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Characterization of vapor draw vessel performance for low-volatility solid precursor delivery



James E. Maslar, William A. Kimes, Brent A. Sperling, Ravindra K. Kanjolia


Low volatility precursors are widely utilized in chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes. Compared to gases and high volatility liquid precursors, delivery of low volatility liquid and solid precursors can be problematic, with solid precursors being particularly so. To investigate some of these delivery issues, the performance of a vapor draw vessel was characterized for the delivery of pentakis(dimethylamido) tantalum (PDMAT), a low-volatility solid precursor at preferable delivery temperatures, for reduced-pressure cyclical CVD and ALD processes. Vessel characterization involved determining 1) a source efficiency as a function of process conditions and 2) the degree of PDMAT decomposition as a function of temperature and vessel idle time. The PDMAT partial pressure, flow rate, and mass per injection used to determine the source efficiency were determined from measurements obtained using a custom-designed non- dispersive infrared gas analyzer. For a series of injections after an idle/purge sufficiently long to saturate the vessel head space, the source efficiency decreased, from a maximum slightly less than unity for the first injection, until a consistent value was reached that was approximately one half to one third of the maximum value. A comparable trend was observed for mass per injection. For the conditions used in this investigation, the source efficiency decreased when injection time was increased to longer than 1 s, when pressure was decreased, and when carrier gas flow rate was increased. Although the corresponding mass per injection increased with these changes, the increase was less than that predicted had the carrier gas been saturated. The source efficiency did not depend strongly on temperature and only moderately on vessel idle durations (4 s to 16 s). The degree of PDMAT decomposition was evaluated by measuring the partial pressure of dimethylamine (the primary PDMAT decomposition product under the condi
Journal of Vacuum Science & Technology A


atomic layer deposition, ALD, chemical vapor deposition, CVD, non-dispersive infrared gas analyzer, NDIR, pentakis(dimethylamido) tantalum, PDMAT, precursor delivery, vapor draw vessel


Maslar, J. , Kimes, W. , Sperling, B. and Kanjolia, R. (2020), Characterization of vapor draw vessel performance for low-volatility solid precursor delivery, Journal of Vacuum Science & Technology A, [online], (Accessed November 27, 2022)
Created December 10, 2020, Updated September 8, 2022