| 摘要 |
991,174. Semi-conductor devices. WESTERN ELECTRIC CO. Inc. July 28, 1961 [Dec. 9, 1960], No. 27529/61. Drawings to Specification. Heading H1K. An electrical contact to an oxide-coated semiconductor body is formed by depositing on the oxide coating an active metal layer, and depositing on the latter a contact metal layer and heating to transfer at least a portion of the oxygen of the oxide layer to the active metal to form an oxide thereof. The active metal used is one of the following:-titanium, zirconium, niobium, tantalum, thorium or vanadium; and the contact metal used is one of the following:-gold, silver, palladium, rhodium, copper, nickel or platinum. The semi-conductor body may be of germanium, silicon or gallium arsenide. Sufficient active metal is deposited to ensure (a) that the oxide of the active metal, which goes into solid solution in the metal, does not affect the latter's conducting properties and (b) that substantially all the oxygen of the oxide coat is removed so that there is either an intimate contact between the semi-conductor and the active metal or that the oxide layer is thin enough to permit tunnelling. Deposition of the active metal may be by evaporation techniques except in the case of tantalum which is sputtered. The contact metal layer may be either vapour deposited or sputtered. The invention is described in detail in connection with a solar cell comprising a silicon wafer provided with a shallow, broad area, PN-junction, due to the introduction of phosphorus by diffusion techniques. The residual glass layer formed in this process is removed by etching, the cleaned surface being exposed to air at room temperature to provide the oxide surface. Titanium and silver are then used for the active and contact metal deposits. The other surface of the wafer is provided with a standard silver-aluminium eutectic alloy contact. In a further embodiment the thickness of the silicon dioxide may be increased artificially by an amount sufficient to inhibit diffusion of significant impurities from a surrounding phosphorus vapour. Zirconium is then deposited as an active metal according to a prescribed pattern and final layer of niobium is added. On heating the zirconium reacts with the silicon dioxide, and at these points only can phosphorus diffuse into the silicon in the subsequent doping process, the remainder of the silicon dioxide acting as a mask. |
