h/sub FE/ instability and 1/f noise in bipolar transistors

Abstract

A series of accelerated life tests, with high-temperature storage and electric ageing, for NPN silicon planar transistors is discussed. It was found that at low current the current gain h/sub FE/ increases with time during the tests, and its drift is correlated with initial measured 1/f noise in the transistors. The correlation coefficient of relative drift Delta h/sub FE//h/sub FE/ and 1/f noise spectral density Si/sub B/(f) is far larger than that of Delta h/sub FE//h/sub FE/ and other initial DC parameters. A quantitative theory for the h/sub FE/ drift which can satisfactorily explain the h/sub FE/ drift characteristics in the tests is discussed. The model proves that h/sub FF/ drift and 1/f noise can be attributed to the same physical origin. Both are caused by the modulation of carrier traps near the Si-SiO/sub 2/ interface leading to Si surface recombination. 1/f noise measurement, therefore, can be used as a fast and nondestructive tool to predict h/sub FE/ instability of bipolar transistors.<>