Patent Application
20130081937
The present invention relates to magnetic data recording and more particularly to bit patterned media and to a method for manufacturing such a media using a patterned topography to control oxide and magnetic layer formation during deposition.
A key component of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
As the data density of magnetic recording systems increases, it becomes necessary to fit more bits of ever smaller size closer together on a magnetic media. When the data density becomes too large, the grains of the magnetic media become so small that they become thermally unstable. One way to mitigate this is to construct the media as a bit patterned media. Such a media includes individual isolated magnetic islands that are separated by non-magnetic material or non-magnetic spaces. Developments to produce such bit patterned media have proven to be expensive and time consuming for use in a manufacturing environment. In addition, the ability to construct such a bit patterned media at high data density has run in to manufacturing limitations such as with regard to the lithographic processes and other processes used to construct such a media. Therefore, there remains a need for a process for manufacturing a bit patterned media in a cost and time efficient manner that can produce a bit patterned media having a high data density.
The present invention provides a method for manufacturing a magnetic media that includes forming a patterned topography that includes an array of raised regions surrounded by a recessed region; and simultaneously co-sputter depositing a magnetic alloy and a non-magnetic material.
The magnetic alloy advantageously grows over the raised regions and the non-magnetic segregant grows preferentially in the recessed region between the raised regions. The raised region is formed as an array that can include features formed as elliptical islands.
In another embodiment of the invention a magnetic media can be constructed by a method that includes depositing a seed layer and forming a stamp having a pattern formed thereon. The stamp is coated with a segregant promoter material, and the stamp is placed against the seed layer so as to print the segregant promoter material onto the seed layer. A co-sputtering of a magnetic material and a segregant material is then performed.
The segregant promoter can be a self-assembled monolayer material, which can be a hydrocarbon polymer with silane and thiol termination such as HS—(CH2)n—Si(X)3, where n>2 and X is Cl or OCH3. When this material is oxidized such as by ultraviolet (UV)/ozone exposure, the subsequent co-sputtering causes the magnetic material to grow preferentially (or selectively) over the seed layer and causes the non-magnetic segregant (e.g. oxide) to grow preferentially (or selectively) over the segregant promoter layer.
This process for forming a bit patterned media eliminates the need for costly, time consuming etching processes to define the location of magnetic islands on the media and also avoids potential damage to the magnetic media that might arise from the use of such etching.
These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout.
For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale.
The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.
Referring now to
At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 can access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in
During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation.
The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, storage means and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125.
With reference to
With reference now to
The segregant promoter 602 can be a hydrocarbon polymer with silane and thiol termination such as HS—(CH2)n—Si(X)3, where n>2, and X is Cl or OCH3. The stamp 402 can be constructed of SiO2/polydimethylsiloxane (PDMS) (as will be discussed below). The segregant promoter layer 602 which can be a thiol-terminated organosilane may be deposited onto the SiO2/PDMS stamp surface by either wet chemical or dry vapor-phase methods. In the wet chemical method, the stamp is dipped into a 1 mM solution of the organosilane in toluene. Extra physisorbed and unattached molecules are removed by repeated rinsing in pure toluene. Vapor phase silylation is performed at 100 degrees C. in a vacuum oven. If necessary to remove excess material, the vacuum can be maintained for additional time in order to evaporate extra physisorbed molecules from the surface.
If the segregant promoter material 602 is a self-assembled monolayer such as that described above, the patterned segregant promoter 602 can be converted to an oxide like state through a UV/ozone exposure process. Such a process is illustrated by Y. Zhang, et al., J. Am. Chem. Soc., vol. 120 pp. 2654-2655 (1998), which is incorporated herein by reference. UV/ozone cleaning ovens (e.g. UVOCS) may be used for initial tests. UV tools currently used for lubricant bonding in media manufacturing may be used with nitrogen purge turned off and with ventilation installed for ozone disposal. Other materials 602, and other conversion methods, such as exposure to plasma, electrons or heat may also be used, as long as a chemical contrast pattern is produced that causes selective growth of the media segregant around the islands of magnetic film in the target pattern.
Optionally, the exposed seed layer 306 can be cleaned or reduced to remove an oxide layer. This can be accomplished by light sputtering or ion milling. These processes, however, may not be sufficiently selective so they must be carefully performed so as not to damage or remove the segregant promoter layer 602. Another option is exposure to H+ plasma, which can reduce oxidized metals back to the metallic state, but may be selective enough not to damage the patterned segregant promoter material 602.
With reference now to
The magnetic alloy 1004 (which can be referred to as a “storage layer” since it stores the magnetic bit of information) can actually include various magnetic materials. For example, the magnetic material 1004 can be several layers of materials each having different magnetic properties, such as each having a different magnetic coercivity. The magnetic layer 1004 can be constructed as a multi-layer structure with fine laminations of CoPt and/or CoPd. The magnetic layer 1004 can also be constructed as an exchange spring structure with a high magnetic coercivity layer, a low magnetic coercivity layer and a thin, non-magnetic coupling layer between the high and low coercivity layers. Again, whatever structure is used for layer 1004, this magnetic material is deposited simultaneously (co-sputtered) with the segregant material 1002.
With continued reference to
Then, with reference to
It should be pointed out, that the above process has been discussed as specifically applied to constructing a magnetic media for magnetic date recording. However, the process of selectively co-sputtering an array of structures from a stamp printed base material can also be used in other applications as well. For example, such a method can be useful in the construction of an array of cells of in a nonvolatile cross-point memory. Other examples of possible applications include the formation of array of cells of a phase change material in a dielectric matrix, such as might be useful in the construction of a memory cell. The process could also be applied to the construction of an array of cells of a memristor material in a dielectric matrix, which could also be useful in the construction of a memory cell array. The process could also be useful in the construction of an array of electrically conductive vias in a dielectric matrix or to the construction of an array of Magnetic Random Access Memory (MRAM) cells in a dielectric matrix. In order for the above described process to be effectively implemented, the structures being constructed should be fairly uniformly distributed over an area of interest, and all of the features should be below a critical feature size. The above segregation only occurs over a certain limited length scale.
Bit Patterned Media Fabricated by Templated Growth from a Printed Topographic Pattern:
In the previously discussed process, the growth of magnetic islands was based on the idea that “wetting” (or very loosely “epitaxy) could control where the magnetic material verses oxide would grow during co-sputtering. Once a pattern of metal islands surrounded by oxide was created, continued sputtering resulted in the oxide preferring to grow on the pre-existing oxide, and the metal on the pre-existing metal. A process will now be discussed which relies on a completely different growth mechanism. Instead of using a chemical contrast to initiate a desired growth pattern, this embodiment relies on “nucleation” of the magnetic islands as specific locations. Although all of the details are not understood, it has been found that grains can nucleate on topographic features on a substrate, and this nucleation can be used to initiate magnetic island growth at desired locations. In this invention, one can form raised islands on a substrate, and during co-sputtering of a magnetic material and a segregant, the magnetic metal will tend to grow at these raised islands which form nucleation sites.
With particular reference to
Then, with reference to
As before, the layer 1402 can be formed of a thiol-terminated organosilane, which can be post-processed via exposure to ultraviolet light (UV), heat, or plasma to convert the dot patterned layer 1402 into an oxide-like material. However, in this case, other materials could be used as well, since this process relies primarily on the topography of the layer 1402 as will be seen. Also, it is not necessary that the layer 1402 be patterned by microcontact printing. For example, the layer 1402 could also be formed by nanoimprinting a UV or heat curable polymeric material to form a protruding island patterned. If nanoimprinting is used, the nanoimprint template (or mold) will have a hole pattern rather than an island pattern (since nanoimprinting produces an inverse image of its mold). If nanoimprinting is used, a thin skin (or “residual layer”) may be formed between the protruding islands. This skin layer is acceptable and may be left in place. The pattern could also be formed by etching into an under-layer (rather than depositing a patterned layer).
With reference now to
With reference now to
The raised islands 1402 provide nucleation sites, where the growth of the magnetic alloy 1804 initiates. Although the islands 1402 are shown as having the same general size and shape as the finished magnetic islands, it is possible that a much smaller feature (such as a tiny protruding asperity or point) could be used instead. The process would be the same, initiating the growth of magnetic islands separated by non-magnetic segregant. That would provide a well defined single point where the magnetic grain structure could start growing, and it would grow outward from there.
When using larger topographic islands 1402 like those shown, it is not clearly understood where exactly the growth nucleates on the island, and it is not known whether the growth self-terminates at the island edges. It is known, however, that this growth on these islands works to form a well-defined pattern of magnetic islands. Surprisingly, and unexpectedly, this growth on a topographically patterned substrate works even better than the previously described growth over a chemical contrast pattern. It should also be pointed out that both of these processes (chemical contrast and topographic patterns) could be used together rather than separately as shown here.
The original topography of the protruding island pattern created previously with reference to
The magnetic material 1804 may be a single layer with a single alloy, or it may be multiple layers with varying magnetic properties. A very thin non-magnetic layer may be included along with magnetic layers. Periodic multi-layers, such as Co—Pd may be used. In all of these cases, the magnetic layer or layers are co-sputtered along with the nonmagnetic segregant, at least for some of the layers.
With reference now to
While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
The present invention is a Continuation in Part of commonly assigned U.S. patent application Ser. No. 13/251,125, entitled FABRICATION OF BIT PATTERNED MEDIA USING MICROCONTACT PRINTING, which was filed on Sep. 30, 2011.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13251125 | Sep 2011 | US |
| Child | 13370131 | US |
