Patent Application
20050196546
The present invention relates to a method of forming a magnetic film, a method of forming a magnetic pattern and a method of manufacturing a magnetic recording medium, and more particularly to a method of forming a magnetic film which can process a magnetic film including a recording portion and a non-recording portion in accordance with a recording pattern.
The performance of a hard disk drive (HDD) has remarkably been enhanced continuously with the development of a computer as a mass storage device capable of carrying out the high-speed access and transfer of data. In particular, an areal density has been enhanced at an annualized rate of 60% to 100% for these 10 years and a further enhancement in the recording density has been required.
In order to enhance the recording density of the hard disk drive (HDD), it is necessary to reduce a track width or a recording bit length. However, there is a problem in that adjacent tracks are apt to interfere with each other if the track width is reduced. More specifically, the reduction in the track width causes a problem in that magnetic recording information is easily overwritten over the adjacent track in recording and a problem in that a cross talk is apt to be generated by a leaking magnetic field from the adjacent track in reproduction. Both of these problems cause a reduction in the S/N ratio of a reproducing signal and a deterioration in an error rate.
For these problems, a magnetic recording medium of a discrete track type (hereinafter referred to as a discrete track medium) has been proposed as a method of reducing an interference between the adjacent tracks and implementing a high track density. The discrete track medium proposed currently is obtained by providing a trench between the tracks of a magnetic film to be a recording portion (a guard band) to magnetically separate each track from the adjacent track. In this method, however, it is hard to implement the stable flying of a magnetic head over the magnetic recording medium because a physical trench is present between the tracks.
On the other hand, although it is possible to stabilize the flying characteristics of the magnetic head over the magnetic recording medium by carrying out a flattening processing after filling the trench between the tracks with a non-magnetic substance, there is a problem in that a manufacturing process is complicated and a manufacturing cost is thus increased.
As a method of avoiding these problems, there has been investigated a processing method of irradiating ion on a magnetic film to locally modify a magnetic characteristic (for example, see Japanese Publication JP-T-2002-501300 and JP-A-2003-22525). In a method described in JP-T-2002-501300, a light ion is irradiated on a laminated film and the atom of an interface between the laminated films is subjected to mixing by the shock, thereby modifying the magnetic characteristic of an irradiating portion. In a method described in JP-A-2003-22525, moreover, local heat generation caused by the irradiation of ion beam is utilized to modify the magnetic characteristic of the irradiating portion.
The invention provides new technique for avoiding the conventional problems described above, and it is a first object of the invention to provide a method of forming a magnetic film which can form a magnetic film including portions having different coercive forces. Moreover, it is a second object of the invention to provide a method of forming a magnetic pattern which utilizes the method and it is a third object of the invention to provide a method of manufacturing a magnetic recording medium which utilizes the method.
A method of forming a magnetic film according to the invention which attains the first object is characterized in that at least one ion selected from Cr, Al, Nb and Mo is locally implanted into a thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt; and boron ion is then implanted into a whole surface of the thin film subjected to the implantation, and a heat treatment is thereafter carried out.
According to the invention, the portion of the film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt into which only a boron ion is implanted becomes a magnetic film having a CuAuI type ordered structure by a heat treatment and thus has a very high magnetic anisotropy. More specifically, boron acts to promote a change to the CuAuI type ordered structure in the heat treatment. Therefore, the portion into which only the boron ion is implanted is sufficiently changed to have the CuAuI type ordered structure by a subsequent heat treatment.
On the other hand, in the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted, the coercive force is reduced without a sufficient change to the CuAuI type ordered structure even if the heat treatment is carried out. More specifically, in the heat treatment, the boron acts to promote the change to the CuAuI type ordered structure. However, the action for suppressing the change to the CuAuI type ordered structure by at least one selected from Cr, Al, Nb and Mo is greater than the action described above. Therefore, the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted is not sufficiently changed to have the CuAuI type ordered structure.
As a result, there is formed a magnetic film in which the portion into which only the boron ion is locally implanted is sufficiently changed to have the CuAuI type ordered structure and has a large coercive force, and the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted is not sufficiently changed to have the CuAuI type ordered structure but has a small coercive force.
Moreover, the boron ion is implanted into the whole surface of the thin film so that the surface roughness of the whole surface of the magnetic film obtained after the heat treatment is reduced. More specifically, the boron acts to reduce the surface roughness in the heat treatment. Therefore, it is possible to reduce the surface roughness of the whole surface of the magnetic film into which the boron ion is implanted by a subsequent heat treatment.
According to the method of forming a magnetic film in accordance with the invention, therefore, it is possible to form a magnetic film having different coercive forces between the portion into which only the boron ion is implanted and the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted. Consequently, it is possible to form the discrete track medium without providing the conventional trench. Therefore, it is possible to form a magnetic pattern substantially having no surface concavo-convex portion.
The method of forming a magnetic film according to the invention is characterized in that a portion having only the boron ion implanted therein which is obtained after the heat treatment has a CuAuI type ordered structure. According to the invention, since the portion into which only the boron ion is implanted after the heat treatment has the CuAuI type ordered structure, it exhibits a very high magnetic anisotropy. As a result, the magnetic film having the high magnetic anisotropy produces an advantage that the thermal stability of a recording magnetization can be enhanced.
In the method of forming a magnetic film according to the invention, it is preferable that the thin film should be obtained by laminating a film containing at least one of Fe and Co as the main component and a film containing at least one of Pd and Pt as the main component.
In the method of forming a magnetic film according to the invention, it is preferable that the thin film should be a compositionally modulated film obtained by modulating compositions of at least one of Fe and Co and at least one of Pd and Pt in a direction of a thickness of the film. According to the invention, it is supposed that an interface diffusion is caused during the heat treatment so that the activation energy of the diffusion is reduced if the thin film is the compositionally modulated film. Consequently, it is also possible to change the thin film to have the CuAuI type ordered structure at a low heat treatment temperature.
A method of forming a magnetic pattern according to the invention which attains the second object is characterized in that at least one ion selected from Cr, Al, Nb and Mo is implanted by using a mask into a predetermined portion of a thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt and a boron ion is then implanted into a whole surface of the thin film subjected to the implantation, and a heat treatment is thereafter carried out.
According to the invention, in the same manner as the case of the method of forming a magnetic film, there is formed a magnetic pattern in which the portion into which only the boron ion is locally implanted is sufficiently changed to have the CuAuI type ordered structure and thus has a large coercive force, and the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted is not sufficiently changed to have the CuAuI type ordered structure but has a small coercive force. When the boron ion is implanted into the whole surface of the thin film, moreover, the surface roughness of the whole surface of the thin film obtained after the heat treatment is reduced. According to the method of forming a magnetic pattern in accordance with the invention, therefore, it is possible to form a discrete track medium having the magnetic pattern without providing a conventional trench. Consequently, it is possible to form a magnetic pattern substantially having no surface concavo-convex portion.
In a method of manufacturing a magnetic recording medium according to the invention which attains the third object, a method of manufacturing a magnetic recording medium having at least a non-magnetic substrate and a magnetic film provided on the non-magnetic substrate is characterized in that the magnetic film is obtained by locally implanting at least one ion selected from Cr, Al, Nb and Mo into a thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt and then implanting a boron ion into a whole surface of the thin film subjected to the implantation, and thereafter carrying out a heat treatment. According to the invention, it is possible to manufacture the magnetic recording medium such as a discrete track medium having a predetermined magnetic pattern without forming a conventional trench. Therefore, it is possible to manufacture a magnetic recording medium substantially having no surface concavo-convex portion.
The method of manufacturing a magnetic recording medium according to the invention is characterized in that the local implantation of at least one ion selected from Cr, Al, Nb and Mo is carried out by using a mask.
As described above, according to the method of forming a magnetic film, the method of forming a magnetic pattern and the method of manufacturing a magnetic recording medium in accordance with the invention, it is possible to increase the coercive force of the portion into which only the boron ion is implanted, and furthermore, to reduce the coercive force of the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted. By implanting the boron ion into the whole surface of the thin film, moreover, it is possible to reduce the surface roughness of the whole surface of the magnetic film obtained after the heat treatment. As a result, it is possible to form the magnetic film having different coercive forces between the portion into which only the boron ion is implanted and the portion into which at least one ion selected from Cr, Al, Nb and Mo and the boron ion are implanted. Therefore, it is possible to form a desirable magnetic pattern substantially having no surface concavo-convex portion by implanting at least one ion selected from Cr, Al, Nb and Mo into a predetermined portion by using a mask, for example.
By forming, as a track pattern taking the shape of a concentric circle, the portion into which only the boron ion is implanted on a disk-shaped non-magnetic substrate, particularly, it is possible to manufacture a magnetic recording medium such as a discrete track medium having a predetermined magnetic pattern to be the portion into which only the boron ion is implanted without forming a conventional trench. The magnetic recording medium thus manufactured substantially has no surface concavo-convex portion and a manufacturing cost can also be reduced.
FIGS. 1(a) to 1(b) are view showing a process according to an example of a method of forming a magnetic film in accordance with the invention,
FIGS. 3(a) to 3(d) are views showing a process according to an example of a method of forming a compositionally modulated film in accordance with the invention.
A method of forming a magnetic film, a method of forming a magnetic pattern and a method of manufacturing a magnetic recording medium according to the invention will be sequentially described below with reference to the drawings. The scope of the invention is not restricted by the embodiment which will be described below.
(Magnetic Film Forming Method)
The method of forming a magnetic film according to the invention is characterized in that at least one ion 6 selected from Cr, Al, Nb and Mo is locally implanted into a thin film 4 containing, as main components, at least one of Fe and Co and at least one of Pd and Pt which are formed on a substrate 1, and a boron ion 20 is then implanted into the whole surface of the thin film after the implantation, and a heat treatment is thereafter carried out.
A non-magnetic substrate is used for the substrate 1, and an aluminum alloy substrate, a glass substrate and a silicon substrate which are generally used as the substrate of a magnetic film are taken as an example.
The thin film 4 formed on the substrate 1 may be a thin laminated film obtained by alternately providing a first film 2 containing at least one of Pd and Pt as a main component and a second film 3 containing at least one of Fe and Co as the main component or may be a compositionally modulated film formed by alternately deposing at least one of Pd and Pt (a Pt atom 41 in
In the case in which the thin film 4 is a thin laminated film, the first film 2 is not particularly restricted if the film contains at least one of Pd and Pt as a main component. For example, Pd, Pt and Pd—Pt can be preferably taken as at least one of Pd and Pt, and Pt is particularly preferable. Moreover, the second film 3 is not particularly restricted if the film contains at least one of Fe and Co as the main component. For example, Fe, Co and Fe—Co can be preferably taken as at least one of Fe and Co, and Fe is particularly preferable.
For the thin laminated film, it is desirable that the first film 2 and the second film 3 should be constituted by an element of Pt—Fe, Pt—Co or Pt—Co—Fe which is provided on the substrate 1 and is then heat treated, and can be a magnetic film having a high magnetic anisotropy. In particular, it is desirable that the thin laminated film should be obtained by providing a Pt film to be the first film 2 and an Fe film to be the second film 3.
The thin laminated film can be formed by various film forming means such as sputtering. For the lamination of the first film 2 and the second film 3, it is possible to carry out sputtering over each target having respective film forming elements at a predetermined power for a predetermined time by using the same target, thereby forming the first film 2 and the second film 3 constituted by a desirable composition.
In the case in which the thin film 4 is a compositionally modulated film, a compositionally modulated film having the composition of at least one of Fe and Co and at least one of Pd and Pt modulated is not particularly restricted. For example, there is desired a compositionally modulated film having the composition of at least one of Fe and Co and at least one of Pd and Pt modulated in the direction of the thickness of the film as shown in
For the compositionally modulated film, it is possible to illustrate a compositionally modulated film in which Pt and Fe are alternately deposited and a portion having a higher rate of Pt and a portion having a higher rate of Fe are provided periodically.
In the compositionally modulated film thus illustrated, a rate of Pt to the total of Pt and Fe is preferably higher than 50 atomic % and is equal to or lower than 90 atomic % and is more preferably equal to or higher than 60 atomic % and equal to or lower than 90 atomic % in the portion having a higher rate of Pt. By depositing the portion having a higher rate of Pt within the range of the rate described above, it is possible to form a magnetic film with a CuAuI type ordered structure having a high magnetic anisotropy by a subsequent heat treatment. In some cases in which the rate of Pt is higher than 90 atomic %, it is impossible to form the magnetic film with the CuAuI type ordered structure having the high magnetic anisotropy even if the heat treatment is subsequently carried out. In the case in which the rate of Pt is higher than 50 atomic % and is equal to or lower than 90 atomic %, the rate of Fe is lower than 50 atomic % and is equal to or higher than 10 atomic % with respect to the total of Fe and Pt.
For such a compositionally modulated film, more specifically, a compositionally modulated film including three portions having ratios of a Pt atom to an Fe atom of 3:1, 1:1 and 1:3 as one cycle is taken as an example.
The method of forming a compositionally modulated film is not particularly restricted but the following methods using the Pt atom and the Fe atom are taken as an example as shown in
(1) The Pt atom 41 corresponding to 75% of a necessary amount for forming a Pt monoatomic atom is deposited on the non-magnetic substrate 1 by sputtering. The Pt atom 41 has an amount of 75% at which a perfect monoatomic layer cannot be formed. Therefore, a first portion thus formed has 25% of defects as shown in
(2) Next, the Fe atom 42 corresponding to 75% of a necessary amount for forming an Fe monoatomic layer is deposited on the first portion by the sputtering. 25% of the Fe atom 42 fills in the defect of the first portion by a surface diffusing effect, and at the same time, 50% of the residue of the Fe atom 42 forms a second portion. As a result, the first portion is set to have a ratio of Pt to Fe of 3:1 as shown in
(3) Then, the Pt atom 41 corresponding to 75% of a necessary amount for forming a Pt monoatomic layer is deposited on the second portion by the sputtering. 50% of the Pt atom 41 fills in the defect of the second portion by the surface diffusing effect, and at the same time, 25% of the residue of the Pt atom 41 forms a third portion. As a result, the second portion is set to have a ratio of Pt to Fe of 1:1 as shown in
(4) Thereafter, the Fe atom 42 corresponding to 75% of a necessary amount for forming the Fe monoatomic layer is deposited on the third portion by the sputtering. The Fe atom 42 is deposited to fill in all of the defects of the third portion by the surface diffusing effect, and the third portion is set to have a ratio of Pt to Fe of 1:3 as shown in
The film formed at the steps of (1) to (4) has the three portions (the first portion, the second portion and the third portion) set to be one cycle, and has a composition modulating structure in which the portions have different ratios of the Pt atom to the Fe atom of 3:1, 1:1 and 1:3 respectively. Such a compositionally modulated film has a distortion generated by the periodic shift of a composition ratio as compared with a laminated film in which monoatomic layers are provided alternately. For this reason, it is supposed that the mutual diffusion of the Pt atom 41 and the Fe atom 42 is easily caused and the CuAuI type ordered structure can be thus obtained at a lower energy.
The thin film 4 is formed until a thickness (which implies a total thickness) is 3 nm to 30 nm, for example. In some cases in which the thickness of the thin film 4 is smaller than 3 nm, it is impossible to form a magnetic film with the CuAuI type ordered structure having a high magnetic anisotropy by a subsequent heat treatment. If the thickness of the thin film 4 is greater than 30 nm, a granular growth becomes remarkable in the subsequent heat treatment. As a result, in some cases in which a magnetic film which is obtained is applied to a magnetic recording medium, for example, a bad influence is caused, that is, a medium noise is increased. In the case in which the thin film 4 is a thin laminated film, the thickness of the first film 2 and that of the second film 3 may be equal to or different from each other or the thickness of each of the first films 2 and that of each of the second films 3 may be equal to or different from each other. If the thickness of the thin film 4 is 3 nm to 30 nm, moreover, the number of laminated layers is not particularly restricted.
The thin film 4 has a disordered phase with a face centered cubic structure (fcc) and has a low magnetic anisotropy and coercive force before the heat treatment, and is formed by regulating the composition of the film in such a manner that it becomes a magnetic film with the CuAuI type ordered structure having a high magnetic anisotropy after the heat treatment. The disordered phase of the face centered cubic structure (fcc) has a random array of the Fe atom and the Pt atom, for example, and has a low magnetic anisotropy and coercive force. Moreover, the CuAuI type ordered structure implies a face centered tetragonal structure (fct) and has an atomic arrangement in which the Fe atom and the Pt atom are laminated alternately in a c-axis direction, for example.
For the composition of the thin film to be the magnetic film with the CuAuI type ordered structure having a high magnetic anisotropy after the heat treatment, a composition of F1-xMx (F represents at least one of Fe and Co, M represents at least one of Pd and Pt, and x represents an atomic ratio of 0.3 to 0.65) is desirable. The composition of the thin film 4 is regulated to have such a composition. In the invention, the magnetic film obtained after the heat treatment has the CuAuI type ordered structure with the composition of F1-xMx (F represents at least one of Fe and Co, M represents at least one of Pd and Pt, and x represents an atomic ratio of 0.3 to 0.65). Therefore, the magnetic film obtained after the heat treatment has a very high magnetic anisotropy. When the crystal structure of the thin film is changed from the disordered phase with the face centered cubic structure (fcc) to an ordered phase with the face centered tetragonal structure (fct) in which a lattice constant is increased in an a-axis direction and is reduced in the c-axis direction by the heat treatment, a super lattice is formed on a so-called atomic level in which the Fe atom and the Pt atom are alternately provided for each atomic layer in the c-axis direction for the reduction, for example. Therefore, the anisotropy of the atomic arrangement produces a uniaxial magnetic anisotropy which is very high in the c-axis direction. As a result, the magnetic film having a high magnetic anisotropy produces an advantage that the thermal stability of a recording magnetization can be enhanced. The change from the disordered phase to the ordered phase described above is generally referred to as an order-disorder transformation.
The thin film 4 contains, as main components, at least one of Fe and Co and at least one of Pd and Pt, and usually includes other components to be a magnetic recording medium of an isolated particle system. For the other components, oxide and fluorocarbon are taken as an example.
At least one selected from Cr, Al, Nb and Mo is locally implanted into the thin film 4 which has not been heat treated by ion implantation. The ion 6 to be implanted may be at least one or more selected from Cr, Al, Nb and Mo. The ion 6 to be one selected from Cr, Al, Nb and Mo has an effect of suppressing the change to the CuAuI type ordered structure of the thin film 4 (hereinafter referred to as an ordering suppressing effect). In the following, one selected from Cr, Al, Nb and Mo will also be referred to as “Cr”.
In the thin film 4 having the ion 6 such as Cr implanted therein, the change to the CuAuI type ordered structure is suppressed in a subsequent heat treatment. More specifically, it is possible to produce an advantage that the change to the CuAuI type ordered structure is hard to sufficiently perform. In the invention, the ion 6 such as Cr is locally implanted into the predetermined portion of the thin film 4 and the heat treatment is then carried out. Consequently, it is hard to sufficiently change a portion 7 having the ion 6 such as Cr implanted therein to have the CuAuI type ordered structure. Thus, it is possible to carry out a change to a magnetic film 11 having a small coercive force. Even if the boron ion 20 which will be described below is implanted into the portion 7 having the ion 6 such as Cr implanted therein, the function of suppressing the change to the CuAuI type ordered structure is greater than the action of the boron (the function of promoting the change to the CuAuI type ordered structure). In the heat treatment, therefore, the portion 7 having the ion 6 such as Cr implanted therein is not sufficiently changed to have the CuAuI type ordered structure.
In the invention, the amount of implantation of the ion 6 such as Cr is set within a range in which the coercive force of the portion 7 (portion 9) having the ion 6 such as Cr implanted therein after the heat treatment is reduced as greatly as possible. For example, it is preferable that the amount of implantation of Cr should be set within a range of 5 to 10 atomic % with the composition of the thin film 4. It is preferable that the amount of Al should be set within a range of 5 to 10 atomic % with the composition of the thin film 4 obtained before the heat treatment. It is preferable that the amount of implantation of Nb should be set within a range of 2.5 to 10 atomic % with the composition of the thin film 4 obtained before the heat treatment. It is preferable that the amount of implantation of Mo should be set within a range of 5 to 10 atomic % with the composition of the thin film 4 obtained before the heat treatment. When the ion 6 such as Cr within these ranges is implanted, the portion 7 having the ion 6 such as Cr implanted therein (a portion including the boron ion 20) becomes a portion 9 having a small coercive force even if the heat treatment is carried out. In some cases in which the amount of implantation of the ion 6 such as Cr is less than 5 atomic % or 2.5 atomic %, it is impossible to sufficiently exhibit the suppressing effect of causing the implanted portion 7 to be sufficiently changed to have the CuAuI type ordered structure with difficulty. On the other hand, in some cases in which the amount of implantation of the ion 6 such as Cr is larger than 10 atomic %, the surface roughness of the implanted portion 7 is increased.
The implantation of the ion 6 such as Cr is carried out by the ion implantation. The ion implantation uses an ion implanting equipment. In the case in which the ion 6 such as Cr is to be implanted, it is desirable that an implanting voltage should be set within a range of 5 keV to 50 keV when the thickness of the thin film 4 is 3 nm to 30 nm, which is not absolutely determined depending on the ion to be implanted. By implanting the ion 6 such as Cr at the implanting voltage within this range, it is possible to implant the ion 6 such as Cr into each portion in the direction of the thickness of the thin film 4, for example. In the case in which the thickness of the thin film 4 is small, it is desirable that the implanting voltage should be set to have a smaller value within the range. In the case in which the thickness of the thin film 4 is great, it is desirable that the implanting voltage should be set to have a greater value within the range. In some cases in which the implanting voltage is lower than 5 keV, the ion 6 such as Cr cannot be sufficiently implanted into the deep part of the thin film 4 so that the change to the CuAuI type ordered structure cannot be suppressed sufficiently when the thickness of the thin film 4 is 3 nm to 30 nm. On the other hand, when the implanting voltage is higher than 50 keV, the ion 6 such as Cr is implanted into an underlayer film so that a soft magnetic characteristic is deteriorated in some cases in which the thickness of the thin film 4 is 3 nm to 30 nm, for example, the underlayer film is provided to be a soft magnetic underlayer under the thin film 4, for example.
The boron ion 20 is an interstitial element and is implanted into the whole surface of the thin film into which the ion 6 such as Cr is implanted and which has not been heat treated. The boron has an effect of promoting the change to the CuAuI type ordered structure, and furthermore, an effect of reducing the surface roughness of the magnetic film 11 obtained after the heat treatment. In the thin film into which only the boron ion 20 is implanted, the change to the CuAuI type ordered structure is promoted in a subsequent heat treatment. More specifically, there is an effect of easily carrying out the change to the CuAuI type ordered structure having a large coercive force. In the invention, the boron ion 20 is implanted and the heat treatment is subsequently carried out so that only a portion 8 into which only the boron ion 20 is implanted can easily be changed to have the CuAuI type ordered structure and can be changed to the magnetic film 11 having a large coercive force. As a result, the portion 8 into which only the boron ion 20 is implanted becomes a portion 10 having a large coercive force and the portion 7 into which the ion 6 such as Cr and the boron ion 20 are implanted becomes the portion 9 having a small coercive force.
Moreover, the boron ion 20 is implanted into the whole surface of the thin film so that the surface roughness of the whole surface of the magnetic film 11 obtained by the execution of the heat treatment after the implantation of the boron ion 20 is reduced. More specifically, the boron acts to reduce the surface roughness of the thin film in the heat treatment. Therefore, it is possible to reduce the surface roughness of the whole surface of the magnetic film (the magnetic film into which the boron ion 20 is implanted) 11 which is obtained by a subsequent heat treatment.
It is preferable that the amount of implantation of the boron ion 20 should be set within a range of 2 to 10 atomic % with the composition of the portion into which the boron ion 20 is implanted. The boron ion 20 within this range is implanted so that the portion 8 into which only the boron ion 20 is implanted is heat treated and thus becomes the portion 10 having a large coercive force. Moreover, the surface roughness of the whole surface of the magnetic film 11 into which the boron ion 20 is implanted is reduced. In some cases in which the amount of implantation of the boron ion 20 is smaller than 2 atomic %, the portion 8 into which only the boron ion 20 is implanted cannot be sufficiently changed to have the CuAuI type ordered structure so that the magnetic film having a high magnetic anisotropy and a large coercive force cannot be obtained. On the other hand, in some cases in which the amount of implantation of the boron ion 20 is larger than 10 atomic %, the effect of promoting the change to the CuAuI type ordered structure is reduced.
The implantation of the boron ion 20 is carried out by the ion implantation. The ion implantation uses an ion implanting equipment. In the case in which the boron ion 20 is to be implanted, it is desirable that an implanting voltage should be set within a range of 2 keV to 6 keV when the thickness of the thin film 4 is 3 nm to 30 nm. By implanting the boron ion 20 at the implanting voltage within this range, it is possible to implant the boron ion 20 into each portion in the direction of the thickness of the thin film 4, for example. In the case in which the thickness of the thin film 4 is small, it is desirable that the implanting voltage should be set to have a smaller value within the range. In the case in which the thickness of the thin film 4 is great, it is desirable that the implanting voltage should be set to have a greater value within the range. In some cases in which the implanting voltage is lower than 2 keV, the boron ion 20 cannot be sufficiently implanted into a deep part in the direction of the thickness of the thin film 4 when the thickness of the thin film 4 is 3 nm to 30 nm. On the other hand, when the implanting voltage is higher than 6 keV, the boron ion 20 is implanted into an underlayer film so that a soft magnetic characteristic is deteriorated in some cases in which the thickness of the thin film 4 is 3 nm to 30 nm, for example, the underlayer film is provided to be a soft magnetic underlayer under the thin film 4, for example.
The heat treatment in the invention serves to sufficiently change only the portion 8 into which only the boron ion 20 is implanted to have the CuAuI type ordered structure, thereby obtaining the magnetic film 11 including the portion 10 having a large coercive force. More specifically, the local implantation of the ion 6 such as Cr and the implantation of the boron ion 20 into the whole surface can suppress the change to the CuAuI type ordered structure in the portion 7 into which the ion 6 such as Cr and the boron ion 20 are implanted by a subsequent heat treatment, and furthermore, can promote the change to the CuAuI type ordered structure in the portion 8 into which only the boron ion 20 is implanted. Consequently, the portion 7 into which the ion 6 such as Cr and the boron ion 20 are implanted by the heat treatment can be prevented from being changed sufficiently to have the CuAuI type ordered structure, and furthermore, sufficiently change the portion 8 having the boron ion 20 implanted therein to have the CuAuI type ordered structure. As a result, the portion 7 having the ion 6 such as Cr and the boron ion 20 implanted therein is brought into the state of the portion 9 having a small coercive force, and furthermore, the portion 8 having only the boron ion 20 implanted therein is brought into the state of the portion 10 having a large coercive force.
For example, in a patterned magnetic recording medium such as a magnetic recording medium of a discrete track type or a magnetic recording medium of a discrete bit type, it is desirable that the portion 10 having a large coercive force (that is, the portion into which only the boron ion 20 is implanted) and the portion 9 having a small coercive force (that is, the portion into which the boron ion 20 and the ion 6 such as Cr are implanted) should have a difference between the coercive forces of 2000 Oe or more, for example. The patterned magnetic recording medium having the difference in the coercive force can decrease the width of a track or a recording bit length without causing a reduction in an S/N ratio and a deterioration in an error rate.
The conditions of the heat treatment are set in such a manner that the change to the CuAuI type ordered structure of the portion 8 having only the boron ion 20 implanted therein can be promoted. The conditions of the heat treatment are not absolutely determined depending on the amount of implantation of the boron ion 20, and the pressure of a heat treatment atmosphere is preferably equal to or lower than 5×10−6 Torr, for example. In some cases in which the pressure of the heat treatment atmosphere is higher than 5×10−6 Torr, a deterioration is caused by the oxidation of the magnetic film 11. Moreover, a heat treatment temperature is preferably set within a range of 300° C. to 750° C. In some cases in which the heat treatment temperature is lower than 300° C., the change to the CuAuI type ordered structure in the portion 8 having only the boron ion 20 implanted therein is not sufficiently carried out. In some cases in which the heat treatment temperature is higher than 750° C., the shape of the surface of the magnetic film 11 is changed. Furthermore, the heat treatment time is preferably 5 to 10000 seconds. In some cases in which the heat treatment time is shorter than 5 seconds, the change to the CuAuI type ordered structure in the portion 8 having only the boron ion 20 implanted therein is not sufficiently carried out. In some cases in which the heat treatment time is longer than 10000 seconds, the substrate 1 is deformed depending on the material of the substrate 1 which is used.
On the conditions of the heat treatment, the thin film subjected to the local implantation of the ion 6 such as Cr and the implantation of the boron ion 20 into the whole surface (the thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt) is heat treated. Consequently, the portion 7 having the ion 6 such as Cr and the boron ion 20 implanted therein is not sufficiently changed to have the CuAuI type ordered structure and the portion 8 having only the boron ion 20 implanted therein is sufficiently changed to have the CuAuI type ordered structure so that the portion 7 having the ion 6 such as Cr and the boron ion 20 implanted therein can be brought into the state of the portion 9 having a small coercive force and the portion 8 having only the boron ion 20 implanted therein can be brought into the state of the portion 10 having a large coercive force. For example, the ion 6 such as Cr is locally implanted into the thin film 4 in which the Pt atom and the Fe atom are deposited alternately and the boron ion 20 is implanted into a whole surface, and the heat treatment is then carried out. Consequently, it is possible to obtain a magnetic film having a high ratio of the coercive forces of approximately 7:1 between the portion 8 having only the boron ion 20 implanted therein and the portion 7 having the ion 6 such as Cr and the boron ion 20 implanted therein (a ratio of 13.2:1 (8200 Oe/622 Oe) in the case in which the amount of implantation of the boron ion is 5 atomic % (only the boron ion 20 is implanted) and the case in which the amount of implantation of the Cr ion is 10 atomic % and the amount of implantation of the boron ion is 5 atomic % in an example which will be described below), for example.
In the method of forming a magnetic film according to the invention, the boron ion 20 is implanted into the whole surface of the thin film. Consequently, it is possible to reduce the surface roughness of the whole surface of the magnetic film 11 obtained after the heat treatment. The reduction in the surface roughness of the whole surface of the magnetic film 11 can stabilize the flying characteristic of a magnetic head to fly by an air flow over the magnetic recording medium having the magnetic film 11, and furthermore, manufacture can be carried out without forming a trench on the guard band of the magnetic recording medium as in the conventional art. Therefore, it is possible to produce an advantage that an increase in a manufacturing cost can be suppressed.
In the method of forming a magnetic film according to the invention described above, an underlayer film 31 and an intermediate film 32 can be provided as a ground between the substrate 1 and the magnetic film 11 as shown in
The underlayer film 31 is provided to be a soft magnetic underlayer on the substrate 1 formed by a non-magnetic material, and is formed by a material of NiFe, NiFeNb or FeCo in a thickness of 5 nm to 200 nm, for example. The underlayer film 31 can be formed by sputtering, for example.
The intermediate film 32 is provided on the underlayer film 31 in order to control the crystal orientation of the magnetic film, and is formed by a material such as MgO in a thickness of 0.5 nm to 5 nm, for example. The intermediate film 32 can also be formed by the sputtering, for example.
(Magnetic Pattern Forming Method)
Next, description will be given to the method of forming a magnetic pattern according to the invention.
The method of forming a magnetic pattern according to the invention is characterized in that the local implantation of the ion such as Cr is carried out by using a mask in the method of forming a magnetic film described above. More specifically, the same method is characterized in that the ion such as Cr is implanted by using the mask into the predetermined portion of a thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt and a boron ion is then implanted into the whole surface of the thin film subjected to the implantation, and a heat treatment is thereafter carried out. In this case, the thin film may be the thin film 4 in which the first film 2 containing at least one of Pd and Pt as a main component and the second film 3 containing at least one of Fe and Co as a main component are laminated as shown in
The material of a mask 5 is not particularly restricted but it is possible to optionally use various materials represented by a resist and a silicon stencil which are formed by photolithography. In the invention, particularly, the opening portion of the mask 5 is set to be a portion other than a track pattern taking the shape of a concentric circle for forming a discrete track medium, for example. Consequently, the portion into which the ion such as Cr having an ordering suppressing effect is implanted can be set to be the portion other than the track pattern and a portion into which the ion such as Cr is not implanted (a portion having only the boron ion implanted therein) can be set to be the track pattern. By setting the opening portion of the mask 5 to be a portion other than a dot-like pattern for forming a discrete bit medium, for example, it is possible to set the portion into which the ion such as Cr having the ordering suppressing effect is implanted to be a portion other than the dot pattern and to set the portion having only the boron ion implanted therein to be the dot pattern.
After the ion such as Cr is implanted into the film which has not been heat treated by such a method, the boron ion is implanted into the whole surface of the thin film subjected to the implantation by the implantation method. Consequently, the portion having only the boron ion implanted therein can be set to have the track pattern taking the shape of a concentric circle having a large coercive force, and the portion having the ion such as Cr and the boron ion implanted therein can be set to take a pattern having a small coercive force.
According to the method of forming a magnetic pattern in accordance with the invention, therefore, it is possible to form a portion having a small coercive force to take the shape of a pattern, thereby forming a magnetic pattern substantially having no surface concavo-convex portion in a very simple process.
As a mask for forming a track pattern taking the shape of a concentric circle to be provided in a discrete track medium, for example, it is possible to use a mask having a mask pattern in which the width of the mask is approximately 30 nm to 250 nm and the track pitch of the mask is approximately 50 nm to 300 nm. As a mask for forming a dot-like bit pattern to be provided on a discrete bit medium, moreover, it is possible to use a mask having a mask pattern in which the diameter of the mask is approximately 10 nm to 100 nm and the dot pitch of the mask is approximately 20 nm to 200 nm, for example.
(Magnetic Recording Medium Manufacturing Method)
Next, description will be given to the method of manufacturing a magnetic recording medium according to the invention.
The method of manufacturing a magnetic recording medium according to the invention utilizes the method of forming a magnetic pattern described above, and the method of manufacturing a magnetic recording medium having at least a non-magnetic substrate and a magnetic film provided on the non-magnetic substrate is characterized in that an ion such as Cr is locally implanted into a thin film containing, as main components, at least one of Fe and Co and at least one of Pd and Pt, and a boron ion is then implanted into the whole surface of the thin film subjected to the implantation and a heat treatment is thereafter carried out. Since the magnetic recording medium to be manufactured is formed in the same configuration as the configuration shown in
In the magnetic recording medium to be manufactured, the underlayer film 31 and the intermediate film 32 shown in
According to the method of manufacturing a magnetic recording medium in accordance with the invention, it is possible to manufacture a magnetic recording medium such as a discrete track medium or a discrete bit medium to be a patterned medium including a predetermined magnetic pattern without forming a conventional trench. Consequently, it is possible to manufacture a magnetic recording medium substantially having no surface concavo-convex portion.
The invention will be described below in more detail with reference to examples of the method of manufacturing a magnetic recording medium.
By using a glass substrate having a thickness of 0.635 mm as the non-magnetic substrate 30, NiFeNb was formed by sputtering so as to be the underlayer film 31 in a thickness of 150 nm, and furthermore, MgO was formed thereon by the sputtering so as to be the intermediate film 32 in a thickness of 3 nm. The Pt atom 41 corresponding to 75% of a necessary amount for forming a Pt single atomic layer was deposited, by the sputtering, on the intermediate film 32 thus formed, and subsequently, the Fe atom 42 corresponding to 75% of a necessary amount for forming an Fe single atomic layer was deposited by the sputtering. Then, the deposition of the Pt atom 41 and that of the Fe atom 42 were alternately repeated, and the depositions were alternately carried out until the number of repetitions is 63. Thus, a thin film was formed. The thin film thus obtained was a compositionally modulated film having a ratio of the Pt atom 41 to the Fe atom 42 of 3:1, 1:1 and 1:3 as one cycle respectively, and the atomic composition ratio of the compositionally modulated film was Pt45Fe55 as a result of a composition analysis to be carried out by an energy dispersive spectrometer ADS) and the thin film had a total thickness of 20 nm. The thin film was formed by providing a Pt target and an Fe target on a rotatable target plate, rotating the target plate and stopping the target plate in a predetermined position, and carrying out sputtering over the respective targets.
A Cr ion and a boron (B) ion were sequentially implanted into the thin film thus obtained so that two types of films (samples 5 and 6) were fabricated. The ions were implanted by using an ion implanting equipment (manufactured by Nisshin Denki Co., Ltd.; Model No. NH20SR). The amounts of implantation of the Cr ion and the boron ion in the thin film were expressed in values obtained by measuring the thin films subjected to the implantation by means of the Rutherford backscattering spectroscopy (RBS). In the samples 5 and 6, the Cr ion was implanted into the thin films in the amounts of implantation of 5 atomic % and 10 atomic % at an implanting voltage of 18 keV and the boron ion was implanted into the films in the amount of implantation of 5 atomic % at an implanting voltage of 4 keV.
Moreover, only the boron (B) ion was implanted into the thin film obtained as described above and a film (sample 4) was thus fabricated. In the sample 4, the boron ion 30 was implanted into the thin film in the amount of implantation of 5 atomic % at an implanting voltage of 4 keV.
Furthermore, there were fabricated two types of films (samples 2 and 3) in which only the Cr ion was implanted into the thin film obtained as described above. In the samples 2 and 3, the Cr ion was implanted into the thin film in the amounts of implantation of 5 atomic % and 10 atomic % at an implanting voltage of 18 keV
The five types of films (the samples 2 to 6) thus obtained and the film (the sample 1) into which the ion (the Cr ion or the boron ion) is not implanted were heat treated respectively so that a magnetic film was fabricated. The heat treatment was carried out on a condition of 600° C. and 3600 seconds in a vacuum atmosphere of 5×10−7 Torr or less. The magnetic characteristic of the magnetic film obtained after the heat treatment was examined and a result is shown in Table 1. The crystal structure of the magnetic film was determined by an X-ray diffraction. Referring to the magnetic characteristic, a coercive force Hc in an in-plane direction was measured by means of a vibrating sample magnetometer (VSM).
As is apparent from the result of the Table 1, the sample 4 having only the boron ion implanted therein had a large coercive force. In case of the sample 4, it was found that the coercive force is lager than that of the sample 1 into which neither the Cr ion nor the boron ion is implanted and that the boron ion has an effect of promoting a change to a CuAuI type ordered structure. Both of the samples 5 and 6 having the Cr ion and the boron ion implanted therein had small coercive forces. Thus, a high ratio of the coercive forces of approximately 7:1 or more was obtained between the sample 4 having only the boron ion implanted therein and the sample 5 having the Cr ion and the boron ion implanted therein, and a high ratio of the coercive forces of 13.2:1(8200 Oe/622 Oe) was obtained between the samples 4 and 6.
Referring to the samples 1 to 6, moreover, a surface roughness Ra of the magnetic film obtained after the heat treatment (an arithmetic mean roughness (JIS B0601-2001)) was calculated by converting data obtained from an atomic force microscope (AFM) respectively, and a result is shown in Table 2.
As is apparent from the result of the Table 2, both the sample 4 in the case in which the boron ion is implanted into a film having a thickness of 20 nm at an implanting voltage of 4 keV and the samples 5 and 6 in the case in which the Cr ion is implanted into the film having a thickness of 20 nm at an implanting voltage of 18 keV and the boron ion is implanted into the film having a thickness of 20 nm at an implanting voltage of 4 keV had small surface roughnesses (Ra) of the magnetic film. Referring to the non-recording portion of the magnetic recording medium, it is preferable that the surface roughness (Ra) should be smaller than 1.0 nm. All of the samples 4 to 6 were set within a preferable range. Moreover, the surface roughness Ra of the sample 4 was smaller than the surface roughness Ra of the sample 1, and furthermore, the surface roughness Ra of each of the samples 5 and 6 was smaller than the surface roughness Ra of each of the samples 2 and 3. Consequently, it was found that the boron ion has an effect of reducing the surface roughness of the magnetic film obtained after the heat treatment.
Two types of films (samples 7 and 8) were fabricated in the same manner as in the example 1 except that an Al ion was implanted into a film which has not been heat treated in place of the Cr ion according to the example 1. In the samples 7 and 8, the Al ion was implanted into the thin film in the amounts of implantation of 5 atomic % and 10 atomic % at an implanting voltage of 9 keV Referring to the magnetic characteristic of the film thus fabricated, a coercive force Hc in an in-plane direction was measured by means of a vibrating sample magnetometer (VSM) in the same manner as in the example 1. A result is shown in Table 3.
As is apparent from the result of the Table 3, both of the samples 7 and 8 have small coercive forces. Thus, it was found that Al has an effect of suppressing a change to a CuAuI type ordered structure in the same manner as Cr.
Four types of films (samples 9 to 12) were fabricated in the same manner as in the example 1 except that an Nb ion was implanted into a film which has not been heat treated in place of the Cr ion according to the example 1. In the samples 9 to 12, the Nb ion was implanted into the thin film in the amounts of implantation of 2.5 to 20 atomic % at an implanting voltage of 35 keV. Referring to the magnetic characteristic of the film thus fabricated, a coercive force Hc in an in-plane direction was measured by means of a vibrating sample magnetometer (VSM) in the same manner as in the example 1. A result is shown in Table 4. In case of the sample 1, the Nb ion is not implanted.
As is apparent from the result of the Table 4, all of the samples 9 to 12 have small coercive forces. Thus, it was found that Nb has an effect of suppressing a change to a CuAuI type ordered structure in the same manner as Cr.
Two types of films (samples 13 and 14) were fabricated in the same manner as in the example 1 except that an Mo ion was implanted into a film which has not been heat treated in place of the Cr ion according to the example 1. In the samples 13 and 14, the Mo ion was implanted into the thin film in the amounts of implantation of 5 atomic % and 10 atomic % at an implanting voltage of 40 keV Referring to the magnetic characteristic of the film thus fabricated, a coercive force Hc in an in-plane direction was measured by means of the vibrating sample magnetometer (VSM) in the same manner as in the example 1. A result is shown in Table 5. In case of the sample 1, the Mo ion is not implanted.
As is apparent from the result of the Table 5, both of the samples 13 and 14 have small coercive forces. Thus, it was found that Mo has an effect of suppressing a change to a CuAuI type ordered structure in the same manner as Cr.
After the ion such as Cr is locally implanted in a predetermined amount into the film which has not been heat treated, accordingly, the boron ion is implanted into the whole surface of the thin film subjected to the implantation by an implantation method and is then heat treated. Consequently, it is possible to reduce the coercive force of the portion into which the ion such as Cr and the boron ion are implanted, and furthermore, to increase the coercive force of the portion into which only the boron ion is implanted. As a result, it is possible to form a magnetic film having a high ratio of the coercive forces between the portion into which the ion such as Cr and the boron ion are implanted and the portion into which only the boron ion is implanted.
| Number | Date | Country | Kind |
|---|---|---|---|
| P. 2004-033849 | Feb 2004 | JP | national |
