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Large area deposition of 〈100〉-textured diamond films by a 60-kW microwave plasma CVD reactor
Diamond and Related Materials 11 (2002) 596–600
Large area deposition of N100M-textured diamond films by a 60-kW microwave plasma CVD reactor Yutaka Andoa,*, Yoshihiro Yokotaa, Takeshi Tachibanaa,1, Akihiko Watanabea, Yoshiki Nishibayashia, Koji Kobashia, Takashi Hiraob, Kenjiro Ourab a
FCT ProjectyJFCC, 6F, Center for Advanced Research Projects, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan b Faculty of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
Abstract Diamond films were deposited on silicon wafers of 25–152 mm in diameter by a 60-kW 915-MHz plasma CVD system with a input power of 15–60 kW at a gas pressure of 11.3–17.7 kPa using H2 –CH4 or H2 –CH4 –CO2 gas mixtures. Growth orientation of the diamond films and a parameters for the different growth conditions have been investigated in order to control the morphology of the diamond films of 152 mm in diameter. It was clearly seen that the a parameters for the 60-kW system were greater than those for conventional microwave plasma CVD systems in the substrate temperature–CH4 concentration plane. This means that the contour of the a parameter shifts to the higher substrate temperature and the lower CH4 concentration, as compared with the results of the conventional CVD systems. It was also found that the parameter range of diamond growth by the 60-kW reactor is broader than that of the conventional CVD systems. Based on the present study, N100M-textured diamond films were successfully grown almost uniformly on the entire surface of a 152-mmf Si substrate by choosing appropriate process conditions. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: Diamond growth; Morphology; Textured film; 60 kW CVD
1. Introduction Diamond possesses unrivalled semiconductor properties such as wide bandgap, high carrier transport speed, high breakdown field, and high thermal conductivity, coupled with high optical transparency and chemical stability. It is predicted that this material will be utilized for various components, including robust electronic devices and packaging for the coming generation w1x. Since chemical vapor deposition (CVD) processes and the apparatus of diamond films were established approximately two decades ago by a Japanese group w2x, many studies have been carried out to understand their material properties and prove their potential for practical applications. Unfortunately, most of the R&D efforts were limited in laboratory scale, despite the fact that they are primarily motivated by industrial applications, and less *Corresponding author. Tel.: q81-6-6879-4146; fax: q81-6-68794147. E-mail address: [email protected] (Y. Ando). 1 Present address: Electronics Research Laboratory, Kobe Steel Ltd., 1-5-5, Takatsukadai, Nishi-ku, Hyogo 651-2271, Japan.
emphasis was placed on scale-up technologies. Many issues, including scale up, cost reduction, reproducibility, etc. have been left unresolved in the individual efforts. Irrespective of specific applications of CVD diamond films, a large size, production-type CVD apparatus is necessary to upgrade the present CVD technology. Several efforts have already been made to develop a diamond CVD apparatus and processes for high deposition rate and large area coverage. For instance, 76-mm silicon (Si) wafers were uniformly covered with polycrystalline diamond films, though its growth rate was as small as 0.5 mmyh w3x. On the other hand, at an increased rate of ;5 mmyh, high quality diamond films of 0.1–1.2 mm in thickness were grown on a wafer of 57 mm in diameter using a CVD reactor equipped with a 5-kW microwave source w4x. Schelz and co-workers compared 915-MHz microwave with conventionallyused 2.45 GHz, in an attempt to deposit diamond films on large size substrates. They concluded that diamond films of a similar quality could be synthesized as long as the power density of the plasma is similar w5x. Regarding the large-scale apparatus, Sevillano and Wil-
0925-9635/02/$ - see front matter 䊚 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 - 9 6 3 5 Ž 0 2 . 0 0 0 1 8 - 3
Y. Ando et al. / Diamond and Related Materials 11 (2002) 596–600
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Fig. 1. Dependence of growth rate Rg (square) and Raman signal width WR (full width at half maximum; circle) of diamond on the gas pressure Pr (a), the microwave input power Pw (b), and the substrate temperature Ts (c).
liams successfully constructed a large microwave CVD reactor using a 915-MHz microwave to enlarge the coating area w6x. Koidl and co-workers, sharing a similar awareness of the present issue, developed a reactor of unique design and demonstrated diamond films on Si wafers of 100 mm in diameter w7x. In the present study, the 915-MHz microwave plasma CVD was employed to develop basic CVD process technologies for high purity and high quality diamond films, including nucleation and growth orientation control, elimination of impurity and residual stress, and cost analyses and minimization. Numerous data accumulated so far by using lower power (;1.5 kW) microwave plasma CVD were a good guide to exploring process conditions in the large reactor, while it was also of interest to us to investigate whether larger scale plasma could produce high quality diamond films at a higher rate. Some preliminary investigations have already been reported w8x. The present paper focuses on the growth orientation of diamond crystals and the a parameter under various growth conditions using the 60-kW, 915MHz CVD system.
5000 sccm of H2, 4–200 sccm of CH4, and 0–100 sccm of CO2. The gas pressure Pr was 11.3–17.7 kPa (85– 133 torr). The microwave input power Pw was 15–60 kW. The substrates were mounted on a water-cooled Mo holder, but heated by the plasma. The substrate temperature Ts, a dependent parameter, was ranged from 950 to 1370 K (680–1100 8C) as measured by a twowavelength optical pyrometer. The morphology was observed using a scanning electron microscope. The a parameter was calculated by comparing the facet shapes of an isolated diamond particle before and after the growth. The growth orientation was determined by means of X-ray diffraction. The quality of diamond films was evaluated with Raman spectroscopy using an Ar laser operated at 514.5 nm.
2. Experimental An overmoded microwave plasma CVD reactor equipped with a 60-kW power supply (ASTeXySeki Technotron) was used to explore process conditions for diamond growth. The apparatus and its operation procedure have been described in detail by Tachibana et al. w8x. The substrates were silicon wafers of 25, 51 and 152 mm in diameter. The 25- and 51-mm substrates were single-crystalline, while the 152-mm substrates were polycrystalline, chosen by considering their availability and for comparison. The source gas was 1200–
Fig. 2. Variation of a parameter and film texture on CH4 concentration Cm and substrate temperature Ts.
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Fig. 3. Typical film morphologies deposited at the conditions (a–d) shown in the Fig. 2 observed by SEM.
3. Results and discussion Fig. 1a–c shows the dependence of the growth rate Rg and the Raman signal width WR on the gas pressure Pr (Fig. 1a), the microwave input power Pw (Fig. 1b), and the substrate temperature Ts (Fig. 1c), respectively. The gas flow rates of hydrogen and methane were fixed as 2000 sccm and 100 sccm, respectively. As seen in Fig. 1a,b, when neither Pw nor Pr is fixed, both Rg and WR shows no dependence, while it is obvious in Fig. 1c that both Rg and WR increase as Ts increases. Substrate temperature seems to be the most influential parameter. As a matter of fact, Ts is a function of Pw and Pr. Substrate temperature thus reflects the energy density of the plasma. When Pw and Pr is 60 kW and 16.7 kPa (125 torr), corresponding Ts is 1320 K (1050 8C), Rg and WR were 7 mmyh and 11 cmy1, respectively. In this case, the conversion efficiency from CH4 to diamond on a 152-mmf substrate exceeds 10%, calculated by the mass increase of the substrate. It is two orders of magnitude higher than that obtained by an ASTeX 1.5 kW system. The a parameters were evaluated from the change in the isolated crystal shape with time, and the approximate curves for as1.5 and 3 are shown in Fig. 2. At the legion of lower Ts and higher CH4 concentrations Cm, the value of a is larger than 3. A decrease in Cm or increase in Ts leads to decrease of a. This tendency is
similar to the results reported in many literatures (e.g. w9,10x). However, it is seen that the curves are shifted toward the higher Ts and the lower Cm side. This result is consistent with the fact that the conversion efficiency from CH4 to diamond is higher. The domains of N100M and N111M oriented growth measured by XRD are also shown in Fig. 2. A N100Mtextured film, the corners surrounded by {111} faces, like a pyramid (Fig. 3b), was grown at the condition of a;3 and not at higher Cm (indicated by ‘b’ in Fig. 2). In this region, the film is grown in conformity with the selective evolutionary growth model w11x. The films with N111M preferred orientation, however, were grown under the condition of a)3. This result is in contradiction to the conventional one. It is not certain at the present stage how the N111M oriented films are grown at the region of a)3. From SEM observations (Fig. 3), twinning occurs considerably for the N111M oriented film (Fig. 3c,d) and the pyramidal shape of diamond faces is difficult to find. Similar results have been observed for a 5-kW microwave plasma CVD system which also have a water-cooled substrate holder and operated at high gas pressure ()13.3 kPa) w12x. As described above, the curves for the a parameters shift to the higher Ts and the lower Cm as compared with the results of the conventional CVD systems. This means that very high Ts and low Cm are necessary to control the morphology of the diamond films. To over-
Y. Ando et al. / Diamond and Related Materials 11 (2002) 596–600
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come this problem, a H2–CH4–CO2 gas mixture has been used for the deposition. Fig. 4 shows a preliminary result of the deposition using the H2–CH4–CO2 gas mixture. Cubic shape of diamond grains were grown (a;1) on the Si substrate under the condition of (CH4qCO2)y(H2qCH4 qCO2 )s1%, CO2 yCH4s 0.17, and Ts;1270 K. The a parameter was reduced by adding CO2. Fig. 4b shows a fractured cross section of the diamond film deposited with the condition of a;1 on the N100M-textured diamond film of a pyramidal shape surface. Based on these results, growth orientation and film morphology were manipulated. For example, when the condition range was CH4 y(CH4qH2)s2%, 60 kW microwave input, 14.0–17.7 kPa (105–133 torr), and 1170–1280 K (900–1010 8C), the grown diamond grains have a pyramidal shape surface and a N100Mtexture almost uniformly on the entire surface of 51(Fig. 5a), 25- (Fig. 5d) and 152- (Fig. 5e) mm substrates. The surface appears like black velvet to the naked eye; lusterless to the normal direction to the substrate, but glossy to the oblique angle. This is due to the facets having almost the same angle ;54.78 to the substrate plane. The films shown in Fig. 5b,c are non-textured. SEM images of the 152-mmf diamond films at the center (f), the intermediate (g), and the edge (h) are also shown. The used 152-mmf substrates were polycrystalline so that the orientation behavior is independent of substrate. Fig. 4. Diamond grains deposited at the growth condition of a;1 on Si substrate (a) and a fractured cross section of the diamond film deposited with the condition of a;1 on a N100M-textured diamond film (b).
4. Conclusion In order to control the morphology of large area diamond films, diamond deposition using a 60-kW
Fig. 5. Photograph of the diamond films deposited on 51 (a,b), 25 (c,d), and 152 (e) mm diameter substrate. SEM images of the 152-mmf diamond films at the center (f), the intermediate (g), and the edge (h) are also shown.
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microwave plasma CVD system and characterization with SEM, XRD, and Raman have been carried out. The 60-kW CVD system shows the growth rate of 7 mmyh and a conversion efficiency of excess 10% from CH4 to diamond. The contour of the a parameter shifts toward the higher substrate temperature and the lower CH4 concentration as compared with the results of the smaller CVD systems. It was also found that the parameter range of diamond growth by the 60-kW reactor is broader than that of the conventional CVD systems. Furthermore, N100M-textured diamond films with pyramidal shape surface were successfully grown almost uniformly on the entire surface of a 152-mmf Si substrate by choosing an appropriate process condition. Acknowledgments This work was supported by the FCT Project, which was consigned to JFCC by NEDO.
References w1x L.S. Pan, D.R. Kania, Diamond: Electronic Properties and Applications, Kluwer Academic, Boston, 1995. w2x M. Kamo, et al., United States Patent 4434188 (1984). w3x H.A. Naseem, W.D. Brown, et al., Thin Solid Films 308–309 (1997) 141. w4x V. Ralchenko, I. Sychov, I. Vlasov, et al., Diamond Relat. Mater. 8 (1999) 189. w5x S. Schelz, C. Campillo, M. Moisan, Diamond Relat. Mater. 7 (1998) 1675. w6x E. Sevillano, B.E. Williams, Diamond Films Tech. 8 (1998) 73. w7x M. Funer, ¨ C. Wild, P. Koidl, Appl. Phys. Lett. 72 (1998) 1149. w8x T. Tachibana, Y. Ando, A. Watanabe, Y. Nishibayashi, K. Kobashi T. Hirao, K. Oura, Diamond Relat. Mater., to be published as a special issue of Proc. 7th Intl. Conf. New Diamond Sci. Tech., Hong Kong, July 2000. w9x P. Koidl, C. Wild, N. Herres, Proc. NIRIM Intern. Symp. on Advanced Materials ’94, 13–17 March 1994, Tsukuba (Japan), 1994, p. 1. w10x A. Gicquel, F. Silva, K. Hassouni, J. Electrochem. Soc. 147 (6) (2000) 2218. w11x A. Van der Drift, Philips Res. Rep. 22 (1967) 267. w12x Y. Ando, T. Tachibana, K. Kobashi, Diamond Relat. Mater. 10 (2001) 312.
Large area deposition of N100M-textured diamond films by a 60-kW microwave plasma CVD reactor Yutaka Andoa,*, Yoshihiro Yokotaa, Takeshi Tachibanaa,1, Akihiko Watanabea, Yoshiki Nishibayashia, Koji Kobashia, Takashi Hiraob, Kenjiro Ourab a
FCT ProjectyJFCC, 6F, Center for Advanced Research Projects, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan b Faculty of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
Abstract Diamond films were deposited on silicon wafers of 25–152 mm in diameter by a 60-kW 915-MHz plasma CVD system with a input power of 15–60 kW at a gas pressure of 11.3–17.7 kPa using H2 –CH4 or H2 –CH4 –CO2 gas mixtures. Growth orientation of the diamond films and a parameters for the different growth conditions have been investigated in order to control the morphology of the diamond films of 152 mm in diameter. It was clearly seen that the a parameters for the 60-kW system were greater than those for conventional microwave plasma CVD systems in the substrate temperature–CH4 concentration plane. This means that the contour of the a parameter shifts to the higher substrate temperature and the lower CH4 concentration, as compared with the results of the conventional CVD systems. It was also found that the parameter range of diamond growth by the 60-kW reactor is broader than that of the conventional CVD systems. Based on the present study, N100M-textured diamond films were successfully grown almost uniformly on the entire surface of a 152-mmf Si substrate by choosing appropriate process conditions. 䊚 2002 Elsevier Science B.V. All rights reserved. Keywords: Diamond growth; Morphology; Textured film; 60 kW CVD
1. Introduction Diamond possesses unrivalled semiconductor properties such as wide bandgap, high carrier transport speed, high breakdown field, and high thermal conductivity, coupled with high optical transparency and chemical stability. It is predicted that this material will be utilized for various components, including robust electronic devices and packaging for the coming generation w1x. Since chemical vapor deposition (CVD) processes and the apparatus of diamond films were established approximately two decades ago by a Japanese group w2x, many studies have been carried out to understand their material properties and prove their potential for practical applications. Unfortunately, most of the R&D efforts were limited in laboratory scale, despite the fact that they are primarily motivated by industrial applications, and less *Corresponding author. Tel.: q81-6-6879-4146; fax: q81-6-68794147. E-mail address: [email protected] (Y. Ando). 1 Present address: Electronics Research Laboratory, Kobe Steel Ltd., 1-5-5, Takatsukadai, Nishi-ku, Hyogo 651-2271, Japan.
emphasis was placed on scale-up technologies. Many issues, including scale up, cost reduction, reproducibility, etc. have been left unresolved in the individual efforts. Irrespective of specific applications of CVD diamond films, a large size, production-type CVD apparatus is necessary to upgrade the present CVD technology. Several efforts have already been made to develop a diamond CVD apparatus and processes for high deposition rate and large area coverage. For instance, 76-mm silicon (Si) wafers were uniformly covered with polycrystalline diamond films, though its growth rate was as small as 0.5 mmyh w3x. On the other hand, at an increased rate of ;5 mmyh, high quality diamond films of 0.1–1.2 mm in thickness were grown on a wafer of 57 mm in diameter using a CVD reactor equipped with a 5-kW microwave source w4x. Schelz and co-workers compared 915-MHz microwave with conventionallyused 2.45 GHz, in an attempt to deposit diamond films on large size substrates. They concluded that diamond films of a similar quality could be synthesized as long as the power density of the plasma is similar w5x. Regarding the large-scale apparatus, Sevillano and Wil-
0925-9635/02/$ - see front matter 䊚 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 - 9 6 3 5 Ž 0 2 . 0 0 0 1 8 - 3
Y. Ando et al. / Diamond and Related Materials 11 (2002) 596–600
597
Fig. 1. Dependence of growth rate Rg (square) and Raman signal width WR (full width at half maximum; circle) of diamond on the gas pressure Pr (a), the microwave input power Pw (b), and the substrate temperature Ts (c).
liams successfully constructed a large microwave CVD reactor using a 915-MHz microwave to enlarge the coating area w6x. Koidl and co-workers, sharing a similar awareness of the present issue, developed a reactor of unique design and demonstrated diamond films on Si wafers of 100 mm in diameter w7x. In the present study, the 915-MHz microwave plasma CVD was employed to develop basic CVD process technologies for high purity and high quality diamond films, including nucleation and growth orientation control, elimination of impurity and residual stress, and cost analyses and minimization. Numerous data accumulated so far by using lower power (;1.5 kW) microwave plasma CVD were a good guide to exploring process conditions in the large reactor, while it was also of interest to us to investigate whether larger scale plasma could produce high quality diamond films at a higher rate. Some preliminary investigations have already been reported w8x. The present paper focuses on the growth orientation of diamond crystals and the a parameter under various growth conditions using the 60-kW, 915MHz CVD system.
5000 sccm of H2, 4–200 sccm of CH4, and 0–100 sccm of CO2. The gas pressure Pr was 11.3–17.7 kPa (85– 133 torr). The microwave input power Pw was 15–60 kW. The substrates were mounted on a water-cooled Mo holder, but heated by the plasma. The substrate temperature Ts, a dependent parameter, was ranged from 950 to 1370 K (680–1100 8C) as measured by a twowavelength optical pyrometer. The morphology was observed using a scanning electron microscope. The a parameter was calculated by comparing the facet shapes of an isolated diamond particle before and after the growth. The growth orientation was determined by means of X-ray diffraction. The quality of diamond films was evaluated with Raman spectroscopy using an Ar laser operated at 514.5 nm.
2. Experimental An overmoded microwave plasma CVD reactor equipped with a 60-kW power supply (ASTeXySeki Technotron) was used to explore process conditions for diamond growth. The apparatus and its operation procedure have been described in detail by Tachibana et al. w8x. The substrates were silicon wafers of 25, 51 and 152 mm in diameter. The 25- and 51-mm substrates were single-crystalline, while the 152-mm substrates were polycrystalline, chosen by considering their availability and for comparison. The source gas was 1200–
Fig. 2. Variation of a parameter and film texture on CH4 concentration Cm and substrate temperature Ts.
Y. Ando et al. / Diamond and Related Materials 11 (2002) 596–600
598
Fig. 3. Typical film morphologies deposited at the conditions (a–d) shown in the Fig. 2 observed by SEM.
3. Results and discussion Fig. 1a–c shows the dependence of the growth rate Rg and the Raman signal width WR on the gas pressure Pr (Fig. 1a), the microwave input power Pw (Fig. 1b), and the substrate temperature Ts (Fig. 1c), respectively. The gas flow rates of hydrogen and methane were fixed as 2000 sccm and 100 sccm, respectively. As seen in Fig. 1a,b, when neither Pw nor Pr is fixed, both Rg and WR shows no dependence, while it is obvious in Fig. 1c that both Rg and WR increase as Ts increases. Substrate temperature seems to be the most influential parameter. As a matter of fact, Ts is a function of Pw and Pr. Substrate temperature thus reflects the energy density of the plasma. When Pw and Pr is 60 kW and 16.7 kPa (125 torr), corresponding Ts is 1320 K (1050 8C), Rg and WR were 7 mmyh and 11 cmy1, respectively. In this case, the conversion efficiency from CH4 to diamond on a 152-mmf substrate exceeds 10%, calculated by the mass increase of the substrate. It is two orders of magnitude higher than that obtained by an ASTeX 1.5 kW system. The a parameters were evaluated from the change in the isolated crystal shape with time, and the approximate curves for as1.5 and 3 are shown in Fig. 2. At the legion of lower Ts and higher CH4 concentrations Cm, the value of a is larger than 3. A decrease in Cm or increase in Ts leads to decrease of a. This tendency is
similar to the results reported in many literatures (e.g. w9,10x). However, it is seen that the curves are shifted toward the higher Ts and the lower Cm side. This result is consistent with the fact that the conversion efficiency from CH4 to diamond is higher. The domains of N100M and N111M oriented growth measured by XRD are also shown in Fig. 2. A N100Mtextured film, the corners surrounded by {111} faces, like a pyramid (Fig. 3b), was grown at the condition of a;3 and not at higher Cm (indicated by ‘b’ in Fig. 2). In this region, the film is grown in conformity with the selective evolutionary growth model w11x. The films with N111M preferred orientation, however, were grown under the condition of a)3. This result is in contradiction to the conventional one. It is not certain at the present stage how the N111M oriented films are grown at the region of a)3. From SEM observations (Fig. 3), twinning occurs considerably for the N111M oriented film (Fig. 3c,d) and the pyramidal shape of diamond faces is difficult to find. Similar results have been observed for a 5-kW microwave plasma CVD system which also have a water-cooled substrate holder and operated at high gas pressure ()13.3 kPa) w12x. As described above, the curves for the a parameters shift to the higher Ts and the lower Cm as compared with the results of the conventional CVD systems. This means that very high Ts and low Cm are necessary to control the morphology of the diamond films. To over-
Y. Ando et al. / Diamond and Related Materials 11 (2002) 596–600
599
come this problem, a H2–CH4–CO2 gas mixture has been used for the deposition. Fig. 4 shows a preliminary result of the deposition using the H2–CH4–CO2 gas mixture. Cubic shape of diamond grains were grown (a;1) on the Si substrate under the condition of (CH4qCO2)y(H2qCH4 qCO2 )s1%, CO2 yCH4s 0.17, and Ts;1270 K. The a parameter was reduced by adding CO2. Fig. 4b shows a fractured cross section of the diamond film deposited with the condition of a;1 on the N100M-textured diamond film of a pyramidal shape surface. Based on these results, growth orientation and film morphology were manipulated. For example, when the condition range was CH4 y(CH4qH2)s2%, 60 kW microwave input, 14.0–17.7 kPa (105–133 torr), and 1170–1280 K (900–1010 8C), the grown diamond grains have a pyramidal shape surface and a N100Mtexture almost uniformly on the entire surface of 51(Fig. 5a), 25- (Fig. 5d) and 152- (Fig. 5e) mm substrates. The surface appears like black velvet to the naked eye; lusterless to the normal direction to the substrate, but glossy to the oblique angle. This is due to the facets having almost the same angle ;54.78 to the substrate plane. The films shown in Fig. 5b,c are non-textured. SEM images of the 152-mmf diamond films at the center (f), the intermediate (g), and the edge (h) are also shown. The used 152-mmf substrates were polycrystalline so that the orientation behavior is independent of substrate. Fig. 4. Diamond grains deposited at the growth condition of a;1 on Si substrate (a) and a fractured cross section of the diamond film deposited with the condition of a;1 on a N100M-textured diamond film (b).
4. Conclusion In order to control the morphology of large area diamond films, diamond deposition using a 60-kW
Fig. 5. Photograph of the diamond films deposited on 51 (a,b), 25 (c,d), and 152 (e) mm diameter substrate. SEM images of the 152-mmf diamond films at the center (f), the intermediate (g), and the edge (h) are also shown.
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microwave plasma CVD system and characterization with SEM, XRD, and Raman have been carried out. The 60-kW CVD system shows the growth rate of 7 mmyh and a conversion efficiency of excess 10% from CH4 to diamond. The contour of the a parameter shifts toward the higher substrate temperature and the lower CH4 concentration as compared with the results of the smaller CVD systems. It was also found that the parameter range of diamond growth by the 60-kW reactor is broader than that of the conventional CVD systems. Furthermore, N100M-textured diamond films with pyramidal shape surface were successfully grown almost uniformly on the entire surface of a 152-mmf Si substrate by choosing an appropriate process condition. Acknowledgments This work was supported by the FCT Project, which was consigned to JFCC by NEDO.
References w1x L.S. Pan, D.R. Kania, Diamond: Electronic Properties and Applications, Kluwer Academic, Boston, 1995. w2x M. Kamo, et al., United States Patent 4434188 (1984). w3x H.A. Naseem, W.D. Brown, et al., Thin Solid Films 308–309 (1997) 141. w4x V. Ralchenko, I. Sychov, I. Vlasov, et al., Diamond Relat. Mater. 8 (1999) 189. w5x S. Schelz, C. Campillo, M. Moisan, Diamond Relat. Mater. 7 (1998) 1675. w6x E. Sevillano, B.E. Williams, Diamond Films Tech. 8 (1998) 73. w7x M. Funer, ¨ C. Wild, P. Koidl, Appl. Phys. Lett. 72 (1998) 1149. w8x T. Tachibana, Y. Ando, A. Watanabe, Y. Nishibayashi, K. Kobashi T. Hirao, K. Oura, Diamond Relat. Mater., to be published as a special issue of Proc. 7th Intl. Conf. New Diamond Sci. Tech., Hong Kong, July 2000. w9x P. Koidl, C. Wild, N. Herres, Proc. NIRIM Intern. Symp. on Advanced Materials ’94, 13–17 March 1994, Tsukuba (Japan), 1994, p. 1. w10x A. Gicquel, F. Silva, K. Hassouni, J. Electrochem. Soc. 147 (6) (2000) 2218. w11x A. Van der Drift, Philips Res. Rep. 22 (1967) 267. w12x Y. Ando, T. Tachibana, K. Kobashi, Diamond Relat. Mater. 10 (2001) 312.