Low-frequency noise in polysilicon emitter bipolar transistors

The low-frequency noise in polysilicon emitter bipolar transistors is investigated. Transistors with various geometries and various properties of the oxide layer at the monosilicon polysilicon interface are studied. The main 1/f noise source proved to be located in the oxide layer. This source causes both 1/f noise in the base current S/sub Ib/ and 1/f noise in the emitter series resistance S/sub re/ The magnitude of the 1/f noise source depends on the properties of the oxide layer. The 1/f noise is ascribed to barrier height fluctuations of the oxide layer resulting in transparency fluctuations for both minority and majority carriers in the emitter, giving rise to S/sub Ib/ and S/sub re/ respectively. It is also shown that a low transparency of the oxide layer also reduces the contribution of mobility fluctuations to S/sub Ib/.<
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