Abstract:
Provided herein are methods for depositing a spin-on-glass composition over an imprinted resist; curing the spin-on-glass composition to form a cured spin-on-glass composition; and forming a patterned mask by etching the cured spin-on-glass composition, the resist, and an underlying mask composition, wherein the patterned mask comprises features of the cured spin-on-glass composition atop the mask composition, and wherein curing the spin-on-glass composition is configured to prevent shifting or toppling of the spin-on glass composition from atop the mask composition while forming the patterned mask.

Description:
CROSS-REFERENCE 
       [0001]    This application is a division of U.S. patent application Ser. No. 13/798,130, filed Mar. 13, 2013, which claims the benefit of U.S. Provisional Patent Application 61/672,271 filed Jul. 16, 2012. 
     
    
     BACKGROUND 
       [0002]    Imprint resists are mainly designed to optimize their feature filling and release properties; they usually do not provide sufficient mechanical stability and etch resistance. 
     
    
     
       DRAWINGS 
         [0003]      FIG. 1  shows a block diagram of an overview of an electron curing reverse-tone process of one embodiment. 
           [0004]      FIG. 2  shows a block diagram of an overview flow chart of an electron curing reverse-tone process of one embodiment. 
           [0005]      FIG. 3  shows a block diagram of an overview flow chart of a continuation of an electron curing reverse-tone process of one embodiment. 
           [0006]      FIG. 4  shows a block diagram of an overview flow chart of a second continuation of an electron curing reverse-tone process of one embodiment. 
           [0007]      FIG. 5A  shows for illustrative purposes only an example of spin coating an etch-resistant layer of one embodiment. 
           [0008]      FIG. 58  shows for illustrative purposes only an example of electron beam curing of etch-resistant material of one embodiment. 
           [0009]      FIG. 6A  shows for illustrative purposes only an example of resist layer imprinted pattern of one embodiment. 
           [0010]      FIG. 6B  shows for illustrative purposes only an example of 2-step reverse-tone etching process of one embodiment. 
           [0011]      FIG. 6C  shows for illustrative purposes only an example of an electron beam cured hard mask patterned template of one embodiment. 
           [0012]      FIG. 7A  shows for illustrative purposes only an example of etch-resistant layer filled imprinted pattern features of one embodiment. 
           [0013]      FIG. 7B  shows for illustrative purposes only an example of electron beam curing of one embodiment. 
           [0014]      FIG. 8  shows for illustrative purposes only an example of a cured structurally transformed etch-resistant layer material molecule of one embodiment. 
           [0015]      FIG. 9  shows for illustrative purposes only an example of coercivity and signal amplitude vs. magnetic diameter advantages of the electron curing reverse-tone process of one embodiment. 
           [0016]      FIG. 10A  shows for illustrative purposes only an example of a controlled predetermined voltage and dose determination method of one embodiment. 
           [0017]      FIG. 10B  shows for illustrative purposes only an example of a statistical size and placement distribution quality analysis of one embodiment. 
           [0018]      FIG. 11  shows for illustrative purposes only an example of feature size distribution of one embodiment. 
           [0019]      FIG. 12  shows for illustrative purposes only an example of evaluating reverse tone electron beam curing feature placement of one embodiment. 
           [0020]      FIG. 13  shows for illustrative purposes only an example of a placement distribution function of one embodiment. 
           [0021]      FIG. 14  shows for illustrative purposes only an example of a placement error grid of one embodiment. 
           [0022]      FIG. 15  shows for illustrative purposes only an example of placement evaluation of one embodiment. 
           [0023]      FIG. 16  shows for illustrative purposes only an example of plotted placement regularity numbers of one embodiment. 
       
    
    
     DESCRIPTION 
       [0024]    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 present invention. 
       General Overview: 
       [0025]    It should be noted that the descriptions that follow, for example, in terms of an electron curing a reverse-tone process is described for illustrative purposes and the underlying system may apply to any number and multiple types of reverse-tone processes. 
         [0026]    In an embodiment the fabrication of BPM pattern at various densities including 250 Gb/in 2 , 450 Gb/in 2 , 500 Gb/in 2 , 1 Tb/in 2 , 1.5 Tb/in 2  and 2 Tb/in 2  to 5 Tb/in 2  uses a “reverse-tone” process including a wet reverse-tone process, in which a silicon-rich, etch-resistant material (such as HSQ) is deposited including spin-coated on a resist pattern and then etched back through multi-step reactive ion etching (RIE) to form a negative tone replica of the original. 
         [0027]    In some embodiments increasing areal density may cause narrowing of the process window feature mechanical instability during etch-back may increase dot placement error (the “shifting dots” problem), insufficient etch resistance, and non-homogeneity of resist material at this scale degrades the dot size uniformity. 
         [0028]      FIG. 1  shows a block diagram of an overview of an electron curing reverse-tone process of one embodiment.  FIG. 1  shows an electron curing reverse-tone process  100  which begins with a process for example spin-coating an etch-resistant layer on an imprinted resist pattern fabricated on a hard mask layer of a substrate  105 . 
         [0029]    The etch-resistant layer covers and fills the pattern features of the imprinted resist pattern. A controlled electron beam dose is used for curing the etch-resistant layer using a controlled electron beam dose  110  that structurally transforms the etch-resistant layer material. The curing may be done alternatively before or after the spin on glass (SOG) etch-back, the two alternatives lead to different characteristics in the results, but both increase the pattern quality. The electron beam curing structural transformation is creating mechanical stability and reducing drift of etch area and pattern feature position when etching the hard mask material  120 . Etching the hard mask material is achieved using a 2-step reverse-tone etching process  130 . A first predefined etch performs an etch-back of the electron beam cured etch-resistant layer to expose the imprinted resist pattern. 
         [0030]    A second predefined etch is used for removing the imprinted resist and etching a pattern into the hard mask layer down to the substrate  140 . The second predefined etch removes the imprinted resist pattern and forms a negative tone replica of the original pattern. The remaining electron beam cured etch-resistant layer can be removed creating a hard mask patterned template used for replicating semiconductors and stacks including high density bit patterned media (BPM)  150 . The removal of the electron beam cured etch-resistant layer includes using a wet-chemical process such as sodium hydroxide (NaOH). Alternatively the remaining HSQ itself is used as part of the mask for the etching of the underlying stack or semiconductor. Replicating stacks including high density bit patterned media (BPM) includes using the mask for etching of magnetic layers of stacks by ion beam etching. 
       Detailed Description: 
     Controlled Electron Beam Curing Process: 
       [0031]      FIG. 2  shows a block diagram of an overview flow chart of an electron curing reverse-tone process of one embodiment.  FIG. 2  shows a substrate with a hard mask layer deposited thereon  200 . A resist layer with imprinted pattern  210  is fabricated on the hard mask layer, established for example by an ultraviolet (UV)-imprint process. A process may be used to descum the imprinted resist layer  220  to reduce the residual resist layer. The descum process removes a portion of the resist material exposing the hard mask layer between pattern features. Alternatively in one embodiment the imprinted resist layer is not descummed to avoid any potential alterations in the imprinted pattern. An etch- resistant layer  230  including hydrogen silsesquioxane (HSQ)  235  is deposited including spin-coated on the imprinted resist pattern  240 . 
         [0032]    An apparatus is used to cure the etch-resistant layer using electron beam dose  250  which is controlled to create mechanical stability  252  in the etch-resistant layer. The mechanical stability will reduce drift of etch area and pattern feature position  256 . The electron beam curing dose is controlled to a predetermined voltage and dose  270  to achieve electron beam curing  260  of the etch-resistant layer material. The predetermined voltage  303  of  FIG. 3  may include electron beam irradiated at an acceleration voltage. The acceleration voltage affects electron penetration depth. The sample structure in part is used in the determination of the predetermined voltage including acceleration voltages of several hundred volts, 2 kV, 3 kV, 10, 20, 50 and 100 kV. The electron beam curing may cause the hydrogen silsesquioxane (HSQ) to change from the “cage” structure to a cross-linked “network” structure, shrinks its volume and may increase its density, resulting in a HSQ film of higher etch resistance and better homogeneity. Description of the processing continues in  FIG. 3 . 
       First Predefined Etch: 
       [0033]      FIG. 3  shows a block diagram of an overview flow chart of a continuation of an electron curing reverse-tone process of one embodiment.  FIG. 3  shows a description processes the continue from  FIG. 2  including the controlled electron beam irradiation  300  including thermal, ion beam, electron beam, x-ray, photon, ultraviolet (UV), deep ultraviolet (DUV), vacuum ultraviolet (VUV), plasma, microwave, or other types of irradiation  305 . 
         [0034]    The controlled electron beam dose uses a predetermined voltage  303  for an acceleration voltage. The electron beam irradiation  300  is used to structurally transform etch-resistant layer material  310  which reduces volume  312 , increases refractive index N  314  and increases densification  316 . 
         [0035]    In one embodiment curing the etch-resistant layer  320  is performed on the etch-resistant layer  350 . The electron beam irradiation step is added before a reverse-tone process including a 2-step etch-back and etching. The curing may increase the mechanical stability of the HSQ features during the 2-step reverse-tone processing, thus greatly alleviating the “shifting dots” problem. When the e-beam treatment is performed before the HSQ etch-back, the process tends to produce features with bigger size. 
         [0036]    After curing the etch-resistant layer  320  a 2-step reverse-tone etching process  330  is used to etch the hard mask material. A first predefined etch  340  including reactive ion etching (RIE)  342  using tetrafluoromethane (CF 4 )  346  is used to etch-back cured etch-resistant layer  360 . This embodiment continues as described in  FIG. 4 . 
         [0037]    In another embodiment before the electron beam curing process the first predefined etch  340  is used to etch-back the uncured etch-resistant layer  355 . 
         [0038]    The electron beam curing  260  of  FIG. 2  is used for curing the etch-resistant layer  320  in the etched back etch-resistant layer  380 . The 2-step reverse-tone etching process  330  continues as described in  FIG. 4 . 
       Second Predefined Etch: 
       [0039]      FIG. 4  shows a block diagram of an overview flow chart of a second continuation of an electron curing reverse-tone process of one embodiment.  FIG. 4  shows subsequent processing continuing from  FIG. 3 . The two embodiments of the electron curing reverse-tone process  100  processing up to this point both produce electron beam cured and etched back etch-resistant layer  400 . The 2-step reverse-tone etching process  330  of  FIG. 3  continues with a second predefined etch  410  including reactive ion etching (RIE)  412  using oxygen gas (O 2 )  416 . 
         [0040]    The second predefined etch  410  performs an etch of a hard mask layer  430  and removes the imprinted resist layer  435 . This process is etching a pattern down to the substrate  440 . The electron beam cured and etched back etch-resistant layer reduces pattern feature placement drift errors  442  and increases pattern feature size uniformity  446 . The remaining HSQ itself can be used as part of the mask for the etching of the underlying stack or semiconductor. The second predefined etch  410  can alternatively be followed by a stripping process to remove the etched back etch-resistant layer  450  and forming a negative tone replica of the original pattern. 
         [0041]    The etched hard mask including a carbon hard mask layer and alternatively including the etched back electron beam cured etch-resistant layer create a hard mask patterned template  460 . In one embodiment subsequent processes include a substrate ion milled using patterned hard mask  465  for patterning of the substrate including a BPM magnetic stack. The resulting hard mask patterned template  460  may be used for subsequent replication of high-density (&gt;1 Tb/in t ) patterned media. BPM replicated using the hard mask patterned template produced by the electron curing reverse-tone process  100  may have 1.5 Tb/in 2  density, corresponding to a minimum dot-to-dot distance of 22.1 nm. The electron curing reverse-tone process  100  increases the quality of the replicated BPM pattern at &gt;1 Tb/in 2  density, producing arrays with markedly increased dot size at a minimum dot-to-dot distance of 22.1 nm. The hard mask patterned template  460  with reduced pattern feature placement drift errors and increased pattern feature size uniformity is used for replicating semiconductors  470  and used for replicating stacks  480  including high density bit patterned media (BPM)  490 . The electron curing reverse-tone process  100  creates the advantages of placement accuracy and size uniformity thereby increasing the replicated quality of semiconductors and stacks. 
         [0042]    Spin coating an etch-resistant layer: 
         [0043]      FIG. 5A  shows for illustrative purposes only an example of spin coating an etch-resistant layer of one embodiment.  FIG. 5A  shows a substrate  500  with a hard mask layer  510  deposited thereon. The substrate  500  includes magnetic layers of a stack including a bit patterned media (BPM). An imprinted resist layer  520  on the hard mask layer  510  includes an array of one or more imprinted resist pattern feature  528  created using the imprinted pattern  530 . Alternatively in one embodiment the imprinted resist layer is not descummed to avoid any potential alterations in the imprinted pattern and an etch-resistant material is deposited onto the resist pattern  540 . The etch-resistant material deposition includes spin coating. 
         [0044]    A descum process  534  is used to descum the imprinted resist layer  532 . The descum process  534  removes excess resist material from each pattern feature  538  and exposes portions of the hard mask layer  510 . An etch-resistant material is deposited onto the resist pattern  540 . An etch-resistant layer material  545  including hydrogen silsesquioxane (HSQ)  235  of  FIG. 2  is used to develop mechanical stability and to reduce pattern feature placement drift error and increase pattern feature size uniformity when cured using a controlled dose of electron beams. Each pattern feature  538  is filled by the etch-resistant layer material  545  and which covers the exposed portions of the hard mask layer  510 .  FIG. 58  describes other processes that follow. 
       Electron Beam Curing: 
       [0045]      FIG. 58  shows for illustrative purposes only an example of electron beam curing of etch-resistant material of one embodiment.  FIG. 5B  shows a continuation of processing from  FIG. 5A .  FIG. 5B  shows the substrate  500 , hard mask layer  510  and examples of the pattern feature  538 . An electron beam curing of etch-resistant material  550  is performed using a controlled electron beam dose  555 . The controlled electron beam dose  555  projects electron beams which flood the etch-resistant layer material  545 . The controlled electron beam dose  555  structurally transforms the molecules of the etch-resistant layer material  545  to create mechanical stability. 
         [0046]    The 2-step reverse-tone etching process  330  of  FIG. 3  uses the first predefined etch  340  of  FIG. 3  including a reactive ion etching using CF 4    565 . The reactive ion etching using CF 4    565  is used to etch back electron beam cured etch-resistant material  560 . The first predefined etch  340  of  FIG. 3  creates etched back cured etch-resistant material  575 . 
         [0047]    The second predefined etch  410  of  FIG. 4  of the 2-step reverse-tone etching process  330  of  FIG. 3  including the reactive ion etching using O 2    585  is used to etch a hard mask pattern  580 . The reactive ion etching using O 2    585  removes the resist material and etches into the hard mask layer  510  down to the substrate  500 . Imprint resist is not etch resistant and may not serve as a good mask for some processes. However, it is easier to imprint holes in imprint resist than making resist pillars by the imprint process. A “reverse-tone” process instead of directly using the imprinted resist pattern as a etch mask uses the etch resistance material for example HSQ material to create the mask. The etched back cured etch-resistant material  575  is used to increase pattern feature placement accuracy and size uniformity. The second predefined etch  410  of  FIG. 4  produces a patterned hard mask layer  595 . The etched etch-resistant material  590  is removed using for example a wet-chemical etch including a NaOH solution process and reveals the patterned hard mask layer  595  on the substrate  500 . The removal the etched etch-resistant material  590  for example HSQ prior to IBE of for example the magnetic stacks may tend to re-deposit the HSQ on the final product during IBE, leaving a layer of unwanted coating. 
         [0048]    Alternatively the etched etch-resistant material  590  removal process is not included where by the remaining etch-resistant material  590  for example HSQ is used as part of the mask as well. A subsequent process including using a RIE process is used to transfer the pattern into an underlying Si substrate followed by a process to remove the HSQ/carbon mask stack. The patterned hard mask layer  595  on the substrate  500  creates a hard mask patterned template  598 . The hard mask patterned template  598  is used for used for replicating semiconductors and stacks including high density bit patterned media (BPM). 
       Resist Layer Imprinted Pattern: 
       [0049]      FIG. 6A  shows for illustrative purposes only an example of resist layer imprinted pattern of one embodiment.  FIG. 6A  shows the substrate  500 , deposited hard mask layer  510  and imprinted resist layer  520 . The imprinted pattern  530  creates each imprinted resist pattern feature  528 . The descum process  534  is used to descum the imprinted resist layer  532 . The descum process  534  removes excess resist from the pattern feature  538  and removes resist down to the hard mask layer  510 . Alternatively in one embodiment the imprinted resist layer is not descummed to avoid any potential alterations in the imprinted pattern. Processing continues wherein etch-resistant material is deposited onto the resist pattern  540 . The etch-resistant layer material  545  covers any exposed surface of the hard mask layer  510  and fills each pattern feature  538 . Descriptions of continuing processes are shown in  FIG. 6B . 
       2-Step Reverse-Tone Etching Process: 
       [0050]      FIG. 6B  shows for illustrative purposes only an example of 2-step reverse-tone etching process of one embodiment.  FIG. 6B  shows processes continuing from  FIG. 6A .  FIG. 6B  shows another embodiment of the electron curing reverse-tone process  100 . The substrate  500  has the deposited hard mask layer  510  upon which are the uncured etch resistant material and descummed patterned resist. 
         [0051]    In this embodiment the 2-step reverse-tone etching process  330  of  FIG. 3  uses the first predefined etch  340  of  FIG. 3  before the electron beam curing process. The first predefined etch  340  of  FIG. 3  includes the reactive ion etching using CF 4    565  used to process an etch-back of the uncured etch-resistant material  600 . The reactive ion etching using CF 4    565  produces etched back uncured etch-resistant material  620 . 
         [0052]    The controlled electron beam dose  555  is used for electron beam curing of etched back etch-resistant material  630 . The electron beam curing process results in etched back cured etch-resistant material  575 . The etched back cured etch-resistant material  575  has structurally transformed molecules with increased mechanical stability. Descriptions of subsequent processes are shown in  FIG. 6C . 
       Hard Mask Patterned Template: 
       [0053]      FIG. 6C  shows for illustrative purposes only an example of an electron beam cured hard mask patterned template of one embodiment. In this embodiment the 2-step reverse-tone etching process  330  of  FIG. 3  includes using the second predefined etch  410  of  FIG. 4  including the reactive ion etching using O 2    585  after the electron beam curing process. The reactive ion etching using O 2    585  is used to etch a hard mask pattern  580  down to the substrate  500 . The reactive ion etching using O 2    585  removes the imprinted resist layer. The reactive ion etching using O 2    585  produces a patterned hard mask layer  595 . The etched etch-resistant material  590  is used to increase pattern feature placement accuracy and size uniformity. 
         [0054]    Following the reactive ion etching using O 2    585 , an alternative stripping process is used to remove the etched etch-resistant material  587  including a NaOH solution wet-chemical etch  588  removes the etched etch-resistant material  590 . In the alternate the remaining HSQ itself is used as part of the mask for the etching of the underlying stack or semiconductor. The patterned hard mask layer  595  on the substrate  500  creates the hard mask patterned template  598  used for replicating semiconductors  470  of  FIG. 4  and used for replicating stacks  480  of  FIG. 4  including high density bit patterned media (BPM)  490  of  FIG. 4 . 
       Etch-Resistant Layer Filled Imprinted Pattern Features: 
       [0055]      FIG. 7A  shows for illustrative purposes only an example of etch-resistant layer filled imprinted pattern features of one embodiment.  FIG. 7A  shows the substrate  500  with the hard mask layer  510  deposited thereon. The resist layer with imprinted pattern  210  includes multiples of an imprinted pattern feature  705  which in this example is an inverted tapered pillar. The etch-resistant layer  230  spin coated on the imprinted resist covers the resist material. The etch-resistant material including HSQ of an etch-resistant layer fills each imprinted pattern feature  700  of one embodiment. 
       Electron Beam Curing: 
       [0056]      FIG. 7B  shows for illustrative purposes only an example of electron beam curing of one embodiment.  FIG. 7B  shows the substrate  500  with the hard mask layer  510  deposited thereon. An example of an imprinted pattern feature  705  is shown through the etch-resistant layer  230  including HSQ is shown as transparent for ease of viewing. The etch-resistant material has filled each imprinted pattern feature  705  embedding the etch-resistant material in the resist matrix. 
         [0057]    A controlled electron beam emitting apparatus  710  is used to produce for example flooding electron beams  720  into the etch-resistant layer  230 . The flooding electron beams  720  diffuse as they penetrate the etch-resistant material. The controlled electron beam emitting apparatus  710  regulates the strength of the emitted electron beams using a predetermined voltage and dose. The predetermined voltage is controlled to enable the flooding electron beams  720  to saturate the volume and depth of the etch-resistant layer  230  thus curing the etch-resistant materials to structurally transform the molecules of the etch-resistant layer  230 . 
         [0058]    The etch-resistant layer  230  using HSQ is structurally transformed at a curing dose including ˜1000 μC/cm 2  to 50,000 μC/cm 2 . The process affected by the changes in HSQ properties includes the toppling and shifting in HSQ pillars and the strength and adhesion may help the pillars stand including stress vs. strength, and material failure. The molecular structural transformation reduces volume  312  of  FIG. 3 , increases refractive index n  314  of  FIG. 3  and increases densification  316  of  FIG. 3  of the etch-resistant layer  230 . The transformed electron beam cured etch-resistant layer  230  has increased mechanical stability. Etching through the cured etch-resistant layer  230  produces reduced pattern feature placement drift error and increased pattern feature size uniformity. 
         [0059]    Electron beam curing structural transformation: 
         [0060]      FIG. 8  shows for illustrative purposes only an example of a cured structurally transformed etch-resistant layer material molecule of one embodiment.  FIG. 8  shows controlled electron beam dose  555  of  FIG. 5B  produces electron beam curing  260  directed into an uncured etch-resistant layer material molecule  810 . An uncured etch-resistant layer material molecule of a silicon-rich, etch-resistant material including HSQ has a “cage” or cubic structure. The organic resist material is already cross-linked during the UV-imprint process. The electron beam has effects on the imprint resist as well. If electron-beam exposure is done on a UV-cured imprint resist film only, the resist seems first to turn more carbon-like (with increased refractive index and reduced thickness). At very high electron beam doses, the resist film starts to disappear. However, these effects do not render the cured HSQ 2-step reverse-tone process un-workable. The molecule has silicon (Si) atoms at each corner which are linked by oxygen (O) atoms. A hydrogen (H) atom is attached to each silicon (Si) atom adding to the volume of the molecule. 
         [0061]    Each cured structurally transformed etch-resistant layer material molecule  820  has a cross-linked “network” structure caused by an atomic redistribution reaction. The etch-resistant layer  545  using for example HSQ is structurally transformed at a curing dose of for an example in ranges from 1,000 μC/cm 2  to 50,000 μC/cm 2 . The electron beam curing structural transformation shrinks the molecule&#39;s volume and increases its density resulting in increased etch resistance. The electron beam curing increased etch resistance creates mechanical stability preventing pattern feature shifts in position and size degradations during etching. This advantage of electron beam curing produces replications of pattern feature arrays with markedly increased placement accuracy and size uniformity increasing the quality of replications for example semiconductors and stacks including BPM patterned at &gt;1 Tb/in 2  density. 
         [0000]    Coercivity and Signal Amplitude vs. Magnetic Diameter: 
         [0062]      FIG. 9  shows for illustrative purposes only an example of coercivity and signal amplitude vs. magnetic diameter advantages of the electron curing reverse-tone process of one embodiment.  FIG. 9  shows a chart plotting the coercivity and signal amplitude vs. magnetic diameter  900 . The chart shows that signal amplitude increases  910  and coercivity decreases  920  as the magnetic diameter [nm]  930  increases. The electron curing reverse-tone process  100  reduces pattern feature placement drift errors  442  of  FIG. 4  and increases pattern feature size uniformity  446  of  FIG. 4 . 
         [0063]    The electron beam curing dose is controlled to a predetermined voltage and dose  270  of  FIG. 2  of the electron beams to regulate voltage and dose duration based on type and thicknesses of imprinted resist materials, etch-resistant materials, hard mask layer and substrate. The reduced pattern feature placement drift errors and increased pattern feature size uniformity enables the magnetic diameter [nm]  930  of the pattern features to be optimized, including the maximized magnetic diameter [nm]  930  that produces the least coercivity and most signal amplitude of the substrate magnetic features etched using the hard mask patterned template  460  of  FIG. 4 . The pattern features size uniformity narrows magnetic dots switching field distribution and the pattern features placement accuracy reduces “jitter” during signal read-back. 
       Predetermined Voltage and Dose: 
       [0064]      FIG. 10A  shows for illustrative purposes only an example of a controlled predetermined voltage and dose determination method of one embodiment.  FIG. 10A  shows the electron beam curing  260  is controlled to a predetermined voltage and dose  270 . Controlled voltage and dose are determined by evaluating reverse tone features quality  1000  assures the quality of the products produced. A method for evaluating reverse tone features quality  1010  is used to predetermine the voltage and dose used in the electron beam curing  260 . The evaluation method uses analysis of electron beam curing  260  product results, for example bit-patterned media (BPM), where statistics can be obtained  1012 . 
         [0065]    A statistical size and placement distribution quality analysis  1014  is performed for each statistical analysis reference group  1016 . The statistical analysis reference group  1016  includes targeted pattern features and density  1018 , hard mask and substrate layer materials used  1020  and electron beam voltage and dose settings  1022 . The quality of the size of the pattern features and placement of the patterned features are analyzed. Patterned features size and placement errors from reverse tone process can be separated  1024 . The statistical size and placement distribution analysis  1014  is programmed to evaluate the size and placement decoupled  1026 . One evaluation is a reverse tone feature size analysis  1030  which is described further in  FIG. 10B . The other evaluation is a reverse tone feature placement analysis algorithm  1050  described further in  FIG. 108  of one embodiment. 
       Size and Placement Distribution Analysis: 
       [0066]      FIG. 10B  shows for illustrative purposes only an example of a statistical size and placement distribution quality analysis of one embodiment.  FIG. 10B  shows the continuation of the descriptions of the statistical size and placement distribution quality analysis  1014  of  FIG. 10A . The reverse tone feature size analysis  1030  of  FIG. 10A  includes a mean binary (M B ) size distribution function  1032 . A calculation of distribution function M B    1034  used in a size evaluation  1040 . The size evaluation  1040  is used in the assessment of the targeted pattern features and density  1018  of  FIG. 10A  quality achieved for the electron beam voltage and dose settings  1022  of  FIG. 10A  used on the etch-resistant materials. 
         [0067]      FIG. 10B  shows a description of the reverse tone feature placement analysis algorithm  1050  of  FIG. 10A  which develops one number to describe placement error  1052 . The one number to describe placement error  1052  is arrived using a mean probability (m p ) distribution function  1054 . A calculation of distribution function m p    1056  is programmed wherein random domain templates can be used  1062  with no need to pre-determine the grid  1060 . The result of the calculation of distribution function m p    1056  quantifies feature placement regularity described by a single parameter  1064 . The feature placement regularity described by a single parameter  1064  is used in a placement evaluation  1070  to assess of the quality of the targeted pattern features and density  1018  of  FIG. 10A  reached for the electron beam voltage and dose settings  1022  of  FIG. 10A  used on the etch-resistant materials. The joint results of the size evaluation  1030  and placement evaluation  1070  are used to determine voltage and dose resulting in targeted reverse tone features quality  1080  of one embodiment. 
       Feature Size Distribution: 
       [0068]      FIG. 11  shows for illustrative purposes only an example of feature size distribution of one embodiment.  FIG. 11  shows the reverse tone feature size analysis  1030  which uses a sample image for each statistical analysis reference group  1100  electron beam curing process result obtained using a scanning electron microscope (SEM) of one embodiment. 
         [0069]    The data collected in the histogram  1110  is an analysis of the brightness of all the pixels in the original SEM image of the features for example dots. The histogram  1110  distribution (horizontal axis) is from 0 to 255 to correspond to a gray scale for example a 256-level brightness. The histogram  1110  distribution (horizontal axis) is used to set the brightness “threshold” to turn the original gray-scale (0-255) image into a binary image ( 0  and  1 ) that is used to determine a size (brightness) threshold  1120 . The threshold  1120  is used as a filter to create binary  1130  feature size data from the SEM  1105 . The binary  1130  is used to create M B    1140  a binary representation of the SEM  1105 . The M B    1140  is a filtered and “smoothened” version of the binary  1130  through several image processing operations to make the size calculation more stable. In binary  1130  there are smaller dots near the large dots, these small dots may be interpreted by computer as individual dots, that&#39;s why filtering is applied to “smoothen” the binary  1130  image. The M B    1140  data is shown as a size distribution  1150  which is compared to a targeted size quality  1160  as a basis for a size evaluation of one embodiment. 
       Feature Placement Evaluation: 
       [0070]      FIG. 12  shows for illustrative purposes only an example of evaluating reverse tone electron beam curing feature placement of one embodiment. The placement of the features can affect for example ultimate read/write functioning quality of the features in for example BPM.  FIG. 12  shows algorithm step 1  1200  used in analyzing feature placement  1210  in the reverse tone feature placement analysis algorithm  1050  of  FIG. 10A . The M B    1140  is used to create M  1230  where M is the same size as the image M B    1240 . M  1230  includes points where the points represent (x i , y i ) and (x i , y i ) is the center of a feature, i=1, N  1250 . The analysis of M  1230  includes M(x,y)=1 if (x,y)=(x i ,y i ), i=1, 2, . . . N and 0 everywhere else  1260 . Additional descriptions of the evaluation follow in  FIG. 13  of one embodiment. 
       Placement Distribution Function: 
       [0071]      FIG. 13  shows for illustrative purposes only an example of a placement distribution function of one embodiment.  FIG. 13  shows the continuation of the process from  FIG. 12 . An algorithm step 3  1300  is used to perform a distribution function  1310 . M  1230  has in window m i    1325  showing the random domain area used in this distribution function  1310 . An enlargement of m i    1325  is shown in m i  feature placements  1330 . Included in the m i  feature placements  1330  is (x i , y i )  1335  which equals m i    1325  center point coordinates. The collection of coordinate points is shown in m p  placement data  1340 . A calculation distribution function m p    1350  wherein m p  is analogous to a wave function Ψ (x,y) (in quantum mechanics)  1352 . An m p  value is the probability of finding a neighboring feature  1354  for the targeted pattern features and density  1018  of  FIG. 10A . A distribution function: m p =m i /N  1360  includes a value for N: total number of features  1362  and where m i  M, centered at (x i , y i )  1364 . The placement distribution process continues and is described further in  FIG. 14  of one embodiment. 
       Placement Error Grid: 
       [0072]      FIG. 14  shows for illustrative purposes only an example of a placement error grid of one embodiment.  FIG. 14  shows the continuation of the placement error determination from  FIG. 13 .  FIG. 14  includes algorithm step  4   1400  used to create a placement error grid  1410 . Random domain templates can be used  1062  of  FIG. 10B  where there is no need to pre-determine the grid  1060  of  FIG. 10B . A peak location determines the grid  1420  increments and peak width is used to determine placement error  1430 . The grid  1470  includes the x-y coordinates of “pixels”, the small squares in the x-y plane corresponding to the pixels in the original image. The grid  1470  includes vertical z-coordinates which are “counts” corresponding to how many neighboring dots are found at the particular pixel location. The x, y and z coordinates are used to create m p    1440 . The m p    1440  data is used to transition from m p  to placement error  1450  quantification as one number. A placement error relief grid  1460  shows a three dimensional (3D) representation of the grid  1470 . Additional steps are described in  FIG. 15  of one embodiment. 
       Placement Evaluation: 
       [0073]      FIG. 15  shows for illustrative purposes only an example of placement evaluation of one embodiment.  FIG. 15  shows the continuing process from  FIG. 14  including algorithm step 5  1500 . Algorithm step 5  1500  is used for placement evaluation  1505  of the images of the random domain templates. The images include in this example SEM 1  1510 , SEM 2  1520 , SEM 3  1530 , SEM 4  1540 , SEM 5  1550  and SEM 6  1560 . Corresponding to the images are m p  1  1515 , m p  2  1525 , m p  3  1535 , m p  4  1545 , m p  5  1555  and m p  6  1565 . The m p  grids show how the placements can vary with different electron beam curing voltage and dose settings. The evaluations performed are used to determine which settings produce the targeted results. The further evaluation is described in  FIG. 16  of one embodiment. 
       Plotted Placement Regularity Number: 
       [0074]      FIG. 16  shows for illustrative purposes only an example of plotted placement regularity numbers of one embodiment.  FIG. 16  shows a continuance of the process from  FIG. 15  including algorithm step 6  1600 . Algorithm step 6  1600  is used to determine each calculated feature placement error  1610 . The calculated feature placement error  1610  is used to determine the probability of finding a neighboring feature  1620 . The calculated feature placement error plotting  1630  charts the feature placement error for each image based on the P_error (nm). The P_error (nm) is one number to describe placement regularity  1660 . Each plotted placement regularity number  1670  for images 1-6 can create a curved output. A P_error curves monotonously when features become irregularly placed  1640 . The results are used to compare to a targeted placement quality  1650  for the placement evaluation  1070  of  FIG. 10B . 
         [0075]    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.