JP5863882B2 - Patterning of magnetic thin films using high energy ions. - Google Patents

Description

  The present invention relates generally to patterning of magnetic thin films, and more particularly to a method for patterning magnetic thin films of magnetic recording media using high energy ions.

  There is always a need for higher density information storage media for computers. A storage medium that is popular today is a hard disk drive (HDD). An HDD is a non-volatile storage device that stores digitally encoded data on a high-speed rotating disk having a magnetic surface. The disc is circular and has a central hole. The disk is made of a non-magnetic material, usually glass or aluminum, and is coated on one or both sides with a magnetic thin film, such as an alloy thin film based on cobalt. The HDD records data by magnetizing a region of the magnetic film in one of two specific orientations, allowing binary data storage using a thin film. The stored data is read by detecting the orientation of the magnetization region of the film.

  A typical HDD design consists of a spindle that holds one or more disks spaced sufficiently to allow a read / write head to access one or both sides of one or more disks. The disc is fixed to the spindle by a clamp inserted in the central hole of the disc. The disc is spun at a very high speed. Information is written to and read from the disk as it rotates by the read / write head. The head moves very closely to the surface of the magnetic thin film. The read / write head is used to detect and / or modify the magnetization of the material directly beneath it. There is one head for each magnetic disk surface of the spindle. The arm moves the heads across the spinning disks so that each head has access to almost the entire surface of the corresponding disk.

  In conventional magnetic media, each bit cell includes a plurality of randomly distributed magnetic grains. Ideally, the plurality of magnetic grains are physically separated from each other to achieve improved write capability, signal-to-noise ratio (SNR), and thermal stability.

  As the areal density of magnetic recording media increases, the number of bit cells per square inch increases. This reduces the size of the bit cell. In order to effectively measure transitions, a minimum number of magnetic grains in the bit cell is required. As the size of the bit cell is reduced, the magnetic grain size must be correspondingly reduced to provide a minimum number of magnetic grains in the bit cell. If magnetic grain separation and magnetic grain size reduction are driven to ensure low noise, the recording density will be limited due to thermal disturbances.

  In order to improve the recording density, it is desirable to reduce the recording cell size on the medium, but this causes a weakening of the signal magnetic field strength generated from the medium. In order to meet the SNR required for the recording system, the noise must be reduced in response to the weakening of the signal strength. The medium noise is mainly caused by the fluctuation of the magnetization transition, and this fluctuation is proportional to the size of the magnetization reversal unit made of magnetic grains. Therefore, in order to reduce the media noise, it is necessary to separate the magnetic grains by breaking the exchange interaction between the magnetic grains.

  The magnetic energy of a single isolated magnetic grain is given by the product of the magnetic anisotropy energy density and the grain volume. In order to reduce the magnetization transition width, it is desirable to reduce the media thickness. It is also desirable to reduce the grain size to meet the requirements for low noise. The reduced magnetic grain size significantly reduces the magnetic grain volume and further reduces the magnetic energy of the grains. If the magnetic energy of a particular magnetic grain in the magnetic medium is several hundred times the thermal energy at the operating temperature (eg, room temperature), the resistance to thermal disturbance is considered sufficient. However, if the magnetic energy of the magnetic grains is less than 100 times the thermal energy, the magnetization direction of the magnetic grains may be reversed by thermal disturbance, possibly leading to loss of recorded information.

  Various options have been proposed to overcome the problem of thermal disturbance. One option is to use a magnetic material with high magnetic anisotropy. With this magnetic material, the recording saturation field of the head must be higher in order to write to the magnetic medium. Another option is to use heat assisted recording, in which case a highly anisotropic magnetic material is used and the recording part is heated by light irradiation during recording. This heat reduces the magnetic grain anisotropy and the recording saturation magnetic field. This makes it possible to write on a magnetic medium with a conventional magnetic head.

  As the areal density increases, there is still a minimum number of magnetic grains required per bit cell, and there is a limit to how small magnetic grains can actually be achieved.

  The alternative magnetic medium being investigated is a patterned medium, where the magnetic parts alternate with non-magnetic parts. For example, a bit pattern medium may have a magnetic portion that defines a magnetic domain as an island surrounded by a non-magnetic portion. The track pattern medium may have, for example, concentric tracks of magnetic parts separated by non-magnetic parts.

  Various options have been proposed for producing these media, but there is still a need to come up with a method that is cost effective and compatible with mass production. It is in this context that the embodiments of this disclosure were born.

  The concepts and methods of this disclosure allow for the mass production of magnetic media in which some portions of the magnetic thin film exhibit different magnetic properties than other portions of the magnetic thin film.

  In one aspect, the present disclosure is a method for patterning a magnetic thin film on a substrate. The method includes providing a pattern around the magnetic thin film, the selected region of the pattern allowing high energy ions of one or more elements to penetrate and impact a portion of the magnetic thin film. . High energy ions of one or more elements are generated with sufficient energy to penetrate a selected area of the pattern and a portion of the magnetic thin film proximate to the selected area. The substrate is arranged to receive high energy ions. The portion of the magnetic thin film proximate to the selected region exhibits different magnetic properties than other selected portions of the magnetic thin film.

  In another aspect, the present disclosure is a method of patterning a magnetic medium having two sides with a magnetic thin film on both sides. The method includes providing a pattern around the magnetic thin film on both sides of the magnetic medium, the selected region of the pattern having high energy ions of one or more elements penetrating and impinging on a portion of the magnetic thin film. Is possible. High energy ions of one or more elements are generated with sufficient energy to penetrate a selected area of the pattern on both sides of the magnetic medium and a portion of the magnetic thin film adjacent to the selected area. The magnetic medium is arranged to receive high energy ions. The portions of the magnetic thin film proximate to the selected areas on both sides of the magnetic medium exhibit different magnetic properties than other selected portions of the magnetic thin film.

  These and other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

2 is a process flow diagram illustrating an exemplary method of this disclosure. It is a partial top view which shows the typical mask for using it as a pattern around a magnetic thin film. FIG. 2 shows a representative patterned resist disposed around a magnetic thin film. FIG. 2 is a schematic diagram showing a process chamber for use in the present disclosure, illustrating the first disc holder device of the present disclosure. It is sectional drawing which shows the pattern around a magnetic thin film. It is sectional drawing which shows the magnetic thin film after ion penetration. It is a figure which shows helium ion penetration | invasion distribution over a resist and a magnetic thin film. It is a figure which shows helium ion penetration | invasion distribution over a resist and a magnetic thin film. It is a figure which shows the magnetization curve of the part of the magnetic film which was not used for helium ion implantation. It is a figure which shows the magnetization curve of the part of the magnetic film used for helium ion implantation. It is a figure which shows boron ion penetration | invasion distribution over a resist and a magnetic thin film. It is a figure which shows boron ion penetration | invasion distribution over a resist and a magnetic thin film. It is a figure which shows the density | concentration of the boron ion and cobalt ion in the magnetic thin film after boron ion implantation. It is a figure which shows the magnetization curve of the part of the magnetic film which was not provided to boron ion implantation. It is a figure which shows the magnetization curve of the part of the magnetic film used for boron ion implantation. It is a figure which shows a silicon ion penetration | invasion distribution over a magnetic thin film. It is a figure which shows the depth distribution of the silicon ion in the magnetic thin film after silicon ion implantation.

    The present disclosure will now be described in detail with reference to the drawings, which are provided as illustrative examples of the present disclosure so as to enable those skilled in the art to practice the disclosure. Notably, the following figures and examples are not intended to limit the scope of the present disclosure to a single embodiment, but may be different by replacing some or all of the elements described or illustrated. Embodiments are possible. Further, if an element of the present disclosure is partially or fully feasible using known components, in order to understand the present disclosure of such known components Only those portions that are necessary will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the present disclosure. In the present specification, embodiments showing unique components should not be considered limiting. On the contrary, the disclosure is intended to cover other embodiments that include a plurality of the same components, and vice versa, unless explicitly stated differently herein. In addition, applicants do not intend to regard any terms in the specification and claims as unusual or special unless explicitly stated as such. Furthermore, this disclosure covers the present and future known equivalents of known components referred to herein by way of example.

  In general, the present disclosure contemplates providing a pattern with selected regions that allow ions of one or more elements to penetrate and impact portions of the magnetic thin film. High energy ions of one or more elements are generated with sufficient energy to penetrate a selected region of the pattern and a portion of the magnetic thin film proximate to the selected region. The substrate is arranged to receive high energy ions. The portion of the magnetic thin film adjacent to the selected region exhibits different magnetic characteristics from the other portions of the magnetic thin film. This method can be applied to the production of a hard disk drive, and enables information storage with a very high surface density.

  A representative method of this disclosure is shown in FIG. The method for patterning a magnetic thin film on a substrate includes the following steps. That is, (1) providing a pattern having a selection region that allows high-energy ions of one or more elements to penetrate around the magnetic thin film; and (2) a pattern selection region and the selection region. Generating high energy ions of one or more elements having sufficient energy to penetrate a portion of the adjacent magnetic thin film; and (3) positioning the substrate to receive the high energy ions. And (4) causing the portion of the magnetic thin film proximate to the selected region to exhibit a different magnetic characteristic from the other selected portions of the magnetic thin film.

  In one embodiment, a mask that does not contribute to the penetration of high-energy ions with a selected area that allows the penetration of ions can be used as the pattern. FIG. 2 shows a partial plan view of an exemplary mask 200 for use as a pattern around a magnetic thin film. For example, the mask 200 may be made of a polymer material, such as a polyvinyl alcohol (PVA) material, having a portion 202 that does not contribute to the penetration of high energy ions and a selected region 204 that contributes to the penetration of high energy ions. An exemplary method of making a PVA template is described by Schaper in US Pat. No. 6,849,558, which is incorporated herein by reference. Schaper's teachings may be adapted to make a mask 200 having a portion 202 that does not contribute to the penetration of high energy ions and a selection region 204 that contributes to the penetration of high energy ions. For example, the thickness of the portion 202 may be selected such that high energy ions do not penetrate the portion 202 completely. Although portion 202 is shown to be round, as those skilled in the art will appreciate, the shape and location of portion 202 may be chosen to be beneficial. For example, the shape of portion 202 can be oval, square, rectangular, or any other shape depending on the needs of the application.

  In yet other embodiments, a resist may be coated over the magnetic thin film and a pattern may be created in the resist using, for example, nanoimprint lithography. There are two well-known types of nanoimprint lithography that can be applied to the present disclosure. The first is thermoplastic nanoimprint lithography (T-NIL), which includes the following steps. (1) coating the substrate with a thermoplastic polymer resist; (2) bringing a mold having a desired three-dimensional pattern into contact with the resist; and applying a predetermined pressure; Heating above the glass transition temperature; (4) pushing the mold into the resist when the resist is above the glass transition temperature; and (5) cooling the resist and separating the mold from the resist. Leaving a desired three-dimensional pattern in the resist.

  The second type of nanoimprint lithography is optical nanoimprint lithography (P-NIL), which includes the following steps. That is, (1) a step in which a photocurable liquid resist is applied to a substrate, and (2) a step in which a transparent mold having a desired three-dimensional pattern is pushed into the liquid resist until the mold contacts the substrate. (3) the liquid resist is cured with ultraviolet light to convert the liquid resist into a solid, and (4) the mold is separated from the resist to leave a desired three-dimensional pattern in the resist. . In P-NIL, the mold is made from a transparent material such as fused silica.

  FIG. 3 shows a cross-sectional view of an exemplary pattern 300 after nanoimprint lithography. The patterned resist 310 on the magnetic thin film 320 attached to the substrate 330 is shown with a depression 340 in the selected area 350 where the resist is substantially extruded. However, a small amount of resist remains in the selected region 350 so as to cover the surface of the magnetic thin film 320. This is common in nanoimprint processes. When the resist pattern is used as a mask for ion implantation, it is not necessary to remove the entire resist layer where the implantation seed is implanted. However, the remaining layers must be thin enough so that the implant species do not cause a substantial barrier to penetrate. Further, the difference between the thick resist location and the thin remaining resist location is sufficiently thick so that the resist with the thick resist can stop the ionic species before they reach the magnetic thin film. There must be. Alternatively, the thin residual resist in selected area 350 can be removed with an isotropic resist removal process such as a descum process or a weak ash process or any other suitable technique.

  In nanoimprint lithography, the imprint process extrudes resist to form selected regions 350, thus controlling the amount of resist that is extruded when a mold having a plurality of protrusions corresponding to the depressions 340 is brought into contact with the resist and pressure is applied. There is a need. In general, to control the amount of resist extruded during the stamping process, the width w of the recess 340 may be approximately the same dimension as the depth d of the recess 340, and the resist height h is the recess. At least approximately the same as the depth d of 340. If the depth d of the recess 340 is substantially greater than the width w of the recess 340, the amount of resist that is extruded can be very high, so that the pattern can be accurately transferred from the mold to the resist 310. It may not be practical.

  The nanoimprint lithography process may be implemented using an all-disk nanoimprint scheme, where the mold is large enough to imprint across one surface. Instead, a step-and-repeat imprint process can be used. In the preferred embodiment, an all-disk scheme is used. The nanoimprint process may also be performed on both sides at once. For example, a disk may first be coated with a resist layer on both sides. The disc then enters the press and the mold is pressed against both sides of the disc to imprint the desired pattern on both sides of the disc simultaneously.

  Conventional photolithographic processes may also be used, in which case the photoresist is spun on the disk, followed by exposure of the resist through a mask and development of the exposed resist.

  After patterning, there is a resist pattern on the disk, and the selected area 350 of the pattern allows high energy ions to penetrate and strike the portion of the magnetic thin film 320 proximate to the selected area 350. The portion of the resist other than the selected region 350, for example the portion 360, has a thickness sufficient to prevent the penetration of high energy ions, thereby preventing the high energy ions from colliding with the magnetic thin film.

  If the mask 200 is used instead, the mask 200 is placed in close proximity to the magnetic thin film, and the selected region 204 of the mask 200 is a magnetic thin film in which high energy ions penetrate the mask and are close to the selected region 204. It is possible to collide with the part. In one embodiment, the mask 200 is positioned proximate to the magnetic thin film. In other embodiments, the mask 200 is positioned in contact with a magnetic thin film or a magnetic thin film covered with a coating. The coating may contribute to mask deposition. The coating may also act as a protective coating over the magnetic thin film. The coating may be a carbon layer that acts as a protective coating over the magnetic thin film.

  Referring now again to FIG. 1, at step 104, sufficient energy for the high energy ions of one or more elements to strike the portion of the magnetic thin film proximate to the selected region through the selected region of the pattern. It is generated with In one embodiment, a vacuum chamber is provided and one or more gases containing a compound of one or more elements are pumped in. By using a high voltage, the plasma is ignited and high energy ions of one or more elements are released.

  At step 106, the substrate is positioned to receive high energy ions. In one embodiment, the substrate is placed in a vacuum chamber in which high energy ions of one or more elements are generated. In one embodiment, the substrate is placed in a plasma containing one or more high energy ions. In one embodiment, the substrate is biased to attract high energy ions. When mask 200 is used, high energy ions pass through selected area 204 of mask 200 and impinge on the portion of the magnetic thin film proximate to selected area 204. When resist 310 is used as a pattern, high energy ions pass through selected area 350 and impinge on the portion of the magnetic thin film proximate to selected area 350. In one embodiment, the high energy ions penetrate the portion of the magnetic thin film proximate the selected region 350. In one embodiment, the high energy ions partially penetrate the portion of the magnetic thin film proximate the selected region 350. In one embodiment, the high energy ions substantially penetrate the portion of the magnetic thin film proximate the selected region 350.

  In one embodiment, plasma ion immersion implantation may be used to achieve a high implant dose at low energy. Sputtered magnetic thin films are typically only a few tens of nanometers thick, so low ion energy is effective, and high doses provide high throughput. Further, as is apparent from FIG. 4, plasma ion implantation on both sides of the disk may be performed simultaneously. While double-sided plasma ion implantation is preferred, single-sided plasma ion implantation may be used without departing from the spirit of this disclosure. In single-sided plasma ion implantation, the first surface is implanted, then the disk is turned over and the second surface is implanted.

  A plasma ion implantation tool 400 configured to process a disk, eg, a substrate with a magnetic thin film, is shown in FIG. 4 and has a pattern around the magnetic thin film, the selected region of the pattern being one or more. The high energy ions of these elements can penetrate and collide with the magnetic thin film portion.

  Referring to FIG. 4, the chamber 410 is maintained in a vacuum state by a vacuum pump 420. A gas supply 430 is connected to the chamber 410 by a pipe 432 and a valve 435. More than one gas may be supplied through valve 435 and multiple gas supplies and valves may be used. For example, a dopant gas containing one or more seed elements may be supplied to the chamber 410. A rod 440 holds the disc 450. A radio frequency (RF) power source 460 is connected between the rod 440 and the wall of the chamber 410. The wall of chamber 410 is connected to electrical ground. In addition to the RF power source, an impedance matching device and a power source for applying a direct current (DC) bias may be included. The rod 440 may be coated with graphite or silicon to protect it from the plasma. Furthermore, the rod and its surface are highly conductive so as to facilitate excellent electrical contact between the rod and the disk. The disk 450 may be secured in place using a clamp 455 or other means. The clamp 455 not only secures the disk 450 in place, but also ensures an excellent electrical connection between the disk 450 and the rod 440. The rod is configured to support many discs (only three discs 450 are shown for ease of illustration). Further, the chamber 410 may be configured to hold a number of rods on which a disk for simultaneous plasma ion implantation is mounted. The rod 440 is easily moved into and out of the chamber 410.

  The processing of the disk by the plasma ion implantation tool 400 proceeds as follows. One or more of the disks 450 are mounted on the rod 440. A rod 440 is loaded into the chamber 410. The vacuum pump 420 operates to achieve the desired chamber pressure. The desired gas containing the implanted species is leaked from gas supply 430 through valve 435 and into the chamber until the desired operating pressure is achieved. The RF power source 460 operates to ignite a plasma that surrounds one or more surfaces of the disk 450. A DC power source may be used to control the energy of ions that are implanted into the magnetic film. An RF bias may also be used.

  Ions that can be easily implanted from plasma and that are effective in modifying the magnetic properties of common sputtered magnetic thin films such as Co-Pt and Co-Pd include hydrogen, helium, boron, sulfur, aluminum, lithium, Neon and germanium, and combinations of these elements. This list is not intended to be exhaustive. Any ion that is easily formed in the plasma and effective to modify the magnetic properties of the magnetic thin film is sufficient. Ideally, ions that can change the magnetic properties of the magnetic thin film to a weaker or more magnetic location that is thermally stable with a minimum dose are preferred.

  Further details of the plasma ion implantation chamber and processing method are available in US Pat. Nos. 7,288,491 and 7,291,545 to Collins et al., Which are incorporated herein by reference. The main difference between the chamber of the present disclosure and the chamber such as Collins is a different configuration for holding the substrate. The disc holder of the present disclosure allows for double-sided implantation at once, but in Collins et al. The substrate is placed on the wafer chuck throughout the process. Those skilled in the art will understand how plasma ion implantation tools and methods such as Collins can be utilized with this disclosure.

  After placing the substrate to receive the high energy ions at step 106, the portion of the magnetic thin film proximate the selected region may be subjected to thermal excitation at step 108. In one embodiment, radio frequency or microwave energy may be used to heat the selected area. In yet other embodiments, the substrate may be heated. In still other embodiments, a laser or flash anneal may be performed. In some embodiments, a rapid thermal anneal or furnace may be used.

  As those skilled in the art will appreciate, the thermal excitation step 108 may be performed with the resist layer still on the magnetic film. In some embodiments, the resist layer may be removed, and then the magnetic thin film is subjected to thermal excitation. In this embodiment, a magnetic thin film having both a portion subjected to ion implantation and a portion not subjected to ion implantation is subjected to thermal excitation. This approach may be advantageously used with certain types of magnetic thin films that may benefit from thermal excitation, such as portions of the magnetic thin film that have not been subjected to ion implantation.

  If a mask 200, such as a PVA mask, is used, the process may additionally include removal of the mask 200. In one embodiment, the PVA mask may be removed using a process that dissolves the PVA mask 200, for example using an aqueous solution. In some embodiments, non-aqueous solutions may be used. In some embodiments, the mask 200 is removed and then the magnetic thin film is subjected to thermal excitation. In this embodiment, a magnetic thin film having both a portion subjected to ion implantation and a portion not subjected to ion implantation is subjected to thermal excitation. This approach may be advantageously used with certain types of magnetic thin films that may benefit from thermal excitation, such as portions of the magnetic thin film that have not been subjected to ion implantation. In some embodiments, the thermal excitation step 108 may be performed with the mask 200 still present.

  In some embodiments, the magnetic thin film is subjected to thermal excitation in this chamber 410 by incorporating a suitable heat source in the chamber 410 of the ion implantation tool 400 and selectively turning on the heat source after ion implantation. May be.

  After thermal excitation of the high energy ion step 106 and / or step 108, the portion of the magnetic thin film proximate to the selected region exhibits different magnetic properties than the other selected regions, as illustrated at step 110. In one embodiment, high energy ions that penetrate a portion of the magnetic thin film proximate to the selected region 350 cause that portion of the magnetic thin film proximate the selected region to exhibit different magnetic properties than other selected regions. If resist is used as the pattern, this process may additionally include a resist stripping step. The resist stripping step may be facilitated by conventional descum and ash operations in the plasma ion implantation chamber prior to removing the disk. The resist stripping step may be a wet chemical process that is well known in the art. In some embodiments, the resist stripping step may be performed before the thermal excitation step 108, as described above.

  The energy of the ions obtained from the plasma implantation process ranges from about 100 eV to about 15 kev. However, for implanting magnetic thin films with a thickness of several tens of nanometers, the desired energy range is from about 1 kev to about 11 kev. The energy range chosen is based on the element chosen, the resist thickness, the ion stopping capability of the resist, and the desired magnetic properties. For example, a bias voltage of about 1 kV to 11 kV may be used to generate the desired energy range.

  FIG. 5 is a cross-sectional view of the pattern 510 disposed around the magnetic thin film 520, and the arrow 530 represents the approximate bombard direction of high-energy ions. The high energy ions penetrate the selection region 540 of the resist 510 and enter a part 550 of the magnetic thin film 520 adjacent to the selection region 540.

  FIG. 6 is a cross-sectional view of the magnetic thin film 520 after ion implantation, and the portion 550 is subjected to ion implantation. The portion 550 of the magnetic thin film 520 exhibits different magnetic properties than other selected target portions 560 of the magnetic thin film 520.

  The following examples are provided to illustrate various applications of ion implantation to achieve the desired magnetic properties.

  Experiments have been performed to determine the ion stopping properties of the resist for helium and boron ions at a certain bias voltage.

  Helium ion implantation: Experiments were conducted on helium ion implantation at bias voltages of 7 kV and 2 kV. At 7 kV, the resist thickness required to prevent helium ion penetration through the resist layer was about 120 nm. The resist thickness of the selected region of the pattern can be 45 nm, and helium ions can still penetrate the 20 nm thick Co-based magnetic thin film proximate to the selected region of the pattern. At 2 kV, the resist thickness required to prevent helium ion penetration through the resist layer was about 85 nm. The resist thickness in the selected area of the pattern can be 10 nm, and helium ions can still penetrate the 20 nm thick Co-based magnetic thin film proximate to the selected area of the pattern.

Boron ion implantation: An experiment was conducted on boron ion implantation with a bias voltage of 9 kV. At 9 kV, the resist thickness required to prevent boron ions from penetrating the resist layer was about 65 nm. The resist thickness of the selected region of the pattern can be 10 nm, and boron ions can still penetrate the 20 nm thick Co-based magnetic thin film proximate to the selected region of the pattern.
Magnetic Properties Example 1a:

  A glass substrate sputtered with a soft underlayer of about 100 nm of FeNi alloy was used. An approximately 20 nm CoCrPt alloy magnetic thin film layer was sputtered onto the FeNi alloy soft underlayer. Samples prepared as described above were subjected to a plasma containing helium ions by pumping the dopant gas helium into the process chamber. The process chamber pressure is about 15 millitorr, the RF bias voltage is about 2 kV, the source power is about 500 watts, the dopant gas helium is pumped at a flow rate of about 300 sccm, and the implantation time is about 25 seconds. there were. Optionally, an inert gas may also be pumped to assist in plasma generation. For example, argon at a flow rate of about 16 sccm may be fed.

  The distribution of He ion penetration into the sample was examined using a simulation program with the process parameters described above. A simulation program known as TRIM can be used to perform the simulation. The TRIM program is available at www. srim. available from org as part of a group of programs known as SRIM. 7A and 7B show the results of the simulation. Referring now to FIG. 7A, it is clear that a resist of about 85 nm thickness is sufficient to prevent high energy He ions from penetrating into the CoCrPt magnetic thin film layer. Referring now to FIG. 7B, a resist layer of about 10 nm and a carbon layer of about 28 angstroms are successfully penetrated by high energy ions, and the high energy ions penetrate substantially throughout the about 20 nm CoCrPt magnetic thin film layer. It is clear that

For samples that were not subjected to He ion implantation, the magnetic properties of the magnetic film were measured using a physical property measurement system to establish a baseline. After subjecting the sample to He ion implantation, the magnetic properties of the portion of the magnetic film subjected to He ion implantation were measured using a physical property measurement system. FIG. 7C shows the magnetization curve of the magnetic film that was not subjected to He ion implantation. It is clear from FIG. 7C that the saturation magnetism (Ms) is about 1.36 Tesla. FIG. 7D shows the magnetization curve of the portion of the magnetic film subjected to He ion implantation. The saturation magnetism (Ms) of the portion of the magnetic film subjected to He ion implantation is reduced to about 0.1 Tesla compared to the baseline magnetic thin film not subjected to He ion implantation. Thus, a magnetic thin film can be subjected to He ion implantation under appropriate process conditions to substantially change the magnetic properties to a state where selected portions exhibit significantly different magnetic properties.
Example 1b:

  A sample similar to that used in Example 1a was used in Example 1b, except that the sample was subjected to thermal annealing. The thermal anneal was performed at about 100 degrees Celsius and about 200 degrees Celsius in a vacuum at a pressure of about 10 Torr to about 5 Torr for about 1 hour.

After subjecting the sample to thermal annealing, the magnetic properties of the portions of the magnetic film that were subjected to both He ion implantation and thermal annealing were measured using a physical property measurement system. The baseline magnetic curve of the magnetic film not subjected to He ion implantation shows a saturation magnetism (Ms) of about 1.36 Tesla. The magnetization curve of the portion of the magnetic film subjected to both He ion implantation and thermal annealing at 100 degrees Celsius showed a saturation magnetism (Ms) of about 0.01 Tesla. The magnetization curve of the portion of the magnetic film subjected to both He ion implantation and thermal annealing at 200 degrees Celsius showed a saturation magnetism (Ms) of about 0.03 Tesla. Based on the results of the samples of Examples 1a and 1b, it is clear that the thermal annealing of the samples further lowered the saturation magnetism (Ms) of the portion of the magnetic thin film subjected to annealing. Thus, a magnetic thin film may be subjected to both He ion implantation and thermal annealing under appropriate process conditions to substantially change the magnetic properties to a state in which selective portions exhibit significantly different magnetic properties. The experiment was performed with a bias voltage of about 2 kV, but the bias voltage can range from 1 kV to 11 kV, preferably from 1 kV to 3 kV.
Example 2:

  A sample similar to that used in Example 1a was used for boron ion intrusion. The sample prepared as described above was subjected to a plasma containing boron ions by pumping dopant gas BF3 into the process chamber. The process chamber pressure is maintained at about 15 millitorr, the RF bias voltage is about 9 kV, the source power is about 500 watts, the dopant gas BF3 is pumped at a flow rate of about 300 sccm, and the implantation time is about 20 seconds. there were. Optionally, an inert gas may also be pumped to assist in plasma generation. For example, argon at a flow rate of about 16 sccm may be fed.

  The distribution of boron ion penetration into the sample was examined using a simulation program with the process parameters described above. 8A and 8B show the results of the simulation. Referring now to FIG. 8A, it is apparent that a resist of about 65 nm thickness is sufficient to prevent high energy boron ions from penetrating into the CoCrPt magnetic thin film layer. As is apparent from FIG. 8A, a resist layer of about 10 nm and a carbon layer of about 28 Å may be successfully penetrated by high energy ions. High energy ions can also penetrate substantially throughout the approximately 20 nm CoCrPt magnetic thin film layer.

  Referring to FIG. 8C, the concentration of boron and Co atoms was determined using a secondary ion mass spectrometer (SIMS). From FIG. 8C, it is clear that the Co concentration was essentially intact. It is also clear that the boron concentration remained constant over a depth of about 10 nm and then gradually decreased.

  For samples that were not subjected to boron ion implantation, the magnetic properties of the magnetic film were measured using a physical property measurement system to establish a baseline. After subjecting the sample to boron ion implantation, the magnetic film subjected to boron ion implantation was measured using a physical property measurement system. FIG. 8D shows the magnetization curve of the magnetic film that was not subjected to boron ion implantation. As is apparent from FIG. 8D, the saturation magnetism (Ms) is about 1.36 Tesla. FIG. 8E shows the magnetization curve of the portion of the magnetic film subjected to boron ion implantation. As is clear from FIG. 8E, the saturation magnetism (Ms) of the portion of the magnetic film subjected to boron ion implantation has dropped to about 0.5 Tesla compared to the magnetic thin film not subjected to boron ion implantation. . Under these experimental conditions, boron ion implantation reduced the magnetization by about 50%.

Thus, the magnetic thin film may be subjected to boron ion implantation under certain process conditions to change the magnetic properties of selected portions to exhibit different magnetic properties. For example, the magnetic properties of the selected portion may be changed to show weaker magnetic properties than the portion that was not subjected to boron ion implantation. The experiment was performed with a bias voltage of about 9 kV, but the bias voltage may be in the range of 1 kV to 11 kV, preferably in the range of 7 kV to 11 kV.
Example 3

  A silicon substrate sputtered with a Co alloy layer of about 20 nm was prepared as a sample for this example. The prepared sample was subjected to a plasma containing silicon ions by pumping the dopant gas SiH4 into the process chamber. The process chamber pressure was about 30 millitorr, the RF bias voltage was about 9 kV, the source power was about 500 watts, the dopant gas SiH4 was pumped at a flow rate of about 75 sccm, and the implantation time was about 20 seconds. .

  The distribution of silicon ion penetration into the sample was examined using a simulation program with process parameters as described above. FIG. 9A shows the result of the simulation. Referring now to FIG. 9A, it is clear that Si penetrates to a depth of about 5-6 nm, with some tails up to a depth of 10 nm.

  After subjecting the sample to silicon ion implantation, the depth distribution of Si implantation in the 20 nm Co film was measured using SIMS. FIG. 9B shows the depth distribution of Si implantation. It is clear from FIG. 9B that Si ions have penetrated to a depth of about 5-6 nm. It is worth noting that the distribution of Si ion penetration depth, investigated using a simulation program, is in good correlation with the actual measurement of Si penetration depth.

  In some embodiments, after ion implantation, the magnetic thin film may be subjected to thermal excitation, for example by thermal annealing. It is expected that thermal annealing may further reduce the saturation magnetism (Ms) of the portion of the magnetic thin film subjected to thermal excitation, as is apparent from Example 1b.

  As is apparent from the above examples, the resist thickness required to prevent high energy ions from penetrating the resist layer and colliding with the magnetic thin film depends on the element type used, the process parameters, Depending on the desired penetration depth of the ions into the magnetic thin film proximate to the selected region of the resist layer, allowing the penetration of charged ions. As the dimensions of selected regions of the resist layer that allow the penetration of charged ions are reduced, the resist thickness needs to be reduced to allow an effective nanolithographic process during pattern generation. As the resist thickness decreases, the resist layer may no longer be able to prevent the penetration of high energy ions in regions other than the selected region.

  One way to overcome this problem is to add a dopant to the resist that increases the resistance to penetration of charged ions. For example, the resist may be doped with a silicon-containing compound that increases the resistance to penetration of charged ions through the resist. Other dopants that can be used to increase resistance to penetration of charged ions include compounds containing sulfur and phosphorus. In one embodiment, nanoparticles may be added as an additive to adjust the resistance to penetration of charged ions. For example, aluminum oxide (Al 2 O 3), silicon dioxide (SiO 2), ceria (CeO 2), and titanium dioxide (TiO 2) nanoparticles may be used to adjust the resistance to penetration of charged ions.

  As is apparent from the above examples, different elemental species have different effects on magnetic properties based on process parameters and the desired penetration depth of ions into the magnetic thin film. For example, one or more elements may be advantageously used to modify the magnetic properties of the magnetic film. As an example, a combination of helium and boron may realize additional benefits. For example, helium with a lower molecular weight can penetrate deeper into the magnetic film using a lower bias voltage and change the magnetic properties. Larger molecular weight boron is used either before or after helium penetration to further influence the magnetic properties of the magnetic thin film and prevent helium ions from escaping from the magnetic thin film over time. May act as.

  While helium and boron combinations have been described, those skilled in the art will appreciate that various other substitutions and combinations of elements to derive magnetic and other properties that are advantageous for maintaining and enhancing magnetic property modifications. May be used sequentially or together.

  Also, as is apparent from the above example, different element species may be used to modify the magnetic properties of the magnetic thin film. For example, a compound containing an element that enhances the magnetic properties of a thin film by ion implantation may be used. For example, platinum ion implantation may enhance the magnetic properties of the magnetic thin film.

  The present disclosure can be used with various types of magnetic recording media. For example, the teachings of the present disclosure may be used with recording media having a granular magnetic structure. The present disclosure may also be used for multilayer magnetic thin films. The magnetic thin film may also be a continuous magnetic film and may be used in patterned media. The pattern medium may be a bit pattern medium or a track pattern medium. In one embodiment, the magnetic thin film may be made from a highly anisotropic magnetic material suitable for heat assisted magnetic recording.

  The present disclosure allows for very short process times. For example, it may take about 10 seconds to drive a disc. Input and output vacuum load locks allow high speed transfer of the discs into and out of the chamber, eliminating the loss of pump failure, and therefore very high throughput is expected. Those skilled in the art will understand how automatic transfer systems, robots, and load lock systems can be integrated with the plasma ion implanter of the present disclosure.

  In certain embodiments, the present disclosure provides a method for selectively modifying the magnetic properties of a portion of a magnetic thin film of a magnetic medium. Selective modification can be advantageously used to increase one or more of the desirable properties such as areal density, write capability, SNR and thermal stability of the magnetic media.

  Although the present disclosure has been described with particular reference to preferred embodiments, it will be understood by those skilled in the art that changes and modifications in shape and detail may be made without departing from the spirit and scope of the disclosure. Should be readily apparent. The appended claims are intended to cover such changes and modifications.

Claims (7)

A magnetic recording medium comprising a substrate on which a plasma-doped magnetic thin film is disposed, the magnetic thin film comprising a cobalt alloy layer,
It said cobalt alloy layer, the first has a pattern of areas, the helium ions are first depth with an ion density and ion concentration in the second doped helium ions of the first doped boron ions implanted in, the boron ions are implanted with a short second depth than said first depth, said first region having a doped ion concentration is, and the first close to the area region Showing different magnetic properties,
Magnetic recording medium. The de-loop ion concentration remains substantially constant over a depth of about 10 nm,
The magnetic recording medium according to claim 1. The doped ions are selected from the group consisting of hydrogen, helium, boron, sulfur, aluminum, lithium, neon, germanium, and combinations thereof;
The magnetic recording medium according to claim 1. The plasma-doped magnetic thin film includes Co-Pt.
The magnetic recording medium according to claim 1. The plasma-doped magnetic thin film includes Co-Pd.
The magnetic recording medium according to claim 1. The plasma-doped magnetic thin film includes a CoCrPt alloy.
The magnetic recording medium according to claim 1. Furthermore, including a soft lower layer containing FeNi alloy,
The plasma-doped magnetic thin film is disposed on the soft underlayer,
The magnetic recording medium according to claim 1.

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