| 摘要 |
1,136,304. Semi-conductor devices. RADIO CORPORATION OF AMERICA. 26 April, 1966 [10 May, 1965], No. 18134/66. Heading H1K. An impurity is diffused into a wafer of semiconductor material from a source comprising a wafer of a nitride of the impurity element having a surface layer of an oxide of the impurity element. The semi-conductor and source wafers are placed close together with their major faces parallel, and are heated to a temperature at which the oxide vaporizes and the impurity element diffuses into the semiconductor wafer. A plurality of wafers may be simultaneously diffused in the apparatus of Fig. 1 (not shown), which comprises an electrically heated furnace tube (16) open at one end, the other end being closed and having oxygen and inert gas inlet tubes (24, 26). A plurality of wafers (42) of boron nitride are placed in alternate slots (42a) in a V-shaped quartz boat (44) and heated in a stream of oxygen to produce surface layers (48) of boron oxide. A pair of silicon wafers (14), placed back-to-back, are inserted in each of the slots (14a) between the boron nitride wafers (42) and the assembly heated in a stream of inert gas to vaporize the boron oxide and produce P-type surface layers (12, Fig. 1b in the silicon wafers. The diffusion depth may be increased by removing the boron nitride wafers and reheating the silicon wafers. Traces of oxygen in the inert gas and exposure to the atmosphere when the silicon wafers are removed ensure that the surfaces of the boron nitride wafers remain oxidized. The inert gas may be argon, nitrogen, helium, or forming gas. The impurity sources may also comprise surface-oxidized wafers of gallium nitride, indium nitride or aluminium nitride and may be produced by compacting powdered material. Boron nitride wafers may also be oxidized by boiling in sodium hydroxide, by washing in hot water, or by heating in steam. The invention may also be applied to germanium wafers but the diffusion temperature used must be below its melting-point. |
