| 摘要 |
1,196,014. Etching. BROWN, BOVERI & CO. Ltd. 25 Sept., 1967 [27 Sept., 1966], No. 43544/67. Heading B6J. [Also in Division H1] The triggering characteristics of a PNPN device which is to have a shorted emitter are continuously tested while the emitter layer is subjected to a selective etching treatment in an electrically conductive etchant. As shown, a PNPN Si wafer 8 is submerged in a conductive etchant 11 comprising HNO 3 , CH 3 COOH and HF in vol. proportions of 4: 2: 1.5 while voltage pulses from a source 15 are supplied between the device anode 13 and a gold wire measuring electrode 5 which is compression bonded to the emitter layer of the wafer 8 beneath an insulating mask and which is uncovered so as to contact the etchant 11. The pulses from the source 15 have an amplitude smaller than the triggering voltage for the device, but the voltage-rise rate is sufficient to produce triggering as long as the emitter junction is not shorted. When the etching process is sufficiently advanced for shorting to occur the pulses fail to trigger the device, and a control means 16, 18, 19 operates a valve which directs a jet of water on to the wafer 8 to rinse away the etchant 11. A layer of Ni is then vapour deposited over the etched surface and sintered. In an alternative application a desired triggering current is achieved by a similar procedure. The zones of the wafer 8 may be formed entirely by diffusion, or the emitter layer may be produced by alloying an Au foil containing Sb to the wafer. In this case the Au foil comprises the etching mask, being itself etched with aqua regia. The measuring electrode 5 comprises a spring in contact with the foil. |
