Ti/Ni(80%)Cr(20%) Thin-Film Resistor With a Nearly Zero Temperature Coefficient of Resistance for Integration in a Standard CMOS Process
A thin-film resistor out of Ni(80%)Cr(20%) for integration in a standard complementary metal-oxide-semiconductor process with a temperature coefficient of resistance (TCR) below 10 ppm/K was realized by applying a thin Ti layer underneath. The Ti-layer thickness and the temperature and duration of furnace annealing after deposition were optimized in different experiments. The combination of 5-nm Ti + 10-nm NiCr and a 30-min heat treatment at 350degC in a forming gas ambient was found to yield a sheet resistance of about 140 Omega/sq and a TCR of below 10 ppm/K. The long-term drift of the sheet resistance after 1000 h at 200degC was about 0.3%. A transmission electron microscopy analysis was conducted to investigate the structure of the film and a possible change during annealing. An Auger analysis was conducted for film surface analysis.
Structural and Electrical Properties of NiCr Thin Films Annealed at Various Temperatures in a Vacuum and a Nitrogen Ambient for π -Type Attenuator Applications
NiCr thin films were prepared on SiO 2 /Si substrates using a magnetron co-sputtering technique and were annealed at various temperatures in a vacuum (3 X 10 -6 Torr) and a nitrogen ambient. The crystallinity of the films annealed in a vacuum ambient was higher than that of films annealed in nitrogen ambient. Samples annealed above 500°C in nitrogen ambient exhibited a second phase in the NiCr films. The incorporation of oxygen into the NiCr films produced the decrease of crystallinity and significantly influenced the temperature coefficient of resistance of the films.
Some aspects of auger electron spectra of 3d transition metal oxides
Auger electron spectra of the transition metals Cr, Mn, Fe, Co and Ni as well as their oxides have been investigated in the energy range between 0–100 eV. In each case of the clean metal surface the observed spectrum consists essentially of one Auger line identified asM2,3VV transition. After oxidation a line doublet is observed revealing two transitions instead of one. Additional new Auger peaks appear in the low energy range between 0–30 eV. The “splitting” of the Auger line can be explained as resulting from aM2,3VdVd and aM2,3VpVp transition. The latter is characteristic for the compound and can in a simple way be interpreted as a cross transition.