US3516920A - Sputtering apparatus - Google Patents

Sputtering apparatus Download PDF

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US3516920A
US3516920A US644923A US3516920DA US3516920A US 3516920 A US3516920 A US 3516920A US 644923 A US644923 A US 644923A US 3516920D A US3516920D A US 3516920DA US 3516920 A US3516920 A US 3516920A
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target
electron
sputtering
source
gun
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US644923A
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Emil C Muly Jr
Robert M Oman
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National Research Corp
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Nat Res Corp
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C23C14/354—Introduction of auxiliary energy into the plasma
    • C23C14/355—Introduction of auxiliary energy into the plasma using electrons, e.g. triode sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
    • C23C14/354—Introduction of auxiliary energy into the plasma
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/34—Gas-filled discharge tubes operating with cathodic sputtering

Definitions

  • Dielectric targets are sputtered by neutralizing positive ion collection at the target using a separate source of electron bombardment instead of the conventional radio frequency voltage source connected to the target.
  • the apparatus can also be utilized for sputtering conductive targets with the usual high voltage connector going to the electron source instead of the target.
  • the present invention relates to cathode sputtering apparatus of the type described for instance in US. Pat. 3,021,271 to Wehner. It is a special problem in this art to sputter dielectric material targets because the sputter target must be biased negatively to attract positive ions, but a dielectric cannot drain positive charges formed by impinging ions. The art has solved this problem by utilizing high frequency target voltage sources (Wehner, Advances in Electronics and Electron Physics, vol. 7 (1955)).
  • the high frequency voltage source adds undue complexity, cost and bulk to the sputtering apparatus and involves problems of tuning and shielding to prevent unauthorized radio broadcasting from the voltage source.
  • This object is achieved by using a separate high energy electron gun to charge the electrically floating target.
  • the target is a dielectric (or an electric floating conductor) the electrons impinging on the target face cause positive ion collection by charging the target negative with respect to the plasma.
  • the single apparatus is useful for sputtering of both conductors and dielectrics.
  • the electron gun is constructed to impinge electrons on a wide area of the target to assure substantial uniformity of charge.
  • the electron beam formed by practical ineX- pensive apparatus is not uniform, per se. But the mobility of electrons reaching the target surface is sufficient to compensate for this deficiency.
  • This apparatus avoids the need for a high frequency power supply with its attendant problems and indeed, can utilize the direct current high voltage power supplies now used for direct connection to conductive targets.
  • the power supply would be connected to the electron gun of the present invention.
  • FIG. 1 is a diagram of a first and preferred embodiment and FIG. 2 is a similar diagram of a second embodiment.
  • the apparatus of FIG. 1 comprises a source of electrons 10 which is a thermionic filament 12 inside a grounded metal tube 14 with an exit port 16 adjacent to which is an auxiliary anode electrode 18 and opposed thereto being a main anode electrode 20.
  • a source of electrons 10 which is a thermionic filament 12 inside a grounded metal tube 14 with an exit port 16 adjacent to which is an auxiliary anode electrode 18 and opposed thereto being a main anode electrode 20.
  • a plasma forms in this region.
  • a target 24 of dielectric material is mounted parallel to the electron path.
  • Opposing the target is a substrate 26 ice to be coated with sputtered target material and having an aperture 28 therein.
  • an electron gun 30 mounted behind the substrate is an electron gun 30 of well known design, per se, after Pierce.
  • the gun comprises the usual elements; heater 32, cathode 34, grid 36 and anode 38.
  • the gun is powered by a conventional industrial power supply 40 with current control 42. In operation the gun produces a wide beam 44 of electrons striking the target to charge it to its desired negative operating potential and neutralize positive ions on the target surface.
  • the apparaus described above is mounted in a vacuum chamber (not shown) which is evacuated to a pressure of about 2 1O torr as indicated on the drawing.
  • the gun 30 can operate for reasonably long periods of time before operation is limited by erosion of the cathode 34 or arcing due to backstreaming ions generated in the electron beam 44 and/or in the basic plasma formed at 22 between electron source 10 and anode 20.
  • the sputtering operation can be conducted in the medium provided by residual air molecules or the apparatus evacuated to a lower pressure and backfilled to a pressure of 2 10" torr by bleeding in a desired gas such as argon or hydrogen.
  • Electrical voltage sources (not shown) are provided to bias the gun cathode to about 4000 volts negative and the anodes 18, 20 to low positive voltages as indicated on the drawing.
  • the magnetic field H is typically about 10-20 gauss for preventing divergence of the low energy electron beam obtained from source 10. This low field has little effect on the high energy electron beam 44 or on the ions formed in the plasma.
  • FIG. 2 A second embodiment of the invention is shown in FIG. 2 wherein the gun 30 is mounted at a right angle to its original FIG. 1 position and the magnetic field strength H is increased to several hundred gauss to bend the electron beam 44 around to target 24. This avoids the use of an aperture in substrate 28.
  • the sputtering can be conducted at higher pressures, say 10 torr while a separate pump is provided to evacuate gun 30 to the lower pressure (below 10 torr) necessary for its effective operation.
  • the apertures 39 of anode 38 and 1 or 28 of substrate 26 can be utilized to maintain this pressure differential.
  • the electron gun can be provided with beam bending and other ion trap means as shown in US. Pat. 3,046,936 to Simons.
  • the electron source 30 may be operated in a pulsating fashion to pcriodically charge target 24 if desired. It is therefore intended that the above disclosure shall be read as illustrative and not in a limiting sense.
  • a sputtering device comprising means for forming a plasma and a target located to draw positive ions from said plasma when the target is sufficiently negatively charged for sputtering, the improvement wherein a source of electrons is provided apart from said target and plasma forming means, said source being constructed and arranged to spray electrons on said target to provide said negative charge, at least in part for sputtering.
  • the apparatus comprising means for focussing the electrons through the aperture and spreading them beyond the aperture to cover a large target area.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)
  • Physical Vapour Deposition (AREA)

Description

June 23, 1970 E. c. MULY ,'JR ET SPUTTERING APPARATUS Filed June 9, 1967 2x10 Torr FIG. I
United States Patent 3,516,920 SPUTTERING APPARATUS Emil C. Muly, Jr., Needham, and Robert M. Oman,
Wellesley, Mass., assignors to National Research Corporation, Newton Highlands, Mass., a corporation of Massachusetts Filed June 9, 1967, Ser. No. 644,923 Int. Cl. C23c 15/00 US. Cl. 204-298 3 Claims ABSTRACT OF THE DISCLOSURE Dielectric targets are sputtered by neutralizing positive ion collection at the target using a separate source of electron bombardment instead of the conventional radio frequency voltage source connected to the target. The apparatus can also be utilized for sputtering conductive targets with the usual high voltage connector going to the electron source instead of the target.
The present invention relates to cathode sputtering apparatus of the type described for instance in US. Pat. 3,021,271 to Wehner. It is a special problem in this art to sputter dielectric material targets because the sputter target must be biased negatively to attract positive ions, but a dielectric cannot drain positive charges formed by impinging ions. The art has solved this problem by utilizing high frequency target voltage sources (Wehner, Advances in Electronics and Electron Physics, vol. 7 (1955)).
The high frequency voltage source adds undue complexity, cost and bulk to the sputtering apparatus and involves problems of tuning and shielding to prevent unauthorized radio broadcasting from the voltage source.
It is the object of the present invention to provide an alternative apparatus for sputtering dielectrics which avoids or is less vulnerable to the foregoing drawbacks.
This object is achieved by using a separate high energy electron gun to charge the electrically floating target. When the target is a dielectric (or an electric floating conductor) the electrons impinging on the target face cause positive ion collection by charging the target negative with respect to the plasma. The single apparatus is useful for sputtering of both conductors and dielectrics. The electron gun is constructed to impinge electrons on a wide area of the target to assure substantial uniformity of charge. The electron beam formed by practical ineX- pensive apparatus is not uniform, per se. But the mobility of electrons reaching the target surface is sufficient to compensate for this deficiency. This apparatus avoids the need for a high frequency power supply with its attendant problems and indeed, can utilize the direct current high voltage power supplies now used for direct connection to conductive targets. The power supply would be connected to the electron gun of the present invention.
Embodiments of the invention are now described with reference to the accompanying drawings wherein FIG. 1 is a diagram of a first and preferred embodiment and FIG. 2 is a similar diagram of a second embodiment.
The apparatus of FIG. 1 comprises a source of electrons 10 which is a thermionic filament 12 inside a grounded metal tube 14 with an exit port 16 adjacent to which is an auxiliary anode electrode 18 and opposed thereto being a main anode electrode 20. There is an electron path between the electron source and anode indicated by line 22. A plasma forms in this region. A target 24 of dielectric material is mounted parallel to the electron path. Opposing the target is a substrate 26 ice to be coated with sputtered target material and having an aperture 28 therein.
Mounted behind the substrate is an electron gun 30 of well known design, per se, after Pierce. The gun comprises the usual elements; heater 32, cathode 34, grid 36 and anode 38. The gun is powered by a conventional industrial power supply 40 with current control 42. In operation the gun produces a wide beam 44 of electrons striking the target to charge it to its desired negative operating potential and neutralize positive ions on the target surface.
The apparaus described above is mounted in a vacuum chamber (not shown) which is evacuated to a pressure of about 2 1O torr as indicated on the drawing. At
these pressures the gun 30 can operate for reasonably long periods of time before operation is limited by erosion of the cathode 34 or arcing due to backstreaming ions generated in the electron beam 44 and/or in the basic plasma formed at 22 between electron source 10 and anode 20.
The sputtering operation can be conducted in the medium provided by residual air molecules or the apparatus evacuated to a lower pressure and backfilled to a pressure of 2 10" torr by bleeding in a desired gas such as argon or hydrogen.
Electrical voltage sources (not shown) are provided to bias the gun cathode to about 4000 volts negative and the anodes 18, 20 to low positive voltages as indicated on the drawing. The magnetic field H is typically about 10-20 gauss for preventing divergence of the low energy electron beam obtained from source 10. This low field has little effect on the high energy electron beam 44 or on the ions formed in the plasma.
A second embodiment of the invention is shown in FIG. 2 wherein the gun 30 is mounted at a right angle to its original FIG. 1 position and the magnetic field strength H is increased to several hundred gauss to bend the electron beam 44 around to target 24. This avoids the use of an aperture in substrate 28.
Other variations within the scope of the present invention will be apparent to those skilled in the art. For instance, the sputtering can be conducted at higher pressures, say 10 torr while a separate pump is provided to evacuate gun 30 to the lower pressure (below 10 torr) necessary for its effective operation. The apertures 39 of anode 38 and 1 or 28 of substrate 26 can be utilized to maintain this pressure differential. The electron gun can be provided with beam bending and other ion trap means as shown in US. Pat. 3,046,936 to Simons. The electron source 30 may be operated in a pulsating fashion to pcriodically charge target 24 if desired. It is therefore intended that the above disclosure shall be read as illustrative and not in a limiting sense.
What is claimed is:
1. In a sputtering device comprising means for forming a plasma and a target located to draw positive ions from said plasma when the target is sufficiently negatively charged for sputtering, the improvement wherein a source of electrons is provided apart from said target and plasma forming means, said source being constructed and arranged to spray electrons on said target to provide said negative charge, at least in part for sputtering.
2. The apparatus of claim 1 wherein the said sputtering device has a substrate in opposing relationship to the target and wherein the said source of electrons is located behind the substrate and wherein the substrate has an aperture, the apparatus comprising means for focussing the electrons through the aperture and spreading them beyond the aperture to cover a large target area.
3. The apparatus of claim 1 wherein the target floats 4 electrically and the said electron source is the principal means for biasing the target. JOHN H. MACK, Primary Examiner References Cited S. S. KANTER, Assistant Examiner UNITED STATES PATENTS 5 U.S. C1.X.R. 3,324,019 6/1967 Laegreid et a1 204298 204 .192 3,287,243 11/1966 Libenza 204192 3,271,286 9/1966 Lepselter 204192
US644923A 1967-06-09 1967-06-09 Sputtering apparatus Expired - Lifetime US3516920A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4030996A (en) * 1971-09-07 1977-06-21 Telic Corporation Electrode type glow discharge method and apparatus
US20040060813A1 (en) * 2002-09-30 2004-04-01 Roman Chistyakov High-power pulsed magnetron sputtering

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3271286A (en) * 1964-02-25 1966-09-06 Bell Telephone Labor Inc Selective removal of material using cathodic sputtering
US3287243A (en) * 1965-03-29 1966-11-22 Bell Telephone Labor Inc Deposition of insulating films by cathode sputtering in an rf-supported discharge
US3324019A (en) * 1962-12-11 1967-06-06 Schjeldahl Co G T Method of sputtering sequentially from a plurality of cathodes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3324019A (en) * 1962-12-11 1967-06-06 Schjeldahl Co G T Method of sputtering sequentially from a plurality of cathodes
US3271286A (en) * 1964-02-25 1966-09-06 Bell Telephone Labor Inc Selective removal of material using cathodic sputtering
US3287243A (en) * 1965-03-29 1966-11-22 Bell Telephone Labor Inc Deposition of insulating films by cathode sputtering in an rf-supported discharge

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4030996A (en) * 1971-09-07 1977-06-21 Telic Corporation Electrode type glow discharge method and apparatus
US20040060813A1 (en) * 2002-09-30 2004-04-01 Roman Chistyakov High-power pulsed magnetron sputtering
WO2004031435A2 (en) * 2002-09-30 2004-04-15 Zond, Inc. High-power pulsed magnetron sputtering
WO2004031435A3 (en) * 2002-09-30 2004-09-30 Zond Inc High-power pulsed magnetron sputtering
US7147759B2 (en) 2002-09-30 2006-12-12 Zond, Inc. High-power pulsed magnetron sputtering
US20070119701A1 (en) * 2002-09-30 2007-05-31 Zond, Inc. High-Power Pulsed Magnetron Sputtering

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