I–V and low frequency noise characterization of poly and amorphous silicon Ti- and Co-salicide resistors

Accurate characterization of polysilicon resistors can help in the design and the fabrication of deep-sub-micron CMOS technologies. In this paper we have studied poly and amorphous silicon Ti- and Co-salicide resistors. In order to discriminate between contact and bulk material contribution transmission line model (TLM) test structures are well adapted for both current–voltage (I–V) and low frequency noise (LFN) characterization. Measurements are undertaken as a function of the geometry (inter-electrode length and electrode width) and of the bias current.From I–V measurements sheet resistance of the different bulk materials (poly or amorphous silicon) and contact resistances of the two different processes (TiSi2 or CoSi2) are extracted.Experimentally noise voltage spectral density is measured and converted in resistance spectral density. Noise spectra were always fitted with a 1/f component and white noise. Then, like for I–V characterization (i.e. analyzing the noise of different sample lengths), the contact and bulk 1/f noise contribution is extracted. When contact noise is found to be negligible, bulk material noise is directly modelled according to Hooge relation; otherwise we can only estimate the bulk material. Then the normalised α parameter is used to compare material quality.