio of the oxide powders of the plural kinds of metals having different valences. A method for manufacturing the sputter target according to claim 1. The method according to claim 1, wherein the metal is a transition metal. The method according to claim 3, wherein the transition metal is at least one of Ti, V, Cr, Mn, Fe, Nb, Cu, Ni, Co, Mo, Ta, W, Zr, Ru, and Ag. A method for producing the sputter target according to the above. The method according to claim 3, wherein the transition metal is one or both of Mo and W. Among the transition metals, a metal powder of a transition metal whose melting point in an oxide state is lower than a melting point in a metal state is mixed with an oxide powder, and when the mixture is sintered under pressure, an oxide of the transition metal is mixed. The method for producing a sputter target according to claim 4, wherein the powder is sintered at a temperature higher than the firing temperature when the powder is sintered under pressure to obtain a sputter target of a saturated oxide. The method for producing a sputter target according to any one of claims 3 to 6, wherein a powder of an element other than a transition metal is further added to the mixture. A metal powder obtained by mixing at least one kind of metal powder and at least one kind of metal oxide powder or mixing a plurality of kinds of metal oxide powders having different valences and sintering the mixture under pressure. A sputter target comprising an unsaturated oxide. The sputter target according to claim 8, wherein the relative density after the pressure sintering is 80% or more. The sputter target according to claim 8, wherein the metal is a transition metal. 11. The method according to claim 10, wherein the transition metal is at least one of Ti, V, Cr, Mn, Fe, Nb, Cu, Ni, Co, Mo, Ta, W, Zr, Ru, and Ag. The described sputter target. The sputter target according to claim 10, wherein the transition metal is one or both of Mo and W. The sputter target according to any one of claims 10 to 12, wherein a powder of an element other than the transition metal is further added to the mixture. A sputter target comprising a metal unsaturated oxide and having a relative density of 80% or more.

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