- Email: [email protected]
Segregation and diffusion of impurities from doped Si1−xGex films into silicon
Thin Solid Films 369 (2000) 222±225
www.elsevier.com/locate/tsf
Segregation and diffusion of impurities from doped Si12xGex ®lms into silicon S. Kobayashi a,*, T. Aoki a, N. Mikoshiba a, M. Sakuraba b, T. Matsuura b, J. Murota b a
Department of Electronic Engineering and Joint Research Center for High-technology, Tokyo Institute of Polytechnics, Atsugi 243-0297, Japan b Laboratory for Electronic Intelligent Systems, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
Abstract The segregation and diffusion of boron from in-situ doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms into Si at 750±8508C were investigated and compared with those properties of phosphorus diffusion from the Si12xGex ®lm. It was found that boron segregates in the Si12xGex ®lm rather than in Si, while phosphorus segregates in Si rather than in the Si12xGex ®lm. The segregation coef®cient of boron, de®ned as the ratio of the active boron concentration in the Si to that in the Si12xGex ®lm, was about 0.4 at 8508C in the case of the Si0.75Ge0.25 ®lm p as a diffusion source, and decreased with increasing Ge fraction. It was found that the boron diffusion pro®les in Si were normalized by x/ t even though the segregation of boron occurred. The diffusion characteristics of boron in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface boron concentration of the diffused layer, which is also the case with phosphorous diffusion from a Si12xGex ®lm. The high concentration diffusion characteristics of boron and phosphorus in Si were similar to those reported using conventional diffusion source. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Boron; Phosphorus; Diffusion; Segregation; Silicon; Germanium
1. Introduction The Si12xGex heterostructure has attracted much interest for the fabrication of high speed devices [1,2] using silicon based technology for future digital and analog circuits. In order to realize the high performance Si12xGex heterodevice such as super self-aligned shallow junction MOSFET (S 3EMOSFET) [3,4] utilizing an ultrashallow junction as the source and drain regions made of selective Si12xGex epitaxy [5], the exact control of the impurity distribution and high Ge fractions in the Si12xGex layer is necessary. The in-situ doping properties during Si12xGex epitaxial growth on Si [6±8] and the diffusion properties of impurities from the doped Si12xGex ®lms with x around 0.25 into Si [9± 11] were reported. However, little is known about the diffusion properties of impurities from the doped Si12xGex ®lms with the high Ge fraction at the low diffusion temperature. In the previous work, we studied segregation and diffusion properties of P from the doped Si12xGex (0:25 # x # 0:8) ®lms into Si at 750±8508C [12]. In this work, B diffusion into Si at 750±8508C in a N2 ambient from the high-quality in-situ B-doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms was investigated. A segregation of B between the Si12xGex ®lm and Si, and the diffusion characteristics of B in Si are * Corresponding author.
discussed in the comparison with those of P diffusion from the Si12xGex ®lm.
2. Experiment The in-situ B-doped Si12xGex epitaxial growth on Si was carried out at 5508C in a SiH4, GeH4, B2H6 and H2 by using an ultraclean hot-wall low-pressure chemical vapor deposition (CVD) system, the details of which were described elsewhere [8]. The substrates used were n-type Si wafers of 3.0±5.0 V cm with mirror polished (100) surfaces. The wafers were cleaned in several cycles in a 4:1 solution of H2SO4 and H2O2, a high-purity dionized (DI) water rinse, and 1±2% HF with a ®nal rinse in DI water, and then the wafers, placed on a quartz boat, were transported into the reactor through a N2 purged transfer chamber. The wafers were heated up to 5508C while purging with H2 gas. For the in-situ B-doped Si12xGex epitaxial growth, the total gas pressure was about 30 Pa. The partial pressure of SiH4 was 6.0 Pa. The Ge fraction x of B-doped Si12xGex ®lms was 0.2, 0.6 and 0.85, where the partial pressure of GeH4 was 0.25, 2.0 and 6.0 Pa, respectively. The partial pressure of B2H6 was 1.25 £ 10 23 and 3.75 £ 10 23 Pa. The thickness of the deposited B-doped Si12xGex ®lms was in the range of 5000± Ê . After the surface of the B-doped Si12xGex was 8000 A
0040-6090/00/$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S00 40-6090(00)0081 1-7
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
223
Fig. 1. B diffusion pro®les at 8508C from (a) the doped Si0.75Ge0.25 ®lm for 45 h, where the B concentration of the ®lm is about 9.0 £ 10 19 cm 23 and (b) the Si0.15Ge0.85 ®lm for 90 h into Si, where the B concentration of the ®lm is about 9.0 £ 10 19 cm 23, respectively.
covered with CVD SiO2 to avoid out-diffusion of B, diffusion was carried out in dry N2 environment at 750, 800 and 8508C for 15±300 h. The electrically active B concentration was determined by differential resistance measurements using the four-point probe method with anodic oxidation followed by conversion using Irvin's curves [13] in the case of the Si substrate, and the relational data between the carrier concentration and the resistivity obtained by Hall measurements [8] in the case of the Si12xGex ®lm. 3. Results and discussion
®lm. The segregation coef®cient at 8508C is 0.4 for the Si0.75Ge0.25 ®lm as a diffusion source and decreases with increasing Ge fraction, as shown in Fig. 2. On the other hand, the segregation coef®cient of P at 8508C was 2.5 for the Si0.75Ge0.25 ®lm as a diffusion source and increased with increasing Ge fraction [12]. pFig. 3 shows the B concentration in the diffused layer vs. x/ t in the case of Si0.75Ge0.25 ®lm as a diffusion source, where x is the distance from the surface of the diffused layer and t is the diffusion time. The surface B concentration of the diffused layer is the same value for the different diffusion time, even though the segregation of B occurred.
Fig. 1a,b show typical active B diffusion pro®les at 8508C from the in-situ B-doped Si0.75Ge0.25 and Si0.15Ge0.85 ®lms, respectively, as the diffusion source. The B concentration discontinuity at the interface is clearly observed and the surface B concentration of the diffused layer is lower than the B concentration of the diffusion source. This signi®es the segregation of B in the Si12xGex ®lm rather than in Si. On the contrary, P segregates in Si rather than in the Si12xGex ®lm [12]. The segregation is caused by a difference in the band structure between Si and Si12xGex and the charge state of a dopant ion [9]. Since the concentration pro®le in the Si12xGex ®lm in the present condition did not change with the transition of the diffusion time, it is considered that the diffusion coef®cient in the Si12xGex ®lm is enough large compared with that in Si. To de®ne the segregation coef®cient, the B concentration in the constant value region was taken for the Si12xGex side. For the Si side, the surface B concentration of the diffused layer was used. That is the segregation coef®cient was de®ned as the ratio of the active B concentration at the surface of the diffused layer in Si to that in the Si12xGex
Fig. 2. Ge fraction dependence of the segregation coef®cient of active B and active P at 8508C.
224
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
p Fig. 3. Dependence of the B concentration in Si on x/ t in the case of the Si0.75Ge0.25 ®lm as a diffusion source.
The B diffusion pro®les obtained for different diffusion times can be expressed by only one curve for each diffusion temperature. Fig. 4pshows the B concentration in the diffused layer vs. x/ t in the case of the Si0.35Ge0.65 ®lm as a diffusion source. Although the Ge fraction of the Si12xGex ®lm becomes higher, the B diffusion pro®les can be expressed by only one curve for each diffusion temperature. To make a comparison between Figs. 3 and 4, the surface B concentration of the diffused layer at 750 and 8008C are almost the same value, respectively, and the diffusion
p Fig. 4. Dependence of the B concentration in Si on x/ t in the case of Si0.35Ge0.65 ®lm as a diffusion source.
Fig. 5. Dependence of the diffusion coef®cient at 1 £ 10 19 cm 23 on the temperature in the case of the Si0.35Ge0.65 ®lm as a diffusion source. The surface B concentration of the diffused layer in Si is 1.5±3.0 £ 10 19 cm 23. The data of Sultan et al. are also plotted where the typical diffusion source is B implanted poly-Si and the surface B concentration is above 1 £ 10 20 cm 23.
pro®les can be expressed by almost the same curve for each temperature. This means that the B diffusion characteristics in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface B concentration. It is well known that the B diffusion is enhanced and the B concentration abruptly fall in the vicinity of the junction depth in the case of the high surface B concentration above 2 £ 10 19 cm 23 [14]. The diffusion pro®le at 8508C shows these features where the surface B concentration is 3 £ 10 19 cm 23. The diffusion coef®cient in Si is determined by the Boltzmann±Matano method p[15], since the B diffusion pro®les were normalized by x/ t in the present conditions. Fig. 5 shows the temperature dependence of the diffusion coef®cient at 1 £ 10 19 cm 23 in the case of the Si0.35Ge0.65 ®lm as a diffusion source. The data at 800±9508C reported by Sultan et al. [16] are plotted, where the diffusion source was B implanted polycrystalline Si and the surface B concentration was about 1 £ 10 20 cm 23. The data of Sultan's and the extrapolation towards the low temperature is in the same order of the present results at 750±8508C. The slightly lower value in the present work is reasonable, if we consider that the surface B concentration in the diffused layer in the present work is lower than that in Sultan's. The B diffusion characteristics in Si are described as follows, (1) the diffusion pro®les do not depend on the Ge
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
fraction, (2) the diffusion pro®les depend on the surface concentration of the diffused layer which are determined by the impurity concentration of the diffusion source and the segregation coef®cient, (3) the diffusion coef®cients are almost the same as those reported using other source. These features were also seen in the case of P diffusion from the Si12xGex ®lm. Consequently, the high concentration diffusion characteristics of B and P in Si from the doped Si12xGex source at 750±8508C are similar to those reported using conventional diffusion source. 4. Conclusions We studied segregation and diffusion of B from in-situ doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms into Si at 750±8508C and discussed segregation and diffusion properties in comparison with those of P diffusion from doped Si12xGex ®lm. It was found that B segregates in the Si12xGex ®lm rather than in Si. The segregation coef®cient was about 0.4 at 8508C in the case of the Si0.75Ge0.25 ®lm as a diffusion source and decreased with increasing Ge fraction. The segregation properties of B contrast to those p of P. The B diffusion pro®les in Si were normalized by x/ t even though the segregation of B occurred. The diffusion characteristics of B in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface B concentration. These characteristics were also seen in the case of P diffusion from a Si12xGex ®lm. The high concentration diffusion characteristics of B and P in Si were similar to those reported using conventional diffusion source. Acknowledgements This work was partially carried out in the Superclean
225
Room of the Laboratory for Electronic Intelligent Systems, Research Institute of Electrical Communication, Tohoku University under the Cooperative Research Project Program, and partially supported by a Grant-in-Aid for Scienti®c Research from Ministry of Education, Science, Sports and Culture of Japan. References [1] G.L. Patton, J.H. Comfort, B.S. Meyerson, et al., Electron. Device Lett. EDL-11 (1990) 171. [2] P.M. Garone, V. Venkertaraman, J.C. Strum, Electron. Device Lett. EDL-13 (1992) 56. [3] K. Goto, J. Murota, F. Honma, T. Matsuura, Y. Sawada, in: E.M. Middlesworth, H. Massoud (Eds.), 5th Int. Symp. ULSI Science and Technology, Electrochemical Society, Pennington, NJ, 1995, p. 512. [4] J. Murota, M. Ishii, K. Goto, M. Sakuraba, T. Matsuura, Y. Kudoh, M. Koyanagi, Proc. 27th Euro. Solid-State Device Research Conference, Stuttgart, Germany 22±24 (1997) 376. [5] F. Honma, J. Murota, K. Goto, T. Maeda, Y. Sawada, Jpn. J. Appl. Phys. 33 (1994) 2300. [6] C. Tsai, S.M. Jang, J. Tsai, R. Reif, J. Appl. Phys. 69 (1991) 8158. [7] S.M. Jang, K. Liao, R. Reif, J. Electrochem. Soc. 142 (1995) 3520. [8] J. Murota, M. Sakuraba, T. Matsuura, Defects in Silicon III, Electrochemical Society, Pennington PV99-1 (1999) 189. [9] S.M. Hu, D.C. Ahlgren, P.A. Ronsheim, J.O. Chu, Phys. Rev. Lett. 67 (1991) 1450. [10] N. Moriya, L.C. Feldman, S.W. Downey, C.A. King, A.B. Emerson, Phys. Rev. Lett. 75 (1995) 1981. [11] D.T. Grider, M.C. Ozturk, S.P. Ashburn, J.J. Wortman, G. Harris, D. Maher, J. Electron. Mater. 24 (1995) 1369. [12] S. Kobayashi, M. Iizuka, T. Aoki, N. Mikoshiba, M. Sakuraba, T. Matsuura, J. Murota, J. Appl. Phys. 86 (1999) 5480. [13] J.C. Irvin, Bell Syst. Tech. 41 (1962) 387. [14] C. Matano, Jpn. J. Phys. 8 (1933) 109. [15] R.B. Fair, J. Electrochem. Soc. 122 (1975) 800. [16] S. Sultan, M. Lobo, S. Bhattacharya, et al., J. Electron. Mater. 22 (1993) 1129.
www.elsevier.com/locate/tsf
Segregation and diffusion of impurities from doped Si12xGex ®lms into silicon S. Kobayashi a,*, T. Aoki a, N. Mikoshiba a, M. Sakuraba b, T. Matsuura b, J. Murota b a
Department of Electronic Engineering and Joint Research Center for High-technology, Tokyo Institute of Polytechnics, Atsugi 243-0297, Japan b Laboratory for Electronic Intelligent Systems, Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577, Japan
Abstract The segregation and diffusion of boron from in-situ doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms into Si at 750±8508C were investigated and compared with those properties of phosphorus diffusion from the Si12xGex ®lm. It was found that boron segregates in the Si12xGex ®lm rather than in Si, while phosphorus segregates in Si rather than in the Si12xGex ®lm. The segregation coef®cient of boron, de®ned as the ratio of the active boron concentration in the Si to that in the Si12xGex ®lm, was about 0.4 at 8508C in the case of the Si0.75Ge0.25 ®lm p as a diffusion source, and decreased with increasing Ge fraction. It was found that the boron diffusion pro®les in Si were normalized by x/ t even though the segregation of boron occurred. The diffusion characteristics of boron in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface boron concentration of the diffused layer, which is also the case with phosphorous diffusion from a Si12xGex ®lm. The high concentration diffusion characteristics of boron and phosphorus in Si were similar to those reported using conventional diffusion source. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Boron; Phosphorus; Diffusion; Segregation; Silicon; Germanium
1. Introduction The Si12xGex heterostructure has attracted much interest for the fabrication of high speed devices [1,2] using silicon based technology for future digital and analog circuits. In order to realize the high performance Si12xGex heterodevice such as super self-aligned shallow junction MOSFET (S 3EMOSFET) [3,4] utilizing an ultrashallow junction as the source and drain regions made of selective Si12xGex epitaxy [5], the exact control of the impurity distribution and high Ge fractions in the Si12xGex layer is necessary. The in-situ doping properties during Si12xGex epitaxial growth on Si [6±8] and the diffusion properties of impurities from the doped Si12xGex ®lms with x around 0.25 into Si [9± 11] were reported. However, little is known about the diffusion properties of impurities from the doped Si12xGex ®lms with the high Ge fraction at the low diffusion temperature. In the previous work, we studied segregation and diffusion properties of P from the doped Si12xGex (0:25 # x # 0:8) ®lms into Si at 750±8508C [12]. In this work, B diffusion into Si at 750±8508C in a N2 ambient from the high-quality in-situ B-doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms was investigated. A segregation of B between the Si12xGex ®lm and Si, and the diffusion characteristics of B in Si are * Corresponding author.
discussed in the comparison with those of P diffusion from the Si12xGex ®lm.
2. Experiment The in-situ B-doped Si12xGex epitaxial growth on Si was carried out at 5508C in a SiH4, GeH4, B2H6 and H2 by using an ultraclean hot-wall low-pressure chemical vapor deposition (CVD) system, the details of which were described elsewhere [8]. The substrates used were n-type Si wafers of 3.0±5.0 V cm with mirror polished (100) surfaces. The wafers were cleaned in several cycles in a 4:1 solution of H2SO4 and H2O2, a high-purity dionized (DI) water rinse, and 1±2% HF with a ®nal rinse in DI water, and then the wafers, placed on a quartz boat, were transported into the reactor through a N2 purged transfer chamber. The wafers were heated up to 5508C while purging with H2 gas. For the in-situ B-doped Si12xGex epitaxial growth, the total gas pressure was about 30 Pa. The partial pressure of SiH4 was 6.0 Pa. The Ge fraction x of B-doped Si12xGex ®lms was 0.2, 0.6 and 0.85, where the partial pressure of GeH4 was 0.25, 2.0 and 6.0 Pa, respectively. The partial pressure of B2H6 was 1.25 £ 10 23 and 3.75 £ 10 23 Pa. The thickness of the deposited B-doped Si12xGex ®lms was in the range of 5000± Ê . After the surface of the B-doped Si12xGex was 8000 A
0040-6090/00/$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S00 40-6090(00)0081 1-7
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
223
Fig. 1. B diffusion pro®les at 8508C from (a) the doped Si0.75Ge0.25 ®lm for 45 h, where the B concentration of the ®lm is about 9.0 £ 10 19 cm 23 and (b) the Si0.15Ge0.85 ®lm for 90 h into Si, where the B concentration of the ®lm is about 9.0 £ 10 19 cm 23, respectively.
covered with CVD SiO2 to avoid out-diffusion of B, diffusion was carried out in dry N2 environment at 750, 800 and 8508C for 15±300 h. The electrically active B concentration was determined by differential resistance measurements using the four-point probe method with anodic oxidation followed by conversion using Irvin's curves [13] in the case of the Si substrate, and the relational data between the carrier concentration and the resistivity obtained by Hall measurements [8] in the case of the Si12xGex ®lm. 3. Results and discussion
®lm. The segregation coef®cient at 8508C is 0.4 for the Si0.75Ge0.25 ®lm as a diffusion source and decreases with increasing Ge fraction, as shown in Fig. 2. On the other hand, the segregation coef®cient of P at 8508C was 2.5 for the Si0.75Ge0.25 ®lm as a diffusion source and increased with increasing Ge fraction [12]. pFig. 3 shows the B concentration in the diffused layer vs. x/ t in the case of Si0.75Ge0.25 ®lm as a diffusion source, where x is the distance from the surface of the diffused layer and t is the diffusion time. The surface B concentration of the diffused layer is the same value for the different diffusion time, even though the segregation of B occurred.
Fig. 1a,b show typical active B diffusion pro®les at 8508C from the in-situ B-doped Si0.75Ge0.25 and Si0.15Ge0.85 ®lms, respectively, as the diffusion source. The B concentration discontinuity at the interface is clearly observed and the surface B concentration of the diffused layer is lower than the B concentration of the diffusion source. This signi®es the segregation of B in the Si12xGex ®lm rather than in Si. On the contrary, P segregates in Si rather than in the Si12xGex ®lm [12]. The segregation is caused by a difference in the band structure between Si and Si12xGex and the charge state of a dopant ion [9]. Since the concentration pro®le in the Si12xGex ®lm in the present condition did not change with the transition of the diffusion time, it is considered that the diffusion coef®cient in the Si12xGex ®lm is enough large compared with that in Si. To de®ne the segregation coef®cient, the B concentration in the constant value region was taken for the Si12xGex side. For the Si side, the surface B concentration of the diffused layer was used. That is the segregation coef®cient was de®ned as the ratio of the active B concentration at the surface of the diffused layer in Si to that in the Si12xGex
Fig. 2. Ge fraction dependence of the segregation coef®cient of active B and active P at 8508C.
224
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
p Fig. 3. Dependence of the B concentration in Si on x/ t in the case of the Si0.75Ge0.25 ®lm as a diffusion source.
The B diffusion pro®les obtained for different diffusion times can be expressed by only one curve for each diffusion temperature. Fig. 4pshows the B concentration in the diffused layer vs. x/ t in the case of the Si0.35Ge0.65 ®lm as a diffusion source. Although the Ge fraction of the Si12xGex ®lm becomes higher, the B diffusion pro®les can be expressed by only one curve for each diffusion temperature. To make a comparison between Figs. 3 and 4, the surface B concentration of the diffused layer at 750 and 8008C are almost the same value, respectively, and the diffusion
p Fig. 4. Dependence of the B concentration in Si on x/ t in the case of Si0.35Ge0.65 ®lm as a diffusion source.
Fig. 5. Dependence of the diffusion coef®cient at 1 £ 10 19 cm 23 on the temperature in the case of the Si0.35Ge0.65 ®lm as a diffusion source. The surface B concentration of the diffused layer in Si is 1.5±3.0 £ 10 19 cm 23. The data of Sultan et al. are also plotted where the typical diffusion source is B implanted poly-Si and the surface B concentration is above 1 £ 10 20 cm 23.
pro®les can be expressed by almost the same curve for each temperature. This means that the B diffusion characteristics in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface B concentration. It is well known that the B diffusion is enhanced and the B concentration abruptly fall in the vicinity of the junction depth in the case of the high surface B concentration above 2 £ 10 19 cm 23 [14]. The diffusion pro®le at 8508C shows these features where the surface B concentration is 3 £ 10 19 cm 23. The diffusion coef®cient in Si is determined by the Boltzmann±Matano method p[15], since the B diffusion pro®les were normalized by x/ t in the present conditions. Fig. 5 shows the temperature dependence of the diffusion coef®cient at 1 £ 10 19 cm 23 in the case of the Si0.35Ge0.65 ®lm as a diffusion source. The data at 800±9508C reported by Sultan et al. [16] are plotted, where the diffusion source was B implanted polycrystalline Si and the surface B concentration was about 1 £ 10 20 cm 23. The data of Sultan's and the extrapolation towards the low temperature is in the same order of the present results at 750±8508C. The slightly lower value in the present work is reasonable, if we consider that the surface B concentration in the diffused layer in the present work is lower than that in Sultan's. The B diffusion characteristics in Si are described as follows, (1) the diffusion pro®les do not depend on the Ge
S. Kobayashi et al. / Thin Solid Films 369 (2000) 222±225
fraction, (2) the diffusion pro®les depend on the surface concentration of the diffused layer which are determined by the impurity concentration of the diffusion source and the segregation coef®cient, (3) the diffusion coef®cients are almost the same as those reported using other source. These features were also seen in the case of P diffusion from the Si12xGex ®lm. Consequently, the high concentration diffusion characteristics of B and P in Si from the doped Si12xGex source at 750±8508C are similar to those reported using conventional diffusion source. 4. Conclusions We studied segregation and diffusion of B from in-situ doped Si12xGex (0:25 # x # 0:85) epitaxial ®lms into Si at 750±8508C and discussed segregation and diffusion properties in comparison with those of P diffusion from doped Si12xGex ®lm. It was found that B segregates in the Si12xGex ®lm rather than in Si. The segregation coef®cient was about 0.4 at 8508C in the case of the Si0.75Ge0.25 ®lm as a diffusion source and decreased with increasing Ge fraction. The segregation properties of B contrast to those p of P. The B diffusion pro®les in Si were normalized by x/ t even though the segregation of B occurred. The diffusion characteristics of B in Si do not depend on the Ge fraction of the diffusion source, but depend on the surface B concentration. These characteristics were also seen in the case of P diffusion from a Si12xGex ®lm. The high concentration diffusion characteristics of B and P in Si were similar to those reported using conventional diffusion source. Acknowledgements This work was partially carried out in the Superclean
225
Room of the Laboratory for Electronic Intelligent Systems, Research Institute of Electrical Communication, Tohoku University under the Cooperative Research Project Program, and partially supported by a Grant-in-Aid for Scienti®c Research from Ministry of Education, Science, Sports and Culture of Japan. References [1] G.L. Patton, J.H. Comfort, B.S. Meyerson, et al., Electron. Device Lett. EDL-11 (1990) 171. [2] P.M. Garone, V. Venkertaraman, J.C. Strum, Electron. Device Lett. EDL-13 (1992) 56. [3] K. Goto, J. Murota, F. Honma, T. Matsuura, Y. Sawada, in: E.M. Middlesworth, H. Massoud (Eds.), 5th Int. Symp. ULSI Science and Technology, Electrochemical Society, Pennington, NJ, 1995, p. 512. [4] J. Murota, M. Ishii, K. Goto, M. Sakuraba, T. Matsuura, Y. Kudoh, M. Koyanagi, Proc. 27th Euro. Solid-State Device Research Conference, Stuttgart, Germany 22±24 (1997) 376. [5] F. Honma, J. Murota, K. Goto, T. Maeda, Y. Sawada, Jpn. J. Appl. Phys. 33 (1994) 2300. [6] C. Tsai, S.M. Jang, J. Tsai, R. Reif, J. Appl. Phys. 69 (1991) 8158. [7] S.M. Jang, K. Liao, R. Reif, J. Electrochem. Soc. 142 (1995) 3520. [8] J. Murota, M. Sakuraba, T. Matsuura, Defects in Silicon III, Electrochemical Society, Pennington PV99-1 (1999) 189. [9] S.M. Hu, D.C. Ahlgren, P.A. Ronsheim, J.O. Chu, Phys. Rev. Lett. 67 (1991) 1450. [10] N. Moriya, L.C. Feldman, S.W. Downey, C.A. King, A.B. Emerson, Phys. Rev. Lett. 75 (1995) 1981. [11] D.T. Grider, M.C. Ozturk, S.P. Ashburn, J.J. Wortman, G. Harris, D. Maher, J. Electron. Mater. 24 (1995) 1369. [12] S. Kobayashi, M. Iizuka, T. Aoki, N. Mikoshiba, M. Sakuraba, T. Matsuura, J. Murota, J. Appl. Phys. 86 (1999) 5480. [13] J.C. Irvin, Bell Syst. Tech. 41 (1962) 387. [14] C. Matano, Jpn. J. Phys. 8 (1933) 109. [15] R.B. Fair, J. Electrochem. Soc. 122 (1975) 800. [16] S. Sultan, M. Lobo, S. Bhattacharya, et al., J. Electron. Mater. 22 (1993) 1129.