| 摘要 |
1,013,465. Semi-conductor devices. STANDARD TELEPHONES & CABLES Ltd. Feb. 13, 1964 [Feb. 15, 1963], No. 6259/63. Heading H1K. A P-N junction is established in a semiconductor body by diffusion from a buried source of impurity. To form the buried source a layer including a doping element of the opposite conductivity type from the semiconductor body is deposited on one face of the body; this layer may, but need not, be diffused into the body at this stage. A second layer of semi-conductor material is then formed on the said face to bury the impurity contained in the first layer. The buried impurity is subsequently diffused, or further diffused, into the original body material to produce a P-N junction which may be at a considerable depth (e.g. 40 microns) below the free surface of the second layer. The resulting structure is suitable for use as a high voltage diode. In Fig. 3 a layer 2 of boron-rich silicon has been formed on one surface of an N-type silicon body 1 by vapour phase epitaxial deposition and subsequently diffused into it; and this layer has been covered by a layer 5 of P-type silicon which also extends over the surface of the still N-type silicon outside the in-diffused region 2. The final diffusion produces the P-N junction 4A of Fig. 4. Subsequent shaping and the formation, by indiffusion of phosphorous, of an N+type layer on the opposite surface of the body results in a mesa diode (Fig. 5, not shown). Fig. 7 shows a portion of a slice 12 of N- silicon to which has been applied first a boronrich silicon layer 10 and a surmounting layer of more N-silicon. Heat treatment in an oxidizing atmosphere produces the extensive P-type region 16, whose conductivity is greatest at 10, forming a deep P-N junction at 14 and also produces an oxide coating 15. A hole (Fig. 9, not shown) may be excavated from the surface layer 15 to the depth of the region 10 so that an electrode may be attached to the P-zone in its most conductive region. In either of the above embodiments P may replace N and vice versa, in which case phosphorous replaces boron. The epitaxially deposited boron-silicon layer may be replaced by a vapour-phase deposited film of boric oxide. Boron from this film is then diffused into the body, any excess boric oxide dissolved away in hydrofluoric acid, and the new boron-doped surface covered with further silicon to form the buried source. |
