ZENER DIODE AND METHOD OF MAKING THE SAME

摘要

1,203,886. Zener diodes. HITACHI Ltd. 25 Sept., 1968 [25 Sept., 1967; 27 Sept., 1967 (2)], No. 45591/68. Heading H1K. A Zener diode comprises a layer of silicon of one conductivity type having an impurity concentration of 1 x 1017 to 4 x 1019 atoms. cm-3 and an epitaxial layer of the opposite conductivity type having an impurity concentration of 2 x 1019 to 1 x 1021 atoms. cm-3, the impurity concentration gradient being 2 x 1021 to 7 x 1023 atoms. cm-4 across the PN junction between the layers. The first layer may comprise a single crystal wafer or may be an epitaxial layer deposited on a high conductivity substrate of the same conductivity type. The epitaxial layer of the opposite conductivity type may be produced by decomposition of SiH 4 , Si 2 H 6 , SiHCl 3 SiCl 4 , GeH 4 , GeCl 4 or Gel 4 and may be doped with PH 3 , AsH 3 , PCl 3 , BCl 3 or B 2 H 6 . The diodes are provided with ohmic contacts of Al, Au, Ni, Ni-Au, or Au-Sb by vapour deposition, plating, or alloying. The surface of the wafer may be sandblasted before plating with Ni. The devices may be punched out of a sheet and the edges etched. The thickness of the epitaxial layer is selected so that formation of the ohmic contact does not cause deterioration or shorting of the junction. The epitaxial deposition conditions are discussed.