Note: Descriptions are shown in the official language in which they were submitted.
5;26
SPEC IFICATION
me present inventien relates ~o impro~remellks in the
coating o~ glass sheet~ or other substra~e~ with ~hin :Eilms o:E
a ~elected coating materiai and more particularly to the coat-
ing of ~uch substrates by the cath~de sp~lt~ering process.
~ he proces~ of ~pu~ter-coating in~rolves ~n bombard-
ing a target o~ the coating ma~erial in an ionized gas atmos-
phere in a chamber in which a c~ntrolle~ vacuum i9 mai~ltain0d
~o cau~e atomic particles o~ the coa~ing ma~erial t~ be dis-
lodged and deposi~;ed on the substra~es t~G be coated. One
10 ~ype ~ appara~us employed for carrying out ~he proces~
embodies a plurali~y of aligned , ind~pendently con~rolled: ;
contiguous chamber~ including a~ entry chamber~ a c~a~i~g
chamber and an exit: chamber, ~putter-coa~ing means in ~he
~orm cf a sub~qtaDk~ally rec~angular ¢a~lhode mounted h~r~o~t~lly
in the upper portion of~ the coati~g chamber and ha~ ig ~ sheet
: or layer Or a selected coatlng material carr~ed by the bottQm
surface ther~of and con~eyor mearl~ for movin~ khe subskra~es
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1~35;26
(~lass sheets) in a horizontally disposed po~ition through the
successive chambers and beneath the ~pukter-coating means such
that a continuous film of the selected coating material will
be deposited on the upper surfa¢es o~ the substrates. The
cathode comprises a housing including a top wall, a bottom
~all and side and end walls which define a clo~ed chamber
therein. The walls o~ the cathode are pre~erably formed
of aluminum of the desired thickness and.are welded together
along their meetin~ edges,
In such a process, the thin films desposited on the
substrates are usually of a metal such as, for example,
nickel, gold, chromium1 copper, molybdenum or t~tanium, or
allo~s Or these metals, Typical sputtering conditio~s are
5,000 volts potential on khe ~arget (coa~ing m~terial~ and a
resulting current dansity o~ 0~1 to 1.0 ma/cm2 for a t-ime
period o~ 0.2 to several minutes depending on the thickness of
coating.desired It wlll be appreciated that thi~ pote~tial
on the tar~et in the ionized gas atmosphere of th~ coating
chamber will gsnerate a very h~gh temperature whichi~ends to
heat the me~al cathode to an undesirable degree, On the other
hand, it i9 desirable tha~ the cathode be operated as hot as
possible without damage to the m~terlals of which it.i~:con-
~tructed since the heat aids in keepin~ the oathod~.in a clean
and operable condition~ :
~. In order to maintain acceptable working conditions~ it
is essential that the cathode~ be maintained at a tempera~ure ..
compatible with the materials of cDnstruction and to this end
di~ferent methods ha~e been propo~sd for effe~ting ~he cooling
thereo~, However, the cooling procedure~ heratofore u~illzed ~.
30 have not proven wholly sati~ackory in meeting khe requirem2nts
of continuou~ commercial operation. - -
A typical cooling procedure heretofore utilized ha~ been
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83~i26
~o circulate ordinary tap water directly from the water main
through the cathode chamber at a pressure of such magnitude
that it will exert a pressure o~ a~out 3 lb~. p,s.i. on th~
walls of the cathode. However, this pressure together with
the atmospheric pressure of about 14.7 lbs. p.s.i. on the
wat~r supply-results in a total pressure of abou~ 17~7 lbs.
p~s.i~ bein~ imposed on the walls o~ ~he cathode. On the other
hand, in the operation of a continuous sput-ter-coatin~ apparatus
of the character re~erred to above~ the coating chamber is
pumped down from atmosphere to a pressure usually in the
range of 2 to 6x10-2 torr and preferably of about 4xlO-2 torr,
which pr~ssure is maintained constan~ The ou~ward pressure
exerted by the tap water on the walls o~ the cathode coupled
with the vacuum created within the coating chamber places an
undue stress on the walls of the cathode and more par~icularly
on the welded joints securing ~he walls ~iogether. The result-
ing s~eady rate o~ stress, commonly referred to as creep,
causes a gradual weakening and eventual rupture o~.the..weIded
joints between the walls of the ca~hode resulting ln leaks
which necessitates removal of the ca~hode for repair and
~ep~acement~ This is, of cour3e, highly objectionali:not only
~rom the standpoint of increased maintenance costs~.bu~ also
because of the loss of produc~ion timeO
The present invention comprehends a:new a~d~lmproved
procedure for internally ~ooling the cathodes emplo~ed in the
sputter-coating o~ thin ~ilms of a ma~erial on glass shee~ or
other substrates.
Another object of the inven~ion is the provision o~ an
improved method and apparatus which involves the internal cooling
i 3 of the cathode b~ circulaking a cooling medium, suah as oil,
therethrough und~r a cons~an~ head pres~ure in ~uch a.manner a~
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~3~5~ 6
to reduce the pre~sure di~ferential acrosq the cathode walls
and thereby minimize the stresses and resulting ~krains
therein.
A further object of the :invention is the provision
o~ a method and apparatus in which air and other gases are
continuou~ly withdrawn from ~he cooling system as the oil
circulates through the cathode such that the pressure of the
oil upon the walls o~ the cathode is less khan atmospheric
pressure.
With reference to the accompanying drawings. -
Fig. 1 is a vertical longitudinal sec~ional v~ew
through one form of continuous spu~ter-coating apparatus
with which the present inven~ion may be employed,
Fig. 2 is a diagramatic ~iew showing ~he cooling
~y~em ~or the ca~hode,
Fig. 3 is a vertical kransverse section ~aken substan-
tially along line 3--3 of Fig 1, a~d
Fig~ 4 is a ver~ical section through the cathode
taken substant ially along line 1~ --4 of Fig . 3 .
The ~putter-coating appara~u~ illu~tra~ed in Fig. 1,
with which the pre~ent invention may be empl~ed, co~prises
~our succ~ssive, contiguo~s 0nclo~ure~ ~hich define ~our indep-
endently con~rol~ed chambers - an entry chamber lO, a heating
and cleaning chamber 11, a coating chamber 12 and an ex~t
chamber 13. The chambers are rectangular in shape and the dimen~
sions thereof, especlally the heigh~j are kept ~o a mininum
in order to minimize the in~ernal ~olume and ~hereb~ ~he
vacuum pumping re~uired,
Each o~ ~he chamber~ i~ subsl;antially closed e~c~pt
for aii~ elongatcd entrance opening and an elongated exit opening.
The.~outer ~all 14 o~ the entry chamber 10 i~ provided with an
entrance opening 15, while ~he ou~er end wall 16 of exit
chamber 13 is pro~ided with a discharge ope~lng 17. The
1~8`35~6
chambers are al90 separa~ed by parkition walls 1~, 19 and 20
Provided with similar openings 217 22 and 23 respectively.
All o~ the openings are positioned a~ ~he same heigh~ to allow
for ingress and egress of the glass sheets or other ~ubstrates
a~ they are moved into9 through and out of the successive
chambers. Pre~erably, qulck-opening and clo~ing vacuum-
ti~ht closllres are provided ov~r at least some of the elong-
a~ed openings to reduce the vacuum pumping requiremen~s.
These closures are open when a substrate is moved through the
opening and closed when no substra~e is in the opening~
Each of the chambers is provided with at least one
outlet tube 2~, preferably lo¢ated at the bottom of the chamber.
Each tube communicates with a vacuum pump (not shown) and a
valve 25 is provided on each tube to independently control the
pressure within the respecti~ chamber. Inlet ~ubes 2~ extend
through the top o~ ~he c`oating chamber and eommuni¢a~e with a
source of inert gas, preferably argon. A valve 27 i9 provided
on each tube 26 to control ~he flow of gas into the.coQting
cha~ber~ -
Conveyor mean~ indicated generally by ~he numeral 2
are located in the low~r portion o~ the chambers ~o.tran3por~
the substrates 29 to be coated through the sequence ~ chamber~.
l'hè ~ubstra~e3 are preferably carried upon rigid.metal platens
~0, The conveyor.means illustrated in Fig. !3' compr~ses a
plural~ty o~ ho~20ntally ali~ned transversa sha~ts 31 mounted
at opposite ends in bearings 3~ and 33 supported upon the base
34 of the apparatus, Keyed to each sha~k ~ djacen~ th~
op~osite end~ thereof, are gears 35 and 36 and ~rained abou~
these gears are endle~ chains 37 and 3B respectivel~ which
convey the platens and substrates through successive chambers.
The endlesq chains are drlven by suitable drive means, no~
sho~n.
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1~83S26
Heatin~ means 39 (Fig 1) co~prising elongated,
tubular radiation heaters ~0, are mounted in the upper portion
of the chamber 11. These heaters are preferably hig~-intensity
radiation heaters and a reflector ~1, moun~ed above the heaters,
is used to cohc~n~rate the heat on the passing sub~trates 29
The substrakes are heated prior to coating to promote out-
gassing and thereby attain additional surfa~e cleaning and
improved adherence of the coating~ A ~low-discharge cleaning
electrode 42, which may be in the form of a closed loop, i~
located at the top of chamber 11. The elec~rode is supported
b~ a rod 43 and vol~age is supplied to the elec~rode by the
high-voltage D.C. power source 44. One side of the source is
~rounded and the other side thereof connected to ~he rod 43.
$hields ~5 may be position2d below the elec~rode tha~ are
~ust large enough to preven~ the substrates frq~ "seeing" the
electrode as they pass through the chamber. The electrode may
be operated either as an ordinary spu~tering electrode with
the shields which prevent the electrode ma~erial ~rom being
deposited on the substrate~ or at power levels below ~hat
required for spu~tering without the shields, The ionized ion~
of the gas will bombard khe surfaces of the substrate~ ~o clean
~hem bu~ no sput~ersd material is deposi~ed in ei~her case.
Sputter-coating ca~hodes 46 and ~7 (to be more f~lly
hereinaPter de~cr~bed) are mounted in ~he upper portion o~ the
coatin~ chamber 12~ The cathodes are u~ed ~o deposit a. thin
film of a metal on the substra~e5 and voltage is applied to
these cathodes by hi~h-voltage D.C power sources 4~ and 49
respectiYely. All power ~ources are pre~erably ground~d ~o khe
apparatus ~uch that the apparatus wlll act a~ the anode for
~0 the cleaning and sputtering op~ra~ions.
~ In practice, one or moro cathod~s may be u~ed in the
coating chamber~ Ssveral ca~hode~ o~ di~ferent materials may
be applie~ consecutively as) for example5 making cakhode 46 of
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1~83~2~;
one metal and cathode 47 o~ a di~ferent metal. Or the cathode
47 ma~ be used to deposit a ~hin protective layer of a silic-
eous material, such as Pyrex glass on a previously deposited
film of metal. Also the coating chamber can be increased in
len~th and a greater numb~r of cathodes of the ~ame material
used to increase ~he deposition rate and therefore the product-
ion rate.
In operation, the glass sheet substrates to be coated
are Pirst cleaned by a conventional washing opera~ion and are
then passed into the entry chamber 10, with the smooth contin-
UOU3 sur~ace to be coated fac ing upward . The vacuum pumping
in the entry chamber removes most of the air, moiskure, and
other contaminates which may leak in through the entrance
opening. The substrate~ 29, carried by the platens 30, are
moved by the conveyor means 2~ into the he~ting and cleaning
chamber 11 where they are heated by the heaters 40 and then
cleaned by the cleaning electrode 42. The ~ubstrates then
move at a controlled speed into the coa~ng chamber 12 where
a continuous film of the selected coating material or materials
is spu~tered on the clean upper surfa¢es thereo~ After belng
coated, the substrates move into ~he exit chamber 13 where
they ~re cooled before being removed from the apparatus
~hrough the opening 17~
- As brought out above, under typical operating condit-
io~s, ~,OOO volts potential may be applied on the target,
(coating material) and ~his high potential generates an exce~s
amount of heat that must be rap~d~ removed in order ~o pro-
duce a commerciall~ satis~ac~ory coating on the substrates
without damage ~o the apparatus or the glass substrates. Ths
30 present inven~ion is particularly concerned with ~he provision
of a new and improved method and means ~or ef~ecting a more
controlled func~ioning of the cathode.
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3~zfi
Each of ~he cathodes 46 and 47, as illustrated in
Figs. ~ and 4, is o:~ substantially box-like form comprising
a hou~ing includin~ a top wall 50, a bottom wall 517 side
walls 52 and ~3 and end walls 54 and ~5 which define within
the housing a closed chamber 56. The slde and end wall~ are
- sealed to the top and bo~tom walls preferably by welding.
The cathodes extend transversely within the coating chamber
12 and are located in ~he upper portion thereo~ by support
lmits 57, 5~ and 59 mounted on the top wall 60 o~ the coat-
10 ing chamber 12.
Each of these support units includes a metal ring
61 ~ertically aligned wi~h an opening 62 in the top wall of
the coatin~ chamber. An annular insulating member 63 having
a depending collar 64 is disposed above the ring 61, with a
cover plate 65, having a central aperture therein, positioned
above said insulating member The ring has tapped holes for
receiving bolts 66 passing through openings in the insulati~g
~ember 63 and ~ov~r pla~e 65. An 0-ring 67 i9 located between
the ring 61 and insula~ing member 63 to provide a vacuum-
tight aèal, while an 0-ring 6~ between ~he insula~ing member
63 and cover plate 65 serves the same purpo~e.
Secured to the top wall 50 of tha cathode housing,
as by welding, is an annular ~leeve 69 which is received in
concentr~c rela~ion within the collar 64 depending from
insulating member 63. This sleeve is provided at its upper
; end with a centrally disposed aper~ure in an inw~rdly ~urned
rim~70 formed with tapped hole~ to receive bo.lts 71 passing
through the cover plate 65. An 0-ring 72 is located around
the bolts to a~ord an additional vacuum-tight seal.
: The coatin~ material ~target) is carried by the
under surface of the bottom wall 51 o~ ~he cathode.hous!ing
and consists of a sheet or layer 73 of ~he seleaked me~al or
me~al allQy which is to be. deposited upon the upper ~urrace
- . . . , ~, .
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83S26
of the substrates as they pass therebeneath. The coating
material may be applied to a support plate 74 by electro_
platin~, brazing or in some other ~uitable manner.
A thin foil sheet 75 of a ~oft, thermally conduct-
ive material, such as aluminum or indium~ is pre~erably
positioned between the bo~tom wall 51 of ~he'catho~è housing
and said support plate. The support plate is secured to the
cathode housing by bolts 76~
The required electrical power for the cathodes 46
and ~7 can be supplied there~o ~rom the respec~ive po~er
~ources 4~ and ~9 through power lines 77 and 7~ connected to
conductor rods 79 a3sociated with the suppor~ unit~ 5~.
Grounded shielding pla~e~ ~0 are seoured bo the ~op wall of
the coating chamber a short dis~ance from the edges o~ the
cathodes to prs~ent reverse spu~tering of the mater~al on
the edges of the cathodes~
To pro~ide for the ¢ontinuous circulation of the
cooling medium through ~he cathodes ~6 and 471 each cathode
is~provided wi~h an inlet pipe ~1 adjacent one end thereo~
and an outlet pipe ~2 adjacent the opposi~e end. Ea~h pipe
passes downwardly through bhe aligned aper~ures in the cover
plate 65 and ~leeve 69 o~ the re3pec~ive suppor~ uni~ 57 and
59 and communicates with the cathode chamber 56 throu~h an
opening ~3 in the top wall 50 o~ ~he cathode housing.
The improved means contemplated by the present
inve~bion for internally cooling the cathode~ i~ illustrated
diagramaticall~ in Fig. 2. Such means com:~ises a reservoir
which may be in the form of an elongated crlindrical ~ank
containing a upply o~ the oil used for cooling ~he cathode~
Connected to the bottom of the tank ~4 is a pipe ~5 leading
to a coolin~ unit ~6, while connec~ed to the bottom o~ ~he
cooling unit i3 one end o~ khe pipe ~1, the opposite end o~
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~8352~
which communicates with the cathode chamber. The outlet pipe
~2 conducts the cooling medium ~rom the cathode chamber to a
pump ~7 w~lich returns the oil through a line ~3~ back to the
tank ~Is, It will thus be seen that the oil is con-tinuou~ly
recirculated through a closed system under a constant head
pressure from the reservoir to and through the ca~hode and9
upon exitlng from the cathode, is pumped baGk to the reservoir.
The amount of oil contained in the closed sys~em
is such ~hat tha tank ~ is maintained about hal~ full, the
level of the oil being indica~ed a~ ~9~ Connected ~o the top
of ~he tank ~4 and communicating with ~he space above khe
oil suppl~ is one end of a pipe 90 which leads to a vacuum
pump 91. The vacuum pump i5 continuously opera~ed to with-
draw any air and other gases from.~he cooling system. As a
result, the pressure o~ the atmospharic air i9 substracted
from the head pre~sure of the oil on the walls of the cathode
so that the pressure exerted on the walls o~ the cathode is
. less than atmospheri¢ pre~sure, While the pressure exerted
on the walls o~ the cathode housing may vary as operating
20 conditlons dictate it is usually in the range o~ 2 to ~ lb~. .
p.s.i., and preferably about 3 14s. p.s.i.
The continued mainkenance of the vacuum in the
upper part of the tank ~4 will effect ths withdrawal o~ air
~hat may lea~ into the system a~ well as any gasas tha~ may
be released ~ro~m the oil. The oil can be of any typ~ ordin-
arily recommended ~or heat transfer applica~ions.
; It will thus be apparent ~hat the oll cooling ~
system of the present in~ention overcomes the objec~ional
features present in prior water cooling systems in that the
pressure of ~he oil on the walls o~ ~h~ cathode will be less
than atmospheric pres3ure. This will, of course, result in
reducing the pressure differential acro~s the walls o~ the
cathode housing with the ~onsequenk reduc~ion of the ~tresses
.
1~83~Z6
and resulting strains kherein. This greatly le~sens the
- liabili-ty o.~ leaks ocCUrring in the welded joints between
the walls of the cathode housing resultin~ in much les~
maintenance costs as well as in reduced !'down time" in the
operation of the coating apparatusO Another advantage in the
use o* oil as the cooling medium is that it also aliminates
corrosion in the system due to salts in ~he tap water here-
tofore used.
~hile this lnvention is not limited to use with
any part icular type of cathode, it is of ~pec ial ut ility whan
employed in the internal cooling of ~he type of cathode des-
cribed above in a continuous sputtering process.
It ls to be understood ~hat the words used herein
to describe the invention are words of description rather than
of lim~tation and that ~he scope o~ the invention is ~o be
limited only inso~ar as s~t forth in the appended claim~
. -12
