Patent Application
20060114802
The present invention relates to data storage media and more particularly, this invention relates to a long-term stable data storage medium.
The preservation of data and knowledge has been, and continues to be, one of the top priorities of modern civilization. Information is being produced in greater quantities and with greater frequency than at any time in history. Electronic media, especially the Internet, make it possible for almost anyone to become a “publisher.” The ease with which electronic information can be created and “published” makes much of what is available today, gone tomorrow. Thus there is an urgent need to preserve this information before it is forever lost.
Optical media presently include compact discs (CDs), digital video discs (DVDs), laser discs, and specialty items. Optical media has found great success as a medium for storing music, video and data due to its durability, long life, and low cost.
A CD typically comprises an underlayer of clear polycarbonate plastic. During manufacturing, the polycarbonate is injection molded against a master having protrusions (or pits) in a defined pattern that creates an impression of microscopic bumps arranged as a single, continuous, spiral track of data on the polycarbonate. Then, a thin, reflective aluminum layer is sputtered onto the disc, covering the bumps. Next a thin acrylic layer is sprayed over the aluminum to protect it. A label is then printed onto the acrylic.
During playback, the reader's laser beam passes through the polycarbonate layer, reflects off the aluminum layer and hits an opto-electronic device that detects changes in light. The bumps reflect light differently than the lands, and an opto-electronic sensor detects that change in reflectivity. The electronics in the reader interpret the changes in reflectivity in order to read the bits that make up the data.
The data stored on the CD is retrieved by a CD player that focuses a laser on the track of bumps. The laser beam passes through the polycarbonate layer, reflects off the aluminum layer and hits an opto-electronic device that detects changes in light. The bumps reflect light differently than the lands, and the opto-electronic sensor detects that change in reflectivity. The electronics in the drive interpret the changes in reflectivity in order to read the bits that make up the bytes.
A DVD is very similar to a CD, and is created and read in generally the same way (save for multilayer DVDs, described below). However, a standard DVD holds about seven times more data than a CD. Single-sided, single-layer DVDs can store about seven times more data than CDs. A large part of this increase comes from the pits and tracks being smaller on DVDs. To increase the storage capacity even more, a DVD can have multiple layers, several layers being readable on each side.
A DVD player functions similarly to the CD player described above. However, in a DVD player, the laser can focus either on the semi-transparent reflective material behind the closest layer, or, in the case of a double-layer disc, through this layer and onto the reflective material behind the inner layer. The laser beam passes through the polycarbonate layer, bounces off the reflective layer behind it and hits an opto-electronic device, which detects changes in light.
One problem with each of these technologies is that currently available media is unsuitable for long-term data storage, long term meaning one hundred years or more. The polycarbonate on the disc is porous, and allows water to wick into the structure. The water over time will corrode the metallic backlayer, eventually rendering the media unreadable. Additionally, the polymer coatings deteriorate over time. In the time of several hundred years, the polymer coatings could become so brittle that any attempts to read the media would result in destroying the disc. The discs may crack, even without any external forces being brought to bear thereon. Similarly, the dye layer in writeable media would also deteriorate over the course of several hundred years.
What is therefore needed is a way to collect, archive and preserve the burgeoning amounts of digital content, especially materials that are created only in digital formats, for current and future generations. To accomplish this, what is needed is a new data storage medium that is long-term stable. What is also needed is a data storage medium that is readable after 1000 years.
To overcome the aforementioned drawbacks and provide the desirable advantages, an optical medium includes a substrate having a data track thereon being readable with an optical reader. The substrate is constructed of a corrosion-resistant material that does not substantially deteriorate over a period of one hundred years. In this embodiment, no material covers the data track.
An optical medium according to another embodiment includes a substrate having a data area and a periphery. A supplemental layer is coupled to the substrate in at least the data area, the supplemental layer having a data track thereon being readable with an optical reader. The substrate and supplemental layer are constructed of a corrosion-resistant material that does not substantially deteriorate over a period of one hundred years.
In one embodiment, the substrate includes a central hub, an outer periphery, and a data area extending between the hub and periphery, the data track being positioned in the data area. The data area can be recessed from a bottom plane of the medium, preferably such that the data track has a focal depth about the same as a focal depth of a compact disc (CD), digital video disc (DVD), etc. so that the data track is readable by a consumer-grade CD and/or DVD player
In a further embodiment, a second data area is positioned on an opposite side of the substrate relative to the first data track. As before, the second data area can be recessed from a top plane of the medium.
As an option, a peripheral flange may extend downwardly from the periphery.
Preferred materials from which the construct the substrate and/or supplemental layer include gold, ceramic, stainless steel, fused silica quartz, carbonite, a graphite composite, and combinations thereof.
Several options exist for creating the data track. One method includes forming the data track by stamping. The data track can also be formed by electron or ion exposure. The data track can also be formed by electrons or ions passing through apertures of a mask.
Accordingly, the optical media described herein provides an archive medium that is particularly adapted for long term storage off data including audio data, video data, and software.
Other aspects and advantages of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
For a fuller understanding of the nature and advantages of the present invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings.
FIGS. 6A-E are detailed views, not to scale, taken from circle 6A/B/C/D/E of
FIGS. 11A-B is a partial cross sectional view, not to scale, of another embodiment of an optical medium.
The following description is the best embodiment presently contemplated for carrying out the present invention. This description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein.
The data area in this embodiment includes a data track that is preferably readable using a standard optical media reader, e.g., CD or DVD drive. Note
As shown particularly in
A peripheral flange 208 may extend downwardly from the periphery 204 of the medium 200. The flange may or may not have the same axial thickness as the hub 202. The flange serves a protective role, keeping the data area of the disk from contacting a surface upon which it is resting, thereby preventing scratching and soiling of the data area. The flange can also be used to stabilize the disk in a reader, e.g., rollers could engage the flange.
At least the data area, and preferably the entire medium 200, is fabricated of a material that is durable, corrosion-resistant, and does not deteriorate over time, e.g., at least 100 years. Illustrative materials include gold, ceramic, stainless steel, fused silica quartz, carbonite, graphite composites, etc. Such materials are believed to be able to maintain a readable data track for a minimum of about 1000 years. Gold is a preferred material, as it is reflective, and will not move or deteriorate. Also, after several hundred years in storage, the user may need to clean the data area before use. Because gold is very noncorrosive, a mild acid, solvents, etc. can be used to clean the exposed data area. In applications where fire resistance is desired, a material having a high melting point can be selected.
In another embodiment, shown in
As shown in
As shown in
Optionally, an optically transmissive protective outer sublayer 610, e.g., of diamond-like carbon, can be added.
As shown in
The data track can be a single, continuous and extremely long spiral track of data, as is typical of current CDs and DVDs for compatibility with current optical readers. The data track can also be formed in linear rows, or any other desired pattern. The surface features, e.g., pits and lands, of the data track are readable with an optical reading device. The data track can be formed on the data area of the medium shown in
The data track can also be formed using electron or ion beam technology.
Accordingly, standard electron or ion beam lithography machine sinter technology can be combined with raster image control technology to write an image pattern to target media, thereby combining the fine feature size detail of electron or ion beam lithography with the imaging speed of rastering.
The system described herein can write data such as audio data, video data, software, etc. to an optical medium very quickly, e.g., in less than one minute, and even in less than one second. The system is able to write data to any type of optical media of any material, and would extend to future types of optical media that are presently under development or have yet to be discovered.
Electron guns have been widely used in the semiconductor industry to define electronic components with features down to about 5 nanometers. Such guns are suitable for use in the present invention. In general, an electron gun includes a small heater that heats a cathode. When heated, the cathode emits a cloud of electrons. Two anodes turn the cloud into an electron beam. An accelerating anode attracts the electrons and accelerates them toward the target (here, an optical medium) at a very high speed. A focusing anode, e.g., deflection plates and Einzel lens, focuses the stream of electrons into a very fine beam. By adjusting the power to the accelerating anode, the speed of the electrons, and thus their energy, can be set to create the desired depth of the pits being created on the medium. By adjusting the power to the heater, the number of electrons emitted can be controlled, which in turn affects the depth and width of the pits.
Many cathode types and sizes are available: tantalum disc cathodes, tungsten hairpins, single-crystal lanthanum hexaboride (LaB6) cathodes, barium oxide (BaO) cathodes, or thoria-coated (ThO2) iridium cathodes. UHV technology is preferably used throughout. The guns can be run in vacuums from 10−11 torr up to 10−5 torr for the various refractory metal cathodes. A minimum vacuum recommended for LaB6 or BaO cathodes is roughly 1×10−7 torr. Thoria cathodes can be run up to 10−4 torr and above
Suitable electron guns include the EGG-3101, EGPS-3101, EMG-12, and EGPS-12 available from Kimball Physics, 311 Kimball Hill Road, Wilton, N.H. 03086-9742 USA. One skilled in the art will recognize that there are several manufacturers of electron guns that are also suitable for use with the system, including those having larger and smaller spot sizes.
Where ion beam technology is used, the system of the present invention can incorporate therein a positive ion source or a negative ion source. Illustrative ion species which perform the bombardment are Ar+, O2+, Ga+, Cs+, Li+, Na+, K+, Rb+, etc.
A preferred embodiment implements a Focused Ion Beam (FIB) system. A FIB system takes charged particles from a source, focuses them into a beam through electromagnetic/electrostatic lenses, and then scans across small areas of the target using deflection plates or scan coils. The FIB system produces high resolution imaging by collecting the secondary electron emission produced by the beam's interaction with the target surface. Contrast is formed by raised areas of the sample (hills) producing more secondary electrons than depressed areas (valleys).
In a preferred embodiment, the FIB system uses gallium ions from a field emission liquid metal ion (FE-LMI) source. In operation, a gallium (Ga+) primary ion beam hits the sample surface and sputters a small amount of material, the displaced material leaving the surface as either secondary ions (i+ or i−) or neutral atoms (n0). The primary ion beam also produces secondary electrons (e-). As the primary beam rasters on the sample surface, the signal from the sputtered ions or secondary electrons is collected to form an image.
At low primary beam currents, very little material is sputtered; modern FIB systems can achieve 5 nm imaging resolution. At higher primary currents, a great deal of material can be removed by sputtering, allowing precision milling of the specimen down to a sub-micron scale.
Many variables and material properties affect the sputtering rate of a sample. These include beam current, sample density, sample atomic mass, and incoming ion mass. A preferred ion species is Ga+.
Additionally, gas-assisted etching can be used. When a gas is introduced near the surface of the sample during milling, the sputtering yield can increase depending on the chemistry between the gas and the sample. For instance, by injecting a reactive gas into the mill process, the aspect ratio of the ion beam's cutting depth can be dramatically altered such that it is possible to reach the lower metallization line without disturbing the upper layer metallization. This results in less redeposition and more efficient milling. Two typical gasses are iodine and xenon difluoride.
If the sample is non-conductive, a low energy electron flood gun can be used to provide charge neutralization. In this manner, by imaging with positive secondary ions using the positive primary ion beam, even highly insulating samples may be imaged and milled without a conducting surface coating, as would be required in a SEM. This feature is particularly useful for writing surface features directly to the polymeric layer of an optical medium.
Suitable ion guns include the ILG-2, IGPS-2, E/IMG-16, E/IGPS-16, available from Kimball Physics, 311 Kimball Hill Road, Wilton, N.H. 03086-9742 USA. Another suitable ion gun is the IOG 25 Gallium Liquid Metal Ion Gun, available from Ionoptika Ltd, Epsilon House, Chilworth Science Park, Southampton, Hampshire SO16 7NS, UK. One skilled in the art will recognize that there are several manufacturers of ion guns that are also suitable for use with the system, including those having larger and smaller spot sizes.
In both the electron beam and ion beam systems, the steering mechanism can use rastering technology to aim the electron beam at the optical medium along the data path. One preferred steering mechanism includes steering coils under control of the controller. Steering coils are copper windings that create magnetic fields that affect the direction of the electron beam. One set of coils creates a magnetic field that moves the electron beam in the X direction, while another set moves the beam in the Y direction. By controlling the voltages in the coils, the electron beam can be positioned at any point on the medium. Because rastering can be performed very quickly, a full data track can be transferred to the optical medium in a fraction of a second.
The raster pattern can be generated by a computer using a standard X-Y grid corresponding to points on the medium. The grid has a density sufficient to allow writing to all necessary points on the medium. The steering mechanism, in turn, directs the electron beam to the points on the medium corresponding to data points on the grid, where a pulse is emitted. A simple raster controller in this type of system can be similar to the controller used in cathode ray tubes (CRTs).
Alternatively, the raster pattern can be set to follow a data track, such as a spiral. The steering coils are energized in such a way that the electron beam moves along the data track, the electron beam pulsing at selected points along the data track. In this type of system, for example, the field emitted by the steering coils in the X and Y directions can follow generally sinusoidal curves where the amplitudes of the curves gradually increase as the beam moves from the inner diameter of the media to its periphery along a spiral data track.
As mentioned above, the surface features are created by electron or ion beam pulses. In most electron or ion guns, including those available from Kimball Physics, the beam may be turned off and on while the gun is running. The way this is accomplished depends on the particular gun design. Often several beam pulsing methods are available for a particular gun.
Pulsing includes stopping and starting the flow of electrons or ions in a fast cycle. This pulsing is usually accomplished by rapidly switching the grid voltage to its cut off potential to stop the beam. The grid provides the first control over the beam and usually can be used to shut off the beam. In an electron gun, if the grid voltage is sufficiently negative with respect to the cathode, it will suppress the emission of the electrons, first from the edge of the cathode and at higher (more negative) voltages from the entire cathode surface. The minimum voltage required to completely shut off the flow of electrons to the target is called the grid cut off. The grid voltage can be controlled by the controller manipulating the power supply; thus, in most guns, the beam can be turned off while the gun is running by setting the grid to the cut off voltage.
The grid voltage can be controlled by several different methods, one being capacitive. Many guns can be equipped with a capacitor-containing device (either a separate pulse junction box or cylinder, or a cable with a box) that receives a signal from an external pulse generator (available from the gun manufacturer). The grid power supply and pulse generator outputs are superimposed to produce the voltage at the grid aperture. The general pattern of the beam pulsing is a square wave with a variable width (time off and time on) and a variable repetition rate. Capacitive pulsing can provide the fastest rise/fall time and shortest pulse length of the various methods. However, the capacitor does not permit long pulses or DC operation. If there is a separate grid lead on the gun, this capacitive pulsing option can be added to most existing gun systems without modification.
A typical pulse length is ˜20-100 nanoseconds, defined as the time the beam is on, measured as the width at 50% of full beam and may include some ringing. The rise/fall time is typically ˜10 nanoseconds measured between 10% and 90% of full beam. Shortening the rise/fall will typically increase ringing. Pulsing performance may also depend on the performance of the user-supplied pulse generator.
Not all guns are designed to be pulsed. For example, a few electron guns have a positive grid in order to extract more electrons, and so these guns do not usually have grid cut off, unless a dual grid supply is ordered. In some high-current electron guns, the optical design, the position of the cathode, does not allow for cut-off with the grid, and so a different option, called blanking, must be used to interrupt the beam instead of pulsing.
Beam blanking deflects the electron beam to one side of the electron gun tube to interrupt the flow of electrons to the target without actually turning off the beam. The voltage applied to the blanker plate in the gun is controlled by a potentiometer on the power supply. Blanking can be used to pulse the final beam current repeatedly on and off in response to a TTL signal input. The blanker voltage required for beam cutoff depends on the gun configuration and on the beam energy, and can be readily determined from the reference materials accompanying the electron gun from the manufacturer.
In both the electron and ion beam methods, the surface features can be made significantly smaller than has heretofore been possible. This is due to the fine detail (e.g., ˜5 nanometer) and sharp edges afforded by electron beam technology. For instance, the surface features can have a length along a data track thereof of less than about 500 nanometers, less than about 200 nanometers, less than about 100 nanometers, and less than about 50 nanometers. In this way, the data storable on a single medium can be greatly improved, limited only by the wavelength of the optical system used. For discs having surface features finer than a DVD, a reader capable of reading finer-than-DVD features is used. For even finer surface features, for example, ultraviolet, microwave and x-ray optical systems may be required.
Also note that the surface features created can have almost perfectly straight edges.
In another variation, the electron or ion beam can be used to create “pits and lands” of varying reflectivity on a surface having nanostructures that affect the reflectivity of light. The shapes of the nanostructures determine the amount of reflectivity (if any) of the surface. Thus, a reflective layer is not needed. Those skilled in the art will appreciate that the shape and size of the nanofeatures can vary, and will be able to select a shape and size without undue experimentation.
A electron or ion mill-resistant mask 1222 is placed over the medium 1204. The mask 1222 has apertures therethrough in a data track pattern representing the desired pit structure to be transferred to the optical medium 1204.
The beam 1208 or flood 1220 of electrons or ions is directed at the mask 1222. If a diffuse beam is being used, for instance, the steering mechanism 1210 can be used to sweep the beam 1208 across the medium 1204. The steering mechanism 1210 can also be used in conjunction with a beam blanker (not shown) to sequentially bombard different sections of the mask 1222 and medium 1204. Some electrons or ions pass through the apertures of the mask 1222 and bombard the optical medium 1204 in the data track pattern, thereby creating surface features on the optical medium 1204. Particularly, the electrons or ions displace or oblate the material they strike, creating pits. The resultant pits and lands along the data track represent data. At least the medium receiving portion 1202 should be positioned in a vacuum chamber 1214 maintained at a vacuum of 1×10−3 Torr or below. Note that the emitting portion of the gun 1206 should also be positioned in the vacuum chamber 1214.
The mask 1222, which will be described in more detail below, can be reused to create many copies of the media. And because commercially available media is formed of relatively soft materials (e.g., polycarbonate and aluminum), the electron or ion source 1206 can be operated at a lower power, thereby reducing the wear on the mask.
Accordingly, standard electron or ion beam lithography machine sinter technology can be combined with reusable masking technology to write an image pattern to target media, thereby combining the fine feature size detail of electron or ion beam lithography with the imaging speed of masking.
Referring to
In a variation, the substrate upon which the resist rests can be of a durable material that is ion or electron mill resistant. The resist is formed to a height high enough to withstand substantial milling. Upon patterning of the resist, the structure is milled to create the apertures in the substrate. The resist will be milled away as well, but due to the increased height, will remain long enough to allow defining of the apertures in the substrate. Then the resist can be removed from the substrate, leaving a mill resistant mask having a long life.
In operation 1908, the medium is ejected from the system. In operation 1910, a label is then printed onto the medium using a printing device known in the art, or affixed as an adhesive layer. In this way, the damaged area of the medium is covered and is nonapparent to the end user. The side of the label adjacent the medium is preferably nonreflective so as not to reflect the reader's laser during playback. Also note that a protective layer can optionally be added prior to affixing the label.
In a variation on the above, the beam of electrons or ions is swept across the mask in a controlled manner, such as in a serpentine path, back and forth along parallel paths, etc. In a further variation, instead of sweeping the beam across the mask, areas of the mask are sequentially exposed by a flood of electrons or ions. In either of these embodiments, a beam blanker, pulse generator, on/off control, etc. can be used to control the duration of the exposure.
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
