In this work, a growth
mechanism of an intermetallic Co3Sn2 thin film
is studied in situ with
a quartz crystal microbalance (QCM) and quadrupole mass spectrometer
(QMS). The film is deposited by atomic layer deposition (ALD) from
CoCl2(TMEDA) and Bu3SnH precursors (TMEDA = N,N,N′,N′-tetramethylethylenediamine). Balanced reaction
equations are resolved by fitting the QMS and QCM data, and a step-by-step
growth mechanism is determined for the process. During the CoCl2(TMEDA) pulse, only 1-chlorobutane is formed as a byproduct.
However, during the Bu3SnH pulse, two byproducts, BuCl
and Bu3SnCl, were clearly detected, indicating that two
competing reaction pathways exist during that pulse. Preliminary studies
on another intermetallic ALD process, Ni3Sn2, revealed that the reactions occur similarly as in the Co3Sn2 process.