||||||||||||||||||||||||||||||||lllll||||||||||||||||||||||||||||||||||||||
`
`USOO7147759BQ
`
`(12) United States Patent
`Chistyakov
`
`(10) Patent N0.:
`(45} Date of Patent:
`
`US 7,147,759 32
`*Dee. 12, 2006
`
`(54}
`
`I-lIGH-POW'ER PULSE!) MAGNETRON
`SPUTTERING
`
`[75)
`
`Inventor: Roman (Ihistyakav. .Midover. MA
`(US)
`
`(73) Assignee:
`
`lend, Int:a Mansfield. MA {US}
`
`( * ) Notice:
`
`Subject to an};r disclaimer. the term of this
`patent is extended or adiusted under 35
`U.S.C. 154(bJ by 0 days.
`
`This patent is subject to a terminal dis—
`claimer.
`
`.:
`
`.
`2
`( I) Appl No
`(22) Filed:
`
`.
`I} n
`I 65 277
`l
`Sep. 30! 2002
`
`(65)
`
`Prior Pubiicatlun Data
`
`A?" 1* 2004
`
`US 20042't)(l60813 A]
`Int ('1
`(2006.01)
`C33C' 14/35
`2041192.12;204J'192.13;
`[52} us. Cl.
`204298.03; 204f29806: 204E298.08; EMF-29314:
`204139319
`204519112.
`(58,“- Field of Classification Search
`204i192.13_. 293.03. 298.06, 293.08, 298.14.
`2t)4!298.19. 298.26
`See application file for complete search history.
`‘
`"
`Reference.» (“ed
`U5. [)KI‘EN'J‘ DOCUMENTS
`
`(‘1)
`
`[56)
`
`3,515.92!) A
`4,953J74 A
`213?:31333‘
`:2
`5.615.324 A
`$875.2”? A
`5342.039 A
`6.083.36l A
`6.296.742 Bl
`
`6.5197!) Milly. Jr. ct al.
`8!]990 Eldridge et' a].
`372-87
`12:13:? £23.33:°_‘..‘.‘.‘:..1111:111111111".3211;
`4.199.}. Hating
`2:199? Osmanow
`3.1999 5pm” et' al.
`112000 Kobttyashi CI. {Il-
`IUIEUDI Kouznetsov
`
`204.192J2
`
`3723.5
`
`.........
`
`(“hiang et at.
`6.52002
`6.393.929 Bl “
`732002 Wang. eta].
`6,413,382 Bl
`8:2002 Gopalraja c1' :11.
`5.435.251 131
`333002 39“?“ et al.
`E44038” Bl
`932002
`lIIlllaId
`5.456.642 Bl
`3:200! Kawamatn ct al.
`20020033430 Al
`11-2005 Chistyakov ............ £04.-‘l92.l2
`IUDS.’(J252763 Al °
`FOREIGN l‘A'I‘EN'I‘ DOCUMENTS
`
`.104’298111
`104-19311
`204t298.ll
`
`DE
`
`91933
`3310351 A]
`[Continued]
`
`OTHER PUBLICATIONS
`
`Booth. et 31.. The Transition From Symmetric 'I'o Asymmetric
`Dischar es In Pulsed 13.56 MHz Ca aci Coo led Plasmas .l.
`3
`P
`[Y
`P
`-
`Appl. Phys... Jul.
`[5. 199?. pp. 552-560. vol. 82 {2). American
`Institute of Physics.
`
`[Continued]
`
`Primary Examiner Rodney G. McDonald
`(74) Attorney.
`.stgeut. or Firm—Kurt Rauschenbach:
`Rauschenbach Patent law Group. l.l_.C.‘
`[57}
`ABSTRACT
`
`Magnetically enhanced Sputtering methods and apparatus
`are described. A magnetically enhanced sputtering source
`according. to the present invention includes an anode and a
`cathode assembly having a target that is positioned adjacent
`to the anode. An ionization source generates a weakly-
`ionized plasma proximate to the anode and the cathode
`assembly. A magnet is positioned to
`tenet-ate a magnetic
`field proximate to the kaly-ionired plgtisrna. The magnetic
`field substantially traps electrons in the weakly-ionized
`plasma proximate to the sputtering target. A power supply
`produces an electric field in a gap between the anode and the
`cathode assembly. The electric field generates excited atoms
`in a... was. ionized plasma and generates secondary
`electrons from the sputtering target. The secondary electrons
`room: the minted atoms. thereby creating a strongly-tonined
`plasma havmg ions that impact a surtace ol the sputtering
`target 10 generate Splll‘lct'lttg flux.
`
`6.342.132 Bl
`
`Iiiflttl Rnssnagel
`
`50 Claims. 18 Drawing Sheets
`
`
`
`GILLETTE 1201
`
`GILLETTE 1201
`
`

`

`US 7,147,759 32
`Page 2
`
`FOREIGN PKIENT DOCUMENTS
`
`I:'P
`GB
`.IT’
`.1?
`W0
`W0
`WC)
`
`0 733 139 Al
`1339910
`5'?194254
`10204633
`WOS'SIMSGS
`W0 93-10532
`WO 01398553 Al
`
`’l‘
`
`3.31997
`[2"19?3
`11:198.?
`3.31998
`2-1995
`9: 1998
`12-90131
`
`OTHER PUBLIC ATIONS
`
`Bunshah. et al.. Deposition Technologies For Films And Coatings.
`Materials Science Series. pp.
`[76-183. Noyes Publications. Park
`Ridge. New Jersey.
`Daugherty. et at. Attachment—Dominated Electmn-Beam-Ionizeit
`Discharges. Applied Seiencc Letters. May 15. 1976. vol. IS. No. it).
`.Mnerican Institute of Physics.
`Goto. et a1" Dual Excitation Reactive Ion Eteher for Low Energy
`Plasma Processing. J. Vac. Sci.
`'Icchnol. A. Sep..'0et. 1992. pp.
`3048-3054, vol. Ill. No. 5. American Vacuum Society.
`liouznetsov. at al.. A Novel Poised Magnetron Spotter Technique
`Utilizing Very High Target Power Densities. Surface 8: lCoatings
`Tecimology. pp. 290-293. Elsevier Sciences SA.
`Iindquist. ct 3.1.. High Selectivity Plasma Etching Of Silicon Diox-
`ide With A Dual Frequency 2?-"2 MHZ Capacitive 11F Discharge.
`Macak. Reactive Splitter Deposition Process of A1203 and Charac-
`terization 01' A Novel High Plasma Density Pulsed Magnetron
`DiSChargc. Liukoping Studies in Science And Technology. 1999. pp.
`[—2. Sweden.
`Macak. et 31.. Ionized Splitter Deposition Using M Extremely lligh
`Plasma Density Pulsed Magnetron Discharge. J. Vac. Sci. Technol.
`A.. JUL-Aug.
`.1000. pp.
`[533-1531 vol.
`[8. No. 4. American
`Vacuum Society.
`
`Mozgrin. et a1 ., High-Current Low-Pressure Quasi Stationary Dis-
`charge In A Magnelic F icld'. Experimental Research. Plastria Phys-
`ics Reports. [995. pp. 400-409. vol. 2|..No. 5. Mozgrin. Feitsov.
`Khodachenko.
`
`induced Drift Currents In Circular Planar
`Rossnagei. er al..
`Magnetrons. J. Vac. Sci. Technol. A.. .Ian..'I"eb. 198?. pp. 38-91. vol.
`5. No. 1, American Vacuum Society.
`Sheridan. el al.. Electron Velocity Distribution Functions In A
`Sputtering Magnetron Discharge For The EXP; Direction. J. Vac.
`Sci. Technol. A.. Jul..-'Aug. [9%. pp. Elli-2176. vol. 16. No. 4.
`American Vacuum Society.
`Sleinlzu'uchel1 A Simple Formula For Low—Energy Sputtering Yields.
`Applied Physics .-\.. [985. pp. 37-42. vol. 36. Springer-Voting.
`I'urenko. et 3].. Magnetron Discharge In The Vapor Of '1he Cathode
`Material. Soviet Technical Physics Letters. Jul. [989. pp. 519-520;
`vol. 15. No. 7. New York. US.
`
`Encyclopedia Of Low Temperature Plasma. p. [19. vol. 3.
`Encyclopedia Of Low 'l'empcrnttlre Plasma. p. 123. vol. 3.
`Sugimoto. el al; Magnetic Condensation Ol'A Photoexcited Plasma
`During Fluoropoiymer Sputtering; J. Appl. Phys; Feb. 15. [991}; pp.
`1093-2099; vol. 67. No. 4; American Institute of Physics; New
`York. US.
`
`Yamaya. ct :11: Use Of A I'IelicorI-Wave Excited Plasma For All!»
`minum~Dopcd Znt’l Thin-Film Sputtering; Appl. Phys. I..elt.; Jan.
`[2. [998; pp. 235-2332 vol. T2; N0. 2; American Institute of Physics:
`New York US.
`
`* cited by examiner
`
`

`

`US. Patent
`
`Dec.12,2006
`
`Sheet 1 of 18
`
`US 7,147,759 32
`
`100
`\
`
`102
`
`PULSED
`132
`
`POWER
`SUPPLY
`
`
`
`
`
`|_l“—14
`‘W 1| V\\\\\\\\'\V§'£\\\\ \‘\\ it““\\\\\".III." L 'V
`m.szmwnm»:YIIIVMMI.
`\a/
`
`
`
`
`~“\.\‘\‘\\‘\\‘\\\‘I“‘\\‘\\‘\“‘\\\\\‘.‘B
`
`
`
`
`
`
`
`
`PRIOR ART
`FIG. 1
`
`

`

`US. Patent
`
`Dec.12,2006
`
`Sheet 2 of 18
`
`US 7,147,759 32
`
`V;§
`
`\
`
`MC
`
`'a"
`
`m/
`
`n
`
`V/
`
`g6
`
`[I
`
`x
`y.
`m
`W
`flWEZW/W
`21%!
`“$3
`//V.
`—
`2:“
`-
`A
`42 EWH”H
`fi
`fr
`m E D)
`21B l‘
`7,!
`\\\:‘L\‘\\\\l\\\‘\\\1\\‘l_\“mu-ml.In
`,4
`m
`,5
`mmnyllmllawr\\\\
`,4
`54 233 m“m
`. mIII/IIIlf\f/\”/\fl/lffdIffi'l/ffl/M’Iflfl’flll‘tlffi
`
`l"{W{WZ}!i7'
`if/fi’f’x/fl/y’
`
`EEERN.
`
`[/2
`17%;"
`W
`W W
`
`2“ \\\\\\\\\\\\\\‘Q 248
`§
`
`

`

`US. Patent
`
`Dec. 12, 2006
`
`Sheet 3 of 18
`
`US 7,147,759 B2
`
`mM”/4
`V/
`
`E/H
`
`mmm\\\\\\
`
`mg
`[All/I”
`
`mwN
`
`\\\._I§\\ka¥4:.\\\47/4,...//x]M\x...rm.\\
`
`
`
`
`umm”)mmm......wmw‘‘nimw”Emu”MWIf\\g///“Jim”0..m...........mm........4N).......\4...”67/M‘FEE;
`
`
`
`
`ii?
`
`mmw
`
`m.9".
`
`mvm\.
`
`

`

`US. Patent
`
`Dec. 12, 2006
`
`Sheet 4 0f 18
`
`US 7,147,759 B2
`
`m2...
`
`h.—
`
`JP
`
`tn1—:
`
`.gr
`
`.3"
`
`.S‘
`
`‘—
`q—n
`
`.9
`
`VI"
`
`9 L
`
`L
`
`momvow
`
`..........................................................................................->220?..>3.er
`
`oom
`
`flmm>>0&
`
`_—_1------u-
`
`--.--..—--—-----.-q.--—-u~--~o-u_.._*--------
`
`IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
`
`.................-232-3.0..
`
`_-+___---_
`
`9mmom.
`
`«on
`
`

`

`US. Patent
`
`Dec. 12, 2006
`
`Sheet 5 0f 18
`
`US 7,147,759 B2
`
`~200V
`
`-30kV
`
`~100V—5kV
`
`~10A*5000A
`
`-0.1A-100A
`
`~1kW-10MW
`
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
`IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
`
`324
`l
`
`lllllllllllllllllllllll
`
`~0.flikW—1GOKW
`
`‘1
`
`tzta t4
`
`t5
`
`FIG. 5
`
`
`

`

`U.S. Patent
`
`Dec. 12 2006
`
`Sheet 6 0f18
`
`'i-‘Efi==\\\idl!E\lf::§:§
`
`
`
`
`
`
`
`
`
`_B
`
`M
`
`:_=\J‘a.
`
`
`
`
`
`
`
`.|..I.|.|.iul|1ll|
`
`
`Illa-I'll
`
`d1
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Dec. 12 2006
`
`Sheet 7 0f18
`
` i
`
`11.1.1.1:.
`
`w .L‘.\ \1
` _—-—-
`
`715%.h.://lfl
`
`1
`
`

`

`U.S. Patent
`
`US 7,147,759 BZ
`
`
`
`.wfil‘mk‘l/gaggin—
`1‘Eda-nfifrlll.’
`
`
`E13,»Pill-':!§
`
`
`‘\
`
`lllll
`
`gg
`
`
`
`,,....Iii.1...!iflg.
`
`\g
` (‘H/.5:
`
`g.”
`
`
`

`

`a.wmu
`
`AA
`
`
`
`1“!"i‘drrm'Elli:.\\unaguji”;.1.
`
`
`2mlflx\§§E¢N
`@:1q
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`D
`
`
`
`

`

`US. Patent
`
`Dec. 12. 2006
`
`Sheet 10 01'18
`
`US 7.147359 B2
`
`450
`
`460
`
`MATCHING
`UNIT
`
`V41
`
`
`
`
`
`I77?};ll,”flag;
`
`gig“tititxWk
`
` tittiit.)m\ttiittit“;imAttitig“!m2
`
`
`\thithml"WVWitI.»mwmy?Iwa“itEmaW“Am.
`ttiWWtWi
`
`.u\\i\\\tt\i\OWN“mgrMWWWV\E“A.m2
`diary“???I’dfflglifilffszffidf\“lagMM0w4..xmX.“Am\mmE“a.“mt
`
`
`
`
`
`Wifllf/AIW'JI/flIll/l/flfffillfllfllflfllflfl‘a
`
`211 m
`
`“mm\§
`
`\
`.t
`
`’fij
`
`FIG. 7
`
`
`
`
`
`
`

`

`7.,4
`
`H...
`
`2B
`
`w90:
`
`US. Patent
`
`m.D
`
`a...u.
`
`mS
`
`mf0
`
`SU
`
`a9mmom
`
`
`
`.........................................................................................:ggorngxrr%x0manvow
`
`canmmaom
`
`mom
`
`2650..-Edi
`
`H.msE.h“3w.JmN.:o“
`
`

`

`US- Patent
`
`Dec. 12, 2006
`
`Sheet 12 of 13
`
`US 7$147,759 32
`
`
`
`§mam
`
`(a.o_“_
`
`mm
`
`m .aD
`
`:8“
`
`EE\.qu
`
`v
`
`.DNN
`
`81
`
`arm.mwm
`
`
`
`

`

`US. Patent
`
`Dec. 12. 2006
`
`Sheet 13 0f18
`
`US 7.147.759 B2
`
`7.1.4
`
`KAI.
`
`11.111111\
`
`
`
` §.\\.\1§§§\1\\1\1\1\1\§1§41111...\1..11...1.11.11..1.1.
`
`111.11%...111.
`
`%.
`
`\“‘\‘\\“‘\\\‘
`
`1%.}.
`fur/.fznhflffflffdrf’lffffffdfift7;?.49.
`\111“.
`1.5
`W§1\§1
`
`mm
`
`r/f/J/IJ5V/f/fi'flfllflffliijflfllfl/IAW/Mllllft
`
`W§1
`
`\
`
`FIG. 10
`
`3?.
`[155‘
`
` ”/4?er
`
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Dec. 12, 2006
`
`Sheet 14 0f18
`
`US 7,147,759 B2
`
`472
`
`MATCHING
`UNIT
`
`‘WW\\§
`\gag...
`ZVdr.//
`\\\\\§§‘
`%§\\\
`\\\
`
`4m:
`
`\\\\\
`\um
`“.\“““‘
`k“'\.‘“\\\\“\
`“‘\I‘
`VIIIIIIIIIIIII
`
`I!
`
`If)(a
`
`;n\\\“
`
`SE
`
`1mm
`
`WI”!
`
`238
`#I/I/I/I/fl/IIWMI/M/IlllWI/M/IJIIJV/W/J/1
`
`FIG. 11
`
`
`
`
`
`
`
`

`

`US. Patent
`
`Dec..12,2006
`
`Sheet 15 of 18
`
`US 7,147,759 32
`
`500
`
`
`
`PUMP DOWN CHAMBER
`
`604
`
`PRESSURE
`CORRECT?
`
`PASS FEED GAS INTO CHAMBER
`
`PROXIMATE TO A CATHODE (TARGET ASSEMBLY
`
`608
`
`802
`
`CHM“
`
` Y
`
`
`
`
`
`
`GAS
`CHAMBE R
`PRESSURE
`PRESSURE
`
`
`CORRECT?
`CORRECT?
`
`
`
`Y
`
`
`
`
`APPLY APPROPRIATE MAGNETIC
`FIELD PROXIMATE TO FEED GAS
`
`614
`
`
`
`FIG. 12
`
`IONIZE SPUTTERING GAS TO
`GENERATE WEAKLY—IONIZED PLASMA
`
`
`FIG. 12A
`
`

`

`US. Patent
`
`Dec..12,2006
`
`Sheet 16 of 18
`
`US 7,147,759 32
`
`GENERATE STRONGLY-IONIZED SUBSTANTIALLY
`
`UNIFORM PLASMA FROM WEAKLY—IONIZED PLASMA
`
`MONITOR SPU'ITER DEPOSITION
`
`
`
`
`
`
`
`DEPOSITION
`
`COMPLETE
`?
`
`FIG. 128
`
`

`

`US. Patent
`
`Dec. 12, 2006
`
`Sheet 17 of 18
`
`US 7,147,759 32
`
`PUMP DOWN CHAMBER
`
`604
`
`
`
`PRESSURE
`CORRECT?
`
`550
`
`swim“
`
`
`
`
`
`
`
`
`
`GAS
`
`CHAMBER
`PRESSURE
`PRESSURE
`
`
`
`CORRECT?
`
` 614
`
`Y
`
`608
`
`PASS FEED GAS INTO CHAMBER
`
`PROXIMATE TO A CATHODE (TARGET ASSEMBLY
`
`
`
`FIG. 13A
`
`FIG. 133
`
`FIG. 13
`
`

`

`US. Patent
`
`Dec..12.,2006
`
`Sheet 13 of 18
`
`US 7,147,759 32
`
`GENERATE STRONGLY—IONIZED SUBSTANTlALLY
`
`
`
`
`GAS
`STRONGLY-
`ONIZED"
`
`
`
`
`UNIFORM PLASMA FROM WEAKLY—IDNIZED PLASMA
`
` MONITOR SPUTTER RATE
`
` INCREASE HIGH-POWER
`
` FIG. 138
`
`
`PULSE TO CATHODE
`(TARGET) ASSEMBLY
`
`TO INCREASE
`SPUT‘I’ER RATE
`
`SPUTTER
`RATE
`SUFFJCENT
`
`
`SPUTTER
`DEPOSITION
`
`
`

`

`1
`HIGH-POWER PULSED MAGNETRON
`SPUTTE RI NG
`
`BACKGROUND OF INVENTION
`
`Sputtering is a well-loiowo technique for depositing films
`on substrates. Sputtering is the physical ejection of atoms
`from a target sttrface and is sometimes referred to as
`physical vapor deposition (FWD). Ions. such as argon ions.
`are generated and then directed to a target surface where the
`ions physically sputter target material atoms. The target
`material atoms ballistically flow to a substrate where 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
`establishing an electrical discharge in a gas between two
`parallel-plate electrodes inside a chamber. A potential of
`several kilovolts is typically applied between planar elec-
`trodes in an inert gas atmosphere (cg... argon] at pressures
`that are between about 10" and lil‘1 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 accelerated across the cathode dark space.
`The target has a lower potential than the region in which the
`plasma is formed. Therefore, 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 from the target. The sputtered atoms then
`propagate to a substrate where they deposit a film of
`sputtered target material. The plasma is replenished by
`electron-ion pairs loaned by the collision of neutral mol-
`ecules with secondary electrons generated at
`the target
`surface.
`
`3ft
`
`4!]
`
`43
`
`Magnetron sputtering systems use magnetic fields that are
`shaped to trap and to concentrate secondary electrons. which
`are produced by ion bombardment ofthe target surface. The
`plasma discharge generated by a magnetron sputtering sys-
`tem is located proximate to the surface 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 magnetron sputtering system is a planar
`magnetron sputtering system. Planar magnetron sputtering
`systems are similar in configuration to diode sputtering
`systems. However. the magnets (upenuanent or electromag-
`nets) 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
`normal to the cathode surface. Electrons are trapped in the
`electric and magnetic fields. The trapped electrons enhance
`the efficiency 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 uniformity. However.
`the tihn
`uniformity can be increased by mechanically moving the
`substrate andror the magnetron. but such systems are rela—
`ti vely 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-unifitnn matuter.
`
`fall
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`This invention is described with particularity in the
`detailed description. 'I‘he above and further advantages of
`
`’
`
`US 1147.759 B2
`
`2
`
`Jr
`
`I It
`
`this invention may be better understood by referring to the
`following description in conjunction with the accompanying
`drawings.
`in which like numerals indicate like structural
`elements and featttres in various figures. The drawings are
`not necessarily to scale. emphasis instead being placed upon
`illustrating the principles of the invention.
`FIG.
`1
`illustrates a cross—sectional view of a known
`
`magnetron sputtering apparatus having a pulsed power
`source.
`
`FIG. 2 illustrates a erases-sectional view map embodiment
`of a magnet‘mu sputtering apparatus according to the present
`invention.
`FIG. 3 illustrates a cross-sectional view of the anode and
`
`IS
`
`the cathode assembly ofthc magnetron sputtering apparatus
`of FIG. 2.
`
`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 illustrates graphical representations ol‘ the absolute
`value of applied voltage. current. and power as a function of
`[line 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 proximate to the cathode assem~
`bly for various electron ExB drill currents according to the
`present invention.
`FIG.
`3'
`illustrates a cross-sectional view of another
`embodiment ol'a magnetron sputtering apparatus according
`to the present invention.
`FIG. 8 illustrates a graphical representation of pulse
`power as a 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 embodiments of cathode assemblies according 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 crosseectiona] 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 3.13 A and 13 B which is a flowchart
`
`of an illustrative process of controlling sputtering rate
`according lo the present invention.
`
`DETAIL ED DESCRIPTION
`
`"lhc magnetic and electric fields in magnetron sputtering
`systems are concentrated in narrow regions close to the
`surface 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-uniform erosion or wear of the
`target that results in poor target tttiliratiou.
`Increasing the power applied between the target itlld the
`anode can increase the amount of ionized gas and. therefore.
`increase the target tttiliiratiott. l-[owever. undesirable target
`heating and target damage can occur. Furthermore. increas-
`ing the voltage applied between the target and the anode
`increases the probability of establishing an undesirable
`electrical discharge Ian electrical are} in the process cham-
`ber.
`
`

`

`3
`
`4
`
`US 1,147,759 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
`confined by the magnetic fields produced by the magnet 126.
`The [magnetic confinement is strongest in a confinement
`region 142 where there is relatively low magnetic field
`intensity. The confinement region 142 is substantially 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 else-Where 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 in
`undesirable non-uniform emsion of the target material 1.16
`and. thus relatively poor ttu'get utilization.
`Dramatically increasing the power applied to the plasma
`can result in tnore uniform erosion o l‘ the target material 116.
`However. the :uuotllll ol'applicd power necessary to achieve
`this increased uniformity can increase the probability of
`generating an electrical breakdown condition that leads to an
`undesirable electri ‘al discharge between the cathode assent-
`bly 114 and the anode 130 regardless of the duration ofthe
`pulses. An tmdesirable electrical discharge will corrupt the
`sputtering process and cause contamination in the vacuum
`chamber 104. Additionally, the increased power can over-
`heat the target and cause target damage.
`F It]. 2 illustrates a cross~sectional view ofan embodiment
`
`to
`
`15
`
`Eli
`
`3t]
`
`l’nlsing the power applied to the plasma can be advanta-
`geous since the average discharge power can remain low
`while relatively large power pulses etut be periodically
`applied. Additionally. the duration of these large voltage
`pulses can be preset so as to reduce the probability of i
`establishing an electrical breakdown condition leading to an
`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
`magnetron 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 performed. The vacuum chamber 104 is positioned in
`fluid communication with a vacuum pump 106 via a conduit
`1011.
`'111e vacuum pump 106 is adapted to evacuate the
`vacuum chamber 11.14 to high vacuum. The pressure inside
`the vacuum chamber 104 is generally less than 100 Pa
`during operation. A Iced gas source .109. such as an argon
`gas solute.
`is introduced into the vacutuu chamber 104
`through a gas inlet 110. The gas [low is controlled by a valve
`112.
`The magnetron sputtering apparatus 100 also includes a
`cathode assembly 114 having a target material 116. The
`cathode assembly 114 is generally in the shape of a circular
`disk. The cathode assembly 114 is electrically connected to
`a first output 118 of the pulsed power supply 102 with an
`electrical transmission line 120. The cathode assembly 114
`is typically coupled to the negative potential of the pulsed
`powur supply 102. In order to isolate the cathode assembly
`114 from the vacuum chamber 104. rut insulator 122 can be
`used to pass the electrical transmission line 120 tl'rrough a
`wall ol‘thc vacuum chamber 104. A grottndcd 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 127
`on the inside ol'the ring and its north pole 128 on the outside
`of the ring. Many other mag-net configurations can also be
`used.
`An anode 130 is positioned in the vacuum chamber 104
`proximate to the cathode assembly 114. The anode 130 is
`typically coupled to ground. A second output 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 chamber. The
`chamber 202 is coupled in fluid communication to a vacuum
`system 204 through a vacuum control system 206. In one
`_ embodiment. the chamber 202 is electrically coupled to
`ground potential. The chamber 202 is coupled by one or
`tnore gas lines 2|]"lr
`to a Iced gas sottroe 208.
`In one
`embodiment, the gas lines 20‘1r are isolated from the chamber
`and other components by insulators 209. Additionally. the
`gas lines 207 can be isolated from the feed gas source using
`in-line insulating couplers (not shown]. A gas [low control
`system 210 controls the gas flow to the chamber 202. The
`gas source 208 can contain any feed gas. such as argon. In
`some embodiments. the feed gas includes a mixture 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
`front 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 [i'eqtrency {RF} power source. In
`other embodiments (not shown). the substrate support 212 is
`cottpled to ground potential or is electrically floating.
`The magnetron sputtering apparatus 200 also includes a
`cathode assembly 216.
`in one embodiment.
`the cathode
`assembly 216 includes a cathode 218 and a sputtering target
`220 composed of target material. The sputtering target 220
`is in contact with the cathode 218. In one embodiment. the
`sputtering target 220 is positioned inside the cathode 218.
`The distance from the sputtering target 220 to the substrate
`211 can vary from a few centimeters to about one hundred
`’ centimeters.
`111.:
`target material can be any matuiat suitable for
`sputtering. For example. the target material can be a metallic
`
`4t)
`
`.13
`
`in operation the pulsed power supply 102 applies a
`voltage pulse between the cathode assembly 114 and the
`anode 130 that has a sufficient amplitude to ioniae the argon
`feed gas in the vacuum chamber 10:1. This typical ionization
`process is referred to as direct ionization or atomic ioniza-
`tion by electron impact and can be described as follows:
`.-\r+e' -'-F.-1r‘+2e'
`
`where Ar represents a neutral argon atom in the feed gas
`and e‘ represents an ioni7ing 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.
`The negatively biased cathode assembly 114 attracts
`positively charged ions with sullicient acceleration so that
`
`6|]
`
`

`

`q
`
`US 2,147,759 B2
`
`6
`
`material, polymer material. superconductive material, mag-
`netic material including ferromagnetic 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 ol‘
`a matching 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
`the pulsed power supply 234 is cottpled to an anode 238. An
`insulator 240 isolates the anode 238 [tom a grounded wall ot‘
`the chamber 202. Another insulator 242 isolates the anode
`238 from the cathode assembly 216.
`In one embodiment. the first output 232 of the pulsed
`poWer supply 234 is directly coupled to the cathode assem-
`bly 216 (not shown). I.L1 one embodiment. the second output”
`236 of the pulsed power supply 234 is coupled to ground
`(not shown}. In this embodiment.
`the anode 238 is also
`coupled to ground (not shown}.
`In 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 emothcr embodiment {not
`shown). the first output 232 of the pulsed power supply 234
`couples a positive voltage impulse to the anode 238.
`In one embodiment. the pulsed power supply 234 gener-
`ates peak voltage levels of up to about 30.000\’. 'l‘ypical
`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. 'l‘ypical operating currents varying
`from less than a few amperes to more than a few thousand
`zuuperes depending on the Sire ol' 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 betvveen about one microsecond
`and several seconds.
`
`The anode 238 is positioned so as to limit a gap 244
`between the anode 238 and the cathode assembly 216 that is
`suflieicnt‘ 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 centimeters (l0 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 relerence to FIG. 3.
`
`Jr
`
`to
`
`15
`
`In one embodiment. the magnet assembly 252 includes
`switching electro-magnets. which generate a pulsed mag-
`netic field proximate to the cathode assembly 216. In some
`embodiments. additional magnet assemblies (not slmwn)
`can be placed at various locations throughout the chamber
`202 to direct different types of sputtered target materials 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 field 254. In other embodiments, the magnetic
`field 254 is generated by energizing a current source {not
`shown] that is coupled to electric—magnets. In one embodi—
`ment. the strength of the magnetic field 254 is between about
`one hundred and two thousand gauss. After the ntamtetic
`field 254 is generated. the feed gas from the gas source 208
`is supplied to the chamber 202 by the gas flow control
`system 210. In one embodiment. the reed gas is supplied to
`the chamber 202 directly between the cathode assembly 216
`and the anode 238.
`
`In one embodiment. the pulsed power supply 234 is a
`component
`in an ioniration source that generates the
`weakly-ionimd plasma. The pulsed power supply applies a
`voltage pulse between the cathode assembly 216 and the
`anode 238. In one elubodiment. 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—ionized 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 pro-ionized
`plasma. In one embodiment, the peak plasma density oI'the
`pie-ionized plasma is between about l0‘I and ID” cm‘3 for
`argon feed gas. The pressure in the chamber can vary From
`_ about 10“:4 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 function of the loca-
`tion of the measurement in the pre-ioni'nzd plasma.
`ln 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 discharge
`current of between about 0.1 ttmperes and one hundred
`amperes in order to generate the weaklydonized plasma. In
`some embodiments the width oi" the pulse can be in on the
`order of 0.] microseconds up to one hundred seconds.
`Specific parameters of the pulse are dismissed herein in more
`detail in connection with FIG. 4 and FIG. 5.
`
`3ft
`
`4t)
`
`43
`
`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 plastua. In one
`embodiment.
`the anode shield 248 is coupled to ground .7
`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 the magnet
`assembly 252 is adapted to create a magnetic [ield 254
`proximate to the cathode assembly 216. The magnet assem-
`bly 252 cart
`include penuanent magnets 256, or alterna-
`tively. elector-magnets (not shown). The configuration 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 embodiment. prior to the generating ofthe weakly-
`ionized plasma. the pulsed power supply 234 generates a
`potential difference 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-ionized or pro-ionized pIasma. In this embodiment.
`the DC power supply is adapted to generate a voltage that is
`large enough to ignite the pro—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
`pro-ionized plasma. The value ol‘ the current depends on the
`power level generated by the power supply and is a function
`ofthe size of the magnetron. Additionally. the presence of a
`_’ magnetic field in the region 245 can have a dramatic eli'ect
`on the value of