Structural and loss characterization of SiON layers for optical waveguide applications

11:15am-I1:30am Th13

Structural aiid Loss C1iar;lctcriz;ttion o f SiON Layers fur Optical Wavcgnide Applications

lcridun A y , Atilla Aydinli

llilkcnt University, Dcpaitrticiit ofl'hysics, 06533 Ankara, Turkey e-mail: aydirili~~~.frn.bilk~i~t.edu.tr, Phone: +90 3 12 290 1579

Chris Rocloffzen

Tlnivcrsity of Twente, Departinerit of Electrical Engineering, 7500 AE, Enschetlc, Thc Ncthcrlatids, e-mail: ~.I~.roclofiien~~el.utwente.tll,Plione: +3 1 53480 28 16

Alfied Driessen

University of 'I'wente, Departnicnt of Applied Physics, 7500 AE, Enschede, The Netherlands, c-tnail: A.~ricsscn~cl.utwettte.nl, Phonc:+3 1 53 489 2744

Silicon oxytiitride films for optical wavcguide applications were grown att 350°C in a PECVD reactor. ATK-FTIK spectroscopy was used to identify the borid structure and absorption characteristics in the mid-infrared region. Anncaling of the films was performed together with close monitoring of the N- H bond at 3400 cm-' and corrclated with optical loss measurements. The possibility of a new method for the reduction of tlie N-€I bonds without

&"m

PECVD Deposition. Silicon oxynitridc films were grown on a parallel plate PECVD reactor at 13.56 MHz and 350 "C. 71ie index of rcfraction of the filmcould

be changed between 1.46 and 2.0 by controlling the flow rates of 2%SiH4/N2, NzO and NH3 precursor gascs, Fig. I .

1 . 6 6 e 0 1 . 6 4 o tu L 1 . 6 0 c .- e- f3

E

-

--

-

Ifigure 1: Variation of the index of refiactiun with ttic change of flow rate of N20 am1NH3 at constant

2%SiH.+N2 flow rate of 180 sccm.

FTIR Cliaracterization. l h c compositional properties of oxynitridcs arc expected to vary bctwccn those of silicon oxide and nitride. Therefore, monitoring of

their bond striictirre should result it1 a

bcticr control of the properties of SiON films. In tlie absorption spectrum of thc Sic), filnis, (Fig.2) the characteristic vibrations arc obseived: Si-0 rocking and stcctching vibrations at 490 em-' and 1070 cm" respectively, Si-H stretching and bending vibrations at 2230 and 800 em-' and 0-H strctching at 3500 em? and N-H stretching at 3350 an-' [I]. As seen from Pig. 2, with increasing NzO flow rate the N-H bond absorption is reduced, whilc that of 0 - H absorption has increased.

- 7 " ' " " ' l

W a y e I I U ~b n r ( e m . ' )

Figure 2: FTlR spachimi of PECVD silicon oxide

films.

In ttic absorption spcctruin of silicon nitrides therc is no significant change with the flow ra,tc change of NH3. The

characteristic absorption bands iit'c idcntificd as Si-N stretching a i d bcridiiig

vibrations a t 850 & 1170 cin-', Si-11

strctcliing :it '1200 en<' arid N-11 strctctiirig at 3350 cir1-l ,[2].

Ocvirig lo the abovc consitict'citions SiON films were grown with NzOantl NI13 t l o ~ ratcs of 225 &L 15 sccrn rcspcctivcly with

the refractive indcx of I .5 I .

Anilealing Study, I'hc Iitsi ovct-tunc: of

the N-H stretching vitwaiion is ltnowii to

be tlic t i l a i n citusc oi" the optical loss at 1 .SS ptn wavelength region. Thcrcforc our

tirst coriccrn is to rcducc this absorption be c h i n a t i o n of thc N-H bond incorporated

into the filtti [B]. Silicoil oxynitriclc filius

wcrc anricalcd at tiiffcfcrciti tcrnpcixii!rcs and the N-11 absorption band was rnoaiiored (Vig.3). l'hc 14-H peak W L I S

obscl-vcd to bc clirriimiied ;It 1000 "(~: within the dctectiori limit. 1;oi. inore sensitive analysis il Si A'riz prisiii was uscd. The cvancscciit wave pclietratirlg

pin ofthc SION film close l o thc ititcrihcc.

We obscivc that tticrc is still resitltml N-€1 absorption prcsciit cvcri at IOOO "C annealing, in conlrast with si InjJk

alisoIqJtion cxlJcritIlCfltS. Ii disaippcars coinplctcly at I 150 "C aftcr. 4 hrs aincaling (Fig.4).

illto thC SlON fihil S?ltTl~JlCS ollly d J O L 1 i

.z

4 L M 40041 3791 3 5 N 3250 3000

Wave tiuniber (mi')

lrigrire 4. ATP, stody of tlic miiuiiliiig bcliavior of

tlic N-11 Iroiiil.

1)cconvolution of the N-13 band shows scvcrel diffcrcnt specics of N-II bonds soinc of wtiicli disappear upon auncaling suggcsting that it inay bc possible to control thcrn through appropr.i;dc process pr:nnctcrs drrring growth.

Optical loss of thc dcpositcd and ~un~calctl

SiON f i l m was rncasiiml aiid found to he

correlated with the obtained A1'R rcsults. Conclusiuri. 1'lic cornpositional propcrtics

of SiObJ films were invcsiigatcd. Il-hc N-H

alwqtiori, rcsponsihlc for the optical loss,

\vas nionitorcd by ATR-FTlR aiid showccl rcsidual a,bsorption cvcn aftcr 1000 C:

annealing. Ucconvoliition of thc N-H haild

showcd scvclal N - l l spccics. l h c optical loss at 1.55 pin was i'ccltrccd by ;uiriealirig

Nefercnccs: dJOVc 1100 (:.

[I] D.V. Tsu, ( i , Lucovsky, M.J. Miiiitiiti, 'Lucid atomic stitictiirc i i i thiii filiris of silicon riiidclc a r i d siliciiii iliimidc prodocad Iry i-ciiiiite plasiila-

aiillaiiccd clicliic;il-vapor ilcpositicm', I'hys. Rcv.

I<, 33, 7060-7076, (19W).

[Z] <i.N.l':irsi~iis, < i . Lucovsky, ' Silicoii-liyitrogoii

hiltiil-stlctcliiii~~ viblatiozis ill Iiyclroganatcd :iriiorlihous silicon - riitiogcii alloys', l'liys. Rcv. 15,

41, I664-l601, (1090).

131 C.M.M. llcnisse, K.Z. T r o d , b',li.i'.M. Ikibrakcii, W.F. villi del, Wcg, M. ilcndriks, 'Aniicaliiig of p1;isriia siliciiii oxynitdc filins', J .

Appl. l'liys.., 60, 2536-2541, 19x6.