Plasma-enhanced chemical apo deposi ion o SiO2 om
aSi„CH3…3Cl p ecu so and mix u es A ÕO2as plasma gas
A. Ba anco
Ins i u o de Ciencia de Ma e iales de Se illa (CSIC-Uni e sidad de Se illa) and Dp o de Quı
´mica
Ino ga
´nica, A da, Ame
´ ico Vespucio s/n, 41092 Se illa, Spain
J. Co ino
Dp o de Fı
´sica A o
´mica, Molecula y Nuclea , Facul ad de Fı
´sica, Uni e sidad de Se illa, A da. Reina
Me cedes s/n, Se illa, Spain
F. Yube o
Ins i u o de Ciencia de Ma e iales de Se illa (CSIC-Uni e sidad de Se illa) and Dp o de Quı
´mica
Ino ga
´nica, A da, Ame
´ ico Vespucio s/n, 41092 Se illa, Spain
T. Gi a deau and S. Camelio
Labo a oi e de Me
´ allu gie-Physique Ba
ˆ SP2M, Bd. Pie e e Ma ie Cu ie, 86962 Fu u oscope Chasseneuil
Cedex, F ance
C. Cle c
Cen e de Spec ome
´ ie Nucle
´ai e e de Spec ome
´ ie de Masse, IN2P3-CNRS, Ba . 104-108,
F-91405 O say, F ance
A. R. Gonzalez-Elipea)
Ins i u o de Ciencia de Ma e iales de Se illa (CSIC-Uni e sidad de Se illa) and Dp o de Quı
´mica
Ino ga
´nica, A da. Ame
´ ico Vespucio s/n, 41092 Se illa, Spain
共Recei ed 3 Janua y 2003; accep ed 31 Ma ch 2003; published 16 May 2003兲
Silicon dioxide hin ilms ha e been p epa ed a oom empe a u e by emo e plasma-enhanced
chemical apo deposi ion in a downs eam eac o by using Si(CH3)3Cl as a ola ile p ecu so and
a mic owa e elec on cyclo on esonance ex e nal sou ce. Expe imen s a e done a cons an
p essu e by changing he ela i e amoun o A species Rin he plasma gas. The aim was o ob ain
hin ilms wi h low densi y and, he e o e, low e ac i e index. Cha ac e iza ion o he species o
he plasma is ca ied ou by op ical emission spec oscopy. The changes o he plasma condi ions a e
co ela ed wi h he g owing a e and mic os uc u e o he ilms, he la e de e mined by a omic
o ce mic oscopy and in a ed spec oscopy. I is ound ha he g owing a e o he ilms dec eases
and hei oughness inc eases as Rinc eases. The op ical p ope ies o SiO2 hin ilms a e analyzed
by op ical ellipsome y. A dec ease in he e ac i e index is ound o he ilms g own wi h high
alues o R. The possible ou es o ac i a ion o he p ecu so and he o ma ion o he SiO2 hin
ilms a e discussed. © 2003 Ame ican Vacuum Socie y. 关DOI: 10.1116/1.1577134兴
I. INTRODUCTION
Silicon dioxide hin ilms a e p epa ed by a la ge a ie y
o me hods including plasma-enhanced chemical apo
deposi ion 共PECVD兲. This echnique is widely used o his
pu pose because i pe mi s a low deposi ion empe a u e,
high deposi ion a e, e c.1T adi ionally, SiO2 hin ilms ha e
been deposi ed om SiH4/O2o SiH4/N2O plasmas.1,2
O he silicon p ecu so s used a e SiCl4,1,3 e a-
e hoxysilane 关(TEOS) Si(O(C2H5)4)兴,4hexame hyldisilox-
ane 关(HDMSO) O(Si(CH3)3)2兴,5and mo e ecen ly, e am-
e hylsilane 关(TMS) Si(CH3)4兴6,7 and clo o ime hylsilane
关(TMSCl) Si(CH3)3Cl兴.8These p ecu so s ha e been u i-
lized in pu e o m o mixed wi h oxygen o N2O. The e a e
some ad an ages in using o ganosilicon p ecu so s, such as
hei sa e handling, he ac ha hey yield a be e s ep
co e age, and he possibili y o p epa e ino ganic SiO2as
well as polyme ic SiOxCyHz hin ilms, depending on he
dilu ion deg ee o he p ecu so in he oxidizing gas.9,10
Mo e ecen ly, he use o TMS o p epa ing SiO2 hin ilms
by PECVD has been in oduced because he ilms deposi ed
wi h TMS⫹O2mix u es p oduce be e wa e epellen lay-
e s han hin ilms deposi ed by using an e hoxide-like
e ame hoxysilane⫹O2.11 O he au ho s ha e also shown
ha by using TMS⫹O2, i is possible o deposi hyd opho-
bic SiOx hin ilms in a co ona discha ge plasma a a mo-
sphe ic p essu e.6In addi ion, since TMS and TMSCl do no
con ain oxygen, i is possible o deposi SiC and polyme ic
SiCxHy hin ilms12,13 wi hou adding o he plasma CH4o
o he hyd oca bons, as has o be done when using SiH4.
Howe e , in con as wi h he ample li e a u e exis ing abou
he use o SiH4, TEOS, o HDMSO, much less is known
abou he use o TMS o TMSCl. In p e ious wo ks, we ha e
employed he p ecu so TMSCl o ob ain s oichiome ic
SiO2o SiOxCyHz hin ilms in a emo e mic owa e elec on
cyclo on esonance 共ECR兲-PECVD eac o wo king in a
downs eam con igu a ion.8,14 Mo eo e , we showed ha un-
de ou expe imen al con igu a ion, he exis ence o a SiuCl
a兲Au ho o whom co espondence should be add essed; elec onic mail:
[email p o ec ed]
900 900J. Vac. Sci. Technol. A 21„4…, JulÕAug 2003 0734-2101Õ2003Õ21„4…Õ900Õ6Õ$19.00 ©2003 Ame ican Vacuum Socie y
bond in TMSCl makes his p ecu so mo e suscep ible han
TMS o chemical a ack by he exci ed species o he
plasma.8
The use o SiO2 hin ilms as an an i e lec i e coa ing in,
o example, pho o ol aic cells,15 equi es he ab ica ion o
low e ac i e index po ous coa ings o his ma e ial. This
can be done by inc easing he o al p essu e o he plasma
chambe du ing deposi ion. This pa ame e usually a o s he
condensa ion p ocesses in he gas phase and, he e o e, leads
o an enhancemen o po osi y. Howe e , as a d awback, his
p ocedu e usually has de imen al e ec s wi h espec o he
mechanical s abili y o he laye s because o he poo adhe-
sion be ween he la ge agg ega es o med in he gas phase.
The p esen a icle epo s he p epa a ion a oom em-
pe a u e o SiO2 hin ilms by using he TMSCl p ecu so
and mix u es A /O2as plasma gas in a emo ely coupled
PECVD sys em. I has been ound ha , o a cons an wo k-
ing p essu e, he oughness, g owing a e, and o he mic o-
s uc u al cha ac e is ics o he ilms depend on he a io be-
ween he plasma gases and p ecu so . F om his s udy, some
clues a e deduced abou he eac ion mechanism o he TM-
SCl p ecu so and he deposi ion p ocesses leading o he
o ma ion o he SiO2 hin ilm. The dependence o he op-
ical p ope ies o he ilms on hei mic os uc u al cha ac-
e is ics is also examined and discussed in ela ion wi h he
pa ame e s o he deposi ion p ocess.
II. EXPERIMENT
Silicon dioxide hin ilms ha e been p epa ed a oom
empe a u e by a emo e PECVD p ocedu e. Si(CH3)3Cl has
been used as ola ile p ecu so o Si. The plasma eac o has
a ‘‘downs eam’’ con igu a ion wi h an ex e nal mic owa e
ECR sou ce 共SLAN兲ope a ed a 400 W. The sou ce was
sepa a ed om he eac o by a me allic g id p e en ing he
mic owa e i adia ion o he subs a es. This g id allows
easy con ol o he plasma igni ion and he sepa a ion o he
deposi ion a ea om he plasma egion. Also, owing o he
p esence o he g id, i is expec ed ha mos ac i a ed spe-
cies in he deposi ion zone a e neu al, al hough i canno be
uled ou ha some elec ons and posi i ely cha ged plasma
species a i e a he sample posi ion. The dis ance om he
subs a e and g id was 10 cm. Pieces o one side polished
Si共100兲wa e s o 3 cm2we e placed in he eac o , while he
p ecu so was dosed on op o hei su ace h ough a dis-
pe sal ing placed 6 cm om he subs a e o ensu e i s ho-
mogeneous spa ial dis ibu ion. The base p essu e o he sys-
em is lowe han 10⫺6To . A ully de ailed desc ip ion o
he expe imen al se up has been p esen ed elsewhe e.8,16 P e-
cu so and plasma gases we e dosed by sui able mass low
con olle s. Thus, ixed low a es o 10 sccm o he oxygen
and 5 sscm o he p ecu so we e used, while he low a e
o A was a ied in he ange 0–5 sccm. Pu e oxygen o
mix u es A /O2we e supplied o he sou ce. A o al p essu e
o ⬃2⫻10⫺2To was main ained cons an ly in he cham-
be du ing deposi ion by adjus ing he pumping capaci y o
he sys em wi h a h o le al e. We ha e shown p e iously
ha his p essu e co esponds o he maximum in he depo-
si ion a e when pu e oxygen is used as plasma gas.8The
main pa ame e ollowed in his wo k is he a io Rbe ween
he A low and he o al low o gases supplied o he eac-
ion chambe 共i.e., Ris he mass low o A di ided by he
addi ion o he mass lows o A , O2, and TMSCl兲. This
ela i e es ima ion o he A added o he plasma gas p o-
ides a mo e app op ia e desc ip ion o he p ocess han he
me e A /O2 a io.
Op ical emission spec oscopy was ca ied ou du ing hin
ilm deposi ion. The ligh emi ed by he plasma was col-
lec ed by an op ical ibe which was posi ioned 4 cm down-
s eam om he sou ce cen e h ough a hole in he SLAN ai
cooling ing. The ibe was joined o a monoch oma o
Jobin–Y on HR250 wi h a 1200 g oo es/mm g a ing and
equipped wi h a R928 Hamama su pho omul iplie .
The g ow h a e was measu ed wi h a qua z-c ys al moni-
o placed beside he subs a e. The ypical hickness o he
s udied samples was abou 500 nm.
A omic o ce mic oscopy 共AFM兲images we e ob ained in
ai by using a Topome ix Explo e mic oscope wo king in
he noncon ac mode. The can ile e 共supplied by Topome-
ix兲wi h a sp ing cons an o 42.6 Nm⫺1was oscilla ed a
130 kHz. Ampli ude educ ion was moni o ed while he su -
ace is scanned a a ypical a e o one line pe second. The
scanne was calib a ed in he X,Y, and Zdi ec ions wi h
g a ings p o ided wi h he equipmen . Bo h opog aphic
共cons an o ce兲and di ec signal 共cons an heigh 兲images
we e acqui ed.
Fou ie ans o m in a ed 共FT-IR兲spec a we e collec ed
in ansmission mode a no mal geome y in a Nicole 510
spec ome e o samples deposi ed on Si共100兲wa e s. The
hicknesses o he analyzed samples ha e been chosen o
a oid he sa u a ion o he in a ed signal, hus enabling he
compa ison o he ela i e in ensi y o he bands.
Ru he o d backsca e ing spec oscopy 共RBS兲measu e-
men s o he ilms we e pe o med in he Ion Accele a o
ARAMIS 共O say, F ance兲using 1.5 MeV
␣
pa icles. The
ene gy esolu ion o he de ec o used in he RBS measu e-
men s was 15 keV. The spec a we e simula ed using he
RUMP code. The samples ha e been deposi ed on Si共100兲and
channeling was used o imp o e he sensi i i y o he ech-
nique o he SiO2 hin ilms.
Spec oscopic ellipsome y expe imen s we e pe o med
using a SOPRA comme cially a ailable sys em. The mea-
su emen s o ellipsome ic pa ame e s we e made wi hin a
wa eleng h ange om 0.21
␮
m o1.2
␮
m a di e en
angles o incidence 共65°, 70°, and 75°兲. These a e he mos
sensi i e angles, since hey a e close o he B ews e angle o
a silicon subs a e. Fo he s udied ilms, he i s s ep o he
analysis p ocedu e consis s o a eg ession using a Cauchy
law o simula e he e ac i e index n(␭), he ex inc ion co-
e icien k(␭), and he hickness o he laye . In a second
s ep, he laye hickness was ixed as de e mined he ein and
a poin -by-poin ex ac ion o he complex e ac i e index
was pe o med a each wa eleng h.
901 Ba anco
e al.
: Plasma enhanced chemical apo deposi ion o SiO2901
JVST A - Vacuum, Su aces, and Films
III. RESULTS AND DISCUSSION
A. Plasma cha ac e iza ion and deposi ion p ocess
Op ical emission spec a o he plasma we e eco ded o
inc easing alues o R. The spec a o oxygen/a gon plasmas
共wi hou p ecu so 兲a e domina ed by sha p lines due o
emission om a omic oxygen o a gon and by se e al mo-
lecula bands esul ing om ansi ions be ween low ib a-
ional le els o he O2
⫹species. The addi ion o he p ecu so
o he eac o inc eases he emission om he lines o a omic
hyd ogen in de imen o hose o oxygen o a gon. Thus, he
op ical emission spec a o he A /O2/TMSCl mix u e, apa
om he lines due o oxygen and a gon, exhibi s ong emis-
sion lines due o H*共lines o he Balme se ies兲and o he
exci ed species such as CH*,CO
*,CO
⫹,OH
*, e c., he
la e e y likely coming om he agmen a ion and oxida-
ion o he p ecu so molecule. A sys ema ic analysis o he
a ia ion in in ensi y o some selec ed lines can be used o
unde s and some o he eac ion pa hways o species in he
plasma. Figu e 1 shows he a ia ion o he in ensi y o emis-
sion lines/bands (A *a 750 nm, O*a 777 nm, H*a 486
nm, OH*a 306.4 nm, CH*a 431.4 nm, and CO*a 507.1
nm兲wi h R. The assignmen s o hese signals ha e been done
in ag eemen wi h he Re s. 17 and 18. The plo o Fig. 1
shows a ne inc ease in he in ensi y o he A *line as R
inc eases, while he O*emission inc eases only e y sligh ly
and he H*emission dec eases. On he o he hand, he emis-
sions co esponding o CH*and OH*bands inc ease as R
inc eases. The in ensi y o he CO* emains p ac ically con-
s an when A is added o he discha ge.
As a i s app oxima ion, he in ensi y o H*lines can be
aken as a ace o he deg ee o agmen a ion o he p ecu -
so molecule in he plasma 共no e, howe e , ha his is no
igo ously ue because he elec on densi y and/o empe a-
u e may also con ibu e o changes in he in ensi y o he H*
emission兲. Figu e 1 clea ly shows ha he yield o his p o-
cess dec eases as he A con en in he plasma inc eases. I is
also impo an o men ion ha , o a gi en alue o R, he
in ensi y o all emission lines inc eases wi h he mic owa e
powe .
The g ow h a e o he SiO2 hin ilm was also de e mined
as a unc ion o R. Figu e 2 shows ha he deposi ion a e o
he ilm diminishes almos linea ly wi h R. We would also
like o s ess ha no deposi ion was obse ed when only pu e
A was used as plasma gas o when TMS was used as a
silicon p ecu so molecule ins ead o TMSCl. In he case o
TMS, no deposi ion is obse ed ei he when O2o mix u es
A /O2a e used as plasma gas,8while o TMSCl, he g ow h
a e inc eases o inc easing p ecu so low.
B. Thin- ilm cha ac e iza ion
The hin- ilm samples p epa ed in his wo k we e ana-
lyzed by RBS o de e mine hei composi ion. All o hem
had a silicon dioxide s oichiome y 共i.e., O/Si a io equal o
2兲and no aces o Cl o C we e de ec ed. The e o e, he
samples, a leas up o he sensi i i y limi o he RBS spec-
oscopy 共⭐5 a .% o C and ⭐1 a .% o Cl兲, can be con-
side ed as ee om hese elemen s p esen in he TMSCl
p ecu so .
The mic os uc u e o he deposi ed SiO2 hin ilms was
in es iga ed by AFM and FT-IR. Figu e 3 shows as an ex-
ample wo AFM images o he su ace o SiO2 hin ilms
co esponding o R⫽0关i.e., Fig. 3共a兲兴 and R⫽0.6 关i.e., Fig.
3共b兲兴. These images clea ly show ha he oughness o he
ilms inc eases wi h he ela i e concen a ion o A . A mo e
quan i a i e e alua ion o he oughness o he ilms is p o-
ided by he oo -mean-squa e 共 ms兲su ace oughness al-
ues. Figu e 4 shows he a ia ion o he ms su ace ough-
ness o SiO2 hin ilms p epa ed wi h inc easing ela i e
FIG. 1. In ensi y o he indica ed emission lines exci ed in he plasma eac o
as a unc ion o R.
FIG. 2. Deposi ion a e o SiO2 hin ilms as a unc ion o R. The line is
plo ed o guide he eyes.
902 Ba anco
e al.
: Plasma enhanced chemical apo deposi ion o SiO2902
J. Vac. Sci. Technol. A, Vol. 21, No. 4, JulÕAug 2003
amoun s o A in he plasma gas. I is ound ha he ms
su ace oughness inc eases as he A concen a ion in he
plasma inc eases.
Figu e 5 shows FT-IR spec a o SiO2samples p epa ed
wi h inc easing concen a ions o A . I is impo an o no e
ha no signals om o ganic g oups8a e de ec ed in he
FT-IR spec a o any o he deposi ed hin ilms, indica ing
ha e en i he in es iga ed p ocess is ca ied ou a oom
empe a u e, he comple e emo al o o ganic g oups akes
place. The di e en peaks and shoulde s in he 400–1500
cm⫺1 egion ha e been a ibu ed o he ib a ional modes o
elemen al SiO4 e ahed al o ming he s uc u e o he SiO2
hin ilms.14,19–21 They can be assigned o a ans e sal op i-
cal (TO1) ocking mode 共460 cm⫺1兲,aTO
2bending mode
共800 cm⫺1兲, an asymme ic s e ching mode 共 he big band a
⬃1070 cm⫺1兲,aTO
4asymme ic mode 共1170 cm⫺1兲, and i s
co esponding longi udinal mode LO4共1200 cm⫺1兲. These
wo la e bands gi e ise o he well de ined shoulde a he
igh -hand side o he mos in ense band a ⬃1090 cm⫺1.
SiuOH and SiuO⫺ ocking 共578 cm⫺1兲and s e ching
共960 cm⫺1兲modes can be also de ec ed in he spec a. The
960 cm⫺1peak inc eases wi h he alue o Rin ag eemen
wi h an inc ease o he inco po a ion o OH⫺g oups in he
less compac SiO2 hin ilms. The ela i e in ensi y o he
shoulde a 1200 cm⫺1共due o he con ibu ion o se e al
elemen al bands as has been men ioned he ein兲has some-
imes been aken as a measu e o he deg ee o po osi y o
he ilms 共see Re . 14 and e e ences he ein and Re . 19兲.
Al hough some o he ac o s besides compac ness may con-
ibu e o his in ensi y, he esul s ob ained he e show a pa -
allel endency o shoulde in ensi y, ms su ace oughness
alues and, as i will be shown in he nex subsec ion, de-
c ease in he densi y o he ilms.
C. Op ical p ope ies
The op ical p ope ies o he SiO2 hin ilms p epa ed un-
de di e en condi ions we e de e mined by spec oscopic
ellipsome y. Figu e 6 shows he e ac i e index n(␭) and
he ex inc ion coe icien k(␭) as a unc ion o he wa e-
leng h ␭, o hin ilms p epa ed wi h di e en alues o R.
The plo shows ha he e ac i e index o he ilms de-
c eases as he ela i e amoun o A in he plasma gas in-
c eases, o he en i e wa eleng h ange.
FIG. 3. AFM images o SiO2 hin ilms p epa ed wi h R⫽0共a兲and 0.6 共b兲.
FIG. 4. ms su ace oughness o SiO2 hin ilms as a unc ion o R. The line
is plo ed o guide he eyes.
FIG. 5. FT-IR spec a o SiO2 hin ilms p epa ed wi h di e en alues o R.
903 Ba anco
e al.
: Plasma enhanced chemical apo deposi ion o SiO2903
JVST A - Vacuum, Su aces, and Films
I is possible o es ima e changes in he densi y
␳
o he
SiO2 hin ilms om he a ia ion o hei e ac i e indices.
I has been epo ed22,23 ha in he case o SiO2,⌬
␳
⫽5
⫻⌬ngcm⫺3. In he p esen case, a maximum change o
0.023 is ound in he alue o n o p ac ically all o he
isible egion. This di e ence in ngi es a maximum di e -
ence in densi y ⌬
␳
⫽0.11 gcm⫺3, be ween he mos and
leas compac SiO2 hin ilms epo ed he e. The less com-
pac ilms a e hose p epa ed a high alues o R. This en-
dency ag ees wi h he highe deg ee o oughness and po os-
i y deduced om he AFM and FT-IR cha ac e iza ion
analysis o he samples 共c . Figs. 3–5兲.
I is also wo h no ing ha all o he samples we e o ally
anspa en 共k alues equal o ze o on he whole spec al
ange兲wi h independence o he R alue, and ha no ligh
sca e ing was de ec ed in any o he deposi ed ilms, as i
would happen i he size o he agg ega es we e la ge enough
o sca e isible ligh . The high anspa ency o he hin
ilms suppo s he possible use o he less compac hin ilms
as an i e lec i e coa ings o pho o ol aic o simila
applica ions.15
D. Plasma-enhanced chemical apo deposi ion
hin- ilm o ma ion wi h TMSCl and mix u es A ÕO2
The choice o TMSCl as ola ile p ecu so o Si a he
han TMS has been imposed, unde ou expe imen al condi-
ions, by he ac ha no hin- ilm deposi ion is ound in his
la e case ei he by using pu e O2o mix u es O2/A as
plasma gas. This esul s con as s wi h hose epo ed by
o he au ho s showing he o ma ion o SiO2 hin ilms by
using TMS in plasma mic owa e eac o s wi h downs eam
con igu a ions.13,24 Jaube eau e al.25 ha e epo ed ha an
a e glow A plasma may yield a la ge agmen a ion o he
TMS molecule, mainly ia SiuC bond b eaking. This p o-
cess p incipally gene a es Si(CH3) agmen s. Radicals
o med h ough he dissocia ion o CuH bonds 关i.e., SiCxHy
adicals (y⬍3x)] may be also p oduced, hough wi h
smalle e iciency. In ou sys em, a p ocess simila o he i s
one does no seem o occu because he e is no deposi ion
wi h TMS unde any condi ion o wi h TMSCl wi h an A
plasma. Howe e , we belie e ha he polyme iza ion o in-
e media e adicals o silicon p oduced h ough an al e na i e
mechanism could con ibu e o he o ma ion o he ilm 共see
nex 兲.
The di e en beha io ound in ou expe imen by using
TMS o TMSCl p ecu so s8poin s o ha a SiuCl bond in
he p ecu so molecule a o s i s decomposi ion by he
plasma o p oduce SiO2 hin ilms. The ac ha no chlo ine
is de ec ed in he ilms suppo s ha his a om is emo ed
du ing he i s s ages o he eac ion mechanism and ha no,
o e y ew, agmen s con aining his a om a i e o he
g owing ilm su ace. Thus, i is e y likely ha he i s o
one o he ini ial s eps in he deposi ion mechanism o he
ilms is he a ack o he SiuCl bond by some ac i a ed
species o he plasma and/o ee elec ons. Since in ou ex-
pe imen al con igu a ion he concen a ion o ee elec ons
and ionic species in he deposi ion zone mus be a he small,
we assume ha oxygen species a e mos impo an o he
ac i a ion o he p ecu so molecule. Thus, such ac i a ion
could be w i en schema ically as
Si共CHx兲yCl⫹O→Si共CHx兲yO⫹Cl*.
Wi h his p ocess, we p opose ha ac i a ed oxygen species
in e ene in he ini ial ac i a ion s eps o he p ecu so mol-
ecule leading o he emo al o chlo ine and he o ma ion o
Si-con aining adicals, ei he in he gas phase o adso bed on
he su ace. I has o be men ioned ha he in ensi y o he
O*emission line a 777 nm emains p ac ically cons an in-
dependen ly o he alue o he pa ame e R, a ea u e ha
poin s o a complex na u e o he whole deposi ion p ocess
and s esses he need o conside ing o he pa ame e s, like
concen a ion and ene gy o ee elec ons, o he adicals, he
ole o A , e c., which a e no accessible in ou expe imen .
Al hough, we do no ha e enough e idence o p opose a
comple e mechanism o accoun o he o ma ion o he
SiO2 hin ilms, in line wi h he p e ious esul s by
Jaube eau25 and o he au ho s,9,10 i is easonable o assume
ha he o ma ion o he oxide ilm om TMSCl is a p ocess
ha in ol es he adso p ion on he subs a e o ei he he
p ecu so molecule o some eac i e agmen s esul ing
om i s ac i a ion and e en ual agmen a ion. On he su -
ace, he compe i ion be ween he polyme iza ion o hese
agmen s o yield SiOxCyHzpolyme ic chains and he oxi-
da ion o e ching o o ganic agmen s o hese ilms leading
o he emo al o o ganic componen s will con ol he o -
ma ion o SiuO bonds. In ac , p e ious esul s o ou labo-
a o y using TMSCl and pu e oxygen plasmas8showed ha
i is possible o deposi SiOxCyHz hin ilms when he low o
oxygen is lowe han ha o he p ecu so low. In he p esen
in es iga ion, he inc ease wi h Ro he in ensi y o he emis-
FIG. 6. Re ac i e index nand ex inc ion coe icien k o SiO2 hin ilms
deposi ed wi h di e en alues o R.
904 Ba anco
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: Plasma enhanced chemical apo deposi ion o SiO2904
J. Vac. Sci. Technol. A, Vol. 21, No. 4, JulÕAug 2003

sion lines o OH*and CH*species 共c . Fig. 1兲migh indi-
ca e ha he A addi ion a o s he e ching and oxida ion a
he su ace o he o ganosilicon agmen s, a p ocess ha has
been epo ed p e iously by o he au ho s.25,26,22
Wi hin his phenomenological desc ip ion, i is possible o
econcile he high oughness wi h he low g owing a e as
well as he SiO2composi ion o he p epa ed hin ilms by
assuming ha in e media e siliconelike laye s and/o ag-
men s a e being p oduced du ing he deposi ion o he ilms.
Then, his polyme ic ma e ial deposi ed on he su ace is
u he oxidized by he plasma o yield gases (CO2and H2O)
ha would be deso bed whe eas SiCxOyHzlaye s o ag-
men s a e being inco po a ed on o he su ace. The elease o
ola ile compounds is likely o yield ilms wi h a la ge
oughness and po osi y as has been ac ually obse ed he e by
AFM and FT-IR cha ac e iza ion.
IV. CONCLUSIONS
I has been shown ha TMSCl is a sui able p ecu so o
he deposi ion o SiO2 hin ilms by PECVD using mix u es
A /O2as plasma gas and a mic owa e ECR plasma sys em
in a downs eam con igu a ion. Unde hese condi ions, no
deposi ion was ound by using TMS, hus indica ing ha he
exis ence o a CuCl bond a o s he plasma ac i a ion o
he p ecu so molecule. SiO2wi h no aces o Cl was ob-
ained in all cases. This suppo s ha Cl is being emo ed
du ing he i s s eps o ac i a ion o he p ecu so molecule.
I has been ound ha he hin- ilm mic os uc u e and
g ow h a e depend on he plasma condi ions. Inc easing he
ela i e concen a ion o A in he plasma gas a cons an
o al p essu e leads o a dec ease in he g owing a e by a
ac o o 0.6 and, unexpec edly, o an inc ease in he ilm
oughness and po osi y. As a consequence, he e ac i e in-
dex o he ilms can be ailo ed by con olling he ela i e
concen a ion o A in he plasma gas. This echnique could
be e y use ul o he syn hesis o an i e lec i e SiO2 hin
ilms o in e es in pho o ol aic and simila applica ions.
ACKNOWLEDGMENTS
The au ho s hank he Minis e io de Ciencia y Tecnologı
´a
共P ojec No. MAT2001-2820兲and he EU 共P ojec No.
ERK6-CT-1999-00015兲 o inancial suppo .
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JVST A - Vacuum, Su aces, and Films