Adsorption and desorption kinetics of tetrakis(dimethylamino)titanium and dimethylamine on TiN surfaces

Titanium nitride (TiN) can be deposited using the organometallic precursor tetrakis(dimethylamino)titanium (Ti[N(CH3)(2)](4)) (TDMAT). Deviations from conformal TiN film growth have been observed in trench structures using TD MAT. This nonconformal deposition may be associated with readsorption and s ite blocking by the dimethylamine (HN(CH,),) (DMA) reaction product. To und erstand the deviations from conformal TiN deposition in trench structures, the adsorption and desorption kinetics for TDMAT and DMA were measured on a sputter-deposited TiN surface using laser induced thermal desorption (LITD ) techniques. The LITD measurements revealed that DMA has a higher sticking coefficient than TDMAT. The sticking coefficients for both TDMAT and DMA w ere also dependent on surface coverage. The initial sticking coefficient fo r TDMAT is S-0 = 0.23 with a coverage-dependence approximated by S(theta) = 0.25 exp(- 4.7 theta) where theta is the normalized surface coverage. The initial sticking coefficient for DMA is S-0 = 0.70 and the coverage-depende nce is approximated by S(theta)= 0.86 exp(-3.7 theta). The observed desorpt ion kinetics of DMA following TDMAT and DMA exposures on TiN were also cove rage-dependent. The isothermal desorption measurements could be fit using a simple first-order desorption rate expression, k(d) = v(d)exp[-E-d(theta)/ RT] where E(theta) is the coverage-dependent desorption energy, E-d(theta)= E-theta-E(1)theta. Assuming a desorption preexponential of v(d)=1x10(13) s( -1), the observed isothermal desorption measurements for DMA desorption fol lowing both TDMAT and DMA exposures could be fit using E-0 = 29.1 kcal mol( -1) and E-1 = 8.2 kcal mol(-1). These measured adsorption and desorption ki netics are consistent with DMA readsorption as a major contributor to nonco nformal TiN growth in trench structures using TDMAT. (C) 1999 Published by Elsevier Science B.V. All rights reserved.