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Effect of stress on accumulation of oxygen in silicon implanted with helium and hydrogen
Physica B 308–310 (2001) 317–320
Effect of stress on accumulation of oxygen in silicon implanted with helium and hydrogen A. Misiuka,*, A. Barcza, V. Rainerib, J. Ratajczaka, J. Bak-Misiukc, I.V. Antonovad, W. Wierzchowskie, K. Wieteskaf a
Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland b CNR-IMETEM, Stradale Primosole 50, I-95121 Catania, Italy c Institute of Physics, PAS, Al. Lotnikow 32/46, 02-668 Warsaw, Poland d Institute of Semiconductor Physics, RAS, Novosibirsk, Russia e Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland f Institute of Atomic Energy, 00-450 Swierk-Otwock, Poland
Abstract Pronounced oxygen segregation in helium-implanted Czochralski silicon, Cz-Si : He, treated at 1000–1400 K under atmospheric or enhanced, up to 1.2 109 Pa, hydrostatic pressure, HP, is observed. Annealing of hydrogen-implanted Cz-Si : H at 720–920 K-105 Pa also results in the oxygen accumulation in the damaged volume while no accumulation is detected at X1 GPa and at X1230 K. The HP effect on transformation of post-implantation defects and on oxygen diffusivity can be responsible for oxygen accumulation in Cz-Si : (He, H). r 2001 Elsevier Science B.V. All rights reserved. Keywords: Si : He; Si : H; Hydrostatic pressure; Oxygen accumulation
1. Introduction Defect formation in silicon implanted with helium (inert dopant) or hydrogen (creating a weak H–Si bond) has become, in last years, a topic of considerable interest, both for practical reasons (gettering of contaminants and ‘‘smart cut’’ process) and for the extraordinary gas pressures attained in He/H-filled clusters and bubbles created upon annealing [1,2]. Enhanced hydrostatic pressure (HP) of inert gas (Ar) at annealing (HT-HP treatment) of He- and Himplanted silicon affects strongly its structure [3,4]. The effect of stress induced by enhanced Ar pressure on accumulation (gettering) of oxygen in He- and H-
*Corresponding author. Tel.: +48-22-548-7792; fax: +4822-847-06-031. E-mail address: [email protected] (A. Misiuk).
implanted Czochralski silicon (Cz-Si) is the main subject of the present work.
2. Experimental Cz-Si wafers (of 0 0 1 orientation), with concentration of interstitial oxygen, co ; up to 1 1018 cm3, were implanted with helium (Cz-Si : He, He+ doses, D ¼ 5 1015 23 1017 cm2, energy p300 keV, He+ projected range, Rp p1:35 mm) or hydrogen (Cz-Si : H, 16 2 H+ 2 dose 4 10 cm , energy 130 keV, Rp ¼ 0:5 mm). Cz-Si : He and Cz-Si : H were treated under Ar pressure up to 1.2 GPa at temperature up to 1400 K for up to 10 h. The defect structure of the samples was investigated by transmission electron microscopy (TEM), X-ray reciprocal space mapping (XRRSM) and synchrotron topography done at HASYLAB, Hamburg. Oxygen and hydrogen depth profiles in the
0921-4526/01/$ - see front matter r 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 0 1 ) 0 0 8 8 1 - X
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annealed/treated samples were determined by secondary ion mass spectrometry (SIMS).
3. Results and discussion The He implantation into Si results in creation of disturbed He-containing zone near Rp : The kind and concentration of defects (mostly He-filled clusters and bubbles) are dependent on He dose and energy, substrate temperature (in our case p350 K) as well as on the conditions of subsequent annealing/HT-HP treatment. During the annealing He atoms escape the Si matrix; this He removal is increasing with temperature [4]. TEM image of Cz-Si : He sample treated at 870 K is presented in Fig. 1. Annealing of such samples at 1270 K-105 Pa for 1 h results in creation of bubbles while only dislocations were detected in Cz-Si : He (co ¼ 1 1018 cm3, D ¼ 5 1016 cm2, 150 keV, Rp ¼ 0:88 mm) treated at 1270 K-1.15 GPa for 1 h. As it follows from XRRSM, enhanced HP results in decreased intensity of X-ray diffuse scattering, an evidence of a better structural perfection of HT-HP treated CzSi : He as compared to that annealed at 105 Pa. No oxygen accumulation at implantation-damaged zone was detected for Cz-Si : He (D ¼ 5 1016 cm2)
Fig. 1. TEM image of Cz-Si : He sample (co ¼ 1 1018 cm3, D ¼ 5 1015 cm2, 300 keV, Rp ¼ 1:35 mm) treated at 870 K1.1 GPa for 10 h.
annealed below 1000 K at 105 Pa. The treatment under 1.1–1.2 GPa at 870–1000 K for 10 h results in the SIMSdetectable oxygen accumulation at damaged areas. Both the annealing and HT-HP treatment at 1270–1400 K results in the accumulation (Fig. 2). Hydrogen implantation into Si also leads to creation of disturbed H-containing region. The generated H-filled clusters/bubbles are dependent on H dose and energy, temperature (Tp470 K) as well as on conditions of the annealing. During the annealing/HT-HP treatment H atoms outdiffuse from the Si matrix, the H loss being substantially suppressed under HP [3]. TEM image of the Cz-Si : H sample treated at 920 K1.2 GPa is presented in Fig. 3. Two different disturbed areas were detected. The first one at a depth of 0.45– 0.55 mm, corresponding to Rp of the main implanted species, H+ 2 , contains small bubbles and dislocations; the second one at the 0.8–1.0 mm depth originated from single H+ ions present in the implanting beam and exhibits comparatively large bubbles. The prolonged annealing/treatment at temperatures up to 1400 K resulted in complete removal of hydrogen; however, numerous dislocations were still detected in Cz-Si treated at 1320 K-1.2 GPa for t ¼ 0:5 h. As it can be deduced from XRRSM [3,4] and synchrotron topographs, the intensity of X-ray diffuse scattering is lower and overall structural perfection is better in the case of the HT-HP treated Cz-Si : H samples, as compared to that annealed at 105 Pa. The as-implanted Cz-Si : H sample (co ¼ 8 1017 cm3) indicated no oxygen accumulation near Rp ; annealing of that sample at 720 K-105 for 0.5 h resulted
Fig. 2. SIMS depth profiles of oxygen in Cz-Si : He samples (co ¼ 1 1018 cm3, D ¼ 5 1016 cm2, 150 keV, Rp ¼ 0:88 mm) annealed/treated at 1270 K for 1 h.
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Fig. 4. Depth profiles of hydrogen and oxygen in Cz-Si : H samples, as-implanted and annealed at 720 K-105 Pa for 0.5 h.
Fig. 3. TEM image of Cz-Si : H sample (co ¼ 8 1017 cm3, D ¼ 4 1016 cm2, 130 keV, Rp ¼ 0:5 mm) treated at 920 K1.2 GPa for 0.5 h.
in a marked oxygen gettering by defects in the implantation-damaged layer (Fig. 4) and in hydrogen loss. The Cz-Si : H samples treated at (720–920) K-(1.1– 1.2) GPa for up to 1 h do not indicate the oxygen accumulation (Fig. 5). Some traces of that accumulation were detected in Cz-Si : H treated at 920/1070 K-1.1 GPa for X1 h, while no accumulation was detected for the samples annealed at 1320 K-105 Pa or treated at (1230– 1370) K-(1–1.2) GPa. The major differences, in respect of oxygen accumulation in Cz-Si : He vs. Cz-Si : H can be outlined as follows: (a) Oxygen accumulation was detected only in CzSi : He annealed at >1000 K–105 Pa; HP resulted in more pronounced gettering of oxygen. It is contrary to the case of Cz-Si : H where oxygen accumulation was detected upon annealing at 720–870 K-105 Pa. (b) High HP in Cz-Si : H treated at 720–870 K and at higher temperatures prohibited oxygen accumulation in damaged areas. Effect of oxygen accumulation in implantation damaged and in the near-surface areas of Cz-Si : He, H is related to oxygen gettering on defects. Probably it
Fig. 5. Depth profiles of hydrogen and oxygen in Cz-Si : H samples, annealed/treated at 920 K-105 Pa and 920 K-1.2 GPa for 0.5 h.
occurs mostly at the surface of initially He- or H-filled clusters and bubbles. Under HT-HP, more numerous but smaller size clusters are formed. The gettering activity is increasing with HP. Most probably, the oxygen accumulation in the CzSi : H samples subjected to short-time anneals at 720– 870 K-105 Pa originates from increased diffusivity of oxygen in the presence of hydrogen [5]. The oxygen gettering was negligible in HP-HT treated Cz-Si : H. It
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means that HP affects strongly oxygen diffusivity; oxygen mobility decreases dramatically with HP. From comparison of oxygen depth profiles for Cz-Si : He and Cz-Si : H, implanted with comparable He and H doses (hence, with similar extent of damage near Rp ) and treated at >1000 K it follows also that the HP effect on the resultant defect structure of Cz-Si : He and Cz-Si : H is different. Both the annealed and HT-HP treated CzSi : He samples exhibit gettering activity at >1000 K, while the HT-HP processing of Cz-Si : H results in some specific structural changes in implantation-damaged areas. The implantation damaged area of HT-HP treated Cz-Si : H ceases to be active in respect of the oxygen accumulation. In summary, this paper demonstrates an appearance of the enormous effect of oxygen segregation within the damaged volume. In order to realise the magnitude of this phenomenon, let us consider the integral of the oxygen peak formed as a result of the implantation and the HT-HP treatment of Cz-Si : He (Fig. 2, solid circles). Here oxygen content amounts to about 1016 cm2. This would correspond to the oxygen contained in the Cz-Si slab of about 100 mm thickness. Taking the existing data for oxygen diffusion in Si, such extended transport within the semiconductor can be excluded. An alternative source of oxygen to be eventually gettered in the vicinity of Rp would be the oxygen contamination of the
ambient gas. However, even in such a case the transport from the surface would be enormous. So further investigation is definitely needed to solve that question.
Acknowledgements This work was supported in part by the Polish Committee for Scientific Research (grants no. 8T11B 072 19 and 2P 03B 14018).
References [1] G.F. Cerofolini, G. Calzolari, F. Corni, C. Nobili, G. Ottaviani, R. Tonini, Mater. Sci. Eng. B 71 (2000) 196. [2] V. Raineri, S. Coffa, E. Szilagyi, J. Gyulai, E. Rimini, Phys. Rev. B 61 (2000) 937. [3] A. Misiuk, J. Bak-Misiuk, A. Barcz, A. Romano-Rodriguez, I.V. Antonova, V.P. Popov, C.A. Londos, J. Jun, Int. J. Hydrogen Energy 26 (2001) 483. [4] A. Misiuk, J. Bak-Misiuk, I.V. Antonova, V.P. Popov, V. Raineri, A. Romano-Rodriguez, A. Bachrouri, H.B. Surma, J. Ratajczak, J. Katcki, J. Adamczewska, E.P. Neustroev, Comput. Mater. Sci. 21 (2001) 515. [5] L. Zhong, F. Shimura, J. Appl. Phys. 73 (1993) 707.
Effect of stress on accumulation of oxygen in silicon implanted with helium and hydrogen A. Misiuka,*, A. Barcza, V. Rainerib, J. Ratajczaka, J. Bak-Misiukc, I.V. Antonovad, W. Wierzchowskie, K. Wieteskaf a
Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland b CNR-IMETEM, Stradale Primosole 50, I-95121 Catania, Italy c Institute of Physics, PAS, Al. Lotnikow 32/46, 02-668 Warsaw, Poland d Institute of Semiconductor Physics, RAS, Novosibirsk, Russia e Institute of Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw, Poland f Institute of Atomic Energy, 00-450 Swierk-Otwock, Poland
Abstract Pronounced oxygen segregation in helium-implanted Czochralski silicon, Cz-Si : He, treated at 1000–1400 K under atmospheric or enhanced, up to 1.2 109 Pa, hydrostatic pressure, HP, is observed. Annealing of hydrogen-implanted Cz-Si : H at 720–920 K-105 Pa also results in the oxygen accumulation in the damaged volume while no accumulation is detected at X1 GPa and at X1230 K. The HP effect on transformation of post-implantation defects and on oxygen diffusivity can be responsible for oxygen accumulation in Cz-Si : (He, H). r 2001 Elsevier Science B.V. All rights reserved. Keywords: Si : He; Si : H; Hydrostatic pressure; Oxygen accumulation
1. Introduction Defect formation in silicon implanted with helium (inert dopant) or hydrogen (creating a weak H–Si bond) has become, in last years, a topic of considerable interest, both for practical reasons (gettering of contaminants and ‘‘smart cut’’ process) and for the extraordinary gas pressures attained in He/H-filled clusters and bubbles created upon annealing [1,2]. Enhanced hydrostatic pressure (HP) of inert gas (Ar) at annealing (HT-HP treatment) of He- and Himplanted silicon affects strongly its structure [3,4]. The effect of stress induced by enhanced Ar pressure on accumulation (gettering) of oxygen in He- and H-
*Corresponding author. Tel.: +48-22-548-7792; fax: +4822-847-06-031. E-mail address: [email protected] (A. Misiuk).
implanted Czochralski silicon (Cz-Si) is the main subject of the present work.
2. Experimental Cz-Si wafers (of 0 0 1 orientation), with concentration of interstitial oxygen, co ; up to 1 1018 cm3, were implanted with helium (Cz-Si : He, He+ doses, D ¼ 5 1015 23 1017 cm2, energy p300 keV, He+ projected range, Rp p1:35 mm) or hydrogen (Cz-Si : H, 16 2 H+ 2 dose 4 10 cm , energy 130 keV, Rp ¼ 0:5 mm). Cz-Si : He and Cz-Si : H were treated under Ar pressure up to 1.2 GPa at temperature up to 1400 K for up to 10 h. The defect structure of the samples was investigated by transmission electron microscopy (TEM), X-ray reciprocal space mapping (XRRSM) and synchrotron topography done at HASYLAB, Hamburg. Oxygen and hydrogen depth profiles in the
0921-4526/01/$ - see front matter r 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 0 1 ) 0 0 8 8 1 - X
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annealed/treated samples were determined by secondary ion mass spectrometry (SIMS).
3. Results and discussion The He implantation into Si results in creation of disturbed He-containing zone near Rp : The kind and concentration of defects (mostly He-filled clusters and bubbles) are dependent on He dose and energy, substrate temperature (in our case p350 K) as well as on the conditions of subsequent annealing/HT-HP treatment. During the annealing He atoms escape the Si matrix; this He removal is increasing with temperature [4]. TEM image of Cz-Si : He sample treated at 870 K is presented in Fig. 1. Annealing of such samples at 1270 K-105 Pa for 1 h results in creation of bubbles while only dislocations were detected in Cz-Si : He (co ¼ 1 1018 cm3, D ¼ 5 1016 cm2, 150 keV, Rp ¼ 0:88 mm) treated at 1270 K-1.15 GPa for 1 h. As it follows from XRRSM, enhanced HP results in decreased intensity of X-ray diffuse scattering, an evidence of a better structural perfection of HT-HP treated CzSi : He as compared to that annealed at 105 Pa. No oxygen accumulation at implantation-damaged zone was detected for Cz-Si : He (D ¼ 5 1016 cm2)
Fig. 1. TEM image of Cz-Si : He sample (co ¼ 1 1018 cm3, D ¼ 5 1015 cm2, 300 keV, Rp ¼ 1:35 mm) treated at 870 K1.1 GPa for 10 h.
annealed below 1000 K at 105 Pa. The treatment under 1.1–1.2 GPa at 870–1000 K for 10 h results in the SIMSdetectable oxygen accumulation at damaged areas. Both the annealing and HT-HP treatment at 1270–1400 K results in the accumulation (Fig. 2). Hydrogen implantation into Si also leads to creation of disturbed H-containing region. The generated H-filled clusters/bubbles are dependent on H dose and energy, temperature (Tp470 K) as well as on conditions of the annealing. During the annealing/HT-HP treatment H atoms outdiffuse from the Si matrix, the H loss being substantially suppressed under HP [3]. TEM image of the Cz-Si : H sample treated at 920 K1.2 GPa is presented in Fig. 3. Two different disturbed areas were detected. The first one at a depth of 0.45– 0.55 mm, corresponding to Rp of the main implanted species, H+ 2 , contains small bubbles and dislocations; the second one at the 0.8–1.0 mm depth originated from single H+ ions present in the implanting beam and exhibits comparatively large bubbles. The prolonged annealing/treatment at temperatures up to 1400 K resulted in complete removal of hydrogen; however, numerous dislocations were still detected in Cz-Si treated at 1320 K-1.2 GPa for t ¼ 0:5 h. As it can be deduced from XRRSM [3,4] and synchrotron topographs, the intensity of X-ray diffuse scattering is lower and overall structural perfection is better in the case of the HT-HP treated Cz-Si : H samples, as compared to that annealed at 105 Pa. The as-implanted Cz-Si : H sample (co ¼ 8 1017 cm3) indicated no oxygen accumulation near Rp ; annealing of that sample at 720 K-105 for 0.5 h resulted
Fig. 2. SIMS depth profiles of oxygen in Cz-Si : He samples (co ¼ 1 1018 cm3, D ¼ 5 1016 cm2, 150 keV, Rp ¼ 0:88 mm) annealed/treated at 1270 K for 1 h.
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Fig. 4. Depth profiles of hydrogen and oxygen in Cz-Si : H samples, as-implanted and annealed at 720 K-105 Pa for 0.5 h.
Fig. 3. TEM image of Cz-Si : H sample (co ¼ 8 1017 cm3, D ¼ 4 1016 cm2, 130 keV, Rp ¼ 0:5 mm) treated at 920 K1.2 GPa for 0.5 h.
in a marked oxygen gettering by defects in the implantation-damaged layer (Fig. 4) and in hydrogen loss. The Cz-Si : H samples treated at (720–920) K-(1.1– 1.2) GPa for up to 1 h do not indicate the oxygen accumulation (Fig. 5). Some traces of that accumulation were detected in Cz-Si : H treated at 920/1070 K-1.1 GPa for X1 h, while no accumulation was detected for the samples annealed at 1320 K-105 Pa or treated at (1230– 1370) K-(1–1.2) GPa. The major differences, in respect of oxygen accumulation in Cz-Si : He vs. Cz-Si : H can be outlined as follows: (a) Oxygen accumulation was detected only in CzSi : He annealed at >1000 K–105 Pa; HP resulted in more pronounced gettering of oxygen. It is contrary to the case of Cz-Si : H where oxygen accumulation was detected upon annealing at 720–870 K-105 Pa. (b) High HP in Cz-Si : H treated at 720–870 K and at higher temperatures prohibited oxygen accumulation in damaged areas. Effect of oxygen accumulation in implantation damaged and in the near-surface areas of Cz-Si : He, H is related to oxygen gettering on defects. Probably it
Fig. 5. Depth profiles of hydrogen and oxygen in Cz-Si : H samples, annealed/treated at 920 K-105 Pa and 920 K-1.2 GPa for 0.5 h.
occurs mostly at the surface of initially He- or H-filled clusters and bubbles. Under HT-HP, more numerous but smaller size clusters are formed. The gettering activity is increasing with HP. Most probably, the oxygen accumulation in the CzSi : H samples subjected to short-time anneals at 720– 870 K-105 Pa originates from increased diffusivity of oxygen in the presence of hydrogen [5]. The oxygen gettering was negligible in HP-HT treated Cz-Si : H. It
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means that HP affects strongly oxygen diffusivity; oxygen mobility decreases dramatically with HP. From comparison of oxygen depth profiles for Cz-Si : He and Cz-Si : H, implanted with comparable He and H doses (hence, with similar extent of damage near Rp ) and treated at >1000 K it follows also that the HP effect on the resultant defect structure of Cz-Si : He and Cz-Si : H is different. Both the annealed and HT-HP treated CzSi : He samples exhibit gettering activity at >1000 K, while the HT-HP processing of Cz-Si : H results in some specific structural changes in implantation-damaged areas. The implantation damaged area of HT-HP treated Cz-Si : H ceases to be active in respect of the oxygen accumulation. In summary, this paper demonstrates an appearance of the enormous effect of oxygen segregation within the damaged volume. In order to realise the magnitude of this phenomenon, let us consider the integral of the oxygen peak formed as a result of the implantation and the HT-HP treatment of Cz-Si : He (Fig. 2, solid circles). Here oxygen content amounts to about 1016 cm2. This would correspond to the oxygen contained in the Cz-Si slab of about 100 mm thickness. Taking the existing data for oxygen diffusion in Si, such extended transport within the semiconductor can be excluded. An alternative source of oxygen to be eventually gettered in the vicinity of Rp would be the oxygen contamination of the
ambient gas. However, even in such a case the transport from the surface would be enormous. So further investigation is definitely needed to solve that question.
Acknowledgements This work was supported in part by the Polish Committee for Scientific Research (grants no. 8T11B 072 19 and 2P 03B 14018).
References [1] G.F. Cerofolini, G. Calzolari, F. Corni, C. Nobili, G. Ottaviani, R. Tonini, Mater. Sci. Eng. B 71 (2000) 196. [2] V. Raineri, S. Coffa, E. Szilagyi, J. Gyulai, E. Rimini, Phys. Rev. B 61 (2000) 937. [3] A. Misiuk, J. Bak-Misiuk, A. Barcz, A. Romano-Rodriguez, I.V. Antonova, V.P. Popov, C.A. Londos, J. Jun, Int. J. Hydrogen Energy 26 (2001) 483. [4] A. Misiuk, J. Bak-Misiuk, I.V. Antonova, V.P. Popov, V. Raineri, A. Romano-Rodriguez, A. Bachrouri, H.B. Surma, J. Ratajczak, J. Katcki, J. Adamczewska, E.P. Neustroev, Comput. Mater. Sci. 21 (2001) 515. [5] L. Zhong, F. Shimura, J. Appl. Phys. 73 (1993) 707.