Method apparatus and system for accessing discontinuous media tracks

An apparatus, system, and method are disclosed for accessing discontinuous media tracks. The apparatus, in one embodiment, accesses discontinuous media tracks of a storage medium having one or more independently formed storage regions thereon. Each storage region may include a set of track segments. A memory may be provided to store track offset information for each storage region. A mapping module may collect track offset information, calculate a physical offset between adjacent storage regions, define a track, create a table, and store the track offset information in the memory. The apparatus may further include a tracking module to sense a position of a head relative to a centerline of a track segment within a current storage region, access offset information, and align a storage head with a closely aligned track segment within a subsequent storage region. Consequently, discontinuous media tracks may be accessed by a storage access device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to storage media and more particularly relates to accessing discontinuous media tracks on a storage medium.

2. Description of the Related Art

Traditionally, the storage capacity and the areal density of magnetic storage media, such as disks used within disk drives, have been limited by certain restraints such as material characteristics, manufacturing processes, metrological limitations, mechanical capabilities, and the like. For example, conventional multigrain magnetic media is generally created by covering a flat substrate with a thin layer of magnetic alloy that forms random clusters of magnetically charged grains on the substrate surface.

The conventional process of creating media storage has been limited by several physical constraints, including a natural occurrence called the superparamagnetic effect, i.e. the fluctuation of magnetization due to thermal agitation. The superparamagnetic effect influences a storage medium when bit cells of magnetically charged grain clusters, are defined by grains so small that magnetization becomes unstable. In such circumstances, fluctuation of magnetization can cause erasure of data. Consequently, the areal density of thermally stable storage media has typically been restricted to around 150 Gbit/in2with conventional multigrain magnetic media.

Recently, however, patterned media comprising an ordered array of highly uniform islands has been developed as an alternative to circumvent some of the limitations traditionally associated with magnetic media. Independent magnetic islands corresponding to bits or track segments that are thermally stable can be formed on the surface of the storage media. Each island of the patterned media may be capable of storing one or more bits. As a result of the magnetic isolation provided by the islands, storage media can be created with greater areal densities and storage capacities than possible with conventional multigrain magnetic media technology.

Patterned media can be formed by a variety of methods known to those skilled in the art. One proposed method to create patterned media is nanoimprint lithography or nanoimprint replication. In this method, a stamper, or a master template, may be formed having a nm-scale pattern. The stamper may subsequently be used to stamp, or create, formed patterns on the surface of a substrate at a relatively low cost compared to other methods for patterning. The formed patterns may be covered with a magnetic layer to form independent magnetic domains.

One method suitable for creating a patterned stamper, either directly or indirectly, uses e-beam lithography. E-beam lithography, in certain embodiments, can be used to create islands having dimensions around the scale of about 25 nm or less, corresponding to areal densities of about 300 Gbit/in2or greater. These high resolution patterns are beyond the dimensions achievable using optical lithography, a technique commonly used in the electronics industry to make integrated circuits. E-beam exposure tools may be similar to those used to create masks for optical lithography; however, generating patterns for patterned media generally requires a higher resolution e-beam exposure system than is needed for conventional e-beam mask generation.

Patterned media, which overcomes some of the traditional challenges associated with magnetic media, can beneficially provide storage media with greater areal densities and storage capacities. However, the mass production of patterned media presents some challenges that have hindered patterned media from becoming readily available in the market.

First, because predefined patterns are typically formed into the substrate of a storage medium or disk, tracks and bit alignment is fixed during fabrication instead of during a servowriting process as is commonly done with conventional magnetic media. Consequently, storage devices and read/write mechanisms must be able to follow preformed tracks and compensate for errors, such as centering errors, shape irregularities, or the like. Ideally, a servo system would able to function efficiently despite misaligned features within the patterned media. However, due to the high flying speeds and small features associated with reading and writing data, currently available servo systems are able to adjust to only minor variations within the patterned media.

Second, creating patterns for master templates by writing high resolution patterns using e-beam lithography can be prohibitively time-consuming. Typically, e-beam lithography tools operating at their best resolution are using the smallest beam diameter and a very limited current. Depending on the detail of the pattern, the beam current available, the sensitivity of a selected resist, and the time associated with mechanical motion of the stage, the total write time required to create a pattern for a whole disk surface may take months to years to complete, depending on the size of the pattern. Larger patterns require greater amounts of time for completion. Drawn out write times may be unacceptable, considering the associated cost and the delicacy of the e-beam writing system. In certain instances, the e-beam may fail long before the completion of the e-beam writing process.

A contemplated solution to reduce the size of e-beam written patterns is to create a small section of a pattern using e-beam lithography, and then to replicate the section using other methods. Media patterns tend to be periodic, and repeated patterned sections do not pose serious problems. However, forming multiple sections on the surface of a storage medium presents several physical limitations that affect the continuity of individual data tracks around the disk. Due to the scale of the pattern features, perfect alignment of track segments from individual sections is nearly impossible and would require extremely sensitive manufacturing environments that for the foreseeable future appears to be too costly for practical use. Furthermore, misaligned media tracks from a more cost-effective production environment may disrupt a servo system when transitioning between patterned sections.

From the foregoing discussion, it should be apparent that a need exists for a method, apparatus, and system for accessing discontinuous media tracks created in a cost-effective production environment. Beneficially, such an apparatus, system, and method would enable storage media to maximize the areal density and storage capacity of a given storage area and would enable economical and efficient implementation of high resolution patterned media.

SUMMARY OF THE INVENTION

The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available storage media. Accordingly, the present invention has been developed to provide an apparatus, system, and method for accessing discontinuous media tracks that overcome many or all of the above-discussed shortcomings in the art.

The apparatus, in one embodiment, accesses discontinuous media tracks on a storage medium having more than one independently formed storage region thereon. Each storage region may include a set of track segments. In certain embodiments, a memory is provided to store offset information for each storage region. The offset information may correspond to one or more track segments. In one embodiment, each track is defined as a collection of closely aligned track segments that preferably includes one track from each storage region.

In one embodiment, the apparatus includes one or more stamped storage regions. The stamped storage regions may be formed from a master template patterned directly or indirectly by e-beam lithography. Consequently, selected media patterns may be formed for a small area, or storage region, and may be replicated to cover the surface of a storage medium, such as a disk.

The apparatus may be provided with a logic unit containing a tracking module configured to functionally execute the necessary steps of sensing a head position within a current storage region, accessing offset information, and aligning a storage head with a closely aligned track segment within a subsequent storage region. In a further embodiment, a mapping module may record head positioning and offset information and may create a table defining the location of one or more track segments within a storage region. The table may subsequently be stored in memory. In certain embodiments, the mapping module further calculates a physical offset between adjacent storage regions. Consequently, a storage device may access discontinuous media tracks by referencing offset information stored in memory.

A system of the present invention is also presented to access discontinuous media tracks. In particular, the system, in one embodiment, includes a storage device having a storage medium with independently formed storage regions and a storage access device such as a computer. Each storage region includes one or more track segments that may form part of a discontinuous track. The storage device may store offset information for each storage region. In one embodiment, offset information is stored for each track segment on the storage media. In addition, the storage device may sense a head position within a current storage region, access offset information, and align a storage head with a closely aligned track segment within a subsequent storage region. In certain embodiments, the storage device may collect offset information during a mapping process.

A method of the present invention is also presented for accessing discontinuous media tracks. The method in the disclosed embodiments substantially includes the steps necessary to carry out the functions presented above with respect to the operation of the described apparatus and system. In one embodiment, the method includes the steps of providing a storage medium with independently formed storage regions thereon, sensing a position of a head within a current storage region, accessing track offset information corresponding to a closely aligned track segment within a subsequent storage region, and adjusting a head position to align with the closely aligned track segment within the subsequent storage region.

In one embodiment, the subsequent storage region is a storage region adjacent to the current storage region. In an alternative embodiment, the subsequent storage region comprises a storage region nonadjacent to the current storage region. Thus, the head may align with a designated track segment in a contiguous or noncontiguous storage region. In one embodiment, a 2:1 interleave scheme is used to provide the head time to adjust to a track offset.

The method may further include mapping the storage medium to determine the location of the various track segments. In one embodiment, the mapping process is conducted during manufacture. Alternately, the mapping process may be conducted in response to a formatting operation. In one embodiment, mapping includes calculating a physical offset between adjacent storage regions. In certain embodiments, the positioning of the head and offset information may be recorded and may be stored in a non-volatile memory.

In a further embodiment, the method includes defining a track having a track segment from each storage region. The track segment may be a closely aligned track segment within a subsequent storage region. Accessing a track may include advancing from a current storage region to a nonadjacent storage region. Alternatively, the head may access a track by advancing from a current storage region to an adjacent storage region.

The method may further include creating a table defining the location of one or more track segments within a storage region. The table may subsequently be stored in a memory. As a result, track segments located on individually formed storage regions may be accessed by referencing offset information stored in the memory.

The present invention enables a storage device to store and access data on a storage medium comprising more than one independently formed storage region such as a patterned media surface formed by inexact pattern replication. A tracking module enables accessing discontinuous media tracks comprising track segments from the various storage regions. These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1depicts one embodiment of a discontinuous media track accessing system100of the present invention. The track accessing system100, in the depicted embodiment, includes a storage device110and a storage access device such as a computer120. As illustrated, the storage device110includes a storage medium130, a tracking module140, an optional mapping module150, and a memory160. The computer120accesses information stored on the storage medium130. The tracking module140, the mapping module150, and the memory160facilitate locating track segments formed on the storage medium130.

To provide high density storage, the storage medium130may include independently formed storage regions, resulting in discontinuous media tracks as discussed above. Forming storage regions independently may contribute to efficient, cost-effective production of high density storage media. The tracking module140senses the position of a read/write mechanism, such as a head, relative to the formed track segments on the storage medium130. The tracking module may access offset information stored in the memory160in order to anticipate positioning relative to a subsequent track segment.

The mapping module150maps the surface of a storage medium130, such as a disk, enabling the collection of offset information. The offset information may include information regarding the location of track segments and the physical offset of the formed storage regions. In one embodiment, the mapping module stores the information in the memory160. Consequently, the tracking module140may reference stored offset information to position the head of the storage device110.

In certain embodiments, the tracking module140and the mapping module150may be combined within the storage device110. Alternatively, the mapping module150may be independent and may be located in a separate device.

FIG. 2illustrates in greater detail one embodiment of the storage medium130depicted inFIG. 1. In the depicted embodiment, the storage medium130is a disk200stamped to form multiple storage regions210. Alternatively, the storage medium130may be any medium configured to store information in various independently formed storage regions210.

Those of skill in the art will appreciate that the independently formed storage regions210may be formed by a variety of methods. In certain embodiments, a master template commonly known as a ‘mother’ or ‘father’ that corresponds to a single storage region210may be used to form a ‘daughter’ template comprising multiple storage regions210. In one embodiment, the daughter template is used to stamp an entire disk200in a single operation. In another embodiment, the disk200is stamped multiple times by a single template.

A storage region210may include multiple track segments220, which may be selected to form one or more tracks230. In one embodiment, a track230includes a track segment220from each storage region210. The track segments220selected to form a track230may be the closest or next to closest aligned track segments220within subsequent storage regions210.

In certain embodiments, the storage regions210may be located contiguous to each other as depicted. Contiguous storage regions210enable the storage medium130to provide maximum storage density within a defined surface area, though storage regions210may be spaced by an unformed area or the like. The storage medium130may have storage regions210of varying size and number. Additionally, the formed storage regions210may alternate in size and type, and may not be uniform. The offset between storage regions210may correspond to one or more physical dimensions or directions. For instance, the offset may be radial, circumferential, rotational, horizontal, lateral, or the like.

Those of skill in the art will further recognize that patterned storage regions210may be formed using a variety of methods. For example, the storage regions210may be imprinted using techniques such as imprint lithography to form patterned track segments220. Alternatively, a method such as shadow masking may be used. In other embodiments, multigrain media, single domain islands, or other forms of track segments220capable of storing data may be formed into storage regions210using alternative processes. Thus, the invention is not limited to the illustrated embodiments.

In a select embodiment, one or more storage regions210are stamped onto a substrate of a storage medium130by imprinting a resist layer with a master template patterned bye-beam lithography. The pattern may subsequently be etched into the surface of the substrate. Multiple storage regions210may be formed on the substrate simultaneously or individually.

In certain embodiments, the formed storage regions210have patterned features with dimensions ranging between about 15–30 nm. Dense media patterns with high resolution features enable storage of greater amounts of data in smaller areas. As mentioned, however, perfect alignment of track segments220in adjacent storage regions210is extremely difficult to achieve, particularly when dealing with nano-scale media patterns. In certain embodiments, however, storage regions210that are positioned close together and nearly aligned may contribute to greater areal densities. Furthermore, precise positioning of a read/write mechanism, such as a head of a disk drive, may be required in order to efficiently access data store on the storage medium130. Additional tracking information and time to reposition the read/write mechanism over track segments220may compensate for disruptions caused by the offset of the storage regions210.

Referring now toFIGS. 1 and 2, in order to access a discontinuous media track230, the tracking module140may sense the position of a head relative to a centerline of a track segment220within a storage region210. Offset information for each storage region210may be stored in the memory160. As a result, the tracking module140may access the offset information in order to accurately position the head over the desired track segments220of the storage regions210. In one embodiment, the offset information may be stored in a table defining the location of the track segments220within a storage region210.

FIG. 3illustrates one example of a mapping table300containing offset information for each track segment220of the various storage regions210. The offset information may be determined by performing one or more procedures to determine the location of at least one track segments220within a storage region210. In one embodiment, the location of a track segment220may be determined by locating a closely aligned track segment of a subsequent storage region210. An offset defined by the relative location of the other track segment220may be recorded and used to access track segments220. Those of skill in the art will recognize that alternative methods may be used to define and store offset information relative to the location of track segments220. Thus, the present invention is not limited to the disclosed embodiments.

The schematic flow chart diagrams that follow are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of one embodiment of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

FIG. 4illustrates one embodiment of an access method400of the present invention. As depicted, the access method400includes providing402a storage medium with independently formed storage regions210, collecting404track offset information, sensing406a head position within a storage region210, accessing408track offset information, and adjusting410the head position to align with the closely aligned track segment in another storage region210.

The access method400for accessing discontinuous media tracks230enables manufacturer to more efficiently produce and access viable storage media130with greater storage densities. The access method400and table creation method500ofFIG. 5will be discussed with reference to the embodiments illustrated inFIGS. 1–3. Those of skill in the art, however, will recognize that the methods may be accomplished using a variety of embodiments and/or configurations and are not, therefore, limited to the depicted embodiments.

The access method400begins and a storage medium130with multiple independently formed storage regions210is provided402. Because the storage regions210are formed independently, the track segments220of the storage regions210may be offset from adjoining storage regions210. In order to properly position the head relative to the track segments220, the physical offset between adjacent storage regions210is determined.

In one embodiment, the tracking module140senses and records head positioning. As the head senses track segments220, track offset information may be determined and may be stored in memory160. In certain embodiments, the mapping module140calculates a physical offset between adjacent storage regions. Subsequently, the determined track offset information may be used to collect404track offset information. In one embodiment, a table300of track offset information may be created and stored in memory160. One embodiment of a method to create an offset information table300will be discussed in greater detail in relation toFIG. 5.

In a further embodiment, a track230may be defined. In certain embodiments, a media track230may include a track segment220from each storage region210. Track segments220may include a defined centerline that is offset from the centerline of a track segment220from a different storage region210. Hence a media track230may include track segments220from adjacent storage regions210that have centerlines that are closely aligned to the centerline of adjacent track segments220. Alternatively, a media track230may include track segments220that are closely aligned on a nonadjacent storage region210. In certain embodiments, the mapping module150and/or the tracking module140may define media tracks230from non-aligned storage regions210.

A discontinuous media track230may be accessed using a variety of methods and configurations. In one embodiment, the storage medium130comprises nine adjacent storage regions210, similarly formed and evenly distributed on the disk200. The track230may subsequently be defined with a 2:1 interleave scheme, as illustrated inFIG. 2. Data stored on a complete track230may consequently be accessed in two revolutions of the disk200. The use of intermediate storage regions210interspersed between consecutive storage regions210such as a 2:1 interleave scheme provide time and space to perform servo corrections and/or to locate a subsequent track segment220. Thus, the allocation of intermediate storage regions enables the present invention to function effectively with discontinuous media such as patterned media formed by inexact pattern replication.

To determine head positioning, a storage device110, or a tracking module140, senses406the head of the storage device110relative to the centerline of a track segment220within a current storage region210. Once the current position of the head is determined, track offset information may be accessed408to determine the physical adjustment necessary to position the head in a subsequent storage region210.

In one embodiment, the head position is adjusted410to align with the closest aligned track segment220within another storage region210. The tracking module104may access the stored track offset information in the memory160and may align the head in the subsequent storage region210relative to the determined track offset. Consequently, the access method400enables access of data stored in multiple storage regions210on a storage medium130. The physical offset between the storage regions210may be determined and stored such that a head may be correctly positioned relative to a selected track segment220within a storage regions210.

FIG. 5is a flow chart diagram illustrating one embodiment of a table creation method500of the present invention. The table creation method500may include mapping502a storage medium, determining504the physical offset between adjacent storage regions210, defining506a track230having a track segment220from each storage region210, organizing508track offset information in a table, and storing510the table in the memory160. The table creation method500may correspond to step404for collecting offset information as discussed in relation toFIG. 4.

In one embodiment, the mapping module140maps502the storage medium130to determine the location of the track segments220. The mapping module140may further determine504the physical offset between the storage regions210. Alternatively, the tracking module140may locate one or more track segments220and may determine504the physical offset between adjacent storage regions210. The tracking module140or the mapping module150may define506a media track230having a track segment220from each storage region210.

In one embodiment, the tracking module140determines which track segments220most closely align with adjacent storage regions210. Subsequently, the tracking module140may define a track230that may be accessed by a servo system. Hence, the storage regions210may be physically misaligned during production, yet a tracking module140may determine an accessible track230that may be used in a servo system.

The subsequent track offset information may be organized508into one or more tables, such as the mapping table300ofFIG. 3, and the table may be stored in the memory160. As a result, the tracking module140may access the table(s) stored in the memory to determine head positioning in order to access data stored on discontinuous data tracks230.