US 6,447,655 B2
`(10) Patent N0.:
`(12) United States Patent
`Lantsman
`(45) Date of Patent:
`Sep. 10, 2002
`
`
`USOO6447655B2
`
`(54) DC PLASMA POWER SUPPLY FORA
`SPUTTER DEPOSITION
`
`6,051,114 A *
`6,190,512 B1
`
`................ 204/1923
`4/2000 Yao et al.
`2/2001 Lantsman .............. 204/192.12
`
`(76)
`
`Inventor: Alexander D. Lantsman, 303 Sea
`Spray La., Neptune, NJ (US) 07753
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U~S~C~ 154(b) by 0 days.
`
`(21) Appl. No.: 09/838,039
`
`(22)
`
`Filed:
`
`Apr. 20, 2001
`
`OTHER PUBLICATIONS
`English abstract of JP 2—254160.*
`Rossnagel, “Handbook of Plasma Processing Technology”,
`Noyes Publications, 1990, USA, pp. 47—58.
`Wasa, “Handbook of Sputter Deposition Technology”,
`Noyes Publications, 1992, USA, pp. 97—122.
`Roth, “Industrial Plasma Engineering”, Institute of Physics
`Publishing, 1995, United Kingdom, pp. 283—390.
`
`* cited by examiner
`
`Related US. Application Data
`(60) Egggswnal apphcatlon No. 60/207,453, filed on May 30,
`
`Primary Examiner—Steven H. VerSteeg
`(57)
`ABSTRACT
`
`Int. Cl.7 ................................................ C23C 14/34
`(51)
`(52) us. Cl.
`.............................. 204/298.08; 204/298.03
`(58) Field of Search ....................... 204/19213, 298.03,
`204/298.08; 323/234, 205, 299, 318, 304
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`DC plasma power supply for a sputter deposition of material
`layers on a substrate includes a plasma controller and a
`Plasma input for the settings of the output voltage and output
`current providing plasma ignition and termination With no
`arcing and no striking voltage. Pre-defined voltages are
`applied in the vacuum state before sputtering and after
`sputtering until vacuum is restored in a sputtering apparatus.
`
`6,007,879 A * 12/1999 Scholl
`
`................... 204/192.12
`
`20 Claims, 11 Drawing Sheets
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`GILLETTE-1009
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`TSMC et al. v. Zond, Inc.
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`Sep. 10, 2002
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`Sep. 10, 2002
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`US. Patent
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`US. Patent
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`Sep. 10, 2002
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`US. Patent
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`Sep. 10, 2002
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`US 6,447,655 132
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`US 6,447,655 B2
`
`1
`DC PLASMA POWER SUPPLY FOR A
`SPUTTER DEPOSITION
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`Provisional Patent Application No. 60/207,453 filed with
`US. PTO on May 30, 2000.
`STATEMENT REGARDING FEDERALLY
`SPONSORED RESEARCH OR DEVELOPMENT
`
`Not applicable
`REFERENCE TO A MICROFICHE APPENDIX
`
`Not applicable
`BACKGROUND OF THE INVENTION
`
`invention relates generally to power supplies
`Present
`technologies and specifically to the DC plasma supplies for
`a sputter deposition of material layers on a substrate, and it
`was originally disclosed in Provisional Patent Application
`No. 60/207,453 filed with US PTO on May 30, 2000.
`DC plasma power supplies are used as sources of energy
`at a sputter deposition in the apparatuses, typically of a
`magnetron design,
`in the semiconductor industry. DC
`plasma power supplies are manufactured by the companies
`worldwide, including Advanced Energy Industries, Inc. of
`Fort Collins, Colo., USA.
`Maj or drawbacks of the DC plasma power supplies of the
`prior art are intensive and repetitive arcing at plasma igni-
`tion and plasma termination and a need in the striking
`voltage to initiate a plasma in a sputtering apparatus of either
`magnetron or non-magnetron design.
`Cumulative negative effects of the arcing are severe
`damage to substrates (wafers), caused by the induced par-
`ticle contamination and soft X-rays, deterioration of elec-
`trical integrity of a sputtering apparatus and of a DC plasma
`power supply, and induced electromagnetic interference.
`Plasma at arcing represents a short circuit and a DC
`plasma power supply generates at arcing the repetitive
`0.1—10 microsecond pulses (surges) of the output current
`typically exceeding 10—100 times the nominal output current
`at a sputter deposition and reaching hundreds of amps.
`Repetition rate of these pulses may vary from 0.1 to 10—50
`kHz. The surges of the output current result
`in micro-
`evaporation of the target material and in the particle con-
`tamination of a substrate.
`
`The spikes of the output voltage of 1.5—2.5 kV accompany
`the surges of the current at arcing and these instabilities may
`last from several to hundreds of milliseconds. Arcing in a
`sputtering apparatus also results in release of the particles of
`different origin otherwise suspended by stable plasma off the
`perimeter of a substrate. At arcing these particles fall onto a
`substrate and contaminate it, representing one of the major
`sources of the yield losses at sputtering.
`To initiate plasma a DC plasma power supply of the prior
`art produces a striking voltage, also typically in a range of
`1.5—2.5 kV, and a striking voltage itself promotes arcing in
`a sputtering apparatus at plasma ignition.
`Soft X-rays are generated at arcing by the spikes of the
`output voltage exceeding or about 1 kV,
`including the
`striking voltages, and they are detrimental to the dielectric
`layers on a substrate and also represent an environmental
`hazard.
`
`High voltage spikes also deteriorate electrical integrity
`and reliability of a sputtering apparatus, specifically, of a
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`cathode assembly. High voltage spikes and surge currents at
`arcing deteriorate electrical integrity and reliability of a DC
`plasma power supply of the prior art. They are also a source
`of AC and RF electrical interference for devices and instru-
`
`ments of a sputtering apparatus and of the other electronic
`systems. Arcing at plasma ignition and plasma termination
`tends to be supported by the energy stored in the DC plasma
`power supplies of the prior art. This phenomenon dictates
`use of the reactive components with the reduced nominal
`value in the output filters of these power supplies. It results
`in the less effective filtering and higher ripples of the output
`voltage and output current during a sputter deposition. These
`ripples themselves may promote various plasma instabilities
`and arcing at sputtering.
`The invented DC plasma power supply provides plasma
`ignition and termination with no arcing regardless of the
`amount of energy stored in the power supply itself, offering
`more margins for better filtering and lower ripples at sput-
`tering.
`
`BRIEF SUMMARY OF THE INVENTION
`
`invention
`A DC plasma power supply of the present
`corrects the drawbacks of the prior art. Present invention is
`based on a theory of the plasmas, teaching that a DC plasma
`discharge becomes stable at the applied voltages greater than
`a specific voltage Vmin (Handbook of plasma processing
`technology, S. M. Rossnagel et al 1990, Noyes Publications,
`pp. 47—58; Industrial plasma engineering, J. R. Roth 1995,
`IOP Publishing, pp. 283—390; Handbook of sputter deposi-
`tion technology, K. Wasa et al 1992, Noyes Publications, pp.
`97—122; US. Pat. No. 6,190,512 Soft plasma ignition in
`plasma processing chambers).
`Value of voltage Vmin depends on composition and
`pressure of the process gas(es), design properties of a
`sputtering target and a sputtering apparatus, and it can be
`measured prior to the processing of a product substrate.
`Results of these measurements are used in the invented
`
`DC plasma power supply to define the settings for the arcing
`free plasma ignition and termination.
`The invented DC plasma power supply effectively elimi-
`nates arcing, high voltage spikes, and soft X-ray radiation at
`plasma ignition and at plasma termination during a sputter
`deposition, and it does not require a striking voltage to
`initiate a plasma.
`The invented DC plasma power supply reduces particle
`contamination and damage to a substrate at a sputter depo-
`sition. It also increases electrical integrity of a sputtering
`apparatus and its own electrical integrity by limiting the
`output voltages and output currents to the values required for
`sputtering. It also reduces the AC and RF electrical inter-
`ference and a soft X-ray hazard.
`These and other advantages of the invented DC plasma
`power supply are achieved by means of preventing exposure
`of the process gas(es) at sputtering to the output voltages
`lower than Vmin, by means of dynamic control of the mode
`of operation, and by means of controlled and gradual tran-
`sitions from a gaseous state to a plasma state and from a
`plasma state to a gaseous state in a sputtering apparatus.
`It is objective of the present invention to increase yield at
`a sputter deposition by eliminating arcing in a sputtering
`apparatus at plasma ignition and termination.
`It is another objective of the present invention to increase
`electrical integrity of a sputtering apparatus.
`It is another objective of the present invention to increase
`electrical integrity of a DC plasma power supply.
`
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`US 6,447,655 B2
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`3
`It is another objective of the present invention to reduce
`the AC and RF electromagnetic interference and the soft
`X-ray hazard caused by arcing at plasma ignition and
`termination.
`
`It is another objective of the present invention to reduce
`limitation to filtering of the ripples of the output voltage and
`output current of a DC plasma power supply.
`The invention is particularly useful
`in production by
`means of a sputter deposition of the Very Large Scale
`Integration (VLSI) devices in the semiconductor industry,
`optical and magneto-optical media, ultra thin film magnetic
`heads for computer hard drives, and in other related indus-
`tries.
`
`The above and other objectives and advantages of the
`present invention shall be made apparent from the accom-
`panying drawings and the description thereof.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanied drawings, which are incorporated in
`and constitute a part of this application, illustrate embodi-
`ments of the invention and, together with a general descrip-
`tion of the invention given above, and with the detailed
`description of the embodiments given below, serve to
`eXplain the principles of the invention.
`FIG. 1 is a schematic view of one embodiment
`
`the
`
`invented DC plasma power supply.
`FIG. 2 is a schematic view of another embodiment of
`
`power supply 1 shown on FIG. 1.
`FIG. 3 is a schematic view of embodiment of plasma
`controller 9 of power supply 1 shown on FIGS. 1—2.
`FIG. 4 is a typical timing diagram of embodiments shown
`on FIGS. 1—3.
`FIG. 5 is a schematic view of another embodiment the
`
`invented DC plasma power supply.
`FIG. 6 is a schematic view of another embodiment of
`
`power supply 50 shown on FIG. 5.
`FIG. 7 is a schematic view of embodiment of plasma
`controller 51 of power supply 50 shown on FIGS. 5—6.
`FIG. 8 is a typical timing diagram of embodiments shown
`on FIGS. 5—7.
`
`FIG. 9 is a diagram illustrating method of measurement of
`settings Vmin, Amin.
`FIG. 10 is a schematic view of a DC plasma power supply
`of the prior art.
`FIG. 11 is a typical timing diagram of a DC plasma power
`supply of the prior art.
`FIGS. 1—11 share the same denotations for common
`
`functional devices, inputs, outputs, signals, and time inter-
`vals.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`At a sputter deposition a DC plasma power supply typi-
`cally operates in the power mode, and between cycles of a
`sputter deposition it operates in the voltage mode. A mode
`of operation is a hardware configuration and/or a software
`algorithm used to regulate the output of a power supply. In
`the power mode Pout=Vout*Aout=Set Point, in the voltage
`mode Vout=Set Point, in the current mode Aout=Set Point,
`and in the energy mode Eout=Pout*(Process Time)=Set
`Point. Here Pout, Vout, Aout and Eout are the output power,
`output voltage, output current and output energy
`respectively, and “Set Point” corresponds to a commanded
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`value at the output of a DC plasma power supply. Typically,
`the power mode provides the most consistent performance
`of the deposited films, while the energy mode is used for the
`most delicate sputtering processes. The voltage mode is
`commonly used for the sputtering apparatus and personnel
`safety reasons between the cycles of sputtering.
`Further in the description of the present invention the
`power and the energy modes of operation may be assumed
`interchangeably, wherever the power mode is mentioned.
`Settings Vmin can be measured with a test substrate in the
`same sputtering apparatus filled with the gas(es) at pressure
`per the process recipe prior to the processing of a product
`substrate, as illustrated on FIG. 9. At these measurements a
`DC plasma power supply, either invented or of the prior art,
`is set to the voltage mode. During the test a commanded
`value Vp of the output voltage is slowly increased from 0
`(zero) to Vp(maX), corresponding to a stable plasma dis-
`charge in the sputtering apparatus, and further Vp is slowly
`decreased back from Vp(maX) to 0 (zero).
`Minimal steady state output voltages Vmin(l), Vmin(2)
`and output currents Amin(l), Amin(2) at the voltages Vp(l)
`and Vp(2) respectively are measured during this test. Volt-
`age Vp(1) relates to the minimal commanded value of the
`output voltage at plasma ignition corresponding to a stable
`plasma discharge after the arcing state. Respectively, voltage
`Vp(2) relates to the minimal commanded value of the output
`voltage at plasma termination corresponding to a stable
`plasma discharge before the arcing state. Voltage Vp(maX)
`relates to a commanded value of the output voltage greater
`than Vp(l) and Vp(2) but lower or about a typical value at
`sputtering.
`Values V3, A3 and V4, A4 (not to scale) are a graphical
`illustration of the repetitive peak output voltages and surge
`currents during the arcing state at plasma ignition and
`termination, respectively.
`Settings Vmin are defined as the minimal output voltages
`Vmin(l), Vmin(2) providing stable plasma discharges. The
`corresponding values for the output current and the output
`power at Vout=Vmin are Amin and Pmin=Vmin*Amin
`respectively. At the output voltage equal to or greater than
`Vmin, voltage at a sputtering target is stable. As indicated on
`FIG. 9, voltages Vmin(l) and Vmin(2) may differ. Voltage
`Vmin(l) at plasma ignition is expected to be higher than
`voltage Vmin(2) at plasma termination. Either both values of
`Vmin(l) and Vmin(2) may be communicated to the invented
`power supply, one for each of the corresponding transitions
`specifically, or just the greater one of these voltages. For
`simplicity of the description only, further in disclosure of
`this invention and pictorially on FIG. 4 and FIG. 6, voltage
`Vmin(l) as a greater of the voltages Vmin(l), Vmin(2) is
`chosen as the single value for Vmin.
`In embodiments of the invented power supply shown on
`FIGS. 1—3, 5—7 are used settings V1=Vmin+Vs, A1=Amin+
`As, P1=Pmin+Ps=V1*A1=(Vmin+Vs)*(Amin+As), where
`Vs, As, Ps are optional safety margins. Typically, safety
`margins Vs, As and Ps are 10—100 times smaller than Vmin,
`Amin, and Pmin, respectively.
`The purpose of the safety margins is to assure that at
`plasma ignition and termination the output voltage of the
`invented DC plasma power supply of an individual physical
`design, or more accurately voltage at the target assembly of
`a sputtering apparatus, does not decrease below Vmin during
`the transitions of the mode and of the output. In practical
`systems there is also a small but finite voltage drop associ-
`ated with losses in the wiring between the power supply and
`a sputtering apparatus. This voltage drop may be included in
`
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`US 6,447,655 B2
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`5
`either Vmin or Vs. It is specifically small at the arcing free
`plasma ignition and termination provided by the invented
`power supply.
`In disclosure of the present invention a voltage drop due
`to the losses in the wiring is considered included in the
`margin Vs. Accordingly, no distinction is further made
`between the output voltage of the invented power supply and
`the voltage at the target assembly of a sputtering apparatus.
`Setting V1 is substantially smaller than the output voltage
`at sputtering. Current A1 at Vout=V1 is typically 10—100
`times smaller than a typical current at sputtering, and the
`same is true for the output power P1. For practical purposes,
`at Vout=V1 a sputter deposition has not started yet, but the
`process gas(es) is pre-ignited and a weak but stable plasma
`is established in a sputtering apparatus. Values of Vmin and
`Amin can be further reduced by means of external sources
`of ionization, by increasing temporarily pressure of the
`process gas(es) in a sputtering apparatus (“pressure bursts”)
`and by other means known to those skilled in the art.
`FIG. 1 illustrates DC plasma power supply 1 in accor-
`dance with one embodiment of the present invention. AC
`power from an external source is transmitted to power
`module 2 via AC input 12. Module 2 converts AC power in
`the highly regulated DC power, delivered through output
`filter 3, current monitor 4, and voltage monitor 5 to output
`terminals 6, 7. Typically, power supply 1 has the floating
`output terminals with negative terminal 6 connected to a
`target assembly and positive terminal 7 connected to the
`chassis of a sputtering apparatus.
`A sputtering apparatus provides interfaces to program
`input 13, to plasma input 14, and to cycle input 15. Inputs
`13—15 can be implemented as analog, digital or manual
`means or can be represented by a data interface like RS-232,
`etc. In description of the present invention further arbitrarily
`assumed and presented pictorially on FIG. 4, 8 that inputs
`13, 14 are analog inputs, and input 15 is a digital input.
`Commanded value of the output at
`terminals 6, 7 is
`communicated via input 13. Input 14 is used for communi-
`cating the settings Vmin, Amin. Via input 15 are commu-
`nicated the beginning and the end of a cycle of a sputter
`deposition, defined as transition of a sputtering apparatus
`from the vacuum state before introduction and back to the
`
`vacuum state after evacuation of the process gas(es) respec-
`tively.
`Typically, before and after a cycle of a sputter deposition
`a sputtering apparatus via input 15 defines the voltage mode
`for power supply 1 and via input 13 sets the output voltage
`Vout to 0 (zero).
`Power supply 1 may also have other interfaces to a
`computerized sputtering apparatus and/or manual controls,
`displays, and other supplemental means.
`Control module 8 administers the output and mode of
`operation of power supply 1. Module 8 is connected to
`module 2 via interface 18 (output “a”), to monitors 4 and 5
`via interfaces 19 and 16 (inputs “b”, “c”), and to plasma
`controller 9 via mode interface 11 and output interface 17
`(inputs “d”, “e”).
`Module 8 administers the mode of operation of power
`supply 1 by responding to interface 11 and it sets the output
`at terminals 6 and 7 by responding to interface 17. Monitors
`4 and 5 provide module 8 with the output current feedback
`Afb and output voltage feedback Vfb, respectively.
`Transitions between the modes are executed with no
`
`output voltage drop below Vmin. Plasma controller 9 is
`connected to inputs 13, 14 and 15 and via interfaces 11 and
`
`10
`
`15
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`20
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`25
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`30
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`35
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`40
`
`45
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`50
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`55
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`60
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`65
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`6
`17 to inputs “d” and “e” of module 8, administering the
`mode of operation and the output. At the beginning of the
`cycle of a sputter deposition controller 9 confirms the
`voltage mode and also switches control over the output from
`input 13 to input 14.
`During a cycle of a sputter deposition controller 9 defines
`settings V1, P1 for the output voltage and output power at
`plasma ignition and termination and provides dynamic con-
`trol over a mode of operation of power supply 1.
`If a commanded value of the output power per input 13 is
`lower than the setting P1, controller 9 via interface 11 and
`module 8 sets power supply 1 to the voltage mode, and via
`interface 17 and module 8 sets the output voltage at termi-
`nals 6, 7 to V1.
`If a commanded value of the output power per input 13 is
`greater than the setting P1, controller 9 via interface 11 and
`module 8 sets power supply 1 to the power mode and
`switches control over the output of power supply 1 at
`terminals 6, 7 to input 13.
`When a commanded value per input 13 is equal to P1 it
`corresponds to a request of the same output voltage V1 and
`output current A1 as set up by controller 9. As a result, the
`described transitions between the modes and of the output
`are performed with no output voltage drop below Vmin as
`assured by the safety margins of a sufficient value. During a
`cycle of a sputter deposition after a sputtering apparatus is
`filled with the process gas(es), a sputter deposition begins by
`communicating via input 13 a commanded value of the
`output power at terminals 6, 7.
`Until a sputtering apparatus is filled with the process
`gas(es), a commanded value per input 13 is equal to 0 (zero)
`and thus lower than setting P1.
`Controller 9 holds power supply 1 in the voltage mode
`and sets the output voltage at terminals 6, 7 to V1 starting
`from the vacuum state until a sputtering apparatus is filled
`with the process gas(es) and until a commanded value per
`input 13 starts exceeding setting P1. As a result, process
`gas(es) during plasma ignition is not exposed to voltages
`lower than Vmin.
`
`As a commanded value per input 13 starts exceeding the
`setting P1, controller 9 switches power supply 1 from the
`voltage mode to the power mode and at the same time it
`switches control over the output at terminals 6, 7 from input
`14 to input 13.
`Further the output power increases from P1 to a com-
`manded level of P2. The output voltage and output current
`at Pout=P2 are V2 and A2 respectively. Output power P2
`may vary during sputtering, and later it stays at a level higher
`than P1 till the end of a sputter deposition.
`At the end of a sputter deposition a commanded value per
`input 13 decreases from P2 to 0 (zero). Accordingly, as it
`decreases to the value of setting P1, controller 9 switches
`power supply 1 back to the voltage mode and sets the output
`voltage at terminals 6, 7 to V1. Voltage V1 stays applied
`until vacuum is restored in a sputtering apparatus. As a
`result, process gas(es) during plasma termination is not
`exposed to voltages lower than Vmin.
`At the end of the cycle of a sputter deposition controller
`9 confirms the voltage mode and also switches control over
`the output from input 14 back to input 13. Power supply 1
`stays in the voltage mode till the beginning of the next cycle
`of sputtering, while the output voltage Vout is set to 0 (zero)
`per input 13.
`If the output power temporarily decreases below setting
`P1 during a sputter deposition, power supply 1 will termi-
`
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`US 6,447,655 B2
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`7
`nate and re-ignite plasma with no arcing and no need in a
`striking voltage, as described above.
`In another embodiment of power supply 1 shown on FIG.
`2, controllers 9 is a stand-alone apparatus interfaced with a
`sputtering apparatus and with DC plasma power supply 10
`of the prior art (FIG. 10). In other embodiments of power
`supply 1 the elements and functions of controller 9 may be
`in part or fully incorporated in the means of power supply 10
`and of a sputtering apparatus.
`In embodiment shown on FIG. 3, controller 9 comprises
`read-write memory 23, register 22, comparator 28, comput-
`ing unit 21, and discriminator 24. Settings Vmin, Amin are
`communicated to unit 21 via interface 14. Register 22
`contains codes of the safety margins Vs, As, and unit 21
`calculates settings V1, A1, and P1. In memory 23 are stored
`and available for retrieval setting Vmin, Amin and the
`settings calculated by unit 21.
`Comparator 28, unit 21, and discriminator 24 can be
`implemented either by means of electronic hardware or as
`software programs or as a combination of thereof.
`Setting V1 is communicated via interface 25 to discrimi-
`nator 24, and setting P1 is communicated via interface 26 to
`comparator 28. Comparator 28 via interface 11 and module
`8 sets power supply 1 to the voltage mode if a commanded
`value per input 13 is lower than setting P1, otherwise it sets
`power supply 1 to the power mode.
`Input 15 and comparator 28 via interface 27 also controls
`the state of discriminator 24:
`
`before and after a cycle of a sputter deposition (input 15
`is in the inactive state):
`discriminator 24 connects input 13 to module 8 and
`disconnects unit 21 from module 8; these commu-
`tations set power supply 1 to the voltage mode and
`also set the output voltage to 0 (zero) per input 13;
`during a cycle of a sputter deposition (input 15 is in the
`active state):
`in the voltage mode (a commanded value at input 13 is
`lower than setting P1):
`discriminator 24 connects unit 21 to module 8 and
`
`disconnects input 13 from module 8; and these
`commutations set
`the output voltage to V1 at
`plasma ignition and plasma termination;
`in the power mode (a commanded value at input 13 is
`greater than setting P1):
`discriminator 24 connects input 13 to module 8 and
`disconnects unit 21 from module 8; and these
`commutations set
`the output power to a com-
`manded value per input 13.
`A typical timing diagram of a sputter deposition with
`power supply 1 is shown on FIG. 4. On or prior to T1
`settings Vmin, Amin are communicated to controller 9 by a
`sputtering apparatus via input 14, retrieved from memory 23
`or entered manually in controller 9. At T<T1 before a cycle
`of sputtering begins a signal at input 15 is in the inactive
`state, arbitrarily shown as a low state. In response to input
`15, controller 9 via interface 11 and module 8 sets power
`supply 1 to the voltage mode. At the same time controller 9
`via interface 17 and module 8 sets the output voltage at
`terminals 6, 7 to 0 (zero) as commanded per input 13 by a
`sputtering apparatus between the cycles of deposition. At T1
`a sputtering apparatus starts a cycle of a sputter deposition
`by setting the signal at input 15 to the active state, arbitrarily
`shown as a high state. Controller 9 continues to hold power
`supply 1 in the voltage mode but it switches control over the
`output from input 13 to input 14 and sets the output voltage
`to V1 till a commanded value per input 13 is lower than P1.
`
`8
`
`At T2 process gas(es) starts filling a sputtering apparatus
`in presence of the output voltage V1 applied to a sputtering
`target.
`At T3 pressure of the process gas(es) reaches the level per
`a process recipe.
`At T4 a commanded value of the output power at input 13
`starts increasing from the initial value of 0 (zero) reaching
`P1 at T5, and after T5 it exceeds the setting P1.
`Accordingly, at T5 controller 9 via interface 11 and
`module 8 switches power supply 1 from the voltage mode to
`the power mode and switches control over the output at
`terminals 6, 7 to input 13. These transitions are executed
`with no output voltage drop below Vmin, and it is beneficial,
`but not critical, if they take little time.
`By T6 the a commanded value of the output power per
`input 13 increases to P2 and further it stays at a level higher
`then P1 till T7.
`
`At T7 a sputtering apparatus sets a commanded value per
`input 13 to 0 (zero), and power supply 1 starts gradual
`transitioning of the output power from P2 to 0 (zero).
`By T9 the output power decreases from P2 to P1, and after
`T9 it continues decreasing reaching Pout=0 at T11.
`Accordingly, at T9 controller 9 switches power supply 1
`back to the voltage mode and switches control over the
`output at terminals 6, 7 from input 13 to input 14, thus
`setting the output voltage to V1. These transitions are
`executed with no output voltage drop below Vmin, and it is
`beneficial, but not critical, if they take little time. Voltage V1
`stays until vacuum is restored in a sputtering apparatus.
`At T10 evacuation of the process gas(es) starts, and by
`T11 vacuum is restored in a sputtering apparatus.
`At T12 a sputtering apparatus sets signal at input 15 to the
`inactive state and sets a commanded value per input 13 to 0
`(zero). Accordingly, at T12 controller 9 confirms the voltage
`mode for power supply 1, sets the output voltage to 0 (zero),
`and a cycle of a sputter deposition is completed.
`Power supply 1 stays in the voltage mode from T9 to T5
`of the next cycle of sputtering. Power supply 1 provides the
`free of arcing plasma ignition and termination and it does not
`require a striking voltage to initiate plasma in a sputtering
`apparatus.
`Another embodiment of the present invention is shown on
`FIG. 5. In this embodiment DC plasma power supply 50
`operates during plasma ignition and termination in the
`power mode, but
`in a way preventing exposure of the
`process gas(es) to