| 摘要 |
1,167,266. Semi-conductor devices. INTERNATIONAL RECTIFIER CORP. 23 March, 1967 [12 May, 1966], No. 13779/67. Heading H1K. A junction of non-uniform depth is formed in a semi-conductor wafer by polishing selected regions of one face of the wafer and roughening others and then diffusing a conductivity determining impurity into the treated face. In the embodiment the faces of an N-type wafer are polished and the peripheral area on one face roughened by sandblasting using alumina or silicon carbide grit. The wafer is then heated at 1250‹ C. for 2 hours in a flow of vaporised boron anhydride to give the junction configuration shown in Fig. 5. After lapping the upper face to re-expose the N-type material in the central area contacts are applied to P layer on the lower face and to the re-exposed N material and the surrounding P-type zone on the upper face to form a transistor.
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