S. G. dos Santos Filho

Electrical and Mechanical Properties of Post-Annealed SiCxNy Films

Amorphous SiCxNy films have been deposited on (100) Si substrates by RF magnetron sputtering of a SiC target in a variable nitrogen-argon atmosphere. The as-deposited films were submitted to thermal anneling in a furnace under argon atmosphere at 1000 °C for 1 hour. Composition and structure of unannealed and annealed samples were investigated by RBS and FTIR. To study the electrical characteristics of SiCxNy films, Metal-insulator-semiconductor (MIS) structures were fabricated. Elastic modulus and hardness of the films were determined by nanoindentation. The results of these studies showed that nitrogen content and thermal annealing affect the electrical, mechanical and structural properties of SiCxNy films.

Physical and Electrical Characterization of Thin Nickel Films Obtained from Electroless Plating onto Aluminum

In this work, nickel was deposited onto smooth aluminum surfaces using the electroless plating technique, which is selective, does not consume surface and does not need an external current source. Before electroless nickel deposition, the aluminum surface was previously covered using a nickel displacement solution. Physical and electrical characterization of the Ni/Al structure was performed with the aid of Rutherford Backscattering Spectrometry (RBS), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and C-V measurements. For the C-V measurements, MOS capacitors were fabricated using basic microelectronics steps. During the displacement reaction in solution 0.1 M NiCl 2 /0.1 M HF/0.108 M NH 4 F, aluminum was partially consumed and the surface RMS microroughness gradually increased from 16.8 to 129.8 nm after immersion from 0 to 45 s, respectively. The surface RMS microroughness slightly increased to 133.1 nm after electroless plating for 180 s in solution 0.063 M NiCl 2 /0.09 M Na 2 H 2 PO 2 /0.2 M (NH 4 )HC 6 H 5 O 7 /0.1 M NH 4 OH at 85 °C. As a result, a final nickel thickness of 307 nm and small grains with diameter of approximately 0.5 μm were obtained. In conclusion, electroless plating onto aluminum with a good control can be used as an alternative Ni bumping base for Al bondpads without substantial lateral corrosion. Also, the electrical characteristics of the Ni/Al/SiO 2 /Si structure did not substantially deteriorate (especially the flat hand voltage shift was lower than 0.15 V).

Characterization of the semi-insulating properties of AlHfO3.5 for power devices

Physical and electrical characterization of hafnium aluminates gate dielectrics was carried out to investigate their semi-insulating characteristics as passivating layer for power devices. The deposited films were annealed in pure nitrogen to simulate the thermal budget during a conventional CMOS processing. C-V measurements were performed having as a result a high-frequency behavior of the flat band voltage (VFB) and values greater than or equal to zero. On the other hand, the leakage phenomenon was modeled with a simplified electrical model using a leakage admittance YC whose influence was predominant at the accumulation region. Using X-ray reflectometry (XRR), the average thickness obtained was 15.5nm and a leakage process was inferred to occur for AlHfO3.5 due to the observed phase separation and crystallization that occurs after annealing in pure N2.

Physical characterization of ultrathin silicon oxynitrides grown by Rapid Thermal Processing aiming to MOS tunnel devices

Oxynitrides were grown in a homemade Rapid Thermal Processor (RTP) using a low mass quartz carrier, to obtain thin oxynitrides over large areas of 3 inches silicon p-type wafers. Layers with thickness varying from 0.97 to 2.39 nm with uniformity better than 0.4%, were obtained at 700 and 850°C, in a mixed ambient of nitrogen and oxygen (4N2:3O2 in volume). The nitrogen concentration was obtained with the aid of X-ray photoelectron spectroscopy (XPS) and was 0.6 at%. On the other hand, the Si/O ratio in the oxynitride was approximately 1.9, indicating an almost stoichiometric SiO2 with a small amount of nitrogen. In addition, using the 16O(α, α) elastic-scattering signal at 3.039MeV, the planar concentration of oxygen was 5.5×1015cm2 for the oxynitride grown at 850°C during 40s.

Physical Characterization of Cu-Ni-P Thin Films aiming at Cu/Cu-Ni-P Thermocouples

Cu-Ni-P thin films have a high-thermoelectric power, which allows the fabrication of very sensitive heat-flux sensors based on planar technology. In this work, (100) silicon surfaces were pre-activated in a diluted hydrofluoric acid solution containing PdCl2. Following, Cu-Ni-P thin films were chemically deposited using an alkaline chemical bath containing 15 g/l NiSO4.6H2O; 0.2 g/l CuSO4.5H2O; 15 g/l Na2HPO2.H2O and 60 g/l Na3C6H5O7.2H2O at temperature of 80 °C where NH4OH was added until pH was 8.0. It was noteworthy that the stoichiometric percentages of Ni and Cu vary substantially for immersion times in the range of 1 to 3 min and they become almost stable at 50% and 35%, respectively, when the immersion time is higher than 3 min. In addition, the percentage of P remains almost constant around 1718 % for all the immersion times studied. On the other hand, the sheet resistance also varies substantially for immersion times in the range of 1 to 3 min. Based on the surface morphology, smaller grains with size in the range of 0.02 to 0.1 μm are initially grown on the silicon surface and exposed regions of silicon without deposits are also observed for immersion times in the range of 1 to 3min. Therefore, the discontinuities and non uniformities of the films are promoting, respectively, the observed behaviours of sheet resistance and stoichiometry.

FIA-automated system used to electrochemically measure nitrite and its interfering chemicals through a 1-2 DAB / Au electrode: gain of sensitivity at upper potentials

The measurement of nitrite and its interfering-chemicals (paracetamol, ascorbic acid and uric acid) was performed employing a Flow-injection Analysis (FIA) system, which was automated using solenoid valves and air-pump. It is very important to quantify nitrite from river water, food and biologic fluids due to its antibacterial capacity in moderated concentrations, or its toxicity for human health even at low concentrations (> 20 μmol L−1 in blood fluids). Electrodes of the electrochemical planar sensor were defined by silk-screen technology. The measuring electrode was made from gold paste covered with 1-2 cis Diaminobenzene (DAB), which allowed good selectivity, linearity, repeatability, stability and optimized gain of sensitivity at 0.5 VAg/AgCl Nafion®117 (6.93 μA mol−1 L mm−2) compared to 0.3 VAg/AgCl Nafion® 117. The reference electrode was obtained from silver/palladium paste modified with chloride and covered with Nafion® 117. The auxiliary electrode was made from platinum paste. It was noteworthy that nitrite response adds to the response of the studied interfering-chemicals and it is predominant for concentrations lower than 175 μmol L−1.