For the first time successful application of thin boron oxide films grown by atomic layer deposition (ALD) as dopant source for shallow silicon doping is presented. ALD of B2O3 was carried out using tris(dimethylamido)borane and ozone as precursors. A growth per cycle of 0.3 Aå was obtained for 50 °C deposition temperature. Pure B2O3 films were highly instable after exposure to air but could be protected by thin Sb2O5 films that were in-situ grown by ALD as well. Rapid thermal annealing resulted in high concentration of active boron close to the silicon surface. The dependence of the doping results on the thickness of the initial B2O3 films could be shown and the favourable capping properties of the Sb2O5 material, which is chemically very stable in the as-deposited state but volatile and hence self-destructive at the annealing temperatures, were demonstrated.

Radio frequency plasma power dependence of the moisture permeation barrier characteristics of Al2O3 films deposited by remote plasma atomic layer deposition Comparison between ZnO films grown by plasma-assisted atomic layer deposition using H2O plasma and O2 plasma as oxidant J. Vac. Sci. Technol. A 31, 01A142 (2013); 10.1116/1.4771666Substrate-biasing during plasma-assisted atomic layer deposition to tailor metal-oxide thin film growth J. Vac. Sci. Technol. A 31, 01A106 (2013); 10.1116/1.4756906Reaction mechanisms during plasma-assisted atomic layer deposition of metal oxides: A case study for Al 2 O 3Plasma-assisted atomic layer deposition (PALD) was carried for growing thin boron oxide films onto silicon aiming at the formation of dopant sources for shallow boron doping of silicon by rapid thermal annealing (RTA). A remote capacitively coupled plasma source powered by GaN microwave oscillators was used for generating oxygen plasma in the PALD process with tris(dimethylamido)borane as boron containing precursor. ALD type growth was obtained; growth per cycle was highest with 0.13 nm at room temperature and decreased with higher temperature. The as-deposited films were highly unstable in ambient air and could be protected by capping with in-situ PALD grown antimony oxide films. After 16 weeks of storage in air, degradation of the film stack was observed in an electron microscope. The instability of the boron oxide, caused by moisture uptake, suggests the application of this film for testing moisture barrier properties of capping materials particularly for those grown by ALD. Boron doping of silicon was demonstrated using the uncapped PALD B 2 O 3 films for RTA processes without exposing them to air. The boron concentration in the silicon could be varied depending on the source layer thickness for very thin films, which favors the application of ALD for semiconductor doping processes.

Silver (Ag) layers were deposited by remote plasma enhanced atomic layer deposition (PALD) using Ag(fod)(PEt3) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) as precursor and hydrogen plasma on silicon substrate covered with thin films of SiO2, TiN, Ti/TiN, Co, Ni, and W at different deposition temperatures from 70  to 200 °C. The deposited silver films were analyzed by x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive x-ray spectroscopy, four point probe measurement, ellipsometric measurement, x-ray fluorescence (XRF), and x-ray diffraction (XRD). XPS revealed pure Ag with carbon and oxygen contamination close to the detection limit after 30 s argon sputtering for depositions made at 120 and 200 °C substrate temperatures. However, an oxygen contamination was detected in the Ag film deposited at 70 °C after 12 s argon sputtering. A resistivity of 5.7 × 10−6 Ω cm was obtained for approximately 97 nm Ag film on SiO2/Si substrate. The thickness was determined from the SEM cross section on the SiO2/Si substrate and also compared with XRF measurements. Polycrystalline cubic Ag reflections were identified from XRD for PALD Ag films deposited at 120 and 200 °C. Compared to W surface, where poor adhesion of the films was found, Co, Ni, TiN, Ti/TiN and SiO2 surfaces had better adhesion for silver films as revealed by SEM, TEM, and AFM images.

Ferroelectric capacitors made by lead zirconate titanate (PZT) thin films and iridium electrodes are fabricated on three-dimensional structures and their properties are investigated. The iridium films are grown by Plasma Enhanced MOCVD at 300°C, while the PZT films are deposited by thermal MOCVD at different process temperatures between 450°C and 550°C. The step coverage and composition uniformity of the PZT films on trench holes and lines are investigated. Phase separation of PZT films has been observed on both 3D and planar structures. No clear dependences of the crystallization and composition of PZT on 3D structure topography have been found. STEM EDX line scans show a uniform Zr/(Zr+Ti) concentration ratio along the 3D profile but the variation of the Pb/(Zr+Ti) concentration ratio is large because of the phase separation. 3D ferroelectric capacitors show good ferroelectric properties but have much higher leakage currents than 2D ferroelectric capacitors. Nevertheless, during cycling tests the degradation of the remnant polarization between 2D and 3D capacitors is similar after 109 switching cycles. In addition, the sidewalls and bottoms of the 3D structures seem to have comparable remnant polarizations with the horizontal top surfaces.

The advanced silicon semiconductor technology requires doping methods for production of ultra‐shallow junctions with sufficiently low sheet resistance. Furthermore, advanced 3‐dimensional topologies may require controlled local doping that cannot be achieved by ionimplantation. Here, the application of the atomic layer deposition (ALD) method for pre‐deposition of dopant sources is presented. Antimony oxide and boron oxide were investigated for such application. Ozone‐based ALD was carried out on silicon wafers by using triethylantimony or tris‐(dimethylamido)borane. Very homogeneous Sb2O5 deposition could be achieved on flat silicon wafers and in trench structures. The thermal stability of antimony oxide layers was investigated by rapid thermal annealing experiments. The layers were not stable above 750 °C. Therefore, this material failed to act as dopant source so far. In contrast, ultra‐shallow boron doping of silicon from ALD grown boron oxide films was successful. However, pure B2O3 films were highly unstable after exposure to ambient air. The boron oxide films could be protected by thin Sb2O5 or Al2O3 films that were in‐situ grown by ALD. Low temperature ALD of Al2O3 at 50 °C from trimethylaluminium (TMA) and ozone was investigated in detail with respect of its protective effect on boron oxide. Interestingly, it was observed that already one ALD cycle of TMA and O3 resulted in significant increase in stability of the boron oxide in air. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Iridium thin films are deposited on sub-micrometer three-dimensional trench structures by plasma-enhanced metal-organic chemical vapor deposition (PE-MOCVD). The iridium precursor used in this study is (ethylcyclopentadienyl)(1,5cyclooctadiene)iridium [Ir (EtCp)(1,5-COD)]. Various process conditions at substrate temperatures from 300°C to 450°C, with and without plasma enhancement, are investigated and compared. Crystal structure of the deposited iridium films is analyzed by X-ray diffraction (XRD).Step coverage of the deposited iridium films on three-dimensional trench structures is analyzed by scanning electron microscopy (SEM). Surface morphology is quantitatively evaluated by atomic force microscopy (AFM) and the electrical resistivity of the deposited Ir films is measured by the four-point probe method.