US20120273999A1 - Method for patterning a stack - Google Patents
Method for patterning a stack Download PDFInfo
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- US20120273999A1 US20120273999A1 US13/097,841 US201113097841A US2012273999A1 US 20120273999 A1 US20120273999 A1 US 20120273999A1 US 201113097841 A US201113097841 A US 201113097841A US 2012273999 A1 US2012273999 A1 US 2012273999A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/86—Re-recording, i.e. transcribing information from one magnetisable record carrier on to one or more similar or dissimilar record carriers
- G11B5/865—Re-recording, i.e. transcribing information from one magnetisable record carrier on to one or more similar or dissimilar record carriers by contact "printing"
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/004—Photosensitive materials
- G03F7/0041—Photosensitive materials providing an etching agent upon exposure
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/03—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by deforming with non-mechanical means, e.g. laser, beam of particles
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
- G11B5/59633—Servo formatting
- G11B5/59638—Servo formatting apparatuses, e.g. servo-writers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
- G11B5/743—Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks
- G11B5/746—Bit Patterned record carriers, wherein each magnetic isolated data island corresponds to a bit
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/855—Coating only part of a support with a magnetic layer
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- Optics & Photonics (AREA)
- Moving Of The Head To Find And Align With The Track (AREA)
Abstract
The embodiments disclose a method for patterning a stack, including embedding servo patterns within a final template and creating positions of plural cross-tracked shifted position error signal (PES) fields incrementally from the embedded servo patterns on the final template.
Description
- In a recording system based on certain patterns, the media is fundamentally different from conventional continuous media, as the magnetic regions are laid out as periodic arrays of dots/islands where the information is stored and the region surrounding the dots is non-magnetic. Current methods to create a patterned master template for making the final media are expensive, create less efficient storage, are time consuming and take months to get results.
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FIG. 1 shows a block diagram of an overview of a method for patterning a stack of one embodiment. -
FIG. 2A shows a block diagram of an overview flow chart of a method for patterning a stack of one embodiment. -
FIG. 2B shows a block diagram of an overview flow chart of a secondary master template of one embodiment. -
FIG. 2C shows a block diagram of an overview flow chart of a cross track shifting to avoid partial domain dots of one embodiment. -
FIG. 3A shows for illustrative purposes only an example ofstack servo sectors 310 of one embodiment. -
FIG. 3B shows for illustrative purposes only an example of stack 300 servo sections of one embodiment. -
FIG. 4A shows for illustrative purposes only an example of a low domain dot density process of one embodiment. -
FIG. 4B shows for illustrative purposes only an example of a lower dot density precursor guiding pattern of one embodiment. -
FIG. 4C shows for illustrative purposes only an example of a density multiplicative guided self assembly process of one embodiment. -
FIG. 4D shows for illustrative purposes only an example of a primary imprint template of one embodiment. -
FIG. 5A shows for illustrative purposes only an example of a quartz wafer of one embodiment. -
FIG. 5B shows for illustrative purposes only an example of a servo pattern of one embodiment. -
FIG. 5C shows for illustrative purposes only an example of fluid resist removal of one embodiment. -
FIG. 5D shows for illustrative purposes only an example of etching a quartz wafer of one embodiment. -
FIG. 5E shows for illustrative purposes only an example of a secondary master template of one embodiment. -
FIG. 6A shows for illustrative purposes only an example of a primary imprint template of one embodiment. -
FIG. 6B shows for illustrative purposes only an example of an overlay resist layer of one embodiment. -
FIG. 6C shows for illustrative purposes only an example of a servo overlay process of one embodiment. -
FIG. 6D shows for illustrative purposes only an example of a quartz wafer of one embodiment. -
FIG. 6E shows for illustrative purposes only an example of a high density final template of one embodiment. -
FIG. 7A shows for illustrative purposes only an example of unaligned domain dots of one embodiment. -
FIG. 7B shows for illustrative purposes only an example of DC erasing of one embodiment. -
FIG. 8 shows for illustrative purposes only an example of position error signal (PES) fields of one embodiment. -
FIG. 9A shows for illustrative purposes only an example of a cross track shift increment of one embodiment. -
FIG. 9B shows for illustrative purposes only an example of the incremental cross track shifting of one embodiment. -
FIG. 10 shows for illustrative purposes only an example of servo sector reading of one embodiment. -
FIG. 11A shows for illustrative purposes only an example of partial dot noise of one embodiment. -
FIG. 11B shows for illustrative purposes only an example of avoided partial dot noise of one embodiment. -
FIG. 12 shows for illustrative purposes only an example of a cross track shifted PES field pairs operation of one embodiment. - In a following description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the embodiments.
- It should be noted that the descriptions that follow, for example, in terms of a method for patterning a stack is described for illustrative purposes and the underlying system can apply to any number and multiple types of bit patterned stack or media. In one embodiment, the manufacturing of a bit patterned stack can be implemented as bit pattered media (BPM). Bit patterned stacks use servo sectors to position the heads. In one embodiment the embedded servo patterns are created using multiple templates that reduce mastering time. In another embodiment multiple PES field pairs are created using incremental position shifts in a cross track direction and used to select the PES field pair that is positioned to avoid partial domain dot noise and produce the highest signal to noise ratio. In one embodiment an efficient method to reduce the time to develop a high quality extendible master imprint template may reduce cost and speed manufacturing of high quality BPM. It should be noted that in the descriptions that follow, the term position error signal is also represented by the capital letters PES which carry the same meaning.
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FIG. 1 shows a block diagram of an overview of a method for patterning a stack of one embodiment.FIG. 1 shows a block diagram of an overview of a method for patterning a stack of one embodiment.FIG. 1 shows a method for patterning a stack for bit patterned media creating a lower domain dot densityprecursor guiding pattern 100 to pattern an entire high density primarymaster imprint template 110. The lower domain dot densityprecursor guiding pattern 100 has a low domain dot density that is very uniform with near perfect symmetry. Patterning an entire high density primarymaster imprint template 110 using the lower domain dot densityprecursor guiding pattern 100 reduces mastering time of one embodiment. - The high density
primary imprint template 110 is used in aservo overlay process 150. Theservo overlay process 150 embeds the servo pattern designs 120 within the high densityprimary imprint template 110 using a separatesecondary master template 140 to form a high densityfinal template 160. The separatesecondary master template 140 is created quickly further reducing the mastering time. The process to create the separatesecondary master template 140 includes the use of an e-beam writer to position the servo pattern designs 120 on the quartz wafer that is processed to create an etched template. The e-beam writer process includes the calculation and recording of multiple PES field pairs 130. - The multiple PES field pairs 130 are positioned to read burst from the domain dots in the final servo patterns embedded within the stack media. The initial PES field pair is positioned over the servo pattern as it is transmitted to the e-beam writer. Additional PES field pairs are positioned using incremental cross track shifting relative to the initial position.
- The high density
final template 160 is used to imprint stacks 165. An ion beam etching process kills the magnetic properties of non-servo dots in the servo sectors on the imprinted stacks. The imprinted stacks are processed with DC erasing to realign the magnetic dots in one direction. One or more completed stacks is placed into ahard disk drive 170. Thehard disk drive 170 reads the servo bursts from the dot magnetic fields in the servo sector patterned regions and synchronously decodes the PES signals from the servo bursts. The multiple PES field pairs 130 register the PES signal from the domain dot zones in each servo section. The preamble has been locked to the phase locked loop to allow readback data to be read and decoded synchronously with the burst and operation. Each PES field pair is positioned differently along the cross track radial. These multiple locations may or may not have a boundary crossing over one or more domain dot. A readback trace is used to evaluate the multiple readback trace results 180. A readback trace that shows a low signal to noise ratio indicated partial domain dot noise. Partial domain dot noise is an indicator that the boundaries of the PES field pair crosses over one or more domain dot. The evaluation of the readback trace showing a low signal to noise ration may disable PES field pairs with partialdomain dot noise 185. The readback trace evaluation may enable the PES field pair with the highest signal tonoise ratio 190. The method for patterning a stack reduces mastering time for a master template, is cost effective and provides accurate positioning of the servo pattern guided head for high quality and reliable read operations using a patterned stack such as bit-patterned media. -
FIG. 2A shows a block diagram of an overview flow chart of a method for patterning a stack of one embodiment.FIG. 2A shows a time saving step in the method for patterning a stack. The fabrication of the lower densityprecursor guiding pattern 100 is a layer of spun resist 200 on anon-magnetic substrate 202. The resist is processed with ane-beam writer 204 to pattern a low domain dot density for example 250 Gdpsi. The resist 200 includes for example positive and negative types of resist materials. The positive results in pillars being formed and the negative results in holes or cylindrical recesses. The lower densityprecursor guiding pattern 100 is the pattern guide for a multiplicative guidedself assembly process 210 such as diblock copolymer. The multiplicative guidedself assembly process 210 doubles the number of dots in both direction thereby quadrupling the density to 1,000 Gdpsi or 1 Tdpsi. The multiplicative guidedself assembly process 210 increases the density patterning an entire high densityprimary imprint template 220. The high densityprimary imprint template 160 is used in processes that continue inFIG. 2B . The use of the lower starting dot density reduces the mastering time. The lower densityprecursor guiding pattern 100 is very uniform and has near perfect symmetry. This method is cost effective and speeds the overall production. -
FIG. 2B shows a block diagram of an overview flow chart of a secondary master template of one embodiment.FIG. 2B shows the separatesecondary master template 140 ofFIG. 1 being fabricated using spun resist 200 on top of aclear quartz wafer 230. The designedservo patterns 120 are loaded into thee-beam writer 204 to guide the operation. Thee-beam writer 204 generates bursts of beams filling the servo patterns and their boundaries onto the resist 200. The electron beams harden the resist duplicating the servo patterns. The area of the resist 200 outside the boundaries of the servo patterns remain fluid. When thee-beam writer 204 has completed patterning the entireclear quartz wafer 230 servo sectors the uncured fluid resist 200 is removed. The surface of theclear quartz wafer 230 is exposed after the removal of the fluid resist 200. - The positions of the
servo patterns 120 being processed by thee-beam writer 204 are recorded. The recorded servo pattern designs 120 positioning is used to create multiple PES field pairs 130. The PES field pairs are used to receive the readback signals from areas of the servo patterns. Each pair of the PES field pairs are oriented 90 degrees to one another in relation to the track direction. The positioning of each set of PES field pairs is adjusted to incrementally cross track shift PES field pairs 256. The cross track shift increment includes for example ¼ of the domain dot diameter. Two or more PES field pairs are created including the initial position of the servo patterns used to guide the e-beam writer. The PES field pairs are used in the processes that continue inFIG. 2C . - The
e-beam writer 204 and resist 200 lead to the cure and remove uncured fluid resist 240 processes. The surface of theclear quartz wafer 230 is exposed and ready to etch theclear quartz wafer 242. The exposed surface unprotected by the hardened resist 200 is etched using for example ion-beam etching. The hardened resist 200 is removed upon completion to the etching. The topography created by the etching creates a servo patternedclear quartz wafer 244. The servo patternedclear quartz wafer 244 is inverted to form a mirroredsecondary master template 246. The previous process inFIG. 2A places the high densityprimary imprint template 160 ofFIG. 1 into aservo overlay process 248. - A layer of resist 200 is spun on top of the high density
primary imprint template 160 ofFIG. 1 . The mirroredsecondary master template 246 is set into the resist 200. The etched areas of the inverted mirroredsecondary master template 246 are filled by capillary action with the fluid resist 200. The non-etched areas sit on a thin film of the resist 200 close to the surface of the high densityprimary imprint template 160 ofFIG. 1 . UV light is projected through the back of theclear quartz wafer 230 to cure and harden the resist 200. The hardened resist is etched. The pillars of the high densityprimary imprint template 160 ofFIG. 1 are etched for example in the low thin film resist 200 areas the pillars are etched to the surface of thenon-magnetic substrate 202 ofFIG. 2A and the pillars within the servo boundaries are not. This creates the high-density final template 254 for imprinting the embeddedservo patterns 250. The high-density final template 254 is used to imprint stacks 165. Anion beam etching 252 process is used to kill magnetic properties ofnon servo dots 254 in the imprinted stacks. The imprinted stacks are used in processes that continue inFIG. 2C . -
FIG. 2C shows a block diagram of an overview flow chart of a cross track shifting to avoid partial domain dots of one embodiment.FIG. 2C shows the continuation of the processes fromFIG. 2B . The imprinted stacks with the embeddedservo patterns 250 undergo a constant magnetic field such as DC erasing 258 to realign the magnetic properties in one direction. One or more imprinted stacks are placed into thehard disk drive 170. The multiple PES field pairs 130 including the incrementally cross track shift PES field pairs 256 are set up in thehard disk drive 170. The preamble is locked with a phase lockedloop 260 to synchronously decode the multiple PES bursts 262. - The
hard disk drive 170 proceeds to readservo sectors 266. The magnetic fields of the domain dots in theservo sectors 266 produces PES bursts 268. - The head in the hard disk drive reads the PES bursts 268 as a readback signal. The multiple PES field pairs 270 receive the readback signals. The electronics in the
hard disk drive 170 synchronously decode the multiple PES bursts 262 and readback signals received by the multiple PES field pairs 270. The readback signals are used to evaluate the multiple results in areadback trace 274.Minimum noise criteria 272 are adjustable and established for use in the evaluation. PES burst that are read from domain dots that are crossed by the boundary of a PES field create modulation or partial domain dot noise. The partialdomain dot noise 278 received by any of the PES field pairs 276 are registered as a low signal tonoise ratio 280. The low signal tonoise ratio 280 indicates high partialdomain dot noise 278 thereby lowering the ratio. The low signal tonoise ratio 280 evaluation is that minimum noise criteria have not been met 282. The position of the PES pair boundary crosses over domain dots creating the partial domain dot noise. Any of the PES pairs where low signal tonoise ratio 280 data is received may disable those PES field pairs 284. The multiple PES field pairs positioning having been incrementally cross track shifted may produce at least one pair whose boundaries do not cross over domain dots. The PES field pair that shows the highest signal tonoise ratio 290 may indicate that minimum noise criteria have been met 292. The highest signal tonoise ratio 290 may enablePES burst pair 294. The selection process of the PES field pair with the highest signal tonoise ratio 290 provides accurate position error signals used to reposition the head. This may prevent read errors while using the patterned stack. The method for patterning a stack is a cost effective, time savings and effective method of patterning a stack and increasing production of patterned stacks and media such as bit-patterned media. -
FIG. 3A shows for illustrative purposes only an example ofstack servo sectors 310 of one embodiment. The method of patterning astack 300 is the patterning of theservo sectors 310 of astack 300. Theservo sectors 310 are wedge shapedservo sector 340 areas that project outwardly in a radial position from the center of for example a disk shapedstack 300. Theservo sectors 310 are spaced evenly, around thecircular stack 300 leaving openother data sectors 320 betweenservo sectors 310 as shown inFIG. 3A . The wedge shapedservo sectors 310 are islands of domain dots used to store data such as Gray code, SAM and provide PES feedback. The Gray code for example includes 20-bit binary code data used to identify the positions of tracks and sectors. The Gray code is written into theservo sectors 310. The instructions are written into domain dot servo islands located in each track as shown inservo sector detail 330 ofFIG. 3B . -
FIG. 3B shows for illustrative purposes only an example ofstack 300 servo sections of one embodiment.FIG. 3B shows a portion of thestack 300 that is divided intoservo sectors 310 andother data sectors 320. Theservo sector detail 330 illustrates the wedge shapedservo sector 340 that is divided by the tracks in tomultiple servo section 350 regions. The servo patterns are embedded in eachservo section 350. The electronics in the hard disk drive use feedback from the heads, which read the Gray code pattern, to very accurately position, and constantly correct the radial position of the appropriate head over the desired track, at the beginning of eachservo section 350, to compensate for variations in platter geometry, caused by mechanical stress and thermo expansion and contraction. The PES feedback to the head establish the actual position of the head which is compared to the designed position in the Gray code embedded servo patterns. Partial domain dot noise can increase errors in the reading of the Gray code and PES. Position errors create errors in the search and placement of data which can lead to loss or inaccessibility to retrieve data. A portion of the Gray code is embedded at the start of each sector which is referred to as an embedded servo pattern. The embedded servo pattern data is permanent. The permanent nature of the data thereby means position errors caused by partial domain dot noise can also be permanent. The accuracy of the servo patterns created by the avoided partial domain dot results of the method to pattern astack 300 provides the permanent position error free environment for this permanent data record on astack 300. -
FIG. 4A shows for illustrative purposes only an example of a low domain dot density process of one embodiment.FIG. 4A shows thenon-magnetic substrate 400 on top of which is spun a layer of resist 410. An e beam writer projectedelectron beams 420 to pattern the resist and substrate. -
FIG. 4B shows for illustrative purposes only an example of a lower dot density precursor guiding pattern of one embodiment. Thesubstrate 410 has a low domaindot density pattern 430 created by the e beam writer. The low domaindot density pattern 430 on thesubstrate 410 forms a lower dot densityprecursor guiding pattern 440. The low densityprecursor guiding pattern 440 density can be for example 250 Gdpsi. -
FIG. 4C shows for illustrative purposes only an example of a density multiplicative guided self assembly process of one embodiment. On top of the low densityprecursor guiding pattern 440 is sputtered 450 aclear plastic 410 such as a copolymer for example Polymethyl Methacrylate. Theclear plastic 410 chemically treats the dots of the low densityprecursor guiding pattern 440. The density multiplicative guided self assembly process doubles the dots in both directions in a hex pattern. The chemically treated dots and structure are baked and the clear plastic is lifted off to reveal the higher density of dots. The multiplicative process such as diblock copolymer doubles the number of dots in both 90 degree directions thereby quadrupling of the density. -
FIG. 4D shows for illustrative purposes only an example of a primary imprint template of one embodiment. The results of the guided process using the low dot densityprecursor guiding pattern 440 ofFIG. 4B creates a pattern withhigher density 460. The pattern withhigher density 460 forms aprimary imprint template 470 with a domain dot density for example 1,000 Gdpsi or 1 Tdpsi of one embodiment. -
FIG. 5A shows for illustrative purposes only an example of a quartz wafer of one embodiment.FIG. 5A shows the creation of the separatesecondary master template 140. The substrate is aclear quartz wafer 500. Fluid resist 510 is applied over the entire surface of theclear quartz wafer 500. -
FIG. 5B shows for illustrative purposes only an example of a servo pattern of one embodiment.FIG. 5B shows an e beam writer projectingelectron beams 520 by following theservo pattern 530. The EBW directsbeams 520 in the areas outside of theservo pattern 530 to harden the fluid resist 510 on theclear quartz wafer 500 where wanted according to theservo pattern 530 used to guide the EBW. -
FIG. 5C shows for illustrative purposes only an example of fluid resist removal of one embodiment. The resist 510 in the areas inside theservo pattern 530 is still fluid on theclear quartz wafer 500. The fluid resist 510 is removed with a cleaning process that washes away the still fluid resist 510. This leaves the surface of theclear quartz wafer 500 uncovered in the non hardened resistareas 540. -
FIG. 5D shows for illustrative purposes only an example of etching a quartz wafer of one embodiment.FIG. 5D shows the resist 510 was removed from the non hardened resistareas 540 of theclear quartz wafer 500. The surface of theclear quartz wafer 500 is etched 550 removing a portion of the quartz material inside theservo pattern 530 areas. -
FIG. 5E shows for illustrative purposes only an example of a secondary master template of one embodiment.FIG. 5E shows the hardened resist 510 is removed. This leaves topography of lower etched 550 servo pattern island areas and raised areas on theclear quartz wafer 500 surfaces of thesecondary master template 140 in the servo sectors. The secondary master template is inverted to use in a servo overlay process of one embodiment. -
FIG. 6A shows for illustrative purposes only an example of a primary imprint template of one embodiment. Theservo overlay process 150 ofFIG. 1 begins with aprimary imprint template 600. Theprimary imprint template 600 has a high domain dot density such as 1 Tdpsi. -
FIG. 6B shows for illustrative purposes only an example of an overlay resist layer of one embodiment. On top of theprimary imprint template 600 is spun an overlay resistlayer 610. The overlay resistlayer 610 is spun with sufficient volume to fill the etched areas of asecondary master template 140 ofFIG. 1 . -
FIG. 6C shows for illustrative purposes only an example of a servo overlay process of one embodiment. Set into the overlay resistlayer 610 spun on top of theprimary imprint template 600 is thesecondary master template 140. Thesecondary master template 140 is inverted to create a mirrored image of theservo patterns 620 etched into the surface of theclear quartz wafer 500 surface. The fluid resist fills the etched areas by capillary action. The resist pressed by the bottom surface of thesecondary master template 140 forms athin film 640.FIG. 6C shows in the illustration the front side of theprimary imprint template 600 transparent to reveal thepillar structure 630 of the domain dots on top of thesubstrate 410. -
FIG. 6D shows for illustrative purposes only an example of a quartz wafer of one embodiment. The overlay resistlayer 610 has filled the etched areas of the mirrored servo patterns. Ultra violet (UV)light 660 is projected through the back of the clear quartzsecondary master template 140 ofFIG. 1 . TheUV light 660 sets or cures the resist forming a hard resist layer with the mirrored topography of thesecondary master template 620. TheUV light 660 sets or cures the resistthin film 640 that is in contact with the surface of theprimary imprint template 600 with thepillar structure 630 of the domain dots and primary imprint template hardened resist 650 on top of thesubstrate 410. -
FIG. 6E shows for illustrative purposes only an example of a high density final template of one embodiment. Ion beam etching is used to remove the hardened overlay resistlayer 610. The Ion beam etching also removes thepillar structure 630 material that forms the domain dots under thethin film 640 of resist. The thicker raised mirrored topography of thesecondary master template 620 is not removed. The high densityfinal template 695 is used toimprint stacks 165 ofFIG. 1 of one embodiment. -
FIG. 7A shows for illustrative purposes only an example of unaligned domain dots of one embodiment.FIG. 7A shows a patternedstack servo section 700. The patternedstack servo section 700 includes the killeddots 680 with magnetic properties removed by ion beams. The patternedstack servo section 700 indicates theservo pattern boundary 670 within which there are domain dots with non-realignedmagnetic fields 690. The domain dots with non-realignedmagnetic fields 690 are characterized by magnetic properties that are cancelling each other or producing random results. The magnetic fields are realigned using a constant magnetic field as shown inFIG. 7B of one embodiment. -
FIG. 7B shows for illustrative purposes only an example of DC erasing of one embodiment.FIG. 7B shows the patternedstack servo section 700. The patternedstack servo section 700 includes the killeddots 680 with magnetic properties removed by ion beams. The patternedstack servo section 700 indicates theservo pattern boundary 670 within which there are pillar structured domain dots. The patternedstack servo section 700 is placed in a constant magnetic field such as DC erasing 710. The domain dots with non-realignedmagnetic fields 690 ofFIG. 7A are effected by the constant magnet field and the magnetic properties are realigned in one direction and restore clear magnetic responses. The domain dots with magnetic fields realigned 730 then have magnetic properties that can be used for read write operations. This process produces a DC erased patternedstack servo section 720. The DC erased patternedstack servo section 720 realignment is produced on the entire stack. After DC erasing 710 the stack for example a bit-patterned media can be placed in a hard disk drive for read write operations of one embodiment. -
FIG. 8 shows for illustrative purposes only an example of PES fields of one embodiment.FIG. 8 shows the relative position of the PES fields to the DC erased patternedstack servo section 720. During the process to create thesecondary master template 140 ofFIG. 1 the EBW the multiple PES fields are established. The PES fields are electronic device in the head. APES field A 800 is combined with aPES field B 810 set at 90 degrees fromPES field A 800 from to form aPES field pair 820. The position of thePES field pair 820 is over the DC erased patternedstack servo section 720 to register readback from positioning bursts made during read write operations of one embodiment. -
FIG. 9A shows for illustrative purposes only an example of a cross track shift increment of one embodiment.FIG. 9A shows adomain dot 900 such as those on the DC erased patternedstack servo section 720 ofFIG. 7B . Two or more sets of PES fields are defined to register the readback signals received from theservo sections 350 ofFIG. 3B . The positioning of each set of PES field pairs is shifted across atrack direction 920 using a shift distance equal to one crosstrack shift increment 910. The crosstrack shift increment 910 is adjustable and includes for example a one-quarter (¼) 919domain dot 900 diameter increment of one embodiment. -
FIG. 9B shows for illustrative purposes only an example of the incremental cross track shifting of one embodiment. The creation of thesecondary master template 140 ofFIG. 1 includes during the servo pattern designs 120 positioning using thee beam writer 204 ofFIG. 2A the positions of the PES fields are recorded. The position of the initial PESfield pair A-B 930 is the position of the servo pattern. Additional PES field pairs are shifted in the radial direction across thetrack direction 920 ofFIG. 9A by one crosstrack shift increment 910. -
FIG. 9B shows four PES field pairs PESfield pair A-B 930, PESfield pair C-D 940, PESfield pair E-F 950, and PESfield pair G-H 960. PESfield pair A-B 930 is a set of two field pairsPES field A 932 and the second set at a 90 degree orientation from the firstPES field B 934. PESfield pair A-B 930 is positioned at the initial servo pattern position. PESfield pair C-D 940 is a set of two field pairsPES field C 942 and the second set at a 90 degree orientation from the firstPES field D 944. PESfield pair C-D 940 is positioned one crosstrack shift increment 910 from PESfield pair A-B 930. PESfield pair E-F 950 is a set of two field pairsPES field E 952 and the second set at a 90 degree orientation from the firstPES field F 954. PESfield pair E-F 950 is positioned one crosstrack shift increment 910 from PESfield pair C-D 940. PESfield pair G-H 960 is a set of two field pairsPES field G 962 and the second set at a 90 degree orientation from the firstPES field H 964. PESfield pair G-H 960 is positioned one crosstrack shift increment 910 from PESfield pair E-F 950. - The initial servo pattern positioned PES field pair A-B 930 may or may not have boundaries that cross over a
domain dot 900 ofFIG. 9A . If it does it may receive partial domain dot noise. The PES field pairs positioned cross track by one crosstrack shift increment 910 may or may not receive partial domain dot noise. Minimum noise criteria is adjustable and for example evaluate partial domain dot noise that is generated by a percentage=>75% of the dot is exposed to a burst to be unacceptable or by a percentage<50% of the dot is exposed to a burst (the sweet spot) is exposed it does not register and is acceptable. The cross track shifting may allow selection of the PES field pair that records the highest signal to noise ratio indicating avoided partial domain dot noise of one embodiment. -
FIG. 10 shows for illustrative purposes only an example of servo sector reading of one embodiment.FIG. 10 shows thestack 300 patterned using the high densityfinal template 160 ofFIG. 1 and configured as a stack disk placed in thehard disk drive 170. The head of thehard disk drive 170 includes the four PES field pairs including PESfield pair A-B 930, PESfield pair C-D 940, PES field pair E-F 950 and PESfield pair G-H 960. The preamble is locked with a phase lockedloop 260 to allow synchronous decoding of the PES burst signals. The continuous servo patterning 264 process begins to read the head position using the information in theservo sectors 310 ofFIG. 3A of one embodiment. -
FIG. 11A shows for illustrative purposes only an example of partial dot noise of one embodiment. Thestack 300 ofFIG. 3A has been put into thehard disk drive 170 ofFIG. 1 . Themechanical systems 1110 in thehard disk drive 170 ofFIG. 1 reads aPES burst 1120. The head in thehard disk drive 170 serially reads the magnetic fields of the dots in the embedded servo pattern designs in the servo sectors. The magnetic fields are referred to as “servo bursts”. The dots that have been killed emit a weak magnetic field that is flipping and these create a white noise that is registered in the readback trace. Partial domain dots of crossed by the PES field boundaries increase the level of noise in addition to the white noise. The PES burst 1120 produces a position error signal (PES). The PES is received by the multiple PES field pairs 130 ofFIG. 1 . The 90 degree orientation of the PES field pair provides the trigonometric sine and cosine values of the PES. Those values are synchronously decoded and recorded in areadback trace 1112. The PES bursts cause a magnetic response in the domain dots. The PES received by aPES field pair 1100 may generate partialdomain dot noise 1130 if the boundary of the PES field pair crosses adomain dot 1140. Partialdomain dot noise 1130 may register a low signal to noise ratio on thereadback trace 1112 which may indicate a high level of partialdomain dot noise 1130. When the boundary of thePES field pair 1100 does not cross adomain dot 1160 or thePES field pair 1100 does not extend over adomain dot 1150 no partialdomain dot noise 1130 is registered. The readback trace synchronously received data is used to turn off those PES field pairs that receive low signal to noise ratios indicating partial dot erasures. -
FIG. 11B shows for illustrative purposes only an example of avoided partial dot noise of one embodiment. Themechanical systems 1110 in thehard disk drive 170 ofFIG. 1 generate aPES burst 1120. The PES burst 1120 produces a position error signal (PES). The PES is received by the multiple PES field pairs 130 ofFIG. 1 . The 90 degree orientation of the PES field pair provides the trigonometric sine and cosine values of the PES. Those values are synchronously decoded and recorded in areadback trace 1112. The PES bursts cause a magnetic response in the domain dots. - The position of the PES field pairs 1170 in
FIG. 11B has been cross track shifted by 3 units of the crosstrack shift increment 910 ofFIG. 9A . The cross track shifting has aligned the boundaries of the PES field pairs 1170 to avoid crossing adomain dot 1160. The avoidance of a partial domain dot eliminates or reduces the partialdomain dot noise 1130 ofFIG. 11A . The lower level of noise received in thereadback trace 1112 may produce the highest signal to noise ratio. The readback trace synchronously received data is used to turn off those PES field pairs that receive low signal to noise ratios indicating partial dot erasures. In the example shown inFIG. 11B the PES field pairs 1170 may not be turned off. The cross track shifting avoids partialdomain dot noise 1130 ofFIG. 11A and the PES information may provide accurate positioning of the head using the data in the servo sectors. -
FIG. 12 shows for illustrative purposes only an example of a cross track shifted PES field pairs operation of one embodiment.FIG. 12 shows for example four PES field pairs including PESfield pair A-B 930, PESfield pair C-D 940, PES field pair E-F 950 and PESfield pair G-H 960. The domain dot zones from which the PES field pair receives the PES lie along a track. PESfield pair A-B 930 is in theinitial positioning 1200. The pair boundaries cross over domain dots. The PES signals received by four PES field pairs are synchronously decoded and recorded in thereadback trace 1280. - The PES signals received by PES
field pair A-B 930 indicates increasedlevels 1202 ofpartial dot noise 1240. This may cause a low signal to noise ratio. The electronic systems in thehard disk drive 170 ofFIG. 1 may disable 1250 PESfield pair A-B 930. - PES
field pair C-D 940 is in a position that includes cross tract shift no. 1 ¼dot size 1210. This one unit of the crosstrack shift increment 910 ofFIG. 9A shift positions the boundaries so that they also cross over domain dots. The PES signals received by PESfield pair C-D 940 indicates increasedlevels 1212 ofpartial dot noise 1240. This may cause a low signal to noise ratio. The electronic systems in thehard disk drive 170 ofFIG. 1 may disable 1250 PESfield pair C-D 940. - PES
field pair E-F 950 is in a position that includes cross tract shift no. 2 ¼dot size 1220. This two unit of the crosstrack shift increment 910 ofFIG. 9A shift positions the boundaries so that they also cross over domain dots. The PES signals received by PESfield pair E-F 950 indicates increasedlevels 1222 ofpartial dot noise 1240. This may cause a low signal to noise ratio. The electronic systems in thehard disk drive 170 ofFIG. 1 may disable 1250 PESfield pair E-F 950. - PES
field pair G-H 960 is in a position that includes cross tract shift no. 3 ¼dot size 1230. This three unit of the crosstrack shift increment 910 ofFIG. 9A shift positions the boundaries so that they do not cross over domain dots. The PES signals received by PESfield pair G-H 960 indicates decreasednoise levels 1232 indicatingpartial dot noise 1240 has been avoided. This may cause a high signal to noise ratio. The electronic systems in thehard disk drive 170 ofFIG. 1 may leave enabled 1270 PESfield pair G-H 960. - The operations and results of the cross track shifting provide accurate positioning of the head using the information recorded in the
servo sectors 310 of FIG. 3A. The method for patterning a stack reduces mastering time in a cost effective manner. The time and cost saved and the increased accuracy creates increased production of quality patterned stacks. - The foregoing has described the principles, embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. The above described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.
Claims (20)
1. A method for patterning a stack, comprising:
embedding servo patterns within a final template; and
creating positions of plural cross-tracked shifted position error signal (PES) fields incrementally from the embedded servo patterns on the final template.
2. The method of claim 1 , further comprising before embedding the servo patterns within the final template, embedding the servo patterns using a secondary master template; and patterning an entire higher density primary master imprint template using a lower domain dot density precursor guiding pattern.
3. The method of claim 2 , wherein the primary master imprint template is patterned using lower domain dot density precursor guiding pattern with density multiplicatives.
4. The method of claim 3 , wherein the secondary master template servo pattern impression is mirrored onto the primary imprint template and the density multiplicatives are a diblock copolymer guided self-assembly process.
5. The method of claim 1 , wherein the cross-tracked shifted PES fields have incremental shifts of multiple PES fields that are used to read PES signals to avoid partial domain dot erasures.
6. The method of claim 5 , further comprising disabling a PES field pair using a detection of partial dot noise recorded on a readback trace.
7. The method of claim 1 , wherein the PES field are created using cross track shifting to determine PES field pair positions producing a highest signal to noise ratio.
8. The method of claim 7 , wherein a number of multiple position error signal bursts are adjustable based on a coarseness of the servo patterns and a size of domain dots.
9. The method of claim 7 , wherein the PES fields are configured as a set of PES fields oriented 90 degrees to one another in a cross track direction.
10. The method of claim 1 , wherein the master template is used as a stencil to embed servo patterns on a final master imprint template to make bit-patterned stacks.
11. An apparatus, comprising:
means for setting PES field pairs positions shifts incrementally to control positioning changes; and
means for shifting the PES field pairs positions using the incremental shift value to avoid partial domain dot erasures.
12. The apparatus of 11, further comprising means for adjusting the incremental shift value equal to ¼ domain dot to refine positioning shifts.
13. The apparatus of 11, further comprising means for adjusting a direction of the incremental shifts to include cross tracks that are parallel to tracks.
14. The apparatus of 11, further comprising means for changing the positioning of the PES field pairs incrementally to avoid partial domain dot erasures that do not fall on any track boundary.
15. The apparatus of 11, further comprising means for repeating the cross track shifting of the PES field pairs to any number of pairs.
16. The apparatus of 11, further comprising means for embedding the servo patterns into a high density final template to be used as a stencil to embed servo patterns to make bit-patterned stacks or media.
17. A template, comprising:
a lower density precursor template;
a high density template;
one or more embedded servo patterns; and
a separate secondary master template, wherein the separate secondary master template is configured to create the one or more embedded servo patterns to combine with the high density template and wherein the lower density precursor template is configured to create a primary imprint template to form a high density final template for use in making bit-patterned stacks.
18. The template of claim 17 , wherein the primary imprint template is configured to reduce mastering time using the lower domain dot density template.
19. The template of claim 17 , wherein one or more servo patterns are embedded within the high density final template using a secondary master template with mirrored servo patterns.
20. The final template of claim 17 , wherein the one or more embedded servo patterns within the high density final template are read using cross track shifted PES fields to avoid partial dot erasures and to produce the highest signal to noise ratio.
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US13/097,841 US20120273999A1 (en) | 2011-04-29 | 2011-04-29 | Method for patterning a stack |
US14/699,412 US9905259B2 (en) | 2011-04-29 | 2015-04-29 | Imprint template and methods thereof |
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US13/097,841 US20120273999A1 (en) | 2011-04-29 | 2011-04-29 | Method for patterning a stack |
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US13/097,841 Abandoned US20120273999A1 (en) | 2011-04-29 | 2011-04-29 | Method for patterning a stack |
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US20150302881A1 (en) | 2015-10-22 |
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