Magnetic Field B
+
E
x
x x Bx
-
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What is a Magnetron
The most common type of magnetron can be found inside a microwave oven.
This is a magnetron tube.
Control of these highly mobile plasma electrons is the key to all forms of plasma control
Conversion of a neutral atom
into an ion by electron collision
(for ion energies < 1keV).
Ar+
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Ionising collisions
Ions and electrons lost from the discharge can be replaced by ionising collisions
⇒ e- + Ar e- + e- + Ar+
in a plasma
0+ e-
e1+
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Electron motion in a combined electric & magnetic field
e-
SN E
B ExB
B
x
B
e-
NS
e-

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Negatively biased target
A magnetron sputtering plasma
This is characterised by the parameter γ. For every ion impacting on the target γ electrons are released by secondary emission.
For most metals, γ ~ 0.1, and is insensitive to ion impact energy
ttrraannssffeerr ffrroomm tthhee iinn--ccoommiinngg ppaarrttiiccllee..
UUnnlliikkee mmaannyy ootthheerr vvaappoouurr pphhaassee tteecchhnniiqquueess tthheerree iiss nnoo mmeellttiinngg ooff tthhee mmaatteerriiaall..
OOtthheerr nnaammeess ffoorr SSPPUUTTTTEERRIINNGG wweerree SSPPLLUUTTTTEERRIINNGG aanndd CCAATTHHOODDEE DDEESSIINNTTEEGGRRAATTIIOONN..
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What is a Magnetron
ee-
Ar+ Ar
e-
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Double Ionisation
If an electron collides with an Argon ion, there is a possibility of the Argon losing another electron, becoming doubly ionised
KKeeyy ffoorr uunnddeerrssttaannddiinngg ddiissccoovveerryy ooff eelleeccttrroonnss aanndd ppoossiittiivvee iioonnss iinn llooww pprreessssuurree ggaass ddiisscchhaarrggeess aanndd aattoomm ssttrruuccttuurree ((JJ..JJ.. TThhoommssoonn,, RRuutthheerrffoorrdd)),, 11889977----
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What is magnetron sputtering?
Magnetron Sputtering is a plasma vacuum coating technique and here are some of the questions that will be answered in this section: What’s sputtering? What’s a magnetron? What’s a plasma?
++
-
-V
Resulting erosion of the sputter target
High density plasma generated by the combine electrical and magnetic field
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Magnetron sputtering plasma
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Secondary electron emission
Electrons lost from the discharge can be replaced by secondary emission - electrons liberated from the target due to ion impact.
PPllaassmmaa PPaarraammeetteerrss DDeennssiittyy ((nnee,, nnii)) EElleeccttrroonn tteemmppeerraattuurree ((TTee)) UUssuuaallllyy mmeeaassuurreedd iinn eelleeccttrroonn vvoollttss ((11eeVV == 1122000000°°cc)) PPllaassmmaa ppootteennttiiaall ((VVpp))
40 m 50 cm 5m 100 m
2 cm
For 5 mtorr of argon (~300K) with 5eV electrons
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What is sputtering?
Atom or ion with kinetic energy
Surface
Atom, ion
e-
TThhee iimmppaacctt ooff aann aattoomm oorr iioonn oonn aa ssuurrffaaccee pprroodduucceess ssppuutttteerriinngg ffrroomm tthhee ssuurrffaaccee aass aa rreessuulltt ooff tthhee mmoommeennttuumm
MMeeaann ffrreeee ppaatthhss
MMaaggnneettiicc ttrraapp
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Basic concepts
‘‘GGaass’’ ooff cchhaarrggeedd ppaarrttiicclleess EElleeccttrroonnss ((nneeggaattiivvee)) IIoonnss ((ppoossiittiivvee))
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The history of sputtering?
TThhee vveerrbb ttoo SSPPUUTTTTEERR oorriiggiinnaatteess ffrroomm LLaattiinn SSPPUUTTAARREE ((TToo eemmiitt ssaalliivvaa wwiitthh nnooiissee))..
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Sustaining a discharge
Particles lost from the discharge must be replaced. This can be achieved by
Secondary emission of electrons
Ionising collisions
A Magnetron is comprised of : A CATHODE = electron source An ANODE = electron collector A combined ELECTRIC & MAGNETIC FIELD B E
xE B
+
x
x-x x
x
Electric Field E
PPhheennoommeennoonn ffiirrsstt ddeessccrriibbeedd 115500 yyeeaarrss aaggoo…… GGrroovvee ((11885522)) aanndd ppllüücckkeerr ((11885588)) ffiirrsstt rreeppoorrtteedd vvaappoorriizzaattiioonn aanndd ffiillmm ffoorrmmaattiioonn ooff mmeettaall ffiillmmss bbyy ssppuutttteerriinngg..
Collision type
Electron – electron Electron – argon (Momentum loss) Electron – argon (Ionisation) Electron – argon (Double ionisation) Argon – argon