Low frequency noise in npn and pnp polysilicon emitter bipolar junction transistors

Abstract

Low frequency noise characteristics of a high voltage, high performance complementary polysilicon emitter (PE) bipolar transistors are described. The influence of the base biasing resistance, emitter geometry, and temperature on the noise spectra are discussed. The npn transistors studied exhibited 1/f and shot noise, but the pnp transistors, are characterized by significant generation-recombination noise contributions to the total noise. For both types of transistors, the measured output noise is determined primarily by the noise sources in the polysilicon-monosilicon interface. The level of the 1/f noise is proportional to the square of the base current both for npn and pnp transistors. The contribution of the 1/f noise in the collector current is also estimated. The area dependence of 1/f noise in both types of transistors, as well as other npn bipolar transistors are presented. Low frequency noise in a low voltage (5V and 10V), high performance npn transistor technology are also presented. For these transistors, the effect of different base implant and rapid thermal annealing conditions, polysilicon emitter thicknesses, and surface etching conditions on the noise magnitude were studied, and these results are also reported. Finally, results pointing to the possible origin of 1/f noise in PE BJTs are presented.