| 摘要 |
1,025,453. Semi-conductor devices &c. STANDARD TELEPHONES & CABLES Ltd. Jan. 29, 1964, No. 3783/64. Heading H1K. To mount a semi-conductor wafer a layer of an alloy containing gold and the semi-conductor is formed on one of the faces of the wafer and a mixture containing gold and a conductivity type determining impurity is added to the surface of this layer. The wafer is then placed with its prepared face in contact with a mount and heated in a neutral or reducing atmosphere so that on subsequent cooling the wafer becomes firmly attached to the mount. In an embodiment planar transistor structures are formed in an N-type silicon slice by diffusion into one face. The other face is lapped and the slice washed and dried. The slice is heated to 400‹ C. and gold containing a small amount of antimony evaporated on to form a layer of molten alloy with the silicon. This layer is solidified by cooling the slice to below 200‹ C. and a further amount of gold/antimony alloy deposited at this reduced temperature. Next the slice is separated into individual wafers each of which is placed with its alloy layer in contact with a gold-plated header. The assemblies are passed through a furnace at 450‹ C. (in a nitrogen or nitrogen/hydrogen atmosphere) when the gold/antimony acts as a brazing metal to join the wafers to the headers. Each device is provided with leads and encapsulated. In variants the temperature of the slice may be progressively reduced during the alloying operation and the alloy deposited in other than two stages. Arsenic may replace antimony in the doping impurity and boron may instead be used if the original slice is of P-type conductivity. Instead of doped gold a doped gold/ silicon alloy may be deposited during the process. The header may be nickel-plated or may be unplated iron/cobalt/nickel alloy. Germanium or intermetallic compounds may replace the silicon as semi-conductor. Devices other than transistors may be similarly mounted. |
