| 摘要 |
1,252,636. Semi - conductor devices. WESTERN ELECTRIC CO. Inc. 20 March, 1969 [25 March, 1968], No. 14587/69. Heading H1K. In the manufacture of a (Gunn-effect) semiconductor device, two spaced apart ohmic contacts are formed to an epitaxial layer of the conductivity type grown on a substrate; these contacts are made to extend through at least substantially the depth of the layer. The substrate may later be removed. As described, a high resistivity gallium arsenide wafer has an N-type epitaxial layer grown on one of its faces. This layer is provided with a silicon oxide masking layer 14 which exposes only the desired contact areas. The masked wafer is then immersed in molten tin 19 saturated with gallium arsenide and the temperature raised to dissolve the exposed parts 16 of the epitaxial layer. The melt is then cooled to redeposit gallium arsenide, now heavily doped with tin, in these parts. The excess melt is poured off and the wafer cleaned. After provision of thin film contacts, the substrate wafer is partially lapped off. The still self-supporting assembly is then bonded, at the contacted surface, to a first beryllia block. After this, the wafer may be further reduced in thickness or completely removed, for example by etching (with I.R. thickness monitoring). A further beryllia block is then bonded to this face of the assembly. In practice many devices are produced in one wafer which is subdivided after the stage in which the first beryllia blocks are bonded to the contacted surfaces. Alternative heatdissipating supports are metal blocks thermocompression bonded to thin layers of semiinsulating substrate. Removal of semi-conductor at the contact area of the epitaxial layer and its replacement may be made separate processes. |
