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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/224342986 High-Efficiency PFC Abatement System Utilizing Plasma Decomposition and Ca(OH) /CaO Immobilization Article in IEEE Transactions on Semiconductor Manufacturing December 2008 DOI: 10.1109/TSM.2008.2005400 Source: IEEE Xplore CITATIONS 6 9 authors, including: Katsumasa Suzuki Taiyo Nippon Sanso Corporation 15 PUBLICATIONS 28 CITATIONS SEE PROFILE READS 1,167 Akinobu Teramoto Hiroshima University 512 PUBLICATIONS 3,161 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Chemical Reaction Clarification View project Development of Laser Absorption Spectroscopy View project All content following this page was uploaded by Akinobu Teramoto on 31 May 2014. The user has requested enhancement of the downloaded file. 668 IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING, VOL. 21, NO. 4, NOVEMBER 2008 High-Efficiency PFC Abatement System Utilizing Plasma Decomposition and Ca(OH)7/CaO Immobilization Katsumasa Suzuki, Yoshio Ishihara, Member, IEEE, Kaoru Sakoda, Yasuyuki Shirai, Akinobu Teramoto, Member IEEE, Masaki Hirayama, Tadahiro Ohmi, Fellow, IEEE, Takayuki Watanabe, and Takashi Ito, Senior Member IEEE Abstract--In order to minimize contributions to global warming, it is important to develop a perfiuorocompound (PFC) abatement system that can remove PFCs effectively with low electric power. We have developed a new PFC abatement system consisting mainly of a 2-MHz ICP plasma source and two Ca(OH)2 /CaO columns operated under a decompression pressure. Reactive fluorinated compounds including SiF4 are immobilized in the Ca(OH)2 /CaO columns without a water scrubber. Stable compounds such as CF4 are excited by the 2-MHz ICP plasma. When the emissions from an Si oxidation film etching process chamber were treated by this abatement system, F2 equivalent removal efficiency was 99.6%, which was about one order of magnitude larger than that of a conventional abatement system. But the CO2 equivalent removal efficiency was calculated to be 91.4% because over 95% of CO2 equivalent emissions were caused by the plasma source power consumption of 2.4 kWh. It means that minimization of the plasma source power consumption, depending on PFC emissions, is a very effective method of minimizing contributions to global warming in a manner similar to improving the PFC removal efficiency. Index Terms--Abatement, calcium, plasma. I. INTRODUCTION p ERFLUOROCOMPOUNDS (PFCs) are widely used in semiconductor manufacturing for plasma processes such as dielectric film etching and chemical--vapor deposition (CVD) chamber cleaning. Due to their long atmospheric lifetimes and high global warming potential (GWP), PFCs, such as tetrafluoromethane (CF4), hexafluoroethane (C2F6), octofluoropropane (C3F8), and octofluorocyclobutane (c-C4F8) promote the greenhouse effect. Table I shows GWProo, that is defined as a relative GWP value calculated for the period of 100 years against CO2, and the atmospheric lifetime for typical fluorinated compounds [1]. To prevent further global warming, the semicon- Manuscript received February 20, 2008; revised July 19, 2008. Current ver- sion published November 05, 2008. K. Suzuki is with Taiyo Nippon Sanso Corporation, Tsukuba 300-2611, Japan, and also with the Graduate School of En ineering, Tohoku University, Sendai 980-8579, Japan (e-mail: @tn-sanso.co.jp). Y. Ishihara and K. Sakoda are with Taiyo Nippon Sanso Corporation, Tsukuba 300-2611, Japan. Y. Shirai, A. Teramoto, M. Hirayama, and T. Ohmi are with the New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan. T. Watanabe is with Ube Material Industries, Ltd., Ube 755-8510, Japan. T. Ito is with the Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. Color versions of some of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TSM.2008.2005400 TABLE I GLOBAL WARMING POTENTIAL FOR 100 YEARS (GWP100) AND ATMOSPHERIC LIFETIME FOR FLUORINATED COMPOUNDS CO2 CF4 C2F6 C3F8 c-C4F8 Lifetime (years) 50-200 50,000 10,000 2,600 3,200 GWP100 (100 years horizon ) 1 5,700 11,900 8,600 10,000 ductor industry is committed to reducing the emission of PFCs to 10% below the emission level of 1995 by 2010 [2]. Thus, many developments of PFC emissions reduction have been performed in four general areas: process optimization, alternative chemistries, capture/recovery, and abatement [3]--[14]. On the other hand, the volume of PFCs used in semiconductor manufacturing has been increasing with the growth in production of semiconductor devices. In addition, PFCs do not completely decompose in the plasma process chambers and are generated as byproducts [5], [6]. Particularly, CF4 and SiF4 are generated as the byproducts in etching processes that use CF3 ions and CF2 radicals. They are also generated in the cleaning process for CVD chambers. Therefore, a high efficiency PFC abatement system is necessary for the reconciliation of semiconductor industry growth and global warming prevention. Combustion-type abatement systems [10] and atmospheric pressure plasma resolution-type abatement systems [11], [12] are generally utilized as point-of-use removal equipment. Tonnis et al. [13] and Kuroki et al. [14] reported on PFC abatement systems utilizing an inductively coupled plasma discharged under a decompression pressure. But the PFC removal efficiencies of these systems are about 90%-98% and are not efficient enough to prevent global warming. In addition, since the formation of deposits in the exhaust pipe, corrosion of the exhaust pipe and fluorine acid drainage are likely to occur in these systems, thus frequent maintenance and hazardous material treatments are required. To prevent these problems, a large amount of purge gas is required and, as a result, a large amount of energy is required to decompose the PFCs and the purge gases. The focus of this paper is to develop a safe PFC abatement system that has minimal environmental impact and, at the same 0894-6507/$25.00 2008 IEEE Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. SUZUKI et al.: HIGH-EFFICIENCY PFC ABATEMENT SYSTEM UTILIZING PLASMA DECOMPOSITION 669 time, improves productivity. This paper describes the distinguishing features and performance of a newly developed PFC abatement system. The experimental results show that the PFC abatement system can treat the emissions exhausted from a Si oxidation film etching process chamber. The removal efficiency is discussed on the basis of CO equivalent emissions, which takes into account the plasma source power consumption. II. CONCEPT OF PFC ABATEMENT SYSTEM A. Newly Developed The basic concept of the PFC abatement system is to decompose PFCs with lower plasma source power consumption and immobilize reactive fluorinated compounds by utilizing a solid reactant. To implement this concept, the PFC abatement system was operated under a decompression pressure to introduce fluorinated compounds, that retain their energetic state, into the column filled with newly developed Ca(OH) /CaO as the solid reactant. There are three reasons for utilizing the Ca(OH) /CaO admixture which is made by dehydration of Ca(OH) . One reason is that the resulting product, CaF , is nonhazardous and stable and another reason is that a water scrubber is not required. The latter eliminates the need for fluorine acid drainage treatments. Thus, this abatement system using Ca(OH) /CaO is not only safer than the conventional system but also suitable for semiconductor manufacturing facilities that are limited in water supply. The third reason is explained by the reaction mechanisms Fig. 1. Scanning electron microscopy image of Ca(OH) /CaO. Ca OH COF CaF CO H O (1) CaO H O Ca OH (2) Although Ca(OH) is necessary to react with the fluorinated compound, a significant amount of moisture is generated by the reaction shown by (1). As shown by (2), the generated H O reacts with CaO and generates another Ca(OH) . Thus, H O is used as an intermediate for the fluorination reaction of CaO and only a small amount of moisture is exhausted downstream. A reactant with a high specific surface area should be used to promote the reaction mentioned above because it would raise the collision probability between gases and Ca(OH) /CaO. In addition, the grain diameter should be several millimeters to reduce the pressure loss. Unfortunately, the specific surface area of conventional Ca(OH) /CaO is only 0.1-10 m /g when its grain diameter is 2-6 mm [15]. On the other hand, the newly developed Ca(OH) /CaO has many micropores in the range of 10 to 100 nm as shown in Fig. 1. This structure allows the developed Ca(OH) /CaO to have a specific surface area of 60-70 m /g and a grain diameter of 2-6 mm simultaneously. This means that the specific surface area of the developed Ca(OH) /CaO is about two orders of magnitude larger than that of conventional Ca(OH) /CaO. B. System Configuration Fig. 2 shows a schematic diagram of the PFC abatement system that mainly consists of a 2-MHz ICP plasma source (LG3000, Landmark Technology Corporation), two Fig. 2. Schematic diagram of the newly developed PFC abatement system. Ca(OH) /CaO columns, two conductance control valves, and two dry vacuum pumps. We call the upstream column a presystem and the plasma source and the downstream column a main system. In the presystem, Ca(OH) /CaO in the upstream column immobilizes reactive fluorinated compounds, such as F , HF, COF , and SiF , which are included in emissions exhausted from a process chamber. Deposition caused by SiF and corrosion caused by F and/or HF are efficiently prevented because the pressure between the upstream pump and the presystem is under a decompression pressure range of over several kPa. Thus, the presystem serves to reduce the maintenance frequency of the pipe connected between the main system and the presystem. By the same token, a reduction of the purge gas flow rate introduced into the dry vacuum pump is also possible. Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. 670 IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING, VOL. 21, NO. 4, NOVEMBER 2008 In the main system, stable compounds, such as CF , C F , and C F , which pass through the presystem, are excited by the 2-MHz ICP plasma and are immobilized by Ca(OH) /CaO in the downstream column under a decompression pressure range of several hundred Pa. The gas temperature in the plasma is several hundred K under this operational pressure range and increases when this pressure is increased. Thus, preventive measures against the chamber's thermal fracture are made easier in comparison with atmospheric pressure plasma resolution-type abatement systems. An additional advantage is that the excited compounds can be introduced into the Ca(OH) /CaO column while maintaining their energetic state because the collision frequency between excited compounds is comparatively small under this operation pressure. PFC removal efficiencies can be over 99% because recombination of CF is prevented by this feature. However, it is difficult to utilize Ca(OH) /CaO effectively because the collision frequency between the excited compound and the Ca(OH) /CaO is comparatively small under this operation pressure. It is necessary to utilize the column with a large diameter to decrease the velocity of gases in the column as this measure. In addition, the plasma source power consumption can be lower than that of the atmospheric pressure plasma source because the utilization of the power supply frequency of 2 MHz decreases circuit losses. Since there is a direct correspondence between electric power consumption and CO equivalent emission, this suggests that CO emissions can be decreased by minimizing the electric power consumption. However, because the differential pressure caused by the column is different depending on the amount of Ca(OH) /CaO in the column, it is necessary to control the pressure at the column by using the conductance control valve after exchanging the Ca(OH) /CaO. III. EXPERIMENT The PFC abatement system was built as described in the preceding section. It is imperative that SiF is removed at the presystem to treat the emissions exhausted from an Si oxidation film etching process chamber because SiF decomposition in the plasma source generates SiO . First, the reactivity of Ca(OH) /CaO was evaluated by using SiF since it has a large bond dissociation energy of 6.03 eV and a small free energy of formation of 16.7 eV and is, thereby, one of the least reactive gases. In this experiment, a sample gas of 3vol%SiF /Ar (Ar as balanced gas) was introduced into a Ca(OH) /CaO column and was exhausted out through a conductance control valve by utilizing a dry vacuum pump until SiF was detected with a nondispersive infrared (ND-IR)-type gas monitor. Fig. 3 shows a schematic diagram for this experiment. The pressure in the Ca(OH) /CaO column was maintained at 1.3 kPa. The sample gas passed through the Ca(OH) /CaO column at a velocity of 10.3 cm/s. The lower detection limit for SiF concentration was approximately 1000 parts per million by volume (ppmv) for a minimum signal-to-noise ratio of 3:1 under a pressure of 1.3 kPa. Because SiF reacts with Ca(OH) /CaO at the upstream side of the column, there is a transient zone of reaction in which a gradient in the number of immobilized F atoms is formed as shown in Fig. 4. The horizontal axis and the vertical axis show Fig. 3. Schematic diagram of experiment to evaluate the reactivity of Ca(OH) /CaO. Fig. 4. Schematic diagram of the progress state of the reaction in the Ca(OH) /CaO column. the number of F atoms and the height of column, respectively. As an example, the number of F atoms at a height of H is almost zero at and is F at . Similarly, the number of F atoms at is zero at H H and F at H H . Thus, the height of Ca(OH) /CaO quantity, which is one of the conditions, has no influence on the length of the transient zone of reaction, which is generally called the mass transfer zone (MTZ). Therefore, the utilization efficiency was defined as the ratio of the removed number of F equivalent molecules to Ca atom number in the reaction zone, which is the area outside of MTZ. Next, the PFC removal efficiency of the main system was evaluated by using the CF which could pass through the presystem. Fig. 5 shows a schematic diagram for this experi- ment. The plasma source power consumption was kept constant at 3.6 kWh. The sample gas, a mixture of CF /O /Ar/H was pumped through a plasma source, a Ca(OH) /CaO column, and a conductance control valve by utilizing a dry vacuum pump. The total flow rate, the CF flow rate and the pressure in the plasma source were 1000-1600 cm /min, 50-200 cm /min, and 300 Pa, respectively. When the total flow rate was 1600 cm /min, the sample gas flowed to the Ca(OH) /CaO column from the plasma source within a time of 130 ms and passed through the Ca(OH) /CaO column at a velocity of 17 cm/s. Lastly, the performance of the PFC abatement system shown in Fig. 1 was evaluated by using the emissions exhausted from a Si oxidation film etching process chamber. C F and C F were introduced into the etching chamber as process gases at a Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. SUZUKI et al.: HIGH-EFFICIENCY PFC ABATEMENT SYSTEM UTILIZING PLASMA DECOMPOSITION 671 Fig. 5. Schematic diagram of experiment to evaluate CF removal efficiency of main system. Fig. 6. Specific surface area dependence of reaction efficiency. flow rate of 4 and 18 cm /min, respectively. The plasma source power consumption was 2.4 kWh. The emissions were measured by a Fourier transform infrared (FT-IR) absorption spectrometer which was positioned at the downstream side of the dry vacuum pump. The FT-IR mainly consists of ZeSe cell windows, KBr optics, a 10-cm path length gas cell, and a liquid nitrogen cooled mercury cadmium telluride (MCT) detector. The lower detection limit for CF concentration was approximately 1 ppmv at a minimum signal-tonoise ratio of 3:1. This means that this FT-IR is capable of detecting CF with a flow rate of 0.001 cm /min when the total gas flow rate is 1000 cm /min. Thus, if the initial CF flow rate is 100 cm /min, it is possible to determine a 99.99% removal efficiency. The concentration of each compound was calculated based on the absorption intensities measured at the appropriate wavelength for each compound. The flow rate of each compound was obtained by multiplying the total flow rate by the concentration of each compound. F equivalent removal efficiency, useful as a general figure of merit, was calculated based on the F equivalent flow rate at the inlet and outlet of the PFC abatement system. IV. RESULTS A. SiF Removal by Presystem Fig. 6 shows the Ca utilization efficiency of Ca(OH) /CaO evaluated by using 3vol% SiF /Ar (Ar as balanced gas) under a pressure of 1.3 kPa and a velocity of 10.3 cm/s. The horizontal axis and the vertical axis show the specific surface area of Ca(OH) /CaO and the Ca utilization efficiency, respectively. The Ca utilization efficiency increased proportionally with the specific surface area. As an example, the Ca utilization efficiency was around 16% when the specific surface was 60 m /g. This figure shows that the presystem can remove SiF . Furthermore, it was confirmed that the Ca utilization efficiency could be improved by raising the reaction pressure. When the pressure was 13 kPa, the Ca utilization efficiency of Ca(OH) /CaO, which had a specific surface area of 60 m /g, was around 25%. In addition, it was confirmed that the Ca utilization efficiency could be improved to about 85% by using F Fig. 7. Infrared absorption spectra at the inlet and outlet of the Ca(OH) /CaO column. instead of SiF . This suggests that the Ca utilization efficiency depends strongly on the gas element. B. CF Removal by Main System CF removal efficiency of the main system was evaluated by using a CF /O /Ar/H gas mixture under a plasma source power consumption of 3.6 kWh and a pressure of 300 Pa. The flow rates of CF , O , H , and Ar were 100, 300, 150, and 450 cm /min, respectively. Fig. 7 shows the infrared absorption spectra measured by FT-IR at the inlet and outlet of the Ca(OH) /CaO column. The horizontal axis and the vertical axis show the wave number and the absorption intensity, respectively. COF , CO , and HF were detected only at the inlet as byproducts. In other words, this figure shows that only CF among the fluorinated compounds passed through the Ca(OH) /CaO column. Fig. 8 shows the CF removal efficiency of the main system. The plasma source power consumption and the pressure were 3.6 kWh and 300 Pa, respectively. The CF flow rate was 50-200 cm /min, and the O and H flow rates were both three times larger than the CF flow rate. Ar was added to make the total flow rate 1600 cm /min. The horizontal axis and the vertical axis show the initial CF flow rate and the CF emissions, respectively. The CF emissions increased with increasing initial CF flow rate. Dotted lines in this figure show a removal efficiency of 99.9% or 99.99%. In the range where the initial CF flow rate was less than 200 cm /min, the removal efficiency was over 99.9%. Furthermore, when the Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. 672 IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING, VOL. 21, NO. 4, NOVEMBER 2008 Fig. 8. CF removal efficiency of the main system. The CF flow rate was 50-200 cm /min. Fig. 10. CO equivalent emissions at the inlet and outlet of the Ca(OH) /CaO column. The flow rate of CF , O , H , and Ar were 200, 600, 600, and 400 cm /min, respectively. Plasma source power consumption was 3.6 kWh. Fig. 9. Infrared absorption spectra at the inlet and outlet of the abatement system. initial CF flow rate was less than 100 cm /min, the removal efficiency was over 99.99%. C. Performance of PFC Abatement System Fig. 9 shows the infrared absorption spectra measured by FT-IR at the inlet and outlet of the PFC abatement system positioned at the exhaust line of an Si oxidation film etching process chamber. The horizontal axis and the vertical axis show the wave number and the absorption intensity, respectively. With the exception of CO and CF , most compounds, such as COF , C F , C F , CHF , and SiF , were detected only at the inlet side. In other words, this figure shows that all fluorinated compounds except for CF were removed by the PFC abatement system. The PFC removal efficiency of the PFC abatement system was evaluated by comparison of the total amount of detected compounds. The average flow rates of F equivalent emissions at the inlet and outlet of the PFC abatement system were calculated to be 46.84 and 0.17 cm /min, respectively. The removal efficiency based on the F equivalent emissions was calculated to be 99.6%, which is about one order of magnitude larger than that of a conventional abatement system. As mentioned above, this system does not use water for C-F species stabilization and does not emit H O. This means that the water scrubber to treat the hydrogen fluoride drainage could be eliminated. V. DISCUSSION In order to view this problem from the perspective of global warming prevention, the removal efficiency should be described using CO equivalent emissions. In this case, CO equivalent emissions are calculated based on the sum of each compound's emission origin and the electric power consumption origin. The former is given by multiplying the flow rate of each compound by each GWP . The latter is given by multiplying the electric power consumption by the CO equivalent factor of 0.368 kg-CO /kW, when electricity supplied by Tokyo Electric Corporation is used [16]. The CO equivalent factor is equal to a one-hour average of a CO equivalent flow rate of 3.12 L/min. For example, Hattori et al. showed that a plasma source power consumption of 5.9 kWh was needed to decompose CF at 96.5% removal efficiency by utilizing the atmospheric pressure plasma abatement system [11]. Because the plasma source power consumption of 5.9 kWh was calculated to have a CO equivalent flow rate of 18.41 L/min, reducing electric power consumption is as important as reducing PFC emissions. At first, the CO equivalent removal efficiency of the main system was evaluated in the case where the initial CF flow rate was 200 cm /min, which is shown in Fig. 8. Fig. 10 shows the calculation result of the CO equivalent emissions at the inlet and outlet of Ca(OH) /CaO column. Because the only greenhouse gas in the emissions was CF , of which GWP was 5700, CO equivalent flow rate of emissions origin at the inlet and outlet of the main system were calculated to be 1140 and 0.57 L/min, respectively. In addition, a CO equivalent flow rate of 11.23 L/min, which was derived from the plasma source power consumption of 3.6 kWh, was added to that of the outlet. Thus, the average flow rates of CO equivalent emissions at the inlet and outlet of the PFC abatement system were calculated to be 1140 and 11.80 L/min, respectively. Based on this, the CO equivalent removal efficiency was calculated to be 99.0%. Next, the CO removal efficiency of the PFC abatement system was evaluated for the case shown in Fig. 9. Fig. 11 shows the calculation result of the CO equivalent emissions at the inlet and outlet of the PFC abatement system. CO equivalent flow rate of emissions origin at the inlet and outlet of the PFC abatement system were calculated to be 89.16 and Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. SUZUKI et al.: HIGH-EFFICIENCY PFC ABATEMENT SYSTEM UTILIZING PLASMA DECOMPOSITION 673 This PFC abatement system can treat the emissions exhausted from an Si oxidation film etching process chamber without a water scrubber and provides a way to have minimal environmental impact and, at the same time, improve productivity. Fig. 11. CO equivalent emissions at the inlet and outlet of the abatement system. C F and C F were introduced into the process chamber at a flow rate of 4 and 18 cm /min, respectively. Plasma source power consumption was 2.4 kWh. 0.17 L/min, respectively. In addition, the CO equivalent flow rate of 7.49 L/min, which was derived from the plasma source power consumption of 2.4 kWh, was added to that of the outlet. Thus, the average flow rates of CO equivalent emissions at the inlet and outlet of the PFC abatement system were calculated to be 89.16 and 7.66 L/min, respectively. Based on this, the CO equivalent removal efficiency was calculated to be 91.4%. These results show that the ratio of the plasma source power consumption origin in CO equivalent flow rate is more than 95% in both cases and the ratio in the case of Fig. 9 is comparatively larger. It means that minimization of the plasma source power consumption, depending on PFC emissions, is a very effective means for minimizing contributions to global warming in a manner similar to improving the PFCs removal efficiency. In other words, the development of a more efficient plasma source is very important for the resolution of this problem. VI. CONCLUSION We have developed a PFC abatement system consisting mainly of a 2-MHz ICP plasma source and two Ca(OH) /CaO columns and is operated under a decompression pressure. The presystem immobilizes reactive fluorinated compounds, which include SiF , by utilizing a Ca(OH) /CaO reactant with a specific surface area of 60 m /g in the upstream column and reduces the frequency of exhaust pipe maintenance required. The main system, that excites stable compounds which pass through the presystem by utilizing a 2-MHz ICP plasma and immobilizes these excited compounds by Ca(OH) /CaO in the downstream column, could remove CF with F equivalent removal efficiency of over 99.9%, which was one order of magnitude larger than that of a conventional system. When the emissions exhausted from an Si oxidation film etching process chamber were treated by this PFC abatement system, the F equivalent removal efficiency and the CO equivalent removal efficiency were 99.6% and 91.4%, respectively. The discrepancy between the two efficiencies was attributed to the fact that over 95% of CO equivalent emissions were caused by the plasma source power consumption of 2.4 kWh. REFERENCES [1] J. T. Houghton, Y. Ding, D. J. Griggs, M. Noguer, P. J. Van Der Linden, X. Dai, K. Maskell, and C. A. Johnson, Climate Change 2001: The Scientific Basis Cambridge Univ., , Cambridge, Rep. of IPCC, 2001, p. 47, Contribution of Working Group 1 to the Third Assess. [2] International Technology Roadmap for Semiconductors 1999, p. 248. [3] L. Beu, P. T. Brown, J. Latte, J. U. Rapp, T. Gilliland, T. Tamayo, J. Harrison, J. Davison, A. Cheng, J. Jewett, and W. Worth, "Perfluorocompound (PFC) emissions reduction," Int. SEMATECH Technology Transfer #98053508A-TR, 1998. [4] L. Beu and P. T. Brown, "Motorola's strategy for reducing PFC emissions," in Proc. Electron. Manuf. Technol. Symp., 1998, pp. 277-285. [5] I. Namose, "Optimization of gas utilization in plasma processes," in Proc. 2002 Int. Symp. Semiconductor Manufacturing, Tokyo, Japan, 2002, pp. 261-264. [6] E. M. Chan, G. Loh, and C. C. Allgood, "Process optimization and PFC emission reduction using a c-C F chamber cleaning process on a novellus concept 1 dielectric PECVD tool," IEEE Trans. Semicond. Manuf., vol. 17, no. 4, pp. 497-503, Nov. 2004. [7] S. Nakamura, M. Itano, H. Aoyama, K. Shibahara, S. Yokoyama, and M. Hirose, "Comparative studies of perfluorocarbon alternative gas plasmas for contact hole etch," Jpn. J. Appl. Phys., vol. 42, no. 9A, pp. 5759-5764, Sept. 2003. [8] Y. Tajima, T. Futatsuki, T. Abe, and S. Tazawa, "PFC recycling system by continuous gas chromatography," IEEE Trans. Semicond. Manuf., vol. 18, no. 4, pp. 495-500, Nov. 2005. [9] V. Vartanian, L. Beu, T. Stephens, J. Rivers, B. Perez, E. Tonnis, M. Kiehlbauch, and D. Graves, "Long-term evaluation of the litmas "blue" plasma device for point-of-use (POU) perfluorocompound and hydrofluorocarbon abatement," Int. SEMATECH Technology Transfer #99123865B-ENG, 2000. [10] W. Worth, T. A. Tamayo, P. E. , and R. F. Cambio, "Analysis of data for perfluorocompound (PFC) emission control systems," Int. SEMATECH Technology Transfer #95062847A-ENG, 1995. [11] K. Hattori, K. Sakurai, N. Watanabe, H. Mangyou, S. Hasaka, and K. Shibuya, "Application of atmospheric plasma abatement system for exhausted gas from MEMS etching process," in Proc. 2006 Int. Symp. Semiconductor Manufacturing, Tokyo, Japan, 2006, pp. 39-42. [12] M. T. Radoiu, "Studies on atmospheric plasma abatement of PFCs," Radiation Physics and Chemistry, vol. 69, no. 2, pp. 113-120, Feb. 2004. [13] E. J. Tonnis and D. B. Graves, "Inductively coupled, point-of-use plasma abatement of perfluorinated compounds and hydrofluorinated compounds from etch processes utilizing O and H O as additive gases," J. Vac. Sci. Technol., vol. A18, no. 2, pp. 393-400, Mar./Apr. 2000. [14] T. Kuroki, J. Mine, M. Okubo, T. Yamamoto, and N. Saeki, "CF decomposition using inductively coupled plasma: Effect of power frequency," IEEE Trans. Ind. Appl., vol. 41, no. 1, pp. 215-220, Jan./Feb. 2005. [15] K. Kawabata, H. Yoshimatsu, K. Suzuki, A. Osaka, Y. Miura, and H. Kawasaki, "CO fixation by Ca(OH) at high temperature," J. Ceram. Soc. Jpn., vol. 102, no. 12, pp. 1173-1176, Dec. 1994. [16] "Ministry of the environment Japan.," Manual for Calculating and Reporting the Amount of Greenhouse Gas Emissions 2006, pp. 1125-1126 [Online]. Available: http://www.env.go.jp/earth/ghg-santeikohyo/manual/index.html, Available Katsumasa Suzuki was born in Osaka, Japan, in 1972. He received the B.S. and M.S. degrees in mechanical engineering from Osaka Prefecture University, Osaka, Japan, in 1995 and 1997, respectively. He is currently working toward the Ph.D. degree at Tohoku University. In 1997, he joined Nippon Sanso Corporation (present-day Taiyo Nippon Sanso Corporation), Tsukuba, Japan, and has been with the Leading Edge Technology Development Department, where he has engaged in the research and development of analytical absorption spectroscopy and PFC abatement system. Mr. Suzuki is a member of the Japan Society of Applied Physics. Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. 674 IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING, VOL. 21, NO. 4, NOVEMBER 2008 Yoshio Ishihara (M'99) was born on June 4, 1959. He received the B.E. degree in chemical engineering from Niigata University, Niigata, Japan, in 1982, and the Ph.D. degree in electronics from Tohoku Univer- sity, Sendai, Japan, in 1995. In 1982, he joined Kawasaki Laboratories, Nippon Sanso Corporation, Kawasaki, Japan, where he worked on the development of the high purity gas delivery system for semiconductor manufacturing. From 1987 to 1989, he was a Visiting Researcher on the Faculty of Engineering of Tohoku University, where he was engaged in the research of ion implantation technology for low temperature processes of ULSI manufacturing. In 1989, he worked on the development of the ultra-high vacuum technology and research of ultra clean gas supply system at the Kawasaki Laboratories, Nippon Sanso Corporation, Kawasaki. From 1998 to 2003, he was a Research Manager at the Tsukuba Laboratories, Nippon Sanso Corporation. He did research as the Manager of the new wafer processes and ultra clean technology for next-generation devices, particularly in situ monitoring and analysis of trace impurities in processes and surface cleanliness control technology. In 2003, he was a Technology Manager at the Marketing Department, Electronics Division, Nippon Sanso Corporation, Tsukuba, Japan. In 2004, due to annexation with Taiyo Toyo Sanso Corporation, he became a Technology Marketing General Manager at the Marketing Department, Electronics, Taiyo Nippon Sanso Corporation. His current research interests include recycling and reuse technology of rare gases for high density and low electron temperature plasma processing and the new gas technology for advanced wafer processing of Si semiconductors. He has over 70 scientific publications and over 70 patents. Dr. Ishihara serves as a member of the editorial committee of the Vacuum Society of Japan, a member of the gas facility committee of the SEMI, and a member of the technology road-map committee of the SEAJ (Semiconductor Equipment Association of Japan). He is a member of the Japan Society of Ap- plied Physics, Institute of Electronics, Information and Communication Engineers of Japan, Vacuum Society of Japan, Japan Association of Aerosol Science and Technology, and the Electrochemical Society. Akinobu Teramoto (M'02) received the B.S. and M.S. degrees in electronic engineering, in 1990 and 1992, respectively, and the Ph.D. degree in electrical engineering, in 2001, all from Tohoku University, Sendai, Japan. From 1992 to 2002, he worked for Mitsubishi Electric Corporation, Hyogo, Japan, where he has been engaged in the research and development of thin silicon dioxide films. In 2002, he moved to Tohoku University and he is presently an Associate Professor at the New Industry Creation Hatchery Center, Tohoku University. He is currently engaged in an advanced semiconductor device technologies and process technologies, such as SOI MOS transistors, accumulation-mode transistors, variation and noise of transistors, high-quality low-temperature oxidation, nitridation, and chemical-vapor deposition processes using microwave-exited high-density plasma. Dr. Teramoto is a member of the Electrochemical Society, the Institute of Electronics, Information and Communication Engineers of Japan, and the Japan Society of Applied Physics. Masaki Hirayama received the B.S., M.S., and Ph.D. degrees in electrical engineering from Tohoku University, Sendai, Japan, in 1991, 1993, and 1997, respectively. From 1997 to 2001, he was a Research Associate in the Department of Electronics, Faculty of Engineering, Tohoku University. Since 2002, he has been with the New Industry Creation Hatchery Center (NICHe), Tohoku University, where he is an Assistant Professor. His current research interests include design of microwave-excited plasma process equipments for semiconductor and flat-panel display manufacturing, plasma diagnostics, and advanced plasma processing. Kaoru Sakoda was born in Osaka, Japan, in 1962. He received the B.S. degree in industrial chemical engineering from Doshisha University, Kyoto, Japan, in 1986. In 1986, he joined Taiyo Sanso Corporation (present-day Taiyo Nippon Sanso Corporation), Osaka, and has been with the Leading Edge Technology Development Department, Tsukuba, Japan. He worked on the development of the purifiers of sulfuric acid and hydrogen peroxide, and the development of a fluorine generator. Yasuyuki Shirai received the Ph.D. degree in electronic engineering from Tohoku University, Sendai, Japan, in 1998. From 1992 to 2006, he worked for Fujikin Incorporated, Osaka, Japan. In 2006, he moved to Tohoku University and he is presently an Associate Professor at the New Industry Creation Hatchery Center, Tohoku University. He has been engaged in an ultra clean gas distribution system and gas exhaust system. Tadahiro Ohmi (M'81-SM'01-F'03) received the B.S., M.S., and Ph.D. degrees in electrical engineering from Tokyo Institute of Technology, Tokyo, Japan, in 1961, 1963, and 1966, respectively. Prior to 1972, he served as a Research Associate in the Department of Electronics, Tokyo Institute of Technology, where he worked on Gunn diodes such as velocity overshoot phenomena, multivalley diffu- sion and frequency limitation of negative differential mobility due to an electron transfer in the multival- leys, high-field transport in semiconductors such as unified theory of space-charge dynamics in negative differential mobility materials, Bloch-oscillation-induced negative mobility and Bloch oscillators, and dynamics in injection lasers. In 1972, he moved to Tohoku University, Sendai, Japan, where he is currently a Professor at the New Industry Creation Hatchery Center. He is currently engaged in research on high-performance ULSI such as ultrahigh-speed ULSI based on gas-isolated-interconnect metal-substrate SOI technology, base store image sensor (BASIS) and high-speed flat-panel display, and advanced semiconductor process technologies such as low kinetic-energy particle bombardment processes including high-quality oxidation, high-quality metallization, very-low-temperature Si epitaxy, and crystallinity-controlled film growth technologies from single-crystal, grain-size-controlled polysilicon and amorphous highly selective CVD, highly selective RIE, and high-quality ion implantation with low-temperature annealing capability based on the ultraclean technology concept supported by newly developed ultraclean gas supply system, ultrahigh vacuum-compatible reaction chamber with self-cleaning function, and ultraclean wafer surface cleaning technology. His research activities are summarized by the publication of over 800 original papers and the application of 800 patents. Dr. Ohmi serves as the President of the Institute of Basic Semiconductor Technology-Development (Ultra Clean Society). He is a Fellow of the Insti- tute of Electricity, Information and Communication Engineers of Japan. He is a member of the Institute of Electronics of Japan, the Japan Society of Applied Physics, and the Electrochemical Society. He received the Ichimura Award in 1979, the Inoue Harushige Award, in 1989, the Ichimura Prizes in Industry-Mer- itorious Achievement Prize, in 1990, the Okouchi Memorial Technology Prize, in 1991, the Minister of State for Science and Technology Award for the Promotion of Invention (the Invention Prize), in 1993, the IEICE Achievement Authorized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply. SUZUKI et al.: HIGH-EFFICIENCY PFC ABATEMENT SYSTEM UTILIZING PLASMA DECOMPOSITION 675 Award, in 1997, the Okouchi Memorial Technology Prize, in 1999, the Werner Kern Award, in 2001, the ECS Electronics Division Award, the Medal with Purple Ribbon from Government of Japan, and the Best Collaboration Award (the Prime Minister's Award), in 2003. Takayuki Watanabe was born in Kyoto, Japan, in 1967. He received the B.S. and M.S. degrees in resources engineering from Yamaguchi University, Yamaguchi, Japan, in 1989 and 1991, respectively. In 1991, he joined Ube Chemical Industries Corporation (present-day Ube Material Industries Corp.), Ube, Japan, where he worked on the development of high reactivity calcium oxide and magnesium oxide. Takashi Ito (M'04-SM'06) received the B.S., M.S., and Ph.D. degrees in electronics engineering from Tokyo Institute of Technologies, Tokyo, Japan, in 1969, 1971, and 1974, respectively. In 1974, he joined Fujitsu Laboratories Ltd., where he had been engaged in research and development of semiconductor technologies for high-performance LSIs. He was assigned as the Head of the Silicon Technology Laboratory, Fujitsu Laboratories, Ltd., in 2001, and as Chief Scientist and Director of Akiruno Technology Center, Fujitsu, Ltd., in 2003. In 2004, he moved to Tohoku University, Sendai, Japan, as a Professor of the Graduate School of Engineering. Dr. Ito is a member of IEICE, JSPA, and ECS. He received the Teshima, Watanabe, Ohm Technology, Ohkouchi, and Yamazaki Awards in 1975, 1981, 1999, 2000, and 2006, respectively. View publicAatuionthstoatsrized licensed use limited to: TOHOKU UNIVERSITY. Downloaded on March 05,2010 at 00:29:34 EST from IEEE Xplore. Restrictions apply.