TELLURIUM (II) TRIALKYLSILYLS
Alkyl silyl compounds Te(SiR3)2 where R is SiMe3, SiEt3 and SitBuMe2 were synthesized in good yields. [[i], [ii]]. While Te(SiMe3)2, and Te(SiEt3)2 are liquids at room temperature, Te(tBuMe2Si)2Te is solid. The compounds were characterized by 1H and 13C NMR spectroscopy, mass spectroscopy, elemental analysis and TGA. Single crystals of Te(SitBuMe2)2 suitable for X-ray diffraction were obtained from hexane solution and its crystal structure was determined.
Alkylsilyl compounds of tellurium were reported to be versatile ALD precursors for metal telluride films when combined with metal chloride
precursors.[[iii]]
[i] M. R. Detty and M. D. Seidler, J. Org. Chem., 47, 1354 (1982),
[ii] T.Hatanpää, V. Pore, M. Ritala and M. Leskelä, ECS Trans., 17th EUROCVD Conference, Vienna 2009.
[iii] T. Hatanpää, M. Ritala, M. Leskelä, https://doi.org/10.1016/j.ccr.2013.07.002 , Coordination Chemistry Reviews, 2013, Vol. 257, Iss. 23–24, p.3297-3322, « Precursors as enablers of ALD technology: Contributions from University of Helsinki », https://www.sciencedirect.com/science/article/abs/pii/S0010854513001422
Bis(trimethylsilyl)tellurium Te(SiMe3)2
TGA/DSC of Te(SiMe3)2
Bis(trimethylsilyl)tellurium (Hexamethyldisilyltellurium) Te(SiMe3)2 is liquid with boiling point 50° C/ 2.5 Torr.
Synthesis of Te(SiMe3)2:
Approach A) Te powder (200 mesh, 1eq.) and lithium hydride LiH (2eq.) in 40 ml tetrahydrofuran (THF) were refluxed for 4 hours with stirring. All black Te powder disappeared (a muddy color precipitate formed). After cooling mixture to -20° C trimethylchlorosilane SiMe3Cl (2eq.) was added. After warming up the mixture to room temperature and 4 hours stirring, it was filtered under inert atmosphere and the solvent was removed by distillation, and hexamethyldisilyltellurium Te(SiMe3)2 was purified by vacuum distillation. (b.p. 50° C/ 2.5 Torr)
Approach B: The synthesis was done using 2eq. Na metal, 1 eq. Te powder, 2eq. Me3SiCl and catalytic amount of naphthalene C10H8. Te(SiMe3)2 was obtained as yellow liquid which turns black, yield 56%.
Characterisation: 1H-NMR (200 MHz, CDCl3): δ 0.58 (18H, CH3, s); 13C{1H} NMR (50 MHz): δ 5.82 (SiCH3).
Bis(trimethylsilyl)tellurium Te(SiMe3)2 was characterized by TGA/DSC (Fig ). Most of the precursor evaporated at temperature 90-115°C, with residual mass 4.91%
Te(SiMe3)2 (+MeOH) for Te thin films by MOVPE
Hexamethyldisilyltellurium Te(SiMe3)2, combined with methanol MeOH as reducing agent, was applied as precursor for the growth of thin Te films on Si (100)/100 nm TiN substrates by MOCVD at 100°C temperature and 20 mTorr base pressure. The Te precursor [Te(SiMe3)2] was evaporated at 50°C, while methanol was evaporated at 20° C. The substrate temperature during the deposition was kept at 100° C. The Te(SiMe3)2 flow rate was 0.06 g/min, whereas MeOH flow rate was kept at 0.4 g/min. Thickness and morphology of the deposited Te layers was studied by field emission SEM: it was determined that 80 nm thick Te film was formed on TiN layer between Si (100) substrate and Te film. The Te film is also very uniform.[i]
[i] C Dussarrat - US Patent App. 12/212,350, 2008 - , http://www.freepatentsonline.com/EP2067876.html
United States Patent Application 20090137100 , http://www.freepatentsonline.com/y2009/0137100.html, « Tellurium Precursors for GST Films in an ALD or CVD Process »
Te(SiMe3)2 (+Ge(NMe2)4 and/or Sb(NMe2)3) for GeTe, SbTe3 and GeSbTe (GST) films by CVD
Tellurium bis(trimethylsilyl) Te(SiMe3)2, combined with Ge(NMe2)4 and/or Sb(NMe2)3, was applied as Te source for the growth of GeTe, Sb2Te3 or GeSbTe (GST) thin films by CVD. Layer deposition was performed at 200° C.-400° C temperatures and low pressure (<500 mTorr). Te(SiMe3)2 and Ge(NMe2)4 precursors were filled into separate containers connected to direct liquid injection (DLI) systems connected to the CVD reactor; the vapor of Te and Ge precursors was introduced to the CVD reactor at fixed flow rates. Highly conformal GeTe, Sb2Te3 or GeSbTe (GST) layers were deposited on Si, SiO2, Si3N4, TiN substrates.[i]
[i] M. Xiao, L. Yang, US 8765223B2, 2009, patents.google.com/patent/US8765223B2/en
https://patentimages.storage.googleapis.com/e7/ff/5c/30cf11bb548182/US8765223.pdf
« Binary and Ternary Metal Chalcogenide Materials and Method of Making and Using Same »
Bis(triethylsilyl)tellurium Te(SiEt3)2
Synthesis of Te(SiEt3)2. The synthesis was done using 2 eq. Li metal, 1 eq. Te, 1 eq. Et3SiCl and catalytical amount of naphthalene C10H8. Te(SiEt3)2 as a brownish liquid at RT was obtained (yield 80.4%).
Characterisation of Te(SiEt3)2: 1H-NMR (200 MHz, CDCl3): δ 0.83 (6H, SiCH2, m), 1.02 (9H, CH3, m); 13C{1H} NMR (50 MHz): δ 9.03 (SiCH2), 9.30 (CH3); MS (EI, 70 eV): m/z 360 [M]+, 331 [M – Et]+, 303 [(Et3Si)TeSiEtH]+, 245 [(Et3Si)Te]+, 217 [Et2SiTeH]+, 187 [EtSiTe]+, 158 [SiTe]+.
Te(SiEt3)2 (+BiCl3/ ZnCl2/ SbCl3/ GeCl2*dioxane) for Bi2Te3, ZnTe, Sb2Te3, GeTe films by ALD
Te(SiEt3)2 (evaporated at 45°C) was utilized for ALD growth of Bi2Te3, ZnTe, Sb2Te3, GeTe layers (by using BiCl3@140°C/ ZnCl2@360°C/ SbCl3@30°C / GeCl2*dioxane@70°C) as co-precursors, correspondingly, on glass and Si substrates, at pressure 10 mbar and N2 as carrier
gas. The most suitable growth temperatures were depenfing on the grown layer nature: low growth temperature were the best for Sb2Te3 and GeTe (60°C and 90°C); intermediate temperature 165°C was optimal for Bi2Te3 layers, whereas higher temperature
( 400°C) was necessary for growing good-quality ZnTe films. [[i]]
[i] T. Hatanpää, V. Pore, M. Ritala, M. Leskelä, ECS Trans. 2009, Vol.25, Iss.8, 609-616, « Alkylsilyl Compounds of Selenium and Tellurium: New Precursors for ALD », doi: 10.1149/1.3207647 , http://ecst.ecsdl.org/content/25/8/609.short
https://www.researchgate.net/profile/Markku_Leskelae/publication/266642227_Alkylsilyl_Compounds_of_Selenium_and_Tellurium_New_Precursors_for_ALD/links/55d447f608ae0b8f3ef94848.pdf
Te(SiEt3)2 (+SbCl3) for Sb2Te3 films by ALD
Te(SiEt3)2 (+GeCl2·(1,4-dioxane)) for GeTe films by ALD
Te(SiEt3)2 was applied as tellurium ALD precursor for the growth of Sb2Te3, and GeTe films by ALD , with SbCl3 and GeCl2·C4H8O2 (1,4-dioxane complex of GeCl2) as Sb and Ge sources, respectively. The reaction mechanisms of Sb2Te3 ALD deposition (at 60°C) from Te(SiEt3)2 and SbCl3, and of GeTe ALD (at 90 °C) from Te(SiEt3)2 and GeCl2·C4H8O2 were studied in situ by quadrupole mass spectrometry (QMS) and quartz crystal microbalance (QCM). It was found that the byproduct in both binary telluride processes is Et3SiCl, and about 78% (36%) of it was released during the SbCl3 (GeCl2·C4H8O2) pulse. This means that the reactive sites for the metal precursors were −Te(SiEt3) surface groups (cf. −OH surface groups in the oxide ALD processes that use H2O as the oxygen source). The dioxane, on the other hand, was expectedly found to be released entirely during the GeCl2·C4H8O2 pulse.
Te(SiEt3)2 (+SbCl3, GeCl2·(1,4-dioxane)) for Ge2Sb2Te5 films by ALD
Te(SiEt3)2 was tested as well as Te source for the ALD growth of phase change material germanium antimony telluride, Ge2Sb2Te5 (GST) (with SbCl3 and GeCl2·C4H8O2
as co-reactants). When depositing GST the mechanism of the SbCl3-(Et3Si)2Te reaction changed in the way that during the SbCl3 pulse only ~50% of the byproduct Et3SiCl was released. Same effect was experienced on surfaces of Al2O3 and Au for the SbCl3-(Et3Si)2Te
process.[i]
[i] K. Knapas, T. Hatanpää, M. Ritala, M. Leskelä, Chem. Mater., 2010, 22 (4), pp 1386–1391, DOI: 10.1021/cm902180d, « In Situ Reaction Mechanism Studies on Atomic Layer Deposition of Sb2Te3 and GeTe from (Et3Si)2Te and Chlorides »
Te(SiEt3)2 (+SbCl3, GeCl2·(1,4-dioxane)) for GeTe, Sb2Te3, Ge2Sb2Te5 ALD
Fig. GST layers deposited in trenches using Ti(SiEt3)2 by ALD
Te(SiEt3)2, combined with SbCl3 and/or GeCl2·C4H8O2, was applied as Te precursor for the ALD deposition of GeTe, Sb2Te3, Ge2Sb2Te5 layers for phase-change
random-access memories applications. Typical saturative ALD growth behavior was observed for all three precursors. Excellent conformality on a high aspect-ratio trench structure was achieved for the GST films deposited at 90°C. [[i]]
[i] V. Pore, T. Hatanpää, M. Ritala, M. Leskelä, J. Am. Chem. Soc., 2009, 131 (10), pp 3478–3480, DOI: 10.1021/ja8090388, « Atomic Layer Deposition of Metal Tellurides and Selenides Using Alkylsilyl Compounds of Tellurium and Selenium », https://pubs.acs.org/doi/abs/10.1021/ja8090388
Bis(t-butyl-dimethylsilyl)tellurium Te(SitBuMe2)2
Bis(t-butyl-dimethylsilyl)tellurium Te(SitBuMe2)2 was synthesized, characterized and its crystal structure was solved by single crystal XRD. Thermal properties of Te(SitBuMe2)2 were studied by TGA. Te(SitBuMe2)2 appeared to very volatile and thermally stable and was therefore suggested to be suitable as ALD precursor. Reactivity of Te(SitBuMe2)2 was preliminarily studied by mixing it with different metal precursors in solution. It was found that the compound is highly reactive against many metal halides and other metal compounds.
Synthesis of Te(SitBuMe2)2: 1 eq. Te powder was added to 2 eq. Li in dry THF and catalytic amount of naphthalene. The solution was refluxed under Ar for 4 hours; the solution turned from clear colorless through violet color to clear solution + white precipitate. The solution was cooled to 0 °C and 2 eq. tBuMe2SiCl was added in one portion. The reaction mixture was stirred at room temperature overnight, then evaporated and toluene was added. The toluene solution was then filtered, evaporated and heated under vacuum to sublime away naphthalene. Yellowish crystalline solid Te(SitBuMe2)2 (mp. 44 °C) was obtained (yield 77.2%).
Characterisation: 1H-NMR (200 MHz, CDCl3): δ 0.50 (6H, CH3, s), 0.99 (9H, CH3,s); 13C{1H} NMR (50 MHz): δ 1.80 (SiCH3), 11.1 (C(CH3)3), 27.02 (CH3); MS (EI, 70 eV): m/z 360 [M]+, 303 [(tBuMe2Si)TeSiMe2]+, 261, 245 [(tBuMe2Si)Te]+, 229 [CH2Me2CMeSiTe]+, 188 [Me2SiTe]+, 173 [MeSiTe]+. [i]
[i] T. Hatanpää, V. Pore, M. Ritala, M. Leskelä, ECS Trans. 2009, Vol.25, Iss.8, 609-616, « Alkylsilyl Compounds of Selenium and Tellurium: New Precursors for ALD », doi: 10.1149/1.3207647, http://ecst.ecsdl.org/content/25/8/609.short
https://www.researchgate.net/profile/Markku_Leskelae/publication/266642227_Alkylsilyl_Compounds_of_Selenium_and_Tellurium_New_Precursors_for_ALD/links/55d447f608ae0b8f3ef94848.pdf
Te(SitBuMe2)2 for Ge2Sb2Te5 and ZnTe films by ALD
Te(SitBuMe2)2 was successfully tested for ALD growth of Ge2Sb2Te5 layers, for which low growth temperature (60-90°C) was found to be the most suitable; in contrary the best ZnTe films were obtained at higher temperature 400°C.
Bis(triisopropylsilyl)tellurium Te(SiiPr3)2
Fig. TGA (atm. press, inert atm.) of Te(SitBuMe2)2, Te(SiiPr3)2 (and for comparison Te(SiMe3)2 and Te(GeiPr3)2)
Bis(triisopropylsilyl)tellurium Te(SiiPr3)2 was proposed as potential Te CVD/ALD precursor.
The volatility of Te(SiiPr3)2 (and for comparison bis(t-butyl-dimethylsilyl)tellurium Te(SitBuMe2)2, as well as Te(SiMe3)2 and Te(GeiPr3)2), was investigated by thermo-gravimetric analysis (TGA) under inert atmosphere at atmospheric pressure. All these compounds could be volatized without significant residues (the decomposition of the molecules did not occur, though some of the complexes were heated at quite high temperature (>300°C). Te(SitBuMe2)2 was ranked second in terms of volatility (full evaporation at ~240°C), whereas Te(SiiPr3)2 and Te(GeiPr3)2 where third, exhibiting roughly the same evaporation pattern (with Te(SiiPr3)2 being slightly more volatile, possibly due to lower atomic weight of Si vs. Ge) (Fig.) The most volatile precursor was Te(SiMe3)2 (in agreement with its lowest molecular mass): full evaporation achieved already at 180°C.
The volatility and evaporation patterns of all these Te complexes (including Te(SiiPr3)2 ) fits the criteria for CVD/ALD applications, making them promising as precursors
for the growth of Te-containing layers.[i]
[i] Sh. Okubo, K. Yanagita, J. Gatineau – US Patent US8101237B2 , 2012, « Tellurium precursors for film deposition », https://patents.google.com/patent/US8101237B2/en
Share this page