Patent Application
20140322431
A hard disc drive (HDD) may be used by a computer system for operations. In fact, most computing systems are not operational without some type of data storage such as a HDD to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the HDD is a component for use in a computer system or may be used as a component of dedicated remote data storage systems for use in cloud computing. A HDD often uses a media or substrate such as a hard disc. The hard disc may be composed of a material that has varying characteristics.
Reference will now be made in detail to various embodiments of the present invention. While the invention will be described in conjunction with these embodiments, it should be understood that the described embodiments are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as described in the various embodiments and as defined by the appended claims.
Furthermore, in the following description of embodiments, numerous specific details are set forth in order to provide a thorough understanding of various embodiments of the present invention. However, it will be recognized by one of ordinary skill in the art that embodiments of the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of embodiments of the present invention.
The discussion will begin with a brief overview of the present invention. The discussion will then focus on a hard disc drive (HDD) and components connected therewith. The discussion will then focus on embodiments of predicting a characteristic of an overcoat or film. In particular, the present technology is for predicting one or more characteristics of an overcoat or film where the characteristics include mass density, sp3/sp2 bonding ratio, and graphitization. In one embodiment, the overcoat or film is diamond like carbon (DLC) that is a layer in a disc employed in a HDD.
A HDD may include one or several discs where the discs are each composed of a plurality of layers. One such layer may be a media suitable for recording data to and subsequently reading the data from the media. The disc may have many other layers such as substrates or an overcoat. The overcoat may be a layer over the media such that the overcoat offers a measure of protection to the media. In practice, the overcoat may be a film comprised of a variety of different materials including carbon. During the manufacturing process, different layers of the disc may be tested or probed to determine characteristics of the disc and its layers. For example, the overcoat layer may be tested or probed to determine its mass density or sp3/sp2 content ratio.
Different technique used to determine the mass density of a carbon overcoat layer includes x-rays and refraction. For example, mass density may be measured on thicker carbon overcoat (COC) films by X-Ray Reflectivity (XRR) and the sp3/sp2 content ratio by X-ray Photoelectron Spectroscopy (XPS). These two methods require several hours of measurements and of modeling and fitting. For example, XRR and XPS usually requires several hours to complete. This time period makes it prohibitive to test every disc or even a substantial portion of every disc being manufactured. These techniques may also be difficult to automate. Moreover, the x-rays in these techniques may also damage the disc itself.
In one embodiment, the present technology tests or probes an overcoat of a disc during a manufacturing process of the disc. The overcoat or film may first be deposited over a recording media of the disc. A microscope is used to probe the overcoat. For example, the microscope may employ Raman spectroscopy to probe the atomic structure of the overcoat. The probing results in data that is generated. In one embodiment, the probing includes data related to the in-plane bond-stretching motion of pairs of carbon sp2 atoms. The data may be analyzed by a computer system. The computer system may fit the data to a line or curve. For example, the data may be fit to a Gaussian curve with a G band. The G band may have an associated G position and G width. In one embodiment, the position (Gpos) is mapped in function of the full width at half maximum (Gwidth) of the G Gaussian band. The calculated or fitted data curve may then be used to predict mass density, sp3/sp2 bonding ratio, and graphitization of the overcoat layer.
The present technology offers nondestructive and fast predictions of the mass density, sp3/sp2 bonding ratio, and graphitization of the overcoat layer. The present technology is compatible with disc manufacturing techniques and high throughput, to make the predictions. In one embodiment, the present technology employs Raman spectroscopy to gather data and make the predictions. In one embodiment, a method relies on plotting the variation of the Raman G band position in function of its width at half maximum. This method can be used to characterize COO films and used as a quick process monitoring and failure analysis method. The present technology is capable of automation and may test every disc manufactured or a pre-determined portion. The fast throughput of the present technology allows it to be implemented on a manufacturing line for quick process monitoring and as a failure analysis method.
The basic HDD model includes a magnetic storage disc, hard disc, or media that spins at a designed rotational speed. Layers of the media may comprise a segregant and may be etched using the present technology. An actuator arm with a suspended slider is utilized to reach out over the disc. The slider may comprise one or more magnetic read and write transducers or heads for reading and writing information to or from a location on the disc. The slider may also comprise a heater coil designed to change shape when heat is transferred to the heater coil by means of electric current. The slider is mounted on a suspension which connects to the actuator arm. In the case of multiple platter drives, there can be multiple suspensions attaching to multiple actuator arms as components of a head stack assembly. The head stack assembly also includes a voice coil which is part of a motor used for moving the arms to a desired location on the disc(s).
With reference now to
In general, HDD 110 has an outer housing 113 usually including a base portion (shown) and a top or cover (not shown). In one embodiment, housing 113 contains a disc pack having at least one media or magnetic disc 138. The disc pack (as represented by disc 138) defines an axis of rotation and a radial direction relative to the axis in which the disc pack is rotatable.
A spindle motor assembly having a central drive hub 130 operates as the axis and rotates the disc 138 or discs of the disc pack in the radial direction relative to housing 113. An actuator assembly 140 includes one or more actuator arms 145. When a number of actuator arms 145 are present, they are usually represented in the form of a comb that is movably or pivotally mounted to base/housing 113. An actuator arm controller 150 is also mounted to base 113 for selectively moving the actuator arms 145 relative to the disc 138. Actuator assembly 140 may be coupled with a connector assembly, such as a flex cable to convey data between arm electronics and a host system, such as a computer, wherein HDD 110 resides.
In one embodiment, each actuator arm 145 has extending from it at least one cantilevered integrated lead suspension (ILS) 120. The ILS 120 may be any form of lead suspension that can be used in a data access storage device. The level of integration containing the slider 121, ILS 120, and read and write head is called the head stack assembly.
The ILS 120 has a spring-like quality, which biases or presses the air-bearing surface of slider 121 against disc 138 to cause slider 121 to fly at a precise distance from disc 138. Slider 121 may have a pole tip which protrudes at various lengths from slider 121. Slider 121 may also contain a read head, a write head and a heater coil. ILS 120 has a hinge area that provides for the spring-like quality, and a flexing cable-type interconnect that supports read and write traces and electrical connections through the hinge area. A voice coil 112, free to move within a conventional voice coil motor magnet assembly is also mounted to actuator arms 145 opposite the head stack assemblies. Movement of the actuator assembly 140 causes the head stack assembly to move along radial arcs across tracks on the surface of disc 138. In one embodiment, actuator arm controller 150 controls a plurality of actuator arms associated with a plurality of discs.
Reference will now be made to
In one embodiment, overcoat 202 is designed to be over media 204 such that it covers a surface of media 204 and may or may not be in physical contact with media 204. In one embodiment, overcoat 202 protects media 204 from corrosion while allowing data to be written to and read from media 204. Overcoat 202 may be a film or thin film. Overcoat 202 may be comprises of a variety of different materials and may be a carbon overcoat (COC). In one embodiment, overcoat 202 is comprised of diamond like carbon (DLC) which includes atoms bonded to one another at various hybrid orbitals including sp2 and sp3 orbitals. Overcoat 202 may comprise other characteristics such as mass density and graphitization. Different qualities of materials and different manufacturing environment variables may cause the characteristics of overcoat 202 to fluctuate or vary. This may be true between a first overcoat over a first disc and second overcoat over a second disc even if the first and second overcoats are produced using the same manufacturing equipment and processes. Therefore, probing or other testing techniques are employed to determine the characteristics of an overcoat. Parameters may be established for the characteristics of the overcoat and a determination may be made as to whether the characteristics of overcoat 202 fall within the parameters. The parameters may set limits as to what levels are acceptable for a disc to be used for a HDD.
Reference will now be made to
In one embodiment, microscope 302 is used to project light 306 onto a surface of overcoat 202. Light 306 may be generated by a laser associated with microscope 302. Light 306 has characteristics such as wavelength and frequency that are known to microscope 302 and/or computer 304. In one embodiment, light 306 is reflected and scattered by the surface of overcoat 202 and becomes scattered light 308. At least a portion of scattered light 308 may be intercepted by sensor associated with microscope 302. The sensor is able to determine characteristics of scattered light 308 such as it wavelength and frequency. The characteristics of scattered light 308 may be referred to as data. The data generated or gathered by microscope 302 and its components may be sent to computer 304.
Computer 304 is a computer system capable of manipulating data via a processor and memory. Computer 304 may be a standard computer system such as a general purpose computer system, a person computer, a server computer, or may be built as a specific use computer system designed for the present technology and for the manufacturing of discs for HDDs. Computer 304 may be attached or coupled to microscope 302 or may be connected to microscope 302 via cables or wireless communication channels. Computer 304 may be physically proximate to microscope 302 or may be physically remote and connected via a network. Other components may be in place to send data from microscope 302 to computer 304 such as a router. In one embodiment, computer 304 controls the components and processes of microscope 302. In one embodiment, computer 304 is a component of microscope 302. The present technology may require various computations to take place, such computations may take place at computer 304 or a portion of the computation may occur at microscope 302 and a portion at computer 304.
In one embodiment, computer 304 knows the characteristics of light 306 projected by microscope 302 and knows the characteristics of scattered light 308 received by microscope 302. By analyzing the differences between light 306 and scattered light 308, computer 304 may make determinations or predictions about the characteristic of overcoat 202 or other material. In one embodiment, microscope 302 and computer 304 are used to measure the in-plane bond stretching motion of pairs of carbon (C) sp2 atoms in overcoat 202. Computer 304 is capable of plotting data and fitting lines or curves with their associated equations to the plotted data. In one embodiment, data acquisition and analysis by microscope 302 and computer 304 are automated. In one embodiment, the processes used to probe and make predication about overcoat 202 via microscope 302 and computer 304 takes approximately two minutes.
Reference will now be made to
In one embodiment, overcoat 202 also contains open chains of carbon such as structure 412. Chains and rings form small clusters of sp2 bonded atoms. These sp2 clusters are linked together by sp3 bonding to form the continuous diamond like carbon overcoat (DL-COC) film. Moreover, the microstructure of a DL-COC film is amorphous, meaning no long range order, which means that the size of the sp2 clusters is very small, about 1 nanometer in diameter. Overcoat 202 may be comprised of a plurality of atoms bonded into either structure 400, 410, or 412 patterns, or a combination thereof.
Raman spectroscopy is sensitive to the in-plane bond stretching motion of any pair of sp2 carbon atoms. This means that the Raman spectroscopy can detect any pair of atoms arranged in rings or in chains. The G band of the Raman spectrum is the measurement of the in-plane bond stretching motion of all pairs of sp2 carbon atoms. Thus the G band comes from C-C pairs inside rings and chains.
Reference will now be made to
G band 504 may be described as a Raman G band. G band 504 may be fitted by a Gaussian line using the following equation: Gband=Intensity*exp{−[(x−Gpos)/(√2*Gwidth/2)]̂2}, where x is the Raman shift. Plot 500 demonstrates that the higher the values of Gpos 508 and Gwidth 506 are, the denser and higher the sp3 content is in the overcoat. Additionally, if Gpos 508 and Gwidth 506 are low then the film is graphitized, meaning that it has a lower sp3 content and a high sp2 content.
Gpos 508 and Gwidth 506 may be employed to make other plots used to make predictions regarding characteristics of the overcoat. For example, a second plot, not depicted, may be made by computer 304 of
A third plot, not depicted, may also be generated to show a comparison between a “low sp3-low density” overcoat, such as a CHx deposited by CVD, and a “high sp3 content-high density” overcoat deposited by filtered cathodic arc (FCAC). The third plot would show that at room temperature (21 C) it is clear that the high sp3 content and high density of the FCAC is correlated with its higher Gpos and Gwidth than the CHX (CVD) overcoat. After thermal annealing, the third plot shows that FCAC is more thermally stable than CHx (CVD). Therefore the present technology may be used to create tables or charts that depict a comparison and ranking of different overcoats.
At 602, an overcoat is probed via a microscope using inelastic scattering of a photon by optical phonons from the overcoat to generate data related to in-plane bond-stretching motion of pairs of atoms of the overcoat. For example, the overcoat may be overcoat 202 of
The overcoat may be comprised of carbon or diamond like carbon and may be a thin film. A carbon overcoat may be comprised of sp2 and sp3 atoms in bonding pairs. The overcoat may be a layer in a disc to be used in a HDD such as disc 200 of
At 604, the data is fit to a curve at a computer system. The computer system may be computer 304 of
At 606, a position (Gpos) is mapped in function of a full width at half maximum (Gwidth) of a G band of a Gaussian line. The Gpos may be Gpos 508 and the Gwidth may be Gwidth 506 of
At 608, a characteristic of the overcoat is predicted based on the curve at the computer system. For example, the characteristics may be a mass density of the overcoat, an sp3/sp2 bonding ratio of the overcoat, and a graphitization of the overcoat. The characteristic may be based on the Gpos and the Gwidth mapping. Step 608 may be referred to as predicting, generating, determining, or characterizing.
At 702, an overcoat is deposited over a media for a disc. The overcoat may be comprised of carbon or diamond like carbon and may be a thin film. A carbon overcoat may be comprised of sp2 and sp3 atoms in bonding pairs. The overcoat may be a layer in a disc to be used in a HDD such as disc 200 of
At 704, the overcoat is probed via a microscope using inelastic scattering of a photon by optical phonons from the overcoat to generate data related to in-plane bond-stretching motion of pairs of atoms of the overcoat. For example, the overcoat may be overcoat 202 of
It should be appreciated that different steps of the manufacturing process may occur faster or slower than one another. For example, step 702 may occur faster than step 704. To compensate, a plurality of microscopes may be employed such that a plurality of discs may be probed simultaneously during the manufacturing process. The plurality of microscope may all be associated with the same computer system or may each be associated with a different computer system. Alternatively, the manufacturing process may only test a pre-determined number of discs being manufactured. For example, one a hundred or one in a thousand discs may be probed.
At 706, the data is fit to a curve at a computer system. The computer system may be computer 304 of
At 708, a position (Gpos) is mapped in function of a full width at half maximum (Gwidth) of a G band of a Gaussian line. The Gpos may be Gpos 508 and the Gwidth may be Gwidth 506 of
At 710, a characteristic of the overcoat is predicted based on the curve at the computer system. For example, the characteristics may be a mass density of the overcoat, an sp3/sp2 bonding ratio of the overcoat, and a graphitization of the overcoat. The characteristic may be based on the Gpos and the Gwidth mapping.
At 712, provided the characteristic of the overcoat is outside of a parameter, a manufacturing process for the disc is stopped. For example, parameters may be established at the computer system or another computer system that indicate acceptable measurements for the predicted characteristics of the overcoat. A deviation outside of the parameters may indicate that there is a problem or issue with the overcoats being manufactured making the discs unsuitable for use in a HDD. It may therefore be desirable to stop the manufacturing process rather than continuing to manufacture unsuitable discs. By stopping the manufacturing process, the problem or issue may be diagnosed and correct and the manufacturing process may then resume again. Alternatively, if the predictions of the characteristics of the overcoat are outside of pre-determined parameters, the system used for the manufacturing may generate a notification such as a warning light rather than stopping the manufacturing process.
The present technology may be employed to manufacture discs of varying quality. For example, a company may manufacture several different models of HDDs where different models are lower or higher in quality. The different levels of quality may be due to a plurality of factors one of which may be the quality of the overcoat of the disc. Therefore, a higher quality HDD may require a higher quality overcoat over the disc. Thus, parameters may be employed in the manufacturing process to sort the discs according to the level of quality of the overcoat.
At 714, provided the characteristic of the overcoat is outside of a parameter, the disc is discarded. For example, if the predicted characteristics of the overcoat have deviated significantly outside of the parameters for suitable use in a HDD, the disc may be discarded to ensure a specified level of quality in the HDD.
At 716, provided the characteristic of the overcoat is inside of a parameter, the disc is placed in hard disc drive. Such a placement may be automated and may refer to the next step in the manufacturing process.
At 802, a diamond like carbon film is probed via a microscope employing Raman spectroscopy using inelastic scattering of a photon by optical phonons from the overcoat to generate data related to in-plane bond-stretching motion of pairs of sp2 atoms of the diamond like carbon film. For example, the diamond like carbon film may be overcoat 202 of
The overcoat may be comprised of carbon or diamond like carbon and may be a thin film. A carbon overcoat may be comprised of sp2 and sp3 atoms in bonding pairs. The overcoat may be a layer in a disc to be used in a HDD such as disc 200 of
At 804, the data is fit to a Gaussian curve at a computer system. The computer system may be computer 304 of
At 806, a characteristic of the diamond like carbon film is predicted based on the Gaussian curve at the computer system. For example, the characteristics may be a mass density of the overcoat, an sp3/sp2 bonding ratio of the overcoat, and a graphitization of the overcoat. The characteristic may be based on the Gpos and the Gwidth mapping.
Example embodiments of the present technology are thus described. Although the subject matter has been described in a language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. Additionally, in various embodiments of the present technology, the steps and methods described herein do not need to be carried out in the order specified, nor do all steps need to be carried out to accomplish the purposes of the technology.
