#Jounol of PhotopolymerSclence qnd Technology
Volu me 16, Number2( 2003)163-164
O2003TAPJ

Gommunkation

Room TemperaturePhotochemicalFabricationof Silica GlassCoatings
using VacuumUltraviolet Excimer Lamps
Chihiro Kato, Satomi Tanaka, Yasuhiro Naganuma and Toyohiko Shindo*Kanagawa Industrial TechnoIogy Research I nstitute,
705-I, Shimo-imaizumi,Ebina, Kanagawa, Japan* Contamination Control Services,-3,529 Shimohtzawa,Sagamihara, Kanagawa, Japancoating
SiO2,photochemical,
Keywords: excimerlamp,VUV, polysilazane,

L. Introduction
Recently it becomes possible to fabricate silica
glass coatings onto various kinds of materials byheating coated polysilazane films ; (-SiHz-NH-)"
This technique attracts much interestsin[-3].
wide area of industry for making protective hardcoatings, electrical insulating layers, thermal orchemical resistive films, highly transparentor antiToreflection coatings, and gas barrier coatings.
produce high quality silica glass coatings from thepolysilazane precursor, heating processes above
600 C' are necessary to remove residual nitrogen
Lowering of theatoms or Si-OH impurities.
process temperature is necessary for fabricatinghigh quality silica glass coatings onto thermallyunstable substrates such as plastics orsemiconductivedevices.
In this paper, we demonstrate a room
temperature photochemical fabrication of silica
glass coatings by utilizing a vacuum ultraviolet(V[JV) light inadiation obtainable by recently
developed high power xenon excimer lamps.
The quality of the photochemically fabricatedcoatings are elucidated here by spectroscopicallyinvestigating their chemical structwes, ffid
comparedwith the thermally fabricated coatings.
2. Experimental
Polysilazane solutions, used as received from
Clariant Japan without further purification, werediluted with toluene, and spin-coatedonto Si (100)substrates(10 x l0 x 0.5 rnrn, both sidespolished).
The Si substratesare carefully wiped with ethanol,and then photolytically cleaned by the VUVReceived
Accepted

April 1, 2003
May 28, 2003

Spin-coating wasinadiation just before using.
performed at 1500 rpm for 120 s, yielding film
thicknesses- 500 nm after drying onto a hot plate
at 50 C' for 10 minutes.
A xenon excimer lamp (Quark Systems,QEX230SX, 172 nm, -8 mWcm2) was employed toirradiate VUV light on the sample. Irradiation
The larnp was placed
time was about I hour.
within a small stainless chamber together with thepolysilazane-coatedSi substrate, and then filledwith atmosphericpressureddry air at -5 l/min flow
The distance between the larnp and the Sirate.
substratewas kept about 2 - 3 mm.
A quartz tube muffle oven (Asahi Rika ARF50K) was used to thermally fabricating thecoatings. In this case,sampleswere kept heatedin air for about I hour.
An X-ray photoelectron spectrometer(Ulvac-PhiPHI-5500) was used to measure the X-ray
photoelecfron specfra ()(PS) with aluminum Kq, Xray source. An FT-IR spectrometer (ShimadzuFTIR-8200PC) was used to obtain infrared (IR)absorption spectra with wavenumber resolution of4 cm-I.
3. Results and discussion
3.1 XPS specfra
Figure I shows Si2p, Nls and Ols XPS spectraof thermally (a-f) or photochemically (g) fabricatedcoatings from polysilazane, respectively. )(PS
give
information
about
atomicspecûa
concentrations and chemical bonds at the surface(1 - 4 nm depth). As shown in the fig. l(a-f),chemical shifts toward higher binding energy \Mere163