Hydrogen gettering by buried layers formed in oxygen-implanted silicon (Si:O

 prepared by O²⁺ implantation at the energy 200 keV and doses 10¹⁴ and 10¹⁷ cm⁻²) was

 investigated after annealing of Si:O at temperatures up to 1570 K, including also

 processing under enhanced hydrostatic pressure, up to 1.2 GPa. Depending on processing

 conditions, buried layers containing SiO₂₋x clusters and/or precipitates were formed. To

 produce hydrogen-rich Si:O,H structures, Si:O samples were subsequently treated in RF

 hydrogen plasma. As determined using secondary ion mass spectrometry, hydrogen was

 accumulated in sub-surface region as well as within implantation-disturbed areas. It has

 been found that hydrogen was still present in Si:O,H structures formed by oxygen

 implantation with the dose D = 10⁷  cm⁻² even after post-implantation annealing up to

 873 K. It is concluded that hydrogen accumulation within the disturbed areas in Si:O as

 well as in SOI structures can be used for recognition of defects

Antonova, I.V.

Barcz, A.

Misiuk, A.

Prujszczyk, M.

Ulyashin, A.

Semiconductor Physics Quantum Electronics & Optoelectronics

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 161-165.© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine161PACS 52.40.Hf, 61.05.C-, 68.37.Ps, 82.80.MsHydrogen gettering in annealed oxygen-implanted siliconA. Misiuk1, A. Barcz1, A. Ulyashin2, I.V. Antonova3, M. Prujszczyk11Institute of Electron Technology, Al. Lotnikow 46, 02-668 Warsaw, Poland Phone: +48 22 5487792; fax: + 48 22 8470631; E-mails: misiuk@ite.waw.pl; barcz@ite.waw.pl; prujsz@ite.waw.pl2SINTEF, P.O. Box 124 Blindern, NO-0314 Oslo, NorwayPhone: +47 95480849; fax: +47 22067926; e-mail: alexander.g.ulyashin@sintef.no3Institute of Semiconductor Physics, SB RAS, pr. Lavrentieva, 13, Novosibirsk, Russia; Phone: (7 3832) 332493; fax: (7 3832) 332771; e-mail: antonova@isp.nsc.ruAbstract. Hydrogen gettering by buried layers formed in oxygen-implanted silicon (Si:O prepared by O2+ implantation at the energy 200 keV and doses 1014 and 1017 cm–2) was investigated after annealing of Si:O at temperatures up to 1570 K, including also processing under enhanced hydrostatic pressure, up to 1.2 GPa. Depending on processing conditions, buried layers containing SiO2–x clusters and/or precipitates were formed. To produce hydrogen-rich Si:O,H structures, Si:O samples were subsequently treated in RF hydrogen plasma. As determined using secondary ion mass spectrometry, hydrogen was accumulated in sub-surface region as well as within implantation-disturbed areas. It has been found that hydrogen was still present in Si:O,H structures formed by oxygen implantation with the dose D = 107 cm–2 even after post-implantation annealing up to 873 K. It is concluded that hydrogen accumulation within the disturbed areas in Si:O as well as in SOI structures can be used for recognition of defects.Keywords: Cz-Si, implantation, oxygen, hydrogen, high temperature, high pressure, gettering, defects.Manuscript received 02.02.10; accepted for publication 25.03.10; published online 30.04.10.1. IntroductionSilicon-on-insulator structures (SOI) can be produced by O2+ implantation into Czochralski grown silicon (Cz-Si) at doses -217 cm102 D  and subsequent annealing of resulting Si:O at high temperatures (HT) approximately up to 1600 K [1]. Microstructure of the SOI samples depends, among other factors, on the implanted oxygen ion energy E, on D, HT and on processing time t. An enhanced hydrostatic pressure (HP) applied upon processing of the Si:O samples results in formation of specific structures with an improved quality of the SiOx/Si interface [1, 2]. In the case of self-implanted silicon (Si:Si), buried defect layers can getter hydrogen embedded into Si from hydrogen plasma [3]. This effect is now investigated for the SOI-like structures produced from Si:O prepared by oxygen implantation into Cz-Si with the doses of -217 cm101D  and processed under HT-HP [1, 2, 4]. Such structures are interesting in view of possible application of the hydrogen decoration/gettering for the recognition of the structural defects in SOI-like structures.2. ExperimentalCz-Si wafers of (001) orientation and the interstitial oxygen concentration cO  11018cm–3 were implanted with O2+ at room temperature. Sample labelling and implantation parameters are listed in Table. Afterwards, the Si:O samples were annealed for up to 10 h in purified Ar atmosphere at HT  1570 K under HP  1.2 GPa. To introduce hydrogen, the Si:O samples were subsequently treated for 2 h at 530 K in RF hydrogen plasma by using a plasma enhanced chemical vapour deposition (PECVD) reactor [3].Table. Sample labelling, E, D (calculated for implanted oxygen atoms) and projected range of implanted ions, Rp.Sample E, keV D, cm–2 Rp, nmA 200 1·1014 400B 200 1·1017 400Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 161-165.© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine162The depth profiles of hydrogen and oxygen in the as-prepared Si:O,H samples as well as in the samples subjected to subsequent annealing for 1 h at 723 K or 873 K were determined using secondary ion mass spectrometry (SIMS) with Cs+ ions for sample sputtering. Transmission electron microscopy (TEM) was used for defect structure determination.3. Results and discussionTwo types of Si:O samples were investigated (Table): samples A were prepared by low dose O2+ implantation. In what follows, they will be considered as the reference ones. The B samples were prepared by implantation with the oxygen dose only 2-3 times lower than that used in high dose SIMOX processing ( -217 cm102 D ). In both cases implantation resulted in the creation of an amorphous silicon ( Si-a ) layer in the projected range (Rp) area.Upon annealing, this Si-a  buried layer was subjected to solid phase epitaxial re-growth (SPER).Depending on the HT, HP and other processing conditions, buried x2SiO   nanoclusters, precipitates and/or semi-continuous layers can be formed near Rp [6].The treatment of the as-implanted reference sample A in hydrogen plasma resulted in a remarkable hydrogen enrichment of the sub-surface area, up to about 300-nm depth, while no hydrogen was observed near Rp (Fig. 1).Fig. 1. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the as-implanted A Si:O sample. Surface enrichment with hydrogen can be attributed to the in-diffusion of hydrogen towards the sub-surface defect area disturbed by hydrogen plasma treatment itself as well as to the presence of near-surface defects induced due to oxygen implantation.No hydrogen gettering near Rp was detected in the reference samples A after the plasma treatment and processing at 923 K (Fig. 2) as well as at higher temperatures. The near-surface hydrogen-enriched layer was, however, much narrower (compare Figs 2 and 1). This means that most of implantation-induced defects formed by implantation of O2+ ions are healed at T  923 K upon HT(HP) processing of low dose implanted samples. As a result, in-diffusion of hydrogen during the plasma treatment was limited to the depths below 100 nm (Fig. 2). The relatively small damages near Rp in the A Si:O samples were healed in effect of SPER, so they did not create the gettering sites for accumulation of hydrogen. For the as-implanted B Si:O sample ( -217 cm101D ), plasma treatment leads to the almost depth-independent accumulation of hydrogen within the sub-surface area up to about 200-nm depth, with -320H cm101c . This treatment of the as-implanted B Si:O sample (prepared using the 103 higher dose of implanted oxygen comparing to that in the A Si:O sample, Table) also does not result in remarkable hydrogen content near Rp. Contrary to the case of as-implanted Si:O,H sample B, the hydrogen content within the deeper areas of the B Si:O,H samples processed at 920-1570 K follows in general the profile of implanted oxygen and depends on HP applied upon processing (Figs 3, 4, 6, 7). Fig. 2. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the A Si:O sample processed for 10 h at 923 K under 105 Pa. Processing the B Si:O sample at 923 K results in a distinguished hydrogen gettering near Rp, with the hydrogen concentration cH reaching -318 cm107   (Fig. 3, compare to Fig. 2).Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 161-165.© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine163Fig. 3. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample processed for 10 h at 923 K under 105 Pa. Fig. 4. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample processed for 5 h at 1230 K under 108 Pa. abFig. 5. TEM images of the B Si:O samples ( -217 cm10D ) processed for 5 h at 1570 K under 107 Pa (a) and 1.2 GPa (b) (compare to [5]).The peak concentration of hydrogen cHaccumulated near Rp is dependent crucially on the HT-HP processing conditions. In the case of B Si:O sample processed at 1230 K under 108 Pa, this concentration exceeds -320 cm101  (Fig. 4).Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 161-165.© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine164The quasi-continuous x2SiO   layers were formed near Rp (Fig. 5) in the case of B Si:O samples processed at 1570 K (temperature close to that used at SIMOX processing); the sample microstructure is strongly dependent on HP (compare Figs 5a and b). These samples indicate specific accumulation of hydrogen (Figs 6, 7).Fig. 6. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample ( -217 cm10D ) processed for 5 h at 1570 K under 107 Pa (compare to Fig. 5a).Fig. 7. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample ( -217 cm10D ) processed for 5 h at 1570 K under 0.6 GPa.It is clearly seen that hydrogen content within the deeper areas of the B Si:O samples processed at 923-1570 K corresponds to the profile of implanted oxygen and depends on HP applied upon processing. The profiles of oxygen and those of gettered hydrogen depend on the microstructure and therefore on the presence of numerous, HT, HP-induced effects, among them [6]: – mobility and solubility of implanted oxygen as well as of silicon interstitials and other implantation-induced defects (such as vacancies, V),– stability of oxygen agglomerates,– diffusivity of oxygen as well as of silicon interstitials, Sii, and of vacancies,– the misfit at the SiO2/Si boundary.Oxygen clustering and precipitation in Cz-Si produce shear stress at the Si/SiO x2  boundary. This stress is attributed to the enlarged volume of x2SiO precipitates (in comparison to that of the host Si lattice). Other reason of the internal stress is the difference in thermal expansion of x2SiO   and Si. The misfit and so the shear stress at the x2SiO   precipitate/Si matrix boundary are affected by HT and HP in accordance [6] with Eq. (1):  ,11HPHT43x2x2x2x2SiOSiSiSiOSiSiOSiO0KKGKK(1)where 0 is the misfit at the x2SiO    precipitate/Si matrix boundary at 295 K under 105 Pa; Si and x-2SiO –coefficients of volume thermal expansion; SiK and x-2SiOK – bulk moduli; GSi – shear modulus (the bottom indexes denote the respective material), and ΔHT = HTexperiment – 295 K.It means that the shear stress at the Si/SiO x2boundary changes (typically decreases) with HT and HP. For example, in the case of HP = 1.3 GPa applied at room temperature, the HP induced change of misfit at the Si/SiO2  boundary,  (= 0) can be estimated as equal to about -3104.2   [6]. The values of K, G and are dependent on temperature and pressure; however, these dependences are not known, especially for high temperatures and pressures. Accumulated hydrogen in the Si:O,H samples remains to be detectable even after subsequent annealing of the Si:O,H structures at temperatures up to 873 K (Figs 8, 9). This suggests chemical interaction of hydrogen with oxygen (probably in the form of sub-stoichiometric x2SiO  ), while some part of hydrogen may be bonded to defects (to Si dangling bonds, etc.) Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 161-165.© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine165[4]. It is necessary to note that similar effects (accumulation of hydrogen at Rp and stability of the SiO,H structures at high temperatures) were reported earlier for the helium-implanted Si:He samples annealed in hydrogen-containing ambient [7-9].Fig. 8. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample ( -217 cm10D ) after processing for 5 h at 1570 K under 1.2 GPa (compare to Fig. 5b) and subjected for 1 h to desorption annealing at 723 K under 105 Pa.Fig. 9. SIMS depth profiles of oxygen and hydrogen in Si:O,H structure obtained for the B Si:O sample ( -217 cm10D ) processed for 5 h at 1570 K under 107 Pa (compare to Figs 5a and 6) and subjected for 1 h to desorption annealing at 873 K under 1.1 GPa.4. ConclusionsThe specific character of hydrogen interaction with defects and oxygen in silicon has been stated for the processed SOI-like structures prepared by oxygen implantation into silicon. This suggests a possibility to use hydrogen plasma treatments for the detection of structural as well as oxygen-related defects in SOI and similar structures prepared by oxygen implantation into monocrystalline silicon.References1. A. Misiuk, A. Barcz, J. Ratajczak, L. Bryja, Effect of high hydrostatic pressure during annealing on silicon implanted with oxygen // J. Mater. Sci.: Mater. in Electronics // 14, p. 295-298 (2003).2. I.V. Antonova, A. Misiuk, C.A. Londos, Electrical properties of multiple-layer structures formed by implantation of nitrogen or oxygen and annealed under high pressure // J. Appl. Phys. 99, p. 033506 1-6 (2006).3. A.G. Ulyashin, J.S. Christinsen, B.G. Svensson, R. Kogler, W. Skorupa // Nucl. Instrum. Meth. Phys. Res. B 253 (2006).4. A. Misiuk, A. Ulyashin, A. Barcz, P. Formanek, Accumulation of hydrogen within implantation-damaged areas in processed Si:N and Si:O // Solid State Phenom. 156-158, p. 319-324 (2010).5. A. Misiuk, J. Ratajczak, J. Katcki, I.V. Antonova, in: Science and Technology of Semiconductor-on-Insulator Structures and Devices Operating in a Harsh Environment, Eds D. Flandre et al. Kluver Academic Publishers, 2005, p. 91-96.6. A. Misiuk, Effect of high hydrostatic pressure during annealing on oxygen containing (oxygen implanted) silicon, in: New Developments in Materials Science Research, Ed. B.M. Caruta. Nova Science Publishers, Inc., New York, p. 181-226 (2007).7. R. Job, A.G. Ulyashin, W.R. Fahrner, A.I. Ivanov, L. Palmetshofer, Oxygen and hydrogen accumulation at buried implantation-damaged layers in hydrogen and helium-implanted Czochralski silicon // Appl. Phys. A 72, p. 325-332 (2001).8. A.G. Ulyashin, A.I. Ivanov, R. Job, W.R. Fahrner, F.F. Komarov, A.V. Frantskevich, The hydrogen gettering at post-implantation hydrogen plasma treatments of helium and hydrogen implanted Czochralski silicon // Mater. Sci. Eng. B 73, p. 64-68 (2000).9. R. Job, W.R. Fahrner, A.I. Ivanov, L. Palmetshofer, A.G. Ulyashin, The comparison of oxygen and hydrogen gettering at high-temperature post-implantation annealing of hydrogen and helium implanted Czochralski silicon, in: Defect and Impurity Engineering Semiconductors and Devices II, Eds S. Ashok, J. Chevallier, K. Sumino, B.L. Sopori, N. Goetz // MRS Symposium Proc. Series, 510, p. 425-431 (1998).

Hydrogen gettering in annealed oxygen-implanted silicon

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Hydrogen gettering in annealed oxygen-implanted silicon

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Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)