Plasma-enhanced and thermal atomic layer deposition of Al2O3 using dimethylaluminum isopropoxide, [Al(CH3)2(μ-O i Pr)]2, as an alternative aluminum precursor
(Color online) Thermogravimetric analysis (TGA) curves for DMAI and TMA (open-crucible). The TGA was carried out at atmospheric pressure using a Seiko Instruments TG-DTA instrument at a heating rate of 10 °C min−1 under a flow of N2 (99.999%, 30 sccm).
(Color online) Saturation curves for the DMAI dose for plasma-enhanced ALD with and without DMAI bubbling (Ar, 50 sccm) and thermal ALD with bubbling. Lines serve as a guide to the eye.
(Color online) Increase of Al2O3 thickness as a function of ALD cycles, measured using in situ spectroscopic ellipsometry, showing a linear increase in thickness with the number of cycles with no nucleation delay.
(Color online) Quadrupole mass spectrometry (QMS) results for DMAI at 150 °C. (a) DMAI cracking pattern and QMS profiles for (b) plasma-enhanced and (c) thermal DMAI ALD processes. The masses were assigned as follows: m/z = 15, CH3 + (for following CH4 and fragments of HO i Pr and DMAI); m/z = 18, H2O+; m/z = 28, CO+ or CH x + (from HO i Pr or DMAI cracking); m/z = 44, CO2 + or CH x + (from HO i Pr or DMAI cracking); m/z = 60, HO i Pr+, and m/z = 116, [Al(CH3)2(O i Pr)]+ (DMAI monomer).
(Color online) Growth per cycle as a function of deposition temperature for the plasma-enhanced and thermal ALD of Al2O3 using DMAI and TMA as precursors. Lines serve as a guide to the eye.
(Color online) Film composition as a function of deposition temperature obtained using Rutherford backscattering spectrometry and elastic recoil detection. (a) The number of Al atoms deposited per cm2 per cycle, (b) the O/Al ratio, (c) the H concentration, and (d) the mass density of the films. Lines serve as a guide to the eye.
(Color online) XPS depth profiles of Al2O3 films deposited by plasma-enhanced ALD using DMAI at (a) 200 °C (42.5 nm thick) and (b) 25 °C (50.2 nm thick).
(Color online) Al 2p peaks from the XPS spectra of Al2O3 films deposited by plasma-enhanced ALD using DMAI at (a) 200 °C, showing an oxide environment only, and (b) 25 °C, with evidence of Al(OH)3 (hydroxyl), AlO(OH) (oxyhydroxyl) and Al(CO x ) y (carbonate) species. Inset: the C 1s peak observed in films deposited at 25 °C, indicative of carbonate species.
(Color online) Al 2p peaks from the XPS spectra of Al2O3 films deposited by thermal ALD using DMAI at (a) 200 °C, showing an oxide environment only, and (b) 100 °C, with evidence of OH species.
(Color online) Effective lifetime (τ eff) of the minority charge carriers as a function of injection level for double-side-polished n- and p-type floatzone Si wafers (∼3.5 and ∼2 Ω cm, respectively) coated on both sides with 30 nm Al2O3 by plasma-enhanced ALD using (a) DMAI and (b) TMA at 200 °C.9 Data are shown for the as-deposited films and films annealed for 10 min at 400 °C under N2.
General properties of TMA and DMAI precursors. The vapor pressures of the precursors were measured as previously reported.66
Properties of Al2O3 deposited onto Si wafers by ALD using DMAI and TMA at 200 °C in an Oxford Instruments OpAL™ reactor.
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