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`US007147759B2
`
`(I2) United States Patent
`Chistyakov
`
`(10) Patent No.:
`(45; Date of Patent:
`
`US 7,147,759 B2
`*Dec. 12. 2006
`
`(54)
`
`I-IIGH-POW'ER PULSED MAGNETR()N
`SPUTTERING
`
`(75)
`
`[nve11tor: Roman (Ihisiyakov. _-Miclover. MA
`(US)
`
`(73) Assignee: Zond, Inc- Mansfield. MA (US)
`
`*
`
`Notice:
`
`Sub'ee1 to am: disclaimer. the term 01' this
`J
`.
`patent is extended or adjusted under 35
`U.S.C. l54(bJ by 0 days.
`
`This patent is subject‘ to a terminal dis-
`claimer.
`
`_:
`
`’
`2
`( I) Appl No
`(22) Filed:
`
`.
`0 0
`I 65 277
`I
`Sep_ 30! 2002
`
`(65)
`
`Prior Pnhlicntlun Data
`
`""1”'1* 2004
`
`Us 2004m0603]3 A]
`H” [M C]
`l?.0Ufi.0ll
`C'.?3C' I-I/35
`204)'192.12;2U4."l92.l3;
`{S2} U.5. Cl.
`304/39333.1304339310512043393-03:304f'293-141
`204393-19
`204! 192.12,
`(58) Field of Classification Search
`209192.13, 298.03. 298.06, 293.08, 298.14.
`204!29S.19. 298.26
`See application file for complete search history.
`‘
`.,
`Reference” (“ed
`[j__|'§_ [>A'1‘[;N'y |)Q("UM15N['3
`
`(56)
`
`3,515.92!) A
`4,‘.-l‘i3.l74 A
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`'_;‘61‘5'.n:1 ‘A
`§_S75.2m A
`5_942_U39 A
`5.081361 A
`6.296.742 Bl
`
`’\?lL|l}". Jr. ct al.
`6.-‘I970
`8."l*)90 Eldridge cl‘ -Tl.l-
`10.-"1990 P
`t L
`53199] (iii '3 3
`41997 Ruling
`3.1999 Gamma“,
`31999 Spmul cl. at
`'l,r_:_'!uDU Kubayflshi at m_
`l[l.'2Ul}l Kottznetsov
`
`6.342.132 Bl
`
`I-‘Emil Rossnagel
`
`3-72-'37
`SUSII
`4,_j,f..1_g
`"
`'
`3.u’,.8fi
`
`.'_'U4.192.|2
`
`....... ..
`
`6.-"2002 Chiang et al.
`5.393.929 Bl “
`Wlfliil Wang. eta].
`I5,-El-13,333 Bl
`$2002 Gopztlraja ct‘ :11.
`6.436.251 131
`3'?-'00?’ B‘_m_°“ e‘ “L
`6-440-382 Bl
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`j
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`ll-"2005 (.‘h:'sty.1.kov .......... ..
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`FOREIGN l"‘A'I‘l£N'I‘ DOCUMENTS
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`O'[_‘HER PU]3LIC‘_a\T]ONs
`
`Booth. ui al.. The 'l'r.'msition From Symmetric "Io Atsytttntetric
`
`Discharges In Pulsed 13.56 Mil: Capacity Coupled Plasmas. J.
`Appl. Phys... Jul.
`I5.
`I997. pp. 552-560. vol. 82 ('2). Alriericztrl
`Institute of Physics.
`
`[_'Contiuuecl]
`
`Primarjr £:'.mmr‘ner Rodney G. McIJo11:Ild
`(74)
`.*lt'.:'t).P‘!E£’Ir‘.
`steam. or Finn-—KurI Rrmschenhach:
`Rauschenbaclt Patent law Group. l.I_.(.‘
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`Magnetically enhanced sputtering methods. and apparatus
`are described. A magnetically enlianced :-zputtering source
`according. to the present invention includes an anode and 3
`cathode assem hly having a target that is positioned adjacent
`to the anode. A11 ionization source generates a weakly-
`ionized plasma proximate to the anode and the cathode
`ttssetjlhly. A magnet is positioned to
`enerate at rnagrtetic:
`lie-ld proximate to the Weetkly-ioni1.ed piismn. The Inzlgtlctic
`field siabstanthllly traps electrons in the weakly-ionized
`plasma proximate to the sputtering target. A power supply
`pmduces an electric Held in it gap between the anode and the
`cathode assembly. The electric field genemtes excited atoms
`v
`,
`_
`_
`-
`-
`.
`111
`the weakly ionized plasma and generates secondary
`clcelrnlls front the sputtering target. The secondary eleclrurls
`lonize the ettctled atoms. tliereby crezttt-t'tga Sl:l'DI]gl)«'-1U1'l1?‘2€.‘d
`plasma hzwnlg ions that impact a surtace ol the sputtering
`target ll) g9lJ{.'I'€llC Sl'|l.ll'lCI'l1'lg flux.
`
`50 Claims. 18 Drawing Sheets
`
`
`
`INTEL 1201
`
`INTEL 1201
`
`

`
`US 7,147,759 B2
`Page 2
`
`FOREIGN P.-N1" ENT DOCUMENTS
`
`El’
`GB
`JP
`JP
`W0
`W0
`WC)
`
`0 733 139 A1
`1339910
`57194254
`10204633
`WO95fl436S
`W0 93:’-10532
`W0 |]|:'98553 Al
`
`”‘
`
`8.’ 1 997
`12»'19'F3
`11-I982
`3.31998
`2-1995
`9» 1998
`12-“E0111
`
`OTHER PUBLICATIONS
`
`Bttnshah. ct n1.. Deposition Technologies For Films And Coatings.
`Materials Science Series. pp. 176-183. Noyes Pttblicntions. Park
`Ridge. New Jersey.
`Dzttlgltetty. et at. A1iilL'11lTlE—nl‘D(!lTI1flfllE{1 Electwn—Be~am—Ioni:cett
`Dischnrgcs. Applied Scicncc Lcttcrs. May 15. 19'?fi. vol. ES. No. If}.
`American Instirtttc of Physics.
`Goto. et :11.. Dual Excitation Reactive Ion Etcher for Low Energy
`Plzuitna Processing.
`.1. Vac. Sci. Tcchnol. A. Sep..'Uv.'1. 1992. pp.
`3048-3054, vol. 11.1. No. 5. American Vacuum Society.
`I-2.oI.t2.ncisov. ot al.. A Novel Pulsed Magnetron Sputtcr '1'ccl1.niquc
`Utilizing. Very High Target Power Dcnsitics. Sttrfaoc 8: Coatings
`Technology. pp. 290-293. Elscvicr Sciences SA.
`Iindquist. ct a.1.. High Sclcctiv.-‘ity Plasrtttt Etching Of Silicon Diox-
`idc With A Dual Frequency 2?r'2 M112 Capacitive RF Discharge.
`Macak. Reactive Sputtcr Deposition Process of A1203 and Charac-
`terization 01' A Novel High Plasma Density Pulsed Magnetron
`Discharge. Liukoping Studies in Sc-iencc And Technology. 1999. pp.
`1—.?. Sweden.
`Macak. ct ui.. Ionized Sputtcr Deposition Using An Exuumely High
`Plasrna 1Jensil'y Pulsed Magnetron Discharge. J. Vac. Sci. Technnl.
`A..
`.1u.l..-‘Aug.
`.1000. pp. 1533-1537. vol. 18. No. 4. Arnericnn
`‘vitcuum Society.
`
`Mozgrin. et a1., 1-Iigh-Current Low-Pressure Quasi -Slationnry Dis-
`t.:ha.rgc In A Magnetic F lC1Ll'. Experimental Research. Plasma Phys-
`ics Reports. 1995. pp. 400-409. vol. 21.. No. 5. Mozgrin. Fcitsov.
`Khodachenko.
`
`induced Drift Cturcnts In Circular Planar
`Rossnagcl. at al..
`Magnctrons. J. Vac. Sci. Tcchnol. A.. .la.n..'I*'cb. 198?. pp. 38-91. vol.
`5. No. 1, Atnerican \r’acuun1 Society.
`Sheridan. el
`:tl.. Electron '\.’elos:iry Distribution Functions In A
`Sputtering Magnetron Discharge For The EX13 Direction. J. Vac.
`Sci. Tccltnol. A..
`.lu|.:'Aug. 19943. pp. .1173-.?]'?6. vol. 16. No. 4.
`American Vacuunt Society.
`Sleinhruchei. A Simple Funnula For 1.Dw—F.J1eIgy Sputtering Yields.
`Applied Physics .-\., 1985. pp. 37-42. vol. 36. Spt'ingct'-Vct'1a,«3__
`Turcnl-tn. ct a].. Magnctron Discharge I.n The Vapor Of '1he |.’.”at11odo
`Material. Soviet Technical Physics Letters. Jul. 1989. pp. 519-520;
`vol. 15. No. 7. New York. US.
`
`Encyclopedia Of Low Temperature Plasma. p. 119. vol. 3.
`Encyclopedia Of Low '1'ctnpcrnt1Irc Plasrntt. p. 123. vol. 3.
`Sugimnto. cl ti]; Magnetic C'ondcnsa1'ion Ot'A l’11ot'ocxcitod P1flh‘1'1'1E1
`During Fluoropolymor Sputtering; J. Appl. Phys.; Feb. 15. 1991}; pp.
`.1093-2099; vol. 67. No. 4; .-\n1eriL'a.n Institute of Physics; New
`York. US.
`
`lien: Of A llclicon-Wstve Excited l’l:tsI11a For Alt!»
`Yamaya. ct :t1:
`u1inun1~Dopr.*d .?.nt'.1 Thin-Film Sputtering; Appl. Phys. I..elt.; Jan.
`12. 1998; pp. 235-23?; vol. '12; No. 2; American Institute of Physics:
`New York US.
`
`* cited by e=xamjnct'
`
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`Dec. 12,2006
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`

`
`US. Patent
`
`Dec. 12, 2005
`
`Sheet 16 of 18
`
`US 7,147,759 B2
`
`
`
`GENERATE STRONGLY-IONIZED SUBSTANTIALLY
`
`UNIFORM PLASMA FROM WEAKLY-IONIZED PLASMA
`
`
`
`
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`
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`

`
`U.S. Patent
`
`Dec..12.,2006
`
`Sheet 17 of 13
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`US 7,147,759 B2
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`
`

`
`US. Patent
`
`Dec. 12, 2006
`
`Sheet 13 of 18
`
`US 7,147,759 B2
`
`GENERATE STRONGLY-IONIZED SUBSTANHALLY
`
`
`
`GAS
`
`STRON GLY-
`ONIZED7
`
`
`UNIFORM PU-KSMA FROM WEAKLY-IDNIZED PLASMA
`
` MONITOR SPUTTER RATE
`
` INCREASE HIGH-POWER
`
`
`PULSE TO CATHODE
`(TARGET) ASSEMBLY
`
`TO INCREASE
`SPUTTER RATE
`
`SPUTTER
`RATE
`SUFFICENT
`
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` FIG. 13B
`
`

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`US 1147.759 B2
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`
`this invention may be better understood by referring to the
`tollowitig description in conjunction with the accompanying
`drawings.
`in which like numerals indicate like structttral
`elements and features in various ligures. The drawings are
`not necessarily to scale. emphasis instead being placed upon
`illustrating the principles ol' the invention.
`FIG.
`1
`illustrates a cross—sectional view of a known
`
`magnetron sputtering apparatus having a pulsed power
`source.
`
`FIG. 2 illustrates a cross-sectional view ol'an embodiment
`of a magnetron sputtering apparatus according to the present
`invention.
`FIG. 3 illustrates a cross-sectional view of the anode and
`
`IS
`
`the cathode assembly of the magnetron sputtering apparatus
`of FIG. 2.
`
`1
`HIGH—POWER PULSEI] MAGNETRON
`SPUTTE RI NG
`
`BACKGROUND OF INVENT'ION
`
`Sputtering is a well-known technique for depositing films
`on substrates. Sputtering is the physical ejection of atoms
`from a target surface and is sometimes referred to as
`physical vapor depositititt [P\-D). Ions. sttch as argon ions.
`are generated and then d.irc-cted to a target surface where the
`ions physically sputter target material atoms. The target
`material atoms ballistically tlow to a substrate wlterc they
`deposit as a lilrn of target material.
`Diode sputtering systems include a target and an anode.
`Sputtering is achieved in a diode sputtering system by
`establislting an electrical discharge in a gas l}c‘.'I\'L'et3t1 two
`parallel-plat'e eltcctrodcs inside a chamber. A potential of
`several kilovolts is typically applied between planar elec-
`trodes in an inert gas atrnosphert-.~ (e.g.. argon] at pressures
`that are between about 10" and ID‘: Torr. A plasma dis-
`charge is then formed. The plasma discharge is separated
`from each electrode by what is referred to as the dark space.
`The plasma discharge has a relatively constant positive
`potential with respect to the target. Ions are drawn out of the
`plasma. and are accelerat'ed across the cathode dark space.
`The target has a lower potential than the region in which the
`plasma is fanned. '[hereforc, the target attracts positive ions.
`Positive ions move towards the target with a high velocity.
`Positive ions impact the target and cause atoms to physically
`dislodge or sputter front the target. The sputtered atoms the11
`propagate to a substrate where they deposit a film of
`sputtered target materiztl. The plasma is replenished by
`electron-ion pairs lhnned by the collision of neutral mol-
`ecules with secottdary electrons generated at
`the target
`surface.
`
`FIG. 4 illustrates a graphical representation of the applied
`power of a pulse as a function of time For periodic pulses
`applied to the plasma in the magnetron sputtering system of
`FIG. 2.
`
`FIG. 5 illttstnates graphical representations ol the absolute
`value of applied voltage. cttt'rcLtl. and power as a litnctiott of
`time for periodic pulses applied to the plasma in the mag-
`netron sputtering system of FIG. 2.
`FIG. 6A through FIG. 6D illustrate various simulated
`magnetic field distributions proxintme to the cathode assent-
`bly for various electron Exli dritt currents according to the
`present invention.
`FIG.
`7 illustrates El cross-sectional view of another
`embodiment ola magnetron sputtering apparatus according
`to the present invetttion.
`FIG. 8 illustrates a gntpltical representation of pulse
`power as at function of time for periodic pulses applied to the
`plasma in the magnetron sputtering system of FIG. 7.
`FIG. 9A through FIG. 9C are cross-sectional views of
`various embodilnellts til‘ cathode assemblies acctirding to the
`present invention.
`FIG. 10 illustrates a cross-sectional view of another
`
`illustrative embodiment" ofa magnetron sputtering apparatus
`according to the present‘ invention.
`FIG. 11 is a cross-sectional view of another illustrative
`embodiment of a magnetron sputtering apparatus according
`to the present invention.
`FIG. 12 is a flowchart ofun illustrative process ofsputter
`deposition according to the present invention.
`FIG. 13 includes FIG S.l3 A and 13 B which is a tiowchart
`
`of an illustrative process of controlling sputtering rate
`according to the present invention.
`
`DETAIL ED DESCRIPTION
`
`The magnetic and electric fields in 1nag;netmn sputtering
`systems are concentrated in narrow regions close to the
`surliace of the target. These narrow regions are located
`between the poles of the magnets used For producing the
`magnetic field. Most of the ionization of the sputtering gas
`occurs in these localized regions. The location of the ion-
`ization regions causes a non-unil‘orm emsinn or wear of the
`target that results in poor target utiliration.
`lncreasitig the power applied between the target zutd the
`anode can increase the amount of ionized gas and. therefiire.
`increase the target utiliiratiott. j-lowever. undesirable target
`heating and target damage can occur. Furtliermore. increas-
`ing the voltage applied between the target and the anode
`increases the probability of establishing an undesirable
`electrical discharge (an electrical are} in the process cham-
`her.
`
`4!]
`
`43
`
`Magnetron sputtering systems use magnetic fields that are
`shaped to trap and to concentrate secondary electrons. which
`are produced by ion bnmbardnient ofthe target surface. The
`plasma discharge generated by a magnetron sputtering sys-
`tem is located proximate to the surliace of the target and has
`a high density of electrons. The high density of electrons
`causes ionization of the sputtering. gas in a region that is
`close to the target surface.
`One type of ruagnetron sputtering system is a planar
`magnetron sputtering system. Planar magnetron sputtering
`systems are similar in configuration to diode sputtering
`systerns. However. the iuagrnets {permanent or electromag-
`ttets) in planar magnetron sputtering systems are placed
`behind the cathode. The magnetic field lines generated by
`the magnets enter and leave the target cathode substantially
`nonnal to the cathode surface. Electrons are trapped in the
`electric and magnetic fields. The trapped electrons enhance
`the cfiiciency of the discharge and reduce the energy dissi-
`pated by electrons arriving at the substrate.
`Conventional magnetron sputtering systems deposit films :
`that have relatively low ttniformity. However.
`the tihn
`unitiarmity can be increased by mechanically moving the
`substrate andfor the magnetron. but such systems are rela-
`tively complex and expensive to implement. Conventional
`magnetron sputtering systems also have relatively poor
`target utilization. By poor target utilization. we mean that the
`target material erodes in a non-unifiinn manner.
`
`6|]
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`This invention is described with particularity in the
`detailed description. The above and further advantages of
`
`’
`
`

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`US 1147.759 B2
`
`the ions sputter the target material 116. A portion of the
`spunened target material 116 is deposited on the substrate
`134.
`
`The electrons. which cause the ionization. are generally
`conlined by the magnetic fields produced by the magnet 126.
`The magnetic cottfincmetlt
`is strongest in a cotilinemcttl
`region 142 where there is relatively low magnetic field
`intensity. The conlinetnent region 142 is sttbstantially in the
`shape of a ring that
`is located proximate to the target
`material. Generally. a higher concentration of positively
`charged ions in the plasma is present in the confinement
`region 142 than elsewhere in the chamber 104. Conse-
`quently. the target material 116 is eroded rapidly in areas
`directly adjacent‘ to the higher concentration of positively
`charged ions. The rapid erosion in these areas results it1
`undesirable non-unil‘orm erosion of the target material 1.16
`and. thus relatively poor target utilization.
`Dramatically increasing the power applied to the plasma
`can result in more unifortn erosion o l‘ the target material 116.
`Ilovvevcr. the zunottltl Ltlapplicd power necessary to achieve
`this increased uniformity can increase the probability of
`generating an electrical breakdown condition that leads to an
`undesirable electri ‘at discharge between the cathode assem-
`bly 114 and the anode I30 regardless of the duration ofthe
`pulses. An tnidesirable electrical discharge will corrupt the
`sputtering process and cause contamination in the vacuutu
`chamber 104. I-\dditionally_. the increased power can over-
`heat‘ the target and cause target damage.
`F It]. 2 illustrates a eross~sectional view ofan embodiment
`
`Ill
`
`15
`
`3!]
`
`Pulsing the power applied to tI1e plasma can be advanta-
`geous since the average discharge power can reniain low
`while relatively large power pulses (.1111 be periodically
`applied. Additionally.
`tI1e duration of these large voltage
`pulses can be preset so as to reduce the probability of i
`establishing an electrical breakdown condition leading to art
`undesirable electrical discharge. However, very large power
`pulses can still result‘ in undesirable electrical discharges and
`undesirable target heating regardless of their duration.
`FIG.
`1
`illustrates a cross-sectional view of a known
`ntagnetrort sputtering apparatus 100 having a pulsed power
`source 102. The known magnetron sputtering apparatus 100
`includes a vacuum chamber 104 where the sputtering pro-
`cess is perfonned. The vacuum chamber 104 is positioned in
`fluid conirnunication with a vacuum pump 106 via a conduit
`I08.
`'lhe vacuum pump 106 is adapted to evacuate the
`vacuum chamber ll}-1 to big vacuum. The pressure inside
`the vacuum chamber 104 is generally less than 100 Pa
`during operation. A Feed gas source .109. such as an argon
`gas sottrce.
`is inlrodttced into the vaettttln chamber 104
`th.rough a gas inlet 110. The gas Iiow is controlled by a valve
`112.
`The ntagnetron sputtering apparatus 100 also includes a
`cathode assembly I14 having a target material 116. The
`cathode assembly 114 is generally in the shape of a circular
`disk. The cathode assentbly H4 is electrically connected to
`a Iirsl output 118 of the pulsed power supply 102 with an
`electrical trartstnission line 120. The cathode assembly 114
`is typically coupled to the negative potential of the pulsed
`power supply 102. In order to isolate the cathode assembly
`114 from the vacuum chamber 104. am insulator 122 can be
`used to pass the electrical transmission line 120 through a
`wall olithc vacuum chamber 104. A grounded shield .124 can
`be positioned behind the cathode assembly 114 to protect a
`magnet 126 from bombarding ions. The magnet 126 shown
`in FIG. 1 is generally ring—shaped having its south pole 12'.-’
`on the inside ofthe ring, and its north pole 128 on the outside
`of the ring. Many other magnet configurations. can also be
`used.
`An anode 130 is positioned in the vacuum chamber 104
`proximate to the cathode assembly H4. The anode 130 is
`typically coupled to ground. A second outpttt 132 of the
`pulsed power supply 102 is also typically coupled to ground.
`A substrate 134 is positioned in the vacuum chamber 104 on
`a substrate support 135 to receive the sputtered target
`material 116. The substrate 134 can be electrically connected
`to a bias voltage power supply 136 with a transmission line
`138. In order to isolate the bias voltage power supply 136
`from the vacuum chamber 104. an insulator 140 can be used
`to pass the electrical transmission line 138 through a wall of
`the vacuum chamber 104.
`
`of a magnetron sputtering apparatus 200 according to the
`present invention. The magnetron sputtering apparatus 200
`includes a chamber 202, such as a vacuum cliatnber. The
`chamber 202 is coupled in fluid communication to it vacuum
`system 204 through a vacuum control system 206. la one
`_ embodiment. the chamber 202 is electrically coupled to
`ground potential. The chamber 202 is coupled by one or
`tnore gas lines 207 to a teed gas source 208.
`In one
`embodiment. the gas lines 20‘? are isolated from the cliamber
`and other components by insulators 209. Additionally. the
`gas lilies 207 can be isolated from the feed gas source using
`in-line insulating couplers (not shown]. A gas flow‘ control
`system 210 controls the gas How to the chamber 202. The
`gas source 208 can contain any feed gas, such as argon. In
`some embodiutents. the feed gas includes a mixtttrc of gases.
`In some embodiments. the feed gas includes a reactive gas.
`A substrate 211 to be sputter coated is supported in the
`chamber 202 by a substrate support 212. The substrate 211
`can be any type of work piece such as a semiconductor
`wafer.
`In one embodiment.
`the substrate support 212 is
`electrically coupled to an output 213 ofa bias voltage source
`214. An insulator 215 isolates the bias voltage source 214
`from a wall of the chamber 202. In one embodiment. the bias
`voltage source 214 is an alternating current (AC) power
`source. such as a radio [requency (RF) power source. Itt
`other embodiments (not shovvn). the substrate support 212 is
`coupled to ground potential or is electrically floating.
`The magnetron sputtering apparatus 200 also includes a
`cathode assembly 216.
`In one ernboditnent.
`the cathode
`assembly 216 includes a cathode 218 and a sputtering target
`220 composed of target niateiial. The sputtering target 220
`is in contact with the cathode 218. In one embodirnent. the
`sputtering target 220 is positioned inside the cathode 218.
`The distance from the sputtering target 220 to the substrate
`211 can vary from ti few centimeters to about one hundred
`’ centimeters.
`The target material can be any material suitable for
`sputtering. For example. the target material can be a metallic
`
`40
`
`:13
`
`the pulsed power supply 102 applies a
`I.l1 operation.
`voltage pulse between the cathode assembly 114 and the
`anode 13!} that has a suflicient amplitude to ionize the argon
`feed gas in the vacuum chamber 104. This typical ioni7.ation
`process is referred to as direct ionization or atomic ioniza-
`tion by electron impact and can be described as follows:
`.-\r+e' -arr.-if ‘+2:-'
`
`where Ar represents a neutral augon atom in the Feed gas
`and e‘ represents an ioniring electron generated in response
`to the voltage pulse applied between the cathode assembly
`114 and the anode 130. The collision between the neutral
`
`argon atom and the ionizing electron results in an argon ion
`(AF) and two electrons.
`Tlte negatively biased cathode assembly ll-tl attracts
`positively charged ions with sullicient acceleration so that
`
`6|]
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`US 1147.759 B2
`
`6
`
`material, polymer material. superconductive material, 111ag-
`netic material including lizrrontagnetic material, non-mag-
`netic material. conductive material. non-conductive mate-
`rial. composite material. reactive material. or a refractory
`material.
`
`The cathode assembly 216 is coupled to an output 222 of
`a matcltiug unit 224. An insulator 226 isolates the cathode
`assembly 216 from a grounded wall of the chamber 202. An
`input 230 o l‘ the matching unit 224 is coupled to a [irst output
`232 of a pulsed power supply 234. A second output 236 of
`tlte pulsed power supply 234 is coupled to an anode 238. An
`insulator 240 isolates the anode 238 from a grounded wall of
`the chamber 202. Another insulator 242 isolates the anode
`238 from the cathode assembly 216.
`Ill one embodiment. the lirst output 232 of the pulsed
`power supply 234 is directly coupled to the cathode assent-
`bly 216 (not sllown). in one embodiment. the second output‘
`236 of the pulsed power supply 234 is coupled to ground
`(not shown}. In this etubodiment.
`the anode 238 is also
`coupled to grottnd (not shown}.
`It] one embodiment (not shown)- the first output 232 of the
`pulsed power supply 234 couples a negative voltage impulse
`to the cathode assembly 216. In emother embodiment {not
`shown). the lirst output 232 of the pulsed power supply 234
`couples 3 positive voltage impulse to the anode 238.
`in one embodiment. the pulsed power supply 234 gener-
`ates peak voltage levels of up to about 3tl.D00\’. Typical
`operating voltages are generally between about 100V and 30
`kV_ In one embodiment,
`the pulsed power supply 234
`generates peak current levels of less than one ampere to
`about 5.000 A or more depending on the size of the mag-
`netron sputtering system. Typical operating currents varying
`trout less than a Few autperes to more than a few thousand
`aniperes depending on the size of the magnetron sputtering
`system. In one embodiment, the power pulses have a rep-
`etition rate that is below 1 kHz.
`In one embodiment. the
`pulse width of the pulses generated by the pulsed power
`supply 234 is substantially between about one microsecond
`and several seconds.
`
`The anode 238 is positionerl so as to l'on1t a gap 244
`between the anode 238 and the cathode assembly 216 that is
`suflicicnt to allow current to flow through a region 245
`between the anode 238 and the cathode assembly 216. In one
`embodiment.
`the gap 244 is between approximately 0.3
`centimeters (0.3 cm) and ten centirnetcrs (10 cm). The
`volume of region 245 is determined by the area of the
`sputtering target 220. The gap 244 and the total volume of
`region 245 are parameters in the ionization process as will
`be discussed with relierence to FIG. 3.
`
`Jr
`
`Ill
`
`15
`
`In one embodiment, the magnet assembly 252 includes
`switching clectro-inagnets. which generate a pulsed mag-
`netic field proximate to the cathode assembly 216. In some
`embodiments. additional magnet assemblies (not shown)
`can he placed at various locations throughout the chamber
`202 to dlrerst dillierenl types of sputtered target tnaterials to
`the substrate 212.
`
`la one embodiment. the magnetron sputtering apparatus
`200 is operated by generating the magnetic field 254 proxi-
`mate to the cathode assembly 216. In the embodiment shown
`in FIG. 2, the permanent magnets 256 continuously generate
`the magnetic lield 254. In other embodiments, the magnetic
`held 254 is generated by energizing a current source {not
`shown} that is coupled to electro—rnag_nets. ln one embodi-
`ment, the strength of the magnetic field 254 is between about
`{me hundred and two thousand gauss. After the magtetic
`field 254 is generated. the feed gas fI‘DLI'l the gas source 208
`is supplied to the chamber 202 by the gas llow control
`system 210. In one embodiment. the feed gas is supplied to
`the chamber 302 directly between the eatltode assembly 216
`and the anode 238.
`
`in one ernbodiment. the pulsed power supply 234 is a
`component
`in an lt‘}l'll.J:':ll.lttl‘l source that generates the
`weakly-ionized plasma. The pulsed power supply applies a
`voltage pulse between the cathode assembly 216 and the
`anode 238. In one embodiment. the pulsed power supply 234
`applies a negative voltage pulse to the cathode assembly
`216. The amplitude and shape of the voltage pulse are such
`that a weakly—ion_i2'ed plasma is generated in the region 246
`between the anode 238 and the cathode assembly 216. The
`weakly-ionized plasma is also referred to as a pre-ionized
`plasma. In one ernbodiment. the peak plasma density ofthe
`pre-ionized plasma is between about I05 and l0” cm" for
`argon lie,-ed gas. The pressure in the chamber can vary from
`_ about 10“ to 10 Torr. The peak plasma density of the
`pre—ionized plasma depends on the properties of the specific
`magnetron sputtering system and is a fitiiction of the loca-
`tion of the measurement in the pre-ioniaard plasma.
`In one embodiment. the pulsed power supply 234 getter-
`ates a low power pulse having an initial voltage of between
`about one hundred volts and five kilovolts with a discltatgc
`current of between about 0.1 amperes and one hundred
`amperes in order to generate the weakly-ionized plasma. In
`some embodiruents the width ofthe pulse can be in on the
`order of 0.] microseconds up to one hundred seconds.
`Specific parameters of the pulse are discussed herein in more
`detail in connection with FIG. 4 and FIG. 5.
`
`40
`
`-'13
`
`An anode shield 248 is positioned adjacent to the anode
`238 so as to protect the interior wall ofthe chamber 202 from
`being exposed to sputtered target material. Additionally, the
`anode shield 248 can Function as an electric shield to
`electrically isolate the anode 238 from the plasma. In one
`embodiment.
`the anode shield 248 is coupled to ground ..'
`potential. An insulator 250 is positioned to isolate the anode
`shield 248 from the anode 238.
`The magnetron sputtering apparatus 200 also includes a
`magnet assembly 252.
`In one embodimenL t.l'tr: magnet
`assembly 252 is adapted to create a magnetic lield 254
`proximate to the cathode assembly 216. The magnet assem-
`bly 252 can include pennanenl magnets 256, or alterna-
`tively, electm-magnets (not shown). The cottftgttration of the
`magnet assembly 252 can be varied depending on the
`desired shape and strength of the magnetic field 254. In
`alternate embodiments. the magnet assembly can have either
`a balanced or unbalzmced configuration.
`
`In one entboditnettt, prior to the generating ofthe weakly-
`ionizcd plasma. the pulsed power supply 234 generates a
`potential di'El"erenee between the cathode assembly 216 and
`the anode 238 before the feed gas is supplied between the
`cathode assembly 216 and the anode 238.
`In another embodiment. a direct current (DC) power
`supply {not shown} is used to generate and maintain the
`weakly-iottizcd or pre-ionized plasma. In this embodiment.
`the DC power supply is adapted to generate it voltage that is
`large enough to ignite the pre—ionized plasma.
`In one
`embodiment.
`the DC power supply generates an initial
`voltage of several kilovolts with a discharge current of
`several hundred milliamps between the cathode assembly
`216 and the anode 238 in order to generate and maintain the
`pre-ionianed plasma. The value ol’ the current