Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1999-09-02
2001-05-15
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298090, C204S298150, C204S298230, C204S298250, C204S298280, C118S058000, C118S069000, C118S503000, C118S719000
Reexamination Certificate
active
06231732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to substrate handling and coating systems, and more particularly to a novel dual mode step and dwell or pass-through design for the construction of a sputtering machine apparatus for coating computer memory media, and including a cylindrical shaped vacuum chamber and apparatus for the holding, transporting, heating, cooling, and coating of a multiplicity of disk substrates.
2. Brief Description of the Prior Art
Hard disk drives provide fast, non-volatile, rewritable and economical computer memory. Virtually all disk media, such as magnetic hard disks, magneto-optical disks and phase-change optical disks, involve coatings by various physical deposition techniques such as sputtering or chemical deposition. Currently, the computer memory disk media industry utilizes two general types of sputtering machines for the sputter-deposition of a succession of various layers onto the disk surfaces to produce the memory media.
The first type of sputtering machine is an in-line or “pass-through” machine. It consists of either a linear arrangement of relatively small individual but connected chambers, or one or two long chambers with vacuum transition locks at each end of the line. Processing stations are located either along the long chambers or at each individual chamber. During deposition, a multiple-disk substrate carrier, called a pallet, continuously passes in front of the sputtering targets or sources. U.S. Pat. No. 4,894,133, issued to Hedgcoth and entitled “Method and Apparatus for Making Magnetic Recording Disk.” describes such an in-line machine. Another example is taught by U.S. Pat. No. 4,749,465, issued to Flint et al. and entitled “In-Line Disk Sputtering System.” This machine uses a massive block with a semi-circular groove rather than the conventional pallet to hold the disks. Still another example of this type of machine is taught by U.S. Pat. No. 3,290,670, issued to Charschan et al. and entitled “Apparatus for Processing Materials in a Controlled Atmosphere.” Vendors of large machines of this type include Ulvac of Japan, Leybold of Germany, and Wilder Associates (formally Circuit Processing Apparatus) of the USA. In addition, some companies custom build their own large in-line machines for in-house use.
A second type of sputtering machine is a stationary or “static deposition” machine. In these machines, a single disk substrate moves in succession from one processing station to the next, where various processing steps, such as heating, sputtering and cooling, take place while the substrate remains fixed with respect to the processing source (hence the terminology “static machine”). Typically, the processing stations in static systems are arranged along a circular path so that the disk input (loading) and output (unloading) stations are adjacent to each other. Such is the layout of the machine taught in U.S. Pat. No. 5,425,611, issued to Hughes et al. and entitled “Substrate Handling and Processing System.” The Intevac MDP-250 memory disk sputtering system made by Intevac is another example of a static system. Of similar layout is another commercial machine, the Circulus
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built by Balzers/Leybold. Yet another example of a static machine adopting a folded linear design is described in U.S. Pat. No. 4,500,407, issued to Boys and entitled “Disk or Wafer Handling and Coating System.” This machine also has the input and output stations adjacent to each other. An exception is the in-line static machine offered by Ulvac, where a pallet carrying several disks stops in front of a group of individual sputtering targets (or sources) each facing a disk in the pallet.
None of the above-described sputtering machines fully satisfies the requirements for the mass production of high-quality hard disks or wafers. The first-mentioned type of machines have relatively high throughput but usually produce excessive debris and defects in the coated disks. Such contamination debris arise from several sources. One source is attributable to the entrance vacuum lock, where rapid pumping of the load-lock stirs the air violently, causing transfer of small particles of debris from the pallet and the chamber interior to the surface of the disks. The debris particles are generally knocked off the disks by after-coating buffing and/or burnishing, leaving defects in the magnetic memory layer and other layers.
A second source of particulate debris in pass-through machines is the vibrational motion of the disks in the pallet as the pallet moves through the machine. Since the pallet makes many passes through the machine before cleaning, a relatively thick layer of coating gradually builds up on the pallet. The stress in the films builds up with thickness. The combined film stress, thermal cycling and abrasive action between the disk edge and the pallet holder lead to shedding of particulate debris. Some shedding of debris at the disk holder may also occur upon loading the disk onto the pallet; such shedding may occur even if sophisticated robots are used. The pallet-related debris also lead to defects in the layers including the magnetic memory layer.
Arcing or spitting in the carbon overcoat deposition station presents another source of magnetic defects. Most of today's hard disks use hydrogenated carbon (also called diamond-like carbon or DLC) as the overcoat or protective layer. Unlike electrically conductive graphite, hydrogenated carbon is a dielectric. It builds up an insulating layer on various areas of the sputtering target, causing sporadic arcing. The arc-accelerated particles can penetrate the magnetic memory layer and produce memory defects. Although this problem may be minimized by reducing the power supplied to the sputtering target, this also decreases the carbon sputtering rate and accordingly reduces the machine throughput. A better solution to the arcing problem involves the use of a high temperature substrate and a different, e.g., silicon carbide (SiC), overcoat in lieu of the conventional hydrogenated carbon overcoat. However, the SiC sputter-deposition is normally conducted at an elevated temperature, i.e., 700° C. or above to obtain the necessary crystalline structure. Most of the current machines of the first-mentioned type use aluminum pallets that tend to warp, soften or even melt at elevated temperatures. Other pallet materials with higher melting points could be used, but the cost would be prohibitively high.
A static machine carries a single disk at a time sequentially from one processing station to the next. Because no pallet is used, the shedding of debris is greatly reduced, and the process temperature may be higher than that in a typical pass-through machine. As a result, such machines generally produce disks with fewer magnetic defects and debris contamination compared with a pass-through machine. However, these machines have their own drawbacks. First, the one-disk-at-a-time processing in a typical static machine causes its throughput to be two to four times lower than that of a typical pass-through machine. In addition, unless a pass-through machine can be made totally compatible with high-temperature processing, as described in detail below, the problem of arcing during carbon deposition will persist, making it practically impossible to raise the throughput of the machine by simply raising the power to the sputtering target. Finally, because the equipment costs of the two types of machines are similar, the per-disk manufacturing cost for a static machine is generally noticeably higher than that for a pass-through machine. In short, because future magnetic hard disk drives, with higher packing densities, will command low-cost disks with extremely low defects, there is an urgent need to raise the throughput of a static machine to the level of a pass-through machine without sacrificing quality or cost.
Current magnetic disk sputtering machines have several additional limitations. One of the most severe limitations is that they generally are not compatible with high-temperature proc
Hollars Dennis R.
Zubeck Robert B.
Hamrick Claude A. S.
Nguyen Nam
Oppenheimer Wolff & Donnelly LLP
SciVac
Ver Steeg Steven H.
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