Patent Application
20160097118
A deposition system, in accordance with various embodiments, mounts a substrate within a sealed chamber and supplies a radio frequency energy to an inductive source affixed to the sealed chamber with the inductive source having an inductive coil surrounding a tube. Coupling the radio frequency energy into a gas pumped into the sealed chamber creates plasma to uniformly deposit a thin layer on a surface of the substrate.
Without limitation, the present disclosure is generally directed to data storage media, and more particularly, systems and methods for forming overcoat layers on magnetic data recording media.
Controlling uniformity of a protective layer, such as a carbon overcoat (COC) layer, on a rotatable data recording medium can enhance mechanical and recording performance of the medium. An area of the medium having the relatively thinnest COC layer poses a risk of media corrosion, carbon-lube issues and durability performance. Moreover, it has been found that variations in the circumferential once-around (OAR) carbon thickness can adversely impact the bit error rate (BER) readback performance of the media.
Existing sources for carbon film deposition generally use a hot filament cathode to emit electrons by thermionic emission. Acceleration of the electrons results in a plasma in a chemical vapor deposition (CVD) media overcoat process. The plasma physics and surface chemistry (on all surfaces within the chamber, including the substrate) dictate the uniformity, deposition rate and properties of the resulting carbon thin films. While the hot filament design is an effective electron source, due to a number of factors such as aging and carburization, a filament can become unstable over time, which directly affects the carbon range performance and overall media quality.
Accordingly, various embodiments of the present disclosure are generally directed to the use of a so-called ACT (advanced carbon technology) source that uses inductively coupled plasma (ICP) in a plasma enhanced chemical vapor deposition (CVD) process. As explained below, an inductive coil operated at a suitable radio frequency (RF) generates couples into a gas in a deposition chamber to create plasma. The gas is cracked to direct deposition ions, such as carbon, onto a substrate. A dual-sided arrangement can be used so that protective overcoat layers, such as COC thin film layers, and other types of layers, can be concurrently formed on opposing sides of the substrate.
This advantageously eliminates the need for the use of carbon filaments and the associated control efforts associated with the filament, anode, gas flow, magnetic assemblies and shields that have heretofore been necessary to accommodate the deficiencies of the carbon filaments. It is contemplated that the various embodiments presented herein provide better, more uniform layer deposition with higher reliability and controllability.
These and other features will become apparent beginning with a review of
The substrate 104 can take a variety of forms including but not limited to a rotatable data magnetic recording medium with various layers such as recording layers, interlayers, barrier layers, soft magnetic underlayers, heat sink layers, etc. Other forms of substrates can be used, however, including non-magnetic recording media. Moreover, while the system 100 is described in terms of depositing a protective layer, the skilled artisan can readily modify the system 100 to configure the system to deposit other layers of a recording medium as required.
For purposes of the present discussion, the thin films 102 will be contemplated as comprising carbon overcoat (COC) protective layers with a uniform thickness of nominally from about 3 angstroms, Å (3×10−10 meters, m) to about 20 Å. Other thicknesses and thickness ranges can be used as desired including but not limited to thicknesses of up to about 40 Å. It will be noted that the system 100 eliminates the need for the use of a carbon filament as an electron source to deposit the film material, as generally represented at 106 in
Referring again to
A pair of inductive sources 110 is shown to provide the energy to enact the deposition process. Each of the inductive sources 110 include a tube (barrel) 112 surrounded by an inductive coil 114. The coils 114 are driven by respective radio frequency (RF) sources 116. A suitable RF frequency at an input power level of up to about 500 watts, W is applied.
A pair of gas sources 118 provides an inlet flow of gas into the chamber 108. While shown separately in
The gas takes a plasma state from the excitation provided by the inductive sources 110, directing ions (in this case, carbon) to the substrate 104. Magnet assemblies 120 and shields 122 can be used to control the ionic flow and deposition process. The shields may be grounded via reference voltage connection path 124. In some cases, a negative voltage bias can be applied to the substrate 104 to enhance and control the deposition process. The bias voltage is supplied by a direct current (DC) voltage source 126. Any suitable voltage can be used, such as nominally −120 VDC. Other features (not separately illustrated) can be incorporated into the system 100 including cooling systems, cathode and/or anode plates or structures, etc.
It will be appreciated that the various embodiments disclosed herein can provide a number of benefits. The system eliminates the need to use a separate filament member (such as 106,
The tube length, material, number of windings, etc. Can be varied based on application requirements. Gas injection through the central tube provides uniform presentation and flow of the ions to the substrate. Different RF frequencies can be tuned for particular applications.
Next, step 156 supplies radio frequency energy with the inductive coil of an inductive source to form plasma. The plasma is subsequently cracked in step 158 to release carbon from the hydrocarbon plasma before depositing the elemental carbon uniformly on a surface of the substrate. As a result of routine 150, a thin layer of carbon is formed on the substrate with a uniform thickness, which optimizes substrate performance in assorted data storage environments. It is noted that the various steps of routine 150 are not required or limiting. As such, any aspect of routine 150 can be altered or removed and additional steps and decisions can be added.
It is to be understood that even though numerous characteristics of various embodiments of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of various embodiments, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present technology to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the particular elements may vary depending on the particular application without departing from the spirit and scope of the present disclosure.
The present application makes a claim of domestic priority to U.S. Provisional Patent Application No. 62/058,310 filed Oct.1, 2014, the contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62058310 | Oct 2014 | US |
