Paper TF-ThP5
Atomic Layer Deposition of Titanium Nitride Using Titanium Tetrachloride and Hydrazine

Thursday, October 21, 2010, 6:00 pm, Room Southwest Exhibit Hall

The atomic layer deposition (ALD) of high quality metal nitrides at low process temperatures has remained a challenge. The use of organometallic precursors to reduce the deposition temperature can lead to carbon incorporation and poor electrical performance. One possibility is to use halide precursors together with hydrazine instead of ammonia for the ALD of metal nitrides. Thermochemical calculations indicate that heats of reaction are more favorable and reaction temperatures should be lower with hydrazine. In this work, TiN ALD was performed using titanium tetrachloride (TiCl₄) and hydrazine (N₂H₄). In situ quartz crystal microbalance (QCM) measurements revealed a TiN ALD growth rate of 16 ng/cm² at 225°C. The TiCl₄ and N₂H₄ reactions were both observed to be self-limiting. At higher temperatures, TiN ALD is difficult to examine using the QCM because of thermal stability issues. X-ray diffraction (XRD) and X-ray reflectivity (XRR) studies revealed that TiN ALD deposited at 275°C resulted in the purest cubic polycrystalline TiN film. TiN ALD at 275^oC also displayed the highest growth rate of 0.36 Å/cycle and a film density of 4.7 g/cm³. Fourier transform infrared (FTIR) studies of the TiCl₄ and N₂H₄ reactions at 275°C observed that primary (-NH₂) and secondary (-NH) amines are formed after hydrazine exposures. The FTIR spectra contained no evidence of any chlorine-containing salt on the surface. Elemental analysis of the TiN ALD grown at 275^oC revealed no chlorine impurities within the X-ray photoelectron (XPS) instrument detection limit of 1 at%. However, oxygen was present at 14 at% that is attributed to oxidation after exposure to air. The use of hydrazine should facilitate the deposition of TiN ALD films at process temperatures <300°C.