In Situ Reaction Mechanism Study on Atomic Layer Deposition of Intermetallic Co3Sn2 Thin Films

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.