- Email: [email protected]
Acetone cluster ion beam irradiation on solid surfaces
Nuclear Instruments and Methods in Physics Research B xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Acetone cluster ion beam irradiation on solid surfaces H. Ryuto ⇑,1, Y. Kakumoto, S. Itozaki, M. Takeuchi, G.H. Takaoka Photonics and Electronics Science and Engineering Center, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
a r t i c l e
i n f o
Article history: Received 27 November 2012 Received in revised form 7 March 2013 Accepted 3 April 2013 Available online xxxx Keywords: Acetone Cluster ion beam Silicon Sputtering
a b s t r a c t Acetone cluster ions were produced by the adiabatic expansion method without using a support gas. The acceleration voltage of the acetone cluster ion beam was from 3 to 9 kV. The sputter depths of silicon irradiated with acetone cluster ion beams increased with acceleration voltage and fluence of the acetone cluster ion beams. The sputter depth was close to that induced by the ethanol cluster ion beam accelerated at the same acceleration voltage. The sputtering yield of silicon by the acetone cluster ion beam at an acceleration voltage of 9 kV was approximately 100 times larger than that for an argon monomer ion beam at 9 keV. The sputter depths of silicon dioxide irradiated with the acetone cluster ion beams were smaller than those of silicon, but larger than those induced by ethanol cluster ion beams. The XPS analysis of silicon surface indicated that the silicon surface was more strongly oxidized by the irradiation of acetone cluster ion beam than ethanol cluster ion beam. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction The densities of integrated circuits have been continuously increasing to improve the performance of semiconductor devices. The radiation damage during the processing of semiconductor substrates are a serious drawback to the production of high density devices. The cluster ion beam technique is one of the newly developed processing techniques which cause less radiation damage. A cluster beam is a flow of aggregates of atoms or molecules bound by intermolecular forces, such as van der Waals force and hydrogen bonding. The characteristic features, such as a high sputtering yield, surface smoothing effect, and low radiation damage, are considered to be caused by the high-density energy deposition and low-energy irradiation effect of cluster ions [1]. Recently, characteristic properties of the irradiation effects of cluster ions composed of polyatomic molecules have been reported [2–4]. The sputtering yield of silicon induced by an ethanol cluster ion was approximately 100 times larger than that by an argon monomer ion [2,3]. The radiation damage caused by the irradiation of an ethanol cluster ion beam was smaller than that by an argon monomer ion beam [2,3]. The silicon surfaces irradiated with water cluster ion beams were oxidized [4]. These irradiation effects were thought to originate in the chemical properties of the molecules which comprise the clusters. According to the molecular dynamics calculations, the local temperature of the solid surface increases by the high-density irradiation effect of clusters [5,6].
⇑ Corresponding author. 1
E-mail address: [email protected] (H. Ryuto). Formerly, H. Akiyoshi.
The high temperature may enhance the chemical interaction between the solid surface and molecules which comprise the clusters. Water, ethanol, and acetone are common solvent in the semiconductor industry, and used for different purposes according to their chemical properties. So far, the irradiation effects of ethanol and water cluster ions on silicon surfaces have been investigated. In this study, acetone cluster ion beams were irradiated on silicon surfaces to investigate the irradiation effects of acetone cluster ions.
2. Experimental procedure Acetone clusters were produced by the adiabatic expansion method [7]. Vaporized acetone was ejected to a vacuum chamber through a supersonic nozzle to form acetone clusters. No support gas was used to produce acetone clusters. Fig. 1 shows a schematic view of the experimental apparatus. The apparatus consists of three vacuum chambers. Acetone clusters were produced at the first vacuum chamber using an acetone cluster source. The acetone cluster source consists of an acetone container and a supersonic nozzle. In the previous study, an O-ring sealed Laval nozzle had been used to produce ethanol clusters [2,3] or water clusters [4]. A metal gasket seal was used for the connection between the acetone container and nozzle to prevent hot acetone vapor from damaging the vacuum seal. Acetone was filled in the acetone container through a thin tube from outside of the vacuum chamber. The acetone was heated to increase vapor pressure using the heater attached on the outer wall of the acetone container. The typical temperature was 93 °C, which corresponds to the acetone vapor pressure of 0.3 MPa. The typical variation of the temperature was approximately ±1 °C, which
0168-583X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2013.04.027
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027
2
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research B xxx (2013) xxx–xxx
acetone
manometer
deflector W filament thermometer acetone container
sample or Faraday cup
skimmer
heater
nozzle
vacuum pump
einzel vacuum lens pump vacuum pump
electrode for retarding voltage
vacuum pump
acceleration electrode
Fig. 1. Schematic view of acetone cluster ion beam apparatus. Fig. 2. Cluster size distribution of acetone cluster ion beam.
corresponds to ±8 kPa variation of vapor pressure. The temperature was measured using a K-type thermocouple inserted into the pipe placed approximately at the center of the acetone container. The temperature of the heater was also measured to avoid overheating of the heater. The pressure of the acetone vapor was monitored using a manometer outside of the vacuum chamber. The vaporized acetone was ejected through the supersonic nozzle to the vacuum chamber. A stainless steel conical nozzle was used. The nozzle diameter was 0.3 mm. The vacuum chamber was evacuated using a Roots pump. The middle of the jet was selected using a skimmer to avoid disintegration of the acetone clusters by shock waves. The acetone clusters were ionized in the second vacuum chamber by the electron impact method. The typical acceleration voltage and current of the electrons were 200 V and 200 mA, respectively. Singly charged cluster ions are assumed in the following discussions. The vacuum pressure of the second vacuum chamber was kept low by the differential pumping method using an additional vacuum chamber placed between the first and second vacuum chambers. The ionized acetone clusters were accelerated with the acceleration voltage typically from 3 to 9 kV. The monomers and small clusters were removed from the beam by the retarding voltage method. The retarding voltage method is based on the phenomenon that the velocity of the nozzle flow is highly uniform, typically within 10% [7,8]. The kinetic energy of acetone clusters calculated on the basis of this phenomenon is 0.32 eV/ molecule. The retarding voltage of 32 V was applied to eliminate monomers and small clusters. The retarding voltage corresponds to the minimum cluster size of 100 molecules. The acetone cluster ion beam was accelerated again after the removal of the monomer and small clusters. The transverse divergence of the beam was suppressed using an einzel lens. The current of the acetone cluster ion beam was measured using a Faraday cup placed in the third vacuum chamber. A voltage of approximately 300 V was applied to the electron suppressor of the Faraday cup. The Faraday cup was attached on a vertical linear motion feedthrough. A target holder was also attached on the linear motion feedthrough. The target was irradiated at the maximum of the beam current distribution. The horizontal position of the beam was fine-tuned using an electrostatic deflector positioned between the einzel lens and target holder. Fig. 2 shows the cluster size distribution of acetone cluster ion beam measured by the time of flight method. A pulse of an acetone cluster ion beam was produced by the electrostatic deflector, on which a high voltage pulse was applied. The time width of the pulse was 1 ls. The beam signal was measured using a Faraday cup with a 10 mm diameter collimator instead of a microchannel plate to measure the cluster size distribution of intense cluster ion beams that was suitable for the
application in the semiconductor industry. The signal from the Faraday cup was measured using a digital oscilloscope. The mode of the cluster size distribution of the acetone cluster ion beam was approximately 1900 molecules. The sputter depths of silicon and silicon dioxide surfaces induced by the irradiation of acetone cluster ion beams were measured by irradiating acetone cluster ion beams on silicon and silicon dioxide surfaces masked with a stainless-steel mesh and measuring the depths using a step profiler, Ambios Technology XP-2. The typical uncertainty in the sputter depth was approximately ±8%. The X-ray photoelectron spectrometry (XPS) was performed using Shimadzu AXIS-165. 3. Results and discussion Fig. 3 shows the acceleration voltage dependence of the sputter depths of silicon (squares) and silicon dioxide (circles) induced by the irradiation of acetone cluster ion beams. The fluence (U) of the acetone cluster ion beam was 1 1015 ions/cm2. The sputter depth of silicon approximately linearly increased with acceleration voltage. The sputter depths were close to the sputter depths induced by ethanol cluster ion beams, which were accelerated at the same acceleration voltages and irradiated with the same fluence [3]. The
Fig. 3. Acceleration voltage dependence of sputter depths of silicon and silicon dioxide induced by acetone cluster ion beams.
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research B xxx (2013) xxx–xxx
Fig. 4. Fluence dependence of sputter depths of silicon and silicon dioxide induced by acetone cluster ion beams.
sputtering yield of silicon measured at an acceleration voltage of 9 kV was approximately 100 times larger than that for an argon monomer ion beam at 9 keV [9]. The sputter depths of silicon dioxide also increased with acceleration voltage, but systematically smaller than those of silicon. Moreover, the sputter depths of silicon dioxide induced by acetone cluster ion beams were a few times larger than those induced by ethanol cluster ion beams. Therefore, it can be said that an ethanol cluster ion beam is more effective in selective sputtering between silicon and silicon dioxide than an acetone cluster ion beam in the range of the acceleration voltage from 3 to 9 kV.
Intensity (arb. unit)
(a)
3
Fig. 4 shows the fluence dependence of the sputter depths of silicon (squares) and silicon dioxide (circles) induced by the irradiation of acetone cluster ion beams. The acceleration voltage of the acetone cluster ion beam was 9 kV. The sputter depth of silicon approximately linearly increased with fluence of the acetone cluster ion beam. The sputter depth of silicon dioxide also increased with fluence. The sputter depths of silicon dioxide were also systematically smaller than those of silicon. Fig. 5 shows the Si 2p XPS spectra of (a) the silicon surface without irradiation and (b) the silicon surface irradiated with an acetone cluster ion beam. The acceleration voltage and fluence of the acetone cluster ion beam were 9 kV and 1 1015 ions/cm2, respectively. The silicon surface was oxidized by the irradiation of the acetone cluster ion beam [10–12]. The contribution of silicon carbide may be possible [13], but no clear peak of silicon carbide was observed in the C 1s XPS spectrum of the silicon surface irradiated with the acetone cluster ion beam. The silicon surface was more strongly oxidized by the irradiation of the acetone cluster ion beam than ethanol cluster ion beam [3]. The smallness of the thickness of the oxidized layer formed by the irradiation of an ethanol cluster ion beam was attributed to the high sputtering yield. The strong oxidation effects together with the high sputtering yield may be the characteristic property of the interaction between an acetone cluster ion beam and silicon surface. 4. Conclusion Acetone cluster ion beams were produced by the adiabatic expansion method without using a support gas. The sputter depths of silicon and silicon dioxide increased with the acceleration voltage and fluence of the acetone cluster ion beam. The sputter depth of silicon induced by the acetone cluster ion beam was close to that induced by the ethanol cluster ion beam accelerated at the same acceleration voltage. The sputter depths of silicon dioxide induced by the acetone cluster ions were systematically smaller than those of silicon. The sputter depths of silicon dioxide were larger than those induced by ethanol cluster ion beams, so an ethanol cluster ion beam may be more effective in selective sputtering between silicon and silicon dioxide. The silicon surface was oxidized by the irradiation of an acetone cluster ion beam. The strong oxidation effects together with the high sputtering yield may be the characteristic property of the acetone cluster ion irradiation.
Unirradiated Acknowledgement
Binding energy (eV)
(b)
A part of this work was conducted in Kyoto-Advanced Nanotechnology Network, supported by ‘‘Nanotechnology Network’’ of the Ministry of Education, Culture, Sports, Science and Technology, Japan. The present work was supported in part by JSPS KAKENHI Grant No. 22560329.
Intensity (arb. unit)
References Va=9 kV Φ=1x1015 ions/cm2
Binding energy (eV)
[1] I. Yamada, Nucl. Instrum. Meth. B 148 (1999) 1. [2] H. Ryuto, K. Sugiyama, R. Ozaki, G.H. Takaoka, Appl. Phys. Express 2 (2009) 016504. [3] H. Ryuto, R. Ozaki, H. Mukai, G.H. Takaoka, Vacuum 84 (2010) 1419. [4] H. Ryuto, K. Tada, G.H. Takaoka, Vacuum 84 (2010) 501. [5] C.L. Cleveland, U. Landman, Science 257 (1992) 355. [6] H.-P. Chen, U. Landman, Science 260 (1993) 1304. [7] O.F. Hagena, W. Obert, J. Chem. Phys. 56 (1972) 1793. [8] O.F. Hagena, K. Varma, Rev. Sci. Instrum. 39 (1968) 47. [9] H.H. Anderson, H.L. Bay, in: R. Behrisch (Ed.), Sputtering by Particle Bombardment I, Springer-Verlag, Berlin, 1981, p. 145. [10] Shimadzu, ESCA data table C144-3031. [11] G. Hollinger, F.J. Himpsel, Appl. Phys. Lett. 44 (1984) 93. [12] O. Benkherourou, J.P. Deville, J. Vac. Sci. Technol., A 6 (1988) 3125. [13] A.R. Chourasia, Surf. Sci. Spectra 8 (2001) 45.
Fig. 5. Si 2p XPS spectra of (a) silicon surface without irradiation and (b) silicon surface irradiated with acetone cluster ion beam.
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027
Contents lists available at SciVerse ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Acetone cluster ion beam irradiation on solid surfaces H. Ryuto ⇑,1, Y. Kakumoto, S. Itozaki, M. Takeuchi, G.H. Takaoka Photonics and Electronics Science and Engineering Center, Kyoto University, Nishikyo, Kyoto 615-8510, Japan
a r t i c l e
i n f o
Article history: Received 27 November 2012 Received in revised form 7 March 2013 Accepted 3 April 2013 Available online xxxx Keywords: Acetone Cluster ion beam Silicon Sputtering
a b s t r a c t Acetone cluster ions were produced by the adiabatic expansion method without using a support gas. The acceleration voltage of the acetone cluster ion beam was from 3 to 9 kV. The sputter depths of silicon irradiated with acetone cluster ion beams increased with acceleration voltage and fluence of the acetone cluster ion beams. The sputter depth was close to that induced by the ethanol cluster ion beam accelerated at the same acceleration voltage. The sputtering yield of silicon by the acetone cluster ion beam at an acceleration voltage of 9 kV was approximately 100 times larger than that for an argon monomer ion beam at 9 keV. The sputter depths of silicon dioxide irradiated with the acetone cluster ion beams were smaller than those of silicon, but larger than those induced by ethanol cluster ion beams. The XPS analysis of silicon surface indicated that the silicon surface was more strongly oxidized by the irradiation of acetone cluster ion beam than ethanol cluster ion beam. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction The densities of integrated circuits have been continuously increasing to improve the performance of semiconductor devices. The radiation damage during the processing of semiconductor substrates are a serious drawback to the production of high density devices. The cluster ion beam technique is one of the newly developed processing techniques which cause less radiation damage. A cluster beam is a flow of aggregates of atoms or molecules bound by intermolecular forces, such as van der Waals force and hydrogen bonding. The characteristic features, such as a high sputtering yield, surface smoothing effect, and low radiation damage, are considered to be caused by the high-density energy deposition and low-energy irradiation effect of cluster ions [1]. Recently, characteristic properties of the irradiation effects of cluster ions composed of polyatomic molecules have been reported [2–4]. The sputtering yield of silicon induced by an ethanol cluster ion was approximately 100 times larger than that by an argon monomer ion [2,3]. The radiation damage caused by the irradiation of an ethanol cluster ion beam was smaller than that by an argon monomer ion beam [2,3]. The silicon surfaces irradiated with water cluster ion beams were oxidized [4]. These irradiation effects were thought to originate in the chemical properties of the molecules which comprise the clusters. According to the molecular dynamics calculations, the local temperature of the solid surface increases by the high-density irradiation effect of clusters [5,6].
⇑ Corresponding author. 1
E-mail address: [email protected] (H. Ryuto). Formerly, H. Akiyoshi.
The high temperature may enhance the chemical interaction between the solid surface and molecules which comprise the clusters. Water, ethanol, and acetone are common solvent in the semiconductor industry, and used for different purposes according to their chemical properties. So far, the irradiation effects of ethanol and water cluster ions on silicon surfaces have been investigated. In this study, acetone cluster ion beams were irradiated on silicon surfaces to investigate the irradiation effects of acetone cluster ions.
2. Experimental procedure Acetone clusters were produced by the adiabatic expansion method [7]. Vaporized acetone was ejected to a vacuum chamber through a supersonic nozzle to form acetone clusters. No support gas was used to produce acetone clusters. Fig. 1 shows a schematic view of the experimental apparatus. The apparatus consists of three vacuum chambers. Acetone clusters were produced at the first vacuum chamber using an acetone cluster source. The acetone cluster source consists of an acetone container and a supersonic nozzle. In the previous study, an O-ring sealed Laval nozzle had been used to produce ethanol clusters [2,3] or water clusters [4]. A metal gasket seal was used for the connection between the acetone container and nozzle to prevent hot acetone vapor from damaging the vacuum seal. Acetone was filled in the acetone container through a thin tube from outside of the vacuum chamber. The acetone was heated to increase vapor pressure using the heater attached on the outer wall of the acetone container. The typical temperature was 93 °C, which corresponds to the acetone vapor pressure of 0.3 MPa. The typical variation of the temperature was approximately ±1 °C, which
0168-583X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2013.04.027
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027
2
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research B xxx (2013) xxx–xxx
acetone
manometer
deflector W filament thermometer acetone container
sample or Faraday cup
skimmer
heater
nozzle
vacuum pump
einzel vacuum lens pump vacuum pump
electrode for retarding voltage
vacuum pump
acceleration electrode
Fig. 1. Schematic view of acetone cluster ion beam apparatus. Fig. 2. Cluster size distribution of acetone cluster ion beam.
corresponds to ±8 kPa variation of vapor pressure. The temperature was measured using a K-type thermocouple inserted into the pipe placed approximately at the center of the acetone container. The temperature of the heater was also measured to avoid overheating of the heater. The pressure of the acetone vapor was monitored using a manometer outside of the vacuum chamber. The vaporized acetone was ejected through the supersonic nozzle to the vacuum chamber. A stainless steel conical nozzle was used. The nozzle diameter was 0.3 mm. The vacuum chamber was evacuated using a Roots pump. The middle of the jet was selected using a skimmer to avoid disintegration of the acetone clusters by shock waves. The acetone clusters were ionized in the second vacuum chamber by the electron impact method. The typical acceleration voltage and current of the electrons were 200 V and 200 mA, respectively. Singly charged cluster ions are assumed in the following discussions. The vacuum pressure of the second vacuum chamber was kept low by the differential pumping method using an additional vacuum chamber placed between the first and second vacuum chambers. The ionized acetone clusters were accelerated with the acceleration voltage typically from 3 to 9 kV. The monomers and small clusters were removed from the beam by the retarding voltage method. The retarding voltage method is based on the phenomenon that the velocity of the nozzle flow is highly uniform, typically within 10% [7,8]. The kinetic energy of acetone clusters calculated on the basis of this phenomenon is 0.32 eV/ molecule. The retarding voltage of 32 V was applied to eliminate monomers and small clusters. The retarding voltage corresponds to the minimum cluster size of 100 molecules. The acetone cluster ion beam was accelerated again after the removal of the monomer and small clusters. The transverse divergence of the beam was suppressed using an einzel lens. The current of the acetone cluster ion beam was measured using a Faraday cup placed in the third vacuum chamber. A voltage of approximately 300 V was applied to the electron suppressor of the Faraday cup. The Faraday cup was attached on a vertical linear motion feedthrough. A target holder was also attached on the linear motion feedthrough. The target was irradiated at the maximum of the beam current distribution. The horizontal position of the beam was fine-tuned using an electrostatic deflector positioned between the einzel lens and target holder. Fig. 2 shows the cluster size distribution of acetone cluster ion beam measured by the time of flight method. A pulse of an acetone cluster ion beam was produced by the electrostatic deflector, on which a high voltage pulse was applied. The time width of the pulse was 1 ls. The beam signal was measured using a Faraday cup with a 10 mm diameter collimator instead of a microchannel plate to measure the cluster size distribution of intense cluster ion beams that was suitable for the
application in the semiconductor industry. The signal from the Faraday cup was measured using a digital oscilloscope. The mode of the cluster size distribution of the acetone cluster ion beam was approximately 1900 molecules. The sputter depths of silicon and silicon dioxide surfaces induced by the irradiation of acetone cluster ion beams were measured by irradiating acetone cluster ion beams on silicon and silicon dioxide surfaces masked with a stainless-steel mesh and measuring the depths using a step profiler, Ambios Technology XP-2. The typical uncertainty in the sputter depth was approximately ±8%. The X-ray photoelectron spectrometry (XPS) was performed using Shimadzu AXIS-165. 3. Results and discussion Fig. 3 shows the acceleration voltage dependence of the sputter depths of silicon (squares) and silicon dioxide (circles) induced by the irradiation of acetone cluster ion beams. The fluence (U) of the acetone cluster ion beam was 1 1015 ions/cm2. The sputter depth of silicon approximately linearly increased with acceleration voltage. The sputter depths were close to the sputter depths induced by ethanol cluster ion beams, which were accelerated at the same acceleration voltages and irradiated with the same fluence [3]. The
Fig. 3. Acceleration voltage dependence of sputter depths of silicon and silicon dioxide induced by acetone cluster ion beams.
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027
H. Ryuto et al. / Nuclear Instruments and Methods in Physics Research B xxx (2013) xxx–xxx
Fig. 4. Fluence dependence of sputter depths of silicon and silicon dioxide induced by acetone cluster ion beams.
sputtering yield of silicon measured at an acceleration voltage of 9 kV was approximately 100 times larger than that for an argon monomer ion beam at 9 keV [9]. The sputter depths of silicon dioxide also increased with acceleration voltage, but systematically smaller than those of silicon. Moreover, the sputter depths of silicon dioxide induced by acetone cluster ion beams were a few times larger than those induced by ethanol cluster ion beams. Therefore, it can be said that an ethanol cluster ion beam is more effective in selective sputtering between silicon and silicon dioxide than an acetone cluster ion beam in the range of the acceleration voltage from 3 to 9 kV.
Intensity (arb. unit)
(a)
3
Fig. 4 shows the fluence dependence of the sputter depths of silicon (squares) and silicon dioxide (circles) induced by the irradiation of acetone cluster ion beams. The acceleration voltage of the acetone cluster ion beam was 9 kV. The sputter depth of silicon approximately linearly increased with fluence of the acetone cluster ion beam. The sputter depth of silicon dioxide also increased with fluence. The sputter depths of silicon dioxide were also systematically smaller than those of silicon. Fig. 5 shows the Si 2p XPS spectra of (a) the silicon surface without irradiation and (b) the silicon surface irradiated with an acetone cluster ion beam. The acceleration voltage and fluence of the acetone cluster ion beam were 9 kV and 1 1015 ions/cm2, respectively. The silicon surface was oxidized by the irradiation of the acetone cluster ion beam [10–12]. The contribution of silicon carbide may be possible [13], but no clear peak of silicon carbide was observed in the C 1s XPS spectrum of the silicon surface irradiated with the acetone cluster ion beam. The silicon surface was more strongly oxidized by the irradiation of the acetone cluster ion beam than ethanol cluster ion beam [3]. The smallness of the thickness of the oxidized layer formed by the irradiation of an ethanol cluster ion beam was attributed to the high sputtering yield. The strong oxidation effects together with the high sputtering yield may be the characteristic property of the interaction between an acetone cluster ion beam and silicon surface. 4. Conclusion Acetone cluster ion beams were produced by the adiabatic expansion method without using a support gas. The sputter depths of silicon and silicon dioxide increased with the acceleration voltage and fluence of the acetone cluster ion beam. The sputter depth of silicon induced by the acetone cluster ion beam was close to that induced by the ethanol cluster ion beam accelerated at the same acceleration voltage. The sputter depths of silicon dioxide induced by the acetone cluster ions were systematically smaller than those of silicon. The sputter depths of silicon dioxide were larger than those induced by ethanol cluster ion beams, so an ethanol cluster ion beam may be more effective in selective sputtering between silicon and silicon dioxide. The silicon surface was oxidized by the irradiation of an acetone cluster ion beam. The strong oxidation effects together with the high sputtering yield may be the characteristic property of the acetone cluster ion irradiation.
Unirradiated Acknowledgement
Binding energy (eV)
(b)
A part of this work was conducted in Kyoto-Advanced Nanotechnology Network, supported by ‘‘Nanotechnology Network’’ of the Ministry of Education, Culture, Sports, Science and Technology, Japan. The present work was supported in part by JSPS KAKENHI Grant No. 22560329.
Intensity (arb. unit)
References Va=9 kV Φ=1x1015 ions/cm2
Binding energy (eV)
[1] I. Yamada, Nucl. Instrum. Meth. B 148 (1999) 1. [2] H. Ryuto, K. Sugiyama, R. Ozaki, G.H. Takaoka, Appl. Phys. Express 2 (2009) 016504. [3] H. Ryuto, R. Ozaki, H. Mukai, G.H. Takaoka, Vacuum 84 (2010) 1419. [4] H. Ryuto, K. Tada, G.H. Takaoka, Vacuum 84 (2010) 501. [5] C.L. Cleveland, U. Landman, Science 257 (1992) 355. [6] H.-P. Chen, U. Landman, Science 260 (1993) 1304. [7] O.F. Hagena, W. Obert, J. Chem. Phys. 56 (1972) 1793. [8] O.F. Hagena, K. Varma, Rev. Sci. Instrum. 39 (1968) 47. [9] H.H. Anderson, H.L. Bay, in: R. Behrisch (Ed.), Sputtering by Particle Bombardment I, Springer-Verlag, Berlin, 1981, p. 145. [10] Shimadzu, ESCA data table C144-3031. [11] G. Hollinger, F.J. Himpsel, Appl. Phys. Lett. 44 (1984) 93. [12] O. Benkherourou, J.P. Deville, J. Vac. Sci. Technol., A 6 (1988) 3125. [13] A.R. Chourasia, Surf. Sci. Spectra 8 (2001) 45.
Fig. 5. Si 2p XPS spectra of (a) silicon surface without irradiation and (b) silicon surface irradiated with acetone cluster ion beam.
Please cite this article in press as: H. Ryuto et al., Acetone cluster ion beam irradiation on solid surfaces, Nucl. Instr. Meth. B (2013), http://dx.doi.org/ 10.1016/j.nimb.2013.04.027