| 摘要 |
929,477. Semi-conductor devices. HUGHES AIRCRAFT CO. Jan. 16, 1962 [Feb. 24, 1961], No. 1556/62. Class 37. A rectifier comprises a semi-conductive slice 21 on which a second slice 22 is bonded by means of an insulating layer 23, an electrode 32 being made to form a PN junction with an exposed part of the slice 21 within a cavity 28 of the second slice 22, a conductive cap 34 sealing off the cavity and making contact with the electrode 32. A second conductive cap 31 is attached beneath the slice 21. A number of such rectifiers are made at the same time from a large slice of silicon 21 of 0.55 ohms/cm. secured to a second slice of inferior silicon 22 by means of an intervening layer of glass 23. The slice 22 and glass layer 23 are drilled ultrasonically to provide a number of pits 28. The final layer of glass may be removed by etching with hydrofluoric acid to expose the silicon slice 21. A second ultrasonic tool may now be employed to separate the slice into separate pitted portions. A cap 31 of an alloy known under the Trade name "Kovar" and which is plated with gold with 0.1 to 0.5% by weight antimony or arsenic, is alloyed to the bottom of the slice 21. A gold or aluminium wire 32 with 2.5% by weight of gallium or 1% by weight of boron is electroformed on to the exposed surface of the silicon slice to form a PN junction therewith. As shown in Fig. 7 a cap 34 of molybdenum or tantalum coated with a layer of gold and an overcoat of tin is alloyed to the top of the slice 22 to seal off the cavity 28 while making contact with the electrode 32. The layer of tin enables the cap 34 to be alloyed at a temperature which does not disturb the cap 31. The silicon slice 21 may be doped with boron in which event the electrode 32 contains from 0.1% to 0.5% by weight of arsenic or antimony. The slice 21 may be N-type germanium with the gold electrode 32 containing boron, gallium, or indium; or may be P-type germanium with the gold electrode containing arsenic or antimony. As shown in Fig. 8 the cap used to cover the cavity 28 may be of gold-plated tantalum, like the cap 31, but be perforated so that it can be alloyed on to the slice 22 at the same time as cap 31 is alloyed on to slice 21 but still allow the electro-forming of the junction with electrode 32. When the junction has been formed, a solder pellet 37 is melted into the perforation of cap 36 to seal off the cavity and connect the electrode 32. The glass seal is chosen to have a coefficient of expansion equal to that of the semi-conductor slices. |
