Main properties of Al2O3 thin films deposited by magnetron sputtering of an Al2O3 ceramic target at different radio-frequency power and argon pressure and their passivation effect on p-type c-Si wafers

Abstract

In this work, 50-nm thick Al 2 O 3 thin films were deposited at room temperature by magnetron sputtering from an Al 2 O 3 ceramic target at different RF power and argon pressure values. The sputtering technique could be preferred to conventional atomic layer deposition for an industrial application, owing to its simplicity, availability, and higher deposition rate. The resulting thin films were characterized by UV/Vis/NIR spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The deposited Al 2 O 3 material was always highly transparent and amorphous in nature. It was found that the O/Al ratio is higher when the Al 2 O 3 layer is deposited at lower RF power or higher argon pressure. Also, some argon incorporation into the films was observed at low deposition pressure. On the other hand, the performance of the previously characterized Al 2 O 3 thin films in the passivation of 2.25-Ωcm p-type float zone c-Si wafer surfaces was evaluated by the quasi-steady-state photoconductance technique. The best effective carrier lifetime value at one-sun illumination, 0.34 ms (corresponding to a surface recombination velocity of 41 cm/s), was obtained with the 50-nm Al 2 O 3 deposited at the higher argon pressure studied, 0.67 Pa (5.0 mTorr), with the lowest RF power studied, 150 W (corresponding to a power density of 3.3 W/cm 2), and after an annealing process, in this case at 350 ºC for 20 min with forming gas. It was assumed that the reduction of the surface passivation quality at higher RF power or lower argon pressure is a consequence of an increased surface damage, and, probably, to a decrease of the O/Al ratio of the Al 2 O 3 passivation material. These assumptions were confirmed with the obtainment of a lifetime of 0.73 ms (a surface recombination velocity equal to 19 cm/s) with a simple experiment with Al 2 O 3 deposited with progressively varied sputtering conditions started from minimal silicon surface damage conditions: 50 W (corresponding to a power density of 1.1 W/cm 2) and 6.67 Pa (50 mTorr). Finally, comments about further improvement of the effective lifetime (up to 1.25 ms, corresponding to a surface recombination velocity of 11 cm/s) with preliminary experiments about the incorporation of an intrinsic hydrogenated amorphous silicon interlayer are included.

Fabrication of Nearly‐Hyperuniform Substrates by Tailored Disorder for Photonic Applications

“…Functionalization of the substrate surface plays a key role in the deposition process as the surface charges of the Al 2 O 3 layer give rise to an electrostatic force for attracting and immobilizing nanospheres. The need for such a layer poses only a minor requirement on substrates for real‐world applications as Al 2 O 3 or an alternative functionalization layer can be deposited by several means, i.e., magnetron‐sputter deposition, solution‐based deposition, or atomic layer deposition (ALD), on many different kind of substrates, in case of atomic layer deposition even on almost arbitrary surface topographies with extreme aspect ratios. The substrates are then immersed into a colloidal dispersion of polymethylmethacrylate (PMMA) nanospheres with a predefined particle size statistics and ionic strength (see also sketch in Figure a).…”

Modulation of argon pressure as an option to control transmittance and resistivity of ZnO:Al films deposited by DC magnetron sputtering: on the dark yellow films at 10-7 Torr base pressures

“…For the analysis of the chemical composition of the material, the AZO thin films were measured by X-ray photoelectron spectroscopy (XPS) by using a PHI Multitechnique system (from Physical Electronics) with a monochromatic Xray source from the AlKα line with energy of 1486.8 eV. The measurements were obtained after an erosion treatment with an argon ion sputtering performed in the XPS system, and, due to the difficulty in identifying the Ar 2p 3/2 peak (which must be located at about 241.83 eV, according to the average value of data compiled by Moulder et al for argon implanted in silicon [15]), the binding energies of the recorded spectra were charge-corrected by referencing the center of the whole Ar 2p signal to 242.05 eV, according to our previous observation on argon implanted in sputtering-deposited Al 2 O 3 [16].…”

Chemical Solution Deposition of Al(OH)3‐AlOOH Films: Application for Surface Sensitizing of Rigid and Flexible Substrates to Improve the Adhesion in Coating Technology Areas

“…It is interesting to note that the glass/Al(OH) 3 -AlOOH samples obtained here by chemical solution deposition are less transparent that our previously reported Al 2 O 3 thin films obtained by radio-frequency sputtering. [24] An explanation for this is the difference in the composition of the chemically deposited samples (the Al 2 O 3 phase may be present in a very low proportion), as well as a difference in the surface roughness. Regarding the latter, the opaque appearance of the glass/ Al(OH) 3 -AlOOH samples, as can be seen in Figure 2, is characteristic of rough surfaces, since such roughness leads to an observable scattering of the light (such scattered light is not detected by the spectrophotometer during the measuring since it is dispersed to other directions when it reaches or leaves the Al(OH) 3 -AlOOH thin film; this is a diffuse transmittance, and it is not measured with the spectrophotometer that we used).…”