(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2005/0092596 A1
`
` Kouznetsov (43) Pub. Date: May 5, 2005
`
`
`US 20050092596A1
`
`(54) METHOD AND APPARATUS FOR PLASMA
`GENERATION
`
`Publication Classification
`
`(76)
`
`Inventor: Vladimir Kouznetsov, Nynashamn
`(SE)
`
`Correspondence Address:
`NIXON & VANDERHYE, PC
`1100 N GLEBE ROAD
`8TH FLOOR
`
`ARLINGTON, VA 22201-4714 (US)
`
`(21) AP111. N0.:
`
`10/480,826
`
`(22) PCT Filed:
`
`Jun. 14, 2002
`
`(86) PCT No.2
`
`PCT/SE02/01160
`
`(30)
`
`Foreign Application Priority Data
`
`Jun. 14, 2001
`
`(SE) .......................................... 0102134-4
`
`Int. Cl.7 ..................................................... C23C 14/00
`(51)
`(52) US. Cl.
`........................................................ 204/192.12
`
`(57)
`
`ABSTRACT
`
`In a simple method and device for producing plasma flows
`of a metal and/or a gas electric discharges are periodically
`produced between the anode and a metal magnetron sput-
`tering cathode in crossed electric and magnetic fields in a
`chamber having a low pressure of a gas. The discharges are
`produced so that each discharge comprises a first period with
`a low electrical current passing between the anode and
`cathode for producing a metal vapor by magnetron sputter-
`ing, and a second period with a high electrical current
`passing between the anode and cathode for producing an
`ionization of gas and the produced metal vapor. Instead of
`the first period a constant current discharge can be used.
`Intensive gas or metal plasma flows can be produced without
`forming contracted arc discharges. The selfsputtering phe-
`nomenon can be used.
`
`ionizing
`
`
`
`
`Sputtering
`
`
` Sputtering
`
`
`
`
`Ionizing
`
`TSMC et al. v. Zond, Inc.
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`TSMC et al. v. Zond, Inc.
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`Patent Application Publication May 5, 2005 Sheet 1 0f 13
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`US 2005/0092596 A1
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`Fig. 1c
`
`
`
`Unbalanced
`Type I
`
`Balanced
`
`Unbalanced
`Type II
`
`
`
`Balanced
`
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`US 2005/0092596 A1
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`Fig. 19
`
` permanent
`magnets
`
`
`Fig. 1h
`
`sputtered
`surface
`
`
`
`
`
`
`was!
`
`
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`
`rear
`surface
`
`
`
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`Patent Application Publication May 5, 2005 Sheet 3 0f 13
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`Udischar
`ge
`(relative units)
`
`
`
`-
`I
`Fig. 23
`
`
`
`
`I I I
`
`l
`
`U1
`
`low current
`
`.
`
`u2 _________M
`
`l
`
`
`ltransition
`
`Idischarge
`(relative units)
`
`Deposition rate
`— — — Gas plasma flux intensity
`
`Flg _ 2b
`
`Deposition
`rate
`(relative
`units)
`
`
`
`
`
`
`6 Driving
`current
`(relative
`units)
`
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`Patent Application Publication May 5, 2005 Sheet 4 0f 13
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`GILLETTE-1004 / Page 5 of 27
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`
`
`mamas
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`Patent Application Publication May 5, 2005 Sheet 6 0f 13
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`US 2005/0092596 A1
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`Fig.6a
`
`Fig.6b
`
` Iomzmg
`Spuflefing
`
`I
`
`be
`
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`Patent Application Publication May 5, 2005 Sheet 8 0f 13
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`US 2005/0092596 A1
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`GILLETTE-1004 / Page 9 of 27
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`Patent Application Publication May 5, 2005 Sheet 9 0f 13
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`Patent Application Publication May 5, 2005 Sheet 10 0f 13
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`Fig.10
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`Patent Application Publication May 5, 2005 Sheet 12 0f 13
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`GILLETTE-1004 / Page 13 of 27
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`Patent Application Publication May 5, 2005 Sheet 13 0f 13
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`US 2005/0092596 A1
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`May 5, 2005
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`METHOD AND APPARATUS FOR PLASMA
`GENERATION
`
`TECHNICAL FIELD
`
`[0001] The present invention relates to methods and appa-
`ratus for generating plasma flows and in particular metals
`plasma flows obtained by discharges in crossed electric and
`magnetic fields.
`
`BACKGROUND OF THE INVENTION
`
`[0002] Electrical discharges in crossed fields (EXB dis-
`charges) attract much attention due to their importance for
`science and technology. In science EXB discharges are
`important in the field of plasma physics and cosmic physics.
`In technology EXB discharges are used in devices for
`thermonuclear fusion,
`in vacuum technology such as in
`vacuum pumps, vacuum measurements, for coating work
`pieces using e.g. magnetron sputtering, in plasma accelera-
`tors, and as plasma emitters in ion sources.
`
`[0003] The motion of charged particles in stationary
`crossed fields and quasi-stationary EXB discharges have
`been studied since 1921, see the article by A. W. Hull, “The
`effect of a uniform magnetic field on the motion of electrons
`between coaxial cylinders”, Phys. Rev. 18, 1921, pp. 31-57,
`and by H. C. Early, W. G. Dow, “Supersonic Wind at Low
`Pressures Produced by Arc in Magnetic Field”, Phys. Rev.
`79, 1950, p. 186. Such discharges could be classified accord-
`ing to different parameters such as gas pressure, strength and
`configuration of the magnetic field used, electrode configu-
`ration etc. For the purposes herein these discharges are best
`classified according to the intensity or generally the behav-
`iour of the discharge or driving current.
`
`[0004] According to this classification using the driving
`current, quasi-stationary discharges in crossed fields could
`be divided in two classes: low intensity and high intensity
`current discharges. It is necessary to note that the transition
`current depends on many parameters, in particular on the
`dimensions of the apparatus used, and can vary for hundreds
`of amperes. Low intensity current discharges in crossed
`fields could be called such discharges which produce a
`plasma inside a magnetic configuration with a density less
`than 1018 m"3 and high intensity current discharges could be
`called such discharges which produce a plasma having a
`density of more than 1018 m'3, the plasma density defined as
`the number of particles per unit volume.
`
`[0005] Low intensity current discharges in crossed fields
`are widely used in vacuum technology such as in vacuum
`pumps, for coating work pieces, e.g. in magnetron sputter
`deposition. Typical discharge devices are Penning cells and
`cylindrical and planar DC-magnetrons. The low driving
`current results in a low-density plasma, less than 1018 m"3 as
`indicated above.
`
`[0006] High intensity current discharges have been mostly
`used for generating dense plasma for the goals of thermo-
`nuclear fusion. Typical discharge devices include Homopo-
`lar I, Ixion and F I devices. The typical plasma density is
`about 1018-1023 m'3.
`
`[0007] The second important characteristic of discharges
`in crossed fields is the voltage drop between the electrodes.
`
`the rate of
`[0008] For a low intensity driving current
`neutral gas ionization is low and balances the plasma losses
`
`to form an equilibrium plasma density at a low level. The
`electrical resistance of the anode-cathode gap is high result-
`ing in a high anode-cathode potential drop. As soon as an
`opposite process becomes energetically possible a strongly
`enhanced ionization process should arise.
`
`[0009] Two methods have been described for plasma
`ionization in systems using with discharges in crossed
`electric and magnetic fields. Their practical applicability
`depends on system dimensions and the strength of the
`magnetic field. The method generally accepted in systems of
`sufficiently large dimensions using a strong magnetic field is
`the so called “Rotating Plasma Approach”. This approach is
`based on the fact that the electric field penetrates into the
`plasma and that the plasma is magnetized, see B. Lehnert,
`“Rotating Plasmas”, Nuclear Fusion 11, 1971, pp. 485-533.
`Another approach is based on fact that the electric field is
`concentrated preferably near the cathode of the discharge.
`This approach is used for processes in systems using a low
`magnetic field and non-magnetized ions. This approach
`could be called e.g. “Secondary Electron Approach”, see B.
`S. Danilin and B. K. Sirchin, Magnetron Sputtering Sys-
`tems, Moskva, Radio i Sviaz, 1982. As will be obvious from
`the following this invention deals with both kinds of systems
`and therefore both plasma approaches will be used.
`
`[0010] Alfvén has postulated, see H. Alfvén, “On the
`Origin of the Solar System”, Clarendon Press, Oxford, 1954,
`that a strongly enhanced ionization process should arise
`when the mutual plasma-neutral gas velocity reaches the
`critical value vc, the Alfvén limit, given by
`Vc=(25¢i/mi)1/2
`
`[0011] where ¢i is the ionization potential, e is the charge
`of the electron and mi is the ion mass.
`
`[0012] For devices having a low sputtering rate and low
`plasma losses it results in an anode-cathode voltage drop
`limitation during the starting period of the discharge. For
`devices having a high sputtering rate it results in an anode-
`cathode voltage drop limitation during all of the discharge
`time. The voltage drop or critical voltage VC is given by
`VC=CVCB
`
`[0013] where C is a constant and B is the strength of
`magnetic field in the discharge device. In the case of a high
`sputtering rate, the ionization potential ¢i of the sputtered
`atoms creates the metal vapor. It means that the discharge
`voltage has to depend on the sputtering cathode material.
`
`[0014] This phenomenon was demonstrated both by inves-
`tigation of plasma motion through a neutral gas and by
`experiments with planar magnetron sputtering devices, see
`U. V. Fahleson, “Experiments with Plasma Moving through
`Neutral Gas”, Physics Fluids, Vol. 4, 1961, pp. 123-127, and
`D. V. Mozgrin,
`I. K. Fetisov, and G. V. Khodachenko,
`“High-Current Low-Pressure Quasi-Stationary Discharge in
`a Magnetic Field: Experimental Research”, Plasma Physics
`Reports, Vol. 21, No. 5, 1995, pp. 400-409. In the latter
`publication the high current,
`low voltage discharge in a
`magnetron magnetic configuration is called as a “high-
`current diffuse regime”.
`
`It means that the transition from a low intensity
`[0015]
`current EXB discharge to a high intensity current discharge
`has to be followed by a decrease of the discharge voltage.
`Typical anode-cathode potential drops for low intensity
`
`GILLETTE-1004 / Page 15 of 27
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`US 2005/0092596 A1
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`May 5, 2005
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`current, quasi-stationary discharges are in the range of about
`10-03 kV and for high intensity current discharges in the
`range of about 300-10 V.
`
`If quasi-stationary discharges are implemented in
`[0016]
`magnetron sputtering devices,
`in a first regime effective
`cathode sputtering is obtained but a low ionization rate of the
`sputtering gas and metal vapor. In a second regime an
`opposite state occurs having a low sputtering rate but a high
`ionization rate of the sputtering gas. Thus, it can be said that
`it
`is impossible to generate, by a separate low intensity
`current quasi-stationary discharge, or by a separate high
`intensity current discharge in crossed fields, highly ionized
`metal plasma fluxes.
`
`[0017] The devices using EXB discharges can operate for
`a short time in the transient, i.e. the non-quasi-stationary,
`regime. In this regime it is possible to overcome the Alfvén
`limit of discharge voltage as well for high current dis-
`charges, see the article by B. Lehnert cited above. High
`current, high voltage non-quasi-stationary discharges occur
`in magnetron sputtering devices and are very important for
`magnetron sputtering applications because those discharges
`allow obtaining a fully ionized impermeable plasma in the
`magnetron magnetic configuration. But, as will be shown
`hereinafter, if transient discharges are implemented in mag-
`netron sputtering devices by either high intensity current
`discharges or by low intensity current discharges it
`is
`impossible to generate highly ionized intensive metal
`plasma fluxes.
`
`[0018] Metal plasma fluxes can be produced by low cur-
`rent quasi-stationary EXB discharges in a magnetron con-
`figuration for sputtering atoms in a moderate pressure, of
`e.g. 1-100 mTorr, and with a low-density plasma In this case
`the plasma is produced by an RF-induction coil mounted in
`the deposition chamber. The electron density produced in
`induction plasmas is about 1017-1018 m'3.
`
`[0019] This method of coating work pieces has important
`implications for the filling of high-aspect-ratio trenches and
`vias encountered in microelectronic fabrication processes as
`well as in sputtering magnetic materials and modifying the
`properties of thin films by energetic ion deposition, see J.
`Hopwood and F. Qian, “Mechanisms for highly ionized
`magnetron sputtering”, J. Appl. Phys. 78 (12), 15 Jul. 1995,
`pp. 758-765.
`
`[0020] The drawbacks of this method of metal plasma
`production include the complexity of the RF-ionization
`technique and the high pressure of the sputtering gas
`required for producing the low-density plasma. The high
`pressure of the sputtering gas is required because of the high
`energy consumption necessary for producing a low-density
`plasma.
`
`[0021] The discharges in crossed fields could be imple-
`mented by simple techniques and within an extremely wide
`range of operating pressures: from 10'11 up to 102 Torr.
`Low-pressure magnetron discharges, up to 10—5 Torr, can be
`achieved because of the selfsputtering phenomenon, see for
`example S. Kadlec and J. Musil, “Low pressure magnetron
`sputtering and selfsputtering discharges”, Vacuum, Vol. 47,
`pp. 307-311, 1996. This method of coating work pieces has
`important implications for the etching of surfaces by metal
`ions for increasing the adhesion of deposited layers and for
`the filling of high-aspect-ratio trenches and vias encountered
`in micro-electronic fabrication.
`
`[0022] The currents necessary for generating a dense
`plasma and sustaining it by high intensity current EXB
`discharges are large enough for cathode spots, and possibly
`also for anode spots, to be formed at the cold electrode
`surfaces. Devices having such electrodes should therefore
`have a natural tendency of forming spoke-shaped azimuthal
`plasma inhomogeneities, arc discharges, see B. A. Tozer,
`“Rotating Plasma”, Proc. IEEE, Vol. 112, 1965, pp. 218-228.
`Such conditions are strongly pronounced in all types of
`devices during the starting period of the discharges where a
`large driving current is needed for neutral gas burn-out.
`
`[0023] Having cold electrodes and neutral-plasma phe-
`nomena in mind, the experiments on plasma spoke forma-
`tion can be summarized as follows:
`
`a. In the Homopolar III experiments it was found
`[0024]
`that during the starting period the discharge current was
`confined to a set of about 10 to 12 narrow radial spokes,
`arcs, rotating with the plasma. See W. R. Baker, A.
`Bratenal, A. W. De Sliva, W. B. Kunkel, Proc. 4th Int.
`Conf. Ionization Phenomena in Gases 2, Uppsala 1959,
`North-Holland Publishing Comp., Amsterdam, p. 1171,
`and W. B. Kunkel, W. R. Baker, A. Bratenahl, K.
`Halbach, “Boundary Effects in Viscous Rotating Plas-
`mas”, Physics Fluids, Vol. 6, 1963, pp. 699-708.
`
`b. In the Leatherhead Homopolar device having
`[0025]
`a negative polarity one or two spokes were observed to
`arise during the initial breakdown of the discharge.
`They were soon smeared out to form spirals with an
`increasing velocity in the outward radial direction, see
`P. B. Barber, M. L. Pilcher, D. A. Swift, B. A. Tozer, C.
`r. de la VIe conference internationale sur les phe-
`nomenes d’ionization dans le gas 2, Paris, 1963, p. 395.
`
`c. In the Kruisvuur I device a single eccentric
`[0026]
`structure rotating around the axis with a velocity close
`to E/B was observed, see C. E. Rasmussen, E. P.
`Barbian, J. Kistemaker, “Ionization and current growth
`in an ExB discharge”, Plasma Physics, Vol. 11, 1969,
`pp. 183-195.
`
`[0027] From the experiments mentioned above and others,
`arc formation is clearly seen to be connected with the
`starting period of the high intensity current EXB discharges
`in most devices.
`
`SUMMARY OF THE INVENTION
`
`It is an object of the present invention to provide
`[0028]
`methods and apparatus allowing production of intensive,
`preferably gas or gas-metal or most preferably metal plasma
`flows.
`
`[0029] The problems, which the invention thus intends to
`solve, comprise:
`
`1. How to produce intensive, preferably gas or
`[0030]
`gas-metal or preferably metal plasma flows by ioniza-
`tion of gas and metal vapor produced using planar
`magnetron sputtering cathodes by a simple technique
`for producing discharges in crossed fields.
`
`2. How to produce these plasma flows without
`[0031]
`forming contracted arc discharges.
`
`3. How to provide pulsed discharges in crossed
`[0032]
`fields using the selfsputtering phenomenon.
`
`GILLETTE-1004 / Page 16 of 27
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`May 5, 2005
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`[0033] Thus, generally in a method for producing a plasma
`flow successive low and high intensity current quasi-station-
`ary and non quasi-stationary discharges in crossed electric
`and magnetic fields are used,
`the term “crossed fields”
`meaning “crossed electric and magnetic fields” herein. For
`producing the plasma a succession of discharges is thus
`used, i.e. pulsed discharges are used. The discharges that are
`well separated in time are defined to be quasi-stationary in
`the cases where at least the most important physical param-
`eters, such as current and voltage, are substantially constant
`or slowly varying during most of the discharge time, and are,
`if this condition is not fulfilled, non-quasi stationary. The
`plasma flow producing procedure can include the following
`steps:
`
`1. Alow intensity current, high voltage discharge
`[0034]
`in a magnetron magnetic configuration is used for metal
`vapor production. The following ionization of vapor is
`obtained by a high intensity current,
`low or high
`voltage discharge in the same magnetic configuration.
`The second, ionizing discharge starts immediately after
`the first one or with some, relatively small time delay.
`The parameters of the pulses and time delay of the
`second pulse are defined by the requirements imposed
`by the high ionization of sputtered vapor blobs.
`
`2. The metal vapor can be produced by a direct
`[0035]
`current discharge, i.e. not by pulsed discharges. In this
`case the metal vapor produces a continuous vapor flow
`out of the magnetic configuration where the discharge
`is made. If ionizing pulses follow having a sufficient
`frequency and driving current it is possible to produce
`a continuous metal plasma flow having a modulated
`intensity.
`
`[0036] The following basic schemes can be used:
`
`1. The plasma can be produced in a magnetron
`[0037]
`magnetic configuration in which combined or succes-
`sive low and high intensity current non-quasi-station-
`ary discharges in crossed fields are used.
`
`2. The plasma can be produced in a magnetron
`[0038]
`magnetic configuration in which a low intensity current
`quasi-stationary discharge is combined with or fol-
`lowed by a high intensity current non-quasi-stationary
`discharge, the discharges made in crossed fields.
`
`3. The plasma can be produced in a magnetron
`[0039]
`magnetic configuration in which combined direct cur-
`rent discharges and high current non-quasi-stationary
`discharges in crossed fields are used.
`
`4. The plasma can be produced in a magnetron
`[0040]
`magnetic configuration in which combined low inten-
`sity current non-quasi-stationary discharges and high
`intensity current quasi-stationary discharges in crossed
`fields are used.
`
`5. The plasma can be produced in a magnetron
`[0041]
`magnetic configuration in which combined successive
`low and high intensity current non-quasi-stationary
`discharges and high intensity current quasi-stationary
`discharges in crossed fields are used.
`
`6. The plasma can be produced in a magnetron
`[0042]
`magnetic configuration in which combined high inten-
`sity current non-quasi-stationary discharges and high
`intensity current quasi-stationary discharges in crossed
`fields are used.
`
`[0043] The combinations of discharges in crossed electric
`and magnetic fields mentioned above made in a magnetron
`magnetic configuration allow the production of plasma flows
`of preferably gas or gas and metal or most preferably of a
`metal plasma flow. For quasi-stationary discharges the
`choice of method can be based on the different efficiencies
`
`of the low and high current intensity discharges for sputter-
`ing and ionization in the different cases.
`
`[0044] The discharges in crossed fields have, as has been
`mentioned above, a natural
`tendency of forming spoke-
`shaped azimuthal plasma inhomogeneities—arc discharges.
`The probability of the transition of an EXB discharge in
`magnetron type devices to a contracted arc discharge
`increases with an increasing driving current. In low current
`discharges arcing occurs very rarely and it is possible to
`prevent the transition to arc discharges by specially adapted
`arc suppression schemes in the discharge power supply. In
`high current discharges there is a very high probability of arc
`discharges being formed and solutions to the problem of
`suppressing arc formation using similar schemes are not
`efficient. As will be described herein, arc suppression can be
`achieved using a now discovered phenomenon of depen-
`dence of arc formation on the plasma confinement properties
`of the magnetron magnetic configuration and on the time
`between discharges. The balanced magnetron magnetic con-
`figuration has relatively low plasma confinement properties.
`Therefore,
`for achieving efficient arc suppression,
`it
`is
`necessary to use a magnetic field having a high strength. In
`this case the plasma losses caused by diffusion will decrease
`as B"2 in the case of classic diffusion or as a B"1 in the case
`of Bohm diffusion, where B is the strength of the magnetic
`field. It was found that for a balanced magnetron magnetic
`configuration, in order to achieve efficient arc suppression,
`it is necessary to have a magnetic field strength of the radial
`B component of about 0.07-0.3 T, the radial direction here
`taken as directions parallel to the substantially flat surface of
`the cathode or target. Unbalanced and cusp-shaped magnetic
`configurations have improved plasma confinement proper-
`ties; therefore, for effective arc suppression it is sufficient to
`have a magnetic field strength of about 004-0.3 T.
`
`[0045] The plasma confinement properties of the magnetic
`configuration strongly affect the lower limit of the operating
`pressure used in the space at the cathode. It was found that
`for improving the plasma confinement properties the oper-
`ating pressure of the EXB discharge should be decreased.
`For a certain operating frequency a gas atmosphere is
`required only for starting the discharge. After the starting
`period it is possible to initiate the discharge by the residual
`plasma density left from the previous pulse. In this case
`metal vapor is produced by using the selfsputtering phe-
`nomenon and the plasma in the magnetic trap contains
`primarily ions of the target metal. The plasma flow from the
`magnetic trap contains preferably ions of the target metal as
`well.
`
`[0046] Generally, it can be said that the primary concept of
`the method described herein is to combine the magnetic
`configuration having improved plasma confinement proper-
`ties with low and high intensity current quasi-stationary
`discharges and non-quasi-stationary discharges or DC and
`high intensity current discharges for generating stable and
`intensive plasma flows. Low and high intensity current
`quasi-stationary discharges and non-quasi-stationary dis-
`charges are produced one after another with a repeating
`
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`US 2005/0092596 A1
`
`May 5, 2005
`
`frequency exceeding a minimal critical value depending on
`the plasma confinement properties of the magnetic trap. In
`the case of DC sputtering discharges, a high rate of ioniza-
`tion of gas and metal vapor is produced by a periodic
`repetition of the ionizing discharges.
`
`[0047] The methods and devices described herein can be
`used both in the “Rotating Plasma Approach” and the
`“Secondary Electron Approach” mentioned above.
`
`[0048] Additional objects and advantages of the invention
`will be set forth in the description which follows, and in part
`will be obvious from the description, or may be learned by
`practice of the invention. The objects and advantages of the
`invention may be realized and obtained by means of the
`methods, processes, instrumentalities and combinations par-
`ticularly pointed out in the appended claims.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0049] While the novel features of the invention are set
`forth with particularly in the appended claims, a complete
`understanding of the invention, both as to organization and
`content, and of the above and other features thereof may be
`gained from and the invention will be better appreciated
`from a consideration of the following detailed description of
`non-limiting embodiments presented hereinbelow with ref-
`erence to the accompanying drawings, in which:
`
`[0050] FIGS. la-lf are schematic views of different mag-
`netron magnetic configurations used in magnetron sputter-
`ing, in which —FIG. 1a is a view of a first type of an
`unbalanced magnetron magnetic configuration,
`
`[0051] FIG. 1b is a view of a balanced magnetron mag-
`netic configuration,
`
`[0052] FIG. IC is a view of a second type of an unbalanced
`magnetron magnetic configuration,
`
`[0053] FIGS. 1d and 16 are views illustrating the mag-
`netic configuration created by permanent magnets placed
`behind the target and an electromagnetic coil placed in front
`of the target,
`
`[0054] FIG. If is a view of a cusp-shaped magnetic
`configuration,
`
`[0055] FIG. 1g is a view from above of a magnetic
`configuration typical of magnetrons having a rotating mag-
`net,
`
`[0056] FIG. 1h is a schematic cross-sectional view show-
`ing the magnetic force lines in the magnetic configuration of
`FIG. lg,
`
`[0057] FIGS. 2a and 2b are schematic diagrams illustrat-
`ing limits between low and high current discharges of the
`quasi-stationary and non-quasi-stationary type respectively,
`
`[0058] FIGS. 3a and 3b are schematic diagrams of current
`and voltage pulses respectively as functions of time for
`sputtering and ionizing discharges in crossed fields,
`
`[0059] FIG. 4 is a schematic diagram of periodic current
`pulses of the kind illustrated in FIG. 3a as a function of time,
`
`[0060] FIG. 5 is a schematic diagram similar to that of
`FIG. 4 showing an alternative shape of the current pulses,
`
`[0061] FIG. 6 is a schematic diagram similar to that of
`FIG. 4 showing current pulses superimposed on a constant
`current level,
`
`[0062] FIG. 7a is a schematic diagram of the conductivity
`and plasma density as a function of time in a plasma
`confinement region,
`
`[0063] FIG. 7b is a schematic diagram substantially iden-
`tical to that of FIG. 4 showing the driving current pulses for
`producing the conductivity and plasma density of FIG. 7a,
`
`[0064] FIG. 8a is an electrical circuit diagram of a device
`for producing a metal vapor and the ionization thereof, the
`device having two pulsed power supplies connected in
`parallel,
`
`[0065] FIG. 8b is a diagram similar to that of FIG. 8a of
`a device including a single pulsed power supply having a
`variable impedance,
`
`[0066] FIG. 8c is a diagram similar to that of FIG. 8a of
`a device having a single pulsed power supply combined with
`a DC power supply,
`
`[0067] FIG. 9 is a detailed electrical circuit diagram
`corresponding to the diagram of FIG. 8a,
`
`[0068] FIG. 10 is a detailed electrical circuit diagram
`corresponding to the diagram of FIG. 8b,
`
`[0069] FIG. 11 is a detailed electrical circuit diagram
`corresponding to the diagram of FIG. 8c,
`
`[0070] FIG. 12a is a schematic cross-sectional view of a
`plasma source utilizing discharges in crossed electric and
`magnetic fields for gas or gas and metal or metal plasma
`production, corresponding to the second type of unbalanced
`magnetron magnetic configuration shown in FIG. 1c, and
`
`[0071] FIG. 12b is a schematic view similar to that of
`FIG. 12a illustrating a plasma source utilizing discharges in
`crossed electric and magnetic fields for gas or gas and metal
`or metal plasma production, corresponding to the types of
`magnetron magnetic configurations shown in FIGS. 1d and
`1f
`
`DETAILED DESCRIPTION
`
`[0072] The magnet configurations of magnetron sputtering
`cathodes preferably used in the conventional art
`for a
`magnetic field strength of up to 0.1 T are illustrated in FIGS.
`lb-lf. Thus, in FIG. 1b a balanced magnetron magnetic
`configuration is shown whereas in FIGS. 1a and IC unbal-
`anced magnetron magnetic configurations are shown. The
`altering of the magnetic field configuration is here made by
`altering the configuration of the permanent magnets in the
`magnetron source.
`
`[0073] Thus, in the schematic diagram of FIG. 1a a first
`type of an unbalanced magnetron magnetic configuration is
`illustrated. The magnetron sputtering cathode 1 is a substan-
`tially fiat body of the material to be sputtered and can have
`the shape of circular disc or a rectangular plate. At the rear
`or bottom surface of the cathode a permanent magnet
`assembly is illustrated comprising an outer magnet 2 and a
`central magnet 3, the central magnet located at the center of
`the rear side of the cathode and the outer magnet located at
`the edge of the rear side of the cathode. The lines having
`arrows show the direction of magnetic force lines. The
`
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`US 2005/0092596 A1
`
`May 5, 2005
`
`strength of the central permanent magnet 3 is selected to be
`larger than the strength of the outer magnet 2 so that among
`the magnetic field lines 4, generally going from the north
`poles to the south poles of the magnets, some field lines
`extend only between the poles of the central permanent
`magnet.
`
`In the view of a balanced magnetron magnetic
`[0074]
`configuration in FIG. 1b it is seen to have substantially the
`same set-up as the magnetron configuration as in FIG. 1a
`However, the strength of the central magnet is selected to be
`equal to the strength of the outer magnet so that substantially
`all magnetic field lines extend between a pole of the central
`magnet 3 and a pole of the outer magnet 2. The shaded area
`in the figure is the area of plasma confinement and also the
`area in which the power dissipation of the discharge occurs.
`
`In the schematic of FIG. lc a view of a second type
`[0075]
`of an unbalanced magnetron magnetic configuration is illus-
`trated, in which the strength of the permanent magnets is
`selected in still another way. Here, some field lines extend
`between the poles of the outer magnet, the field lines starting
`or ending at the central magnet all having their other ends at
`the outer magnet.
`
`[0076] The unbalanced configurations as shown in FIGS.
`1a and 1b are classified as Type I or Type II respectively, see
`B. Window and N. Savvides, “Charged particle fluxes from
`planar magnetron sputtering sources”, J. Vac. Sci. Technol,
`A 4(2), 1986, pp. 196-202.
`
`[0077] An alternative way to accomplish different mag-
`netic configurations is to use an external, preferably toroidal,
`magnetic coil, see I. Ivanov, P. Kazansky, L. Hultman, I.
`Petrov, and J-E. Sundgren, “Influence of an external axial
`magnetic field on the plasma characteristics and deposition
`conditions during direct current planar magnetron sputter-
`ing”, J. Vac. Sci. Technol., A 12(2), 1994, pp. 314-320. Thus,
`in the views of FIGS. 1d, 16 and 1f magnetic configurations
`created by permanent magnets 2, 3 placed behind the target
`1 and an electromagnetic coil 5 placed in front of the target
`are shown. In FIGS. 1d and 16 the coil has a diameter larger
`than the diameter of the target. The arrows show the direc-
`tion of the magnetic field. In FIG. If a cusp-shaped magnetic
`configuration is shown in which the coil 5 has a diameter
`smaller than the diameter of the target and of the outer
`magnet. The electromagnetic coil 5 has a height been, i.e. the
`extension thereof in a direction perpendicular to the plane of
`the cathode 1, and an inner di