Silicon Substrates For Applications Research Articles

An experimental study on laser ablation of Ultra-thin SiNx layer of PERC solar cell

In this work, a nanosecond green laser (532 nm) is used to generate narrow openings by removing an ultra-thin (85 nm) SiN x layer that is coated on a silicon substrate for application in the fabrication of Passivated Emitter and Rear Contact (PERC) solar cells. An experimental analysis is presented to identify the optimal range of laser parameters for an efficient ablation with minimal damage to the silicon substrate. The ablated samples were characterized using a 3D profilometer to obtain the surface profiles and scanning electron microscope imaging to observe the surface quality. Further, energy-dispersive X-ray line analysis and atom probe tomography were performed to evaluate the nitrogen content on the surface and along the depth, respectively. The experimental results suggest that the SiN x layer starts to ablate only above a threshold laser fluence of 1.4 J/cm2, while the surface bulged out for laser fluence slightly below the ablation threshold. The central part of the ablated region was clean with a negligible nitrogen concentration at the surface, about ∼0.03% at a fluence of 2.4 J/cm2. Nitrogen concentration reduces continuously and almost becomes zero at 80 nm depth, suggesting complete ablation of the SiN x layer for establishing electrical contacts. The ablation width was close to the laser spot diameter only at lower values of the laser fluence. The lowest value of ablation depth was about 180 nm, suggesting that only about 95 nm layer of the silicon is ablated. The study demonstrates that nanosecond laser ablation is a potential technique for ablation of the SiN x layer of PERC solar cells but requires choosing the optimal parameters.

Fabrication of Ge-ZnS multilayered optical filters for mid-infrared applications

Germanium/Zinc Sulphide (Ge/ZnS) single and multilayers are deposited by ion assisted electron beam deposition on Silicon substrates for applications in the 2-15 µm wavelength region. Refractive indices of Ge and ZnS thin films are extracted from measured reflectance and transmittance spectra. Several types of mid-infrared filters (high-, anti-reflection coatings and dichroic filters) with a number of layers ranging from 3 to 29 are then designed and deposited. The optical responses of fabricated mid-infrared filters show a good agreement between experimental spectra and simulation in the case of high- and anti-reflection coatings in the long-wave infrared but also for dichroic filters with a low transmittance in the mid-wave infrared and broadband bandpass in the long-wave infrared.

Low temperature synthesis by spray pyrolysis of La0.9Sr0.1Co0.2Fe0.8O3 thin films using ethanol and water as a solvent and their microstructural characterization

The synthesis via spray pyrolysis was investigated of lanthanum ferrite films doped with strontium and cobalt (LSCF) on silicon substrates for application as cathodes in solid oxide fuel cells (SOFCs). The following precursors were utilized: La(NO3)3·6H2O, SrCl2·6H2O, CO(NO3)2·6H2O, and Fe(NO3)3·9H2O, with La:Sr:Co:Fe (9:1:2:8) stoichiometry. A solution of water and ethanol (1:3 proportion) was used. The relation among the morphology of the films, i) the temperature of the substrate and ii) the distance of deposition was investigated. The results indicate that it is possible to obtain the LSCF film with a porous morphology at 200°C and at a distance of deposition of 120mm. This morphology is adequate for applications of LSCF as a cathode for use in solid oxide fuel cells.

Electrosynthesis and characterization of polymer films on silicon substrates for applications in micromanipulation

Aniline and p-phenylenediamine were electrochemically oxidized in aqueous solutions by potentiodynamic deposition using cyclic voltammetry (CV) technique. Resulting polymer films electrodeposited on Si substrates were identified by infrared spectroscopy as polyaniline and poly(p-phenylenediamine) films. Cyclic voltammograms demonstrated that poly(p-phenylenediamine) films are non conductive contrary to polyaniline films which are conductive and electropolymerized through an autocatalytic mechanism. The morphological features (thickness, roughness, morphology) of the electrodeposited polymer films were determined using profilometry, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Adhesion force properties of polymer films were also studied by means of force–distance curves obtained by atomic force microscopy. The influence of some experimental parameters (potential scan rate, number of potential scans) was also studied. Thus, it was shown that the potential scan rate strongly influenced both morphological features and force adhesion, when the influence of the number of potential scans was less important. Under optimal conditions, it was possible to obtain low adhesive polymer films that could be useful to coat the fingers of the gripper and improve the Si objects manipulation tasks.

A Strategic Review on Growth of InP on Silicon Substrate for Applications in High Frequency RF Devices

A review is presented on the advances in InAlAs/InGaAs High Electron Mobility transistors (HEMT) on silicon substrates for high frequency and low noise applications. Although InAlAs/InGaAs HEMTs on InP and GaAs substrates have been much appreciated due to their superior performance, their widespread applications have been hindered due to higher cost of the substrates. Silicon has been used as an alternative substrate considering the benefits of low cost, technological maturity and integration of III-V and silicon technology inspite of the constraints like lattice mismatch and large difference in thermal expansion coefficient.

Design and characterization of terahertz-absorbing nano-laminates of dielectric and metal thin films

A terahertz-absorbing thin-film stack, containing a dielectric Bragg reflector and a thin chromium metal film, was fabricated on a silicon substrate for applications in bi-material terahertz (THz) sensors. The Bragg reflector is to be used for optical readout of sensor deformation under THz illumination. The THz absorption characteristics of the thin-film composite were measured using Fourier transform infrared spectroscopy. The absorption of the structure was calculated both analytically and by finite element modeling and the two approaches agreed well. Finite element modeling provides a convenient way to extract the amount of power dissipation in each layer and is used to quantify the THz absorption in the multi-layer stack. The calculation and the model were verified by experimentally characterizing the multi-layer stack in the 3-5 THz range. The measured and simulated absorption characteristics show a reasonably good agreement. It was found that the composite film absorbed about 20% of the incident THz power. The model was used to optimize the thickness of the chromium film for achieving high THz absorption and found that about 50% absorption can be achieved when film thickness is around 9 nm.

Patterned micropads made of copper nanowires on silicon substrate for application as chipto substrate interconnects

Patterned micropads made of metallic nanowires,50 µm in diameter, are fabricated on a silicon substrate. An aluminium film patterned withSiO2 is anodized to fabricate a patterned nanoporous alumina (PNA)template in which metallic nanowires are electrodeposited.SiO2 that is deposited using the plasma-enhanced chemical vapour deposition process isdemonstrated to be an effective barrier to anodization for the fabrication of highaspect ratio PNA templates. Current–voltage characteristics of an individualcopper nanowire micropad display ohmic behaviour with a low resistance value of5.5 mΩ. Thenanowires are able to withstand the solder reflow process. Cu nanowire/Sn solder reflow reaction leadsto Cu6Sn5 intermetallic formation. These micropads made of metallic nanowires have the potentialfor application as chip to substrate interconnects. Nanostructure synthesis iscarried out using standard microelectronics fabrication techniques that wouldenable easy integration of such nanodevices into routine silicon manufacturing.

00/00935 Substrate to substrate aluminized bonding of 10 cm round silicon substrates for application in solar photovoltaics

00/00935 Substrate to substrate aluminized bonding of 10 cm round silicon substrates for application in solar photovoltaics