On the geometry dependence of the 1/f noise in CMOS compatible junction diodes

This paper examines in detail the low-frequency (LF) noise behavior of Si n(+)p junction diodes in forward operation. Diodes fabricated on various types of Si substrates (FZ, epitaxial, and Ct) and with different geometries are studied in the current range 0.1-250 mu A in order to investigate the impact of these parameters. It is demonstrated that different kinds of 1/f noise behavior can be distinguished which point toward a different origin. The nature of the 1/f noise is most clearly identified by inspecting the variation of the frequency exponent with forward bias. On the one hand, what could be called "peripheral" or "surface" 1/f noise shows a frequency exponent which reduces with increasing forward current, a trend which is also observed for the corresponding ideality factor. When the 1/f noise is predominantly generated in the volume of the material (bulk origin), a more or less constant frequency exponent is found. It is also concluded that in many cases, no unique area or perimeter dependence is found when comparing the noise power spectral density of diodes with a different geometry. It will finally be shown that there exists a close correlation between the different 1/f noise sources and the different reverse current components, which are a sensitive function of the starting material characteristics and processing details.