Frequency noise level of as ion implanted TiN-Ti-Si structures

Abstract

This paper presents a possibility of using frequency noise level measurements to study the properties of Ti silicides. We have sputter deposited sequentially a 100 nm thick titanium layer and a 50 nm TiN layer on p-type Si (111) wafers. The TiN/Ti/Si structures were implanted with As+ at 350 keV, to doses from 1 X 10(15) to 1 X 10(16) ions/cm(2). The projected range of arsenic ions is near Si-Ti interface. The samples were annealed in vacuum at temperatures up to 800 degrees C. Methods of characterization of samples include frequency noise level measurements, Rutherford backscattering, and electrical measurements. Annealing induce the Ti-Si reaction, the top TiN layer remaining stable throughout the processing. Silicidation depends on the annealing time and temperature, and on the implanted dose. In samples implanted up to 5 X 10(15) ions/cm(2) the low resistivity TiSi phase is formed at 750 degrees C. For higher implanted doses silicidation is retarded. In this case TiSi is formed initially, transforming to the TiSi phase for longer annealing times. Noise spectra show that the noise level depend on the implanted As dose, and that for some frequencies, the implanted samples have higher noise level compared to the unimplanted samples.