Abstract:
Monolithically integrated pressure sensors of outstanding quality and versatility are produced through micromechanical surface structures definition techniques. A microphonic cavity in the semiconductor substrate is monolithically formed by
cutting by plasma etching the front side or the back side of the silicon wafer a plurality of trenches or holes deep enough to extend for at least part of its thickness into a purposely made doped buried layer of opposite type of conductivity of the substrate and of the epitaxial layer grown over it; electrochemically etching through such trenches, the silicon of the buried layer with an electrolytic solution suitable for selectively etching the doped silicon of said opposite type of conductivity, making the silicon of the buried layer porous; and oxidizing and leaching away the silicon so made porous.
Preferably, the trenches or holes for accessing the doped buried layer are cut through the epitaxial layer and not through the rear of the monocrystalline silicon substrate thus avoiding the burden of precisely aligning the mask on the rear surface with the masks that are used on the front surface of the substrate. Moreover, the thickness of the substrate is normally much greater than that of the epitaxial layer and thus the need to cut relatively deep and narrow trenches requiring the use of special plasma etching equipment is avoided.
Abstract:
A miniscule fuel cell is realized on a doped monocrystalline silicon subtrate. The microporous catalytic electrodes permeable to a gaseous fuel or an oxygen containing gas are constituted by a plurality of coplanar and parallel strips (3,4) of a catalytic metallic material electroplated or sputtered over an heterogeneous columnar skeleton structure of monocrystalline silicon (1,2) purposely formed by etching the silicon substrate to realize the plurality of parallel trenches (7,8) for ducting reagent and products of the electrode reactions to and from the microporous catalytic electrode formed thereon. The spaced parallel strips (3,4) constituting the microporous catalytic electrode permeable to gases are electrically connected one to the other by parallel strips (5,6) of conducting material alternate to the microporous strips of catalytic electrode material. The whole composite electrode structure of the half-cell is in electrical contact with the conducting substrate of monocrystalline silicon in correspondence of said strips of conducting material deposited over the crests of separation between adjacent parallel trenches etched in the silicon substrate, and optionally also in correspondence of the heterogeneous columnar skeleton of conducting monocrystalline silicon in case it is not completely removed by an eventual chemical and/or electrochemical final etching step after having deposited thereon the catalytic metal to form a self-sustaining microporous structure. Two half-cells thus formed on distinct silicon substrates are thereafter placed one against the other sandwiching, at least over the cell area, a thin film of permionic membrane substantially impermeable to fluids.
Abstract:
The infrared detector device (1) comprises a PN junction (9, 10) formed by a first semiconductor material region (9) doped with rare earth ions and by a second semiconductor material region (10) of opposite doping type (P). The detector device comprises a waveguide (8) formed by a projecting structure (6) extending on a substrate (2) including a reflecting layer (4) and laterally delimited by a protection and containment oxide region (11). At least one portion of the waveguide (8) is formed by the PN junction and has an end fed with light to be detected. The detector device (1) has electrodes (18, 13) disposed laterally to and on the waveguide (8) to allow an efficient gathering of charge carriers generated by photoconversion.
Abstract:
A process for the production of hydrogen for micro fuel cells is described, comprising the successive steps of: - continuously supplying a catalytic bed (14) with an aqueous solution of Sodium Borohydride, the catalytic bed being made of at least one metal chosen among Cobalt, Nickel, Platinum, Ruthenium with obtainment of hydrogen and of a by-product comprising Sodium metaborate, - continuously recovering the hydrogen thus obtained and - supplying, with said hydrogen as it is as obtained, a micro fuel cell which provides its transformation into electric energy. An apparatus is also described for the actuation of the above described process.