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Characterization of ALD-deposited Al oxide films for high-k purposes: A chemical investigation
ARTICLE IN PRESS
Materials Science in Semiconductor Processing 9 (2006) 1000–1005
Characterization of ALD-deposited Al oxide films for high-k purposes: A chemical investigation S.G. Alberici, A. Giussani STMicroelectronics N.V., Physics Laboratory, FTM Division, Via C. Olivetti 2, 20041 Agrate Brianza, Milan, Italy
Abstract ALD aluminum oxides from H2O and Al(CH3)3 precursors have been deposited in the pilot line at ST Microelectronics Agrate, as a high-k inter-poly dielectric. The deposition has been followed by some conditioning steps dedicated to the investigation of the chemical film stability. ToF–SIMS, AES and XPS have been used in order to perform this study. ToF–SIMS analyses revealed that, after a N2 RTP, hydrogen becomes strongly reduced in the film and silicon migrates from the substrate to the surface; moreover an AlN signal is detected across the film as a result of NH3 annealing and/or of N2 RTP. The chemical affinity of the film towards nitrogen incorporation is proven also by AES and XPS, the latter showing the presence of AlN at the surface in case of N2 RTP. Finally Si is found at the surface of the RTP treated samples even at the AES and XPS sensitivity. r 2006 Published by Elsevier Ltd. Keyword: Chemical investigation
1. Introduction Scaling down of devices for future microelectronics applications (more specifically, flash memories) is accomplished by choosing suitable materials as inter-poly dielectrics (IPD) in substitution of the currently used oxide–nitride–oxide (ONO) stack. It is known that from the 10 nm range downwards, the ONO films begin to fail in terms of charge retention properties [1,2]. Leakage current through the IPD has to be kept as low as possible at any operating condition [3]. These constraints and many others lead to evaluate alternative materials to SiO2 for IPD applications. Corresponding author. Tel.: +39 039 6035168; fax: +39 039 6035530. E-mail address: [email protected] (S.G. Alberici).
1369-8001/$ - see front matter r 2006 Published by Elsevier Ltd. doi:10.1016/j.mssp.2006.10.017
High-k dielectrics are among the candidates, as they can combine a low electrical thickness with a quite large physical thickness. A concern regarding the integration of high-k materials is their thermal stability: as-deposited films are usually amorphous but they undergo crystallization during the subsequent process steps [4]. Although crystalline highk’s may have a higher dielectric constant than those amorphous [4], several drawbacks must be considered: for instance, grain boundaries could give rise to high leakage current and could serve as a path for dopant diffusion [5]. For a large number of high-k dielectrics, N incorporation to the film has proved efficient in improving the thermal stability [6–8] and suppressing the dopant penetration [5]. Anyhow, most of those investigations have been carried out on high-k gate oxides: being thickness-dependent [4,6],
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
crystallization must be studied in the thickness range of interest for IPD applications. In this work, aluminum oxide was deposited by Atomic Layer Deposition (ALD) from H2O and Al(CH3)3 precursors on RCA-rinsed Si. We focused on finding out a way to inhibit Al2O3 crystallization, which is expected to take place during the process and cause high leakage current. Towards this end, the Al2O3 film has been subjected to a NH3 conditioning step before undergoing the final RTP that simulates the process thermal budget. Time of Flight–Secondary Ion Mass Spectrometry (ToF– SIMS), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) were used for this characterization. Transmission Electron Microscopy (TEM) support was requested to study the structural evolution of the film under the proposed thermal treatments.
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Fig. 1. ToF–SIMS depth profile of the as-deposited sample (ref.).
2. Experimental On as-received p-type Si (1 0 0) bare wafers, a standard RCA rinsing was performed prior to any deposition; then 12.7 nm aluminum oxide films were deposited via ALD from H2O and Al(CH3)3 pre cursors at 573 K. After the deposition, the following split was performed: (1) as-deposited (ref.); (2) ref.+N2 RTP at 1303 K, 15 s; (3) ref.+NH3 annealing at 973 K, 10 min; (4) ref.+NH3 annealing at 973 K, 10 min+ N2 RTP at 1303 K, 15 s. The samples were characterized with a ToF– SIMS IV system from ION-TOF GmbH, equipped with a Dual Source Column; a Physical Electronics 680 as an AES and a Physical Electronics 5700 as a XPS. Auger analyses were carried out with a 10 nA 10 keV primary electron beam and a 1.5 keV Ar+ beam for sputtering at a rate of 2.5 nm EOT/min (EOT ¼ Equivalent silicon Oxide Thickness). XPS surface spectra were obtained at 13.5 kV, 30 mA using a monochromatized Al Ka X-ray source. In both cases a 1 cm2 sample was cut from the original wafer and analyzed. 3. Results and discussion Fig. 1 shows the ToF–SIMS depth profile acquired from the ‘‘ref.’’ sample. The main components appear homogeneously distributed all along the film and the interface definition looks pretty narrow. Concerning the artifacts, it should be kept in mind that, when going from the film to the
Fig. 2. ToF–SIMS H, Si and AlN depth profiles for samples 3 and 4.
substrate, the AlO18 signal can interfere with the SiHO signal. Fig. 2 shows a comparison between samples 3 and 4 concerning the H, Si and AlN profiles. Whereas almost no Si migration is observed in the case of the NH3 annealing, Si moves from the substrate to the surface as a result of the RTP (a similar Si diffusion is observed on sample 2—not shown). Moreover, in samples 3H and 4H has outgassed from the bulk, which is likely to be correlated with an increase in the film density (a similar observation can be done for sample 2—not shown). Finally, the AlN signal indicates that the alumina nitridation decreases with depth, being higher in sample 4 where the ammonia treatment is followed by the high temperature RTP
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S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
(note that AlN interferes with SiCH once the substrate is reached). With regard to C residues induced by the TMA precursor (not shown), no particular differences have been found among all the samples. Fig. 3 reports the AES depth profiles obtained for samples 3 and 4. Whereas the N2 RTP gives a N peak close to the detection limit only at the surface (not shown), the NH3 annealing proves to be efficient in incorporating some nitrogen: N is indeed detected along the first half of the film with an intensity that decreases with depth. If a subsequent N2 RTP is performed, the thickness of Al2O3 impacted by nitridation does not extend signifi-
cantly. The N 1s peak dependence on the thermal treatments was studied by XPS with a take-off angle (ToA) of 301 and a pass energy (PE) of 58.70 eV (Fig. 4). All the spectra were calibrated against the C 1s peak of adventitious carbon (284.5 eV), in order to compensate the shifts induced by the films charging up under X-ray. On the surface of the as-deposited sample a small amount of N is found. This nitrogen is probably bound to O and C atoms and adsorbed during exposition to air [9,10]. Under the N2 RTP treatment, the N peak broadens and becomes more intense. The component at the lowest binding energy (BE) can be due to AlN formation [9],
Fig. 3. AES depth profiles for samples 3 and 4.
Fig. 4. XPS N 1s surface spectra (ToA ¼ 301, PE ¼ 58.70 eV).
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
whereas the components in the BE interval E(397–400) eV can be explained by an increased amount of N–H, N–C, N–O bonds at the surface [9,11–13]. If NH3 annealing is performed, N–H species (NH3, NH2) can adsorb onto the surface: the components at high BE become more intense [14]. In sample 4 the final N2 RTP facilitates in dehydrogenating the surface, forming further aluminum nitride [14]. Another interesting result is that Si is detected even at the AES and XPS sensitivity at the surface of samples 2 and 4. By AES, Si has been followed as Si KLL, that is normally less intense than Si LMM. With the latter there was indeed the risk of
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overlapping with a secondary Al peak. Fig. 5 shows that Si KLL is detected in the case of samples 2 and 4 (here a primary beam current of 20 nA was used in order to increase the signal). XPS Si 2p spectra were taken at a ToA of 301 with a PE of 23.50 eV. Particular attention was paid to this analysis. Use of the monochromatic source turned out to be mandatory in order to distinguish the Si 2p peak from the Al 2p energy loss peak and to avoid satellites from the Al 2s peak. The possibility of Al KLL presence in this region was taken into account as well. The results are shown in Fig. 6: a Si peak appears only in the case of the RTP treated samples. Analog conclusions were obtained looking at the Si 2s peak (not shown). This Si could
Fig. 5. AES Si KLL surface spectra (20 nA 10 kV).
Fig. 6. XPS Si 2p surface spectra (ToA ¼ 301, PE ¼ 23.50 eV).
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S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
Fig. 7. TEM diffraction pattern from sample 4.
be partially oxidized and nitridated, giving an additional small contribution to the N 1s peak at BE 397.5 eV [11]. Electron spectroscopy data bring additional information with respect to ToF–SIMS: Si is present at the surface of samples 2 and 4 at fractions of at%, that is the AES and XPS sensitivity limit. The hypothesis that this Si peak comes from the interface has been excluded by repeating the analyses at a higher ToA: at 651 the Si 2p/Al 2p ratio decreases with respect to the ratio got at 301 (not shown). Al2O3 crystallization could explain the Si presence at the surface of samples 2 and 4 at the AES/ XPS sensitivity: Si diffusion through grain boundaries could have happened. TEM diffraction patterns indeed show that sample 2 is polycrystalline, sample 3 is amorphous, whereas sample 4 appears partially crystalline in an amorphous matrix (Fig. 7). A plan-view of sample 4 (Fig. 8) makes evident the presence of crystallites, whose nature is likely to be related to the AlN signal detected by XPS. With this in mind, further analyses are ongoing in order to better understand the AlN formation in the Al2O3 matrix. Aluminum nitride insertion could be promising, as this compound has a dielectric constant comparable to alumina [15,16] and its formation could obstacle the crystallization when undergoing further thermal budgets, possibly limiting the risk of current leakage through the film grain boundaries.
Fig. 8. TEM plan-view from sample 4.
4. Conclusions ALD aluminum oxides are among the proposed films to function as IPDs. By ALD we were able to deposit homogeneous films. As a result of a high temperature RTP, two main effects have been observed: Si moves from the substrate towards the surface and H outgasses from the film. Al nitridation takes place when NH3 and/or N2 RTP is performed on the samples. In particular, the nitrogen incorporation induced by the ammonia annealing seems to slow the film crystallization that would otherwise fully take place after the final RTP. An improvement of the NH3 treatment is under study: some parameters, like temperature and ammonia flow, may still be varied in order to increase the nitrogen doping and maintain the alumina amorphous. As already said, this is expected to prevent high leakage current through grain boundaries. Anyhow, electrical measurements will be carried out to verify this hypothesis and to make correlations with the analytical data.
Acknowledgments We would like to thank Rossella Piagge (for providing the samples and for the helpful discussions) and Giuseppe Pavia (for TEM analyses), ST Microelectronics, FTM Division; Claudia Wiemer, MDM-INFM Laboratory, for helpful discussions.
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
References [1] M. Alessandri, et al. High-k Materials in Flash Memories. ECS Transactions, Volume 1, Physics and Technology of high-k Gate Dielectric III, Los Angeles Fall meeting 2005, in press. [2] Chen Y-Y, et al. Jpn J Appl Phys 2005;44(4A):1704–10. [3] Govoreanu B, et al. Solid State Electron 2005;49:1841–8. [4] Jakschik S, et al. Thin Solid Films 2003;425:216–20. [5] Quevedo-Lopez MA, et al. J Appl Phys 2005;97(043508): 1–15. [6] Pant G, et al. Appl Phys Lett 2006;88(032901):1–3. [7] Visokay MR, et al. Appl Phys Lett 2002;80(17):3183–5. [8] Toyoda S, et al. Appl Phys Lett 2005;87(182908):1–3. [9] Liao HM, et al. J Vac Sci Technol A 1993;11(5):2683.
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[10] Mahmood A, et al. Diamond Relat Mater 2003;12:1319. [11] Moulder JF, et al. Handbook of X-ray photoelectron spectroscopy. Physical Electronics Inc.; 1995. p. 227. [12] Soto G, et al. Appl Surf Sci 2001;183:246–58. [13] Sanchez-Lopez JC, et al. NanoStruct Mater 1999;11(2): 252–3. [14] Liu H, Rogers Jr. JW. J Vac Sci Technol A 1999;17(2): 325–31. [15] Engelmark F. AlN and high-k Thin Films for IC and Electroacoustic Applications, Acta Universitatis Upsaliensis, Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, vol. 757, 2002. p. 65. [16] Wilk GD, et al. J Appl Phys 2001;89:5254.
Materials Science in Semiconductor Processing 9 (2006) 1000–1005
Characterization of ALD-deposited Al oxide films for high-k purposes: A chemical investigation S.G. Alberici, A. Giussani STMicroelectronics N.V., Physics Laboratory, FTM Division, Via C. Olivetti 2, 20041 Agrate Brianza, Milan, Italy
Abstract ALD aluminum oxides from H2O and Al(CH3)3 precursors have been deposited in the pilot line at ST Microelectronics Agrate, as a high-k inter-poly dielectric. The deposition has been followed by some conditioning steps dedicated to the investigation of the chemical film stability. ToF–SIMS, AES and XPS have been used in order to perform this study. ToF–SIMS analyses revealed that, after a N2 RTP, hydrogen becomes strongly reduced in the film and silicon migrates from the substrate to the surface; moreover an AlN signal is detected across the film as a result of NH3 annealing and/or of N2 RTP. The chemical affinity of the film towards nitrogen incorporation is proven also by AES and XPS, the latter showing the presence of AlN at the surface in case of N2 RTP. Finally Si is found at the surface of the RTP treated samples even at the AES and XPS sensitivity. r 2006 Published by Elsevier Ltd. Keyword: Chemical investigation
1. Introduction Scaling down of devices for future microelectronics applications (more specifically, flash memories) is accomplished by choosing suitable materials as inter-poly dielectrics (IPD) in substitution of the currently used oxide–nitride–oxide (ONO) stack. It is known that from the 10 nm range downwards, the ONO films begin to fail in terms of charge retention properties [1,2]. Leakage current through the IPD has to be kept as low as possible at any operating condition [3]. These constraints and many others lead to evaluate alternative materials to SiO2 for IPD applications. Corresponding author. Tel.: +39 039 6035168; fax: +39 039 6035530. E-mail address: [email protected] (S.G. Alberici).
1369-8001/$ - see front matter r 2006 Published by Elsevier Ltd. doi:10.1016/j.mssp.2006.10.017
High-k dielectrics are among the candidates, as they can combine a low electrical thickness with a quite large physical thickness. A concern regarding the integration of high-k materials is their thermal stability: as-deposited films are usually amorphous but they undergo crystallization during the subsequent process steps [4]. Although crystalline highk’s may have a higher dielectric constant than those amorphous [4], several drawbacks must be considered: for instance, grain boundaries could give rise to high leakage current and could serve as a path for dopant diffusion [5]. For a large number of high-k dielectrics, N incorporation to the film has proved efficient in improving the thermal stability [6–8] and suppressing the dopant penetration [5]. Anyhow, most of those investigations have been carried out on high-k gate oxides: being thickness-dependent [4,6],
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
crystallization must be studied in the thickness range of interest for IPD applications. In this work, aluminum oxide was deposited by Atomic Layer Deposition (ALD) from H2O and Al(CH3)3 precursors on RCA-rinsed Si. We focused on finding out a way to inhibit Al2O3 crystallization, which is expected to take place during the process and cause high leakage current. Towards this end, the Al2O3 film has been subjected to a NH3 conditioning step before undergoing the final RTP that simulates the process thermal budget. Time of Flight–Secondary Ion Mass Spectrometry (ToF– SIMS), Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS) were used for this characterization. Transmission Electron Microscopy (TEM) support was requested to study the structural evolution of the film under the proposed thermal treatments.
1001
Fig. 1. ToF–SIMS depth profile of the as-deposited sample (ref.).
2. Experimental On as-received p-type Si (1 0 0) bare wafers, a standard RCA rinsing was performed prior to any deposition; then 12.7 nm aluminum oxide films were deposited via ALD from H2O and Al(CH3)3 pre cursors at 573 K. After the deposition, the following split was performed: (1) as-deposited (ref.); (2) ref.+N2 RTP at 1303 K, 15 s; (3) ref.+NH3 annealing at 973 K, 10 min; (4) ref.+NH3 annealing at 973 K, 10 min+ N2 RTP at 1303 K, 15 s. The samples were characterized with a ToF– SIMS IV system from ION-TOF GmbH, equipped with a Dual Source Column; a Physical Electronics 680 as an AES and a Physical Electronics 5700 as a XPS. Auger analyses were carried out with a 10 nA 10 keV primary electron beam and a 1.5 keV Ar+ beam for sputtering at a rate of 2.5 nm EOT/min (EOT ¼ Equivalent silicon Oxide Thickness). XPS surface spectra were obtained at 13.5 kV, 30 mA using a monochromatized Al Ka X-ray source. In both cases a 1 cm2 sample was cut from the original wafer and analyzed. 3. Results and discussion Fig. 1 shows the ToF–SIMS depth profile acquired from the ‘‘ref.’’ sample. The main components appear homogeneously distributed all along the film and the interface definition looks pretty narrow. Concerning the artifacts, it should be kept in mind that, when going from the film to the
Fig. 2. ToF–SIMS H, Si and AlN depth profiles for samples 3 and 4.
substrate, the AlO18 signal can interfere with the SiHO signal. Fig. 2 shows a comparison between samples 3 and 4 concerning the H, Si and AlN profiles. Whereas almost no Si migration is observed in the case of the NH3 annealing, Si moves from the substrate to the surface as a result of the RTP (a similar Si diffusion is observed on sample 2—not shown). Moreover, in samples 3H and 4H has outgassed from the bulk, which is likely to be correlated with an increase in the film density (a similar observation can be done for sample 2—not shown). Finally, the AlN signal indicates that the alumina nitridation decreases with depth, being higher in sample 4 where the ammonia treatment is followed by the high temperature RTP
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S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
(note that AlN interferes with SiCH once the substrate is reached). With regard to C residues induced by the TMA precursor (not shown), no particular differences have been found among all the samples. Fig. 3 reports the AES depth profiles obtained for samples 3 and 4. Whereas the N2 RTP gives a N peak close to the detection limit only at the surface (not shown), the NH3 annealing proves to be efficient in incorporating some nitrogen: N is indeed detected along the first half of the film with an intensity that decreases with depth. If a subsequent N2 RTP is performed, the thickness of Al2O3 impacted by nitridation does not extend signifi-
cantly. The N 1s peak dependence on the thermal treatments was studied by XPS with a take-off angle (ToA) of 301 and a pass energy (PE) of 58.70 eV (Fig. 4). All the spectra were calibrated against the C 1s peak of adventitious carbon (284.5 eV), in order to compensate the shifts induced by the films charging up under X-ray. On the surface of the as-deposited sample a small amount of N is found. This nitrogen is probably bound to O and C atoms and adsorbed during exposition to air [9,10]. Under the N2 RTP treatment, the N peak broadens and becomes more intense. The component at the lowest binding energy (BE) can be due to AlN formation [9],
Fig. 3. AES depth profiles for samples 3 and 4.
Fig. 4. XPS N 1s surface spectra (ToA ¼ 301, PE ¼ 58.70 eV).
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
whereas the components in the BE interval E(397–400) eV can be explained by an increased amount of N–H, N–C, N–O bonds at the surface [9,11–13]. If NH3 annealing is performed, N–H species (NH3, NH2) can adsorb onto the surface: the components at high BE become more intense [14]. In sample 4 the final N2 RTP facilitates in dehydrogenating the surface, forming further aluminum nitride [14]. Another interesting result is that Si is detected even at the AES and XPS sensitivity at the surface of samples 2 and 4. By AES, Si has been followed as Si KLL, that is normally less intense than Si LMM. With the latter there was indeed the risk of
1003
overlapping with a secondary Al peak. Fig. 5 shows that Si KLL is detected in the case of samples 2 and 4 (here a primary beam current of 20 nA was used in order to increase the signal). XPS Si 2p spectra were taken at a ToA of 301 with a PE of 23.50 eV. Particular attention was paid to this analysis. Use of the monochromatic source turned out to be mandatory in order to distinguish the Si 2p peak from the Al 2p energy loss peak and to avoid satellites from the Al 2s peak. The possibility of Al KLL presence in this region was taken into account as well. The results are shown in Fig. 6: a Si peak appears only in the case of the RTP treated samples. Analog conclusions were obtained looking at the Si 2s peak (not shown). This Si could
Fig. 5. AES Si KLL surface spectra (20 nA 10 kV).
Fig. 6. XPS Si 2p surface spectra (ToA ¼ 301, PE ¼ 23.50 eV).
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S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
Fig. 7. TEM diffraction pattern from sample 4.
be partially oxidized and nitridated, giving an additional small contribution to the N 1s peak at BE 397.5 eV [11]. Electron spectroscopy data bring additional information with respect to ToF–SIMS: Si is present at the surface of samples 2 and 4 at fractions of at%, that is the AES and XPS sensitivity limit. The hypothesis that this Si peak comes from the interface has been excluded by repeating the analyses at a higher ToA: at 651 the Si 2p/Al 2p ratio decreases with respect to the ratio got at 301 (not shown). Al2O3 crystallization could explain the Si presence at the surface of samples 2 and 4 at the AES/ XPS sensitivity: Si diffusion through grain boundaries could have happened. TEM diffraction patterns indeed show that sample 2 is polycrystalline, sample 3 is amorphous, whereas sample 4 appears partially crystalline in an amorphous matrix (Fig. 7). A plan-view of sample 4 (Fig. 8) makes evident the presence of crystallites, whose nature is likely to be related to the AlN signal detected by XPS. With this in mind, further analyses are ongoing in order to better understand the AlN formation in the Al2O3 matrix. Aluminum nitride insertion could be promising, as this compound has a dielectric constant comparable to alumina [15,16] and its formation could obstacle the crystallization when undergoing further thermal budgets, possibly limiting the risk of current leakage through the film grain boundaries.
Fig. 8. TEM plan-view from sample 4.
4. Conclusions ALD aluminum oxides are among the proposed films to function as IPDs. By ALD we were able to deposit homogeneous films. As a result of a high temperature RTP, two main effects have been observed: Si moves from the substrate towards the surface and H outgasses from the film. Al nitridation takes place when NH3 and/or N2 RTP is performed on the samples. In particular, the nitrogen incorporation induced by the ammonia annealing seems to slow the film crystallization that would otherwise fully take place after the final RTP. An improvement of the NH3 treatment is under study: some parameters, like temperature and ammonia flow, may still be varied in order to increase the nitrogen doping and maintain the alumina amorphous. As already said, this is expected to prevent high leakage current through grain boundaries. Anyhow, electrical measurements will be carried out to verify this hypothesis and to make correlations with the analytical data.
Acknowledgments We would like to thank Rossella Piagge (for providing the samples and for the helpful discussions) and Giuseppe Pavia (for TEM analyses), ST Microelectronics, FTM Division; Claudia Wiemer, MDM-INFM Laboratory, for helpful discussions.
ARTICLE IN PRESS S.G. Alberici, A. Giussani / Materials Science in Semiconductor Processing 9 (2006) 1000–1005
References [1] M. Alessandri, et al. High-k Materials in Flash Memories. ECS Transactions, Volume 1, Physics and Technology of high-k Gate Dielectric III, Los Angeles Fall meeting 2005, in press. [2] Chen Y-Y, et al. Jpn J Appl Phys 2005;44(4A):1704–10. [3] Govoreanu B, et al. Solid State Electron 2005;49:1841–8. [4] Jakschik S, et al. Thin Solid Films 2003;425:216–20. [5] Quevedo-Lopez MA, et al. J Appl Phys 2005;97(043508): 1–15. [6] Pant G, et al. Appl Phys Lett 2006;88(032901):1–3. [7] Visokay MR, et al. Appl Phys Lett 2002;80(17):3183–5. [8] Toyoda S, et al. Appl Phys Lett 2005;87(182908):1–3. [9] Liao HM, et al. J Vac Sci Technol A 1993;11(5):2683.
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[10] Mahmood A, et al. Diamond Relat Mater 2003;12:1319. [11] Moulder JF, et al. Handbook of X-ray photoelectron spectroscopy. Physical Electronics Inc.; 1995. p. 227. [12] Soto G, et al. Appl Surf Sci 2001;183:246–58. [13] Sanchez-Lopez JC, et al. NanoStruct Mater 1999;11(2): 252–3. [14] Liu H, Rogers Jr. JW. J Vac Sci Technol A 1999;17(2): 325–31. [15] Engelmark F. AlN and high-k Thin Films for IC and Electroacoustic Applications, Acta Universitatis Upsaliensis, Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, vol. 757, 2002. p. 65. [16] Wilk GD, et al. J Appl Phys 2001;89:5254.