Lateral complementary transistor structure for the simultaneous fabrication of functional blocks

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Heretofore, the schemes for fabricating a complementary transistor structure in a monolithic functional block entailed either some additional, difficult-to-control processing steps or a sacrifice in isolation of the collector regions of one type of transistor. This paper describes an isolated p-n-p transistor structure fabricated by the same technique used for the conventional all n-p-n transistor functional block without any additional processing steps. The basic p-n-p transistor has a lateral structure. During the p-type base diffusion of the n-p-n transistor, two concentric p-type regions at close distance are selectively diffused into an isolated n-type region such as that used for the collector of an n-p-n transistor. The center p-type diffused region forms the emitter and the outer ring forms the collector. The n-type space between these two regions serves as the base. The current gain of this transistor is not high, typically around unity. However, by amplifying the collector current of the p-n-p transistor with an n-p-n transistor, the composite transistor acts like a high gain p-n-p transistor and the composite current gain can be made comparable to that of the n-p-n transistor in the same functional block. The lateral complementary transistor has been used extensively and successfully for the fabrication of linear functional blocks such as those used in the Advanced Minuteman Program.