Low sheet resistance titanium nitride films by low-temperature plasma-enhanced atomic layer deposition using design of experiments methodology

A design of experiments methodology was used to optimize the sheet resistance of titanium nitride (TiN) films produced by plasma-enhanced atomic layer deposition (PE-ALD) using a tetrakis(dimethylamino) titanium precursor in a N-2/H-2 plasma at low temperature (250 degrees C). At fixed chamber pressure (300 mTorr) and plasma power (300W), the plasma duration and N-2 flow rate were the most significant factors. The lowest sheet resistance values (163 Omega/sq. for a 20nm TiN film) were obtained using plasma durations similar to 40s, N-2 flow rates >60 standard cubic centimeters per minute, and purge times similar to 60 s. Time of flight secondary ion mass spectroscopy data revealed reduced levels of carbon contaminants in the TiN films with lowest sheet resistance (163 Omega/sq.), compared to films with higher sheet resistance (400-600 Omega/sq.) while transmission electron microscopy data showed a higher density of nanocrystallites in the low-resistance films. Further significant reductions in sheet resistance, from 163 Omega/sq. to 70 Omega/sq. for a 20nm TiN film (corresponding resistivity similar to 145 mu Omega.cm), were achieved by addition of a postcycle Ar/N-2 plasma step in the PE-ALD process. (C) 2014 American Vacuum Society.