A MAGNETIC LAYER OF A MAGNETIC RECORDING DISK, AND RELATED MAGNETIC RECORDING DISKS

The present disclosure relates to magnetic recording disks having a magnetic recording layer that includes a plurality of three-dimensional segregant structures. Each three-dimensional segregant structure extends from a first radius of the recording disk to a second radius of the recording disk, and each three-dimensional segregant structure is made of a first segregant material. The magnetic recording layer also includes a plurality of magnetic grains between adjacent three-dimensional segregant structures, and a second segregant material between adjacent magnetic grains. The present disclosure also relates to corresponding methods of manufacturing such a magnetic recording layer.

BACKGROUND

The present disclosure relates to magnetic layers in magnetic recording media, and related methods of manufacture. There is a continuing need to improve magnetic recording media and related methods of manufacture, e.g., in a manner that improves the signal to noise ratio.

SUMMARY

The present disclosure includes embodiments of a magnetic recording disk including:

a substrate comprising at least a first major surface;

a nucleation layer present on the first major surface; and

a magnetic recording layer present on the nucleation layer, wherein the magnetic recording layer includes:a plurality of three-dimensional segregant structures, wherein each three-dimensional segregant structure extends from a first radius of the recording disk to a second radius of the recording disk, and wherein each three-dimensional segregant structure is made of a first segregant material; anda plurality of magnetic grains between adjacent three-dimensional segregant structures; anda second segregant material between adjacent magnetic grains.

The present disclosure also includes embodiments of a method of manufacturing at least a portion of a magnetic layer of a magnetic recording disk, wherein the method includes:

providing a substrate having at least a first major surface;

forming a pattern on the first major surface of the substrate, wherein the pattern includes a plurality of sacrificial, discrete structures, wherein each sacrificial, discrete structure extends from a first radius of the recording disk to a second radius of the recording disk, and wherein each sacrificial, discrete structure includes:a base in contact with the first major surface of the substrate; andan exterior surface having a shape, wherein the exterior surface includes an end that is opposite the base;

depositing at least one layer of segregant material so that the at least one layer of segregant material conforms to the shape of the exterior surface of each sacrificial, discrete structure;

removing a portion of the at least one layer of segregant material in a direction from the end of each sacrificial, discrete structure toward the substrate to expose at least the end of each sacrificial, discrete structure, wherein a portion of the at least one layer of segregant material remains to define a plurality of three-dimensional segregant structures in contact with the first major surface of the substrate; and

removing each sacrificial, discrete structure to expose the substrate and so that each three-dimensional segregant structure has at least two sidewalls that protrude from the substrate, wherein each three-dimensional segregant structure extends from the first radius of the recording disk to the second radius of the recording disk.

DETAILED DESCRIPTION

The present disclosure relates to a magnetic recording layer in magnetic recording disks, and related methods of manufacturing such magnetic recording layers.

Magnetic recording media are widely used in various applications, particularly in the computer industry for data/information storage and retrieval applications, typically in disk form. Nonlimiting examples of magnetic recording disks are described in U.S. Pat. No. 7,986,493 (Weller et al.) and U.S. Pat. No. 9,324,353 (Hellwig et al.), wherein the entirety of each of said patents is incorporated herein by reference.

Three-dimensional segregant structures are included in a magnetic recording layer according to the present disclosure prior to growing magnetic grains. By including three-dimensional segregant structures in a magnetic recording layer, at least some of the magnetic grains can grow so that that the portion of each magnetic grain that is adjacent to an edge of a given three-dimensional segregant structure aligns with the edge of the three-dimensional segregant structure, which can facilitate relatively sharp transitions during, e.g., writing to a magnetic recording disk. Having relatively more sharp transitions can improve (increase) the signal to noise ratio. In some embodiments, because magnetic grains are relatively more aligned instead of random arranged, a relatively more uniform thermal gradient can occur during write operations, e.g., during heat-assisted magnetic recording (HAMR).

A non-limiting example of a magnetic recording layer in a magnetic recording disk according to the present disclosure is described herein below with respect toFIGS.1A-1C. It is noted thatFIGS.1A-1Care schematic drawings and are not drawn to scale.

FIG.1Ashows a top view of a magnetic recording disk100having a central opening107and an outer perimeter105.

According to the present disclosure, the magnetic recording disk includes three-dimensional segregant structures, which help guide subsequent growth of magnetic grains. As shownFIG.1B, which is a close-up view of a portion of the magnetic recording layer170of the magnetic recording disk100shown inFIGS.1A and1C, three-dimensional segregant structures120and125. Each of the three-dimensional segregant structures120and125extend from a first radius to a second radius of the magnetic recording disk100, where the second radius is longer than the first radius. The first radius and second radius can be any desired lengths. As discussed below, three-dimensional segregant structures can facilitate relatively sharp transitions during, e.g., writing to the magnetic recording disk100. In some embodiments, the first radius can correspond to approximately the innermost radius of a magnetic disk and the second radius can correspond to approximately the outermost radius of the magnetic disk to provide “full surface” coverage. For example, as shown inFIG.1A, a first radius can approximately correspond to innermost radius101, which extends from center103of disk100to the perimeter104of the opening107. Alternatively, a three-dimensional segregant structure could have a first radius that extends beyond the innermost perimeter104of magnetic disk100so that the first radius is longer than radius101. As also shown inFIG.1A, a second radius can approximately correspond to outermost radius102, which extends from center103of disk100to the outer perimeter105of disk100. Alternatively, a three-dimensional segregant structure could have a second radius that extends partially to the outermost perimeter102of magnetic disk100so that the second radius is shorter than radius102. It is noted that the first radius may extend “approximately” to the innermost radius of the disk and the second radius may extend “approximately” to the outermost radius of the disk because there may be a “dead zone” at the innermost radius and/or outermost radius due to limitations of patterning at those locations.

Three-dimensional segregant structures can extend in a continuous manner from a first radius to a second radius along a variety of paths. Non-limiting examples of paths include linear (e.g., approximately straight) path from the first radius to the second radius, a curvilinear path from the first radius to the second radius, combinations of these, and the like.

Still referring toFIG.1B, magnetic recording layer170also includes a plurality of magnetic grains141,143,145,147, and149between adjacent three-dimensional segregant structures. As shown, magnetic grains145,147, and149are between adjacent three-dimensional segregant structures120and125. As discussed below with respect toFIGS.2A-2G, the three-dimensional segregant structures such as120and125are formed in magnetic recording layer170prior to growing magnetic grains such as magnetic grains141,143,145,147, and149so that at least some of the magnetic grains can grow in an aligned manner with respect to an adjacent edge of a three-dimensional segregant structure. Having at least some magnetic grains aligned in this manner can facilitate relatively sharp transitions during, e.g., writing to the magnetic recording disk100as indicated by dashed lines110.

Three-dimensional segregant structures according to the present disclosure such as three-dimensional segregant structures120and125can have a width that is selected based on one or more factors such as, manufacturing capability, magnetic grain density, disk operation, and the like.

For example, it is desirable to have width121of three dimensional segregant structure120help guide growth of magnetic grains141,143,145, and147in an aligned manner while at the same time not permitting growth on top of three dimensional segregant structure120.

Referring toFIG.1C, three-dimensional segregant structure120has a first surface123in contact with the surface161of nucleation layer160and a second surface124opposite the first surface123. As can be seen, the second surface124of three-dimensional segregant structure120does not have a magnetic grain over second surface124, which is desirable to maintain the relatively sharp transitions created by edge115with respect to adjacent magnetic grains141and143and created by edge116with respect to adjacent magnetic grains145and147. In some embodiments, to help facilitate no grain growth on second surface124, the width121can be selected to be less than half the grain diameter.

As another example, the width of three-dimensional segregant structures120and125can impact the space that is available for magnetic grains, which impacts the magnetic grain density.

In some embodiments, a three-dimensional segregant structures according to the present disclosure can have a width121of 5 nanometers or less, 4 nanometers or less, 3.5 nanometers or less, 3 nanometers or less, 2.5 nanometers or less, or even 2 nanometers or less. In some embodiments, a three-dimensional segregant structures according to the present disclosure can have a width of less than 3 nanometers (e.g., from 0.1 nanometers to less than 3 nanometers).

Three-dimensional segregant structures according to the present disclosure such as three-dimensional segregant structures120and125can have a pitch that is selected based on one or more factors such as, manufacturing capability, magnetic grain density, disk operation, and the like. As used herein, “pitch” refers the distance between adjacent three-dimensional segregant structures. Referring toFIG.1B, three-dimensional segregant structures120and125have a pitch111. As can be seen, pitch111permits one or more (e.g., 2 to 3) magnetic grains to be present between adjacent three-dimensional segregant structures120and125. As the pitch decreases for a given width of three-dimensional segregant structure, then the space that is available for magnetic grains reduces, which impacts the magnetic grain density. In some embodiments, adjacent three-dimensional segregant structures according to the present disclosure can have a pitch of 30 nanometers or less. For example, a pitch from 9 to 30 nanometers, from 9 to 25 nanometers, or even from 9 to 20 nanometers.

Three-dimensional segregant structures according to the present disclosure such as three-dimensional segregant structures120and125can have a height that is selected based on a variety of factors. As discussed above, one of the main purposes three-dimensional segregant structures according to the present disclosure is to guide subsequent growth of magnetic grains in an aligned manner. Thus, it is desirable that three-dimensional segregant structures according to the present disclosure have a height that at least facilitates subsequent magnetic grain growth. Referring toFIG.1C, three-dimensional segregant structure120has a height122. As shown inFIG.1C, height122is less than the height of adjacent magnetic grains141and145, but three-dimensional segregant structure120could have a height that is substantially the same as adjacent magnetic grains141and145, if desired.

Three-dimensional segregant structures according to the present disclosure include segregant material, which is a non-magnetic material that physically and magnetically decouples/segregates magnetic grains such as magnetic grains141and145. In some embodiments, a segregant material includes one or more oxides, nitrides, carbides, and mixtures thereof. Non-limiting examples of non-magnetic material that can be used as segregant material include BN, BC, C, SiC, SiN, TiC, TiN, CrN, TiO2, Al2O3, Nb2O5, SiO2, MoO3, Cr2O3, Ta2O5, ZrO2, V2O5, WO3, Y2O3, and mixtures thereof. Nonlimiting examples of non-magnetic material that can be used as segregant material in the present disclosure are described in U.S. Pat. No. 7,429,427 (Wu et al.) and U.S. Pat. No. 9,324,353 (Hellwig et al.), wherein the entirety of each of said patents is incorporated herein by reference.

In addition to three-dimensional segregant structures120and125, which are present prior to forming magnetic grains such as141and145, segregant material can be present throughout magnetic layer170as segregant material150, which also physically and magnetically decouples/segregates magnetic grains. Segregant material150can be deposited, e.g., when forming magnetic grains as discussed below. The segregant material150can be made of the same or different segregant material as three-dimensional segregant structures (e.g.,120and125) according to the present disclosure.

Referring toFIG.1Cit can be seen that magnetic recording disk100has a variety of layers. By way of example,FIG.1Cshows substrate150having a first major surface151and a second major surface152opposite first major surface151; a nucleation layer160present on the first major surface151. Nucleation layer160has a first major surface161and a second major surface162opposite first major surface161. On top of nucleation layer160is magnetic recording layer170discussed in detail above with respect toFIG.1B. Although not shown, one or more additional layers can be provided under and/or over magnetic layer170. Non-limiting examples of such an adhesion layer, a “soft” magnetic underlayer, a protective overcoat (such as of a diamond-like carbon (DLC)) and/or lubricant topcoat (such as of a perfluoropolyether material) as shown in U.S. Pat. No. 7,429,427 (Wu et al.).

According to the present disclosure, a pattern of sacrificial, discrete structures can be formed so that the sacrificial, discrete structures can be used as mandrels to ultimately define three-dimensional segregant structures that have a desirable size, e.g., thin enough to avoid having magnetic grains nucleate on top of the three-dimensional segregant structures while at the same time having boundaries and critical dimensions (e.g., line edge roughness (LER and/or linewidth roughness (LWR)) that facilitate guiding subsequent growth of magnetic grains in an aligned manner. Further, manufacturing three-dimensional segregant structures according to the present disclosure advantageously permits desirable density of three-dimensional segregant structures over a relatively large area.

A non-limiting method of manufacturing three-dimensional segregant structures in a magnetic recording layer for subsequent formation of magnetic grains will now be described in connection withFIGS.2A-2G. LikeFIGS.1A-1C,FIGS.2A-2Gare not drawn to scale.FIG.2Aillustrates an initial stack of layers that includes a substrate201, an interlayer203, a layer205sacrificial material (to be used a “mandrel” described below), and a layer of hard mask material207.

Substrate201can include one or more non-magnetic layers such as layer150inFIG.1C. Substrate201can function as the base layer for a magnetic recording medium and include materials which allow deposition of one or more additional media layers at elevated temperatures, e.g., on the order of 600-700° C. Substrate201can be made of glass, ceramic, glass-ceramic, polymeric material, or a composite or laminate of these materials. Non-limiting examples of specific materials that can be used in substrate201include chromium, chromium alloy, aluminum, aluminum alloy, silicon, quartz, combinations of these and the like. In some embodiments, layer150is non-magnetic metal or alloy. Substrate201can have a thickness in the range from 5 nm to 100 nm, or even from 10 nm to 100 nm.

Layer203can include one or more layers (such as a nucleation layer160inFIG.1C) deposited on layer201. Layer203can also be referred to as a non-magnetic seed or underlayer (sometimes referred to as an “intermediate” layer or as an “interlayer”), and serves to (1) prevent magnetic interaction between any soft magnetic underlayer that may be present and one or more “hard” recording layers such as magnetic recording layer170inFIG.1C; (2) promote desired microstructural and magnetic properties of the at least one magnetically hard recording layer such as170, e.g., by serving to establish a crystallographically oriented base layer for inducing growth of a desired plane in the overlying perpendicular magnetically hard recording film or layer; and/or (3) establish a high surface roughness in order to induce grain separation in the magnetically hard recording layer.

Layer203can be made out of one or more non-limiting non-magnetic materials such as magnesium oxide (MgO), MTO, Ru, TiCr, Ru/CoCr37Pt6, RuCr/CoCrPt, combinations of these, and the like. Layer203can have a thickness in the range from 0.5 nm to 30 nm, or even from 1 nm to 20 nm.

Layer205can be a single layer or one or more layers of sacrificial material that can be patterned into a plurality of sacrificial, discrete structures as described below inFIG.2C. A wide variety of materials can be used for layer205and can be selected on the ability to form the layer205into sacrificial, discrete structures via a pattern of resist material, to be used as a mandrel to shape a layer of segregant material into three-dimensional segregant structures, while at the same time being able to be selectively removed relative to the segregant material used to form the three-dimensional segregant structures. In some embodiments, a sacrificial material for layer205can be selected from a wide variety of segregant materials as discussed above with respect to three-dimensional segregant structure120but that is different from layer230of segregant material in a manner that permits the sacrificial, discrete structures that are formed to be “directionally” removed toward the underlying nucleation layer203to expose nucleation layer203and selectively removed relative to the three-dimensional segregant structures, as discussed below. For example, sacrificial material for layer205can include carbon (C) while layer230of segregant material is made of silicon dioxide. In some embodiments, a sacrificial material for layer205can be selected from a wide variety of polymer materials that may not be considered segregant materials.

Layer205can be deposited by a variety of techniques such as sputtering, chemical vapor deposition (CVD), combinations of these, and the like.

Layer205can have a variety of thicknesses that can be selected based on the pattern that is formed into layer205as discussed inFIG.2Bbelow as well as the height242of three-dimensional segregant structures (e.g., three-dimensional segregant structure231) discussed below inFIG.2G. In some embodiments, layer205can have thickness of 50 nanometers (nm) or less, 30 nm or less, 20 nm or less, 15 nm or less, 10 nanometers or less, or even 5 nanometers or less. In some embodiments, layer205can have thickness of from 0.5 to 50 nm, from 0.5 to 30 nm, from 1 to 15 nanometers, or even from 1 to 5 nanometers.

As shown inFIG.2A, one or more layers207of hard mask material can be deposited over the layer205of sacrificial material. The hard mask material and thickness can be selected to facilitate transferring the photoresist pattern shown inFIG.2Binto the layer205of sacrificial material.

A wide variety of hard mask materials can be used for layer107. Non-limiting examples include one or more oxides, one or more metals, and combinations thereof. For example, non-limiting examples of oxides include SiO2, TiOx, and TaOx, and non-limiting examples of metals include chromium (Cr), titanium (Ti), and tantalum (Ta).

Layer207can have a thickness to facilitate transferring the photoresist pattern shown inFIG.2Binto the layer205of sacrificial material. In some embodiments, layer207can have thickness of 10 nm or less, or even 5 nanometers or less. In some embodiments, layer207can have thickness of from 0.5 to 5 nm, or even from 1 to 3 nanometers.

As shown inFIG.2B, a pattern of photoresist material can be formed on layer207. A variety of techniques can be used to form a photoresist pattern such as nanoimprint lithography technology. A non-limiting example of using nanoimprint lithography to manufacture a magnetic recording layer in a magnetic recording disk is described in U.S. Pat. No. 7,986,493 (Weller et al.), wherein the entirety of said patent is incorporated by reference. Other techniques that provide desirable resolution below 100 nm include photolithography, e-beam lithography, block copolymer self-assembly, combinations of these, and the like.

A wide variety of organic polymers can be used as photoresist materials and can be positive-tone and/or negative-tone photoresists.

With respect to nanoimprinting, at least one layer of uncured photoresist material is coated over the at least one layer of hard mask material and formed into a pattern in the resist material by nanoimprinting. For example, a layer of photoresist material can be coated onto layer207by inkjet dispensing and/or spin-coating. The photoresist layer can be deposited to provide a thickness that ultimately provides the desired dimensional features of the sacrificial, discrete structures (e.g., height223inFIG.2C) and impacts the height of three-dimensional segregant structures (e.g., height242inFIG.2G). In some embodiments, the photoresist can be coated to have a thickness of 30 nm or less, or even 20 nanometers or less. In some embodiments, the photoresist can be coated to have a thickness from 10 to 30 nm.

After coating the uncured photoresist material, an embossing mold/template can be used to form a pattern that includes features209and210in the uncured photoresist material. The embossing mold includes features to be reproduced into the sacrificial material in layer205. Each of the features in the embossing mold help define dimensions (e.g., height, width, and length) that correspond to the dimensions of a pattern to be reproduced in the cured photoresist material. The uncured photoresist material can be cured by exposing it to ultraviolet radiation and/or thermal radiation to at least partially cure (e.g., to substantially completely cure) the uncured photoresist material so that the cured photoresist material maintains the pattern that corresponds to the embossing mold after the embossing mold is removed.

As shown inFIG.2B, the cured photoresist pattern includes features209and210, which will be transferred into layer205to form sacrificial, discrete structures219and221, respectively. A variety of three-dimensional shapes and sizes can be selected for features209and210, which ultimately determine the shape and size of sacrificial, discrete structures219and221, respectively. Similar to the three-dimensional segregant structures120and125inFIG.1B, features209and210extend continuously along a direction from a first radius of a magnetic disk to a second radius of the magnetic disk. And as shown inFIG.2B, features209and210are square in cross-section to form cuboids. Alternatively, a wide variety of cross-sectional shapes could be used instead since only a portion of the corresponding sacrificial, discrete structures219and221near layer203are used to define three-dimensional segregant structures, such as231, after etching coating230, discussed below.

As shown inFIG.2B, feature209has a height211, a width213, and a pitch215. The width213determines the width225of sacrificial, discrete structure219; the height211determines the height223of sacrificial, discrete structure219; and the pitch215determines the pitch217, all of which are discussed below with respect toFIGS.2C and2G.

The pattern or periodicity of features such as209and211can be selected as desired. For example, the features209and211, along with dimensions211,213, and215, can be repeated across a portion or the entire magnetic recording layer of the corresponding magnetic recording disk.

Turning now toFIG.2C, the pattern of photoresist shown inFIG.2Bis transferred into layer205of sacrificial layer to form a plurality of sacrificial, discrete structures such as219and221. Referring to sacrificial, discrete structure219, for example, it extends from a first radius of the corresponding recording disk to a second radius of the recording disk similar to three-dimensional segregant structure120discussed above. As shown inFIG.2E, sacrificial, discrete structure219is a cuboid having one side or base251in contact with a major surface of the interlayer203. The remaining three sides252,253, and254of cuboid219form an exterior surface having a shape of a square in cross-section. As can be seen, end252is opposite the base251.

According to the present disclosure, “sacrificial, discrete structures” (also referred to as “sacrificial mandrels”) are used as mandrels to shape a layer of segregant material coated over the sacrificial, discrete structures in a conforming manner so that a portion of the layer of segregant material can be removed to form the three-dimensional segregant structures as shown inFIG.2Gbelow. Sacrificial, discrete structures can be made of material discussed above with respect to layer205.

Referring toFIG.2Cagain, the sacrificial, discrete structures can have a width225that determines pitch240of three-dimensional segregant structures shown inFIG.2Gand discussed below.

As shown inFIG.2C, the sacrificial, discrete structures can also have a pitch217that, along with the thickness of coating230, determines the pitch241of three-dimensional segregant structures, which is discussed below inFIG.2G. As used with respect to217, “pitch” refers to the distance between adjacent sacrificial, discrete structures. In some embodiments, adjacent sacrificial, discrete structures according to the present disclosure can have a pitch of 60 nanometers or less. For example, a pitch from 10 to 50 nanometers, or even from 15 to 40. The sacrificial, discrete structures can have a height223, which in part defines (along with how much etching is performed) the height242of three-dimensional segregant structures such as231, which is discussed below.

The pattern of photoresist can be transferred into sacrificial layer205by any desired lithography technique to ultimately remove all of the resist material, all of the hard mask material, and at least a portion of the sacrificial material. For example, depending the type of hard mask material selected, a dry plasma etch can be applied to transfer the pattern into the hard mask layer207first. A non-limiting example of such a dry plasma etch includes a CF4reactive-ion etch (RIE), which can be used for a hard mask material such as SiO2. In some embodiments, after transferring the photoresist pattern into the hard mask layer207, another etching process can be used to transfer the pattern into the layer205of sacrificial material. A non-limiting example of such an etching process includes an oxygen RIE to etch the pattern into the layer205which is made of material “etchable” by oxygen RIE such as, e.g., carbon (C). In some embodiments, as shown inFIG.2E, any residual sacrificial material from layer105that is between sacrificial, discrete structures219and221, if present, can be removed, thereby leaving only sacrificial, discrete structures219and221on interlayer203and exposing the interlayer203between sacrificial, discrete structures219and221. Alternatively, in some embodiments, as shown inFIG.2F, only a portion of sacrificial material is removed, thereby leaving a residual thickness218of sacrificial material from layer205between sacrificial, discrete structures219and221. Such a residual thickness of sacrificial material can protect the interlayer203during subsequent etching of segregant material in coating230. For example, if the coating230of segregant material is etched with a dry plasma etch process (e.g., CF4RIE) then the residual thickness218can help protect the interlayer203after removing the segregant material and exposing interlayer203when the portion of segregant coating230between sacrificial, discrete structures219and221is removed. In some embodiments, the residual thickness218can be 20 nm or less, 15 nm or less, or even 10 nanometers or less. In some embodiments, the residual thickness218can be from 3 to 10 nm, or even from 5 to 10 nm. After forming the plurality of sacrificial, discrete structures on a substrate, at least one layer of segregant material can be deposited over the sacrificial, discrete structures so that the at least one layer of segregant material conforms to the shape of the exterior surface of each sacrificial, discrete structure. For example, as shown inFIG.2D, a layer230of segregant material is deposited over sacrificial, discrete structures219and221. As can be seen inFIG.2E, the layer230conforms to the exterior shape of sacrificial, discrete structure219defined by sides252,253, and254. The layer230of segregant material can be selected from any of the materials discussed above with respect to three-dimensional segregant structure120.

The thickness of layer230on sidewalls253and254determines the width243of three dimensional segregant structure231, which corresponds to the width121of three dimensional segregant structure120discussed above.

Coating230can be deposited by a variety of techniques such as sputtering (physical vapor deposition (PVD)), chemical vapor deposition (CVD), atomic layer deposition (ALD), vacuum thermal evaporation, electron beam evaporation, laser beam evaporation, combinations of these, and the like.

Coating230can be selected from a wide variety of segregant materials as discussed above with respect to three-dimensional segregant structure120. Also, as mentioned above with respect to sacrificial layer205, the material for sacrificial layer205is selected to be different from coating230so that coating230can be selectively removed relative to sacrificial, discrete structures such as219and221.

After applying at least one layer of segregant material, a portion of the at least one layer can be “directionally” removed toward the underlying substrate and selectively removed relative to the sacrificial, discrete structures (does not remove sacrificial, discrete structures) so that a portion of the segregant material remains to define the three-dimensional segregant structures when subsequently removed the sacrificial mandrels to expose the underlying interlayer and deposit magnetic grains. Referring toFIG.2E, the at least one layer of segregant material230is removed in a direction as indicated by arrows250from the end252of sacrificial, discrete structure219toward the nucleation layer203to expose at least the end252of sacrificial, discrete structure219and a portion of each of sidewalls253and254. A portion of layer230along each of sidewalls253and254remains in contact with nucleation layer203to define the three-dimensional segregant structures231and233.

A portion of the at least one layer230can be “directionally” removed toward the underlying substrate using any desired technique such as dry etching process. A non-limiting example of such a dry etching process includes a plasma etching process such as CF4RIE. Any desired etching conditions can be selected to remove a portion of layer230as described herein.

The sacrificial, discrete structures can be removed to expose the underlying substrate so that magnetic grains and additional segregant material can be deposited between the three-dimensional segregant structures. Referring toFIGS.2E and2G, the sacrificial, discrete structures219and221can be “directionally” removed toward the underlying nucleation layer203to expose nucleation layer203and selectively removed relative to the three-dimensional segregant structures231,233,235, and237(does not remove the three-dimensional segregant structures).

The sacrificial, discrete structures can be “directionally” removed toward the underlying substrate using any desired technique such as a dry etching process. A non-limiting example of a dry etching process includes a plasma dry etching process such as oxygen RIE. Any desired etching conditions can be selected to remove the sacrificial, discrete structures as described herein.

Referring toFIG.2G, the three-dimensional segregant structures231,233,235, and237remain and are ready to have the remainder of the magnetic layer formed by depositing magnetic grains and additional segregant material between adjacent three-dimensional segregant structures. As can be seen, each three-dimensional segregant structures231,233,235, and237has a height, a width, and two sidewalls. For example, three-dimensional segregant structure231has a height242and a width243.

The height242of three-dimensional segregant structure231is similar to height122discussed above inFIG.1C. As mentioned, three-dimensional segregant structures according to the present disclosure can have a height that at least facilitates subsequent magnetic grain growth. In some embodiments, three-dimensional segregant structures according to the present disclosure can have a height of 15 nm or less, 10 nm or less, 5 nm or less, or even 3 nm or less. In some embodiments, three-dimensional segregant structures according to the present disclosure can have a height from 1 nm to 15 nm.

The width243of three-dimensional segregant structure231is similar to width121discussed above inFIG.1B. As mentioned, three-dimensional segregant structures according to the present disclosure can have a width to help guide subsequent growth of magnetic grains in an aligned manner while at the same time not permitting growth on top of three dimensional segregant structure, which is desirable to maintain the relatively sharp transitions created by the aligned growth. Also, the width of three-dimensional segregant structures can impact the space that is available for magnetic grains, which impacts the magnetic grain density.

In some embodiments, a three-dimensional segregant structures according to the present disclosure can have a width243of 5 nanometers or less, 4 nanometers or less, 3.5 nanometers or less, 3 nanometers or less, 2.5 nanometers or less, or even 2 nanometers or less. In some embodiments, a three-dimensional segregant structures according to the present disclosure can have a width243of less than 3 nanometers (e.g., from 0.1 nanometers to less than 3 nanometers).

As shown inFIG.2G, three-dimensional segregant structure231also has two sidewalls245and246that protrude from the major surface of interlayer203. The sidewalls245and246extend continuously along a direction from a first radius of a magnetic disk to a second radius of the magnetic disk.

The pitch240of three-dimensional segregant structure231and233is determined by the width225of sacrificial, discrete structures219and is similar to pitch111discussed above inFIG.1B. As mentioned, pitch permits one or more (e.g., 2 to 3) magnetic grains to be present between adjacent three-dimensional segregant structures. As the pitch decreases for a given width of three-dimensional segregant structure, then the space that is available for magnetic grains reduces, which impacts the magnetic grain density. As mentioned above, in some embodiments, adjacent three-dimensional segregant structures according to the present disclosure can have a pitch of 30 nanometers or less. For example, a pitch from 9 to 30 nanometers, from 9 to 25 nanometers, or even from 9 to 20 nanometers.

The pitch241of three-dimensional segregant structure233and235is determined by the pitch217of sacrificial, discrete structures219and221, and the thickness of coating230. Pitch241can be the same or different from pitch240. In some embodiments, the pitch240is the same as pitch241and is one-half of the pitch217.

As mentioned, after removing the sacrificial, discrete structures to expose the underlying nucleation layer, the remainder of the magnetic layer can be formed by any desired method of depositing magnetic grains and additional segregant material between adjacent three-dimensional segregant structures.

Magnetic grains and/or additional segregant material can be deposited by sputtering. The size of magnetic grains can be from 5 to 15 nanometers, or even from 8 to 10 nanometers.

Additional segregant material is discussed above with respect to segregant material150.

Non-liming examples of magnetic material for forming magnetic grains includes FePt among many others.

A non-limiting example of forming magnetic grains and additional segregant material is described in U.S. Pat. No. 9,324,353 (Hellwig et al.), wherein the entirety of said patent is incorporated herein by reference

Example

An example of forming three-dimensional segregant structures according to the present disclosure was performed in a manner similar to that described above with respect toFIGS.2A-2E and2G.

A 15 nm thick carbon (C) sacrificial, mandrel layer205was deposited (by sputtering) onto a substrate201(glass disk with multiple stack layers) and a top nucleation layer203, MgO. Then a 2 nm thick hard mask (HM) layer207of SiO2was deposited onto the C layer205by sputtering.

Then, a 20 nm thick organic polymeric resist layer was coated onto layer207by inkjet dispensing. Then a nanoimprinting process was performed to generate a pattern in the resist layer of linear, sacrificial, discrete structures having a pitch of 32 nm.

Then, the resist pattern was transferred into the hard mask (HM) layer207of SiO2by CF4reactive-ion etch (ME). Then oxygen RIE was used to etch the pattern into C mandrel layer205. Finally, remaining SiO2hard mask material was removed by CF4RIE, to leave only sacrificial, discrete structures (C mandrel structures) on the nucleation layer203, with no residual thickness between the sacrificial, discrete structures.

Then, a 3 nm thick SiO2segregant layer was deposited onto the sacrificial, discrete structures and exposed nucleation layer203, by sputtering.

Then, CF4RIE was performed to selectively etch away segregant SiO2on top of the sacrificial, discrete structures and nucleation layer203, leaving only a portion of the segregant layer along the sidewalls of each sacrificial, discrete structure.

Then, oxygen RIE was used to etch away the sacrificial, discrete structures (C mandrels) to expose the underlying nucleation layer203between each pair of segregant sidewalls extending from nucleation layer203.

FIG.3Ais a top view of an SEM of linear, three-dimensional segregant structures330extending in approximately straight lines. The linear, three-dimensional segregant structures330are the light lines.FIG.3Bis cross-sections, transmission electron microscopy (TEM) image of a portion of the SEM image ofFIG.3A. The linear, three-dimensional segregant structures330are the light lines. The dark outline is iridium used for contrast.