Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Patent
1996-06-21
1998-02-10
Breneman, R. Bruce
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
2041921, 20429805, 20429806, 20429807, 20429808, 20429812, 20429816, 20429821, 118723R, 118723VE, 118723MP, 118723E, 427569, 427580, 427585, 427523, C23C 1434, C23C 1600
Patent
active
057165009
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method and an apparatus for generation of a discharge in own vapors of a radio frequency electrode for sustained self-sputtering of the electrode.
BACKGROUND OF THE INVENTION
The self-sputtering of an electrode-cathode by an ion bombardment in own vapor of this electrode, denoted also as the "sustained self-sputtering", is an extraordinary sputtering regime in which the discharge producing necessary ions for an ion bombardment and sputtering of an electrode is maintained in own vapors of this electrode. In this regime an evaporation of the electrode material contributes to the sputtering, because an extremely high power density typical for these discharges causes high temperature of the electrode surface. High current density connecting with heavy ion bombardment and intensive emission of electrons on the cathode surface can be assumed as particular kind of plasma arc generated in the system. Contributions of different discharge regimes to the overall production of the cathode metal vapor depend on experimental conditions, particularly on (i) the power used for generation of the discharge, (ii) cooling of the electrode, and (iii) material and geometry of the electrode. This regime was first reported by Hosokawa et al. in 1980 (Anelva Corp. Japan). In their report the cylindrical copper target was sputtered in an argon discharge generated in a cylindrical DC magnetron. When the DC power supplied into the magnetron reached the particular threshold value, a contribution of copper ions to the total ion bombardment of the target was high enough to produce high partial pressure of copper vapors to maintain the discharge without argon. In this case the inflow of argon was closed and the discharge was maintained only in pure copper vapor, released from the copper target electrode by its bombardment by Copper ions themselves. Kukla et al (1990, Leybold AG, Germany) observed this sustained self-sputtering in a planar magnetron also with a copper target using particularly optimized magnetic field for increasing the target erosion area. They reported a minimum target DC power of about 80 W/cm.sup.2, necessary for an initiation of the sustained self-sputtering. In latest reports by Posadowski (1993) and Shingubara et al (1993) similar magnetron devices were used for the sustained self-sputtering of copper at power densities of about 100-250 W/cm.sup.2. No other target material but copper was reported as a suitable target material for the sustained self-sputtering. The reason can be ascribed to a high sputtering yield of copper in the ion bombardment with respect to other metals. No sputtering devices were reported to generate the self-sputtering regime but magnetrons, in which the sputtering rates are relatively high due to magnetic confinement of the discharge at the target electrode (cathode) surface and low operation pressures of the gas as compared to ordinary sputtering systems. This lower operation pressure is important for maintenance of the discharge in metal vapors, because the necessary evaporation temperature of targets is lower at lower pressures and the relative density of vapors in the working gas can be therefore higher. Regardless to this advantage of magnetrons the sustained self-sputtering mode was carried out only by copper and silver targets.
In the present invention is utilized a sputtering and evaporation principle developed recently by one of the inventors (L. Bardos, Czech patent application 1990) for the film sputtering into hollow substrates and tubes. The sputtering is carried out in the radio frequency (RF) generated plasma jet in a working gas flowing in the hollow RF electrode, which plays role of a "hollow cathode" while the "anode" is the RF plasma itself. The hollow RF electrode can serve as a target sputtered by ions generated in the plasma jet. The electrode material can react with an active gas in the plasma jet and a product of this reaction can be deposited as a thin film onto substrate surfaces.
SUMMARY OF THE INVENTION
An
REFERENCES:
patent: 3830721 (1974-08-01), Gruen et al.
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patent: 4588490 (1986-05-01), Cuomo et al.
patent: 4637853 (1987-01-01), Bumble et al.
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"Effect of Discharge Current and Sustained Self-Sputtering", Hosokawa et al., Sep. 22-26, 1980, pp. 11-14, Proceedings of The Eighth International Vacuum Congress, vol. 1 Thin Films, Cannes France.
"Highest Rate Self-Sputtering Magnetron Source", Kukla et al., pp. 1968-1970, Great Britain, 1990.
Sustained Self-Sputtering Using a Direct Current M:agnetron Source, W. Posadowski and Z. Radzimski, J. VAc. Sci. Technol. A, vol. 11, No. 6, Nov./Dec. 1993, pp. 2980-2984.
Sustained Self-Sputtering of Copper Film Employing DC Magnetron Source, S. Shingubara et al., Oct. 5-7, 1993 San Diego, USA, Oct. 26-27, 1993, Tokyo, Japan, 2 pages.
Barankova Hana
Bardos Ladislav
Berg Soren
Breneman R. Bruce
McDonald Rodney G.
Surfcoat Oy
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