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 TiwN CH3.2x4. TDMAT.. Deviations from conformal TiN film growth have been observed in trench structures using TDMAT. This nonconformal deposition may be associated with readsorption and site blocking by the dimethylamine HN CH3.2. DMA.reaction product. To understand 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 were also dependent on surface coverage. The initial sticking coefficient for TDMAT is S0s0.23 with a coverage-dependence approximated by S u.s0.25 exp y4.7 u. where u is the normalized surface coverage. The initial sticking coefficient for DMA is S0s0.70 and the coverage-dependence is approximated by S u.s0.86 exp y3.7 u.. The observed desorption kinetics of DMA following TDMAT and DMA exposures on TiN were also coverage-dependent. The isothermal desorption measurements could be fit using a simple first-order desorption rate expression, kdsndexpwyEd u.rRT x where E u. is the coverage-dependent desorption energy, Ed u.sE0yE1u . Assuming a desorption preexponential of nds1=1013 sy1, the observed isothermal desorption measurements for DMA desorption following both TDMAT and DMA exposures could be fit using E s29.1 kcal moly1 0 and E1s8.2 kcal moly1. These measured adsorption and desorption kinetics are consistent with DMA readsorption as a major contributor to nonconformal TiN growth in trench structures using TDMAT. q1999 Published by Elsevier Science B.V. All rights reserved