On 1/F Noise in Polysilicon Emitter Bipolar Transistors: Coherence between Base Current Noise and Emitter Series Resistance Noise

The 1/f noise in polysilicon emitter bipolar transistors is investigated 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 SIb and 1/f noise in the emitter series resistance Sre. 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 SIb and Sre, respectively. This model predicts SIb and Sre to be correlated. Our experimental results show a correlation factor in the range of 0.3 to 0.5. The deviation from full correlation is ascribed to local inhomogeneities in the oxide layer.