Moisture permeation is widely recognized as one of the most important causes of degradation in time of the
performances of photovoltaic modules, especially thin film ones. B-Dry®i is a newly developed edge sealant tape which
is able to block moisture penetration into PV modules for thousands of hours in Damp Heat Test (DHT) conditions,
thanks to the presence of a getter material. Visco-elastic behavior, even at relatively high temperatures, makes B-Dry®
especially suitable to guarantee mechanical stability of PV modules operating in hot and humid climates.
The patterned getter film at wafer level has been proven to be the viable technical solution to integrate a getter film in vacuum packaged MEMS. The different MEMS vacuum bonding technologies such as eutectic, direct fusion and anodic bonding guarantee a suitable combination of time and temperature to properly activate the getter film. However, before any MEMS vacuum bonding process it has been discovered that a caustic chemical treatment of the getter film both cleans the film and enhances its performance without measurable degradation of its structural integrity. For example, caustic chemical treatment with SC1 with NH4OH and SC2 with HCl did not affect the morphology and the sorption capacities of the getter film and significantly increased the sorption capacity. The getter film at wafer level can withstand also treatment with a highly aggressive HNO3 process. Therefore, we demonstrated the full compatibility of the getter film towards both temperature and chemical treatment with regards to the activation and capacity of the getter film.
The evolution from ceramic packages to wafer to wafer hermetic sealing poses tremendous technical challenges to integrate a proper getter inside the MEMs to assure a long term stability and reliability of the devices. The state of the art solution to integrate a getter inside the MEMs of the last generation consists in patterning the getter material with a specific geometry onto the Si cap wafer. The practical implementation of this solution consists in a 4” or 6” Si wafers with grooves or particular incisures, where the getter material is placed in form of a thick film. The typical thickness of these thick films is in the range of few microns, depending on the gas load to be handled during the lifetime of the device. The structure of the thick getter film is highly porous in order to improve sorption performances, but at the same time there are no loose particles thanks to a proprietary manufacturing method. The getter thick film is composed of a Zr special alloy with a proper composition to optimize the sorption performances. The getter thick film can be placed selectively into grooves without affecting the lateral regions, surrounding the grooves where the hermetic sealing is performed.
A set of InP/GaInAs 30 periods superlattices with a wide range of barrier and well thicknesses were grown on (100) InP substrates by metal organic vapor phase epitaxy (MOVPE). Their optical response was measured at room temperature by spectroscopic ellipsometry from 1.8 to 5 eV. The nominal structures were checked by two methods of multi-layer modelling: full simulation using bulk dielectric functions for each layer and effective medium approximation, with the appropriate volume fractions. The thicknesses of well, barrier, and oxide overlayer were determined, and the effects of the interface region were discussed. The dielectric functions derived from the measured tg (psi) and cos(Delta) spectra were compared with the simulated ones obtained from the fitted structural model.
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