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Reduction of surface roughness by Ta2O5 film formation with O2 cluster ion assisted deposition
Nuclear Instruments and Methods in Physics Research B 206 (2003) 870–874 www.elsevier.com/locate/nimb
Reduction of surface roughness by Ta2O5 film formation with O2 cluster ion assisted deposition Y. Fujiwara a
a,b,*
, N. Toyoda a, K. Mochiji b, T. Mitamura b, I. Yamada
a
Laboratory of Advanced Science and Technology for Industry, Himeji Institute of Technology, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan b Faculty of Engineering, Himeji Institute of Technology, Shosha, Himeji, Hyogo 671-2201, Japan
Abstract Ta2 O5 films were deposited on a rough surface with O2 cluster ion beam assisted deposition and the reduction of surface roughness was studied. Stoichiometric Ta2 O5 thin films were deposited with O2 cluster ion assisted deposition, and the film structure was very dense without porous and columnar structures. Smooth Ta2 O5 surfaces were realized even though they were deposited on a rough surface when O2 cluster ion energy was 7 keV. As the surface smoothing effect by O2 cluster ion irradiation was not dominant at O2 cluster ion energy of 7 keV, smooth Ta2 O5 surface was mainly originated by additional deposition of very thin Ta2 O5 films. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 68.55.)a; 78.20.Ci Keywords: O2 cluster ion; Average roughness; Ta2 O5 ; Sputtering
1. Introduction Techniques to deposit very smooth multilayer films have become more important to fulfill the rapid progress of state-of-the-art devices, such as photonic crystal, magnetic sensor head, interference filter and magnetic memory, etc. However, once rough surface is formed in a mid-layer of these multilayers during deposition, there is no way to improve the roughness of interfaces or top
* Corresponding author. Address: Laboratory of Advanced Science and Technology for Industry, Himeji Institute of Technology, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 6781205, Japan. Tel.: +81-791-58-0249; fax: +81-791-58-0242. E-mail address: [email protected] (Y. Fujiwara).
surface with conventional deposition techniques. Usually, these roughness are propagated to the upper layers and the roughness increases with increasing the number of layers. Therefore, it is important to develop a deposition technique that improves surface roughness during depositions. We have been studying the gas cluster ion beam (GCIB) process for various applications which requires low-energy ion beams, such as shallow implantation, surface cleaning, smoothing and thin film formation [1–4]. As gas cluster ion shows surface smoothing effect, it is very promising to employ GCIB in a deposition process in order to obtain very flat multilayer films. Also, as a gas cluster is combined with thousands of atoms, the energy per constituent atom is only several eV/ atom. In the case of deposition which employs
0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(03)00881-4
Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
atomic or molecular ions, sometimes energetic particles cause significant damages in a target. Therefore low-energy characteristics of the gas cluster ion are adequate to deposit damage-sensitive materials. Even though the energy per atom in cluster ion is very low, the energy density at bombarded area becomes very high because thousands of low-energy atoms hit the local area several nm in diameter. This effect enhances chemical reactions at the bombarded area and enables to obtain high-quality films without heating the substrate itself [5]. In this study, O2 GCIB assisted deposition for Ta2 O5 and SiO2 was studied and its surface smoothing effects are particularly investigated.
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accumulation charge of 10 lC. A cross-section of Ta2 O5 /SiO2 multilayer film was observed by a scanning electron microscope (SEM). In order to investigate sputtering and smoothing effects of O2 cluster ions, Ta2 O5 film was firstly deposited without O2 -GCIB, which had average roughness of 1.5 nm. Subsequently, this rough Ta2 O5 was irradiated by O2 -GCIB with various ion energies. Also, O2 -GCIB assisted deposition was performed on this rough Ta2 O5 surface and its smoothing effects by additional Ta2 O5 film with O2 -GCIB assisted deposition were investigated with an atomic force microscope (AFM) with a scan area of 1 lm 1 lm.
3. Results and discussion 2. Experimental O2 cluster ion beam assisted deposition system was based on ion beam assist deposition (IBAD) system. O2 neutral clusters were formed by supersonic expansion through a Laval nozzle (0.1 mm diameter in the orifice) in a source chamber [6]. Inlet gas pressure in a nozzle was 0.5 MPa. An average O2 cluster size was 1000 atoms/cluster, measured by time-of-flight mass spectrometer [7]. In the deposition chamber, there were O2 cluster ionizer, accelerator and an electron beam evaporator. The deposition chamber was separated from a source chamber by a skimmer 0.1 mm in diameter. O2 cluster ions were ionized by electron bombardment and were accelerated up to an energy ranging from 4 to 10 keV. After the accelerator, O2 cluster ion beam was scanned to get uniform irradiation at a target. Granular Ta2 O5 were evaporated from an electron beam evaporator with simultaneous irradiation of O2 cluster ions under vacuum pressure of 3.5 103 Pa. Deposition rate was monitored by a quartz crystal /s. thickness monitor, and it was normally 1.0 A Substrate temperature was maintained around 100 °C during deposition due to radiations from evaporator. The film composition was determined by using Rutherford backscattering spectrometry (RBS). The incident Heþ energy was 2 MeV, and the detector was located at 170° direction with a total
Fig. 1 shows RBS spectra of the tantalum oxide films deposited with 7 keV O2 -GCIB and without O2 -GCIB. The compositions of the tantalum oxide films were obtained from the areas of Ta and O peaks in RBS spectra. Without O2 -GCIB, the composition was Ta2 O4:64 , this result indicated that there was a lack of oxygen in tantalum oxide film. However, with O2 -GCIB assisted deposition, the composition of tantalum oxide was Ta2 O4:98 . Taking into account of the experimental error, it can be concluded that the tantalum oxide film was sufficiently oxidized due to enhancements of chemical reaction of O2 cluster ion bombardment.
Fig. 1. RBS spectra of O2 cluster ion beam assisted deposition and electronic beam deposition.
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Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
Fig. 2. Ta2 O5 /SiO2 multilayer film: (a) the cross-section of Ta2 O5 /SiO2 multilayer film, (b) the surface of top of the multilayer film, and (c) typical surface of SiO2 single layer film formed by non-assisted deposition.
Fig. 2(a) shows a cross-sectional SEM image of Ta2 O5 /SiO2 multilayer film. The bright and dark layers in Fig. 2(a) correspond to Ta2 O5 and SiO2 , respectively. The 1st, 4th, 5th and 6th layers from the top were formed with O2 -GCIB assisted deposition. The cluster ion energy and ion current density were 7 keV and 1.0 lA/cm2 , respectively. The 2nd and 3rd layers (Ta2 O5 /SiO2 ) were formed without O2 -GCIB. The structure of the film with O2 -GCIB assisted deposition (The 1st, 4th, 5th and 6th layer) was uniform and shows dense without porous or columnar growth. Interfaces between these layers were quite flat. The layers without O2 GCIB assist had large grains with coarse interface. AFM images of the top surface of multilayer (the 1st layer) and SiO2 surface without O2 -GCIB (2nd layer) were shown in Fig. 2(b) and (c), respectively. The surface roughness of the SiO2 film without O2 GCIB was 1.5 nm. It should be noted here that the average surface roughness of 7th layer was improved to 0.7 nm even though Ta2 O5 was deposited on a rough surface with average roughness of 1.5 nm. This result indicates that there is a surface smoothing effect with O2 -GCIB assisted deposition. To explore whether surface smoothing effect were caused by sputtering or additional thin film deposition, O2 cluster ions with various energies were irradiated to a rough Ta2 O5 surface, and the irradiated surface was observed with AFM. Fig. 3 shows O2 cluster ion dose dependence of surface roughness of Ta2 O5 films which were initially
Fig. 3. Dependence of average roughness of Ta2 O5 film on O2 cluster ion dose.
formed by electron beam evaporation. O2 cluster ions energy of 7 and 9 keV were irradiated with ion dose from 5 1015 to 1 1017 ions/cm2 . The initial average roughness and peak-to-valley of Ta2 O5 were 1.3 and 14 nm, respectively. When the cluster ion energy was 10 keV, the average roughness decreased with increasing ion dose from initial value of 1.3–0.5 nm at an ion dose of 1 1017 ions/ cm2 . As there was a slight removal of material after 10 keV O2 -GCIB irradiation, the dominant
Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
smoothing effect was supposed to be sputtering of Ta2 O5 . However, when the cluster ion energy was 7 keV, the average roughness did not change. It means that there was no surface smoothing effect by sputtering with 7 keV O2 -GCIB. Since the reduction of surface roughness of Ta2 O5 /SiO2 multilayer occurred at 7 keV as shown in Fig. 3, it can be estimated that the surface smoothing is not caused by sputtering of materials but by deposition of thin films on a rough surface. In the case of Ar cluster ion beams, threshold energy of sputtering for various materials stayed around 6–7 keV [8,9]. This result also suggests that the smooth Ta2 O5 film on a rough surface is originated by Ta2 O5 film deposition itself at acceleration energy of 7 keV. To investigate the required thickness to obtain smooth Ta2 O5 on a rough surface, Ta2 O5 films with O2 -GCIB assisted deposition were deposited on a rough Ta2 O5 surface. Fig. 4 shows thickness of O2 -GCIB assisted deposition dependence of average roughness and peak-to-valley (P –V ) value of Ta2 O5 films. Preparation of initial Ta2 O5 film was the same as the one used in Fig. 3. The average
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roughness and P –V value of the initial surface were 1.3 and 14 nm, respectively. The cluster ion energy was 4 and 7 keV, and ion current density was 1.1 lA/cm2 . When the cluster ion energy was 4 keV, there was no reduction of average roughness even after deposition of 100 nm thick Ta2 O5 film. When the cluster ion energy was 7 keV, the average roughness of Ta2 O5 film was decreased with additional Ta2 O5 film thickness first. It dropped from the initial value of 1.3 to 0.7 nm at Ta2 O5 thickness of 10 nm. And at Ta2 O5 thickness of 20 nm, it showed saturated average roughness of 0.5 nm. It is surprising that the surface roughness improved significantly by depositing very thin films (20 nm), which is slightly thicker than the initial P –V value (14 nm). In the case of conventional deposition methods, it is quite difficult to improve surface roughness with such a additional thin film deposition. From these results, the gas cluster ion assisted deposition is very promising method to form multilayer films with very flat interfaces.
4. Conclusions
Fig. 4. Dependence of average roughness and peak-to-valley of Ta2 O5 film on thickness of O2 cluster ion assisted deposition.
Smooth Ta2 O5 films depositions were performed with O2 cluster ion beam assisted deposition. From the RBS spectra, the tantalum oxide film with O2 -GCIB assisted deposition was sufficiently oxidized. From SEM cross-section images, Ta2 O5 film formed with O2 -GCIB assisted deposition was high density and uniform structures. Also, very smooth Ta2 O5 films were realized even though they were deposited on the rough surface. As there was no surface smoothing effects due to sputtering of materials at 7 keV, the surface smoothing was originated by deposition of additional thin films with O2 -GCIB. When Ta2 O5 film was deposited on a rough surface, smooth Ta2 O5 surface was obtained by deposition of very thin films with 20 nm of thickness, which was close to 15 nm of P –V value. From these results, O2 GCIB assisted deposition improves the surface roughness by depositing on a rough surface and it is promising to apply for multilayer film formations.
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Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
Acknowledgements This work is supported by New Energy and Industrial Technology Development Organization (NEDO).
References [1] I. Yamada, W.L. Brown, J.A. Northby, M. Sosnowski, Nucl. Instr. and Meth. B 79 (1993) 223. [2] I. Yamada, G.H. Takaoka, M. Akizuki, C.E. Ascheron, J. Matsuo, in: S. Coffa, et al. (Eds.), Proceedings of the Tenth International Conference on Ion Implantation Technology, Elsevier, Amsterdam, 1955, p. 1002. [3] J. Matsuo, H. Abe, G.H. Takaoka, I. Yamada, Nucl. Instr. and Meth. B 99 (1995) 244.
[4] M. Akizuki, J. Matsuo, M. Harada, S. Ogasawara, A. Doi, K. Yoneda, T. Yamaguchi, G.H. Takaoka, C.E. Ascheron, I. Yamada, Nucl. Instr. and Meth. B 99 (1995) 229. [5] I. Yamada, J. Matsuo, Z. Insepov, T. Aoki, T. Seki, N. Toyoda, Nucl. Instr. and Meth. B 164–165 (2000) 944. [6] G.H. Takaoka, G. Sugahara, R.E. Hummel, J.A. Northby, M. Sosnowski, I. Yamada, Mater. Res. Soc. Symp. Proc. 316 (1994) 1005. [7] N. Toyoda, M. Saito, N. Hagiwara, J. Matsuo, I. Yamada, Proceedings of IIT of 12th International Conference on Ion Implantation Technology, 1999, p. 1234. [8] H.H. Andersen, H.L. Bay, in: R. Behrisch (Ed.), Sputtering by Particle Bombardment I, Springer-Verlag, Berlin, 1981. [9] N. Matsunami, Y. Yamamura, Y. Ichikawa, N. Itoh, Y. Kazumata, S. Miyagawa, K. Morita, R. Shimizu, H. Tawara, Atomic Data Nucl. Data Tables 31 (1984) 1.
Reduction of surface roughness by Ta2O5 film formation with O2 cluster ion assisted deposition Y. Fujiwara a
a,b,*
, N. Toyoda a, K. Mochiji b, T. Mitamura b, I. Yamada
a
Laboratory of Advanced Science and Technology for Industry, Himeji Institute of Technology, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan b Faculty of Engineering, Himeji Institute of Technology, Shosha, Himeji, Hyogo 671-2201, Japan
Abstract Ta2 O5 films were deposited on a rough surface with O2 cluster ion beam assisted deposition and the reduction of surface roughness was studied. Stoichiometric Ta2 O5 thin films were deposited with O2 cluster ion assisted deposition, and the film structure was very dense without porous and columnar structures. Smooth Ta2 O5 surfaces were realized even though they were deposited on a rough surface when O2 cluster ion energy was 7 keV. As the surface smoothing effect by O2 cluster ion irradiation was not dominant at O2 cluster ion energy of 7 keV, smooth Ta2 O5 surface was mainly originated by additional deposition of very thin Ta2 O5 films. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 68.55.)a; 78.20.Ci Keywords: O2 cluster ion; Average roughness; Ta2 O5 ; Sputtering
1. Introduction Techniques to deposit very smooth multilayer films have become more important to fulfill the rapid progress of state-of-the-art devices, such as photonic crystal, magnetic sensor head, interference filter and magnetic memory, etc. However, once rough surface is formed in a mid-layer of these multilayers during deposition, there is no way to improve the roughness of interfaces or top
* Corresponding author. Address: Laboratory of Advanced Science and Technology for Industry, Himeji Institute of Technology, 3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 6781205, Japan. Tel.: +81-791-58-0249; fax: +81-791-58-0242. E-mail address: [email protected] (Y. Fujiwara).
surface with conventional deposition techniques. Usually, these roughness are propagated to the upper layers and the roughness increases with increasing the number of layers. Therefore, it is important to develop a deposition technique that improves surface roughness during depositions. We have been studying the gas cluster ion beam (GCIB) process for various applications which requires low-energy ion beams, such as shallow implantation, surface cleaning, smoothing and thin film formation [1–4]. As gas cluster ion shows surface smoothing effect, it is very promising to employ GCIB in a deposition process in order to obtain very flat multilayer films. Also, as a gas cluster is combined with thousands of atoms, the energy per constituent atom is only several eV/ atom. In the case of deposition which employs
0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(03)00881-4
Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
atomic or molecular ions, sometimes energetic particles cause significant damages in a target. Therefore low-energy characteristics of the gas cluster ion are adequate to deposit damage-sensitive materials. Even though the energy per atom in cluster ion is very low, the energy density at bombarded area becomes very high because thousands of low-energy atoms hit the local area several nm in diameter. This effect enhances chemical reactions at the bombarded area and enables to obtain high-quality films without heating the substrate itself [5]. In this study, O2 GCIB assisted deposition for Ta2 O5 and SiO2 was studied and its surface smoothing effects are particularly investigated.
871
accumulation charge of 10 lC. A cross-section of Ta2 O5 /SiO2 multilayer film was observed by a scanning electron microscope (SEM). In order to investigate sputtering and smoothing effects of O2 cluster ions, Ta2 O5 film was firstly deposited without O2 -GCIB, which had average roughness of 1.5 nm. Subsequently, this rough Ta2 O5 was irradiated by O2 -GCIB with various ion energies. Also, O2 -GCIB assisted deposition was performed on this rough Ta2 O5 surface and its smoothing effects by additional Ta2 O5 film with O2 -GCIB assisted deposition were investigated with an atomic force microscope (AFM) with a scan area of 1 lm 1 lm.
3. Results and discussion 2. Experimental O2 cluster ion beam assisted deposition system was based on ion beam assist deposition (IBAD) system. O2 neutral clusters were formed by supersonic expansion through a Laval nozzle (0.1 mm diameter in the orifice) in a source chamber [6]. Inlet gas pressure in a nozzle was 0.5 MPa. An average O2 cluster size was 1000 atoms/cluster, measured by time-of-flight mass spectrometer [7]. In the deposition chamber, there were O2 cluster ionizer, accelerator and an electron beam evaporator. The deposition chamber was separated from a source chamber by a skimmer 0.1 mm in diameter. O2 cluster ions were ionized by electron bombardment and were accelerated up to an energy ranging from 4 to 10 keV. After the accelerator, O2 cluster ion beam was scanned to get uniform irradiation at a target. Granular Ta2 O5 were evaporated from an electron beam evaporator with simultaneous irradiation of O2 cluster ions under vacuum pressure of 3.5 103 Pa. Deposition rate was monitored by a quartz crystal /s. thickness monitor, and it was normally 1.0 A Substrate temperature was maintained around 100 °C during deposition due to radiations from evaporator. The film composition was determined by using Rutherford backscattering spectrometry (RBS). The incident Heþ energy was 2 MeV, and the detector was located at 170° direction with a total
Fig. 1 shows RBS spectra of the tantalum oxide films deposited with 7 keV O2 -GCIB and without O2 -GCIB. The compositions of the tantalum oxide films were obtained from the areas of Ta and O peaks in RBS spectra. Without O2 -GCIB, the composition was Ta2 O4:64 , this result indicated that there was a lack of oxygen in tantalum oxide film. However, with O2 -GCIB assisted deposition, the composition of tantalum oxide was Ta2 O4:98 . Taking into account of the experimental error, it can be concluded that the tantalum oxide film was sufficiently oxidized due to enhancements of chemical reaction of O2 cluster ion bombardment.
Fig. 1. RBS spectra of O2 cluster ion beam assisted deposition and electronic beam deposition.
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Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
Fig. 2. Ta2 O5 /SiO2 multilayer film: (a) the cross-section of Ta2 O5 /SiO2 multilayer film, (b) the surface of top of the multilayer film, and (c) typical surface of SiO2 single layer film formed by non-assisted deposition.
Fig. 2(a) shows a cross-sectional SEM image of Ta2 O5 /SiO2 multilayer film. The bright and dark layers in Fig. 2(a) correspond to Ta2 O5 and SiO2 , respectively. The 1st, 4th, 5th and 6th layers from the top were formed with O2 -GCIB assisted deposition. The cluster ion energy and ion current density were 7 keV and 1.0 lA/cm2 , respectively. The 2nd and 3rd layers (Ta2 O5 /SiO2 ) were formed without O2 -GCIB. The structure of the film with O2 -GCIB assisted deposition (The 1st, 4th, 5th and 6th layer) was uniform and shows dense without porous or columnar growth. Interfaces between these layers were quite flat. The layers without O2 GCIB assist had large grains with coarse interface. AFM images of the top surface of multilayer (the 1st layer) and SiO2 surface without O2 -GCIB (2nd layer) were shown in Fig. 2(b) and (c), respectively. The surface roughness of the SiO2 film without O2 GCIB was 1.5 nm. It should be noted here that the average surface roughness of 7th layer was improved to 0.7 nm even though Ta2 O5 was deposited on a rough surface with average roughness of 1.5 nm. This result indicates that there is a surface smoothing effect with O2 -GCIB assisted deposition. To explore whether surface smoothing effect were caused by sputtering or additional thin film deposition, O2 cluster ions with various energies were irradiated to a rough Ta2 O5 surface, and the irradiated surface was observed with AFM. Fig. 3 shows O2 cluster ion dose dependence of surface roughness of Ta2 O5 films which were initially
Fig. 3. Dependence of average roughness of Ta2 O5 film on O2 cluster ion dose.
formed by electron beam evaporation. O2 cluster ions energy of 7 and 9 keV were irradiated with ion dose from 5 1015 to 1 1017 ions/cm2 . The initial average roughness and peak-to-valley of Ta2 O5 were 1.3 and 14 nm, respectively. When the cluster ion energy was 10 keV, the average roughness decreased with increasing ion dose from initial value of 1.3–0.5 nm at an ion dose of 1 1017 ions/ cm2 . As there was a slight removal of material after 10 keV O2 -GCIB irradiation, the dominant
Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
smoothing effect was supposed to be sputtering of Ta2 O5 . However, when the cluster ion energy was 7 keV, the average roughness did not change. It means that there was no surface smoothing effect by sputtering with 7 keV O2 -GCIB. Since the reduction of surface roughness of Ta2 O5 /SiO2 multilayer occurred at 7 keV as shown in Fig. 3, it can be estimated that the surface smoothing is not caused by sputtering of materials but by deposition of thin films on a rough surface. In the case of Ar cluster ion beams, threshold energy of sputtering for various materials stayed around 6–7 keV [8,9]. This result also suggests that the smooth Ta2 O5 film on a rough surface is originated by Ta2 O5 film deposition itself at acceleration energy of 7 keV. To investigate the required thickness to obtain smooth Ta2 O5 on a rough surface, Ta2 O5 films with O2 -GCIB assisted deposition were deposited on a rough Ta2 O5 surface. Fig. 4 shows thickness of O2 -GCIB assisted deposition dependence of average roughness and peak-to-valley (P –V ) value of Ta2 O5 films. Preparation of initial Ta2 O5 film was the same as the one used in Fig. 3. The average
873
roughness and P –V value of the initial surface were 1.3 and 14 nm, respectively. The cluster ion energy was 4 and 7 keV, and ion current density was 1.1 lA/cm2 . When the cluster ion energy was 4 keV, there was no reduction of average roughness even after deposition of 100 nm thick Ta2 O5 film. When the cluster ion energy was 7 keV, the average roughness of Ta2 O5 film was decreased with additional Ta2 O5 film thickness first. It dropped from the initial value of 1.3 to 0.7 nm at Ta2 O5 thickness of 10 nm. And at Ta2 O5 thickness of 20 nm, it showed saturated average roughness of 0.5 nm. It is surprising that the surface roughness improved significantly by depositing very thin films (20 nm), which is slightly thicker than the initial P –V value (14 nm). In the case of conventional deposition methods, it is quite difficult to improve surface roughness with such a additional thin film deposition. From these results, the gas cluster ion assisted deposition is very promising method to form multilayer films with very flat interfaces.
4. Conclusions
Fig. 4. Dependence of average roughness and peak-to-valley of Ta2 O5 film on thickness of O2 cluster ion assisted deposition.
Smooth Ta2 O5 films depositions were performed with O2 cluster ion beam assisted deposition. From the RBS spectra, the tantalum oxide film with O2 -GCIB assisted deposition was sufficiently oxidized. From SEM cross-section images, Ta2 O5 film formed with O2 -GCIB assisted deposition was high density and uniform structures. Also, very smooth Ta2 O5 films were realized even though they were deposited on the rough surface. As there was no surface smoothing effects due to sputtering of materials at 7 keV, the surface smoothing was originated by deposition of additional thin films with O2 -GCIB. When Ta2 O5 film was deposited on a rough surface, smooth Ta2 O5 surface was obtained by deposition of very thin films with 20 nm of thickness, which was close to 15 nm of P –V value. From these results, O2 GCIB assisted deposition improves the surface roughness by depositing on a rough surface and it is promising to apply for multilayer film formations.
874
Y. Fujiwara et al. / Nucl. Instr. and Meth. in Phys. Res. B 206 (2003) 870–874
Acknowledgements This work is supported by New Energy and Industrial Technology Development Organization (NEDO).
References [1] I. Yamada, W.L. Brown, J.A. Northby, M. Sosnowski, Nucl. Instr. and Meth. B 79 (1993) 223. [2] I. Yamada, G.H. Takaoka, M. Akizuki, C.E. Ascheron, J. Matsuo, in: S. Coffa, et al. (Eds.), Proceedings of the Tenth International Conference on Ion Implantation Technology, Elsevier, Amsterdam, 1955, p. 1002. [3] J. Matsuo, H. Abe, G.H. Takaoka, I. Yamada, Nucl. Instr. and Meth. B 99 (1995) 244.
[4] M. Akizuki, J. Matsuo, M. Harada, S. Ogasawara, A. Doi, K. Yoneda, T. Yamaguchi, G.H. Takaoka, C.E. Ascheron, I. Yamada, Nucl. Instr. and Meth. B 99 (1995) 229. [5] I. Yamada, J. Matsuo, Z. Insepov, T. Aoki, T. Seki, N. Toyoda, Nucl. Instr. and Meth. B 164–165 (2000) 944. [6] G.H. Takaoka, G. Sugahara, R.E. Hummel, J.A. Northby, M. Sosnowski, I. Yamada, Mater. Res. Soc. Symp. Proc. 316 (1994) 1005. [7] N. Toyoda, M. Saito, N. Hagiwara, J. Matsuo, I. Yamada, Proceedings of IIT of 12th International Conference on Ion Implantation Technology, 1999, p. 1234. [8] H.H. Andersen, H.L. Bay, in: R. Behrisch (Ed.), Sputtering by Particle Bombardment I, Springer-Verlag, Berlin, 1981. [9] N. Matsunami, Y. Yamamura, Y. Ichikawa, N. Itoh, Y. Kazumata, S. Miyagawa, K. Morita, R. Shimizu, H. Tawara, Atomic Data Nucl. Data Tables 31 (1984) 1.