On the origin of 1/f noise in polysilicon emitter bipolar transistors

Low frequency noise in polysilicon emitter bipolar transistors (BJT) with different emitter areas (AE) was studied. In BJTs with submicron emitter area, random telegraph signals of different amplitudes and frequencies were found. Averaging of noise spectra from different submicron BJTs gives 1/f noise of the same level (normalized to the emitter area) as 1/f noise found in transistors with large emitter areas. The sheet density of traps (NT) located within the polysilicon–crystalline silicon interfacial layer and responsible for 1/f noise was estimated to be ⩾3×108 cm−2.