Ni-Fe alloy sputtering target for forming magnetic thin films, magnetic thin film, and method of manufacturing the Ni-Fe alloy sputtering target

An Ni--Fe alloy material suitable for forming a ferromagnetic Ni--Fe alloy thin film is provided. The magnetic thin film produces a small number of particles during sputtering, and excels in corrosion resistance and magnetic properties. A method of manufacturing an Ni--Fe alloy sputtering target used to make the thin film is also provided. In addition, an Ni--Fe alloy sputtering target for forming magnetic thin films is provided. The sputtering target is characterized in that it has: an oxygen content of 50 ppm or less; an S content of 10 ppm or less; a carbon content of 50 ppm or less, and a total content of metal impurities other than the alloy components of 50 ppm or less. Such an Ni--Fe alloy target can be produced by melting and alloying high-purity materials obtained by dissolving the raw materials in hydrochloric acid, and performing ion exchange, activated-charcoal treatment, and electrolytic refining.

FIELD OF THE INVENTION
 The present invention relates to an Ni--Fe sputtering target for forming
 magnetic thin films, and specifically to an Ni--Fe sputtering target for
 forming ferromagnetic thin films.
 BACKGROUND OF THE INVENTION
 In recent years, magnetic recording devices for computers, such as hard
 disks, have rapidly been downsized, and their capacities have been
 increased. The recording density of such devices is estimated to reach 20
 Gb/in.sup.2 in a few years. Therefore, conventional induction-type heads
 used as playing heads have approached their limit, and alternatively,
 magneto-resistance-effect-type (MR) heads have begun to be used. Use of
 the MR heads is expected to grow rapidly in the future in a worldwide
 scale accompanying the growth of the personal computer market. In coming
 years, the practical use of giant magneto-resistance-effect-type (GMR)
 heads, expected for their further higher density, will be realized.
 Ni--Fe alloys have been studied for use as a ferromagnetic film of the
 spin-valve film used in GMR heads.
 Ni--Fe alloys are normally produced by sintering or melting. However,
 conventional Ni--Fe alloys release a large amount of gases, produce a
 large number of particles during sputtering, and have the problem of
 corrosion resistance. Also, their magnetic properties are not found to be
 satisfactory.
 OBJECT OF THE PRESENT INVENTION
 It is an object of the present invention to provide means for forming a
 ferromagnetic film which releases less gases, produces fewer particles
 during sputtering, and has good magnetic properties.
 SUMMARY OF THE PRESENT INVENTION
 In order to solve the above problems, the inventors of the present
 invention repeated studies, and discovered that impurity elements, in
 particular, oxygen, sulfur, carbon, nitrogen, and hydrogen increased the
 release of gases and the production of particles, and that such impurities
 were the cause of lowered corrosion resistance. In addition to the above,
 the inventors discovered that the magnetic properties depended mainly on
 the crystalline structure of the thin film, and that the magnetic
 properties were improved when the crystals were large columnar crystals.
 According to the present invention, and based on the above stated findings,
 an Ni--Fe alloy sputtering target for forming magnetic thin films is
 provided such that it has an oxygen content of 50 ppm or less, a sulfur
 content of 10 ppm or less, a carbon content of 50 ppm or less, and a
 content of total metal impurities other than the alloy components of 50
 ppm or less. Preferably, the content of oxygen is 10 ppm or less, the
 content of sulfur is 1 ppm or less, the content of carbon is 10 ppm or
 less, and the content of total metal impurities other than the alloy
 components is 10 ppm or less.
 In addition, the Ni--Fe alloy sputtering target has a nitrogen content of
 10 ppm or less and a hydrogen content of 1 ppm or less. Preferably, the
 content of nitrogen is 1 ppm or less, and the content of hydrogen is 0.5
 ppm or less.
 According to another aspect of the present invention, a magnetic thin film
 formed by sputtering an Ni--Fe alloy target as described above is also
 disclosed.
 According to yet another aspect of the present invention, a method of
 manufacturing the above discussed Ni--Fe alloy sputtering target is
 provided. The method includes the step of alloying by: melting high-purity
 Ni and high-purity Fe obtained by dissolving material Ni and Fe in
 hydrochloric acid to form an aqueous solution of chlorides; removing
 impurity metal ions by allowing the aqueous solution of chlorides to
 contact an ion exchange resin; evaporating to dryness or concentrating the
 obtained solution; dissolving it in water to form an aqueous solution of
 chloride having pH between 0 and 3; removing organic matters in the
 solution using activated charcoal; and conducting electrolytic refining of
 the aqueous solution as an electrolytic solution. The method also includes
 the step of casting the obtained alloy.
 In addition, the method of manufacturing an Ni--Fe alloy sputtering target
 can include obtaining Ni or Fe by electrolytic refining and subjecting it
 to degassing.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 An Ni--Fe alloy sputtering target for forming magnetic thin films according
 to the present invention comprises an Ni--Fe alloy containing 70% by
 weight or more Ni. Although typical examples are two-component alloys of
 Ni and Fe, the examples further include alloys also containing Co, Cr, Rh,
 Nb, or Ta.
 In the Ni--Fe alloy sputtering target according to the present invention,
 the contents of impurities, i.e., elements other than Ni and Fe, are
 reduced. In particular, the contents of oxygen, sulfur, carbon, nitrogen,
 and hydrogen are reduced as much as possible, because such elements lower
 the corrosion resistance of the target, cause particles to occur, and
 deteriorate magnetic properties. Among these elements, oxygen and sulfur
 especially lower the corrosion resistance. Furthermore, since oxygen makes
 crystals finer and nitrogen deviates crystal orientation, both cause the
 deterioration of magnetic properties. Carbon also causes particles to
 occur. Therefore, the content of oxygen should be 50 ppm or below,
 preferably 10 ppm or below; the content of sulfur should be 10 ppm or
 below, preferably 1 ppm or below; and the content of carbon should be 50
 ppm or below, preferably 10 ppm or below.
 Furthermore, the content of nitrogen should be 10 ppm or below, preferably
 1 ppm or below; and the content of hydrogen should be 1 ppm or below,
 preferably 0.5 ppm or below.
 Exceeding the above contents is not preferred because of increase in
 occurrence of particles, significant lowering of corrosion resistance, and
 marked deterioration of magnetic properties.
 The inventor of the present invention found that the impurities in the
 Ni--Fe alloy were originated from electrolytic Ni and Fe materials. The
 inventor carried out the high purification of each of the Ni and Fe
 materials.
 By the combination of ion exchange and electrolytic refining, activated
 charcoal treatment, and degassing as required in the method for high
 purification of Ni and Fe materials, extremely high-purity Ni and Fe can
 be obtained.
 For example, the following method can be used.
 High-purity Ni and high-purity Fe can be obtained by: dissolving material
 Ni and Fe in hydrochloric acid to form an aqueous solution of chlorides;
 removing impurity metal ions by allowing the aqueous solution of chlorides
 to contact an ion exchange resin; evaporating to dryness or concentrating
 the obtained solution; dissolving the concentrated solution in water to
 form an aqueous solution of chloride having pH between 0 and 3; removing
 organic matters in the solution using activated charcoal; and conducting
 electrolytic refining of the aqueous solution as an electrolytic solution.
 Although the purity of the Ni and Fe utilized are not particularly limited,
 those of three-nine purity (99.9%) which are normally marketed are
 sufficient.
 The above Ni material, or Fe material, is charged in a vessel and dissolved
 in hydrochloric acid. The type of hydrochloric acid utilized is not
 particularly limited, for instance, industrial low purity hydrochloric
 acid may be used. This is because impurities contained in hydrochloric
 acid can also be removed by practicing the present invention.
 Equipment for dissolving Ni or Fe is preferably provided by a cooling tower
 for the effective use of hydrochloric acid and a hydrogen chloride gas
 recovering unit. The material of the equipment is preferably quartz,
 graphite, Teflon, or polyethylene.
 The dissolving temperature is 10 to 100.degree. C. If the temperature is
 less than 10.degree. C., the dissolving rate decreases, and if the
 temperature is more than 100.degree. C., evaporation becomes vigorous and
 loss of the aqueous solution increases.
 When Ni is highly purified, the Ni solution is extracted, concentrated, and
 adjusted to have a hydrochloric acid concentration of 5 to 12 N by adding
 hydrochloric acid. A hydrochloric concentration of less than 5 N, or more
 than 12 N, is not preferred because Co is not absorbed and removed by the
 ion exchange resin.
 The above nickel chloride solution adjusted to have a hydrochloric acid
 concentration of 5 to 12 N is allowed to contact an anion exchange resin
 to absorb impurities in the solution. The ion exchange resin used in the
 present invention is not particularly limited if it is an anion exchange
 resin. Examples include DOWEX 1.times.8, DOWEX 2.times.8 (Muromachi
 Chemicals Co., Ltd.), and DIAION SA 10A.
 Since Co, Fe, and U form chloride complexes in concentrated hydrochloric
 acid, and are present as anions, they are adsorbed on anion exchanged
 resins. On the other hand, since Ni and alkali metals such as Na, K and
 Th, present as impurities do not form chloride complexes, they are not
 adsorbed, but flow out of the column.
 At this time, for proper separation of Ni and Co, the flow rate of the
 solution is preferably SV=0.01 to 1. Here, "SV" stands for space velocity,
 and is the quantity of the solution per hour divided by the volume of the
 packed ion exchange resin. If SV is 0.01 or less, the productivity
 decreases, and if SV is 1 or more, Fe and Co are not sufficiently adsorbed
 and high-purity Ni cannot be obtained.
 Through the above operations, Co and U impurities are separated from Ni.
 Co and U adsorbed on the anion exchange resin can be eluted easily by the
 use of hydrochloric acid of a concentration less than 1N. Therefore, the
 anion exchange resin can be recovered by eluting Co and U at a suitable
 time, considering the adsorption capacity of the anion exchange resin.
 The purification of Fe can be performed in the same manner as the
 purification of Ni.
 Since the nickel chloride, or iron chloride solution, eluted from the ion
 exchange resin has a high hydrochloric acid content, it cannot be used for
 electrolytic refining as it is. Therefore, by evaporating to dryness or
 concentrating the eluted nickel chloride, or iron chloride, solution and
 adding pure water, an aqueous solution of a pH between 0 and 3 is obtained
 and used as the electrolytic solution.
 The evaporation to dryness, or concentration, step may be carried out with
 a rotary evaporator or the like. The temperature for evaporation to
 dryness or concentration is 80.degree. C. or above, preferably
 100.degree.C. or above. A temperature below 80.degree. C. is not preferred
 because evaporation to dryness or concentration takes a long time.
 Evaporation to dryness or concentration carried out with an aspirator
 under a weakly reduced pressure will reduce the time taken. The material
 of the equipment used for the evaporation to dryness or concentration step
 is preferably quartz, graphite, or Teflon. Hydrochloric acid gas produced
 during evaporation to dryness or concentration can be cooled and
 concentrated for reuse as hydrochloric acid for dissolving Ni or Fe.
 Small quantities of organic substances (styrene, divinylbenzene, amines,
 etc.) may flow out of the ion exchange resin and mix in the solution. An
 activated charcoal treatment is carried out to remove such organic
 substances. Since activated charcoal may contain impurities, it is
 preferable to use activated charcoal after treating with an acid such as
 hydrochloric acid to remove such impurities. Although the activated
 charcoal treatment is normally carried out after the nickel chloride, or
 iron chloride, solution and water is added to adjust the pH to 0 to 3, the
 activated charcoal treatment is not necessarily carried out in this order,
 but may be carried out at any time between the ion exchange and
 electrolytic refining steps.
 The pH of the electrolytic solution comprising the aqueous solution of
 high-purity Ni or high-purity Fe is 0 to 3, preferably 0.5 to 2. A pH
 below 0 is not preferred because a large quantity of hydrogen will be
 produced and current efficiency will decrease. A pH above 3 is also not
 preferred because Ni or Fe precipitates as nickel hydroxide or iron
 hydroxide.
 The concentration of Ni or Fe in the electrolytic solution during
 electrolytic refining is 10 to 100 g/l , preferably 20 to 80 g/l. A
 concentration less than 10 g/l is not preferred because a large quantity
 of hydrogen will be produced, current efficiency will decrease, and the
 concentration of impurities in electrodeposited Ni or Fe will increase. A
 concentration more than 110 g/l is also not preferred because nickel
 chloride or iron chloride will deposit affecting the electrodeposited
 state.
 The range of current densities are preferably between 0.01 and 10
 A/dm.sup.2. A current density less than 0.01 A/dm.sup.2 is not effective,
 because the productivity will decrease. A current density more than 10
 A/dm.sup.2 is also not preferred because the concentration of impurities
 will increase and current efficiency will decrease.
 Temperature during electrolysis is in a range between 10 and 90.degree. C.,
 preferably between 35 and 55.degree. C. Temperature below 10.degree. C. is
 not preferred because current efficiency will decrease, and temperature
 above 90.degree. C. is also not preferred because the evaporation of the
 electrolytic solution will increase.
 As the anode, crude Ni or crude Fe is used.
 As the cathode, an Ni, Fe or titanium plate is used.
 The material for the electrolytic vessel is preferably polyvinyl chloride,
 polypropylene, or polyethylene.
 In electrolytic refining, it is preferred to isolate the cathode from the
 anode with a diaphragm or an anion exchange membrane, and to feed to the
 cathode side at least intermittently the aqueous solution of high-purity
 Ni or high-purity Fe (acting as the catholyte) refined by ion exchange and
 activated-charcoal treatment, so that impurities eluted from the anode do
 not migrate toward the cathode, and also to extract from the anode side at
 least intermittently the anolyte having a high impurity content. The
 quantity of the catholyte fed at this time is preferably the same or more
 than the quantity of the anolyte extracted.
 The diaphragm or the anion exchange membrane available in the present
 invention is not particularly limited. Examples of diaphragms include
 Filter Cloth P-2020 and PP-100 (Azumi Filter Paper Co., Ltd.) and Tevylon
 1010, and examples of anion exchange membrane include Ionac MA-3475
 (Muromachi Chemical co., Ltd.).
 The extracted anolyte can be recycled and reused by adjusting the
 hydrochloric acid concentration to 5 to 12 N, then allowing it to contact
 an anion exchange resin, whereby electrolytic refining can be carried out
 continuously.
 For the purpose of the present invention, "at least intermittently" means
 "continuously or intermittently".
 Thus a trace of Th, or alkali metals such as Na and K, remaining in the
 electrolytic solution after the above electrolytic refining can be
 separated from Ni or Fe.
 By the heat treatment of recovered electrodeposited Ni or electrodeposited
 Fe in a reducing atmosphere, such as H.sub.2, gas components such as
 oxygen can be removed. The temperature for the heat treatment is
 preferably 800 to 1550.degree. C., and more preferably 100 to 1500.degree.
 C. If the temperature is below 800.degree. C., degassing takes a long
 time, while if the temperature is above 1550.degree. C., Ni or Fe is
 partially melted to cause contamination from the crucible.
 More preferably, electron-beam melting is performed. In electron-beam
 melting, an electrode (here, electrodeposited Ni or electrodeposited Fe)
 is first produced, and it is melted again to obtain high-purity ingots.
 Volatile components evaporate while an electrode is melted at a high
 temperature under a high vacuum. For example, when the melting quantity is
 5 kg, electron-beam melting is performed under the following conditions:
 current: 0.7A; voltage: 20 kV; degree of vacuum: 10.sup.-5 mmHg; and time:
 2 hr.
 High-purity Ni and high-purity Fe obtained by the above methods are melted
 and alloyed, then cast. The obtained Ni--Fe alloy ingot is machined to
 fabricate a target for sputtering. Basically, the purity of the target is
 the same as the purity of the ingot.
 By sputtering the thus obtained target, a magnetic thin film can be formed.
 The Ni--Fe alloy magnetic thin film obtained by sputtering has the purity
 same as the purity of the target, that is, an oxygen content of 50 ppm or
 less, a sulfur content of 10 ppm or less, a carbon content of 50 ppm or
 less, and a total content of metal impurities other than alloy components
 of 50 ppm or less. Furthermore, the crystalline structure is columnar.
 The magnetic properties of such a magnetic thin film are especially good
 because the crystalline structure is columnar.

Although the present invention is described below in detail referring to
 examples, the present invention is not limited to these examples.
 EXAMPLE 1
 Crude nickel lumps of a purity shown in Table 1 were placed in a dissolver,
 and charged in a vessel containing an 11.6 N aqueous solution of
 hydrochloric acid. The temperature was raised to 95.degree. C. to form an
 aqueous solution of nickel chloride of a hydrochloric acid concentration
 of 9 N and a nickel concentration of 50 g/l.
 This aqueous solution was passed through a polypropylene column (150 mm in
 diameter.times.1200 mm in length) packed with an anion exchange resin
 (DOWEX 2.times.8, Muromachi Chemicals Co., Ltd.) at SV=0.1 to adsorb and
 remove Co and U.
 The obtained refined aqueous solution of nickel chloride was evaporated to
 dryness at 110.degree. C. using a rotary evaporator. This was dissolved in
 pure water to make 10 liters of the solution. The nickel content at this
 time was about 50 g/l. After the pH was adjusted to 1, organic substances
 were removed by activated charcoal. This high-purity nickel solution was
 continuously added to the cathode chamber of the electrolytic vessel. The
 activated charcoal had been washed by 6 N hydrochloric acid to remove
 impurities such as Fe.
 Next, electrolytic refining was carried out at a current density of
 2A/dm.sup.2 and a temperature of 50.degree. C. using a nickel plate as the
 cathode. At this time, the anode side was partitioned from the cathode
 side with a diaphragm (PP2020, Azumi Filter Paper Co., Ltd.). The aqueous
 solution of high-purity nickel chloride was fed to the cathode side at a
 rate of 1 liter/hour, and was extracted from the anode side at the same
 rate. In 40 hours, the yield of obtained electrodeposited product was 83%.
 The electrodeposited state was a flat surface free of unevenness, and no
 peeling of the electrodeposited nickel occurred.
 On the other hand, Fe was purified in the same manner as Ni. This is, crude
 iron lumps of a purity shown in Table 1 were placed in an anode chamber,
 and charged in a vessel containing a 6 N aqueous solution of hydrochloric
 acid. The iron lumps were dissolved at 20.degree. C. to form an aqueous
 solution of iron chloride of an iron concentration of 50 g/l.
 This aqueous solution was passed through a polypropylene column (150 mm in
 diameter.times.1200 mm in length) packed with an anion exchange resin
 (DOWEX 2.times.8, Muromachi Chemicals Co., Ltd.) at SV=0.2 to adsorb Fe
 and remove Co and Ni. Then, pure water has Fe eluted.
 The obtained refined aqueous solution of iron chloride was evaporated to
 dryness at 110.degree. C. using a rotary evaporator. This was dissolved in
 pure water to make 10 liters of the solution. The iron content at this
 time was about 50 g/l. After the pH was adjusted to 2, organic substances
 were removed by activated charcoal. This high-purity Fe solution was
 continuously added to the cathode chamber of the electrolytic vessel. The
 activated charcoal had been washed by 6 N hydrochloric acid to remove
 impurities such as Fe.
 Next, electrolytic refining was carried out at a current density of
 2A/dm.sup.2 and a temperature of 50.degree. C. using an iron plate as the
 cathode. At this time, the anode side was partitioned from the cathode
 side with a diaphragm (PP2020, Azumi Filter Paper Co., Ltd.). The aqueous
 solution of high-purity iron chloride was fed to the cathode side at a
 rate of 1 liter/hour, and was extracted from the anode side at the same
 rate. In 40 hours, the yield of obtained electrodeposited product was 90%.
 The electrodeposited state was a flat surface free of unevenness, and no
 peeling of the electrodeposited Fe occurred.
 Furthermore, the obtained electrodeposited Ni and electrodeposited Fe were
 subjected to electron beam melting, and machined to fabricate a target for
 sputtering. The contents of impurities in electrodeposited Ni and
 electrodeposited Fe, and those after electron beam melting, are shown in
 Table 1.
 TABLE 1
 Example 1
 Unit: ppm
 Electro- Electro-
 Material depos- Material depos- Ni-Fe
 Ni ited Ni EB Ni Fe ited Fe EB Fe alloy
 Ni Balance Balance Balance 20 1 1 82%
 Fe 20 1 1 Balance Balance Balance 18%
 O 80 50 7 100 20 5 8
 N 15 1 &lt;1 25 1 &lt;1 &lt;1
 C 50 5 5 30 5 5 5
 S 10 &lt;1 &lt;1 40 &lt;1 &lt;1 &lt;1
 H 10 1 0.2 5 1 0.2 0.1
 Na 40 &lt;0.1 &lt;0.1 5 &lt;0.1 &lt;0.1 &lt;0.1
 K 1 &lt;0.1 &lt;0.1 5 &lt;0.1 &lt;0.1 &lt;0.1
 Cr 0.5 &lt;0.1 &lt;0.1 5 1 1 0.5
 Cu 25 5 3 1 1 0.5 2
 Al 1 &lt;0.1 &lt;0.1 1 0.5 0.5 0.5
 Co 25 5 5 50 10 10 8
 Ca 0.1 &lt;0.1 &lt;0.1 1 &lt;0.1 &lt;0.1 1
 Mg 0.1 &lt;0.1 &lt;0.1 1 &lt;0.1 &lt;0.1 &lt;0.1
 As 1 0.5 &lt;0.1 1 0.5 0.1 &lt;0.1
 Pb 2 0.1 0.1 2 1 1 0.5
 Si 1 &lt;0.1 &lt;0.1 1 &lt;0.1 &lt;0.1 &lt;0.1
 Zn 1 &lt;0.1 &lt;0.1 2 &lt;0.1 &lt;0.1 &lt;0.1
 Total of 97.7 11.4 9 75 14.6 13.7 13.1
 metal
 im-
 purities
 The obtained refined Ni and refined Fe were melted and alloyed in a ratio
 of 82:18 in a CaO crucible. The contents of impurities contained in the
 resultant Ni--Fe alloy were, oxygen: 8 ppm, sulfur: less than 1 ppm,
 carbon: 5ppm, nitrogen: less than 1 ppm, hydrogen: 0.1 ppm, and total
 metal impurities other than Ni and Fe: 13.1 ppm.
 The compositions of each material and the Ni--Fe alloy are also shown in
 Table 1.
 This alloy ingot was machined to fabricate a disc-shaped target for
 sputtering having a diameter of 50 mm and a thickness of 5 mm. This target
 for sputtering was joined to a copper packing plate using an In--Sn alloy
 solder. Using magnetron sputtering equipment, an Ni--Fe alloy thin film
 was formed on a 3-inch Si wafer by sputtering. The number of particles
 having diameters of 0.3 .mu.m or larger produced on the wafer during
 sputtering was counted. Furthermore, the observation of the
 cross-sectional structure of the thin film was conducted.
 EXAMPLE 2
 Operations of Example 1 were repeated except that activated charcoal
 without acid treatment was used. The purity of Ni and Fe obtained by these
 operations are shown in Table 2. It is found that the Fe content in Ni is
 high. If activated charcoal containing less Fe is used, this problem does
 not arise. Even if the Fe content is high, no problems arise when an
 Ni--Fe alloy is produced.
 The obtained refined Ni and refined Fe were melted and alloyed in a ration
 of 82:18 in an Al.sub.2 O.sub.3 crucible. The contents of impurities
 contained in the resultant N--Fe alloy were: oxygen: 20 ppm; sulfur: 1
 ppm; carbon: 5 ppm; nitrogen: 4 ppm; hydrogen: 0.2 ppm; and total metal
 impurities other than Ni and Fe: 16 ppm.
 The compositions of each material and the Ni--Fe alloy are also shown in
 Table 2.
 TABLE 2
 Example 1
 Unit: ppm
 Electro- Electro-
 Material depos- Material depos- Ni-Fe
 Ni ited Ni EB Ni Fe ited Fe EB Fe alloy
 Ni Balance Balance Balance 20 3 3 82%
 Fe 20 5 5 Balance Balance Balance 18%
 O 80 60 15 100 30 20 20
 N 15 1 1 25 5 5 4
 C 50 5 5 30 5 5 5
 S 10 1 1 40 1 1 1
 H 10 1 0.2 5 1 0.2 0.2
 Na 40 &lt;0.1 &lt;0.1 5 &lt;0.1 &lt;0.1 &lt;0.1
 K 1 &lt;0.1 &lt;0.1 5 &lt;0.1 &lt;0.1 &lt;0.1
 Cr 0.5 &lt;0.1 &lt;0.1 5 1 1 0.5
 Cu 25 5 3 1 1 0.5 2
 Al 1 &lt;0.1 &lt;0.1 1 0.5 0.5 0.5
 Co 25 5 5 50 10 10 8
 Ca 0.1 &lt;0.1 &lt;0.1 1 &lt;0.1 &lt;0.1 1
 Mg 0.1 &lt;0.1 &lt;0.1 1 &lt;0.1 &lt;0.1 &lt;0.1
 As 1 0.5 &lt;0.1 1 0.5 0.1 &lt;0.1
 Pb 2 0.1 0.1 2 1 1 0.5
 Si 1 2 2 1 2 2 3
 Zn 1 4 &lt;0.1 2 &lt;0.1 4 &lt;0.1
 Total of 97.7 17.2 10.9 75 16.5 19.5 16
 metal
 im-
 purities
 A target for sputtering was fabricated as in Example 1 and subjected to the
 sputtering test. The number of particles on the wafer was counted, and the
 observation of the cross-sectional structure of the thin film was
 conducted.
 COMATIVE EXAMPLE 1
 Commercially available material Ni of three-nine purity (oxygen: 80 ppm, S:
 10 ppm, C: 65 ppm, H: 10 ppm, N: 15 ppm, total impurity metal elements
 other than Ni and Fe: 97.7 ppm) and commercially available material Fe of
 three-nine purity (oxygen: 100 ppm, S: 40 ppm, C: 40 ppm, H: 5 ppm, N: 25
 ppm, total impurity metal elements other than Ni and Fe: 75 ppm) were
 subjected to high-frequency melting and alloyed at a ratio of 82:18. As
 the result, an Ni--Fe alloy of impurity contents of: oxygen: 100 ppm; S:
 30 ppm; C: 60 ppm; H: 2 ppm; N: 25 ppm; and total impurity metal elements
 other than Ni and Fe: 74.3 ppm was obtained.
 The compositions of each material and the Ni--Fe alloy are also shown in
 Table 3.
 TABLE 3
 Comparative Example 1
 Unit: ppm
 Material Ni Material Fe Ni--Fe alloy
 Ni Balance 20 82%
 Fe 20 Balance 18%
 O 80 100 100
 N 15 25 25
 C 65 40 60
 S 10 40 30
 H l0 5 2
 Na 40 5 10
 K 1 5 1
 Cr 0.5 5 3
 Cu 25 1 15
 Al 1 1 1
 Co 25 50 40
 Ca 0.1 1 1
 Mg 0.1 1 &lt;0.1
 As 1 1 &lt;0.1
 Pb 2 2 2
 Si 1 1 1
 Zn 1 2 &lt;0.1
 Total of metal 97.7 75 74.3
 impurities
 A target for sputtering was fabricated in the same manner as previously
 described in Examples 1 and 2 and subjected to the sputtering test. The
 number of particles on the wafer was counted, and the observation of the
 cross-sectional structure of the thin film was conducted.
 The results of counting the number of particles in the sputtering test and
 the results of structure observation for Examples 1 and 2 and Comparative
 Example 1 are shown in Table 4.
 TABLE 4
 Number of particles Thin film crystalline structure
 Example 1 5 Large columnar crystal
 Example 2 30 Columnar crystal
 Comparative 140 Isometric crystal
 Example 1
 The results showed that the Ni--Fe alloy target for sputtering for forming
 magnetic thin films according to the present invention, which had an
 oxygen content of 50 ppm or less, an S content of 10 ppm or less, a carbon
 content of 50 ppm or less, and a total content of metal impurities other
 than the alloy components of 50 ppm or less, produced fewer particles than
 the Comparative Example 1. The crystalline structure of the thin film was
 columnar.
 In particular, the Ni--Fe alloy target for sputtering for forming magnetic
 thin films according to the present invention, which had an oxygen content
 of 10 ppm or less, an S content of 1 ppm or less, a carbon content of 10
 ppm or less, and a total content of metal impurities other than the alloy
 components of 10 ppm or less, produced an extremely small number of
 particles. The thin film having crystalline structure of the large
 columnar crystals was able to be obtained.
 Whereas, the thin film obtained using a target of the Comparative Example 1
 produced a large number of particles, the crystalline structure was fine
 isometric crystals, and the magnetic properties were unsatisfactory.
 By the use of the Ni--Fe alloy sputtering target for forming magnetic thin
 films according to the present invention, which has an oxygen content of
 50 ppm or less, an S content of 10 ppm or less, a carbon content of 50 ppm
 or less, and a total content of metal impurities other than the alloy
 components of 50 ppm or less, a magnetic film producing a small number of
 particles, and having good magnetic properties can be formed. The Ni--Fe
 alloy sputtering target according to the present invention is useful as
 the material for forming magnetic thin films.