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-Ib and 1/f noise in the emitter series resistance S-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-Ib acid S-re respectively. It is also shown that a low transparency of the oxide layer also reduces the contribution of mobility fluctuations to S-Ib.