Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1998-08-07
2001-03-20
Dang, Thi (Department: 1763)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S570000, C118S7230MP, C118S7230ER, C118S7230ER, C118S7230HC
Reexamination Certificate
active
06203862
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to systems and methods for processing a substrate using plasmas created through generated ions and, more particularly, to processing systems and methods which utilize two or more ion sources.
BACKGROUND OF THE INVENTION
Commercial plasma sources are used for both deposition onto and etching from surfaces for a wide variety of industrial applications, especially semiconductor, optical, and magnetic thin film processing. The plasma formed by such sources generates reactive neutral and ionic species which can chemically and/or physically interact with surfaces to deposit or remove material.
In many processes, the use of energetic ions from the plasma source can result in the deposition of materials with unique properties or allow the etching of surfaces under conditions which would not otherwise be effective. An ion source mounted in a vacuum chamber in which the substrate is positioned is a common method for processing substrates in a plasma. A gas with specific chemical properties is supplied to the ion source for ionization. The plasma generated is a mixture of various reactive neutral and ionic chemical species as well as energetic electrons. The energy of the ionic species interacting with the surface depends upon plasma electrical properties and pressure. Typically, the energy of ions bombarding the substrate is controlled by means of a substrate bias. Alternatively, if the substrate is electrically floating, the ion energy will be determined by the electron energy distribution which determines the difference between the plasma potential and the potential at the surface for which there is zero net current (floating potential). Control of the ion energy is desirable since deposition or etching process characteristics and resulting materials properties often depend strongly on this parameter.
In some applications, it is desirable to process both sides of a substrate simultaneously. This is typical in the deposition of thin layers of various materials in the manufacture of magnetic hard disks used in magnetic memory systems. In this case, ion sources are positioned on opposite sides of the disk. However, ion sources which utilize an anode for establishing a plasma potential tend to exhibit plasma instability and oscillation when two such sources are operated simultaneously in a processing chamber. Such unstable behavior does not permit predictable ion generation and process stability. Also, it has proven difficult to coat thin films with properties which will satisfy the requirements of a protective film on a hard disk. Thinner coatings permit the head to fly closer to the magnetics of the disk as to permit an increase in areal density. In this application, depositing overcoatings, the coating should have sufficient hardness, density, and adhesion as well as practical qualities including high deposition rates and low numbers of macroscopic particles on the surface. Accordingly, there is a need for improved substrate processing systems and methods wherein two or more ion sources may operate in a stable manner in a processing chamber and wherein the properties of the deposited layers may be improved for their intended purpose.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, a substrate processing system is provided. The substrate processing system comprises a processing chamber, a substrate holder positioned in the processing chamber, a gas source for supplying a process gas to the processing chamber, first and second ion sources located in the processing chamber and a power source for energizing the first and second ion sources. Each of these ion sources ionizes the process gas to produce ions for processing a substrate disposed on the substrate holder. The first and second ion sources include first and second anodes, respectively. The power source energizes the first and second anodes in a time multiplexed manner such that only one of the first and second ion sources is energized at any time.
The power source preferably comprises means for applying a pulsed, periodic voltage to each of the first and the second anode at a frequency less than about 100 kHz. In a preferred embodiment, the frequency is in a range of about 1 to 5 kHz. The pulsed, periodic voltage applied to each of the first anode and the second anode preferably has a duty cycle less than or equal to 50%.
The first and second ion sources are generally positioned on opposite sides of the substrate in the processing system. In some systems however, ion sources may also be positioned on the same side of the substrate and may be employed for example, to feed different gases through as to achieve multilayer depositions. Ions of the process gas from the first and second ion sources may be deposited on the substrate or may be used to etch the substrate.
According to another aspect of the invention, a method for processing a substrate is provided. The method comprises the steps of positioning a substrate in a processing chamber, supplying a process gas to the processing chamber and ionizing the process gas with first and second ion sources located in the chamber to produce ions of the process gas for processing the substrate. The first and second ion sources include first and second anodes, respectively. The method further comprises the step of energizing the first anode and the second anode such that only one of the first and second ion sources is energized at any time.
According to a further aspect of the invention, a method for operating two or more ion sources in a process chamber is provided. Each of the two or more ion sources has an anode. The method comprises the step of energizing the anodes of the ion sources in a time multiplexed manner such that only one of the ion sources is energized at any time.
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Bluck Terry
McGinnis Sean P.
Rogers James H.
Cole Stanley Z.
Dang Thi
Intevac, Inc.
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