Note: Descriptions are shown in the official language in which they were submitted.
I J 1~7 ~; 7 I r
131CS 1~1 :
. 17.1~-75 ,~
`
' ~ s~
~ etl]od Or manufac$urin~r~semiconductor clevices in whic}-
a glas.s eoating is pro~ided, and semicollductor de~-i.ces
manu~actured acoording to said method"~
~t ' sF~
' ~
The invention relates to a method Or mallu- ~ ~
1~
facturing se]niconductor devices in which a glass coat-
ing is provid~d on a semiconductor slice compris:ing
one or more of' said scn2iconductor device~s in an :i.nter-
mediate sta~re or in a ~inal stagre of` manu:~actllre, ~y
mealls o~ elee-trophores:is usin~ a dlspe-rsi~n o:~ ~lass
partielo~s ~ a l:l.qu2.clllledium, hereinafter tc:rmed dis~
r ~ c . ~ n~ 't. l ttl) C~ ~lt ~ ' ' 3 0 O ~ '; U L~ V' ~ IJ U ,~iJ.' U '~
tect vital parts of semicoi-iduc-tor device.s~ preseilt a~ s
the surface, for exanlple, ~-junotions~ ending at t}le ~'
surf'ace~which are to be cxpc)sed to comparal;ively h~6rh
rcverse ~olta~e.s dur~ng use~, or parts wllich ar~ s-~,ns:L- `
tiv~ to atmoc;pherLc inf'luences, `,
Upon providin6r such coatin6rs, lort~>-lastj.ng'
t5 ~hormal troatlllents at modérately hiCrh teltlperal;ure ca~
ad~ersoly ;Lnfluence thc e1oc~r:Lcal propcrties o~ t]lû
. semLconductor devices. Witll a view to a reasollable
protective effect against atmospheric influellces, the ~-
.coatLng shoulcl bc sufficiently th:icl~. Howc~er in the
?0 case o~ large layer tllick~lesses, tllerllla11y causcd 5tre.s--
se~ ma-~ occur and these Illay d~amag,e the semiconcluo~or ~'
dev.l.ce. :~n order to ~ro~i.de a gla3s coa-t:Lngr with a '.
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.
PHN 7872 ,~
17 ~ 1 2 0 75
1~47~L7~ ~
. .
reasonal~le thiekness and to avoid therma:L treatments ~,
Of lon~ duration, aeeording to a known methocl the
~lass layer was cloposited e, ectrophoreticai.ly from
a disporsion of fino-granular glass particles in a ~ f~
dispersion medium, for example, water, me-thanol or
ethyl aeetate. The charge of the glass particles ori~
ginated from ions àdhering ~o the particlos. Such a
deposited layer has suffieient adhesion to the device
- to ~lithstand`, for example, rinsing treatmc-nts. For a
better adhesion and screening ef:t`éc t j a thern1al trc~t
me2nt at a moclerately hl~ll tomperaturo and o:~ on]y a ~ ~,
. f
short clurat~.on ma~ thon su:~:fiee . 1~ r~
~t has been louncl, howe~2rer, that the electro-~
phoretie depo.sition is of-ten n~ b produced uniforl11l 2~ 2;
over the semiconductor surfaee cmd the deposit is
somot-:imes entiroly restricted to those parts of the i
semieoncluct-or sli.ce surf~e which are present in the
immediate proximit~ Or the eleetrode eonnec tion pro- i
vidod for the eleetro~ ores~is. :I:t has furtIlerl11ore been
establi.slled that non-uniforlll eoatiIl~s in the malIu:Eac-
ture Or varlous types of semiconductor devlces occ~lr ,
to dif ferent extent . i~.
A first idea whieh has led to the present :;n- i-
ventit>tI is that the above-ment.ioned phenomena may be
relcl ed to rosistances in tllo slice itsel.f. As i.s
,,
confir111ed by oxperiment-2, non-.unirorm deposits occur
particulariy st;roI~ y :in those scmicond1lctol sl.ices
'.
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P~IN 7~72 ,~
- 1' 7 . 1 2 . 7 5 ~:
.
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which consist at least f or, the gr~3ater par t Or material
o.f .a comparal;ively hi~,h res:isti.vity, : .
The invention is furthermore based on the idc.a
p. that. in tl1e above-described 1;nown method the suspension ,
, used has a comparatively high conduc-t:ivit:y, so that the `,
internal rcsistances between the electrode connect.ion ~`
provided on the slice and the varlous parts of the se-
miconduc tor slice surface exposed to the suspensi.on,
in particular those surfaoe par ts ~hich are present
~ at some dis,tan~oe from the connection-, need not be , ~ ,~
negligibly small witl1~ respect to the resistance be~
tween each o:E the sur*aco parts and the coul1ter-el~c- '" !~
,~ , troci e provid ed in iihe su s pen s io~ . , .
It has further been considered that the charge `~ `,
I5 ~ of: the iOllS o:l~ la given sign adhering to the parti.cles ii'' .
are naturally: compensatec1 for b~ ions di~;solv~3d in'' the ; ' j
dispersion medium. Both types o: ~ons are foLmed frol~ ,I .
dissoclable sul~ ~;ances ~ hereina*ter termed auxi,liary ,
.. . ~ disp~rsion aj~ents, suitable for that purpose and added
.' 20 to the coDventional ~.ispersion media~ in w~1ioh the (
ions of one char6e type must be cQpable of adher:Lng l; .
to the sus,pended parl;:;oles and the ions of oppos:~,te
Gharge type mu~;t preferably remain dissolve(l :Ln sai.d . i
mediwn by ~):inding to the dipo1es o~ the molecules o~
the dlsperF;ion medluI,n *or wh.ich purpc se I;ho saic1 ions
Or opposite charg(3 type shoul,d pre:C`erably be, comp.lra~
, tlvely small . Consequ(3l; l;:1.y the mobi.l.ity of sa:Ld i.ons
' , ' ' . . ' ~' ~
,
PllN 7P72
17.12.75
. ' " , ,' " ' ' ,. ~
~ 7~7~ ~ ~
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of opposite ehalge type i~ comparativcsly -lar~e~ An
othor supposi-tion is, that said small ions should form
a eomparatively clense cloud ln the po].ar mediul;lLIrollnd
~ each dispersed cliarged partiele so as to main-tain the
dispersion. For such a comparatively dense ion cloud
a correspondingly high ion concentration must be formed
.- in the solution. The said comparatively hig]l concentra-
tion Or dissolved ions and their eompnratively l~rge
niobility are responsible for tlle comparatively ll:i~rh
eonduetivity of the dispersions used :in thes abovc-
me~nt:ioned lulown ritetllod It :i5 to be noted that clue to
~h~s very small mobil.ity o~ the disl~ersed parS;:ic].os, t ~ ~'
, , Ille COnt'l'.ibUCiOn oI saicl a-t~spcriecl pa:r~icles to the ti
- eonductivity of the dispersi.on is neg].igible.
~_1 s~
- ~ further iclea underlying tlle invention is .
that for t]le electrop~loretie deposit:Lon of glass on ~i
semieonduetor slices, glass dispersion.~ of a con~e-
niently lo~ conductivity may preferably be utiliYed.
Aeeording to th~s invention a method of manu-
I`aetur~ng semicoIldtlctor desviees in ~llich a glass eoat-
lng is provided on a semiconductor ~lice compr~.s
one or Illore of said se~ico~dtlctor devices in an illter-
mediate stage or in a final sta~re of manufacture~ by
mecms of electrophoresis using a disp~srsion of glass
particlei in a liquj.d di.spersion medium, is characteriz
ed in that ~ disper.;ion of thc-, ~lass particles is used
~ith a sy~seific conductivi ty o~ at most 10 o}1m cm 1
'
. '' ' '' ' '" '; ' ~
,
l !'
l'llN 7872
. 17.12.75
; 3L~4:7~L7~ ~ ~
It is to be noted that the fact should be takell i~ltO
acçount.that the dispc-~rsion medium in itsel~ llas a
lower cond~ctivity tl1an.tlle dispersion preparec1 witl
it so that the liqu:id dispersion mediwn should be
.. , ~t~
chosen .from liquids having a speci.~ic cond1lctlvity of`
less than 10 ohm cm . l~rater and methanol, for
examplc, have a spècif`ic concluc-tivity of more tllan
10 ohm cm . A lligher specif`ic concluctivity has ~ ! .
aLso been measured for etllyl acet:ate. Hydrolysls can ; ~ r
increase t1le coMclllctivi-ty of etllyl acetate. ~ i~
It is to be noted that in ~:i.old3 otthor tllan
sc~niconductor techl1ology, d:i.sporsions ~or e:Lcctro-
~;LOre8:ig wltll a conduct:Lvity of le~s t~l.m 10 lû o}lm ICm
ar~ known por se, ~or example, ~or the depos:ition of
piglllents or carbon particles in the manu:~acture of
disp~ay tube~
According to a proferred embodimc?nt, an apolar
liquid dispersion mecliuln is u.æed. Such an apolar clis- .
pet~sion meclium has a conductivity o~ its o~n whicll is
le~5 ~llan 1û 10 ollm 1Cm 1. 1.
It is recolmll~ndablo to C,]lOOSe tllo l~qu:Ld
dispersion mediulll froln tlle hydrocarbons~ pre~erably
tl1e sat~rated hydrocarbons. rhese have rl very low .
conduc-tl~rity o.~ tlleir own. The d:isper.sion mediulll need
not cohs:i.st of a single liqllid llydrOC,arbOn bllt Illcly
also cons.ist-oi a liquicl~nixtllre of hydrocarbons.
~ccordir3g to.a furt}lcl pre~orred embodimc?nt
.' ' ' ~
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.. . . .
p~ T 7~72 ! ~-
1 7 .1~ . 7~ I ~
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the dispersion comprises at least one allxil:iary dis-
persion agent in tho rorm of an ionisab~e material,
Wh.iCll ..material compr.iscs a po].yvalent metal and at
~ least one ion ~ith at leasl. olle apolar orgc~ic group.
A polyvalent metal is to be eonsidered here as a Inetal
having a valene)r larger than 1. Sueh auxiliary disper-
sion agents are ~nown ~ fiO. Tho di:sociation of sueh
an auxiliary di.spers:ion agent in an apolar d:i.sper.s:ion
medium is proba~ly made possible by the occurrence o~ ~
Yan der Waals~ -rorces ~e-tween t}le apolar liqu:id and ! E
the apolar ~roup(s) o~ tlle above~ elltiolled ion, as a
J'e9Ul t of Wlli,Ch SUC11 an lon :is di~so:Lved i.n ~he apola
liqu:id. Tll~ pol~cl:L~ I.fl~ wi~ cr-~l.
thereto prol~ably forllls a morlovalent complo~ ion wh;.el
is adher~d to the glass particles, so that sai~a par~
tieles obta:Ln a eertain eharge ~rhich i.s oî opposite
. ï! ~
Si.6'11 Wit}l respect to the ehargo of tlle iO13S dissolv-
ed in the di.spersioll medium. Thc gl'OUpS bound to the
pluraly valent metal 3 in the monovalent eomple~ :ion n
~0 may provi.~le n contr:L~ution to the dispers:ion o.{ tho
glass particles. ' 1
Yan der Waalsl ~orccs are g~nc:rally low with -
res~ect to electrostatic bindin~r forces ~etweer~ :iotls
.
of mutually opposite sign or ~ctween an ion and a
' ~:
dipole.mole~cul.e. In order to nlalie dissociation of
~h~ au~ili.ary.dispersioII agellt nevertlleless posslble, ~ .
-tl-le apol.ar part of the ions d:issolved in the clispel-s:ion
'. ' ' . . . '' ,,
'~ ' '. . '
~ _ " ~
.r, .
. . ~'IIN 7~7.
. 17.~2..75
.~ ' ' .'"'"' , ' . ~
mecIium should be ~airly Iarge. For exaIllpIe, the apola.r
part may consist o~ a cha.ln of an alipIatic hydrocarbon
grollp having a conveniently large number o~ carboII atomsr
The mobllity of the lon which is a dec.isive ~actor oi`
the conductivity of the dispersion, is very small clue
. to the compara-tive size of` the ion.
Fur-tIIerlllors~ the lo~ conductivity Inay also be
ascribed to the low concentration of dissolved iOllS, '.
inter alia by a low degree of dissocia-(;ion of' the All~i-
li.ary clispers:ion agent. For ch.arge compeIlsation a cloucl
Or dissolv0d ions are f`ormed around the disp~r~cd glass '
particles whicIl cloucl is ratI~ r :klli.n~ .,th.eiapolar:.di:G~.
r ~ .L o ~ e d iun
~ocordln~ to ~ :.~urth0T pre~orred omhodiIllont a ,.
polyIller is added to the disp~rsion as a binder f`or the
~lass part:icl0s, As a result o~ this the adhesion b~
twoen the deposited glass particlcs is improved. ~s ,l ~
is kr~own ~r so, S~ICh a polymer binder may provide c~n ~ ~
~f'f~ctive contrl~ut~.on to the dispersion of solicl par~
ticl~s in an apo:Lar di.spersion mc3dium as a reinforci.n~
and stabilizing agcnt. Xn particular in the preseIIt
case o:f th-3 suspension o~ lass particl0.s which hav
a polar strllct~re thQms~lves, polymors wh:ich ma~ be
active as r0inPcircin~ cmd stabiliY;ing agc3n tS OE~ Qtic~larly
~`S~[Lil. l;~ur thern~oro the polymers ma~r adhere t:o the par~
ti.cles and ~ I;heir apt-lar p~rt S till~U Late a V~l dcr 1 ,
Wnalst bon~ to th~ mc)lecll]:es o~ the apolar Illo~ium. 'J'l-le . ~.
~ 8
.
- -~ n~N 7~72 `
17,12,75
7~7~ :
.., . 1~
polymer may compr:ise side chains of at least 4, fo
example, 10-20, carbon atoms. Polylne-thaciy:l:Lc acicl
compounds may be very useful. In a short duratio
thermal treatment possibly sucoeeding the depositlon
of the glass coating, such compounds may rapicll~ dis- `i
appear, also due to depolymcr:isation. '~ ~-
It has no-~ ~een found that it is poss:ible by ~;
means Or the method according to tlle invent:ion, to
ef~icaciously pro~ide glass coatings of uniform thick- ,.
ness on semieonductor slices of comparative1y higrh
resistances ln lateral directiorls, e~ren on 91:iccs
t~
av;n~ an average ~ ternal resistance in lateral t
dlrectiorls oi` at loast 500 ohnls per squaxe.
Glass eoatings are partlcularly usefu] for ¦
semlconductor devices having pn-junctions, for which
a high brea~clown voltage is roquired. In thct manufac-
ture of such devices use is made of a semiconductor
slice of high resistivi-ty in ~-hich, one or more æones
of opposito con~uctivi-ty types are pro~ided, for
c~ampl~,by d:ifrusion. A sliee thus treatcd s~
consists Or the original high-ohmic material for -the ,
greater part Or its thickness. In particular in that ¦
- càse non-uniform glass depo~its are obtained witl~
the ~l0~ method. The method ~ccording to the inventic~
llo~ makes it possible to suGcess~ully cone slices
}liCh conslst of sellliconductoL Inaterial having a re-
siistivity Or at least 20 Ohm.cnl over the greatex part
' ' ' '' ~
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PIIN r/~72 ¦ ~
47~7~ , ~
of their thicl~ness.
- . Xn semiconductor dev~.ces wlt;}~ higrll-oll~ic sub-
strates, f`or example, diodes ~Yith h:igh brea~idown voltlge
~ and many thyristors, glass coatings are u.secl in order
to obviate lo~ breakdo-~n volttges by peri.pher~l dis-
turbances wllere ~-jw~ctions are encling ~ the semi-
conductor surfaoe. In a pre~errecl embodiment a ~serni~
conductor s~ice_is used WhiCll comprises a higll-o]lmic .
eubstrate on which on a-t least one side at leas-t one .
semieonductor zono of a diiferel1t conducti.vil:y .nd/or
conductivity type :is l~rov.iclecl. Accordingr to 9aid pJ'e-
fcrled el~ odilllont, on the sicle o:C tlle providocl sem:i-
concluc~or Y.onetSj a net~York Or grooves is proviclecl
do~Yn to in the hig}l-ohmic substratej after which the ;
glass coating i5 also deposi-ted in the grooves f`roIll the
dispersion in the apolar disp-rsion medium. In this ~;
manner~ junctiolls debouch;.n~; into the grooves~. .
may be covered with a stabilising glass layer. S:ince
- the groovos extend lnto tho hig}l-ohmic nlaterial the
~ various senliconduc-tor parts enclosed by the grooves
are connec-ted tog-3t}ler only by h:igh-ohin:ic su~stra-te
material causing non-negli~rible lateral resistances
in the slice. When g1ass coatings are fornied oii sen
conductor slices using knot~7ri ~ispersions of glass
~5 partic1es :i.n l;olar dis},ersiol1 me~licl the coatirig.s pl-O-
~ .
duce~ ma~r le of non~uI~ ornl thi.c]clless or ~na~ 1e-ve . ~.
parts of t}le sllce uncoated, whereas a glas~s COting i
,' ~
.'' ''. ` . '' '' ' ~
, ' _ 11)''- . ', '
' ; .~",
~ IN 7872
" , , , , . 1 17.12.75
~7~L7~
on the sen1iconductor surfa.ce o r a substantially ~Ini-
form thic];ness is obtained over the whole are of tlle
slice by m~clns Or the metllod according to the inven- ,
tion. , ,
- ~ further ilnportant aspect of the mcthod ac-
cord.ing to -the invention is as folLows. In the l;nown
,deposition~ only exposecl senliconductor and possib:Ly
metallically conducti~e surI`ace parts are covered,
whereas insu'Lating layers already present, also i~
these are eon~paratively thin, remain uncoverecl. By ~ E
means oI` t;ho method aecording to the invention, S~II'- ' ~.
' ~no(3 parts consistin~ o~ insulAI;Ion nl~terial are aL,so
~overe~l witn tho giass pa~t~e-.es. ~s a result of` thls j
an improved protection o-f vi.tal parts Or the semicon~
ductor device t.o be manufactured oan be obt~ined.
The invention furthormore extonds to semicon~
ductor devices obtained by meaIls of -the methocl accord-' ,,
ing to the iDvention. ' , 'I ' ~;
The inventi.on wlll now be dcseribed in greater , .
,20, dotAil Wit]l rc:~ercnco to an elJIbodilllent.
ln t,his embodilllent,a glass coa-tinG is,provid- ~ ~'
' ed on a silico~ slice which has been'obtQined, for i
example~ as follows~
, Startin~ material, is a disc-shaped sliee :'o~ ,
2S . monocrystallinf~ sllicon }iav:in~ a resistivity of approx.i- -
~ . .
matel~ 50 oI~nl.em. ~Yle s:Lice has. a diameter o~ approxi-
m~toly 50 nlln and a thic~ ess o~ 200/unl. ~t has been
. '' ' '' ' ' '' ~
.
' ! g~
I~lN` "7 8 7 2
, ~ 17. i2.`~ ~.,
.'' ' `' ~ ",' ~ ,~,
.
~47
. i i,,
obtained frolu a rod-shape(l sin~le crystal by sawing
in the direction Or r 100~ -planes~ a~ter ~hich the
slice has bQen ~iven thc above thicl~ness by grinclin~,
~ polishing and etchine
One or more zones destined fGr semiconclucto
devices to be n~anurac-turecl are provided on one side
by means of ~o~Yn metllods, for example, by d:ifIusion
and pos.sibly ep.itaxial dcposition, ~-thlch zonc o:r Y,OIleS `
differs or dirfer in conductivity type and/or conduc- `~
tivity from tllose Or the rema:in:ln~r pc~rt o~ the origi-
n~l mater~al of tho slice. Saicl remalnln~r part ~YhiC]~.
constitutes the ~reator ~art o:E` the thicl~.ness o:~` the
Slj ce ~rill hereinafter be re~errecl to as the hi~?h-O}l!l~j_C
~ ~substrate. A layer of insulatiug matcrial, ~or e~am~le
t5 Or silicon oxide, may be providecl according to a desir- --
ed.pattern on the scmiconciuctor surface on -tlle siclc? o~
the proviclc?d zone~s).
On l;he rele~ant side of the sl:ice ~here the ,, r~
zonc(s) is (nrc) sl.tuated g:rc-oYes are no~r for~i~ecl, :
~0 ex~mple, accord:illg to a net~-rork of scr:ibirl~ lan~s alon~
wh:ich the s.l.:ice can be sevc?red into a number of semicon- ~ ~`
ductor clevices. Said ~rooves may be prov:Ldcd in kno~rn
manll-?r, in ~Yhich first a possiblc layc~r of insulation ~.
matcrial accordine to the pattern Or grooves is re- `
moved Accordingr to the ciesirecl pattcrn o~ ~rooves,
t;]le silicon iS ctch(cl anisotropically (US:).}l~,' an e l;C]I~
resistan-t mask.in~) do~Yn to a de~th cxcceclin~; t}le thic3i- -~
- 12
~ .
: ~ ~:
l"lN.7872 7:
2~ 75 ,
~47~ ~
- .
ness of the provide.d zone(s) 011 t~lC relevant si.de of
t}le sliee. Julletions in the semieoncluctor mat.erial,
for example, between SUCll a zone ancl t]le substrate
~ material, may mer~e at the surraee~ a-t the ~alls Or ;
the grooves
A dispersioll of glass par-tieles in a su.:Ltable ;
liquid disporsion n~edi.um is preparod for use in the
elcetropllore-tie deposition Or a glass eoati~g on the :
. se~nieondue-tor sliee surfaee. The glass parti.elcs eon- '.. .
sistof a su:Lta~le high-ohlllie ~lass on the basis o:~
sil.ieon oxide, lead oxide and alu~i.n.iulll o~i.clo~ u.ld.
hio]l glass ~oI`volls at app:roxilnato:l.y 8~oo to 850C .
~ ~cc ^~ th:7.~ ~ i.J ~ v~ ?:L' ~ î ~r .~m:i- r :
eondlletor uses. . ! 1
Tho gra.in dian~eter of the glass particles i5 '~ .
between approximately 0.1 ancl 10/um ~ith an a~rerage
, ~nlue Or approximately 3/um. ;
~ As a liquivl dispersion llled:iuln is usod a mix- ..
t~lro Or isopnrarri.ns havillg 9-12 earbon atoms por molo-
~20 eule, il~ tl~is eas0 a mixtvu:rc? whieh :is eommc?reially .
available as "Sholl Sol T0".
~ .
~or the auxiliary dispersion agents to be
addcd is used a mixture eomprisillg -
-1 part by ~eight Or a ealcium soap of dide-
25. eyl estc?r o.~ suJ.rJllosuceil]ie aeidj
1 par~ by ~eig]lt o~ a ehrorlliuln soap o~ a
.mlxture Or allc)rl salieyla.tcs, the all;yl group o~ whieh
. " ," ~
~. , . ' , . . ' ~
. ~ 13 - - ~
.',,` ' '." .' "' ` ~
PllN 7~7'.
. . 17.12.75
7~
comprises 8~ carbon atoms.
1 part by we:ight; of a co-polymer of lauryl
stcaryl methacrylate c~nd 2-methyl,5-vinyl pyridinc~ d
~ 3 parts ~y wcight of a suitable solven-t, Por
example xyleno.
Such a 7nixture is commercially ~vailab]e as
~'A S ~ - 3i' o~ Shell Cy. 0.75 g of said m:ixture is
dlssol~.ed in 1 l of the abo~e~montiome~l isoparaPri
mixture. OP this mixture tlle calciuln soap and the
c~lromlum soap :~orm the ionisab].o aux:i.liary clisper~sio
a~en~.s. Tho co polymer ~orllls a re:inforcin6r c~nd sta-
bili.~.inGr agenl
In the present example a furtller re:;nforci.ng
.
- and stabiliz.in~r agent in the form of a lauryl st~aryl
polym~thacrylate solution of 20 g per litre of the al- `.
ready mentiollecl isoparafrin mixture is us~
The suspension is prepared by add.intr~r;
10 g oP the ~rlass parti:cles to be suspendec1
20 lnl Or tlle ~A.~.~.3~-sv:Lution clnd
10 ml of -tho lauryl stearyl polymethacry].~-te
SOltltiOll ~ ~,
to 1 litre of the isoparclffin n1ixture "Shell So]. T0".
The specif`lc conclucti~;ity of the dispersion is 5x10 2ol~m
crn
~n.c~g~ por-l;:;on oP th6 serlliconduc~or sl.ic~
to bc covered is connected to c~n electric :Load melllbor
.cons:i.stin~r of p].atinulll by means oP a cj.a~ and hullg
'', ' - ' ~
,
IN r/ 8 7 2
. . 17. I~ . 75
,
~L'~'k`7~.7~L .
in -the suspellsiol~, the sl:i.ce forlIlin~,r on~ e].cc trocle in
the electrop]loresis bat~l, A p1.ati.nurll coullter--c.1.ectrodc
in -th~ rorm of a d:isc having a diamctcr of 5 Clll iS ar-
~ i~arc,ed diroctly opposite thQ s~.cle ~:ith l;he groovcs,
so tllat tlle mutual d:Lstance be twee,n t]-le slice *o bc
treatod an~l the platinum counter-electrode :is approxi-
- mately 1~ mm everywhore. '
' . A volta~e o~ 200 volts i.s thcn appliec~ acros~s
tho electrodes, the semiconductor slico being nogat:ive-
ly b:Lasecl rolat.Lve to the cowlter-ei.ecl:rod~. A~tc,~r ~p-
prox:Lmatoly 1 mLnute a unLform i.ayor ap])rox:i.mclteLy 'l5/u
th:Lcl~ htl5 beon provided on tlle semicollductor s i. Lcc ~sur-
~aco on the side with the groovo.s and covers the sc.~nli-
conductor slicc surrace and, iLf preserlt, insulating
,
layei~ portlons.
Aft~.?r dryill~, thc sltce witll the result:Lng
coati..ng,of glass particles, mainly bonclccl by mctll.c~- ;
crylato~ :is s~lLj'ected to a tllermal tro.ltlllcllt in air
1t: 1 telllpcra~ul~o o:~ 500C ~or 10 Ill:L31u~o.s, c~ ? 01' -
~20 ganic chcllllcal con~t:Ltuellts, for cxalllple, tho nletha- ~'
crylate, dis~u~pear.ing par-tly by depolynler:isa*:Lon .~ld'
~ ~ evuporltion, and partly by oxlclation~ Tlle glass par-
- . ticles arc then fuscd to rorm a dcnsc glass layer by
llcating at ~OO~C for approx,inlatcly 7 nlinutos.
I~or conlpari.so)~, silllilar solnico3lductor sl:i.ces
erc Sll~J ecl:~d to c:Loctrop~lo:rctic coa-Ling t:reatlllellt~
.Ln 1 dis~C?rC;.iOIl of ~lus9 p~J~tiC~.CS il3 1lieth~llo.1. as t~
.. , ;
1S
, ,' ' ' ''' ' "' .
.. - , ~
PIIN 7872
- 17.12.75
dispersion med:ium and ~lC13 lS an auxil~ary d:ispersion
agent The speeific condllc-t:ivity of the dispersioll in
Dlethanol was between 6~10 5 o]lnl cm and 10~10 501lm cm
dispersion in eil-lyl.lc~tate was also usecl wl~ich had a
specific conducti~ity o~ 3xlO 90hlll Clll 1, Mle slices
were not coated electr-opll.oretically ~ith a layer of
glass par-tieles or we]-e only eoated elecl:rophoretieally
near tlle provided ~leetrod~ con)lee-t:Lon. l~rhen using
an~ of said d:Lsper.sio*s ~:itll polar cl.L.~p~r.ioll med:ia
1n no deposit:ion o:~ ~J.ass plr-ticle~ ~as Obta.:LrlC`CI clt .. ln~'
sur~aec3 portiolls a~ which insu].atin~ layorc~ olo a:l.-
ready pres~llt.
Results sirnilar -to the glass coat;in~ proee~s
according t;o the abov~ eJllbodlment are obt:a:ined in si-
. .
mil.lrly treating semiconductor slices clest:incd for
th~rristors, in whieh on eitller sid~ ~ones have been
dif~sQd in a hi.gl--ohmie silieon .sl:ie6 and. a networl~
o~` grooveci llave been prov:i.decl on both sic1'3s down l;o the
substl~ate. Tl~e lat~ral rosistaneo Oe saicl slico9 iS on
, 20 an average 200 ohms per square. T~o dise-s~lapecl eounter-
olec-trodes are usecl,one on each s.ide o~ the selniconduc-
tor slice ancl at equal distances t]ler~.~roin.
It ~-lll be obviou~ l;llat the invention is not
restrictecl to the above embodinlQnts W:it]l d:ispers:ion.s
~5 -:i.n apo.lar media and l:llat .~mic.olJdue1;or .ql.iees Or selni-
eondue-tol materi..l:l. other than silieon and/or i.i.t]l
hetero~ nctions ean be provi.dod with ~la.ss eoatin~S
~ ec~rresI)orldi~l~JJIlmner ~it]lout ~ p~:rtin~ :t`30JII t~e
.~e~ e c~:e tl~o ~ l.i.on.
.
. ~ 16
