基本信息
摘要：1,064,646. Semi-conductor pressure transducers. SIEMENS & HALSKE A.G. Aug. 4, 1964 [July 23, 1963], No. 30698/64. Heading H1K. [Also in Divisions G1 and H4] A semi-conductor electromechanical transducer consists of a junction transistor having a pressure-transmitting needle bearing on the emitter electrode or emitter zone of the transistor whose design is such that the current density in the vicinity of the needle is greater than that in any adjacent surface region. The embodiment shown in Fig. 3 is an oxide-protected NPN silicon planar transistor having a drop-shaped emitter zone 13 formed by diffusion into the base zone 12. The aluminium emitter electrode 14 is similar in shape to the emitter region and its pointed end faces a similarly shaped base electrode 15 to provide a region of maximum current density between the electrodes. The needle is so placed that its axis intersects the line between the tips of the electrodes. Placing the point of the needle in a region of highcurrent density compensates for the loss of sensitivity arising from the use of a blunted needle to avoid damage to the semi-conductor surface. The needle is preferably made of sapphire, ruby, or boron carbide, but may possibly be made of the softer molybdenum. The pressure sensitivity of the transistor varies with its collector current. A suitable direct current bias may be applied to the unstressed transistor so that the transistor may be operated in an area of high-pressure sensitivity. To avoid the use of pressures sufficient to give non- elastic deformation of the semi-conductor this means that the transistor should be operated with the lowest standing collector current consistent with a reasonable current gain. To assist in operating the transistor in the chosen area a mechanical bias may be applied to the needle. To obtain high sensitivity the junctions should be very close to the surface of the transistor provided that they are not so close as to be damaged by the needle. This is essential only in the region of the needle and localized etching may be used so that the needle may be placed near the junction. Many uses of the transducer are suggested-an aircraft variometer is described. The Specification gives the relationship between the collector current of a conventional planar transistor with a horseshoe-shaped base electrode and the position of a needle applied at constant pressure to points across the emitter, base, and collector of the transistor.
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