Patent Application
20100276390
The present invention relates to the manufacture of magnetic disks and, more particularly, a method of creating a master bit-patterned media disk.
Hard disk drives have developed as an efficient and cost effective solution for data storage. Since the introduction of the first magnetic disk drive, storage density capabilities have increased by many orders of magnitude, with an average steady increase of nearly fifty percent per year. Main stream technology has consisted of storing information on continuous granular media having out-of-plane anisotropy and being associated with a soft underlayer which helps concentrate the magnetic flux underneath the write pole of the head, thus increasing the write field efficiency.
However, it is generally accepted that this technology will reach its limit at an areal density between 500 Gbit/in2 and 1 Terabit/in2. This limit is set by the so-called “recording trilemma” which is the difficulty to reconcile three requirements of magnetic recording technology: i) a sufficient number of grains per bit to insure a large enough signal to noise ratio, ii) a sufficient stability of the magnetization of each grain against thermal fluctuations, iii) the ability to switch the magnetization of the grain with the field available from the write head. Several solutions are under investigation to circumvent this trilemma, including Heat Assisted Magnetic Recording (HAMR), Microwave Assisted Magnetic Recording (MAMR), bit-patterned media, with combinations of these approaches also being possible.
Bit-patterned media, in particular, presents one of the most promising methods to overcome the density limitations imposed by the trilemma. In conventional media, the magnetic recording layer is a thin film of a magnetic alloy, which naturally forms a random mosaic of nanometer-scale grains that behave as independent magnetic elements. Each recorded bit is made up of many of these random grains. In bit-patterned media, on the other hand, the magnetic layer is created as an ordered array of highly uniform islands or dots, each dot being capable of storing an individual bit.
One challenge associated with bit-patterned media is in the creation of a bit-patterned media master disk. One of the very first steps in making the bit-patterned media is the creation of a master, which is then used to make the copies and finally these copies are used to make stampers for the bit-patterned media print process. The positional accuracy of the bits is extremely important during the mastering process, since all of the errors in the master propagate and possibly amplify through the subsequent disks. Even worse, compensation for errors in the master is not possible and the proliferation of errors from the master cannot be controlled. Until now, the bit-patterned media master pattern has been created one pass at a time. Unfortunately, the accuracy of dot placement using these traditional methods is less than perfect due to the following somewhat uncontrollable factors: (1) larger mechanical disturbances (e.g., environmental factors, disk flutter, bearing inaccuracies, etc.) from track to track; (2) jitter due to electronic-beam blanking switching; (3) electronic beam deflection jitter; and (4) electronic beam current variation.
These and other shortcomings of the prior art are addressed by embodiment of the present invention. More particularly, the present invention provides advantages over the prior art in that an efficient and accurate method of mastering bit-patterned media is provided. The method generally comprises:
exposing a first area of resist to an electronic beam for a predetermined amount of time sufficient to create a first media dot in a first row of media dots;
deflecting the electronic beam to a second area of resist; and
exposing the second area of resist to the electronic beam for a predetermined amount of time sufficient to create a first media dot in a second row of media dots.
In accordance with at least some embodiments of the present invention, the electronic beam may be on or activated during the deflection step. Accordingly, it is one aspect of the present invention to enhance the efficiency with which bit-patterned media is mastered by allowing the electronic beam to be on during the entire mastering process or at least during each revolution of the substrate.
Traditionally, the mastering process could take up to several days to complete. Utilizing embodiments of the present invention, the bit-patterned media mastering process throughput is increased since the electronic beam is on all of the time and the efficiency of the process is nearly 100%. Accordingly, the amount of time needed to complete the mastering process can be reduced by days, thereby allowing a significant savings of money and resources. The only energy that gets wasted during the mastering process is the energy produced by the electronic beam during the deflection step. However, since the deflection step occurs so rapidly, the amount of energy wasted is minimal.
The above-described embodiments and configurations are not intended to be complete nor exhaustive. As will be appreciated, other embodiments of the invention are possible utilizing, alone or in combination, one or more features set forth above or described below.
Several drawings have been developed to assist with understanding the invention. Following is a brief description of the drawings that illustrate the invention and its various embodiments.
It should be understood that the drawings are not necessarily to scale, and that in certain instances, the disclosure may not include details which are not necessary for an understanding of the present invention, such as conventional details of fabrication and assembly, by those of skill in the art. Also, while the present disclosure describes the invention in connection with those embodiments presented, it should be understood that the invention is not strictly limited to these embodiments.
With reference now to
The controller 204 is adapted to generally control the overall mastering process including rotation of the media substrate as well as determining how long each area on the substrate (or a resist on the substrate) should be exposed to an electronic beam to create a dot. Accordingly, the controller 204 may be provided with logic to control the decisions that need to be made during the mastering process or determine that human intervention is required to address a particular issue. To support its decision making ability, the controller 204 may also be provided with inputs from external devices or sensors (e.g., feedback inputs relating to the current position of the electronic beam manipulator(s) 216, feedback inputs relating to substrate rotation speed, feedback inputs relating to electronic beam strength, feedback inputs relating to environmental temperatures, pressures, moisture, and so on).
Based on information received from these various inputs, the controller 204 makes a control decision and provides a control input to the pattern generator 208. The pattern generator 208 is basically a waveform generator that is operable to generate a control waveform that can be transferred to and understood by the electronic beam manipulator(s) 216.
After the pattern generator 208 has generated the appropriate waveform or waveforms, depending upon the number of manipulators in the electronic beam manipulator(s) 216, the pattern generator 208 forwards the waveform(s) to the electronic beam manipulator(s) 216. In the event that the pattern generator generates a digital waveform, the waveform is first passed through the digital-to-analog module 212, which converts the digital waveform to an analog waveform and then forwards the analog version of the waveform to the electronic beam manipulator(s) 216.
The electronic beam manipulator(s) 216 receive the control waveform(s) and adjust the position of the electronic beam accordingly. As can be seen in
One example of waveforms provided to the first and second deflectors 312, 316, respectively, is depicted in
Referring back to
In accordance with at least some embodiments of the present invention, the deflectors 312, 316 comprise a pair of capacitive plates through which the electronic beam 308 passes. The relative voltage applied to each plate in the pair of capacitive plates may be adjusted, thereby altering the electronic field between the plates. This alteration of the electronic field between the plates may cause the electronic beam 308 to be deflected along either the x or y-axis, depending upon the orientation of the plates in the deflector 312, 316. If there is no difference in voltage between the two plates, then the electronic beam 308 will pass through the plates without having its path altered. However, if there is a difference in voltage between the two plates in a deflector, then the electronic beam 308 will be “bent” or otherwise have its trajectory manipulated as it passes through the deflector. This enables the deflectors 312, 316 to guide the electronic beam 308 based on the voltage waveforms applied to one plate while maintaining the other plate at a substantially constant voltage (e.g., the base voltage depicted in
In accordance with at least some embodiments of the present invention, the y-axis may be oriented substantially parallel to a radial line emanating from the center of the substrate 304 which is being mastered. The x-axis may be oriented substantially orthogonal to the y-axis and may lie in the same plane as the y-axis (i.e., the plane corresponding to the top surface of the substrate 304). Moreover, the x-axis may be oriented substantially parallel to a line which is tangential to the outer edge of the substrate (assuming the substrate is circular or cylindrical). Accordingly, the electronic beam 308 is directed toward the substrate 304 and travels in the direction of the z-axis while the deflectors 312, 316 control the positioning of the electronic beam 308 along the x and y-axis.
As can be seen in more detail in
As can be seen in
As can be seen in
With reference now to
In operation, a first area in the first row 704 is exposed to the electronic beam 308 for a predetermined amount of time sufficient to cure a resin on the substrate 304 and, thereby, permanently create a dot on the substrate. This predetermined amount of time is typically around 200 ns, but may vary depending upon the strength of the electronic beam, the characteristics of the resin, and other design considerations.
During the predetermined amount of time, the electronic beam 308 is manipulated along the x-axis via the second deflector 316 such that the electronic beam 308 follows the same area while the substrate 304 is rotated. This manipulation of the electronic beam 308 in the down-track direction during substrate 304 rotation helps to reduce the dragging effect or smearing of dots in the down-track direction. In other words, if the electronic beam 308 were not moved to track the rotation of the substrate 304, each dot would be slightly longer along the x-axis than it is along the y-axis.
After the predetermined amount of time has passed, the electronic beam 308 is moved to a first area in the second row 708. During this step, the first deflector 312 guides the electronic beam 308 along the y-axis from the first row 704 to the second row 708 and the second deflector 316 guides the electronic beam 308 slightly down-track (along the x-axis) to the first area in the second row 708. This particular step may take less than 1 ns. Thus, the electronic beam 308 does not need to be turned off because this short amount of time is not sufficient to cure the resin between dots. Additionally, the deflection occurs so quickly that a minimal amount of energy from the beam 308 is wasted and no energy is wasted by switching the beam 308 off.
This first area in the second row 708 is exposed to the electronic beam 308 for a predetermined amount of time sufficient to cure the resin on the substrate 304 and permanently create a dot in the second row 708.
Thereafter, the electronic beam 308 is again manipulated, but this time back to the first row 708. The first deflector 312 guides the beam 308 in a cross-track direction while the second deflector 316 guides the beam 308 in a down-track direction. Accordingly, a second area (down-track from the first area) in the first row 704 is exposed to the electronic beam 308 for a predetermined amount of time sufficient to cure the resin on the substrate 304 and permanently create another dot in the first row 704.
Again, after a predetermined amount of time has passed, the method continues with the deflectors 312, 316 moving the electronic beam 308 back to a second area (down-track from the first area) in the second row 708. This second area in the second row 708 is exposed to the electronic beam 308 for a predetermined amount of time sufficient to cure the resin on the substrate 304 and permanently create another dot in the second row 708. The method continues until the substrate has completed a rotation and the first and second rows 704, 708 have been mastered. After the first and second rows 704, 708 have been mastered, the electronic beam 308 is deflected down to the third row 712 and the third and fourth rows 712, 716 of dots are mastered similarly to the first and second rows 704, 708 (i.e., both rows are mastered during the same rotation of the substrate 304).
Although embodiments of the present invention have described the mastering of two adjacent tracks during a single rotation of a substrate, one skilled in the art will appreciate that the invention is not so limited. More specifically, embodiments of the present invention may be utilized to master more than two tracks during a single rotation of a substrate. Accordingly, an electronic beam may be moved to a first, then a second, then a third (and possibly a fourth, fifth, sixth, etc.) row before moving back to the first row to create another dot in the first row. The methodology with which the electronic beam is moved between rows may vary depending upon the number of rows that are being mastered during a single rotation and the relative orientation of dots in adjacent rows. There may be several ways of mastering three or more adjacent tracks of rows of dots during a single rotation of the substrate and such variants will become apparent after reviewing the present disclosure.
The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing description for example, various features of the invention have been identified. It should be appreciated that these features may be combined together into a single embodiment or in various other combinations as appropriate for the intended end use of the band. The dimensions of the component pieces may also vary, yet still be within the scope of the invention. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, though the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g. as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.
The present invention, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and\or reducing cost of implementation. Rather, as the following claims reflect, inventive aspects lie in less than all features of any single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this Detailed Description, with each claim standing on its own as a separate preferred embodiment of the invention.
