Effect of fluorine flow and deposition temperature on physical characteristics and
stability of fluorine-doped siloxane-based low-dielectric-constant material
Yi-Lung Cheng, Jiung Wu, and Tai-Jung Chiu
Citation: Journal of Vacuum Science & Technology A 28, 456 (2010); doi: 10.1116/1.3383402
View online: http://dx.doi.org/10.1116/1.3383402
View Table of Contents: http://scitation.aip.org/content/avs/journal/jvsta/28/3?ver=pdfcov Published by the AVS: Science & Technology of Materials, Interfaces, and Processing
Articles you may be interested in
Characteristics of ultra low-k nanoporous and fluorinated silica based films prepared by plasma enhanced chemical vapor deposition
J. Appl. Phys. 114, 214102 (2013); 10.1063/1.4845755
Effect of decamethylcyclopentasiloxane and trifluoromethane electron cyclotron resonance plasmas on F–SiCOH low dielectric constant film deposition
J. Appl. Phys. 106, 013302 (2009); 10.1063/1.3159880
Electrical properties of fluorine-doped silicon-oxycarbide dielectric barrier for copper interconnect J. Vac. Sci. Technol. B 24, 2621 (2006); 10.1116/1.2366541
Thermal stability of low dielectric constant porous silica films Appl. Phys. Lett. 87, 262909 (2005); 10.1063/1.2159093
Plasma deposition of low-dielectric-constant fluorinated amorphous carbon J. Appl. Phys. 86, 2739 (1999); 10.1063/1.371119
characteristics and stability of fluorine-doped siloxane-based
low-dielectric-constant material
Yi-Lung Chenga兲
Department of Electrical Engineering, National Chi-Nan University, Nan-Tou, Taiwan, Republic of China
Jiung Wu
Department of Materials Science and Engineering, National Chiao-Tung University, Hsin-chu, Taiwan, Republic of China
Tai-Jung Chiu
Department of Electrical Engineering, National Chi-Nan University, Nan-Tou, Taiwan, Republic of China
共Received 11 December 2009; accepted 15 March 2010; published 8 April 2010兲
The effects of SiF4flow rate and deposition temperature on the physical properties and stability of
fluorine-doped organo-silica-glass共OFSG兲 films were investigated. The porosity of the as-deposited OFSG dielectrics declines as the flow rate of SiF4 gas and the deposition temperature increase,
increasing the dielectric constant. However, newly formed Si–F bonds have less electronic polarizability, reducing the dielectric constant. These traded-off properties yield a minimum dielectric constant of the OFSG film deposited at 250 ° C with a SiF4 flow rate of 100 SCCM
共SCCM denotes cubic centimeter per minute at STP兲. The stability of Si–F bonds in the OFSG films is related to the deposition conditions. OFSG films deposited a higher SiF4 flow rate
共⬎400 SCCM兲 or a lower deposition temperature 共⬍300 °C兲 have lower thermal stability and are less well protected against moisture because of the instability of Si–F bonds. Therefore, more attention should be paid to the conditions for depositing fluorine-doped OFSG dielectrics. © 2010
American Vacuum Society. 关DOI: 10.1116/1.3383402兴
I. INTRODUCTION
To reduce resistance-capacitance 共RC兲 delay of ultra-large-scale integrated circuits, copper, and low-k materials 共k⬍3.9兲 have replaced traditional aluminum and SiO2,
respectively.1–3Among all low-k materials in copper metal-lization, fluorinated silicate glass 共FSG兲 共SixOFy兲 has been
extensively applied. However, FSG does not have a low enough k value共k=3.4–3.7兲 to meet the requirements of the next generation.4,5 Therefore, carbon-doped silicates or organo-silica-glass 共OSG兲 films with dielectric constants of 2.7–3.2 have become the major candidates for intermetal di-electric applications in ultra-large-scale integrated circuits.6–8 However, their poorer mechanical strength and adhesion ability than those of standard SiO2films are limiting factors
from a process integration point of view.
Our previous works combined FSG and OSG low-k film properties to produce fluorine-doped organo-silica-glass 共OFSG兲 films with superior electrical and mechanical prop-erties, as well as excellent adhesion to OSG films.9,10 How-ever, the stability of fluorine in OFSG films is unclear. The present work studies the effects of the SiF4 flow and the
deposition temperature on the physical and stability proper-ties of OFSG films. The mechanisms of changes in the film structure under various SiF4 flow rates and deposition tem-peratures and under thermal and moisture-induced stress are proposed and discussed.
II. EXPERIMENT
The film deposition was carried out with 13.56 MHz op-erating rf in an applied material DxZ plasma-enhanced chemical vapor deposition system. The substrates were 200 mm-thick B-doped p-type silicon wafers with 共100兲 orienta-tion. Films were deposited from reagent mixtures consisting of 150 SCCM 共SCCM denotes cubic centimeter per minute at STP兲 of oxygen 共O2兲, 600 SCCM of trimethysilane, and
various SiF4 flow rates from 0 to 600 SCCM. The process
pressure and rf power were set to 4 torr and 600 W, respec-tively. The deposition temperature was varied from 200 to 400 ° C.
The thickness and refractive index of the 300–500 nm-thick films were determined by reflectometry and ellipsom-etry. Atomic composition was determined by x-ray photo-electron spectroscopy 共XPS兲 using a Physical Electronics 5000LS ESCA spectrometer after sputtering with an Ar+ beam to remove the top 2 nm of the film. Transmission Fou-rier transform infrared共FT-IR兲 spectra were obtained using a Bio-Rad spectrometer at 4 cm−1resolution. All spectra were averages of 32 scans, background corrected to a silicon ref-erence. Dielectric constant and residual stress were measured using a mercury probe at 1 MHz and a Flexus stress mea-surement system, respectively.
III. RESULTS AND DISCUSSIONS
Figure1plots the deposition rates of OFSG films as func-tions of the SiF4flow rate and the deposition temperature. In
both cases, the deposition rate declined as the SiF4flow rate
and the deposition temperature increased. The decrease in the deposition rate with the deposition temperature reveals a desportion or decomposition-dominated deposition mecha-nism. Additionally, as shown in Fig.1共a兲, as SiF4was intro-duced into the reactor to form the OFSG film, the deposition rate declined from 517 to 446 nm/min, and thereafter de-creased slightly as the SiF4 flow rate was further increased. This result suggests that the deposited OFSG film underwent structural changes because of the introduction of the SiF4
process gas. In addition, SiF4 may also act as an etchant in
the process of deposition, making the deposition rate of OFSG lower than that of OSG process.
Figure 2 plots the refractive index共633 nm wavelength兲 of the as-deposited OFSG film as functions of the SiF4 flow
rate and the deposition temperature. The refractive index in-creases with increasing the SiF4 flow and deposition
tem-perature. It was reported that the refractive index of dielectric films with constant composition and bonding structure can be used to determine film density.11Hence, a higher
refrac-tive index represents a higher film density, and thus lower porosity. Therefore, increasing the SiF4 flow rate or
deposi-tion temperature may destroy the porous structure in the de-posited films.
To evaluate the reduction in the porosity by the introduc-tion of the SiF4gas or an increase in the deposition tempera-ture during OFSG film deposition, the compositions of as-deposited OFSG films were analyzed by XPS and FT-IR. As SiF4 gas was added into the reactor and its flow rate was increased, the film’s fluorine content increased, the carbon content decreased, and the silicon to oxygen concentration ratio varied little, as shown in Fig. 3. Calculating the FT-IR bonding peak intensity of the OFSG films, as presented in Table I, reveals that the absorption peak of Si–H bonding almost disappears when the SiF4gas participates in the
reac-tion. Then, the peak intensity of Si– CH3 bonding declined
and that of Si–F bonding increased as the SiF4gas flow was
increased, indicating that most of the Si–H and Si– CH3
bonds are replaced by Si–F bonds and that the Si–H bonds are replaced first. With respect to the deposition temperature
(a) 0 100 200 300 400 500 600 400 420 440 460 480 500 520 540 Temperature=350oC Deposi ti on rat e (nm /m in )
SiF4 flow rate (sccm) (b) 200 250 300 350 400 350 400 450 500 550 600 650 700 750 SiF4=100 sccm Deposi ti on rat e (nm /m in ) Deposition temperature (oC)
FIG. 1. Deposition rate of OFSG films as function of共a兲 SiF4flow rate and
共b兲 deposition temperature. (a) 0 100 200 300 400 500 600 1.40 1.41 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 1.50 Temperature=350oC Ref ract iv e index (633 nm )
SiF4 flow rate (sccm) (b) 200 250 300 350 400 1.42 1.43 1.44 1.45 1.46 1.47 1.48 1.49 SiF4=100 sccm Ref ract iv e index (633 nm ) Deposition temperature (oC)
FIG. 2. Refractive index of OFSG films at 633 nm wavelength as function of
共a兲 SiF4flow rate and共b兲 deposition temperature.
457 Cheng, Wu, and Chiu: Effect of fluorine flow and deposition temperature on physical characteristics and stability 457
effect that is shown in Fig. 3共b兲, the fluorine and carbon contents of the OFSG films decreased slightly, while the sili-con and oxygen sili-contents increased as the deposition tem-perature increased. Additionally, the peak intensity of the Si–F stretching mode decreases upon increasing the deposi-tion temperature. This result suggests that the Si– CH3 and
Si–F bonds in the OFSG films are replaced by Si–Si and Si–O bonds at a higher deposition temperature. Moreover, the decreasing magnitude of Si–F bonds revealed by a de-crease in FT-IR peak intensity with increasing the deposition temperature differs from the results of XPS analysis, sug-gesting that more fluorine reacts with carbon to form C–F bonds at a lower deposition temperature. This result is veri-fied by F共1s兲 XPS analysis with the observation of C–F bonding. It is also observed that the peak position of Si–O–Si shifts to a higher wave number and the stretching mode of the Si–O–Si cagedlike structure at 1130 cm−1共Refs.12and 13兲 decreases as the deposition temperature increases,
indi-TABLEI. Relative S–F, Si– CH3, and Si–H bond contents incorporated in
OFSG films deposited at various SiF4flow rates and deposition
tempera-tures. 关Note: relative content=peak height for bonds 共Si–F, Si–CH3, and
Si–H兲/peak height for Si–O–Si bond 共at 1050 cm−1兲.兴
Temperature= 350 ° C SiF4 共SCCM兲 Si–F 共%兲 Si– CH3 共%兲 Si–H 共%兲 0 0 23.40 1.85 100 7.64 17.62 0 200 8.33 15.75 0 400 9.57 13.52 0 600 10.85 12.24 0 SiF4= 100 SCCM Temperature 共°C兲 Si–F 共%兲 Si– CH3 共%兲 Si–H 共%兲 200 11.21 24.48 0 250 9.67 21.60 0 300 8.45 18.57 0 350 7.64 17.62 0 400 7.48 15.74 0 (a) 0 1 2 3 4 5 6 7 8 0 100 200 300 400 500 600 0 10 20 30 40 50 60 Temperature=350oC Si atom O atom C atom F atom
SiF4 flow rate (sccm)
At o m ic cont ent (% ) At om ic cont ent (% ) (b) 200 250 300 350 400 10 15 20 25 30 35 40 45 50 55 60 3 4 5
SiF4=100 sccm Si atomO atom C atom F atom TemperatureoC At omi c cont ent (% ) At omi c cont ent (% )
FIG. 3. Composition of OFSG films as function of共a兲 SiF4flow rate and共b兲
deposition temperature. (a) 0 100 200 300 400 500 600 3.0 3.1 3.2 3.3 3.4 3.5 3.6 Temperature=350oC Di el ect ri c const ant
SiF4 flow rate (sccm) (b) 200 250 300 350 400 3.0 3.1 3.2 3.3 3.4 3.5 SiF4=100 sccm Di el ect ri c const ant Deposition temperatureoC
FIG. 4. Dielectric constant of OFSG films at 633 nm wavelength as function
cating that the Si–O–Si bond strength is restored to be simi-lar to SiO2and the porosity structure is reduced as the
depo-sition temperature increases.
Based on the aforementioned results, the possible chemi-cal reactions responsible for the deposition of the OFSG films with the effects of SiF4 flow rate and the deposition
temperature can be described as the following reactions: Without SiF4, Plasma CVD CH3 o C Si Si o Si o Si o H H CH3 C C H H H o Si H H H H o H o Si Si o Si C H H H o Si C H H H H H CH3 o C Si Si o Si o Si o H H CH3 C C H H H o Si H H H H o H o Si Si o Si C H H H o Si C H H H H H CH3 o C Si Si o Si o Si o H H CH3 C C H H H o Si H H H H o H o Si Si o Si C H H H o Si C H H H H H O2 Si CH3 CH3 CH3 CH3 O2 Si CH3 CH3 CH3 CH3 Si CH3 CH3 CH3 CH3 Plasma CVD
Effect of SiF4flow rate,
O2 F Si F F F Si CH3 CH3 CH3 CH3 CH3 o C Si Si o Si o Si o F F CH3 C C H F F o Si H H F H o H o Si Si o Si C H H F o Si C H H H F H Plasma CVD F o Si SiF oCHSi o Si o 3 C F F o Si H F o H o Si Si o Si F F o Si F H Low SiF4 High SiF4 o Si Si o O2 F Si F F F F Si F F F Si CH3 CH3 CH3 CH3 Si CH3 CH3 CH3 CH3 CH3 o C Si Si o Si o Si o F F CH3 C C H F F o Si H H F H o H o Si Si o Si C H H F o Si C H H H F H CH3 o C Si Si o Si o Si o F F CH3 C C H F F o Si H H F H o H o Si Si o Si C H H F o Si C H H H F H Plasma CVD F o Si SiF oCHSi o Si o 3 C F F o Si H F o H o Si Si o Si F F o Si F H Low SiF4 High SiF4 o Si Si o
Effect of deposition temperature
O O O O2222 FFF F Si Si Si Si FFF F FFF F FFF F Si Si Si Si CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 ooo o C C C C Si Si Si
Si SiSiSiSi oooo SiSiSiSi oooo SiSiSiSi oooo
FFF F F CH F CH F CH F CH3333 C C C C C C C C H H H H FFF F FFF F ooo o Si Si Si Si H H H H H H H H FFFF HHHH ooo o H H H H ooo o SiSiSiSi Si Si Si Si ooo o Si Si Si Si C H C H C H C H H H H H FFF F ooo o SiSiSiSi C C C C H H H H H H H H H H H H FFF F H H H H
PlasmaPlasmaPlasmaPlasma
CVD CVD CVD CVD FFFF ooo o Si Si Si
Si SiSiSiSiOOOO ooooCHCHCHCHSiSiSiSi3333oooo SiSiSiSi oooo
C C C C FFF F O O O O ooo o Si Si Si Si H H H H O O O O ooo o H H H H ooo o SiSiSiSi Si Si Si Si ooo o Si Si Si Si FFF F OOOO ooo o SiSiSiSi FFF F H H H H Low Temp. Low Temp. Low Temp. Low Temp. High Temp. High Temp. High Temp. High Temp. SiSiSiSi Si Si Si Si SiSiSiSi ooo o ooo o O O O O2222 FFF F Si Si Si Si FFF F FFF F FFF F FFF F Si Si Si Si FFF F FFF F FFF F Si Si Si Si CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 Si Si Si Si CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 CH CH CH CH3333 ooo o C C C C Si Si Si
Si SiSiSiSi oooo SiSiSiSi oooo SiSiSiSi oooo
FFF F F CH F CH F CH F CH3333 C C C C C C C C H H H H FFF F FFF F ooo o Si Si Si Si H H H H H H H H FFFF HHHH ooo o H H H H ooo o SiSiSiSi Si Si Si Si ooo o Si Si Si Si C H C H C H C H H H H H FFF F ooo o SiSiSiSi C C C C H H H H H H H H H H H H FFF F H H H H CH CH CH CH3333 ooo o C C C C Si Si Si
Si SiSiSiSi oooo SiSiSiSi oooo SiSiSiSi oooo
FFF F F CH F CH F CH F CH3333 C C C C C C C C H H H H FFF F FFF F ooo o Si Si Si Si H H H H H H H H FFFF HHHH ooo o H H H H ooo o SiSiSiSi Si Si Si Si ooo o Si Si Si Si C H C H C H C H H H H H FFF F ooo o SiSiSiSi C C C C H H H H H H H H H H H H FFF F H H H H
PlasmaPlasmaPlasmaPlasma
CVD CVD CVD CVD FFFF ooo o Si Si Si
Si SiSiSiSiOOOO ooooCHCHCHCHSiSiSiSi3333oooo SiSiSiSi oooo
C C C C FFF F O O O O ooo o Si Si Si Si H H H H O O O O ooo o H H H H ooo o SiSiSiSi Si Si Si Si ooo o Si Si Si Si FFF F OOOO ooo o SiSiSiSi FFF F H H H H Low Temp. Low Temp. Low Temp. Low Temp. High Temp. High Temp. High Temp. High Temp. SiSiSiSi Si Si Si Si SiSiSiSi ooo o ooo o .
Figure 4 plots the dielectric constant 共relative permittiv-ity兲 of the as-deposited OFSG film as a function of the SiF4
flow rate and the deposition temperature. The dielectric con-stant is lowest at 250 ° C with a SiF4flow rate of 100 SCCM;
it increased with increasing the SiF4flow rate and the desition temperature. These results are attributable to the po-rosity and polarizability effects of the as-deposited OFSG films. The porosity arises from the deteriorated Si–O–Si tet-rahedral network by the presence of terminal CH3, CHx, or H
groups. Consequently, OFSG films deposited at lower SiF4 flow rates or lower deposition temperatures contain more po-rous structures. Studies of FSG films14,15 have shown that Si–F bonds replace Si–O bonds in the SiO2 matrix in the
FSG films, reducing the dielectric constant due to less elec-tronic polarizability of Si–F bonds. In the deposited OFSG film in this study, Si–F bonds mainly replaced Si– CHx or
Si–H bonds. Pauling found that fluorine is significantly less polarizable,16 thus produces a film with a lower dielectric constant. As a result, the contributions of porosity and
polar-izability to the dielectric constant of OFSG films are traded-off as Si–F bonds replace Si– CHx bonds. Therefore, when
fluorine is introduced into the matrix of OSG films, the di-electric constant decreases because the Si–F bonds with lower electronic polarizability are formed and the porosity of the structure is not destroyed since the Si–F bonds initially replace Si–H bonds. Further increasing the amount of fluo-rine would clearly destroy the porous structure and thereby increases the dielectric constant.
Thermal stability tests were performed on the OFSG films that were deposited at various SiF4flow rates and deposition
temperatures in a N2environment at 500 ° C for 1 h
anneal-ing. Figure5presents changes in composition and dielectric constant. The carbon content of annealed films declined upon annealing, especially for the OSG film because of a high degree of porosity structure. Additionally, OFSG films formed at a higher SiF4 flow rate or a lower deposition
tem-perature exhibit a greater drop in fluorine content. Although the bonding strength of Si–F is stronger than that of Si–C共or Si– CH3兲 or Si–H, formed Si–F bonds in OFSG films
depos-ited at a higher SiF4flow rate or a lower deposition
tempera-(a) 0 100 200 300 400 500 600 0 1 2 3 4 5 0 1 2 3 4 5 6 C atom F atom Dielectric constant
SiF4 flow rate (sccm)
At om ic cont ent reduct io n (% ) Temperature=350oC Di el ect ri c const ant in crease (% ) (b) 200 250 300 350 400 0 1 2 3 4 5 0 2 4 6 8 10 12 14 C atom F atom Dielectric constant TemperatureoC At om ic cont ent reduct io n (% ) SiF4=100 sccm Di el ect ri c const ant in crease (% )
FIG. 5. Change in composition and dielectric constant for OFSG films upon
seven cycles of annealing at 500 ° C for 1 h each as function of共a兲 SiF4flow
rate and共b兲 deposition temperature.
459 Cheng, Wu, and Chiu: Effect of fluorine flow and deposition temperature on physical characteristics and stability 459
ture are still weak and such bonds are destroyed and decom-posed upon annealing at high temperature, producing a larger degradation in dielectric constant.
A stacked film with a SiCN/OFSG//TaN/Cu/SiO2/Si structure, which OFSG films were prepared under various deposition conditions, was annealed at 500 ° C for seven cycles, each for 1 h. The film interface state was observed by an optical microscopy. The inset in Fig. 6 presents bubble defects shown in the OFSG films that were formed at a higher SiF4flow rate or a lower deposition temperature.
Fig-ure 6 presents the probability of occurrence of such bubble defects determined by inspecting 25 sites. Higher failure rates were associated with OFSG films deposited at higher SiF4flow rates and lower deposition temperatures. A bubble
defect was analyzed by scanning electron microscopy, which indicated that the interface between the barrier metal and the OFSG film was the main location of delamination. One pos-sible cause is that fluorine atoms associated with the unstable Si–F bonds in the OFSG films diffused into the interface during thermal annealing and accumulated there, causing delamination at the interface.
The films with more Si–F dipole bonds or more porosity structures were more hydrophilic and exhibited poorer mois-ture impedance. To investigate the effect of moismois-ture on the OFSG films formed under various deposition conditions, OFSG films made at various SiF4 flow rates and deposition temperatures were exposed at 120 ° C, 100% relative humid-ity, and the pressure of 2 atm for 500 h. The film structure and residual stress changed upon the absorption of moisture. Figures 7 and 8 show the change in residual stress and di-electric constant, respectively, as functions of storage time. The properties of OFSG films degraded more than those of OSG films without incorporated fluorine, suggesting that Si–F bonding may promote the absorption of water beyond that of porous structures. On the other hand, OFSG films deposited at higher SiF4flow rates and lower deposition
tem-peratures exhibit a larger shift in residual stress and dielectric
constant, indicating that weak Si–F bonds accelerate the re-action with moisture, which destroys the structure of the film.
IV. CONCLUSION
The effects of SiF4 flow rate and deposition temperature on the physical characteristics and stability of the OFSG films were studied. The porosity structure of as-deposited OFSG dielectrics, declined as the SiF4 flow rate and the
deposition temperature increased, increasing the dielectric constant. However, newly formed Si–F bonds have less elec-tronic polarizability and therefore reduce the dielectric con-stant. Therefore, these traded-off properties yield a minimum dielectric constant of the OFSG film at a deposition tempera-ture of 250 ° C and a SiF4flow rate of 100 SCCM.
Addition-ally, the stability of Si–F bonds is related to the deposition conditions. OFSG films deposited at a higher SiF4flow rate
200 250 300 350 400 0 10 20 30 40 50 60 70 80 SiF4=0 sccm SiF4=100 sccm SiF4=200 sccm SiF4=400 sccm SiF4=600 sccm Bubbl e P robabi lity (% ) TemperatureoC 1PPm TaN Cu OFSG Cut 1PPm TaN Cu OFSG TaN Cu OFSG Cut
FIG. 6.共Color online兲 Probability of occurrence of bubble defect for OFSG
films deposited at various SiF4flow rates and deposition temperatures.
0h 24h 168h 500h -7 -6 -5 -4 -3 -2 -1 0 Fi lm st ress change (% )
Moisture exposure time
SiF4=0 sccm/350oC SiF4=100 sccm/250oC SiF4=100 sccm/300oC SiF4=100 sccm/350oC SiF4=400 sccm/350oC SiF4=600 sccm/350oC
FIG. 7. Change in residual stress for OFSG films deposited at various SiF4
flow rates and deposition temperatures during the moisture test.
0h 24h 168h 500h 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 SiF4=0 sccm/350oC SiF4=100 sccm/250oC SiF4=100 sccm/300oC SiF4=100 sccm/350oC SiF4=400 sccm/350oC SiF4=600 sccm/350oC Di e lect ri c const ant
Moisture exposure time
FIG. 8. Change in dielectric constant for OFSG films deposited at various
共⬎400 sccm兲 or a lower deposition temperature 共⬍300 °C兲 have worse thermal stability and moisture pro-tection resistance because of the instability of Si–F bonds. Consequently, more attention must be paid to the deposition conditions of fluorine-doped organo-silica-glass dielectrics.
ACKNOWLEDGMENT
The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract No. NSC 98-2221-E-260-037.
1International Technology Roadmap for semiconductors 2005,
Semicon-ductor Industry Association, 2005.
2J. Lubguban, Jr., Y. Kurata, T. Inokuma, and S. Hasegawa, J. Appl. Phys.
87, 3715共2000兲.
3M. Yoshimaru, S. Koizumi, and K. Shimokawa, J. Vac. Sci. Technol. A
15, 2908共1997兲.
4F. Iacona, G. Ceriola, and G. Spoto, J. Electrochem. Soc. 148, F47
共2001兲.
5S. P. Kim, S. K. Choi, Y. Park, and I. Chung, Appl. Phys. Lett. 79, 185
共2001兲.
6K. Kim, J. Song, D. Kwon, and G. S. Lee, Appl. Phys. Lett. 72, 1247
共1998兲.
7S. W. Lim, Y. Shimogaki, Y. Nakano, K. Tada, and H. Komiyama, J.
Electrochem. Soc. 146, 4196共1999兲.
8Q. Wu and K. K. Gleason, J. Vac. Sci. Technol. A 21, 388共2003兲.
9Y. L. Cheng et al., J. Phys. Chem. Solids 69, 518共2008兲.
10Y. L. Cheng et al., Thin Solid Films 447–448, 681共2004兲.
11J.-S. Chou and S.-C. Lee, J. Appl. Phys. 77, 1805共1995兲.
12M. G. Albrecht and C. Blanchette, J. Electrochem. Soc. 145, 4019
共1998兲.
13T. C. Chang et al., Thin Solid Films 332, 351共1998兲.
14M. J. Shapiro, S. V. Nguyen, T. Matsuda, and D. Dobuzinsky, Thin Solid
Films 270, 503共1995兲.
15K. Kim, D. H. Kwon, G. Nallapati, and G. S. Lee, J. Vac. Sci. Technol. A
16, 1509共1998兲.
16C. Kittle, Introduction to Solid State Physics, 7th ed.共Wiley, New York,
1996兲, Chap. 13.
461 Cheng, Wu, and Chiu: Effect of fluorine flow and deposition temperature on physical characteristics and stability 461
