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Physical and electrical properties of ZrO2 and YSZ high-k gate dielectric thin films grown by RF magnetron sputtering
Thin Solid Films 475 (2005) 354 – 358 www.elsevier.com/locate/tsf
Physical and electrical properties of ZrO2 and YSZ high-k gate dielectric thin films grown by RF magnetron sputtering S.H. Jeonga, I.S. Baea, Y.S. Shina, S.-B. Leea, H.-T. Kwakb, J.-H. Booa,* a
Department of Chemistry, Sungkyunkwan University, 300 Chunchun-Dong, Jangan-Gu, Suwon 440-746, Korea b Department of Chemistry, Kookmin University, Seoul 136-702, Korea Available online 11 September 2004
Abstract Thin films of ZrO2 were deposited on p-Si(100) substrates using RF magnetron sputtering technique. To investigate the influence of the sputtering parameters, e.g., annealing temperature, different O2-flux, RF power and target to substrate distance on the physical and electrical properties of the as-grown films, systematic investigation using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope and energy dispersive X-ray (SEM–EDX), C–V, and I–V were carried out in this work. Deposited ZrO2 films had polycrystalline after annealing sample at high temperature. Their silicon oxide (SiO2) layers were formed between high-k film (i.e., ZrO2 and YSZ) and Si substrate either after annealing samples at high temperature or introducing O2-flux the sputtering process step. The high-k thin films have to be deposited amorphous structure without SiO2 interlayers. We also investigated the electrical properties of both the a-ZrO2 and a-YSZ films prepared without O2-flux at room temperature with conditions of various RF power and target to substrate distance. The dielectric constant of amorphous YSZ was determined to be about 24 using metal–insulator– semiconductor (MIS) capacitor structure. The smallest leakage current density of the YSZ film grown at 150 W and at room temperature was obtained to be about 10 10 at 1 V. D 2004 Elsevier B.V. All rights reserved. Keywords: RF magnetron sputtering; ZrO2 films; YSZ films; High-k gate dielectrics; Leakage current
1. Introduction Recently, as metal oxide semiconductor field effect transistor (MOSFET) devices are scaled down to b100 nm, problems of conventional silicon oxide (SiO2) appeared. SiO2 layer suffered from basic problem of high tunneling leakage current and reduced drive current due to low dielectric constant (k=3.9) with thickness decreased (b2 nm) [1,2]. Hence, high-k gate dielectrics such as Ta2O5, TiO2, HfO2, ZrO2, CeO2, Y2O3 stabilized ZrO2 (YSZ) [2–6] were studied to replace SiO2. Most of these materials, however, were not thermally stable directly on Si, due to the formation of metal silicides in the course of fabrication.
* Corresponding author. Tel.: +82 31 290 7072; fax: +82 31 290 7075. E-mail address: [email protected] (J.-H. Boo). 0040-6090/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.07.023
ZrO2 and YSZ are one of the most attractive andidates due to its high-k values (~25 and ~27, respectively), wide band gap (approximately 5.1–7.8 eV) [7,8], and good thermal stability in contact with Si [9]. Due to their excellent properties, ZrO2 and YSZ films have been extensively studied as gate dielectric [10]. Wang et al. [11] studied the 6nm-thick epitaxial crystalline YSZ films with electrical equivalent oxide thickness (EOT) of 1.46 nm and found that the leakage current was about 1.110 3 A/cm2 at 1 V. In addition, Zhu and Liu [6] also studied the 6-nm-thick amorphous YSZ films with EOT=1.46 nm and obtained a leakage current to be about 7.5810 5 A/cm2 at 1 V. Moreover, amorphous films exhibited isotropic electrical properties and can easily be deposited. In this work, the influence of the sputtering parameter such as, O2-flux, annealing temperature, RF power and target-to-substrate distance (D ts) on physical and electrical properties of amorphous ZrO2 and YSZ films that were
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area of the capacitors was 2.410 4 cm2. The I–V and C–V curves were measured using a HP4140B pico-A and a Bonton 7200 capacitor meter, respectively.
3. Results and discussion Fig. 1(a) shows X-ray diffraction patterns of ZrO2 thin films grown at room temperature without O2-flux. The RF power was 150 W and the annealing temperature varied from 600 to 1200 8C. Below 600 8C, there were no typical diffraction peaks, indicating an amorphous structure. Between 800 and 1000 8C, the films were mainly grown in the [111] orientation, while the crystal growth direction was changed to be [012], at an annealing temperature in the range of 1000–1200 8C. The polycrystal film could thus be obtained after annealing over 800 8C. With oxygen flux, the same tendency of X-ray diffraction pattern as Fig. 1(a) was observed (not shown). However, the relative intensity was decreased substantially, suggesting the poor crystallinity in these cases. The FT-IR spectra of ZrO2 films are shown in Fig. 1(b). The peaks at 794.6 and 1083.9 cm 1 were mostly due to Si– O–Si and Si–O stretching of the silicon oxide layers. The
Fig. 1. (a) X-ray diffraction patterns of ZrO2 thin films obtained with different annealing temperatures. (b) FT-IR spectra of ZrO2 thin films obtained with different O2 flux and annealing.
prepared at low temperature by RF magnetron sputtering method have been studied.
2. Experimental Both ZrO2 and YSZ films were prepared by the RF magnetron sputtering method. The purity of the ZrO2 target was above 99.99% with a diameter of 1 in. The YSZ target were prepared with 8 wt.% Y2O3-stabilized ZrO2. The sputtering gas (Ar) with a purity of 99.99% were introduced to the chamber and controlled by the standard mass-flow controllers. The sputtering pressure was 32 mTorr and p type Si(100) wafer were used as substrates without heating. The substrate–target distance was changed from 30 to 50 mm and RF power was controlled from 80 to 200 W. The structural properties of the films were characterized by X-ray diffraction (XRD) using Cu K a radiation (RIGAKU, D/MAX-2200 ultima). The interlayers between high-k film and substrate were analyzed with Fourier transform infrared (FT-IR, AVATAR 320) spectroscopy. The thickness and interlayers formation were observed using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) (XL 30 ESEM-FEG). The electrical properties were measured by metal–insulator–semiconductor (MIS) capacitor structures with Al gate electrodes. The
Fig. 2. (a) SEM and EDX image of a ZrO2 thin film grown at RT and 150 W with oxygen flux of 20 sccm. (b) Variation of ZrO2 film growth rates of with RF power magnitude (n).
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Fig. 3. (a) High-frequency C–V measurement of ZrO2 capacitors with various D ts. C–V characteristics of ZrO2 (b) and YSZ (c) films grown at different RF power: 80 (n), 120 ( ), 150 (E), and 200 (z) W.
!
reason of rising SiO2 layers was due to interdiffusion caused by oxygen diffusion into the interlayer during annealing. To prove this phenomenon clearly, YSZ film synthesis was also carried out under the same deposition condition of annealing and O2-flux as the same experiments of ZrO2 film deposition did. The deposited ZrO2 and YSZ films had the SiO2 layers between film and substrate.
Fig. 2(a) shows typical SEM image as well as EDX result obtained from the ZrO2 thin film that grown at room temperature and 150 W with oxygen. The cross-sectional EDX data show the SiO2 layer formation at the interface region between ZrO2 film layer and Si substrate. The interfacial SiO2 layers were formed between high-k film and silicon substrate either loading O2-flux or after annealing sample. Similarly, several papers [11–13] reported that the formation of an interfacial SiO2 layer in YSZ film surface induced lower dielectric constant than that of YSZ during film deposition due to residual oxygen in the chamber and high oxygen diffusivities of YSZ. Deposited high-k films had polycrystalline after annealing sample at high temperature. However, the high-k films have to be prepared to amorphous structure without interfacial SiO2 layer. Moreover, we investigated the electrical properties of both a-ZrO2 and a-YSZ films, which were prepared without O2-flux at room temperature under condition of various RF powers and D ts. With cross-sectional SEM image, one could calculate the film thickness as well as growth rate. Fig. 2(b) shows the variation of film growth rate as a function of RF power magnitudes at D ts of 40 mm. With increasing RF power, the growth rate is linearly increased within our experimental condition. Fig. 3(a) showed the results for the high frequency C–V measurement of ZrO2 capacitors at various D ts. The dielectric constants of the ZrO2 films deposited at D ts of 35, 40, and 50 mm were found to be 10.87, 23.38, and 20.81, respectively. These values were determined from the capacitance (C i) in the accumulation region of the 1 MHz C–V curves. The C–V characteristics of both the ZrO2 and the YSZ gate dielectrics with different RF powers were shown in the Fig. 3(b) and (c), respectively. All samples were prepared at room temperature with D ts=40 mm. The dielectric constants of these films are summarized in Table 1. The classical operational modes of ideal MIS structures with distinct inversion, depletion, and accumulation were clearly revealed in the C–V characteristics of all the dielectric films except for ZrO2 film at 200 W. Fig. 4(a) reveal that the leakage current density decreased with decreasing the target to substrate distance. Fig. 4(b) and (c) showed the I–V characteristics of both ZrO2 and YSZ gate dielectrics grown at different RF power: 80, 120, 150, and 200 W. The leakage current decreased with increasing RF power. In addition, this was caused from, that films became dense at a low D ts and high RF power. Gao et al. [13] reported that the packing density increased with the increasing sputtering power and decreased with increasing Table 1 The dielectric constants of both ZrO2 and YSZ films with different RF powers k ZrO2 k YSZ
80 W
120 W
150 W
200 W
21.57 13.70
21.60 24.10
23.35 22.54
7.29 10.38
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4. Conclusions We have deposited ZrO2 thin films on p-Si(100) substrate by RF magnetron sputtering in order to study an influence of deposition parameters (such as annealing temperature, reactive gas, RF power, and Y2O3 dopant) on the physical and electrical properties of the as-grown films. XRD showed that a highly oriented cubic ZrO2 thin film in the [111] direction was obtained after annealing at 800 8C. On the other hand, tetragonal ZrO2 thin film was also grown on Si (100) substrate and the main film growth direction was also changed to be [012] direction at above 800 8C of annealing temperature. FT-IR data show that both ZrO2 and YSZ films, which were deposited under conditions of annealing and O2-flux, had the SiO2 layers between the films and substrate. We investigated the electrical properties of the films of both a-ZrO2 and a-YSZ films which were prepared without O2-flux at room temperature under the conditions of various RF powers and D ts. The C–V characteristics of all the dielectric films that involved distinct inversion, depletion, and accumulation were clearly revealed in MIS structure except for ZrO2 film at 200 W. The leakage current decreased with decreasing D ts and increasing RF power. Because of a low D ts and high RF power, films became dense so that the leakage current decreased. In addition, the leakage current of YSZ films is smaller than that of ZrO2. This reasoned that the stabilization of film increased with increasing dopant content. The smallest leakage current density of the YSZ film grown at 150 W and room temperature was obtained to be about 10 10 at 1 V of gate voltage. The dielectric constant of amorphous YSZ was determined to be about 24 by MIS capacitor structure.
Acknowledgements This work was supported by the BK21 project of the Ministry of Education Korea, by the CAPST (Center for Advanced Plasma Surface Technology) and by the Korea Science and Engineering Foundation (project No. R012003-000-10019-0) at the Sungkyunkwan University. Fig. 4. (a) I–V curves of ZrO2 capacitors with various D ts. I–V characteristics of ZrO2 (b) and YSZ (c) films grown at different RF power: 80 (n), 120 ( ), 150 (E), and 200 (z) W.
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D ts. In addition, the leakage current of YSZ films is smaller than that of ZrO2 films. This suggests that the stabilization of film with Y2O3 increased with increasing dopant content [14]. The leakage current of film decreased with decreasing D ts and increasing power. However, the C–V characteristics of both ZrO2 and the YSZ gate dielectrics were poorly revealed at too high RF power (200 W) and short D ts (35 mm). The smallest leakage current density of the YSZ film grown at 150 W and room temperature was obtained to be about 10 10 at 1 V of gate voltage.
References [1] Paul A. Packen, Science 24 (1999) 2079. [2] Z.J. Luo, X. Guo, T.P. Ma, T. Tamagawa, Appl. Phys. Lett. 79 (2001) 2803. [3] D. Han, J. Kang, C. Lin, R. Han, Chin. Phys. 12 (2003) 325. [4] W. Qi, R. Nieh, B.H. Lee, L. Kang, Y. Jeon, Appl. Phys. Lett. 77 (2000) 3269. [5] Y. Nishikawa, N. Fukushima, N. Yasuda, K. Nakayama, S. Ikegawa, Jpn. J. Appl. Phys. P1 41 (2002) 2480. [6] J. Zhu, Z.G. Liu, Mater. Lett. 57 (2003) 4297. [7] R.H. French, S.J. Glass, F.S. Ohuchi, Y.N. Xu, W.T. Ching, Phys. Rev. 49 (1994) 5133. [8] D.K. Fork, D.B. Fenner, Appl. Phys. Lett. 57 (1990) 1137.
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[9] K. Hubbard, D.G. Schlom, J. Mater. Res. 11 (1996) 2757. [10] K. Endo, T. Tatsumi, Jpn. J. Appl. Phys. P2 42 (2003) 685. [11] S.J. Wang, C.K. Ong, S.Y. Xu, P. Chen, W.C. Tjiu, J.W. Chai, A.C.H. Huan, W.J. Yoo, J.S. Lim, W. Feng, W.K. Choi, Appl. Phys. Lett. 78 (2001) 1604. [12] S.J. Wang, C.K. Ong, Appl. Phys. Lett. 80 (2002) 2541.
[13] (a) P. Gao, L.J. Meng, M.P. dos Santos, V. Teixeira, M. Andritschky, Thin Solid Films 377 (2000) 32; (b) P. Gao, L.J. Meng, M.P. dos Santos, V. Teixeira, M. Andritschky, Thin Solid Films 377 (2000) 557. [14] S. Horita, M. Watanabe, A. Masuda, Mater. Sci. Eng., B, Solid-State Mater. Adv. Technol. 54 (1998) 79.
Physical and electrical properties of ZrO2 and YSZ high-k gate dielectric thin films grown by RF magnetron sputtering S.H. Jeonga, I.S. Baea, Y.S. Shina, S.-B. Leea, H.-T. Kwakb, J.-H. Booa,* a
Department of Chemistry, Sungkyunkwan University, 300 Chunchun-Dong, Jangan-Gu, Suwon 440-746, Korea b Department of Chemistry, Kookmin University, Seoul 136-702, Korea Available online 11 September 2004
Abstract Thin films of ZrO2 were deposited on p-Si(100) substrates using RF magnetron sputtering technique. To investigate the influence of the sputtering parameters, e.g., annealing temperature, different O2-flux, RF power and target to substrate distance on the physical and electrical properties of the as-grown films, systematic investigation using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscope and energy dispersive X-ray (SEM–EDX), C–V, and I–V were carried out in this work. Deposited ZrO2 films had polycrystalline after annealing sample at high temperature. Their silicon oxide (SiO2) layers were formed between high-k film (i.e., ZrO2 and YSZ) and Si substrate either after annealing samples at high temperature or introducing O2-flux the sputtering process step. The high-k thin films have to be deposited amorphous structure without SiO2 interlayers. We also investigated the electrical properties of both the a-ZrO2 and a-YSZ films prepared without O2-flux at room temperature with conditions of various RF power and target to substrate distance. The dielectric constant of amorphous YSZ was determined to be about 24 using metal–insulator– semiconductor (MIS) capacitor structure. The smallest leakage current density of the YSZ film grown at 150 W and at room temperature was obtained to be about 10 10 at 1 V. D 2004 Elsevier B.V. All rights reserved. Keywords: RF magnetron sputtering; ZrO2 films; YSZ films; High-k gate dielectrics; Leakage current
1. Introduction Recently, as metal oxide semiconductor field effect transistor (MOSFET) devices are scaled down to b100 nm, problems of conventional silicon oxide (SiO2) appeared. SiO2 layer suffered from basic problem of high tunneling leakage current and reduced drive current due to low dielectric constant (k=3.9) with thickness decreased (b2 nm) [1,2]. Hence, high-k gate dielectrics such as Ta2O5, TiO2, HfO2, ZrO2, CeO2, Y2O3 stabilized ZrO2 (YSZ) [2–6] were studied to replace SiO2. Most of these materials, however, were not thermally stable directly on Si, due to the formation of metal silicides in the course of fabrication.
* Corresponding author. Tel.: +82 31 290 7072; fax: +82 31 290 7075. E-mail address: [email protected] (J.-H. Boo). 0040-6090/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2004.07.023
ZrO2 and YSZ are one of the most attractive andidates due to its high-k values (~25 and ~27, respectively), wide band gap (approximately 5.1–7.8 eV) [7,8], and good thermal stability in contact with Si [9]. Due to their excellent properties, ZrO2 and YSZ films have been extensively studied as gate dielectric [10]. Wang et al. [11] studied the 6nm-thick epitaxial crystalline YSZ films with electrical equivalent oxide thickness (EOT) of 1.46 nm and found that the leakage current was about 1.110 3 A/cm2 at 1 V. In addition, Zhu and Liu [6] also studied the 6-nm-thick amorphous YSZ films with EOT=1.46 nm and obtained a leakage current to be about 7.5810 5 A/cm2 at 1 V. Moreover, amorphous films exhibited isotropic electrical properties and can easily be deposited. In this work, the influence of the sputtering parameter such as, O2-flux, annealing temperature, RF power and target-to-substrate distance (D ts) on physical and electrical properties of amorphous ZrO2 and YSZ films that were
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area of the capacitors was 2.410 4 cm2. The I–V and C–V curves were measured using a HP4140B pico-A and a Bonton 7200 capacitor meter, respectively.
3. Results and discussion Fig. 1(a) shows X-ray diffraction patterns of ZrO2 thin films grown at room temperature without O2-flux. The RF power was 150 W and the annealing temperature varied from 600 to 1200 8C. Below 600 8C, there were no typical diffraction peaks, indicating an amorphous structure. Between 800 and 1000 8C, the films were mainly grown in the [111] orientation, while the crystal growth direction was changed to be [012], at an annealing temperature in the range of 1000–1200 8C. The polycrystal film could thus be obtained after annealing over 800 8C. With oxygen flux, the same tendency of X-ray diffraction pattern as Fig. 1(a) was observed (not shown). However, the relative intensity was decreased substantially, suggesting the poor crystallinity in these cases. The FT-IR spectra of ZrO2 films are shown in Fig. 1(b). The peaks at 794.6 and 1083.9 cm 1 were mostly due to Si– O–Si and Si–O stretching of the silicon oxide layers. The
Fig. 1. (a) X-ray diffraction patterns of ZrO2 thin films obtained with different annealing temperatures. (b) FT-IR spectra of ZrO2 thin films obtained with different O2 flux and annealing.
prepared at low temperature by RF magnetron sputtering method have been studied.
2. Experimental Both ZrO2 and YSZ films were prepared by the RF magnetron sputtering method. The purity of the ZrO2 target was above 99.99% with a diameter of 1 in. The YSZ target were prepared with 8 wt.% Y2O3-stabilized ZrO2. The sputtering gas (Ar) with a purity of 99.99% were introduced to the chamber and controlled by the standard mass-flow controllers. The sputtering pressure was 32 mTorr and p type Si(100) wafer were used as substrates without heating. The substrate–target distance was changed from 30 to 50 mm and RF power was controlled from 80 to 200 W. The structural properties of the films were characterized by X-ray diffraction (XRD) using Cu K a radiation (RIGAKU, D/MAX-2200 ultima). The interlayers between high-k film and substrate were analyzed with Fourier transform infrared (FT-IR, AVATAR 320) spectroscopy. The thickness and interlayers formation were observed using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) (XL 30 ESEM-FEG). The electrical properties were measured by metal–insulator–semiconductor (MIS) capacitor structures with Al gate electrodes. The
Fig. 2. (a) SEM and EDX image of a ZrO2 thin film grown at RT and 150 W with oxygen flux of 20 sccm. (b) Variation of ZrO2 film growth rates of with RF power magnitude (n).
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Fig. 3. (a) High-frequency C–V measurement of ZrO2 capacitors with various D ts. C–V characteristics of ZrO2 (b) and YSZ (c) films grown at different RF power: 80 (n), 120 ( ), 150 (E), and 200 (z) W.
!
reason of rising SiO2 layers was due to interdiffusion caused by oxygen diffusion into the interlayer during annealing. To prove this phenomenon clearly, YSZ film synthesis was also carried out under the same deposition condition of annealing and O2-flux as the same experiments of ZrO2 film deposition did. The deposited ZrO2 and YSZ films had the SiO2 layers between film and substrate.
Fig. 2(a) shows typical SEM image as well as EDX result obtained from the ZrO2 thin film that grown at room temperature and 150 W with oxygen. The cross-sectional EDX data show the SiO2 layer formation at the interface region between ZrO2 film layer and Si substrate. The interfacial SiO2 layers were formed between high-k film and silicon substrate either loading O2-flux or after annealing sample. Similarly, several papers [11–13] reported that the formation of an interfacial SiO2 layer in YSZ film surface induced lower dielectric constant than that of YSZ during film deposition due to residual oxygen in the chamber and high oxygen diffusivities of YSZ. Deposited high-k films had polycrystalline after annealing sample at high temperature. However, the high-k films have to be prepared to amorphous structure without interfacial SiO2 layer. Moreover, we investigated the electrical properties of both a-ZrO2 and a-YSZ films, which were prepared without O2-flux at room temperature under condition of various RF powers and D ts. With cross-sectional SEM image, one could calculate the film thickness as well as growth rate. Fig. 2(b) shows the variation of film growth rate as a function of RF power magnitudes at D ts of 40 mm. With increasing RF power, the growth rate is linearly increased within our experimental condition. Fig. 3(a) showed the results for the high frequency C–V measurement of ZrO2 capacitors at various D ts. The dielectric constants of the ZrO2 films deposited at D ts of 35, 40, and 50 mm were found to be 10.87, 23.38, and 20.81, respectively. These values were determined from the capacitance (C i) in the accumulation region of the 1 MHz C–V curves. The C–V characteristics of both the ZrO2 and the YSZ gate dielectrics with different RF powers were shown in the Fig. 3(b) and (c), respectively. All samples were prepared at room temperature with D ts=40 mm. The dielectric constants of these films are summarized in Table 1. The classical operational modes of ideal MIS structures with distinct inversion, depletion, and accumulation were clearly revealed in the C–V characteristics of all the dielectric films except for ZrO2 film at 200 W. Fig. 4(a) reveal that the leakage current density decreased with decreasing the target to substrate distance. Fig. 4(b) and (c) showed the I–V characteristics of both ZrO2 and YSZ gate dielectrics grown at different RF power: 80, 120, 150, and 200 W. The leakage current decreased with increasing RF power. In addition, this was caused from, that films became dense at a low D ts and high RF power. Gao et al. [13] reported that the packing density increased with the increasing sputtering power and decreased with increasing Table 1 The dielectric constants of both ZrO2 and YSZ films with different RF powers k ZrO2 k YSZ
80 W
120 W
150 W
200 W
21.57 13.70
21.60 24.10
23.35 22.54
7.29 10.38
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4. Conclusions We have deposited ZrO2 thin films on p-Si(100) substrate by RF magnetron sputtering in order to study an influence of deposition parameters (such as annealing temperature, reactive gas, RF power, and Y2O3 dopant) on the physical and electrical properties of the as-grown films. XRD showed that a highly oriented cubic ZrO2 thin film in the [111] direction was obtained after annealing at 800 8C. On the other hand, tetragonal ZrO2 thin film was also grown on Si (100) substrate and the main film growth direction was also changed to be [012] direction at above 800 8C of annealing temperature. FT-IR data show that both ZrO2 and YSZ films, which were deposited under conditions of annealing and O2-flux, had the SiO2 layers between the films and substrate. We investigated the electrical properties of the films of both a-ZrO2 and a-YSZ films which were prepared without O2-flux at room temperature under the conditions of various RF powers and D ts. The C–V characteristics of all the dielectric films that involved distinct inversion, depletion, and accumulation were clearly revealed in MIS structure except for ZrO2 film at 200 W. The leakage current decreased with decreasing D ts and increasing RF power. Because of a low D ts and high RF power, films became dense so that the leakage current decreased. In addition, the leakage current of YSZ films is smaller than that of ZrO2. This reasoned that the stabilization of film increased with increasing dopant content. The smallest leakage current density of the YSZ film grown at 150 W and room temperature was obtained to be about 10 10 at 1 V of gate voltage. The dielectric constant of amorphous YSZ was determined to be about 24 by MIS capacitor structure.
Acknowledgements This work was supported by the BK21 project of the Ministry of Education Korea, by the CAPST (Center for Advanced Plasma Surface Technology) and by the Korea Science and Engineering Foundation (project No. R012003-000-10019-0) at the Sungkyunkwan University. Fig. 4. (a) I–V curves of ZrO2 capacitors with various D ts. I–V characteristics of ZrO2 (b) and YSZ (c) films grown at different RF power: 80 (n), 120 ( ), 150 (E), and 200 (z) W.
!
D ts. In addition, the leakage current of YSZ films is smaller than that of ZrO2 films. This suggests that the stabilization of film with Y2O3 increased with increasing dopant content [14]. The leakage current of film decreased with decreasing D ts and increasing power. However, the C–V characteristics of both ZrO2 and the YSZ gate dielectrics were poorly revealed at too high RF power (200 W) and short D ts (35 mm). The smallest leakage current density of the YSZ film grown at 150 W and room temperature was obtained to be about 10 10 at 1 V of gate voltage.
References [1] Paul A. Packen, Science 24 (1999) 2079. [2] Z.J. Luo, X. Guo, T.P. Ma, T. Tamagawa, Appl. Phys. Lett. 79 (2001) 2803. [3] D. Han, J. Kang, C. Lin, R. Han, Chin. Phys. 12 (2003) 325. [4] W. Qi, R. Nieh, B.H. Lee, L. Kang, Y. Jeon, Appl. Phys. Lett. 77 (2000) 3269. [5] Y. Nishikawa, N. Fukushima, N. Yasuda, K. Nakayama, S. Ikegawa, Jpn. J. Appl. Phys. P1 41 (2002) 2480. [6] J. Zhu, Z.G. Liu, Mater. Lett. 57 (2003) 4297. [7] R.H. French, S.J. Glass, F.S. Ohuchi, Y.N. Xu, W.T. Ching, Phys. Rev. 49 (1994) 5133. [8] D.K. Fork, D.B. Fenner, Appl. Phys. Lett. 57 (1990) 1137.
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[9] K. Hubbard, D.G. Schlom, J. Mater. Res. 11 (1996) 2757. [10] K. Endo, T. Tatsumi, Jpn. J. Appl. Phys. P2 42 (2003) 685. [11] S.J. Wang, C.K. Ong, S.Y. Xu, P. Chen, W.C. Tjiu, J.W. Chai, A.C.H. Huan, W.J. Yoo, J.S. Lim, W. Feng, W.K. Choi, Appl. Phys. Lett. 78 (2001) 1604. [12] S.J. Wang, C.K. Ong, Appl. Phys. Lett. 80 (2002) 2541.
[13] (a) P. Gao, L.J. Meng, M.P. dos Santos, V. Teixeira, M. Andritschky, Thin Solid Films 377 (2000) 32; (b) P. Gao, L.J. Meng, M.P. dos Santos, V. Teixeira, M. Andritschky, Thin Solid Films 377 (2000) 557. [14] S. Horita, M. Watanabe, A. Masuda, Mater. Sci. Eng., B, Solid-State Mater. Adv. Technol. 54 (1998) 79.